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-07523

Type - Supplemental Exploration Plan

Lease(s) - OCS-G26254 Block - 393 Mississippi Canyon Area

Operator - Shell Offshore Inc.

Wells A, Q, Q(ST), R, S and T

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:

December 15, 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

Public Information Copy

November 2, 2011 

Ms. Liz Peuler, Section Chief 

Bureau of Ocean Energy Management 

1201 Elmwood Park Boulevard 

New Orleans, LA 70123-2394 

 

Attn: Plans Group MS 5231 

SUBJECT: Supplemental Exploration Plan 

 OCS-G 26254, Mississippi Canyon Block 393 

 Offshore Alabama and 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. (Shell) requests your approval of this Supplemental Exploration Plan to drill Well Locations A, Q, 

QST, R, S & T. Depending on rig availability operations could commence as early as May 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 $17,210.00 is attached to the Proprietary 

copy of the Plan. 

Should you require additional information, please contact Tracy Albert at 504.728.4652 or tracy.albert@shell.com. 

Sincerely, 

Sylvia A. Bellone 

Page 1 Public Information Copy
SHELL OFFSHORE INC. 

SUPPLEMENTAL EXPLORATION PLAN 

for 

OCS-G 26254, Mississippi Canyon Block 393 

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 

11/14/2011 Section 2J (Proprietary) Provided addtl. structure map (Proprietary) 11/17/2011 

 

 

 

Page 3 Public Information Copy
SUPPLEMENTAL EXPLORATION PLAN 

OCS-G 26254, MISSISSIPPI CANYON BLOCK 393 

OFFSHORE, ALABAMA AND 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
Acronyms and Abbreviations 

ABS American Bureau of Shipping 

ACP Area Contingency Plan 

ADDS Aerial Dispersant Delivery System 

ADIOS Automated Data Inquiry for Oil Spills 

APD Application for Permit to Drill 

AUV autonomous underwater vehicle 

bbl barrels 

BOEM Bureau of Ocean Energy Management 

BOP blowout preventers 

BPD barrels per day (bbl/day) 

BSEE Bureau of Safety and Environmental 

Enforcement 

CCA Clean Caribbean & Americas 

CFR Code of Federal Regulations 

CGA Clean Gulf Associates 

CH4 methane 

CO carbon monoxide 

CO2 carbon dioxide 

COTP USCG Captain of the Port 

CP Coastal Preserve 

DOCD Development Operations Coordination 

Document 

DP dynamically positioned 

EA Environmental Assessment 

EDRC effective daily recovery capacity 

EEZ Exclusive Economic Zone 

EFH Essential Fish Habitat 

EIA Environmental Impact Analysis 

EIS Environmental Impact Statement 

EP Exploration Plan 

EPA Environmental Protection Agency 

ESA Endangered Species Act 

ESR Enhanced Surface Rendering 

ESI Environmental Sensitivity Index 

FAD fish-attracting device 

GB Garden Banks 

GOM Gulf of Mexico 

GMFMC Gulf of Mexico Fishery Management 

Council 

H2S hydrogen sulfide 

HAPC Habitat Area of Particular Concern 

HSE health, safety, and environment 

IMO International Maritime Organization 

IPF impact-producing factor 

IRCS Incidence Response Command System 

ISB In-situ burning 

ISO International Organization for 

Standardization 

MARPOL International Convention for the 

Prevention of Pollution from Ships 

MC Mississippi Canyon 

MGD million gallons per day 

MMBO million barrels of oil 

MMC Marine Mammal Commission 

MMPA Marine Mammal Protection Act 

MMS Minerals Management Service 

MSRC Marine Spill Response Company 

MWCC Marine Well Containment Company 

NAAQS National Ambient Air Quality Standards 

NCP National Contingency Plan 

NEPA National Environmental Policy Act 

NMFS National Marine Fisheries Service 

NOAA National Oceanic and Atmospheric 

Administration 

NOx nitrogen oxides 

NPDES National Pollutant Discharge Elimination 

System 

NPS National Park Service 

NRC National Research Council 

NTL Notice to Lessees 

NWR National Wildlife Refuge 

OCS Outer Continental Shelf 

OCSLA Outer Continental Shelf Lands Act 

OSAT Operational Science Advisory Team 

OSRA Oil Spill Risk Analysis 

OSRAM Oil Spill Risk Analysis Model 

OSRL Oil Spill Response Limited 

OSRB Oil Spill Response Barge 

OSRO Oil Spill Removal Organization 

OSRP Oil Spill Response Plan 

OSRV Oil Spill Response Vessel 

PAH polycyclic aromatic hydrocarbon 

PM particulate matter 

PSD Prevention of Significant Deterioration 

R&D Research and development 

ROV remotely operated vehicle 

RRT Regional Response Team 

SEAE Environmental Site Assessment 

Shell Shell Offshore Inc. 

SBM synthetic-based mud 

SEP Supplemental Exploration Plan 

SOx sulfur oxides 

SP State Park 

SWSS Sperm Whale Seismic Study 

U.S.C Unites States Code 

USCG U.S. Coast Guard 

USDOI U.S. Department of the Interior 

USEPA U.S. Environmental Protection Agency 

VOC volatile organic compound 

USFWS U.S. Fish and Wildlife Service 

WCD worst case discharge 

WCEP Whooping Crane Eastern Partnership 

WMA Wildlife Management Area 

Page 5 Public Information Copy
SECTION 1: PLAN CONTENTS

A. DESCRIPTION, OBJECTIVES & SCHEDULE

Shell Offshore Inc. (Shell) is submitting a supplemental Exploration Plan (EP) for MC Block 393, OCS-G 

26254. Shell submitted an Initial EP for this lease for subsea wells A through I in 2005. This Plan received 

an environmental site assessment (SEAE) from the BOEM due to its proximity to the Eastern Gulf of Mexico 

(Plan N-8379 approved July 18, 2005). Shell submitted a supplemental Plan for subsea wells J through P, 

which also received SEAE (Plan S-7357 approved April 7, 2010). Shell is now submitting a Supplemental EP 

that includes six exploration wells: A (previously cleared in Plan N-8379) Q, QST, R, S & T. The wells will be 

drilled and temporarily abandoned with 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 BSEE regulations. 

The drilling activities are planned to commence on or about May 1, 2012 and last approximately 100 days per 

well, except for the Q and QST, which are estimated to take approximately 107 and 62 days, respectively. 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 are not intended to be a 

limitation. 

The lease area is 75 miles from the nearest shoreline, 162 miles from the onshore support base at Port 

Fourchon, Louisiana, and 100 miles from the helicopter base at Boothville, Louisiana. Water depths at the 

wellsites range from 7,300’ to 7,390’ (Attachment 1A). 

The proposed rig is a moored 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 MC 393 

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 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 plat (Attachment 1A) and BOEM forms (Attachments 1B through 1H). 

C. RIG SAFETY AND POLLUTION FEATURES: 

The rig planned for use, Transocean Nautilus or similar, will comply with all of the regulations of the ABS, IMO 

and 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 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:

Page 6 Public Information Copy
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 do not contain hydrocarbons and can be discharged 

directly overboard. The salt water from the discharge of the fresh water makers and engine coolers is routed 

to the cuttings chute to provide a flush to keep the chute clear. All other non-contaminated drains are, 

where feasible, routed to the starboard caisson. 

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 have to be collected in portable tanks and sent to 

shore for processing. Two headers are routed for the contaminated drains, one for oily water, which is 

routed to the separator tanks, and one for waste oil, which is routed to the waste oil tanks. In the areas 

where a spillage of oily water or hydrocarbon is possible, two foot valves are supplied, one for each header. 

The operator will make the decision on where to route the spillage. Separation and waste oil tanks are 

supplied in each of the aft columns. The headers in each of the decks are sealed from one another by using 

seal pots to prevent gas migration throughout the rig. 

3) Mud Drain System 

A separate drain system is furnished for the mud handling areas. Sumps are provided in the following areas 

to collect mud spills: 

 Mud Pump Rooms 

 Auxiliary Machinery Room 

 Sack Storage Room 

 Shale Shaker Room 

The drains are pumped by two pneumatic mud drain pumps, which can route the drains either to overboard 

in the case of water-based muds, or to the main deck for collection into drums in the case of oil-based muds. 

4) Oily Water Processing 

The oily water is initially routed to the Separator Tanks. One tank is located in the 28.5 m flat in each of the aft 

columns. The tank has sufficient residence time to allow for natural separation of oil and water. The oil is 

manually drained to the Waste Oil Holding Tank located in the 28.5 m flat in each of the aft columns from where 

it is pumped to the International Shore Connection for collection into drums. The residual water in the separator 

is routed to the Oily Water Separator for further processing. 

The Oily Water Separator is a compact, single stage, gravity-type vessel using a coalescer plate pack principle 

of separation. The oily water is drawn into the separator where the majority of the oil separates in the 

gravity stage below the oil chamber into which it rises and collects. The water pump draws the liquid 

through a multi-stage plate pack, which encourages the remaining oil droplets to coalesce and rise through 

the pack to the oil chamber. Clean water is drawn from the rear end of the unit by the water pump to an 

overboard discharge connection. Capacitance probes are fitted to detect the oil level in the oil chamber, 

Page 7 Public Information Copy
controlling the pump to give fully automatic operation. A 15-ppm oil content meter is installed on the water 

outlet to prevent oil discharges to the sea if any of the separation or monitoring systems should fail. 

When oil/air covers the lower probe, the water pump stops, the oily water inlet valve closes, and the water 

inlet and oil/air discharge valves open to discharge the oil to the Waste Oil Holding Tank. When the top 

probe again senses water, the inlet oily water valve opens, the oil/air and water inlet valves close, and the 

pump again starts. 

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

D. Storage Tanks - Transocean Nautilus (or similar) 

Type of Storage Tank Type of

Facility

Tank

Capacity 

(bbls)

Number 

of

Tanks

Total

Capacity 

(bbls)

Fluid

Gravity (API)

Diesel Tank in Pontoon Drilling Rig 2202 4 8808 Marine Diesel (0.87 

SG)

Diesel Tank in Pontoon Drilling Rig 4554 4 18,216 Marine Diesel (0.87 

SG)

Diesel Day Tank 3rd Deck Drilling Rig 196 2 392 Marine Diesel (0.87 

SG)

Diesel Settling Tank 3rd

Deck

Drilling Rig 225 1 225 Marine Diesel (0.87 

SG)

Diesel Settling Tank 3rd

Deck

Drilling Rig 271 1 271 Marine Diesel (0.87 

SG)

Lube Oil Tank 3rd Deck Drilling Rig 55 1 55 Lube Oil (0.93 SG)

Lube Oil Tank 3rd Deck Drilling Rig 37 2 74 Lube Oil (0.93 SG)

Hyd. Oil Tank 3rd Deck Drilling Rig 55 1 55 Hydraulic Oil (0.93 

SG)

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 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. 

Page 8 Public Information Copy
 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 ISO 14001 certification. 

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

Page 9 Public Information Copy
Attachment 1A – Bathymetry and Surface Locations 

Page 10 Public Information Copy
Attachment 1B 

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

Minerals Management Service OMB Approval Expires: 12/31/2011 

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 26254 Area: MC Block(s): 393 Project Name (If Applicable): Corinth

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

Boothville, LA

Distance to Closest Land (Miles): 75

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? X Yes No

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

*Well A approved 7/7/05 N-08379, **Wells Q - T requested in this plan.

X

*

Yes X

*

*

No

Tentative Schedule of Proposed Activities

Proposed Activity Start Date End Date No. of Days

Drill well Q 05/01/2012 08/16/2012 107

Drill well Q Sidetrack 08/17/2012 10/18/2012 62

Drill well A 03/01/2013 06/09/2013 100

Drill well R 03/01/2014 06/09/2014 100

Drill well S 03/01/2015 06/09/2015 100

Drill well T 03/01/2016 06/09/2016 100

Description of Drilling Rig Description of Production Platform

Jackup Drillship Caisson Tension leg platform

Gorilla Jackup Platform rig Well protector Compliant tower

X Semisubmersible Submersible Fixed platform Guyed tower

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

Drilling Rig Name (If Known): Transocean Nautilus 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
Attachment 1C 

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): A 

(Previously cleared in Plan N-08379)

Subsea Completion

Anchor Radius (if applicable) in feet: 15,500’ X Yes No

Surface Location Bottom-Hole Location (For Wells)

Lease No. OCS-G 26254 OCS-G 26254

Area Name Mississippi Canyon Mississippi Canyon

Block No. 393 393

Blockline

Departures

(in feet)

N/S Departure: 5,576’ FNL N/S Departure: 5,576’ FNL 

E/W Departure: 1,868’ FEL E/W Departure: 1,868’ FEL

Lambert X-Y 

coordinates

X: 1,344,532 X: 1,344,532

Y: 10,385,464 Y: 10,385,464

Latitude/

Longitude

Latitude 28.6149 Latitude 28.6149

Longitude -87.9224 Longitude -87.9224

TVD (Feet): 25,100’ MD (Feet): 25,100’ Water Depth (Feet): 7,385

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

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

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
Attachment 1D 

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): Q Subsea Completion

Anchor Radius (if applicable) in feet: 15,500’ X Yes No

Surface Location Bottom-Hole Location (For Wells)

Lease No. OCS-G 26254 OCS-G 26254

Area Name Mississippi Canyon Mississippi Canyon

Block No. 393 393

Blockline

Departures

(in feet)

N/S Departure: 5,451’ FNL N/S Departure: 4,777’ FNL 

E/W Departure: 5,238’ FEL E/W Departure: 6,875’ FWL

Lambert X-Y 

coordinates

X: 1,341,162 X: 1,337,435

Y: 10,385,589 Y: 10,386,263

Latitude/

Longitude

Latitude: 28.6152 Latitude 28.6169

Longitude –87.9330 Longitude -87.9446

TVD (Feet): 25,841’ MD (Feet): 27,256’ Water Depth (Feet): 7,375’

