E 

 BIOLOGICAL, PHYSICAL, AND SOCIOECONOMIC INFORMATION 

(a) Chemosynthetic Communities Report 

The seafloor disturbing activities proposed in this plan are in approximately 5,837-5,838' of 

water. The wells will be drilled with a DP drillship, DP semi-submersible drilling rig, or a semisubmersible drilling rig. 

Maps 

A map prepared using 3-D seismic data to depict bathymetry, seafloor and shallow geological 

features, and surface location of the proposed well is included in Section A. 

Analysis 

Features or areas that could support high-density chemosynthetic communities are not located 

within 2,000' of each proposed muds and cuttings discharge location. 

Features or areas that could support high-density chemosynthetic communities are not located 

within 250' of any seafloor disturbances. 

(b) Topographic Features Map 

The proposed activities are not within 1,000' of a no-activity zone or within the 3-mile radius 

zone of an identified topographic feature. Therefore, no map is required per NTL No. 2008-G04. 

(c) Topographic Features Statement (Shunting) 

Anadarko does not plan to drill more than two wells from the same surface location within the 

Protective Zone of an identified topographic feature. Therefore, the topographic features 

statement required by NTL No. 2008-G04 is not applicable. 

(d) Live Bottoms (Pinnacle Trend) Map 

The activities proposed in this plan are not within 200' of any pinnacle trend feature with vertical 

relief equal to or greater than 8'. Therefore, no map is required per NTL No. 2008-G04. 

(e) Live Bottoms (Low Relief) Map 

The activities proposed in this plan are not within 100' of any live bottom low relief features. 

Therefore, no map is required per NTL No. 2008-G04. 
 

(f) Potentially Sensitive Biological Features 

The activities proposed in this plan are not within 200' of any potentially sensitive biological 

features. Therefore, no map is required per NTL No. 2008-G04. 

(g) Remotely Operated Vehicle (ROV) Monitoring Survey Plan 

Walker Ridge Block 51 is located within Deepwater Grid Area 10. This grid is no longer 

considered a “relatively untested deepwater or remote area”, and, therefore, under the guidance 

set out in NTL No. 2008-G04, a Remotely Operated Vehicle Monitoring Survey Plan is not 

required. 

(h) Threatened and Endangered Species Information 

Under Section 7 of the Endangered Species Act (ESA) all federal agencies must ensure that any 

actions they authorize, fund, or carry out are not likely to jeopardize the continued existence of a 

listed species, or destroy or adversely modify its designated critical habitat. 

In accordance with the 30 CFR 250, Subpart B, effective May 14, 2007, and further outlined in 

Notice to Lessees (NTL) 2008-G04, lessees/operators are required to address site-specific 

information on the presence of federally listed threatened or endangered species and critical 

habitat designated under the ESA and marine mammals protected under the Marine Mammal 

Protection Act (MMPA) in the area of proposes activities under this plan. 

Currently there are no designated critical habitats for the listed species in the Gulf of Mexico 

Outer Continental Shelf; however, it is possible that one or more of these species could be seen 

in the area of our operations. The following table reflects the Federally-listed endangered and 

threatened species in the lease area and along the northern Gulf coast: 
 

Species Scientific Name Status 

Potential Presence Critical Habitat 

Designated in 

Gulf of Mexico 

Lease 

Area Coastal 

Marine Mammals 

Sperm whale Physeter macrocephalus E X -- None

West Indian manatee Trichechus manatus latirostris E -- X Florida (Peninsular)

Blue whale Balaenoptera musculus E Xa -- None

Fin whale Balaenoptera physalus E Xa -- None

Humpback whale Megaptera novaeangliae E Xa -- None

North Atlantic right whale Eubalaena glacialis E Xa -- None

Sei whale Balaenoptera borealis E Xa -- None

Sea Turtles 

Loggerhead turtle Caretta caretta T X X None

Green turtle Chelonia mydas T, Eb X X None

Leatherback turtle Dermochelys coriacea E X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Birds 

Piping Plover Charadrius melodus T -- X 

Coastal Texas, Louisiana, 

Mississippi, Alabama, 

and Florida (Panhandle)

Whooping Crane Grus americana E -- X 

Coastal Texas 

(Aransas National 

Wildlife Refuge)

Fishes 

Gulf sturgeon Acipenser oxyrinchus desotoi T -- X 

Coastal Louisiana, 

Mississippi, Alabama, 

and Florida (Panhandle)

Smalltooth sawfish Pristis pectinata E -- X Southwest Florida and 

the Florida Keys

Invertebrates

Elkhorn coral Acropora palmata E -- X Flower Garden Banks

Terrestrial Mammals 

Beach mice (Alabama, 

Choctawhatchee, 

Perdido Key, St. Andrew)

Peromyscus polionotus E -- X Alabama and Florida 

(Panhandle) beaches 

Abbreviations: E = endangered; T = threatened.   a

   The blue, fin, humpback, North Atlantic right, and sei whales are rare or extralimital in the Gulf of Mexico and are unlikely

to be present in the lease area. b

   The green sea turtle is threatened, except for the Florida breeding population, which is listed as endangered.

The Environmental Impact Analysis in Section N of this plan further discusses potential impacts 

and mitigation measures related to threatened and endangered species. 

(i) Archaeological Report 

Walker Ridge Block 51 is not located in an area designated as having high archaeological 

potential and, as such, an Archaeological Report is not required per NTL No. 2011-JOINT-G01. 

However, an Archaeological Report prepared by C&C Technologies covering the proposed 

Walker Ridge Block 51 well location areas was previously submitted to BOEM on October 27, 

2011 associated with Plan Control No.: S-7513 (Survey No. 23476). The survey covered Walker 

Ridge Block 51 and 52. The survey was conducted in accordance with the latest guidelines 

established by the BOEMRE in 2011. 
 

(j) Air and Water Quality Information

This EP does not propose activities for which the State of Florida is an affected State. Therefore, 

the discussion required per NTL 2008-G04 is not applicable to this EP. 

(k) Socioeconomic Information 

The activities proposed in this plan are not located offshore Florida. Therefore, socioeconomic 

information required per NTL 2008-G04 is not applicable to this EP. 
 

F 

WASTE AND DISCHARGE INFORMATION 

The following estimates were prepared utilizing Anadarko’s experience with similar drilling 

operations. Estimated maximum discharge rates are reflected below. Projected amounts may 

vary during the course of drilling operations. 

(a) Projected Generated Wastes 

Type of Waste Composition Projected Amount Treatment/Storage/Disposal 

Synthetic-based 

drilling fluids 

Synthetic-based drilling 

muds 

15,000 bbls/well Re-use and/or transport to shore in 

DOT approved containers to 

Fourchon, Louisiana and on to 

base/transfer station. If recycled, 

returned to vendor (Bariod or MI). 

Cuttings wetted with 

synthetic-based fluids 

Cuttings coated with 

synthetic drilling 

muds/fluids, including 

drilled out cement 

6,500 bbls/well Treated and discharge overboard 

*Note, an estimated 5-10% of cuttings 

may be transported to shore in DOT 

approved containers and on to the 

base/transfer station if oil still 

remains. 

Water-based drilling 

fluids 

Water based drilling 

muds (NaCl saturated, 

seawater, freshwater, 

barite) 

25,000 bbls/well Discharge overboard or at seafloor 

Cuttings wetted with 

water-based fluids 

Cuttings coated with 

water-based drilling 

muds/fluids 

1,500 bbls/well Discharge overboard 

Chemical product 

waste (well treatment 

fluids) 

Ethylene glycol 

Methanol 

500 bbls/well 

125 bbls/well 

Transport to shore in DOT approved 

containers to Fourchon, Louisiana for 

pick up. 

Completion Fluids Brine, spent acid, prop 

sand, debris 

3,000 bbls/well Transport to shore in DOT approved 

containers to Fourchon, Louisiana and 

on to Newpark Base. 

Non-pollutant 

completion fluids 

Low density uninhibited 

completion brines 

5,000 bbls/well Discharge overboard 

Workover fluids Brine, spent acid, prop 

sand, debris 

3,000 bbls/well Transport to shore in DOT approved 

containers to Fourchon, Louisiana and 

on to Newpark Base. 

Trash Refuse generated during 

operations 

250 bbls/well Transport to shore in disposal bags by 

vessel to shorebase for pickup by 

municipal operations. 

*Sanitary Wastes Treated human body 

waste 

750,000 gals/well Chlorinate and discharge overboard 

*Domestic Waste Gray water 750,000 gals/well Chlorinate and discharge overboard 

Deck drainage Platform washings and 

rainwater 

525,000 bbls/well Treat for oil and grease and discharge 

overboard 

Produced water N/A N/A N/A 

Desalinization Unit Seawater 52,500 bbls/well Discharge overboard 

Wash water Drill water (fresh) 7,500 bbls/well Discharge overboard 

Blowout preventer 

fluid 

Blend (3% Stack Magic 

& Filtered Fresh Water) 

19,821 gals/well Discharge at seafloor 

Ballast water Seawater 47,650 m3/year Discharge overboard 

Bilge water Seawater 47,550 bbls/well Discharge overboard through 15 ppm 

equipment 

Excess cement at the 

seafloor 

Nitrified cement slurry 501 bbls/well Discharge at seafloor 

Fire water Seawater 20,571,300 bbls/well Discharge overboard 

Cooling water Seawater 20,571,300 bbls/well Discharge overboard 
 

Produced Sand N/A N/A N/A 

Used oil Excess oil from engines 537.5 bbls/well Transport in DOT approved containers 

to shore for recycling 

*The rig is designed for maximum personnel capacity of 200 people. The discharge rates are based off of 

maximum personnel capacity but will generally not have this many personnel onboard during drilling and/or 

completion operations. 

(b) Projected Ocean Discharges

Type of Waste Total Amount to be 

Discharged 

Discharge Rate Discharge Method 

*Sanitary Wastes 750,000 gals/well 25 gals per person daily Chlorinate and discharge overboard 

*Domestic waste 750,000 gals/well 25 gals per person daily Chlorinate and discharge overboard 

Deck drainage 525,000 bbls/well 3,500 bbls/day Treat for oil and grease and discharge 

Blowout preventer fluid 19,821 gals/well 925 gals/week/well; 

Vents on a weekly basis 

Discharge at seafloor 

Desalinization Unit 52,500 bbls/well 350 bbls/day Discharge overboard 

Wash water 7,500 bbls/well 50 bbls/day Discharge overboard 

Ballast water 47,650 m3/year Not continuous Discharge overboard 

Bilge water 47,550 bbls/well 317 bbls/day Discharge overboard through 15 ppm 

equipment 

Excess cement at the 

seafloor 

501 bbls/well 20 bbls/min Discharge at seafloor 

Fire water 20,571,300 bbls/well 137,142 bbls/day Discharge overboard 

Cooling water 20,571,300 bbls/well 137,142 bbls/day Discharge overboard 

Cuttings wetted with waterbased fluids 1,500 bbls/well 1,000 bbls/hr max Discharge overboard 

Water-based drilling fluids 25,000 bbls/well 1,000 bbls/hr max Discharge overboard or at seafloor 

Cuttings wetted with 

synthetic-based fluids 

6,500 bbls/well N/A Treated and discharge overboard 

*Note, an estimated 5-10% of 

cuttings may be transported to shore 

in DOT approved containers and on 

to the base/transfer station if oil still 

remains. 

Non-pollutant completion 

fluids 

5,000 bbls/well 100 bbl/hour Discharge overboard 

*The rig is designed for maximum personnel capacity of 200 people. The discharge rates are based off of 

maximum personnel capacity but will generally not have this many personnel onboard during drilling and/or 

completion operations. 

(c) Modeling Report 

The proposed activities under this plan do not meet the U.S. Environmental Protection Agency 

requirements for an individual NPDES permit. Therefore, modeling report requirements per 

NTL No. 2008-G04 is not applicable to this EP. 
 

G 

AIR EMISSIONS INFORMATION 

(a) Screening Questions 

Screening Questions for EP’s Yes No 

Is any calculated Complex Total (CT) Emission amount (in tons) associated with your 

proposed exploration activities more than 90% of the amounts calculated using the 

following formulas: CT = 3400D2/3 for CO, and CT = 33.3D for the other air pollutants 

(where D = distance to shore in miles)? 

 No 

Do your emission calculations include any emission reduction measures or modified 

emission factors? 

 No 

Are your proposed exploration activities located east of 87.5 W longitude? No 

Do you expect to encounter H2S at concentrations greater than 20 parts per million (ppm)? No 

Do you propose to flare or vent natural gas for more than 48 continuous hours from any 

proposed well? 

 No 

Do you propose to burn produced hydrocarbon liquids? No 

(b) Emissions Worksheets 

Air emissions worksheets have been prepared using a DP Drillship, a DP Semi-submersible and 

a Semi-Submersible drilling rig. Air emissions worksheets are available upon request. 

(c) Summary Information 

Air emissions from the undrilled “A” and “B” locations from Plan Control No: N-9291; and 

locations “C” and “D” from Plan Control No: S-7513 are being carried forward in the following 

tables to reflect Anadarko’s current drilling schedule. No revisions are being requested to the 

previously approved well locations under this plan. The following tables summarize information 

regarding the peak year emissions generated from the Plan Emissions and Complex Total 

Emissions: 

If drilled with a DP Drillship: 

Air Pollutant Plan Emission 

Amounts1

 (tons) 

2013

Calculated 

Exemption 

Amounts2

 (tons)

Calculated Complex 

Total Emission 

Amounts3

 (tons)

Particulate matter (PM) 101.16 5,094.90 101.16 

Sulphur dioxide (SO2) 464.07 5,094.90 464.07 

Nitrogen oxides (NOx) 3,477.40 5,094.90 3,477.40 

Volatile organic compounds (VOC) 104.32 5,094.90 104.32 

Carbon monoxide (CO) 758.71 97,261.26 758.71 

If drilled with a DP Semi-submersible: 

Air Pollutant Plan Emission 

Amounts1

 (tons) 

2013

Calculated 

Exemption 

Amounts2

 (tons)

Calculated Complex 

Total Emission 

Amounts3

 (tons)

Particulate matter (PM) 100.19 5,094.90 100.19 

Sulphur dioxide (SO2) 459.60 5,094.90 459.60 

Nitrogen oxides (NOx) 3,443.91 5,094.90 3,443.91 

Volatile organic compounds (VOC) 103.32 5,094.90 103.32 

Carbon monoxide (CO) 751.40 97,261.26 751.40 
 

If drilled with a Semi-Submersible: 

Air Pollutant Plan Emission 

Amounts1

 (tons) 

2013

Calculated 

Exemption 

Amounts2

 (tons)

Calculated Complex 

Total Emission 

Amounts3

 (tons)

Particulate matter (PM) 43.67 5,094.90 43.67 

Sulphur dioxide (SO2) 200.35 5,094.90 200.35 

Nitrogen oxides (NOx) 1,501.24 5,094.90 1,501.24 

Volatile organic compounds (VOC) 45.04 5,094.90 45.04 

Carbon monoxide (CO) 327.54 97,261.26 327.54 

*Calculated complex total emission amounts (tons) are based on 192 days. The maximum estimated is in 2013. 

Proposed Activity Start Date End Date No. of Days 

Drill and complete Location “CC” 2/12/2013 7/12/2013 150 

Drill and complete Location “DD” 1/1/2014 5/31/2014 150 

Air emissions from well locations under Plan Control No.: N-9291 and Plan Control No.: S-7513 

are being carried forward in the following table to reflect Anadarko’s current drilling schedule. 

No revisions are being requested to the previously approved well locations under this plan: 

Activity Start Date End Date No. of Days 

The following “Shenandoah” well locations for WR 51 are mentioned below for reference only: 

Drill and complete Location “C”–Plan Control No.: S-7513 6/29/2012 9/14/2012 77* 

Drill and complete Location “D”–Plan Control No.: S-7513 9/14/2012 2/11/2013 150 

Drill and complete Location “A”–Plan Control No.: N-9291 1/1/2015 5/31/2015 150 

Drill and complete Location “B”–Plan Control No.: N-9291 1/1/2016 5/31/2016 150 

*In early September 2012, the WR 51 #1 wellbore, OCS-G31938, which was drilled at the approved “C” location, 

was junked and abandoned before reaching objective section, due to a mechanical failure. A replacement well was 

spud at the approved “D” location (back-up location) and is currently being drilled. 

The air emission calculations were calculated by: 

Bridget O’Farrell 

Regulatory Analyst 

(832) 636-1694 

Bridget.OFarrell-Villarreal@anadarko.com 
 

H

OIL SPILL INFORMATION 

(a) Oil Spill Response Planning 

(i) OSRP Information 

All the proposed activities and facilities in this EP are covered by the Regional Oil Spill 

Response Plan (OSRP) approved on August 24, 2012 for Anadarko Petroleum Corporation and 

its subsidiaries, Anadarko US Offshore Corporation and Anadarko E&P Company L.P. 

(Company Numbers 00981, 02219 and 00148, respectively) in accordance with 30 CFR Part 

254. 

(ii) Spill Response Sites 

Primary Response Equipment Location(s) Preplanned Staging Location(s) 

Galveston, Texas 

Harvey, Louisiana 

Houma, Louisiana 

Lake Charles, Louisiana 

Leeville, Louisiana 

Venice, Louisiana 

Galveston, Texas 

Harvey, Louisiana 

Fourchon, Louisiana 

Cameron, Louisiana 

Leeville, Louisiana 

Venice, Louisiana 

(iii) OSRO Information 

Anadarko maintains a contract with Clean Gulf Associates (CGA) for spill response equipment. 

Various equipment locations are staged throughout the Gulf of Mexico. CGA equipment can be 

referenced on their website: http://www.cleangulfassoc.com/. Personnel would be obtained from 

the Marine Spill Response Corporation’s (MSRC) STARS network, including a supervisor to 

operate the equipment. 

In addition Anadarko has a contract with the Marine Spill Response Corporation (MSRC) for 

spill response equipment. MSRC stages equipment throughout the Gulf of Mexico and has 

recently completed a large expansion of its resources, with particular focus on deepwater. The expansion 

is known as “Deep Blue”. MSRC capabilities and a complete equipment listing are available online at: http://www.msrc.org/. 

Anadarko is a member of the Helix Well Containment Group (HWCG), a combination of the 

Helix Fast Response System (HFRS) and the common equipment and services. This agreement 

allows access to subsea well containment and well shut-in equipment. 

Anadarko is also a member of the Marine Well Containment Company (MWCC), which 

provides access to containment response capabilities and includes subsea dispersant injection 

equipment. 
 

(iv) Worst-Case Scenario Determination 

Category Regional OSRP EP 

Type of Activity Exploratory Exploratory 

Facility Location 

(area/block) GB 346 WR 51 

Facility Designation * GB 346 “A” “C” 

Distance to Nearest 

Shoreline 118 miles 153 miles 

 Storage Tanks (total) N/A N/A 

 Flowlines (on facility) N/A N/A 

 Pipelines N/A N/A 

 Uncontrolled Blowout 350,000 bopd** 80,000 bopd 

Type of Oil(s) Crude Oil Crude Oil 

API Gravity 30.1o 26o

* Note–for the OSRP exploratory worst case discharge scenario only the Area/Block is referenced in the OSRP. Exploratory drilling facility 

designations (proposed well location names) are typically not included in the OSRP. 

** The volume denoted in the Regional OSRP is higher than the NTL No. 2010-N06 (256,700 bopd) and BOEMRE (321,108 

bopd) calculations approved under EP Plan Control No. N-9579. Anadarko elected to denote a higher volume in the 

Regional OSRP for planning purposes to demonstrate equipment response capabilities per previous discussions with Rusty 

Wright. 

Anadarko has determined that the worst-case scenarios from the activities proposed in this 

Supplemental EP do not supersede the worst-case scenario for Garden Banks Block 346. 

Since Anadarko has the capability to respond to the worst-case spill scenario included in our 

Regional OSRP, and since the worst-case scenarios determined for our EP does not replace the 

worst-case scenario in our Regional OSRP approved on August 24, 2012, I hereby certify that 

Anadarko has the capability to respond, to the maximum extent practicable, to a worst-case 

discharge, or a substantial threat of such a discharge, resulting from the activities proposed in our 

EP. 

(b) Worst-Case Discharge Volume Assumptions 

Worst-case discharge (WCD) calculations and assumptions within this section utilized guidelines 

and requirements pursuant with NTL No. 2010-N06. A Supplemental EP, Plan Control No.: 

S-7513 was previously approved for Walker Ridge Block 51 on March 7, 2012; the plan 

included the information necessary to comply with NTL No. 2010-N06. Within the approved 

plan, the WCD volume for Walker Ridge Block 51 was determined to be 80,000 bopd. The 

supplemental well locations requested within this plan do not exceed the previously approved 

WCD volume for Walker Ridge Block 51; therefore, no additional WCD volume assumptions 

are provided within this plan. 
 

(c) Oil Spill Response Discussion

For the purpose of NEPA analysis, the largest spill volume originating from the proposed 

activity would be an uncontrolled blowout of the well during drilling operations at 80,000 barrels 

of crude oil with an API gravity of 26o

. A discussion of the blowout scenario from this proposed 

activity is included within this Supplemental EP in accordance with NTL No. 2010-N06. 

Land Segment and Resource Identification Modeling

Trajectory of a spill and the probability of its impacting a land segment have been projected 

utilizing information in the BSEE Oil Spill Risk Analysis Model (OSRAM) for the Central Gulf 

of Mexico. Additional information may be referenced in the “Oil-Spill Risk Analysis: 

Contingency Planning Statistics for Gulf of Mexico OCS Activities” (OCS Report MMS 2004-

026), using the average conditional probability for 3, 10, and 30 day impacts. 

Walker Ridge Block 51 is located within Launch Area 47. According to the OSRAM, the 

trajectory indicates a 3% probability of potential impact to the shoreline in Cameron Parish, 

Louisiana. The results are shown in Table H-2. 

Cameron Parish is identified as the most probable potential impacted parish or county within the 

Gulf of Mexico for this operation. Cameron Parish is located in Louisiana and includes Sabine 

National Wildlife Refuge (NWR), Cameron Prairie NWR, Lacassine NWR, Little Pecan Island 

Natural Area (NA), Peveto Woods NA, Lower Neches Wildlife Management Area (WMA), and 

Rockefeller WMA. 

Response 

Anadarko will make every effort to respond to the worst-case discharge as effectively as 

possible. Response equipment available to respond to the worst-case discharge and the estimated 

time of a spill response from oil spill detection to equipment deployment on-site is included in 

Table H-3. The table estimates individual times needed for procurement, load out, travel time to 

the site and deployment. In the event of an actual incident equipment and times can vary. 

For the purpose of response scenario discussion, an uncontrolled blowout of the well would be 

considered the largest potential spill volume at 80,000 barrels of crude oil. An ADIOS 

weathering model was run based on a similar type of oil expected to be produced from this well. 

Based on this information, approximately 21% (16,800 barrels) of the initial volume would be 

evaporated/dispersed within 24 hours. 

If approved and appropriate, 4 sorties (8,000 gallons) from the Basler aircraft and 8 sorties 

(9,600 gallons) from two DC-3 aircrafts could disperse approximately 7,540 barrels of oil. 

If the conditions are appropriate, and the necessary approvals and permits have been obtained, 

in-situ burning may be utilized. Based on in-situ burn operations during Deepwater Horizon, 

approximately 5% (3,160 barrels) of the worst case discharge volume after natural 

evaporation/dispersion. 
 

Although unlikely in a spill lasting thirty (30) days, potential shoreline impact in Cameron 

Parish, Louisiana could occur depending on environmental conditions (wind, currents and 

temperature) at the time of an incident. Nearshore response may include the use of shoreline 

boom on beach areas, or protection/sorbent boom on vegetated areas. Surveillance and real time 

trajectories would aide in determining the most appropriate strategies to respond to a spill. 

Table H.3 provides an example of offshore and nearshore equipment, response times, and 

personnel to respond to a spill of 63,200 barrels, which is the estimated amount that would 

remain considering natural evaporation/dispersion at 24 hours. This amount could be further 

reduced through the application of aerial and subsea dispersants, provided such applications were 

approved. 

Anadarko’s contingency plan for dealing with this worst-case discharge would be to activate 

its Spill Management Team and equipment resources as described in its Gulf of Mexico 

Regional Oil Spill Response Plan (OSRP) and provide continuous support for the duration of the 

event. Response resources are activated and supplemented according to need. These resources 

would remain engaged in the response until the incident is deemed complete or until released by 

Unified Command. 

Anadarko is a member of the Helix Well Containment Group (HWCG), a combination of the 

Helix Fast Response System (HFRS) and the common equipment and services. This agreement 

allows access to subsea well containment and well shut-in equipment. 

Anadarko is also a member of the Marine Well Containment Company (MWCC), which 

provides access to containment response capabilities and includes subsea dispersant injection 

equipment. 

In the event of a blowout, Anadarko may: 

 1. Evacuate personnel, if necessary. Deploy emergency responders in an effort to preserve 

human life, if necessary. 

 2. Assess the damage and attempt to stop the flow at the source, if safe to do so, to reduce 

the amount of oil discharged. 

 3. Notify agencies. 
 

 4. Assess the amount of oil that has been spilled and calculate additional potential of oil 

flow. A continuous aerial surveillance program would be used to assess the growth of the 

slick and the volume of oil on the water. Observations of the size of the slick on the 

water, combined with observations at the source, would be used to provide a constant 

update. Additional potential to release fuel from the remaining tanks onboard the 

appropriate DP drillship or DP semi-submersible drilling rig would be determined by 

marine surveyors. Operations and Unified Command would continue to assess the 

adequacy of response equipment capacities based on this continually updated mass 

balance. 

 5. Convene the Spill Management Team (SMT). Organize Unified Command and establish 

objectives and priorities. 

 6. Monitor the oil spill with aerial surveillance and obtain trajectories. If oil is seaward 

bound, going away from land, discuss additional strategies with Unified Command. 

 7. If oil is moving in the direction of a shoreline and weather conditions are favorable, 

request approval to utilize dispersants. 

 a. Prior to commencing application operations, conduct an on-site survey in consultation 

with natural resource specialists to determine if any threatened or endangered species 

are present in the projected application area or otherwise at risk from dispersant 

application. 

 b. Upon approval, mobilize one Basler aircraft and two DC-3 aircrafts from Houma, with 

surveillance aircraft and spotter. Mobilize MSRC contracted aircraft(s) if needed. 

Rotate aircraft, spraying the leading edge of the spill and working back to the source. 

Monitor/sample for effectiveness (USCG SMART Team). Truck additional 

dispersants from CGA/MSRC stockpile to Houma, if necessary. 

 c. Dispersants are most effective when applied as soon after discharge as possible, since 

weathering of the oil decreases dispersant effectiveness. The estimated window of 

opportunity for most effective use of dispersants is within 48-72 hours post-release. 

The oil may still be dispersible after 72 hours on the water surface, but the 

effectiveness of dispersant use would likely be diminished after the oil has been on the 

water for more than three days. Ultimately, the USCG SMART monitoring protocol 

will be used to determine whether or not dispersant operations are effective. 

 d. Once the CGA HOSS barge is on location and in the skimming mode, dispersants 

would only be used if required and approved. 

 8. Deploy offshore mechanical oil containment and recovery equipment. Attempt to recover 

as much oil at sea as possible, utilizing: 
 

 a. The CGA HOSS barge, will be positioned in a stationary mode, will be situated downwind and down-current from location for long-duration, high-volume skimming. 

Based on average travel times, the HOSS barge could be on location within 

approximately 41 hours of the release. The de-rated skimming capacity of the HOSS 

barge is 43,000 bbls per day. However, only the oil encountered by a skimmer can be 

recovered. In order to maximize oil encounter rate, boom will be deployed in a 

V-configuration in front of the HOSS barge to funnel oil to the skimmers. If 

necessary, temporary barges can be activated to support continuous skimming 

operations. (These barges arrive on-site at approximately the same time as the HOSS 

barge.) For an on-going release, multiple barges are deployed to provide for 

continuous off-loading of skimmer storage vessels and shuttling of recovered oil to an 

onshore waste handling facility. Sufficient barges are available to provide enough 

temporary storage for continuous recovery operations. 

 b. CGA’s Fast Response Units (FRU) could arrive on-scene between approximately 

16-27 hours of the initial release. These skimmers operate downstream of the HOSS 

barge and are used to recover pockets and streamers of oil that may move past the 

large stationary skimmer. Each FRU has 200 barrels of on-board storage. Approval 

will be requested to decant water after gravity separation, through a hose forward of 

the skimmer, to optimize temporary storage capacity. A 42" Boom will be utilized to 

concentrate oil so that it is thick enough to be skimmed. 

 9. Dispersants, Fast Response Units (FRU), Oil Spill Response Vessels (OSRV or R/V) 

would typically work daylight hours only. The HOSS barge can operate continuously, 

including night operations. Available technology will be considered such as remote 

sensing devices that will enable 24 hour surveillance, trajectories, and planning. All 

response vessels are designed to be able to remain offshore continuously throughout the 

response. Even if sea conditions prohibit effective skimming, these resources would 

remain offshore until skimming operations could be commenced again. Safety would 

remain the first priority. 

 10. Prepare Site-Specific Waste Management Plan, Site Safety Plan, Decontamination Plans, 

Communications and Medical Plans. 

 11. If oil becomes a threat to any shoreline, data from the aerial surveillance, weather reports, 

and trajectories would be used to direct onshore teams to deploy protection/containment 

boom with reference to Area Contingency Plans and in coordination with State and 

Federal On-Scene Coordinators. 

 a. Implement pre-designated strategies. 

 b. Identify resources at risk in spill vicinity. 

 c. Develop/implement appropriate protection tactics. 

 12. Establish Site-Specific Wildlife Rescue and Rehabilitation Plan. 
 

The following types of additional support may be required for a blowout lasting 120 days. 

 Additional Oil Spill Removal Organization (OSRO) personnel to relieve equipment 

operators 

 Vessels for supporting offshore operations 

 Field safety personnel 

 Continued surveillance and monitoring of oil movement 

 Helicopter, video cameras 

 Infra red (night time spill tracking) capabilities, X-band radar 

 Barge to transport recovered oil from offshore skimming system, and temporary 

storage barges to onshore disposal sites that are identified in Area Contingency Plans 

(ACP) 

 Logistics needed to support equipment: 

- Staging areas 

- Parts, trailers, and mechanics to maintain skimmers and boom 

- Fueling facilities 

- Decontamination stations 

- Dispersant stockpile transported from Houston to Houma or other potential 

command post locations 

- Communications equipment and technicians 

 Logistics needed to support responder personnel 

- Medical aid stations 

- Safety personnel

- Food 

- Berthing 

- Additional clothing/safety supplies 

- Decontamination stations 

Containment Response Information 

Anadarko has the capability to respond and contain, to the maximum extent practicable as 

defined in 30 CFR 254.6 and 30 CFR 250.26(d)(1), to the estimated worst case discharge (WCD) 

associated with the proposed activity within 30 days. Deployment time for surface containment 

equipment is subject to availability and location, weather conditions, potential security zones 

around the spill site, and site/well specific assessment data. Personnel safety is always first and 

foremost. Refer to further details on equipment and timing provided in Section H–Oil Spill 

Information and Table H-3 of the EP. 

