CITY INTRACOASTAL CITY FRESHWATER CAMERON 

Public Information
Noble Energy, Inc. Page L-1

Revised Exploration Plan 10/6/2011

Mississippi Canyon 948 & 949 (OCS-G 28030 & 32363)

Section L

Onshore Support Facilities Information

A. General

Provide a listing in the table below of the onshore facilities that will be used to provide supply and

service support for the proposed activities:

Name of Shorebase Location Existing/New/Modified

C Port 1 Slip 4 Port Fourchon, LA Existing

B. Support Base Construction or Expansion

There will be no new construction of an onshore support base, nor will we expand the existing shorebase

as a result of the operations proposed in this Exploration Plan.
Noble Energy, Inc. Page L-2

Revised Exploration Plan 10/6/2011

Mississippi Canyon 948 & 949 (OCS-G 28030 & 32363)

C. Waste Disposal

Provide information in the table below on the onshore facilities you will use to store and dispose of any

solid and liquid wastes generated by the proposed activities.

Type of Waste Composition

Solid and Liquid

Wastes Transport

Method

Name/Location

of Facility Amount Disposal Method

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

EXAMPLE: Synthetic-based

drilling fluid or mud internal olefin, ester

Below deck storage

tanks on offshore

support vessels

Newport

Environmental

Services Inc.,

Ingleside, TX X bbl/well Recycled

Oil-based drilling fluid or mud N/A N/A N/A N/A N/A

Synthetic-based drilling fluid or

mud Internal Olefin 25 bbl transport

US Fluids

Port Fourchon 150 bbls Injection

Synthetic-based drilling fluid or

mud Internal Olefin Boat tank

Baroid

Port Fourchon,

LA 10,153 bbls Reclamation

Cuttings wetted with Water-based

fluid Seawater Seafloor N/A N/A N/A

Cuttings wetted with Syntheticbased fluid

Interfaces, cement

contamination Cutting boxes

Newpark

Environmental

Fourchon, LA 300 bbls Injection

Cuttings wetted with oil-based

fluids N/A N/A N/A N/A N/A

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

Produced sand N/A N/A N/A N/A N/A

Will you have additional wastes that are not permitted for discharge? If yes, fill in

the appropriate rows.

Lbs/

month

Recylables

Plastic, paper,

aluminum

Approved

Compactor Bags

Tech Oil, New

Iberia, LA 1,000 lbs Recycled

Trash and debris Household Debris

Approved

Compactor Bags

C Port 1

Fourchon, LA 95,000 lbs Landfill/Disposal

Used oil 40 wt, 90 wt & hyd

DOT approved tote

tank

American

Recovery

Houma, LA 24,200 gals Recycled

Scrap Irons

Iron, Copper, Brass &

Stainless

4’ x 8’ Solid Bin

Basket

C Port Chouest

Offshore

Fourchon, LA 74,250 lbs Recycled

Chemical product wastes

Paint, Oily Rags, Gloves

& Tyvek Suits DOT approved drum

American

Recovery

Houma, LA 9,900 lbs

Processed,

Recycled/Disposed

Spent, dirty completion fluid Calcium Bromide

Offshore Support

Vessels

Newpark

Environmental

Fourchon, LA 2,000 bbls Injection

Completion fluid filtration media

& wash water

Diatomaceous Earth

and Water

25-bbl Cuttings

Boxes

Newpark

Environmental

Fourchon, LA 800 bbls Injection
Noble Energy, Inc. Page M-1

Revised Exploration Plan 10/6/2011

Mississippi Canyon 948 & 949 (OCS-G 28030 & 32363)

Section M

Coastal Zone Management Act (CZMA) Information

Relevant enforceable policies were considered in certifying consistency for Louisiana. A certificate of

Coastal Zone Management Consistency for the state of Louisiana is enclosed as Attachment M-1.

Noble Energy, Inc. Page M-2

Revised Exploration Plan 10/06/11

Mississippi Canyon 948/949 (OCS-G 28030/32363)

For Mississippi:

As authorized by the Federal Coastal Zone Management Act (CZMA), The State of Mississippi

developed a Coastal Management Program (CMP) to allow for the review of proposed Federal license

and permit activities affecting any coastal use or resources, in or outside of the Mississippi Coastal

Zone.

The OCS related oil and gas exploratory and development activities having potential impact on the

Mississippi Coastal Zone are based on the location of the proposed facilities, access to those sites, best

practical techniques for drilling locations, drilling equipment guidelines for the prevention of adverse

environmental effects, effective environmental protection, emergency plans and contingency plans.

Below are goals identified by the State of Mississippi and Noble’s comments and/or corresponding

cross references:

Mississippi Coastal Program (MCP) Enforceable Policies

Goal 1: To provide for reasonable industrial expansion in the coastal area and to ensure the

efficient utilization of waterfront industrial sites so that suitable sites are conserved for water

dependent industry.

The activities proposed in this Revised Exploration Plan are based out of Fourchon, Louisiana and 148

miles from the Mississippi coast. The activities will not provide any industrial expansion on the coastal

area of Mississippi. Therefore Mississippi coastal areas will be conserved for water dependent

industry.

Goal 2: To favor the preservation of the coastal wetlands and ecosystems, except where a specific

alteration of specific coastal wetlands would serve a higher public interest in compliance with the

public purposes of the public trust in which the coastal wetlands are held.

Goal 2 is addressed in Section N, Environmental Impact Analysis and Section H, Oil Spill Information.

The nearest proposed activities will be 148 miles from the Mississippi coast.

Goal 3: To protect, propagate and conserve the state’s seafood and aquatic life in connection

with the revitalization of the seafood industry of the State of Mississippi.

Goal 3 is addressed in Section N, Environmental Impact Analysis and Section H, Oil Spill Information.

Due to the distance from shore, minimal impact to the seafood industry could occur if an incident were

to transpire.

Goal 4: To conserve the air and waters of the state, and to protect, maintain and improve the

quality thereof for public use, for the propagation of wildlife, fish and aquatic life, and for

domestic, agricultural, industrial, recreational and other legitimate beneficial uses.
Noble Energy, Inc. Page M-3

Revised Exploration Plan 10/06/11

Mississippi Canyon 948/949 (OCS-G 28030/32363)

Goal 4 is addressed in Section B, General Information, Section G, Air Emissions Information, and

Section N, Environmental Impact Analysis.

Goal 5: To put to beneficial use to the fullest extent of which they are capable the water

resources of the state, and to prevent the waste, unreasonable use, or unreasonable method of use

of water.

The activities proposed in this plan are based in Mississippi Canyon 948 and 949. As such,

Mississippi’s water resources are not anticipated to be impacted by the proposed activities. Activities

occurring at the sites in the OCS will be conducted in accordance with Noble’s Regional Oil Spill

Response Plan referenced in Section H of this Revised Exploration Plan.

Goal 6: To preserve the state’s historical and archaeological resources, to prevent their

destruction, and to enhance these resources wherever possible.

Goal 6 is addressed in Section B, General Information, and Section H, Environmental Impact Analysis.

Goal 7: To encourage the preservation of natural scenic qualities in the coastal area.

Goal 7 is addressed in Section F, Waste Discharges Information, Section H, Oil Spill Information,

Section G, Air Emissions Information, and Section N, Environmental Impact Analysis.

Goal 8: To assist local governments in the provision of public facilities services in a manner

consistent with the coastal program.

As the proposed activities are located 148 miles from the Mississippi coast and are based out of a

shorebase in Fourchon, Louisiana, local governments should not be affected.

A certificate of Coastal Zone Management Consistency for the state of Mississippi is enclosed as

Attachment M-2.

Noble Energy, Inc. Page N-1

Revised Exploration Plan 10/6/2011

Mississippi Canyon 948 & 949 (OCS-G 28030 & 32363)

Section N

Environmental Impact Analysis (EIA)

See attachment N – 1.
Environmental Impact Analysis

INITIAL EXPLORATION PLAN

Mississippi Canyon Block 948 (OCS‐G 28030)

Mississippi Canyon Block 949 (OCS‐G 32363)

Offshore Louisiana

August 2011

Prepared for:

Noble Energy

100 Glenborough Drive, Suite 100

Houston, Texas  77067

Telephone (381) 872‐3100

Prepared by:

CSA International, Inc.

8502 SW Kansas Avenue

Stuart, Florida  34997

Telephone: (772) 219‐3000
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page ii

Contents

Page

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

A.  Impact‐Producing Factors .......................................................................................5

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

A.2 Physical Disturbance to the Seafloor ............................................................................................ 8

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

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

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

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

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

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

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

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

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

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

A.9.4 Other Accidents Not Analyzed in Detail .......................................................................... 16

B.  Affected Environment...........................................................................................17

C.  Impact Analysis.....................................................................................................19

C.1 Physical/Chemical Environment.................................................................................................. 19

C.1.1 Air Quality........................................................................................................................ 19

C.1.2 Water Quality .................................................................................................................. 22

C.2 Seafloor Habitats and Biota......................................................................................................... 24

C.2.1 Soft Bottom Benthic Communities.................................................................................. 24

C.2.2 High‐Density Deepwater Benthic Communities.............................................................. 26

C.2.3 Designated Topographic Features................................................................................... 28

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

C.2.5 Eastern Gulf Live Bottoms............................................................................................... 29

C.3 Threatened, Endangered, and Protected Species and Critical Habitat.......................................29

C.3.1 Sperm Whale (Endangered) ............................................................................................ 31

C.3.2 West Indian Manatee (Endangered) ............................................................................... 34

C.3.3 Endangered Mysticete Whales........................................................................................ 36

C.3.4 Non‐Endangered Marine Mammals (Protected)............................................................. 36

C.3.5 Sea Turtles (Endangered/Threatened)............................................................................ 39

C.3.6 Piping Plover (Threatened).............................................................................................. 42

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

C.3.8 Gulf Sturgeon (Threatened)............................................................................................. 45

C.3.9 Smalltooth Sawfish (Endangered) ................................................................................... 45

C.3.10 Beach Mice (Endangered)................................................................................................ 46

C.3.11 Elkhorn Coral (Endangered)............................................................................................. 47
Contents

(continued)

Page

Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page iii

C.4 Coastal and Marine Birds ............................................................................................................ 47

C.4.1 Marine Birds .................................................................................................................... 47

C.4.2 Shorebirds and Coastal Nesting Birds.............................................................................. 50

C.5 Fisheries Resources..................................................................................................................... 52

C.5.1 Pelagic Communities and Ichthyoplankton..................................................................... 52

C.5.2 Essential Fish Habitat....................................................................................................... 54

C.6 Archaeological Resources............................................................................................................ 57

C.6.1 Shipwreck Sites................................................................................................................ 57

C.6.2 Prehistoric Archaeological Sites ...................................................................................... 59

C.7 Coastal Habitats and Protected Areas......................................................................................... 60

C.8 Socioeconomic and Other Resources.......................................................................................... 63

C.8.1 Recreational and Commercial Fishing ............................................................................. 63

C.8.2 Public Health and Safety.................................................................................................. 64

C.8.3 Employment and Infrastructure ...................................................................................... 65

C.8.4 Recreation and Tourism .................................................................................................. 66

C.8.5 Land Use .......................................................................................................................... 67

C.8.6 Other Marine Uses .......................................................................................................... 68

D.  Environmental Hazards.........................................................................................68

D.1 Geologic Hazards......................................................................................................................... 68

D.2 Severe Weather........................................................................................................................... 68

D.3 Currents and Waves.................................................................................................................... 69

E.  Alternatives ..........................................................................................................69

F.  Mitigation Measures.............................................................................................69

G.  Consultation.........................................................................................................69

H.  Preparers..............................................................................................................69

I.  References.............................................................................................................70
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page iv

List of Tables

Table Page

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

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

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

3 Conditional probabilities expressed as percentage chance that an oil spill starting

at Launch Point 3 will contact a certain parish, county, or coastline within

120 days (From: BOEMRE, 2011a,b Appendix C) ................................................................ 13

4 Estimated air pollutant emissions over the life of the proposed project in

Mississippi Canyon Blocks 948 and 949 .............................................................................. 20

5 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 (Data from: Rowe and Kennicutt, 2009; Wei, 2006)................24

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

the northern Gulf Coast....................................................................................................... 31

7 Transient fish species that may be present in Mississippi Canyon Blocks 948 and

949 (From: National Marine Fisheries Service, 2009) ......................................................... 55

8 Wildlife refuges, wilderness areas, and state and national parks within the

geographic range of the potential shoreline contacts after 120 days................................61

List of Figures

Figure Page

1 Distance of wellsites from onshore support base at Port Fourchon, Louisiana, and

helicopter base at Houma, Louisiana .................................................................................... 2

2 Bathymetric map of the lease area showing proposed well surface locations...................18

3 Location of selected environmental features in relation to the lease area........................44
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page v

Acronyms and Abbreviations

ADIOS Automated Data Inquiry for Oil Spills

bbl barrel

BHL bottom hole location

BLPD barrels of liquid per day

BOEMRE Bureau of Ocean Energy Management,

Regulation and Enforcement

BOP blowout preventer

BOPD barrels of oil per day

BPD barrels per day

CO carbon monoxide

CGA Clean Gulf Associates

DP dynamically positioned (drillship)

EP Exploration Plan  

EA Environmental Assessment

EDRC estimated daily recovery capacity

EEZ Exclusive Economic Zone

EFH Essential Fish Habitat

EIA Environmental Impact Analysis

EIS Environmental Impact Statement

ESA Endangered Species Act

EW Ewing Bank

FAD fish‐attracting device

GPS global positioning system

GMFMC Gulf of Mexico Fishery Management

Council

HAPC Habitat Area of Particular Concern

HOSS high‐volume open sea skimmer

IPF impact‐producing factor

MARPOL International Convention for the

Prevention of Pollution from Ships

MGD million gallons per day

MMBO million barrels of oil

MMPA Marine Mammal Protection Act

MMS Minerals Management Service

MMSCFD million standard cubic feet per day

MSRC Marine Spill Response Corporation

MWCC Marine Well Containment Company

NAAQS National Ambient Air Quality Standards

NMFS National Marine Fisheries Service

NOAA National Oceanic and Atmospheric

Administration

NOx nitrogen oxides

NPDES National Pollutant Discharge Elimination

System

NPS National Park Service

NRC National Research Council

NTL Notice to Lessees

NWR National Wildlife Refuge

OCS Outer Continental Shelf

OSAT Operational Scientific Advisory Team

OSRA Oil Spill Risk Analysis

OSRP Oil Spill Response Plan

PAH polycyclic aromatic hydrocarbon

PM particulate matter

PSD Prevention of Significant Deterioration

SBM synthetic‐based mud

SHL surface hole location

SOx sulfur oxides

SWSS Sperm Whale Seismic Study

TTI/E Ten Thousand Islands/Everglades Unit

USCG U.S. Coast Guard

USEPA U.S. Environmental Protection Agency

USFWS U.S. Fish and Wildlife Service

VOC volatile organic compound

WCD worst case discharge

WCEP Whooping Crane Eastern Partnership

WD West Delta
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 1

Introduction

Noble Energy, Inc. (Noble) is submitting an Initial Exploration Plan (EP) for Mississippi Canyon

Block 948 (MC 948) and Mississippi Canyon Block 949 (MC 949).  Noble proposes to drill three

exploratory wells, Wells F, G, and H, in MC 948 using a dynamically‐positioned (DP)

semisubmersible drilling rig.  The anticipated spud dates for each of the wells is as follows:

Well H‐1, January 2012; Well G‐1, January 2013; and Well F‐1, January 2014.  It is anticipated to

take approximately 100 days to drill and complete each well.  The surface hole locations (SHLs)

and bottom hole locations (BHLs) of Wells F and G will be located in MC 948.  For Well H, the

SHL will be located in MC 948 and the BHL will be located in MC 949.  This Environmental Impact

Analysis (EIA) information provides an analysis of all three well locations based on their SHLs.

The lease area is 68 miles (mi) (110 kilometers [km]) south of the nearest shoreline, 116 mi

(185 km) from the onshore support base at Port Fourchon, Louisiana, and 159 mi (256 km) from

the helicopter base at Houma, Louisiana (Figure 1).  Water depth at the wellsites ranges from

1,838 to 1,843 m (6,030 to 6,045 ft).   

This EIA was prepared for submittal to the Bureau of Ocean Energy Management, Regulation

and Enforcement (BOEMRE, formerly Minerals Management Service [MMS]) in accordance with

applicable regulations, including 30 CFR 250.212(o) and 250.227, and is a project‐ and

site‐specific analysis of Noble’s planned activities.  As specified in NTL 2008‐G04, an EIA is a

project‐specific analysis that focuses on the impacts of a specific plan to the extent feasible.  

Potential impacts have been analyzed at a broader level in the Gulf of Mexico deepwater

operations and activities Environmental Assessment (EA) (MMS, 2000), Programmatic

Environmental Impact Statements (EISs) for the Outer Continental Shelf (OCS) Oil and Gas

Leasing Programs (MMS, 2007a,b, 2008), the Gulf of Mexico OCS Oil and Gas Lease Sale: 2011

Western Planning Area Lease Sale 218; Draft Supplemental Environmental Impact Statement

(BOEMRE, 2011a), and the most recent Gulf of Mexico OCS Oil and Gas Lease Sale: 2011 Central

Planning Area Lease Sale 2012; Draft Supplemental Environmental Impact Statement

(BOEMRE, 2011b).  The analysis from these documents is incorporated herein by reference.

Statistics from offshore drilling in the U.S. Gulf of Mexico provide a reasonable basis for

evaluating oil spill risk during exploratory drilling.  According to Holand (1997), the average

frequency of a loss of well control incident or “blowout” during exploratory drilling in the

U.S. Gulf of Mexico is 0.00593 blowouts per wells drilled, or one (1) blowout per 169 exploration

wells drilled.  Similarly, the MMS Safety and Environmental Management Program blowout

incident rate for 1996 to 1999 was approximately five (5) blowouts per 1,000 well starts, or

1/200 (MMS, 2000).  More recently in its supplemental EIS for the Western Gulf of Mexico

Planning Area, BOEMRE confirmed that “significant changes to the spill rates for the entire OCS

are not anticipated” (BOEMRE, 2011a).
Mississippi Canyon Blocks 948 and 949 

Environmental Impact Analysis for Initial Exploration Plan 

Figure 1. Distance of wellsites from onshore support base at Port Fourchon, Louisiana, and helicopter base at Houma, 
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 3

Historically, most blowouts have not resulted in oil spills.  Of 151 well blowouts in the Gulf of

Mexico from 1971 to 1995, only 18 (12%) resulted in oil spills.  The total volume released from

all these spills was 1,000 barrels (bbl) of crude oil and condensate (MMS, 2007b).  Between

1964 and 1999, almost all offshore spills (94%) from drilling and production‐related operations

on the U.S. OCS were less than or equal to 1 bbl in size (Anderson and LaBelle, 2000).  As the

BOEMRE recognized in its Interim Final Safety Rule, following the Macondo incident, “Based on

the occurrence of only a single catastrophic blowout, the GOM Deepwater wells drilled

historically (4,123) and the forecasted future drilling activity in the GOM (160) wells per year),

the baseline risk of a catastrophic blowout is estimated to be about once every 26 years”

75 Federal Register 63,365 (October 10, 2010).

Noble’s Regional Oil Spill Response Plan (OSRP) was originally approved by the MMS on

December 7, 2009, and a revised and updated OSRP was submitted to BOEMRE on May 4, 2011.  