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

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

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
Attachment 1E 

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): Q ST Subsea Completion

Anchor Radius (if applicable) in feet: 15,500’ X Yes No

Surface Location Bottom-Hole Location (For Wells)

Lease No. OCS-G 26254 OCS-G 26254

Area Name Mississippi Canyon Mississippi Canyon

Block No. 393 393

Blockline

Departures

(in feet)

N/S Departure: 5,451’ FNL N/S Departure: 5,904’ FNL

E/W Departure: 5,238’ FEL E/W Departure: 2,208’ FEL

Lambert X-Y 

coordinates

X: 1,341,162 X: 1,344,192

Y: 10,385,589 Y: 10,385,136

Latitude/

Longitude

Latitude 28.6152 Latitude 28.6140

Longitude –87.9330 Longitude -87.9235

TVD (Feet): 25,255’ MD (Feet): 26,390’ Water Depth (Feet): 7,375’

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

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

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
Attachment 1F 

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): R Subsea Completion

Anchor Radius (if applicable) in feet: 15,500’ X Yes No

Surface Location Bottom-Hole Location (For Wells)

Lease No. OCS-G 26254 OCS-G 26254

Area Name Mississippi Canyon Mississippi Canyon

Block No. 393 393

Blockline

Departures

(in feet)

N/S Departure: 6,617’ FSL N/S Departure: 6,617’ FSL

E/W Departure: 3,236’ FWL E/W Departure: 3,236’ FWL

Lambert X-Y 

coordinates

X: 1,333,796 X: 1,333,796

Y: 10,381,817 Y: 10,381,817

Latitude/

Longitude

Latitude 28.6046 Latitude 28.6046

Longitude -87.9558 Longitude -87.9558

TVD (Feet): 26,300’ MD (Feet): 26,300’ Water Depth (Feet): 7,311’

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

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

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 15 Public Information Copy
Attachment 1G 

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): S Subsea Completion

Anchor Radius (if applicable) in feet: 15,500’ X Yes No

Surface Location Bottom-Hole Location (For Wells)

Lease No. OCS-G 26254 OCS-G 26254

Area Name Mississippi Canyon Mississippi Canyon

Block No. 393 393

Blockline

Departures

(in feet)

N/S Departure: 1,040’ FNL N/S Departure: 1,040’ FNL

E/W Departure: 3,640’ FWL E/W Departure: 3,640’ FWL 

Lambert X-Y 

coordinates

X: 1,334,200 X: 1,334,200

Y: 10,390,000 Y: 10,390,000

Latitude/

Longitude

Latitude 28.6272 Latitude 28.6272

Longitude -87.9548 Longitude -87.9548

TVD (Feet): 26,450’ MD (Feet): 26,450’ Water Depth (Feet): 7,301’

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

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

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 16 Public Information Copy
Attachment 1H 

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): T Subsea Completion

Anchor Radius (if applicable) in feet: 15,500’ X Yes No

Surface Location Bottom-Hole Location (For Wells)

Lease No. OCS-G 26254 OCS-G 26254

Area Name Mississippi Canyon Mississippi Canyon

Block No. 393 393

Blockline

Departures

(in feet)

N/S Departure: 5,045’ FNL N/S Departure: 5,045’ FNL

E/W Departure: 7,145’ FWL E/W Departure: 7,145’ FWL 

Lambert X-Y 

coordinates

X: 1,337,705 X: 1,337,705

Y: 10,385,995 Y: 10,385,995

Latitude/

Longitude

Latitude 28.6329 Latitude 28.6329

Longitude -87.9438 Longitude -87.9438

TVD (Feet): 25,840’ MD (Feet): 25,840’ Water Depth (Feet): 7,358’

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

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

X = Y =

XPaperwork 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 17 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., 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., 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 18 Public Information Copy
J. Blowout scenario

Summary 

This Section 2j was prepared by Shell pursuant to the guidance provided in the BOEM’s NTL 2010-N06 with 

respect to blowout and worst case discharge scenario descriptions. 

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

/containment, and recovery. 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 with the goal of safe and environmentally sound well construction. Shell continues to invest 

independently in research and development to improve safety and reliability of our well systems. We are 

actively complying with all applicable laws, regulations, rules and Notice to Lessees. 

Shell is investing in R&D to improve containment systems. As outlined in Shell’s OSRP, and detailed in EP 

Section 9a (ii), Shell has contracts with ORSOs to provide the resources necessary to respond to this WCD 

scenario. 

The WCD blowout scenario for Corinth is calculated for the MC-393 Q location near-crest penetration of the 

target sand and based on the guidelines outlined in NTL No. 2010-N06 along with subsequent Frequently 

Asked Questions (FAQ). Shell submitted MC 807 A as the worst-case scenario to the BOEM for inclusion in our 

Regional OSRP. In the unlikely event of a spill, Shell’s Regional OSRP (August 2011) is designed to contain 

and respond to a spill that exceeds this WCD. This WCD does not take into account potential flow mitigating 

factors such as well bridging, obstructions in wellbore, reservoir barriers, and early intervention including 

containment capabilities. 

Uncontrolled blowout (volume first day) 364,000 bbl 

Uncontrolled blowout rate (first 30-days average daily rate) 353,000 bopd 

Duration of flow (days) based on relief well 128 days

Total volume of spill (bbls) for 128 days 44.9 MMBO

Table 2.1 Worst Case Discharge Summary 

The MC 393 project is located approximately 75 miles east-southeast of the nearest shoreline in the Gulf of 

Mexico (GOM), in water depths of approximately 7,375’ on MC-393. The structural component of the target is 

defined by a faulted nose approximately one mile long by three miles wide, with the top of the objective near 

-25,000’ subsea (SS). The structure does not contain any previously drilled wells, but may have connected 

aquifer or hydrocarbons with the current (2011) well being drilled in MC-348. The only objective horizon with 

predicted flow potential is the target reservoir of Jurassic age. 

1) Purpose 

Pursuant to 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 Appomattox (MC-392) and Vicksburg 

(DC-353) well data along with 3D seismic data. 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 

Page 19 Public Information Copy
This attachment has been developed to document the additional information requirements for EP’s as 

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

(MODU) Deepwater Horizon. 

Page 20 Public Information Copy
3) Information Requirements 

a) Blowout scenario 

Six locations in this submitted SEP were assessed for WCD. The MC-393 well from the Q location 

deviated near the crest of the structure represents the highest flow potential. The Q well will be 

drilled to the target reservoir as outlined in the Geological and Geophysical Information (Section 3) of 

the EP using a subsea wellhead system, conductor, surface and intermediate casing program, and 

using a MODU rig with a marine riser and subsea blowout preventer. A hydrocarbon influx and a well 

control event are modeled to occur from the target reservoir. The simulated blowout modeled results 

in unrestricted flow from the well at the seafloor, which represents the WCD (no restrictions in 

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

b) Estimated flow rate of the potential blowout 

Category EP 

Type of Activity Drilling 

Facility Location (area/block) MC-393 

Facility Designation MODU 

Distance to Nearest Shoreline (miles) 75 Statute miles

Uncontrolled blowout (volume first day) 364,000 bbl 

Uncontrolled blowout rate (first 30-days average daily rate) 353,000 bopd 

Table 2.2 Estimated Flow Rates of a Potential Blowout 

c) Total volume and maximum duration of the potential blowout 

Duration of flow (days) 128 days total duration to drill relief well 

(14 rig mob, 3 transit, 80 spud to top sand, 31 ranging). 

Total volume of spill (bbls) 44.9 MMBO based on 128 days flowing. 

Note: From MBAL/Prosper 

Table 2.3 Estimated Duration and Volume of a Potential Blowout 

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. 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 sand face. Given the substantial fluid 

velocities inherent in the WCD, 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 the outflow rates. However, this WCD scenario does 

not include any bridging. 

f) Likelihood for intervention to stop the blowout. 

Page 21 Public Information Copy
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 Drilling Safety 

Rule with respect to Remotely Operated Vehicle (ROV) hot stab capabilities, a deadman system, and 

an auto shear system. 

Additionally the Deepwater Nautilus (moored semi-submersible) has a gas handler system at the top 

of the riser consisting of two annular preventers that can be closed in to allow hydrocarbons in the 

riser to be contained or circulated thru the rig’s well control system. The rig has two shearing rams in 

the BOP for added redundancy. Also, the Nautilus is equipped with a deadman system and an auto 

shear system. 

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. Shell has an active portfolio of well operations in the GOM which will be 

supported by a total of four to six MODU rigs in 2011 – 2015 timeframe. The dynamically positioned 

rigs under contract, the Noble Danny Adkins, Noble Globetrotter I and the Noble Bully I 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 is the distinct possibility that other noncontracted rigs in the GOM could be utilized whether for increased expediency or better suitability. All 

efforts will be made at the time to secure the appropriate rig. Shell’s current contracted rigs capable 

of operating at Corinth water depths and reservoir depths without constraints are in the following 

table: 

Rig Name Rig Type

Noble Danny Adkins dynamically positioned semisubmersible

Noble Globetrotter I * dynamically positioned drillship

Noble Bully I * dynamically positioned drillship

Deepwater Nautilus moored semisubmersible

Noble Jim Thompson moored semisubmersible

Table 2.4 Shell Contracted Rigs Capable at Corinth. 

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

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

* Globetrotter I & Bully I estimated arrival Q1 2012. 

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

Page 22 Public Information Copy
Relief well operations will immediately take priority and displace any activity from Shell’s contracted 

rig fleet. Table 2.4 above lists the Shell contracted rigs capable of operating at Corinth. 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 80 days to drill down to the last casing 

string above the blowout zone, plus approximately 31 days for precision ranging activity to intersect 

the blowout well bore. Total time to drill a relief well would be ~128 days for the MC 393 wells. 

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 mooring activity is not 

expected to delay initiation of relief well drilling operations. Shell has three deepwater anchor 

handlers, the Laney, Dino, and Ross Chouest, on long term contract to support its moored rigs. 

It is not possible to drill relief wells from any existing platforms due to being over fifteen (15) miles to 

the nearest structure. 

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 

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 Notices 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 Corinth. 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 

Page 23 Public Information Copy
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 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 monitored 24/7 virtually by 

onshore teams consisting of geoscientists, petrophysicists, well engineers, and 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 Foremen 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. 

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 2f 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 2011-2015 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 

Page 24 Public Information Copy
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 

MC 807 Subsea Well A 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). 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 a 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 

BOEM Gulf of Mexico Region. 

Page 25 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: 

Location A:

AOA Geophysics, Inc. (2004), “Shallow Hazards Assessment MC393 (OCS G-26254), DC353 (OCS G-25852), 

DC354 (OCS G-23507), DC397 (OCS G-25853), AND DC398 (OCS G-25854) Mississippi Canyon and DeSoto 

Canyon Areas, Gulf of Mexico”, AOA Report No. 3038.3-SHL-DES, prepared for Shell Offshore Inc. 

Fugro Geoservices, Inc (2007) Archaeological Assessment, Proposed Anchor Locations Block 393, Mississippi 

Canyon Area, Gulf of Mexico”, Fugro Report No. 2407-1083, prepared for Shell Deepwater Development. 

Locations Q, QST, R, S, T:

Fugro Geoservices, Inc. (2011), “Shallow Hazards and Archaeological Assessment DeSoto Canyon Block 353 

and Vicinity Appomattox Extension Project (OCS-G-25852) Gulf of Mexico”, Fugro Report No. 2411-5001, 

prepared for Shell Exploration and Production Company. 

Fugro GeoConsulting, Inc. (2009), “Shallow Drilling Hazards and Archaeological Assessment, Mississippi 

Canyon Blocks 347, 348, 391, 392 and Vicinity, Gulf of Mexico”, Fugro Report No. 27.2008-5022, prepared for 

Shell Exploration and Production Company. 

F. Shallow Hazards Assessment

Proposed Location A, Mississippi Canyon 393 (Previously Approved):

For Proposed Location A, a review was made of the available geological and geophysical data within 985’ of

the well site and to the surface casing depth of ~11,000’ MD (10,925 TVDSS). At the surface, there is no 

evidence of fault scarps, gas vents, hydrate mounds, unstable slopes, slumping, active mud gullies (crown 

cracks, collapsed depressions), furrows, sinkholes, surface channels, or reefs. There are no manmade 

hazards such as pipelines, wellheads, shipwrecks, ordnance, or communication cables. The Fugro 2007 report 

shows three wooden cylinders possibly covered by netting 674’ ESE of this proposed location. In the 

subsurface, there is no evidence of faults, gas-charged sediments, shallow-water flow, or buried channels. 

The shallow stratigraphy at this location was described by AOA Geophysics. These units are different than the 

subsequent Fugro 2011 report. The Fugro units will be used with the AOA equivalents referenced in 

parentheses in this text (Attachment 3F with AOA nomenclature). 

 Unit 1 from 7,399’-8,803’ TVDSS (AOA Units 1, 2, and 3) consists of approximately 233’ of 

hemipelagic clays and mass transport complex deposits. 290’ of clays overlying mass 

transport complex deposits, 263’ of channel overbank deposits associated with a large buried 

Page 26 Public Information Copy
channel, 263’ of clays, and 355’ of mass transport complex deposits with clays and 

overbank deposits. 

 Unit 2 from 8,803’-9,896’ TVDSS (AOA Unit 4) consists of 509’ of channel-margin and 

channel deposits overlying 584’ of mass transport complex deposits. 

 Unit 3 from 9,896’-11,231’ TVDSS (AOA Unit 5) consists of 664’ of mass transport complex 

and possible channel deposits and 671’ of mass transport complex deposits with possible 

channel deposits. A possible sheet sand is identified 3,371’ below the mud line. 

 Unit 4 from 11,231’-13,155’ TVDSS (AOA below Unit 5) is are 793’ of interbedded mass 

transport complex and channel deposits overlying 1,131’ of interbedded mass transport 

complex and channel deposits. 

