UNITED STATES GOVERNMENT MEMORANDUM

To: Public Information (MS 5030)

Plans Section, Office of Field 

Operations (MS 5231)

Public Information copy of Exploration Plan

Control # - S-07514

Type - Supplemental Exploration Plan

Lease(s) - OCS-G17001 Block - 508 Walker Ridge Area

OCS-G18730 Block - 507 Walker Ridge Area

Operator - Shell Offshore Inc.

Subsea Wells G, H and I

DP SEMISUBMERSIBLE

Attached is a copy of the subject plan for public comments on issues that 

should be addressed in an Environmental Assessment.

It has been deemed submitted as of this date and is under review for approval.

Michelle Griffitt

Plan Coordinator

Description -

Rig Type -

Subject:

From:

November 22, 2011
Shell Offshore Inc.

P. O. Box 61933

New Orleans, LA 70161-1933

United States of America

Tel +1 504 728 7215

Fax +1 504 728 6747

Telex http://www.shell.com/eandp-en

Email Sylvia.bellone@shell.com

September 26, 2011 

Ms. Liz Peuler, Section Chief 

Bureau of Ocean Energy Management, 

Regulation and Enforcement 

1201 Elmwood Park Boulevard 

New Orleans, LA 70123-2394 

 

Attn: Plans Group MS 5231 

SUBJECT: Supplemental Exploration Plan 

 OCS-G 18730 & 17001, Walker Ridge Blocks 507 & 508 

 Unit No. 754306006 

 Offshore, Louisiana 

Dear Ms. Peuler: 

 

In compliance with 30 CFR 250.103 and NTLs 2008-G04, 2009-G27 and 2010-N06, giving Exploration Plan guidelines, 

Shell Offshore Inc (SOI) requests your approval of this Supplemental Exploration Plan to drill Well Locations G, H & I. 

Depending on rig availability operations could commence as early as February 2012. 

This Plan consists of a series of attachments describing our intended operations. The attachments we desire to be 

exempted from disclosure under the Freedom of Information Act are marked “Confidential” and excluded from the 

Public Information Copies of this submittal. The cost recovery fee receipt of $10,326.00 is attached to the Proprietary 

copy of the Plan (pay.gov tracking No. 254AVGH8). 

Should you require additional information, please contact me as shown above. 

Sincerely, 

Sylvia A. Bellone 

Page 1 Public Information Copy
SHELL OFFSHORE INC. 

SUPPLEMENTAL EXPLORATION PLAN 

for 

OCS-G 18730, Walker Ridge Block 507 

OCS-G 17001, Walker Ridge Block 508 

Walker Ridge 508 Unit 

PUBLIC INFORMATION COPY 

PREPARED BY: 

Tracy W. Albert 

 Regulatory Specialist 

504.728.4652 

tracy.albert@shell.com

Page 2 Public Information Copy
REVISIONS TABLE:

Date of Request Plan Section What was Corrected Date Resubmitted 

10/3/2011 Corrected cover letter 

Section 6 

Section 17 

Signature on letter 

Provided attachment 6A chemo map 

Provided TCZM approval number. 

10/3/2011 

10/11/2011 Section 2J Provided PVT data used in WCD 10/21/2011 

 

 

Page 3 Public Information Copy
Supplemental Exploration Plan 

OCS-G 18730, Walker Ridge Block 507 

OCS-G 17001, Walker Ridge Block 508 

Walker Ridge 508 Unit 

Offshore, Louisiana 

Table of Contents

Section 1 PLAN CONTENTS

Section 2 GENERAL INFORMATION

Section 3 GEOLOGICAL AND GEOPHYSICAL INFORMATION

Section 4 HYDROGEN SULFIDE (H2S) INFORMATION

Section 5 MINERAL RESOURCE CONSERVATION INFORMATION

Section 6 BIOLOGICAL, PHYSICAL AND SOCIOECONOMIC INFORMATION

Section 7 WASTE AND DISCHARGE INFORMATION

Section 8 AIR EMISSIONS INFORMATION

Section 9 OIL SPILL INFORMATION

Section 10 ENVIRONMENTAL MONITORING INFORMATION

Section 11 LEASE STIPULATIONS INFORMATION

Section 12 ENVIRONMENTAL MITIGATION MEASURES INFORMATION

Section 13 RELATED FACILITIES AND OPERATIONS INFORMATION

Section 14 SUPPORT VESSELS AND AIRCRAFT INFORMATION

Section 15 ONSHORE SUPPORT FACILITIES INFORMATION

Section 16 SULPHUR OPERATIONS INFORMATION

Section 17 COASTAL ZONE MANAGEMENT ACT (CZMA) INFORMATION

Section 18 ENVIRONMENTAL IMPACT ANALYSIS (EIA) 

Section 19 ADMINISTRATIVE INFORMATION

 

 

 

 

Page 4 Public Information Copy
SECTION 1: PLAN CONTENTS

A. DESCRIPTION, OBJECTIVES & SCHEDULE

Shell Offshore Inc. (Shell) is submitting a Supplemental Exploration Plan (SEP/Plan) for Walker Ridge (WR) 

Blocks 507 and 508. BP Exploration & Production filed the initial EP for Lease OCS-G 17001 for the drilling of 

wells A and B (Plan Control Number N-8155). Shell submitted a Supplemental EP for wells C and D in WR 

508, which was approved by BOEMRE on May 23, 2006 (Plan Control Numbers S-6899), and three revised 

EP’s for wells B, C & D (Plan Control Numbers R-4538, R-4429 and R-4309). Shell also filed supplemental

plan S-7129 for wells E and F, approved November 2, 2007. Shell is now submitting a Supplemental EP that 

includes three exploration wells in WR 508 and 509: G, H, and I. The wells will be drilled and temporarily 

abandoned (cement plugs and corrosion cap in accordance with 30 CFR 250.1721) until the wells are 

completed and developed under future plans. If the wells are unsuccessful, they will be permanently plugged 

and abandoned in accordance with BOEM regulations. 

The drilling activities are planned to commence on or about February 1, 2012 and take last approximately 149

days per well. The timeframe to complete the initial drilling activities is an estimate based on the best 

available information regarding downhole conditions likely to be encountered while drilling each well and not 

intended to be a limitation. 

The lease area is 178 miles from the nearest shoreline, 193 miles from the onshore support base at Port 

Fourchon, Louisiana, and 221 miles from the helicopter base at Amelia, Louisiana. Water depths at the 

wellsites range from 9,554 to 9,578 feet (Attachment 1-A). 

The proposed Rig is a DP semi-submersible, a self-contained drilling vessel with accommodations for a crew 

which includes quarters, galley and sanitation facilities. The Rig will comply with the requirements in the Interim 

Final Rules. The drilling activities will be supported by the support vessels and aircraft as well as onshore 

support facilities as listed in Sections 14 and 15 of the SEP. Shell has employed or contracted with trained 

personnel to carry out its exploration activities. Shell is committed to local hire, local contracting and local 

purchasing to the maximum extent possible. Shell personnel and contractors are experienced at operating in 

the Gulf of Mexico and are well versed in all Federal and State laws regulating operations. Shell’s employees 

and contractors share Shell’s deep commitment to operating in a safe and environmentally responsible manner. 

Shell, through its parent and affiliate corporations, has extensive experience safely exploring for oil and gas in 

the Gulf of Mexico. Shell will draw upon this experience in organizing and carrying out its planned WR 507 and 

508 drilling program. Shell believes that the best way to manage blowouts is to prevent them from happening. 

Significant effort goes into the design and execution of wells and into building and maintaining staff 

competence. In the unlikely event of a spill, Shell’s Regional OSRP is designed to contain and respond to a spill 

that meets or exceeds the WCD as detailed in Section 9 of this SEP. The WCD does not take into account 

potential flow mitigating factors such as well bridging, obstructions in wellbore, reservoir barriers, or early 

intervention. We continue to invest in Research and Development (R&D) to improve safety and reliability of our 

well systems. All operations will be conducted in accordance with applicable federal and state laws, regulations, 

and lease and permit requirements. Shell will have trained personnel and monitoring programs in place to 

ensure such compliance. 

B. LOCATION

See attached location plats and BOEM forms (Attachments 1-A and 1-B). 

C. RIG SAFETY AND POLLUTION FEATURES: 

The rig to be used on Stones will be the Noble Danny Adkins (or similar), a dynamically positioned MODU. The 

BOP stack on this rig is equipped with two fit for purpose shearing rams, one casing shear ram and one blind 

shear ram. Also, the Noble Danny Adkins is equipped with a deadman/autoshear system, an acoustic backup 

control system, and an emergency disconnect system for disconnecting and closing the shear rams. 

The rig will comply with all of the regulations of the American Bureau of Shipping (ABS), International Maritime 

Organization (IMO) and the United States Coast Guard (USCG). All drilling operations will be conducted under 

the provisions of 30 CFR, Part 250, Subpart D, and other applicable regulations and notices, including those 

regarding the avoidance of potential drilling hazards and safety and pollution prevention control. Such 

Page 5 Public Information Copy
measures as inflow detection and well control, monitoring for loss of circulation and seepage loss, and casing 

design will be our primary safety measures. Pollution prevention measures are as follows:

DRAIN SYSTEM POLLUTION FEATURES 

Drains are provided on the Rig in all spaces and on all decks where water or oil can accumulate. The drains 

are divided into two categories, non-contaminated and contaminated. All deck drains are fitted with a 

removable strainer plate to prevent debris entering the system. 

Deck Drainage from rainfall, Rig washing, deck washing, and runoff from curbs and gutters, including drip 

pans and work areas, are discharged depending on if it came into contact with the contaminated or noncontaminated areas of the Rig. 

1) Non-contaminated Drains 

Non-contaminated drains are designated as drains that under normal circumstances do not contain 

hydrocarbons, and can be discharged directly overboard. These are mostly located around the main deck and 

outboard in places where it is unlikely that hydrocarbons will be found. 

Drains within 50 feet of a designated chemical storage area which uses the weather deck as a primary 

containment means shall be designated “normally plugged.” An adequate number of drains around the rig 

shall be designated as “normally open” to allow run-off of rain water. Normally open drains shall have a plug 

located in a conspicuous area near the drain which can be easily installed in the event of a spill. 

The rig’s drain plug program consist at a minimum of a weekly check of all deck drains leading to the sea to 

verify that their status is as designated If normally open they shall verify that the drain is open and that the 

plug is available in the area. If normally closed they shall verify that the plug is securely installed in the 

drain. 

In the event a leak or spill is observed, the event shall be contained (drain plug installation and / or spill kit 

deployment as appropriate) and reported immediately. 

Rig personnel shall ensure that the perimeter kick-plates on weather decks are maintained and drain plugs 

are in place as needed to ensure a proper seal. 

2) Contaminated Drains 

Contaminated drains are designated as drains that contain hydrocarbons and cannot be discharged 

overboard. When oil-based mud is used for drilling it will be collected in portable tanks and sent to shore for 

processing. 

3) Oily Water Processing 

Oily water is collected in an oily water tank. It must be separated and not pumped overboard until oil content 

is < 15 ppm. The separated oil is pumped to a dirty oil tank and has to be sent ashore for disposal. On board 

the MODU, an oil record log will be kept according to instructions included in the log. Any and all pollution 

pans are subjected to a sheen test before being pumped out. If the water passes the sheen test then it is 

pumped over board. If it does not pass the sheen test then the water/oil mixture is pumped to a dirty oil tank 

and sent to shore for disposal. All waste oil that is sent in to be disposed of is recorded in the MODU’s oil log 

book. 

All discharges will be in accordance with applicable EPA NPDES permits. See Section 18 of this Plan. 

4) Lower Hull Bilge System 

• The main bilge system is designed to drain the pontoons. There are Gould’s electrically driven, self 

priming centrifugal pumps - one for each main pump room. The aux pumps can be pump out with the 

bilge pump but has to be lined up manually from the main pump room. 

• Bilge water is pumped overboard after a sheen test has been completed. 

Page 6 Public Information Copy
• The pontoon bilge pumps are operable from the Bridge, and have audible and visual bilge alarms set for 

high and low levels. 

• Portable submersible pumps are carried onboard the rig to service all column void spaces and are also 

used for emergency bilge pump in the event of the main pump room flooding. 

• Alternate means of pumping the bilges in each pontoon pump room include the use of: 

• The ballast system emergency bilge valve which is operated from the control panel. 

• Portable submersible pumps 

• Emergency bilge suction line connected directly to the ballast manifold. (Main Pump rooms only) 

The Bilge pumps are manual/automatic type pumps. They are equipped with sensors that give a high and a 

high-high alarm. They are set to a point at which the water gets to a certain point they will automatically turn 

on to pump water out in order to keep flooding under control. The pumps are also capable of being put in 

manual mode in which they can be turned on by hand. 

5) Emergency Bilge System 

Main ballast pumps may also be used for emergency bilge pumping directly from the pump rooms via 

remotely actuated direct bilge suction valves on the ballast system. These valves will operate in a fully 

flooded compartment. The ballast pumps can be supplied from the emergency switchboard. 

6) Oily Water Drain/Separation System

Oily water/engine room bilge water is collected in an oily water tank. It must be separated and not pumped 

overboard until oil content is < 15 ppm. The separated oil is pumped to a dirty oil tank and has to be sent 

ashore for disposal. On board all drilling Units, an oil record log has to be kept according to instructions 

included in the log. The rig floor has two skimmer tanks and each is subjected to a sheen test before 

pumping overboard to ensure environmental safety. All three anchor winch windlasses have skimmer tanks 

and are subjected to sheen tests before discharge as well. 

7) Drain, Effluent and Waste Systems 

• The Rig’s drainage system is designed in line with our environmental and single point discharge 

policies. Drains are either hazardous, i.e. from a hazardous area as depicted on the Area Classification 

drawings, or non-hazardous drains from nonhazardous areas. 

• To prevent migration of hazardous materials and flammable gas from hazardous to non-hazardous 

areas, the drainage systems are segregated. 

• The Rig drainage systems tie into oily water separators that take out elements in the drainage that 

could harm the environment. This is part of Noble’s initiative to be good stewards of the environment. 

The oily water separators divide the drainage system into these sections: 

8) Rig Floor Drainage 

The Rig floor has been outfitted with a Facet International MAS 34-3 separator. The separator has coalescent 

plates that remove the solids from the drainage, and the remaining drainage goes to a skimmer tank. From 

the skimmer tank it is drained to one of the column dirty oil tank systems where it is then sent through 2 

separators and cleaned further to reduce oil content to less than 15 ppm. 

9) Columns #3 & 4 

The drains on the decks and machinery spaces are separated at mid ship and directed to either the #3 or #4 

columns. The separators in these columns go through three cycles of circulation and remove oil to less than 

15 ppm, then discharge the clean product to sea. 

10) Main Engine Rooms 

• The engine rooms have their own drainage and handling system. The engine rooms are outfitted with 

a dirty oil tank and the drainage in the tank is processed through the separator, the waste from the 

separator goes back to the dirty oil tank and the clean water (less than 15ppm) goes overboard. 

• The locations and models of the separators are as follows: 

• Column #3 – Westfalia WSD-18

Page 7 Public Information Copy
• Column #4 – Westfalia WSD-18

• Drill Floor – Facet International MAS 34-3 

11) Helideck Drains 

The helideck has a dedicated drainage system around its perimeter to drain heli-fuel from a helicopter 

incident. The fuel can be diverted to the designated heli-fuel recovery tank which is located under the 

Helideck structure. 

Operating configurations are as follows: 

 The overboard piping valves and hydrocarbons take on valves are closed and locked. To unlock 

overboard or take on valves a permit has to be filled out. 

 The oily water collection tank overflow valve is closed. 

 The drill floor drains are lined-up to the drill floor skimmer tank. The skimmer tanks have a high 

alarm which sounds by means of an air horn. Before tanks are pumped out a sheen test is 

performed. Water is pumped out the skimmer tanks down the shunt line. The oil containment side is 

pumped out into 550 gal tote tanks. 

 The BOP test area drains are normally lined-up to drain overboard. 

 The oily water separator continuously circulates the oily water collection tank. Waste oil is discharged 

into the waste oil tank and oily water is re-circulated back into the oily water collection tank. Clean 

water is pumped overboard, which is controlled and monitored by the oil content detector, set at 15 

ppm. 

 The solids control system is capable of being isolated for cuttings collection. 

 The bilge system is normally pumped directly overboard after a sheen test has been performed. 

 The engine dirty oil sump can be drained down to the Port column oily water separator which 

discharges water overboard from the water side and oil is pumped out into a 550 gallon tote tank on 

the containment side. There is a high audible alarm on the ballast control panel. 

D. Storage Tanks - Noble Danny Adkins (or similar) 

Tank Name Tank Number of Total Contents

Capacity (bbls) Tanks Capacity (bbls) Gravity (API)

Fuel Oil Storage PFO-1 2652 1 2652 No. 2 diesel

Fuel Oil Storage PFO-2 1743 1 1743 No. 2 diesel

Fuel Oil Storage PFO-3 5844 1 5844 No. 2 diesel

Fuel Oil Storage PFO-4 4399 1 4399 No. 2 diesel

Fuel Oil Storage SFO-1 4540 1 4540 No. 2 diesel

Fuel Oil Storage SFO-2 3400 1 3400 No. 2 diesel

Fuel Oil Storage SFO-3 4399 1 4399 No. 2 diesel

Fuel Oil Storage SFO-4 821 1 821 No. 2 diesel

Fuel Oil Settling Tanks 129 4 516 No. 2 diesel

Fuel Oil Day Tanks 115 4 460 No. 2 diesel

PDT-3 (EDG) tank 63 1 63 No. 2 diesel

Fuel Oil Settling Tanks SST-1, SST-2, PST-1, PST-2 are each 129 Bbls.

Fuel Oil Day Tanks SDT-1, PDT-1, PDT-2 are each 115 Bbls. and SDT-2 = 100 Bbls.

Page 8 Public Information Copy
E. Pollution Prevention Measures 

Pursuant to NTL 2008-G04 the proposed operations covered by this SEP do not require Shell to specifically 

address the discharges of oils and greases from the Rig during rainfall or routine operations. Nevertheless, 

Shell has provided this information as part of its response to 1(c) above. 

F. Additional Measures

 

 Health, safety, and environment (HSE) are the primary topics in pre-tour and pre-job safety 

meetings. The discussion around no harm to people or environment is a key mindset. All personnel 

are reminded daily to inspect work areas for safety issues as well as potential pollution issues. 

 All tools that come to and from the rig have their pollution pans inspected and cleaned, and plug 

installation confirmed prior to leaving the dock and prior to loading on the boat. 

 Preventive maintenance of rig equipment includes visual inspection of hydraulic lines and reservoirs 

on a routine scheduled basis. 

 All pollution pans on rig are inspected daily. 

 Containment dikes are installed around all oil containment, drum storage areas, fuel vents, and fuel 

storage tanks. 

 All used oil and fuel is collected and sent to shore for recycling. 

 Direct overboard drains on the rig are checked regularly to verify drain plugs are installed. 

 All trash containers are checked and emptied daily, and trash containers are kept covered. Trash is 

collected in a compactor and shipped to shore for disposal. 

 The rig is involved in a recycling program for cardboard, plastic, paper, glass, and aluminum. 

 Fuel hoses are changed on an annual basis. 

 Spill prevention fittings are installed on all liquid take-on hoses. 

 Shell has obtained International Organization for Standardization (ISO) 14001 certification. 

 Shell will use low-sulfur fuel to reduce air pollutant impacts. 

Page 9 Public Information Copy
Attachment 1-A 

WATER DEPTH

Page 10 Public Information Copy
 

Attachment 1-B 

U. S. Department of the Interior OMB Control Number: 1010-0151 

Minerals Management Service OMB Approval Expires: December 31, 2011 

OCS PLAN INFORMATION FORM 

General Information

Type of OCS Plan: X Exploration Plan (EP) Development Operations Coordination Document (DOCD)

Company Name: Shell Offshore Inc. MMS Operator Number: 0689

Address: P. O. Box 61933 Contact Person: Tracy Albert

New Orleans, LA 70161-1933 Phone Number: 504.728.4652

E-Mail Address: tracy.albert@shell.com

Lease(s): OCS-G 18730 & 17001 Area: Walker Ridge Block(s): 507 & 508 Project Name (If Applicable): Stones

Objective(s): X Oil Gas Sulphur Salt Onshore Base: Fouchon & 

Amelia, LA

Distance to Closest Land (Miles): 178

Description of Proposed Activities (Mark all that apply)

X Exploration drilling Development drilling

Well completion Installation of production platform

Well test flaring (for more than 48 hours) Installation of production facilities

Installation of caisson or platform as well protection structure Installation of satellite structure

Installation of subsea wellheads and/or manifolds Commence production

Installation of lease term pipelines Other (Specify and describe)

Have you submitted or do you plan to submit a Conservation Information Document to accompany this 

plan?

Yes X No

Do you propose to use new or unusual technology to conduct your activities? Yes X No

Do you propose any facility that will serve as a host facility for deepwater subsea development? Yes X No

Do you propose any activities that may disturb an MMS-designated high-probability archaeological area? Yes X No

Have all of the surface locations of your proposed activities been previously reviewed and approved by 

MMS?

Yes X No

Tentative Schedule of Proposed Activities

Proposed Activity Start Date End Date No. of Days

Drill Well G and suspend 2/1/2012 6/29/2012 149

Drill Well H and suspend 6/30/2012 11/26/2012 149

Drill Well I and suspend 11/27/2012 4/25/2013 149

Description of Drilling Rig Description of Production Platform

Jackup Drillship Caisson Tension leg platform

Gorilla Jackup Platform rig Well protector Compliant tower

Semisubmersible Submersible Fixed platform Guyed tower

X DP Semisubmersible Other (Attach Description) Subsea manifold Floating production system

Drilling Rig Name (If Known): Noble Danny Adkins or similar Spar Other (Attach Description)

Description of Lease Term Pipelines

From (Facility/Area/Block) To (Facility/Area/Block) Diameter (Inches) Length (Feet)

N/A

MMS FORM MMS-137 (December 2008 - Supersedes all previous editions of form MMS-137 which may not be used.) 

Page 11 Public Information Copy
OCS PLAN INFORMATION FORM (CONTINUED) 

Include one copy of this page for each proposed well/structure 

Proposed Well/Structure Location

Well or Structure Name/Number (If renaming well or structure, reference previous name): G Subsea Completion

Anchor Radius (if applicable) in feet: N/A X Yes No

Surface Location Bottom-Hole Location (For Wells)

Lease No. OCS-G 17001

Area Name Walker Ridge

Block No. 508

Blockline

Departures

(in feet)

N/S Departure: 4350' FSL

E/W Departure: 5440' FWL

Lambert XY 

coordinates

X: 2365600

Y: 9603390

Latitude/

Longitude

Latitude 26.4487

Longitude -90.7832

TVD (Feet): MD (Feet): Water Depth (Feet): 9,558’

Anchor Locations for Drilling Rig or Construction Barge (If anchor radius supplied above, not necessary)

Anchor Name

or No.

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor

Paperwork Reduction Act of 1995 Statement: The Paperwork Reduction Act of 1995 (44 U.S.C. Chapter 

35) requires us to inform you that MMS collects this information as part of an applicant’s Exploration Plan or 

Development Operations Coordination Document submitted for MMS approval. We use the information to 

facilitate our review and data entry for OCS plans. We will protect proprietary data according to the Freedom of 

Information Act and 30 CFR 250.196. An agency may not conduct or sponsor, and a person is not required to 

respond to, a collection of information unless it displays a currently valid Office of Management and Budget 

Control Number. The use of this form is voluntary. The public reporting burden for this form is included in the 

burden for preparing Exploration Plans and Development Operations Coordination Documents. We estimate that 

burden to average 580 hours per response, including the time for reviewing instructions, gathering and 

maintaining data, and completing and reviewing the form. Direct comments regarding the burden estimate or 

any other aspect of this form to the Information Collection Clearance Officer, Mail Stop 4230, Minerals 

Management Service, 1849 C Street, N.W., Washington, DC 20240.

MMS FORM MMS-137 (December 2008 - Supersedes all previous editions of form MMS-137 which may not be used.)

Page 12 Public Information Copy
OCS PLAN INFORMATION FORM (CONTINUED) 

Include one copy of this page for each proposed well/structure 

Proposed Well/Structure Location

Well or Structure Name/Number (If renaming well or structure, reference previous name): H Subsea Completion

Anchor Radius (if applicable) in feet: N/A X Yes No

Surface Location Bottom-Hole Location (For Wells)

Lease No. OCS- G 17001

Area Name Walker Ridge

Block No. 508

Blockline

Departures

(in feet)

N/S Deprture: 3868’ FSL

E/W Departure: 4809' FWL

Lambert XY 

coordinates

X: 2364969

Y: 9602908

Latitude/

Longitude

Latitude 26.4474

Longitude -90.7852

TVD (Feet): MD (Feet): Water Depth (Feet): 9,554’

Anchor Locations for Drilling Rig or Construction Barge (If anchor radius supplied above, not necessary)

Anchor Name

or No.

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor

Paperwork Reduction Act of 1995 Statement: The Paperwork Reduction Act of 1995 (44 U.S.C. Chapter 

35) requires us to inform you that MMS collects this information as part of an applicant’s Exploration Plan or 

Development Operations Coordination Document submitted for MMS approval. We use the information to 

facilitate our review and data entry for OCS plans. We will protect proprietary data according to the Freedom of 

Information Act and 30 CFR 250.196. An agency may not conduct or sponsor, and a person is not required to 

respond to, a collection of information unless it displays a currently valid Office of Management and Budget 

Control Number. The use of this form is voluntary. The public reporting burden for this form is included in the 

burden for preparing Exploration Plans and Development Operations Coordination Documents. We estimate that 

burden to average 580 hours per response, including the time for reviewing instructions, gathering and 

maintaining data, and completing and reviewing the form. Direct comments regarding the burden estimate or 

any other aspect of this form to the Information Collection Clearance Officer, Mail Stop 4230, Minerals 

Management Service, 1849 C Street, N.W., Washington, DC 20240.