The OSRP provides a detailed plan for Noble to respond rapidly and to effectively manage any oil

spills that may result from drilling and production operations.  Noble has designed its response

program based on a regional capability of responding to a range of spill volumes that increase

from small operational spills up to a worst case discharge (WCD) from a well blowout.  Noble’s

program meets the response planning requirements of the relevant coastal states and

applicable Federal oil spill planning regulations.  All activities planned for MC 948 and 949 are

covered under this regional OSRP in accordance with 30 CFR 254.  The OSRP includes

information regarding Noble’s regional oil spill organization and dedicated response assets,

potential spill risks, and local environmental sensitivities.  The OSRP also describes personnel

and equipment mobilization, the incident management team organization, and an overview of

actions and notifications to be taken in the event of a spill.

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

NTL 2008‐G04.  The main impact‐related discussions are in Section A (Impact‐Producing Factors)

and Section C (Impact Analysis). Table 1 lists and summarizes the NTLs that are referenced in

this EIA.
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 4

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

Analysis (EIA).

NTL Title Summary

2010‐N10

Statement of Compliance with

Applicable Regulations and

Evaluation of Information

Demonstrating Adequate Spill

Response and Well Containment

Resources

Informs operators using subsea blowout preventers (BOPs) or

surface BOPs on floating facilities that applications for well permits

must include a statement signed by an authorized company official

stating that the operator will conduct all activities in compliance

with all applicable regulations, including the increased safety

measures regulations (75 Federal Register 63,346).  Informs

operators that BOEMRE will be evaluating whether each operator

has submitted adequate information demonstrating that it has

access to and can deploy containment resources to promptly

respond to a blowout or other loss of well control.

2010‐N06

Information Requirements for

Exploration Plans, Development and

Production Plans, and Development

Operations Coordination Documents

on the OCS

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

blowout scenario and worst case discharge scenario, and provides

guidance regarding the information required in blowout scenario

and worst case discharge scenario descriptions.

2009‐G40 Deepwater Benthic Communities

Guidance for avoiding and protecting high‐density deepwater

benthic communities (including chemosynthetic and deepwater

coral communities) from damage caused by OCS oil and gas

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

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

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

seafloor disturbances.

2009‐G39 Biologically‐Sensitive Underwater

Features and Areas

Guidance for avoiding and protecting biologically sensitive

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

live bottom areas, and other potentially sensitive biological

features) when conducting OCS operations in water depths less

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

2009‐G06 Military Warning and Water Test

Areas

Provides contact links to individual command headquarters for the

military warning and water test areas in the Gulf of Mexico.  Lease

stipulations require lessees or designated operators to enter into

an agreement with the appropriate individual military command

headquarters concerning the control of electromagnetic emissions

and use of boats and aircraft in the applicable warning area or

water test area before commencing such traffic.

2008‐G04

Information Requirements for

Exploration Plans and Development

Operations Coordination Documents

Guidance on the information requirements for OCS plans,

including EIA requirements and information regarding compliance

with the provisions of the Endangered Species Act and Marine

Mammal Protection Act.

2007‐G04

Vessel Strike Avoidance and

Injured/Dead Protected Species

Reporting

Recommends protected species identification training,

recommends that vessel operators and crews maintain a vigilant

watch for marine mammals and slow down or stop their vessel to

avoid striking protected species, and requires operators to report

sightings of any injured or dead protected species.

2007‐G03 Marine Trash and Debris Awareness

and Elimination

Instructs operators to exercise caution in the handling and disposal

of small items and packaging materials; requires the posting of

placards at prominent locations on offshore vessels and

structures; and mandates a yearly marine trash and debris

awareness training and certification process.

2005‐G07 Archaeological Resource Surveys and

Reports

Provides guidance on regulations regarding archaeological

discoveries, specifies requirements for archaeological resource

surveys and reports, and outlines options for protecting

archaeological resources.
Mississippi Canyon Blocks 948 and 949 Agust 2011

Environmental Impact Analysis for Initial Exploration Plan Page 5

A.  Impact‐Producing Factors

Table 2 is a matrix of impact‐producing factors (IPFs) and potentially affected environmental

resources adapted from Form MMS‐142.  An “X” indicates that an IPF could reasonably be

expected to affect a certain resource, and a dash (‐‐) indicates there is a reasonable expectation

of no impact or negligible impact.  Where there may be an effect, an analysis is provided in

Section C.  Potential IPFs for the proposed activity are listed below and briefly discussed in the

following subsections:

 Drilling rig presence (including noise and lights);

 Physical disturbance to the seafloor;

 Air pollutant emissions;

 Effluent discharges;

 Water intake;

 Onshore waste disposal;  

 Marine debris;

 Support vessel and helicopter traffic; and

 Accidents.

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

DP drillships and DP semisubmersibles use a geographic positioning system (GPS) and sensors in

conjunction with their own propellers and thrusters to maintain position.  Essentially, through

satellite navigation, the location of the vessel is precisely monitored, and thrusters positioned at

various locations about the vessel’s hull are activated to provide any required stationkeeping

adjustment.  This allows operations at sea where mooring or anchoring is not feasible.

The DP semisubmersible proposed in the EP associated with this EIA will be on site for an

estimated 300 days (100 days/well) over a 3‐year period.  The physical presence of the drilling

rig in the ocean can attract pelagic fishes and other marine life, as discussed in Section C.5.1.

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

in some cases infrasonic frequencies (MMS, 2000).  Drilling noise from drillships and

semisubmersibles is not particularly intense and is strongest at low frequencies, averaging

10 to 500 Hz (Richardson et al., 1995).  Sound and vibrations from a drilling rig flow into the

water either through the air or through the risers (MMS, 2000).  Drilling rigs also maintain

exterior lighting for navigational and aviation safety in accordance with applicable Federal safety

regulations.
Mississippi Canyon Blocks 948 and 949 

Environmental Impact Analysis for Initial Exploration Plan 

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

negligible impact.

Environmental Resources

Impact‐producing Factors

Drilling Rig

Presence (incl.

noise & lights)

Physical

Disturbance

to Seafloor

Air

Pollutant

Emissions

Effluent

Discharges

WaterIntake

Onshore

Waste

Disposal

Marine

Debris

Sup

Vesse

Tra

Physical/Chemical Environment

Air quality and greenhouse gases  ‐‐ ‐‐ X(9) ‐‐ ‐‐  ‐‐ ‐‐ Water quality  ‐‐ ‐‐ ‐‐ X ‐‐  ‐‐ ‐‐ 

Seafloor Habitats and Biota

Soft bottom benthic communities  ‐‐ ‐‐ ‐‐ X ‐‐  ‐‐ ‐‐ High‐density deepwater benthic communities  ‐‐ ‐‐(4) ‐‐ ‐‐(4) ‐‐  ‐‐ ‐‐ Designated topographic features  ‐‐ ‐‐(1) ‐‐ ‐‐(1) ‐‐  ‐‐ ‐‐ Pinnacle trend area live bottoms  ‐‐ ‐‐(2) ‐‐ ‐‐(2) ‐‐  ‐‐ ‐‐ Eastern Gulf live bottoms  ‐‐ ‐‐(3) ‐‐ ‐‐(3) ‐‐  ‐‐ ‐‐ 

Threatened, Endangered, and Protected Species and Critical Habitat

Sperm whale (endangered) X(8) ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ XWest Indian manatee (endangered)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ XEndangered mysticete whales  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Non‐endangeredmarinemammals(protected) X ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Sea turtles (endangered/threatened) X(8) ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ XPiping Plover (threatened)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Whooping Crane (endangered)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Gulf sturgeon (threatened)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Smalltooth sawfish (endangered) Elkhorn coral (endangered) Beach mice (endangered)  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ 

Coastal and Marine Birds

Marine birds X ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Shorebirds and coastal nesting birds  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ 

Fisheries Resources

Pelagic communities and ichthyoplankton X ‐‐ ‐‐ X X ‐‐ ‐‐ Essential Fish Habitat X ‐‐ ‐‐ X X  ‐‐ ‐‐ 

Archaeological Resources

Shipwreck sites  ‐‐ ‐‐(7) ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Prehistoric archaeological sites  ‐‐ ‐‐(7) ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ 

Coastal Habitats and Protected Areas

Beaches  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Wetlands and seagrass beds  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Coastal wildlife refuges and wilderness areas  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ 

Socioeconomic and Other Resources

Recreational and commercial fishing X ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Public health and safety  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Employment and infrastructure  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Recreation and tourism  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Land use  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ Other marine uses  ‐‐ ‐‐ ‐‐ ‐‐ ‐‐  ‐‐ ‐‐ 

WCD = worst case discharge.
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Environmental Impact Analysis for Initial Exploration Plan Page 7

Table 2 Footnotes and Applicability:

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

anchors will be on the seafloor within the following:

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

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

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

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

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

the Topographic Features Stipulation attached to an OCS lease.

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

no‐activity zone.  There are no submarine banks in the blocks.

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

(Pinnacle Trend) Stipulation attached to an OCS lease.

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

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

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

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

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

 No impacts on high‐density deepwater benthic communities are anticipated.  There are no features

indicative of high‐density chemosynthetic communities or coral communities within 610 m (2,000 ft) of

any drilling mud/cuttings discharge location.  A DP semisubmersible is proposed for this project and

there will be no impacts from anchoring.  

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

 Well locations F, G, and H are classified as H2S absent per Revised Exploration Plan, Control No. R‐4986,

approved October 30, 2009.

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

impact these environmental resources.  If the proposed action is located a sufficient distance from a resource

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

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

analyzed in Section C.

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

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

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

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

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

 No impacts on archaeological resources are expected.  A DP semisubmersible drilling unit will be used

therefore there will be no anchoring.  The lease area is not on the list of high‐probability blocks for

shipwrecks, no unidentified shipwreck signatures were observed during the archaeological assessment,

and it is well beyond the 60‐m depth contour used by the BOEMRE as the seaward extent for prehistoric

archaeological site potential in the Gulf of Mexico.

(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, including drilling rig presence

and emissions, support vessel and helicopter traffic, and accidents, are analyzed in Section C.

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

 Not applicable.

   
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Environmental Impact Analysis for Initial Exploration Plan Page 8

A.2 Physical Disturbance to the Seafloor

In water depths of 600 m (1,969 ft) or greater, use of DP drillships and DP semisubmersibles

reduce physical disturbances to only a very small area of the seafloor around the wellbore (SHL)

where the bottom template and blowout preventer (BOP) are located.  Depending on the

specific well configuration, this area is generally about 0.25 ha (0.62 ac) (MMS 2007b).

A.3 Air Pollutant Emissions

Air pollutant emissions are estimated to be insignificant according to EP Section G.  Offshore air

pollutant emissions will result from operations of the drilling rig, as well as service vessels and

helicopters.  These emissions occur mainly from combustion of diesel fuel.  The combustion of

fuels occurs on diesel fuel‐powered generators, pumps, or motors and from lighter fuel motors.  

Primary air pollutants typically associated with OCS activities are suspended particulate matter

(PM), sulfur oxides (SOx), nitrogen oxides (NOx), volatile organic compounds (VOCs), and carbon

monoxide (CO).

The Air Quality Emissions Report prepared in accordance with BOEMRE requirements

demonstrates that the projected emissions are below exemption levels set by the applicable

regulations in 30 CFR 250.303.  Based on the projected emissions and the distance to shore,

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

pollutants.  No further analysis or control measures are required.

A.4 Effluent Discharges

Effluent discharges are summarized in EP Section F.  All offshore discharges will be in

accordance with requirements of the National Pollutant Discharge Elimination System (NPDES)

General Permit No. GMG290000 issued by the U.S. Environmental Protection Agency (USEPA).  

Any discharges will be in compliance with the permit terms and will be monitored as required by

the permit.

Water‐based drilling muds and cuttings will be released at the seafloor during the initial well

intervals before the marine riser is set that allows returns to the surface.  Excess cement slurry

will also be released at the seafloor during casing installation for the riserless portion of the

drilling operations.  Any muds associated with synthetic based drilling muds (SBMs) will be

collected on the rig and transported to Port Fourchon for disposal in an approved facility.  All

cuttings wetted with SBMs will be discharged overboard per the NPDES permit.

Other effluent discharges in accordance with the NPDES permit will include excess cement,

non‐contact cooling water, treated sanitary and domestic wastes, deck drainage, desalination

unit brine, uncontaminated fresh water and seawater, and ballast water.

A.5 Water Intake

Seawater will be drawn from the ocean for once‐through, non‐contact cooling of machinery on

the drilling rig.  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. GMG 290000 does

not specify requirements for existing facilities (those that started construction before
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Environmental Impact Analysis for Initial Exploration Plan Page 9

July 16, 2006).  The rig planned for use in the EP associated with this EIA is not a “new” facility as

defined by the NPDES permit and therefore is not subject to the cooling water intake

regulations.

A.6 Onshore Waste Disposal

Wastes generated during drilling are tabulated in EP Section F.  Approximately 50 bbl of trash

will be generated each month due to operations, or a total of 1,250 bbl for the three (3) wells

proposed under the EP associated with this EIA.  This trash will be transported to shore in

disposal bags where it will be picked up by municipal operators for final disposal in accordance

with applicable regulations.  

A.7 Marine Debris

Noble will comply with all regulations relating to solid wastes handling and disposal, including

the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78)

Annex V requirements, the USEPA’s and U.S. Coast Guard’s (USCG) regulations, along with those

of the BOEMRE.  For example, BOEMRE regulations at 30 CFR 250.300(a) and (b)(6) prohibit

operators from deliberately discharging containers and other similar materials (i.e., trash and

debris) into the marine environment, and 30 CFR 250.300(c) requires durable identification

markings on equipment, tools and containers (e.g., 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.  In addition to its regulations in Part 250, BOEMRE

has issued NTL 2007‐G03, which instructs operators to exercise caution in the handling and

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

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

awareness training and certification process.

A.8 Support Vessel and Helicopter Traffic

Noble will use existing shorebase facilities at Port Fourchon, Louisiana, for onshore support for

vessel activities.  Air transportation (helicopters) will come out of facilities in Houma, Louisiana.  

No terminal expansion or construction is planned at either location.

The project will be supported by one (1) crew boat and two (2) supply vessels.  The crew boat

will make four (4) round‐trips per week and the supply vessel will make two (2) round‐trips per

week.  The boats will normally move to the project area via the most direct route from the

shorebase.

A helicopter will make an estimated 10 round‐trips per week between the drilling rig and the

heliport.  The helicopter will be used to transport personnel and small supplies and will normally

take the most direct route of travel between the shorebase and the lease area when air traffic

and weather conditions permit.  Helicopters typically maintain a minimum altitude of 213 m

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

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

park properties.
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Environmental Impact Analysis for Initial Exploration Plan Page 10

A.9 Accidents

A.9.1 Types of Accidents Evaluated

The analysis in this EIA focuses on two potential accidents:

 Small diesel fuel spills, which is the most likely type of spill during OCS exploration activities;

and

 WCD for the EP associated with this EIA, which is an oil spill resulting from an uncontrolled

blowout.

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

well as Noble’s spill response plans.  Impacts are analyzed in Section C.

The lease sale EIS (MMS, 2007b) analyzes three (3) other types of accidents: chemical spills,

vessel collisions, and loss of well control.  The information in the lease sale EIS is incorporated

here.  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; BOEMRE, 2011a,b), the most likely type of

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

diesel fuel 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.  As spill size

increases the incident rate declines dramatically (MMS, 2007b; BOEMRE, 2011a,b).  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 diesel 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 and response actions, it is

expected that impacts from a small spill would be minimal (BOEMRE, 2011a,b).

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

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

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

readily degraded by aerobic microbial oxidation.  Diesel is so light that it will not sink to the

seafloor.  Diesel dispersed in the water column can adhere to suspended sediments, but this

generally occurs only in coastal areas with high‐suspended solids loads (NRC, 2003) and would

not be expected to occur to any appreciable degree in offshore waters of the Gulf of Mexico.  

Diesel fuel is readily and completely degraded by naturally occurring microbes (National Oceanic

and Atmospheric Administration [NOAA], 2006).

For purposes of this EIA, the fate of a small diesel fuel spill was estimated using NOAA’s ADIOS2

(Automated Data Inquiry for Oil Spills) model.  This model uses the physical properties of oils in

its database to predict the rate of evaporation and dispersion over time, as well as changes in

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

a small diesel fuel spill would be evaporated or dispersed within 24 hours.  The area of the sea
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Environmental Impact Analysis for Initial Exploration Plan Page 11

surface with diesel fuel on it during this 24‐hour period would range from 0.5 to 5 ha

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

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

indicate that a small diesel fuel spill would not have any impacts on coastal or shoreline

resources.  The lease area is 68 mi (110 km) south of the nearest shoreline.  Modeling results

discussed below indicate that a spill in the lease area would have a 4% or less probability of

reaching any coastline within 10 days after a spill.  By this time, essentially 100% of a small

diesel fuel spill would have been dispersed or evaporated by natural processes, without taking

into account Noble’s response measures.  MMS (2007b) similarly concluded that spills

<1,000 bbl are not expected to persist as a slick on the surface of the water beyond a few days

and are unlikely to make landfall or reach coastal waters prior to breaking up.  MMS (2007b)

noted that this conclusion is supported by a previous analysis of 3‐day trajectory model runs,

previous weathering analyses, and historical records of spill incidents.

Spill Response.  In the unlikely event the shipboard prevention procedures fail to prevent a

diesel fuel spill, response equipment and trained personnel would be activated so that any spill

effects would be localized and would result only in short‐term environmental consequences.  

EP Section H – Attachment H‐1 provides a detailed discussion of Noble’s response to a small

diesel fuel spill.

