OCS Report 

MMS 2007-040 

Oil-Spill Risk Analysis: 

Gulf of Mexico Outer Continental Shelf (OCS) 

Lease Sales, Central Planning Area and 

Western Planning Area, 2007-2012, and 

Gulfwide OCS Program, 2007-2046

U.S. Department of the Interior 

Minerals Management Service 

Environmental Division 

OCS Report 

MMS 2007-040

Oil-Spill Risk Analysis: 

Gulf of Mexico Outer Continental Shelf (OCS) 

Lease Sales, Central Planning Area and 

Western Planning Area, 2007-2012, and 

Gulfwide OCS Program, 2007-2046 

By: 

Zhen-Gang Ji 

Walter R. Johnson 

Charles F. Marshall 

Eileen M. Lear (Editor)

U.S. Department of the Interior 

Minerals Management Service 

Environmental Division June 2007 
ii 

2007 Gulf of Mexico OSRA 

Contents

List of Figures ............................................................................................................................... iii

List of Tables ..................................................................................................................................v 

Introduction......................................................................................................................................1 

 Framework of the Analysis........................................................................................................1 

The Proposed Actions and the Gulfwide OCS Program............................................................1 

Domain/Study Areas..................................................................................................................2 

Hypothetical Spill Locations......................................................................................................3 

Estimated Volume of Oil Resources..........................................................................................3 

Environmental Resources ..........................................................................................................4 

Oil-Spill Risk Analysis ....................................................................................................................9 

Probability of Oil Spills Occurring............................................................................................9 

Oil-Spill Trajectory Simulations..............................................................................................11 

Conditional Probabilities of Contact........................................................................................14 

Combined Probabilities of Contact..........................................................................................15 

Discussion......................................................................................................................................16 

References Cited ............................................................................................................................16 
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2007 Gulf of Mexico OSRA 

List of Figures 

 Figure Page 

1. Domain and Study Areas for the Oil-Spill Risk Analysis..................................... 19 

2a. Locations of 50 Cluster Subareas for Launching Hypothetical Spills .................. 20 

2b. Enlargement of Cluster Subareas .......................................................................... 21 

3. Locations of Texas State Offshore Waters, Flower Garden Banks, Alabama 

State Offshore Waters, Chandeleur Islands, Florida Middle Ground, and 

Boundary Target 1.................................................................................................22 

4. Locations of Stetson Bank, Louisiana (Eastern) State Offshore Waters, Big 

Bend Seagrass, Boundary Target 2, Tortugas Ecological Reserve, and North 

Florida Straits ........................................................................................................ 23 

5. Locations of 7 1⁄2 Fathoms, Louisiana (Western) State Offshore Waters, 

Florida Panhandle State Offshore Waters, Florida Keys National Marine 

Sanctuary, Boundary Target 3, and South Florida Straits.....................................24 

6. Locations of Mexican Waters, Sonnier Bank, Mississippi State Offshore 

Waters, Florida Peninsula State Offshore Waters, and Boundary Target 4 .......... 25 

7. Locations of Diving Bird Habitat.......................................................................... 26 

8. Locations of Gulls, Terns, and Charadriid Allie Habitat ...................................... 27 

9. Locations of Raptor Bird Habitat .......................................................................... 28 

10. Locations of Charadriid Shorebird Habitat ........................................................... 29 

11. Locations of Wading Bird Habitat ........................................................................ 30 

12. Locations of Waterfowl Habitat ............................................................................ 31 

13. Locations of Snowy Plover Habitat....................................................................... 32 

14. Locations of Brown Pelican Habitat ..................................................................... 33 

15. Locations of Whooping Crane Habitat.................................................................. 34 

16. Locations of Bald Eagle Habitat ........................................................................... 35 

17. Locations of Piping Plover Habitat ....................................................................... 36 

18. Known Shoreline Locations of Gulf Sturgeon Habitat ......................................... 37 

19. Locations of Alabama Beach Mouse and Choctawatchee Beach Mouse 

Habitats.................................................................................................................. 38 

20. Locations of Perdido Key Beach Mouse and St. Andrew Beach Mouse 

Habitats.................................................................................................................. 39
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2007 Gulf of Mexico OSRA 

 Figure Page 

21. Locations of Texas Coastal Bend Area Beaches, Texas Galveston Area 

Beaches, Louisiana Beaches, Alabama Gulf Shores, Florida Big Bend 

Beaches, and Florida Ten Thousand Islands ......................................................... 40 

22. Locations of Texas Matagorda Area Beaches, Texas Sea Rim State Park, 

Alabama/Mississippi Gulf Islands, Florida Panhandle Beaches, and Florida 

Southwest Beaches ................................................................................................41 

23. Locations of Gulf of Mexico Counties and Parishes (set 1).................................. 42 

24. Locations of Gulf of Mexico Counties and Parishes (set 2).................................. 43 

25. Locations of Mexico Sea Turtle Mating Habitat, Mexico Sea Turtle General 

Coastal Habitat, Mexico Marine Mammal Habitat, Texas Sea Turtle Nesting 

Habitat-Matagorda Area, Mississippi Sea Turtle Mating Habitat, 

Mississippi Sea Turtle General Coastal Habitat, Mississippi Marine 

Mammal Habitat, Florida Sea Turtle Mating Habitat-Panhandle Area, 

Florida Sea Turtle General Coastal Habitat-Panhandle Area, Florida 

Panhandle Marine Mammal Habitat, and Florida Sea Turtle Nesting 

Habitat-Peninsula Area..........................................................................................44 

26. Locations of Louisiana Sea Turtle General Coastal Habitat-West, Louisiana 

West Marine Mammal Habitat, Mississippi/Alabama Sea Turtle Nesting 

Habitats, Florida Sea Turtle Nesting Habitat-Tortugas Area, Florida Sea 

Turtle Mating Habitat-Tortugas Area, Florida Sea Turtle General Coastal 

Habitat-Tortugas Area, and Florida Tortugas Marine Mammal Habitat............... 45 

27. Locations of Texas Sea Turtle Mating Habitat, Texas Sea Turtle General 

Coastal Habitat, Texas Marine Mammal Habitat, Louisiana Sea Turtle 

Nesting Habitat, Louisiana Sea Turtle Mating Habitat, Florida Sea Turtle 

Nesting Habitat-Florida Keys, Florida Sea Turtle Mating Habitat-Florida 

Keys, and Florida Sea Turtle General Coastal Habitat-Florida Keys ...................46 

28. Locations of Mexico Sea Turtle Nesting Habitat, Texas Sea Turtle Nesting 

Habitat-Galveston Area, Louisiana Sea Turtle General Coastal Habitat-East, 

Louisiana East Marine Mammal Habitat, and Florida Sea Turtle Nesting 

Habitat-Panhandle Area.........................................................................................47 

29. Locations of Texas Sea Turtle Nesting Habitat-Coastal Bend Area, Texas 

Sea Turtle Nesting Habitat-Sea Rim Area, Alabama Sea Turtle Mating 

Habitat, Alabama Sea Turtle General Coastal Habitat, Alabama Marine 

Mammal Habitat, Florida Sea Turtle Mating Habitat-Peninsula Area, 

Florida Sea Turtle General Coastal Habitat-Peninsula Area, and Florida 

Peninsula Marine Mammal Habitat....................................................................... 48
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2007 Gulf of Mexico OSRA 

 Figure Page 

30. Locations of Florida Panhandle Manatee Areas and Florida Southwest 

Manatee Areas....................................................................................................... 49 

31. Locations of Louisiana/Mississippi/Alabama Manatee Areas, Florida Big 

Bend Manatee Areas, and Florida Ten Thousand Islands Manatee Areas............50 

List of Tables

1a. Oil-spill occurrence probability estimates for offshore spills greater than or equal 

to 1,000 barrels resulting from the proposed actions in the Western and Central 

Gulf of Mexico Planning Areas (2007-20012) and the Gulfwide Program (2007-

2046)............................................................................................................................... 51 

1b. Oil-spill occurrence probability estimates for offshore spills greater than or equal 

to 10,000 barrels resulting from the proposed actions in the Western and Central 

Gulf of Mexico Planning Areas (2007-20012) and the Gulfwide Program (2007-

2046)............................................................................................................................... 52 

2. Probabilities (expressed as percent chance) of one or more offshore spills greater 

than or equal to 1,000 barrels occurring from a proposed action in the Central 

GOM Planning Area and contacting certain offshore environmental resource 

locations within 10 days for the low and high oil resource estimates............................ 53 

3a. Probabilities (expressed as percent chance) of one or more offshore spills greater 

than or equal to 1,000 barrels occurring from a proposed action in the Central 

GOM Planning Area and contacting certain onshore environmental resource 

habitats, recreational beaches, or Texas county shorelines within 10 days for low 

and high oil resource estimates ...................................................................................... 54 

3b. Probabilities (expressed as percent chance) of one or more offshore spills greater 

than or equal to 1,000 barrels occurring from a proposed action in the Central 

GOM Planning Area and contacting the shoreline of Louisiana parishes or 

Mississippi, Alabama, and Florida counties within 10 days for low and high oil 

resource estimates .......................................................................................................... 55 

4. Probabilities (expressed as percent chance) of one or more offshore spills greater 

than or equal to 1,000 barrels occurring from a proposed action in the Western 

GOM Planning Area and contacting certain offshore environmental resource 

locations within 10 days for the low and high oil resource estimates............................ 56 

5a. Probabilities (expressed as percent chance) of one or more offshore spills greater 

than or equal to 1,000 barrels occurring from a proposed action in the Western 

GOM Planning Area and contacting certain onshore environmental resource 

habitats, recreational beaches, or Texas county shorelines within 10 days for low 

and high oil resource estimates ...................................................................................... 57 
vi 

2007 Gulf of Mexico OSRA 

 Figure Page 

5b. Probabilities (expressed as percent chance) of one or more offshore spills greater 

than or equal to 1,000 barrels occurring from a proposed action in the Western 

GOM Planning Area and contacting the shoreline of Louisiana parishes or 

Mississippi, Alabama, and Florida counties within 10 days for low and high oil 

resource estimates .......................................................................................................... 58 

6. Probabilities (expressed as percent chance) of one or more offshore spills greater 

than or equal to 1,000 barrels occurring from a proposed action in the Western 

or Central GOM Planning Area and contacting a certain onshore

environmental resource habitat within 10 days for the low and high oil resource 

estimates......................................................................................................................... 59
Introduction 

The Federal Government plans to offer U.S. Outer Continental Shelf (OCS) lands in the 

Central and Western Planning Areas of the Gulf of Mexico (GOM) for oil and gas leasing 

(see figure 1). Because oil spills may occur from activities associated with offshore oil 

exploration, production, and transportation resulting from these lease sales, the Minerals 

Management Service (MMS) conducts a formal oil-spill risk analysis (OSRA) to support the 

environmental impact statement (EIS) completed prior to conducting the proposed leasing of 

these areas. This report summarizes results of that analysis, the objective of which was to 

estimate the risk of oil-spill contact to sensitive offshore and onshore environmental resources 

and socioeconomic features from oil spills accidentally occurring from the OCS activities. 

The occurrence of oil spills is fundamentally a matter of probability. There is no certainty 

regarding the amount of oil that would be produced, or the size or likelihood of a spill that 

would occur, during the estimated life of a given lease sale. Neither can the winds and ocean 

currents that transport oil spills be known for certain. A probabilistic event such as an oil-spill 

occurrence or oil-spill contact to an environmentally sensitive area cannot be predicted, only 

an estimate of its likelihood (its probability) can be quantified. 

