SECTION 18: ENVIRONMENTAL IMPACT ANALYSIS

INITIAL DEVELOPMENT OPERATIONS COORDINATION DOCUMENT

for

Mississippi Canyon Block 762 (OCS-G 07957)

Mississippi Canyon Block 807 (OCS-G 07963)

Offshore Louisiana

January 2012

Prepared for:

Shell Offshore Inc.

P.O. Box 61933

New Orleans, Louisiana 70161

Telephone: (504) 728-6021 

Prepared by:

CSA International, Inc.

8502 SW Kansas Avenue

Stuart, Florida 34997

Telephone: (772) 219-3000
Introduction

Project Summary

Shell Offshore Inc. (Shell) is submitting an Initial Development Operations Coordination 

Document (DOCD) for Mississippi Canyon Blocks 762 and 807 (MC 762 and 807) that includes 

the installation and operation of a tension leg platform (TLP) in MC 807, drilling and completion 

of 24 development wells in MC 807, and installation of subsea infrastructure to tie back 6 wells 

in MC 762 to the new TLP in MC 807. The 24 wells in MC 807 will be direct vertical access 

(DVA) wells to be drilled from the proposed TLP. Flowlines and sleds will be installed in MC 762 

along with the associated umbilicals, production manifold, and jumpers. Production from MC 

762 will commence to the TLP in MC 807.

Shell submitted a Supplemental Exploration Plan (SEP) for locations in Mississippi Canyon 762 

on April 12, 2011, which was approved by the former Bureau of Ocean Energy Management, 

Regulation and Enforcement (BOEMRE) on July 11, 2011 (Plan Control No. N-9570). Shell also 

submitted an SEP for locations in Mississippi Canyon 807 on August 10, 2011 (Plan Control 

No. S-07499), which was approved on November 22, 2011. 

The lease area is 53 miles (85 km) from the nearest shoreline, 91 miles (146 km) from the 

onshore support base at Port Fourchon, Louisiana, and 82 miles (132 km) from the helicopter 

base at Boothville, Louisiana. All miles in this Environmental Impact Analysis (EIA) are statute 

miles. Water depths at the proposed TLP site and wellsites in MC 807 are approximately 

3,028 ft (923 m) and 3,150 ft (960 m) at the wellsites in MC 762.

The installation of subsea facilities will commence during the last quarter of 2012 followed by 

installation of the TLP in the second quarter of 2013. A platform rig located on the TLP will be 

used for drilling of the DVA wells in MC 807. Drilling & completion of DVA wells will commence 

during the last quarter of 2013 and be completed by the second quarter of 2024. First 

production is anticipated during the last quarter of 2013.

Purpose of the EIA

This EIA was prepared pursuant to the requirements of the Outer Continental Shelf Lands Act 

(OCSLA), 43 U.S.C. §§ 1331-1356, and other regulations, including 30 CFR 550.212(o) and 

550.227. The EIA is a project- and site-specific analysis of Shell‟s planned activities under this 

Initial DOCD. On October 1, 2011, the BOEMRE reorganized into two separate agencies: 

Bureau of Ocean Energy Management (BOEM) and Bureau of Safety and Environmental 

Enforcement (BSEE). Shell understands that the BOEM will review this EIA and prepare a 

Site-Specific Environmental Assessment (SEA) for the project. This EIA complies with guidance 

provided in existing Notice to Lessees and Operators (NTLs) issued by the former Minerals 

Management Service (MMS) and BOEMRE, including NTL 2008-G04. Throughout this EIA, when 

existing guidance and general agency activities are referred to, “BOEM” is meant to subsume 

the former agencies and to represent the continuous regulatory entity now called BOEM. The 

former agency names (MMS and BOEMRE) are used when referring to particular historical 

documents published under those names. In addition, until NTLs are reissued by BOEM and/or 

BSEE, the EIA will refer to the former BOEMRE as BOEM when addressing NTLs.

The EIA presents data, analyses, and conclusions to support BOEM reviews as required by the 

National Environmental Policy Act (NEPA) and other relevant Federal laws, including the 

Endangered Species Act (ESA) and Marine Mammal Protection Act (MMPA). It also identifies 

some of 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 Initial DOCD. The EIA also incorporates 

the revised blowout scenario and worst case discharge (WCD) information required by 

NTL 2010-N06.

The BOEM has performed numerous environmental evaluations of oil and gas activities on the 

Gulf of Mexico Outer Continental Shelf (OCS). Potential impacts were analyzed at a broader 

level in the Programmatic Environmental Impact Statement (EIS) for the OCS Oil and Gas 

Leasing Program (MMS, 2007a) and in multi-lease-sale EISs for the Western and Central Gulf of 

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

Gulf of Mexico deepwater operations and activities (MMS, 2000) and a Grid EA for the Marco 

Polo Project in Green Canyon Block 608 (Grid 13) (MMS, 2003).

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

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

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

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

noise on threatened and endangered species, and other IPFs. The studies inform agency 

decision-making on lease offerings, mitigation measures and lease stipulations, operational 

requirements, and permit restrictions. This substantial body of work, which in part forms the 

basis for the evaluation presented here, will allow the BOEM and other regulatory agencies to 

evaluate Shell‟s Initial DOCD and ensure that oil and gas exploration and development activities 

are performed in an environmentally sound manner, with minimal impacts on the environment. 

Shell has incorporated these comprehensive environmental analyses by reference and built on 

them with project- and site-specific analyses.

OCS Regulatory Framework

The regulatory framework for OCS activities in the Gulf of Mexico has been summarized by 

MMS (2010). Under the OCSLA, the U.S. Department of the Interior (USDOI) is responsible for 

the administration of mineral exploration and development of the OCS. Within the USDOI, the 

BOEM and BSEE are 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 

BSEE offshore regulations are in 30 CFR Parts 250, 251, 252, 254, 256, 270, 282 and the BOEM 

offshore regulations are in 30 CFR Parts 550, 551, 552, 556, 559, 560, 570, 580, 581, 582, 

and 585.

In implementing its responsibilities under the OCSLA and NEPA, the BOEM must consult 

numerous Federal departments and agencies that have authority to govern and maintain ocean 

resources pursuant to other Federal laws. Among these are the U.S. Coast Guard (USCG), 

U.S. Environmental Protection Agency (USEPA), U.S. Fish and Wildlife Service (USFWS), and the 

National Oceanic and Atmospheric Administration (NOAA) through the National Marine Fisheries 

Service (NMFS). Federal regulations establish consultation and coordination processes with 

Federal, State, and local agencies (e.g., the ESA, MMPA, Coastal Zone Management Act of 

1972, and the Magnuson-Stevens Fishery Conservation and Management Act).

NTLs are formal documents issued by the BOEM that provide clarification, description, or 

interpretation of a regulation or standard; provide guidelines on implementing a special lease 

stipulation or regional requirement; provide a better understanding of the scope and meaning 

of a regulation by explaining the BOEM interpretation of a requirement; or transmit 

administrative information such as current telephone listings or changes in BOE personnel or 

office address. Table 1 lists and summarizes the NTLs applicable to this EIA.
Table 1. Notices to Lessees and Operators (NTLs) applicable to this Environmental Impact 

Analysis (EIA).

NTL Title Summary

2012-JOINT-G01

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.

2012-BSEE-G01 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.

2010-N10

Statement of Compliance with 

Applicable Regulations and 

Evaluation of Information 

Demonstrating Adequate Spill 

Response and Well Containment 

Resources

Informs operators using subsea blowout preventers (BOPs) or 

surface BOPs on floating facilities that applications for well 

permits must include a statement signed by an authorized 

company official stating that the operator will conduct all 

activities in compliance with all applicable regulations, 

including the increased safety measures regulations 

(75 FR 63346). Informs operators that the BOEM will be 

evaluating whether each operator has submitted adequate 

information demonstrating that it has access to and can deploy 

containment resources to promptly respond to a blowout or 

other loss of well control.

2010-N06

Information Requirements for 

Exploration Plans, Development 

and Production Plans, and 

Development Operations 

Coordination Documents on the 

OCS

Rescinds the limitations set forth in NTL 2008-G04 regarding a 

blowout scenario and worst case discharge (WCD) scenario, 

and provides guidance regarding the information required in 

blowout scenario and WCD scenario descriptions.

2009-G40 Deepwater Benthic Communities

Guidance for avoiding and protecting high-density deepwater 

benthic communities (including chemosynthetic and 

deepwater coral communities) from damage caused by OCS oil 

and gas activities in water depths greater than 984 ft (300 m). 

Prescribes separation distances of 2,000 ft (610 m) from each 

mud and cuttings discharge location and 250 ft (76 m) from all 

other seafloor disturbances.

2009-G39 Biologically Sensitive Underwater 

Features and Areas

Guidance for avoiding and protecting biologically sensitive 

features and areas (i.e., topographic features, pinnacles, 

low-relief live bottom areas, and other potentially sensitive 

biological features) when conducting OCS operations in water 

depths less than 984 ft (300 m) in the Gulf of Mexico.

2009-G06 Military Warning and Water Test 

Areas

Provides contact links to individual command headquarters for 

the military warning and water test areas in the Gulf of 

Mexico. Lease stipulations require lessees or designated 

operators to enter into an agreement with the appropriate 

individual military command headquarters concerning the 

control of electromagnetic emissions and use of boats and 

aircraft in the applicable warning area or water test area 

before commencing such traffic.

2008-G04

Information Requirements for 

Exploration Plans and 

Development Operations 

Coordination Documents

Guidance on the information requirements for OCS plans, 

including EIA requirements and information regarding 

compliance with the provisions of the Endangered Species Act 

and Marine Mammal Protection Act.
Table 1. (Continued).

NTL Title Summary

2005-G07 Archaeological Resource Surveys 

and Reports

Provides guidance on regulations regarding archaeological 

discoveries, specifies requirements for archaeological resource 

surveys and reports, and outlines options for protecting 

archaeological resources.

Oil Spill Prevention and Contingency Planning

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

BOEM as a fundamental component of the planned drilling program that certifies Shell‟s 

capability to respond to the maximum extent practicable to a WCD (30 CFR §254.2) 

(see DOCD Section 9). The OSRP demonstrates Shell‟s capabilities to rapidly and effectively 

manage oil spills that may result from drilling operations. Despite the extremely low likelihood 

of a large oil spill occurring during the project, Shell has designed its response program based 

upon a regional capability of responding to a range of spill volumes that increase from small 

operational spills to 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 §550 for 

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

Section C (Impact Analysis).
A. Impact-Producing Factors

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

Form BOEM-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:

 TLP and 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 Tension Leg Platform and Drilling Rig Presence (including noise and lights)

The MC 807 DVA wells will be drilled with a platform rig located on the proposed TLP. Offshore 

support vessels will be in the vicinity to provide assistance as necessary.

Drilling operations produce noise that includes strong tonal components at low frequencies, 

including infrasonic frequencies in at least some cases (MMS, 2000). The installation and 

operation of the TLP will also generate noise of variable duration and intensity from machinery. 

Underwater noise from deepwater floating facilities such as the TLP is generally weak due to 

positioning of machinery above the water and the relatively small surface area that comes into 

contact with the water (MMS, 2000). Platforms, including TLPs and drilling rigs, also maintain 

exterior lighting for navigational and aviation safety in accordance with Federal regulations.

A.2 Physical Disturbance to the Seafloor

The installation of the TLP includes the use of non-anchored vessels for the placement of 

16 tendon piles into the seafloor. Shell estimates that the area of disturbance for the 16 

tendon piles is approximately 0.02 ac (0.01 ha). 

The platform drilling rig is located on the TLP and will not directly disturb the seafloor. There 

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

the wellbore and blowout preventers (BOP). Physical disturbance of the seafloor will be limited 

to the proximal area where the wellbore penetrates the substrate. 
Table 2. Matrix of impact-producing factors and affected environmental resources. X = potential impact; dash (--) = no impact or negligible 

impact.

Environmental Resources

Impact-producing Factors

Platform and 

Drilling Rig 

Presence (incl. 

noise & lights)

Physical 

Disturbance 

to Seafloor

Air 

Pollutant 

Emissions

Effluent 

Discharges

Water 

Intake

Onshore 

Waste 

Disposal

Marine 

Debris

Support 

Vessel/Helo 

Traffic

Accidents

Small Fuel 

Spill

Large Oil 

Spill

Physical/Chemical Environment

Air quality -- -- X -- -- -- -- -- X(6) X(6)

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

Seafloor Habitats and Biota

Soft bottom benthic communities -- X -- -- -- -- -- -- -- X(6)

High-density deepwater benthic communities -- --(4) -- --(4) -- -- -- -- -- X(6)

Designated topographic features -- --(1) -- --(1) -- -- -- -- -- --

Pinnacle trend area live bottoms -- --(2) -- --(2) -- -- -- -- -- --

Eastern Gulf live bottoms -- --(3) -- --(3) -- -- -- -- -- --

Threatened, Endangered, and Protected Species and Critical Habitat

Sperm whale (endangered) X(8) -- -- -- -- -- -- X(8) X(6,8) X(6,8)

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

Endangered mysticete whales -- -- -- -- -- -- -- -- -- --

Non-endangered marine mammals (protected) X -- -- -- -- -- -- X X(6) X(6)

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

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

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

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

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

Coastal and Marine Birds

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

Shorebirds and coastal nesting birds -- -- -- -- -- -- -- X -- X(6)

Fisheries Resources

Pelagic communities and ichthyoplankton X -- -- X X -- -- -- X(6) X(6)

Essential Fish Habitat X -- -- X X -- -- -- X(6) X(6)

Archaeological Resources

Shipwreck sites -- --(7) -- -- -- -- -- -- -- X(6)

Prehistoric archaeological sites -- --(7) -- -- -- -- -- -- -- X(6)

Coastal Habitats and Protected Areas

Beaches -- -- -- -- -- -- -- -- -- X(6)

Wetlands and seagrass beds -- -- -- -- -- -- -- X -- X(6)

Coastal wildlife refuges and wilderness areas -- -- -- -- -- -- -- -- -- X(6)

Socioeconomic and Other Resources

Recreational and commercial fishing X -- -- -- -- -- -- -- X(6) X(6)

Public health and safety -- -- -- -- -- -- -- -- -- X(6)

Employment and infrastructure -- -- -- -- -- -- -- -- -- X(6)

Recreation and tourism -- -- -- -- -- -- -- -- -- X(6)

Land use -- -- -- -- -- -- -- -- -- X(6)

Other marine uses -- -- -- -- -- -- -- -- -- X(6)
Table 2 Footnotes and Applicability:

(1) Activities that may affect a marine sanctuary or topographic feature. Specifically, if the well, platform site, or 

any anchors will be on the seafloor within the following:

(a) 4-mi zone of the Flower Garden Banks, or the 3-mi zone of Stetson Bank;

(b) 1,000-m, 1-mi, or 3-mi zone of any topographic feature (submarine bank) protected by the Topographic 

Features Stipulation attached to an Outer Continental Shelf (OCS) lease;

(c) Essential Fish Habitat (EFH) criteria of 500 ft from any no-activity zone; or

(d) Proximity of any submarine bank (500-ft buffer zone) with relief greater than 2 m that is not protected by 

the Topographic Features Stipulation attached to an OCS lease.

 Not applicable. The lease is not within or near any marine sanctuary, topographic feature, or 

no-activity zone. There are no submarine banks in the block.

(2) Activities with any bottom disturbance within an OCS lease block protected through the Live Bottom 

(Pinnacle Trend) Stipulation attached to an OCS lease.

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

(3) Activities within any Eastern Gulf OCS block where seafloor habitats are protected by the Live Bottom 

(Low-Relief) Stipulation attached to an OCS lease. 

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

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

 No impacts on high-density deepwater benthic communities are anticipated. There is minor, shallow 

buried seafloor faulting in the vicinity of the proposed tension leg platform (TLP) and well locations in 

MC 807; however, no high-density chemosynthetic communities or coral communities will be disturbed 

by drilling mud or cuttings discharges or the TLP tendon piles. 

(5) Exploration or production activities where H2S concentrations greater than 500 ppm might be encountered. 

 DOCD Section 4 contains Shell’s request for classification as an area absent of H2S.

(6) All activities that could result in an accidental spill of produced liquid hydrocarbons or diesel fuel that you 

determine would impact these environmental resources. If the proposed action is located a sufficient distance 

from a resource that no impact would occur, the EIA can note that in a sentence or two.

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

analyzed in Section C.

(7) All activities that involve seafloor disturbances, including anchor emplacements, in any OCS block designated 

by the BOEM as having high-probability for the occurrence of shipwrecks or prehistoric sites, including such 

blocks that will be affected that are adjacent to the lease block in which your planned activity will occur. If the 

proposed activities are located a sufficient distance from a shipwreck or prehistoric site that no impact would 

occur, the EIA can note that in a sentence or two.

 No impacts on archaeological resources are expected. The lease is not on the list of high-probability 

blocks for historic shipwrecks (MMS, 2008a). The archaeological survey detected 5,637 unidentified 

sonar contacts within the survey area. The distribution patterns and acoustic characteristics of these 

sonar targets indicate that they are modern debris primarily associated with prior industrial waste 

dumping or field development activities. The lease is beyond the 60-m depth contour and therefore 

prehistoric archaeological sites are not likely; further, no landforms or features were identified that 

might be high probability prehistoric sites. 

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

mammals or sea turtles or their critical habitats. 

 IPFs that may affect marine mammals, sea turtles, or their critical habitats include TLP and 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.
Non-anchored vessels will be used for flowline, jumper, and subsea hardware installation. 

There will be no anchoring impacts, but placement of the subsea equipment on the seafloor will 

directly disturb a small area of seafloor estimated to be less than 1 ac (0.4 ha). Flowlines and 

umbilicals will be installed from multiple locations in MC 762 and MC 807. The total length of 

flowlines is approximately 35,200 ft (10,700 m) and the length of the umbilical is approximately 

17,700 ft (5,400 m). The MMS (2007b) estimated an area of seafloor disturbance area 

between 1.2 ac (0.5 ha) and 2.5 ac (1.0 ha) per kilometer of pipeline or flowline installation. 

Using the upper range value of 2.5 ac (1.0 ha) per kilometer of pipeline or flowline installation, 

the total area disturbed during flowline or pipeline installation is therefore approximately 40 ac 

(16 ha).

By summing this value with the TLP tendon pile impact and the subsea equipment impact, the 

total footprint and seafloor disturbance from these permanent structures is estimated to be 

approximately 40 ac (16 ha).

A.3 Air Pollutant Emissions

Estimates of air pollutant emissions are provided in DOCD Section 8. Offshore air pollutant 

emissions will result from installation activities for the proposed TLP in MC 807 and subsea 

installations in MC 762, production operation activities on the TLP, and operations of the drilling 

rig, service vessels and helicopters. These emissions occur mainly from combustion of diesel 

fuel and/or fuel gas. 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 (see DOCD Section 8) prepared in accordance with BOEM 

requirements shows that the projected emissions from emission sources associated with the 

proposed activities meet the BOEM exemption criteria for PM, SOx, VOCs, and CO. The 

proposed activities are therefore exempt from further air quality review pursuant to 30 CFR 

§550.303(d). Projected emissions from emission sources associated with the proposed 

activities in the TLP and related construction activity years do not meet the BOEM exemption 

criteria for NOx. Once construction activities are completed, annual NOx emissions are predicted 

to be below the BOEM exemption criteria. Air quality dispersion modeling was necessary to 

determine the impact of NOx on onshore ambient air in the years in which projected emissions 

exceed the BOEM exemption criteria. 