A.9.3 Crude Oil Spill (Worst Case Discharge)

Spill Size.  In accordance with requirements of NTL 2010‐N06, Noble has estimated a WCD for

the EP associated with this EIA as 179,138 bbl of oil (EP Section H).

Historically, blowouts are rare events and most do not result in oil spills.  Holand (1997)

estimated a probability of 0.0021 for a blowout during exploration drilling based on U.S. Gulf of

Mexico data.  An updated analysis using the SINTEF database estimates a blowout frequency of

0.0017 per exploratory well for non‐North Sea locations (International Association of Oil & Gas

Producers, 2010).  As noted by MMS (2007b), from 1992 to 2005, half of blowouts lasted less

than half a day, and fewer than 10% of blowouts resulted in spilled oil.  BOEMRE is in the

process of updating these spill frequency estimates to include the recent Macondo incident;

however, significant changes to the spill rates for the entire OCS are not anticipated based on

currently available data (BOEMRE, 2011a,b).

As noted in the introduction, the baseline risk of a catastrophic blowout is estimated to be once

every 26 years (BOEMRE Interim Final Safety Rule 75 Federal Register 63,365 –

October 10, 2010).   

Included in EP Section H are Noble’s calculations and information as required by NTL 2010‐N06,

which include 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.  Noble will also

comply with NTL 2010‐N10 and the Interim Final Drilling Safety Rule, which specifies 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
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Environmental Impact Analysis for Initial Exploration Plan Page 12

predict spill fate.  While this model has received some criticism recently (Earthjustice, 2011), it is

still the most widely, scientifically accepted model for estimating the fate of an oil spill.   

The primary criticism of the OSRA model results as provided in Ji et al. (2004) was that the

model did not evaluate the fate of a spill over time periods longer than 30 days, nor does it

predict the fate of a release that continues over a period of weeks or months, as occurred in the

Macondo (Deepwater Horizon) incident.  Also as noted by Ji et al. (2004), the OSRA model does

not take into account the chemical composition or biological weathering of oil spills, the

spreading and splitting of oil spills, or spill response activities.  The model does not assume a

particular spill size but has generally been used by the BOEMRE/MMS to evaluate contact

probabilities for spills greater than 1,000 bbl.

To address this criticism a 120‐day OSRA model was run for the two most recent BOEMRE

Supplemental EISs for the Western and Central Gulf of Mexico Planning Areas (BOEMRE,

2011a,b) in order to estimate the impacts of a possible future catastrophic long‐duration oil

spill.  In this OSRA model run, a hypothetical high‐volume, long‐duration oil spill was assumed to

have occurred, and the analysis emphasized modeling a spill that continued for 90 consecutive

days, with each trajectory tracked for up to 120 days.  

The OSRA model run for this analysis was conducted for five hypothetical launch points in the

Central and Western Gulf of Mexico Planning Areas.  These launch point locations were

deliberately placed in areas identified as having a high possibility of finding the largest oil

volumes in each region.  

The five launch point areas were as follows:

1. Central Gulf of Mexico shelf area west of the Mississippi River—lat. 28.98660 N,

long. 92.17851 W;

2. Central Gulf of Mexico shelf area east of the Mississippi River—lat. 29.91388 N,

long. 88.15338 W;

3. Central Gulf of Mexico slope area—lat. 27.31998 N, long. 90.22203 W;

4. Western Gulf of Mexico shelf area—lat. 27.55423 N, long. 96.76627 W; and

5. Western Gulf of Mexico slope area—lat. 27.51367 N, long. 94.51836 W.

The results for Launch Point 3, the nearest location to this project area are presented in Table 3.   

OSRA is a preliminary risk assessment model.  In the event of an actual oil spill, real time

monitoring and trajectory modeling would be conducted using current and wind data available

from the rigs and permanent production structures in the area.  Satellite and aerial monitoring

of the plume and real time trajectory modeling using wind and current data would continue on a

daily basis to help position equipment and human resources throughout the duration of any

major spill or uncontrolled release.

   
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Environmental Impact Analysis for Initial Exploration Plan Page 13

Table 3.   Conditional probabilities expressed as percentage chance that an oil spill starting at

Launch Point 3 will contact a certain parish, county, or coastline within 120 days

(From: BOEMRE, 2011a,b Appendix C).

Season Winter Spring Summer Fall

Day 3 10 30 120 3 10 30 120 3 10 30 120 3 10 30 120

County or Parish Percent Chance

Cameron, Texas  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  ‐‐  ‐‐ 

Willacy, Texas  ‐‐  ‐‐  ‐‐  3  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  ‐‐  3

Kenedy, Texas  ‐‐  ‐‐  ‐‐  8  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  9  ‐‐  ‐‐  ‐‐  5

Kleberg, Texas  ‐‐  ‐‐  1 6  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  4  ‐‐  ‐‐  1 6

Nueces, Texas  ‐‐  ‐‐  1 6  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  1 2

Aransas, Texas  ‐‐  ‐‐  ‐‐  5  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  3  ‐‐  ‐‐  ‐‐  2

Calhoun, Texas  ‐‐  ‐‐  1 6  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  6  ‐‐  ‐‐  1 4

Matagorda, Texas  ‐‐  ‐‐  2 17  ‐‐  ‐‐  3 4  ‐‐  ‐‐  ‐‐  11  ‐‐  ‐‐  1 6

Brazoria, Texas  ‐‐  ‐‐  3 12  ‐‐  ‐‐  1 3  ‐‐  ‐‐  2 8  ‐‐  ‐‐  1 5

Galveston, Texas  ‐‐  ‐‐  3 10  ‐‐  ‐‐  3 6  ‐‐  ‐‐  2 5  ‐‐  ‐‐  ‐‐  2

Jefferson, Texas  ‐‐  ‐‐  1 4  ‐‐  ‐‐  7 9  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  2

Cameron, Louisiana  ‐‐  ‐‐  1 4  ‐‐  ‐‐  11 12  ‐‐  1 1 4  ‐‐  ‐‐  ‐‐  4

Vermilion, Louisiana  ‐‐  ‐‐  1 2  ‐‐  ‐‐  5 6  ‐‐  1 1 2  ‐‐  ‐‐  ‐‐  ‐‐ 

Iberia, Louisiana  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  4 4  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Terrebonne, Louisiana  ‐‐  1 2 3  ‐‐  4 12 14  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  ‐‐  ‐‐ 

Lafourche, Louisiana  ‐‐  ‐‐  1 1  ‐‐  2 8 10  ‐‐  ‐‐  1 2  ‐‐  ‐‐  ‐‐  ‐‐ 

Jefferson, Louisiana  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  2 2  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  ‐‐ 

Plaquemines, Louisiana  ‐‐  ‐‐  ‐‐  1  ‐‐  2 10 2  ‐‐  ‐‐  1 2  ‐‐  ‐‐  ‐‐  ‐‐ 

Jackson, Mississippi  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Baldwin, Alabama  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Bay, Florida  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Franklin, Florida  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Monroe, Florida  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  1

Dade, Florida  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  ‐‐ 

Coastline

Texas  ‐‐  ‐‐  12 78  ‐‐  ‐‐  14 24  ‐‐  ‐‐  6 54  ‐‐  ‐‐  4 41

Louisiana  ‐‐  1 6 14  ‐‐  9 52 60  ‐‐  1 4 13  ‐‐  ‐‐  ‐‐  6

Mississippi  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Alabama  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1 1  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐ 

Florida  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  1 4  ‐‐  ‐‐  ‐‐  2  ‐‐  ‐‐  ‐‐  2

Tamaulipas, Mexico   ‐‐  ‐‐  ‐‐  4  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  10  ‐‐  ‐‐  ‐‐  10

Veracruz‐Llave, Mexico   ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1 7  ‐‐  ‐‐  ‐‐  ‐‐ 

Tabasco, Mexico  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  ‐‐  1  ‐‐  ‐‐  ‐‐  ‐‐ 

“‐‐” = Values <0.5%; any areas where percent chance within 120 days of all seasons are all <0.5% are not shown.

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,

influencing potential effects to marine organisms and ecosystems.  The most important

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

column, formation of water‐in‐oil emulsions, photochemical oxidation, microbial degradation,

adsorption to suspended particulate matter, and stranding on shore or sedimentation to the

seafloor (NRC, 2003).

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

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

hydrocarbons are lost rapidly by evaporation and dissolution from a slick on the water surface.  
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Environmental Impact Analysis for Initial Exploration Plan Page 14

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.  

Photo‐oxidation attacks mainly the medium and high molecular weight PAHs in the oil on the

water surface.  

Spill Response.  The BOEMRE has issued recent NTLs and guidance documents that clarify

additional oil‐spill requirements after the Macondo incident occurred (BOEMRE, 2011a,b).  

These spill‐response‐related NTLs are listed in Table 2 and the guidance documents are as

follows:  

NTL 2010‐N10—Statement of Compliance with Applicable Regulations and Evaluation of

Information Demonstrating Adequate Spill Response and Well Containment Resources:

This NTL, effective November 8, 2010, applies only to operators conducting operations

using subsea or surface BOP’s on floating facilities.  It explains that lessees and operators

submit a statement signed by an authorized company official with each application for a

well permit indicating that they will conduct all of their authorized activities in

compliance with all applicable regulations, including the Increased Safety Measures

Regulations at 75 FR 63346.  The NTL also informs lessees that BOEMRE will be

evaluating whether or not each operator has submitted adequate information

demonstrating that it has access to and can deploy surface and subsea containment

resources that would be adequate to promptly respond to a blowout or other loss of well

control.  The NTL notifies the operator that BOEMRE intends to evaluate the adequacy of

each operator to comply in the operator’s current OSRP; therefore, there is an incentive

for voluntary compliance.

NTL 2010‐N06—Information Requirements for Exploration Plans, Development and Production

Plans, and Development Operations Coordination Documents on the OCS:

This NTL, effective June 18, 2010, explains the procedures for the lessee or operator to

submit supplemental information for new or previously submitted EP’s, DPP’s, or

DOCD’s.  The required supplemental information includes the following: (1) a description

of the blowout scenario as required by 30 CFR 250.213(g) and 250.243(h); (2) a

description of their assumptions and calculations used in determining the volume of the

worst‐case discharge required by 30 CFR 250.219(a)(2)(iv) (for EP’s) or 30 CFR

250.250(a)(2)(iv) (for DPP’s and DOCD’s); and (3) a description of the measures proposed

that would enhance the ability to prevent a blowout, to reduce the likelihood of a

blowout, and to conduct effective and early intervention in the event of a blowout,

including the arrangements for drilling relief wells and any other measures proposed.  

The early intervention methods of the third requirement could actually include the

surface and subsea containment resources that BOEMRE announced in NTL 2010‐N10,

which states that BOEMRE will begin reviewing to ensure that the measures are

adequate to promptly respond to a blowout or other loss of well control.

Noble submitted an updated Gulf of Mexico Regional OSRP on May 4, 2011.  The OSRP provides

a detailed plan by which Noble will rapidly respond to and effectively manage oil spills that may

result from drilling and production operations.
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 15

In the event of a worst case discharge spill, Noble has access to surface and subsea

response/containment capabilities that could be implemented through various organizations

under contract.  Noble's primary spill response equipment provider is Clean Gulf Associates

(CGA).  

CGA has four (4) skimming vessels capable of operating in shallow waters and the

offshore/nearshore areas.  These vessels have Oleophilic brush pack skimming systems

operating in troughs built into the hulls; below deck storage; and marine electronics packages

including marine, aircraft and company frequency radios, radar, moving map plotters (GPS),

satellite phone, and depth finders.  CGA also offers nine (9) Fast Response Systems staged

throughout the Gulf of Mexico available for offshore use.  

The CGA high‐volume open sea skimmer (HOSS) barge consists of a skimming system built into

an oil recovery barge.  There are four 1,000‐bbl recovered oil storage tanks built into the hull

where oil can be separated and offloaded.  Skimming operations are conducted from the control

room overlooking the skimmer deck.  The estimated daily recovery capacity (EDRC) for the

HOSS barge is approximately 43,000 bbl.

CGA is currently adding to its equipment stockpile, and has recently acquired 11 sets of Koseq

skimming arms and two Aqua Guard skimmers.  In addition, an x‐band/infra‐red tracking system

is on order.  

Noble also has an agreement with the Marine Spill Response Corporation (MSRC) as a secondary

spill response equipment provider (see EP Section H).  MSRC has access to a broad base of oil

spill response resources, at the center of which is a fleet of 15 dedicated Responder Class Oil

Spill Response Vessels (OSRVs), designed and built specifically to recover spilled oil.  The OSRVs

are approximately 210 ft long, have temporary storage for 4,000 bbls of recovered oil, and have

the ability to separate oil and water aboard ship using two oil‐water separation systems.  To

enable the OSRV to sustain cleanup operations, recovered oil is transferred into other vessels or

barges.  

In addition to these 15 OSRVs, MSRC is outfitted with other specialized response vessels and

support equipment, including:  

 19 oil spill response barges with storage capacities between 12,000 and 68,000 bbl;  

 68 shallow water barges;  

 600,000 feet of boom;  

 Over 240 skimming systems;  

 Six self‐propelled skimming vessels 10 to 18 m (32 to 58 ft);  

 Seven mobile communications suites comprising telephone and computer connections and

UHF and VHF marine, aviation, and business band radios;  

 Various small crafts and shallow‐water vessels;  

 One C‐130 dispersant aircraft; and

 One King Air dispersant/spotter aircraft.  

The primary response equipment locations are Houma, Venice, and Belle Chasse, Louisiana.  The

preplanned staging areas if a response becomes necessary are Houma, Port Fourchon, Venice,

and Theodore, Louisiana.  See EP Section H (Attachment H‐1) for a detailed description of

Noble’s site‐specific response to the worst case spill for this plan.
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 16

A.9.4 Other Accidents Not Analyzed in Detail

The lease sale EIS (MMS, 2007b) discusses three (3) other types of accidents: chemical spills,

vessel collisions, and loss of well control.  The information from the EIS on these topics remains

valid and is incorporated by reference into this document.  These accidents are discussed briefly

below along with a hydrogen sulfide (H2S) release.  There are no other site‐specific issues raised

by drilling the wells proposed in the EP associated with this EIA.

Chemical Spills.  Chemicals are stored and used to condition drill muds and during production

and in well completions, stimulation, and workover procedures.  The relative quantity of their

use is reflected in the largest volumes spilled.  Completion fluids compose the largest quantity of

fluids used and thus are the largest releases.  Between 5 and 15 chemical spills are anticipated

each year, with the majority being <50 bbl in size.  The most common chemicals spilled are

methanol, ethylene glycol, and zinc bromide.  Additional production chemicals are needed in

deepwater operations where gas hydrates tend to form.  Spill volumes are anticipated to remain

about the same, but spill frequency can be expected to improve because of advances in subsea

processing (BOEMRE, 2011a,b).

Synthetic‐based Fluid Spills.  Synthetic‐based muds have been used since the mid 1990s.  In

deepwater drilling, SBMs may be preferred over petroleum oil‐based muds (OBMs) because of

SBMs superior performance properties.  The synthetic oils used in SBMs are relatively nontoxic

to the marine environment and have the potential to biodegrade.  Three SBM spills of

>1,000 bbl occurred between 2001 and 2004.  Between 5 and 20 SBM releases are anticipated

each year, with the majority being <50 bbl in size.  The volume of the synthetic portion of the

drilling fluids rather than the total volume of the drilling muds is now used to describe spill size.  

Accidental riser disconnects could result in the release of large quantities of drilling fluids and

are of particular concern when SBMs are in use (BOEMRE, 2011a,b).  

Vessel Collisions.  BOEMRE data show that from 1996 to 2009 there were 226 OCS‐related

collisions.  Most collision mishaps are the result of service vessels colliding with platforms or

vessel collisions with pipeline risers.  Approximately 10% of vessel collisions with platforms in

the OCS caused diesel fuel spills.  Fires resulted from hydrocarbon releases in several of the

collision incidents.  To date, the largest diesel fuel spill associated with a collision occurred in

1979 when an anchor‐handling boat collided with a drilling platform in the Main Pass leasing

area, spilling 1,500 bbl of diesel fuel.  Diesel fuel is the product most frequently spilled while oil,

natural gas, corrosion inhibitor, hydraulic fluid, and lube oil have also been released as the result

of a vessel collision.  Human error accounts for approximately half of all reported vessel

collisions from 2006 to 2009.  As summarized in MMS (2007b; BOEMRE, 2011a,b), vessel

collisions occasionally occur during routine operations.  Some of these collisions have caused

spills of diesel fuel or chemicals.  Noble will comply with all USCG and BOEMRE‐mandated safety

requirements to minimize the potential for vessel collisions.

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

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

a broad term that includes very minor up to the most serious well control incidents, while

blowouts are considered to be a subset of more serious incidents with greater risk of oil spill or

human injury (MMS, 2007b).  Loss of well control may result in the release of SBMs or loss of oil.  

Noble has a robust system in place to prevent loss of well control.  Measures to prevent a

blowout, reduce the likelihood of a blowout, and conduct effective and early intervention in the
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 17

event of a blowout are described in EP Section H as required by NTL 2010‐06.  The potential for

a loss‐of‐well‐control event will be minimized by adhering to the requirements of applicable

regulations such as the Interim Final Drilling Safety Rule and NTL 2010‐N10, which specify

additional safety measures for OCS activities.  

H2S Release.  Well locations F, G, and H are classified as H2S absent, per Revised Exploration Plan

Control No. R‐4986, which was approved on October 30, 2009.  Based on this, no further

discussion of H2S is warranted.  

B.  Affected Environment

The lease area is in the north‐central Gulf of Mexico, 68 mi (110 km) south of the nearest

shoreline and 116 mi (185 km) from the onshore support base at Port Fourchon, Louisiana

(Figure 1).  Water depth at the wellsites ranges from 1,838 to 1,843 m (6,030 to 6,045 ft)

(Figure 2).  There is no evidence of significant fluid expulsion features or high‐density deepwater

benthic communities near the wellsites (Geoscience Earth & Marine Services, Inc. [GEMS],

2011).   

A detailed description of the regional affected environment is provided in EISs prepared in 2007

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

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

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

regional descriptions remain valid and are incorporated by reference.  General background

information is presented below, and brief descriptions of each potentially affected resource are

presented in Section C, including site‐specific and/or new information if available.