The OSRA was conducted in three parts corresponding to different aspects of the overall 

problem. 

(1) The probability of oil-spill occurrence, which is based on spill rates derived from 

historic data and on estimated volumes of oil produced and transported. 

(2) The trajectories of oil spills from hypothetical spill locations to locations of various 

environmental resources, which are simulated using the OSRA Model (Smith et al., 

1982). 

(3) The combination of results of the first two to estimate the overall oil-spill risk if there 

is oil development. 

This report is available from the MMS’s Internet site (http://www.mms.gov). 

Framework of the Analysis

The Proposed Actions and the Gulfwide OCS Program 

The proposed Federal actions addressed in this report are oil and gas lease sales in the Central 

Planning Area (CPA) and Western Planning Area (WPA) of the Gulf of Mexico OCS (see 

figure 1). Under the Proposed Final Outer Continental Shelf Oil and Gas Leasing Program: 

July 2007-June 2012 (USDOI, MMS, 2007a) (5-Year Program), two sales would be held each 

year—one in the CPA and one in the WPA. The purpose of the proposed Federal actions is to 

offer for lease those areas that may contain economically recoverable oil and natural gas 

resources. The Gulfwide OCS Program comprises all future operations that will occur over a 

40-year time period (2007-2046) from proposed, existing, and future leases in the Western 

and Central GOM Planning Areas. The development scenario assumes that the oil produced in 

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2007 Gulf of Mexico OSRA 
the lease areas will be transported to shore predominantly by pipelines, with a small quantity 

transported by barge and shuttle tankers (LaBelle, 2001). 

The proposed actions analyzed in this report are one “typical” CPA lease sale and one 

“typical” WPA lease sale. A set of ranges for resource estimates and projected exploration 

and development activities developed for each “typical” proposed action was used to analyze 

spill risk. The analyses of oil-spill risk for these “typical” proposed actions are expected to be 

“typical” of any of the other proposed CPA or WPA sales scheduled in the 5-Year Program. 

In other words, each of the proposed sales in the 5-Year Program is expected to be within the 

ranges used for the analyzed “typical” proposed action in the corresponding planning area. 

Domain/Study Areas 

The domain (shown in figure 1) defines the geographic boundaries that encompass the 

environmental resources at risk from a hypothetical oil spill from OCS operations in the lease 

areas. Although few hypothetical oil spills were likely to extend beyond the borders of the 

domain within 30 days after release (the maximum elapsed time considered), we have tracked 

and tabulated spills that would travel beyond the open-ocean boundaries. These spills could 

contact land or other environmental resources outside the domain. 

The two study areas are the areas of the CPA and WPA that encompass the offshore waters 

within the Gulf of Mexico (beginning 3 miles offshore Louisiana, Mississippi, and Alabama; 

and 3 leagues offshore Texas) and extend seaward to the limits of the Exclusive Economic 

Zone (see figure 1). 

The study areas were divided into offshore subareas based upon ranges in water depth. These 

water depth ranges reflect the technological requirements and related physical and economic 

impacts as a consequence of the oil and gas potential, exploration and development activities, 

and lease terms unique to each water-depth range. 

A cluster analysis (Everitt, 1993) is used to further divide the subareas into 50 hypothetical 

spill sites. Cluster analysis is a multivariate technique that groups entities based on similar 

characteristics. In this case, the MMS used the probability of contact to shoreline segments to 

identify offshore areas that showed similar risk based on similarity in patterns of trajectories. 

The study area and the hypothetical spill sites (launch subareas), which are used to represent 

oil-spill risks from drilling and production at a fixed facility, are shown in figures 2a and 2b. 

To account for the risk of spills occurring from the transportation of oil to shore via pipeline, 

generalized pipeline corridors originating within each of the offshore cluster areas and 

terminating at existing major oil pipeline shore bases were identified. These pipeline corridors 

represent the complex matrix of pipeline systems existing offshore that are likely to be used in 

support of each proposed action. The oil volume estimated to be produced within each cluster 

area was proportioned among likely pipeline corridor routes, representing the transportation 

of the oil beginning within a cluster area and terminating at Federal/State boundaries 

proximate to known pipeline shore bases. 

2 

2007 Gulf of Mexico OSRA 
Hypothetical Spill Locations

The OSRA Model initiated hypothetical oil spills uniformly in space and time from within 

each study area, as shown in figures 2a and 2b. At 1/10o intervals in the north-south direction 

(about 11 kilometers [km]) and 1/10o intervals in the east-west direction (about 10 km), the 

model launched an oil spill every 1.0 day. At this resolution, there were 4,125 total launch 

points in space, and a total of 5,760 oil-spill trajectories were launched from each spatial grid 

point over a period from 1986 to 1999. The spatial resolution of the spill simulations was well 

within the spatial resolution of the input data, and the interval of time between releases was 

sufficiently short to sample weather-scale changes in the input winds (Price et al., 2002). 

The sensitivity tests on the OSRA Model (Price et al., 2002) indicated that, statistically, the 

above-mentioned spatial resolution (1/10o by 1/10o) and time resolution (1.0 day) are 

sufficient to represent the spatial and time variations of the particle trajectories in the area. 

Estimated Volume of Oil Resources 

For this analysis, both benefits and risks are functions of the volume of oil produced and are 

mutually dependent. For example, greater volumes of produced oil are associated with greater 

economic benefits as well as greater risks. If the benefits are evaluated by assuming 

production of a specific amount of oil, then the corresponding risks should be stated 

conditionally, such as “the risks are . . . , given that the volume is . . . .” Any statements about 

the likelihood of a particular volume of oil being developed also apply to the likelihood of the 

corresponding benefits and risks. 

The resource estimates are presented for the following scenarios: 

Proposed Action—the range of oil resources estimated to be leased, discovered, and 

produced over a 40-year time period as a result of a typical WPA or CPA lease sale, as 

found in the proposed 5-Year Program for 2007-2012.

OCS Program—the range of oil resources estimated to be leased, discovered, and 

produced as a result of prior lease sales, the proposed actions, and future lease sales that 

will occur during the life of a proposed action (40 years). 

The range in oil resource projections used to develop the proposed actions and OCS Program 

scenarios are based on resource and reserves estimates as presented in the 2006 Assessment of 

Undiscovered Technically Recoverable Oil and Gas Resources of the Nation’s Outer 

Continental Shelf, 2006 (USDOI, MMS, 2006), current industry information, and historical 

trends. The resource estimates for the proposed actions are based on two factors: (1) the 

conditional estimates of undiscovered, unleased, conventionally recoverable oil and gas 

resources in the proposed lease sale areas; and (2) estimates of the portion or percentage of 

these resources assumed to be leased, discovered, developed, and produced as a result of the 

proposed actions. The estimates of undiscovered, unleased, conventionally recoverable oil and 

gas resources are based upon a comprehensive appraisal of the conventionally recoverable 

petroleum resources of the Nation as of January 1, 2003. Due to the inherent uncertainties 

associated with an assessment of undiscovered resources, probabilistic techniques were 

3 

2007 Gulf of Mexico OSRA 
employed, and the results were reported as a range of values corresponding to different 

probabilities of occurrence. A thorough discussion of the methodologies employed and the 

results obtained in the assessment are presented in USDOI, MMS (2006). The estimates of 

the portion of the resources assumed to be leased, discovered, developed, and produced as a 

result of the proposed actions are based upon logical sequences of events that incorporate past 

experience, current conditions, and foreseeable development strategies. A wealth of historical 

data and information derived from over 50 years of oil and gas exploration, development, and 

production activities were used extensively by MMS. The undiscovered, unleased, 

conventionally recoverable resource estimates for the proposed actions are expressed as 

ranges, from low to high. The range reflects a range of projected economic valuations of the 

produced oil and gas. 

The projected life of all exploration, development, production, and abandonment activities 

that result from a typical proposed lease sale is assumed to be 40 years. This is based on 

averages for the amount of time required for these activities for GOM leases. The projected 

oil production (in billion barrels [Bbbl]) for a typical proposed lease sale and the OCS 

Program are as follows: 

Environmental Resources 

Estimated 

Production Analysis 

Proposed Action (Bbbl) Period 

Low Estimate: Western GOM 0.242 40 years 

 Central GOM 0.776 40 years 

High Estimate: Western GOM 0.423 40 years 

 Central GOM 1.292 40 years 

Estimated Analysis 

Production 

(Bbbl)

OCS Program Period

Low Estimate: Western GOM 6.629 40 years 

 Central GOM 21.933 40 years 

 Gulfwide 28.562 40 years 

High Estimate: Western GOM 8.060 40 years 

 Central GOM 24.510 40 years 

 Gulfwide 32.570 40 years 

The environmental resources considered in this analysis were selected by MMS analysts in 

the Gulf of Mexico OCS Region after consultation with the U.S. Fish and Wildlife Service. 

The analysts used geographic digital information on the biological, physical, and 

socioeconomic resources that could be exposed to contact from OCS oil spills to create maps 

of resource locations vulnerable to oil-spill impact. These maps depict locations that were 

analyzed by the OSRA Model, representing either the locations of onshore environmental 

resource habitats or the surface waters overlying or surrounding offshore environmental 

features (see figures 3 through 31). The MMS used data derived from the Central Offshore 

Resource Information System (CORIS) (USDOI, MMS, 1999) and other databases. The 

4 

2007 Gulf of Mexico OSRA 
CORIS data were developed and supported by Federal and State agencies and the oil industry 

operating along the Gulf Coast. 

All onshore, coastal environmental resource locations were represented by one or more 

partitions of the coastline, herein called land. The study area coastline was partitioned into 

162 equidistant land segments of approximately 10-mile (16-km) length. The partitions were 

formed by creating straight lines between two points projected onto the coast; therefore, the 

actual miles of shoreline represented by each land segment may be greater than 10 miles, 

depending upon the complexity of the coastal area. 

In addition, the State offshore waters were included as environmental resources. Texas and 

Florida State offshore waters are extended 3 marine leagues (1 marine league = 1,8228.3 feet 

[ft]) seaward from the baseline from which the breadth of the territorial sea is measured. 

Louisiana State offshore waters are extended 3 imperial nautical miles (1 imperial nautical 

mile = 6,080 ft) seaward of the baseline from which the breadth of the territorial sea is 

measured. Mississippi and Alabama State offshore waters are extended 3 nautical miles (1 

nautical mile = 6,076 ft) seaward of the baseline from which the breadth of the territorial sea 

is measured. In order to tabulate the number of spills traveling beyond the study area, the 

borders of the domain were divided into four boundary segments. 

The environmental resources and socioeconomic features examined in this OSRA and the 

figures illustrating their locations are shown below. Periods of habitat or beach use are 

identified in parentheses. 