This location was selected to minimize the potential for shallow water flow. The potential for shallow water 

flow is as follows: 

 Unit 1 (AOA Geophysics Units 1-3) - Low 

 Unit 2 (AOA Geophysics Unit 4) - Low 

 Unit 3 (AOA Geophysics Unit 5) - Negligible 

 Unit 4 –(AOA Geophysics below Unit 5) - Negligible 

This location was selected to minimize the potential for encountering shallow gas. Potential for shallow gas is 

as follows: 

 Unit 1 (AOA Geophysics Units 1-3) - Negligible 

 Unit 2 (AOA Geophysics Unit 4) - Negligible 

 Unit 3 (AOA Geophysics Unit 5) - Negligible 

 Unit 4 –(AOA Geophysics below Unit 5) - Negligible 

This location was selected in order to avoid all identified amplitude anomalies. The closest amplitude 

anomalies to this location are approximately 1,000’ northwest, 3,630’ to 6,250’ below the mud line, and 

1,600’ northwest, 940’ to 3,090’ below the mud line. 

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

with amplitudes applied and AUV high-resolution data, this location appears suitable for the planned activity. 

Proposed Location Q & QST, Mississippi Canyon 393:

For Proposed Location Q, a review was made of the available geological and geophysical data within 985’ of

the well site and to the surface casing depth of ~11,000’ MD (10,925’ TVDSS). At the surface, there is no 

evidence of fault scarps, gas vents, hydrate mounds, unstable slopes, slumping, active mud gullies (crown 

cracks, collapsed depressions), furrows, sinkholes, surface channels, or reefs. There are no manmade 

hazards such as pipelines, wellheads, shipwrecks, ordnance, communication cables, or debris, including that 

caused by hurricanes. In the subsurface, there is no evidence of faults, gas-charged sediments, shallowwater flow, or buried channels. 

The shallow stratigraphy at this location is divided into 5 units (Attachment 3G). 

 Unit 1 from 7,375’-8,784’ TVDSS consists of 110’ of hemipelagic drape over 300’ of mass 

transport deposits, over approximately 999’ of mass transport deposits, stratified sediments 

and channelized deposits. 

 Unit 2 from 8,784’-9,944’ TVDSS consists of channel-levees deposited over rotated slides. 

 Unit 3 from 9,944’-11,360’ TVDSS consists predominately of clay with minor channels. 

 Unit 4 from 11,360’-12,898’ TVDSS is identified as 1,538’ of channel levee complexes. 

 Unit 5 from 12,898’-17,222’ TVDSS is identified as 4,324’ of sands in mud and basin floor 

sands. 

Page 27 Public Information Copy
 Unit 1 - Low 

 Unit 2 - Low 

 Unit 3 - Low 

 Unit 4 - Low 

 Unit 5 - Low 

This location was selected in order to avoid all identified amplitude anomalies. Amplitude anomalies were 

identified in Units 1-5. The closest amplitude anomaly to this location is approximately 900’ north of this 

proposed location in Unit 3. 

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

with amplitudes applied and AUV high-resolution data, this location appears suitable for the planned activity. 

Proposed Location S, Mississippi Canyon 393:

For Proposed Location S, a review was made of the available geological and geophysical data within 985’ of

the well site and to the surface casing depth of ~11,000’ MD (10,925 TVDSS). At the surface, there is no 

evidence of fault scarps, gas vents, hydrate mounds, unstable slopes, slumping, active mud gullies (crown 

cracks, collapsed depressions), furrows, sinkholes, surface channels, or reefs. There are no manmade 

hazards such as pipelines, wellheads, shipwrecks, ordnance, communication cables, or debris, including that 

caused by hurricanes. In the subsurface, there is no evidence of faults, gas-charged sediments, shallowwater flow, or buried channels. 

The shallow stratigraphy at this location is divided into 5 units (Attachment 3I). 

 Unit 1 from 7,301’-8,581’ TVDSS consists of 110’ of hemipelagic drape over 300’ of mass 

transport deposits, over approximately 870’ of more mass transport deposits, stratified 

sediments and channelized deposits 

 Unit 2 from 8,581’-9,864’ TVDSS consists of channel-levees deposited over rotated slides. 

 Unit 3 from 9,864’-11,318’ TVDSS consists predominately of clay with minor channels. 

 Unit 4 from 11,318’-12,812’ TVDSS is identified as 1,494’ of channel levee complexes. 

 Unit 5 from 12,812’-17,314’ TVDSS is identified as 4,502’ of sands in mud and basin floor 

sands. 

This location was selected to minimize the potential for shallow water flow. The potential for shallow water 

flow is as follows: 

 Unit 1 - Low 

 Unit 2 - Low 

 Unit 3 - Low 

 Unit 4 - Moderate 

 Unit 5 - Low 

This location was selected to minimize the potential for encountering shallow gas. Potential for shallow gas is 

as follows: 

 Unit 1 - Low 

 Unit 2 - Low 

 Unit 3 - Low 

 Unit 4 - Low 

 Unit 5 - Low 

This location was selected in order to avoid all identified amplitude anomalies. Amplitude anomalies were 

identified in Units 1-5. The closest amplitude anomaly to this location is approximately 850 west of this 

proposed location in Unit 4. 

Page 28 Public Information Copy
Based on a high-resolution geophysical survey, consisting of frequency enhanced 3-D seismic, ESR’s, ESR’s 

with amplitudes applied and AUV high-resolution data, this location appears suitable for the planned activity. 

Proposed Location T, Mississippi Canyon 393:

For Proposed Location T, a review was made of the available geological and geophysical data within 985’ of

the well site and to the surface casing depth of ~11,000’ MD (10,925 TVDSS). At the surface, there is no 

evidence of fault scarps, gas vents, hydrate mounds, unstable slopes, slumping, active mud gullies (crown 

cracks, collapsed depressions), furrows, sinkholes, surface channels, or reefs. There are no manmade 

hazards such as pipelines, wellheads, shipwrecks, ordnance, communication cables, or debris, including that 

caused by hurricanes. In the subsurface, there is no evidence of faults, gas-charged sediments, shallowwater flow, or buried channels. 

The shallow stratigraphy at this location is divided into 5 units (Attachment 3J). 

 Unit 1 from 7358’-8696’ TVDSS consists of 110’ of hemipelagic drape over 300’ of mass 

transport deposits, over approximately 928’ of more mass transport deposits, stratified 

sediments and channelized deposits 

 Unit 2 from 8696’-9964’ TVDSS consists of channel-levees deposited over rotated slides. 

 Unit 3 from 9964’-11,396’ TVDSS consists predominately of clay with minor channels. 

 Unit 4 from 11,396’-12,885’ TVDSS is identified as 1489’ of channel levee complexes. 

 Unit 5 from 12,885’-17,367’ TVDSS is identified as 4482’ of sands in mud and basin floor 

sands. 

This location was selected to minimize the potential for shallow water flow. The potential for shallow water 

flow is as follows: 

 Unit 1 - Low 

 Unit 2 - Low 

 Unit 3 - Low 

 Unit 4 - Moderate 

 Unit 5 - Low 

This location was selected to minimize the potential for encountering shallow gas. Potential for shallow gas is 

as follows: 

 Unit 1 - Low 

 Unit 2 - Low 

 Unit 3 - Low 

 Unit 4 - Low 

 Unit 5 - Low 

This location was selected in order to avoid all identified amplitude anomalies. Amplitude anomalies were 

identified in Units 1-5. The closest amplitude anomaly to this location is approximately 800’ west of this 

proposed location in Unit 3. 

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

with amplitudes applied and AUV high-resolution data, this location appears suitable for the planned activity. 

Shell will comply with NTL 2008-G05. 

 

G. High-Resolution Seismic Lines

Proprietary data. The ESR Maps can be found in Section 6, Attachments 6A through 6E. 

Page 29 Public Information Copy
This location was selected to minimize the potential for shallow water flow. The potential for shallow water 

flow is as follows: 

 Unit 1 - Low 

 Unit 2 - Low 

 Unit 3 - Low 

 Unit 4 - Moderate 

 Unit 5 - Low 

This location was selected to minimize the potential for encountering shallow gas. Potential for shallow gas is 

as follows: 

 Unit 1 - Low 

 Unit 2 - Low 

 Unit 3 - Low 

 Unit 4 - Low 

 Unit 5 - Low 

This location was selected in order to avoid all identified amplitude anomalies. Amplitude anomalies were 

identified in Units 1-5. The closest amplitude anomaly to this location is approximately 1,000’ southeast of 

this proposed location in Unit 3. 

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

with amplitudes applied and AUV high-resolution data, this location appears suitable for the planned activity. 

Proposed Location R, Mississippi Canyon 393:

For Proposed Location R, a review was made of the available geological and geophysical data within 985’ of

the well site and to the surface casing depth of ~11,000’ MD (10,925 TVDSS). At the surface, there is no 

evidence of fault scarps, gas vents, hydrate mounds, unstable slopes, slumping, active mud gullies (crown 

cracks, collapsed depressions), furrows, sinkholes, surface channels, or reefs. There are no manmade 

hazards such as pipelines, wellheads, shipwrecks, ordnance, communication cables, or debris, including that 

caused by hurricanes. In the subsurface, there is no evidence of faults, gas-charged sediments, shallowwater flow, or buried channels. 

The shallow stratigraphy at this location is divided into 5 units (Attachment 3H). 

 Unit 1 from 7,311’-8,707’ TVDSS consists of 110’ of hemipelagic drape over 300’ of mass 

transport deposits, over approximately 986’ of more mass transport deposits, stratified 

sediments and channelized deposits. 

 Unit 2 from 8,707’-10,032’ TVDSS consists of channel-levees deposited over rotated slides. 

 Unit 3 from 10,032’-11,464’ TVDSS consists of predominately clay with minor channels. 

 Unit 4 from 11,464’-12,918’ TVDSS is identified as 1,454’ of channel levee complexes. 

 Unit 5 from 12,918’-17,555’ TVDSS is identified as 4,637’ of sands in mud and basin floor 

sands. 

This location was selected to minimize the potential for shallow water flow. The potential for shallow water 

flow is as follows: 

 Unit 1 - Low 

 Unit 2 - Low 

 Unit 3 - Low 

 Unit 4 - Moderate 

 Unit 5 - Low 

This location was selected to minimize the potential for encountering shallow gas. Potential for shallow gas is 

as follows: 

Page 30 Public Information Copy
 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 31 Public Information Copy
SECTION 4: HYDROGEN SULFIDE (H2S) INFORMATION 

A. Concentration 

10-40 ppm. 

B. Classification

 

Based on 30 CFR 250.490 (c), Shell requests that the Regional Supervisor, Field Operations, classify the area in the 

proposed drilling operations as an area where H2S is known. 

C. H2S Contingency Plan

When the APD is submitted to BSEE, Shell will also include the H2S Contingency Plan prepared according to 30 CFR 

250.490(f) before conducting the proposed exploration activities. 

D. 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.

Page 32 Public Information Copy
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 33 Public Information Copy
SECTION 6: BIOLOGICAL, PHYSICAL, AND SOCIOECONOMIC INFORMATION

A. Chemosynthetic Communities Report

The following reports were used in this analysis: 

Fugro Geoservices, Inc. (2011), “Shallow Hazards and Archaeological Assessment DeSoto Canyon Block 

353 and Vicinity Appomattox Extension Project (OCS-G 25852) Gulf of Mexico”, Fugro Report No. 2411-

5001, prepared for Shell Exploration and Production Company. 

Fugro GeoConsulting, Inc. (2009), “Shallow Drilling Hazards and Archaeological Assessment, Mississippi 

Canyon Blocks 347, 348, 391, 392 and Vicinity, Gulf of Mexico”, Fugro Report No. 27.2008-5022, 

prepared for Shell Exploration and Production Company. 

Fugro Geoservices, Inc (2007) Archaeological Assessment, Proposed Anchor Locations Block 393, 

Mississippi Canyon Area, Gulf of Mexico”, Fugro Report No. 2407-1083, prepared for Shell Deepwater 

Development. 

AOA Geophysics, Inc. (2004), “Shallow Hazards Assessment MC393 (OCS-G 26254), DC353 (OCS-G 

25852), DC354 (OCS-G 23507), DC397 (OCS-G 25853), and DC398 (OCS-G 25854) Mississippi Canyon 

and DeSoto Canyon Areas, Gulf of Mexico”, AOA Report No. 3038.3-SHL-DES, prepared for Shell Offshore 

Inc. 

Proposed Location A and Generic 15,500’ Radial Anchor Pattern (Previously Approved)

There are no high-density deepwater benthic communities located within 2,000’ of the proposed mud and 

cuttings discharge location. 

There are no high-density deepwater benthic communities located within the 16,500’ anchor pattern. This 

is a generic 15,500’ anchor pattern plus an additional 1,000’ buffer area beyond the proposed maximum 

anchor radius. 

There is no evidence within this area of seafloor or near-surface hydrocarbon-charged sediments 

associated with surface faulting, acoustic void zones associated with surface faulting, mounds, knolls, gas 

seeps, oil seeps, or hard bottom. 

Currently, there are no flowlines or umbilicals within the 16,500’ radius of the proposed location.

This proposed location and associated anchor pattern will not interfere with identified seafloor sonar 

targets or with previously drilled well sites. There are 10 sonar targets and one previously drilled wellsite 

identified within the 16,500’ radius of the proposed location. These are listed in the following table with 

the recommended avoidance distance. ROV Targets #1 and #2 are the only sonar targets identified 

within 2000’ of this proposed location (ROV#1 1780’ ESE with avoidance distance of 100’ and ROV#2

674’ ESE with avoidance distance of 200’). 

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

Surface Renderings (ESR’s), ESR’s with amplitudes applied and AUV high-resolution data, this proposed 

location appears suitable for the planned activity (Attachment 6A). 

Page 34 Public Information Copy
Target From Location A Avoidance [ft] Target Description

ROV#1 1,780' ESE 100 Metal Barrel

ROV#2 674' ESE 200 Three wooden cylinders with netting

AUV#8 13,560' WNW 100 Modern Debris

AUV#9 13,097' NW 100 Amorphous

AUV#10 11,994' SW 500 Geologic

AUV#11 5,589' WNW 100 Modern Debris

AUV#12 12,371' SWS 100 Amorphous

Contact15 14,418' 100 Disturbed Seafloor

Contact19 16,382' 100 Modern Debris

Contact20 8,683' 100 Modern Debris

DC353 #1 7,511 ESE 500 Drilled wellsite - Shell

Table 6.1. Targets within Proposed Anchor Radius. 

