UNITED STATES GOVERNMENT MEMORANDUM

To: Public Information (MS 5030)

Plans Section, Office of Field 

Operations (MS 5231)

Public Information copy of Exploration Plan

Control # - S-07480

Type - Supplemental Exploration Plan

Lease(s) - OCS-G22919 Block - 984 Mississippi Canyon Area

OCS-G22920 Block - 985 Mississippi Canyon Area

OCS-G31534 Block - 940 Mississippi Canyon Area

Operator - Shell Offshore Inc.

SubseaWells I, G, F, E, D, J, K, H(ST01)and No.1STwest

DP SEMISUBMERSIBLE

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

should be addressed in an Environmental Assessment.

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

Michelle Griffitt

Plan Coordinator

Description -

Rig Type -

Subject:

From:

August 30, 2011
Shell Offshore Inc

P. O. Box 61933

New Orleans, LA 70161-1933

United States of America

Tel +1 504 728 7215

Fax +1 504 728 6747

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

Email sylvia.bellone@shell.com

May 9, 2011 

Ms. Liz Peuler, Section Chief 

Bureau of Ocean Energy Management, 

Regulation and Enforcement 

1201 Elmwood Park Boulevard 

New Orleans, LA 70123-2394 

 

Attn: Plans Group MS 5231 

SUBJECT: Supplemental Exploration Plan – Mississippi Canyon Block 940, 984 and 985 

 OCS-G 31534, OCS-G 22919 and OCS-G 22920 

 

Gentlemen: 

 

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 I, J and K to the previously approved subject leases. 

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

exploration well was 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. 

The cost recovery fee for this Plan is attached to the confidential copy. 

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

Sincerely, 

Sylvia A. Bellone 
SHELL OFFSHORE INC. 

SUPPLEMENTAL EXPLORATION PLAN 

for 

MISSISSIPPI CANYON BLOCK 940 (OCS-G 31534) 

MISSISSIPPI CANYON BLOCK 984 (OCS-G 22919) 

MISSISSIPPI CANYON BLOCK 985 (OCS-G 22920)

PUBLIC INFORMATION 

PREPARED BY: 

Sylvia A. Bellone 

Regulatory Specialist 

504.728.7215 

Sylvia.bellone@shell.com

 
REVISIONS TABLE Plan S-7480:

Date of Request Plan Section What Changed Date Replied 

5/25/11 Plan Section 1A 

Section 3F 

Added sentence about 

TA & installing 

corrosion cap after 

work is complete. 

Revised for previously 

approved wells and 

included an ESR. 

6/13/11 

7/13/11 Section 7A & 7b Updated waste and 

discharge table 

7/13/11

7/14/11 Sections 3F & 6A Updated wells 

discussed in 

assessments 

7/14/11

 Section 9 Updated worse case 

discharge comparison 

table for new regional 

oil spill response WCD 

number 

8/9/11

 

 
SUPPLEMENTAL EXPLORATION PLAN 

MISSISSIPPI Canyon Area 

Blocks 940, 984 & 985 

Table of Contents

1. Plan Contents 

2. General Information 

3. Geological and Geophysical 

4. Hydrogen Sulfide - 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 

 

 

 
SECTION 1: PLAN CONTENTS

A. DESCRIPTION, OBJECTIVES & SCHEDULE

This Supplemental Exploration Plan (EP/Plan) 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 31534, 22919 & 22920, Mississippi Canyon Blocks 940, 984 and 985. Wells A and B were 

submitted in Plan N-6091 by Energen Resources MAQ, Inc. in April 1988. Well C was submitted in Plan S-4798 

by Energen Resources MAQ, Inc. in November 1998. Wells D through G were submitted under Plan N-9220 and 

are not drilled. Well H (Well #1 and 3 sidetracks) was drilled by Anadarko under Plan N-9393 and also covered 

in Plan R-5022 approved 3/17/2010. This Plan will be for the drilling of three new Wells I, J and K. The wells 

will be drilled and temporarily abandoned (cement plug and corrosion cap) until the wells are completed and 

developed under future plan. If the well is unsuccessful, it will be permanently plugged and abandon in 

accordance with BOEM regulations. 

Shell’s Plan, as detailed in its EP, is to use a single semi-submersible, the M/V Noble Danny Adkins or equivalent 

(the “Rig”), to drill up to three (3) exploration wells in the Mississippi Canyon Area, located approximately 67 

miles from the nearest coastline (Louisiana), 117 miles from the supply base at Port Fourchon, Louisiana, and 

92 miles from the helicopter terminal at Amelia, Louisiana. Water depths in the lease range from approximately 

3,978’ to 4,164’. The initial drilling activities are planned to commence on or about October 2011 and take 

approximately 145 days per well. The timeframe to complete the initial drilling activities is an estimate based 

on the best available information regarding downhole conditions likely to be encountered while drilling each well 

and not intended to be a limitation. The timeframe for drilling the first well will further define the timing for 

further development of the prospect. 

The Rig is a DP Semi-submersible and is equipped with state-of-the-art drilling and well control equipment. The 

Rig will comply with the requirements in the Interim Final Rules. The drilling activities will be supported by the 

support vessels and aircraft as well as onshore support facilities as listed in Sections 14 and 15 of the EP. Shell 

has employed or contracted with trained personnel to carry out its exploration activities. Shell is committed to 

local hire, local contracting and local purchasing to the maximum extent possible. Shell personnel and 

contractors are experienced at operating in the Gulf of Mexico and are well versed in all Federal and State laws 

regulating operations. Shell’s employees and contractors share Shell’s deep commitment to operating in a safe 

and environmentally responsible manner. 

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

the Gulf of Mexico. Shell will draw upon this experience in organizing and carrying out its planned MC 940 

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. 

B. LOCATION

 See attached BOEM forms and location plat. 

 
C. RIG SAFETY AND POLLUTION FEATURES: 

The rig (Noble Danny Adkins or similar) 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 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. 

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: 

3⁄4 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. 

3⁄4 The oily water collection tank overflow valve is closed. 

3⁄4 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. 

3⁄4 The BOP test area drains are normally lined-up to drain overboard. 

3⁄4 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. 

3⁄4 The solids control system is capable of being isolated for cuttings collection. 

3⁄4 The bilge system is normally pumped directly overboard after a sheen test has been performed. 

3⁄4 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. 

 
D. Storage Tanks - Noble Danny Adkins 

Type of Storage Tank Type of Tank Number of Total Fluid 

Facility Capacity 

(bbls) 

Tanks Capacity 

(bbls) 

Gravity (API) 

Fuel oil MODU 2652 1 2652 No. 2 diesel 

Fuel oil MODU 1,743 1 1743 No. 2 diesel 

Fuel oil MODU 5767 1 5767 No. 2 diesel 

Fuel oil MODU 4399 1 4399 No. 2 diesel 

Fuel oil MODU 2652 1 2652 No. 2 diesel 

Fuel oil MODU 3250 1 3250 No. 2 diesel 

Fuel oil MODU 4399 1 4399 No. 2 diesel 

Fuel oil MODU 2618 1 2618 No. 2 diesel 

Fuel oil MODU 115 4 460 No. 2 diesel 

Fuel oil MODU 129 4 516 No. 2 diesel 

E. Pollution Prevention Measures 

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

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

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

F. Additional Measures

 

3⁄4 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. 

3⁄4 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. 

3⁄4 Preventive Maintenance of Rig equipment includes visual inspection of hydraulic lines and reservoirs 

on routine scheduled basis. 

3⁄4 All pollution pans on Rig are inspected daily. 

3⁄4 Containment dikes are installed around all oil containment, drum storage areas, fuel vents, and fuel 

storage tanks. 

3⁄4 All used oil and fuel is collected and sent in for recycling. 

3⁄4 Every drain on the Rig is assigned a number on a checklist. The checklist is used daily to verify 

drain plugs are installed. 

3⁄4 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. 

3⁄4 The Rig is involved in a recycling program for cardboard, plastic, paper, glass, and aluminum. 

3⁄4 Fuel hoses and SBM are changed on annual basis. 

3⁄4 TODO spill prevention fittings are installed on all liquid take on hoses. 

3⁄4 Waste paint thinner is recycled on board with a solvent still to reduce hazard of shipping and 

storage. 

3⁄4 All equipment on board utilizes Envirorite hydraulic fluid as opposed to hydraulic oil. Shell has 

obtained ISO14001 certification. 
U. S. Department of the Interior OMB Control Number: 1010-0049 

Minerals Management Service OMB Approval Expires: August 31, 2006 

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 22920 & 22919 Area: Miss. Canyon Block(s): 984, 985 Project Name (If Applicable): NA 

Objective(s): X Oil Gas Sulphur Salt Onshore 

Base:Fouchon & 

Boothville

Distance to Closest Land (Miles): 67 

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? 

Locs D, E, F & G apprvd Plan Ctl No. N-9220 7/30/08, Loc H apprvd Plan Ctr No. N-9383 6/12/09 

*X Yes X No 

Tentative Schedule of Proposed Activities 

Proposed Activity Start 

D t

End 

D t

No. of Days 

See attached 

 

 

 

 

 

Description of Drilling Rig Description of Production Platform 

 Jackup Drillship Caisson Tension leg platform

 Gorilla Jackup Platform rig Well protector Compliant tower 

 Semisubmersible Submersible Fixed platform Guyed tower

X DP 

Semisubmersible

 Other (Attach 

Description)

 Subsea 

manifold

 Floating production 

system Drilling Rig Name (If Known): Noble Danny Adkins or similar rig 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 (August 2003) Page 1 of 11 PUBLIC INFORMATION 
Tentative Schedule of Proposed Activities 

Proposed Activity Start Date End Date No. of Days 

Drill Well I & ST 10/01/2011 04/28/2011 210 

Drill Well G 9/30/2012 2/22/2013 145 

Drill Well F 9/30/2013 2/22/2014 145 

Drill Well E 9/30/2014 2/22/2015 145 

Drill Well D 9/30/2015 2/22/2016 145 

Drill Well J 9/29/2016 2/21/2017 145 

Drill Well K 9/29/2017 2/21/2018 145 

Sidetrack Well 1 (H surface location drilled) 9/29/2018 12/3/2018 65 

MMS Form MMS-137 (August 2003) Page 2 of 11 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): Well D Subsea Completion 

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

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 22919 

Area Name Mississippi Canyon 

Block No. 984 

Blockline 

Departures 

(in feet)

N/S Departure: 7255 FNL 

 E/W Departure: 5075 FEL 

Lambert X-Y 

coordinates 

X: 945,325 

 Y: 10,162,025 

Latitude/ 

Longitude

Latitude 27.98637884

Longitude -89.15419168

TVD (Feet): MD (Feet): Water Depth (Feet): 4,097 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

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 (August 2003) Page 3 of 11 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): Well E Subsea Completion 

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

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 22920 

Area Name Mississippi Canyon 

Block No. 985 

Blockline 

Departures 

(in feet)

N/S Departure: 1260 FNL 

 E/W Departure: 6259 FEL 

Lambert X-Y 

coordinates 

X: 959,981 

 Y: 10,168,020 

Latitude/ 

Longitude

Latitude 28.00356754

Longitude -89.10911696

TVD (Feet): MD (Feet): Water Depth (Feet): 4,196 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

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

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

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

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

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

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

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

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

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

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

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

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

MMS Form MMS-137 (August 2003) Page 4 of 11 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): Well F Subsea Completion 

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

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 22920 

Area Name Mississippi Canyon 

Block No. 985 

Blockline 

Departures 

(in feet)

N/S Departure: 2906 FNL 

 E/W Departure: 7244 FEL 

Lambert X-Y 

coordinates 

X: 958996 

 Y: 10166374 

Latitude/ 

Longitude

Latitude 27.99899457

Longitude -89.11208014

TVD (Feet): MD (Feet): Water Depth (Feet): 4170 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

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

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

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

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

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

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

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

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

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

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

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

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

MMS Form MMS-137 (August 2003) Page 5 of 11 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): Well G Subsea Completion 

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

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 22919 

Area Name Mississippi Canyon 

Block No. 984 

Blockline 

Departures 

(in feet)

N/S Departure: 807.50 FNL 

 E/W Departure: 6977.25 FWL 

Lambert X-Y 

coordinates 

X: 941537.24 

 Y: 10168472.51 

Latitude/ 

Longitude

Latitude 28.0039244

Longitude -89.1662783

TVD (Feet): MD (Feet): Water Depth (Feet): 4015 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

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

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

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

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

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

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

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

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

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

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

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

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

MMS Form MMS-137 (August 2003) Page 6 of 11 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): Well 1ST (H) Subsea Completion 

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

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 22919 

Area Name Mississippi Canyon 

Block No. 984 

Blockline 

Departures 

(in feet)

N/S Departure: 807.50 FNL 

 E/W Departure: 7077.25 FWL 

Lambert X-Y 

coordinates 

X: 941637.24 

 Y: 10168472.51 

Latitude/ 

Longitude

Latitude 28.0039278

Longitude -89.1659685

TVD (Feet): MD (Feet): Water Depth (Feet): 4044 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

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 (August 2003) Page 7 of 11 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): Well I Subsea Completion 

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

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 31534 

Area Name Mississippi Canyon 

Block No. 940 

Blockline 

Departures 

(in feet)

N/S Departure: 730 FSL 

 E/W Departure: 8209 FWL 

Lambert X-Y 

coordinates 

X: 942769 

 Y: 10170010 

Latitude/ 

Longitude

Latitude 28.0082106

Longitude -89.1625469

TVD (Feet): MD (Feet): Water Depth (Feet): 3978 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

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 (August 2003) Page 8 of 11 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): Well I-ST (West) Subsea Completion 

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

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 31534 

Area Name Mississippi Canyon 

Block No. 940 

Blockline 

Departures 

(in feet)

N/S Departure: 730 FSL 

 E/W Departure: 8209 FWL 

Lambert X-Y 

coordinates 

X: 942769 

 Y: 10170010 

Latitude/ 

Longitude

Latitude 28.0082106

Longitude -89.1625469

TVD (Feet): MD (Feet): Water Depth (Feet): 3978 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

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 (August 2003) Page 9 of 11 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): Well J Subsea Completion 

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

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 31534 

Area Name Mississippi Canyon 

Block No. 940 

Blockline 

Departures 

(in feet)

N/S Departure: 502 FSL 

 E/W Departure: 8366 FWL 

Lambert X-Y 

coordinates 

X: 942926 

 Y: 10169782 

Latitude/ 

Longitude

Latitude 28.0075914

Longitude -89.1620480

TVD (Feet): MD (Feet): Water Depth (Feet): 3978 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

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 (August 2003) Page 10 of 11 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): Well K Subsea Completion 

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

Surface Location Bottom-Hole Location (For Wells) 

Lease No. OCS-G 22919 

Area Name Mississippi Canyon 

Block No. 984 

Blockline 

Departures 

(in feet)

N/S Departure: 476 FNL 

 E/W Departure: 6658 FWL 

Lambert X-Y 

coordinates 

X: 941218 

 Y: 10168804 

Latitude/ 

Longitude

Latitude 28.0048189

Longitude -89.1672855

TVD (Feet): MD (Feet): Water Depth (Feet): 4025 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor 

Chain on Seafloor 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

 X = Y = 

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 (August 2003) Page 11 of 11 PUBLIC INFORMATION 

 

SECTION 2: GENERAL INFORMATION

A. Application and Permits

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

need to be obtained. 

B. Drilling Fluids 

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

C. Production

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

of DOCDs. 

D. Oil Characteristics 

Information regarding oil characteristics is not included in this EP as such information is only necessary in the 

case of DOCDs. 

E. New Or Unusual Technology

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

activities in this EP. 

F. Bonding

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

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

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

G. Oil Spill Financial Responsibility (OSFR)

Shell Offshore Inc (SOI), BOEMRE 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.” 

H. Deepwater well control statement

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

conduct other emergency well control operations. 

I. Suspension of Production

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

necessary in the case of DOCDs. 

 
J. Blowout scenario

Summary 

This Section 2j was prepared by Shell Offshore Incorporated (SOI) 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 design and execution of wells and into building and maintaining staff 

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

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

and Notices to Lessees. 

Shell is a founding member of the Marine Well Containment Corporation (MWCC) and will have access to an 

integrated subsea well control and containment system that can be rapidly deployed through the MWCC. The 

MWCC is a non-profit organization that owns, manages, and provides fully trained crews and operates the 

subsea containment system during a response. The near term containment response capability will be 

addressed in Shell’s NTL No. 2010-N10 submission at the time an Application to Drill (APD) is submitted and 

will include lessons learned and from 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 Vito is calculated for the MC 940 #1 ST3BP00 location, 

which is planned as a Northeast penetration of the Lower Miocene NMP Sand, based on the guidelines 

outlined in NTL No. 2010-N06 along with subsequent Frequently Asked Questions (FAQ). The WCD for MC 

940 #1 ST3BP00, or a similarly targeted well, falls below the WCD exploratory scenario for MC 391 C included 

in our Regional OSRP (October 2010). 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 the wellbore, reservoir barriers, 

or early intervention. 

Uncontrolled blowout (volume first day) 314,000 bbl 

Uncontrolled blowout rate (first 30-days average daily rate) 280,000 bopd 

Duration of flow (days) based on relief well 185 days 

Total volume of spill (bbls) for 185 days 48 MMBO 

Table 1 Worst Case Discharge Summary 

The Vito discovery is located approximately 67 miles from the nearest coastline in the Gulf of Mexico (GOM), 

in water depths of approximately 4100 feet (ft) across the discovery. Vito is a three-way, sub-salt closure 

against salt and salt weld and is located approximately 12 miles south of the Mars platform in Mississippi 

Canyon. The crest of the Vito NMP structure at the MC940 #1 ST3BP00 is at approximately 28,120’ TVDss 

(28,202’ TVD). To date, the Vito partnership has drilled four penetrations at Vito, the discovery well, MC984 

#1 ST00 BP01 and 3 subsequent sidetracks; the MC984 #1 ST00 BP02, the MC940 #1 ST1 BP00, and the 

MC984 #1 ST2 BP00. All wells/sidetracks at Vito have been drilled from Surface Location H. The discovery 

well and the subsequent sidetracks were drilled in 2009 – 2010, with operations suspended in May 2010 due 

to the Drilling Moratorium. The primary objective of the proposed MC940 #1 ST3 BP00, with predicted WCD 

flow potential, is the NMP reservoir of Lower Miocene age. Additional WCD scenarios were evaluated for Vito, 

in which other sands and well locations were considered. However, the WCD numbers for these wells/sands 

are lower than the WCD number calculated for the NMP as these sands are thinner, of lower quality, and 

flowed at substantially lower rates than the NMP case represented for the WCD. These shallower sands will 

be cased off prior to the well path penetrating the NMP reservoir package. 

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

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

calculations used to determine the WCD and the measures taken to 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 Vito wells and 

seismic. These parameters are better than or consistent with the estimates 

used by Shell to justify the investment. Therefore, these assumed parameters were used to calculate the 

WCD. They do not reflect probabilistic estimates. 

2) Background 

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

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

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

the exploration well at the MC-252 Macondo location. 

3) Information Requirements 

a) Blowout scenario 

All well and sidetrack locations addressed in this EP were assessed for WCD using the expected 

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

The MC940 #1 ST3 BP00 deviated well from the approved “H” surface location and a bottom hole 

location (BHL) on the northern crest of the Vito structure represented the well with the highest flow 

potential. The MC940 #1 ST3 BP00 well will be drilled through the NMP reservoir as outlined in the 

Geological and Geophysical Information Section of the Revised Vito EP, and described above, using a 

subsea wellhead system, conductor, surface and intermediate casing program, and using a DP rig 

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

event are modeled to occur from the Lower Miocene NMP reservoir. Other sands were modeled; 

however, the NMP represented the highest WCD number. 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 

Table 2 Estimated Flow Rates of a Potential Blowout 

c) Total volume and maximum duration of the potential blowout 

Duration of flow (days) 185 days total duration to drill relief well 

(14 rig mob, 3 transit, 135 spud to top NMP, 33 ranging). 

Total volume of spill (bbls) 48 MMBO based on 185 days flowing. 

Note: From CMG dynamic reservoir models 

Table 3 Estimated Duration and Volume of a Potential Blowout 

 

Category EP 

Type of Activity Drilling 

Facility Location (area/block) MC 984 

Facility Designation DP 

Distance to Nearest Shoreline (miles) 67 Statute miles 

Uncontrolled blowout (volume first day) 314,000 bbl 

Uncontrolled blowout rate (first 30-days average daily rate) 280,000 bopd 
There is usually a decline in the discharge rate as time progresses, which is illustrated by the 

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

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

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

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

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

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

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

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

 Omitted from Public Information Copies. 

e) Potential for the well to bridge over 

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

including in-situ stress, rock strength, and fluid velocities at the sand face. Given the substantial fluid 

velocities inherent in the WCD, and the scenario as defined where the formation is not supported by 

a cased and cemented wellbore, it is possible that the borehole may fail/collapse/bridge over within 

the span of a few days, significantly reducing the outflow rates. However, this WCD scenario does 

not include any bridging. 

f) Likelihood for intervention to stop the blowout. 

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

the key focus of our operations. This is derived from robust standards, well design, prudent 

operations, competency of personnel, and strong HSE focus. Collectively, these constitute a robust 

system making blowouts extremely rare events. 

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

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

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

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

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

deadman system, and an autoshear system. 

The rig to be used on Vito will be the Noble Danny Adkins, a dynamically positioned MODU. The BOP 

stack on this rig has two shearing rams for additional redundancy. Also, the Noble Danny Adkins is 

equipped with a deadman system, an autoshear system, and an additional acoustic backup system 

for disconnecting and closing the shear rams. 

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

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

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

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

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

control another deepwater control incident. 

Should the interventions at the well not be possible, specialized equipment can be used to connect to 

a riser stub, damaged connector, casing stub or to the sea floor and allow the well to be shut-in to 

contain the blowout. The subsea containment assembly and other specialized connection devices will 

be available from the Marine Well Containment Company (MWCC) or other Shell/industry sources and 

will be specifically addressed in Shell’s NTL No. 2010-N10 submission. 

Shell is investing in Research and Development activities on its own to identify additional containment 

components and equipment that will potentially increase the range of applications and effectiveness 

for equipment similar to that of MWCC, and systems that can be deployed more effectively in the 

water column that resemble “tents or capture domes”, and enhance well shut-in capability. 

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

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

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

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

used in some scenarios. Additionally, in the event of a blowout, there is the distinct possibility that 

other non-contracted rigs in the GOM could be utilized whether for increased expediency or better 

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

rigs capable of operating at Vito water depths and reservoir depths without technical constraints are 

shown in the Table 4 below: 

Rig Name Rig Type

Noble Danny Adkins Dynamically positioned semi

Noble Bully 1* Dynamically positioned drill ship

Transocean  Deepwater Nautilus** Moored semi

Noble Jim Thompson Moored semi

Table 4 Shell Contracted Rigs Capable at Vito. 

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

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

*Bully 1 estimated arrival October 2011. 

**The Transocean Deepwater Nautilus estimated availability is April 2011 

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

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

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

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

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

to the site. The relief well will take approximately 135 days to drill down to the last casing string 

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

blowout well bore. The expected total time to mobilize and drill a relief well would be 185 days for 

Vito. 

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

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

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

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

It is not possible to drill relief wells from any existing platforms (ATP’s Titan Platform) due to rig 

capability limitations and a distance of over 4 miles to the Vito well. 

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

blowout. 

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

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

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

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

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

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

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

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

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

systematic identification and mitigation process (Safety Case). The Safety Case requirement is 

ingrained into Shell’s Health, Security, Safety, Environment, and Social Performance Control 

Framework. All Shell contracted rigs in the GOM have been operating with a Safety Case and will 

continue to do so. A Safety Case requires both the owner and contractors to systematically identify 

the risks in drilling operations and align plans to mitigate those risks; an alignment which is critical 

before drilling begins. 

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

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

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

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

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

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

planning, providing their specific expertise. A Drill the Well On Paper (DWOP) exercise is conducted 

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

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

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

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

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

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

standards and industry standards. 

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

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

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

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

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

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

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

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

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

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

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

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

close communication with both the drilling foreman and Shell representative to report any observed 

anomalies so appropriate action can be taken. 

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

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

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

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

monitoring specialist for an added layer of redundancy. 

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

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

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

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

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

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

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

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

strong safety culture in our operations. 

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

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

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

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

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

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

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

The WCCP specifically addresses implementing actions at the emergency site that will ensure 

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

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

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

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

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

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

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

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

k) Arrangements for drilling a relief well 

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

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

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

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

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

A generic relief well description is outlined in the WCCP. 

l) Assumptions and calculations used in approved or proposed OSRP 

The NTL No. 2010-N06 Worst Case Discharge for Shells Regional Oil Spill Response Plan, highest 

subsea well, was previously submitted August 1, 2011. 

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

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

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

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

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

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

containment and recovery operations. 

 
SECTION 3: Geological & Geophysical Information

A. Geological description

Omitted from Public Information Copies. 

B. Structure contour maps.

Omitted from Public Information Copies. 

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

Omitted from Public Information Copies. 

Geological Structure Cross-section(s)

Omitted from Public Information Copies

E. Shallow Hazards Report – see below 

F. Shallow Hazards Assessment

History

Shell previously received approval to drill Proposed Locations D, E, F, and G. Shell then added Proposed 

Locations I, J, and K but has not received approval to drill. On May 25, 2011, the BOEM required Shell 

comply with current NTL2009-G40 to protect deepwater benthic communities. To comply, Shell is updating 

its exploration plans and certifying its distance from said benthic communities. 

Shallow Hazards Assessment

GEMS prepared a Geologic, Stratigraphic, and Archeological Assessment on Blocks 940, 984, and 985 of 

Mississippi Canyon in October 2007 for Shell. The project number is 0507-1331. C&C Technologies conducted 

an Archeological Assessment Report for Shell in October 2007 on Mississippi Canyon Blocks 895-898, 939-

942, and 983-986. The job number is 072657-072954. The archeological survey detected 106 unidentified 

sidescan sonar targets, several drag scars, and geological features within the survey. There were no sonar 

contacts with acoustic signature that require archeological avoidance or further investigation. Anadarko 

previously drilled Well #1 in MC 984. The well is centered at X = 941,637; Y= 10,168,473. Shell now requests 

approval to drill Proposed Locations No. 1ST (Formerly H), D, E, F, G, I, IST, J, and K using the DP vessel 

Noble Danny Adkins. (There are no anchors associated with this Plan.) Fluid expulsion features will be 

avoided by at least 250’, sonar contacts will be avoided by 50’. There are no flowlines in the vicinity of the 

proposed locations. 

Archeological Statement

Per the archeological assessment report, there are no recommended avoidance areas. Nevertheless, Shell 

will avoid all unidentified sonar contacts by at least 50 ft. 

Proposed Locations:

MC 984 Proposed Location D 

 X = 943,325 5075’ FEL 

 Y = 10,162,025 7255’ FNL 
Proposed Location D will be positioned in a water depth of approximately -4097‘. Proposed Location D will 

be positioned west of the major graben that trends north-south through the area. There is no evidence of 

seafloor or near-surface faulting, slumping, amplitudes or fluid expulsion features in the vicinity of Proposed 

Location D. Proposed Location D will not disturb any high-density areas of chemosynthetic communities. 

MC 985 Proposed Location E 

 X = 959,981 6259’ FEL 

 Y = 10,168,020 1260’ FNL 

Proposed Location E will be located in a water depth of approximately -4164’. Proposed Location E will be 

located southeast of seafloor faults identified 400’, 890’, and 1090’ away. There are no indications of 

seafloor or near-surface fluid expulsion features or amplitudes identified on side-scan sonar or sub-bottom 

profiler data. There is no other evidence of seafloor or near-surface faulting, slumping, amplitudes or fluid 

expulsion features in the vicinity of Proposed Location E. Proposed Location E will not disturb any highdensity areas of chemosynthetic communities. 

MC 985 Proposed Location F 

 X = 958,996 7244’ FEL 

 Y = 10,166,374 2906’ FNL 

Proposed Location F will be located in a water depth of approximately -4,136’. A seafloor fault is identified 

480’ northwest of Proposed Location F. Other faults are identified 1,510’ to the southeast and 1400’ to the 

southwest of Proposed Location F. There are no indications of seafloor or near-surface fluid expulsion 

features or amplitudes identified on side-scan sonar or sub-bottom profiler data. There is no other evidence 

of seafloor or near-surface faulting, slumping, amplitudes or fluid expulsion features in the vicinity of 

Proposed Location F. 

MC 984 Proposed Location G 

 X = 941,108 6808’ FWL 

 Y = 10,168,532 748’ FNL 

Proposed Location G will be located in a water depth of approximately -4044’. Proposed Location G will be 

positioned west of the major graben that trends north-south through the area. There is no evidence of 

seafloor or near-surface faulting, slumping, amplitudes or fluid expulsion features in the vicinity of Proponed 

Location G. 

MC 984 Rig Center for Locations I, J, K: 

X= 942,153 7,563’ FWL 

Y=10,169,281 1’ FNL 

The water depth at rig center is approximately -4,000’. There are no seafloor faults within 1,500’ of rig 

center. There are no amplitudes or fluid expulsion features within 2,000’ of rig center. 

MC 940 Proposed Location I: 

X= 942,769 8,209’ FWL 

Y= 10,170,010 730’ FSL 

The water depth at Proposed Location I is -3,978’. The seafloor slopes to the southwest at a gradient of 1.6° 

on a relatively featureless ramp. The closest unidentified side-scan sonar targets numbers 386 and 276 are 

approximately 3,000’ to the northwest and 2,900’ to the northeast, respectively. The archeologist did not 

designate any special avoidance for these. (C&C Technologies, 2007) Previously drilled MC984 #1 is located 

1,900’ southwest of the proposed location. The Crosby Field is to the northeast in MC 898 and 899. The 

platform, flowlines, and pipelines associated with the Crosby field are over 10 miles from Proposed Location I. 