Listing of Environmental Resources Figure

6 Bird Habitats 

Diving Bird Habitat 7 

Gulls, Terns, And Charadriid Allies Habitat 8 

Raptor Bird Habitat 9 

Charadriid Shorebird Habitat 10 

Wading Bird Habitat 11 

Waterfowl Habitat 12 

5 Endangered Bird Habitats 

Snowy Plover Habitat (Feb-Aug) 13 

Brown Pelican Habitat 14 

Whooping Crane Habitat (Nov-Apr) 15 

Bald Eagle Habitat 16 

Piping Plover Habitat (July-May) 17 

5 Other Endangered Species Habitats 

Gulf Sturgeon - Known Shoreline Locations 18 

Alabama Beach Mouse Habitat 19 

Choctawhatchee Beach Mouse Habitat 19 

Perdido Key Beach Mouse Habitat 20 

St. Andrew Beach Mouse Habitat 20 

5 

2007 Gulf of Mexico OSRA 
Listing of Environmental Resources Figure

 11 Major Recreational Coastal Areas 

TX Coastal Bend Area Beaches (Apr-Sept) 21 

TX Matagorda Area Beaches (Apr-Sept) 22 

TX Galveston Area Beaches (Apr-Sept) 21 

TX Sea Rim State Park (Apr-Sept) 22 

LA Beaches (Apr-Nov) 21 

AL/MS Gulf Islands (Apr-Nov) 22 

AL Gulf Shores (Apr-Nov) 21 

FL Panhandle Beaches (Apr-Nov) 22 

FL Big Bend Beaches (Apr-Nov) 21 

FL Southwest Beaches (Apr-Nov) 22 

FL Ten Thousand Islands (Apr-Nov) 21 

9 Marine Mammal Habitats 

Mexico Marine Mammal Habitat 25 

TX Marine Mammal Habitat 27 

LA West Marine Mammal Habitat 26 

LA East Marine Mammal Habitat 28 

MS Marine Mammal Habitat 25 

AL Marine Mammal Habitat 29 

FL Panhandle Marine Mammal Habitat 25 

FL Peninsula Marine Mammal Habitat 29 

FL Tortugas Marine Mammal Habitat 26 

9 Manatee Habitats 

FL Panhandle Manatee Areas (Apr-Nov) 30 

FL Panhandle Manatee Areas (Dec-Mar) 30 

FL Big Bend Manatee Areas (Apr-Nov) 31 

FL Big Bend Manatee Areas (Dec-Mar) 31 

FL Southwest Manatee Areas (Apr-Nov) 30 

FL Southwest Manatee Areas (Dec-Mar) 30 

FL Ten Thousand Islands Manatee Areas (Apr-Nov) 31 

FL Ten Thousand Islands Manatee Areas (Dec-Mar) 31 

LA/MS/AL Manatee Areas (Apr-Nov) 31 

30 Sea Turtle Habitats 

Mexico Sea Turtle Nesting Habitat (Apr-Sept) 28 

Mexico Sea Turtle Mating Habitat (Mar-July) 25 

Mexico Sea Turtle General Coastal Habitat 25 

TX Sea Turtle Nesting Habitat - Coastal Bend Area (Apr-Sept) 29 

TX Sea Turtle Nesting Habitat - Matagorda Area (Apr-Sept) 25 

TX Sea Turtle Nesting Habitat - Galveston Area (Apr-Sept) 28 

TX Sea Turtle Nesting Habitat - Sea Rim Area (Apr-Sept) 29 

TX Sea Turtle Mating Habitat (Mar-July) 27 

TX Sea Turtle General Coastal Habitat 27 

LA Sea Turtle Nesting Habitat (Apr-Nov) 27 

LA Sea Turtle Mating Habitat (Mar-Jul) 27 

LA Sea Turtle General Coastal Habitat - West 26 

LA Sea Turtle General Coastal Habitat - East 28 

6 

2007 Gulf of Mexico OSRA 
Listing of Environmental Resources Figure

MS Sea Turtle Nesting Habitat (Apr-Nov) 26 

MS Sea Turtle Mating Habitat (Mar-Jul) 25 

MS Sea Turtle General Coastal Habitat 25 

AL Sea Turtle Nesting Habitat (Apr-Nov) 26 

AL Sea Turtle Mating Habitat (Mar-Jul) 29 

AL Sea Turtle General Coastal Habitat 29 

FL Sea Turtle Nesting Habitat - Panhandle Area (Apr-Nov) 28 

FL Sea Turtle Nesting Habitat - Peninsula Area (Apr-Nov) 25 

FL Sea Turtle Nesting Habitat - Keys Area (Apr-Nov) 27 

FL Sea Turtle Nesting Habitat - Tortugas Area (Apr-Nov) 26 

FL Sea Turtle Mating Habitat - Panhandle Area (Mar-Jul) 25 

FL Sea Turtle Mating Habitat - Peninsula Area (Mar-Jul) 29 

FL Sea Turtle Mating Habitat - Keys Area (Mar-Jul) 27 

FL Sea Turtle Mating Habitat - Tortugas Area (Mar-Jul) 26 

FL Sea Turtle General Coastal Habitat - Panhandle Area 25 

FL Sea Turtle General Coastal Habitat - Peninsula Area 29 

FL Sea Turtle General Coastal Habitat - Keys Area 27 

FL Sea Turtle General Coastal Habitat - Tortugas Area 26 

Counties/Parishes 

Cameron, TX 23 

Willacy, TX 24 

Kenedy, TX 23 

Kleberg, TX 24 

Nueces, TX 23 

Aransas, TX 24 

Calhoun, TX 23 

Matagorda, TX 24 

Brazoria, TX 23 

Galveston, TX 24 

Chambers, TX 23 

Jefferson, TX 24 

Cameron, LA 23 

Vermilion, LA 24 

Iberia, LA 23 

St. Mary, LA 24 

Terrebonne, LA 23 

Lafourche, LA 24 

Jefferson, LA 23 

Plaquemines, LA 24 

St. Bernard, LA 23 

Hancock & Harrison, MS 24 

Jackson, MS 23 

Mobile, AL 24 

Baldwin, AL 23 

Escambia, FL 24 

Santa Rosa, FL 23 

Okaloosa, FL 24 

Walton, FL 23 

Bay, FL 24 

7 

2007 Gulf of Mexico OSRA 
Listing of Environmental Resources Figure

Gulf, FL 23 

Franklin, FL 24 

Wakulla, FL 23 

Jefferson, FL 24 

Taylor, FL 23 

Dixie, FL 24 

Levy, FL 23 

Citrus, FL 24 

Hernando, FL 23 

Pasco, FL 24 

Pinellas, FL 23 

Hillsborough, FL 24 

Manatee, FL 23 

Sarasota, FL 24 

Charlotte, FL 23 

Lee, FL 24 

Collier, FL 23 

Monroe, FL 24 

8 Offshore State Waters 

Mexican Waters 6 

TX State Offshore Waters 3 

LA (Eastern) State Offshore Waters 4 

LA (Western) State Offshore Waters 5 

MS State Offshore Waters 6 

AL State Offshore Waters 3 

FL Panhandle State Offshore Waters 5 

FL Peninsula State Offshore Waters 6 

4 Texas Offshore Resource 

7 1/2 Fathoms 5 

Flower Gardens Banks 3 

Stetson Bank 4 

Sonnier Bank 6 

1 Louisiana Offshore Resource 

Chandeleur Islands 3 

4 Florida Offshore Resources 

Big Bend Seagrass 4 

FL Middle Ground 3 

FL Keys National Marine Sanctuary 5 

Tortugas Ecological Reserve 4 

8 

2007 Gulf of Mexico OSRA 
Listing of Environmental Resources Figure

6 Boundary Targets 

Boundary Target 1 3 

Boundary Target 2 4 

Boundary Target 3 5 

Boundary Target 4 6 

North FL Straits 4 

South FL Straits 5 

Oil-Spill Risk Analysis 

The OSRA was conducted in three parts corresponding to different aspects of the overall 

problem: (1) the probability of oil-spill occurrence, (2) the trajectories of oil spills from 

hypothetical spill locations to various environmental resources, and (3) a combination of the 

first two to estimate the overall oil-spill risk of combined occurrence and contact if there is oil 

development. The second and third parts were completed for the analysis of spills from the 

proposed actions. 

Risk analyses may be characterized as “hazard-based” or “risk-based.” A hazard-based 

analysis examines possible events regardless of their low (or high) likelihood. For example, a 

potential impact would not lose significance because the risk has been reduced due to an 

increase in the level of control, such as engineering standards. A risk-based analysis, on the 

other hand, does take into account the likelihood of the event occurring or the measures that 

can be taken to mitigate against its potential impacts. 

This OSRA is designed for use as a risk-based assessment. Therefore, the likelihood of oil 

spills (≥ 1,000 barrels [bbl] in size) occurring on the OCS plays an integral role in the 

analysis. In addition to the estimated chance of spills occurring, the analysis entails an 

extensive oil-spill trajectory model. Results from the trajectory analysis provide input to the 

final product by estimating where spills might travel on the ocean’s surface and what 

resources might be contacted. 

Results from the OSRA are, therefore, expressed as the combined probability of spills both 

occurring and contacting modeled offshore and coastal environmental resource locations. 

Note that the analysis estimates spill contacts, not impacts. Further measures that should be 

evaluated to determine impacts, such as the natural weathering of oil spills and cleanup 

activities, are not directly factored into the analysis but should be added to the interpretation 

of its results. 

Probability of Oil Spills Occurring 

The probability of oil spills occurring assumes that spills occur independently of each other as 

a Poisson process. The Poisson process is a statistical distribution commonly used to model 

random events. The probability of oil spills occurring is based on spill rates derived from past 

OCS platform and OCS pipeline experience and all tanker experience in U.S. waters, and 

9 

2007 Gulf of Mexico OSRA 
depends on the volume of oil produced and transported. All types of accidental spills greater 

than or equal to 1,000 bbl were considered in this analysis. These spills include those from 

well blowouts, other accidents that occur on platforms, and during transportation of oil to 

shore. These spills were classified as either platform, pipeline, or tanker spills. This 

classification allows the analyst to compare the risks from each spill source between a 

proposed action and any alternatives. 

Anderson and LaBelle (1994, 2000) examined oil-spill occurrence rates applicable to the 

OCS. Their results, adjusted for recent experience and based upon more complete databases 

than were available for earlier analyses (Anderson and LaBelle, 1990; Lanfear and Amstutz, 

1983), indicated some significant changes in the spill rates for platforms and pipelines. In 

addition, they developed estimated occurrence rates for tanker spills that have occurred in 

U.S. waters. This report uses the updated spill occurrence rates. 

Spill rates are expressed as number of spills per billion barrels (spills/Bbbl), defined as 

109 bbl, of oil produced or transported. Only spills greater than or equal to 1,000 bbl are 

addressed because smaller spills may not persist long enough to be simulated by trajectory 

modeling. Another consideration is that these large spills are likely to be identified and 

reported; therefore, these records are more comprehensive than those of smaller spills. 

(Smaller spills are addressed in the EIS for each proposed action without the use of trajectory 

modeling.) 

Two basic criteria were used in selecting volume of oil handled as the risk exposure variable: 

(1) the exposure variable should be simple to define, and (2) it should be a quantity that can 

be estimated. The volume of oil produced or transported was the chosen exposure variable 

primarily for the following reasons: historic volumes of oil produced and transported are well 

documented; using these volumes makes the calculation of the estimated oil-spill occurrence 

rate simple—the ratio of the number of historic spills to the volume of oil produced or 

transported; and future volumes of oil production and transportation are routinely estimated. 

Estimates of volume to be developed for a proposed action and the Gulfwide OCS Program, 

which were prepared by analysts in the MMS Resource Evaluation Division, GOM Regional 

Office, are derived from the assessment of oil resources by using comprehensive geological 

and geophysical databases and related models. In addition, the MMS analysts estimate other 

exposure variables, such as number of platforms and tanker trips, as a function of the volume 

of oil estimated to be produced or transported. 