MMS FORM MMS-137 (December 2008 - Supersedes all previous editions of form MMS-137 which may not be used.)

Page 13 Public Information Copy
OCS PLAN INFORMATION FORM (CONTINUED) 

Include one copy of this page for each proposed well/structure 

Proposed Well/Structure Location

Well or Structure Name/Number (If renaming well or structure, reference previous name): I Subsea Completion

Anchor Radius (if applicable) in feet: N/A X Yes No

Surface Location Bottom-Hole Location (For Wells)

Lease No. OCS-G 17001

Area Name Walker Ridge

Block No. 508

Blockline

Departures

(in feet)

N/S Departure: 100’ FSL

E/W Departure: 7740’ FWL

Lambert XY 

coordinates

X: 2367900

Y: 9599140

Latitude/

Longitude

Latitude 26.4369

Longitude -90.7764

TVD (Feet): MD (Feet): Water Depth (Feet): 9,578’

Anchor Locations for Drilling Rig or Construction Barge (If anchor radius supplied above, not necessary)

Anchor Name

or No.

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor

Paperwork Reduction Act of 1995 Statement: The Paperwork Reduction Act of 1995 (44 U.S.C. Chapter 

35) requires us to inform you that MMS collects this information as part of an applicant’s Exploration Plan or 

Development Operations Coordination Document submitted for MMS approval. We use the information to 

facilitate our review and data entry for OCS plans. We will protect proprietary data according to the Freedom of 

Information Act and 30 CFR 250.196. An agency may not conduct or sponsor, and a person is not required to 

respond to, a collection of information unless it displays a currently valid Office of Management and Budget

Control Number. The use of this form is voluntary. The public reporting burden for this form is included in the 

burden for preparing Exploration Plans and Development Operations Coordination Documents. We estimate that 

burden to average 580 hours per response, including the time for reviewing instructions, gathering and 

maintaining data, and completing and reviewing the form. Direct comments regarding the burden estimate or 

any other aspect of this form to the Information Collection Clearance Officer, Mail Stop 4230, Minerals 

Management Service, 1849 C Street, N.W., Washington, DC 20240.

MMS FORM MMS-137 (December 2008 - Supersedes all previous editions of form MMS-137 which may not be used.)

Page 14 Public Information Copy
SECTION 2: GENERAL INFORMATION

A. Application and Permits

There are no individual or site-specific permits other than general NPDES Permit and rig move notification that 

need to be obtained. 

B. Drilling Fluids 

See Section 7, Table 7A for a list of drilling fluids to be used. 

C. Production

Information regarding production is not included in this SEP as such information is only necessary in the case 

of DOCDs. 

D. Oil Characteristics

Information regarding Oil Characteristics is not included in this SEP as such information is only necessary in 

the case of DOCDs. 

E. New Or Unusual Technology

Shell is not proposing to use new or unusual technology as defined in 30 CFR 250.200 to carry out the proposed 

activities in this SEP. 

F. Bonding

The bond requirement for the activities proposed in this SEP are satisfied by an area-wide bond furnished and 

maintained according to 30 CFR Part 256, Subpart I-Bonding; NTL No. 2000-G16, “Guideline for General Lease 

Surety Bonds” and National NTL No. 2008-N07, “Supplemental Bond Procedures.”

G. Oil Spill Financial Responsibility (OSFR)

Shell Offshore Inc (SOI), BOEM Operator Number 0689, has demonstrated oil spill financial responsibility for the 

wells proposed in the SEP according to 30 CFR Parts 250 and 253, and NTL No. 2008-N05, “Guidelines for Oil 

Spill Financial Responsibility for Covered Facilities.”

H. Deepwater well control statement

Shell Offshore Inc (SOI), BOEM Operator Number 0689, has the financial capability to drill a relief well and 

conduct other emergency well control operations. 

I. Suspension of Production

Information regarding Suspension of Production is not included in this SEP as such information is only 

necessary in the case of DOCDs. 

Page 15 Public Information Copy
J. Blowout scenario

Summary 

This Section 2j was prepared by Shell Offshore Inc. (Shell) pursuant to the guidance provided in the Bureau 

of Ocean Energy Management, Regulation and Enforcement’s (BOEMRE) Notice to Lessees (NTL) No. 2010-

N06 with respect to blowout and worst case discharge scenario descriptions. Shell intends to comply with all 

applicable laws, regulations, rules and Notices to Lessees. 

Shell focuses on an integrated, three-pronged approach to a blowout, including prevention, intervention 

/containment, and recovery. 

1. Shell believes that the best way to manage blowouts is to prevent them from happening. 

Significant effort goes into design and execution of wells and into building and maintaining staff 

competence. Shell continues to invest independently in Research and Development (R&D) to 

improve safety and reliability of our well systems. 

2. Shell is a founding member of the Marine Well Containment Company (MWCC), which provides 

robust well containment (shut-in and controlled flow) capabilities. Additionally, Shell is investing 

in R&D to improve containment systems. 

3. As outlined in Shell’s Oil Spill Response Plan (OSRP), and detailed in EP Section 9a (ii), Shell has 

contracts with Oil Spill Removal Organizations (OSROs) to provide the resources necessary to 

respond to this Worst Case Discharge (WCD) scenario. The capabilities for on-water recovery, 

aerial and subsea dispersant application, in-situ burning, and nighttime monitoring and tracking 

have been significantly increased. 

The WCD blowout scenario is calculated for well location H in corresponding exploration plan, which is 

planned as a western penetration of the Upper and Lower Wilcox Sands, based on the guidelines outlined in 

NTL No. 2010-N06 along with subsequent Frequently Asked Questions (FAQ). The WCD for the Stones H 

well, or a similarly targeted well, falls below the WCD exploratory scenario for MC-805 MB-01 (Olympus) 

included in our Regional OSRP (July 2011). In the unlikely event of a spill, Shell’s Regional OSRP is designed 

to contain and respond to a spill that meets or exceeds this WCD. 

The WCD scenario, in terms of both initial and the sustained rates, has a low probability of being realized. 

Some of the factors that are likely to reduce rates and volumes, and are not included in the WCD calculation, 

include but are not limited to, obstructions or equipment in the wellbore, well bridging, and early 

intervention, such as containment capabilities. 

Uncontrolled blowout (volume first day) 42,000 bbl 

Uncontrolled blowout rate (first 30-days average daily rate) 33,000 bopd 

Duration of flow (days) based on relief well 180 days

Total volume of spill (bbls) for 180 days 5.2 MMBO

Table 1 Worst Case Discharge Summary 

The Stones discovery is located in the Gulf of Mexico (GOM), approximately 200 miles south of New Orleans, 

Louisiana, in water depths of 7,500 – 9,500 feet (ft) across the discovery. Stones is a four-way, faulted 

closure; a large, east-dipping fault with up to 1100’ of throw forms a key trapping element along the 

northeast side of the structure. To date, the Stones partnership has drilled four penetrations: the discovery 

well (WR508 #1), the WR508 #2 appraisal well (drilled to a TD of 12,509 ft tvdss, which did not penetrate 

the objective section), and the WR508 #3 appraisal well (with 1 additional bypass). The only objective 

horizons of the proposed Stones H well with predicted flow potential are the Upper and Lower Wilcox 

reservoirs of early Paleogene age, and the Stones H well is expected to encounter the Upper Wilcox reservoir 

at 26,331 ft tvdss. Additional WCD scenarios were evaluated for alternate well locations at Stones; however, 

the WCD numbers for these wells are lower than the WCD number calculated for the Stones H well, as these 

wells are expected to encounter less net pay and have a longer wellbore length and thus greater wellbore 

friction. These wells flowed at substantially lower rates than the Stones H well case represented for the WCD. 

Page 16 Public Information Copy
Any shallower sands will be cased off prior to the well path penetrating the Wilcox reservoir package, and 

are not expected to be oil-bearing. 

1) Purpose 

Pursuant with 30 CFR 250.213(g), 250.219, 250.250, and NTL No. 2010-N06, this document provides a 

blowout scenario description, further information regarding any potential oil spill, the assumptions and 

calculations used to determine the WCD and the measures taken to 1) enhance the ability to prevent a 

blowout and 2) respond and manage a blowout scenario if it were to occur. These calculations are based on 

best technical estimates of subsurface parameters that are derived from the offset wells and seismic. These 

parameters are better than or consistent with the estimates used by Shell to justify the investment. 

Therefore, these assumed parameters were used to calculate the WCD. They do not reflect probabilistic 

estimates. 

2) Background 

This attachment has been developed to document the additional information requirements for Exploration 

Plans as requested by NTL No. 2010-N06 in response to the explosion and sinking of the Mobile Offshore 

Drilling Unit (MODU) Deepwater Horizon and the resulting subsea well blowout and recovery operations of 

the exploration well at the MC-252 Macondo location. 

3) Information Requirements 

a) Blowout scenario 

All well locations addressed in this EP were assessed for Worst Case Discharge using the expected 

well path, the expected reservoir thickness, structural elevation, and rock/fluid properties for each. 

The Stones H deviated well with a bottom hole location (27,871 ft tvdss) on the western side of the 

Stones structure represented the highest 30-day average flow potential. The Stones H well will be 

drilled through the Upper and Lower Wilcox reservoirs as outlined in the Geological and Geophysical 

Information Section of the Stones EP, and described above, utilizing a typical subsea wellhead 

system, conductor, surface and intermediate casing program, and using a DP rig with a marine riser 

and subsea Blowout Preventer. A hydrocarbon influx and a well control event are modeled to occur 

from the Upper and Lower Wilcox reservoirs. The simulated blowout model results in unrestricted 

flow from the well at the seafloor which represents the worst case discharge, no restrictions in the 

wellbore, failure/loss of the subsea BOP, and a blowout to the seabed. 

b) Estimated flow rate of the potential blowout 

Table 2 Estimated Flow Rates of a Potential Blowout 

c) Total volume and maximum duration of the potential blowout 

Duration of flow (days) 180 days total duration to drill relief well 

(14 rig mob, 3 transit, 130 spud to top Wilcox, 33 ranging).

Total volume of spill (bbls) 5.2 MMBO based on 180 days flowing. 

Note: From CMG dynamic reservoir model

Table 3 Estimated Duration and Volume of a Potential Blowout 

Category EP 

Type of Activity Drilling 

Facility Location (area/block) WR-508

Facility Designation DP

Distance to Nearest Shoreline (miles) 182 Statute miles

Uncontrolled blowout (volume first day) 42,000 bbl 

Uncontrolled blowout rate (first 30-days average daily rate) 33,000 bopd 

Page 17 Public Information Copy
There is usually a decline in the discharge rate as time proceeds, which is illustrated by the 

differences between the first 24-hour volume and 30-day average rate. The total volume calculated 

until a well is killed in a potential blowout further demonstrates this decline. At very short times, e.g. 

during the first 24 hours, the pressure profile in the reservoir changes from the moment when a well 

first starts flowing to a pseudo-steady state pressure profile with time, and as a result the rate 

declines. At somewhat longer time scales, effects such as reservoir voidage and the impact of 

boundaries can cause the rate to drop continuously with production. Simulation and material balance 

models can include these effects and form the basis of the NTL No. 2010-N06 estimates for 24-hour 

and 30-day rates as well as maximum duration volumes. 

d) Assumptions and calculations used in determining the worst case discharge (Proprietary)

e) Potential for the well to bridge over 

Mechanical failure/collapse of the borehole in a blowout scenario is influenced by several factors 

including in-situ stress, rock strength and fluid velocities at the sandface. Based on the nodal analysis 

and reservoir simulation models outlined above, a seabed blowout would create a high drawdown at 

the sand face. Given the substantial fluid velocities inherent in the worst case discharge, and the 

scenario as defined where the formation is not supported by a cased and cemented wellbore, it is 

possible that the borehole may fail/collapse/bridge over within the span of a few days, significantly 

reducing outflow rates. However, this WCD scenario does not include any bridging or consideration 

of solids production with the oil and gas. 

f) Likelihood to stop the blowout 

Safety of operations is our top priority. Maintaining well control at all times to prevent a blowout is 

the key focus of our operations. Our safe drilling record is based on our robust standards, 

conservative well design, prudent operations practices, competency of personnel, and strong HSE 

focus. Collectively, these constitute a robust system making blowouts extremely rare events. 

Intervention Devices: Notwithstanding these facts, the main scenario for recovery from a blowout 

event is via intervention with the BOP attached to the well. There are built in redundancies in the 

BOP system to allow activation of selected components with the intent to seal off the well bore. As a 

minimum, the Shell contracted rig fleet in the GOM will have redundancies meeting the Interim Final 

Drilling Safety Rule with respect to Remotely Operated Vehicle (ROV) hot stab capabilities, a 

deadman system, and an autoshear system. 

The rig to be used on Stones will be the Noble Danny Adkins (or similar), a dynamically positioned 

MODU. The BOP stack on this rig is equipped with two fit for purpose shearing rams, one casing shear 

ram and one blind shear ram. Also, the Noble Danny Adkins is equipped with a deadman/autoshear 

system, an acoustic backup control system, and an emergency disconnect system for disconnecting and 

closing the shear rams. 

Containment: The experience of gaining control over the Macondo well has resulted in a better 

understanding of the necessary equipment and systems for well containment. As a result, industry 

and government are better equipped and prepared today to contain an oil well blowout in deepwater 

(See page 17 of the Decision Memorandum dated October 1, 2010). Shell is further analyzing these 

advances and incorporating them into its comprehensive approach to help prevent and, if needed, 

control another deepwater control incident. 

Pursuant to NTL No. 2010-N10, Shell will provide additional information regarding our containment 

capabilities in a subsequent filing. 

g) Availability of a rig to drill a relief well and rig package constraints 

Blowout intervention can be conducted from an ROV equipped vessel, the existing drilling rig or from 

another drilling rig. The dynamically positioned rigs under contract, the Noble Danny Adkins and the 

Bully 1, will be the preferred rigs for blowout intervention work. However, moored rigs can also be 

used in some scenarios. Additionally, in the event of a blowout, there are other non-contracted rigs 

in the GOM could be utilized for increased expediency or better suitability (e.g. Transocean 

Page 18 Public Information Copy
Discoverer Clear Leader, etc). All efforts will be made at the time to secure the appropriate rig. 

Shell’s current contracted rigs capable of operating at Stones water depths and reservoir depths 

without technical constraints are shown in the Table 4 below: 

Rig Name Rig Type

Noble Danny Adkins Dynamically positioned semi

Noble Bully 1* Dynamically positioned drill ship

Table 4 Shell Contracted Rigs Capable at Stones. 

Above are current as of July 2011. Future modifications may change the rig’s capability.

Rig capabilities need to be assessed on a work scope specific basis. 

*Bully 1 estimated arrival November 2011. Full riser kit will arrive sometime thereafter. 

h) Time taken to contract a rig, move it onsite, and drill a relief well 

Relief well operations will immediately take priority and displace any activity from Shell’s contracted 

rig fleet. The list of rigs capable of operating at Stones is tabled above. It is expected to take an 

average of 14 days to safely secure the well that the rig is working on up to the point the rig departs 

location, and an additional 3 days transit to mobilize to the relief well site depending on distance to 

the site. The relief well will take approximately 130 days to drill down to the last casing string above 

the blowout zone, plus approximately 33 days for precision ranging activity to intersect the blowout 

well bore. The expected total time to mobilize and drill a relief well would be 180 days for this well. 

If a moored rig is chosen to conduct the relief well operations, anchor handlers would be prioritized 

to prepare mooring on the relief well site while the rig is being mobilized. This activity is not expected 

to delay initiation of relief well drilling operations. Shell has 3 deepwater anchor handlers (the Laney, 

Dino, and Ross Chouest) on long term contract to support its moored rigs. 

i) Measures proposed to enhance ability to prevent blowout and to reduce likelihood of a 

blowout. 

Shell believes that the best way to manage blowouts is to prevent them from happening. Detailed 

below are the measures employed by Shell with the goal of no harm to people or the environment. 

The Macondo incident has highlighted the importance of these practices. The lessons learned from 

the investigation are, and will continue to be, incorporated into our operations. 

Standards: Shell’s well design and operations adhere to internal corporate standards, the Code of 

Federal Regulations, and industry standards. A robust management of change process is in place to 

handle un-defined or exception situations. Ingrained in the Shell standards for well control is the 

philosophy of multiple barriers in the well design and operations on the well. 

Risk Management: Shell believes that prevention of major incidents is best managed through the 

systematic identification and mitigation process (Safety Case). All Shell contracted rigs in the GOM 

have been operating with a Safety Case and will continue to do so. A Safety Case requires both the 

owner and contractors to systematically identify the risks in drilling operations and align plans to 

mitigate those risks; an alignment which is critical before drilling begins.

Well Design Workflow: The Well Delivery Process (WDP) is a rigorous internal assurance process 

with defined decision gates. The WDP leverages functional experts (internal and external) to examine 

the well design at the conceptual and detailed design stages for robustness before making a 

recommendation to the management review board. Shell’s involvement in global deepwater drilling, 

starting in the GOM in the mid-1980’s, provides a significant depth and breadth of internal drilling 

and operational expertise. Third party vendors and rig contractors are involved in all stages of the 

Page 19 Public Information Copy
planning, providing their specific expertise. A Drill the Well On Paper (DWOP) exercise is conducted 

with rig personnel and vendors involved in execution of the well. This forum communicates the well 

plan, and solicits input as to the safety of the plan and procedures proposed. 

Well and rig equipment qualification, certification, and quality assurance: All rigs will meet 

all applicable rules, regulations, and Notice to Lessees. Shell works closely with rig contractors to 

ensure proper upkeep of all rig equipment, which meets or exceeds the strictest of Shell, industry, or 

regulatory requirements. Well tangibles are governed by our internal quality assurance/control 

standards and industry standards. 

MWD/LWD/PWD Tools: Shell intends to use these tools at Stones. The MWD/LWD/PWD tools are 

run on the drill string so that data on subsurface zones can be collected as the well advances in real 

time instead of waiting until the drill string is pulled to run wireline logs. Data from the tools are 

monitored and interpreted real time against prognosis to provide early warning of abnormal 

pressures to allow measures to be taken to progress the well safely. 

Mud Logger: Mud logging personnel continually monitor returning drilling fluids for indications of

hydrocarbons, utilizing both a hot wire and a gas chromatograph. An abrupt increase in gas or oil 

carried in the returning fluid can be an indication of an impending kick. The mud logger also monitors 

drill cuttings returned to the surface in the drilling fluid for changes in lithology that can be an 

indicator that the well has penetrated or is about to penetrate a hydrocarbon-bearing interval. Mud 

logging instruments also monitor penetration rate to provide an early indication of drilling breaks that 

show the bit penetrating a zone that could contain hydrocarbons. The mud logging personnel are in 

close communication with both the offshore drilling foremen and onshore Shell representative(s) to 

report any observed anomalies so appropriate action can be taken. 

Remote Monitoring: The Real Time Operating Center has been used by Shell to complement and 

support traditional rig-site monitoring since 2003. Well site operations are lived virtually by onshore 

teams consisting of geoscientists, petrophysicists, well engineers, and 24/7 monitoring specialists. 

The same real time well control indicators monitored by the rig personnel are watched by the 

monitoring specialist for an added layer of redundancy. 

Competency and Behavior: A structured training program for Well Engineers and Foreman is 

practiced, which includes internal professional examinations to verify competency. Other industry 

training in well control, such as by International Association of Drilling Contractors (IADC) and 

International Well Control Forum (IWCF) are also mandated. Progressions have elements of 

competency and Shell continues to have comprehensive internal training programs. The best systems 

and processes can be defeated by lack of knowledge and/or improper values. We believe that a 

combination of HSE tools (e.g. stop work, pre-job analysis, behavior based safety, DWOPs, audits), 

management HSE involvement and enforcement (e.g. compliance to life saving rules) have created a 

strong safety culture in our operations. 

j) Measures to conduct effective and early intervention in the event of a blowout. 

The response to a blowout is contained in our Well Control Contingency Plan (WCCP) which is a 

specific requirement of our internal well control standards. The WCCP in turn is part of the wider 

emergency response framework within Shell that addresses the overall organization response to an 

emergency situation. Resources are dedicated to these systems and drills are run frequently to test 

preparedness (security, medical, oil spill, and hurricane). This same framework is activated and 

tested during hurricane evacuations, thereby maintaining a fresh and responsive team. 

Page 20 Public Information Copy
The WCCP specifically addresses implementing actions at the emergency site that will ensure 

personnel safety, organizing personnel and their roles in the response, defining information 

requirements, establishing protocols to mobilize specialists and pre-selecting sources, and developing 

mobilization plans for personnel, material and services for well control procedures. The plan 

references individual activity checklists, a roster of equipment and services, initial information 

gathering forms, a generic description of relief well drilling, strategy and guidelines, intervention 

techniques and equipment, site safety management, exclusion zones, and re-boarding. 

As set forth in 3f of this document, Shell is currently analyzing recent advances in containment 

technology and equipment and will incorporate them as they become available. 

k) Arrangements for drilling a relief well 

The size of the Shell contracted rig fleet in the GOM from 2010-2015 ensures that there is adequate 

well equipment (e.g. casing and wellhead) available for relief wells. Rigs and personnel will also be 

readily available within Shell, diverted from their active roles elsewhere. Resources from other 

operators can also be leveraged should the need arise. Generally, relief well plans will mirror the 

blowout well, incorporating any learning on well design based on root cause analysis of the blowout. 

A generic relief well description is outlined in the WCCP. 

l) Assumptions and calculations used in approved or proposed OSRP 

Shell has submitted MC-508 MB-01 (Olympus) as the new exploratory worst-case scenario to the 

BOEMRE for inclusion in our Regional OSRP. 

Shell has designed a response program (Regional OSRP August 2011) based upon a regional 

capability of responding to a range of spill volumes, from small operational spills up to and including 

the WCD from an exploration well blowout. Shell’s program is developed to fully satisfy federal oil 

spill planning regulations. The Regional OSRP presents specific information on the response program 

that includes a description of personnel and equipment mobilization, the incident management team 

organization, and the strategies and tactics used to implement effective and sustained spill 

containment and recovery operations. 

K. Chemical Products

Information regarding chemical products is not included in this SEP as such information is not required by 

BOEMRE GOMR. 

Page 21 Public Information Copy
SECTION 3: GEOLOGICAL AND GEOPHYSICAL INFORMATION 

A. Geological description

Proprietary data 

B. Structure Contour Map(s)

Proprietary data 

C. Interpreted 2D and/or 3D Seismic line(s)

Proprietary data 

D. Geological Structure Cross-section(s)

Proprietary data 

E. Shallow Hazards Report

The following reports were used for our analysis: 

Geoscience Earth & Marine Services, Inc. (GEMS) prepared a Geologic and Stratigraphic Assessment Report 

(Number 0306-1151) for Shell on 24 May 2006. Fugro GeoServices, Inc. (FGSI) acquired the high-resolution 

geophysical survey data utilizing FGSI’s Autonomous Underwater Vehicle (AUV) aboard the Fugro Enterprise 

in September and October of 2009. The quality of the collected geophysical data was good, and the data 

were suitable for interpretation. Fugro GeoConsulting, Inc. (FGCI) prepared an Integrated Geophysical and 

Geotechnical Field Development Planning Study based on the AUV data (Job No. 27.2009-2328), and 

delivered to Shell in May 2010. The Report was previously submitted to the BOEM with Supplemental EP S06899 on May 12, 2006. 

Additionally, enclosed are copies of FGSI AUV Archaeological Assessment Report (Number 2411-1019) for 

Shell covering Walker Ridge blocks 420, 464, 508, and 552. The Archaeological report is dated July 12, 2011. 

 

F. Shallow Hazards Assessment

Shell seeks BOEMRE approval of its Supplemental Exploration Plan for Proposed Locations G, H, and I in 

Walker Ridge Block 508. Shell plans to use a dynamically positioned vessel in the category of Noble Danny 

Adkins at Proposed Locations G, H, and I. 

 

The following wells are in the vicinity of Proposed Locations G, H, and I: 

Shell Well #1 in Walker Ridge 508 X = 2,376,971 Y= 9,605,100 

Shell Well #2 in Walker Ridge 508 X= 2,368,107 Y= 9,604,808 

Shell Well #3 in Walker Ridge 464 X = 2,367,381 Y= 9,617,757 

Regional Overview

Walker Ridge Block 508 straddles the Sigsbee Escarpment and abyssal plain. The southern half of the block is 

in an area of seafloor furrows that make for variable seafloor strength. At the proposed locations, the soils at 

the base of the furrows are of higher than normal sheer strength due to active erosion. The ridges between 

the furrows have not experienced the maximum erosion forces, thus, the soils are relatively soft. Proposed 

Locations G, H, and I are positioned between seafloor furrows. 

There are no fluid expulsion features, faults, or chemosynthetic communities within 2000 feet of the 

proposed locations. There are piston cores, drilling splays, anchor chain scars, and previously drilled wells in 

the vicinity of Proposed Locations G, H, and I but none are within 2000’ of the locations.

Page 22 Public Information Copy
Well Information

 

Walker Ridge 508, Proposed Location G: 

X = 2,365,600 5,440’ FWL 

Y = 9,603,390 4,350’ FSL

Proposed Location G will be in a water depth of approximately 9,558 feet. 

The stratigraphy at Proposed Location G consists of 224 feet of hemipelagic drape and MTD. Unit 2 has 327 

feet of muds and silts with possible thin sands. Unit 3 consists of 165 feet of muds and slits. Unit 4 consists 

of 601feet of muds and tubiditic channels with low amplitude. Unit 5 has 270 feet of muds, turbiditic 

channels and MTD. This is underlain by 608 feet of muds and silts with interbedded MTD. Unit 7 consists of 

576 feet of muds and silts with interbedded MTD. Unit 8 has 524 feet of mass-transport deposits of muds 

and silts, some sand rich turbidites with interbedded mass transport deposits. 

Units 1 to 7 exhibit low to negligible potential for shallow gas and over-pressured sands. Unit 8 has 

moderate potential for shallow water flow and shallow gas. Nevertheless, the drilling program will be 

designed to minimize any drilling risks encountered. The site appears suitable for the proposed drilling 

program. 