The potential WCD will be further evaluated during the Application for Permit to Drill (APD) 

process, including the Well Containment Screening Tool (WCST) and associated subsea 

containment plan for enhanced planning purposes. 

There will be no new or unusual technology deployed that has not been previously deployed for 

Gulf of Mexico oil spill prevention, control, and/or cleanup. 
 

Table H-1 

Worst Case Discharge Calculation 

(Based on Blowout during Drilling Operations)

Calculations for Uncontrolled Blowout of Well Block 51 

 i. Type of Oil (crude, condensate, diesel) Crude Oil 

 ii. API Gravity 26 ̊

 iii. EP Location Used for NTL No. 2010-N06 WCD for WR 51 SEP Location “C” 

 iv. Largest Anticipated WCD Rate during blowout 80,000 bopd 

 v. WCD Total for Drilling Operations for WR 51 (> 10 miles from shore) 

per NTL 2010-N06: 80,000 bopd 
 

Table H-2 

Trajectory by Land Segment 

Following are the average conditional probabilities (expressed as percent chance) that an oil spill starting at a 

particular launch area will contact a land segment as included in the BSEE Oil Spill Risk Analysis Model (OSRAM) 

for the Central Gulf of Mexico. This information can be found on the BSEE website using 3/10/30 day potential 

impact, as applicable. The results are listed below. 

Area/Block/ 

Well Location 

Per NTL 2010-N06 

OCS-G Launch 

Area Land Segment and/or Resource 

Conditional Probability (%) 

3 

days 

10 

days 

30 

days 

Walker Ridge 

Block 51 

Location “C” 

Drilling 

(153 miles from 

shore) 

G31938 LA 47 

Central 

Planning 

Area 

Matagorda County, TX 

Brazoria County, TX 

Galveston County, TX 

Jefferson County, TX 

Cameron Parish, LA 

Vermilion Parish, LA 

Terrebonne Parish, LA 

Plaquemines Parish, LA 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

1 

1 

2 

1 

3 

1 

1 

1 
Table H-3 

WCD Scenario Drilling Activities – Based on an uncontrolled blowout of well (153 miles from shore) Walker Ridge Block 51“C” 80,000 bbls of crude oil (initial volume) 63,200 bbls (after evaporation/dispersion) API Gravity 26o 

Offshore Equipment from Spill Detection to Equipment Deployment Response Time: Walker Ridge Block 5

Offshore Equipment 

Owner/Location Initial Staging 

Hours to 

Staging 

Area 

Time to 

Procure 

(1) 

Time 

to 

Load Out 

(2) 

Tra

Tim

(Stag

Spi

(3

Type 

Derated 

Capacity 

(bbls) 

Storage 

(bbls) 

No. of 

Units/ 

Persons 

Basler Spray Aircraft DC 3 Spray Aircraft Aero Commander 

-- -- 

-- -- 

1 2 2 

ASI/Houma Houma 

0 0 1 1 1 2 

HOSS Barge Operators Tugs 

43,000 4,000 1 

8 3 

CGA/Harvey STARS VOO 

Harvey 

1 2 4 4 0 36 

Deep Blue Responder LFF 100 Brush + OSRV 6,600' 44" Sea Sentry Boom 660' 67" LAMOR 

18,086 4,000 1 

1 

14 crew MSRC/Fourchon Fourchon 

0 2 2 

2 0 34 

FRU Operators Utility Boat 

4,251 200 1 

6 1 

CGA/Ingleside STARS VOO 

Ingleside 

0 2 2 1 2 23 

FRU Operators Utility Boat 

4,251 200 1 

6 1 

CGA/Galveston STARS VOO 

Galveston 

0 2 2 1 2 17 

FRU Operators Utility Boat 

4,251 200 1 

6 1 

CGA/Lake Charles STARS VOO 

Cameron 

.5 

2 2 1 2 16

FRU Operators Utility Boat 

4,251 200 1 

6 1 

CGA/Harvey STARS VOO 

Harvey 

.5 

2 2 1 2 15 

FRU Operators Utility Boat 

8,502 400 2 

12 

2 

CGA/Venice STARS VOO 

Venice 

0 2 2 1 2 14 

FRU Operators Utility Boat 

8,502 400 2 

12 

2 

CGA/Leeville STARS VOO 

Leeville 

.5 

2 2 1 2 12 

Koseq Skimming Arms Operators Vessel w/ storage/hull 

17,830 

2,000 

1 set 

6 1 

CGA/Fourchon STARS VOO 

Fourchon 

0 2 2 1 12 12 

Spill Team Area Responders (STARS) called out by Marine Spill Response Corporation (MSRC) Vessel of Opportunity=VOO EMS=Enterprise Marine Services (available through contract with CGA) T&T=T&T Marine (available through contract with CGA)
Offshore Equipment, cont. 

Owner/Location Initial Staging 

Hours to 

Staging 

Area 

Time to 

Procure 

(1) 

Time 

to 

Load Out 

(2) 

Trav

Tim

(Stagi

Spil

(3) 

Type 

Derated 

Capacity 

(bbls) 

Storage 

(bbls) 

No. of 

Units/ 

Persons 

MSRC 452 Offshore Barge Tugs 1 Crucial Disk 88/30 1,980' 44" Sea Sentry II Boom 660' 67" LAMOR

11,122 45,000 1 

3 1 

6 crew 

MSRC/Fort Jackson VOO 

Fort Jackson 

1 2 0 37 

CTCo 5001 Operators Tug 

-- 47,000 1 

12 

2 

EMS/Amelia STARS VOO 

Amelia 

0 2 4 4 0 32 

CTCo 2607 Operators Tug 

-- 23,000 1 

6 1 

EMS/Amelia STARS VOO 

Amelia 

0 2 4 4 0 32 

CTCo 2608 Operators Tug 

-- 23,000 1 

6 1 

EMS/Amelia STARS VOO 

Amelia 

0 2 4 4 0 32 

10,000' 42" Auto Boom VOO 

-- -- 40 

20 crew 

CGA/Harvey STARS Harvey .5 2 1 2 15 

5,000' 42" Auto Boom VOO 

-- -- 20 

10 crew 

CGA/Lake Charles STARS Cameron .5 2 1 2 16.5 

5,000' 42" Auto Boom VOO 

-- -- 20 

10 crew 

CGA/Galveston STARS Galveston 0 2 1 2 17 

2,500' 42" Auto Boom VOO 

-- -- 12 

6 crew 

CGA/Ingleside STARS Ingleside 0 2 1 2 23 

2,500' 42" Auto Boom VOO 

-- -- 12 

6 crew 

CGA/Pascagoula STARS Pascagoula 0 2 1 2 20 

6,679' 44" Sea Sentry II Boom VOO 

-- -- 20 

10 crew 

MSRC/Lake Charles STARS Lake Charles 

0 2 

1 2 23 

1,980' 44" Sea Sentry II Boom VOO 

-- -- 12 

6 crew 

MSRC/Fort Jackson STARS Fort Jackson 

0 2 

1 2 23.5 

22,400' 42" Boom VOO 

-- -- 80 

25 crew AMPOL/New Iberia New Iberia 0 2 1 2 14 

4,800' 42" Boom VOO 

-- -- 18 

9 crew AMPOL/Harvey Harvey 0 2 1 2 15 

Spotter Helo Surveillance Helo Hand Held Radios 

-- -- -- 

-- -- -- 

1 1 

30 

PHI/Fourchon PHI/Fourchon STARS 

Spill Site Spill Site Fourchon 

1 1 

1.5 

1 1 

1.5 

-- -- -- 

1.5 1.5 

2 

Total 124,046 149,600 
Nearshore Equipment from Spill Detection to Equipment Deployment Response Time: Walker Ridge Block 5

Nearshore Equipment* 

Owner/Location Initial Staging 

Hours to 

Staging 

Area 

Time to 

Procure 

(1) 

Time 

to 

Load Out 

(2) 

Trave

Time 

(Stagin

Spill) 

(3) 

Type 

Derated 

Capacity 

(bbls) 

Storage 

(bbls) 

No. of 

Units/ 

Persons 

Basler Spray Aircraft DC 3 Spray Aircraft Aero Commander 

-- -- 1 

2 2 

ASI/Houma Houma 

0 0 1 1 1 1 

Trinity SWS Operators 

21,500 249 1 

4 

CGA/Leeville STARS Fourchon 0 2 1 2 25 

Trinity SWS Operators 

21,500 249 1 

4 

CGA/Morgan City STARS Morgan City 0 2 1 2 26 

SWS Egmopol Operators 

3,000 100 1 

3 

CGA/Galveston STARS Galveston 0 2 1 2 35 

SWS Egmopol Operators 

3,000 100 1 

3 

CGA/Morgan City STARS Morgan City .5 2 1 2 32 

SWS Marco Operators 

3,588 34 1 

3 

CGA/Leeville STARS Leeville .5 2 1 2 20 

SWS Marco Operators 

3,588 20 1 

3 

CGA/Lake Charles STARS Cameron .5 2 1 2 30 

R/V Grand Bay Operators 

5,000 65 1 

3 

CGA/Venice STARS Venice .5 2 2 .5 9 

R/V RW Armstrong Operators 

5,000 65 1 

3 

CGA/Leeville STARS Leeville .5 2 2 .5 8 

R/V Bastian Bay Operators 

5,000 65 1 

3 

CGA/Lake Charles STARS Cameron .5 2 2 .5 10.5 

R/V Timbalier Bay Operators 

5,000 65 1 

3 

CGA/Galveston STARS Galveston 0 2 2 .5 11 

CTCo 2604 Operators Tugs 

-- 20,000 1 

6 1 

EMS/Amelia Amelia 

0 2 4 4 0 16 

CTCo 2605 Operators Tugs 

-- 20,000 1 

6 1 

EMS/Amelia Amelia 

0 2 4 4 0 16 

CTCo 2606 Operators Tugs 

-- 20,000 1 

6 1 

EMS/Amelia Amelia 

0 2 4 4 0 16 

CTCo 2609 Operators Tugs 

-- 23,000 1 

6 1 

EMS/Amelia Amelia 

0 2 4 4 0 16 

2,000' Beach Boom -- -- 6 CGA/Galveston Galveston 0 1 2 17 1,000' Beach Boom -- -- 4 CGA/Ingleside Ingleside 0 1 2 23 2,000' Beach Boom -- -- 6 CGA/Pascagoula Pascagoula 0 1 2 20 10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/New Iberia New Iberia 0 2 1 1 15 

10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/Houston Houston 1 2 1 1 10 
Nearshore Equipment, cont. 

Owner/Location Initial Staging 

Hours to 

Staging 

Area 

Time to 

Procure 

(1) 

Time 

to 

Load Out 

(2) 

Trave

Time 

(Stagin

Spill) 

(3) 

Type 

Derated 

Capacity 

(bbls) 

Storage 

(bbls) 

No. of 

Units/ 

Persons 

10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/Port Arthur Port Arthur 0 2 1 1 9.5 

10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/Houma Fourchon .5 2 1 1 12.5 

10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/Port Allen Port Allen 0 2 1 1 16 

20,000' 18" Boom VOO 

-- -- 20 

8 crew Oil Mop/Belle Chasse Venice .5 2 1 1 14 

15,000' 18" Boom VOO 

-- -- 14 

6 crew Oil Mop/Gretna Gretna 0 2 1 1 15 

31,500' 18" Boom VOO 

-- -- 10 

30 crew AMPOL/New Iberia New Iberia 0 2 0 .5 15 

22,700' 18" Boom VOO 

-- -- 8 

24 crew AMPOL/Harvey Harvey 0 2 0 1 15 

Wildlife Support Trailer -- -- 1/ 2 crew CGA/Harvey Harvey .5 1 2 6 Bird Scare Cannons -- -- 2 CGA/Venice Venice .5 1 2 4 Bird Scare Cannons -- -- 1 CGA/Galveston Galveston 0 1 2 5 Bird Scare Cannons -- -- 1 CGA/Ingleside Ingleside 0 1 2 6 Bird Scare Cannons -- -- 2 CGA/Harvey Harvey .5 1 2 4 Bird Scare Cannons -- -- 2 CGA/Lake Charles Cameron .5 1 2 4.5 Bird Scare Cannons -- -- 2 CGA/Pascagoula Pascagoula 0 1 2 5.25 Spotter Helo Surveillance Helo Hand Held Radios 

-- -- -- 

-- -- -- 

1 1 

30 

PHI/Fourchon PHI/Fourchon STARS 

Spill Site Spill Site Fourchon 

1 1 

1.5 

1 1 

1.5 

-- -- -- 

.5 .5 

2 

Total 76,176 84,012 

*Some equipment may be used offshore up to approximately 25 miles from shore 
 

H-3 (continued) 

Operational Limitations of Response Equipment 

 HOSS Barge–8 foot seas 

 Fast Response Unit (FRU)–8 foot seas 

 Oil Spill Response Vessel (OSRV and R/V)–4 foot seas 

 Boom–3 foot seas, 20 knot winds 

 Dispersants–winds more than 25 knots, visibility less than 3 nautical miles or ceiling less than 

1,000 feet 
 

I 

Environmental Monitoring and Environmental Mitigation Measures 

(a) Monitoring 

If required, Anadarko will monitor loop currents per NTL 2009-G02. 

Anadarko subscribes to Wilkins Weather Service which provides real-time weather 

conditions such as tropical depressions, storms and/or hurricanes entering the Gulf. 

(b) Incidental Takes 

Although marine mammals may be seen in the area, Anadarko does not believe that its 

operations proposed under this EP will result in the harassment, capture, collection or 

killing of any mammals covered by the Marine Mammal Protection Act. 

Anadarko will operate in accordance with applicable regulations, including: 

 NTL No. 2007-G02 “Implementation of Seismic Survey Mitigation Measures and 

Protected Species Observer Program” 

 BSEE NTL No. 2012-G01 “Marine Trash and Debris Awareness and 

Elimination”, and 

 JOINT NTL No. 2012-G01 “Vessel Strike Avoidance and Injured/Dead Protected 

Species Reporting” 
 

J 

LEASE STIPULATIONS INFORMATION 

Stipulation No.8 (Lease Sale 205)–Protected Species 

This stipulation is meant to reduce the potential taking of federally protected species. 

Anadarko will operate in accordance with JOINT NTL No. 2012-G01 to minimize the 

risk of vessel strikes to protected species and will report observations of injured or dead 

protected species. Anadarko will operate in accordance with BSEE NTL No. 2012-G01 

to prevent intentional and/or accidental introduction of debris into the marine 

environment. 

Environmental Mitigation Measures 

There is no reason to believe that any of the endangered, protected, or threatened species 

of marine mammals as listed in the ESA will be incidentally “taken” as a result of the 

operations proposed under this plan. In the event of an incidental take, Anadarko’s 

mitigation measures will adhere and be implemented in accordance to the requirements 

set forth in NTL 2008-G04. 
 

K 

Support Vessels and Aircraft Information 

(a) General 

Type Max. Total Fuel Tank 

Storage Capacity 

Max. No. in Area at 

any Time 

Trip Frequency or Duration 

Supply Vessel 336,227 gallons 1 2 trips/week 

Helicopter 735.3 gallons 1 10 trips/week 

Crew Vessel 50,000 gallons 1 3 trips/week 

Tug Boats 218,300 gallons 1-2 Duration of operation 

Anchor Handling Vessel 450,698 gallons 1-2 Duration of operation 

(b) Diesel Oil Supply Vessels 

Fuel for the rig will be transported via a supply vessel as follows: 

a. Size of fuel supply vessel: 230 feet 

b. Carrying capacity of fuel supply vessel: 336,227 gallons 

c. Frequency that fuel supply vessel will visit the facilities: once per week 

d. Routes the fuel supply vessel will use to travel between the 

onshore support base and proposed facility: 

6 miles from Port Fourchon to the mouth of Bayou 

Lafourche, then approximately 168 miles to WR 51 

(c) Vicinity Map 

A vicinity map is included in this section as Attachment K-1. 

(d) Solid and Liquid Wastes Transportation 

Type of 

Waste 

Composition Total 

Projected 

Amount 

Rate Transport 

Method 

Name/Location of Facility Disposal 

Method 

Syntheticbased drilling 

fluid or mud 

Synthetic- based 

drilling muds 

30,000 bbls 15,000 

bbls/well 

Re-use 

and/or 

transport to 

shore in 

DOT 

approved 

containers. 

Waste - Port Fourchon, LA and 

on to Newpark Fourchon 

Transfer Station #1 & #2. 

Newpark Transfer Station 

Morgan City. Newpark 

Transfer Station Port Arthur. 

USLL Galveston and Fourchon 

Transfer Station. If recycled, 

returned to vendor (Bariod or 

MI). 

Re-used and/or 

recycled; if 

can’t be reused 

and/or 

recycled the 

waste is 

disposed of at 

Newpark 

(injection 

disposal 

facility) or 

USLL 

(landfarm). 

Cuttings 

containing 

syntheticbased mud 

Cuttings coated 

with ester-based 

synthetic drilling 

muds 

650-1,300 

bbls 

325-650 

bbls/well* 

*An 

estimated 

5-10% of 

cuttings may 

be 

Re-use 

and/or 

transport to 

shore in 

DOT 

approved 

containers. 

Waste - Port Fourchon, LA and 

on to Newpark Fourchon 

Transfer Station #1 & #2. 

Newpark Transfer Station 

Morgan City. Newpark 

Transfer Station Port Arthur. 

USLL Galveston and Fourchon 

Transfer Station. If recycled, 

Re-used and/or 

recycled; if 

can’t be reused 

and/or 

recycled the 

waste is 

disposed of at 

Newpark 
 

transported 

to shore 

returned to vendor (Bariod or 

MI). 

(injection 

disposal 

facility) or 

USLL 

(landfarm). 

Chemical 

product waste 

(well 

treatment 

fluids) 

Ethylene glycol 

Methanol 

1,000 bbls 

250 bbls 

100 

bbls/month 

25 

bbls/month 

Transport to 

shore in 

DOT 

approved 

containers 

for pick up 

Chemwaste in Sulphur, LA 

and Veolia Port Arthur, TX or 

to Newpark, Port Arthur as 

non-hazardous waste. 

Can be 

returned to 

vendor and/or 

used at another 

facility; MEG 

is solidified 

and disposed 

of in a landfill. 

Methanol is 

incinerated or 

used for fuels 

for blending. 

Completion 

fluids 

Brine, spent acid, 

prop sand, debris 

6,000 bbls 3,000 

bbls/well 

Transport to 

shore in 

DOT 

approved 

containers 

and/or vessel 

tanks for 

pick up 

Sent to Port Fourchon, LA and 

on to Newpark Fourchon 

Transfer Station #1 & #2. 

Newpark Transfer Station 

Morgan City. Newpark 

Transfer Station Port Arthur. 

USLL Galveston and Fourchon 

Transfer Station 

Unused brine 

can be 

returned to 

vendor and/or 

stored for use 

on another job. 

Used brine and 

spent acid is 

transferred to 

Newpark’s 

Processing & 

Transfer 

facility for 

injection. 

Workover 

fluids 

Brine, spent acid, 

prop sand, debris 

6,000 bbls 3,000 

bbls/well 

Transport to 

shore in 

DOT 

approved 

containers 

and/or vessel 

tanks for 

pick up 

Sent to Port Fourchon, LA and 

on to Newpark Fourchon 

Transfer Station #1 & #2. 

Newpark Transfer Station 

Morgan City. Newpark 

Transfer Station Port Arthur. 

USLL Galveston and Fourchon 

Transfer Station 

Unused brine 

can be 

returned to 

vendor and/or 

stored for use 

on another job. 

Used brine and 

spent acid is 

transferred to 

Newpark’s 

Processing & 

Transfer 

facility for 

injection. 

Trash and 

debris 

Refuse generated 

during 

operations 

500 bbls 50 

bbls/month 

Transport to 

shore in 

disposal bags 

by vessel to 

shorebase for 

pickup by 

municipal 

operations 

Recycled Material in ARC, 

New Iberia, LA. Trash 

disposed of at SWDI landfill. 

Recycled 

and/or 

disposed in 

landfill. 

Used oil Excess oil from 

engines 

1,075 bbls 430 bbls/120 

days 

Transport in 

DOT 

approved 

containers to 

shore for 

pick up 

American Recovery Fourchon, 

LA 

Recycled 

*Total amount assumes 2 wells at 150 days/well 
Walker Ridge Block 51 

Environmental Impact Analysis

Figure 1. Location of Walker Ridge Block 51.
 

L 

ONSHORE SUPPORT FACILITIES INFORMATION

(a) General 

Per NTL No. 2008-G04, the following tables reflect the onshore facilities Anadarko may 

utilize to provide supplies and service support for the activities proposed in this EP. 

Name Primary Location(s) Existing/New/Modified 

Anadarko Service Base Fourchon, Louisiana Existing 

Anadarko Service Base 

(Helicopter base) 

Houma, LA Existing 

Name *Alternate Locations Existing/New/Modified 

Anadarko Service Base Galveston, TX Existing 

Anadarko Service Base Cameron, LA Existing 

Anadarko Service Base Lake Charles, LA Existing 

Anadarko Service Base Houma, LA Existing 

Anadarko Service Base Pascagoula, MS** Existing 

*In the unlikely event Anadarko’s primary service base cannot be utilized Anadarko will exercise the use of an 

alternate service base during drilling and/or completion operations.

**Helicopter base only 

(b) Support Base 

No support base construction or expansion is planned for these activities. 

(c) Waste Disposal 

Disposed wastes describe those wastes generated by the proposed activity that are 

disposed of by means other than by release into the water of the GOM at the site where 

they are generated. These wastes can be disposed of by offsite release, injection, 

encapsulation, or placement at either onshore or offshore permitted locations for the 

purposes of returning them back to the environment. 

Type of 

Waste 

Composition Total 

Projected 

Amount 

Rate Transport 

Method 

Name/Location of Facility Disposal 

Method 

Syntheticbased drilling 

fluid or mud 

Synthetic- based 

drilling muds 

30,000 bbls 15,000 

bbls/well 

Re-use 

and/or 

transport to 

shore in 

DOT 

approved 

containers. 

Waste - Port Fourchon, LA and 

on to Newpark Fourchon 

Transfer Station #1 & #2. 

Newpark Transfer Station 

Morgan City. Newpark 

Transfer Station Port Arthur. 

USLL Galveston and Fourchon 

Transfer Station. If recycled, 

returned to vendor (Bariod or 

MI). 

Re-used and/or 

recycled; if 

can’t be reused 

and/or 

recycled the 

waste is 

disposed of at 

Newpark 

(injection 

disposal 

facility) or 

USLL 

(landfarm). 
 

Cuttings 

containing 

syntheticbased mud 

Cuttings coated 

with ester-based 

synthetic drilling 

muds 

650-1,300 

bbls 

325-650 

bbls/well* 

*An 

estimated 

5-10% of 

cuttings may 

be 

transported 

to shore 

Re-use 

and/or 

transport to 

shore in 

DOT 

approved 

containers. 

Waste - Port Fourchon, LA and 

on to Newpark Fourchon 

Transfer Station #1 & #2. 

Newpark Transfer Station 

Morgan City. Newpark 

Transfer Station Port Arthur. 

USLL Galveston and Fourchon 

Transfer Station. If recycled, 

returned to vendor (Bariod or 

MI). 

Re-used and/or 

recycled; if 

can’t be reused 

and/or 

recycled the 

waste is 

disposed of at 

Newpark 

(injection 

disposal 

facility) or 

USLL 

(landfarm). 

Chemical 

product waste 

(well 

treatment 

fluids) 

Ethylene glycol 

Methanol 

1,000 bbls 

250 bbls 

100 

bbls/month 

25 

bbls/month 

Transport to 

shore in 

DOT 

approved 

containers 

for pick up 

Chemwaste in Sulphur, LA 

and Veolia Port Arthur, TX or 

to Newpark, Port Arthur as 

non-hazardous waste. 

Can be 

returned to 

vendor and/or 

used at another 

facility; MEG 

is solidified 

and disposed 

of in a landfill. 

Methanol is 

incinerated or 

used for fuels 

for blending. 

Completion 

fluids 

Brine, spent acid, 

prop sand, debris 

6,000 bbls 3,000 

bbls/well 

Transport to 

shore in 

DOT 

approved 

containers 

and/or vessel 

tanks for 

pick up 

Sent to Port Fourchon, LA and 

on to Newpark Fourchon 

Transfer Station #1 & #2. 

Newpark Transfer Station 

Morgan City. Newpark 

Transfer Station Port Arthur. 

USLL Galveston and Fourchon 

Transfer Station 

Unused brine 

can be 

returned to 

vendor and/or 

stored for use 

on another job. 

Used brine and 

spent acid is 

transferred to 

Newpark’s 

Processing & 

Transfer 

facility for 

injection. 

Workover 

fluids 

Brine, spent acid, 

prop sand, debris 

6,000 bbls 3,000 

bbls/well 

Transport to 

shore in 

DOT 

approved 

containers 

and/or vessel 

tanks for 

pick up 

Sent to Port Fourchon, LA and 

on to Newpark Fourchon 

Transfer Station #1 & #2. 

Newpark Transfer Station 

Morgan City. Newpark 

Transfer Station Port Arthur. 

USLL Galveston and Fourchon 

Transfer Station 

Unused brine 

can be 

returned to 

vendor and/or 

stored for use 

on another job. 

Used brine and 

spent acid is 

transferred to 

Newpark’s 

Processing & 

Transfer 

facility for 

injection. 

Trash and 

debris 

Refuse generated 

during 

operations 

500 bbls 50 

bbls/month 

Transport to 

shore in 

disposal bags 

by vessel to 

shorebase for 

pickup by 

municipal 

operations 

Recycled Material in ARC, 

New Iberia, LA. Trash 

disposed of at SWDI landfill. 

Recycled 

and/or 

disposed in 

landfill. 
 

Used oil Excess oil from 

engines 

1,075 bbls 430 bbls/120 

days 

Transport in 

DOT 

approved 

containers to 

shore for 

pick up 

American Recovery Fourchon, 

LA 

Recycled 

*Total amount assumes 2 wells at 150 days/well 
 

M 

COASTAL ZONE MANAGEMENT ACT INFORMATION 

No additional enforceable policies/Coastal Zone Management Act consistency 

certification statements are included within this Supplemental EP. Coastal Zone 

Management consistency was previously given by Louisiana with Plan Control No: 

N-9291 for the approved Initial EP. Coastal Zone Management consistency was given by 

Texas and Mississippi associated with Plan Control No.: S-7513 for the approved 

Supplemental EP. Alabama and Florida are not affected states. 
 

N

ENVIRONMENTAL IMPACT ANALYSIS 

The proposed well locations in Walker Ridge Block 51 will utilize the Environmental 

Impact Analysis (EIA) from the previously approved Walker Ridge Block 51 #1 and #2 

(Location “C” and “D”). A copy of the Walker Ridge Block 51 “C” and “D” EIA is 

attached since the proposed “CC” and “DD” locations are within 100' of the approved 

locations. 
Environmental Impact Analysis

SUPPLEMENTAL EXPLORATION PLAN

for

Walker Ridge Block 51 (OCS G‐31938)

Offshore Louisiana

August 2011

Prepared for:

Bridget O’Farrell‐Villarreal

Regulatory Analyst

Anadarko Petroleum Corporation

1201 Lake Robbins Drive  

The Woodlands, Texas  77380

Telephone: (832) 636‐1694

Prepared by:

CSA International, Inc.

8502 SW Kansas Avenue

Stuart, Florida  34997

Telephone: (772) 219‐3000
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page ii

Contents

Page

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

A.  Impact‐Producing Factors .......................................................................................5

A.1 Drilling Rig Presence (including noise and lights)........................................................................... 5

A.2 Physical Disturbance to the Seafloor.............................................................................................. 8

A.3 Air Pollutant Emissions ................................................................................................................... 8

A.4 Effluent Discharges......................................................................................................................... 8

A.5 Water Intake................................................................................................................................... 9

A.6 Onshore Waste Disposal................................................................................................................. 9

A.7 Marine Debris ................................................................................................................................. 9

A.8 Support Vessel and Helicopter Traffic ............................................................................................ 9

A.9 Accidents ...................................................................................................................................... 10

A.9.1 Types of Accidents Evaluated ........................................................................................... 10

A.9.2 Small Fuel Spill .................................................................................................................. 10

A.9.3 Crude Oil Spill (Worst Case Discharge) ............................................................................. 11

A.9.4 Other Accidents Not Analyzed in Detail............................................................................ 16

B.  Affected Environment...........................................................................................17

C.  Impact Analysis.....................................................................................................19

C.1 Physical/Chemical Environment................................................................................................... 19

C.1.1 Air Quality ......................................................................................................................... 19

C.1.2 Water Quality.................................................................................................................... 21

C.2 Seafloor Habitats and Biota.......................................................................................................... 23

C.2.1 Soft Bottom Benthic Communities ................................................................................... 23

C.2.2 High‐Density Deepwater Benthic Communities ............................................................... 26

C.2.3 Designated Topographic Features .................................................................................... 28

C.2.4 Pinnacle Trend Area Live Bottoms.................................................................................... 29

C.2.5 Eastern Gulf Live Bottoms................................................................................................. 29

C.3 Threatened, Endangered, and Protected Species and Critical Habitat ........................................ 29

C.3.1 Sperm Whale (Endangered).............................................................................................. 31

C.3.2 West Indian Manatee (Endangered)................................................................................. 34

C.3.3 Endangered Mysticete Whales ......................................................................................... 35

C.3.4 Non‐Endangered Marine Mammals (Protected) .............................................................. 36

C.3.5 Sea Turtles (Endangered/Threatened) ............................................................................. 39

C.3.6 Piping Plover (Threatened) ............................................................................................... 42

C.3.7 Whooping Crane (Endangered) ........................................................................................ 42

C.3.8 Gulf Sturgeon (Threatened).............................................................................................. 44

C.3.9 Smalltooth Sawfish (Endangered)..................................................................................... 45

C.3.10 Beach Mice (Endangered)................................................................................................. 45

C.3.11 Elkhorn Coral (Endangered).............................................................................................. 46
Contents

(Continued)

Page

Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page iii

C.4 Coastal and Marine Birds.............................................................................................................. 46

C.4.1 Marine Birds...................................................................................................................... 46

C.4.2 Shorebirds and Coastal Nesting Birds............................................................................... 49

C.5 Fisheries Resources ...................................................................................................................... 51

C.5.1 Pelagic Communities and Ichthyoplankton ...................................................................... 51

C.5.2 Essential Fish Habitat........................................................................................................ 53

C.6 Archaeological Resources............................................................................................................. 56

C.6.1 Shipwreck Sites ................................................................................................................. 56

C.6.2 Prehistoric Archaeological Sites........................................................................................ 57

C.7 Coastal Habitats and Protected Areas.......................................................................................... 58

C.8 Socioeconomic and Other Resources........................................................................................... 61

C.8.1 Recreational and Commercial Fishing .............................................................................. 61

C.8.2 Public Health and Safety ................................................................................................... 62

C.8.3 Employment and Infrastructure ....................................................................................... 63

C.8.4 Recreation and Tourism.................................................................................................... 64

C.8.5 Land Use............................................................................................................................ 65

C.8.6 Other Marine Uses............................................................................................................ 65

D.  Environmental Hazards.........................................................................................66

D.1 Geologic Hazards .......................................................................................................................... 66

D.2 Severe Weather............................................................................................................................ 66

D.3 Currents and Waves ..................................................................................................................... 66

E.  Alternatives ..........................................................................................................67

F.  Mitigation Measures .............................................................................................67

G.  Consultation.........................................................................................................67

H.  Preparers..............................................................................................................67

I.  References.............................................................................................................68
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page iv

List of Tables

Table Page

1 Notices to Lessees and Operators (NTLs) referenced in this Environmental Impact

Analysis (EIA) ......................................................................................................................... 4

2 Matrix of impact‐producing factors and affected environmental resources........................ 6

3 Conditional probabilities expressed as percent chance that an oil spill starting at

Launch Point 3 will contact a certain parish, county, or coastline within 120 days

(Modified from: BOEMRE, 2011b, Appendix C) .................................................................. 13

4 Benthic community data from stations near the lease area and in greater water

depths and more distant stations in more similar depths sampled during the

Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology Study

(Adapted from: Wei, 2006; Rowe and Kennicutt, 2009)..................................................... 24

5 Federally‐listed endangered and threatened species potentially occurring in the

lease area and along the northern Gulf Coast .................................................................... 30

6 Wildlife refuges, wilderness areas, and State and National parks within the

geographic range of the potential shoreline contacts after 120 days

(From: BOEMRE, 2011a)...................................................................................................... 59

List of Figures

Figure Page

1 Location of Walker Ridge Block 51 ........................................................................................ 3

2 Bathymetric map of the lease area showing proposed well surface locations................... 18

3 Location of selected environmental features in relation to the lease area........................ 43
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page v

Acronyms and Abbreviations

ADIOS Automated Data Inquiry for Oil Spills

bbl barrel

BHL bottom hole location

BLPD barrels of liquid per day

BOEMRE Bureau of Ocean Energy Management,

Regulation and Enforcement

BOPD barrels of oil per day

B.P. Before Present

CEI Coastal Environments, Inc.