Anderson and LaBelle (1994, 2000) analyzed platform and pipeline spills in Federal waters 

that occurred from OCS oil and gas development from 1964 through 1999 and crude oil 

tanker spills that occurred in U.S. waters from 1974 through 1999. In these analyses, every 

spill record was examined and verified to the furthest extent possible. Each spill was 

classified for size, product spilled, and spill source according to its applicability to the 

analysis. 

10 

2007 Gulf of Mexico OSRA 
For this OSRA study, the analysis used the following spill rates based on a 15-year period 

(1985-1999), as found in Anderson and LaBelle (2000) as best representing current 

technology. The rates are based on number of spills per billion barrels of oil (spills/Bbbl) 

produced at OCS platforms or transported by OCS pipelines or OCS tankers. 

Oil Spill Rates Based on 1985-1999 Data (Anderson and LaBelle, 2000)

 

Spill Source

No. of Spills

≥ 1,000 bbl

No. of Spills

≥ 10,000 bbl

OCS Platforms 0.13 spills/Bbbl 0.05 spills/Bbbl 

OCS Pipelines 1.38 spills/Bbbl 0.34 spills/Bbbl 

OCS Tankers 0.72 spills/Bbbl 0.25 spills/Bbbl 

Using Bayesian techniques, Devanney and Stewart (1974) showed that the probability of n

oil-spill contacts can be described by a negative binomial distribution. Smith et al. (1982), 

however, noted that when actual exposure is much less than historical exposure, as is the case 

here, the negative binomial distribution can be approximated by a Poisson distribution. The 

Poisson distribution has a significant advantage in calculations because it is defined by only 

one parameter, the assumed number of spills. If p(n,i) is the probability of exactly n contacts 

to environmental resource i, then: 

(,) !

n i

i e pni

n

λ λ − ⋅ =

where n is the specific number of spills (0, 1, 2, ..., n), e is the base of the natural logarithm, 

and λ is the parameter of the Poisson distribution. For oil spills, the Poisson parameter (λ) is 

equal to the spill rate multiplied by the volume of oil to be produced or transported. The spill 

rate has dimensions of number of spills/Bbbl, and the volume is expressed in Bbbl. Therefore, 

λ denotes the mean number of spills estimated to occur as a result of production or 

transportation of a specific volume of oil. 

Oil-spill occurrence estimates for spills greater than or equal to 1,000 bbl were calculated for 

production and transportation of oil during the 40-year analysis period associated with the 

proposed actions in the WPA, CPA, and the Gulfwide OCS Program (2007-2046). These 

probabilities are based on the volume of oil estimated to be found, produced, and transported 

over the life of a typical lease sale and on the rates that have been calculated for oil spills from 

OCS platforms, pipelines, and tankers by Anderson and LaBelle (2000). The probabilities of 

one or more oil spills greater than or equal to 1,000 bbl occurring as a result of OCS 

exploration, development, and production and transportation resulting from a typical lease 

sale or the OCS Program are found in table 1a. The probabilities for spills greater than or 

equal to 10,000 bbl are shown in table 1b. 

Oil-Spill Trajectory Simulations 

The OSRA Model, originally developed by Smith et al. (1982) and enhanced by MMS over 

the years (LaBelle and Anderson, 1985; Ji et al., 2002, 2004a, 2004b), simulates oil-spill 

11 

2007 Gulf of Mexico OSRA 
transport using realistic data fields of winds and ocean currents in the GOM. An oil spill on 

the ocean surface moves around by the complex surface ocean currents exerting a shear force 

on the spilled oil from below. In addition, the prevailing wind exerts an additional shear force 

on the spill from above, and the combination of the two forces causes the transportation of the 

oil spill away from its initial spill location. In the OSRA Model, the velocity of a hypothetical 

oil spill is the linear superposition of the surface ocean current and the wind drift caused by 

the winds. The model calculates the movement of hypothetical spills by successively 

integrating time sequences of two spatially gridded input fields: the surface ocean currents 

and the sea-level winds, both of which were generated by other computer models using many 

observations of relevant physical parameters. In this fashion, the OSRA Model generates 

time sequences of hypothetical oil-spill locations–essentially, oil-spill trajectories. 

At each successive time step, the OSRA Model compares the location of the hypothetical 

spills against the geographic boundaries of shoreline and designated offshore environmental 

resources. The model counts the occurrences of oil-spill contact to these areas during the time 

periods that the habitat is known to be used by the resource. Finally, the frequencies of oilspill contact are computed for designated oil-spill travel times (e.g., 3, 10, or 30 days) by 

dividing the total number of oil-spill contacts by the total number of hypothetical spills 

initiated in the model from a given hypothetical spill location. The frequencies of oil-spill 

contact are the model-estimated probabilities of oil-spill contact. The OSRA Model output 

provides the estimated probabilities of contact to all identified offshore environmental 

resources and segments of shoreline from locations chosen to represent hypothetical oil spills 

from oil production and transportation facilities, at several selected oil-spill travel times. 

There are factors not explicitly considered by the OSRA Model that can affect the transport of 

spilled oil as well as the dimensions, volume, and nature of the oil spills contacting 

environmental resources or the shoreline. These include possible cleanup operations, 

chemical composition or biological weathering of oil spills, or the spreading and splitting of 

oil spills. The OSRA analysts have chosen to take a more environmentally conservative 

approach by presuming persistence of spilled oil over the selected time duration of the 

trajectories. 

In the trajectory simulation portion of the OSRA Model, many hypothetical oil-spill 

trajectories are produced by numerically integrating a temporally and spatially varying ocean 

current field, and superposing on that an empirical wind-induced drift of the hypothetical oil 

spills (Samuels et al., 1982). Collectively, the trajectories represent a statistical ensemble of 

simulated oil-spill displacements produced by a field of winds derived from observations and 

numerically derived ocean currents. The winds and currents are assumed to be statistically 

similar to those that will occur in the Gulf during future offshore activities. In other words, 

the oil-spill risk analysts assume that the frequency of strong wind events in the wind field is 

the same as what will occur during future offshore activities. By inference, the frequencies of 

contact by the simulated oil spills are the same as what could occur from actual oil spills 

during future offshore activities. 

Another portion of the OSRA Model tabulates the contacts by the simulated oil spills. The 

model contains the geographical boundaries of a variety of identified environmental features. 

12 

2007 Gulf of Mexico OSRA 
At every integration time step, the OSRA Model tracks the locations of the simulated spills 

and counts the number of oil-spill contacts to segments of shoreline (counties/parishes). A 

contact to shore will stop the trajectory of an oil spill; no re-washing is assumed in this model. 

After specified periods of time, the OSRA Model will divide the total number of contacts to 

the coastline segments by the total number of simulated oil spills from a given geographic 

location. These ratios are the estimated probabilities of oil-spill contact from offshore 

activities at that geographic location, assuming spill occurrence. 

Conducting an oil-spill risk analysis requires detailed information on ocean currents and wind 

fields (Ji, 2004). The ocean currents used are numerically computed from an ocean circulation 

model of the GOM driven by analyzed meteorological forces (the near-surface winds and the 

total heat fluxes) and observed river inflow into the GOM (Herring et al., 1999; Oey et al., 

2004; Oey, 2005). The models used are versions of the Princeton Ocean Model (POM), which 

is an enhanced version of the earlier constructed Mellor-Blumberg Model. It is a threedimensional, time-dependent, primitive equation model using orthogonal curvilinear 

coordinates in the horizontal and a topographically conformal coordinate in the vertical. The 

use of these coordinates allows for a realistic coastline and bottom topography, including a 

sloping shelf, to be represented in the model simulation. The model incorporates the MellorYamada turbulence closure model to provide a parameterization of the vertical mixing 

process through the water column. 

The prognostic variables of the model are velocity, temperature, salinity, turbulence kinetic 

energy, and turbulence macroscale. The momentum equations are nonlinear and incorporate a 

variable Coriolis parameter. Prognostic equations governing the thermodynamic quantities 

(temperature and salinity) account for water mass variations brought about by highly timedependent coastal upwelling processes. The processes responsible for eddy production, 

movement, and eventual dissipation are also included in the model physics. Other computed 

variables include density, vertical eddy viscosity, and vertical eddy diffusivity. 

Two separate model runs were used to calculate the trajectories for this statistical report. The 

first was a 9-year simulation performed by Dynalysis of Princeton (Herring, et al., 1999). The 

POM was driven by winds and heat fluxes over the 9-year period, 1986 through 1994, which 

were analyzed by the European Center for Medium-Range Weather Forecasts. The second 

ocean model calculation was performed by Princeton University (Oey, 2005; Oey, et al., 

2004). This simulation covered the 7-year period, 1993 through 1999, and the results were 

saved at 1-hour intervals. This run included the assimilation of sea surface altimeter 

observations, to improve the ocean model results. The surface currents were then computed 

for input into the OSRA Model along with the concurrent wind field. The OSRA Model used 

the same wind field to calculate the empirical wind drift of the simulated spills. The statistics 

for the contacts by the trajectories forced by the two model runs were combined for the 

average probabilities. 

The ocean model simulations were extensively skill-assessed with many observations from 

the GOM (Herring et al., 1999; Oey, et al., 2004, Oey, 2005). These extensive sets of 

observations afford a rigorous test of the model’s ability to reproduce ocean transport as well 

as prominent features of the Gulf such as the Loop Current and strong mesoscale eddies, 

13 

2007 Gulf of Mexico OSRA 
which are easily observed from satellite-borne instrumentation. With these observations and 

other current measurements from moored current meters, a good determination of the model’s 

veracity was made. Both the POM models did an excellent job in reproducing the 

characteristics of the GOM surface currents both on and off the continental shelf. The surface 

current field manifests all the dominant structures in time and space as the observed currents 

and is, therefore, applicable in the statistical estimation of future spill risk that the OSRA 

Model makes. 

Trajectories of hypothetical spills were initiated every 1.0 day from each of the launch points 

in space over the simulation period from January 1, 1986 to December 31, 1999. The chosen 

number of trajectories per site was small enough to be computationally practical and large 

enough to reduce the random sampling error to an insignificant level. Also, the weather-scale 

changes in the winds are at least minimally sampled with simulated spills started every 1.0 

day. 

The OSRA Model integrates the spill velocities (a linear superposition of surface ocean 

currents and empirical wind drift) by integrating in time to produce the spill trajectories. The 

time step selected was 1 hour to fully utilize the spatial resolution of the ocean current field 

and to achieve a stable set of trajectories. The velocity field was bilinearly interpolated from 

the 3-hourly or 1-hourly grid to get velocities at 1-hour intervals. Smaller time steps did not 

produce significant differences in the simulated trajectories after 30 model days, so the 1-hour 

time step was chosen for this analysis. Ji et al. (2004a) summarized the latest improvement on 

the OSRA Model and the model sensitivity tests. 

Conditional Probabilities of Contact 

The probability that an oil spill will contact a specific environmental resource within a given 

time of travel from a certain location or spill point is termed a conditional probability, the 

condition being that a spill is assumed to have occurred. Each trajectory was allowed to 

continue for as long as 30 days. However, if the hypothetical spill contacted shoreline sooner 

than 30 days after the start of the spill, the spill trajectory was terminated, and the contact was 

recorded. 