The nearest seafloor fault to the location is approximately 1,000’ east of the proposed location. The proposed 

well will intersect a small fault at 676’ bml. The casing program will be designed to minimize flow potential. 
MC 940 Proposed Location J: 

X= 942,926 8,366’ FWL 

Y= 10,169,782 502’ FSL 

 The water depth at the proposed location is -3,978’. The seafloor slopes to the southwest at a gradient of 

1.3° on a relatively featureless ramp. The closest unidentified side-scan sonar targets numbers 386 and 276 

are approximately 3,300’ northwest and 3,050’ northeast, respectively. The archeologist did not designate 

any special avoidance for these. (C&C Technologies, 2007) Previously drilled MC984 #1 is located 1,850’ 

southwest of the proposed location. The Crosby Field is to the northeast in MC 898 and 899. The platform, 

flowlines, and pipelines associated with the Crosby field are over 10 miles from Proposed Location J. The 

nearest seafloor fault to the location is approximately 1,000’ east of the proposed location. The proposed well 

will intersect a small fault at 644’ bml. The casing program will be designed to minimize flow potential. 

MC 984 Proposed Location K: 

X= 941,218 6,658’ FWL 

Y=10,168,804 476’ FNL 

The water depth at the proposed location is -4,025’. The seafloor slopes to the southwest at a gradient of 

1.5° on a relatively featureless ramp. Previously drilled MC984 #1 is located 520’ southeast of Proposed 

Location K. The closest unidentified sidescan sonar target number 386 is approximately 4,500’ to the 

northwest. Unidentified sonar target 276 is 4,900’ northeast of the proposed location. The archeologist did 

not designate any special avoidance for these. (C&C Technologies, 2007) The Crosby Field is to the 

northeast in MC 898 and 899. The platform, flowlines, and pipelines associated with the Crosby field are over 

10 miles from Proposed Location K. There are no seafloor faults within 1,500’ of the proposed location. 

There are no shallow faults that intersect the proposed well. The casing program will be designed to 

minimize flow potential. 

General Statements 

Based on a high-resolution geophysical survey consisting of deep-towed Side scan Sonar and Sub-Bottom 

Profiler, Sparker, Mini-Sparker, Frequency Enhanced 3-D seismic, Enhanced Surface Renderings (ESRs) and 

ESRs with amplitudes applies, MC 984, Proposed Location D, E, F, G and No. 1ST (H) appear suitable for the 

planned activity. 

 

Based on evaluation of 3-D exploration seismic data with high resolution AUV data, multibeam echosounder, 

side-scan sonar, and subbottom profiler data, amplitude, and amplitude Enhanced Surface renderings, the rig 

center and Proposed Locations I, IST, J, and K appear suitable for the proposed activities. 

Larry Gibson Vernessa Bradford 

Senior Staff Geologist Shallow Hazards Interpreter 

 
G. High-Resolution Seismic Lines

Seismic omitted from Public Information Copies. See attached ESR. 

H & I Stratigraphic Column with Time vs depth table

Omitted from Public Information Copies

SECTION 4: Hydrogen Sulfide

A. Concentration 

0 ppm. 

B. Classification

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

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

confirmed. 

 

C. H2S Contingency Plan

In accordance with 30 CFR 250.490(f) a Contingency Plan was not required for this Lease. 

D. Modeling Report

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

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

 
SECTION 5: Minerals Resource Conservation

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

necessary in the case of DOCDs. 
SECTION 6: Biological, Physical and Socioeconomic Information

A. Chemosynthetic Communities Report

ANCHOR CLEARANCE AND CHEMOSYNTHETIC

ORGANISMS COMMENTS

History

GEMS prepared a Geologic, Stratigraphic, and Archeological Assessment on Blocks 940, 984, and 985 of 

Mississippi Canyon in October 2007 for Shell. The project number is 0507-1331. 

C&C Technologies conducted an Archeological Assessment Report for Shell in October 2007 on Mississippi 

Canyon Blocks 895-898, 939-942, and 983-986. The job number is 072657-072954. 

 

The archeological survey detected 106 unidentified sidescan sonar targets, several drag scars, and geological 

features within the survey. There were no sonar contacts with acoustic signature that require archeological 

avoidance or further investigation. 

Shell previously drilled Well #1 in MC 984. The well is centered at X = 941,637 Y 10,168,473. Shell now 

requests approval to drill Proposed Locations D, E, F, G, No 1 ST (Fromerly H) I, IST J, and K using the DP 

vessel Danny Adkins or similar rig. Shell had approval for a 15,500 ft radius to drill Well # 1. Shell plans to 

use the approved radius but will maintain a 1,000 ft buffer and not set anchors beyond 14,500 ft. The 

proposed locations are within that radius, thus, no change is requested. 

 

There are no flowlines in the vicinity of the proposed locations. 

Chemosynthetic Community Statement

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

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

For the proposed locations D, E, F, G, No 1 ST (Formerly H), I, IST, J, and K: 

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

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

2. At least 250’ 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). 

Currently, there are no pipelines in the vicinity of Proposed Locations D, E, F, G, No 1 ST (Formerly H) I, IST, 

J, and K. Previously drilled wellsites in the vicinity include Shell’s MC 985 No. 1, Exxon’s MC 941 No. 1, and 

ATP’s MC 941 No. 1 and No. 2 wellsites. 

Proposed Locations

MC 984 Proposed Location D 

 X = 943,325 5075’ FEL 

 Y = 10,162,025 7255’ FNL 

Proposed Location D will be positioned in a water depth of approximately -4097‘. Proposed Location D will be 

positioned west of the major graben that trends north-south through the area. There is no evidence of 

seafloor or near-surface faulting, slumping, amplitudes or fluid expulsion features in the vicinity of Proposed 

Location D. Proposed Location D will not disturb any high-density areas of chemosynthetic communities. 
MC 985 Proposed Location E 

 X = 959,981 6259’ FEL 

 Y = 10,168,020 1260’ FNL 

Proponed Location E will be located in a water depth of approximately -4164’. Proposed Location E will be 

located southeast of seafloor faults identified 400’, 890’, and 1090’ away. There are no indications of 

seafloor or near-surface fluid expulsion features or amplitudes identified on side-scan sonar or sub-bottom 

profiler data. There is no other evidence of seafloor or near-surface faulting, slumping, amplitudes or fluid 

expulsion features in the vicinity of Proposed Location E. Proposed Location E will not disturb any highdensity areas of chemosynthetic communities. 

MC 985 Proposed Location F 

 X = 958,996 7244’ FEL 

 Y = 10,166,374 2906’ FNL 

Proposed Location F will be located in a water depth of approximately -4,136’. A seafloor fault is identified 

480’ northwest of Proposed Location F. Other faults are identified 1,510’ to the southeast and 1400’ to the 

southwest of Proposed Location F. There are no indications of seafloor or near-surface fluid expulsion 

features or amplitudes identified on side-scan sonar or sub-bottom profiler data. There is no other evidence 

of seafloor or near-surface faulting, slumping, amplitudes or fluid expulsion features in the vicinity of 

Proposed Location F. 

MC 984 Proposed Location G 

 X = 941,108 6808’ FWL 

 Y = 10,168,532 748’ FNL 

Proponed Location G will be located in a water depth of approximately -4044’. Proposed Location G will be 

positioned west of the major graben that trends north-south through the area. There is no evidence of 

seafloor or near-surface faulting, slumping, amplitudes or fluid expulsion features in the vicinity of Proponed 

Location G. 

MC 984 Rig Center for Locations I, J, K: 

X= 942,153 7,563’ FWL 

Y=10,169,281 1’ FNL 

The water depth at rig center is approximately -4,000’. There are no seafloor faults within 1,500’ of rig 

center. There are no amplitudes or fluid expulsion features within 2,000’ of rig center. 

MC 940 Proposed Location I: 

X= 942,769 8,209’ FWL 

Y= 10,170,010 730’ FSL 

The water depth at Proposed Location I is -3,978’. The seafloor slopes to the southwest at a gradient of 1.6° 

on a relatively featureless ramp. The closest unidentified side-scan sonar targets numbers 386 and 276 are 

approximately 3,000’ to the northwest and 2,900’ to the northeast, respectively. The archeologist did not 

designate any special avoidance for these. (C&C Technologies, 2007) Previously drilled MC984 #1 is located 

1,900’ southwest of the proposed location. The Crosby Field is to the northeast in MC 898 and 899. The 

platform, flowlines, and pipelines associated with the Crosby field are over 10 miles from Proposed Location I. 

The nearest seafloor fault to the location is approximately 1,000’ east of the proposed location. The proposed 

well will intersect a small fault at 676’ bml. The casing program will be designed to minimize flow potential. 

MC 940 Proposed Location J: 

X= 942,926 8,366’ FWL 

Y= 10,169,782 520’ FSL 

 The water depth at the proposed location is -3,978’. The seafloor slopes to the southwest at a gradient of 

1.3° on a relatively featureless ramp. The closest unidentified side-scan sonar targets numbers 386 and 276 

are approximately 3,300’ northwest and 3,050’ northeast, respectively. The archeologist did not designate 
any special avoidance for these. (C&C Technologies, 2007) Previously drilled MC984 #1 is located 1,850’ 

southwest of the proposed location. The Crosby Field is to the northeast in MC 898 and 899. The platform, 

flowlines, and pipelines associated with the Crosby field are over 10 miles from Proposed Location J. The 

nearest seafloor fault to the location is approximately 1,000’ east of the proposed location. The proposed well 

will intersect a small fault at 644’ bml. The casing program will be designed to minimize flow potential. 

MC 984 Proposed Location K: 

X= 941,218 6,658’ FWL 

Y=10,168,804 476’ FNL 

The water depth at the proposed location is -4,025’. The seafloor slopes to the southwest at a gradient of 

1.5° on a relatively featureless ramp. Previously drilled MC984 #1 is located 520’ southeast of Proposed 

Location K. The closest unidentified sidescan sonar target number 386 is approximately 4,500’ to the 

northwest. Unidentified sonar target 276 is 4,900’ northeast of the proposed location. The archeologist did 

not designate any special avoidance for these. (C&C Technologies, 2007) The Crosby Field is to the 

northeast in MC 898 and 899. The platform, flowlines, and pipelines associated with the Crosby field are over 

10 miles from Proposed Location K. There are no seafloor faults within 1,500’ of the proposed location. 

There are no shallow faults that intersect the proposed well. The casing program will be designed to 

minimize flow potential. 

General Statements 

Based on a high-resolution geophysical survey consisting of deep-towed Side scan Sonar and Sub-Bottom 

Profiler, Sparker, Mini-Sparker, Frequency Enhanced 3-D seismic, Enhanced Surface Renderings (ESRs) and 

ESRs with amplitudes applies, MC 984, Proposed Locations D, E, F, G and No. 1 ST (Formerly H) appear 

suitable for the planned activity. 

 

Based on evaluation of 3-D exploration seismic data with high resolution AUV data, multibeam echosounder, 

side-scan sonar, and subbottom profiler data, amplitude, and amplitude Enhanced Surface renderings, the rig 

center and Proposed Locations I, J, and K appear suitable for the proposed activities. 

Larry Gibson Vernessa Bradford 

Senior Staff Geologist Shallow Hazards Interpreter 

B – 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. 

G. Remotely Operated Vehicle (ROV) Monitoring Plan

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

Mississippi Canyon 940, 984 and 985 are all located in Grid 13. Grid 13 is an area that has adequate ROV survey 

coverage; therefore we are not proposing to run the pre and post ROV survey in accordance with the NTL. 

H. Threatened and Endangered Species Information

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

these species has been designated in the Gulf of Mexico. 

Common Name Scientific Name T/E Status

Hawksbill Turtle Eretmochelys imbricata E 

Green Turtle Chelonia mydas T 

Kemp's Ridley Turtle Lepidochelys kempii E 

Leatherback Turtle Dermochelys coriacea E 

Loggerhead Turtle Caretta caretta T 
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. 

I. 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. 

J. 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. 
SECTION 7: Waste and Discharge Information

A. Discharge to GOM or Downhole

Note: Please specify if the amount reported is a total or per well amount Supplmental EP - MC 940, 984 and 985

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

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

EXAMPLE: Cuttings wetted with ynthetic based fluid 

Cuttings generated while using synthetic 

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

Water-based drilling fluid barite, additives, mud 35,000 bbl/well 17,500 bbls /day discharge overboard Cuttings wetted with water-based fluid

cuttings coated with water based drilling 

mud 3,180 bbls/well 795 bbls /day discharge overboard 

Cuttings wetted with synthetic-based fluid 

Cuttings generated while using synthetic based drilling fluid. 13,700 bbls/well 275 bbls /day discharge overboard 

Will humans be there? If yes, expect conventional waste

EXAMPLE: Sanitary waste water X liter/person/day NA chlorinate and discharge Domestic waste (kitchen water, shower water) grey water 160 bbls/day NA

Grinded to less than 25 mm mesh size and discharge overboard 

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

Treated in the MSD** prior to dischargto meet NPDES limits 

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

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

Drained overboard through deck scuppers 

Will you conduct well treatment, completion, or workover? 

well treatment fluids NA NA NA NA well completion fluids NA NA NA NA workover fluids NA NA NA NA 

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

Desalinization unit discharge Rejected water from watermaker unit 74,100 bbls / well Blowout prevent fluid Water based 400 bbls/well 0.2 bbls /day Subsea BOP @ seafloor Ballast water Uncontaminated seawater 390,000 bbls / well 2,6890 bbls / day discharge overboard Bilge water

Bilge and drainage water will be treated to MARPOL standards (< 15ppm oil in water). 390,000 bbls / well 2,6890 bbls / day

Bilge and drainage water will be treate

to MARPOL standards (< 15ppm oil 

water). 

Excess cement at seafloor Cement slurry

246 bbls/well (assume planned 100% excess is discharged) 246 bbls /day 

discharged through shunt line, 77' belo

waterline 

Fire water Treated seawater 11,000 bbls / well 2,000 bbls / month scuppers Cooling water Treated seawater 23,295,000 bbls / well 456,343 bbl/day/well

discharged through shunt line, 77' belo

waterline 

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

Produced water NA NA

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

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

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

THE GOM

Projected generated waste Projected ocean discharges 
B. Landfill, inject, incinerate or recycle table

C. Modeling Report

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

Supplmental EP - MC 940, 984 and 985

Solid and Liquid 

Wastes transportation 

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

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

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

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

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

Newpark Environmental, Fourchon, 

LA 120 bbls/day Recycled

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

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

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

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

Produced sand NA NA NA NA NA

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

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

Omega Waste Managmenet, W. 

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

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

Republic/BFI landfill, Sorrento, LA or 

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

Used oil and glycol

used oil, oily rags and

pads, empty drums and 

cooking oil drums on supply boat

Omega Waste Managmenet, W. 

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

Hazardous Waste

paints, solvents and unused 

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

Universal Waste Items

Batteries, lamps, glass and 

mercury-contaminated 

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

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

Waste Disposal

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

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

yes, fill in the appropriate rows. 

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

Projected generated waste
SECTION 8: AIR EMISSIONS INFORMATION

A. Emissions Worksheet and Screening Questions 

Screening Questions for EP’s Yes No 

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

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

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

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

x 

Do your emission calculations include any emission reduction measures or 

modified emission factors? x 

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

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

(ppm)? x 

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

From any proposed well? x 

Do you propose to burn produced hydrocarbon liquids? x 

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

provide: 

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

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

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

do not need to include the entire set of worksheets. 

Air Pollutant Plan 

Emission1 

Amounts 

(tons) 

Calculated 

Exemption2

Amounts 

(tons) 

Calculated 

Complex Total 

Emission 

Amounts3

(tons) 

PM 

SOx 

NOx 

VOC 

CO 

1

 For activities proposed in your EP or DOCD, list the projected emissions calculated from the worksheets. 2

 List the exemption amounts for your proposed activities calculated by using the formulas in 30 CFR 250.303(d). 3

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

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

(1) Worksheets

Worksheets are attached. 

 
 AIR QUALITY SCREENING CHECKLIST 

OMB Appro

COMPANY Shell Offshore IncAREA Mississippi CanyonBLOCK 940, 984 & 985LEASE G31534, G22919 & G22920

PLATFORM VitoWELL D,E,F,G,I(+st),J,K, ST at Well 1 (H Surface Location)COMPANY CONTACT Sylvia BelloneTELEPHONE NO. 504-728-7215REMARKSREMARKSLEASE TERM PIPELINE CONSTRUCTION INFORMATION:

YEAR NUMBER OF TOTAL NUMBER OF CONSTRUCTION DAYS

PIPELINES

199920002001200220032004200520062007

2008

2009-2014

Form MMS-139 (August 2003)
AIR EMISSION CALCULATIONS OM

OMB Approval E

COMPANY AREA BLOCK LEASE PLATFORM WEShell Offshore Inc Mississippi Canyon 940, 984 & 985 G31534, G22919 & G22920 Vito D,E

at WLoca

Emitted Substance

Year

 PM SOx NOx VOC 

2011-2018 33.83 154.58 1158.88 34.90 

Allowable 2231.10 2231.10 2231.10 2231.10 
COMPANY AREA BLOCK LEASE PLATFORM WELL

Shell Offshore Inc Mississippi Canyon 940, 984 & 985 G31534, G22919 & G22920 Vito D,E,F,G,I(+st),J,K, ST at Well 1 (H Surface Location)

Basis for various estimates Used in this AQR

ScheduleSchedule is as below. 

Proposed Activity Start Date End Date No. of Days

Drill Well G 9/30/2012 2/22/2013 145

Drill Well F 9/30/2013 2/22/2014 145

Drill Well E 9/30/2014 2/22/2015 145

Drill Well D 9/30/2015 2/22/2016 145

Drill Well K 9/29/2017 2/21/2018 145

Sidetrack Well 1 (H surface location drilled) 9/29/2018 12/3/2018 65

Many cells are linked or are used as links in other sheets- change cell contents OR add/delete rows/columnwith caution!

Tentative Schedule of Proposed Activities

Drill Well I & ST 10/1/2011 4/28/2011 210Drill Well J

9/29/2016 2/21/2017

145

For conservatism (and simplicity given that individual wells will be drilled across calender years) in completing the AQR, assume 210 days per calender year of drilling

160111A1.msg

per calender year of drilling. 

160111A1.msg
COMPANY AREA BLOCK LEASE PLATFORM WELL

Shell Offshore Inc Mississippi Canyon 940, 984 & 985 G31534, G22919 & G22920 Vito D,E,F,G,I(+st),J,K, ST at Well 1 (H Surface Location)

Basis for various estimates Used in this AQR Many cells are linked or are used as links in other sheets- change cell contents OR add/delete rows/column

with caution!

Noble Danny Adkins main Engine Operating scenarios (Modes)per embedded emailScenario 1 – Riser less drilling (top hole) Four engines online @ 35 to 45%Scenario 2 - Riser less drilling Running casing/ cementing  Four Engines online @ 30 to 40 %Scenario 3 - Transit (5 knot log speed)  Four engines online @ 65% Scenario 4 – Drilling ahead with BOP deployed  Four Engines online @ 40 to 50% 

Engine Op Mode 1 Op Mode 2 Op Mode 3 Op Mode 4

1 45 40 65 50

2 45 40 65 503 45 40 65 504 45 40 65 505 00 0 06 00 0 0

% Load

EB112514.msg

7 00 0 08 00 0 0

Frequency of scenario occurrence in Campaign, % 0 0 10 90

Individual Eng HP, nameplate 6169 6169 6169 6169Total HP delivered from all 8 engines in Campaign, by scenario

0 0 1603.94 11104.2

Average % Load delivered from each 

engine in Campaign 0.0% 0.0% 3.3% 22.5%

25.8%

Given Mode 3 and 4 are highest load modes, assume rig operates in mode 3 (transit) 10% of time and remainder in Mode 4 (90% of time as a conservative estimate for emissions)For simplification, the above average % loads are added to arrive at a single Overall Operating Mode (Load Factor) for all Engine loads will vary from above: the % shown is the AVERAGE thru-out the campaign for each engine and is used to estimate ANNUAL emissions
COMPANY AREA BLOCK LEASE PLATFORM WELL

Shell Offshore Inc Mississippi Canyon 940, 984 & 985 G31534, G22919 & G22920 Vito D,E,F,G,I(+st),J,K, ST at Well 1 (H Surface Location)

Basis for various estimates Used in this AQR Many cells are linked or are used as links in other sheets- change cell contents OR add/delete rows/column

with caution!

Support Vessel EmissionsRiserless 10 days

3 OSVs per day

@ 9440 HP EA

.30 Crew Boats per day

@ 5400 HP

Deepening 200 days

1 OSV average on location

@ 9440 HP

.30 Crew Boats per day

@ 5400 HP

The above data is tabulated as follows and used in the AQR:Equipment HP Rating Hr/day Duration/year 

(Days)

Riserless Support vessel OSV (>600 hp) 9440 24 10Riserless Support vessel OSV (>600 hp) 9440 24 10Riserless Support vessel OSV (>600 hp) 9440 24 10

On average one vessel withn 25 miles at any give time. Shell policy restricts D/P to < 50% near rig. When in standby away from rig but within 25 miles load wil be < 50% (conserve fuel). When transiting into/out of 25 miles, vessels can be restricted 

to <50% loadOn average one vessel withn 25 miles at any give time. Shell policy restricts D/P to < 50% near rig. When in standby away from rig but within 25 miles load wil be < 50% (conserve fuel). When transiting into/out of 25 miles, vessels can be restricted On average one vessel withn 25 miles at any give time. Shell policy restricts D/P to < 50% near rig. When in standby away from rig but within 25 miles load wil be < 50% (conserve fuel). When transiting into/out of 25 miles, vessels can be restricted to <50% load

Comment

6C3E8FDB.msg

Riserless Support vessel Crew Boat (>600 hp) 5400 8 10Deepening Support vessel OSV (>600 hp) 9440 24 200Deepening Support vessel Crew Boat 5400 8 200

Becauise of the 50% load limits, set all support 

vessel load factors = 50%

MiscellaneousAssume emergency diesel is tested for 1 hr/week = 210 days/7 days = 30 weeks = 30 days per campaign testing occursAssume cement units are used 7.5% of the time during deepening = 0.075 *200 = 15 days per campaign

On average crew vessels will be within 25 miles 30% of time. To model this set hr/d=8. Shell policy restricts D/P to < 50% near rig. When in standby away from rig but within 25 miles load wil be < 50% (conserve fuel). When transiting into/out of 25 miles, vessels can be restricted to <50% loadOn average one vessel withn 25 miles at any give time. Shell policy restricts D/P to < 50% near rig. When in standby away from rig but within 25 miles load wil be < 50% (conserve fuel). When transiting into/out of 25 miles, vessels can be restricted 

to <50% loadOn average crew vessels will be within 25 miles 30% of time. To model this set hr/d=8. Shell policy restricts D/P to < 50% near rig. When in standby away from rig but within 25 miles load wil be < 50% (conserve fuel). When transiting into/out of 25 miles, vessels can be restricted to <50% load

When transiting into/out of 25 miles, vessels can be restricted

to <50% load
AIR EMISSION COMPUTATION FACTORS

Fuel Usage Conversion Factors Natural Gas Turbines Natural Gas Engines Diesel Recip. Engine 

SCF/hp-hr 9.524 SCF/hp-hr 7.143 GAL/hp-hr 0.0483 A

Equipment/Emission Factors units PM SOx NOx VOC CO NG Turbines gms/hp-hr 0.00247 1.3 0.01 0.83 AP42 NG 2-cycle lean gms/hp-hr 0.00185 10.9 0.43 1.5 ANG 4-cycle lean gms/hp-hr 0.00185 11.8 0.72 1.6 ANG 4-cycle rich gms/hp-hr 0.00185 10 0.14 8.6 A

Diesel Recip. < 600 hp. gms/hp-hr 1 1.468 14 1.12 3.03 A

Diesel Recip. > 600 hp. gms/hp-hr 0.32 1.468 11 0.33 2.4 ADiesel Boiler lbs/bbl 0.084 2.42 0.84 0.008 0.21 AP4NG Heaters/Boilers/Burners lbs/mmscf 7.6 0.593 100 5.5 84 AP42 1.4NG Flares lbs/mmscf 0.593 71.4 60.3 388.5 APLiquid Flaring lbs/bbl 0.42 6.83 2 0.01 0.21 AP42 Tank Vapors lbs/bbl 0.03 E&Fugitives lbs/hr/comp. 0.0005 AGlycol Dehydrator Vent lbs/mmscf 6.6 LGas Venting lbs/scf 0.0034

Sulfur Content Source Value Units

Fuel Gas 3.33 ppm

Diesel Fuel 0.4 % weight

Produced Gas( Flares) 3.33 ppm

Produced Oil (Liquid Flaring) 1 % weight

Form MMS-139 (August 2003)Page 2 of 8
AIR EMISSION CALCULATIONS 

COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Shell Offshore Inc Mississippi Canyon 940, 984 & 985

G31534, G22919 & G22920

Vito

D,E,F,G,I(+st),J,K, ST at Well 1 (H Surface Location)

Sylvia Bellone

504-728-7215

OPERATIONS EQUIPMENT RATING MAX. FUEL % Average Eng ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO 

DRILLING PRIME MOVER>600hp diesel 6169 297.9627 25.75% 1841.41 24 210 4.35 19.95 149.47 4.48 32.61 Noble Danny PRIME MOVER>600hp diesel 6169 297.9627 25.75% 1841.41 24 210 4.35 19.95 149.47 4.48 32.61 Atkins PRIME MOVER>600hp diesel 6169 297.9627 25.75% 1841.41 24 210 4.35 19.95 149.47 4.48 32.61 

PRIME MOVER>600hp diesel 6169 297.9627 25.75% 1841.41 24 210 4.35 19.95 149.47 4.48 32.61 PRIME MOVER>600hp diesel 6169 297.9627 25.75% 1841.41 24 210 4.35 19.95 149.47 4.48 32.61 PRIME MOVER>600hp diesel 6169 297.9627 25.75% 1841.41 24 210 4.35 19.95 149.47 4.48 32.61 PRIME MOVER>600hp diesel 6169 297.9627 25.75% 1841.41 24 210 4.35 19.95 149.47 4.48 32.61 PRIME MOVER>600hp diesel 6169 297.9627 25.75% 1841.41 24 210 4.35 19.95 149.47 4.48 32.61 RECIP.>600hp diesel (emergency generator) 2549 123.1167 n/a 2954.80 1 30 1.80 8.24 61.76 1.85 13.47 

AUX EQUIP>600hp diesel (cementing unit 1) 2000 96.6 n/a 2318.40 24 15 1.41 6.47 48.46 1.45 10.57 

AUX EQUIP<600hp diesel (cementing unit 2) 490 23.667 n/a 568.01 24 15 1.08 1.58 15.11 1.21 3.27 

Riserless Support vessel OSV (>600 hp) 9440 455.952 50% 5471.42 24 10 6.65 30.52 228.72 6.86 49.90 

Riserless Support vessel OSV (>600 hp) 9440 455.952 50% 5471.42 24 10 6.65 30.52 228.72 6.86 49.90 

Riserless Support vessel OSV (>600 hp) 9440 455.952 50% 5471.42 24 10 6.65 30.52 228.72 6.86 49.90 

Riserless Support vessel Crew Boat (>600 hp) 5400 260.82 50% 3129.84 8 10 3.81 17.46 130.84 3.93 28.55 

Deepening Support vessel OSV (>600 hp) 9440 455.952 50% 5471.42 24 200 6.65 30.52 228.72 6.86 49.90 Deepening Support vessel Crew Boat 5400 260.82 50% 3129.84 8 200 3.81 17.46 130.84 3.93 28.55 

DRILLING OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 

WELL TEST GAS FLARE 0 0 0 0.00 0.00 0.00 0.00 

See Sheet "Basis 

for estimates"Engine loads 

will vary from 

below- the % 

shown are 

AVERAGES thruout the 

campaign

2011-2018 YEAR TOTAL 73.30 332.89 2497.65 75.68 544.91 

EXEMPTION 

CALCULATI DISTANCE FROM LAND IN MILES 

67.0
COMPANY AREA BLOCK LEASE 

Shell Offshore Inc Mississippi Canyon 940, 984 & 985 G31534, G22919 & G22920 

Proposed Limits for EP

Proposed Limit

Source Year Total Fuel Consumed in the Year, 

gal

Comment Proposed Compliance 

Assurance method

Equal to sum of Daily Consumption in 

Column F of Emissions spreadsheet times 

total days of drilling in the year

NDA Main 

Engines

All years 3,093,568 Limiting total fuel consumed in the period ensures 

average annual emissions as estimated won't be exceeded (while still allowing for short periods of time where fuel usage may be higher than the daily fuel usage from Column F might be exceeded due to currents, drilling conditions, etc)

Maintain logs of fuel consumall main engines, and rig locRetain records through duraEP for inspection if requestBOEM.

Source Year Proposed Limit Comment Proposed Compliance 

Assurance method

Support 

vessels

All years All vessels will maintain total engine 

HP less than or equal to 50% design load while within 25 nautical miles of rig.

Since emission estimates assume all vessels are at or below 50% through-out the campaign, limiting loads to 50% or less will ensure average annual emissions are not exceeded in any given year.

Maintain logs of all vessel loand locations. Retain recordthrough duration of EP for inspection if requested by B
Section 9: OIL SPILL INFORMATION

A. Oil Spill Response Planning

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

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

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

pending approval. An update to the OSRP Certification in accordance with 30 CFR 254.2 was deemed 

submitted to the BOEMRE August 4, 2011. 

 Spill Response Sites: 

Primary Response Equipment Locations Preplanned Staging Location(s) 

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

Charles, LA 

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

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

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

Worst Case Scenario Determination: 

Category Regional OSRP EP 

Type of Activity1 Drilling Rig Drilling Rig 

Facility Location (area/block) MC 807 MC 984 

Facility Designation2 Subsea well “A” Subsea well No. 1 (H) 

Distance to Nearest Shoreline (miles) 53 67 

Volume3

Storage tanks (total) 

Flowlines (on facility) 

Pipelines 

Uncontrolled blowout (volume per day) 

Total Volume 

N/A 

N/A 

N/A 

465,000* BOPD 

465,000 Bbls 

N/A 

N/A 

N/A 

314,000** BOPD 

314,000 Bbls 

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

diesel) 

Crude oil Crude oil 

API Gravity(s)4 26o 25.9o 

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

**24 hour rate (280,000 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 worstcase 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 August 1, 2011, 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.