The Macondo incident resulted in impacts on water quality in the area of the spill.  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).  Despite more limited information on the water quality of deep water, it is

clear that the condition of the offshore waters of the Gulf of Mexico were altered by the

Macondo incident.  Various monitoring efforts and environmental studies are in progress, but it

is currently impossible to estimate precisely the long‐term impacts that this spill will have on

offshore water quality (BOEMRE, 2011a,b).

The lease area is located approximately 53 mi (85 km) south‐southwest of the site where the

Macondo incident occurred.  Based on an analysis of satellite imagery (ESRI, 2010), the surface

slick did extend over the lease area.  In light of the current information available, there is

evidence to suggest that water quality in the lease area was temporarily affected by the

Macondo incident.  Prior to the Macondo incident, water quality in deep, offshore waters of the

Gulf of Mexico 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 long‐term change

in water quality conditions in the lease area of MC 948 and 949 from those predicted in the

multi‐lease‐sale EISs (MMS 2007b, 2008; BOEMRE, 2011a,b).
Mississippi Canyon Blocks 948 and 949 

Environmental Impact Analysis for Initial Exploration Plan 

Figure 2. Bathymetric map of the lease area showing proposed well surface locations. (Water depth in meters.)
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 19

C.  Impact Analysis

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

Impacts have been analyzed extensively in the multi‐lease‐sale EISs for the Western and Central

Gulf of Mexico Planning Areas (MMS, 2007b, 2008) as well as the environmental assessment for

Gulf of Mexico deepwater operations and activities (MMS, 2000).  The information in these

documents is incorporated by reference.  Potential site‐specific issues are addressed in this

section.

C.1 Physical/Chemical Environment

C.1.1 Air Quality

There are no site‐specific air quality data for the project area due to the distance from shore.  

Because of the distance from shore‐based pollution sources and the lack of sources offshore, air

quality at the wellsites 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 January 2011 all Louisiana, Mississippi, Alabama, and Florida coastal counties and parishes

are in attainment with the National Ambient Air Quality Standards (NAAQS) for all criteria

pollutants (USEPA, 2010).  Three metropolitan areas in Texas are nonattainment areas for

8‐hour ozone (Beaumont‐Port Arthur, Dallas‐Fort Worth, and Houston‐Brazoria), and El Paso

County is a nonattainment area for PM‐10 (USEPA, 2010).

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.

As noted earlier, based on calculations made pursuant to applicable regulations, emissions from

drilling activities are not expected to be significant because they are below exemption levels.  

Therefore, the only potential effect on air quality would be from a small diesel fuel spill and a

large oil spill (WCD).

BOEMRE has reexamined the analysis for air quality presented in MMS 2007b and 2008 based

on additional information and in consideration of the Macondo incident.  No substantial new

information was found that would alter the potential impacts on air quality presented in

previous multi‐lease‐sale EISs (BOEMRE, 2011a,b).

Impacts of Air Pollutant Emissions

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

emissions will result from the drilling rig operations, helicopters, and service vessels.  These

emissions occur mainly from combustion or burning of diesel fuel.  The combustion of fuels

occurs primarily on diesel fuel ‐powered generators, pumps, or motors and from lighter fuel

motors.  Primary air pollutants typically associated with OCS activities are suspended PM, SOx,

NOx, VOCs, and CO.  Emissions of pollutants into the atmosphere from these activities are not
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 20

projected to have significant effects on onshore air quality because of the prevailing

atmospheric conditions, emission rates and heights, and resulting pollutant concentrations.  As

the BOEMRE found in the multi‐lease‐sale EISs, the incremental contribution of activities similar

to Noble’s proposed activities to the cumulative impacts is not significant and will not cause or

contribute to a violation of any national ambient air quality standard (MMS, 2007b, 2008).  Since

the BOEMRE completed the multi‐lease‐sale EISs, the USEPA has adopted a new short‐term

NAAQS for nitrogen dioxide.  The standard has not yet been implemented in the Gulf Coast

states, but given the levels of expected emissions and the distance of the project from shore,

emissions from Noble’s proposed EP are not likely to contribute to violations of any NAAQS

onshore.

Carbon dioxide (CO2) and CH4 emissions from the project will constitute a small incremental

contribution to greenhouse gas emissions from all OCS activities.  According to the

Programmatic EIS (MMS, 2007a), estimated CO2 emissions from all OCS activities in the

2007‐2012 leasing program are about 0.08% to 0.016% of the global CO2 emissions from fossil

fuel combustion.  Greenhouse gas emissions may contribute to climate change, with important

effects on temperature, rainfall, frequency of severe weather, ocean acidification, and sea level

rise (Intergovernmental Panel on Climate Change, 2007).  Greenhouse gas emissions from this

proposed project 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 lease sale EIS (MMS, 2007b) or Programmatic EIS

(MMS, 2007a).

Due to the distance from shore, routine operations in the project area are not expected to have

any impact on air quality conditions along the coast, including nonattainment areas.  As noted in

the lease sale EIS (MMS, 2007b), emissions of air pollutants from routine activities in the Central

Gulf of Mexico Planning Area are projected to have minimal impacts to onshore air quality

because of the prevailing atmospheric conditions, emission heights, emission rates, and the

distance of these emissions from the coastline.  The Air Quality Emissions Report

(see EP Section G) prepared in accordance with BOEMRE requirements shows that the projected

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

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

No further analysis or control measures are required (Table 4).

Table 4. Estimated air pollutant emissions over the life of the proposed project in

Mississippi Canyon Blocks 948 and 949.

Year Estimated Tons

PM SOx NOx VOC CO

2012 54.22 248.72 1,863.70 55.91 406.63

2013 54.22 248.72 1,863.70 55.91 406.63

2014 54.22 248.72 1,863.70 55.91 406.63

Total Project 54.22 248.72 1,863.70 55.91 406.63

Exemption Calculation 2,264.40 2,264.40 2,264.40 2,264.40 56,643.69

CO = carbon monoxide; NOx = nitrogen oxides; PM = particulate matter; SOx = sulfur oxides; VOC = volatile organic

compound.
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 21

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

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

quality area.  The BOEMRE is required to notify the National Park Service (NPS) and U.S. Fish and

Wildlife Service (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 mi (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 102 mi (164 km) from the Breton Wilderness Area.  

Noble does not anticipate any impact on the Class I area, but will comply with any emissions

requirements as directed by BOEMRE.  

Impacts of a Small Fuel Spill

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

and discussed in EISs prepared for lease sales in 2007 and 2008 (MMS, 2007b, 2008).  The

probability of a small spill would be minimized by Noble’s preventative measures during routine

operations, including diesel fuel transfer.  In the unlikely event of a spill, implementation of

Noble’s OSRP will reduce the potential impacts.  EP Section H includes a detailed discussion of

the spill response measures that would be employed (see Attachment H‐1).  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 diesel fuel spill would affect air quality near the spill site by introducing VOCs through

evaporation.  The ADIOS2 model (see Section A.9.2) indicates that over 90% of a small diesel

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

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

conditions.

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

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

Impacts of a Large Oil Spill (WCD)

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

analyzed and discussed in the lease sale EISs (MMS, 2007b, 2008; BOEMRE, 2011a,b).  

A large oil spill (WCD) could potentially 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.  Realtime wind and current data from the project area would be available at the time

of a spill and would be used to assess the fate and effects of VOCs released.  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.  However, in‐situ burning would occur only after authorization

from USEPA.

Due to the lease area location (68 mi [110 km]) from the nearest shoreline), most air quality

impacts would occur in offshore waters with minimal chance to affect onshore air quality.
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 22

C.1.2 Water Quality

There are no site‐specific water quality data for the lease area.  Due to the lease location in

deep, offshore waters, water quality is expected to be good, with low levels of contaminants.  As

noted in the lease sale EIS (MMS, 2007b), deepwater areas in the northern Gulf of Mexico are

relatively homogeneous with respect to temperature, salinity, and oxygen.  Kennicutt (2000)

noted that the deepwater region has little evidence of contaminants in the dissolved or

particulate phases of the water column.  However, there are localized occurrences of natural

seepage of oil, gas, and brines in near‐surface sediments and up through the water column.

The lease area is located approximately 53 mi (85 km) south‐southwest from the site where the

Macondo incident occurred.  Based on the general circulation pattern seen in the Gulf of Mexico

and on satellite imagery (ESRI, 2010), the surface slick from that discharge did extend over the

lease area during the spill and water quality at the lease site may have been impacted.

IPFs potentially affecting water quality are effluent discharges and two (2) types of accidents:

a small diesel fuel spill and a large oil spill (WCD).

Impacts of Effluent Discharges

In general, turbid water can be expected to extend between a few hundred meters and several

kilometers down current from the discharge point for water‐based drilling muds and cuttings.  

No SBMs or cuttings will be released and all NPDES permit limitations and requirements will be

met.  There will be no persistent impacts on water quality in the lease area (NRC, 1983;

Neff, 1987; Neff et al., 2000).  

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

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

met, therefore, little or no impact on water quality is anticipated.

Deck drainage includes all effluents resulting from rain, deck washings, and runoff from curbs,

gutters, and drains, including drip pans in work areas.  Rainwater that falls on uncontaminated

areas of the drilling rig will flow overboard without treatment.  However, rainwater that falls on

the drilling rig deck and other areas such as chemical storage areas and places where equipment

is exposed will be collected and oil and water separated to meet NPDES permit requirements.  

Based on adherence to permit limits and applicable regulations, 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,

resulting in little or no impact on water quality.

Support vessels will discharge treated sanitary and domestic wastes.  These will have a slight

effect on water quality in the immediate vicinity of the discharges.  All support vessel discharges

will be in accordance with USCG regulations and, as applicable, the NPDES Vessel General

Permit, and therefore are not expected to cause significant impacts on water quality.

Impacts of a Small Fuel Spill

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

analyzed and discussed in recent EISs (MMS, 2007b, 2008).  The probability of a small spill would
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 23

be minimized by Noble’s preventative measures during routine operations, including diesel fuel

transfer.  In the unlikely event of a spill, implementation of Noble’s OSRP will potentially help

mitigate and reduce the impacts.  EP Section H provides detail on spill response measures in

addition to the summary information provided in this EIA.  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 diesel fuel spill in offshore waters would produce a slick on the water surface and

increase the concentrations of petroleum hydrocarbons and their degradation products.  The

extent and persistence of impacts would depend on the meteorological and oceanographic

conditions at the time and the effectiveness of spill response measures.  However, it is

estimated that over 90% of a small diesel fuel spill would be evaporated or dispersed within

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

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

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

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

molecular weight and can be readily degraded by aerobic microbial oxidation.  Diesel is so light

that it is not possible for the oil to sink and pool on the seafloor.  Diesel dispersed in the water

column can adhere to suspended sediments, but this generally occurs only in coastal areas with

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

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

by naturally occurring microbes (NOAA, 2006).

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

expected to make landfall or reach coastal waters due to both response efforts that would be

undertaken as well as natural attenuation (see Section A.9.2).

Impacts of a Large Oil Spill (WCD)

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

analyzed and discussed in the lease sale EISs (MMS, 2007b, 2008).  A large spill would affect

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

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

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

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

the surface, although new information from the Macondo incident indicates that plumes of

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

(Camilli et al., 2010; Hazen et al., 2010; Joint Analysis Group, 2010a,b,c;).  However, dispersants

would be applied only after approval from the USEPA.  Small droplets in the water may adhere

to suspended sediment and be removed from the water column (Operational Scientific Advisory

Team [OSAT] 2010).

Due to the lease area location (68 mi or 110 km from the nearest shoreline), it is expected that

most water quality impacts would occur in offshore waters, especially in the event of a spill

lasting less than 30 days.  Based on the revised OSRA modeling (BOEMRE, 2011a,b), there is a

78% chance that oil from a spill in this lease area would reach shorelines in Texas and a

60% chance of contacting coastlines in Louisiana within 120 days.
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 24

C.2 Seafloor Habitats and Biota

Water depths at the proposed SHLs range from 1,838 to 1,843 m (6,030 to 6,045 ft).  The

seafloor is relatively smooth and expected to be composed of consolidated soft marine clays.  

No areas of possible hard bottom or microseepages were seen within 610 m (2,000 ft) of the

wellsites (GEMS, 2011).   

Based on the absence of hard bottom areas detected by side‐scan sonar during the hazards

survey, the seafloor is expected to consist mainly of soft bottom communities.  The geohazards

assessment did not identify any features that could support high‐density deepwater benthic

communities within 610 m (2,000 ft) of the wellsites.  The potential for encountering shallow

gas at the proposed wellsites is generally negligible to low with minor concentrations of gas

potentially occurring in sand‐rich layers; therefore, the presence of chemosynthetic

communities is considered unlikely (GEMS, 2011).

C.2.1 Soft Bottom Benthic Communities

There are no site‐specific benthic community data from the lease area.  However, during the

Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology study, several stations

were sampled in similar water depths in the region of the lease area (Rowe and Kennicutt,

2009).  Table 5 summarizes benthic community data from Stations MT4 and MT5, 28 mi (45 km)

west‐southwest and 49 mi (79 km) south, respectively, from the lease area.

Table 5. 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 (Data from: Rowe and Kennicutt, 2009; Wei, 2006).

Station Water Depth

(m)

Abundance

Meiofauna

(individuals/m2)

Macroinfauna

(individuals/m2)

Megafauna

(individuals/ha)

MT4 1,402 246,058 3,262 1,548

MT5 2,281 128,964 1,763 1,111

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 of the lease area typically range from about 100,000 to

300,000 individuals/m2 (Rowe and Kennicutt, 2009).  Data from nearby stations (Table 5) are

within this range.  Nematodes and harpacticoid copepods were the two dominant meiofaunal

groups, 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 lease area

(approximately 1,840 m) are expected to be about 1,740 individuals/m2

.  However, actual

densities are highly variable.  Macroinfaunal densities at the stations noted in Table 5 range

from 1,763 to 3,262 individuals/m2

.
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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.  MC 948 and 949 are close to both Zones 2E and 3E.  Zone 2E includes stations

ranging in depth from 663 to 1,828 m (2,175 to 5,998 ft), with the most abundant species being

the polychaetes Aricidea suecica, Litocorsa attenata, Paralacydonia paradoxa, and

Tharyx marioni, and the bivalve Heterodonta sp. D.  Zone 3E includes stations ranging in depth

from 2,275 to 3,314 m (7,464 to 10,873 ft), with the most abundant species being the

polychaetes Paraonella monilaris and Tharyx marioni, the bivalves Heterodonta sp. B and C., and

the isopod Macrostylis sp.

Megafaunal densities from nearby stations range from 1,111 to 1,548 individuals/ha (Table 5).  

Common megafauna included motile groups such as decapod crustaceans, echinoderms

(ophiuroids and 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 g C/m2 in the top 15 cm of sediments (Rowe and Kennicutt, 2009).

Impacts of Effluent Discharges

Drilling muds and cuttings are the only effluents that are likely to affect benthic communities.  

During initial well interval(s) before the marine riser is set, cuttings and seawater‐based “spud

mud” will be released at the seafloor.  Excess cement slurry will also be released at the seafloor

during casing installation for the riserless portion of the drilling operations.  Cement slurry

components typically include cement mix and some of the same chemicals used in water‐based

drilling muds (Boehm et al., 2001).  The main impacts will be burial and smothering of benthic

organisms within several meters to tens of meters around the wellbore.  Soft bottom sediments

disturbed by cuttings, drilling muds, and cement slurry will eventually be recolonized through

larval settlement and migration from adjacent areas.  Because some deep‐sea biota grow and

reproduce slowly, recovery could occur over a period of several months to years.

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

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

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

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

adhering SBMs tend to clump together and form thick cuttings piles close to the drillsite.  Areas

of SBM cuttings deposition may develop elevated organic carbon concentrations and anoxic

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

concentrations of approximately 1,000 mg/kg or higher, benthic infaunal communities may be

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

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

as opportunistic species that tolerate low oxygen and high 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.
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The areal extent of impacts from drilling discharges will be small.  Assuming a typical effect

radius of 500 m (1,640 ft), the affected area around each wellsite represents about 3% of the

seafloor within a lease block.  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 in the region.

Impacts of a Large Oil Spill (WCD)

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

hundred meters of the wellsite.  The MMS in its lease sale EIS (2007b) estimates that a severe

subsurface blowout could resuspend and disperse sediments within a 300‐m (984‐ft) radius.  

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

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

30 days and dispersed over a much wider area.  Based on previous studies, surface sediments at

the project area are assumed to largely be silt and clay (Rowe and Kennicutt, 2009).

Previous lease sale EIS documents (MMS, 2007a, 2008) indicated 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 incident, subsurface plumes were reported at

a water depth of about 1,100 m (3,600 ft), extending at least 22 mi (35 km) from the wellsite

and persisting for more than a month (Camilli et al., 2010; BOEMRE, 2011a,b).  The subsurface

plumes apparently resulted from the use of dispersants at the wellhead (Joint Analysis Group,

2010c).  While the behavior and impacts of subsurface plumes are not well known, a subsurface

plume could contact the seafloor and affect benthic communities beyond the 300‐m (984‐ft)

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

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

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

2003).

C.2.2 High‐Density Deepwater Benthic Communities

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

that could support high‐density chemosynthetic communities, or features or areas that could

support high‐density deepwater corals and other associated high‐density hard bottom

communities.  Chemosynthetic communities were discovered in the central Gulf of Mexico in

1984 and have been studied extensively (MacDonald, 2002).  Deepwater coral communities are

also known from numerous locations in the Gulf of Mexico (Brooke and Schroeder, 2007;

CSA International, Inc., 2007).  These communities occur almost exclusively on authigenic

carbonates created by chemosynthetic communities.

The nearest known chemosynthetic community site is in MC 969 approximately 69 mi (112 km)

east‐southeast from the lease area in MC 948.  The nearest identified deep water coral

communities are in MC 943, 14 mi (22 km) west of MC 948.

The geohazards assessment of the lease area did not identify any features that could support

high‐density deepwater benthic communities within 610 m (2,000 ft) of the proposed drilling

mud/cuttings discharge locations.  No potential hydrocarbon seepage areas were defined in the

study area, the area has negligible to low potential for gaseous sediments, and the potential for
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Environmental Impact Analysis for Initial Exploration Plan Page 27

significant, densely‐populated deepwater benthic communities is considered to be negligible

(GEMS, 2011).   

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

(drilling muds and cuttings), and a large oil spill (WCD) from a well blowout at the seafloor.  

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

and dissipate on the sea surface.

Impacts of Effluent Discharges

The shallow hazards study did not identify any features that could support high‐density

deepwater benthic communities within 610 m (2,000 ft) of the proposed drilling locations, and

the presence of chemosynthetic communities in the lease area is considered remote.  

