OCS EIS/EA 

MMS 2002-081 

Programmatic Environmental 

Assessment for Grid 16 

Site-Specific Evaluation of BP Exploration and 

Production, Inc.’s Initial Development Operations 

Coordination Document, N-7469 

Thunder Horse Project 

Mississippi Canyon Block 777 Unit 

(Blocks 775, 776, 777, 778, 819, 820, 821, and 822) 

U.S. Department of the Interior 

Minerals Management Service 

Gulf of Mexico OCS Region
OCS EIS/EA 

MMS 2002-081 

Programmatic Environmental 

Assessment for Grid 16 

Site-Specific Evaluation of BP Exploration and 

Production, Inc.’s Initial Development Operations 

Coordination Document, N-7469 

Thunder Horse Project 

Mississippi Canyon Block 777 Unit 

(Blocks 775, 776, 777, 778, 819, 820, 821, and 822) 

Prepared by 

Minerals Management Service 

Gulf of Mexico OCS Region 

Published by 

U.S. Department of the Interior 

Minerals Management Service 

Gulf of Mexico OCS Region 

New Orleans 

December 2002 

MITIGATION FOR N-7469 

Mitigation 2.02 (Advisory) – Potential to exceed exemption level, DOCD 

A deviation from your DOCD (such as additional drilling time, changes in the drilling schedule, 

and/or the use of higher horsepower equipment, especially for the drilling rig and construction barges) 

could potentially cause the annual emissions exemption level for NOx to be exceeded. Therefore, if such 

a deviation occurs, please be advised that you will immediately prepare a revised DOCD pursuant to 30 

CFR 250.204(q)(2) to include the recalculated emission amounts and the air quality modeling required by 

30 CFR 250.303(e). You will not proceed with the actions that could cause the potential exceedance until 

the revised DOCD has been submitted to and approved by this office. 

Mitigation 2.05 (Advisory) – Fuel usage or run time documentation 

The projected NOx emissions amounts in your plan were calculated using historic fuel consumption 

rates. Therefore, please be advised that you will maintain records of the total monthly fuel consumption 

for the drilling rig and provide the information to this office upon request. 

Mitigation 2.06 (Reminder) – Flaring beyond 48 hours 

Your plan indicates well test flaring for more than 48 continuous hours. Please be reminded that 30 

CFR 250.1105(a)(3) requires you to obtain approval from the Regional Supervisor for Production and 

Development prior to conducting the proposed flaring activities. 
v

TABLE OF CONTENTS 

Page 

Fgures...........................................................................................................................................................ix 

Tables...........................................................................................................................................................xi 

Abbreviations and Acronyms ....................................................................................................................xiii 

Introduction.................................................................................................................................................xv 

1. The Proposed Action ............................................................................................................................1 

1.1. Purpose and Need for the Proposed Action................................................................................1 

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

2. Alternatives to the Proposed Action .....................................................................................................8 

2.1. Nonapproval of the Proposal ......................................................................................................8 

2.2. Approval of the Proposal with Existing and/or Added Mitigation.............................................8 

2.2.1. Mitigative Measures Identified in the PEA....................................................................9 

2.2.2. Mitigation Proposed by the Operator.............................................................................9 

3. Description of the Affected Environment...........................................................................................10 

3.1. Physical Elements of the Environment.....................................................................................10 

3.1.1. Water Quality...............................................................................................................10 

3.1.1.1. Coastal Waters...............................................................................................10 

3.1.1.2. Offshore Waters ............................................................................................11 

3.1.2. Air Quality ...................................................................................................................12 

3.2. Biological Resources ................................................................................................................13 

3.2.1. Sensitive Coastal Environments...................................................................................13 

3.2.1.1. Coastal Barrier Beaches and Associated Dunes............................................13 

3.2.1.2. Wetlands........................................................................................................13 

3.2.1.3. Seagrasses......................................................................................................14 

3.2.2. Deepwater Benthic Communities/Organisms..............................................................14 

3.2.2.1. Chemosynthetic Communities ......................................................................14 

3.2.2.2. Coral Reefs....................................................................................................15 

3.2.2.3. Deepwater Benthos .......................................................................................15 

3.2.2.3.1. Megafauna...................................................................................15 

3.2.2.3.2. Macrofauna .................................................................................17 

3.2.2.3.3. Meiofauna ...................................................................................18 

3.2.2.3.4. Microbiota...................................................................................18 

3.2.3. Marine Mammals .........................................................................................................18 

3.2.3.1. Nonendangered and Nonthreatened Species .................................................19 

3.2.3.2. Endangered and Threatened Species.............................................................23 

3.2.4. Sea Turtles ...................................................................................................................25 

3.2.5. Birds.............................................................................................................................28 

3.2.6. Essential Fish Habitat and Fish Resources ..................................................................30 

3.2.6.1. Essential Fish Habitat....................................................................................30 

3.2.6.2. Description of Fish Resources.......................................................................30 

3.2.7. Gulf Sturgeon...............................................................................................................31 

3.3. Socioeconomic Conditions and Other Concerns ......................................................................32 

3.3.1. Economic and Demographic Conditions .....................................................................32 

3.3.1.1. Socioeconomic Impact Area .........................................................................32 

3.3.1.2. Population and Education..............................................................................32 

3.3.1.3. Infrastructure and Land Use..........................................................................33 
vi

3.3.1.4. Navigation and Port Usage............................................................................33 

3.3.1.5. Employment ..................................................................................................34 

3.3.1.6. Current Economic Baseline Data ..................................................................35 

3.3.1.7. Environmental Justice ...................................................................................36 

3.3.1.8. Commercial Fisheries....................................................................................37 

3.3.1.9. Recreational Resources .................................................................................38 

3.3.1.9.1. Federal and State Reserves .........................................................39 

3.3.1.9.2. Marine Recreational Activities ...................................................39 

3.3.1.10. Archaeological Resources.........................................................................................40 

3.3.1.10.1. Prehistoric ................................................................................................40 

3.3.1.10.2. Historic.....................................................................................................40 

4. Potential Environmental Effects .........................................................................................................41 

4.1. Physical Elements of the Environment.....................................................................................41 

4.1.1. Impacts on Water Quality ............................................................................................41 

4.1.1.1. Coastal...........................................................................................................41 

4.1.1.2. Offshore.........................................................................................................42 

4.1.2. Impacts on Air Quality.................................................................................................42 

4.2. Biological Resources ................................................................................................................43 

4.2.1. Impacts on Sensitive Coastal Environments................................................................43 

4.2.1.1. Coastal Barrier Beaches and Associated Dunes............................................43 

4.2.1.2. Wetlands........................................................................................................43 

4.2.1.3. Seagrasses......................................................................................................44 

4.2.2. Impacts on Deepwater Benthic Communities/Organisms ...........................................45 

4.2.2.1. Chemosynthetic Communities ......................................................................45 

4.2.2.2. Deepwater Benthos and Sediment Communities ..........................................46 

4.2.3. Impacts on Marine Mammals ......................................................................................47 

4.2.4. Impacts on Sea Turtles.................................................................................................49 

4.2.5. Impacts on Coastal and Marine Birds..........................................................................51 

4.2.5.1. Nonthreatened and Nonendangered Birds.....................................................51 

4.2.5.2. Threatened and Endangered Birds ................................................................52 

4.2.6. Impacts on Fish Resources...........................................................................................53 

4.2.6.1. Essential Fish Habitat and Fish Resources....................................................53 

4.2.6.2. Gulf Sturgeon ................................................................................................54 

4.3. Socioeconomic Conditions and Other Concerns ......................................................................54 

4.3.1. Impacts on Economic and Demographic Conditions...................................................54 

4.3.1.1. Population and Education..............................................................................54 

4.3.1.2. Infrastructure and Land Use..........................................................................55 

4.3.1.3. Navigation and Port Usage............................................................................55 

4.3.1.4. Employment ..................................................................................................55 

4.3.2. Impacts on Environmental Justice ...............................................................................57 

4.3.3. Impacts on Commercial Fisheries................................................................................57 

4.3.4. Impacts on Recreational Resources and Beach Use ....................................................58 

4.3.5. Impacts on Archaeological Resources .........................................................................58 

4.3.5.1. Prehistoric......................................................................................................58 

4.3.5.2. Historic..........................................................................................................59 

4.4. Cumulative Effects ...................................................................................................................61 

4.4.1. Water Quality...............................................................................................................61 

4.4.1.1. Coastal...........................................................................................................61 

4.4.1.2. Offshore.........................................................................................................62 
vii

4.4.2. Air Quality ...................................................................................................................63 

4.4.3. Sensitive Coastal Environments...................................................................................63 

4.4.3.1. Coastal Barrier Beaches and Associated Dunes............................................63 

4.4.3.2. Wetlands........................................................................................................63 

4.4.3.3. Seagrasses......................................................................................................64 

4.4.4. Deepwater Benthic Communities/Organisms..............................................................64 

4.4.4.1. Chemosynthetic Communities ......................................................................64 

4.4.4.2. Coral Reefs....................................................................................................64 

4.4.4.3. Deepwater Benthos and Sediment Communities ..........................................64 

4.4.5. Marine Mammals .........................................................................................................64 

4.4.6. Sea Turtles ...................................................................................................................65 

4.4.7. Coastal and Marine Birds.............................................................................................65 

4.4.8. Essential Fish Habitat and Fish Resources ..................................................................66 

4.4.9. Gulf Sturgeon...............................................................................................................66 

4.4.10. Economic and Demographic Conditions .....................................................................66 

4.4.10.1. Population and Education ...........................................................................66 

4.4.10.2. Infrastructure and Land Use........................................................................66 

4.4.10.3. Navigation and Port Usage..........................................................................66 

4.4.10.4. Employment ................................................................................................67 

4.4.11. Environmental Justice..................................................................................................67 

4.4.12. Commercial Fisheries ..................................................................................................67 

4.4.13. Recreational Resources and Beach Use .......................................................................67 

4.4.14. Archaeological Resources............................................................................................67 

4.4.14.1. Prehistoric ...................................................................................................67 

4.4.14.2. Historic........................................................................................................67 

5. Consultation and Coordination ...........................................................................................................68 

6. Bibliography .......................................................................................................................................68 

7. Preparers .............................................................................................................................................88 

8. Appendices .........................................................................................................................................87 

Appendix A Proposed Activity Schedule .........................................................................................A-1 

Appendix B Accidental Oil Spill Review.........................................................................................B-1 

Appendix C Waste Tables................................................................................................................C-1 

Appendix D Geology........................................................................................................................D-1 

Appendix E Socioeconomic Tables ................................................................................................. E-1 

Appendix F Meteorological Conditions........................................................................................... F-1 

Appendix G Physical Oceanography................................................................................................G-1 

Appendix H Other Information on Grid 16 ......................................................................................H-1 

Appendix I Air Emissions Data ....................................................................................................... I-1 
ix

FIGURES 

Page 

Figure 1. Grid 16 in Relationship to the Gulf Coastline and to Other Grids. ........................................xvi

Figure 2. Protraction Diagrams and Blocks in Grid 16 with Highlighted Thunder Horse 

Project Blocks........................................................................................................................xvii

Figure 3. Bathymetry of Grid 16. ..........................................................................................................xix

Figure 4. Military Warning Areas, H2S Blocks, and Ordnance Disposal Area. .....................................xx

Figure 5. Leasehold Positions within Grid 16. ......................................................................................xxi

Figure 6. Active Lease Status and Plans Submitted .............................................................................xxii

Figure 7. Publicly Announced Prospects (initially announced blocks) and Wells Drilled 

 in Grid 16. ............................................................................................................................xxiii

Figure 8. Active and Proposed Pipelines and Wellbore Information ..................................................xxiv

Figure 9. Status of Existing Wells Drilled in Grid 16...........................................................................xxv

Figure 10. Distance from Grid 16 to BP’s Primary Shore Base. ............................................................xxv

Figure 1-1. Major Drill Centers and PDQ Locations. ..................................................................................3

Figure 3-1. Known Chemosynthetic Communities and Pinnacles.............................................................16

Figure 3-2. Satellite Photograph Shows the Distribution of the U.S. Population Light Intensity..............39
xi

TABLES 

Page 

Table 1. Protraction Diagram, Blocks, Leases, and Acreage in Grid 16...............................................xv

Table 1-1. Proposed Location of the Thunder Horse Semisubmersible Production, Drilling, and 

Quarters Facility in Mississippi Canyon Block 778..................................................................3

Table 1-2. Type of Support Vessel for Each Type of Operation and Frequency of Trips..........................5

Table 3-1. Listing of Counties and Parishes of the Coastal Impact Area .................................................33

Table 3-2. Area of Longline Fishing Ban, Eastern Planning Area ...........................................................38

Table 3-3. Shipwrecks in Grid 16 Area ....................................................................................................41

Table B-1. Historical Record of OCS Spills >1,000 Barrels from OCS Facilities, 1985–1999.............. B-6

Table B-2. Historical Record of OCS Spills >1,000 Barrels from OCS Pipelines, 1985–1999.............. B-6

Table B-3. Historical Record of OCS Spills >1,000 Barrels from OCS Blowouts, 1985–1999 ............. B-7

Table B-4. Spill Rates Used to Estimate the Future Potential for Spills ................................................. B-7 

Table B-5. Spill Risk Estimate for Facilities........................................................................................... B-8 

Table C-1. Drilling Wastes Table - 4-Way Subsalt Wells (estimated 7 wells) ....................................... C-3

Table C-2. Drilling Wastes Table - 4-Way Extra Salt Well (estimated 3 wells)..................................... C-5

Table C-3. Drilling Wastes Table - 3-Way Subsalt Wells (estimated 8 wells) ....................................... C-7

Table C-4. Production Wastes Table - All Wells .................................................................................. C-10

Table C-5. Synthetic-Based Drilling Fluid and Cuttings Disposition ................................................... C-11

Table E-1. Onshore Allocations.............................................................................................................. E-3

Table E-2. Population Forecast from 2000 to 2041 by Year and by Coastal Subarea (in thousands) .... E-5

Table E-3. Employment Forecast from 2000 to 2041 by Year and by Subarea (in thousands) .............. E-6

Table E-4. Estimated Employment Impacts for BP's DOCD for the Proposed Action Known as 

Thunder Horse (peak employment is projected for the year 2004 as shown) ....................... E-7

Table E-5. Estimated Opportunity Cost Employment Associated with the Cleanup and Remediation 

of a Worst Case Spill (based on 141,000 bbl spilled; Year 2004)......................................... E-8

Table H-1. Lease Status...........................................................................................................................H-3

Table H-2. Plans Status .........................................................................................................................H-10

Table H-3. Well Status ..........................................................................................................................H-14

Table H-4. Platforms in Grid 16............................................................................................................H-20

Table H-5. Proposed Plan Platforms .....................................................................................................H-20
xiii

ABBREVIATIONS AND ACRONYMS 

AHTS anchor-handling tug/supply 

 (vessel) 

BAST best available and safest technology 

bbl barrel(s) 

BOD biochemical oxygen demand 

B.P. before present 

BP BP Exploration and Production, Inc. 

bpd barrels per day 

Btu British thermal unit 

CEI Coastal Environments, Inc. 

CER categorical exclusion review 

CFR Code of Federal Regulations 

cm centimeter 

CO carbon monoxide 

COD chemical oxygen demand 

CPA Central Planning Area 

CSA Continental Shelf Associates 

CZM Coastal Zone Management 

DC Drill Center 

DDT Dichlorodiphenyltrichloroethane 

DHPTG downhole pressure and 

 temperature gauge 

DM Departmental Manual 

DOCD Development Operations 

 Coordination Document 

DO dissolved oxygen 

DOI Department of the Interior (U.S.) 

 (also: USDOI) 

DTS distributed temperature sensor 

DWOP Deepwater Operations Plan 

EA environmental assessment 

EEZ Exclusive Economic Zone 

EFH essential fish habitat 

EIA Energy Information Administration 

EIS environmental impact statement 

E&P exploration and production 

EP Exploration Plan 

EPA Eastern Planning Area 

ESA Endangered Species Act 

ESS expandable sand screen 

et al. and others 

et seq. and the following 

EWTA Eglin Water Test Area 

FAA Federal Aviation Administration 

FSL from the south line of the lease 

FWL from the west line of the lease 

FMC Fishery Management Council 

FMP Fishery Management Plan 

FONSI Finding of No Significant Impact 

FR Federal Register

ft foot 

FWS Fish and Wildlife Service 

gal gallon 

GMFMC Gulf of Mexico Fishery Management 

 Council 

GOM Gulf of Mexico 

GulfCet Gulf Cetaceans (MMS-funded study) 

H2S hydrogen sulfide 

hp horsepower 

HPHT high pressure, high temperature 

in inch 

kg kilogram 

km kilometer 

LATEX Texas-Louisiana Shelf Circulation 

 and Transport Process Program 

 (MMS-funded study) 

lb pound 

LDHI low-dosage hydrate inhibitor 

LOOP Louisiana Offshore Oil Port 

LTL Letter to Lessees and Operators 

MARPOL International Convention for the 

 Prevention of Pollution from Ships 

mi mile 

mph miles per hour 

mm millimeter 

MMS Minerals Management Service 

MODU mobile offshore drilling unit 

MSA Metropolitan Statistical Area 

MWA military warning area 

NAAQS National Ambient Air Quality 

 Standards 

NBS National Biological Service 

NEPA National Environmental Policy Act, 

 as amended 

NGMCS Northern Gulf of Mexico 

 Continental Slope Study 

NMFS National Marine Fisheries Service 

NOX nitrogen oxide 

NOAA National Oceanic and Atmospheric 

 Administration 

NORM naturally occurring radioactive 

 material 

NPDES National Pollutant and Discharge 

 Elimination System 

NRC National Response Corporation 

NTL Notice to Lessees and Operators 

OBM oil-based mud 

OCS Outer Continental Shelf 

OCSLA Outer Continental Shelf Lands 

 Act, as amended 

OPEC Organization for Petroleum Exporting 

 Countries 

OSRA Oil Spill Risk Analysis 

P production 
xiv

PAH polynuclear aromatic hydrocarbons 

PM particulate matter 

PEA programmatic environmental 

 assessment 

PDQ production, drilling, and quarters 

 facility 

P.L. Public Law 

PCB polychlorinated biphenyl 

PLET pipeline end termination 

ppb parts per billion 

ppm parts per million 

ppt parts per thousand 

PSD Prevention of Significant 

 Deterioration 

RCRA Resource Conservation and 

 Recovery Act 

ROC retention on cuttings 

ROW right-of-way 

SBF synthetic-based fluid 

SBM synthetic-based mud 

SCR steel catenary riser 

SEA site-specific environmental 

 assessment 

SIC Standard Industrial Classification 

SOX sulphur oxide 

SOP suspension of production 

SOV spill occurrence variable 

TLP tension leg platform 

TV transport variable 

USCG U.S. Coast Guard 

USDOC U.S. Department of Commerce 

USDOI U.S. Department of the Interior 

 (also: DOI) 

USEPA U.S. Environmental Protection 

 Agency 

VOC volatile organic compounds 

VRU vapor recovery unit 

WBM water-based mud 

WI well injection 

WPA Western Planning Area 
xv

INTRODUCTION 

The Minerals Management Service (MMS) developed a comprehensive strategy for postlease 

National Environmental Policy Act (NEPA) compliance in deepwater areas (water depths greater than 

1,312 ft or 400 m) of the Central and Western Planning Areas of the Gulf of Mexico (GOM). You can 

find an in-depth discussion of this strategy on our Internet site at the following address: 

www.gomr.mms.gov/homepg/regulate/environ/strategy/strategy.html. 

The MMS’s strategy led to the development of a biologically-based grid system to ensure broad and 

systematic analysis of the GOM's deepwater region. The grid system divided the Gulf into 17 areas or 

"grids" of biological similarity. Under this strategy, the MMS will prepare a programmatic environmental 

assessment (PEA) to address proposed development activities within each of the 17 grids. The PEA will 

also address categorical exclusion criterion C.(10)(1) (from 516 DM 6 Appendix 10). This criterion 

requires the MMS to prepare an environmental assessment for "... areas of ... relatively untested deep 

water or remote areas." A Grid PEA will be comprehensive in terms of the impact-producing factors and 

environmental and socioeconomic resources described and analyzed. The PEA will also include a sitespecific evaluation on a development proposal within the grid's boundaries. 

Once a PEA for a grid has been completed, it will serve as a reference document to implement the 

"tiering" (40 CFR 1502.20) concept detailed in NEPA’s implementing regulations. Future environmental 

evaluations may reference appropriate sections from the PEA to reduce reiteration of issues and effects 

previously addressed in the "grid" document. This will allow the subsequent environmental analyses for 

individual plans within the grid to focus on specific issues and effects related to the proposals. 

This PEA characterizes the environment of Grid 16 and also examines the effects that may result 

from the site-specific activities proposed in BP’s Initial Unit Development Operations Coordination 

Document (DOCD) for the Thunder Horse project (N-7469). To the extent possible, the PEA will also 

evaluate other potential activities proposed or known within Grid 16. 

Figure 1 shows the relationship of Grid 16 to the Gulf’s coastline and to the other 16 grids. The 

Mississippi Canyon Block 777 Unit is highlighted. 

Figure 2 depicts the protraction diagrams and blocks that are contained in Grid 16. The highlighted 

blocks are the proposed location for the Thunder Horse project activities. 

Current Status of Grid 16 

The purpose of this section is to provide the reader with a "state of the grid." Information in this 

section is based on current MMS data and publicly announced prospects that are projected for Grid 16. 

Figure 1 shows the relationship of Grid 16 to the coastline and to the other grids in the GOM. Figure 2 

depicts the portions of the protraction diagrams and the blocks that constitute Grid 16. 

Grid 16 includes portions of the Viosca Knoll, Mississippi Canyon, and Atwater Valley Outer 

Continental Shelf (OCS) protraction diagrams. Table 1 provides information on the protraction diagrams, 

blocks, leases, and acreage in Grid 16. 

Table 1 

Protraction Diagram, Blocks, Leases, and Acreage in Grid 16 

Protraction Diagram No. of Grid 

Blocks 

Approximate Acreage 

in Grid 

No. of Grid 

Blocks Leased 

Percentage of Grid 

Blocks Leased 

Viosca Knoll 26 149,760 23 88% 

Mississippi Canyon 280 1,612,800 228 81% 

Atwater Valley 86 495,360 54 63% 

Grid Totals 392 2,257,920 305 78% 

Mississippi Canyon constitutes approximately 71 percent of the total number of blocks in the grid. It 

also contains about 75 percent of the total number of leases in the grid. Atwater Valley is the second 

largest component of the grid. It contains approximately 22 percent of the total number of blocks in the 
xvi

 

 Figure 1. Grid 16 in Relationship to the Gulf Coastline and to Other Grids. 
xvii

 Figure 2. Protraction Diagrams and Blocks in Grid 16 with Highlighted Thunder Horse Project Blocks. 
xviii

grid and has about 18 percent of the total leases. Viosca Knoll has about 7 percent of the total number of 

blocks and over 7 percent of the leases. Overall, about 78 percent of all the blocks in the grid are leased. 

Figure 3 depicts the bathymetry of Grid 16 in 500-m contour intervals. 

Three Military Warning Areas (MWA’s) impinge on the northeast portion of Gird 16. See Figure 4 

for the boundaries of these MWA’s (W-155B, W-155C, and EWTA-1). All blocks that are contained 

within the MWA’s will have stipulations included within their leases regarding specific Department of 

Defense mitigative measures, i.e., hold and save harmless, electromagnetic emissions, and operational 

considerations. For additional information regarding these stipulations, see the Central and Western 

Planning Area Multisale Final EIS 2002-2007. Figure 4 also shows that an ordnance disposal area is 

located on the west flank of Grid 16. Though this disposal area is inactive, it may contain unexploded 

munitions and other ordnance. Operators must exercise special precautions and care when conducting 

ground-founding or seafloor disturbing activities within the disposal area. 

One block (Mississippi Canyon, Block 900) within the grid is known to contain concentrations of 

hydrogen sulfide (H2S), which requires special precautions and plans from the operator. See the MMS’s 

Operating Regulations (30 CFR 250, Subparts D, E, F, and H) for specific H2S requirements based on 

operational considerations. For additional information regarding H2S and operational activities, see the 

Multisale EIS 2002-2007. 

Approximately 90 percent of the blocks in Grid 16 are located within 200 km of the Breton National 

Wilderness Area. Operators may be required to mitigate their air emissions if their rates exceed 

established thresholds. 

At present, there are 25 operators and/or leaseholders in Grid 16. These operators include 

Amerada Hess Corporation 

Amoco Production Company 

Anadarko Petroleum Corporation 

BHP Petroleum (GOM) Inc. 

BP Exploration & Production Inc. 

Burlington Resources Offshore Inc. 

Chevron U.S.A. Inc. 

Conoco Inc. 

Dominion Exploration & Production, 

Inc. 

EEX Corporation 

Enterprise Oil Gulf of Mexico Inc. 

Exxon Mobil Corporation 

Kerr-McGee Oil & Gas Corporation 

LLOG Exploration Offshore, Inc. 

Marathon Oil Company 

Mariner Energy, Inc. 

Mobil Oil Exploration & Producing 

Southeast Inc. 

Murphy Exploration & Production 

Company 

Phillips Petroleum Company 

Samedan Oil Corporation 

Shell Offshore Inc. 

Spinnaker Exploration Company, L.L.C. 

Texaco Exploration and Production Inc. 

TotalFinaElf E & P USA, Inc. 

Vastar Resources, Inc.

Figure 5 depicts the leasehold position of these operators within Grid 16. 

The grid’s active lease status and plans submitted data are portrayed in Figure 6. A total of 74 

(19%) of the leased blocks have Exploration Plans (EP's) approved by the MMS. There are 15 (4% 

of the leased blocks) DOCD’s filed within the grid. Twenty-eight blocks are in units. One lease 

has a suspension of production (SOP). A total of five leases are currently producing within the 

grid. 

There are 14 publicly announced prospects contained within Grid 16. Figure 7 shows the 

location of these prospects, as well as the locations of wells drilled within the grid. 

At this time, there are four existing and two more proposed surface structures within Grid 16. 

There are numerous proposed and existing pipelines within the grid. The pipeline locations and 

wellbore status are depicted on Figure 8. 

Figure 9 depicts the status of wells drilled within Grid 16. 

There are numerous onshore support bases that are available along the Gulf Coast and that 

could serve as logistical infrastructure for Grid 16. In the current proposal, BP chose their C-Port 

Shore Base at Pass Fourchon, Louisiana, as its primary onshore base to support the proposed 

operations. Figure 10 shows the relationship of Grid 16 to the shore base. The distance in miles 

from the Grid to the shore base is also depicted on Figure 10. 
xix

Figure 3. Bathymetry of Grid 16. 
xx

Figure 4. Military Warning Areas, H2S Blocks, and Ordnance Disposal Area. 
xxi

 Figure 5. Leasehold Positions within Grid 16. 
xxii

. 

Figure 6. Active Lease Status and Plans Submitted. 
xxiii

 Figure 7. Publicly Announced Prospects (initially announced blocks) and Wells Drilled in Grid 16. 
xxiv

Figure 8. Active and Proposed Pipelines and Wellbore Information. 
xxv

STs = 92

40%

P&As = 39

17%

TAs = 49

21%

COM = 28

12%

DSIS = 14

6%

DRL = 4

2%

APDs = 2

1%

Other = 2

1%

Figure 9. Status of Existing Wells Drilled in Grid 16. 

Figure 10. Distance from Grid 16 to BP’s Primary Shore Base. 
1 

1. THE PROPOSED ACTION 

1.1. PURPOSE AND NEED FOR THE PROPOSED ACTION

Under the Outer Continental Shelf Lands Act (OCSLA), as amended, the U.S. Department of the 

Interior (USDOI or DOI) is required to manage the leasing, exploration, development, and production of 

oil and gas resources on the Federal OCS. The Secretary of the Interior oversees the OCS oil and gas 

program and is required to balance orderly resource development with protection of the human, marine, 

and coastal environments while simultaneously ensuring that the public receives an equitable return for 

these resources and that free-market competition is maintained. 

The purpose of this programmatic environmental assessment (PEA) is two-fold. It assesses the 

specific and cumulative impacts associated with the proposed action and also provides information on the 

deepwater area within Grid 16. The document can be used as a basis to allow most subsequent activities 

proposed in the grid to be processed as categorical exclusion reviews (CER's). However, if it is 

determined that a subsequent proposal will require preparation of a site-specific environmental 

assessment (SEA), the PEA provides sufficient information so it can be referenced (tiered) in the SEA. 

The SEA will be focused on a few key issues. The grid area was determined by the MMS's implementing 

regulations for the National Environmental Policy Act (NEPA) to be an area of “relatively untested deep 

water” [516 DM Chapter 6, Appendix 10, C.(10)(1)]. To properly characterize the grid, the PEA captures 

all of the available environmental and operational information for the area. Chapter 3 describes the 

environment at the specific site of the proposed activities and in the broader grid area. Analyses within 

Chapter 4 examine the potential effects of the proposed action and other reasonably foreseeable activities 

within the grid on the environment in the vicinity of the proposal and on the broader grid area. 

BP Exploration and Production, Inc.'s (BP) Initial Unit Development Operations Coordination 

Document (DOCD) represents an action that cannot be categorically excluded because it represents 

activities in relatively untested deep water [516 DM Chapter 6, Appendix 10, C.(10)(1)]. 

This PEA of the Grid implements the "tiering" process outlined in 40 CFR 1502.20, which 

encourages agencies to tier environmental documents, eliminating repetitive discussions of the same 

issue. By use of tiering from the most recent Central and Western Planning Area Multisale Final EIS 

2002-2007 (USDOI, MMS, 2002) and by summarizing and referencing related environmental documents, 

this PEA concentrates on environmental effects and issues specific to the proposed action and proposed 

activities within the Grid. 

1.2. DESCRIPTION OF THE PROPOSED ACTION

The Thunder Horse project area is located approximately 251 km (156 mi) southeast of New Orleans 

and approximately 106-109 km (66-68 mi) from the Louisiana coastline. The project area encompasses 

the Mississippi Canyon Block 777 Unit, Agreement No. 754398003, and is composed of eight contiguous 

blocks: Mississippi Canyon, Blocks 775, 776, 777, 778, 819, 820, 821, and 822 (OCS-G 19997, 9866, 

9867, 9868, 12168, 14656, 14657, and 14658, respectively). BP holds 75 percent of the working interest 

in the unit and ExxonMobil owns the remaining 25 percent interest. BP is the designated operator. 

A number of Exploration Plans (EP's) have been approved for the unit. These include N-6604, R3409, R-3652, S-5817, S-5899, and S-5995. These EP's proposed drilling operations for Mississippi 

Canyon, Blocks 776, 777, 778, and 822. 

BP's initial unit DOCD proposes to develop two separate but closely related discoveries in their eightblock unit. Four blocks, Mississippi Canyon, Blocks 777, 778, 821, and 822, hold the first discovery 

known as "Thunder Horse South." The initial Thunder Horse discovery well, Mississippi Canyon, Block 

778, Well No. 1, was temporarily abandoned on June 29, 1999. This well is located in approximately 

1,829 m (6,000 ft) of water. 

The remaining four blocks in the unit, Mississippi Canyon, Blocks 775, 776, 819, and 820, hold the 

second discovery known as "Thunder Horse North." Its discovery well, Mississippi Canyon, Block 776, 

Well No 1, was temporarily abandoned on November 22, 2000. This well is located in approximately 

1,646 m (5,400 ft) of water. 
2 

Wells for the Thunder Horse project will be located in five major subsea well clusters, with additional 

satellite subsea production (P) and water injection (WI) wells (Figure 1-1). The well cluster concept will 

allow one drilling rig located directly above the cluster to reach all wells without relocating the rig. Initial 

drilling projections include 27 wells (17 P and 10 WI), with the addition of approximately 16 

recompletions and 16 sidetracks planned in mid-to-late life of the project. 

Of the 27 wells included in the DOCD, 18 are new locations that will be drilled, as well as completed 

and produced. The remaining nine wells are predrill locations and have been permitted through approved 

EP's. These wells have either been drilled or will be drilled in 2002 prior to the MMS's final decision on 

this DOCD. 

There are a total of 16 wells proposed for the Thunder Horse South development — 10 production 

and 6 injection wells. Of these 16 wells, 10 are under the production, drilling, and quarters facility (PDQ) 

(2 WI, 8 P). The PDQ will be moored directly over the major Thunder Horse South Drill Center (DC) — 

DC 41, in Mississippi Canyon Block 778. The other DC’s of Thunder Horse South are as follows: 

• DC 42—satellite WI well 

• DC 43—satellite P well (Mississippi Canyon 822#1, Discovery Well) 

• DC 44—water injection drill center with three WI wells 

• DC 45—satellite P well (Mississippi Canyon 822 #3) 

In addition, there are three drill centers proposed for the Thunder Horse North development that will 

be tied-back to the PDQ. These drill centers contain a total of 11 wells (7 production and 4 injection 

wells): 

• DC 31—drill center with three P and two WI wells 

• DC 32—single production well (Mississippi Canyon 776 #1, Discovery Well) 

• DC 33—drill center with three P and two WI wells 

Many of the 16 recompletions and 16 sidetracks proposed in the DOCD are still notional at this time. 

For the purposes of evaluating future air emissions, BP included 20 sidetracks/deepening of wells within 

the DOCD. BP also estimated the timing of these activities in the plan. 

Two mobile drilling units (MODU's) are planned for the drilling program prior to initiating 

hydrocarbon production from the unit. The first is Diamond Offshore's self-propelled, semisubmersible, 

Ocean Confidence. This rig can be either dynamically-positioned or moored. For the 2002 predrill 

program, this rig will be dynamically positioned. BP's air emission calculations for this DOCD address 

this fact. For subsequent years, the DOCD assumes that the rig will continue to be dynamically 

positioned. If BP decides to moor the rig at a later date, they will be required to submit data regarding the 

areas disturbed by the rig's anchors and that portion of the mooring lines that would lie on the sea bottom. 

An environmental evaluation of these areas will be required prior to installing the mooring system. 

The second MODU is the Transocean Sedco Forex, Discoverer Enterprise, a dynamically-positioned 

drillship. After installation of the PDQ and commencement of production operations, the planned drilling 

schedule assumes the use of two MODU's and the PDQ's drilling rig (simultaneous drilling and 

production operations). 

BP proposes to install a floating semisubmersible PDQ structure in Mississippi Canyon, Block 778, 

as the primary development and production facility for its initial field activities. The PDQ facility will be 

manned and will be permanently anchored on location by a 16-line (4 by 4 spread), semitaut or catenary 

mooring system composed of conventional 152-mm (6-in) steel spiral strand wire, chain, and suction pile 

anchors. The mooring lines will be unequally spaced between adjacent groups in order to allow a large 

subsea corridor for riser connection at the aft end of the PDQ. The lines in each group radiate away from 

the hull at an angle of about five degrees from one another. The water depth at the PDQ's location is 

approximately 1,840 m (6,037 ft). Table 1-1 depicts the proposed location for the PDQ semisubmersible. 
3 

Figure 1-1. Major Drill Centers and PDQ Locations. 

Table 1-1 

Proposed Location of the Thunder Horse Semisubmersible Production, Drilling, and Quarters Facility 

in Mississippi Canyon Block 778 

Surface Location Distance from Lease 

Lines 

Lambert X-Y Coordinates Latitude/Longitude 

Semisubmersible Drilling 

and Production Facility 

FWL 2,444 ft 

FSL 445 ft 

X = 1,158,764.01 

Y = 10,233,085.15 

Lat. 28o 11′ 26.205" N. 

Long. 88o 29′ 44.318" W. 

 Note: FWL is from the west line of the lease. 

 FSL is from the south line of the lease. 
4 

The hull of the PDQ will be comprised of four columns, a ring pontoon, and an integrated deck box. 

The PDQ's deck measures approximately 139 m (455 ft) by approximately 101 m (330 ft). The hull will 

have a load carrying capacity of approximately 68,000 short tons of combined lightship and variable deck 

load above the column tops. The hull has been designed to support up to 16 steel catenary risers that will 

be supported on the forward, starboard, and aft pontoons. Subsea flowlines and pipelines are attached to 

the aft, starboard, and forward pontoons; umbilicals are connected at the deck box level and hung through 

guide tubes that extend to the keel level. The upper hull supports the mooring line chain jacks at the 

structure's columns and four fairleads are located on each column. The PDQ has designed 

accommodations for up to 188 personnel. The PDQ and associated equipment have a 25-year design life. 

The PDQ scheduled to be installed with a dynamically positioned derrick barge. 

Production from the subsea wells in the drill centers is commingled at a manifold and directed to 

flowlines that tie back to the PDQ using steel catenary risers. Subsea wells remote to the drill centers are 

tied back to the PDQ through available slots on the drill center manifold. 

Thunder Horse North and Thunder Horse South produce back to the PDQ through separate dual 

flowlines, which are arranged for round trip pigging from the PDQ. At Thunder Horse North, one of the 

flowlines is used for well testing and servicing, in addition to production. In Thunder Horse South, a 

separate test line is run parallel to the production lines and forms a piggable loop with one of the 

production lines. 

The Thunder Horse South base case production system will consists of eight production wells located 

directly beneath the PDQ at DC 41 and two satellite wells located to the south. The wells at DC 41 are 

each tied into a 20-slot manifold arrangement, consisting of two, 10-slot manifolds, (DC 41 West, DC 41 

East), using a rigid well jumper. The two satellite wells are tied back with single non-piggable flowlines 

to production slots on the DC 41 manifolds. The manifolds are lined up in series and each has two 

production headers and a test header. Interconnecting jumpers are used to connect the manifold headers. 

The production and test flowlines are connected to the manifolds with rigid jumpers. 

The Thunder Horse North production system consists of three wells at DC 33, one well at DC 32, and 

three wells at DC 31. The manifold at each of the Thunder Horse North drill centers has a production 

header, a test header, and a spare header for possible future production. The dual flowlines from the PDQ 

manifold connect to the DC 33 manifold headers and run through to pick up the DC 32 manifold in series 

and then the DC 31 manifold where the lines terminate and are joined with a jumper to enable round trip 

pigging from the PDQ. The clustered wells are connected to the manifolds with rigid well jumpers. 

Valves in the subsea manifolds and trees will be controlled by a redundant multiplexed electrohydraulic control system connected by an umbilical between the manifold and the PDQ. In addition, 

dedicated steel tubes will also be used to deliver the following chemicals to injection points on the subsea 

equipment: corrosion inhibitor, methanol, low-dosage hydrate inhibitor (LDHI), scale inhibitor, and 

asphaltene inhibitor. 

Reservoir management includes pressure maintenance, which is achieved by a water injection system. 

BP also plans to inject its produced water as a part of these operations. 

 The Thunder Horse North water injection system consists of a single pipeline supplying water to two 

water injection wells in the vicinity of DC 33 and two water injection wells in the vicinity of DC 31. 

Connections are made to the wells by utilizing pipeline end termination sleds (PLET’s) with vertical hubs 

and rigid well jumpers. The Thunder Horse South water injection system consists of two water injection 

wells directly beneath the PDQ at DC 41, one well at DC 42, and three wells at a dedicated water 

injection drill center, DC 44, located to the northeast of the PDQ. A single pipeline originating on the 

PDQ supplies water to the well at DC 42 and the wells at DC 41. The pipeline terminates in a PLET with 

multiple hubs at DC 42 to feed the DC 42 well with a rigid well jumper and to feed the DC 41 wells 

through a subsea pipeline from DC 42 to DC 41. The water injection header at DC 41 extends across 

both of the DC 41 manifolds by means of an interconnecting jumper. The three wells at DC 44 will be 

supplied water by a single pipeline originating on the PDQ and terminating in a PLET with vertical hubs 

for rigid well jumper connections. 

BP plans to file lease-term pipeline applications for the Thunder Horse flowlines and related subsea 

architecture around October 2003. 

The deepwater development is located approximately 108 km (67 mi) from the nearest Louisiana 

shoreline. The project will use existing onshore support bases in Fourchon (BP's C-Port Shore Base, 

primary base) and Venice (back up base), Louisiana, to support the proposed activities [about 195 km and 
5 

146 km (121 mi and 91 mi), respectively, to the proposed PDQ location]. Table 1-2 depicts the types of 

support vessels expected to be used displayed with the corresponding type of operations, and the 

frequency of trips. 

 

Table 1-2 

Type of Support Vessel for Each Type of Operation and Frequency of Trips 

Type of Operations and 

Frequency of Trips Type of Support Vessel Drilling/ 

Completion 

Facility 

Installation 

Hook-Up/ 

Commissioning 

Production 

Workboat 4 weekly 3 weekly 

Crew Boat 6 weekly 4 weekly 

Manifold Installation 2 

Flowline Installation 1 

Jumper Installation 2 

Installation Support Vessel 1 

Umbilical Installation Support 4 

Large Supply Vessel 13 

Tug Boat 14 

Large Freight Boat 11 

Infield Riser Installation 1 

Dive Support (spool pieces) 2 

Pre-lay PDQ Moorings 2 

PDQ Mooring Hookup 1 

Liquid hydrocarbon production from the Thunder Horse project will depart the PDQ facility in a 

proposed right-of-way pipeline (ROW G-23429; Segment Number 13633) to be owned and operated by 

Proteus Oil Pipeline Company, LLC (MMS Qualification Number 2530). The proposed Proteus oil 

pipeline is a 61-71 cm (24-28 in), bi-directional pipeline that will carry liquid hydrocarbons 

approximately 111 km (69 mi) from the PDQ facility in Mississippi Canyon, Block 778, to a proposed 

Platform E in South Pass Area, South Addition, Block 89. The new four-pile, Platform E is proposed to 

be set as an accessory structure for the Proteus pipeline. The water depth at the platform's location is 

approximately 120 m (393 ft). The platform will be unmanned. No processing or pumping equipment is 

currently proposed for the platform. 

From Platform E, liquid hydrocarbon production will depart in a proposed right-of-way pipeline 

(ROW G-23068; Segment Number 13534) to be owned and operated by Endymion Oil Pipeline 

Company, LLC (MMS Qualification Number 2529). The proposed Endymion Oil Pipeline is a 76-cm 

(30-in), bi-directional pipeline. It will carry the liquid hydrocarbons approximately 87 km (54 mi) from 

Platform E to a landfall at the existing BP facilities on Grand Isle, Louisiana, and ultimately terminate at 

the Louisiana Offshore Oil Port (LOOP) storage facilities near the Clovelly Oil and Gas Field. 

Produced natural gas from the Thunder Horse project will depart the PDQ facility in a proposed rightof-way pipeline (ROW G-23428; Segment Number 13632) to be owned and operated by Okeanos Gas 

Gathering Company, LLC (MMS Qualification Number 2545). The proposed Thunder Horse lateral to 

the Okeanos Gas Pipeline System will be a 51-cm (20-in), bi-directional pipeline to carry the processed 

natural gas approximately 40 km (25 mi) from the PDQ facility in Mississippi Canyon, Block 778, 

through a PLET and jumper located in Mississippi Canyon, Block 428, to the proposed Na Kika gas 

lateral of the Okeanos Gas Pipeline System. 

Earlier in 2002, ExxonMobil was pursuing options for separate oil and gas pipelines to transport its 

share of the Thunder Horse project's production to existing facilities in the South Pass Area. Recently, 

ExxonMobil Pipeline Company joined the Mardi Gras Transportation System as an owner in the Proteus 

and Endymion oil pipelines that will extend from the Thunder Horse facilities to Clovelly, Louisiana. As 

a result, the Thunder Horse project is currently planning one export oil pipeline (Proteus/Endymion) but 

continues to consider two gas export pipelines, one for BP's share of natural gas production (to be shipped 
6 

in the Okeanos pipeline), and the other for ExxonMobil's share of the project's production. The 

ExxonMobil gas export pipeline is described in the next paragraph. 

A 51-cm (20-in) natural gas export pipeline is currently proposed to transport ExxonMobil's "take-inkind" gas production approximately 161 km (100 mi) from the PDQ facility to a new riser platform near 

ExxonMobil's existing facilities in West Delta Area, Block 73. Water depth at West Delta Area, Block 

73, is approximately 53 m (175 ft). The export natural gas pipeline riser from the PDQ will be a 46-cm 

(18-in) steel catenary riser (SCR). The route is planned to begin at Mississippi Canyon, Block 778, and 

proceed northwest to Mississippi Canyon, Block 325, then continue west to West Delta Area, South 

Addition, Block 144, and finally northwest to West Delta Area, Block 73. 

Proposed Activity Schedule 

BP's proposed activity schedule for their Thunder Horse project is contained in Appendix A. 

Exploration and delineation activities are continuing on this project. Predrilling operations using two 

MODU's began in 2002. The Mississippi Canyon, Block 776, Well No. 2 and the Mississippi Canyon, 

Block 777, Well No. 1 will be drilled by the Ocean Confidence in the Thunder Horse North area. The 

Mississippi Canyon, Block 778, Well No. 2, batch setting of the Mississippi Canyon, Block 778, Well 

No. 3 and Mississippi Canyon, Block 778, Well No. 4, as well as the deepening of Mississippi Canyon 

Block 778, Well No. 3, are also part of the 2002 predrill program. These activities were permitted under 

existing approved EP's. Some subsea component installation activities (tree installation) are expected to 

begin in early 2003. It is currently anticipated that the PDQ's moorings will be prelaid in May 2004, 

immediately followed by installation of manifolds, flowlines, and jumper measurement in June to October 

2004. The full PDQ mooring and umbilical installation is expected between November 2004 and March 

2005. 

New or Unusual Technology 

BP has proposed the use of several new or unusual technologies in its DOCD. They are discussed 

briefly below. See the Environmental Report submitted with BP's DOCD for a full discussion of these 

technologies (BP, 2001). Each proposed technology was individually evaluated for any potential 

environmental effects. Engineering review of the new or unusual technologies was also conducted by the 

MMS in its review of BP's conceptual deepwater operations plan (DWOP). 

High-Pressure Water Injection Pumps 

The individual pump process conditions for water injection on the Thunder Horse project are 50,000 

barrels per day (bpd) at 8,500 psig and 75,000 bpd at 6,500 psig. (Note: Four or more of these pumps 

will be required, depending on sparing.) These conditions will require the use of a multistage, centrifugal 

pump design that has not been previously manufactured in this configuration. The development plan 

includes a plan for design, manufacture, and testing. A one-year period exists in the schedule to design, 

manufacture, test, and incorporate lessons learned from this prototype into the delivery plan. These 

pumps will be electrically powered. 

Environmental review of the multistage centrifugal pump system determined that it will not interact 

with the environment any differently than the traditional water flood pumping system. Air emissions 

were included and considered in the environmental evaluation. 

High-Pressure, High-Temperature (HPHT) Flowline and Riser Design 

The wells for the Thunder Horse project will be drilled from a number of discrete locations or drilling 

centers, where production will be commingled at a manifold and then connected by a flowline and steel 

catenary riser system to the PDQ platform. Key components of this system, from a technology 

standpoint, will include the flowline connectors, the flowline and coating, flowline insulation, and finally, 

the steel catenary riser configuration. Flow assurance studies and PDQ size/weight considerations have 

indicated that the peak fluid flowrate can be met by a combination of 305-mm (12-in) and 254-mm (10-

in) diameter flowlines, and 203-mm (8-in) diameter service and test lines. Using high strength steel, the 

wall thicknesses for the design pressures will be between 30 and 40 mm. These sizes are at or beyond the 
7 

current industry production experience for high strength, steel. However, BP has successfully made test 

joints of pipe with one supplier. Manufacturing capacity and technology issues for both the riser and 

flowline pipe are still under review. Operating temperatures in the pipelines may be as high as 270o

 F, 

but insulation will be required on the lines to allow operator intervention time to depressurize and 

stabilize the system before the contents cool to the hydrate formation temperature of 80o

 F. The coating 

system will be selected to give thermal performance and withstand installation, pressure and thermal 

cycling, and hydrostatic loads. A development program is ongoing to prove the chosen insulation system. 

Thermal Cycling 

Flowlines are being designed to withstand the number of heating and cooling cycles anticipated over 

the project's design life of 25 years, including an adequate margin of safety on the number of cycles. 

Designing properly for good fatigue performance eliminates any spill risk associated with thermal 

cycling. 

End Expansion 

Flowlines are designed to expand at the ends. This expansion is to be accommodated by PLET’s that 

slide and steel flowline jumpers and connectors designed to absorb the flowline expansions and reaction 

loads, respectively. Jumpers and connectors are being designed to accommodate cyclic fatigue and high 

reaction loads to eliminate leakage potential. 

Lateral Deflections 

Some longer flowlines will build up significant mid-line compressive loads that may lead to lateral 

deflections. These lateral deflections will relieve local axial compressive loads (e.g., the flowline wants 

to expand, and the only way this can happen in the middle of a flowline is via lateral deflections). 

Although these lateral deflections are difficult to predict, BP has conducted extensive soil test results to 

better understand the soil resistance to axial and lateral flowline movement. These data are entered into 

finite-element computer models, and other analytical models, to better predict flowline deflection 

behavior and resulting stresses. There is no buckling of the cross-section, thus no issues with leakage 

from this type of buckle. 

Flowline Creep 

This is more commonly known as "flowline walking" and is associated with transients in the thermal 

cycling process. BP is currently investigating this phenomenon and will apply corrective measures if it is 

shown to be a problem. 

HPHT Riser Connections 

Due to water depth, large riser size, and HPHT (see section above) characteristics of the anticipated 

production, hard pipe steel catenary risers will be required to terminate subsea flowlines onboard the PDQ 

semisubmersible floating unit. The attachment of these steel risers to the semisubmersible requires an 

accommodation of dynamic angular motion and/or steady trim/list of the unit. This is conventionally 

done onboard tension leg (TLP) platforms and spars in the Gulf of Mexico via elastomeric and steel 

(laminated) flex-joints. However, the proposed application requires an extension of both angular 

capability and HPHT conditions versus previous TLP and spar experience. An experienced supplier has 

been selected to develop the Thunder Horse flex joints. Testing of a full-scale prototype to confirm the 

design is planned before manufacturing the production units. 

Environmental reviews of the above HPHT flowline and riser design, its operational implications, and 

riser connection proposals determined that use of these technologies will not constitute additional risks to 

the environment compared to available "conventional" technologies. 
8 

Intelligent Wells Interface 

Different fiber optic measurement systems may be deployed down-hole at some of the proposed 

production wells. The systems may include pressure and temperature, replacing the conventional 

electronic downhole pressure and temperature gauges (DHPTG) and distributed temperature sensor 

(DTS). Water injection wells will have DTS sensors only. The proposed development project will be the 

first application utilizing fiber optic, downhole instrumentation sensors within subsea wells tied back to 

the host facility via the subsea control system. Novel technologies include the fiber optic tubing hanger 

connector, the connection system through the subsea tree and the fiber optic subsea distribution system. 

The regulations of 30 CFR 250.122 require the use of Best Available and Safest technologies (BAST). 

The fiber optic downhole technology is passive and inherently more reliable in the high temperature 

environment than conventional electronics and, therefore, exceeds BAST standards. The sensors are 

required to operate for the life of field. The project has already initiated a development and qualification 

program. The program will deliver a fiber optic connection system between the downhole cables through 

the tubing hanger to a tree-mounted connector. 

The use of fiber optic systems may actually improve downhole measurements considering the HPHT 

conditions expected in the production wells. Intelligent well interface technology is not expected to 

interface with the environment any differently than conventional technology and may prove to be more 

reliable. 

Expandable Sand Screens (ESS) and Solid Expandable Pipe 

ESS has been chosen as the primary method of downhole sand control for the Thunder Horse North 

wells. The ability to effectively shutoff water in a sand control environment, achieve the well potentials, 

and simplify the completion operations has driven the choice of ESS over conventional sand control 

methods. This is a new technology which has so far had limited application in the GOM but has been run 

in other areas of the world. BP is committed to the development of this technology along with solid 

expandable pipe and has set up a centrally funded project that is working with the Thunder Horse team to 

develop these products within our development timeframe. It is BP's intention to ensure that ESS is 

qualified for Thunder Horse conditions and extensively field tried prior to installation at the project. 

Solid expandable pipe is being evaluated as an option to run in conjunction with ESS to assist water 

shutoff and also as a contingency casing and replacement for liner hangers during drilling operations. 

An environmental evaluation of the EES and solid expandable pipe technologies determined that 

these new technologies should not interface with the environment any differently than the corresponding 

conventional technologies. In fact, enhanced sand control would minimize sand disposal onshore 

(overboard disposal of sand is not allowed by the USEPA). 

2. ALTERNATIVES TO THE PROPOSED ACTION 

2.1. NONAPPROVAL OF THE PROPOSAL

BP would not be allowed to drill, complete, and produce the 27 wells proposed in its Initial Unit 

DOCD. This alternative would result in no impact from the proposed action but could discourage the 

development of much needed hydrocarbon resources, and thereby result in a loss of royalty income for 

the United States and energy for America. Considering these aspects and the fact that we anticipate minor 

environmental and human effects resulting from the proposed action, this alternative was not selected for 

further analysis. 

2.2. APPROVAL OF THE PROPOSAL WITH EXISTING AND/OR ADDED MITIGATION

Measures that BP proposes to implement to limit potential environmental effects are discussed in 

their Initial Unit DOCD and throughout this PEA. The MMS’s lease stipulations, Outer Continental Shelf 

Operating Regulations, Notices to Lessees and Operators, and other regulations and laws were identified 

throughout this environmental assessment as existing mitigation to minimize potential environmental 
9 

effects associated with the proposed action. Additional information on these measures can be found in 

the Final Multisale EIS (USDOI, MMS, 2002). This alternative was selected for evaluation in this PEA. 

2.2.1. Mitigative Measures Identified in the PEA 

Mitigation 2.02 (Advisory) – Potential to exceed exemption level, DOCD 

A deviation from your DOCD (such as additional drilling time, changes in the drilling schedule, 

and/or the use of higher horsepower equipment, especially for the drilling rig and construction barges) 

could potentially cause the annual emissions exemption level for NOX to be exceeded. Therefore, if such 

a deviation occurs, please be advised that you will immediately prepare a revised DOCD pursuant to 30 

CFR 250.204(q)(2) to include the recalculated emission amounts and the air quality modeling required by 

30 CFR 250.303(e). You will not proceed with the actions that could cause the potential exceedance until 

the revised DOCD has been submitted to and approved by this office. 