 
B. Oil Spill Response Discussion

1) Volume of the Worst Case Discharge 

Please refer to Table above and complete discussion in Section 2J. 

 2) Trajectory Analysis 

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

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

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

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

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

Area/Block OCS-G Launch 

Area Land Segment Contact % 

Exploratory 

MC 984 22919 58 

Galveston, TX 1 

Jefferson, TX 1 

Cameron, LA 3 

Vermilion, LA 2 

Iberia, LA 1 

Terrebonne, LA 3 

Lafourche, LA 3 

Jefferson, LA 1 

Plaquemines, LA 8 

St. Bernard, LA 1 

Okaloosa, FL 1 

 

Table 9.C.1 Probability of Land Segment Impact 

C. Resource Identification 

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

the 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 Tobago WCD scenario. 

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

within the Gulf of Mexico for the Exploratory Worst Case Discharge. The Plaquemines Parish has a 

total area of 2,429 square miles of which, 845 square miles of it is land and 1,584 square miles is 

water. Plaquemines Parish includes two National Wildlife Refuges and one Wildlife Management 

Area including the Breton National Wildlife Refuge, the Delta National Wildlife Refuge, and the Pass 

a Loutre Wildlife Management Area. Key ESI maps for Plaquemines Parish and the legend are 

shown in Figures 9.C.1 through 9.C.5. 

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

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

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

applicable. 

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

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

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

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

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

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

D. Worst Case Discharge Response 

Shell will make every effort to respond to the Vito Worst Case Discharge as effectively as possible. 

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

Group to better determine subsurface and surface evaporation and dispersion rates. Below is a table 

outlining the applicable evaporation and dispersion quantities: 

Mississippi Canyon 940, 984 & 985 

Calculations 

(BBLS) 

i. 30 Day Average WCD = 280,000 bbls 

ii. Subsurface dispersion – 25% (Water Depth = ~9,500’) -70,000 bbls 

iii. REMAINING WCD AFTER SUBSURFACE DISPERSION 210,000 bbls 

iv. Surface dispersion and evaporation – 25% -52,500 bbls 

TOTAL REMAINING ~157,500 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 IRCS is designed to contain oil flow in 

the unlikely event of an underwater well blowout, and is designed, constructed, tested, and 

available for rapid response. 

Shell’s specific containment response will be addressed in Shell’s NTL10 submission at the time the 

APD is submitted. 

 

 

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 762,324 

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

equipment equals approximately 606,284 barrels. 

 

De-rated Recovery Rate

(bopd) 

Storage 

(bbls) 

Offshore Recovery 516,021 539,600 

Offshore Storage 211,500 

Nearshore Recovery 90,263 11,224 

Total 606,284 762,324 

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

 See attachment 9.D.4 Offshore On-Water Recovery Activation List 

See attachment 9.D.5 Offshore On-Water Storage Activation List 

 See attachment 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. 

 See attachment 9.D.7 Aerial Surveillance Activation List 

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

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

the first 12 hour operating day of the response. These aerial systems could disperse approximately 

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. 

 See attachment 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. 

 See attachment 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.

 See attachment 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 aeriallydeployed oil ignition system. At least one support/safety boat would be present during active 

burning operations to provide logistics, safety and monitoring support. Depending upon a number of 

factors, up to 4 burns per 12-hour day could be completed per ISB fire team. Most fire boom 

systems can be used for approximately 8-12 burns before being replaced. Fire intensity and weather 

will be the main determining factors for actual burns per system. Although the actual amount of oil 

that will be removed per burn is dependent on many factors, recent data suggests that a typical 

burn might eliminate approximately 750 barrels. For planning purposes and based on the above 

assumptions, a single task force of four fire teams with the appropriate weather and safety 

conditions could complete four burns per day and remove up to ~12,000 bbls/day. In-situ burning 

nearshore and along shorelines may be a possible option based on several conditions and with 

appropriate approvals, as outlined in Section 19, In-situ Burn Plan (OSRP). In-situ burning along 

certain types of shorelines may be used to minimize physical damage where access is limited or if it 

is determined that mechanical/manual removal may cause a substantial negative impact on the 

environment. All safety considerations will be evaluated. In addition, Shell will assess the situation 

and can make notification within 48 hours of the initial spill to begin ramping up fire boom 

production through contracted OSRO(s). There are potential limitations that need to be assessed 

prior to ISB operations. Some limitations include atmospheric and sea conditions; oil weathering; air 

quality impacts; safety of response workers; and risk of secondary fires. 

 See attachment 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. 

 See attachment 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: 

 See attachment 9.D.12 Shoreline Protection and Wildlife Support List 

(9c) Modeling Report 

 

Shell did not model a potential oil or hazardous substance spill. 

 

 
Figure 9.C.1 Environmental Sensitivity Index Map Legend 
Figure 9.C.2 South Pass ESI Map 
Figure 9.C.3 Garden Island Pass ESI Map 
. 

Figure 9.C.4 Pass a Loutre West ESI Map 
Figure 9.C.5 Main Pass ESI Map 
Table 9.D.4 Offshore On-Water Recovery Activation List 
Table 9.D.4 Offshore On-Water Recovery Activation List (continued) 
Table 9.D.4 Offshore On-Water Recovery Activation List (continued) 
Table 9.D.4 Offshore On-Water Recovery Activation List (continued) 
* - These components are additional operational requirements that must be procured by OSROs in addition to the system identified.

Table 9.D.4 Offshore On-Water Recovery Activation List (continued) 
Table 9.D.5 Offshore On-Water Storage Activation List 
Table 9.D.6 Nearshore On-Water Recovery Activation List 
Table 9.D.6 Nearshore On-Water Recovery Activation List (continued) 
Table 9.D.6 Nearshore On-Water Recovery Activation List (continued) 
Table 9.D.7 Aerial Surveillance Activation List 
Table 9.D.8 Offshore Aerial Dispersant Activation List 
Table 9.D.9 Offshore Boat Spray Dispersant Activation List 

Table 9.D.10 Subsea Dispersant Package Activation List 
Table 9.D.11 In-Situ Burn Equipment Activation List 
Table 9.D.11 In-Situ Burn Equipment Activation List (continued) 
Table 9.D.12 Shoreline Protection and Wildlife Support List 
SECTION 10: Environmental Monitoring Information

A. Monitoring Systems 

A rig based Acoustic Doppler Current Profiler (ADCP) is used to continuously monitor the current beneath 

the Rig. Metocean conditions such as sea states, wind speed, ocean currents, etc. will also be continuously 

monitored 

B. Incidental Takes 

No incidental takes are anticipated. Shell implements the mitigation measures and monitors for incidental 

takes of protected species according to the following notices to lessees and operators from the Minerals 

Management Service: 

 

 NTL No.2007-G03 “Marine Trash and Debris Awareness and Elimination” 

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

C. 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. 
SECTION 11: Lease Stipulations Information

Leases OCS-G 22919, 22920 and 31534 are not part of a Biological Sensitive Area, known Chemosynthetic Area, 

Military Warning Area or Shipping Fairway. They are designated as having a high potential for containing 

archeological properties. 

SECTION 12: Environmental Mitigation Measure Information

A. Impacts to Marine and coastal environments 

The proposed action will implement mitigation measures required by laws and regulations, including all 

applicable Federal & State requirements concerning air emissions, discharges to water, and solid waste 

disposal, as well as any additional permit requirements and Shell policies. Project activities will be conducted in 

accordance with the Regional Oil Spill Response Plan. The EIA attached as Section 18 to this plan discusses 

impacts and mitigation measures. 

B. Incidental Takes 

We do not anticipate any incidental takes related to the proposed operations. Shell implements the mitigation 

measures and monitors for incidental takes of protected species according to the following notices to lessees 

and operators from the Minerals Management Service: 

NTL No.2007-G03 “Marine Trash and Debris Awareness and Elimination” 

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

SECTION 13: Related Facilities and Operations Information

Information regarding Related Facilities and Operations Information, transportation systems, & produced liquid 

hydrocarbon transportation vessels are not included in this EP as such information is only necessary in the case of 

DOCDs. 

SECTION 14: Support Vessels and Aircraft Information

A. General 

Type Maximum Fuel Tank Storage 

Capacity (Bbls) 

Maximum No. In Area at Any 

Time 

Trip Frequency or 

Duration 

Noble Danny Adkins 

Crew Boats 1040 2 Twice per week 

Offshore Support Vessels 9750 3 145 days/well 

Helicopter 22 1 Once per day 

B. Diesel Oil Supply Vessels 

Size of Fuel Supply 

Vessel 

Capacity of Fuel Supply 

Vessel 

Frequency of Fuel 

Transfers 

Route Fuel Supply Vessel Will 

Take 

280 foot length 9750 1 week Port Fourchon to MC 984 

C. 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 Tanks below deck onboard 

OSV 

D. Solid and Liquid Wastes Transportation 

See Table 7B. 

E. Vicinity Map – See attached. 

SECTION 15: Onshore Support Facilities Information

A. General 

Name Location Existing/New/Modified 

Boothville PHI Heliport Boothville, LA Existing 

C-Port II Fourchon, LA Existing 

The existing onshore support base for air transportation will be PHI Heliport in Boothville, LA located at 38963 

Highway 23. The existing onshore base for installation water traffic will be the Fourchon Terminal located on 

Bayou LaFourche, south of Leesville, LA approximately three miles from the Gulf of Mexico. Marine support 

for the drilling operation will be from C-Port II located in Fourchon, LA. 

B. 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. 

C. 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. 

D. Waste Disposal 

 See Table 7B. 

SECTION 16: Sulphur Operations Information

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

necessary in the case of DOCDs. 

SECTION 17: Coastal Zone Management Act (CZMA) Information

Concurrence with Louisiana CZM was obtained in Plan N-9220 for leases OCS-G 22919 and 22920 (filed by 

Anadarko). Concurrence with Louisiana and Texas CZM was obtained in Plan N-9383 for Leases OCS-G 22919 

and OCS-G 31534 filed by Shell. 
SECTION 18: Environmental Impact Analysis (EIA)

See following report prepared by CSA. 

 
Environmental Impact Analysis 

SUPPLEMENTAL EXPLORATION PLAN 

Mississippi Canyon Block 940 (OCS-G 31534)

Mississippi Canyon Block 984 (OCS-G 22919) 

Mississippi Canyon Block 985 (OCS-G 22920) 

Offshore Louisiana 

May 2011 

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 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page ii 

CONTENTS 

Page 

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

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

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

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

Oil Spill Prevention and Contingency Planning .................................................................................... 5 

EIA Organization ................................................................................................................................. 5 

A. Impact-Producing Factors ....................................................................................... 6

A.1 Drilling Rig Presence (including noise and lights) ........................................................................ 6 

A.2 Physical Disturbance to the Seafloor .......................................................................................... 6 

A.3 Air Pollutant Emissions .............................................................................................................. 9 

A.4 Effluent Discharges .................................................................................................................... 9 

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

A.6 Onshore Waste Disposal .......................................................................................................... 10 

A.7 Marine Debris .......................................................................................................................... 10 

A.8 Support Vessel and Helicopter Traffic ...................................................................................... 10 

A.9 Accidents ................................................................................................................................. 11 

A.9.1 Types of Accidents Evaluated ....................................................................................... 11 

A.9.2 Small Fuel Spill ............................................................................................................. 11 

A.9.3 Crude Oil Spill (Worst Case Discharge) .......................................................................... 12 

A.9.4 Other Accidents Not Analyzed in Detail ........................................................................ 15 

B. Affected Environment ........................................................................................... 16

C. Impact Analysis ..................................................................................................... 18

C.1 Physical/Chemical Environment ............................................................................................... 18 

C.1.1 Air Quality .................................................................................................................... 18 

C.1.2 Water Quality ............................................................................................................... 20 

C.2 Seafloor Habitats and Biota ..................................................................................................... 22 

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

C.2.2 High-Density Deepwater Benthic Communities ............................................................ 25 

C.2.3 Designated Topographic Features................................................................................. 27 

C.2.4 Pinnacle Trend Area Live Bottoms ................................................................................ 28 

C.2.5 Eastern Gulf Live Bottoms ............................................................................................ 28 

C.3 Threatened, Endangered, and Protected Species and Critical Habitat ...................................... 28 

C.3.1 Sperm Whale (Endangered) .......................................................................................... 30 

C.3.2 Florida Manatee (Endangered) ..................................................................................... 33 

C.3.3 Endangered Mysticete Whales ..................................................................................... 34 

C.3.4 Non-Endangered Marine Mammals (Protected) ........................................................... 35 

C.3.5 Sea Turtles (Endangered/Threatened) .......................................................................... 38 

C.3.6 Piping Plover (Threatened) ........................................................................................... 41 

C.3.7 Whooping Crane (Endangered) ..................................................................................... 43 
CONTENTS 

(Continued) 

Page 

Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page iii 

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

C.3.9 Beach Mice (Endangered) ............................................................................................. 45 

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

C.4.1 Marine and Pelagic Birds .............................................................................................. 46 

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

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

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

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

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

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

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

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

C.8 Socioeconomic and Other Resources ....................................................................................... 60 

C.8.1 Recreational and Commercial Fishing ........................................................................... 60 

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

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

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

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

C.8.6 Other Marine Uses ....................................................................................................... 66 

C.9 Cumulative Impacts ................................................................................................................. 67 

C.9.1 Cumulative Impacts to Physical/Chemical Resources .................................................... 68 

C.9.2 Cumulative Impacts to Biological Resources ................................................................. 69 

C.9.3 Cumulative Impacts to Socioeconomic Resources ......................................................... 71 

D. Environmental Hazards ......................................................................................... 72

D.1 Geologic Hazards ..................................................................................................................... 72 

D.2 Severe Weather ....................................................................................................................... 72 

D.3 Currents and Waves ................................................................................................................ 72 

E. Alternatives .......................................................................................................... 72

F. Mitigation Measures ............................................................................................. 73

G. Consultation ......................................................................................................... 74

H. Preparers .............................................................................................................. 74

I. References ............................................................................................................. 74
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page iv 

LIST OF TABLES 

Table Page 

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

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

2 Matrix of impact-producing factors and affected environmental resources ....................... 7 

3 Conditional probabilities of a spill in the lease area contacting shoreline segments 

(From: Ji et al., 2004) ...................................................................................................... 13 

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

depths sampled during the Northern Gulf of Mexico Continental Slope Habitats 

and Benthic Ecology Study (From: Wei, 2006; Rowe and Kennicutt, 2009) ...................... 23 

5 Federally-listed endangered and threatened species in the lease area and along 

the northern Gulf coast ................................................................................................... 29 

LIST OF FIGURES 

Figure Page 

1 Vicinity map for the lease area .......................................................................................... 2 

2 Bathymetric map of the lease area showing proposed well surface locations .................. 17 

3 Location of selected environmental features in relation to the lease area ....................... 42
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page v 

ACRONYMS AND ABBREVIATIONS 

ADIOS Automated Data Inquiry for Oil Spills 

ASI Airborne Support, Inc. 

BOEMRE Bureau of Ocean Energy Management, 

 Regulation and Enforcement 

BPD bbl/day 

CCA Clean Caribbean & Americas 

CGA Clean Gulf Associates 

CH4 methane 

CO carbon monoxide 

CO2 carbon dioxide 

DP dynamically positioned 

EA Environmental Assessment 

EEZ Exclusive Economic Zone 

EFH Essential Fish Habitat 

EIA Environmental Impact Analysis 

EIS Environmental Impact Statement 

EP Exploration Plan 

ESA Endangered Species Act 

FAD fish-attracting device 

GC Green Canyon 

GMFMC Gulf of Mexico Fishery Management 

Council 

H2S hydrogen sulfide 

HAPC Habitat Area of Particular Concern 

HSE health, safety, and environment 

IPF impact-producing factor 

ISB in-situ burning 

ISO International Organization for 

Standardization 

MARPOL International Convention for the 

Prevention of Pollution from Ships 

MC Mississippi Canyon 

MGD million gallons per day 

MMBO million barrels of oil 

MMPA Marine Mammal Protection Act 

MMS Minerals Management Service 

MSRC Marine Spill Response Corporation 

MWCC Marine Well Containment Company 

NAAQS National Ambient Air Quality Standards 

NEPA National Environmental Policy Act 

NMFS National Marine Fisheries Service 

NOAA National Oceanic and Atmospheric 

Administration 

NOx nitrogen oxides 

NPDES National Pollutant Discharge Elimination 

System 

NPS National Park Service 

NRC National Research Council 

NTL Notice to Lessees 

NWR National Wildlife Refuge 

OCS Outer Continental Shelf 

OCSLA Outer Continental Shelf Lands Act 

OSAT Operational Science Advisory Team 

OSRA Oil Spill Risk Analysis 

OSRL Oil Spill Response Limited 

OSRP Oil Spill Response Plan 

PAH polycyclic aromatic hydrocarbon 

PM particulate matter 

PSD Prevention of Significant Deterioration 

ROV remotely operated vehicle 

SBM synthetic-based mud 

SOx sulfur oxides 

SWSS Sperm Whale Seismic Study 

USCG U.S. Coast Guard 

USDOI U.S. Department of the Interior 

USEPA U.S. Environmental Protection Agency 

VOC volatile organic compound 

USFWS U.S. Fish and Wildlife Service 

WCD worst case discharge 

WCEP Whooping Crane Eastern Partnership 

WMA Wildlife Management Area 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 1 

INTRODUCTION 

Project Summary 

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

Canyon (MC) Blocks 940, 984, and 985. Shell submitted an Initial EP for wells D, E, F and G in 

MC 984 and MC 985, which was approved by the Minerals Management Service (MMS, now 

Bureau of Ocean Energy Management, Regulation and Enforcement [BOEMRE]) on July 30, 

2008 (Plan Control No. N-9220). An Initial EP for well H with a surface location in MC 984 was 

approved by the MMS on June 12, 2009 (Plan Control No. N-9383) with BHL in MC 940. Shell is 

now submitting a Supplemental EP that includes eight exploration wells in MC 940, 984, and 

985, of which one will be a side-track of well H. These wells are D, E, F, G, H-ST, I, J, and K. This 

Supplemental EP also incorporates the revised blowout scenario and worst case discharge 

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

The lease area is 67 miles (108 km) from the nearest shoreline, 117 miles (188 km) from the 

onshore support base at Port Fourchon, Louisiana, and 92 miles (148 km) from the helicopter 

base at Boothville, Louisiana (Figure 1). Water depths at the wellsites range from 1,213 to 

1,269 m (3,978 to 4,164 ft). 

The Noble Danny Adkins, a dynamically positioned (DP) semisubmersible rig, or a similar rig, 

will be used for drilling. Drilling of wells is expected to commence during the last quarter of 

2011. The average time to drill a well will be approximately 145 days. The side-track well 

(H-ST) will take about 65 days to be drilled. 

Purpose of the EIA 

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

Outer Continental Shelf Lands Act (OCSLA), 43 U.S.C. §§ 1331-1356, and BOEMRE regulations, 

including 30 CFR 250.212(o) and 250.227. The EIA is a project- and site-specific analysis of 

Shell’s planned activities under this EP. The EIA also evaluates potential impacts in accordance 

with NTL 2008-G04 issued by the BOEMRE. 

The EIA presents data, analysis, and conclusions to support BOEMRE reviews as required by 

the National Environmental Policy Act (NEPA) and other relevant Federal laws, including the 

Endangered Species Act (ESA) and Marine Mammal Protection Act (MMPA), as the agency 

considers this Supplemental EP for approval. It also identifies the mitigation measures Shell 

will implement in connection with the planned activities. 

As specified in NTL 2008-G04, an EIA is a project-specific analysis that focuses on the impacts 

of a specific plan. This EIA addresses the impact-producing factors (IPFs), resources, and 

impacts associated with the activities proposed in this Supplemental EP including drilling of 

wells. The EIA also incorporates the revised blowout scenario and WCD information required 

by NTL 2010-N06. 
Mississippi Canyon Blocks 940, 984, and 985 

Environmental Impact Analysis for Supplemental EP 

Figure 1. Vicinity map for the lease area. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 3 

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

the Gulf of Mexico Outer Continental Shelf (OCS). Potential impacts were analyzed at a 

broader level in the Programmatic Environmental Impact Statement (EIS) for the OCS Oil and 

Gas Leasing Program (MMS, 2007a) and in recent multi-lease-sale EISs for the Western and 

Central Gulf of Mexico Planning Areas (MMS, 2007b, 2008), as well as the Environmental 

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

Grid EA for the Marco Polo Development in Green Canyon (GC) 608 (Grid 13) (MMS, 2003). 

These studies generated critical data and advanced industry’s and BOEMRE’s large body of 

existing knowledge on the Gulf of Mexico OCS. They analyze everything from potential 

impacts on the natural environment to the socioeconomic effects of exploration and 

development activities. They include numerous technical studies ranging from the likely 

trajectory of spilled oil to the effects of underwater noise on threatened and endangered 

species. They inform agency decision-making on lease offerings, mitigation measures and 

lease stipulations, operational requirements, and permit restrictions. This substantial body of 

work, which in part forms the basis for the evaluation presented here, will allow the BOEMRE 

and other regulatory agencies to evaluate Shell’s Supplemental EP and ensure that oil and gas 

exploration and development activities are performed in an environmentally sound manner, 

with minimal impacts on the environment. Shell has incorporated these comprehensive 

environmental analyses by reference and built on them with project-specific and site-specific 

analyses. 

OCS Regulatory Framework 

The regulatory framework for OCS activities in the Gulf of Mexico has been summarized by 

MMS (2010). Under the OCSLA, the U.S. Department of the Interior (USDOI) is responsible for 

the administration of mineral exploration and development of the OCS. Within the USDOI, the 

BOEMRE is charged with the responsibility of managing and regulating the development of 

OCS oil and gas resources in accordance with the provisions of the OCSLA. The BOEMRE 

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

In implementing its responsibilities under the OCSLA and NEPA, the BOEMRE must consult 

numerous Federal departments and agencies that have authority to govern and maintain 

ocean resources pursuant to other Federal laws. Among these are the U.S. Coast Guard 

(USCG), U.S. Environmental Protection Agency (USEPA), U.S. Fish and Wildlife Service (USFWS), 

and the National Oceanic and Atmospheric Administration (NOAA) through the National 

Marine Fisheries Service (NMFS). Federal regulations establish consultation and coordination 

processes with Federal, State, and local agencies (e.g., the ESA, MMPA, Coastal Zone 

Management Act of 1972, and the Magnuson-Stevens Fishery Conservation and Management 

Act). 

NTLs are formal documents issued by the BOEMRE that provide clarification, description, or 

interpretation of a regulation or standard; provide guidelines on implementing a special lease 

stipulation or regional requirement; provide a better understanding of the scope and meaning 

of a regulation by explaining the BOEMRE interpretation of a requirement; or transmit 

administrative information such as current telephone listings or changes in BOEMRE personnel 

or office address. Table 1 lists and summarizes the NTLs that are referenced in this EIA. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 4 

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

Impact Analysis (EIA). 

NTL Title Summary

2010-N10 

Statement of Compliance with 

Applicable Regulations and 

Evaluation of Information 

Demonstrating Adequate Spill 

Response and Well Containment 

Resources 

Informs operators using subsea blowout preventers (BOPs) or 

surface BOPs on floating facilities that applications for well permits 

must include a statement signed by an authorized company official 

stating that the operator will conduct all activities in compliance 

with all applicable regulations, including the increased safety 

measures regulations (75 FR 63346). Informs operators that the 

BOEMRE will be evaluating whether each operator has submitted 

adequate information demonstrating that it has access to and can 

deploy containment resources to promptly respond to a blowout or 

other loss of well control.

2010-N06 

Information Requirements for 

Exploration Plans, Development and 

Production Plans, and Development 

Operations Coordination Documents 

on the OCS

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

blowout scenario and worst case discharge scenario, and provides 

guidance regarding the information required in blowout scenario 

and worst case discharge scenario descriptions. 

2009-G40 Deepwater Benthic Communities 

Guidance for avoiding and protecting high-density deepwater 

benthic communities (including chemosynthetic and deepwater 

coral communities) from damage caused by Outer Continental Shelf 

(OCS) oil and gas activities in water depths greater than 300 m 

(984 ft). Prescribes separation distances of 610 m (2,000 ft) from 

each mud and cuttings discharge location and 76 m (250 ft) from all 

other seafloor disturbances. 

2009-G39 Biologically-Sensitive Underwater 

Features and Areas 

Guidance for avoiding and protecting biologically sensitive features 

and areas (i.e., topographic features, pinnacles, low-relief live 

bottom areas, and other potentially sensitive biological features) 

when conducting OCS operations in water depths less than 300 m 

(984 ft) in the Gulf of Mexico. 

2009-G06 Military Warning and Water Test 

Areas 

Provides contact links to individual command headquarters for the 

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

stipulations require lessees or designated operators to enter into an 

agreement with the appropriate individual military command 

headquarters concerning the control of electromagnetic emissions 

and use of boats and aircraft in the applicable warning area or 

water test area before commencing such traffic.

2008-G04 

Information Requirements for 

Exploration Plans and Development 

Operations Coordination Documents

Guidance on the information requirements for OCS plans, including 

EIA requirements and information regarding compliance with the 

provisions of the Endangered Species Act and Marine Mammal 

Protection Act. 

2007-G04 

Vessel Strike Avoidance and 

Injured/Dead Protected Species 

Reporting 

Recommends protected species identification training, 

recommends that vessel operators and crews maintain a vigilant 

watch for marine mammals and slow down or stop their vessel to 

avoid striking protected species, and requires operators to report 

sightings of any injured or dead protected species.

2007-G03 Marine Trash and Debris Awareness 

and Elimination 

Instructs operators to exercise caution in the handling and disposal 

of small items and packaging materials; requires the posting of 

placards at prominent locations on offshore vessels and structures; 

and mandates a yearly marine trash and debris awareness training 

and certification process. 

2005-G07 Archaeological Resource Surveys 

and Reports 

Provides guidance on regulations regarding archaeological 

discoveries, specifies requirements for archaeological resource 

surveys and reports, and outlines options for protecting 

archaeological resources. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 5 

Oil Spill Prevention and Contingency Planning 

Shell submitted a Gulf of Mexico Regional Oil Spill Response Plan (OSRP) to the BOEMRE as a 

fundamental component of the planned drilling program on October 26, 2010. The OSRP 

certifies that Shell has the capability to respond to the maximum extent practicable to a WCD 

(30 CFR 254.2). The OSRP demonstrates Shell’s capabilities to rapidly and effectively manage 

oil spills that may result from drilling operations. Despite the extremely low likelihood of a 

large oil spill event occurring during the project, Shell has designed its response program based 

upon a regional capability of responding to a range of spill volumes that increase from small 

operational spills up to and including a WCD from a well blowout. Shell’s program meets the 

response planning requirements of the relevant coastal states and Federal oil spill planning 

regulations. The OSRP includes information regarding Shell’s regional oil spill organization and 

dedicated response assets, potential spill risks, and local environmental sensitivities. The OSRP 

presents specific information on the response program that includes a description of 

personnel and equipment mobilization, the incident management team organization, and the 

strategies and tactics used to implement effective and sustained spill containment and 

recovery operations. 

EIA Organization 

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

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

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

Section C (Impact Analysis). 

 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 6 

A. IMPACT-PRODUCING FACTORS 

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

Form MMS-142. An “X” indicates that an IPF could reasonably be expected to affect a certain 

resource, and a dash (--) indicates no impact or negligible impact. Where there may be an 

effect, an analysis is provided in Section C. Potential IPFs for the proposed activity are listed 

below and briefly discussed in the following subsections: 

• Drilling rig presence (including noise and lights);

• Physical disturbance to the seafloor; 

• Air pollutant emissions; 

• Effluent discharges; 

• Water intake; 

• Onshore waste disposal; 

• Marine debris; 

• Support vessel and helicopter traffic; and 

• Accidents. 

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

The wells will be drilled using the Noble Danny Adkins or a similar DP semisubmersible. The rig 

will be on site for an estimated 145 days per well. Four offshore support vessels will be used 

during the drilling program and at least one of these will always be in the vicinity of the drilling 

rig to provide assistance as necessary. The physical presence of a drilling rig in the ocean can 

attract pelagic fishes and other marine life, as discussed in Section C.5.1. A semisubmersible 

maintains buoyancy using ballasted, watertight pontoons located below the sea surface. The 

operating deck is located above the tops of passing waves. Structural columns connect the 

pontoons and operating deck. When the rig moves its location, the pontoons are de-ballasted 

so that the rig can float on the sea surface. The Noble Danny Adkins uses thrusters to hold or 

adjust its position. 

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

including infrasonic frequencies in at least some cases (MMS, 2000). Drilling noise from 

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

10 to 500 Hz (Richardson et al., 1995). From a semisubmersible, sound and vibration are 

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

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

regulations. 

A.2 Physical Disturbance to the Seafloor 

Semisubmersibles like the Noble Danny Adkins do not use anchors for holding or stabilization 

during drilling operations. There will be minimal disturbance to the seafloor and soft bottom 

communities during positioning of the wellbore and BOP. Physical disturbance of the seafloor 

will be limited to the area where the wellbore penetrates the substrate, where mud and drill 

cuttings will be deposited. 
Mississippi Canyon Blocks 940, 984, and 985 

Environmental Impact Analysis for Supplemental EP 

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

Environmental Resources 

Impact-producing Factors

Drilling Rig 

Presence (incl. 

noise & lights) 

Physical 

Disturbance 

to Seafloor 

Air 

Pollutant 

Emissions 

Effluent 

Discharges

Water Intake 

Onshore 

Waste 

Disposal 

Marin

Debris 

Physical/Chemical Environment

Air quality and greenhouse gases -- -- X -- -- -- -- Water quality -- -- -- X -- -- -- 

Seafloor Habitats and Biota

Soft bottom benthic communities -- -- -- 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 and Critical Habitat

Sperm whale (endangered) X(8) -- -- -- -- -- -- Florida manatee (endangered) -- -- -- -- -- -- -- Endangered mysticete whales -- -- -- -- -- -- -- Non-endangered marine mammals (protected) X -- -- -- -- -- -- Sea turtles (endangered/threatened) X(8) -- -- -- -- -- -- Piping Plover (threatened) -- -- -- -- -- -- -- Whooping Crane (endangered) -- -- -- -- -- -- -- Gulf sturgeon (threatened) -- -- -- -- -- -- -- Beach mice (endangered) -- -- -- -- -- -- -- 

Coastal and Marine Birds

Marine and pelagic birds X -- -- -- -- -- -- Shorebirds and coastal nesting birds -- -- -- -- -- -- -- 

Fisheries Resources

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

Archaeological Resources

Shipwreck sites -- --(7) -- -- -- -- -- Prehistoric archaeological sites -- --(7) -- -- -- -- -- 

Coastal Habitats and Protected Areas

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

Socioeconomic and Other Resources

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

WCD = worst case discharge. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 8 

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 blocks. 