The trajectories simulated by the model represent only hypothetical pathways of oil slicks; 

they do not involve any direct consideration of cleanup, dispersion, or weathering processes 

that could alter the quantity or properties of oil that might eventually contact the 

environmental resource locations. However, an implicit analysis of weathering and decay can 

be considered by choosing a travel time for the simulated oil spills when they contact 

environmental resource locations that represent the likely persistence of the oil slick on the 

water surface. The MMS performed an analysis of the likely weathering and cleanup of a 

typical offshore oil spill of 1,000 bbl or greater occurring under the proposed action scenarios 

(USDOI, MMS, 2007b). The analysis of the slick’s fate showed that a typical GOM oil slick 

of 1,000 bbl or greater, exposed to typical winds and currents, would not persist on the water 

surface beyond 10 days. Therefore, the OSRA Model trajectories were analyzed only up to 

10 days. Any spill contacts occurring on or before this elapsed time are reported in the 

probability tables. Conditional probabilities of contact with environmental resource locations 

14 

2007 Gulf of Mexico OSRA 
and land segments within 10 days of travel time were calculated for each of the hypothetical 

spill sites by the model to serve as input into the final calculation of risk. 

Combined Probabilities of Contact 

A critical difference exists between the conditional probabilities and the combined 

probabilities calculated. Conditional probabilities depend only on the winds and currents in 

the study area. Combined probabilities, on the other hand, depend not only on the physical 

conditions, but also on the chance of spill occurrence, the estimated volume of oil to be 

produced or transported, and the oil transportation scenario. The combined probabilities for 

this analysis of the proposed action activities are presented in tables 2-6. 

In calculating the combined probabilities, those that represent probabilities of both oil-spill 

occurrence and contact, the following steps are performed: 

(1) For a set of nt environmental resources and nl launch points, the conditional probabilities 

can be represented in a matrix form. Let [C] be an nt × nl matrix, where each element ci,j

is the probability that an oil spill will contact environmental resource i, given that a spill 

occurs at launch point j. Note that launch points can represent potential starting points of 

spills from production areas or transportation routes. 

(2) Spill occurrence can be represented by another matrix [S]. With nl launch points and ns

production sites, the dimensions of [S] are nl × ns. Let each element sj,k be the estimated 

mean number of spills occurring at launch point j owing to production of a unit volume 

(1 Bbbl) of oil at site k. These spills can result from either production or transportation. 

The sj,k can be determined as a function of the volume of oil (spills/Bbbl). Each column 

of [S] corresponds to one production site and one transportation route. If alternative and 

mutually exclusive transportation routes are considered for the same production site, 

they can be represented by additional columns of [S], thus increasing ns. 

(3) Matrix [U] is defined as 

[U] = [C] × [S] 

Matrix [U]—which has dimensions nt × ns—is termed the unit risk matrix. Each element 

ui,k corresponds to the estimated mean number of spills occurring and contacting 

environmental resource i, owing to the production of a unit volume (1 Bbbl) of oil at 

site k. 

(4) With [U], the mean contacts to each environmental resource are estimated, given a set of 

oil volumes at each site. Let [V] be a vector of dimension ns where each element vk

corresponds to the volume of oil expected to be found at production site k. Then, if [L] is 

a vector of dimension nt, where each element λi corresponds to the mean number of 

contacts to environmental resource i, the formula is 

[L] = [U] × [V] 

15 

2007 Gulf of Mexico OSRA 
Thus, estimates of the mean number of oil spills that are likely to occur and contact 

environmental resources (or land segments) can be calculated. (Note that as a statistical 

parameter, the mean number can assume a fractional value, even though fractions of oil spills 

have no physical meaning.) 

Discussion 

As one might expect, environmental resource locations closest to the spill sites had the 

greatest risk of contact. As the model run duration increases, more of the identified 

environmental resources and shoreline segments could have meaningful probabilities of 

contact (>0.5%). The longer transit times up to 10 days allowed by the model enable more 

hypothetical spills to reach the environmental resources and the shoreline from more distant 

spill locations. With increased travel time, the complex patterns of wind and ocean currents 

produce eddy-like motions of the oil spills and multiple opportunities for a spill to make 

contact with any given environmental resource or shoreline segment. 

For instance, table 2 provides the probabilities (expressed as percent chance) of one or more 

offshore spills greater than or equal to 1,000 bbl, and the number of spills (mean), of the 

estimated volume of oil produced from the proposed action in the Gulf of Mexico CPA that 

could occur and contact a certain offshore environmental resource within 10 days. Only one 

resource (Louisiana (Western) State Offshore Waters) has a probability of more than 10 

percent of being contacted by the spilled oil, if there is an oil spill from the proposed action in 

the CPA. 

It should be noted that the study area does not extend into the Atlantic Ocean, where oil spills 

in the Gulf might be transported via the exiting Loop Current. However, on average, less than 

0.5 percent of the simulated spills made it across the northern or southern Florida Straits 

boundary within 30 days. 

References Cited 

Anderson, C.M., and R.P. LaBelle. 1990. Estimated Occurrence Rates for Accidental Oil 

Spills on the U.S. Outer Continental Shelf: Oil and Chemical Pollution 6:21-35. 

Anderson, C.M., and R.P. LaBelle. 1994. Comparative Occurrence Rates for Offshore Oil 

Spills. Spill Science and Technology Bulletin 1(2):131-141. 

Anderson, C.M., and R.P. LaBelle. 2000. Update of Comparative Occurrence Rates for 

Offshore Oil Spills. Spill Science and Technology Bulletin 6(5-6):303-321. 

Devanney, M.W., III, and R.J. Stewart. 1974. Analysis of Oilspill Statistics, April 1974. 

Massachusetts Institute of Technology (Cambridge) Report No. MITSG-74-20. 

Prepared for the Council on Environmental Quality. 

16 

2007 Gulf of Mexico OSRA 
Everitt, B.S. 1993. Cluster Analysis. 3rd Edition. Edward Arnold. 

Herring, H. J., M. Inoue, G. L. Mellor, C. N. K. Mooers, P. P. Niiler, L-Y. Oey, R. C. 

Patchen, F. M. Vukovich, and W. J. Wiseman, Jr. 1999. Coastal Ocean Modeling 

Program for the Gulf of Mexico. Report Numbers 115.1, 115.2, and 115.3 with 

appendices 115A through 115O-P. Prepared for the Minerals Management Service. 

Ji, Z.-G., 2004, Use of Physical Sciences in Support of Environmental Management. 

Environmental Management, 34(2), Springer-Services and Business Media., New 

York, NY, pp. 159-169. 

Ji, Z.-G., W.R. Johnson, C.F. Marshall, G.B. Rainey, and E.M. Lear, 2002, Oil-Spill Risk 

Analysis: Gulf of Mexico Outer Continental Shelf (OCS) Lease Sales, Central Planning 

Area and Western Planning Area, 2003-2007, and Gulfwide OCS Program, 2003-2042. 

Minerals Management Service, Herndon, VA, OCS Report 2002-032, 61 pp. 

Ji, Z.-G., W.R. Johnson, and C.F. Marshall, 2004a, Deepwater Oil-Spill Modeling For 

Assessing Environmental Impacts. Coastal Environment V (Brebbia et al., eds), WIT 

Press, Southampton, MA, pp. 349-358. 

Ji, Z.-G., W.R. Johnson, C.F. Marshall, and E.M. Lear, 2004b, Oil-Spill Risk Analysis: 

Contingency Planning Statistics for Gulf of Mexico OCS Activities. Minerals 

Management Service, Herndon, VA, OCS Report 2004-026, 62 pp. 

LaBelle, R. P. 2001. Overview of US Minerals Management Service Activities in Deepwater 

Research. Marine Pollution Bulletin 43(7-12): 256-261. 

LaBelle, R. P., and C. M. Anderson. 1985. The Application of Oceanography to Oil-Spill 

Modeling for the Outer Continental Shelf Oil and Gas Leasing Program: Marine 

Technology Society Journal 19(2):19-26. 

Lanfear, K.J., and D.E. Amstutz. 1983. A Reexamination of Occurrence Rates for Accidental 

Oil Spills on the U.S. Outer Continental Shelf: Proceedings of the Eighth Conference 

on the Prevention, Behavior, Control, and Cleanup of Oil Spills, San Antonio, Texas, 

February 28-March 3, 1983. 

Oey, L.-Y. 2005. Circulation Model of the Gulf of Mexico and the Caribbean Sea: 

Development of the Princeton Regional Ocean Forecast (& Hindcast) System - PROFS, 

and Hindcast Experiment for 1992-1999. Final Report. OCS Study MMS 2005-049. 

U.S. Dept. of the Interior, Minerals Management Service, Environmental Division, 

Herndon, Virginia. 174 pp. 

Oey, L.-Y., P. Hamilton, and H.-C. Lee. 2004. Modeling and Data Analyses of Circulation 

Processes in the Gulf of Mexico: Final Report. OCS Study MMS2003-074. U.S. 

Department of the Interior, Minerals Management Service, Gulf of Mexico OCS 

Region, New Orleans, LA. 140 pp. 

17 

2007 Gulf of Mexico OSRA 
Price, J. M., W. R. Johnson, Z.-G. Ji, C. F. Marshall, and G. B. Rainey. 2002. Sensitivity 

Testing for Improved Efficiency of a Statistical Oil Spill Risk Analysis Model. 

Submitted to Journal of Marine Systems. 

Samuels, W. B., N. E. Huang, and D.E. Amstutz. 1982. An Oil Spill Trajectory Analysis 

Model with a Variable Wind Deflection Angle. Ocean Engineering 9:347-360. 

Smith, R. A., J. R. Slack, T. Wyant, and K. J. Lanfear. 1982. The Oil Spill Risk Analysis 

Model of the U.S. Geological Survey. U.S. Geological Survey Professional Paper 1227. 

U.S. Department of the Interior, Minerals Management Service (USDOI, MMS). 

1999. Relational Database Design for Coastal and Offshore Resource Information 

System ( CORIS ). Version 1.2. U.S. Dept. of the Interior, Minerals Management 

Service, Information Technology Division, Systems Application Branch. April 1999. 

USDOI, MMS. 2006. Assessment of Undiscovered Technically Recoverable Oil and Gas 

Resources of the Nation’s Outer Continental Shelf, 2006. MMS Fact Sheet RED-2006-

01b U.S. Dept. of the Interior, Minerals Management Service, Resource Evaluation 

Division, Herndon, VA. 6 pp. 

USDOI, MMS. 2007a. Proposed Final Program, Outer Continental Shelf Oil and Gas 

Leasing Program: 2007-2012. U.S. Dept. of the Interior, Minerals Management 

Service, Herndon, VA. 2 vols. 

USDOI/MMS. 2007b. Gulf of Mexico OCS Oil and Gas Lease Sales: 2007-2012, Western 

Planning Area Sales 204, 207, 210, 215, and 218; Central Planning Area Sales 205, 

2206, 208, 213, 216, and 222, Final Environmental Impact Statement. OCS EIS/EA 

MMS 2007-018. U.S. Dept. of the Interior, Minerals Management Service, Gulf of 

Mexico OCS Region, New Orleans, LA. 2 vols. 

18 

2007 Gulf of Mexico OSRA 
MS AL 

LA

TX

Study Area for

WPA Proposed Action Study Area for

CPA Proposed Action

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

Figure 1. Domain and Study Areas for the Oil-Spill Risk Analysis. (The shaded areas re

analyzed for the Gulfwide OCS Program.)