Mitigation 2.05 (Advisory) – Fuel usage or run time documentation 

The projected NOX emissions amounts in your plan were calculated using historic fuel consumption 

rates. Therefore, please be advised that you will maintain records of the total monthly fuel consumption 

for the drilling rig and provide the information to this office upon request. 

Mitigation 2.06 (Reminder) – Flaring beyond 48 hours 

Your plan indicates well test flaring for more than 48 continuous hours. Please be reminded that 30 

CFR 250.1105(a)(3) requires you to obtain approval from the Regional Supervisor for Production and 

Development prior to conducting the proposed flaring activities. 

2.2.2. Mitigation Proposed by the Operator 

BP will comply with the military stipulations on its leases by contacting the headquarters of Eglin Air 

Force Base to enter into an agreement concerning the control of electromagnetic emissions and the use of 

boats and aircraft in the warning areas (BP, 2002). 

BP’s corporate headquarters mandates that their new projects will use the best available technology 

for handling operational discharges. In addition, BP operates it facilities under an environmental 

management system and they are ISO 14001 certified. 

In order to meet the power requirements and minimize potential emissions, the Thunder Horse project 

has optimized energy efficiency in equipment design and selection. BP has conducted an extensive 

energy efficiency study to ensure that the facilities at the Thunder Horse project have the least emissions 

considering cost, weight, and space. 

BP conducted a “driver study” to select the optimum combination of engine driven equipment versus 

electric motor driven equipment. The scope of this study included life cycle costs, including capital cost, 

fuel cost, operating cost, and maintenance cost, in addition to total emissions for life of the project. BP 

selected the “all electric” option in the study. Under this option, the larger loads, such as compressors and 

water injection pumps, are driven by electric motors. While mechanical drive turbines have historically 

driven these large loads in the Gulf of Mexico, the “all electric” option minimizes NOX, as well as CO2

emissions (which is a BP internal goal tied to Greenhouse Gas Reductions) and still provides needed 

operational flexibility and equipment efficiency. The “all electric” option created the least emissions in 

the appropriate load profile cases. 

BP also intends to minimize the environmental effects from their Thunder Horse project by: 

• eliminating all routine flaring through engineering design or through operational 

controls; 

• eliminating venting through the use of vapor recovery units (VRU’s); 

• capturing emissions from the glycol de-hydrator by VRU’s; 
10 

• reducing fugitive emissions by engineering design and incorporating BP's “no leaks” 

initiative; 

• minimizing waste for land disposal; and 

• using low sulfur diesel for the drilling rig and separate diesel powered engines 

(cranes) or for emergency and essential generators. 

At this time, BP proposes to discharge its drill cuttings overboard if the retention on cuttings (ROC) 

concentrations of SBM is less than 6.9 percent. BP intents to reduce or eliminate these discharges as 

technology improves. 

The Thunder Horse project will co-mingle and re-inject produced water to support pressure 

maintenance for the reservoir. The option of overboard discharge of produced water per NPDES general 

permit requirements will be retained as a contingency. 

BP engineers have selected five LM 2500 gas turbines to deliver the 93 mw power load requirements 

of the Thunder Horse project. These turbines will supply electric power for the “all electric” option for 

compression, water injection pumps, and export pipeline pumps that will all use VFD’s to enhance 

performance and efficiency. 

Process heating will utilize waste heat recovery to eliminate the need for fired heaters on the facility. 

3. DESCRIPTION OF THE AFFECTED ENVIRONMENT 

3.1. PHYSICAL ELEMENTS OF THE ENVIRONMENT

3.1.1. Water Quality 

3.1.1.1. Coastal Waters 

Coastal water quality along the north-central Gulf is addressed here because Grid 16 and the Thunder 

Horse project are located off the mouth of the Mississippi River and because accidental spills could make 

landfall in this region. The service bases for development of Grid 16 are located on or near the coast, and 

marine transportation to and from the grid would traverse coastal waters. 

The bays, estuaries, and nearshore coastal waters of the north-central Gulf are highly important in that 

they provide important feeding, breeding, and/or nursery habitat for many commercially important 

invertebrates and fishes, as well as sea turtles, birds, and mammals. Water quality governs the suitability 

of these waters for animal as well as human use. Furthermore, the egg, larval, and juvenile stages of 

marine biota dependent upon these coastal areas are typically more sensitive to water quality degradation 

than adult stages. The quality of coastal waters is, therefore, an important issue. A comprehensive 

assessment of water quality in the coastal areas of the GOM is contained in the USEPA’s estuarine report 

(1999b). 

More than 30 percent of the estuaries along the north-central Gulf have impaired water quality to the 

point that they cannot support beneficial uses such as aquatic life support or recreational and commercial 

fisheries (USEPA, 1999b). Some of the industries and activities contributing to water quality degradation 

include petrochemical, agricultural, power production, pulp and paper, fish processing, municipal waste, 

shipping, and dredging operations. There are over 3,700 known point sources of contamination that flow 

into the Gulf (Weber et al., 1992 in USDOI, MMS, 1997a; USDOI, MMS, 2000) with municipalities, 

refineries, and petrochemical plants accounting for the majority of these point sources. Vessels from the 

shipping and fishing industries, as well as recreational boaters, add contaminants to coastal water in the 

form of bilge water, waste, spills, and leaching from antifouling paints. Many millions of cubic feet of 

sediments are moved each year in coastal areas due to channelization, dredging, dredged material 

disposal, and shoreline modification in support of shipping, oil and gas operations, and other coastal 

activities. Water quality may be affected by these activities as they can facilitate saltwater intrusion, 

increased turbidity, and release of contaminants. Point-source discharges are regulated by governmental 

entities and water quality is expected to improve. 

Nonpoint sources of contamination from forestry, agriculture, and urban runoff are difficult to 

regulate and probably have the greatest impact on coastal water quality. Inland cities, farms, ranches, and 

various industries drain into waterways that empty into the Gulf. About 80 percent of U.S. croplands are 
11 

upstream of the northern Gulf coastal waters. The Gulf coastal area alone used 10 million pounds of 

pesticides in 1987 (USDOC, NOAA, 1992 cited in USDOI, MMS, 1997a). Nutrient enrichment from 

nitrogen and phosphorus compounds, mostly from river runoff, is another major contributing factor to the 

water quality problem. It can lead to noxious algal blooms, reduced seagrasses, fish kills, and oxygen 

depletion. It is estimated that the Mississippi River alone contributes more than 341,000 pounds of 

phosphorus and 1.68 million pounds of nitrogen to the Gulf per day (USDOI, MMS, 1997a; USDOI, 

MMS, 2000). 

Water quality in coastal waters of the northern GOM is highly influenced by season. For example, 

salinity in open water near the coast may vary between 29 and 32 ppt during fall and winter but decline to 

20 ppt during spring and summer due to increased runoff (USDOI, MMS, 2000). Oxygen and nutrient 

concentrations also vary seasonally. 

Biological indicators of poor coastal water quality are evident in that 50 percent of the largest U.S. 

fish kills between 1980 and 1989 occurred in Texas and 50 percent of shellfish beds in Louisiana are 

closed annually because of contamination (USDOC, NOAA, 1992 cited in USDOI, MMS, 1997a; 

USDOI, MMS 2000). Despite the fact that the Gulf States had a number of “hot spots” for certain 

locations and contaminants, the area did not fare that badly when compared to other U.S. coastal waters as 

characterized in NOAA’s National Status and Trends Mussel Watch Program (USDOI, MMS, 2001b). 

Sediment contamination in U.S. coastal waters is highly related to proximity to large industrialized 

cities. High levels for certain contaminants have been reported for all Gulf States waters (O’Connor and 

Beliaeff, 1995). At least some contaminants are bioavailable, as evidenced by the 1986-1999 Mussel 

Watch Program (USDOI, MMS, 2001b). Cadmium, copper, and zinc increases have been noted in 

mollusks at eight sites between Pascagoula Bay, Mississippi, and the Mississippi River. Since these sites 

are in or west of the mouth of the Mississippi River, the trend is attributed to increased discharges of 

those metals from the river (USDOC, NOAA, 1998). 

3.1.1.2. Offshore Waters 

Offshore marine waters in the GOM are characterized by higher salinity (36.0-36.5 ppt) than 

nearshore coastal waters (USDOI, MMS, 1997a; USDOI, MMS, 2000). The five watermasses identified 

in Appendix G (Physical Oceanography) can be recognized by their chemical characteristics such as 

salinity, dissolved oxygen (DO), nitrate, phosphate, and silicate. The Mississippi River exerts 

considerable influence on the Gulf, including the offshore. 

The depth distribution of nutrients and DO in the deep water of the Gulf is similar to that of the 

Atlantic Ocean. The DO is highest at the surface due to photosynthesis and exchange with the 

atmosphere, and it generally decreases with depth due to respiration by various organisms (including 

bacteria), although higher oxygen concentrations may be encountered in cold watermasses. Nutrient 

concentrations are lowest in the upper water layers where they become depleted by photosynthetic 

activity and are highest in deep water. Usually nutrient and oxygen concentrations in the open water of 

the deep Gulf are not measurably affected by anthropogenic inputs. 

Two water quality phenomena occur in the Gulf: (1) development of a nepheloid layer and (2) 

development of a hypoxic or oxygen-depleted zone. Portions of the Gulf experience a nepheloid layer; a 

thin, near-bottom, highly turbid zone that may play a role in transporting material, including 

contaminants, from nearshore to offshore waters. Hypoxic bottom waters may be present in the northern 

Gulf off the mouth of the Mississippi River. This hypoxic area may be very large (16,500 km2

), ranging 

from the river delta to Freeport, Texas, and is probably exacerbated by human inputs (USDOI, MMS, 

1997a; USDOI, MMS, 2002). Near-hypoxic conditions, unrelated to the river plume, may also be 

observed in the oceanic oxygen minimum at depths between 200-400 m (656-1312 ft); these conditions 

are low enough (2.5-3.0 mg/l) to affect the biota (USDOI, MMS, 2000). 

Generally, the water quality in the offshore areas of the Gulf, particularly over deep water, could be 

considered significantly better than that of the coastal waters (USDOI, MMS, 1997a and USDOI, MMS, 

2002). However, petroleum-related volatile organic carbons have been detected at offshore locations. 

Offshore Texas, Louisiana, and Alabama show detectable levels of petroleum hydrocarbons, likely from 

natural seeps (USDOI, MMS, 1997a and USDOI, MMS, 2000). Similarly, trace metal concentrations are 

low relative compared to coastal waters (Boyle et al., 1984 in USDOI, MMS, 1997a; USDOI, MMS, 

2000). 
12 

Recent research found that the concentration of hydrocarbons in slope sediments (except in seep 

areas) was lower than previous reports for shelf and coastal sediments. No consistent decrease with 

increasing water depth was apparent below 300 m (984 ft) (Gallaway et al., 2002). In general, the Central 

Gulf had higher levels of hydrocarbons, particularly those from terrestrial sources, than the Western and 

Eastern Gulf (Gallaway and Kennicutt, 1988). Total organic carbon was also highest in the Central Gulf. 

Hydrocarbons in sediments have been determined to influence biological communities of the Gulf slope, 

even when present in trace amount (Gallaway and Kennicutt, 1988). 

Deepwater sediments, with the exception of barium concentrations in the vicinity of previous drilling 

activity, do not appear to contain elevated levels of metal contaminants (USDOI, MMS, 1997a; USDOI, 

MMS, 2000). Reported total hydrocarbons, including biogenic (e.g., from plankton and other biological 

sources) hydrocarbons, in sediments collected from the Gulf slope range from 5 to 86 ng/g (Kennicutt et 

al., 1987 in USDOI, MMS, 1997a; USDOI, MMS, 2000). Petroleum hydrocarbons, including aromatic 

hydrocarbons (<5 ppb), were present at all sites sampled, apparently varying more by distance along an 

isopleth than by depth (one transect from 300 to 3,000 m, 984 to 9,843 ft) (Gallaway et al., 2002; USDOI, 

MMS, 1997a). Land-derived material is widespread in the Gulf due to large riverine inputs and transport 

across the shelf to the slope by slumping, slope failure (Gallaway et al., 2002), and other processes. 

Natural seepage is considered to be a major source of petroleum hydrocarbons in the Gulf slope area 

(Kennicutt et al., 1987; Gallaway et al., 2002; USDOI, MMS, 1997a; USDOI, MMS, 2000). 

3.1.2. Air Quality 

Grid 16 is located west of 87.5° W. longitude and hence falls under the MMS's jurisdiction for 

enforcement of the Clean Air Act. The air over the OCS water is not classified, but it is presumed to be 

better than the National Ambient Air Quality Standards (NAAQS) for all criteria pollutants. The blocks 

involved with the Thunder Horse project in OCS waters are located southeast of Plaquemines Parish, 

Louisiana. Plaquemines Parish is an area that is in attainment of all of the NAAQS and for PSD purposes 

is classified as a Class II area. 

The influence to onshore air quality is dependent upon meteorological conditions and air pollution 

emitted from operational activities. The pertinent meteorological conditions regarding air quality are the 

wind speed and direction, the atmospheric stability, and the mixing height (which govern the dispersion 

and transport of emissions). The typical synoptic wind flow for the Grid 16 area is driven by the 

clockwise circulation around the Bermuda High, resulting in a prevailing southeasterly to southerly flow, 

which is conducive to transporting emissions toward shore. However, superimposed upon this synoptic 

circulation are smaller meso-scale wind flow patterns, such as the land/sea breeze phenomenon. In 

addition, there are other synoptic scale patterns that occur periodically, namely tropical cyclones, and 

mid-latitude frontal systems. Because of the routine occurrence of these various conditions, the winds 

blow from all directions in the area of concern (USDOI, MMS, 1988). 

Atmospheric stability is typically expressed by using Pasquill-Gifford stability classes. Not all of the 

Pasquill-Gifford stability classes are routinely found in the offshore GOM. Specifically, the “F” stability 

class is rare. The “F” stability class is characterized by the extremely Hcondition (i.e., a strong radiative 

inversion) that usually develops at night, over land, with rapid radiative cooling of the ground surface and 

the air directly above it. This type of atmospheric stability strongly limits the vertical dispersion of 

emitted air pollutants. The large heat capacity of the GOM is simply incapable of loosing enough heat 

overnight to set up a strong radiative inversion. Likewise, the “A” stability class is also rare. This 

stability class is characterized by the extremely unstable condition that develops over land with very rapid 

warming of the ground surface and the air directly above it and the occurrence of colder air aloft. This 

type of atmospheric stability strongly enhances the vertical dispersion of air pollutants. Once again, the 

large heat capacity of the GOM does not allow for the ocean surface warming rapidly. Therefore, the 

most common stability classes over the GOM are slightly unstable to neutral, which are conducive to only 

a moderate amount of buoyant vertical dispersion. 

The mixing height is a measure of the upward extent for the vertical dispersion of emitted air 

pollutants. Offshore mixing heights are rather shallow, generally less than 1,000 m (3,281 ft), as 

compared to onshore mixing heights, which are typically greater than 2,000 m (6,362 ft) during the day. 

Close to shore, the mixing height over the water increases notably from the typical offshore level, due to 

the water being shallower and the influence of the land, which penetrates out over the water for a short 
13 

distance. Thus, with a typical southeasterly to southerly wind flow, which is conducive to transporting 

emissions toward shore, the extent of the vertical dispersion will increase as the shoreline is approached. 

This has the effect of lowering the resultant air pollutant concentration arising from emissions. The 

composite of these meteorological conditions that influence the dispersion and transport of emissions is 

represented by an exemption level, which can be compared to the projected air pollutant emissions for a 

proposed action. 

Appendix I contains air emissions data for the proposed action. Please refer to this appendix for 

Tables depicting each drill center’s projected emissions and the MMS’s corresponding exemption levels. 

3.2 BIOLOGICAL RESOURCES

3.2.1. Sensitive Coastal Environments 

3.2.1.1. Coastal Barrier Beaches and Associated Dunes 

General information on the types and status of coastal landforms in the Central and Western Gulf is 

contained in USDOI, MMS (2001b). The brief description below is a summary of the coastal barrier 

beaches and associated dunes information contained in that document. 

Barrier landforms include islands, spits, dunes, and beaches. The landforms are usually long and 

narrow in shape, having been formed by sediment transported by rivers, waves, currents, storm surges, 

and winds. Barrier landforms are in a state of constant change and they can be classified into two main 

types: 

(1) Transgressive—where the shoreline is moving inland and marine deposits overlay 

terrestrial ones. This type is usually rapidly eroding, low profile, sparsely vegetated, 

with numerous washover channels, or 

(2) Regressive—where the shoreline is moving seaward and terrestrial sediments are 

becoming overlain over the marine ones. This type is higher profile, well-vegetated 

dunes, with few if any washover channels (USDOI, MMS, 2001a). 

Both types are important ecologically. Barrier islands, particularly vegetated ones with fresh- and/or 

saltwater pools, may serve as habitat for a variety of fairly specialized species, including birds. The 

islands and spits protect the bays, lagoons, estuaries, salt marshes, seagrass beds, and other wetlands, 

some of which may contain threatened or endangered species. 

3.2.1.2. Wetlands 

Wetlands are common along the Gulf Coast, especially along coastal Louisiana. They include 

seagrass meadows, mudflats, mangroves, marshes (fresh, brackish, salt), and hardwood and cypresstupelogum swamps. These areas may occur in isolated pockets, narrow bands, or cover large areas of the 

coast (USDOI, MMS, 2001a). 

High productivity, high detritus input, and extensive nutrient recycling characterize coastal wetlands. 

They are important habitats for a large number of invertebrate, fish, reptile, bird, and mammal species, 

including rare, endangered, or threatened species, and high value commercial and recreational species for 

at least part of their life cycles. Since the 1980's, wetland areas have declined significantly (USDOI, 

MMS, 2001a). For these reasons, wetlands are an important issue when assessing impacts of coastal 

developments and/or accidental spills (in situations where spills may impinge on the coast).

The GOM coastal wetlands represent about half of the Nation’s total wetland area. These wetlands 

help support the exceptionally productive coastal fisheries (e.g., Gulf ports account for four of the top five 

ports in the U.S. in terms of landed weight) and about 75 percent of the migratory waterfowl traversing 

the country (Johnston et al., 1995). NOAA data (1991) and Johnston et al. (1995) estimated that, 

although wetlands have decreased substantially over the last 30 years, about 1.3 million ha of marshes, 

estuarine shrub-scrub, and freshwater forested/shrub-scrub remain on the Gulf Coast. Of these three 

categories, 80 percent is marsh, 19 percent is estuarine scrub-shrub, and 1 percent is forested wetland. 

Louisiana has the greatest area with 55 percent of the total (representing 69% of total marsh) followed by 

Florida (18%) (including 97% of total scrub-shrub, mostly mangrove), Texas (14%), and Mississippi 

(2%) (Johnston et al., 1995). 
14 

The National Biological Service (NBS) provides more recent calculations of wetland losses than the 

NOAA data, with updates every three years based on satellite imagery. The NBS suggests that wetland 

losses are greater than previously thought, although the rate of loss appears to be declining (Johnston et 

al., 1995). 

3.2.1.3. Seagrasses 

Seagrass communities are extremely productive, providing essential habitat for wintering waterfowl, 

as well as spawning and feeding habitat for several commercial and recreational species of fish and 

shellfish, and endangered or threatened species of manatee and sea turtles. Seagrass habitat loss in the 

Gulf has been extensive over the last 50 years. Although found in isolated patches and narrow bands 

along the entire Gulf Coast in shallow, clear, estuarine areas, seagrass meadows occur extensively along 

the eastern coast between Mobile Bay and Florida Bay. Florida contains about 693,000 ha of the 1.02 

million ha estimated for all the Gulf States (Handley, 1995). Louisiana has a large amount of submerged 

vegetation but only a small area of seagrass habitat (about 5,657 ha in 1988) (Handley, 1995). 

3.2.2. Deepwater Benthic Communities/Organisms 

Marine benthic communities consist of a wide variety of single-celled organisms, plants, 

invertebrates, and fish. Their lifestyles are extremely varied as well and can include absorption of 

dissolved organic material, symbiosis (e.g., chemosynthetic communities), collection of food through 

filtering, mucous webs, seizing, or other mechanisms. 

3.2.2.1. Chemosynthetic Communities 

Chemosynthetic communities are defined as persistent, largely sessile assemblages of marine 

organisms dependent upon symbiotic chemosynthetic bacteria as their primary food source (MacDonald, 

1992). Chemosynthetic clams, mussels, and tube worms are similar to (but not identical with) the 

hydrothermal vent communities of the eastern Pacific (Corliss et al., 1979). Chemosynthetic 

communities were discovered in association with hydrocarbon seeps in the northern GOM. Bacteria live 

within specialized cells in these invertebrate organisms and are supplied with oxygen and chemosynthetic 

compounds by the host via specialized blood chemistry (Fisher, 1990). The host, in turn, lives off the 

organic products subsequently released by the chemosynthetic bacteria and may even feed on the bacteria 

themselves. Free-living chemosynthetic bacteria may also live in the substrate within the invertebrate 

communities and may compete with their symbionts for sulfide and methane energy sources. 

Initial discoveries of cold-water seep communities indicated that they are primarily associated with 

hydrocarbon and H2S seep areas (Kennicutt et al., 1985; Brooks et al., 1986a). Since the initial discovery 

in 1984 of chemosynthetic communities dependent on hydrocarbon seepage in the GOM off the west 

coast of Florida, their geographic range has been found to include the Texas, Louisiana, and Alabama 

continental slope with a depth range varying from less than 500 m to 2,200 m (1,640 to 7,218 ft) (Rosman 

et al., 1987; MacDonald, 1992). Four general community types have been described by MacDonald et al. 

(1990). These are communities dominated by vestimentiferan tube worms, mytilid mussels, vesicomyid, 

and infaunal lucinid or thyasirid clams. These faunal groups tend to display distinctive characteristics in 

terms of how they aggregate, the size of aggregations, the geological and chemical properties of the 

habitats in which they occur and, to some degree, the heterotrophic fauna that occur with them. 

The reliance of deep-sea chemosynthetic communities on nonphotosynthetic carbon sources limits 

their distribution in the Gulf to areas where hydrocarbon sources are available. Within the northern Gulf, 

chemosynthetic communities are generally associated with slow oil and gas seeps, rapid expulsion mud 

volcanoes, and mineral seeps (Roberts and Carney, 1997). The most common energy source for the Gulf 

communities is a hydrocarbon seep. Hydrocarbon reservoirs beneath the Gulf may include faults within 

source rock that have allowed oil and gas to migrate upward to the seafloor over the past several million 

years (Sassen et al., 1993). Hydrocarbons seeping to the surface diffuse through overlying sediments 

where bacterial degradation creates the chemosynthetic substrate taken up by symbiotic invertebrates. 

Vestimentiferan tube worms and lucinid and vesicomyid clams rely on hydrogen sulfide (H2S), whereas 

mytilid mussels used dissolved methane (CH4). Mud volcanoes and mineral seeps provide similar 
15 

chemosynthetic source material, but their occurrence in the Gulf is far less extensive than oil and gas 

seeps. 

Hydrocarbon seep communities in the Central Gulf have been reported to occur at water depths 

between 290 and 2,200 m (951 and 7,218 ft) (Roberts et al., 1990; MacDonald, 1992). The total number 

of chemosynthetic communities in the Gulf is now known to exceed 50 (MacDonald, 1992; Boland, 

personal observations, 2000; Gallaway et al., 2000). 

A review for the potential occurrence of chemosynthetic communities associated with Grid 16 and the 

the Thunder Horse project was performed for this EA. The conclusion of this analysis determined that 

there are no known chemosynthetic communities located within Grid 16. The nearest known 

chemosynthetic community is located in Viosca Knoll, Block 826, approximately 143 km (77 nmi) from 

the Thunder Horse development (Figure 3-1). 

3.2.2.2. Coral Reefs 

Coral reefs are particularly sensitive to human disturbance from increased sediments (e.g., from 

dredging), nutrient inputs (e.g., from sewage effluents), and physical damage (e.g., from anchoring). In 

the GOM, shallow-water coral reefs are associated with topographic highs such as the well-known East 

and West Flower Gardens and a number of others in the Central Planning Area (CPA). None of these are 

located in the deepwater areas of Grid 16. 

Currently, there is little information regarding deepwater coral reefs and their abundance in the Gulf 

(USDOI, MMS, 2000). Moore and Bullis (1960) collected more than 136 kg (300 lb) of scleractinian 

coral, Lophelia prolifera, from a depth of 421-512 m (1,381-1,680 ft), about 20 nmi from Viosca Knoll, 

Block 907 (USDOI, MMS, 2000). Recently, there have been observed reports of large amounts of L. 

prolifera video recorded in Viosca Knoll, Block 826 (Roberts, personal communication, 2002), as well as 

video recordings of Madrapora oculata, another deepwater scleractinian coral, found in Green Canyon, 

Block 238 (Childs, personal observation, 2002). Known hard bottoms supporting potential unknown 

coral reef habitat are avoided as a consequence of the MMS's Chemosynthetic Community NTL (NTL 

No. 2000-G20). 

3.2.2.3. Deepwater Benthos 

Marine benthic communities consist of a wide variety of organisms. It is convention in the Gulf 

region to classify benthic animals according to size as megafauna (large, usually mobile animals on the 

surface), macrofauna (retained on 0.25- to 0.50-mm mesh size sieve), meiofauna (0.063-mm screen; 

mostly nematode worms), and microfauna (protists and bacteria). The four types are discussed briefly 

below. 

3.2.2.3.1. Megafauna 

Animals of a size typically caught in trawls and large enough to be easily visible (e.g., crabs, shrimp, 

benthic fish, etc.) are called megafauna. In the Gulf, most are crustaceans, echinoderms, or benthic fish. 

Benthic megafaunal communities in the Central Gulf appear to be typical of most temperate continental 

slope assemblages found at depths from 300 to 3,000 m (984 to 9,843 ft) (USDOI, MMS, 2001a). 

Exceptions include the chemosynthetic communities discussed previously. 

Megafaunal invertebrate and benthic fish densities appear to decline with depth between the upper 

slope and the abyssal plain (Pequegnat 1983; Pequegnat et al., 1990). This phenomenon is generally 

believed to be related to the low productivity in deep, offshore Gulf waters (USDOI, MMS, 2001a). 

Megafaunal communities in the offshore Gulf have historically been zoned by depth strata, which are 

typified by certain species assemblages (Menzies et al., 1973; Pequegnat, 1983; Gallaway et al., 1988; 

Gallaway, 1988a-c; Pequegnat et al., 1990; USDOI, MMS, 2001a). These zones include the following: 

• Shelf/Slope Transition Zone (100-500 m or 328-1,640 ft) — Echinoderms, 

crustaceans, and several species of abundant fish. 
16 

Figure 3-1. Known Chemosynthetic Communities and Pinnacles. 
17 

• Archibenthal Zone (Horizon A) (500-775 m or 1,640-2,543 ft) — Galatheid crabs, rat 

tail fishes, large sea cucumbers, and sea stars are abundant. 

• Archibenthal Zone (Horizon B) (800-1,000 m or 2,625 to 3,281 ft) — Galatheid 

crabs and rat tail fishes are abundant; fishes, echinoderms, and crustaceans decline; 

characterized by the red crab, Chaceon quinquedens. 

• Upper Abyssal Zone (1,000-2,000 m or 3,281-6,562 ft) — Number of fish species 

decline while the number of invertebrate species appear to increase; sea cucumbers, 

Mesothuria lactea and Benthodytes sanguinolenta are common; galatheid crabs 

include 12 species of the deep-sea genera Munida and Munidopsis, while the shallow 

brachyuran crabs decline. 

• Mesoabyssal Zone (2,300-3,000 m or 7,546-9,843 ft) — Fish species are few and 

echinoderms continue to dominate the megafauna. 

• Lower Abyssal Zone (3,200-3,800 m or 10,499 to 12,468 ft) — Large asteroid, 

Dytaster insignis, is the most common megafaunal species. 

Carney et al. (1983) postulated a simpler system of zonation having three zones: (1) a distinct shelf 

assemblage in the upper 1,000 m (3,281 ft); (2) indistinct fauna between 1,000 and 2,000 m (3,281-6,562 

ft); and (3) a distinct slope fauna between 2,000 and 3,000 m (6,562-9,843 ft). 

The baseline Northern Gulf of Mexico Continental Slope Study (NGMCS) conducted in the mid- to 

late 1980’s trawled 5,751 individual fish and 33,695 invertebrates, representing 153 and 538 taxa, 

respectively. That study also collected 56,052 photographic observations, which included 76 fish taxa 

and 193 non-fish taxa. Interestingly, the photographic observations were dominated by holothurians, 

bivalves, and sea pens, groups that were not sampled effectively (if at all) by trawling. Decapod 

crustaceans dominated the trawls and were fourth in the photos from an abundance perspective. Decapod 

density generally declined with depth but with peaks at 500 m (1,640 ft) and between 1,100 and 1,200 m 

(3,609 and 3,937 ft), after which depth abundance was quite low. Fish density, while variable, was 

generally high at depths between 300 and 1,200 m (984 and 3,937 ft); it then declined substantially. 

Gallaway et al. (2002) concluded that megafaunal composition changes continually with depth such 

that a distinct upper slope fauna penetrates to about 1,200 m (3,937 ft) depths and a distinct deep-slope 

fauna is present below 2,500 m (8,202 ft). A broad transition zone characterized by low abundance and 

diversity occurs between depths of 1,200 and 2,500 m (3,937 and 8,203 ft). The proposed Thunder Horse 

development, at a depth of approximately 1,829 m (6,001 ft), lies within this broad transition zone. 

3.2.2.3.2. Macrofauna 

The benthic macrofaunal component of the NGMCS Study (Gallaway et. al., 2002) included 

sampling in nearby areas at similar depths, both east and west of the Thunder Horse project. A transect 

(the central transect) of 11 baseline stations through Grids 12, 13, and 14 from 305 m (1,000 ft) to nearly 

the 3,000-m (9,843-ft) contour was sampled in this study. All of these data are relevant to the proposed 

Thunder Horse development because they were taken from the same geographic area and encompass the 

same depths and substrates. 

The NGMCS Study examined 69,933 individual macrofauna from over 1,548 taxa; 1,107 species 

from 46 major groups were identified (Gallaway et al., 2002). Polychaetes (407 species), mostly depositfeeding forms (196 taxa), dominated in terms of numbers. Carnivorous polychaetes were more diverse, 

but less numerous than deposit-feeders, omnivores, or scavengers (Pequegnat et al., 1990; Gallaway et al., 

2001). Polychaetes were followed in abundance by nematodes, ostracods, harpacticoid copepods, 

bivalves, tanaidacids, bryozoans, isopods, amphipods, and others. Overall abundance of macrofauna 

ranged from 518 to 5,369 individuals/m2

 (Gallaway et al., 1988). The central transect (4,938 

individuals/m2

) had higher macrofaunal abundance than either the Eastern or Western Gulf transects 

(4,869 and 3,389 individuals/m2

, respectively) (Gallaway et al., 2002). 

In the GOM, macrofaunal density and biomass declines with depth from approximately 5,000 

individuals/m2

 on the lower shelf-upper slope to several hundred individuals/m2 on the abyssal plain 
18 

(USDOI, MMS, 2001a). This decline in benthos has been attributed to the relatively low productivity of 

the Gulf offshore open waters (USDOI, MMS, 2001a). However, Pequegnat et al. (1990) reported middepth maxima of macrofauna in the upper slope at some locations of high organic particulate matter, and 

Gallaway et al. (2002) noted that the decline with depth is not clear cut and is somewhat obscured by 

sampling artifacts. 

There is some suggestion that sizes of individual macrofauna decrease with depth (Gallaway et al., 

2002) and that size of individuals are generally small. Macrofaunal abundance appears to be higher in 

spring than in fall (Gallaway et al., 2002). 

Macrofauna in the Gulf appears to have lower densities but higher diversities than the Atlantic, 

especially above 1,000 m (3,281 ft), whereas at deep depths the fauna are less dissimilar in densities and 

very similar in diversities (Gallaway et al., 2002). 

3.2.2.3.3 Meiofauna 

Meiofauna (primarily composed of small nematode worms), as with megafauna and macrofauna, also 

decline in abundance with depth (Pequegnat et al., 1990; Gallaway et al., 2002; USDOI, MMS, 2001a). 

The overall density (mean of 707,000/m2

) of meiofauna is approximately two orders of magnitude greater 

than the macrofauna throughout the depth range of the slope (Gallaway et al., 1988). These authors 

reported 43 major groups of meiofauna with nematodes, harpacticoid copepods (adults and larvae), 

polychaetes, ostracods, and Kinorhyncha accounting for 98 percent of the total numbers. Nematodes and 

harpacticoids were dominant in terms of numbers, but polychaetes and ostracods were dominant in terms 

of biomass, a feature that was remarkably consistent across all stations, regions, seasons, and years 

(Gallaway et al., 2002). Meiofaunal densities appeared to be somewhat higher in the spring than in the 

fall. Meiofaunal densities reported in the NGMCS Study are among the highest recorded worldwide 

(Gallaway et al., 2002). There is also evidence that the presence of chemosynthetic communities may 

enrich the density and diversity of meiofauna in the immediate surrounding area (Gallaway et al., 2002). 

The above conclusions were partially based on the collections from the NGMCS Study stations in 

adjacent Grid areas (the Central Gulf transect) (see also “Macrofauna” above). The Central Gulf transect 

appeared to contain a higher abundance of meiofauna than transects in the Eastern or Western Gulf, and, 

in general, there was a trend of decreasing meiofauna numbers with depth (Gallaway et al., 2002). 

3.2.2.3.4 Microbiota 

Less is known about the microbiota than the other groups in the GOM, especially in deep water 

(USDOI, MMS, 2000). A recent MMS publication (USDOI, MMS, 2001b) provides information on this 

subject. An overview is provided below. 

As reported by Rowe (CSA, 2000), the microbiota of the deep Gulf sediments is not well 

characterized. While direct counts have been coupled with some in situ and repressurized metabolic 

studies performed in other deep ocean sediments (Deming and Baross, 1993), none have been made in the 

deep GOM. Cruz-Kaegi (1998) made direct counts using a fluorescing nuclear stain at several depths 

down the slope, allowing bacterial biomass to be estimated from their densities and sizes. Mean biomass 

was estimated to be 2.37 g C·m-2 for the shelf and slope combined, and 0.37 g C·m-2 for the abyssal plain. 

In terms of biomass, data indicate that bacteria are the most important component of the functional 

infaunal biota. Cruz-Kaegi (1998) developed a carbon cycling budget based on estimates of biomass and 

metabolic rates in the literature. She discovered that, on the deep slope of the Gulf, the energy from 

organic carbon in the benthos is cycled through bacteria. 

3.2.3. Marine Mammals 

Twenty-nine species of marine mammals are known to occur in the GOM (Davis et al., 2000). The 

Gulf’s marine mammals are represented by members of the taxonomic order Cetacea, which is divided 

into the suborders Mysticeti (i.e., baleen whales) and Odontoceti (i.e., toothed whales, dolphins, and their 

allies), as well as the order Sirenia, which include the manatee and dugong. Within the GOM, there are 

28 species of cetaceans (7 mysticete and 21 odontocete species) and 1 sirenian species, the manatee 

(Jefferson et al., 1992). 
19 

3.2.3.1. Nonendangered and Nonthreatened Species 

Cetaceans – Mysticetes 

Bryde’s Whale (Balaenoptera edeni) 

The Bryde’s whale (Balaenoptera edeni) is the second smallest of the balaenopterid whales; it is 

generally confined to tropical and subtropical waters (i.e., between lat. 40o N. and lat. 40o S.) (Cummings, 

1985). Unlike some baleen whales, it does not have a well-defined breeding season in most areas; thus, 

calving may occur throughout the year. The Bryde’s whale feeds on small pelagic fishes and 

invertebrates (Leatherwood and Reeves, 1983; Cummings, 1985; Jefferson et al., 1993). 

There are more records of Bryde’s whale than of any other baleen whale species in the northern 

GOM. It is likely that the Gulf represents at least a portion of the range of a dispersed, resident 

population of Bryde’s whale (Jefferson and Schiro, 1997). Bryde’s whale in the northern Gulf, with few 

exceptions, have been sighted along a narrow corridor near the 100-m (328-ft) isobath (Davis and 

Fargion, 1996; Davis et al., 2000). Most sightings have been made in the DeSoto Canyon region and off 

western Florida, though there have been some in the west-central portion of the northeastern Gulf. Group 

sizes range from one to seven animals. 

Minke Whale (Balaenoptera acutorostrata) 

The minke whale (Balaenoptera acutorostrata) is a small rorqual that is widely distributed in tropical, 

temperate, and polar waters. Minke whales may be found offshore but appear to prefer coastal waters. 

Their diet consists of invertebrates and fishes (Leatherwood and Reeves, 1983; Stewart and Leatherwood, 

1985; Jefferson et al., 1993; Würsig et al., 2000). 

The North Atlantic population migrates southward during winter months to the Florida Keys and the 

Caribbean Sea. There are 10 reliable records of minke whales in the GOM and all are the result of 

strandings (Jefferson and Schiro, 1997). Most records from the Gulf have come from the Florida Keys, 

although strandings in western and northern Florida, Louisiana, and Texas have been reported (Jefferson 

and Schiro, 1997). Sightings data suggest that minke whales either migrate into Gulf waters in small 

numbers during the winter or, more likely, that sighted individuals represent strays from low-latitude 

breeding grounds in the western North Atlantic (Jefferson and Schiro, 1997; Davis et al., 1998 and 2000). 

Cetaceans — Odontocetes 

Pygmy and Dwarf Sperm Whales (Family Kogiidae) 

The pygmy sperm whale (Kogia breviceps) and its congener, the dwarf sperm whale (K. sima), are 

medium-sized toothed whales that feed on cephalopods and, less often, on deep-sea fishes and shrimps 

(Leatherwood and Reeves, 1983; Jefferson et al., 1993; Caldwell and Caldwell, 1989). Hence, they 

inhabit oceanic waters in tropical to warm temperate zones (Jefferson and Schiro, 1997). They appear to 

be most common in waters over the continental slope and along the shelf edge. Little is known of their 

natural history, although a recent study of Kogia in South Africa has determined that these two species 

attain sexual maturity much earlier and live fewer years than other similarly sized toothed whales (Plön 

and Bernard, 1999). 

Kogia have been sighted throughout the Gulf in waters that vary broadly in depth and seafloor 

topographies (Mullin et al., 1991; Davis et al., 1998 and 2000). The GulfCet I study reported these 

animals in waters with a mean bottom depth of 929 m (3,048 ft) (Davis et al., 1998). Kogia have been 

sighted over the continental shelf, but there is insufficient evidence that they regularly inhabit continental 

shelf waters. Kogia sightings were made during GulfCet aerial surveys (1992-97) in all waters between 

the 100-m and 2,000-m (328-ft and 6,562-ft) isobaths. Data also indicate that Kogia may associate with 

frontal regions along the shelf break and upper continental slope, areas with high epipelagic zooplankton 

biomass (Baumgartner, 1995). During the GulfCet II study, Kogia were widely distributed in the oceanic 

northern Gulf, including slope waters of the Eastern Gulf. Kogia frequently strand on the coastline of the 

northern Gulf, more often in the Eastern Gulf (Jefferson and Schiro, 1997). Between 1984 and 1990, 22 

pygmy sperm whales and 10 dwarf sperm whales stranded in the GOM. 
20 

Beaked Whales (Family Ziphiidae) 

Two genera and four species of beaked whales occur in the GOM. These encompass (1) three species 

of the genus Mesoplodon (Sowerby’s beaked whale [M. bidens], Blainville’s beaked whale [M. 

densirostris], and Gervais’ beaked whale [M. europaeus]) and (2) one species of the genus Ziphius 

(Cuvier’s beaked whale [Ziphius cavirostris]). Morphological similarities among species in the genus 

Mesoplodon make identification of free-ranging animals difficult. Generally, beaked whales appear to 

prefer oceanic waters, although little is known of their respective life histories. Stomach content analyses 

suggest that these whales feed primarily on deepwater cephalopods, although they also consume some 

mesopelagic fishes and deepwater benthic invertebrates (Leatherwood and Reeves, 1983; Heyning, 1989; 

Mead, 1989; Jefferson et al., 1993). 

In the northern Gulf, beaked whales are broadly distributed in waters greater than 1,000 m (3,281 ft) 

over lower slope and abyssal landscapes (Davis et al., 1998 and 2000). Group sizes of beaked whales 

observed in the northern Gulf comprise 1-4 individuals per group (Mullin et al., 1991; Davis and Fargion, 

1996; Davis et al., 2000). Sightings data indicate that Cuvier’s beaked whale is probably the most 

common beaked whale in the Gulf (Jefferson and Schiro, 1997; Davis et al., 1998 and 2000). Wursig et 

al., (2000) indicate there are 18 documented strandings of Cuvier’s beaked whales in the GOM. The 

Gervais’ beaked whale is probably the most common mesoplodont in the northern Gulf, as suggested by 

stranding records (Jefferson and Schiro, 1997). Wursig et al. (2000) states that there are four verified 

stranding records of Blainville’s beaked whales from the GOM. Additionally, one beaked whale sighted 

during GulfCet II was determined to be a Blainville’s beaked whale (Davis et al., 2000). Sowerby’s 

beaked whale is represented in the Gulf by only a single record, a stranding in Florida; this record is 

considered extralimital since this species normally occurs much farther north in the North Atlantic 

(Jefferson and Schiro, 1997). 

Dolphins (Family Delphinidae) 

Atlantic Spotted Dolphin (Stenella frontalis) 

The Atlantic spotted dolphin (Stenella frontalis) is endemic to the Atlantic Ocean within tropical to 

temperate zones. Surveys in the northern Gulf documented the Atlantic spotted dolphin primarily over 

the continental shelf and shelf edge in waters that were less than 250 m (820 ft) in depth, although some 

individuals were sighted along the slope in waters of up to approximately 600 m (1,969 ft) (Davis et al., 

1998). Mills and Rademacher (1996) found the principal depth range of the Atlantic spotted dolphin to be 

much shallower at 15-100 m (49-328 ft) water depth. Griffin and Griffin (1999) found Atlantic spotted 

dolphins on the eastern Gulf continental shelf in waters greater than 20 m (65 ft) [30 km (19 mi) from the 

coast]. A satellite-tagged Atlantic spotted dolphin was found to prefer shallow water habitat and make 

short dives (Davis et al., 1996). Atlantic spotted dolphins are sighted more frequently in areas east of the 

Mississippi River (Mills and Rademacher, 1996). Perrin et al. (1994a) relate accounts of brief 

aggregations of smaller groups of Atlantic spotted dolphins (forming a larger group) off the coast of 

northern Florida. While not well substantiated, these dolphins may demonstrate seasonal nearshoreoffshore movements that appear to be influenced by prey availability and water temperature (Wursig et 

al., 2000). They are known to feed on a wide variety of fishes, cephalopods, and benthic invertebrates 

(Leatherwood and Reeves, 1983; Jefferson et al., 1993; Perrin et al., 1994a). 

Bottlenose Dolphin (Tursiops truncatus) 

The bottlenose dolphin (Tursiops truncatus) is a common inhabitant of the continental shelf and 

upper slope waters of the northern Gulf. It is the most widespread and common cetacean observed in the 

northern GOM. Sightings of this species in the northern Gulf are rare beyond approximately the 1,200-m 

(3,937-ft) isobath (Mullin et al., 1994b; Jefferson and Schiro, 1997; Davis et al., 2000). There appears to 

be two ecotypes of bottlenose dolphins, a coastal form and an offshore form (Hersh and Duffield, 1990; 

Mead and Potter, 1990). The coastal or inshore stock(s) is genetically isolated from the offshore stock 

(Curry and Smith, 1997). Genetic data also support the concept of relatively discrete bay, sound, and 

estuary stocks (Waring et al., 1999). In the northern GOM, bottlenose dolphins appear to have an almost 

bimodal distribution: a shallow water (16-67 m or 52-220 ft) and a shelf break (about 250 m or 820 ft) 
21 

region. These regions may represent the individual depth preferences of the coastal and offshore forms 

(Baumgartner, 1995). Little is known of the behavior or ranging patterns of offshore bottlenose dolphins. 

Bottlenose dolphins are opportunistic feeders, taking a wide variety of fishes, cephalopods, and shrimp 

(Davis and Fargion, 1996; Jefferson and Schiro, 1997; Wells and Scott, 1999). Mating and calving 

occurs primarily from February through May. 

Clymene Dolphin (Stenella clymene) 

The Clymene dolphin (Stenella clymene) is endemic to the Atlantic Ocean and found only in tropical 

and subtropical waters (Perrin and Mead, 1994). Data suggest that Clymene dolphins are widespread 

within deeper Gulf waters (i.e., shelf edge and slope) (Davis et al., 2000; Würsig et al., 2000). The 

Clymene dolphin represents a significant component of the northern GOM cetacean assemblage (Mullin 

et al., 1994c). However, the few records of the Clymene dolphin in the northern Gulf in the past were 

probably a result of this species’ recently clarified taxonomic status and the tendency for observers to 

confuse it with other species (Jefferson and Schiro, 1997). Sightings made during GulfCet surveys 

indicate the Clymene dolphin to be widely distributed in the western oceanic Gulf during spring and in 

the northeastern Gulf during summer and winter. Also, most sightings tended to occur in the central 

portion of the GOM, west of the Mississippi Delta and east of Galveston Bay. Clymene dolphins have 

been sighted in water depths of 612-1,979 m (2,008-6,493 ft) (Davis et al., 1998). This species appears to 

feed on fishes and cephalopods (Leatherwood and Reeves, 1983; Jefferson et al., 1993; Mullin et al., 

1994a). 

False Killer Whale (Pseudorca crassidens) 

The false killer whale (Pseudorca crassidens) occurs in oceanic waters of tropical and warm 

temperate zones (Odell and McClune, 1999). Most sightings have been made in waters exceeding 200 m 

(656 ft), although there have been sightings over the continental shelf (Davis and Fargion, 1996). 

Although sample sizes are small, most false killer whale sightings have been east of the Mississippi River 

(Mullin and Hansen, 1999). False killer whales primarily eat fish and cephalopods, but they have been 

known to attack other toothed whales (Leatherwood and Reeves, 1983; Jefferson et al., 1993). 

Fraser’s Dolphin (Lagenodelphis hosei) 

The Fraser’s dolphin (Lagenodelphis hosei) has a pantropical distribution (Perrin et al., 1994c) in 

oceanic waters and in areas where deep water approaches the coast. Fraser’s dolphins feed on fishes, 

cephalopods, and crustaceans (Leatherwood and Reeves, 1983; Jefferson et al., 1993; Jefferson and 

Schiro, 1997). This species was previously known to occur in the northern Gulf based on a mass 

stranding in the Florida Keys in 1981 (Hersh and Odell, 1986). From 1992 to 1996, there were at least 

three strandings in Florida and Texas (Würsig et al., 2000). GulfCet ship-based surveys led to sightings 

of two large herds (greater than 100 individuals) and first-time recordings of sounds produced by these 

animals (Leatherwood et al., 1993). Fraser’s dolphins have been sighted in the western and eastern Gulf 

at depths of around 1,000 m (3,281 ft) (Leatherwood et al., 1993; Davis and Fargion, 1996; Jefferson and 

Schiro, 1997; Davis et al., 2000). 

Killer Whale (Orcinus orca) 

The killer whale (Orcinus orca) is a cosmopolitan species that occurs in all oceans and seas 

(Dahlheim and Heyning, 1999). Generally, they appear to inhabit coastal, cold temperate and subpolar 

zones. Most killer whale sightings in the northern Gulf have been in waters greater than 200 m (656 ft) 

deep, although there are sightings made over the continental shelf (Davis and Fargion, 1996). Killer 

whales are found almost exclusively in a broad area of the north-central Gulf (Jefferson and Schiro, 1997; 

O’Sullivan and Mullin, 1997; Mullin and Hansen, 1999). There was a sighting in May 1998 of killer 

whales in DeSoto Canyon (Ortega, personal communication, 1998). Worldwide, killer whales feed on 

marine mammals, marine birds, sea turtles, cartilaginous and bony fishes, and cephalopods (Leatherwood 

and Reeves, 1983; Jefferson et al., 1993). An attack by killer whales on a group of pantropical spotted 

dolphins was observed during one of the GulfCet surveys (O’Sullivan and Mullin, 1997). 
22 

Melon-headed Whale (Peponocephala electra) 

The melon-headed whale (Peponocephala electra) is a deepwater, pantropical species (Perryman et 

al., 1994) that feeds on cephalopods and fishes (Leatherwood and Reeves, 1983; Jefferson et al., 1993; 

Mullin et al., 1994c; Jefferson and Schiro, 1997). Sightings of this species in the northern Gulf have been 

primarily in continental slope waters west of the Mississippi River (Jefferson and Schiro, 1997; Davis et 

al., 1998 and 2000; Mullin and Hansen, 1999). The first two records of this species’ occurrence in the 

Gulf are from strandings, one in Texas in 1990 and the other in Louisiana in 1991 (Barron and Jefferson, 

1993). GulfCet surveys resulted in many sightings of melon-headed whales, suggesting that this species 

is a regular inhabitant of the GOM (e.g., Mullin et al., 1994b). 

Pantropical Spotted Dolphin (Stenella attenuata) 

The pantropical spotted dolphin (Stenella attenuata) is distributed in tropical and subtropical marine 

waters of the world (Perrin and Hohn, 1994). It is the most common cetacean in the oceanic northern 

Gulf (Mullin et al., 1994a; Davis and Fargion, 1996; Davis et al., 2000). Pantropical spotted dolphins are 

typically found in waters deeper than 1,200 m (3,937 ft) deep (Mullin et al., 1994a; Davis et al., 1998 and 

2000) but have been sighted over the continental shelf (Mullin et al., 1994a). It feeds on epipelagic fishes 

and cephalopods (Leatherwood and Reeves, 1983; Jefferson et al., 1993). 

Pygmy Killer Whale (Feresa attenuata) 

The pygmy killer whale (Feresa attenuata) occurs in tropical and subtropical waters throughout the 

world (Ross and Leatherwood, 1994), although little is known of its biology or ecology. Its diet includes 

cephalopods and fishes, though reports of attacks on other dolphins have been reported (Leatherwood and 

Reeves, 1983; Jefferson et al., 1993). The pygmy killer whale does not appear to be common in the Gulf; 

most records are of strandings (Jefferson and Schiro, 1997). Fourteen strandings have been documented 

from southern Florida to south Texas. Four ship sightings occurred during the GulfCet surveys, once off 

the south Texas coast in November and three in the spring in the west-central portion of the GulfCet study 

area. Sightings of this species have been at depths of 500-1,000 m (1,640-3,281 ft) (Jefferson and Schiro, 

1997; Davis et al., 1998 and 2000). 

Risso’s Dolphin (Grampus griseus) 

The Risso’s dolphin (Grampus griseus) is a pantropical species that inhabits deep oceanic and 

continental slope waters of tropical and warm temperate zones (Kruse et al., 1999). Risso’s dolphins in 

the northern Gulf have been frequently sighted along the shelf edge, along the upper slope, and most 

commonly, over or near the 200-m (656-ft) water isobath just south of the Mississippi River in recent 

years (Würsig et al., 2000). A strong correlation between Risso’s dolphin distribution and the steeper 

portions of the upper continental slope is most likely the result of cephalopod distribution along the 

continental slope (Baumgartner, 1997; Davis et al., 2000). Risso’s dolphins have been sighted over the 

continental shelf at water depths less than 200 m (656 ft) (Mullin et al., 1994a; Davis et al., 1998). 

Strandings and GulfCet sightings have occurred in all seasons in the GOM and it is likely that Risso’s 

dolphins occur year round in the GOM. Risso’s dolphins feed primarily on squid and secondarily on 

fishes and crustaceans (Leatherwood and Reeves, 1983; Jefferson et al., 1993; Baumgartner, 1997; 

Würsig et al., 2000). 

Rough-toothed Dolphin (Steno bredanensis) 

The rough-toothed dolphin (Steno bredanensis) occurs in tropical to warm temperate marine waters 

globally (Miyazaki and Perrin, 1994). Sightings in the northern Gulf occur primarily over the deeper 

waters (950-1,100 m or 3,117-3,609 ft) off the continental shelf (Mullin et al., 1994a; Davis et al., 1998). 

Most sightings of the rough-toothed dolphin have been west of the Mississippi River (Mullin and Hansen, 

1999); however, a mass stranding of 62 rough-toothed dolphins occurred near Cape San Blas, Florida, on 

December 14, 1997. Four of the stranded dolphins were rehabilitated and released; three carried satellitelinked transmitters (Wells et al., 1999b). Water depth at tracking locations of these individuals averaged 
23 

195 m (640 ft). Data from the tracked individuals, in addition to sightings at Santa Rosa Beach on 

December 28-29, 1998 (Rhinehart et al., 1999), suggest a regular occurrence of this species in the 

northern Gulf. This species feeds on cephalopods and fishes (Leatherwood and Reeves, 1983; Jefferson 

et al., 1993). 

Short-finned Pilot Whale (Globicephala macrorhynchus) 

The short-finned pilot whale (Globicephala macrorhynchus) is found in warm temperate to tropical 

marine waters of the world, generally in deep offshore areas (Bernard and Reilly, 1999). In the northern 

Gulf, it is most commonly sighted along the continental slope at depths of 250-2,000 m (820-6,562 ft) 

(Jefferson and Schiro, 1997; Davis et al., 1998 and 2000). Short-finned pilot whales have been sighted 

almost exclusively west of the Mississippi River (Mullin and Hansen, 1999). There was one sighting of 

short-finned pilot whales in the slope in the eastern Gulf during GulfCet II, in the extreme western part of 

the study area (Davis et al., 2000). Stranding records have declined dramatically over the past decade, 

which contributes to the evidence (though not conclusively) that this population may be declining in the 

GOM. Squid are the predominant prey, with fishes being consumed occasionally. 

