UNITED STATES GOVERNMENT MEMORANDUM

To: Public Information (MS 5030)
Plans Section, Office of Field Operations (MS 5231)

Public Information copy of Exploration Plan

Control # - S-07514

Type - Supplemental Exploration Plan

Lease(s) - OCS-G17001 Block - 508 Walker Ridge Area OCS-G18730 Block - 507 Walker Ridge Area

Operator - Shell Offshore Inc.

Subsea Wells G, H and I

DP SEMISUBMERSIBLE

Attached is a copy of the subject plan for public comments on issues that should be addressed in an Environmental Assessment.

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

Michelle Griffitt
Plan Coordinator Description -

Rig Type - Subject: From: November 22, 2011Shell Offshore Inc.
P. O. Box 61933 New Orleans, LA 70161-1933
United States of America
Tel +1 504 728 7215
Fax +1 504 728 6747 Telex http://www.shell.com/eandp-en Email Sylvia.bellone@shell.com

September 26, 2011

Ms. Liz Peuler, Section Chief Bureau of Ocean Energy Management, Regulation and Enforcement 1201 Elmwood Park Boulevard New Orleans, LA 70123-2394

Attn: Plans Group MS 5231

SUBJECT: Supplemental Exploration Plan OCS-G 18730 & 17001, Walker Ridge Blocks 507 & 508 Unit No. 754306006 Offshore, Louisiana

Dear Ms. Peuler:

In compliance with 30 CFR 250.103 and NTLs 2008-G04, 2009-G27 and 2010-N06 , giving Exploration Plan guidelines, Shell Offshore Inc (SOI) requests your approval of this Suppl emental Exploration Plan to drill Well Locations G, H & I. Depending on rig availability operations could commence as early as February 2012.

This Plan consists of a series of attachments describing our intended operations. The attachments we desire to be exempted from disclosure under the Freedom of Informat ion Act are marked “Confidential” and excluded from the Public Information Copies of this submittal. The cost reco very fee receipt of $10,326.00 is attached to the Proprietary copy of the Plan (pay.gov tracking No. 254AVGH8).

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

Sincerely,

Sylvia A. Bellone

## SHELL OFFSHORE INC.

SUPPLEMENTAL EXPLORATION PLAN

for

OCS-G 18730, Walker Ridge Block 507 OCS- G 17001 , Walker Ridge Block 508

Walker Ridge 508 Unit



# PUBLIC INFORMATION COPY

PREPARED BY:



## Tracy W. Albert Regulatory Specialist

504.728.4652

tracy.albert@shell.com

### REVISIONS TABLE:

Date of Request Plan Section What was Corrected Date Resubmitted 10/3/2011 Corrected cover letter
Section 6
Section 17 Signature on letter Provided attachment 6A chemo map Provided TCZM approval number. 10/3/2011

10/11/2011 Section 2J Provided PVT data used in WCD 10/21/2011Supplemental Exploration Plan OCS-G 18730, Walker Ridge Block 507 OCS- G 17001 , Walker Ridge Block 508 Walker Ridge 508 Unit Offshore, Louisiana

Table of Contents

Section 1 P LAN C ONTENTS Section 2 G ENERAL I NFORMATION Section 3 G EOLOGICAL AND G EOPHYSICAL IN FORMATION Section 4 HYDROGEN SULFIDE ( H 2 S ) INFORMATION Section 5 M INERAL R ESOURCE C ONSERVATION INFORMATION Section 6 B IOLOGICAL , P HYSICAL AND S OCIOECONOMIC INFORMATION Section 7 W ASTE AND D ISCHARGE INFORMATION Section 8 A IR E MISSIONS INFORMATION Section 9 O IL S PILL I NFORMATION Section 10 E NVIRONMENTAL M ONITORING INFORMATION Section 11 L EASE S TIPULATIONS INFORMATION Section 12 E NVIRONMENTAL M ITIGATION M EASURES INFORMATION Section 13 R ELATED F ACILITIES AND O PERATIONS INFORMATION Section 14 S UPPORT V ESSELS AND A IRCRAFT INFORMATION Section 15 O NSHORE S UPPORT F ACILITIES INFORMATION Section 16 S ULPHUR O PERATIONS INFORMATION Section 17 C OASTAL Z ONE M ANAGEMENT A CT ( CZMA ) INFORMATION Section 18 E NVIRONMENTAL I MPACT A NALYSIS ( EIA ) Section 19 A DMINISTRATIVE INFORMATIONSECTION 1: PLAN CONTENTS

A. DESCRIPTION, OBJECTIVES & SCHEDULE

Shell Offshore Inc. (Shell) is submitting a Supplemental Exploration Plan (S EP /Plan) for Walker Ridge (WR) Blocks 507 and 508. BP Exploration & Production filed the initial EP for Lease OCS-G 17001 for the drilling of wells A and B (Plan Control Number N-8155). Shell submitted a Supplemental EP for wells C and D in WR 508, which was approved by BOEMRE on May 23, 2006 (Plan Control Numbers S- 6899 )

, and three revised EP’s for wells B, C & D (Plan Control Numbers R-4538, R-4429 and R- 4309 ). Shell also filed supplement al plan S-7129 for wells E and F, approved November 2, 2007. Shell is now submitting a Supplemental EP that includes three exploration wells in WR 508 and 509: G, H, and I. The wells will be drilled and temporarily abandoned (cement plugs and corrosion cap in accordance with 30 CFR 250.1721) until the wells are completed and developed under future plans. If the wells are unsuccessful, they will be permanently plugged and abandoned in accordance with BOEM regulations.

The drilling activities are planned to commence on or about February 1, 2012 and take last approximately 1 49 days per well. The timeframe to complete the initial drilling activities is an estimate based on the best available information regarding downhole conditions likely to be encountered while drilling each well and not intended to be a limitation.

The lease area is 178 miles from the nearest shoreline, 193 miles from the onshore support base at Port Fourchon, Louisiana, and 221 miles from the helicopter base at Amelia, Louisiana. Water depths at the wellsites range from 9,554 to 9,578 f ee t (Attachment 1- A)

. The proposed Rig is a DP semi-submersible, a self-contained drilling vessel with accommodations for a crew which includes quarters, galley and sanitation facilities. The Rig will comply with the requirements in the Interim Final Rules. The drilling activities will be supported by the support vessels and aircraft as well as onshore support facilities as listed in Sections 14 and 15 of the SEP. Shell has employed or contracted with trained personnel to carry out its exploration activities. Shell is committed to local hire, local contracting and local purchasing to the maximum extent possible. Shell personnel and contractors are experienced at operating in the Gulf of Mexico and are well versed in all Federal and State laws regulating operations. Shell’s employees and contractors share Shell’s deep commitment to operating in a safe and environmentally responsible manner.

Shell, through its parent and affiliate corporations, has extensive experience safely exploring for oil and gas in the Gulf of Mexico. Shell will draw upon this experience in organizing and carrying out its planned WR 507 and 508 drilling program. Shell believes that the best way to manage blowouts is to prevent them from happening. Significant effort goes into the design and execution of wells and into building and maintaining staff competence. In the unlikely event of a spill, Shell’s Regional OSRP is designed to contain and respond to a spill that meets or exceeds the WCD as detailed in Section 9 of this SEP. The WCD does not take into account potential flow mitigating factors such as well bridging, obstructions in wellbore, reservoir barriers, or early intervention. We continue to invest in Research and Development (R&D) to improve safety and reliability of our well systems. All operations will be conducted in accordance with applicable federal and state laws, regulations, and lease and permit requirements. Shell will have trained personnel and monitoring programs in place to ensure such compliance.

B. LOCATION

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

C. RIG SAFETY AND POLLUTION FEATURES :

The rig to be used on Stones will be the Noble Danny Adkins (or similar), a dynamically positioned MODU. The BOP stack on this rig is equipped with two fit for purpose shearing rams, one casing shear ram and one blind shear ram. Also, the Noble Danny Adkins is equipped with a deadman/autoshear system, an acoustic backup control system, and an emergency disconnect system for disconnecting and closing the shear rams.

The rig will comply with all of the regulations of the American Bureau of Shipping (ABS), International Maritime Organization (IMO) and the United States Coast Guard (USCG). All drilling operations will be conducted under the provisions of 30 CFR, Part 250, Subpart D , and other applicable regulations and notices, including those regarding the avoidance of potential drilling hazards and safety and pollution prevention control. Suc hmeasures as inflow detection and well control, monitoring for loss of circulation and seepage loss, and casing

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

DRAIN SYSTEM POLLUTION FEATURES

Drains are provided on the Rig in all spaces and on all decks where water or oil can accumulate. The drains are divided into two categories, non-contaminated and contaminated. All deck drains are fitted with a removable strainer plate to prevent debris entering the system.

Deck Drainage from rainfall, Rig washing, deck washing, and runoff from curbs and gutters, including drippans and work areas, are discharged depending on if it came into contact with the contaminated or noncontaminated areas of the Rig.

1) Non-contaminated Drains

Non-contaminated drains are designated as drains that under normal circumstances do not contain hydrocarbons, and can be discharged directly overboard. These are mostly located around the main deck and outboard in places where it is unlikely that hydrocarbons will be found.

Drains within 50 feet of a designated chemical storage area which uses the weather deck as a primary containment means shall be designated “normally plugged.” An adequate number of drains around the rig shall be designa ted as “normally open” to allow run -off of rain water. Normally open drains shall have a plug located in a conspicuous area near the drain which can be easily installed in the event of a spill.

The rig’s drain plug program consist at a minimum of a week ly check of all deck drains leading to the sea to verify that their status is as designated If normally open they shall verify that the drain is open and that the plug is available in the area. If normally closed they shall verify that the plug is securely installed in the drain.

In the event a leak or spill is observed, the event shall be contained (drain plug installation and / or spill kit deployment as appropriate) and reported immediately.

Rig personnel shall ensure that the perimeter kick-plates on weather decks are maintained and drain plugs are in place as needed to ensure a proper seal.

2) Contaminated Drains

Contaminated drains are designated as drains that contain hydrocarbons and cannot be discharged overboard. When oil-based mud is used for drilling it will be collected in portable tanks and sent to shore for processing.

3) Oily Water Processing

Oily water is collected in an oily water tank. It must be separated and not pumped overboard until oil content
is < 15 ppm. The separated oil is pumped to a dirty oil tank and has to be sent ashore for disposal. On board the MODU, an oil record log will be kept according to instructions included in the log. Any and all pollution pans are subjected to a sheen test before being pumped out. If the water passes the sheen test then it is pumped over board. If it does not pass the sheen test then the water/oil mixture is pumped to a dirty oil tank and sent to shore for disposal. All waste oil that is sent in to be disposed of is recorded in the MODU’s o il log book.

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

4) Lower Hull Bilge System

• The main bilge system is designed to drain the pontoons. There are Gould’s electrically driven, self priming centrifugal pumps - one for each main pump room. The aux pumps can be pump out with the bilge pump but has to be lined up manually from the main pump room.

• Bilge water is pumped overboard after a sheen test has been completed.• The pontoon bilge pumps are operable from the Bridge, and have audible and visual bilge alarms set for

high and low levels.

• Portable submersible pumps are carried onboard the rig to service all column void spaces and are also used for emergency bilge pump in the event of the main pump room flooding.

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

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

• Portable submersible pumps

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

The Bilge pumps are manual/automatic type pumps. They are equipped with sensors that give a high and a high -high alarm. They are set to a point at which the water gets to a certain point they will automatically turn on to pump water out in order to keep flooding under control. The pumps are also capable of being put in manual mode in which they can be turned on by hand.

5) Emergency Bilge System

Main ballast pumps may also be used for emergency bilge pumping directly from the pump rooms via remotely actuated direct bilge suction valves on the ballast system. These valves will operate in a fully flooded compartment. The ballast pumps can be supplied from the emergency switchboard.

6) Oily Water Drain/Separation System

Oily water/engine room bilge water is collected in an oily water tank. It must be separated and not pumped overboard until oil content is < 15 ppm. The separated oil is pumped to a dirty oil tank and has to be sent

as hore for disposal. On board all drilling Units, an oil record log has to be kept according to instructions included in the log. The rig floor has two skimmer tanks and each is subjected to a sheen test before pumping overboard to ensure environmental safet y. All three anchor winch windlasses have skimmer tanks and are subjected to sheen tests before discharge as well.

7) Drain, Effluent and Waste Systems

• The Rig’s drainage system is designed in line with our environmental and single point discharge policies. Drains are either hazardous, i.e. from a hazardous area as depicted on the Area Classification drawings, or non-hazardous drains from nonhazardous areas.

• To prevent migration of hazardous materials and flammable gas from hazardous to non-hazardou s areas, the drainage systems are segregated.

• The Rig drainage systems tie into oily water separators that take out elements in the drainage that could harm the environment. This is part of Noble’s initiative to be good stewards of the environment. The oily water separators divide the drainage system into these sections:

8) Rig Floor Drainage

The Rig floor has been outfitted with a Facet International MAS 34-3 separator. The separator has coalescent plates that remove the solids from the drainage, and the remaining drainage goes to a skimmer tank. From the skimmer tank it is drained to one of the column dirty oil tank systems where it is then sent through 2 separators and cleaned further to reduce oil content to less than 15 ppm.

9) Columns #3 & 4

Th e drains on the decks and machinery spaces are separated at mid ship and directed to either the #3 or #4 columns. The separators in these columns go through three cycles of circulation and remove oil to less than
15 ppm, then discharge the clean product to sea.

10) Main Engine Rooms

• The engine rooms have their own drainage and handling system. The engine rooms are outfitted with a dirty oil tank and the drainage in the tank is processed through the separator, the waste from the separator goes back to the dirty oil tank and the clean water (less than 15ppm) goes overboard.

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

• Column #3

–

Westfalia WSD- 18• Column #4

– Westfalia WSD- 18

• Drill Floor

–

Facet International MAS 34-3

11) Helideck Drains

The helideck has a dedicated drainage system around its perimeter to drain heli-fuel from a helicopter incident. The fuel can be diverted to the designated heli-fuel recovery tank which is located under the Helideck structure.

Operating configurations are as follows:

 The overboard piping valves and hydrocarbons take on valves are closed and locked. To unlock overboard or take on valves a permit has to be filled out.
 The oily water collection tank overflow valve is closed.
 The drill floor drains are lined-up to the drill floor skimmer tank. The skimmer tanks have a high alarm which sounds by means of an air horn. Before tanks are pumped out a sheen test is performed. Water is pump ed out the skimmer tanks down the shunt line. The oil containment side is pumped out into 550 gal tote tanks.
 The BOP test area drains are normally lined-up to drain overboard.
 The oily water separator continuously circulates the oily water collection tank. Waste oil is discharged into the waste oil tank and oily water is re -circulated back into the oily water collection tank. Clean water is pumped overboard, which is controlled and monitored by the oil content detector, set at 15
ppm.  The solids control system is capable of being isolated for cuttings collection.
 The bilge system is normally pumped directly overboard after a sheen test has been performed.
 The engine dirty oil sump can be drained down to the Port column oily water separator which discharges water overboard from the water side and oil is pumped out into a 550 gallon tote tank on the containment side. There is a high audible alarm on the ballast control panel.

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

Tank Name Tank Number of Total Contents Capacity (bbls) Tanks Capacity (bbls) Gravity (API)

Fu el Oil Storage PFO

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

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

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

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

- 1 4540 1 4540 No. 2 diesel

Fuel Oil Storage SFO

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

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

- 4 821 1 821 No. 2 diesel
Fuel Oil Settling Tanks 129 4 516 No. 2 diesel
Fuel Oil Day Tanks 115 4 460 No. 2 diesel

PDT

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

Fuel Oil Settling Tanks SST

- 1, SST

- 2, PST

- 1, PST

- 2 are each 129 Bbls. Fuel Oil Day Tanks SDT

- 1, PDT

- 1, PDT

- 2 are each 115 Bbls. and SDT

- 2 = 100 Bbls.E. Pollution Prevention Measures

Pursuant to NTL 2008-G04 the proposed operations covered by this SEP do not require Shell to specifically address the discharges of oils and greases from the Rig during rainfall or routine operations. Nevertheless, Shell has provided this information as part of its response to 1(c) above.

F. Additional Measures

 Health, safety, and environment (HSE) are the primary topics in pre-tour and pre-job safety meetings. The discussion around no harm to people or environment is a key mindset. All personnel are reminded daily to inspect work areas for safety issues as well as potential pollution issues.

 All tools that come to and from the rig have their pollution pans inspected and cleaned, and plug installation confirmed prior to leaving the dock and prior to loading on the boat.

 Preventive maintenance of rig equipment includes visual inspection of hydraulic lines and reservoirs on a routine scheduled basis.

 All pollution pans on rig are inspected daily.

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

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

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

 All trash containers are checked and emptied daily, and trash containers are kept covered. Trash is collected in a compactor and shipped to shore for disposal.

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

 Fuel hoses are changed on an annual basis.

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

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

 Shell will use low-sulfur fuel to reduce air pollutant impacts.Attachment 1-A



### WATER DEPTHAttachment 1-B

U. S . Department of the Interior OMB Control Number: 1010 -0151 Minerals Management Service OMB Approval Expires: December 31, 20 11 OCS PLAN INFORMATION FORM



### Gener al 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

- 1 933 Phone Number: 504.728.4652

E

- Mail Address: tracy.albert@shell.com
Lease(s): OCS

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

Objective(s): X Oil Gas Sulp hur Salt Onshore Base: Fouchon & Amelia, LA Distance to Closest Land (Miles): 1 78



### Description of Proposed Activities (Mark all that apply)

X Exploration drilling Development drilling
Well completion Installation of production platform

Well test fl aring (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

Install ation of lease term pipelines Other (Specify and describe)
Have you submitted or do you plan to submit a Conservation Information Document to accompany this plan? Yes X No

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

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

Do you propose any activities that may disturb an MMS

- designated high

- probability archaeological area? Yes X No

Have all of the surface loc ations of your proposed activities been previously reviewed and approved by
MMS? Yes X No



### Tentative Schedule of Proposed Activities
Proposed Activity Start Date End Date No. of Days

Drill Well G and suspend 

### 2/1/2012 6/29/2012 149

Drill Well H and susp end 

### 6/30/2012 11/26/2012 149

Drill Well I and suspend 

### 11/27/2012 4/25/2013 149



### Description of Drilling Rig Description of Production Platform
Jackup Drillship Caisson Tension leg platform
Gorilla Jackup Platform rig Well prot ector Compliant tower

Semisubmersible Submersible Fixed platform Guyed tower

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

Drilling Rig Name (If Known): Noble Danny Adkins or similar Spar Other (Att ach 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 us ed.)OCS PLAN INFORMATION FORM (CONTINUED) Include one copy of this page for each proposed well/structure



### Proposed Well/Structure Location

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

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

Surface Location Bottom

- Hole Location (For Wells)

Lease No. OCS

- G 17001

Area Name Walker Ridge

Block No. 508

Blockline Departures (in feet) N/S Departure: 4350' FSL

E/W Departure: 5440' FWL

Lambert X

Y coordinates X: 2365600

Y: 9603390

Latitude/ Longitude Latitude 26.4487

Longitude

- 90.7832

TVD (Feet): MD (Feet): Water Depth (Feet): 9

, 558’

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

Anchor Name
or No. Area Block X Coordinate Y Coordinate Length of Anchor Chain on Seafloor

Paperwork Reduction Act of 1995 Statement: The Paperwork Reduction Act of 1995 (44 U .S.C. Chapter 35) requires us to inform you that MMS collects this information as part of an applicant’s Exploration Plan or Development Operations Coordination Document submitted for MMS approval. We use the information to facilitate our review and data entry for OCS plans. We will protect proprietary data according to the Freedom of Information Act and 30 CFR 250.196. An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a curre ntly 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 estima te 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 I nformation 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.)OCS PLAN INFORMATION FORM (CONTINUED) Include one copy of this page for each proposed well/structure



### Proposed Well/Structure Location

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

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

Surface Location Bottom

- Hole Location (For Wells)

Lease No. OCS

- G 17001

Area Name Walker Ridge

Block No. 508

Blockline Departures (in feet) N/S Deprture: 3868’ FSL

E/W Departure: 4809' FWL

Lambert X

Y coordinat es X: 2364969

Y: 9602908

Latitude/ Longitude Latitude 26.4474

Longitude

- 90.7852

TVD (Feet): MD (Feet): Water Depth (Feet): 9

, 554’

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

Anchor Name
or No. Area Block X Coordinate Y Coordinate Length of Anchor Chain on Seafloor

Paperwork Reduction Act of 1995 Statement: The Paperwork Reduction Act of 1995 (44 U.S.C. Chapter 35) requ ires 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 M anagement 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 aver age 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.)OCS PLAN INFORMATION FORM (CONTINUED) Include one copy of this page for each proposed well/structure



### Proposed Well/Structure Location

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

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

Surface Location Bottom

- Hole Location (For Wells)

Lease No. OCS

- G 17001

Area Name Walker Ridge

Block No. 508

Blockline Departures (in feet) N/S Departure: 100’ FSL

E/W Departure: 7740’ FWL

Lambert X

Y coordinates X: 2367900

Y: 9599140

Latitude/ Longitude Latitude 26.4369

Longitude

- 90.7764

TVD (Feet): MD (Feet): Water Depth (Feet ): 9

, 57 8 ’

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

Anchor Name
or No. Area Block X Coordinate Y Coordinate Length of Anchor Chain on Seafloor

Paperwork Reduction Act of 1995 Statement: The Paperwork Reduction Act of 1995 (44 U.S.C. Chapter 35) requires us to inform yo u 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 prop rietary 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 re sponse, 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, M ail 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.)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- wi de 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- N0 7 , “Supplemental Bond Proc ed ures.”

G. Oil Spill Financial Responsibility (OSFR)

Shell Offshore Inc (SOI), BOEM Operator Number 0689, has demonstrated oil spill financial responsibility for the wells proposed in the SEP according to 30 CFR Parts 250 and 253 , and NTL No. 2008

- N0 5 , “Guidelines for Oil Spill Financial Responsibility for Covere d Facilities.”

H. Deepwater well control statement

Shell Offshore Inc (SOI), BOEM Operator Number 0689, has the financial capability to drill a relief well and conduct other emergency well control operations.

I. Suspension of Production

Information regarding Suspension of Production is not included in this SEP as such information is only necessary in the case of DOCDs.J. Blowout scenario

Summary

This Section 2j was prepared by Shell Offshore Inc. (Shell) pursuant to the guidance provided in the Bureau of Ocean Energy Management, Regulation and Enforcement’s (BOEMRE) Notice to Lessees (NTL) No. 2010- N06 with respect to blowout and worst case discharge scenario descriptions. Shell intends to comply with all applicable laws, regulations, rules and Notices to Lessees.

Shell focuses on an integrated, three-pronged approach to a blowout, including prevention, intervention /containment, and recovery.

1. Shell believes that the best way to manage blowouts is to prevent them from happening. Significant effort goes into design and execution of wells and into building and maintaining staff competence. Shell continues to invest independently in Research and Development (R&D) to improve safety and reliability of our well systems.

2. Shell is a founding member of the Marine Well Containment Company (MWCC), which provides robust well containment (shut-in and controlled flow) capabilities. Additionally, Shell is investing in R&D to improve containment systems.

3. As outlined in Shell’s Oil Spill Response Plan (OSRP ), and detailed in EP Section 9a (ii), Shell has contracts with Oil Spill Removal Organizations (OSROs) to provide the resources necessary to respond to this Worst Case Discharge (WCD) scenario. The capabilities for on-water recovery, aerial and subsea dispersant application, in-situ burning, and nighttime monitoring and tracking have been significantly increased.

The WCD blowout scenario is calculated for well location H in corresponding exploration plan, which is planned as a western penetration of the Upper and Lower Wilcox Sands, based on the guidelines outlined in NTL No. 2010-N06 along with subsequent Frequently Asked Questions (FAQ). The WCD for the Stones H well, or a similarly targeted well, falls below the WCD exploratory scenario for MC-805 MB-01 (Olympus ) included in our Regional OSRP (July 2011). In the unlikely event of a spill, Shell’s Regional OSRP is designed to contain and respond to a spill that meets or exceeds this WCD.

The WCD scenario, in terms of both initial and the sustained rates, has a low probability of being realized. Some of the factors that are likely to reduce rates and volumes, and are not included in the WCD calculation, include but are not limited to, obstructions or equipment in the wellbore, well bridging, and early
int ervention, such as containment capabilities.

Uncontrolled blowout (volume first day) 4 2

, 000 bbl
Uncontrolled blowout rate (first 30

- days average daily rate) 3 3

, 000 bopd Duration of flow (days) based on relief well 180 days
Total volume of spill ( bb ls) for 180 days 5 .2 MMBO
Table 1 Worst Case Discharge Summary

The Stones discovery is located in the Gulf of Mexico (GOM), approximately 200 miles south of New Orleans, Louisiana, in water depths of 7,500

– 9,500 feet (ft) across the discovery. Stones is a four-way, faulted closure; a large, east- dipping fault with up to 1100’ of throw forms a key trapping element along the northeast side of the structure. To date, the Stones partnership has drilled four penetrations: the discovery well (WR508 #1), the WR508 #2 appraisal well (drilled to a TD of 12,509 ft tvdss, which did not penetrate the objective section), and the WR508 #3 appraisal well (with 1 additional bypass). The only objective horizons of the proposed Stones H well with predicted flow potential are the Upper and Lower Wilcox reservoirs of early Paleogene age, and the Stones H well is expected to encounter the Upper Wilcox reservoir at 26,331 ft tvdss. Additional WCD scenarios were evaluated for alternate well locations at Stones; however, the WCD numbers for these wells are lower than the WCD number calculated for the Stones H well, as these wells are expected to encounter less net pay and have a longer wellbore length and thus greater wellbore friction. These wells flowed at substantially lower rates than the Stones H well case represented for the WCD.Any shallower sands will be cased off prior to the well path penetrating the Wilcox reservoir package, and

are not expected to be oil-bearing.

1) Purpose

Pursuant with 30 CFR 250.213(g), 250.219, 250.250, and NTL No. 2010-N06, this document provides a blowout scenario description, further information regarding any potential oil spill, the assumptions and calculations used to determine the WCD and the measures taken to 1) enhance the ability to prevent a blowout and 2) respond and manage a blowout scenario if it were to occur. These calculations are based on best technical estimates of subsurface parameters that are derived from the offset wells and seismic. These parameters are better than or consistent with the estimates used by Shell to justify the investment. Therefore, these assumed parameters were used to calculate the WCD. They do not reflect probabilistic
estimates.

2) Background

This attachment has been developed to document the additional information requirements for Exploration Plans as requested by NTL No. 2010-N06 in response to the explosion and sinking of the Mobile Offshore Drilling Unit (MODU) Deepwater Horizon and the resulting subsea well blowout and recovery operations of the exploration well at the MC-252 Macondo location.

3) Information Requirements

a) Blowout scenario

All well locations addressed in this EP were assessed for Worst Case Discharge using the expected well path, the expected reservoir thickness, structural elevation, and rock/fluid properties for each. The Stones H deviated well with a bottom hole location ( 27,871 ft tvdss) on the western side of the Stones structure represented the highest 30 -day average flow potential. The Stones H well will be drilled through the Upper and Lower Wilcox reservoirs as outlined in the Geological and Geophysical Information Section of the Stones EP, and described above, utilizing a typical subsea wellhead system, conductor, surface and intermediate casing program, and using a DP rig with a marine riser and subsea Blowout Preventer. A hydrocarbon influx and a well control event are modeled to occur from the Upper and Lower Wilcox reservoirs. The simulated blowout model results in unrestricted flow from the well at the seafloor which represents the worst case discharge, no restrictions in the wellbore, failure/loss of the subsea BOP, and a blowout to the seabed.

b) Estimated flow rate of the potential blowout

Table 2 Estimated Flow Rates of a Potential Blowout

c) Total volume and maximum duration of the potential blowout

Duration of flow (days) 180 days total duration to drill relief well (14 rig mob, 3 transit, 130 spud to top Wilcox , 33 ranging).

Total volume of spill (bbls) 5 .2 MMBO based on 180 days flowing. Note: From CMG dynamic reservoir model

Table 3 Estimated Duration and Volume of a Potential Blowout Category EP Type of Activity Drilling Facility Location (area/b lock) WR

- 508 Facility Designation DP Distance to Nearest Shoreline (miles) 182 Statute miles Uncontrolled blowout (volume first day) 4 2

, 000 bbl Uncontrolled blowout rate (first 30

- days average daily rate) 3 3

, 000 bopdThere is usually a decline in the discharge rate as time proceeds, which is illustrated by the

differences between the first 24-hour volume and 30-day average rate. The total volume calculated until a well is killed in a potential blowout further demonstrates this decline. At very short times, e.g. during the first 24 hours, the pressure profile in the reservoir changes from the moment when a well first starts flowing to a pseudo-steady state pressure profile with time, and as a result the rate declines. At somewhat longer time scales, effects such as reservoir voidage and the impact of boundaries can cause the rate to drop continuously with production. Simulation and material balance models can include these effects and form the basis of the NTL No. 2010-N06 estimates for 24-hour and 30-day rates as well as maximum duration volumes.

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

e) Potential for the well to bridge over

Mechanical failure/collapse of the borehole in a blowout scenario is influenced by several factors including in-situ stress, rock strength and fluid velocities at the sandface. Based on the nodal analysis and reservoir simulation models outlined above, a seabed blowout would create a high drawdown at the sand face. Given the substantial fluid velocities inherent in the worst case discharge, and the scenario as defined where the formation is not supported by a cased and cemented wellbore, it is possible that the borehole may fail/collapse/bridge over within the span of a few days, significantly reducing outflow rates. However, this WCD scenario does not include any bridging or consideration of solids production with the oil and gas.

f) Likelihood to stop the blowout

Safety of operations is our top priority. Maintaining well control at all times to prevent a blowout is the key focus of our operations. Our safe drilling record is based on our robust standards, conservative well design, prudent operations practices, competency of personnel, and strong HSE focus. Collectively, these constitute a robust system making blowouts extremely rare events.

Intervention Devices: Notwithstanding these facts, the main scenario for recovery from a blowout event is via intervention with the BOP attached to the well. There are built in redundancies in the BOP system to allow activation of selected components with the intent to seal off the well bore. As a minimum, the Shell contracted rig fleet in the GOM will have redundancies meeting the Interim Final Drilling Safety Rule with respect to Remotely Operated Vehicle (ROV) hot stab capabilities, a deadman system, and an autoshear system.

The r ig to be used on Stones will be the Noble Danny Adkins (or similar), a dynamically positioned MODU. The BOP stack on this rig is equipped with two fit for purpose shearing rams, one casing shear ram and one blind shear ram. Also, the Noble Danny Adkins is equipped with a deadman/autoshear system, an acoustic backup control system, and an emergency disconnect system for disconnecting and closing the shear rams.

Containment: The experience of gaining control over the Macondo well has resulted in a better understanding of the necessary equipment and systems for well containment. As a result, industry and government are better equipped and prepared today to contain an oil well blowout in deepwater (See page 17 of the Decision Memorandum dated October 1, 2010). Shell is further analyzing these advances and incorporating them into its comprehensive approach to help prevent and, if needed, control another deepwater control incident.

