Tolbert, Michael

From: Tolbert, Michael

Sent: Friday, January 28, 2011 10:21 AM

To: 'sylvia.bellone@shell.com'

Cc: Peuler, Elizabeth; Hill, Chiquita; Wetzel, Nick; Saucier, Michael

Subject: Supplemental Exploration Plan S-7445 for Lease OCS-G 7493 (GB 427)

Page 1 of 1

1/28/2011

This email is to notify you that the following Supplemental Exploration Plan received October 28, 2010, amended 

 November 19 and 30, December 3 and 9, 2010, and January 6, 21, and 27, 2011, has been deemed submitted in 

accordance with 30 CFR 250.231(a) and 232(d) as of January 28, 2011:

Control Number - S-7445

Type - Supplemental Exploration Plan

Operator – Shell Offshore Inc.

Lease(s) - OCS-G 7493 (Block 427, Garden Banks Area)

Activities Proposed – Add Wells O, P, and Q

Michael Tolbert 

Petroleum Engineer 

Office of Field Operations, Plans Section

Phone: (504) 736-2867 

email: Michael.Tolbert@boemre.gov 

 
Shell Offshore Inc

P. O. Box 61933

New Orleans, LA 70161-1933

United States of America

Tel +1 504 728 7215

Fax +1 504 728 6747

Email sylvia.bellone@shell.com

January 26, 2011 

Office of Field Operations 

Bureau of Ocean Energy Management 

Regulation & Enforcement 

1201 Elmwood Park Boulevard 

New Orleans, LA 70123-2394 

 

Attn: Mike Tolbert 

 Plans Group MS 5321 

SUBJECT: Supplemental Exploration Plan 

 OCS-G 7493, Garden Banks Block 427 

 Garden Banks 471 Unit 

 Offshore, Louisiana 

 S- 07445

In response to your information requests for subject plan received January 11, 2011 and January 18, 2011 

concerning days required to drill a relief well, the following is furnished to the BOEM for public information: 

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

rig fleet. The dynamically positioned rig, Noble Danny Adkins, which is currently under contract to 

Shell, will be the preferred rig for blowout intervention work. 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 

a further estimated 3 days transit to mobilize to the relief well site. Additionally, in the event of a 

blowout, there is the distinct possibility that other non-Shell contracted rigs in the GOM could be 

utilized whether for increased expediency or better suitability. 

The worst case discharge scenario is based upon an 11 3⁄4” liner with ~4000’ of open hole to the top 

of the reservoir. The time to drill the relief well is approximately 71 days and an additional estimated 

21 days to maneuver the relief well through precision ranging to intersect the well that has blown 

out. Therefore the total time to mobilize, transit and drill a relief well for Cardamom is 109 days. 

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

Kind regards 

Sylvia A. Bellone 
 U. S. Department of the Interior OMB Control Number: 1010-0051 

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

OCS PLAN INFORMATION FORM 

General Information 

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

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

Address: P. O. Box 61933 Contact Person: Sylvia Bellone 

New Orleans, LA 70161-1933 Phone Number: (504) 728-7215 

 E-Mail Address: sylvia.bellone@shell.com

Lease(s): OCS-G 7493 Area: Garden Banks Block(s): 427 Project Name (If Applicable): NA 

Objective(s): X Oil Gas Sulphur Salt Onshore Base: Fourchon & Amelia Distance to Closest Land (Miles): 130 

Description of Proposed Activities (Mark all that apply)

X Exploration drilling Development drilling 

Well completion Installation of production platform 

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

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

Installation of subsea wellheads and/or manifolds Commence production 

Installation of lease term pipelines Other (Specify and describe) 

Have you submitted or do you plan to submit a Conservation Information Document to accompany this plan? Yes X No 

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

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

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

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

Tentative Schedule of Proposed Activities 

Proposed Activity Start Date End Date No. of Days 

Preset anchors 12/01/10 12/31/10 30 

Drill O 01/01/11 06/11/11 160 

Drill P 01/01/12 06/10/12 160 

Drill Q 01/01/13 06/13/13 160 

 

Description of Drilling Rig Description of Production Platform

 Jackup Drillship Caisson Tension leg platform

 Gorilla Jackup Platform rig Well protector Compliant tower 

X Semisubmersible Submersible Fixed platform Guyed tower

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

Drilling Rig Name (If Known): Noble Jim Thompson Spar Other (Attach Description) 

Description of Lease Term Pipelines 

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

N/A 

 

 Form MMS-137 (December 2008 – Supersedes all previous editions of form MMS=137 which may not be used.) Page 1 of 4 

	



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): O Subsea Completion 

Anchor Radius (if applicable) in feet: 14500’ X Yes No 

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 7493 

Area Name Garden Banks 

Block No. 427 

Blockline 

Departures 

(in feet)

N/S Departure: 5965' FNL 

 E/W Departure: 1400' FEL 

Lambert X-Y 

coordinates 

X: 1,836,040 

 Y: 10,004,915 

Latitude/ 

Longitude

Latitude 

27.56962046 

Longitude 

-92.39596682 

TVD (Feet): MD (Feet): Water Depth (Feet): 2721’ 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 

 

 

 

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

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

Exploration Plan or Development Operations Coordination Document submitted for MMS approval. 

We use the information to facilitate our review and data entry for OCS plans. We will protect 

proprietary data according to the Freedom of Information Act and 30 CFR 250.196. An agency may 

not conduct or sponsor, and a person is not required to respond to, a collection of information unless it 

displays a currently valid Office of Management and Budget Control Number. The use of this form is 

voluntary. The public reporting burden for this form is included in the burden for preparing Exploration 

Plans and Development Operations Coordination Documents. We estimate that burden to average 580 

hours per response, including the time for reviewing instructions, gathering and maintaining data, and 

completing and reviewing the form. Direct comments regarding the burden estimate or any other 

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

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

 Form MMS-137 (December 2008 – Supersedes all previous editions of form MMS=137 which may not be used.) Page 2 of 4 

	



 	




 
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): P Subsea Completion 

Anchor Radius (if applicable) in feet: 14500’ X Yes No 

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 7493 

Area Name Garden Banks 

Block No. 427 

Blockline 

Departures 

(in feet)

N/S Departure: 5470' FNL 

 E/W Departure: 1920' FEL 

Lambert X-Y 

coordinates 

X: 1,835,520 

 Y: 10,005,410 

Latitude/ 

Longitude

Latitude 

27.57098950 

Longitude 

-92.39756494 

TVD (Feet): MD (Feet): Water Depth (Feet): 2721’ 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 

 

 

 

 

 

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

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

Exploration Plan or Development Operations Coordination Document submitted for MMS approval. 

We use the information to facilitate our review and data entry for OCS plans. We will protect 

proprietary data according to the Freedom of Information Act and 30 CFR 250.196. An agency may 

not conduct or sponsor, and a person is not required to respond to, a collection of information unless it 

displays a currently valid Office of Management and Budget Control Number. The use of this form is 

voluntary. The public reporting burden for this form is included in the burden for preparing Exploration 

Plans and Development Operations Coordination Documents. We estimate that burden to average 580 

hours per response, including the time for reviewing instructions, gathering and maintaining data, and 

completing and reviewing the form. Direct comments regarding the burden estimate or any other 

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

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

 Form MMS-137 (December 2008 – Supersedes all previous editions of form MMS=137 which may not be used.) Page 3 of 4 

	



 	




 
OCS PLAN INFORMATION FORM (CONTINUED) 

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

Proposed Well/Structure Location

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

Anchor Radius (if applicable) in feet: 14500’ X Yes No 

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 7493 

Area Name Garden Banks 

Block No. 427 

Blockline 

Departures 

(in feet)

N/S Departure: 6470' FNL 

 E/W Departure: 880' FEL 

Lambert X-Y 

coordinates 

X: 1,836,560 

 Y: 10,004,410 

Latitude/ 

Longitude

Latitude 

27.56822388 

Longitude 

-92.39436890 

TVD (Feet): MD (Feet): Water Depth (Feet): 2721’ 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 

 

 

 

 

 

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

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

Exploration Plan or Development Operations Coordination Document submitted for MMS approval. 

We use the information to facilitate our review and data entry for OCS plans. We will protect 

proprietary data according to the Freedom of Information Act and 30 CFR 250.196. An agency may 

not conduct or sponsor, and a person is not required to respond to, a collection of information unless it 

displays a currently valid Office of Management and Budget Control Number. The use of this form is 

voluntary. The public reporting burden for this form is included in the burden for preparing Exploration 

Plans and Development Operations Coordination Documents. We estimate that burden to average 580 

hours per response, including the time for reviewing instructions, gathering and maintaining data, and 

completing and reviewing the form. Direct comments regarding the burden estimate or any other 

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

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

 Form MMS-137 (December 2008 – Supersedes all previous editions of form MMS=137 which may not be used.) Page 4 of 4 

	



 	



Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

9 OIL SPILLS INFORMATION 

 (9a) Oil Spill Response Planning

(i) All the proposed activities and facilities in this EP 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 and is pending approval. An OSRP Certification in accordance with 30 CFR 254.2 was 

submitted and accepted by the BOEMRE on December 3, 2010. 

 (ii) 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 

(iii) 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. 

(iv) Worst Case Scenario Determination 

Category Regional OSRP EP 

Type of Activity1 Drilling Rig Drilling Rig 

Facility Location (area/block) MC 391 GB 427 

Facility Designation2 C O 

Distance to Nearest Shoreline (miles) 72 137 

Volume3

Storage tanks (total) 

Flowlines (on facility) 

Pipelines 

Uncontrolled blowout (volume per day) 

Total Volume 

N/A 

N/A 

N/A 

405,000 BOPD 

405,000 Bbls 

N/A 

N/A 

N/A 

143,000* BOPD 

143,000 Bbls 

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

API Gravity(s)4 37.5o 24o 

*24 hour rate (131,000 BOPD 30 day average) 

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, 

submitted October 26, 2010, and since the worst-case scenario determined for our SEP does not replace the appropriate worstcase 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. 
Hill, Chiquita

From: sylvia.bellone@shell.com

Sent: Thursday, December 02, 2010 5:10 PM

To: Hill, Chiquita

Subject: RE: S-7445, GB 427, OCS-G07493, Shell Offshore Inc.

Attachments: image001.jpg; 20111201CorrectedPagesEP.docx

Page 1 of 1

12/3/2010

Chiquita, here is the oil characteristics from your request below.

I believe this is all the pending information that I owe you at this time so the clock can start again.

If this is not the case please advise what you are still waiting on from me.

Thanks Sylvia Bellone 504‐728‐7215

From: Hill, Chiquita [mailto:Chiquita.Hill@boemre.gov] 

Sent: Friday, November 19, 2010 10:15 AM 

To: Bellone, Sylvia A SEPCO-UAS/E/DEC 

Subject: S-7445, GB 427, OCS-G07493, Shell Offshore Inc.

 

Request for more information for the Geological Review

The geologic description needs expansion.

Request for more information for the Chemosynthetic Communities Biological Review

The BOEMRE requests more information to do a deepwater benthic communities review for 

Shell Offshore Inc. Plan S-7445, Garden Banks Block 427, Lease OCS-G 07493. NTL No. 

2009-G40 requires map(s) and analysis for potential impacts on deepwater benthic 

communities (deepwater coral and chemosynthetic invertebrate communities). Neither 

seafloor features nor geologic features maps showing the location of the proposed action are 

included with the operator¿s submitted materials. An analysis of potential impacts to such 

communities is also absent and is required. 

Also see attachments for our new checklist request

Chiquita Hill

Regulatory Specialist

Bureau of Ocean Energy Management, 

Regulation, and Enforcement

Field Operations/Plans Section

E-mail Chiquita.Hill@BOEMRE.GOV

(504) 736-2668

 

 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

2 GENERAL INFORMATION

(2a) Application and Permits

There are no individual or site-specific permits other than general NPDES Permit that need to be obtained. 

(2b) Drilling Fluids 

Type of Drilling Fluid Estimated Volume of Drilling Fluid Used 

per Well

Synthetic-Based (internal olefin, ester) 14,500 bbls/well

Water-based (seawater, freshwater, barite) 50,000 bbls/well

Oil-based (diesel, mineral oil) 0 bbls

 (2c) Production

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

necessary in the case of DOCDs. 

(2d) Oil Characteristics Provide the chemical and physical characteristics of the oils that will 

be produced, transported, or stored. 

Characteristic U Sand 

Value 

Analytical Methodologies 

Should Be Compatible With: 

1. Gravity (API) 25.5 ASTM D4052 

2. Flash Point (oC Unknown ASTM D93/IP 34 

3. Pour Point (oC) 27 deg C ASTM D97 

4. Viscosity (Centipoise at 25 oC) Unknown ASTM D445 

5. Wax Content (wt %) Unknown 

Precipitate with 2-

butanon/dichloromethane 

(1 to 1 volume) at -10 oC 

6. Asphaltene Content (wt %) 1.0 wt% IP-Method 143/84 

7. Resin Content (wt %) 8.4 wt% Jokuty et al., 1996 

8. Boiling point distribution including, for each 

fraction, the percent volume or weight and the 

boiling point range in oC 

Unknown ASTM D2892 (TBP distillation) or 

ASTM D2887/5307 

9. Sulphur (wt %) 2.2 wt% ASTM D4294 

Note: If the distillation information in Item No. 8 in the above table is not available, the GOMR may accept the following 

information in lieu of Items Nos. 5, 6, 7, and 8: weight percent total of saturates, aromatics, waxes, asphaltenes, and resins; and 

total BTEX (ppm) using analytical methods compatible with the Hydrocarbon Groups methodology found in Jokuty et al., 1996). 

All in wt% Topped Basis 
SARA (Topped Basis) All in wt %

Well # Saturates Aromatics Resin Asphaltenes

A16ST3 (U Sand Res B) 45.8 44.8 8.4 1.0

 

Identify the oil you analyze. Refer to the following sample chart. 

Oil from one well 

·Area/Block 

·MMS platform 

·API Well No. 

·Completion perforation 

 interval 

·MMS’s reservoir name 

·Sample date 

·Sample No.(if more than 

one is taken) 

Garden Banks 427 

Auger 

60-807-40101-03 

31,525ft MD 

U Sand Reservoir B 

March 15th 2010 

35926-35 

(2e) 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. 

(2f) Bonding

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

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

Surety Bonds;” and National NTL No. 2003-N06, “Supplemental Bond Procures.” 

(2g) Oil Spill Financial Responsibility (OSFR)

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

for the facilities proposed in the EP according to 30 CFR Part 253, and NTL No. 99-N01, “Guidelines for 

Oil Spill Financial Responsibility for Covered Facilities.” 

(2h) 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. 

(2i) Suspension of Production

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

only necessary in the case of DOCDs. 
Hill, Chiquita

From: sylvia.bellone@shell.com

Sent: Friday, November 19, 2010 5:02 PM

To: Hill, Chiquita

Subject: RE: S-7445, GB 427, OCS-G07493, Shell Offshore Inc.

Attachments: image001.jpg; 201119CorrectedPagesEP.docx

Page 1 of 2

11/23/2010

In answer to your requests for information:

1. Here is the revised geological information

2. Here is the waste and discharge information

3. I need more clarification on what specifically is not contained in our Section 6a, Anchor clearance and

chemosynthetic organisms comments.

4. We did take fluid samples in another well drilled to this zone, so I will provide the information

requested for General Information, Oil Characteristics.

Thanks Sylvia Bellone 504‐728‐7215

From: Hill, Chiquita [mailto:Chiquita.Hill@boemre.gov] 

Sent: Friday, November 19, 2010 10:20 AM 

To: Bellone, Sylvia A SEPCO-UAS/E/DEC 

Subject: RE: S-7445, GB 427, OCS-G07493, Shell Offshore Inc.

 

Waste and Discharge Information

Chiquita Hill

Regulatory Specialist

Bureau of Ocean Energy Management, 

Regulation, and Enforcement

Field Operations/Plans Section

E-mail Chiquita.Hill@BOEMRE.GOV

(504) 736-2668

 

From: Hill, Chiquita 

Sent: Friday, November 19, 2010 10:15 AM 

To: 'Sylvia.bellone@shell.com' 

Subject: S-7445, GB 427, OCS-G07493, Shell Offshore Inc.

 

Request for more information for the Geological Review

The geologic description needs expansion.

Request for more information for the Chemosynthetic Communities Biological Review

The BOEMRE requests more information to do a deepwater benthic communities review for 

Shell Offshore Inc. Plan S-7445, Garden Banks Block 427, Lease OCS-G 07493. NTL No. 

Plans for Treating, storing, or downhole disposal of wastes
2009-G40 requires map(s) and analysis for potential impacts on deepwater benthic 

communities (deepwater coral and chemosynthetic invertebrate communities). Neither 

seafloor features nor geologic features maps showing the location of the proposed action are 

included with the operator¿s submitted materials. An analysis of potential impacts to such 

communities is also absent and is required. 

Also see attachments for our new checklist request

Chiquita Hill

Regulatory Specialist

Bureau of Ocean Energy Management, 

Regulation, and Enforcement

Field Operations/Plans Section

E-mail Chiquita.Hill@BOEMRE.GOV

(504) 736-2668

 

 

Page 2 of 2

11/23/2010
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

7 Waste and Discharge Information

(7a) Projected Generated Wastes

Type of Waste Composition Projected Amount Describe how it will it be 

treated, stored, or downhole 

disposed of 

at your facility 

Spent Drilling Fluids Synthetic-based drilling muds 7,000 bbls/well Re-used. 

Spent Drilling Fluids Water based drilling fluid 50,000 bbl/well Discharge at mudline prior to 

riser installation. 

Washed Cuttings 

from water based 

hole interval 

Cuttings coated with water 

based drilling muds 

2500 bbls/well Discharge at mudline prior to 

riser installation. 

Washed Drill cuttings 

from synthetic based 

hole interval 

Drill cuttings 6,500 bbls/well Treated cuttings will be 

discharged overboard during 

drilling of SBM interval. 

Cuttings will pass through 

cuttings dryer substantially 

reducing ROC percentage 

from worst case quoted 

below. 

Sanitary Waste Treated human body waste 

from toilets 

87 bbls/day USCG-approved MSD with 

chlorination. 

Starboard Caisson 

Domestic Waste Gray water (laundry, galley, 

lavatory) 

215 bbls/day Food grinder. 

Starboard Caisson 

Produced water Formation water NA NA 

Excess cement Cement slurry 1000 bbls/well Discharged at mudline 

Desalination unit 

brine water 

Rejected water from 

watermaker unit 

400 gals/day Cuttings chute 

Deck drainage Platform washings and 

rainwater

10 bbls/hr Oily water is treated in Oily 

Water Separator 

Starboard Caisson 

Trash and debris Plastic, Paper, Aluminum, 

Glass, and other refuse 

1 cubic meter/day Recyclables to ARC, New 

Iberia, LA. Nonrecycleables to landfill at 

Avondale, LA 

Transported in big bags. 

Cooling water Seawater with no addition of 

chemicals 

130,600 bbls/day Starboard Caisson 

Fire water Seawater with no addition of 

chemicals 

130,600 bbls/day Starboard Caisson 

Ballast water Uncontaminated seawater 

used to maintain proper draft 

3500 bbls/day (average) Starboard Caisson 

Blowout Preventer 

Fluid 

Stackmagic 200/0/5% 

glycol based on 2% mixture 

with potable water 

100 bbls/well Discharged at mudline 
Shell Offshore Inc

P. O. Box 61933

New Orleans, LA 70161-1933

United States of America

Tel +1 504 728 7215

Fax +1 504 728 6747

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

Email sylvia.bellone@shell.com

October 26, 2010 

Regional Supervisor 

Office of Field Operations 

Bureau of Ocean Energy Management 

Regulation & Enforcement 

1201 Elmwood Park Boulevard 

New Orleans, LA 70123-2394 

 

Attn: Plans Group 

 MS 5321 

SUBJECT: Supplemental Exploration Plan 

 OCS-G 7493, Garden Banks Block 427 

 Garden Banks 471 Unit 

 Offshore, Louisiana

 

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

guidelines, Shell Offshore Inc (SOI) requests your approval of this Supplemental Exploration Plan requesting 

approval to drill Well Locations O, P & Q. Depending on rig availability operations could commence as early 

as January 1, 2011. 

The NTL 2010-06 Worst Case Blowout requirements for our Regional Oil Spill Response Plan highest 

exploration well, were previously submitted October 26, 2010 with our Supplemental Exploration Plan for 

Mississippi Canyon Blocks 391, 392 and 348, Plan Control No. R-5066. 

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

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

excluded from the Public Information Copies of this submittal. 

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

Kind regards 

Sylvia A. Bellone 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

1. Plan Contents 

2. General Information 

3. Geological and Geophysical 

4. H2S 

5. Mineral Resource Conservation 

6. Biological, Physical and Socioeconomic 

 Information 

7. Waste and Discharge Information 

8. Air Emission Information 

9. Oil Spill Information 

10. Environmental Monitoring 

11. Lease Stipulations 

12. Environmental Mitigation Measures 

13. Related Facilities and Operations Information 

14. Support Vessels and Aircraft 

15. Onshore Support Facilities Information 

16. Sulphur Operations 

17. Coastal Zone Management Act Information 

18. Environmental Impact Analysis 

19. Administrative Information 

 

 

 
 U. S. Department of the Interior OMB Control Number: 1010-0051 

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

OCS PLAN INFORMATION FORM 

General Information 

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

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

Address: P. O. Box 61933 Contact Person: Sylvia Bellone 

New Orleans, LA 70161-1933 Phone Number: (504) 728-7215 

 E-Mail Address: sylvia.bellone@shell.com

Lease(s): OCS-G 7493 Area: Garden Banks Block(s): 427 Project Name (If Applicable): Cardamom 

Objective(s): X Oil Gas Sulphur Salt Onshore Base: Fourchon & Amelia Distance to Closest Land (Miles): 130 

Description of Proposed Activities (Mark all that apply)

X Exploration drilling Development drilling 

Well completion Installation of production platform 

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

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

Installation of subsea wellheads and/or manifolds Commence production 

Installation of lease term pipelines Other (Specify and describe) 

Have you submitted or do you plan to submit a Conservation Information Document to accompany this plan? Yes X No 

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

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

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

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

Tentative Schedule of Proposed Activities 

Proposed Activity Start Date End Date No. of Days 

Preset anchors 12/01/10 12/31/10 30 

Drill O 01/01/11 06/11/11 160 

Drill P 01/01/12 06/10/12 160 

Drill Q 01/01/13 06/13/13 160 

 

Description of Drilling Rig Description of Production Platform 

 Jackup Drillship Caisson Tension leg platform

 Gorilla Jackup Platform rig Well protector Compliant tower 

X Semisubmersible Submersible Fixed platform Guyed tower

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

Drilling Rig Name (If Known): Noble Jim Thompson Spar Other (Attach Description) 

Description of Lease Term Pipelines 

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

N/A 

 

MMS Form MMS-137 Page 1 of 4 

PUBLIC INFORMATION
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): O Subsea Completion 

Anchor Radius (if applicable) in feet: 14500’ Yes X No 

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 7493 

Area Name Garden Banks 

Block No. 427 

Blockline 

Departures 

(in feet)

N/S Departure: 5965' FNL 

 E/W Departure: 1400' FEL 

Lambert X-Y 

coordinates 

X: 1,836,040 

 Y: 10,004,915 

Latitude/ 

Longitude

Latitude 

27.56962046 

Longitude 

-92.39596682 

TVD (Feet): MD (Feet): Water Depth (Feet): 2721’ 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 

 

 

 

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

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

Exploration Plan or Development Operations Coordination Document submitted for MMS approval. 

We use the information to facilitate our review and data entry for OCS plans. We will protect 

proprietary data according to the Freedom of Information Act and 30 CFR 250.196. An agency may 

not conduct or sponsor, and a person is not required to respond to, a collection of information unless it 

displays a currently valid Office of Management and Budget Control Number. The use of this form is 

voluntary. The public reporting burden for this form is included in the burden for preparing Exploration 

Plans and Development Operations Coordination Documents. We estimate that burden to average 580 

hours per response, including the time for reviewing instructions, gathering and maintaining data, and 

completing and reviewing the form. Direct comments regarding the burden estimate or any other 

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

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

MMS Form MMS-137 Page 2 of 4 

PUBLIC INFORMATION 

 
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): P Subsea Completion 

Anchor Radius (if applicable) in feet: 14500’ Yes X No 

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 7493 

Area Name Garden Banks 

Block No. 427 

Blockline 

Departures 

(in feet)

N/S Departure: 5470' FNL 

 E/W Departure: 1920' FEL 

Lambert X-Y 

coordinates 

X: 1,835,520 

 Y: 10,005,410 

Latitude/ 

Longitude

Latitude 

27.57098950 

Longitude 

-92.39756494 

TVD (Feet): MD (Feet): Water Depth (Feet): 2721’ 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 

 

 

 

 

 

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

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

Exploration Plan or Development Operations Coordination Document submitted for MMS approval. 

We use the information to facilitate our review and data entry for OCS plans. We will protect 

proprietary data according to the Freedom of Information Act and 30 CFR 250.196. An agency may 

not conduct or sponsor, and a person is not required to respond to, a collection of information unless it 

displays a currently valid Office of Management and Budget Control Number. The use of this form is 

voluntary. The public reporting burden for this form is included in the burden for preparing Exploration 

Plans and Development Operations Coordination Documents. We estimate that burden to average 580 

hours per response, including the time for reviewing instructions, gathering and maintaining data, and 

completing and reviewing the form. Direct comments regarding the burden estimate or any other 

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

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

MMS Form MMS-137 Page 3 of 4 

PUBLIC INFORMATION 

 
OCS PLAN INFORMATION FORM (CONTINUED) 

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

Proposed Well/Structure Location

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

Anchor Radius (if applicable) in feet: 14500’ Yes X No 

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 7493 

Area Name Garden Banks 

Block No. 427 

Blockline 

Departures 

(in feet)

N/S Departure: 6470' FNL 

 E/W Departure: 880' FEL 

Lambert X-Y 

coordinates 

X: 1,836,560 

 Y: 10,004,410 

Latitude/ 

Longitude

Latitude 

27.56822388 

Longitude 

-92.39436890 

TVD (Feet): MD (Feet): Water Depth (Feet): 2721’ 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 

 

 

 

 

 

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

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

Exploration Plan or Development Operations Coordination Document submitted for MMS approval. 