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

Trend) Stipulation attached to an OCS lease. 

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

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

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

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

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

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

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

any drilling mud/cuttings discharge location. Because a semisubmersible will be used, there will be no 

seafloor disturbances due to anchoring. 

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

• Based on CFR 250.417(c), Shell is requesting that the BOEMRE classify the area 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 BOEMRE as having high-probability for the occurrence of shipwrecks or prehistoric sites, including such 

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

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

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

• No impacts on archaeological resources are expected. The lease area is on the list of high-probability 

blocks for shipwrecks. The archaeological survey detected 106 unidentified sidescan sonar targets, 

several drag scars, and geological features within the survey area, of which 23 were in MC 940, 984, and 

985. There were no sonar contacts with acoustic signature that require archaeological avoidance or 

further investigation. The lease is well beyond the 60-m depth contour used by the BOEMRE as the 

seaward extent for prehistoric archaeological site potential in the Gulf of Mexico. Because a dynamically 

positioned semisubmersible will be used, there will be no seafloor disturbances due to anchoring. 

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

or sea turtles or their critical habitats. 

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

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

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

• Not applicable.
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 9 

A.3 Air Pollutant Emissions 

Air pollutant emissions are estimated in Supplemental EP Section 8. Offshore air pollutant 

emissions will result from operations of the drilling rig, as well as service vessels and 

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

fuels occurs on diesel-powered generators, pumps, or motors and from lighter fuel motors. 

Primary air pollutants typically associated with OCS activities are suspended particulate matter 

(PM), sulfur oxides (SOx), nitrogen oxides (NOx), volatile organic compounds (VOCs), and 

carbon monoxide (CO). 

The Air Quality Emissions Report prepared in accordance with the BOEMRE requirements 

shows that the projected emissions for the drilling rig are below exemption levels; therefore, 

according to 30 CFR 250.303, the emissions will not significantly affect the air quality of the 

onshore area for any of the criteria pollutants. No further analysis or control measures are 

required. However, Shell will use low sulfur fuel (0.05% by weight) to further reduce any 

possible impacts. 

A.4 Effluent Discharges 

Effluent discharges are summarized in Supplemental EP Section 7. All offshore discharges will 

be in accordance with the National Pollutant Discharge Elimination System (NPDES) General 

Permit No. GMG290000 issued by the USEPA. Discharges will be in compliance with and 

monitored as required by the permit. 

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

intervals before the marine riser is set that allows returns to the surface. Excess cement slurry 

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

drilling operations. 

A synthetic-based mud (SBM) system will be used after the riser is installed. The SBM will not 

be discharged but will be recovered and transported to the shorebase for recycling by the mud 

company. SBM cuttings will be discharged overboard via a downpipe to 515 ft below the 

water surface, after treatment with a cuttings dryer, which is expected to reduce retention of 

the SBM fluid on cuttings to well below the NPDES permit requirement of 6.9%. The estimated 

volume of cleaned SBM drill cuttings to be discharged is 6,500 barrels (bbl)/well. 

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

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

unit brine, uncontaminated fire water and ballast water. 

A.5 Water Intake 

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

the drilling rig. The estimated intake and discharge of cooling water is 130,600 bbl/day (BPD) 

(5.48 million gallons per day [MGD]). The rig will also use another 130,600 BPD (5.48 MGD) 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 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 10 

entrainment of aquatic organisms. Construction of the rig planned for use in this 

Supplemental EP, the Noble Danny Atkins, started prior to July 17, 2006, and therefore is not 

subject to the cooling water intake permit requirements of NPDES Permit GMG 290000. If a 

similar type rig is selected, it will comply with all applicable NPDES requirements. 

A.6 Onshore Waste Disposal 

Wastes generated during drilling are tabulated in Supplemental EP Section 7. Waste volume is 

estimated to be approximately 7,000 bbl/well. Exploration and Production (E&P) waste will be 

collected and disposed of at Newpark Environmental Services or US Liquids of Louisiana 

(Fourchon, Louisiana). Non-hazardous trash and debris and non-recyclable waste will be 

transported to the Republic/BFI landfill in Sorrento, Louisiana, or the parish landfill in 

Avondale, Louisiana. Additionally, non-hazardous recyclable waste will be recycled at Omega 

Waste Management, Patterson, Louisiana, or at ARC of New Iberia, New Iberia, Louisiana, via 

the Recycle the Gulf Program. Hazardous waste such as paints, solvents, and unused 

chemicals will be disposed of at Safety Kleen Systems, Inc., Denton, Texas, while used oil will 

be sent to Omega Waste Management for recycling, and glycol will be sent to Safety Kleen 

Systems, Inc. for recycling. Universal waste including batteries, lamps, glass, and 

mercury-contaminated waste will be recycled at Lamp Environmental Industries, Hammond, 

Louisiana. Oil filters, oily rags and pads, empty drums, and cooking oil will be sent to Omega 

Waste Management, Patterson, Louisiana for recycling. At the onshore facilities, wastes will 

be recycled or disposed of according to all applicable regulations. 

A.7 Marine Debris 

Trash and debris released into the marine environment can harm marine mammals, turtles, 

and birds through entanglement and ingestion. Shell will adhere to the International 

Convention for the Prevention of Pollution from Ships (MARPOL 73/78) Annex V requirements, 

USEPA and USCG regulations, and BOEMRE regulations and NTLs regarding solid wastes. The 

BOEMRE regulations at 30 CFR 250.300(a) and (b)(6) prohibit operators from deliberately 

discharging containers and other similar materials (e.g., trash and debris) into the marine 

environment, and 30 CFR 250.300(c) requires durable identification markings on equipment, 

tools and containers (especially drums), and other material. USCG and USEPA regulations 

require operators to become proactive in avoiding accidental loss of solid waste items by 

developing waste management plans, posting informational placards, manifesting trash sent 

to shore, and using special precautions such as covering outside trash bins to prevent 

accidental loss of solid waste. Shell complies with NTL 2007-G03, which instructs operators to 

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

the posting of placards at prominent locations on offshore vessels and structures, and 

mandates a yearly marine trash and debris awareness training and certification process. 

Shell’s compliance with all applicable laws, regulations, and NTL 2007-G03 will avoid significant 

impacts on the environment. 

A.8 Support Vessel and Helicopter Traffic 

Shell will use existing shorebased facilities at Port Fourchon and Boothville, Louisiana, for 

onshore support for water and air transportation, respectively. No terminal expansion or 

construction is planned at either location. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 11 

The supply base at Port Fourchon is operated by Shell and located on Bayou LaFourche, 

approximately 3 miles (5 km) from the Gulf of Mexico. During drilling, the project will be 

supported by two crew boats and four offshore support vessels; crew boats will make two 

round-trips per week between the drilling facility and the onshore supply base, while at least 

one support vessel will be in the field at all times. The boats will normally move to the project 

area via the most direct route from the shorebase. 

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

make one round-trip daily between the drilling rig and the heliport. The helicopter will be 

used to transport personnel and small supplies and will normally take the most direct route of 

travel between the helicopter base and the lease area when air traffic and weather conditions 

permit. Helicopters typically maintain a minimum altitude of 213 m (700 ft) while in transit 

offshore, 305 m (1,000 ft) over unpopulated areas or across coastlines, and 610 m (2,000 ft) 

over populated areas and sensitive habitats such as wildlife refuges and park properties. 

A.9 Accidents 

A.9.1 Types of Accidents Evaluated 

The analysis in this EIA focuses on two potential accidents: 

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

and 

• An oil spill resulting from an uncontrolled blowout. A blowout resulting in a 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 Supplemental EP Section 2j. In 

accordance with NTL 2010-N06, the estimated rate is 314,000 bbl for the first day with a 

30-day average of 280,000 BPD. The estimated time to drill a relief well is 185 days, and 

the total volume of a spill over this duration would be 48 million barrels of oil (MMBO). 

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

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

The lease sale EIS (MMS, 2007b) analyzes three other types of accidents: chemical spills, vessel 

collisions, and loss of well control. These accidents are discussed briefly in Section A.9.4. 

A.9.2 Small Fuel Spill 

Spill Size. According to the analysis in MMS (2007b), the most likely type of small spill 

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

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

future OCS activities in the Western and Central Gulf of Mexico Planning Areas (MMS, 2007b). 

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

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

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

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

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

oceanographic conditions at the time, as well as the effectiveness of spill response activities. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 12 

However, given the open ocean location of the lease area, the duration of a small spill and the 

opportunity for impacts to occur would be very brief. 

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

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

[NRC], 2003). The constituents of these oils are light to intermediate in molecular weight and 

can be readily degraded by aerobic microbial oxidation. Diesel is so light that it will not sink to 

the seafloor. Diesel dispersed in the water column can adhere to suspended sediments, but 

this generally occurs only in coastal areas with high suspended solids loads (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. 

The lease area is 67 miles (108 km) from the nearest shoreline (Louisiana). Modeling results 

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

contacting the nearest Louisiana shoreline (Plaquemines Parish) within 10 days after a spill. By 

this time, essentially 100% of a small fuel spill would have been dispersed or evaporated by 

natural processes, even if no response measures were implemented. MMS (2007b) similarly 

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

water beyond a few days and are unlikely to make landfall or reach coastal waters prior to 

breaking up. MMS (2007b) noted that this conclusion is supported by a previous analysis of 

3-day trajectory model runs, previous weathering analyses, and historical records of spill 

incidents. 

Spill Response. In the unlikely event 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. 

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

A.9.3 Crude Oil Spill (Worst Case Discharge) 

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

event will be minimized by Shell’s well control and blowout prevention measures detailed in 

Supplemental EP Section 2j. Blowouts are rare events and most do not result in oil spills. 

Holand (1997) estimated a probability of 0.0021 for a 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 development 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. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 13 

The risk of a blowout during this project is significantly lower than indicated by these statistics 

because the well design and drilling program were developed using information gathered 

during the drilling of the previous well (H) in MC 940. During drilling of the previous well, the 

reservoirs were fully logged and evaluated. Substantial data associated with the reservoirs 

were gathered including core, pressure, and fluid data. Data gained during these earlier 

operations provide substantial information that was used in preparing for the proposed 

operation. 

Spill Size. In accordance with requirements of NTL 2010-N06, Shell has estimated a WCD for 

this Supplemental EP as 314,000 BPD for the first day with a 30-day average of 280,000 BPD. 

The estimated time to drill a relief well is 185 days, and the total volume of a spill over this 

duration would be 48 MMBO. The detailed analysis of this calculation can be found in 

Supplemental EP Section 2j. 

Shell has a robust system in place to prevent blowouts. Included in Supplemental EP 

Sections 2j and 9b is Shell’s response to NTL 2010-N06, which includes descriptions of 

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

early intervention in the event of a blowout. Shell will also comply with NTL 2010-N10 and the 

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

Spill Trajectory. The fate of a large oil spill in the lease area would depend on meteorological 

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

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

predict spill fate. The OSRA report by Ji et al. (2004) provides conditional contact probabilities 

for shoreline segments. The results for Launch Area 58 (where the lease area is located) are 

presented in Table 3. The model predicts no shoreline contact within 3 days. After 10 days, 

three Louisiana parishes may be contacted. After 30 days, 11 counties and parishes from 

Texas to the Florida Panhandle may be contacted. Plaquemines Parish, Louisiana, has the 

greatest probability of shoreline contact, with a 4% and 8% chance within 10 and 30 days, 

respectively. 

Table 3. Conditional probabilities of a spill in the lease area contacting shoreline segments 

(From: Ji et al., 2004). Values are conditional probabilities that a hypothetical spill in 

the lease area (represented by OSRA Launch Area 58) 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

C10 Galveston, Texas -- -- 1

C12 Jefferson, Texas -- -- 1

C13 Cameron, Louisiana -- -- 3

C14 Vermilion, Louisiana -- -- 2

C15 Iberia, Louisiana -- -- 1

C17 Terrebonne, Louisiana -- 1 3

C18 Lafourche, Louisiana -- 2 3

C19 Jefferson, Louisiana -- -- 1

C20 Plaquemines, Louisiana -- 4 8

C21 St. Bernard, Louisiana -- -- 1

C28 Okaloosa, Florida -- -- 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%). 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 14 

The OSRA model does not evaluate the fate of a spill over time periods longer than 30 days, 

nor does it predict the fate of a release that continues over a period of weeks or months. Also 

as noted by Ji et al. (2004), the OSRA model does not take into account the chemical 

composition or biological weathering of oil spills, the spreading and splitting of oil spills, or spill 

response activities. The model does not assume a particular spill size but has generally been 

used by the BOEMRE to evaluate contact probabilities for spills greater than 1,000 bbl. 

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

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

oil, and thereby influence its harmful effects on marine organisms and ecosystems. The most 

important weathering processes include spreading, evaporation, dissolution, dispersion into 

the water column, formation of water-in-oil emulsions, photochemical oxidation, microbial 

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

seafloor (NRC, 2003). 

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

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

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

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

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

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

slowly. Photooxidation attacks mainly the medium and high molecular weight PAHs in the oil 

on the water surface. 

Spill Response. Shell is a founding member of the Marine Well Containment Company 

(MWCC) and has access to an integrated subsea well control and containment system that can 

be rapidly deployed through the MWCC. The MWCC is a non-profit organization that manages 

and provides fully trained crews and operates the subsea containment system during a 

response. The near-term containment response capability will be specifically addressed in 

Shell’s NTL 2010-N10 submission at the time an Application to Drill (APD) is submitted and will 

include equipment and services available to Shell through MWCC’s development of near-term 

capability and other industry sources. Shell is a member of Clean Caribbean & Americas (CCA), 

Marine Spill Response Corporation (MSRC), Clean Gulf Associates (CGA), and Oil Spill Response 

Limited (OSRL), organizations that are committed to providing the resources necessary to 

respond to a spill as outlined in Shell’s OSRP (October 2010). 

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 

[Bromwich, 2010]). Shell is further analyzing these advances and incorporating them into a 

comprehensive approach to help prevent and, if needed, control another deepwater control 

incident. Shell is also investing in research and development to improve containment systems. 

The primary offshore response would involve mechanical recovery. The primary response 

equipment that would be mobilized to the spill location for spills in normal and adverse 

weather conditions is included in the Offshore On-Water Recovery Activation List in the OSRP. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 15 

Chemical dispersion capabilities are also readily available from resources such as MSRC at 

Stennis, Mississippi, and Coolidge, Arizona; CGA/Airborne Support, Inc. (ASI) in Houma, 

Louisiana; Oil Spill Response in South Hampton, UK and Singapore; and CCA in Ft. Lauderdale, 

Florida. Available equipment for surface and subsea application of dispersants, 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. 

See Supplemental 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 surface and subsea containment capabilities that could be 

implemented in the event of the worst case spill at this site. 

A.9.4 Other Accidents Not Analyzed in Detail 

The lease sale EIS (MMS, 2007b) discusses three other types of accidents: chemical spills, 

vessel collisions, and loss of well control. These accidents are discussed briefly below. No 

hydrogen sulfide (H2S) is expected at this site, and no other site-specific issues have been 

identified for this Supplemental EP. The analysis in the lease sale EIS for these topics is 

incorporated by reference. 

Chemical Spill. Chemicals are used in drilling operations to achieve technical goals in the 

drilling process, improve the efficiency and safety of drilling, and protect associated 

equipment. Chemicals used during exploration and drilling include surfactants, bentonite 

clays, olefins, inorganic salts, glycols, polymers, barite, and calcium carbonate. Supplies are 

renewed on a regular basis by transfer in containers from supply boats (Boehm et al., 2001). 

In addition to chemicals used in drilling fluids, the following chemicals are likely to be used on 

the rig: ethylene glycol (blowout prevention control fluid, closed cooling loops for crane and 

main engines and brake coolers), cement (used to cement casing in place), solvents (used in 

painting operations), hydraulic fluids (used in cranes and other hydraulic rig equipment), 

lubricating oil and grease (used in reciprocating and electrical equipment), and sodium 

hypochlorite (dilute, used as laundry bleach and disinfectant). 

A study of environmental risks of chemical products used in OCS activities determined that 

only two chemicals could potentially affect the marine environment: zinc bromide and 

ammonium chloride (Boehm et al., 2001). The risk of a spill for these chemicals is very low. 

Most other chemicals are either nontoxic or used in small quantities. No significant impacts 

are expected from chemical spills. 

Vessel Collisions. As summarized in MMS (2007b), vessel collisions occasionally occur during 

routine operations. Most collision mishaps are the result of service vessels colliding with 

platforms or vessel collisions with pipeline risers. Some of these collisions have caused spills of 

diesel fuel or chemicals. Shell will comply with all USCG and BOEMRE-mandated safety 

requirements to minimize the potential for vessel collisions. 

Loss of Well Control. A loss of well control is the uncontrolled flow of a reservoir fluid that 

may result in the release of gas, condensate, oil, drilling fluids, sand, or water. Loss of well 

control is a broad term that includes minor to serious well control incidents, while blowouts 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 16 

are considered to be a subset of more serious incidents with greater risk of oil spill or human 

injury (MMS, 2007b). Loss of well control may result in the release of synthetic drilling fluid or 

loss of oil. Shell has a robust system in place to prevent loss of well control. Included in this 

Supplemental EP is Shell’s response to NTL 2010-N06, which includes descriptions of measures 

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

intervention in the event of a blowout. Shell will also comply with NTL 2010-N10 and the 

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

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

H2S Release. Based on CFR 250.417(c), Shell requests that the Regional Supervisor, Field 

Operations, classify the area in the proposed drilling operations as an area where the absence 

of H2S has been confirmed. 

B. AFFECTED ENVIRONMENT 

The lease area is in the north-central Gulf of Mexico, 67 miles (108 km) from the nearest 

shoreline, 117 miles (188 km) from the onshore support base at Port Fourchon, Louisiana, and 

92 miles (148 km) from the helicopter base at Boothville, Louisiana (Figure 1). 

The seafloor gradient in the MC 940, 984, and 985 study area ranges from near flat to 

approximately 15.4o

. The average slope is 1.77o indicating the study area in general is flat. The

greatest seafloor gradients occur along seafloor fault escarpments. The seabed morphology in 

this portion of the slope consists of a series of ridges and valleys, the axes of which trend 

approximately northwest-southeast parallel to the axis of the Mississippi Canyon and 

perpendicular to the regional bathymetric contours (GEMS, 2007). The wellsites are in areas 

of the seafloor that slope gently southeast, east-southeast or southwest at angles between 

1.3o

 and 2.5o on a relatively featureless ramp, with water depths ranging from 1,213 to 

1,269 m (3,978 to 4,164 ft) (Figure 2). The sidescan sonar survey confirmed the presence of 

one subsea well in the lease area and the absence of other man-made infrastructure, including 

pipelines. 

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

(MMS, 2007b, 2008), including meteorology, oceanography, geology, air and water quality, 

benthic communities, threatened and endangered species, biologically sensitive resources, 

archaeological resources, socioeconomic conditions, and other marine uses. These regional 

descriptions are based on extensive literature reviews and are incorporated by reference. 

General background information is presented below, and brief descriptions of each potentially 

affected resource are presented in Section C, including site-specific and/or new information if

available. 

The local environment in the lease area is not known to be unique with respect to 

physical/chemical, biological, or socioeconomic conditions. Baseline environmental conditions 

in the lease area are expected to be consistent with the regional description of continental 

slope locations evaluated in recent lease sale EISs (MMS, 2007b, 2008). 

The lease area is approximately 68 miles (110 km) southwest of the Macondo spill site. Based 

on an analysis of satellite imagery (ESRI, 2010), the surface slick extended over the lease area 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 17 

at various times prior to capping of the well; therefore, existing water quality in the lease area 

could have been temporarily affected. Macondo spill impacts are addressed in Section C.9

(Cumulative Impacts) where available and applicable. 

Figure 2. Bathymetric map of the lease area showing proposed well surface locations. Well H was 

drilled previously and will be side-tracked; the others are new wells to be drilled. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 18 

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

Mexico deepwater operations and activities (MMS, 2000) and a Grid EA for the Marco Polo 

Development in GC 608 (MMS, 2003). Site-specific issues are addressed in this section as 

appropriate. 

C.1 Physical/Chemical Environment 

C.1.1 Air Quality 

There are no site-specific air quality data for the project area. Due to the distance from 

shorebased pollution sources, offshore air quality is expected to be good. The attainment 

status of Federal OCS waters is unclassified because there is no provision in the Clean Air Act 

for classification of areas outside State waters (MMS, 2007b). 

As of April 2011, all Louisiana, Mississippi, Alabama, and Florida coastal counties and parishes 

are in attainment of the National Ambient Air Quality Standards (NAAQS) for all criteria 

pollutants (USEPA, 2011). Two metropolitan areas in Texas are nonattainment areas for 8-h 

ozone (Dallas-Fort Worth, and Houston-Brazoria), and El Paso County is a nonattainment area 

for PM10 (USEPA, 2011). 

Winds in the region are driven by the clockwise circulation around the Bermuda High 

(MMS, 2007b). The Gulf of Mexico is located to the southwest of this center of circulation, 

resulting in a prevailing southeasterly to southerly flow, which is conducive to transporting 

emissions toward shore. However, circulation is also affected by tropical cyclones (hurricanes) 

during summer and fall, and by extratropical cyclones (cold fronts) during winter. 

IPFs potentially affecting air quality are air pollutant emissions and two types of accidents: 

a small fuel spill and a large oil spill (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 operation of the drilling rig as well as helicopters and 

service vessels. These emissions occur mainly from combustion or burning of diesel fuel. The 

combustion of fuels occurs primarily on diesel-powered generators, pumps, or motors and 

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

suspended PM, SOx, NOx, VOCs, and CO. 

Due to the distance from shore, routine operations in the project area are not expected to 

have any impact on air quality conditions along the coast, including nonattainment areas. As 

noted in the lease sale EIS (MMS, 2007b), emissions of air pollutants from routine activities in 

the Central Gulf of Mexico Planning Area are projected to have minimal impacts to onshore air 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 19 

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

the distance of these emissions from the coastline. The Air Quality Emissions Report (see 

Supplemental EP Section 8) prepared in accordance with BOEMRE requirements shows that 

the projected emissions for PM, SOx, NOx, VOCs, and CO are below exemption levels; 

therefore, according to 30 CFR 250.303, the emissions will not significantly affect the air 

quality of the 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 Wilderness Area, which is part of the Breton National Wildlife Refuge (NWR), is 

designated under the Clean Air Act as a Prevention of Significant Deterioration (PSD) Class I air 

quality area. The BOEMRE is required to notify the National Park Service (NPS) and the USFWS 

if emissions from proposed projects may affect the Breton Class I area. Additional review and 

mitigation measures may be required for sources within 186 miles (300 km) of the Breton 

Class I area that exceed emission limits agreed upon by the administering agencies 

(NPS, 2010). The lease area is approximately 99 miles (159 km) from the Breton Wilderness 

Area. Shell does not anticipate any impact on the Class I area but will comply with any 

emissions requirements as directed by the BOEMRE. 

Impacts of a Small Fuel Spill 

Potential impacts of a small spill on air quality are expected to be consistent with those 

analyzed and discussed in recent EISs (MMS, 2007b, 2008). The probability of a small spill 

would be minimized by Shell’s preventative measures during routine operations, including fuel 

transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and 

reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response 

measures. Given the open ocean location of the lease area, the extent and duration of air 

quality impacts from a small spill would not be significant. 

A small fuel spill would affect air quality near the spill site by introducing VOCs through 

evaporation. The ADIOS2 model (see Section A.9.2) indicates that more than 90% of a small 

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

with diesel fuel on it would range from 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 impacts of a large oil spill on air quality are expected to be consistent with those 

analyzed and discussed in recent EISs (MMS, 2007b, 2008). 

A large oil spill (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 ISB of the floating oil. 

Burning would generate a plume of black smoke and result in emissions of NOx, SOx, CO, and 

PM, as well as greenhouse gases. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 20 

Due to the lease area location (67 miles [108 km] from the nearest shoreline), most air quality 

impacts would occur in offshore waters. Depending on the spill trajectory and the 

effectiveness of spill response measures, coastal air quality could also be affected. Based on 

the OSRA modeling predictions (Table 3), Plaquemines Parish, Louisiana, is the coastal area 

most likely to be affected. 

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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on air quality 

are expected. 

C.1.2 Water Quality 

There are no site-specific water quality data for the lease area. Due to the lease location in 

deep, offshore waters, water quality is expected to be good, with low levels of contaminants. 

As noted in the lease sale EIS (MMS, 2007b), deepwater areas in the northern Gulf of Mexico 

are relatively homogeneous with respect to temperature, salinity, and oxygen. Kennicutt 

(2000) noted that the deepwater region has little evidence of contaminants in the dissolved or 

particulate phases of the water column. However, there are localized occurrences of natural 

seepage of oil, gas, and brines in near-surface sediments and up through the water column. 

The lease area is approximately 68 miles (110 km) southwest of the Macondo spill site. Based 

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

spill, and therefore existing water quality in the lease area could have been temporarily 

affected. The Operational Science Advisory Team (OSAT, 2010) reported that after August 

2010, waters and sediments in the deepwater Gulf of Mexico beyond 1.8 miles (3 km) from the 

Macondo wellsite were below USEPA acute and chronic benchmarks for PAHs and were not 

hypoxic. These observations indicate that baseline environmental conditions in the lease area 

are unlikely to have been significantly altered by the spill. 

IPFs potentially affecting water quality are effluent discharges and two types of accidents: 

a small fuel spill and a large oil spill (WCD). 

Impacts of Effluent Discharges 

Discharges of treated SBM cuttings will produce temporary, localized increases in suspended 

solids in the water column around the drilling rig. In general, turbid water can be expected to 

extend between a few hundred meters and several kilometers down current from the 

discharge point (NRC, 1983; Neff, 1987). All NPDES permit limitations and requirements will 

be met. After discharge, SBM retained on cuttings would be expected to adhere tightly to the 

cuttings particles and, consequently, would not produce much turbidity as the cuttings sink 

through the water column (Neff et al., 2000). There will be no persistent impacts on water 

quality in the lease area. 

Treated sanitary and domestic wastes may have a slight transient effect on water quality in the 

immediate vicinity of these discharges. All NPDES permit limitations and requirements will be 

met and little or no impact on water quality is anticipated. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 21 

Deck drainage includes all effluents resulting from rain, deck washings, and runoff from curbs, 

gutters, and drains, including drip pans in work areas. Rainwater that falls on uncontaminated 

areas of the drilling rig will flow overboard without treatment. However, rainwater that falls 

on the drilling rig deck and other areas such as chemical storage areas and places where 

equipment is exposed will be collected and oil and water separated to meet NPDES permit 

requirements. Little or no impact on water quality is anticipated. 

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

uncontaminated cooling water, fire water, and ballast water are expected to be diluted rapidly 

and have little or no impact on water quality. 

Support vessels will discharge treated sanitary and domestic wastes. These will have a slight 

effect on water quality in the immediate vicinity of the discharges. All support vessel 

discharges will be in accordance with USCG regulations and, as applicable, the NPDES Vessel 

General Permit, and therefore are not expected to cause significant impacts on water quality.

Impacts of a Small Fuel Spill 

Potential impacts of a small spill on water quality are expected to be consistent with those 

analyzed and discussed in recent EISs (MMS, 2007b, 2008). The probability of a small spill 

would be minimized by Shell’s preventative measures during routine operations, including fuel 

transfer. In the unlikely event of a spill, implementation of Shell’s OSRP will mitigate and 

reduce the impacts. Supplemental EP Sections 2j and 9b provide detail on spill response 

measures. Given the open ocean location of the lease area, the extent and duration of water 

quality impacts from a small spill would not be significant. 

A small fuel spill in offshore waters would produce a slick on the water surface and increase 

the concentrations of petroleum hydrocarbons and their degradation products. The extent 

and persistence of impacts would depend on the meteorological and oceanographic conditions 

at the time and the effectiveness of spill response measures. However, it is estimated that 

more than 90% of a small diesel spill would be evaporated or dispersed within 24 hours (see 

Section A.9.2). The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha 

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

The water-soluble fractions of diesel are dominated by two- and three-ringed PAHs, which are 

moderately volatile (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 occurs only in coastal areas 

with high suspended solid loads (NRC, 2003) and would not be expected to occur to any 

appreciable degree in offshore waters of the Gulf of Mexico. Diesel oil is readily and 

completely degraded by naturally occurring microbes (NOAA, 2006). 

A small fuel spill would not affect coastal water quality because the spill would not be 

expected to make landfall or reach coastal waters prior to breaking up (see Section A.9.2). 

Impacts of a Large Oil Spill (WCD) 

Potential impacts of a large oil spill on water quality are expected to be consistent with those 

analyzed and discussed in recent EISs (MMS, 2007b, 2008). A large spill would affect water 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 22 

quality by producing a slick on the water surface and increasing the concentrations of 

petroleum hydrocarbons and their degradation products. The extent and persistence of 

impacts would depend on the meteorological and oceanographic conditions at the time and 

the effectiveness of spill response measures. Most of the oil would be expected to form a slick 

at the surface, although new information from the Macondo spill indicates that plumes of 

submerged oil droplets can be produced when subsea dispersants are applied at the wellhead 

(Camilli et al., 2010; Hazen et al., 2010; Joint Analysis Group, 2010a,b,c). A report by 

Kujawinski et al. (2011) indicates that chemical components of subsea dispersants used during 

the Macondo spill persisted for up to two months and were detectable up to 186 miles 

(300 km) from the wellsite at a water depth of 1,000 to 1,200 m (3,280 to 3,937 ft). 