CH4 methane

CFR Code of Federal Regulations

CGA Clean Gulf Associates

CO carbon monoxide

CO2 carbon dioxide

DP dynamically positioned  

EP Exploration Plan  

EA Environmental Assessment

EEZ Exclusive Economic Zone

EFH Essential Fish Habitat

EIA Environmental Impact Analysis

EIS Environmental Impact Statement

ESA Endangered Species Act

FAD fish‐attracting device

FR Federal Register

GPS global positioning system

GMFMC Gulf of Mexico Fishery Management

Council

H2S hydrogen sulfide

HAPC Habitat Area of Particular Concern

HFRS Helix Fast Response System

HOSS high‐volume open sea skimmer

HWCG Helix Well Containment Group

IPF impact‐producing factor

MARPOL International Convention for the

Prevention of Pollution from Ships

MMBO million barrels of oil

MMC Marine Mammal Commission

MMPA Marine Mammal Protection Act

MMS Minerals Management Service

MMSCFD million standard cubic feet per day

MWCC Marine Well Containment Company

NAAQS National Ambient Air Quality Standards

NMFS National Marine Fisheries Service

NOAA National Oceanic and Atmospheric

Administration

NOx nitrogen oxides

NO2 nitrogen dioxide

NPDES National Pollutant Discharge Elimination

System

NPS National Park Service

NRC National Response Corporation

NRDA Natural Resource Damage Assessment

NTL Notice to Lessees

NWR National Wildlife Refuge

OBM oil‐based mud

OCS Outer Continental Shelf

OSAT Operational Scientific Advisory Team

OSRA Oil Spill Risk Analysis

OSRP Oil Spill Response Plan

PAH polycyclic aromatic hydrocarbon

PM particulate matter

PSD Prevention of Significant Deterioration

SBF synthetic‐based fluid

SBM synthetic‐based mud

SHL surface hole location

SOx sulfur oxides

SWSS Sperm Whale Seismic Study

USCG U.S. Coast Guard

USEPA U.S. Environmental Protection Agency

USFWS U.S. Fish and Wildlife Service

VOC volatile organic compound

WCD worst case discharge

WR Walker Ridge
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 1

Introduction

Anadarko Petroleum Corporation (Anadarko) is submitting an Supplemental Exploration Plan

(EP) for Walker Ridge Block 51 (WR 51).  The EP includes two wells designated C and D to be

drilled in the northeastern quadrant corner of WR 51.  Both wells C and D will be drilled in 2012.  

All surface hole locations (SHLs) and bottom hole locations (BHLs) will be in WR 51.  This

Environmental Impact Assessment (EIA) provides an analysis of both exploratory wells based on

their SHLs.

The lease area is 153 miles (246 km) south‐southwest of the nearest shoreline (Louisiana),

174 miles (280 km) from the onshore support base at Port Fourchon, Louisiana, and 192 miles

(309 km) from the helicopter base at Houma, Louisiana (Figure 1).  Water depth at wellsites C

and D is 1,779 m (5,838 ft)  The drilling rig is yet to be determined but will be either a

dynamically positioned (DP) drillship, a DP semisubmersible, or an anchored semisubmersible.

This EIA was prepared for submittal to the Bureau of Ocean Energy Management, Regulation

and Enforcement (BOEMRE, formerly Minerals Management Service [MMS]) in accordance with

applicable regulations, and is a project‐ and site‐specific analysis of Anadarko’s planned

activities.  As specified in the Notice to Lessees and Operators (NTL) 2008‐G04, an EIA is a

project‐specific analysis that focuses on the impacts of a specific plan to the extent feasible.  

Potential impacts have been analyzed at a broader level in the Programmatic Environmental

Impact Statement (EIS) for the Outer Continental Shelf (OCS) Oil and Gas Leasing Program

(MMS, 2007a) and in lease sale EISs for the Western and Central Gulf of Mexico Planning Areas

(MMS, 2007b, 2008).  The analyses from these documents are incorporated here by reference.  

Also incorporated are the post‐Macondo incident Draft Supplemental EIS for the Central

Planning Area and Final Supplemental EIS for the Western Planning Area lease sales

(BOEMRE, 2011a,b), which present updated environmental baseline information relative to the

Macondo incident, have been reviewed.   

Statistics from offshore drilling in the U.S. Gulf of Mexico provide a reasonable basis for

evaluating oil spill risk during exploratory drilling.  According to Holand (1997), the average

frequency of a loss of well control incident or “blowout” during exploratory drilling in the

U.S. Gulf of Mexico is 0.00593 blowouts per well drilled, or one blowout per 169 exploration

wells drilled.  Similarly, the MMS Safety and Environmental Management Program blowout

incident rate for 1996 to 1999 was approximately five blowouts per 1,000 well starts, or one

blowout per 200 well starts (MMS, 2000).  More recently, in its Draft Supplemental EIS for the

Central Gulf of Mexico Planning Area, BOEMRE confirmed that “significant changes to the spill

rates for the entire OCS are not anticipated” (BOEMRE, 2011a).  

Historically, most blowouts have not resulted in oil spills.  Of 151 well blowouts in the Gulf of

Mexico from 1971 to 1995, only 18 (12%) resulted in oil spills, with a total combined volume of

1,000 barrels (bbl) of crude oil and condensate released (MMS, 2000).  Between 1964 and 1999,

almost all offshore spills (94%) from drilling and production‐related operations on the OCS were

less than or equal to 1 bbl in size (Anderson and LaBelle, 2000).  According to BOEMRE’s Interim

Final Drilling Safety Rule (75 Federal Register (FR) 63365 dated 10 October 2010) issued

following the Macondo incident, the baseline risk of a catastrophic blowout is estimated to be

about once every 26 years.
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 2

Anadarko submitted an updated Gulf of Mexico Regional Oil Spill Response Plan (OSRP) to

BOEMRE on 21 July 2011.  In addition, Anadarko submitted a Regional OSRP Certification Letter

per 30 Code of Federal Regulations (CFR) 254.2(b) to BOEMRE on 21 July 2011.  The Certification

Letter was accepted by BOEMRE on 27 July 2011.  The OSRP details Anadarko’s plan for

response to rapidly and effectively manage oil spills that may result from drilling and production

operations.  Anadarko has designed its response program based on a regional capability of

response to spills ranging from small operational spills to a worst case discharge (WCD) from a

well blowout.  Anadarko’s spill response program meets the response planning requirements of

the relevant coastal states and applicable Federal oil spill planning regulations and also includes

information regarding Anadarko’s regional oil spill organization and dedicated response assets,

potential spill risks, and local environmental sensitivities.  The OSRP describes personnel and

equipment mobilization, the incident management team organization, and an overview of

actions and notifications to be taken in the event of a spill.

This EIA is organized into Sections A through I corresponding to the information required by

NTL 2008‐G04.  The main impact‐related discussions are in Section A (Impact‐Producing Factors)

and Section C (Impact Analysis).  Table 1 lists and summarizes the NTLs applicable to this EIA.
Walker Ridge Block 51 

Environmental Impact Analysis 

Figure 1. Location of Walker Ridge Block 51.
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 4

Table 1. Notices to Lessees and Operators (NTLs) referenced in this Environmental Impact

Analysis (EIA).

NTL Title Summary

2010‐N10

Statement of Compliance with

Applicable Regulations and

Evaluation of Information

Demonstrating Adequate Spill

Response and Well Containment

Resources

Informs operators using subsea blowout preventers (BOPs) or

surface BOPs on floating facilities that applications for well

permits must include a statement signed by an authorized

company official stating that the operator will conduct all

activities in compliance with all applicable regulations, including

the increased safety measures regulations (75 FR 63346).  

Informs operators that BOEMRE will be evaluating whether each

operator has submitted adequate information demonstrating

that it has access to and can deploy containment resources to

promptly respond to a blowout or other loss of well control.

2010‐N06

Information Requirements for

Exploration Plans, Development and

Production Plans, and Development

Operations Coordination Documents

on the OCS

Rescinds the limitations set forth in NTL 2008‐G04 regarding a

blowout scenario and worst case discharge scenario, and

provides guidance regarding the information required in blowout

scenario and worst case discharge scenario descriptions.

2009‐G40 Deepwater Benthic Communities

Guidance for avoiding and protecting high‐density deepwater

benthic communities (including chemosynthetic and deepwater

coral communities) from damage caused by Outer Continental

Shelf (OCS) oil and gas activities in water depths greater than

300 m (984 ft).  Prescribes separation distances of 610 m

(2,000 ft) from each mud and cuttings discharge location and

76 m (250 ft) from all other seafloor disturbances.

2009‐G39 Biologically‐Sensitive Underwater

Features and Areas

Guidance for avoiding and protecting biologically sensitive

features and areas (i.e., topographic features, pinnacles, low

relief live bottom areas, and other potentially sensitive biological

features) when conducting OCS operations in water depths less

than 300 m (984 ft) in the Gulf of Mexico.

2009‐G06 Military Warning and Water Test

Areas

Provides contact links to individual command headquarters for

the military warning and water test areas in the Gulf of Mexico.  

Lease stipulations require lessees or designated operators to

enter into an agreement with the appropriate individual military

command headquarters concerning the control of

electromagnetic emissions and use of boats and aircraft in the

applicable warning area or water test area before commencing

such traffic.

2008‐G04

Information Requirements for

Exploration Plans and Development

Operations Coordination Documents

Guidance on the information requirements for OCS plans,

including EIA requirements and information regarding

compliance with the provisions of the Endangered Species Act

and Marine Mammal Protection Act.

2007‐G04

Vessel Strike Avoidance and

Injured/Dead Protected Species

Reporting

Recommends protected species identification training,

recommends that vessel operators and crews maintain a vigilant

watch for marine mammals and slow down or stop their vessel

to avoid striking protected species, and requires operators to

report sightings of any injured or dead protected species.

2007‐G03 Marine Trash and Debris Awareness

and Elimination

Instructs operators to exercise caution in the handling and

disposal of small items and packaging materials; requires the

posting of placards at prominent locations on offshore vessels

and structures; and mandates a yearly marine trash and debris

awareness training and certification process.

2005‐G07 Archaeological Resource Surveys

and Reports

Provides guidance on regulations regarding archaeological

discoveries, specifies requirements for archaeological resource

surveys and reports, and outlines options for protecting

archaeological resources.
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 5

A.  Impact‐Producing Factors

Table 2 is a matrix of impact‐producing factors (IPFs) and potentially affected environmental

resources adapted from Form MMS‐142.  An “X” indicates that an IPF could reasonably be

expected to affect a certain resource, and a dash (‐‐) indicates no impact or negligible impact.  

Where there may be an effect, an analysis is provided in Section C.  Potential IPFs for the

proposed activity are listed below and briefly discussed in the following sections.

• Drilling rig presence (including noise

and lights)

• Physical disturbance to the seafloor

• Air pollutant emissions

• Effluent discharges

• Water intake

• Onshore waste disposal

• Marine debris

• Support vessel and helicopter traffic

• Accidents

A.1 Drilling Rig Presence (including noise and lights)

Three types of exploratory drilling rigs are available for this project:

• Dynamically‐positioned (DP) drillship;

• DP semisubmersible; and

• Anchored semisubmersible.

DP drillships and DP semisubmersibles use a global positioning system (GPS), specific computer

software, and sensors in conjunction with and their own propellers and thrusters to maintain

position.  Essentially, through satellite navigation and, the location of the vessel is precisely

monitored, and thrusters positioned at various locations about the vessel’s hull are activated to

provide any required stationkeeping adjustment.  This allows operations at sea where mooring

or anchoring is not feasible.

An anchored semisubmersible requires the placement of anchors on the seafloor and thus is

subject to NTL 2009‐G40, which requires that anchors be placed a minimum of 76 m (250 ft)

from deepwater benthic communities.   

The drilling vessel for the wells proposed in this EP will be on site for an estimated 350 days

(175 days/well).  The physical presence of the drilling rig in the ocean can attract pelagic fishes

and other marine life, as discussed in Section C.5.1.

Drilling operations produce noise that includes strong tonal components at low frequencies, and

in some cases infrasonic frequencies (MMS, 2000).  Drilling noise from drillships and

semisubmersibles is not particularly intense and is strongest at low frequencies, averaging

10 to 500 Hz (Richardson et al., 1995).  From a drilling rig, sound and vibration paths to the

water flow either through the air or through the risers (MMS, 2000).  Drilling rigs also maintain

exterior lighting for navigational and aviation safety in accordance with applicable Federal safety

regulations.
Walker Ridge Block 51 

Environmental Impact Analysis 

Table 2. Matrix of impact‐producing factors and affected environmental resources. X = potential impact; dash (‐‐) = no imp

Impact‐producing Factors

Environmental Resources Drilling Rig Presence (incl.

noise & lights)

Physical

Disturbance

to Seafloor

Air

Pollutant

Emissions

Effluent

Discharges

WaterIntake

Onshore

Waste

Disposal

Marine

Debris

Sup

Vesse

Tra

Physical/Chemical Environment

Air quality and greenhouse gases  ‐‐  ‐‐  ‐‐X(9)  ‐‐  ‐‐  ‐‐  ‐‐  Water quality  ‐‐  ‐‐  ‐‐  X ‐‐  ‐‐  ‐‐  

Seafloor Habitats and Biota

Soft bottom benthic communities ‐‐  X  ‐‐  X ‐‐  ‐‐  ‐‐  High‐density deepwater benthic communities  ‐‐  X(4) ‐‐  X(4)  ‐‐  ‐‐  ‐‐  Designated topographic features  ‐‐  ‐‐(1)  ‐‐  ‐‐(1)  ‐‐  ‐‐  ‐‐  Pinnacle trend area live bottoms  ‐‐  ‐‐(2)  ‐‐  ‐‐(2)  ‐‐  ‐‐  ‐‐  Eastern Gulf live bottoms  ‐‐  ‐‐(3)  ‐‐  ‐‐(3)  ‐‐  ‐‐  ‐‐  

Threatened, Endangered, and Protected Species and Critical Habitat

Sperm whale (endangered) X(8)  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  XWest Indian manatee (endangered) ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  XEndangered mysticete whales  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Non‐endangeredmarinemammals(protected) X ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Sea turtles (endangered/threatened) X(8)  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  XPiping Plover (threatened)  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Whooping Crane (endangered) ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Gulf sturgeon (threatened)  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Smalltooth sawfish (endangered) ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Beach mice (endangered) ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Elkhorn coral (endangered) ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  

Coastal and Marine Birds

Marine birds X ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Shorebirds and coastal nesting birds  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  

Fisheries Resources

Pelagic communities and ichthyoplankton X ‐‐  ‐‐  X X ‐‐  ‐‐  Essential Fish Habitat X ‐‐  ‐‐  X X  ‐‐  ‐‐  

Archaeological Resources

Shipwreck sites  ‐‐  ‐‐(7)  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Prehistoric archaeological sites  ‐‐  ‐‐(7)  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  

Coastal Habitats and Protected Areas

Beaches ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Wetlands and seagrass beds  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Coastal wildlife refuges and wilderness areas  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  

Socioeconomic and Other Resources

Recreational and commercial fishing X ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Public health and safety  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Employment and infrastructure  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Recreation and tourism  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Land use  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  Other marine uses  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  

WCD = worst case discharge.
Walker Ridge Block 51 August 2011

Environmental Impact Analysis    Page 7

Table 2 Footnotes and Applicability:

(1) Activities that may affect a marine sanctuary or topographic feature.  Specifically, if the well, rig site, or any

anchors will be on the seafloor within the following:

(a) 4‐mi zone of the Flower Garden Banks, or the 3‐mi zone of Stetson Bank;

(b) 1,000‐m, 1‐mi, or 3‐mi zone of any topographic feature (submarine bank) protected by the Topographic

Features Stipulation attached to an Outer Continental Shelf (OCS) lease;

(c) Essential Fish Habitat (EFH) criteria of 500 ft from any no‐activity zone; or

(d) Proximity of any submarine bank (500‐ft buffer zone) with relief greater than 2 m that is not protected by

the Topographic Features Stipulation attached to an OCS lease.

• Not applicable.  The lease is not within or near any marine sanctuary, topographic feature, or

no‐activity zone.  There are no submarine banks in the blocks.

(2) Activities with any bottom disturbance within an OCS lease block protected through the Live Bottom

(Pinnacle Trend) Stipulation attached to an OCS lease.

• The Live Bottom (Pinnacle Trend) Stipulation is not applicable to the lease area.

(3) Activities within any Eastern Gulf OCS block where seafloor habitats are protected by the Live Bottom

(Low‐Relief) Stipulation attached to an OCS lease.  

• The Live Bottom (Low‐Relief) Stipulation is not applicable to the lease area.

(4) Activities on blocks designated by the BOEMRE as being in water depths 300 m or greater.

• No impacts on high‐density deepwater benthic communities are anticipated.  There are no features

indicative of high‐density chemosynthetic communities or coral communities within 610 m (2,000 ft) of

any drilling mud/cuttings discharge location.   

(5) Exploration or production activities where H2S concentrations greater than 500 ppm might be encountered.  

• Previously drilled wells in the WR area did not indicate the presence of H2S in the target sands and

BOEMRE has classified the area as “H2S absent” in accordance with CFR 250.490(c).

(6) All activities that could result in an accidental spill of produced liquid hydrocarbons or diesel fuel that you

determine would impact these environmental resources.  If the proposed action is located a sufficient distance

from a resource that no impact would occur, the EIA can note that in a sentence or two.

• Accidental hydrocarbon spills could affect the resources marked (X) in the matrix, and impacts are

analyzed in Section C.

(7) All activities that involve seafloor disturbances, including anchor emplacements, in any OCS block designated

by the BOEMRE as having high‐probability for the occurrence of shipwrecks or prehistoric sites, including such

blocks that will be affected that are adjacent to the lease block in which your planned activity will occur.  If the

proposed activities are located a sufficient distance from a shipwreck or prehistoric site that no impact would

occur, the EIA can note that in a sentence or two.

• No impacts on archaeological resources are expected.  The lease area is not on the list of high‐probability

blocks for shipwrecks and is well beyond the 60‐m depth contour used by the BOEMRE as the seaward

extent for prehistoric archaeological site potential in the Gulf of Mexico.

(8) All activities that you determine might have an adverse effect on endangered or threatened marine mammals

or sea turtles or their critical habitats.  

• IPFs that may affect marine mammals, sea turtles, or their critical habitats include drilling rig presence

and emissions, support vessel and helicopter traffic, and accidents.  See Section C.

(9) Production activities that involve transportation of produced fluids to shore using shuttle tankers or barges.

• Not applicable.
Walker Ridge Block 51 August 2011

Environmental Impact Analysis    Page 8

A.2 Physical Disturbance to the Seafloor

In water depths of 600 m (1,969 ft) or greater, DP drillships and DP semisubmersibles disturb

only a very small area of the seafloor around the wellbore (SHL) where the bottom template and

blowout preventer are located.  Depending upon the specific well configuration, this area is

generally about 0.25 ha (0.62 ac).

Anchoring causes physical compaction of the seafloor beneath the anchor, and chains or lines

can disturb the bottom as well as resuspend sediments as they move about.  A disturbed area

on the sea bottom called the “anchor sweep” forms by the swing arc of anchor lines scraping

across the bottom within the range allowed by the anchoring system configuration

(BOEMRE, 2011a,b).  Anchored semisubmersibles disturb approximately 2 to 3 ha (5 to 7 ac) of

seafloor at each wellsite, depending on the number of anchors and their mooring configurations

(MMS, 2007b).

A.3 Air Pollutant Emissions

Air pollutant emissions are calculated in EP Section G and are estimated to be insignificant.  

Offshore air pollutant emissions will result from operations of the drilling rig, as well as service

vessels and helicopters.  These emissions occur mainly from combustion of diesel fuel.  The

combustion of fuels occurs on diesel‐powered generators, pumps, or motors and from lighter

fuel motors.  Primary air pollutants typically associated with OCS activities are suspended

particulate matter (PM), sulfur oxides (SOx), nitrogen oxides (NOx), volatile organic compounds

(VOCs), and carbon monoxide (CO).

The Air Quality Emissions Report prepared in accordance with BOEMRE requirements

demonstrates that the projected emissions are below exemption levels set by the applicable

regulations in 30 CFR 250.303.  Based on this and the distance to shore, it can be concluded that

the emissions will not significantly affect the air quality of the onshore area for any of the

criteria pollutants.  No further analysis or control measures are required.

A.4 Effluent Discharges

Effluent discharges are summarized in EP Section F.  All offshore discharges will be in

accordance with requirements of the National Pollutant Discharge Elimination System (NPDES)

General Permit No. GMG 290000 issued by the U.S. Environmental Protection Agency (USEPA).  

Any discharges will be in compliance with the permit terms and monitored as required by the

permit.

Water‐based drilling muds and cuttings will be released at the seafloor during the initial well

intervals before the marine riser that allows their return to the surface is set.  Excess cement

slurry will also be released at the seafloor during casing installation for the riserless portion of

the drilling operations.  Synthetic‐based drilling muds (SBMs) will be collected on the rig and

either reused by the vendor, or transported to Port Fourchon for recycling and/or disposal in an

approved facility.  Cuttings wetted with SBMs will be discharged to the seafloor in accordance

with the NPDES permit.
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Other effluent discharges in accordance with the NPDES permit will include excess cement,

non‐contact cooling water, treated sanitary and domestic wastes, deck drainage, desalination

unit brine, uncontaminated fresh water and seawater, and ballast water.

A.5 Water Intake

Seawater will be drawn from the ocean for once‐through, non‐contact cooling of machinery on

the drilling rig.  Section 316(b) of the Clean Water Act requires NPDES permits to ensure that the

location, design, construction, and capacity of cooling water intake structures reflect the best

technology available to minimize adverse environmental impact from impingement and

entrainment of aquatic organisms.  The current NPDES General Permit No. GMG 290000 does

not specify requirements for existing facilities (those that started construction before

16 July 2006).  The rigs being considered for use for activities described in this EP are not “new”

facilities as defined by the NPDES permit and therefore are not subject to the cooling water

intake regulations.

A.6 Onshore Waste Disposal

Wastes generated during drilling are tabulated in EP Section F.  Approximately 50 bbl of trash

will be generated each month of operations, or a total of 583 bbl over the life of this project.  

This trash will be transported in disposal bags to shore, where it will be picked up by municipal

operators for final disposal in accordance with applicable regulations.  

A.7 Marine Debris

Anadarko will comply with all regulations relating to solid wastes handling and disposal,

including the International Convention for the Prevention of Pollution from Ships

(MARPOL 73/78) Annex V requirements and USEPA and U.S. Coast Guard (USCG) regulations, as

well as those of the BOEMRE.  For example, BOEMRE regulations at 30 CFR 250.300(a) and

(b)(6) prohibit operators from deliberately discharging containers and other similar materials

(i.e., trash and debris) into the marine environment, and 30 CFR 250.300(c) requires durable

identification markings on equipment, tools, and containers (especially drums), and other

material.  USEPA and USCG regulations require operators to become proactive in avoiding

accidental loss of solid waste items by developing waste management plans, posting

informational placards, manifesting trash sent to shore, and using special precautions such as

covering outside trash bins to prevent accidental loss of solid waste.  In addition to the

regulations in 30 CFR 250, MMS issued NTL 2007‐G03, which instructs operators to exercise

caution in the handling and disposal of small items and packaging materials, requires the posting

of placards at prominent locations on offshore vessels and structures, and mandates a yearly

marine trash and debris awareness training and certification process.

A.8 Support Vessel and Helicopter Traffic

Anadarko will use existing shorebase facilities at Port Fourchon, Louisiana, for onshore support

for vessel activities.  Air transportation (helicopters) will be based at facilities in Houma, Louisiana.  

No terminal expansion or construction is planned at either location.

The project will be supported by one crew boat and one supply vessel.  The crew vessel will

make three round‐trips per week, and the supply vessel will make two round‐trips per week.  

The boats typically will move to the project area via the most direct route from the shorebase.
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A helicopter will make one round‐trip daily between the drilling rig and the heliport.  The

helicopter will be used to transport personnel and small supplies and will normally take the

most direct route of travel between the shorebase and the lease area when air traffic and

weather conditions permit.  Helicopters typically maintain a minimum altitude of 213 m (700 ft)

while in transit offshore, 305 m (1,000 ft) over unpopulated areas or across coastlines, and

610 m (2,000 ft) over populated areas and sensitive habitats such as wildlife refuges and park

properties.

A.9 Accidents

A.9.1 Types of Accidents Evaluated

The analysis in this EIA focuses on two potential accidents:

• A small fuel spill, which is the most likely type of spill during OCS exploration activities; and

• The WCD for this EP, which is an oil spill resulting from an uncontrolled blowout.

The following subsections summarize assumptions about the sizes and fates of these spills, as

well as Anadarko’s spill response plans.  Impacts are analyzed in Section C.

MMS (2007b) and BOEMRE (2011a,b) analyze three other types of accidents: chemical spills,

vessel collisions, and loss of well control.  These types of accidents are discussed briefly in

Section A.9.4.

A.9.2 Small Fuel Spill

Spill Size.  According to the analyses in MMS (2007b) and BOEMRE (2011a,b), the most likely

type of small spill (<1,000 bbl) as a result of OCS activities is a minor diesel fuel spill.  Historically,

most diesel spills have been <1 bbl, and this size is predicted to be the most common in ongoing

and future OCS activities in the Western and Central Gulf of Mexico Planning Areas.  As the spill

size increases, the incident rate declines dramatically (MMS, 2007b; BOEMRE, 2011a,b).  The

average size for spills <1 bbl is 0.07 bbl, and the median size for spills of 1 to 10 bbl is 3 bbl

(MMS, 2007b).  For this analysis, a small diesel fuel spill of 3 bbl is assumed.  Operational

experience suggests that the most likely cause of such a spill would be a hose rupture resulting

in the loss of the contents of a fuel transfer hose, which is less than 3 bbl.

Spill Fate.  The fate of a small fuel spill in the lease area would depend on meteorological and

oceanographic conditions at the time, as well as the effectiveness of spill response activities.  

However, given the open ocean location of the lease area and response actions, it is expected

that impacts from a small spill would be minimal (BOEMRE, 2011a,b).

The water‐soluble fractions of diesel are dominated by two‐ and three‐ringed polycyclic

aromatic hydrocarbons (PAHs), which are moderately volatile (National Research Council, 2003).  

The constituents of these oils are light to intermediate in molecular weight and can be readily

degraded by aerobic microbial oxidation.  Diesel is so light that it will not sink to the seafloor.  

Diesel dispersed in the water column can adhere to suspended sediments, but this generally

occurs only in coastal areas with high suspended solids loads (National Research Council, 2003)

and would not be expected to occur to any appreciable degree in offshore waters of the Gulf of

Mexico.  Diesel oil is readily and completely degraded by naturally occurring microbes (National

Oceanic and Atmospheric Administration [NOAA], 2006).
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For purposes of this EIA, the fate of a small diesel fuel spill was estimated using NOAA’s ADIOS2

(Automated Data Inquiry for Oil Spills) model.  This model uses the physical properties of oils in

its database to predict the rate of evaporation and dispersion over time, as well as changes in

the density, viscosity, and water content of the product spilled.  It is estimated that over 90% of

a small diesel spill would be evaporated or dispersed within 24 hours.  The area of the sea

surface with diesel fuel on it during this 24‐hour period would range from 0.5 to 5 ha

(1.2 to 12 ac) depending on sea state and weather conditions.

The ADIOS2 results, coupled with spill trajectory information discussed below for a large spill,

indicate that a small fuel spill would not have any impacts on coastal or shoreline resources.  

The lease area is 153 miles (246 km) from the nearest shoreline (Louisiana).  Modeling results

discussed below indicate that a spill in the lease area would have a 4% or less probability of

reaching the coastal areas of Louisiana within 10 days after a spill.  By that time, essentially

100% of a small fuel spill would have been dispersed or evaporated by natural processes,

without taking into account Anadarko’s response measures.  MMS (2007b) similarly concluded

that spills <1,000 bbl are not expected to persist as a slick on the surface of the water beyond a

few days and are unlikely to make landfall or reach coastal waters prior to breaking up.  MMS

(2007b) noted that this conclusion is supported by a previous analysis of 3‐day trajectory model

runs, previous weathering analyses, and historical records of spill incidents.

Spill Response.  In the unlikely event the shipboard prevention procedures fail to prevent a fuel

spill, response equipment and trained personnel would be activated so that any spill effects

would be localized and would result only in short‐term environmental consequences.  

EP Section 9b provides a detailed discussion of Anadarko’s response to a spill.

A.9.3 Crude Oil Spill (Worst Case Discharge)

Spill Size.  In accordance with requirements of NTL 2010‐N06, Anadarko has estimated a WCD

for this EP as 80,000 barrels of oil per day (BOPD).  The estimated maximum time to drill a relief

well is 171 days, and the total volume of a spill over this duration would be 13,680,000 barrels

of oil.  The detailed analysis of this calculation can be found in EP Section H.