Proposed Location Q & QST and Generic 15,500’ Radial Anchor Pattern

There are no high-density deepwater benthic communities located within 2000’ of the proposed mud and 

cuttings discharge location. 

There are no high-density deepwater benthic communities located within the 16,500’ anchor pattern. This 

is a generic 15,500’ anchor pattern plus an additional 1000’ buffer area beyond the proposed maximum 

anchor radius. 

There is no evidence within this area of seafloor or near-surface hydrocarbon-charged sediments 

associated with surface faulting, acoustic void zones associated with surface faulting, mounds, knolls, gas 

seeps, oil seeps, or hard bottom. 

Currently, there are no flowlines or umbilicals within the 16,500’ radius of the proposed location.

This proposed location and associated anchor pattern (including disturbances caused by anchors, anchor 

chains, wire ropes, and cables located on the seafloor prior to being pulled taut and attached to the 

MODU) will not interfere with identified seafloor sonar targets or with previously drilled well sites. There 

are eight sonar targets and two previously drilled wellsites identified within the 16,500’ radius of the 

proposed location. These are listed in the following table with the recommended avoidance distance. 

There are no seafloor sonar targets identified within 2,000’ of the proposed location. 

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

ESR’s with amplitudes applied and AUV high-resolution data, this proposed location appears suitable for 

the planned activity (Attachment 6B).

Page 35 Public Information Copy
Target From Location Q Avoidance [ft] Target Description

ROV#1 5,087' ESE 100 Metal Barrel

ROV#2 3,975' ESE 200 Three wooden cylinders with netting

AUV#8 10,310' WNW 100 Modern Debris

AUV#9 10,975' NWN 100 Amorphous

AUV#10 10,030' SWS 500 Geologic

AUV#11 2,321' WNW 100 Modern Debris

AUV#12 11,933' S 100 Amorphous

Contact20 11,449' E 100 Modern Debris

DC353 #1 10,729' ESE 500 Drilled wellsite - Shell

MC392 #1 14,385' SW 500 Drilled wellsite - Anadarko

Table 6.2. Targets within Proposed Anchor Radius. 

Proposed Location R and Generic 15,500’ Radial Anchor Pattern

There are no high-density deepwater benthic communities located within 2,000’ of the proposed mud and 

cuttings discharge location. 

There are no high-density deepwater benthic communities located within the 16,500’ anchor pattern. This 

is a generic 15,500’ anchor pattern plus an additional 1000’ buffer area beyond the proposed maximum 

anchor radius. 

There is no evidence within this area of seafloor or near-surface hydrocarbon-charged sediments 

associated with surface faulting, acoustic void zones associated with surface faulting, mounds, knolls, gas 

seeps, oil seeps, or hard bottom. 

Currently, there are no flowlines or umbilicals within the 16,500’ radius of the proposed location.

This proposed location and associated anchor pattern (including disturbances caused by anchors, anchor 

chains, wire ropes, and cables located on the seafloor prior to being pulled taut and attached to the 

MODU) will not interfere with identified seafloor sonar targets or with previously drilled well sites. There 

are eight sonar targets and three previously drilled wellsites identified within the 16,500’ radius of the 

proposed location. These are listed in the following table with the recommended avoidance distance. 

There are no seafloor sonar targets identified within 2000’ of the proposed location. 

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

ESR’s with amplitudes applied and AUV high-resolution data, this proposed location appears suitable for 

the planned activity (Attachment 6C) 

Page 36 Public Information Copy
Target From Location R Avoidance [ft] Target Description

ROV#1 12,752' ENE 100 Metal Barrel

ROV#2 11,784' ENE 200 Three wooden cylinders with netting

AUV#6 12,546' W 100 Amorphous

AUV#8 7,655' NNW 100 Modern Debris

AUV#9 13,371' NNE 100 Amorphous

AUV#10 5,412' SSE 500 Geologic

AUV#11 7,072' NE 100 Modern Debris

AUV#12 10,768' SE 100 Amorphous

MC348#3 13,720' NW 500 Drilled wellsite - Shell

MC392 #1 6,111' SW 500 Drilled wellsite - Anadarko

MC392 #1 14,971' WNW 500 Drilled wellsite - Shell

Table 6.3. Targets within Proposed Anchor Radius. 

Proposed Location S and Generic 15,500’ Radial Anchor Pattern

There are no high-density deepwater benthic communities located within 2000’ of the proposed mud and 

cuttings discharge location. 

There are no high-density deepwater benthic communities located within the 16,500’ anchor pattern. This 

is a generic 15,500’ anchor pattern plus an additional 1000’ buffer area beyond the proposed maximum 

anchor radius. 

There is no evidence within this area of seafloor or near-surface hydrocarbon-charged sediments 

associated with surface faulting, acoustic void zones associated with surface faulting, mounds, knolls, gas 

seeps, oil seeps, or hard bottom. 

There are flowlines and umbilicals associated with MC348 #1 and MC348 #2 approximately 14,000’ to 

the northwest and within the 16,500’ radius of the proposed location. There will be a 500’ avoidance 

distance for anchors and associated equipment from these flowlines and umbilicals. 

This proposed location and associated anchor pattern (including disturbances caused by anchors, anchor 

chains, wire ropes, and cables located on the seafloor prior to being pulled taut and attached to the 

MODU) will not interfere with identified seafloor sonar targets or with previously drilled well sites. There 

are eight sonar targets and five previously drilled wellsites identified within the 16,500’ radius of the 

proposed location. These are listed in the following table with the recommended avoidance distance. 

There are no seafloor sonar targets identified within 2,000’ of the proposed location. 

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

ESR’s with amplitudes applied and AUV high-resolution data, this proposed location appears suitable for 

the planned activity (Attachment 6D). 

Page 37 Public Information Copy
Target From Location S Avoidance [ft] Target Description

ROV#1 13,062' SE 100 Metal Barrel

ROV#2 11,952' SE 200 Three wooden cylinders with netting

AUV#6 15,031' SW 100 Amorphous

AUV#7 14,958' NNW 100 Modern Debris

AUV#8 2,870' WSW 100 Modern Debris

AUV#9 5,259' NNE 100 Amorphous

AUV#10 13,214' SSE 500 Geologic

AUV#11 5,951' SE 100 Modern Debris

MC348 #1 14,103' NW 500 Drilled wellsite - Marathon

MC348 #2 15,109' NW 500 Drilled wellsite - Marathon

MC348#3 9,161' W 500 Drilled wellsite - Shell

MC392 #1 12,333' SW 500 Drilled wellsite - Anadarko

MC392 #1 14,720' WSW 500 Drilled wellsite - Shell

Table 6.4. Targets within Proposed Anchor Radius. 

Proposed Location T and Generic 15,500’ Radial Anchor Pattern

There are no high-density deepwater benthic communities located within 2000’ of the proposed mud and 

cuttings discharge location. 

There are no high-density deepwater benthic communities located within the 16,500’ anchor pattern. This 

is a generic 15,500’ anchor pattern plus an additional 1000’ buffer area beyond the proposed maximum 

anchor radius. 

There is no evidence within this area of seafloor or near-surface hydrocarbon-charged sediments 

associated with surface faulting, acoustic void zones associated with surface faulting, mounds, knolls, gas 

seeps, oil seeps, or hard bottom. 

Currently, there are no flowlines or umbilicals within the 16,500’ radius of the proposed location.

This proposed location and associated anchor pattern (including disturbances caused by anchors, anchor 

chains, wire ropes, and cables located on the seafloor prior to being pulled taut and attached to the 

MODU) will not interfere with identified seafloor sonar targets or with previously drilled well sites. There 

are eight sonar targets and three previously drilled wellsites identified within the 16,500’ radius of the 

proposed location. These are listed in the following table with the recommended avoidance distance. AUV 

Sonar Target #11 is the only sonar target identified within 2000’ of this proposed location (1,456’ ENE 

with avoidance distance of 100’). 

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

ESR’s with amplitudes applied and AUV high-resolution data, this proposed location appears suitable for 

the planned activity (Attachment 6E). 

Page 38 Public Information Copy
Target From Location T Avoidance [ft] Target Description

ROV#1 8,567' ESE 100 Metal Barrel

ROV#2 7,456' ESE 200 Three wooden cylinders with netting

AUV#8 6,968' NW 100 Modern Debris

AUV#9 9,304' NNW 100 Amorphous

AUV#10 9,210' SWS 500 Geologic

AUV#11 1,456' ENE 100 Modern Debris

AUV#12 12,724' SSE 100 Amorphous

DC353 #1 14,170' E 500 Drilled wellsite - Shell

MC348#3 13,970' NW 500 Drilled wellsite - Shell

MC392 #1 11,628' SW 500 Drilled wellsite - Anadarko

Table 6.5 Targets within Proposed Anchor Radius

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, 

Mississippi Canyon Block 393 is located in Grid 17. Grid 17 is an area that does not have adequate ROV survey 

coverage; therefore we will run the pre- and post-ROV survey in accordance with NTL 2008-G06. 

Survey No. 1 will be conducted using the rig based ROV equipped with video imaging capabilities prior to 

commencing operations on the well. The survey pattern will consist of six transects centered on the existing 

well with tracks extending 100 meters away from the well on bearings of 30°, 90°, 150°, 210°, 270°, and 

330°. The seafloor will be videotaped continuously along each track and close-up footage recorded of any 

animals or features. An identical survey will be conducted following drilling operations but prior to moving 

the rig off location. During both surveys, all biological and physical observations will be documented using 

Form MMS-141. Complete documentation, including videotapes, of both surveys will be submitted to the 

BOEM within 60 days of the final survey. 

H. Threatened and Endangered Species Information

There are 5 species of sea turtles that may be found in the Gulf of Mexico (see Table 6.6 below). 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

Table 6.6 – Threatened and Endangered Sea Turtles 

There are 29 species of marine mammals that may be found in the Gulf of Mexico (see Table 6.7 below). 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. 

Page 39 Public Information Copy
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

Table 6.7 – Threatened and Endangered Marine Mammals 

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

species. 

I. Archaeological Report

The following reports were used in this analysis: 

Fugro Geoservices, Inc (2007) Archaeological Assessment, Proposed Anchor Locations Block 393, Mississippi 

Canyon Area, Gulf of Mexico”, Fugro Report No. 2407-1083, prepared for Shell Deepwater Development. 

Fugro GeoConsulting, Inc. (2009), “Shallow Drilling Hazards and Archaeological Assessment, Mississippi 

Canyon Blocks 347, 348, 391, 392 and Vicinity, Gulf of Mexico”, Fugro Report No. 27.2008-5022, prepared for 

Shell Exploration and Production Company. 

Fugro Geoservices, Inc. (2011), “Shallow Hazards and Archaeological Assessment DeSoto Canyon Block 353 

and Vicinity Appomattox Extension Project (OCS-G-25852) Gulf of Mexico”, Fugro Report No. 2411-5001, 

prepared for Shell Exploration and Production Company. 

Page 40 Public Information Copy
Archaeological Analysis

Fugro (2007) performed a high-resolution geophysical survey over three proposed anchor locations within 

Block 393, in order to evaluate for evidence of shipwrecks. They identified two sonar contacts (ROV#1, 

ROV#2). The first contact is a cylindrical metal object, interpreted as a drum, and therefore is probable 

modern debris. The second contact is partially buried, and has the appearance of being three wooden 

cylindrical objects, with possible netting draped over them. Both contacts should be avoided. There were no 

other unusual depressions, scours, sediment changes, or unidentified seafloor targets observed that could 

represent unidentified shipwreck remains. 

Fugro (2009) performed a high resolution geophysical survey, identifying twelve sonar contacts. Sonar 

contacts 1, 2, and 10 are all small isolated features that are likely geologic in origin. Sonar contacts 7, 8, and 

11 are isolated linear features that are interpreted as probable modern debris. The remaining six contacts are 

classified as unidentified amorphous objects. None of the twelve sonar contacts are interpreted as 

archaeologically significant. There are no other unusual depressions, scours, sediment changes, or 

unidentified seafloor targets observed within the survey area that could represent unidentified shipwreck 

remains.

Fugro (2011) performed a survey extension to the 2009 high resolution geophysical survey identifying 37 

sonar contacts. A majority of the sonar targets observed are fairly small in size and measure less than 25’ in 

length and width. Contacts Nos. 1-14 and 16-20 appear as hard contacts, likely representing man-made 

debris. Contacts Nos. 15 and 25-37 appear geologic in origin. Sonar contact No. 19 is at the terminus of an 

anchor drag scar. The drag scar runs in a north-south direction and is within 10,000’ of the DC353 #1 well 

location. The drag scar and associated contact are interpreted to be the result of prior construction activities. 

No unusual depressions, scours, sediment changes, or unidentified seafloor targets were observed that could 

represent unidentified shipwreck remains. 

Shell will comply with all conditions of NTL 2008-G20. 

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 in this Plan. 