Walker Ridge 508, Proposed Location H: 

 X = 2,364,969 4,809’ FWL

Y= 9,602,908 3,868’ FSL

 

Proposed Location H will be in a water depth of approximately 9,554 feet. 

The stratigraphy at Proposed Location H consists of 226 feet of hemipelagic drape and MTD. Unit 2 has 328 

feet of muds and silts with possible thin sands. Unit 3 consists of 164 feet of muds and slits. Unit 4 consists 

of 608feet of muds and tubiditic channels with low amplitude. Unit 5 has 272 feet of muds, turbiditic 

channels and MTD. This is underlain by 642 feet of muds and silts with interbedded MTD. Unit 7 consists of 

575 feet of muds and silts with interbedded MTD. Unit 8 has 529 feet of mass-transport deposits of muds 

and silts, some sand rich turbidites with interbedded mass transport deposits. 

Units 1 to 7 exhibit low to negligible potential for shallow gas and over-pressured sands. Unit 8 has 

moderate potential for shallow water flow and shallow gas. Nevertheless, the drilling program will be 

designed to minimize any drilling risks encountered. The site appears suitable for the proposed drilling 

program. 

Walker Ridge 508, Proposed Location I: 

 X = 2,367,900 7,740’ FWL

Y= 9,599,140 100’ FSL

 

Proposed Location I will be in a water depth of approximately 9,578 feet. 

The stratigraphy at Proposed Location I consists of 219 feet of hemipelagic drape and MTD. Unit 2 has 292 

feet of muds and silts with possible thin sands. Unit 3 consists of 142 feet of muds and slits. Unit 4 consists 

of 649 feet of muds and tubiditic channels with low amplitude. Unit 5 has 200 feet of muds, turbiditic 

channels and MTD. This is underlain by 588 feet of muds and silts with interbedded MTD. Unit 7 consists of 

701 feet of muds and silts with interbedded MTD. Unit 8 has 355 feet of mass-transport deposits of muds 

and silts, some sand rich turbidites with interbedded mass transport deposits. 

Units 1 to 7 exhibit low to negligible potential for shallow gas and over-pressured sands. Unit 8 has 

moderate potential for shallow water flow and shallow gas. Nevertheless, the drilling program will be 

designed to minimize any drilling risks encountered. The site appears suitable for the proposed drilling 

program 

Currently, there are no pipelines in the vicinity of Proposed Locations G, H, and I. 

Page 23 Public Information Copy
Based on a high-resolution geophysical survey consisting of frequency enhanced 3-D seismic, Enhanced 

Surface Renderings, and Enhanced Surface Renderings with Amplitudes applied, AUV surveys, and side scan 

sonar, Walker Ridge Block 508, Proposed Locations G, H, and I will not disturb any chemosynthetic 

communities. 

Kevin Bradford Vernessa J. Bradford 

Geophysicist Shallow Hazards Interpreter 

 

G. High-Resolution Seismic Lines

Proprietary data - ESR Map can be found in Section 6. 

 H & I Stratigraphic Column with Time vs depth table

Proprietary data 

J. Geochemical Information

This information is not required for Plans submitted in the GOM Region. 

K. Future G&G Activities

This information is not required for Plans submitted in the GOM Region. 

Page 24 Public Information Copy
SECTION 4: HYDROGEN SULFIDE (H2S) INFORMATION 

A. Concentration 

 0 ppm. 

B. Classification

 

Based on CFR 250.490(c), SOI requests that the Regional Supervisor, Field Operations, determine the zones in the 

proposed drilling operations in this plan to be classified as an area where the absence of H2S has been confirmed. 

C. Modeling Report

We do not anticipate to encounter or handle H2S at concentrations greater than 500 parts per million (ppm) and therefore 

have not included modeling for H2S.

SECTION 5. MINERAL RESOURCE CONSERVATION INFORMATION 

Information regarding Mineral Resource Conservation is not included in this SEP as such information is only necessary in 

the case of DOCDs. 

Page 25 Public Information Copy
SECTION 6: BIOLOGICAL, PHYSICAL, AND SOCIOECONOMIC INFORMATION

A. Chemosynthetic Communities Report

ANCHOR CLEARANCE AND CHEMOSYNTHETIC

ORGANISMS COMMENTS

History

Geoscience Earth & Marine Services, Inc. (GEMS) prepared a Geologic and Stratigraphic Assessment Report 

(Number 0306-1151) for Shell on 24 May 2006. Fugro GeoServices, Inc. (FGSI) acquired the high-resolution 

geophysical survey data utilizing FGSI’s Autonomous Underwater Vehicle (AUV) aboard the Fugro Enterprise 

in September and October of 2009. The quality of the collected geophysical data was good, and the data 

were suitable for interpretation. Fugro GeoConsulting, Inc. (FGCI) prepared an Integrated Geophysical and 

Geotechnical Field Development Planning Study based on the AUV data (Job No. 27.2009-2328), and 

delivered to Shell in May 2010. The Report was previously submitted to the BOEM with Supplemental EP S06899 on May 12, 2006. 

Additionally, enclosed are copies of FGSI AUV Archaeological Assessment Report (Number 2411-1019) for 

Shell covering Walker Ridge blocks 420, 464, 508, and 552. The Archaeological report is dated July 12, 2011. 

 

Shell seeks BOEMRE approval of its Supplemental Exploration Plan for Proposed Locations G, H, and I in 

Walker Ridge Block 508. Shell plans to use a dynamically positioned vessel in the category of Noble Danny 

Adkins at Proposed Locations G, H, and I. 

 

The following wells are in the vicinity of Proposed Locations G, H, and I: 

Shell Well #1 in Walker Ridge 508, X = 2,376,971 Y = 9,605,100 

Shell Well #2 in Walker Ridge 508, X= 2,368,107 Y= 9,604,808 

Shell Well #3 in Walker Ridge 464, X = 2,367,381 Y= 9,617,757 

Chemosynthetic Community Statement

Per MMS NTL No. 2009-G40, Deepwater Benthic Communities, Attachment A 

ASSOCIATED ANCHORS – NO ANCHOR DISTURBANCES WITHIN 250 FEET OF CHEMOSYNTHETIC COMMUNITIES

For the three proposed locations G, H, I and the cleared well radii: 

Shell will observe the following separation distances from high-density deepwater benthic communities: 

1. At least 2,000 feet from each proposed muds and cuttings discharge location; 

2. At least 250 feet from the location of all other proposed seafloor disturbances (including those caused 

by anchors, anchor chains, wire ropes, seafloor template installation, and pipeline construction). 

Seafloor disturbances include all “temporary” disturbances caused during mooring operations (e.g., 

anchor deployment, setting, and retrieval) as well as those caused by anchoring activities conducted 

prior to a MODU arriving on location (e.g., pre-installation of suction piles and cables; where seafloor 

impacts are much greater while the cables are located on the seafloor prior to being pulled taut and 

attached to the MODU). 

Archaeological Report Information

Seafloor features noted are: well splays, drilling mud, anchor chain scars, and disturbed seafloor areas. A 

total of nine-hundred and sixty-two (962) side scan sonar targets are noted within the development area. 

Nine-hundred and fifty six (956) of the nine-hundred and sixty-two (962) of these targets are randomly 

scattered with similar appearances that measure less than 20 feet in length, less than 10 feet in width, and 

do not display a height above the surrounding seafloor. (FGSI Report No. 2400-1019 pg. 5) 

Page 26 Public Information Copy
Recent deep-water AUV surveys, verified by ROV video, have also shown contacts of this appearance may 

represent non-biologic partially cemented mud vent tubes. These cemented vent tubes are the result of 

erosional seafloor forces which wash away surrounding softer unconsolidated sediments surrounding the vent 

tube leaving only a partially cemented sediment vent core, which are left rising above the seafloor. These 

non-biologic partially cemented mud vent tubes can be identified on sonar records as "dark specks" not unlike 

those identified on the sonar records collected during this survey. These dark-specks were also previously 

identified during the FGCI report. 

The dark specks are defined as relict cemented vent tubes or their debris. These cemented vent tubes are 

believed to be remnants of small, partially mud filled fluid expulsion pathways that initially occupied the 

bottom of pockmarks and were exposed by erosion. 

None of the 956 (including Nos. 379, 374 and 369 which are within the 2000’ clearance area for well location 

I) sonar contacts described above are deemed archaeologically significant. Multiple debris fields containing 

numerous smaller debris targets, similar to the “dark specks” noted by FGCI, were noted during the current 

Archaeological Assessment. 

There were six (6) sonar contacts (Nos. 156, 375, 419, 421, 445, and 539) noted within the survey area that 

are larger than the “dark-specks” discussed above or correlate to known infrastructure. Sonar contact No. 

156 measures 68.9 feet in length, 3.5 feet in width, and no measurable height above the surrounding 

seafloor. This contact is linear in shape and is interpreted as modern debris, possibly a section of pipeline or 

cable. Contact no. 419 measures 57.4 feet in length, 44.5 feet in width, with a height of 11.7 feet above the 

surrounding seafloor. This contact is geologic in origin and is interpreted as a rafted block. Sonar contact No. 

421 was noted in the vicinity of the reported position of an Acoustic Doppler Current Profiler (ADCP) and 

likely represents the weights at the base of the ADCP string. Sonar contact No. 445 measures 74.9 feet in 

length, 4.4 feet in width, and no measurable height above the surrounding seafloor. This contact is linear in 

shape and is interpreted as modern debris, possibly a section of pipeline or cable. Sonar contact No. 539 was 

noted at the location of an anchor touch-down point and probably represents disturbed seafloor sediments. 

These five (5) sonar contacts are interpreted as modern debris, disturbed sediments, or existing 

infrastructure and are not deemed archaeologically significant. 

The sixth sonar contact larger than the “dark specks” is contact No. 375. The contact measures 87.1 feet 

long 33.1 feet wide, and 18.54 feet above the seafloor. Its coordinates are X = 2,375,889 and Y = 

9,598,109. This contact appears irregular in shape and may contain numerous smaller debris targets. Due to 

its larger dimensions and the fact that this contact cannot reliably be identified, it will be avoided by 1000 

feet. This feature is NOT believed to be of historic significance. 

There are no other side scan sonar contacts deemed as archaeologically significant. There are no other 

unusual depressions, scours, sediment changes or unidentified seafloor target observed within the survey 

area that could represent unidentified shipwreck remains. 

It is possible that historic shipwreck materials may not be detected by the geophysical instruments or may be 

observed as modern debris. If wooden planking or other cultural materials that could represent shipwreck 

remains are encountered, BOEMRE archeologists will be contacted to provide an assessment of these 

artifacts. 

Regional Overview

Walker Ridge Block 508 straddles the Sigsbee Escarpment and abyssal plain. The southern half of the block is 

in an area of seafloor furrows that make for variable seafloor strength. At Proposed Locations G, H, and I, 

the soils at the base of the furrows are of higher than normal sheer strength due to active erosion. The 

ridges between the furrows have not experienced the maximum erosion forces, thus, the soils are relatively 

soft. Proposed Locations G, H and I were positioned between furrows. 

There are no fluid expulsion features, faults, or chemosynthetic communities within 2,000 feet of the 

proposed locations. There are piston cores, drilling splays, anchor chain scars, and previously drilled wells in 

the vicinity of Proposed Locations G, H, and I but none are within 2,000’ of the locations.

Page 27 Public Information Copy
Location Information

Walker Ridge 508, Proposed Location G: 

X = 2,365,600 5,440’ FWL

Y = 9,603,390 4,350’ FSL

Walker Ridge 508, Proposed Location H: 

 X = 2,364,969 4,809’ FWL

Y= 9,602,908 3,868’ FSL

Walker Ridge 508, Proposed Location I: 

 X = 2,367,900 7,740’ FEL

Y = 9,599,140 100’ FSL

Proposed Locations G, H, and I will be drilled using a dynamically positioned vessel, thus, no anchoring is 

required. There are no fluid expulsion features, faults, or chemosynthetic communities within 2,000 feet of 

the proposed locations. 

Currently, there are no pipelines in the vicinity of Proposed Locations G, H, and I. 

Based on a high-resolution geophysical survey consisting of frequency enhanced 3-D seismic, Enhanced 

Surface Renderings, and Enhanced Surface Renderings with Amplitudes applied, AUV surveys, and side scan 

sonar, Walker Ridge Block 508, Proposed Locations G, H, and I will not disturb any chemosynthetic 

communities. 

Kevin Bradford Vernessa J. Bradford 

Geophysicist Shallow Hazards Interpreter 

B - F 

Pursuant to NTL No. 2008-G04 the proposed operations covered by this SEP do not involve operations 

impacting the following: Topographic features map, Topographic features statement (shunting), Live 

bottoms, (Pinnacle Trend) map, Live bottoms (low relief) map, or potentially sensitive biological features 

map. 

G. Remotely Operated Vehicle (ROV) Monitoring Plan

In accordance with the provisions of NTL 2008-G06, Remotely Operated Vehicle Surveys in Deepwater, Walker 

Ridge 508 is located in Grid 11. Grid 11 is an area that has adequate ROV survey coverage; therefore we are not 

proposing to run the pre- and post-ROV survey in accordance with the NTL. 

H. Threatened and Endangered Species Information

There are 5 species of sea turtles that may be found in the Gulf of Mexico (see table). No critical habitat for 

these species has been designated in the Gulf of Mexico. 

Common Name Scientific Name T/E Status

Hawksbill Turtle Eretmochelys imbricata E

Green Turtle Chelonia mydas T

Kemp's Ridley Turtle Lepidochelys kempii E

Leatherback Turtle Dermochelys coriacea E

Loggerhead Turtle Caretta caretta T

Page 28 Public Information Copy
There are 29 species of marine mammals that may be found in the Gulf of Mexico (see table). Of the species 

listed as Endangered, only the Sperm whale is commonly found in the project area. No critical habitat for 

these species has been designated in the Gulf of Mexico. 

Common Name Scientific Name T/E Status

Atlantic Spotted Dolphin Stenella frontalis

Blainville's Beaked Whale Mesoplodon densirostris

Blue Whale Balaenoptera musculus E

Bottlenose Dolphin Tursiops truncatus

Bryde's Whale Balaenoptera edeni

Clymene Dolphin Stenella clymene

Cuvier's Beaked Whale Ziphius cavirostris

Dwarf Sperm Whale Kogia simus

False Killer Whale Pseudorca crassidens

Fin Whale Balaenoptera physalus E

Fraser's Dolphin Lagenodelphis hosei

Gervais' Beaked Whale Mesoplodon europaeus

Humpback Whale Megaptera novaeangliae E

Killer Whale Orcinus orca

Melon-headed Whale Peponocephala electra

Minke Whale Balaenoptera acutorostrata

Northern Right Whale Eubalaena glacialis E

Pantropical Spotted Dolphin Stenella attenuata

Pygmy Killer Whale Feresa attenuata

Pygmy Sperm Whale Kogia breviceps

Risso's Dolphin Grampus griseus

Rough-toothed Dolphin Steno bredanensis

Sei Whale Balaenoptera borealis E

Short-finned Pilot Whale Globicephala macrorhynchus

Sowerby's Beaked Whale Mesoplodon bidens

Sperm Whale Physeter macrocephalus E

Spinner Dolphin (Long-snouted) Stenella longirostris

Striped Dolphin Stenella coeruleoalba

West Indian manatee Trichechus manatus E

Section 18 discusses potential impacts and mitigation measures related to threatened and endangered 

species. 

I. Archaeological Report

Seafloor features noted are: well splays, drilling mud, anchor chain scars, and disturbed seafloor areas. A 

total of nine-hundred and sixty-two (962) side scan sonar targets are noted within development area. Ninehundred and fifty six (956) of the nine-hundred and sixty-two (962) of these targets are randomly scattered 

with similar appearances that measure less than 20 feet in length, less than 10 feet in width, and do not 

display a height above the surrounding seafloor. Contacts of this nature have previously been identified as 

industrial waste barrels, discarded munitions, and other recent man-made debris. 

Recent deep-water AUV surveys, verified by ROV video, have also shown contacts of this appearance may 

represent non-biologic partially cemented mud vent tubes. These cemented vent tubes are the result of 

erosional seafloor forces which wash away surrounding softer unconsolidated sediments surrounding the vent 

tube leaving only a partially cemented sediment vent core, which are left rising above the seafloor. These 

non-biologic partially cemented mud vent tubes can be identified on sonar records as "dark specks" not unlike 

those identified on the sonar records collected during this survey. These dark-specks were also previously 

identified during the FGCI report. 

Page 29 Public Information Copy
None of the 956 (including Nos. 379, 374 and 369 which are within the 2,000’ clearance area for well location 

I) sonar contacts described above are deemed archaeologically significant. Multiple debris fields containing 

numerous smaller debris targets, similar to the “dark specks” noted by FGCI, were noted during the current 

Archaeological Assessment. These debris fields are not deemed archaeologically significant. 

There were six (6) sonar contacts (Nos. 156, 375, 419, 421, 445, and 539) noted within the survey area that 

are larger than the “dark-specks” discussed above or correlate to known infrastructure. Sonar contact no. 156 

measures 68.9 feet in length, 3.5 feet in width, and no measurable height above the surrounding seafloor. 

This contact is linear in shape and is interpreted as modern debris, possibly a section of pipeline or cable. 

Contact no. 419 measures 57.4 feet in length, 44.5 feet in width, with a height of 11.7 feet above the 

surrounding seafloor. This contact is geologic in origin and is interpreted as a rafted block. Sonar contact no. 

421 was noted in the vicinity of the reported position of an Acoustic Doppler Current Profiler (ADCP) and 

likely represents the weights at the base of the ADCP string. Sonar contact no. 445 measures 74.9 feet in 

length, 4.4 feet in width, and no measurable height above the surrounding seafloor. This contact is linear in 

shape and is interpreted as modern debris, possibly a section of pipeline or cable. Sonar contact no. 539 was 

noted at the location of an anchor touch-down point and probably represents disturbed seafloor sediments. 

These five (5) sonar contacts are interpreted as modern debris, disturbed sediments, or existing 

infrastructure and are not deemed archaeologically significant. 

The sixth sonar contact larger than the “dark specks” is contact no. 375. The contact measures 87.1 feet 

long 33.1 feet wide, and 18.54 feet above the seafloor. This contact appears irregular in shape and may 

contain numerous smaller debris targets. Due to its larger dimensions and the fact that this contact cannot 

reliably be identified, it should be avoided by 1000 feet. 

There are no other side scan sonar contacts deemed as archaeologically significant. There are no other 

unusual depressions, sours, sediment changes or unidentified seafloor target observed within the survey area 

that could represent unidentified shipwreck remains. 

It is possible that historic shipwreck materials may not be detected by the geophysical instruments or may be 

observed as modern debris. If wooden planking or other cultural materials that could represent shipwreck 

remains are encountered, BOEM archeologists will be contacted to provide an assessment of these artifacts. 

Shell will comply with all conditions of NTL 2005-G07. 

J. Air and Water Quality Information

Pursuant to NTL 2008-G04 the proposed operations covered by this SEP do not require Shell to provide 

additional information relating to air and water quality information. For specific information relating to air 

and water quality information please refer to Section 18. 

K. Socioeconomic Information

Pursuant to NTL 2008-G04 the proposed operations covered by this SEP do not require Shell to provide 

additional information relating to air and water quality information. For specific information relating to 

socioeconomic information please refer to Section 18. 

Page 30 Public Information Copy
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H (WR 807_4 DC3)X: 2,364,969Y: 9,602,908 G (WR 807_4 Stones #4)

X: 2,365,600Y: 9,603,390

I (WR 807_4 DC2)X: 2,367,900 Y: 9,599,140

Well No. 1

Well No. 2

Well No. 3

10 00 ' Avo idan ce Area

20 00 ' C el arance R adi u s

20 0 0 ' Cle ara nce Radiu s

20 00 ' C el arance R adi u s

WALKER RIDGE

9 8

7

6 5 4 3 1 2

99

98 97 96

95

94

92 93

91

90

89 88

87

86

85

84

82 83 81 80 79 78 77 76 75 74 73

72

71

70

69 68

67

66

65 64

63 62

61

60 59 58

57 55 54 56 53 52 51 50 49 48 47 46 45 4443 42 41 40 39 38 37 36 35 34 33 32 31

29 30 28

27

26

24 25 23

22

21

17 19 18 20 16

15

14 13

12 11 10

962

961

959 960 958

957 956

955

954 953 952 951 949 950 948 947

946 945

944 943

942

941

940

939

938

937

936

935 934 932 933 931 930 929 928 926 927

924 925

923

922 921 919 920 918 917 916

915 914

913 912 911 910 909 907 908 905 906 904

903 902 901

900

899

898 896 897 895 894 893 892 891

890 889

888

887

886

885

884

883

882

881

880 879

877 878

876

875

873 874

872 871 870

869

868

867 866 865

864

863

862

861

860

859

857 858

856

855 854 853 852 851 850 849 848 846 847

845

844

843

841 842

840

839

838

837

836

835

834

833

831 832

830

829

828

827

826 825

824

823 822

821

820

819 818

817

816 815 814813 812

811

810

809 808 807 806 805 804 803 802 801 800

799

798

797

796 795

794

791793 792

790

789

788 787 786 785

783 784 782 781 780 779 778 777 776 775 774

773

772

771

769 770

768

767

766

765

764

763

762

761 760 759 758 757756 755 754 753 752 751 750 749

748

747 746

745 744 743 742 741 740 739 738 737 736 734 735 733 732 731 730 729 728 727 726 725 723 724

722

721

720 719

718

717

716 715

714

713 712

711 710 709 708

707

706

705

704

703

702

701

700

699

698 697 696 695 694693 692 691 690 689

688 687 686 685 684 683 682 681 680

678 679

677 676 675 674

673 672 671

670 669 668

667 664 666 665 663

662 660 661 659 658 657 656 655 654 653

652 651 648 649 650 647 646 645

642644 643 641 640

639

638 636 637

635 634 633

632

631

630 627 628 629 626

625

624

623

622 621

620

618619 617

616

615 614 613 612

611 610

609

608

607

606 605 604 603 602

601

600

599 598

597596

595

594

593

592 591 590 589

588 587 586 585 584 583 582 581 580 579 578 577 576 575 574

573

572 571

570 569 568 567 566

564 565 563 562 561 560 559 557 556 558555 554 553 552 550 551 549 548 547 546 545 544 543 542 541 540 539 538 536537 535 534 533 532 531530 529 528 527 525 526 524 522 523 521 520

519

518

517 516 515

514 513 512 511 510 509 508 507

506

505 504

503

502

501 500

499

498

497 495 496

494

493

492

491

490

489

488

487 486 485

484 483 482

481

480

479

478

477

476

475 474

473

472 471

470

469

468 467 466

465

464

463

462

461 460 459 458 457 456

455 454

453 452

451

450 449

448 447

446

445

444

442 443 441

440

438 439 437 436

435

434

433

432 431

430

429

428 427

426

425 424

423 422 421

420

419

418

417

416

415

414

413

412

411

410409

408

407

406 405

404

403

402 401

400

399

398 397 396

395

394

393

392

391 390389 388 387 386 385

384

383 382 381 380

379 378 377 376 375

374 373 372

371

370

369 368 367

366 365 364

363 361 362

360 359

358

357 356

355 354 353 352

351 350 349

348 347

346

345

344 343 342 341

340 339 338 337 336 335 334 333 331 332

330 329 328 327 326

325

324 323 321 322 320

319

318

317 316

315 314 313 312 311 309310

307 308

306 305

304

302 303

301 300 299 297 298

296 294 293 295 292

291

290

289

288 287 286 285 283 284 282 281 280 279

278 277 276 275 274 273 272 271 270 269 268

267

266 265 264 263 262

261 260 258 259 257 255 256

254

253

251 252 250 248 249 247 246 243 244 245 242

241 240 239 238237 235 236

234 233 232 231

230

229 228 227

226 224225 223

222

221

220 219

218

217

216 215 214 213 212 211 210 209 208 207 206 205 204 203202 201 200 198 199 197 196 195 194

193

192 191 190

189 187 188

186

185 184 183 182 181 180 179

178

177 176 175 174 173

172

171

169 168 170 167 166 165 164 163 162 161 160 159 158 157 156

155 154 153 152 151 150 149 148 147

146

145

143144 142 141 140 138 139 137 135136 134

133 132 130 131

129

128 127

126

125 124 123

122 121

120

119

118 117 116

115

114 113

112 110 111

109

108 107

106 105 104 103 102 100 101

PC-9BPC-9

PC-9A

PC-7APC-7B

PC-8APC-8B

PC-5C

PC-5APC-5B

PC-4APC-4B

PC-3A

PC-2APC-2B

PC-1B

PC-19APC-19B

PC-18A

PC-15APC-15B

PC-14APC-14B

PC-13A

PC-12B

PC-12A

PC-17A PC-17B

PC-11B

PC-11A

PC-10APC-10B

-8500

-8600

-8400

-8300

-8700

-8200

-8100

-8000

-7700

-7800

-7900

-8800

-8900

-9000

-9100

-9200

-7600

-9300

-7500

-7400

-7300

-9400

-7200

-7100

-7000

-6900

-6800

-9500

-6700

-9600

-6600

-6500

-9700

-6400

-6400

-6600

-6900

-6500

-6400

-6900

-9700

-7500

-7200

-7000

-6900

-7400

-7300

-6700

-6500

-6800

-6800

-7100

-9600

-6600

-7000

-9700

-7000

-6800

-6600

-6800

-6700

-6500

-7100

-6500

-6400

WR464

G32690

PETROBRAS

WR509

G18731 WR507 SHELL

G18730

SHELL

WR422

G32681

ENI

WR552

G18737

SHELL

WR420

G32680

STATOIL

WR508

G17001

SHELL

WR551

G21861

SHELL

WR553

G17004

SHELL

WR550

G25254

MARATHON

WR597

G26409

SHELL

WR596

G21862

SHELL

WR42

G32682

ENI

WR376

G33375

PETROBRAS

WR375

G26394

SHELL

WR377

G33376

EXXONMOBIL

WR374

G31958

HUNT OIL

WR463

WR421

WR466

WR419

WR554WR510

WR465

WR506

WR462WR418

WR594 WR595 WR598

WR55WR51WR46

WR378

WR59WR37

23300002330000

23450002345000

23600002360000

23750002375000

23900002390000

24050002405000

957500095900009605000962000096350009650000

90°40'30"W

90°40'30"W

90°45'0"W

90°45'0"W

90°49'30"W

90°49'30"W

26°33'0"N26°28'30"N26°24'0"N

Page 31 
SECTION 7: WASTE AND DISCHARGE INFORMATION 

A. Projected Ocean Discharges

Note: Please specify if the amount reported is a total or per well amount Supplmental EP - Stones

Type of Waste and Composition Composition Projected Amount Discharge rate Discharge Method

Will drilling occur ? If yes, you should list muds and cuttings

EXAMPLE: Cuttings wetted with ynthetic based 

fluid 

Cuttings generated while using 

synthetic based drilling fluid. X bbl/well X bbl/day discharge pipe

Water-based drilling fluid barite, additives, mud 33000 17,000 discharge overboard

Cuttings wetted with water-based fluid

cuttings coated with water based 

drilling mud 1536 bbls/well 768 bbls /day discharge overboard

Cuttings wetted with synthetic-based fluid 

Cuttings generated while using 

synthetic based drilling fluid. 5630 bbls/well 88.5 bbls /day discharge overboard

Synthetic based drilling fluid adhering to washed 

drill cuttings

Synthetic based drilling fluid adhering 

to washed drill cuttings 2252 bbls/well 28.4 bbls /day

Overboard discharge line to 39.4’ 

below the water level

Chemical product waste 50 bbls / well 2 bbls / day

Treated to meet NPDES limits and 

discharged overboard

Will humans be there? If yes, expect conventional waste

EXAMPLE: Sanitary waste water X liter/person/day NA chlorinate and discharge

Domestic waste (kitchen water, shower water) grey water 160 bbls/day NA

Grinded to less than 25 mm mesh 

size and discharge overboard

Sanitary waste (toilet water) treated sanitary waste 100 bbls/day NA

Treated in the MSD** prior to 

discharge to meet NPDES limits

Is there a deck? If yes, there will be Deck Drainage

Deck Drainage Contaminated wash and rainwater 3,900 bbls / well 20 bbls / day

Drained overboard through deck 

scuppers

Will you conduct well treatment, completion, or workover? 

well treatment fluids NA NA NA NA

well completion fluids NA NA NA NA

workover fluids NA NA NA NA

Miscellaneous discharges. If yes, only fill in those associated with your activity. 