Historically, blowouts are rare events and most do not result in oil spills.  Holand (1997)

estimated a probability of 0.0021 for a deep drilling blowout during exploration drilling based on

U.S. Gulf of Mexico data.  An updated analysis using the SINTEF database estimates a blowout

frequency of 0.0017 per exploratory well for non‐North Sea locations (International Association

of Oil & Gas Producers, 2010).  As noted by MMS (2007b), from 1992 to 2005, half of blowouts

lasted less than half a day, and fewer than 10% of blowouts resulted in spilled oil.  BOEMRE is in

the process of updating these spill frequency estimates to include the recent Macondo event;

however, significant changes to the spill rates for the entire OCS are not anticipated

(BOEMRE, 2011a,b).  As noted in the Introduction, the baseline risk of a catastrophic blowout is

estimated to be once every 26 years (BOEMRE Interim Final Drilling Safety Rule, 75 FR 63365,

10 October 2010).  

Included in EP Section H are Anadarko’s calculations and information as required by

NTL 2010‐N06, including descriptions of measures to prevent a blowout, reduce the likelihood of

a blowout, and conduct effective and early intervention in the event of a blowout.  Anadarko

will also comply with NTL 2010‐N10 and the Interim Final Drilling Safety Rule, which specifies

additional safety measures for OCS activities.
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Spill Trajectory.  The fate of a large oil spill in the lease area would depend on meteorological

and oceanographic conditions at the time.  The Oil Spill Risk Analysis (OSRA) model is a

computer simulation of oil spill transport that uses realistic data for winds and currents to

predict spill fate.  Although this model has received some criticism recently (Earthjustice, 2011),

it is still the most widely scientifically accepted model for estimating the fate of small fuel spills.  

The primary criticism of the OSRA model results as provided in Ji et al. (2004) was that the

model did not evaluate the fate of a spill over time periods longer than 30 days, nor does it

predict the fate of a release that continues over a period of weeks or months, as in the Macondo

(Deepwater Horizon) incident.  Also as noted by Ji et al. (2004), the OSRA model does not take

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

splitting of oil spills, or spill response activities.  The model does not assume a particular spill size

but has generally been used by the BOEMRE/MMS to evaluate contact probabilities for spills

greater than 1,000 bbl.

To address this criticism, a special OSRA run was conducted for the recent BOEMRE Central and

Western Gulf of Mexico Planning Area Supplemental EISs (BOEMRE, 2011a,b) in order to

estimate the impacts of a possible future catastrophic long‐duration oil spill.  In this OSRA model

run a hypothetical high volume, long‐duration oil spill was assumed to have occurred, and the

analysis emphasized modeling a spill that continued for 90 consecutive days, with each

trajectory tracked for up to 120 days.

The OSRA model run for this revised analysis was conducted for five hypothetical launch points

in the Central and Western Gulf of Mexico Planning Areas.  These launch points were

deliberately located in areas identified as having a high possibility of containing large oil

reserves.  

The five launch point areas were as follows:

1. Central Gulf of Mexico shelf area west of the Mississippi River (28.98660° N

latitude, 92.17851° W longitude);

2. Central Gulf of Mexico shelf area east of the Mississippi River (29.91388° N latitude,

88.15338° W longitude);

3. Central Gulf of Mexico slope area (27.31998° N latitude, 90.22203° W longitude);

4. Western Gulf of Mexico shelf area (27.55423° N latitude, 96.76627° W longitude); and

5. Western Gulf of Mexico slope area (27.51367° N latitude, 94.51836° W longitude).

The results for Launch Point 3, the nearest location to this project area, are presented in

Table 3.

OSRA is a preliminary risk assessment model.  In the event of an actual oil spill, real‐time

monitoring and trajectory modeling would be conducted using current and wind data available

from the rigs and permanent production structures in the area.  Satellite and aerial monitoring

of the plume and real‐time trajectory modeling using wind and current data would continue on

a daily basis to help position equipment and human resources throughout the duration of any

major spill or uncontrolled release.
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Table 3. Conditional probabilities expressed as percent chance that an oil spill starting at

Launch Point 3 will contact a certain parish, county, or coastline within 120 days

(Modified from: BOEMRE, 2011b, Appendix C).

Season Winter Spring Summer Fall

Day 3 10 30 120 3 10 30 120 3 10 30 120 3 10 30 120

County or Parish Percent Chance

Cameron, Texas  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  ‐‐  2

Willacy, Texas  ‐‐  ‐‐  ‐‐  3  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  ‐‐  3

Kenedy, Texas  ‐‐  ‐‐  ‐‐  8  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  9  ‐‐  ‐‐  ‐‐  5

Kleberg, Texas  ‐‐  ‐‐  1 6  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  4  ‐‐  ‐‐  1 6

Nueces, Texas  ‐‐  ‐‐  1 6  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  1 2

Aransas, Texas  ‐‐  ‐‐  ‐‐  5  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  3  ‐‐  ‐‐  ‐‐  2

Calhoun, Texas  ‐‐  ‐‐  1 6  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  6  ‐‐  ‐‐  1 4

Matagorda, Texas  ‐‐  ‐‐  2 17  ‐‐  ‐‐  3 4  ‐‐  ‐‐  ‐‐  11  ‐‐  ‐‐  1 6

Brazoria, Texas  ‐‐  ‐‐  3 12  ‐‐  ‐‐  1 3  ‐‐  ‐‐  2 8  ‐‐  ‐‐  1 5

Galveston, Texas  ‐‐  ‐‐  3 10  ‐‐  ‐‐  3 6  ‐‐  ‐‐  2 5  ‐‐  ‐‐  1 4

Jefferson, Texas  ‐‐  ‐‐  1 4  ‐‐  ‐‐  7 9  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  2

Cameron, Louisiana  ‐‐  ‐‐  1 4  ‐‐  ‐‐  11 12  ‐‐  1 1 4  ‐‐  ‐‐  ‐‐  4

Vermilion, Louisiana  ‐‐  ‐‐  1 2  ‐‐  ‐‐  5 6  ‐‐  1 1 2  ‐‐  ‐‐  ‐‐  ‐‐ 

Iberia, Louisiana  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  4 4  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Terrebonne, Louisiana  ‐‐  1 2 3  ‐‐  4 12 14  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  ‐‐  ‐‐ 

Lafourche, Louisiana  ‐‐  ‐‐  1 1  ‐‐  2 8 10  ‐‐  ‐‐  1 2  ‐‐  ‐‐  ‐‐  ‐‐ 

Jefferson, Louisiana  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  2 2  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  ‐‐ 

Plaquemines, Louisiana  ‐‐  ‐‐  ‐‐  1  ‐‐  2 10 12  ‐‐  ‐‐  1 2  ‐‐  ‐‐  ‐‐  ‐‐ 

Jackson, Mississippi  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Baldwin, Alabama  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Bay, Florida ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Franklin, Florida  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Monroe, Florida  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  1

Dade, Florida  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  ‐‐ 

“‐‐” = Values <1.0%.  Areas where there is <0.5% chance of contact within 120 days are not shown.

Weathering.  Following an oil spill, several physical, chemical, and biological processes,

collectively called weathering, interact to change the physical and chemical properties of the oil,

influencing potential effects to marine organisms and ecosystems.  The most important

weathering processes include spreading, evaporation, dissolution, dispersion into the water

column, formation of water‐in‐oil emulsions, photochemical oxidation, microbial degradation,

adsorption to suspended particulate matter, and stranding on shore or sedimentation to the

seafloor (National Research Council, 2003).

Weathering decreases the concentration of oil and produces changes in its chemical

composition, physical properties, and toxicity.  The more toxic, light aromatic and aliphatic

hydrocarbons are lost rapidly by evaporation and dissolution from a slick on the water surface.  

Evaporated hydrocarbons are degraded rapidly by sunlight.  Biodegradation of oil on the water

surface and in the water column by marine bacteria removes first the n‐alkanes and then the

light aromatics from the oil.  Other petroleum components are biodegraded more slowly.  

Photo‐oxidation attacks mainly the medium and high molecular weight PAHs in the oil on the

water surface.  
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Spill Response.  BOEMRE has issued recent NTLs following the Macondo spill that clarify

additional oil‐spill prevention and response planning requirements.  These NTLs are summarized

in Table 2, and additional BOEMRE (2011a) guidance is provided below.  

NTL 2010‐N10 – Statement of Compliance with Applicable Regulations and Evaluation of

Information Demonstrating Adequate Spill Response and Well Containment Resources:  

This NTL, effective November 8, 2010, applies only to operators conducting operations using

subsea or surface BOPs on floating facilities.  It explains that lessees and operators submit a

statement signed by an authorized company official with each application for a well permit

indicating that they will conduct all of their authorized activities in compliance with all

applicable regulations, including the Increased Safety Measures Regulations at 75 FR 63346.  

The NTL also informs lessees that BOEMRE will be evaluating whether or not each operator

has submitted adequate information demonstrating that it has access to and can deploy

surface and subsea containment resources that would be adequate to promptly respond to

a blowout or other loss of well control.  The NTL notifies the operator that BOEMRE intends

to evaluate the adequacy of each operator to comply in the operator’s current OSRP;

therefore, there is an incentive for voluntary compliance.

NTL 2010‐N06 – Information Requirements for Exploration Plans, Development and

Production Plans, and Development Operations Coordination Documents on the OCS:

This NTL, effective June 18, 2010, explains the procedures for the lessee or operator to

submit supplemental information for new or previously submitted EPs, DPPs, or DOCDs.  

The required supplemental information includes the following: 1) a description of the

blowout scenario as required by 30 CFR 250.213(g) and 250.243(h); 2) a description of their

assumptions and calculations used in determining the volume of the worst‐case discharge

required by 30 CFR 250.219(a)(2)(iv) (for EPs) or 30 CFR 250.250(a)(2)(iv) (for DPPs and

DOCDs); and 3) a description of the measures proposed that would enhance the ability to

prevent a blowout, to reduce the likelihood of a blowout, and to conduct effective and early

intervention in the event of a blowout, including the arrangements for drilling relief wells

and any other measures proposed.  The early intervention methods of the third

requirement could actually include the surface and subsea containment resources that

BOEMRE announced in NTL 2010‐N10, which states that BOEMRE will begin reviewing to

ensure that the measures are adequate to promptly respond to a blowout or other loss of

well control.

Anadarko submitted an updated Gulf of Mexico Regional OSRP to BOEMRE on 21 July 2011.  In

addition, Anadarko submitted a Regional OSRP Certification Letter per 30 CFR 254.2(b) to

BOEMRE on 21 July 2011.  The OSRP provides a detailed plan for Anadarko to respond to and

rapidly and effectively manage oil spills that may result from drilling and production operations.  

The OSRP contains detailed information on “Quick Response” procedures including

• responsibilities of all Anadarko and contract personnel to report any observed discharge

from known or unknown sources;

• procedures to locate and determine the size of a discharge; and  

• Contact information for alerting the spill management team complete with names, phone

numbers, and locations.

In the event of a WCD, Anadarko has access to surface and subsea response/containment

capabilities that could be implemented through various organizations under contract.  

Anadarko's primary spill response equipment provider is Clean Gulf Associates (CGA).  
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CGA has four skimming vessels capable of operating in shallow waters and offshore/nearshore

areas.  These vessels have oleophilic brush pack skimming systems operating in troughs built

into the hulls; below deck storage; and marine electronics packages including marine, aircraft

and company frequency radios, radar, moving map plotters, GPS, satellite phone, and depth

finders.  CGA also offers nine Fast Response Systems staged throughout the Gulf of Mexico

available for offshore use.  

The CGA high‐volume open sea skimmer (HOSS) barge consists of a skimming system built into

an oil recovery barge.  There are four 1,000‐bbl recovered oil storage tanks built into the hull

where oil can be separated and offloaded.  Skimming operations are conducted from the control

room overlooking the skimmer deck.  The estimated daily recovery capacity for the HOSS barge

is approximately 43,000 bbl.

CGA is currently adding to its equipment stockpile and has recently acquired 11 sets of

Koseq skimming arms and two Aqua Guard skimmers.  In addition, an x‐band radar/infrared

tracking system is installed on the HOSS barge.

Anadarko also has a contract with National Response Corporation (NRC) for additional spill

response equipment.  NRC has a dedicated fleet for the Gulf of Mexico and has additional

available equipment staged throughout the U.S.  NRC oil spill response vessels include the

Admiral, Energy, and Liberty; their oil spill response barges Defender and Valiant are equipped

with spill containment and recovery gear to respond on request.

NRC's supplemental offshore skimming systems are stored on trailers as units consisting of

skimmers, boom, and hydraulic power sources in various locations.  Units can be mobilized to a

staging area and loaded onto a supplemental offshore vessel.  Vessels of Opportunity will be

needed for deployment.

Anadarko also is a member of the Marine Well Containment Company (MWCC).  In the event of

an incident, MWCC can provide a 15,000‐psi single ram capping stack and dispersant injection

capability.  MWCC can also install and operate the interim containment system, including subsea

flowlines, manifold, and risers.  The interim system is engineered to be used in depths up to

3,048 m (10,000 ft) and has the capacity to contain 60,000 barrels of liquid per day (BLPD)

(and 120 million standard cubic feet per day [MMSCFD] of gas) with potential for expansion.

In addition, Anadarko is a member of the Helix Well Containment Group (HWCG), a part of the

Helix Fast Response System (HFRS), and has available all the common response equipment and

services of the HWCG group.  Anadarko’s membership allows access to subsea well containment

and well shut‐in equipment including the Q4000 and Helix Producer I vessels to facilitate control

and containment of spills.  At full production capacity, the HFRS can handle up to approximately

55,000 BOPD; 70,000 BLPD; and 95 MMSCFD of gas at 10,000 psi in water depths to 2,438 m

(8,000 ft).  HWCG also can provide a 10,000‐ or 15,000‐psi dual ram capping stack, in addition to

those available through MWCC.

See EP Section H for a detailed description of Anadarko’s site‐specific response to the WCD for

this plan.
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A.9.4 Other Accidents Not Analyzed in Detail

MMS (2007b) discusses three other types of accidents: chemical spills, vessel collisions, and loss

of well control.  The information from the EIS on these topics remains valid and is incorporated

by reference into this document.  These accidents are discussed briefly below along with a

hydrogen sulfide (H2S) release.  There are no other site‐specific issues raised by well drilling

proposed in this EP.

Chemical Spills.  Chemicals are stored and used to condition drill muds and during production

and in well completions, stimulation, and workover procedures.  The relative quantity of their

use is reflected in the largest volumes spilled.  Completion fluids are the largest quantity used

and comprise the largest releases.  Between 5 and 15 chemical spills are anticipated each year,

with the majority being <50 bbl in size.  The most common chemicals spilled are methanol,

ethylene glycol, and zinc bromide.  Additional production chemicals are needed in deepwater

operations where gas hydrates tend to form.  Spill volumes are anticipated to remain about the

same, but spill frequency can be expected to decrease because of advances in subsea processing

(BOEMRE, 2011a,b).

Riser Disconnect SBM Spills.  In deepwater drilling, SBMs are preferred over petroleum oil‐based

muds (OBMs) due to the superior environmental properties of SBMs.  The synthetic base fluid

used in SBMs are less toxic to the marine environment and have the potential to biodegrade.  

SBMs have been used in the Gulf of Mexico since the mid‐1990s, and between 5 and 20 SBM

releases are anticipated each year as a result of offshore drilling programs.  The majority of

these releases are <50 bbl in size, but accidental riser disconnects may result in the release of

medium (238 to 2,380 bbl) to large (>2,381 bbl) quantities of drilling fluids.  Riser disconnect

accidents are of particular concern when SBMs are in use (BOEMRE, 2011c).

Vessel Collisions.  BOEMRE data show that from 1996 to 2009 there were 226 OCS‐related

collisions.  Most collision mishaps are the result of service vessels colliding with platforms or

vessel collisions with pipeline risers.  Approximately 10% of vessel collisions with platforms in

the OCS resulted in diesel spills, and in several collision incidents, fires resulted from

hydrocarbon releases.  To date, the largest diesel spill associated with a collision occurred in

1979 when an anchor‐handling boat collided with a drilling platform in the Main Pass leasing

area, spilling 1,500 bbl.  Diesel fuel is the product most frequently spilled, although oil, natural

gas, corrosion inhibitor, hydraulic fluid, and lube oil have also been released as the result of

vessel collisions.  Human error accounts for approximately half of all reported vessel collisions

from 2006 to 2009.  As summarized in MMS (2007b) and BOEMRE (2011a), vessel collisions

occasionally occur during routine operations.  Some of these collisions have caused spills of

diesel fuel or chemicals.  Anadarko will comply with all USCG‐ and BOEMRE‐mandated safety

requirements to minimize the potential for vessel collisions.

Loss of Well Control.  A loss of well control is the uncontrolled flow of a reservoir fluid that may

result in the release of gas, condensate, oil, drilling fluids, sand, or water.  Loss of well control is

a broad term that includes very minor up to the most serious well control incidents, while

blowouts are considered to be a subset of more serious incidents with greater risk of oil spill or

human injury (MMS, 2007b).  Loss of well control may result in the release of synthetic drilling

fluid or loss of oil.  Anadarko has a robust system in place to prevent loss of well control.  

Measures to prevent a blowout, reduce the likelihood of a blowout, and conduct effective and

early intervention in the event of a blowout are described in EP Section H as required by

NTL 2010‐06.  The potential for a loss‐of‐well‐control event will be minimized by adhering to the
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Environmental Impact Analysis    Page 17

requirements of applicable regulations such as the Interim Final Drilling Safety Rule and

NTL 2010‐N10, which specify additional safety measures for OCS activities.  

H2S Release.  On 31 March 2009, BOEMRE classified the area in WR 51 as H2S absent in

accordance with 30 CFR 250.490(c).  In accordance with 30 CFR 250.417(c), Anadarko requests

WR Block 51 (OCS‐G 31938), be classified by the BOEMRE as an area where the “absence” of

hydrogen sulfide has been confirmed.  Based on this, no further discussion of H2S is warranted.  

B.  Affected Environment

The lease area is in the western Gulf of Mexico, 153 miles (246 km) from the nearest shoreline

(Louisiana), and 174 miles (280 km) from the onshore support base at Port Fourchon, Louisiana

(Figure 1).  

Based on the Site Clearance Survey by AOA Geophysics Inc. (2011), water depth at the wellsites

is 1,779 m (5,838 ft) (Figure 2).  There is no evidence of significant seafloor or subsurface

faulting, fluid expulsion features, or high‐density deepwater benthic communities near the

wellsites (AOA, 2011).

A detailed description of the regional affected environment is provided in recent lease sale EISs,

including meteorology, oceanography, geology, air and water quality, benthic communities,

threatened and endangered species, biologically sensitive resources, archaeological resources,

socioeconomic conditions, and other marine uses (MMS, 2007b, 2008).  These regional

descriptions remain valid and are incorporated by reference.  General background information is

presented below, and brief descriptions of each potentially affected resource, including

site‐specific and/or new information if available, are presented in Section C.

The Macondo spill resulted in impacts to water quality in the area of the spill.  In addition to the

oil slick on the sea surface, plumes of submerged oil droplets were produced when subsea

dispersants were applied at the wellhead (Camilli et al., 2010; Hazen et al., 2010; Joint Analysis

Group, 2010a,b,c).  Despite limited information on the water quality of deep water, it is clear

that the condition of the offshore waters of the Gulf of Mexico was altered by the Macondo

event.  Various monitoring efforts and environmental studies are in progress, but it is not

currently possible to precisely estimate the long‐term impacts the spill will have on offshore

water quality (BOEMRE, 2011a,b).

The lease area is located approximately 233 miles (375 km) southwest of the Macondo spill site.  

Based on an analysis of satellite imagery (ESRI, 2010), the surface slick did not extend over the

lease area and there is no indication that water quality in the lease area was affected.  Prior to

the Macondo incident, water quality in deep, offshore waters of the Gulf of Mexico was

expected to be good, with low levels of contaminants (Kennicutt, 2000).  Based on the

information currently available, there is no reason to expect any change in water quality

conditions in the lease area from those predicted in the recent lease sale EISs (MMS, 2007b,

2008; BOEMRE, 2011a,b).
Walker Ridge Block 51 

Environmental Impact Analysis 

Figure 2. Bathymetric map of the lease area showing proposed well surface locations. (Water depth in meters.)
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 19

C.  Impact Analysis

This section analyzes the potential direct and indirect impacts of routine activities and accidents.  

Impacts have been analyzed extensively in recent lease sale EISs for the Central and Western

Gulf of Mexico Planning Areas (MMS, 2007b, 2008; BOEMRE, 2011a,b) as well as the

environmental assessment for Gulf of Mexico deepwater operations and activities (MMS, 2000).  

The information in these documents is incorporated by reference.  Potential site‐specific issues

are addressed in this section.

C.1 Physical/Chemical Environment

C.1.1 Air Quality

There are no site‐specific air quality data for the project area due to the distance from shore.  

Because of the distance from shore‐based pollution sources and the lack of sources offshore, air

quality at the wellsites is expected to be good.  The attainment status of Federal OCS waters is

unclassified because there is no provision in the Clean Air Act for classification of areas outside

State waters (MMS, 2007b).

As noted earlier, based on calculations made pursuant to applicable regulations, emissions from

drilling activities are not expected to be significant as they are below exemption levels.  

Therefore, the only potential effects to air quality would be from routine air pollutant emissions,

a small fuel spill, and a large oil spill (WCD).

BOEMRE has reexamined the analysis for air quality presented in MMS (2007b, 2008) based on

additional information and in consideration of the Macondo oil spill event.  No substantial new

information was found that would alter the potential impacts on air quality presented in

previous lease sale EISs (BOEMRE, 2011a,b).

Impacts of Air Pollutant Emissions

Air pollutant emissions are the only routine IPF likely to affect air quality.  Offshore air pollutant

emissions will result from the drilling rig operations and helicopters and service vessels.  These

emissions occur mainly from combustion or burning of diesel fuel.  The combustion of fuels

occurs primarily on diesel‐powered generators, pumps, or motors and from lighter fuel motors.  

Primary air pollutants typically associated with OCS activities are suspended PM, SOx, NOx, VOCs,

and CO.  Emissions of pollutants into the atmosphere from these activities are not projected to

have significant effects on onshore air quality because of the prevailing atmospheric conditions,

emission rates and heights, and resulting pollutant concentrations.  As the BOEMRE found in the

lease sale EISs, the incremental contribution of activities similar to Anadarko’s proposed

activities to the cumulative impacts is not significant and will not cause or contribute to a

violation of any National Ambient Air Quality Standard (NAAQS) (MMS, 2007b, 2008).  Since the

BOEMRE completed the lease sale EISs, the USEPA has adopted a new short‐term NAAQS for

nitrogen dioxide (NO2).  The standard has not yet been implemented in the Gulf Coast States,

but given the levels of expected emissions and the distance of the project from shore, emissions

from the activities described in Anadarko’s proposed EP are not likely to contribute to violations

of any NAAQS onshore.
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Environmental Impact Analysis Page 20

Carbon dioxide (CO2) and methane (CH4) emissions from the project would constitute a small

incremental contribution to greenhouse gas emissions from all OCS activities.  According to the

Programmatic EIS (MMS, 2007a), estimated CO2 emissions from all OCS activities in the

2007‐2012 leasing program are about 0.08% to 0.016% of the global CO2 emissions from fossil

fuel combustion.  Greenhouse gas emissions may contribute to climate change, with important

effects on temperature, rainfall, frequency of severe weather, ocean acidification, and sea level

rise (Intergovernmental Panel on Climate Change, 2007).  Greenhouse gas emissions from this

proposed project represent a negligible contribution to the total greenhouse gas emissions from

reasonably foreseeable activities in the Gulf of Mexico area and would not significantly alter any

of the climate change impacts evaluated in the lease sale EIS (MMS, 2007b) or Programmatic EIS

(MMS, 2007a).

Due to the distance from shore, routine operations in the project area are not expected to have

any impact on air quality conditions along the coast, including nonattainment areas.  As noted in

the lease sale EIS (MMS, 2007b), emissions of air pollutants from routine activities in the Central

Gulf of Mexico Planning Area are projected to have minimal impacts to onshore air quality

because of the prevailing atmospheric conditions, emission heights, emission rates, and the

distance of these emissions from the coastline.  The Air Quality Emissions Report

(see EP Section G) prepared in accordance with BOEMRE requirements shows that the projected

emissions are below exemption levels; therefore, according to 30 CFR 250.303, the emissions

will not significantly affect the air quality of the onshore area for any of the criteria pollutants.  

No further analysis or control measures are required.

The Breton Wilderness Area, which is part of the Breton National Wildlife Refuge (NWR), is

designated under the Clean Air Act as a Prevention of Significant Deterioration (PSD) Class I air

quality area.  The BOEMRE is required to notify the National Park Service (NPS) and U.S. Fish and

Wildlife Service (USFWS) if emissions from proposed projects may affect the Breton Class I area.  

Additional review and mitigation measures may be required for sources within 186 miles

(300 km) of the Breton Class I area that exceed emission limits agreed upon by the administering

agencies (NPS, 2010).  The lease area is approximately 228 miles (367 km) from the Breton

Wilderness Area, so air quality impacts on the Wilderness Area are not expected.

Impacts of a Small Fuel Spill

Potential impacts of a small spill on air quality are expected to be consistent with those analyzed

and discussed in EISs prepared for recent lease sales (MMS, 2007b, 2008; BOEMRE, 2011a,b).  

The probability of a small spill would be minimized by Anadarko’s preventative measures during

routine operations, including fuel transfer.  In the unlikely event of a spill, implementation of

Anadarko’s OSRP will reduce the potential impacts.  EP Section H includes a detailed discussion

of the spill response measures that would be employed.  Given the open ocean location of the

lease area, the extent and duration of air quality impacts from a small spill would not be

significant.

A small fuel spill would affect air quality near the spill site by introducing VOCs through

evaporation.  The ADIOS2 model (see Section A.9.2) indicates that over 90% of a small diesel

spill would be evaporated or dispersed within 24 hours.  The area of the sea surface with diesel

fuel on it would range from 0.5 to 5 ha (1.2 to 12 ac) depending on sea state and weather

conditions.
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 21

A small fuel spill would not affect coastal air quality because the spill would not be expected to

make landfall or reach coastal waters prior to breaking up (see Section A.9.2).

Impacts of a Large Oil Spill (WCD)

Potential impacts of a large oil spill on air quality are expected to be consistent with those

analyzed and discussed in recent lease sale EISs (MMS, 2007b, 2008; BOEMRE, 2011a,b).

A large oil spill (WCD) could potentially affect air quality by introducing VOCs through

evaporation from the slick.  The extent and persistence of impacts would depend on the

meteorological and oceanographic conditions at the time and the effectiveness of spill response

measures.  Realtime wind and current data from the project area would be available at the time

of a spill and would be used to assess the fate and effects of VOCs released.  Additional air

quality impacts could occur if response measures included in situ burning of the floating oil.  

Burning would generate a plume of black smoke and result in emissions of NOx, SOx, CO, and

PM, as well as greenhouse gases.  However, in situ burning would occur only after authorization

from the USEPA.

Due to the lease area location (153 miles [246 km]) from the nearest shoreline (Louisiana), most

air quality impacts would occur in offshore waters with minimal chance to affect onshore air

quality.

C.1.2 Water Quality

There are no site‐specific water quality data for the lease area.  Due to the lease location in

deep, offshore waters, water quality is expected to be good, with low levels of contaminants.  As

noted in a recent lease sale EIS (MMS, 2007b), deepwater areas in the northern Gulf of Mexico

are relatively homogeneous with respect to temperature, salinity, and oxygen.  Kennicutt (2000)

noted that the deepwater region has little evidence of contaminants in the dissolved or

particulate phases of the water column.  However, there are localized occurrences of natural

seepage of oil, gas, and brines in near‐surface sediments and up through the water column.

The lease area is located approximately 233 miles (375 km) from the Macondo spill site.  Based

on the general circulation pattern seen in the Gulf of Mexico and satellite imagery (ESRI, 2010),

the surface slick from that discharge did not extend over the lease area during the spill.  The

existing water quality in the lease area is not expected to have been affected by the Macondo

release.

IPFs potentially affecting water quality are effluent discharges and two types of accidents ‐ 

a small fuel spill and a large oil spill (WCD).

Impacts of Effluent Discharges

In general, turbid water can be expected to extend between a few hundred meters and several

kilometers down current from the discharge point for water‐based drilling muds and cuttings.  

SBMs will be collected on the rig and either reused by the vendor, or transported to Port

Fourchon for recycling and/or disposal in an approved facility.  Cuttings wetted with SBMs will

be discharged to the seafloor in accordance with the NPDES permit.  All NPDES permit

limitations and requirements will be met.  There will be no persistent impacts on water quality

in the lease area (National Research Council, 1983; Neff, 1987; Neff et al., 2000).  
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 22

Treated sanitary and domestic wastes, including those from support vessels, may have a slight

transient effect on water quality in the immediate vicinity of these discharges.  All NPDES permit

limitations and requirements and USCG regulations (as applicable) will be met, therefore, little

or no impact on water quality is anticipated.

Deck drainage includes all effluents resulting from rain, deck washings, and runoff from curbs,

gutters, and drains, including drip pans in work areas.  Rainwater that falls on uncontaminated

areas of the drilling rig will flow overboard without treatment.  However, rainwater that falls on

the drilling rig deck and other areas such as chemical storage areas and places where equipment

is exposed will be collected and oil and water separated to meet NPDES permit requirements.  

Based on adherence to permit limits and applicable regulations, little or no impact on water

quality is anticipated.

Other discharges in accordance with the NPDES permit, such as desalination unit brine and

uncontaminated cooling water, fire water, and ballast water are expected to be diluted rapidly,

resulting in little or no impact on water quality.

Impacts of a Small Fuel Spill

Potential impacts of a small spill on water quality are expected to be consistent with those

analyzed and discussed in recent EISs (MMS, 2007b, 2008; BOEMRE, 2011a,b).  The probability

of a small spill would be minimized by Anadarko’s preventative measures during routine

operations, including fuel transfer.  In the unlikely event of a spill, implementation of Anadarko’s

OSRP will potentially help mitigate and reduce the impacts.  EP Section H provides detail on spill

response measures in addition to the summary information provided in this EIA.  Given the open

ocean location of the lease area, the extent and duration of water quality impacts from a small

spill would not be significant.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the

concentrations of petroleum hydrocarbons and their degradation products.  The extent and

persistence of impacts would depend on the meteorological and oceanographic conditions at

the time and the effectiveness of spill response measures.  However, it is estimated that over

90% of a small diesel spill would be evaporated or dispersed within 24 hours (see Section A.9.2).  

The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha (1.2 to 12 ac)

depending on sea state and weather conditions.

The water‐soluble fractions of diesel are dominated by two‐ and three‐ringed PAHs, which are

moderately volatile (National Research Council, 2003).  The constituents of these oils are light to

intermediate in molecular weight and can be readily degraded by aerobic microbial oxidation.  

Diesel is so light that it is not possible for the oil to sink and pool on the seafloor.  Diesel

dispersed in the water column can adhere to suspended sediments, but this generally occurs

only in coastal areas with high suspended solid loads (National Research Council, 2003) and

would not be expected to occur to any appreciable degree in offshore waters of the Gulf of

Mexico.  Diesel oil is readily and completely degraded by naturally occurring microbes

(NOAA, 2006).