Monitoring programs on the Gulf of Mexico continental slope have shown that benthic impacts

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

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

Inc., 2004, 2006; Neff et al., 2005).  Because of the water depth of the lease area, drilling

discharges would be expected to result in thinner, more diffuse accumulations on the seafloor

than those documented in the literature.  Although small amounts of cuttings particles may

reach areas inhabited by high‐density deepwater benthic communities, the discharges are not

expected to result in significant impacts to these communities.

Impacts of a Large Oil Spill (WCD)

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

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

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

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

depth of about 1,100 m (3,600 ft), extending at least 22 mi (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 high‐density deepwater benthic communities beyond the 300‐m

(984‐ft) radius estimated by MMS (2007a, 2008), depending on its extent, trajectory, and

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

and approval process for the use of dispersants, and such approval would be obtained from the

USEPA prior to the use of dispersants.

The biological effects and expected fate of the oil remaining in the Gulf of Mexico from the

Macondo incident are still unknown due to the depth and magnitude of this event.  Hazen et al.

(2010) reported changes in plume hydrocarbon composition with distance from the source.  

Incubation experiments with environmental isolates demonstrated faster than expected

hydrocarbon biodegradation rates at 5 °C (41 F).  Based on these results, Hazen et al. (2010)

suggested the potential exists for intrinsic bioremediation of the oil plume in the deep‐water

column without substantial oxygen drawdown.

Potential impacts of oil on high‐density deepwater benthic communities are discussed by MMS

in its lease sale EIS (2007b).  Although chemosynthetic communities live among hydrocarbon

seeps, natural seepage is very constant and occurs at low rates compared to the potential rates

of oil release from a blowout.  In addition, seep organisms also require unrestricted access to
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Environmental Impact Analysis for Initial Exploration Plan Page 28

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 (1) or more commercial and recreational fishery

habitats.  Sublethal effects could be long‐lasting and affect the resilience of coral colonies to

natural disturbances (e.g., elevated water temperature and diseases).

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

recent (October 2010) survey of deepwater coral habitats near the site where the Macondo

incident occurred (BOEMRE, 2010; 2011a,b).  Government and academic researchers were

working at a site 1,400 m (4,600 ft) deep and approximately 7 mi (11 km) southwest of the

Macondo wellhead when they visually observed dead and dying corals with sloughing tissue and

discoloration.  Much of the soft coral observed in an area measuring about 15 to 40 m

(50 to 130 ft) was covered by what appeared to be a brown substance.  Ninety percent of

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

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

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

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

remotely operated vehicle 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 incident.  Charles Fisher, a Penn State biological oceanographer, anticipated

publishing the results of this sampling effort in March of 2011, but these results have not yet

appeared in press.

C.2.3 Designated Topographic Features

The block is not within or near a designated topographic feature or a no‐activity zone as

identified in NTL 2009‐G39.  The nearest designated topographic feature is located in

West Delta, Southern Addition (WD) Block 147 approximately 60 mi (96 km) north‐northwest

from the project area.

There are no IPFs associated with either routine operations or accidents that could cause

impacts to designated topographic features due to the distance from the lease area.  A small

diesel fuel spill would float and dissipate on the surface and would not reach these seafloor

features.

In the event of a WCD, a surface slick would not contact these seafloor features.  If a subsurface

plume were to occur, impacts on these features would be unlikely due to the distance and the

difference in water depth.  Near‐bottom currents in the region are predicted to flow along the

isobaths (Nowlin et al., 2001) and typically would not carry a plume up onto the continental

shelf edge.

C.2.4 Pinnacle Trend Area Live Bottoms

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

NTL 2009‐G39, the nearest pinnacle trend block is Main Pass Block 290, which lies 83 mi

(134 km) to the east‐northeast of MC 949.  
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Environmental Impact Analysis for Initial Exploration Plan Page 29

There are no IPFs associated with either routine operations or accidents that could cause

impacts to pinnacle trend area live bottoms due to the distance from the lease area.  A small

diesel fuel spill would float on the surface and would not reach these seafloor features.

In the event of a WCD, a surface slick would not contact these seafloor features.  If a subsurface

plume were to occur, impacts on these features would be unlikely due to the distance and the

difference in water depth.  Near‐bottom currents in the region are predicted to flow along the

isobaths (Nowlin et al., 2001) and typically would not carry a plume up onto the continental

shelf edge.

C.2.5 Eastern Gulf Live Bottoms

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

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

nearest block covered by the live bottom stipulation, as defined by NTL 2009‐G39, is

Destin Dome Block 573 approximately 109 mi (175 km) east‐northeast from the lease area.

There are no IPFs associated with either routine operations or accidents that could cause

impacts to eastern Gulf live bottom areas due to the distance from the lease area.  A small diesel

fuel spill would float and dissipate on the surface and would not reach these seafloor features.

In the event of a WCD, a surface slick would not contact these seafloor features.  If a subsurface

plume were to occur, impacts on these features would be unlikely due to the distance and the

difference in water depth.  Near‐bottom currents in the region are predicted to flow along the

isobaths (Nowlin et al., 2001) and typically would not carry a plume up onto the continental

shelf.

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

This section discusses species listed as endangered or threatened under the Endangered Species

Act (ESA).  In addition, it includes all marine mammal species in the region, which are protected

under the Marine Mammal Protection Act (MMPA).

Endangered or threatened species that may occur in the project area and/or along the northern

Gulf Coast are listed in Table 6.  The table also indicates the location of critical habitat

(if designated in the Gulf of Mexico).  Critical habitat is defined as (1) specific areas within the

geographical area occupied by the species at the time of listing, if they contain physical or

biological features essential to conservation, and those features may require special

management considerations or protection; and (2) specific areas outside the geographical area

occupied by the species if the agency determines that the area itself is essential for

conservation.  The National Marine Fisheries Service (NMFS) has jurisdiction for ESA‐listed

cetaceans, sea turtles, and fishes in the Gulf of Mexico.  The USFWS has jurisdiction for

ESA‐listed birds and the West Indian Manatee.

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.
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As mandated by the ESA, BOEMRE consulted with NMFS and USFWS on possible and potential

impacts from the proposed leasing in the Western Gulf of Mexico Planning Area on

endangered/threatened species and their designated critical habitat (MMS, 2007a,b).  

A biological assessment was prepared for each consultation.  The formal ESA consultation with

NMFS was concluded with receipt of the Biological Opinion on July 3, 2007 (NMFS, 2007).  The

Biological Opinion concludes that the proposed lease sales and associated activities in the

Gulf of Mexico in the current 5‐Year Program are not likely to jeopardize the continued

existence of threatened and endangered species under NMFS jurisdiction or destroy or

adversely modify designated critical habitat.  The informal ESA consultation with USFWS was

concluded with a letter dated September 14, 2007.  The USFWS concurred with the BOEMRE’s

determination that proposed actions of the current 5‐Year Program were not likely to adversely

affect the threatened/endangered species or designated critical habitat under USFWS

jurisdiction.  Following the Macondo incident, the BOEMRE requested reinitiation of ESA

consultation with both NMFS and USFWS on July 30, 2010.  The NMFS responded with a letter

to BOEMRE on September 24, 2010.  The USFWS responded with a letter to BOEMRE on

September 27, 2010.  However, since that date the NMFS and USFWS have placed this

consultation on hold given that the environmental baseline needs to be updated with results of

the NRDA process.  NRDA data have yet to be released and the existing consultations will remain

in effect until the reinitiated consultations are completed (BOEMRE, 2011b).  The existing

consultation recognizes that BOEMRE‐required mitigations and other reasonable and prudent

measures should reduce the likelihood of impacts from BOEMRE‐authorized activities.

Coastal endangered or threatened species include the West Indian Manatee, Piping Plover,

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

designated for all of these species as indicated in Table 6 and discussed in individual sections.

Two (2) other coastal species (Bald Eagle and Brown Pelican) discussed by BOEMRE in its lease

sale EIS (2007b) are no longer listed as endangered or threatened.  These are discussed under

Coastal and Marine Birds.

The sperm whale and five (5) 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.

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 based on available data at this time.  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.   
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Table 6. 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

Lease Area Coastal in Gulf of Mexico

Marine Mammals

Sperm whale Physeter macrocephalus E X ‐‐ None

West Indian manatee Trichechus manatus latirostris E ‐‐ X Florida (Peninsular)

Blue whale Balaenoptera musculus E Xa ‐‐ None

Fin whale Balaenoptera physalus E Xa ‐‐ None

Humpback whale Megaptera novaeangliae E Xa ‐‐ None

North Atlantic right whale Eubalaena glacialis E Xa ‐‐ None

Sei whale Balaenoptera borealis E Xa ‐‐ None

Sea Turtles

Loggerhead turtle Caretta caretta T X X None

Green turtle Chelonia mydas T, E

b X X None

Leatherback turtle Dermochelys coriacea E X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Birds

Piping Plover Charadrius melodus T  ‐‐  X

Coastal Texas, Louisiana,

Mississippi, Alabama, and

Florida (Panhandle)

Whooping Crane Grus americana E  ‐‐  X

Coastal Texas

(Aransas National Wildlife

Refuge)

Fishes

Gulf sturgeon Acipenser oxyrinchus desotoi T  ‐‐  X

Coastal Louisiana, Mississippi,

Alabama, and Florida

(Panhandle)

Smalltooth sawfish Pristis pectinata E  ‐‐  X Southwest Florida and the

Florida Keys

Invertebrates

Elkhorn coral Acropora palmata E ‐‐ X Flower Garden Banks

Terrestrial Mammals

Beach mice (Alabama,

Choctawhatchee,

Perdido Key, St. Andrew)

Peromyscus polionotus E  ‐‐  X Alabama and Florida

(Panhandle) beaches

Abbreviations: E = endangered; T = threatened.   a

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

to be present in the lease area. b

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

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 the 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 NOAA Fisheries (Waring et al.,

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

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

features such as eddies associated with the Gulf of Mexico Loop Current (Jochens et al., 2008).  

Sperm whale populations in the north‐central Gulf of Mexico are present there throughout the

year (Davis et al., 2000).  Results of a multi‐year tracking study show female sperm whales

typically concentrated along the upper continental slope between the 200‐ and 1,000‐m
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Environmental Impact Analysis for Initial Exploration Plan Page 32

(656‐ and 3,280‐ft) depth contours (Jochens et al., 2008).  Male sperm whales were more

variable in their movements and were documented in water depths greater than 3,000 m

(9,843 ft).  Generally, groups of sperm whales sighted in the Gulf of Mexico during the

MMS‐funded Sperm Whale Seismic Study (SWSS) consisted of mixed‐sex groups comprising

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

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

through the vicinity of the lease area.  Movements of satellite‐tracked individuals suggest that

this area of the Gulf continental slope is within the home range of the Gulf of Mexico population

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

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

vessel and helicopter traffic; and two (2) types of accidents – a small diesel fuel spill or a large oil

spill (WCD).  Effluent discharges are likely to have negligible impacts on sperm whales due to

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

the mobility of these marine mammals.  Compliance with NTL 2007‐G03 will minimize the

potential for marine debris‐related impacts on sperm whales.

Current threats to sperm whale populations worldwide are discussed in a final recovery plan for

the sperm whale recently published by NOAA (NMFS, 2010a).  Threats are defined as “any factor

that could represent an impediment to recovery” and these include fisheries interactions,

anthropogenic noise, vessel interactions, contaminants and pollutants, disease, injury from

marine debris, research, predation and natural mortality, direct harvest, competition for

resources, loss of prey base due to climate change and ecosystem change, and cable laying.  In

the Gulf of Mexico, the impacts from many of these threats are identified as either low or

unknown (BOEMRE, 2011a,b).

Impacts of Drilling Rig Presence, Noise, and Lights

Noise from routine drilling activities has the potential to disturb sperm whales.  Sperm whales

appear to have good low‐frequency hearing, but the available data do not indicate a consistent

response to anthropogenic noise (Jochens et al., 2008).  Noise associated with drilling is

relatively weak in intensity, and an individual animal’s noise exposure would be transient.  There

are other OCS facilities and activities near the lease area, and the region as a whole has a large

number of similar sources.  Due to the limited scope and short duration of drilling activities, this

project would represent a small temporary contribution to the overall noise regime.

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

its Biological Opinion for the Five‐Year Leasing Plan for Western and Central Planning Areas.  The

analysis noted that semisubmersible drilling rigs show low sound source levels and concluded

that drilling is not expected to produce amplitudes sufficient to cause hearing or behavioral

effects in sperm whales; therefore, these effects are insignificant (NMFS, 2007).

Drilling rig lighting and rig presence are not identified as IPFs for sperm whales in recent lease

sale EISs (MMS, 2007b, 2008) or the NMFS (2007) Biological Opinion.

Impacts of Support Vessel and Helicopter Traffic

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

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

concerning the frequency of vessel strikes is presented in the lease sale EIS (MMS, 2007b).  To
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Environmental Impact Analysis for Initial Exploration Plan Page 33

reduce the potential for vessel strikes, the BOEMRE has issued NTL 2007‐G04, which

recommends protected species identification training and that vessel operators and crews

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

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

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

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

are required to reduce vessel speed to 10 knots or less when mother/calf pairs, pods, or large

assemblages of cetaceans are observed near an underway vessel when safety permits.  

Compliance with this NTL will minimize the likelihood of vessel strikes as well as reduce the

chance for disturbing sperm whales.

The NMFS (2007) analyzed the potential for vessel strikes and harassment of sperm whales in its

Biological Opinion for the Five‐Year Leasing Plan for Western and Central Planning Areas.  With

implementation of the mitigation measures in NTL 2007‐G04, NMFS concluded that the

likelihood of collisions between vessels and sperm whales would be reduced to insignificant

levels.  The NMFS concluded that the observed avoidance of passing vessels by sperm whales is

an advantageous response to avoid a potential threat and is not expected to result in any

significant effect on migration, breathing, nursing, breeding, feeding, or sheltering to individuals,

or have any consequences at the level of the population.  With implementation of the vessel

strike avoidance measures requirement to maintain a distance of 90 m (295 ft) from sperm

whales, the NMFS concluded that the potential for harassment of sperm whales would be

reduced to discountable levels.

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

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

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

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

360 m (1,180 ft) lateral distance from the aircraft.  Additional reactions were seen when aircraft

circled certain whales to make further observations.  Based on other studies of cetacean

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

the aircraft were short‐term and probably of no long‐term biological significance.

While flying offshore in the Gulf of Mexico, helicopters maintain altitudes above 213 m (700 ft)

during transit to and from the working area.  In the event that a whale is seen during transit, 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 the lease

sale EISs (MMS, 2007b, 2008) and by the NMFS (2007) in its Biological Opinion for the Five‐Year

Leasing Plan for Western and Central Planning Areas.  Oil impacts on marine mammals are

discussed by Geraci and St. Aubin (1990).  For the EP associated with this EIA, there are no

unique site‐specific issues with respect to spill impacts on these animals that were not analyzed

in the previous documents.
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Environmental Impact Analysis for Initial Exploration Plan Page 34

The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

routine operations including diesel fuel transfer.  In the unlikely event of a spill, implementation

of Noble’s OSRP will mitigate and lessen the potential for impacts on sperm whales.  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 diesel 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 diesel fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.  The area of the sea surface with diesel fuel on it would

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation,

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and

noise of response vessels and aircraft (Marine Mammal Commission [MMC], 2010).  However,

due to the limited areal extent and short duration of water quality impacts from a small diesel

fuel spill, as well as the mobility of sperm whales, no significant impacts would be expected.

Impacts of a Large Oil Spill (WCD)

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

(MMS, 2007b, 2008) and by the NMFS (2007) in its Biological Opinion for the Five‐Year Leasing

Plan for Western and Central Planning Areas.  For the EP associated with this EIA, there are no

unique site‐specific issues with respect to spill impacts on these animals.

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

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

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

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

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

the activities and noise of response vessels and aircraft.  Complications of the above may lead to

dysfunction of immune and reproductive systems, physiological stress, declining physical

condition, and death.  Behavioral responses can include displacement of animals from prime

habitat, disruption of social structure, changing prey availability and foraging distribution and/or

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

migration (MMC, 2010).

In the event of a large spill, the level of vessel and aircraft activity associated with spill response

could disturb sperm whales and potentially result in vessel strikes, entanglement, or other injury

or stress.  Response vessels would operate in accordance with NTL 2007‐G04 to reduce the

potential for striking or disturbing these animals.

C.3.2 West Indian Manatee (Endangered)

Most of the manatee population is located in peninsular Florida (USFWS, 2001).  Manatee

sightings in Louisiana have been increasing as they extend their presence farther west of Florida
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Environmental Impact Analysis for Initial Exploration Plan Page 35

in the warmer months (Wilson, 2003).  A species description is presented in the lease sale EIS

(MMS, 2007b) and in the recovery plan for this species (USFWS, 2001).

IPFs potentially affecting manatees include support vessel and helicopter traffic and a large oil

spill (WCD).  A small diesel fuel spill in the lease area would be unlikely to affect manatees, as

the lease area is approximately 68 mi (110 km) from the nearest shoreline (Louisiana).  As

explained in Section A.9.2, a small diesel fuel spill would not be expected to make landfall or

reach coastal waters prior to breaking up.  Compliance with NTL 2007‐G03 will minimize the

potential for marine debris‐related impacts on manatees.

Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb manatees, and there is also a risk of vessel

strikes, which are identified as a threat in the recovery plan for this species (USFWS, 2001).  

To reduce the potential for vessel strikes, the BOEMRE has issued NTL 2007‐G04, which

recommends protected species identification training and that vessel operators and crews

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

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

protected species.  Compliance with this NTL will minimize the likelihood of vessel strikes, and

no significant impacts on manatees are expected.

Helicopter traffic also has the potential to disturb manatees.  Rathbun (1988) reported that

manatees were disturbed more by helicopters than by fixed‐wing aircraft; however, the

helicopter was flown at a relatively low altitude of 20 to 160 m (66 to 525 ft).  Helicopters used

in support operations maintain a minimum altitude of 213 m (700 ft) while in transit offshore,

305 m (1,000 ft) over unpopulated areas or across coastlines, and 610 m (2,000 ft) over

populated areas and sensitive habitats such as wildlife refuges and park properties.  This

mitigation measure will minimize the potential for disturbing manatees, and no significant

impacts are expected.

Impacts of a Large Oil Spill (WCD)

The revised OSRA results (BOEMRE, 2011a,b) summarized in Table 3 predicts that during the

spring there is a 9% chance of an oil spill from this location impacting shorelines along the

Louisiana coast within 10 days due to wind and current conditions seen in that season.  There is

no critical manatee habitat designated in the areas potentially affected and it is doubtful any

manatees would be impacted.