We use the information to facilitate our review and data entry for OCS plans. We will protect 

proprietary data according to the Freedom of Information Act and 30 CFR 250.196. An agency may 

not conduct or sponsor, and a person is not required to respond to, a collection of information unless it 

displays a currently valid Office of Management and Budget Control Number. The use of this form is 

voluntary. The public reporting burden for this form is included in the burden for preparing Exploration 

Plans and Development Operations Coordination Documents. We estimate that burden to average 580 

hours per response, including the time for reviewing instructions, gathering and maintaining data, and 

completing and reviewing the form. Direct comments regarding the burden estimate or any other 

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

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

MMS Form MMS-137 Page 4 of 

PUBLIC INFORMATION 

 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

1. PLAN CONTENTS

(1a) DESCRIPTION, OBJECTIVES & SCHEDULE

This Supplemental Exploration Plan (SEP) with appendices, including an Environmental Impact Analysis (EIA) 

found in Section 18, describes the drilling activities Shell Offshore Inc. (Shell) plans to conduct with respect to 

OCS-G 7493, Garden Banks Block 427. 

Shell’s plan, as detailed in its SEP, is to use a single semisubmersible Mobile Offshore Drilling Unit, the M/V 

Noble Jim Thompson or equivalent rig (the “Rig”), to drill up to three (3) exploration wells in the Garden Banks 

Area, Block 427 (GB 427), located approximately 130 miles from the nearest coastline (Louisiana), 173 miles 

from the supply base at Port Fourchon, Louisiana, and 163 miles from the helicopter terminal at Amelia, 

Louisiana. Water depths in the lease range from approximately 640 to 884 m (2,100 to 2,900 ft). Water depth at 

the wellsite surface locations is 829 m (2,721 ft). The initial drilling activities are planned to commence on or 

about January 1, 2011 and take last approximately 160 days. 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 timeframe for drilling the first well 

will further define the timing for further development of the prospect. GB 427-2 (O location in 

EP) will be the first well drilled with a surface location in GB Block 427; however, 17 exploratory and 

development wells drilled by Shell have targeted objectives in GB Block 427. Consequently, the fundamental 

geology of the block is well understood.

The Rig is a moored semisubmersible drilling vessel and is equipped with state-of-the-art drilling and well 

control equipment. It is a largely self-contained drilling vessel, with accommodations for a crew of up to 138 

persons on board, including quarters, galley and sanitation facilities. The Rig will comply with the requirements 

in NTL 2010-N05 and 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 GB 427 

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 (October 2010) is designed to contain and 

respond to a spill that meets or exceeds the WCD detailed in section 9 of this EP. 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. 

(1b) LOCATION

See attached Map. 

 
X= 1,837,440.00’

Y=10,010,880.00’

X= 1,821,600.00’

Y=10,010,880.00’

O

Q

P

GB 427

(OCS-G 7493)

X=1,821,600.00’

Y=9,995,040.00’

X=1,837,440.00’

Y=9,995,040.00’

N ATTACHMENT

SHELL

PROPOSED SURFACE LOCATIONS & BATHYMETRY

EXPLORATION PLAN

SHELL OCS G 7493 GARDEN BANKS BLK 427

O 1400’ FEL & 5965’ FNL OF BLK. 427

X=1,836,040.00 Y=10,004,915.00

P 1920’ FEL & 5470’ FNL OF BLK. 427

PROPOSED SURFACE LOCATIONS

SHELL, OCS-G 7493, GARDEN BANKS BLK. 427

GARDEN BANKS AREA

OFFSHORE LOUISIANA

2000’

X=1,835,520.00 Y=10,005,410.00

Q 880’ FEL & 6470’ FNL OF BLK. 427

X=1,836,560.00 Y=10,004,410.00
(1c) RIG SAFETY AND POLLUTION FEATURES: 

The Rig we plan to use will comply with all of the regulations of the American Bureau of Shipping (ABS), 

International Maritime Organization (IMO) and the United States Coast Guard (USCG). All drilling operations 

will be conducted under the provisions of 30 CFR, Part 250, Subpart D, and other applicable regulations and 

notices, including those regarding the avoidance of potential drilling hazards and safety and pollution prevention 

control. Such measures as inflow detection and well control, monitoring for loss of circulation and seepage loss, 

and casing design will be our primary safety measures. Primary pollution prevention measures are contaminated 

and non-contaminated drain system, mud drain system, and oily water processing. 

DRAIN SYSTEM POLLUTION FEATURES 

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

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

removable strainer plate to prevent debris entering the system. 

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

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

1.) Non-contaminated Drains 

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

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

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

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

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

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

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

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

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

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

drain. 

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

deployment as appropriate) and reported immediately. 

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

in place as needed to ensure a proper seal. 

2.) Contaminated Drains 

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

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

3.) Mud Drain System 

 None 

 
4.) 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 has to be kept according to instructions included in the log. Any 

and all pollution pans are subjected to a sheen test before being pumped out. If the water passes the sheen 

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

a dirty oil tank and sent to shore for disposal. All waste oil that is sent in to be disposed of is recorded in 

the MODU’s oil log book. 

All discharges will be in accordance with applicable NPDES permits. See Attachment 18, EIA, Section 

C.1.1.2, Water Quality. 

5.) Lower Hull Bilge System 

• The main bilge system is designed to drain the pontoons. There are Goulds 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 line 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. 

6.) 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. 

7.) Oily Water Drain/Separation System

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

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

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

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

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

skimmer tanks and are subjected to sheen tests before discharge as well 

8.) Drain, Effluent and Waste Systems 

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

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

non-hazardous drains from nonhazardous areas. 

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

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

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

water separators divide the drainage system into these sections: 

9.) 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. 

10.) Columns #3 & 4 

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

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

15ppm, then discharge the clean product to sea. 

11.) 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 

12.) Helideck Drains 

The heli-deck 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 out the skimmer tanks down the shunt line. 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/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 in Port column oily water separator which discharges 

water overboard from the water side and oil being pumped out into a 550 gal tote tank oil containment 

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

 
 (1d) Storage Tanks 

Type of Storage Tank Type of 

Facility 

Tank 

Capacity 

(bbls) 

Number 

of 

Tanks 

Total 

Capacity 

(bbls) 

Fluid 

Gravity (API) 

Diesel Tank in Pontoon Drilling Rig 4451 2 8902 Marine Diesel (0.91 SG) 

Diesel Tank in Footing Drilling Rig 2748 1 2748 Marine Diesel (0.91 SG) 

Diesel Settling Tanks Drilling Rig 110 2 220 Marine Diesel (0.91 SG) 

Standby Generator Diesel Drilling Rig 7.1 1 7.1 Marine Diesel (0.91 SG) 

Jet Fuel Tank Drilling Rig 27 1 27 Jet Fuel A (0.91 SG) 

 Lube Oil Tank Drilling Rig 10 1 10 Lube Oil (0.91 SG) 

 

(1e) Pollution Prevention Measures 

Pursuant to NTL No. 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 in 1(c) above. 

(1f) Additional Measures

 

HSE (health safety and environment) are the primary topics in pre-tour and pre-job safety meetings. The 

discussion around no harm to people or environment is a key mindset. All personnel are reminded daily to 

inspect work areas for safety issues as well as potential pollution issues. 

All tools that come to and from the Rig have their pollution pans inspected, cleaned and confirmation of plugs 

installed prior to leaving dock and prior to loading on the boat. 

Preventive Maintenance of Rig equipment include visual inspection of hydraulic lines and reservoirs on routine 

scheduled basis. 

All pollution pans on Rig are inspected daily. 

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

All used oil and fuel is collected and sent in for recycling. 

Every drain on the Rig is assigned a number on a checklist. The checklist is used daily to verify drain plugs are 

installed. 

All trash containers are checked and emptied daily. The trash containers are kept covered. Trash is disposed of 

in a compactor and shipped in via boat. 

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

Fuel hoses and SBM are changed on annual basis. 

TODO spill prevention fittings are installed on all liquid take on hoses. 

Waste paint thinner is recycled on board with a solvent still to reduce hazard of shipping and storage. 

All equipment on board utilizes Envirorite hydraulic fluid as opposed to hydraulic oil. Shell has obtained 

ISO14001 certification. 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

2 GENERAL INFORMATION

(2a) Application and Permits

There are no individual or site-specific permits other than general NPDES Permit that need to be obtained. 

(2b) Drilling Fluids 

Type of Drilling Fluid Estimated Volume of Drilling Fluid Used 

per Well 

Synthetic-Based (internal olefin, ester) 14,500 bbls/well 

Water-based (seawater, freshwater, barite) 50,000 bbls/well 

Oil-based (diesel, mineral oil) 0 bbls 

 (2c) Production

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

in the case of DOCDs. 

(2d) Oil Characteristics

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

necessary in the case of DOCDs.

(2e) 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. 

(2f) Bonding

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

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

Bonds;” and National NTL No. 2003-N06, “Supplemental Bond Procures.” 

(2g) Oil Spill Financial Responsibility (OSFR)

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

the facilities proposed in the EP according to 30 CFR part 253, and NTL No. 99-N01, “Guidelines for Oil Spill 

Financial Responsibility for Covered Facilities.” 

 
(2h) 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. 

(2i) Suspension of Production

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

only necessary in the case of DOCDs. 

(2j) Blowout scenario

Summary 

This Section 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 focuses on an integrated, three-pronged approach to a blowout, including prevention, 

intervention /containment, and recovery. Shell believes that the best way to manage blowouts is to 

prevent them from happening. Significant effort goes into the design and execution of wells and into 

building and maintaining staff competence with the goal of safe and environmentally sound well 

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

improve safety and reliability of our well systems. Shell intends to comply with all applicable laws, 

regulations, rules and Notice to Lessees. 

Shell is a founding member of the Marine Well Containment Company (MWCC) and will have 

access to an integrated subsea well control and containment system that can be rapidly deployed 

through the MWCC. MWCC is a non-profit organization that owns, manages, and provides fully 

trained crews and operates the subsea containment system during a response. The near term 

containment response capability will include lessons learned and equipment used in the Macondo 

response. Shell is investing in R&D to improve containment systems. Also, Shell is a member of 

Clean Caribbean America (CCA), Marine Spill Response Corporation (MSRC), Clean Gulf 

Associates (CGA), and OSRL/EARL to provide the resources necessary to respond to a spill as 

outlined in our Regional Oil Spill Response Plan (OSRP, October 2010). 

The Worst Case Discharge (WCD) blowout scenario for this EP is calculated for the GB 427 O 

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

Frequently Asked Questions (FAQ). The WCD for GB 427 O falls below the WCD exploratory 

scenario (MC 391) included in our Regional OSRP. In the unlikely event of a spill, Shell’s Regional 

OSRP (October 2010) is designed to contain and respond to a spill that meets or exceeds this WCD. 

The WCD does not take into account potential flow mitigating factors such as well bridging, 

obstructions in wellbore, reservoir barriers, or early intervention. 

Uncontrolled blowout (volume first day) 143,000 bbl 

Uncontrolled blowout rate (first 30-days average daily rate) 131,000 bopd 

Duration of flow (days) based on relief well 109 days 

Total volume of spill (bbls) for 109 days 12.3 MMBO 

Table 1 Worst Case Discharge Summary 

 
Shell is submitting a Supplemental Exploration Plan for GB 427 (OCS-G 7493) to appraise its 

recent Cardamom discovery. While the Cardamom discovery comprises multiple reservoirs, this 

Supplemental EP and NTL-06 documentation pertain to appraising one reservoir – the U sand. 

Three wells, each with unique surface and U sand bottom hole locations, are described in the 

Supplemental EP. The WCD forecast in this document pertains to the well location that, in the event 

of loss of well control, discharges the largest volume before containment. 

The GB 427-2 will be the first well drilled with a surface location in GB Block 427; however, 17 

exploratory and development wells drilled by Shell have targeted objectives in GB Block 427. 

Consequently, the fundamental geology of the block is well understood. 

For this appraisal, Shell plans to submit in Q4 2010 an APD for drilling a new blue water well. 

Given success, the well will be secured for later completion in ~Q2 2012.

Subsurface Description: 

Omitted from public information copies. 

Blowout Scenario 

1) Purpose 

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

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

and calculations used to determine the WCD and the measures taken to firstly enhance the ability to 

prevent a blowout and secondly to 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 

The GB 427-2 well is drilled to the U sand, as outlined in the Geological and Geophysical 

Information Section of the approved Supplemental EP and described above, using a subsea 

wellhead system, conductor, surface and intermediate casing program, and using a MODU 

rig with a marine riser and subsea blowout preventer (BOP). A hydrocarbon influx and a well 

control event are modeled to occur from the U Sand during a trip out of the hole. The 

simulated blowout modeled results in unrestricted flow from the well at the seafloor, which 

represents the WCD (no restrictions in wellbore, failure/loss of the subsea BOP, and a 

blowout to the seabed). 
b) Estimated flow rate of the potential blowout 

Category Initial EP 

Type of Activity Drilling 

Facility Location (area/block) GB-427 

Facility Designation MODU 

Distance to Nearest Shoreline (miles) 130 miles 

Uncontrolled blowout (volume first day) 143,000 bbl 

Uncontrolled blowout rate (first 30-days average daily rate) 131,000 bopd 

Table 2 Estimated Flow Rates of a Potential Blowout 

c) Total volume and maximum duration of the potential blowout 

Duration of flow (days) 109 days total duration 

(14 days to contract/mob rig 95 

days to drill relief well) 

Total volume of spill (bbls) 12.3 MMBO 

Note: based on MBAL Material 

balance reservoir model * 

* Note: The U sand model was constructed using observations from analogue fields in the 

area which indicate that moderate aquifer support is likely. Model and model outputs can be 

provided to the BOEMRE in electronic form upon request. 

Table 3 Estimated Duration and Volume of a Potential Blowout 

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

differences between the first 24-hour volume and 30-day average rate. At very short times, 

e.g. during the first 24 hours, the pressure profile in the reservoir changes from the moment 

when a well first starts flowing to a pseudo-steady state pressure profile with time, and as a 

result the rate declines. At somewhat longer time scales, effects such as reservoir voidage and 

the impact of boundaries can cause the rate to drop continuously with production. Simulation 

and material balance models can include these effects and form the basis of the NTL No. 

2010-N06 calculations for 24-hour and 30-day rates as well as maximum duration volumes. 

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

Information omitted from public information copies. 

The NTL 2010-06 Worst Case Blowout requirements for our Regional Oil Spill Response Plan 

highest exploration well, were previously submitted October 26, 2010 with our Supplemental 

Exploration Plan for Mississippi Canyon Blocks 391, 392 and 348, Plan Control No. R-5066

 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

3 GEOLOGICAL AND GEOPHYSICAL INFORMATION

(Public Information)

(3a) Geological description

Omitted from Public Information Copies 

(3b) Structure Contour Map(s)

Omitted from Public Information Copies 

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

Omitted from Public Information Copies 

(3d) Geological Structure Cross-section(s)

Omitted from Public Information Copies 

(3e) Shallow Hazards Report

The following reports were used for our analysis: 

- Fugro-McClelland Anchoring Report Proposed Tension Leg Platform and M/V George 

Richardson for GB 426, 427, 470 and 471 dated February 22, 1990 

- Fugro’s Archeological Assessment Garden Banks Block 427 Report 2410-1061 dated May 

2010 (based on Fugro report No. 0201-0526) 

- Chance’s Hazard Study of GB 426, 427, 470, and 471 dated September 1985, 

- C& C Technologies Engineering and Hazard Study for 10” x 6” Pipeline Route in GB 341 to 

426, Report No. 3566-3662 dated March 2003 

- C& C Technologies Engineering and Hazard Study for 12” x 8” Pipeline Route in GB 341 to 

426, Report No. 3567-3663 dated June 2003 

- Shell’s high resolution 3-D surveys 
(3f) Shallow Hazards Assessment

SITE SPECIFIC COMMENTS

History

Shell’s Auger TLP is centered in GB426 at X = 1,820,750 Y= 9,996,240. The anchors for the TLP 

extend into blocks 426 and 427. Two of the lateral mooring anchors are within the requested anchor 

pattern radius. None of the Auger Platform wells have surface locations in block 427. Shell now 

seeks approval to use the anchored vessel Noble Jim Thompson or similar rig with a radius of 

14,500’ (plus an additional 1000’ buffer) to perform its planned operations on proposed locations O, 

P, and Q. Within this anchor pattern radius, there are two Auger Lateral mooring system lines: 

C1A-L1 is located at X = 1,826,623 Y = 10,003,220 

C1A-L2 is located at X = 1,829,722 Y = 9,997,196 

 

Flowlines flank the Auger dome on all sides. Existing pipelines surround and cross the proposed 

radius. Shell will maintain a buffer of at least 500’ when setting anchors. Shell will not set anchors 

at the intersection of the pipelines. 

To assess the proposed anchor radius and surrounding area, Shell used the following data: 

- Fugro-McClelland Anchoring Report Proposed Tension Leg Platform and M/V George 

Richardson for GB 426, 427, 470 and 471 dated February 22, 1990 

- Fugro’s Archeological Assessment Garden Banks Block 427 Report 2410-1061 dated May 

2010 (based on Fugro report No. 0201-0526) 

- Chance’s Hazard Study of GB 426, 427, 470, and 471 dated September 1985, 

- C& C Technologies Engineering and Hazard Study for 10” x 6” Pipeline Route in GB 341 to 

426, Report No. 3566-3662 dated March 2003 

- C& C Technologies Engineering and Hazard Study for 12” x 8” Pipeline Route in GB 341 to 

426, Report No. 3567-3663 dated June 2003 

- Shell’s high resolution 3-D surveys 

Well Locations Information

The proposed locations will use a 14,500’ (plus 1000’ buffer) radius. The rig center will be 

X = 1,836,144 Y = 10,004,512 

The well centers are: 

Proposed Location O: X = 1836040 Y = 10004915 

Proposed Location P: X = 1835520 Y = 10005410 

Proposed Location Q: X = 1836560 Y = 10004410 

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

Enhanced Surface Renderings, and Enhanced Surface Renderings with amplitudes applied, deep-tow 

data, Archeological Assessment, side scan sonar, and Subbottom profiler data, the planned 

anchoring operations for GB 427 are suitable for the planned activities. 

David Garner Vernessa Bradford 

Staff Geological Engineer Shallow Hazards Interpreter 
 (3g) High-Resolution Seismic Lines

Omitted from Public Information Copies 

. 

(3h) & (3i) Stratigraphic Column with Time vs depth table

Omitted from Public Information Copies 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

4 Hydrogen Sulfide 

(4a) Concentration 

0 ppm. 

(4b) Classification

Based on CFR 250.67 (c), SOI requests that the Regional Supervisor, Field Operations, determine 

the zones in the proposed drilling operations in this plan to be classified as an area where the absence 

of H2S has been confirmed. 

(4d) Modeling Report

We do not anticipate to encounter or handle H2S at concentrations greater than 500 parts per million 

(ppm) and therefore have not included modeling for H2S. 

5. Mineral Resource Conservation Information

Information regarding Mineral Resource Conservation is not included in this EP as such information 

is only necessary in the case of DOCDs. 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

6 Biological, Physical, and Socioeconomic Information

(6a) Chemosynthetic Communities Report

ANCHOR CLEARANCE AND CHEMOSYNTHETIC 

ORGANISMS COMMENTS

History

Shell located the Auger TLP in GB426. The anchors for the TLP extend into blocks 426 and 427. 

None of the Auger Platform wells have a surface location in block 427. Shell now seeks approval to 

use the anchored vessel Noble Jim Thompson in Garden Banks Block 427 using a radius of 14,500’ 

(plus an additional 1000’ buffer) to perform its planned operations on proposed locations O, P, and 

Q. 

To assess the proposed archeological status, well locations, anchor radius and surrounding area, 

Shell used the following data: 

- Fugro-McClelland Anchoring Report Proposed Tension Leg Platform and M/V George 

Richardson for GB 426, 427, 470 and 471 dated February 22, 1990 

- Fugro’s Archeological Assessment Garden Banks Block 427 Report 2410-1061 dated May 

2010 (based on Fugro report No. 0201-0526) 

- Chance’s Hazard Study of GB 426, 427, 470, and 471 dated September 1985, 

- C& C Technologies Engineering and Hazard Study for 10” x 6” Pipeline Route in GB 341 to 

426, Report No. 3566-3662 dated March 2003 

- C& C Technologies Engineering and Hazard Study for 12” x 8” Pipeline Route in GB 341 to 

426, Report No. 3567-3663 dated June 2003 

- Shell’s high resolution 3-D surveys 

Flowlines flank the Auger dome on all sides. 

Chemosynthetic Community Statement

Per 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 O, P, Q and the associated anchor radius: 

 
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). 

 `

Anchor Pattern Analysis

The proposed locations will be set in a 14,500’ radius. The center of the rig will be 

X = 1,836,144 Y = 10,004,512 

The proposed well centers are: 

Proposed Location O: X = 1836040 Y = 10004915 

Proposed Location P: X = 1835520 Y = 10005410 

Proposed Location Q: X = 1836560 Y = 10004410 

The seafloor east of the diapir is relatively smooth. The proposed locations are east of the base of 

the Auger diaper in GB427. There are four amplitudes and fluid expulsion features on its crest. 

From left to right, their center coordinates are: 

1 X = 1828115.61 Y = 10001005.83 

2 X = 1829096.38 Y = 10001119.85 

3 X = 1830134.70 Y = 10002291.81 

4 X = 1830808.04 Y = 10002577.53 

Shell has designated a 250’ avoidance zone around each fluid expulsion feature. Outside these 

avoidance zones, the subsurface has a dark reflectivity, interpreted as authigenic. Shell has also 

elected to avoid this area of dark reflectivity by 250’. 

The Auger dome has numerous seafloor faults that radiate from its crest. The faults also curve 

around the perimeter of the dome. These faults are usually small displacements affecting the 

shallow sediments and the seafloor. Vertical displacement of the subsurface reflectors was generally 

less than 10 feet and seafloor displacement is less than 5 feet. 

Because of these conditions, the placement of the suction anchors will be optimized. The suction 

anchors will be located to minimize penetration of shallow seafloor faults on the eastern side of the 

dome. Shell will set the anchors using ROV to survey the area before installation. Anchors 2, 3, 4, 

5, 6, 7, and 8 will be installed undressed (without rope) due to their proximity to faults and pipelines. 

The Auger Lateral Mooring System has two lines within the proposed radius. The coordinates are: 

Auger Lateral Line 3: 

X = 1826896.33 Y = 10003502.30 

Auger Lateral Line 4: 

X = 1830117.92 Y = 9997246.92 

Shell will observe an anchor/suction buffer of 500’ from these lines. 
Archeological Assessment

Per the archeological report, there are items of modern drilling debris such as drill pipe on the 

seafloor. One item is an unidentified contact measuring 25’ long by 25’ wide. This contact is a mud 

mat associated with former construction, shipping, or fishing activities. Its location is approximately 

X = 1822600; Y = 9995240. Previously drilled GB 471 Well # 1 is located at X = 1823472; Y = 

9994628. The mud mat and the well are outside the proposed radius. 

There are no landforms or identified features that might be high probability prehistoric sites, such as 

natural levees or point bar deposits. The regional probability for historic shipwrecks in this area is 

low. Within the study area, a modern day shipwreck, the shrimp boat Saint Mary sunk in 1990. Its 

coordinates are X = 1821348; Y = 10000919. The boat has a 750’ avoidance radius around it. A 

500’ avoidance buffer has been place along each existing pipeline. 

Slope Stability

Shell conducted a detailed study on the Auger Dome to assess the surface stability for anchoring. A 

determination of sediment run out in case of slope failure was calculated. The anchor placement 

took this sediment run out into consideration. A slope stability factor of safety of 1.3 or greater is 

deemed stable. Per Shell’s assessment, the sediment on the dome meets this requirement. Shell 

used the following methods to do the assessment: 

3-D seismic data for seafloor bathymetric profiles upslope from proposed manifold locations, 

towards salt dome high 

Deep geotechnical borings at Auger for generalized soil conditions (stratigraphy and mechanical 

properties) 

Slope Conclusions and Recommendations

• Based on infinite slope results with Auger soil data, the study profiles are in the “stable” 

range (i.e., FoS ~ 1.3-1.5 at zones of maximum slope). 

• Based on debris flow simulations of possible “seafloor failure zones,” Proposed Location O 

is ~200’ outside of the maximum run-out predicted with Auger soil data, while Proposed 

Locations P and Q are ~400’ to 750’ inside the maximum predicted runout, respectively. 

• Collective results indicate that risk to proposed manifold locations is low to moderate 

(increasing to the south). 

• Moving the proposed manifold locations to 500’ outside the maximum predicted run-out 

carries minimal risk. 
Overview

NTL Numbers 2009-G40, 2009-G39, 2008-G20 and 2008-G05: Shell evaluated the seafloor and 

archeological data on GB Blocks 426, 427, 471, and 472. Within the proposed 14,500’ radius plus 

1000’ buffer, the anchor radius is designed to minimize impact on areas of potential fluid expulsion and 

seafloor faults. Per BOEMRE regulations, Shell’s anchors will remain at least 250’ from potential 

fluid expulsion features and amplitudes. 

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

Enhanced Surface Renderings, and Enhanced Surface Renderings with amplitudes applied, deep-tow 

data, Archeological Assessment, side scan sonar, and 

Subbottom profiler data, the planned anchoring operations for GB 427 is suitable for the planned 

activities. 