A small fuel spill would not affect coastal water quality because the spill would not be expected

to make landfall or reach coastal waters due to both response efforts that would be undertaken

as well as natural attenuation (see Section A.9.2).
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Environmental Impact Analysis Page 23

Impacts of a Large Oil Spill (WCD)

Potential impacts of a large oil spill on water quality are expected to be consistent with those

analyzed and discussed in recent lease sale EISs (MMS, 2007b, 2008).  A large spill would affect

water quality by producing a slick on the water surface and increasing the concentrations of

petroleum hydrocarbons and their degradation products.  The extent and persistence of impacts

would depend on the meteorological and oceanographic conditions at the time and the

effectiveness of spill response measures.  Most of the oil would be expected to form a slick at

the surface, although new information from the Macondo spill indicates that plumes of

submerged oil droplets can be produced when subsea dispersants are applied at the wellhead

(Camilli et al., 2010; Hazen et al., 2010; Joint Analysis Group, 2010a,b,c).  However, dispersants

would be applied only after approval from the USEPA.  Small droplets in the water may adhere

to suspended sediment and be removed from the water column (Operational Scientific Advisory

Team [OSAT], 2010).

Due to the lease area location (153 miles or 246 km from the nearest shoreline [Louisiana]), it is

expected that most water quality impacts would occur in offshore waters, especially in the

event of a spill lasting less than 30 days (Table 3).  

C.2 Seafloor Habitats and Biota

Water depth at the proposed SHLs range is 1,779 m (5,838 ft).  The seafloor dips less than 1o to

the southwest and to the east at the proposed wellsites C and D respectively.  WR 51 lies

generally within an area of irregular seafloor but shows no evidence of instability. The

immediate regions around the proposed well locations have no evidence of seafloor instability

within 610 m (2,000 ft) of the wellsites. No areas of possible hard bottom or microseepages

were seen within 610 m (2,000 ft) of these wellsites (AOA Geophysics Inc., 2011).   

Based on the absence of hard bottom areas detected by side‐scan sonar during the Site

Clearance Survey, the seafloor is expected to consist mainly of soft bottom communities.  The

Site Clearance Survey did not identify any features that could support high‐density deepwater

benthic communities within 610 m (2,000 ft) of the wellsites.  No areas of gaseous sediments or

possible hydrocarbon seepage were defined in the study area, and the presence of

chemosynthetic communities is considered low (AOA Geophysics, Inc., 2011).  If an anchored

semisubmersible is used, fault scarps that occur within the anchor touchdown zones should be

avoided.  In addition, there are five sites, two in the notional anchor touchdown area

(1,524 to 3,962 m [5,000 to 13,000 ft]) and three in the additional 305 m (1,000 ft) buffer area

around location C, and four sites, one in the notional anchor touchdown area (1,524 to 3,962 m

[5,000 to 13,000 ft]) and one in the additional 305 m (1,000 ft) buffer area around location D

that are interpreted to have potential seepage of hydrocarbons which may host high‐density

chemosynthetic communities.  These features must be avoided by 152 m (500 ft) in accordance

with NTL 2009‐G40.

C.2.1 Soft Bottom Benthic Communities

There are no site‐specific benthic community data from the lease area.  However, data from the

Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology Study (Wei, 2006;

Rowe and Kennicutt, 2009) can be used to describe typical benthic communities in the area.  

Table 4 summarizes data from the B1 station, 24 mi (39 km) away in water depth slightly greater
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 24

than that of the wellsites C and D, and station NB3 in more comparable depth at 1,874 m

(6,148 ft).  Sediments at the NB3 station were predominantly clay (57.6%) and silt (31.8%).

Table 4. Benthic community data from stations near the lease area and in greater water depths

and more distant stations in more similar depths sampled during the Northern Gulf of

Mexico Continental Slope Habitats and Benthic Ecology Study (Adapted from:

Wei, 2006; Rowe and Kennicutt, 2009).  

Abundance

Station

Distance to

Lease Area

(miles)

Water

Depth

(m)

Meiofauna

(individuals/m2)

Macroinfauna

(individuals/m2)

Megafauna

(individuals/ha)

B1 24 2,256 157,417 1,446 252

NB3 28 1,874 162,245 1,342 191

Meiofaunal and megafaunal abundances from Rowe and Kennicutt (2009); macroinfaunal abundance from

Wei (2006).

Densities of meiofauna (animals passing through a 0.5‐mm sieve but retained on a 0.062‐mm

sieve) in water depths representative of the lease area (1,779 m [5,837 ft]) typically range from

approximately 165,000 to 800,000 individuals/m2 (Rowe and Kennicutt, 2009).  Nematodes,

nauplii, and harpacticoid copepods were the three dominant meiofaunal groups, accounting for

about 90% of total abundance.  

The benthic macroinfauna is characterized by small mean individual sizes and low densities,

both of which reflect the meager primary production in Gulf of Mexico surface waters

(Wei, 2006).  Densities decrease exponentially with water depth.  Based on an equation

presented by Wei (2006), macroinfaunal densities in the water depths of the lease area are

expected to be about 1,800 individuals/m2

, or greater than the numbers for the closest locations

listed in Table 4.

Polychaetes are typically the most abundant macroinfaunal group on the northern Gulf of

Mexico continental slope, followed by amphipods, tanaids, bivalves, and isopods.  Wei (2006)

recognized four depth‐dependent faunal zones (1 through 4), two of which are divided

horizontally.  The lease area is in Zone 3W.  This zone, with stations in water depths of

1,875 to 3,008 m (6,152 to 9,869 ft), had the polychaetes Levinsenia uncinata, Paraonella

monilaris, and Tachytrypane sp. A; the bivalve Heterodonta sp.; and the isopod

Macrostylis “256” as the most abundant taxa.

Megafaunal densities from nearby Station NB3 was 191 individuals/ha (Table 4).  Densities of

300 to 800 individuals/ha were reported from other stations located at a depth range similar to

that of the lease area.  Common megafauna included motile groups such as decapods,

ophiuroids, holothurians, and demersal fishes, as well as sessile groups such as sponges and

anemones.

Bacteria also are an important component in terms of biomass and cycling of organic carbon

(Cruz‐Kaegi, 1998).  Bacterial biomass at the depth range of the lease area typically is about

1 to 2 g C/m2 in the top 15 cm of sediments (Rowe and Kennicutt, 2009).

IPFs potentially affecting benthic communities are physical disturbance to the seafloor, effluent

discharges (drilling muds and cuttings), and a large oil spill (WCD) resulting from a well blowout
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 25

at the seafloor.  A small fuel spill would not affect benthic communities because the diesel fuel

would float and dissipate on the sea surface.

Physical Disturbance to the Seafloor

In water depths such as are encountered in the lease area, DP drillships or semisubmersibles

disturb the seafloor only around the wellbore (SHL) where the bottom template and blowout

preventer are located.  Depending upon the specific well configuration, this area is generally

about 0.25 ha (0.62 ac).  An anchored semisubmersible will cause physical compaction of the

seafloor beneath the anchors, and the anchor chains or lines can disturb the bottom as they

move about.  This type of bottom disturbance is called the “anchor sweep” and is formed by the

swing arc of anchor lines scraping across the bottom.  Anchored semisubmersibles disturb

approximately 2 to 3 ha (5 to 7 ac) of seafloor at each wellsite, depending on the number of

anchors and their mooring configurations (MMS, 2007b).

The areal extent of these impacts from both DP or anchored drilling rigs will be small compared

to the lease area itself, and these type soft bottom communities are ubiquitous along the

northern Gulf of Mexico continental slope (Gallaway, 1988; Gallaway et al., 2003; Rowe and

Kennicutt, 2009).  Impacts from the physical disturbance of the seafloor during this project will

have no significant impact on soft bottom benthic communities in the region.

Impacts of Effluent Discharges

Drilling muds and cuttings are the only effluents that are likely to affect benthic communities.  

During initial well interval(s) before the marine riser is set, cuttings and seawater‐based “spud

mud” will be released at the seafloor.  Excess cement slurry will also be released at the seafloor

during casing installation for the riserless portion of the drilling operations.  Cement slurry

components typically include cement mix and some of the same chemicals used in water‐based

drilling muds (Boehm et al., 2001).  The main impacts will be burial and smothering of benthic

organisms within several meters to tens of meters around the wellbore.  Soft bottom sediments

disturbed by cuttings, drilling muds, and cement slurry will eventually be recolonized through

larval settlement and migration from adjacent areas.  Because some deep‐sea biota grow and

reproduce slowly, recovery may require several years.

Discharges of washed SBM cuttings from the rig may affect benthic communities, primarily

within several hundred meters of the wellsite.  The fate and effects of SBM cuttings have been

reviewed by Neff et al. (2000), and monitoring studies have been conducted in the Gulf of

Mexico by Continental Shelf Associates, Inc. (2004, 2006).  In general, washed cuttings with

adhering SBMs tend to clump together and form thick cuttings piles close to the drillsite.  Areas

of SBM cuttings deposition may develop elevated organic carbon concentrations and anoxic

conditions (Continental Shelf Associates, Inc., 2006).  Where SBM cuttings accumulate in

concentrations of approximately 1,000 mg/kg or higher, benthic infaunal communities may be

adversely affected due to both the toxicity of the base fluid and organic enrichment (with

resulting anoxia) (Neff et al., 2000).  Infaunal numbers may increase and diversity may decrease

as opportunistic species that tolerate low oxygen and high H2S predominate (Continental Shelf

Associates, Inc., 2006).  As the base synthetic fluid is decomposed by microbes, the area will

gradually return to pre‐drilling conditions.  Disturbed sediments will be recolonized through

larval settlement and migration from adjacent areas.
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 26

The areal extent of impacts from drilling discharges will be small.  Assuming a typical effect

radius of 500 m (1,640 ft), the affected area around each wellsite would represent about 3% of

the seafloor within a lease block.  Soft bottom communities are ubiquitous along the northern

Gulf of Mexico continental slope (Gallaway, 1988; Gallaway et al., 2003; Rowe and

Kennicutt, 2009).  Impacts from drilling discharges during this project will have no significant

impact on soft bottom benthic communities in the region.

Impacts of a Large Oil Spill (WCD)

The most likely effects of a subsea blowout on benthic communities would be within a few

hundred meters of the wellsite.  The MMS (2007b) estimated that a severe subsurface blowout

could resuspend and disperse sediments within a 300‐m (984‐ft) radius.  While coarse sediments

(sands) would probably settle at a rapid rate within 400 m (1,312 ft) from the blowout site, fine

sediments (silts and clays) could be resuspended for more than 30 days and dispersed over a

much wider area.  Based on previous studies, surface sediments at the project area are assumed

to largely be silt and clay (Rowe and Kennicutt, 2009).

Recent lease sale EISs (MMS, 2007a, 2008) indicated that oil spills would be unlikely to affect

benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the spill

location.  However, during the Macondo spill, subsurface plumes were reported at a water

depth of about 1,100 m (3,600 ft), extending at least 22 miles (35 km) from the wellsite and

persisting for more than a month (Camilli et al., 2010).  The subsurface plumes apparently

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c).  While the

behavior and impacts of subsurface plumes are not well known, a subsurface plume could

contact the seafloor and affect benthic communities beyond the 300‐m (984‐ft) radius

estimated by MMS (2007a, 2008), depending on its extent, trajectory, and persistence.  This

contact could result in smothering and/or toxicity to benthic organisms.  The affected area

would be recolonized by benthic organisms over a period of months to years (National Research

Council, 2003).

C.2.2 High‐Density Deepwater Benthic Communities

As defined by NTL 2009‐G40, high‐density deepwater benthic communities are features or areas

that could support high‐density chemosynthetic communities, or features or areas that could

support high‐density deepwater corals and other associated high‐density hard bottom

communities.  Chemosynthetic communities were discovered in the central Gulf of Mexico in

1984 and have been studied extensively (MacDonald, 2002).  Deepwater coral communities are

also known from numerous locations in the Gulf of Mexico (Brooke and Schroeder, 2007;

CSA International, Inc., 2007).  These communities occur almost exclusively on authigenic

carbonates created by chemosynthetic communities.

The nearest known chemosynthetic community site is located  approximately 52 miles (83 km)

north‐northwest of the lease area in Green Canyon Block 310.  The nearest identified deepwater

coral community is located in WR 269, approximately 16 miles (26 km) south‐southwest of the

lease area.

No mounds, depressions, or hard bottom features occur within a 2,000‐ft radius around the

proposed wellsites.  Therefore, the potential for high‐density chemosynthetic communities

within 2,000 ft of the proposed location is low (AOA Geophysics Inc., 2011).
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 27

IPFs potentially affecting high‐density deepwater benthic communities include physical

disturbance of the seafloor, effluent discharges (drilling muds and cuttings), and a large oil spill

(WCD) from a well blowout at the seafloor.  A small fuel spill would not affect benthic

communities because the diesel fuel would float and dissipate on the sea surface.

Physical Disturbance to the Seafloor

In water depths such as are encountered in the lease area, DP drillships or semisubmersibles

disturb the seafloor only around the wellbore (SHL) where the bottom template and blowout

preventer are located.  Depending upon the specific well configuration, this area is generally

about 0.25 ha (0.62 ac).  An anchored semisubmersible will cause physical compaction of the

seafloor beneath the anchors, and the anchor chains or lines can disturb the bottom as they

move about.  This type of bottom disturbance is called the “anchor sweep” and is formed by the

swing arc of anchor lines scraping across the bottom.  Anchored semisubmersibles disturb

approximately 2 to 3 ha (5 to 7 ac) of seafloor at each wellsite, depending on the number of

anchors and their mooring configurations (MMS, 2007b).

The areal extent of these impacts from both DP or anchored drilling rigs will be small, and

NTL 2009‐G40 requires that high‐density deepwater benthic communities and features or areas

that could support high‐density chemosynthetic communities, or deepwater corals communities

be avoided.  Impacts from the physical disturbance of the seafloor during this project should

have no impact on chemosynthetic or deepwater coral communities in the region.

Impacts of Effluent Discharges

The Site Clearance Survey (AOA Geophysics Inc., 2011) did not identify any features that could

support high‐density deepwater benthic communities within 610 m (2,000 ft) of the proposed

drilling locations, and the presence of chemosynthetic communities in the lease area is

considered remote.  Monitoring programs on the Gulf of Mexico continental slope have shown

that benthic impacts from drilling discharges typically are concentrated within about 500 m

(1,640 ft) of the wellsite, although detectable deposits may extend beyond this distance

(Continental Shelf Associates, Inc., 2004, 2006; Neff et al., 2005).  Because of the water depth of

the lease area, drilling discharges would be expected to result in thinner, more diffuse

accumulations on the seafloor than those documented in the literature.  Although small

amounts of cuttings particles may reach areas inhabited by high‐density deepwater benthic

communities, the discharges are not expected to result in significant impacts to these

communities.

Impacts of a Large Oil Spill (WCD)

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect

benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the spill

location.  However, during the Macondo spill, subsurface plumes were reported at a water

depth of about 1,100 m (3,600 ft), extending at least 22 miles (35 km) from the wellsite and

persisting for more than a month (Camilli et al., 2010).  The subsurface plumes apparently

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c).  While the

behavior and impacts of subsurface plumes are not well known, a subsurface plume could have

the potential to contact high‐density deepwater benthic communities beyond the 300‐m

(984‐ft) radius estimated by MMS (2007a, 2008), depending on its extent, trajectory, and
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persistence.  Potential impacts on sensitive resources would be an integral part of the decision

and approval process for the use of dispersants, and such approval would be obtained from the

USEPA prior to the use of dispersants.

The biological effects and expected fate of the oil remaining in the Gulf of Mexico from the

Deepwater Horizon blowout are still unknown due to the depth and magnitude of this event.  

Hazen et al. (2010) reported changes in plume hydrocarbon composition with distance from the

source.  Incubation experiments with environmental isolates demonstrated faster than expected

hydrocarbon biodegradation rates at 5 °C.  Based on these results, Hazen et al. (2010) suggested

the potential exists for intrinsic bioremediation of the oil plume in the deep water column

without substantial oxygen drawdown.

Potential impacts of oil on high‐density deepwater benthic communities are discussed in MMS

(2007b).  Although chemosynthetic communities live among hydrocarbon seeps, natural

seepage is very constant and occurs at low rates compared to the potential rates of oil release

from a blowout.  In addition, seep organisms also require unrestricted access to oxygenated

water at the same time as exposure to hydrocarbon energy sources (MacDonald, 2002).  Oil

droplets or oiled sediment particles could come into contact with chemosynthetic organisms or

deepwater corals.  As discussed by MMS (2007b), impacts could include loss of habitat,

biodiversity, and live coral coverage; destruction of hard substrate; change in sediment

characteristics; and reduction or loss of one or more commercial and recreational fishery

habitats.  Sublethal effects could be long‐lasting and affect the resilience of coral colonies to

natural disturbances (e.g., elevated water temperature and diseases).

The potential for a spill to affect deepwater corals is indicated by preliminary findings from a

recent (October 2010) survey of deepwater coral habitats near the Macondo spill site

(BOEMRE, 2010).  Government and academic researchers were working at a site 1,400 m

(4,600 ft) deep and approximately 7 miles (11 km) southwest of the Macondo wellhead when

they observed dead and dying corals with sloughing tissue and discoloration.  Much of the soft

coral observed in an area measuring about 15 to 40 m (50 to 130 ft) was covered by what

appeared to be a brown substance.  Out of 40 large corals, 90% were heavily affected and

showed dead and dying parts and discoloration.  Another site 400 m (1,312 ft) farther away had

a colony of stony corals similarly affected and partially covered with a similar brown substance.  

Until laboratory analyses are conducted, scientists cannot be certain what caused the impacts.  

Sediment and coral samples were collected with a remotely operated vehicle and brought to the

surface for analyses.  Further testing will also determine if the substance is oil, and if so,

whether it is consistent with the release from the Macondo spill.  

C.2.3 Designated Topographic Features

The block is not within or near a designated topographic feature or a no‐activity zone as

identified in NTL 2009‐G39.  The nearest designated topographic feature is Sweet Bank in Green

Canyon Block 90, located 66 miles (106 km) north‐northwest of the lease area.

There are no IPFs associated with either routine operations or accidents that could cause

impacts to designated topographic features due to the distance from the lease area.  A small

fuel spill would float and dissipate on the surface and would not reach these seafloor features.

In the event of an oil spill from a well blowout, a surface slick would not contact these seafloor

features.  If a subsurface plume were to occur, impacts on these features would be unlikely due
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to the distance and the difference in water depth.  Near‐bottom currents in the region are

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume

up onto the continental shelf edge.

C.2.4 Pinnacle Trend Area Live Bottoms

The lease area is not covered by the Live Bottom (Pinnacle Trend) Stipulation.  As defined by

NTL 2009‐G39, the nearest pinnacle trend is Main Pass Block 290, which lies 248 miles (399 km)

northeast from the lease area.  

There are no IPFs associated with either routine operations or accidents that could cause

impacts to pinnacle trend area live bottoms due to the distance from the lease area.  A small

fuel spill would float on the surface and would not reach these seafloor features.

In the event of an oil spill from a well blowout, a surface slick would not contact these seafloor

features.  If a subsurface plume were to occur, impacts on these features would be unlikely due

to the distance and the difference in water depth.  Near‐bottom currents in the region are

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume

up onto the continental shelf edge.

C.2.5 Eastern Gulf Live Bottoms

The lease area is not covered by the Live Bottom (Low‐Relief) Stipulation, which applies to

Eastern Gulf of Mexico Planning Area leases in water depths of 100 m (328 ft) or less.  The

nearest block covered by the live bottom stipulation, as defined by NTL 2009‐G39, is

Destin Dome Block 573, approximately 288 miles (464 km) north‐northeast of the lease area.

There are no IPFs associated with either routine operations or accidents that could cause

impacts to eastern Gulf live bottom areas due to the distance from the lease area.  A small fuel

spill would float and dissipate on the surface and would not reach these seafloor features.

In the event of an oil spill from a well blowout, a surface slick would not contact these seafloor

features.  If a subsurface plume were to occur, impacts on these features would be unlikely due

to the distance and the difference in water depth.  Near‐bottom currents in the region are

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume

up onto the continental shelf.

C.3 Threatened, Endangered, and Protected Species and Critical Habitat

This section discusses species listed as endangered or threatened under the Endangered Species

Act (ESA).  In addition, it includes all marine mammal species in the region, which are protected

under the Marine Mammal Protection Act (MMPA).

Endangered or threatened species that may occur in the project area and/or along the northern

Gulf Coast are listed in Table 5.  The table also indicates the location of critical habitat

(if designated in the Gulf of Mexico).  Critical habitat is defined as (1) specific areas within the

geographical area occupied by the species at the time of listing, if they contain physical or

biological features essential to conservation, and those features may require special

management considerations or protection; and (2) specific areas outside the geographical area

occupied by the species if the agency determines that the area itself is essential for

conservation.  The National Marine Fisheries Service (NMFS) has jurisdiction for ESA‐listed
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cetaceans, sea turtles, and fishes in the Gulf of Mexico.  The USFWS has jurisdiction for

ESA‐listed birds and the West Indian manatee.

Table 5. Federally‐listed endangered and threatened species potentially occurring in the lease

area and along the northern Gulf Coast.

Potential Presence

Species Scientific Name Status Lease

Area Coastal

Critical Habitat

Designated in

Gulf of Mexico

Marine Mammals

Sperm whale Physeter macrocephalus E X  ‐‐  None

West Indian manatee Trichechus manatus latirostris E  ‐‐  X Florida (Peninsular)

Blue whale Balaenoptera musculus E Xa  ‐‐  None

Fin whale Balaenoptera physalus E Xa  ‐‐  None

Humpback whale Megaptera novaeangliae E Xa  ‐‐  None

North Atlantic right whale Eubalaena glacialis E Xa  ‐‐  None

Sei whale Balaenoptera borealis E Xa  ‐‐  None

Sea Turtles

Loggerhead turtle Caretta caretta T X X None

Green turtle Chelonia mydas T, E

b X X None

Leatherback turtle Dermochelys coriacea E X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Birds

Piping Plover Charadrius melodus T  ‐‐  X

Coastal Texas, Louisiana,

Mississippi, Alabama,

and Florida (Panhandle)

Whooping Crane Grus americana E  ‐‐  X

Coastal Texas

(Aransas National

Wildlife Refuge)

Fishes

Gulf sturgeon Acipenser oxyrinchus desotoi T  ‐‐  X

Coastal Louisiana,

Mississippi, Alabama,

and Florida (Panhandle)

Smalltooth Sawfish Pristis pectinata E  ‐‐  X Southwest Florida and

the Florida Keys

Invertebrates

Elkhorn coral Acropora palmata E  ‐‐  X Flower Garden Banks

Terrestrial Mammals

Beach mice (Alabama,

Choctawhatchee,

Perdido Key, St. Andrew)

Peromyscus polionotus E  ‐‐  X Alabama and Florida

(Panhandle) beaches

Abbreviations: E = endangered; T = threatened.   a

   The blue, fin, humpback, North Atlantic right, and sei whales are rare or extralimital in the Gulf of Mexico and are unlikely

to be present in the lease area. b

   The green sea turtle is threatened, except for the Florida breeding population, which is listed as endangered.

As mandated by the ESA, BOEMRE consulted NMFS and the USFWS on possible and potential

impacts from the proposed leasing in the Gulf of Mexico on endangered/threatened species and

their designated critical habitat (MMS, 2007a,b).  A Biological Assessment was prepared for each

consultation.  The formal ESA consultation with NMFS was concluded with receipt of the

Biological Opinion on 3 July 2007 (NMFS, 2007).  The Biological Opinion concludes that the

proposed lease sales and associated activities in the Five‐Year Leasing Plan for Western and

Central Planning Areas 2007‐2012 are not likely to jeopardize the continued existence of

threatened and endangered species under NMFS jurisdiction or destroy or adversely modify

designated critical habitat.  The informal ESA consultation with USFWS was concluded with a

letter dated 14 September 2007.  The USFWS concurred with MMS’s determination that
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proposed actions of the current Five‐Year Leasing Plan were not likely to adversely affect

threatened/endangered species or designated critical habitat under USFWS jurisdiction.  

Following the Macondo spill, BOEMRE requested to reinitiate an ESA consultation with both

NMFS and USFWS on 30 July 2010.  The NMFS responded with a letter to BOEMRE on

24 September 2010, and the USFWS responded with a letter to BOEMRE on 27 September 2010.  

At present, the NMFS and USFWS have placed the consultation process on hold because they

feel the environmental baseline information needs to be updated for the post‐Macondo spill

environment based on the results of the Natural Resource Damage Assessment (NRDA) process.  

The NRDA data have yet to be released, and the existing consultation remains in effect

(BOEMRE, 2011a).  The existing consultation recognizes that BOEMRE‐required mitigations and

other reasonable and prudent measures should reduce the likelihood of impacts from all

BOEMRE‐authorized activities in the Gulf of Mexico.

Coastal endangered or threatened species that may occur along the northern Gulf Coast include

the West Indian manatee, Piping Plover, Whooping Crane, Gulf sturgeon, and four subspecies of

beach mice.  Critical habitat has been designated for all of these species as indicated in Table 5

and discussed in individual sections.

Two other coastal species (Bald Eagle and Brown Pelican) are discussed in the MMS (2007b)

lease sale EIS are no longer listed as endangered or threatened.  These species are discussed

here under Coastal and Marine Birds.

The sperm whale and five species of sea turtles are the only endangered or threatened species

likely to occur at or near the lease area.  No critical habitat has been designated for these

species in the Gulf of Mexico.

Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic right

whale, and sei whale) also have been reported from the Gulf of Mexico but are considered rare

or extralimital there (Würsig et al., 2000).  No critical habitat has been designated for these

species in the Gulf of Mexico.

C.3.1 Sperm Whale (Endangered)

The only endangered marine mammal likely to be present at or near the project area is the

sperm whale (Physeter macrocephalus).  Resident populations of sperm whales occur within the

Gulf of Mexico.  A species description is presented in a recent lease sale EIS (MMS, 2007b).  Gulf

of Mexico sperm whales are classified as an endangered species and a “strategic stock” (defined

as a stock that may have unsustainable human‐caused impacts) by NOAA Fisheries (Waring

et al., 2009).  No critical habitat for the sperm whale has been designated in the Gulf of Mexico.

The distribution of sperm whales in the Gulf of Mexico is correlated with mesoscale physical

features such as eddies associated with the Gulf of Mexico Loop Current (Jochens et al., 2008).  

Sperm whale populations in the north‐central Gulf of Mexico are present there throughout the

year (Davis et al., 2000).  Results of a multi‐year tracking study show female sperm whales

typically concentrated along the upper continental slope between the 200‐ and 1,000‐m

(656‐ and 3,280‐ft) depth contours (Jochens et al., 2008).  Male sperm whales were more

variable in their movements and were documented in water depths greater than 3,000 m

(9,843 ft).  Generally, groups of sperm whales sighted in the Gulf of Mexico during the

MMS‐funded Sperm Whale Seismic Study (SWSS) consisted of mixed‐sex groups comprising

adult females and immatures, and groups of bachelor males.  Typical group size for mixed
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groups was 10 individuals (Jochens et al., 2008).  SWSS results show that sperm whales transit

through the vicinity of the lease area.  Movements of satellite‐tracked individuals suggest that

this area of the Gulf continental slope is within the home range of the Gulf of Mexico population

(within the 95% utilization distribution) (Jochens et al., 2008).

IPFs potentially affecting sperm whales include drilling rig presence, noise, and lights; support

vessel and helicopter traffic; and two types of accidents – a small fuel spill and a large oil spill

(WCD).  Effluent discharges are likely to have negligible impacts on sperm whales due to rapid

dispersion, the small area of ocean affected, the intermittent nature of the discharges, and the

mobility of these marine mammals.  Compliance with NTL 2007‐G03 will minimize the potential

for marine debris‐related impacts on sperm whales.

Current threats to sperm whale populations worldwide are discussed in a final recovery plan for

the sperm whale recently published by NOAA (NMFS, 2010a).  Threats are defined as “any factor

that could represent an impediment to recovery,” and include fisheries interactions,

anthropogenic noise, vessel interactions, contaminants and pollutants, disease, injury from

marine debris, research, predation and natural mortality, direct harvest, competition for

resources, loss of prey base due to climate change and ecosystem change, and cable laying.  In

the Gulf of Mexico, the impacts from many of these threats are identified as either low or

unknown (BOEMRE, 2011a,b).

Impacts of Drilling Rig Presence, Noise, and Lights

Noise from routine drilling activities has the potential to disturb sperm whales.  Sperm whales

appear to have good low‐frequency hearing, but the available data do not indicate a consistent

response to anthropogenic noise (Jochens et al., 2008).  Noise intensity associated with drilling

is relatively weak, and the noise exposure of an individual animal would be transient.  There are

other OCS facilities and activities near the lease area, and the region as a whole has a large

number of similar noise sources.  Due to the limited scope and short duration of drilling

activities, this project would represent a small temporary contribution to the overall noise

regime.

NMFS analyzed the potential for impacts of drilling‐related noise on sperm whales in its

Biological Opinion for the Gulf of Mexico Oil and Gas Activities: Five‐Year Leasing Plan for

Western and Central Planning Areas 2007‐2012 (NMFS, 2007).  The analysis noted that

semisubmersible drilling rigs emit low sound source levels and concluded that drilling is not

expected to produce amplitudes sufficient to cause hearing or behavioral effects in sperm

whales; therefore, these effects are insignificant (NMFS, 2007).

Drilling rig lighting and rig presence are not identified as IPFs for sperm whales in recent lease

sale EISs (MMS, 2007b, 2008) or the NMFS (2007) Biological Opinion.

Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb sperm whales, and there is also a risk of vessel

strikes, which are identified as a threat in the recovery plan for this species (NMFS, 2010a).  Data

concerning the frequency of vessel strikes are presented in a recent lease sale EIS

(MMS, 2007b).  To reduce the potential for vessel strikes, MMS issued NTL 2007‐G04, which

recommends protected species identification training and that vessel operators and crews

maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid
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striking protected species, and requires operators to report sightings of any injured or dead

protected species.  When whales are sighted, vessel operators and crews are required to

attempt to maintain a distance of 91 m (300 ft) or greater whenever possible.  Vessel operators

are required to reduce vessel speed to 10 knots or less when mother/calf pairs, pods, or large

assemblages of cetaceans are observed near an underway vessel, when safety permits.  

Compliance with this NTL will minimize the likelihood of vessel strikes as well as reduce the

chance for disturbing sperm whales.

NMFS (2007) analyzed the potential for vessel strikes and harassment of sperm whales.  With

implementation of the mitigation measures in NTL 2007‐G04, NMFS concluded that the

likelihood of collisions between vessels and sperm whales would be reduced to insignificant

levels.  NMFS concluded that the observed avoidance of passing vessels by sperm whales is an

advantageous response to avoid a potential threat and is not expected to result in any

significant effect on migration, breathing, nursing, breeding, feeding, or sheltering to individuals,

or have any consequences at the level of the population.  With implementation of the vessel

strike avoidance measures requirement to maintain a distance of 90 m (295 ft) from sperm

whales, the NMFS concluded that the potential for harassment of sperm whales would be

reduced to discountable levels.

Helicopter traffic also has the potential to disturb sperm whales.  Smultea et al. (2008)

documented responses of sperm whales offshore Hawaii to fixed wing aircraft flying at an

altitude of 245 m (800 ft).  A reaction to the initial pass of the aircraft was observed during

3 (12%) of 24 sightings.  All three reactions consisted of a hasty dive and occurred at less than

360 m (1,180 ft) lateral distance from the aircraft.  Additional reactions were seen when aircraft

circled certain whales to make further observations.  Based on other studies of cetacean

responses to sound, the authors concluded that the observed reactions to brief overflights by

the aircraft were short‐term and probably of no long‐term biological significance.