Once oil enters the ocean, a variety of physical, chemical, and biological processes acts to 

disperse the oil slick. These processes include spreading, evaporation of the more volatile 

constituents, dissolution into the water column, emulsification of small droplets, 

agglomeration sinking, microbial modification, photochemical modification, and biological 

ingestion and excretion (NRC, 2003). Marine water quality would be temporarily affected by 

the dissolved components and small oil droplets that do not rise to the surface or are mixed 

down by surface turbulence. Dispersion by currents and microbial degradation removes the 

oil from the water column or dilutes the constituents to background levels. 

A large oil spill could result in a release of gaseous hydrocarbons that could affect water 

quality. During the Macondo spill, large volumes of methane (CH4) were released, causing 

localized oxygen depletion as methanotrophic bacteria rapidly metabolized the hydrocarbons 

(Joye et al., 2011; Kessler et al., 2011). However, a broader study of the deepwater Gulf of 

Mexico found that although some stations had slightly depressed dissolved oxygen 

concentrations relative to climatological background values, concentrations were not low 

enough to indicate hypoxia (<2.0 mg/L) (OSAT, 2010). Stations revisited around the Macondo 

wellhead in October 2010 showed no measurable oxygen depression (OSAT, 2010). 

Due to the lease area location (67 miles [108 km] from the nearest shoreline), most water 

quality impacts would occur in offshore waters. Depending on the spill trajectory and the 

effectiveness of spill response measures, coastal water quality could be affected. Based on the 

OSRA modeling predictions (Table 3), nearshore waters and embayments of Plaquemines 

Parish, Louisiana, are the most likely coastal areas where water quality could be affected. 

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 

detailed in Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on water 

quality are expected. 

C.2 Seafloor Habitats and Biota 

Water depths at the proposed well surface locations range from 1,213 to 1,269 m 

(3,978 to 4,164 ft). The seafloor is expected to consist mainly of soft bottom. The 

chemosynthetic community assessment based on the hazards report by GEMS (2007) did not 

identify any features that could support high-density deepwater benthic communities within 

610 m (2,000 ft) of the wellsites. See Supplemental EP Section 6a for further information. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 23 

According to the BOEMRE (2011), existing information for the deepwater Gulf of Mexico 

indicates that the seafloor is composed primarily of soft sediments; hard bottom communities 

are rare. MC 940, 984, and 985 are within deepwater Grid 13, and the BOEMRE website 

indicates that ROV coverage of the seafloor in this grid is adequate to characterize the area 

(BOEMRE, 2011). 

C.2.1 Soft Bottom Benthic Communities 

Data from the recent Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology 

study (Wei, 2006; Rowe and Kennicutt, 2009) can be used to describe typical benthic 

communities in the area. Table 4 summarizes data from two nearby stations in similar water 

depths. Sediments at these two stations were predominantly clay (46% to 54%) and silt 

(43% to 45%). 

Table 4. Benthic community data from stations near the lease area and in similar water 

depths sampled during the Northern Gulf of Mexico Continental Slope Habitats and 

Benthic Ecology Study (From: Wei, 2006; Rowe and Kennicutt, 2009). 

Station 

Location 

Relative to 

Lease Area 

Water Depth

(m) 

Abundance 

Meiofauna

(individuals/m2) 

Macroinfauna

(individuals/m2) 

Megafauna

(individuals/ha) 

MT-3 15 mi NNE 987 885,995 4,924 1,034 

MT-4 21 mi SE 1,401 246,058 3,262 1,548 

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

(2006). 

Meiofauna (animals passing through a 0.5-mm sieve but retained on a 0.062-mm sieve) 

densities in water depths representative of the lease area typically range from about 

250,000 to 650,000 individuals/m2 (Rowe and Kennicutt, 2009). Nematodes, nauplii, and 

harpacticoid copepods were the three dominant groups in the meiofauna, accounting for 

about 90% of total abundance. 

The benthic macroinfauna is characterized by small mean individual sizes and low densities, 

both of which are a reflection of the meager primary production in Gulf of Mexico surface 

waters (Wei, 2006). Densities decrease exponentially with water depth. Based on an equation 

presented by Wei (2006), macroinfaunal densities in the water depths of the wellsites are 

expected to be about 2,621 to 2,733 individuals/m2, lower than the values in Table 4. 

Polychaetes are typically the most abundant macroinfaunal group on the northern Gulf of 

Mexico continental slope, followed by amphipods, tanaids, bivalves, and isopods. Wei (2006) 

recognized four depth-dependent faunal zones (1 through 4), two of which are divided 

horizontally. The lease area is in Zone 2E, which consists of stations on the mid 

Texas-Louisiana Slope ranging in depth from 625 to 1,828 m (2,050 to 5,997 ft). The five most 

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

Tharyx marioni, and Paralacydonia paradoxa and the bivalve Heterodonta sp. 

Megafaunal density from nearby stations MT-3 and MT-4 was 1,034 and 1,548 individuals/ha, 

respectively (Table 4). Densities of 300 to 2,000 individuals/ha were reported from other 

stations in a similar depth range. Common megafauna included motile groups such as 
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Environmental Impact Analysis for Supplemental EP Page 24 

decapods, ophiuroids, holothurians, and demersal fishes, as well as sessile groups such as 

sponges and anemones. 

Bacteria are also an important component in terms of biomass and cycling of organic carbon 

(Cruz-Kaegi, 1998). Bacterial biomass at the depth range of the lease area typically is about 

1 to 2 grams of carbon per square meter (g C/m2

) in the top 15 cm of sediments (Rowe and 

Kennicutt, 2009). 

IPFs potentially affecting benthic communities are 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. There will be no disturbance to soft bottom communities on the seafloor 

during positioning of the DP semisubmersible Noble Danny Adkins. 

Impacts of Effluent Discharges 

Drilling muds and cuttings are the only effluents that are likely to affect benthic communities. 

During initial well interval(s) before the marine riser is set, cuttings and seawater-based “spud 

mud” will be released at the seafloor. Excess cement slurry will also be released at the 

seafloor during casing installation for the riserless portion of the drilling operations. Cement 

slurry components typically include cement mix and some of the same chemicals used in 

water-based drilling muds (Boehm et al., 2001). The main impacts will be burial and 

smothering of benthic organisms within several meters to tens of meters around the wellbore. 

Soft bottom sediments disturbed by cuttings, drilling muds, and cement slurry will eventually 

be recolonized through larval settlement and migration from adjacent areas. Because some 

deep-sea biota grow and reproduce slowly, recovery may require several years. 

Discharges of treated SBM cuttings from the rig may affect benthic communities, primarily 

within several hundred meters of the wellsites. The fate and effects of SBM cuttings have 

been reviewed by Neff et al. (2000), and monitoring studies have been conducted in the Gulf 

of Mexico by Continental Shelf Associates, Inc. (2004, 2006). In general, cuttings with adhering 

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 and concentrations 

exceed approximately 1,000 mg/kg, benthic infaunal communities may be adversely affected 

due to both the toxicity of the base fluid and organic enrichment (with resulting anoxia) 

(Neff et al., 2000). Infaunal numbers may increase and diversity may decrease as opportunistic 

species that tolerate low oxygen and high H2S predominate (Continental Shelf Associates, Inc., 

2006). As the base synthetic fluid is decomposed by microbes, the area will gradually return to 

pre-drilling conditions. Disturbed sediments will be recolonized through larval settlement and 

migration from adjacent areas. 

The areal extent of impacts from drilling discharges will be small. Assuming a typical effect 

radius of 500 m (1,640 ft), the affected area around each wellsite would represent about 3% of 

the seafloor within a lease block. For the eight surface locations in this exploration drilling 

program, the total impact area would be 628 ha (1,552 ac). Soft bottom communities are 

ubiquitous along the northern Gulf of Mexico continental slope (Gallaway, 1988; Gallaway et 

al., 2003; Rowe and Kennicutt, 2009). Impacts from drilling discharges during this project will 

have no significant impact on soft bottom benthic communities on a regional basis. This 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 25 

conclusion is in accord with the findings of the EA for Grid 13 prepared by MMS (2003), which 

concluded that development activities in this area would have minimal impacts on the 

ecological function, biological productivity, or distribution of soft bottom communities. 

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 wellsites. 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. Previous studies characterized surface sediments in the 

vicinity of the site as about 50% clay and 45% silt (Rowe and Kennicutt, 2009). 

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect 

benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical 

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the 

spill location. However, during the Macondo spill, subsurface plumes were reported at a 

water depth of about 1,100 m (3,600 ft), extending at least 22 miles (35 km) from the wellsites 

and persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently 

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). This 

observation is supported by Kujawinski et al. (2011) in their report that chemical components 

of subsea dispersants used during the Macondo spill persisted for up to two months and were 

detected up to 186 miles (300 km) from the wellsite at a water depth of 1,000 to 1,200 m 

(3,280 to 3,937 ft). However, estimated dispersant concentrations in the subsea plume were 

below levels known to be toxic to marine life. While the behavior and impacts of subsurface 

plumes are not well known, a subsurface plume could contact the seafloor and affect benthic 

communities beyond the 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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on soft 

bottom communities are expected. 

C.2.2 High-Density Deepwater Benthic Communities 

As defined by NTL 2009-G40, high-density deepwater benthic communities are features or 

areas that could support high-density chemosynthetic communities, or features or areas that 

could support high-density deepwater corals and other associated high-density hard bottom 

communities. Chemosynthetic communities were discovered in the central Gulf of Mexico in 

1984 and have been studied extensively (MacDonald, 2002). Deepwater coral communities 

are also known from numerous locations in the Gulf of Mexico (Brooke and Schroeder, 2007; 

CSA International, Inc., 2007). These communities occur almost exclusively on authigenic 

carbonates created by chemosynthetic communities, and on shipwrecks. The nearest known 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 26 

chemosynthetic community site is located approximately 7 miles (11 km) to the northnortheast in MC 853 (Brooks et al., 2009). 

The chemosynthetic community assessment included in this Supplemental EP, based on the 

shallow hazards report by GEMS (2007), did not identify any features that could support 

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

mud/cuttings discharge locations. 

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

(drilling muds and cuttings), and a large oil spill (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. Because a DP drilling rig will be used, there will be no anchoring 

impacts. 

Impacts of Effluent Discharges 

The chemosynthetic community assessment included in this Supplemental EP, based on the 

shallow hazards report by GEMS (2007), did not identify any features that could support 

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

mud/cuttings discharge locations. Monitoring programs on the Gulf of Mexico continental 

slope have shown that benthic impacts from drilling discharges typically are concentrated 

within about 500 m (1,640 ft) of the wellsites, although detectable deposits may extend 

beyond this distance (Continental Shelf Associates, Inc., 2004, 2006; Neff et al., 2005). If 

high-density deepwater communities are associated with the more distant expulsion features 

and mud volcanoes identified in the hazards survey, significant impacts on these communities 

will be avoided because of the distance from the discharge location. 

Impacts of a Large Oil Spill (WCD) 

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect 

benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical 

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the 

spill location. However, during the Macondo spill, subsurface plumes were reported at a 

water depth of about 1,100 m (3,600 ft), extending at least 22 miles (35 km) from the wellsites 

and persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently 

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). This 

observation is supported by Kujawinski et al. (2011) in their report that chemical components 

of subsea dispersants used during the Macondo spill persisted for up to two months and were 

detectable up to 186 miles (300 km) from the wellsite at a water depth of 1,000 to 1,200 m 

(3,280 to 3,937 ft). However, estimated dispersant concentrations in the subsea plume were 

below levels known to be toxic to marine life. While the behavior and impacts of subsurface 

plumes are not well known, a subsurface plume could have the potential to contact 

high-density deepwater benthic communities beyond the 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 compared to the potential rates of oil release 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 27 

from a blowout. In addition, seep organisms require unrestricted access to oxygenated water 

at the same time as exposure to hydrocarbon energy sources (MacDonald, 2002). Oil droplets 

or oiled sediment particles could come into contact with chemosynthetic organisms or 

deepwater corals. As discussed by MMS (2007b), impacts could include loss of habitat, 

biodiversity, and live coral coverage; destruction of hard substrate; change in sediment 

characteristics; and reduction or loss of one or more commercial and recreational fishery 

habitats. Sublethal effects could be long-lasting and affect the resilience of coral colonies to 

natural disturbances (e.g., elevated water temperature and diseases). 

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

recent (October 2010) survey of deepwater coral habitats near the Macondo spill site 

(BOEMRE, 2010). Government and academic researchers were working at a site 1,400 m 

(4,600 ft) deep and approximately 7 miles (11 km) southwest of the Macondo wellhead when 

they observed dead and dying corals with sloughing tissue and discoloration. The study 

location was about 61 miles (99 km) from the lease area. Much of the soft coral observed in 

an area measuring about 15 to 40 m (50 to 130 ft) was covered by what appeared to be a 

brown substance. Ninety percent of 40 large corals were heavily affected and showed dead 

and dying parts and discoloration. Another site 400 m (1,312 ft) away had a colony of stony 

corals similarly affected and partially covered with a similar brown substance. Until laboratory 

analyses are conducted, scientists cannot be certain what caused the impacts. Sediment and 

coral samples were collected with an ROV and brought to the surface for analyses. Further 

testing will also determine if the substance is oil, and if so, whether it is consistent with the 

release from the Macondo spill. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on 

deepwater benthic communities are expected. 

C.2.3 Designated Topographic Features 

The blocks are not within or near a designated topographic feature or a no-activity zone as 

identified in NTL 2009-G39. The nearest topographic feature is Sackett Bank, located 45 miles 

(73 km) northwest of the lease area. 

There are no IPFs associated with either routine operations or accidents that could cause 

impacts to designated topographic features due to the distance from the lease area. A small 

fuel spill would float and dissipate on the surface and would not reach these seafloor features. 

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

features. If a subsurface plume were to occur, impacts on these features would be unlikely 

due to the distance and the difference in water depth. Near-bottom currents in the region are 

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume 

up onto the continental shelf edge. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 28 

C.2.4 Pinnacle Trend Area Live Bottoms 

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

NTL 2009-G39, the nearest pinnacle trend blocks are about 92 miles (149 km) from the lease 

area, along the shelf edge south of Alabama. 

There are no IPFs associated with either routine operations or accidents that could cause 

impacts to pinnacle trend area live bottoms due to the distance from the lease area. A small 

fuel spill would float on the surface and would not reach these seafloor features. 

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

features. If a subsurface plume were to occur, impacts on these features would be unlikely 

due to the distance and the difference in water depth. Near-bottom currents in the region are 

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume 

up onto the continental shelf edge. 

C.2.5 Eastern Gulf Live Bottoms 

The lease area is not covered by the Live Bottom (Low-Relief) Stipulation, which applies to 

Eastern Gulf of Mexico Planning Area leases in water depths of 100 m (328 ft) or less. The 

nearest blocks covered by the live bottom stipulation, as defined by NTL 2009-G39, are about 

125 miles (202 km) from the project area. 

There are no IPFs associated with either routine operations or accidents that could cause 

impacts to eastern Gulf live bottom areas due to the distance from the lease area. A small fuel 

spill would float and dissipate on the surface and would not reach these seafloor features. 

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

features. If a subsurface plume were to occur, impacts on these features would be unlikely 

due to the distance and the difference in water depth. Near-bottom currents in the region are 

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume 

up onto the continental shelf. 

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

This section discusses species listed as endangered or threatened under the ESA. In addition, it 

includes all marine mammal species in the region, which are protected under the MMPA. 

Endangered or threatened species that may occur in the project area and/or along the 

northern Gulf coast are listed in Table 5. The table also indicates the location of critical habitat 

(if designated in the Gulf of Mexico). Critical habitat is defined as (1) specific areas within the 

geographical area occupied by the species at the time of listing, if they contain physical or 

biological features essential to conservation, and those features may require special 

management considerations or protection; and (2) specific areas outside the geographical area 

occupied by the species if the agency determines that the area itself is essential for 

conservation. The NMFS has jurisdiction over ESA-listed cetaceans, sea turtles, and fishes in 

the Gulf of Mexico. The USFWS has jurisdiction over ESA-listed birds and the Florida manatee. 

The sperm whale and five species of sea turtles are the only endangered or threatened species 

likely to occur at or near the lease area. No critical habitat has been designated for these 

species in the Gulf of Mexico. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 29 

Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic 

right whale, and sei whale) also have been reported from the Gulf of Mexico but are 

considered rare or extralimital there (Würsig et al., 2000). No critical habitat has been 

designated for these species in the Gulf of Mexico.

Coastal endangered or threatened species include the Florida manatee, Piping Plover, 

Whooping Crane, Gulf sturgeon, and four subspecies of beach mouse. Critical habitat has 

been designated for all of these species as indicated in Table 5 and discussed in individual 

sections. 

Table 5. Federally-listed endangered and threatened species in the lease area and along the 

northern Gulf coast. 

Species Scientific Name Status 

Potential Presence Critical Habitat 

Designated in 

Gulf of Mexico 

Lease 

Area Coastal 

Marine Mammals

Sperm whale Physeter macrocephalus E X -- None

Florida manatee Trichechus manatus latirostris E -- X Florida 

(Peninsular)

Blue whale Balaenoptera musculus E X

a

-- None

Fin whale Balaenoptera physalus E X

a

-- None

Humpback whale Megaptera novaeangliae E X

a

-- None

North Atlantic right whale Eubalaena glacialis E X

a

-- None

Sei whale Balaenoptera borealis E X

a

-- None

Sea Turtles

Loggerhead turtle Caretta caretta T X X None

Green turtle Chelonia mydas T, EbX X None

Leatherback turtle Dermochelys coriacea E X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Birds

Piping Plover Charadrius melodus T -- X 

Coastal Texas, Louisiana, 

Mississippi, Alabama, 

and Florida (Panhandle)

Whooping Crane Grus americana E -- X 

Coastal Texas 

(Aransas National 

Wildlife Refuge)

Fishes

Gulf sturgeon Acipenser oxyrinchus desotoi T -- X 

Coastal Louisiana, 

Mississippi, Alabama, 

and Florida (Panhandle)

Terrestrial Mammals

Beach mouse (Alabama, 

Choctawhatchee, Perdido 

Key, St. Andrew)

Peromyscus polionotus E -- X Alabama and Florida 

(Panhandle) beaches 

Abbreviations: E = Endangered; T = Threatened. 

a

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

unlikely to be present in the lease area. 

b

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

Two other coastal species (Bald Eagle and Brown Pelican) discussed by MMS (2007b) are no 

longer listed as endangered or threatened; these are discussed under Coastal and Marine 

Birds. 

There are no other endangered animals or plants in the Gulf of Mexico that are reasonably 

likely to be affected by either routine or accidental events. Other species occurring at certain 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 30 

locations in the Gulf of Mexico such as the smalltooth sawfish (Pristis pectinata), elkhorn coral 

(Acropora palmata), staghorn coral (Acropora cervicornis), and Florida salt marsh vole 

(Microtus pennsylvanicus dukecampbelli) are remote from the lease area and highly unlikely to 

be affected. 

C.3.1 Sperm Whale (Endangered) 

The only endangered marine mammal likely to be present at or near the project area is the 

sperm whale (Physeter macrocephalus). Resident populations of sperm whales occur within 

the Gulf of Mexico. A species description is presented in a recent lease sale EIS (MMS, 2007b). 

Gulf of Mexico sperm whales are classified as an endangered species and a “strategic stock” 

(defined as a stock that may have unsustainable human-caused impacts) by NMFS (Waring 

et al., 2009). No critical habitat for the sperm whale has been designated in the Gulf of 

Mexico. 

The distribution of sperm whales in the Gulf of Mexico is correlated with mesoscale physical 

features such as eddies associated with the Gulf of Mexico Loop Current (Jochens et al., 2008). 

Sperm whale populations in the north-central Gulf of Mexico are present there throughout the 

year (Davis et al., 2000). Results of a multi-year tracking study show female sperm whales 

typically concentrated along the upper continental slope between the 200- and 1,000-m 

(656- and 3,280-ft) depth contours (Jochens et al., 2008). Male sperm whales were more 

variable in their movements and were documented in water depths greater than 3,000 m 

(9,843 ft). Generally, groups of sperm whales sighted in the Gulf of Mexico during the 

MMS-funded Sperm Whale Seismic Study (SWSS) consisted of mixed-sex groups comprising 

adult females and immatures, and groups of bachelor males. Typical group size for mixed 

groups was 10 individuals (Jochens et al., 2008). SWSS results show that sperm whales transit 

through the vicinity of the lease area. Movements of satellite-tracked individuals suggest that 

this area of the Gulf continental slope is within the home range of the Gulf of Mexico 

population (within the 95% utilization distribution) (Jochens et al., 2008). 

IPFs potentially affecting sperm whales include drilling rig presence, noise, and lights; support 

vessel and helicopter traffic; and two types of accidents – a small fuel spill and a large oil spill 

(WCD). Effluent discharges are likely to have negligible impacts on sperm whales due to rapid 

dispersion, the small area of ocean affected, the intermittent nature of the discharges, and the 

mobility of these marine mammals. Compliance with NTL 2007-G03 will minimize the 

potential for marine debris-related impacts on sperm whales. 

Impacts of Drilling Rig Presence, Noise, and Lights 

Noise from routine drilling activities has the potential to disturb sperm whales. Sperm whales 

appear to have good low-frequency hearing, but the available data do not indicate a consistent 

response to anthropogenic noise (Jochens et al., 2008). Noise associated with drilling is 

relatively weak in intensity, and an individual animal’s noise exposure would be transient. 

There are other OCS facilities and activities near the lease area, and the region as a whole has 

a large number of similar sources. Due to the limited scope, timing, and geographic location of 

drilling activities, this project would represent a small temporary contribution to the overall 

noise regime. 

The NMFS (2007) analyzed the potential for impacts of drilling-related noise on sperm whales 

in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 31 

Western Planning Areas of the Gulf of Mexico. The analysis noted that drilling rigs show low 

sound source levels and concluded that drilling is not expected to produce amplitudes 

sufficient to cause hearing or behavioral effects in sperm whales; therefore, these effects are 

insignificant (NMFS, 2007). 

Although drilling rig lighting and rig presence were considered potential factors affecting 

sperm whales, NMFS’s 2007 Biological Opinion and recent lease sale EISs (MMS, 2007b, 2008) 

did not identify rig lighting and presence as IPFs for sperm whales. 

Impacts of Support Vessel and Helicopter Traffic 

Support vessel traffic has the potential to disturb sperm whales, and there is also a risk of 

vessel strikes, which are identified as a threat in the recovery plan for this species 

(NMFS, 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 BOEMRE has issued 

NTL 2007-G04, which recommends protected species identification training and that vessel 

operators and crews maintain a vigilant watch for marine mammals and slow down or stop 

their vessel to avoid striking protected species, and requires operators to report sightings of 

any injured or dead protected species. When whales are sighted, vessel operators and crews 

are required to attempt to maintain a distance of 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 (295 ft) from sperm whales, the NMFS concluded that the 

potential for harassment of sperm whales would be reduced to discountable levels. 

Helicopter traffic also has the potential to disturb sperm whales. Smultea et al. (2008) 

documented responses of sperm whales offshore Hawaii to fixed wing aircraft flying at an 

altitude of 245 m (800 ft). A reaction to the initial pass of the aircraft was observed during 

three (12%) of 24 sightings. All three reactions consisted of a hasty dive and occurred at less 

than 360 m (1,180 ft) lateral distance from the aircraft. Additional reactions were seen when 

aircraft circled certain whales to make further observations. Based on other studies of 

cetacean responses to sound, the authors concluded that the observed reactions to brief 

overflights by the aircraft were short-term and probably of no long-term biological 

significance. 

While flying offshore in the Gulf of Mexico, helicopters maintain altitudes above 213 m (700 ft) 

during transit to and from the working area. In the event that a whale is seen during transit, 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 32 

the helicopter will not approach or circle the animals. Although responses are possible based 

on the Smultea et al. (2008) study, the NMFS (2007) concluded that this altitude would 

minimize the potential for disturbing sperm whales. Therefore, no significant impacts are 

expected. 

Impacts of a Small Fuel Spill 

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

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

Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. Oil 

impacts on marine mammals are discussed by Geraci and St. Aubin (1990). For this 

Supplemental EP there are no unique site-specific issues with respect to spill impacts on these 

animals. 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts on sperm whales. Supplemental EP 

Sections 2j and 9b provide detail on spill response measures. Given the open ocean location 

of the lease area, the duration of a small spill and opportunity for impacts to occur would be 

very brief. 

A small fuel spill in offshore waters would produce a slick on the water surface and increase 

the concentrations of petroleum hydrocarbons and their degradation products. The extent 

and persistence of impacts would depend on the meteorological and oceanographic conditions 

at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed 

naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from 

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities 

and noise of response vessels and aircraft (Marine Mammal Commission [MMC], 2010). 

However, due to the limited areal extent and short duration of water quality impacts from a 

small fuel spill, as well as the mobility of sperm whales, no significant impacts would be 

expected. 

Impacts of a Large Oil Spill (WCD) 

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

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

Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. Oil 

impacts on marine mammals are discussed by Geraci and St. Aubin (1990). For this 

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

animals. 

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

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

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

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 33 

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

from the activities and noise of response vessels and aircraft. Complications of the above may 

lead to dysfunction of immune and reproductive systems, physiological stress, declining 

physical condition, and death. Behavioral responses can include displacement of animals from 

prime habitat, disruption of social structure, changing prey availability and foraging 

distribution and/or patterns, changing reproductive behavior/productivity, and changing 

movement patterns or migration (MMC, 2010). 

Studies have shown that the cetacean epidermis functions as an effective barrier to noxious 

substances found in petroleum (Geraci and St. Aubin, 1985). Unlike other mammals, 

penetration of such substances in cetacean skin is impeded by tight intercellular bridges, the 

vitality of the superficial cells, the thickness of the epidermis, and the lack of sweat glands and 

hair follicles. In addition, cetacean skin is free from hair or fur, which in other marine 

mammals not found in the Gulf of Mexico (e.g., pinnipeds and otters) tends to collect oil 

and/or tar. 

In the event of a large spill, the level of vessel and aircraft activity associated with spill 

response could disturb sperm whales and potentially result in vessel strikes, entanglement, or 

other injury or stress. Response vessels would operate in accordance with NTL 2007-G04 to 

reduce the potential for striking or disturbing these animals. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on sperm 

whales are expected. 

C.3.2 Florida Manatee (Endangered) 

Most of the manatee population is located in peninsular Florida (USFWS, 2001). Manatees 

regularly migrate farther west of Florida in the warmer months (Wilson, 2003) into Alabama 

and Louisiana coastal environs, with some individuals traveling as far as west Texas (Fertl et al., 

2005). A species description is presented in a recent lease sale EIS (MMS, 2007b) and in the 

recovery plan for this species (USFWS, 2001). 

IPFs potentially affecting manatees include support vessel and helicopter traffic and a large oil 

spill (WCD). A small fuel spill in the lease area would be unlikely to affect manatees, as the 

lease area is approximately 67 miles (108 km) from the nearest shoreline (Louisiana). As 

explained in Section A.9.2, a small fuel spill would not be expected to make landfall or reach 

coastal waters prior to breaking up. Compliance with NTL 2007-G03 will minimize the 

potential for marine debris-related impacts on manatees. 

Impacts of Support Vessel and Helicopter Traffic 

Support vessel traffic has the potential to disturb manatees, and there is also a risk of vessel 

strikes, which are identified as a threat in the recovery plan for this species (USFWS, 2001). To 

reduce the potential for vessel strikes, the BOEMRE has issued NTL 2007-G04, which 

recommends protected species identification training and that vessel operators and crews 

maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 34 

striking protected species, and requires operators to report sightings of any injured or dead 

protected species. Compliance with this NTL will minimize the likelihood of vessel strikes, and 

no significant impacts on manatees are expected. 

Helicopter traffic, if present, also has the potential to disturb manatees. Rathbun (1988) 

reported that manatees were disturbed more by helicopters than by fixed-wing aircraft; 

however, the helicopter was flown at a relatively low altitude of 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 Texas, Louisiana, and Florida 

shorelines could be contacted by a spill within 30 days. There is no critical habitat designated 

in these areas, and the number of manatees potentially present is a small fraction of the 

population in peninsular Florida. 

In the event that manatees were exposed to oil, effects could include direct impacts from oil 

exposure, as well as indirect impacts due to response activities and materials (e.g., vessel 

traffic, noise, and dispersants) (MMC, 2010). Direct physical and physiological effects can 

include skin irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous 

membranes; inhalation of toxic fumes; ingestion of oil (and dispersants) directly or via 

contaminated prey (or contaminated vegetation, in the case of manatees); and stress from the 

activities and noise of response vessels and aircraft. Complications of the above may lead to 

dysfunction of immune and reproductive systems, physiological stress, declining physical 

condition, and death. Behavioral responses can include displacement of animals from prime 

habitat, disruption of social structure, changing prey availability and foraging distribution 

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

patterns or migration (MMC, 2010). 

In the event that a large spill reached coastal waters where manatees were present, the level 

of vessel and aircraft activity associated with spill response could disturb manatees and 

potentially result in vessel strikes, entanglement, or other injury or stress. Response vessels 

would operate in accordance with NTL 2007-G04 to reduce the potential for striking or 

disturbing these animals, and therefore no significant impacts are expected. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on manatees 

are expected. 

C.3.3 Endangered Mysticete Whales 

Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic 

right whale, and sei whale) also have been reported from the Gulf of Mexico but are 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 35 

considered rare or extralimital there (Würsig et al., 2000). No critical habitat has been 

designated for these species in the Gulf of Mexico. 

Due to the rare occurrence of these whales in the Gulf of Mexico and the limited scope and 

duration of the project, it is highly unlikely that any endangered mysticete would come into 

contact with any project activities, either routine operations or accidents. The NMFS (2007) 

did not include any of these mysticete whales as affected species in its Biological Opinion for 

the Five-Year Oil and Gas Leasing Program in the Central and Western Planning Areas of the 

Gulf of Mexico. Potential impacts are analyzed in recent lease sale EISs (MMS, 2007b, 2008), 

and those analyses are incorporated by reference. If any of these whales were present in the 

area, potential impacts would be the same as those discussed below in Section C.3.4. 