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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: Corinth

Type of Waste and Composition Composition Projected Amount Discharge rate Discharge Method Answer yes or no

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 No

Spent Water based drilling fluid barite, additives, water 20,000 bbls / well 4000 bbls / day

Overboard and seafloor discharge prior 

to marine riser installation No

Spent Synthetic-based drilling fluid barite, additives, synthetic based mud 2500 bbls / well NA Synthetic based mud is recycled No

Drill cuttings from water based hole interval

cuttings coated with water based drilling 

mud 3500 bbls / well 1000 bbls / day

Shunt through a downpipe to 15’ below 

the water’s surface No

Washed drill cuttings from synthetic based hole interval

cuttings coated with synthetic based 

drilling mud 3500 bbls / well 100 bbls / day

Shunt through a downpipe to 15’ below 

the water’s surface No

Synthetic based drilling fluid adhering to washed drill 

cuttings barite, additives, synthetic based mud 55 bbls/ well 2.5 bbls / day

Shunt through a downpipe to 15’ below 

the water’s surface

Chemical product waste Chemical product waste NA NA NA No

Will humans be there? If yes, expect conventional waste

EXAMPLE: Sanitary waste water X liter/person/day NA chlorinate and discharge No

Domestic waste (kitchen water, shower water) grey water 21,600 bbls/well 180 bbls / day

Grinded to less than 25 mm mesh size 

and discharge overboard No

Sanitary waste (toilet water) treated sanitary waste 7080 bbls/well 60 bbls / day

Treated in the MSD** prior to discharge 

to meet NPDES limits No

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

Deck Drainage Wash and rainwater

10,800 bbls / well 

Rainfall Dependant 100 bbls / day

Oily water is treated in Oily Water 

Separator discharded Port and 

Starboard Caisson No

Will you conduct well treatment, completion, or workover? 

well treatment fluids NA NA NA NA No

well completion fluids NA NA NA NA No

workover fluids NA NA NA NA No

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

Desalinization unit discharge Rejected water from watermaker unit 1140 bbls / well 10 bbls /day

Shunt through a downpipe to 15’ below 

the water’s surface No

Blowout prevent fluid Water based 90 bbls/well 1 bbls/day Disharge at seafloor No

Ballast water Uncontaminated seawater 132,000 bbls / well 2,000 bbls / day

Dischard Port and Starboard low sea 

chests, 75.5' below waterline No

Bilge water

Bilge and drainage water will be treated to 

MARPOL standards (< 15ppm oil in water). 100,000 bbls / well 2,000 bbls / day

Oily water is treated in Oily Water 

Separator discharded Port and 

Starboard Caisson No

Excess cement at seafloor Cement slurry

420 bbls/well (assume planned 

100% excess is discharged) 420 bbls / well

Discharged at the seafloor during 

riserless drilling No

Fire water Seawater 31,500,000 bbls / well 260,000 bbls / day Port and Starboard Caisson No

Cooling water Seawater 31,500,000 bbls / well 260,000 bbls / day Port and Starboard Caisson No

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

Produced water NA NA NA 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 

Downhole 

Projected generated waste Projected ocean discharges Disposal

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B. Projected Generated Wastes 

Supplmental EP: Corinth

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 - Fourchon, LA 2,500 bbls/well Recycled

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

Cuttings wetted with Synthetic-based fluid 

Drill cuttings from synthetic 

based interval storage tank on supply boat. Newpark - Fourchon, LA 75 bbls / well Recycled

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 bbls / well 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 450 bbls / well 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 85 bbls / well recycled

Hazardous Waste

paints, solvents and unused 

chemicals drums on supply boat Safety Kleep, Denton, TX 330 bbls / well recycled

Universal Waste Items

Batteries, lamps, glass and 

mercury-contaminated 

waste drums on supply boat Lamp Environmental, Hammond, LA 10 bbls/ well landfill

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

SOx

NOx

VOC

CO

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

 Note: AQR Worksheets are included in this Plan. 

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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 

(Operator Number 0689) in accordance with 30 CFR 250. Updates to the Regional OSRP were filed with 

the BSEE October 26, 2010, March 15, 2011, May 31, 2011, July 6, 2011 and August 1, 2011 and are 

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

BSEE on August 4, 2011. Spill Response sites are as follows: 

Primary Response Equipment Locations Preplanned Staging Location(s) 

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

Charles, LA

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

Table 9.1 – Response Equipment and Staging Areas 

The names of the OSRO’s under contract include Clean Gulf Associates (CGA), Marine Spill Response 

Company (MSRC), Clean Caribbean America (CCA), and OSRL/EARL. 

Category Regional OSRP EP

Type of Activity1 Drilling Rig Drilling Rig 

Facility Location (area/block) MC 807 MC 393

Facility Designation2Subsea well A◊ Subsea well Q

Distance to Nearest Shoreline (miles) 53 75

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

364,000** BOPD

364,000 Bbls

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

diesel)

Crude oil Crude oil

API Gravity(s)426o 37.5o

Table 9.2 - Worst Case Scenario Determination 

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

**24 hour rate (353,000 BOPD 30 day average) 

◊MC 807 Subsea Well A 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). 

Since Shell has the capability to respond to the appropriate worst-case spill scenario included in its regional 

OSRP, updated with the BOEM 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 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

1. 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 BOEM Oil Spill Risk Analysis Model (OSRAM) for the Central and Western 

Gulf of Mexico available on the BOEM 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

MC 393 26254 57

Cameron, LA 1

Vermilion, LA 1

Iberia, LA -

Terreboone, LA 2

Lafourche, LA 2

Jefferson, LA -

Plaquemines, LA 21

St. Benard, LA 3

Hancok & Harrison, MS 1

Jackson, MS 1

Mobile, AL 1

Baldwin, AL 1

Escambia, FL 1

Okaloosa, FL 1

Walton, FL 1

Bay. FL 1

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 BOEM 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 Mississippi Canyon 393 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. 

Examples of Environmental Sensitivity maps for Plaquemines Parish are detailed in the following 

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

9.C.5. 

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 MC 393 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: 

Mississippi Canyon 393

Calculations

(BBLS)

i. 30 Day Average WCD = 353,000 bbls

ii. Subsurface dispersion – 25% (Water Depth = ~7,375’) -88,200 bbls

iii. REMAINING WCD AFTER SUBSURFACE DISPERSION 264,800 bbls

iv. Surface dispersion and evaporation – 25% -66,200 bbls

TOTAL REMAINING ~198,600 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. 

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 

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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 to the maximum extent practicable, within 43.5 hours 

based on the equipment’s effective de-rated recovery 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 COTP and the RRT. 

Subsea Control and Containment: Shell, as a founding member of the Marine Well Containment 

Company (MWCC), will have access to the Incidence Response Command System (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 MC 393 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 585,800 

barrels/day. Temporary storage associated with the identified skimming and temporary storage 

equipment equals approximately 498,124 barrels. 

De-rated Recovery Rate

(bopd)

Storage

(bbls)

Offshore Recovery and 

Storage 478,907 480,900

Nearshore Recovery and 

Storage 106,993 17,224

Total 585,840 498,124

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

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 

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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 in 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 

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 

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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 clean-up operations. Each response mode is schematically 

represented to show optimum deployment and 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. 

B. 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 and Storage Activation List

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Table 9.D.5 Nearshore On-Water Recovery and Storage Activation List (continued) 

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Table 9.D.5 Nearshore On-Water Recovery and Storage Activation List (continued) 

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Table 9.D.5 Nearshore On-Water Recovery and Storage Activation List (continued) 

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Table 9.D.6 Aerial Surveillance Activation List 

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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) 

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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 BOEM: 

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

Lease OCS-G 26254 was part of Lease Sale #190, held on March 17, 2004. The lease is in its primary term. The 

lease is not part of a Biological Sensitive Area, known Chemosynthetic Area, or Shipping Fairway. See Section 6 of 

this plan for site specific archeological information. 

Stipulation No. 3 – Military Areas 

This lease is in the Water Test Area of the Eglin Water Test Areas 1 and 3. Shell will hold and save harmless the 

U.S. Government, its contractors and subcontractors, or any of its officers, agents or employees with regard to this 

Lease. Electromagnetic emissions will be conducted as to not interfere with the Department of Defense operations. 

Shell will enter into an agreement with the Commander of the Air Armament Center in Eglin AFB, Florida, when 

operating boats, ships and aircraft traffic in the designated warning area. 

Stipulation No. 6 – Protected Species 

This Stipulation is addressed in the following sections of this plan: 

Section 6h, Threatened or endangered species, critical habitat, and marine mammal information 

Section 10b, Environmental Monitoring Information, Incidental takes 

Section 12b, Environmental Mitigation Measures Information, Incidental takes 

Section 18, Environmental Impact Assessment 

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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 OSRP. 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 BOEM: 

NTL 2007-G03 “Marine Trash and Debris Awareness and Elimination”

NTL 2007-G04 “Vessel Strike Avoidance and Injured/Dead Protected Species Reporting”

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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

Tug boats 200,000 2 Three days

Anchor handling vessel 100,000 3 20 days

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 MC 393

C. Drilling Fluids Transportation 

The following table is required for operations in the State of Florida and is being provided as 

information only: 

Type of Material Quantity Being Transported Transportation Method

Dry Bulk (Cement, Barite, Gel) 12,000 sacks 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 18.1 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

Boothville Heliport Boothville, LA Existing

The onshore support bases for water and air transportation will be the existing terminals in Boothville and 

Fourchon, Louisiana. The Fourchon boat facility is operated by Shell 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 Boothville, LA is located at 38963 Hwy. 23, Boothville, LA 70041. 

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. 

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SECTION 16: SULPHUR OPERATIONS INFORMATION

Information regarding Sulphur Operations is not included in this SEP as we are not proposing to conduct 

sulphur operations. 

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SECTION 17: COASTAL ZONE MANAGEMENT ACT (CZMA) INFORMATION

Louisiana Coastal Zone Consistency was granted in Plan N-8379 on June 2, 2005, and is not required for 

Supplmental Exploration Plans. 

Alamaba Coastal Zone Consistency is required for a Supplemental Exploration Plan and the consistency 

follows. 

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ALABAMA

COASTAL ZONE MANAGEMENT 

CONSISTENCY CERTIFICATION 

SUPPLEMENTAL EXPLORATION PLAN 

Type of Plan 

 

MISSISSIPPI CANYON Block 393

 Area and Blocks 

OCS-G 26254

Lease Number 

The proposed activities described in detail in this Plan will comply with Alabama's State and Local Coastal 

Resources Management Act of 1978, Coastal Resources Program, and Coastal Area Management 

Enforceable Policies. 

We have considered all of Alabama's Enforceable Policies in making this certification of consistency. 

SHELL OFFSHORE INC.

Operator 

____________________________________________ 

Sylvia Bellone 

Certifying Official 

 11/02/2011

Date 

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Coastal Zone Management Consistency Information 

For the State of Alabama 

In accordance with 30 CFR 250.226(a) and (b), Shell is hereby providing the following information in 

support of Section 18 (Environmental Impact Analysis) of our Exploration Plan for this lease. 

The regulations found in 15 CFR 930.58 identifies necessary data and information to be furnished to the 

State agency. The information is as follows: 

A. CONSISTENCY CERTIFICATION

A Coastal Zone Consistency Certification for activities that affect the State of Alabama is 

provided in Section 17 of this SEP. 

B. OTHER INFORMATION

(1) Shell shall utilize a shore base in Fourchon, Louisiana for water support and PHI’s 

Boothville terminal for air traffic for the proposed activities. 

(2) As per NTL 2008-G04, the following items have been identified as being required: 

 A discussion of the method of disposal of wastes and discharges is provided in Section 7 

of this EP. 

 Oil Spill Information is provided in Section 9 of this SEP. 

 All operations are covered by Shell’s regional OSRP, which has been updated and is 

pending approval by BOEM. The Plan is available upon request. 

(3) Following is an evaluation that includes findings relating the coastal effects of the 

proposed activities and associated facilities to the relevant enforceable policies of the 

Alabama’s Coastal Management Program:

 

All activities shall be consistent with Alabama’s coastal management program and shall 

comply with all relevant rules and regulations. Pollution shall be prevented or reduced at the 

source; pollution that cannot be prevented shall be recycled in an environmentally safe 

manner; pollution that cannot be prevented or recycled shall be treated in an 

environmentally safe manner; and disposal or other release into the environment shall be 

employed only as a last resort and should be conducted in an environmentally safe manner. 

All activities comply with all applicable provisions of the administrative code. No activities are 

planned within special management areas. Activities will be carried out avoid unnecessary 

conflicts with other uses of the vicinity. 

COASTAL RESOURCE USE POLICIES

Coastal Development – All activities shall be conducted in a manner that minimizes significant 

impacts to coastal resources. No adverse effects to Alabama’s coastal area are expected in 

association with the proposed activities. 

 

Mineral Resource Exploration and Extraction – No conflicts with any other mineral resource 

exploration and extraction are expected. 

Commercial Fishing – All uses and activities shall be planned, sited, designed, constructed, 

operated and maintained to avoid to the maximum extent practicable adverse disruptions to 

fishery migratory patterns. 

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Hazard Management- Effective emergency plans are in place, practiced, and updated as 

necessary. The best practical techniques shall be utilized to prevent the release of pollutants 

or toxic substances into the environment.

Shoreline Erosion - All uses and activities shall be planned, sited, designed, constructed 

operated and maintained to avoid to the maximum extent practicable adverse alteration of 

protective coastal features 

Recreation – We have considered the general factors utilized by permitting authorities and 

have determined that the proposed activities shall cause no adverse impacts on areas of 

public use or concern, and all uses and activities shall be planned, sited, designed, 

constructed operated and maintained to avoid to the maximum extent practicable adverse 

alteration of these areas. The BOEM has regulations in place which explicitly prohibit the 

disposal of equipment, cables, chains, chains, containers or other materials which may pose 

an unreasonable risk to public health, property, aquatic life, wildlife, recreation, navigation, 

commercial fishing, or other uses of the ocean into offshore waters. Although marine debris 

gets lost from time to time, the impact on Gulf Coast recreational beaches is expected to be 

minimal. No impacts are expected to adversely affect Public access to tidal and submerged 

lands, navigable waters and beaches or other public recreational resources. 

Transportation- Alabama’s transportation resources are not expected to be impacted, as 

shore bases in Fourchon and Boothville, Louisiana will be utilized for the proposed 

operations. Also, boats will not travel through any sensitive coastal areas off of the coast of 

Alabama. 

NATURAL RESOURCE PROTECTION POLICIES

Biological Productivity - All uses and activities shall be planned, sited, designed, constructed

operated and maintained to avoid to the maximum extent practicable adverse alteration of 

biologically valuable areas. All uses and activities shall be planned, sited, designed, 

constructed, operated and maintained to avoid to the maximum extent practicable reductions 

in long-term biological productivity of the coastal ecosystem. No impacts are expected to 

adversely affect the biological productivity of the area. 