Spinner Dolphin (Stenella longirostris) 

The spinner dolphin (Stenella longirostris) occurs worldwide in tropical oceanic waters (Perrin and 

Gilpatrick, 1994; Jefferson and Schiro, 1997). In the northern Gulf, most sightings of spinner dolphins 

have been east of the Mississippi River at depths of 500-1,800 m (1,640-5,906 ft) (Jefferson and Schiro, 

1997; Mullin and Hansen, 1999; Davis et al., 2000). Spinner dolphins have mass stranded on two 

occasions in the GOM, each time on the Florida coast. Spinner dolphins appear to feed on fishes and 

cephalopods (Würsig et al., 2000). 

Striped Dolphin (Stenella coeruleoalba) 

The striped dolphin (Stenella coeruleoalba) occurs in tropical and subtropical oceanic waters (Perrin 

et al., 1994a). Sightings in the northern Gulf occur primarily over the deeper waters beyond the 

continental shelf (Jefferson and Schiro, 1997; Davis et al., 2000; Würsig et al., 2000). Striped dolphins 

feed primarily on small, mid-water squid and fishes (especially lanternfish). 

3.2.3.2. Endangered and Threatened Species 

Cetaceans — Mysticetes 

Blue Whale (Balaenoptera musculus) 

The blue whale (Balaenoptera musculus) is the largest animal known. It feeds almost exclusively on 

concentrations of zooplankton (Yochem and Leatherwood, 1985; Jefferson et al., 1993). The blue whale 

occurs in all major oceans of the world; some blue whales are resident, some are migratory (Jefferson et 

al., 1993; USDOC, NMFS, 1998). Those that migrate move to feeding grounds in polar waters during 

spring and summer, after wintering in subtropical and tropical waters (Yochem and Leatherwood, 1985). 

Records of the blue whale in the northern Gulf consist of two strandings on the Texas coast (Lowery, 

1974). There appears to be little justification for considering the blue whale to be a regular inhabitant of 

the GOM (Jefferson and Schiro, 1997). 

Fin Whale (Balaenoptera physalus) 

The fin whale (Balaenoptera physalus) is an oceanic species that occurs worldwide in marine waters 

and is most commonly sighted where deep water approaches the coast (Jefferson et al., 1993). Fin whales 

feed on concentrations of zooplankton, fishes, and cephalopods (Leatherwood and Reeves, 1983; 

Jefferson et al., 1993). The fin whale makes seasonal migrations between temperate waters, where it 

mates and calves, and polar feeding grounds that are occupied during summer months. Their presence in 

the northern Gulf is considered rare (Würsig et al., 2000). Sightings in the northern Gulf have typically 
24 

been made in oceanic waters, chiefly in the north-central region of the Gulf (Mullin et al., 1991). There 

are seven reliable reports of fin whales in the northern Gulf, indicating that fin whales are not abundant in 

the GOM (Jefferson and Schiro, 1997). Sparse sighting data on this species suggest that individuals in the 

northern Gulf may be extralimital strays from their western Atlantic population (Jefferson and Schiro, 

1997; Würsig et al., 2000). 

Humpback Whale (Megaptera novaeangliae) 

The humpback whale (Megaptera novaeangliae) occurs in all oceans, feeding in higher latitudes 

during spring, summer, and autumn, and migrating to a winter range over shallow tropical banks, where 

they calve and presumably conceive (Jefferson et al., 1993). Humpback whales feed on concentrations of 

zooplankton and fishes using a variety of techniques that concentrate prey for easier feeding (Winn and 

Reichley, 1985; Jefferson et al., 1993). There have been occasional reports of humpback whales in the 

northern Gulf off Florida: a confirmed sighting of a humpback whale in 1980 in the coastal waters off 

Pensacola (Weller et al., 1996); two questionable records of humpback whale sightings from 1952 and 

1957 off the coast of Alabama (Weller et al., 1996); a stranding east of Destin, Florida, in mid-April 1998 

(Mullin, personal communication, 1998); and a confirmed sighting of six humpback whales in May 1998 

in DeSoto Canyon (Ortega, personal communication, 1998). Most recently, a lone humpback whale was 

photographed at Main Pass, Block 281, in December 2001. Humpback whales sighted in the GOM may 

be extralimital strays during their breeding season or during their migrations (Würsig et al., 2000). The 

time of the year (winter and spring) and the small size of the animals involved in many sightings suggest 

the likelihood that these records are of inexperienced juveniles on their first return migration northward 

(Weller et al., 1996). 

Northern Right Whale (Eubalaena glacialis) 

The northern right whale (Eubalaena glacialis) inhabits primarily temperate and subpolar waters. 

Northern right whales range from wintering and calving grounds in coastal waters of the southeastern 

United States to summer feeding, nursery, and mating grounds in New England waters and northward to 

the Bay of Fundy and the Scotian Shelf. During the winter, a portion of the population moves from the 

summer foraging grounds to the calving/breeding grounds off Florida, Georgia, and South Carolina. 

Right whales forage primarily on subsurface concentrations of zooplankton such as calanoid copepods by 

skim feeding with their mouths agape (Watkins and Schevill, 1976; Leatherwood and Reeves, 1983; 

Jefferson et al., 1993). 

Confirmed historical records of northern right whales in the GOM consist of a single stranding in 

Texas (Schmidly et al., 1972) and a sighting off Sarasota County, Florida (Moore and Clark, 1963; 

Schmidly, 1981). The northern right whale is not considered a resident (year-round or seasonal) of the 

GOM; existing records probably represent extralimital strays from the wintering grounds of this species 

off the southeastern United States from Georgia to northeastern Florida (Jefferson and Schiro, 1997). 

Sei Whale (Balaenoptera borealis) 

The sei whale (Balaenoptera borealis) is an oceanic species that is not often seen close to shore 

(Jefferson et al., 1993). They occur in marine waters from the tropics to polar regions but are more 

common in mid-latitude temperate zones (Jefferson et al., 1993). Sei whales feed on concentrations of 

zooplankton, small fishes, and cephalopods (Gambell, 1985; Jefferson et al., 1993). The sei whale is 

represented in the northern Gulf by only four reliable records (Jefferson and Schiro, 1997). One stranding 

was reported for the Florida Panhandle and three strandings were in eastern Louisiana (Jefferson and 

Schiro, 1997). This species’ occurrence in the northern Gulf is considered most likely to be accidental. 

Cetaceans — Odontocetes 

Sperm Whale (Physeter macrocephalus) 

The sperm whale (Physeter macrocephalus) inhabits marine waters from the tropics to the pack-ice 

edges of both hemispheres, although generally only large males venture to the extreme northern and 
25 

southern portions of their range (Jefferson et al., 1993). In general, sperm whales seem to prefer certain 

areas within each major ocean basin, which historically have been termed “grounds” (Rice, 1989). As 

deep divers, sperm whales generally inhabit oceanic waters, but they do come close to shore where 

submarine canyons or other geophysical features bring deep water near the coast (Jefferson et al., 1993). 

Sperm whales prey on cephalopods, demersal fishes, and benthic invertebrates (Rice, 1989; Jefferson et 

al., 1993). 

The sperm whale is the only great whale that is considered to be common in the northern Gulf (Fritts 

et al., 1983b; Mullin et al., 1991; Davis and Fargion, 1996; Jefferson and Schiro, 1997). Sighting data 

suggest a northern Gulfwide distribution over slope waters. Congregations of sperm whales are 

commonly found in waters over the shelf edge in the vicinity of the Mississippi River delta in waters that 

are 500-2,000 m (1,640-6,562 ft) in depth (Mullin et al., 1994a; Davis and Fargion, 1996; Davis et al., 

2000). Sperm whale sightings in the northern Gulf chiefly occur in waters with a mean seafloor depth of 

1,105 m (3,626 ft) (Davis et al., 1998). Mesoscale biological and physical patterns in the environment are 

important in regulating sperm whale habitat use (Griffin, 1999). The GulfCet II study found that most 

sperm whales were concentrated along the slope in or near cyclones (Davis et al., 2000). Low-salinity, 

nutrient-rich water from the Mississippi River may contribute to enhanced primary and secondary 

productivity in the north-central Gulf, and thus provide resources that support the year-round presence of 

sperm whales south of the delta. 

Consistent sightings in the region indicate that there is a resident population of sperm whales in the 

northern Gulf consisting of adult females, calves, and immature individuals (Mullin et al., 1994b; Davis 

and Fargion, 1996; Sparks et al., 1996; Jefferson and Schiro, 1997; Davis et al., 2000). Also, recent 

sightings were made in 2000 and 2001 of solitary mature male sperm whales in the DeSoto Canyon area 

(Lang, personal communication, 2001). Sperm whales in the Gulf are currently considered a separate 

stock from those in the Atlantic and Caribbean (Waring et al., 1997). 

Sirenians 

West Indian Manatee (Trichechus manatus) 

The West Indian manatee (Trichechus manatus) is the only sirenian known to occur in tropical and 

subtropical coastal waters of the southeastern U.S., GOM, Caribbean Sea, and the Atlantic coast of 

northern and northeastern South America (Reeves et al., 1992; Jefferson et al., 1993; O’Shea et al., 1995). 

During warmer months, manatees are common along the west coast of Florida from the Everglades 

National Park northward to the Suwannee River in northwestern Florida and less common farther 

westward. In winter, the population moves southward to warmer waters. Manatees are uncommon along 

the Florida Panhandle and are infrequently found (strandings and sightings) as far west as Louisiana and 

Texas (Powell and Rathbun, 1984; Rathbun et al., 1990; Schiro et al., 1998). One manatee that died in 

Louisiana waters was determined to be from Tampa Bay, Florida; this determination was based on a 

photoidentification rematch (Schiro et al., 1998). The manatees occasionally appearing in south Texas 

waters might be strays from Mexico rather than Florida (Powell and Rathbun, 1984). 

Manatees are herbivores that feed opportunistically on submerged, floating, and emergent vegetation 

(USDOI, FWS, 1995). Distribution of the manatee is limited to low-energy, inshore habitats supporting 

the growth of seagrasses (Hartman, 1979). Manatees primarily use open coastal (shallow nearshore) areas 

and estuaries; and they are also found far up freshwater tributaries. Shallow grass beds with access to 

deep channels are preferred feeding areas in coastal and riverine habitats (USDOI, FWS, 1995). 

Notwithstanding their association with coastal areas, a manatee was documented offshore at several OCS 

work barges where it was grazing on algae growing on the vessel’s sides and bottom. Multiple sightings 

of the animal were made in October 2001 and occurred in waters exceeding 1,500 m (4,922 ft) in depth 

south of Mobile Bay, Alabama. 

3.2.4. Sea Turtles 

Of the seven or eight extant species of sea turtles, five are known to inhabit the waters of the GOM 

(Pritchard, 1997): the green turtle, the loggerhead, the hawksbill, the Kemp’s ridley, and the leatherback. 

As a group, sea turtles possess elongated, paddle-like forelimbs that are modified for swimming and 
26 

shells that are depressed and streamlined (Márquez-M., 1990; Ernst et al., 1994; Pritchard, 1997). Sea 

turtles spend nearly all of their lives in the water and only depend on land (specifically sandy beaches) as 

nesting habitat. They mature slowly and are long-lived. Generally, their distributions are primarily 

circumtropical, although various species differ widely in their seasonal movements, geographical ranges, 

and behavior. There are also considerable differences in behavior among populations of the same species 

(Márquez-M., 1990). All sea turtle species inhabiting the GOM are listed as either endangered or 

threatened under the Endangered Species Act of 1973, as amended (Pritchard, 1997). 

Hard-shell Sea Turtles (Family Cheloniidae) 

Green Sea Turtle (Chelonia mydas) 

The green sea turtle (Chelonia mydas) is the largest hard-shelled sea turtle; adults commonly reach 

100 cm (39 in) in carapace length and 150 kg (331 lb) in weight (USDOC, NMFS, 1990a). The green sea 

turtle is commonly found in tropical and subtropical marine waters with extralimital occurrences 

generally between latitude 40 o

N. and latitude 40 oS. (USDOC, NMFS and USDOI, FWS, 1991a; Hirth, 

1997). In U.S. Atlantic waters, green sea turtles are found around the U.S. Virgin Islands, Puerto Rico, 

and Atlantic and Gulf Coasts of the U.S. from Texas to Massachusetts. 

Green sea turtles primarily occur in coastal waters, where they forage on seagrasses, algae, and 

associated organisms (Carr and Caldwell, 1956; Hendrickson, 1980). Small green sea turtles are 

omnivorous. Adult green sea turtles in the Caribbean and GOM are herbivorous, feeding primarily on 

seagrasses and, to a lesser extent, on algae and sponges. The adult feeding habitats are beds of seagrasses 

and algae in relatively shallow, protected waters; juveniles may forage in areas such as coral reefs, 

emergent rocky bottom, sargassum mats, and in lagoons and bays. Green sea turtles in the Western Gulf 

are primarily restricted to the Texas coast where seagrass meadows and algae-laden jetties provide them 

developmental habitat, especially during warmer months (Landry and Costa, 1999). Movements between 

principal foraging areas and nesting beaches can be extensive, with some populations regularly 

conducting transoceanic migrations (USDOC, NMFS and USDOI, FWS, 1991a; Ernst et al., 1994; Hirth, 

1997). 

Hawksbill Sea Turtle (Eretmochelys imbricata) 

The hawksbill (Eretmochelys imbricata) is a small- to medium-sized sea turtle that occurs in tropical 

to subtropical waters of the Atlantic, Pacific, and Indian Oceans. The species is widely distributed in the 

Caribbean Sea and western Atlantic Ocean. In the continental U.S., the hawksbill has been recorded in 

coastal waters of each of the Gulf States and along the Atlantic coast from Florida to Massachusetts 

(USDOC, NMFS, 1993), although sightings north of Florida are rare (Hildebrand, 1982). They are 

considered to be the most tropical of all sea turtle species and the least commonly reported sea turtle 

species occurring in the Gulf (Márquez-M., 1990; Hildebrand, 1995). 

Coral reefs are generally recognized as the resident foraging habitat for both juveniles and adults. 

Adult hawksbills feed primarily on sponges (Carr and Stancyk, 1975; Meylan, 1988) and demonstrate a 

high degree of selectivity, feeding on a relatively limited number of sponge species, primarily 

demosponges (Ernst et al., 1994). Texas and Florida are the only states in the U.S. where hawksbills are 

sighted with any regularity (USDOC, NMFS, 1993). Stranded hawksbills have been reported in Texas 

(Hildebrand, 1982; Amos, 1989) and in Louisiana (Koike, 1996); these tend to be either hatchlings or 

yearlings. A hawksbill was captured accidentally in a purse seine net just offshore Louisiana (Rester and 

Condrey, 1996). 

Kemp’s Ridley Sea Turtle (Lepidochelys kempi) 

The Kemp’s ridley (Lepidochelys kempi) is the smallest sea turtle species and occurs chiefly in the 

GOM. It may also be found along the northwestern Atlantic coast of North America as far north as 

Newfoundland. It is the most imperiled of the world’s sea turtles. 

In the northern Gulf, Kemp’s ridleys are most abundant in coastal waters from Texas to west Florida 

(Ogren, 1989; Márquez-M., 1990 and 1994; Rudloe et al., 1991). Kemp’s ridleys display strong seasonal 

fidelity to tidal passes and adjacent beachfront environs of the northern Gulf (Landry and Costa, 1999). 
27 

There is little prolonged utilization of waters seaward of the 50-m (164-ft) isobath by this species 

(Renaud, 2001). Adult Kemp’s ridley turtles usually occur only in the Gulf, but juvenile and immature 

individuals sometimes range between tropical and temperate coastal areas of the northwestern Atlantic 

and Gulf (Márquez-M., 1990). Within the Gulf, juvenile and immature Kemp’s ridleys have been 

documented along the Texas and Louisiana coasts, at the mouth of the Mississippi River, and along the 

west coast of Florida, as quoted in stranding reports (Ogren, 1989; Márquez-M., 1990). 

Loggerhead Sea Turtle (Caretta caretta) 

The loggerhead (Caretta caretta) is a large sea turtle that inhabits temperate and tropical marine 

waters of the Atlantic, Pacific, and Indian Oceans. This species is wide-ranging throughout its range and 

is capable of living in varied habitat types for a relatively long time (Márquez-M., 1990; USDOC, NMFS 

and USDOI, FWS, 1991b; Ernst et al., 1994). Loggerheads feed primarily on benthic invertebrates but 

are capable of feeding on a wide range of food items (Ernst et al., 1994). Juvenile and subadult 

loggerheads are omnivorous, foraging on pelagic crabs, molluscs, jellyfish, and vegetation captured at or 

near the surface (Dodd, 1988; Plotkin et al., 1993). Adult loggerheads forage on benthic invertebrates 

(Dodd, 1988). The loggerhead is the most abundant species of sea turtle occurring in U.S. waters of the 

Atlantic, from Florida to Cape Cod, Massachusetts. The loggerhead is probably the most common sea 

turtle species in the northern Gulf (e.g., Fritts et al., 1983a; Fuller and Tappan, 1986; Rosman et al., 1987; 

Lohoefener et al., 1990) and is currently listed as a threatened species. 

Aerial surveys indicate that loggerheads are largely abundant in water depths less than 100 m (328 ft) 

(Shoop et al., 1981; Fritts et al., 1983a). During the GulfCet aerial surveys, loggerheads were sighted 

throughout the northern Gulf continental shelf waters near the 100-m (328-ft) isobath (Davis et al., 2000). 

Loggerheads were also sighted over very deep waters (>1,000 m or 3,281 ft). Sightings indicate that 

loggerhead distribution is not as coastal-associated as that of Kemp’s ridley and green sea turtles (Landry 

and Costa, 1999). Loggerheads have also been sighted seaward of the shelf break in the northeast U.S. 

(Shoop and Kenney, 1992). Loggerhead abundance in continental slope waters of the eastern Gulf 

increased appreciably during winter (Davis et al., 2000). 

Leatherback Sea Turtle (Family Dermochelyidae) 

Leatherback Sea Turtle (Dermochelys coriacea) 

The leatherback (Dermochelys coriacea) is the largest and most distinctive sea turtle. This species 

possesses a unique skeletal morphology, most evident in its flexible, ridged carapace, and in cold water 

maintains a core body temperature several degrees above ambient. They also have unique deep-diving 

abilities (Eckert et al., 1986). This species is the most wide-ranging sea turtle, undertaking extensive 

migrations from the tropics to boreal (cold-temperate regions of the northern latitudes) waters (Morreale 

et al., 1996; Hughes et al., 1998). Though considered oceanic, leatherbacks will occasionally enter bays 

and estuaries (Hoffman and Fritts, 1982; Knowlton and Weigle, 1989; Shoop and Kenney, 1992). 

Leatherbacks feed primarily on gelatinous zooplankton such as jellyfish, siphonophores, and salps 

(Brongersma, 1972), although they may ingest some algae and vertebrates (Ernst et al., 1994). 

Leatherbacks’ stomach contents have been analyzed and data suggest that they may feed at the surface, at 

depth within deep scattering layers, or on the benthos. Florida is the only site in the continental U.S. 

where leatherbacks regularly nest (USDOC, NMFS and USDOI, FWS, 1992b; Ernst et al., 1994; Meylan 

et al., 1995). The leatherback is currently listed as an endangered species. 

Sightings of leatherbacks are common in oceanic waters of the northern GOM (Leary, 1957; Fritts et 

al., 1983b; Lohoefener et al., 1988, 1990; Collard, 1990; Davis et al., 2000). Based on a summary of 

several studies, Davis and Fargion (1996) concluded that the primary habitat of the leatherback in the 

northwestern Gulf is oceanic waters (>200 m or 656 ft). It has been suggested that the region from 

Mississippi Canyon east to DeSoto Canyon appears to be an important habitat area for leatherbacks 

(Davis and Fargion, 1996). Most sightings of leatherbacks made during the GulfCet surveys occurred 

slightly north of DeSoto Canyon (Davis and Fargion, 1996; Davis et al., 2000). The nearly disjunct 

summer and winter distributions of leatherback sightings over the continental slope in the Eastern Gulf 

during GulfCet II indicate that specific areas may be important to this species either seasonally or for 

short periods of time. These specific locations are most probably correlated with oceanographic 
28 

conditions and resulting concentrations of prey. Other clustered sightings of leatherbacks have been 

reported for the northern Gulf: 8 leatherbacks were sighted one day in DeSoto Canyon (Davis and 

Fargion, 1996), 11 during one day just south of the Mississippi River Delta (Lohoefener et al., 1990), and 

14 during another day in DeSoto Canyon (Lohoefener et al., 1990). 

3.2.5. Birds 

Marine Birds 

Most species of marine birds that are listed as either threatened or endangered inhabit nearshore 

waters along the coast and the continental shelf of the GOM and rarely occur in deepwater areas (USDOI, 

MMS, 2001a). Forty-three species of seabird representing four ecological categories have been 

documented from deepwater areas of the Gulf: summer migrants (e.g., shearwaters, storm-petrels, 

boobies), summer residents that breed in the Gulf (e.g., sooty, least, and sandwich terns), winter residents 

(e.g., gannets, gulls, and jaegers), and permanent resident species (e.g., laughing gull, royal, and bridled 

terns) (Hess and Ribic 2000, USDOI, MMS, 2001a). The most abundant species typically found in 

deepwater areas include terns, storm-petrels, and gulls (Hess and Ribic, 2000). 

Seabirds’ presence in the Gulf changes seasonally with species diversity with overall abundance 

being highest in the spring and summer and lowest in fall and winter. Seabirds also tend to associate with 

various oceanic conditions including specific sea-surface temperatures and salinities (e.g., laughing gull, 

black and sooty terns), areas of high plankton productivity (e.g., laughing gulls, pomarine jaeger, 

Audubon’s shearwater, band-rumped storm-petrel, bridled tern), and particular currents (pomarine jaeger) 

(Hess and Ribic, 2000). Various birds (especially passerines) that seasonally migrate over the Gulf may 

use offshore oil and gas platforms and merchant, cruise, and naval ships as artificial islands for rest and 

shelter during inclement weather. 

Shorebirds 

Shorebirds are those members of the order Charadriiformes that are generally restricted to coastline 

margins (beaches, mudflats, etc.). The GOM shorebirds comprise five taxonomic families--Jacanidae 

(jacanas), Haematopodidae (oystercatchers), Recurvirostridae (stilts and avocets), Charadriidae (plovers), 

and Scolopacidae (sandpipers, snipes, and allies) (Hayman et al., 1986). An important characteristic of 

almost all shorebird species is their strongly developed migratory behavior, with some shorebirds 

migrating from nesting places in the far north to the southern part of South America (Terres, 1991). Both 

spring and fall migrations take place in a series of "hops" to staging areas where birds spend time feeding 

heavily to store up fat for the sustained flight to the next staging area; many coastal habitats along the 

GOM are critical for such purposes. Along the Gulf Coast, 44 species of shorebirds have been recorded; 

only six species nest in the area. The remaining species are wintering residents and/or "staging" 

transients (Pashley, 1991). Although variations occur between species, most shorebirds begin breeding at 

1-2 years of age and generally lay 3-4 eggs per year. They feed on a variety of marine and freshwater 

invertebrates and fish, and small amounts of plant life. 

Marsh and Wading Birds 

The following families of mostly wading birds have some representatives in the northern Gulf: 

Ardeidae (herons, egrets, and bitterns), Ciconiidae (storks), Threskiornithidae (ibises and spoonbills), and 

Gruidae (cranes). They have long legs that allow them to forage by wading into shallow water, while 

their long bills and usually long necks are used to probe under water or to make long swift strokes to seize 

fish, frogs, aquatic insects, crustaceans, and other prey (Terres, 1991). Seventeen species of wading birds 

in the Order Ciconiiformes are currently known to nest in the U.S., and all except the wood stork nest in 

the northern Gulf coastal region (Martin, 1991). Within the Gulf Coast region, Louisiana supports the 

majority of nesting wading birds. Great egrets are the most widespread nesting species in the Gulf region 

(Martin, 1991). 

Along the GOM, most members of the family Rallidae have compact bodies; therefore, they are not 

labeled wading birds. They are also elusive and rarely seen within the low vegetation of fresh and saline 
29 

marshes, swamps, and rice fields (Bent, 1926; National Geographic Society, 1983; Ripley and Beehler, 

1985). 

Waterfowl 

Waterfowl belong to the taxonomic order Anseriformes and include swans, geese, and ducks. A total 

of 36 species are regularly reported along the north-central and western Gulf Coast. They include 1 swan, 

5 geese, 11 surface-feeding (dabbling) ducks and teal, 5 diving ducks (pochards), and 14 others (including 

the wood duck, whistling ducks, sea ducks, the ruddy duck, and mergansers) (Clapp et al., 1982; National 

Geographic Society, 1983; Madge and Burn, 1988). Many species usually migrate from wintering 

grounds along the Gulf Coast to summer nesting grounds in the north. Waterfowl migration pathways 

have traditionally been divided into four parallel north-south paths, or "flyways," across the North 

American continent. The Gulf Coast serves as the southern terminus of the Mississippi (Louisiana, 

Mississippi, and Alabama) flyway. Waterfowl are highly social and possess a diverse array of feeding 

adaptations related to their habitat (Johnsgard, 1975). 

Endangered and Threatened Species 

The following coastal and marine bird species that inhabit or frequent the northern GOM coastal areas 

are recognized by FWS as either endangered or threatened: piping plover, southeastern snowy plover, 

bald eagle, and brown pelican. The southeastern snowy plover is a species of concern to the State of 

Florida. 

Piping Plover 

The piping plover (Charadrius melodus) is a migratory shorebird that is endemic to North America. 

The piping plover breeds on the northern Great Plains, in the Great Lakes, and along the Atlantic Coast 

(Newfoundland to North Carolina); and winters on the Atlantic and Gulf Coasts from North Carolina to 

Mexico and in the Bahamas and West Indies. Hypothetically, plovers may have a preferred prey base 

and/or the substrate coloration provides protection from aerial predators due to camouflage from 

chromatic matching in specific wintering habitat. Such areas include coastal sand flats and mud flats in 

proximity to large inlets or passes, which may attract the largest concentrations of piping plovers 

(Nicholls and Baldassarre, 1990). Similarly, nesting habitat in the north includes open flats along the 

Missouri River and the Great Lakes. This species remains in a precarious state given its low population 

numbers, sparse distribution, and continued threats to habitat throughout its range. 

Southeastern Snowy Plover 

The following account of the southeastern snowy plover (Charadrius alexandrius tenuirostris) is 

taken from Gore and Chase (1989). The species nests on coastal sand beaches and interior alkali flats. 

Observed nest sites in the Florida Panhandle ranged from the Florida-Alabama border eastward beyond 

Little St. George. At some locations more than 1.5 breeding pairs/km were counted. Most nests are near 

the front dune and close to vegetation. Vehicles and humans may cause nest failure. Human activity is 

absent near the beaches of Eglin West and Eglin East because Eglin Air Force Base has restricted areas. 

This may account for a high nest count in part of this area. 

Bald Eagle 

The bald eagle (Haliaeetus leucocephalus) is the only species of sea eagle that regularly occurs on the 

North American continent (USDOI, FWS, 1984). Its range extends from central Alaska and Canada to 

northern Mexico. The bulk of the bald eagle's diet is fish, though it will opportunistically take birds, 

reptiles, and mammals (USDOI, FWS, 1984). The general tendency is for winter breeding in the south 

with a progressive shift toward spring breeding in northern locations. In the southeast, nesting activities 

generally begin in early September; egg laying begins as early as late October and peaks in late 

December. The historical nesting range of the bald eagle within the southeast United States included the 

entire coastal plain and shores of major rivers and lakes. There are certain general elements that seem to 
30 

be consistent among nest site selection. These include (1) the proximity of water (usually within about 1 

km or 1⁄2 mi) and a clear flight path to a close point on the water, (2) the largest living tree in a span, and 

(3) an open view of the surrounding area. The proximity of good perching trees may also be a factor in 

site selection. An otherwise suitable site may not be used if there is excessive human activity in the area. 

The current range is limited, with most breeding pairs occurring in peninsular Florida and Louisiana, and 

some in South Carolina, Alabama, and east Texas. Sporadic breeding takes place in the rest of the 

southeastern states and in the Florida Panhandle. One hundred twenty nests have been found in 

Louisiana; only three nests occurred within 8 km (5 mi) of the coast (Patrick, written communication, 

1997). The bald eagle was listed as endangered in 1967 in response to its declines due to DDT and other 

organochlorines that affected the species' reproduction (USDOI, FWS, 1984). In July 1995, the FWS 

reclassified the bald eagle from endangered to threatened in the lower 48 states (Federal Register, 1995). 

Brown Pelican 

The brown pelican (Pelicanus occidentalis) is one of two pelican species in North America. It feeds 

entirely upon fish captured by plunge diving in coastal waters. Organochlorine pesticide pollution 

apparently contributed to the endangerment of the brown pelican. In recent years, there has been a 

marked increase in brown pelican populations along its entire former range. The population of brown 

pelicans and their habitat in Alabama, Florida, Georgia, North and South Carolina, and point’s northward 

along the Atlantic Coast were removed from the endangered species list in 1985. Within the remainder of 

the range, which includes coastal areas of Louisiana and Mississippi, the brown pelican remains listed as 

endangered (Federal Register, 1985). 

3.2.6. Essential Fish Habitat and Fish Resources 

3.2.6.1. Essential Fish Habitat 

Healthy fish resources and fishery stocks depend on essential fish habitat (EFH); waters and substrate 

necessary to fish for spawning, breeding, feeding, and growth to maturity. Due to the wide variation of 

habitat requirements for all life history stages for managed species, EFH has been identified throughout 

the Gulf of Mexico, including all coastal and marine waters and substrates from the shoreline to the 

seaward limit of the Exclusive Economic Zone (EEZ). 

There are Fishery Management Plans (FMP) in the GOM region for shrimp, red drum, reef fishes, 

coastal migratory pelagics, stone crabs, spiny lobsters, coral and coral reefs, billfish, and highly migratory 

species. The Gulf of Mexico Fishery Management Council (FMC) Generic Amendment for Addressing 

Essential Fish Habitat Requirements amends the first seven FMP’s listed above, identifying 

estuarine/inshore and marine/offshore EFH for over 450 managed species (about 400 in the Coral FMP). 

Although not part of the Gulf of Mexico Fishery Management Council’s FMP’s, separate Fishery 

Management Plans have been finalized by NMFS for Atlantic tunas, swordfish and sharks, and the 

Atlantic billfish fishery. The Gulf of Mexico FMC Generic Amendment also identifies threats to EFH and 

makes a number of general and specific habitat preservation recommendations for pipelines and oil and 

gas exploration and production activities within State waters and OCS areas. These recommendations can 

be found in the Final EIS for Lease Sale 181 (USDOI, MMS, 2001; page III-91). Pelagic species would 

be the only managed fisheries in the grid area and for the Thunder Horse development. 

3.2.6.2. Description of Fish Resources 

The GOM supports a great diversity of fish resources. The distribution and abundance of these 

resources are not random and are governed by a variety of ecological factors such as temperature, salinity, 

primary productivity, bottom types, and many other physical and biological factors. There are 

considerable inshore and offshore differences in fish resources. The majority of the GOM fisheries are 

dependent upon wetland, estuarine, and nearshore habitats (USDOI, MMS, 2001b). 

Fish can be classified as demersal (bottom-dwelling), oceanic pelagic, or mesopelagic (midwater). 

Demersal (or benthic) fish have been addressed above under the megafauna descriptions 

(Chapter 3.2.2.3.1.). There are no commercial fisheries directed at demersal species in the Grid 16 area 

and in the vicinity of the Thunder Horse project. Oceanic pelagic and mesopelagic fishes are discussed 
31 

briefly below. Additional life history information on important commercial invertebrate fish resources of 

the GOM is contained in USDOI, MMS (2000 and 2001a). 

Oceanic Pelagics (Including Highly Migratory Species) 

Common oceanic pelagic species include the large predatory tunas, marlins, sailfish, swordfish, 

dolphins, wahoo, and mako sharks. Other pelagics include halfbeaks, flyingfishes, and driftfishes 

(Stromateidae). Lesser known oceanic pelagics include opah, snake mackerels (Gempylidae), 

ribbonfishes (Trachipteridae), and escolar. 

Oceanic pelagic species occur throughout the GOM, especially at or beyond the shelf edge. Oceanic 

pelagics are reportedly associated with mesoscale hydrographic features such as fronts, eddies, and 

discontinuities. Fishermen contend that yellowfin tuna aggregate near sea-surface temperature boundaries 

or frontal zones; however, Power and May (1991) found no correlation between longline catches of 

yellowfin tuna and sea-surface temperature (defined from satellite imagery) in the GOM. Many of the 

oceanic fishes associate with drifting Sargassum seaweed, which provides feeding and/or nursery habitat. 

Mesopelagic fish assemblages in GOM collections are numerically dominated by myctophids 

(lanternfishes), with gonostomatids (bristlemouths) and sternoptychids (hatchet fishes) common but less 

abundant. These fishes make extensive vertical migrations during the night from mesopelagic depths 

(200-1,000 m; 656-3,281 ft) to feed in upper, more productive layers of the water column (Hopkins and 

Baird, 1985). Mesopelagic fishes are important ecologically because they transfer substantial amounts of 

energy between mesopelagic and epipelagic zones. 

The GOM appears to be a distinct zoogeographic province based upon analysis of lanternfish 

distribution (Bakus et al., 1977). The GOM lanternfish assemblage was characterized by species with 

tropical and subtropical affinities. This was particularly true for the eastern GOM where Loop Current 

effects on species distributions were most pronounced. Gartner et al. (1987) collected 17 genera and 49 

species of lanternfish in trawls fished at discrete depths from stations in the Western, Central, and Eastern 

Gulf. The most abundant species in decreasing order of importance were Ceratoscopleus warmingii, 

Notolychus valdiviae, Lepidophanes guentheri, Lampanyctus alatus, Daiphus dumerili, Benthosema 

suborbitale, and Myctophum affine. Ichthyoplankton collections from oceanic waters yielded high 

numbers of mesopelagic larvae as compared with larvae of other groups (Richards et al., 1989). 

Lanternfishes generally spawn year-round, with peak activity in spring and summer (Gartner, 1993). 

3.2.7. Gulf Sturgeon 

The Gulf sturgeon (Acipenser oxyrhynchus desotoii) is the only listed threatened fish species in the 

GOM. A subspecies of the Atlantic sturgeon, Gulf sturgeon are classified as anadromous, with immature 

and mature fish participating in freshwater migrations. Gill netting and biotelemetry have shown that 

subadults and adults spend 8-9 months each year in rivers and 3-4 of the coolest months in estuaries or 

Gulf waters. Sturgeon less than about two years old remain in riverine habitats and estuaries throughout 

the year (Clugston, 1991). According to Wooley and Crateau (1985), Gulf sturgeon occurred in most 

major riverine and estuarine systems from the Mississippi River to the Suwannee River, Florida, and 

marine waters of the Central and Eastern GOM south to Florida Bay. Important waters west-to-east and 

north-to-south are Biloxi Bay, Pascagoula Bay, Mobile Bay, Choctawhatchee Bay, the Apalachicola 

River, the Ochlockounee River, and the Suwannee River. It is not possible, at present, to estimate the size 

of Gulf sturgeon populations throughout the range of the species, but extant occurrences in 1996 include 

the Mississippi River and Lake Pontchartrain, Louisiana, to Charlotte Harbor, Florida (Patrick, personal 

communication, 1996). Eggs have now been discovered in six locations within the Choctawhatchee River 

system in Florida and Alabama (Fox and Hightower, 1998). During the riverine stage, adults cease 

feeding, undergo gonadal maturation, and migrate upstream to spawn. Spawning occurs over coarse 

substrate in deep holes. The decline of the Gulf sturgeon is believed to be due to overfishing, the 

damming of coastal rivers, and the degradation of water quality (Barkuloo, 1988). 
32 

3.3. SOCIOECONOMIC CONDITIONS AND OTHER CONCERNS

3.3.1. Economic and Demographic Conditions 

3.3.1.1. Socioeconomic Impact Area 

The MMS defines the GOM impact area for population, labor, and employment as that portion of the 

GOM coastal zone whose social and economic well-being (population, labor, and employment) is directly 

or indirectly affected by the OCS oil and gas industry. For this analysis, the coastal impact area consists 

of 80 counties and parishes along the U.S. portion of the GOM. This area includes 24 counties in Texas, 

26 parishes in Louisiana, four counties in Mississippi, two counties in Alabama, and 24 counties in the 

Panhandle of Florida. Inland counties and parishes are included where offshore oil and gas activities are 

known to exist, where offshore-related petroleum industries are established, and where one or more 

counties or parishes within a Metropolitan Statistical Area (MSA) are on the coast; all counties and 

parishes within the MSA are included. 

Note that activities proposed for the Grid 16 area are expected to have economic consequences 

throughout all 10 of the Gulf’s coastal subareas and are likely to have global effects. Most of the 

probable changes in population, labor, and employment resulting from the proposed activities would 

occur in the 24 counties in Texas and the 26 parishes in Louisiana because the oil and gas industry is best 

established in this region. Some of the likely changes in population, labor, and employment resulting 

from the proposed activities would also occur in the six Alabama and Mississippi counties due to having 

an established oil and gas industry and its proximity to the offshore location. Changes in economic 

factors (in minor service and support industries) from the proposed activities would occur, to a much 

lesser extent, in the 24 counties of the Florida Panhandle because of its economy only marginally includes 

primary and support industries for oil and gas development 

For analysis purposes, MMS has divided the impact area (defined geographically in the first 

paragraph of this section) into the subareas listed below. This impact area is based on the results of a 

recent MMS socioeconomic study, “Cost Profiles and Cost Functions for Gulf of Mexico Oil and Gas 

Development Phases for Input-Output Modeling.” One of the objectives of this study was to allocate 

expenditures from the offshore oil and gas industry to the representative onshore subarea where the 

dollars were spent. Table E-1 (Appendix E) presents these findings in percentage terms. In the table, the 

IMPLAN number is the code given to the industry (sector) by the input-output software (IMPLAN) used 

to calculate impacts in Chapter 4 of this document. It is analogous to the standardized industry code 

(SIC). As shown in the table, very little has been spent in the Florida subareas. This is to be expected 

given the lack of offshore leasing in this area and Florida’s attitude towards oil and gas development off 

their beaches. The table also makes clear the reason for including all of the GOM subareas in the 

economic impact area. Expenditures in Texas to several sectors are either exclusively found there or 

make up a very large percentage of the total. In addition, a significant percentage of total sector 

expenditures is allocated to each Louisiana subarea. The following subareas (which include the 

counties/parishes as listed below) are considered as the economic impact area for the proposed activities 

(Table 3-1). 

3.3.1.2. Population and Education 

Table E-2 (Appendix E) depicts baseline population projections for the potential impact area. 

Baseline projections are for the impact area in the absence of the proposed activities. The analysis area 

consists of highly populated metropolitan areas (such as the Houston MSA, which predominates Subarea 

TX-2) and sparsely populated rural areas (as is much of Subarea TX-1). Some communities in the 

analysis area experienced extensive growth during the late 1970’s and early 1980’s when OCS activity 

was booming. Following the drop in oil prices, many of these same areas experienced a loss in 

population (Gramling, 1984; Laska et al., 1993). All subarea populations are expected to grow at a higher 

rate than the United States’ average annual population growth rate over the life of the proposed actions, 

reflecting the region migration pattern of favoring the south and west over the northeast and Midwest 

(USDOC, Bureau of the Census, 2001). This is a continuation of historic trends. Average annual 

population growth projected over the life of the proposed actions range from a low of 0.45 percent for 

Subarea LA-3 (dominated by the Orleans MSA) to a high of 3.27 percent for Subarea FL-3 in the lower 
33 

panhandle of Florida. Over the same time period, the population for the United States is expected to grow 

at about 1.36 percent per year. 

At present, the 2000 U.S. Census data for education at the county/parish level have not been released. 

The last available data at this level is the 1990 Census data. Therefore, this analysis uses the 2000 U.S. 

Census Supplementary Survey Profile educational attainment data for the Gulf States. For people 25 

years and over, 75.2 percent of the population in the U.S. has graduated from high school, while 20.3 

percent has received a bachelor’s degree. Texas’ educational attainment percentages are higher than the 

national average for both categories: 76.8 and 23.5 percent, respectively. Louisiana, while higher than the 

national average for high school graduates, 76.7 percent, is lower for college degrees, 19.5 percent. 

Mississippi’s educational attainments are lower than the Nation’s for both categories—74.3 and 18.6 

percent, respectively. Alabama, like Louisiana, has a higher than national high school graduation rate 

(76.0%), but a lower rate for bachelor’s degree (20.2%). Florida mirrors Texas; its educational 

attainments are higher than the national rates—81.9 and 23.2 percent, respectively. 

Table 3-1 

Listing of Counties and Parishes of the Coastal Impact Area 

LA-1 LA-2 LA-3 MA-1 

Acadia, LA Ascension, LA Jefferson, LA Baldwin, AL 

Calcasieu, LA Assumption, LA Orleans, LA Hancock, MS 

Cameron, LA East Baton Rouge, LA Plaquemines, LA Harrison, MS 

Iberia, LA Iberville, LA St. Bernard, LA Jackson, MS 

Lafayette, LA Lafourche, LA St. Charles, LA Mobile, AL 

St. Landry, LA Livingston, LA St. James, LA Stone, MS 

St. Martin, LA St. Mary, LA St. John the Baptist, LA 

Vermilion, LA Tangipahoa, LA St. Tammany, LA 

 Terrebonne, LA 

 West Baton Rouge, LA 

TX-1 TX-2 FL-1 FL-3 

Aransas, TX Brazoria, TX Bay, FL Charlotte, FL 

Calhoun, TX Chambers, TX Escambia, FL Citrus, FL 

Cameron, TX Fort Bend, TX Okaloosa, FL Collier, FL 

Jackson, TX Galveston, TX Santa Rosa, FL Hernando, FL 

Kenedy, TX Hardin, TX Walton, FL Hillsborough, FL 

Kleberg, TX Harris, TX Lee, FL 

Nueces, TX Jefferson, TX FL-2 Manatee, FL 

Refugio, TX Liberty, TX Pasco, FL 

San Patricio, TX Matagorda, TX Dixie, FL Pinellas, FL 

Victoria, TX Montgomery, TX Franklin, FL Sarasota, FL 

Willacy, TX Orange, TX Gulf, FL 

 Waller, TX Jefferson, FL FL-4 

 Wharton, TX Levy, FL 

 Taylor, FL Miami-Dade, FL 

 Wakulla, FL Monroe, FL 

3.3.1.3. Infrastructure and Land Use 

The Gulf of Mexico OCS Region has one of the highest concentrations of oil and gas activities in the 

world. The offshore oil and gas industry has experienced dramatic changes over recent years, particularly 

since 1981. Historically, most of the activities have been concentrated on the continental shelf off the 

coasts of Texas and Louisiana. Future activities are expected to extend into progressively deeper waters 

and into the Eastern Planning Area (EPA). To date, only exploration activities have taken place off the 

shores of the State of Florida. The high level of offshore oil and gas activity in the GOM is accompanied 
34 

by an extensive development of onshore service and support facilities. The major types of onshore 

infrastructure include gas processing plants, navigation channels, oil refineries, pipelines and pipeline 

landfalls, pipecoating and storage yards, platform fabrication yards, separation facilities, service bases, 

terminals, and other industry-related installations such as landfills and disposal sites for drilling and 

production wastes. 

Land use in the impact area varies from state to state. The coasts of Florida and Texas are a mixture 

of urban, industrial, recreational beaches, wetlands, forests, and agricultural areas. Alabama’s coastal 

impact area is predominantly recreational beaches, and small residential and fishing communities. 

Mississippi’s coast consists of barrier islands, some wetlands, recreational beaches, and urban areas. 

Louisiana’s coast impact area is mostly vast areas of wetlands; some small communities and industrial 

areas extend inward from the wetlands. 

3.3.1.4. Navigation and Port Usage 

A service base is a community of businesses that load, store, and supply equipment, supplies, and 

personnel needed at offshore work sites. Although a service base may primarily serve the OCS planning 

area and subarea in which it is located, it may also provide significant services for the other OCS planning 

areas and subareas. As OCS operations have progressively moved into deeper waters, larger vessels with 

deeper drafts have been phased into service, mainly for their greater range of travel, greater speed of 

travel, and larger carrying capacity. Service bases with the greatest appeal for deepwater activity have 

several common characteristics: strong and reliable transportation system; adequate depth and width of 

navigation channels; adequate port facilities; existing petroleum industry support infrastructure; location 

central to OCS deepwater activities; adequate worker population within commuting distance; and 

insightful strong leadership. Typically, deeper draft service vessels require channels with depths of 6-8 m 

(20-26 ft). The proposed activities are expected to impact Port Fourchon, Louisiana, the designated 

service base for the proposed action and likely service base for most of the Grid 16 area. Venice, 

Louisiana, is named as a back-up service base for the proposed activities associated with the Thunder 

Horse project. Historically, Terrebonne and Lafourche Parishes have been the primary staging and 

support area for offshore oil and gas exploration and development. The Port of Fourchon, at the mouth of 

Bayou Lafourche on the Gulf of Mexico, is a major onshore staging area for OCS oil and gas activities in 

the CPA and WPA and the headquarters of LOOP. Chapter 3.3.3.2 in the Multisale EIS for the CPA and 

WPA discusses the Port Fourchon area in detail. 

3.3.1.5. Employment 

Table E-3 (Appendix E) depicts baseline employment projections for the potential impact area. 

Baseline projections are for the impact area in the absence of the proposed Thunder Horse activities. 

Average annual employment growth projected over the life of the proposed actions range from a low of 

1.19 percent for Subarea LA-3 (predominated by the Orleans MSA) to a high of 5.43 percent for Subarea 

FL-3 in the lower panhandle of Florida. Over the same time period, employment for the United States is 

expected to grow at about 2.25 percent per year, while the GOM analysis area is expected to grow at 

about 2.06 percent per year. As stated above, this represents growth in general employment for the 

subareas. Continuation of existing trends, both in OCS activity and other industries in the area, are 

included in the projections. 

The industrial composition for the subareas in the WPA and that in the CPA are similar. With the 

exception of Subareas LA-2, LA-3, and FL-4, the top four ranking sectors in terms of employment in the 

analysis area are the service, manufacturing, retail trade, and State and local government sectors. In 

Subareas LA-2 and LA-3, construction replaces manufacturing as one of the top four industries on the 

basis of employment. In Subarea FL-4, transportation, communication, and public utilities replaces 

manufacturing as one of the top four industries on the basis of employment. The service industry 

employs more people in all subareas. The service industry is also the fastest growing industry. 
35 

3.3.1.6. Current Economic Baseline Data 

Oil and natural gas prices are used to evaluate the oil and gas industry’s ability to economically 

develop resources. Since the beginning of 2002, oil prices have surged more than 35 percent, but drilling 

for oil has declined by 3 percent. Over the same period, natural gas prices also have risen by nearly 30 

percent, while drilling for natural gas has dropped nearly 15 percent. The reasons behind the drilling 

decline are different for oil than natural gas. An overhang in the capacity to produce oil, i.e., political 

uncertainty and OPEC production restraints have pushed world oil prices upward, although excess 

capacity is about 10 percent of world oil consumption, is restraining oil drilling. However, a continued 

adjustment to previous declines in natural gas prices is driving down natural gas drilling. Natural gas 

drilling was greatly stimulated by the strong rise in natural gas prices that occurred in 1999 and 2000. 

Natural gas drilling is still adjusting to the sharp decline in natural gas prices that occurred in 2001 despite 

recent gains in natural gas prices. Also, relatively high inventory levels of natural gas in storage raise the 

possibility of slippage in natural gas prices. 

As of August 16, 2002, Henry Hub Natural Gas closed at $3.10 per million Btu (an increase of 5.62% 

or $0.165 from a year ago) (Oilnergy, 2002). During September 2001, natural gas futures plummeted 

below $2 per thousand cubic feet for the first time since April 1999 amid concerns that the U.S. economy 

may slip into a recession. Natural gas demand from manufacturers, which accounts for about a quarter of 

U.S. consumption, was down and a turnaround in the economy was not expected in the short term 

(Houston Chronicle On-line, 2001a). U.S. natural gas consumption varies by 40 percent of Gross 

Domestic Production. As the economy strengthens, drilling for oil and natural gas is likely to pick up 

(Federal Reserve Bank of Dallas what year). 

With world oil markets on edge over rising tensions between the United States and Iraq and 

uncertainty over OPECS’s plans for production, September 2002 crude oil futures closed at $29.06 on 

August 14, 2002, on the New York Mercantile Exchange. Crude has been on the rise much of August 

because of concerns over Iraq. The rally in crude oil futures were spurred by unexpected high declines in 

U.S. crude inventories as reported by the American Petroleum Institute and Energy Information 

Administration (EIA). The EIA also reported that Japan’s largest oil company, Nippon Oil, had increased 

its crude stockpiles by 2.45 million barrels since June to cushion potential cuts in supplies from the 

Persian Gulf. 

Exploration and production (E&P) expenditures are another indicator of the energy industry’s 

strength. Lehman Brothers mid-year update of its original E&P spending survey of 279 companies 

indicates that U.S. 2002 E&P expenditures are expected to fall by 20.2 percent. This compares with a 

17.9 percent decline cited in the company’s December 2001 survey. However, the survey did reveal that 

58 percent of the companies surveyed expect to increase E&P budgets in 2003. 

In addition to E&P spending, drilling rig use is employed by the industry as a barometer of economic 

activity. After having hovered around 90 percent or better for most of 2000 through May 2001 before 

declining in June 2001 to a low around 50 percent in November 2001 before rebounding from November 

2001 to April 2002 to around 70 percent where it hovered throughout the summer of 2002. As of 

August 16, 2002, the fleet utilization rate for all marketed mobile rigs in the GOM was 65.0 percent (One 

Offshore, 2002). By drilling rig type, this percentage breaks down into a 66.2 percent fleet utilization rate 

for jackups (average day rates of $16,200-$75,000); 57.5 percent for semisubmersibles (average day rates 

of $30,000-$125,000); 87.5 percent for drillships (average day rates are not available); and 57.1 percent 

for submersibles (average day rates of $21,000-$22,500). Platform rigs in the Gulf recorded a 37.8 

percent fleet utilization rate, while inland barges had a 48.3 percent utilization rate. Offshore drilling rig 

day rates continue to decline for some rig markets but have improved in the Gulf of Mexico jackup and 

floating rig day rates. In the GOM, 76-m to 91-m (250-ft to 300-ft) rated jackup drilling units continued 

their slow improvement. Utilization among this group of rigs has been boosted by the departure of some 

units from the region and continued strong demand for higher-specification rigs at the top-end of the fleet. 

Deepwater floating rig day rates spiked up in August 2002, mostly due to the strength of two contracts 

signed in late July. Day rates for mid-water depth semisubmersible drilling rigs continue to seesaw along 

with demand for rigs of this class. Since utilization of semisubmersible rigs has increased for two 

consecutive months, so have day rates for these rigs (One Offshore, 2002). 

As rig utilization rates have fallen and the market has become much softer, drilling contractors are no 

longer lamenting the lack of skilled crews to run their rigs. While some contractors are recruiting 
36 

vigorously, some are only recruiting for deepwater vessels, while others are not recruiting at all or only at 

the entry level. With some operators still “stinging” from laying off too many crews during the last 

downturn, it appears that many companies are more careful about laying off crews this time in response to 

a slowing market. If companies begin laying off personnel, when the market turns up again, drilling 

contractors may once again be left out in the cold when it comes to recruiting skilled personnel (One 

Offshore, 2001b). 

The still depressed GOM rig market continues to hit offshore service vessel (OSV) operators hard, 

with the smaller vessel owners hit the hardest. The most significant barometer of rig activity is what the 

energy companies are thinking, even if commodity prices are high enough to make money. The June 

2002 utilization rates for supply boats and crewboats used by the offshore oil and gas industry decreased 

from the June 2001 Figures and for the most part, average day rates for these vessels followed suit. 

However, anchor-handling tug/supply vessels (AHTS) utilization and average day rates increased over the 

same time period. Average day rates for AHTS vessels ranged from $12,500 for under 6,000-hp vessels 

(up $2,000 or 19 % from last year’s rate) to $15,500 for over 6,000-hp vessels (up $3,000 or 24% from 

last year’s rate); utilization rates were 100 percent for both. Supply boat average day rates ranged from 

$5,390 for boats up to 61 m (200 ft) (down $3,010 or 36% from a year ago) and $10,725 for boats 61 m 

and over (up $125 or 1% from a year ago); utilization was 61 percent and 96 percent, respectively. 

Crewboat average day rates ranged from $2,100 for boats under 38 m (125 ft) to $3,000 for boats 38 m 

and over (both down about 22% from last year’s average rates); utilization was 71 percent and 82 percent, 

respectively (Greenberg, 2002). 

Commencing with Central GOM Lease Sale 178 Part 1 in March 2001, new royalty relief provisions 

for both oil and gas production in the GOM’s deep and shallow waters were enacted. These rules will 

govern the next three years of lease sales. Central Gulf Lease Sale 178 Part 1 resulted in 534 leases (an 

increase of 59.88% or 200 blocks from Central Gulf Lease Sale 175 in March 2000). Of these 534 leases, 

348 were in shallow water (0-400 m). This increase of 67.30 percent from the last Central Gulf lease sale 

largely reflects the intensified interest in natural gas due to higher prices over the last year and the new 

royalty relief provisions. The 186 blocks receiving bids in deepwater (greater than 400 m) reflect an 

increase of 47.62 percent or 60 blocks. Again, this dramatic increase in leasing could be a result of the 

recently issued royalty relief provisions. Western GOM Lease Sale 180 and Central GOM Lease Sale 

178 Part 2, offering the newly available United States’ blocks beyond the U.S. Exclusive Economic Zone, 

were held on August 22, 2001. No bids were received for blocks offered in Central Gulf Lease Sale 178 

Part 2. Of the 4,114 blocks offered in Western Gulf Lease Sale 180, 320 received bids. About 55 percent 

of blocks receiving bids (177 blocks) in Western Gulf Lease Sale 180 are in deepwater, and 175 of these 

deepwater blocks were leased. In Sale 181 in the Eastern GOM held on December 5, 2001, all 95 

deepwater blocks receiving bids were leased. In Central GOM Sale 182, held March 20, 2002, 307 

shallow-water blocks and 199 deepwater blocks received bids. In Western GOM Sale 184, held 

August 21, 2002, 164 shallow-water blocks and 159 deepwater blocks received bids. 