In the event that manatees were exposed to oil, effects could include direct impacts from oil

exposure, as well as indirect impacts due to response activities and materials (e.g., vessel traffic,

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

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

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

(or contaminated vegetation, in the case of manatees); and stress from the activities and noise

of response vessels and aircraft.  Complications of the above may lead to dysfunction of immune

and reproductive systems, physiological stress, declining physical condition, and death.  

Behavioral responses can include displacement of animals from prime habitat, disruption of

social structure, changing prey availability and foraging distribution and/or patterns, changing

reproductive behavior/productivity, and changing movement patterns or migration

(MMC, 2010).
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In the event that a large oil spill reached coastal waters where manatees were present, the level

of vessel and aircraft activity associated with spill response could disturb manatees and

potentially result in vessel strikes, entanglement, or other injury or stress.  Response vessels

would operate in accordance with NTL 2007‐G04 to reduce the potential for striking or

disturbing these animals, and therefore no significant impacts are expected.

C.3.3 Endangered Mysticete Whales

Five (5) 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 in that area (Würsig et al., 2000).  No critical habitat has been designated for

these species in the Gulf of Mexico.

Due to the rare occurrence of these whales in the Gulf of Mexico and the limited scope and

duration of the project, it is highly unlikely that any endangered mysticete would come into

contact with any project activities, either routine operations or accidents.  The NMFS (2007) did

not include any of these mysticete whales as affected species in its Biological Opinion for the

Five‐Year Leasing Plan for Western and Central Planning Areas.  Potential impacts are analyzed

in recent lease sale EISs (MMS, 2007b, 2008), and those analyses are incorporated by reference.  

If any of these whales were present in the area, potential impacts would be the same as those

discussed below in Section C.3.4.

C.3.4 Non‐Endangered Marine Mammals (Protected)

Excluding the seven endangered species that have been cited previously, there are 22 additional

species of marine mammals that may be found in the Gulf of Mexico.  All marine mammals are

protected species under the MMPA.  This includes two mysticete whales, the dwarf and pygmy

sperm whales, 4 species of beaked whales, and 14 species of delphinids.  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 the lease sale EIS

(MMS, 2007b).

Mysticete whales.  Two non‐endangered mysticete whales are known from the Gulf of Mexico.  

The Bryde’s whale (Balaenoptera edeni) has been sighted most frequently along the 100‐m

(328‐ft) isobath (Davis and Fargion, 1996; Davis et al., 2000).  Most sightings have been made in

the DeSoto Canyon region and off western Florida, although there have been some in the

west‐central portion of the northeastern Gulf.  The minke whale (Balaenoptera acutorostrata) is

considered rare in the Gulf of Mexico, with the only confirmed records coming from strandings

(Würsig et al., 2000).  Based on the available data, it is possible that Bryde’s whales could occur

in the lease area.

Dwarf and pygmy sperm whales.  At sea, it is difficult to differentiate dwarf sperm whales

(Kogia sima) from pygmy sperm whales (Kogia breviceps), and sightings are often grouped

together as “Kogia spp.”  Both species have a worldwide distribution in temperate to tropical

waters.  In the Gulf of Mexico, both species occur primarily along the continental shelf edge and

in deeper waters off the continental shelf (Mullin et al., 1991).  Either species could occur in the

lease area.
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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 is extralimital.  Due to the difficulties of at‐sea identification,

beaked whales in the Gulf of Mexico are identified either as Cuvier’s beaked whales or are

grouped into an undifferentiated complex (Mesoplodon spp. and Ziphius spp.).  In the northern

Gulf of Mexico, they are broadly distributed in waters greater than 1,000 m (3,281 ft) over lower

slope and abyssal landscapes (Davis et al., 2000).  Any of these species could occur in the lease

area.

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 the 14 species could occur in the lease area.

IPFs potentially affecting non‐endangered marine mammals include drilling rig presence, noise,

and lights; support vessel and helicopter traffic; and two (2) types of accidents (a small diesel

fuel spill and a large oil spill [WCD]).  Effluent discharges are likely to have negligible impacts on

marine mammals due to rapid dispersion, the small area of ocean affected, the intermittent

nature of the discharges, and the mobility of marine mammals.  Compliance with NTL 2007‐G03

will minimize the potential for marine debris‐related impacts on marine mammals.

Impacts of Drilling Rig Presence, Noise, and Lights

Noise from routine drilling activities has the potential to disturb marine mammals.  Most

odontocetes (toothed whales and dolphins) use higher frequency sounds than the dominant low

frequencies produced by OCS drilling activities (Richardson et al., 1995).  Noise associated with

drilling is relatively weak in intensity, and an individual animal’s noise exposure would be

transient.  There are other OCS facilities and activities near the lease area, and the region as a

whole has a large number of similar sources.  Due to the limited scope and short duration of

drilling activities, this project would represent a small temporary contribution to the overall

noise regime, and any short‐term impacts are not expected to be biologically significant to

marine mammal populations.

Drilling rig lighting and rig presence are not identified as IPFs for marine mammals in lease sale

EISs (MMS, 2007b, 2008).

Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb marine mammals, and there is also a risk of

vessel strikes.  Data concerning the frequency of vessel strikes is presented in the lease sale EIS

(MMS, 2007b).  To reduce the potential for vessel strikes, the BOEMRE has issued

NTL 2007‐G04, which recommends protected species identification training and that vessel
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operators and crews maintain a vigilant watch for marine mammals and slow down or stop their

vessel to avoid striking protected species, and requires operators to report sightings of any

injured or dead protected species.  Vessel operators and crews are required to attempt to

maintain a distance of 91 m (300 ft) or greater when whales are sighted and 45 m (150 ft) when

small cetaceans are sighted.  When cetaceans are sighted while a vessel is underway, vessels

must attempt to remain parallel to the animal’s course and avoid excessive speed or abrupt

changes in direction until the cetacean has left the area.  Vessel operators are required to

reduce vessel speed to 10 knots or less when mother/calf pairs, pods, or large assemblages of

cetaceans are observed near an underway vessel, when safety permits.  Compliance with this

NTL will minimize the likelihood of vessel strikes as well as reduce the chance for disturbing

marine mammals, and therefore no significant impacts are expected.

Aircraft traffic also has the potential to disturb marine mammals (Würsig et al., 1998).  However,

while flying offshore, helicopters maintain altitudes above 213 m (700 ft) during transit to and

from the working area.  This altitude will minimize the potential for disturbing marine mammals,

and no significant impacts are expected (MMS, 2007b).

Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008),

and oil impacts on marine mammals in general are discussed by Geraci and St. Aubin (1990).  For

the EP associated with this EIA, there are no unique site‐specific issues with respect to spill

impacts on these animals.

The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

diesel fuel transfer.  In the unlikely event of a spill, implementation of Noble’s OSRP is expected

to lessen the potential for impacts on marine mammals.  EP Section H provides detail on spill

response measures, along with a summary of those measures in this EIA.  Given the open ocean

location of the lease area, the limited duration of a small spill and response efforts, it is

expected that any impacts would be brief and minimal.

A small diesel 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 diesel fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.  The area of the sea surface with diesel fuel on it would

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation,

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and

noise of response vessels and aircraft (MMC, 2010).  However, due to the limited areal extent

and short duration of water quality impacts from a small diesel fuel spill, as well as the mobility

of marine mammals, no significant impacts would be expected.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine mammals are discussed in the Outer Continental Oil and Gas

Leasing Program EIS for 2007 and 2008 as well as the original deepwater EIS from 2000
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Environmental Impact Analysis for Initial Exploration Plan Page 39

(MMS, 2000; 2007b; and 2008).  For the EP associated with this EIA, there are no unique

site‐specific issues.  Impacts of oil spills on marine mammals can include direct impacts from oil

exposure, as well as indirect impacts due to response activities and materials (e.g., vessel traffic,

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

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

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

contaminated vegetation, in the case of manatees); and stress from the activities and noise of

response vessels and aircraft.  Complications of the above may lead to dysfunction of immune

and reproductive systems, physiological stress, declining physical condition, and death.  

Behavioral responses can include displacement of animals from prime habitat, disruption of

social structure, changing prey availability and foraging distribution and/or patterns, changing

reproductive behavior/productivity, and changing movement patterns or migration

(MMC, 2010).

In the event of a large spill, the level of vessel and aircraft activity associated with spill response

could disturb marine mammals and potentially result in vessel strikes, entanglement, or other

injury or stress.  Response vessels would operate in accordance with NTL 2007‐G04 to reduce

the potential for striking or disturbing these animals, and therefore no significant impacts are

expected.

C.3.5 Sea Turtles (Endangered/Threatened)

Five (5) species of endangered or threatened sea turtles may be found near the lease area.  

Endangered species are the leatherback (Dermochelys coriacea), Kemp's ridley (Lepidochelys

kempii), and hawksbill (Eretmochelys imbricata) turtles.  The loggerhead turtle (Caretta caretta)

is a threatened species.  The green turtle (Chelonia mydas) is listed as threatened, except for the

Florida and Pacific Coast of Mexico breeding populations, which are listed as endangered.  

Species descriptions are presented in the lease sale EIS (MMS, 2007b).

BOEMRE has reexamined the impacts analysis presented in MMS 2007b and 2008 for the five

sea turtles species that inhabit the Gulf of Mexico based on additional information and in

consideration of the Macondo incident.  Information from the 5‐year status reviews for federally

listed sea turtles in the Gulf of Mexico has been incorporated in the 2011 Draft Supplemental EIS

for the Western Gulf of Mexico Planning Area Lease Sale 218 (BOEMRE, 2011a,b).  However, no

new information from previous EISs was found that would alter the potential impacts on sea

turtles.  In most foreseeable cases, exposure to hydrocarbons persisting in the sea following the

dispersal of an oil slick will result in sublethal impacts (e.g., decreased health, reproductive

fitness, and longevity; and increased vulnerability to disease) to sea turtles.

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.

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;
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 Green and leatherback turtles – Green and leatherback turtles infrequently nest on Florida

Panhandle beaches (Florida Fish and Wildlife Conservation Commission, 2011);

 Kemp’s ridley turtles – The main Kemp’s ridley nesting site is Rancho Nuevo beach,

Tamaulipas, Mexico (NMFS et al., 2010).  Kemp’s ridley turtles typically do not nest

anywhere near the project area, although there have been occasional reports of Kemp’s

ridleys nesting in Alabama (Share the Beach, 2010); and

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

IPFs potentially affecting sea turtles include drilling rig presence, noise, and lights; support

vessel and helicopter traffic; and two (2) types of accidents (a small diesel fuel spill and a large

oil spill [WCD]).  Effluent discharges are likely to have negligible impacts on sea turtles due to

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

Compliance with NTL 2007‐G03 will minimize the potential for marine debris‐related impacts on

sea turtles.

Impacts of Drilling Rig Presence, Noise, and Lights  

Offshore drilling activities produce a broad array of sounds at frequencies and intensities that

may be detected by sea turtles (Geraci and St. Aubin, 1987).  Potential impacts may include

behavioral disruption and temporary or permanent displacement from the area near the sound

source.  Certain sea turtles, especially loggerheads, may be attracted to offshore structures

(Lohoefener et al., 1990) and, thus, may be more susceptible to impacts from sounds produced

during routine operations.  Helicopters and service vessels may also affect sea turtles due to

machinery noise and/or visual disturbances.  The most likely impacts would be short‐term

behavioral changes such as diving and evasive swimming, disruption of activities, or departure

from the area.  Due to the limited scope and short duration of drilling activities, these

short‐term impacts are not expected to be biologically significant to sea turtle populations.

Artificial lighting can disrupt the nocturnal orientation of sea turtle hatchlings (Witherington,

1997; Tuxbury and Salmon, 2005).  However, hatchlings may rely less on light cues when they

are offshore than when they are emerging on the beach (Salmon and Wyneken, 1990).  The

NMFS (2007) concluded that the effects of lighting from offshore structures on sea turtle

hatchlings are insignificant.

Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb sea turtles, and there is also a risk of vessel

strikes.  Data show that vessel traffic is one cause of sea turtle mortality in the Gulf of Mexico

(Lutcavage et al., 1997).  While adult sea turtles are visible at the surface during the day and in

clear weather, they can be difficult to spot from a moving vessel when resting below the water

surface, during nighttime, or during periods of inclement weather.  To reduce the potential for

vessel strikes, the BOEMRE has issued NTL 2007‐G04, which recommends protected species

identification training and that vessel operators and crews maintain a vigilant watch for sea

turtles and slow down or stop their vessel to avoid striking protected species, and requires

operators to report sightings of any injured or dead protected species.  When sea turtles are

sighted, vessel operators and crews are required to attempt to maintain a distance of 45 m

(150 ft) or greater whenever possible.  Compliance with this NTL will minimize the likelihood of

vessel strikes as well as reduce the chance for disturbing sea turtles (NMFS, 2007).
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Helicopter traffic also has the potential to disturb sea turtles.  However, while flying offshore,

helicopters maintain altitudes above 213 m (700 ft) during transit to and from the working area.  

This altitude will minimize the potential for disturbing sea turtles, and no significant impacts are

expected.

Impacts of a Small Fuel Spill

Potential spill impacts on sea turtles are discussed in recent EISs (MMS, 2007b, 2008) and by the

NMFS (2007) in its Biological Opinion for the Five‐Year Leasing Plan for Western and Central

Planning Areas.  For the EP associated with this EIA, there are no unique site‐specific issues with

respect to spill impacts on these animals.

The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

diesel fuel transfer.  In the unlikely event of a spill, implementation of Noble’s OSRP is expected

to minimize potential impacts on sea turtles.  EP Section H provides 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 diesel 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 diesel fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.  The area of the sea surface with diesel fuel on it would

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation,

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

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and

noise of response vessels and aircraft (MMC, 2010).  However, due to the limited areal extent

and short duration of water quality impacts from a small diesel fuel spill, no significant impacts

would be expected.

A small diesel fuel spill in the lease area would be unlikely to affect sea turtle nesting beaches,

as the lease area is 68 mi (110 km) from the nearest shoreline (Louisiana).  As explained in

Section A.9.2, a small diesel fuel spill would not be expected to make landfall or reach coastal

waters prior to breaking up.

Impacts of a Large Oil Spill (WCD)

Impacts of oil spills on sea turtles can include direct impacts from oil exposure, as well as

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

dispersants).  Direct physical and physiological effects can include skin irritation, inflammation,

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

smoke (e.g., from in situ burning of oil); ingestion of oil (and dispersants) directly or via

contaminated food; and stress from the activities and noise of response vessels and aircraft.  

Complications of the above may lead to dysfunction of immune and reproductive systems,

physiological stress, declining physical condition, and death.  Behavioral responses can include

displacement of animals from prime habitat, disruption of social structure, changing food

availability and foraging distribution and/or patterns, changing reproductive
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behavior/productivity, and changing movement patterns or migration (MMC, 2010).  In the

unlikely event of a spill, implementation of Noble’s OSRP is expected to minimize the potential

for these types of impacts on sea turtles.  EP Section H provides 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).

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 2007‐G04 to reduce the

potential for striking or disturbing these animals, and therefore no significant impacts are

expected.

C.3.6 Piping Plover (Threatened)

The Piping Plover (Charadrius melodus) is a migratory shorebird that overwinters along the

southeastern U.S. and Gulf of Mexico coasts.  This threatened species is in decline as a result of

hunting, habitat loss and modification, predation, and disease (USFWS, 2003).  Critical

overwintering habitat has been designated, including beaches in Texas, Louisiana, Mississippi,

Alabama, and Florida (Figure 3).  Piping Plovers inhabit coastal sandy beaches and mudflats,

feeding by probing for invertebrates at or just below the surface.  They use beaches adjacent to

foraging areas for roosting and preening (USFWS, 2010a).  A species description is presented in

the lease sale EIS (MMS, 2007b).

A large oil spill (WCD) is the only IPF potentially affecting Piping Plovers.  There are no IPFs

associated with routine project activities that could affect these birds.  A small diesel fuel spill in

the lease area would be unlikely to affect Piping Plovers because a small diesel fuel spill would

not be expected to make landfall or reach coastal waters prior to breaking up (see explanation

in Section A.9.2).

Impacts of a Large Oil Spill (WCD)

The lease area is 70 mi (113 km) from the nearest shorelines inhabited by Piping Plovers.  The

revised OSRA results (BOEMRE, 2011a,b) summarized in Section A.9.3 (Table 3) predict there is

a 4% probability that a spring oil spill in this lease area would reach a shoreline designated as

critical habitat for the wintering Piping Plover within 10 days.  Plovers could physically oil

themselves while foraging on oiled shores or secondarily contaminate themselves through

ingestion of oiled intertidal sediments and prey (MMS, 2007b).  Plovers congregate and feed

along tidally exposed banks and shorelines, following the tide out and foraging at the water’s

edge.  It is possible that some deaths of Piping Plovers could occur, especially if spills occur

during winter months when plovers are most common along the coastal Gulf or if spills
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contacted critical habitat.  Impacts could also occur from vehicular traffic on beaches and other

activities associated with spill cleanup.  Noble has extensive resources available to protect and

rehabilitate wildlife in the event of a spill reaching the shoreline, as detailed in the OSRP.

C.3.7 Whooping Crane (Endangered)

The Whooping Crane (Grus americana) is an omnivorous wading bird and an endangered

species.  There are three wild populations in North America (Whooping Crane Eastern

Partnership [WCEP], 2010).  One population winters along the Texas coast at Aransas NWR and

summers at Wood Buffalo National Park in Canada.  This population represents the majority of

the world’s population of free‐ranging Whooping Cranes and reached a record population of

270 at Aransas NWR in December 2008 (WCEP, 2010).  A non‐migrating population has been

re‐introduced in central Florida, and another re‐introduced population summers in Wisconsin

and migrates to the southeastern U.S. for the winter.  Whooping Cranes breed, migrate, winter,

and forage in a variety of habitats, including coastal marshes and estuaries, inland marshes,

lakes, ponds, wet meadows and rivers, and agricultural fields (USFWS, 2007).  About 9,000 ha

(22,240 ac) of salt flats on Aransas NWR and adjacent islands comprise the principal wintering

grounds of the Whooping Crane.  Aransas NWR is designated as critical habitat for the species

(Figure 3).  A species description is presented in a recent lease sale EIS (MMS, 2007b).