Desalinization unit discharge Rejected water from watermaker unit 74,100 bbls / well 380 bbls /day

Discharged overboard 35 feet below 

waterline 

Blowout prevent fluid Water based 400 bbls/well 0.2 bbls /day Subsea BOP @ seafloor

Ballast water Uncontaminated seawater 390,000 bbls / well 2,6890 bbls / day discharge overboard

Bilge water

Bilge and drainage water will be 

treated to MARPOL standards (< 15ppm 

oil in water). 390,000 bbls / well 2,6890 bbls / day

Bilge and drainage water will be 

treated to MARPOL standards (< 

15ppm oil in water).

Excess cement at seafloor Cement slurry

436 bbls/well (assume 

planned 100% excess is 

discharged) 436 bbls /day 

discharged through shunt line, 77' 

below waterline

Fire water Treated seawater 11,000 bbls / well 2,000 bbls / month

Drained overboard through deck 

scuppers

Cooling water Treated seawater 23,295,000 bbls / well 456,343 bbl/day/well

discharged through shunt line, 77' 

below waterline

Will you produce hydrocarbons? If yes fill in for produced water.

Produced water NA NA

Will you be covered by an individual or general NPDES permit ? GENERAL PERMIT GMG290103

NOTE: If you will not have a type of waste, enter NA in the row. 

TABLE 7A: WASTES YOU WILL GENERATE, TREAT AND DOWNHOLE DISPOSE OR DISCHARGE TO THE GOM

Projected generated waste Projected ocean discharges 

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B. Projected Generated Wastes 

Supplmental EP - Stones

Solid and Liquid Wastes 

transportation 

Type of Waste Composition Transport Method Name/Location of Facility Amount Disposal Method

Will drilling occur ? If yes, fill in the muds and cuttings.

EXAMPLE: Oil-based drilling fluid or mud NA NA NA NA NA

Oil-based drilling fluid or mud NA NA NA NA NA

Synthetic-based drilling fluid or mud used SBF and additives Drums on barges

Newpark Environmental, Fourchon, 

LA 120 bbls/day Recycled

Cuttings wetted with Water-based fluid NA NA NA NA NA

Cuttings wetted with Synthetic-based fluid NA NA NA NA NA

Cuttings wetted with oil-based fluids NA NA NA NA NA

Will you produce hydrocarbons? If yes fill in for produced sand.

Produced sand NA NA NA NA NA

EXAMPLE: trash and debris cardboard, aluminum, barged in a storage bin shorebase z tons total recycle

Trash and debris - recyclables trash and debris storage bins on supply boat

Omega Waste Managmenet, W. 

Patterson, LA or ARC, New Iberia, LA 200 lbs/month recylce

Trash and debris - non-recyclables trash and debris storage bins on supply boat

Republic/BFI landfill, Sorrento, LA or 

the parish landfill, Avondale, LA 400 lbs/month landfill

Used oil and glycol

used oil, oily rags and pads, 

empty drums and cooking drums on supply boat

Omega Waste Managmenet, W. 

Patterson, LA or ARC, New Iberia, LA 20 bbls/month recycled

Hazardous Waste

paints, solvents and unused 

chemicals drums on supply boat Safety Kleep, Denton, TX 60 bbls/mo recycled

Universal Waste Items

Batteries, lamps, glass and 

mercury-contaminated 

waste drums on supply boat Lamp Environmental, Hammond, LA 50 bbls/mo landfill

NOTE: If you will not have a type of waste, enter NA in the row. 

Waste Disposal

TABLE 7B. WASTES YOU WILL TRANSPORT AND/OR DISPOSE OF ONSHORE 

Will you have additional wastes that are not permitted for discharge? If 

yes, fill in the appropriate rows. 

Note: Please specify whether the amount reported is a total or per well

Projected generated waste

C. Modeling Report

Shell did not model the trajectory for discharges because it is not required in the GOM. 

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SECTION 8: AIR EMISSIONS INFORMATION 

A. Emissions Worksheet and 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)?

x

Do your emission calculations include any emission reduction measures or 

modified emission factors? x

Are your proposed exploration activities located east of 87.5° W longitude? x

Do you expect to encounter H2S at concentrations greater than 20 parts per million 

(ppm)? x

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

From any proposed well? x

Do you propose to burn produced hydrocarbon liquids? x

B. If you answer no to all of the above screening questions from the appropriate table, 

provide: 

(1) Summary information regarding the peak year emissions for both Plan Emissions and Complex 

Total Emissions, if applicable. This information is compiled on the summary form of the two 

sets of worksheets. You can submit either these summary forms or use the format below. You 

do not need to include the entire set of worksheets. 

Air Pollutant

Plan 

Emission1 

Amounts 

(tons)

Calculated 

Exemption2

Amounts 

(tons)

Calculated

Complex Total 

Emission 

Amounts3

(tons)

PM 144.86 6060.60 NA

SOx 663.94 6060.60 NA

NOx 4975.65 6060.60 NA

VOC 149.41 6060.60 NA

CO 1085.59 109,192.59 NA

1

 For activities proposed in your EP or DOCD, list the projected emissions calculated from the 

worksheets. 

2

 List the exemption amounts for your proposed activities calculated by using the formulas in 30 CFR 

250.303(d). 

3

 List the complex total emissions associated with your proposed activities calculated from the 

worksheets 

 (2) Contact: Tracy Albert, (504) 728-4652, tracy.albert@shell.com

(1) Worksheets

Because the answers to all the questions set forth above are “no” further worksheets are not required.

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SECTION 9: OIL SPILL INFORMATION

A. Oil Spill Response Planning

All the proposed activities and facilities in this SEP will be covered by the Regional OSRP filed by Shell 

Offshore Inc (0689) in accordance with 30 CFR 250. An update to the Regional OSRP was filed with the 

BOEMRE October 26, 2010, March 15, 2011, May 31, 2011, July 6, 2011 and August 1, 2011 and is 

pending approval. An updated OSRP Certification in accordance with 30 CFR 254.2 was accepted by the 

BOEMRE on August 4, 2011. 

 Spill Response Sites: 

Primary Response Equipment Locations Preplanned Staging Location(s) 

Fourchon, LA; Cameron, LA; Houma, LA; Lake 

Charles, LA

Lake Charles, LA ; Cameron, LA ; Fourchon ; LA

The names of the oil spill removal organizations (OSRO’s) under contract include Clean Gulf Associates 

(CGA), Marine Spill Response Company (MSRC), Clean Caribbean America (CCA), and OSRL/EARL. 

Worst Case Scenario Determination: 

Category Regional OSRP EP

Type of Activity1 Drilling Rig Drilling Rig 

Facility Location (area/block) MC 807 WR 508

Facility Designation2Subsea well A Subsea well H

Distance to Nearest Shoreline (miles) 53 182

Volume3

Storage tanks (total)

Flowlines (on facility)

Pipelines

Uncontrolled blowout (volume per day)

Total Volume

N/A

N/A

N/A

465,000* BOPD◊

465,000 Bbls

N/A

N/A

N/A

42,000** BOPD

42,000 Bbls

Type of Oil(s) - (crude oil, condensate, 

diesel)

Crude oil Crude oil

API Gravity(s)426o 28o

 *24 hour rate (365,000 BOPD 30 day average) 

**24 hour rate (33,000 BOPD 30 day average) 

◊MC 807 Subsea Well A (Olympus) was submitted as subsea WCD in our OSRP update of August 1, 

2011 and was covered for 2010-N06 in Plan S-7499 (pending BOEM approval). 

Footnotes: 

1. Types of activities include pipeline, platform, caisson, subsea completion or manifold, and mobile drilling rig. 

2. E.g., Well No. 2, Platform JA, Pipeline Segment No. 6373. 

3. Your regional OSRP worst-case scenario volume must be taken from the appropriate section of your regional OSRP. For EP’s, the 

worst-case scenario volume must be determined by using the daily worst-case discharge volume determined using the guidance at 

30 CFR 254.47(b). For DOCD’s, the daily worst-case discharge volume must be determined by using the guidance at 30 CFR 

254.47 (a) and/or (b), as appropriate. 

4. Provide API gravity of all oils given under “Type of Oil(s)” above. Estimate for EP’s.

Since Shell Offshore Inc. has the capability to respond to the appropriate worst-case spill scenario included in 

its regional OSRP, filed with the BOEMRE October 26, 2010, March 15, 2011, May 31, 2011, July 6, 2011 and 

August 1, 2011 and is pending approval, and since the worst-case scenario determined for our Plan does not 

replace the appropriate worst-case scenario in our regional OSRP, I hereby certify that Shell Offshore Inc. 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 SEP. 

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B. Oil Spill Response Discussion

Volume of the Worst Case Discharge 

Please refer to Section 2j and 9(iv) of this SEP. 

2. Trajectory Analysis 

Trajectories of a spill and the probability of it impacting a land segment have been projected 

utilizing information in the BOEMRE Oil Spill Risk Analysis Model (OSRAM) for the Central and 

Western Gulf of Mexico available on the BOEMRE website using 30 day impact. Offshore areas along 

the trajectory between the source and land segment contact could be impacted. The land segment 

contact probabilities are shown in Table 9.C.1. 

Area/Block OCS-G

Launch

Area Land Segment Contact %

Exploratory

WR 508 48

Calhoun, TX -

Matagorda, TX 1

Brazoria, TX 1

Galveston, TX 2

Jefferson, TX 1

Cameron, LA 2

Vermilion, LA 1

Iberia, LA -

St. Mary, LA -

Terrebonne, LA 1

Lafourche, LA -

Jefferson, LA -

Plaquemines, LA 2

Table 9.C.1 Probability of Land Segment Impact 

C. Resource Identification

The locations identified in Table 9.C.1 are the highest probable land segments to be impacted using 

the BOEMRE Oil Spill Risk Analysis Model (OSRAM). The environmental sensitivities are identified 

using the appropriate National Oceanic and Atmospheric Administration (NOAA) Environmental 

Sensitivity Index (ESI) maps for the given land segment. ESI maps provide a concise summary of 

coastal resources that are at risk if an oil spill occurs nearby. Examples of at-risk resources include 

biological resources (such as birds and shellfish beds), sensitive shorelines (such as marshes and 

tidal flats), and human-use resources (such as public beaches and parks). 

In the event an oil spill occurs, ESI maps can help responders meet one of the main response 

objectives: reducing the environmental consequences of the spill and the cleanup efforts. 

Additionally, ESI maps can be used by planners to identify vulnerable locations, establish protection 

priorities, and identify cleanup strategies. 

The following is a list of resources of special economic or environmental importance that potentially 

could be impacted by the Walker Ridge 508 WCD scenario. 

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Onshore/Nearshore: Plaquemines Parish has been identified as the most probable impacted 

Parish within the Gulf of Mexico for the Greater than 10 Mile Worst Case Discharge and the 

Exploratory Worst Case Discharge. Plaquemines Parish has a total area of 2,429 square miles of 

which, 845 square miles of it is land and 1,584 square miles is water. Plaquemines Parish includes 

two National Wildlife Refuges: Breton National Wildlife Refuge and Delta National Wildlife Refuge. 

This area is also a nesting ground for the brown pelican, an endangered species. Examples of 

Environmental Sensitivity maps for Plaquemines Parish are detailed in the following pages. Example 

ESI maps for Plaquemines Parish and the legend are shown in Figures 9.C.1 through 9.C.5. 

Cameron Parish is identified as the most probable impacted Parish within the Gulf of Mexico for the 

Exploratory Worst Case Discharge. Cameron Parish is located in the southwest corner of Louisiana 

and has a total area of 1,932 square miles of which, 1,313 square miles of it is land and 619 square 

miles is water. Cameron Parish includes four National Wildlife Refuges including the Cameron Prairie 

National Wildlife Refuge, East Cove National Wildlife Refuge, Sabine National Wildlife Refuge and 

part of the Lacassine National Wildlife Refuge. 

Galveston County has been identified as the most probable impact Parish within Gulf of Mexico for 

the Exploratory Worst Case Discharge at 2%. Galveston County is located on the plains of the Texas 

Gulf Coast in the southeastern part of the state. The county is bounded on the northeast by 

Galveston Bay and on the northwest by Clear Creek and Clear Lake. Much of the county covers 

Galveston Bay, and is bounded to the south by the Galveston Seawall and beaches on the Gulf of 

Mexico. Galveston County has a total area of 873 square miles which 398 square miles is land and 

474 square miles (54.35%) is water. 

Offshore: An offshore spill may require an Essential Fishing Habitat (EFH) Assessment. This 

assessment would include a description of the spill, analysis of the potential adverse effects on EFH 

and the managed species; conclusions regarding the effects on the EFH; and proposed mitigation, if 

applicable. 

Significant pre-planning of joint response efforts was undertaken in response to provisions of the 

National Contingency Plan (NCP). Area Contingency Plans (ACPs) were developed to provide a well 

coordinated response to oil discharges and other hazardous releases. The One Gulf Plan is specific 

to the Gulf of Mexico to advance the unity of policy and effort in each of the Gulf Coast ACPs. 

Strategies used for the response to an oil spill regarding protection of identified resources are 

detailed in the One Gulf Plan and relevant Gulf Coast ACP. 

D. Worst Case Discharge Response 

Shell will make every effort to respond to the WR 508 Worst Case Discharge as effectively as 

possible. Applied Science Associates (ASA) conducted a deepwater blowout simulation for The 

Response Group to better determine subsurface and surface evaporation and dispersion rates. 

Below is a table outlining the applicable evaporation and dispersion quantities: 

Walker Ridge 508

Calculations

(BBLS)

i. 30 Day Average WCD = 33,000 bbls

ii. Subsurface dispersion – 25% (Water Depth = ~9,558 ft) -8,200 bbls

iii. REMAINING WCD AFTER SUBSURFACE DISPERSION 24,800 bbls

iv. Surface dispersion and evaporation – 25% -6,200 bbls

TOTAL REMAINING ~18,600 bbls

Table 9.D.1 Oil Remaining After Subsurface and Surface Dispersion 

Shell has contracted OSROs to provide equipment, personnel, materials and support vessels as well 

as temporary storage equipment to be considered in order to cope with a WCD spill. Under adverse 

weather conditions, major response vessels and Transrec skimmers are still effective and safe in sea 

states of 6-8 ft. If sea conditions prohibit safe mechanical recovery efforts, then natural dispersion 

and airborne chemical dispersant application (visibility & wind conditions permitting) may be the 

only safe and viable recovery option. 

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MSRC OSRV 8 foot seas

VOSS System 4 foot seas

Expandi Boom 6 foot seas, 20 knot winds

Dispersants Winds more than 25 knots,

Visibility less than 3 nautical miles, or

Ceiling less than 1,000 feet.

Table 9.D.2 Operational Limitations of Response Equipment 

Upon notification of the spill, Shell would request a partial or full mobilization of contracted 

resources, including, but not limited to, skimming vessels, oil storage vessels, dispersant aircraft, 

subsea dispersant, shoreline protection, wildlife protection, and containment equipment. Following 

is a list of the contracted resources including de-rated recovery capacity, personnel, and estimated 

response times (procurement, load out, travel time to the site, and deployment). The Incident 

Commander or designee may contact other service companies if the Unified Command deems such 

services necessary to the response efforts. 

Based on the anticipated worst case discharge scenario, Shell can be onsite with dedicated, 

contracted on water oil spill recovery equipment with adequate response capacity to contain and 

recover surface oil, and prevent land impact, within 27 hours (based on the equipment’s Estimated 

Daily Response Capacity (EDRC)). Shell will continue to ramp up additional on-water mechanical 

recovery resources as well as apply dispersants and in-situ burning as needed and as approved 

under the supervision of the USCG Captain of the Port (COTP) and the Regional Response Team 

(RRT). 

Subsea Control and Containment: Shell, as a founding member of the MWCC, will have access 

to the IRCS that can be rapidly deployed through the MWCC. The IRCS is designed to contain oil 

flow in the unlikely event of an underwater well blowout, and is designed, constructed, tested, and 

available for rapid response. Shell’s specific containment response for WR 508 will be addressed in 

Shell’s NTL 2010-N10 submission at the time the APD is submitted. 

 Table 9.D.9 Control, Containment, and Subsea Dispersant Package Activation List 

Mechanical Recovery (skimming): Response strategies include skimming utilizing available 

OSROs Oil Spill Response Vessels (OSRVs), Oil Spill Response Barges (OSRBs), ID Boats, and Quick 

Strike OSRVs. There is a combined de-rated recovery rate capability of approximately 562,000 

barrels/day. Temporary storage associated with the identified skimming and temporary storage 

equipment equals approximately 461,000 barrels. 

De-rated Recovery Rate

(bopd)

Storage

(bbls)

Offshore Recovery and 

Storage 455,480 444,700

Nearshore Recovery and 

Storage 106,993 17,224

Total 562,473 461,924

Table 9.D.3 Mechanical Recovery Combined De-Rated Capability 

 Table 9.D.4 Offshore On-Water Recovery and Storage Activation List 

 Table 9.D.5 Nearshore On-Water Recovery and Storage 5ctivation List 

Oil Storage: The strategy for transferring, storing and disposing of oil collected in these recovery 

zones is to utilize two 150,000-160,000 ton (dead weight) tankers mobilized by Shell (or any other 

tanker immediately available). The recovered oil would be transferred to Motiva’s Norco, LA storage 

and refining facility, or would be stored at Delta Commodities, Inc. Harvey, LA facility.

Aerial Surveillance: Aircraft can be mobilized to detect, monitor, and target response to oil spills. 

Aircraft and spotters can be mobilized within hours of an event. 

Table 9.D.6 Aerial Surveillance Activation List

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Aerial Dispersant: Depending on proximity to shore and water depth, dispersants may be a viable 

response option. If appropriate and approved, 4 to 5 sorties from three DC-3’s can be made within 

the first 12 hour operating day of the response. These aerial systems could disperse approximately 

7,704 to 9,630 barrels of oil per day. Additionally, 3 to 4 sorties from the BE90 King Air and 3 to 4 

sorties from the Hercules C-130A within the first 12 hour operating day of the response could 

disperse 4,600 to 6,100 barrels of oil per day. For continuing dispersant operations, the CCA’s Aerial 

Dispersant Delivery System (ADDS) would be mobilized. The ADDS has a dispersant spray capability 

of 5,000 gallons per sortie. 

 Table 9.D.7 Offshore Aerial Dispersant Activation List 

Vessel Dispersant: Vessel dispersant application is another available response option. If 

appropriate, vessel spray systems can be installed on offshore vessels of opportunity using inductor 

nozzles (installed on fire-water monitors), skid mounted systems, or purpose-built boom arm spray 

systems. Vessels can apply dispersant within the first 12-24 hours of the response and continually as 

directed. 

 Table 9.D.8 Offshore Boat Spray Dispersant Activation List 

Subsea Dispersant: Shell has contracted with Wild Well Control for a subsea dispersant package. 

Subsea dispersant application has been found to be highly effective at reducing the amount of oil 

reaching the surface. Additional data collection, laboratory tests and field tests will help in facilitating 

the optimal application rate and effectiveness numbers. For planning purposes, the system has the 

potential to disperse approximately 24,500 to 34,000 barrels of oil per day.

 Table 9.D.9 Control, Containment, and Subsea Dispersant Package Activation List 

In-Situ Burning: Open-water in-situ burning (ISB) also may be used as a response strategy, 

depending on the circumstances of the release. ISB services may be provided by the primary OSRO 

contractors. If appropriate conditions exist and approvals are granted, one or multiple ISB task 

forces could be deployed offshore. Task forces typically consist of two to four fire teams, each with 

two vessels capable of towing fire boom, guide boom or tow line with either a handheld or aeriallydeployed oil ignition system. At least one support/safety boat would be present during active 

burning operations to provide logistics, safety and monitoring support. Depending upon a number of 

factors, up to 4 burns per 12-hour day could be completed per ISB fire team. Most fire boom 

systems can be used for approximately 8-12 burns before being replaced. Fire intensity and weather 

will be the main determining factors for actual burns per system. Although the actual amount of oil 

that will be removed per burn is dependent on many factors, recent data suggests that a typical 

burn might eliminate approximately 750 barrels. For planning purposes and based on the above 

assumptions, a single task force of four fire teams with the appropriate weather and safety 

conditions could complete four burns per day and remove up to ~12,000 bbls/day. In-situ burning 

nearshore and along shorelines may be a possible option based on several conditions and with 

appropriate approvals, as outlined in Section 19, In-situ Burn Plan (OSRP). In-situ burning along 

certain types of shorelines may be used to minimize physical damage where access is limited or if it 

is determined that mechanical/manual removal may cause a substantial negative impact on the 

environment. All safety considerations will be evaluated. In addition, Shell will assess the situation 

and can make notification within 48 hours of the initial spill to begin ramping up fire boom 

production through contracted OSRO(s). There are potential limitations that need to be assessed 

prior to ISB operations. Some limitations include atmospheric and sea conditions; oil weathering; air 

quality impacts; safety of response workers; and risk of secondary fires. 

 Table 9.D.10 In-Situ Burn Equipment Activation List 

 Shoreline Protection: If the spill went unabated, shoreline impact in Plaquemines Parish, LA; 

Cameron Parish, LA; and Galveston County, TX would depend upon existing environmental 

conditions. Nearshore response may include the deployment of shoreline boom on beach areas, or 

protection and sorbent boom on vegetated areas. Strategies would be based upon surveillance and 

real time trajectories provided by The Response Group that depict areas of potential impact given 

actual sea and weather conditions. Strategies from the New Orleans, Louisiana Area Contingency 

Plan, Unified Command would be consulted to ensure that environmental and special economic 

resources would be correctly identified and prioritized to ensure optimal protection. Shell has access 

to shoreline response guides that depict the protection response modes applicable for oil spill cleanup operations. Each response mode is schematically represented to show optimum deployment and 

Page 39 Public Information Copy
operation of the equipment in areas of environmental concern. Supervisory personnel have the 

option to modify the deployment and operation of equipment allowing a more effective response to 

site-specific circumstances. 

 Table 9.D.11 Shoreline Protection and Wildlife Support List 

Wildlife Protection: If wildlife is threatened due to a spill, the contracted OSRO’s have resources 

available to Shell, which can be utilized to protect and/or rehabilitate wildlife. The resources under 

contract for the protection and rehabilitation of affected wildlife are in Table 9.D.11. 

New or unusual technology in regards to spill, prevention, control and clean-up: 

Shell will use our normal well design and construction processes with multiple barrier approach as 

well as new stipulations mandated by NTL 2008-N05. Response techniques will utilize new learnings 

from Macondo response to include in-situ burning and subsea dispersant application. Mechanical 

recovery advancements are continuing to be made to incorporate utilization of Koseq arms outfitted 

on barges, conversion of Platform Support Vessels for Oil Spill Response, and inclusion of nighttime 

spill detection radar to improve tracking capabilities (X-Band radar, infrared sensing, etc.). In 

addition, new response technologies/techniques are continuing to be considered by Shell and the 

appropriate government organizations for incorporation into our planned response. Any additional 

response technologies/techniques presented at the time of response will be used at the discretion of 

the Unified Command and USCG. 

C. Modeling Report

Shell did not model oil or hazardous substance spills. 

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Figure 9.C.1 Environmental Sensitivity Index Map Legend 

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Figure 9.C.2 South Pass ESI Map 

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Figure 9.C.3 Garden Island Pass ESI Map 

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. 