Pursuant to NTL No. 2010-N10 , Shell will provide additional information regarding our containment capabilities in a subsequent filing.

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

Blowout intervention can be conducted from an ROV equipped vessel, the existing drilling rig or from another drilling rig. The dynamically positioned rigs under contract, the Noble Danny Adkins and the Bully 1, will be the preferred rigs for blowout intervention work. However, moored rigs can also be used in some scenarios. Additionally, in the event of a blowout, there are other non-contracted rigs in the GOM could be utilized for increased expediency or better suitability (e.g. TransoceanDiscoverer Clear Leader, etc). All efforts will be made at the time to secure the appropriate rig.

Shell’s current contr acted rigs capable of operating at Stones water depths and reservoir depths without technical constraints are shown in the Table 4 below:



### Rig Name Rig Type Noble Danny Adkins Dynamically positioned semi Noble Bully 1* Dynamically positioned drill ship

Table 4 Shell Contracted Rigs Capable at Stones.

Above are current as of July 2011. Future modifications may change the rig’s capability. Rig capabilities need to be assessed on a work scope specific basis. *Bully 1 estimated arrival November 2011. Full riser kit will arrive sometime thereafter.



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

Relief well operations will immediately take priority and displace any activity from Shell’s contracted rig fleet. The list of rigs capable of operating at Stones is tabled above. It is expected to take an average of 14 days to safely secure the well that the rig is working on up to the point the rig departs location, and an additional 3 days transit to mobilize to the relief well site depending on distance to the site. The relief well will take approximately 130 days to drill down to the last casing string above the blowout zone, plus approximately 33 days for precision ranging activity to intersect the blowout well bore. The expected total time to mobilize and drill a relief well would be 180 days for this well.

If a moored rig is chosen to conduct the relief well operations, anchor handlers would be prioritized to prepare mooring on the relief well site while the rig is being mobilized. This activity is not expected to delay initiation of relief well drilling operations. Shell has 3 deepwater anchor handlers (the Laney, Dino, and Ross Chouest) on long term contract to support its moored rigs.

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

Shell believes that the best way to manage blowouts is to prevent them from happening. Detailed below are the measures employed by Shell with the goal of no harm to people or the environment. The Macondo incident has highlighted the importance of these practices. The lessons learned from the investigation are, and will continue to be, incorporated into our operations.

Standards: Shell’s well design and operations adhere to internal corporate standards, the Code of Federal Regulations, and industry standards. A robust management of change process is in place to handle un-defined or exception situations. Ingrained in the Shell standards for well control is the philosophy of multiple barriers in the well design and operations on the well.

Risk Management: Shell believes that prevention of major incidents is best managed through the systematic identification and mitigation process (Safety Case). All Shell contracted rigs in the GOM have been operating with a Safety Case and will continue to do so. A Safety Case requires both the owner and contractors to systematically identify the risks in drilling operations and align plans to mitigate those risks; an alignment which is critical before drilling begins.

Well Design Workflow: The Well Delivery Process (WDP) is a rigorous internal assurance process with defined decision gates. The WDP leverages functional experts (internal and external) to examine the well design at the conceptual and detailed design stages for robustness before making a recommendation to the management review board. Shell’s involvement in global deepwater drilling, starting in the GOM in the mid- 1980’s, provides a significant depth and breadth of internal drilling and operational expertise. Third party vendors and rig contractors are involved in all stages of theplanning, providing their specific expertise. A Drill the Well On Paper (DWOP) exercise is conducted

with rig personnel and vendors involved in execution of the well. This forum communicates the well plan, and solicits input as to the safety of the plan and procedures proposed.

Well and rig equipment qualification, certification, and quality assurance: All rigs will meet all applicable rules, regulations, and Notice to Lessees. Shell works closely with rig contractors to ensure proper upkeep of all rig equipment, which meets or exceeds the strictest of Shell, industry, or regulatory requirements. Well tangibles are governed by our internal quality assurance/control standards and industry standards.

MWD/LWD/PWD Tools: Shell intends to use these tools at Stones. The MWD/LWD/PWD tools are run on the drill string so that data on subsurface zones can be collected as the well advances in real time instead of waiting until the drill string is pulled to run wireline logs. Data from the tools are monitored and interpreted real time against prognosis to provide early warning of abnormal pressures to allow measures to be taken to progress the well safely.

Mud Logger: Mud logging personnel continually monitor returning drilling fluids for indications of hydrocarbons, utilizing both a hot wire and a gas chromatograph. An abrupt increase in gas or oil carried in the returning fluid can be an indication of an impending kick. The mud logger also monitors drill cuttings returned to the surface in the drilling fluid for changes in lithology that can be an indicator that the well has penetrated or is about to penetrate a hydrocarbon-bearing interval. Mud logging instruments also monitor penetration rate to provide an early indication of drilling breaks that
show the bit penetrating a zone that could contain hydrocarbons. The mud logging personnel are in close communication with both the offshore drilling foremen and onshore Shell representative(s) to report any observed anomalies so appropriate action can be taken.

Remote Monitoring: The Real Time Operating Center has been used by Shell to complement and support traditional rig-site monitoring since 2003. Well site operations are lived virtually by onshore teams consisting of geoscientists, petrophysicists, well engineers, and 24/7 monitoring specialists. The same real time well control indicators monitored by the rig personnel are watched by the monitoring specialist for an added layer of redundancy.

Competency and Behavior: A structured training program for Well Engineers and Foreman is practiced, which includes internal professional examinations to verify competency. Other industry training in well control, such as by International Association of Drilling Contractors (IADC) and International Well Control Forum (IWCF) are also mandated. Progressions have elements of competency and Shell continues to have comprehensive internal training programs. The best systems and processes can be defeated by lack of knowledge and/or improper values. We believe that a combination of HSE tools (e.g. stop work, pre-job analysis, behavior based safety, DWOPs, audits), management HSE involvement and enforcement (e.g. compliance to life saving rules) have created a strong safety culture in our operations.

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

The response to a blowout is contained in our Well Control Contingency Plan (WCCP) which is a specific requirement of our internal well control standards. The WCCP in turn is part of the wider emergency response framework within Shell that addresses the overall organization response to an emergency situation. Resources are dedicated to these systems and drills are run frequently to test preparedness (security, medical, oil spill, and hurricane). This same framework is activated and tested during hurricane evacuations, thereby maintaining a fresh and responsive team.The WCCP specifically addresses implementing actions at the emergency site that will ensure

personnel safety, organizing personnel and their roles in the response, defining information requirements, establishing protocols to mobilize specialists and pre-selecting sources, and developing mobilization plans for personnel, material and services for well control procedures. The plan references individual activity checklists, a roster of equipment and services, initial information gathering forms, a generic description of relief well drilling, strategy and guidelines, intervention techniques and equipment, site safety management, exclusion zones, and re-boarding.

As set forth in 3f of this document, Shell is currently analyzing recent advances in containment technology and equipment and will incorporate them as they become available.

k) Arrangements for drilling a relief well

The size of the Shell contracted rig fleet in the GOM from 2010-2015 ensures that there is adequate well equipment (e.g. casing and wellhead) available for relief wells. Rigs and personnel will also be readily available within Shell, diverted from their active roles elsewhere. Resources from other operators can also be leveraged should the need arise. Generally, relief well plans will mirror the blowout well, incorporating any learning on well design based on root cause analysis of the blowout. A generic relief well description is outlined in the WCCP.

l) Assumptions and calculations used in approved or proposed OSRP

Shell has submitted MC-508 MB- 01 (Olympus) as the new exploratory worst-case scenario to the BOEMRE for inclusion in our Regional OSRP.

Shell has designed a response program (Regional OSRP August 2011 ) based upon a regional capability of responding to a range of spill volumes, from small operational spills up to and including
the WCD from an ex ploration well blowout. Shell’s program is developed to fully satisfy federal oil spill planning regulations. The Regional OSRP presents specific information on the response program that includes a description of personnel and equipment mobilization, the incident management team organization, and the strategies and tactics used to implement effective and sustained spill containment and recovery operations.

K. Chemical Products

Information regarding chemical products is not included in this SEP as such information is not required by BOEMRE GOMR.SECTION 3: GEOLOGICAL AND GEOPHYSICAL INFORMATION

A. Geological description

Proprietary data

B. Structure Contour Map(s)

Proprietary data

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

Proprietary data

D. Geological Structure Cross-section(s)

Proprietary data

E. Shallow Hazards Report

The following reports were used for our analysis:

Geoscience Earth & Marine Services, Inc. (GEMS) prepared a Geologic and Stratigraphic Assessment Report (Number 0306-1151) for Shell on 24 May 2006. Fugro GeoServices, Inc. (FGSI) acquired the high-resolution geophysical survey data utilizing FGSI’s Autonomous Underwater Vehicle (AUV) aboard the Fugro Enterprise in September and October of 2009. The quality of the collected geophysical data was good, and the data were suitable for interpretation. Fugro GeoConsulting, Inc. (FGCI) prepared an Integrated Geophysical and Geotechnical Field Development Planning Study based on the AUV data (Job No. 27.2009-2328), anddelivered to Shell in May 2010. The Report was previously submitted to the BOEM with Supplemental EP S06899 on May 12, 2006.

Additionally, enclosed are copies of FGSI AUV Archaeological Assessment Report (Number 2411-1019) for Shell covering Walker Ridge blocks 420, 464, 508, and 552. The Archaeological report is dated July 12, 2011.

F. Shallow Hazards Assessment

Shell seeks BOEMRE approval of its Supplemental Exploration Plan for Proposed Locations G, H, and I in Walker Ridge Block 508. Shell plans to use a dynamically positioned vessel in the category of Noble Danny Adkins at Proposed Locations G, H, and I.

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

Shell Well #1 in Walker Ridge 508 X = 2,376,971 Y= 9,605,100 Shell Well #2 in Walker Ridge 508 X= 2,368,107 Y= 9,604,808 Shell Well #3 in Walker Ridge 464 X = 2,367,381 Y= 9,617,757

Regional Overview

Walker Ridge Block 508 straddles the Sigsbee Escarpment and abyssal plain. The southern half of the block is in an area of seafloor furrows that make for variable seafloor strength. At the proposed locations, the soils at the base of the furrows are of higher than normal sheer strength due to active erosion. The ridges between the furrows have not experienced the maximum erosion forces, thus, the soils are relatively soft. Proposed Locations G, H, and I are positioned between seafloor furrows.

There are no fluid expulsion features, faults, or chemosynthetic communities within 2000 feet of the proposed locations. There are piston cores, drilling splays, anchor chain scars, and previously drilled wells in the vicinity of Proposed Locations G, H, and I but none are within 2000’ of the locations.Well Information

Walker Ridge 508, Proposed Location G: X = 2,365,600 5
, 440’ FWL Y = 9,603,390 4, 350’ FSL

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

The stratigraphy at Proposed Location G consists of 224 feet of hemipelagic drape and MTD. Unit 2 has 327 feet of muds and silts with possible thin sands. Unit 3 consists of 165 feet of muds and slits. Unit 4 consists of 601feet of muds and tubiditic channels with low amplitude. Unit 5 has 270 feet of muds, turbiditic channels and MTD. This is underlain by 608 feet of muds and silts with interbedded MTD. Unit 7 consists of 576 feet of muds and silts with interbedded MTD. Unit 8 has 524 feet of mass-transport deposits of muds and silts, some sand rich turbidites with interbedded mass transport deposits.

Units 1 to 7 exhibit low to negligible potential for shallow gas and over-pressured sands. Unit 8 has moderate potential for shallow water flow and shallow gas. Nevertheless, the drilling program will be designed to minimize any drilling risks encountered. The site appears suitable for the proposed drilling
program.

Walker Ridge 508, Proposed Location H: X = 2,364,969 4
, 809’ FWL Y= 9,602,908 3, 868’ FSL

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

The stratigraphy at Proposed Location H consists of 226 feet of hemipelagic drape and MTD. Unit 2 has 328 feet of muds and silts with possible thin sands. Unit 3 consists of 164 feet of muds and slits. Unit 4 consists of 608feet of muds and tubiditic channels with low amplitude. Unit 5 has 272 feet of muds, turbiditic channels and MTD. This is underlain by 642 feet of muds and silts with interbedded MTD. Unit 7 consists of 575 feet of muds and silts with interbedded MTD. Unit 8 has 529 feet of mass-transport deposits of muds and silts, some sand rich turbidites with interbedded mass transport deposits.

Units 1 to 7 exhibit low to negligible potential for shallow gas and over-pressured sands. Unit 8 has moderate potential for shallow water flow and shallow gas. Nevertheless, the drilling program will be designed to minimize any drilling risks encountered. The site appears suitable for the proposed drilling
program.

Walker Ridge 508, Proposed Location I: X = 2,367,900 7
, 740’ FWL Y= 9,599,140 100’ FSL

Proposed Location I will be in a water depth of approximately 9, 57 8 feet.

The stratigraphy at Proposed Location I consists of 219 feet of hemipelagic drape and MTD. Unit 2 has 292 feet of muds and silts with possible thin sands. Unit 3 consists of 142 feet of muds and slits. Unit 4 consists of 649 feet of muds and tubiditic channels with low amplitude. Unit 5 has 200 feet of muds, turbiditic channels and MTD. This is underlain by 588 feet of muds and silts with interbedded MTD. Unit 7 consists of 701 feet of muds and silts with interbedded MTD. Unit 8 has 355 feet of mass-transport deposits of muds and silts, some sand rich turbidites with interbedded mass transport deposits.

Units 1 to 7 exhibit low to negligible potential for shallow gas and over-pressured sands. Unit 8 has moderate potential for shallow water flow and shallow gas. Nevertheless, the drilling program will be designed to minimize any drilling risks encountered. The site appears suitable for the proposed drilling
program

Currently, there are no pipelines in the vicinity of Proposed Locations G, H, and I.Based on a high-resolution geophysical survey consisting of frequency enhanced 3-D seismic, Enhanced

Surface Renderings, and Enhanced Surface Renderings with Amplitudes applied, AUV surveys, and side scan sonar, Walker Ridge Block 508, Proposed Locations G, H, and I will not disturb any chemosynthetic
communities.

Kevin Bradford Vernessa J. Bradford Geophysicist Shallow Hazards Interpreter

G. High- Res olution Seismic Lines

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

H & I Stratigraphic Column with Time vs depth table

Proprietary data

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

K. Future G&G Activities This information is not required for Plans submitted in the GOM Region.SECTION 4: HYDROGEN SULFIDE (H 2 S) INFORMATION

A. Concentration

0 ppm.

B. Classification

Based on CFR 250. 490 (c), SOI requests that the Regional Supervisor, Field Operations, determine the zones in the proposed drilling operations in this plan to be classified as an area where the absence of H 2 S has been confirmed.

C. Modeling Report

We do not anticipate to encounter or handle H 2 S at concentrations greater than 500 parts per million (ppm) and therefore have not included modeling for H 2 S.

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.SECTION 6: BIOLOGICAL, PHYSICAL, AND SOCIOECONOMIC INFORMATION

A. Chemosynthetic Communities Report

ANCHOR CLEARANCE AND CHEMOSYNTHETIC

ORGANISMS COMMENTS

History

Geoscience Earth & Marine Services, Inc. (GEMS) prepared a Geologic and Stratigraphic Assessment Report (Number 0306-1151) for Shell on 24 May 2006. Fugro GeoServices, Inc. (FGSI) acquired the high-resolution geophysical survey data utilizing FGSI’s Autonomous Underwater Vehicle (AUV) aboard the Fugro Enterprise in September and October of 2009. The quality of the collected geophysical data was good, and the data were suitable for interpretation. Fugro GeoConsulting, Inc. (FGCI) prepared an Integrated Geophysical and Geotechnical Field Development Planning Study based on the AUV data (Job No. 27.2009-2328), anddelivered to Shell in May 2010. The Report was previously submitted to the BOEM with Supplemental EP S06899 on May 12, 2006.

Additionally, enclosed are copies of FGSI AUV Archaeological Assessment Report (Number 2411-1019) for Shell covering Walker Ridge blocks 420, 464, 508, and 552. The Archaeological report is dated July 12, 2011.

Shell seeks BOEMRE approval of its Supplemental Exploration Plan for Proposed Locations G, H, and I in Walker Ridge Block 508. Shell plans to use a dynamically positioned vessel in the category of Noble Danny Adkins at Proposed Locations G, H, and I.

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

Shell Well #1 in Walker Ridge 508, X = 2,376,971 Y = 9,605,100 Shell Well #2 in Walker Ridge 508, X= 2,368,107 Y= 9,604,808 Shell Well #3 in Walker Ridge 464, X = 2,367,381 Y= 9,617,757

Chemosynthetic Community Statement

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

ASSOCIATED ANCHORS

– NO ANCHOR DISTURBANCES WITHIN 250 FEET OF CHEMOSYNTHETIC COMMUNITIES

For the three proposed locations G, H, I and the cleared well radii:
Shell will observe the following separation distances from high-density deepwater benthic communities :

1. At least 2,000 feet from each proposed muds and cuttings discharge location;
2. At least 250 feet from the location of all other proposed seafloor disturbances (including those caused by anchors, anchor chains, wire ropes, seafloor template installation, and pipeline construction). Seafloor disturbances include all “temporary” disturbances caused during mooring operations (e.g., anchor deployment, setting, and retrieval) as well as those caused by anchoring activities conducted prior to a MODU arriving on location (e.g., pre-installation of suction piles and cables; where seafloor impacts are much greater while the cables are located on the seafloor prior to being pulled taut and attached to the MODU).

Archaeological Report Information

Seafloor features noted are: well splays, drilling mud, anchor chain scars, and disturbed seafloor areas. A total of nine-hundred and sixty-two (962) side scan sonar targets are noted within the development area. Nine-hundred and fifty six (956) of the nine-hundred and sixty-two (962) of these targets are randomly scattered with similar appearances that measure less than 20 feet in length, less than 10 feet in width, and do not display a height above the surrounding seafloor. (FGSI Report No. 2400-1019 pg. 5)Recent d eep -water AUV surveys, verified by ROV video, have also shown contacts of this appearance may

represent non-biologic partially cemented mud vent tubes. These cemented vent tubes are the result of erosional seafloor forces which wash away surrounding softer unconsolidated sediments surrounding the vent tube leaving only a partially cemented sediment vent core, which are left rising above the seafloor. These non-biologic partially cemented mud vent tubes can be identified on sonar records as "dark specks" not unlike those identified on the sonar records collected during this survey. These dark-specks were also previously identified during the FGCI report.

The dark specks are defined as relict cemented vent tubes or their debris. These cemented vent tubes are believed to be remnants of small, partially mud filled fluid expulsion pathways that initially occupied the bottom of pockmarks and were exposed by erosion.

None of the 956 (including Nos. 379, 374 and 369 which are within the 2000’ clearance area for well location I) sonar contacts described above are deemed archaeologically significant. Multiple debris fields containing numerous smaller debris targets, similar to the “dark specks” noted by FGCI, were noted during the current Archaeological Assessment

.

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

- specks” discussed above or correlate to known infrastructure. Sonar contact No. 156 measures 68.9 feet in length, 3.5 feet in width, and no measurable height above the surrounding seafloor. This contact is linear in shape and is interpreted as modern debris, possibly a section of pipeline or cable. Contact no. 419 measures 57.4 feet in length, 44.5 feet in width, with a height of 11.7 feet above the surrounding seafloor. This contact is geologic in origin and is interpreted as a rafted block. Sonar contact N o. 421 was noted in the vicinity of the reported position of an Acoustic Doppler Current Profiler (ADCP) and likely represents the weights at the base of the ADCP string. Sonar contact No. 445 measures 74.9 feet in length, 4.4 feet in width, and no measurable height above the surrounding seafloor. This contact is linear in shape and is interpreted as modern debris, possibly a section of pipeline or cable. Sonar contact No. 539 was noted at the location of an anchor touch-down point and probably represents disturbed seafloor sediments. These five (5) sonar contacts are interpreted as modern debris, disturbed sediments, or existing infrastructure and are not deemed archaeologically significant.

The sixth sonar contact larger than the “dark specks” is contact No. 375. The contact measures 87.1 feet long 33.1 feet wide, and 18.54 feet above the seafloor. Its coordinates are X = 2,375,889 and Y = 9,598,109. This contact appears irregular in shape and may contain numerous smaller debris targets. Due to its larger dimensions and the fact that this contact cannot reliably be identified, it will be avoided by 1000 feet. This feature is NOT believed to be of historic significance.

There are no other side scan sonar contacts deemed as archaeologically significant. There are no other unusual depressions, scours, sediment changes or unidentified seafloor target observed within the survey area that could represent unidentified shipwreck remains.

It is possible that historic shipwreck materials may not be detected by the geophysical instruments or may be observed as modern debris. If wooden planking or other cultural materials that could represent shipwreck remains are encountered, BOEMRE archeologists will be contacted to provide an assessment of these artifacts.

Regional Overview

Walker Ridge Block 508 straddles the Sigsbee Escarpment and abyssal plain. The southern half of the block is in an area of seafloor furrows that make for variable seafloor strength. At Proposed Locations G, H, and I, the soils at the base of the furrows are of higher than normal sheer strength due to active erosion. The ridges between the furrows have not experienced the maximum erosion forces, thus, the soils are relatively soft. Proposed Locations G, H and I were positioned between furrows.

There are no fluid expulsion features, faults, or chemosynthetic communities within 2,000 feet of the proposed locations. There are piston cores, drilling splays, anchor chain scars, and previously drilled wells in the vicinity of Proposed Locations G, H, and I but none are within 2, 000’ of the locations.Location Information

Walker Ridge 508, Proposed Location G: X = 2,365,600 5
, 440’ FWL Y = 9,603,390 4
, 350’ FSL

Walker Ridge 508, Proposed Location H: X = 2,364,969 4
, 809’ FWL Y= 9,602,908 3, 868’ FSL

Walker Ridge 508, Proposed Location I: X = 2,367,900 7, 740’ FEL
Y = 9,599,140 100’ FSL

Proposed Locations G, H, and I will be drilled using a dynamically positioned vessel, thus, no anchoring is required. There are no fluid expulsion features, faults, or chemosynthetic communities within 2,000 feet of the proposed locations.

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

Based on a high-resolution geophysical survey consisting of frequency enhanced 3-D seismic, Enhanced Surface Renderings, and Enhanced Surface Renderings with Amplitudes applied, AUV surveys, and side scan sonar, Walker Ridge Block 508, Proposed Locations G, H, and I will not disturb any chemosynthetic
communities.

Kevin Bradford Vernessa J. Bradford Geophysicist Shallow Hazards Interpreter

B - F

Pursuant to NTL No. 2008-G04 the proposed operations covered by this SEP do not involve operations impacting the following: Topographic features map, Topographic features statement (shunting), Live bottoms, (Pinnacle Trend) map, Live bottoms (low relief) map, or potentially sensitive biological features

map.

G. Remotely Operated Vehicle (ROV) Monitoring Plan

In accordance with the provisions of NTL 2008-G06 , Remotely Operated Vehicle Surveys in De ep water
, Walker Ridge 508 is located in Grid 11 . Grid 11 is an area that has adequate ROV survey coverage; therefore we are not proposing to run the pre- and post-ROV survey in accordance with the NTL.

H. Threatened and Endangered Species Information

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

Common Name Scientific Name T/E Status
Hawksbill Turtle Eretmochelys imbricata E
Green Turtle Chelonia mydas T Kemp's Ridley Turtle Lepidochelys kempii E
Leatherback Turtle Dermochelys coriacea E Loggerhead Turtle Caretta caretta TThere are 29 species of marine mammals that may be found in the Gulf of Mexico (see table). Of the species

listed as Endangered, only the Sperm whale is commonly found in the project area. No critical habitat for these species has been designated in the Gulf of Mexico.

Common Name Scientific Name T/E Status Atlantic Spotted Dolphin Stenella frontalis
Blainville's Beaked Whale Mesoplodon de nsirostris
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 Ps eudorca 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

Mink e 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 Dolp hin Steno bredanensis
Sei Whale Balaenoptera borealis E
Short

- finned Pilot Whale Globicephala macrorhynchus Sowerby's Beaked Whale Mesoplodon bidens Sperm Whale Physeter macrocephalus E Spinner Dolphin (Long

- snouted) Stenella longirostris Striped Dolphin Stenella coeruleoalba
West Indian manatee Trichechus manatus E

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

I. Archaeological Report

Seafloor features noted are: well splays, drilling mud, anchor chain scars, and disturbed seafloor areas. Atotal of nine-hundred and sixty-two (962) side scan sonar targets are noted within development area. Ninehundred and fifty six (956) of the nine-hundred and sixty-two (962) of these targets are randomly scattered with similar appearances that measure less than 20 feet in length, less than 10 feet in width, and do not display a height above the surrounding seafloor. Contacts of this nature have previously been identified as industrial waste barrels, discarded munitions, and other recent man-made debris.

Recent deep-water AUV surveys, verified by ROV video, have also shown contacts of this appearance may represent non-biologic partially cemented mud vent tubes. These cemented vent tubes are the result of erosional seafloor forces which wash away surrounding softer unconsolidated sediments surrounding the vent tube leaving only a partially cemented sediment vent core, which are left rising above the seafloor. These non-biologic partially cemented mud vent tubes can be identified on sonar records as "dark specks" not unlike those identified on the sonar records collected during this survey. These dark-specks were also previously identified during the FGCI report.None of the 956 (including Nos. 379, 374 and 369 which are within the 2, 000’ clearance area for well location

I) sonar contacts described above are deemed archaeologically significant. Multiple debris fields containing numerous smaller debris targets, similar to the “dark specks” not ed by FGCI, were noted during the current Archaeological Assessment. These debris fields are not deemed archaeologically significant.

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

- specks” discussed above or correlate to known infrastructure. Sonar contact no. 156 measures 68.9 feet in length, 3.5 feet in width, and no measurable height above the surrounding seafloor. This contact is linear in shape and is interpreted as modern debris, possibly a section of pipeline or cable. Contact no. 419 measures 57.4 feet in length, 44.5 feet in width, with a height of 11.7 feet above the surrounding seafloor. This contact is geologic in origin and is interpreted as a rafted block. Sonar contact no. 421 was noted in the vicinity of the reported position of an Acoustic Doppler Current Profiler (ADCP) and likely represents the weights at the base of the ADCP string. Sonar contact no. 445 measures 74.9 feet in length, 4.4 feet in width, and no measurable height above the surrounding seafloor. This contact is linear in shape and is interpreted as modern debris, possibly a section of pipeline or cable. Sonar contact no. 539 was noted at the location of an anchor touch-down point and probably represents disturbed seafloor sediments. These five (5) sonar contacts are interpreted as modern debris, disturbed sediments, or existing infrastructure and are not deemed archaeologically significant.

The sixth sonar contact larger than the “dark specks” is contact no. 375. The contact measures 87.1 feet long 33.1 feet wide, and 18.54 feet above the seafloor. This contact appears irregular in shape and may contain numerous smaller debris targets. Due to its larger dimensions and the fact that this contact cannot reliably be identified, it should be avoided by 1000 feet.

There are no other side scan sonar contacts deemed as archaeologically significant. There are no other unusual depressions, sours, sediment changes or unidentified seafloor target observed within the survey area that could represent unidentified shipwreck remains.

It is possible that historic shipwreck materials may not be detected by the geophysical instruments or may be observed as modern debris. If wooden planking or other cultural materials that could represent shipwreck remains are encountered, BOEM archeologists will be contacted to provide an assessment of these artifacts.

Shell will comply with all conditions of NTL 2005 -G07

.

J. Air and Water Quality Information

Pursuant to NTL 2008-G04 the proposed operations covered by this SEP do not require Shell to provide additional information relating to air and water quality information. For specific information relating to air and water quality information please refer to Section 18

.