A large oil spill (WCD) is the only IPF potentially affecting Whooping Cranes.  A small diesel fuel

spill in the lease area would also be unlikely to affect Whooping Cranes, due to the distance

from Aransas NWR.  As explained in Section A.9.2, a small diesel fuel spill would not be

expected to make landfall or reach coastal waters prior to breaking up.

Impacts of a Large Oil Spill (WCD)

A large oil spill is unlikely to affect Whooping Cranes as the lease area is approximately 469 mi

(754 km) from its critical habitat (Aransas NWR) and the revised OSRA modeling (BOEMRE,

2011a,b) predicts a 3% probability that an oil spill originating in this lease area would reach the

Matagorda Island area of the Aransas NWR in Calhoun County, Texas, within 30 days and an

11% probability of oil reaching that area in 120 days.  

In the event of oil exposure, Whooping Cranes could physically oil themselves while foraging in

oiled areas or secondarily contaminate themselves through ingestion of contaminated shellfish,

frogs, and fishes.  It is possible that some death of Whooping Cranes could occur.  In the event

of a spill, Noble would work with the applicable State and Federal agencies to prevent and/or

mitigate impacts from a spill.
Mississippi Canyon Blocks 948 and 949 

Environmental Impact Analysis for Initial Exploration Plan 

Figure 3. Location of selected environmental features in relation to the lease area. Shown are Essential Fish Habitat 

coral reefs; Habitat Areas of Particular Concern (HAPCs) for northwestern Gulf of Mexico reefs and banks an

bluefin tuna; and critical habitat for beach mice, Gulf sturgeon, Piping Plover, and Whooping Crane.
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 45

C.3.8 Gulf Sturgeon (Threatened)

The Gulf sturgeon (Acipenser oxyrinchus desotoi) is a threatened fish species that inhabits major

rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida

(Barkuloo, 1988; Wakeford, 2001).  An anadromous fish that migrates from the sea upstream

into coastal rivers to spawn in freshwater, it historically ranged from the Mississippi River to

Charlotte Harbor, Florida (Wakeford, 2001).  Today, this range has contracted to encompass

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida.  

Populations have been depleted or even extirpated throughout this range by fishing, shoreline

development, dam construction, water quality changes, and other factors (Barkuloo, 1988;

Wakeford, 2001).  These declines prompted the listing of the Gulf sturgeon as a threatened

species in 1991.  The best known populations occur in the Apalachicola and Suwannee Rivers in

Florida (Carr, 1996; Sulak and Clugston, 1998), the Choctawhatchee River in Alabama (Fox et al.,

2000), and the Pearl River in Mississippi/Louisiana (Morrow et al., 1998).  Critical habitat in the

Gulf extends from Lake Borgne, Louisiana (St. Bernard Parish) to Suwannee Sound, Florida

(Levy County) (NMFS, 2010b) (Figure 3).  A species description is presented in the lease sale EIS

(MMS, 2007b) and in the recovery plan for this species (USFWS and Gulf States Marine Fisheries

Commission, 1995).

A large oil spill (WCD) is the only IPF potentially affecting Gulf sturgeon.  There are no IPFs

associated with routine project activities that could affect these fishes.  A small diesel fuel spill in

the lease area would be unlikely to affect Gulf sturgeon because a small diesel fuel spill would

not be expected to make landfall or reach coastal waters prior to breaking up (see explanation

in Section A.9.2).

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on Gulf sturgeon are discussed in lease sale EISs (MMS, 2000, 2007b,

2008) and by the NMFS (2007) in its Biological Opinion for the Five‐Year Leasing Plan for

Western and Central Planning Areas.  For the EP associated with this EIA, there are no unique

site‐specific issues with respect to this species.

The lease area is about 136 mi (219 km) from the nearest Gulf sturgeon critical habitat.  The

revised OSRA modeling (Table 3) predicts that a spill in the lease area has 1% or less probability

of contacting the coastal areas inhabited by Gulf sturgeon within 30 or 120 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 an estuarine or 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).

C.3.9 Smalltooth Sawfish (Endangered)

Smalltooth sawfish (Pristis pectinata) are found in the tropical and subtropical Atlantic Ocean.  

In the western Atlantic they have historically ranged from New York to Brazil, including the Gulf

of Mexico and Caribbean Sea.  This sawfish primarily occurs in estuarine and coastal habitats

such as bays, lagoons, and rivers.  The smalltooth sawfish was listed as endangered on

April 1, 2003, under the ESA.  The critical habitat consists of two units: the Charlotte Harbor

Estuary Unit, which comprises approximately 221,459 acres of coastal habitat; and the
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Ten Thousand Islands/Everglades Unit (TTI/E), which comprises approximately 619,013 acres of

coastal habitat. The two units are located along the southwestern coast of Florida between

Charlotte Harbor and Florida Bay.

A large oil spill (WCD) is the only IPF potentially affecting smalltooth sawfish.  There are no IPFs

associated with routine project activities that could affect these fishes.  A small diesel fuel spill in

the lease area would be unlikely to affect smalltooth sawfish because a small diesel fuel spill

would not be expected to make landfall or reach coastal waters prior to breaking up (see

explanation in Section A.9.2).

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on smalltooth sawfish are similar to those for other coastal and estuarine

species, which are discussed by MMS in lease sale EISs (2000, 2007b, 2008) and by NMFS in its

Biological Opinion (2007).  For the EP associated with this EIA, there are no unique site‐specific

issues with respect to this species.

In the event of oil reaching smalltooth sawfish habitat, the fish could be affected by direct

ingestion, ingestion of oiled prey, or the absorption of dissolved petroleum products through

the gills.   

C.3.10 Beach Mice (Endangered)

Four subspecies of endangered beach mice (Peromyscus polionotus) occur on the barrier islands

of Alabama and the Florida Panhandle.  They are the Alabama, Choctawatchee, Perdido Key, and

St. Andrew beach mice.  Critical habitat has been designated for all four subspecies; Figure 3

shows the critical habitat combined for all four subspecies.  Species descriptions are provided in

a recent lease sale EIS (MMS, 2007b).  

A large oil spill (WCD) is the only IPF potentially affecting beach mice.  There are no IPFs

associated with routine project activities that could affect these animals due to the distance

from shore and the lack of any onshore support activities near their habitat.  A small diesel fuel

spill in the lease area would not affect beach mice because a small diesel fuel spill would not be

expected to make landfall or reach coastal waters prior to breaking up (see explanation in

Section A.9.2).

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on beach mice are discussed in the lease sale EISs (MMS, 2007b, 2008).  

For the EP associated with this EIA, there are no unique site‐specific issues with respect to these

species that were not analyzed in these documents.

The lease area is about 157 mi (252 km) southwest from the nearest beach mouse critical

habitat.  The revised OSRA modeling summarized in Section A.9.3 (Table 3) predicts that a spill

in the lease area has a 1% or less probability of reaching either the Alabama or Florida

shorelines inhabited by beach mice within 120 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
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Environmental Impact Analysis for Initial Exploration Plan Page 47

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.  However, any such impacts are unlikely due to the distance from

shore and anticipated response actions that would occur in the event of a spill.

C.3.11 Elkhorn Coral (Endangered)  

Elkhorn coral (Acropora palmata) is found primarily in shallow waters with temperatures

between 26 °C to 30 °C (79 °F to 86 °F) and significant water movement.  They were one of the

most abundant species in waters ranging from 1 to 5 m (3.3 to 16 ft) deep, and a few colonies

have been reported from waters as deep as 20 m (66 ft).  Elkhorn coral exist in the Caribbean,

the Bahamas, and Florida Keys.  Its normal range reached as far north as Biscayne National Park,

Florida, and as far south as Venezuela.  However, it has been suggested that as a result of

climate change, the range of elkhorn coral has expanded northward along the Florida Peninsula

and into the northern parts of the Gulf of Mexico.  In the northern Gulf of Mexico, elkhorn coral

has been found within the coral cap region of the Flower Gardens Marine Sanctuary

(NOAA, 2011).

There are no IPFs associated with routine project activities that could affect this species in the

northern Gulf.  A small diesel fuel spill would not affect elkhorn coral colonies because the oil

would float and dissipate on the sea surface.  A WCD accidental spill would be unlikely to affect

this area.  A surface slick would not reach these features.  Although there are reports of

subsurface plumes resulting from the use of subsea dispersants during the Macondo incident,

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 this area.

C.4 Coastal and Marine Birds

C.4.1 Marine Birds

Marine birds include seabirds and other species that may occur in the pelagic environment of

the project areas (Clapp et al., 1982a,b, 1983; Peake, 1996; Hess and Ribic, 2000).  Seabirds

spend much of their lives offshore over the open ocean, except during breeding season when

they nest along the coast.  In addition, other birds such as waterfowl, marsh birds, and

shorebirds may occasionally be present over open ocean areas.  No endangered or threatened

bird species are likely to occur at the project area due to the distance from shore.  For a

discussion of shorebirds and coastal nesting birds, see Section C.4.2.

Seabirds of the northern Gulf of Mexico were surveyed from ships during the GulfCet II program.  

Hess and Ribic (2000) reported that terns, storm‐petrels, shearwaters, and jaegers were the

most frequently sighted seabirds in the deepwater area.  From these surveys, four ecological

categories of seabirds were documented in the deepwater areas of the Gulf: summer migrants

(shearwaters, storm petrels, boobies); summer residents that breed in the Gulf (Sooty Tern,

Least Tern, Sandwich Tern, Magnificent Frigatebird); winter residents (gannets, gulls, jaegers);

and permanent resident species (Laughing Gulls, Royal Terns, Bridled Terns) (Hess and Ribic,

2000).
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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 rigs for resting,

feeding, or as temporary shelter from inclement weather (Russell, 2005).  Some birds may be

attracted to offshore structures because of the lights and the fish populations that aggregate

around these structures.

IPFs potentially affecting marine and pelagic birds include drilling rig presence, noise, and lights;

support vessel and helicopter traffic; and two (2) types of accidents (a small diesel fuel spill and

a large oil spill [WCD]).  Effluent discharges are likely to have negligible impacts on the birds due

to rapid dispersion, the small area of ocean affected, the intermittent nature of the discharges,

and the mobility of these animals.  Compliance with NTL 2007‐G03 will minimize the potential

for marine debris‐related impacts on marine birds.

Impacts of Drilling Rig Presence, Noise, and Lights

Birds that frequent rigs may be exposed to contaminants including air pollutants and routine

discharges, but significant impacts are unlikely due to rapid dispersion.  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 rig collisions appear to be

similar.  In some cases, migrants simply do not see a part of the rig 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 rigs probably benefit from their stay, particularly in spring

(Russell, 2005).  Due to the limited scope and short duration of drilling activities in the EP

associated with this EIA, any impacts on populations of either seabirds or trans‐Gulf migrant

birds are not expected to be significant.

A recent study in the North Sea indicated that rig 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 (Nederlandse Aardolie Maatschappij,

2007).  The numbers varied greatly, from none at all to some tens of thousands of birds per

night per rig, with an apparent effect radius of up to 3 mi (5 km).  A study in the Gulf of Mexico

also noted the phenomenon, but did not recommend mitigation (Russell, 2005).  Factors to

consider in evaluating this impact in the Gulf of Mexico would include the lower incidence of

cloudy and foggy days in the Gulf of Mexico vs. the North Sea.  Due to the limited scope and

short duration of drilling activities proposed in the EP associated with this EIA, lighting impacts,

collisions, or other adverse effects are unlikely, and no significant impacts are expected.
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Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters are unlikely to significantly disturb pelagic birds in open,

offshore waters.  It is likely that individual birds would experience, at most, only short‐term

behavioral disruption, and the impact would not be significant.

Impacts of a Small Fuel Spill

Potential spill impacts on marine birds are discussed in recent EISs (MMS, 2007b, 2008).  For the

EP associated with this EIA, there are no unique site‐specific issues with respect to spill impacts

on these animals.

The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

routine operations including diesel fuel transfer.  In the unlikely event of a spill, implementation

of Noble’s OSRP will reduce the potential for impacts on marine and pelagic birds.  EP Section H

provides 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 diesel 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 diesel fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.  The area of the sea surface with diesel fuel on it would

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

Birds exposed to oil on the sea surface could experience direct physical and physiological effects

including skin irritation; chemical burns of skin, eyes, and mucous membranes; and inhalation of

toxic fumes.  Due to the limited areal extent and short duration of water quality impacts from a

small diesel fuel spill, secondary impacts due to ingestion of oil via contaminated prey or

reductions in prey abundance are unlikely.  Due to the low densities of birds in open ocean

areas, the small area affected, and the brief duration of the surface slick, no significant impacts

on pelagic birds would be expected.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine and pelagic birds are discussed in recent EISs (MMS, 2007b,

2008).  For the EP associated with this EIA, there are no unique site‐specific issues with respect

to spill impacts on these animals.

Pelagic seabirds could be exposed to oil from a spill at the project area.  Hess and Ribic (2000)

reported that terns, storm‐petrels, shearwaters, and jaegers were the most frequently sighted

seabirds in the deepwater Gulf of Mexico (>200 m).  Powers (1987) indicates that seabird

densities over the open ocean typically are <10 birds/km2

.  The number of pelagic birds that

could be affected in open, offshore waters would depend on the extent and persistence of the

oil slick.

The recent Macondo incident 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
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Environmental Impact Analysis for Initial Exploration Plan Page 50

Masked Booby (International Bird Rescue Research Center, 2010).  The Northern Gannet is

among the species with the largest numbers of birds affected by the spill.

BOEMRE has reexamined the analysis for coastal and marine birds presented in MMS 2007b and

2008 and determined that no new information from previous EISs was found that would alter

the potential impacts on marine and pelagic birds from a large oil spill (BOEMRE, 2011a,b).

C.4.2 Shorebirds and Coastal Nesting Birds

Threatened and endangered bird species (Piping Plover and Whooping Crane) have been

discussed previously in Section C.3.  Various species of non‐endangered birds are also found

along the northern Gulf Coast, including diving birds, shorebirds, marsh birds, wading birds, and

waterfowl.  Gulf Coast marshes and beaches also provide important feeding grounds and

nesting habitats.  Species that breed on beaches, flats, dunes, bars, barrier islands, and similar

habitats include the Sandwich Tern, Wilson’s Plover, Black Skimmer, Forster’s Tern, Gull‐Billed

Tern, Laughing Gull, Least Tern, and Royal Tern (USFWS, 2010b).  Additional information is

presented in recent lease sale EISs (MMS, 2007b, 2008).

The Eastern Brown Pelican (Pelecanus occidentalis) has been delisted from its endangered status

(USFWS, 2010c), although still listed as endangered by the State of Mississippi (Mississippi

Natural Heritage Program, 2003) and as a species of special concern by the State of Florida

(Florida Fish and Wildlife Conservation Commission, 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 in deep offshore waters (Fritts and Reynolds, 1981; Peake, 1996; Hess and Ribic, 2000).  

Nearly half the southeastern population of Brown Pelicans live in the northern Gulf Coast,

generally nesting on protected islands (USFWS, 2010b).

The Southern Bald Eagle (Haliaeetus leucocephalus) was delisted from its threatened status in

the lower 48 states on June 28, 2007.  The Bald Eagle is a terrestrial raptor widely distributed

across the southern U.S., including coastal habitats along the Gulf of Mexico.  The Gulf Coast is

inhabited by both wintering migrant and resident Bald Eagles (Johnsgard, 1990; Ehrlich et al.,

1992).

IPFs potentially affecting shorebirds and coastal nesting birds include support vessel and

helicopter traffic and a large oil spill (WCD).  A small diesel fuel spill in the lease area would be

unlikely to affect shorebirds or coastal nesting birds, as the lease area is 68 mi (110 km) from the

nearest shoreline.  As explained in Section A.9.2, a small diesel fuel spill would not be expected

to make landfall or reach coastal waters prior to breaking up.  Compliance with NTL 2007‐G03

will minimize the potential for marine debris‐related impacts on shorebirds.

Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters will transit coastal areas near Port Fourchon and Houma,

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).
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Vessel traffic may disturb some foraging and resting birds.  Flushing distances vary between

species and between individuals (Rodgers and Schwikert, 2002).  The disturbances will be

limited to flushing birds away from vessel pathways; known distances are from 20 to 49 m

(65 to 160 ft) for personal watercraft and 23 to 58 m (75 to 190 ft) for an outboard‐powered

boat (Rodgers and Schwikert, 2002).  Flushing distances may be similar or less for the support

vessels to be used for Noble’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 disturbances to

nesting birds, eggs, and chicks is not expected.  Vessel operators will use designated navigation

channels and comply with posted speed and wake restrictions while transiting sensitive inland

waterways.  Due to the limited scope and short duration of drilling activities, any short‐term

impacts are not expected to be biologically significant to coastal bird populations.

Aircraft traffic can cause some disturbance to birds onshore and offshore.  Responses are highly

dependent on the type of aircraft, the bird species, the activities that animals were previously

engaged in, and previous exposures to overflights (Efroymson et al., 2000).  Helicopters seem to

cause the most intense responses over other human disturbances for some species (Bélanger

and Bédard, 1989).  However, Federal Aviation Administration Advisory Circular No. 91‐36D

recommends that pilots maintain a minimum altitude of 610 m (2,000 ft) when flying over

noise‐sensitive areas such as wildlife refuges, parks, and areas with wilderness characteristics.  

This is greater than the distance (slant range) at which aircraft overflights have been reported to

cause behavioral effects on most species of birds studied (Efroymson et al., 2000).  With these

guidelines in effect, it is likely that individual birds would experience, at most, only short‐term

behavioral disruption.

Impacts of Large Oil Spill (WCD)

The revised OSRA modeling results (BOEMRE, 2011a,b) summarized in Section A.9.3 predict that

there is a 78% chance that a winter oil spill in this lease area would reach shorelines in Texas

within 120 days and a 60% chance that a spring oil spill would contact coastlines in Louisiana

within 120 days.

Data from the Macondo incident provide additional information about the species of coastal

birds that may be affected in the event of a catastrophic spill of a similar nature and duration.  

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, over 2,000 oiled birds have been collected alive and about 1,200 released (NMFS,

2010c).  According to the International Bird Rescue Research Center (2010), bird species that

have been treated for oiling include the following:

 Brown Pelican

 White Pelican

 Masked Booby

 Magnificent Frigatebird

 Laughing Gull

 Herring Gull

 Northern Gannet

 Black Crowned Night Heron

 Tri‐colored Heron

 Green Heron

 Cattle Egret

 Snowy Egret

 Reddish Egret

 Least Bittern

 Common Tern

 Royal Tern

 Caspian Tern

 Sandwich Tern
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 Forsters Tern

 Black Tern

 Gull‐billed Tern

 Least Tern

 Black Skimmer

 Black Oystercatcher

 White Ibis

 Roseate Spoonbill

 Willet

 Sanderling

 Dunlin

 Semipalmated Sandpiper

 Killdeer

 King Rail

 Clapper Rail

 Virginia Rail

According to the USFWS (2010d), species with the largest numbers of dead, oiled birds were

Laughing Gull, Northern Gannet, Brown Pelican, Royal Tern, Black Skimmer, Least Tern,

unidentified Gull, and unidentified Tern.  There are no reports of Bald Eagle oiling.