Water Quality - The proposed activities shall be carried out in conformance with applicable 

water quality laws, standards, and regulations. All discharges shall be covered by an NPDES 

permit. There shall be no discharge of untreated produced water, drilling muds, or cuttings 

resulting from energy exploration and production activities to the coastal waters of Alabama. 

Produced waters that are discharged offshore are diluted and dispersed to very near 

background levels at a distance of 1,000 m and are undetectable at a distance of 3,000 m 

from the discharge point. The BOEM regulations, the USEPA’s NPDES general permit, and 

the USCG regulations implementing MARPOL 73/78 Annex V prohibit the disposal of any 

trash and debris into the marine environment. 

Water Resources - All uses and activities shall be planned, sited, designed, constructed, 

operated and maintained to avoid to the maximum extent practicable detrimental discharges 

into coastal waters. 

Air Quality - The proposed activities shall be carried out in conformance with applicable air 

quality laws, standards, and regulations. Emissions from the proposed activities are not 

expected to have significant impacts on onshore air quality because of the prevailing 

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atmospheric conditions, emission heights, emission rates, and the distance of these 

emissions from the coastline. 

Wetlands and Submerged Grass beds - All uses and activities shall be planned, sited, 

designed, constructed operated and maintained to avoid to the maximum extent practicable 

reductions of natural circulation patterns within or into wetlands and submerged grass beds. 

Pipeline and navigation canals are considered the most significant impacting factors to 

wetlands and neither is proposed in the SEP. Proposed activities are not expected to have 

any adverse impact on sea grass communities. 

Beach and Dune Protection - Effective environmental protection plans are in place, practiced, 

and updated as necessary. No significant impacts to the physical shape and structure of 

barrier beaches and associated dunes are expected to occur. In the unlikely event of a spill 

contacting a barrier beach, sand removal during cleanup would be minimized. 

Wildlife Habitat Protection - We have considered the general factors utilized by permitting 

authorities and have determined that the proposed activities shall cause no adverse impacts 

on wildlife habitat areas. All uses and activities shall be planned, sited, designed, constructed 

operated and maintained to avoid to the maximum extent practicable adverse alteration of 

wildlife habitats or coastal wildlife. Proposed activities are in OCS waters, so they are located 

away from critical wildlife and vegetation areas. Access routes from shore base operations 

shall pose no adverse impacts on these critical wildlife and vegetation areas. 

Endangered Species 

No impacts are expected to adversely affect wildlife and fishery habitat, especially the 

designated Critical Habitats of Endangered Species. 

Beach mice – Potential impacts include oil spills, oil-spill response activities, consumption of 

beach trash and debris and coastal habitat degradation. No significant impacts to beach 

mice are expected to occur. Protective measures required under the Endangered Species Act 

should prevent any oil-spill response and cleanup activities from having significant impact to 

beach mice and their habitat. 

Marine birds– Potential impact-producing factors for marine birds in the offshore environment 

include helicopter and service vessel traffic and noise, air emissions, degradation of water 

quality, habitat degradation, and ingestion discarded trash and debris from service vessels 

and OCS structures. Adverse impacts to endangered coastal and marine birds are expected 

to be sublethal. 

Sea turtles – Potential impact-producing factors from the proposed activities that may affect 

sea turtles include water quality degradation from operational discharges, noise from 

helicopter and vessel traffic and operating platforms, vessel collisions, brightly lit platforms, 

and swallowing or getting tangled in OCS-related trash and debris. Routine activities are 

expected to be sublethal and unlikely to have significant adverse effects on the size and 

recovery of any sea turtle species or population in the Gulf of Mexico. 

Sturgeon – Drilling mud discharges may contain chemicals toxic to sturgeon, at 

concentrations four or five orders of magnitude higher than concentrations found a few 

meters from the discharge point. These discharges dilute to background levels within 1000m 

of the discharge point. No impacts from the proposed activities are expected. 

Cultural Resources Protection - All uses and activities shall be planned, sited, designed, 

constructed, operated and maintained to avoid to the maximum extent practicable adverse 

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alteration of cultural resources. No impacts are expected to adversely affect historical, 

architectural, or archaeological sites. Should any historical, architectural, or archaeological 

resource be discovered in the course of conducting authorized activities, the Alabama 

Department of Environmental Management and the Alabama State Historical Officer shall be 

notified. 

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SECTION 18: ENVIRONMENTAL IMPACT ANALYSIS (EIA)

Introduction 

Project Summary 

Shell is submitting a SEP for MC Block 393. Shell submitted an initial EP for Well A in MC 393, 

which was approved by the former Minerals Management Service (MMS) on 7 July 2005 

(Plan Control No. N-8379). Shell is now submitting a SEP that includes six exploration wells in 

MC 393; these are A, Q, QST (a sidetrack to be drilled from the Q surface hole location), R, S, 

and T. This SEP also incorporates the revised blowout scenario and worst case discharge (WCD) 

information as required by Notice to Lessees and Operators (NTL) 2010-N06. 

The lease area is 75 miles (120 km) from the nearest shoreline (Louisiana), 162 miles (261 km) 

from the onshore support base at Port Fourchon, Louisiana, and 100 miles (161 km) from the 

helicopter base at Boothville, Louisiana (Figure 18.1). All miles in this EIA are statute miles. 

Water depths at the wellsites range from 7,301 to 7,385 ft (2,225 to 2,251 m).

The Transocean Deepwater Nautilus, a moored semisubmersible rig, or an equivalent rig will be 

used for drilling. Drilling of wells will commence during the second quarter of 2012 and should 

be finished by the second quarter of 2016. The average time to drill a well will be approximately 

100 days for wells A, R, S, T, and 107 and 62 days for Q and QST, respectively. 

Purpose of the EIA 

This Environmental Impact Analysis (EIA) was prepared pursuant to the requirements of the 

Outer Continental Shelf Lands Act (OCSLA), 43 United States Code (U.S.C.) §§ 1331-1356, and 

other regulations, including 30 Code of Federal Regulations (CFR) 250.212(o) and 250.227. The 

EIA is a project- and site-specific analysis of Shell’s planned activities under this EP. In keeping 

with the reorganization of the Bureau of Ocean Energy Management, Regulation, and 

Enforcement (BOEMRE) on October 1, 2011, into two separate agencies, Shell understands that 

the new Bureau of Ocean Energy Management (BOEM) will review this EIA and prepare a 

site-specific environmental assessment (SEA) for the project. This EIA complies with guidance 

provided in existing NTLs issued by the former MMS and BOEMRE, including NTL 2008-G04. 

Throughout this EIA, when existing guidance and general agency activities are referred to, 

“BOEM” is meant to subsume the former agencies and to represent the continuous regulatory 

entity now called BOEM. The former agency names (MMS and BOEMRE) are used only when 

referring to particular historical documents published under those names. In addition, until 

regulations promulgated under 30 Code of Federal Regulations (CFR) & NTLs are reissued under 

one of the two new agencies, the EIA will refer to the former BOEMRE as BOEM when addressing 

30 CFR or the NTLs. 

The EIA presents data, analysis, and conclusions to support BOEM 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 BOEM 

considers this SEP for approval. It also identifies the mitigation measures Shell will implement in 

connection with the planned activities. 

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Figure 18.1. Vicinity map for the lease area. 

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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 SEP including drilling of wells. The EIA also 

incorporates the revised blowout scenario and WCD information required by NTL 2010-N06. 

The BOEM 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 multi-lease-sale EISs for the Western and Central Gulf of Mexico 

Planning Areas (MMS, 2007b, 2008b), as well as the Environmental Assessment (EA) for Gulf of 

Mexico deepwater operations and activities (MMS, 2000) and a Grid EA for the Thunder Horse 

Project in MC 777 [Grid 16] (MMS, 2002). 

These studies generated critical data and advanced the large body of existing knowledge on the 

Gulf of Mexico OCS. They analyze potential impacts on the natural environment, the 

socioeconomic effects of exploration and development activities, and other regional resources. 

Numerous technical studies address the likely trajectory of spilled oil, the effects of underwater 

noise on threatened and endangered species, and other IPFs. The studies 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 BOEM and other regulatory agencies to 

evaluate Shell’s SEP 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 

BOEM 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 BOEM operating 

regulations are in 30 CFR Parts 250, 251, and 254. 

In implementing its responsibilities under the OCSLA and NEPA, the BOEM 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 BSEE 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 BOEM interpretation of a requirement; or transmit administrative 

information such as current telephone listings or changes in BOEM personnel or office address. 

Table 18.1 lists and summarizes the NTLs that are referenced in this EIA. 

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Table 18.1. 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 BOEM 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 WCD scenario, and 

provides guidance regarding the information required in 

blowout scenario and worst case discharge scenario 

descriptions.

2009-G40 Deepwater Benthic 

Communities

Guidance for avoiding and protecting high-density 

deepwater benthic communities (including 

chemosynthetic and deepwater coral communities) from 

damage caused by 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 

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NTL Title Summary

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.

Oil Spill Prevention and Contingency Planning 

Shell submitted an update to the Gulf of Mexico Regional Oil Spill Response Plan (OSRP) to the 

BOEM 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 SEP 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 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 18.2 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 Transocean Deepwater Nautilus or a similar moored 

semisubmersible rig. The rig will be on site for an estimated 100 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 rig 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 Nautilus uses 

anchors 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 

The semisubmersible rig will be held in place by either suction pile anchors or variable load 

anchors that will be deployed with an anchor radius of 15,500 ft (4,727 m) and within a 

clearance distance of 16,500 ft (5,029 m) around each wellsite. According to the MMS (2007b) 

semisubmersible rigs disturb about 5-7 ac (2-3 ha), depending on their mooring configurations. 

In taking the more conservative approach of 7 ac (3 ha) the total seafloor disturbance area is 

estimated to be 35 ac (15 ha) for the six wellsites (five surface locations). During anchor 

deployment, cables will be resting on the seafloor only during the pre- and post-installation 

phase; once the rig arrives on location, cables are pulled taut towards the rig. The cables do not 

sweep the seafloor or cross any sensitive features, and therefore are expected to have little or no 

physical impact on the seafloor. 

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Table 18.2. 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 

and 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 -- -- -- -- -- 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 18.2 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 BOEM 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. Features or areas that could support high-density chemosynthetic 

communities are not located within 250 ft (76 m) of any seafloor disturbances resulting from the use of 

anchors 

(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 BOEM classify the area in the proposed drilling operations as 

an area where the presence 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 BOEM 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 on the list of archaeology survey 

blocks but not on the list of high-probability blocks for shipwrecks (MMS, 2008a). The seafloor patterning 

and acoustic characteristics of the sonar targets detected during the archaeological survey conclude that 

they are either geologic in origin or are modern debris. However, there was one partially buried sonar 

contact along a proposed anchor location that will be avoided during anchor placement. The lease is well 

beyond the 60-m depth contour used by the BOEM as the seaward extent for prehistoric archaeological 

site potential in the Gulf of Mexico. 

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

or sea turtles or their critical habitats. 

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

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

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

Not applicable. 

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A.3 Air Pollutant Emissions 

Estimates of air pollutant emissions are provided in SEP 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 BOEM requirements shows that 

the projected emissions are below exemption levels; therefore, according to 30 CFR 250.303, the 

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

pollutants. No further analysis or control measures are required. However, Shell will use 

low-sulfur fuel to further reduce any possible impacts. 

A.4 Effluent Discharges 

Effluent discharges are summarized in SEP Section 7. 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 mud 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 provided in SEP Section 7. 

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 

(SEP 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 impacts from impingement and entrainment of 

aquatic organisms. Construction of the rig planned for use in this SEP, the Transocean 

Deepwater Nautilus, started prior to 17 July 2006, and therefore is not subject to the cooling 

water intake permit requirements of NPDES Permit GMG290000. If a different rig is selected, it 

will comply with applicable NPDES requirements. 

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A.6 Onshore Waste Disposal 

Wastes generated during drilling are tabulated in SEP 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, 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 or ARC 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 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 BOEM regulations and NTLs regarding solid wastes. BOEM 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 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 Boothville, 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 and support vessels 

will make two round-trips per week between the drilling facility and the onshore supply base, and 

there will likely be at least one vessel in the field at all times. The boats will normally move to 

the project area via the most direct route from the shorebase. Two tugboats and three anchorhandling vessels will assist in mobilization and demobilization of the rig. 

The air transportation base will be the PHI Heliport in Boothville, 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. 

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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 SEP 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). 

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 75 miles (120 km) from the nearest shoreline (Louisiana). Modeling results 

discussed below indicate that a spill in the lease area would have a 21% probability of contacting 

the nearest Louisiana shoreline (Plaquemines 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 

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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. SEP 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 

SEP 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 MC 348 and 392, and DeSoto Canyon 353. 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 SEP, using the requirements prescribed by NTL 

2010-N06. The WCD is 364,000 bbl for the first day with a 30-day average of 353,000 barrels 

per day (BPD). The estimated time to drill a relief well is 128 days, and the total volume of a 

spill over this duration is estimated to be 44.9 million barrels of oil (MMBO). The detailed 

analysis of this calculation can be found in SEP Section 2j. The WCD scenario for this SEP, 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. 

Shell has a robust system in place to prevent blowouts. Included in SEP 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 57 (where the lease 

area is located) are presented in Table 18.3. The model predicts shoreline contact with 

4 parishes in Louisiana within 3 or 10 days. After 30 days, 14 counties and parishes from 

Cameron, Louisiana to Bay, Florida may be contacted. Plaquemines Parish, Louisiana has the 

greatest probability of shoreline contact, with a 21% chance within 30 days. 

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Table 18.3. 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 57) 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

C13 Cameron, LA -- -- 1

C14 Vermilion, LA -- -- 1

C17 Terrebonne, LA -- 1 2

C18 Lafourche, LA -- 1 2

C20 Plaquemines, LA 4 14 21

C21 St. Bernard, LA -- 1 3

C22 Hancock and Harrison, 

MS -- -- 1

C23 Jackson, MS -- -- 1

C24 Mobile, AL -- -- 1

C25 Baldwin, AL -- -- 1

C26 Escambia, AL -- -- 1

C28 Okaloosa, FL -- -- 1

C29 Walton, FL -- -- 1

C30 Bay, FL -- -- 1

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 

BOEM 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 

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 for Permit to 

Drill (APD) is submitted and will include equipment and services available to Shell through 

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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 well 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 SEP 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. 