K. Socioeconomic Information

Pursuant to NTL 2008-G04 the proposed operations covered by this SEP do not require Shell to provide additional information relating to air and water quality information. For specific information relating to socioeconomic information please refer to Section 18

.!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(H (WR 807_4 DC3)X: 2,364,969Y: 9,602,908G (WR 807_4 Stones #4)X: 2,365,600Y: 9,603,390I (WR 807_4 DC2)X: 2,367,900Y: 9,599,140Well No. 1Well No. 2Well No. 3 1 0 0 0 ' A v o i d a n c e A r e a

2 0 0 0 ' C l e a r a n c e R a d i u s 2 0 0 0 ' C l e a r a n c e R a d i u s

2 0 0 0 ' C l e a r a n c e R a d i u sWALKER RIDGE9876543219998979695949392919089888786858483828180797877767574737271706968676665646362616059585756555453525150494847464544434241403938373635343332313029282726252423222120191817161514 13121110962961960959958957956955954953952951950949948947946945944943942941940939938937936935934933932931930929928927926925924923922921920919918917916915914913912911910909908907906905904903902901900899898897896895894893892891890889888887886885884883882881880879878877876875874873872871870869868867866865864863862861860859858857856855854853852851850849848847846845844843842841840839838837836835834833832831830829828827826825824823822821820819818817816815814813812811810809808807806805804803802801800799798797796795794793792791790789788787786785784783782781780779778777 776775774773772771770769768767766765764763762761760759758757756755754753752751750749748747746745744743742741740739738737736735734733732731730729728727726725724723722721720719718717716715714713712711710709708707706705704703702701700699698697696695694693692691690689688687686685684683682681680679678677676675674673672671670669668667666665664663662661660659658657656655654653652651650649648647646645644643642641640639638637636635634 633632631630629628627626625624623622621620619618617616615614613612611610609608607606605604603602601600599 598597596595594593592591590589588587586585584 583582581 580579578577576575574573572571570569568567566565564563562561560559558557556555554553552551550549548547546545544543542541540539538537536535534533532531530529528527526525524523522521520519518517516515514513512511510509508507506505504503502501500499498497496495494493492491490489488487486485484483482481480479478477476475474473472471470469468467466465464463462461460459458457456455454453452451450449448447446445444443442441440439438437436435434433432431430429428427426425424423422421420419418417416415414413412411410409408407406405404403402401400399398397396395394393392391390389388387386385384383382381380379378377376375374373372371370369368367366365364363362361360359358357356355354353352351350349348347346345344343342341340339338337336335334333332331330329328327326325324323322321320319318317316315314313312311310309308307306305304303302301300299298297296295294293292291290289288287286285284283282281280279278277276275274273272271270269268267266265264263262261260259258257256255254253252251250249248247246245244243242241240239238237236235234233232231230229 228227226225224223222221220219218217216215214213212211210209208207206205204203202201200199198197196195194193192191190189188187186185184183182181180179178177176175174173172171170169168167166165164163162161160159158157156155154153152151150149148147146145144143142141140139138137136135134133132131130129128127126125124123122121120119118117116115114113112111110109108107106105104103102101100PC-9PC-9BPC-9APC-7BPC-7APC-8BPC-8APC-5CPC-5BPC-5APC-4BPC-4APC-3APC-2BPC-2APC-1BPC-19BPC-19APC-18APC-15BPC-15APC-14BPC-14APC-13APC-12BPC-12APC-17BPC-17APC-11BPC-11APC-10BPC-10A

-850 0 - 86 00 -8 400 - 8 3 00

-8700 - 82 0 0 -810 0

- 8000

- 77 0 0

- 780 0

-79 00 - 88 00

-8 9 00 -9 00 0 -9 100

- 9 2 0 0

- 7600 -93 0 0

-7500

- 7400

- 7 300

-9 4 0 0 -7 2 00

-7100 -7 00 0

-6900 - 6800

- 9 50 0 -6700

-96 0 0

-6 60 0

-650 0 -97 0 0

-6400

-6 400

-6600

-6900

-6500

-6400

- 6 9 00 -9 7 0 0 -7 500 -7 20 0

- 70 0 0

-6900 - 740 0 - 73 00

-67 00 -650 0 - 6 8 0 0

-68 00 -71 00 - 96 0 0

-6600

-7000 - 9 7 0 0 - 70 00

-68 00

-6600

-6800 -6 700 -6500 -71 00

- 6 500

-6400WR464G32690PETROBRASWR509G18731SHELLWR507G18730SHELLWR422G32681ENIWR552G18737SHELLWR420G32680STATOILWR508G17001SHELLWR551G21861SHELLWR553G17004SHELLWR550G25254MARATHONWR597G26409SHELLWR596G21862SHELLWR423G32682ENIWR376G33375PETROBRASWR375G26394SHELLWR377G33376EXXONMOBILWR374G31958HUNT OILWR463WR421WR466WR419WR554WR510WR465WR506WR462WR418WR598WR595WR594WR555WR511WR467WR378WR599WR379233000023300002345000234500023600002360000237500023750002390000239000024050002405000

9575000 9575000

9590000 9590000

9605000 9605000

9620000 9620000

9635000 9635000

9650000 965000090°40'30"W90°40'30"W90°45'0"W90°45'0"W90°49'30"W90°49'30"W

26°33'0"N 26°33'0"N

26°28'30"N 26°28'30"N

26°24'0"N 26°24'0"N$LATXALMSFLGALLHILUHEKCDCGCDDGBAWWRMCACELEBVNHHFMFPEIGAWCAPVESSECRKSTLSMPAMSMSEVKGIVKPENBRWDMSEWMOSPMBCSBSCSACALPELPWPELBOBACSALLM ACEBMMISATProject AreaKEY MAPMAP INFORMATIONDrawing: Stones_Amplitude_Map.m xdAuthor:david.irick@shell.com09/07/2011Date:Produced by GeomaticsSHELL EXPLORATION & PRODUCTION COMPANYSEABED AMPLITUDE MAPWalker Ridge AreaBlock 508This Map has been prepared byShell from a variety of sources bothwithin Shell and third party information(ESRI and GOM3).The map may be subject to errorsof judgement and/or opinion.Information from third party sourcescan not be confirmed or gauranteedby Shell.Important - Please NoteMAP INFORMATIONGOM_NAD1927_UTM15NfeetProjection: Transverse_MercatorFalse_Easting: 1640416.666667False_Northing: 0.000000Central_Meridian: -93.000000Scale_Factor: 0.999600Latitude_Of_Origin: 0.000000Linear Unit: Foot_USGCS_North_American_1927Datum: D_North_American_1927MAP SCALE1:30,000!.Location2000' Clearance RadiusSonar Contacts!Disturbed Sediments!Irregular!Linear!Rafted Block!Small Debris Target!Weights for ADCP!(High Reflective Sonar Contact!(Post-Drilled Well1000' Avoidance Area!(Soil Sample (Piston Core)NOAA Contours (100ft Intervals)GOM3 Lease BlockGulf of Mexico0 0.511.5 20.25Nautical Miles

Relative AmplitudeLowHigh$SECTION 7: WASTE AND DISCHARGE INFORMATION

A. Projected Ocean DischargesB. Projected Generated Wastes

C. Modeling Report

Shell did not model the trajectory for discharges because it is not required in the GOM.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 = 3400D 2/3 for CO, and CT 33.3D for the other air pollutants (where D distance to shore in miles)? x

Do your emission calculations include an y 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 H 2 S 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
Emission 1

Amounts (tons) Calculated

Exemption 2

Amounts (tons) Calculated

Complex Total
Emission
Amounts 3 (tons)

PM 144.86 6060.60 NA
SO x 663.94 6060.60 NA
NOx 4975.65 6060.60 NA
VOC 149.41 6060.60 NA
CO 1085.59 109,192.59 NA

1 For activities proposed in your EP or DOCD, list the projected emissions calculated from the worksheets.
2 List the exemption amounts for your proposed activities calculated by using the formulas in 30 CFR 250.303(d).
3 List the complex total emissions associated with your proposed activities calculated from the worksheets

(2) Contact: Tracy Albert, (504) 728-4652

, tracy.albert@shell.com

(1) Worksheets

Because the answers to all the questions set forth above are “no” further worksheets are not required.SECTION 9: OIL SPILL INFORMATION

A. Oil Spill Response Planning

All the proposed activities and facilities in this SEP will be covered by the Regional OSRP filed by Shell Offshore Inc (0689) in accordance with 30 CFR 250. An update to the Regional OSRP was filed with the BOEMRE October 26, 2010, March 15, 2011, May 31, 2011, July 6, 2011 and August 1, 2011 and is pending approval. An updated OSRP Certification in accordance with 30 CFR 254.2 was accepted by the BOEMRE on August 4, 2011.

Spill Response Sites: Primary Response Equipment Locations Preplanned Staging Location(s) Fourchon, LA; Cameron, LA; Houma, LA; Lake

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

The names of the oil spill removal organizations (OSRO’s) under contract include Clean Gulf Associates (CGA), Marine Spill Response Company (MSRC), Clean Caribbean America (CCA), and OSRL/EARL.

Worst Case Scenario Determination: Category Regional OSRP EP Type of Activity 1 Drilling Rig Drilling Rig Facility Location (area/block) MC 807 WR 508 Facility Designation 2 Subsea well A Subsea well H Distance to Nearest Shoreline (miles) 5 3 182

Volume 3 Storage tanks (total) Flowlines (on facility) Pipelines Uncontrolled blowout (volume per day)
Total Volume N/A N/A N/A

4 65 ,000 * BOPD ◊

4 65 ,000 Bbls N/A N/A N/A

42 ,000* * BOPD

42 ,000 Bbls Type of Oil(s)

- (crude oil, condensate, diesel) Crude oil Crude oil

API Gravity(s) 4 2 6 o 2 8 o

*24 hour rate (365,000 BOPD 30 day average) **24 hour rate ( 33 ,000 BOPD 30 day average)

◊ MC 807 Subsea Well A (Olympus) was submitted as subsea WCD in our OSRP update of August 1, 2011 and was covered for 2010-N06 in Plan S-7499 (pending BOEM approval).

Footnotes:
1. Types of activities include pipeline, platform, caisson, subsea completion or manifold, and mobile drilling rig. 2. E.g., Well No. 2, Platform JA, Pipeline Segment No. 6373. 3. Your regional OSRP worst-case scenario volume must be taken from the appropriate section of your regional OSRP. For EP’s, the worst-case scenario volume must be determined by using the daily worst-case discharge volume determined using the guidance at 30 CFR 254.47(b). For DOCD’s, the daily worst -case discharge volume must be determined by using the guidance at 30 CFR 254.47 (a) and/or (b), as appropriate. 4. Provide API gravity of all oils given under “Type of Oil(s)” above. Estimate for EP’s.

Since Shell Offshore Inc. has the capability to respond to the appropriate worst-case spill scenario included in its regional OSRP, filed with the BOEMRE October 26, 2010, March 15, 2011, May 31, 2011

, July 6, 2011 and August 1, 2011 and is pending approval, and since the worst-case scenario determined for our Plan does not replace the appropriate worst-case scenario in our regional OSRP, I hereby certify that Shell Offshore Inc. has the capability to respond, to the maximum extent practicable, to a worst-case discharge, or a substantial threat of such a discharge, resulting from the activities proposed in our SEP.B. Oil Spill Response Discussion

Volume of the Worst Case Discharge Please refer to Section 2j and 9(iv) of this SEP.

2. Trajectory Analysis

Trajectories of a spill and the probability of it impacting a land segment have been projected utilizing information in the BOEMRE Oil Spill Risk Analysis Model (OSRAM) for the Central and Western Gulf of Mexico available on the BOEMRE website using 30 day impact. Offshore areas along the trajectory between the source and land segment contact could be impacted. The land segment contact probabilities are shown in Table 9.C.1.

Area/Block OCS

- G Launch
Area Land Segment Contact %

Exploratory
WR 508 48 Calhoun, TX

- Matagorda, TX 1 Brazoria, TX 1 Galveston, TX 2 Jefferson, TX 1

Camer on, LA 2 Vermilion, LA 1 Iberia, LA

- St. Mary, LA

- Terrebonne, LA 1 Lafourche, LA

- Jefferson, LA

- Plaquemines, LA 2

Table 9.C.1 Probability of Land Segment Impact C. Resource Identification

The locations identified in Table 9.C.1 are the highest probable land segments to be impacted using the BOEMRE Oil Spill Risk Analysis Model (OSRAM). The environmental sensitivities are identified using the appropriate National Oceanic and Atmospheric Administration (NOAA) Environmenta l Sensitivity Index (ESI) maps for the given land segment. ESI maps provide a concise summary of coastal resources that are at risk if an oil spill occurs nearby. Examples of at-risk resources include biological resources (such as birds and shellfish beds), sensitive shorelines (such as marshes and tidal flats), and human-use resources (such as public beaches and parks).

In the event an oil spill occurs, ESI maps can help responders meet one of the main response objectives: reducing the environmental consequences of the spill and the cleanup efforts. Additionally, ESI maps can be used by planners to identify vulnerable locations, establish protection priorities, and identify cleanup strategies.

The following is a list of resources of special economic or environmental importance that potentially could be impacted by the Walker Ridge 508 WCD scenario.Onshore/Nearshore: Plaquemines Parish has been identified as the most probable impacted

Parish within the Gulf of Mexico for the Greater than 10 Mile Worst Case Discharge and the Exploratory Worst Case Discharge. Plaquemines Parish has a total area of 2,429 square miles of which, 845 square miles of it is land and 1,584 square miles is water. Plaquemines Parish includes two National Wildlife Refuges: Breton National Wildlife Refuge and Delta National Wildlife Refuge. This area is also a nesting ground for the brown pelican, an endangered species. Examples of Environmental Sensitivity maps for Plaquemines Parish are detailed in the following pages. Example ESI maps for Plaquemines Parish and the legend are shown in Figures 9.C.1 through 9.C.5.

Cameron Parish is identified as the most probable impacted Parish within the Gulf of Mexico for the Exploratory Worst Case Discharge. Cameron Parish is located in the southwest corner of Louisiana and has a total area of 1,932 square miles of which, 1,313 square miles of it is land and 619 square miles is water. Cameron Parish includes four National Wildlife Refuges including the Cameron Prairie National Wildlife Refuge, East Cove National Wildlife Refuge, Sabine National Wildlife Refuge and part of the Lacassine National Wildlife Refuge.

Galveston County has been identified as the most probable impact Parish within Gulf of Mexico for the Exploratory Worst Case Discharge at 2%. Galveston County is located on the plains of the Texas Gulf Coast in the southeastern part of the state. The county is bounded on the northeast by Galveston Bay and on the northwest by Clear Creek and Clear Lake. Much of the county covers Galveston Bay, and is bounded to the south by the Galveston Seawall and beaches on the Gulf of Mexico. Galveston County has a total area of 873 square miles which 398 square miles is land and 474 square miles (54.35%) is water.

Offshore: An offshore spill may require an Essential Fishing Habitat (EFH) Assessment. This assessment would include a description of the spill, analysis of the potential adverse effects on EFH and the managed species; conclusions regarding the effects on the EFH; and proposed mitigation, if applicable.

Significant pre-planning of joint response efforts was undertaken in response to provisions of the National Contingency Plan (NCP). Area Contingency Plans (ACPs) were developed to provide a well coordinated response to oil discharges and other hazardous releases. The One Gulf Plan is specific to the Gulf of Mexico to advance the unity of policy and effort in each of the Gulf Coast ACPs. Strategies used for the response to an oil spill regarding protection of identified resources are detailed in the One Gulf Plan and relevant Gulf Coast ACP.

D. Worst Case Discharge Response

Shell will make every effort to respond to the WR 508 Worst Case Discharge as effectively as possible. Applied Science Associates (ASA) conducted a deepwater blowout simulation for The Response Group to better determine subsurface and surface evaporation and dispersion rates. Below is a table outlining the applicable evaporation and dispersion quantities:

Walker Ridge 508 Calculations (BBLS)

i. 30 Day Average WCD = 33, 000 bbls

ii. Subsurface dispersion

– 25% (Water Depth = ~9,558 ft)

- 8,200 bbls

iii. REMAINING WCD AFTER SUBSURFACE DISPERSION 24,800 bbls

iv. Surface dispersion and evaporation

– 25%

- 6,200 bbls

TOTAL REMAINING ~18,600 bbls

Table 9.D.1 Oil Remaining After Subsurface and Surface Dispersion

Shell has contracted OSROs to provide equipment, personnel, materials and support vessels as well as temporary storage equipment to be considered in order to cope with a WCD spill. Under adverse weather conditions, major response vessels and Transrec skimmers are still effective and safe in sea states of 6-8 ft. If sea conditions prohibit safe mechanical recovery efforts, then natural dispersion and airborne chemical dispersant application (visibility & wind conditions permitting) may be the only safe and viable recovery option.MSRC OSRV 8 foot seas VOSS System 4 foot seas Expandi Boom 6 foot seas, 20 knot winds Dispersants Winds more than 25 knots, Visibility less than 3 nautical miles, or Ceiling less than 1, 000 feet.

Table 9.D.2 Operational Limitations of Response Equipment

Upon notification of the spill, Shell would request a partial or full mobilization of contracted resources, including, but not limited to, skimming vessels, oil storage vessels, dispersant aircraft, subsea dispersant, shoreline protection, wildlife protection, and containment equipment. Following is a list of the contracted resources including de-rated recovery capacity, personnel, and estimated response times (procurement, load out, travel time to the site, and deployment). The Incident Commander or designee may contact other service companies if the Unified Command deems such services necessary to the response efforts.

Based on the anticipated worst case discharge scenario, Shell can be onsite with dedicated, contracted on water oil spill recovery equipment with adequate response capacity to contain and recover surface oil, and prevent land impact, within 27 hours (based on the equipment’s Estimated Daily Response Capacity (EDRC)). Shell will continue to ramp up additional on-water mechanical recovery resources as well as apply dispersants and in-situ burning as needed and as approved under the supervision of the USCG Captain of the Port (COTP) and the Regional Response Team (RRT).

Subsea Control and Containment: Shell, as a founding member of the MWCC, will have access to the IRCS that can be rapidly deployed through the MWCC. The IRCS is designed to contain oil flow in the unlikely event of an underwater well blowout, and is designed, constructed, tested, and available for rapid response. Shell’s specific containment response for WR 508 will be addressed in Shell’s NTL 2010-N10 submission at the time the APD is submitted.

Table 9.D.9 Control, Containment, and Subsea Dispersant Package Activation List

Mechanical Recovery (skimming): Response strategies include skimming utilizing available OSROs Oil Spill Response Vessels (OSRVs), Oil Spill Response Barges (OSRBs), ID Boats, and Quick Strike OSRVs. There is a combined de-rated recovery rate capability of approximately 562,000 barrels/day. Temporary storage associated with the identified skimming and temporary storage equipment equals approximately 461,000 barrels.

De

- rated Recovery Rate (bopd) Storage (bbls) Offshore Recovery and
S torage 455,480 444,700 Nearshore Recovery and Storage 106,993 17,224

Total 562,473 461,924

Table 9.D.3 Mechanical Recovery Combined De-Rated Capability

Table 9.D.4 Offshore On-Water Recovery and Storage Activation List Table 9.D.5 Nearshore On-Water Recovery and Storage 5ctivation List

Oil Storage: The strategy for transferring, storing and disposing of oil collected in these recovery zones is to utilize two 150,000-160,000 ton (dead weight) tankers mobilized by Shell (or any other tanker immediately available). The recovered oil would be transferred to Motiva’s Norco, LA storage and refining facility, or would be stored at Delta Commodities, Inc. Harvey, LA facility.

Aerial Surveillance: Aircraft can be mobilized to detect, monitor, and target response to oil spills. Aircraft and spotters can be mobilized within hours of an event.

Table 9.D.6 Aerial Surveillance Activation ListAerial Dispersant: Depending on proximity to shore and water depth, dispersants may be a viable

response option. If appropriate and approved, 4 to 5 sorties from three DC- 3’s can be made within the first 12 hour operating day of the response. These aerial systems could disperse approximately 7,704 to 9,630 barrels of oil per day. Additionally, 3 to 4 sorties from the BE90 King Air and 3 to 4 sorties from the Hercules C-130A within the first 12 hour operating day of the response could disperse 4,600 to 6,100 barrels of oil per day. For continuing dispersant operations, the CCA’s Aerial Dispersant Delivery System (ADDS) would be mobilized. The ADDS has a dispersant spray capability of 5,000 gallons per sortie.

Table 9.D.7 Offshore Aerial Dispersant Activation List

Vessel Dispersant: Vessel dispersant application is another available response option. If appropriate, vessel spray systems can be installed on offshore vessels of opportunity using inductor nozzles (installed on fire-water monitors), skid mounted systems, or purpose-built boom arm spray systems. Vessels can apply dispersant within the first 12-24 hours of the response and continually as directed.

Table 9.D.8 Offshore Boat Spray Dispersant Activation List

Subsea Dispersant: Shell has contracted with Wild Well Control for a subsea dispersant package. Subsea dispersant application has been found to be highly effective at reducing the amount of oil reaching the surface. Additional data collection, laboratory tests and field tests will help in facilitating the optimal application rate and effectiveness numbers. For planning purposes, the system has the potential to disperse approximately 24,500 to 34,000 barrels of oil per day.

Table 9.D.9 Control, Containment, and Subsea Dispersant Package Activation List

In -Situ Burning: Open-water in-situ burning (ISB) also may be used as a response strategy, depending on the circumstances of the release. ISB services may be provided by the primary OSRO contractors. If appropriate conditions exist and approvals are granted, one or multiple ISB task forces could be deployed offshore. Task forces typically consist of two to four fire teams, each withtwo vessels capable of towing fire boom, guide boom or tow line with either a handheld or aeriallydeployed oil ignition system. At least one support/safety boat would be present during active burning operations to provide logistics, safety and monitoring support. Depending upon a number of factors, up to 4 burns per 12-hour day could be completed per ISB fire team. Most fire boom systems can be used for approximately 8-12 burns before being replaced. Fire intensity and weather will be the main determining factors for actual burns per system. Although the actual amount of oil that will be removed per burn is dependent on many factors, recent data suggests that a typical burn might eliminate approximately 750 barrels. For planning purposes and based on the above assumptions, a single task force of four fire teams with the appropriate weather and safety conditions could complete four burns per day and remove up to ~12,000 bbls/day. In-situ burning nearshore and along shorelines may be a possible option based on several conditions and with appropriate approvals, as outlined in Section 19, In-situ Burn Plan (OSRP). In-situ burning along certain types of shorelines may be used to minimize physical damage where access is limited or if it is determined that mechanical/manual removal may cause a substantial negative impact on the environment. All safety considerations will be evaluated. In addition, Shell will assess the situation and can make notification within 48 hours of the initial spill to begin ramping up fire boom production through contracted OSRO(s). There are potential limitations that need to be assessed prior to ISB operations. Some limitations include atmospheric and sea conditions; oil weathering; air quality impacts; safety of response workers; and risk of secondary fires.

Table 9.D.10 In -Situ Burn Equipment Activation List

Shoreline Protection: If the spill went unabated, shoreline impact in Plaquemines Parish, LA; Cameron Parish, LA; and Galveston County, TX would depend upon existing environmental conditions. Nearshore response may include the deployment of shoreline boom on beach areas, or protection and sorbent boom on vegetated areas. Strategies would be based upon surveillance and real time trajectories provided by The Response Group that depict areas of potential impact given actual sea and weather conditions. Strategies from the New Orleans, Louisiana Area Contingency Plan, Unified Command would be consulted to ensure that environmental and special economic resources would be correctly identified and prioritized to ensure optimal protection. Shell has accessto shoreline response guides that depict the protection response modes applicable for oil spill cleanup operations. Each response mode is schematically represented to show optimum deployment andoperation of the equipment in areas of environmental concern. Supervisory personnel have the

option to modify the deployment and operation of equipment allowing a more effective response to site-specific circumstances.

Table 9.D.11 Shoreline Protection and Wildlife Support List

Wildlife Protection: If wildlife is threatened due to a spill, the contracted OSRO’s have resources available to Shell, which can be utilized to protect and/or rehabilitate wildlife. The resources under contract for the protection and rehabilitation of affected wildlife are in Table 9.D.11.

New or unusual technology in regards to spill, prevention, control and clean- up: Shell will use our normal well design and construction processes with multiple barrier approach as well as new stipulations mandated by NTL 2008 -N05. Response techniques will utilize new learnings from Macondo response to include in-situ burning and subsea dispersant application. Mechanical recovery advancements are continuing to be made to incorporate utilization of Koseq arms outfitted on barges, conversion of Platform Support Vessels for Oil Spill Response, and inclusion of nighttime spill detection radar to improve tracking capabilities (X-Band radar, infrared sensing, etc.). In addition, new response technologies/techniques are continuing to be considered by Shell and the appropriate government organizations for incorporation into our planned response. Any additional response technologies/techniques presented at the time of response will be used at the discretion of the Unified Command and USCG.

C. Modeling Report

Shell did not model oil or hazardous substance spills.Figure 9.C.1 Environmental Sensitivity Index Map LegendFigure 9.C.2 South Pass ESI MapFigure 9.C.3 Garden Island Pass ESI Map

### .

Figure 9.C.4 Pass a Loutre West ESI MapFigure 9.C.5 Main Pass ESI MapTable 9.D.4 Offshore On-Water Recovery and Storage Activation ListTable 9.D.4 Offshore On-Water Recovery and Storage Activation List (continued)Table 9.D.4 Offshore On-Water Recovery and Storage Activation List (continued)Table 9.D.4 Offshore On-Water Recovery and Storage Activation List (continued)Table 9.D.5 Nearshore On-Water Recovery Activation ListTable 9.D.5 Nearshore On- Wat er Recovery Activation List (continued)Table 9.D.5 Nearshore On-Water Recovery Activation List (continued)Table 9.D.5 Nearshore On-Water Recovery Activation List (continued)Table 9.D.6 Aerial Surveillance Activation List

Table 9.D.7 Offshore Aerial Dispersant Activation ListTable 9.D.8 Offshore Boat Spray Dispersant Activation List

Table 9.D.9 Control, Containment, and Subsea Dispersant Package Activation ListTable 9.D.10 In-Situ Burn Equipment Activation ListTable 9.D.10 In-Situ Burn Equipment Activation List (continued)Table 9.D.10 In-Situ Burn Equipment Activation List (continued)Table 9.D.10 In-Situ Burn Equipment Activation List (continued)

Table 9.D.10 In-Situ Burn Equipment Activation List (continued)Table 9.D.11 Shoreline Protection and Wildlife Support ListSECTION 10 : ENVIRONMENTAL MONITORING INFORMATION

A. Monitoring Systems

A rig-based Acoustic Doppler Current Profiler (ADCP) is used to continuously monitor the current beneath the Rig. Metocean conditions such as sea states, wind speed, ocean currents, etc. will also be continuously monitored.

B. Incidental Takes

No incidental takes are anticipated. Shell implements the mitigation measures and monitors for incidental takes of protected species according to the following notices to lessees and operators from the Minerals Management Service:

NTL 2007-G03 “Marine Trash and Debris Awareness and Elimination” NTL 2007-G04 “Vessel Strike Avoidance and Injured/Dead Protected Species Reporting”

C. Flower Garden Banks National Marine Sanctuary

The operations proposed in this SEP will not be conducted within the Protective Zones of the Flower Garden Banks and Stetson Bank.SECTION 11 : LEASE STIPULATIONS INFORMATION

Lease s OCS- G 18730 and 17001 are not part of a Biological Sensitive Area, known Chemosynthetic Area, or Shipping Fairway. See Section 6 of this plan for site specific archeological information.

SECTION 12 : ENVIRONMENTAL MITIGATION MEASURE INFORMATION

A. Impacts to Marine and coastal environments

The proposed action will implement mitigation measures required by laws and regulations, including all applicable Federal & State requirements concerning air emissions, discharges to water, and solid waste disposal, as well as any additional permit requirements and Shell policies. Project activities will be conducted in accordance with the Regional Oil Spill Response Plan. Section 18 of this plan discusses impacts and mitigation

measures.

B. Incidental Takes

We do not anticipate any incidental takes related to the proposed operations. Shell implements the mitigation measures and monitors for incidental takes of protected species according to the following notices to lessees and operators from the Minerals Management Service:

NTL 2007-G03 “Marine Trash and Debris Awareness and Elimination” NTL 2007-G04 “Vessel Strike Avoidance and Injured/Dead Protected Species Reporting”

SECTION 13 : RELATED FACILITIES AND OPERATIONS INFORMATION

Information regarding Related Facilities and Operations Information, transportation systems, & produced liquid hydrocarbon transportation vessels are not included in this SEP as such information is only necessary in the case of DOCDs.SECTION 14 : SUPPORT VESSELS AND AIRCRAFT INFORMATION

A. General

Type Maximum Fuel Tank

Sto rage Capacity (Gals) Maximum No. In Area at Any Time Trip Frequency or Duration

Crew Boats 8,000 2 Twice per week Offshore Support Vessels 120,000 3 Twice per week Helicopter 76 0 1 Once per day

B. Diesel Oil Supply Vessels

Size of Fuel Supply Vessel Cap acity of Fuel Supply Vessel Frequency of Fuel Transfers Route Fuel Supply Vessel Will Take

280 foot length 100,000 gals. 1 week Port Fourchon to WR 508

C. Drilling Fluids Transportation

This Plan does not propose activities in the State of Florida; therefore the following table is not required. It is being provided for information only.

Type of Material Quantity Being Transported Transportation Method Dry Bulk (Cement, Barite, Gel) 12,000 sx max combined Below deck dry bulk tanks onboard OSV Synthetic

- base drilling fluids 11,000 bbls max per voyage Tanks below deck onboard OSV

D. Solid and Liquid Wastes Transportation

See Section 7, Table 7B.

E. Vicinity Map

See Section 18, Figure 1 for Vicinity Map.SECTION 15 : ONSHORE SUPPORT FACILITIES INFORMATION

A. General

Name Location Existing/New/Modified

Fourchon Port Fourchon, LA Existing

Amelia PHI Heliport Amelia LA Existing

The onshore support bases for water and air transportation will be the existing terminals in Amelia and Fouchon, Louisiana. The Fouchon boat facility is operated by SOI and is located on Bayou Lafourche

, south of Leeville, LA approximately 3 miles from the Gulf of Mexico. The existing onshore air support base in Amelia, LA is located at 4008 Lake Palourde Road, Amelia, LA 703 40

.

B. Support Base Construction or Expansion

This Section does not apply to this SEP as Shell does not plan to construct a new onshore support base or expand an existing one to accommodate the activities proposed in this SEP.

C. Support Base Construction or Expansion Timetable

This Section does not apply to this SEP as Shell does not plan to construct a new onshore support base or expand an existing one to accommodate the activities proposed in this SEP.

D. Waste Disposal

See Section 7, Tables 7A and 7B.

E. Air emissions

Not required by BOEM GOM.

F. Unusual solid and liquid wastes

Not required by BOEM GOM.

SECTION 16 : SULPHUR OPERATIONS INFORMATION

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

SECTION 17 : COASTAL ZONE MANAGEMENT ACT (CZMA) INFORMATION

Louisiana Coastal Zone Consistency was granted in Plan N-8155 and is not required for Suppl e mental Exploration Plans. Texas Coastal Zone Consistency was granted in Plan S-7129.SECTION 18. ENVIRONMENTAL IMPACT ANALYSIS (EIA)



# Introduction

Project Summary

Shell Offshore Inc. (Shell) is submitting a Supplemental Exploration Plan (EP) for Walker Ridge (WR) Block 507 and 508 . Shell submitted a Supplemental EP for wells C and D in WR 508, which was approved by the Minerals Management Service (MMS, now Bureau of Ocean Energy Management, Regulation and Enforcement [BOEMRE]) on 23 May 2 00 6 (Plan Control

No. S- 6899 ). Shell is now submitting a Supplemental EP that includes three exploration wells in
WR 507 and 508 ; these wells are G, H, and I. This Supplemental EP also incorporates the revised blowout scenario and worst case discharge (WCD) information as required by Notice to Lessees (NTL) 2010 -N06.

The lease area is 178 miles (286 km) from the nearest shoreline, 193 miles (311 km) from the onshore support base at Port Fourchon, Louisiana, and 221 miles (356 km) from the helicopter base at Amelia, Louisiana ( Figure 1 ). All miles in this EIA are statute miles. Water depths at the wellsites range from 9,554 to 9,578 ft (2,912 to 2,919 m).

The Noble Danny Adkins or a similar dynamically positioned (DP) semisubmersible rig will be used for drilling. Drilling of wells will commence during the first quarter of 2012 and should be finished by the second quarter of 2013. The average time to drill a well will be approximately

149 days.



## Purpose of the EIA

This Environmental Impact Analysis (EIA) was prepared pursuant to the requirements of the Outer Continental Shelf Lands Act (OCSLA), 43 U.S.C. §§ 1331-1356, and BOEMRE regulations, including 30 CFR 250.21 2( o) and 250.2 27. The EIA is a project- and site-specific analysis of Shell’s planned activities under this EP . The EIA also evaluates potential impacts in accordance with Notice to Lessee ( NT L) 2008 -G04 issued by the BOEMRE.

The EIA presents data, analysis, and conclusions to support BOEMRE reviews as required by the National Environmental Policy Act (NEPA) and other relevant Federal laws, including the Endangered Species Act (ESA) and Marine Mammal Protection Act (MMPA), as the agency considers this Supplemental EP for approval. It also identifies the mitigation measures Shell will implement in connection with the planned activities.

As specified in NTL 2008-G04, an EIA is a project-specific analysis that focuses on the impacts of a specific plan. This EIA addresses the impact-producing factors (IPFs), resources, and impacts associated with the activities proposed in this Supplemental EP including drilling of wells. The EIA also incorporates the revised blowout scenario and worst case discharge (WCD) information required by NTL 2010 -N06.

### Figure 1. Vicinity map for the lease area.

### The BOEMRE has performed numerous environmental evaluations of oil and gas activities on

the Gulf of Mexico Outer Continental Shelf (OCS). Potential impacts were analyzed at a broader level in the Programmatic Environmental Impact Statement (EIS) for the OCS Oil and Gas Leasing Program (MMS, 2007a) and in recent multi-lease-sale EISs for the Western and Central Gulf of Mexico Planning Areas (MMS, 2007b, 2008), as well as the Environmental Assessment (EA) for Gulf of Mexico deepwater operations and activities (MMS, 2000).