Vernessa Bradford 

Shallow Hazards Coordinator 

6(b) – 6(f)

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

operations impacting the following: Topographic features map, Topographic features statement 

(shunting), Live bottoms, (Pinnacle Trend) map, Live bottoms (low relief) map, potentially sensitive 

biological features map. 

 (6g) Remotely Operated Vehicle (ROV) Monitoring Plan

In accordance with the provisions of NTL No. 2008-G06, Remotely Operated Vehicle Surveys in Deepwater, 

Garden Banks 427 is located in Grid 6. Grid 6 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. 

(6h) Threatened and Endangered Species Information

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

habitat for these species has been designated in the Gulf of Mexico. 

Common Name Scientific Name T/E Status

Hawksbill Turtle Eretmochelys imbricata E 

Green Turtle Chelonia mydas T 

Kemp's Ridley Turtle Lepidochelys kempii E 

Leatherback Turtle Dermochelys coriacea E 

Loggerhead Turtle Caretta caretta T 

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

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

critical habitat for these species has been designated in the Gulf of Mexico. 
Common Name Scientific Name T/E Status

Atlantic Spotted Dolphin Stenella frontalis 

Blainville's Beaked Whale Mesoplodon densirostris 

Blue Whale Balaenoptera musculus E 

Bottlenose Dolphin Tursiops truncatus 

Bryde's Whale Balaenoptera edeni 

Clymene Dolphin Stenella clymene 

Cuvier's Beaked Whale Ziphius cavirostris 

Dwarf Sperm Whale Kogia simus 

False Killer Whale Pseudorca crassidens 

Fin Whale Balaenoptera physalus E 

Fraser's Dolphin Lagenodelphis hosei 

Gervais' Beaked Whale Mesoplodon europaeus 

Humpback Whale Megaptera novaeangliae E 

Killer Whale Orcinus orca 

Melon-headed Whale Peponocephala electra 

Minke Whale Balaenoptera acutorostrata 

Northern Right Whale Eubalaena glacialis E 

Pantropical Spotted Dolphin Stenella attenuata 

Pygmy Killer Whale Feresa attenuata 

Pygmy Sperm Whale Kogia breviceps 

Risso's Dolphin Grampus griseus 

Rough-toothed Dolphin Steno bredanensis 

Sei Whale Balaenoptera borealis E 

Short-finned Pilot Whale Globicephala macrorhynchus 

Sowerby's Beaked Whale Mesoplodon bidens 

Sperm Whale Physeter macrocephalus E 

Spinner Dolphin (Long-snouted) Stenella longirostris 

Striped Dolphin Stenella coeruleoalba 

West Indian manatee Trichechus manatus E 

The EIA, EP Attachment 18, discusses potential impacts and mitigation measures related to 

threatened and endangered species. 

 (6i) Archaeological Report

Garden Banks 427 is on the list of blocks with a high probability for archeological resources. Enclosed are 

copies of the Fugro Geoservices, Inc. Archeological Assessment Report for Garden Banks 427 dated May 

2010. 

Per the archeological report, there are items of modern drilling debris such as drill pipe on the 

seafloor. One item is an unidentified contact measuring 25’ long by 25’ wide. This contact is a mud 

mat associated with former construction, shipping, or fishing activities. Its location is approximately 

X = 1822600; Y = 9995240. Previously drilled GB 471 Well # 1 is located at X = 1823472; Y = 

9994628. The mud mat and the well are outside the proposed radius. 

There are no landforms or identified features that might be high probability prehistoric sites, such as 

natural levees or point bar deposits. The regional probability for historic shipwrecks in this area is 

considered to be low. 
Within the study area, a modern day shipwreck, the shrimp boat Saint Mary sunk in 1990. Its 

coordinates are x = 1821348; Y = 10000919. The boat has a 750’ avoidance radius around it. A 

500’ avoidance buffer has been place along each existing pipeline. 

Shell will comply with all conditions of 2005-G07. 

(6j) Air and Water Quality Information

Pursuant to NTL No. 2008-G04 the proposed operations covered by this EP 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 the EIA, Attachment 18. 

(6k) Socioeconomic Information

Pursuant to NTL No. 2008-G04 the proposed operations covered by this EP 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 the EIA, Attachment 18. 

Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

7 Waste and Discharge Information

(7a) Projected Generated Wastes

Type of Waste Composition Projected Amount 

 

Spent Drilling 

Fluids 

Synthetic-based drilling muds 7,000 bbls/well 

Spent Drilling 

Fluids 

Water based drilling fluid 50,000 bbl/well 

Washed Cuttings 

from water based 

hole interval 

Cuttings coated with water based drilling muds 2500 bbls/well 

Washed Drill 

cuttings from 

synthetic based 

hole interval 

Drill cuttings 6,500 bbls/well 

Sanitary Waste Treated human body waste from toilets 87 bbls/day 

Domestic Waste Gray water (laundry, galley, lavatory) 215 bbls/day 

Produced water Formation water NA 

Excess cement Cement slurry 1000 bbls/well 

Desalination unit 

brine water 

Rejected water from watermaker unit 400 gals/day 

Deck drainage Platform washings and rainwater 10 bbls/hr 

Trash and debris Plastic, Paper, Aluminum, Glass, and other 

refuse 

1 cubic meter/day 

Cooling water Seawater with no addition of chemicals 130,600 bbls/day 

Fire water Seawater with no addition of chemicals 130,600 bbls/day 

Ballast water Uncontaminated seawater used to maintain 

proper draft 

3500 bbls/day (average) 

Blowout Preventer 

Fluid 

Stackmagic 200/0/5% 

glycol based on 2% mixture with potable water 

100 bbls/well 
(7b) Projected Ocean Discharges

Type of Waste Total Amount to be 

Discharged 

Discharge Rate Discharge Method 

Water based mud 50,000 bbls 1,714 bbls/hr Seafloor discharge prior 

to marine riser 

installation 

Washed Drill 

cuttings from 

synthetic based hole 

interval 

6,500 bbls 780 bbls/day 

maximum 

331 bbls/day while 

drilling only 

Shunt through a 

downpipe to 25’ below 

the water’s surface 

Synthetic based 

drilling fluid 

adhering to washed 

drill cuttings 

1,400 bbls 67 bbls/day while 

drilling only 

(maximum) 

Shunt through a 

downpipe to 25’ below 

the water’s surface 

Drill Cuttings from 

water base drilling 

interval 

2500 bbls 100 bbls/hr while 

drilling only 

Seafloor discharge prior 

to marine riser 

installation 

Chemical product 

waste 

NA NA NA 

Excess cement 900 bbls 900 bbls/well Discharged at the 

seafloor during riserless 

drilling 

Cooling water 15,672 kbbls 130,600 bbls/day Discharged overboard 

Sanitary waste 14,000 bbls 25 gal/person/day Treated in the MSD** 

prior to discharge to 

meet NPDES limits 

Domestic waste 42,000 bbls 75 gal/person/day Grinded to less than 25 

mm mesh size and 

discharge overboard 

Desalination unit 

brine water 

1,600 bbls/well 400 gals/day Discharged overboard 

Deck drainage 38,500 bbls 10 bbls/hr (dependent 

on rainfall) 

Discharged overboard 

Ballast water 560,000 bbls 3,500 bbls/day Discharged overboard 

Firewater Bypass 10,900 kbbls 130,600 bbls/day Discharged overboard 

(7c) Modeling Report

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

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

8 AIR EMISSIONS INFORMATION

(8a) Emissions Worksheet and Screening Questions 

Screening Questions for EP’s Yes No 

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

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

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

other air pollutants (where D distance to shore in miles)?

x

Do your emission calculations include any emission reduction measures or 

modified emission factors? x

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

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

(ppm)? x

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

From any proposed well? x

Do you propose to burn produced hydrocarbon liquids? x

(8b) If you answer no to all of the above screening questions from the appropriate table, provide: 

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

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

worksheets. You can submit either these summary forms or use the format below. You do not need 

to include the entire set of worksheets. 

Air Pollutant Plan 

Emission1 

Amounts 

(tons) 

Calculated 

Exemption2

Amounts 

(tons) 

Calculated 

Complex Total 

Emission 

Amounts3

(tons) 

PM 19.46 4329 19.46 

SOx 20.95 4329 20.95 

NOx 655.83 4329 655.83 

VOC 20.85 4329 20.85 

CO 143.05 87251.82 143.05 

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: Sylvia Bellone, (504) 728-7215, Sylvia.Bellone@ shell.com

(1) Worksheets

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

 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

9 OIL SPILLS INFORMATION

 (9a) Oil Spill Response Planning

(i) All the proposed activities and facilities in this EP 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 and is pending approval. 

 (ii) 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 

(iii) 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. 

(iv) Worst Case Scenario Determination 

Category Regional OSRP EP 

Type of Activity1 Drilling Rig Drilling Rig 

Facility Location (area/block) MC 391 GB 427 

Facility Designation2 Subsea wells Subsea wells 

Distance to Nearest Shoreline (miles) 72 137 

Volume3

Storage tanks (total) 

Flowlines (on facility) 

Pipelines 

Uncontrolled blowout (volume per day) 

Total Volume 

N/A 

N/A 

N/A 

405,000 BOPD 

405,000 Bbls 

N/A 

N/A 

N/A 

143,000* BOPD 

143,000 Bbls 

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

API Gravity(s)4 37.5o 24o 

*24 hour rate (131,000 BOPD 30 day average) 

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, submitted October 26, 2010, and since the worst-case scenario determined for our EP 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 EP. 

 
(9b) Oil Spill Response Discussion

A. Volume of the Worst Case Discharge 

Please refer to Section 2j of this EP 

B. 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 

GB 427 20 

Kleberg, TX 

Nueces, TX 

Aransas, TX 

Calhoun, TX 

Matagorda, TX 

Brazoria, TX 

Galveston, TX 

Jefferson, TX 

Cameron, LA 

Vermillion, LA 

Iberia, LA 

Terrebonne, LA 

Plaquemines, LA 

1% 

1% 

1% 

1% 

3% 

2% 

6% 

4% 

9% 

3% 

1% 

2% 

1% 

Table 9.C.1 Probability of Land Segment Impact 

C. Resource Identification 

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

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

appropriate National Oceanic and Atmospheric Administration (NOAA) Environmental Sensitivity Index 

(ESI) maps for the given land segment. ESI maps provide a concise summary of coastal resources that are at 

risk if an oil spill occurs nearby. Examples of at-risk resources include biological resources (such as birds and 

shellfish beds), sensitive shorelines (such as marshes and tidal flats), and human-use resources (such as public 

beaches and parks). 

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

reducing the environmental consequences of the spill and the cleanup efforts. Additionally, ESI maps can be 

used by planners to identify vulnerable locations, establish protection priorities, and identify cleanup strategies. 

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

impacted by the Cardamom WCD scenario. 

Onshore/Nearshore: 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. 

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 Cardamom 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: 

Garden Banks 427 

Calculations 

(BBLS) 

i. 30 Day Average WCD = 131,000 bbls 

ii. Subsurface dispersion – 25% (Water Depth = ~2,700) -32,700 bbls 

iii. REMAINING WCD AFTER SUBSURFACE DISPERSION 98,300 bbls 

iv. Surface dispersion and evaporation – 25% -24,500 bbls 

TOTAL REMAINING ~73,800 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. 

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

(MWCC), will have access to a fully integrated subsea well control and containment system that can be rapidly 

deployed through the MWCC. The Marine Well Containment System (MWCS) is designed to contain oil flow 

in the unlikely event of an underwater well blowout, address a variety of scenarios in the Gulf of Mexico, 

operate in deepwater depths up to 10,000 feet, and is capable of containing/collecting 100,000 barrels per day 

(4.2 million gallons per day). Furthermore, the equipment is designed, constructed, tested, and available for 

rapid response. 

 
By using lessons learned from the recent Gulf of Mexico subsea well blowout incident, the MWCS has been 

designed to have components that will be fully tested and maintained in a state of continuous readiness, 

including a knowledgeable deployment staff. Additionally the system is designed to be flexible and adaptable 

for a variety of potential future scenarios. Equipment will have the capability to be connected to the well or sea 

floor to provide full containment of the hydrocarbons for a multitude of scenarios in the Gulf of Mexico. It is 

designed to operate in a wide range of weather conditions, oil flow rates and is designed to be scalable to allow 

for future expansion. 

This system, when operational, will connect by risers to vessels that are designed to safely capture, store and 

offload the oil. This improves safety and environmental protection by fully securing the well via capping and 

shut-in or by containing the oil flow until the well is under control. It also enhances safe operations by 

reducing congestion (e.g. fewer vessels, risers / flowlines). MWCC equipment will include well containment 

assemblies, flowlines and risers, subsea utility modules (hydraulic power, hydrate control, dispersant injection) 

and marine capture vessels. 

The MWCC LLC is expected to be fully formed by the end of October 2010. Mutual aid agreements, formal 

contracts for the BP containment equipment, and other call-off contracts for necessary response vessels are 

expected to be in place by the end of December 2010. All these contracts and the functional specifications of 

the MWCS will be available for review by the BOEM at that point. Containment capability of the MWCC will 

include the near term capability from the BP equipment, other former BP responders, and mutual aid 

equipment from MWCC members as well as the MWCS as it is delivered in phases. These subsea well 

containment resources, systems, and equipment will include: 

Marine Vessels 

• Helix Producer 1 floating production unit 

• Helix Q-4000 DP3 mobile offshore drilling unit 

Subsea Containment Equipment: 

• GE Latching Cap 

• Flex joint overshot 

• 2 manifolds 

• 3” flexible pipe 

• 6” flexible pipe 

• Single valve manifold tree 

• Subsea shut-off device 

• Flex joint transition spool 

• Three ram capping stack 

• Subsea chokes 

Riser Systems: 

• 2 free standing riser systems 

• Drill string riser/ polished bore receptacle system 

• Light duty Intervention system (under mutual aid assistance) 

Subsea Utility Systems: 

• Hydrate injection system 

• Subsea autonomous dispersant injection (SADI) system 

• Subsea sourced dispersant injection system 

• Hydrate remediation system (under mutual aid assistance) 

• Subsea hydraulic accumulator and distribution system (under mutual aid assistance) 

In the interim until the full MWCS is in place and available, containment equipment from BP and other 

responders to the BP event will be available as it is retrieved and refurbished. 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. 

Any needed additional drill rigs or ships, remotely operated vessels and heavy lift installation vessels will be 

immediately contracted and available at the beginning of an incident. 

Appendix D of the OSRP contains a list of companies that Shell has under contract or through mutual aid 

agreements to provide all resources needed to provide subsea containment capabilities. 

 
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 865,993 barrels/day. Temporary 

storage associated with the identified skimming and temporary storage equipment equals approximately 

836,574 barrels. 

 

De-rated Recovery Rate 

(bopd) 

Storage 

(bbls) 

Offshore Recovery 476,365 273,400 

Offshore Storage 211,500 

Nearshore Recovery 106,993 17,224 

Total 583,298 502,124 

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

 Table 9.D.4 Offshore On-Water Recovery Activation List 

Table 9.D.5 Offshore On-Water Storage Activation List 

 Table 9.D.6 Nearshore On-Water Recovery Activation 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.7 Arial Surveillance Activation List 

Aerial Dispersant: Depending on proximity to shore and water depth, dispersants may be a viable response 

option. If appropriate and approved, 4 to 5 sorties from three DC-3’s can be made within the first 12 hour 

operating day of the response. These aerial systems could disperse approximately 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.8 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.9 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.10 Subsea Dispersant Package Activation List 

 
In-Situ Burning: Open-water in-situ burning (ISB) also may be used as a response strategy, depending on the 

circumstances of the release. ISB services may be provided by the primary OSRO contractors. If appropriate 

conditions exist and approvals are granted, one or multiple ISB task forces could be deployed offshore. Task 

forces typically consist of two to four fire teams, each with two vessels capable of towing fire boom, guide 

boom or tow line with either a handheld or aerially-deployed 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.11 In-Situ Burn Equipment Activation List 

Shoreline Protection: If the spill went unabated, shoreline impact in St. Bernard or Plaquemines Parish, LA 

would depend upon existing environmental conditions. Nearshore response may include the deployment of 

shoreline boom on beach areas, or protection and sorbent boom on vegetated areas. Strategies would be based 

upon surveillance and real time trajectories provided by The Response Group that depict areas of potential 

impact given actual sea and weather conditions. Strategies from the New Orleans, Louisiana Area Contingency 

Plan, The Response Group and Unified Command would be consulted to ensure that environmental and special 

economic resources would be correctly identified and prioritized to ensure optimal protection. The Response 

Group shoreline response guides depict the protection response modes applicable for oil spill clean-up 

operations. Each response mode is schematically represented to show optimum deployment and operation of 

the equipment in areas of environmental concern. Supervisory personnel have the option to modify the 

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

 Table 9.D.12 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 the following table: 

 Table 9.D.12 Shoreline Protection and Wildlife Support List 

(9c) Modeling Report

Shell did not model oil or hazardous substance spills. 

 
10 Environmental Monitoring Information

(10a) 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 

(10b) 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 No.2007-G03 “Marine Trash and Debris Awareness and Elimination” 

 NTL No.2007-G04 “Vessel Strike Avoidance and Injured/Dead Protected Species 

Reporting” 

(10c) Flower Garden Banks National Marine Sanctuary 

The operations proposed in this EP will not be conducted within the Protective Zones of the Flower Garden 

Banks and Stetson Bank. 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

11 Lease Stipulations Information

Lease OCS-G 7493 is not part of a Biological Sensitive Area, known Chemosynthetic Area, or Shipping 

Fairway. It is on the list of areas that the BOEM has identified as having a high probability for archeological 

resources. See Section 6i of this plan for site specific archeological information. 

12 Environmental Mitigation Measure Information

(12a) 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. The EIA attached as Section 18 to 

this plan discusses impacts and mitigation measures. 

(12b) 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 No.2007-G03 “Marine Trash and Debris Awareness and Elimination” 

NTL No.2007-G04 “Vessel Strike Avoidance and Injured/Dead Protected Species Reporting”

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 EP as such information is only necessary in 

the case of DOCDs. 

 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

14 Support Vessels and Aircraft Information

(14a) General 

Type Maximum Fuel Tank Storage 

Capacity 

Maximum No. In Area at Any 

Time 

Trip Frequency or 

Duration 

Crew Boats 405 2 Twice per week 

Offshore Support Vessels 7952 3 Twice per week 

Tug Boats 5750 2 Once per rig move 

Anchor Handling Vessel 8995 3 Once per rig move 

Helicopter 18.2 (or 764 Gals) 1 Once per day 

(14b) Diesel Oil Supply Vessels 

Size of Fuel Supply 

Vessel 

Capacity of Fuel Supply 

Vessel 

Frequency of Fuel 

Transfers 

Route Fuel Supply Vessel Will 

Take 

280 foot length 7952 1 week Port Fourchon to GB 427 

(14c) Drilling Fluids Transportation 

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 Drums on St. Mary Mud 

Company's supply boat 

Water Based drilling 

fluids 

12,000 bbls max per voyage Below deck liquid mud 

tanks onboard OSV 

(14d) Solid and Liquid Wastes Transportation 

Type of Waste 

Approx. Composition 

Total 

Amount 

Name/Location Rate Transport Method 

Synthetic drilling mud 7000 

bbls/well 

Halliburton Baroid, At end of well Tanks on Boats 

Chemical products 

and general hazardous 

waste 

100 

bbls/year 

Safety Kleen System Inc. 

Denton, TX 76208 

or 

Lamp Environmental Industries 

Hammond, LA 

4 bbls/day Drums on work boats 

Trash and debris 

(Non-recyclables) 

118 

bbls/month 

Newpark Environmental 

Services Inc. 

Ingleside, TX 

or 

Bridge City, TX 

7 bbls/day Storage bins on crew boat 

Trash and debris 

(recyclables) 

60 

bbls/month 

Omega Waste Management Inc 

1900 Hwy 90 West Patterson, 

LA 70392 

or 

ARC 

New Iberia, LA 

3 bbls/day Storage bins on crew boat 

(14e) Vicinity Map 

See Attached. 

Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

15 Onshore Support Facilities Information

(15a) General 

Name Location Existing/New/Modified 

Fourchon Port Fourchon, LA Existing 

Amelia PHI Heliport Boothville, 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 Leesville, 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, Morgan City, LA 70380. 

(15b) Support Base Construction or Expansion 

This Section does not apply to this EP as Shell does not plan to construct a new onshore support base or 

expand an existing one to accommodate the activities proposed in this EP. 

(15c) Support Base Construction or Expansion Timetable 

This Section does not apply to this EP as Shell does not plan to construct a new onshore support base or 

expand an existing one to accommodate the activities proposed in this EP. 

(15d) Waste Disposal 

Name/Location of 

Facility 

Type of Waste Amount Rate Disposal Method 

182 N. Doucet 

Drive, Golden 

Meadow, Louisiana, 

LA 70367 

Synthetic Drilling Mud 6500 bbls/ well N/A Recycled 

Newpark 

Environmental 

Services Inc 

Ingleside or Bridge 

City, TX 

Non-hazardous 

Trash and Debris 

Non-Recyclables 

118 bbls/month 7 bbls/day Land farmed 

Safety Kleen System 

Inc 

Denton, TX 

Paint, solvents, unused 

chemicals, etc 

730 bbls/yr 2 bbls/day Hazardous waste 

disposal 

U. S. Filter 

New Orleans, LA 

Used Oil & Glycol 3650 bbls/yr 10 bbls/day Recycled 

Lamp 

Environmental 

Industries, Inc. 

Hammond, LA 

Batteries, lamps, glass, 

mercury 

24 bbls/yr 2 bbls/month Recycled 

Omega Waste 

Management Inc 

Patterson, LA 

Oil Filters, rags, pads, 

empty drums, cooking 

oil 

60 bbls/yr 5 bbls/month Recycled 

ARC 

New Iberia, LA 

Non-hazardous 

Trash and Debris 

Recyclables 

90 bbls/month 3 bbls/day Recycled 
Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

16 Sulphur Operations Information

Information regarding Sulfur Operations Information is not included in this SEP as such information is 

only necessary in the case of DOCDs. 

17 Coastal Zone Management Act (CZMA) Information

LOUISIANA

COASTAL ZONE MANAGEMENT 

CONSISTENCY CERTIFICATION 

SUPPLEMENTAL EXPLORATION PLAN 

Type of Plan 

 

Garden Banks Block 427

Area and Blocks 

OCS-G 07493

 Lease Numbers 

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

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

Policies. 

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

SHELL OFFSHORE INC. (SOI)

Operator 

_____________________________________________ 

Sylvia A. Bellone 

Certifying Official 

 10/28/2010 

Date 

I-1 

 
TEXAS

COASTAL ZONE MANAGEMENT 

CONSISTENCY CERTIFICATION 

Supplemental Exploration Plan

Type of Plan 

Garden Banks Block 427

Area and Blocks 

 OCS-G 07498

Lease Numbers 

The proposed activities described in detail in this Plan will comply with Texas’ State and Local Coastal 

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

Policies. 

/ 

SHELL OFFSHORE INC. (SOI)

Operator 

____________________________ 

Sylvia A. Bellone 

Certifying Official 

 10/28/2010 

Date 

I-2
Coastal Zone Management Consistency Information 

For the State of Texas 

In accordance with Subpart E of 15 CFR 903 “Consistency for Outer Continental Shelf (OCS) Exploration, 

Development and Production Activities” and as required by 15 CFR 930.58, Shell Offshore INC (SOI) is 

hereby providing the following information in support of the Environmental Impact Analysis submitted as 

Attachment 18 of our Supplemental EP for GB 427. 15 CFR 930.58 identifies necessary data and information 

to be furnished to the State agency. The information is as follows: 

(a) CONSISTENCY CERTIFICATION

A Coastal Zone Consistency Certification for activities that affect the State of Texas is provided above. 

OTHER INFORMATION

A detailed description of the proposed activities, coastal effects, and comprehensive information sufficient to 

support this Consistency Certification is presented in the above-mentioned EP. As per NTL 2008-G04, the 

following items have been identified as being required: 

• A discussion of the method of disposal of wastes and discharges is provided in Attachment 7 of the 

above-mentioned EP. 

• Oil Spill Information is provided in Attachment 9 of the above-mentioned EP. All operations are 

covered by Shell Offshore Inc's Regional Oil Spill Response Plan, which is being updated with the 

BOEM. The Plan is available upon request. 

(2) Following is an evaluation that includes findings relating the coastal effects of the proposed activities 

and associated facilities to the relevant enforceable policies of the Texas’ Coastal Management Program

(TCMP), Title 31, Part 16, Chapter 501, Subchapter B:

(Category 2) 

Construction, Operation & Maintenance of Oil & Gas Exploration & Production 

Facilities 

No operations are proposed in or near any critical areas. The proposed activities are explorative in nature, so 

no facility construction is proposed. The proposed activities are located approximately 170 miles from the 

Texas shoreline; therefore we expect no adverse impacts to CNRAs or beach access and use rights of the 

public. All activities shall be conducted in a manner that minimizes significant impacts to coastal resources. 

No adverse effects to Texas’ coastal area are expected in association with the proposed activities. 

(Category 3) 

Discharges of Wastewater and Disposal of Waste from Oil and Gas Exploration and Production 

Activities 

No discharge of wastewater or disposal of waste from the proposed activities will occur in the Texas’ coastal 

zone, therefore no impact to Texas’ coastal waters is expected. 