C.3.4 Non-Endangered Marine Mammals (Protected) 

In addition to the seven endangered species that have been cited previously, 22 other species 

of marine mammals occur in the Gulf of Mexico, including two mysticete whales, the dwarf 

and pygmy sperm whales, 4 species of beaked whales, and 14 species of delphinids 

(see Supplemental EP Section 6h). All marine mammals are protected species under the 

MMPA. The most common non-endangered cetaceans in the deepwater environment are 

odontocetes such as the pantropical spotted dolphin, spinner dolphin, and clymene dolphin. 

A brief summary is presented below, and additional information on these groups is presented 

in a recent lease sale EIS (MMS, 2007b). 

Mysticete whales. Two non-endangered mysticete whales are known from the Gulf of Mexico. 

The Bryde’s whale (Balaenoptera edeni) has been sighted most frequently along the 100-m 

(328-ft) isobath (Davis and Fargion, 1996; Davis et al., 2000). Most sightings have been made 

in the DeSoto Canyon region and off western Florida, although there have been some in the 

west-central portion of the northeastern Gulf. The minke whale (Balaenoptera acutorostrata) 

is considered rare in the Gulf of Mexico, with the only confirmed records coming from 

strandings (Würsig et al., 2000). Based on the available data, it is possible that Bryde’s whales 

could occur in the lease area. 

Dwarf and pygmy sperm whales. At sea, it is difficult to differentiate dwarf sperm whales 

(Kogia sima) from pygmy sperm whales (Kogia breviceps), and sightings are often grouped 

together as “Kogia spp.” Both species have a worldwide distribution in temperate to tropical 

waters. In the Gulf of Mexico, both species occur primarily along the continental shelf edge 

and in deeper waters off the continental shelf (Mullin et al., 1991; Mullin, 2007). Either 

species could occur in the lease area. 

Beaked whales. Four species of beaked whales are known from the Gulf of Mexico. They are 

Blainville’s beaked whale (Mesoplodon densirostris), Cuvier’s beaked whale (Ziphius 

cavirostris), Sowerby’s beaked whale (Mesoplodon bidens), and Gervais’ beaked whale 

(Mesoplodon europaeus). Stranding records in the Gulf of Mexico suggest that Gervais’ 

beaked whale is the most common and Sowerby’s beaked whale is extralimital. Due to the 

difficulties of at-sea identification, beaked whales in the Gulf of Mexico are identified either as 

Cuvier’s beaked whales or are grouped into an undifferentiated complex (Mesoplodon spp. 

and Ziphius spp.). In the northern Gulf of Mexico, they are broadly distributed in waters 

greater than 1,000 m (3,281 ft) over lower slope and abyssal landscapes (Davis et al., 2000). 

Any of these species could occur in the lease area.
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Delphinids. Fourteen species of delphinids are known from the Gulf of Mexico, including 

Atlantic spotted dolphin (Stenella frontalis), bottlenose dolphin (Tursiops truncatus), clymene 

dolphin (Stenella clymene), false killer whale (Pseudorca crassidens), Fraser’s dolphin 

(Lagenodelphis hosei), killer whale (Orcinus orca), melon-headed whale (Peponocephala 

electra), pantropical spotted dolphin (Stenella attenuata), pygmy killer whale (Feresa 

attenuata), short-finned pilot whale (Globicephala macrorhynchus), Risso’s dolphin (Grampus 

griseus), rough-toothed dolphin (Steno bredanensis), spinner dolphin (Stenella longirostris), 

and striped dolphin (Stenella coeruleoalba). The most common non-endangered cetaceans in 

the deepwater environment are the pantropical spotted dolphin, spinner dolphin, and 

clymene dolphin. However, any of these species could occur in the lease area. 

IPFs potentially affecting non-endangered marine mammals include drilling rig presence, noise, 

and lights; support vessel and helicopter traffic; and two types of accidents (a small fuel spill 

and a large oil spill represented by the WCD for this Supplemental 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. Compliance with NTL 2007-G03 will minimize the potential for marine 

debris-related impacts on marine mammals. 

Impacts of Drilling Rig Presence, Noise, and Lights 

Noise from routine drilling activities has the potential to disturb marine mammals. Most 

odontocetes (toothed whales and dolphins) use sounds that are higher than the low-frequency 

dominant frequencies produced by OCS drilling activities (Richardson et al., 1995). Noise 

associated with drilling is relatively weak in intensity, and an individual animal’s noise 

exposure would be transient. There are other OCS facilities and activities near the lease area, 

and the region as a whole has a large number of similar sources. Due to the limited scope, 

timing, and geographic extent of drilling activities, this project would represent a small 

temporary contribution to the overall noise regime, and any short-term impacts are not 

expected to be biologically significant to marine mammal populations. 

Drilling rig lighting and rig presence are not identified as IPFs for marine mammals in recent 

lease sale EISs (MMS, 2007b, 2008). 

Impacts of Support Vessel and Helicopter Traffic 

Support vessel traffic has the potential to disturb marine mammals, and there is also a risk of 

vessel strikes. Data concerning the frequency of vessel strikes is presented in the lease sale EIS 

(MMS, 2007b). To reduce the potential for vessel strikes, the BOEMRE has issued 

NTL 2007-G04, which recommends protected species identification training and that vessel 

operators and crews maintain a vigilant watch for marine mammals and slow down or stop 

their vessel to avoid striking protected species, and requires operators to report sightings of 

any injured or dead protected species. Vessel operators and crews are required to attempt to 

maintain a distance of 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 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 37 

this NTL will minimize the likelihood of vessel strikes as well as reduce the chance for 

disturbing marine mammals, and therefore no significant impacts are expected. 

Aircraft traffic also has the potential to disturb marine mammals (Würsig et al., 1998). 

However, while flying offshore, helicopters maintain altitudes above 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 Supplemental EP, there are no unique site-specific issues with respect to spill impacts 

on these animals. 

The probability of a fuel spill will be minimized by Shell’s preventative measures during fuel 

transfer. In the unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate 

and reduce the potential for impacts on marine mammals. Supplemental EP Sections 2j 

and 9b provide detail on spill response measures. Given the open ocean location of the lease 

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

A small fuel spill in offshore waters would produce a slick on the water surface and increase 

the concentrations of petroleum hydrocarbons and their degradation products. The extent 

and persistence of impacts would depend on the meteorological and oceanographic conditions 

at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed 

naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from 

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities 

and noise of response vessels and aircraft (MMC, 2010). However, due to the limited areal 

extent and short duration of water quality impacts from a small fuel spill, as well as the 

mobility of marine mammals, no significant impacts would be expected. 

Impacts of a Large Oil Spill (WCD) 

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008) 

and by Geraci and St. Aubin (1990). For this Supplemental EP, there are no unique site-specific 

issues. 

Impacts of oil spills on marine mammals can include direct impacts from oil exposure, as well 

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

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

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

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

(or contaminated vegetation, in the case of manatees); and stress from the activities and noise 

of response vessels and aircraft. Complications of the above may lead to dysfunction of 

immune and reproductive systems, physiological stress, declining physical condition, and 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 38 

death. Behavioral responses can include displacement of animals from prime habitat, 

disruption of social structure, changing prey availability and foraging distribution and/or 

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

migration (MMC, 2010). 

In the event of a large spill, the level of vessel and aircraft activity associated with spill 

response could disturb marine mammals and potentially result in vessel strikes, entanglement, 

or other injury or stress. Response vessels would operate in accordance with NTL 2007-G04 to 

reduce the potential for striking or disturbing these animals, and therefore no significant 

impacts are expected. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide 

detail on spill response measures. Therefore, no significant spill impacts on marine mammals 

are expected. 

C.3.5 Sea Turtles (Endangered/Threatened) 

As listed in Supplemental EP Section 6h, five species of endangered or threatened sea turtles 

may be found near the lease area. Endangered species are the leatherback (Dermochelys 

coriacea), Kemp's ridley (Lepidochelys kempii), and hawksbill (Eretmochelys imbricata) turtles. 

The loggerhead turtle (Caretta caretta) is a threatened species. The green turtle (Chelonia 

mydas) is listed as threatened, except for the Florida breeding population, which is listed as 

endangered. Species descriptions are presented in a recent lease sale EIS (MMS, 2007b). 

Leatherbacks and loggerheads are the most likely species to be present near the lease area as 

adults. Green, hawksbill, and Kemp’s ridley turtles are typically inner shelf and nearshore 

species, unlikely to occur near the lease area as adults. Hatchlings or juveniles of any of the 

sea turtles may be present in deepwater areas, including the lease area, where they may be 

associated with Sargassum and other flotsam. 

All five sea turtle species in the Gulf of Mexico are migratory and use different marine habitats 

according to their life stage. These habitats include high-energy beaches for nesting females 

and emerging hatchlings and pelagic convergence zones for hatchling and juvenile turtles. As 

adults, green, hawksbill , and loggerhead turtles forage primarily in shallow, benthic habitats. 

Leatherbacks are the most pelagic of the sea turtles, feeding primarily on jellyfish. 

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

• Loggerhead turtles – Loggerheads nest in significant numbers along the Florida Panhandle 

and, to a lesser extent, from Texas through Alabama (MMS, 2007b). The nearest 

significant nesting area of loggerhead turtles is found in Louisiana, on beaches within the 

Breton NWR; 

• Green and leatherback turtles – Green and leatherback turtles infrequently nest on Florida 

Panhandle beaches (Florida Fish and Wildlife Conservation Commission, 2010); 

• Kemp’s ridley turtles – The main Kemp’s ridley nesting site is Rancho Nuevo beach, 

Tamaulipas, Mexico (NMFS et al., 2010). Approximately 200 Kemp’s ridley turtles nested 

on Texas beaches in 2009 (Sea Turtle Restoration Project, 2011). Kemp’s ridley turtles 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 39 

typically do not nest anywhere near the project area, although there have been occasional 

reports of Kemp’s ridleys nesting in Alabama (Share the Beach, 2010); and 

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

IPFs potentially affecting sea turtles include drilling rig presence, noise, and lights; support 

vessel and helicopter traffic; and two types of accidents (a small fuel spill and a large oil spill 

represented by the WCD for this Supplemental 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. Compliance with NTL 2007-G03 will minimize the 

potential for marine debris-related impacts on sea turtles. 

Impacts of Drilling Rig Presence, Noise, and Lights 

Offshore drilling activities produce a broad array of sounds at frequencies and intensities that 

may be detected by sea turtles (Geraci and St. Aubin, 1987). Potential impacts may include 

behavioral disruption and temporary or permanent displacement from the area near the 

sound source. Certain sea turtles, especially loggerheads, may be attracted to offshore 

structures (Lohoefener et al., 1990) and, thus, may be more susceptible to impacts from 

sounds produced during routine operations. Helicopters and service vessels may also affect 

sea turtles due to machinery noise and/or visual disturbances. The most likely impacts would 

be short-term behavioral changes such as diving and evasive swimming, disruption of 

activities, or departure from the area. Due to the limited scope, timing, and geographic extent 

of drilling activities, these short-term impacts are not expected to be biologically significant to 

sea turtle populations. 

Artificial lighting can disrupt the nocturnal orientation of sea turtle hatchlings (Witherington, 

1997; Tuxbury and Salmon, 2005). However, hatchlings may rely less on light cues when they 

are offshore than when they are emerging on the beach (Salmon and Wyneken, 1990). The 

NMFS (2007) concluded that the effects of lighting from offshore structures on sea turtles are 

insignificant. 

Support Vessel and Helicopter Traffic 

Support vessel traffic has the potential to disturb sea turtles, and there is also a risk of vessel 

strikes. Data show that vessel traffic is one cause of sea turtle mortality in the Gulf of Mexico 

(Lutcavage et al., 1997). While adult sea turtles are visible at the surface during the day and in 

clear weather, they can be difficult to spot from a moving vessel when resting below the water 

surface, during nighttime, or during periods of inclement weather. To reduce the potential for 

vessel strikes, the BOEMRE has issued NTL 2007-G04, which recommends protected species 

identification training and that vessel operators and crews maintain a vigilant watch for sea 

turtles and slow down or stop their vessel to avoid striking protected species, and requires 

operators to report sightings of any injured or dead protected species. When sea turtles are 

sighted, vessel operators and crews are required to attempt to maintain a distance of 45 m 

(150 ft) or greater whenever possible. Compliance with this NTL will minimize the likelihood of 

vessel strikes as well as reduce the chance for disturbing sea turtles (NMFS, 2007). 

Helicopter traffic also has the potential to disturb sea turtles. However, while flying offshore, 

helicopters maintain altitudes above 213 m (700 ft) during transit to and from the working 

area. This altitude will minimize the potential for disturbing sea turtles, and no significant 

impacts are expected. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 40 

Impacts of a Small Fuel Spill 

Potential spill impacts on sea turtles are discussed in recent EISs (MMS, 2007b, 2008) and by 

the NMFS (2007) in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the 

Central and Western Planning Areas of the Gulf of Mexico. For this Supplemental EP, there are 

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

The probability of a fuel spill will be minimized by Shell’s preventative measures during fuel 

transfer. In the unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate 

and reduce the potential for impacts on sea turtles. Supplemental EP Sections 2j and 9b

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 67 miles (108 km) from the nearest shoreline (Louisiana). As explained in 

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

prior to breaking up. 

Impacts of a Large Oil Spill (WCD) 

Impacts of oil spills on sea turtles can include direct impacts from oil exposure, as well as 

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

dispersants). Direct physical and physiological effects can include skin irritation, inflammation, 

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

and smoke (e.g., from in-situ burning of oil); ingestion of oil (and dispersants) directly or via 

contaminated food; and stress from the activities and noise of response vessels and aircraft. 

Complications of the above may lead to dysfunction of immune and reproductive systems, 

physiological stress, declining physical condition, and death. Behavioral responses can include 

displacement of animals from prime habitat, disruption of social structure, changing food 

availability and foraging distribution and/or patterns, changing reproductive 

behavior/productivity, and changing movement patterns or migration (MMC, 2010). In the 

unlikely event of a spill, implementation of Shell’s OSRP is expected to mitigate and reduce the 

potential for these types of impacts on sea turtles. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. 

Studies of oil effects on loggerheads in a controlled setting (Lutcavage et al., 1995) suggest 

that sea turtles show no avoidance behavior when they encounter an oil slick, and any sea 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 41 

turtle in an affected area would be expected to be exposed. Sea turtles’ diving behaviors also 

put them at risk. Sea turtles rapidly inhale a large volume of air before diving and continually 

resurface over time, which may result in repeated exposure to volatile vapors and oiling 

(NMFS, 2007). 

The OSRA results summarized in Table 3 predict that some shorelines that support sea turtle 

nesting could be contacted within 10 to 30 days. The nearest nesting area of loggerhead 

turtles is found in St. Bernard Parish, Louisiana, on beaches within the Breton NWR. This area 

has a contact probability of 1% after 30 days. The modeling also predicts a 1% probability of 

contacting Florida Panhandle shorelines that support significant loggerhead sea turtle nesting. 

Spilled oil reaching sea turtle nesting beaches could have effects on nesting sea turtles and egg 

development (NMFS, 2007). An oiled beach could affect nest site selection or result in no 

nesting at all (e.g., false crawls). Upon hatching and successfully reaching the water, 

hatchlings are subject to the same types of oil spill exposure hazards as adults. Hatchlings that 

contact oil residues while crossing a beach can exhibit a range of effects, from acute toxicity to 

impaired movement and normal bodily functions (NMFS, 2007). 

Data from the recent Macondo spill provides additional information about potential impacts of 

a large oil spill on sea turtles to supplement the analysis presented in the lease sale EIS 

(MMS, 2007b). According to NMFS (2010a), approximately 600 dead turtles have been 

reported since the Macondo spill. Species include Kemp’s ridley turtles (481 individuals), 

loggerhead turtles (67 individuals), and green turtles (29 individuals). Oiled turtles include 

18 dead individuals and 456 live, oiled animals that were either captured or stranded. Also, 

278 turtle nests were translocated (271 loggerhead, 4 Kemp’s ridley, and 3 green turtles) and 

more than 14,000 hatchlings were released. The strandings and captures ranged from the 

Louisiana/Texas border to Cape San Blas in the Florida Panhandle. 

In the event of a large spill, the level of vessel and aircraft activity associated with spill 

response could disturb sea turtles and potentially result in vessel strikes, entanglement, or 

other injury or stress. Response vessels would operate in accordance with NTL 2007-G04 to 

reduce the potential for striking or disturbing these animals, and therefore no significant 

impacts are expected. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on sea turtles 

are expected. 

C.3.6 Piping Plover (Threatened) 

The Piping Plover (Charadrius melodus) is a migratory shorebird that overwinters along the 

southeastern U.S. and Gulf of Mexico coasts. This threatened species is in decline as a result of 

hunting, habitat loss and modification, predation, and disease (USFWS, 2003). Critical 

overwintering habitat has been designated, including beaches in Texas, Louisiana, Mississippi, 

Alabama, and Florida (Figure 3). Piping Plovers inhabit coastal sandy beaches and mudflats, 

feeding by probing for invertebrates at or just below the surface. They use beaches adjacent 

to foraging areas for roosting and preening (USFWS, 2010a). A species description is 

presented in a recent lease sale EIS (MMS, 2007b). 
Mississippi Canyon Blocks 940, 984, and 985 

Environmental Impact Analysis for Supplemental EP 

Figure 3. Location of selected environmental features in relation to the lease area. Shown are Essential Fish 

coral reefs; Habitat Areas of Particular Concern (HAPC) for northwestern Gulf of Mexico reefs and bbluefin tuna; critical habitat for beach mice, Gulf sturgeon, Piping Plover, and Whooping Crane; and 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 43 

A large oil spill (WCD) is the only IPF potentially affecting Piping Plovers. There are no IPFs 

associated with routine project activities that could affect these birds. A small fuel spill in the 

lease area would be unlikely to affect Piping Plovers because a small fuel spill would not be 

expected to make landfall or reach coastal waters prior to breaking up (see explanation in 

Section A.9.2). 

Impacts of a Large Oil Spill (WCD) 

The lease area is 69 miles (112 km) from the nearest shoreline inhabited by Piping Plovers. 

The OSRA results summarized in Table 3 predict that Texas, Louisiana, and Florida shorelines 

designated as critical habitat for the wintering Piping Plover could be contacted by a spill 

within 30 days. Plaquemines Parish, which has the highest probability of contact for the 

10-day and 30-day intervals, includes Piping Plover critical habitat. 

Plovers could become externally oiled while foraging on oiled shores or be exposed internally 

through ingestion of oiled intertidal sediments and prey (MMS, 2007b). Plovers congregate 

and feed along tidally exposed banks and shorelines, following the tide out and foraging at the 

water’s edge. It is possible that some deaths of Piping Plovers could occur, especially if spills 

occur during winter months when plovers are most common along the coastal Gulf or if spills 

contacted critical habitat. Impacts could also occur from vehicular traffic on beaches and 

other activities associated with spill cleanup. Shell has extensive resources available to protect 

and rehabilitate wildlife in the event of a spill reaching the shoreline, as detailed in the OSRP. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on Piping 

Plovers are expected. 

C.3.7 Whooping Crane (Endangered) 

The Whooping Crane (Grus americana) is an omnivorous wading bird and an endangered 

species. There are three wild populations in North America (Whooping Crane Eastern 

Partnership [WCEP], 2010). One population winters along the Texas coast at Aransas NWR and 

summers at Wood Buffalo National Park in Canada. This population represents the majority of 

the world’s population of free-ranging Whooping Cranes and reached a record population of 

270 at Aransas NWR in December 2008 (WCEP, 2010). A non-migrating population has been 

re-introduced in central Florida, and another re-introduced population summers in Wisconsin 

and migrates to the southeastern U.S. for the winter. Whooping Cranes breed, migrate, 

winter, and forage in a variety of habitats, including coastal marshes and estuaries, inland 

marshes, lakes, ponds, wet meadows and rivers, and agricultural fields (USFWS, 2007). About 

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 (Figure 3). A species description is presented in a recent lease sale EIS 

(MMS, 2007b). 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 44 

A large oil spill (WCD) is the only IPF potentially affecting Whooping Cranes. A small fuel spill 

in the lease area would also be unlikely to affect Whooping Cranes due to the distance from 

Aransas NWR. As explained in Section A.9.2, a small fuel spill would not be expected to make 

landfall or reach coastal waters prior to breaking up. 

Impacts of a Large Oil Spill (WCD) 

A large oil spill is unlikely to affect Whooping Cranes because the lease area is approximately 

445 miles (716 km) from its critical habitat (Aransas NWR, Texas) and the OSRA modeling 

predicts no contact with shorelines of the Aransas NWR within 30 days. 

In the event of oil exposure, Whooping Cranes could become externally oiled while foraging in 

oiled areas or internally exposed to oil through ingestion of contaminated shellfish, frogs, and 

fishes. It is possible that some death of Whooping Cranes could occur. Shell has extensive 

resources available to protect and rehabilitate wildlife in the event of a spill reaching the 

shoreline, as detailed in the OSRP. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on Whooping 

Cranes are expected. 

C.3.8 Gulf Sturgeon (Threatened) 

The Gulf sturgeon (Acipenser oxyrinchus desotoi) is a threatened fish species that inhabits 

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida 

(Barkuloo, 1988; Wakeford, 2001). An anadromous fish that migrates from the sea upstream 

into coastal rivers to spawn in freshwater, it historically ranged from the Mississippi River to 

Charlotte Harbor, Florida (Wakeford, 2001). Today, this range has contracted to encompass 

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida. 

Populations have been depleted or even extirpated throughout this range by fishing, shoreline 

development, dam construction, water quality changes, and other factors (Barkuloo, 1988; 

Wakeford, 2001). These declines prompted the listing of the Gulf sturgeon as a threatened 

species in 1991. The best known populations occur in the Apalachicola and Suwannee Rivers 

in Florida (Carr, 1996; Sulak and Clugston, 1998), the Choctawhatchee River in Alabama (Fox et 

al., 2000), and the Pearl River in Mississippi/Louisiana (Morrow et al., 1998). Critical habitat in 

the Gulf extends from Lake Borgne, Louisiana (St. Bernard Parish) to Suwannee Sound, Florida 

(Levy County) (NMFS, 2010b) (Figure 3). A species description is presented in a recent lease 

sale EIS (MMS, 2007b) and in the recovery plan for this species (USFWS and Gulf States Marine 

Fisheries Commission, 1995). 

A large oil spill (WCD) is the only IPF potentially affecting Gulf sturgeon. There are no IPFs 

associated with routine project activities that could affect this species. A small fuel spill in the 

lease area would be unlikely to affect Gulf sturgeon because a small fuel spill would not be 

expected to make landfall or reach coastal waters prior to breaking up (see explanation in 

Section A.9.2). 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 45 

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 Supplemental EP, there 

are no unique site-specific issues with respect to this species. 

The lease area is about 130 miles (209 km) from the nearest Gulf sturgeon critical habitat. The 

OSRA modeling (Table 3) predicts that a spill in the lease area has a 1% probability of 

contacting the coastal areas inhabited by Gulf sturgeon within 30 days. 

In the event of oil reaching Gulf sturgeon habitat, the fish could be affected by direct ingestion, 

ingestion of oiled prey, or the absorption of dissolved petroleum products through the gills. 

Based on the life history of this species, subadult and adult Gulf sturgeon would be most 

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

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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Shell has extensive resources available to 

protect coastal and estuarine wildlife and habitats in the event of a spill reaching the shoreline, 

as detailed in the OSRP. Supplemental EP Sections 2j and 9b provide detail on spill response 

measures. Therefore, no significant spill impacts on Gulf sturgeon are expected. 

C.3.9 Beach Mice (Endangered) 

Four subspecies of endangered beach mouse (Peromyscus polionotus) occur on the barrier 

islands of Alabama and the Florida Panhandle. They are the Alabama, Choctawatchee, Perdido 

Key, and St. Andrew beach mouse. Critical habitat has been designated for all four subspecies; 

Figure 3 shows the critical habitat combined for all four subspecies. Species descriptions are 

provided in a recent lease sale EIS (MMS, 2007b). 

A large oil spill (WCD) is the only IPF potentially affecting subspecies of beach mouse. There 

are no IPFs associated with routine project activities that could affect these animals due to the 

distance from shore and the lack of any onshore support activities near their habitat. A small 

fuel spill in the lease area would not affect any subspecies of beach mouse because a small 

fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up 

(see explanation in Section A.9.2). 

Impacts of a Large Oil Spill (WCD) 

Potential spill impacts on beach mice are discussed in recent EISs (MMS, 2007b, 2008). For 

this Supplemental EP, there are no unique site-specific issues with respect to these species. 

The lease area is about 166 miles (267 km) from the nearest beach mouse critical habitat. The 

OSRA modeling predicts that a spill in the lease area would not contact beach mouse critical 

habitat within 30 days. (Okaloosa County, Florida, which has a 1% probability after 30 days, 

does not include any critical habitat.) 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 46 

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 

detailed in Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b provide 

detail on spill response measures. Therefore, no significant spill impacts on beach mice are 

expected. 

C.4 Coastal and Marine Birds 

C.4.1 Marine and Pelagic Birds 

A variety of seabirds may occur in the pelagic environment of the project areas (Clapp et al., 

1982a,b, 1983; Peake, 1996; Hess and Ribic, 2000). Seabirds spend much of their lives offshore 

over the open ocean, except during breeding season when they nest along the coast. In 

addition, other birds such as waterfowl, marsh birds, and shorebirds may occasionally be 

present over open ocean areas. No endangered or threatened bird species are likely to occur 

at the project area due to the distance from shore. For a discussion of shorebirds and coastal 

nesting birds, see Section C.4.2. 

Seabirds of the northern Gulf of Mexico were surveyed from ships during the GulfCet II 

program. Hess and Ribic (2000) reported that terns, storm-petrels, shearwaters, and jaegers 

were the most frequently sighted seabirds in the deepwater area. From these surveys, four 

ecological categories of seabirds were documented in the deepwater areas of the Gulf: 

summer migrants (e.g., shearwaters, storm petrels, and boobies); summer residents that 

breed in the Gulf (e.g., Sooty Tern, Least Tern, Sandwich Tern, and Magnificent Frigatebird); 

winter residents (e.g., gannets, gulls, and jaegers); and permanent resident species 

(e.g., Laughing Gull, Royal Tern, and Bridled Tern) (Hess and Ribic, 2000). 

Common seabird species include Wilson’s Storm-Petrel (Oceanites oceanicus), Magnificent 

Frigatebird (Fregata magnificens), Northern Gannet (Morus bassanus), Masked Booby 

(Sula dactylatra), Brown Booby (Sula leucogaster), Cory’s Shearwater (Calonectris diomedea), 

Greater Shearwater (Puffinus gravis), and Audubon Shearwater (Puffinus lherminieri). Seabirds 

are distributed Gulf-wide and are not specifically associated with the lease area. 

Relationships with hydrographic features were found for several seabird species, possibly due 

to effects of hydrography on nutrient levels and productivity of surface waters where birds 

forage. GulfCet II did not estimate bird densities; however, Powers (1987) indicates that 

seabird densities over the open ocean typically are <10 birds/km2

. 

Trans-Gulf migrant birds including shorebirds, wading birds, and terrestrial birds may also be 

present in the lease area. Migrant birds may use offshore structures and platforms for resting, 

feeding, or as temporary shelter from inclement weather (Russell, 2005). Some birds may be 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 47 

attracted to offshore structures because of the lights and the fish populations that aggregate 

around these structures. 

IPFs potentially affecting marine and pelagic birds include drilling rig presence, noise, and 

lights; support vessel and helicopter traffic; and two types of accidents (a small fuel spill and a 

large oil spill represented by the WCD for this Supplemental 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. 

Compliance with NTL 2007-G03 will minimize the potential for marine debris-related impacts 

on birds. 

Impacts of Drilling Rig Presence, Noise, and Lights 

Birds that frequent platforms may be exposed to contaminants including air pollutants and 

routine discharges, but significant impacts are unlikely due to rapid dispersion of effluents and 

air pollutants. Birds migrating over water have been known to strike offshore structures, 

resulting in death or injury (Wiese et al., 2001; Russell, 2005). Mortality of migrant birds at tall 

towers and other land-based structures has been reviewed extensively, and the mechanisms 

involved in platform collisions appear to be similar. In some cases, migrants simply do not see 

a part of the platform until it is too late. In other cases, navigation may be disrupted by noise 

(Russell, 2005). On the other hand, offshore structures are suitable stopover habitats for most 

trans-Gulf migrant species, and most of the migrants that stop over on platforms probably 

benefit from their stay, particularly in spring (Russell, 2005). Due to the limited scope, timing, 

and geographic extent of drilling activities in this Supplemental EP, any impacts on populations 

of either seabirds or trans-Gulf migrant birds are not expected to be significant. 

A recent study in the North Sea indicated that platform lighting causes circling behavior in 

various birds, especially on cloudy nights; apparently the birds’ geomagnetic compass is upset 

by the red part of the spectrum from the lights currently in use (Poot et al., 2008). The 

numbers varied greatly, from none at all to some tens of thousands of birds per night per 

platform, with an apparent effect radius of up to 3 miles (5 km). A study in the Gulf of Mexico 

also noted the phenomenon, but did not recommend mitigation (Russell, 2005). Factors to 

consider in evaluating this impact in the Gulf of Mexico would include the lower incidence of 

cloudy and foggy days in the Gulf of Mexico vs. the North Sea. Due to the limited scope and 

short duration of drilling activities proposed in this Supplemental EP, lighting impacts, 

collisions, or other adverse effects are unlikely, and no significant impacts are expected. 

Impacts of Support Vessel and Helicopter Traffic 

Support vessels and helicopters are unlikely to significantly disturb pelagic birds in open, 

offshore waters. It is likely that individual birds would experience, at most, only short-term 

behavioral disruption, and the impact would not be significant. 

Impacts of a Small Fuel Spill 

Potential spill impacts on marine birds are discussed in recent EISs (MMS, 2007b, 2008). For 

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

these animals. 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 48 

OSRP will mitigate and reduce the potential for impacts on marine and pelagic birds. 