Note that whereas the exemption criteria are based on NOx emissions, the modeled significance 

level and the NAAQS are dependent on emissions of nitrogen dioxide (NO2 ) 

[30 CFR §550.303(e)]. Using a conservative approach, emissions of NOx were assumed to be 

NO2 equivalent for modeling purposes. As demonstrated in the air dispersion modeling report 

(see DOCD Section 8), the proposed activities do not exceed the significant impact level for 

the annual averaging period for NO2. Since modeled NO2 concentrations are less than the 

significant impact level for the NO2 annual NAAQS, no further action is required. Additionally, 

when combined with an appropriate background monitored value, modeled NO2 concentrations 

are below the NO2 1-hour NAAQS; therefore, no further action is required.

A.4 Effluent Discharges

Effluent discharges are summarized in DOCD Section 7. Offshore discharges will be in 

accordance with the National Pollutant Discharge Elimination System (NPDES) General Permit 

No. GMG290000 issued by the USEPA. Discharges will be in compliance with and monitored as 

required by the permit.

A synthetic-based mud (SBM) system will be used for drilling activities. Unused or residual SBM 

will be collected and transported to Port Fourchon, Louisiana, for recycling. SBM cuttings will 
be discharged overboard via a downpipe below the water surface, after treatment that complies 

with NPDES permit limitations for SBM fluid retained on cuttings. The estimated volume of SBM 

cuttings to be discharged is provided in DOCD Section 7.

Produced water and process effluents, including well treatment fluids, completion fluids, and 

workover fluids, will be discharged overboard via a downpipe below the water surface, after 

treatment that complies with NPDES permit limitations for these fluids. Other effluent 

discharges may include excess cement, non-contact cooling water, treated sanitary and 

domestic wastes, deck drainage, desalination unit brine, uncontaminated fire water, and ballast 

water. All effluents will comply with monitoring and limitations of the NPDES permit. 

A.5 Water Intake

Seawater will be drawn from several meters below the ocean surface for various services, 

including firewater, utility water, and once-through non-contact cooling of machinery on the 

TLP (DOCD Table 7a).

Section 316(b) of the Clean Water Act requires NPDES permits to ensure that the location, 

design, construction, and capacity of cooling water intake structures (CWIS) reflect the best 

technology available to minimize adverse environmental impact from impingement and 

entrainment of aquatic organisms. The current general NPDES Permit No. GMG290000 

specifies requirements for new facilities for which construction commenced after July 17, 2006 

with a cooling water intake structure having a design intake capacity of greater than 2 million 

gallons of water per day, of which at least 25% is used for cooling purposes. The drilling rig 

and new TLP, however, do not trigger the cooling water intake permit requirements of the 

NPDES permit because the design intake capacity will be less than the 2 million gallons per day 

or 25% cooling water thresholds. . 

The drilling rig and new TLP will be located in the deepwater environment and the seawater 

intakes are located approximately 45 ft below the water surface. Based on Gulf of Mexico data 

from the Southeast Area Monitoring and Assessment Program (SEAMAP), larval fish densities 

decrease with water depth, and are lower in the deepwater environment than in shallower 

water. High flow intakes associated with activation of firewater pumps are infrequent and of 

short duration and the larger fish species that inhabit the deepwater environment have little 

potential for impingement due to their breakaway speed from a challenging intake velocity. As 

noted in this section, cooling water demand is below regulatory thresholds. The operational 

features of the platform combined with the geographical area characteristics suggest that no 

significant impact from intake impingement and entrainment is expected.

A.6 Onshore Waste Disposal

Wastes generated during production activities as well as drilling and completion activities are 

tabulated in DOCD Section 7. Non-hazardous trash and debris and non-recyclable waste will 

be transported to the Jefferson Parish Landfill, Louisiana. Recyclable trash and debris will be 

recycled at Omega Waste Management, Patterson, Louisiana, or ARC, New Iberia, Louisiana. 

Hazardous waste such as paints, solvents, and unused chemicals will be disposed of at Safety 

Kleen Systems, Inc., Denton, Texas, or Lamp Environmental, Hammond, Louisiana. Used oil 

and glycol will be sent to Omega Waste Management for recycling. Exploration and production 

waste, such as sands and sludges will be transported to Newpark Environmental, Fourchon, 

Louisiana. At the onshore facilities, wastes will be recycled or disposed of according to 

applicable regulations.
A.7 Marine Debris

Trash and debris released into the marine environment can harm marine mammals, turtles, and 

birds through entanglement and ingestion. Shell will adhere to the International Convention for 

the Prevention of Pollution from Ships (MARPOL 73/78) Annex V requirements, USEPA and 

USCG regulations, and BOEM regulations and NTLs regarding solid wastes. BOEM regulations 

at 30 CFR §250.300(a) and (b)(6) prohibit operators from deliberately discharging containers 

and other similar materials (e.g., trash and debris) into the marine environment, and 

30 CFR §250.300(c) requires durable identification markings on equipment, tools and containers 

(especially drums), and other material. USCG and USEPA regulations require operators to 

become proactive in avoiding accidental loss of solid waste items by developing waste 

management plans, posting informational placards, manifesting trash sent to shore, and using 

special precautions such as covering outside trash bins to prevent accidental loss of solid waste. 

Shell complies with NTL 2012-BSEE-G01, which instructs operators to exercise caution in the 

handling and disposal of small items and packaging materials, requires the posting of placards 

at prominent locations on offshore vessels and structures, and mandates a yearly marine trash 

and debris awareness training and certification process. Shell‟s compliance with applicable 

laws, regulations, and NTL 2012-BSEE-G01 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.

Marine support for the drilling operation will be from Edison Chouest, Inc. located at Port 

Fourchon, Louisiana. During installation, drilling, and completion activities the project will be 

supported by crew boats, offshore supply vessels, a frac boat, tug boats, installation vessels, 

utility vessels, and helicopters (see DOCD Section 14). Operations will be supported by 

supply vessels and helicopters. There will likely be at least one vessel in the field at all times. 

The supply vessels will normally move to the project area via the most direct route from the 

shorebase. Helicopters will be used to transport personnel and small supplies and will normally 

take the most direct route of travel between the helicopter base and the lease area when air 

traffic and weather conditions permit. Helicopters typically maintain a minimum altitude of 

700 ft (213 m) while in transit offshore, 1,000 ft (305 m) over unpopulated areas or across 

coastlines, and 2,000 ft (610 m) over populated areas and sensitive habitats such as wildlife 

refuges and park properties.

Additional vessels of varying sizes will be used to install and commission the TLP. The duration 

of the main TLP installation and commissioning activities is limited (several months); therefore, 

impacts from this additional traffic is expected to be minimal. 

A.9 Accidents

A.9.1 Types of Accidents Evaluated

The analysis in this EIA focuses on two potential accidents:

 a small fuel spill, which is the most likely type of spill during OCS development activities; and

 an oil spill resulting from an uncontrolled blowout. A blowout resulting in a large oil spill is 

an extremely rare event, and the probability of such an event will be minimized by Shell‟s 

well control and blowout prevention measures as detailed in DOCD Section 2j.

The following subsections summarize assumptions about the sizes and fates of these spills, as 

well as Shell‟s spill response plans. Impacts are analyzed in Section C.
The lease sale EIS (MMS, 2007b) analyzes three other types of accidents: chemical spills, vessel 

collisions, and loss of well control. These accidents are discussed briefly in Section A.9.4.

A.9.2 Small Fuel Spill

Spill Size. According to the analysis in MMS (2007b), the most likely type of small spill 

(<1,000 barrels [bbl]) as a result of OCS activities is a minor diesel fuel spill. Historically, most 

diesel spills have been <1 bbl, and this size is predicted to be the most common in ongoing and 

future OCS activities in the Western and Central Gulf of Mexico Planning Areas (MMS, 2007b). 

The average size for spills <1 bbl is 0.07 bbl, and the median size for spills of 1 to 10 bbl is 

3 bbl (MMS, 2007b). For this analysis, a small diesel fuel spill of 3 bbl is assumed. Operational 

experience suggests that the most likely cause of such a spill would be a hose rupture resulting 

in the loss of the contents of a fuel transfer hose, which is less than 3 bbl.

Spill Fate. The fate of a small fuel spill in the lease area would depend on meteorological and 

oceanographic conditions at the time, as well as the effectiveness of spill response activities. 

However, given the open ocean location of the lease area, the duration of a small spill and the 

opportunity for impacts to occur would be very brief.

The water-soluble fractions of diesel are dominated by two- and three-ringed polycyclic 

aromatic hydrocarbons (PAHs), which are moderately volatile (National Research Council [NRC], 

2003). The constituents of these oils are light to intermediate in molecular weight and can be 

readily degraded by aerobic microbial oxidation. Diesel‟s density is such that it will not sink 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 Automated Data Inquiry for Oil 

Spills 2 (ADIOS2) model. This model uses the physical properties of oils in its database to 

predict the rate of evaporation and dispersion over time, as well as changes in the density, 

viscosity, and water content of the product spilled. It is estimated that over 90% of a small 

diesel spill would be evaporated or dispersed within 24 hours. The area of the sea surface with 

diesel fuel on it would range from 1.2 to 12 ac (0.5 to 5 ha) depending on sea state and 

weather conditions.

The ADIOS2 results, coupled with spill trajectory information discussed below for a large spill, 

indicate that a small fuel spill would not affect coastal or shoreline resources. The lease area 

(MC 762 and 807) is approximately 53 miles (85 km) from the nearest coastline (Louisiana). 

Modeling results discussed below indicate that a spill in the lease area would have no shoreline 

contact within 3 days and a 4% probability of contacting the nearest Louisiana shoreline 

(Plaquemines Parish) within 10 days after a spill. After 3 days, essentially 100% of a small fuel 

spill would have dispersed or evaporated by natural processes, even if no response measures 

were implemented. MMS (2007b) similarly concluded that spills <1,000 bbl are not expected to 

persist as a slick on the surface of the water beyond a few days and are unlikely to make 

landfall or reach coastal waters prior to breaking up. MMS (2007b) noted that this conclusion is 

supported by a previous analysis of 3-day trajectory model runs, previous weathering analyses, 

and historical records of spill incidents.

Spill Response. In the unlikely event of a fuel spill, response equipment and trained personnel 

would be available to ensure that spill effects are localized and would result only in short-term 

localized environmental consequences. DOCD Section 9b provides a detailed discussion of 

Shell‟s response to a spill.
A.9.3 Large Oil Spill

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

event will be minimized by Shell‟s well control and blowout prevention measures detailed in 

DOCD Section 2j. Blowouts are rare events and most do not result in oil spills. Holand 

(1997) estimated a probability of 0.00142 for a blowout during deep development drilling based 

on U.S. Gulf of Mexico data. An updated analysis using the SINTEF database estimates a 

blowout frequency of 0.00035 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 

the blowouts in the Gulf of Mexico lasted less than half a day, and fewer than 10% of blowouts 

resulted in spilled oil.

The risk of a blowout during this project is lower than indicated by these statistics because the 

well design and drilling program were developed using information gathered during drilling of 

the previous wells in MC 807. During drilling of the previous wells, the reservoirs were logged 

and evaluated. Substantial data associated with the reservoirs were gathered including core, 

pressure, and fluid data. Data gained during these earlier operations provide substantial 

information that was used in preparing for the proposed operation.

Spill Size. Shell has calculated a WCD for this Initial DOCD, using the requirements prescribed 

by NTL 2010-N06. The WCD is 446,000 bbl for the first day with a 30-day average of 

359,500 barrels of oil per day (BOPD). The detailed analysis of this calculation can be found in 

DOCD Section 2j. The WCD scenario for this Initial DOCD, in terms of both initial and the 

sustained rates, has a low probability of being realized. Some of the factors that are likely to 

reduce rates and volumes, which are not included in the WCD calculation, include, but are not 

limited to, obstructions or equipment in the wellbore, well bridging, and early intervention such 

as containment.

Shell has a robust system in place to prevent blowouts. Included in DOCD 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, the launch area nearest to the lease 

area) 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, 

including 2 Texas counties, 8 Louisiana parishes and 1 Florida county 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, 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%).

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 BOEM to evaluate contact probabilities for spills greater than 1,000 bbl.

Weathering. Following an oil spill, several physical, chemical, and biological processes, 

collectively called weathering, interact to change the physical and chemical properties of the oil, 

and thereby influence its harmful effects on marine organisms and ecosystems. The most 

important weathering processes include spreading, evaporation, dissolution, dispersion into the 

water column, formation of water-in-oil emulsions, photochemical oxidation, microbial 

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

seafloor (NRC, 2003).

Weathering decreases the concentration of oil and produces changes in its chemical 

composition, physical properties, and toxicity. The more toxic, light aromatic and aliphatic 

hydrocarbons are lost rapidly by evaporation and dissolution from the slick on the water 

surface. Evaporated hydrocarbons are degraded rapidly by sunlight. Biodegradation of oil on 

the water surface and in the water column by marine bacteria removes first the n-alkanes and 

then the light aromatics from the oil. Other petroleum components are biodegraded more 

slowly. Photooxidation attacks mainly the medium and high molecular weight PAHs in the oil 

on the water surface.

Spill Response. Shell is a founding member of the Marine Well Containment Company (MWCC) 

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

rapidly deployed through the MWCC. The MWCC is a non-profit organization that assists with 

the subsea containment system during a response. The near-term containment response 

capability will be specifically addressed in Shell‟s NTL 2010-N10 submission at the time an 

Application for Permit to Drill 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, Marine Spill Response Corporation, Clean Gulf 

Associates, and Oil Spill Response Limited, organizations that are committed to providing the 

resources necessary to respond to a spill as outlined in Shell‟s OSRP.

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

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

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

deepwater (see page 17 of the Decision Memorandum dated 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 well control incident. Shell 

is also investing in research and development to improve containment systems.
Mechanical recovery capabilities are addressed in the OSRP. The primary mechanical recovery 

response equipment that could be mobilized to the spill location for spills in normal and adverse 

weather conditions is included in the Offshore On-Water Recovery Activation List in the OSRP.

Chemical dispersion capabilities are also readily available from resources identified in the 

OSRP. Available equipment for surface and subsea application of dispersants, response times, 

and support resources are identified in the OSRP.

Open-water in situ burning may also be used as a response strategy, depending on the 

circumstances of the release. If appropriate conditions exist and approval from the Unified 

Command is received, one or multiple in situ burning task forces could be deployed offshore.

See DOCD Sections 2j and 9b for a detailed description of Shell‟s site-specific response to a 

large spill for this plan. These sections, along with Shell‟s OSRP, also include a description of 

surface and subsea containment capabilities that could be implemented in the event of a large 

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 Initial DOCD. The analysis in the lease sale EIS for these topics is 

incorporated by reference.

Chemical Spill. Chemicals are used in drilling and producing operations to achieve technical 

goals in the drilling process, improve the efficiency and safety of drilling, and protect associated 

equipment. Chemicals used during drilling include surfactants, bentonite clays, olefins, 

inorganic salts, glycols, polymers, barite, and calcium carbonate. Supplies are renewed on a 

regular basis by transfer in containers from supply boats (Boehm et al., 2001). In addition to 

chemicals used in drilling fluids, the following chemicals are likely to be used on the rig: 

ethylene glycol (blowout prevention control fluid, used in closed cooling loops for crane and 

main engines and brake coolers), cement (used to cement casing in place), solvents (used in 

painting operations), hydraulic fluids (used in cranes and other hydraulic rig equipment), 

lubricating oil and grease (used in reciprocating and electrical equipment), and sodium 

hypochlorite (dilute, used as laundry bleach and disinfectant).

A study of environmental risks of chemical products used in OCS activities determined that only 

two chemicals could potentially affect the marine environment: zinc bromide and ammonium 

chloride (Boehm et al., 2001). The project addressed by this Initial DOCD does not anticipate 

the use of ammonium chloride but will use zinc bromide during well completion. Most other 

chemicals are either nontoxic or used in small quantities. Spill response capabilities are 

addressed in the OSRP. No significant impacts are expected from chemical spills. 

Vessel Collisions. As summarized in MMS (2007b), vessel collisions occasionally occur during 

routine operations. Most collision mishaps are the result of service vessels colliding with 

platforms or vessel collisions with pipeline risers. Some of these collisions have caused spills of 

diesel fuel or chemicals. Shell will comply with USCG and BOEM-mandated safety requirements 

to minimize the potential for vessel collisions.

Loss of Well Control. A loss of well control is the uncontrolled flow of a reservoir fluid that may

result in the release of gas, condensate, oil, drilling fluids, sand, or water. Loss of well control 

is a broad term that includes minor to serious well control incidents, while blowouts are 

considered to be a subset of more serious incidents with greater risk of oil spill or human injury 

(MMS, 2007b). Loss of well control may result in the release of oil. Shell has a robust system 
in place to prevent loss of well control. Included in this Initial DOCD 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 DOCD Sections 2j and 9b for 

further information.

H2S Release. DOCD Section 4 contains Shell‟s request for classification as an area absent of 

H2S.

B. Affected Environment

The lease area is on the continental slope in the northwestern Gulf of Mexico, 53 miles (85 km) 

from the nearest shoreline, 91 miles (146 km) from the onshore support base at Port Fourchon, 

Louisiana, and 82 miles (132 km) from the helicopter base at Boothville, Louisiana.

The wellsites in MC 807 are at a water depth of approximately 3,028 ft (923 m) (DOCD 

Figure 1b). There are minor, shallow seafloor and buried landslide features within the vicinity 

of the wellsite locations and the proposed TLP in MC 807; however, no high-density areas of 

chemosynthetic communities will be disturbed. The installations in MC 762 (UTA, EDM, 

manifold, and PLETs) are at a water depth of approximately 3, 150 ft (960 m). These subsea 

facilities will be located near the center of a near-surface ancient slump valley, but no 

high-density areas of chemosynthetic communities will be disturbed. 

The archaeological assessment confirmed the existence of modern debris primarily associated 

with prior industrial waste dumping or field development activities. A historical industrial waste 

dump site has been identified west of MC 807 and south of MC 762, in MC 806. This dump site 

received containerized wastes until the site was closed. Shell‟s procedure “Waste Barrel 

Avoidance and Release Response in the Mississippi Canyon Area,” which has been previously 

approved by MMS and BOEM1, is included in DOCD Section 6a and 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 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.

The high-resolution geophysical survey included frequency enhanced three-dimensional seismic, 

enhanced surface renderings (ESRs), ESRs with amplitudes applied, and an autonomous 

underwater vehicle survey. According to the results of this survey, the proposed wellsite 

locations and proposed TLP in MC 807 as well as locations for the subsea facilities in MC 762 

appear suitable for the planned activity (C&C Technologies, 2009).