(Category 4) 

Construction and Operation of Solid Waste Treatment, Storage, and Disposal 

Facilities 

No construction of solid waste facilities or expansion of existing facilities in the coastal zone are proposed in 

the attached plan, therefore, no adverse effects on any features of Texas’ coastal cone are expected. 
(Category 5) 

Prevention, Response, and Remediation of Oil Spills 

The proposed activities will be covered under an approved Regional Oil Spill Response Plan. The plan is in 

place, practiced, and updated as necessary. The best practical techniques shall be utilized to prevent the release 

of pollutants or toxic substances into the environment. All involved vessels and facilities are designed to be 

capable of prompt response and adequate removal of accidental discharges of oil. In addition, the proposed 

activities are 170 miles from shore; therefore no damages to natural resources are expected as the result of an 

unauthorized discharge of oil into coastal waters. 

(Category 6) 

Discharge of Municipal and Industrial Waste Water to Coastal Waters 

No discharges from the proposed activities will occur in coastal waters. The proposed activities are 170miles 

from shore, therefore there will be no effect on coastal waters. 

(Category 8) 

Development in Critical Areas 

None of the proposed activities will occur in a critical area; therefore no effects to Texas’ coastal zone are 

expected. The activity will not jeopardize the continued existence of species listed as endangered or 

threatened, and will not result in likelihood of the destruction or adverse modification of a habitat determined 

to be a critical habitat under the Endangered Species Act. The activity will not cause or contribute to violation 

of any applicable surface water quality standards. The activity will not violate any requirement imposed to 

protect a marine sanctuary. 

(Category 9) 

Construction of Waterfront Facilities and Other Structures on Submerged lands 

No waterfront facilities or other structures are proposed on submerged lands in the Texas coastal zone, 

therefore the proposed activities are not expected to have any adverse impacts on submerged lands. 

(Category 10) 

Dredging and Dredged Material Disposal and Placement 

No dredging or disposal/placement of dredged material is proposed, therefore no adverse effects to coastal 

waters, submerged lands, critical areas, coastal shore areas, or Gulf beaches are expected. 

(Category 11) 

Construction in the Beach / Dune System 

The proposed activities do not include any construction projects in critical dune areas or areas adjacent to or on 

Gulf beaches, therefore, no impact to Texas’ beach or dune systems are expected. 

(Category 15) 

Alteration of Coastal Historic Areas 

The proposed activities do not include any alteration or disturbance of a coastal historic area; therefore, no 

impacts to are expected to adversely affect any historical, architectural, or archaeological site in Texas’ coastal 

zone. 

(Category 16) 

Transportation 

The proposed activities do not include any transportation construction projects within the coastal zone; 

therefore, no impacts to Texas’ coastal zone are expected. 
(Category 17) 

Emission of Air Pollutants 

The proposed activities shall be carried out in conformance with applicable air quality laws, standards, and 

regulations. Emissions from the proposed activities are not expected to have significant impacts on onshore 

air quality because of the prevailing atmospheric conditions, emission heights, emission rates, and the distance 

of these emissions from the coastline. The proposed activities will occur approximately 170 miles from shore 

and will be within the exemption limits set by BOEM, therefore, no impacts to Texas’ coastal zone is expected. 

(Category 18) 

Appropriations of Water 

The proposed activities do not include the impoundment or diversion of state water, therefore, no impacts to 

Texas’ coastal zone is expected. 

(Category 20) 

Marine Fishery Management 

The proposed activities are located approximately 170 miles from shore and are not expected to have any 

effect on marine fishery management or fishery migratory patterns within waters in the coastal zone of Texas. 

(Category 22) 

Administrative Policies 

The necessary information for applicable agencies to make an informed decision on the proposed activities has 

been provided 

In conclusion, all activities shall be consistent with Texas’ coastal management program and shall comply with 

all relevant rules and regulations. No activities are planned within any critical areas. Activities will be carried 

out avoiding unnecessary conflicts with other uses of the vicinity.

 

 

I-3

18. Environmental Impact Analysis (EIA)
Environmental Impact Analysis

Supplemental Exploration Plan

Garden Banks Area

Block 427 (OCS‐G 7493)

27 October 2010

Prepared for:

Sylvia Bellone

Shell Offshore Inc.

P. O. Box 61933

New Orleans, Louisiana  70161

Telephone: (504) 728‐7215

Prepared by:

CSA International, Inc.

8502 SW Kansas Avenue

Stuart, Florida  34997

Telephone: (772) 219‐3000
Garden Banks Block 427 (Lease OCS‐G 7493)    October 2010

Environmental Impact Analysis for Supplemental Exploration Plan Page ii

Contents

Page

INTRODUCTION ................................................................................................................................... 1

Project Summary ..................................................................................................................................... 1

Purpose of the EIA ................................................................................................................................... 1

OCS Regulatory Framework..................................................................................................................... 3

Oil Spill Prevention and Contingency Planning........................................................................................ 3

EIA Organization ...................................................................................................................................... 3

A.  IMPACT‐PRODUCING FACTORS ....................................................................................................... 5

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

A.2 Physical Disturbance to the Seafloor............................................................................................... 5

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

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

A.5 Water Intake .................................................................................................................................... 8

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

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

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

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

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

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

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

A.9.4 Other Accidents Not Analyzed in Detail .............................................................................. 13

B.  AFFECTED ENVIRONMENT............................................................................................................. 14

C.  IMPACT ANALYSIS ......................................................................................................................... 16

C.1 Physical/Chemical Environment .................................................................................................... 16

C.1.1 Air Quality............................................................................................................................ 16

C.1.2 Water Quality ...................................................................................................................... 18

C.2 Seafloor Habitats and Biota ........................................................................................................... 20

C.2.1 Soft Bottom Communities................................................................................................... 21

C.2.2 High‐Density Deepwater Benthic Communities.................................................................. 23

C.2.3 Designated Topographic Features....................................................................................... 25

C.2.4 Pinnacle Trend Area Live Bottoms ...................................................................................... 25

C.2.5 Eastern Gulf Live Bottoms................................................................................................... 25

C.3 Threatened, Endangered, and Protected Species and Critical Habitat ......................................... 26

C.3.1 Sperm Whale (Endangered) ................................................................................................ 27

C.3.2 Florida Manatee (Endangered) ........................................................................................... 30

C.3.3 Other Marine Mammals (Protected)................................................................................... 32

C.3.4 Sea Turtles (Endangered/Threatened)................................................................................ 34

C.3.5 Piping Plover (Threatened).................................................................................................. 37

C.3.6 Whooping Crane (Endangered)........................................................................................... 38

C.3.7 Gulf Sturgeon (Threatened) ................................................................................................ 39
Contents

(continued)

Page

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Environmental Impact Analysis for Supplemental Exploration Plan Page iii

C.3.8 Beach Mice (Endangered) ................................................................................................... 40

C.4 Coastal and Marine Birds............................................................................................................... 41

C.4.1 Marine and Pelagic Birds..................................................................................................... 41

C.4.2 Shore Birds and Coastal Nesting Birds................................................................................. 43

C.5 Fisheries Resources........................................................................................................................ 45

C.5.1 Pelagic Communities and Ichthyoplankton......................................................................... 45

C.5.2 Essential Fish Habitat........................................................................................................... 48

C.6 Archaeological Resources.............................................................................................................. 51

C.6.1 Shipwreck Sites.................................................................................................................... 51

C.6.2 Prehistoric Archaeological Sites .......................................................................................... 52

C.7 Coastal Habitats and Protected Areas........................................................................................... 53

C.8 Socioeconomic and Other Resources............................................................................................ 55

C.8.1 Recreational and Commercial Fishing ................................................................................. 55

C.8.2 Public Health and Safety...................................................................................................... 57

C.8.3 Employment and Infrastructure.......................................................................................... 58

C.8.4 Recreation and Tourism ...................................................................................................... 59

C.8.5 Land Use .............................................................................................................................. 60

C.8.6 Other Marine Uses .............................................................................................................. 60

C.9 Cumulative Impacts ....................................................................................................................... 61

C.9.1 Cumulative Impacts to Physical /Chemical Resources........................................................ 62

C.9.2 Cumulative Impacts to Biological Resources....................................................................... 63

C.9.3 Cumulative Impacts to Socioeconomic Resources.............................................................. 65

D.  ENVIRONMENTAL HAZARDS ......................................................................................................... 66

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

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

D.3 Currents and Waves....................................................................................................................... 67

E.  ALTERNATIVES .............................................................................................................................. 67

F.  MITIGATION MEASURES................................................................................................................ 67

G.  CONSULTATION ............................................................................................................................ 68

H.  PREPARERS ................................................................................................................................... 68

I.  REFERENCES................................................................................................................................... 68
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Environmental Impact Analysis for Supplemental Exploration Plan Page iv

List of Tables

Table Page

1 Notices to Lessees and Operators (NTLs) that are referenced in this EIA............................. 4

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

3 Conditional probabilities of a spill in Garden Banks Block 427 contacting shoreline

segments (From: Ji et al., 2004) .......................................................................................... 12

4 Federally‐listed endangered and threatened species in the lease area and along

the northern Gulf coast....................................................................................................... 26

List of Figures

Figure Page

1 Location of Garden Banks Block 427 ..................................................................................... 2

2 Bathymetric map of Garden Banks Block 427..................................................................... 15
Garden Banks Block 427 (Lease OCS‐G 7493)    October 2010

Environmental Impact Analysis for Supplemental Exploration Plan Page 1

Introduction

Project Summary

Shell Offshore Inc. (Shell) is submitting a Supplemental Exploration Plan (EP) for Garden Banks

Block 427 (GB 427) that includes drilling of up to three (3) exploration wells using a

semisubmersible rig.  GB 427 is approximately 209 km (130 mi) from the nearest coastline

(Louisiana), 278 km (173 mi) from the supply base at Port Fourchon, Louisiana, and 262 km

(163 mi) from the helicopter terminal at Amelia, Louisiana (Figure 1).  Water depth at the well

locations is 829 m (2,721 ft).  Drilling of each well is estimated to require 160 days.

Purpose of the EIA

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

Outer Continental Shelf Lands Act (OCSLA), 43 U.S.C. §§ 1331‐1356, and the regulations of the

Bureau of Ocean Energy Management, Regulation and Enforcement (BOEM, formerly Minerals

Management Service [MMS]), including 30 CFR 250.212(o) and 250.227.  This 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 Lessees (NTL) 2008‐G04 issued by the

BOEM.  The EIA presents data, analysis, and conclusions to assist the BOEM in complying with

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 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 this EP to the extent feasible.  BOEM has performed numerous environmental evaluations

of oil and gas activities in the Gulf of Mexico Outer Continental Shelf (OCS).  Potential impacts

have been 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 Planning Areas (MMS, 2007b, 2008), as well as the Environmental

Assessment for Gulf of Mexico deepwater operations and activities (MMS, 2000).

These studies provide data and a large body of knowledge on the Gulf of Mexico OCS.  They

analyze everything from potential impacts on the natural environment to the socioeconomic

effects of exploration 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 BOEM and

other regulatory agencies to evaluate Shell’s EP and ensure that oil and gas exploration

activities are performed in an environmentally sound manner, with minimal impacts to the

environment.  Shell has incorporated these comprehensive environmental analyses by

reference and built on them with project‐specific and site‐specific analyses.

Baseline environmental conditions in the northern Gulf of Mexico have been affected recently

by the Macondo well spill in Mississippi Canyon Block 252 and associated remediation efforts.  

The impacts of the spill are currently under investigation, and the best available information

does not provide a complete understanding of its effects at this time.  Macondo spill impacts

are addressed in Section C.9 (Cumulative Impacts) where available and applicable.
Garden Banks Block 427 (Lease OCS‐G 7493) 

Environmental Impact Analysis for Supplemental Exploration Plan 

Figure 1. Location of Garden Banks Block 427.
Garden Banks Block 427 (Lease OCS‐G 7493)    October 2010

Environmental Impact Analysis for Supplemental Exploration Plan Page 3

OCS Regulatory Framework

The regulatory framework for OCS activities in the Gulf of Mexico has been summarized by

MMS (2010).  Under the OCSLA, the U.S. Department of the Interior (USDOI) is responsible for

the administration of mineral exploration and development of the OCS.  Within the USDOI, the

BOEM is charged with the responsibility of managing and regulating the development of OCS

oil and gas resources in accordance with the provisions of the OCSLA.  The BOEM operating

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

In implementing its responsibilities under the OCSLA, the BOEM must consult with 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 specific consultation and coordination

processes with Federal, State, and local agencies (i.e., the ESA, MMPA, Coastal Zone

Management Act of 1972 [CZMA], and the Magnuson‐Stevens Fishery Conservation and

Management Act [MSFCMA]).

NTLs are formal documents issued by the BOEM that provide clarification, description, or

interpretation of a regulation or standard; provide guidelines on the implementation of a

special lease stipulation or regional requirement; provide a better understanding of the scope

and meaning of a regulation by explaining BOEM interpretation of a requirement; or transmit

administrative information such as current telephone listings and a change in BOEM personnel

or office address.  Table 1 lists and summarizes the NTLs that are referenced in this EIA.

Oil Spill Prevention and Contingency Planning

Shell has prepared a Gulf of Mexico Regional Oil Spill Response Plan (OSRP) as a fundamental

component of the planned drilling program (submitted to the BOEM as a separate document).  

The OSRP demonstrates Shell’s capabilities to rapidly and effectively manage oil spills that may

result from exploratory drilling operations.  Despite the extremely low likelihood of a large oil

spill event occurring during exploration, 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 worst case discharge (WCD) from an exploration 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.  The main impact‐related discussions are in Section A (Impact‐Producing

Factors) and Section C (Impact Analysis).
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Environmental Impact Analysis for Supplemental Exploration Plan Page 4

Table 1. Notices to Lessees and Operators (NTLs) that are referenced in this EIA.

NTL Title Summary

2010‐N06 Information Requirements

for Exploration Plans,

Development and

Production Plans, and

Development Operations

Coordination Documents

on the OCS

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

scenario and worst case discharge scenario, and provides guidance

regarding the information required in blowout scenario and worst

case discharge scenario descriptions.

2010‐N05 Increased Safety

Measures for Energy

Development on the OCS

Requires operators to submit (1) a general statement by the

operator’s Chief Executive Officer certifying the operator’s compliance

with all operating regulations at 30 CFR 250 and (2) a separate

statement certifying compliance with four specific safety items.  

Operators using a subsea blowout preventer (BOP) or a subsea BOP

stack on a floating platform are required to submit additional BOP

configuration and well control system information.

2009‐G40 Deepwater Benthic

Communities

Guidance for avoiding and protecting high‐density deepwater benthic

communities (including chemosynthetic and deepwater coral

communities) from damage caused by Outer Continental Shelf (OCS)

oil and gas activities in water depths greater than 300 m (984 ft).

Prescribes separation distances of 610 m (2,000 ft) from each mud and

cuttings discharge location and 76 m (250 ft) from all other seafloor

disturbances.

2009‐G39 Biologically‐Sensitive

Underwater Features and

Areas

Guidance for avoiding and protecting biologically sensitive features

and areas (i.e., topographic features, pinnacles, low‐relief live bottom

areas, and other potentially sensitive biological features) when

conducting OCS operations in water depths less than 300 m (984 ft) in

the Gulf of Mexico.

2009‐G06 Military Warning and

Water Test Areas

Provides contact links to individual command headquarters for the

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

stipulations require lessees or designated operators to enter into an

agreement with the appropriate individual military command

headquarters concerning the control of electromagnetic emissions and

use of boats and aircraft in the applicable warning area or water test

area before commencing such traffic.

2008‐G04 Information Requirements

for Exploration Plans and

Development Operations

Coordination Documents

Guidance on the information requirements for OCS plans, including

EIA requirements and information regarding compliance with the

provisions of the Endangered Species Act and Marine Mammal

Protection Act.

2007‐G04 Vessel Strike Avoidance

and Injured/Dead

Protected Species

Reporting

Recommends protected species identification training, recommends

that vessel operators and crews maintain a vigilant watch for marine

mammals and slow down or stop their vessel to avoid striking

protected species, and requires operators to report sightings of any

injured or dead protected species.

2007‐G03 Marine Trash and Debris

Awareness and

Elimination

Instructs operators to exercise caution in the handling and disposal of

small items and packaging materials; requires the posting of placards

at prominent locations on offshore vessels and structures; and

mandates a yearly marine trash and debris awareness training and

certification process.

2005‐G07 Archaeological Resource

Surveys and Reports

Provides guidance on regulations regarding archaeological discoveries,

specifies requirements for archaeological resource surveys and

reports, and outlines options for protecting archaeological resources.
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Environmental Impact Analysis for Supplemental Exploration Plan Page 5

A.  Impact‐Producing Factors

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

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

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

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

proposed activity are listed below and discussed briefly 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 exploration wells will be drilled using a moored semisubmersible such as the Noble Jim

Thompson or a similar drilling rig.  The rig will be onsite for an estimated 160 days per well.

The physical presence of a floating structure in the ocean can attract pelagic fishes and other

marine life as discussed in Section C.5.1.  The Noble Jim Thompson has hull dimensions of

106 x 100 x 40 m (349 x 328 x 130 ft) and an operating draft of 24 m (79 ft).  

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 and be towed by tugs.

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 paths to

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

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

regulations.

A.2 Physical Disturbance to the Seafloor

The drilling rig will be held in place by up to 12 suction pile anchors deployed within a 4,420‐m

(14,500‐ft) permitted radius around the wellsites.  The suction pile system reduces seabed

disruption because suction piles are placed accurately and not dragged across the seafloor.  

The total seafloor disturbance area is estimated to be 490 ha (1,210 ac) per well.  Cables will

be resting on the seafloor only during the pre‐ and  post‐installation phase; once the rig arrives

on location, cables are pulled taut towards the rig.  The cables do not sweep the seafloor or

cross any sensitive features, and therefore are expected to have little or no physical impact on

the seafloor.
Garden Banks Block 427 (Lease OCS‐G 7493) 

Environmental Impact Analysis for Supplemental Exploration Plan Table 2. Matrix of impact‐producing factors and affected environmental resources. X = potential impact; dash (‐‐) = no i

Environmental Resources

Impact‐producing Factors for Routine Activities

Drilling Rig

Presence (incl.

noise & lights)

Physical

Disturbance

to Seafloor

Air

Pollutant

Emissions

Effluent

Discharges

WaterIntake

Onshore

Waste

Disposal

Marine

Debris

Sup

Vesse

Tra

Physical/Chemical Environment

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

Seafloor Habitats and Biota

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

Threatened, Endangered, and Protected Species

Sperm whale (endangered) X(8) ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ X(8) XFlorida manatee (endangered)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ X(8) XOther marine mammals (protected) X ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ X Sea turtles (endangered/threatened) X(8) ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ X(8) XPiping Plover (threatened)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Whooping Crane (endangered)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Gulf sturgeon (threatened)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Beach mice (endangered)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ 

Coastal and Marine Birds

Marine and pelagic birds X ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ X Shore birds and coastal nesting birds  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ X 

Fisheries Resources

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

Archaeological Resources

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

Coastal Habitats

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

Socioeconomic and Other Resources

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

WCD = worst case discharge.
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Environmental Impact Analysis for Supplemental Exploration Plan Page 7

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 BOEM as being in water depths 300 m or greater.

• No impacts on chemosynthetic communities or deepwater corals are anticipated.  There are no features

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

any drilling mud/cuttings discharge.  Anchor avoidance zones (150 m or 500 ft) have been established

around four amplitude and fluid expulsion features on the crest of the Auger diapir (dome) that could

support chemosynthetic and/or deepwater coral communities.

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

• Not applicable.  Shell is requesting that BOEM classify the lease as “H2S absent.”

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

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

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

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

analyzed in Section C.

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

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

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

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

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

• No impacts on archaeological resources are expected.  Because the lease is on the list of high‐probability

blocks for shipwrecks, an archaeological assessment was conducted.  A 229‐m (750‐ft) avoidance radius

has been established around a modern day shipwreck (the shrimp boat Saint Mary, sunk in 1990).  The

lease is beyond the 60‐m depth contour and therefore prehistoric archaeological sites are not likely;

further, no landforms or features were identified that might be high probability prehistoric sites.

(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 operations, and accidents.  See Section C.

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

• Not applicable.
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Environmental Impact Analysis for Supplemental Exploration Plan Page 8

A.3 Air Pollutant Emissions

Air pollutant emissions are estimated in EP Section 8.  Offshore air pollutant emissions will

result from the operations of the drilling rig , as well as service vessels and helicopters.  These

emissions occur mainly from combustion of diesel fuel.  The combustion of fuels occurs on

diesel‐powered generators, pumps, or motors and from lighter fuel motors.  Primary air

pollutants typically associated with OCS activities are suspended particulate matter (PM),

sulfur oxides (SOx), nitrogen oxides (NOx), volatile organic compounds (VOCs), and carbon

monoxide (CO).  

The Air Quality Emissions Report prepared in accordance with BOEM requirements shows that

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

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

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

use low sulfur fuel (0.05% by weight) to further reduce any possible impacts.

A.4 Effluent Discharges

Effluent discharges are summarized in 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

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

drilling operations.

A synthetic‐based drilling fluid (SBF) system will be used after the riser is installed.  The SBF will

not be discharged but will be recovered and transported to the shore base for recycling by the

mud company.  SBF cuttings will be discharged overboard after treatment with a cuttings

dryer, which is expected to reduce retention on cuttings to well below the NPDES permit

requirement of 6.9%.

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 the ocean for once‐through, non‐contact cooling of machinery on

the drilling rig.  The estimate intake and discharge of cooling water is 130,600 barrels (bbl) per

day (BPD) (5.5 million gallons per day [MGD]).  The rig will also use another 130,600 BPD for

fire water.

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.  Final regulations for Phase III facilities were published in

June 2006 and apply to new offshore oil and gas facilities designed to use more than 2 MGD, of
Garden Banks Block 427 (Lease OCS‐G 7493)    October 2010

Environmental Impact Analysis for Supplemental Exploration Plan Page 9

which at least 25 percent is for cooling.  The current general NPDES permit No. GMG 290000

specifies for new facilities (those that started construction after 16 July 2006) that (1) the

cooling water intake structure must be designed and constructed so that the maximum

through‐screen design intake velocity is 0.5 ft/s, and (2) the operator must minimize

impingement mortality of fish and shellfish and minimize entrainment of entrainable life

stages of fish and shellfish through the use of cooling water intake design and construction

technologies or operational measures.   The rig planned for use in this EP is not a “new” facility

as defined by the NPDES permit and therefore is not subject to the cooling water intake

regulations.

A.6 Onshore Waste Disposal

Wastes generated during drilling are tabulated in EP Section 7.  Volumes are estimated to be

118 bbl/month for non‐recyclables and 60 bbl/month for recyclables.  This includes plastic,

paper, aluminum, glass, food, and other refuse.  Non‐recyclable trash will be transported to

Newpark Environmental Services, Inc. (Ingleside or Bridge City, Texas).  Recyclables will be

transported to Omega Waste Management Inc. (West Patterson, Louisiana) or ARC (New

Iberia, 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 MMS regulations and NTLs regarding solid wastes.  BOEM

regulations at 30 CFR 250.300(a) and (b)(6) prohibit operators from deliberately discharging

containers and other similar materials (i.e., trash and debris) into the marine environment, and

30 CFR 250.300(c) requires durable identification markings on equipment, tools and containers

(especially drums), and other material.  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 that instructs operators to exercise caution in the

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

at prominent locations on offshore vessels and structures, and mandates a yearly marine trash

and debris awareness training and certification process.

A.8 Support Vessel and Helicopter Traffic

During drilling, the project will be supported by two crew boats and three supply vessels, each

making three round‐trips per week between the drilling rig and the onshore support base in

Port Fourchon, Louisiana.  The specific vessels will vary, but the crew boats will typically be

47 m (155 ft) in length and the supply boats typically will range from 73 to 85 m (240 to 280 ft).  

The boats will normally move to the project area via the most direct route from the Port

Fourchon facility.
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Environmental Impact Analysis for Supplemental Exploration Plan Page 10

Two tug boats and three anchor handling vessels will assist in bringing the rig to the lease area,

mooring it, and removing the drilling rig and anchors after drilling.  The anchor handling

vessels are expected to be the Laney Chouest (106 m [348 ft]), Dino Chouest (106 m [348 ft]),

and Ross Chouest (80 m [262 ft]).

A helicopter will make one round‐trip daily between the drilling rig and the support base in

Amelia, Louisiana.  The helicopter will be used to transport personnel and small supplies and

will normally take the most direct route of travel between Amelia and the project area when

air traffic and weather conditions permit.  Helicopters typically maintain a minimum altitude of

213 m (700 ft) while in transit offshore, 305 m (1,000 ft) over unpopulated areas or across

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

refuges and park properties.

Shell will use existing shore base facilities at both locations; no terminal expansion or

construction is planned.

A.9 Accidents

A.9.1 Types of Accidents Evaluated

The analysis in this EIA focuses on two potential accidents:

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

• The worst case discharge (WCD) for this EP, calculated in accordance with NTL 2010‐N06,

which is a crude oil spill of 143,000 BPD resulting from a well blowout.

The following subsections summarize assumptions about the size and fate 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 Planning Areas (MMS, 2007b).  The average

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

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

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

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

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

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

However, given the open ocean location of the lease area, the duration of a small spill and the

opportunity for impacts to occur would be very brief.

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

aromatic hydrocarbons (PAH), which are moderately volatile (National Research Council [NRC],

2003).  The constituents of these oils are light to intermediate in molecular weight and can be
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readily degraded by aerobic microbial oxidation.  Diesel is so light that it will not sink to the

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

generally only occurs 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 0.5 to 5 ha (1.2 to 12 ac) depending on sea state and

weather conditions.

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

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

GB 427 is approximately 209 km (130 mi) from the nearest coastline (Louisiana).  Modeling

results discussed below indicate that a spill in the lease area would not contact any shoreline

within 3 days after a spill.  By this time, essentially 100% of a small fuel spill would have been

dispersed or evaporated by natural processes, without taking into account Shell’s response

measures.  MMS (2007b) similarly concluded that spills <1,000 bbl are not expected to persist

as a slick on the surface of the water beyond a few days and are unlikely to make landfall or

reach coastal waters prior to breaking up.  MMS (2007b) noted that this conclusion is

supported by a previous analysis of 3‐day trajectory model runs, previous weathering analyses,

and historical records of spill incidents.