19

2007 Gulf of Mexico OSRA
Figure 2a. Locations of Cluster Subareas. (The cluster subarea boundaries have been t

AL 

MS

LA

TX

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

20

2007 Gulf of Mexico OSRA
Figure 2b. Enlargement of Cluster Subareas. (The cluster subarea boundaries have been th

21

2007 Gulf of Mexico OSRA

31o30o29o28o27o26o25o

97o 96o 95o 94o 93o 92o 91o 90o 

LA

TX

W1-4

W2-4

W2-3

W3-3

W3-4

W4-4

W3-2W4-1

W4-2

W5-2

W6-1

W5-1

W4-3

W1-3

W1-2

W1-1

W2-1

W3-1

W6-2

C2-1

W2-2

C2-2

C2-3

C3-2

C4-4

C5-3

C6-4

C4-2

C2
TX

LA

MS AL 

M

e

x

i

c

o

Texas State

Offshore Waters

Flower

Garden Banks

Boundary Target 1

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

Chandeleur Islands

Alabama State

Offshore Waters

Figure 3. Locations of Texas State Offshore Waters, Flower Garden Banks, Alabama S

Islands, Florida Middle Ground, and Boundary Target 1. (Shading is not to s

22

2002 Gulf of Mexico OSRA
TX

LA

MS AL 

M

e

x

i

c

o

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

Stetson Bank

Louisiana (Eastern

State Offshore Wate

Boundary Target 2

Big 

Tortug

Figure 4. Locations of Stetson Bank, Louisiana (Eastern) State Offshore Waters, Big B

Tortugas Ecological Reserve, and North Florida Straits. (Shading is not to sc

23

2002 Gulf of Mexico OSRA
TX

LA

MS AL 

M

e

x

i

c

o

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

7 1/2 Fathoms

Louisiana (Western)

State Offshore Waters

Florida Panhandl

State Offshore Wa

Boundary Target 3 

Figure 5. Locations of 7 1/2 Fathoms, Louisiana (Western) State Offshore Waters, Flo

Florida Keys National Marine Sanctuary, Boundary Target 3, and South Flor

24

2002 Gulf of Mexico OSRA
TX

LA

MS AL 

M

e

x

i

c

o

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

Mexican Waters

Sonnier Bank

MississippiState Offshore Wat

F

Figure 6. Locations of Mexican Waters, Sonnier Bank, Mississippi State Offshore Wat

Waters, and Boundary Target 4. (Shading is not to scale.)

25

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA MS AL 

M

e

x

i

c

o

26

2002 Gulf of Mexico OSRA Diving Birds

Figure 7. Locations of Diving Bird Habitat. (Shading is not to scale.)
31o

30o29o28o27o26o25o

24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA MS AL 

M

e

x

i

c

o

Gulls, Terns, and Charadriid Allies

Figure 8. Locations of Gulls, Terns, and Charadriid Allies Habitat. (Shading is not to sc

27

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA MS AL 

M

e

x

i

c

o

Raptor Birds

Figure 9. Locations of Raptor Bird Habitat. (Shading is not to scale.)

28

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA

MS AL 

M

e

x

i

c

o

Charadriid Shorebirds

Figure 10. Locations of Charadriid Shorebird Habitat. (Shading is not to scale.)

29

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA

MS AL 

M

e

x

i

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o

Figure 11. Locations of Wading Bird Habitat. (Shading is not to scale.)

30

2002 Gulf of Mexico OSRA Wading Birds
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA

MS AL 

M

e

x

i

c

o

Waterfowl

Figure 12. Locations of Waterfowl Habitat. (Shading is not to scale.)

31

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA

MS AL 

M

e

x

i

c

o Snowy Plovers

Figure 13. Locations of Snowy Plover Habitat (February-August). (Shading is not to s

32

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA

MS AL 

M

e

x

i

c

o

Brown Pelicans

Figure 14. Locations of Brown Pelican Habitat. (Shading is not to scale.)

33

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA

MS AL 

M

e

x

i

c

o

Whooping Cranes

Figure 15. Locations of Whooping Crane Habitat (November-April). (Shading is not 

34

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA

MS AL 

M

e

x

i

c

o

Bald Eagles

Figure 16. Locations of Bald Eagle Habitat. (Shading is not to scale.)

35

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

TX

LA

MS AL 

M

e

x

i

c

o

Piping Plovers

Figure 17. Locations of Piping Plover Habitat (July-May). (Shading is not to scale.)

36

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA

MS AL 

M

e

x

i

c

o

Gulf Sturgeon

Figure 18. Known Shoreline Locations of Gulf Sturgeon Habitat. (Shading is not to s

37

2002 Gulf of Mexico OSRA
TX

LA

MS AL 

M

e

x

i

c

o

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

Choctawatc

Beach Mou

Alabama

Beach Mouse

Figure 19. Locations of Alabama Beach Mouse and Choctawatchee Beach Mouse Hab

38

2002 Gulf of Mexico OSRA
TX

LA

MS AL 

M

e

x

i

c

o

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

St. An

Beach 

Perdido Key

Beach Mouse

Figure 20. Locations of Perdido Key Beach Mouse and St. Andrew Beach Mouse Hab

39

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

Texas Coastal Bend 

Area Beaches

Texas Galveston

Area Beaches Louisiana Beaches

Figure 21. Locations of Texas Coastal Bend Area Beaches, Texas Galveston Area Beach

Gulf Shores, Florida Big Bend Beaches, and Florida Ten Thousand Islands. (Suse for Texas beaches is April-September, and periods of use for all other bea

Alabama

Gulf Shores

F

TX

LA

MS AL 

M

e

x

i

c

o

40

2002 Gulf of Mexico OSRA
TX

LA

MS AL 

M

e

x

i

c

o

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

Texas Matagorda Area Beaches

Texas Sea Rim 

State Park

Alabama/Mississippi

Gulf Islands

Florida Panh

Figure 22. Locations of Texas Matagorda Area Beaches, Texas Sea Rim State Park, A

Florida Panhandle Beaches, and Florida Southwest Beaches. (Shading is nobeaches is April-September, and periods of use for all other beaches is Apri

41

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

C1

C11

C9

C7

C5

C3

C13

C15

C17 C19

C1 - Cameron, TXC3 - Kenedy, TXC5 - Nueces, TXC7 - Calhoun, TXC9 - Brazoria, TX

C11 - Chambers, TXC13 - Cameron, LAC15 - Iberia, LAC17 - Terrebonne, LAC19 - Jefferson, LAC21 - St. Bernard, LAC23 - Jackson, MS

C23 C25 C27 C29

C21

Figure 23. Locations of Gulf of Mexico Counties and Parishes (set 1). (Shading is not t

C3

C25 - Baldwin, ALC27 - Santa Rosa, FLC29 - Walton, FLC31 - Gulf, FLC33 - Wakulla, FLC35 - Taylor, FLC37 - Levy, FLC39 - Hernando, FLC41 - Pinellas, FLC43 - Manatee, FLC45 - Charlotte, FLC47 - Collier, FL

TX

LA

MS AL 

M

e

x

i

c

o

42

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

C2 - Willacy, TXC4 - Kleberg, TXC6 - Aransas, TXC8 - Matagorda, TX

C10 - Galveston, TXC12 - Jefferson, TXC14 - Vermilion, LAC16 - St. Mary, LAC18 - LaFourche, LAC20 - Plaquemines, LAC22 - Hancock & Harrison, MSC24 - Mobile, AL

C26 - Escambia, FLC28 - Okaloosa, FLC30 - Bay, FLC32 - Franklin, FLC34 - Jefferson, FLC36 - Dixie, FLC38 - Citrus, FLC40 - Pasco, FLC42 - Hillsborough, FLC44 - Sarasota, FLC46 - Lee, FLC48 - Monroe, FL

C2

C12

C10

C8

C6

C4

C16

C14

C18 C20

C22 C24 C26

C28

C30

TX

LA

MS AL 

M

e

x

i

c

o

Figure 24. Locations of Gulf of Mexico Counties and Parishes (set 2). (Shading is not 

43

2002 Gulf of Mexico OSRA
Figure 25. Locations of Mexico Sea Turtle Mating Habitat (March-July), Mexico Sea 

(January-December), Mexico Marine Mammal Habitat (January-December)

Matagorda Area (April-September) Mississippi Sea Turtle Mating Habitat 

General Coastal Habitat (January-December) Mississippi Marine Mammal Sea Turtle Mating Habitat-Panhandle Area (March-July), Florida Sea Turtle Area (January-December), Florida Panhandle Marine Mammal Habitat (JanTurtle Nesting Habitat-Peninsula Area (April-November). (Shading is not t

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

TX

LA

MS AL 

Mexico

Fl

H

Florida Sea 

Habitat-Panha

Sea Turtle Gen

Panhandle Area, 

Marine M

Mississippi Sea Turtle

Mating Habitat, Mississippi 

Sea Turtle General Coastal Habitat, 

and Mississippi Marine Mammal Habitat

Texas Sea Turtle

Nesting HabitatMatagorda Area

Mexico Sea Turtle Mating Habitat, 

Mexico Sea Turtle General Coastal Habitat, 

and Mexico Marine Mammal Habitat

44

2002 Gulf of Mexico OSRA
TX

LA

MS AL 

M

e

x

i

c

o

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

Louisiana Sea Turtle General 

Coastal Habitat-West, and Louisiana West 

Marine Mammal Habitat

Mississippi/Alabam

Sea Turtle Nesting Hab

Florida Sea Turtle 

Tortugas Area, Florid

Habitat-Tortugas A

Turtle General Coasta

Area, and Florida T

Mammal 

Figure 26. Locations of Louisiana Sea Turtle General Coastal Habitat-West (January-D

Mammal Habitat (January-December), Mississippi/Alabama Sea Turtle NesFlorida Sea Turtle Nesting Habitat-Tortugas Area (April-November), FloridArea (March-July), Florida Sea Turtle General Coastal Habitat-Tortugas ArTortugas Marine Mammal Habitat (January-December). (Shading is not to 

45

2002 Gulf of Mexico OSRA
Figure 27. Locations of Texas Sea Turtle Mating Habitat (March-July), Texas Sea Tur

December), Texas Marine Mammal Habitat (January-December), Louisiana November) Louisiana Sea Turtle Mating Habitat (March-July), Florida Sea (April-November), Florida Sea Turtle Mating Habitat-Florida Keys (MarchCoastal Habitat-Florida Keys (January-December). (Shading is not to scale

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

Texas Sea Turtle Mating Habitat, 

Texas Sea Turtle General Coastal Habitat, 

and Texas Marine Mammal Habitat 

Louisiana Sea Turtle 

Nesting Habitat, 

Louisiana Sea Turtle 

Mating Habitat 

Florida Se

Habitat-

Florida Se

Habitat-

and Florida 

Coastal Hab

TX

LA

MS AL 

Mexico

46

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86o 

TX

LA MS AL 

M

e

x

i

c

o

Mexico Sea Turtle

Nesting Habitat

Texas Sea Turtle Nesting

Habitat-Galveston Area

Louisiana Sea Turtle General Coast

Habitat-East, Louisiana East Marin

Mammal Habitat

Florida Se

Nesting Habitat-P

Figure 28. Locations of Mexico Sea Turtle Nesting Habitat (April-September), Texas 

Area (April-September), Louisiana Sea Turtle General Coastal Habitat-EasMarine Mammal Habitat (January-December), and Florida Sea Turtle NestNovember). (Shading is not to scale.)

47

2002 Gulf of Mexico OSRA
31o

30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

TX

LA MS AL 

Texas Sea Turtle Nesting 

Habitat-Coastal Bend Area

Texas Sea Turtle

Nesting HabitatSea Rim Area

Alabama Sea Turtl

Mating Habitat, Alaba

Sea Turtle General Co

Habitat, and Alabam

Marine Mammal Hab

Florida Sea T

Peninsula Ar

General Coa

Area, and Flo

Mam

Figure 29. Locations of Texas Sea Turtle Nesting Habitat-Coastal Bend Area (April-Se

Habitat-Sea Rim Area (April-September), Alabama Sea Turtle Mating Habit

General Coastal Habitat (January-December), Alabama Marine Mammal HaSea Turtle Mating Habitat-Peninsula Area (March-July), Florida Sea Turtle 

Area, and Florida Peninsula Marine Mammal Habitat (January-December). 