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

(MMS, 2007b, 2008b), including meteorology, oceanography, geology, air and water quality, 

benthic communities, threatened and endangered species, biologically sensitive resources, 

archaeological resources, socioeconomic conditions, and other marine uses. These regional 

descriptions are based on extensive literature reviews and are incorporated by reference. 

 

1

MMS approval of West Boreas Supplemental Exploration Plan, MS 5231 December 16, 2008, Control No. S-07273, Mississippi 

Canyon Area Block 762, Lease OCS-G 07957; Mississippi Canyon Area Block 806, Lease OCS-G 07962 and BOEM approval of 

the Supplement to the Conceptual Deepwater Operations Plan for Mars B project, August 12, 2010, MS 5220.
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.

Other than the aforementioned seafloor features, the local environment in the lease area is not 

known to be unique with respect to physical/chemical, biological, or socioeconomic conditions. 

Baseline environmental conditions in the lease area are expected to be consistent with the 

regional description of continental slope locations evaluated in recent lease sale EISs 

(MMS, 2007b, 2008b).

The lease area is approximately 65 miles (104 km) southwest of the Macondo spill site. Based 

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

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

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

Impacts) where available and applicable.

C. Impact Analysis

This section analyzes the potential direct and indirect impacts of routine activities and 

accidents. Cumulative impacts are discussed in Section C.9.

Impacts have been analyzed extensively in recent multi-lease-sale EISs for the Western and 

Central Gulf of Mexico Planning Areas (MMS, 2007b, 2008b) 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 Green Canyon Block 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 August 30, 2011, Louisiana, Mississippi, Alabama, and Florida coastal counties and 

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

metropolitan area in Texas (Houston-Galveston-Brazoria) is a nonattainment area for 8-hour 

ozone.

Winds in the region are driven by the clockwise circulation around the Bermuda High 

(MMS, 2007b). The Gulf of Mexico is located to the southwest of this center of circulation, 

resulting in a prevailing southeasterly to southerly flow, which is conducive to transporting 

emissions toward shore. However, circulation is also affected by tropical cyclones (hurricanes) 

during summer and fall and by extratropical cyclones (cold fronts) during winter.

IPFs potentially affecting air quality are air pollutant emissions and two types of accidents: 

a small fuel spill and a large oil spill.

Impacts of Air Pollutant Emissions

Air pollutant emissions are the only routine IPF likely to affect air quality. Offshore air pollutant 

emissions will result from the installation activities for the proposed TLP in MC 807 and subsea 
installations in MC 762, production operation activities on the TLP, and operation of the drilling 

rig, helicopters and service vessels. These emissions occur mainly from combustion or burning 

of diesel fuel and/or fuel gas. 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 

impact air quality along the coast. As noted in the lease sale EIS (MMS, 2007b), emissions of 

air pollutants from routine activities in the Central Gulf of Mexico Planning Area are projected to 

have minimal impacts on onshore air quality because of the prevailing atmospheric conditions, 

emission heights, emission rates, and the distance of these emissions from the coastline.

The Air Quality Emissions Report (see DOCD Section 8) prepared in accordance with BOEM 

requirements shows that the projected emissions from emission sources associated with the 

proposed activities meet the BOEM exemption criteria for PM, SOx, VOCs, and CO. The 

proposed activities are therefore exempt from further air quality review pursuant to 30 CFR 

§550.303(d). Projected emissions from emission sources associated with the proposed 

activities in the TLP and related construction activity years do not meet the BOEM exemption 

criteria for NOx. Once construction activities are completed, annual NOx emissions are predicted 

to be below the BOEM exemption criteria. Air quality dispersion modeling was necessary to 

determine impact of NOx on onshore ambient air in the years in which projected emissions 

exceed the BOEM exemption criteria. 

Note that whereas the exemption criteria are based on NOx emissions, the modeled significance 

level and the NAAQS are dependent on emissions of nitrogen dioxide (NO2) [30 CFR §

550.303(e)]. Using a conservative approach, emissions of NOx were assumed to be NO2

equivalent for modeling purposes. As demonstrated in the air dispersion modeling report 

(see DOCD Section 8), the proposed activities do not exceed the significant impact level for 

the annual averaging period for NO2. Since modeled NO2 concentrations are less than the 

significant impact level for the NO2 annual NAAQS, no further action is required. Additionally, 

when combined with an appropriate background monitored value, modeled NO2 concentrations 

are below the NO2 1-hour NAAQS; therefore, no further action is required.

The Breton Wilderness Area, which is part of the Breton National Wildlife Refuge (NWR), is 

designated under the Clean Air Act as a Prevention of Significant Deterioration (PSD) Class I air 

quality area. The BOEM coordinates with the National Park Service (NPS) and the USFWS if 

emissions from proposed projects may affect the Breton Class I area. Additional review and 

mitigation measures may be required for sources within 186 miles (300 km) of the Breton 

Class I area that exceed emission limits agreed upon by the administering agencies (NPS, 

2010). The lease area is approximately 87 miles (140 km) from the Breton Wilderness Area. 

As demonstrated in the air dispersion modeling report (see DOCD Section 8), Shell does not 

anticipate impact on the Class I area, but will comply with requirements as directed by the 

BOEM.

Impacts of a Small Fuel Spill

Potential impacts of a small spill on air quality are expected to be consistent with those 

analyzed and discussed in recent EISs (MMS, 2007b, 2008b). The probability of a small spill 

would be minimized by Shell‟s preventative measures during routine operations, including fuel 

transfer. In the unlikely event of a spill, implementation of Shell‟s OSRP will mitigate and 

reduce the impacts. DOCD 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 likely affect air quality near the spill site by introducing VOCs through 

evaporation. The ADIOS2 model (see Section A.9.2) indicates that more than 90% of a small 
diesel spill would be evaporated or dispersed within 24 hours. The area of the sea surface with 

diesel fuel on it would range from 1.2 to 12 ac (0.5 to 5 ha) depending on sea state and 

weather conditions.

A small fuel spill would not affect coastal air quality because the spill would not be expected to 

make landfall or reach coastal waters prior to breaking up (see Section A.9.2).

Impacts of a Large Oil Spill

Potential impacts of a large oil spill on air quality are expected to be consistent with those 

analyzed and discussed in recent EISs (MMS, 2007b, 2008b).

A large oil spill would likely affect air quality by introducing VOCs through evaporation from the 

slick. The extent and persistence of impacts would depend on the meteorological and 

oceanographic conditions at the time and the effectiveness of spill response measures. 

Additional air quality impacts could occur if response measures included in situ burning of the 

floating oil. Burning would generate a plume of black smoke and result in emissions of NOx, 

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

Due to the lease area location (53 miles [85 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 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 

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

and reduce the impacts. DOCD 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. 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. There are localized occurrences of natural seepage of oil, gas, and brines in 

near-surface sediments that may move up into the water column.

The lease area is approximately 65 miles (104 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 water quality in the lease area could have been temporarily affected. The 

Operational Science Advisory Team (OSAT, 2010) reported that after August 2010, waters and 

sediments in the deepwater Gulf of Mexico beyond 1.8 miles (3 km) from the Macondo wellsite 

were below USEPA acute and chronic benchmarks for PAHs and were not hypoxic. These 

observations indicate that baseline environmental conditions in the lease area are unlikely to 

have been significantly altered by the spill.

IPFs potentially affecting water quality are effluent discharges and two types of accidents: 

a small fuel spill and a large oil spill.

Impacts of Effluent Discharges

Discharges of treated SBM cuttings will produce temporary, localized increases in suspended 

solids in the water column around the TLP and drilling rig. In general, turbid water can be 
expected to extend between a few hundred meters and several kilometers down current from 

the discharge point (NRC, 1983; Neff, 1987). NPDES permit limitations and requirements will 

be met. After discharge, SBM retained on cuttings would be expected to adhere tightly to the 

cuttings particles and, consequently, would not produce much turbidity as the cuttings sink 

through the water column (Neff et al., 2000). There will be no persistent impacts on water 

quality in the lease area.

Treated sanitary and domestic wastes may have a slight transient effect on water quality in the 

immediate vicinity of these discharges. NPDES permit limitations and requirements will be met 

and little or no impact on water quality is anticipated.

Potential constituents in produced water, including salts, petroleum hydrocarbons, some metals, 

and naturally occurring radioactive material, may degrade water quality in the immediate 

vicinity of the discharge point. Compliance with NPDES permit requirements would result in only 

short-term localized impacts to receiving waters (MMS 2007b).

Deck drainage includes 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 TLP and drilling rig will flow overboard without treatment. However, rainwater that 

falls on the drilling rig and TLP decks 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 and construction vessels will discharge rain water and treated sanitary and domestic 

wastes. These will have a slight effect on water quality in the immediate vicinity of the 

discharges. Support vessel discharges will be in accordance with USCG regulations and, as 

applicable, the NPDES Vessel General Permit, and therefore are not expected to cause 

significant impacts on water quality.

Impacts of a Small Fuel Spill

Potential impacts of a small spill on water quality are expected to be consistent with those 

analyzed and discussed in recent EISs (MMS, 2007b, 2008b). The probability of a small spill 

would be minimized by Shell‟s preventative measures during routine operations, including fuel 

transfer. In the unlikely event of a spill, implementation of Shell‟s OSRP will mitigate and 

reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Given the open ocean location of the lease area, the extent and duration of water quality 

impacts from a small spill would not be significant.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the 

concentrations of petroleum hydrocarbons and their degradation products. The extent and 

persistence of impacts would depend on the meteorological and oceanographic conditions at 

the time and the effectiveness of spill response measures. However, it is estimated that more 

than 90% of a small diesel spill would be evaporated or dispersed within 24 hours 

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

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

The water-soluble fractions of diesel are dominated by two- and three-ringed PAHs, which are 

moderately volatile (NRC, 2003). The constituents of these oils are light to intermediate in 

molecular weight and can be readily degraded by aerobic microbial oxidation. Diesel‟s density 

is such that it will not sink and pool on the seafloor. Diesel dispersed in the water column can 
adhere to suspended sediments, but this generally occurs only in coastal areas with 

high-suspended solid loads (NRC, 2003) and would not be expected to occur to any appreciable 

degree in offshore waters of the Gulf of Mexico. Diesel oil is readily and completely degraded 

by naturally occurring microbes (NOAA, 2006).

A small fuel spill would not affect coastal water quality because the spill would not be expected 

to make landfall or reach coastal waters prior to breaking up (see Section A.9.2).

Impacts of a Large Oil Spill

Potential impacts of a large oil spill on water quality are expected to be consistent with those 

analyzed and discussed in recent EISs (MMS, 2007b, 2008b). A large spill would likely affect 

water quality by producing a slick on the water surface and increasing the concentrations of 

petroleum hydrocarbons and their degradation products. The extent and persistence of 

impacts would depend on the meteorological and oceanographic conditions at the time and the 

effectiveness of spill response measures. Most of the oil would be expected to form a slick at 

the surface, although observations following the Macondo spill indicate that plumes of 

submerged oil droplets can be produced when subsea dispersants are applied at the wellhead 

(Camilli et al., 2010; Hazen et al., 2010; Joint Analysis Group, 2010a,b,c). A report by 

Kujawinski et al. (2011) indicates that chemical components of subsea dispersants used during 

the Macondo spill persisted for up to two months and were detectable up to 186 miles (300 km) 

from the wellsite at a water depth of 3,280 to 3,937 ft (1,000 to 1,200 m).

Once oil enters the ocean, a variety of physical, chemical, and biological processes act to 

disperse the oil slick. These processes include spreading, evaporation of the more volatile 

constituents, dissolution into the water column, emulsification of small droplets, agglomeration 

sinking, microbial modification, photochemical modification, and biological ingestion and 

excretion (NRC, 2003). Marine water quality would be temporarily affected by the dissolved 

components and small oil droplets that do not rise to the surface or are mixed down by surface 

turbulence. Dispersion by currents and microbial degradation removes the oil from the water 

column or dilutes the constituents to background levels.

A large oil spill could result in a release of gaseous hydrocarbons that could affect water quality. 

During the Macondo spill, large volumes of methane (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 showed slight depression of dissolved oxygen concentrations 

relative to climatological background values, the findings were not indicative of hypoxia 

(<2.0 mg/L) (OSAT, 2010). Stations revisited around the Macondo wellhead in October 2010 

showed no measurable oxygen depressions (OSAT, 2010).

Due to the lease area location (53 miles [85 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 to be affected.

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

event will be minimized by Shell‟s well control and blowout prevention measures detailed in 

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

and reduce the impacts. DOCD 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 in MC 762 and 807 are approximately 

3,150 ft (960 m) and 3,028 ft (923 m) respectively. See DOCD Section 6a for further 

information.

According to the BOEM (2011a), existing information for the deepwater Gulf of Mexico indicates 

that the seafloor is composed primarily of soft sediments; hard bottom communities are rare. 

MC 762 and 807 are within deepwater Grids 12 and 13, respectively, where remotely operated 

vehicle (ROV) coverage of the seafloor is considered adequate to characterize the area 

(BOEM, 2011b).

C.2.1 Soft Bottom Benthic Communities

Data from the 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

14 mi (23 km) 

W

990 885,995 4,924 1,034

MT-4

26 mi (42 km) 

SSW 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 

220,000 to 890,000 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 depth of the wellsites are 

expected to be about 3,400 individuals/m2, lower than the values in station MT-3 and similar to 

station MT-4 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 2,050 to 5,997 ft (625 to 1,828 m). The five most 

abundant species in Zone 2E are 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 200 to 3,000 individuals/ha were reported from other stations in a similar depth 

range. Common megafauna included motile groups such as decapods, ophiuroids, 

holothurians, and demersal fishes, as well as sessile groups such as sponges and anemones.

Bacteria are also an important component in terms of biomass and cycling of organic carbon 

(Cruz-Kaegi, 1998). Bacterial biomass at the depth range of the lease area typically is about 

1 to 2 grams of carbon per square meter (g C m−

2

) in the top 6 in. (15 cm) of sediments 

(Rowe and Kennicutt, 2009).

IPFs potentially affecting benthic communities are physical disturbance to the seafloor, effluent 

discharges (drilling mud and cuttings), and a large oil spill resulting from a well blowout at the 

seafloor. A small fuel spill would not affect benthic communities because the diesel fuel would 

float and dissipate on the sea surface.

Impacts of Physical Disturbance to the Seafloor

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

activities proposed in this Initial DOCD. The total seafloor disturbance area is estimated to be 

approximately 40 ac (16 ha) for the subsea facilities in MC 762 and TLP in MC 807. The 

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

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

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

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

basis.

Impacts of Effluent Discharges

Discharges of treated SBM cuttings from the rig may affect benthic communities, primarily 

within several hundred meters of the wellsites. The fate and effects of SBM cuttings have been 

reviewed by Neff et al. (2000), and monitoring studies have been conducted in the Gulf of 

Mexico by Continental Shelf Associates, Inc. (2004, 2006). In general, cuttings with adhering 

SBM tend to clump together and form thick cuttings piles close to the drillsite. Areas of 

SBM cuttings deposition may develop elevated organic carbon concentrations and anoxic 

conditions (Continental Shelf Associates, Inc., 2006). Where SBM cuttings accumulate and 

concentrations exceed approximately 1,000 mg/kg, benthic infaunal communities may be 

adversely affected due to both the toxicity of the base fluid and organic enrichment (with 

resulting anoxia) (Neff et al., 2000). Infaunal numbers may increase and diversity may 

decrease as opportunistic species that tolerate low oxygen and high H2S predominate 

(Continental Shelf Associates, Inc., 2006). As the base synthetic fluid is decomposed by 

microbes, the area will gradually return to pre-drilling conditions. Disturbed sediments will be 

recolonized through larval settlement and migration from adjacent areas.

The areal extent of impacts from drilling discharges will be small; the typical effect radius is 

1,640 ft (500 m) around each wellsite. The 23 surface locations in this development drilling 

program and 1 well that will be completed are DVA wells from the new TLP, therefore, the total 

impact area would be approximately equivalent to that of one well, which is 195 ac (79 ha). 

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

(Gallaway, 1988; Gallaway et al., 2003; Rowe and Kennicutt, 2009). Impacts from drilling 

discharges during this project will have no significant impact on soft bottom benthic 

communities on a regional basis.

Impacts of a Large Oil Spill

The most likely effects of a subsea blowout on benthic communities would be within a few 

hundred meters of the wellsites. The MMS (2007b) estimates that a severe subsurface blowout 
could resuspend and disperse sediments within a 984-ft (300-m) radius. While coarse 

sediments (sands) would probably settle at a rapid rate within 1,312 ft (400 m) from the 

blowout site, fine sediments (silts and clays) could be resuspended for more than 30 days and 

dispersed over a much wider area. Previous studies characterized surface sediments in the 

vicinity of the site as about 50% clay and 45% silt (Rowe and Kennicutt, 2009).

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect 

benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical 

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the spill 

location. However, during the Macondo spill, subsurface plumes were reported at a water 

depth of about 3,600 ft (1,100 m), extending at least 22 miles (35 km) from the 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). Chemical 

components of subsea dispersants used during the Macondo spill persisted for up to two 

months and were detected up to 186 miles (300 km) from the wellsite at a water depth of 

3,280 to 3,937 ft (1,000 to 1,200 m) (Kujawinski et al. 2011). However, estimated dispersant 

concentrations in the subsea plume were below levels known to be toxic to marine life. While 

the behavior and impacts of subsurface plumes are not well known, a subsurface plume could 

contact the seafloor and affect benthic communities beyond the 984-ft (300-m) radius 

estimated by MMS (2007a, 2008), depending on its extent, trajectory, and persistence. This 

contact could result in smothering and/or toxicity to benthic organisms. The affected area 

would be recolonized by benthic organisms over a period of months to years (NRC, 2003).

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on soft bottom communities are expected.

C.2.2 High-Density Deepwater Benthic Communities

As defined by NTL 2009-G40, high-density deepwater benthic communities are features or 

areas that could support high-density chemosynthetic communities, high-density deepwater 

corals, or other associated high-density hard bottom communities. Chemosynthetic 

communities were discovered in the central Gulf of Mexico in 1984 and have been studied 

extensively (MacDonald, 2002). Deepwater coral communities are also known from numerous 

locations in the Gulf of Mexico (Brooke and Schroeder, 2007; CSA International, Inc., 2007). 

These communities occur almost exclusively on authigenic carbonates created by 

chemosynthetic communities, and on shipwrecks. The nearest known chemosynthetic 

community site is located approximately 43 miles (68 km) from MC 762 (Brooks et al., 2009).

None of the known high-density deepwater benthic community locations listed in 

NTL 2009-G40 are in MC 762 and 807 or adjacent blocks. The chemosynthetic community 

assessment by C&C Technologies (2009) did not identify features that could support highdensity deepwater benthic communities within 2,000 ft (610 m) of the proposed drilling mud 

and cuttings discharge locations (see DOCD Section 6a for additional information).

IPFs potentially affecting high-density deepwater benthic communities are physical disturbance 

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

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

diesel fuel would float and dissipate on the sea surface.
Impacts of Physical Disturbance to the Seafloor

The chemosynthetic community assessment by C&C Technologies (2009) did not identify 

features that could support high-density deepwater benthic communities within 2,000 ft 

(610 m) of the proposed drilling mud and cuttings discharge locations (see DOCD Section 6a

for additional information).