3.3.1.7. Environmental Justice 

On February 11, 1994, President Clinton issued an executive order to address questions of equity in 

the environmental and health conditions of impoverished communities. The most effective way of 

assuring that environmental endangerment is not concentrated in minority or low-income neighborhoods 

is to locate and identify these neighborhoods from the outset of a proposed project. While low incomes 

tend to coincide with concentrations of minority populations – African American, Hispanic, Native 

American, and/or Asian people – living on low incomes also include fishermen and timber harvesters. 

Minority populations within the Grid 16 impact area include African American and Hispanic persons, 

Native American tribal members, and Asians. 

The web site www.NativeWeb.org lists tribes that are located in the impact area including the 

Chitimacha, Tunica-Biloxi, Coushatta, Houma, and Jena Band of Choctaws. In the early 1970's, only the 

Coushatta tribe was federally recognized. Today, four of the five tribes have Federal status, with the 

United Houma Nation still awaiting a finding on its petition. Since members of both the Houma Nation 

and the Bayou Lafourche community of the Biloxi-Chitimacha-Choctaw live principally around the 

bayou and close to Port Fourchon, they could be directly affected by increases in oil and gas activities 

from the Grid 16 area and the proposed action. 
37 

3.3.1.8. Commercial Fisheries 

More than 26 percent (40% excluding Alaska) of commercial fish landings in the continental U.S. 

occur in the GOM. In 1999, the GOM placed second in total landed weight (almost 1 million tons) and 

third in value ($776 million) considering all U.S. regions (USDOC, NMFS, 2001). The most important 

species, such as menhaden, shrimps, oyster, crabs, and drums, are all species that depend heavily on 

estuarine habitats and the fisheries are restricted to the continental shelf. Menhaden was the most 

valuable finfish landed in 1999, accounting for $78.5 million in total value. The GOM shrimp fishery, 

however, is the most valuable fishery in the U.S., and the Gulf fishery accounts for 71.5 percent of total 

domestic production. 

Commercial fishing in deeper waters, i.e., >200 m (>656 ft), of the GOM is characterized by fewer 

species, and lower landed weights and values than the inshore fisheries. Historically, the deepwater 

offshore fishery contributes less than 1 percent to the regional total weight and value (USDOI, MMS, 

2001a). Target species can be classified into three groups: (1) epipelagic fishes, (2) reef fishes, and (3) 

invertebrates. In general, Grid 16 and the Thunder Horse development is beyond the normal depth range 

of commercial reef fishes and invertebrates. While it is possible that new species of demersal fish or 

invertebrates may be pursued in the future, if other fisheries fail, it appears unlikely at present because of 

the high cost and risk of fishing at extreme water depths. In addition, considerable time, effort, and 

finances would have to be expended to develop new markets for new species. Thus, if new fisheries 

develop in the deepwater Gulf, the most likely target species would be the epipelagic fishes, normally 

fished using surface longlines. 

Epipelagic commercial fishes include dolphin, sharks (silky, and tiger; many species of shark are now 

protected and harvest is prohibited including mako and thresher), snake mackerels (escolar and oilfish), 

swordfish, tunas (bigeye, blackfin, bluefin, and yellowfin), and wahoo (USDOI, MMS, 2001a). These 

species are widespread in the Gulf and probably occur in Grid 16. Oceanic pelagic fishes were not landed 

in high quantities relative to other finfish groups. However, during 1983-1993 in the Eastern Gulf (very 

near the Thunder Horse development), they were very valuable, ranking second to reef fishes in average 

dollar value of landings. The most important species, yellowfin tuna and swordfish, were caught 

primarily by surface longline in oceanic waters offshore the shelf break. Since these fisheries operate in 

the open Gulf, catches responsible for specific State landings could have been made in waters outside the 

region. 

Grid 16 and the Thunder Horse development are relatively near an area that is closed to longline 

fishing. On November 1, 2000, the NMFS put into effect a new regulation to reduce bycatch and bycatch 

mortality in the pelagic longline fishery. Two rectangular areas in the Gulf of Mexico (one of which lies 

over a portion of the DeSoto Canyon area and the area of the proposed action) are closed year-round to 

pelagic longline fishing. These closed areas cover 32,800 mi2 (84,950 km2

). This region has been 

identified by the NMFS as a swordfish nursery area, and where there has historically been a low ratio of 

swordfish kept to the number of undersized swordfish discarded, which over the period of 1993-1998 has 

averaged less than one swordfish kept to one swordfish returned. The area closure is expected to produce 

approximately a 4 percent reduction in Gulf and Atlantic undersized swordfish bycatch. The DeSoto 

Canyon area coordinates are shown in Table 3-2. 
38 

Table 3-2 

Area of Longline Fishing Ban, Eastern Planning Area 

Upper Area Lower Area 

Boundary Location Boundary Location 

North 30 oN. latitude North 28 oN. latitude 

South 28 oN. latitude South 26 oN. latitude 

East 86 oW. longitude East 84 oW. longitude 

West 88 oW. longitude West 86 oW. longitude 

The Thunder Horse development lies only 50 km (27 nmi) to the west of the northern closure area. 

This proximity to the closed longline area may restrict the activities in the immediate vicinity of the 

Thunder Horse project. Additional information or greater depth of discussion on commercial fisheries 

can be found in the Final EIS for Lease Sale 181 (USDOI, MMS, 2001). A map showing the location of 

the longline fishing ban areas and the EPA sale area is shown in Figure III-9 of the Final EIS for Lease 

Sale 181 (USDOI, MMS, 2001). 

3.3.1.9. Recreational Resources 

Over the past 20 years, the northern Gulf of Mexico coastal zone has become increasingly 

domesticated with residential and recreational land use predominating the transition. Figure 3-2 below is 

a satellite photograph that shows the distribution of the population throughout the United States by light 

intensity. The most intense light indicates population centers. One notices immediately that nearly all of 

the Gulf Coast is a concentrated band of light. In addition to homes, condominiums and some industry, 

that same coastline is one of the major recreational regions of the United States, particularly for marine 

fishing and beach activities, both of which are viewed as public assets, belonging to no one individual or 

company. There is a diversity of natural and developed landscapes and seascapes, including coastal 

beaches, barrier islands, estuarine bays and sounds, river deltas, and tidal marshes. Other recreational 

resources are publicly owned and administered, such as national and State seashores, parks, beaches, and 

wildlife lands, as well as designated preservation areas, such as historic and natural sites and landmarks, 

wilderness areas, wildlife sanctuaries, research reserves and scenic rivers. Gulf Coast residents and 

tourists from throughout the nation, as well as from foreign countries, use these resources extensively and 

intensively for recreational activity. Commercial and private recreational facilities and establishments, 

such as resorts, marinas, amusement parks, and ornamental gardens, also serve as primary-interest areas. 

Locating, identifying, and observing coastal and marine birds, is part of a growing interest in the 

interrelationships of any given ecosystem. 

Although there is recreational use of the Central Gulf Coast year round, the primary season is the 

spring and summer. 

More than 25 years ago, Congress set aside outstanding examples of Gulf coastal beach and barrier 

island ecosystems to be managed by the National Park Service for the preservation, enjoyment, and 

understanding of their inherent value. State and county legislation added to this preservation program so 

that today there is a lengthy list of reserves, refuges, and public parks. 

The United States coastline potentially affected by the development of Grid 16 is from Lafourche 

Parish east to St. Bernard Parish in Louisiana. It includes Jefferson and Plaquemines Parishes and 

encompasses the confluence of the Mississippi River with the sea forming one of the largest delta systems 

in the United States (Alabama Seaport, 2001; page 25). This section describes some of the coastline 

according to topography, discrete human and other biological populations, barrier island formations, and 

special preservation areas. This gives the reader the chance to put in geographical context the textual 

descriptions. Likewise, the reader will note that these parishes host a plethora of ecological 

characteristics that humans use for recreation, research, conservation, and mineral extraction. 
39 

 Figure 3-2. Satellite Photograph Shows the Distribution of the U.S. Population Light Intensity. 

Source: National Aeronautics and Space Administration, Astronomy Picture of the Day, 

November 27, 2000. 

http://antwrp.gsfc.nasa/gov/apod/image/0011/earthlights2_dmsp_big.jpg 

3.3.1.9.1. Federal and State Reserves 

The three parishes of Cameron, Lafourche, and Jefferson comprise the Federal reserves of the 

Barataria-Terrebonne National Estuary Program, the Atchafalaya National Wildlife Refuge, and the Jean 

Lafitte National Historic Park and Reserve. Additional acreage is in wildlife management areas that are 

either owned or managed by the State of Louisiana, Department of Wildlife and Fisheries. Within the 

impact area, these areas are Pointe-au-Chien in Terrebonne and Lafourche Parishes; Wisner Wildlife 

Management Area in Lafourche Parish, close to Port Fourchon; Pass a Loutre in Plaquemines Parish; and 

Biloxi Wildlife. 

3.3.1.9.2. Marine Recreational Activities 

In coastal Louisiana, marine fishing and diving are also important to the State’s economy. This 

marine industry generates millions of dollars in sales of equipment, transportation, food, lodging, 

insurance, and services and accounts for thousands of jobs. Just over one-third of the marine recreational 

fishing trips in the Gulf of Mexico extend into offshore water under Federal jurisdiction. According to 

statistics from the NMFS, fishermen catch a variety of species, from barracudas and sharks to drums, 

snappers, and flounders (http://www.st.nmfs.gov/pls/webpls, August 28, 2002). Recreational diving trips 

are popular in nearshore and offshore waters near natural and artificial reefs. Indeed, in a study for the 

MMS, researchers found that fishing, party, and diving trips originating from Louisiana’s coast numbered 

over 3 million in 1999, higher than any of the other three states lining the Gulf of Mexico (Hiett and 

Milon 2002; pages 2-4). 
40 

3.3.1.10. Archaeological Resources 

Archaeological resources are any material remains of human life or activities that are at least 50 years 

of age and that are of archaeological interest. The archaeological resources regulation (30 CFR 250.194) 

provides specific authority to each MMS Regional Director to require archaeological resource surveys, 

analyses, and reports. Surveys are required prior to any exploration or development activities on leases 

within the high-probability areas (NTL 2002-G01). 

3.3.1.10.1. Prehistoric 

Available geologic 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, and that the low sea-stand occurred 

during the period 20,000-17,000 years before present (B.P.) (Nelson and Bray, 1970). Sea level in the 

northern Gulf reached its present stand around 3,500 years B.P. (Coastal Environments, Inc., 1986). 

During periods that the continental shelf was exposed above sea level, the area was open to habitation 

by prehistoric peoples. The advent of early man into the GOM region is currently accepted to be around 

12,000 years B.P. (Aten, 1983). According to the sea-level curve for the northern GOM proposed by 

Coastal Environments, Inc. (CEI), sea level at 12,000 B.P. would have been approximately 45 m (148 ft) 

below the present still stand (CEI, 1977 and 1982). On this basis, the continental shelf shoreward of the 

45-m to 60-m (148-ft to 197-ft) bathymetric contours has potential for prehistoric sites dating after 12,000 

B.P. Because of inherent uncertainties in both the depth of sea level and the entry date of prehistoric man 

into North America, MMS adopted the 12,000 years B.P. and the 60-m (197 ft) water depth as the 

seaward extant of the prehistoric archaeological high-probability area. 

Based on the extreme water depth of Grid 16 and the Thunder Horse project lease blocks, oil or gas 

activities will not impact any prehistoric archaeological resources. 

3.3.1.10.2. Historic 

With the exception of the Ship Shoal Lighthouse structure, historic archaeological resources on the 

OCS consist of historic shipwrecks. A historic shipwreck is defined as a submerged or buried vessel, at 

least 50 years old, that has foundered, stranded, or wrecked and is presently lying on or embedded in the 

seafloor. This includes vessels (except abandoned hulks) that exist intact or as scattered components on 

or in the seafloor. A 1977 MMS archaeological resources baseline study for the northern GOM 

concluded that two-thirds of the total number of shipwrecks in the northern Gulf lie within 1.5 km (0.9 

mi) of shore and most of the remainder lie between 1.5 and 10 km (0.9 and 6.2 mi) of the coast (CEI, 

1977). A subsequent MMS study published in 1989 found that changes in the late 19th and early 20th 

century sailing routes increased the frequency of shipwrecks in the open sea in the Eastern Gulf to nearly 

double that of the Western and Central Gulf (Garrison et al., 1989). The highest observed frequency of 

shipwrecks occurred within areas of intense marine traffic, such as the approaches and entrances to 

seaports and the mouths of navigable rivers and straits. 

Review of the Garrison et al. (1989) and Pearson et al. (2002) shipwreck database lists eight 

shipwrecks that fall within Grid 16 (in the Mississippi Canyon and Viosca Knoll areas). These 

shipwrecks are listed in Table 3-3. Five of the shipwrecks listed by the Garrison et al. (1989) and Pearson 

et al. (2002) studies are known only through the historical record and, to date, have not been located on 

the ocean floor. Three of the wrecks, the U-166, Alcoa Puritan, and the Robert E. Lee, have been located 

on the seafloor by pipeline or lease block side-scan-sonar surveys. The Garrison et al. (1989) and Pearson 

et al. (2002) shipwreck databases should not be considered exhaustive lists of shipwrecks. Regular 

reporting of shipwrecks did not occur until late in the 19th century, and losses of several classes of 

vessels, such as small coastal fishing boats, were largely unreported in official records. 

Wrecks occurring in deeper water would have a moderate to high preservation potential, as can be 

seen by the copper-sheathed wreck in Mississippi Canyon, Block 74, just three lease blocks west of Grid 

16. In the deep water, temperature at the seafloor is extremely cold, which slows the oxidation of ferrous 

metals and help to preserve wood features. The cold water would also eliminate woodeating shipworm 

Terredo navalis (Anuskiewicz, 1989). 
41 

Aside from acts of war, hurricanes cause the greatest number of wrecks in the Gulf. The wreckage of 

the 19th-century steamer New York, which was destroyed in a hurricane in 1846, lies in 16 m (52 ft) of 

water and has been documented by the MMS (Irion and Anuskiewicz, 1999) as scattered over the ocean 

floor in a swath over 457 m (1,500 ft) long. Shipwrecks occurring in shallow water nearer to shore are 

more likely to have been reworked and scattered by subsequent storms than those wrecks occurring at 

greater depths on the OCS. Historic research indicates that shipwrecks occur less frequently in Federal 

waters. However, these wrecks are likely to be better preserved, less disturbed, and, therefore, more 

likely to be eligible for nomination to the National Register of Historic Places than are wrecks in 

shallower State waters. 

Table 3-3 

Shipwrecks in Grid 16 Area 

Area Vessel Name Date of Loss 

Viosca Knoll Bradford C. French 1916 

Viosca Knoll Unknown Unknown 

Mississippi Canyon Providence 1982 

Mississippi Canyon Western Empire 1875 

Mississippi Canyon German Submarine U-166* 1942 

Mississippi Canyon Alcoa Puritan* 1942 

Mississippi Canyon Robert E. Lee* 1942 

Mississippi Canyon Heedless 1962 

*Deepwater shipwrecks located by side-scan sonar. 

4. POTENTIAL ENVIRONMENTAL EFFECTS 

4.1. PHYSICAL ELEMENTS OF THE ENVIRONMENT

4.1.1. Impacts on Water Quality 

4.1.1.1. Coastal 

The proposed Thunder Horse project is located approximately 108 km (67 mi) from the nearest 

Louisiana coastline (the closest shoreline is the Mississippi River’s active delta area). Effects to coastal 

waters from the project would primarily be associated with onshore support activities. BP plans to use 

existing onshore support bases at Port Fourchon (primary base), Terrebonne Parish, and Venice 

(secondary base), Plaquemines Parish, Louisiana. No expansion of these onshore facilities is expected to 

result from the proposed activities. No increase in maintenance dredging of access canals is expected. 

Waste waters would be discharged from the onshore bases as well as support vessels. State 

regulations are in place to control contaminants associated with these waste discharges. Minor, transient 

changes in localized water quality would be intermittent, resulting from such waste discharges. 

Accidental spills could also affect coastal waters. See Appendix B for a discussion of these potential 

effects. 

Offshore sediment disturbance described below is not likely to impact coastal water quality since the 

coastal area is characterized by turbid, contaminated water discharged from the Mississippi River. 

Conclusion 

Since the proposed action would use existing onshore support bases and these facilities are not 

expected to expand as a result of the project’s activities, only discharges from these support bases and 

associated vessel traffic would result in effects to coastal waters. The level of these effects is expected to 

be very minor and transient, negligibly affecting coastal water quality. Offshore activities associated with 

the project are not expected to adversely affect coastal water quality because of the water depth and the 

distal location of the project. 
42 

4.1.1.2. Offshore 

Localized sediment disturbance will occur from the emplacement of anchors and the mooring system 

associated with the PDQ facility as well as from other subsea infrastructure, e.g., drilled wells, manifolds, 

umbilicals, and other subsea equipment. Sediments will also be disturbed from the installation of risers 

and from oil and gas lease-term and right-of-way pipelines. Sediment disturbance and increased turbidity 

would create little effect on the offshore water quality because the inputs would be localized and limited 

in amount and the disturbances would be spread out over time. Light limitation, one of the effects of high 

turbidity, is not an issue in the deepwater area of Grid 16. Surface sediments in the deepwater GOM are 

relatively pristine so that any turbidity created by bottom disturbances would not decrease water quality 

other than for the expected increase in total suspended solids (TSS). In conclusion, any effects from 

elevated turbidity would be short term, localized, and reversible. 

BP will not discharge its produced water from the Thunder Horse project. They plan to co-mingle 

and reinject the produced water to support pressure maintenance of the producing reservoirs. 

Sanitary and domestic waste discharges from personnel on-site are expected to increase nutrient input 

and biological oxygen demand (BOD) slightly, but this is not normally a concern in open oceanic waters. 

Other minor discharges from development activities such as deck drainage, excess cement, other well 

fluids, and cooling water would affect water quality (e.g., TSS, nutrients, chlorine, and BOD) within tens 

of meters of the discharge. 

Accidental spills are examined in Appendix B. Oil from a spill would weather dependent upon a 

number of factors, particularly the characteristics of the released oil and oceanographic conditions. Some 

of the subsurface oil may disperse within the water column, as in the case of the Ixtoc I seafloor blowout. 

Evidence from a recent experiment in the North Sea indicated that oil released during a deepwater 

blowout [844 m (2,769 ft) water depth] would quickly rise to the surface and form a slick (Johansen et al., 

2001). Once the oil enters the ocean, a variety of physical, chemical, and biological processes act to 

disperse the oil slick. These include spreading, evaporation of the more volatile constituents, dissolution 

into the water column, emulsification of small droplets, agglomeration sinking, microbial modification, 

photochemical modification, and biological ingestion and excretion. Some oil from the slick would be 

mixed into the water and dispersed by wind and waves. The quality of marine waters would be 

temporarily affected by the dissolved components and small, dispersed oil droplets that do not rise to the 

surface are mixed down by surface turbulence. Dispersion by currents and microbial degradation remove 

the oil from the water column or dilute the constituents to background levels. 

Decommissioning effects would presumably be similar in scope and magnitude with offshore 

construction and installation operations. All discharges would adhere to existing regulatory discharge 

criteria designed to mitigate adverse environmental effects. 

Conclusion 

Near-bottom water quality would be affected by sediments disturbed during the period of installation 

of subsea infrastructure, including the moorings and anchors and the risers and pipelines that would 

transport the oil and gas from the Thunder Horse field. Any effects from the elevated turbidity would be 

short term, localized, and reversible. 

Offshore effects from an accidental spill of oil would affect water quality immediately under the slick 

(top few meters of the water column). Operator-initiated activities to contain and clean up an oil spill 

would begin as soon as possible after an event. However, the remaining portion of the discharged oil 

would weather, disperse, and biodegrade within a short period of time so that no significant long-term 

effects on offshore water quality are expected to occur. 

4.1.2. Impacts on Air Quality 

Air quality will be affected in the immediate vicinity of the production facilities, the drilling rigs, and 

the attending vessels and aircraft. The operator provided air emissions data for the next 12 years. The 

cumulative impact from emissions for BP’s Supplemental Exploration Plan and this Development 

Operations Coordination Document will not exceed the MMS’s exemption level. Activities associated 

with these plans are not expected to significantly affect onshore air quality. Impacts from NOx emissions 
43 

will be highest during the years when production and construction are taking place. Emissions of SOx

will be highest during the days when temporary flaring occurs. 

Air quality would be affected in the event of a blowout or oil spill. The VOC’s, which would escape, 

are precursors to photochemically produced ozone. A spike in VOC’s could contribute to a 

corresponding spike in ozone, especially if the release were to occur on a hot sunny day in a NO2-rich 

environment. The corresponding onshore area is in attainment for ozone. If a fire occurs, particulate and 

combustible emissions will be released in addition to the VOC’s. 

Conclusion 

The air quality in the immediate vicinity of the proposed activities will be affected by the projected 

emissions. However, the proposed action is not expected to result in any significant impacts to air 

quality. 

4.2. BIOLOGICAL RESOURCES

4.2.1. Impacts on Sensitive Coastal Environments 

4.2.1.1. Coastal Barrier Beaches and Associated Dunes 

The following section describes potential impacts to coastal barrier beaches and associated dunes 

from oil spills that might occur as a result of activities proposed in Grid 16. Appendix B describes the 

probability of an oil spill and the estimated dispersal characteristics should a spill occur. Spill response 

and effectiveness is also discussed in Appendix B. 

Contact between an oil slick and a beach primarily depends upon environmental conditions and the 

nature of the oil spilled. It is not very likely that severe adverse impacts would occur to dunes from a spill 

within the Grid 16 area. For storm tides to carry oil from a spill across and over the dunes, strong 

southerly or easterly winds must persist for an extended period of time, prior to or immediately after the 

spill. The strong winds that would be required to raise the water level sufficiently to contact dunes would 

also result in oil slick dispersal, thereby reducing impact severity at a landfall site. In addition, a study in 

Texas showed that oil on vegetated sand dunes had no deleterious effects on the existing vegetation or on 

the recolonization of the oiled sand by plants (Webb, 1988). 

The cleanup operations associated with large oil spills can affect the stability of barrier beaches more 

than the spill itself. If large quantities of sand were removed during spill cleanup operations, a new beach 

profile and sand configuration would be established in response to the reduced sand supply and volume. 

The net result of these changes could be accelerated rates of shoreline erosion at the contact site and down 

drift of that site. This situation would be accentuated in sand-starved or eroding barrier beaches, such as 

those found on the Louisiana coast. State governments around the Gulf have recognized these problems 

and have established policies to limit sand removal by cleanup operations. 

Conclusion 

Actions proposed in Grid 16 are not expected to adversely alter barrier beach or dune configurations 

significantly as a result of a related oil spill, should one occur. 

4.2.1.2. Wetlands 

A description of a hypothetical oil spill associated with the proposed action is provided in Appendix 

B. The information below regarding potential effects of oil spills on wetlands is based on analyses in the 

Final Multisale EIS (USDOI, MMS, 2002). 

Data in Appendix B indicate that a very low probability exists for an oil spill to occur from the 

Thunder Horse development. As discussed in USDOI, MMS 2002, distant offshore spills have an even 

further diminished probability of impacting inland wetland shorelines and seagrasses, largely due to the 

sheltered locations of these habitats. 

An inland, fuel-oil spill may occur at a shore base or as a result of a vessel collision. The probability 

of an inland, fuel-oil spill occurring in association with the proposed action is very small. However, 
44 

should a spill occur inshore or in nearshore waters, it presents a much greater potential for adversely 

impacting wetlands and seagrasses than an offshore spill, due simply to their proximity to the spill. Oil 

could accumulate in sheens and thick layers in the marsh and in protected pools and embayments. 

The works of several investigators (Webb et al., 1981 and 1985; Alexander and Webb, 1983, 1985, 

and 1987; Lytle, 1975; Delaune et al., 1979; Fischel et al., 1989) were used to evaluate effects of potential 

spills to area wetlands. For wetlands along the central Louisiana area, the critical oil concentration is 

assumed to be 1.0 l/m2

 of marsh. Concentrations above this would result in longer-term effects to 

wetland vegetation, including some plant mortality and loss of land. Concentrations less than this may 

cause diebacks for one growing season or less, depending upon the concentration and the season during 

which contact occurs. 

Conclusion 

It is highly unlikely that significant adverse impacts to wetlands would result from a spill associated 

with the proposed Thunder Horse project. If a spill does occur offshore, oceanographic and 

meteorological conditions are very unlikely to move the spilled oil far enough in a short enough time to 

cause oil contacts with wetlands. If an unlikely, project-related fuel-oil spill occurs inshore, some 

wetlands in the vicinity of the spill may be adversely impacted. 

4.2.1.3. Seagrasses 

Seagrasses have generally experienced little or no damage from oil spills (Chan, 1977; Zieman et al., 

1984). The relatively low susceptibility of seagrasses in the northern GOM to oil-spill impacts is partly 

the result of their location, which is subtidal, generally landward of barrier islands and in a region with a 

small tidal range. Furthermore, it should be noted that seagrasses are much less common in Louisiana, 

the most likely landfall for a spill event, than elsewhere in the Gulf. 

The lack of low-tide exposure protects seagrasses from direct contact with spilled oil. The degree of 

impact depends on water depth, the nature of the oil, and the tidal and weather events in the affected area 

during the presence of the floating oil. Another reason for the low susceptibility of seagrass to oil spills is 

that a large percentage of their biomass is found in the buried root and rhizome, from which the leaves 

generate. An oil spill that moves over a seagrass area would not be expected to directly cause anything 

but slight damage to the vegetation. Some seagrass dieback for one growing season might occur, largely 

depending upon water currents and weather. No permanent loss of seagrass habitat is expected to result 

from such spills. 

During extremely low water conditions such as wind-driven tidal events, seagrass beds might be 

exposed to the air and could potentially be impacted directly by an oil slick. Even then, their roots and 

rhizomes remain buried in the water bottom. Given the geography of the coastal area discussed, a strong 

wind that could lower the water that much generally would be a northerly or westerly wind, which would 

push water out of bays and estuaries and drive a slick away from the coast. In this situation, oil that was 

already in the bay or sound would be driven against the southern or eastern shores. Any seagrass beds 

that may be exposed there might be contacted. 

The greatest oil-spill effect to seagrass communities has been to the diversity and populations of the 

epifaunal community found in the grass bed. Should water turbulence and turbidity increase sufficiently, 

some oil on the water surface may be emulsified. Suspended particles in the water column will adsorb oil 

from a sheen as well as from emulsified droplets, causing some particulates to clump together and 

decrease their suspendability. Typically, submerged vegetation reduces water velocity among the 

vegetation as well as for a short distance above it. Reduced flow velocity or turbulence further enhances 

sedimentation. 

Minute oil droplets, whether emulsified or bound to suspended particulates, may adhere to vegetation 

or other marine life; they may be ingested by animals, particularly by filter and sedimentation feeders; or 

they may settle onto bottom sediments in or around a bed. In these situations, oil has a limited life 

because it will be degraded chemically and biologically (Zieman et al., 1984). 

The potential danger to a seagrass community from an oil-spill event is a reduction for up to two 

years of the diversity or population of epifauna and benthic fauna found in grass beds. The degree of 

impact further depends on the time of year, water depth, currents, and weather in the affected area during 
45 

the presence of a slick, as well as oil characteristics such as density, solubility, ability to emulsify, and 

toxicity. 

A more damaging scenario would involve the secondary impacts of a slick that remains, for a period 

of time, over a submerged bed of vegetation in a protected embayment during typical fair-weather 

conditions. This would reduce light levels in the bed. If light reduction continues for several days, 

chlorophyll content in the leaves will be reduced (Wolfe et al., 1988), causing the grasses to yellow, 

reducing their productivity. By itself, shading from an oil slick should not last long enough to cause 

mortality. This depends upon the slick thickness, currents, weather, efforts to clean up the slick, and the 

nature of the embayment. 

Also, a slick that remains over a submerged vegetation bed in an embayment will reduce or eliminate 

oxygen exchange between the air and the water of the embayment. Currents may not flush adequately 

oxygenated water from the larger waterbody to the shallow embayment. Seagrasses and related epifauna 

might be stressed and perhaps suffocated if the biochemical oxygen demand is high, as would be expected 

for a shallow waterbody that contains submerged vegetation, with its usual detritus load, and an additional 

burden of spilled oil (Wolfe et al., 1988). 

The cleanup of slicks that come to rest in shallow or protected waters (0-1.5 m [0-5 ft] deep) may be 

performed using “john” boats, booms, anchors, and skimmers mounted on boats or shore vehicles. 

Personnel assisting in oil-spill cleanup in water shallower than about 1 m (3-4 ft) may readily wade 

through the water to complete their tasks. Foot traffic and cleanup equipment can easily damage the 

seagrass beds. Oil can also be worked more deeply into their sediments by these activities. 

As described for wetlands, oil that penetrates or is buried into the water bottom is less available for 

dissolution, oxidation, or microbial degradation. Oil may then be detectable in the sediments for five 

years or more, depending upon circumstances. 

Navigational vessels that vary their route from established navigation channels can directly scar 

shallow beds of submerged vegetation with their props, keels (or flat bottoms), and anchors (Durako 

et al., 1992). 

Conclusion 

It is highly unlikely that significant adverse impacts to seagrasses would result from a spill associated 

with the proposed Thunder Horse project. If a spill does occur offshore, oceanographic and 

meteorological conditions are very unlikely to move oil far enough in a short enough time to cause oil 

contacts with seagrasses. If an unlikely, project-related fuel-oil spill occurs inshore, some wetlands in the 

vicinity of the spill may be adversely impacted; however, seagrasses are unlikely to be impacted directly. 

4.2.2. Impacts on Deepwater Benthic Communities/Organisms 

4.2.2.1. Chemosynthetic Communities 

A review for the potential occurrence of chemosynthetic communities was performed for the Thunder 

Horse project and for the Grid 16 area. This review was conducted using the most recent available 

information. No areas for potential chemosynthetic communities were identified in the areas, including 

the 457-m (1500-ft) avoidance distance from the discharging structure, required by NTL 2000-G20. No 

other potential chemosynthetic community areas were identified within 152 m (500 ft) of all 16 anchor 

locations or anchor chain/cable impacting areas for the semi-submersible drill site as well as the other 

drill sites that will be using dynamically positioned drilling units. The closest known chemosynthetic 

community is located in Viosca Knoll, Block 826, more than 72 nmi to the northeast of the Thunder 

Horse development. The absence of chemosynthetic communities in this review does not preclude the 

discovery of additional communities as new data become available from future operations within the grid. 

Conclusion 

The proposed Thunder Horse project would not have an impact on known chemosynthetic 

communities and no potential communities are located in the vicinity of the proposed activities, as 

indicated by geophysical characteristics. 
46 

4.2.2.2. Deepwater Benthos and Sediment Communities 

The deepwater benthos in the immediate vicinity of the proposed Thunder Horse project would be 

impacted by the discharge of drilling mud and cuttings, placement of mooring lines and anchors, and well 

site locations (the dynamically positioned drill sites would not have anchor impacts). The most common 

adverse impact would be physical smothering by sediments. Invertebrates, many with some degree of 

mobility, typically dominate the megafaunal benthic communities at the project depth of about 1,840 m 

(6,076 ft). The macrofauna is dominated by deposit-feeding polychaete worms with varying degrees of 

mobility and tolerance to disturbance. The meiofauna, primarily composed of small nematode worms, is 

more abundant than macrofauna, and their numbers decline with depth. Little is known of the microbiota 

in deepwater, but it probably includes hydrocarbon-degrading forms. None of the benthic communities 

found around the Thunder Horse project are unique to the area and appear to be widespread throughout 

the Gulf, where depths, substrates, and other environmental factors are similar. 

The effects of drilling muds and cuttings on the deepwater benthos would be limited for the following 

reasons: 

• Low Toxicity. The synthetic-based fluids (SBF) are expensive and are recycled. Any 

unusable portion of the SBF is sent to approved recycling/disposal sites onshore. The 

SBF cuttings would be treated to conform to regulatory guidelines. The SBF’s are 

essentially nontoxic, and the composite formulation of the discharged fluid adhering 

to the cuttings has a very low toxicity to aquatic organisms. Most of the SBF in 

current use can easily pass the USEPA's 96-hour, LC50 criteria of 30,000 ppm 

(McKelvie and Ayers, 1999). Test results with four types of SBF’s on algae, mysids, 

copepods, mussels, and amphipods range from 277 to 1,000,000 ppm (McKelvie and 

Ayers, 1999). Dose response studies on fish by Payne et al. (2001a and b) 

demonstrated that sediments contaminated with Hibernia (Grand Banks, 

Newfoundland) source cuttings containing an aliphatic hydrocarbon-based synthetic 

drilling fluid had a very low toxicity potential. Acute toxicity was not observed in 

juvenile flounder exposed for up to two months to sediment containing 

approximately 6,000 ppm of diesel-range (aliphatic) hydrocarbons. 

• Limited Biological Effects. The only direct biological effect reported for SBF’s and 

associated cuttings in the field environment has been smothering of benthic animals 

by physical and/or anoxic conditions. Anoxia is caused by the rapid biodegradation 

of the SBF. Organic enrichment due to the introduction of carbon into a carbon-poor 

environment has also been noted (Gallaway and Beaubien, 1997). 

• Limited Affected Area. Cuttings from wells drilled with SBF tend to clump together 

and are transported to the bottom relatively quickly. Thus, the affected area would be 

relatively small. The vast majority of historical literature [based on the more toxic 

oil-based mud (OBM) or water-based mud (WBM) that tend to disperse farther] 

indicates biological effects generally do not occur beyond 500 m (1,640 ft) from the 

source, although several papers have noted subtle effects beyond that range. Most 

relevant is the recent research in the North Sea (Jensen et al., 1999) that studied a 

number of platforms that used only SBF’s. That study found no benthic effects (i.e., 

benthic effects as measured by subtle community changes) beyond 250 m (820 ft) in 

most cases, and 500 m (1,640 ft) in a few cases. However, one must note that the 

North Sea is a shallower environment than the deepwater GOM. 

The anchor system for the semisubmersible PDQ and mooring lines should have minimal effects on 

the benthos. Installation of the suction-pile anchors and activities at the proposed well sites would 

physically disturb the benthos in the immediate vicinity. The benthos would also be affected in the 

unlikely event of a subsea blowout that caused disturbance and slumping of the surrounding seabed. 
47 

Conclusion 

Structure emplacement (including anchor installations and moorings), well drilling, and completion 

operations would disturb benthic communities by smothering and displacing them from patches within 

limited distances of the well site locations and within a small area of the anchors and chains or cables that 

contact the bottom. Partial recovery of the community would occur within weeks or months of the 

disturbance probably followed by a more or less full recovery within 1-2 years. This would not result in a 

significant impact on the benthic communities because of the duration and area extent of the proposed 

activities would be limited. 

Routine production activities would not significantly impact the benthos. A subsea blowout would 

physically disturb the benthos within a small radius of the blowout, but most of the released fluids are 

expected to go to the surface and not interact with deepwater benthos. 

4.2.3. Impacts on Marine Mammals 

Some potential effects on GOM marine mammals include disturbance (subtle changes in behavior, 

interruption of previous activities, or short- or long-term displacement); masking of sound (calls from 

conspecifics, important cues such as surf or predators, reverberations from own calls); stress 

(physiological); and hearing impairment (permanent or temporary) by explosions and other strong noise 

sources. 

The major impact-producing factors affecting marine mammals as a result of routine OCS activities 

within Grid 16 and associated with the proposed Thunder Horse project include the noise generated by 

helicopters, vessels, and operating facilities; vessel traffic; underwater obstacles; explosive structure 

removals; jetsam and flotsam from associated support vessels and structure facilities; degradation of 

water quality from operational discharges; accidental chemical/waste spills or releases; and spill-response 

actions. 

Some effluents are routinely discharged into offshore marine waters. However, BP has chosen not to 

discharge its produced water from the Thunder Horse development. It is expected that cetaceans may 

have some interaction with other routine discharges. Direct effects to cetaceans are expected to be 

sublethal. Since OCS discharges are diluted and dispersed in the offshore environment, impacts to 

cetaceans are expected to be negligible relative to the contaminants introduced into the Gulf from national 

and international watersheds. The proposed use of low-toxicity, synthetic-based fluids during the 

Thunder Horse project should further reduce the possibility of adverse impact to marine mammals or their 

prey. 

Helicopter activity and the associated noise have the potential to disrupt marine mammals. The FAA 

Advisory Circular 91-36C encourages pilots to maintain higher than minimum altitudes (noted below) 

over noise-sensitive areas. Corporate helicopter policy states that helicopters should maintain a minimum 

altitude of 213 m (700 ft) while in transit offshore and 152 m (500 ft) while working between platforms. 

In addition, guidelines and regulations promulgated by the NMFS under the authority of the Marine 

Mammal Protection Act include provisions specifying that helicopter pilots maintain an altitude of 305 m 

(1,000 ft) within 91 m (300 ft) of marine mammals. It is unlikely that cetaceans would be affected by 

routine OCS helicopter traffic operating at these altitudes, provided pilots do not alter their flight patterns 

to more closely observe or photograph marine mammals. Temporary disturbance to cetaceans may occur 

on occasion as a helicopter approaches or departs an OCS facility, if animals are near the facility. 

Routine overflights may elicit a startle response from, and interrupt cetaceans nearby (depending on the 

activity of the animals) (Richardson et al., 1995). Both the noise and the shadow cast by the helicopter 

can elicit a response. Occasional overflights probably have no long-term consequences on cetaceans; 

however, frequent overflights could have long-term consequences if they repeatedly disrupt necessary 

activities, such as feeding and breeding. As more prospects are developed within Grid 16, the helicopter 

activity is expected to increase. However, such disturbance is believed negligible relative to other sources 

of noise (e.g., vessel traffic). 

Well development activities associated with the Thunder Horse project could produce sounds at 

intensities and frequencies heard by cetaceans. It is expected that noise from drilling and completion 

activities will be somewhat constant for the next few years and continue with sporadic drilling and 

completion work into the year 2015. As more prospects are developed within Grid 16, the drilling, 
48 

completion, and production activities and associated noise are expected to increase. Odontocetes 

echolocate and communicate at higher frequencies than the dominant sounds generated by drilling units. 

Sound levels in this range are not expected to be generated by drilling operations (Gales, 1982). 

Bottlenose dolphins are one of the few species in which low-frequency sound detection has been studied. 

Researchers have found that these dolphins have poor sensitivity at the level where most industrial noise 

energy is concentrated. 

The Thunder Horse project’s vessel traffic estimates during drilling and completion operations are 

four workboats and six crew boats per week, dropping to three and four, respectively, during production 

activities. Dozens of other support vessels will be utilized during the project’s various installation 

operations. As with other potential sources of disturbance, vessel activity is expected to increase as more 

development occurs within Grid 16. Noise from support-vessel traffic may elicit a startle and/or 

avoidance reaction from cetaceans or mask their sound reception. There is the possibility of short-term 

disruption of movement patterns and behavior, but such disruptions are unlikely to affect survival or 

productivity. Long-term displacement of animals from an area is also a consideration. Toothed whales 

exposed to recurring vessel disturbance could be stressed or otherwise affected in a negative but 

inconspicuous way. 

Increased vessel traffic also increases the probability of collisions between ships and marine 

mammals, which may result in injury or death to some animals. The MMS issued NTL 2002-G14, 

“Vessel Strike Avoidance and Injured/Dead Protected Species Reporting,” to help mitigate vessel/marine 

mammal strikes. Smaller delphinids may “bow-ride” vessels that are in transit from a shorebase to an 

offshore location in Grid 16. Vessels may also be a threat to smaller, coastal delphinids, where the 

majority of OCS vessel traffic occurs. Marine mammalogists conducting surveys in the CPA during the 

summer of 2001 documented an adult killer whale that bore conspicuous and aged scarring across its back 

that were indubitably the result of a collision with a motor vessel. 

Of particular concern for the Thunder Horse project and Grid 16 is the presence of sperm whales. An 

area of sperm whale concentration south of the mouth of the Mississippi River has been the subject of 

research for the last three years. Sperm whales have consistently been observed in the area and there is 

speculation that these whales are year round residents. Although this area is not located in Grid 16, shorebased support vessels would be transiting through the sperm whale area enroute to Grid 16. Also, smaller 

numbers of sperm whales have been observed in nearly all areas of the Gulf and may very likely occur, at 

least sporadically, in Grid 16. Deep-diving whales (including sperm whales, beaked whales, and pygmy 

and dwarf sperm whales, all of which occur in this area) are more vulnerable to vessel strikes because of 

the extended surface period required to recover from extended deep dives. These animals also 

periodically congregate on the surface in “social groups” and, during these times, may be distracted from, 

or oblivious to, vessel approaches. Support vessel activity in Grid 16 or adjacent waters would increase 

the risk of vessel strikes to sperm whales and other deep-diving cetaceans. Limited observations on an 

NMFS cruise off the mouth of the Mississippi River in the summer of 2000 indicated that sperm whales 

appeared to avoid passing service vessels. However, the strong preference of sperm whales for an area 

between Grid 16 and the onshore support bases is a source of concern. 

Many types of materials, including plastics, are used during drilling and production operations. If 

some of this material is accidentally lost overboard, cetaceans may consume it. The result of ingesting 

some materials lost overboard can be lethal, and the probabilities of occurrence, ingestion, and lethal 

effect are unknown. The MMS issued NTL 2002-G13, “Marine Trash and Debris Awareness and 

Elimination” to help mitigate the potential threat to marine mammals, fish, sea turtles, and other marine 

animals from marine trash and debris. 

The ability of marine mammals, and sperm whales in particular, to avoid underwater obstacles is 

unknown. Sperm whales have been entangled in deepsea cables (USDOI 2001; Heezen, 1957). The 

underwater mooring lines, steel catenary risers, pipelines, and other paraphernalia associated with the 

PDQ and numerous wells of the Thunder Horse project will support a large underwater presence. Whales 

would normally be expected to detect the structures through echolocation; however, if noise from drilling, 

vessels, etc., masks or distorts feedback to the whale, these underwater obstacles may be a source of 

concern. 

Information on potential accidental oil spills associated with the Thunder Horse project is located in 

Appendix B. The worst-case scenario is a blowout that could result in a spill of up to 141,000 bbl/day. 

Such a spill is highly unlikely. However, if it did occur, it could result in negative effects to sperm 
49 

whales and other oceanic marine mammal species. The expected impacts would involve the oiling of 

animals and prey and probable displacement from the impacted area. Sperm whales may use this area as 

foraging, nursery, and possibly mating habitat. Spill-response activities could also disrupt normal 

behavioral activities of marine mammals in the area. 

Conclusion 

The routine activities associated with the Thunder Horse project are not expected to have long-term 

adverse effects on the size and productivity of any marine mammal species or population stock endemic 

to the northern GOM. Accidental events (e.g., collisions with vessels, oil spills) are expected to be rare 

and the MMS has regulations and NTL’s in place to greatly restrict their possibility. 

However, small numbers of marine mammals could be injured or killed by collision with support 

vessels and by eating indigestible debris, particularly plastic items, lost from support vessels, drilling rigs, 

and fixed and floating platforms. The likelihood of such “takes” are greater within or enroute to this grid 

than many other grids within the Gulf because surveys indicate there are increased concentrations of 

sperm whales in waters adjacent to Grid 16. Such cases of “takes” are expected to be rare due to diligent 

watches for marine mammals on the support vessels as mandated by NTL 2002-G14. Conclusive 

evidence is lacking as to whether anthropogenic noise has or has not caused long-term displacements of, 

or reductions in, marine mammal populations. Obstacles posed by underwater structures and the 

consequences that may have on marine mammals are unknown. Contaminants in waste discharges and 

drilling muds might indirectly affect marine mammals through food-chain involvement. Hydrocarbon 

spills in the area could impact marine mammals. The spill’s magnitude and fate would determine the 

species and numbers of animals impacted. Spills and spill-response activities in Grid 16 may temporarily 

displace marine mammals, such as the endangered sperm whale, from important foraging, nursery, and/or 

mating habitat. 

4.2.4. Impacts on Sea Turtles 

As stated in the above section, multiple vessel trips per week are expected during the lifetime of the 

Thunder Horse project. During installation operations, dozens of other support vessels will be used. 

Transportation corridors will be through areas where Kemp’s ridley, green, loggerhead, and leatherback 

sea turtles have been sighted. Multiple helicopter trips per week are also expected. Noise from supportvessel traffic and helicopter overflights may elicit a startle reaction from sea turtles and there is the 

possibility of short-term disruption of activity patterns. Sounds from approaching aircraft are detectable 

in the air far earlier than in water. There are no systematic studies published concerning the reactions of 

sea turtles to aircraft overflights, and anecdotal reports are scarce. It is assumed that aircraft noise could 

be heard by a sea turtle at or near the surface and may cause it to alter its activity (Advanced Research 

Projects Agency, 1995). In the wild, most sea turtles spend at least 3-6 percent of their time at the 

surface. Despite the brevity of their respiratory phases, sea turtles sometimes spend as much as 19-26 

percent of their time at the surface engaged in surface basking, feeding, orientation, and mating 

(Lutcavage et al., 1997). Sea turtles located in shallower waters have shorter surface intervals, whereas 

turtles occurring in deeper waters have longer surface intervals. Sea turtles exposed to recurring vessel 

disturbance could be stressed or otherwise affected in a negative but inconspicuous way. As other blocks 

in Grid 16 are developed, the increased vessel traffic would elevate the probability of collisions between 

vessels and turtles, potentially resulting in injury or death to some animals. The MMS’s NTL 2002-G14 

is designed to mitigate vessel/animal collisions. 

Activities associated with the Thunder Horse project could generate sounds at intensities and 

frequencies that could be heard by turtles. There is evidence suggesting that turtles may be receptive to 

low-frequency sounds, which is at the level where most industrial noise energy is concentrated. Potential 

effects on turtles include disturbance (subtle changes in behavior and interruption of activity), masking of 

other sounds (e.g., surf, predators, vessels), and stress (physiological). Such noise is expected to have 

sublethal effects on sea turtles. 

Many types of materials, including plastics, are used during development and production operations. 

Some of this material could be accidentally lost overboard where sea turtles can consume it. The result of 

ingesting materials lost overboard could be lethal. Leatherback turtles (a species known to inhabit Grid 
50 

16) do mistake plastics for jellyfish and may be more vulnerable to gastrointestinal blockage than other 

sea turtle species. Sea turtles could also become entangled in debris lost by vessels or platforms 

associated with the Thunder Horse project. The MMS’s NTL 2002-G13 will help mitigate some of these 

concerns. As more blocks are developed in the Grid 16 area, the probability of OCS-related flotsam in 

the area would increase. More flotsam increases the risks to sea turtles. 

Some effluents will be discharged into offshore marine waters as a result of the Thunder Horse 

project and will be regulated by USEPA NPDES permit. BP has chosen to reinject its produced water 

from the project, thereby substantially reducing its operational discharges. Turtles may have some 

interaction with other discharges from the project. Very little information exists on the impact of drilling 

fluids on Gulf sea turtles (Tucker and Associates, Inc., 1990). Exposure to these discharges could result 

in sublethal effects to subadult and adult sea turtles. However, hatchling and young juveniles exposed to 

these discharges may be more susceptible to adverse effects. The proposed use of synthetic-based drilling 

fluids in the Thunder Horse project would reduce the toxicity, and subsequently the potential for injury or 

death, to sea turtles and/or their prey. 

Little or no damage is expected to the physical integrity, species diversity, or biological productivity 

of live-bottom habitat utilized by sea turtles as a result of the proposed action unless a spill occurs that 

impacts these areas. Since sea turtle habitat in the Gulf includes inshore, neritic, and oceanic waters, as 

well as numerous beaches in the region, sea turtles could be impacted by accidental spills resulting from 

operations associated with the proposed action. 

A spill of the magnitude calculated under a worst-case scenario could result in negative impacts to 

any of the five sea turtle species inhabiting the Gulf. The expected impacts from a large spill would 

involve the oiling of animals and prey, and probable displacement from the impacted area. Historically, 

the majority of spills are small, less than a barrel, and do not pose a significant threat to sea turtles. 

A large, persistent spill in oceanic waters could have an impact on any hatchling or juvenile sea 

turtles that it contacts. All neonate sea turtles undertake a passive voyage via oceanic waters following 

nest evacuation. Depending on the species and population, their voyage in oceanic waters may last 10 or 

more years. Beaches of the Gulf and the Caribbean Sea are used as nesting habitat, and hatchlings 

evacuating these nesting beaches emigrate to oceanic waters seaward of their nesting sites. Surface drifter 

card data (Lugo-Fernandez et al., 2001) indicate that circulation patterns in the Caribbean Sea and 

southern GOM may transport neonate and young juvenile sea turtles from these areas to oceanic waters 

off the coasts of Texas and Louisiana. Moreover, these journeys begin as pulsed events, with many 

hatchlings emerging and emigrating offshore at the same times. Consequently, if an oil spill occurred in 

Grid 16, timing could be a significant factor. A spill that coincided with a pulsed hatchling event could 

impact multiple turtles, particularly neonate or young juvenile sea turtles associating with oceanic fronts 

or refuging in sargassum mats where oil slicks, decomposing residues, and tarballs are likely to 

accumulate. Oceanic waters of the GOM (including those of Grid 16) are also inhabited by subadult and 

adult leatherback and loggerhead sea turtles; however, adults of any endemic sea turtle species may be 

found offshore. Sea turtles (and most notably hatchlings and juveniles) coming into contact with the spill 

could suffer sublethal leading to lethal (over time) exposure. Aggregations of sea turtles may be exposed 

in one spill event. Prey species may be negatively impacted, thereby impacting sea turtles that would 

otherwise feed on them. Turtles may be temporarily displaced from the impacted areas. The magnitude 

of impacts to sea turtles would depend upon the oils that they are exposed to, their concentrations, and the 

period of exposure. 

Spill-response activities could also disrupt normal behavioral activities of sea turtles in the area and 

cause animals to temporarily vacate the spill-response area. 

Conclusion 

Routine activities resulting from the Thunder Horse project have the potential to harm sea turtles or 

temporarily displace them from important habitat areas. These animals could be impacted by the 

degradation of water quality resulting from operational discharges; noise generated by helicopter and 

vessel traffic, platforms, and drillships; brightly-lit platforms; vessel collisions; and jetsam and flotsam 

generated by service vessels and OCS facilities. Collisions with OCS service vessels and ingestion of 

plastic materials have the potential to cause lethal effects. However, most Thunder Horse project impacts 

are expected to have sublethal effects. Contaminants in waste discharges and drilling fluids might 
51 

indirectly affect sea turtles through food-chain effects. Routine activities associated with the Thunder 

Horse project are unlikely to have significant adverse effects on the size and recovery of any sea turtle 

species or population in the GOM. 

Oil spills are accidental events. Populations of sea turtles in the northern Gulf may be exposed to 

residuals of oil spilled and attributed to the proposed action during their lifetimes. Chronic or acute 

exposure has the potential to debilitate or kill sea turtles. In most foreseeable cases, exposure to spilled 

hydrocarbons persisting in the sea following the dispersal of an oil slick would result in sublethal impacts 

(e.g., decreased health, reproductive fitness, and longevity; and increased vulnerability to disease) to sea 

turtles. Sea turtle hatchlings exposed to and becoming fouled by spilled oil or consuming associated 

tarballs persisting in the sea following the dispersal of an oil slick have the greatest risks from a spill. 

4.2.5. Impacts on Coastal and Marine Birds 

4.2.5.1. Nonthreatened and Nonendangered Birds 

This section discusses the possible effects of the proposed action on coastal and marine birds of the 

GOM and its contiguous waters and wetlands. Air emissions, water quality degradation resulting from 

discharges, helicopter and service-vessel traffic and noise, light attraction, and discarded trash and debris 

from service vessels and platforms could impact coastal and marine birds. Associated spill-response 

activities may also impact coastal and marine birds. Any effects would be especially critical for 

intensively managed populations such as endangered and threatened species that need to maintain a viable 

reproductive population size or that depend upon a few key habitats. Emissions of pollutants into the 

atmosphere from activities associated with the proposed action are expected to have minimal effects on 

offshore air quality because of the prevailing atmospheric conditions, emission heights, and pollutant 

concentrations. Such emissions are expected to have negligible effects on onshore air quality because of 

the atmospheric regime, emission rates, and distance of these emissions from the coastline. These 

judgments are based on average steady state conditions; however, there will be days of low mixing 

heights and low wind speeds that could decrease air quality. These conditions are characterized by fog 

formation, which in the Gulf occurs mostly during winter. However, impacts from offshore sources are 

reduced in winter because the frequency of significant onshore winds decreases (25%) and the removal of 

pollutants by rain increases. The summer is more conducive to air quality effects as onshore winds occur 

more frequently, approximately 50 percent of the time. 

Helicopter and service-vessel traffic related to the proposed action could sporadically disturb feeding, 

resting, or nesting behavior of birds or cause abandonment of preferred habitat. These impact-producing 

factors could contribute to indirect population loss through reproductive failure resulting from nest 

abandonment. The FAA (Advisory Circular 91-36C) and corporate helicopter policy state that, when 

flying over land, the specified minimum altitude is 610 m (2,000 ft) over populated areas and biologically 

sensitive areas such as wildlife refuges and national parks. However, pilots traditionally have taken great 

pride in not disturbing birds. It is expected that approximately 10 percent of helicopter trips would occur 

at altitudes somewhat below the minimums listed above as a result of inclement weather or emergency 

situations. Although these incidents are only seconds in duration and sporadic in frequency, they can 

disrupt coastal bird behavior and, at worst, possibly result in habitat or nest abandonment. 