Figure 9.C.4 Pass a Loutre West ESI Map 

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Figure 9.C.5 Main Pass ESI Map 

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Table 9.D.4 Offshore On-Water Recovery and Storage Activation List 

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Table 9.D.4 Offshore On-Water Recovery and Storage Activation List (continued) 

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Table 9.D.4 Offshore On-Water Recovery and Storage Activation List (continued) 

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Table 9.D.4 Offshore On-Water Recovery and Storage Activation List (continued) 

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 Table 9.D.5 Nearshore On-Water Recovery Activation List 

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Table 9.D.5 Nearshore On-Water Recovery Activation List (continued) 

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Table 9.D.5 Nearshore On-Water Recovery Activation List (continued) 

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Table 9.D.5 Nearshore On-Water Recovery Activation List (continued) 

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Table 9.D.6 Aerial Surveillance Activation List 

Table 9.D.7 Offshore Aerial Dispersant Activation List 

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Table 9.D.8 Offshore Boat Spray Dispersant Activation List 

Table 9.D.9 Control, Containment, and Subsea Dispersant Package Activation List 

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Table 9.D.10 In-Situ Burn Equipment Activation List 

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Table 9.D.10 In-Situ Burn Equipment Activation List (continued) 

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Table 9.D.10 In-Situ Burn Equipment Activation List (continued) 

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Table 9.D.10 In-Situ Burn Equipment Activation List (continued) 

Table 9.D.10 In-Situ Burn Equipment Activation List (continued) 

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Table 9.D.11 Shoreline Protection and Wildlife Support List 

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SECTION 10: ENVIRONMENTAL MONITORING INFORMATION

A. Monitoring Systems 

A rig-based Acoustic Doppler Current Profiler (ADCP) is used to continuously monitor the current beneath 

the Rig. Metocean conditions such as sea states, wind speed, ocean currents, etc. will also be continuously 

monitored. 

B. Incidental Takes 

No incidental takes are anticipated. Shell implements the mitigation measures and monitors for incidental 

takes of protected species according to the following notices to lessees and operators from the Minerals 

Management Service: 

NTL 2007-G03 “Marine Trash and Debris Awareness and Elimination”

NTL 2007-G04 “Vessel Strike Avoidance and Injured/Dead Protected Species Reporting”

C. Flower Garden Banks National Marine Sanctuary 

The operations proposed in this SEP will not be conducted within the Protective Zones of the Flower Garden 

Banks and Stetson Bank. 

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SECTION 11: LEASE STIPULATIONS INFORMATION

Leases OCS-G 18730 and 17001 are not part of a Biological Sensitive Area, known Chemosynthetic Area, or Shipping 

Fairway. See Section 6 of this plan for site specific archeological information. 

SECTION 12: ENVIRONMENTAL MITIGATION MEASURE INFORMATION

A. Impacts to Marine and coastal environments 

The proposed action will implement mitigation measures required by laws and regulations, including all 

applicable Federal & State requirements concerning air emissions, discharges to water, and solid waste 

disposal, as well as any additional permit requirements and Shell policies. Project activities will be conducted in 

accordance with the Regional Oil Spill Response Plan. Section 18 of this plan discusses impacts and mitigation 

measures. 

B. Incidental Takes 

We do not anticipate any incidental takes related to the proposed operations. Shell implements the mitigation 

measures and monitors for incidental takes of protected species according to the following notices to lessees 

and operators from the Minerals Management Service: 

NTL 2007-G03 “Marine Trash and Debris Awareness and Elimination”

NTL 2007-G04 “Vessel Strike Avoidance and Injured/Dead Protected Species Reporting”

SECTION 13: RELATED FACILITIES AND OPERATIONS INFORMATION

Information regarding Related Facilities and Operations Information, transportation systems, & produced liquid 

hydrocarbon transportation vessels are not included in this SEP as such information is only necessary in the case of 

DOCDs. 

 

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SECTION 14: SUPPORT VESSELS AND AIRCRAFT INFORMATION

A. General 

Type Maximum Fuel Tank 

Storage Capacity (Gals)

Maximum No. In Area at 

Any Time

Trip Frequency or 

Duration

Crew Boats 8,000 2 Twice per week

Offshore Support Vessels 120,000 3 Twice per week

Helicopter 760 1 Once per day

B. Diesel Oil Supply Vessels 

Size of Fuel Supply 

Vessel

Capacity of Fuel Supply 

Vessel

Frequency of Fuel 

Transfers

Route Fuel Supply Vessel Will 

Take

280 foot length 100,000 gals. 1 week Port Fourchon to WR 508

C. Drilling Fluids Transportation 

 

This Plan does not propose activities in the State of Florida; therefore the following table is not required. 

It is being provided for information only. 

Type of Material Quantity Being Transported Transportation Method

Dry Bulk (Cement, Barite, 

Gel)

12,000 sx max combined Below deck dry bulk tanks 

onboard OSV

Synthetic-base drilling fluids 11,000 bbls max per voyage Tanks below deck onboard 

OSV

D. Solid and Liquid Wastes Transportation 

See Section 7, Table 7B. 

E. Vicinity Map 

See Section 18, Figure 1 for Vicinity Map. 

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SECTION 15: ONSHORE SUPPORT FACILITIES INFORMATION

A. General 

Name Location Existing/New/Modified

Fourchon Port Fourchon, LA Existing

Amelia PHI Heliport Amelia LA Existing

The onshore support bases for water and air transportation will be the existing terminals in Amelia and 

Fouchon, Louisiana. The Fouchon boat facility is operated by SOI and is located on Bayou Lafourche, 

south of Leeville, LA approximately 3 miles from the Gulf of Mexico. The existing onshore air support 

base in Amelia, LA is located at 4008 Lake Palourde Road, Amelia, LA 70340. 

B. Support Base Construction or Expansion 

This Section does not apply to this SEP as Shell does not plan to construct a new onshore support base 

or expand an existing one to accommodate the activities proposed in this SEP. 

C. Support Base Construction or Expansion Timetable 

This Section does not apply to this SEP as Shell does not plan to construct a new onshore support base 

or expand an existing one to accommodate the activities proposed in this SEP. 

D. Waste Disposal 

See Section 7, Tables 7A and 7B. 

E. Air emissions 

Not required by BOEM GOM. 

F. Unusual solid and liquid wastes 

Not required by BOEM GOM. 

SECTION 16: SULPHUR OPERATIONS INFORMATION

Information regarding Sulphur Operations is not included in this SEP as we are not proposing to conduct 

sulphur operations. 

SECTION 17: COASTAL ZONE MANAGEMENT ACT (CZMA) INFORMATION

Louisiana Coastal Zone Consistency was granted in Plan N-8155 and is not required for Supplemental 

Exploration Plans. Texas Coastal Zone Consistency was granted in Plan S-7129.

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SECTION 18. ENVIRONMENTAL IMPACT ANALYSIS (EIA)

Introduction 

Project Summary 

Shell Offshore Inc. (Shell) is submitting a Supplemental Exploration Plan (EP) for Walker Ridge 

(WR) Block 507 and 508. Shell submitted a Supplemental EP for wells C and D in WR 508, which 

was approved by the Minerals Management Service (MMS, now Bureau of Ocean Energy 

Management, Regulation and Enforcement [BOEMRE]) on 23 May 2006 (Plan Control 

No. S-6899). Shell is now submitting a Supplemental EP that includes three exploration wells in 

WR 507 and 508; these wells are G, H, and I. This Supplemental EP also incorporates the revised 

blowout scenario and worst case discharge (WCD) information as required by Notice to Lessees 

(NTL) 2010-N06. 

The lease area is 178 miles (286 km) from the nearest shoreline, 193 miles (311 km) from the 

onshore support base at Port Fourchon, Louisiana, and 221 miles (356 km) from the helicopter 

base at Amelia, Louisiana (Figure 1). All miles in this EIA are statute miles. Water depths at the 

wellsites range from 9,554 to 9,578 ft (2,912 to 2,919 m). 

The Noble Danny Adkins or a similar dynamically positioned (DP) semisubmersible rig will be 

used for drilling. Drilling of wells will commence during the first quarter of 2012 and should be 

finished by the second quarter of 2013. The average time to drill a well will be approximately 

149 days. 

Purpose of the EIA 

This Environmental Impact Analysis (EIA) was prepared pursuant to the requirements of the 

Outer Continental Shelf Lands Act (OCSLA), 43 U.S.C. §§ 1331-1356, and BOEMRE regulations, 

including 30 CFR 250.212(o) and 250.227. The EIA is a project- and site-specific analysis of 

Shell’s planned activities under this EP. The EIA also evaluates potential impacts in accordance 

with Notice to Lessee (NTL) 2008-G04 issued by the BOEMRE. 

The EIA presents data, analysis, and conclusions to support BOEMRE reviews as required by the 

National Environmental Policy Act (NEPA) and other relevant Federal laws, including the 

Endangered Species Act (ESA) and Marine Mammal Protection Act (MMPA), as the agency 

considers this Supplemental EP for approval. It also identifies the mitigation measures Shell will 

implement in connection with the planned activities. 

As specified in NTL 2008-G04, an EIA is a project-specific analysis that focuses on the impacts of 

a specific plan. This EIA addresses the impact-producing factors (IPFs), resources, and impacts 

associated with the activities proposed in this Supplemental EP including drilling of wells. The 

EIA also incorporates the revised blowout scenario and worst case discharge (WCD) information 

required by NTL 2010-N06. 

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Figure 1. Vicinity map for the lease area. 

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The BOEMRE has performed numerous environmental evaluations of oil and gas activities on 

the Gulf of Mexico Outer Continental Shelf (OCS). Potential impacts were analyzed at a broader 

level in the Programmatic Environmental Impact Statement (EIS) for the OCS Oil and Gas Leasing 

Program (MMS, 2007a) and in recent multi-lease-sale EISs for the Western and Central Gulf of 

Mexico Planning Areas (MMS, 2007b, 2008), as well as the Environmental Assessment (EA) for 

Gulf of Mexico deepwater operations and activities (MMS, 2000). 

These studies generated critical data and advanced the large body of existing knowledge on the 

Gulf of Mexico OCS. They analyze everything from potential impacts on the natural 

environment to the socioeconomic effects of exploration and development activities. They 

include numerous technical studies ranging from the likely trajectory of spilled oil to the effects 

of underwater noise on threatened and endangered species. They inform agency 

decision-making on lease offerings, mitigation measures and lease stipulations, operational 

requirements, and permit restrictions. This substantial body of work, which in part forms the 

basis for the evaluation presented here, will allow the BOEMRE and other regulatory agencies to 

evaluate Shell’s Supplemental EP and ensure that oil and gas exploration and development 

activities are performed in an environmentally sound manner, with minimal impacts on the 

environment. Shell has incorporated these comprehensive environmental analyses by reference 

and built on them with project and site-specific analyses. 

OCS Regulatory Framework 

The regulatory framework for OCS activities in the Gulf of Mexico has been summarized by 

MMS (2010). Under the OCSLA, the U.S. Department of the Interior (USDOI) is responsible for 

the administration of mineral exploration and development of the OCS. Within the USDOI, the 

BOEMRE is charged with the responsibility of managing and regulating the development of 

OCS oil and gas resources in accordance with the provisions of the OCSLA. The BOEMRE 

operating regulations are in 30 CFR Parts 250, 251, and 254. 

In implementing its responsibilities under the OCSLA and NEPA, the BOEMRE must consult 

numerous Federal departments and agencies that have authority to govern and maintain ocean 

resources pursuant to other Federal laws. Among these are the U.S. Coast Guard (USCG), 

U.S. Environmental Protection Agency (USEPA), U.S. Fish and Wildlife Service (USFWS), and the 

National Oceanic and Atmospheric Administration (NOAA) through the National Marine 

Fisheries Service (NMFS). Federal regulations establish consultation and coordination processes 

with Federal, State, and local agencies (e.g., the ESA, MMPA, Coastal Zone Management Act of 

1972, and the Magnuson-Stevens Fishery Conservation and Management Act). 

NTLs are formal documents issued by the BOEMRE that provide clarification, description, or 

interpretation of a regulation or standard; provide guidelines on implementing a special lease 

stipulation or regional requirement; provide a better understanding of the scope and meaning 

of a regulation by explaining the BOEMRE interpretation of a requirement; or transmit 

administrative information such as current telephone listings or changes in BOEMRE personnel 

or office address. Table 1 lists and summarizes the NTLs that are referenced in this EIA. 

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Table 1. Notices to Lessees and Operators (NTLs) that are 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 the 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 (WCD), 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 984 ft (300 m). 

Prescribes separation distances of 2,000 ft (610 m) from each mud 

and cuttings discharge location and 250 ft (76 m) 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 984 ft (300 m) 

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.

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Oil Spill Prevention and Contingency Planning 

Shell submitted an update to the Gulf of Mexico Regional Oil Spill Response Plan (OSRP) to the 

BOEMRE as a fundamental component of the planned drilling program. The OSRP certifies that 

Shell has the capability to respond to the maximum extent practicable to a WCD (30 CFR 254.2) 

(see Supplemental EP Section 9). The OSRP demonstrates Shell’s capabilities to rapidly and 

effectively manage oil spills that may result from drilling operations. Despite the extremely low 

likelihood of a large oil spill event occurring during the project, Shell has designed its response 

program based upon a regional capability of responding to a range of spill volumes that increase 

from small operational spills up to and including a WCD from a well blowout. Shell’s program 

meets the response planning requirements of the relevant coastal states and Federal oil spill 

planning regulations. The OSRP includes information regarding Shell’s regional oil spill 

organization and dedicated response assets, potential spill risks, and local environmental 

sensitivities. The OSRP presents specific information on the response program that includes a 

description of personnel and equipment mobilization, the incident management team 

organization, and the strategies and tactics used to implement effective and sustained spill 

containment and recovery operations. 

EIA Organization 

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

NTL 2008-G04, which provides guidance regarding information required by 30 CFR Part 250 for 

EPs. The main impact-related discussions are in Section A (Impact-Producing Factors) and 

Section C (Impact Analysis). 

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A. Impact-Producing Factors 

Table 2 is a matrix of 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 subsections: 

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; and 

Accidents. 

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

The wells will be drilled using the Noble Danny Adkins or a similar DP semisubmersible. The rig 

will be on site for an estimated 149 days per well. Three offshore support vessels will be used 

during the drilling program and at least one of these will always be in the vicinity of the drilling 

rig to provide assistance as necessary. The physical presence of a drilling rig in the ocean can 

attract pelagic fishes and other marine life, as discussed in Section C.5.1. A semisubmersible 

maintains buoyancy using ballasted, watertight pontoons located below the sea surface. The 

operating deck is located above the tops of passing waves. Structural columns connect the 

pontoons and operating deck. When the rig moves its location, the pontoons are de-ballasted 

so that the rig can float on the sea surface. The Noble Danny Adkins uses thrusters to hold or 

adjust its position. 

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

including infrasonic frequencies in at least some cases (MMS, 2000). Drilling noise from 

semisubmersibles is not particularly intense and is strongest at low frequencies, averaging 10 to 

500 Hz (Richardson et al., 1995). From a semisubmersible, sound and vibration are transmitted 

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

lighting for navigational and aviation safety in accordance with Federal regulations. 

A.2 Physical Disturbance to the Seafloor 

Semisubmersibles like the Noble Danny Adkins do not use anchors for holding or stabilization 

during drilling operations. There will be minimal disturbance to the seafloor and soft bottom 

communities during positioning of the wellbore and blowout preventers (BOP). Physical 

disturbance of the seafloor will be limited to the proximal area where the wellbore penetrates 

the substrate, where mud and drill cuttings will be deposited. 

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

negligible impact. 

Environmental Resources

Impact-producing Factors

Drilling Rig 

Presence (incl. 

noise & lights)

Physical 

Disturbance 

to Seafloor

Air Pollutant 

Emissions

Effluent 

Discharges

Water 

Intake

Onshore 

Waste 

Disposal

Marine 

Debris

Support 

Vessel/Helo 

Traffic

Accidents

Small Fuel 

Spill

Large Oil 

Spill

Physical/Chemical Environment

Air quality and greenhouse gases -- -- X -- -- -- -- -- X(6) X(6)

Water quality -- -- -- X -- -- -- -- X(6) X(6)

Seafloor Habitats and Biota

Soft bottom benthic communities -- -- -- X -- -- -- -- -- X(6)

High-density deepwater benthic communities -- --(4) -- --(4) -- -- -- -- -- X(6)

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) -- -- -- -- -- -- X(8) X(6,8) X(6,8)

Florida manatee (endangered) -- -- -- -- -- -- -- X(8) -- X(6,8)

Endangered mysticete whales -- -- -- -- -- -- -- -- -- --

Non-endangered marine mammals (protected) X -- -- -- -- -- -- X X(6) X(6)

Sea turtles (endangered/threatened) X(8) -- -- -- -- -- -- X(8) X(6,8) X(6,8)

Piping Plover (threatened) -- -- -- -- -- -- -- -- -- X(6)

Whooping Crane (endangered) -- -- -- -- -- -- -- -- -- X(6)

Gulf sturgeon (threatened) -- -- -- -- -- -- -- -- -- X(6)

Beach mice (endangered) -- -- -- -- -- -- -- -- -- X(6)

Coastal and Marine Birds

Marine and pelagic birds X -- -- -- -- -- -- X X(6) X(6)

Shorebirds and coastal nesting birds -- -- -- -- -- -- -- X -- X(6)

Fisheries Resources

Pelagic communities and ichthyoplankton X -- -- X X -- -- -- X(6) X(6)

Essential Fish Habitat X -- -- X X -- -- -- X(6) X(6)

Archaeological Resources

Shipwreck sites -- --(7) -- -- -- -- -- -- -- X(6)

Prehistoric archaeological sites -- --(7) -- -- -- -- -- -- -- X(6)

Coastal Habitats and Protected Areas

Beaches -- -- -- -- -- -- -- -- -- X(6)

Wetlands and seagrass beds -- -- -- -- -- -- -- X -- X(6)

Coastal wildlife refuges and wilderness areas -- -- -- -- -- -- -- -- -- X(6)

Socioeconomic and Other Resources

Recreational and commercial fishing X -- -- -- -- -- -- -- X(6) X(6)

Public health and safety -- -- -- -- -- -- -- -- -- X(6)

Employment and infrastructure -- -- -- -- -- -- -- -- -- X(6)

Recreation and tourism -- -- -- -- -- -- -- -- -- X(6)

Land use -- -- -- -- -- -- -- -- -- X(6)

Other marine uses -- -- -- -- -- -- -- -- -- X(6)

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Table 2 Footnotes and Applicability: 

(1) Activities that may affect a marine sanctuary or topographic feature. Specifically, if the well, platform 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 block. 

(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 2,000 ft (610 m) of 

any drilling mud/cuttings discharge location. Because a semisubmersible will be used, there will be no 

seafloor disturbances due to anchoring. 

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

 Based on CFR 250.490(c), Shell requests that the BOEMRE classify the area in the proposed drilling 

operations as an area where the absence of H2S has been confirmed. 

(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. The archaeological survey detected 962 unidentified sidescan sonar targets within 

the survey area. The seafloor patterning and acoustic characteristics of these sonar targets conclude that 

they are modern debris. However, there was one irregularly shaped sonar contact that could not be 

reliably identified and will have an archaeological avoidance zone of 1,000 ft (300 m). The lease 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. Because a dynamically positioned semisubmersible will be used, 

there will be no seafloor disturbances due to anchoring. 

(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. 

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A.3 Air Pollutant Emissions 

Air pollutant emissions are estimated in Supplemental EP Section 8. 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 the BOEMRE requirements shows 

that the projected emissions for the drilling rig 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. 

However, Shell will use low-sulfur fuel to further reduce any possible impacts. 

A.4 Effluent Discharges 

Effluent discharges are summarized in Supplemental EP Section 7. All offshore discharges will 

be in accordance with the National Pollutant Discharge Elimination System (NPDES) General 

Permit No. GMG290000 issued by the USEPA. Discharges will be in compliance with 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 is set that allows returns to the surface. Excess cement slurry 

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

drilling operations. 

A synthetic-based mud (SBM) system will be used after the riser is installed. Unused or residual 

SBM will be collected and transported to Port Fourchon, Louisiana, for disposal in an approved 

facility. SBM cuttings will be discharged overboard via a downpipe below the water surface, 

after treatment that complies with the 6.9% NPDES permit requirement for retention of SBM 

fluid on cuttings. The estimated volume of SBM cuttings to be discharged is 5,200 barrels (bbl) 

per well. 

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 fire water and ballast water. 

A.5 Water Intake 

Seawater will be drawn from several meters below the ocean surface for various services 

including firewater and once-through non-contact cooling of machinery on the drilling rig 

(Supplemental EP Table 7a). 

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. Construction of the rig planned for use in this Supplemental EP, the 

Noble Danny Atkins, started prior to 17 July 2006, and therefore is not subject to the cooling 

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water intake permit requirements of NPDES Permit GMG 290000. If a different rig is selected, it 

will comply with all applicable NPDES requirements. The design and operational features of the 

rig combined with the geographical area of operation suggest impingement and entrainment 

impacts will be below a level of concern. 

A.6 Onshore Waste Disposal 

Wastes generated during drilling are tabulated in Supplemental EP Section 7. Non-hazardous 

trash and debris and non-recyclable waste will be transported to the Republic/BFI landfill in 

Sorrento, Louisiana, or the parish landfill in Avondale, Louisiana. Additionally, non-hazardous 

recyclable waste will be recycled at Omega Waste Management, Patterson, Louisiana, or at ARC 

of New Iberia, New Iberia, Louisiana. Hazardous waste such as paints, solvents, and unused 

chemicals will be disposed of at Safety Kleen Systems, Inc., Denton, Texas, while used oil and 

glycol will be sent to Omega Waste Management for recycling. Universal waste including 

batteries, lamps, glass, and mercury-contaminated waste will be recycled at Lamp 

Environmental Industries, Hammond, Louisiana. At the onshore facilities, wastes will be 

recycled or disposed of according to all applicable regulations. 

A.7 Marine Debris 

Trash and debris released into the marine environment can harm marine mammals, turtles, and 

birds through entanglement and ingestion. Shell will adhere to the International Convention for 

the Prevention of Pollution from Ships (MARPOL 73/78) Annex V requirements, USEPA and 

USCG regulations, and BOEMRE regulations and NTLs regarding solid wastes. BOEMRE 

regulations at 30 CFR 250.300(a) and (b)(6) prohibit operators from deliberately discharging 

containers and other similar materials (e.g., 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. USCG and USEPA 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. 

Shell complies with 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. Shell’s compliance with all applicable laws, 

regulations, and NTL 2007-G03 will avoid significant impacts on the environment. 

A.8 Support Vessel and Helicopter Traffic 

Shell will use existing shorebased facilities at Port Fourchon and Amelia, Louisiana, for onshore 

support for water and air transportation, respectively. No terminal expansion or construction is 

planned at either location. 

The supply base at Port Fourchon is operated by Shell and located on Bayou LaFourche, 

approximately 3 miles (5 km) from the Gulf of Mexico. During drilling, the project will be 

supported by two crew boats and three offshore support vessels; crew boats will make two 

round-trips per week between the drilling facility and the onshore supply base, while at least 

one support vessel will be in the field at all times. The boats will normally move to the project 

area via the most direct route from the shorebase. 

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The air transportation base will be the PHI Heliport in Amelia, Louisiana. 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 helicopter base and the lease area when air traffic and weather conditions permit. 

Helicopters typically maintain a minimum altitude of 700 ft (213 m) while in transit offshore, 

1,000 ft (305 m) over unpopulated areas or across coastlines, and 2,000 ft (610 m) 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 development activities; and 

An oil spill resulting from an uncontrolled blowout. A blowout resulting in a large oil spill is an 

extremely rare event, and the probability of such an event will be minimized by Shell’s well 

control and blowout prevention measures as detailed in Supplemental EP Section 2j.

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

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

The lease sale EIS (MMS, 2007b) analyzes three other types of accidents: chemical spills, vessel 

collisions, and loss of well control. These accidents are discussed briefly in Section A.9.4. 

A.9.2 Small Fuel Spill 

Spill Size. According to the analysis in MMS (2007b), 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 (MMS, 2007b). 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, the duration of a small spill and the 

opportunity for impacts to occur would be very brief. 

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

aromatic hydrocarbons (PAHs), which are moderately volatile (National Research Council [NRC], 

2003). The constituents of these oils are light to intermediate in molecular weight and can be 

readily degraded by aerobic microbial oxidation. Diesel’s density is such that it will not 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 solids loads (NRC, 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). 

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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 

would range from 1.2 to 12 acres (0.5 to 5 ha) 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 178 miles (286 km) from the nearest shoreline (Louisiana). Modeling results 

discussed below indicate that a spill in the lease area would have a 1% probability of contacting 

the nearest Louisiana shoreline (Terrebonne Parish) within 30 days after a spill. By that time, 

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

processes, even if no response measures were implemented. 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 of a fuel spill, response equipment and trained personnel 

would be available to ensure that any spill effects are localized and would result only in 

short-term environmental consequences. Supplemental EP Section 9b provides a detailed 

discussion of Shell’s response to a spill.

A.9.3 Large Crude Oil Spill 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures detailed in 

Supplemental EP Section 2j. 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. 

The risk of a blowout during this project is significantly lower than indicated by these statistics 

because the well design and drilling program were developed using information gathered during 

the drilling of the previous wells in WR 508. During drilling of the previous wells, the reservoirs 

were logged and evaluated. Substantial data associated with the reservoirs were gathered 

including core, pressure, and fluid data. Data gained during these earlier operations provide 

substantial information that was used in preparing for the proposed operation. 

Spill Size. Shell has calculated a WCD for this Supplemental EP, using the requirements 

prescribed by NTL 2010-N06. The WCD is 42,000 bbl for the first day with a 30-day average of 

33,000 BPD. The estimated time to drill a relief well is 180 days, and the total volume of a spill 

over this duration is estimated to be 5.2 million barrels of oil (MMBO). The detailed analysis of 

this calculation can be found in Supplemental EP Section 2j. The WCD scenario for this 

Supplemental EP, in terms of both initial and the sustained rates, has a low probability of being 

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realized. Some of the factors that are likely to reduce rates and volumes, and are not included 

in the WCD calculation, include but are not limited to obstructions or equipment in the 

wellbore, well bridging, and early intervention such as containment capabilities. 