Impacts of Effluent Discharges

The chemosynthetic community assessment included in this Initial DOCD did not identify 

features that could support high-density deepwater benthic communities within 2,000 ft 

(610 m) of the proposed drilling mud and cuttings discharge locations (C&C Technologies, 

2009). Monitoring programs on the Gulf of Mexico continental slope have shown that benthic 

impacts from drilling discharges typically are concentrated within about 1,640 ft (500 m) of the 

wellsites, although detectable deposits may extend beyond this distance (Continental Shelf 

Associates, Inc., 2004, 2006; Neff et al., 2005). If high-density deepwater communities are 

associated with any distant expulsion features identified in the hazards survey, significant 

impacts on these communities will be avoided because of the distance from the discharge 

location.

Impacts of a Large Oil Spill 

Previous analyses (MMS, 2007a, 2008b) concluded that oil spills would be unlikely to affect 

benthic communities beyond the immediate vicinity of the wellhead (i.e., due to physical 

impacts of a blowout) because the oil would rise quickly to the sea surface directly over the spill 

location. However, during the Macondo spill, subsurface plumes were reported at a water 

depth of about 3,600 ft (1,100 m), extending at least 22 miles (35 km) from the 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). Chemical 

components of subsea dispersants used during the Macondo spill persisted for up to two 

months and were detectable up to 186 miles (300 km) from the wellsite at a water depth of 

3,280 to 3,937 ft (1,000 to 1,200 m) (Kujawinski et al. 2011). However, estimated dispersant 

concentrations in the subsea plume were below levels known to be toxic to marine life. While 

the behavior and impacts of subsurface plumes are not well known, a subsurface plume could 

have the potential to contact high-density deepwater benthic communities beyond the 984-ft 

(300-m) radius estimated by MMS (2007a, 2008), depending on its extent, trajectory, and 

persistence. Potential impacts on sensitive resources would be an integral part of the decision 

and approval process for the use of dispersants. The chemosynthetic community assessment 

by C&C Technologies (2009) did not identify high-density deepwater benthic communities that 

would be affected by this development activity within 2,000 ft (610 m) of the proposed drilling 

mud and cuttings discharge locations. Potential impacts of oil on high-density deepwater 

benthic communities are discussed by MMS (2007b).

Although chemosynthetic communities live among hydrocarbon seeps, natural seepage occurs 

at a relatively constant rate compared to the potential rates of oil release from a blowout. In 

addition, seep organisms require unrestricted access to oxygenated water at the same time as 

exposure to hydrocarbon energy sources (MacDonald, 2002). Oil droplets or oiled sediment 

particles could come into contact with chemosynthetic organisms or deepwater corals. As 

discussed by MMS (2007b), impacts could include loss of habitat, biodiversity, and live coral 

coverage; destruction of hard substrate; change in sediment characteristics; and reduction or 

loss of one or more commercial and recreational fishery habitats. Sublethal effects could be 

long lasting and affect the resilience of coral colonies to natural disturbances (e.g., elevated 

water temperature and diseases).
The potential for a spill to affect deepwater corals is indicated by preliminary findings from an 

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

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

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

corals with sloughing tissue and discoloration. The study location was about 61 miles (98 km) 

from the lease area. Much of the soft coral observed in an area measuring about 50 by 130 ft 

(15 by 40 m) was covered by what appeared to be a brown substance. Ninety percent of 

40 large corals were heavily affected and showed dead and dying parts and discoloration. 

Another site 1,312 ft (400 m) away had a colony of stony corals similarly affected and partially 

covered with a similar brown substance. Until laboratory analyses are conducted, scientists 

cannot be certain what caused the impacts. Sediment and coral samples were collected with 

an ROV and brought to the surface for analyses. Further testing will also determine if the

substance is oil, and if so, whether it is consistent with the release from the Macondo spill.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD 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 designated topographic feature is Sackett Bank, 

located 32 miles (51 km) north-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. 

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 85 miles (137 km) north-northeast 

of 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. 

C.2.5 Eastern Gulf Live Bottoms

The lease area is not covered by the Live Bottom (Low-Relief) Stipulation, which applies to 

Eastern Gulf of Mexico Planning Area leases in water depths of 328 ft (100 m) or less. The 

nearest blocks covered by the live bottom stipulation, as defined by NTL 2009-G39, are about 

122 miles (196 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. 

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 designated critical 

habitat 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 and fishes in the Gulf of 

Mexico. The USFWS has jurisdiction over ESA-listed birds and the Florida manatee. These two 

agencies share federal jurisdiction over sea turtles, with NMFS having lead responsibility at sea 

and USFWS on nesting beaches.

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, EbX X None

Green turtle Chelonia mydas T, EcX X None

Leatherback turtle Dermochelys coriacea E X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Birds

Piping Plover Charadrius melodus T -- X

Coastal Texas, Louisiana, 

Mississippi, Alabama, 

and Florida (Panhandle)

Whooping Crane Grus americana E -- X

Coastal Texas 

(Aransas National 

Wildlife Refuge)

Fishes

Gulf sturgeon Acipenser oxyrinchus desotoi T -- X

Coastal Louisiana, 

Mississippi, Alabama, 

and Florida (Panhandle)

Terrestrial Mammals

Beach mouse (Alabama, 

Choctawhatchee, 

Perdido Key, St. Andrew)

Peromyscus polionotus E -- X

Alabama and Florida 

(Panhandle) beaches

Abbreviations: E = Endangered; T = Threatened.

a The blue, fin, humpback, North Atlantic right, and sei whales are rare or extralimital in the Gulf of Mexico and are 

unlikely to be present in the lease area.

b The loggerhead turtle is composed of nine distinct population segments (DPS) that are considered “species.” The only 

DPS that may occur in the project area (Northwest Atlantic DPS) is listed as threatened (76 FR 58868; September 22, 

2011).

c The green sea turtle is threatened, except for the Florida breeding population, which is listed as endangered.

The sperm whale and five species of sea turtles are the only endangered or threatened species 

likely to occur at or near the lease area. No critical habitat has been designated for these 

species in the Gulf of Mexico.
Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic right 

whale, and sei whale) also have been reported from the Gulf of Mexico but are considered rare 

or extralimital there (Würsig et al., 2000). No critical habitat has been designated for these 

species in the Gulf of Mexico.

Coastal endangered or threatened species include the Florida manatee, Piping Plover, 

Whooping Crane, Gulf sturgeon, and four subspecies of beach mouse. Critical habitat has been 

designated for all of these species as indicated in Table 5 and discussed in individual sections.

Two other coastal species (Bald Eagle and Brown Pelican) discussed by MMS (2007b) are no 

longer listed as endangered or threatened; these species are discussed in Section C.4.2, 

Shorebirds and Coastal Nesting Birds.

There are no other endangered animals or plants in the Gulf of Mexico that are reasonably 

likely to be affected by either routine or accidental events. Other species occurring at certain 

locations in the Gulf of Mexico such as the smalltooth sawfish (Pristis pectinata), elkhorn coral 

(Acropora palmata), staghorn coral (Acropora cervicornis), and Florida salt marsh vole 

(Microtus pennsylvanicus dukecampbelli) are remote from the lease area and highly unlikely to 

be affected.

C.3.1 Sperm Whale (Endangered)

The only endangered marine mammal likely to be present at or near the project area is the 

sperm whale (Physeter macrocephalus). Resident populations of sperm whales occur within the 

Gulf of Mexico. A species description is presented in a recent lease sale EIS (MMS, 2007b). 

Gulf of Mexico sperm whales are classified as an endangered species and a “strategic stock” 

(defined as a stock that may have unsustainable human-caused impacts) by NMFS (Waring 

et al., 2009). No critical habitat for the sperm whale has been designated in the Gulf of Mexico.

The distribution of sperm whales in the Gulf of Mexico is correlated with mesoscale physical 

features such as eddies associated with the Loop Current (Jochens et al., 2008). Sperm whale 

populations in the north-central Gulf of Mexico are present there throughout the year (Davis et 

al., 2000). Results of a multi-year tracking study show female sperm whales typically 

concentrated along the upper continental slope between the 656- and 3,280-ft (200- and 

1,000-m) depth contours (Jochens et al., 2008). Male sperm whales were more variable in 

their movements and were documented in water depths greater than 9,843 ft (3,000 m). 

Generally, groups of sperm whales sighted in the Gulf of Mexico during the MMS-funded Sperm 

Whale Seismic Study (SWSS) consisted of mixed-sex groups comprising adult females and 

immatures, and groups of bachelor males. Typical group size for mixed groups was 

10 individuals (Jochens et al., 2008). SWSS results show that sperm whales transit through the 

vicinity of the lease area. Movements of satellite-tracked individuals suggest that this area of 

the Gulf continental slope is within the home range of the Gulf of Mexico population (within the 

95% utilization distribution) (Jochens et al., 2008).

IPFs potentially affecting sperm whales include TLP and drilling rig presence, noise, and lights; 

support vessel and helicopter traffic; and two types of accidents – a small fuel spill and a large 

oil spill. Effluent discharges are likely to have negligible impacts on sperm whales due to rapid 

dispersion, the small area of ocean affected, the intermittent nature of the discharges, and the 

mobility of these marine mammals. Compliance with NTL 2012-BSEE-G01 will minimize the 

potential for marine debris-related impacts on sperm whales.

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

Noise from routine drilling activities as well as installation and operation of the TLP 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 noise sources. Due to 

limited scope, timing, and geographic extent, drilling and installation activities would represent 

a small temporary contribution to the overall noise regime. The operation of the TLP would 

represent an incremental contribution of noise to the ambient levels in MC 807. The type of 

noise produced by the TLP would be similar to other existing sources of noise in the region. 

The NMFS (2007) analyzed the potential for impacts of drilling-related noise on sperm whales in 

its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the Central and Western 

Planning Areas of the Gulf of Mexico. The analysis noted that drilling rigs show low sound 

source levels and concluded that drilling is not expected to produce amplitudes sufficient to 

cause hearing or behavioral effects in sperm whales; therefore, these effects are insignificant 

(NMFS, 2007). Any impacts from noise emitted during platform operations are not expected to 

be biologically significant to marine mammal populations (MMS 2007b).

Although platform and drilling rig lighting and presence were considered potential factors 

affecting sperm whales, NMFS‟s 2007 Biological Opinion and recent lease sale EISs (MMS, 

2007b, 2008b) did not identify these as IPFs for sperm whales.

Impacts of Support Vessel and Helicopter Traffic

Vessel traffic supporting routine operations and temporary TLP installation and commissioning 

activities has the potential to disturb sperm whales, and there is also a risk of vessel strikes, 

which are identified as a threat in the recovery plan for this species (NMFS, 2010a). Data 

concerning the frequency of vessel strikes are presented in the lease sale EIS (MMS, 2007b). 

To reduce the potential for vessel strikes, the BOEM has issued NTL 2012-JOINT-G01, which 

recommends protected species identification training and that vessel operators and crews 

maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid 

striking protected species, and requires operators to report sightings of any injured or dead 

protected species. When whales are sighted, vessel operators and crews are required to 

attempt to maintain a distance of 300 ft (91 m) or greater whenever possible. Vessel operators 

are required to reduce vessel speed to 10 knots or less, when safety permits, when mother/calf 

pairs, pods, or large assemblages of cetaceans are observed near an underway vessel. 

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 2012-JOINT-G01, 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 295 ft (90 m) from sperm whales, the NMFS concluded that the potential 

for harassment of sperm whales would be reduced to discountable levels.

Helicopter traffic also has the potential to disturb sperm whales. Smultea et al. (2008) 

documented responses of sperm whales offshore Hawaii to fixed wing aircraft flying at an 

altitude of 800 ft (245 m). A reaction to the initial pass of the aircraft was observed during 

three (12%) of 24 sightings. All three reactions consisted of a hasty dive and occurred at less 

than 1,180 ft (360 m) lateral distance from the aircraft. Additional reactions were seen when 
aircraft circled certain whales to make further observations. Based on other studies of cetacean 

responses to sound, the authors concluded that the observed reactions to brief overflights by 

the aircraft were short-term and probably of no long-term biological significance.

While flying offshore in the Gulf of Mexico, helicopters maintain altitudes above 700 ft (213 m) 

during transit to and from the working area. In the event that a whale is seen during transit, 

the helicopter will not approach or circle the animals. Although responses are possible based 

on the Smultea et al. (2008) study, the NMFS (2007) concluded that this altitude would 

minimize the potential for disturbing sperm whales. Therefore, no significant impacts are 

expected.

Impacts of a Small Fuel Spill

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

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

Gas Leasing Program in the Central and Western Planning Areas of the Gulf of Mexico. Oil 

impacts on marine mammals are discussed by Geraci and St. Aubin (1990). For this Initial

DOCD 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. 

DOCD Sections 2j and 9b provide detail on spill response measures. Given the open ocean 

location of the lease area, the duration of a small spill and opportunity for impacts to occur 

would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the 

concentrations of petroleum hydrocarbons and their degradation products. The extent and 

persistence of impacts would depend on the meteorological and oceanographic conditions at 

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 1.2 to 

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and 

noise of response vessels and aircraft (Marine Mammal Commission [MMC], 2011). However, 

due to the limited areal extent and short duration of water quality impacts from a small fuel 

spill, as well as the mobility of sperm whales, no significant impacts would be expected.

Impacts of a Large Oil Spill

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

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

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 Initial

DOCD, 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, 2011). Direct physical and physiological effects can include skin irritation, 

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

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

from the activities and noise of response vessels and aircraft. Complications of the above may 
lead to dysfunction of immune and reproductive systems, physiological stress, declining physical 

condition, and death. Behavioral responses can include displacement of animals from prime 

habitat, disruption of social structure, changing prey availability and foraging distribution and/or 

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

migration (MMC, 2011).

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) tend 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 2012-JOINTG01 to reduce the potential for striking or disturbing these animals. The Macondo spill provides 

information about potential impacts of a large oil spill that supplements the analysis presented 

in the lease sale EIS (MMS, 2007b). According to NMFS (2010b), however, all stranding and 

mortality data will be considered preliminary until all necropsies have been completed.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD 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 Gulf of Mexico 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 west as Texas

(Fertl et al., 2005). A species description is presented in a recent lease sale EIS (MMS, 2007b) 

and in the recovery plan for this species (USFWS, 2001).

IPFs potentially affecting manatees include support vessel and helicopter traffic and a large oil 

spill. A small fuel spill and effluent discharge in the lease area would be unlikely to affect 

manatees, as the lease area is approximately 53 miles (85 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 2012-BSEE-G01 will 

minimize the potential for marine debris-related impacts on manatees.

Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic supporting routine operations and TLP installation and commissioning 

activities has the potential to disturb manatees, and there is also a risk of vessel strikes, which 

are identified as a threat in the recovery plan for this species (USFWS, 2001). To reduce the 

potential for vessel strikes, the BOEM has issued NTL 2012-JOINT-G01, which recommends 

protected species identification training and that vessel operators and crews maintain a vigilant 

watch for marine mammals and slow down or stop their vessel to avoid striking protected 

species, and requires operators to report sightings of any injured or dead protected species. 

Compliance with NTL 2007-G04 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 relatively low altitudes of 66 to 525 ft (20 to 160 m). 

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

transit offshore, 1,000 ft (305 m) over unpopulated areas or across coastlines, and 2,000 ft 

(610 m) over populated areas and sensitive habitats such as wildlife refuges and park 

properties. This mitigation measure will minimize the potential for disturbing manatees, and no 

significant impacts are expected.

Impacts of a Large Oil Spill

The OSRA results summarized in Table 3 predict that some Texas, Louisiana, and Florida 

shorelines could be contacted by a spill within 10 to 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, 2011). 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, 2011).

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 2012-JOINT-G01 to reduce the potential for striking or 

disturbing these animals, and therefore no significant impacts are expected.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on manatees are expected.

C.3.3 Endangered Mysticete Whales

Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic right 

whale, and sei whale) also have been reported from the Gulf of Mexico but are considered rare 

or extralimital there (Würsig et al., 2000). No critical habitat has been designated for these 

species in the Gulf of Mexico.

Due to the rare occurrence of these whales in the Gulf of Mexico, it is 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, 2008b), and those analyses are incorporated by reference. If any of these 

whales were present in the area, potential impacts would be the same as those discussed 

below in Section C.3.4.

C.3.4 Non-Endangered Marine Mammals (Protected)

In addition to the seven endangered species that have been cited previously, 22 additional 

species of marine mammals may be found 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 DOCD 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 species of non-endangered mysticete whales are known from the Gulf 

of Mexico: the Bryde‟s whale (Balaenoptera edeni) and minke whale (Balaenoptera 

acutorostrata). The Bryde‟s whale (Balaenoptera edeni) has been sighted most frequently 

along the 328-ft (100-m) isobath (Davis and Fargion, 1996; Davis et al., 2000). Most sightings 

have been made in the DeSoto Canyon region and off western Florida, although there have 

been some in the west-central portion of the northeastern Gulf. The minke whale is considered 

rare in the Gulf of Mexico, with the only confirmed records coming from strandings (Würsig 

et al., 2000). Based on the available data, it is possible that Bryde‟s whales could occur in the 

lease area.

Dwarf and pygmy sperm whales. At sea, it is difficult to differentiate dwarf sperm whales 

(Kogia sima) from pygmy sperm whales (Kogia breviceps), and sightings are often grouped 

together as “Kogia spp.” Both species have a worldwide distribution in temperate to tropical 

waters. In the Gulf of Mexico, both species occur primarily along the continental shelf edge and 

in deeper waters off the continental shelf (Mullin et al., 1991; Mullin, 2007). Either species 

could occur in the lease area.

Beaked whales. Four species of beaked whales are known from the Gulf of Mexico. They are 

Blainville‟s beaked whale (Mesoplodon densirostris), Cuvier‟s beaked whale (Ziphius cavirostris), 

Sowerby‟s beaked whale (Mesoplodon bidens), and Gervais‟ beaked whale (Mesoplodon 

europaeus). Stranding records in the Gulf of Mexico suggest that Gervais‟ beaked whale is the 

most common and Sowerby‟s beaked whale is extralimital. Due to the difficulties of at-sea 

identification, beaked whales in the Gulf of Mexico are identified either as Cuvier‟s beaked 

whales or are grouped into an undifferentiated complex (Mesoplodon spp. and Ziphius spp.). 

In the northern Gulf of Mexico, they are broadly distributed in waters greater than 3,281 ft 

(1,000 m) over lower slope and abyssal landscapes (Davis et al., 2000). Any of these species 

could occur in the lease area.