While flying offshore in the Gulf of Mexico, helicopters maintain altitudes above 213 m (700 ft)

during transit to and from the working area.  In the event that a whale is seen during transit, the

helicopter will not approach or circle the animals.  Although responses are possible (Smultea

et al., 2008), the NMFS (2007) concluded that this altitude would minimize the potential for

disturbing sperm whales.  Therefore, no significant impacts are expected.

Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals including sperm whales are discussed in recent lease

sale EISs (MMS, 2007b, 2008) and by NMFS (2007).  Oil impacts on marine mammals are

discussed by Geraci and St. Aubin (1990).  For this EP, there are no unique site‐specific issues

with respect to spill impacts on these animals that were not analyzed in the previous

documents.

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during

routine operations including fuel transfer.  In the unlikely event of a spill, implementation of

Anadarko’s OSRP will mitigate and lessen the potential for impacts on sperm whales.  Given the

open ocean location of the lease area, the duration of a small spill and opportunity for impacts

to occur would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the

concentrations of petroleum hydrocarbons and their degradation products.  The extent and
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persistence of impacts would depend on the meteorological and oceanographic conditions at

the time and the effectiveness of spill response measures.  Section A.9.2 discusses the likely fate

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally

within 24 hours.  The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha

(1.2 to 12 ac), depending on sea state and weather conditions.

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation,

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and

noise of response vessels and aircraft (Marine Mammal Commission [MMC], 2010).  However,

due to the limited areal extent and short duration of water quality impacts from a small fuel

spill, as well as the mobility of sperm whales, no significant impacts would be expected.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine mammals including sperm whales are discussed in recent EISs

(MMS, 2007b, 2008) and by NMFS (2007).  For this EP, there are no unique site‐specific issues

with respect to spill impacts on these animals.

Impacts of oil spills on sperm whales can include direct impacts from oil exposure, as well as

indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and

dispersants) (MMC, 2010).  Direct physical and physiological effects can include skin irritation,

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of

toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey; and stress from

the activities and noise of response vessels and aircraft.  Complications of the above may lead to

dysfunction of immune and reproductive systems, physiological stress, declining physical

condition, and death.  Behavioral responses can include displacement of animals from prime

habitat, disruption of social structure, changing prey availability and foraging distribution and/or

patterns, changing reproductive behavior/productivity, and changing movement patterns or

migration (MMC, 2010).

In the event of a large spill, the level of vessel and aircraft activity associated with spill response

could disturb sperm whales and potentially result in vessel strikes, entanglement, or other injury

or stress.  Response vessels would operate in accordance with NTL 2007‐G04 to reduce the

potential for striking or disturbing these animals.

C.3.2 West Indian Manatee (Endangered)

Most of the manatee population is located in peninsular Florida (USFWS, 2001).  Manatee

sightings in Louisiana have increased as the species extends its presence farther west of Florida

in the warmer months (Wilson, 2003).  A species description is presented in a recent lease sale

EIS (MMS, 2007b) and in the recovery plan for this species (USFWS, 2001).

IPFs potentially affecting manatees include support vessel and helicopter traffic and a large oil

spill (WCD).  A small fuel spill in the lease area would be unlikely to affect manatees, as the lease

area is approximately 153 miles (246 km) from the nearest shoreline (Louisiana).  As explained in

Section A.9.2, a small fuel spill would not be expected to make landfall or reach coastal waters

prior to breaking up.  Compliance with NTL 2007‐G03 will minimize the potential for marine

debris‐related impacts on manatees.
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Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb manatees, and there is also a risk of vessel

strikes, which are identified as a threat in the recovery plan for this species (USFWS, 2001).  To

reduce the potential for vessel strikes, MMS issued NTL 2007‐G04, which recommends

protected species identification training and that vessel operators and crews maintain a vigilant

watch for marine mammals and slow down or stop their vessel to avoid striking protected

species, and requires operators to report sightings of any injured or dead protected species.  

Compliance with this NTL will minimize the likelihood of vessel strikes, and no significant

impacts on manatees are expected.

Helicopter traffic also has the potential to disturb manatees.  Rathbun (1988) reported that

manatees were disturbed more by helicopters than by fixed‐wing aircraft; however, the

helicopter was flown at a relatively low altitude of 20 to 160 m (66 to 525 ft).  Helicopters used

in support operations maintain a minimum altitude of 213 m (700 ft) while in transit offshore,

305 m (1,000 ft) over unpopulated areas or across coastlines, and 610 m (2,000 ft) over

populated areas and sensitive habitats such as wildlife refuges and park properties.  This

mitigation measure will minimize the potential for disturbing manatees, and no significant

impacts are expected.

Impacts of a Large Oil Spill (WCD)

In the event that manatees were exposed to oil, effects could include direct impacts from oil

exposure, as well as indirect impacts due to response activities and materials (e.g., vessel traffic,

noise, and dispersants) (MMC, 2010).  Direct physical and physiological effects can include skin

irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes;

inhalation of toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey

(or contaminated vegetation, in the case of manatees); and stress from the activities and noise

of response vessels and aircraft.  Complications of the above may lead to dysfunction of immune

and reproductive systems, physiological stress, declining physical condition, and death.  

Behavioral responses can include displacement of animals from prime habitat, disruption of

social structure, changing prey availability and foraging distribution and/or patterns, changing

reproductive behavior/productivity, and changing movement patterns or migration

(MMC, 2010).

In the event that a large spill reached coastal waters where manatees were present, the level of

vessel and aircraft activity associated with spill response could disturb manatees and potentially

result in vessel strikes, entanglement, or other injury or stress.  Response vessels would operate

in accordance with NTL 2007‐G04 to reduce the potential for striking or disturbing these

animals, and therefore no significant impacts are expected.

C.3.3 Endangered Mysticete Whales

Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic right

whale, and sei whale) also have been reported from the Gulf of Mexico but are considered rare

or extralimital there (Würsig et al., 2000).  No critical habitat has been designated for these

species in the Gulf of Mexico.   

Due to the rare occurrence of these whales in the Gulf of Mexico and the limited scope and

duration of the project, it is highly unlikely that any endangered mysticete would come into
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contact with any project activities, either routine operations or accidents.  NMFS did not include

any of these mysticete whales as affected species in its Biological Opinion (NMFS, 2007).  

Potential impacts are analyzed in recent lease sale EISs (MMS, 2007b, 2008), and those analyses

are incorporated by reference.  If any of these whales were present in the area, potential

impacts would be the same as those discussed below in Section C.3.4.

C.3.4 Non‐Endangered Marine Mammals (Protected)

Excluding the seven endangered species that have been cited previously, there are 22 additional

species of marine mammals that may be found in the Gulf of Mexico.  This includes two

mysticete whales, the dwarf and pygmy sperm whales, 4 species of beaked whales, and

14 species of delphinids.  All marine mammals are protected species under the MMPA.  The

most common non‐endangered cetaceans in the deepwater environment are odontocetes such

as the pantropical spotted dolphin, spinner dolphin, and clymene dolphin.  A brief summary is

presented below, and additional information on these groups is presented in a recent lease sale

EIS (MMS, 2007b).

Mysticete whales.  Two non‐endangered mysticete whales are known from the Gulf of Mexico.  

The Bryde’s whale (Balaenoptera edeni) has been sighted most frequently along the 100‐m

(328‐ft) isobath (Davis and Fargion, 1996; Davis et al., 2000).  Most sightings have been made in

the DeSoto Canyon region and off western Florida, although there have been some in the

west‐central portion of the northeastern Gulf.  The minke whale (Balaenoptera acutorostrata) is

considered rare in the Gulf of Mexico, with the only confirmed records coming from strandings

(Würsig et al., 2000).  Based on the available data, it is possible that Bryde’s whales could occur

in the lease area.

Dwarf and pygmy sperm whales.  At sea, it is difficult to differentiate dwarf sperm whales

(Kogia sima) from pygmy sperm whales (Kogia breviceps), and sightings are often grouped

together as Kogia spp.  Both species have a worldwide distribution in temperate to tropical

waters.  In the Gulf of Mexico, both species occur primarily along the continental shelf edge and

in deeper waters off the continental shelf (Mullin et al., 1991).  Either species could occur in the

lease area.

Beaked whales.  Four species of beaked whales are known from the Gulf of Mexico.  They are

Blainville’s beaked whale (Mesoplodon densirostris), Cuvier’s beaked whale (Ziphius cavirostris),

Sowerby’s beaked whale (Mesoplodon bidens), and Gervais’ beaked whale (Mesoplodon

europaeus).  Stranding records in the Gulf of Mexico suggest that Gervais’ beaked whale is the

most common and Sowerby’s is extralimital.  Due to the difficulties of at‐sea identification,

beaked whales in the Gulf of Mexico are identified either as Cuvier’s beaked whales or are

grouped into an undifferentiated complex (Mesoplodon spp. and Ziphius spp.).  In the northern

Gulf of Mexico, they are broadly distributed in water depths greater than 1,000 m (3,281 ft) over

lower slope and abyssal landscapes (Davis et al., 2000).  Any of these species could occur in the

lease area.

Delphinids.  Fourteen species of delphinids are known from the Gulf of Mexico, including

Atlantic spotted dolphin (Stenella frontalis), bottlenose dolphin (Tursiops truncatus), clymene

dolphin (Stenella clymene), false killer whale (Pseudorca crassidens), Fraser’s dolphin

(Lagenodelphis hosei), killer whale (Orcinus orca), melon‐headed whale (Peponocephala electra),

pantropical spotted dolphin (Stenella attenuata), pygmy killer whale (Feresa attenuata),
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short‐finned pilot whale (Globicephala macrorhynchus), Risso’s dolphin (Grampus griseus),

rough‐toothed dolphin (Steno bredanensis), spinner dolphin (Stenella longirostris), and striped

dolphin (Stenella coeruleoalba).  Any of these species could occur in the lease area.  The most

common non‐endangered cetaceans in the deepwater environment are the pantropical spotted

dolphin, spinner dolphin, and clymene dolphin.

IPFs potentially affecting non‐endangered marine mammals include drilling rig presence, noise,

and lights; support vessel and helicopter traffic; and two types of accidents ‐ a small fuel spill

and a large oil spill (WCD).  Effluent discharges are likely to have negligible impacts on marine

mammals due to rapid dispersion, the small area of ocean affected, the intermittent nature of

the discharges, and the mobility of marine mammals.  Compliance with NTL 2007‐G03 will

minimize the potential for marine debris‐related impacts on marine mammals.

Impacts of Drilling Rig Presence, Noise, and Lights

Noise from routine drilling activities has the potential to disturb marine mammals.  Most

odontocetes (toothed whales and dolphins) use higher frequency sounds than the dominant low

frequencies produced by OCS drilling activities (Richardson et al., 1995).  Noise intensity

associated with drilling is relatively weak, and the noise exposure of an individual animal would

be transient.  There are other OCS facilities and activities near the lease area, and the region as a

whole has a large number of similar sources.  Due to the limited scope and short duration of

drilling activities, this project would represent a small temporary contribution to the overall

noise regime, and any short‐term impacts are not expected to be biologically significant to

marine mammal populations.

Drilling rig lighting and rig presence are not identified as IPFs for marine mammals in recent

lease sale EISs (MMS, 2007b, 2008).

Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb marine mammals, and there is also a risk of

vessel strikes.  Data concerning the frequency of vessel strikes are presented in a recent lease

sale EIS (MMS, 2007b).  To reduce the potential for vessel strikes, MMS issued NTL 2007‐G04,

which recommends protected species identification training and that vessel operators and

crews maintain a vigilant watch for marine mammals and slow down or stop their vessel to

avoid striking protected species, and requires operators to report sightings of any injured or

dead protected species.  Vessel operators and crews are required to attempt to maintain a

distance of 91 m (300 ft) or greater when whales are sighted and 45 m (150 ft) when small

cetaceans are sighted.  When cetaceans are sighted while a vessel is underway, vessels must

attempt to remain parallel to the animal’s course and avoid excessive speed or abrupt changes

in direction until the cetacean has left the area.  Vessel operators are required to reduce vessel

speed to 10 knots or less when mother/calf pairs, pods, or large assemblages of cetaceans are

observed near an underway vessel, when safety permits.  Compliance with NTL 2007‐G04 will

minimize the likelihood of vessel strikes as well as reduce the chance for disturbing marine

mammals, and therefore no significant impacts are expected.

Aircraft traffic also has the potential to disturb marine mammals (Würsig et al., 1998).  However,

while flying offshore, helicopters maintain altitudes above 213 m (700 ft) during transit to and

from the working area.  This altitude will minimize the potential for disturbing marine mammals,

and no significant impacts are expected (MMS, 2007b).
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Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008),

and oil impacts on marine mammals in general are discussed by Geraci and St. Aubin (1990).  For

this EP, there are no unique site‐specific issues with respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during fuel

transfer.  In the unlikely event of a spill, implementation of Anadarko’s OSRP is expected to

lessen the potential for impacts on marine mammals.  EP Section H provides detail on spill

response measures, along with a summary of those measures in this EIA.  Given the open ocean

location of the lease area, the limited duration of a small spill and response efforts, it is

expected that any impacts would be brief and minimal.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the

concentrations of petroleum hydrocarbons and their degradation products.  The extent and

persistence of impacts would depend on the meteorological and oceanographic conditions at

the time and the effectiveness of spill response measures.  Section A.9.2 discusses the likely fate

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally

within 24 hours.  The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha

(1.2 to 12 ac), depending on sea state and weather conditions.

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation,

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and

noise of response vessels and aircraft (MMC, 2010).  However, due to the limited areal extent

and short duration of water quality impacts from a small fuel spill, as well as the mobility of

marine mammals, no significant impacts would be expected.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine mammals are discussed in MMS (2000, 2007b, 2008).  For this

EP, there are no unique site‐specific issues.  Impacts of oil spills on marine mammals can include

direct impacts from oil exposure, as well as indirect impacts due to response activities and

materials (e.g., vessel traffic, noise, and dispersants) (MMC, 2010).  Direct physical and

physiological effects can include skin irritation, inflammation, or necrosis; chemical burns of

skin, eyes, and mucous membranes; inhalation of toxic fumes; ingestion of oil (and dispersants)

directly or via contaminated prey (or contaminated vegetation, in the case of manatees); and

stress from the activities and noise of response vessels and aircraft.  Complications of the above

may lead to dysfunction of immune and reproductive systems, physiological stress, declining

physical condition, and death.  Behavioral responses can include displacement of animals from

prime habitat, disruption of social structure, changing prey availability and foraging distribution

and/or patterns, changing reproductive behavior/productivity, and changing movement

patterns or migration (MMC, 2010).

In the event of a large spill, the level of vessel and aircraft activity associated with spill response

could disturb marine mammals and potentially result in vessel strikes, entanglement, or other

injury or stress.  Response vessels would operate in accordance with NTL 2007‐G04 to reduce

the potential for striking or disturbing these animals, and therefore no significant impacts are

expected.
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C.3.5 Sea Turtles (Endangered/Threatened)

Five species of endangered or threatened sea turtles may be found near the lease area.  

Leatherback (Dermochelys coriacea), Kemp's ridley (Lepidochelys kempii), and hawksbill

(Eretmochelys imbricata) turtles are endangered.  The loggerhead turtle (Caretta caretta) is

currently a threatened species; however, in March 2010, NMFS and USFWS proposed to list the

Northwest Atlantic Ocean population of loggerhead turtles as endangered (75 FR 12598).  The

green turtle (Chelonia mydas) is listed as threatened, except for the Florida and Pacific Coast of

Mexico breeding populations, which are listed as endangered.  Species descriptions are

presented in MMS (2007b).

The extent and scope of the Macondo spill represents new information not assessed in the

existing ESA Section 7 consultation under the current 5‐Year Program.  As a result of this new

information, BOEMRE reinitiated ESA Section 7 consultation on the existing Gulf of Mexico lease

sale EIS with NMFS and the USFWS on 30 July 2010.  The NMFS responded with a letter to

BOEMRE on 24 September 2010, and the USFWS responded with a letter to BOEMRE on

27 September 2010.  However, NMFS and the USFWS have placed the consultation process on

hold pending the results of the NRDA post‐Macondo spill data review, which has yet to be

released.  The existing consultation currently remains in effect (BOEMRE, 2011a).   

BOEMRE (2011a,b) reexamined the impacts analyses presented in MMS (2007b, 2008) for the

five sea turtle species that inhabit the Gulf of Mexico based on additional information and in

consideration of the Macondo spill.  No new information was found that would alter the

potential impacts on sea turtles described in previous EISs.  In most foreseeable cases, exposure

to hydrocarbons persisting in the sea following the dispersal of an oil slick will result in sublethal

impacts (e.g., decreased health, reproductive fitness, and longevity; and increased vulnerability

to disease) to sea turtles.

Leatherbacks and loggerheads are the most likely species to be present near the lease area as

adults.  Green, hawksbill, and Kemp’s ridley turtles are typically inner shelf and nearshore

species, unlikely to occur near the lease area as adults.  Hatchlings or juveniles of any of the sea

turtle species may be present in deepwater areas, including the lease area, where they may be

associated with Sargassum and other flotsam.

Sea turtle nesting in the northern Gulf of Mexico can be summarized by species as follows:

• Loggerhead turtles – Loggerheads nest in significant numbers along the Florida Panhandle

and, to a lesser extent, from Texas through Alabama (MMS, 2007b).  The nearest significant

nesting area of loggerhead turtles is found in Louisiana, on beaches within the Breton NWR;

• Green and leatherback turtles – Green and leatherback turtles infrequently nest on Florida

Panhandle beaches (Florida Fish and Wildlife Conservation Commission, 2010);

• Kemp’s ridley turtles – The main Kemp’s ridley nesting site is Rancho Nuevo beach,

Tamaulipas, Mexico (NMFS et al., 2010).  Kemp’s ridley turtles typically do not nest

anywhere near the project area, although there have been occasional reports of Kemp’s

ridleys nesting in Alabama (Share the Beach, 2010); and

• Hawksbill turtles – Hawksbills typically do not nest anywhere near the project area.

IPFs potentially affecting sea turtles include drilling rig presence, noise, and lights; support

vessel and helicopter traffic; and two types of accidents ‐ a small fuel spill and a large oil spill

(WCD).  Effluent discharges are likely to have negligible impacts on sea turtles due to rapid

dispersion, the small area of ocean affected, and the intermittent nature of the discharges.  
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Compliance with NTL 2007‐G03 will minimize the potential for marine debris‐related impacts on

sea turtles.

Impacts of Drilling Rig Presence, Noise, and Lights  

Offshore drilling activities produce a broad array of sounds at frequencies and intensities that

may be detected by sea turtles (Geraci and St. Aubin, 1987).  Potential impacts may include

behavioral disruption and temporary or permanent displacement from the area near the sound

source.  Certain sea turtles, especially loggerheads, may be attracted to offshore structures

(Lohoefener et al., 1990) and, thus, may be more susceptible to impacts from sounds produced

during routine operations.  Helicopters and service vessels may also affect sea turtles due to

machinery noise and/or visual disturbances.  The most likely impacts would be short‐term

behavioral changes such as diving and evasive swimming, disruption of activities, or departure

from the area.  Due to the limited scope and short duration of drilling activities, these

short‐term impacts are not expected to be biologically significant to sea turtle populations.

Artificial lighting can disrupt the nocturnal orientation of sea turtle hatchlings (Witherington,

1997; Tuxbury and Salmon, 2005).  However, hatchlings may rely less on light cues when they

are offshore than when they are emerging on the beach (Salmon and Wyneken, 1990).  The

NMFS (2007) concluded that the effects of lighting from offshore structures on sea turtles are

insignificant.

Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb sea turtles, and there is also a risk of vessel

strikes.  Data show that vessel traffic is one cause of sea turtle mortality in the Gulf of Mexico

(Lutcavage et al., 1997).  While adult sea turtles are visible at the surface during the day and in

clear weather, they can be difficult to spot from a moving vessel when resting below the water

surface, during nighttime, or during periods of inclement weather.  To reduce the potential for

vessel strikes, MMS issued NTL 2007‐G04, which recommends protected species identification

training and that vessel operators and crews maintain a vigilant watch for sea turtles and slow

down or stop their vessel to avoid striking protected species, and requires operators to report

sightings of any injured or dead protected species.  When sea turtles are sighted, vessel

operators and crews are required to attempt to maintain a distance of 45 m (150 ft) or greater

whenever possible.  Compliance with this NTL will minimize the likelihood of vessel strikes as

well as reduce the chance for disturbing sea turtles (NMFS, 2007).

Helicopter traffic also has the potential to disturb sea turtles.  However, while flying offshore,

helicopters maintain altitudes above 213 m (700 ft) during transit to and from the working area.  

This altitude will minimize the potential for disturbing sea turtles, and no significant impacts are

expected.

Impacts of a Small Fuel Spill

Potential spill impacts on sea turtles are discussed in recent EISs (MMS, 2007b, 2008) and the

NMFS Biological Opinion (NMFS, 2007).  For this EP, there are no unique site‐specific issues with

respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during fuel

transfer.  In the unlikely event of a spill, implementation of Anadarko’s OSRP is expected to

minimize potential impacts on sea turtles.  EP Section H provides detail on spill response

measures.  Given the open ocean location of the lease area, the duration of a small spill and

opportunity for impacts to occur would be very brief.
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A small fuel spill in offshore waters would produce a slick on the water surface and increase the

concentrations of petroleum hydrocarbons and their degradation products.  The extent and

persistence of impacts would depend on the meteorological and oceanographic conditions at

the time and the effectiveness of spill response measures.  Section A.9.2 discusses the likely fate

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally

within 24 hours.  The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha

(1.2 to 12 ac), depending on sea state and weather conditions.

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation,

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and

noise of response vessels and aircraft.  However, due to the limited areal extent and short

duration of water quality impacts from a small fuel spill, no significant impacts would be

expected.

A small fuel spill in the lease area would be unlikely to affect sea turtle nesting beaches, as the

lease area is 153 miles (246 km) from the nearest shoreline (Louisiana).  As explained in

Section A.9.2, a small fuel spill would not be expected to make landfall or reach coastal waters

prior to breaking up.

Impacts of a Large Oil Spill (WCD)

Impacts of oil spills on sea turtles can include direct impacts from oil exposure, as well as

indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and

dispersants).  Direct physical and physiological effects can include skin irritation, inflammation,

or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes and

smoke (e.g., from in situ burning of oil); ingestion of oil (and dispersants) directly or via

contaminated food; and stress from the activities and noise of response vessels and aircraft.  

Complications of the above may lead to dysfunction of immune and reproductive systems,

physiological stress, declining physical condition, and death.  Behavioral responses can include

displacement of animals from prime habitat, disruption of social structure, changing food

availability and foraging distribution and/or patterns, changing reproductive

behavior/productivity, and changing movement patterns or migration.  In the unlikely event of a

spill, implementation of Anadarko’s OSRP is expected to minimize the potential for these types

of impacts on sea turtles.  EP Section H provides detail on spill response measures.

Studies of oil effects on loggerheads in a controlled setting (Lutcavage et al., 1995) suggest that

sea turtles show no avoidance behavior when they encounter an oil slick, and any sea turtle in

an affected area would be expected to be exposed.  Sea turtles’ diving behaviors also put them

at risk.  Sea turtles rapidly inhale a large volume of air before diving and continually resurface

over time, which may result in repeated exposure to volatile vapors and oiling (NMFS, 2007).

Spilled oil reaching sea turtle nesting beaches could have effects on nesting sea turtles and egg

development (NMFS, 2007).  An oiled beach could affect nest site selection or result in no

nesting at all (e.g., false crawls).  Upon hatching and successfully reaching the water, hatchlings

are subject to the same types of oil spill exposure hazards as adults.  Hatchlings that contact oil

residues while crossing a beach can exhibit a range of effects, from acute toxicity to impaired

movement and normal bodily functions (NMFS, 2007).

In the event of a large spill, the level of vessel and aircraft activity associated with spill response

could disturb sea turtles and potentially result in vessel strikes, entanglement, or other injury or

stress.  Response vessels would operate in accordance with NTL 2007‐G04 to reduce the
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potential for striking or disturbing these animals, and therefore no significant impacts are

expected.

C.3.6 Piping Plover (Threatened)

The Piping Plover (Charadrius melodus) is a migratory shorebird that overwinters along the

southeastern U.S. and Gulf of Mexico coasts.  This threatened species is in decline as a result of

hunting, habitat loss and modification, predation, and disease (USFWS, 2003).  Critical

overwintering habitat has been designated, including beaches in Texas, Louisiana, Mississippi,

Alabama, and Florida (Figure 3).  Piping Plovers inhabit coastal sandy beaches and mudflats,

feeding by probing for invertebrates at or just below the surface.  They use beaches adjacent to

foraging areas for roosting and preening (USFWS, 2010a).  A species description is presented in a

recent lease sale EIS (MMS, 2007b).

A large oil spill (WCD) is the only IPF potentially affecting Piping Plovers.  There are no IPFs

associated with routine project activities that could affect these birds.  A small fuel spill in the

lease area would be unlikely to affect Piping Plovers because a small fuel spill would not be

expected to make landfall or reach coastal waters prior to breaking up (see explanation in

Section A.9.2).

Impacts of a Large Oil Spill (WCD)

The lease area is 153 miles (246 km) from the nearest shorelines inhabited by Piping Plovers

(Figure 3).  The revised OSRA results (BOEMRE, 2011a) summarized in Section A.9.3 (Table 3)

predict that during the spring there is a 4% probability that an oil spill from the lease area would

reach a shoreline designated as critical habitat for the Piping Plover within 10 days.  Plovers

could physically oil themselves while foraging on oiled shores or secondarily contaminate

themselves through ingestion of oiled intertidal sediments and prey (MMS, 2007b).  Plovers

congregate and feed along tidally exposed banks and shorelines, following the tide out and

foraging at the water’s edge.  It is possible that some deaths of Piping Plovers could occur,

especially if spills occur during winter months when plovers are most common along the coastal

Gulf or if spills contacted critical habitat.  Impacts could also occur from vehicular traffic on

beaches and other activities associated with spill cleanup.  Anadarko has extensive resources

available to protect and rehabilitate wildlife in the event of a spill reaching the shoreline, as

detailed in the OSRP.

C.3.7 Whooping Crane (Endangered)

The Whooping Crane (Grus americana) is an omnivorous wading bird and an endangered

species.  There are three wild populations in North America (Whooping Crane Eastern

Partnership, 2010).  One population winters along the Texas coast at Aransas NWR and

summers at Wood Buffalo National Park in Canada; this population represents the majority of

the world’s population of free‐ranging Whooping Cranes and reached a record population of

270 at Aransas NWR in December 2008 (Whooping Crane Eastern Partnership, 2010).  A

non‐migrating population has been reintroduced in central Florida, and another reintroduced

population summers in Wisconsin and migrates to the southeastern U.S. for the winter.  

Whooping Cranes breed, migrate, winter, and forage in a variety of habitats, including coastal

marshes and estuaries, inland marshes, lakes, ponds, wet meadows and rivers, and agricultural

fields (USFWS, 2007).  About 9,000 ha (22,240 ac) of salt flats on Aransas NWR and adjacent

islands comprise the principal wintering grounds of the Whooping Crane.  Aransas NWR is

designated as critical habitat for the species.  A species description is presented in a recent lease

sale EIS (MMS, 2007b).
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Environmental Impact Analysis 

Figure 3. Location of selected environmental features in relation to the lease area.
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A large oil spill (WCD) is the only IPF potentially affecting Whooping Cranes.  A small fuel spill in

the lease area would also be unlikely to affect Whooping Cranes, due to the distance from

Aransas NWR.  As explained in Section A.9.2, a small fuel spill would not be expected to make

landfall or reach coastal waters prior to breaking up.

Impacts of a Large Oil Spill (WCD)

A large oil spill is unlikely to affect Whooping Cranes as the lease area is approximately

314 miles (505 km) from its critical habitat designated in the Aransas NWR.  The revised OSRA

modeling (BOEMRE, 2011b) predicts that there is a 3% or less probability that an oil spill

originating in the lease area would reach the Aransas NWR within 30 days and a 17% probability

of oil reaching that area in 120 days.

In the event of oil exposure, Whooping Cranes could physically oil themselves while foraging in

oiled areas or secondarily contaminate themselves through ingestion of contaminated shellfish,

frogs, and fishes.  It is possible that some Whooping Crane deaths could occur.  In the event of a

spill, Anadarko would work with the applicable State and Federal agencies to prevent impacts

from a spill.

C.3.8 Gulf Sturgeon (Threatened)

The Gulf sturgeon (Acipenser oxyrinchus desotoi) is a threatened fish species that inhabits major

rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida

(Barkuloo, 1988; Wakeford, 2001).  An anadromous fish that migrates from the sea upstream

into coastal rivers to spawn in freshwater, it historically ranged from the Mississippi River to

Charlotte Harbor, Florida (Wakeford, 2001).  Today, this range has contracted to encompass

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida.  

Populations have been depleted or even extirpated throughout this range by fishing, shoreline

development, dam construction, water quality changes, and other factors (Barkuloo, 1988;

Wakeford, 2001).  These declines prompted the listing of the Gulf sturgeon as a threatened

species in 1991.  The best known populations occur in the Apalachicola and Suwannee Rivers in

Florida (Carr, 1996; Sulak and Clugston, 1998), the Choctawhatchee River in Alabama (Fox et al.,

2000), and the Pearl River in Mississippi/Louisiana (Morrow et al., 1998).  Critical habitat in the

Gulf extends from Lake Borgne, Louisiana (St. Bernard Parish) to Suwannee Sound, Florida

(Levy County) (NMFS, 2010b) (Figure 3).  A species description is presented in a recent lease sale

EIS (MMS, 2007b) and in the recovery plan for this species (USFWS and Gulf States Marine

Fisheries Commission, 1995).

A large oil spill (WCD) is the only IPF potentially affecting Gulf sturgeon.  There are no IPFs

associated with routine project activities that could affect these fish.  A small fuel spill in the

lease area would be unlikely to affect Gulf sturgeon because a small fuel spill would not be

expected to make landfall or reach coastal waters prior to breaking up (see explanation in

Section A.9.2).

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on Gulf sturgeon are discussed in recent lease sale EISs (MMS, 2007b,

2008) and by NMFS (2007).  For this EP, there are no unique site‐specific issues with respect to

this species.

The lease area is approximately 232 miles (373 km) from the nearest Gulf sturgeon critical

habitat.  The revised OSRA modeling (BOEMRE, 2011a) predicts that a spill in the lease area has
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1% or less probability of contacting any coastal areas inhabited by Gulf sturgeon within 30 or

120 days.

In the event of oil reaching Gulf sturgeon habitat, the fish could be affected by direct ingestion,

ingestion of oiled prey, or the absorption of dissolved petroleum products through the gills.  

Based on the life history of this species, subadult and adult Gulf sturgeon would be most

vulnerable to an estuarine or marine oil spill, and would be vulnerable only from 1 September

through 30 April when this species is foraging in estuarine and shallow marine habitats

(NMFS, 2007).