Shell has a robust system in place to prevent blowouts. Included in Supplemental EP Sections 2j

and 9b is Shell’s response to NTL 2010-N06, which includes 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. Shell will also comply with NTL 2010-N10 and the Interim Final Drilling 

Safety Rule, which specify additional safety measures for OCS activities. 

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 the fate of a spill of at least 1,000 bbl. The OSRA report by Ji et al. (2004) provides 

conditional contact probabilities for shoreline segments. The results for Launch Area 48 (where 

the lease area is located) are presented in Table 3. The model predicts no shoreline contact 

within 3 or 10 days. After 30 days, 8 counties and parishes from Texas to Louisiana may be 

contacted. Plaquemines and Cameron Parish, Louisiana, as well as Galveston County, Texas, 

have the greatest probability of shoreline contact, with a 2% chance within 30 days. 

Table 3. Conditional probabilities of a spill in the lease area contacting shoreline segments 

(From: Ji et al., 2004). Values are conditional probabilities that a hypothetical spill in 

the lease area (represented by OSRA Launch Area 48) could contact shoreline 

segments within 3, 10, or 30 days. 

Shoreline 

Segment County or Parish and State Conditional Probability of Contacta

(%)

3 Days 10 Days 30 Days

C08 Matagorda, TX -- -- 1

C09 Brazoria, TX -- -- 1

C10 Galveston, TX -- -- 2

C12 Jefferson, TX -- -- 1

C13 Cameron, LA -- -- 2

C14 Vermilion, LA -- -- 1

C17 Terrebonne, LA -- -- 1

C20 Plaquemines, LA -- -- 2

a Conditional probability refers to the probability of contact within the stated time period, assuming that a spill has 

occurred (-- indicates less than 0.5%). 

The OSRA model does 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. 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 to evaluate contact probabilities for spills greater than 1,000 bbl.

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, 

and thereby influence its harmful effects on 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 

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degradation, adsorption to suspended PM, and stranding on shore or sedimentation to the 

seafloor (NRC, 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 the 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. Photooxidation attacks mainly the medium and high molecular weight PAHs in the oil on 

the water surface. 

Spill Response. Shell is a founding member of the Marine Well Containment Company (MWCC) 

and has access to an integrated subsea well control and containment system that can be rapidly 

deployed through the MWCC. The MWCC is a non-profit organization that assists with the 

subsea containment system during a response. The near-term containment response capability 

will be specifically addressed in Shell’s NTL 2010-N10 submission at the time an Application to 

Drill (APD) is submitted and will include equipment and services available to Shell through 

MWCC’s development of near-term capability and other industry sources. Shell is a member of 

Clean Caribbean & Americas (CCA), Marine Spill Response Corporation (MSRC), Clean Gulf 

Associates (CGA), and Oil Spill Response Limited (OSRL), organizations that are committed to 

providing the resources necessary to respond to a spill as outlined in Shell’s Regional OSRP.

The experience of gaining control over the Macondo well has resulted in a better understanding 

of the necessary equipment and systems for well containment. As a result, industry and 

government are better equipped and prepared today to contain an oil well blowout in 

deepwater (see page 17 of the Decision Memorandum dated 1 October 2010 [Bromwich, 

2010]). Shell is further analyzing these advances and incorporating them into a comprehensive 

approach to help prevent and, if needed, control another deepwater control incident. Shell is 

also investing in research and development to improve containment systems. 

The primary offshore response would involve mechanical recovery. The primary response 

equipment that would be mobilized to the spill location for spills in normal and adverse weather 

conditions is included in the Offshore On-Water Recovery Activation List in the OSRP. 

Chemical dispersant stockpiles are readily available from Gulf Coast State suppliers such as 

MSRC in Texas, Louisiana, Mississippi, and Florida; MWCC; CGA/Airborne Support, Inc. in 

Louisiana and Texas; and Clean Caribbean and Americas in Florida. Additional supplies are 

available from international vendors. Available equipment for surface and subsea application of 

dispersants, response times, and support resources are identified in the OSRP. 

Open-water in situ burning may also be used as a response strategy, depending on the 

circumstances of the release. If appropriate conditions exist and approval from the Unified 

Command is received, one or multiple in situ burning task forces could be deployed offshore. 

See Supplemental EP Sections 2j and 9b for a detailed description of Shell’s site-specific 

response to a large oil spill for this plan. These sections, along with Shell’s OSRP, also include a 

description of surface and subsea containment capabilities that could be implemented in the 

event of a large oil spill at this site. 

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A.9.4 Other Accidents Not Analyzed in Detail 

The lease sale EIS (MMS, 2007b) discusses three other types of accidents: chemical spills, vessel 

collisions, and loss of well control. These accidents are discussed briefly below. No hydrogen 

sulfide (H2S) is expected at this site, and no other site-specific issues have been identified for this 

Supplemental EP. The analysis in the lease sale EIS for these topics is incorporated by reference. 

Chemical Spill. Chemicals are used in drilling operations to achieve technical goals in the drilling 

process, improve the efficiency and safety of drilling, and protect associated equipment. 

Chemicals used during exploration and drilling include surfactants, bentonite clays, olefins, 

inorganic salts, glycols, polymers, barite, and calcium carbonate. Supplies are renewed on a 

regular basis by transfer in containers from supply boats (Boehm et al., 2001). In addition to 

chemicals used in drilling fluids, the following chemicals are likely to be used on the rig: ethylene 

glycol (blowout prevention control fluid, used in closed cooling loops for crane and main engines 

and brake coolers), cement (used to cement casing in place), solvents (used in painting 

operations), hydraulic fluids (used in cranes and other hydraulic rig equipment), lubricating oil 

and grease (used in reciprocating and electrical equipment), and sodium hypochlorite (dilute, 

used as laundry bleach and disinfectant). 

A study of environmental risks of chemical products used in OCS activities determined that only 

two chemicals could potentially affect the marine environment: zinc bromide and ammonium 

chloride (Boehm et al., 2001). The risk of a spill for these chemicals is very low. Most other 

chemicals are either nontoxic or used in small quantities. No significant impacts are expected 

from chemical spills. 

Vessel Collisions. As summarized in MMS (2007b), vessel collisions occasionally occur during 

routine operations. Most collision mishaps are the result of service vessels colliding with 

platforms or vessel collisions with pipeline risers. Some of these collisions have caused spills of 

diesel fuel or chemicals. Shell 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 minor to 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. Shell has a robust system in place to prevent loss of well control. Included in this 

Supplemental EP is Shell’s response to NTL 2010-N06, which includes 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. Shell will also comply with NTL 2010-N10 and the 

Interim Final Drilling Safety Rule, which specify additional safety measures for OCS activities. 

See Supplemental EP Sections 2j and 9b for further information. 

H2S Release. Based on CFR 250.490(c), Shell has requested that the proposed drilling area be 

classified as an area where the absence of H2S has been confirmed. 

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B. Affected Environment 

The lease area is in the north-central Gulf of Mexico, 178 miles (286 km) from the nearest 

shoreline, 193 miles (311 km) from the onshore support base at Port Fourchon, Louisiana, and 

221 miles (356 km) from the helicopter base at Amelia, Louisiana (Figure 1).

WR 508 straddles the Sigsbee Escarpment and abyssal plain in an area of seafloor furrows. 

Proposed well locations G, H, and I are positioned between seafloor furrows where the soils are 

relatively soft, with water depths ranging from 9,554 to 9,578 ft (2,912 to 2,919 m) (Figure 2; 

Geoscience Earth & Marine Services, Inc. [GEMS], 2006; Fugro GeoConsulting, Inc. [FGCI], 2010). 

The sidescan sonar survey confirmed the presence of piston cores, drilling splays, anchor chain 

scars, and previously drilled wells in the lease area but none are within 2,000 ft (610 m) of the 

proposed wellsites. There were 961 sonar contacts that were not archaeologically significant 

and 1 contact above the seafloor that was larger than the others. This contact is irregular in 

shape and may be made up of smaller debris targets, but it could not be reliably identified 

(Fugro GeoServices, Inc. [FGSI], 2011). 

A detailed description of the regional affected environment is provided in recent EISs 

(MMS, 2007b, 2008), 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. These regional 

descriptions are based on extensive literature reviews and are incorporated by reference. 

General background information is presented below, and brief descriptions of each potentially 

affected resource are presented in Section C, including site-specific and/or new information if 

available. 

The local environment in the lease area is not known to be unique with respect to 

physical/chemical, biological, or socioeconomic conditions. Baseline environmental conditions 

in the lease area are expected to be consistent with the regional description of continental slope 

locations evaluated in recent lease sale EISs (MMS, 2007b, 2008). 

The lease area is approximately 214 miles (345 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 prior to capping of the well; therefore, existing water quality in the lease area was not likely 

to have been affected. Macondo spill impacts are addressed in Section C.9 (Cumulative 

Impacts) where available and applicable. 

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

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C. Impact Analysis 

This section analyzes the potential direct and indirect impacts of routine activities and accidents. 

Cumulative impacts are discussed in Section C.9. Impacts have been analyzed extensively in 

recent multi-lease-sale EISs for the Western and Central Gulf of Mexico Planning Areas (MMS, 

2007b, 2008). Site-specific issues are addressed in this section as appropriate. 

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 

shorebased pollution sources, offshore air quality 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 of 21 April 2011 all Louisiana, Mississippi, Alabama, and Florida coastal counties and parishes 

are in attainment of the National Ambient Air Quality Standards (NAAQS) for all criteria 

pollutants (USEPA, 2011). Two metropolitan areas in Texas are nonattainment areas for 8-h 

ozone (Dallas-Fort Worth, and Houston-Brazoria), and El Paso County is a nonattainment area 

for PM10 (USEPA, 2011).

Winds in the region are driven by the clockwise circulation around the Bermuda High 

(MMS, 2007b). The Gulf of Mexico is located to the southwest of this center of circulation, 

resulting in a prevailing southeasterly to southerly flow, which is conducive to transporting 

emissions toward shore. However, circulation is also affected by tropical cyclones (hurricanes) 

during summer and fall and by extratropical cyclones (cold fronts) during winter. 

IPFs potentially affecting air quality are air pollutant emissions and two types of accidents: 

a small fuel spill and a large oil spill. 

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 operation of the drilling rig as well as 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. 

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 

Supplemental EP Section 8) prepared in accordance with BOEMRE requirements shows that the 

projected emissions for PM, SOx, NOx, VOCs, and CO are below exemption levels; therefore, 

according to 30 CFR 250.303, the emissions will not significantly affect the air quality of the 

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onshore area for any of the criteria pollutants. No further analysis or control measures are 

required. However, Shell will use low-sulfur fuel to further reduce any possible impacts. 

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 coordinates with the National Park Service (NPS) and the 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. Shell does not 

anticipate any impact on the Class I area, but will comply with any emissions requirements as 

directed by the BOEMRE. 

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 recent EISs (MMS, 2007b, 2008). The probability of a small spill would be 

minimized by Shell’s preventative measures during routine operations, including fuel transfer. 

In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the 

impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. 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 more than 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 1.2 to 12 acres (0.5 to 5 ha) depending on sea state and 

weather conditions. 

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 

Potential impacts of a large oil spill on air quality are expected to be consistent with those 

analyzed and discussed in recent EISs (MMS, 2007b, 2008). 

A large oil spill would 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. 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. 

Due to the lease area location (178 miles [286 km] from the nearest shoreline), most air quality 

impacts would occur in offshore waters. Depending on the spill trajectory and the effectiveness 

of spill response measures, coastal air quality could also be affected. Based on the OSRA 

modeling predictions (Table 3), Plaquemines and Cameron Parish, Louisiana, as well as 

Galveston County, Texas, are the coastal areas most likely to be affected. 

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A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on air quality are expected. 

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 the 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 approximately 214 miles (345 km) southwest of the Macondo spill site. Based 

on satellite imagery (ESRI, 2010), the surface slick did not extend over the lease area during the 

spill, and therefore existing water quality in the lease area was unlikely to have been affected. 

The Operational Science Advisory Team (OSAT, 2010) reported that after August 2010, waters 

and sediments in the deepwater Gulf of Mexico beyond 1.8 miles (3 km) from the Macondo 

wellsite were below USEPA acute and chronic benchmarks for PAHs and were not hypoxic. 

These observations indicate that baseline environmental conditions in the lease area are 

unlikely to have been significantly altered by the spill. 

IPFs potentially affecting water quality are effluent discharges and two types of accidents: 

a small fuel spill and a large oil spill. 

Impacts of Effluent Discharges 

Discharges of treated SBM cuttings will produce temporary, localized increases in suspended 

solids in the water column around the drilling rig. In general, turbid water can be expected to 

extend between a few hundred meters and several kilometers down current from the discharge 

point (NRC, 1983; Neff, 1987). All NPDES permit limitations and requirements will be met. After 

discharge, SBM retained on cuttings would be expected to adhere tightly to the cuttings 

particles and, consequently, would not produce much turbidity as the cuttings sink through the 

water column (Neff et al., 2000). There will be no persistent impacts on water quality in the 

lease area. 

Treated sanitary and domestic wastes may have a slight transient effect on water quality in the 

immediate vicinity of these discharges. All NPDES permit limitations and requirements will be 

met and 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. 

Little or no impact on water quality is anticipated. 

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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 quality. 

Support vessels will discharge treated sanitary and domestic wastes. These will have a slight 

effect on water quality in the immediate vicinity of the discharges. All support vessel discharges 

will be in accordance with USCG regulations and, as applicable, the NPDES Vessel General 

Permit, and therefore are not expected to cause significant impacts 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). The probability of a small spill would 

be minimized by Shell’s preventative measures during routine operations, including fuel 

transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce 

the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. 

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 more 

than 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 1.2 to 

12 acres (0.5 to 5 ha) 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 (NRC, 2003). The constituents of these oils are light to intermediate in 

molecular weight and can be readily degraded by aerobic microbial oxidation. Diesel’s density is 

such that it will not 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 (NRC, 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 prior to breaking up (see Section A.9.2).

Impacts of a Large Oil Spill 

Potential impacts of a large oil spill on water quality are expected to be consistent with those 

analyzed and discussed in recent 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). A report by Kujawinski et al. (2011) 

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indicates that chemical components of subsea dispersants used during the Macondo spill 

persisted for up to two months and were detectable up to 186 miles (300 km) from the wellsite 

at a water depth of 3,280 to 3,937 ft (1,000 to 1,200 m). 

Once oil enters the ocean, a variety of physical, chemical, and biological processes act to 

disperse the oil slick. These processes include spreading, evaporation of the more volatile 

constituents, dissolution into the water column, emulsification of small droplets, agglomeration 

sinking, microbial modification, photochemical modification, and biological ingestion and 

excretion (NRC, 2003). Marine water quality would be temporarily affected by the dissolved 

components and small oil droplets that do not rise to the surface or are mixed down by surface 

turbulence. Dispersion by currents and microbial degradation removes the oil from the water 

column or dilutes the constituents to background levels. 

A large oil spill could result in a release of gaseous hydrocarbons that could affect water quality. 

During the Macondo spill, large volumes of methane (CH4) were released, causing localized 

oxygen depletion as methanotrophic bacteria rapidly metabolized the hydrocarbons (Joye et al., 

2011; Kessler et al., 2011). However, a broader study of the deepwater Gulf of Mexico found 

that although some stations had slightly depressed dissolved oxygen concentrations relative to 

climatological background values, concentrations were not low enough to indicate hypoxia 

(<2.0 mg/L) (OSAT, 2010). Stations revisited around the Macondo wellhead in October 2010 

showed no measurable oxygen depression (OSAT, 2010). 

Due to the lease area location (178 miles [286 km] from the nearest shoreline), most water 

quality impacts would occur in offshore waters. Depending on the spill trajectory and the 

effectiveness of spill response measures, coastal water quality could be affected. Based on the 

OSRA modeling predictions (Table 3), nearshore waters and embayments of Cameron and 

Plaquemines Parish, Louisiana, and Galveston County, Texas, are the most likely coastal areas 

where water quality could be affected. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on water quality are expected. 

C.2 Seafloor Habitats and Biota 

Water depths at the proposed well surface locations range from 9,554 to 9,578 ft (2,912 to 

2,919 m). The seafloor at the wellsites is expected to consist mainly of soft bottom. The 

chemosynthetic community assessment based on the hazards report by GEMS (2006) and FGCI 

(2010) did not identify any features that could support high-density deepwater benthic 

communities within 2,000 ft (610 m) of the wellsites. See Supplemental EP Section 6a for 

further information. 

According to the BOEMRE (2011), existing information for the deepwater Gulf of Mexico 

indicates that the seafloor is composed primarily of soft sediments; hard bottom communities 

are rare. WR 508 is within deepwater Grid 11, and the BOEMRE website indicates that ROV 

coverage of the seafloor in this grid is adequate to characterize the area (BOEMRE, 2011). 

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C.2.1 Soft Bottom Benthic Communities 

Data from the recent 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 two nearby stations in similar water 

depths. Sediments at those two stations were predominantly clay (55% to 58%) and silt 

(39% to 41%). 

Table 4. Benthic community data from stations near the lease area and in similar water depths 

sampled during the Northern Gulf of Mexico Continental Slope Habitats and Benthic 

Ecology Study (From: Wei, 2006; Rowe and Kennicutt, 2009). 

Station

Location 

Relative to 

Lease Area

Water 

Depth

(m)

Abundance

Meiofauna

(individuals/m2)

Macroinfauna

(individuals/m2)

Megafauna

(individuals/ha)

NB-5 30 mi SW 2,110 117,263 706 1,600

B-3 63 mi SW 2,649 155,817 814 362

Meiofaunal and megafaunal abundance from Rowe and Kennicutt (2009); macroinfaunal abundance from Wei (2006). 

Meiofauna (animals passing through a 0.5-mm sieve but retained on a 0.062-mm sieve) 

densities in water depths representative of the lease area typically range from about 100,000 to 

180,000 individuals/m2 (Rowe and Kennicutt, 2009). Nematodes, nauplii, and harpacticoid 

copepods were the three dominant groups in the meiofauna, accounting for about 90% of total 

abundance. 

The benthic macroinfauna is characterized by small mean individual sizes and low densities, 

both of which are a reflection of 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 wellsites are 

expected to be about 800 individuals/m2, similar to the values 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, which consists of stations on the most complex 

bathymetric features in the northern Gulf of Mexico, including the Alaminos Canyon, basins and 

non-basins sites and the Sigsbee Escarpment. These stations range in depth from 6,150 to 

9,870 ft (1,875 to 3,008 m). The five most abundant species in Zone 3W were the polychaetes 

Levinsenia uncinata, Paraonella monilaris, and Tachytrypane sp. and two bivalve 

Heterodonta spp.

Megafaunal density from nearby stations NB-5 and B-3 was 1,600 and 362 individuals/ha, 

respectively (Table 4). Densities of 1,300 to 1,900 individuals/ha were reported from other 

stations in a similar depth range. Common megafauna included motile groups such as 

decapods, ophiuroids, holothurians, and demersal fishes, as well as sessile groups such as 

sponges and anemones. 

Page 87 Public Information Copy
Bacteria are also 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 grams of carbon per square meter (g C/m2) in the top 15 cm of sediments (Rowe and 

Kennicutt, 2009). 

IPFs potentially affecting benthic communities are effluent discharges (drilling muds and 

cuttings) and a large oil spill resulting 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. There will be no disturbance to soft bottom communities on the seafloor during 

positioning of the DP semisubmersible Noble Danny Adkins. 

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 treated SBM cuttings from the rig may affect benthic communities, primarily 

within several hundred meters of the wellsites. 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, cuttings with adhering 

SBM 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 and concentrations 

exceed approximately 1,000 mg/kg, 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. 

The areal extent of impacts from drilling discharges will be small. Assuming a typical effect 

radius of 1,640 ft (500 m), the affected area around each wellsite would represent about 3% of 

the seafloor within a lease block. For the three surface locations in this exploration-drilling 

program, the total impact area would be 448 acres (181 ha). 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 on a regional basis. 

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Impacts of a Large Oil Spill 

The most likely effects of a subsea blowout on benthic communities would be within a few 

hundred meters of the wellsites. The MMS (2007b) estimates that a severe subsurface blowout 

could resuspend and disperse sediments within a 984-ft (300-m) radius. While coarse sediments 

(sands) would probably settle at a rapid rate within 1,312 ft (400 m) from the blowout site, fine 

sediments (silts and clays) could be resuspended for more than 30 days and dispersed over a 

much wider area. Previous studies characterized surface sediments in the vicinity of the site as 

about 50% clay and 45% silt (Rowe and Kennicutt, 2009). 

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 3,600 ft (1,100 m), extending at least 22 miles (35 km) from the wellsites 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). This 

observation is supported by Kujawinski et al. (2011) in their report that chemical components of 

subsea dispersants used during the Macondo spill persisted for up to two months and were 

detected up to 186 miles (300 km) from the wellsite at a water depth of 3,280 to 3,937 ft

(1,000 to 1,200 m). However, estimated dispersant concentrations in the subsea plume were 

below levels known to be toxic to marine life. 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 984-ft (300-m) 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 (NRC, 2003). 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on soft bottom communities are 

expected. 

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, and on shipwrecks. 

The chemosynthetic community assessment included in this Supplemental EP, based on the 

shallow hazards reports by GEMS (2006) and FGCI (2010), did not identify any features that 

could support high-density deepwater benthic communities within 2,000 ft (610 m) of the 

proposed drilling mud/cuttings discharge locations. 

Page 89 Public Information Copy
IPFs potentially affecting high-density deepwater benthic communities are effluent discharges 

(drilling muds and cuttings), and a large oil spill 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. Because a DP drilling rig will be used, there will be no anchoring impacts. 

Impacts of Effluent Discharges 

The chemosynthetic community assessment included in this Supplemental EP, based on the 

shallow hazards reports by GEMS (2006) and FGCI (2010), did not identify any features that 

could support high-density deepwater benthic communities within 2,000 ft (610 m) of the 

proposed drilling mud/cuttings discharge locations. Monitoring programs on the Gulf of Mexico 

continental slope have shown that benthic impacts from drilling discharges typically are 

concentrated within about 1,640 ft (500 m) of the wellsites, although detectable deposits may 

extend beyond this distance (Continental Shelf Associates, Inc., 2004, 2006; Neff et al., 2005). If 

high-density deepwater communities are associated with the more distant expulsion features 

and mud volcanoes identified in the hazards survey, significant impacts on these communities 

will be avoided because of the distance from the discharge location. 

Impacts of a Large Oil Spill 

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 3,600 ft (1,100 m), extending at least 22 miles (35 km) from the wellsites 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). This 

observation is supported by Kujawinski et al. (2011) in their report that chemical components of 

subsea dispersants used during the Macondo spill persisted for up to two months and were 

detectable up to 186 miles (300 km) from the wellsite at a water depth of 3,280 to 3,937 ft

(1,000 to 1,200 m). However, estimated dispersant concentrations in the subsea plume were 

below levels known to be toxic to marine life. 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 984-ft (300-m) radius estimated by MMS (2007a, 

2008), depending on its extent, trajectory, and persistence. Potential impacts on sensitive 

resources would be an integral part of the decision and approval process for the use of 

dispersants. 

Potential impacts of oil on high-density deepwater benthic communities are discussed by 

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 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). 

Page 90 Public Information Copy
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 4,600 ft 

(1,400 m) deep and approximately 7 miles (11 km) southwest of the Macondo wellhead when 

they observed dead and dying corals with sloughing tissue and discoloration. The study location 

was about 171 miles (275 km) from the lease area. Much of the soft coral observed in an area 

measuring about 50 to 130 ft (15 to 40 m) was covered by what appeared to be a brown 

substance. Ninety percent of 40 large corals were heavily affected and showed dead and dying 

parts and discoloration. Another site 1,312 ft (400 m) 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 an ROV 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. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on deepwater benthic communities 

are expected. 

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 topographic feature is Ewing Bank, located 107 miles 

(172 km) north 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 

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 blocks are about 236 miles (380 km) from the lease 

area, along the shelf edge south of Alabama. 

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. 

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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 328 ft (100 m) or less. The 

nearest blocks covered by the live bottom stipulation, as defined by NTL 2009-G39, are about 

272 miles (438 km) from the project 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 ESA. In addition, it 

includes all marine mammal species in the region, which are protected under the 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 NMFS has jurisdiction over ESA-listed cetaceans, sea turtles, and fishes in the 

Gulf of Mexico. The USFWS has jurisdiction over ESA-listed birds and the Florida manatee. 

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. 

Coastal endangered or threatened species include the Florida manatee, Piping Plover, 

Whooping Crane, Gulf sturgeon, and four subspecies of beach mouse. Critical habitat has been 

designated for all of these species as indicated in Table 5 and discussed in individual sections. 

Page 92 Public Information Copy
Table 5. 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

Florida manatee Trichechus manatus 

latirostris

E -- X

Florida 

(Peninsular)

Blue whale Balaenoptera musculus E X

a

-- None

Fin whale Balaenoptera physalus E X

a

-- None

Humpback whale Megaptera novaeangliae E X

a

-- None

North Atlantic right whale Eubalaena glacialis E X

a

-- None

Sei whale Balaenoptera borealis E X

a

-- None

Sea Turtles

Loggerhead turtle Caretta caretta T

b X X None

Green turtle Chelonia mydas T, Ec 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)

Terrestrial Mammals

Beach mouse (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 loggerhead turtle is currently classified as threatened throughout its range. In March 2010, NMFS and USFWS 

proposed to list the Northwest Atlantic Ocean population of loggerhead turtles as endangered (75 FR 12598).

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

Two other coastal species (Bald Eagle and Brown Pelican) discussed by MMS (2007b) are no 

longer listed as endangered or threatened; these are discussed under Coastal and Marine Birds. 

There are no other endangered animals or plants in the Gulf of Mexico that are reasonably likely 

to be affected by either routine or accidental events. Other species occurring at certain 

locations in the Gulf of Mexico such as the smalltooth sawfish (Pristis pectinata), elkhorn coral 

(Acropora palmata), staghorn coral (Acropora cervicornis), and Florida salt marsh vole (Microtus 

pennsylvanicus dukecampbelli) are remote from the lease area and highly unlikely to be 

affected. 