Delphinids. Fourteen species of delphinids are known from the Gulf of Mexico, including 

Atlantic spotted dolphin (Stenella frontalis), bottlenose dolphin (Tursiops truncatus), Clymene 

dolphin (Stenella clymene), false killer whale (Pseudorca crassidens), Fraser‟s dolphin 

(Lagenodelphis hosei), killer whale (Orcinus orca), melon-headed whale (Peponocephala 

electra), pantropical spotted dolphin (Stenella attenuata), pygmy killer whale (Feresa 

attenuata), short-finned pilot whale (Globicephala macrorhynchus), Risso‟s dolphin (Grampus 

griseus), rough-toothed dolphin (Steno bredanensis), spinner dolphin (Stenella longirostris), 

and striped dolphin (Stenella coeruleoalba). The most common non-endangered cetaceans in 

the deepwater environment are the pantropical spotted dolphin, spinner dolphin, and Clymene 

dolphin. However, any of these species could occur in the lease area.
IPFs potentially affecting non-endangered marine mammals include TLP and drilling rig 

presence, noise, and lights; support vessel and helicopter traffic; and two types of accidents 

(a small fuel spill and a large oil spill). Effluent discharges are likely to have negligible impacts 

on marine mammals due to rapid dispersion, the small area of ocean affected, the intermittent 

nature of the discharges, and the mobility of marine mammals. Compliance with NTL 2012-

BSEE-G01 will minimize the potential for marine debris-related impacts on marine mammals.

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

Noise from routine drilling and installation activities as well as operation of the TLP has the 

potential to disturb marine mammals. Most odontocetes (toothed whales and dolphins) use 

higher frequency sounds than those produced by OCS drilling activities (Richardson et al., 

1995). Noise intensity associated with drilling is relatively weak, and the noise exposure of an

individual animal would be transient. There are other OCS facilities and activities in the lease 

area, and the region as a whole has a large number of similar sources. Due to limited scope, 

timing, and geographic extent, drilling and installation activities would represent a small 

temporary contribution to the overall noise regime. The operation of the TLP would represent 

an incremental contribution of noise to the ambient levels in MC 807. The type of noise 

produced by the TLP would be similar to other existing sources of noise in the lease area. 

Impacts are not expected to be biologically significant to marine mammal populations.

Platform and drilling rig lighting and presence are not identified as IPFs for marine mammals in 

recent lease sale EISs (MMS, 2007b, 2008b).

Impacts of Support Vessel and Helicopter Traffic

Vessel traffic supporting routine operations and TLP installation and commissioning activities 

has the potential to disturb marine mammals, and there is also a risk of vessel strikes. Data 

concerning the frequency of vessel strikes are presented in the lease sale EIS (MMS, 2007b). 

To reduce the potential for vessel strikes, the BOEM has issued NTL 2012-JOINT-G01, which 

recommends protected species identification training and that vessel operators and crews 

maintain a vigilant watch for marine mammals and slow down or stop their vessel to avoid 

striking protected species, and requires operators to report sightings of any injured or dead 

protected species. Vessel operators and crews are required to attempt to maintain a distance 

of 300 ft (91 m) or greater when whales are sighted and 150 ft (45 m) when small cetaceans 

are sighted. When cetaceans are sighted while a vessel is underway, vessels must attempt to 

remain parallel to the animal‟s course and avoid excessive speed or abrupt changes in direction 

until the cetacean has left the area. Vessel operators are required to reduce vessel speed to 

10 knots or less when mother/calf pairs, pods, or large assemblages of cetaceans are observed 

near an underway vessel, when safety permits. Compliance with this NTL will minimize the 

likelihood of vessel strikes as well as reduce the chance for disturbing marine mammals, and 

therefore no significant impacts are expected.

Aircraft traffic also has the potential to disturb marine mammals (Würsig et al., 1998). 

However, while flying offshore, helicopters maintain altitudes above 700 ft (213 m) during 

transit to and from the working area. This altitude will minimize the potential for disturbing 

marine mammals, and no significant impacts are expected (MMS, 2007b).

Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008b), 

and oil impacts on marine mammals in general are discussed by Geraci and St. Aubin (1990). 

For this Initial DOCD, 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. DOCD Sections 2j and 9b provide 

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

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

A small fuel spill in offshore waters would produce a slick on the water surface and increase the 

concentrations of petroleum hydrocarbons and their degradation products. The extent and 

persistence of impacts would depend on the meteorological and oceanographic conditions at 

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 1.2 to 

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and 

noise of response vessels and aircraft (MMC, 2011). However, due to the limited areal extent 

and short duration of water quality impacts from a small fuel spill, as well as the mobility of 

marine mammals, no significant impacts would be expected.

Impacts of a Large Oil Spill

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008b) 

and by Geraci and St. Aubin (1990). For this Initial DOCD, 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, 2011). 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, 2011).

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 2012-JOINTG01 to reduce the potential for striking or disturbing these animals, and therefore no significant 

impacts are expected. The Macondo spill provides information about potential impacts of a 

large oil spill that supplements the analysis presented in the lease sale EIS (MMS, 2007b). 

According to NMFS (2010b), however, all stranding and mortality data will be considered 

preliminary until all necropsies have been completed.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD 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 DOCD 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

distinct population segment (DPS) of loggerhead turtle (Caretta caretta) that occurs in the Gulf 

of Mexico is listed as threatened, although other DPSs are endangered. The green turtle 

(Chelonia mydas) is listed as threatened, except for the Florida breeding population, which is 

listed as endangered. Species descriptions are presented in a recent lease sale EIS 

(MMS, 2007b).

Leatherbacks and loggerheads are the most likely species to be present near the lease area as 

adults. Green, hawksbill, and Kemp‟s ridley turtles are typically inner shelf and nearshore 

species, unlikely to occur near the lease area as adults. Hatchlings or juveniles of any of the 

sea turtles may be present in deepwater areas, including the lease area, where they may be 

associated with Sargassum and other flotsam.

All five sea turtle species in the Gulf of Mexico are migratory and use different marine habitats 

according to their life stage. These habitats include high-energy beaches for nesting females 

and emerging hatchlings and pelagic convergence zones for hatchling and juvenile turtles. As 

adults, green, hawksbill, and loggerhead turtles forage primarily in shallow, benthic habitats. 

Leatherbacks are the most pelagic of the sea turtles, feeding primarily on jellyfish.

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

 Loggerhead turtles – Loggerheads nest in significant numbers along the Florida Panhandle 

and, to a lesser extent, from Texas through Alabama (MMS, 2007b). The nearest significant 

nesting area of loggerhead turtles is found in Louisiana, on beaches within the Breton NWR;

 Green and leatherback turtles – Green and leatherback turtles infrequently nest on Florida 

Panhandle beaches (Florida Fish and Wildlife Conservation Commission, 2011);

 Kemp‟s ridley turtles – The main Kemp‟s ridley nesting site is Rancho Nuevo beach, 

Tamaulipas, Mexico (NMFS et al., 2011). Approximately 200 Kemp‟s ridley turtles nested on 

Texas beaches in 2009 (Sea Turtle Restoration Project, 2011). Kemp‟s ridley turtles typically 

do not nest anywhere near the project area, although there have been occasional reports of 

Kemp‟s ridleys nesting in Alabama (Share the Beach, 2010); and

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

IPFs potentially affecting sea turtles include TLP and drilling rig presence, noise, and lights; 

support vessel and helicopter traffic; and two types of accidents – a small fuel spill and a large 

oil spill. Effluent discharges are likely to have negligible impacts on sea turtles due to rapid 

dispersion, the small area of ocean affected, and the intermittent nature of the discharges. 

Compliance with NTL 2012-BSEE-G01 will minimize the potential for marine debris-related 

impacts on sea turtles.

Impacts of Platform and 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 and 
installation activities, these short-term impacts are not expected to be biologically significant to 

sea turtle populations. The operation of the TLP would represent an incremental contribution 

of noise to the ambient levels in MC 807. This noise would be of variable duration and 

intensity, depending on the type of machinery used on the TLP and would be similar to other 

existing sources of noise in the ease area. Any impacts caused by the presence of the TLP are 

not likely to have significant long-term effects on sea turtle species (MMS, 2007b). 

Artificial lighting can disrupt the nocturnal orientation of sea turtle hatchlings (Witherington, 

1997; Tuxbury and Salmon, 2005). However, hatchlings may rely less on light cues when they 

are offshore than when they are emerging on the beach (Salmon and Wyneken, 1990). The 

NMFS (2007) concluded that the effects of lighting from offshore structures on sea turtles are 

insignificant.

Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic supporting routine operations and temporary TLP installation and 

commissioning activities has the potential to disturb sea turtles, and there is also a risk of 

vessel strikes. Data show that vessel traffic is one cause of sea turtle mortality in the Gulf of 

Mexico (Lutcavage et al., 1997). While adult sea turtles are visible at the surface during the 

day and in clear weather, they can be difficult to spot from a moving vessel when resting below 

the water surface, during nighttime, or during periods of inclement weather. To reduce the 

potential for vessel strikes, the BOEM has issued NTL 2012-JOINT-G01, which recommends 

protected species identification training and that vessel operators and crews maintain a vigilant 

watch for sea turtles and slow down or stop their vessel to avoid striking protected species, and 

requires operators to report sightings of any injured or dead protected species. When sea 

turtles are sighted, vessel operators and crews are required to attempt to maintain a distance 

of 150 ft (45 m) or greater whenever possible. Compliance with this NTL will minimize the 

likelihood of vessel strikes as well as reduce the chance for disturbing sea turtles (NMFS, 2007).

Helicopter traffic also has the potential to disturb sea turtles. However, while flying offshore, 

helicopters maintain altitudes above 700 ft (213 m) during transit to and from the working area. 

This altitude will minimize the potential for disturbing sea turtles, and no significant impacts are 

expected.

Impacts of a Small Fuel Spill

Potential spill impacts on sea turtles are discussed in recent EISs (MMS, 2007b, 2008b) and by 

the NMFS (2007) in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in the 

Central and Western Planning Areas of the Gulf of Mexico. For this Initial DOCD, 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. DOCD Sections 2j and 9b provide detail 

on spill response measures. Given the open ocean location of the lease area, the duration of a 

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

A small fuel spill in offshore waters would produce a slick on the water surface and increase the 

concentrations of petroleum hydrocarbons and their degradation products. The extent and 

persistence of impacts would depend on the meteorological and oceanographic conditions at 

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 1.2 to 

12 ac (0.5 to 5 ha), depending on sea state and weather conditions.
Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and 

noise of response vessels and aircraft (MMS, 2007b; NMFS, 2010e). 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 53 miles (85 km) from the nearest shoreline (Louisiana). As explained in 

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

waters prior to breaking up.

Impacts of a Large Oil Spill

Impacts of oil spills on sea turtles can include direct impacts from oil exposure, as well as 

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

dispersants). Direct physical and physiological effects can include skin irritation, inflammation, 

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

and smoke (e.g., from in situ burning of oil); ingestion of oil (and dispersants) directly or via 

contaminated food; and stress from the activities and noise of response vessels and aircraft. 

Complications of the above may lead to dysfunction of immune and reproductive systems, 

physiological stress, declining physical condition, and death. Behavioral responses can include 

displacement of animals from prime habitat, disruption of social structure, changing food 

availability and foraging distribution and/or patterns, changing reproductive 

behavior/productivity, and changing movement patterns or migration (MMS, 2007b; NMFS,

2010e). 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. DOCD Sections 2j and 9b

provide detail on spill response measures.

Studies of oil effects on loggerheads in a controlled setting (Lutcavage et al., 1995) suggest 

that sea turtles show no avoidance behavior when they encounter an oil slick, and any sea 

turtle in an affected area would be expected to be exposed. Sea turtles‟ diving behaviors also 

put them at risk. Sea turtles rapidly inhale a large volume of air before diving and continually 

resurface over time, which may result in repeated exposure to volatile vapors and oiling 

(NMFS, 2007).

The OSRA results summarized in Table 3 predict that some shorelines that support sea turtle 

nesting could be contacted within 10 to 30 days. The nearest nesting area of loggerhead 

turtles is found in St. Bernard Parish, Louisiana, on beaches within the Breton NWR. 

Loggerhead turtles also nest to a lesser extent in Okaloosa County, Florida. Both these areas 

have contact probabilities of 1% after 30 days. Spilled oil reaching sea turtle nesting beaches 

could have effects on nesting sea turtles and egg development (NMFS, 2007). An oiled beach

could affect nest site selection or result in no nesting at all (e.g., false crawls). Upon hatching 

and successfully reaching the water, hatchlings are subject to the same types of oil spill 

exposure hazards as adults. Hatchlings that contact oil residues while crossing a beach can 

exhibit a range of effects, from acute toxicity to impaired movement and normal bodily 

functions (NMFS, 2007).

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 2012-JOINTG01 to reduce the potential for striking or disturbing these animals, and therefore no significant 

impacts are expected. The Macondo spill provides information about potential impacts of a 
large oil spill that supplements the analysis presented in the lease sale EIS (MMS, 2007b).

According to NMFS (2010b), however, all data on sea turtle strandings will be considered 

preliminary until all necropsies have been completed.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD 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 1). Piping Plovers inhabit coastal sandy beaches and mudflats, 

feeding by probing for invertebrates at or just below the surface. They use beaches adjacent 

to foraging areas for roosting and preening (USFWS, 2010a). A species description is presented 

in a recent lease sale EIS (MMS, 2007b).

A large oil spill is the only IPF potentially affecting Piping Plovers. There are no IPFs associated 

with routine project activities that could affect these birds. A small fuel spill in the lease area 

would be unlikely to affect Piping Plovers because a small fuel spill would not be expected to 

make landfall or reach coastal waters prior to breaking up (see explanation in Section A.9.2).

Impacts of a Large Oil Spill

The lease area is 55 miles (89 km) from the nearest shoreline inhabited by Piping Plovers. The 

OSRA results summarized in Table 3 predict that Texas and Louisiana shorelines designated as 

critical habitat for the wintering Piping Plover could be contacted by a spill within 10 to 30 days. 

Plaquemines Parish, Louisiana, which has the highest probability of contact for the 10- and 

30-day intervals (4% and 8%, respectively), includes Piping Plover critical habitat.

Plovers could become externally oiled while foraging on oiled shores or be exposed internally 

through ingestion of oiled intertidal sediments and prey (MMS, 2007b). Plovers congregate and 

feed along tidally exposed banks and shorelines, following the tide out and foraging at the 

water‟s edge. It is possible that some deaths of Piping Plovers could occur, especially if spills 

occur during winter months when plovers are most common along the coastal Gulf or if spills 

contacted critical habitat. Impacts could also occur from vehicular traffic on beaches and other 

activities associated with spill cleanup. Shell has extensive resources available to protect and 

rehabilitate wildlife in the event of a spill reaching the shoreline, as detailed in the OSRP.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on Piping Plovers are expected.
Figure 1. Location of selected environmental features in relation to the lease area. 
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 

reintroduced in central Florida, and another reintroduced population summers in Wisconsin and 

migrates to the southeastern United States for the winter. Whooping Cranes breed, migrate, 

winter, and forage in a variety of habitats, including coastal marshes and estuaries, inland 

marshes, lakes, ponds, wet meadows and rivers, and agricultural fields (USFWS, 2007). About 

22,240 ac (9,000 ha) of salt flats on Aransas NWR and adjacent islands comprise the principal 

wintering grounds of the Whooping Crane. Aransas NWR is designated as critical habitat for 

the species (Figure 1). A species description is presented in a recent lease sale EIS 

(MMS, 2007b).

A large oil spill is the only IPF potentially affecting Whooping Cranes due to the distance from 

Aransas NWR. 

Impacts of a Large Oil Spill

A large oil spill is has a low probability of affecting Whooping Cranes because the lease area is 

approximately 435 miles (700 km) from its critical habitat (Aransas NWR, Texas). 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 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 

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

and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on Whooping Cranes are expected.

C.3.8 Gulf Sturgeon (Threatened)

The Gulf sturgeon (Acipenser oxyrinchus desotoi) is a threatened fish species that inhabits 

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida 

(Barkuloo, 1988; Wakeford, 2001). An anadromous fish that migrates from the sea upstream 

into coastal rivers to spawn in freshwater, it historically ranged from the Mississippi River to 

Charlotte Harbor, Florida (Wakeford, 2001). Today, this range has contracted to encompass 

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida. 

Populations have been depleted or even extirpated throughout this range by fishing, shoreline 

development, dam construction, water quality changes, and other factors (Barkuloo, 1988; 

Wakeford, 2001). These declines prompted the listing of the Gulf sturgeon as a threatened 

species in 1991. The best known populations occur in the Apalachicola and Suwannee Rivers in 

Florida (Carr, 1996; Sulak and Clugston, 1998), the Choctawhatchee River in Alabama (Fox et 

al., 2000), and the Pearl River in Mississippi/Louisiana (Morrow et al., 1998). Critical habitat in 

the Gulf extends from Lake Borgne, Louisiana (St. Bernard Parish), to Suwannee Sound, Florida 

(Levy County) (NMFS, 2010c) (Figure 1). A species description is presented in a recent lease 
sale EIS (MMS, 2007b) and in the recovery plan for this species (USFWS and Gulf States Marine 

Fisheries Commission, 1995).

A large oil spill is the only IPF potentially affecting Gulf sturgeon. There are no IPFs associated 

with routine project activities that could affect this species. A small fuel spill in the lease area 

would be unlikely to affect Gulf sturgeon because a small fuel spill would not be expected to 

make landfall or reach coastal waters prior to breaking up (see explanation in Section A.9.2).

Impacts of a Large Oil Spill

Potential spill impacts on Gulf sturgeon are discussed in recent EISs (MMS, 2007b, 2008b) and 

by the NMFS (2007) in its Biological Opinion for the Five-Year Oil and Gas Leasing Program in 

the Central and Western Planning Areas of the Gulf of Mexico. For this Initial DOCD, there are 

no unique site-specific issues with respect to this species.

The lease area is about 117 miles (188 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 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 

DOCD 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. DOCD 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: the Alabama, Choctawhatchee, Perdido Key, and 

St. Andrew beach mice. Critical habitat has been designated for all four subspecies; Figure 1

shows the critical habitat combined for all four subspecies. Species descriptions are provided in 

a recent lease sale EIS (MMS, 2007b).

A large oil spill is the only IPF potentially affecting subspecies of beach mouse. There are no 

IPFs associated with routine project activities that could affect these animals due to the 

distance from shore and the lack of onshore support activities near their habitat. 

Impacts of a Large Oil Spill 

Potential spill impacts on beach mice are discussed in recent EISs (MMS, 2007b, 2008b). For 

this Initial DOCD, there are no unique site-specific issues with respect to these species.

The lease area is about 158 miles (254 km) from the nearest beach mouse critical habitat. The 

OSRA modeling predicts that a spill in the lease area would not contact beach mouse critical 

habitat within 30 days. In the event of oil contacting these beaches, beach mice could 

experience several types of direct and indirect impacts. Contact with spilled oil could cause skin 

and eye irritation and subsequent infection; matting of fur; irritation of sweat glands, ear 
tissues, and throat tissues; disruption of sight and hearing; asphyxiation from inhalation of 

fumes; and toxicity from ingestion of oil and contaminated food. Indirect impacts could include 

reduction of food supply, destruction of habitat, and fouling of nests. Impacts could also occur 

from vehicular traffic and other activities associated with spill cleanup.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD 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 

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 TLP and drilling rig presence, noise, 

and lights; support vessel and helicopter traffic; and two types of accidents - a small fuel spill 

and a large oil spill. Effluent discharges are likely to have negligible impacts on the birds due to 

rapid dispersion, the small area of ocean affected, the intermittent nature of the discharges, 

and the mobility of these animals. Compliance with NTL 2012-BSEE-G01 will minimize the 

potential for marine debris-related impacts on birds.
Impacts of Platform and 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). The presence of the proposed TLP 

is not expected to have an adverse effect on seabirds or migrant birds. 