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. Other than the 

presence of hydrogen sulfide (H2S), which is addressed below, no other site-specific issues have 

been identified for this SEP. 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 project addressed by this SEP does not anticipate the use of 

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zinc bromide or ammonium chloride. 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 USCG and BOEM-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 SEP 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 SEP 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 presence of H2S has been confirmed. An H2S contingency plan 

will be prepared and filed with the APD. 

B. Affected Environment 

The lease area is in the north-central Gulf of Mexico, 75 miles (120 km) from the nearest 

shoreline (Louisiana), 162 miles (261 km) from the onshore support base at Port Fourchon, 

Louisiana, and 100 miles (161 km) from the helicopter base at Boothville, Louisiana 

(Figure 18.1).

There is no evidence of seafloor or near-surface faulting, slumping, anomalous amplitudes or 

fluid expulsion features in the vicinity of the proposed well locations A, Q, QST, R, S, and T in 

MC 393. Water depths at these well locations range from 7,301 to 7,385 ft (2,225 to 2,251 m) 

(Section 1, Attachment 1A). The side-scan sonar survey confirmed the absence of pipelines 

and flowlines in the vicinity of MC 393. The sonar targets identified were not within 2,000 ft (610 

m) of the proposed wellsites except for one target that was located 1,456 ft (444 m) from 

proposed well location T (AOA Geophysics, Inc., 2004; Fugro Geoservices, Inc., 2009a) and two 

targets that were located 674 ft (205 m) and 1,780 ft (543 m) from Location A (Fugro 

Geoservices, Inc., 2007). 

A detailed description of the regional affected environment is provided in recent EISs 

(MMS, 2007b, 2008b), 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. 

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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, 2008b). 

The lease area is approximately 28 miles (46 km) southeast of the Macondo spill site. Based on 

an analysis of satellite imagery (ESRI, 2010), the surface slick extended over the lease area prior 

to capping of the well; therefore, existing water quality in the lease area could have been 

temporarily affected. Macondo spill impacts are addressed in Section C.9 (Cumulative Impacts) 

where available and applicable. 

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, 2008b). 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 30 August 2011, all Louisiana, Mississippi, Alabama, and Florida coastal counties and 

parishes are in attainment of the NAAQS for all criteria pollutants (USEPA, 2011). One coastal 

metropolitan area in Texas (Houston-Galveston-Brazoria) is nonattainment for 8-h ozone. 

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. 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 

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emissions from the coastline. The Air Quality Emissions Report (see SEP Section 8) prepared in 

accordance with BOEM 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 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 BOEM 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 94 miles (151 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 BOEM. 

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, 2008b). 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. 

SEP 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, 2008b). 

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 (75 miles [120 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 18.3), Plaquemines Parish, Louisiana is the coastal area most likely 

to 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 as detailed in

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SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 28 miles (46 km) southeast of the Macondo spill site. Based on 

satellite imagery (ESRI, 2010), the surface slick extended over the lease area during the spill, and 

therefore existing water quality in the lease area could have been temporarily 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). 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. 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. 

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. 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. 

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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, 2008b). 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. SEP 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, 2008b). 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) 

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. 

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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 (75 miles [120 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 18.3), nearshore waters and embayments of Plaquemines Parish, Louisiana, 

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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 7,301 to 7,385 ft (2,225 to 2,251 

m). The seafloor at the wellsites is expected to consist mainly of soft bottom. The 

chemosynthetic community assessment based on the hazards report by AOA Geophysics, Inc. 

(2004) and Fugro Geoservices, Inc. (2007, 2009b and 2011) did not identify any features that 

could support high-density deepwater benthic communities within 2,000 ft (610 m) of the 

wellsites. See SEP 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. MC 

393 is within deepwater Grid 16, and the BOEM website indicates that remotely operated vehicle 

(ROV) coverage of the seafloor in this grid is adequate to characterize the area (BOEMRE, 2011). 

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 18.4 summarizes data from two nearby stations in similar water 

depths. Sediments at those two stations were predominantly clay (51% to 57%) and silt 

(35% to 41%). 

Table 18.4. 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)

S-37 12 mi SE 2,384 291,179 2,192 1,451

S-36 27 mi NE 1,828 799,963 4,481 359

Meiofaunal and megafaunal abundance from Rowe and Kennicutt (2009); macroinfaunal 

abundance from Wei (2006). 

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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 120,000 to 

290,000 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 

1,300 individuals/m2, lower than the values in Table 18.4. 

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 2E, which consists of stations on the mid Texas-Louisiana slope, west flank 

of the Mississippi Fan, mid Mississippi Canyon, head of De Soto Canyon and mid West Florida 

Terrace. These stations range in depth from 2,051 to 5,997 ft (625 to 1,828 m). The five most 

abundant species in Zone 2E were the polychaetes Litocorsa antennata, Aricidea suecica,Tharyx 

marioni, Paralacydonia paradoxa, and one bivalve Heterodonta sp. 

Megafaunal density from nearby stations S-37 and S-36 was 1,451 and 359 individuals/ha, 

respectively (Table 18.4). Densities of 250 to 1,600 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. 

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 soft bottom benthic communities are physical disturbance to the 

seafloor, effluent discharges (drilling mud and cuttings), and a large oil spill resulting from a well 

blowout at the seafloor. A small fuel spill would not affect soft bottom benthic communities 

because the diesel fuel would float and dissipate on the sea surface. 

Impacts of Physical Disturbance to the Seafloor 

There will be minimal disturbance to soft bottom communities on the seafloor during positioning 

and anchoring of the semisubmersible Transocean Deepwater Nautilus. Shell is proposing anchor 

radii of 15,500 ft (4,724 m) for the wellsites; the total anchor clearance radius will be 16,500 ft 

(5,029 m). Cables may initially be laid on the seafloor anywhere within the anchor radius (except 

for avoidance zones based on the hazards survey as detailed in SEP Section 6a). According to 

the MMS (2007b) semisubmersible rigs disturb about 5-7 ac (2-3 ha), depending on their 

mooring configurations. The total seafloor disturbance area is estimated to be 35 ac (15 ha) for 

the six wellsites (five surface locations). During anchor deployment, cables will be resting on the 

seafloor only during the pre- and post-installation phase; once the rig arrives on location, cables 

are pulled taut towards the rig. The cables do not sweep the seafloor or cross any sensitive 

features, and therefore they are expected to have little or no physical impact on benthic 

communities. 

The seafloor in the project area is expected to consist of soft bottom benthic habitat. Small 

anchor and/or cable scars created during the project will likely remain on the bottom for months 

to years (Shinn et al., 1993). In a recent study of drillsites on the Gulf of Mexico continental 

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slope, Continental Shelf Associates, Inc. (2006) detected anchor scars up to 14 years after drilling 

was completed. These features will eventually disappear as sediments are redistributed by 

currents and benthic organisms. 

Soft bottom communities are ubiquitous along the northern Gulf of Mexico continental slope 

(Gallaway et al., 2003; Rowe and Kennicutt, 2009). Physical disturbance to the seafloor during 

this project will have no significant impact on soft bottom benthic communities on a regional 

basis. 

Impacts of Effluent Discharges 

Drilling mud 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 mud (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 mud, 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; the typical effect radius is 

1,640 ft (500 m) around each wellsite. For the five surface locations in this exploration-drilling 

program, the total impact area would be 970 acres (390 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. 

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). 

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Previous analyses (MMS, 2007a, 2008b) 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, 2008b), 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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, high-density deepwater corals, or 

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 SEP, based on the shallow hazards 

reports by AOA Geophysics, Inc. (2004) and Fugro Geoservices, Inc. (2007, 2009b & 2011), 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. 

IPFs potentially affecting high-density deepwater benthic communities are effluent discharges 

(drilling mud 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. 

Impacts of Physical Disturbance to the Seafloor 

Features or areas that could support high-density benthic communities are not located within 250 

ft (76 m) of any areas where seafloor disturbance may result from the use of anchors (including 

those caused by anchors, anchor chains, and wire ropes ) (AOA Geophysics, Inc., 2004; Fugro 

Geoservices, Inc., 2007, 2009b, 2011). 

Impacts of Effluent Discharges 

The chemosynthetic community assessment included in this SEP, based on the shallow hazards 

reports by AOA Geophysics, Inc. (2004) and Fugro Geoservices, Inc. (2007, 2009b, 2011), did 

Page 118 Public Information Copy
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, 2008b) 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, 2008b), 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). 

The potential for a spill to affect deepwater corals is indicated by preliminary findings from an 

October 2010 survey of deepwater coral habitats near the Macondo spill site (BOEMRE, 2010). 

Government and academic researchers working at a site 4,600 ft (1,400 m) deep and 

approximately 7 miles (11 km) southwest of the Macondo wellhead observed dead and dying 

corals with sloughing tissue and discoloration. The study location was about 29 miles (47 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. 

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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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 designated topographic feature is in the West Delta 

Area, South Addition Block 147 , located 94 miles (151 km) west 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 43 miles (69 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. 

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 

54 miles (86 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. 

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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 18.5. 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 18.5 and discussed in individual 

sections.

Table 18.5 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, Eb 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

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Table 18.5 (Continued.) 

Species Scientific Name Status

Potential 

Presence Critical Habitat 

Designated in

Gulf of Mexico Lease 

Area Coastal

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 composed of nine distinct population segments (DPS) that are considered “species.” The 

only DPS that may occur in the project area (Northwest Atlantic DPS) is listed as threatened (76 FR 58868; 

September 22, 2011). 

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. 

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 

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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). 

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, 2008b) 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 BOEM 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 

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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. 

Impacts of a Small Fuel Spill 

Potential spill impacts on marine mammals including sperm whales are discussed in recent EISs 

(MMS, 2007b, 2008b) 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 SEP 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. SEP 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, 2008b) and by the NMFS (2007) in its Biological Opinion for the Five-Year Oil and 

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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 SEP, there 

are no unique site-specific issues with respect to spill impacts on these animals. 

Impacts of oil spills on sperm whales can include direct impacts from oil exposure, as well as 

indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and 

dispersants) (MMC, 2010). Direct physical and physiological effects can include skin irritation, 

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 

toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey; and stress from 

the activities and noise of response vessels and aircraft. Complications of the above may lead to 

dysfunction of immune and reproductive systems, physiological stress, declining physical 

condition, and death. Behavioral responses can include displacement of animals from prime 

habitat, disruption of social structure, changing prey availability and foraging distribution and/or 

patterns, changing reproductive behavior/productivity, and changing movement patterns or 

migration (MMC, 2010). 

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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 75 miles (120 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 BOEM has issued NTL 2007-G04, which recommends 

protected species identification training and that vessel operators and crews maintain a vigilant 

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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). 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 18.3 predict that some Louisiana, Mississippi, Alabama, 

and Florida 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 

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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 

Mexico. Potential impacts are analyzed in recent lease sale EISs (MMS, 2007b, 2008b), 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 SEP 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 De Soto 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 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.

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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, 2008b). 

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 BOEM 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).

Impacts of a Small Fuel Spill 

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008b), 

and oil impacts on marine mammals in general are discussed by Geraci and St. Aubin (1990). 

For this SEP, 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. SEP Sections 2j and 9b provide 

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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, 2008b) 

and by Geraci and St. Aubin (1990). For this SEP, there are no unique site-specific issues. 

Impacts of oil spills on marine mammals can include direct impacts from oil exposure, as well as 

indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and 

dispersants) (MMC, 2010). Direct physical and physiological effects can include skin irritation, 

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 

toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey (or contaminated 

vegetation, in the case of manatees); and stress from the activities and noise of response vessels 

and aircraft. Complications of the above may lead to dysfunction of immune and reproductive 

systems, physiological stress, declining physical condition, and death. Behavioral responses can 

include displacement of animals from prime habitat, disruption of social structure, changing prey 

availability and foraging distribution and/or patterns, changing reproductive 

behavior/productivity, and changing movement patterns or migration (MMC, 2010). 

In the event of a large spill, the level of vessel and aircraft activity associated with spill response 

could disturb marine mammals and potentially result in vessel strikes, entanglement, or other 

injury or stress. Response vessels would operate in accordance with NTL 2007-G04 to reduce 

the potential for striking or disturbing these animals, and therefore no significant impacts are 

expected. 

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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 SEP 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). 

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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. 

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 

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(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 BOEM 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, 2008b) 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 SEP, there are no unique sitespecific 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. SEP 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, 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 75 miles (120 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., 

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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. SEP 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 18.3 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 21% after 30 days. 

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 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 

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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 18.3). 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).

Impacts of a Large Oil Spill 

The lease area is 77 miles (124 km) from the nearest shoreline inhabited by Piping Plovers. The 

OSRA results summarized in Table 18.3 predict that Louisiana and Mississippi shorelines 

designated as critical habitat for the wintering Piping Plover could be contacted by a spill within 

30 days. Plaquemines Parish, which has a 21% 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on Piping Plovers are expected.

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Figure 18.3. Location of selected environmental features in relation to the lease area. 

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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 18.3). 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 518 miles (833 km) from its critical habitat (Aransas NWR, Texas) and the 

OSRA modeling predicts that a spill in the lease area will not contact the shorelines of the 

Aransas NWR within 30 days. 

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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 

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Borgne, Louisiana (St. Bernard Parish) to Suwannee Sound, Florida (Levy County) (NMFS, 2010c) 

(Figure 18.3). 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, 2008b) 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 SEP, there are no unique sitespecific issues with respect to this species. 

The lease area is about 112 miles (181 km) from the nearest Gulf sturgeon critical habitat. The 

OSRA modeling (Table 18.3) predicts 1% probability that a spill in the lease area will 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 

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 

SEP 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. 

SEP 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 18.3 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, 2008b). For this 

SEP, there are no unique site-specific issues with respect to these species. 