Supplemental EP Sections 2j and 9b provide detail on spill response measures. Given the 

open ocean location of the lease area, the duration of a small spill and opportunity for impacts 

to occur would be very brief. 

A small fuel spill in offshore waters would produce a slick on the water surface and increase 

the concentrations of petroleum hydrocarbons and their degradation products. The extent 

and persistence of impacts would depend on the meteorological and oceanographic conditions 

at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed 

naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from 

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

impacts on these animals. 

Pelagic seabirds could be exposed to oil from a spill at the project area. Hess and Ribic (2000) 

reported that terns, storm-petrels, shearwaters, and jaegers were the most frequently sighted 

seabirds in the deepwater Gulf of Mexico (>200 m). Powers (1987) indicates that seabird 

densities over the open ocean typically are <10 birds/km2

. The number of pelagic birds that 

could be affected in open, offshore waters would depend on the extent and persistence of the 

oil slick. 

The recent Macondo spill provides relevant information about the species of pelagic birds that 

may be affected in the event of a large oil spill. Birds that have been treated for oiling include 

several pelagic species such as the Northern Gannet, Magnificent Frigatebird, and Masked 

Booby (International Bird Rescue Research Center, 2010). The Northern Gannet is among the 

species with the largest numbers of birds affected by the spill. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on marine 

and pelagic birds are expected. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 49 

C.4.2 Shorebirds and Coastal Nesting Birds 

Threatened and endangered bird species (Piping Plover and Whooping Crane) have been 

discussed previously in Section C.3. Various species of non-endangered birds are also found 

along the northern Gulf coast, including diving birds, shorebirds, marsh birds, wading birds, 

and waterfowl. Gulf Coast marshes and beaches also provide important feeding grounds and 

nesting habitats. Species that breed on beaches, flats, dunes, bars, barrier islands, and similar 

habitats include the Sandwich Tern, Wilson’s Plover, Black Skimmer, Forster’s Tern, Gull-Billed 

Tern, Laughing Gull, Least Tern, and Royal Tern (USFWS, 2010b). Additional information is 

presented in recent lease sale EISs (MMS, 2007b, 2008). 

The Brown Pelican (Pelecanus occidentalis) was delisted from federal endangered status in 

2009 (USFWS, 2010c). However, this species is listed as a species of greatest conservation 

need by the State of Mississippi (Mississippi Department of Wildlife, Fisheries and Parks, 2011) 

and as a species of special concern by the State of Florida (Florida Fish and Wildlife 

Conservation Commission, 2010). Brown Pelicans inhabit coastal habitats and forage within 

both coastal waters and waters of the inner continental shelf. Aerial and shipboard surveys, 

including GulfCet and GulfCet II, indicate that Brown Pelicans do not occur over deep offshore 

waters (Fritts and Reynolds, 1981; Peake, 1996; Hess and Ribic, 2000). Nearly half the 

southeastern population of Brown Pelicans lives in the northern Gulf Coast, generally nesting 

on protected islands (USFWS, 2010b). 

The Bald Eagle (Haliaeetus leucocephalus) was delisted from its threatened status in the 

continental United States on June 28, 2007. The Bald Eagle is a terrestrial raptor widely 

distributed across the southern U.S., including coastal habitats along the Gulf of Mexico. The 

Gulf coast is inhabited by both wintering migrant and resident Bald Eagles (Johnsgard, 1990; 

Ehrlich et al., 1992). 

IPFs potentially affecting shorebirds and coastal nesting birds include support vessel and 

helicopter traffic and a large oil spill (WCD). A small fuel spill in the lease area would be 

unlikely to affect shorebirds or coastal nesting birds, as the lease area is 67 miles (108 km) 

from the nearest shoreline. As explained in Section A.9.2, a small fuel spill would not be 

expected to make landfall or reach coastal waters prior to breaking up. Compliance with 

NTL 2007-G03 will minimize the potential for marine debris-related impacts on shorebirds. 

Impacts of Support Vessel and Helicopter Traffic 

Support vessels and helicopters will transit coastal areas near Port Fourchon and Boothville, 

Louisiana, where shorebirds and coastal nesting birds may be found. These activities could 

periodically disturb individuals or groups of birds within sensitive coastal habitats 

(e.g., wetlands that may support feeding, resting, or breeding birds). 

Vessel traffic may disturb some foraging and resting birds. Flushing distances vary among 

species and individuals (Rodgers and Schwikert, 2002). The disturbances will be limited to 

flushing birds away from vessel pathways; known distances are from 20 to 49 m (65 to 160 ft) 

for personal watercraft and 23 to 58 m (75 to 190 ft) for outboard-powered boats (Rodgers 

and Schwikert, 2002). Flushing distances may be similar or less for the support vessels to be 

used for Shell’s project, and some species such as gulls are attracted to boats. Support vessels 

will not approach nesting or breeding areas on the shoreline, so nesting birds, eggs, and chicks 

will not be disturbed. Vessel operators will use designated navigation channels and comply 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 50 

with posted speed and wake restrictions while transiting sensitive inland waterways. Due to 

the limited scope, timing, and geographic extent of drilling activities, any short-term impacts 

are not expected to be biologically significant to coastal bird populations. 

Aircraft traffic can cause some disturbance to birds onshore and offshore. Responses are 

highly dependent on the type of aircraft, the bird species, the activities that animals were 

previously engaged in, and previous exposures to overflights (Efroymson et al., 2000). 

Helicopters seem to cause the most intense responses over other human disturbances for 

some species (Bélanger and Bédard, 1989). However, Federal Aviation Administration 

Advisory Circular No. 91-36D recommends that pilots maintain a minimum altitude of 610 m 

(2,000 ft) when flying over noise-sensitive areas such as wildlife refuges, parks, and areas with 

wilderness characteristics. This is greater than the distance (slant range) at which aircraft 

overflights have been reported to cause behavioral effects on most species of birds studied 

(Efroymson et al., 2000). With these guidelines in effect, it is likely that individual birds would 

experience, at most, only short-term behavioral disruption. 

Impacts of Large Oil Spill (WCD) 

The OSRA results summarized in Table 3 predict that shorelines of Texas, Louisiana, and 

Florida that include habitat for shorebirds and coastal nesting birds could be affected within 

30 days. 

Data from the recent Macondo spill provides additional information about the species of 

coastal birds that may be affected in the event that a large oil spill reached coastal habitats; 

this information supplements the analysis presented in the lease sale EIS (MMS, 2007b). 

According to USFWS (2010d) and based on the latest reports, about 5,000 dead birds had been 

collected since the spill began, and about 1,900 of the dead animals were visibly oiled. In 

addition, more than 2,000 oiled birds have been collected alive and about 1,200 released 

(NMFS, 2010a). According to the International Bird Rescue Research Center (2010), bird 

species that were treated for oiling following the Macondo spill include the following: 

• Brown Pelican 

• White Pelican 

• Masked Booby 

• Magnificent Frigatebird 

• Laughing Gull 

• Herring Gull 

• Northern Gannet 

• Black Crowned Night Heron 

• Tri-colored Heron 

• Green Heron 

• Cattle Egret 

• Snowy Egret 

• Reddish Egret 

• Least Bittern 

• Common Tern 

• Royal Tern 

• Caspian Tern 

• Sandwich Tern 

• 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 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 51 

According to the USFWS (2010d), species with the largest numbers of dead, oiled birds were 

Laughing Gull, Northern Gannet, Brown Pelican, Royal Tern, Black Skimmer, Least Tern, 

unidentified Gull, and unidentified Tern. There are no reports of Bald Eagle oiling. 

Coastal birds can be exposed to oil as they float on the water’s surface, dive during foraging, or 

wade in oiled coastal waters. Oiled birds can lose the ability to fly, dive for food, or float on 

the water, which could lead to drowning (USFWS, 2010e). Oil interferes with the water 

repellency of feathers and can cause hypothermia under certain conditions. As birds groom 

themselves, they can ingest and inhale the oil on their bodies. Scavengers such as Bald Eagles 

and gulls can be exposed to oil by feeding on carcasses of contaminated fish and wildlife. 

While ingestion can kill animals immediately, more often it results in lung, liver, and kidney 

damage, which can lead to death. Bird eggs may be damaged if an oiled adult sits on the nest 

or if oil covers the eggs. 

As noted above, the Brown Pelican was recently removed from the endangered species list. 

More than 300 dead Brown Pelicans were collected in the Gulf following the Macondo spill, 

(USFWS, 2010d). These data indicate that the Brown Pelican may be particularly at risk of 

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

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

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on shorebirds 

and coastal nesting birds are expected. 

C.5 Fisheries Resources 

C.5.1 Pelagic Communities and Ichthyoplankton 

Biggs and Ressler (2000) reviewed the biology of pelagic communities in the deepwater 

environment of the northern Gulf of Mexico. The biological oceanography of the region is 

dominated by the influence of the Loop Current, whose surface waters are among the most 

oligotrophic in the world’s oceans. Superimposed on this low-productivity condition are 

productive “hot spots” associated with entrainment of nutrient-rich Mississippi River water 

and mesoscale oceanographic features. Anticyclonic and cyclonic hydrographic features play 

an important role in determining biogeographic patterns and controlling primary productivity 

in the northern Gulf of Mexico (Biggs and Ressler, 2000). 

Most fishes inhabiting shelf or oceanic waters of the Gulf of Mexico have planktonic eggs and 

larvae (Ditty, 1986; Ditty et al., 1988; Richards et al., 1989, 1993). Pelagic eggs and larvae 

become part of the planktonic community for various lengths of time (10 to 100 days, 

depending on the species) (MMS, 2007b). 

IPFs potentially affecting pelagic communities and ichthyoplankton include drilling rig 

presence, noise, and lights; effluent discharges; water intakes; and two types of accidents 

(a small fuel spill and a large oil spill [WCD]). 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 52 

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 Effluent Discharges 

Treated sanitary and domestic wastes may have a slight effect on the pelagic environment in 

the immediate vicinity of these discharges. These wastes may have elevated levels of 

nutrients, organic matter, and chlorine, but will be diluted rapidly to undetectable levels within 

tens to hundreds of meters from the source. Minimal impacts on water quality, plankton, and 

nekton are anticipated. 

Deck drainage may have a slight effect on the pelagic environment in the immediate vicinity of 

these discharges. Deck drainage from contaminated areas will be passed through an oil and 

water separator prior to release, and discharges will be monitored for visible sheen. The 

discharges may have slightly elevated levels of hydrocarbons but will be diluted rapidly to 

undetectable levels within tens to hundreds of meters from the source. Minimal impacts on 

water quality, plankton, and nekton are anticipated. 

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

uncontaminated cooling water, fire water, and ballast water, are expected to be diluted 

rapidly and have little or no impact on water column biota. 

Impacts of Water Intakes 

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

on the drilling rig. The estimated intake and discharge of cooling water is 130,600 BPD 

(5.48 MGD) and another 130,600 BPD (5.48 MGD) 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. 

 Construction of the rig planned for use in this Supplemental EP, the Noble Danny Atkins, 

started prior to July 17, 2006, and therefore is not subject to the cooling water intake permit 

requirements of NPDES Permit GMG 290000. If a similar type rig is selected, it will comply 

with all applicable NPDES requirements 

Impacts of a Small Fuel Spill 

Potential spill impacts on fisheries resources are discussed in recent EISs (MMS, 2007b, 2008). 

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

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts on pelagic communities, including 

ichthyoplankton. Supplemental EP Sections 2j and 9b provide detail on spill response 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 53 

measures. Given the open ocean location of the lease area, the duration of a small spill and 

opportunity for impacts to occur would be very brief. 

A small fuel spill in offshore waters would produce a slick on the water surface and increase 

the concentrations of petroleum hydrocarbons and their degradation products. The extent 

and persistence of impacts would depend on the meteorological and oceanographic conditions 

at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed 

naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from 

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

A small fuel spill could have localized impacts on phytoplankton, zooplankton, 

ichthyoplankton, 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 in 

the upper layers of the water column are especially vulnerable to oiling; certain toxic fractions 

of spilled oil may be lethal to these life stages. Impacts would be potentially greater if local 

scale currents retained planktonic larval assemblages (and the floating oil slick) within the 

same water mass. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on pelagic 

communities and ichthyoplankton are expected. 

C.5.2 Essential Fish Habitat 

Essential Fish Habitat (EFH) is defined as those waters and substrate necessary to fish for 

spawning, breeding, feeding, and growth to maturity. Under the Magnuson-Stevens Fishery 

Conservation and Management Act, as amended, Federal agencies are required to consult on 

activities that may adversely affect EFH designated in Fishery Management Plans developed by 

the regional Fishery Management Councils. 

The Gulf of Mexico Fishery Management Council (GMFMC) has prepared Fishery Management 

Plans for corals and coral reefs, 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). The EFH 

for most of these GMFMC-managed species is on the continental shelf in waters shallower 

than 183 m (600 ft). The shelf edge is the outer boundary for coastal migratory pelagic fishes, 

reef fishes, and shrimp. EFH for corals and coral reefs includes some shelf-edge topographic 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 54 

features on the Texas-Louisiana OCS, the nearest of which is Sackett Bank, located 45 miles 

(73 km) north-northwest of the lease area. 

Highly migratory pelagic fishes, which occur as transients in the lease area, are the only 

remaining group for which EFH has been identified in the deepwater Gulf of Mexico. Species 

in this group, including tunas, swordfishes, billfishes, and sharks, are managed by NMFS. 

Highly migratory species with EFH at or near the lease area include the following 

(NMFS, 2009): 

• Atlantic bigeye tuna (juveniles, 

adults) 

• Atlantic bluefin tuna (spawn, eggs, 

larvae, adults) 

• Atlantic skipjack tuna (spawn, 

adults) 

• Atlantic yellowfin tuna (all) 

• Atlantic swordfish (all) 

• Blue marlin (juveniles, adults) 

• White marlin (juveniles, adults) 

• Sailfish (juveniles, adults) 

• Longbill spearfish (juveniles, adults) 

• Oceanic whitetip shark (all) 

• Silky shark (all) 

• Longfin mako shark (all) 

• Bigeye thresher shark (all) 

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

habitat for Atlantic bluefin tuna, and NMFS (2009) has designated a Habitat Area of Particular 

Concern (HAPC) for this species. The HAPC covers much of the deepwater Gulf of Mexico, 

including the lease area (Figure 3). The areal extent of the HAPC is approximately 300,000 km2 

(15,000 mi2). The prevailing assumption is that Atlantic bluefin tuna follow an annual cycle of 

foraging in June through March off the eastern United States and Canadian coasts, followed by 

migration to the Gulf of Mexico to spawn in April, May, and June (NMFS, 2009). 

Other HAPCs have been identified in the Gulf of Mexico by the GMFMC (2005). These include 

the Florida Middle Grounds, Madison-Swanson Marine Reserve, Tortugas North and South 

Ecological Reserves, Pulley Ridge, and several individual reefs and banks of the northwestern 

Gulf of Mexico (Figure 3). The nearest of these is Jakkula Bank, located 146 miles (236 km) 

west of lease area MC 984. 

Routine IPFs potentially affecting EFH include (1) drilling rig presence, noise, and lights; 

(2) effluent discharges; and (3) water intakes. In addition, two types of accidents – a small fuel 

spill and a large oil spill (WCD) – may impact EFH and fisheries resources. 

Impacts of Drilling Rig Presence, Noise, and Lights 

The drilling rig, as a floating structure in the deepwater environment, will act as an FAD. In 

oceanic waters, the FAD effect would be most pronounced for epipelagic fishes such as tunas, 

dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting surface 

structures (Holland et al., 1990; Higashi, 1994; Relini et al., 1994). This FAD effect would 

possibly enhance feeding of epipelagic predators by attracting and concentrating smaller fish 

species. Because the drilling rig is a single, temporary structure, any impacts on EFH for highly 

migratory pelagic fishes are considered minor. 

Impacts of Effluent Discharges 

Other effluent discharges affecting EFH by diminishing ambient water quality include drilling 

muds and cuttings, treated sanitary and domestic wastes, deck drainage, and miscellaneous 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 55 

discharges such as desalination unit brine and uncontaminated cooling water, fire water, and 

ballast water. Impacts on water quality have been discussed previously. No significant 

impacts on EFH for highly migratory pelagic fishes are expected from these discharges. 

Impacts of Water Intakes 

As noted previously, cooling water intake will cause entrainment and impingement of 

plankton, including fish eggs and larvae (ichthyoplankton). Due to the limited scope, timing, 

and geographic extent of drilling activities, any short-term impacts on EFH for highly migratory 

pelagic fishes are not expected to be biologically significant. 

Impacts of a Small Fuel Spill 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts on EFH. Supplemental EP Sections 2j 

and 9b provide detail on spill response measures. Given the open ocean location of the lease 

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

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

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

A small fuel spill in offshore waters would produce a slick on the water surface and increase 

the concentrations of petroleum hydrocarbons and their degradation products. The extent 

and persistence of impacts would depend on the meteorological and oceanographic conditions 

at the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed 

naturally within 24 hours. The area of the sea surface with diesel fuel on it would range from 

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

A small fuel spill could have localized impacts on EFH for highly migratory pelagic fishes, 

including tunas, swordfishes, billfishes, and sharks. These species occur as transients in the 

lease area. A spill would also produce short-term impact on water quality in the HAPC for 

spawning Atlantic bluefin tuna, which covers much of the deepwater Gulf of Mexico. The 

affected area would represent a negligible portion of the HAPC, which covers 297,312 km2

(114,793 mi2) of the Gulf of Mexico. 

A small fuel spill would not affect EFH for corals and coral reefs; the nearest coral EFH is 

Sackett Bank, located 45 miles (73 km) north-northwest of the lease area. A small fuel spill 

would float and dissipate on the sea surface and would not contact these features. 

Impacts of a Large Oil Spill (WCD) 

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

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

An oil spill in offshore waters would temporarily increase hydrocarbon concentrations on the 

water surface and potentially the subsurface as well. Given the extent of EFH designations in 

the Gulf of Mexico (GMFMC, 2005; NMFS, 2009), some impact on EFH would be unavoidable. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 56 

A large spill could affect the EFH for many managed species including shrimp, stone crab, spiny 

lobster, coral and coral reefs, reef fishes, coastal migratory pelagic fishes, and red drum. It 

would result in adverse impacts on water quality and water column biota including 

phytoplankton, zooplankton, ichthyoplankton, and nekton. In coastal waters, sediments could 

be contaminated and result in persistent degradation of the seafloor habitat for managed 

demersal fish and shellfish species. 

The lease area is within the HAPC for spawning Atlantic bluefin tuna (NMFS, 2009). A large 

spill could temporarily degrade the HAPC due to increased hydrocarbon concentrations in the 

water column, with the potential for lethal or sublethal impacts on spawning tuna and their 

offspring. Potential impacts would depend in part on the timing of a spill, as this species 

migrates to the Gulf of Mexico to spawn in April, May, and June (NMFS, 2009). 

The pinnacle trend area, located 92 miles (149 km) north from the lease area, is designated as 

EFH under the corals and coral reefs management plan. An accidental spill would be unlikely 

to affect this area. A surface slick would not reach these features. Although there are reports 

of subsurface plumes resulting from the use of subsea dispersants during the Macondo spill, 

the distance and difference in water depth are factors that would make an impact unlikely. 

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

2001) and typically would not carry a plume up onto the continental shelf edge. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on EFH are 

expected. 

C.6 Archaeological Resources 

C.6.1 Shipwreck Sites 

MC 940, 984, and 985 are in an area with high potential for historic shipwrecks. An 

Archaeological Assessment conducted by C&C Technologies, Inc. (2007) detected 106 

unidentified sidescan sonar targets, several drag scars, and other geological features within 

the survey area. Twenty-three of these sonar targets were in MC 940, 984, and 985. There 

were no sonar contacts with acoustic signature that require archaeological avoidance or 

further investigation. No shipwrecks were found within MC 940, 984, and 985. 

Because there are no historic shipwreck sites in the lease area, there are no routine IPFs that 

are likely to affect these resources. Impacts of a large oil spill (WCD) are the only IPFs 

considered. A small fuel spill would not affect shipwrecks because the oil would float and 

dissipate on the sea surface. 

Impacts of a Large Oil Spill (WCD) 

The MMS (2007b) estimated that a severe subsurface blowout could resuspend and disperse 

sediments within a 300-m (984-ft) radius. Because there are no historic shipwrecks in the 

lease area, the WCD would not result in any impact on archaeological resources. 
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Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect 

archaeological sites beyond the immediate vicinity of the wellhead (i.e., due to physical 

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the 

spill location. However, during the Macondo spill, subsurface plumes were reported at a 

water depth of about 1,100 m (3,600 ft), extending at least 22 miles (35 km) from the wellsite 

and persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently 

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). While the 

behavior and impacts of subsurface plumes are not well known, a subsurface plume could 

have the potential to contact shipwreck sites beyond the 300-m (984-ft) radius estimated by 

MMS (2007a, 2008), depending on its extent, trajectory, and persistence. If oil from a subsea 

spill should come into contact with wooden shipwrecks on the seafloor it could adversely 

affect their condition or preservation. Should there be any indication that potential shipwreck 

sites could be affected, in accordance with NTL 2005-G07 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 Texas, Louisiana, and 

Florida shorelines could be contacted by a spill within 30 days. Also as noted by MMS (2007b), 

should an oil spill contact a coastal historic site, such as a fort or a lighthouse, the major 

impact would be a temporary, reversible visual impact from oil contact and contamination of 

the site and its environment. 

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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on historic 

shipwrecks are expected. 

C.6.2 Prehistoric Archaeological Sites 

With water depths ranging from 1,213 to 1,269 m (3,978 to 4,164 ft), the wellsites are well 

beyond the 60-m (197-ft) depth contour used by the BOEMRE as the seaward extent for 

prehistoric archaeological site potential in the Gulf of Mexico. Because prehistoric 

archaeological sites are not found in the lease area, the only relevant IPF is a large oil spill 

(WCD). A small fuel spill would not affect prehistoric archaeological resources because the oil 

would float and dissipate on the sea surface. 

Impacts of a Large Oil Spill (WCD) 

Because prehistoric archaeological sites are not found in the lease area, they would not be 

affected by the physical effects of a subsea blowout. The MMS (2007b) estimates that a 

severe subsurface blowout could resuspend and disperse sediments within a 300-m (984-ft) 

radius. 
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Along the northern Gulf coast, prehistoric sites occur frequently along the barrier islands and 

mainland coast and along the margins of bays and bayous (MMS, 2007b). The OSRA modeling 

summarized in Table 3 predicts that Texas, Louisiana, and Florida shorelines could be 

contacted by a spill within 30 days. A spill reaching a prehistoric site along these shorelines 

could coat fragile artifacts or site features and compromise the potential for radiocarbon 

dating organic materials in a site (although other dating methods are available and it is 

possible to decontaminate an oiled sample for radiocarbon dating). Coastal prehistoric sites 

could also be damaged by spill cleanup operations (e.g., by destroying fragile artifacts and 

disturbing the provenance of artifacts and site features). 

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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on 

archaeological resources are expected. 

C.7 Coastal Habitats and Protected Areas 

Coastal habitats in the northeastern Gulf of Mexico that may be affected by oil and gas 

activities are described in recent EISs (MMS, 2007b, 2008) and in a literature review by Collard 

and Way (1997). Sensitive coastal habitats are also tabulated in the OSRP. Coastal habitats 

inshore of the project area include barrier beaches and dunes, wetlands, and submerged 

seagrass beds. Generally, most of the northeastern Gulf is fringed by barrier beaches, with 

wetlands and/or submerged seagrass beds occurring in sheltered areas behind the barrier 

islands and in estuaries. 

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

likely to affect beaches and dunes, wetlands, seagrass beds, coastal wildlife refuges, 

wilderness areas, or any other managed or protected coastal area. The support bases at 

Port Fourchon and Boothville are not located in a wildlife refuge or a wilderness area. 

Potential impacts of support vessel traffic are briefly addressed below. 

A small fuel spill in the lease area would be unlikely to affect coastal habitats, as the lease area 

is 67 miles (108 km) from the nearest shoreline. As explained in Section A.9.2, a small fuel spill 

would not be expected to make landfall or reach coastal waters prior to breaking up. 

Impacts of Support Vessel Traffic 

For OCS activities in general, support operations, including crew boats and supply boats, may 

have a minor incremental impact on coastal habitats. Over time with a large number of vessel 

trips, vessel wakes can erode shorelines along inlets, channels, and harbors. Support 

operations, including crew boats and supply boats as detailed in Supplemental EP Section 14, 

may have a minor incremental impact on coastal habitats or protected areas. Impacts will be 

minimized by following the speed and wake restrictions in harbors and channels. 

Impacts of a Large Oil Spill (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 
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Environmental Impact Analysis for Supplemental EP Page 59 

submerged seagrass beds. For this Supplemental EP, there are no unique site-specific issues 

with respect to coastal habitats. 

The OSRA results summarized in Table 3 predict that shorelines of Texas, Louisiana, and 

Florida could be affected within 30 days. Plaquemines Parish, Louisiana, has the highest 

probability of contact for the 10-day and 30-day intervals (4% and 8%, respectively). Two 

other Louisiana parishes (Terrebonne and Lafourche) may be contacted within 10 days. After 

30 days, 11 counties or parishes may be contacted from Galveston, Texas, to the Okaloosa 

County in the Florida Panhandle. 

The shorelines within the geographic range predicted by the OSRA modeling include extensive 

barrier beaches and wetlands, with submerged seagrass beds occurring in sheltered areas 

behind the barrier islands and in estuaries. National wildlife refuges and other protected areas 

along the coast are discussed in the lease sale EIS (MMS, 2007b) and Shell’s OSRP. Coastal 

wildlife refuges, wilderness areas, and state and national parks within the geographic range of 

the potential shoreline contacts after 30 days include the following: 

• Galveston Island State Park 

• Brazoria NWR 

• Apffel Park 

• Seawolf Park 

• Old Fort Travis Park 

• Atkinson Island Wildlife 

Management Area (WMA) 

• Ft. Anahuac Park 

• Anahuac NWR 

• McFaddin NWR 

• Sea Rim State Park 

• J.D. Murphree WMA 

• Texas Point NWR 

• Sabine NWR 

• Cameron Prairie NWR 

• LaCassine NWR 

• Little Pecan Island Preserve 

• Peveto Woods Sanctuary 

• Lower Neches WMA 

• Rockefeller State Wildlife Refuge 

and Game Preserve 

• Paul J. Rainey WMA 

• Marsh Island WMA 

• Cypremort Point State Park 

• Atchafalaya Delta WMA 

• Mandalay NWR 

• Isles Dernieres Barrier Islands Refuge 

• Pointe Au Chien WMA 

• Wisner WMA 

• Grand Isle State Park 

• Salvador WMA 

• Jean Lafitte National Historical Park 

and Preserve 

• Delta NWR 

• Pass a Loutre WMA 

• Breton NWR 

• St. Bernard State Park 

• Biloxi WMA 

• Bayou Sauvage NWR 

• Gulf Islands National Seashore 

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

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

within 30 days, or from a spill persisting for more than 30 days. Additional NWRs and 

managed wildlife areas occur along the Gulf coast. These areas include habitats such as 

barrier beach and dune systems, wetlands, and submerged seagrass beds that support diverse 

wildlife, including endangered or threatened species. 

The level of impacts from oil spills on coastal habitats depends on many factors, including the 

oil characteristics, the geographic location of the landfall, and the weather and oceanographic 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 60 

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 

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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on coastal 

habitats are expected. 

C.8 Socioeconomic and Other Resources 

C.8.1 Recreational and Commercial Fishing 

The main commercial fishing activity in deep waters of the northern Gulf of Mexico is pelagic 

longlining for tunas, swordfishes, and other billfishes (Continental Shelf Associates, Inc., 2002). 

Pelagic longlining has occurred historically in the project area, primarily during spring and 

summer. In August 2000, the Federal government closed two areas in the northeastern Gulf of 

Mexico to longline fishing (65 Federal Register 47214, August 1, 2000). The lease is outside of 

the closure areas. 

Longline gear consists of monofilament line deployed from a moving vessel and generally 

allowed to drift for 4 to 5 hours (Continental Shelf Associates, Inc., 2002). As the mainline is 

put out, baited leaders and buoys are clipped in place at regular intervals. It takes 

8 to 10 hours to deploy a longline and about the same time to retrieve it. Longlines are often 

set near oceanographic features such as fronts or downwellings, with the aid of sophisticated 

on-board temperature sensors, depth finders, and positioning equipment. Vessels are 
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Environmental Impact Analysis for Supplemental EP Page 61 

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 Texas and Louisiana. The nearby 

Mars and Ursa TLPs are known sites of recreational fishing in the region (Continental Shelf 

Associates, Inc. (2002). 

The only routine IPF potentially affecting fisheries is drilling rig presence (including noise and 

lights). Two potential accidents are also addressed below – a small fuel spill and a large oil spill 

(WCD). 

Impacts of Drilling Rig Presence 

There is a slight possibility of pelagic longlines becoming entangled in the drilling rig. For 

example, in January 1999, a portion of a pelagic longline snagged on the acoustic Doppler 

current profiler of a drillship working in the Gulf of Mexico (Continental Shelf Associates, Inc., 

2002). The line was removed without incident. Generally, longline fishers use radar and are 

aware of offshore structures and ships when placing their sets. Therefore, little or no impact 

on pelagic longlining is expected. 

No adverse impacts on fishing activities are anticipated. Other factors such as effluent 

discharges are likely to have negligible impacts on commercial or recreational fisheries due to 

rapid dispersion, the small area of ocean affected, and the intermittent nature of the 

discharges. 

Impacts of a Small Fuel Spill 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b

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

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

Pelagic longlining activities in the lease area, if any, could be interrupted in the event of a small 

fuel spill. The area of the sea surface with diesel fuel on it would range from 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). 
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Impacts of a Large Oil Spill (WCD) 

Potential spill impacts on fishing activities are discussed in recent EISs (MMS, 2007b, 2008). 

For this Supplemental EP, there are no unique site-specific issues with respect to this activity. 