A study in the North Sea indicated that platform lighting causes circling behavior in various 

birds, especially on cloudy nights; apparently the birds‟ geomagnetic compass is upset by the 

red part of the spectrum from the lights currently in use (Poot et al., 2008). The numbers 

varied greatly, from none at all to some tens of thousands of birds per night per platform, with 

an apparent effect radius of up to 3 miles (5 km). A study in the Gulf of Mexico also noted the 

phenomenon, but did not recommend mitigation (Russell, 2005). Factors to consider in 

evaluating this impact in the Gulf of Mexico would include the lower incidence of cloudy and 

foggy days in the Gulf of Mexico versus the North Sea. Due to the limited scope and short 

duration of installation, drilling and completion activities proposed in this Initial DOCD, lighting 

impacts, collisions, or other adverse effects are unlikely, and no significant impacts are 

expected during the drilling and completion phase of this project. The presence of the new TLP 

would result in permanent additional lighting as well as potential for impacts and collisions by 

birds. Any impacts on populations of either seabirds or trans-Gulf migrant birds are not 

expected to be significant.

Impacts of Support Vessel and Helicopter Traffic

Vessels and helicopters supporting routine operations and temporary TLP installation and 

commissioning activities are unlikely to significantly disturb pelagic birds in open, offshore 

waters. It is likely that individual birds would experience, at most, only short-term behavioral 

disruption, and the impact would not be significant.

Impacts of a Small Fuel Spill

Potential spill impacts on marine birds are discussed in recent EISs (MMS, 2007b, 2008b). For 

this Initial DOCD, there are no unique site-specific issues with respect to spill impacts on these 

animals.

The probability of a fuel spill will be minimized by Shell‟s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of 

Shell‟s OSRP will mitigate and reduce the potential for impacts on marine and pelagic birds. 

DOCD Sections 2j and 9b provide detail on spill response measures. Given the open ocean 

location of the lease area, the duration of a small spill and opportunity for impacts to occur 

would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the 

concentrations of petroleum hydrocarbons and their degradation products. The extent and 

persistence of impacts would depend on the meteorological and oceanographic conditions at 

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 1.2 to 

12 ac (0.5 to 5 ha), depending on sea state and weather conditions.
Birds exposed to oil on the sea surface could experience direct physical and physiological 

effects including skin irritation; chemical burns of skin, eyes, and mucous membranes; and 

inhalation of toxic fumes. Due to the limited areal extent and short duration of water quality 

impacts from a small fuel spill, secondary impacts due to ingestion of oil via contaminated prey 

or reductions in prey abundance are unlikely. Due to the low densities of birds in open ocean 

areas, the small area affected, and the brief duration of the surface slick, no significant impacts 

on pelagic birds would be expected.

Impacts of a Large Oil Spill

Potential spill impacts on marine and pelagic birds are discussed in recent EISs (MMS, 2007b, 

2008b). For this Initial DOCD, 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 (>656 ft [>200 m]). Powers (1987) indicates that 

seabird densities over the open ocean typically are <10 birds/km2. The number of pelagic birds 

that could be affected in open, offshore waters would depend on the extent and persistence of 

the oil slick.

The Macondo spill provides relevant information about the species of pelagic birds that may be 

affected in the event of a large oil spill. Birds that have been treated for oiling include several 

pelagic species such as the Northern Gannet, Magnificent Frigatebird, and Masked Booby 

(USFWS, 2011). The Northern Gannet is among the species with the largest numbers of birds 

affected by the spill.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on marine and pelagic birds are expected.

C.4.2 Shorebirds and Coastal Nesting Birds

Threatened and endangered bird species (Piping Plover and Whooping Crane) have been 

discussed previously in Section C.3. Various species of non-endangered birds are also found 

along the northern Gulf Coast, including diving birds, shorebirds, marsh birds, wading birds, 

and waterfowl. Gulf Coast marshes and beaches also provide important feeding grounds and 

nesting habitats. Species that breed on beaches, flats, dunes, bars, barrier islands, and similar 

habitats include the Sandwich Tern, Wilson‟s Plover, Black Skimmer, Forster‟s Tern, Gull-Billed 

Tern, Laughing Gull, Least Tern, and Royal Tern (USFWS, 2010b). Additional information is 

presented in recent lease sale EISs (MMS, 2007b, 2008b).

The Brown Pelican (Pelecanus occidentalis) was delisted from Federal endangered status in 

2009 (USFWS, 2010c). However, this species is listed as a species of greatest conservation 

need by the State of Mississippi (Mississippi Department of Wildlife, Fisheries and Parks, 2011) 

and as a species of special concern by the State of Florida (Florida Fish and Wildlife 

Conservation Commission, 2011). Brown Pelicans inhabit coastal habitats and forage within 

both coastal waters and waters of the inner continental shelf. Aerial and shipboard surveys, 

including GulfCet and GulfCet II, indicate that Brown Pelicans do not occur over deep offshore 

waters (Fritts and Reynolds, 1981; Peake, 1996; Hess and Ribic, 2000). Nearly half the 

southeastern population of Brown Pelicans lives in the northern Gulf Coast, generally nesting on 

protected islands (USFWS, 2010b).
IPFs potentially affecting shorebirds and coastal nesting birds include support vessel and 

helicopter traffic and a large oil spill, as the lease area is 53 miles (85 km) from the nearest 

shoreline. Compliance with NTL 2012-BSEE-G01 will minimize the potential for marine debrisrelated impacts on shorebirds.

Impacts of Support Vessel and Helicopter Traffic

Vessels and helicopters supporting routine operations and temporary TLP installation and 

commissioning activities will transit coastal areas near Port Fourchon and Boothville, Louisiana, 

where shorebirds and coastal nesting birds may be found. These activities could periodically 

disturb individuals or groups of birds within sensitive coastal habitats (e.g., wetlands that may 

support feeding, resting, or breeding birds).

Vessel traffic may disturb some foraging and resting birds. Flushing distances vary among 

species and individuals (Rodgers and Schwikert, 2002). The disturbances will be limited to 

flushing birds away from vessel pathways; known distances are from 65 to 160 ft (20 to 49 m) 

for personal watercraft and 75 to 190 ft (23 to 58 m) for outboard-powered boats (Rodgers and 

Schwikert, 2002). Flushing distances may be similar or less for the support vessels to be used 

for Shell‟s project, and some species such as gulls are attracted to boats. Support vessels will 

not approach nesting or breeding areas on the shoreline, so nesting birds, eggs, and chicks will 

not be disturbed. Vessel operators will use designated navigation channels and comply with 

posted speed and wake restrictions while transiting sensitive inland waterways. Due to the 

limited scope, timing, and geographic extent of drilling and TLP installation activities, any shortterm impacts are not expected to be biologically significant to coastal bird populations.

Aircraft traffic can cause some disturbance to birds onshore and offshore. Responses are highly 

dependent on the type of aircraft, the bird species, the activities that animals were previously 

engaged in, and previous exposures to overflights (Efroymson et al., 2000). Helicopters seem 

to cause the most intense responses over other human disturbances for some species (Bélanger 

and Bédard, 1989). However, Federal Aviation Administration Advisory Circular No. 91-36D 

recommends that pilots maintain a minimum altitude of 2,000 ft (610 m) when flying over 

noise-sensitive areas such as wildlife refuges, parks, and areas with wilderness characteristics. 

This is greater than the distance (slant range) at which aircraft overflights have been reported 

to cause behavioral effects on most species of birds studied (Efroymson et al., 2000). With 

these guidelines in effect, it is likely that individual birds would experience, at most, only shortterm behavioral disruption.

Impacts of Large Oil Spill

The OSRA results summarized in Table 3 predict that shorelines of Texas and Louisiana that 

include habitat for shorebirds and coastal nesting birds could be affected within 30 days.

Data from the Macondo spill provides additional information about the species of coastal birds 

that may be affected in the event that a large oil spill reached coastal habitats; this information 

supplements the analysis presented in the lease sale EIS (MMS, 2007b). According to USFWS 

(2010d) and based on the latest reports, about 5,000 dead birds had been collected since the 

spill began, and about 1,900 of the dead animals were visibly oiled. In addition, more than 

2,000 oiled birds have been collected alive and about 1,200 released (NMFS, 2010b). 

According to the USFWS (2011), bird species that were visibly oiled following the Macondo spill 

include the following:

 Brown Pelican

 Masked Booby

 Magnificent Frigatebird

 Laughing Gull

 Herring Gull

 Northern Gannet

 Black Crowned Night Heron

 Tri-colored Heron
 Green Heron

 Cattle Egret

 Snowy Egret

 Reddish Egret

 Common Tern

 Royal Tern

 Caspian Tern

 Sandwich Tern

 Forster's Tern

 Least Tern

 Black Skimmer

 White Ibis

 Roseate Spoonbill

 Willet

 Sanderling

 Semipalmated Sandpiper

 Clapper Rail

According to the USFWS (2011), species with the largest numbers of dead, oiled birds were 

Laughing Gull, Northern Gannet, Brown Pelican, Royal Tern, Black Skimmer, Least Tern, 

unidentified Gull, and unidentified Tern.

Coastal birds can be exposed to oil as they float on the water‟s surface, dive during foraging, or 

wade in oiled coastal waters. Oiled birds can lose the ability to fly, dive for food, or float on the 

water, which could lead to drowning (USFWS, 2010e). Oil interferes with the water repellency 

of feathers and can cause hypothermia under certain conditions. As birds groom themselves, 

they can ingest and inhale the oil on their bodies. Scavengers such as Bald Eagles and gulls 

can be exposed to oil by feeding on carcasses of contaminated fish and wildlife. While 

ingestion can kill animals immediately, more often it results in lung, liver, and kidney damage, 

which can lead to death. Bird eggs may be damaged if an oiled adult sits on the nest or if oil 

covers the eggs.

As noted above, the Brown Pelican was recently removed from the endangered species list. 

More than 300 dead Brown Pelicans were collected in the Gulf following the Macondo spill, 

(USFWS, 2010d). These data indicate that the Brown Pelican may be particularly at risk of 

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

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

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD 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 TLP and drilling rig 

presence, noise, and lights; effluent discharges; water intakes; and two types of accidents -

a small fuel spill and a large oil spill.

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

The proposed TLP-mounted drilling rig, as a floating structure in the deepwater environment, 

will act as a fish-attracting device (FAD). In oceanic waters, the FAD effect would be most 

pronounced for epipelagic fishes such as tunas, dolphin, billfishes, and jacks, which are 

commonly attracted to fixed and drifting surface structures (Holland et al., 1990; Higashi, 1994; 

Relini et al., 1994). This FAD effect could possibly enhance the feeding of epipelagic predators 

by attracting and concentrating smaller fish species. Because the TLP is a single structure, 

impacts on fish populations, whether beneficial or adverse, are considered minor.

Impacts of Effluent Discharges

Discharges of treated SBM cuttings will produce temporary, localized increases in suspended 

solids in the water column around the TLP and drilling rig. In general, turbid water can be 

expected to extend between a few hundred meters and several kilometers down current from 

the discharge point (NRC, 1983; Neff, 1987). NPDES permit limitations and requirements will 

be met. 

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.

Produced water and process effluents, including well treatment fluids, completion fluids, and 

workover fluids, will be discharged overboard via a downpipe below the water surface, after 

treatment that complies with the 29 mg/l NPDES permit requirements for oil and grease. 

Potential constituents such as salts, petroleum hydrocarbons, some metals, and naturally 

occurring radioactive material in produced water may degrade water quality in the immediate 

vicinity of the discharge point. Compliance with NPDES permit requirements would result in only 

short-term localized impacts to receiving waters (MMS 2007b). 

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

uncontaminated cooling water, fire water, and ballast water, are expected to be diluted rapidly 

and have little or no impact on water column biota.

Impacts of Water Intakes

Seawater will be drawn from several meters below the ocean surface for various services

including firewater, utility water, and once-through non-contact cooling of machinery on the 

platform drilling rig and TLP (DOCD Table 7a). Section 316(b) of the Clean Water Act requires 

NPDES permits to ensure that the location, design, construction, and capacity of cooling water 

intake structures reflect the best technology available to minimize adverse environmental 

impact from impingement and entrainment of aquatic organisms. The current general NPDES 

Permit No. GMG290000 specifies requirements for new facilities for which construction 
commenced after July 17, 2006, with a cooling water intake structure having a design intake 

capacity of greater than 2 million gallons of water per day, of which at least 25% is used for 

cooling purposes. The drilling rig and new TLP, however, do not trigger the cooling water 

intake permit requirements of the NPDES permit because the design intake capacity will be less 

than the 2 million gallons per day or 25% cooling water thresholds. 

The drilling rig and new TLP will be located in the deepwater environment and the seawater 

intakes are located approximately 45 ft below the water surface. Based on Gulf of Mexico data 

from the SEAMAP, larval fish densities decrease with water depth, and are lower in the 

deepwater environment than in shallower water. High flow intakes associated with activation of 

firewater pumps are infrequent and of short duration and the larger fish species that inhabit the 

deepwater environment have little potential for impingement due to their breakaway speed 

from a challenging intake velocity. As noted in this section, cooling water demand is below 

regulatory thresholds. The operational features of the platform combined with the geographical 

area characteristics suggest that no significant impact from intake impingement and 

entrainment is expected.

Impacts of a Small Fuel Spill

Potential spill impacts on fisheries resources are discussed in recent EISs (MMS, 2007b, 2008b). 

For this Initial DOCD, 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. DOCD Sections 2j and 9b provide detail on spill response 

measures. Given the open ocean location of the lease area, the duration of a small spill and 

opportunity for impacts to occur would be very brief.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the 

concentrations of petroleum hydrocarbons and their degradation products. The extent and 

persistence of impacts would depend on the meteorological and oceanographic conditions at 

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 1.2 to 

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

A small fuel spill could have localized impacts on phytoplankton, zooplankton, ichthyoplankton, 

and nekton. Due to the limited areal extent and short duration of water quality impacts, a 

small fuel spill would be unlikely to produce detectable impacts on pelagic communities.

Impacts of a Large Oil Spill

A large oil spill could affect water column biota including phytoplankton, zooplankton, 

ichthyoplankton, and nekton. A large spill that persisted for weeks or months would be more 

likely to affect these communities. While adult and juvenile fishes may actively avoid a large 

spill, planktonic eggs and larvae would be unable to avoid contact. Eggs and larvae of fishes in 

the upper layers of the water column are especially vulnerable to oiling; certain toxic fractions 

of spilled oil may be lethal to these life stages. Impacts would be potentially greater if local 

scale currents retained planktonic larval assemblages (and the floating oil slick) within the same 

water mass.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

DOCD Section 2j. In the unlikely event of a spill, implementation of Shell‟s OSRP will mitigate 
and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on pelagic communities and ichthyoplankton are 

expected.

C.5.2 Essential Fish Habitat

Essential Fish Habitat (EFH) is defined as those waters and substrate necessary to fish for 

spawning, breeding, feeding, and growth to maturity. Under the Magnuson-Stevens Fishery 

Conservation and Management Act, as amended, Federal agencies are required to consult on 

activities that may adversely affect EFH designated in Fishery Management Plans developed by 

the regional Fishery Management Councils.

The Gulf of Mexico Fishery Management Council (GMFMC) has prepared Fishery Management 

Plans for corals and coral reefs, shrimps, stone crab, spiny lobster, reef fishes, coastal 

migratory pelagic fishes, and red drum. In 2005, the EFH for these managed species was 

redefined in Generic Amendment No. 3 to the various Fishery Management Plans (GMFMC, 

2005). The EFH for most of these GMFMC-managed species is on the continental shelf in 

waters shallower than 600 ft (183 m). The shelf edge is the outer boundary for coastal 

migratory pelagic fishes, reef fishes, and shrimps. EFH for corals and coral reefs includes some 

shelf-edge topographic features on the Texas-Louisiana OCS, the nearest of which is Sackett 

Bank, located 32 miles (51 km) north-northwest of the lease area.

EFH has been identified in the deepwater Gulf of Mexico for highly migratory pelagic fishes, 

which occur as transients in the lease area. Species in this group, including tunas, swordfishes, 

billfishes, and sharks, are managed by NMFS. Highly migratory species with EFH at or near the 

lease area include the following (NMFS, 2009):

 Atlantic bluefin tuna (spawning, 

eggs, larvae, adults)

 Atlantic skipjack tuna (spawning, 

adults)

 Atlantic yellowfin tuna (spawning, 

juveniles, adults)

 Bigeye tuna (juveniles)

 Atlantic swordfish (larvae, juveniles, 

adults)

 Blue marlin (juveniles, adults)

 White marlin (juveniles, adults)

 Longbill spearfish (juveniles, adults)

 Oceanic whitetip shark (all)

 Sailfish (juveniles)

 Silky shark (all)

 Shortfin mako shark (all) 

 Longfin mako shark (all)

 Bigeye tresher shark (all)

 Whale shark (all)

Research indicates the central and western Gulf of Mexico may be important spawning habitat 

for Atlantic bluefin tuna, and NMFS (2009) has designated a Habitat Area of Particular Concern 

(HAPC) for this species. The HAPC covers much of the deepwater Gulf of Mexico, including the 

lease area (Figure 1). The areal extent of the HAPC is approximately 15,000 mi2 

(300,000 km2). 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 1). The nearest of these is Jakkula Bank, located 141 miles (226 km) 

west of the lease area.

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

presence, noise, and lights; effluent discharges; and water intakes. In addition, two types of 
accidents–a small fuel spill and a large oil spill–may potentially affect EFH and fisheries 

resources.

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

The TLP, 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 and TLP are a single structure, any impacts on EFH for highly migratory 

pelagic fishes are considered minor.

Impacts of Effluent Discharges

Other effluent discharges potentially affecting EFH by diminishing ambient water quality include 

produced water and process effluents, drilling mud and cuttings, treated sanitary and domestic 

wastes, deck drainage, and miscellaneous discharges such as desalination unit brine and 

uncontaminated cooling water, fire water, and ballast water. Impacts on water quality have 

been discussed previously. No significant impacts on EFH for highly migratory pelagic fishes 

are expected from these discharges.

Impacts of Water Intakes

As noted previously, cooling water intake will cause entrainment and impingement of plankton, 

including fish eggs and larvae (ichthyoplankton). Due to the limited scope, timing, and 

geographic extent of drilling and installation activities, any short-term impacts on EFH for highly 

migratory pelagic fishes are not expected to be biologically significant. The drilling rig and new 

TLP will be located in the deepwater environment and the seawater intakes are located 

approximately 45 ft below the water surface. Based on Gulf of Mexico data from the SEAMAP, 

larval fish densities decrease with water depth, and are lower in the deepwater environment 

than in shallower water. High flow intakes associated with activation of firewater pumps are 

infrequent and of short duration and the larger fish species that inhabit the deepwater 

environment have little potential for impingement due to their breakaway speed from a 

challenging intake velocity. As noted in this section, cooling water demand is below regulatory 

thresholds. The operational features of the platform combined with the geographical area 

characteristics suggest that no significant impact from intake impingement and entrainment is 

expected.