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

fuel spill, response equipment and trained personnel would be available to ensure that any

spill effects are localized and would result only in short‐term environmental consequences.  

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

A.9.3 Crude Oil Spill (Worst Case Discharge)

Spill Size.  In accordance with requirements of NTL 2010‐N06, Shell has estimated a worst case

discharge of 143,000 BPD of crude oil from a well blowout.  The detailed analysis of this

calculation can be found in EP Section 2j.

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

estimated a probability of 0.0021 for a 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.

Shell has a robust system in place to prevent blowouts.  Included in 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‐N05 and the Interim Final Drilling

Safety Rule, which specify increased safety measures for OCS activities.
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Spill Trajectory.  The fate of a large oil spill in the lease area would depend on meteorological

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

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

predict spill fate.  The OSRA report by Ji et al. (2004) provides conditional contact probabilities

for shoreline segments.  The results for Launch Area 20 (where GB 427 is located) are

presented in Table 3.  The model predicts no shoreline contacts within 3 days of a spill.  One

Louisiana parish (Cameron) could be contacted within 10 days.  After 30 days, 13 counties or

parishes may be contacted, including 8 Texas counties and 5 Louisiana parishes.  Cameron

Parish, Louisiana, has the highest probability of contact for the 10 and 30 day intervals.

Table 3. Conditional probabilities of a spill in Garden Banks Block 427 contacting shoreline

segments (From: Ji et al., 2004).  Values are conditional probabilities that a

hypothetical spill in the block (represented by Oil Spill Risk Analysis Launch Area 20)

could contact shoreline segments within 3, 10, or 30 days.

Shoreline

Segment County or Parish and State Conditional Probability of Contacta (%)

3 Days 10 Days 30 Days

C04 Kleberg, TX ‐‐ ‐‐ 1

C05 Nueces, TX ‐‐ ‐‐ 1

C06 Aransas, TX ‐‐ ‐‐ 1

C07 Calhoun, TX ‐‐ ‐‐ 1

C08 Matagorda, TX ‐‐ ‐‐ 3

C09 Brazoria, TX ‐‐ ‐‐ 2

C10 Galveston, TX ‐‐ ‐‐ 6

C12 Jefferson, TX ‐‐ ‐‐ 4

C13 Cameron, LA ‐‐ 1 9

C14 Vermilion, LA ‐‐ ‐‐ 3

C15 Iberia, LA  ‐‐ ‐‐ 1

C17 Terrebonne, LA ‐‐ ‐‐ 2

C20 Plaquemines, LA ‐‐ ‐‐ 1

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

occurred (‐‐ indicates less than 0.5%).

The OSRA model does not evaluate the fate of a spill over time periods longer than 30 days,

nor does it predict the fate of a release that continues over a period of weeks or months, as in

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

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

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

size but has generally been used by the BOEM/MMS 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 particulate matter, 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
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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.  The primary offshore response would involve mechanical recovery.  The

primary response equipment that would be mobilized for spills in normal and adverse weather

conditions to this location is listed in the Offshore On‐Water Recovery Activation List in the

OSRP.  The initial response time is 16 hours, with other equipment totaling 214,460 BPD

recovery capacity and 250,800 bbl oil storage capacity available.  Depending on the severity of

any adverse weather, larger equipment (Marine Spill Response Corporation Oil Spill Response

Vessel [MSRC OSRV] – Responders) may be more safely utilized in a response.  Predicted initial

response time of the nearest Responder is approximately 17 hours.

Chemical dispersion capabilities are also readily available from resources such as MSRC at

Stennis, Mississippi, and Coolidge, Arizona; CGA/ASI in Houma, Louisiana; Oil Spill Response in

South Hampton, UK and Singapore; and the Clean Caribbean & Americas in Ft. Lauderdale,

Florida , mobilizing for up to four sorties per day (initial call‐out).  These sorties could apply a

total of 86,800 gallons of dispersant per day, dispersing approximately 37,200 BOPD (assuming

a 1:20 ratio of oil dispersed at 90% efficiency).  Available dispersant application equipment,

response times, and support resources are identified in the OSRP.

Open‐water in‐situ burning (ISB) 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 ISB task forces could be deployed offshore depending

on weather conditions.

See EP Sections 2j and 9b for a detailed description of Shell’s site‐specific response to the

worst case spill for this plan.  These sections, along with Shell’s OSRP, also include a

description of containment capabilities that could be implemented in the event of the worst

case spill for this plan.

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 along

with an H2S release, and there are no other site‐specific issues for this EP.  The analysis in the

lease sale EIS for these topics is incorporated by reference.

Chemical Spill.  Chemicals used in drilling operations are required to overcome technical issues

in the drilling process, improve the efficiency and safety of drilling, and protect associated

equipment.  To perform these tasks, a variety of chemicals may be mixed together to develop

the site‐specific properties required in drilling the well.  Examples of chemicals used to achieve

these properties include surfactants, bentonite clays, olefins, inorganic salts, nut shells, glycols,

polymers, barite, and calcium carbonate.  Supplies are renewed on a regular basis by transfer

in containers from supply boats (Boehm et al., 2001).  Other than chemicals used in drilling

fluids, examples of chemicals that may be found on or transported to the rig include ethylene

glycol (blowout prevention control fluid, closed cooling loops for crane and main engines and

brake coolers), cement (used to cement casing in place), solvents (used in painting operations),
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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).  Both of these chemicals may be used for well

treatment or completion.  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 BOEM‐mandated safety

requirements to minimize the potential for vessel collisions.

Loss of Well Control.  A loss of well control is the uncontrolled flow of a reservoir fluid that

may result in the release of gas, condensate, oil, drilling fluids, sand, or water.  Loss of well

control is a broad term that includes very minor up to the most serious well control incidents,

while blowouts are considered to be a subset of more serious incidents with greater risk of oil

spill or human injury (MMS, 2007b).  Loss of well control may result in the release of synthetic

drilling fluid or loss of oil.  Shell has a robust system in place to prevent loss of well control.  

Included in this Supplemental EP is Shell’s response to NTL 2010‐N06, which includes

descriptions of measures to prevent a blowout, reduce the likelihood of a blowout, and

conduct effective and early intervention in the event of a blowout.  Shell will also comply with

NTL 2010‐N05 and the Interim Final Drilling Safety Rule, which specify increased safety

measures for OCS activities.  See EP Sections 2j and 9b for further information.

H2S Release.  In accordance with 30 CFR 250.417(c), Shell is requesting that the BOEM classify

the lease as “H2S absent.”  Therefore, no significant impacts on the environment are expected

from an H2S release.

B.  Affected Environment

The project location is on the continental slope in the northwestern Gulf of Mexico (Figure 1).  

Water depths in the lease range from about 640 to 884 m (2,100 to 2,900 ft).  The three

surface locations (O, P, and Q) are at a water depth of 829 m (2,721 ft) in the northeast

quadrant of GB 427, to the east of the base of the Auger diapir (dome) (Figure 2).  The seafloor

east of the diapir is relatively smooth and slopes eastward at a gradient of 2.0° (3.5%).  Four

amplitude and fluid expulsion features have been identified on the crest of the Auger diapir

that could support high‐density deepwater benthic communities.  These are not within 610 m

(2,000 ft) of any drilling mud/cuttings discharge.  Shell has designated a 150‐m (500‐ft)

anchoring avoidance zone around each fluid expulsion feature.
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Figure 2. Bathymetric map of Garden Banks Block 427.  (Water depths in units of feet.)

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

2007b, 2008), including meteorology, oceanography, geology, air and water quality, benthic

communities, threatened and endangered species, biologically sensitive resources,

archaeological resources, socioeconomic conditions, and other marine uses.  These regional

descriptions are based on extensive literature reviews and are incorporated by reference.  

General background information is presented below, and brief descriptions of each potentially

affected resource are presented in Section C, including site‐specific and/or new information if

available.

Based on analysis of oceanographic data by Johnson (2008) and online modeling data available

from the NOAA Atlantic Oceanographic and Meteorological Laboratory, surface currents in the

lease area are expected to be relatively weak, generally below 10 cm/s, flowing mainly

eastward.  Model predictions for near‐bottom currents in the area from Nowlin et al. (2001)

suggest speeds on the order of 4 cm/s directed eastward.  A few hundred meters above the
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bottom, current speeds of 8 to 12 cm/s directed eastward also are possible.  Stronger,

westward directed currents occur to the south along the Sigsbee Escarpment.

Other than the aforementioned seafloor features, the local environment in GB 427 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 Macondo spill has resulted in environmental impacts to portions of the Gulf of Mexico.  

The lease area is located approximately 400 km (250 mi) south‐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 at any time.  Therefore, the Macondo spill did not change the existing

environmental conditions at the lease area.

C.  Impact Analysis

This section analyses 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 Planning Areas (MMS, 2007b, 2008) as well as the environmental assessment for Gulf

of Mexico deepwater operations and activities (MMS, 2000).  Site‐specific issues are addressed

in this section as appropriate.

C.1 Physical/Chemical Environment

C.1.1 Air Quality

There are no site‐specific air quality data for the project area.  Due to the distance from

shore‐based 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 October 2010, air quality data for Mississippi, Alabama, and Florida show all three states

in attainment of the National Ambient Air Quality Standards (NAAQS) for all criteria pollutants

(USEPA, 2010a).  Five Louisiana parishes in the Baton Rouge area (Ascension, Iberville, East

Baton Rouge, West Baton Rouge, and Livingston) are moderate nonattainment areas for 8‐h

ozone.  The Louisiana Department of Environmental Quality has submitted a request to USEPA

for a determination that the Baton Rouge Area should be redesignated to full attainment with

existing ozone standards.  On 10 February 2010, USEPA removed these parishes from the 1‐h

ozone nonattainment areas; however, no change in 8‐h ozone status has yet been issued.  

Three metropolitan areas in Texas are nonattainment areas for 8‐h ozone (Beaumont‐Port

Arthur, Dallas‐Fort Worth, and Houston‐Brazoria), and El Paso County is a nonattainment area

for PM‐10 (USEPA, 2010a).

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
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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 (WCD).

 Impacts of Air Pollutant Emissions 

Air pollutant emissions are the only routine IPF likely to affect air quality.  Offshore air

pollutant emissions will result from the drilling rig operations and helicopters and service

vessels.  These emissions occur mainly from combustion or burning of diesel fuel.  The

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

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

suspended PM, SOx, NOx, VOCs, and CO.

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 Western Planning Area are projected to have minimal impacts to onshore air quality

because of the prevailing atmospheric conditions, emission heights, emission rates, and the

distance of these emissions from the coastline.  The Air Quality Emissions Report (see

EP Section 8) prepared in accordance with BOEM requirements shows that the projected

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

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

No further analysis or control measures are required.  However, Shell will use low sulfur fuel

(0.05% by weight) to further reduce any possible impacts.

The Breton National 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.  Proposed new or modified sources located within 300 km (186 mi) of

the Class I air quality area are asked to consult with the Federal Land Manager to determine

whether emission impact modeling to the Class I area should be conducted and submitted to

the Federal Land Manager for review (NPS, 2010).  The lease area is approximately 375 km

(233 mi) from the Breton National Wilderness Area.  Due to the distance and the projected

emissions below the exemption levels, it is therefore concluded that there will be negligible, if

any, air quality impacts on the PSD Class I area.

 Impacts of a Small Fuel Spill 

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

EP, there are no unique site‐specific issues with respect to spill impacts on air quality.  The

probability of a small spill would be minimized by Shell’s preventative measures during routine

operations, including fuel transfer.  In the unlikely event of a spill, implementation of Shell’s

OSRP will mitigate and reduce the impacts.  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 over 90% of a small diesel

spill would be evaporated or dispersed within 24 hours.  The area of the sea surface with
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diesel fuel on it would range from 0.5 to 5 ha (1.2 to 12 ac) depending on sea state and

weather conditions.

A small fuel spill would not affect coastal air quality because the spill would not be expected to

make landfall or reach coastal waters prior to breaking up (see Section A.9.2).

 Impacts of a Large Oil Spill (WCD) 

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

EP, there are no unique site‐specific issues with respect to spill impacts on air quality.

A large oil spill (WCD) would affect air quality by introducing VOCs through evaporation from

the slick.  The extent and persistence of impacts would depend on the meteorological and

oceanographic conditions at the time and the effectiveness of spill response measures.  

Additional air quality impacts could occur if response measures included in‐situ burning of the

floating oil.  Burning would generate a plume of black smoke and result in emissions of NOx,

SO2, CO, and PM, as well as greenhouse gases.

Due to the lease location (209 km [130 mi] 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 be affected.  OSRA modeling

predicts no shoreline contacts within 3 days of a spill (Table 3).  One Louisiana parish

(Cameron) could be contacted within 10 days, and after 30 days, 13 counties or parishes may

be contacted, including 8 Texas counties and 5 Louisiana parishes.  The OSRA model does not

evaluate the fate of a spill over time periods longer than 30 days, nor does it predict the fate of

a release that continues over a period of weeks or months.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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 located approximately 400 km (250 mi) south‐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 has not been

affected.

IPFs potentially affecting water quality are effluent discharges and two types of accidents:

a small fuel spill and a large oil spill (WCD).
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 Impacts of Effluent Discharges 

Discharges of water‐based drilling muds and cuttings will produce temporary, localized

increases in suspended solids and barium 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).  During well

intervals when synthetic‐based mud (SBM) is used, it will not be discharged except for small

amounts adhering to cuttings.  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).

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.

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 spill impacts on water quality are discussed in recent EISs (MMS, 2007b, 2008).  For

this EP, there are no unique site‐specific issues with respect to spill impacts on water quality.  

The probability of a small spill would be minimized by Shell’s preventative measures during

routine operations including fuel transfer.  In the unlikely event of a spill, implementation of

Shell’s OSRP will mitigate and reduce the impacts.  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

over 90% of a small diesel spill would be evaporated or dispersed within 24 hours (see

Section A.9.2).  The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha

(1.2 to 12 ac) depending on sea state and weather conditions.
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The water‐soluble fractions of diesel are dominated by two‐ and three‐ringed polycyclic

aromatic hydrocarbons (PAH), 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 is so light that it is not possible for the oil to sink and pool on the

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

generally only occurs 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 (WCD) 

A large oil spill (WCD) 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).  Small droplets in the water may adhere to suspended sediment and be removed

from the water column.

Due to the lease location (209 km [130 mi] 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.  OSRA

modeling predicts no shoreline contacts within 3 days of a spill (Table 3).  One Louisiana parish

(Cameron) could be contacted within 10 days, and after 30 days, 13 counties or parishes may

be contacted, including 8 Texas counties and 5 Louisiana parishes.  The OSRA model does not

evaluate the fate of a spill over time periods longer than 30 days, nor does it predict the fate of

a release that continues over a period of weeks or months.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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 in the lease range from about 640 to 884 m (2,100 to 2,900 ft).  Although there

are no site‐specific benthic studies, the seafloor is expected to consist predominantly of soft

bottom communities.  Four amplitude and fluid expulsion features have been identified on the

crest of the Auger diapir that could support high‐density deepwater benthic communities.  

These are not within 610 m (2,000 ft) of any drilling mud/cuttings discharge, and anchor

avoidance zones of 150 m (500 ft) have been established around them.
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C.2.1 Soft Bottom Communities

With water depths in the lease ranging from about 640 to 884 m (2,100 to 2,900 ft), the lease

area falls into the Upper or Lower Archibenthal Zone as defined by Gallaway (1988).  Seafloor

sediments within the lease area are expected to be predominantly soft clay.  Predominantly

soft bottom communities are expected to be present.  Based on the most recent studies of the

deepwater Gulf of Mexico, macrofaunal densities in the water depth of the lease area are

expected to be about 5,000 individuals/m2 (Rowe and Kennicutt, 2009).  Continental Shelf

Associates, Inc. (2006) reported densities of 750 to 5,380 individuals/m2 for two nearby sites in

slightly greater water depths (1,033 to 1,125 m [3,390 to 3,690 ft]).

Meiofauna (animals passing through a 0.5‐mm sieve but retained on a 0.062‐mm sieve) and

microbiota are also important components of the deep‐sea benthos.  Meiofaunal densities in

water depths of the lease area are expected to range from about 200,000 to

400,000 individuals/m2 (Rowe and Kennicutt, 2009).  Available data suggest that bacteria are

the most important component in terms of biomass and that much of the organic carbon

supplying the benthos cycles through bacteria (Cruz‐Kaegi, 1998).  Bacterial biomass at the

depth range of the lease area is about 1 to 2.5 g C/m2 in the top 15 cm of sediments (Rowe and

Kennicutt, 2009).

IPFs potentially affecting benthic communities are physical disturbance to the seafloor,

effluent discharges (drilling muds and cuttings), and a large oil spill (WCD) resulting from a well

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

diesel fuel would float and dissipate on the sea surface.

 Impacts of Physical Disturbance to the Seafloor 

The drilling rig will be held in place by up to 12 suction pile anchors deployed within a 4,420‐m

(14,500‐ft) permitted radius around the wellsites.  The suction pile system reduces seabed

disruption because suction piles are placed accurately and not dragged across the seafloor.  

The total seafloor disturbance area is estimated to be 490 ha (1,210 ac) per well.  Cables will

be resting on the seafloor only during the pre‐ and  post‐installation phase; once the rig arrives

on location, cables are pulled taut towards the rig.  The cables do not sweep the seafloor or

cross any sensitive features, and therefore they are expected to have little or no physical

impact on benthic communities.

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

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

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

continental slope, Continental Shelf Associates, Inc. (2006) detected anchor scars up to

14 years after drilling was completed.  These features will eventually disappear as sediments

are redistributed by currents and benthic organisms.

The areal extent of physical disturbance from the suction piles including the area where cables

will rest temporarily on the seafloor is 21% of the lease block area.  Soft‐bottom communities

are ubiquitous along the northern Gulf of Mexico continental slope (Gallaway et al., 2003;

Rowe and Kennicutt, 2009).  Physical disturbance to the seafloor during this project will have

no significant impact on soft‐bottom benthic communities in the region.
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 Impacts of Effluent Discharges 

Drilling muds and cuttings are the only effluents that are likely to affect benthic communities.  

During initial well interval(s) before the marine riser is set, cuttings and seawater‐based “spud

mud” will be released at the seafloor.  Excess cement slurry will also be released at the

seafloor during casing installation for the riserless portion of the drilling operations.  Cement

slurry components typically include cement mix and some of the same chemicals used in

water‐based drilling muds (Boehm et al., 2001).  The main impacts will be burial and

smothering of benthic organisms within several meters to tens of meters around the wellbore.  

Soft bottom sediments disturbed by cuttings, drilling muds, and cement slurry will eventually

be recolonized through larval settlement and migration from adjacent areas.  Because some

deep‐sea biota grow and reproduce slowly, recovery may require several years.

Discharges of washed SBM cuttings from the rig during later well intervals also 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, washed cuttings with adhering SBMs tend to clump together and form thick cuttings

piles close to the drillsite.  Areas of SBM cuttings deposition may develop elevated organic

carbon concentrations and anoxic conditions (Continental Shelf Associates, Inc., 2006).  Where

SBM cuttings accumulate in concentrations of approximately 1,000 mg/kg or higher, benthic

infaunal communities may be adversely affected due to both the toxicity of the base fluid and

organic enrichment (with resulting anoxia) (Neff et al., 2000).  Infaunal numbers may increase

and diversity may decrease as opportunistic species that tolerate low oxygen and high

hydrogen sulfide 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.

Two of the monitoring sites studied by Continental Shelf Associates, Inc. (2006) were GB 516

and GB 602, both located near the lease area for this EP.  Both sites had seven wells drilled

using SBM.  Post‐drilling surveys indicated that the near‐field zone at these sites consisted of a

mosaic of poor benthic conditions alternating with areas of moderately high benthic habitat

quality.  In contrast, far‐field “reference” sites exhibited aerobic boundary layer conditions

with well‐developed healthy infaunal communities.  Post‐drilling communities at GB 516 were

dominated by pioneering infauna, which are quick to colonize disturbed habitats.  Microbial

mats were observed at some stations.  These sites were sampled only 5 to 14 months after

drilling.  Because some deep‐sea biota grow and reproduce slowly, recovery may require

several years (Continental Shelf Associates, Inc., 2006).

The areal extent of impacts from drilling discharges will be small.  Assuming a typical effect

radius of 500 m (1,640 ft), the affected area would represent about 3% of the seafloor within

the lease block.  Soft‐bottom communities are ubiquitous along the northern Gulf of Mexico

continental slope (Gallaway et al., 2003; Rowe and Kennicutt, 2009).  Impacts from drilling

discharges during this project will have no significant impact on soft‐bottom benthic

communities in the region.
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 Impacts of a Large Oil Spill (WCD) 

The most likely effects of a subsea blowout on benthic communities would be within a few

hundred meters of the wellsite.  The MMS (2007b) estimates that a severe subsurface blowout

could resuspend and disperse sediments within a 300‐m (984‐ft) radius.  While coarse

sediments (sands) would probably settle at a rapid rate within 400 m (1,312 ft) from the

blowout site, fine sediments (silts and clays) could be resuspended for more than 30 days and

dispersed over a much wider area.  Based on previous studies, surface sediments at the

project area are assumed to largely be silt and clay (Gallaway, 1988).

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect

benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the

spill location.  However, during the Macondo spill, subsurface plumes were reported at a

water depth of about 1,100 m (3,600 ft), extending at least 35 km (22 mi) from the wellsite

and persisting for more than a month (Camilli et al., 2010).  The subsurface plumes apparently

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c).  While the

behavior and impacts of subsurface plumes are not well known, a subsurface plume could

contact the seafloor and affect benthic communities beyond the 300 m (984 ft) radius

estimated by MMS (2007a, 2008) depending on its extent, trajectory, and persistence.  This

contact could result in smothering and/or toxicity to benthic organisms.  The affected area

would be recolonized by benthic organisms over a period of months to years (NRC, 2003).

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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.  None of the known high‐density

deepwater benthic community locations listed in NTL 2009‐G40 are in GB 427 or adjacent

blocks.

Four amplitude and fluid expulsion features have been identified on the crest of the Auger

diapir that could support chemosynthetic communities (see EP Section 6a for additional

information).   Shell has designated a 76 m (250 ft) avoidance zone around each fluid expulsion

feature.  Outside these avoidance zones, the subsurface has a dark reflectivity, interpreted as

authigenic.  Shell has also elected to avoid this area of dark reflectivity by 76 m (250 ft), for a

total avoidance distance of 152 m (500 ft).
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IPFs potentially affecting high‐density deepwater benthic communities are physical

disturbance to the seafloor, effluent discharges (drilling muds and cuttings), and a large oil spill

(WCD) from a well blowout at the seafloor.  A small fuel spill would not affect benthic

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

 Impacts of Physical Disturbance to the Seafloor 

Anchor avoidance zones of 152 m (500 ft) have been established around the four amplitude

and fluid expulsion features identified on the crest of the Auger diapir that could support

chemosynthetic and/or deepwater coral communities (see EP Section 6a for additional

information).  Therefore, anchoring impacts on these communities will be avoided.

 Impacts of Effluent Discharges 

The features on the crest of the Auger diapir are more than 1,500 m (5,000 ft) from the

wellsites (see EP Section 6a for additional information).  Monitoring programs on the Gulf of

Mexico continental slope have shown that benthic impacts of drilling discharges typically are

concentrated within about 500 m (1,640 ft) of the wellsite, although detectable deposits may

extend beyond this distance (Continental Shelf Associates, Inc., 2004, 2006; Neff et al., 2005).  

Therefore, drilling mud and cuttings discharges are not expected to significantly affect

high‐density deepwater benthic communities.

 Impacts of a Large Oil Spill (WCD) 

Features in GB 427 that could support high‐density deepwater benthic communities are far

enough away from any wellsite (at least 1,500 m or 5,000 ft) that they are unlikely to be

affected by sediment resuspension from a blowout, as the effect radius estimated by

MMS (2007b) is 300 m (984 ft).

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect

benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the

spill location.  However, during the Macondo spill, subsurface plumes were reported at a

water depth of about 1,100 m (3,600 ft), extending at least 35 km (22 mi) from the wellsite

and persisting for more than a month (Camilli et al., 2010).  The subsurface plumes apparently

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c).  While the

behavior and impacts of subsurface plumes are not well known, a subsurface plume could

have the potential to contact high‐density deepwater benthic communities beyond the 300‐m

(984‐ft) radius estimated by MMS (2007a, 2008) depending on its extent, trajectory, and

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 as compared to the potential rates of oil

release from a blowout.  In addition, seep organisms also require unrestricted access to

oxygenated water at the same time as exposure to hydrocarbon energy sources (MacDonald,

2002).  Oil droplets or oiled sediment particles could come into contact with chemosynthetic

organisms or deepwater corals.  As discussed by MMS (2007b), impacts could include loss of

habitat, biodiversity, and live coral coverage; destruction of hard substrate; change in

sediment characteristics; and reduction or loss of one or more commercial and recreational
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Environmental Impact Analysis for Supplemental Exploration Plan Page 25

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).

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on deepwater benthic communities are

expected.

C.2.3 Designated Topographic Features

The block is not within or near a designated topographic feature or a no‐activity zone as

identified in NTL 2009‐G39.  The nearest topographic features are Sidner Bank, 36 km (23 mi)

north and Rezak Bank, 42 km (26 mi) north.  The East Flower Garden Banks are 117 km (72 mi)

to the west‐northwest.

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; subsurface currents in the lease area

generally flow along the isobaths (Nowlin et al., 2001; Johnson, 2008) and typically would not

carry a plume upslope from the lease area.