48

2002 Gulf of Mexico OSRA
TX

LA

MS AL 

M

e

x

i

c

o

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

Florida Panhand

Manatee Area

Figure 30. Locations of Florida Panhandle Manatee Areas (December-March and Apri

Manatee Areas (December-March and April-November). (Shading is not to 

49

2002 Gulf of Mexico OSRA
TX

LA

MS AL 

M

e

x

i

c

o

31o30o29o28o27o26o25o24o

97o 96o 95o 94o 93o 92o 91o 90o 89o 88o 87o 86

Figure 31. Locations of Louisiana/Mississippi/Alabama Manatee Areas (April-Novem

(December-March and April-November), and Florida Ten Thousand Islands 

and April-November). (Shading is not to scale.)

50

2002 Gulf of Mexico OSRA

Louisiana/Mississipp

Alabama Manatee Are
51 

2007 Gulf of Mexico OSRA 

Table 1a. Oil-spill occurrence probability estimates for offshore spills greater than or equal to 1,000 

from the proposed actions in the Western and Central Gulf of Mexico Planning Areas (2007-2012) Program (2007-2046) 

 

 

 Mean Number Mean Number Probability (% cha

 Volume of spills from of spills of one or more spill

 (Bbbl) platforms pipelines tankers (total) platforms pipelines 

Proposed Actions

 Western (Low Estimate) 0.242 0.03 0.33 0.00 0.37 3 28  Central (Low Estimate) 0.776 0.10 1.07 0.00 1.17 10 66  Western (High Estimate) 0.423 0.05 0.55 0.02 0.62 5 42  Central (High Estimate) 1.292 0.17 1.78 0.00 1.95 15 83 

OCS Program

 Western (Low Estimate) 6.63 0.86 9.15 0.00 10.01 58 **  Central (Low Estimate) 21.93 2.85 30.27 0.00 33.12 94 **  Gulfwide (Low Estimate) 28.56 3.71 39.42 0.00 43.13 98 **  Western (High Estimate) 8.06 1.05 10.49 0.33 11.87 65 **  Central (High Estimate) 24.51 3.19 31.90 1.01 36.09 96 **  Gulfwide (High Estimate) 32.57 4.23 44.95 0.00 49.18 99 **  Note: Bbbl = billion barrels; n = less than 0.5%; ** = greater than 99.5%.  "Platforms" refers to facilities used in exploration, development, or production. 
52 

2007 Gulf of Mexico OSRA

Table 1b. Oil-spill occurrence probability estimates for offshore spills greater than or equal to 10,000 

from the proposed actions in the Western and Central Gulf of Mexico Planning Areas (2007-2012) Program (2007-2046) 

  

 Mean Number Mean Number Probability (% cha

 Volume of spills from of spills of one or more spil

 (Bbbl) platforms pipelines tankers (total) platforms pipelines 

Proposed Actions

 Western (Low Estimate) 0.242 0.01 0.08 0.00 0.09 1 8  Central (Low Estimate) 0.776 0.04 0.26 0.00 0.30 4 23  Western (High Estimate) 0.423 0.02 0.14 0.01 0.16 2 13  Central (High Estimate) 1.292 0.06 0.44 0.00 0.50 6 36 

OCS Program

 Western (Low Estimate) 6.63 0.33 2.25 0.00 2.59 28 90  Central (Low Estimate) 21.93 1.10 7.46 0.00 8.55 67 **  Gulfwide (Low Estimate) 28.56 1.43 9.71 0.00 11.14 76 **  Western (High Estimate) 8.06 0.40 2.58 0.11 3.10 33 92  Central (High Estimate) 24.51 1.23 7.86 0.35 9.43 71 **  Gulfwide (High Estimate) 32.57 1.63 11.07 0.00 12.70 80 **  Note: Bbbl = billion barrels; n = less than 0.5%; ** = greater than 99.5%.  "Platforms" refers to facilities used in exploration, development, or production. 
 Table 2. Probabilities (expressed as percent chance) of one or more offshore spills 

greater than or equal to 1,000 barrels occurring from a proposed action in 

the Central GOM Planning Area and contacting certain offshore environmental 

resource locations within 10 days for low and high oil resource estimates 

 Offshore Environmental Low Estimate High Estimate 

 Resource Locations prob mean prob mean 

 Texas State Offshore Waters 2 0.02 3 0.03 

 7 1/2 Fathoms n 0.00 n 0.00 

 Flower Gardens Banks 2 0.02 3 0.03 

 Stetson Bank n 0.00 1 0.01 

 Alabama State Offshore Waters n 0.00 1 0.01 

 Louisiana (Eastern) State Offshore Waters 6 0.06 9 0.10 

 Louisiana (Western) State Offshore Waters 23 0.27 35 0.43 

 Mississippi State Offshore Waters 1 0.01 1 0.01 

 Chandeleur Islands 3 0.03 5 0.05 

 Sonnier Bank 3 0.03 5 0.05 

 Florida Panhandle State Offshore Waters n 0.00 n 0.00 

 Florida Peninsula State Offshore Waters n 0.00 n 0.00 

 Big Bend Seagrass n 0.00 n 0.00 

 Florida Middle Ground n 0.00 n 0.00 

 Florida Keys National Marine Sanctuary n 0.00 n 0.00 

 Tortugas Ecological Reserve n 0.00 n 0.00 

 Boundary Target 1 n 0.00 n 0.00 

 Boundary Target 2 n 0.00 n 0.00 

 Boundary Target 3 n 0.00 n 0.00 

 Boundary Target 4 n 0.00 n 0.00 

 North Florida Straits n 0.00 n 0.00 

 South Florida Straits n 0.00 n 0.00 

 Mexican Waters n 0.00 n 0.00 

Notes: ** = Greater than 99.5%; n = less than 0.5% 

53 

2007 Gulf of Mexico OSRA 
 Table 3a. Probabilities (expressed as percent chance) of one or more offshore spills 

greater than or equal to 1,000 barrels occurring from a proposed action in 

the Central GOM Planning Area and contacting certain onshore environmental 

resource habitats, recreational beaches, or Texas county shorelines within 

10 days for low and high oil resource estimates 

 Onshore Environmental Resource 

 Habitats, Recreational Beaches, Low Estimate High Estimate 

 Texas County Shorelines prob mean prob mean 

 Diving Bird Habitat 10 0.11 16 0.18 

 Gull, Tern & Charadriid Allies Habitat 19 0.21 30 0.35 

 Raptor Bird Habitat 3 0.03 4 0.04 

 Charadriid Shorebird Habitat 20 0.22 30 0.35 

 Wading Bird Habitat 15 0.16 23 0.26 

 Waterfowl Habitat 23 0.26 35 0.42 

 Snowy Plover Habitat 7 0.08 12 0.13 

 Brown Pelican Habitat 10 0.11 16 0.18 

 Whooping Crane Habitat n 0.00 n 0.00 

 Bald Eagle Habitat 18 0.20 29 0.34 

 Piping Plover 16 0.18 26 0.30 

 Gulf Sturgeon Known Shoreline Locations 6 0.06 9 0.10 

 Alabama Beach Mouse Habitat n 0.00 n 0.00 

 Choctawhatchee Beach Mouse Habitat n 0.00 n 0.00 

 Perdido Key Beach Mouse Habitat n 0.00 n 0.00 

 St. Andrew Beach Mouse Habitat n 0.00 n 0.00 

 TX Coastal Bend Area Beaches n 0.00 n 0.00 

 TX Matagorda Area Beaches n 0.00 n 0.00 

 TX Galveston Area Beaches n 0.00 1 0.01 

 TX Sea Rim State Park n 0.00 n 0.00 

 LA Beaches 5 0.05 8 0.09 

 AL/MS Gulf Islands n 0.00 1 0.01 

 AL Gulf Shores n 0.00 n 0.00 

 FL Panhandle Beaches n 0.00 n 0.00 

 Fl Big Bend Beaches n 0.00 n 0.00 

 FL Southwest Beaches n 0.00 n 0.00 

 FL Ten Thousand Islands n 0.00 n 0.00 

 Cameron, TX n 0.00 n 0.00 

 Willacy, TX n 0.00 n 0.00 

 Kenedy, TX n 0.00 n 0.00 

 Kleberg, TX n 0.00 n 0.00 

 Nueces, TX n 0.00 n 0.00 

 Aransas, TX n 0.00 n 0.00 

 Calhoun, TX n 0.00 n 0.00 

 Matagorda, TX n 0.00 n 0.00 

 Brazoria, TX n 0.00 n 0.00 

 Galveston, TX n 0.00 1 0.01 

 Chambers, TX n 0.00 n 0.00 

 Jefferson, TX n 0.00 1 0.01 

 