These studies generated critical data and advanced the large body of existing knowledge on t he Gulf of Mexico OCS. They analyze everything from potential impacts on the natural environment to the socioeconomic effects of exploration and development activities. They include numerous technical studies ranging from the likely trajectory of spilled oil to the effects of underwater noise on threatened and endangered species. They inform agency decision-making on lease offerings, mitigation measures and lease stipulations, operational requirements, and permit restrictions. This substantial body of work, which in part forms the basis for the evaluation presented here, will allow the BOEMRE and other regulatory agencies to
evaluate Shell’s Supplemental EP and ensure that oil and gas exploration and development activities are performed in an environmentally sound manner, with minimal impacts on the environment. Shell has incorporated these comprehensive environmental analyses by reference and built on them with project and site-specific analyses.



## OCS Regulatory Framework

The regulatory framework for OCS activities in the Gulf of Mexico has been summarized by MMS (2010). Under the OCSLA, the U.S. Department of the Interior (USDOI) is responsible for the administration of mineral exploration and development of the OCS. Within the USDOI, the BOEMRE is charged with the responsibility of managing and regulating the development of OCS oil and gas resources in accordance with the provisions of the OCSLA. The BOEMRE operating regulations are in 30 CFR Parts 250, 251, and 254.

In implementing its responsibilities under the OCSLA and NEPA, the BOEMRE must consult numerous Federal departments and agencies that have authority to govern and maintain ocean resources pursuant to other Federal laws. Among these are the U.S. Coast Guard (USCG), U.S. Environmental Protection Agency (USEPA), U.S. Fish and Wildlife Service (USFWS), and the National Oceanic and Atmospheric Administration (NOAA) through the National Marine Fisheries Service (NMFS). Federal regulations establish consultation and coordination processes with Federal, State, and local agencies (e. g. , the ESA, MMPA, Coastal Zone Management Act of 1972, and the Magnuson-Stevens Fishery Conservation and Management Act).

NTLs are formal documents issued by the BOEMRE that provide clarification, description, or interpretation of a regulation or standard; provide guidelines on implementing a special lease stipulation or regional requirement; provide a better understanding of the scope and meaning of a regulation by explaining the BOEMRE interpretation of a requirement; or transmit administrative information such as current telephone listings or changes in BOEMRE personnel
or office address. Table 1 lists and summarizes the NTLs that are referenced in this EIA.Table 1. Notices to Lessees and Operators (NTLs) that are referenced in this Environmental Impact Analysis (EIA).

NTL Title Summary

2010

- N10 Statement of Compliance with

Applicable Regulations and Evaluation of Information Demonstrating Adequate Spill Response and Well Containment Resources Informs operators usin g 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 appl icable regulations, including the increased safety measures regulations (75 FR 63346). Informs operators that the BOEMRE will be evaluating whether each operator has submitted adequate information demonstrating that it has access to and can deploy
contain ment resources to promptly respond to a blowout or other loss of well control.

2010

- N06 Information Requirements for

Exploration Plans, Development and Production Plans, and Development Operations Coordination Documents on the OCS Rescinds the limitations set forth in NTL 2008

- G04 regarding a blowout scenario and worst case discharge scenario (WCD), and provides guidance regarding the information required in blowout scenario and worst case discharge scenario descriptions.

2009

- G40 Deepwater Benthic Commun ities Guidance for avoiding and protecting high

- density deepwater benthic communities (including chemosynthetic and deepwater coral communities) from damage caused by Outer Continental Shelf (OCS) oil and gas activities in water depths greater than 984 ft (300 m). Prescribes separation distances of 2,000 ft (610 m) from each mud and cuttings discharge location and 250 ft (76 m) from all other seafloor disturbances.

2009

- G39 Biologically

- Sensitive Underwater

Features and Areas Guidance for avoiding and pro tecting 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 In formation 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 Spe cies Act and Marine Mammal
Protection Act.

2007

- G04 Vessel Strike Avoidance and

Injured/Dead Protected Species Reporting Recommends protected species identification training, recommends that vessel operators and crews maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid striking protected species, and requires operators to report sightings of any injured or dead protected species.

2007

- G03 Marine Trash and Debris Awareness

and Elimination Instructs operators to exercise caution in the handling and disposal of small items and packaging materials; requires the posting of placards at prominent locations on offshore vessels and structures; and mandates a yearly marine trash and debris awareness training and certification pro cess.

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 re sources.

## Oil Spill Prevention and Contingency Planning

Shell submitted an update to the Gulf of Mexico Regional Oil Spill Response Plan (OSRP) to the BOEMRE as a fundamental component of the planned drilling program

. The OSRP certifies that Shell has the capability to respond to the maximum extent practicable to a WCD (30 CFR 254.2) (see Supplemental EP Section 9 ) . The OSRP demonstrates Shell’s capabilities to rapidly and effectively manage oil spills that may result from drilling operations. Despite the extremely low likelihood of a large oil spill event occurring during the project, Shell has designed its response program based upon a regional capability of responding to a range of spill volumes that increase from small operational spills up to and including a WCD from a well blowout. Shell’s program meets the response planning requirements of the relevant coastal states and Federal oil spill planning regulations. The OSRP includes information regarding Shell’s regional oil spill organization and dedicated response assets, potential spill risks, and local environmental sensitivities. The OSRP presents specific information on the response program that includes a description of personnel and equipment mobilization, the incident management team organization, and the strategies and tactics used to implement effective and sustained spill containment and recovery operations.



## EIA Organization

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

NTL 2008 -G04, which provides guidance regarding information required by 30 CFR Part 250 for

EP s. The main impact-related discussions are in Section A (Impact-Producing Factors) and

Section C (Impact Analysis).

# A. Impact-Producing Factors

Table 2 is a matrix of IPFs and potentially affected environmental resources adapted from Form

MMS- 142. An “X” indicates that an IPF could reasonably be expected to affect a certain resource, and a dash (

-- ) indicates no impact or negligible impact. Where there may be an effect, an analysis is provided in Section C . Potential IPFs for the proposed activity are listed below and briefly discussed in the following subsections:

Drilling rig presence (including noise and lights); Physical disturbance to the seafloor; Air pollutant emissions; Effluent discharges; Water intake; Onshore waste disposal; Marine debris; Support vessel and helicopter traffic; and
Accidents.



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

The wells will be drilled using the Noble Danny Adkins or a similar DP semisubmersible. The rig will be on site for an estimated 149 days per well. Three offshore support vessels will be used during the drilling program and at least one of these will always be in the vicinity of the drilling rig to provide assistance as necessary. The physical presence of a drilling rig in the ocean can attract pelagic fishes and other marine life, as discussed in Section C.5.1 . A semisubmersible maintains buoyancy using ballasted, watertight pontoons located below the sea surface. The operating deck is located above the tops of passing waves. Structural columns connect the pontoons and operating deck. When the rig moves its location, the pontoons are de-ballasted so that the rig can float on the sea surface

. The Noble Danny Adkins uses thrusters to hold or adjust its position.

Drilling operations produce noise that includes strong tonal components at low frequencies, including infrasonic frequencies in at least some cases (MMS, 2000). Drilling noise from semisubmersibles is not particularly intense and is strongest at low frequencies, averaging 10 to

500 Hz (Richardson et al., 1995). From a semisubmersible, sound and vibration are transmitted to the water either through the air or the risers (MMS, 2000). Drilling rigs also maintain exterior lighting for navigational and aviation safety in accordance with Federal regulations.



## A.2 Physical Disturbance to the Seafloor

Semisubmersibles like the Noble Danny Adkins do not use anchors for holding or stabilization during drilling operations. There will be minimal disturbance to the seafloor and soft bottom communities during positioning of the wellbore and blowout preventers (BOP). Physical disturbance of the seafloor will be limited to the proximal area where the wellbore penetrates the substrate, where mud and drill cuttings will be deposited.

### Table 2. Matrix of impact-producing factors and affected environmental resources. X = potential impact; dash (

-- ) = no impact or negligible impact.

Environmental Resources Impact

- producing Factors
Dri lling Rig Presence (incl. noise & lights) Physical

Disturbance to Seafloor Air Pollutant

Emissions Effluent

Discharges Water

Intake Onshore

Waste Disposal Marine

Debris Support

Vessel/Helo Traffic Accidents

Small Fuel Spill Large Oil

Spill Physi cal/Chemical Environment Air quality and greenhouse gases

-- -- X

-- -- -- -- -- X (6) X (6) Water quality

-- -- -- X

-- -- -- -- X (6) X (6) Seafloor Habitats and Biota Soft bottom benthic communities

-- -- -- X

-- -- -- -- -- X (6) High

- density deepwater benthic communities

-- -- (4)

-- -- (4)

-- -- -- -- -- X (6) Designated topographic features

-- -- (1)

-- -- (1)

-- -- -- -- -- -- Pinnacle trend area live bottoms

-- -- (2)

-- -- (2)

-- -- -- -- -- -- Eastern Gulf live bottoms

-- -- (3)

-- -- (3)

-- -- -- -- - - -- Threatened, Endangered, and Protected Species and Critical Habitat Sperm whale (endangered) X (8)

-- -- -- -- -- -- X (8) X (6,8) X (6,8) Florida manatee (endangered)

-- -- -- -- -- -- -- X (8)

-- X (6,8) Endangered mysticete whales

-- -- -- -- -- -- -- -- -- -- Non

- endangered marine mammals (protected) X

-- -- -- -- -- -- X X (6) X (6) Sea turtles (endangered/threatened) X (8)

-- -- -- -- -- -- X (8) X (6,8) X (6,8) Piping Plover (threatened)

-- -- -- -- -- -- -- -- -- X (6) Whooping Crane (endangered)

-- -- -- -- -- -- -- -- -- X (6) Gulf sturgeon (threatened)

-- -- -- -- -- -- -- -- -- X (6) Beach mice (endangered)

-- -- -- -- -- -- -- -- -- X (6) Coastal and Marine Birds Marine and pelagic birds X

-- -- -- -- -- -- X X (6) X (6) Shorebirds and coastal ne sting 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 wilder ness 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)Table 2 Footnotes and Applicability:

(1) Activities that may affect a marine sanctuary or topographic feature. Specifically, if the well, platform site, or any anchors will be on the seafloor within the following: (a) 4-mi zone of the Flower Garden Banks, or the 3-mi zone of Stetson Bank; (b) 1,000-m, 1-mi, or 3-mi zone of any topographic feature (submarine bank) protected by the Topographic Features Stipulation attached to an Outer Continental Shelf (OCS) lease; (c) Essential Fish Habitat (EFH) criteria of 500 ft from any no-activity zone; or (d) Proximity of any submarine bank (500-ft buffer zone) with relief greater than 2 m that is not protected by the Topographic Features Stipulation attached to an OCS lease.

 Not applicable. The lease is not within or near any marine sanctuary, topographic feature, or no-activity
zone. There are no submarine banks in the block.

(2) Activities with any bottom disturbance within an OCS lease block protected through the Live Bottom (Pinnacle Trend) Stipulation attached to an OCS lease.

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

(3) Activities within any Eastern Gulf OCS block where seafloor habitats are protected by the Live Bottom (Low-Relief) Stipulation attached to an OCS lease.

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

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

 No impacts on high-density deepwater benthic communities are anticipated. There are no features indicative of high-density chemosynthetic communities or coral communities withi n 2,000 ft (610 m) of any drilling mud/cuttings discharge location. Because a semisubmersible will be used, there will be no seafloor disturbances due to anchoring.

(5) Exploration or production activities where H 2 S concentrations greater than 500 ppm might be encountered.

 Based on CFR 250.490(c), Shell requests that the BOEMRE classify the area in the proposed drilling operations as an area where the absence of H 2 S has been confirmed.

(6) All activities that could result in an accidental spill of produced liquid hydrocarbons or diesel fuel that you determine would impact these environmental resources. If the proposed action is located a sufficient distance from a resource that no impact would occur, the EIA can note that in a sentence or two.

 Accidental hydrocarbon spills could affect the resources marked (X) in the matrix, and impacts are analyzed in Section C

. (7) All activities that involve seafloor disturbances, including anchor emplacements, in any OCS block designated by the BOEMRE as having high-probability for the occurrence of shipwrecks or prehistoric sites, including such blocks that will be affected that are adjacent to the lease block in which your planned activity will occur. If the proposed activities are located a sufficient distance from a shipwreck or prehistoric site that no impact would occur, the EIA can note that in a sentence or two.

 No impacts on archaeological resources are expected. The lease area is not on the list of high-probability blocks for shipwrecks. The archaeological survey detected 962 unidentified sidescan sonar targets within the survey area. The seafloor patterning and acoustic characteristics of these sonar targets conclude that they are modern debris. However, there was one irregularly shaped sonar contact that could not be reliably identified and will have an archaeological avoidance zone of 1,000 ft (300 m). The lease is well beyond the 60-m depth contour used by the BOEMRE as the seaward extent for prehistoric archaeological site potential in the Gulf of Mexico. Because a dynamically positioned semisubmersible will be used, there will be no seafloor disturbances due to anchoring.

(8) All activities that you determine might have an adverse effect on endangered or threatened marine mammals
or sea turtles or their critical habitats.

 IPFs that may affect marine mammals, sea turtles, or their critical habitats include drilling rig presence and emissions, support vessel and helicopter traffic, and accidents. See Section C

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

 Not applicable.

## A.3 Air Pollutant Emissions

Air pollutant emissions are estimated in Supplemental EP Section 8 . Offshore air pollutant emissions will result from operations of the drilling rig, as well as service vessels and helicopters. These emissions occur mainly from combustion of diesel fuel. The combustion of fuels occurs on diesel-powered generators, pumps, or motors and from lighter fuel motors. Primary air pollutants typically associated with OCS activities are suspended particulate matter (PM), sulfur oxides (SO
x 

### ), nitrogen oxides (NO
x 

### ), volatile organic compounds (VOCs), and carbon monoxide (CO).

The Air Quality Emissions Report prepared in accordance with the BOEMRE requirements shows that the projected emissions for the drilling rig are below exemption levels; therefore, according to 30 CFR 250.303, the emissions will not significantly affect the air quality of the onshore area for any of the criteria pollutants. No further analysis or control measures are required. However, Shell will use low-sulfur fuel to further reduce any possible impacts.



## A.4 Effluent Discharges

Effluent discharges are summarized in Supplemental EP Section 7 . All offshore discharges will be in accordance with the National Pollutant Discharge Elimination System (NPDES) General Permit No. GMG290000 issued by the USEPA. Discharges will be in compliance with and monitored as required by the permit.

Water-based drilling muds and cuttings will be released at the seafloor during the initial well intervals before the marine riser is set that allows returns to the surface. Excess cement slurry also will be released at the seafloor during casing installation for the riserless portion of the drilling operations.

A synthetic-based mud (SBM) system will be used after the riser is installed. Unused or residual SBM will be collected and transported to Port Fourchon, Louisiana, for disposal in an approved facility. SBM cuttings will be discharged overboard via a downpipe below the water surface, after treatment that complies with the 6.9% NPDES permit requirement for retention of SBM fluid on cuttings. The estimated volume of SBM cuttings to be discharged is 5,200 barrels (bbl) per well.

Other effluent discharges in accordance with the NPDES permit will include excess cement, non-contact cooling water, treated sanitary and domestic wastes, deck drainage, desalination unit brine, uncontaminated fire water and ballast water.



## A.5 Water Intake

Seawater will be drawn from several meters below the ocean surface for various services including firewater and once-through non-contact cooling of machinery on the drilling rig ( Supplemental EP Table 7a ).

Section 316(b) of the Clean Water Act requires NPDES permits to ensure that the location, design, construction, and capacity of cooling water intake structures reflect the best technology available to minimize adverse environmental impact from impingement and entrainment of aquatic organisms. Construction of the rig planned for use in this Supplemental EP , the
Noble Danny Atkins , started prior to 17 July 2006, and therefore is not subject to the cooling

### water intake permit requirements of NPDES Permit GMG 290000

. If a different rig is selected, it

will comply with all applicable NPDES requirements. The design and operational features of the rig combined with the geographical area of operation suggest impingement and entrainment impacts will be below a level of concern.



## A.6 Onshore Waste Disposal

Wastes generated during drilling are tabulated in Supplemental EP Section 7 . Non-hazardous trash and debris and non-recyclable waste will be transported to the Republic/BFI landfill in Sorrento, Louisiana, or the parish landfill in Avondale, Louisiana. Additionally, non-hazardous recyclable waste will be recycled at Omega Waste Management, Patterson, Louisiana, or at ARC of New Iberia, New Iberia, Louisiana. Hazardous waste such as paints, solvents, and unused chemicals will be disposed of at Safety Kleen Systems, Inc., Denton, Texas, while used oil and glycol will be sent to Omega Waste Management for recycling. Universal waste including batteries, lamps, glass, and mercury-contaminated waste will be recycled at Lamp Environmental Industries, Hammond, Louisiana. At the onshore facilities, wastes will be recycled or disposed of according to all applicable regulations.



## A.7 Marine Debris

Trash and debris released into the marine environment can harm marine mammals, turtles, and birds through entanglement and ingestion. Shell will adhere to the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) Annex V requirements, USEPA and USCG regulations, and BOEMRE regulations and NTLs regarding solid wastes. BOEMRE regulations at 30 CFR 250.300(a) and (b)(6) prohibit operators from deliberately discharging containers and other similar materials (e. g. , trash and debris) into the marine environment, and

30 CFR 250.300(c) requires durable identification markings on equipment, tools and containers (especially drums), and other material. USCG and USEPA regulations require operators to become proactive in avoiding accidental loss of solid waste items by developing waste management plans, posting informational placards, manifesting trash sent to shore, and using special precautions such as covering outside trash bins to prevent accidental loss of solid waste. Shell complies with NTL 2007-G03, which instructs operators to exercise caution in the handling and disposal of small items and packaging materials, requires the posting of placards at prominent locations on offshore vessels and structures, and mandates a yearly marine trash and debris awareness training and certification process. Shell’s compliance with all applicable laws, regulations, and NTL 2007-G03 will avoid significant impacts on the environment.



## A.8 Support Vessel and Helicopter Traffic

Shell will use existing shorebased facilities at Port Fourchon and Amelia, Louisiana, for onshore support for water and air transportation, respectively. No terminal expansion or construction is planned at either location.

The supply base at Port Fourchon is operated by Shell and located on Bayou LaFourche, approximately 3 miles (5 km) from the Gulf of Mexico. During drilling, the project will be supported by two crew boats and three offshore support vessels; crew boats will make two round-trips per week between the drilling facility and the onshore supply base, while at least one support vessel will be in the field at all times. The boats will normally move to the project
area via the most direct route from the shorebase.

### The air transportation base will be the PHI Heliport in Amelia, Louisiana. A helicopter will make

one round-trip daily between the drilling rig and the heliport. The helicopter will be used to transport personnel and small supplies and will normally take the most direct route of travel between the helicopter base and the lease area when air traffic and weather conditions permit. Helicopters typically maintain a minimum altitude of 700 ft (213 m) while in transit offshore, 1,000 ft (305 m) over unpopulated areas or across coastlines, and 2,000 ft ( 610 m) over populated areas and sensitive habitats such as wildlife refuges and park properties.



## A.9 Accidents

A.9.1 Types of Accidents Evaluated

The analysis in this EIA focuses on two potential accidents:

A small fuel spill, which is the most likely type of spill during OCS development activities; and An oil spill resulting from an uncontrolled blowout. A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j.

The following subsections summarize assumptions about the sizes and fates of these spills, as well as Shell’s spill response plans. Impacts are analyzed in Section C

.
The lease sale EIS (MMS, 2007b) analyzes three other types of accidents: chemical spills, vessel collisions, and loss of well control. These accidents are discussed briefly in Section A.9.4

.


### A.9.2 Small Fuel Spill

Spill Size . According to the analysis in MMS (2007b), the most likely type of small spill (<1,000 bbl) as a result of OCS activities is a minor diesel fuel spill. Historically, most diesel spills
have been < 1 bbl, and this size is predicted to be the most common in ongoing and future OCS activities in the Western and Central Gulf of Mexico Planning Areas (MMS, 2007b). The average size for spills < 1 bbl is 0.07 bbl, and the median size for spills of 1 to 10 bbl is 3 bb l (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 178 miles ( 286 km) from the nearest shoreline (Louisiana). Modeling results discussed below indicate that a spill in the lease area would have a 1% probability of contacting the nearest Louisiana shoreline (Terrebonne Parish) within 30 days after a spill. By th at time, essentially 100% of a small fuel spill would have been dispersed or evaporated by natural processes, even if no response measures were implemented. MMS (2007b) similarly concluded that spills <1,000 bbl are not expected to persist as a slick on the surface of the water beyond a few days and are unlikely to make landfall or reach coastal waters prior to breaking up. MMS (2007b) noted that this conclusion is supported by a previous analysis of 3-day trajectory model runs, previous weathering analyses, and historical records of spill incidents.

Spill Response . In the unlikely event of a fuel spill, response equipment and trained personnel would be available to ensure that any spill effects are localized and would result only in short-term environmental consequences. Supplemental EP Section 9b provides a detailed discussion of Shell’s response to a spill.



### A.9.3 Large Crude Oil Spill

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures detailed in Supplemental EP Section 2j

. Blowouts are rare events and most do not result in oil spills. Holand (1997) estimated a probability of 0.0021 for a deep drilling blowout during exploration drilling based on U.S. Gulf of Mexico data. An updated analysis using the SINTEF database estimates a blowout frequency of 0.0017 per exploratory well for non-North Sea locations (International Association of Oil & Gas Producers, 2010). As noted by MMS (2007b), from

1992 to 2005, half of blowouts lasted less than half a day, and fewer than 10% of blowouts resulted in spilled oil.

The risk of a blowout during this project is significantly lower than indicated by these statistics because the well design and drilling program were developed using information gathered during the drilling of the previous wells in WR 508. During drilling of the previous wells, the reservoirs were logged and evaluated. Substantial data associated with the reservoirs were gathered including core, pressure, and fluid data. Data gained during these earlier operations provide substantial information that was used in preparing for the proposed operation.

Spill Size . Shell has calculated a WCD for this Supplemental EP, using the requirements prescribed by NTL 2010-N06. The WCD is 42,000 bbl for the first day with a 30-day average of 33,000 BPD. The estimated time to drill a relief well is 180 days, and the total volume of a spill over this duration is estimated to be 5.2 million barrels of oil (MMBO). The detailed analysis of
this calculation can be found in Supplemental EP Section 2j . The WCD scenario for this Supplemental EP, in terms of both initial and the sustained rates, has a low probability of being

### realized. Some of the factors that are likely to reduce rates and volumes, and are not included

in the WCD calculation, include but are not limited to obstructions or equipment in the wellbore, well bridging, and early intervention such as containment capabilities.

Shell has a robust system in place to prevent blowouts. Included in Supplemental EP Sections 2j
and 9b is Shell’s response to NTL 2010 -N06, which includes descriptions of measures to prevent a blowout, reduce the likelihood of a blowout, and conduct effective and early intervention in the event of a blowout. Shell will also comply with NTL 2010 -N10 and the Interim Final Drilling

Sa fety Rule, which specify additional safety measures for OCS activities.

Spill Trajectory . The fate of a large oil spill in the lease area would depend on meteorological and oceanographic conditions at the time. The Oil Spill Risk Analysis (OSRA) model is a computer simulation of oil spill transport that uses realistic data for winds and currents to predict the fate of a spill of at least 1,000 bbl. The OSRA report by Ji et al. (2004) provides conditional contact probabilities for shoreline segments. The results for Launch Area 48 (where the lease area is located) are presented in Table 3 . The model predicts no shoreline contact within 3 or 10 days. After 30 days, 8 counties and parishes from Texas to Louisiana may be contacted. Plaquemines and Cameron Parish, Louisiana, as well as Galveston County, Texas,
ha ve the greatest probability of shoreline contact, with a 2% chance within 30 days.

Table 3. Conditional probabilities of a spill in the lease area contacting shoreline segments (From: Ji et al., 2004). Values are conditional probabilities that a hypothetical spill in the lease area (represented by OSRA Launch Area 48) could contact shoreline segments within 3, 10, or 30 days.

Shoreline Segment County or Parish and State Conditional Probability of Co ntact a (%) 3 Days 10 Days 30 Days C08 Matagorda, TX

-- -- 1 C09 Brazoria, TX

-- -- 1 C10 Galveston, TX

-- -- 2 C12 Jefferson, TX

-- -- 1 C13 Cameron, LA

-- -- 2 C14 Vermilion, LA

-- -- 1 C17 Terrebonne, LA

-- -- 1 C20 Plaquemines, LA

-- -- 2

a Conditional probability refers to the probability of contact within the stated time period, assuming that a spill has occurred (

-- indicates less than 0.5%).



### The OSRA model does not evaluate the fate of a spill over time periods longer than 30 days, nor
do es it predict the fate of a release that continues over a period of weeks or months. Also as noted by Ji et al. (2004), the OSRA model does not take into account the chemical composition or biological weathering of oil spills, the spreading and splitting of oil spills, or spill response activities. The model does not assume a particular spill size but has generally been used by the BOEMRE to evaluate contact probabilities for spills greater than 1,000 bbl.

Weathering . Following an oil spill, several physical, chemical, and biological processes, collectively called weathering, interact to change the physical and chemical properties of the oil, and thereby influence its harmful effects on marine organisms and ecosystems. The most important weathering processes include spreading, evaporation, dissolution, dispersion into the water column, formation of water- in -oil emulsions, photochemical oxidation, microbial

### degradation, adsorption to suspended PM , and stranding on shore or sedimentation to the

seafloor (NRC, 2003).

Weathering decreases the concentration of oil and produces changes in its chemical composition, physical properties, and toxicity. The more toxic, light aromatic and aliphatic hydrocarbons are lost rapidly by evaporation and dissolution from the slick on the water surface. Evaporated hydrocarbons are degraded rapidly by sunlight. Biodegradation of oil on the water surface and in the water column by marine bacteria removes first the n-alkanes and then the light aromatics from the oil. Other petroleum components are biodegraded more slowly. Photooxidation attacks mainly the medium and high molecular weight PAHs in the oil on
the water surface.

Spill Response . Shell is a founding member of the Marine Well Containment Company (MWCC) and has access to an integrated subsea well control and containment system that can be rapidly deployed through the MWCC. The MWCC is a non-profit organization that assists with the subsea containment system during a response. The near-term containment response capability will be specifically addressed in Shell’s NTL 2010 -N10 submission at the time an Application to Drill (APD) is submitted and will include equipment and services available to Shell through MWCC’s development of near -term capability and other industry sources. Shell is a member of Clean Caribbean & Americas (CCA), Marine Spill Response Corporation (MSRC), Clean Gulf Associates (CGA), and Oil Spill Response Limited (OSRL), organizations that are committed to providing the resources necessary to respond to a spill as outlined in Shell’s Regional OSRP.

The experience of gaining control over the Macondo well has resulted in a better understanding of the necessary equipment and systems for well containment. As a result, industry and government are better equipped and prepared today to contain an oil well blowout in deepwater (see page 17 of the Decision Memorandum dated 1 October 2010 [Bromwich, 2010]). Shell is further analyzing these advances and incorporating them into a comprehensive approach to help prevent and, if needed, control another deepwater control incident. Shell is also investing in research and development to improve containment systems.

The primary offshore response would involve mechanical recovery. The primary response equipment that would be mobilized to the spill location for spills in normal and adverse weather conditions is included in the Offshore On-Water Recovery Activation List in the OSRP.

Chemical dispersant stockpiles are readily available from Gulf Coast State suppliers such as MSRC in Texas, Louisiana, Mississippi, and Florida; MWCC; CGA/Airborne Support, Inc. in Louisiana and Texas; and Clean Caribbean and Americas in Florida. Additional supplies are available from international vendors. Available equipment for surface and subsea application of dispersants, response times, and support resources are identified in the OSRP.

Open -water in situ burning may also be used as a response strategy, depending on the circumstances of the release. If appropriate conditions exist and approval from the Unified Command is received, one or multiple in situ burning task forces could be deployed offshore.

See Supplemental EP Sections 2j and 9b for a detailed description of Shell’s site -specific response to a large oil spill for this plan. T hese 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. No hydrogen sulfide (H 2 

### S) is expected at this site, and no other site-specific issues have been identified for this Supplemental EP. The analysis in the lease sale EIS for these topics is incorporated by reference.

Chemical Spill . Chemicals are used in drilling operations to achieve technical goals in the drilling process, improve the efficiency and safety of drilling, and protect associated equipment. Chemicals used during exploration and drilling include surfactants, bentonite clays, olefins, inorganic salts, glycols, polymers, barite, and calcium carbonate. Supplies are renewed on a regular basis by transfer in containers from supply boats (Boehm et al., 2001). In addition to chemicals used in drilling fluids, the following chemicals are likely to be used on the rig: ethylene glycol (blowout prevention control fluid, used in closed cooling loops for crane and main engines and brake coolers), cement (used to cement casing in place), solvents (used in painting operations), hydraulic fluids (used in cranes and other hydraulic rig equipment), lubricating oil and grease (used in reciprocating and electrical equipment), and sodium hypochlorite (dilute, used as laundry bleach and disinfectant).

A study of environmental risks of chemical products used in OCS activities determined that only two chemicals could potentially affect the marine environment: zinc bromide and ammonium chloride (Boehm et al., 2001). The risk of a spill for these chemicals is very low. Most other chemicals are either nontoxic or used in small quantities. No significant impacts are expected from chemical spills.

Vessel Collisions . As summarized in MMS (2007b), vessel collisions occasionally occur during routine operations. Most collision mishaps are the result of service vessels colliding with platforms or vessel collisions with pipeline risers. Some of these collisions have caused spills of diesel fuel or chemicals. Shell will comply with all USCG and BOEMRE-mandated safety requirements to minimize the potential for vessel collisions.

Loss of Well Control . A loss of well control is the uncontrolled flow of a reservoir fluid that may result in the release of gas, condensate, oil, drilling fluids, sand, or water. Loss of well control is a broad term that includes minor to serious well control incidents, while blowouts are considered to be a subset of more serious incidents with greater risk of oil spill or human injury (MMS, 2007b). Loss of well control may result in the release of synthetic drilling fluid or loss of oil. Shell has a robust system in place to prevent loss of well control. Included in this Supplemental EP is S hell’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

Int erim Final Drilling Safety Rule, which specify additional safety measures for OCS activities.

See Supplemental EP Sections 2j and 9b for further information.

H 2 

### S Release . Based on CFR 250.4 90 (c), Shell has requested that the proposed drilling area be
classified as an area where the absence of H 2 

### S has been confirmed.

# B. Affected Environment

The lease area is in the north-central Gulf of Mexico, 178 miles (286 km) from the nearest shoreline, 193 miles (311 km) from the onshore support base at Port Fourchon, Louisiana, and 221 miles (356 km) from the helicopter base at Amelia, Louisiana ( Figure 1 ).