Pelagic longlining activities in the lease area and other fishing activities in the northern Gulf of 

Mexico could be interrupted in the event of a large oil spill. A spill may or may not result in 

fishery closures, depending on the duration of the spill, the oceanographic and meteorological 

conditions at the time, and the effectiveness of spill response measures. The recent Macondo 

spill provides information about the potential extent of fishery closures in the event of a large 

oil spill in the Gulf of Mexico (NMFS, 2010c). At its peak on July 12, 2010, closures 

encompassed 217,821 km2

 (84,101 mi2), or 34.8% of the U.S. Exclusive Economic Zone (EEZ) in 

the Gulf of Mexico. 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on fishing 

activities are expected. 

C.8.2 Public Health and Safety 

There are no IPFs associated with routine operations that are expected to affect public health 

and safety. Impacts of a small fuel spill and a large oil spill (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. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. 

A small fuel spill would not have any impacts on public health and safety because it would 

affect only a small area of the open ocean 67 miles (108 km) from the nearest shoreline and 

nearly all of the diesel fuel would evaporate or disperse naturally within 24 hours. Response 

crews would be equipped with appropriate safety equipment to avoid injury and health 

effects. A small fuel spill would not be expected to make landfall or reach coastal waters prior 

to breaking up (see Section A.9.2). 

Impacts of a Large Oil Spill (WCD) 

In the event of a large spill from a blowout, the main safety and health concerns are those of 

the offshore personnel involved in the incident and those responding to the spill. The 

proposed activities will be covered by the OSRP, and, in addition, the drilling rig maintains a 

Shipboard Oil Pollution Emergency Plan as required under MARPOL 73/78. 

Depending on the spill rate and duration, the physical/chemical characteristics of the oil, the 

meteorological and oceanographic conditions at the time, and the effectiveness of spill 

response measures, the public could be exposed to oil on the water and along the shoreline, 

through skin contact or inhalation of VOCs. Crude oil is a highly flammable material, and any 
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Environmental Impact Analysis for Supplemental EP Page 63 

smoke or vapors from a crude oil fire can cause irritation. Exposure to large quantities of 

crude oil may pose a health hazard. 

Data from the recent Macondo spill provide relevant information about the types of health 

issues that may occur in the event of a large oil spill (Centers for Disease Control and 

Prevention, 2010a). Wildlife cleaning and rehabilitation workers have reported concerns 

including scrapes and cuts, itchy or red skin or rash, and symptoms of headache or feeling 

faint, dizzy, or fatigued. Hand, shoulder, or back pain was also reported by some wildlife 

cleaning workers. Personnel working on offshore vessels or providing direct oversight to 

offshore vessels, including USCG personnel, civilian contractors, and other responders who 

were exposed to oil and dispersants, had 7 to 12 times higher 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 is exposure to 

seasonal temperature extremes resulting in heat stress in the summer and hypothermia in the 

winter. Initial symptoms from cleanup workers who sought medical care in Louisiana were 

typical of acute exposure to hydrocarbons or H2S such as headaches, dizziness, nausea, 

vomiting, cough, respiratory distress, and chest pain (Solomon and Janssen, 2010). Health 

effects reported from previous oil spills, such as the Exxon Valdez in 1989, were primarily 

acute injuries consisting of headaches, throat irritation, and sore or itchy eyes, but respiratory 

problems and dermatitis along with chronic airway disease have also been reported (Solomon 

and Janssen, 2010). 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on public 

health and safety are expected. 

C.8.3 Employment and Infrastructure 

There are no IPFs associated with routine operations that are expected to affect employment 

and infrastructure. The project involves drilling with support from existing shorebase facilities 

in Louisiana. No new or expanded facilities will be constructed, and no new employees are 

expected to move permanently into the area. The project will have a negligible impact on 

socioeconomic conditions such as local employment, existing offshore and coastal 

infrastructure (including major sources of supplies, services, energy, and water), and minority 

and lower income groups. Impacts of a small fuel spill and a large oil spill (WCD) are addressed 

below. 

Impacts of a Small Fuel Spill 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b

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

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

A small fuel spill that is dissipated within a few days would have little or no economic impact, 

as the spill response would use existing facilities, resources, and personnel. 
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Impacts of a Large Oil Spill (WCD) 

Potential socioeconomic impacts of an oil spill are discussed in recent EISs (MMS, 2007b, 

2008). For this Supplemental EP, there are no unique site-specific issues with respect to 

employment and coastal infrastructure. A large spill could cause economic impacts in several 

ways: it could result in extensive fishery closures that put fishermen out of work; it could result 

in temporary employment as part of the response effort; it could result in adverse publicity 

that affects employment in coastal recreation and tourism industries; and it could result in 

another suspension of OCS drilling activities, including service and support operations that are 

an important part of local economies. 

The lease area is 67 miles (108 km) from the nearest shoreline. Based on OSRA modeling as 

summarized in Table 3, Texas, Louisiana, and Florida 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. 

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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on 

employment and infrastructure are expected. 

C.8.4 Recreation and Tourism 

There are no known recreational uses of the lease area. Recreational resources and tourism in 

coastal areas would not be affected by any routine activities due to the distance from shore. 

Compliance with NTL 2007-G03 will minimize the chance of trash or debris being lost 

overboard from the drilling rig and subsequently washing up on beaches. 

Impacts of a Small Fuel Spill 

The probability of a fuel spill will be minimized by Shell’s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell’s 

OSRP will mitigate and reduce the potential for impacts. Supplemental EP Sections 2j and 9b

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

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

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 Supplemental EP, there are no unique site-specific issues with 

respect to these impacts. 

Impacts on recreation and tourism would vary depending on the duration of the spill and its 

fate including the effectiveness of response measures. A large spill that reached coastal 
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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, Plaquemines Parish, Louisiana, is the area most 

likely to be contacted by a spill. However, shorelines from Galveston, Texas, to the Florida 

Panhandle could be contacted. These areas 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 and ongoing studies have 

explored the economic impacts of the Macondo spill including tourism and “brand” damage 

(IEM, 2010; Oxford Economics, 2010). The U.S. Travel Association has estimated the economic 

impact of the Macondo spill on tourism across the Gulf Coast over a 3-year period at 

$22.7 billion (Oxford Economics, 2010). There are ongoing efforts to accelerate recovery by 

informing public perceptions; creating travel incentives; and providing access to capital, low 

interest loans, and tax incentives for affected businesses (U.S. Travel Association, 2010). 

A blowout resulting in a large oil spill (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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on recreation 

and tourism are expected. 

C.8.5 Land Use 

Land use along the northern Gulf coast is discussed in recent lease sale EISs (MMS, 2007b, 

2008). There are no routine IPFs potentially affecting land use. The project will use existing 

onshore support facilities in Louisiana. The land use at the existing shorebase sites is 

industrial. The project will not involve any new construction or changes to existing land use 

and, therefore, will not have any impacts. Levels of boat and helicopter traffic, as well as 

demand for goods and services including scarce coastal resources, will represent a small 

fraction of the level of activity occurring at the shorebases. 

A large oil spill (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 shorebases and facilities. 

Impacts of a Large Oil Spill (WCD) 

The initial response for a large oil spill would be staged out of existing facilities, with no effect 

on land use. A large spill could have limited temporary impacts on land use along the coast if 

additional staging areas were needed. For example, during the Macondo spill, temporary 

staging areas were established in Louisiana, Mississippi, Alabama, and Florida for spill response 

and cleanup efforts. In the event of a large spill in the lease area, similar temporary staging 

areas could be needed. These areas would eventually return to their original use as the 

response is demobilized. 

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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 66 

provide detail on spill response measures. Therefore, no significant spill impacts on land use 

are expected. 

C.8.6 Other Marine Uses 

The lease area is not located within any USCG-designated fairway or shipping lane. MC 940, 

984, and 985 are not in a designated Military Warning Area. Shell will comply with BOEMRE 

requirements and lease stipulations to avoid impacts on uses of the area by military vessels 

and aircraft. 

A discontinued industrial waste dump area that was active in the 1970s is located to the 

west-northwest of the lease area. Shell has prepared a BOEMRE-approved plan for “Waste 

Barrel Avoidance and Release Response in the Mississippi Canyon Area” that applies to 

operations that could cause a disturbance of a seafloor barrel. Shell’s over-arching policy is to 

avoid barrel contact. The plan specifies a safe stand-off distance from the waste barrels of 

10 m (33 ft) and requires that potential impact locations be surveyed with an ROV to maximize 

barrel avoidance. In the unlikely event that contact is suspected or has been made with any 

wastes from a barrel, the plan specifies actions to be taken for the topside safety of personnel 

handling the equipment. The plan also outlines barrel impact reporting procedures. There will 

be no anchor impacts because a DP semisubmersible will be used for drilling. 

There are no IPFs from routine project activities that are likely to affect shipping or other 

marine uses. Physical disturbance to the existing well will be prevented by the 152-m (500-ft) 

avoidance zone established around these features. 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. 

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 BOEMRE requirements and lease 

stipulations to avoid impacts on uses of the area by military vessels and aircraft. 

In the event of a large spill requiring numerous vessels in the area, coordination would be 

required to ensure that no anchoring or seafloor-disturbing activities occur near the existing 

pipelines and flowlines. In addition, the procedures detailed in Shell’s Waste Barrel Avoidance 

and Release Response Plan would be adhered to during response to any spill in the 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 Supplemental EP Section 2j. In the unlikely event of a spill, implementation of 

Shell’s OSRP will mitigate and reduce the impacts. Supplemental EP Sections 2j and 9b

provide detail on spill response measures. Therefore, no significant spill impacts on other 

marine uses are expected. 
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C.9 Cumulative Impacts 

For purposes of NEPA, cumulative impact is defined as “the impact on the environment which 

results from the incremental impact of the action when added to other past, present, and 

reasonably foreseeable future actions regardless of what agency (Federal or non-Federal) or 

person undertakes such other actions” (40 CFR 1508.7). Any single activity or action may have 

a negligible impact(s) by itself, but when combined with impacts from other activities in the 

same area and/or time period, substantial impacts may result. 

Prior Studies. MC 984 and 985 were acquired in Lease Sale # 178-1 on 18 March 2001. 

MC 940 was acquired in Lease Sale #205 in October, 2007. Prior to the lease sales, MMS 

prepared a multisale EIS in which it analyzed the environmental impact of activities that might 

occur in the multi-lease-sale area. The MMS also recently analyzed the cumulative impacts of 

OCS development activities similar to those planned in this Supplemental EP in several 

documents. The level and types of activities planned in Shell's Supplemental EP are within the 

range of activities described and evaluated in the Final EIS for Gulf of Mexico OCS Oil and Gas 

Lease Sales 2007-2012: Western Planning Area Sales 204, 207, 210, 215, and 218, and Central 

Planning Area Sales 205, 206, 208, 213, 216, and 222 (MMS, 2007b), as updated by a 2008 

Final Supplemental EIS for Gulf of Mexico OCS Oil and Gas Lease Sales 2009-2012: Central 

Planning Area Sales 208, 213, 216, and 222 and Western Planning Area Sales 210, 215, and 218 

(MMS, 2008). Past, present, and reasonably foreseeable activities were identified in the 

cumulative effects scenario. These documents are incorporated by reference. 

Description of Activities Reasonably Expected to Occur in the Vicinity of Project Area. Shell 

currently is unaware of any projects that are planned to occur in lease blocks adjacent to those 

included in this Supplemental EP. 

Cumulative Impacts of Activities in the Supplemental EP. The MMS (2007b) multi-lease-sale 

EIS included a lengthy discussion of cumulative impacts, which analyzed the environmental 

and socioeconomic impacts from the incremental impact of the 11 proposed lease sales, in 

addition to all activities (including non-OCS activities) projected to occur from past, proposed, 

and future lease sales during the 40-year period of 2007 to 2046 (see EIS page 4-301). The EIS 

considered exploration, delineation, and development wells; platform installation; 

service-vessel trips; and oil spills. The EIS examined the potential cumulative effects on each 

specific resource for the entire Gulf of Mexico. 

The level and type of activity proposed in Shell’s Supplemental EP are within the range of 

activities described and evaluated in the recent multi-lease-sale EISs. This EIA incorporates 

and builds on these analyses by examining the potential impacts on physical, biological, and 

socioeconomic resources from the work planned in this Supplemental EP, in conjunction with 

the other reasonably foreseeable activities expected to occur in the Gulf of Mexico, as well as 

the known impacts from the Macondo spill in MC 252. While another large oil spill could have 

significant impacts, the numerous new safety measures implemented by the BOEMRE and 

further mitigation and safety measures proposed by Shell in its Supplemental EP result in a 

drilling program that reduces the likelihood of another large spill and improves the 

effectiveness of any response in the extremely unlikely event that another large spill occurs. 

Thus, for all impacts, the incremental contribution of Shell’s proposed actions to the 

cumulative impacts analysis in these prior analyses is not significant.
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 68 

C.9.1 Cumulative Impacts to Physical/Chemical Resources 

The work planned in this Supplemental EP is limited in geographic scope and duration, and the 

impacts on the physical/chemical environment will be correspondingly limited. 

Air Quality. Emissions from pollutants into the atmosphere from activities are not projected to 

have significant effects on onshore air quality because of the prevailing atmospheric 

conditions, emission rates and heights, and resulting pollutant concentrations. As the 

BOEMRE found in the multi-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). In 

addition, the cumulative contribution to visibility impairment is also very small (MMS, 2007b, 

2008). Since the BOEMRE completed the multi-lease-sale EISs, USEPA has adopted a new 

short-term NAAQS for nitrogen dioxide. The standard has not yet been implemented in the 

Gulf Coast states, but given the levels of expected emissions and the distance of the project 

from shore, emissions from Shell's Supplemental EP are not likely to contribute to violations of 

any NAAQS onshore. 

Climate Change. Carbon dioxide (CO2) and CH4 emissions from the project would constitute a 

small incremental contribution to greenhouse gas emissions from all OCS activities. According 

to the EIS (MMS, 2007a), estimated CO2 emissions from all OCS activities in the 2007-2012

leasing program are about 0.08% to 0.016% of the global CO2 emissions from fossil fuel 

combustion. Greenhouse gas emissions may contribute to climate change, with important 

effects on temperature, rainfall, frequency of severe weather, ocean acidification, and sea 

level rise (Intergovernmental Panel on Climate Change, 2007). In the Gulf of Mexico, sea level 

rise is an important issue due to the ongoing losses in coastal wetlands, particularly in coastal 

Louisiana. Greenhouse gas emissions from the Supplemental EP represent a negligible 

contribution to the total greenhouse gas emissions from reasonably foreseeable activities in 

the Gulf of Mexico area and would not significantly alter any of the climate change impacts 

evaluated in the previous EISs. Globally, Shell is working to reduce greenhouse gas emissions 

by increasing the efficiency of its operations, establishing a substantial capability in CO2

capture and storage, and continuing to research and develop technologies that increase 

efficiency and reduce emissions in hydrocarbon production. Shell’s direct greenhouse gas 

emissions in 2009 were 11% lower than in 2008 and approximately 35% below the 1990 level 

(Shell, 2009). Shell’s ongoing efforts to reduce greenhouse gas emissions should offset any 

incremental contribution from the Supplemental EP. 

Water Quality. Shell’s project will have some minor water quality impacts due to the 

NPDES-permitted discharge of drilling 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 

ISB of floating oil. Monitoring by the USEPA (2010) has found levels of ozone and particulates 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 69 

ranging from “good” to “unhealthy for sensitive groups” on USEPA’s Air Quality Index; these 

are at levels well below those that would cause short-term health problems. The air 

monitoring conducted to date has not found any pollutants at levels expected to cause 

long-term harm (USEPA, 2010). Satellite imagery indicates that the surface slick from the 

Macondo spill did reach the lease area (ESRI, 2010). However, based on the information 

currently available, there is no reason to expect any change in air quality conditions or 

cumulative impacts from those predicted in the multi-lease-sale EISs. 

The Macondo spill also resulted in water quality impacts. In addition to the oil slick on the sea 

surface, plumes of submerged oil droplets were produced when subsea dispersants were 

applied at the wellhead (Camilli et al., 2010; Hazen et al., 2010; Joint Analysis Group, 

2010a,b,c). Satellite imagery indicates that the surface slick from the Macondo spill did reach 

the lease area (ESRI, 2010), and it is also possible that subsurface plumes could have affected 

water quality in or near the lease area. However, OSAT (2010) reported that, after 

August 2010, waters and sediments in the deepwater Gulf of Mexico beyond 1.8 miles (3 km) 

from the Macondo wellsite were below USEPA acute and chronic benchmarks for PAHs and 

were not hypoxic. These observations indicate that baseline environmental conditions in the 

lease area are unlikely to have been significantly altered by the spill. Prior to the incident, 

water quality in deep, offshore waters was expected to be good, with low levels of 

contaminants (Kennicutt, 2000). Based on the information currently available, there is no 

reason to expect any change in water quality conditions or cumulative impacts from those 

predicted in the multi-lease-sale EISs. 

C.9.2 Cumulative Impacts to Biological Resources 

The work planned in this Supplemental EP is limited in geographic scope and duration, and the 

impacts on biological resources will be correspondingly limited. 

Seafloor Habitats and Biota. Effects on seafloor habitats and biota from discharges of drilling 

mud and cuttings are expected to be minor and limited to a small area. There are no areas 

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

wellsites, in compliance with NTL 2009-G40. Soft bottom communities are ubiquitous along 

the northern Gulf of Mexico continental slope, and the extent of benthic impacts during this 

project is insignificant regionally. As noted in the multi-lease-sale EISs, the incremental 

contributions of activities similar to Shell’s proposed activities to the cumulative impacts is not 

significant (MMS, 2007b, 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 

BOEMRE-required mitigation measures including NTLs 2007-G03 and 2007-G04. No significant 

cumulative impacts are expected. 

Coastal and Marine Birds. Some birds may be attracted to offshore structures because of the 

lights and the fish populations that aggregate around these structures. Birds that frequent 

platforms may be exposed to contaminants including air pollutants and routine discharges, but 

significant impacts are unlikely due to rapid dispersion. Shell’s compliance with NTL 2007-G03 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 70 

will minimize the likelihood of debris-related impacts on birds. Support vessel and helicopter 

traffic may disturb some foraging and resting birds; however, it is likely that individual birds 

would experience, at most, only short-term behavioral disruption. Due to the limited scope, 

timing, and geographic extent of drilling activities, collisions or other adverse effects are 

unlikely, and no significant cumulative impacts are expected. 

Fisheries Resources. Drilling rigs function as FADs for some species of epipelagic fishes; the 

aggregations of prey fishes may potentially attract predators. These short-term effects are 

expected to be small given the isolated nature of the drilling rig and would not be considered a 

significant impact on pelagic communities, fishery resources, or EFH. Many exploration and 

production structures occur in the MC lease blocks proposed for the exploration activities. The 

additional effect of the proposed drilling activity would be negligible. 

Coastal Habitats. Due to the distance of the well sites from shore, routine activities are not 

expected to have any impacts on beaches and dunes, wetlands, seagrass beds, coastal wildlife 

refuges, wilderness areas, or any other managed or protected coastal area. The support bases 

at Port Fourchon and Boothville 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 Initial EP, Shell’s NTL 2010-N06 

response, the OSRP, and herein, the likelihood of a catastrophic well control event resulting in 

significant amounts of oil in the water is extremely remote. Therefore, Shell’s proposed 

activities are not expected to result in any cumulative impacts to biological resources affected 

by the Macondo spill, nor should they have any impact on the previously-conducted 

cumulative impact analyses. 

Regarding deepwater benthic communities, the multi-lease-sale EISs (MMS, 2007a, 2008) 

concluded that oil spills would be unlikely to affect benthic communities beyond the 

immediate vicinity of the wellhead (i.e., due to physical impacts of a blowout) because the oil 

would rise quickly to the sea surface directly over the spill location. However, during the 

Macondo spill, subsurface plumes were reported at a water depth of about 1,100 m (3,600 ft), 

extending at least 22 miles (35 km) from the wellsites and persisting for more than a month 

(Camilli et al., 2010). The subsurface plumes apparently resulted from the use of dispersants 

at the wellhead (Joint Analysis Group, 2010c). This observation is supported by Kujawinski et 

al. (2011) in their report that chemical components of subsea dispersants used during the 

Macondo spill persisted for up to two months and were detected up to 186 miles (300 km) 

from the wellsite at a water depth of 1,000 to 1,200 m (3,280 to 3,937 ft). However, estimated 

dispersant concentrations in the subsea plume were below levels known to be toxic to marine 

life. While the behavior and impacts of subsurface plumes are not well known, a subsurface 

plume could contact the seafloor and affect benthic communities beyond the 300-m (984-ft) 

radius estimated by MMS (2007a, 2008), depending on its extent, trajectory, and persistence. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 71 

This contact could result in smothering and/or toxicity to benthic organisms. The affected area 

would be recolonized by benthic organisms over a period of months to years (NRC, 2003). 

C.9.3 Cumulative Impacts to Socioeconomic Resources 

The work planned in this Supplemental EP is limited in geographic scope and duration, and the 

impacts on socioeconomic resources will be correspondingly limited. 

Archaeological Resources. MC 940, 984, and 985 are on the list of leases with a high potential 

for historic shipwrecks. However, an archaeological assessment by C&C Technologies, Inc. 

(2007) indicated that none of the sonar contacts in the lease area were interpreted as historic 

shipwrecks. Also, the lease area is well beyond the 60-m (197-ft) depth contour used by the 

BOEMRE as the seaward extent for prehistoric archaeological site potential in the Gulf of 

Mexico. Therefore, Shell’s operations will have no cumulative impacts on historic shipwrecks 

or prehistoric archaeological resources. 

Socioeconomic Resources. The multi-lease-sale EISs analyzed the cumulative impacts of oil 

and gas exploration and development in the lease area, in combination with other 

impact-producing activities, on commercial fishing, recreational fishing, recreational resources, 

historical and archaeological resources, land use and coastal infrastructure, demographics, and 

environmental justice (MMS, 2007b, pages 4-359 to 4-378). The BOEMRE also analyzed the 

economic impact of oil and gas activities on the Gulf States, finding only minor impacts in most 

of Texas, Mississippi, Alabama, and Florida, more significant impact in parts of Texas, and 

substantial impact on Louisiana. 

Shell’s proposed activities will have negligible cumulative impacts on socioeconomic resources. 

There are no IPFs associated with routine operations that are expected to affect public health 

and safety, employment and infrastructure, recreation and tourism, land use, or other marine 

uses. Due to the distance from shore, it is unlikely that any recreational fishing activity is 

occurring in the project area, and it is unlikely that any commercial fishing activity other than 

longlining occurs at or near the project area. The project will have negligible impacts on 

fishing activities. 

New Information. The only new, potentially significant information available since preparation 

of the multi-lease-sale EISs is the Macondo spill. The spill has resulted in impacts on 

commercial and recreational fishing, recreation and tourism, employment, and public health 

and safety. The Macondo spill resulted in extensive fishery closures in the Gulf of Mexico, 

peaking at 34.8% of the EEZ in the Gulf of Mexico (NMFS, 2010c). The U.S. Travel Association 

has estimated the economic impact of the Macondo spill on tourism across the Gulf Coast over 

a 3-year period at $22.7 billion (Oxford Economics, 2010). Reported health impacts 

(e.g., among spill response and wildlife rehabilitation workers) ranged from cuts and scrapes, 

to upper respiratory symptoms and heat stress, to acute exposure to hydrocarbons or H2S 

(Centers for Disease Control and Prevention, 2010a,b; Solomon and Janssen, 2010). Most of 

these impacts were temporary in nature, although health exposure of clean-up workers could 

have longer-lasting impacts. 

However, for all the reasons discussed in the Initial EP, Shell’s NTL 2010-N06 response, the 

OSRP, and herein, the likelihood of a catastrophic well control event resulting in significant 

amounts of oil in the water is extremely remote. Therefore, Shell’s proposed activities are not 

expected to result in any cumulative impacts to socioeconomic resources affected by the 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 72 

Macondo spill, nor should they have any impact on the previously-conducted cumulative 

impact analyses. 

D. ENVIRONMENTAL HAZARDS 

D.1 Geologic Hazards 

The shallow hazards assessment included in this Supplemental EP, based on the shallow 

hazards report by GEMS (2007), concludes that the wellsites are free of any major geological 

hazards and are suitable for the proposed activities. See Supplemental EP Section 6a for 

supporting geological and geophysical information. 

D.2 Severe Weather 

Under most circumstances, weather is not expected to have any effect on the proposed 

activities. Extreme weather, including high winds, strong currents, and large waves, was 

considered in the design criteria for the drilling rig. High winds and limited visibility during a 

severe storm could disrupt communication and support activities (vessel and helicopter traffic) 

and make it necessary to suspend some activities on the drilling rig for safety reasons until the 

storm or weather event passes. In the event of a hurricane, procedures in Shell’s Hurricane 

Evacuation Plan would be followed. 

D.3 Currents and Waves 

A rig-based acoustic Doppler current profiler will be used to continuously monitor the current 

beneath the rig. Metocean conditions such as sea states, wind speed, ocean currents, etc. will 

also be continuously monitored. Under most circumstances, physical oceanographic 

conditions are not expected to have any effect on the proposed activities. Strong currents 

(e.g., caused by Loop Current eddies and intrusions) and large waves were considered in the 

design criteria for the drilling rig. High waves during a severe storm could disrupt support 

activities (i.e., vessel and helicopter traffic) and make it necessary to suspend some activities 

on the drilling rig for safety reasons until the storm or weather event passes. 

E. ALTERNATIVES 

No formal alternatives were evaluated in this EIA. However, various technical and operational 

options, including the location of the wellsites and the selection of a drilling unit, were 

considered by Shell in developing the proposed action. There are no other reasonable 

alternatives to accomplish the goals of this project. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 73 

F. MITIGATION MEASURES 

The proposed action includes numerous mitigation measures required by laws, regulations, 

and BOEMRE lease stipulations and NTLs. The project will comply with all applicable Federal, 

State, and local requirements concerning air pollutant emissions, discharges to water, and 

solid waste disposal. All project activities will be conducted under Shell’s OSRP and will include 

the measures described in Supplemental EP Section 2j. Additional pollution prevention 

measures, beyond those required by 30 CFR Part 250, include the following: 

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

safety meetings. The discussion around no harm to people or environment is a key 

mindset. All personnel are reminded daily to inspect work areas for safety issues as well as 

potential pollution issues. 

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

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

• Preventive maintenance of rig equipment includes visual inspection of hydraulic lines and 

reservoirs on a routine scheduled basis. 

• All pollution pans on rig are inspected daily. 

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

and fuel storage tanks. 

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

• 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 collected in a compactor and shipped to shore for disposal. 

• The rig is involved in a recycling program for cardboard, plastic, paper, glass, and 

aluminum. 

• Fuel hoses are changed on annual basis. 

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

• Waste paint thinner is recycled on board with a solvent to further reduce hazards of 

shipping and storage. 

• All equipment on board utilizes Envirorite hydraulic fluid as opposed to hydraulic oil. 

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

• Shell will use low sulfur fuel (0.05% by weight) to reduce air pollutant impacts. 

• Use of a DP rig (no anchors) and high resolution sonar for well location planning will 

minimize the potential for barrel impact. Shell has prepared a BOEMRE-approved plan for 

“Waste Barrel Avoidance and Release Response in the Mississippi Canyon Area” that 

applies to anchoring and other operations that could cause a disturbance of a seafloor 

barrel. The plan specifies a safe stand-off distance from the waste barrels of 10 m (33 ft) 

and requires that anchor locations be surveyed with an ROV to maximize barrel avoidance. 

In the unlikely case that contact is suspected or has been made with any wastes from a 

barrel, the plan specifies actions to be taken for the topside safety of personnel handling 

the equipment. The plan also outlines barrel impact reporting procedures. 
Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 74 

G. CONSULTATION 

No persons or agencies were consulted regarding potential impacts associated with the 

proposed activities during the preparation of this EIA. 

H. PREPARERS 

The EIA was prepared at the direction of Shell Offshore Inc. by its contractor, CSA 

International, Inc. Contributors included the following: 

• Sylvia Bellone (Regulatory Specialist, Shell Exploration & Production Co.); 

• Lori Downs (Environmental Team Leader, Shell Exploration & Production Co.); 

• Rob Kuehn (Environmental Engineer, Shell Exploration & Production Co.); 

• Warren Moity (Environmental Specialist, Shell Exploration & Production Co.); 

• Victoria Broje (Spill Response Specialist, Shell Global Solutions US Inc.); 

• Steve Truchon (Environmental Ecologist, Shell Global Solutions US Inc.); 

• Phil Smith (Incident Command Manager, Shell Exploration & Production Co.); 

• Erling Westlein (Environmental Engineer, Shell Exploration & Production Co.); 

• Tracy Albert (Regulatory Specialist, Offshore Technical Compliance LLC); 

• William Heim (Appraisal Team Leader, Shell Exploration & Production Co.); 

• Aaron Hildebrandt (Geologist, Shell Exploration and Production Co.); 

• Arpad Ozsdolay (Geophysicist, Shell Exploration & Production Co.);

• Carlyle Kalloo (Senior Scientist, CSA International, Inc.); 

• Neal Phillips, Ph.D. (Senior Scientist, CSA International, Inc.); 

• Deborah Fawcett (Project Scientist II, CSA International, Inc.); 

• Stephen Viada (Senior Scientist, CSA International, Inc.); 

• Keith VanGraafeiland (GIS/Remote Sensing Specialist, CSA International, Inc.); and 

• Kim Dunleavy (Technical Editor, CSA International, Inc.). 

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Mississippi Canyon Blocks 940, 984, and 985 May 2011 

Environmental Impact Analysis for Supplemental EP Page 83 

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SECTION 19: Administrative Information

A. Exempted Information Description (Public Information Copies Only) 

The following attachments were excluded from the public information copies of this plan: 

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 

 

B. Bibliography 

3⁄4 GEMS prepared a Geologic, Stratigraphic, and Archeological Assessment on Blocks 940, 984, and 

985 of Mississippi Canyon in October 2007, Project Number 0507-1331. 

3⁄4 C&C Technologies conducted an Archeological Assessment Report in October 2007 on Mississippi 

Canyon Blocks 895-898, 939-942, and 983-986, Project Number 072657-072954.