 Notes: ** = Greater than 99.5%; n = less than 0.5% 

54 

2007 Gulf of Mexico OSRA 
 Table 3b. Probabilities (expressed as percent chance) of one or more offshore 

spills greater than or equal to 1,000 barrels occurring from a proposed 

action in the Central GOM Planning Area and contacting the shoreline of 

Louisiana parishes or Mississippi, Alabama, and Florida counties within 

10 days for low and high oil resource estimates—Continued 

 Low Estimate High Estimate 

 Parish or County Shoreline prob mean prob mean 

 Cameron, LA 2 0.02 3 0.03 

 Vermilion, LA 2 0.02 2 0.02 

 Iberia, LA 1 0.01 1 0.01 

 St. Mary, LA n 0.00 n 0.00 

 Terrebonne, LA 4 0.04 6 0.06 

 Lafourche, LA 4 0.04 6 0.06 

 Jefferson, LA 2 0.02 3 0.03 

 Plaquemines, LA 10 0.10 15 0.17 

 St. Bernard, LA 1 0.01 1 0.01 

 Hancock, MS n 0.00 n 0.00 

 Harrison, MS n 0.00 n 0.00 

 Jackson, MS n 0.00 n 0.00 

 Mobile, AL n 0.00 n 0.00 

 Badwin, AL n 0.00 n 0.00 

 Escambia, FL n 0.00 n 0.00 

 Santa Rosa, FL n 0.00 n 0.00 

 Okaloosa, FL n 0.00 n 0.00 

 Walton, FL n 0.00 n 0.00 

 Bay, FL n 0.00 n 0.00 

 Gulf, FL n 0.00 n 0.00 

 Franklin, FL n 0.00 n 0.00 

 Wakulla, FL n 0.00 n 0.00 

 Jefferson, FL n 0.00 n 0.00 

 Taylor, FL n 0.00 n 0.00 

 Dixie, FL n 0.00 n 0.00 

 Levy, FL n 0.00 n 0.00 

 Citrus, FL n 0.00 n 0.00 

 Hernando, FL n 0.00 n 0.00 

 Pasco, FL n 0.00 n 0.00 

 Pinellas, FL n 0.00 n 0.00 

 Hillsborough, FL n 0.00 n 0.00 

 Manatee, FL n 0.00 n 0.00 

 Sarasota, FL n 0.00 n 0.00 

 Charlotte, FL n 0.00 n 0.00 

 Lee, FL n 0.00 n 0.00 

 Collier, FL n 0.00 n 0.00 

 Monroe, FL n 0.00 n 0.00 

 Notes: ** = Greater than 99.5%; n = less than 0.5% 

55 

2007 Gulf of Mexico OSRA 
 Table 4. Probabilities (expressed as percent chance) of one or more offshore spills 

greater than or equal to 1,000 barrels occurring from a proposed action in 

the Western GOM Planning Area and contacting certain offshore environmental 

resource locations within 10 days for low and high oil resource estimates 

 Offshore Environmental Low Estimate High Estimate 

 Resource Locations prob mean prob mean 

 Texas State Offshore Waters 10 0.10 16 0.18 

 7 1/2 Fathoms n 0.00 n 0.00 

 Flower Gardens Banks 4 0.04 7 0.08 

 Stetson Bank 2 0.02 4 0.04 

 Alabama State Offshore Waters n 0.00 n 0.00 

 Louisiana (Eastern) State Offshore Waters n 0.00 n 0.00 

 Louisiana (Western) State Offshore Waters 1 0.01 2 0.02 

 Mississippi State Offshore Waters n 0.00 n 0.00 

 Chandeleur Islands n 0.00 n 0.00 

 Sonnier Bank n 0.00 1 0.01 

 Florida Panhandle State Offshore Waters n 0.00 n 0.00 

 Florida Peninsula State Offshore Waters n 0.00 n 0.00 

 Big Bend Seagrass n 0.00 n 0.00 

 Florida Middle Ground n 0.00 n 0.00 

 Florda Keys National Marine Sanctuary n 0.00 n 0.00 

 Tortugas Ecological Reserve n 0.00 n 0.00 

 Boundary Target 1 n 0.00 n 0.00 

 Boundary Target 2 n 0.00 n 0.00 

 Boundary Target 3 n 0.00 n 0.00 

 Boundary Target 4 n 0.00 n 0.00 

 North Florida Straits n 0.00 n 0.00 

 South Florida Straits n 0.00 n 0.00 

 Mexican Waters n 0.00 n 0.00 

 Notes: ** = Greater than 99.5%; n = less than 0.5% 

56 

2007 Gulf of Mexico OSRA 
 Table 5a. Probabilities (expressed as percent chance) of one or more offshore spills 

greater than or equal to 1,000 barrels occurring from a proposed action in 

the Western GOM Planning Area and contacting certain onshore environmental 

resource habitats, recreational beaches, or Texas county shorelines within 

10 days for low and high oil resource estimates 

 Onshore Environmental Resource 

 Habitats, Recreational Beaches, Low Estimate High Estimate 

 Texas County Shorelines prob mean prob mean 

 Diving Bird Habitat 8 0.08 13 0.14 

 Gulls, Terns & Charadriid Allies Habitat 8 0.09 14 0.15 

 Raptor Bird Habitat 8 0.08 13 0.14 

 Charadriid Shorebird Habitat 8 0.09 14 0.15 

 Wading Bird Habitat 8 0.08 14 0.15 

 Waterfowl Habitat 9 0.09 14 0.15 

 Snowy Plover Habitat 6 0.06 10 0.11 

 Brown Pelican Habitat 8 0.08 13 0.14 

 Whooping Crane Habitat 1 0.01 1 0.01 

 Bald Eagle Habitat 1 0.01 2 0.02 

 Piping Plover Habitat 7 0.07 11 0.12 

 Gulf Sturgeon Known Shoreline Locations n 0.00 n 0.00 

 Alabama Beach Mouse Habitat n 0.00 n 0.00 

 Choctawhatchee Beach Mouse Habitat n 0.00 n 0.00 

 Perdido Key Beach Mouse Habitat n 0.00 n 0.00 

 St. Andrew Beach Mouse Habitat n 0.00 n 0.00 

 TX Coastal Bend Area Beaches 1 0.01 1 0.01 

 TX Matagorda Area Beaches 3 0.03 4 0.04 

 TX Galveston Area Beaches 2 0.02 3 0.03 

 TX Sea Rim State Park n 0.00 1 0.01 

 LA Beaches 1 0.01 1 0.01 

 AL/MS Gulf Islands n 0.00 n 0.00 

 AL Gulf Shores n 0.00 n 0.00 

 FL Panhandle Beaches n 0.00 n 0.00 

 FL Big Bend Beaches n 0.00 n 0.00 

 FL Southwest Beaches n 0.00 n 0.00 

 FL Ten Thousand Islands n 0.00 n 0.00 

 Cameron, TX n 0.00 n 0.00 

 Willacy, TX n 0.00 n 0.00 

 Kenedy, TX n 0.00 n 0.00 

 Kleberg, TX n 0.00 n 0.00 

 Nueces, TX n 0.00 n 0.00 

 Aransas, TX n 0.00 1 0.01 

 Calhoun, TX 1 0.01 2 0.02 

 Matagorda, TX 3 0.03 5 0.05 

 Brazoria, TX 1 0.01 2 0.02 

 Galveston, TX 1 0.01 2 0.02 

 Chambers, TX n 0.00 n 0.00 

 Jefferson, TX n 0.00 1 0.01 

 Notes: ** = Greater than 99.5%; n = less than 0.5% 

57 

2007 Gulf of Mexico OSRA 
 Table 5b. Probabilities (expressed as percent chance) of one or more offshore 

spills greater than or equal to 1,000 barrels occurring from a proposed 

action in the Western GOM Planning Area and contacting shorelines of 

Louisiana parishes or Mississippi, Alabama, and Florida counties within 

10 days for low and high oil resource estimates—Continued 

 Low Estimate High Estimate 

 Parish or County Shoreline prob mean prob mean 

 Cameron, LA 1 0.01 1 0.01 

 Vermilion, LA n 0.00 n 0.00 

 Iberia, LA n 0.00 n 0.00 

 St. Mary, LA n 0.00 n 0.00 

 Terrebonne, LA n 0.00 n 0.00 

 Lafourche, LA n 0.00 n 0.00 

 Jefferson, LA n 0.00 n 0.00 

 Plaquemines, LA n 0.00 n 0.00 

 St. Bernard, LA n 0.00 n 0.00 

 Hancock, MS n 0.00 n 0.00 

 Harrison, MS n 0.00 n 0.00 

 Jackson, MS n 0.00 n 0.00 

 Mobile, AL n 0.00 n 0.00 

 Badwin, AL n 0.00 n 0.00 

 Escambia, FL n 0.00 n 0.00 

 Santa Rosa, FL n 0.00 n 0.00 

 Okaloosa, FL n 0.00 n 0.00 

 Walton, FL n 0.00 n 0.00 

 Bay, FL n 0.00 n 0.00 

 Gulf, FL n 0.00 n 0.00 

 Franklin, FL n 0.00 n 0.00 

 Wakulla, FL n 0.00 n 0.00 

 Jefferson, FL n 0.00 n 0.00 

 Taylor, FL n 0.00 n 0.00 

 Dixie, FL n 0.00 n 0.00 

 Levy, FL n 0.00 n 0.00 

 Citrus, FL n 0.00 n 0.00 

 Hernando, FL n 0.00 n 0.00 

 Pasco, FL n 0.00 n 0.00 

 Pinellas, FL n 0.00 n 0.00 

 Hillsborough, FL n 0.00 n 0.00 

 Manatee, FL n 0.00 n 0.00 

 Sarasota, FL n 0.00 n 0.00 

 Charlotte, FL n 0.00 n 0.00 

 Lee, FL n 0.00 n 0.00 

 Collier, FL n 0.00 n 0.00 

 Monroe, FL n 0.00 n 0.00 

 Notes: ** = Greater than 99.5%; n = less than 0.5% 

58 

2007 Gulf of Mexico OSRA 
 Table 6. Probabilities (expressed as percent chance) of one or more offshore spills 

greater than or equal to 1,000 barrels occurring from a proposed action in 

the Western or Central GOM Planning Area and contacting certain onshore

environmental resource habitats within 10 days for low and high oil 

resource estimates 

 Western Central

 Environmental Resource Habitats Low High Low High 

 Mexico Sea Turtle Nesting Habitat n n n n 

 Mexico Sea Turtle Mating Habitat n n n n 

 Mexico Sea Turtle General Coastal Habitat n n n n 

 TX Sea Turtle Nesting Habitat-Galveston Area 2 3 n 1 

 TX Sea Turtle Nesting Habitat-Matagorda Area 3 4 n n 

 TX Sea Turtle Nesting Habitat-Coastal Bend Area 1 1 n n 

 TX Sea Turtle Nesting Habitat-Sea Rim Area n 1 n n 

 TX Sea Turtle Mating Habitat 6 10 1 2 

 TX Sea Turtle General Coastal Habitat 10 16 2 3 

 LA Sea Turtle Nesting Habitat n n 2 4 

 LA Sea Turtle Mating Habitat n n 2 3 

 LA Sea Turtle General Coastal Habitat-East 1 2 23 35 

 LA Sea Turtle General Coastal Habitat-West n n 6 9 

 MS/AL Sea Turtle Nesting Habitat n n 1 1 

 MS Sea Turtle Mating Habitat n n n 1 

 AL Sea Turtle Mating Habitat n n n 1 

 MS Sea Turtle General Coastal Habitat n n 1 1 

 AL Sea Turtle General Coastal Habitat n n n 1 

 FL Sea Turtle Nesting Habitat-Panhandle Area n n n n 

 FL Sea Turtle Mating Habitat-Panhandle Area n n n n 

 FL Sea Turtle Gen. Coast. Habitat-Panhandle Area n n n n 

 FL Sea Turtle Nesting Habitat-Peninsula Area n n n n 

 FL Sea Turtle Mating Habitat-Peninsula Area n n n n 

 FL Sea Turtle General Coastal Habitat-Pen. Area n n n n 

 FL Sea Turtle Nesting Habitat-Tortugas Area n n n n 

 FL Sea Turtle Mating Habitat-Tortugas Area n n n n 

 FL Sea Turtle Gen. Coastal Habitat-Tortugas Area n n n n 

 FL Sea Turtle Nesting Habitat-Keys Area n n n n 

 FL Sea Turtle Mating Habitat-Keys Area n n n n 

 FL Sea Turtle General Coastal Habitat-Keys Area n n n n 

 Mexico Marine Mammal Habitat n n n n 

 TX Marine Mammal Habitat 10 16 2 3 

 LA West Marine Mammal Habitat 1 2 23 35 

 LA East Marine Mammal Habitat n n 6 9 

 MS Marine Mammal Habitat n n 1 1 

 AL Marine Mammal Habitat n n n 1 

 FL Panhandle Marine Mammal Habitat n n n n 

 FL Peninsula Marine Mammal Habitat n n n n 

 FL Tortugas Marine Mammal Habitat n n n n 

 LA/MS/AL Manatee Area (Apr-Nov) n n 1 2 

 FL Panhandle Manatees Areas (Apr-Nov) n n n n 

 FL Panhandle Manatees Areas (Dec-Mar) n n n n 

 FL Big Bend Manatees Areas (Apr-Nov) n n n n 

 FL Big Bend Manatees Areas (Dec-Mar) n n n n 

 FL Southwest Manatees Areas (Apr-Nov) n n n n 

 FL Southwest Manatees Areas (Dec-Mar) n n n n 

 FL Ten Thousand Islands Manatees Areas (Apr-Nov) n n n n 

 FL Ten Thousand Islands Manatees Areas (Dec-Mar) n n n n 

 Notes: ** = Greater than 99.5%; n = less than 0.5% 

59 

2007 Gulf of Mexico OSRA 
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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.