WR 508 straddles the Sigsbee Escarpment and abyssal plain in an area of seafloor furrows. Proposed well locations G, H, and I are positioned between seafloor furrows where the soils are relatively soft, with water depths ranging from 9,554 to 9,578 ft (2,912 to 2,919 m) ( Figure 2 ; Geoscience Earth & Marine Services, Inc. [GEMS], 2006; Fugro GeoConsulting, Inc. [FGCI], 2010). The sidescan sonar survey confirmed the presence of piston cores, drilling splays, anchor chain scars, and previously drilled wells in the lease area but none are within 2,000 ft (610 m) of the proposed wellsites. There were 961 sonar contacts that were not archaeologically significant and 1 contact above the seafloor that was larger than the others. This contact is irregular in shape and may be made up of smaller debris targets, but it could not be reliably identified (Fugro GeoServices, Inc. [FGSI], 2011).

A detailed description of the regional affected environment is provided in recent EISs (MMS, 2007b, 2008), including meteorology, oceanography, geology, air and water quality, benthic communities, threatened and endangered species, biologically sensitive resources, archaeological resources, socioeconomic conditions, and other marine uses. These regional descriptions are based on extensive literature reviews and are incorporated by reference. General background information is presented below, and brief descriptions of each potentially
aff ected resource are presented in Section C , including site-specific and/or new information if
available.

The local environment in the lease area is not known to be unique with respect to physical/chemical, biological, or socioeconomic conditions. Baseline environmental conditions in the lease area are expected to be consistent with the regional description of continental slope locations evaluated in recent lease sale EISs (MMS, 2007b, 2008).

The lease area is approximately 214 miles (345 km) southwest of the Macondo spill site. Based on an analysis of satellite imagery (ESRI, 2010), the surface slick did not extend over the lease area prior to capping of the well; therefore, existing water quality in the lease area was not likely to have been affected. Macondo spill impacts are addressed in Section C.9 (Cumulative Impacts) where available and applicable.Figure 2. Bathymetric map of the lease area showing proposed well surface locations.

# C. Impact Analysis

This section analyzes the potential direct and indirect impacts of routine activities and accidents. Cumulative impacts are discussed in Section C.9

. Impacts have been analyzed extensively in recent multi-lease-sale EISs for the Western and Central Gulf of Mexico Planning Areas (MMS, 2007b, 2008). Si te -specific issues are addressed in this section as appropriate.



## C.1 Physical/Chemical Environment

C.1.1 Air Quality

There are no site-specific air quality data for the project area. Due to the distance from shorebased pollution sources, offshore air quality is expected to be good. The attainment status of Federal OCS waters is unclassified because there is no provision in the Clean Air Act for classification of areas outside State waters (MMS, 2007b).

As of 21 April 2011 all Louisiana, Mississippi, Alabama, and Florida coastal counties and parishes are in attainment of the National Ambient Air Quality Standards (NAAQS) for all criteria pollutants (USEPA, 2011). Two metropolitan areas in Texas are nonattainment areas for 8- h ozone (Dallas-Fort Worth, and Houston-Brazoria), and El Paso County is a nonattainment area
for PM 10 

### (USEPA, 2011 ).

Winds in the region are driven by the clockwise circulation around the Bermuda High (MMS, 2007b). The Gulf of Mexico is located to the southwest of this center of circulation, resulting in a prevailing southeasterly to southerly flow, which is conducive to transporting emissions toward shore. However, circulation is also affected by tropical cyclones (hurricanes) during summer and fall and by extratropical cyclones (cold fronts) during winter.

IPFs potentially affecting air quality are air pollutant emissions and two types of accidents: a small fuel spill and a large oil spill.



### Impacts of Air Pollutant Emissions

Air pollutant emissions are the only routine IPF likely to affect air quality. Offshore air pollutant emissions will result from the operation of the drilling rig as well as helicopters and service vessels. These emissions occur mainly from combustion or burning of diesel fuel. The combustion of fuels occurs primarily on diesel-powered generators, pumps, or motors and from lighter fuel motors. Primary air pollutants typically associated with OCS activities are suspended PM, SO x 

### , NO x 

### , VOCs, and CO.

Due to the distance from shore, routine operations in the project area are not expected to have any impact on air quality conditions along the coast, including nonattainment areas. As noted in the lease sale EIS (MMS, 2007b), emissions of air pollutants from routine activities in the Central Gulf of Mexico Planning Area are projected to have minimal impacts to onshore air quality because of the prevailing atmospheric conditions, emission heights, emission rates, and the
distance of these emissions from the coastline. The Air Quality Emissions Report (see Supplemental EP Section 8 ) prepared in accordance with BOEMRE requirements shows that the projected emissions for PM, SO
x 

### , NO x 

### , 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 BOEMRE coordinates with the National Park Service (NPS) and the USFWS if emissions from proposed projects may affect the Breton Class I area. Additional review and mitigation measures may be required for sources within 186 miles (300 km) of the Breton Class I area that exceed emission limits agreed upon by the administering agencies (NPS, 2010). The lease area is approximately 228 miles (367 km) from the Breton Wilderness Area. Shell does not anticipate any impact on the Class I area, but will comply with any emissions requirements as directed by the BOEMRE.



### Impacts of a Small Fuel Spill

Potential impacts of a small spill on air quality are expected to be consistent with those analyzed and discussed in recent EISs (MMS, 2007b, 2008). The probability of a small spill would be minimized by Shell’s preventative measures during routine operations, including fuel transf er. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the extent and duration of air quality impacts from a small spill would not be significant.

A small fuel spill would affect air quality near the spill site by introducing VOCs through evaporation. The ADIOS2 model (see Section A.9.2 ) indicates that more than 90% of a small diesel spill would be evaporated or dispersed within 24 hours. The area of the sea surface with diesel fuel on it would range from 1.2 to 12 acres (0.5 to 5 ha) depending on sea state and
weather conditions.

A small fuel spill would not affect coastal air quality because the spill would not be expected to make landfall or reach coastal waters prior to breaking up (see Section A.9.2 ).



### Impacts of a Large Oil Spill

Potential impacts of a large oil spill on air quality are expected to be consistent with those analyzed and discussed in recent EISs (MMS, 2007b, 2008).

A large oil spill would affect air quality by introducing VOCs through evaporation from the slick. The extent and persistence of impacts would depend on the meteorological and oceanographic conditions at the time and the effectiveness of spill response measures. Additional air quality impacts could occur if response measures included in situ burning of the floating oil. Burning would generate a plume of black smoke and result in emissions of NO x 

### , SO x 

### , CO, and PM, as well as greenhouse gases.

Due to the lease area location (178 miles [ 286 km] from the nearest shoreline), most air quality impacts would occur in offshore waters. Depending on the spill trajectory and the effectiveness of spill response measures, coastal air quality could also be affected. Based on the OSRA modeling predictions ( Table 3 ), Plaquemines and Cameron Parish, Louisiana, as well as Galveston County, Texas, are the coastal areas most likely to be affected.

### A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an

event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation o f Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on air quality are expected.



### C.1.2 Water Quality

There are no site-specific water quality data for the lease area. Due to the lease location in deep, offshore waters, water quality is expected to be good, with low levels of contaminants. As noted in the lease sale EIS (MMS, 2007b), deepwater areas in the northern Gulf of Mexico are relatively homogeneous with respect to temperature, salinity, and oxygen. Kennicutt (2000) noted that the deepwater region has little evidence of contaminants in the dissolved or particulate phases of the water column. However, there are localized occurrences of natural seepage of oil, gas, and brines in near-surface sediments and up through the water column.

The lease area is approximately 214 miles (345 km) southwest of the Macondo spill site. Based on satellite imagery (ESRI, 2010), the surface slick did not extend over the lease area during the spill, and therefore existing water quality in the lease area was unlikely to have been affected. The Operational Science Advisory Team (OSAT, 2010) reported that after August 2010, waters and sediments in the deepwater Gulf of Mexico beyond 1.8 miles (3 km) from the Macondo wellsite were below USEPA acute and chronic benchmarks for PAHs and were not hypoxic.
These observations indicate that baseline environmental conditions in the lease area are unlikely to have been significantly altered by the spill.

IPFs potentially affecting water quality are effluent discharges and two types of accidents: a small fuel spill and a large oil spill.



### Impacts of Effluent Discharges

Discharges of treated SBM cuttings will produce temporary, localized increases in suspended solids in the water column around the drilling rig. In general, turbid water can be expected to extend between a few hundred meters and several kilometers down current from the discharge point (NRC, 1983; Neff, 1987). All NPDES permit limitations and requirements will be met. After discharge, SBM retained on cuttings would be expected to adhere tightly to the cuttings particles and, consequently, would not produce much turbidity as the cuttings sink through the water column (Neff et al., 2000). There will be no persistent impacts on water quality in the
lease area.

Treated sanitary and domestic wastes may have a slight transient effect on water quality in the immediate vicinity of these discharges. All NPDES permit limitations and requirements will be met and little or no impact on water quality is anticipated.

Deck drainage includes all effluents resulting from rain, deck washings, and runoff from curbs, gutters, and drains, including drip pans in work areas. Rainwater that falls on uncontaminated areas of the drilling rig will flow overboard without treatment. However, rainwater that falls on the drilling rig deck and other areas such as chemical storage areas and places where equipment is exposed will be collected and oil and water separated to meet NPDES permit requirements. Little or no impact on water quality is anticipated.

### Other discharges in accordance with the NPDES permit, such as desalination unit brine and

uncontaminated cooling water, fire water, and ballast water are expected to be diluted rapidly and have little or no impact on water quality.

Support vessels will discharge treated sanitary and domestic wastes. These will have a slight effect on water quality in the immediate vicinity of the discharges. All support vessel discharges will be in accordance with USCG regulations and, as applicable, the NPDES Vessel General Permit, and therefore are not expected to cause significant impacts on water quality.



### Impacts of a Small Fuel Spill

Potential impacts of a small spill on water quality are expected to be consistent with those analyzed and discussed in recent EISs (MMS, 2007b, 2008). The probability of a small spill would be minimized by Shell’s preventative measures during routine operations, in cluding fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the extent and duration of water quality impacts from a small spill would not be significant.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the concentrations of petroleum hydrocarbons and their degradation products. The extent and persistence of impacts would depend on the meteorological and oceanographic conditions at the time and the effectiveness of spill response measures. However, it is estimated that more than 90% of a small diesel spill would be evaporated or dispersed within 24 hours (see

Section A.9.2 ). The area of the sea surface with diesel fuel on it would range from 1.2 to

12 acres (0.5 to 5 ha) depending on sea state and weather conditions.

The water-soluble fractions of diesel are dominated by two- and three-ringed PAHs, which are moderately volatile (NRC, 2003). The constituents of these oils are light to intermediate in molecular weight and can be readily degraded by aerobic microbial oxidation. Diesel’s density is such that it will not sink and pool on the seafloor. Diesel dispersed in the water column can adhere to suspended sediments, but this generally occurs only in coastal areas with high -suspended solid loads (NRC, 2003) and would not be expected to occur to any appreciable degree in offshore waters of the Gulf of Mexico. Diesel oil is readily and completely degraded by naturally occurring microbes (NOAA, 2006).

A small fuel spill would not affect coastal water quality because the spill would not be expected to make landfall or reach coastal waters prior to breaking up (see Section A.9.2 ).



### Impacts of a Large Oil Spill

Potential impacts of a large oil spill on water quality are expected to be consistent with those analyzed and discussed in recent EISs (MMS, 2007b, 2008). A large spill would affect water quality by producing a slick on the water surface and increasing the concentrations of petroleum hydrocarbons and their degradation products. The extent and persistence of impacts would depend on the meteorological and oceanographic conditions at the time and the effectiveness of spill response measures. Most of the oil would be expected to form a slick at the surface, although new information from the Macondo spill indicates that plumes of submerged oil droplets can be produced when subsea dispersants are applied at the wellhead (Camilli et al., 2010; Hazen et al., 2010; Joint Analysis Group, 2010a,b,c). A report by Kujawinski et al. (2011)

### indicates that chemical components of subsea dispersants used during the Macondo spill

persisted for up to two months and were detectable up to 186 miles (300 km) from the wellsite at a water depth of 3,280 to 3,937 ft (1,000 to 1,200 m).

Once oil enters the ocean, a variety of physical, chemical, and biological processes act to disperse the oil slick. These processes include spreading, evaporation of the more volatile constituents, dissolution into the water column, emulsification of small droplets, agglomeration sinking, microbial modification, photochemical modification, and biological ingestion and excretion (NRC, 2003). Marine water quality would be temporarily affected by the dissolved components and small oil droplets that do not rise to the surface or are mixed down by surface turbulence. Dispersion by currents and microbial degradation removes the oil from the water column or dilutes the constituents to background levels.

A large oil spill could result in a release of gaseous hydrocarbons that could affect water quality. During the Macondo spill, large volumes of methane (CH 4 

### ) were released, causing localized oxygen depletion as methanotrophic bacteria rapidly metabolized the hydrocarbons (Joye et al., 2011; Kessler et al., 2011). However, a broader study of the deepwater Gulf of Mexico found that although some stations had slightly depressed dissolved oxygen concentrations relative to climatological background values, concentrations were not low enough to indicate hypoxia (<2.0 mg/L) (OSAT, 2010). Stations revisited around the Macondo wellhead in October 2010 showed no measurable oxygen depression (OSAT, 2010).

Due to the lease area location ( 178 miles [ 286 km] from the nearest shoreline), most water quality impacts would occur in offshore waters. Depending on the spill trajectory and the effectiveness of spill response measures, coastal water quality could be affected. Based on the OSRA modeling predictions ( Table 3 ), nearshore waters and embayments of Cameron and Plaquemines Parish, Louisiana, and Galveston County, Texas, are the most likely coastal areas where water quality could be affected.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on water quality are expected.



## C.2 Seafloor Habitats and Biota

Water depths at the proposed well surface locations range from 9,554 to 9,578 ft (2,912 to 2,919 m). The seafloor at the wellsites is expected to consist mainly of soft bottom. The chemosynthetic community assessment based on the hazards report by GEMS (2006) and FGCI (2010) did not identify any features that could support high-density deepwater benthic communities within 2,000 ft ( 610 m) of the wellsites. See Supplemental EP Section 6a for
further information.

According to the BOEMRE (2011), existing information for the deepwater Gulf of Mexico indicates that the seafloor is composed primarily of soft sediments; hard bottom communities are rare. WR 508 is within deepwater Grid 11, and the BOEMRE website indicates that ROV coverage of the seafloor in this grid is adequate to characterize the area (BOEMRE, 2011).

### C.2.1 Soft Bottom Benthic Communities

Data from the recent Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology study (Wei, 2006; Rowe and Kennicutt, 2009) can be used to describe typical benthic
communities in the area. Table 4 summarizes data from two nearby stations in similar water depths. Sediments at those two stations were predominantly clay ( 55 % to 58%) and silt ( 39 % to 41%).

Table 4. Benthic community data from stations near the lease area and in similar water depths sampled during the Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology Study (From: Wei, 2006; Rowe and Kennicutt, 2009).

Station Location

Relative to
Lease Area Water

Depth (m) Abunda nce

Meiofauna (individuals/m 2 ) Macroinfauna

(individuals/m 2 ) Megafauna

(individuals/ha)

NB

- 5 30 mi SW 2,110 117,263 706 1,600

B

- 3 63 mi SW 2,649 155,817 814 362

Meiofaunal and megafaunal abundance from Rowe and Kennicutt (2009); macroinfaunal abundance from Wei (2006).



### Meiofauna (animals passing through a 0.5-mm sieve but retained on a 0.062-mm sieve) densities in water depths representative of the lease area typically range from about 100,000 to

180 ,000 individuals/m 2 

### (Rowe and Kennicutt, 2009). Nematodes, nauplii, and harpacticoid copepods were the three dominant groups in the meiofauna, accounting for about 90% of total
abundance.

The benthic macroinfauna is characterized by small mean individual sizes and low densities, both of which are a reflection of the meager primary production in Gulf of Mexico surface waters (Wei, 2006). Densities decrease exponentially with water depth. Based on an equation presented by Wei (2006), macroinfaunal densities in the water depths of the wellsites are expected to be about 800 individuals/m 2



### , similar to the values in Table 4

.
Polychaetes are typically the most abundant macroinfaunal group on the northern Gulf of Mexico continental slope, followed by amphipods, tanaids, bivalves, and isopods. Wei (2006) recognized four depth-dependent faunal zones (1 through 4), two of which are divided horizontally. The lease area is in Zone 3W, which consists of stations on the most complex bathymetric features in the northern Gulf of Mexico, including the Alaminos Canyon, basins and non-basins sites and the Sigsbee Escarpment. These stations range in depth from 6,150 to 9,870 ft (1,875 to 3,008 m). The five most abundant species in Zone 3W were the polychaetes Levinsenia uncinata, Paraonella monilaris, and Tachytrypane sp

. and two bivalve
Heterodonta sp p.

Megafaunal density from nearby stations NB-5 and B-3 was 1,600 and 362 individuals/ha, respectively ( Table 4 ). Densities of 1,300 to 1,900 individuals/ha were reported from other stations in a similar depth range. Common megafauna included motile groups such as decapods, ophiuroids, holothurians, and demersal fishes, as well as sessile groups such as sponges and anemones.

### 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/m 2 

### ) in the top 15 cm of sediments (Rowe and Kennicutt, 2009).

IPFs potentially affecting benthic communities are effluent discharges (drilling muds and cuttings) and a large oil spill resulting from a well blowout at the seafloor. A small fuel spill would not affect benthic communities because the diesel fuel would float and dissipate on the
sea surface. There will be no disturbance to soft bottom communities on the seafloor during positioning of the DP semisubmersible Noble Danny Adkins

.


### Impacts of Effluent Discharges

Drilling muds and cuttings are the only effluents that are likely to affect benthic communities. During initial well interval(s) before the marine riser is set, cuttings and seawater- based “spud
mud” will be released at the seafloor. Excess cement slurry will also be released at the seafloor during casing installation for the riserless portion of the drilling operations. Cement slurry components typically include cement mix and some of the same chemicals used in water-based drilling muds (Boehm et al., 2001). The main impacts will be burial and smothering of benthic organisms within several meters to tens of meters around the wellbore. Soft bottom sediments disturbed by cuttings, drilling muds, and cement slurry will eventually be recolonized through larval settlement and migration from adjacent areas. Because some deep-sea biota grow and reproduce slowly, recovery may require several years.

Discharges of treated SBM cuttings from the rig may affect benthic communities, primarily within several hundred meters of the wellsites. The fate and effects of SBM cuttings have been reviewed by Neff et al. (2000), and monitoring studies have been conducted in the Gulf of Mexico by Continental Shelf Associates, Inc. (2004, 2006). In general, cuttings with adhering SBM tend to clump together and form thick cuttings piles close to the drillsite. Areas of SBM cuttings deposition may develop elevated organic carbon concentrations and anoxic conditions (Continental Shelf Associates, Inc., 2006). Where SBM cuttings accumulate and concentrations exceed approximately 1,000 mg/kg, benthic infaunal communities may be adversely affected due to both the toxicity of the base fluid and organic enrichment (with resulting anoxia) (Neff et al., 2000). Infaunal numbers may increase and diversity may decrease as opportunistic species that tolerate low oxygen and high H 2 

### S 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.

Th e areal extent of impacts from drilling discharges will be small. Assuming a typical effect radius of 1,640 ft ( 500 m), the affected area around each wellsite would represent about 3% of the seafloor within a lease block. For the three surface locations in this exploration-drilling program, the total impact area would be 448 acres (181 ha). Soft bottom communities are ubiquitous along the northern Gulf of Mexico continental slope (Gallaway, 1988; Gallaway et al., 2003; Rowe and Kennicutt, 2009). Impacts from drilling discharges during this project will have no significant impact on soft bottom benthic communities on a regional basis.

### Impacts of a Large Oil Spill

The most likely effects of a subsea blowout on benthic communities would be within a few
hund red 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) fr om the blowout site, fine sediments (silts and clays) could be resuspended for more than 30 days and dispersed over a much wider area. Previous studies characterized surface sediments in the vicinity of the site as about 50% clay and 45% silt (Rowe and Kennicutt, 2009).

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical impacts of a blowout) because the oil would rise quickly to the sea surface directly over the spill location. However, during the Macondo spill, subsurface plumes were reported at a water depth of about 3,600 ft ( 1,100 m), extending at least 22 miles (35 km) from the wellsites and persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). This observation is supported by Kujawinski et al. (2011) in their report that chemical components of subsea dispersants used during the Macondo spill persisted for up to two months and were detected up to 186 miles (300 km) from the wellsite at a water depth of 3,280 to 3,937 ft (1,000 to 1,200 m) . However, estimated dispersant concentrations in the subsea plume were below levels known to be toxic to marine life. While the behavior and impacts of subsurface plumes are not well known, a subsurface plume could contact the seafloor and affect benthic communities beyond the 984 -ft ( 300 -m) radius estimated by MMS (2007a, 2008), depending on its extent, trajectory, and persistence. This contact could result in smothering and/or toxicity to benthic organisms. The affected area would be recolonized by benthic organisms over a period of months to years (NRC, 2003).

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, imple mentation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on soft bottom communities are expected.



### C.2.2 High-Density Deepwater Benthic Communities

As defined by NTL 2009 -G40, high-density deepwater benthic communities are features or areas that could support high-density chemosynthetic communities, or features or areas that could support high-density deepwater corals and other associated high-density hard bottom communities. Chemosynthetic communities were discovered in the central Gulf of Mexico in 1984 and have been studied extensively (MacDonald, 2002). Deepwater coral communities are also known from numerous locations in the Gulf of Mexico (Brooke and Schroeder, 2007; CSA International, Inc., 2007). These communities occur almost exclusively on authigenic carbonates created by chemosynthetic communities, and on shipwrecks.

The chemosynthetic community assessment included in this Supplemental EP, based on the shallow hazards reports by GEMS (2006) and FGCI (2010), did not identify any features that could support high-density deepwater benthic communities within 2,000 ft ( 610 m) of the proposed drilling mud/cuttings discharge locations.

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

(drilling muds and cuttings), and a large oil spill from a well blowout at the seafloor. A small fuel spill would not affect benthic communities because the diesel fuel would float and dissipate on the sea surface. Because a DP drilling rig will be used, there will be no anchoring impacts.



### Impacts of Effluent Discharges

The chemosynthetic community assessment included in this Supplemental EP, based on the shallow hazards reports by GEMS (2006) and FGCI (2010), did not identify any features that could support high-density deepwater benthic communities within 2,000 ft ( 610 m) of the proposed drilling mud/cuttings discharge locations. Monitoring programs on the Gulf of Mexico continental slope have shown that benthic impacts from drilling discharges typically are concentrated within about 1,640 ft (500 m) of the wellsites, although detectable deposits may extend beyond this distance (Continental Shelf Associates, Inc., 2004, 2006; Neff et al., 2005). If high -density deepwater communities are associated with the more distant expulsion features and mud volcanoes identified in the hazards survey, significant impacts on these communities will be avoided because of the distance from the discharge location.



### Impacts of a Large Oil Spill

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical impa cts of a blowout) because the oil would rise quickly to the sea surface directly over the spill location. However, during the Macondo spill, subsurface plumes were reported at a water depth of about 3,600 ft ( 1,100 m), extending at least 22 miles (35 km) from the wellsites and persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). This observation is supported by Kujawinski et al. (2011) in their report that chemical components of subsea dispersants used during the Macondo spill persisted for up to two months and were detectable up to 186 miles (300 km) from the wellsite at a water depth of 3,280 to 3,937 ft (1,000 to 1,200 m). However, estimated dispersant concentrations in the subsea plume were below levels known to be toxic to marine life. While the behavior and impacts of subsurface plumes are not well known, a subsurface plume could have the potential to contact high-density deepwater benthic communities beyond the 984 -ft ( 300 -m) radius estimated by MMS (2007a, 2008), depending on its extent, trajectory, and persistence. Potential impacts on sensitive resources would be an integral part of the decision and approval process for the use of dispersants.

Potential impacts of oil on high-density deepwater benthic communities are discussed by MMS (2007b). Although chemosynthetic communities live among hydrocarbon seeps, natural seepage is very constant and occurs at low rates compared to the potential rates of oil release from a blowout. In addition, seep organisms require unrestricted access to oxygenated water at the same time as exposure to hydrocarbon energy sources (MacDonald, 2002). Oil droplets or oiled sediment particles could come into contact with chemosynthetic organisms or deepwater corals. As discussed by MMS (2007b), impacts could include loss of habitat, biodiversity, and live coral coverage; destruction of hard substrate; change in sediment characteristics; and reduction or loss of one or more commercial and recreational fishery habitats. Sublethal effects could be long lasting and affect the resilience of coral colonies to natural disturbances (e.g., elevated water temperature and diseases).

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

recent (October 2010) survey of deepwater coral habitats near the Macondo spill site (BOEMRE, 2010). Government and academic researchers were working at a site 4,600 ft ( 1,400 m) deep and approximately 7 miles (11 km) southwest of the Macondo wellhead when they observed dead and dying corals with sloughing tissue and discoloration. The study location was about 171 miles (275 km) from the lease area. Much of the soft coral observed in an area measuring about 50 to 130 ft (15 to 40 m) was covered by what appeared to be a brown substance. Ninety percent of 40 large corals were heavily affected and showed dead and dying parts and discoloration. Another site 1,312 ft ( 400 m) away had a colony of stony corals similarly affected and partially covered with a similar brown substance. Until laboratory analyses are conducted, scientists cannot be certain what caused the impacts. Sediment and coral samples were collected with an ROV and brought to the surface for analyses. Further testing will also determine if the substance is oil, and if so, whether it is consistent with the release from the Macondo spill.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Se ctions 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on deepwater benthic communities are expected.



### C.2.3 Designated Topographic Features

The block is not within or near a designated topographic feature or a no -activity zone as identified in NTL 2009-G39. The nearest topographic feature is Ewing Bank, located 1 07 miles (1 72 km) north of the lease area.

There are no IPFs associated with either routine operations or accidents that could cause impacts to designated topographic features due to the distance from the lease area. A small fuel spill would float and dissipate on the surface and would not reach these seafloor features.

In the event of an oil spill from a well blowout, a surface slick would not contact these seafloor features. If a subsurface plume were to occur, impacts on these features would be unlikely due to the distance and the difference in water depth. Near-bottom currents in the region are predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume up onto the continental shelf edge.



### C.2.4 Pinnacle Trend Area Live Bottoms

The lease area is not covered by the Live Bottom (Pinnacle Trend) Stipulation. As defined by

NTL 2009 -G39, the nearest pinnacle trend blocks are about 236 miles (380 km) from the lease area, along the shelf edge south of Alabama.

There are no IPFs associated with either routine operations or accidents that could cause impacts to pinnacle trend area live bottoms due to the distance from the lease area. A small fuel spill would float on the surface and would not reach these seafloor features.

### In the event of an oil spill from a well blowout, a surface slick would not contact these seafloor

features. If a subsurface plume were to occur, impacts on these features would be unlikely due to the distance and the difference in water depth. Near-bottom currents in the region are predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume up onto the continental shelf edge.



### C.2.5 Eastern Gulf Live Bottoms

The lease area is not covered by the Live Bottom (Low-Relief) Stipulation, which applies to Eastern Gulf of Mexico Planning Area leases in water depths of 328 ft ( 100 m) or less. The nearest blocks covered by the live bottom stipulation, as defined by NTL 2009-G39, are about

272 miles (438 km) from the project area.

There are no IPFs associated with either routine operations or accidents that could cause impacts to eastern Gulf live bottom areas due to the distance from the lease area. A small fuel spill would float and dissipate on the surface and would not reach these seafloor features.

In the event of an oil spill from a well blowout, a surface slick would not contact these seafloor features. If a subsurface plume were to occur, impacts on these features would be unlikely due to the distance and the difference in water depth. Near-bottom currents in the region are predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume up onto the continental shelf.



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

This section discusses species listed as endangered or threatened under the ESA. In addition, it includes all marine mammal species in the region, which are protected under the MMPA.

Endangered or threatened species that may occur in the project area and/or along the northern
Gulf Coast are listed in Table 5 . The table also indicates the location of critical habitat (if designated in the Gulf of Mexico). Critical habitat is defined as (1) specific areas within the geographical area occupied by the species at the time of listing, if they contain physical or biological features essential to conservation, and those features may require special management considerations or protection; and (2) specific areas outside the geographical area occupied by the species if the agency determines that the area itself is essential for

conservation. The NMFS has jurisdiction over ESA-listed cetaceans, sea turtles, and fishes in the Gulf of Mexico. The USFWS has jurisdiction over ESA-listed birds and the Florida manatee.

The sperm whale and five species of sea turtles are the only endangered or threatened species likely to occur at or near the lease area. No critical habitat has been designated for these species in the Gulf of Mexico.

Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic right whale, and sei whale) also have been reported from the Gulf of Mexico but are considered rare or extralimital there (Würsig et al., 2000). No critical habitat has been designated for these species in the Gulf of Mexico.

Coastal endangered or threatened species include the Florida manatee, Piping Plover, Whooping Crane, Gulf sturgeon, and four subspecies of beach mouse. Critical habitat has been designated for all of these species as indicated in Table 5 and discussed in individual sections.

### Table 5. Federally-listed endangered and threatened species in the lease area and along the
northern Gulf Coast.

Species Scientific Name Status Potential Presence Critical Habitat

Designated in Gulf of Mexico Lease Area Coastal

Marine Mammals Sperm whale Physeter macrocephalus E X

-- None

Florida manatee Trichechus manatus latirostris E

-- X Florida (Penins ular) 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

-- Non e Sea Turtles Loggerhead turtle Caretta caretta T b X X None Green turtle Chelonia mydas T, E c X X None Leatherback turtle Dermochelys coriacea E X X None Hawksbill turtle Eretmochelys imbricata E X X None Kemp’s ridley turtle Lepidochelys kempii E X X None Birds

Piping Plover Charadrius melodus T

-- X Coastal Texas, Louisiana, Mississippi, Alabama, and Florida (Panhandle)

Whooping Crane Grus americana E

-- X Coastal Texas (Aransas National Wildlife Refuge) Fishes

Gulf sturgeon Acipenser oxyrinchu s desotoi T

-- X Coastal Louisiana, Mississippi, Alabama, and Florida (Panhandle) Terrestrial Mammals Beach m ouse (Alabama, Choctawhatchee, Perdido Key, St. Andrew) Peromyscus polionotus E

-- X Alabama and Florida (Panhandle) beaches

Abbreviations: E = Endangered; T = Threatened. a The blue, fin, humpback, North Atlantic right, and sei whales are rare or extralimital in the Gulf of Mexico and are unlikely to be present in the lease area. b The loggerhead turtle is currently classified as threatened throughout its range. In March 2010, NMFS and USFWS proposed to list the Northwest Atlantic Ocean population of loggerhead turtles as endangered ( 75 FR 12598 ). c The green sea turtle is threatened, except for the Florida breeding population, which is listed as endangered.



### Two other coastal species (Bald Eagle and Brown Pelican) discussed by MMS (2007b) are no longer listed as endangered or threatened; these are discussed under Coastal and Marine Birds.