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 pinnacle trend area is about 400 km (250 mi) east‐northeast 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; subsurface currents in the lease area

generally flow along the isobaths (Nowlin et al., 2001; Johnson, 2008) and typically would not

carry a plume upslope from the lease area.

C.2.5 Eastern Gulf Live Bottoms

The lease area is not covered by the Live Bottom (Low‐Relief) Stipulation, which applies to

Eastern Planning Area leases in water depths of 100 m (328 ft) or less.  The nearest live bottom

areas, as defined by NTL 2009‐G39, are nearly 500 km (310 mi) northeast from the project

area.
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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; subsurface currents in the lease area

generally flow along the isobaths (Nowlin et al., 2001; Johnson, 2008) and typically would not

carry a plume upslope from the lease area.

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 4.  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 for ESA‐listed cetaceans, sea turtles, and fishes in the

Gulf of Mexico.  The USFWS has jurisdiction for ESA‐listed birds and the Florida manatee.

Table 4. Federally‐listed endangered and threatened species in the lease area and along the

northern Gulf coast.

Species Scientific Name Status*

Potential Presence Critical Habitat

Designated in

Gulf of Mexico

Lease

Area Coastal

Marine Mammals

Sperm whale Physeter macrocephalus E X  ‐‐  None

Florida manatee

Trichechus manatus

latirostris E  ‐‐  X Florida  (Peninsular)

Sea Turtles

Loggerhead turtle Caretta caretta T X Xa None

Green turtle Chelonia mydas T, Eb X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Leatherback turtle Dermochelys coriacea 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)
Table 4.  (Continued.)

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Species Scientific Name Status*

Potential Presence Critical Habitat

Designated in

Gulf of Mexico

Lease

Area Coastal

Fishes

Gulf sturgeon Acipenser oxyrinchus desotoi T  ‐‐  X

Coastal areas and

rivers in Louisiana,

Mississippi, Alabama,

and Florida

Terrestrial Mammals

Beach mice (Alabama,

Choctawhatchee, Perdido

Key, St. Andrew)

Peromyscus polionotus E  ‐‐  X Alabama and Florida

(Panhandle)

* E = Endangered; T = Threatened.    a

   The loggerhead is the most common sea turtle species nesting along the northern Gulf coast. b

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

endangered.

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.  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.  Due to

the rare occurrence of these whales in the Gulf of Mexico and the limited scope and duration

of the proposed exploratory drilling program, it is highly unlikely that any endangered

mysticete would come into contact with any project activities.  Potential impacts are analyzed

in recent lease sale EISs (MMS, 2007b, 2008) and these species are not discussed further here.

Coastal endangered or threatened species include the Florida manatee, Piping Plover,

Whooping Crane, Gulf sturgeon, and four subspecies of beach mice.  Critical habitat has been

designated for all of these species as indicated in the table and discussed in individual sections.

Two other coastal species (Bald Eagle and Brown Pelican) discussed by MMS (2007b) are no

longer listed as endangered or threatened; these are included 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.  Sperm whales are frequently sighted in the northern Gulf of Mexico in the
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Mississippi Canyon area (Davis et al., 2000).  No critical habitat has been designated in the Gulf

of Mexico.  A species description is presented in a recent lease sale EIS (MMS, 2007b).

Sperm whales are widely distributed in the Gulf of Mexico, but are relatively common on the

continental slope south of the Mississippi River Delta (Davis et al., 2000).  Results of a

multi‐year tracking study show female sperm whales typically concentrated along the upper

continental slope between the 200‐ and 1,000‐m (656‐ and 3,280‐ft) depth contours

(Jochens et al., 2008).  Male sperm whales were more variable in their movements and were

documented in water depths greater than 3,000 m (9,843 ft).

IPFs potentially affecting sperm whales include drilling rig presence, noise, and lights; marine

debris; support vessel and helicopter traffic; and two types of accidents – a small fuel spill and

a large oil spill (WCD).  Effluent discharges are likely to have negligible impacts on sperm

whales due to rapid dispersion, the small area of ocean affected, the intermittent nature of

the discharges, and the mobility of these marine mammals.

 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 (e.g., Shell’s Auger tension‐leg

platform) and the region as a whole has a large number of similar sources.  Due to the limited

scope and short duration of the exploration drilling program, 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 semisubmersible

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).

Drilling rig lighting and rig presence are not identified as IPFs for sperm whales in recent lease

sale EISs (MMS, 2007b, 2008) or the NMFS (2007) Biological Opinion.

 Impacts of Marine Debris 

Marine debris is a general concern for marine mammals, but the disposal of solid waste from

drilling rigs and vessels is prohibited by the BOEM and the USCG under MARPOL 73/78.  

NTL 2007‐G03 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.  Compliance with this NTL will minimize the potential for

marine debris‐related impacts on sperm whales, and no significant impacts are expected.

 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
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(NMFS, 2006).  Data concerning the frequency of vessel strikes is presented in the lease sale

EIS (MMS, 2007b).  To reduce the potential for vessel strikes, the BOEM has issued NTL

2007‐G04, which recommends protected species identification training, 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 91 m (300 ft) or greater whenever possible.  Vessel

operators are required to reduce vessel speed to 10 knots or less when mother/calf pairs,

pods, or large assemblages of cetaceans are observed near an underway vessel when safety

permits.  Compliance with this NTL will minimize the likelihood of vessel strikes as well as

reduce the chance for disturbing sperm whales.

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 90 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.  However, while flying

offshore, helicopters maintain altitudes above 213 m (700 ft) during transit to and from the

working area.  This altitude will minimize the potential for disturbing sperm whales, and no

significant impacts are expected (NMFS, 2007).

 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 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.  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

0.5 to 5 ha (1.2 to 12 ac) depending on sea state and weather conditions.
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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 sperm whales, no significant impacts would be expected.

 Impacts of a Large Oil Spill (WCD) 

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

(MMS, 2007b, 2008) and by 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 EP, there

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

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

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

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

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

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

from the activities and noise of response vessels and aircraft.  Complications of the above may

lead to dysfunction of immune and reproductive systems, physiological stress, declining

physical condition, and death.  Behavioral responses can include displacement of animals from

prime habitat; disruption of social structure; changing prey availability and foraging

distribution and/or patterns; changing reproductive behavior/productivity, and changing

movement patterns or migration (MMC, 2010).

In the event of a large spill, the level of vessel and aircraft activity associated with spill

response could disturb sperm whales and potentially result in vessel strikes, entanglement, or

other injury or stress.  Response vessels would operate in accordance with NTL 2007‐G04 to

reduce the potential for striking or disturbing these animals.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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)

The endangered Florida manatee is a coastal species that does not occur in the project area.  

Manatees do sometimes occur in Louisiana coastal waters during summer months, and vessel

strikes are a major cause of manatee mortality in peninsular Florida, where most of the

manatee population is located (USFWS, 2001).  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 marine debris, support vessel and helicopter

traffic, and a large oil spill (WCD).  A small fuel spill in the lease area would be unlikely to affect

manatees, as the lease area is 209 km (130 mi) from the nearest shoreline (Louisiana).  As
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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.

 Impact of Marine Debris 

Marine debris is a general concern for marine mammals, but the disposal of solid waste from

drilling rigs and vessels is prohibited by the BOEM and the USCG under MARPOL 73/78.  

Compliance with NTL 2007‐G03 will minimize the potential for marine debris‐related impacts

on marine mammals including manatees, and no significant impacts are expected.

 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).  

Data concerning the frequency of vessel strikes is presented in the lease sale EIS (MMS,

2007b).  To reduce the potential for vessel strikes, the BOEM has issued NTL 2007‐G04, which

recommends protected species identification training, that vessel operators and crews

maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid

striking protected species and requires operators to report sightings of any injured or dead

protected species.  Compliance with this NTL will minimize the likelihood of vessel strikes, and

no significant impacts on manatees are expected.

Helicopter traffic also has the potential to disturb manatees.  Rathbun (1988) reported that

manatees were disturbed more by helicopters than fixed‐wing aircraft; however, the

helicopter was flown at a relatively low altitude of 20 to 160 m (66 to 525 ft).  Helicopters used

in support operations maintain a minimum altitude of 213 m (700 ft) while in transit offshore,

305 m (1,000 ft) over unpopulated areas or across coastlines, and 610 m (2,000 ft) over

populated areas and sensitive habitats such as wildlife refuges and park properties.  This

mitigation measure will minimize the potential for disturbing manatees, and no significant

impacts are expected.

 Impacts of a Large Oil Spill (WCD) 

The OSRA results summarized in Table 3 predict that some Louisiana shorelines could be

contacted by a spill within 10 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).
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In the event of a large spill, 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.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on manatees are expected.

C.3.3 Other Marine Mammals (Protected)

Excluding the seven endangered species that have been cited previously, there are

22 additional species of marine mammals that may be found in the Gulf of Mexico (see

EP Section 6h).  All marine mammals are protected species under the MMPA.  The most

common non‐endangered cetaceans in the deepwater environment are odontocetes such as

the pantropical spotted dolphin, spinner dolphin, and clymene dolphin.  Other odontocetes

that may be present include dwarf and pygmy sperm whales, 4 species of beaked whales, and

13 species of dolphins and porpoises.  Additional information is presented in a recent lease

sale EIS (MMS, 2007b).

IPFs potentially affecting non‐endangered marine mammals include drilling rig presence, noise,

and lights; marine debris; support vessel and helicopter traffic; and two types of accidents

(a small fuel spill and a large oil spill represented by the WCD for this EP).  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.

 Impacts of Drilling Rig Presence, Noise, and Lights 

Noise from routine drilling activities has the potential to disturb marine mammals.  Most

odontocetes (toothed whales and dolphins) use sounds that are higher than the low‐frequency

dominant frequencies produced by OCS drilling activities (Richardson et al., 1995).  Noise

associated with drilling is relatively weak in intensity, and an individual animal’s noise

exposure would be transient.  There are other OCS facilities and activities near the lease area

(e.g., Shell’s Auger tension‐leg platform) and the region as a whole has a large number of

similar sources.  Due to the limited scope and short duration of the exploration drilling

program, 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 Marine Debris 

Marine debris is a general concern for marine mammals, but the disposal of solid waste from

drilling rigs and vessels is prohibited by the BOEM and the USCG under MARPOL 73/78.  

Compliance with NTL 2007‐G03 will minimize the potential for marine debris‐related impacts

on marine mammals, and no significant impacts are expected.
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 Impacts of Support Vessel and Helicopter Traffic 

Support vessel traffic has the potential to disturb marine mammals and there is also a risk of

vessel strikes.  Data concerning the frequency of vessel strikes is presented in the lease sale EIS

(MMS, 2007b).  To reduce the potential for vessel strikes, the BOEM has issued NTL 2007‐G04,

which recommends protected species identification training, that vessel operators and crews

maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid

striking protected species, and requires operators to report sightings of any injured or dead

protected species.  Vessel operators and crews are required to attempt to maintain a distance

of 91 m (300 ft) or greater when whales are sighted and 45 m (150 ft) when small cetaceans

are sighted.  When cetaceans are sighted while a vessel is underway, vessels must attempt to

remain parallel to the animal’s course and avoid excessive speed or abrupt changes in

direction until the cetacean has left the area.  Vessel operators are required to reduce vessel

speed to 10 knots or less when mother/calf pairs, pods, or large assemblages of cetaceans are

observed near an underway vessel when safety permits.  Compliance with this NTL will

minimize the likelihood of vessel strikes as well as reduce the chance for disturbing marine

mammals.

Helicopter traffic also has the potential to disturb marine mammals.  However, while flying

offshore, helicopters maintain altitudes above 213 m (700 ft) during transit to and from the

working area.  This altitude will minimize the potential for disturbing marine mammals, and no

significant impacts are expected (MMS, 2007b).

 Impacts of a Small Fuel Spill 

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008)

and oil impacts on marine mammals in general are discussed by Geraci and St. Aubin (1990).  

For this EP, there are no unique site‐specific issues with respect to spill impacts on these

animals.

The probability of a fuel spill will be minimized by Shell’s preventative measures during fuel

transfer.  In the unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate

and reduce the potential for impacts on marine mammals.  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

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation,

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities

and noise of response vessels and aircraft (MMC, 2010).  However, due to the limited areal

extent and short duration of water quality impacts from a small fuel spill, as well as the

mobility of marine mammals, no significant impacts would be expected.
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 Impacts of a Large Oil Spill (WCD) 

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008)

and by Geraci and St. Aubin (1990).  For this EP, there are no unique site‐specific issues.

Impacts of oil spills on marine mammals can include direct impacts from oil exposure, as well

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

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

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

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

contaminated vegetation, in the case of manatees); and stress from the activities and noise of

response vessels and aircraft.  Complications of the above may lead to dysfunction of immune

and reproductive systems, physiological stress, declining physical condition, and death.  

Behavioral responses can include displacement of animals from prime habitat; disruption of

social structure; changing prey availability and foraging distribution and/or patterns; changing

reproductive behavior/productivity, and changing movement patterns or migration

(MMC, 2010).

In the event of a large spill, the level of vessel and aircraft activity associated with spill

response could disturb marine mammals and potentially result in vessel strikes, entanglement,

or other injury or stress.  Response vessels would operate in accordance with NTL 2007‐G04 to

reduce the potential for striking or disturbing these animals.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on marine mammals are expected.

C.3.4 Sea Turtles (Endangered/Threatened)

As listed in EP Section 6h, five species of endangered or threatened sea turtles may be found

near the project area.  Endangered species are the leatherback (Dermochelys coriacea),

Kemp's ridley (Lepidochelys kempii), and hawksbill (Eretmochelys imbricata) sea turtles.  The

loggerhead sea turtle (Caretta caretta) is a threatened species.  The green sea turtle (Chelonia

mydas) is listed as threatened, except for the Florida breeding population, which is listed as

endangered.  Species descriptions are presented in a recent lease sale EIS (MMS, 2007b).

Leatherbacks and loggerheads are the most likely turtles to be present near the project area as

adults.  Green, hawksbill, and Kemp’s ridley turtles are typically inshore species, unlikely to

occur near the project area as adults.  Hatchlings or juveniles of any of the sea turtles may be

present in deepwater areas, where they may be associated with Sargassum and other flotsam.

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

• Loggerhead turtles nest in significant numbers along the Florida Panhandle and, to a lesser

extent, from Texas through Alabama (MMS, 2007b);

• Green and leatherback turtles infrequently nest on Florida Panhandle beaches (Florida Fish

and Wildlife Conservation Commission, 2010a);
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• Kemp’s ridley turtles normally 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 normally do not nest anywhere near the project area.

IPFs potentially affecting sea turtles include drilling rig presence, noise, and lights; marine

debris; support vessel and helicopter traffic; and two types of accidents (a small fuel spill and a

large oil spill represented by the WCD for this EP).  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.

 Impacts of Drilling Rig Presence, Noise, and Lights 

Offshore drilling activities produce a broad array of sounds at frequencies and intensities that

may be detected by sea turtles (Geraci and St. Aubin, 1987).  Potential impacts may include

behavioral disruption and temporary or permanent displacement from the area near the

sound source.  Certain sea turtles, especially loggerheads, may be attracted to offshore

structures (Lohoefener et al., 1990) and, thus, may be more susceptible to impacts from

sounds produced during routine operations.  Helicopters and service vessels may also affect

sea turtles due to machinery noise and/or visual disturbances.  The most likely impacts would

be short‐term behavioral changes such as diving and evasive swimming, disruption of

activities, or departure from the area.  Due to the limited scope and short duration of the

exploration drilling program, 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.

 Impacts of Marine Debris 

Marine debris is a general concern for sea turtles, but the disposal of solid waste from drilling

rigs and vessels is prohibited by the BOEM and the USCG under MARPOL 73/78.  Compliance

with NTL 2007‐G03 will minimize the potential for marine debris‐related impacts on sea

turtles; no significant impacts are expected.

 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 BOEM has issued NTL 2007‐G04, which recommends protected species

identification training, that vessel operators and crews  maintain a vigilant watch for sea

turtles and slow down or stop their vessel to avoid striking protected species, and requires

operators to report sightings of any injured or dead protected species.  When sea turtles are

sighted, vessel operators and crews are required to attempt to maintain a distance of 45 m
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(150 ft) or greater whenever possible.  Compliance with this NTL will minimize the likelihood of

vessel strikes as well as reduce the chance for disturbing sea turtles (NMFS, 2007).

Helicopter traffic also has the potential to disturb sea turtles.  However, while flying offshore,

helicopters maintain altitudes above 213 m (700 ft) during transit to and from the working

area.  This altitude will minimize the potential for disturbing sea turtles, and no significant

impacts are expected.

 Impacts of a Small Fuel Spill 

Potential spill impacts on sea turtles are discussed in recent EISs (MMS, 2007b, 2008) and 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 EP, there are no unique

site‐specific issues with respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by Shell’s preventative measures during fuel

transfer.  In the unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate

and reduce the potential for impacts on sea turtles.  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

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation,

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities

and noise of response vessels and aircraft (MMC, 2010).  However, due to the limited areal

extent and short duration of water quality impacts from a small fuel spill, 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 209 km (130 mi) from the nearest shoreline (Louisiana).  As explained in

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

prior to breaking up.

 Impacts of a Large Oil Spill (WCD) 

Impacts of oil spills on sea turtles can include direct impacts from oil exposure, as well as

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

dispersants).  Direct physical and physiological effects can include skin irritation, inflammation,

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

and smoke (e.g., from in situ burning of oil); ingestion of oil (and dispersants) directly or via

contaminated food; and stress from the activities and noise of response vessels and aircraft.  

Complications of the above may lead to dysfunction of immune and reproductive systems,

physiological stress, declining physical condition, and death.  Behavioral responses can include
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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.  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 may result in repeated exposure to volatile vapors and oiling

(NMFS, 2007).

The OSRA results summarized in Table 3 do not predict any shoreline contacts in Alabama or

the Florida Panhandle within 30 days.  However, some Louisiana and Texas shorelines that

support more limited turtle nesting could be contacted within 10 to 30 days.  It is not known

whether Alabama or Florida Panhandle shorelines could be contacted in the event of a spill

persisting for more than 30 days.

Spilled oil reaching sea turtle nesting beaches could have affects on nesting sea turtles and egg

development (NMFS, 2007).  An oiled beach could affect nest site selection or result in no

nesting at all (e.g., false crawls).  Upon hatching and successfully reaching the water,

hatchlings are subject to the same types of oil spill exposure hazards as adults.  Hatchlings that

contact oil residues while crossing a beach can exhibit a range of effects, from acute toxicity to

impaired movement and normal bodily functions (NMFS, 2007).

In the event of a large spill, the level of vessel and aircraft activity associated with spill

response could disturb sea turtles and potentially result in vessel strikes, entanglement, or

other injury or stress.  Response vessels would operate in accordance with NTL 2007‐G04 to

reduce the potential for striking or disturbing these animals.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on sea turtles are expected.

C.3.5 Piping Plover (Threatened)

The Piping Plover (Charadrius melodus) is a migratory shore bird 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.  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).
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A large oil spill (WCD) is the only IPF potentially affecting Piping Plovers.  There are no IPFs

associated with routine project activities that could affect these birds.  A small fuel spill in the

lease area would be unlikely to affect Piping Plovers, as the lease area is 209 km (130 mi) from

the nearest shoreline (Louisiana) inhabited by these birds.  As explained in Section A.9.2, a

small fuel spill would not be expected to make landfall or reach coastal waters prior to

breaking up.

 Impacts of a Large Oil Spill (WCD) 

The OSRA results summarized in Table 3 predict that Texas and Louisiana shorelines could be

contacted by a spill within 30 days.  These shorelines include designated critical habitat for the

wintering Piping Plover.

Plovers could physically oil themselves while foraging on oiled shores or secondarily

contaminate themselves through ingestion of oiled intertidal sediments and prey (MMS,

2007b).  Plovers congregate and feed along tidally exposed banks and shorelines, following the

tide out and foraging at the water’s edge.  It is possible that some deaths of Piping Plovers

could occur, especially if spills occur during winter months when plovers are most common

along the coastal Gulf or if spills contacted critical habitat.  Impacts could also occur from

vehicular traffic on beaches and other activities associated with spill cleanup.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on Piping Plovers are expected.

C.3.6 Whooping Crane (Endangered)

The Whooping Crane (Grus americana) is an omnivorous, wading bird and an endangered

species.  There are three wild populations in North America (Whooping Crane Eastern

Partnership [WCEP], 2010).  One population winters along the Texas coast at Aransas NWR and

summers at Wood Buffalo National Park in Canada.  This population represents the majority of

the world’s population of free‐ranging Whooping Cranes and reached a record population of

270 at Aransas NWR in December, 2008 (WCEP, 2010).  A non‐migrating population has been

re‐introduced in central Florida, and another re‐introduced population summers in Wisconsin

and migrates to the southeastern U.S. for the winter.  Whooping Cranes breed, migrate,

winter, and forage in a variety of habitats, including coastal marshes and estuaries, inland

marshes, lakes, ponds, wet meadows and rivers, and agricultural fields (USFWS, 2007).  About

9,000 ha (22,240 ac) of salt flats on Aransas NWR and adjacent islands comprise the principal

wintering grounds of the Whooping Crane.  Aransas NWR is designated as critical habitat for

the species.  A species description is presented in a recent lease sale EIS (MMS, 2007b).

A large oil spill (WCD) is the only IPF potentially affecting Whooping Cranes.  There are no IPFs

associated with routine project activities that could affect these birds due to the distance from

shore and the lack of any onshore activities near their habitat.   A small fuel spill in the lease

area would be unlikely to affect Whooping Cranes, as the lease area is 209 km (130 mi) from

the nearest shoreline (Louisiana) and more than 400 km (250 mi) 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.
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 Impacts of a Large Oil Spill (WCD) 

Based on the OSRA modeling results, a spill in the lease area would not contact shorelines near

the Aransas NWR within 30 days.  It is not known whether this area could be contacted in the

event of a spill persisting for more than 30 days.  However, the lease area is more than 400 km

(250 mi) from Aransas NWR.  Therefore, significant impacts on the Whooping Cranes and their

critical habitat are unlikely.

In the event of oil exposure, Whooping Cranes could physically oil themselves while foraging in

oiled areas or secondarily contaminate themselves through ingestion of contaminated

shellfish, frogs, and fishes.  It is possible that some death of Whooping Cranes could occur.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on Whooping Cranes are expected.

C.3.7 Gulf Sturgeon (Threatened)

The Gulf sturgeon (Acipenser oxyrinchus desotoi) is a threatened fish species that inhabits

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida

(Barkuloo, 1988; Wakeford, 2001).  An anadromous fish that migrates from the sea upstream

into coastal rivers to spawn in freshwater, it historically ranged from the Mississippi River to

Charlotte Harbor, Florida (Wakeford, 2001).  Today, this range has contracted to encompass

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida.  

Populations have been depleted or even extirpated throughout this range by fishing, shoreline

development, dam construction, water quality changes, and other factors (Barkuloo, 1988;

Wakeford, 2001).  These declines prompted the listing of the Gulf sturgeon as a threatened

species in 1991.  The best known populations occur in the Apalachicola and Suwannee Rivers

in Florida (Carr, 1996; Sulak and Clugston, 1998), the Choctawhatchee River in Alabama (Fox et

al., 2000), and the Pearl River in Mississippi/Louisiana (Morrow et al., 1998).  Critical habitat in

the Gulf extends from Lake Borgne, Louisiana (St. Bernard Parish) to Suwannee Sound, Florida

(Levy County) (NMFS, 2010b,c).  A species description is presented in a recent lease sale EIS

(MMS, 2007b).

A large oil spill (WCD) is the only IPF potentially affecting Gulf sturgeon. There are no IPFs

associated with routine project activities that could affect these fishes.  A small fuel spill in the

lease area would be unlikely to affect Gulf sturgeon, as the lease area is 209 km (130 mi) from

the nearest shoreline (Louisiana).  As explained in Section A.9.2, a small fuel spill would not be

expected to make landfall or reach coastal waters prior to breaking up.

 Impacts of a Large Oil Spill (WCD) 

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 EP, there are no unique

site‐specific issues with respect to this species.

Gulf sturgeon could be affected if oil reached very shallow waters or coastal rivers of

Louisiana, Mississippi, Alabama, or the Florida Panhandle.  The OSRA results summarized in
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Table 3 predict that Louisiana shorelines could be contacted by a spill within 10 to 30 days.  It

is not known whether Alabama or Florida Panhandle shorelines could be contacted in the

event of a spill persisting for more than 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 would be most vulnerable to an estuarine or marine oil spill, and would be

vulnerable only during winter months (between September 1 through April 30) when this

species is foraging in estuarine and marine habitats (NMFS, 2007).

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on Gulf sturgeon are expected.

C.3.8 Beach Mice (Endangered)

Four subspecies of endangered beach mice (Peromyscus polionotus) occur on the barrier

islands of Alabama and the Florida Panhandle.  They are the Alabama, Choctawatchee, Perdido

Key, and St. Andrew beach mice.  Critical habitat has been designated for all four subspecies.  

Species descriptions are provided in a recent lease sale EIS (MMS, 2007b).  

A large oil spill (WCD) is the only IPF potentially affecting beach mice.  There are no IPFs

associated with routine project activities that could affect these animals due to the distance

from shore and the lack of any onshore support activities near their habitat.  A small fuel spill

in the lease area would not affect beach mice, as the lease area is 209 km (130 mi) from the

nearest shoreline (Louisiana) and more than 500 km (310 mi) from the nearest beach mouse

critical habitat.  As explained in Section A.9.2, a small fuel spill would not be expected to make

landfall or reach coastal waters prior to breaking up.

 Impacts of a Large Oil Spill (WCD) 

Potential spill impacts on beach mice are discussed in recent EISs (MMS, 2007b, 2008).  For

this EP, there are no unique site‐specific issues with respect to these species.  The OSRA

modeling predicts that a spill in the lease area would not contact any shoreline inhabited by

beach mice within 30 days.  It is not known whether Alabama or Florida Panhandle shorelines

could be contacted in the event of a spill persisting for more than 30 days.  However, contact is

unlikely, as the lease area is more than 500 km (310 mi) from the nearest beach mouse critical

habitat.