Page 93 Public Information Copy
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 NMFS (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 656- and 3,280-ft 

(200- and 1,000-m) depth contours (Jochens et al., 2008). Male sperm whales were more 

variable in their movements and were documented in water depths greater than 9,483 ft 

(3,000 m). 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 

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. 

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. 

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 associated with drilling is 

relatively weak in intensity, and an individual animal’s noise exposure 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, timing, and geographic location of drilling 

activities, this project would represent a small temporary contribution to the overall noise 

regime. 

The NMFS (2007) analyzed the potential for impacts of drilling-related noise on sperm whales in 

its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and Western 

Planning Areas of the Gulf of Mexico. The analysis noted that drilling rigs show 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). 

Page 94 Public Information Copy
Although drilling rig lighting and rig presence were considered potential factors affecting sperm 

whales, NMFS’s 2007 Biological Opinion and recent lease sale EISs (MMS, 2007b, 2008) did not 

identify rig lighting and presence as IPFs for sperm whales. 

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 is presented in the lease sale EIS (MMS, 2007b). To 

reduce the potential for vessel strikes, the BOEMRE has 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. When whales are sighted, vessel operators and crews are required to 

attempt to maintain a distance of 300 ft (91 m) 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. 

The NMFS (2007) analyzed the potential for vessel strikes and harassment of sperm whales in its 

Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and Western 

Planning Areas of the Gulf of Mexico. 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. The 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 300 ft (91 m) 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 800 ft (245 m). A reaction to the initial pass of the aircraft was observed during three 

out of 24 sightings (12%). All three reactions consisted of a hasty dive and occurred at less than 

1,180 ft (360 m) 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 700 ft (213 m) 

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 based on the 

Smultea et al. (2008) study, the NMFS (2007) concluded that this altitude would minimize the 

potential for disturbing sperm whales. Therefore, no significant impacts are expected. 

Page 95 Public Information Copy
Impacts of a Small Fuel Spill 

Potential spill impacts on marine mammals including sperm whales are discussed in recent EISs 

(MMS, 2007b, 2008) and by the NMFS (2007) in its Biological Opinion for the Five-Year Oil and 

Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. Oil 

impacts on marine mammals are discussed by Geraci and St. Aubin (1990). For this 

Supplemental 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 Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts on sperm whales. Supplemental EP 

Sections 2j and 9b provide 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 

1.2 to 12 acres (0.5 to 5 ha), 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 

Potential spill impacts on marine mammals including sperm whales are discussed in recent EISs 

(MMS, 2007b, 2008) and by the NMFS (2007) in its Biological Opinion for the Five-Year Oil and 

Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. Oil 

impacts on marine mammals are discussed by Geraci and St. Aubin (1990). For this 

Supplemental 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 

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patterns, changing reproductive behavior/productivity, and changing movement patterns or 

migration (MMC, 2010). 

Studies have shown that the cetacean epidermis functions as an effective barrier to noxious 

substances found in petroleum (Geraci and St. Aubin, 1985). Unlike other mammals, 

penetration of such substances in cetacean skin is impeded by tight intercellular bridges, the 

vitality of the superficial cells, the thickness of the epidermis, and the lack of sweat glands and 

hair follicles. In addition, cetacean skin is free from hair or fur, which in other marine mammals 

not found in the Gulf of Mexico (e.g., pinnipeds and otters) tends to collect oil and/or tar. 

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. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on sperm whales are expected. 

C.3.2 Florida Manatee (Endangered) 

Most of the manatee population is located in peninsular Florida (USFWS, 2001). Manatees 

regularly migrate farther west of Florida in the warmer months (Wilson, 2003) into Alabama and 

Louisiana coastal environs, with some individuals traveling as far as west Texas (Fertl et al., 

2005). 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. A small fuel spill in the lease area would be unlikely to affect manatees, as the lease area is 

approximately 178 miles (286 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. 

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, the BOEMRE has 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, if present, 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 66 to 525 ft (20 to 160 m). 

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Helicopters used in support operations maintain a minimum altitude of 700 ft (213 m) while in 

transit offshore, 1,000 ft (305 m) over unpopulated areas or across coastlines, and 2,000 ft 

(610 m) 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 

The OSRA results summarized in Table 3 predict that some Texas and Louisiana shorelines could 

be contacted by a spill within 30 days. There is no critical habitat designated in these areas, and 

the number of manatees potentially present is a small fraction of the population in peninsular 

Florida. 

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. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on manatees 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 

contact with any project activities, either routine operations or accidents. The NMFS (2007) did 

not include any of these mysticete whales as affected species in its Biological Opinion for the 

Five-Year Oil and Gas Leasing Program in the Central and Western Planning Areas of the Gulf of 

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Mexico. 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) 

In addition to the seven endangered species that have been cited previously, 22 other species of 

marine mammals occur in the Gulf of Mexico, including two mysticete whales, the dwarf and 

pygmy sperm whales, 4 species of beaked whales, and 14 species of delphinids 

(see Supplemental EP Section 6h). 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 328-ft 

(100-m) 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; Mullin, 2007). 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 beaked whale 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 waters greater than 3,281 ft 

(1,000 m) 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), 

short-finned pilot whale (Globicephala macrorhynchus), Risso’s dolphin (Grampus griseus), 

rough-toothed dolphin (Steno bredanensis), spinner dolphin (Stenella longirostris), and striped 

Page 99 Public Information Copy
dolphin (Stenella coeruleoalba). The most common non-endangered cetaceans in the 

deepwater environment are the pantropical spotted dolphin, spinner dolphin, and clymene 

dolphin. However, any of these species could occur in the lease area. 

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). 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 sounds that are higher than the low-frequency 

dominant frequencies produced by OCS drilling activities (Richardson et al., 1995). Noise 

associated with drilling is relatively weak in intensity, and an individual animal’s noise exposure 

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, timing, and 

geographic extent 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 is presented in the lease sale EIS 

(MMS, 2007b). To reduce the potential for vessel strikes, the BOEMRE has 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 300 ft (91 m) or greater when whales are sighted and 150 ft (45 m) 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 this 

NTL 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 700 ft (213 m) 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 Supplemental 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 Shell’s preventative measures during fuel 

transfer. In the unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate 

and reduce the potential for impacts on marine mammals. Supplemental EP Sections 2j and 9b

provide 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 

1.2 to 12 acres (0.5 to 5 ha), 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 

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008) and 

by Geraci and St. Aubin (1990). For this Supplemental 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 

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the potential for striking or disturbing these animals, and therefore no significant impacts are 

expected. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on marine mammals are expected. 

C.3.5 Sea Turtles (Endangered/Threatened) 

As listed in Supplemental EP Section 6h, five species of endangered or threatened sea turtles 

may be found near the lease area. Endangered species are the leatherback (Dermochelys 

coriacea), Kemp's ridley (Lepidochelys kempii), and hawksbill (Eretmochelys imbricata) turtles. 

The loggerhead turtle (Caretta caretta) is a threatened species. The green turtle (Chelonia 

mydas) is listed as threatened, except for the Florida breeding population, which is listed as 

endangered. Species descriptions are presented in a recent lease sale EIS (MMS, 2007b). 

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 

turtles may be present in deepwater areas, including the lease area, where they may be 

associated with Sargassum and other flotsam. 

All five sea turtle species in the Gulf of Mexico are migratory and use different marine habitats 

according to their life stage. These habitats include high-energy beaches for nesting females 

and emerging hatchlings and pelagic convergence zones for hatchling and juvenile turtles. As 

adults, green, hawksbill, and loggerhead turtles forage primarily in shallow, benthic habitats. 

Leatherbacks are the most pelagic of the sea turtles, feeding primarily on jellyfish. 

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, 2011); 

Kemp’s ridley turtles – The main Kemp’s ridley nesting site is Rancho Nuevo beach, Tamaulipas, 

Mexico (NMFS et al., 2010). Approximately 200 Kemp’s ridley turtles nested on Texas 

beaches in 2009 (Sea Turtle Restoration Project, 2011). 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). 

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. Compliance 

with NTL 2007-G03 will minimize the potential for marine debris-related impacts on sea turtles. 

Page 102 Public Information Copy
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, timing, and geographic extent 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, the BOEMRE has 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 150 ft 

(45 m) 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 700 ft (213 m) 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 by the 

NMFS (2007) in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the 

Central and Western Planning Areas of the Gulf of Mexico. For this Supplemental 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 Shell’s preventative measures during fuel 

transfer. In the unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate 

and reduce the potential for impacts on sea turtles. Supplemental EP Sections 2j and 9b

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provide 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 

1.2 to 12 acres (0.5 to 5 ha), 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, 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 178 miles (286 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 

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 (MMC, 2010). In the 

unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate and reduce the 

potential for these types of impacts on sea turtles. Supplemental EP Sections 2j and 9b provide 

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). 

The OSRA results summarized in Table 3 predict that some shorelines that support sea turtle 

nesting could be contacted within 30 days. The nearest nesting area of loggerhead turtles is 

found on beaches within the Breton NWR. This area (Plaquemines Parish) has a contact 

probability of 2% after 30 days. 

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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). 

Data from the recent Macondo spill provides additional information about potential impacts of a 

large oil spill on sea turtles to supplement the analysis presented in the lease sale EIS (MMS, 

2007b). According to NMFS (2010b), approximately 600 dead turtles have been reported since 

the Macondo spill. Species include Kemp’s ridley turtles (481 individuals), loggerhead turtles 

(67 individuals), and green turtles (29 individuals). Oiled turtles include 18 dead individuals and 

456 live, oiled animals that were either captured or stranded. Also, 278 turtle nests were 

translocated (271 loggerhead, 4 Kemp’s ridley, and 3 green turtles) and more than 

14,000 hatchlings were released. The strandings and captures ranged from the Louisiana/Texas 

border to Cape San Blas in the Florida Panhandle. 

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 

potential for striking or disturbing these animals, and therefore no significant impacts are 

expected. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on sea turtles 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 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).

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Figure 3. Location of selected environmental features in relation to the lease area. Shown are Essential Fish Habitat (EFH) for coral and 

coral reefs; Habitat Areas of Particular Concern (HAPC) for northwestern Gulf of Mexico reefs and banks and spawning Atlantic 

bluefin tuna; critical habitat for beach mice, Gulf sturgeon, Piping Plover, and Whooping Crane; and the Macondo spill location. 

Page 106 Public Information Copy
Impacts of a Large Oil Spill 

The lease area is 178 miles (286 km) from the nearest shoreline inhabited by Piping Plovers. The 

OSRA results summarized in Table 3 predict that Texas and Louisiana shorelines designated as 

critical habitat for the wintering Piping Plover could be contacted by a spill within 30 days. 

Plaquemines Parish, which has a 2% probability of contact for the 30-day interval, includes 

Piping Plover critical habitat. 

Plovers could become externally oiled while foraging on oiled shores or be exposed internally 

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. Shell has extensive resources available to protect and 

rehabilitate wildlife in the event of a spill reaching the shoreline, as detailed in the OSRP. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on Piping Plovers are expected. 

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 [WCEP], 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 (WCEP, 2010). A non-migrating population has been 

re-introduced in central Florida, and another re-introduced 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 

22,240 acres (9,000 ha) 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 (Figure 3). A species description is presented in a recent lease sale EIS (MMS, 2007b). 

A large oil spill is the only IPF potentially affecting Whooping Cranes. A small fuel spill in the 

lease area would 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 

A large oil spill has a low probability of affecting Whooping Cranes because the lease area is 

approximately 372 miles (598 km) from its critical habitat (Aransas NWR, Texas) and the OSRA 

modeling predicts 1% probability of contact with shorelines of the Aransas NWR within 30 days. 

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In the event of oil exposure, Whooping Cranes could become externally oiled while foraging in 

oiled areas or internally exposed to oil through ingestion of contaminated shellfish, frogs, and 

fishes. It is possible that some death of Whooping Cranes could occur. Shell has extensive 

resources available to protect and rehabilitate wildlife in the event of a spill reaching the 

shoreline, as detailed in the OSRP. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on Whooping Cranes are expected. 

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, 2010c) (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 is the only IPF potentially affecting Gulf sturgeon. There are no IPFs associated 

with routine project activities that could affect this species. 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 

Potential spill impacts on Gulf sturgeon are discussed in recent EISs (MMS, 2007b, 2008) and by 

the NMFS (2007) in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the 

Central and Western Planning Areas of the Gulf of Mexico. For this Supplemental EP, there are 

no unique site-specific issues with respect to this species. 

The lease area is about 244 miles (393 km) from the nearest Gulf sturgeon critical habitat. The 

OSRA modeling (Table 3) predicts that a spill in the lease area will not contact the coastal areas 

inhabited by Gulf sturgeon within 30 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 

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vulnerable to a marine oil spill, and would be vulnerable only during winter months (from 

1 September through 30 April) when this species is foraging in estuarine and marine habitats 

(NMFS, 2007). 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Shell has extensive resources available to protect coastal and 

estuarine wildlife and habitats in the event of a spill reaching the shoreline, as detailed in the 

OSRP. Supplemental EP Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on Gulf sturgeon are expected. 

C.3.9 Beach Mice (Endangered) 

Four subspecies of endangered beach mouse (Peromyscus polionotus) occur on the barrier 

islands of Alabama and the Florida Panhandle. They are the Alabama, Choctawatchee, Perdido 

Key, and St. Andrew beach mouse. 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 is the only IPF potentially affecting subspecies of beach mouse. 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 any subspecies of beach mouse 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 

Potential spill impacts on beach mice are discussed in recent EISs (MMS, 2007b, 2008). For this 

Supplemental EP, there are no unique site-specific issues with respect to these species. 

The lease area is about 308 miles (496 km) from the nearest beach mouse critical habitat. The 

OSRA modeling predicts that a spill in the lease area would not contact beach mouse critical 

habitat within 30 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. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on beach mice are expected. 

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C.4 Coastal and Marine Birds 

C.4.1 Marine and Pelagic Birds 

A variety of seabirds may occur in the pelagic environment of the project areas (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 

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 Gull, Royal Tern, Bridled Tern) (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 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. 

GulfCet II 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 platforms 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). 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 platforms may be exposed to contaminants including air pollutants and 

routine discharges, but significant impacts are unlikely due to rapid dispersion of effluents and 

air pollutants. 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 

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towers and other land-based structures has been reviewed extensively, and the mechanisms 

involved in platform collisions appear to be similar. In some cases, migrants simply do not see a 

part of the platform 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 platforms probably 

benefit from their stay, particularly in spring (Russell, 2005). Due to the limited scope, timing, 

and geographic extent of drilling activities in this Supplemental 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 platform 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 (Poot et al., 2008). The numbers 

varied greatly, from none at all to some tens of thousands of birds per night per platform, with 

an apparent effect radius of up to 3 miles (5 km). A study in the Gulf of 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 Supplemental 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 

Supplemental 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 Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts on marine and pelagic birds. 

Supplemental EP Sections 2j and 9b provide 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 

1.2 to 12 acres (0.5 to 5 ha), 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 

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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 

Potential spill impacts on marine and pelagic birds are discussed in recent EISs (MMS, 2007b, 

2008). For this Supplemental EP, there are no unique site-specific issues with respect to spill 

impacts on these animals. 

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 

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. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on marine and pelagic birds are 

expected. 

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, 2011). 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 over deep offshore waters 

(Fritts and Reynolds, 1981; Peake, 1996; Hess and Ribic, 2000). Nearly half the southeastern 

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population of Brown Pelicans lives in the northern Gulf Coast, generally nesting on protected 

islands (USFWS, 2010b). 

The Bald Eagle (Haliaeetus leucocephalus) was delisted from its threatened status in the 

continental United 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. A small fuel spill in the lease area would be unlikely to 

affect shorebirds or coastal nesting birds, as the lease area is 178 miles (286 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. 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 Amelia, 

Louisiana, where shorebirds and coastal nesting birds may be found. These activities could 

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 among 

species and individuals (Rodgers and Schwikert, 2002). The disturbances will be limited to 

flushing birds away from vessel pathways; known distances are from 65 to 160 ft (20 to 49 m) 

for personal watercraft and 75 to 190 ft (23 to 58 m) for outboard-powered boats (Rodgers and 

Schwikert, 2002). Flushing distances may be similar or less for the support vessels to be used for 

Shell’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 nesting birds, eggs, and chicks will not 

be disturbed. 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, timing, and geographic extent 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 2,000 ft (610 m) 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. 

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Impacts of Large Oil Spill 

The OSRA results summarized in Table 3 predict that shorelines of Texas and Louisiana that 

include habitat for shorebirds and coastal nesting birds could be affected within 30 days. 

Data from the recent Macondo spill provides additional information about the species of coastal 

birds that may be affected in the event that a large oil spill reached coastal habitats; 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 had been collected 

since the spill began, and about 1,900 of the dead animals were visibly oiled. In addition, more 

than 2,000 oiled birds have been collected alive and about 1,200 released (NMFS, 2010b). 

According to the International Bird Rescue Research Center (2010), bird species that were 

treated for oiling following the Macondo spill 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 

 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’s 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 under certain 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 or if oil covers the eggs. 

As noted above, the Brown Pelican was recently removed from the endangered species list. 

More than 300 dead Brown Pelicans were collected in the Gulf following the Macondo spill, 

(USFWS, 2010d). These data indicate that the Brown Pelican may be particularly at risk of oiling 

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in the event of a large spill reaching coastal waters. Threats to the Brown Pelican include direct 

contact with oil, disturbance by cleanup activities, and long-term habitat contamination. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on shorebirds and coastal nesting 

birds are expected. 

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). 

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). 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 will 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. 

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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 will 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 several meters below the ocean surface for various services 

including firewater and once-through non-contact cooling of machinery on the drilling rig 

(Supplemental EP Table 7a). 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. Construction of the rig planned for use in 

this Supplemental EP, the Noble Danny Atkins, started prior to 17 July 2006, and therefore is not 

subject to the cooling water intake permit requirements of NPDES Permit GMG 290000. If a 

different rig is selected, it will comply with all applicable NPDES requirements. The design and 

operational features of the rig combined with the geographical area of operation suggest 

impingement and entrainment impacts will be below a level of concern. 

Impacts of a Small Fuel Spill 

Potential spill impacts on fisheries resources are discussed in recent EISs (MMS, 2007b, 2008). 

For this Supplemental EP, there are no unique site-specific issues with respect to spill impacts. 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts on pelagic communities, including 

ichthyoplankton. Supplemental EP Sections 2j and 9b provide 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 

1.2 to 12 acres (0.5 to 5 ha), depending on sea state and weather conditions. 

A small fuel spill could have localized impacts on phytoplankton, zooplankton, ichthyoplankton, 

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. 

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Impacts of a Large Oil Spill 

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 in 

the upper layers of the water column are especially vulnerable to oiling; certain toxic fractions 

of spilled oil may be lethal to these life stages. Impacts would be potentially greater if local 

scale currents retained planktonic larval assemblages (and the floating oil slick) within the same 

water mass. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on pelagic communities and 

ichthyoplankton are expected. 

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 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 

600 ft (183 m). 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 Ewing Bank, located 107 miles 

(172 km) north of the lease area. 

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 (NMFS, 2009): 

 Atlantic bigeye tuna (adults) 

 Atlantic bluefin tuna (spawning, 

eggs, larvae, adults) 

 Atlantic skipjack tuna (spawning, 

adults) 

 Atlantic yellowfin tuna (all) 

 Albacore tuna (adults) 

 Atlantic swordfish (larvae, juveniles, 

adults) 

 Blue marlin (juveniles, adults) 

 White marlin (juveniles, adults) 

 Longbill spearfish (adults) 

 Oceanic whitetip shark (all) 

 Longfin mako shark (all) 

 Common thresher shark (all) 

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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 United States and Canadian coasts, followed by 

migration to the Gulf of Mexico to spawn in April, May, and June (NMFS, 2009). 

Other HAPCs have been identified in the Gulf of Mexico by the GMFMC (2005). These include 

the Florida Middle Grounds, Madison-Swanson Marine Reserve, Tortugas North and South 

Ecological Reserves, Pulley Ridge, and several individual reefs and banks of the northwestern 

Gulf of Mexico (Figure 3). The nearest of these is Jakkula Bank, located 114 miles (183 km) 

north-northwest of the lease area. 

Routine IPFs potentially affecting EFH and fisheries resources include drilling rig presence, noise, 

and lights; effluent discharges; and water intakes. In addition, two types of accidents – a small 

fuel spill and a large oil spill – may impact EFH and fisheries resources. 

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). 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, timing, and 

geographic extent 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 Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts on EFH. Supplemental EP Sections 2j 

and 9b provide 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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Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008). For this 

Supplemental 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 

1.2 to 12 acres (0.5 to 5 ha), depending on sea state and weather conditions. 

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 Atlantic bluefin tuna, which covers much of the deepwater Gulf of Mexico. The 

affected area would represent a negligible portion of the HAPC, which covers 297,312 km2

(114,793 mi2) of the Gulf of Mexico. 

A small fuel spill would not affect EFH for corals and coral reefs; the nearest coral EFH is Ewing 

Bank, located 107 miles (172 km) north 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 

Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008). For this 

Supplemental 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, corals and coral reefs, 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, ichthyoplankton, 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 and their offspring. 

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 pinnacle trend area, located 236 miles (380 km) north 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. A surface slick would not reach these features. Although there are reports of 

subsurface plumes resulting from the use of subsea dispersants during the Macondo spill, the 

distance and difference in water depth are factors that would make an impact unlikely. 

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Near-bottom currents in the region are expected to flow along the isobaths (Nowlin et al., 2001) 

and typically would not carry a plume up onto the continental shelf edge. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on EFH are expected. 

C.6 Archaeological Resources 

C.6.1 Shipwreck Sites 

WR 508 is not on the list of leases with high potential for historic shipwrecks. An Archaeological 

Assessment using data collected in 2009 detected 962 unidentified sidescan sonar targets, 

several anchor chain scars, piston cores, and previously drilled wells within the survey area. 

There were 961 sonar contacts deemed to be not archaeologically significant. The remaining 

contact was larger than the others and irregular in shape, indicating that it might be made up of 

smaller debris targets. A 1,000-ft (300-m) avoidance zone will be observed around this contact 

because it is larger than other contacts and could not be reliably identified. 

No historic shipwreck sites occur in the lease area (see Supplemental EP Section 6). A small fuel 

spill would not affect shipwrecks in adjoining blocks because the oil would float and dissipate on 

the sea surface. The impact of a large oil spill that could contact shipwrecks in other areas is 

considered below a level of concern. 

Impacts of a Large Oil Spill 

The MMS (2007b) estimated that a severe subsurface blowout could resuspend and disperse 

sediments within a 984-ft (300-m) radius. Because there are no historic shipwrecks in the lease 

area, a large oil spill would not result in any impact on archaeological resources. 

A spill entering shallow coastal waters could conceivably contaminate an undiscovered 

shipwreck site. The OSRA modeling summarized in Table 3 predicts that Texas and Louisiana 

shorelines could be contacted by a spill within 30 days. Also 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. 

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 

3,600 ft (1,100 m), 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 984-ft (300-m) radius estimated by MMS (2007a, 2008), depending 

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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. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on historic shipwrecks are expected. 

C.6.2 Prehistoric Archaeological Sites 

With water depths ranging from 9,554 to 9,578 ft (2,912 to 2,919 m), the wellsites are well 

beyond the 197-ft (60-m) 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 that 

would reach coastal waters within the 197-ft (60-m) depth contour. 

Impacts of a Large Oil Spill 

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 984-ft (300-m) 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). The OSRA modeling 

summarized in Table 3 predicts that Texas and Louisiana shorelines could be contacted by a spill 

within 30 days. A spill reaching a prehistoric site along these shorelines 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). 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an 

event will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on archaeological resources are 

expected. 

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). Sensitive coastal habitats are also tabulated in the OSRP. 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. 

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Due to the distance from shore, there are no IPFs associated with routine activities that are 

likely to affect beaches and dunes, wetlands, seagrass beds, coastal wildlife refuges, wilderness 

areas, or any other managed or protected coastal area. The support bases at Port Fourchon and 

Amelia are not located in a wildlife refuge or a wilderness area. Potential impacts of support 

vessel traffic are briefly addressed below. 

A small fuel spill in the lease area would be unlikely to affect coastal habitats because the lease 

area is 178 miles (286 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. 

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 Supplemental EP Section 14, 

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 

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 Supplemental EP, there are no unique site-specific issues 

with respect to coastal habitats. 

The OSRA results summarized in Table 3 predict that shorelines of Texas and Louisiana could be 

affected within 30 days. Plaquemines and Cameron Parish, Louisiana and Galveston County, 

Texas, have the highest probability of contact for the 30-day intervals (2%). After 30 days, 

8 counties or parishes may be contacted from Matagorda, Texas, to Plaquemines, Louisiana. 

The shorelines within the geographic range predicted by the OSRA modeling 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 the lease sale EIS (MMS, 2007b) and Shell’s OSRP. Coastal wildlife refuges, 

wilderness areas, and state and national parks within the geographic range of the potential 

shoreline contacts after 30 days include the following: 

 Aransas NWR 

 San Bernard NWR 

 Galveston Island State Park 

 Brazoria NWR 

 Mad Island NWR 

 Big Boggy NWR 

 Apffel Park 

 Peach Point WMA 

 Sea Rim SP 

 Seawolf Park 

 Old Fort Travis Park 

 Atkinson Island WMA 

 Ft. Anahuac Park 

 Anahuac NWR 

 McFaddin NWR 

 J.D. Murphree WMA 

 Texas Point NWR 

 Sabine NWR 

 Cameron Prairie NWR 

 LaCassine NWR 

 Little Pecan Island Preserve 

 Peveto Woods Sanctuary 

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 Lower Neches WMA 

 Rockefeller State Wildlife Refuge and 

Game Preserve 

 Paul J. Rainey WMA 

 Candy Abshier WMA 

 Atchafalaya Delta WMA 

 Mandalay NWR 

 Isles Dernieres Barrier Islands Refuge 

 Pointe Au Chien WMA 

 Wisner WMA 

 Grand Isle State Park 

 Christmas Bay SP 

 Christmas Bay Coastal Preserve 

 Salvador WMA 

 Jean Lafitte National Historical Park 

and Preserve 

 Delta NWR 

 Pass a Loutre WMA 

 Breton NWR 

 St. Bernard State Park 

 Biloxi WMA 

 Bayou Sauvage NWR 

 Gulf Islands National Seashore 

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The OSRA results in Table 3 include only shoreline segments with contact probabilities greater than 

0.5% within 30 days; other coastal areas could be affected at lower contact probabilities within 

30 days, or from a spill persisting for more than 30 days. Additional NWRs and managed wildlife 

areas occur along the Gulf Coast. These areas include habitats such as barrier beach and dune 

systems, wetlands, and submerged seagrass beds that support diverse wildlife, including endangered 

or threatened species. 