Service vessels would use selected nearshore and coastal (inland) navigation waterways, or corridors, 

and adhere to protocol established by the USCG for reduced vessel speeds within these inland areas. 

Routine presence and low speeds of service vessels within these waterways would diminish the effects of 

disturbance from service vessels on nearshore and inland populations of coastal and marine birds. 

Therefore, the effects of routine service-vessel traffic on birds offshore would be negligible. 

Seabirds (e.g., laughing gulls and petrels) may be attracted by lights and/or structures and may remain 

and feed in the vicinity of the PDQ. Operational discharges or runoff in the offshore environment could 

affect these individuals. Impacts may be both direct and indirect. 

Coastal and marine birds are commonly observed entangled and snared in discarded trash and debris. 

In addition, many species ingest small plastic debris, either intentionally or incidentally. Such 

interactions can lead to serious injury and death. The MMS prohibits the disposal of equipment, 

containers, and other materials into offshore waters by lessees (30 CFR 250.300) and NTL 2002-G13. 

Thus, it is expected that coastal and marine birds would seldom become entangled in or ingest OCS-
52 

related trash and debris. MARPOL (Annex V, Public Law 100-220; 101 Statute 1458; effective January 

1989) prohibits the disposal of any plastics at sea or in coastal waters. Thus, due to the low potential for 

interaction between coastal and marine birds and project-related debris, any effects would be negligible. 

A spill >1,000 bbl at the site of the proposed action would have a spill risk for contacting the 

shoreline of 0.5 percent or greater only for Plaquemines Parish, Louisiana, (a 1% risk was calculated) and 

various birds along the coast could experience mortality and reproductive losses should a spill of that size 

occur. Recovery would depend on subsequent influxes of birds from nearby feeding, roosting, and 

nesting habitats. 

Oil-spill cleanup methods often require heavy traffic on beaches and wetland areas, application of oil 

dispersants and bioremediation chemicals, and the distribution and collection of oil containment booms 

and absorbent material. The presence of humans, along with boats, aircraft, and equipment, could also 

disturb coastal birds after a spill. Investigations have shown that oil dispersant mixtures pose a threat to 

bird reproduction similar to that of oil (Albers, 1979; Albers and Gay, 1982). The external exposure of 

adult birds to oil/dispersant emulsions may reduce chick survival more than exposure to oil alone; 

however, successful dispersal of a spill would generally reduce the probability of exposure of coastal and 

marine birds to oil (Butler et al., 1988). It is possible that changes in the size of a breeding population 

may also be a result of disturbance from increased human activity related to cleanup, monitoring, and 

research efforts (Maccarone and Brzorad, 1994). A growing number of studies indicate that current 

rehabilitation techniques are not effective in returning healthy birds to the wild (Anderson et al., 1996; 

Boersma, 1995; Sharp, 1995 and 1996). Deterrent or preventative methods, such as scaring birds from 

the path of an approaching oil slick or the use of booms to protect sensitive colonies, have extremely 

limited applicability. 

4.2.5.2. Threatened and Endangered Birds 

Piping Plover 

The impacts on shorebirds not listed as endangered or threatened discussed above also apply to the 

piping plover. A spill of >1,000 bbl at the site of the proposed action would have a spill risk for 

contacting the shoreline of 0.5 percent for all Gulf Coast areas with one exception; Plaquemines Parish, 

Louisiana, that has a spill risk of 1 percent. Birds along the coast could experience mortality and 

reproductive losses. Recovery would depend on subsequent influxes of birds from nearby feeding and 

roosting habitats. 

Bald Eagle 

The bald eagle feeds on fish, waterfowl, shorebirds, and carrion near water. This bird may come in 

contact with an oil spill by eating contaminated dead and dying prey. Bald eagles have narrow 

preferences for nesting habitat. Any oiling of aquatic feeding habitat resulting in nest site abandonment 

could lead to relocation of a nest to less preferred habitat. This event in turn would reduce population 

growth for this already threatened species. However, the bald eagle has high mobility and, when an oil 

slick enters the feeding habitat, may relocate feeding to unpolluted waters. When relocating feeding far 

from the nest, the eagle would successfully home to its nest after feeding because it prefers to build its 

nest in a highly visible place over the forest canopy with a clear short path from the water. 

Brown Pelican 

The brown pelican is a species of special concern in Louisiana and Mississippi although it is no 

longer listed as endangered or threatened in Florida or Alabama (USDOI, FWS, 1998). It is known to 

nest on Guillard Island, Alabama, a dredged material disposal island in Mobile Bay. There have been no 

reported nesting sites in Mississippi. Impacts to individual brown pelicans would be similar to those 

identified for the nonendangered and nonthreatened species discussed in preceding sections. 
53 

Conclusion 

It is expected that the majority of effects from the major impact-producing factors on coastal and 

marine birds would be sublethal (behavioral effects and nonfatal intakes of discarded debris), causing 

temporary disturbance and displacement of localized groups, mostly in inshore areas. However, chronic 

stress such as digestive upset, partial digestive occlusion, sublethal ingestion, and behavioral changes are 

often difficult to detect. Such stresses can weaken individuals and make them more susceptible to 

infection and disease as well as making migratory species less fit for migration. A spill of >1,000 bbl at 

an offshore well site would have a spill risk for contacting the shoreline of 0.5 percent for all Gulf Coast 

areas with one exception; Plaquemines Parish, Louisiana, where a spill risk of 1 percent is calculated, and 

birds along the coast could experience mortality and reproductive losses, if the spill occurred. Recovery 

would depend on subsequent influxes of birds from nearby feeding, roosting, and nesting habitats. 

4.2.6. Impacts on Fish Resources 

4.2.6.1. Essential Fish Habitat and Fish Resources 

Development activities that have the potential to affect fish and essential fish habitat (EFH) include 

discharge of muds and cuttings, and installation/construction effects on water quality. Production 

activities that may affect fish are those primarily associated with the “artificial reef effect.” 

Drill cuttings with mud adhering to them would be discharged to the water column at the well sites 

and may contain some contaminant metals. Toxicity as well as cadmium and mercury in barite limits are 

set in the Gulf’s general offshore NPDES permit (GMG290000). Contaminant levels, however, would 

reach background levels about 1,000 m (3,281 ft) from the discharge area and would be undetectable 

beyond 3,000 m (9,843 ft) from the site (USDOI, MMS, 2000). The SBF’s are virtually nontoxic, and 

cuttings with adherent SBF are expected to reach the seabed quickly in the form of clumps. Biological 

effects on the benthos are not expected beyond 500 m (1,640 ft) (Jensen et al., 1999). Numerous studies 

have demonstrated that mercury impurities associated with drilling mud barite are virtually not capable of 

being taken up by marine organisms that might come in contact with discharged drilling fluid solids 

(Neff, 1989). 

Accidental oil spills or blowouts also have the potential to affect fish resources. Adult fish will, for 

the most part, avoid the oil (Malins et al., 1982; NRC, 1985; Baker et al., 1991; USDOI, MMS, 2000). 

Farr et al. (1995) reported the behavioral avoidance of dissolved concentrations of a polynuclear aromatic 

hydrocarbon (PAH) as low as 14.7 μg/l by a species of minnow. Furthermore, adult fish must become 

exposed to crude oil for some time, probably on the order of several months for doses and types of oil to 

be encountered in the field, to suffer serious biological damage (Payne et al., 1988). Adult fish also 

possess some capability for metabolizing oil (Spies et al., 1982). 

On the other hand, invertebrate and fish eggs and larvae are known to be very sensitive to oil in water 

(Linden et al., 1979; Longwell, 1977; Baker et al., 1991). However, most fish species produce very large 

numbers of eggs, and larvae spread over wide areas. In order for an oil spill to affect fish resources at the 

population level, it would have to be very large and cover a very large area that corresponded to an area 

of highly concentrated eggs and larvae. In addition, the oil would have to disperse deep enough into the 

water column at levels high enough to cause toxic effects. None of these events would seem likely, even 

in the low-risk, large-spill scenario. However, it should be noted that the use of dispersants, while 

potentially beneficial for surface-using birds, turtles, and mammals, could increase the effects on water 

column organisms including ichthyoplankton. A worst case, in terms of location, would be a spill of 

fresh oil in a shallow, enclosed bay that contained eggs and larvae of important inshore species such as 

menhaden, shrimp, or blue crabs. Oil from the hypothetical offshore blowout would be well weathered 

before it hit shore, if it occurred. In addition, spawning areas of most species of marine fish are 

widespread enough to avoid catastrophic effects at the population level. 

The spill risk (the probability of a spill >1,000 bbl occurring and contacting specific areas) is less than 

0.5 percent for all Gulf Coast areas with one exception; Plaquemines Parish, Louisiana has a spill risk of 1 

percent. 
54 

Conclusion 

The PDQ and its risers are expected to attract a variety of fish species for food and cover. 

Impacts on demersal fish from drilling activities would be negligible. There are no commerciallyvaluable demersal fish species in the area, and effects on bottom fish habitat from cuttings and adherent 

SBF’s would likely be limited to within 500 m (1,640 ft) of the discharge. 

Specific effects from oil spills would depend on several factors including timing, location, volume 

and type of oil, environmental conditions, and countermeasures used. The areas affected by the potential 

spill or blowout scenario would be avoided by adult fish. Fish eggs and larvae of some species of 

invertebrates and fish would be affected by a spill and some would suffer mortality in areas where their 

numbers are concentrated in the upper few meters of water and where oil concentrations under the slick 

are high enough. However, oil and fish concentrations, exposure times, and the area affected would not 

be great enough to cause significant impacts to northern GOM fish populations. 

In summary, it is expected that marine environmental degradation from the proposed action would 

have little effect on fish resources or EFH. The level of marine environmental degradation from the 

Thunder Horse development is expected to cause a small, undetectable decrease in fish populations and 

EFH. 

4.2.6.2. Gulf Sturgeon 

The existing range of the Gulf sturgeon in 1996 extended from the Mississippi River to Charlotte 

Harbor in western Florida (Patrick, personal communication, 1996). Oil spills are the OCS-related factor 

with the most potential to impact the Gulf sturgeon. Gulf sturgeon can take up oil by direct ingestion, 

ingestion of oiled prey, or the absorption of dissolved petroleum products across gill mucus and gill 

epithelium. Upon any exposure to spilled oil, liver enzymes of adult fish oxidize soluble hydrocarbons 

into compounds that are easily excreted in the urine (Spies et al., 1982). Behavior studies of other fish 

species suggest that adult sturgeon are likely to actively avoid an oil spill, thereby limiting the effects and 

lessening the extent of damage (Baker et al., 1991; Malins et al., 1982). In adult Gulf sturgeon, contact 

with or ingestion/absorption of spilled oil could most likely result in nonfatal physiological irritation, 

especially of gill epithelium and the liver. 

Conclusion

The potential exists that Gulf sturgeon could be impacted by oil spills resulting from the proposed 

action. These impacts could cause nonfatal irritation of gill epithelium or liver tissue in a few adults. 

4.3. SOCIOECONOMIC CONDITIONS AND OTHER CONCERNS

4.3.1. Impacts on Economic and Demographic Conditions 

The MMS defined the potential impact region as that portion of the GOM coastal zone whose social 

and economic well-being (population, labor, and employment) is directly or indirectly affected by the 

OCS oil and gas industry. In this section, the MMS projects how and where future changes may occur as 

they correlate with the proposed action and to possible future development within Grid 16. 

4.3.1.1. Population and Education 

The impact region’s population will continue to grow but at a slower rate. Minimal effects on 

population are projected from activities associated with the proposed action and future actions. While 

some of the labor force is expected to be local to the Port Fourchon and Venice, Louisiana, areas, most of 

the additional employees associated with the proposed action are not expected to require local housing. 

Activities related to the proposed activity and future activities are not expected to significantly affect the 

region’s educational level. 
55 

Conclusion 

Activities related to the proposed activity and future activities in Grid 16 are not expected to 

significantly affect the region’s population or educational level. 

 4.3.1.2. Infrastructure and Land Use 

While OCS-related servicing should increase in Port Fourchon, Louisiana, no expansion of these 

physical facilities is expected to result from the proposed activities. Changes in land use throughout the 

region as a result of the proposed and future activities in Grid 16 are expected to be contained and 

minimal. While land use in the impact area will change over time, the majority of this change is 

estimated as general regional growth. Increased OCS deepwater activities are expected to impact Port 

Fourchon and other OCS ports with deepwater capability. The proposed activity is not expected to cause 

expansion to the Port Fourchon support base that BP plans to use as its primary onshore base. 

Conclusion 

The proposed action and future development in Grid 16 are not expected to significantly affect the 

region’s infrastructure or land use. 

4.3.1.3. Navigation and Port Usage 

The proposed action would use the existing onshore support base located in Port Fourchon for 

completion, facility installation, commissioning, and production activities. During construction activities, 

the following round trips are planned for service vessels: 2 for manifold installation, 1 for flowline 

installation, 2 for jumper installation, 4 for umbilical installation support, 13 for large supply items, 14 for 

tug boats, 11 for large freight items, 1 for infield riser installation, and 2 for dive support. During drilling 

and completion activities, 4 round trips for workboats and 6 round trips for crew boats per week are 

expected. During production operations, 3 round trips for workboats and 4 round trip for crew boats per 

week are anticipated. Port Fourchon is capable of providing the services necessary for the proposed 

activities; therefore, no onshore expansion or construction is anticipated with respect to the proposed 

action. 

BP plans to use the Venice shore base facility as its backup base. Both of these shore bases are 

preexisting onshore support facilities and operate 24 hours per day. A small amount of vessel and 

helicopter traffic may originate from bases other than Port Fourchon or Venice in order to address 

changes in weather, market, and operational conditions. 

Conclusion 

No impacts to navigation and port usage are expected as result of this proposed action. 

4.3.1.4. Employment 

The importance of the oil and gas industry to the coastal communities of the GOM is significant, 

particularly in Louisiana, eastern Texas, and coastal Alabama. Dramatic changes in the level of OCS oil 

and gas activities over recent years have resulted in similar fluctuations in population, labor, and 

employment in the GOM region. This economic analysis focuses on the potential direct, indirect, and 

induced impacts of the OCS oil and gas industry on the population and employment of the counties and 

parishes in the impacted region. 

To improve regional economic impact assessments and to make them more consistent with each 

other, the MMS recently developed a methodology for estimating changes to employment and other 

economic factors. The methodology developed to quantify these impacts on population and employment 

takes into account changes in OCS-related employment, along with population impacts resulting from 

these employment changes within each individual coastal subarea. 

The model for the GOM region has two steps. Since there are no publicly available models that 

estimate the expenditures resulting from offshore oil and gas activities, the first step in the model 
56 

estimates the expenditures resulting from BP’s Initial DOCD (for the construction and deployment of the 

semisubmersible PDQ structure, the drilling of 17 producing and 10 water injector wells and 16 recompletions and 16 sidetracks in mid to late life of the proposal) and assigns these expenditures to 

industrial sectors in the 10 MMS coastal subareas defined in Chapter 3. A contracted effort, “Modeling 

the Economic Impacts of Offshore Oil and Gas Activities in the Gulf of Mexico: Methods and 

Applications,” was used for this. The second step in the model uses multipliers from the commercial 

input-output model IMPLAN (using the latest available data, 1999) to translate these expenditures into 

direct, indirect, and induced employment and other economic factors. Direct employment results from 

the first round of industry spending. It is the employment that results from the initial dollars spent by BP 

on the PDQ and development wells from their fabrication/installation or completion through their 

productive lives. Indirect employment results as the initial spending reverberates through the economy. 

First, the suppliers of the goods and services for the PDQ and wells spend the initial direct dollars from 

the industry. Then, these dollars are re-spent by other suppliers until the initial dollars have trickled 

throughout the economy. Labor income produces induced spending by the households receiving that 

income. 

Both the level (the amount spent) and the sectoral (the industry in which it is spent) allocations of 

expenditures can vary considerably. Since local economies vary, a separate set of IMPLAN multipliers is 

used for each MMS coastal subarea to which expenditures are assigned. Each set of multipliers is based 

on the actual historical patterns of economic transactions in the area. Model results for employment are 

presented in number of jobs per year, where one job is defined as a year of employment. This does not 

necessarily mean only one person occupies the position throughout the year. One job may be equal to 

two part-time positions occupied over the year or one person occupying a position for 6 months, while 

another person occupies it for the other 6 months. 

Table E-4 (in Appendix E) shows total employment projections for activities resulting from the 

proposed action for the peak year of 2004. The projections are expressed as absolute numbers and as a 

percentage of the employment levels expected if no development occurs. The baseline projections of 

employment used in this analysis are described in Chapter 3 and Table E-5 (Appendix E). Since these 

baseline projections assume the continuation of existing social, economic, and technological trends, they 

also include employment resulting from the continuation of current patterns in OCS Program activities. 

Based on model results, peak-year (2004) direct employment associated with the proposed action is 

estimated at about 810 jobs. Indirect employment for the peak year is projected at about 290 jobs, while 

induced employment is calculated to be about 360 jobs. Although the majority of employment is 

expected to occur in coastal subarea TX-2, employment is not expected to exceed 1 percent of the total 

employment in any given subarea. Direct, indirect, and induced employment through the productive life 

of the proposal (that associated with drilling and/or completing additional development wells, operation 

and maintenance and workover activities) is expected at about 1,460 jobs per year throughout all subareas 

and should be less than 1 percent of total employment in any subarea. 

The resource costs of cleaning up an oil spill, both onshore and offshore, were not included in the 

above analysis for two reasons. First, oil-spill cleanup activities reflect the spill’s opportunity cost. In 

other words, some of the resources involved in the cleanup of an oil spill, in the absence of that spill, 

would have produced other goods and services (e.g., tourism activities). Secondly, the occurrence of a 

spill is not a certainty. Spills are random accidental events. Given that the PDQ is fabricated and 

installed and the development wells are completed as described in the initial DOCD, the timing, numbers, 

sizes, offshore locations of occurrence, and onshore locations of contact of potential spills occurring over 

the drilling life of the plan are all unknown variables. Appendix B discusses oil spills in general and the 

expected sizes, number, and probability of a spill from the proposed action. Additionally, the cost 

involved in any given cleanup effort is influenced by a variety of factors: whether or not the oil comes 

ashore; the type of coastal environment contacted by the spill; weather conditions at the time of the 

incident; the type and quantity of oil spilled; and the extent and duration of the oiling. Nevertheless, the 

same two-step model used above to project employment for the proposed action was applied to project the 

opportunity cost employment associated with cleaning up an oil spill. In this case, the first step 

considered estimates of the expenditures resulting from oil-spill cleanup activities should a worst-case 

blowout scenario spill occur. The second step incorporated the IMPLAN regional model multipliers to 

translate those expenditures into direct, indirect, and induced employment associated with oil-spill 

cleanup activities. The size of a scenario spill (on which model results are based) is assumed to be as 
57 

much as 141,000 bbl for an uncontrolled blowout. Based on model results, should such a spill occur, it is 

projected to cost about 4,800-11,200 person-years of employment for cleanup and remediation depending 

on whether some of the oil contacts land. Table E-5 (Appendix E) summarizes the direct, indirect, and 

induced opportunity cost employment (by subarea and planning area) for an oil-spill cleanup should such 

a spill occur. Employment impacts from the blowout scenario are expected to be minimal. These impacts 

combined with the employment projected for the proposed activities would only constitute less than 1 

percent of the total employment in any subarea. Employment associated with oil-spill cleanup is expected 

to be of short duration (less than 6 months), aside from employment associated with the legal aspects of a 

spill. 

Conclusion 

No significant impacts to employment, including those that could result from a blowout and related 

spill cleanup scenario, are expected as a result of this proposed action. 

4.3.2. Impacts on Environmental Justice 

Federal agencies are directed by Executive Order 12898 to assess whether their actions would have a 

disproportionate and negative effect on the environment and health of people of ethnic or racial minorities 

or those with low income. The existing onshore facilities that can support the projected deepwater 

developments within Grid 16 are well established along the Gulf Coast. 

Conclusion 

Since sufficient onshore facilities are available to support offshore activities in Grid 16, no effects to 

minorities or people with low incomes in the Gulf counties and parishes are expected. 

4.3.3. Impacts on Commercial Fisheries 

Little or no impact is expected on commercial fishermen from routine project activities. Offshore 

operators do not normally require a large exclusion area, although the USCG could designate and enforce 

an area of 500 m (1,640 ft) from structures, if requested or required. Only seven deepwater structures to 

date have established official safety zones. Also, these safety zones do not restrict vessels less than 30.5 

m (100 ft) in length. 

In the event of a spill, commercial fishermen would actively avoid the area of a spill and the area 

where there are ongoing activities to control a blowout and contain the spilled oil. Even if fish resources 

successfully avoid spills, tainting (oily-tasting fish), public perception of tainting, or the potential of 

tainting commercial catches from oil or dispersants would prevent fishermen (either voluntarily or 

imposed by regulation) from initiating activities in or near the spill area. This in turn could decrease 

landings and/or the value of catches for several months. However, GOM species can be found in many 

adjacent locations; Gulf commercial fishermen do not fish in one locale and have responded to past 

petroleum spills without discernible loss of catch or income by moving elsewhere for a few months. 

There are few new potential fisheries that could occur in the Thunder Horse project area. The most 

likely target species would be epipelagic species that are highly mobile and have the ability to avoid 

disturbed areas. This fishery is traditionally pursued using a highly mobile longliner fleet. This type of 

fishery is less vulnerable to disturbance or loss of fishing space than others, such as trap or bottom 

trawling fisheries. Desirable pelagic fish species may also be attracted to the Thunder Horse 

semisubmersible PDQ facility and could potentially improve commercial catches using fishing techniques 

other than longlining. 

Conclusion 

There would be some unavoidable loss of fishing space due to the physical presence of the 

development that could otherwise have been used for pelagic fishing such as longlining. This impact is 

not considered to be significant because the overall footprint of the development is not large compared to 

the total space available in the Gulf. A large oil spill might have commercial implications but, for the 
58 

most part, the Gulf fishing fleets are highly mobile and cover a wide area. In addition, there are no 

commercially important demersal species at the water depth of this grid. 

4.3.4. Impacts on Recreational Resources and Beach Use 

Millions of annual visitors attracted to the coast are responsible for thousands of local jobs and 

billions of dollars in regional economic activity. They also are responsible, in large part, for the trash and 

debris that litter coastal lands, leaving behind nearly 75 tons of trash per week (Ocean Conservancy, 

2001). Other sources of coastal trash are debris and small leaks from staffed structures in State and 

Federal waters where hydrocarbons are exploited, commercial shrimping and fishing, runoff from storm 

drains, antiquated storm and sewage systems in older cities, and commercial and recreational fishermen 

who discard plastics. In 1996, the U.S. National Park Service finished a study on the origins of marine 

debris on South Padre Island in Texas. They tentatively identified about 13 percent of the 63,000+ items 

collected as being associated with the offshore oil and gas industry (Miller and Echols, 1996:8+). 

In September 2001, the USEPA published its comprehensive National Coastal Condition Report. For 

5 years, USEPA scientists sampled, collected, and analyzed data on the health of coastal habitats, 

especially estuaries. They found that the overall condition of the Gulf of Mexico is poor according to the 

rankings of water clarity (fair), dissolved oxygen (good), and coastal wetland loss, eutrophic condition, 

sedimentation, benthos, and fish tissue (all of which ranked poor (USEPA, 2001). 

Unfortunately, we do not know the specific sources of all the debris and degradation along the Gulf 

coastline; annual “beach sweeps” and the resulting cleanup totals include all coastal beaches – river, lake, 

and sea – and adjacent waters. The deltas and basins of the Mississippi-Atchafalaya and Mobile Rivers 

drain at least 50 percent of the land area of the central and eastern United States. 

Conclusion 

The risk of a large oil spill occurring due to the proposed development operations in Grid 16 is very 

small. In the event such a spill did occur, according to trajectory analysis from the OSRA model, there is 

a negligible chance that the spill would contact land within 30 days of a spill. Project aircraft will 

normally be flying high enough to avoid disturbance to beachgoers. 

BP has an established waste management plan for all of their offshore operations. While some 

accidental loss of solid wastes may occur from time to time, it is expected to have a negligible impact on 

recreational resources. 

4.3.5. Impacts on Archaeological Resources 

4.3.5.1. Prehistoric 

The blocks that compose the Thunder Horse project in Grid 16 (Mississippi Canyon, Blocks 775, 776, 

777, 778, 819, 820, 821, and 822) are not specifically located within either of the MMS's designated highprobability areas for the occurrence of prehistoric or historic archaeological resources. Lease blocks with 

a high probability for prehistoric archaeological resources may only be found landward of a line that 

roughly follows the 60-m (197-ft) bathymetric contour. The MMS recognizes both the 12,000 B.P. date 

and 60-m (197 ft) water depth as the seaward extant of prehistoric archaeological potential on the OCS. 

The average water depth of the Grid 16 area is approximately 1,800 m (5,906 ft). Therefore, the water 

depth is approximately 1,740 m deeper than the earliest known prehistoric archaeological sites in the Gulf 

of Mexico area. Based on the extreme water depth of the grid, there is simply no potential for prehistoric 

archaeological resources in the area. Therefore, any oil and gas development directly associated with the 

Thunder Horse project or within Grid 16 cannot possibly impact prehistoric archaeological resources in 

that block. 

Conclusion 

Based on the extreme water depth of the Thunder Horse project and the Grid 16 area, the proposed oil 

or gas development will not impact any prehistoric archaeological resources. 
59 

4.3.5.2. Historic 

There are areas of the northern Gulf of Mexico that are considered to have a high probability for 

historic period shipwrecks, as defined by two MMS-funded studies and shipwreck models (Garrison et 

al., 1989 and Pearson et al., 2002). These studies refined and expanded the MMS’s shipwreck database in 

the Gulf of Mexico and list about 2,100 wrecks. Statistical analysis of the shipwreck location data 

identified two specific types of high-probability areas -- the first within 10 km (6 mi) of the shoreline, and 

the second proximal to historic ports, barrier islands, and other loss traps. The MMS created highprobability search polygons associated with individual shipwrecks to afford protection to wrecks located 

outside the two aforementioned high-probability areas. 

An archaeological resources stipulation was included in all Gulf of Mexico lease sales from 1974 

through 1994. The language of the stipulation was incorporated into the MMS’s operating regulations on 

November 21, 1994, with few changes. All of the stipulation’s protective measures were adopted in the 

regulations. 

The MMS’s Regional Director of the GOM signed NTL 2002-G01 on December 15, 2001. It 

supersedes all other archaeological NTL’s and LTL’s. This new NTL makes minor technical 

amendments, updates cited regulatory authorities, and continues to mandate a 50-m (164-ft) remotesensing survey line spacing density for historic shipwreck surveys in water depths of 60 m (197 ft) or less. 

The NTL also requires submission of an increased amount of magnetometer data to facilitate the MMS’s 

analyses. Survey and report requirements for prehistoric sites have not been changed. 

Several OCS-related, impact-producing factors may cause adverse impacts to unknown historic 

archaeological resources. Offshore development activities that could result in impacts to an unknown 

historic shipwreck include drilling rig and platform installations (and anchoring associated with the 

installations), activities requiring derrick barges, and pipeline activities. 

Direct physical contact with a shipwreck site could destroy fragile ship remains, such as the hull and 

wooden or ceramic artifacts, and could disturb the site context. The result would be the loss of 

archaeological data on ship construction, cargo, and the social organization of the vessel's crew, and the 

concomitant loss of information on maritime culture for the time period from which the ship dates. 

The proposed action includes the emplacement of two mobile drilling units, the Ocean Confidence

and Discoverer Enterprise. The Ocean Confidence is self-propelled semisubmersible that can either be 

dynamically-positioned or moored. For this DOCD’s proposed action, the rig will be dynamically 

positioned. If BP decides to moor the rig at a later date, they will be required to submit data regarding 

areas that may be disturbed by the rig’s anchors and that portion of the mooring lines that would rest on 

the sea bottom. An archaeological evaluation of these areas will be required prior to installing the 

mooring system. BP also plans to use the Discoverer Enterprise, a dynamically-positioned drillship and 

to install a floating semisubmersible PDQ structure in Mississippi Canyon, Block 778. The anchors 

associated with the PDQ facility have the potential to cause physical impact to historic archaeological 

resources on the seafloor. Based on the plan submitted by the applicant, the manned PDQ floating 

production facility will be permanently anchored with a taut-leg, catenary mooring system consisting of 

conventional wire and chain and anchor piles. Emplacement of the anchor piles and the seafloor contact 

of the wire rope and chain catenary would directly disturb an area of approximately 3.5 ha per pattern. 

Components of a derrick barge’s mooring system would directly disturb approximately 1.9 ha of the 

seafloor at each anchor point. Pile driving associated with the structure emplacement may also cause 

sediment liquefaction an unknown distance from the piling, disrupting upper seafloor stratigraphy in the 

area of liquefaction. 

Pipeline installations also have the potential to cause a physical impact to historic archaeological 

resources. For example, an 8-in pipeline that was installed in March 2001 was laid across an historic 

shipwreck. The water depth was approximately 808 m (2,651 ft). 

Oil spills have the potential to affect historic archaeological resources. Impacts to historic resources 

would be limited to visual impacts and, possibly, to physical impacts associated with spill cleanup 

operations. Offshore operations may also generate tons of ferromagnetic structures and debris, which will 

tend to mask magnetic signatures of significant historic archaeological resources during magnetometer 

surveys. The task of locating historic resources via an archaeological survey is, therefore, made more 

difficult as a result of operational activities. 
60 

The specific locations of archaeological sites cannot be identified without first conducting a remotesensing survey of the seabed and near-surface sediments. The MMS, by virtue of its operational 

regulations under 30 CFR 250.196, requires that an archaeological survey be conducted prior to 

development of leases within the high-probability zones for historic and prehistoric archaeological 

resources. There are approximately 29 lease blocks within the Grid 16 area that falls within the MMS’s 

high-probability shipwreck zone. However, none of the blocks located within the Thunder Horse project 

are located within this zone. In addition, a review of the geophysical report submitted by BP indicated 

that no seafloor features suggestive of historic shipwrecks were recorded during the side-scan sonar 

surveys. Therefore, the aforementioned survey requirement reduces the potential for an impact to occur 

to an historic archaeological resource by an estimated 90 percent. 

Ferromagnetic debris associated with development and production activities has the potential to mask 

the magnetic signatures of historic shipwrecks. It is expected that most ferromagnetic debris associated 

with the proposed action would be removed from the seafloor during the required postlease site clearance 

and verification procedures. Site clearance, however, takes place after the useful life of the structure is 

complete. Therefore, there remains the potential for masking the signatures of historic shipwrecks as a 

result of ferromagnetic debris from OCS oil and natural gas activities. 

Onshore historic properties include sites, structures, and objects such as historic buildings, forts, 

lighthouses, homesteads, cemeteries, and battlefields. Sites already listed on the National Register of 

Historic Places and those considered eligible for the National Register have already been evaluated as 

being able to make a unique or significant contribution to science. At present, unidentified historic sites 

may contain unique historic information and would have to be assessed after discovery to determine the 

importance of the data. 

Onshore development in support of the proposed action, such as construction of new onshore 

facilities or pipelines, could result in the direct physical impact to previously unidentified historic sites. 

This direct physical contact with an historic site could cause physical damage to, or complete destruction 

of, information on the history of the region and the Nation. Each facility constructed must receive 

approval from the pertinent Federal, State, county/parish, and/or community involved. Protection of 

archaeological resources in these cases is expected to be achieved through the various approval processes 

involved. There is, therefore, no expected impact to onshore historic sites from any onshore development 

in support of the proposed action or for future Grid 16 activities. 

Should an oil spill contact a coastal historic site, such as a fort or a lighthouse, the major impact 

would be visual from petroleum contamination of the site and its environment. Impacts to coastal historic 

sites are expected to be temporary and reversible. 

The greatest potential impact to a historic shipwreck as a result of the proposed action would result 

from the emplacement of a derrick barge and its associated anchors and this vessel's support to the 

installation of the PDQ and associated semi-taut or catenary mooring system. The remote-sensing survey 

and archaeological clearance of sites required prior to an operator beginning oil and gas activities on a 

lease are estimated to be 90 percent effective at identifying possible historic shipwreck sites. Since the 

survey and clearance provide a significant reduction in the potential for a damaging interaction between 

an impact-producing factor and a historic shipwreck, there is a very small possibility of the proposed OCS 

activities impacting a historic site. 

According to Garrison et al. (1989) and Pearson et al. (2002), the shipwreck database lists 8 

shipwrecks and 29 high-probability shipwreck blocks that fall within the Grid 16 area. These shipwrecks 

are listed in Table 3-3. Six of these wrecks are 50 years or older and are eligible for listing in the 

National Register of Historic Places. 

Most other activities associated with the proposed action are not expected to impact historic 

archaeological resources. Ferromagnetic debris has the potential to mask the magnetic signatures of 

historic shipwrecks. It is expected that onshore archaeological resources would be protected through the 

review and approval processes of the various Federal, State, and local agencies involved in permitting 

onshore activities. There is a small chance of contact from an oil spill associated with the proposed 

action. Furthermore, the major impact from a spill contact on an historic coastal site, such as a fort or 

lighthouse, would be visual contamination. These impacts would be temporary and reversible. 
61 

Conclusion 

Oil and gas activities associated with the proposed development of the Thunder Horse project located 

within Grid 16 could impact an historic shipwreck because of incomplete knowledge on the location of 

shipwrecks in the Gulf. Although this occurrence is not probable, such an event would result in the 

disturbance or destruction of important historic archaeological information. Other factors associated with 

the proposed action are not expected to affect historic archaeological resources. 

4.4. CUMULATIVE EFFECTS

The MMS addressed the cumulative effects of OCS- and non-OCS-related activities for the CPA and 

the Gulf Coast region as part of the NEPA documentation completed for proposed multisale lease 

activities. The most recent Final EIS applicable to Grid 16 was prepared for Central GOM Lease Sales 

185, 190, 194, 198, and 201 (USDOI, MMS, 2002). This document provides additional information 

applicable to cumulative effects. Specific OCS-related effects from the proposed activities in Grid 16 and 

those related to the Thunder Horse project are addressed in Chapters 4.1-4.3. 

The following discussion provides a summary of cumulative effects for potentially affected resources 

in the CPA of the GOM. For all of the resources discussed below, the incremental contribution of the 

Thunder Horse project to cumulative impacts would be negligible. 

4.4.1. Water Quality 

4.4.1.1. Coastal 

Sources of contamination to coastal waters include large volumes of water entering the Gulf from 

rivers that drain over two-thirds of the contiguous U.S. (Bedinger, 1981; Brooks and Giammona, 1988), 

municipal and industrial point- and nonpoint-source discharges, and accidental spill events. 

Numerous industries and activities contribute to the contamination of Gulf coastal waters. These 

include the petrochemical industry (inclusive of oil and gas development and processing), agriculture, 

urban expansion, municipal and recreational sewerage treatment processes, marinas, commercial fishing, 

maritime shipping, hydromodification activities, forestry, recreational boating, livestock farming, 

manufacturing industry activities, nuclear power plant operations, and pulp and paper mills. Runoff, 

wastewater discharge, accidental spills, and atmospheric deposition from these sources will cause water 

quality changes that may result in nonattainment of Federal water quality standards for some coastal 

waters. Onshore service companies that support the OCS oil and gas industry will contribute to 

cumulative water quality degradation to a minor extent (less than 10%). Spill events from OCS-support 

operations are estimated to constitute about 10 percent of the total spills projected. Spills will result in 

degradation of water quality. Vessel traffic will degrade coastal water quality through routine releases of 

bilge and ballast waters, fuel and tank spills, trash, and domestic and sanitary discharges. The greatest 

impacts from vessel traffic will occur along navigation channels within highly populated, confined 

harbors and anchorages and boat yards due to increased biological oxygen demand (BOD) from sanitary 

and domestic waste discharges and the presence of other compounds used in boat servicing such as 

tributyltin in marine paints. 

Dredging to support coastal development, access for oil and gas activities in State waters, and 

pipeline emplacements are expected to continue to increase each year. Increased turbidity from these 

dredging operations and dumping of sediments into the coastal water will affect the water quality of the 

coastal area. 

Degradation of water quality from the inputs discussed above is expected to continue. The Gulf 

Coast has been heavily used and presently shows some signs of environmental stress. Large areas 

experience nutrient over-enrichment, low-dissolved oxygen, toxin and pesticide contamination, shellfish 

ground closures, and wetland loss. 
62 

4.4.1.2. Offshore 

Offshore sources of contaminants besides OCS oil and gas operations include marine transportation, 

commercial fishing, and natural hydrocarbon seeps. Contaminants released to coastal waters can also be 

transported to offshore marine waters. 

Spills of oil and other substances may occur from vessels transporting crude oil and petroleum 

products, from vessels transporting other products through Gulf waters between U.S. ports, from OCS oil 

and gas production operations, and from vessels associated with other offshore activity (marine 

transportation, recreational ships, etc.). Bottom area disturbances resulting from trawling, anchoring, 

facility and pipeline emplacement, and some well activities would increase water-column turbidity in the 

overlying offshore waters. The extent of anchoring by the maritime industry is not known. Sediment 

disturbance can also result in resuspension of accumulated pollutants (such as trace metals and 

chlorinated hydrocarbons) and nutrients. Bottom disturbances resulting from structure installation on the 

OCS have produced short-lived effects on water quality conditions in the immediate vicinity of the 

emplacement operations (Arthur D. Little, Inc., 1985). Should installation operations occur frequently 

and in proximity of each other, there would be an increased risk of water quality degradation. 

Certain types of blowouts can disturb the bottom and increase turbidity. Should one of these 

blowouts occur, localized, short-term changes in water quality would be expected. However, impacts to 

regional water quality would not be expected to be of consequence. 

Daily operational discharges to offshore waters occur from vessels moving through Gulf waters and 

from oil and gas drilling rigs and production facilities. Vessel traffic associated with the extensive 

maritime industry, oil and gas support operations, and recreational and commercial fishing operations 

routinely discharge contaminants including domestic and sanitary wastes and bilge and ballast waters into 

offshore waters. Bilge and ballast waters can contain petroleum and metallic compounds from incidental 

machinery leaks. Diluted and discharged slowly over large areas, vessel wastes are assumed to contribute 

in a very small way to the long-term, regional degradation of water quality. 

The discharge of drilling fluids, cuttings, and produced water accounts for the bulk of effluent 

volumes from oil and gas exploration, development, and production operations. Major contaminants in 

oil-field wastes can include high salinity and dissolved solids, low pH, high BOD and chemical oxygen 

demand (COD), suspended solids, heavy metals, hydrocarbon compounds, organic acids, priority 

pollutants, hazardous wastes, and radionuclides. The discharge of treated sanitary and domestic wastes 

from rigs and structures may increase suspended solids and nutrients in the receiving water that exert a 

high BOD. Very low levels of residual chlorine will be contained in the treated sanitary waste effluent 

and may affect a small area near the point of discharge. 

Numerous studies have examined the water quality impacts of OCS discharges (such as Avanti 

Corporation, 1993; CSA, 1997a and b; Kennicutt et al., 1995; Neff, 1997). These studies concluded that 

contaminants in produced water and drilling discharges should be undetectable in the water column 

beyond approximately 1,000 m (3,281 ft) from the discharge point. Sediment contamination from 

discharges is primarily dependent on the water depth and current speed. Sediment contaminants from 

OCS discharges may occur from several hundred to several thousand meters from the discharge point 

depending on the volume of discharges. Despite possible sediment accumulation, biological responses to 

contaminant levels retained by the sediments are not expected to be detectable beyond a couple hundred 

meters, and toxic effects to the benthos are expected to be very localized, limited to within a hundred 

meters from the discharge, and of a relatively small magnitude. Toxic effects beyond 100 m (381 ft) 

should be controlled through the USEPA’s NPDES permit requirements. 

Some information is available on the volumes of petroleum hydrocarbon compounds entering Gulf 

waters from various sources (USDOI, MMS, 1997). The OCS oil and gas industry contributes about 4 

percent of the Gulf's regional, long-term hydrocarbon contamination. Natural seepage accounts for 

approximately 27 percent of the total input. Natural hydrocarbon seeps have been documented in the 

deepwater area of the GOM (Brooks et al., 1986 a or b and 1990; USDOI, MMS, 1996). MacDonald et 

al. (1996) identified 63 oil slicks from one or more remote-sensing images. These seeps contribute 

soluble hydrocarbon components into the water column. Seepage of a selected area in the GOM was 

estimated from two images. The data suggest that the natural seepage is on the order of 4.3 x 103

 to 7.8 x 

104

 m3·y

-1 in the 8,200-km2

 image area and 1.1 x 104 to 4.8 x 105 m3·y

-1 in the 15,000-km2

 image area 

(USDOI, MMS, 1996). 
63 

Although the Gulf comprises one of the world's most prolific offshore oil-producing provinces, 

onshore sources of hydrocarbons to Gulf waters far outweigh the contributions from offshore production. 

Coastal sources contribute an order of magnitude more petroleum hydrocarbons to Gulf waters than 

offshore anthropogenic sources. 

Contaminants and high levels of nutrients found in land-based effluents and runoff have been 

identified as potential causes of hypoxia and, possibly, more frequent occurrence of red tide outbreaks. It 

is believed that hypoxia occurring in bottom waters in some areas of the open Gulf is caused by nutrient 

loading coming from the Mississippi River, combined with high summer temperatures, and/or 

phytoplankton blooms in surface waters (Rabalais, 1992). 

Information on elevated levels of contaminants of environmental concern measured in northern Gulf 

offshore waters was summarized by Kennicutt et al. (1988). Some areas within the Gulf (northern Texas 

coast, Louisiana, and Alabama) show signs of contamination. Volatile organic compounds (VOC’s) were 

generally present in the highest levels in coastal and nearshore waters, were highest near known onshore 

point-source discharges, and generally decreased with distance from shore. Chlorinated VOC’s were 

generally restricted to nearshore waters, whereas petroleum-related VOC’s were detected at offshore 

locations. The highest levels of petroleum hydrocarbons were measured near point sources in coastal 

environments and near natural seeps. Trace organochlorine residues appear to exist in many marine 

species. Higher concentrations of pollutants were generally found in organisms from the Mississippi 

Delta in comparison to offshore biota (Kennicutt et al., 1988). 

Gulf Coast States sample the edible tissue of estuarine and marine fish for total mercury. The results 

have been combined in a regional database, the Gulfwide Mercury in Tissue Database. All of the Gulf 

Coast States have published fish consumption advisories for large king mackerel (Ache et al., 2000). 

The Mississippi River will continue to be the major source of contamination of the Gulf. Over time, 

continuing coastal water quality contamination will degrade offshore water quality. As the assimilative 

capacity of coastal waters is exceeded, there will be a subsequent, gradual movement of the area of 

degraded waters farther offshore over time. This degradation will cause short-term loss of the designated 

uses of large areas of shallow offshore waters due to hypoxic and red tide episodes. 

4.4.2. Air Quality 

Effects on air quality within the study area will come primarily from industrial, power generation, and 

urban emissions. Most of the Gulf's coastal areas are currently designated as "attainment" for all the 

National Ambient Air Quality Standards-regulated pollutants. However, the USEPA has designated 

Lafourche Parish in Louisiana as an area of "nonattainment" for ground-level ozone (USEPA, 2001). 

4.4.3. Sensitive Coastal Environments 

4.4.3.1. Coastal Barrier Beaches and Associated Dunes 

Coastal barrier beaches have experienced severe erosion and landward retreat because of human 

activities and natural processes. These adverse effects on barrier beaches and associated dunes have come 

from changes to the natural dynamics of water and sediment flow along the coast. Examples of these 

activities include pipeline canals, channel stabilization structures, beach stabilization structures, 

recreational use of vehicles on dunes and beaches, recreational and commercial development, and 

removal of coastal vegetation. Human activities cause direct impacts as well as accelerate natural 

processes that deteriorate coastal barrier features. Natural processes that contribute to most effects 

include storms, subsidence, and sea-level rise acting upon shorelines with inadequate sand content and 

supply. 

Deterioration of Gulf barrier beaches is expected to continue in the future. Federal, State, and parish 

governments have made efforts over the last 10 years to slow beach erosion. 

4.4.3.2. Wetlands 

Wetland loss in the Deltaic Plain of coastal Louisiana is primarily due to subsidence, erosion, and 

reduced sediment input from the Mississippi River. The conversion of wetlands to agricultural, 

residential, and commercial uses has also been the major cause of wetland loss. Commercial uses include 
64 

dredging for both waterfront developments and coastal oil and gas activities. Wetland loss is projected to 

continue around the Gulf. 

4.4.3.3. Seagrasses 

Seagrasses are adversely affected by several human activities. These activities include changes to 

water quality resulting from riverine input, stream channelization, urban runoff, and industrial discharges; 

physical removal of plants by various forms of dredging, anchoring, and grounding of vessels; and severe 

storms. These impacts and the general decline of seagrasses are expected to continue into the near future. 

Various local, State, and Federal programs are focused upon reversing this trend. 

4.4.4. Deepwater Benthic Communities/Organisms 

4.4.4.1. Chemosynthetic Communities 

No impacts to chemosynthetic communities from non-OCS-related activities are expected. Normal 

fishing practices should not disturb these areas. Other bottom-disturbing activities such as trawling and 

anchoring are virtually nonexistent at water depths greater than 400 m (1,312 ft). 

Several pipelines are proposed with the Thunder Horse project. The pipeline applications will 

undergo individual chemosynthetic community evaluations. Mitigative measures may be included with 

these proposals to ensure dense chemosynthetic communities will not be impacted. 

The most se rious impact-producing factor that may affect deepwater benthos and sediment 

communities is the physical disturbance of the sea bottom. Impacts to deepwater communities in the Gulf 

of Mexico from sources other than OCS activities are considered negligible. Hypoxic conditions at the 

seafloor may affect the deepwater benthos and associated communities. 

4.4.4.2. Coral Reefs 

All of the recognized topographic features in the CPA are protected by "no activity zones" and by 

other operational restriction zones to minimize effects on associated coral reefs. Uncontrolled anchoring 

remains a threat to these areas. Increasing pressure is being exerted on these features from both 

commercial and recreational sources. 

4.4.4.3. Deepwater Benthos and Sediment Communities 

The most serious impact-producing factor that may affect deepwater benthos and sediment 

communities is the physical disturbance of the sea bottom. Within anchoring depths, marine 

transportation vessels may affect localized areas; however, the Grid 16 area is too deep for practical 

vessel anchoring. Hypoxic conditions at the seafloor may affect the deepwater benthos and associated 

communities. 

4.4.5. Marine Mammals 

Cumulative impacts to GOM marine mammals include the degradation of water quality resulting 

from operational discharges, vessel traffic, noise generated at offshore structures, MODU's, helicopters, 

seismic surveys, explosive structure removals, oil spills, oil-spill response activities, loss of debris from 

ocean-going vessels and OCS structures, commercial fishing (capture and removal), pathogens, and 

negative impacts to prey populations. Cumulative impacts on marine mammals are expected to result in a 

number of chronic and sporadic sublethal effects (behavioral effects and nonfatal exposure to or intake of 

non-OCS and OCS-related contaminants or discarded debris) that may stress and/or weaken individuals 

of a local group or population and predispose them to infection from natural or anthropogenic sources. 

Few deaths are expected from oil spills, chance collisions with OCS service vessels, ingestion of debris 

such as plastic material, commercial fishing, and pathogens. Oil spills and associated slicks of any size 

are infrequent events that have the potential to contact marine mammals. Serious injuries or deaths as a 

result of explosive structure removals are not expected due to mitigative measures contained in 

Endangered Species Act (ESA) Section 7 consultations. Disturbance (noise from vessel traffic and 
65 

drilling operations, etc.) and/or exposure to sublethal levels of anthropogenic contaminants may stress 

animals, weaken their immune systems, and make them more vulnerable to parasites and diseases. 

Collisions between cetaceans and ships, though expected to be rare events, could cause serious injury or 

mortality. 

The net result of any disturbance would be dependent upon the size and percentage of the population 

likely to be affected; ecological importance of the disturbed area; environmental and biological 

parameters that influence an animal’s sensitivity to disturbance and stress; or the accommodation time in 

response to prolonged disturbance (Geraci and St. Aubin, 1980). 

4.4.6. Sea Turtles 

Cumulative impact-producing factors that may affect sea turtles and their habitats include structure 

installation, water quality and habitat degradation, trash and flotsam, vessel traffic, seismic surveys, 

explosive structure removals, oil spills, spill-response activities, natural catastrophes, pollution, dredge 

operations, commercial and recreational fishing, beach lighting, and power plant entrainment. Sea turtles 

could be injured or killed from eating marine debris, particularly plastic items, lost from OCS structures 

and/or ocean-going vessels. Deaths due to explosive structure removal operations should be rare 

occurrences due to mitigation measures established in ESA Section 7 consultations. Noise from service 

vessels and from offshore drilling rigs and structures may disrupt the sea turtles’ normal activities and 

may cause physiological stress that make these animals more susceptible to disease or predation. 

Contaminants in waste discharges and drilling muds might indirectly affect sea turtles. Oil spills and 

spill-response activities are potential threats that may be adversely affect sea turtles. Contact with, and 

consumption of, oil and oil-contaminated prey may seriously affect sea turtles. The majority of OCSrelated effects are expected to be sublethal, such as behavioral effects and nonfatal exposures (intake of 

contaminants or debris). 

4.4.7. Coastal and Marine Birds 

Possible impacts to coastal and marine birds can come from air emissions, water quality degradation, 

habitat loss and modification resulting from coastal construction and development, collisions with aircraft 

or vessels, noise from aircraft and vessels, trash and debris, and lighting. Any effects could be especially 

critical to endangered or threatened species that must maintain a viable reproductive population size or 

that are dependent on a few key habitat factors. Aircraft or vessel traffic could sporadically disturb 

feeding, resting, or nesting behavior of birds or cause abandonment of preferred habitat. Birds could 

become entangled and snared in trash and debris. In addition, they may ingest small plastic debris that 

could lead to injury or death. 

Cumulative activities could detrimentally affect coastal and marine birds. It is expected that the 

majority of effects from the major impact-producing factors on coastal and marine birds are sublethal 

(behavioral effects and nonfatal exposure to or intake of contaminants or discarded debris) and will 

usually cause temporary disturbances and displacement of localized groups inshore. However, chronic 

sublethal stress is often undetectable in birds. It can serve to weaken individuals (which is especially 

serious for migratory species) and expose them to infection and disease. Lethal effects, resulting 

primarily from uncontained coastal oil spills and associated spill-response activities in wetlands and other 

biologically sensitive coastal habitats, are expected to remove a number of individuals from any or all 

groups through primary effects from physical oiling and the ingestion of oil, and secondary effects 

resulting from the ingestion of oiled prey. Most birds can potentially produce two or more eggs in one 

breeding season and have them survive to maturity. Populations would increase and recover if the 

average reproductive rate were greater than two offspring successfully surviving to maturity per pair of 

parents, but the time period for recovery would depend on the average reproductive rate. Therefore, 

recruitment of birds through successful reproduction is expected to take a year or more, depending upon 

the species and existing conditions. The net effect of habitat loss from oil spills, new construction, and 

maintenance and use of pipeline corridors and navigation waterways will alter species composition and 

reduce the overall carrying capacity of disturbed area(s) in general. 

The incremental contribution of the proposed action to the cumulative impact would be negligible 

because the effects of the most probable impacts, such as OCS-related operational discharges and 
66 

helicopters and service-vessel noise and traffic, are expected to be sublethal, although some displacement 

of local individuals or groups may occur. It is expected that there will be little interaction between OCSrelated oil spills and coastal and marine birds. 

The cumulative effect on coastal and marine birds is expected to result in a discernible decline in the 

numbers of birds that form localized groups or populations, with associated change in species 

composition and distribution. Some of these changes are expected to be permanent, as exemplified in 

historic census data, and to stem from a net decrease in preferred and/or critical habitat. 

4.4.8. Essential Fish Habitat and Fish Resources 

Degradation of water quality, loss of essential habitat (including wetland loss), pathogens, trash and 

debris, riverine influences, and overfishing could affect fish resources. Eggs and larvae are more 

susceptible than adults to environmental 0contaminants. Portions of the Gulf experience hypoxia during 

portions of the year (LATEX B; Murray, 1998). However, areas of hypoxia typically occur only on the 

continental shelf. 

4.4.9. Gulf Sturgeon 

The Gulf sturgeon can be impacted by cumulative activities such as oil spills, alteration and 

destruction of habitat, and commercial fishing. The effects from contact with spilled oil are expected to 

be nonfatal and last for less than one month. Substantial damage to Gulf sturgeon habitats is expected 

from inshore alteration activities and natural catastrophes. As a result, it is expected that the Gulf 

sturgeon will experience a decline in population sizes and a displacement from their current distribution 

that will last more than one generation. Deaths of adult sturgeon are expected to occur from commercial 

fishing. The incremental contribution of the proposed action to the cumulative impact would be 

negligible because the effect of contact between oil spills from the proposed action and Gulf sturgeon is 

expected to be nonfatal and last less than one month. 

4.4.10. Economic and Demographic Conditions 

The economic and demographic conditions evaluated in this PEA are limited to that portion of the 

GOM's coastal zone whose social and economic well-being (population, labor, and employment) is 

directly or indirectly affected by the OCS oil and gas industry. The energy industry has become 

increasingly more global. While the OCS Program, in general, has played a significant role in the GOM 

region's economy and demography, the activities proposed in Grid 16 are expected to have minimal 

economic and demographic consequences to the region. 

4.4.10.1. Population and Education 

The impact area's population is expected to grow at an average annual rate of 1.5 to 1.0 percent over 

the next 40 years with that growth slowing over time. This population growth is based on the 

continuation of existing conditions including OCS energy development. Activities in Grid 16 are not 

expected to affect the population's growth rate. Education levels are expected to remain unchanged by 

activities within Grid 16. 