There are no other endangered animals or plants in the Gulf of Mexico that are reasonably likely to be affected by either routine or accidental events. Other species occurring at certain locations in the Gulf of Mexico such as the smalltooth sawfish ( Pristis pectinata ), elkhorn coral ( Acropora palmata ), staghorn coral ( Acropora cervicornis ), and Florida salt marsh vole ( Microtus pennsylvanicus dukecampbelli ) are remote from the lease area and highly unlikely to be
affected.

### 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- an d 3,280-ft ( 200 - and 1,000-m) depth contours (Jochens et al., 2008). Male sperm whales were more variable in their movements and were documented in water depths greater than 9,483 ft ( 3,000 m). Generally, groups of sperm whales sighted in the Gulf of Mexico during the MMS-funded Sperm Whale Seismic Study (SWSS) consisted of mixed-sex groups comprising adult females and immatures, and groups of bachelor males. Typical group size for mixed groups was 10 individuals (Jochens et al., 2008). SWSS results show that sperm whales transit through the vicinity of the lease area. Movements of satellite-tracked individuals suggest that this area of the Gulf continental slope is within the home range of the Gulf of Mexico population (within the 95% utilization distribution) (Jochens et al., 2008).

IPFs potentially affecting sperm whales include drilling rig presence, noise, and lights; support vessel and helicopter traffic; and two types of accidents

– a small fuel spill and a large oil spill. Effluent discharges are likely to have negligible impacts on sperm whales due to rapid dispersion, the small area of ocean affected, the intermittent nature of the discharges, and the mobility of these marine mammals. Compliance with NTL 2007 -G03 will minimize the potential
fo r 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 d ri lling rig lighting and rig presence were considered potential factors affecting sperm whales, NMFS’s 2007 Biological Opinion and recent lease sale EISs (MMS, 2007b, 2008) did not identify rig lighting and presence as IPFs for sperm whales.



### Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb sperm whales, and there is also a risk of vessel strikes, which are identified as a threat in the recovery plan for this species (NMFS, 2010a ). Data concerning the frequency of vessel strikes is presented in the lease sale EIS (MMS, 2007b). To reduce the potential for vessel strikes, the BOEMRE has issued NTL 2007-G04, which recommends protected species identification training and that vessel operators and crews maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid striking protected species, and requires operators to report sightings of any injured or dead protected species. When whales are sighted, vessel operators and crews are required to attempt to maintain a distance of 300 ft ( 91 m) or greater whenever possible. Vessel operators are required to reduce vessel speed to 10 knots or less when mother/calf pairs, pods, or large assemblages of cetaceans are observed near an underway vessel when safety permits. Compliance with this NTL will minimize the likelihood of vessel strikes as well as reduce the chance for disturbing sperm whales.

The NMFS (2007) analyzed the potential for vessel strikes and harassment of sperm whales in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. With implementation of the mitigation measures in

NTL 2007 -G04, NMFS concluded that the likelihood of collisions between vessels and sperm whales would be reduced to insignificant levels. The NMFS concluded that the observed avoidance of passing vessels by sperm whales is an advantageous response to avoid a potential threat and is not expected to result in any significant effect on migration, breathing, nursing, breeding, feeding, or sheltering to individuals, or have any consequences at the level of the population. With implementation of the vessel strike avoidance measures requirement to maintain a distance of 300 ft (91 m) from sperm whales, the NMFS concluded that the potential for harassment of sperm whales would be reduced to discountable levels.

Helicopter traffic also has the potential to disturb sperm whales. Smultea et al. (2008) documented responses of sperm whales offshore Hawaii to fixed wing aircraft flying at an altitude of 800 ft ( 245 m). A reaction to the initial pass of the aircraft was observed during three
out of 24 sightings (12%). All three reactions consisted of a hasty dive and occurred at less than 1,180 ft ( 360 m) lateral distance from the aircraft. Additional reactions were seen when aircraft
circled certain whales to make further observations. Based on other studies of cetacean responses to sound, the authors concluded that the observed reactions to brief overflights by the aircraft were short-term and probably of no long-term biological significance.

While flying offshore in the Gulf of Mexico, helicopters maintain altitudes above 700 ft ( 213 m) during transit to and from the working area. In the event that a whale is seen during transit, the helicopter will not approach or circle the animals. Although responses are possible based on the Smultea et al. (2008) study, the NMFS (2007) concluded that this altitude would minimize the potential for disturbing sperm whales. Therefore, no significant impacts are expected.

### Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals including sperm whales are discussed in recent EISs (MMS, 2007b, 2008) and by the NMFS (2007) in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. Oil impacts on marine mammals are discussed by Geraci and St. Aubin (1990). For this Supplemental EP there are no unique site-specific issues with respect to spill impacts on these
animals.

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the potential for impacts on sperm whales. Supplemental EP

Sections 2j and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the duration of a small spill and opportunity for impacts to occur would be very
brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the concentrations of petroleum hydrocarbons and their degradation products. The extent and persistence of impacts would depend on the meteorological and oceanographic conditions at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally
within 24 hours. The area of the sea surface with diesel fuel on it would range from

1.2 to 12 acres (0.5 to 5 ha), depending on sea state and weather conditions.

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and noise of response vessels and aircraft (Marine Mammal Commission [MMC], 2010). However, due to the limited areal extent and short duration of water quality impacts from a small fuel spill, as well as the mobility of sperm whales, no significant impacts would be expected.



### Impacts of a Large Oil Spill

Potential spill impacts on marine mammals including sperm whales are discussed in recent EISs (MMS, 2007b, 2008) and by the NMFS (2007) in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. Oil impacts on marine mammals are discussed by Geraci and St. Aubin (1990). For this Supplemental EP , there are no unique site-specific issues with respect to spill impacts on these
animals.

Impacts of oil spills on sperm whales can include direct impacts from oil exposure, as well as indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and dispersants) (MMC, 2010). Direct physical and physiological effects can include skin irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey; and stress from the activities and noise of response vessels and aircraft. Complications of the above may lead to dysfunction of immune and reproductive systems, physiological stress, declining physical condition, and death. Behavioral responses can include displacement of animals from prime habitat, disruption of social structure, changing prey availability and foraging distribution and/or

### patterns, changing reproductive behavior/productivity, and changing movement patterns or

migration (MMC, 2010).

Studies have shown that the cetacean epidermis functions as an effective barrier to noxious substances found in petroleum (Geraci and St. Aubin, 1985). Unlike other mammals, penetration of such substances in cetacean skin is impeded by tight intercellular bridges, the vitality of the superficial cells, the thickness of the epidermis, and the lack of sweat glands and hair follicles. In addition, cetacean skin is free from hair or fur, which in other marine mammals not found in the Gulf of Mexico (e.g., pinnipeds and otters) tends to collect oil and/or tar.

In the event of a large spill, the level of vessel and aircraft activity associated with spill response could disturb sperm whales and potentially result in vessel strikes, entanglement, or other injury or stress. Response vessels would operate in accordance with NTL 2007 -G04 to reduce the potential for striking or disturbing these animals.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event o f a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on sperm whales are expected.



### C.3.2 Florida Manatee (Endangered)

Most of the manatee population is located in peninsular Florida (USFWS, 2001). Manatees regularly migrate farther west of Florida in the warmer months (Wilson, 2003) into Alabama and Louisiana coastal environs, with some individuals traveling as far as west Texas (Fertl et al.,

2005 ). A species description is presented in a recent lease sale EIS (MMS, 2007b) and in the recovery plan for this species (USFWS, 2001).

IPFs potentially affecting manatees include support vessel and helicopter traffic and a large oil spill. A small fuel spill in the lease area would be unlikely to affect manatees, as the lease area is approximately 178 miles (286 km) from the nearest shoreline (Louisiana). As explained in

Section A.9.2 , a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up. Compliance with NTL 2007 -G03 will minimize the potential for marine debris-related impacts on manatees.



### Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb manatees, and there is also a risk of vessel strikes, which are identified as a threat in the recovery plan for this species (USFWS, 2001). To reduce the potential for vessel strikes, the BOEMRE has issued NTL 2007-G04, which recommends protected species identification training and that vessel operators and crews maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid striking protected species, and requires operators to report sightings of any injured or dead protected species. Compliance with this NTL will minimize the likelihood of vessel strikes, and no significant impacts on manatees are expected.

Helicopter traffic, if present, also has the potential to disturb manatees. Rathbun (1988) reported that manatees were disturbed more by helicopters than by fixed-wing aircraft; however, the helicopter was flown at a relatively low altitude of 66 to 525 ft (20 to 160 m).

### Helicopters used in support operations maintain a minimum altitude of 700 ft ( 213 m) while in

transit offshore, 1,000 ft ( 305 m) over unpopulated areas or across coastlines, and 2,000 ft ( 610 m) over populated areas and sensitive habitats such as wildlife refuges and park properties. This mitigation measure will minimize the potential for disturbing manatees, and no significant impacts are expected.



### Impacts of a Large Oil Spill

The OSRA results summarized in Table 3 predict that some Texas and Louisiana shorelines could be contacted by a spill within 30 days. There is no critical habitat designated in these areas, and the number of manatees potentially present is a small fraction of the population in peninsular
Florida.

In the event that manatees were exposed to oil, effects could include direct impacts from oil exposure, as well as indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and dispersants) (MMC, 2010). Direct physical and physiological effects can include skin irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey (or contaminated vegetation, in the case of manatees); and stress from the activities and noise of response vessels and aircraft. Complications of the above may lead to dysfunction of immune and reproductive systems, physiological stress, declining physical condition, and death. Behavioral responses can include displacement of animals from prime habitat, disruption of social structure, changing prey availability and foraging distribution and/or patterns, changing reproductive behavior/productivity, and changing movement patterns or migration (MMC, 2010).

In the event that a large spill reached coastal waters where manatees were present, the level of vessel and aircraft activity associated with spill response could disturb manatees and potentially result in vessel strikes, entanglement, or other injury or stress. Response vessels would operate
in accordance with NTL 2007 -G04 to reduce the potential for striking or disturbing these animals, and therefore no significant impacts are expected.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout preventi on measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on manatees are expected.



### C.3.3 Endangered Mysticete Whales

Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic right whale, and sei whale) also have been reported from the Gulf of Mexico but are considered rare or extralimital there (Würsig et al., 2000). No critical habitat has been designated for these species in the Gulf of Mexico.

Due to the rare occurrence of these whales in the Gulf of Mexico and the limited scope and duration of the project, it is highly unlikely that any endangered mysticete would come into contact with any project activities, either routine operations or accidents. The NMFS (2007) did not include any of these mysticete whales as affected species in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and Western Planning Areas of the Gulf of

### Mexico. Potential impacts are analyzed in recent lease sale EISs (MMS, 2007b, 2008), and those

analyses are incorporated by reference. If any of these whales were present in the area, potential impacts would be the same as those discussed below in Section C.3.4

.



### C. 3.4 Non-Endangered Marine Mammals (Protected)

In addition to the seven endangered species that have been cited previously, 22 other species of
marine mammals occur in the Gulf of Mexico

, includ ing two mysticete whales, the dwarf and pygmy sperm whales, 4 species of beaked whales, and 14 species of delphinids (see Supplemental EP Section 6h ). All marine mammals are protected species under the

MM PA. The most common non-endangered cetaceans in the deepwater environment are odontocetes such as the pantropical spotted dolphin, spinner dolphin, and clymene dolphin. A brief summary is presented below, and additional information on these groups is presented in a recent lease sale EIS (MMS, 2007b).

Mysticete whales . Two non-endangered mysticete whales are known from the Gulf of Mexico. The Bryde’s whale ( Balaenoptera edeni ) has been sighted most frequently along the 328-ft ( 100 -m) isobath (Davis and Fargion, 1996; Davis et al., 2000). Most sightings have been made in the DeSoto Canyon region and off western Florida, although there have been some in the west-central portion of the northeastern Gulf. The minke whale ( Balaenoptera acutorostrata ) is considered rare in the Gulf of Mexico, with the only confirmed records coming from strandings (Würsig et al., 2000). Based on the available data, it is possible that Bryde’s whales could occur
in the lease area.

Dwarf and pygmy sperm whales . At sea, it is difficult to differentiate dwarf sperm whales ( Kogia sima ) from pygmy sperm whales ( Kogia breviceps ), and sightings are often grouped together as “ Kogia spp.” Both species have a worldwide distribution in temperate to tropical waters. In the Gulf of Mexico, both species occur primarily along the continental shelf edge and in deeper waters off the continental shelf (Mullin et al., 1991; Mullin, 2007). Either species
could occur in the lease area.

Beaked whales . Four species of beaked whales are known from the Gulf of Mexico. They are Blainville’s beaked whale ( Mesoplodon densirostris ), Cuvier’s beaked whale ( Ziphius cavirostris ), Sowerby’s beaked whale ( Mesoplodon bidens ), and Gervais’ beaked whale ( Mesoplodon

europaeus ). Stranding records in the Gulf of Mexico suggest that Gervais’ beaked whale is the most common and Sowerby’s beaked whale is extralimital. Due to the difficulties of at-sea identification, beaked whales in the Gulf of Mexico are identified either as Cuvier’s beaked whales or are grouped into an undifferentiated complex ( Mesoplodon spp. and Ziphius spp.). In the northern Gulf of Mexico, they are broadly distributed in waters greater than 3,281 ft ( 1,000 m) over lower slope and abyssal landscapes (Davis et al., 2000). Any of these species
could occur in the lease area.

Delphinids . Fourteen species of delphinids are known from the Gulf of Mexico, including Atlantic spotted dolphin ( Stenella frontalis ), bottlenose dolphin ( Tursiops truncatus ), clymene dolphin ( Stenella clymene ), false killer whale ( Pseudorca crassidens ), Fraser’s dolphin ( Lagenodelphis hosei ), killer whale ( Orcinus orca ), melon-headed whale ( Peponocephala electra ), pantropical spotted dolphin ( Stenella attenuata ), pygmy killer whale ( Feresa attenuata ),
short

- finned pilot whal e ( 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.

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

associat ed with drilling is relatively weak in intensity, and an individual animal’s noise exposure would be transient. There are other OCS facilities and activities near the lease area, and the region as a whole has a large number of similar sources. Due to the limited scope, timing, and geographic extent of drilling activities, this project would represent a small temporary contribution to the overall noise regime, and any short-term impacts are not expected to be biologically significant to marine mammal populations.

Drilling rig lighting and rig presence are not identified as IPFs for marine mammals in recent lease sale EISs (MMS, 2007b, 2008).



### Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb marine mammals, and there is also a risk of vessel strikes. Data concerning the frequency of vessel strikes is presented in the lease sale EIS (MMS, 2007b). To reduce the potential for vessel strikes, the BOEMRE has issued

NTL 2007 -G04, which recommends protected species identification training and that vessel operators and crews maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid striking protected species, and requires operators to report sightings of any injured or dead protected species. Vessel operators and crews are required to attempt to maintain a distance of 300 ft ( 91 m) or greater when whales are sighted and 150 ft ( 45 m) when small cetaceans are sighted. When cetaceans are sighted while a vessel is underway, vessels

must attempt to remain parallel to the animal’s course and avoid excessive speed or abrupt changes in direction until the cetacean has left the area. Vessel operators are required to reduce vessel speed to 10 knots or less when mother/calf pairs, pods, or large assemblages of cetaceans are observed near an underway vessel, when safety permits. Compliance with this NTL will minimize the likelihood of vessel strikes as well as reduce the chance for disturbing marine mammals, and therefore no significant impacts are expected.

Aircraft traffic also has the potential to disturb marine mammals (Würsig et al., 1998). However, while flying offshore, helicopters maintain altitudes above 700 ft ( 213 m) during transit to and from the working area. This altitude will minimize the potential for disturbing marine mammals, and no significant impacts are expected (MMS, 2007b).

### Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008), and oil impacts on marine mammals in general are discussed by Geraci and St. Aubin (1990). For this Supplemental EP, there are no unique site-specific issues with respect to spill impacts on
these animals.

The probability of a fuel spill will be minimized by Shell’s preventative measu res during fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate and reduce the potential for impacts on marine mammals. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the concentrations of petroleum hydrocarbons and their degradation products. The extent and persistence of impacts would depend on the meteorological and oceanographic conditions at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate
of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from

1.2 to 12 acres (0.5 to 5 ha), depending on sea state and weather conditions.

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and noise of response vessels and aircraft (MMC, 2010). However, due to the limited areal extent and short duration of water quality impacts from a small fuel spill, as well as the mobility of marine mammals, no significant impacts would be expected.



### Impacts of a Large Oil Spill

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008) and by Geraci and St. Aubin (1990). For this Supplemental EP , there are no unique site-specific

issues.

Imp acts 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 min imized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on marine mammals are expected.



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

As listed in Supplemental EP Section 6h , five species of endangered or threatened sea turtles may be found near the lease area. Endangered species are the leatherback ( Dermochelys

coriacea ), Kemp's ridley ( Lepidochelys kempii ), and hawksbill ( Eretmochelys imbricata ) turtles. The loggerhead turtle ( Caretta caretta ) is a threatened species. The green turtle ( Ch elonia mydas ) is listed as threatened, except for the Florida breeding population, which is listed as endangered. Species descriptions are presented in a recent lease sale EIS (MMS, 2007b).

Leatherbacks and loggerheads are the most likely species to be present near the lease area as adults. Green, hawksbill, and Kemp’s ridley turtles are typically inner shelf and nearshore species, unlikely to occur near the lease area as adults. Hatchlings or juveniles of any of the sea turtles may be present in deepwater areas, including the lease area, where they may be
associated with Sargassum and other flotsam.

All five sea turtle species in the Gulf of Mexico are migratory and use different marine habitats according to their life stage. These habitats include high-energy beaches for nesting females and emerging hatchlings and pelagic convergence zones for hatchling and juvenile turtles. As adults, green, hawksbill, and loggerhead turtles forage primarily in shallow, benthic habitats. Leatherbacks are the most pelagic of the sea turtles, feeding primarily on jellyfish.

Sea turtle nesting in the northern Gulf of Mexico can be summarized by species as follows:

Loggerhead turtles

– Loggerheads nest in significant numbers along the Florida Panhandle and, to a lesser extent, from Texas through Alabama (MMS, 2007b). The nearest significant nesting area of loggerhead turtles is found in Louisiana, on beaches within the Breton NWR;
Green and leatherback turtles

– Green and leatherback turtles infrequently nest on Florida Panhandle beaches (Florida Fish and Wildlife Conservation Commission, 2011); Kemp’s ridley turtles – The main Kemp’s ridley nesting site is Rancho Nuevo beach, Tamaulipas, Mexico (NMFS et al., 2010). Approximately 200 Kemp’s ridley turtles nested on Texas beaches in 2009 (Sea Turtle Restoration Project, 2011). Kemp’s ridley turtles typically do not nest anywhere near the project area, although there have been occasional reports of Kemp’s ridleys nesting in Alabama (Share the Beach, 2010); and
Hawksbill turtles

– Hawksbills typically do not nest anywhere near the project area.

IPFs potentially affecting sea turtles include drilling rig presence, noise, and lights; support vessel and helicopter traffic; and two types of accidents (a small fuel spill and a large oil spill). Effluent discharges are likely to have negligible impacts on sea turtles due to rapid dispersion, the small area of ocean affected, and the intermittent nature of the discharges. Compliance with NTL 2007-G03 will minimize the potential for marine debris-related impacts on sea turtles.

### Impacts of Drilling Rig Presence, Noise, and Lights

Offshore drilling activities produce a broad array of sounds at frequencies and intensities that may be detected by sea turtles (Geraci and St. Aubin, 1987). Potential impacts may include behavioral disruption and temporary or permanent displacement from the area near the sound source. Certain sea turtles, especially loggerheads, may be attracted to offshore structures (Lohoefener et al., 1990) and, thus, may be more susceptible to impacts from sounds produced during routine operations. Helicopters and service vessels may also affect sea turtles due to machinery noise and/or visual disturbances. The most likely impacts would be short-term behavioral changes such as diving and evasive swimming, disruption of activities, or departure from the area. Due to the limited scope, timing, and geographic extent of drilling activities, these short-term impacts are not expected to be biologically significant to sea turtle populations.

Artificial lighting can disrupt the nocturnal orientation of sea turtle hatchlings (Witherington, 1997; Tuxbury and Salmon, 2005). However, hatchlings may rely less on light cues when they are offshore than when they are emerging on the beach (Salmon and Wyneken, 1990). The NMFS (2007) concluded that the effects of lighting from offshore structures on sea turtles are insignificant.



### Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb sea turtles, and there is also a risk of vessel strikes. Data show that vessel traffic is one cause of sea turtle mortality in the Gulf of Mexico (Lutcavage et al., 1997). While adult sea turtles are visible at the surface during the day and in clear weather, they can be difficult to spot from a moving vessel when resting below the water surface, during nighttime, or during periods of inclement weather. To reduce the potential for vessel strikes, the BOEMRE has issued NTL 2007-G04, which recommends protected species
iden tification training and that vessel operators and crews maintain a vigilant watch for sea turtles and slow down or stop their vessel to avoid striking protected species, and requires operators to report sightings of any injured or dead protected species. When sea turtles are sighted, vessel operators and crews are required to attempt to maintain a distance of 150 ft ( 45 m) or greater whenever possible. Compliance with this NTL will minimize the likelihood of vessel strikes as well as reduce the chance for disturbing sea turtles (NMFS, 2007).

Helicopter traffic also has the potential to disturb sea turtles. However, while flying offshore, helicopters maintain altitudes above 700 ft ( 213 m) during transit to and from the working area. This altitude will minimize the potential for disturbing sea turtles, and no significant impacts are expected.



### Impacts of a Small Fuel Spill

Potential spill impacts on sea turtles are discussed in recent EISs (MMS, 2007b, 2008) and by the NMFS (2007) in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. For this Supplemental EP , there are no unique site-specific issues with respect to spill impacts on these animals.

The probability of a fuel spi ll will be minimized by Shell’s preventative measures during fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate and reduce the potential for impacts on sea turtles. Supplemental EP Sections 2j and 9b

### provide detail on spill response measures. Given the open ocean location of the lease area, the

duration of a small spill and opportunity for impacts to occur would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the concentrations of petroleum hydrocarbons and their degradation products. The extent and persistence of impacts would depend on the meteorological and oceanographic conditions at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from

1.2 to 12 acres (0.5 to 5 ha), depending on sea state and weather conditions.

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and noise of response vessels and aircraft (MMC, 2010). However, due to the limited areal extent and short duration of water quality impacts from a small fuel spill, no significant impacts would be expected.

A small fuel spill in the lease area would be unlikely to affect sea turtle nesting beaches, as the lease area is 178 miles (286 km) from the nearest shoreline (Louisiana). As explained in

Section A.9.2 , a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up.



### Impacts of a Large Oil Spill

Impacts of oil spills on sea turtles can include direct impacts from oil exposure, as well as indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and dispersants). Direct physical and physiological effects can include skin irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes and smoke (e.g., from in situ burning of oil); ingestion of oil (and dispersants) directly or via contaminated food; and stress from the activities and noise of response vessels and aircraft. Complications of the above may lead to dysfunction of immune and reproductive systems, physiological stress, declining physical condition, and death. Behavioral responses can include displacement of animals from prime habitat, disruption of social structure, changing food availability and foraging distribution and/or patterns, changing reproductive behavior/productivity, and changing movement patterns or migration (MMC, 2010). In the unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate and reduce the potential for these types of impacts on sea turtles. Supplemental EP Sections 2j and 9b provide detail on spill response measures.

Studies of oil effects on loggerheads in a controlled setting (Lutcavage et al., 1995) suggest that sea turtles show no avoidance behavior when they encounter an oil slick, and any sea turtle in an affected area would be expected to be exposed. Sea turtles’ diving behaviors also put them at risk. Sea turtles rapidly inhale a large volume of air before diving and continually resurface over time, which may result in repeated exposure to volatile vapors and oiling (NMFS, 2007).

The OSRA results summarized in Table 3 predict that some shorelines that support sea turtle nesting could be contacted within 30 days. The nearest nesting area of loggerhead turtles is found on beaches within the Breton NWR. This area (Plaquemines Parish) has a contact

pr obability of 2% 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 recent Macondo spill provides additional information about potential impacts of a large oil spill on sea turtles to supplement the analysis presented in the lease sale EIS (MMS, 2007b). According to NMFS (2010b), approximately 600 dead turtles have been reported since the Macondo spill. Species include Kemp’s ridley turtles (481 individuals), loggerhead turtles (67 individuals), and green turtles (29 individuals). Oiled turtles include 18 dead individuals and

456 live, oiled animals that were either captured or stranded. Also, 278 turtle nests were translocated (271 loggerhead, 4 Kemp’s ridley, and 3 green turtles) and more than 14,000 hatchlings were released. The strandings and captures ranged from the Louisiana/Texas border to Cape San Blas in the Florida Panhandle.

In the event of a large spill, the level of vessel and aircraft activity associated with spill response could disturb sea turtles and potentially result in vessel strikes, entanglement, or other injury or stress. Response vessels would operate in accordance with NTL 2007 -G04 to reduce the potential for striking or disturbing these animals, and therefore no significant impacts are expected.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on sea turtles are expected.



### C.3.6 Piping Plover (Threatened)

The Piping Plover (Charadrius melodus) is a migratory shorebird that overwinters along the southeastern U.S. and Gulf of Mexico coasts. This threatened species is in decline as a result of hunting, habitat loss and modification, predation, and disease (USFWS, 2003). Critical overwintering habitat has been designated, including beaches in Texas, Louisiana, Mississippi, Alabama, and Florida ( Figure 3 ). Piping Plovers inhabit coastal sandy beaches and mudflats, feeding by probing for invertebrates at or just below the surface. They use beaches adjacent to foraging areas for roosting and preening (USFWS, 2010a). A species description is presented in a recent lease sale EIS (MMS, 2007b).

A large oil spill is the only IPF potentially affecting Piping Plovers. There are no IPFs associated with routine project activities that could affect these birds. A small fuel spill in the lease area would be unlikely to affect Piping Plovers because a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up (see explanation in Section A.9.2 ).

### Figure 3. Location of selected environmental features in relation to the lease area. Shown are Essential Fish Habitat (EFH) for coral and coral reefs; Habitat Areas of Particular Concern (HAPC) for northwestern Gulf of Mexico reefs and banks and spawning Atlantic bluefin tuna; critical habitat for beach mice, Gulf sturgeon, Piping Plover, and Whooping Crane; and the Macondo spill location.

### Impacts of a Large Oil Spill

The lease area is 178 miles (286 km) from the nearest shoreline inhabited by Piping Plovers. The
OSRA results summarized in Table 3 predict that Texas and Louisiana shorelines designated as critical habitat for the wintering Piping Plover could be contacted by a spill within 30 days. Plaquemines Parish, which has a 2% probability of contact for the 30-day interval, includes Piping Plover critical habitat.

Plovers could become externally oiled while foraging on oiled shores or be exposed internally through ingestion of oiled intertidal sediments and prey (MMS, 2007b). Plovers congregate and feed along tidally exposed banks and shorelines, following the tide out and foraging at the water’s edge. It is possible that some deaths of Piping Plovers coul d occur, especially if spills occur during winter months when plovers are most common along the coastal Gulf or if spills contacted critical habitat. Impacts could also occur from vehicular traffic on beaches and other activities associated with spill cleanup. Shell has extensive resources available to protect and rehabilitate wildlife in the event of a spill reaching the shoreline, as detailed in the OSRP.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will

mi tigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on Piping Plovers are expected.



### C.3.7 Whooping Crane (Endangered)

The Whooping Crane ( Grus americana ) is an omnivorous wading bird and an endangered species. There are three wild populations in North America (Whooping Crane Eastern Partnership [WCEP], 2010). One population winters along the Texas coast at Aransas NWR and summers at Wood Buffalo National Park in Canada. This population represents the majority of
th e world’s population of free -ranging Whooping Cranes and reached a record population of 270 at Aransas NWR in December 2008 (WCEP, 2010). A non-migrating population has been

re -introduced in central Florida, and another re-introduced population summers in Wisconsin and migrates to the southeastern U.S. for the winter. Whooping Cranes breed, migrate, winter, and forage in a variety of habitats, including coastal marshes and estuaries, inland marshes, lakes, ponds, wet meadows and rivers, and agricultural fields (USFWS, 2007). About 22,240 acres (9,000 ha) of salt flats on Aransas NWR and adjacent islands comprise the principal wintering grounds of the Whooping Crane. Aransas NWR is designated as critical habitat for the species ( Figure 3 ). A species description is presented in a recent lease sale EIS (MMS, 2007b).

A large oil spill is the only IPF potentially affecting Whooping Cranes. A small fuel spill in the lease area would be unlikely to affect Whooping Cranes due to the distance from Aransas NWR. As explained in Section A.9.2 , a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up.



### Impacts of a Large Oil Spill

A large oil spill has a low probability of affecting Whooping Cranes because the lease area is approximately 372 miles (598 km) from its critical habitat (Aransas NWR, Texas) and the OSRA modeling predicts 1% probability of contact with shorelines of the Aransas NWR within 30 days.

### In the event of oil exposure, Whooping Cranes could become externally oil ed 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 pre vention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on Whooping Cranes are expected.



### C.3.8 Gulf Sturgeon (Threatened)

The Gulf sturgeon ( Acipenser oxyrinchus desotoi ) is a threatened fish species that inhabits major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida (Barkuloo, 1988; Wakeford, 2001). An anadromous fish that migrates from the sea upstream into coastal rivers to spawn in freshwater, it historically ranged from the Mississippi River to Charlotte Harbor, Florida (Wakeford, 2001). Today, this range has contracted to encompass major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida. Populations have been depleted or even extirpated throughout this range by fishing, shoreline development, dam construction, water quality changes, and other factors (Barkuloo, 1988; Wakeford, 2001). These declines prompted the listing of the Gulf sturgeon as a threatened species in 1991. The best known populations occur in the Apalachicola and Suwannee Rivers in
Fl orida (Carr, 1996; Sulak and Clugston, 1998), the Choctawhatchee River in Alabama (Fox et al., 2000), and the Pearl River in Mississippi/Louisiana (Morrow et al., 1998). Critical habitat in the Gulf extends from Lake Borgne, Louisiana (St. Bernard Parish) to Suwannee Sound, Florida (Levy County) (NMFS, 2010c) ( Figure 3 ). A species description is presented in a recent lease sale EIS (MMS, 2007b) and in the recovery plan for this species (USFWS and Gulf States Marine Fisheries Commission, 1995).

A large oil spill is the only IPF potentially affecting Gulf sturgeon. There are no IPFs associated with routine project activities that could affect this species. A small fuel spill in the lease area would be unlikely to affect Gulf sturgeon because a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up (see explanation in Section A.9.2 ).



### Impacts of a Large Oil Spill

Potential spill impacts on Gulf sturgeon are discussed in recent EISs (MMS, 2007b, 2008) and by the NMFS (2007) in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. For this Supplemental EP , there are no unique site-specific issues with respect to this species.

The lease area is about 244 miles (393 km) from the nearest Gulf sturgeon critical habitat. The OSRA modeling ( Table 3 ) predicts that a spill in the lease area will not contact the coastal areas inhabited by Gulf sturgeon within 30 days.