C.3.9 Smalltooth Sawfish (Endangered)

Smalltooth sawfish (Pristis pectinata) are found in the tropical and subtropical Atlantic Ocean.  

In the Western Atlantic they have historically ranged from New York to Brazil, including the Gulf

of Mexico and Caribbean Sea.  This sawfish primarily occurs in estuarine and coastal habitats

such as bays, lagoons, and rivers.  The smalltooth sawfish was listed as endangered on 1 April

2003, under the ESA.  Its critical habitat consists of two units: the Charlotte Harbor Estuary Unit,

which comprises approximately 89,621 ha (221,459 ac) of coastal habitat; and the Ten Thousand

Islands/Everglades Unit, which comprises approximately 250,506 ha (619,013 ac) of coastal

habitat.  The two units are located along the southwestern coast of Florida between Charlotte

Harbor and Florida Bay.

A large oil spill (WCD) is the only IPF potentially affecting smalltooth sawfish.  There are no IPFs

associated with routine project activities that could affect these fish.  A small fuel spill in the

lease area would be unlikely to affect smalltooth sawfish because a small fuel spill would not be

expected to make landfall or reach coastal waters prior to breaking up (see Section A.9.2).

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on smalltooth sawfish are similar to those discussed for other coastal and

estuarine species in recent lease sale EISs (MMS, 2007b, 2008) and by the NMFS (2007) in its

Biological Opinion.  For this EP, there are no unique site‐specific issues with respect to

smalltooth sawfish.

In the event of oil reaching smalltooth sawfish habitat, the fish could be affected by direct

ingestion, ingestion of oiled prey, or the absorption of dissolved petroleum products through

the gills.   

C.3.10 Beach Mice (Endangered)

Four subspecies of endangered beach mice (Peromyscus polionotus) occur on the barrier islands

of Alabama and the Florida Panhandle.  They are the Alabama, Choctawatchee, Perdido Key, and

St. Andrew beach mice.  Critical habitat has been designated for all four subspecies; Figure 3

shows the critical habitat combined for all four subspecies.  Species descriptions are provided in

a recent lease sale EIS (MMS, 2007b).  

A large oil spill (WCD) is the only IPF potentially affecting beach mice.  There are no IPFs

associated with routine project activities that could affect these animals due to the distance

from shore and the lack of any onshore support activities near their habitat.  A small fuel spill in

the lease area would not affect beach mice because a small fuel spill would not be expected to

make landfall or reach coastal waters prior to breaking up (see Section A.9.2).
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Impacts of a Large Oil Spill (WCD)

Potential spill impacts on beach mice are discussed in recent lease sale EISs (MMS, 2007b,

2008).  For this EP, there are no unique site‐specific issues with respect to these species that

were not analyzed in these documents.

The lease area is about 314 miles (506 km) southwest from the nearest beach mouse critical

habitat.  The revised OSRA modeling summarized in Section A.9.3 predicts that a spill in the

lease area has a 1% or less probability of reaching either the Alabama or Florida shorelines

inhabited by beach mice within 120 days.

In the event of oil contacting these beaches, beach mice could experience several types of direct

and indirect impacts.  Contact with spilled oil could cause skin and eye irritation and subsequent

infection; matting of fur; irritation of sweat glands, ear tissues, and throat tissues; disruption of

sight and hearing; asphyxiation from inhalation of fumes; and toxicity from ingestion of oil and

contaminated food.  Indirect impacts could include reduction of food supply, destruction of

habitat, and fouling of nests.  Impacts could also occur from vehicular traffic and other activities

associated with spill cleanup.  However, any such impacts are unlikely due to the distance from

shore and response actions that would occur in the event of a spill.

C.3.11 Elkhorn Coral (Endangered)  

Elkhorn coral (Acropora palmata) is found primarily in shallow waters with temperatures ranging

between 26 °C and 30 °C (79 and 86 °F) and significant water movement.  Elkhorn coral was

once one of the most abundant species in waters ranging from 1 to 5 m (3.3 to 16 ft) deep in

tropical and subtropical waters.  In the northern Gulf, elkhorn coral has been found within the

coral cap region of the Flower Garden Banks National Marine Sanctuary (Flower Garden Banks

National Marine Sanctuary, 2011).

There are no IPFs associated with routine project activities that could affect this species in the

northern Gulf.  A small fuel spill would not affect elkhorn coral colonies because the oil would

float and dissipate on the sea surface.  A WCD would be unlikely to affect the coral cap region of

the Flower Gardens Bank because of the water depth of the area.  Although subsurface plumes

were reported following the Macondo spill, these plumes resulted from the use of subsea

dispersants at the seafloor.   

C.4 Coastal and Marine Birds

C.4.1 Marine Birds

Marine birds include seabirds and other species that may occur in the pelagic environment of

the project area (Clapp et al., 1982a,b, 1983; Peake, 1996; Hess and Ribic, 2000).  Seabirds spend

much of their lives offshore over the open ocean, except during breeding season when they nest

along the coast.  In addition, other birds such as waterfowl, marsh birds, and shorebirds may

occasionally be present over open ocean areas.  No endangered or threatened bird species are

likely to occur at the project area due to the distance from shore.  For a discussion of shorebirds

and coastal nesting birds, see Section C.4.2.

Seabirds of the northern Gulf of Mexico were surveyed from ships during the GulfCet II program.  

Hess and Ribic (2000) reported that terns, storm‐petrels, shearwaters, and jaegers were the

most frequently sighted seabirds in the deepwater area.  From these surveys, four ecological
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categories of seabirds were documented in the deepwater areas of the Gulf: summer migrants

(shearwaters, storm petrels, boobies); summer residents that breed in the Gulf (Sooty Tern,

Least Tern, Sandwich Tern, Magnificent Frigatebird); winter residents (gannets, gulls, jaegers);

and permanent resident species (Laughing Gulls, Royal Terns, Bridled Terns) (Hess and Ribic,

2000).

Common seabird species include Wilson’s Storm‐Petrel (Oceanites oceanicus), Magnificent

Frigatebird (Fregata magnificens), Northern Gannet (Morus bassanus), Masked Booby

(Sula dactylatra), Brown Booby (Sula leucogaster), Cory’s Shearwater (Calonectris diomedea),

Greater Shearwater (Puffinus gravis), and Audubon’s Shearwater (Puffinus lherminieri).  Seabirds

are distributed Gulf‐wide and are not specifically associated with the lease area.

Relationships with hydrographic features were found for several seabird species, possibly due to

effects of hydrography on nutrient levels and productivity of surface waters where birds forage.  

The GulfCet II study did not estimate bird densities; however, Powers (1987) indicates that

seabird densities over the open ocean typically are <10 birds/km2

.  

Trans‐Gulf migrant birds including shorebirds, wading birds, and terrestrial birds may also be

present in the lease area.  Migrant birds may use offshore structures and rigs for resting,

feeding, or as temporary shelter from inclement weather (Russell, 2005).  Some birds may be

attracted to offshore structures because of the lights and the fish populations that aggregate

around these structures.

IPFs potentially affecting marine and pelagic birds include drilling rig presence, noise, and lights;

support vessel and helicopter traffic; and two types of accidents ‐ a small fuel spill and a large oil

spill (WCD).  Effluent discharges are likely to have negligible impacts on the birds due to rapid

dispersion, the small area of ocean affected, the intermittent nature of the discharges, and the

mobility of these animals.  Compliance with NTL 2007‐G03 will minimize the potential for marine

debris‐related impacts on birds.

Impacts of Drilling Rig Presence, Noise, and Lights

Birds that frequent rigs may be exposed to contaminants including air pollutants and routine

discharges, but significant impacts are unlikely due to rapid dispersion.  Birds migrating over

water have been known to strike offshore structures, resulting in death or injury (Wiese et al.,

2001; Russell, 2005).  Mortality of migrant birds at tall towers and other land‐based structures

has been reviewed extensively, and the mechanisms involved in rig collisions appear to be

similar.  In some cases, migrants simply do not see a part of the rig until it is too late.  In other

cases, navigation may be disrupted by noise (Russell, 2005).  On the other hand, offshore

structures are suitable stopover habitats for most trans‐Gulf migrant species, and most of the

migrants that stop over on rigs probably benefit from their stay, particularly in spring

(Russell, 2005).  Due to the limited scope and short duration of drilling activities described in this

EP, any impacts on populations of either seabirds or trans‐Gulf migrant birds are not expected

to be significant.

A recent study in the North Sea indicated that rig lighting causes circling behavior in various

birds, especially on cloudy nights; apparently the birds’ geomagnetic compass is upset by the

red part of the spectrum from the lights currently in use (Nederlandse Aardolie Maatschappij,

2007).  The numbers varied greatly, from none at all to some tens of thousands of birds per

night per rig, with an apparent effect radius of up to 3 miles (5 km).  A study in the Gulf of
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Mexico also noted the phenomenon but did not recommend mitigation (Russell, 2005).  Factors

to consider in evaluating this impact in the Gulf of Mexico would include the lower incidence of

cloudy and foggy days in the Gulf of Mexico versus the North Sea.  Due to the limited scope and

short duration of drilling activities proposed in this EP, lighting impacts, collisions, or other

adverse effects are unlikely, and no significant impacts are expected.

Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters are unlikely to significantly disturb pelagic birds in open,

offshore waters.  It is likely that individual birds would experience, at most, only short‐term

behavioral disruption, and the impact would not be significant.

Impacts of a Small Fuel Spill

Potential spill impacts on marine birds are discussed in recent EISs (MMS, 2007b, 2008).  For this

EP, there are no unique site‐specific issues with respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during

routine operations including fuel transfer.  In the unlikely event of a spill, implementation of

Anadarko’s OSRP will reduce the potential for impacts on marine and pelagic birds.  

EP Section H provides detail on spill response measures.  Given the open ocean location of the

lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the

concentrations of petroleum hydrocarbons and their degradation products.  The extent and

persistence of impacts would depend on the meteorological and oceanographic conditions at

the time and the effectiveness of spill response measures.  Section A.9.2 discusses the likely fate

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally

within 24 hours.  The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha

(1.2 to 12 ac), depending on sea state and weather conditions.

Birds exposed to oil on the sea surface could experience direct physical and physiological effects

including skin irritation; chemical burns of skin, eyes, and mucous membranes; and inhalation of

toxic fumes.  Due to the limited areal extent and short duration of water quality impacts from a

small fuel spill, secondary impacts due to ingestion of oil via contaminated prey or reductions in

prey abundance are unlikely.  Due to the low densities of birds in open ocean areas, the small

area affected, and the brief duration of the surface slick, no significant impacts on pelagic birds

would be expected.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine and pelagic birds are discussed in recent EISs (MMS, 2007b,

2008).  For this EP, there are no unique site‐specific issues with respect to spill impacts on these

animals.

BOEMRE has reexamined the analyses for coastal and marine birds presented in MMS (2007b,

2008) and determined that no new information was found that would alter the potential

impacts on marine and pelagic birds (BOEMRE, 2011a,b).

Pelagic seabirds could be exposed to oil from a spill at the project area.  Hess and Ribic (2000)

reported that terns, storm‐petrels, shearwaters, and jaegers were the most frequently sighted
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seabirds in the deepwater Gulf of Mexico (>200 m).  Powers (1987) indicates that seabird

densities over the open ocean typically are <10 birds/km2

.  The number of pelagic birds that

could be affected in open, offshore waters would depend on the extent and persistence of the

oil slick.

The recent Macondo spill provides relevant information about the species of pelagic birds that

may be affected in the event of a large oil spill.  Birds that have been treated for oiling include

several pelagic species such as the Northern Gannet, Magnificent Frigatebird, and Masked

Booby (International Bird Rescue Research Center, 2010).  The Northern Gannet is among the

species with the largest numbers of birds affected by the spill.

C.4.2 Shorebirds and Coastal Nesting Birds

Threatened and endangered bird species (Piping Plover and Whooping Crane) have been

discussed previously in Section C.3.  Various species of non‐endangered birds are also found

along the northern Gulf Coast, including diving birds, shorebirds, marsh birds, wading birds, and

waterfowl.  Gulf Coast marshes and beaches also provide important feeding grounds and

nesting habitats.  Species that breed on beaches, flats, dunes, bars, barrier islands, and similar

habitats include the Sandwich Tern, Wilson’s Plover, Black Skimmer, Forster’s Tern, Gull‐Billed

Tern, Laughing Gull, Least Tern, and Royal Tern (USFWS, 2010b).  Additional information is

presented in recent lease sale EISs (MMS, 2007b, 2008).

The Brown Pelican (Pelecanus occidentalis) was delisted from Federal endangered status in 2009

(USFWS, 2010c).  However, this species is listed as a species of greatest conservation need by

the State of Mississippi (Mississippi Department of Wildlife, Fisheries and Parks, 2011) and as a

species of special concern by the State of Florida (Florida Fish and Wildlife Conservation

Commission, 2010).  Brown Pelicans inhabit coastal habitats and forage within both coastal

waters and waters of the inner continental shelf.  Aerial and shipboard surveys, including

GulfCet and GulfCet II, indicate that Brown Pelicans do not occur in deep offshore waters (Fritts

and Reynolds, 1981; Peake, 1996; Hess and Ribic, 2000).  Nearly half the southeastern

population of Brown Pelicans lives in the northern Gulf Coast, generally nesting on protected

islands (USFWS, 2010b).

The Southern Bald Eagle (Haliaeetus leucocephalus) was delisted from its threatened status in

the lower 48 states on 28 June 2007.  The Bald Eagle is a terrestrial raptor widely distributed

across the southern U.S., including coastal habitats along the Gulf of Mexico.  The Gulf Coast is

inhabited by both wintering migrant and resident Bald Eagles (Johnsgard, 1990; Ehrlich et al.,

1992).

IPFs potentially affecting shorebirds and coastal nesting birds include support vessel and

helicopter traffic and a large oil spill (WCD).  A small fuel spill in the lease area would be unlikely

to affect shorebirds or coastal nesting birds, as the lease area is 153 miles (246 km) from the

nearest shoreline (Louisiana).  As explained in Section A.9.2, a small fuel spill would not be

expected to make landfall or reach coastal waters prior to breaking up.  Compliance with

NTL 2007‐G03 will minimize the potential for marine debris‐related impacts on shorebirds.

Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters will transit coastal areas near Port Fourchon and Houma,

Louisiana, where shorebirds and coastal nesting birds may be found.  These activities could
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periodically disturb individuals or groups of birds within sensitive coastal habitats (e.g., wetlands

that may support feeding, resting, or breeding birds).

Vessel traffic may disturb some foraging and resting birds.  Flushing distances vary between

species and between individuals (Rodgers and Schwikert, 2002).  The disturbances will be

limited to flushing birds away from vessel pathways; known distances are from 20 to 49 m

(65 to 160 ft) for personal watercraft and 23 to 58 m (75 to 190 ft) for an outboard‐powered

boat (Rodgers and Schwikert, 2002).  Flushing distances may be similar or less for the support

vessels to be used for Anadarko’s project, and some species such as gulls are attracted to boats.  

Support vessels will not approach nesting or breeding areas on the shoreline, so disturbances to

nesting birds, eggs, and chicks is not expected.  Vessel operators will use designated navigation

channels and comply with posted speed and wake restrictions while transiting sensitive inland

waterways.  Due to the limited scope and short duration of drilling activities, any short‐term

impacts are not expected to be biologically significant to coastal bird populations.

Aircraft traffic can cause some disturbance to birds onshore and offshore.  Responses are highly

dependent on the type of aircraft, the bird species, the activities that animals were previously

engaged in, and previous exposures to overflights (Efroymson et al., 2000).  Helicopters seem to

cause the most intense responses over other human disturbances for some species (Bélanger

and Bédard, 1989).  However, Federal Aviation Administration Advisory Circular No. 91‐36D

recommends that pilots maintain a minimum altitude of 610 m (2,000 ft) when flying over

noise‐sensitive areas such as wildlife refuges, parks, and areas with wilderness characteristics.  

This is greater than the distance (slant range) at which aircraft overflights have been reported to

cause behavioral effects on most species of birds studied (Efroymson et al., 2000).  With these

guidelines in effect, it is likely that individual birds would experience, at most, only short‐term

behavioral disruption.

Impacts of Large Oil Spill (WCD)

Data from the Macondo spill provide additional information about the species of coastal birds

that may be affected in the event of a catastrophic spill of a similar nature and duration.  This

information supplements the analysis presented in the lease sale EIS (MMS, 2007b).  According

to USFWS (2010d) and based on the latest reports, about 5,000 dead birds have been collected

since the spill began, and about 1,900 of the dead animals were visibly oiled.  In addition, over

2,000 oiled birds have been collected alive and about 1,200 released (NMFS, 2010c).  According

to the International Bird Rescue Research Center (2010), bird species that have been treated for

oiling include the following:

• Brown Pelican

• White Pelican

• Masked Booby

• Magnificent Frigatebird

• Laughing Gull

• Herring Gull

• Northern Gannet

• Black Crowned Night Heron

• Tri‐colored Heron

• Green Heron

• Cattle Egret

• Snowy Egret

• Reddish Egret

• Least Bittern

• Common Tern

• Royal Tern

• Caspian Tern

• Sandwich Tern

• Forster’s Tern

• Black Tern

• Gull‐billed Tern

• Least Tern
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• Black Skimmer

• Black Oystercatcher

• White Ibis

• Roseate Spoonbill

• Willet

• Sanderling

• Dunlin

• Semipalmated Sandpiper

• Killdeer

• King Rail

• Clapper Rail

• Virginia Rail

According to the USFWS (2010d), species with the largest numbers of dead oiled birds were

Laughing Gull, Northern Gannet, Brown Pelican, Royal Tern, Black Skimmer, Least Tern,

unidentified Gull, and unidentified Tern.  There are no reports of Bald Eagle oiling.

Coastal birds can be exposed to oil as they float on the water surface, dive during foraging, or

wade in oiled coastal waters.  Oiled birds can lose the ability to fly, dive for food, or float on the

water, which could lead to drowning (USFWS, 2010e).  Oil interferes with the water repellency

of feathers and can cause hypothermia in the right conditions.  As birds groom themselves, they

can ingest and inhale the oil on their bodies.  Scavengers such as Bald Eagles and gulls can be

exposed to oil by feeding on carcasses of contaminated fish and wildlife.  While ingestion can kill

animals immediately, more often it results in lung, liver, and kidney damage, which can lead to

death.  Bird eggs may be damaged if an oiled adult sits on the nest.

As noted above, the Brown Pelican was recently removed from the Federal endangered species

list.  Over 300 dead Brown Pelicans were collected in the Gulf following the Macondo spill,

(USFWS, 2010d).  These data indicate that Brown Pelicans may be particularly at risk of oiling in

the event of a catasrophic spill reaching coastal waters.  Issues for Brown Pelicans include direct

contact with oil, disturbance by cleanup activities, and long‐term habitat contamination.

C.5 Fisheries Resources

C.5.1 Pelagic Communities and Ichthyoplankton

Biggs and Ressler (2000) reviewed the biology of pelagic communities in the deepwater

environment of the northern Gulf of Mexico.  The biological oceanography of the region is

dominated by the influence of the Loop Current, whose surface waters are among the most

oligotrophic in the world’s oceans.  Superimposed on this low‐productivity condition are

productive “hot spots” associated with entrainment of nutrient‐rich Mississippi River water and

mesoscale oceanographic features.  Anticyclonic and cyclonic hydrographic features play an

important role in determining biogeographic patterns and controlling primary productivity in the

northern Gulf of Mexico (Biggs and Ressler, 2000).

Most fishes inhabiting shelf or oceanic waters of the Gulf of Mexico have planktonic eggs and

larvae (Ditty, 1986; Ditty et al., 1988; Richards et al., 1989, 1993).  Pelagic eggs and larvae

become part of the planktonic community for various lengths of time (10 to 100 days,

depending on the species) (MMS, 2007b).

IPFs potentially affecting pelagic communities and ichthyoplankton include drilling rig presence,

noise, and lights; effluent discharges; water intakes; and two types of accidents ‐ a small fuel

spill and a large oil spill (WCD).
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Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as a fish‐attracting

device (FAD).  In oceanic waters, the FAD effect would be most pronounced for epipelagic fishes

such as tunas, dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting

surface structures (Holland et al., 1990; Higashi, 1994; Relini et al., 1994; MMS, 2000, 2007b,

2008).  This FAD effect could possibly enhance the feeding of epipelagic predators by attracting

and concentrating smaller fish species.  Because the drilling rig is a single, temporary structure,

impacts on fish populations, whether beneficial or adverse, are considered minor.

Impacts of Effluent Discharges

Treated sanitary and domestic wastes may have a slight effect on the pelagic environment in the

immediate vicinity of these discharges.  These wastes may have elevated levels of nutrients,

organic matter, and chlorine, but should be diluted rapidly to undetectable levels within tens to

hundreds of meters from the source.  Minimal impacts on water quality, plankton, and nekton

are anticipated.

Deck drainage may have a slight effect on the pelagic environment in the immediate vicinity of

these discharges.  Deck drainage from contaminated areas will be passed through an

oil‐and‐water separator prior to release, and discharges will be monitored for visible sheen.  The

discharges may have slightly elevated levels of hydrocarbons but should be diluted rapidly to

undetectable levels within tens to hundreds of meters from the source.  Minimal impacts on

water quality, plankton, and nekton are anticipated.

Other discharges in accordance with the NPDES permit, such as desalination unit brine and

uncontaminated cooling water, fire water, and ballast water, are expected to be diluted rapidly

and have little or no impact on water column biota.

Impacts of Water Intakes

Seawater will be drawn from the ocean for once‐through, non‐contact cooling of machinery

on the drilling rig.  Rigs considered for use for activities described in this EP are not “new”

facilities as defined by the NPDES permit and therefore are not subject to the cooling water

intake regulations for Phase III facilities under Section 316(b) of the Clean Water Act.

The intake of seawater for cooling water will entrain plankton.  The low intake velocity should

allow most strong‐swimming juvenile fishes and smaller adults to escape entrainment or

impingement.  However, drifting plankton would not be able to escape entrainment with the

exception of a few fast‐swimming larvae of certain taxonomic groups.  Those organisms

entrained may be stressed or killed, primarily through changes in water temperature during the

route from cooling intake structure to discharge structure and mechanical damage (turbulence

in pumps and condensers).  Due to the limited scope and short duration of drilling activities, any

short‐term impacts of entrainment are not expected to be biologically significant to plankton or

ichthyoplankton populations.

Impacts of a Small Fuel Spill

Potential spill impacts on fisheries resources are discussed in recent EISs (MMS, 2007b, 2008).  

For this EP, there are no unique site‐specific issues with respect to spill impacts.
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The probability of a fuel spill will be minimized by Anadarko’s preventative measures during

routine operations including fuel transfer.  In the unlikely event of a spill, implementation of

Anadarko’s OSRP will mitigate the potential for impacts on pelagic communities, including

ichthyoplankton.  EP Section H provides detail on spill response measures.  Given the open

ocean location of the lease area, the duration of a small spill and opportunity for impacts to

occur would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the

concentrations of petroleum hydrocarbons and their degradation products.  The extent and

persistence of impacts would depend on the meteorological and oceanographic conditions at

the time and the effectiveness of spill response measures.  Section A.9.2 discusses the likely fate

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally

within 24 hours.  The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha

(1.2 to 12 ac), depending on sea state and weather conditions.

A small fuel spill could have localized impacts on phytoplankton, zooplankton, and nekton.  Due

to the limited areal extent and short duration of water quality impacts, a small fuel spill would

be unlikely to produce detectable impacts on pelagic communities.

Impacts of a Large Oil Spill (WCD)

A large oil spill could affect water column biota including phytoplankton, zooplankton,

ichthyoplankton, and nekton.  A large spill that persisted for weeks or months would be more

likely to affect these communities.  While adult and juvenile fishes may actively avoid a large

spill, planktonic eggs and larvae would be unable to avoid contact.  Eggs and larvae of fishes are

especially vulnerable to oiling because they inhabit the upper layers of the water column, and

they will die if exposed to certain toxic fractions of spilled oil.  Impacts potentially would be

greater if local‐scale currents retained planktonic larval assemblages (and the floating oil slick)

within the same water mass.

C.5.2 Essential Fish Habitat

Essential Fish Habitat (EFH) is defined as those waters and substrate necessary to fish for

spawning, breeding, feeding, and growth to maturity.  Under the Magnuson‐Stevens Fishery

Conservation and Management Act, as amended, Federal agencies are required to consult on

activities that may adversely affect EFH designated in Fishery Management Plans developed by

the regional Fishery Management Councils.

The BOEMRE (2011a,b) has reexamined the analysis for fish resources and EFH presented in

recent lease EISs (MMS, 2007a,b), in consideration of the Macondo event.  No substantial new

information was found that would alter the impact conclusions for fish resources and EFH

presented in MMS (2007a,b).  

The Gulf of Mexico Fishery Management Council (GMFMC) has prepared Fishery Management

Plans for corals and coral reefs, shrimps, stone crab, spiny lobster, reef fishes, coastal migratory

pelagic fishes, and red drum.  In 2005, the EFH for these managed species was redefined in

Generic Amendment No. 3 to the various Fishery Management Plans (GMFMC, 2005).  The EFH

for most of these GMFMC‐managed species is on the continental shelf in waters shallower than

183 m (600 ft).  The shelf edge is the outer boundary for coastal migratory pelagic fishes, reef

fishes, and shrimps.  EFH for corals and coral reefs includes some shelf‐edge topographic

features on the Texas‐Louisiana OCS, the nearest of which is Sweet Bank located in Green
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Canyon Block 90, 66 miles (106 km) north‐northwest of the lease area along the shelf edge

south of Louisiana.

Highly migratory pelagic fishes, which occur as transients in the lease area, are the only

remaining group for which EFH has been identified in the deepwater Gulf of Mexico.  Species in

this group, including tunas, swordfishes, billfishes, and sharks, are managed by NMFS.  Highly

migratory species with EFH at or near the lease area include the following species and life stages

(NMFS, 2009):

• Atlantic bluefin tuna (spawn, eggs,

larvae, adults)

• Bigeye thresher shark (all)

• Bigeye tuna (adult)

• Blue marlin (juveniles, adults)

• Dusky shark (juveniles, adults)

• Longbill spearfish (adults)

• Longfin mako shark (all)

• Oceanic whitetip shark (all)

• Sailfish (juveniles, adults)

• Shortfin mako shark (all)

• Silky shark (all)

• Skipjack tuna (spawn, adults)

• Swordfish (larvae, juveniles, adults)

• Tiger shark (adults)

• White marlin (juveniles, adults)

• Yellowfin tuna (spawn, juveniles,

adults)

Recent research indicates the central and western Gulf of Mexico may be important spawning

habitat for Atlantic bluefin tuna, and NMFS (2009) has designated a Habitat Area of Particular

Concern (HAPC) for this species.  The HAPC covers much of the deepwater Gulf of Mexico,

including the lease area (Figure 3).  The areal extent of the HAPC is approximately 300,000 km2

(15,000 mi2).  The prevailing assumption is that Atlantic bluefin tuna follow an annual cycle of

foraging in June through March off the eastern U.S. and Canadian coasts, followed by migration

to the Gulf of Mexico to spawn in April, May, and June (NMFS, 2009).  

On 27 May 2011, after an extensive scientific review, NOAA announced that Atlantic bluefin

tuna currently do not warrant species protection under the ESA.  NOAA said the species would

be classified as a species of concern; however, effectively placing bluefin tuna on a watch list as

the agency awaits new data on the impact of a stricter international management regimen.   

A new amendment to the original EFH Generic Amendment was finalized in 2005

(GMFMC, 2005).  One of the most significant proposed changes in this amendment reduced the

extent of EFH relative to the 1998 Generic Amendment by removing the EFH description and

identification from waters between 100 fathoms and the seaward limit of the Exclusive

Economic Zone (EEZ).  The Highly Migratory Species Fisheries Management Plan was amended

in 2009 to update EFH and HAPC to include the bluefin tuna spawning area (NMFS, 2009).   

There are current NTLs (2009‐G39 and 2009‐G40) that provide guidance and clarification of the

regulations with respect to biologically sensitive underwater features and areas and benthic

communities that are considered EFH (MMS, 2009a,b).  A new EFH consultation has been

initiated between BOEMRE’s Gulf of Mexico Region and NOAA’s Southeastern Region.  Some

EFH requirements may change with the new agreement.  Until the new agreement is in place,

the 1999 Programmatic Consultation with the elements described above will be followed

(BOEMRE, 2011a,b).

Other HAPCs have been identified by the GMFMC (2005).  These include the Florida Middle

Grounds, Madison‐Swanson Marine Reserve, Tortugas North and South Ecological Reserves,
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Pulley Ridge, and several individual reefs and banks of the northwestern Gulf of Mexico

(Figure 3).  The nearest of these is Jakulla Bank, located approximately 72 miles (116 km) north

of the lease area.  

Routine IPFs potentially affecting EFH include drilling rig presence, noise, and lights; effluent

discharges; water intakes; and two types of accidents – a small fuel spill and a large oil spill

(WCD).

Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as an FAD.  In

oceanic waters, the FAD effect would be most pronounced for epipelagic fishes such as tunas,

dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting surface

structures (Holland et al., 1990; Higashi, 1994; Relini et al., 1994; MMS, 2000, 2007b, 2008).  

This FAD effect would possibly enhance feeding of epipelagic predators by attracting and

concentrating smaller fish species.  Because the drilling rig is a single, temporary structure, any

impacts on EFH for highly migratory pelagic fishes are considered minor.

Impacts of Effluent Discharges

Other effluent discharges affecting EFH by diminishing ambient water quality include drilling

muds and cuttings, treated sanitary and domestic wastes, deck drainage, and miscellaneous

discharges such as desalination unit brine and uncontaminated cooling water, fire water, and

ballast water.  Impacts on water quality have been discussed previously.  No significant impacts

on EFH for highly migratory pelagic fishes are expected from these discharges.

Impacts of Water Intakes

As noted previously, cooling water intake will cause entrainment and impingement of plankton,

including fish eggs and larvae (ichthyoplankton).  Due to the limited scope and short duration of

drilling activities, any short‐term impacts on EFH for highly migratory pelagic fishes are not

expected to be biologically significant.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during

routine operations including fuel transfer.  In the unlikely event of a spill, implementation of

Anadarko’s OSRP will help diminish the potential for impacts on EFH.  EP Section H provides

detail on spill response measures.  Given the open ocean location of the lease area, the duration

of a small spill and opportunity for impacts to occur would be very brief.

Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008).  For this EP,

there are no unique site‐specific issues with respect to spill impacts.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the

concentrations of petroleum hydrocarbons and their degradation products.  The extent and

persistence of impacts would depend on the meteorological and oceanographic conditions at

the time and the effectiveness of spill response measures.  Section A.9.2 discusses the likely fate

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally

within 24 hours.  The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha

(1.2 to 12 ac), depending on sea state and weather conditions.
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A small fuel spill could have localized impacts on EFH for highly migratory pelagic fishes,

including tunas, swordfishes, billfishes, and sharks.  These species occur as transients in the

lease area.  A spill would also produce short‐term impact on water quality in the HAPC for

spawning bluefin tuna, which covers much of the deepwater Gulf of Mexico.  The areal extent of

the affected area would represent a negligible portion of the HAPC.