4.4.10.2. Infrastructure and Land Use 

Sufficient infrastructure is in place to support activities within Grid 16. Sufficient land is designated 

in commercial and industrial parks and adjacent to the existing ports to minimize potential disruption to 

current residential and business use patterns. While land use in the area will change over time, the 

majority of this change is expected to be general regional growth. 

4.4.10.3. Navigation and Port Usage 

There are approximately 50 shore bases that are traditionally used by the oil and gas industry to 

support activities on the Federal OCS. Certain companies favor some of these bases for their offshore 
67 

operations. No new expansion or construction is expected at these existing shore bases to support 

offshore activities within Grid 16. 

4.4.10.4. Employment 

The oil and gas industry is very important to many of the coastal communities of the GOM, especially 

in Louisiana and eastern Texas. Changes in OCS oil and gas activities have significant employment 

implications to these communities, particularly in industries directly and indirectly related to oil and gas 

development. However, the energy industry has global markets (both for the supply of goods and 

services needed to produce energy and demand for energy products). While mergers, relocations, and 

consolidation of oil and gas companies’ assets have affected employment in the GOM region in recent 

years, employment changes to the coastal communities as a result of activities in Grid 16 are expected to 

be negligible. 

4.4.11. Environmental Justice 

Federal agencies are directed by Executive Order 12898 to assess whether their actions will have a 

disproportionate environmental effect on people of ethnic or racial minorities or with low incomes. Since 

sufficient onshore facilities are available to support offshore activities in Grid 16, no effects to minorities 

or people with low incomes in the Gulf counties and parishes are expected. 

4.4.12. Commercial Fisheries 

Federal and State fishery management agencies will control the "take" of commercial fishes. The 

agencies' primary responsibility is to manage effectively the fishery stock to perpetuate commercially 

important species. Various management plans aimed at selected species have been and will continue to 

be prepared. The Central GOM will remain one of the Nation's most important commercial fisheries area. 

4.4.13. Recreational Resources and Beach Use 

Factors such as land development, civil works projects, and natural phenomena have affected, and 

will continue to affect, beach stabilization, which ultimately affects the recreational use of beaches. Many 

of the people in the adjacent coastal states live in the coastal zone. Pressure on the natural resources 

within the coastal zone is expected to continue or possibly increase. 

Man-induced debris and litter derived from both offshore and onshore sources are likely to diminish 

the tourist potential of beaches and degrade the ambience of shoreline recreational beaches, thereby 

affecting the enjoyment of recreational beaches throughout the planning area. MARPOL Annex V and 

cooperation and support from offshore industries to reduce marine debris through the GOM Program’s 

Marine Debris Action Plan should lead to a decline in the level of human-generated trash that may 

adversely affect recreational beaches throughout the Gulf. 

Although trash from onshore sources will continue to adversely affect the ambience of recreational 

beaches, the level of chronic pollution should decline. Beach use at the regional level is unlikely to 

change. 

4.4.14. Archaeological Resources 

4.4.14.1. Prehistoric 

Grid 16 is located in deep water (greater than 1,000 m or 3,281 ft). It is not located in one of the 

MMS’s designated high-probability areas for prehistoric sites. No potential exists to affect prehistoric 

archaeological resources. 

4.4.14.2. Historic 

According to Garrison et al. (1989) and Pearson et al. (2002), the shipwreck database lists 8 

shipwrecks and 29 high-probability shipwreck blocks that fall within the Grid 16 area. These shipwrecks 
68 

are listed in Table 3-3. Six of these wrecks are 50 years or older and are eligible for listing in the 

National Register of Historic Places. 

Seafloor-disturbing activities such as anchoring have the potential to affect shipwrecks, if present. Inplace mitigating measures would eliminate or minimize potential impacts to these resources. 

5. CONSULTATION AND COORDINATION 

The States of Louisiana and Mississippi have approved Coastal Zone Management (CZM) Programs. 

Therefore, Certificates of Coastal Zone Consistency from the States were required for the proposed 

activities. The MMS mailed the plan and other required and necessary information to the States’ 

appropriate CZM agencies on September 4, 2001. The State of Mississippi provided a letter of its 

concurrence with the CZM Program on September 18, 2002. On September 20, 2002, the Governor’s 

Office from the State of Mississippi also provided a letter regarding the Thunder Horse project. The 

State of Louisiana provided a letter of its concurrence with the CZM Program on September 20, 2002. 

To provide the public with official notice of the proposed activities planned for the Thunder Horse 

development, the MMS published a description of the BP proposal in The Times-Picayune newspaper 

(southeast Louisiana coverage) and in the Mobile Register (southern Mississippi and southern Alabama 

coverage). In these public notices, the MMS requested interested parties to submit comments on issues 

that should be addressed in the PEA. The notices appeared in the newspapers on September 12, 2002. 

No comments were received by the MMS from the newspaper notice. 

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7. PREPARERS 

Coordinator: G. Ed Richardson — Senior Environmental Scientist 

 Latonia Viverette — Environmental Scientist 

Preparers: Rik Anuskiewicz — Archaeologist 

 Darice Breeding — Physical Scientist 

 Greg Boland — Biologist 

 Susan Childs — Biologist 

 Janet Diaz — Environmental Assessment Assistant 

 Mike Gravois — Geographer 

 Stacie Merritt — Physical Scientist 

 Margret Metcalf — Physical Scientist 

 Debbie Miller — Technical Publication Editor 

 Dave Moran — Biologist 

 Tara Montgomery — Geographer 

 Carol Roden — Protected Species Specialist 

 Vicki Zatarain — Economist 

 

Reviewers: Pat Roscigno — Chief, Environmental Sciences Section 

 Dennis Chew — Supervisor, NEPA/CZM Coordination Unit 

8. APPENDICES 

Appendix A — Proposed Activity Schedule 

Appendix B — Accidental Oil Spill Review 

Appendix C — Waste Tables 

Appendix D — Geology 

Appendix E — Socioeconomic Tables 

Appendix F — Meteorological Conditions 

Appendix G — Physical Oceanography 

Appendix H — Other Information on Grid 16 

Appendix I — Air Emissions Data 
A-1 

APPENDIX A 

Proposed Activity Schedule 
A-3 

APPENDIX A 

PROPOSED ACTIVITY SCHEDULE FOR THE THUNDER HORSE PROJECT

The following table depicts the proposed activity schedules for the development of the Thunder Horse 

project. 

Thunder Horse Project Schedule 

Proposed Activity Starting Date Ending Date Activity 

Duration 

Drilling, Completion, & Cleanup Operations 

Drill Center 31

Drilling & Completions 06/29/04 08/04/04 36 days 

Well Cleanup 08/04/04 08/05/04 2 days 

Drilling & Completions 08/02/05 12/20/05 140 days 

Well Cleanup 12/20/05 12/21/05 2 days 

Drilling & Completions 03/28/06 07/24/06 118 days 

Drilling & Completions 07/12/06 11/13/06 124 days 

Drilling & Completions 08/20/11 11/30/11 102 days 

Well Cleanup 11/30/11 12/01/11 2 days 

Drill Center 32

Drilling & Completions 04/10/04 05/21/04 41 days 

Well Cleanup 05/21/04 05/22/04 2 days 

Drill Center 33

Drilling & Completions 09/25/04 02/06/05 133 days 

Well Cleanup 02/06/05 02/07/05 2 days 

Drilling & Completions 01/04/05 02/09/05 36 days 

Well Cleanup 02/09/05 02/10/05 2 days 

Drilling & Completions 04/03/05 08/22/05 141 days 

Drilling & Completions 12/23/05 04/04/06 102 days 

Well Cleanup 04/04/06 04/05/06 2 days 

Drilling & Completions 12/21/11 03/30/12 100 days 

Well Cleanup 03/30/12 03/31/12 2 days 

Drill Center 41

Drilling & Completions 02/19/03 06/23/03 124 days 

Well Cleanup 06/23/03 06/28/03 6 days 

Drilling & Completions 07/02/03 10/26/03 116 days 

Well Cleanup 10/26/03 11/01/03 6 days 

Drilling & Completions 01/26/04 02/27/04 32 days 

Well Cleanup 02/27/04 03/03/04 6 days 

Drilling & Completions 05/19/07 10/21/07 155 days 

Well Cleanup 10/21/07 10/22/07 2 days 

Drilling & Completions 08/11/08 11/24/08 105 days 

Drilling & Completions 11/26/08 03/21/09 115 days 

Well Cleanup 03/21/09 03/22/09 2 days 

Drilling & Completions 11/23/11 03/11/12 109 days 

Drilling & Completions 12/15/12 04/26/13 132 days 

Drilling & Completions 09/19/13 12/21/14 124 days 

Drilling & Completions 09/28/14 01/21/15 115 days 
A-4 

 Thunder Horse Project Schedule (continued). 

Proposed Activity Starting Date Ending Date Activity 

Duration 

Drill Center 42

Drilling & Completions 07/19/03 08/22/03 34days 

Well Cleanup 05/01/05 05/02/05 2days 

Drill Center 44

Drilling & Completions 04/12/05 08/24/05 134 days 

Well Cleanup 08/24/05 08/25/05 2 days 

Drilling & Completions 09/14/05 01/05/06 113 days 

Well Cleanup 01/05/06 01/06/06 2 days 

Drilling & Completions 12/30/05 05/22/06 143 days 

Well Cleanup 05/22/06 05/23/06 2 days 

Drill Center 45

Drilling & Completions 08/22/03 10/30/03 69 days 

Well Cleanup 06/01/05 06/02/05 2 days 

Installation Operations 

Drill Center 31

Flowline Installation 

(incl. PLETs & Sleds) 

07/05/04 07/07/04 3 days 

Jumper Measurement 08/15/04 12/21/04 1 day 

Umbilical Installation 01/31/05 02/02/05 3 days 

Drill Center 32

Manifold Installation 12/21/04 01/21/05 15 days 

Flowline Installation 

(incl. PLETs & Sleds) 

07/02/04 07/16/04 12 days 

Jumper Measurement 08/07/04 08/14/04 5 days 

Jumper Installation 09/26/04 09/29/04 4 days 

Umbilical Installation 01/06/05 01/10/05 5 days 

Drill Center 33 

Manifold Installation 07/08/04 07/12/04 5 days 

Flowline Installation 

(incl. PLETs & Sleds) 

05/27/04 06/12/04 17 days 

Jumper Measurement 08/11/04 08/13/04 3 days 

Jumper Installation 09/23/04 09/25/04 3 days 

Jumper Installation 02/15/05 02/18/05 4 days 

Umbilical Installation 01/10/05 01/15/05 5 days 

Drill Center 41

Prelay PDQ Mooring 05/01/04 06/01/04 32 days 

Manifold Installation 06/02/04 06/25/04 24 days 

Flowline Installation 

(incl. PLETs & Sleds) 

05/01/04 04/04/04 65 days 

Jumper Measurement 07/11/04 08/05/04 20 days 

Jumper Installation 08/27/04 09/15/04 20 days 

PDQ Mooring 11/21/04 12/10/04 19 days 

Jumper Installation 01/30/05 02/03/05 5 days 

Umbilical Installation 01/23/05 03/08/05 45 days 

Tow Rig to Location 11/06/04 11/21/04 15 days 

Remaining Hook Up & Commissioning 11/21/04 12/03/04 13 days 
A-5 

 Thunder Horse Project Schedule (continued). 

Proposed Activity Starting Date Ending Date Activity 

Duration 

Drill Center 43

Jumper Measurement 07/19/04 07/20/04 2 days 

Jumper Installation 09/16/04 09/17/04 2 days 

Umbilical Installation 12/29/04 12/31/04 3 days 

Drill Center 44

Single well—no installation activity 

other than what captured under Drill 

Center 41 

 

Jumper Installation 09/21/04 09/22/04 2 days 

Umbilical Installation 12/26/04 12/28/04 3 days 

PDQ Operations 

Drill Center 41

First Oil 04/11/05 

Production* 04/11/05 04/11/31 9,490 days 

PDQ Drilling 06/10/05 08/27/13 2,998 days 

 *Three injector wells under the PDQ will be cleaned up back to the PDQ, but these operations will not 

involve flaring or storing. 
B-1 

APPENDIX B 

Accidental Oil Spill Review 
B-3

APPENDIX B 

ANALYSIS OF THE POTENTIAL FOR AN ACCIDENTAL OIL SPILL AND POTENTIAL 

FOR IMPACTS FROM THE THUNDER HORSE PROJECT IN GRID 16 

Mississippi Canyon Block 777 Unit 

(Blocks 775, 776, 777, 778, 819, 820, 821, and 822) 

Plan Number N-7469 

Introduction 

The National Environmental Policy Act, as amended, (NEPA) requires Federal agencies to consider 

potential environmental impacts (direct, indirect, and cumulative) of proposed actions as part of an 

agency’s planning and decisionmaking processes. The NEPA analyses address many issues relating to 

potential impacts, including issues that may have a very low probability of occurrence, but which the 

public considers important or for which the environmental consequences could be significant. 

The past several decades of spill data show that effects from accidental oil spills associated with oil 

and gas exploration and development are low probability events in Federal Outer Continental Shelf (OCS) 

waters of the Gulf of Mexico (GOM), yet the issue of oil spills is important to the public. This document 

summarizes key information about the probability of accidental spills from offshore oil and gas activities 

in the GOM. 

Spill Prevention 

The MMS has comprehensive pollution prevention requirements that include numerous redundant 

levels of safety devices, as well as inspection and testing requirements to confirm that these devices work. 

Many of these requirements have been in place since about 1980. Spill trends analysis for the GOM OCS 

show that spills from facilities have decreased over time, indicating that the MMS’s engineering and 

safety requirements have minimized the potential for spill occurrence and associated impacts. Details 

regarding the MMS’s engineering and safety requirements can be found at 30 CFR 250.800, Subpart H. 

OCS Spills in the Past 

This summary of past OCS spills presents data for the period 1985-1999. The 1985-1999 time period 

was chosen to reflect more modern engineering and regulatory requirements and because OCS spill rates 

are available for this period. For the period 1985-1999, there were no spills >1,000 barrels (bbl) from 

OCS platforms, eight spills >1,000 bbl from OCS pipelines, and no spills >1,000 bbl from OCS drilling 

activities (Tables B-1 through B-3). It should be noted that past OCS spills (Tables B-1 through B-3), 

some of which are considerably >1,000 bbl, have not resulted in any documented significant impacts to 

shorelines or other resources. The Final Multisale EIS (USDOI, MMS, 2002) and Final Lease Sale 181 

EIS (USDOI, MMS, 2001) in the Eastern Planning Area provide additional information on past OCS 

spills. 

Estimating Future Potential Spills 

The MMS estimates the risk of future potential spills by using a formula that multiplies several 

variables to result in a numerical expression of risk. These variables include the potential of a spill 

occurring (based on historical OCS spill rates) and a variable for the potential for a spill to be transported 

to environmental resources (based on trajectory modeling). The following subsections describe the spill 

occurrence and transport variables used to estimate risk and the risk calculation for the proposed action.
B-4

Spill Occurrence Variable (SOV) Representing the Potential for a Spill 

The SOV is derived based on past OCS spill frequency; that is, data from past OCS spills are used to 

estimate future potential OCS spills. The MMS has estimated spill rates from the following sources: 

facilities, pipelines, and blowouts. 

Spill rates for facilities and pipelines have been developed for several time periods and an analysis of 

trends for spills is presented in Update of Comparative Occurrence Rates for Offshore Oil Spills (Spill 

Science & Technology Bulletin, 2000). Spill rates for the most recent period analyzed, 1985-1999, are 

presented here. Data for this recent period should reflect more modern spill-prevention requirements. 

Spill rates for facilities and pipelines are based on the number of spills per volume of oil handled. 

Spill rates for drilling activities are based on the number of spills associated with activities occurring 

during drilling operations. These include spills from blowouts, drill rigs, supply vessels, fuel storage, and 

other drilling activities. Spill rates for the period 1985-1999 are shown in Table B-4. It should be noted 

that there were no platform or drilling spills >1,000 bbl for the period 1985-1999. Use of “zero” spills 

would result in a zero spill rate. To provide a non-zero spill rate for conservative future predictions of 

spill occurrence, the spill period was expanded to include older spill data. The spill data period is 

expanded to 1980 to include a spill for facilities. The spill data period is expanded to 1971 to include a 

spill for drilling activities. Spill rates are combined with site-specific data on production or pipeline 

volumes or number of wells being drilled to result in a site-specific SOV. 

Transport Variable (TV) Representing the Potential for a Spill to be Transported to 

Important Environmental Resources 

The TV is derived using an oil-spill trajectory model. This model predicts the direction that winds 

and currents would transport spills. The model uses an extensive database of observed and theoretically 

computed ocean currents and fields that represent a statistical estimate of winds and currents that would 

occur over the life of an oil and gas project, which may span several decades. This model produces the 

TV that can be combined with other variables, such as the SOV, to estimate the risk of future potential 

spills and impacts. 

Risk Calculation for the Proposed Action 

BP Exploration and Production, Inc.'s (BP) Initial Unit Development Operations Coordination 

Document (DOCD) and its amendments propose to initially drill and complete a total of 27 wells (17 

production and 10 water injection wells). In addition, approximately 16 recompletions and 16 sidetracks 

are planned in the mid-to-late life of the fields. The wells will be drilled from eight drill centers and 

production will be tied back to a semisubmersible production facility (PDQ facility) in Mississippi 

Canyon Block 778. BP's Mississippi Canyon, Block 777 Unit is composed of the following blocks: 

Blocks 775 (OCS-G 19997), 776 (OCS-G 9866), 777 (OCS-G 9867), 778 (OCS-G 9868), 819 (OCS-G 

12168), 820 (OCS-G 14656), 821 (OCS-G 14657), and 822 (OCS-G 14658). Liquid hydrocarbon 

production from the Thunder Horse project will depart the PDQ facility in a proposed right-of-way 

pipeline (ROW G-23429; Segment Number 13633) to be owned and operated by Proteus Oil Pipeline 

Company, LLC (MMS Qualification Number 2530). The proposed Proteus oil pipeline is a 61 to 71-cm 

(24-28 in) bi-directional pipeline that will carry liquid hydrocarbons approximately 111 km (69 mi) from 

the PDQ facility in Mississippi Canyon, Block 778, to a proposed Platform E in South Pass Area, South 

Addition, Block 89. A new four-pile, Platform E is proposed to be set as an accessory structure for the 

Proteus pipeline. From Platform E, liquid hydrocarbon production will depart in a proposed right-of-way 

pipeline (ROW G- 23068; Segment Number 13534) to be owned and operated by Endymion Oil Pipeline 

Company, LLC (MMS Qualification Number 2529). The proposed Endymion Oil Pipeline is a 76-cm 

(30-in) bi-directional pipeline. It will carry the liquid hydrocarbons approximately 87 km (54 mi) from 

Platform E to a landfall at the existing BP facilities on Grand Isle, Louisiana, and ultimately terminate at 

the Louisiana Offshore Oil Port (LOOP) storage facilities near the Clovelly Oil and Gas Field. Table B-5 

presents an estimate of spill risk from the facility to resources. The risk estimate for the facility was 

calculated using the spill rate of 0.13 per billion barrels of oil produced, the estimated production for the 

proposed action, and oil-spill trajectory calculations. 
B-5

The coastline and associated environmental resources are presented in Table B-5. The final column 

in Table B-5 presents the result of combining the SOV’s and the TV’s. The risk of a spill impact from the 

facility could be considered to be so low as to be near zero. 

Given the low risk of resources being exposed to spills as a result of the proposed action, spillprevention requirements, and spill-response requirements, significant impacts to environmental resources 

are unlikely. The Final Multisale EIS (USDOI, MMS, 2002) and Final Lease Sale 181 EIS (USDOI, 

MMS, 2001) in the Eastern Planning Area provide additional information on spills and potential impacts. 

The following section provides additional information regarding the spill-response preparedness 

requirements of the MMS. 

Spill Response 

The MMS has extensive requirements both for the prevention of spills and preparedness to respond to 

a spill in the event of an accident. The MMS spill-prevention requirements and the low incidence of past 

OCS spills were addressed earlier in this document. This section presents information on the MMS’s 

requirements for spill-response preparedness. 

MMS Spill-Response Program 

The MMS Oil-Spill Program oversees the review of oil-spill response plans, coordinates inspection of 

oil-spill response equipment, and conducts unannounced oil-spill drills. This program also supports 

continuing research to foster improvements in spill prevention and response. Studies funded by the MMS 

address issues such as spill prevention and response, in-situ burning, and dispersant use. 

In addition, MMS works with the U.S. Coast Guard and other members of the multiagency National 

Response System to further improve spill-response capability in the GOM. The combined resources of 

these groups and the resources of commercially contracted oil-spill response organizations result in 

extensive equipment and trained personnel for spill response in the GOM. 

Spill Response for This Project 

The subject operator has an oil-spill response plan on file with the MMS and has current contracts 

with offshore oil-spill response organizations. 

Potential spill sources for this project include a production spill during the life of the development (25 

years), an accidental blowout (141,000 bbl of oil per day), a spill of liquid oil stored on the platform 

(approximately 21,400 bbl total storage capacity), a spill of liquid oil stored on the largest rig 

(approximately 125,000 bbl total storage capacity), a spill from the offloading of well cleanup fluids 

(maximum transfer volume 60,000 bbl), or a spill from the associated oil flowlines (2,000 bbl), lease-term 

pipelines (13,000 bbl), or the export pipelines. The operator has demonstrated spill-response 

preparedness for accidental releases from these types of potential spills in their oil-spill response plan. 

The MMS will continue to verify the operator’s capability to respond to oil spills via the MMS OilSpill Program. The operator is required to keep their oil-spill response plan up-to-date in accordance with 

MMS regulations. The operator must also conduct an annual drill to demonstrate the adequacy of their 

spill preparedness. The MMS also conducts unannounced drills to further verify the adequacy of an 

operator’s spill-response preparedness; such a drill could be conducted for this proposed action. 

References 

U.S. Dept. of the Interior. Minerals Management Service. 2001. Gulf of Mexico OCS oil and gas lease 

Sale 181: Eastern Planning Area—final environmental impact statement. 2 vols. U.S. Dept. of the 

Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS 

EIS/EA MMS 2001-051. 
B-6

U.S. Dept. of the Interior. Minerals Management Service. 2002. Gulf of Mexico OCS oil and gas lease 

sales: 2003-2007; Central Planning Area Sales 185, 190, 194, 198, and 201; Western Planning Area 

Sales 187, 192, 196, and 200—final environmental impact statement. 2 vols. U.S. Dept. of the 

Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS 

EIS/EA MMS 2002-052. 

 Table B-1 

Historical Record of OCS Spills >1,000 Barrels from OCS Facilities, 1985–1999 

Spill Date Area and Block 

(water depth and 

distance from shore)

Volume Spilled 

(barrels)

Cause of Spill 

 No OCS facility spills >1,000 bbl during the period 1985–1999. 

Table B-2 

Historical Record of OCS Spills >1,000 Barrels from OCS Pipelines, 1985–1999 

Spill Date Area and Block 

(water depth and 

distance from shore)

Volume 

Spilled 

(barrels)

Cause of Spill 

February 7, 1988 South Pass 60 

(75 ft, 3.4 mi) 

15,576 Service vessel’s anchor damaged 

pipeline 

January 24, 1990 Ship Shoal 281 

(197 ft, 60 mi) 

14,423* Anchor drag, flange and valve broke 

off 

May 6, 1990 Eugene Island 314 

(230 ft, 78 mi) 

 4,569 Trawl drag pulled off valve 

August 31, 1992 South Pelto 8 

(30 ft, 6 mi) 

 2,000 Hurricane Andrew, loose drilling rig’s 

anchor drag damaged pipeline 

November 22, 1994 Ship Shoal 281 

(197 ft, 60 mi) 

 4,533* Trawl drag 

January 26, 1998 East Cameron 334 

(264 ft, 105 mi) 

 1,211* Service vessel's anchor drag damaged 

pipeline during rescue operation 

September 29, 1988 South Pass 38 

(110 ft, 6 mi) 

 8,212 Hurricane Georges, mudslide parted 

pipeline 

July 23, 1999 Ship Shoal 241 

(133 ft, 50 mi) 

 3,200 Jack-up barge sat on pipeline 

 * Denotes a condensate spill. 
B-7

Table B-3 

Historical Record of OCS Spills >1,000 Barrels from OCS Blowouts, 1985–1999 

Spill Date Area and Block 

(water depth and 

distance from shore)

Volume 

Spilled 

Barrels

Cause of Spill 

 No OCS blowout spills >1,000 bbl during the period 1985–1999. 

Table B-4 

Spill Rates Used to Estimate the Future Potential for Spills 

Spill Source Volume of Oil 

Handled in 

Billions of Barrels 

Number of 

Wells Drilled 

No. of 

Spills 

>1,000 

Barrels 

Risk of Spill 

from Facilities or 

Pipelines per 

Billion Barrels 

Risk of Spill 

from Drilling 

Blowout per 

Well 

Facilities 7.41 a Not Applicable 1a >0 to <0.13c Not Applicable 

 

Pipelines 5.81 Not Applicable 8 1.38 Not Applicable 

Drilling Not Applicable 23,610 1b Not Applicable >0 to <0.00004c

a

 There were actually zero spills of >1,000 bbl from facilities during the period 1985-1999. The data shown 

represent 1980-1999. The spill period for facility spills was expanded to 1980 to include a spill for facilities to 

result in a nonzero risk. 

b

 There have been no spills of >1,000 bbl from drilling activities during the period 1985-1999. Drilling activities 

include spills from blowouts, drilling rigs, supply vessels, fuel storage, and other drilling activities. The data 

shown represent 1971-1999. One spill of >1,000 bbl occurred during this period – a 1,500-bbl diesel spill from a 

drilling rig damaged in a storm. c

 There were no facility or drilling spills of >1,000 bbl for the period 1985-1999; however, a nonzero spill rate was 

calculated by expanding the facility and drilling period to 1980 and 1971. Therefore, the spill rates for these 

categories are presented as greater than zero but below the rates calculated by expanding the data period. 
B-8

Table B-5 

Spill Risk Estimate for Facilities 

Environmental Resource Spill Occurrence 

Variable (1) 

(%) 

Transport Variable (2) 

within 30 days 

(%) 

Spill Risk (3) 

within 30 days 

(%) 

Counties/Parishes 

Cameron, TX 26 <0.5 <0.5 

Willacy, TX 26 <0.5 <0.5 

Kenedy, TX 26 <0.5 <0.5 

Kleburg, TX 26 <0.5 <0.5 

Nueces, TX 26 <0.5 <0.5 

Aransas, TX 26 <0.5 <0.5 

Calhoun, TX 26 <0.5 <0.5 

Matagorda, TX 26 <0.5 <0.5 

Brazoria, TX 26 <0.5 <0.5 

Galveston, TX 26 <0.5 <0.5 

Chambers, TX 26 <0.5 <0.5 

Jefferson, TX 26 <0.5 <0.5 

Cameron, LA 26 1 <0.5 

Vermilion, LA 26 <0.5 <0.5 

Iberia, LA 26 <0.5 <0.5 

St. Mary, LA 26 <0.5 <0.5 

Terrebonne, LA 26 2 1 

Lafourche, LA 26 2 1 

Jefferson, LA 26 1 <0.5 

Plaquemines, LA 26 10 3 

St. Bernard, LA 26 2 1 

Harrison, MS 26 <0.5 <0.5 

Jackson, MS 26 <0.5 <0.5 

Baldwin, AL 26 <0.5 <0.5 

Mobile, AL 26 <0.5 <0.5 

Escambia, FL 26 <0.5 <0.5 

Santa Rosa, FL 26 <0.5 <0.5 

Okaloosa, FL 26 <0.5 <0.5 

Walton, FL 26 1 <0.5 

Bay, FL 26 1 <0.5 

Gulf, FL 26 <0.5 <0.5 

Franklin, FL 26 <0.5 <0.5 

Wakulla, FL 26 <0.5 <0.5 

Jefferson, FL 26 <0.5 <0.5 

Taylor, FL 26 <0.5 <0.5 

Dixie, FL 26 <0.5 <0.5 

Levy, FL 26 <0.5 <0.5 

Citrus, FL 26 <0.5 <0.5 

Hernando, FL 26 <0.5 <0.5 

Pasco, FL 26 <0.5 <0.5 

Pinellas, FL 26 <0.5 <0.5 

Hillsborough, FL 26 <0.5 <0.5 

Manatee, FL 26 <0.5 <0.5 

Sarasota, FL 26 <0.5 <0.5 

Charlotte, FL 26 <0.5 <0.5 
B-9

Table B-5. Spill Risk Estimate for Facilities (continued). 

Environmental Resource Spill Occurrence 

Variable (1) 

(%) 

Transport Variable (2) 

within 30 days 

(%) 

Spill Risk (3) 

within 30 days 

(%) 

Lee, FL 26 <0.5 <0.5 

Collier, FL 26 <0.5 <0.5 

Monroe, FL 26 <0.5 <0.5 

 

State Offshore Waters 

TX State Offshore Waters 26 1 <0.5 

LA (Western) State Offshore 

Waters 

26 17 4 

LA (Eastern) State Offshore 

Waters 

26 6 2 

MS State Offshore Waters 26 1 <0.5 

AL State Offshore Waters 26 1 <0.5 

FL Panhandle State Offshore 

Waters 

26 4 1 

FL Peninsula State Offshore 

Waters 

26 <0.5 <0.5 

 

Major Recreational Beach 

Areas 

 

TX Coastal Bend area beaches 26 <0.5 <0.5 

TX Matagorda area beaches 26 <0.5 <0.5 

TX Galveston area beaches 26 <0.5 <0.5 

TX Sea Rim State Park 26 <0.5 <0.5 

LA beaches 26 3 1 

AL/MS Gulf Islands 26 1 <0.5 

AL Gulf Shores 26 <0.5 <0.5 

FL Panhandle beaches 26 3 1 

FL Big Bend beaches 26 <0.5 <0.5 

FL Southwest beaches 26 <0.5 <0.5 

FL Ten Thousand Islands 26 <0.5 <0.5 

(1) The percent chance of a spill event occurring from the proposed action. 

(2) The percent chance that winds and currents will move a point projected onto the surface of the 

Gulf beginning within the area of the Mississippi Canyon Block 777 Unit and ending at specified 

shoreline segments or environmental resources within 30 days. These results are the results of a 

numerical model that calculates the trajectory of a drifting point projected onto the surface of the 

water using temporally and spatially varying winds and ocean current fields. These probabilities 

do not factor in the risk of spill occurrence, consideration of the spill size, any spill response or 

cleanup actions, or any dispersion and weathering of the slick with time. Model results used are 

for C6-2 cluster area. 

(3) The probability of a spill occurring and contacting identified environmental features represents the 

weighted risk that accounts for both the risk that a large spill will occur and the risk that it will 

contact locations where the resources occur, given the assumptions already described in (1) 

and (2). 

(4) <0.5 = less than 0.5%. 
C-1 

APPENDIX C 

Waste Tables 
C-3

Table C-1 

Drilling Wastes Table - 4-Way Subsalt Wells (estimated 7 wells) 

Waste Generated during 

Drilling 

Composition/Description Projected Amount Disposal Method Maximum 

Discharge Rate 

Treatment 

Discharge 

Method 

Water-based drilling fluids N/A 

None (see "Muds, cuttings, and cement at the sea floor" below) 

N/A N/A N/A 

Nonaqueous drilling fluids 

Internal olefin/ester blend; or internal olefin/ester/paraffin blend 

2,800 bbl/well discharged (<6.9% retention on cuttings (ROC) with drilled cuttings) 

Discharge overboard 

1,000 bbl/hr Discharge 

through shunt line 40 ft beloseawater surfa

Drill cuttings associated with water-based fluids N/A 

None (see "Muds, cuttings, and cement at the seafloor" below) 

N/A N/A N/A 

Drill cuttings associated with nonaqueous based fluids 

Cuttings coated with synthetic-based drilling mud 

4,000 bbl/well Discharge 

overboard 

1,000 bbl/hr Discharge 

through shunt line 40 ft beloseawater surfa

Sanitary wastes 

Human body waste from toilets and urinals 

30 gal/person/day Discharge 

overboard Continuous 

Marine sanitadevice treatm& discharge overboard 

Domestic wastes 

Discharge from galleys, sinks, and showers (gray water) 

50 gal/person/day Discharge 

overboard Continuous 

Discharge overboard 

Deck drainage Platform washings, drains Dependent on rainfall Discharge overboard Dependent on rainfall Treat with separator to remove free o
C-4

Table C-1. Drilling Wastes Table - 4-Way Subsalt Wells (estimated 7 wells) (continued) 

Waste Generated during 

Drilling 

Composition/Description Projected Amount Disposal Method Maximum 

Discharge Rate 

Treatment 

Discharge 

Method 

Well treatment, workover, or completion fluids 

Calcium chloride (CaCl2)/

Calcium bromide (CaBr) 

Discharge 2,500 bbl/well; dispose as waste onshore: 500 bbl/well; send to shore for reclamation: 2,500 bbl/well 

Discharge overboard; dispose of as waste onshore and send to shore for reclamation 

N/A N/A 

Muds, cuttings, and cement at the seafloor 

Seawater NaCl polymer, drill cuttings, cement (prior to installation of marine riser) 

NaCl WBM–12,000 bbl Cuttings–1,800 bbl 

Discharge at seabed N/A N/A 

Uncontaminated seawater 

Seawater returned to the sea without the addition of chemicals 

Drilling rig oncethrough noncontact cooling water–35,000 bbl/day 

Discharge overboard Continuous N/A 

Desalinization unit water 

Chemically treated seawater associated with the process of creating freshwater from seawater 

25,000 bbl/day Discharge overboard Continuous N/A 

Uncontaminated bilge & ballast water 

 Discharge 

overboard 

Excess cement with cementing chemicals Excess cement 100 bbl Discharge overboard N/A Discharge at seabed withou

treatment 

RCRA exempt wastes in quantities >50 bbl/month 

N/A N/A N/A N/A N/A 

Non-RCRA exempt wastes in quantities >50 bbl/month 

Mud sacks, pails, pallets, shrink wrap, drums 

7,000 sacks, 100 pails, 12 drums, 145 pallets, 145 shrink wrap 

Shipment to shore base for collection by municipal operations 

Hazardous wastes in reportable quantities NORM- contaminated wastes N/A N/A N/A N/A N/A Wastes not addressed in listing above in quantities >50 bbl/month 
C-5

Table C-2 

Drilling Wastes Table - 4-Way Extra Salt Well (estimated 3 wells) 

Waste Generated during 

Drilling 

Composition/ Description Projected Amount Disposal Method Maximum 

Discharge Rate 

Treatment & 

Discharge 

Method 

Water-based drilling fluids N/A 

None (see "Muds, cuttings, & cement at the seafloor" below) 

N/A N/A N/A 

Nonaqueous drilling fluids 

Internal olefin/ester blend or internal olefin/ paraffin blend 

3,000 bbl/well discharged (<6.9% ROC with drilled cuttings) 

Discharge overboard 1,000 bbls/hr 

Discharge through shunt line 40 ft beloseawater surface 

Drill cuttings associated with water-based fluids N/A 

None (see "Muds, cuttings, & cement at the seafloor" below) 

N/A N/A N/A 

Drill cuttings associated with nonaqueous based fluids 

Cuttings coated with synthetic-based drilling mud 

3,100 bbl/well Discharge overboard 1,000 bbl/hr 

Discharge through shunt line 40 ft beloseawater surface 

Sanitary wastes Human body waste from toilets & urinals 30 gal/person/day Discharge overboard Continuous 

Marine sanitation device treatment & discharge overboard 

Domestic wastes 

Discharge from galleys, sinks, and showers (gray water) 

50 gal/person/day Discharge overboard Continuous Discharge overboard 

Deck drainage Platform washings, drains Dependent on rainfall Discharge overboard Dependent on rainfall Treat with separator to remove free oWell treatment, workover, or completion fluids 

Calcium chloride (CaCl2)/Calcium bromide 

(CaBr) 

Discharge: 2,500 bbl/well; dispose as waste on shore: 500 bbl/well; send to shore for reclamation: 2,500 bbl/well 

Discharge overboard, dispose as waste on shore, and send to shore for reclamation 

N/A N/A 
C-6

Table C-2. Drilling Wastes Table - 4-Way Extra Salt Well (estimated 3 wells) (continued). 

Waste Generated during 

Drilling 

Composition/ Description Projected Amount Disposal Method Maximum 

Discharge Rate 

Treatment & 

Discharge 

Method 

Muds, cuttings, & cement at the seafloor 

Seawater, NaCl polymer, drill cuttings, cement (Prior to installation of the marine riser). 

NaCl water-based mud (WBM)–20,000 bbl Cuttings–3,000 bbl 

Discharge at seabed N/A N/A 

Uncontaminated seawater 

Seawater returned to the sea without the addition of chemicals 

Drilling rig once-through noncontact cooling water– 35,000 bbl/day 

Discharge overboard Continuous N/A 

Desalinization unit water 

Chemically treated sea water associated with the process of creating freshwater from seawater 

25,000 bbl/day 

Discharge overboard Continuous N/A 

Uncontaminated Bilge Water 

Discharge overboard 

Uncontaminated ballast water 

 Discharge 

overboard 

Excess cement with cementing chemicals Excess cement 100 bbl Discharge overboard N/A Discharge at seabed withou

treatment 

RCRA exempt wastes in quantities >50 bbl/month 

N/A N/A N/A N/A N/A 

Non-RCRA exempt wastes in quantities >50 bbl/month 

Mud sacks, pails, pallets, shrink wrap, drums 

7,800 sacks, 100 pails, 12 drums, 160 pallets, 160 shrink wrap 

Shipment to shore base for collection by municipal operations 

Hazardous wastes in reportable quantities NORM- contaminated wastes N/A N/A N/A N/A N/A Wastes not addressed in listing above in quantities >50 bbl/month 
C-7

Table C-3 

Drilling Wastes Table - 3-Way Subsalt Wells (estimated 8 wells) 

Waste Generated 

during Drilling 

Composition/ 

Description 

Projected Amount Disposal Method Maximum Discharge 

Rate 

Treatment & 

Discharge Method 

Water-based drilling fluids 

N/A None (see "Muds, 

cuttings, & cement at the seafloor" below) 

N/A N/A N/A 

Nonaqueous drilling fluids 

Internal olefin/ester blend or internal olefin/ paraffin blend

2,300 bbl/well discharge (<6.9% ROC with drilled cuttings 

Discharge overboard 1,000 bbl/hr Discharge through 

shunt line 40 ft below seawater surface 

Drill cuttings associated with water-based fluids 

N/A None (see "Muds, 

cuttings, & cement at the seafloor" below) 

N/A N/A N/A 

Drill cuttings associated with nonaqueous based fluids 

Cuttings coated with synthetic-based drilling mud 2,400 bbl/well 

Discharge overboard 1,000 bbl/hr Discharge through 

shunt line 40 ft below seawater surface 

Sanitary wastes Human body waste 

from toilets & urinals

30 gal/person/day Discharge overboard 

Continuous Treat with marine 

sanitation device and discharge overboard 

Domestic wastes Discharge from 

galleys, sinks, and showers (gray water) 

50 gal/person/day Discharge overboard Continuous Discharge overboard 

Deck drainage Platform washings, 

drains 

Dependent on rainfall 

Discharge overboard Dependent on 

rainfall 

Treat with separator to remove free oil 

Well treatment, work-over, or completion fluids 

Calcium chloride (CaCl2)/Calcium 

bromide (CaBr) 

Discharge: 2,500 bbl/well; dispose as waste on shore: 500 bbl/well; send to shore for reclamation: 2,500 bbl/well 

Discharge overboard dispose as waste onshore and send to shore for reclamation

N/A N/A 

Muds, cuttings, & cement at the seafloor 

Seawater NaCl polymer, drill cuttings, cement (Prior to installation of marine riser) 

NaCl WBM–100,000 bbl Cuttings–2,300 bbl 

Discharge at seabed N/A N/A 
C-8

Table C-3. Drilling Wastes Table - 3-Way Subsalt Wells (estimated 8 wells) (continued). 

Waste Generated 

during Drilling 

Composition/ 

Description 

Projected Amount Disposal Method Maximum Discharge 

Rate 

Treatment & 

Discharge Method 

Uncontaminated seawater 

Seawater returned to the sea without the addition of chemicals 

Drilling rig oncethrough noncontact cooling water– 35,000 bbl 

Discharge overboard Continuous N/A 

Desalinization unit water 

Chemically treated seawater associated with the process of creating freshwater from seawater 

25,000 bbl/day Discharge overboard Continuous N/A 

Uncontaminated bilge water 

 Discharge overboard 

Uncontaminated ballast water 

 Discharge overboard 

Excess cement with cementing chemicals 

Excess cement 100 bbl Discharge overboard N/A Discharge at seabed 

without treatment 

RCRA exempt wastes in quantities >50 bbl/month 

N/A N/A N/A N/A N/A 

Non-RCRA exempt wastes in quantities >50 bbl/month 

Mud sacks, pails, pallets, shrink wrap, drums 

5,000 sacks, 100 pails, 12 drums, 125 pallets, 125 shrink wrap 

Shipment to shore base for collection by municipal operations 

 

Hazardous wastes in reportable quantities NORMcontaminated wastes N/A N/A N/A N/A N/A Wastes not addressed in listing above in quantities >50 bbl/month Produced water Formation water 

containing scale inhibitors and methanol 

140,000 bbl/day (max) 

Injected for formation pressure support 

N/A N/A 

Wastes from use of production chemicals 

Ethylene glycol Low-dosage hydrate inhibitor 

20 gal/day 1,000 bbl (notional) 

Pipe to shore; injected/pipe to shore-3 times/yr 

N/A N/A 
C-9

Table C-3. Drilling Wastes Table - 3-Way Subsalt Wells (estimated 8 wells) (continued). 

Waste Generated 

during Drilling 

Composition/ 

Description 

Projected Amount Disposal Method Maximum Discharge 

Rate 

Treatment & 

Discharge Method 

Produced sand Oil-contaminated 

produced sand 

400 bbl/yr Transport onshore for 

disposal 

N/A N/A 

Sanitary wastes Human body waste 

discharge from toilets and urinals 

5,400 gal/day Discharge overboard Continuous Treat with marine 

sanitation device/ chlorine and discharge overboard 

Domestic wastes Discharge from 

galleys, sinks, and showers (gray water) 

9,000 gal/day Discharge overboard Continuous Treat to remove 

floating solids and discharge overboard 

Deck drainage Platform washings, 

drains 

Dependent on rainfall 

Discharge overboard 15 bbl/hr Treat to remove free 

oil 
C-10

Table C-4 

Production Wastes Table - All Wells 

Waste Generated during 

Production 

Composition/ Description Projected Amount Disposal Method Maximum 

Discharge Rate 

Treatmen

Discharg

Method 

Uncontaminated freshwater or seawater 

Seawater returned to the sea without the addition of chemicals--no freshwater 

5,000 bbl/day Discharge overboard N/A N/A 

Desalinization unit water 

Water associated with the process of creating freshwater from seawater 

25,000 bbl Discharge overboard Continuous N/A 

Uncontaminated bilge water 345 bbl/day Discharge overboard 

 No free oil; 

no treatmendischarge overboard 

Uncontaminated ballast water 345 bbl/day Discharge overboard 

 No free oil; 

no treatmendischarge overboard 

Freshwater or seawater with treatment chemicals added 

Seawater-- hypochlorite treated-once-through noncontact cooling water 

1,000,000 bbl/day Discharge overboard No treatme

discharge overboard 

Hydrostatic tests 

Seawater used to pressure test new piping and subsea system 

6,000 bbl total operation 

Discharge overboard 

 No treatme

discharge overboard 

RCRA exempt wastes in quantities >50 bbl/month 

N/A N/A N/A N/A N/A 

Non-RCRA exempt solid wastes/trash 

Plastic, paper, aluminum, food, & refuse 840 tons 

Transported to shore base for municipal pickup 

Waste Generated during Production 

Composition/ Description Projected Amount Disposal Method Maximum 

Discharge Rate 

Treatment & Discharge Method 

Hazardous wastes in reportable quantities N/A NORM- contaminated wastes N/A Wastes not address to listing above in quantities >50 bbl/ month 

Refuse generated during painting operations N/A N/A N/A 

BP stated in their DOCD that they will adhere to all requirements of the USEPA's offshore general NPDES discharge permit's limitations

stated that their corporate expectations dictate that new projects will use the best available techniques for handling operational discharges. provides data on BP's use of synthetic-based drilling fluid to drill the proposed production wells. BP is not proposing to use oil-based drillproject. 
C-11

Table C-5 

Synthetic-Based Drilling Fluid and Cuttings Disposition 

Type of Drilling Fluid Estimated Volume of Mud 

Used per Well 

Mud Disposal Method Estimated Volume of 

Cuttings Generated per Well 

Cutting

Synthetic 16,000 bbl Return to vendor 4,500 bbl Discha

<6.9% 
D-1

APPENDIX D 

Geology 
D-3

APPENDIX D 

GEOLOGY

General Description

The present day Gulf of Mexico (GOM) is a small ocean basin with an area of more than 1.6 million 

km2

 (0.62 million mi2); its greatest water depth is approximately 3,700 m (12,140 ft). It is almost 

completely surrounded by land, opening to the Atlantic Ocean through the Straits of Florida and to the 

Caribbean Sea through the Yucatan Channel. Underlying the present GOM and the adjacent coast is the 

larger geologic basin that began forming in Triassic time. Over the last 20 million years, clastic 

sediments (sands and silts) have poured into the GOM Basin from the north and west. The centers of 

sediment deposition shifted progressively eastward and southward in response to changes in the source of 

sediment supply. Sediments of more than 15 km (9.32 mi) in thickness have been deposited. Each 

sediment layer is different, reflecting the source of the material and the geologic processes occurring 

during deposition. In places where the Gulf was shallow and intermittently dry, evaporitic deposits such 

as salt were formed. Where gradual subsidence and shallow seas persisted over time, marine plants and 

animals created reefs. Where marine life was abundant, the deposition of limestone was dominant. 

The physiographic provinces in the GOM — shelf, slope, rise, and abyssal plain — reflect the 

underlying geology. In the Gulf, the continental shelf extends seaward from the shoreline to about the 

200-m (656-ft) water depth and is characterized by a gentle slope (less than 1 degree). The shelf is wide 

off Texas, but it is narrower or absent where the Mississippi River delta has extended across the entire 

shelf. The continental slope extends from the shelf edge to the continental rise, usually at about the 

2,000-m (6,562 ft) water depth. The topography of the slope in the Gulf is uneven and is broken by 

canyons, troughs, and escarpments. The gradient on the slope is characteristically 3-6 degrees, but it may 

exceed 20 degrees in some places, particularly along escarpments. The continental rise is the apron of 

sediment accumulated at the base of the slope. It is a gentle incline, with slopes of less than 1 degree, to 

the abyssal plain. The abyssal plain is the flat region of the basin floor at the base of the continental rise. 

The Western Gulf, which includes both the Western and Central Planning Areas, is a clastic province. 

Many wells have been drilled in the Western Gulf, and the geology has been studied in detail for the 

identification and development of natural gas and oil resources. Exploration and development in the 

GOM have resulted in the identification of more than 1,000 fields. 

Sedimentary features, such as deltas, fans, canyons, and sediment flow forms, are formed by the 

erosion of land and deposition of sediments. Structural features, such as faults, folds, and ridges, are 

produced by displacement and deformation of rocks. The regional dip of sediments in the GOM is 

interrupted by salt diapirs, shale diapirs, and growth faults. Deformation has been primarily in response 

to heavy sediment loading. 

The most significant factor controlling the hydrocarbon potential in the northern GOM is the 

environment of deposition. Sediments deposited on the outer shelf and upper slope have the greatest 

potential for hydrocarbon accumulation because it is the optimum zone for encountering the three factors 

necessary for the successful formation and accumulation of oil and gas: source material, reservoir space, 

and geologic traps. The massive shale beds with high organic content are excellent source beds. The 

thick sands and sandstones with good porosity (pore space between the sand grains where oil and gas can 

exist) and permeability (connections between the pore spaces through which oil and gas can flow) provide 

reservoir space. Impermeable shales, salt dome caprocks, and faults serve as seals, trapping oil and gas in 

the pore spaces of the reservoir rocks. 

The geologic horizons with the greatest potential for hydrocarbon accumulation on the continental 

shelf of the northern GOM are of Pliocene and Pleistocene age. Producing horizons become 

progressively younger in a seaward direction. Recent developments in high-energy, 3-D seismic 

technology allow the oil and gas industry to “see” below the regional salt layers and to identify potential 

“subsalt plays” or hydrocarbon traps. 

The presence of hydrogen sulfide (H2S) within formation fluids occurs sporadically throughout the 

GOM OCS. Oil and gas containing certain levels of H2S is called “sour.” Approximately 65 operations 
D-4

have encountered H2S-bearing zones on the GOM OCS to date. Occurrences of H2S offshore Texas are 

in Miocene-age rocks and occur principally within a geographically narrow band. There is some debate 

as to the origin of the H2S in these offshore Texas wells, as they were reported mostly from deep, hightemperature wells drilled with a ligno-sulfonate mud component, which is widely believed to break down 

under high wellbore temperature to generate H2S. The occurrences of H2S offshore Louisiana are mostly 

on or near piercement domes with caprock and are associated with salt and gypsum deposits. The H2S 

from a caprock environment is generally thought to be a reaction product of sulfates and hydrocarbons in 

the presence of sulfate-reducing microbes. In some areas offshore Louisiana, H2S-rich hydrocarbons are 

produced from lower Cretaceous-age limestone deposits not associated with piercement domes. 

Generally, formations of Lower Cretaceous age or older (which are deeply buried in the Gulf) are prone 

to contain H2S in association with their hydrocarbons (cf. Bryan and Lingamallu, 1990). There has also 

been some evidence that petroleum from deepwater plays contain significant amounts of sulfur (cf. Smith, 

written communication, 1996; Thorpe, 1996). 

The concentrations of H2S found in conjunction with hydrocarbons vary extensively. The 

examination of in-house data suggest that H2S concentrations vary from as low as fractional parts per 

million (ppm) to as high as 650,000 ppm in one isolated case (the next highest concentrations of H2S 

reported are about 55,000 and 19,000 ppm). The concentrations of H2S found to date are generally 

greatest in the eastern portion of the Central Planning Area. 

Geologic Hazards

The major geologic hazards that may affect oil and gas activities within the GOM north of 26°N. 

latitude can be generally grouped into the following categories: (1) slope instability and mass transport of 

sediments; (2) gas hydrates; (3) sediment types and characteristics; and (4) tectonics. 

Geologic conditions that promote seafloor instability are variable sediment types, steep slopes, highsedimentation rates, gas hydrates at or near the seafloor, interstitial gas, faulting, areas of lithified and 

mounded carbonates, salt and shale mobilization, and mudflows. Some features that may indicate a 

possible unstable condition include step faulting, deformed bedding, detached blocks, detached masses, 

displaced lithologies, acoustically transparent layers, anomalously thick accumulations of sediment, and 

shallow faulting and fissures. These features can be identified on seismic survey profiles or through sea 

bottom coring samples. 

Mass movement of sediments includes landslides, slumps, and creeps. Sediment types, accumulation 

rates, sediment accumulation over features with seafloor relief, and internal composition and structure of 

the sedimentary layers are all factors that affect seafloor stability. Rapidly accumulated sediments that 

have not had the opportunity to dewater properly are underconsolidated. These underconsolidated 

sediments can be interbedded with normal or overconsolidated sediments and may act as slide zones 

causing mass movement or collapse. A slope of less than 1 degree can be sufficient to cause sliding or 

slumping when high sedimentation rates have resulted in underconsolidation or high pore-pressure 

conditions in the sediments. 

In the deepwater areas of the Gulf, slope stability and soil properties are of great concern in the design 

of oil and gas operations. Slopes steep enough to create conditions conducive to mass transport are found 

regionally on the continental slope. Steeper slopes are found locally along the walls of canyons and 

channels, adjacent to salt structures, and at fault scarps. 

Some of the gas hydrates that occur in the upper sediments of the deepwater Gulf are of biogenic 

rather than petrogenic origin. Methane is the major and often the only component. Gas hydrates are more 

prevalent in deeper waters because of the lower temperature and high pressures at these depths. The 

effect of gas pressure, distribution of gas in pores, solution-dissolution potential, and upward dispersal 

characteristics are factors considered in the engineering design of production facilities. 

Overpressured salt, shale, and mud have a tendency to become plasticized and mobile. Movements of 

overpressured salts and shales could form mounds and diapirs. Large diapirs formed by the upward 

movement of shale or salt originates from a greater depth and do not form an environmental geologic 

hazard by itself. These features have associated faulting and sometimes collapse structures. Their 

upward movement causes slope steepening and consequently slumping. Movement of overpressured mud 

could form mud volcanoes at the seafloor. Soft mud diapirs resulting from delta front muds are excellent 

indicators of an unstable sediment at shallow depths. 
D-5

Evidence of geologic hazards includes hydrocarbon seeps, deformed bedding, detached blocks or 

masses, anomalously thick accumulations of sediments, shallow faulting and fissures, diapirs, sediment 

dikes or mud lumps, displaced lithologies, internal chaotic masses, hummocky topography, en echelon 

faulting, and horst and graben blocks. Evidence of geologic hazards can be obtained or seen by using 

core sampling techniques, high-resolution seismic surveying, and side-scan sonar. Geologic hazards pose 

engineering, structural design, and operational concerns that can usually be effectively mitigated through 

existing technologies or may require the development of new technologies and designs. 

References 

Bryan, F. and S.N. Lingamalu. 1990. Hydrogen sulfide occurrence in Gulf of Mexico outer continental 

shelf operations. U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS 

Region, New Orleans, LA. 8 pp. 

Smith, M. 1996. Written communication. Notes on GRI Offshore Gas Processing Workshop, 

February 13, 1996, New Orleans, LA. 