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The lease area is about 111 miles (179 km) from the nearest beach mouse critical habitat. The 

OSRA modeling predicts that a spill in the lease area has 1% probability of contact with 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on beach mice are expected. 

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. 

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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 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 SEP, any impacts on populations of either seabirds or trans-Gulf migrant 

birds are not expected to be significant. 

A 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 SEP, 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, 2008b). For 

this SEP, 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. SEP 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 

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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 

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, 

2008b). For this SEP, 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 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 

(USFWS, 2011). 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 population of 

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Brown Pelicans lives in the northern Gulf Coast, generally nesting on protected islands (USFWS, 

2010b). 

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 75 miles (120 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 Boothville, 

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. 

Impacts of Large Oil Spill 

The OSRA results summarized in Table 18.3 predict that shorelines of Louisiana, Mississippi, 

Alabama, and Florida that include habitat for shorebirds and coastal nesting birds could be 

affected within 30 days. 

Data from the 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 USFWS (2011), bird species that were visibly oiled following the Macondo spill include the 

following: 

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Brown 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 

Common Tern 

Royal Tern 

Caspian Tern 

Sandwich Tern 

Forster’s Tern

Least Tern 

Black Skimmer 

White Ibis

Roseate Spoonbill 

Willet 

Sanderling 

Semipalmated Sandpiper 

Clapper Rail 

According to the USFWS (2011), 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. 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 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on shorebirds and coastal nesting birds are expected. 

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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. 

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 

(SEP Table 7a). Section 316(b) of the Clean Water Act requires NPDES permits to ensure that 

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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 SEP, the 

Transocean Deepwater Nautilus, started prior to 17 July 2006, and therefore is not subject to the 

cooling water intake permit requirements of NPDES Permit GMG290000. If a different rig is 

selected, it will comply with 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, 2008b). 

For this SEP, 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. SEP 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. 

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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 

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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 in the West Delta Area, South 

Addition, located 94 miles (151 km) west 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 bluefin tuna (spawning, eggs, larvae) 

Atlantic skipjack tuna (spawning, adults) 

Atlantic yellowfin tuna (spawning, juveniles, adults) 

Albacore tuna (adults) 

Atlantic swordfish (larvae, juveniles) 

Blue marlin (juveniles, adults) 

White marlin (juveniles, adults) 

Longbill spearfish (juveniles, adults) 

Oceanic whitetip shark (all) 

Silky shark (all) 

Longfin mako shark (all) 

Bigeye tresher shark (all) 

Whale shark (all) 

Research indicates the central and western Gulf of Mexico may be important spawning habitat for 

Atlantic bluefin tuna, and NMFS (2009) has designated a Habitat Area of Particular Concern 

(HAPC) for this species. The HAPC covers much of the deepwater Gulf of Mexico, including the 

lease area (Figure 3). The areal extent of the HAPC is approximately 300,000 km2 (15,000 mi2). 

The prevailing assumption is that Atlantic bluefin tuna follow an annual cycle of foraging in June 

through March off the eastern U.S. and Canadian coasts, followed by migration to the Gulf of 

Mexico to spawn in April, May, and June (NMFS, 2009). 

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 224 miles (360 km) southwest 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. 

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Impacts of Drilling Rig Presence, Noise, and Lights 

The drilling rig, as a floating structure in the deepwater environment, will act as 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 mud 

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. SEP 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. 

Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008b). For this SEP, 

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 in the 

West Delta Area, South Addition, located 94 miles (151 km) west of the lease area. A small fuel 

spill would float and dissipate on the sea surface and would not contact these features. 

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Impacts of a Large Oil Spill 

Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008b). For this SEP, 

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 43 miles (69 km) north-northwest of the lease area, is 

designated as EFH under the corals and coral reefs management plan. An accidental spill would 

be unlikely to affect this area. 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. 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

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 

MC 393 is not on the list of leases with high potential for historic shipwrecks. Two sonar contacts 

were identified along the impact zones for the proposed anchor array. One of these was 

interpreted as probable modern debris. The second contact could not be reliably identified and 

so will be avoided during anchor placement. None of the other sonar contacts outside of the 

potential impact zone have been interpreted as archaeologically significant (Fugro Geoservices, 

Inc., 2007, 2009a, 2011).

No historic shipwreck sites occur in the lease area (see SEP 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. 

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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 Louisiana, Mississippi, Alabama, 

and Florida 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, 2008b) 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, 2008b), depending 

on its extent, trajectory, and persistence. If oil from a subsea spill should come into contact with 

wooden shipwrecks on the seafloor it could adversely affect their condition or preservation. 

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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 7,301 to 7,385 ft (2,225 to 2,251 m), the wellsites are well 

beyond the 197-ft (60-m) depth contour used by the BOEM 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 18.3 predicts that Texas and Louisiana, Mississippi, Alabama, and Florida 

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). 

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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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 northern Gulf of Mexico that may be affected by oil and gas activities are 

described in recent EISs (MMS, 2007b, 2008b) 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. 

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 

Boothville are not located in wildlife refuges or wilderness areas. 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 75 miles (120 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 SEP 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, 2008b). 

Coastal habitats inshore of the project area include barrier beaches and dunes, wetlands, and 

submerged seagrass beds. For this SEP, there are no unique site-specific issues with respect to 

coastal habitats. 

The OSRA results summarized in Table 18.3 predict that shorelines of Louisiana, Mississippi, 

Alabama, and Florida could be affected within 30 days. Plaquemines Parish, Louisiana has the 

highest probability of contact for the 30-day intervals (21%). After 30 days, 14 counties or 

parishes may be contacted from Cameron, Louisiana, to Bay, Florida. 

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: 

Sabine NWR 

Cameron Prairie NWR 

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Hancock County Marsh Coastal Reserve 

Bon Secour NWR 

Grand Bay NWR 

Choctawatchee Bay Service Water and Impoundment Monitoring Area 

Point Washington Outstanding Florida Water 

Perdido Key State Recreation Area 

Cameron Prairie NWR 

LaCassine NWR 

Little Pecan Island Preserve 

Peveto Woods Sanctuary 

Lower Neches WMA 

Rockefeller WMA 

Paul J. Rainey WMA 

Atchafalaya Delta WMA 

Mandalay NWR 

Isles Dernieres Barrier Islands Refuge 

Pointe Au Chien WMA 

Wisner WMA 

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 

Buccaneer State Park 

Davis Bayou Coastal Preserve 

The Grand Bay Savanna Tract 

Meaher State Park 

Big Lagoon State Recreation Area 

Pensacola Bay Service Water and Impoundment Monitoring Area 

Henderson State Park 

St. Andrew Bay Watershed Service Water and Impoundment Monitoring Area 

Jourdan River Coastal Reserve 

Mississippi Sandhill Crane NWR

Penalver State Park 

Weeks Bay National Estuarine Research Reserve 

Fort Pickens State Park Aquatic Preserve 

St. Andrews State Park Aquatic Preserve 

Biloxi River Coastal Reserve 

Pascagoula River Coastal Reserve 

Gulf State Park 

Deer Lake State Park 

Grand Bay National Estuarine Research Reserve 

W.L. Holland WMA 

Grayton Beach State Park Outstanding Florida Water 

Tarkiln Bayou State Preserve 

Yellow River Wildife Management Area 

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Big Branch Marsh NWR 

Pearl River WMA 

Deer Island State Coastal Preserve 

Wolf River Coastal Reserve 

Old Fort Bayou Coastal Reserve 

Grand Bayou Coastal Preserve 

Bellefontaine Point Coastal Reserve 

Graveline Bay Coastal Reserve 

Bayou Portage Coastal Reserve 

Biloxi Marshes State Coastal Preserve 

The OSRA results in Table 18.3 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 open-water habitat. The critical concentration of oil is that concentration above 

which impacts to wetlands will be long-term and recovery will take longer than two growing 

seasons, and which causes plant mortality and some permanent wetland loss. Critical 

concentrations of various oils are expected to vary broadly for wetland types and wetland plant 

species. Louisiana wetlands are assumed to be more sensitive to oil contact than elsewhere in 

the Gulf because of high cumulative stress (MMS, 2007b). In addition to the direct impacts of oil, 

cleanup activities in marshes may accelerate rates of erosion and retard recovery rates, which 

have been reported to require from years to decades following a spill (MMS, 2007b). 

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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on coastal habitats are expected. 

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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). 

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 7,301 to 7,385 ft (2,225 to 2,251 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 in offshore waters of 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. SEP 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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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, 2008b). For 

this SEP, 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 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on fishing activities are expected. 

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. SEP 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 75 miles (120 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 

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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 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on public health and safety are expected. 

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. SEP 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, 2008b). 

For this SEP, 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 

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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 75 miles (120 km) from the nearest shoreline. Based on OSRA modeling as 

summarized in Table 18.3, Louisiana, Mississippi, Alabama, and Florida 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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. SEP 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 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, 2008b). For this SEP, 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 18.3, areas most likely to be contacted by a spill is Plaquemines Parish, 

Louisiana. 

In addition to the analysis presented by MMS (2007b, 2008b), 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). 

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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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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, 

2008b). 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 

SEP Section 2j. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate 

and reduce the impacts. SEP 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 located within the Eglin Water Test Area (EWTA) 1 Military Warning Area. Shell 

will comply with BOEM 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 BOEM 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 

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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 SEP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. SEP 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. MC 393 was acquired in Lease Sale No. 190 on 17 March 2004. 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 SEP in several documents. 

The level and types of activities planned in Shell's SEP 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, 2008b). 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 may occur in the vicinity of lease block MC 393. 

Cumulative Impacts of Activities in the SEP. The MMS (2007b) multi-lease-sale EIS included a 

lengthy discussion of cumulative impacts, which analyzed the environmental and 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 SEP 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 SEP, 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 

MC 252. While another large oil spill could have significant impacts, the numerous new safety 

measures implemented by the BOEM and further mitigation, and safety measures proposed by 

Shell in its SEP 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. 

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C.9.1 Cumulative Impacts to Physical/Chemical Resources 

The work planned in this SEP 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 BOEM found in the 

multi-lease-sale 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, 2008b). In addition, the 

cumulative contribution to visibility impairment is also very small (MMS, 2007b, 2008b). Since 

the BOEM completed the multi-lease-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 SEP 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 this SEP 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 this SEP. 

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 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 reached 

the lease area (ESRI, 2010). However, based on the information currently available, there is no 

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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 reached the lease area 

(ESRI, 2010), but it is unlikely that subsurface plumes could have permanently 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 SEP 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 BOEM-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 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 

Page 158 Public Information Copy
structures occur in the MC 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 Boothville, Louisiana, are not in wildlife refuges 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 the reasons discussed in this SEP, Shell’s NTL 2010-N06 response, and the OSRP, 

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, 2008b) 

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, 

2008b), 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 SEP is limited in geographic scope and duration, and the impacts on 

socioeconomic resources will be correspondingly limited. 

Archaeological Resources. MC 393 is not on the list of leases with a high potential for historic 

shipwrecks (MMS, 2008a). An archaeological assessment by Fugro Geoservices, Inc. 

(2007, 2009a, 2011) indicated that one of the sonar contacts in the lease area could not be 

reliably identified and will be avoided during anchor placement. Also, the lease area is well 

beyond the 197-ft (60-m) depth contour used by the BOEM 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. 

Page 159 Public Information Copy
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). The EISs 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 the reasons discussed in this SEP, Shell’s NTL 2010-N06 response, and the OSRP, 

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 SEP, based on the shallow hazards report by 

AOA Geophysics, Inc. (2004) and Fugro Geoservices, Inc. (2007, 2009a, 2011) reports 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, autonomous underwater vehicle 

(AUV) surveys, and side-scan sonar. There are previously drilled wells in the vicinity of the 

proposed locations but none are within 2,000 ft (600m) (AOA Geophysics, Inc., 2004; 

Geoservices, Inc., 2007, 2009b, 2011).

See SEP Section 6a for supporting geological and geophysical information. 

Page 160 Public Information Copy
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 

BOEM lease stipulations and NTLs. The project will comply with 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 SEP Section 2f. 

G. Consultation 

No persons or agencies were consulted regarding potential impacts associated with the proposed 

activities during the preparation of this EIA. 

Page 161 Public Information Copy
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.); 

Patrick Jackson (Prospect Team Lead, Corinth Development, Shell Exploration & Production Co.); 

John Harris (Geologist, Corinth Development, Shell Exploration & Production Co.); 

Pilar Rojas (PDT Team Leader, Corinth Development, Shell Exploration & Production Co.); 

Chris Brinkman (Drilling Engineer, Corinth Development, Shell Exploration & Production Co.); 

Ismail Barutcu (Reservoir Engineer, Corinth Development, 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 

Danielle Johnson (Technical Editor, CSA International, Inc.). 

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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 3g. High-Resolution Seismic Lines & Top Hole Progs 

Sections 3h. & 3i. Stratigraphic Column with Time vs. depth table 

 

B. Bibliography 

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Fugro GeoConsulting, Inc. (2009), “Shallow Drilling Hazards and Archaeological Assessment, Mississippi 

Canyon Blocks 347, 348, 391, 392 and Vicinity, Gulf of Mexico”, Fugro Report No. 27.2008-5022, prepared for 

Shell Exploration and Production Company. 

Fugro Geoservices, Inc (2007) Archaeological Assessment, Proposed Anchor Locations Block 393, Mississippi 

Canyon Area, Gulf of Mexico”, Fugro Report No. 2407-1083, prepared for Shell Deepwater Development. 

AOA Geophysics, Inc. (2004), “Shallow Hazards Assessment MC393 (OCS G-26254), DC353 (OCS G-25852), 

DC354 (OCS G-23507), DC397 (OCS G-25853), AND DC398 (OCS G-25854) Mississippi Canyon and DeSoto 

Canyon Areas, Gulf of Mexico”, AOA Report No. 3038.3-SHL-DES, prepared for Shell Offshore Inc. 

CSA Environmental Impact Analysis, September 2011 

Shell’s Regional OSRP, August 2011

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