In the event of oil reaching Gulf sturgeon habitat, the fish could be affected by direct ingestion, ingestion of oiled prey, or the absorption of dissolved petroleum products through the gills. Based on the life history of this species, subadult and adult Gulf sturgeon would be mos t

### vulnerable to a marine oil spill, and would be vulnerable only during winter months (from

1 September through 30 April) when this species is foraging in estuarine and marine habitats (NMFS, 2007).

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Shell has extensive resources available to protect coastal and estuarine wildlife and habitats in the event of a spill reaching the shoreline, as detailed in the

OSRP. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on Gulf sturgeon are expected.



### C.3.9 Beach Mice (Endangered)

Four subspecies of endangered beach mouse ( Peromyscus polionotus ) occur on the barrier islands of Alabama and the Florida Panhandle. They are the Alabama, Choctawatchee, Perdido Key, and St. Andrew beach mouse. Critical habitat has been designated for all four subspecies; Figure 3 shows the critical habitat combined for all four subspecies. Species descriptions are provided in a recent lease sale EIS (MMS, 2007b).

A large oil spill is the only IPF potentially affecting subspecies of beach mouse. There are no IPFs associated with routine project activities that could affect these animals due to the distance from shore and the lack of any onshore support activities near their habitat. A small fuel spill in the lease area would not affect any subspecies of beach mouse because a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up (see explanation

in Section A.9.2 ).



### Impacts of a Large Oil Spill

Potential spill impacts on beach mice are discussed in recent EISs (MMS, 2007b, 2008). For this Supplemental EP , there are no unique site-specific issues with respect to these species.

The lease area is about 308 miles (496 km) from the nearest beach mouse critical habitat. The OSRA modeling predicts that a spill in the lease area would not contact beach mouse critical habitat within 30 days.

In the event of oil contacting these beaches, beach mice could experience several types of direct and indirect impacts. Contact with spilled oil could cause skin and eye irritation and subsequent infection; matting of fur; irritation of sweat glands, ear tissues, and throat tissues; disruption of sight and hearing; asphyxiation from inhalation of fumes; and toxicity from ingestion of oil and contaminated food. Indirect impacts could include reduction of food supply, destruction of habitat, and fouling of nests. Impacts could also occur from vehicular traffic and other activities associated with spill cleanup.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will

mi tigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on beach mice are expected.

## 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/km 2



### .
Trans-Gulf migrant birds including shorebirds, wading birds, and terrestrial birds may also be present in the lease area. Migrant birds may use offshore structures and platforms for resting, feeding, or as temporary shelter from inclement weather (Russell, 2005). Some birds may be attracted to offshore structures because of the lights and the fish populations that aggregate
around these structures.

IPFs potentially affecting marine and pelagic birds include drilling rig presence, noise, and lights; support vessel and helicopter traffic; and two types of accidents (a small fuel spill and a large oil spill). Effluent discharges are likely to have negligible impacts on the birds due to rapid dispersion, the small area of ocean affected, the intermittent nature of the discharges, and the mobility of these animals. Compliance with NTL 2007 -G03 will minimize the potential for marine debris-related impacts on birds.



### Impacts of Drilling Rig Presence, Noise, and Ligh ts

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

tr ans-Gulf migrant species, and most of the migrants that stop over on platforms probably benefit from their stay, particularly in spring (Russell, 2005). Due to the limited scope, timing, and geographic extent of drilling activities in this Supplemental EP, any impacts on populations of either seabirds or trans-Gulf migrant birds are not expected to be significant.

A recent study in the North Sea indicated that platform lighting causes circling behavior in various birds, especially on cloudy nights; apparen tly the birds’ geomagnetic compass is upset by the red part of the spectrum from the lights currently in use (Poot et al., 2008). The numbers varied greatly, from none at all to some tens of thousands of birds per night per platform, with an apparent effect radius of up to 3 miles (5 km). A study in the Gulf of Mexico also noted the phenomenon, but did not recommend mitigation (Russell, 2005). Factors to consider in evaluating this impact in the Gulf of Mexico would include the lower incidence of cloudy and foggy days in the Gulf of Mexico versus the North Sea. Due to the limited scope and short duration of drilling activities proposed in this Supplemental EP , lighting impacts, collisions, or other adverse effects are unlikely, and no significant impacts are expected.



### Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters are unlikely to significantly disturb pelagic birds in open, offshore waters. It is likely that individual birds would experience, at most, only short-term
beh avioral disruption, and the impact would not be significant.



### Impacts of a Small Fuel Spill

Potential spill impacts on marine birds are discussed in recent EISs (MMS, 2007b, 2008). For this Supplemental EP , there are no unique site-specific issues with respect to spill impacts on these
animals.

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the potential for impacts on marine and pelagic birds. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the duration of a small spill and opportunity for impacts to

oc cur would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the concentrations of petroleum hydrocarbons and their degradation products. The extent and persistence of impacts would depend on the meteorological and oceanographic conditions at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from

1.2 to 12 acres (0.5 to 5 ha), depending on sea state and weather conditions.

Birds exposed to oil on the sea surface could experience direct physical and physiological effects including skin irritation; chemical burns of skin, eyes, and mucous membranes; and inhalation of toxic fumes. Due to the limited areal extent and short duration of water quality impacts from a

### small fuel spill, secondary impacts due to ingestion of oil via contaminated prey or reductions in

prey abundance are unlikely. Due to the low densities of birds in open ocean areas, the small area affected, and the brief duration of the surface slick, no significant impacts on pelagic birds would be expected.



### Impacts of a Large Oil Spill

Potential spill impacts on marine and pelagic birds are discussed in recent EISs (MMS, 2007b, 2008). For this Supplemental EP , there are no unique site-specific issues with respect to spill impacts on these animals.

Pelagic seabirds could be exposed to oil from a spill at the project area. Hess and Ribic (2000) reported that terns, storm-petrels, shearwaters, and jaegers were the most frequently sighted seabirds in the deepwater Gulf of Mexico (>200 m). Powers (1987) indicates that seabird densities over the open ocean typically are <10 birds/km 2 

### . The number of pelagic birds that could be affected in open, offshore waters would depend on the extent and persistence of the
oil slick.

The recent Macondo spill provides relevant information about the species of pelagic birds that may be affected in the event of a large oil spill. Birds that have been treated for oiling include several pelagic species such as the Northern Gannet, Magnificent Frigatebird, and Masked Booby (International Bird Rescue Research Center, 2010). The Northern Gannet is among the species with the largest numbers of birds affected by the spill.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shel l’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on marine and pelagic birds are expected.



### C.4.2 Shorebirds and Coastal Nesting Birds

Threatened and endangered bird species (Piping Plover and Whooping Crane) have been discussed previously in Section C.3 . Various species of non-endangered birds are also found along the northern Gulf Coast, including diving birds, shorebirds, marsh birds, wading birds, and waterfowl. Gulf Coast marshes and beaches also provide important feeding grounds and nesting habitats. Species that breed on beaches, flats, dunes, bars, barrier islands, and similar habitats include the Sandwich Tern, Wilson’s Plover, Black Skimmer, Forster’s Tern, Gull -Billed Tern, Laughing Gull, Least Tern, and Royal Tern (USFWS, 2010b). Ad ditional 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 Brown Pelicans lives in the northern Gulf Coast, generally nesting on protected

islands (USFWS, 2010b).

The Bald Eagle ( Haliaeetus leucocephalus ) was delisted from its threatened status in the
continental United States on 28 June 2007. The Bald Eagle is a terrestrial raptor widely distributed across the southern U.S., including coastal habitats along the Gulf of Mexico. The Gulf Coast is inhabited by both wintering migrant and resident Bald Eagles (Johnsgard, 1990; Ehrlich et al., 1992).

IPFs potentially affecting shorebirds and coastal nesting birds include support vessel and helicopter traffic and a large oil spill. A small fuel spill in the lease area would be unlikely to affect shorebirds or coastal nesting birds, as the lease area is 178 miles (286 km) from the nearest shoreline. As explained in Section A.9.2 , a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up. Compliance with NTL 2007 -G03 will minimize the potential for marine debris-related impacts on shorebird s.



### Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters will transit coastal areas near Port Fourchon and Amelia

, Louisiana, where shorebirds and coastal nesting birds may be found. These activities could periodically disturb individuals or groups of birds within sensitive coastal habitats (e.g., wetlands that may support feeding, resting, or breeding birds).

Vessel traffic may disturb some foraging and resting birds. Flushing distances vary among species and individuals (Rodgers and Schwikert, 2002). The disturbances will be limited to flushing birds away from vessel pathways; known distances are from 65 to 160 ft (20 to 49 m) for personal watercraft and 75 to 190 ft (23 to 58 m) for outboard-powered boats (Rodgers and Schwikert, 2002). Flushing distances may be similar or less for the support vessels to be used for Shell’s project, and some species such as gulls are attracted to boats. Su pport 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 3 predict that shorelines of Texas and Louisiana that include habitat for shorebirds and coastal nesting birds could be affected within 30 days.

Data from the recent Macondo spill provides additional information about the species of coastal birds that may be affected in the event that a large oil spill reached coastal habitats; this information supplements the analysis presented in the lease sale EIS (MMS, 2007b). According to USFWS (2010d) and based on the latest reports, about 5,000 dead birds had been collected since the spill began, and about 1,900 of the dead animals were visibly oiled. In addition, more than 2,000 oiled birds have been collected alive and about 1,200 released (NMFS, 2010b). According to the International Bird Rescue Research Center (2010), bird species that were treated for oiling following the Macondo spill include the following:

 Brown Pelican

 White Pelican

 Masked Booby

 Magnificent Frigatebird

 Laughing Gull

 Herring Gull

 Northern Gannet

 Black Crowned Night Heron

 Tri-colored Heron

 Green Heron

 Cattle Egret

 Sno wy Egret

 Reddish Egret

 Least Bittern

 Common Tern

 Royal Tern

 Caspian Tern  Sandwich Tern

 Forster’s Tern

 Black Tern

 Gull-billed Tern

 Least Tern

 Black Skimmer

 Black Oystercatcher

 White Ibis

 Roseate Spoonbill

 Willet

 Sanderling

 Dunlin

 Semipalmated Sandpiper

 Kill deer

 King Rail

 Clapper Rail

 Virginia Rail

According to the USFWS (2010d), species with the largest numbers of dead, oiled birds were Laughing Gull, Northern Gannet, Brown Pelican, Royal Tern, Black Skimmer, Least Tern, unidentified Gull, and unidentified Tern. There are no reports of Bald Eagle oiling.

Coastal birds can be exposed to oil as they float on the water’s surface, dive during foraging, or wade in oiled coastal waters. Oiled birds can lose the ability to fly, dive for food, or float on the water, which could lead to drowning (USFWS, 2010e). Oil interferes with the water repellency of feathers and can cause hypothermia under certain conditions. As birds groom themselves, they can ingest and inhale the oil on their bodies. Scavengers such as Bald Eagles and gulls can be exposed to oil by feeding on carcasses of contaminated fish and wildlife. While ingestion can kill animals immediately, more often it results in lung, liver, and kidney damage, which can lead to death. Bird eggs may be damaged if an oiled adult sits on the nest or if oil covers the eggs.

As noted above, the Brown Pelican was recently removed from the endangered species list. More than 300 dead Brown Pelicans were collected in the Gulf following the Macondo spill, (USFWS, 2010d). These data indicate that the Brown Pelican may be particularly at risk of oiling

### in the event of a large spill reaching coastal waters. Threats to the Brown Pelican include direct

contact with oil, disturbance by cleanup activities, and long-term habitat contamination.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlike ly event of a spill, implementation of Shell’s OSRP will

mi tigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on shorebirds and coastal nesting birds are expected.



## C.5 Fisheries Resources

C.5.1 Pelagic Communities and Ichthyoplankton

Biggs and Ressler (2000) reviewed the biology of pelagic communities in the deepwater environment of the northern Gulf of Mexico. The biological oceanography of the region is
do minated by the influence of the Loop Current, whose surface waters are among the most oligotrophic in the world’s oc eans. 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).

Mo st 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 ( Supplemental EP Table 7a ). Section 316(b) of the Clean Water Act requires NPDES permits to ensure that the location, design, construction, and capacity of cooling water intake structures reflect the best technology available to minimize adverse environmental impact from impingement and entrainment of aquatic organisms. Construction of the rig planned for use in this Supplemental EP, the Noble Danny Atkins , started prior to 17 July 2006, and therefore is not subject to the cooling water intake permit requirements of NPDES Permit GMG 290000. If a different rig is selected, it will comply with all applicable NPDES requirements. The design and operational features of the rig combined with the geographical area of operation suggest impingement and entrainment impacts will be below a level of concern.



### Impacts of a Small Fuel Spill

Potential spill impacts on fisheries resources are discussed in recent EISs (MMS, 2007b, 2008). For this Supplemental EP , there are no unique site-specific issues with respect to spill impacts.

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the potential for impacts on pelagic communities, including ichthyoplankton. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the concentrations of petroleum hydrocarbons and their degradation products. The extent and persistence of impacts would depend on the meteorological and oceanographic conditions at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from

1.2 to 12 acres (0.5 to 5 ha), depending on sea state and weather conditions.

A small fuel spill could have localized impacts on phytoplankton, zooplankton, ichthyoplankton, and nekton. Due to the limited areal extent and short duration of water quality impacts, a small fuel spill would be unlikely to produce detectable impacts on pelagic communities.

### Impacts of a Large Oil Spill

A large oil spill could affect water column biota including phytoplankton, zooplankton, ichthyoplankton, and nekton. A large spill that persisted for weeks or months would be more likely to affect these communities. While adult and juvenile fishes may actively avoid a large spill, planktonic eggs and larvae would be unable to avoid contact. Eggs and larvae of fishes in the upper layers of the water column are especially vulnerable to oiling; certain toxic fractions of spilled oil may be lethal to these life stages. Impacts would be potentially greater if local scale currents retained planktonic larval assemblages (and the floating oil slick) within the same

water mass.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will

mi tigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on pelagic communities and ichthyoplankton are expected.



### C.5.2 Essential Fish Habitat

Essential Fish Habitat (EFH) is defined as those waters and substrate necessary to fish for spawning, breeding, feeding, and growth to maturity. Under the Magnuson-Stevens Fishery Conservation and Management Act, as amended, Federal agencies are required to consult on activities that may adversely affect EFH designated in Fishery Management Plans developed by the regional Fishery Management Councils.

The Gulf of Mexico Fishery Management Council (GMFMC) has prepared Fishery Management Plans for corals and coral reefs, shrimps, stone crab, spiny lobster, reef fishes, coastal migratory pelagic fishes, and red drum. In 2005, the EFH for these managed species was redefined in Generic Amendment No. 3 to the various Fishery Management Plans (GMFMC, 2005). The EFH for most of these GMFMC-managed species is on the continental shelf in waters shallower than 600 ft ( 183 m). The shelf edge is the outer boundary for coastal migratory pelagic fishes, reef fishes, and shrimps. EFH for corals and coral reefs includes some shelf-edge topographic features on the Texas-Louisiana OCS, the nearest of which is Ewing Bank, located 107 miles (172 km) north of the lease area.

Highly migratory pelagic fishes, which occur as transients in the lease area, are the only remaining group for which EFH has been identified in the deepwater Gulf of Mexico. Species in this group, including tunas, swordfishes, billfishes, and sharks, are managed by NMFS. Highly migratory species with EFH at or near the lease area include the following (NMFS, 2009):

 Atlantic bigeye tuna (adults)

 Atlantic bluefin tuna (spawn ing

, eggs, larvae, adults)

 Atlantic skipjack tuna (spawn ing

, adults)

 Atlantic yellowfin tuna (all)

 Albacore tuna (adults)

 Atlantic swordfish (larvae, juveniles, adults)  Blue marlin (juveniles, adults)

 White marlin (juveniles, adults)

 Longbill spearfish (adults)

 Oceanic whitetip shark (all)

 Longfin mako shark (all)

 Common thresher shark (all)

### Recent research indicates the central and western Gulf of Mexico may be important spawning

habitat for Atlantic bluefin tuna, and NMFS (2009) has designated a Habitat Area of Particular Concern (HAPC) for this species. The HAPC covers much of the deepwater Gulf of Mexico, including the lease area ( Figure 3 ). The areal extent of the HAPC is approximately 300,000 km 2 

### (15,000 mi 2 

### ). The prevailing assumption is that Atlantic bluefin tuna follow an annual cycle of foraging in June through March off the eastern United States and Canadian coasts, followed by migration to the Gulf of Mexico to spawn in April, May, and June (NMFS, 2009).

Other HAPCs have been identified in the Gulf of Mexico by the GMFMC (2005). These include the Florida Middle Grounds, Madison-Swanson Marine Reserve, Tortugas North and South Ecological Reserves, Pulley Ridge, and several individual reefs and banks of the northwestern Gulf of Mexico ( Figure 3 ). The nearest of these is Jakkula Bank, located 114 miles (183 km)
north-northwest of the lease area.

Routine IPFs potentially affecting EFH and fisheries resources include drilling rig presence

, noise, and lights ; effluent discharges; and water intakes. In addition, two types of accidents

– a small fuel spill and a large oil spill

– may impact EFH and fisheries resources.



### Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as an FAD. In oceanic waters, the FAD effect would be most pronounced for epipelagic fishes such as tunas, dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting surface structures (Holland et al., 1990; Higashi, 1994; Relini et al., 1994). This FAD effect would possibly enhance feeding of epipelagic predators by attracting and concentrating smaller fish species. Because the drilling rig is a single, temporary structure, any impacts on EFH for highly migratory pelagic fishes are considered minor.



### Impacts of Effluent Discharges

Other effluent discharges affecting EFH by diminishing ambient water quality include drilling muds and cuttings, treated sanitary and domestic wastes, deck drainage, and miscellaneous discharges such as desalination unit brine and uncontaminated cooling water, fire water, and ballast water. Impacts on water quality have been discussed previously. No significant impacts on EFH for highly migratory pelagic fishes are expected from these discharges.



### Impacts of Water Intakes

As noted previously, cooling water intake will cause entrainment and impingement of plankton, including fish eggs and larvae (ichthyoplankton). Due to the limited scope, timing, and geographic extent of drilling activities, any short-term impacts on EFH for highly migratory pelagic fishes are not expected to be biologically significant.



### Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine operations including fuel tr ansfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the potential for impacts on EFH. Supplemental EP Sections 2j
and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.

### Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008). For this

Supplemental EP , there are no unique site-specific issues with respect to spill impacts.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the concentrations of petroleum hydrocarbons and their degradation products. The extent and persistence of impacts would depend on the meteorological and oceanographic conditions at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from

1.2 to 12 acres (0.5 to 5 ha), depending on sea state and weather conditions.

A small fuel spill could have localized impacts on EFH for highly migratory pelagic fishes, including tunas, swordfishes, billfishes, and sharks. These species occur as transients in the lease area. A spill would also produce short-term impact on water quality in the HAPC for spawning Atlantic bluefin tuna, which covers much of the deepwater Gulf of Mexico. The affected area would represent a negligible portion of the HAPC, which covers 297,312 km 2 

### (114,793 mi 2 

### ) of the Gulf of Mexico.

A small fuel spill would not affect EFH for corals and coral reefs; the nearest coral EFH is Ewing Bank, located 107 miles (172 km) north of the lease area. A small fuel spill would float and dissipate on the sea surface and would not contact these features.



### Impacts of a Large Oil Spill

Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008). For this Supplemental EP , there are no unique site-specific issues with respect to EFH.

An oil spill in offshore waters would temporarily increase hydrocarbon concentrations on the water surface and potentially the subsurface as well. Given the extent of EFH designations in
th e Gulf of Mexico (GMFMC, 2005; NMFS, 2009), some impact on EFH would be unavoidable.

A large spill could affect the EFH for many managed species including shrimps, stone crab, spiny lobster, corals and coral reefs, reef fishes, coastal migratory pelagic fishes, and red drum. It would result in adverse impacts on water quality and water column biota including phytoplankton, zooplankton, ichthyoplankton, and nekton. In coastal waters, sediments could be contaminated and result in persistent degradation of the seafloor habitat for managed demersal fish and shellfish species.

The lease area is within the HAPC for spawning Atlantic bluefin tuna (NMFS, 2009). A large spill could temporarily degrade the HAPC due to increased hydrocarbon concentrations in the water column, with the potential for lethal or sublethal impacts on spawning tuna and their offspring. Potential impacts would depend in part on the timing of a spill, as this species migrates to the Gulf of Mexico to spawn in April, May, and June (NMFS, 2009).

The pinnacle trend area, located 236 miles (380 km) north of the lease area, is designated as EFH under the corals and coral reefs management plan. An accidental spill would be unlikely to affect this area. A surface slick would not reach these features. Although there are reports of subsurface plumes resulting from the use of subsea dispersants during the Macondo spill, the distance and difference in water depth are factors that would make an impact unlikely.

### Near-bottom currents in the region are expected to flow along the isobaths (Nowlin et al., 2001)

and typically would not carry a plume up onto the continental shelf edge.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an
event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will

mi tigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on EFH are expected.



## C.6 Archaeological Resources

C.6.1 Shipwreck Sites

WR 508 is not on the list of leases with high potential for historic shipwrecks. An Archaeological Assessment using data collected in 2009 detected 962 unidentified sidescan sonar targets, several anchor chain scars, piston cores, and previously drilled wells within the survey area.

There were 961 sonar contacts deemed to be not archaeologically significant. The remaining contact was larger than the others and irregular in shape, indicating that it might be made up of smaller debris targets. A 1,000-ft (300-m) avoidance zone will be observed around this contact because it is larger than other contacts and could not be reliably identified.

No historic shipwreck sites occur in the lease area (see Supplemental EP Section 6 ). A small fuel spill would not affect shipwrecks in adjoining blocks because the oil would float and dissipate on
the sea surface. The impact of a large oil spill that could contact shipwrecks in other areas is
considered below a level of concern.



### Impacts of a Large Oil Spill

The MMS (2007b) estimated that a severe subsurface blowout could resuspend and disperse
sediments within a 984 -ft ( 300 -m) radius. Because there are no historic shipwrecks in the lease area, a large oil spill would not result in any impact on archaeological resources.

A spill entering shallow coastal waters could conceivably contaminate an undiscovered shipwreck site. The OSRA modeling summarized in Table 3 predicts that Texas and Louisiana shorelines could be contacted by a spill within 30 days. Also as noted by MMS (2007b), should an oil spill contact a coastal historic site, such as a fort or a lighthouse, the major impact would be a temporary, reversible visual impact from oil contact and contamination of the site and its

environment.

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect archaeological sites beyond the immediate vicinity of the wellhead (i.e., due to physical impacts of a blowout) because the oil would rise quickly to the sea surface directly over the spill location. However, during the Macondo spill, subsurface plumes were reported at a water depth of about 3,600 ft (1,100 m), extending at least 22 miles (35 km) from the wellsite and persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). While the behavior and impacts of subsurface plumes are not well known, a subsurface plume could have the potential to contact shipwreck sites beyond the 984 -ft ( 300 -m) radius estimated by MMS (2007a, 2008), depending

### 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 mini mized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on historic shipwrecks are expected.



### C.6.2 Prehistoric Archaeological Sites

With water depths ranging from 9,554 to 9,578 ft (2,912 to 2,919 m)

, the wellsites are well beyond the 197 -ft ( 60 -m) depth contour used by the BOEMRE as the seaward extent for prehistoric archaeological site potential in the Gulf of Mexico. Because prehistoric archaeological sites are not found in the lease area, the only relevant IPF is a large oil spill that would reach coastal waters within the 197-ft (60- m) depth contour.



### Impacts of a Large Oil Spill

Because prehistoric archaeological sites are not found in the lease area, they would not be affected by the physical effects of a subsea blowout. The MMS (2007b) estimates that a severe subsurface blowout could resuspend and disperse sediments within a 984 -ft (300-m) radius.

Along the northern Gulf Coast, prehistoric sites occur frequently along the barrier islands and mainland coast and along the margins of bays and bayous (MMS, 2007b). The OSRA modeling
summarized in Table 3 predicts that Texas and Louisiana shorelines could be contacted by a spill within 30 days. A spill reaching a prehistoric site along these shorelines could coat fragile artifacts or site features and compromise the potential for radiocarbon dating organic materials in a site (although other dating methods are available and it is possible to decontaminate an oiled sample for radiocarbon dating). Coastal prehistoric sites could also be damaged by spill cleanup operations (e.g., by destroying fragile artifacts and disturbing the provenance of artifacts and site features).

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an
event will be minimiz ed by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on archaeological resources are expected.



## C.7 Coastal Habitats and Protected Areas

Coastal habitats in the northeastern Gulf of Mexico that may be affected by oil and gas activities are described in recent EISs (MMS, 2007b, 2008) and in a literature review by Collard and Way (1997). Sensitive coastal habitats are also tabulated in the OSRP. Coastal habitats inshore of the project area include barrier beaches and dunes, wetlands, and submerged seagrass beds. Generally, most of the northeastern Gulf is fringed by barrier beaches, with wetlands and/or submerged seagrass beds occurring in sheltered areas behind the barrier islands and in

estuaries.

### Due to the distance from shore, there are no IPFs associated with routine activities that are

likely to affect beaches and dunes, wetlands, seagrass beds, coastal wildlife refuges, wilderness areas, or any other managed or protected coastal area. The support bases at Port Fourchon and Amelia are not located in a wildlife refuge or a wilderness area. Potential impacts of support vessel traffic are briefly addressed below.

A small fuel spill in the lease area would be unlikely to affect coastal habitats because the lease area is 178 miles (286 km) from the nearest shoreline. As explained in Section A.9.2 , a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up.



### Impacts of Support Vessel Traffic

For OCS activities in general, support operations, including crew boats and supply boats, may have a minor incremental impact on coastal habitats. Over time with a large number of vessel trips, vessel wakes can erode shorelines along inlets, channels, and harbors. Support operations, including crew boats and supply boats as detailed in Supplemental EP Section 14

, may have a minor incremental impact on coastal habitats or protected areas. Impacts will be minimized by following the speed and wake restrictions in harbors and channels.



### Impacts of a Large Oil Spill

Potential spill impacts on coastal habitats are discussed in recent EISs (MMS, 2007b, 2008). Coastal habitats inshore of the project area include barrier beaches and dunes, wetlands, and submerged seagrass beds. For this Supplemental EP , there are no unique site-specific issues with respect to coastal habitats.

The OSRA results summarized in Table 3 predict that shorelines of Texas and Louisiana could be affected within 30 days. Plaquemines and Cameron Parish, Louisiana and Galveston County,
Texas, ha ve the highest probability of contact for the 30 -day intervals ( 2% ). After 30 days, 8 counties or parishes may be contacted from Matagorda, Texas, to Plaquemines, Louisiana.

The shorelines within the geographic range predicted by the OSRA modeling include extensive barrier beaches and wetlands, with submerged seagrass beds occurring in sheltered areas behind the barrier islands and in estuaries. NWRs and other protected areas along the coast are discussed in the lease sale EIS (MMS, 2007b) and Shell’s OSRP. Coastal wildlife refuges, wilderness areas, and state and national parks within the geographic range of the potential shoreline contacts after 30 days include the following:

 Aransas NWR

 San Bernard NWR

 Galveston Island State Park

 Brazoria NWR

 Mad Island NWR

 Big Boggy NWR

 Apffel Park

 Peach Point WMA

 Sea Rim SP

 Seawolf Park

 Old Fort Travis Park  Atkinson Island WMA

 Ft. Anahuac Park

 Anahuac NWR

 McFaddin NWR

 J.D. Murphree WMA

 Texas Point NWR

 Sabine NWR

 Cameron Prairie NWR

 LaCassine NWR

 Little Pecan Island Preserve

 Peveto Woods Sanctuary

###  Lower Neches WMA

 Rockefeller State Wildlife Refuge and

Game Preserve

 Paul J. Rainey WMA

 Candy Abshier WMA

 Atchafalaya Delta WMA

 Mandalay NWR

 Isles Dernieres Barrier Islands Refuge

 Pointe Au Chien WMA

 Wisner WMA

 Grand Isle State Park

 Christmas Bay SP

 Christmas Bay Coastal Preserve

 Salvador WMA

 Jean Lafitte National Historical Park
and Preserve

 Delta NWR

 Pass a Loutre WMA

 Breton NWR

 St. Bernard State Park

 Biloxi WMA

 Bayou Sauvage NWR

 Gulf Islands National Seashore

### The OSRA results in Table 3 include only shoreline segments with contact probabilities greater than

0.5% within 30 days; other coastal areas could be affected at lower contact probabilities within

30 days, or from a spill persisting for more than 30 days. Additional NWRs and managed wildlife areas occur along the Gulf Coast. These areas include habitats such as barrier beach and dune systems, wetlands, and submerged seagrass beds that support diverse wildlife, including endangered or threatened species.

The level of impacts from oil spills on coastal habitats depends on many factors, including the oil characteristics, the geographic location of the landfall, and the weather and oceanographic conditions at the time (MMS, 2007b). Oil that makes it to beaches may be either liquid weathered oil, an oil-and-water mousse, or tarballs (MMS, 2007b). Oil is generally deposited on beaches in lines defined by wave action at the time of landfall. Oil that remains on the beach will thicken as its volatile components are lost. Thickened oil may form tarballs or aggregations that incorporate sand, shell, and other materials into its mass. Tar may be buried to varying depths under the sand. On warm days, both exposed and buried tarballs may liquefy and ooze. Oozing may also serve to expand the size of a mass as it incorporates beach materials. Oil on beaches may be cleaned up manually, mechanically, or both. Some oil can remain on the beach at varying depths and may persist for several years as it slowly biodegrades and volatilizes.

Wetlands are highly sensitive to oiling. The MMS (2007b) predicted that for every 50 bbl of oil contacting wetlands, approximately 6.7 acres (2.7 ha) of wetland vegetation will experience dieback. Thirty percent of these damaged wetlands are assumed to recover within 4 years, and 85% within 10years. About 15% of the contacted wetlands are expected to be converted permanently to openwater habitat. The critical concentration of oil is that concentration above which impacts to wetlands will be long-term and recovery will take longer than two growing seasons, and which causes plant mortality and some permanent wetland loss. Critical concentrations of various oils are expected to vary broadly for wetland types and wetland plant species. Louisiana wetlands are assumed to be more sensitive to oil contact than elsewhere in the Gulf because of high cumulative stress (MMS, 2007b). In addition to the direct impacts of oil, cleanup activities in marshes may accelerate rates of erosion and retard recovery rates, which have been reported to require from years to decades following a spill (MMS, 2007b).

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout p revention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on coastal habitats are expected.



## C.8 Socioeconomic and Other Resources

C.8.1 Recreational and Commercial Fishing

The main commercial fishing activity in deep waters of the northern Gulf of Mexico is pelagic longlining for tunas, swordfishes, and other billfishes (Continental Shelf Associates, Inc., 2002). Pelagic longlining has occurred historically in the project area, primarily during spring and summer. In August 2000, the Federal government closed two areas in the northeastern Gulf of Mexico to longline fishing (65 Federal Register 47214, 1 August 2000). The lease is outside of the closure areas.