Thorpe, H. 1996. Oil and water. Texas Monthly 24(2):88-93 and 140-145. 
E-1

APPENDIX E 

Socioeconomic Tables 
E-3

Table E-1 

Onshore Allocations 

Sector Sector Definition TX-1 TX-2 LA-1 LA-2 LA-3 MA-1 FL-1 FL-2 FL-3 FL-4 

38 Oil & Gas Operations 0.00 0.34 0.09 0.06 0.15 0.00 0.00 0.00 0.00 0.00 50 New Gas Utility Facilities 0.07 0.38 0.05 0.10 0.10 0.10 0.00 0.00 0.00 0.00 53 Misc. Natural Resource 

Facility Construction 

0.03 0.21 0.23 0.15 0.30 0.02 0.00 0.00 0.00 0.00 

56 Maintenance and Repair, 

Other Facilities 

0.06 0.31 0.04 0.08 0.09 0.08 0.00 0.00 0.00 0.00 

57 Other Oil & Gas Field 

Services 

0.00 0.30 0.26 0.12 0.16 0.00 0.00 0.00 0.00 0.00 

160 Office Furniture and 

Equipment 

0.15 0.54 0.00 0.00 0.08 0.23 0.00 0.00 0.00 0.00 

178 Maps and Charts (Misc. 

Publishing) 

0.12 0.59 0.02 0.06 0.11 0.10 0.00 0.00 0.00 0.00 

206 Explosives 0.50 0.50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 209 Chemicals, NEC 0.03 0.64 0.04 0.10 0.04 0.04 0.00 0.00 0.00 0.00 210 Petroleum Fuels 0.11 0.50 0.09 0.16 0.09 0.05 0.00 0.00 0.00 0.00 232 Hydraulic Cement 0.00 0.10 0.00 0.00 0.00 0.10 0.00 0.00 0.00 0.00 258 Steel Pipe and Tubes 0.00 0.50 0.31 0.05 0.07 0.00 0.00 0.00 0.00 0.00 284 Fabricated Plate Work 0.04 0.63 0.06 0.09 0.05 0.14 0.00 0.00 0.00 0.00 290 Iron and Steel Forgings 0.00 0.81 0.00 0.00 0.05 0.00 0.00 0.00 0.00 0.00 307 Turbines 0.05 0.65 0.00 0.10 0.20 0.00 0.00 0.00 0.00 0.00 311 Construction Machinery 

& Equipment 

0.06 0.42 0.00 0.06 0.19 0.11 0.00 0.00 0.00 0.00 

313 Oil & Gas Field 

Machinery & Equipment 

0.03 0.18 0.27 0.18 0.22 0.00 0.00 0.00 0.00 0.00 

331 Special Industrial 

Machinery 

0.00 0.00 0.00 0.38 0.54 0.00 0.00 0.00 0.00 0.00 

332 Pumps & Compressors 0.04 0.30 0.17 0.22 0.09 0.00 0.00 0.00 0.00 0.00 354 Industrial Machines, NEC 0.05 0.66 0.06 0.10 0.06 0.06 0.00 0.00 0.00 0.00 356 Switchgear 0.00 0.63 0.00 0.07 0.11 0.07 0.00 0.00 0.00 0.00 374 Communication 

Equipment, NEC 

0.13 0.50 0.00 0.00 0.25 0.00 0.00 0.00 0.00 0.00 

392 Shipbuilding and Ship 

Repair 

0.09 0.24 0.05 0.24 0.18 0.19 0.00 0.00 0.00 0.00 

399 Transportation 

Equipment, NEC 

0.00 0.78 0.06 0.11 0.00 0.06 0.00 0.00 0.00 0.00 

401 Lab Equipment 0.00 1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 403 Instrumentation 0.01 0.13 0.39 0.27 0.08 0.00 0.00 0.00 0.00 0.00 
E-4

Table E-1. Onshore Allocations (continued). 

Sector Sector Definition TX-1 TX-2 LA-1 LA-2 LA-3 MA-1 FL-1 FL-2 FL-3 FL-4 

435 Demurrage/Warehousing/ 

Motor Freight 

0.11 0.37 0.21 0.09 0.09 0.01 0.00 0.00 0.00 0.00 

436 Water Transport 0.02 0.27 0.10 0.25 0.22 0.04 0.01 0.00 0.01 0.00 437 Air Transport 0.03 0.42 0.11 0.11 0.08 0.02 0.00 0.00 0.00 0.01 441 Communications 0.09 0.51 0.07 0.11 0.11 0.11 0.00 0.00 0.00 0.00 443 Electric Services 0.13 0.36 0.06 0.15 0.12 0.18 0.00 0.00 0.00 0.00 444 Gas 

Production/Distribution 

0.10 0.54 0.08 0.07 0.05 0.03 0.00 0.00 0.00 0.00 

445 Water Supply 0.08 0.43 0.08 0.12 0.05 0.11 0.00 0.00 0.00 0.00 446 Waste Treatment/Disposal 0.00 1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 454 Eating/Drinking 0.00 0.24 0.28 0.08 0.40 0.00 0.00 0.00 0.00 0.00 455 Misc. Retail 0.09 0.48 0.06 0.10 0.15 0.11 0.00 0.00 0.00 0.00 459 Insurance 0.04 0.47 0.07 0.12 0.09 0.00 0.00 0.00 0.00 0.00 462 Real Estate 0.09 0.47 0.04 0.08 0.11 0.08 0.00 0.00 0.00 0.00 469 Advertisement 0.06 0.45 0.06 0.08 0.15 0.08 0.00 0.00 0.00 0.00 470 Other Business Services 0.00 0.60 0.11 0.09 0.06 0.00 0.00 0.00 0.00 0.00 473 Misc. Equipment Rental & 

Leasing 

0.09 0.26 0.22 0.10 0.10 0.01 0.00 0.00 0.00 0.00 

490 Doctors & Veterinarian 

Services 

0.09 0.53 0.06 0.09 0.14 0.08 0.00 0.00 0.00 0.00 

494 Legal Services 0.07 0.48 0.07 0.11 0.19 0.08 0.00 0.00 0.00 0.00 506 Environmental/Engineering 

Services 

0.06 0.38 0.11 0.08 0.08 0.03 0.01 0.00 0.02 0.00 

507 Acct/Misc. Business 

Services 

0.06 0.46 0.05 0.09 0.13 0.07 0.00 0.00 0.00 0.00 

508 Management/Consulting 

Services 

0.04 0.54 0.04 0. 09 0.11 0.05 0.00 0.00 0.00 0.00 

509 Testing/Research Facilities 0.00 0.38 0.14 0.14 0.05 0.00 0.00 0.00 0.00 0.00 
E-5

Table E-2 

Population Forecast from 2000 to 2041 by Year and by Coastal Subarea (in thousands) 

Year LA-1 LA-2 LA-3 MA-1 TX-1 TX-2 FL-1 FL-2 FL-3 FL-4 CGOM WGOM 

2000 667.12 1,009.54 1,337.60 920.12 920.58 5,158.08 774.39 128.07 3,954.32 2,340.67 3,934.36 6,078.66 2001 672.18 1,020.72 1,343.62 930.79 930.98 5,238.54 787.39 129.53 4,022.21 2,362.41 3,967.32 6,169.52 2002 677.35 1,032.14 1,350.07 941.63 941.65 5,320.26 800.68 131.07 4,091.10 2,384.86 4,001.19 6,261.91 2003 682.66 1,043.66 1,356.53 952.61 952.50 5,402.58 813.98 132.59 4,160.29 2,408.00 4,035.47 6,355.07 2004 688.01 1,055.31 1,363.03 963.72 963.47 5,486.16 827.51 134.14 4,230.65 2,431.38 4,070.07 6,449.64 2005 693.29 1,066.73 1,369.47 974.61 974.23 5,567.43 840.64 135.65 4,298.86 2,454.36 4,104.10 6,541.66 2006 698.70 1,078.41 1,376.22 985.73 985.30 5,650.56 854.05 137.23 4,368.60 2,478.49 4,139.06 6,635.87 2007 704.16 1,090.21 1,382.99 996.98 996.51 5,734.94 867.67 138.82 4,439.48 2,502.86 4,174.34 6,731.45 2008 709.66 1,102.14 1,389.80 1,008.35 1,007.84 5,820.57 881.51 140.44 4,511.50 2,527.47 4,209.96 6,828.41 2009 715.20 1,114.20 1,396.65 1,019.86 1,019.30 5,907.49 895.57 142.07 4,584.70 2,552.32 4,245.91 6,926.78 2010 720.38 1,125.14 1,403.21 1,030.25 1,029.64 5,983.33 907.72 143.54 4,647.77 2,575.09 4,278.97 7,012.97 2011 726.20 1,137.43 1,410.76 1,041.94 1,041.44 6,069.85 921.64 145.17 4,720.05 2,601.26 4,316.33 7,111.28 2012 732.08 1,149.85 1,418.35 1,053.77 1,053.36 6,157.62 935.78 146.82 4,793.45 2,627.70 4,354.04 7,210.98 2013 738.00 1,162.40 1,425.99 1,065.73 1,065.43 6,246.66 950.13 148.48 4,868.00 2,654.41 4,392.11 7,312.09 2014 743.97 1,175.09 1,433.66 1,077.82 1,077.63 6,336.99 964.70 150.17 4,943.70 2,681.38 4,430.54 7,414.62 2015 749.53 1,186.60 1,440.99 1,088.74 1,088.63 6,416.17 977.37 151.69 5,009.36 2,706.02 4,465.86 7,504.81 2016 755.65 1,199.33 1,449.10 1,100.87 1,100.92 6,505.30 991.66 153.38 5,083.64 2,733.69 4,504.94 7,606.21 2017 761.83 1,212.18 1,457.25 1,113.13 1,113.34 6,595.66 1,006.17 155.09 5,159.02 2,761.65 4,544.39 7,708.99 2018 768.05 1,225.18 1,465.45 1,125.53 1,125.90 6,687.28 1,020.90 156.81 5,235.52 2,789.89 4,584.21 7,813.17 2019 774.33 1,238.32 1,473.70 1,138.06 1,138.60 6,780.17 1,035.83 158.56 5,313.15 2,818.42 4,624.40 7,918.77 2020 780.19 1,250.28 1,481.58 1,149.44 1,150.11 6,862.28 1,048.94 160.14 5,381.16 2,844.53 4,661.48 8,012.39 2021 786.67 1,263.57 1,490.31 1,162.08 1,162.96 6,954.70 1,063.76 161.94 5,460.95 2,873.84 4,702.62 8,117.67 2022 793.20 1,276.99 1,499.09 1,174.87 1,175.96 7,048.36 1,078.79 163.76 5,538.93 2,903.44 4,744.15 8,224.32 2023 799.79 1,290.56 1,507.92 1,187.80 1,189.10 7,143.29 1,094.04 165.60 5,618.02 2,933.35 4,786.07 8,332.39 2024 806.43 1,304.27 1,516.81 1,200.87 1,202.39 7,239.49 1,109.49 167.46 5,698.24 2,963.56 4,828.38 8,441.88 2025 812.61 1,316.73 1,525.25 1,212.71 1,214.41 7,324.63 1,123.09 169.14 5,765.56 2,991.12 4,867.31 8,539.04 2026 819.36 1,330.72 1,534.24 1,226.06 1,227.98 7,423.27 1,138.95 171.03 5,847.89 3,021.93 4,910.38 8,651.25 2027 826.17 1,344.86 1,543.28 1,239.55 1,241.70 7,523.25 1,155.05 172.95 5,931.39 3,053.06 4,953.86 8,764.95 2028 833.03 1,359.15 1,552.38 1,253.19 1,255.58 7,624.57 1,171.37 174.90 6,016.09 3,084.51 4,997.74 8,880.15 2029 839.95 1,373.59 1,561.52 1,266.98 1,269.61 7,727.25 1,187.92 176.86 6,101.99 3,116.29 5,042.04 8,996.86 2030 846.93 1,388.18 1,570.73 1,280.92 1,283.80 7,831.32 1,204.70 178.84 6,189.12 3,148.39 5,086.75 9,115.12 2031 853.96 1,402.93 1,579.98 1,295.01 1,298.15 7,936.79 1,221.72 180.85 6,277.50 3,180.82 5,131.89 9,234.93 2032 861.06 1,417.83 1,589.29 1,309.26 1,312.65 8,043.68 1,238.98 182.88 6,367.14 3,213.58 5,177.45 9,356.33 2033 868.21 1,432.90 1,598.66 1,323.67 1,327.32 8,152.01 1,256.49 184.93 6,458.06 3,246.69 5,223.43 9,479.33 2034 875.42 1,448.12 1,608.08 1,338.23 1,342.16 8,261.79 1,274.24 187.01 6,550.27 3,280.13 5,269.86 9,603.95 2035 882.70 1,463.50 1,617.56 1,352.96 1,357.16 8,373.06 1,292.25 189.11 6,643.80 3,313.92 5,316.72 9,730.22 2036 890.03 1,479.05 1,627.09 1,367.85 1,372.32 8,485.82 1,310.50 191.23 6,738.67 3,348.06 5,364.02 9,858.15 2037 897.42 1,494.77 1,636.68 1,382.90 1,387.66 8,600.11 1,329.02 193.38 6,834.90 3,382.54 5,411.76 9,987.77 2038 904.88 1,510.65 1,646.32 1,398.12 1,403.17 8,715.93 1,347.80 195.55 6,932.49 3,417.39 5,459.96 10,119.10 2039 912.39 1,526.69 1,656.02 1,413.50 1,418.85 8,833.31 1,366.84 197.75 7,031.48 3,452.59 5,508.61 10,252.16 2040 919.97 1,542.91 1,665.78 1,429.05 1,434.70 8,952.28 1,386.15 199.96 7,131.89 3,488.16 5,557.72 10,386.98 2041 927.62 1,559.31 1,675.60 1,444.78 1,450.74 9,072.84 1,405.74 202.21 7,233.72 3,524.09 5,607.30 10,523.58 
E-6

Table E-3 

Employment Forecast from 2000 to 2041 by Year and by Subarea (in thousands) 

Year LA-1 LA-2 LA-3 MA-1 TX-1 TX-2 FL-1 FL-2 FL-3 FL-4 CGOM WGOM 

2000 377.47 571.95 781.67 515.20 454.25 3,046.85 427.04 44.99 2,248.28 1,306.73 2,246.29 3,501.12001 381.65 580.15 787.95 522.71 460.67 3,095.53 435.03 45.55 2,298.83 1,324.75 2,272.46 3,556.22002 386.15 590.66 793.66 529.89 466.67 3,143.66 442.85 46.10 2,347.94 1,341.81 2,300.36 3,610.32003 391.13 597.79 799.20 537.22 472.64 3,192.77 450.71 46.63 2,396.65 1,358.41 2,325.34 3,665.42004 396.19 605.00 804.77 544.65 478.68 3,242.66 458.72 47.17 2,446.37 1,375.22 2,350.61 3,721.32005 401.12 612.06 810.28 551.90 484.58 3,291.14 466.47 47.69 2,494.20 1,391.66 2,375.37 3,775.72006 406.59 620.40 816.60 559.63 490.78 3,342.60 474.56 48.24 2,543.53 1,408.55 2,403.22 3,833.32007 412.12 628.86 822.98 567.47 497.06 3,394.87 482.78 48.79 2,593.82 1,425.64 2,431.43 3,891.92008 417.74 637.43 829.40 575.41 503.42 3,447.96 491.15 49.34 2,645.12 1,442.94 2,459.98 3,951.32009 423.43 646.11 835.87 583.47 509.87 3,501.87 499.66 49.92 2,697.43 1,460.44 2,488.88 4,011.72010 428.46 653.79 841.92 590.56 515.60 3,548.60 506.92 50.41 2,740.96 1,476.14 2,514.73 4,064.22011 434.19 662.57 849.67 598.72 522.23 3,603.53 515.28 50.97 2,791.75 1,494.05 2,545.16 4,125.72012 440.01 671.47 857.50 606.99 528.94 3,659.31 523.78 51.53 2,843.48 1,512.18 2,575.96 4,188.22013 445.90 680.48 865.39 615.38 535.74 3,715.96 532.42 52.10 2,896.18 1,530.54 2,607.16 4,251.72014 451.88 689.62 873.36 623.88 542.62 3,773.49 541.20 52.68 2,949.85 1,549.11 2,638.74 4,316.12015 457.17 697.71 880.71 631.38 548.75 3,823.42 548.75 53.20 2,995.06 1,565.76 2,666.96 4,372.12016 463.11 706.94 889.98 639.94 555.91 3,882.59 557.39 53.77 3,047.79 1,585.13 2,699.96 4,438.52017 469.12 716.29 899.34 648.63 563.16 3,942.68 566.16 54.35 3,101.45 1,604.74 2,733.38 4,505.82018 475.22 725.76 908.80 657.43 570.51 4,003.70 575.07 54.93 3,156.06 1,624.59 2,767.22 4,574.22019 481.39 735.36 918.37 666.36 577.96 4,065.66 584.12 55.52 3,211.62 1,644.68 2,801.48 4,643.62020 486.90 743.91 927.09 674.27 584.60 4,119.61 591.98 56.06 3,259.01 1,662.71 2,832.17 4,704.22021 493.05 753.66 937.98 683.29 592.41 4,183.83 600.92 56.64 3,314.18 1,683.95 2,867.98 4,776.22022 499.28 763.55 948.98 692.43 600.34 4,249.05 610.00 57.23 3,370.29 1,705.46 2,904.24 4,849.32023 505.58 773.56 960.12 701.70 608.37 4,315.29 619.21 57.83 3,427.35 1,727.25 2,940.97 4,923.62024 511.97 783.70 971.39 711.09 616.50 4,382.57 628.56 58.43 3,485.38 1,749.31 2,978.16 4,999.02025 517.67 792.71 981.53 719.41 623.71 4,440.89 636.71 58.98 3,535.04 1,768.97 3,011.32 5,064.62026 524.21 803.11 993.05 729.03 632.05 4,510.12 646.33 59.60 3,594.89 1,791.57 3,049.40 5,142.12027 530.83 813.64 1,004.71 738.79 640.50 4,580.44 656.09 60.22 3,655.75 1,814.46 3,087.97 5,220.92028 537.54 824.31 1,016.50 748.67 649.07 4,651.84 666.01 60.85 3,717.65 1,837.64 3,127.02 5,300.92029 544.33 835.12 1,028.43 758.69 657.75 4,724.36 676.07 61.48 3,780.59 1,861.11 3,166.57 5,382.12030 551.20 846.08 1,040.50 768.84 666.55 4,798.01 686.28 62.12 3,844.59 1,884.89 3,206.62 5,464.52031 558.17 857.17 1,052.71 779.13 675.46 4,872.81 696.65 62.77 3,909.68 1,908.97 3,247.18 5,548.22032 565.22 868.41 1,065.07 789.55 684.50 4,948.77 707.17 63.43 3,975.88 1,933.35 3,288.25 5,633.22033 572.36 879.80 1,077.57 800.12 693.65 5,025.92 717.85 64.09 4,043.19 1,958.05 3,329.85 5,719.52034 579.59 891.34 1,090.22 810.83 702.93 5,104.27 728.70 64.76 4,111.64 1,983.06 3,371.97 5,807.22035 586.91 903.03 1,103.01 821.68 712.33 5,183.85 739.70 65.43 4,181.25 2,008.40 3,414.63 5,896.12036 594.32 914.88 1,115.96 832.67 721.86 5,264.66 750.88 66.11 4,252.05 2,034.06 3,457.83 5,986.52037 601.83 926.87 1,129.06 843.81 731.51 5,346.73 762.22 66.80 4,324.03 2,060.04 3,501.57 6,078.22038 609.43 939.03 1,142.31 855.10 741.29 5,430.08 773.74 67.50 4,397.24 2,086.36 3,545.87 6,171.32039 617.13 951.34 1,155.72 866.54 751.21 5,514.74 785.42 68.21 4,471.69 2,113.01 3,590.74 6,265.92040 624.93 963.82 1,169.28 878.14 761.25 5,600.71 797.29 68.92 4,547.40 2,140.00 3,636.17 6,361.92041 632.82 976.46 1,183.01 889.89 771.44 5,688.02 809.33 69.64 4,624.39 2,167.34 3,682.18 6,459.4

Source: Woods and Poole Economics, Inc., 2002 
E-7

Table E-4 

Estimated Employment Impacts for BP's DOCD for the Proposed Action Known as Thunder Horse 

(peak employment is projected for the year 2004 as shown) 

Onshore 

Subarea 

Direct 

Employment 

Indirect 

Employment 

Induced 

Employment 

Total 

Employment 

Baseline 

Employment 

Plan 

of B

FL-1 1 1 0 2 458,721 0FL-2 0 0 0 0 47,166 0FL-3 2 1 1 4 2,446,369 0FL-4 0 0 0 1 1,375,217 0EGOM 3 2 2 7 2,952,256 0LA-1 156 30 56 242 396,186 0LA-2 119 41 48 208 605,001 0LA-3 194 54 73 320 804,768 0MA-1 13 4 5 21 544,654 0CGOM 482 129 181 792 1,805,955 0TX-1 20 5 7 33 478,678 0TX-2 306 155 168 628 3,242,655 0WGOM 326 160 175 661 3,721,334 0Total GOM 811 291 357 1460 6,712,356 0
E-8

Table E-5 

Estimated Opportunity Cost Employment Associated with the Cleanup and Remediation of a Worst Case Spil

 (based on 141,000 bbl spilled; Year 2004) 

 Direct Indirect Induced Total Plan as a  Low High Low High Low High Low High 

Baseline 

Employment Low 

FL-1 5 11 3 7 2 5 9 24 458,721 0.00% FL-2 0 0 0 0 0 0 0 0 47,166 0.00% FL-3 8 20 5 14 4 10 17 43 2,446,369 0.00% FL-4 1 3 1 2 1 2 3 7 1,375,217 0.00% EGOM 14 35 9 23 7 17 29 74 2,952,256 0.00% LA-1 257 708 57 161 128 313 442 1,182 396,186 0.11% LA-2 322 831 63 168 151 352 536 1,351 605,001 0.09% LA-3 490 1,082 102 232 279 595 871 1,909 804,768 0.11% MA-1 210 443 41 88 112 234 363 765 544,654 0.07% CGOM 1,279 3,065 263 649 671 1,493 2,213 5,207 1,805,955 0.12% TX-1 231 493 54 118 118 248 402 860 478,678 0.08% TX-2 1,067 2,588 342 827 693 1,570 2,102 4,984 3,242,655 0.06% WGOM 1,298 3,081 395 946 811 1,818 2,504 5,844 3,721,334 0.07% 

Total GOM 2,592 6,180 667 1,617 1,488 3,327 4,747 11,125 6,712,356 0.07% 
F-1

APPENDIX F 

Meteorological Conditions 
F-3

APPENDIX F 

METEOROLOGICAL CONDITIONS

General Description 

The Gulf of Mexico (GOM) is influenced by a maritime subtropical climate controlled mainly by the 

clockwise circulation around the semipermanent area of high barometric pressure commonly known as 

the Bermuda High -- a high-pressure cell. The center of the high is usually located in the Atlantic Ocean 

or sometimes near the Azores Islands off the coast of Spain (Henry et al., 1994). The GOM is located to 

the southwest of this center of circulation. This proximity to the high-pressure system results in a 

predominantly east to southeasterly flow in the GOM region. Two important classes of cyclonic storms 

are occasionally superimposed on this circulation pattern. During the winter months of December 

through March, cold fronts associated with cold continental air masses influence mainly the northern 

coastal areas of the GOM. Behind the fronts, strong north winds bring drier air into the region. During 

the summer and fall months of June through October, tropical cyclones may develop or migrate into the 

GOM. These storms may affect any area of the GOM and substantially alter the local wind circulation 

around them. In coastal areas, the sea breeze effect may become the primary circulation feature during 

the summer months of May through October. In general, however, the maritime subtropical climate is the 

dominant feature in driving all aspects of the weather in this region; as a result, the climate shows 

relatively small diurnal variation in summer. 

Two types of air masses primarily govern the climatology of the GOM region. One type of air mass 

is the warm and moist, maritime tropical air; the other type is very cold and dry, continental polar air. 

During summer months, the mid-latitude polar jet retreats northward, allowing maritime air to dominate 

through the GOM. In the southeastern region of the GOM, the climate is dominated by the warm and 

moist, maritime tropical air year round. 

Pressure, Temperature, and Relative Humidity 

The western extension of the Bermuda High into the GOM dominates the circulation throughout the 

year; the high-pressure center is weakening in winter and strengthening in summer. The average monthly 

pressure shows a west to east gradient during the summer. In the winter, the monthly pressure is more 

uniform. The minimum average monthly pressure occurs during the summer. The maximum pressure 

occurs during the winter as a result of the pressure and influence of transitional continental cold air. 

At coastal locations, the average air temperatures vary with latitude and exposure. Winter 

temperatures depend on the frequency and intensity of penetration by polar air masses from the north. Air 

temperatures over the open Gulf exhibit much smaller variation on a daily and seasonal basis due to the 

moderating effect of the large body of water. 

Due to the presence of the warm, moist, maritime tropical air mass in the southern GOM, the relative 

humidity in this region is high throughout the year. Minimum humidities occur during the late fall and 

winter when cold, continental air masses bring dry air into the northern Gulf. Maximum humidities occur 

during the spring and summer. 

Surface Winds 

Winds are more variable near the coast than over open waters because coastal winds are more directly 

influenced by the moving cyclonic storms that are characteristic of the continent and because of the land 

and sea breeze regime. During the relatively constant summer conditions, the southerly positions of the 

Bermuda High generate predominantly southeasterly winds in the northern Gulf and easterly winds in the 

southern parts of the Gulf. Winter winds usually blow from northeasterly directions and become more 

easterly in the southern parts of the Gulf. 

Precipitation and Visibility 

Precipitation is frequent and abundant throughout the year but does show distinct seasonal variation. 

The highest precipitation rates occur during the warmer months of the year. The warmer months usually 

have convective cloud systems that produce showers and thunderstorms; however, these thunderstorms 
F-4

rarely cause any damage or have attendant hail (USDOC, 1967; Brower et al., 1972). Hail can occur 

when water droplets freeze in the strong updraft of a convective cloud system. Winter rains are 

associated with the frequent passage of frontal systems through the area. Rainfalls are generally slow, 

steady, and relatively continuous, often lasting several days. For example, the annual average 

precipitation in Lake Charles, Louisiana, is 1.35 m (53 in). In the northern parts of the Gulf, snowfalls are 

rare, and when frozen precipitation does occur, it usually melts upon contact with the ground. Incidence 

of frozen precipitation decreases with distance offshore and rapidly reaches zero. In the southern portions 

of the GOM, because of warm climate, the frozen precipitation is unlikely to occur. 

Warm, moist Gulf air blowing slowly over chilled land or water surfaces brings about the formation 

of fog. Fog occurrence decreases seaward, but visibility has been less than 800 m (less than 1⁄2 mile) due 

to offshore fog in the coastal area. Coastal fogs generally last 3 or 4 hours, although particularly dense 

sea fogs may persist for several days. The poorest visibility conditions occur during winter and early 

spring. The period from November through April has the most days with low visibility. Industrial 

pollution and agricultural burning also impact visibility. 

Atmospheric Stability and Mixing Height 

Mixing height is very important because it determines the volume of air available for dispersing 

pollutants. Mixing height is directly related to vertical mixing in the atmosphere. A mixed layer is 

expected to occur under neutral and unstable atmospheric conditions. Vertical mixing is most vigorous 

during unstable conditions. Vertical motion is suppressed during stable conditions. The mixing height 

tends to be lower in winter, and daily variations are smaller than in summer. 

Not all of the Pasquill-Gifford stability classes are found offshore in the GOM. Specifically, the F 

stability class seldom occurs and the G stability class is markedly absent. The G stability class is the 

extremely stable condition that only develops at night over land with rapid radiative cooling. This large 

body of water is simply incapable of losing enough heat overnight to set up a strong radiative inversion. 

Likewise, the A stability class is rarely present but could be encountered during cold air outbreaks in the 

wintertime, particularly over warmer waters. Category A is the extremely unstable condition that requires 

a very rapid warming of the lower layer of the atmosphere, along with cold air aloft. This is normally 

brought about when cold air is advected aloft, and in strong insolation rapidly warms the earth’s surface, 

which, in turn, warms the lowest layer of the atmosphere. Once again, the ocean surface is incapable of 

warming rapidly; therefore, you would not expect to find stability class A over the ocean. For the most 

part, the stability is neutral to slightly unstable. 

In this area, the over-water stability is predominantly unstable, with neutral conditions making up the 

bulk of the remainder of the time (Hsu, 1996; Marks, written communication, 1996 and 1997; Nowlin et 

al., 1998). Stable conditions do occur, although infrequently. 

The mixing heights offshore are quite shallow, 900 m or less (Hsu, 1996; Nowlin et al., 1998). The 

exception to this is close to shore, where the influence of the land penetrates out over the water for a short 

distance. Transient cold fronts also have an impact on the mixing heights; some of the lowest heights can 

be expected to occur with frontal passages and on the cold-air side of the fronts. This effect is caused by 

the frontal inversion. 

Severe Storms 

The GOM is part of the Atlantic tropical cyclone basin. Tropical cyclones generally occur in summer 

and fall seasons; however, the Gulf also experiences winter storms or extratropical storms. These winter 

storms generally originate in middle and high latitudes and have winds that can attain speeds of 15-26 

m/sec (11.2-58.2 mph). The Gulf is an area of cyclone development during cooler months due to the 

contrast of the warm air over the Gulf and the cold continental air over North America. Cyclogenesis, or 

the formation of extratropical cyclones, in the GOM is associated with frontal overrunning (Hsu, 1992). 

The most severe extratropical storms in the Gulf originate when a cold front encounters the subtropical 

jetstream over the warm waters of the Gulf. Statistics of 100-year data of extratropical cyclones reveal 

that most activity occurs above 25o

N. latitude in the Western GOM. The mean number of these storms 

ranges from 0.9 storms per year near the southern tip of Florida to 4.2 over central Louisiana (USDOI, 

MMS, 1988). 
F-5

The frequency of cold fronts in the Gulf exhibits similar synoptic weather patterns during the fourmonth period of December through March. During this time the area of frontal influence reaches south to 

10o

N latitude. Frontal frequency is about nine fronts per month in February (1 front every 3 days on the 

average) and about seven fronts per month in March (1 front every 4-5 days on the average). By May, the 

frequency decreases to about four fronts per month (1 front every 7-8 days), and the region of frontal 

influence retreats to about 15o

N latitude. During June through August, frontal activity decreases to 

almost zero and fronts seldom reach below 25oN latitude. (USDOI, MMS, 1988). 

Tropical cyclones affecting the Gulf originate over the equatorial portions of the Atlantic Ocean, the 

Caribbean Sea, and the GOM. Tropical cyclones occur most frequently between June and November. 

Based on 42 years of data, there are about 9.9 storms per year with about 5.5 of those becoming major 

hurricanes in the Atlantic Ocean (Gray, written communication, 1992). Data from 1886 to 1986 show 

that 44.5 percent of these storms, or 3.7 storms per year, will affect the GOM (USDOI, MMS, 1988). The 

Yucatan Channel is the main entrance of Atlantic storms into the GOM, and a reduced translation speed 

over Gulf waters leads to longer residence times in this basin. The probability of occurrence for a tropical 

storm in Louisiana and Mississippi is on average about 15 percent. 

There is a high probability that tropical storms will cause damage to physical, economic, biological, 

and social systems in the Gulf. Tropical storms also affect OCS operations and activities; platform design 

needs to consider the storm surge, waves, and currents generated by tropical storms. Most of the damage 

is caused by storm surge, waves, and high winds. Storm surge depends on local factors, such as bottom 

topography, coastline configuration, and storm intensity. Water depth and storm intensity control wave 

height during hurricane conditions. Sustained winds for major hurricanes (Saffir-Simpson Category 3 

and above) are higher than 49 m/sec (109.6 mph). 

References 

Brower, W.A., J.M. Meserve, and R.G. Quayle. 1972. Environmental guide for the U.S. Gulf Coast. 

U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Environmental Data 

Service, National Climatic Center, Asheville, NC. 

Gray, W.M. 1992. Written communication. Updated forecast of Atlantic seasonal activity for 1992. 

Henry, J.A., K.M. Portier, and J. Coyne. 1994. The climate and weather of Florida. Sarasota, FL: 

Pineapple Press, Inc. 

Hsu, S.A.. 1992. A study of extratropical cyclogenesis events along the mid- to outer Texas-Louisiana 

shelf. In: Proceedings; Twelfth Annual Gulf of Mexico Information Transfer Meeting. Sponsored 

by the U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New 

Orleans, LA. OCS Study MMS 922-0027. Pp. 341-347. 

Hsu, S.A. 1996. Analysis of ambient pollutant concentrations and meteorological conditions affecting 

EPA Class I and II areas in southeastern Louisiana. Volume II: Appendices. U.S. Dept. of the 

Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS Study 

MMS 96-0063. 364 pp. 

Marks, S. 1996. Written communication. Meteorological file. Observations from rig during drilling of 

Destin Dome 57 #1 well. DD 57 drilling rigs. 300 pp. 

Marks, S. 1997. Written communication. Compilation of meteorological data from actual observations 

in the Destin Dome Unit. 271 pp. 

Nowlin, W.D., Jr., A.E. Jochens, R.O. Reid, and S.F. DiMarco. 1998. Texas-Louisiana shelf circulation 

and transport processes study: Synthesis report. Volumes I and II. U.S. Dept. of the Interior, 

Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 

98-0036 and 98-0036. 502 and 288 pp., respectively. 

U.S. Dept. of Commerce. 1967. United States coast pilot 5. Atlantic Coast, Gulf of Mexico, Puerto Rico 

and Virgin Islands, 6th ed. Washington, DC: U.S. Coast and Geodetic Survey, Environmental 

Science Services Administration. 301 pp. 
F-6

U.S. Dept. of the Interior. Minerals Management Service. 1988. Meteorological database and synthesis 

for the Gulf of Mexico. Prepared by Florida A&M University for the Minerals Management Service, 

Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 88-0064. 486 pp. 
G-1 

APPENDIX G 

Physical Oceanography 
G-3

APPENDIX G 

PHYSICAL OCEANOGRAPHY

The Gulf of Mexico (GOM) is a semienclosed, subtropical sea with a surface area about 1.6 million 

km2

 (0.62 million mi2) (USDOI, MMS, 2000). The main physiographic regions of the Gulf Basin are the 

continental shelf (including the Campeche, Mexican, and U.S. shelves), continental slopes and associated 

canyons, abyssal plains, the Yucatan Channel, and Florida Straits. 

The Gulf of Mexico is unique oceanographically with a basin depth of 3,000 m (9.843 ft) and two 

shallow entrances of Yucatan Channel (1,600-m or 5,250-ft depth) and the Straits of Florida (1,000-m or 

3,281 ft) (USDOI, MMS, 2000). These “shallow” sills prevent the input of cold (2°C or 35.6°F) Atlantic 

bottom water and thus bottom water in the Gulf basin remains relatively warm (about 4°C or 39.2°F). 

The offshore oceanography is dominated by the Loop Current, the main origin of the Gulf Stream, and the 

inshore oceanography is heavily influenced by major freshwater input from precipitation and numerous 

river systems, including some extremely large ones such as the Mississippi and Atchafalaya Rivers. 

There are at least five major identifiable watermasses in the Central/Western Gulf of Mexico 

(USDOI, MMS, 2000): 

• Gulf of Mexico Water—(0-250 m; 0-820 ft); 

• Tropical Atlantic Central Water—(250-400 m; 820-1,312 ft); 

• Antarctic Intermediate Water (phosphate maximum)—(500-700 m; 1,641-2,297 ft); 

• Antarctic Intermediate Water (salinity maximum)—(600-860 m; 1,969-2,822 ft); and 

• Mixed Upper North Atlantic Deep and Caribbean mid water—(1,000-1,100 m; 

3,281-3,609 ft). 

These watermasses can be identified by their different temperatures and chemical signatures based on 

salinity, dissolved oxygen, nitrate, phosphate, and silicate concentrations. Below about 1,650 m (5,414 

ft), temperature, salinity, and oxygen remain fairly constant to the bottom at about 4oC (39.2oF), 35-36 

ppt, 5.0 ml/l, respectively (Gulf Basin Water) (Gallaway et al., 2001). 

In addition to the above watermasses, there is an upper mixed isothermal layer that varies in thickness 

but averages about 75 m (246 ft) in thickness (Pequegnat, 1983). Sea surface (i.e., 0-m depth) 

temperatures within the relevant area are fairly constant throughout the Gulf in August, about 30°C 

(86°F). In January, surface waters cool considerably in northern coastal areas (14-15°C or 57.2-59°F) and 

slightly in the center of the Loop Current to 25°C (77°F). At 1,000-m (3,281 ft) depths, the water 

temperatures are more or less constant at a cool 4.9°C (40.8°F) (USDOI, MMS, 2000). 

Oceanographic fronts are important features of marine systems because they tend to be productive 

areas and also concentrate drifting material such as plankton, which attracts fish, birds, turtles, and 

mammals for feeding purposes. Unfortunately, fronts also may collect debris such as floating plastics or 

contaminants such as oil slicks or tarballs. 

Fronts form along sharp discontinuities in temperature and or salinity; they can be horizontal or 

vertical and surface or subsurface. In the Gulf, semipermanent fronts form along the interface between 

the low salinity coastal or riverine water and offshore water and along edges of major currents (e.g., the 

Loop Current) and eddies. 

The Loop Current, a dominant feature of the Gulf, enters through the Yucatan Strait and exits through 

the Straits of Florida where it becomes the Gulf Stream. The Current flows clockwise around the fairly 

static water in the center of the Gulf. Its influence can be seen in hydrographic data to depths as deep as 

800-1,000 m (2,625-3,281 ft). It is a highly variable current in geographic extent (may go as far north as 

Mississippi-Alabama Shelf), width (25- to 50-km or 16- to 31-mi), and velocity [normally 100-200 

cm/sec (39.4-78.7 in/sec) but up to 300 cm/sec (118.1 in/sec)] (USDOI, MMS, 2000). 

On average, about once a year and on no regular pattern, the Loop Current will form into a “warm 

core eddy” with a diameter of 300-400 km (186-249 mi), a depth to 1,000 m (3,281 ft), and velocities of 

50-200 cm/sec (19.7-78.7 in/sec). These warm-core eddies normally move to the Western Gulf at speeds 

between 2 and 5 km (1and 3 mi) per day, out of the study area and have a life span of about one year. 

Smaller eddies (both clockwise and counterclockwise) are also created by the Loop Current and by other 
G-4

less known sources. Other currents are also present in the Gulf as ephemeral; semipermanent and 

permanent features, primarily wind-driven by prevailing winds and by extreme events such as hurricanes. 

The mechanisms of some currents are poorly known and are still subject to study (USDOI, MMS, 2001). 

Short-lived, intense current jets have been reported at mid-depths (to about 200 m (656 ft); see Figure 3-

17 in USDOI, MMS, 2001) along the Louisiana-Texas slope but little is known about them (USDOI, 

MMS, 2000). Loop Current eddies may be found to about 1,500 m (4,922 ft) and topographic Rossby 

Wave activity may be encountered below 500 m (1,640 ft), with possible intensification below 2,500-m 

(8,202-ft) depth (see Figure 3-17 in USDOI, MMS, 2001). Warm-core Loop Current eddies interacting 

with the continental slope to the north can result in strong eastward flow and negative offshore 

temperature gradients to at least 500 m (1,640 ft) water depth, and cold-core Loop Current frontal eddies 

interacting with the slope can result in westward flow following the slope bathymetry. The most 

characteristic flow pattern in the DeSoto Canyon continental slope region is a two-layer jet with eastward 

flow at the surface and a return flow at depth. The transition between the upper and lower flows varies 

with the offshore forcing but is typically between 200 and 300 m (656 and 984 ft) (Hamilton et al., 2000). 

Coastal currents, based on historical current meter data, for the northern Gulf of Mexico are described 

in Dinnel et al. (1997); their predominant directions are alongshore, east or west depending upon location. 

High frequency currents in continental slope regions near the DeSoto Canyon are dominated by 

inertial oscillations, with periods of about 1 day, that are present in deep water throughout the year. At 

the shelf break, inertial oscillations are present in the summer but not in the winter because of lack of 

stratification in winter. Hurricanes passing over the slope produce a strong inertial response, which can 

persist for many days (Hamilton et al., 2000). 

Average wave heights for the northern Gulf have been reported at 1 m (3 ft) with 94 percent being 2 

m (6.6 ft) or less, with a maximum height to 9.5 m (31 ft) (Quayle and Fulbright, 1977 in USDOI, MMS, 

2001). Because the Gulf of Mexico is an enclosed sea, and thus fetch is somewhat limited, long period, 

large amplitude waves are rare except during extreme events such as hurricanes (McGrail and Carnes, 

1983; NDBC, 1990; and others in USDOI, MMS, 2001). The maximum 100-yr wave height has been 

estimated by Ward et al. (1979) as 21 m (69 ft) for water depths of 100 m (328 ft) and greater (USDOI, 

MMS, 2000). 

References 

Dinnel, S.P., W.J. Wiseman, Jr., and L.J. Rouse, Jr. 1997. Coastal currents in the northern Gulf of 

Mexico. U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, 

New Orleans, LA. OCS Study MMS 97-0005. 113 pp. 

Gallaway, B.J., J.G. Cole, and L.R. Martin. 2000. The deep sea Gulf of Mexico: an overview and guide. 

U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, 

LA. OCS Study MMS 2001-065. 27 pp. 

Hamilton, P., T.J. Berger, J.J. Singer, E. Waddell, J.H. Churchill, R. Leben, T.N. Lee, and W. Sturges. 

2000. DeSoto Canyon eddy intrusion study, final report, Volume II: Technical report. U.S. Dept. of 

the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS 

Study MMS 2000-080. 275 pp. 

Pequegnat, W.E. 1983. The ecological communities of the continental slope and adjacent regimes of the 

northern Gulf of Mexico. Final report to the U.S. Dept. of the Interior, Minerals Management 

Service, Gulf of Mexico OCS Region, New Orleans, LA. Contract No. AA851-CT1-12). 

U.S. Dept. of the Interior. Minerals Management Service. 2000. Gulf of Mexico deepwater operations 

and activities; environmental assessment. U.S. Dept. of the Interior, Minerals Management Service, 

Gulf of Mexico OCS Region, New Orleans, LA. OCS EIS/EA MMS 2000-001. 264 pp. 

U.S. Dept. of the Interior. Minerals Management Service. 2001. Proposed use of floating production, 

storage, and offshore loading systems on the Gulf of Mexico continental shelf, Western and Central 

planning areas, final environmental impact statement. U.S. Dept. of the Interior, Minerals 

Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS EIS/EA MMS 2000-

090. 

Ward, E.G., L. Borgman, and V.J. Cardone. 1979. Statistics of hurricane waves in the Gulf of Mexico. 

J. Petroleum Technology, May 1979. Pp. 632-642. 
H-1

APPENDIX H 

Other Information on Grid 16 
H-3

Table H-1 

Lease Status 

Area Block Lease Company Name 

Lease 

Status 

AT 21 G24206 BHP Petroleum (GOM) Inc. Primary 

AT 22 G24207 Chevron U.S.A. Inc. Primary 

AT 23 G23009 Samedan Oil Corporation Primary 

AT 24 G24208 BHP Petroleum (GOM) Inc. Primary 

AT 25 G24209 BHP Petroleum (GOM) Inc. Primary 

AT 64 G13199 Chevron U.S.A. Inc. Unit 

AT 65 G24214 BHP Petroleum (GOM) Inc. Primary 

AT 66 G23010 Samedan Oil Corporation Primary 

AT 67 G23011 Samedan Oil Corporation Primary 

AT 68 G24215 Dominion Exploration & Production, Inc. Primary 

AT 70 G24216 Dominion Exploration & Production, Inc. Primary 

AT 109 G23015 Exxon Mobil Corporation Primary 

AT 111 G20136 Conoco Inc. Primary 

AT 112 G23016 Dominion Exploration & Production, Inc. Primary 

AT 113 G24218 Dominion Exploration & Production, Inc. Primary 

AT 114 G24219 Dominion Exploration & Production, Inc. Primary 

AT 154 G23020 Exxon Mobil Corporation Primary 

AT 155 G18504 Conoco Inc. Primary 

AT 156 G18505 Conoco Inc. Primary 

AT 157 G24224 Dominion Exploration & Production, Inc. Primary 

AT 196 G23023 Exxon Mobil Corporation Primary 

AT 197 G24228 Exxon Mobil Corporation Primary 

AT 198 G24229 Enterprise Oil Gulf of Mexico Inc. Primary 

AT 199 G20142 Conoco Inc. Primary 

AT 200 G18516 Conoco Inc. Primary 

AT 201 G20143 Conoco Inc. Primary 

AT 202 G18517 Chevron U.S.A. Inc. Primary 

AT 203 G18518 Chevron U.S.A. Inc. Primary 

AT 241 G18528 BP Exploration & Production Inc. Primary 

AT 244 G20146 BHP Petroleum (GOM) Inc. Primary 

AT 245 G20147 BHP Petroleum (GOM) Inc. Primary 

AT 246 G18529 Kerr-McGee Oil & Gas Corporation Primary 

AT 247 G18530 Kerr-McGee Oil & Gas Corporation Primary 

AT 284 G21833 Chevron U.S.A. Inc. Primary 

AT 285 G18546 Chevron U.S.A. Inc. Primary 

AT 286 G18547 Chevron U.S.A. Inc. Primary 

AT 287 G18548 Chevron U.S.A. Inc. Primary 

AT 288 G16895 BHP Petroleum (GOM) Inc. Primary 

AT 289 G18549 BHP Petroleum (GOM) Inc. Primary 

AT 328 G18564 Chevron U.S.A. Inc. Primary 

AT 329 G18565 Chevron U.S.A. Inc. Primary 

AT 330 G18566 Chevron U.S.A. Inc. Primary 
H-4

Table H-1. Lease Status (continued).

Area Block Lease Company Name 

Lease 

Status 

AT 331 G18567 Chevron U.S.A. Inc. Primary 

AT 332 G16898 BHP Petroleum (GOM) Inc. Primary 

AT 333 G16899 BHP Petroleum (GOM) Inc. Primary 

AT 336 G18569 Kerr-McGee Oil & Gas Corporation Primary 

AT 372 G18586 Chevron U.S.A. Inc. Primary 

AT 373 G18587 Chevron U.S.A. Inc. Primary 

AT 374 G18588 Chevron U.S.A. Inc. Primary 

AT 375 G18589 Chevron U.S.A. Inc. Primary 

AT 376 G18590 Chevron U.S.A. Inc. Primary 

AT 379 G21837 BHP Petroleum (GOM) Inc. Primary 

AT 380 G16906 BHP Petroleum (GOM) Inc. Primary 

AT 424 G18602 BP Exploration & Production Inc. Primary 

MC 36 G24038 Spinnaker Exploration Company, L.L.C. Primary 

MC 37 G24039 Amerada Hess Corporation Primary 

MC 38 G15462 Shell Offshore Inc. Primary 

MC 39 G22857 BP Exploration & Production Inc. Primary 

MC 40 G21741 Vastar Resources, Inc. Primary 

MC 80 G24042 Amerada Hess Corporation Primary 

MC 81 G24043 Amerada Hess Corporation Primary 

MC 82 G24044 BP Exploration & Production Inc. Primary 

MC 84 G08484 BP Exploration & Production Inc. Unit 

MC 85 G08797 BP Exploration & Production Inc. Unit 

MC 121 G14631 Shell Offshore Inc. Primary 

MC 122 G14632 Exxon Mobil Corporation Primary 

MC 123 G22862 Samedan Oil Corporation Primary 

MC 124 G24049 Spinnaker Exploration Company, L.L.C. Primary 

MC 125 G24050 Spinnaker Exploration Company, L.L.C. Primary 

MC 126 G18194 Vastar Resources, Inc. Primary 

MC 127 G19925 Vastar Resources, Inc. Primary 

MC 128 G08485 BP Exploration & Production Inc. Unit 

MC 128 G08485 BP Exploration & Production Inc. Unit 

MC 129 G10977 BP Exploration & Production Inc. Unit 

MC 162 G21746 Shell Offshore Inc. Primary 

MC 163 G21747 Shell Offshore Inc. Primary 

MC 164 G14633 Shell Offshore Inc. Primary 

MC 165 G24051 Conoco Inc. Primary 

MC 166 G24052 Conoco Inc. Primary 

MC 167 G08801 Exxon Mobil Corporation Producing 

MC 168 G24053 Conoco Inc. Primary 

MC 170 G16589 BP Exploration & Production Inc. Primary 

MC 171 G15469 BP Exploration & Production Inc. Primary 

MC 172 G15470 BP Exploration & Production Inc. Primary 

MC 173 G09789 BP Exploration & Production Inc. Unit 

MC 204 G24054 Samedan Oil Corporation Primary 

MC 205 G22864 Mariner Energy, Inc. Primary 

MC 208 G18202 Chevron U.S.A. Inc. Primary 
H-5

Table H-1. Lease Status (continued).

Area Block Lease Company Name 

Lease 

Status 

MC 209 G24055 Spinnaker Exploration Company, L.L.C. Primary 

MC 210 G24056 Spinnaker Exploration Company, L.L.C. Primary 

MC 211 G08803 Exxon Mobil Corporation Producing 

MC 212 G24057 Conoco Inc. Primary 

MC 213 G24058 Dominion Exploration & Production, Inc. Primary 

MC 214 G24059 Dominion Exploration & Production, Inc. Primary 

MC 215 G24060 Dominion Exploration & Production, Inc. Primary 

MC 216 G24061 Conoco Inc. Primary 

MC 249 G16593 Chevron U.S.A. Inc. Primary 

MC 250 G18206 BP Exploration & Production Inc. Primary 

MC 251 G14636 BHP Petroleum (GOM) Inc. Primary 

MC 252 G18207 Chevron U.S.A. Inc. Primary 

MC 253 G24062 Conoco Inc. Primary 

MC 254 G24063 Conoco Inc. Primary 

MC 255 G24064 Conoco Inc. Primary 

MC 256 G22865 Conoco Inc. Primary 

MC 257 G24065 Conoco Inc. Primary 

MC 258 G24066 LLOG Exploration Offshore, Inc. Primary 

MC 259 G24067 Conoco Inc. Primary 

MC 287 G18214 Kerr-McGee Oil & Gas Corporation Primary 

MC 288 G18215 Murphy Exploration & Production Company Primary 

MC 290 G19934 TotalFinaElf E&P USA, Inc. Primary 

MC 292 G08806 Chevron U.S.A. Inc. Producing 

MC 293 G16596 Chevron U.S.A. Inc. Primary 

MC 294 G16597 Marathon Oil Company Primary 

MC 295 G15472 Exxon Mobil Corporation Primary 

MC 296 G21164 Chevron U.S.A. Inc. Primary 

MC 297 G15473 Exxon Mobil Corporation Primary 

MC 298 G15474 Exxon Mobil Corporation Primary 

MC 299 G21752 Murphy Exploration & Production Company Primary 

MC 300 G22868 Conoco Inc. Primary 

MC 301 G24069 Conoco Inc. Primary 

MC 302 G24070 Conoco Inc. Primary 

MC 303 G16598 BP Exploration & Production Inc. Primary 

MC 330 G18221 Kerr-McGee Oil & Gas Corporation Primary 

MC 331 G18222 Shell Offshore Inc. Primary 

MC 332 G18223 Chevron U.S.A. Inc. Primary 

MC 336 G16601 Texaco Exploration and Production Inc. Primary 

MC 337 G16602 Chevron U.S.A. Inc. Primary 

MC 338 G16603 Amerada Hess Corporation Primary 

MC 339 G18224 Amerada Hess Corporation Primary 

MC 341 G24071 Conoco Inc. Primary 

MC 342 G24072 Conoco Inc. Primary 

MC 343 G24073 Murphy Exploration & Production Company Primary 

MC 344 G24074 Conoco Inc. Primary 

MC 345 G24075 Murphy Exploration & Production Company Primary 
H-6

Table H-1. Lease Status (continued).

Area Block Lease Company Name 

Lease 

Status 

MC 374 G19943 TotalFinaElf E&P USA, Inc. Primary 

MC 375 G18231 Burlington Resources Offshore Inc. Primary 

MC 376 G19944 Anadarko Petroleum Corporation Primary 

MC 377 G19945 Anadarko Petroleum Corporation Primary 

MC 378 G21166 Murphy Exploration & Production Company Primary 

MC 379 G21167 Murphy Exploration & Production Company Primary 

MC 380 G16604 Chevron U.S.A. Inc. Primary 

MC 381 G16605 Chevron U.S.A. Inc. Primary 

MC 382 G21168 Amerada Hess Corporation Primary 

MC 383 G07937 Shell Offshore Inc. SOP 

MC 385 G07938 Shell Offshore Inc. Unit 

MC 386 G21753 Shell Offshore Inc. Primary 

MC 387 G22873 Conoco Inc. Primary 

MC 418 G19948 Amerada Hess Corporation Primary 

MC 419 G19949 Amerada Hess Corporation Primary 

MC 421 G19950 Anadarko Petroleum Corporation Primary 

MC 422 G21757 Exxon Mobil Corporation Primary 

MC 424 G16606 Chevron U.S.A. Inc. Primary 

MC 425 G16607 Chevron U.S.A. Inc. Primary 

MC 426 G21170 Amerada Hess Corporation Primary 

MC 427 G16608 EEX Corporation Primary 

MC 429 G07944 Shell Offshore Inc. Unit 

MC 430 G09808 Shell Offshore Inc. Unit 

MC 462 G15485 BP Exploration & Production Inc. Primary 

MC 463 G24076 Exxon Mobil Corporation Primary 

MC 464 G19955 Exxon Mobil Corporation Primary 

MC 465 G19956 Exxon Mobil Corporation Primary 

MC 466 G21761 Exxon Mobil Corporation Primary 

MC 469 G16610 Chevron U.S.A. Inc. Primary 

MC 470 G24077 Conoco Inc. Primary 

MC 471 G24078 BP Exploration & Production Inc. Primary 

MC 472 G15486 Shell Offshore Inc. Primary 

MC 473 G24079 Conoco Inc. Primary 

MC 505 G14006 BP Exploration & Production Inc. Primary 

MC 506 G14007 BP Exploration & Production Inc. Primary 

MC 507 G14008 BP Exploration & Production Inc. Primary 

MC 508 G21764 Exxon Mobil Corporation Primary 

MC 509 G21765 Exxon Mobil Corporation Primary 

MC 511 G18250 Chevron U.S.A. Inc. Primary 

MC 512 G21766 Exxon Mobil Corporation Primary 

MC 514 G24085 Conoco Inc. Primary 

MC 515 G24086 Spinnaker Exploration Company, L.L.C. Primary 

MC 516 G24087 Conoco Inc. Primary 

MC 517 G22882 Conoco Inc. Primary 

MC 551 G19964 Exxon Mobil Corporation Primary 

MC 552 G16616 Shell Offshore Inc. Primary 
H-7

Table H-1. Lease Status (continued).