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 6.7 acres (2.7 ha) of wetland vegetation will experience 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 openwater 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). 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event 

will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on coastal habitats are expected. 

C.8 Socioeconomic and Other Resources 

C.8.1 Recreational and Commercial Fishing 

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 Federal Register 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 are 10 to 30 m long, and their trips last from about 1 to 3 weeks. 

The main homeports for longlining vessels are in Louisiana (Dulac and Venice) and Florida (Destin, 

Madeira Beach, and Panama City). 

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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 820 to 

1,804 ft (250 to 550 m). Tilefish are caught by bottom longlining in water depths from about 540 to 

1,476 ft (165 to 450 m) (Continental Shelf Associates, Inc., 2002). The proposed project is in 9,414 ft 

(2,900 m) of water. No conflict with commercial fishing activity is expected to occur. 

Most recreational fishing activity in the region occurs in water depths less than 656 ft (200 m) 

(Continental Shelf Associates, Inc., 1997, 2002). In deeper water, the main attraction to recreational 

fishers would be petroleum platforms offshore Texas and Louisiana. 

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. 

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. 

No adverse impacts on fishing activities 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 Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b provide 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 1.2 to 12 acres (0.5 to 5 ha), 

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 

Potential spill impacts on fishing activities are discussed in recent EISs (MMS, 2007b, 2008). For this 

Supplemental 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 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. Exclusive Economic Zone (EEZ) in the Gulf of Mexico. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event 

will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on fishing activities are expected. 

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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 are addressed below. 

Impacts of a Small Fuel Spill 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b provide 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 178 miles (286 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 

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 proposed activities 

will be covered by the OSRP, and, in addition, 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, the 

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, through skin 

contact or inhalation of VOCs. Crude oil is a highly flammable material, and any smoke or vapors 

from a crude oil fire can cause irritation. Exposure to large quantities of crude oil 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 7 to 12 times higher 

incidence 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 is 

exposure to seasonal temperature extremes resulting in heat stress in the summer and hypothermia 

in the winter. 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). Health effects reported 

from previous oil spills, such as the Exxon Valdez in 1989, were primarily acute injuries consisting of 

headaches, throat irritation, and sore or itchy eyes, but respiratory problems and dermatitis along 

with chronic airway disease have also been reported (Solomon and Janssen, 2010). 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event 

will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on public health and safety are expected. 

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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 are addressed below. 

Impacts of a Small Fuel Spill 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b provide 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 

Potential socioeconomic impacts of an oil spill are discussed in recent EISs (MMS, 2007b, 2008). For 

this Supplemental 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. 

The lease area is 178 miles (286 km) from the nearest shoreline. Based on OSRA modeling as 

summarized in Table 3, Texas and Louisiana coastal areas are the most likely to be contacted by a 

spill. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event 

will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on employment and infrastructure are 

expected. 

C.8.4 Recreation and Tourism 

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 Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b provide 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 

Potential impacts of an oil spill on recreation and tourism are discussed in recent EISs (MMS, 2007b, 

2008). For this Supplemental 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. Based on OSRA modeling as 

summarized in Table 3, areas most likely to be contacted by a spill are Plaquemines and Cameron 

Parish, Louisiana, and Galveston County, Texas. The shorelines along Galveston, Texas, include 

popular beaches and recreational sites along the coast. 

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). There are ongoing efforts to accelerate recovery by informing public perceptions; 

creating travel incentives; and providing access to capital, low interest loans, and tax incentives for 

affected businesses (U.S. Travel Association, 2010). 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event 

will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on recreation and tourism are expected. 

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 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 

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. 

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event 

will be minimized by Shell’s well control and blowout prevention measures as detailed in 

Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

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mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on land use are expected. 

C.8.6 Other Marine Uses 

The lease area is not located within any USCG-designated fairway or shipping lane. WR 508 is not in a 

designated Military Warning Area. Shell will comply with BOEMRE requirements and lease 

stipulations to avoid impacts on uses of the area by military vessels and aircraft. 

There are no IPFs from routine project activities that are likely to affect shipping or other marine 

uses. A large oil spill is the only relevant accident IPF. A small fuel spill would not have any impacts 

on other marine uses, as the spill and response activities would be mainly within the lease area and 

the duration would be brief. 

Impacts of a Large Oil Spill 

An accidental spill would be unlikely to significantly affect shipping or other marine uses. The block is 

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. Shell 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. A blowout resulting in a large oil spill is an extremely rare event, and the probability of 

such an event will be minimized by Shell’s well control and blowout prevention measures as detailed 

in Supplemental EP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will 

mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill 

response measures. Therefore, no significant spill impacts on other marine uses are expected. 

C.9 Cumulative Impacts 

For purposes of NEPA, cumulative impact is defined as “the impact on the environment which results 

from the incremental impact of the action when added to other past, present, and reasonably 

foreseeable future actions regardless of what agency (Federal or non-Federal) or person undertakes 

such other actions” (40 CFR 1508.7). Any single activity or action may have a negligible impact(s) by 

itself, but when combined with impacts from other activities in the same area and/or time period, 

substantial impacts may result. 

Prior Studies. WR 507 and 508 were acquired in Lease Sale No. 157 on 24 April 1996. Prior to the 

lease sale, MMS prepared a multi-sale EIS in which it analyzed the environmental impact of activities 

that might occur in the multi-lease-sale area. The MMS also recently analyzed the cumulative 

impacts of OCS development activities similar to those planned in this Supplemental EP in several 

documents. The level and types of activities planned in Shell's Supplemental EP are within the range 

of activities described and evaluated in the Final EIS for Gulf of Mexico OCS Oil and Gas Lease Sales 

2007-2012: Western Planning Area Sales 204, 207, 210, 215, and 218, and Central Planning Area Sales 

205, 206, 208, 213, 216, and 222 (MMS, 2007b), as updated by a 2008 Final Supplemental EIS for Gulf 

of Mexico OCS Oil and Gas Lease Sales 2009-2012: Central Planning Area Sales 208, 213, 216, and 222 

and Western Planning Area Sales 210, 215, and 218 (MMS, 2008). Past, present, and reasonably 

foreseeable activities were identified in the cumulative effects scenario. These documents are 

incorporated by reference. 

Description of Activities Reasonably Expected to Occur in the Vicinity of Project Area. Other 

exploration and development activities (e.g., the Chinook Field in WR 469 and 452) are occurring in 

the vicinity of lease block WR 507 and 508. 

Cumulative Impacts of Activities in the Supplemental EP. The MMS (2007b) multi-lease-sale EIS 

included a lengthy discussion of cumulative impacts, which analyzed the environmental and 

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socioeconomic impacts from the incremental impact of the 11 proposed lease sales, in addition to all 

activities (including non-OCS activities) projected to occur from past, proposed, and future lease sales 

during the 40-year period of 2007 to 2046 (see MMS, 2007b, page 4-301). The EIS considered 

exploration, delineation, and development wells; platform installation; service-vessel trips; and oil 

spills. The EIS examined the potential cumulative effects on each specific resource for the entire Gulf 

of Mexico. 

The level and type of activity proposed in Shell’s Supplemental EP are within the range of activities 

described and evaluated in the recent multi-lease-sale EISs. This EIA incorporates and builds on these 

analyses by examining the potential impacts on physical, biological, and socioeconomic resources

from the work planned in this Supplemental EP, in conjunction with the other reasonably foreseeable 

activities expected to occur in the Gulf of Mexico, as well as the known impacts from the Macondo 

spill in Mississippi Canyon 252. While another large oil spill could have significant impacts, the 

numerous new safety measures implemented by the BOEMRE and further mitigation and safety 

measures proposed by Shell in its Supplemental EP result in a drilling program that reduces the 

likelihood of another large spill and improves the effectiveness of any response in the extremely 

unlikely event that another large spill occurs. Thus, for all impacts, the incremental contribution of 

Shell’s proposed actions to the cumulative impacts analysis in these prior analyses is not significant.

C.9.1 Cumulative Impacts to Physical/Chemical Resources 

The work planned in this Supplemental EP is limited in geographic scope and duration, and the 

impacts on the physical/chemical environment will be correspondingly limited. 

Air Quality. Emissions from pollutants into the atmosphere from 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 multi-leasesale EISs, the incremental contribution of activities similar to Shell’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 (MMS, 2007b, 2008). In addition, the cumulative contribution to 

visibility impairment is also very small (MMS, 2007b, 2008). Since the BOEMRE completed the multilease-sale EISs, the USEPA has adopted a new short-term NAAQS for NO2 and SO2. The standard has 

not yet been implemented in the Gulf of Mexico, but given the levels of expected emissions and the 

distance of the project from shore, emissions from Shell's Supplemental EP are not likely to 

contribute to violations of any NAAQS onshore. 

Climate Change. Carbon dioxide (CO2) and CH4 emissions from the project would constitute a small 

incremental contribution to greenhouse gas emissions from all OCS activities. According to the 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). In the Gulf of Mexico, sea level rise is an important issue due to the ongoing 

losses in coastal wetlands, particularly in coastal Louisiana. Greenhouse gas emissions from the 

Supplemental EP 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 previous EISs. Globally, Shell is working to reduce 

greenhouse gas emissions by increasing the efficiency of its operations, establishing a substantial 

capability in CO2 capture and storage, and continuing to research and develop technologies that 

increase efficiency and reduce emissions in hydrocarbon production. In 2010, Shell met a voluntary 

target set in 1998 for direct greenhouse gas emissions from its facilities to be at least 5% lower than 

the comparable 1990 level (Shell, 2011). Shell’s ongoing efforts to reduce greenhouse gas emissions 

globally should offset any incremental contribution from the Supplemental EP. 

Water Quality. Shell’s project will have some minor water quality impacts due to the 

NPDES-permitted discharge of drilling mud and cuttings, treated sanitary and domestic wastes, 

excess cement, non-contact cooling water, deck drainage, desalination unit brine, uncontaminated 

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fire water, and ballast water. These effects are expected to be minor (localized to the area within a 

few hundred meters of the drilling rig), and temporary (lasting only hours longer than the disturbance 

or discharge). Any cumulative effects to water quality are expected to be negligible. 

New Information. The only new, potentially significant information available since preparation of the 

multi-lease-sale EISs arises from the Macondo spill. The Macondo spill caused short-term, localized 

air quality impacts (e.g., from evaporation of volatile hydrocarbons and in situ burning of floating oil). 

Monitoring by the USEPA (2010) has found levels of ozone and particulates ranging from “good” to 

“unhealthy for sensitive groups” on USEPA’s Air Quality Index; these are at levels well below those 

that would cause short-term health problems. The air monitoring conducted to date has not found 

any pollutants at levels expected to cause long-term harm (USEPA, 2010). Satellite imagery indicates 

that the surface slick from the Macondo spill did not reach the lease area (ESRI, 2010). However, 

based on the information currently available, there is no reason to expect any change in air quality 

conditions or cumulative impacts from those predicted in the multi-lease-sale EISs. 

The Macondo spill also resulted in water quality impacts. 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). Satellite 

imagery indicates that the surface slick from the Macondo spill did not reach the lease area (ESRI, 

2010), and it is unlikely that subsurface plumes could have affected water quality in or near the lease 

area. OSAT (2010) reported that, after August 2010, waters and sediments in the deepwater Gulf of 

Mexico beyond 1.8 miles (3 km) from the Macondo wellsite were below USEPA acute and chronic 

benchmarks for PAHs and were not hypoxic. These observations indicate that baseline 

environmental conditions in the lease area are unlikely to have been significantly altered by the spill. 

Prior to the incident, water quality in deep, offshore waters 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 or cumulative impacts from those predicted in the 

multi-lease-sale EISs. 

C.9.2 Cumulative Impacts to Biological Resources 

The work planned in this Supplemental EP is limited in geographic scope and duration, and the 

impacts on biological resources will be correspondingly limited. 

Seafloor Habitats and Biota. Effects on seafloor habitats and biota from discharges of drilling mud 

and cuttings are expected to be minor and limited to a small area. There are no areas that may 

support high-density deepwater benthic communities within 2,000 ft (610 m) of the wellsites, in 

compliance with NTL 2009-G40. Areas that may support high-density deepwater benthic 

communities will be avoided as required by NTL 2009-G40. Soft bottom communities are ubiquitous 

along the northern Gulf of Mexico continental slope, and the extent of benthic impacts during this 

project is insignificant regionally. As noted in the multi-lease-sale EISs, the incremental contributions 

of activities similar to Shell’s proposed activities to the cumulative impacts is not significant 

(MMS, 2007b). 

Threatened, Endangered, and Protected Species. Threatened and endangered species reasonably 

likely to occur in the lease area include the sperm whale and five species of sea turtles. Potential 

impact sources include drilling rig presence including noise and lights; marine debris; and support 

vessel and aircraft traffic. Potential effects for these species would be limited and temporary, and 

would be reduced by Shell’s compliance with all BOEMRE-required mitigation measures including 

NTLs 2007-G03 and 2007-G04. No significant cumulative impacts are expected. 

Coastal and Marine Birds. Some birds may be attracted to offshore structures because of the lights 

and the fish populations that aggregate around these structures. Birds that frequent platforms may 

be exposed to contaminants including air pollutants and routine discharges, but significant impacts 

are unlikely due to rapid dispersion. Shell’s compliance with NTL 2007-G03 will minimize the 

likelihood of debris-related impacts on birds. Support vessel and helicopter traffic may disturb some 

foraging and resting birds; however, it is likely that individual birds would experience, at most, only 

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short-term behavioral disruption. Due to the limited scope, timing, and geographic extent of drilling 

activities, collisions or other adverse effects are unlikely, and no significant cumulative impacts are 

expected. 

Fisheries Resources. Drilling rigs function as FADs for some species of epipelagic fishes; and the 

aggregations of prey fishes may potentially attract predators. These short-term effects are expected 

to be small given the isolated nature of the drilling rig and would not be considered a significant 

impact on pelagic communities, fishery resources, or EFH. Exploration and production structures 

occur in the WR lease block proposed for the exploration activities. The additional effect of the 

proposed drilling activity would be negligible. 

Coastal Habitats. Due to the distance of the wellsites from shore, routine activities are not expected 

to have any impacts on beaches and dunes, wetlands, seagrass beds, coastal wildlife refuges, 

wilderness areas, or any other managed or protected coastal area. The support bases at 

Port Fourchon and Amelia, Louisiana, are not in wildlife refuge or wilderness areas. 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. Impacts will be minimized by following the speed and wake restrictions 

in harbors and channels. 

New Information. The only new, potentially significant information available since preparation of the 

multi-lease-sale EISs arises from the Macondo spill. The spill has resulted in impacts on biological 

resources, including visibly oiled and/or dead birds, marine mammals, and sea turtles, as well as 

oiling of coastal habitats from approximately the Texas/Louisiana border to the Florida Panhandle. 

Another large spill could result in significant cumulative impacts to these resources. However, for all 

the reasons discussed in the Initial EP, Shell’s NTL 2010-N06 response, the OSRP, and herein, the 

likelihood of a catastrophic well control event resulting in significant amounts of oil in the water is 

extremely remote. Therefore, Shell’s proposed activities are not expected to result in any cumulative 

impacts to biological resources affected by the Macondo spill, nor should they have any impact on 

the previously conducted cumulative impact analyses. 

Regarding deepwater benthic communities, the multi-lease-sale EISs (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 3,600 ft (1,100 m), extending at least 22 miles (35 km) from the 

wellsites 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). This 

observation is supported by Kujawinski et al. (2011) in their report that chemical components of 

subsea dispersants used during the Macondo spill persisted for up to two months and were detected 

up to 186 miles (300 km) from the wellsite at a water depth of 3,280 to 3,937 ft (1,000 to 1,200 m). 

However, estimated dispersant concentrations in the subsea plume were below levels known to be 

toxic to marine life. 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 984-ft (300-

m) 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 (NRC, 2003). 

C.9.3 Cumulative Impacts to Socioeconomic Resources 

The work planned in this Supplemental EP is limited in geographic scope and duration, and the 

impacts on socioeconomic resources will be correspondingly limited. 

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Archaeological Resources. WR 508 is not on the list of leases with a high potential for historic 

shipwrecks. An archaeological assessment by FGSI (2011) indicated that one of the sonar contacts in 

the lease area could not be reliable identified and will be avoided by 1,000 ft (300 m). Also, the lease 

area is well beyond the 197-ft (60-m) depth contour used by the BOEMRE as the seaward extent for 

prehistoric archaeological site potential in the Gulf of Mexico. Therefore, Shell’s operations will have 

no cumulative impacts on historic shipwrecks or prehistoric archaeological resources. 

Socioeconomic Resources. The multi-lease-sale EISs analyzed the cumulative impacts of oil and gas 

exploration and development in the lease area, in combination with other impact-producing 

activities, on commercial fishing, recreational fishing, recreational resources, historical and 

archaeological resources, land use and coastal infrastructure, demographics, and environmental 

justice (MMS, 2007b, pages 4-359 to 4-378). The BOEMRE also analyzed the economic impact of oil 

and gas activities on the Gulf States, finding only minor impacts in most of Texas, Mississippi, 

Alabama, and Florida, more significant impact in parts of Texas, and substantial impact on Louisiana. 

Shell’s proposed activities will have negligible cumulative impacts on socioeconomic resources. 

There are no IPFs associated with routine operations that are expected to affect public health and 

safety, employment and infrastructure, recreation and tourism, land use, or other marine uses. Due 

to the distance from shore, it is unlikely that any recreational fishing activity is occurring in the 

project area, and it is unlikely that any commercial fishing activity other than longlining occurs at or 

near the project area. The project will have negligible impacts on fishing activities. 

New Information. The only new, potentially significant information available since preparation of the 

multi-lease-sale EISs arises from the Macondo spill. The spill has resulted in impacts on commercial 

and recreational fishing, recreation and tourism, employment, and public health and safety. The 

Macondo spill resulted in extensive fishery closures in the Gulf of Mexico, peaking at 34.8% of the 

EEZ in the Gulf of Mexico (NMFS, 2010d). 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). Reported health impacts (e.g., among spill response and wildlife 

rehabilitation workers) ranged from cuts and scrapes, to upper respiratory symptoms and heat stress, 

to acute exposure to hydrocarbons or H2S (Centers for Disease Control and Prevention, 2010a,b; 

Solomon and Janssen, 2010). Most of these impacts were temporary in nature, although health 

exposure of clean-up workers could have longer-lasting impacts. 

However, for all the reasons discussed in the Supplemental EP, Shell’s NTL 2010-N06 response, the 

OSRP, and herein, the likelihood of a catastrophic well control event resulting in significant amounts 

of oil in the water is extremely remote. Therefore, Shell’s proposed activities are not expected to 

result in any cumulative impacts to socioeconomic resources affected by the Macondo spill, nor 

should they have any impact on the previously conducted cumulative impact analyses. 

D. Environmental Hazards 

D.1 Geologic Hazards 

The shallow hazards assessment included in this Supplemental EP, based on the shallow hazards 

report by GEMS (2006) and FGCI (2010), concludes that the wellsites are free of any major geological 

hazards and are suitable for the proposed activities. There are no fluid expulsion features or faults 

within 2,000 ft (600 m) of the well proposed locations based on results of a high-resolution 

geophysical survey consisting of frequency-enhanced 3-D seismic, enhanced surface renderings, AUV 

surveys, and side scan sonar. There were piston cores, drilling splays, anchor chain scars, and 

previously drilled wells in the vicinity of the proposed locations but none were within 2,000 ft (600m) 

(FGSI, 2011). 

See Supplemental EP Section 6a for supporting geological and geophysical information. 

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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 rig. High winds and limited visibility during a severe storm could disrupt 

communication and 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 in Shell’s Hurricane Evacuation Plan would be followed. 

D.3 Currents and Waves 

A rig-based acoustic Doppler current profiler will be used to continuously monitor the current 

beneath the rig. Metocean conditions such as sea states, wind speed, ocean currents, etc. will also 

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 rig. High 

waves during a severe storm could disrupt support activities (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. However, various technical and operational 

options, including the location of the wellsites and the selection of a drilling unit, were considered by 

Shell in developing the proposed action. There are no other reasonable alternatives to accomplish 

the goals of this project. 

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 Shell’s OSRP and will include the measures described in 

Supplemental EP Section 2j. Additional pollution prevention measures, beyond those required by 30 

CFR Part 250, include the following: 

Health, safety, and environment (HSE) are the primary topics in pre-tour and pre-job safety meetings. 

The discussion around no harm to people or environment is a key mindset. All personnel are 

reminded daily to inspect work areas for safety issues as well as potential pollution issues. 

All tools that come to and from the rig have their pollution pans inspected and cleaned, and plug 

installation confirmed prior to leaving the dock and prior to loading on the boat. 

Preventive maintenance of rig equipment includes visual inspection of hydraulic lines and reservoirs 

on a routine scheduled basis. 

All pollution pans on rig are inspected daily. 

Containment dikes are installed around all oil containment, drum storage areas, fuel vents, and fuel 

storage tanks. 

All used oil and fuel is collected and sent to shore for recycling. 

Drains on the rig are checked regularly to verify drain plugs are installed. 

All trash containers are checked and emptied daily, and trash containers are kept covered. Trash is 

collected in a compactor and shipped to shore for disposal. 

The rig is involved in a recycling program for cardboard, plastic, paper, glass, and aluminum. 

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Fuel hoses are changed on annual basis. 

Spill prevention fittings are installed on all liquid take-on hoses. 

Waste paint thinner is recycled on board with a solvent to further reduce hazards of shipping and 

storage. 

All equipment on board utilizes Envirorite hydraulic fluid as opposed to hydraulic oil. 

Shell has obtained International Organization for Standardization (ISO) 14001 certification. 

Shell will use low-sulfur fuel to reduce air pollutant impacts. 

G. Consultation 

No persons or agencies were consulted regarding potential impacts associated with the proposed 

activities during the preparation of this EIA. 

H. Preparers 

The EIA was prepared at the direction of Shell Offshore Inc. by its contractor, CSA International, Inc. 

Contributors included the following: 

Sylvia Bellone (Regulatory Specialist, Shell Exploration & Production Co.); 

Tracy Albert (Regulatory Specialist, Offshore Technical Compliance LLC); 

Lori Downs (Environmental Team Leader, Shell Exploration & Production Co.); 

Jeffrey McMenis, (Environmental Engineer, Shell Exploration & Production Co.); 

Rob Kuehn (Environmental Engineer, Shell Exploration & Production Co.); 

Martijn Dekker (Development Lead, Stones Development, Shell Exploration & Production Co.); 

Marc Varner (Subsurface Team Lead, Stones Development, Shell Exploration & Production Co.); 

Dana McDiffett (Reservoir Engineer, Stones Development, Shell Exploration & Production Co.); 

Kevin Bradford (Geophysicist, Geo Hazards & Pore Pressure Prediction, Shell Exploration 

& Production Co.); 

James Jorgensen (Well Engineer, North America Projects, Shell Exploration & Production Co.); 

June Mire, Ph.D. (Senior Ecologist and Project Manager, Tetra Tech EM, Inc.); 

Cindy Chandool, Ph.D. (Senior Scientist, CSA International, Inc.); 

Carlyle Kalloo (Senior Scientist, CSA International, Inc.); 

Neal Phillips, Ph.D. (Senior Scientist, CSA International, Inc.); 

Deborah Fawcett (Project Scientist II, CSA International, Inc.); 

Stephen Viada (Senior Scientist, CSA International, Inc.); 

Keith VanGraafeiland (GIS/Remote Sensing Specialist, CSA International, Inc.); and 

Kim Dunleavy (Technical Editor, CSA International, Inc.). 

I. References 

Barkuloo, J.M. 1988. Report on the conservation status of the Gulf of Mexico sturgeon, Acipenser oxyrinchus desotoi. 

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SECTION 19: ADMINISTRATIVE INFORMATION

A. Exempted Information Description (Public Information Copies Only) 

The following attachments were excluded from the public information copies of this plan: 

Section 1b. OCS Plan Information form – Bottom hole locations & proposed total depth 

Section 2j. Blowout Scenario – confidential information for NTL 2010-N06 calculation 

Section 3a. Geologic Description 

Section 3b. Structure Contour Maps 

Section 3c. Interpreted 2D or 3D seismic line(s) 

Section 3d. Cross Section(s) 

Section 3e. Shallow Hazards Report 

Section 3f. Shallow Hazards Assessment – confidential data 

Section 3g. High-Resolution Seismic Lines & Top Hole Progs 

Sections 3h. & 3i. Stratigraphic Column with Time vs. depth table 

 

B. Bibliography 

Geoscience Earth & Marine Services, Inc. (GEMS) prepared a Geologic and Stratigraphic Assessment Report 

(Number 0306-1151), May 2006 

Fugro GeoConsulting, Inc. (FGCI) prepared an Integrated Geophysical and Geotechnical Field Development 

Planning Study based on the AUV data (Job No. 27.2009-2328), May 2010. 

FGSI prepared an AUV Archaeological Assessment Report (Number 2411-1019) covering Walker Ridge blocks 

420, 464, 508, and 552, July 2011. 

CSA International, Inc. Environmental Impact Analysis, July 2011

Shell’s Regional OSRP, August 2011

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