Longline gear consists of monofilament line deployed from a moving vessel and generally allowed to drift for 4 to 5 hours (Continental Shelf Associates, Inc., 2002). As the mainline is put out, baited leaders and buoys are clipped in place at regular intervals. It takes 8 to 10 hours to deploy a longline and about the same time to retrieve it. Longlines are often set near oceanographic features such as fronts or downwellings, with the aid of sophisticated on-board temperature sensors, depth finders, and positioning equipment. Vessels are 10 to 30 m long, and their trips last from about 1 to 3 weeks. The main homeports for longlining vessels are in Louisiana (Dulac and Venice) and Florida (Destin, Madeira Beach, and Panama City).

### It is unlikely that any commercial fishing activity other than longlining occurs at or near the project

area. Benthic species targeted by commercial fishers occur on the upper continental slope, well inshore of the project area. Royal red shrimp are caught by trawlers in water depths of about 820 to 1,804 ft (250 to 550 m). Tilefish are caught by bottom longlining in water depths from about 540 to 1,476 ft (165 to 450 m) (Continental Shelf Associates, Inc., 2002). The proposed project is in 9,414 ft (2,900 m) of water. No conflict with commercial fishing activity is expected to occur.

Most recreational fishing activity in the region occurs in water depths less than 656 ft ( 200 m) (Continental Shelf Associates, Inc., 1997, 2002). In deeper water, the main attraction to recreational fishers would be petroleum platforms offshore Texas and Louisiana.

The only routine IPF potentially affecting fisheries is drilling rig presence (including noise and lights). Two potential accidents are also addressed below

– a small fuel spill and a large oil spill.



### Impacts of Drilling Rig Presence

There is a slight possibility of pelagic longlines becoming entangled in the drilling rig. For example, in January 1999, a portion of a pelagic longline snagged on the acoustic Doppler current profiler of a drillship working in the Gulf of Mexico (Continental Shelf Associates, Inc., 2002). The line was removed without incident. Generally, longline fishers use radar and are aware of offshore structures and ships when placing their sets. Therefore, little or no impact on pelagic longlining is expected.

No adverse impacts on fishing activities are anticipated. Other factors such as effluent discharges are likely to have negligible impacts on commercial or recreational fisheries due to rapid dispersion, the small area of ocean affected, and the intermittent nature of the discharges.



### Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.

Pelagic longlining activities in the lease area, if any, could be interrupted in the event of a small fuel spill. The area of the sea surface with diesel fuel on it would range from 1.2 to 12 ac res (0.5 to 5 ha), depending on sea state and weather conditions. Fishing activities could be interrupted due to the

ac tivities of response vessels operating in the lease area. A small fuel spill would not affect coastal water quality because the spill would not be expected to make landfall or reach coastal waters prior to breaking up (see Section A.9.2 ).



### Impacts of a Large Oil Spill

Potential spill impacts on fishing activities are discussed in recent EISs (MMS, 2007b, 2008). For this Supplemental EP , there are no unique site-specific issues with respect to this activity.

Pelagic longlining activities in the lease area and other fishing activities in the northern Gulf of Mexico could be interrupted in the event of a large oil spill. A spill may or may not result in fishery closures, depending on the duration of the spill, the oceanographic and meteorological conditions at the time, and the effectiveness of spill response measures. The recent Macondo spill provides information about the potential extent of fishery closures in the event of a large oil spill in the Gulf of Mexico (NMFS, 2010d). At its peak on 12 July 2010, closures encompassed 217,821 km 2 

### (84,101 mi 2 

### ), or 34.8% of the U.S. Exclusive Economic Zone (EEZ) in the Gulf of Mexico.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on fishing activities are expected.

### 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, implemen tation of Shell’s OSRP will mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures.

A small fuel spill would not have any impacts on public health and safety because it would affect only a small area of the open ocean 178 miles (286 km) from the nearest shoreline and nearly all of the diesel fuel would evaporate or disperse naturally within 24 hours. Response crews would be equipped with appropriate safety equipment to avoid injury and health effects. A small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up (see

Section A.9.2 ).



### Impacts of a Large Oil Spill

In the event of a large spill from a blowout, the main safety and health concerns are those of the offshore personnel involved in the incident and those responding to the spill. The proposed activities will be covered by the OSRP, and, in addition, the drilling rig maintains a Shipboard Oil Pollution Emergency Plan as required under MARPOL 73/78.

Depending on the spill rate and duration, the physical/chemical characteristics of the oil, the meteorological and oceanographic conditions at the time, and the effectiveness of spill response measures, the public could be exposed to oil on the water and along the shoreline, through skin contact or inhalation of VOCs. Crude oil is a highly flammable material, and any smoke or vapors from a crude oil fire can cause irritation. Exposure to large quantities of crude oil may pose a health
hazard.

Data from the recent Macondo spill provide relevant information about the types of health issues that may occur in the event of a large oil spill (Centers for Disease Control and Prevention, 2010a). Wildlife cleaning and rehabilitation workers have reported concerns including scrapes and cuts, itchy or red skin or rash, and symptoms of headache or feeling faint, dizzy, or fatigued. Hand, shoulder, or back pain was also reported by some wildlife-cleaning workers. Personnel working on offshore vessels or providing direct oversight to offshore vessels, including USCG personnel, civilian contractors, and other responders who were exposed to oil and dispersants, had 7 to 12 times higher incidence of upper respiratory symptoms and cough than those not exposed (Centers for Disease Control and Prevention, 2010b). Another potential occupational hazard for spill response workers is exposure to seasonal temperature extremes resulting in heat stress in the summer and hypothermia in the winter. Initial symptoms from cleanup workers who sought medical care in Louisiana were typical of acute exposure to hydrocarbons or H 2 

### S such as headaches, dizziness, nausea, vomiting, cough, respiratory distress, and chest pain (Solomon and Janssen, 2010). Health effects reported from previous oil spills, such as the Exxon Valdez in 1989, were primarily acute injuries consisting of headaches, throat irritation, and sore or itchy eyes, but respiratory problems and dermatitis along with chronic airway disease have also been reported (Solomon and Janssen, 2010).

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unl ikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on public health and safety are expected.

### 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 Sh ell’s preventative measures during routine operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.

A small fuel spill that is dissipated within a few days would have little or no economic impact, as the spill response would use existing facilities, resources, and personnel.



### Impacts of a Large Oil Spill

Potential socioeconomic impacts of an oil spill are discussed in recent EISs (MMS, 2007b, 2008). For this Supplemental EP , there are no unique site-specific issues with respect to employment and coastal infrastructure. A large spill could cause economic impacts in several ways: it could result in extensive fishery closures that put fishermen out of work; it could result in temporary employment as part of the response effort; it could result in adverse publicity that affects employment in coastal recreation and tourism industries; and it could result in another suspension of OCS drilling activities, including service and support operations that are an important part of local economies.

The lease area is 178 miles (286 km) from the nearest shoreline. Based on OSRA modeling as
summarized in Table 3 , Texas and Louisiana coastal areas are the most likely to be contacted by a spill.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shel l’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on employment and infrastructure are expected.



### C.8.4 Recreation and Tourism

There are no known recreational uses of the lease area. Recreational resources and tourism in coastal areas would not be affected by any routine activities due to the distance from shore. Compliance with NTL 2007-G03 will minimize the chance of trash or debris being lost overboard from the drilling rig and subsequently washing up on beaches.



### Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine operations including fuel transfer. In the unlikel y event of a spill, implementation of Shell’s OSRP will mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Given the open ocean location of the lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.

### A small fuel spill in the lease area would be unlikely to affect recreation and tourism. There are no

known recreational or tourism activities occurring in the lease area, and as explained in

Section A.9.2 , a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up.



### Impacts of a Large Oil Spill

Potential impacts of an oil spill on recreation and tourism are discussed in recent EISs (MMS, 2007b, 2008) . For this Supplemental EP , there are no unique site-specific issues with respect to these impacts.

Impacts on recreation and tourism would vary depending on the duration of the spill and its fate including the effectiveness of response measures. A large spill that reached coastal waters and shorelines could adversely affect recreation and tourism by contaminating beaches and wetlands, resulting in negative publicity that encourages people to stay away. Based on OSRA modeling as
summarized in Table 3 , areas most likely to be contacted by a spill are Plaquemines and Cameron Parish, Louisiana, and Galveston County, Texas. The shorelines along Galveston, Texas

, include popular beaches and recreational sites along the coast.

In addition to the analysis presented by MMS (2007b, 2008), recent and ongoing studies have explored the economic impacts of the Macondo spill including tourism and “brand” damage (IEM, 2010; Oxford Economics, 2010). The U.S. Travel Association has estimated the economic impact of the Macondo spill on tourism across the Gulf Coast over a 3-year period at $22.7 billion (Oxford Economics, 2010). There are ongoing efforts to accelerate recovery by informing public perceptions; creating travel incentives; and providing access to capital, low interest loans, and tax incentives for affected businesses (U.S. Travel Association, 2010).

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout pre vention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on recreation and tourism are expected.



### C.8.5 Land Use

Land use along the northern Gulf Coast is discussed in recent lease sale EISs (MMS, 2007b, 2008). There are no routine IPFs potentially affecting land use. The project will use existing onshore support facilities in Louisiana. The land use at the existing shorebase sites is industrial. The project will not involve any new construction or changes to existing land use and, therefore, will not have any impacts. Levels of boat and helicopter traffic, as well as demand for goods and services including scarce coastal resources, will represent a small fraction of the level of activity occurring at the
shorebases.

A large oil spill is the only relevant accident IPF. A small fuel spill would not have any impacts on land use, as the response would be staged out of existing shorebases and facilities.



### Impacts of a Large Oil Spill

The initial response for a large oil spill would be staged out of existing facilities, with no effect on land use. A large spill could have limited temporary impacts on land use along the coast if additional staging areas were needed. For example, during the Macondo spill, temporary staging areas were established in Louisiana, Mississippi, Alabama, and Florida for spill response and cleanup efforts. In the event of a large spill in the lease area, similar temporary staging areas could be needed. These areas would eventually return to their original use as the response is demobilized.

A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Sh ell’s OSRP will

### mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill

response measures. Therefore, no significant spill impacts on land use are expected.



### C.8.6 Other Marine Uses

The lease area is not located within any USCG-designated fairway or shipping lane. WR 508 is not in a designated Military Warning Area. Shell will comply with BOEMRE requirements and lease stipulations to avoid impacts on uses of the area by military vessels and aircraft.

There are no IPFs from routine project activities that are likely to affect shipping or other marine uses. A large oil spill is the only relevant accident IPF. A small fuel spill would not have any impacts on other marine uses, as the spill and response activities would be mainly within the lease area and
the duration would be brief.



### Impacts of a Large Oil Spill

An accidental spill would be unlikely to significantly affect shipping or other marine uses. The block is not located within any USCG-designated fairway or shipping lane. In the event of a large spill requiring numerous response vessels, coordination would be required to manage the vessel traffic for safe operations. Shell will comply with BOEMRE requirements and lease stipulations to avoid impacts on uses of the area by military vessels and aircraft.

In the event of a large spill requiring numerous vessels in the area, coordination would be required to ensure that no anchoring or seafloor-disturbing activities occur near the existing pipelines and
flowlines. A blowout resulting in a large oil spill is an extremely rare event, and the probability of such an event will be minimized by Shell’s well control and blowout prevention measures as detailed

in Supplemental EP Section 2j . In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response measures. Therefore, no significant spill impacts on other marine uses are expected.



## C.9 Cumulative Impacts

For purpo ses 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- Feder al) or person undertakes such other actions” (40 CFR 1508.7). Any single activity or action may have a negligible impact(s) by itself, but when combined with impacts from other activities in the same area and/or time period, substantial impacts may result.

Prior Studies . WR 507 and 508 were acquired in Lease Sale No. 157 on 24 April 1996. Prior to the lease sale, MMS prepared a multi-sale EIS in which it analyzed the environmental impact of activities that might occur in the multi-lease-sale area. The MMS also recently analyzed the cumulative impacts of OCS development activities similar to those planned in this Supplemental EP in several documents. The level and types of activities planned in Shell's Supplemental EP are within the range
of activities described and evaluated in the Final EIS for Gulf of Mexico OCS Oil and Gas Lease Sales

2007 -2012: Western Planning Area Sales 204, 207, 210, 215, and 218, and Central Planning Area Sales 205, 206, 208, 213, 216, and 222 (MMS, 2007b), as updated by a 2008 Final Supplemental EIS for Gulf of Mexico OCS Oil and Gas Lease Sales 2009-2012: Central Planning Area Sales 208, 213, 216, and 222 and Western Planning Area Sales 210, 215, and 218 (MMS, 2008). Past, present, and reasonably
foreseeable activities were identified in the cumulative effects scenario. These documents are incorporated by reference.

Description of Activities Reasonably Expected to Occur in the Vicinity of Project Area . Other exploration and development activities (e.g., the Chinook Field in WR 469 and 452) are occurring in the vicinity of lease block WR 507 and 508.

Cumulative Impacts of Activities in the Supplemental EP . The MMS (2007b) multi-lease-sale EIS included a lengthy discussion of cumulative impacts, which analyzed the environmental and

### 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 (s ee MMS, 2007b, page 4-301). The EIS considered exploration, delineation, and development wells; platform installation; service-vessel trips; and oil spills. The EIS examined the potential cumulative effects on each specific resource for the entire Gulf
of Mexico.

The level and type of activity proposed in Shell’s Supplemental EP are within the range of activities described and evaluated in the recent multi-lease-sale EISs. This EIA incorporates and builds on these analyses by examining the potential impacts on physical, biological, and socioeconomic resources from the work planned in this Supplemental EP, in conjunction with the other reasonably foreseeable activities expected to occur in the Gulf of Mexico, as well as the known impacts from the Macondo

s pill in Mississippi Canyon 252 . While another large oil spill could have significant impacts, the numerous new safety measures implemented by the BOEMRE and further mitigation and safety measures proposed by Shell in its Supplemental EP result in a drilling program that reduces the likelihood of another large spill and improves the effectiveness of any response in the extremely unlikely event that another large spill occurs. Thus, for all impacts, the incremental contribution of Shell’s proposed actions t o the cumulative impacts analysis in these prior analyses is not significant.



### C.9.1 Cumulative Impacts to Physical/Chemical Resources

The work planned in this Supplemental EP is limited in geographic scope and duration, and the impacts on the physical/chemical environment will be correspondingly limited.

Air Quality

. Emissions from pollutants into the atmosphere from activities are not projected to have significant effects on onshore air quality because of the prevailing atmospheric conditions, emissionrates and heights, and resulting pollutant concentrations. As the BOEMRE found in the multi-leasesale EISs, the incremental contribution of activities similar to Shell’s proposed activities to the cumulative impacts is not significant and will not cause or contribute to a violation of any national ambient air quality standard (MMS, 2007b, 2008). In addition, the cumulative contribution tovisibility impairment is also very small (MMS, 2007b, 2008). Since the BOEMRE completed the multilease-sale EISs, th e USEPA has adopted a new short-term NAAQS for NO 2 

### and SO 2 

### . The standard has not yet been implemented in the Gulf of Mexico, but given the levels of expected emissions and the distance of the project from shore, emissions from Shell's Supplemental EP are not likely to contribute to violations of any NAAQS onshore.

Climate Change . Carbon dioxide (CO 2 

### ) and CH 4 

### 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 CO 2 

### emissions from all OCS activities in the 2007- 2012 leasing program are about 0.08% to 0.016% of the global CO 2 

### emissions from fossil fuel combustion. Greenhouse gas emissions may contribute to climate change, with important effects on temperature, rainfall, frequency of severe weather, ocean acidification, and sea level rise (Intergovernmental Panel on Climate Change, 2007). In the Gulf of Mexico, sea level rise is an important issue due to the ongoing losses in coastal wetlands, particularly in coastal Louisiana. Greenhouse gas emissions from the Supplemental EP represent a negligible contribution to the total greenhouse gas emissions from reasonably foreseeable activities in the Gulf of Mexico area and would not significantly alter any of the climate change impacts evaluated in the previous EISs. Globally, Shell is working to reduce greenhouse gas emissions by increasing the efficiency of its operations, establishing a substantial capability in CO 2 

### 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 tha n the comparable 1990 level (Shell, 2011). Shell’s ongoing efforts to reduce greenhouse gas emissions globally should offset any incremental contribution from the Supplemental EP.

Water Quality . Shell’s project will have some minor water q uality 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 sho rt -term health problems. The air monitoring conducted to date has not found any pollutants at levels expected to cause long-term harm (USEPA, 2010). Satellite imagery indicates that the surface slick from the Macondo spill did not reach the lease area (ESRI, 2010). However, based on the information currently available, there is no reason to expect any change in air quality conditions or cumulative impacts from those predicted in the multi-lease-sale EISs.

The Macondo spill also resulted in water quality impacts. In addition to the oil slick on the sea surface, plumes of submerged oil droplets were produced when subsea dispersants were applied at the wellhead (Camilli et al., 2010; Hazen et al., 2010; Joint Analysis Group, 2010a,b,c). Satellite imagery indicates that the surface slick from the Macondo spill did not reach the lease area (ESRI, 2010), and it is unlikely that subsurface plumes could have affected water quality in or near the lease

area. OSAT (2010) reported that, after August 2010, waters and sediments in the deepwater Gulf of Mexico beyond 1.8 miles (3 km) from the Macondo wellsite were below USEPA acute and chronic benchmarks for PAHs and were not hypoxic. These observations indicate that baseline environmental conditions in the lease area are unlikely to have been significantly altered by the spill. Prior to the incident, water quality in deep, offshore waters was expected to be good, with low levels of contaminants (Kennicutt, 2000). Based on the information currently available, there is no reason to expect any change in water quality conditions or cumulative impacts from those predicted in the
multi -lease-sale EISs.



### C.9.2 Cumulative Impacts to Biological Resources

The work planned in this Supplemental EP is limited in geographic scope and duration, and the impacts on biological resources will be correspondingly limited.

Seafloor Habitats and Biota

. Effects on seafloor habitats and biota from discharges of drilling mud and cuttings are expected to be minor and limited to a small area. There are no areas that may support high-density deepwater benthic communities within 2,000 ft ( 610 m) of the wellsites, in compliance with NTL 2009-G40. Areas that may support high-density deepwater benthic communities will be avoided as required by NTL 2009 -G40. Soft bottom communities are ubiquitous along the northern Gulf of Mexico continental slope, and the extent of benthic impacts during this project is insignificant regionally. As noted in the multi-lease-sale EISs, the incremental contribution s 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

w ould be reduced by Shell’s compliance with all BOEMRE-required mitigation measures including

NTLs 2007 -G03 and 2007-G04. No significant cumulative impacts are expected.

Coastal and Marine Birds . Some birds may be attracted to offshore structures because of the lights and the fish populations that aggregate around these structures. Birds that frequent platforms may be exposed to contaminants including air pollutants and routine discharges, but significant impacts are unlikely due to rapid dispersion. She ll’s c ompliance 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 structures occur in the WR lease block proposed for the exploration activities. The additional effect of the proposed drilling activity would be negligible.

Co astal Habitats . Due to the distance of the wellsites from shore, routine activities are not expected to have any impacts on beaches and dunes, wetlands, seagrass beds, coastal wildlife refuges, wilderness areas, or any other managed or protected coastal area. The support bases at Port Fourchon and Amelia, Louisiana, are not in wildlife refuge or wilderness areas. Support operations, including crew boats and supply boats, may have a minor incremental impact on coastal habitats. Over time with a large number of vessel trips, vessel wakes can erode shorelines along inlets, channels, and harbors. Impacts will be minimized by following the speed and wake restrictions
in harbors and channels.

New Information . The only new, potentially significant information available since preparation of the
multi -lease-sale EISs arises from the Macondo spill. The spill has resulted in impacts on biological resources, including visibly oiled and/or dead birds, marine mammals, and sea turtles, as well as oiling of coastal habitats from approximately the Texas/Louisiana border to the Florida Panhandle. Another large spill could result in significant cumulative impacts to these resources. However, for all
the reasons discussed in the Initial EP, Shell’s NTL 2010 -N06 response, the OSRP, and herein, the likelihood of a catastrophic well control event resulting in significant amounts of oil in the water is extremely remote. Therefore, Shell’s proposed activities are not expected to result in any cumulative impacts to biological resources affected by the Macondo spill, nor should they have any impact on the previously conducted cumulative impact analyses.

Regarding deepwater benthic communities, the multi-lease-sale EISs (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical impacts of a blowout) because the oil would rise quickly to the sea surface directly over the spill location. However, during the Macondo spill, subsurface plumes were reported at a water depth of about 3,600 ft ( 1,100 m), extending at least 22 miles (35 km) from the wellsites and persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). This observation is supported by Kujawinski et al. (2011) in their report that chemical components of subsea dispersants used during the Macondo spill persisted for up to two months and were detected up to 1 86 miles (300 km) from the wellsite at a water depth of 3,280 to 3,937 ft (1,000 to 1,200 m). However, estimated dispersant concentrations in the subsea plume were below levels known to be toxic to marine life. While the behavior and impacts of subsurface plumes are not well known, a subsurface plume could contact the seafloor and affect benthic communities beyond the 984 -ft ( 300

- m) radius estimated by MMS (2007a, 2008), depending on its extent, trajectory, and persistence. This contact could result in smothering and/or toxicity to benthic organisms. The affected area would be recolonized by benthic organisms over a period of months to years (NRC, 2003).



### C.9.3 Cumulative Impacts to Socioeconomic Resources

The work planned in this Supplemental EP is limited in geographic scope and duration, and the impacts on socioeconomic resources will be correspondingly limited.

### Archaeological Resources . WR 508 is not on the list of leases with a high potential for historic

shipwrecks. An archaeological assessment by FGSI (2011) indicated that one of the sonar contacts in the lease area could not be reliable identified and will be avoided by 1,000 ft ( 300 m). Also, the lease area is well beyond the 197-ft ( 60 -m) depth contour used by the BOEMRE as the seaward extent for prehistoric archaeological site potential in the Gulf of Mexico. Therefore, Shell’s operations will have no cumulative impacts on historic shipwrecks or prehistoric archaeological resources.

Socioeconomic Resources . The multi-lease-sale EISs analyzed the cumulative impacts of oil and gas exploration and development in the lease area, in combination with other impact-producing activities, on commercial fishing, recreational fishing, recreational resources, historical and archaeological resources, land use and coastal infrastructure, demographics, and environmental justice (MMS, 2007b, pages 4-359 to 4-378). The BOEMRE also analyzed the economic impact of oil and gas activities on the Gulf States, finding only minor impacts in most of Texas, Mississippi, Alabama, and Florida, more significant impact in parts of Texas, and substantial impact on Louisiana.

Shell’s proposed activities will have negligible cumulative impacts on socioeconomic resources. There are no IPFs associated with routine operations that are expected to affect public health and safety, employment and infrastructure, recreation and tourism, land use, or other marine uses. Due to the distance from shore, it is unlikely that any recreational fishing activity is occurring in the project area, and it is unlikely that any commercial fishing activity other than longlining occurs at or near the project area. The project will have negligible impacts on fishing activities.

New Information . The only new, potentially significant information available since preparation of the
multi -lease-sale EISs arises from the Macondo spill. The spill has resulted in impacts on commercial and recreational fishing, recreation and tourism, employment, and public health and safety. The Macondo spill resulted in extensive fishery closures in the Gulf of Mexico, peaking at 34.8% of the EEZ in the Gulf of Mexico (NMFS, 2010d). The U.S. Travel Association has estimated the economic impact of the Macondo spill on tourism across the Gulf Coast over a 3-year period at $22.7 billion (Oxford Economics, 2010). Reported health impacts (e.g., among spill response and wildlife rehabilitation workers) ranged from cuts and scrapes, to upper respiratory symptoms and heat stress, to acute exposure to hydrocarbons or H 2 

### S (Centers for Disease Control and Prevention, 2010a,b; Solomon and Janssen, 2010). Most of these impacts were temporary in nature, although health exposure of cle an -up workers could have longer-lasting impacts.

However, for all the reasons discussed in the Supplemental EP, Shell’s NTL 2010-N06 response, the OSRP, and herein, the likelihood of a catastrophic well control event resulting in significant amounts of oil in the water is extremely remote. Therefore, Shell’s proposed activities are not expected to result in any cumulative impacts to socioeconomic resources affected by the Macondo spill, nor should they have any impact on the previously conducted cumulative impact analyses.



# D. Environmental Hazards

D.1 Geologic Hazards

The shallow hazards assessment included in this Supplemental EP, based on the shallow hazards report by GEMS (2006) and FGCI (2010), concludes that the wellsites are free of any major geological hazards and are suitable for the proposed activities. There are no fluid expulsion features or faults within 2,000 ft (600 m) of the well proposed locations based on results of a high-resolution geophysical survey consisting of frequency-enhanced 3-D seismic, enhanced surface renderings, AUV surveys, and side scan sonar. There we re piston cores, drilling splays, anchor chain scars, and previously drilled wells in the vicinity of the proposed locations but none we re within 2,000 ft (600m) (FGSI, 2011).

See Supplemental EP Section 6a for supporting geological and geophysical information.

## D.2 Severe Weather

Under most circumstances, weather is not expected to have any effect on the proposed activities. Extreme weather, including high winds, strong currents, and large waves, was considered in the design criteria for the drilling 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
eddi es and intrusions) and large waves were considered in the design criteria for the drilling rig. High waves during a severe storm could disrupt support activities (i.e., vessel and helicopter traffic) and make it necessary to suspend some activities on the drilling rig for safety reasons until the storm or weather event passes.



# E. Alternatives

No formal alternatives were evaluated in this EIA. However, various technical and operational options, including the location of the wellsites and the selection of a drilling unit, were considered by Shell in developing the proposed action. There are no other reasonable alternatives to accomplish the goals of this project.



# F. Mitigation Measures

The proposed action includes numerous mitigation measures required by laws, regulations, and BOEMRE lease stipulations and NTLs. The project will comply with all applicable Federal, State, and local requirements concerning air pollutant emissions, discharges to water, and solid waste disposal. All project activities will be conducted under Shell’s OSRP and will include the measures described in Supplemental EP Section 2j . Additional pollution prevention measures, beyond those required by 30 CFR Part 250, include the following:

Health, safety, and environment (HSE) are the primary topics in pre-tour and pre-job safety meetings. The discussion around no harm to people or environment is a key mindset. All personnel are reminded daily to inspect work areas for safety issues as well as potential pollution issues. All tools that come to and from the rig have their pollution pans inspected and cleaned, and plug installation confirmed prior to leaving the dock and prior to loading on the boat. Preventive maintenance of rig equipment includes visual inspection of hydraulic lines and reservoirs
on a routine scheduled basis. All pollution pans on rig are inspected daily. Containment dikes are installed around all oil containment, drum storage areas, fuel vents, and fuel storage tanks. All used oil and fuel is collected and sent to shore for recycling. Drains on the rig are checked regularly to verify drain plugs are installed. All trash containers are checked and emptied daily, and trash containers are kept covered. Trash is collected in a compactor and shipped to shore for disposal. The rig is involved in a recycling program for cardboard, plastic, paper, glass, and aluminum.

### Fuel hoses are changed on annual basis.

Spill prevention fittings are installed on all liquid take-on hoses. Waste paint thinner is recycled on board with a solvent to further reduce hazards of shipping and
storage. All equipment on board utilizes Envirorite hydraulic fluid as opposed to hydraulic oil. Shell has obtained International Organization for Standardization (ISO) 14001 certification. Shell will use low-sulfur fuel to reduce air pollutant impacts.



# G. Consultation

No persons or agencies were consulted regarding potential impacts associated with the proposed activities during the preparation of this EIA.



# H. Preparers

The EIA was prepared at the direction of Shell Offshore Inc. by its contractor, CSA International, Inc. Contributors included the following:

Sylvia Bellone (Regulatory Specialist, Shell Exploration & Production Co.); Tracy Albert (Regulatory Specialist, Offshore Technical Compliance LLC); Lori Downs (Environmental Team Leader, Shell Exploration & Production Co.); Jeffrey McMenis, (Environmental Engineer, Shell Exploration & Production Co.); Rob Kuehn (Environmental Engineer, Shell Exploration & Production Co.); Martijn Dekker (Development Lead, Stones Development, Shell Exploration & Production Co.); Marc Varner (Subsurface Team Lead, Stones Development, Shell Exploration & Production Co.); Dana McDiffett (Reservoir Engineer, Stones Development, Shell Exploration & Production Co.); Kevin Bradford (Geophysicist, Geo Hazards & Pore Pressure Prediction, Shell Exploration & Production Co.); James Jorgensen (Well Engineer, North America Projects, Shell Exploration & Production Co.); June Mire, Ph.D. (Senior Ecologist and Project Manager, Tetra Tech EM, Inc.); Cindy Chandool, Ph.D. (Senior Scientist, CSA International, Inc.); Carlyle Kalloo (Senior Scientist, CSA International, Inc.); Neal Phillips, Ph.D. (Senior Scientist, CSA International, Inc.); Deborah Fawcett (Project Scientist II, CSA International, Inc.); Stephen Viada (Senior Scientist, CSA International, Inc.); Keith VanGraafeiland (GIS/Remote Sensing Specialist, CSA International, Inc.); and Kim Dunleavy (Technical Editor, CSA International, Inc.).



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Würsig, B., S.K. Lynn, T.A. Jefferson, and K.D. Mullin. 1998. Behaviour of cetaceans in the northern Gulf of Mexico relative to survey ships and aircraft. Aquatic Mammals 24: 41

- 50. Würsig, B., T.A. Jefferson, and D.J. Schmidly. 2000. The Marine Mammals of the Gulf of Mexico. Texas A&M University Press, College Station, TX. 232 pp.SECTION 19 : ADMINISTRATIVE INFORMATION

A. Exempted Information Description (Public Information Copies Only)

The following attachments were excluded from the public information copies of this plan:

Section 1b. OCS Plan Information form

– Bottom hole locations & proposed total depth Section 2j. Blowout Scenario

– confidential information for NTL 2010-N06 calculation Section 3a. Geologic Description Section 3b. Structure Contour Maps Section 3c. Interpreted 2D or 3D seismic line(s) Section 3d. Cross Section(s) Section 3e. Shallow Hazards Report Section 3f . Shallow Hazards Assessment

– confidential data Section 3g. High-Resolution Seismic Lines & Top Hole Progs Sections 3h. & 3i. Stratigraphic Column with Time vs. depth table

B. Bibliography

Geoscience Earth & Marine Services, Inc. (GEMS) prepared a Geologic and Stratigraphic Assessment Report (Number 0306-1151), May 2006

Fugro GeoConsulting, Inc. (FGCI) prepared an Integrated Geophysical and Geotechnical Field Development Planning Study based on the AUV data (Job No. 27.2009-2328), May 2010.

FGSI prepared an AUV Archaeological Assessment Report (Number 2411-1019) covering Walker Ridge blocks 420, 464, 508, and 552, July 2011.

CSA International, Inc. Environmental Impact Analysis, July 20 11

Shell’s Regional OSRP, August 2011