Area Block Lease Company Name 

Lease 

Status 

MC 553 G21175 Amerada Hess Corporation Primary 

MC 554 G21769 Exxon Mobil Corporation Primary 

MC 555 G21770 Exxon Mobil Corporation Primary 

MC 556 G16617 Chevron U.S.A. Inc. Primary 

MC 557 G16618 Chevron U.S.A. Inc. Primary 

MC 558 G15491 Exxon Mobil Corporation Primary 

MC 559 G15492 Exxon Mobil Corporation Primary 

MC 560 G24092 Conoco Inc. Primary 

MC 561 G19965 Burlington Resources Offshore Inc. Primary 

MC 592 G22889 Shell Offshore Inc. Primary 

MC 593 G19969 BP Exploration & Production Inc. Primary 

MC 594 G19970 Shell Offshore Inc. Primary 

MC 595 G21177 Dominion Exploration & Production, Inc. Primary 

MC 596 G22890 Marathon Oil Company Primary 

MC 597 G21178 Amerada Hess Corporation Primary 

MC 598 G19971 Exxon Mobil Corporation Primary 

MC 599 G19972 Exxon Mobil Corporation Primary 

MC 600 G16627 Chevron U.S.A. Inc. Primary 

MC 601 G16628 Chevron U.S.A. Inc. Primary 

MC 602 G22891 Samedan Oil Corporation Primary 

MC 605 G19973 Burlington Resources Offshore Inc. Primary 

MC 636 G15499 Shell Offshore Inc. Primary 

MC 637 G15500 Shell Offshore Inc. Primary 

MC 639 G21180 Dominion Exploration & Production, Inc. Primary 

MC 640 G16630 Chevron U.S.A. Inc. Primary 

MC 642 G16631 Chevron U.S.A. Inc. Primary 

MC 643 G19979 BP Exploration & Production Inc. Primary 

MC 644 G16632 BP Exploration & Production Inc. Primary 

MC 645 G16633 BP Exploration & Production Inc. Primary 

MC 648 G14644 BP Exploration & Production Inc. Primary 

MC 649 G16634 BHP Petroleum (GOM) Inc. Primary 

MC 680 G18271 TotalFinaElf E&P USA, Inc. Primary 

MC 681 G18272 Amerada Hess Corporation Primary 

MC 682 G21776 Chevron U.S.A. Inc. Primary 

MC 683 G16636 Chevron U.S.A. Inc. Primary 

MC 684 G16637 Chevron U.S.A. Inc. Primary 

MC 686 G05862 Shell Offshore Inc. Unit 

MC 687 G05863 Shell Offshore Inc. Unit 

MC 688 G19984 Mobil Oil Exploration & Producing Southeast Inc. Primary 

MC 689 G21777 Exxon Mobil Corporation Primary 

MC 691 G16638 BP Exploration & Production Inc. Primary 

MC 692 G16639 BP Exploration & Production Inc. Primary 

MC 693 G16640 BHP Petroleum (GOM) Inc. Primary 

MC 724 G22897 Chevron U.S.A. Inc. Primary 

MC 725 G22898 BP Exploration & Production Inc. Primary 

MC 726 G24101 BP Exploration & Production Inc. Primary 
H-8

Table H-1. Lease Status (continued).

Area Block Lease Company Name 

Lease 

Status 

MC 727 G24102 BP Exploration & Production Inc. Primary 

MC 728 G16644 Dominion Exploration & Production, Inc. Primary 

MC 729 G19988 Dominion Exploration & Production, Inc. Primary 

MC 730 G07954 Shell Offshore Inc. Unit 

MC 731 G07955 Shell Offshore Inc. Unit 

MC 732 G19989 Mobil Oil Exploration & Producing Southeast Inc. Primary 

MC 733 G19990 Mobil Oil Exploration & Producing Southeast Inc. Primary 

MC 734 G21778 Dominion Exploration & Production, Inc. Primary 

MC 735 G19991 Shell Offshore Inc. Primary 

MC 736 G14652 BP Exploration & Production Inc. Primary 

MC 737 G16645 Chevron U.S.A. Inc. Primary 

MC 768 G22900 Phillips Petroleum Company Primary 

MC 769 G24106 Samedan Oil Corporation Primary 

MC 771 G24107 Dominion Exploration & Production, Inc. Primary 

MC 772 G16647 Dominion Exploration & Production, Inc. Primary 

MC 773 G19996 Dominion Exploration & Production, Inc. Primary 

MC 774 G21186 Murphy Exploration & Production Company Primary 

MC 775 G19997 BP Exploration & Production Inc. Unit 

MC 776 G09866 BP Exploration & Production Inc. Unit 

MC 777 G09867 BP Exploration & Production Inc. Unit 

MC 778 G09868 BP Exploration & Production Inc. Unit 

MC 779 G19998 Shell Offshore Inc. Primary 

MC 812 G22903 BP Exploration & Production Inc. Primary 

MC 814 G24114 BP Exploration & Production Inc. Primary 

MC 815 G18294 BP Exploration & Production Inc. Primary 

MC 816 G18295 BP Exploration & Production Inc. Primary 

MC 817 G18296 Chevron U.S.A. Inc. Primary 

MC 819 G12168 BP Exploration & Production Inc. Unit 

MC 820 G14656 BP Exploration & Production Inc. Unit 

MC 821 G14657 BP Exploration & Production Inc. Unit 

MC 822 G14658 BP Exploration & Production Inc. Unit 

MC 823 G18297 BP Exploration & Production Inc. Primary 

MC 856 G24119 Amerada Hess Corporation Primary 

MC 857 G22908 Amerada Hess Corporation Primary 

MC 859 G16652 BP Exploration & Production Inc. Primary 

MC 860 G18301 Chevron U.S.A. Inc. Primary 

MC 862 G18302 Shell Offshore Inc. Primary 

MC 863 G18303 Shell Offshore Inc. Primary 

MC 864 G15519 Chevron U.S.A. Inc. Primary 

MC 900 G22911 Amerada Hess Corporation Primary 

MC 901 G22912 Amerada Hess Corporation Primary 

MC 903 G16655 BP Exploration & Production Inc. Primary 

MC 904 G18309 Chevron U.S.A. Inc. Primary 

MC 906 G24124 Dominion Exploration & Production, Inc. Primary 

MC 907 G24125 Dominion Exploration & Production, Inc. Primary 

MC 908 G16656 Chevron U.S.A. Inc. Primary 
H-9

Table H-1. Lease Status (continued).

Area Block Lease Company Name 

Lease 

Status 

MC 944 G15522 BHP Petroleum (GOM) Inc. Primary 

MC 945 G15523 BHP Petroleum (GOM) Inc. Primary 

MC 948 G15524 Chevron U.S.A. Inc. Primary 

MC 949 G18311 Chevron U.S.A. Inc. Primary 

MC 988 G15528 Shell Offshore Inc. Primary 

MC 989 G15529 Shell Offshore Inc. Primary 

MC 990 G18317 Chevron U.S.A. Inc. Primary 

MC 991 G18318 Chevron U.S.A. Inc. Primary 

MC 992 G24133 BHP Petroleum (GOM) Inc. Primary 

MC 993 G24134 Marathon Oil Company Primary 

VK 872 G19907 Shell Offshore Inc. Primary 

VK 873 G19908 Shell Offshore Inc. PROD 

VK 874 G24015 Chevron U.S.A. Inc. Primary 

VK 913 G08784 Shell Offshore Inc. Unit 

VK 913 G08784 Amoco Production Company Unit 

VK 914 G08785 BP Exploration & Production Inc. PROD 

VK 915 G06894 BP Exploration & Production Inc. Unit 

VK 916 G21733 Shell Offshore Inc. Primary 

VK 917 G15441 BP Exploration & Production Inc. Primary 

VK 956 G06896 Shell Offshore Inc. Unit 

VK 957 G08475 BP Exploration & Production Inc. Unit 

VK 957 G08475 Shell Offshore Inc. Unit 

VK 959 G22837 Murphy Exploration & Production Company Primary 

VK 960 G14617 BP Exploration & Production Inc. Primary 

VK 961 G15444 BP Exploration & Production Inc. Primary 

VK 962 G15445 BP Exploration & Production Inc. Primary 

VK 999 G21158 Vastar Resources, Inc. Primary 

VK 1000 G16559 Vastar Resources, Inc. Primary 

VK 1001 G16560 Vastar Resources, Inc. Primary 

VK 1002 G21159 Vastar Resources, Inc. Primary 

VK 1003 G21160 TotalFinaElf E&P USA, Inc. Primary 

VK 1004 G14620 BP Exploration & Production Inc. Primary 

VK 1006 G21737 Kerr-McGee Oil & Gas Corporation Primary 

Notes: AT = Atwater Valley 

 MC = Mississippi Canyon 

 VK = Viosca Knoll 
H-10

Table H-2 

Plans Status 

Area Block Control No. Plan Company Name Action Date 

AT 111 N-6413 EP Conoco Inc. 11-May-98 

AT 155 N-6213 EP Conoco Inc. 21-Oct-98 

AT 155 R-3520 EP Conoco Inc. 31-Aug-00 

AT 156 N-6213 EP Conoco Inc. 21-Oct-98 

AT 199 N-6359 EP Conoco Inc. 02-Feb-99 

AT 200 N-6359 EP Conoco Inc. 02-Feb-99 

AT 287 N-7326 EP Chevron U.S.A. Inc. 30-Jan-02 

AT 331 N-7326 EP Chevron U.S.A. Inc. 30-Jan-02 

AT 336 N-6571 EP 

The Louisiana Land and Exploration 

Company 22-Oct-99 

AT 375 N-6300 EP Chevron U.S.A. Inc. 13-Nov-98 

AT 376 N-6300 EP Chevron U.S.A. Inc. 13-Nov-98 

AT 380 N-7313 EP BHP Billiton Petroleum (GOM) Inc. 21-Feb-02 

MC 84 N-4208 EP BP America Production Company 24-Jan-92 

MC 84 N-5841 DOCD BP America Production Company 22-Sep-97 

MC 84 R-2835 EP BP America Production Company 14-Oct-92 

MC 84 S-3630 EP BP America Production Company 31-May-95 

MC 85 N-4418 EP BP America Production Company 26-Feb-93 

MC 85 N-5841 DOCD BP America Production Company 22-Sep-97 

MC 85 R-3398 DOCD BP America Production Company 20-Apr-00 

MC 85 S-3779 EP BP America Production Company 03-Nov-95 

MC 126 N-6208 EP Vastar Resources, Inc. 30-Nov-98 

MC 126 R-3359 EP Vastar Resources, Inc. 14-Oct-99 

MC 127 N-6208 EP Vastar Resources, Inc. 30-Nov-98 

MC 127 N-7195 DOCD Vastar Resources, Inc. 21-Feb-02 

MC 127 R-3298 EP Vastar Resources, Inc. 25-May-99 

MC 127 R-3320 EP Vastar Resources, Inc. 28-Jun-99 

MC 127 R-3339 EP Vastar Resources, Inc. 03-Sep-99 

MC 127 S-5417 EP Vastar Resources, Inc. 04-Jan-01 

MC 129 N-4208 EP BP America Production Company 24-Jan-92 

MC 129 N-5841 DOCD BP America Production Company 22-Sep-97 

MC 129 R-3398 DOCD BP America Production Company 20-Apr-00 

MC 129 R-3539 DOCD BP America Production Company 04-Dec-00 

MC 129 S-3779 EP BP America Production Company 03-Nov-95 

MC 167 N-5701 EP Exxon Mobil Corporation 24-Mar-97 

MC 173 N-5963 DOCD BP America Production Company 26-Feb-98 

MC 173 R-3550 DOCD BP America Production Company 26-Mar-01 

MC 173 R-3568 DOCD BP America Production Company 07-Dec-00 

MC 205 N-7221 EP Mariner Energy, Inc. 28-Sep-01 

MC 211 N-3540 EP Exxon Mobil Corporation 01-Feb-90 

MC 211 N-5701 EP Exxon Mobil Corporation 24-Mar-97 

MC 211 N-6665 DOCD Exxon Mobil Corporation 07-Apr-00 

MC 211 R-3507 DOCD Exxon Mobil Corporation 30-Aug-00 
H-11

Table H-2. Plans Status (continued). 

Area Block Control No. Plan Company Name Action Date 

MC 252 N-6521 EP Texaco Exploration and Production Inc. 16-Jul-99 

MC 292 N-4711 EP Texaco Inc. 30-Mar-94 

MC 292 N-6152 DOCD Texaco Exploration and Production Inc. 14-Oct-98 

MC 292 R-3269 DOCD Texaco Inc. 22-Jan-99 

MC 292 S-4082 EP Texaco Exploration and Production Inc. 30-Aug-96 

MC 299 N-6982 EP Murphy Exploration & Production Company 11-Jan-01 

MC 343 N-7501 EP Murphy Exploration & Production Company 21-Aug-02 

MC 379 N-6549 EP Murphy Exploration & Production Company 22-Sep-99 

MC 382 N-6670 EP Vastar Resources, Inc. 21-Jan-00 

MC 383 N-7443 DOCD Shell Offshore Inc. 17-Jul-02 

MC 383 S-5449 EP Shell Deepwater Development Inc. 15-Jun-01 

MC 418 N-6980 EP Amerada Hess Corporation 03-Jan-01 

MC 419 N-6980 EP Amerada Hess Corporation 03-Jan-01 

MC 429 N-4993 EP BP America Production Company 20-Apr-95 

MC 429 N-7458 DOCD Shell Offshore Inc. 20-Aug-02 

MC 429 R-3194 EP BP America Production Company 22-Apr-98 

MC 429 S-4895 EP Shell Deepwater Development Inc. 22-Feb-99 

MC 429 S-5732 EP Shell Offshore Inc. 26-Oct-01 

MC 465 N-7046 EP Exxon Mobil Corporation 23-Mar-01 

MC 506 N-4918 EP BP Exploration & Oil Inc. 22-Feb-96 

MC 507 N-4919 EP BP Exploration & Oil Inc. 12-Mar-96 

MC 508 N-7046 EP Exxon Mobil Corporation 23-Mar-01 

MC 508 S-5712 EP Exxon Mobil Corporation 10-Sep-01 

MC 509 N-7046 EP Exxon Mobil Corporation 23-Mar-01 

MC 509 R-3641 EP Exxon Mobil Corporation 04-May-01 

MC 509 S-5712 EP Exxon Mobil Corporation 10-Sep-01 

MC 553 N-6607 EP Amerada Hess Corporation 29-Oct-99 

MC 554 N-7233 EP Exxon Mobil Corporation 16-Oct-01 

MC 555 N-7120 EP Exxon Mobil Corporation 23-May-01 

MC 561 N-6986 EP Burlington Resources Offshore Inc. 02-Feb-01 

MC 595 N-6905 EP Dominion Exploration & Production, Inc. 29-Sep-00 

MC 597 N-6607 EP Amerada Hess Corporation 29-Oct-99 

MC 598 N-7233 EP Exxon Mobil Corporation 16-Oct-01 

MC 605 N-6986 EP Burlington Resources Offshore Inc. 02-Feb-01 

MC 636 N-7338 EP Shell Offshore Inc. 27-Feb-02 

MC 637 N-7338 EP Shell Offshore Inc. 27-Feb-02 

MC 637 S-6031 EP Shell Offshore Inc. 01-Nov-02 

MC 687 N-5492 DOCD Shell Offshore Inc. 28-Jan-97 

MC 687 R-3558 EP Shell Deepwater Development Inc. 28-Nov-00 

MC 687 R-3564 EP Shell Deepwater Production Inc. 30-Nov-00 

MC 687 S-3813 EP Shell Offshore Inc. 15-Dec-95 

MC 687 S-3998 EP Shell Offshore Inc. 21-Jun-96 

MC 687 S-5302 EP Shell Deepwater Production Inc. 31-Jul-00 

MC 725 N-7585 EP BP Exploration & Oil Inc. 03-Dec-02 

MC 728 N-5861 EP Chevron U.S.A. Inc. 30-Sep-97 
H-12

Table H-2. Plans Status (continued). 

Area Block Control No. Plan Company Name Action Date 

MC 728 R-3279 EP Chevron U.S.A. Inc. 08-Sep-99 

MC 728 R-3697 EP Chevron U.S.A. Inc. 19-Sep-01 

MC 728 R-3798 EP Dominion Exploration & Production, Inc. 17-May-02 

MC 728 S-5653 EP Chevron U.S.A. Inc. 06-Aug-01 

MC 728 S-5866 EP Dominion Exploration & Production, Inc. 10-Apr-02 

MC 730 S-5964 EP Shell Offshore Inc. 02-Aug-02 

MC 737 N-7178 EP Chevron U.S.A. Inc. 31-Aug-01 

MC 772 N-5861 EP Chevron U.S.A. Inc. 30-Sep-97 

MC 772 R-3697 EP Chevron U.S.A. Inc. 19-Sep-01 

MC 772 S-5618 EP Chevron U.S.A. Inc. 30-May-01 

MC 772 S-5653 EP Chevron U.S.A. Inc. 06-Aug-01 

MC 773 N-6493 EP Mariner Energy, Inc. 11-Jun-99 

MC 773 R-3431 EP Mariner Energy, Inc. 17-Apr-00 

MC 773 S-5544 EP Dominion Exploration & Production, Inc. 23-Mar-01 

MC 773 S-5744 EP Dominion Exploration & Production, Inc. 02-Nov-01 

MC 773 S-5823 EP Dominion Exploration & Production, Inc. 22-Jan-02 

MC 773 S-5881 EP Dominion Exploration & Production, Inc. 08-Apr-02 

MC 776 N-5964 EP BP Exploration & Oil Inc. 12-Jan-98 

MC 776 R-3261 EP BP Exploration & Oil Inc. 02-Dec-98 

MC 776 R-3409 EP BP Exploration & Oil Inc. 21-Mar-00 

MC 776 S-5817 EP BP Exploration & Oil Inc. 24-Jan-02 

MC 776 S-5995 EP BP Exploration & Production Inc. 17-Sep-02 

MC 777 N-5964 EP BP Exploration & Oil Inc. 12-Jan-98 

MC 777 R-3261 EP BP Exploration & Oil Inc. 02-Dec-98 

MC 777 S-5899 EP BP Exploration & Production Inc. 21-May-02 

MC 777 S-5995 EP BP Exploration & Production Inc. 17-Sep-02 

MC 778 N-5964 EP BP Exploration & Oil Inc. 12-Jan-98 

MC 778 R-3261 EP BP Exploration & Oil Inc. 02-Dec-98 

MC 778 S-5817 EP BP Exploration & Oil Inc. 24-Jan-02 

MC 778 S-5995 EP BP Exploration & Production Inc. 17-Sep-02 

MC 815 N-6524 EP Vastar Resources, Inc. 14-Jul-99 

MC 815 R-3334 EP Vastar Resources, Inc. 15-Sep-99 

MC 822 N-6604 EP BP Exploration Inc. 01-Dec-99 

MC 822 R-3652 EP BP Exploration & Oil Inc. 12-Jul-01 

MC 822 S-5995 EP BP Exploration & Production Inc. 17-Sep-02 

MC 860 N-7372 EP Chevron U.S.A. Inc. 22-Apr-02 

MC 864 N-6328 EP Chevron U.S.A. Inc. 30-Jun-99 

MC 864 R-3538 EP Chevron U.S.A. Inc. 16-Nov-00 

MC 864 R-3574 EP Chevron U.S.A. Inc. 16-Jan-01 

MC 904 N-6774 EP Chevron U.S.A. Inc. 22-Jun-00 

MC 944 N-6567 EP BHP Billiton Petroleum (GOM) Inc. 02-Nov-99 

MC 948 N-6774 EP Chevron U.S.A. Inc. 22-Jun-00 

MC 949 N-6774 EP Chevron U.S.A. Inc. 22-Jun-00 

MC 988 N-6625 EP Chevron U.S.A. Inc. 28-Dec-99 

MC 988 N-6715 EP Shell Deepwater Development Inc. 02-Mar-00 
H-13

Table H-2. Plans Status (continued). 

Area Block Control No. Plan Company Name Action Date 

MC 989 N-6625 EP Chevron U.S.A. Inc. 28-Dec-99 

VK 872 N-6264 EP Shell Deepwater Production Inc. 15-Oct-98 

VK 872 N-7119 DOCD Shell Deepwater Development Inc. 18-Jul-01 

VK 872 R-3722 DOCD Shell Offshore Inc. 14-Nov-01 

VK 913 N-4420 EP BP America Production Company 08-Apr-93 

VK 913 N-4421 EP BP America Production Company 25-Mar-93 

VK 914 N-4421 EP BP America Production Company 25-Mar-93 

VK 914 N-6813 DOCD BP America Production Company 27-Oct-00 

VK 914 R-3132 EP BP America Production Company 17-Apr-97 

VK 914 R-3291 EP BP America Production Company 25-Mar-99 

VK 914 S-4166 EP BP America Production Company 20-Dec-96 

VK 915 N-2908 EP BP America Production Company 04-Mar-88 

VK 915 N-5739 DOCD BP America Production Company 26-Jun-97 

VK 915 R-2826 EP BP America Production Company 28-Sep-92 

VK 915 R-3066 EP BP America Production Company 20-May-96 

VK 915 R-3104 EP BP America Production Company 25-Sep-96 

VK 915 R-3240 DOCD BP America Production Company 23-Nov-98 

VK 915 R-3268 DOCD BP America Production Company 08-Jan-99 

VK 915 R-3761 EP BP America Production Company 07-Feb-02 

VK 915 R-3771 EP BP Exploration & Production Inc. 06-Mar-02 

VK 915 S-5427 DOCD BP America Production Company 18-Jan-01 

VK 915 S-5847 EP BP Exploration & Production Inc. 28-Feb-02 

VK 915 S-5865 EP BP Exploration & Production Inc. 22-Mar-02 

VK 916 N-6937 EP Shell Deepwater Development Inc. 01-Nov-00 

VK 916 R-3692 EP Shell Offshore Inc. 10-Oct-01 

VK 916 R-3721 EP Shell Offshore Inc. 13-Nov-01 

VK 917 N-7265 EP Mariner Energy, Inc. 19-Oct-01 

VK 956 N-5588 DOCD Shell Offshore Inc. 13-Mar-97 

VK 956 S-3845 EP Shell Offshore Inc. 10-Apr-96 

VK 957 R-2217 EP BP America Production Company 20-Oct-88 

VK 962 N-7265 EP Mariner Energy, Inc. 19-Oct-01 

VK 1000 N-5695 EP Vastar Resources, Inc. 28-Mar-97 

VK 1001 N-5695 EP Vastar Resources, Inc. 28-Mar-97 

VK 1001 N-5695 EP Vastar Resources, Inc. 10-Mar-99 

VK 1001 R-3202 EP Vastar Resources, Inc. 12-Jun-98 

VK 1003 N-6562 EP TotalFinaElf E&P USA, Inc. 08-Sep-99 

Notes: AT = Atwater Valley 

 EP = Eploration Plan 

 DOCD = Development Operations Coordination Document 

 MC = Mississippi Canyon 

 VK = Viosca Knoll 
H-14

Table H-3 

Well Status 

Area Block Company Name Well Type Status Spud Date TD Date 

AT 24 Conoco Inc. 001 E PA 6/29/2000 8/7/2000 AT 67 BP Exploration & Oil Inc. 001 E CNL AT 113 Shell Deepwater Development Inc. 001 E ST 7/10/2000 7/27/2000 AT 113 Shell Deepwater Development Inc. 001 D PA 8/2/2000 8/12/2000 AT 153 Chevron U.S.A. Inc. 001 E PA 5/5/2001 8/9/2001 AT 155 Conoco Inc. 001 E APD AT 336 Kerr-McGee Oil & Gas Corporation 001 E PA 3/17/2000 5/11/2000 AT 378 Chevron U.S.A. Inc. 001 D ST 7/11/1997 8/29/1997 AT 378 Chevron U.S.A. Inc. 001 D PA 11/13/1997 11/25/199MC 79 Exxon Mobil Corporation 001 E PA 7/13/1996 8/18/1996 MC 84 BP Exploration & Production Inc. 001 E PA 10/18/1992 1/17/1993 MC 84 BP Exploration & Production Inc. 002 D TA 1/16/2002 2/3/2002 MC 85 BP Exploration & Production Inc. 001 E ST 7/2/1996 7/20/1996 MC 85 BP Exploration & Production Inc. 001 E ST 8/15/1996 8/30/1996 MC 85 BP Exploration & Production Inc. 001 E TA 9/15/1996 9/25/1996 MC 85 BP Exploration & Production Inc. SS002 D COM 12/1/2000 12/22/200MC 126 Vastar Resources, Inc. 001 E ST 10/31/1999 11/12/199MC 126 Vastar Resources, Inc. 001 E ST 11/17/1999 11/21/199MC 126 Vastar Resources, Inc. 001 E PA 11/22/1999 11/26/199MC 127 Vastar Resources, Inc. 001 E ST 7/2/1999 7/27/1999 MC 127 Vastar Resources, Inc. 001 D ST 7/29/1999 8/6/1999 MC 127 Vastar Resources, Inc. 001 E ST 8/12/1999 8/17/1999 MC 127 Vastar Resources, Inc. 001 E ST 8/23/1999 8/26/1999 MC 127 Vastar Resources, Inc. 001 E TA 8/27/1999 9/1/1999 MC 127 Vastar Resources, Inc. 002 E ST 9/14/1999 9/25/1999 MC 127 Vastar Resources, Inc. 002 D ST 9/29/1999 9/30/1999 MC 127 Vastar Resources, Inc. 002 E ST 10/3/1999 10/9/1999 MC 127 Vastar Resources, Inc. 002 E TA 10/19/1999 10/23/199MC 127 Vastar Resources, Inc. A001 D TA 4/22/2001 6/8/2001 MC 127 Vastar Resources, Inc. A002 D TA 5/10/2001 10/23/200MC 127 Vastar Resources, Inc. A003 D TA 4/30/2001 7/26/2001 MC 127 Vastar Resources, Inc. A004 D TA 5/2/2001 8/12/2001 
H-15

Table H-3. Well Status (continued). Area Block Company Name Well Type Status Spud Date TD Date MC 127 Vastar Resources, Inc. A005 D TA 5/6/2001 9/12/2001 MC 127 Vastar Resources, Inc. A006 D TA 10/1/2001 11/17/200MC 127 Vastar Resources, Inc. A007 D TA 5/9/2001 9/26/2001 MC 127 Vastar Resources, Inc. A008 D TA 4/22/2001 5/25/2001 MC 127 Vastar Resources, Inc. A009 D ST 4/24/2001 6/25/2001 MC 127 Vastar Resources, Inc. A009 D TA 7/1/2001 7/6/2001 MC 127 Vastar Resources, Inc. A010 D TA 5/4/2001 8/29/2001 MC 129 BP Exploration & Production Inc. 002 D APD MC 129 BP Exploration & Production Inc. SS003 D ST 12/11/2000 3/29/2001 MC 129 BP Exploration & Production Inc. SS003 D COM 4/6/2001 4/8/2001 MC 162 BP Exploration & Oil Inc. 001 E PA 8/5/1994 11/30/199MC 162 BP Exploration & Oil Inc. 002 E PA 5/30/1996 6/14/1996 MC 162 BP Exploration & Oil Inc. 003 E PA 6/2/1997 6/26/1997 MC 173 BP Exploration & Production Inc. SS002 D COM 12/13/2000 1/1/2001 MC 205 Mariner Energy, Inc. 001 E TA 11/25/2001 12/8/2001 MC 211 Exxon Mobil Corporation 001 E ST 2/8/1990 4/5/1990 MC 211 Exxon Mobil Corporation 001 E PA 4/17/1990 5/25/1990 MC 211 Exxon Mobil Corporation 001 E ST 3/28/1997 5/24/1997 MC 211 Exxon Mobil Corporation 001 E ST 6/8/1997 6/18/1997 MC 211 Exxon Mobil Corporation 001 E ST 7/22/1997 9/6/1997 MC 211 Exxon Mobil Corporation 001 E TA 9/12/1997 9/16/1997 MC 211 Exxon Mobil Corporation MA001 D COM 6/23/2000 7/24/2000 MC 211 Exxon Mobil Corporation MA002 D COM 6/25/2000 9/2/2000 MC 211 Exxon Mobil Corporation MA003 E DRL 6/15/2002 7/25/2002 MC 247 Texaco Exploration and Production Inc. 001 D ST 11/6/1997 12/5/1997 MC 247 Texaco Exploration and Production Inc. 001 D PA 12/20/1997 2/18/1998 MC 248 Chevron U.S.A. Inc. 001 E ST 1/11/2000 2/4/2000 MC 248 Chevron U.S.A. Inc. 001 D ST 2/16/2000 2/22/2000 MC 248 Chevron U.S.A. Inc. 001 D PA 2/27/2000 3/14/2000 MC 248 Chevron U.S.A. Inc. 002 E CNL MC 252 Chevron U.S.A. Inc. 001 E ST 9/26/1999 10/6/1999 MC 252 Chevron U.S.A. Inc. 001 E ST 10/19/1999 10/20/199MC 252 Chevron U.S.A. Inc. 001 E TA 10/21/1999 11/29/199MC 291 Texaco Exploration and Production Inc. 001 E PA 8/13/1997 10/20/199MC 292 Chevron U.S.A. Inc. 001 E COM 5/6/1995 9/7/1995 MC 292 Chevron U.S.A. Inc. 002 E ST 9/5/1996 10/1/1996 MC 292 Chevron U.S.A. Inc. 002 E ST 1/24/1997 2/13/1997 MC 292 Chevron U.S.A. Inc. 002 E TA 2/5/1997 3/13/1997 MC 292 Chevron U.S.A. Inc. 003 D ST 2/8/1999 4/15/1999 MC 292 Chevron U.S.A. Inc. 003 E COM 6/8/1999 6/21/1999 
H-16

Table H-3. Well Status (continued). Area Block Company Name Well Type Status Spud Date TD Date MC 292 Chevron U.S.A. Inc. 004 D ST 2/1/1999 3/13/1999 MC 292 Chevron U.S.A. Inc. 004 D COM 7/8/1999 7/16/1999 MC 299 Murphy Exploration & Production Company 001 E ST 4/8/2001 5/4/2001 MC 299 Murphy Exploration & Production Company 001 E PA 5/14/2001 5/23/2001 MC 300 Exxon Mobil Corporation 001 E PA 9/13/1997 10/25/199MC 379 Murphy Exploration & Production Company 001 E PA 1/18/2000 3/17/2000 MC 382 Amerada Hess Corporation 001 E PA 9/3/2001 11/19/200MC 383 Shell Offshore Inc. 001 E PA 6/27/1987 8/31/1987 MC 383 Shell Offshore Inc. 003 D ST 9/7/2001 10/1/2001 MC 383 Shell Offshore Inc. 003 D ST 10/2/2001 10/4/2001 MC 383 Shell Offshore Inc. 003 D DSI 10/10/2001 MC 383 Shell Offshore Inc. K001 D ST 9/9/2001 10/25/200MC 383 Shell Offshore Inc. K001 D DRL 10/26/2001 MC 429 Shell Offshore Inc. 001 E TA 11/8/1995 11/20/199MC 429 Shell Offshore Inc. 002 D ST 3/18/1999 4/21/1999 MC 429 Shell Offshore Inc. 002 D ST 5/1/1999 5/2/1999 MC 429 Shell Offshore Inc. 002 D ST 12/31/2001 1/1/2002 MC 429 Shell Offshore Inc. 002 D ST 1/4/2002 1/4/2002 MC 429 Shell Offshore Inc. 002 D TA 1/7/2002 MC 429 Shell Offshore Inc. 003 D ST 11/2/2001 11/12/200MC 429 Shell Offshore Inc. 003 D ST 11/18/2001 12/2/2001 MC 429 Shell Offshore Inc. 003 D TA 12/5/2001 12/12/200MC 505 Shell Offshore Inc. 001 E PA 8/28/1986 11/8/1986 MC 509 Exxon Mobil Corporation 001 E TA 5/11/2001 11/20/200MC 553 Amerada Hess Corporation 001 D PA 11/16/1999 1/28/2000 MC 555 Exxon Mobil Corporation 001 E ST 5/25/2001 5/27/2001 MC 555 Exxon Mobil Corporation 001 E PA 6/13/2001 10/30/200MC 561 Burlington Resources Offshore Inc. 001 E ST 5/1/2001 6/19/2001 MC 561 Burlington Resources Offshore Inc. 001 E PA 6/29/2001 7/21/2001 MC 595 Dominion Exploration & Production, Inc. 001 E PA 10/15/2000 11/29/200MC 638 Texaco Exploration and Production Inc. 001 E PA 6/28/1996 8/16/1996 MC 687 Shell Offshore Inc. 001 E PA 12/19/1995 1/2/1996 MC 687 Shell Offshore Inc. 002 E ST 3/19/2001 7/27/2001 MC 687 Shell Offshore Inc. 002 E ST 8/13/2001 8/20/2001 MC 687 Shell Offshore Inc. 002 E TA 9/5/2001 2/11/2002 MC 687 Shell Offshore Inc. A001 E COM 9/10/1996 12/31/199MC 687 Shell Offshore Inc. A002 E COM 11/23/1997 6/15/1998 MC 687 Shell Offshore Inc. A003 E COM 9/10/1996 8/20/1997 MC 727 Chevron U.S.A. Inc. 001 E PA 8/21/2000 1/17/2001 MC 728 Dominion Exploration & Production, Inc. 004 E DRL 6/7/2002 MC 730 Shell Offshore Inc. 001 E PA 6/10/1988 8/12/1988 
H-17

Table H-3. Well Status (continued). Area Block Company Name Well Type Status Spud Date TD Date MC 731 Shell Offshore Inc. 001 D ST 11/20/1986 12/1/1986 MC 731 Shell Offshore Inc. 001 E PA 2/23/1987 3/14/1987 MC 772 Dominion Exploration & Production, Inc. 001 E ST 8/30/1998 1/27/1999 MC 772 Dominion Exploration & Production, Inc. 001 E TA 2/10/1999 3/1/1999 MC 773 Dominion Exploration & Production, Inc. 001 E PA 11/17/1999 11/17/199MC 773 Dominion Exploration & Production, Inc. 002 E TA 11/17/1999 12/13/199MC 773 Dominion Exploration & Production, Inc. 002 E TA 12/8/2001 3/15/2002 MC 773 Dominion Exploration & Production, Inc. 003 E ST 5/16/2000 6/4/2000 MC 773 Dominion Exploration & Production, Inc. 003 E TA 6/18/2000 7/4/2000 MC 773 Dominion Exploration & Production, Inc. 003 E TA 4/16/2002 5/13/2002 MC 773 Dominion Exploration & Production, Inc. 004 E TA 4/5/2001 5/2/2001 MC 773 Dominion Exploration & Production, Inc. 005 E ST 4/8/2001 6/3/2001 MC 773 Dominion Exploration & Production, Inc. 005 E TA 6/5/2001 6/6/2001 MC 773 Dominion Exploration & Production, Inc. 006 E DSI 12/4/2001 1/2/2002 MC 773 Dominion Exploration & Production, Inc. 007 E ST 12/6/2001 1/18/2002 MC 773 Dominion Exploration & Production, Inc. 007 E TA 2/6/2002 2/13/2002 MC 773 Dominion Exploration & Production, Inc. 009 D TA 1/28/2002 4/4/2002 MC 776 BP Exploration & Production Inc. 001 D AST MC 776 BP Exploration & Production Inc. 001 E ST 4/26/2000 7/23/2000 MC 776 BP Exploration & Production Inc. 001 D ST 8/3/2000 8/16/2000 MC 776 BP Exploration & Production Inc. 001 D ST 8/29/2000 MC 776 BP Exploration & Production Inc. 001 D TA 9/26/2000 11/11/200MC 776 BP Exploration & Production Inc. 002 D ST 3/7/2002 4/23/2002 MC 776 BP Exploration & Production Inc. 002 D TA 5/1/2002 5/19/2002 MC 777 BP Exploration & Production Inc. 001 E DRL 6/14/2002 7/25/2002 MC 778 BP Exploration & Production Inc. 001 E ST 1/8/1999 4/24/1999 MC 778 BP Exploration & Production Inc. 001 E TA 5/5/1999 6/21/1999 MC 778 BP Exploration & Production Inc. 001 D DSI 4/22/2002 MC 778 BP Exploration & Production Inc. 002 E TA 4/20/2002 6/21/2002 MC 778 BP Exploration & Production Inc. 004 E DSI 4/27/2002 4/28/2002 MC 815 BP Exploration & Production Inc. 001 D ST 12/9/1999 2/1/2000 MC 815 BP Exploration & Production Inc. 001 D PA 2/14/2000 3/13/2000 MC 822 BP Exploration & Production Inc. 001 E TA 12/20/1999 11/30/200MC 822 BP Exploration & Production Inc. 002 E TA 9/24/2001 10/18/200MC 822 BP Exploration & Production Inc. 003 E TA 11/6/2001 1/29/2002 MC 864 Chevron U.S.A. Inc. 001 E PA 1/23/2001 3/14/2001 MC 988 Shell Offshore Inc. 001 E ST 4/1/2000 5/11/2000 MC 988 Shell Deepwater Development Inc. 001 D PA 5/16/2000 6/17/2000 VK 872 Shell Offshore Inc. 001 E ST 11/20/1998 12/6/1998 VK 872 Shell Offshore Inc. SS001 E COM 12/15/1998 12/18/199VK 873 Shell Offshore Inc. 001 E PA 2/21/1988 3/25/1988 
H-18

Table H-3. Well Status (continued). Area Block Company Name Well Type Status Spud Date TD Date VK 914 BP Exploration & Production Inc. SS001 E ST 4/20/1997 4/30/1997 VK 914 BP Exploration & Production Inc. SS001 E ST 6/9/1997 6/25/1997 VK 914 BP Exploration & Production Inc. SS001 E ST 6/27/1997 7/2/1997 VK 914 BP Exploration & Production Inc. SS001 E COM 4/12/1999 5/2/1999 VK 915 BP Exploration & Production Inc. A001 E ST 4/14/1993 6/6/1993 VK 915 BP Exploration & Production Inc. A001 E TA 6/7/1993 7/7/1993 VK 915 BP Exploration & Production Inc. A002 E PA 10/20/1996 12/4/1996 VK 915 BP Exploration & Production Inc. A003 D ST 8/15/1997 1/6/1998 VK 915 BP Exploration & Production Inc. A003 D TA 2/25/1998 2/28/1998 VK 915 BP Exploration & Production Inc. A004 D ST 9/13/1997 1/8/1998 VK 915 BP Exploration & Production Inc. A004 D COM 1/11/1998 1/4/2001 VK 915 BP Exploration & Production Inc. A005 D COM 9/16/1997 12/1/1997 VK 915 BP Exploration & Production Inc. A006 D COM 8/17/1997 4/10/1998 VK 915 BP Exploration & Production Inc. SS001 D COM 1/27/2001 4/2/2001 VK 915 BP Exploration & Production Inc. SS002 D COM 1/9/2002 2/23/2002 VK 915 BP Exploration & Production Inc. SS003 D TA 2/12/2002 3/9/2002 VK 915 BP Exploration & Production Inc. SS004 D ST 3/18/2002 3/25/2002 VK 915 BP Exploration & Production Inc. SS004 D ST 3/29/2002 4/17/2002 VK 915 BP Exploration & Production Inc. SS004 D ST 4/24/2002 4/26/2002 VK 915 BP Exploration & Production Inc. SS004 D TA 5/4/2002 5/6/2002 VK 915 BP Exploration & Production Inc. SS005 D TA 5/18/2002 6/15/2002 VK 916 Shell Offshore Inc. 001 E PA 11/27/2001 12/18/200VK 917 BP Exploration & Production Inc. 001 E TA 11/21/2001 12/8/2001 VK 956 Shell Offshore Inc. 001 E ST 11/16/1985 1/1/1986 VK 956 Shell Offshore Inc. 002 E TA 1/17/1986 2/17/1986 VK 956 Shell Offshore Inc. 002 E ST 2/20/1987 4/30/1987 VK 956 Shell Offshore Inc. 002 E ST 5/27/1987 6/4/1987 VK 956 Shell Offshore Inc. 002 E ST 6/11/1987 6/29/1987 VK 956 Shell Offshore Inc. 002 E PA 7/7/1987 7/21/1987 VK 956 Shell Offshore Inc. A001 E ST 4/2/1997 6/26/1997 VK 956 Shell Offshore Inc. A001 E ST 6/25/1997 7/9/1997 VK 956 Shell Offshore Inc. A001 E COM 7/30/1997 8/16/1997 VK 956 Shell Offshore Inc. A002 E ST 4/6/1996 4/15/1996 VK 956 Shell Offshore Inc. A002 E ST 9/19/1996 9/24/1996 VK 956 Shell Offshore Inc. A002 E COM 1/28/1997 2/7/1997 VK 956 Shell Offshore Inc. A003 E ST 12/19/1996 1/18/1997 VK 956 Shell Offshore Inc. A003 E ST 10/16/1997 11/22/199VK 956 Shell Offshore Inc. A003 D ST 12/5/2001 12/11/200VK 956 Shell Offshore Inc. A003 D COM 12/16/2001 VK 956 Shell Offshore Inc. A004 E ST 11/3/1996 12/4/1996 VK 956 Shell Offshore Inc. A004 E ST 12/4/1996 12/16/199
H-19

Table H-3. Well Status (continued). Area Block Company Name Well Type Status Spud Date TD Date VK 956 Shell Offshore Inc. A004 E COM 2/11/1998 3/5/1998 VK 956 Shell Offshore Inc. A005 E ST 4/3/1996 4/23/1996 VK 956 Shell Offshore Inc. A005 E ST 4/30/1998 4/30/1998 VK 956 Shell Offshore Inc. A005 E COM 5/14/1998 6/27/1998 VK 956 Shell Offshore Inc. A006 E ST 3/8/1997 8/8/1998 VK 956 Shell Offshore Inc. A006 E ST 8/27/1998 10/28/199VK 956 Shell Offshore Inc. A006 E COM 11/6/1998 1/11/1999 VK 956 Shell Offshore Inc. A007 E DSI 4/1/1996 2/20/1997 VK 956 Shell Offshore Inc. A008 E ST 4/4/1996 2/10/1999 VK 956 Shell Offshore Inc. A008 E ST 2/20/1999 3/4/1999 VK 956 Shell Offshore Inc. A008 E COM 3/10/1999 3/15/1999 VK 956 Shell Offshore Inc. A009 E DSI 4/5/1996 3/13/1997 VK 956 Shell Offshore Inc. A010 E DSI 3/30/1996 2/24/1997 VK 956 Shell Offshore Inc. A011 E DSI 3/23/1996 3/2/1997 VK 956 Shell Offshore Inc. A012 E DSI 4/9/1996 3/7/1997 VK 956 Shell Offshore Inc. A013 E ST 4/4/1996 10/1/1999 VK 956 Shell Offshore Inc. A013 E COM 10/5/1999 10/29/199VK 956 Shell Offshore Inc. A014 E COM 9/27/1997 9/6/1999 VK 956 Shell Offshore Inc. A015 E DSI 4/5/1996 2/26/1997 VK 956 Shell Offshore Inc. A016 E DSI 3/28/1996 3/5/1997 VK 956 Shell Offshore Inc. A017 E COM 3/14/1997 5/27/1999 VK 956 Shell Offshore Inc. A018 E DSI 3/31/1996 3/10/1997 VK 956 Shell Offshore Inc. A019 E DSI 3/31/1996 3/1/1997 VK 956 Shell Offshore Inc. A020 E DSI 3/23/1996 3/3/1997 VK 957 Shell Offshore Inc. 001 E ST 1/5/1989 3/20/1989 VK 957 Shell Offshore Inc. 001 E ST 4/2/1989 4/19/1989 VK 957 Shell Offshore Inc. 001 E TA 6/22/1989 7/4/1989 VK 957 Shell Offshore Inc. 003 E ST 5/24/1989 6/10/1989 VK 962 BP Exploration & Production Inc. 001 E TA 10/27/2001 11/15/200VK 1001 Vastar Resources, Inc. 001 E ST 3/20/1999 4/25/1999 VK 1001 Vastar Resources, Inc. 001 E ST 5/2/1999 5/9/1999 VK 1001 Vastar Resources, Inc. 001 D ST 5/13/1999 5/14/1999 VK 1001 Vastar Resources, Inc. 001 D PA 5/15/1999 6/19/1999 VK 1003 TotalFinaElf E&P USA, Inc. 001 E ST 10/1/1999 10/18/199VK 1003 TotalFinaElf E&P USA, Inc. 001 E TA 11/2/1999 12/19/199

 Notes: APD = approval for permit to drill 

AST = approved sidetrack CNL = canceled COM = completed D = development DRL = drilling 

 DSI = drilling shut-in  E = exploration  PA = permanently abandoned  ST = sidetrack  TA = temporarily abandoned 
H-20

Table H-4 

Platforms in Grid 16 

Area Block Lease No. Complex ID No. Water Depth (ft) Company Name 

VK 915 G06894 235 3,236 BP Exploration & Production Inc. 

VK 956 G06896 24229 3,216 Shell Offshore Inc. 

MC 211 G08803 714 4,350 Exxon Mobil Corporation 

MC 127 G19925 876 5,400 Vastar Resources, Inc. 

Notes: MC = Mississippi Canyon 

 VK = Viosca Knoll 

Table H-5 

Proposed Plan Platforms 

Area Block 

Control 

No. Plan Company Name Action Date Site 

Water 

Depth (ft) 

MC 85 R-3398 DOCD Amoco Production Company 4/20/2000 1 5,453 

MC 127 N-7195 DOCD Vastar Resources, Inc. 2/21/2002 A 5,422 

VK 872 N-7119 DOCD Shell Deepwater Development Inc. 7/18/2001 NO 1 3,480 

VK 915 N-5739 DOCD Amoco Production Company 6/26/1997 A 3,250 

VK 915 R-3240 DOCD Amoco Production Company 11/23/1998 A 3,250 

VK 956 N-5588 DOCD Shell Offshore Inc. 3/13/1997 A 3,214 

Notes: DOCD = Development Operations Coordination Document 

 MC = Mississippi Canyon 

 VK = Viosca Knoll 
I-1

APPENDIX I 

Air Emissions Data 
I-3

APPENDIX I 

AIR EMISSIONS DATA

The projected air emissions submitted by BP Exploration and Production for the Thunder Horse 

project are below the MMS exemption levels. BP Exploration and Production has estimated the emissions 

associated with this project. These emission projections are required to represent the worst case. They 

are summarized below. 

Total Emissions (tons) for MC 776 Drill Center 31 

Year PM SOx NOx VOC CO 

2004 4.20 19.28 144.78 4.61 33.28 

2005 13.27 60.89 456.53 13.96 101.30 

2006 22.00 100.92 756.18 22.69 164.98 

2011 9.27 42.51 318.82 9.83 71.25 

2012 10.92 50.10 375.44 11.26 81.92 

2014 33.17 152.18 1140.32 34.21 248.80 

2015 10.47 48.03 359.91 10.80 78.53 

MMS Exemption Level 2131.20 2131.20 2131.20 2131.20 54400.00 

Total Emissions (tons) for MC 776 Drill Center 32 

Year PM SOx NOx VOC CO 

2004 11.23 51.53 386.44 11.86 86.00 

2005 1.86 8.52 63.81 1.91 13.92 

2014 21.83 100.15 750.41 22.51 163.73 

MMS Exemption Level 2131.20 2131.20 2131.20 2131.20 54400.00 

Total Emissions (tons) for MC 776 Drill Center 33 

Year PM SOx NOx VOC CO 

2004 15.40 7.06 529.48 15.88 115.52 

2005 21.94 100.68 754.98 23.18 168.10 

2006 8.46 38.82 291.17 9.00 65.22 

2011 22.82 104.68 784.41 23.53 171.14 

2012 19.00 87.16 653.43 19.87 144.26 

2014 21.83 100.15 750.41 22.51 163.73 

2015 10.92 50.10 375.44 11.26 81.92 

MMS Exemption Level 2131.20 2131.20 2131.20 2131.20 54400.00 
I-4

Total Emissions (tons) for MC 776 Drill Center 41 

Year PM SOx NOx VOC CO 

2004 21.83 100.17 753.16 24.83 178.67 

2005 52.15 239.24 1793.99 54.94 398.59 

2006 21.02 98.60 1862.56 71.70 885.48 

2007 16.74 79.68 2088.57 83.65 1091.59 

2008 16.74 79.68 2088.57 83.65 1091.59 

2009 16.74 79.68 2088.57 83.65 1091.59 

2011 16.74 79.68 2088.57 83.65 1091.59 

2012 16.74 79.68 2088.57 83.65 1091.59 

2013 16.74 79.68 2088.57 83.65 1091.59 

2014 16.74 79.68 2088.57 83.65 1091.59 

2015 16.74 79.68 2088.57 83.65 1091.59 

MMS Exemption 

Level 2264.40 2264.40 2264.40 2264.40 56643.69 

Total Emissions (tons) for MC 776 Drill Center 42 

Year PM SOx NOx VOC CO 

2003 12.10 55.49 416.12 12.75 92.48 

MMS Exemption 

Level 2331.00 2331.00 2331.00 2331.00 57748.97 

Total Emissions (tons) for MC 776 Drill Center 43 

Year PM SOx NOx VOC CO 

2003 6.30 28.91 217.94 7.66 54.72 

2004 1.50 6.87 51.46 1.54 11.23 

2007 10.92 50.10 375.44 11.26 81.92 

2014 10.92 50.10 375.44 11.26 81.92 

MMS Exemption 

Level 2131.20 2131.20 2131.20 2131.20 54400.00 

Total Emissions (tons) for MC 776 Drill Center 44 

Year PM SOx NOx VOC CO 

2005 22.28 102.22 766.27 23.25 168.87 

2006 13.18 60.49 453.86 14.14 102.40 

2020 3.37 15.45 115.77 3.47 25.26 

MMS Exemption 

Level 2197.80 2197.80 2197.80 2197.80 55527.51 
I-5

Total Emissions (tons) for MC 776 Drill Center 45 

Year PM SOx NOx VOC CO 

2003 6.27 28.75 215.75 6.74 48.76 

2004 10.92 50.10 375.44 11.26 81.92 

2008 10.92 50.10 375.44 11.26 81.92 

MMS Exemption 

Level 2264.40 2264.40 2264.40 2264.40 56643.69 

The projected air emissions submitted, by BP Exploration and Production, for the Thunder Horse 

(categorical exclusion review) project are below the MMS exemption levels. BP Exploration and 

Production has estimated the emissions associated with this project. These emission projections are 

required to represent the worst case. They are summarized below: 

Total Emissions (tons) for MC 776 

Year PM SOx NOx VOC CO 

2002 4.19 19.24 144.17 4.33 31.46 

MMS Exemption 

Level 2131.20 2131.20 2131.20 2131.20 54400.00 

Total Emissions (tons) for MC 777 

Year PM SOx NOx VOC CO 

2002 102.10 46.84 350.97 10.53 76.57 

MMS Exemption 

Level 2131.20 2131.20 2131.20 2131.20 54400.00 

Total Emissions (tons) for MC 778 

Year PM SOx NOx VOC CO 

2002 8.90 40.81 305.78 9.17 66.72 

2003 2.11 9.66 72.39 2.17 15.79 

MMS Exemption 

Level 2264.40 2264.40 2264.40 2264.40 56643.69 

Total Emissions (tons) for MC 778 

Year PM SOx NOx VOC CO 

2002 2.48 11.37 85.20 2.56 18.59 

MMS Exemption 

Level 2331.00 2331.00 2331.00 2331.00 57748.97 
The Department of the Interior Mission

As the Nation's principal conservation agency, the Department of the Interior has responsibility 

for most of our nationally owned public lands and natural resources. This includes fostering 

sound use of our land and water resources; protecting our fish, wildlife, and biological diversity; 

preserving the environmental and cultural values of our national parks and historical places; 

and providing for the enjoyment of life through outdoor recreation. The Department assesses 

our energy and mineral resources and works to ensure that their development is in the best 

interests of all our people by encouraging stewardship and citizen participation in their care. 

The Department also has a major responsibility for American Indian reservation communities 

and for people who live in island territories under U.S. administration. 

The Minerals Management Service Mission 

As a bureau of the Department of the Interior, the Minerals Management Service's (MMS) 

primary responsibilities are to manage the mineral resources located on the Nation's Outer 

Continental Shelf (OCS), collect revenue from the Federal OCS and onshore Federal and Indian 

lands, and distribute those revenues. 

Moreover, in working to meet its responsibilities, the Offshore Minerals Management Program 

administers the OCS competitive leasing program and oversees the safe and environmentally 

sound exploration and production of our Nation's offshore natural gas, oil and other mineral 

resources. The MMS Minerals Revenue Management meets its responsibilities by ensuring the 

efficient, timely and accurate collection and disbursement of revenue from mineral leasing and 

production due to Indian tribes and allottees, States and the U.S. Treasury. 

The MMS strives to fulfill its responsibilities through the general guiding principles of: (1) being 

responsive to the public's concerns and interests by maintaining a dialogue with all potentially 

affected parties and (2) carrying out its programs with an emphasis on working to enhance the 

quality of life for all Americans by lending MMS assistance and expertise to economic 

development and environmental protection.