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. DOCD Sections 2j 

and 9b provide detail on spill response measures. Given the open ocean location of the lease 

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

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

Initial DOCD, there are no unique site-specific issues with respect to spill impacts.

A small fuel spill in offshore waters would produce a slick on the water surface and increase the 

concentrations of petroleum hydrocarbons and their degradation products. The extent and 

persistence of impacts would depend on the meteorological and oceanographic conditions at 

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely 

fate of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 
within 24 hours. The area of the sea surface with diesel fuel on it would range from 1.2 to 

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

A small fuel spill could have localized impacts on EFH for highly migratory pelagic fishes, 

including tunas, swordfishes, billfishes, and sharks. These species occur as transients in the 

lease area. A spill would also produce short-term impact on water quality in the HAPC for 

spawning Atlantic bluefin tuna, which covers much of the deepwater Gulf of Mexico. The 

affected area would represent a negligible portion of the HAPC, which covers 114,793 mi2

(297,312 km2) 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 32 miles (51 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 

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

Initial DOCD, there are no unique site-specific issues with respect to EFH.

An oil spill in offshore waters would temporarily increase hydrocarbon concentrations on the 

water surface and potentially the subsurface as well. Given the extent of EFH designations in 

the Gulf of Mexico (GMFMC, 2005; NMFS, 2009), some impact on EFH would be unavoidable.

A large spill could affect the EFH for many managed species including shrimps, stone crab, 

spiny lobster, corals and coral reefs, reef fishes, coastal migratory pelagic fishes, red drum, and 

highly migratory pelagic fishes. 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 invertebrates.

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).

Sackett Bank, located 32 miles (51 km) north-northwest of the lease area, is designated as EFH 

under the corals and coral reefs management plan. An accidental spill would be unlikely to 

reach or affect this feature. Although there are reports of subsurface plumes resulting from the 

use of subsea dispersants during the Macondo spill, the distance and difference in water depth 

are factors that would make an impact unlikely. Near-bottom currents in the region are 

expected to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume 

up onto the continental shelf edge.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in

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

and reduce the impacts. DOCD 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 762 and 807 are not on the list of leases with high potential for historic shipwrecks 

(MMS, 2008a). The archaeological survey conducted by C&C Technologies (2009) detected 
5,637 unidentified sonar targets within the lease area that were classified as modern debris 

associated with prior industrial waste dumping or field development activities. 

Because there are no historic shipwreck sites in the lease area (see DOCD Section 6), there 

are no routine IPFs that are likely to affect these resources. A small fuel spill would not affect 

shipwrecks in adjoining blocks because the oil would float and dissipate on the sea surface. 

The impact of a large oil spill that could contact shipwrecks in other areas is considered below a 

level of concern.

Impacts of a Large Oil Spill

The MMS (2007b) estimated that a severe subsurface blowout could resuspend and disperse 

sediments within a 984-ft (300-m) radius. Because there are no known historic shipwrecks in 

the lease area, a large oil spill would not result in any impact on archaeological resources.

A spill entering shallow coastal waters could conceivably contaminate an undiscovered historic 

shipwreck site. The OSRA modeling summarized in Table 3 predicts that Texas, Louisiana, and 

Florida shorelines could be contacted by a spill within 10 to 30 days. Also as noted by 

MMS (2007b), should an oil spill contact a coastal historic site, such as a fort or a lighthouse, 

the major impact would be a temporary, reversible visual impact from oil contact and 

contamination of the site and its environment.

Previous analyses (MMS, 2007a, 2008) concluded that oil spills would be unlikely to affect 

archaeological sites beyond the immediate vicinity of the wellhead (i.e., due to physical impacts 

of a blowout) because the oil would rise quickly to the sea surface directly over the spill 

location. However, during the Macondo spill, subsurface plumes were reported at a water 

depth of about 3,600 ft (1,100 m), extending at least 22 miles (35 km) from the wellsite and 

persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently 

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). While the 

behavior and impacts of subsurface plumes are not well known, a subsurface plume could have 

the potential to contact shipwreck sites beyond the 984-ft (300-m) radius estimated by 

MMS (2007a, 2008), depending on its extent, trajectory, and persistence. If oil from a subsea 

spill should come into contact with wooden shipwrecks on the seafloor it could adversely affect 

their condition or preservation.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD 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 approximately 3,028 to 3,150 ft (923 to 960 m), the proposed 

well surface locations and subsea installations in MC 807 and 762 are well beyond the 197 ft 

(60 m) depth contour used by the BOEM as the seaward extent for prehistoric archaeological 

site potential in the Gulf of Mexico. Because prehistoric archaeological sites are not found in 

the lease area, the only relevant IPF is a large oil spill that would reach coastal waters within 

the 197 ft (60 m) depth contour.

Impacts of a Large Oil Spill 

Because prehistoric archaeological sites are not found in the lease area, they would not be 

affected by the physical effects of a subsea blowout. The MMS (2007b) estimates that a severe 

subsurface blowout could resuspend and disperse sediments within a 984-ft (300-m) radius.
Along the northern Gulf Coast, prehistoric sites occur frequently along the barrier islands and 

mainland coast and along the margins of bays and bayous (MMS, 2007b). The OSRA modeling 

summarized in Table 3 predicts that Texas, Louisiana, and Florida shorelines could be 

contacted by a spill within 10 to 30 days. A spill reaching a prehistoric site along these 

shorelines could coat fragile artifacts or site features and compromise the potential for 

radiocarbon dating organic materials in a site (although other dating methods are available and 

it is possible to decontaminate an oiled sample for radiocarbon dating). Coastal prehistoric sites 

could also be damaged by spill cleanup operations (e.g., by destroying fragile artifacts and 

disturbing the provenance of artifacts and site features).

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD Sections 2j and 9b provide details on spill response 

measures. Therefore, no significant spill impacts on archaeological resources are expected.

C.7 Coastal Habitats and Protected Areas

Coastal habitats in the northern Gulf of Mexico that may be affected by oil and gas activities are 

described in recent EISs (MMS, 2007b, 2008b) and in a literature review by Collard and Way 

(1997). Sensitive coastal habitats are also tabulated in the OSRP. Coastal habitats inshore of 

the project area include barrier beaches and dunes, wetlands, and submerged seagrass beds. 

Generally, most of the northern 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 53 miles (85 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 the crew boat and supply boats, and 

vessels supporting temporary TLP installation and commissioning activities 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 

the crew boat and supply boats and installation support vessels as detailed in 

DOCD Section 14, and may have a minor incremental impact on coastal habitats or protected 

areas. Impacts will be minimized by following the speed and wake restrictions in harbors and 

channels.

Impacts of a Large Oil Spill

Potential spill impacts on coastal habitats are discussed in recent EISs (MMS, 2007b, 2008b). 

Coastal habitats inshore of the project area include barrier beaches and dunes, wetlands, and 

submerged seagrass beds. For this Initial DOCD, 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- and 30-day intervals (4% and 8%, respectively). After 30 

days, 11 counties or parishes may be contacted from Galveston, Texas, to Okaloosa, Florida.

The shorelines within the geographic range predicted by the OSRA modeling include extensive 

barrier beaches and wetlands, with submerged seagrass beds occurring in sheltered areas 

behind the barrier islands and in estuaries. NWRs and other protected areas along the coast 

are discussed in the lease sale EIS (MMS, 2007b) and Shell‟s OSRP. Coastal wildlife refuges, 

wilderness areas, and state and national parks within the geographic range of the potential 

shoreline contacts after 30 days include the following:

 Brazoria NWR

 McFaddin NWR

 Sabine NWR

 Rockefeller Wildlife Management Area 

(WMA)

 Marsh Island WMA

 Atchafalaya Delta WMA

 Pointe Au Chien WMA

 Grand Isle State Park (SP)

 Salvador WMA

 Breton NWR

 Gulf Islands National Seashore

 Galveston Island SP

 Sea Rim SP

 Cameron Prairie NWR

 Paul J. Rainey WMA

 Cypremort Point SP

 Mandalay NWR

 Wisner WMA

 Jean Lafitte National Historical Park 

and Preserve

 St. Bernard SP

 Pensacola Bay Service Water 

and Impoundment Monitoring 

(SWIM) Area

 Apffel Park

 Murphree WMA

 Lacassine NWR

 Shell Keys NWR

 Isles Dernieres Barrier Islands Refuge

 Delta NWR

 Biloxi WMA

 Choctawhatchee Bay SWIM Area

 Seawolf Park

 Texas Point NWR

 Little Pecan Island Natural Area (NA) 

 Lafitte Woods NA

 Pass A Loutre WMA

 Bayou Sauvage NWR

 Old Fort Travis Park

 Peveto Woods NA

 Atkinson Island WMA

 Lower Neches WMA

 Anahuac NWR

 St. Andrew Bay Watershed SWIM Area

 Fort Anahuac Park

 Candy Abshier WMA
The OSRA results in Table 3 include only shoreline segments with contact probabilities greater 

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

within 30 days, or from a spill persisting for more than 30 days. Additional NWRs and managed 

wildlife areas occur along the Gulf Coast. These areas include habitats such as barrier beach 

and dune systems, wetlands, and submerged seagrass beds that support diverse wildlife, 

including endangered or threatened species.

The level of impacts from oil spills on coastal habitats depends on many factors, including the 

oil characteristics, the geographic location of the landfall, and the weather and oceanographic 

conditions at the time (MMS, 2007b). Oil that makes it to beaches may be either liquid 

weathered oil, an oil-and-water mousse, or tarballs (MMS, 2007b). Oil is generally deposited on 

beaches in lines defined by wave action at the time of landfall. Oil that remains on the beach 

will thicken as its volatile components are lost. Thickened oil may form tarballs or aggregations 

that incorporate sand, shell, and other materials into its mass. Tar may be buried to varying 

depths under the sand. On warm days, both exposed and buried tarballs may liquefy and ooze. 

Oozing may also serve to expand the size of a mass as it incorporates beach materials. Oil on 

beaches may be cleaned up manually, mechanically, or both. Some oil can remain on the 

beach at varying depths and may persist for several years as it slowly biodegrades and 

volatilizes.

Wetlands are highly sensitive to oiling. The MMS (2007b) predicted that for every 50 bbl of oil 

contacting wetlands, approximately 6.7 ac (2.7 ha) of wetland vegetation will experience 

dieback. Thirty percent of these damaged wetlands are assumed to recover within 4 years, and 

85% within 10 years. About 15% of the contacted wetlands are expected to be converted 

permanently to open-water habitat. The critical concentration of oil is that concentration above 

which impacts to wetlands will be long-term and recovery will take longer than two growing 

seasons, and which causes plant mortality and some permanent wetland loss. Critical 

concentrations of various oils are expected to vary broadly for wetland types and wetland plant 

species. Louisiana wetlands are assumed to be more sensitive to oil contact than elsewhere in 

the Gulf because of high cumulative stress (MMS, 2007b). In addition to the direct impacts of 

oil, cleanup activities in marshes may accelerate rates of erosion and retard recovery rates 

(MMS, 2007b).

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD 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 FR 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 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 (Pleoticus robustus) are caught by 

trawlers in water depths of about 820 to 1,804 ft (250 to 550 m). Tilefishes (primarily 

Lophalotilus chamaeleonticeps) are caught by bottom longlining in water depths from about 

540 to 1,476 ft (165 to 450 m) (Continental Shelf Associates, Inc., 2002). The proposed 

project is in 3,028 to 3,150 ft (923 to 960 m) of water. No conflict with commercial fishing 

activity is expected to occur.

Most recreational fishing activity in the region occurs in water depths less than 656 ft (200 m) 

(Continental Shelf Associates, Inc., 1997, 2002). In deeper water, the main attraction to 

recreational fishers would be petroleum platforms in offshore waters of Texas and Louisiana.

The only routine IPF potentially affecting fisheries is TLP and drilling rig presence (including 

noise and lights). Two potential types of accidents are also addressed below – a small fuel spill 

and a large oil spill. 

Impacts of Platform and Drilling Rig Presence

There is a slight possibility of pelagic longlines becoming entangled in the TLP 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. The presence of the TLP would result

in a limited area being unavailable for fishing activity, but this effect is considered 

inconsequential (MMS, 2007b). 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. DOCD Sections 2j and 9b

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

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

Pelagic longlining activities in the lease area, if any, could be interrupted in the event of a small 

fuel spill. The area of the sea surface with diesel fuel on it would range from 1.2 to 12 ac 

(0.5 to 5 ha), depending on sea state and weather conditions. Fishing activities could be 

interrupted due to the activities of response vessels operating in the lease area. A small fuel 

spill would not affect coastal water quality because the spill would not be expected to make 

landfall or reach coastal waters prior to breaking up (see Section A.9.2).

Impacts of a Large Oil Spill 

Potential spill impacts on fishing activities are discussed in recent EISs (MMS, 2007b, 2008b). 

For this Initial DOCD, there are no unique site-specific issues with respect to this activity.

Pelagic longlining activities in the lease area and other fishing activities in the northern Gulf of 

Mexico could be interrupted in the event of a large oil spill. A spill may or may not result in 

fishery closures, depending on the duration of the spill, the oceanographic and meteorological 

conditions at the time, and the effectiveness of spill response measures. The Macondo spill 

provides information about the potential extent of fishery closures in the event of a large oil 
spill in the Gulf of Mexico (NMFS, 2010d). At its peak on July 12, 2010, closures encompassed 

84,101 mi2(217,821 km2), or 34.8% of the U.S. Exclusive Economic Zone (EEZ) in the Gulf of 

Mexico.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on fishing activities are expected.

C.8.2 Public Health and Safety

There are no IPFs associated with routine operations that are expected to affect public health 

and safety. Impacts of a small fuel spill and a large oil spill are addressed below.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Shell‟s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of 

Shell‟s OSRP will mitigate and reduce the potential for impacts. DOCD Sections 2j and 9b

provide detail on spill response measures.

A small fuel spill would not have impacts on public health and safety because it would likely 

affect only a small area of the open ocean 53 miles (85 km) from the nearest shoreline and 

nearly all of the diesel fuel would evaporate or disperse naturally within 24 hours. Response 

crews would be equipped with appropriate safety equipment to avoid injury and health effects. 

A small fuel spill would not be expected to make landfall or reach coastal waters prior to 

breaking up (see Section A.9.2).

Impacts of a Large Oil Spill 

In the event of a large spill from a blowout, the main safety and health concerns are those of 

the offshore personnel involved in the incident and those responding to the spill. The proposed 

activities will be covered by the OSRP, and, in addition, the TLP and drilling rig maintain a 

Shipboard Oil Pollution Emergency Plan as required under MARPOL 73/78.

Depending on the spill rate and duration, the physical/chemical characteristics of the oil, the 

meteorological and oceanographic conditions at the time, and the effectiveness of spill response 

measures, the public could be exposed to oil on the water and along the shoreline, through skin 

contact or inhalation of VOCs. Crude oil is a highly flammable material, and any smoke or 

vapors from a crude oil fire can cause irritation. Exposure to large quantities of crude oil may 

pose a health hazard.

Data from the 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 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 prevalence of upper respiratory symptoms and cough than those not 

exposed (Centers for Disease Control and Prevention, 2010b). Another potential occupational 

hazard for spill response workers is exposure to seasonal temperature extremes resulting in 

heat stress in the summer and hypothermia in the winter. Initial symptoms from cleanup 

workers who sought medical care in Louisiana were typical of acute exposure to hydrocarbons 

or H2S such as headaches, dizziness, nausea, vomiting, cough, respiratory distress, and chest 

pain (Solomon and Janssen, 2010). Health effects reported from previous oil spills, such as the 

Exxon Valdez in 1989, were primarily acute injuries consisting of headaches, throat irritation, 
and sore or itchy eyes, but respiratory problems and dermatitis along with chronic airway 

disease have also been reported (Solomon and Janssen, 2010).

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD 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 will be supported from existing shorebased facilities in 

Louisiana. No new or expanded facilities will be constructed, and no new employees are 

expected to move permanently into the area. The project will have a negligible impact on 

socioeconomic conditions such as local employment, existing offshore and coastal infrastructure 

(including major sources of supplies, services, energy, and water), and minority and lower 

income groups. Impacts of a small fuel spill and a large oil spill are addressed below.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Shell‟s preventative measures during routine 

operations including fuel transfer. In the unlikely event of a spill, implementation of Shell‟s 

OSRP will mitigate and reduce the potential for impacts. DOCD Sections 2j and 9b provide 

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

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

A small fuel spill that is dissipated within a few days would have little or no economic impact, as 

the spill response would use existing facilities, resources, and personnel.

Impacts of a Large Oil Spill

Potential socioeconomic impacts of an oil spill are discussed in recent EISs (MMS, 2007b, 

2008b). For this Initial DOCD, there are no unique site-specific issues with respect to 

employment and coastal infrastructure. A large spill could cause several types of economic 

impacts: extensive fishery closures could put fishermen out of work; temporary employment 

could increase as part of the response effort; adverse publicity that could reduce employment in 

coastal recreation and tourism industries; and OCS drilling activities, including service and 

support operations that are an important part of local economies, could be suspended.

The lease area is 53 miles (85 km) from the nearest shoreline. 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 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 

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

and reduce the impacts. DOCD 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 routine activities due to the distance from shore. 

Compliance with NTL 2012-BSEE-G01 will minimize the chance of trash or debris being lost 

overboard from the TLP and 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. DOCD Sections 2j and 9b

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

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

A small fuel spill in the lease area would be unlikely to affect recreation and tourism. There are 

no known recreational or tourism activities occurring in the lease area, and as explained in 

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

waters prior to breaking up.

Impacts of a Large Oil Spill 

Potential impacts of an oil spill on recreation and tourism are discussed in recent EISs 

(MMS, 2007b, 2008b). For this Initial DOCD, there are no unique site-specific issues with 

respect to these impacts.

Impacts on recreation and tourism would vary depending on the duration of the spill and its 

fate including the effectiveness of response measures. A large spill that reached coastal waters 

and shorelines could adversely affect recreation and tourism by contaminating beaches and 

wetlands, resulting in negative publicity that encourages people to stay away. Based on OSRA 

modeling as summarized in Table 3, Plaquemines Parish, Louisiana, is the area most likely to 

be contacted by a spill. However, shorelines from Galveston, Texas, to Okaloosa, Florida, could 

be contacted. These areas include popular beaches and recreational sites along the coast.

In addition to the analysis presented by MMS (2007b, 2008), recent and ongoing studies have 

explored the economic impacts of the Macondo spill including tourism and “brand” damage 

(IEM, 2010; Oxford Economics, 2010). The U.S. Travel Association has estimated the economic 

impact of the Macondo spill on tourism across the Gulf Coast over a 3-year period at 

$22.7 billion (Oxford Economics, 2010). According to Myers (2011) tourism has rebounded in 

the Gulf Coast states with general increases in hotel occupancy rates and tourism. There are 

ongoing efforts to accelerate recovery by influencing public perceptions; creating travel 

incentives; and providing access to capital, low interest loans, and tax incentives for affected 

businesses (U.S. Travel Association, 2010).