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 (WCD) 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
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detailed in EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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 shore birds 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 shore birds and coastal

nesting birds, see Section C.4.2.

Seabirds of the northeastern 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.  Relationships with

hydrographic features were found for several species, possibly due to effects of hydrography

on nutrient levels and productivity of surface waters where birds forage.  GulfCet II did not

estimate bird densities; however, Powers (1987) indicates that seabird densities over the open

ocean typically are <10 birds/km2

.

IPFs potentially affecting marine and pelagic birds include drilling rig presence, noise, and

lights; marine debris; support vessel and helicopter traffic; and two types of accidents (a small

fuel spill and a large oil spill represented by the WCD for this EP).  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.

 Impacts of Drilling Rig Presence, Noise, and Lights 

Pelagic seabirds and trans‐Gulf migrant birds may be present at the project area.  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.  Birds

that frequent platforms may be exposed to contaminants including air pollutants and routine

discharges, but significant impacts are unlikely due to rapid dispersion.  Birds migrating over

water at night have been known to strike offshore structures, resulting in death or injury

(Wiese et al., 2001; Russell, 2005).  Due to the limited scope and short duration of the

exploration drilling program, collisions or other adverse effects are unlikely, and no significant

impacts are expected.

 Impacts of Marine Debris 

Debris lost overboard from offshore operations can injure or kill birds that ingest or become

entangled in it.  BOEM regulations and Federal law prohibit disposal of trash and debris in the

ocean.  In addition, the BOEM has issued NTL 2007‐G03, which instructs operators to exercise

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

placards at prominent locations on offshore vessels and structures.  A marine trash and debris

awareness training and certification process is required as well.  Compliance with this NTL will
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minimize the likelihood of debris‐related impacts on birds, and no significant impacts are

expected.

 Impacts of Support Vessel and Helicopter Traffic 

Support vessels and helicopters are unlikely to significantly disturb pelagic birds in open,

offshore waters.  It is likely that individual birds would experience, at most, only short‐term

behavioral disruption and the impact would not be significant.

 Impacts of a Small Fuel Spill 

Potential spill impacts on marine birds are discussed in recent EISs (MMS, 2007b, 2008) and for

this EP, there are no unique site‐specific issues with respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by 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.  

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

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

Birds exposed to oil on the sea surface could experience direct physical and physiological

effects including skin irritation; chemical burns of skin, eyes, and mucous membranes; and

inhalation of toxic fumes.  Due to the limited areal extent and short duration of water quality

impacts from a small fuel spill, secondary impacts due to ingestion of oil via contaminated prey

or reductions in prey abundance are unlikely.  Due to the low densities of birds in open ocean

areas, the small area affected, and the brief duration of the surface slick, no significant impacts

on pelagic birds would be expected.

 Impacts of a Large Oil Spill (WCD) 

Potential spill impacts on marine and pelagic birds are discussed in recent EISs (MMS, 2007b,

2008).  For this EP, there are no unique site‐specific issues with respect to spill impacts on

these animals.

Pelagic seabirds could be exposed to oil from a spill at the project area.  Hess and Ribic (2000)

reported that terns, storm‐petrels, shearwaters, and jaegers were the most frequently sighted

seabirds in the deepwater Gulf of Mexico (>200 m).  Powers (1987) indicates that seabird

densities over the open ocean typically are <10 birds/km2

.  The number of pelagic birds that

could be affected in open, offshore waters would depend on the extent and persistence of the

oil slick.

The recent Macondo spill provides relevant information about the species of pelagic birds that

may be affected in the event of a large oil spill.  Birds that have been treated for oiling include
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several pelagic species such as Magnificent Frigatebird, Masked Booby, and Northern Gannet

(International Bird Rescue Research Center, 2010).

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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 Shore Birds 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, shore birds, marsh birds, wading birds,

and waterfowl.  Detailed information is presented in recent lease sale EISs (MMS, 2007b,

2008).

The Eastern Brown Pelican (Pelecanus occidentalis) has been delisted from its endangered

status (USFWS, 2010b), although still listed as endangered by the State of Mississippi

(Mississippi Natural Heritage Program, 2003) and as a species of special concern by the State

of Florida (Florida Fish and Wildlife Conservation Commission, 2010b).  Brown Pelicans inhabit

coastal habitats and forage within both coastal waters and waters of the inner continental

shelf.  Aerial and shipboard surveys, including GulfCet and GulfCet II, indicate that Brown

Pelicans do not occur in deep offshore waters (Fritts and Reynolds, 1981; Peake, 1996;

Hess and Ribic, 2000).  Nearly half the southeastern population of Brown Pelicans live in the

northern Gulf Coast, generally nesting on protected islands (USFWS, 2010c).

The Southern Bald Eagle (Haliaeetus leucocephalus) was delisted from its threatened status on

28 June 2007 in the lower 48 states.  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 shore birds and coastal nesting birds include marine debris; support

vessel and helicopter traffic; and a large oil spill (WCD).  A small fuel spill in the lease area

would be unlikely to affect shore birds or coastal nesting birds, as the lease area is 209 km

(130 mi) 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 Marine Debris 

Debris lost overboard from offshore operations can injure or kill birds that ingest or become

entangled in it.  BOEM regulations and Federal law prohibit disposal of trash and debris in the

ocean.  In addition, the BOEM has issued NTL 2007‐G03, which instructs operators to exercise

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

placards at prominent locations on offshore vessels and structures.  A marine trash and debris

awareness training and certification process is required as well.  Compliance with this NTL will

minimize the likelihood of debris‐related impacts on birds, and no significant impacts are

expected.
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 Impacts of Support Vessel and Helicopter Traffic 

Support vessels and helicopters will transit coastal areas in Louisiana where shore birds 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 between

species and between individuals (Rodgers and Schwikert, 2002).  The disturbances will be

limited to flushing birds away from vessel pathways; known distances are from 20 to 49 m

(65 to 160 ft) for personal water craft and 23 to 58 m (75 to 190 ft) for an outboard‐powered

boat (Rodgers and Schwikert, 2002).  Flushing distances may be similar or less for the support

vessels to be used for Shell’s exploration project, and some species such as gulls are attracted

to boats.  Support vessels will not approach nesting or breeding areas on the shoreline, so

disturbances to nesting birds, eggs and chicks is not expected.  Vessel operators will use

designated navigation channels and comply with posted speed and wake restrictions while

transiting sensitive inland waterways.  Due to the limited scope and short duration of the

exploration drilling program, 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.  Aircraft, especially

helicopters, seem to cause the most intense responses over other human disturbances

(Bélanger and Bédard, 1989).  However, Federal Aviation Administration guidelines and

corporate helicopter policies specify that pilots must maintain a minimum altitude of 213 m

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

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

park properties.  With these guidelines in effect, it is likely that individual birds would

experience, at most, only short‐term behavioral disruption.

 Impacts of Large Oil Spill (WCD) 

The OSRA results summarized in Table 3 predict that shorelines of Louisiana and Texas that

include habitat for shore birds and coastal nesting birds could be affected within 10 to 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 Deepwater Horizon Response (2010) as of 4 October 2010, over 6,100 birds had

been collected dead since April 2010.  However, necropsies (to establish cause of death) have

not been completed on most of the dead animals.  About 2,260 of the dead animals were

visibly oiled.  In addition, over 2,000 oiled birds have been collected alive and about

1,200 released.  According to the International Bird Rescue Research Center (2010), bird

species that have been treated for oiling include

• Brown Pelican

• White Pelican

• Masked Booby

• Magnificent Frigatebird

• Laughing Gull

• Herring Gull

• Northern Gannet

• Black Crowned Night Heron

• Tri‐colored Heron

• Green Heron

• Cattle Egret

• Snowy Egret
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• Reddish Egret

• Least Bittern

• Common Tern

• Royal Tern

• Caspian Tern

• Sandwich Tern

• Forsters Tern

• Black Tern

• Gull‐billed Tern

• Least Tern

• Black Skimmer

• Black Oystercatcher

• White Ibis

• Roseate Spoonbill

• Willet

• Sanderling

• Dunlin

• Semipalmated Sandpiper

• Killdeer

• King Rail

• Clapper Rail

• Virginia Rail

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, 2010d).  Oil interferes with the water

repellency of feathers and can cause hypothermia in the right conditions.  As birds groom

themselves, they can ingest and inhale the oil on their bodies.  Scavengers such as Bald Eagles

and gulls can be exposed to oil by feeding on carcasses of contaminated fish and wildlife.  

While ingestion can kill animals immediately, more often it results in lung, liver, and kidney

damage, which can lead to death.  Bird eggs may be damaged if an oiled adult sits on the nest.

As noted above, the Brown Pelican was recently removed from the endangered species list.  

Following the recent Macondo spill, the USFWS reports that hundreds of dead Brown Pelicans

have been collected in the Gulf, making it second only to the Laughing Gull in confirmed

spill‐related deaths (Audubon, 2010).  These data indicate that Brown Pelicans may be

particularly at risk of oiling in the event of a large spill reaching Louisiana coastal waters.  

Issues for Brown Pelicans include direct contact with oil, disturbance by cleanup activities, and

long‐term habitat contamination.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on shore birds and coastal nesting birds are

expected.

C.5 Fisheries Resources

C.5.1 Pelagic Communities and Ichthyoplankton

Biggs and Ressler (2000) reviewed the biology of pelagic communities in the deepwater

environment of the northern Gulf of Mexico.  The biological oceanography of the region is

dominated by the influence of the Loop Current, whose surface waters are among the most

oligotrophic in the world’s oceans.  Superimposed on this low‐productivity condition are

productive “hot spots” associated with entrainment of nutrient‐rich Mississippi River water

and mesoscale oceanographic features.  Anticyclonic and cyclonic hydrographic features play

an important role in determining biogeographic patterns and controlling primary productivity

in the northern Gulf of Mexico (Biggs and Ressler, 2000).
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Most fishes inhabiting shelf or oceanic waters of the Gulf of Mexico have planktonic eggs and

larvae (Ditty, 1986; Ditty et al., 1988; Richards et al., 1989, 1993).  Pelagic eggs and larvae

become part of the planktonic community for various lengths of time (10 to 100 days

depending on the species) (MMS, 2007b).

IPFs potentially affecting pelagic communities and ichthyoplankton include drilling rig

presence, noise, and lights; water intakes; effluent discharges; and two types of accidents

(a small fuel spill and a large oil spill [WCD]).

 Impacts of Drilling Rig Presence, Noise, and Lights 

The drilling rig, as a floating structure in the deepwater environment, will act as 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 (e.g., 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 Water Intakes 

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

on the drilling rig.  The estimate intake and discharge of cooling water is 130,600 BPD

(i.e., 5.5 million gallons per day, MGD).  The rig will also use another 130,600 BPD for fire

water.  Shell will comply with the NPDES permit conditions, which require that (1) the cooling

water intake structure must be designed and constructed so that the maximum

through‐screen design intake velocity is 0.5 ft/s; and (2) the operator must minimize

impingement mortality of fish and shellfish and minimize entrainment of entrainable life

stages of fish and shellfish through the use of cooling water intake design and construction

technologies or operational measures.  Shell will comply with all NPDES permit conditions to

minimize the risk of entrainment or impingement of marine life.

The intake of seawater for cooling water will entrain plankton.  The low intake velocity should

allow most strong‐swimming juvenile fishes and smaller adults to escape entrainment or

impingement.  However, drifting plankton would not be able to escape entrainment with the

exception of a few fast‐swimming larvae of certain taxonomic groups.  Those organisms

entrained may be stressed or killed, primarily through changes in water temperature during

the route from cooling intake structure to discharge structure and mechanical damage

(turbulence in pumps and condensers).  Due to the limited scope and short duration of the

exploration drilling program, any short‐term impacts entrainment are not expected to be

biologically significant to plankton or ichthyoplankton populations.

 Impacts of Effluent Discharges 

Treated sanitary and domestic wastes may have a slight effect on the pelagic environment in

the immediate vicinity of these discharges.  These wastes may have elevated levels of

nutrients, organic matter, and chlorine, but should be diluted rapidly to undetectable levels

within tens to hundreds of meters from the source.  Minimal impacts on water quality,

plankton, and nekton are anticipated.
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Deck drainage may have a slight effect on the pelagic environment in the immediate vicinity of

these discharges.  Deck drainage from contaminated areas will be passed through an oil‐ and

water separator  prior to release, and discharges will be monitored for visible sheen.  The

discharges may have slightly elevated levels of hydrocarbons, but should be diluted rapidly to

undetectable levels within tens to hundreds of meters from the source.  Minimal impacts on

water quality, plankton, and nekton are anticipated.

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

uncontaminated cooling water, fire water, and ballast water are expected to be diluted rapidly

and have little or no impact on water column biota.

 Impacts of a Small Fuel Spill 

Potential spill impacts on fisheries resource are discussed in recent EISs (MMS, 2007b, 2008)

and for this 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.  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

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

A small fuel could have localized impacts on phytoplankton, zooplankton, and nekton.  Due to

the limited areal extent and short duration of water quality impacts,  small fuel spill would be

unlikely to produce detectable impacts on pelagic communities.

 Impacts of a Large Oil Spill (WCD) 

A large oil spill could affect water column biota including phytoplankton, zooplankton,

ichthyoplankton, and nekton.  A large spill that persisted for weeks or months would be more

likely to affect these communities.  While adult and juvenile fishes may actively avoid a large

spill, planktonic eggs and larvae would be unable to avoid contact.  Eggs and larvae of fishes

are especially vulnerable to oiling because they inhabit the upper layers of the water column,

and they will die if exposed to certain toxic fractions of spilled oil.  Impacts 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 (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response
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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, shrimp, 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).  Except

for corals and coral reefs, the EFH for all of these GMFMC‐managed species is in waters

shallower than 183 m (600 ft) and does not include the lease area.  EFH for corals and coral

reefs includes topographic features on the Texas‐Louisiana OCS, the nearest of which are

Rezak and Sidner Banks (combined as Rezak Sidner Bank in the EFH designation, and located

36 km [23 mi] to the 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):

• Bigeye tuna (juvenile, adult)

• Atlantic bluefin tuna (spawn, eggs,

larvae, adults)

• Atlantic skipjack tuna (spawn,

eggs, larvae, adults)

• Yellowfin tuna (all)

• Swordfish (all)

• Blue marlin (juveniles, adults)

• White marlin (juveniles, adults)

• Sailfish (juveniles, adults)

• Longbill spearfish (juveniles,

adults)

• Great hammerhead shark (all)

• Tiger shark (adult)

• Whale shark (all)

• Longfin mako shark (all)

• Shortfin mako shark (all)

• Bigeye thresher shark (all)

• Common thresher shark (all)

In addition, NMFS (2009) designated a Habitat Area of Particular Concern (HAPC) for spawning

Atlantic bluefin tuna, and this covers much of the deepwater Gulf of Mexico, including the

lease area.

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: East and West Flower Garden Banks, Stetson Bank, Sonnier Bank, MacNeil,
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29 Fathom Bank, Rankin Bright Bank, Geyer Bank, McGrail Bank, Bouma Bank, Rezak Sidner

Bank, Alderice Bank, and Jakkula Bank.  As noted previously, Rezak Sidner Bank is located

36 km (23 mi) to the north of the lease area.

Routine IPFs potentially affecting EFH include drilling rig presence, noise, and lights; water

intakes; effluent discharges; and two types of accidents – a small fuel spill and a large oil spill

(WCD).

 Impacts of Drilling Rig Presence, Noise, and Lights 

The drilling rig, as a floating structure in the deepwater environment, will act as 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 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 are considered minor.

 Impacts of Water Intakes 

As noted previously, cooling water intake will cause entrainment and impingement of

plankton, including fish eggs and larvae (ichthyoplankton).  Due to the limited scope and short

duration of the exploration drilling program, any short‐term impacts are not expected to be

biologically significant to EFH.

 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 are expected from these 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 on EFH.  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) and for this EP,

there are no unique site‐specific issues with respect to spill impacts.

A small fuel spill in offshore waters would produce a slick on the water surface and increase

the concentrations of petroleum hydrocarbons and their degradation products.  The extent

and persistence of impacts would depend on the meteorological and oceanographic conditions

at the time and the effectiveness of spill response measures.  Section A.9.2 discusses the likely

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed

naturally within 24 hours.  The area of the sea surface with diesel fuel on it would range from

0.5 to 5 ha (1.2 to 12 ac) depending on sea state and weather conditions.
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A small fuel 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 areal extent of

the affected area would represent a negligible portion of the HAPC.

A small fuel spill would not affect EFH for corals and coral reefs, which includes topographic

features on the Texas‐Louisiana OCS, the nearest of which are Rezak and Sidner Banks

(combined as Rezak Sidner Bank in the EFH designation, and located 36 km [23 mi] to the

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 (WCD) 

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

there are no unique site‐specific issues with respect to EFH.

An oil spill in offshore waters would temporarily increase hydrocarbon concentrations on the

water surface and potentially the subsurface as well.  Given the extent of EFH designations in

the Gulf of Mexico (GMFMC, 2005; NMFS, 2009), some impact on EFH would be unavoidable.  

A small spill would mainly affect the EFH for several highly migratory species of tunas,

swordfishes, billfishes, and sharks (as listed above).  Effects probably would be undetectable

due to the small percentage of the EFH affected and the relatively short duration of impacts.

A large spill could affect the EFH for many managed species including shrimp, stone crab, spiny

lobster, reef fishes, coastal migratory pelagic fishes, and red drum.  It would result in adverse

impacts on water quality and water column biota including phytoplankton, zooplankton, and

nekton.  In coastal waters, sediments could be contaminated and result in persistent

degradation of the seafloor habitat for managed demersal fish and shellfish species.

The lease area is within the HAPC for Atlantic bluefin tuna spawning (NMFS, 2009).  These and

other migratory species that pass through the area following a spill could be exposed to oil,

which could result in lethal or sublethal impacts.

Rezak Sidner Bank, located 36 km (23 mi) to the north of the lease area, is designated as EFH

under the corals and coral reefs management plan, and also HAPC.  An accidental spill would

be unlikely to affect this feature.  A surface slick would not affect the bank.  As noted

previously, there are reports of subsurface plumes resulting from subsea dispersant use during

the Macondo spill.  However, Rezak Sidner Bank is located on the continental shelf edge and a

plume would have to move upslope to reach it.  Spill impacts are considered unlikely because

the predominant currents are along the isobath.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on EFH are expected.
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C.6 Archaeological Resources

C.6.1 Shipwreck Sites

GB 427 is on the list of leases with a high potential for historic shipwrecks.  Under

NTL 2005‐G07, high‐probability lease blocks require a side‐scan sonar survey with 300‐m line

spacing.  An archaeological assessment prepared by Fugro Geoservices, Inc. for Shell is

included as part of the EP submittal.  Files maintained by the BOEM and Fugro Chance indicate

that one modern shipwreck was identified in the lease area (the shrimp boat Saint Mary, sunk

in 1990), and Shell has established a 229‐m (750‐ft) avoidance radius to protect it.

The only routine IPF potentially affecting shipwreck sites is physical disturbance to the seafloor

(an impact that will be avoided).  Impacts of a large oil spill (WCD) are also considered.  A small

fuel spill would not affect shipwrecks because the oil would float and dissipate on the sea

surface.

 Impacts of Physical Disturbance to the Seafloor 

Shell has established a 229‐m (750‐ft) avoidance radius to protect the shipwreck site identified

in the lease area.  Since Shell’s operations will avoid this area, no impacts on historic

shipwrecks are expected as a result of the proposed activities.

As required by NTL 2005‐G07, should any debris that appears to indicate the presence of a

shipwreck be discovered during the proposed operations, Shell will immediately halt

operations, take steps to ensure the site is not disturbed, and contact the Regional Supervisor,

Leasing and Environment, within 48 hours of the discovery.  Shell will cease operations within

305 m (1,000 ft) of the site until the Regional Director provides instruction on steps to assess

the site’s potential historic significance.  The avoidance radius and compliance with

NTL 2005‐G07 will ensure that there are no significant impacts to shipwreck sites.

 Impacts of a Large Oil Spill (WCD) 

Shell has established a 229‐m (750‐ft) avoidance radius to protect the shipwreck site identified

in the lease area.  The most likely physical effects of a subsea blowout would be within a few

hundred meters of the wellsite.  The MMS (2007b) estimates that a severe subsurface blowout

could resuspend and disperse sediments within a 300‐m (984‐ft) radius.  While coarse

sediments (sands) would probably settle at a rapid rate within 400 m (1,312 ft) from the

blowout site, fine sediments (silts and clays) could be resuspended for more than 30 days and

dispersed over a much wider area.  Based on previous studies, surface sediments at the

project area are assumed to largely be silt and clay (Gallaway, 1988).

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect

archaeological sites beyond the immediate vicinity of the wellhead (i.e., due to physical

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the

spill location.  However, during the Macondo spill, subsurface plumes were reported at a

water depth of about 1,100 m (3,600 ft), extending at least 35 km (22 mi) from the wellsite

and persisting for more than a month (Camilli et al., 2010).  The subsurface plumes apparently

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c).  While the

behavior and impacts of subsurface plumes are not well known, a subsurface plume could

have the potential to contact shipwreck sites beyond the 300 m (984 ft) radius estimated by

MMS (2007a, 2008) depending on its extent, trajectory, and persistence.  If oil from a subsea
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spill should come into contact with wooden shipwrecks on the seafloor it could adversely

affect their condition or preservation.  Should there be any indication that potential shipwreck

sites could be affected, in accordance with NTL  2005‐G07 Shell will immediately halt

operations, take steps to ensure that the site is not disturbed in any way and contact the

Regional Supervisor, Leasing and Environment, within 48 hours of its discovery.  Shell would

cease all operations within 305 m (1,000 ft) of the site until the Regional Director provides

instructions on steps to take to assess the site’s potential historic significance and protect it.

A spill entering shallow coastal waters could conceivably contaminate an undiscovered

shipwreck site.  The OSRA modeling summarized in Table 3 predicts that Louisiana and Texas

shorelines could be contacted by a spill within 10 to 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.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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 about 640 to 884 m (2,100 to 2,900 ft), the lease area is well

beyond the 60‐m (197‐ft) depth contour used by the BOEM as the seaward extent for

prehistoric archaeological site potential in the Gulf of Mexico.  The archaeological assessment

identified no landforms or features that might be high probability prehistoric sites, such as

natural levees or point bar deposits.

Because prehistoric archaeological sites are not found in the lease area, the only relevant IPF is

a large oil spill (WCD).  A small fuel spill would not affect prehistoric archaeological resources

because the oil would float and dissipate on the sea surface.

 Impacts of a Large Oil Spill (WCD) 

Because prehistoric archaeological sites are not found in the lease area, they would not be

affected by the physical effects of a subsea blowout.  The MMS (2007b) estimates that a

severe subsurface blowout could resuspend and disperse sediments within a 300‐m (984‐ft)

radius.

Along the northern Gulf coast, prehistoric sites occur frequently along the barrier islands and

mainland coast and along the margins of bays and bayous (MMS, 2007b).  The OSRA modeling

summarized in Table 3 predicts that Louisiana and Texas shorelines could be contacted by a

spill within 10 to 30 days.  A spill reaching a prehistoric site along these shorelines could coat

fragile artifacts or site features and compromise the potential for radiocarbon dating organic

materials in a site (although other dating methods are available and it is possible to

decontaminate an oiled sample for radiocarbon dating).  Coastal prehistoric sites could also be

damaged by spill cleanup operations (e.g., by destroying fragile artifacts and disturbing the

provenance of artifacts and site features).
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A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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 Oil Spill Response Plan

(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 in a wildlife refuge or a wilderness area.  Potential impacts

of support vessel traffic are addressed briefly below.

A small fuel spill in the lease area would be unlikely to affect coastal habitats, as the lease area

is 209 km (130 mi) 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 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.  This is of

particular concern in coastal Louisiana because of the existing high rate of coastal wetland

loss.  Support operations, including crew boats and supply boats as detailed in 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 (WCD) 

Potential spill impacts on coastal habitats are discussed in recent EISs (MMS, 2007b, 2008).  

Coastal habitats inshore of the project area include barrier beaches and dunes, wetlands, and

submerged seagrass beds.  For this EP, there are no unique site‐specific issues with respect to

coastal habitats.

The OSRA results summarized in Table 3 predict that shorelines of Louisiana and Texas could

be affected within 10 to 30 days.  The model predicts no shoreline contacts within 3 days of a

spill.  One Louisiana parish (Cameron) could be contacted within 10 days.  After 30 days,

13 counties or parishes may be contacted, including 8 Texas counties and 5 Louisiana parishes.  

Cameron Parish, Louisiana, has the highest probability of contact for the 10 and 30 day

intervals.
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The Louisiana and Texas 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.  National wildlife

refuges along the coast are discussed in the lease sale EIS (MMS, 2007b) and Shell’s OSRP.  