A small fuel spill would not affect EFH for corals and coral reefs, the nearest EFH being the

topographic feature of Sweet Bank located in Green Canyon Block 90, 66 miles (106 km) north‐

northwest of the lease area.  A small fuel spill would float and dissipate on the sea surface and

would not contact these features.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008).  For this EP,

there are no unique site‐specific issues with respect to EFH.

An oil spill in offshore waters would temporarily increase hydrocarbon concentrations on the

water surface and potentially the subsurface as well.  Given the extent of EFH designations in

the Gulf of Mexico (GMFMC, 2005; NMFS, 2009), some impact on EFH would be unavoidable.

A large spill could affect the EFH for many managed species including shrimps, stone crab, spiny

lobster, reef fishes, coastal migratory pelagic fishes, and red drum.  It would result in adverse

impacts on water quality and water column biota including phytoplankton, zooplankton, and

nekton.  In coastal waters, sediments could be contaminated and result in persistent

degradation of the seafloor habitat for managed demersal fish and shellfish species.

The lease area is within the HAPC for spawning Atlantic bluefin tuna (NMFS, 2009).  A large spill

could temporarily degrade the HAPC due to increased hydrocarbon concentrations in the water

column, with the potential for lethal or sublethal impacts on spawning tuna.  Potential impacts

would depend in part on the timing of a spill, as this species migrates to the Gulf of Mexico to

spawn in April, May, and June (NMFS, 2009).

The topographic feature of Sweet Bank, located in Grand Canyon Block 90, 66 miles (106 km)

north‐northwest of the lease area, is designated as EFH under the corals and coral reefs

management plan.  An accidental spill would be unlikely to affect this area, since a surface slick

would not reach these features due to their depth.   

C.6 Archaeological Resources

C.6.1 Shipwreck Sites

The BOEMRE (2011a,b) reexamined the analyses for archaeological resources presented in MMS

(2007b, 2008), based on additional information available since the publication of these two

documents and in consideration of the Macondo oil spill.  Substantial new information that

alters the impact conclusion for archaeological resources presented in MMS (2007b, 2008) has

come to light as a result of BOEMRE‐sponsored studies and industry surveys.  Specifically,

evidence of damage to significant cultural resources (i.e., historic shipwrecks) has been shown

to have occurred because of an incomplete knowledge of seafloor conditions in lease areas

>200 m (656 ft) deep that have been exempted from high‐resolution surveys.  Since significant

historic shipwrecks have recently been discovered outside the previously designated
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high‐probability areas (some of which show evidence of impacts from permitted activities prior

to their discovery), beginning in 2011 a survey will be required for exploration and development

projects.  The WR 51 area is not on the list of leases with a high potential for historic shipwrecks.  

There were no indications of wrecks or other archaeological resources detected during the site

clearance survey (AOA Geophysics, Inc., 2011).  Anadarko will abide by the applicable

requirements of NTL 2005‐G07, which stipulate that work be stopped at the project site should

any previously undetected archaeological resource be discovered after work has begun until

appropriate surveys and evaluations have been completed.

Because there are no shipwreck sites in the lease area, there are no routine IPFs that are likely

to affect shipwrecks.  Impacts of a large oil spill (WCD) are the only IPFs considered.  A small fuel

spill would not affect shipwrecks because the oil would float and dissipate on the sea surface.

Impacts of a Large Oil Spill (WCD)

MMS (2007b) estimated that a severe subsurface blowout could resuspend and disperse

sediments within a 300‐m (984‐ft) radius.  Because there are no historic shipwrecks in the lease

area, this impact would not be relevant.

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect

archaeological sites beyond the immediate vicinity of the wellhead (i.e., due to physical impacts

of a blowout) because the oil would rise quickly to the sea surface directly over the spill location.  

However, during the Macondo spill, subsurface plumes were reported at a water depth of about

1,100 m (3,600 ft), extending at least 22 miles (35 km) from the wellsite and persisting for more

than a month (Camilli et al., 2010).  The subsurface plumes apparently resulted from the use of

dispersants at the wellhead (Joint Analysis Group, 2010c).  While the behavior and impacts of

subsurface plumes are not well known, a subsurface plume could have the potential to contact

shipwreck sites beyond the 300‐m (984‐ft) radius estimated by MMS (2007a, 2008), depending

on its extent, trajectory, and persistence.  If oil from a subsea spill should come into contact with

wooden shipwrecks on the seafloor, it could adversely affect their condition or preservation.  

Should there be any indication that potential shipwreck sites could be affected, in accordance

with NTL 2005‐G07 Anadarko will immediately halt operations, take steps to ensure that the site

is not disturbed in any way, and contact the BOEMRE Regional Supervisor, Leasing and

Environment, within 48 hours of its discovery.  Anadarko would cease all operations within

305 m (1,000 ft) of the site until the Regional Supervisor provides instructions on steps to take

to assess the site’s potential historic significance and protect it.

A spill entering shallow coastal waters could conceivably contaminate an undiscovered

shipwreck site.  As noted by MMS (2007b), should an oil spill contact a coastal historic site, such

as a fort or a lighthouse, the major impact would be a temporary, reversible visual impact from

oil contact and contamination of the site and its environment.

C.6.2 Prehistoric Archaeological Sites

Available evidence suggests that sea level in the northern Gulf of Mexico was at least 90 m

(295 ft), and possibly as much as 130 m (427 ft), lower than present sea level during the period

20,000 to 17,000 years Before Present (B.P.) (Nelson and Bray, 1970).  Sea level in the northern

Gulf reached its present stand around 3,500 years B.P. (Pearson et al., 1986).
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During periods that the continental shelf was exposed above sea level, the area was open to

habitation by prehistoric peoples.  The advent of early man into the Gulf of Mexico region is

currently accepted to be around 12,000 years B.P. (Aten, 1983).  The sea‐level curve for the

northern Gulf of Mexico proposed by Coastal Environments, Inc. (CEI) suggests that sea level at

12,000 years B.P. would have been approximately 45 to 60 m (148 to 197 ft) below the

present‐day sea level (CEI, 1977, 1982).  On this basis, the continental shelf shoreward of the

45‐ to 60‐m (148‐ to 197‐ft) bathymetric contours has potential for prehistoric sites dating after

12,000 years B.P.  Because of inherent uncertainties in both the depth of sea level and the entry

date of prehistoric man into North America, the MMS adopted the 60‐m (197‐ft) water depth as

the seaward extent for archaeological site potential in Gulf of Mexico region.

With a water depth of 1,779 m (5,838 ft), the wellsites are well beyond the 60‐m (197‐ft) depth

contour used by the BOEMRE as the seaward extent for prehistoric archaeological site potential

in the Gulf of Mexico.  Because prehistoric archaeological sites are not found in the lease area,

the only relevant IPF is a large oil spill (WCD).  A small fuel spill would not affect prehistoric

archaeological resources because the oil would float and dissipate on the sea surface.

Impacts of a Large Oil Spill (WCD)

Because prehistoric archaeological sites are not found in the lease area, they would not be

affected by the physical effects of a subsea blowout.  The MMS (2007b) estimates that a severe

subsurface blowout could resuspend and disperse sediments within a 300‐m (984‐ft) radius.

Along the northern Gulf Coast, prehistoric sites occur frequently along the barrier islands and

mainland coast and along the margins of bays and bayous (MMS, 2007b).  If a spill did reach a

prehistoric site along these shorelines it could coat fragile artifacts or site features and

compromise the potential for radiocarbon dating organic materials in a site (although other

dating methods are available and it is possible to decontaminate an oiled sample for

radiocarbon dating).  Coastal prehistoric sites could also be damaged by spill cleanup operations

(e.g., by destroying fragile artifacts and disturbing the provenance of artifacts and site features).

C.7 Coastal Habitats and Protected Areas

Coastal habitats in the northeastern Gulf of Mexico that may be affected by oil and gas activities

are described in recent EISs (MMS, 2007b, 2008) and in a literature review by Collard and Way

(1997).  Coastal habitats inshore of the project area include barrier beaches and dunes,

wetlands, and submerged seagrass beds.  Generally, most of the northeastern Gulf is fringed by

barrier beaches, with wetlands and/or submerged seagrass beds occurring in sheltered areas

behind the barrier islands and in estuaries.

Due to the distance from shore, the only IPF associated with routine activities in the lease area

that potentially may affect beaches and dunes, wetlands, seagrass beds, coastal wildlife refuges,

wilderness areas, or any other managed or protected coastal area related to support vessel

traffic.  The support bases at Fourchon and Houma are not in a wildlife refuge or a wilderness

area.  Potential impacts of support vessel traffic are addressed briefly below.

A small fuel spill in the lease area would be unlikely to affect coastal habitats, as the lease area is

153 miles (246 km) from the nearest shoreline.  As explained in Section A.9.2, a small fuel spill

would not be expected to make landfall or reach coastal waters prior to breaking up.
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Impacts of Support Vessel Traffic

For OCS activities in general, support operations, including crew boats and supply boats, may

have a minor incremental impact on coastal habitats.  Over time with a large number of vessel

trips, vessel wakes can erode shorelines along inlets, channels, and harbors.  Support

operations, including crew boats and supply boats as detailed in EP Section K, may have a minor

incremental impact on coastal habitats or protected areas.  Impacts will be minimized by

following the speed and wake restrictions in harbors and channels.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on coastal habitats are discussed in recent EISs (MMS, 2007b, 2008).  

Coastal habitats inshore of the project area include barrier beaches and dunes, wetlands, and

submerged seagrass beds.  For this EP, there are no unique site‐specific issues with respect to

coastal habitats.

The shorelines within the geographic range predicted by the OSRA modeling (Table 3) include

extensive barrier beaches and wetlands, with submerged seagrass beds occurring in sheltered

areas behind the barrier islands and in estuaries.  NWRs and other protected areas along the

coast are discussed in a recent lease sale EIS (MMS, 2007b) and Anadarko’s OSRP.  Coastal and

near coastal wildlife refuges, wilderness areas, and State and National parks within the

geographic range of the potential shoreline contacts after 120  days are presented in Table 6.  

Table 6. Wildlife refuges, wilderness areas, and State and National parks within the geographic

range of the potential shoreline contacts after 120 days (From: BOEMRE, 2011a).

County or Parish Wildlife Refuge, Wilderness Area, or

State/National Park

Lower Rio Grande Valley National Wildlife Refuge

Laguna Atascosa National Wildlife Refuge

Padre Island National Seashore

Isla Blanca Park

Andy Bowie County Park  

Cameron County, Texas

Laguna Madre Estuarine and Coastal Marine Area

Lower Rio Grande Valley National Wildlife Reserve Willacy County, Texas Laguna Atascosa National Wildlife Reserve  

Padre Island National Seashore Willacy County, Texas (continued) Laguna Madre Estuarine And Coastal Marine Area

Padre Island National Seashore Kenedy County, Texas Laguna Madre Estuarine and Coastal Marine Area

Kleberg County, Texas Padre Island National Seashore

Laguna Madre Estuarine and Coastal Marine Area

Laguna Madre Estuarine and Coastal Marine Area

Mustang Island State Park

Lake Corpus Christi State Park

Port Aransas Park

Nueces County, Texas

Mission‐Aransas National Estuarine Research Reserve

Mission‐Aransas National Estuarine Research Reserve

Aransas County, Texas   Aransas National Wildlife Refuge

Goose Island State Park

Mission‐Aransas National Estuarine Research Reserve

Aransas National Wildlife Refuge

Matagorda Island State Park

Guadalupe Delta Wildlife Management Area

Calhoun County, Texas

Welder Flats Coastal Preserve
Table 6.  (Continued).

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County or Parish Wildlife Refuge, Wilderness Area, or

State/National Park

Big Boggy National Wildlife Refuge

Aransas National Wildlife Refuge

Mad Island Wildlife Management Area Matagorda County, Texas  

San Bernard National Wildlife Refuge

San Bernard National Wildlife Refuge

Peach Point Wildlife Management Area

Brazoria National Wildlife Refuge Brazoria County, Texas

Christmas Bay Coastal Preserve and Christmas Bay State Park  

Galveston Island State Park

Brazoria National Wildlife Refuge

Apffel Park

Seawolf Park

Old Fort Travis Park

Atkinson Island Wildlife Management Area

Ft. Anahuc Park

Anahuac National Wildlife Refuge

Galveston County, Texas

Mcfaddin National Wildlife Refuge

Mcfaddin National Wildlife Refuge

Sea Rim State Park

Murphree Wildlife Management Area Jefferson County, Texas  

Texas Point National Wildlife Refuge

Sabine National Wildlife Refuge

Cameron Prairie National Wildlife Refuge

Lacassine National Wildlife Refuge

Little Pecan Island Natural Area

Peveto Woods Natural Area

Lower Neches Wildlife Management Area

Cameron Parish, Louisiana  

Rockefeller Wildlife Management Area

Louisiana Rockefeller Wildlife Management Area Vermilion Parish, Louisiana Paul J. Rainey Wildlife Management Area

Salvador Wildlife Management Area

Jean Lafitte National Historical Park and Preserve

Delta National Wildlife Refuge

Pass‐a‐Loutre Wildlife Management Area

Breton National Wildlife Refuge

Plaquemines Parish, Louisiana  

St. Bernard State Park

The level of impacts from oil spills on coastal habitats depends on many factors, including the oil

characteristics, the geographic location of the landfall, and the weather and oceanographic

conditions at the time (MMS, 2007b).  Oil that makes it to beaches may be either liquid

weathered oil, an oil‐and‐water mousse, or tarballs (MMS, 2007b).  Oil is generally deposited on

beaches in lines defined by wave action at the time of landfall.  Oil that remains on the beach

will thicken as its volatile components are lost.  Thickened oil may form tarballs or aggregations

that incorporate sand, shell, and other materials into its mass.  Tar may be buried to varying

depths under the sand.  On warm days, both exposed and buried tarballs may liquefy and ooze.  

Oozing may also serve to expand the size of a mass as it incorporates beach materials.  Oil on

beaches may be cleaned up manually, mechanically, or both.  Some oil can remain on the beach

at varying depths and may persist for several years as it slowly biodegrades and volatilizes.

Wetlands are highly sensitive to oiling.  The MMS (2007b) predicted that for every 50 bbl of oil

contacting wetlands, approximately 2.7 ha (6.7 ac) of wetland vegetation will experience
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dieback.  Thirty percent of these damaged wetlands are assumed to recover within 4 years, and

85% within 10 years.  About 15% of the contacted wetlands are expected to be converted

permanently to open‐water habitat.  The critical concentration of oil is that concentration above

which impacts to wetlands will be long‐term and recovery will take longer than two growing

seasons, and which causes plant mortality and some permanent wetland loss.  Critical

concentrations of various oils are expected to vary broadly for wetland types and wetland plant

species.  Louisiana wetlands are assumed to be more sensitive to oil contact than elsewhere in

the Gulf because of high cumulative stress (MMS, 2007b).  In addition to the direct impacts of

oil, cleanup activities in marshes may accelerate rates of erosion and retard recovery rates,

which have been reported to require from years to decades following a spill (MMS, 2007b).

C.8 Socioeconomic and Other Resources

C.8.1 Recreational and Commercial Fishing

BOEMRE has reexamined the analysis for recreational and commercial fishing presented in

MMS (2007b, 2008) based on additional information and in consideration of the Macondo spill.  

No new information was found that would alter the potential impacts on commercial fishing

(BOEMRE, 2011a,b).

The main commercial fishing activity in deep waters of the northern Gulf of Mexico is pelagic

longlining for tunas, swordfishes, and other billfishes (Continental Shelf Associates, Inc., 2002).  

Pelagic longlining has occurred historically in the project area, primarily during spring and

summer.  In August 2000, the Federal government closed two areas in the northeastern Gulf of

Mexico to longline fishing (65 FR 47214, 1 August 2000).  The lease is outside of the closure

areas.

Longline gear consists of monofilament line deployed from a moving vessel and generally

allowed to drift for 4 to 5 hours (Continental Shelf Associates, Inc., 2002).  As the mainline is put

out, baited leaders and buoys are clipped in place at regular intervals.  It takes 8 to 10 hours to

deploy a longline and about the same time to retrieve it.  Longlines are often set near

oceanographic features such as fronts or downwellings, with the aid of sophisticated on‐board

temperature sensors, depth finders, and positioning equipment.  Vessels typically are 10 to 30 m

(33 to 98 ft) long, and their trips last from about 1 to 3 weeks.  The main Gulf of Mexico

homeports for longlining vessels are in Louisiana (Dulac and Venice) and Florida (Destin,

Madeira Beach, and Panama City).

It is unlikely that any commercial fishing activity other than longlining occurs at or near the

project area.  Benthic species targeted by commercial fishers occur on the upper continental

slope, well inshore of the project area.  Royal red shrimp are caught by trawlers in water depths

of about 250 to 550 m (820 to 1,804 ft).  Tilefish are caught by bottom longlining in water

depths from about 165 to 450 m (540 to 1,476 ft) (Continental Shelf Associates, Inc., 2002).

Most recreational fishing activity in the region occurs in water depths less than 200 m (656 ft)

(Continental Shelf Associates, Inc., 1997, 2002).  In deeper water, the main attraction to

recreational fishers would be petroleum rigs offshore Texas and Louisiana.  Due to the distance

from shore, it is unlikely that recreational fishing activity is occurring in the lease area.
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The only routine IPF potentially affecting fisheries is drilling rig presence (including noise and

lights).  Two potential accidents are also addressed below – a small fuel spill and a large oil spill

(WCD).

Impacts of Drilling Rig Presence

There is a slight possibility of pelagic longlines becoming entangled in the drilling rig.  For

example, in January 1999, a portion of a pelagic longline snagged on the acoustic Doppler

current profiler of a drillship working in the Gulf of Mexico (Continental Shelf Associates, Inc.,

2002).  The line was removed without incident.  Generally, longline fishers use radar and are

aware of offshore structures and ships when placing their sets.  Therefore, little or no impact on

pelagic longlining is expected.

Because it is unlikely that any recreational fishing activity is occurring in the project area, no

adverse impacts are anticipated.  Other factors such as effluent discharges are likely to have

negligible impacts on commercial or recreational fisheries due to rapid dispersion, the small

area of ocean affected, and the intermittent nature of the discharges.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during

routine operations including fuel transfer.  In the unlikely event of a spill, implementation of

Anadarko’s OSRP will potentially mitigate and reduce the potential for impacts.  EP Section H

provides detail on spill response measures.  Given the open ocean location of the lease area, the

duration of a small spill and opportunity for impacts to occur would be very brief.

Pelagic longlining activities in the lease area, if any, could be interrupted in the event of a small

fuel spill.  The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha

(1.2 to 12 ac), depending on sea state and weather conditions.  Fishing activities could be

interrupted due to the activities of response vessels operating in the lease area.  A small fuel

spill would not affect coastal water quality because the spill would not be expected to make

landfall or reach coastal waters prior to breaking up (see Section A.9.2).

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on fishing activities are discussed in recent EISs (MMS, 2007b, 2008).  For

this EP, there are no unique site‐specific issues with respect to this activity.

Pelagic longlining activities in the lease area and other fishing activities in the northern Gulf of

Mexico could be interrupted in the event of a large oil spill.  A spill may or may not result in

fishery closures, depending on the duration of the spill, the oceanographic and meteorological

conditions at the time, and the effectiveness of spill response measures.  The recent Macondo

spill provides information about the maximum potential extent of fishery closures in the event

of a large oil spill in the Gulf of Mexico (NMFS, 2010d).  At its peak on 12 July 2010, closures

encompassed 217,821 km2 (84,101 mi2

), or 34.8% of the U.S. Gulf of Mexico EEZ.

C.8.2 Public Health and Safety

There are no IPFs associated with routine operations that are expected to affect public health

and safety.  Impacts of a small fuel spill and a large oil spill (WCD) are addressed below.
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Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during

routine operations including fuel transfer.  In the unlikely event of a spill, implementation of

Anadarko’s OSRP will potentially alleviate the potential for impacts.  EP Section H provides detail

on spill response measures.

A small fuel spill would not have any impacts on public health and safety because it would affect

only a small area of the open ocean 153 miles (246 km) from the nearest shoreline and nearly all

of the diesel fuel would evaporate or disperse naturally within 24 hours.  Response crews would

be equipped with appropriate safety equipment to avoid injury and health effects.  A small fuel

spill would not be expected to make landfall or reach coastal waters prior to breaking up

(see Section A.9.2).

Impacts of a Large Oil Spill (WCD)

In the event of a large spill from a blowout, the main safety and health concerns are those of the

offshore personnel involved in the incident and those responding to the spill.  The drilling rig

maintains a Shipboard Oil Pollution Emergency Plan as required under MARPOL 73/78.

Depending on the spill rate and duration, the physical/chemical characteristics of the oil,

meteorological and oceanographic conditions at the time, and the effectiveness of spill response

measures, the public could be exposed to oil on the water and along the shoreline, including

skin contact or breathing VOCs.  Crude oil is a highly flammable material, and any smoke or

vapors from a crude oil fire can cause irritation, and in large quantities may pose a health

hazard.

Data from the recent Macondo spill provide relevant information about the types of health

issues that may occur in the event of a large oil spill (Centers for Disease Control and Prevention,

2010a).  Wildlife cleaning  and rehabilitation workers have reported concerns including scrapes

and cuts, itchy or red skin or rash, and symptoms of headache or feeling faint, dizzy, or fatigued.  

Hand, shoulder, or back pain was also reported by some wildlife‐cleaning workers.  Personnel

working on offshore vessels or providing direct oversight to offshore vessels, including

USCG personnel, civilian contractors, and other responders who were exposed to oil and

dispersants, had a 7 to 12 times higher prevalence of upper respiratory symptoms and cough

than those not exposed (Centers for Disease Control and Prevention, 2010b).  Another potential

occupational hazard for spill response workers in general was heat stress from work in a hot and

humid environment.  Initial symptoms from cleanup workers who sought medical care in

Louisiana were typical of acute exposure to hydrocarbons or H2S such as headaches, dizziness,

nausea, vomiting, cough, respiratory distress, and chest pain (Solomon and Janssen, 2010).

C.8.3 Employment and Infrastructure

There are no IPFs associated with routine operations that are expected to affect employment

and infrastructure.  The project involves drilling with support from existing shorebase facilities in

Louisiana.  No new or expanded facilities will be constructed, and no new employees are

expected to move permanently into the area.  The project will have a negligible impact on

socioeconomic conditions such as local employment, existing offshore and coastal infrastructure

(including major sources of supplies, services, energy, and water), and minority and lower

income groups.  Impacts of a small fuel spill and a large oil spill (WCD) are addressed below.
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Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during

routine operations including fuel transfer.  In the unlikely event of a spill, implementation of

Anadarko’s OSRP will potentially mitigate and reduce the potential for impacts.  EP Section H

provides detail on spill response measures.  Given the open ocean location of the lease area, the

duration of a small spill and opportunity for impacts to occur would be very brief.

A small fuel spill that is dissipated within a few days would have little or no economic impact, as

the spill response would use existing facilities, resources, and personnel.

Impacts of a Large Oil Spill (WCD)

Potential socioeconomic impacts of an oil spill are discussed in recent EISs (MMS, 2007b, 2008).  

For this EP, there are no unique site‐specific issues with respect to employment and coastal

infrastructure.  A large spill could cause economic impacts in several ways: it could result in

extensive fishery closures that put fishermen out of work; it could result in temporary

employment as part of the response effort; it could result in adverse publicity that affects

employment in coastal recreation and tourism industries; and it could result in another

suspension of OCS drilling activities, including service and support operations that are an

important part of local economies.

In addition to the analyses presented by MMS (2007b, 2008) and BOEMRE (2011a,b), a recent

study explored the economic impacts of the Macondo spill on oil and gas industry employment

due to suspension of deepwater drilling (Inter‐Agency Economic Report, 2010).  The study

indicates that during the moratorium, the number of oil industry workers in the Gulf of Mexico

fell by about 2,000 and may have indirectly caused a temporary loss of 8,000 to 12,000 jobs

along the Gulf Coast.  Total spending by drilling operators is estimated to have declined by

$1.8 billion over a 6‐month period; this direct reduction in spending affected employment in the

industries that supply the Gulf drilling industry and in all other industries affected by declines in

consumer and business spending (Inter‐Agency Economic Report, 2010).

C.8.4 Recreation and Tourism

BOEMRE has reexamined the analyses for recreation and tourism presented in MMS (2007b,

2008) based on additional information and in consideration of the Macondo oil spill event.  No

new information was found that would alter the potential impacts on recreation and tourism

(BOEMRE, 2011a,b).

There are no known recreational uses of the lease area.  Recreational resources and tourism in

coastal areas would not be affected by any routine activities due to the distance from shore.  

Compliance with NTL 2007‐G03 will minimize the chance of trash or debris being lost overboard

from the drilling rig and subsequently washing up on beaches.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during

routine operations including fuel transfer.  In the unlikely event of a spill, implementation of

Anadarko’s OSRP will potentially help mitigate and reduce the potential for impacts.  

EP Section H provides detail on spill response measures.  Given the open ocean location of the

lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.
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A small fuel spill in the lease area would be unlikely to affect recreation and tourism.  There are

no known recreational or tourism activities occurring in the lease area, and as explained in

Section A.9.2, a small fuel spill would not be expected to make landfall or reach coastal waters

prior to breaking up.

Impacts of a Large Oil Spill (WCD)

Potential impacts of an oil spill on recreation and tourism are discussed in recent EISs

(MMS, 2007b, 2008).  For this EP, there are no unique site‐specific issues with respect to these

impacts.

Impacts on recreation and tourism would vary depending on the duration of the spill and its fate

including the effectiveness of response measures.  A large spill that reached coastal waters and

shorelines could adversely affect recreation and tourism by contaminating beaches and

wetlands, resulting in negative publicity that encourages people to stay away.  In addition to the

analysis presented by MMS (2007b, 2008), recent and ongoing studies have explored the

economic impacts of the Macondo spill including tourism and “brand” damage (IEM, 2010;

Oxford Economics, 2010).  The U.S. Travel Association has estimated the economic impact of the

Macondo spill on tourism across the Gulf Coast over a 3‐year period at $22.7 billion (Oxford

Economics, 2010).  

C.8.5 Land Use

Land use along the northern Gulf Coast is discussed in recent lease sale EISs (MMS, 2007b,

2008).  There are no routine IPFs potentially affecting land use.  The project will use existing

onshore support facilities in Louisiana.  The land use at the existing shorebase sites is industrial.  

The project will not involve any new construction or changes to existing land use and, therefore,

will not have any impacts.  Levels of boat and helicopter traffic, as well as demand for goods and

services including scarce coastal resources, will represent a small fraction of the level of activity

occurring at the shorebases.

A large oil spill (WCD) is the only relevant accident IPF.  A small fuel spill would not have any

impacts on land use, as the response would be staged out of existing shorebases and facilities.

Impacts of a Large Oil Spill (WCD)

The initial response for a large oil spill would be staged out of existing facilities, with no effect on

land use.  A large spill could have limited temporary impacts on land use along the coast if

additional staging areas were needed.  For example, during the Macondo spill, temporary

staging areas were established in Louisiana, Mississippi, Alabama, and Florida for spill response

and cleanup efforts.  In the event of a large spill in the lease area, similar temporary staging

areas could be needed.  These areas would eventually return to their original use as the

response is demobilized.

C.8.6 Other Marine Uses

The lease area is not located within any USCG‐designated fairway or shipping lane or Military

Warning Area.  Anadarko will comply with BOEMRE requirements and lease stipulations to avoid

impacts on uses of the area by military vessels and aircraft.
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The nearest wellhead to the proposed operations is WR 8 #1, which is more than 1,720 m

(5,642 ft) northeast of the proposed wellsites.  No other man‐made features or other potentially

hazardous seafloor conditions are identified in the vicinity of the proposed well site

(AOA Geophysics Inc., 2011).  

There are no IPFs from routine project activities that are likely to affect other marine uses of the

lease area.  A large oil spill (WCD) is the only relevant accident IPF.  A small fuel spill would not

have any impacts on other marine uses because spill response activities would be mainly within

the lease area and the duration would be brief.

Impacts of a Large Oil Spill (WCD)

An accidental spill would be unlikely to significantly affect shipping or other marine uses.  The

blocks are not located within any USCG‐designated fairway or shipping lane.  In the event of a

large spill requiring numerous response vessels, coordination would be required to manage the

vessel traffic for safe operations.  Anadarko will comply with BOEMRE requirements and lease

stipulations to avoid impacts on uses of the area by military vessels and aircraft.

In the event of a large spill requiring numerous vessels in the area, coordination would be

required to ensure that no anchoring or seafloor‐disturbing activities occur near the existing

pipelines and flowlines.

D.  Environmental Hazards

D.1 Geologic Hazards

The Shallow Hazards Assessment conducted by AOA Geophysics, Inc. (2011) concluded that the

wellsites are free of any significant geological hazards are suitable for the proposed activities.  

See EP Section C for supporting geological and geophysical information.

D.2 Severe Weather

Under most circumstances, weather is not expected to have any effect on the proposed

activities.  Extreme weather, including high winds, strong currents, and large waves, was

considered in the design criteria for the drilling rigs under consideration for this project.  High

winds and limited visibility during a severe storm could disrupt support activities (vessel and

helicopter traffic) and make it necessary to suspend some activities on the drilling rig for safety

reasons until the storm or weather event passes.  In the event of a hurricane, procedures as

outlined in the Hurricane Evacuation Plan would be adhered to.

D.3 Currents and Waves

Metocean conditions such as sea states, wind speed, ocean currents, etc. will be continuously

monitored.  Under most circumstances, physical oceanographic conditions are not expected to

have any effect on the proposed activities.  Strong currents (e.g., caused by Loop Current eddies

and intrusions) and large waves were considered in the design criteria for the drilling rigs under

consideration for this project.  High waves during a severe storm could disrupt support activities
Walker Ridge Block 51 August 2011

Environmental Impact Analysis Page 67

(i.e., vessel and helicopter traffic) and make it necessary to suspend some activities on the

drilling rig for safety reasons until the storm or weather event passes.

E.  Alternatives

No formal alternatives were evaluated in this EIA for an EP.  However, various technical and

operational options, including the location of the wellsites and the selection of a drilling unit,

were considered by Anadarko in developing the proposed action.  

F.  Mitigation Measures

The proposed action includes numerous mitigation measures required by laws, regulations, and

BOEMRE lease stipulations and NTLs.  The project will comply with all applicable Federal, State,

and local requirements concerning air pollutant emissions, discharges to water, and solid waste

disposal.  All project activities will be conducted under guidance by Anadarko’s OSRP and will

include the measures described in EP Section H.

G.  Consultation

No persons or agencies were consulted during the preparation of this EIA.

H.  Preparers

The EIA was prepared by CSA International, Inc.  Contributors included

• M. John Thompson (Senior Scientist);

• Carlyle Kalloo (Senior Scientist);

• Neal Phillips, Ph.D. (Senior Scientist);

• Luis Lagera, Jr., Ph.D. (Senior Scientist);

• Keith VanGraafeiland (GIS/Remote Sensing Specialist);

• Kristen L. Metzger (Library and Information Services Director); and

• Danielle Johnson (Technical Editor).
Walker Ridge Block 51 August 2011

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