In a recent site-specific environmental assessment for a project that is similar to this Initial

DOCD, BOEM evaluated the impacts to socioeconomic factors such as recreation and tourism 

and concluded that those impacts were negligible (BOEM, 2011a).

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on recreation and tourism are expected.

C.8.5 Land Use

Land use along the northern Gulf Coast is discussed in recent lease sale EISs (MMS, 2007b, 

2008b). There are no routine IPFs potentially affecting land use. The project will use existing 

onshore support facilities in Louisiana. The land use at the existing shorebase sites is industrial. 

The project will not involve new construction or changes to existing land use and, therefore, will 

not have any impacts. Levels of boat and helicopter traffic, as well as demand for goods and 

services including scarce coastal resources, will represent a small fraction of the level of activity 

occurring at the shorebases.

A large oil spill is the only relevant accident IPF. A small fuel spill would not have impacts on 

land use, as the response would be staged out of existing shorebases and facilities.

Impacts of a Large Oil Spill

The initial response for a large oil spill would be staged out of existing facilities, with no effect 

on land use. A large spill could have limited temporary impacts on land use along the coast if 
additional staging areas were needed. For example, during the Macondo spill, temporary 

staging areas were established in Louisiana, Mississippi, Alabama, and Florida for spill response 

and cleanup efforts. In the event of a large spill in the lease area, similar temporary staging 

areas could be needed. These areas would eventually return to their original use as the 

response is demobilized.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on land use are expected.

C.8.6 Other Marine Uses

The lease area is not located within any USCG-designated fairway or shipping lane. MC 762 

and 807 are not in a designated Military Warning Area. Shell will comply with BOEM 

requirements and lease stipulations to avoid impacts on uses of the area by military vessels and 

aircraft.

A historical industrial waste dump site was identified in MC 806 (C&C Technologies, Inc., 2009). 

Shell‟s procedure “Waste Barrel Avoidance and Release Response in the Mississippi Canyon 

Area”, which has been previously approved by MMS and BOEM, is included in DOCD Section 

6a and 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 at least 33 ft (10 m) and requires that potential impact 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.

There are no IPFs from routine project activities that are likely to affect shipping or other 

marine uses. A large oil spill is the only relevant accident IPF. A small fuel spill would not have 

impacts on other marine uses, as the spill and response activities would be mainly within the 

lease area and the duration would be brief.

Impacts of a Large Oil Spill

An accidental spill would be unlikely to significantly affect shipping or other marine uses. The 

blocks are not located within any USCG-designated fairway or shipping lane. In the event of a 

large spill requiring numerous response vessels, coordination would be required to manage the 

vessel traffic for safe operations. Shell will comply with BOEM requirements and lease 

stipulations to avoid impacts on uses of the area by military vessels and aircraft.

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

event will be minimized by Shell‟s well control and blowout prevention measures as detailed in 

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

and reduce the impacts. DOCD Sections 2j and 9b provide detail on spill response measures. 

Therefore, no significant spill impacts on other marine uses are expected.

C.9 Cumulative Impacts

For purposes of NEPA, cumulative impact is defined as “the impact on the environment which 

results from the incremental impact of the action when added to other past, present, and 

reasonably foreseeable future actions regardless of what agency (Federal or non-Federal) or 

person undertakes such other actions” (40 CFR §1508.7). Any single activity or action may 

have a negligible impact(s) by itself, but when combined with impacts from other activities in 

the same area and/or time period, substantial impacts may result.
Prior Studies. MC 762 and 807 were acquired in Lease Sale #98 in July 1985. 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 Initial DOCD 

in several documents. The level and types of activities planned in Shell's Initial DOCD are 

within the range of activities described and evaluated in the Final EIS for Gulf of Mexico OCS Oil 

and Gas Lease Sales 2007-2012: Western Planning Area Sales 204, 207, 210, 215, and 218, 

and Central Planning Area Sales 205, 206, 208, 213, 216, and 222 (MMS, 2007b), as updated 

by a 2008 Final Supplemental EIS for Gulf of Mexico OCS Oil and Gas Lease Sales 2009-2012: 

Central Planning Area Sales 208, 213, 216, and 222 and Western Planning Area Sales 210, 215, 

and 218 (MMS, 2008b). Past, present, and reasonably foreseeable activities were identified in 

the cumulative effects scenario of these documents, which are incorporated by reference. The 

proposed action will not result in any additional impacts beyond those evaluated in the Multisale 

and Supplemental EIS (MMS, 2008b). 

Description of Activities Reasonably Expected to Occur in the Vicinity of Project Area. Other 

exploration and development activities may occur in the vicinity of lease blocks MC 762 and 

807. Shell‟s existing Mars A TLP is located in MC 807 in proximity to the proposed new TLP. 

Shell does not anticipate other projects in the vicinity of the project area beyond the types of 

projects analyzed in the Multisale and Supplemental EIS (MMS, 2008b).

Cumulative Impacts of Activities in the Initial DOCD. 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 impacts projected to result from past, proposed, and future lease sales during the 40-year 

period of 2007 to 2046 (see MMS, 2007b). 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 Initial DOCD 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 Initial DOCD, in conjunction with the 

other reasonably foreseeable activities expected to occur and currently occurring in the Gulf of 

Mexico, as well as the known impacts from the Macondo spill in MC 252. While another large 

oil spill could have significant impacts, the numerous new safety measures implemented by the 

BOEM and further mitigation and safety measures proposed by Shell in its Initial DOCD result in 

a drilling program that reduces the likelihood of another large spill and improves the 

effectiveness of any response in the extremely unlikely event that another large spill occurs. 

Thus, for all impacts, the incremental contribution of Shell‟s proposed actions to the cumulative 

impacts analysis in these prior analyses is not significant.

C.9.1 Cumulative Impacts to Physical/Chemical Resources

The work planned in this Initial DOCD is limited in geographic scope, and the impacts on the 

physical/chemical environment will be correspondingly limited.

Air Quality. Emissions from pollutants into the atmosphere from activities are not projected to 

have significant effects on onshore air quality because of the prevailing atmospheric conditions, 

emission rates and heights, and resulting pollutant concentrations. As the BOEM found in the 

multi-lease-sale EISs, the incremental contribution of activities similar to Shell‟s proposed 

activities to the cumulative impacts is not significant and will not cause or contribute to a 

violation of national ambient air quality standard (MMS, 2007b, 2008b). In addition, the 

cumulative contribution to visibility impairment is also very small (MMS, 2007b, 2008b). Since 

the BOEM completed the multi-lease-sale EISs, the USEPA has adopted a new short-term 

NAAQS for nitrogen dioxide (NO2) and sulfur dioxide. The standard has not yet been 

implemented in the Gulf of Mexico, but given the levels of expected emissions and the distance 
of the project from shore, emissions from Shell's Initial DOCD 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 Initial DOCD represent a negligible contribution 

to the total greenhouse gas emissions from reasonably foreseeable activities in the Gulf of 

Mexico area and would not significantly alter any of the climate change impacts evaluated in 

the previous EISs. Globally, Shell is working to reduce greenhouse gas emissions by increasing 

the efficiency of its operations, establishing a substantial capability in CO2 capture and storage, 

and continuing to research and develop technologies that increase efficiency and reduce 

emissions in hydrocarbon production. In 2010, Shell met a voluntary target set in 1998 for 

direct greenhouse gas emissions from its facilities to be at least 5% lower than the comparable 

1990 level (Shell, 2011). Shell‟s ongoing efforts to reduce greenhouse gas emissions should 

offset any incremental contribution from the Initial DOCD.

Water Quality. Shell‟s project will have some minor water quality impacts due to the 

NPDES-permitted discharge of SBM cuttings, produced water and process effluents, 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 TLP and drilling 

rig), and temporary (lasting only hours longer than the disturbance or discharge). Any 

cumulative effects to water quality are expected to be negligible. 

New Information. The only new, potentially significant information available since preparation 

of the multi-lease-sale EISs arises from the Macondo spill. The Macondo spill caused 

short-term, localized air quality impacts, e.g., from evaporation of volatile hydrocarbons and in 

situ burning of floating oil. Monitoring by the USEPA (2010) has found levels of ozone and 

particulates ranging from “good” to “unhealthy for sensitive groups” on USEPA‟s Air Quality 

Index; these are at levels well below those that would cause short-term health problems. The 

air monitoring conducted to date has not found any pollutants at levels expected to cause 

long-term harm (USEPA, 2010). Satellite imagery indicates that the surface slick from the 

Macondo spill did 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 extended 

over the lease area prior to capping of the well (ESRI, 2010); therefore, water quality in or near 

the lease area could have been temporarily affected. 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 Initial DOCD is limited in geographic scope, 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. Areas that may support 

high-density deepwater benthic communities will be avoided as required by NTL 2009-G40. 

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

and the extent of benthic impacts during this project is insignificant regionally. As noted in the 

multi-lease-sale EISs, the incremental contributions of activities similar to Shell‟s proposed 

activities to the cumulative impacts is not significant (MMS, 2007b).

Threatened, Endangered, and Protected Species. Threatened and endangered species 

reasonably likely to occur in the lease area include the sperm whale and five species of sea 

turtles. Potential impact sources include TLP and drilling rig presence including noise and 

lights; marine debris; and support vessel and aircraft traffic. Potential effects for these species 

would be limited, and would be reduced by Shell‟s compliance with BOEM-required mitigation 

measures including NTLs 2012-BSEE-G01 and 2012-JOINT-G01. 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 2012-BSEE-G01 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. 

Collisions or other adverse effects are unlikely, and no significant cumulative impacts are 

expected.

Fisheries Resources. Platforms and rigs function as FADs for some species of epipelagic fishes 

and the aggregations of prey fishes may potentially attract predators. These effects are 

expected to be small given the isolated nature of the TLP and drilling rig and would not be 

considered a significant impact on pelagic communities, fishery resources, or EFH. Exploration 

and production structures occur in the MC lease blocks proposed for the development activities. 

The additional effect of the proposed drilling activity would be negligible.

Coastal Habitats. Due to the distance of the wellsites from shore, routine activities are not 

expected to have any impacts on beaches and dunes, wetlands, seagrass beds, coastal wildlife 

refuges, wilderness areas, or any other managed or protected coastal area. The support bases 

at Port Fourchon and Boothville are not in wildlife refuge or wilderness areas. Support 

operations, including the crew boat and supply boats, may have a minor incremental impact on 

coastal habitats. Over time with a large number of vessel trips, vessel wakes can erode 

shorelines along inlets, channels, and harbors. Impacts will be minimized by following the 

speed and wake restrictions in harbors and channels.

New Information. The only new, potentially significant information available since preparation 

of the multi-lease-sale EISs arises from the Macondo spill. The spill has resulted in impacts on 

biological resources, including visibly oiled and/or dead birds, marine mammals, and sea turtles, 

as well as oiling of coastal habitats from approximately the Texas/Louisiana border to the 

Florida Panhandle. Another large spill could result in significant cumulative impacts to these 

resources. However, for the reasons discussed in the Initial DOCD, 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, 2008b) 

concluded that oil spills would be unlikely to affect benthic communities beyond the immediate 

vicinity of the wellhead (i.e., due to physical impacts of a blowout) because the oil would rise 

quickly to the sea surface directly over the spill location. However, during the Macondo spill, 

subsurface plumes were reported at a water depth of about 3,600 ft (1,100 m), extending at 

least 22 miles (35 km) from the 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). Chemical components of subsea dispersants used during the 

Macondo spill persisted for up to two months and were detected up to 186 miles (300 km) from 

the wellsite at a water depth of 3,280 to 3,937 ft (1,000 to 1,200 m) (Kujawinski et al. 2011). 

However, estimated dispersant concentrations in the subsea plume were below levels known to 

be toxic to marine life. While the behavior and impacts of subsurface plumes are not well 

known, a subsurface plume could contact the seafloor and affect benthic communities beyond 

the 984-ft (300-m) radius estimated by MMS (2007a, 2008b), depending on its extent, 

trajectory, and persistence. This contact could result in smothering and/or toxicity to benthic 

organisms. The affected area would be recolonized by benthic organisms over a period of 

months to years (NRC, 2003).

C.9.3 Cumulative Impacts to Socioeconomic Resources

The work planned in this Initial DOCD is limited in geographic scope, and the impacts on 

socioeconomic resources will be correspondingly limited.

Archaeological Resources. MC 762 and 807 are not on the list of leases with a high potential 

for historic shipwrecks (MMS, 2008a). The archaeological survey conducted by C&C 

Technologies (2009) detected 5,637 unidentified sonar targets within the lease area that were 

identified as modern debris associated with prior industrial waste dumping or field 

development activities. Also, the lease area is well beyond the 197-ft (60-m) depth contour 

used by the BOEM as the seaward extent for prehistoric archaeological site potential in the Gulf 

of Mexico. Therefore, Shell‟s operations will have no cumulative impacts on historic shipwrecks 

or prehistoric archaeological resources.

Socioeconomic Resources. The multi-lease-sale EISs analyzed the cumulative impacts of oil and 

gas exploration and development in the lease area, in combination with other impact-producing 

activities, on commercial fishing, recreational fishing, recreational resources, historical and 

archaeological resources, land use and coastal infrastructure, demographics, and environmental 

justice (MMS, 2007b). The BOEM also analyzed the economic impact of oil and gas activities on 

the Gulf States, finding only minor impacts in most of Texas, Mississippi, Alabama, and Florida, 

more significant impacts in parts of Texas, and substantial impacts on Louisiana.

Shell‟s proposed activities will have negligible cumulative impacts on socioeconomic resources. 

There are no IPFs associated with routine operations that are expected to affect public health 

and safety, employment and infrastructure, recreation and tourism, land use, or other marine 

uses. Due to the distance from shore, it is unlikely that any recreational fishing activity is 

occurring in the project area, and it is unlikely that any commercial fishing activity other than 

longlining occurs at or near the project area. The project will have negligible impacts on fishing 

activities.

New Information. The only new, potentially significant information available since preparation 

of the multi-lease-sale EISs arises from the Macondo spill. The spill has resulted in impacts on 

commercial and recreational fishing, recreation and tourism, employment, and public health and 

safety. The Macondo spill resulted in extensive fishery closures in the Gulf of Mexico, peaking 

at 34.8% of the EEZ in the Gulf of Mexico (NMFS, 2010d). The U.S. Travel Association has 

estimated the economic impact of the Macondo spill on tourism across the Gulf Coast over a 3-

year period at $22.7 billion (Oxford Economics, 2010). There is some indication that tourism is 

recovering in a number of Gulf Coast states (Myers, 2011).
Reported health impacts (e.g., among spill response and wildlife rehabilitation workers) ranged 

from cuts and scrapes, to upper respiratory symptoms and heat stress, to acute exposure to 

hydrocarbons or H2S (Centers for Disease Control and Prevention, 2010a,b; Solomon and 

Janssen, 2010). Most of these impacts were temporary in nature, although health exposure of 

clean-up workers could have longer lasting impacts.

However, for the reasons discussed in the Initial DOCD, Shell‟s NTL 2010-N06 response, the 

OSRP, and herein, the likelihood of a catastrophic well control event resulting in significant 

amounts of oil in the water is extremely remote. Therefore, Shell‟s proposed activities are not 

expected to result in any cumulative impacts to socioeconomic resources affected by the 

Macondo spill, nor should they have any impact on the previously conducted cumulative impact 

analyses.

D. Environmental Hazards

D.1 Geologic Hazards

The shallow hazards assessment was conducted by C&C Technologies, Inc. (2009) and is 

included in the Initial DOCD. The high-resolution geophysical survey consisted of frequency 

enhanced three-dimensional seismic, enhanced surface renderings (ESRs), ESRs with 

amplitudes applied, and an autonomous underwater vehicle survey. According to the results of 

this survey, the wellsites are free of major geological hazards and are suitable for the proposed 

activities. Proposed wellsites in MC 762 and 807 will not interfere with the existing flowlines 

and umbilicals in the area. See DOCD 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 TLP and 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 TLP and 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 TLP 

and drilling rig for safety reasons until the storm or weather event passes.

E. Alternatives

No formal alternatives were evaluated in this EIA. However, various technical and operational 

options, including the location of the wellsites and the selection of a drilling unit, were 

considered by Shell in developing the proposed action. There are no other reasonable 

alternatives to accomplish the goals of this project.
F. Mitigation Measures

The proposed action includes numerous mitigation measures required by laws, regulations, and 

BOEM lease stipulations and NTLs. The project will comply with applicable Federal, State, and 

local requirements concerning air pollutant emissions, discharges to water, and solid waste 

disposal. Project activities will be conducted under Shell‟s OSRP and will include the measures 

described in DOCD Section 2f. As specified previously, Shell‟s procedure “Waste Barrel 

Avoidance and Release Response in the Mississippi Canyon Area” is included in DOCD 

Section 6a. Finally, cooling water intake has been minimized by use of air cooling technologies 

on the platform.

G. Consultation

No persons or agencies were consulted regarding potential impacts associated with the 

proposed activities during the preparation of this EIA.

H. Preparers

The EIA was prepared at the direction of Shell Offshore Inc. by its contractor, CSA 

International, Inc. Contributors included the following:

 Sylvia Bellone (Regulatory Specialist, Shell Exploration & Production Co.);

 Tracy Albert (Regulatory Specialist, Offshore Technical Compliance, LLC);

 Lori Downs (Environmental Team Leader, Shell Exploration & Production Co.);

 Jeffrey McMenis (Environmental Engineer, Shell Exploration & Production Co.);

 Rob Kuehn (Staff Environmental Engineer, Shell Exploration & Production Co.);

 June Mire, Ph.D. (Senior Ecologist and Project Manager, Tetra Tech EM, Inc.);

 Derek Newberry (Mars B Business Opportunity Manager, Shell Exploration & Production Co.);

 Robert Sloan (Mars B/West Boreas Subsurface Coordinator, Shell Exploration & 

Production Co.);

 Dougal Grant (Mars Geologist, Shell Exploration & Production Co.);

 Dubby Denham (Well Engineer, Shell Exploration & Production Co.);

 Kenyatta Miles (Project Engineer, Shell International Exploration and Production, Inc.);

 Cindy Chandool, Ph. D. (Senior Scientist, CSA International, Inc.);

 Carlyle Kalloo (Senior Scientist, CSA International, Inc.);

 John Thompson (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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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

2c. Production Information

2j. Worst Case Discharge Information

4b. H2S Classification Information

5. Mineral Resource Conservation information – proposed formation information

B. Bibliography

Fugro-McClelland Hazards Report #1188-1062 dated April 26, 1988. 

Fugro-McClelland Shallow Hazards report #0201-1387 dated April 20.

GEMS, Report #0403-643 dated August 26, 2003, “Geologic and Stratigraphic Assessment Block 762, 

OCS-G 7957 Mississippi Canyon Area, Gulf of Mexico.”

Seafloor investigation is based on the C&C report number 083985-084126, Archaeological and Hazard 

Report, Blocks 762-763, 806-807,and Vicinity, Mississippi Canyon Area, dated June 2009.