Coastal wildlife and wilderness areas within the geographic range of the potential shoreline

contacts include:

• Anahuac NWR

• Texas Point NWR

• Sabine NWR

• Rockefeller Wildlife Management Area and Game Preserve

• Russell Sage Foundation Marsh Island State Wildlife Refuge

• Shell Keys NWR

• Atchafalaya Delta State Wildlife Management Area

• Isles Dernieres Barrier Island Refuge

• East Timbalier Island NWR

• Pass A Loutre State Wildlife Management Area

• Wisner State Wildlife Management Area

• Delta NWR

• Breton NWR

It is not known whether other, more distant coastal areas could be affected if an oil spill

persisted for more than 30 days.  Additional NWRs and other managed wildlife areas occur

along the Gulf coast of Mississippi, Alabama, and Florida.  These areas include habitats such as

barrier beach and dune systems, wetlands, and submerged seagrass beds that support 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 2.7 ha (6.7 ac) of wetland vegetation will experience

dieback.  Thirty percent of these damaged wetlands are assumed to recover within 4 years,

and 85% within 10 years.  About 15% of the contacted wetlands are expected to be converted

permanently to open‐water habitat.  The critical concentration of oil is that concentration

above which impacts to wetlands will be long term and recovery will take longer than two

growing seasons, and which causes plant mortality and some permanent wetland loss. Critical

concentrations of various oils are expected to vary broadly for wetland types and wetland
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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 (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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.  However, 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 70‐km (43‐mi) 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 250 to 550 m (820 to 1,804 ft).  Tilefish are caught by bottom longlining in

water depths from about 165 to 450 m (540 to 1,476 ft) (Continental Shelf Associates, Inc.,

2002).

Most recreational fishing activity in the region occurs in water depths less than 200 m (656 ft)

(Continental Shelf Associates, Inc., 1997, 2002).  In deeper water, the main attraction to

recreational fishers would be petroleum platforms offshore Louisiana, Mississippi, and Texas.  

Due to the distance from shore, it is unlikely that any recreational fishing activity is occurring in

the project area.

The only routine IPF potentially affecting fisheries is drilling rig presence (including noise and

lights).  Two potential accidents are also addressed below – a small fuel spill and a large oil spill

(WCD).
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 Impacts of Drilling Rig Presence 

There is a slight possibility of pelagic longlines becoming entangled in the drilling rig.  For

example, in January 1999, a portion of a pelagic longline snagged on the acoustic Doppler

current profiler of a drillship working in the Gulf of Mexico (Continental Shelf Associates, Inc.,

2002).  The line was removed without incident.  Generally, longline fishers use radar and are

aware of offshore structures and ships when placing their sets.  Therefore, little or no impact

on pelagic longlining is expected.

Because it is unlikely that any recreational fishing activity is occurring in the project area, no

adverse impacts are anticipated.  Other factors such as effluent discharges are likely to have

negligible impacts on commercial or recreational fisheries due to rapid dispersion, the small

area of ocean affected, and the intermittent nature of the discharges.

 Impacts of a Small Fuel Spill 

The probability of a fuel spill will be minimized by 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.  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 0.5 to 5 ha (1.2 to

12 ac) depending on sea state and weather conditions.  Fishing activities could be interrupted

due to the activities of response vessels operating in the lease area.  A small fuel spill would

not affect coastal water quality because the spill would not be expected to make landfall or

reach coastal waters prior to breaking up (see Section A.9.2).

 Impacts of a Large Oil Spill (WCD) 

Potential spill impacts on fishing activities are discussed in recent EISs (MMS, 2007b, 2008).  

For this EP, there are no unique site‐specific issues with respect to this activity.

Pelagic longlining activities in the lease area and other fishing activities in the northern Gulf of

Mexico could be interrupted in the event of a large oil spill.  A spill may or may not result in

fishery closures, depending on the duration of the spill, the oceanographic and meteorological

conditions at the time, and the effectiveness of spill response measures.  The recent Macondo

spill provides information about the maximum potential extent of fishery closures in the event

of a large oil spill in the Gulf of Mexico (NMFS, 2010c).  At its peak on 12 July 2010, closures

encompassed 217,821 km2 (84,101 mi2

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

the Gulf of Mexico.  As of 15 October 2010, three months after the flow of oil was stopped, the

area has been reduced to 42,686 km2 (16,481 mi2

) or 7% of the EEZ.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on fishing activities are expected.
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C.8.2 Public Health and Safety

There are no IPFs associated with routine operations that are expected to affect public health

and safety.  Impacts of a small fuel spill and a large oil spill (WCD) are addressed below.

 Impacts of a Small Fuel Spill 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine

operations including fuel transfer.  In the unlikely event of a spill, implementation of Shell’s

OSRP will mitigate and reduce the potential for impacts.  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 209 km (130 mi) from the nearest shoreline and

nearly all of the diesel fuel would evaporate or disperse naturally within 24 hours.  Response

crews would be equipped with appropriate safety equipment to avoid injury and health

effects.  A small fuel spill would not be expected to make landfall or reach coastal waters prior

to breaking up (see Section A.9.2).

 Impacts of a Large Oil Spill (WCD) 

In the event of a large spill from a blowout, the main safety and health concerns are those of

the offshore personnel involved in the incident and those responding to the spill.  The

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,

including skin contact or breathing volatile organic compounds.  Crude oil is a highly flammable

material and any smoke or vapors from a crude oil fire can cause irritation, and in large

quantities, may pose a health hazard.

Data from the recent Macondo spill provide relevant information about the types of health

issues that may occur in the event of a large oil spill (Centers for Disease Control and

Prevention, 2010a).  Wildlife cleaning  and rehabilitation workers have reported concerns

including scrapes and cuts, itchy or red skin or rash, and symptoms of headache or feeling

faint, dizzy, or fatigued.  Hand, shoulder, or back pain was also reported by some wildlife

cleaning workers.  Personnel working on offshore vessels or providing direct oversight to

offshore vessels, including USCG personnel, civilian contractors, and other responders who

were exposed to oil and dispersants had 7 to 12 times higher prevalences of upper respiratory

symptoms and cough than those not exposed (Centers for Disease Control and Prevention,

2010b).  Another potential occupational hazard for spill response workers in general was heat

stress from work in a hot and humid environment.  Initial symptoms from cleanup workers

who sought medical care in Louisiana were typical of acute exposure to hydrocarbons or

hydrogen sulfide 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).
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A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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 exploratory wells with support from existing

shore base facilities in Louisiana.  No new or expanded facilities will be constructed, and no

new employees are expected to move permanently into the area.  The project will have a

negligible impact on socioeconomic conditions such as local employment, existing offshore

and coastal infrastructure (including major sources of supplies, services, energy, and water),

and minority and lower income groups.  Impacts of a small fuel spill and a large oil spill (WCD)

are addressed below.

 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.  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 (WCD) 

Potential socioeconomic impacts of an oil spill are discussed in recent EISs (MMS, 2007b,

2008).  For this EP, there are no unique site‐specific issues with respect to employment and

coastal infrastructure.  A large spill could cause economic impacts in several ways: it could

result in extensive fishery closures that put fishermen out of work; it could result in temporary

employment as part of the response effort; it could result in adverse publicity that affects

employment in coastal recreation and tourism industries; and it could result in another

suspension of OCS drilling activities, including service and support operations that are an

important part of local economies.

The lease area is 209 km (130 mi) from the nearest shoreline (Louisiana).  Based on OSRA

modeling as summarized in Table 3, Louisiana and Texas coastal areas are the most likely to be

contacted by a spill.  It is not known whether other, more distant coastal areas could be

affected if an oil spill persisted for more than 30 days.

In addition to the analysis presented by MMS (2007b, 2008), a recent study explored the

economic impacts of the Macondo spill on oil and gas industry employment due to suspension

of deepwater drilling (Inter‐Agency Economic Report, 2010).  The study indicates the types of

employment impacts that could occur in the event of a large oil spill in the lease area.

A blowout resulting in a large oil spill (WCD) 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
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detailed in EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on employment and infrastructure are

expected.

C.8.4 Recreation and Tourism

There are no known recreational uses of the lease area.  Recreational resources and tourism in

coastal areas would not be affected by any routine activities due to the distance from shore.  

Compliance with NTL 2007‐G03 will minimize the chance of trash or debris being lost

overboard from the drilling rig and subsequently washing up on beaches.

 Impacts of a Small Fuel Spill 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine

operations including fuel transfer.  In the unlikely event of a spill, implementation of Shell’s

OSRP will mitigate and reduce the potential for impacts.  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 (WCD) 

Potential impacts of an oil spill on recreation and tourism are discussed in recent EISs

(MMS, 2007b, 2008).  For this EP, there are no unique site‐specific issues with respect to these

impacts.

Impacts on recreation and tourism would vary depending on the duration of the spill and its

fate including the effectiveness of response measures.  A large spill that reached coastal

waters and shorelines could adversely affect recreation and tourism by contaminating beaches

and wetlands, resulting in negative publicity that encourages people to stay away.  Based on

OSRA modeling as summarized in Table 3, Louisiana and Texas coastal areas are the most likely

to be contacted by a spill.  These include popular beaches and recreational sites along the

coast.  It is not known whether other, more distant coastal areas could be affected if an oil spill

persisted for more than 30 days.  

In addition to the analysis presented by MMS (2007b, 2008), recent studies have explored the

economic impacts of the Macondo spill including tourism and “brand” damage (IEM, 2010;

Oxford Economics, 2010).  These studies indicate the broad range of potential economic

impacts that could occur in the event of a large oil spill in the lease area.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on recreation and tourism are expected.
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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 potential 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 shore base.

A large oil spill (WCD) is the only relevant IPF.  A small fuel spill would not have any impacts on

land  use, as the response would be staged out of existing shore bases and facilities.

 Impacts of a Large Oil Spill (WCD) 

The initial response for a large oil spill would be staged out of existing facilities, with no effect

on land use.  A large spill could have limited temporary impacts on land use along the coast if

additional staging areas were needed.  For example, during the Macondo spill, temporary

staging areas were established in Louisiana, Mississippi, Alabama, and Florida for spill response

and cleanup efforts.  In the event of a large spill in the lease area, similar temporary staging

areas could be needed.  These areas would eventually return to their original use as the

response is demobilized.

A blowout resulting in a large oil spill (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  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

There are no IPFs from routine project activities that are likely to affect shipping or other

marine uses.  The lease area is not located within any USCG‐designated fairway or shipping

lane.  Shell will comply with BOEM requirements and lease stipulations to avoid impacts on

uses of the area by military vessels and aircraft.  Based on the map referenced in

NTL 2009‐G06, the lease area is not located in a Military Warning Area.

Shell’s Auger tension‐leg platform is centered in GB 426 and its anchors extend into GB 426

and GB 427.  Flowlines flank the Auger dome on all sides.  Shell proposes a moored drilling rig

with a permitted radius of 4,420 m (14,500 ft) (plus an additional 305‐m [1,000‐ft] buffer) for

exploratory operations in GB 427.  Existing pipelines surround and cross the proposed

anchoring radius.  Shell will maintain a buffer of at least 152 m (500 ft) when setting anchors

and will not set anchors at the intersection of the pipelines.  There are no other known marine

uses of the lease area.

A large oil spill (WCD) is the only relevant accident IPF.  A small fuel spill would not have any

impacts on other marine uses, as the spill and response activities would be mainly within the

lease area and the duration would be brief.
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 Impacts of a Large Oil Spill (WCD) 

An accidental spill would be unlikely to significantly affect shipping or other marine uses.  The

block is not located within any USCG‐designated fairway or shipping lane.  In the event of a

large spill requiring numerous response vessels, coordination would be required to manage

the vessel traffic for safe operations.  Shell will comply with BOEM requirements and lease

stipulations to avoid impacts on uses of the area by military vessels and aircraft.

Shell’s Auger tension‐leg platform is centered in GB 426 and its anchors extend into GB 426

and GB 427.  Flowlines flank the Auger dome on all sides.  Shell proposes a moored drilling rig

with a radius of 4,420 m (14,500 ft) (plus an additional 305‐m [1,000‐ft] buffer) for exploratory

operations in GB 427.  Existing pipelines surround and cross the proposed anchoring radius.  

Shell will maintain a buffer of at least 152 m (500 ft) when setting anchors and will not set

anchors at the intersection of the pipelines.  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 (WCD) 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 EP Section 2j.  In the unlikely event of a spill, implementation of Shell’s OSRP will

mitigate and reduce the impacts.  EP Sections 2j and 9b provide detail on spill response

measures.  Therefore, no significant spill impacts on other marine uses are expected.

C.9 Cumulative Impacts

For purposes of NEPA, cumulative impact is defined as “the impact on the environment which

results from the incremental impact of the action when added to other past, present, and

reasonably foreseeable future actions regardless of what agency (Federal or non‐Federal) or

person undertakes such other actions” (40 CFR 1508.7).  Any single activity or action may have

a negligible impact(s) by itself, but when combined with impacts from other activities in the

same area and/or time period, substantial impacts may result.

Prior Studies.  Prior to lease sale 84, in which Shell obtained GB 427, MMS prepared an EIS (EIS

No. 830644, Final, MMS, MXG 1984 Central/Western Gulf of Mexico OCS Oil/Gas Sales Nos. 81

and 84), in which it analyzed the environmental impact of activities that might occur in that

lease area.  The MMS also recently analyzed the cumulative impacts of a proposed exploration

drilling program similar to the activities planned in this EP in several documents.  The level and

types of activities planned in Shell's 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.  Given

the current regulatory uncertainty regarding project permitting following the lifting of the Gulf

of Mexico deepwater moratorium, Shell currently is unaware of any projects that are planned

to occur within the immediate vicinity of Shell’s proposed project.
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Cumulative Impacts of Activities in the 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 (see EIS page 4‐301).  The EIS

considered exploration, delineation, and development wells; platform installation; and

service‐vessel trips.  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 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 EP, in conjunction with the other reasonably

foreseeable activities expected to occur in the Gulf of Mexico, as well as the known impacts

from the Macondo spill in MC 252.  While another large oil spill could have significant impacts,

the numerous new safety measures implemented by BOEM, and further mitigation and safety

measures proposed by Shell in its EP, result in an environmentally safer drilling program that

reduces the likelihood of another large spill, and improves the effectiveness of any response in

the extremely unlikely event that another large spill occurs.  Thus, for all impacts, the

incremental contribution of Shell’s proposed actions to the cumulative impacts analysis in

these prior analyses is not significant.

C.9.1 Cumulative Impacts to Physical /Chemical Resources

The work planned in this EP is limited in geographic scope and duration, and the impacts on

the physical/chemical environment will be correspondingly limited.  

Air Quality.  Emissions from pollutants into the atmosphere from activities are not projected to

have significant effects on onshore air quality because of the prevailing atmospheric

conditions, emission rates and heights, and resulting pollutant concentrations.  As BOEM

found in the multi‐lease‐sale EISs, the incremental contribution of activities similar to Shell’s

proposed activities to the cumulative impacts is not significant and will not cause or contribute

to a violation of any national ambient air quality standard (MMS, 2007b, 2008).  While portions

of the Gulf Coast have ozone levels that exceed the Federal air quality standard, the

incremental contribution from the types of activities proposed in Shell’s EP is very small (MMS,

2007b, 2008).  In addition, the cumulative contribution to visibility impairment is also very

small (MMS, 2007b, 2008).  Since BOEM completed the multi‐lease‐sale EISs, USEPA has

adopted a new short‐term National Ambient Air Quality Standard for nitrogen dioxide.  The

standard has not yet been implemented in the Gulf Coast states, but preliminary analysis

indicates that emissions from Shell’s EP are not likely to contribute to violations of that

standard.

Climate Change.  CO2 and CH4 emissions from the project would constitute a small incremental

contribution to greenhouse gas emissions from all OCS activities.  According to the

Programmatic EIS (MMS, 2007a), estimated CO2 emissions from all OCS activities in the

2007‐2012 leasing program are about 0.08% to 0.016% of the global CO2 emissions from fossil

fuel combustion.  Greenhouse gas emissions may contribute to climate change, with important

effects on temperature, rainfall, frequency of severe weather, ocean acidification, and sea

level rise (Intergovernmental Panel on Climate Change, 2007).  In the Gulf of Mexico, sea level
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rise is an important issue due to the ongoing dramatic losses in coastal wetlands, particularly

in coastal Louisiana.  Nevertheless, greenhouse gas emissions from the proposed EP in

combination with such emissions from reasonably foreseeable projects in the vicinity are not

expected to significantly change global climate change impacts that could in turn affect the

Gulf of Mexico area.

Water Quality.  Shell’s planned exploration program will have some minor water quality

impacts due to the NPDES‐permitted discharge of drilling muds 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 (2010b) has found levels of ozone and

particulates ranging from “good” to “unhealthy for sensitive groups” on EPA’s Air Quality

Index; these are at levels well below those that would cause short‐term health problems.  The

air monitoring conducted to date has not found any pollutants at levels expected to cause

long‐term harm (USEPA, 2010b).  Satellite imagery provides no evidence that the GB 427 lease

area, which is located approximately 400 km (250 mi) south‐south‐west of the Macondo spill

site, received any surface slicks of oil (ESRI, 2010).  Therefore, 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 extensive 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 provides no evidence that the GB 427 lease area received any

surface slicks of oil (ESRI, 2010), and due to the distance from the lease area, it is unlikely that

subsurface plumes have affected water quality in or near the lease area.  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 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 physical disturbance

to the seafloor during mooring of the drilling rig and from discharges of drilling mud and

cuttings are expected to be minor and limited to a small area.  Areas that may support

high‐density deepwater benthic communities have been 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
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regionally.  As noted in the multi‐lease‐sale EISs, the incremental contributions of activities

similar to Shell’s proposed activities to the cumulative impacts is not significant (MMS, 2007b,

page 4‐325).

Threatened, Endangered, and Protected Species.  Threatened and endangered species

reasonably likely to occur in the lease area include the sperm whale and five species of sea

turtles.  Potential impact sources include drilling rig presence including noise and lights;

marine debris; and support vessel and aircraft traffic.  Potential effects for these species would

be limited and temporary, and would be reduced by Shell’s compliance with all

BOEM‐required mitigation measures including NTLs 2007‐G03 and 2007‐G04.  No significant

cumulative impacts are expected.

Coastal and Marine Birds.  Some birds may be attracted to offshore structures because of the

lights and the fish populations that aggregate around these structures.  Birds that frequent

platforms may be exposed to contaminants including air pollutants and routine discharges, but

significant impacts are unlikely due to rapid dispersion.  Shell’s compliance with NTL 2007‐G03

will minimize the likelihood of debris‐related impacts on birds.  Support vessel and helicopter

traffic may disturb some foraging and resting birds; however, it is likely that individual birds

would experience, at most, only short‐term behavioral disruption.  Due to the limited scope

and short duration of the exploration drilling program, collisions or other adverse effects are

unlikely, and no significant cumulative impacts are expected.

Fisheries Resources.  Drilling rigs are known to be “fish‐attracting devices” such that some

species of epipelagic fishes may be attracted to the rig and potentially attract predators, but

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.  When the drilling rig is on‐site, these effects would be temporarily additive to those

associated with other exploration and production structures in the area, but would occur at

low levels such that the cumulative effect would be negligible.

Coastal Habitats.  Due to the distance 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 are not in a wildlife refuge or a wilderness area.  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 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
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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)

assumed that oil spills would be unlikely to affect benthic communities beyond the immediate

vicinity of the wellhead (i.e., due to physical impacts of a blowout) because the oil would rise

quickly to the sea surface directly over the spill location.  However, during the Macondo spill,

subsurface plumes were reported at a water depth of about 1,100 m (3,600 ft), extending at

least 35 km (22 mi) from the wellsite and persisting for more than a month (Camilli et al.,

2010).  The subsurface plumes apparently resulted from the use of dispersants at the wellhead

(Joint Analysis Group, 2010c).  While the behavior and impacts of subsurface plumes are not

well known, a subsurface plume could contact the seafloor and affect benthic communities

beyond the 300 m (984 ft) radius estimated by MMS (2007a, 2008) depending on its extent,

trajectory, and persistence.  However, due to the distance from the Macondo spill site, it is

unlikely that subsurface plumes have affected any benthic communities in or near the lease

area, and therefore significant cumulative impacts are unlikely.

C.9.3 Cumulative Impacts to Socioeconomic Resources

The work planned in this EP is limited in geographic scope and duration, and the impacts on

socioeconomic resources will be correspondingly limited.

Archaeological Resources.  GB 427 is on the list of leases with a high potential for historic

shipwrecks.  Under NTL 2005‐G07, high‐probability lease blocks require a side‐scan sonar

survey with 300‐m line spacing.  An archaeological assessment prepared by Fugro Geoservices,

Inc. for Shell is included as part of the EP submittal.  Files maintained by the BOEM and Fugro

Chance indicate that one modern shipwreck was identified in the lease area (the shrimp boat

Saint Mary, sunk in 1990), and Shell has established a 229‐m (750‐ft) avoidance radius to

protect it.  Since Shell’s operations will avoid this area, no cumulative impacts on historic

shipwrecks are expected as a result of the proposed activities.

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 archeological resources, land use and coastal infrastructure, demographics, and

environmental justice (MMS, 2007b, pages 4‐359 to 4‐378).  BOEM 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 is the Macondo spill.  The spill has resulted in impacts on
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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 U.S. Exclusive Economic Zone (EEZ) in the Gulf of Mexico (NOAA

Fisheries Service, 2010b,c).  The closures have now been reduced to 7% of the EEZ; state

closures are still in effect in Louisiana.  The U.S. Travel Association has estimated that the

economic impact of the Macondo spill on tourism across the Gulf Coast over a three‐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 hydrogen sulfide

(Centers for Disease Control and Prevention, 2010a, 2010b; Solomon and Janssen, 2010).  

Most of these impacts were temporary in nature, although health exposure of clean‐up

workers could have longer‐lasting impacts.

However, for all the reasons discussed in the 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 analysis concludes that the wellsites are free of any major hazards and are

suitable for the proposed activities.  Shell has designated a 152‐m (500‐ft) avoidance zone

around four amplitude and fluid expulsion features on the crest of the Auger diapir that could

support chemosynthetic and/or deepwater coral communities.

The Auger dome has numerous seafloor faults that radiate from its crest.  There are also faults

that curve around the perimeter of the dome.  These faults are usually small displacements

affecting the shallow sediments and the seafloor.  Because of these conditions, the positioning

of the suction anchors has been optimized.  The suction anchors will be located to minimize

penetration of shallow seafloor faults on the eastern side of the dome.  Shell will set the

anchors using an ROV to survey the area before installation.  Anchors 2, 3, 4, 5, 6, 7, and 8 will

be installed undressed (without rope) due to their proximity to faults and pipelines.

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 support activities (vessel and helicopter traffic) and make it

necessary to suspend some activities on the drilling rig for safety reasons until the storm or

weather event passes.  In the event of a hurricane, procedures as outlined in the Hurricane

Evacuation Plan would be adhered to.
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D.3 Currents and Waves

Under most circumstances, physical oceanographic conditions are not expected to have any

effect on the proposed activities.  Strong currents (e.g., caused by Loop Current eddies and

intrusions) and large waves were considered in the design criteria for the drilling rig.  High

waves during a severe storm could disrupt support activities (i.e., vessel and helicopter traffic)

and make it necessary to suspend some activities on the drilling rig for safety reasons until the

storm or weather event passes.

E.  Alternatives

According to 30 CFR 250.227 and NTL 2008‐G04, alternatives do not need to be evaluated for

exploratory activities.  Therefore, no formal alternatives are evaluated in this EIA.  However,

various technical and operational options were considered by Shell in developing the proposed

action including the location of the wellsites.

Multiple notional surface locations were proposed by the prospect development team with

one surface location being the primary location.  These locations were determined to be the

best for reaching the reservoir objectives that were identified for the wells.  An extensive

analysis was conducted to ensure that there were no seafloor or near‐seafloor issues that

would need to be avoided or mitigated either by moving the locations or by the well design.  

Seafloor slope, faulting, seafloor and near‐seafloor subsurface amplitudes, and soil stability

were all scrutinized to ensure final surface locations were optimal for drilling hazards while still

viable for reaching the objectives.  Slope stability on the escarpment of the Auger dome

proved to be an issue for all the notional surface locations.  A slope stability analysis indicated

stable conditions on the northeast side of the dome.  In the case of failure, a maximum debris

runoff was projected to reach or pass the notional surface locations.  All notional surface

locations were therefore moved past the calculated disturbance area in the event a slump was

to occur.

F.  Mitigation Measures

The proposed action includes numerous mitigation measures required by laws, regulations,

and BOEM lease stipulations and NTLs.  The project will comply with 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 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.
Garden Banks Block 427 (Lease OCS‐G 7493)    October 2010

Environmental Impact Analysis for Supplemental Exploration Plan Page 68

• 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 in for recycling.

• Every drain on the rig is assigned a number on a checklist.  The checklist is used daily to

verify drain plugs are installed.

• All trash containers are checked and emptied daily, and trash containers are kept covered.  

Trash is disposed of in a compactor and shipped in via boat.

• 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.

G.  Consultation

No persons or agencies were consulted during the preparation of this EIA.

H.  Preparers

The EIA was prepared by CSA International, Inc. (CSA).  Contributors included

• Neal Phillips, Ph.D. (Senior Scientist);

• Bruce Graham (Senior Scientist/Marine Specialist);

• Luis Lagera, Ph.D. (Senior Scientist);

• Deborah Kilbane (Staff Scientist/Benthic Ecologist);  

• Kristen Metzger (Director, Library/Information Services);

• Kim Dunleavy (Technical Editor); and

• Keith VanGraafeiland (GIS/Remote Sensing Specialist).

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Supplemental Exploration Plan 

OCS-G 7493, Garden Banks Block 427 

Garden Banks 471 Unit 

Offshore, Louisiana 

19 Administrative Information

(19a) Exempted Information Description (Public Information Copies Only) 

The following attachments were excluded from the public information copies of this plan: 

1b. OCS Plan Information form – Bottom hole locations & proposed total depth 

2j. Blowout Scenario – confidential information for NTL 2010 N06 calculation 

3a. Geologic Description 

3b. Structure Contour Maps 

3c. Interpreted 2D or 3D seismic line(s) 

3d. Cross Section(s) 

3e. Shallow Hazards Report 

3f. Shallow Hazards Assessment – confidential data 

3g. High-Resolution Seismic Lines & Top Hole Progs 

3h. & 3i. Stratigraphic Column with Time vs. depth table 

 

(19b) Bibliography 

Enclosed is Fugro Geoservices, Inc. Archeological Assessment of GB 427 dated May, 2010.