Coastal birds can be exposed to oil as they float on the water’s surface, dive during foraging, or

wade in oiled coastal waters.  Oiled birds can lose the ability to fly, dive for food, or float on the

water, which could lead to drowning (USFWS, 2010e).  Oil interferes with the water repellency

of feathers and can cause hypothermia in the right conditions.  As birds groom themselves, they

can ingest and inhale the oil on their bodies.  Scavengers such as Bald Eagles and gulls can be

exposed to oil by feeding on carcasses of contaminated fish and wildlife.  While ingestion can kill

animals immediately, more often it results in lung, liver, and kidney damage, which can lead to

death.  Bird eggs may be damaged if an oiled adult sits on the nest.

As noted above, the Brown Pelican was recently removed from the endangered species list.  

Over 300 dead Brown Pelicans were collected in the Gulf following the Macondo incident,

(USFWS, 2010d).  These data indicate that Brown Pelicans may be particularly at risk of oiling in

the event of a catastrophic spill reaching coastal waters.  Issues for Brown Pelicans include direct

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

C.5 Fisheries Resources

C.5.1 Pelagic Communities and Ichthyoplankton

Biggs and Ressler (2000) reviewed the biology of pelagic communities in the deepwater

environment of the northern Gulf of Mexico.  The biological oceanography of the region is

dominated by the influence of the Loop Current, whose surface waters are among the most

oligotrophic in the world’s oceans.  Superimposed on this low‐productivity condition are

productive “hot spots” associated with entrainment of nutrient‐rich Mississippi River water and

mesoscale oceanographic features.  Anticyclonic and cyclonic hydrographic features play an

important role in determining biogeographic patterns and controlling primary productivity in the

northern Gulf of Mexico (Biggs and Ressler, 2000).

Most fishes inhabiting shelf or oceanic waters of the Gulf of Mexico have planktonic eggs and

larvae (Ditty, 1986; Ditty et al., 1988; Richards et al., 1989, 1993).  Pelagic eggs and larvae

become part of the planktonic community for various lengths of time (10 to 100 days,

depending on the species) (MMS, 2007b).

IPFs potentially affecting pelagic communities and ichthyoplankton include drilling rig presence,

noise, and lights; effluent discharges; water intakes; and two (2) types of accidents (a small

diesel fuel spill and a large oil spill [WCD]).
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Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as a fish‐attracting

device (FAD).  In oceanic waters, the FAD effect would be most pronounced for epipelagic fishes

such as tunas, dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting

surface structures (e.g., Holland et al., 1990; Higashi, 1994; Relini et al., 1994 MMS 2000, 2007b,

2008).  This FAD effect could possibly enhance the feeding of epipelagic predators by attracting

and concentrating smaller fish species.  Because the drilling rig is a single, temporary structure,

impacts on fish populations, whether beneficial or adverse, are considered minor.

Impacts of Effluent Discharges

Treated sanitary and domestic wastes may have a slight effect on the pelagic environment in the

immediate vicinity of these discharges.  These wastes may have elevated levels of nutrients,

organic matter, and chlorine, but should be diluted rapidly to undetectable levels within tens to

hundreds of meters from the source.  Minimal impacts on water quality, plankton, and nekton

are anticipated.

Deck drainage may have a slight effect on the pelagic environment in the immediate vicinity of

these discharges.  Deck drainage from contaminated areas will be passed through an oil‐ and

water separator prior to release, and discharges will be monitored for visible sheen.  The

discharges may have slightly elevated levels of hydrocarbons but should be diluted rapidly to

undetectable levels within tens to hundreds of meters from the source.  Minimal impacts on

water quality, plankton, and nekton are anticipated.

Other discharges in accordance with the NPDES permit, such as water‐based muds and cuttings,

desalination unit brine and uncontaminated cooling water, fire water, and ballast water, are

expected to be diluted rapidly and have little or no impact on water column biota.

Impacts of Water Intakes

Seawater will be drawn from the ocean for once‐through, non‐contact cooling of machinery

on the drilling rig.  The rig planned for use in the EP associated with this EIA is not a “new”

facility as defined by the NPDES permit and therefore is not subject to the cooling water intake

regulations for Phase III facilities under Section 316(b) of the Clean Water Act.

The intake of seawater for cooling water will entrain plankton.  The low intake velocity should

allow most strong swimming juvenile fishes and smaller adults to escape entrainment or

impingement.  However, drifting plankton would not be able to escape entrainment with the

exception of a few fast swimming larvae of certain taxonomic groups.  Those organisms

entrained may be stressed or killed, primarily through changes in water temperature during the

route from cooling intake structure to discharge structure and mechanical damage (turbulence

in pumps and condensers).  Due to the limited scope and short duration of drilling activities, any

short‐term impacts of entrainment are not expected to be biologically significant to plankton or

ichthyoplankton populations.

Impacts of a Small Fuel Spill

Potential spill impacts on fisheries resources are discussed in recent EISs (MMS, 2007b, 2008).  

For the EP associated with this EIA, there are no unique site‐specific issues with respect to spill

impacts.
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The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

routine operations including diesel fuel transfer.  In the unlikely event of a spill, implementation

of Noble’s OSRP will mitigate the potential for impacts on pelagic communities, including

ichthyoplankton.  EP Section H provides 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 diesel 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 diesel fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.  The area of the sea surface with diesel fuel on it would

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

A small diesel fuel spill could have localized impacts on phytoplankton, zooplankton, and

nekton.  Due to the limited areal extent and short duration of water quality impacts, small diesel

fuel spill would be unlikely to produce detectable impacts on pelagic communities.

Impacts of a Large Oil Spill (WCD)

A large oil spill could affect water column biota including phytoplankton, zooplankton,

ichthyoplankton, and nekton.  A large spill that persisted for weeks or months would be more

likely to affect these communities.  While adult and juvenile fishes may actively avoid a large

spill, planktonic eggs and larvae would be unable to avoid contact.  Eggs and larvae of fishes are

especially vulnerable to oiling because they inhabit the upper layers of the water column, and

they will die if exposed to certain toxic fractions of spilled oil.  Impacts would be potentially

greater if local scale currents retained planktonic larval assemblages (and the floating oil slick)

within the same water mass.

C.5.2 Essential Fish Habitat

Essential Fish Habitat (EFH) is defined as those waters and substrate necessary to fish for

spawning, breeding, feeding, and growth to maturity.  Under the Magnuson‐Stevens Fishery

Conservation and Management Act, as amended, Federal agencies are required to consult on

activities that may adversely affect EFH designated in Fishery Management Plans developed by

the regional Fishery Management Councils.

The Gulf of Mexico Fishery Management Council (GMFMC) has prepared Fishery Management

Plans for corals and coral reefs, shrimp, stone crab, spiny lobster, reef fishes, coastal migratory

pelagic fishes, and red drum.  In 2005, the EFH for these managed species was redefined in

Generic Amendment No. 3 to the various Fishery Management Plans (GMFMC, 2005).  The EFH

for most of these GMFMC‐managed species is on the continental shelf in waters shallower than

183 m (600 ft).  The shelf edge is the outer boundary for coastal migratory pelagic fishes, reef

fishes, and shrimps.  EFH for corals and coral reefs includes some shelf‐edge topographic

features on the Texas‐Louisiana OCS, the nearest of which are shelf edge topographic features in

WD 147 located approximately 60 mi (96 km) north‐northwest from the lease area along the

shelf edge south of Louisiana.
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Highly migratory pelagic fishes, which occur as transients in the lease area, are the only

remaining group for which EFH has been identified in the deepwater Gulf of Mexico.  Species in

this group, including tunas, swordfishes, billfishes, and sharks, are managed by NMFS.  Highly

migratory species with EFH at or near the lease area include those species and life stages listed

in Table 7.

Table 7. Transient fish species that may be present in Mississippi Canyon Blocks 948 and 949

(From: National Marine Fisheries Service, 2009).  

Species Life Stage(s)

Blue marlin Juvenile, adult

White marlin Juvenile, adult

Skipjack tuna Adult, spawn

Yellowfin tuna Juvenile, adult, spawn

Bigeye thresher shark All

Bigeye tuna Juvenile, adult

Bluefin tuna Eggs, larvae, adult, spawn

Common thresher shark All

Longbill spearfish Juvenile, adult

Longfin mako shark All

Night shark All

Oceanic whitetip shark All

Sailfish Juvenile, adult

Silky shark All

Swordfish Larvae, juvenile, adult

Whale shark All

White marlin Juvenile, adult

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

habitat for Atlantic bluefin tuna, and NMFS (2009) has designated a Habitat Area of Particular

Concern (HAPC) for this species.  The HAPC covers much of the deepwater Gulf of Mexico,

including the lease area (Figure 3).  The areal extent of the HAPC is approximately 300,000 km2

(15,000 mi2).  The prevailing assumption is that Atlantic bluefin tuna follow an annual cycle of

foraging in June through March off the eastern United States and Canadian coasts, followed by

migration to the Gulf of Mexico to spawn in April, May, and June (NMFS, 2009).  

In 2005, a new amendment to the original EFH Generic Amendment was finalized (GMFMC,

2005).  One of the most significant proposed changes in this amendment reduced the extent of

EFH relative to the 1998 Generic Amendment by removing the EFH description and

identification from waters between 100 fathoms and the seaward limit of the EEZ.  There are

Fishery Management Plans in the Gulf of Mexico OCS region for shrimps, red drums, reef fishes,

coastal migratory pelagics, stone crabs, spiny lobsters, corals and coral reefs, billfishes, and

highly migratory species.  The Highly Migratory Species Fisheries Management Plan was recently

amended to update EFH and habitat areas of particular concern for the bluefin tuna spawning

area (NMFS, 2009).  There are current NTLs (2009‐G39 and 2009‐G40) that provide guidance and

clarification of the regulations with respect to biologically sensitive underwater features and

areas and benthic communities that are considered EFH (MMS, 2009a,b).  A new EFH

consultation has been initiated between BOEMRE’s Gulf of Mexico Region and NOAA’s

Southeastern Region.  Some EFH requirements may change with the new agreement.  Until the
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Environmental Impact Analysis for Initial Exploration Plan Page 56

new agreement is in place, the 1999 Programmatic Consultation with the elements described

above will be the rule (BOEMRE, 2011a,b).

Other HAPCs have been identified in the Gulf of Mexico by the GMFMC (2005).  These include

the Florida Middle Grounds, Madison‐Swanson Marine Reserve, Tortugas North and South

Ecological Reserves, Pulley Ridge, and several individual reefs and banks of the northwestern

Gulf of Mexico (Figure 3).  The nearest of these is Jakkula Bank, located approximately

170 mi (274 km) from the lease area.  

Routine IPFs potentially affecting EFH include drilling rig presence, noise, and lights; effluent

discharges; water intakes; and two (2) types of accidents – a small diesel fuel spill and a large oil

spill (WCD).

Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as 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 MMS 2000; 2007b, 2008).  This

FAD effect would possibly enhance feeding of epipelagic predators by attracting and

concentrating smaller fish species.  Because the drilling rig is a single, temporary structure, any

impacts on EFH for highly migratory pelagic fishes are considered minor.

Impacts of Effluent Discharges

Other effluent discharges affecting EFH by diminishing ambient water quality include drilling

muds and cuttings, treated sanitary and domestic wastes, deck drainage, and miscellaneous

discharges such as desalination unit brine and uncontaminated cooling water, fire water, and

ballast water.  Impacts on water quality have been discussed previously.  No significant impacts

on EFH for highly migratory pelagic fishes are expected from these discharges.

Impacts of Water Intakes

As noted previously, cooling water intake will cause entrainment and impingement of plankton,

including fish eggs and larvae (ichthyoplankton).  Due to the limited scope and short duration of

drilling activities, any short‐term impacts on EFH for highly migratory pelagic fishes are not

expected to be biologically significant.

Impacts of a Small Fuel Spill

The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

routine operations including diesel fuel transfer.  In the unlikely event of a spill, implementation

of Noble’s OSRP will help diminish the potential for impacts on EFH.  EP Section H provides

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

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

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

associated with this EIA, there are no unique site‐specific issues with respect to spill impacts.

A small diesel 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
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conditions at the time and the effectiveness of spill response measures.  Section A.9.2 discusses

the likely fate of a small diesel fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.  The area of the sea surface with diesel fuel on it would

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

A small diesel 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 areal

extent of the affected area would represent a negligible portion of the HAPC.

A small diesel fuel spill would not affect EFH for corals and coral reefs, the nearest EFH being the

topographic features located approximately 60 mi (96 km) from the lease area along the shelf

edge south of Louisiana.  A small diesel fuel spill would float and dissipate on the sea surface

and would not contact these features.

Impacts of a Large Oil Spill (WCD)

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

associated with this EIA, 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 shrimp, stone crab, spiny

lobster, reef fishes, coastal migratory pelagic fishes, and red drum.  It would result in adverse

impacts on water quality and water column biota including phytoplankton, zooplankton, and

nekton.  In coastal waters, sediments could be contaminated and result in persistent

degradation of the seafloor habitat for managed demersal fish and shellfish species.

The lease area is within the HAPC for 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.  Potential impacts

would depend in part on the timing of a spill, as this species migrates to the Gulf of Mexico to

spawn in April, May, and June (NMFS, 2009).

The topographic features area in WD 147 located 60 mi (96 km) north‐northwest from the lease

area is designated as EFH under the corals and coral reefs management plan.  An accidental spill

would be unlikely to affect this area.  A surface slick would not reach these features.  Although

there are reports of subsurface plumes resulting from the use of subsea dispersants during the

Macondo incident, 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.

C.6 Archaeological Resources

C.6.1 Shipwreck Sites

BOEMRE (2011a,b) has reexamined the analysis for archaeological resources presented in the

multi‐Lease‐sale EIS and the 2009‐2012 Supplemental EIS (MMS 2007b and 2008).  This
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Supplemental EIS is based on additional information available since the publication of these two

documents and in consideration of the Macondo incident.  Substantial new information that

alters the impact conclusion for archaeological resources presented in the multi‐Lease‐sale EIS

and the 2009‐2012 Supplemental EIS has come to light as a result of BOEMRE‐sponsored studies

and industry surveys.  Specifically, evidence of damage to significant cultural resources

(i.e., historic shipwrecks) has been shown to have occurred because of an incomplete

knowledge of seafloor conditions in lease areas >200 m (656 ft) deep that have been exempted

from high‐resolution surveys.  Since significant historic shipwrecks have been recently

discovered outside the previously designated high‐probability areas (some of which show

evidence of impacts from permitted activities prior to their discovery), a survey will now be

required prior to construction beginning in 2011 in the area of potential effect for all

OCS operations as a requirement of the plan permit issued by BOEMRE.

MC 948 and 949 are not on the list of leases with a high potential for historic shipwrecks.  There

were no indications of wrecks or other archaeological resources detected during the site

clearance survey (Fugro Geoservices, Inc., 2007).  Noble will abide by the applicable

requirements of NTL 2005‐G07, which stipulate that work be stopped at the project site should

any previously undetected archaeological resource be discovered after work has begun until

appropriate surveys and evaluations have been completed.

Because there are no known or indicated shipwreck sites in the lease area, there are no routine

IPFs that are likely to affect shipwrecks.  Impacts of a large oil spill (WCD) are the only IPFs

considered.  A small diesel fuel spill would not affect shipwrecks because the oil would float and

dissipate on the sea surface.

Impacts of a Large Oil Spill (WCD)

The MMS (2007b) estimated that a severe subsurface blowout could resuspend and disperse

sediments within a 300‐m (984‐ft) radius.  Because there are no historic shipwrecks in the lease

area, this impact would not be relevant.

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 incident, subsurface plumes were reported at a water depth of

about 1,100 m (3,600 ft), extending at least 22 mi (35 km) from the wellsite and persisting for

more than a month (Camilli et al., 2010).  The subsurface plumes apparently resulted from the

use of dispersants at the wellhead (Joint Analysis Group, 2010c).  While the behavior and

impacts of subsurface plumes are not well known, a subsurface plume could have the potential

to contact shipwreck sites beyond the 300‐m (984‐ft) radius estimated by MMS (2007a, 2008),

depending on its extent, trajectory, and persistence.  If oil from a subsea spill should come into

contact with wooden shipwrecks on the seafloor it could adversely affect their condition or

preservation.  Should there be any indication that potential shipwreck sites could be affected, in

accordance with NTL 2005‐G07 Noble will immediately halt operations, take steps to ensure that

the site is not disturbed in any way, and contact the Regional Supervisor, Leasing and

Environment, within 48 hours of its discovery.  Noble would cease all operations within 305 m

(1,000 ft) of the site until the Regional Director provides instructions on steps to take to assess

the site’s potential historic significance and protect it.
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A spill entering shallow coastal waters could conceivably contaminate an undiscovered

shipwreck site.  The revised OSRA modeling (BOEMRE, 2011a,b) summarized in Table 3 predicts

that there is a 78% probability of oil from a spill in the lease area reaching shorelines in Texas

within 120 days and a 60% probability of contacting coastlines in Louisiana within 120 days.  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.

C.6.2 Prehistoric Archaeological Sites

Available evidence suggests that sea level in the northern Gulf of Mexico was at least 90 m

(295 ft), and possibly as much as 130 m (427 ft), lower than present sea level during the period

20,000‐17,000 years Before Present (B.P.) (Nelson and Bray, 1970).  Sea level in the northern

Gulf reached its present stand around 3,500 years B.P. (Pearson et al., 1986).

During periods that the continental shelf was exposed above sea level, the area was open to

habitation by prehistoric peoples.  The advent of early man into the Gulf of Mexico region is

currently accepted to be around 12,000 years B.P. (Aten, 1983).  The sea‐level curve for the

northern Gulf of Mexico proposed by Coastal Environments, Inc. (CEI) suggests that sea level at

12,000 years B.P. would have been approximately 45‐60 m (148‐197 ft) below the present‐day

sea level (CEI, 1977 and 1982).  On this basis, the continental shelf shoreward of the 45‐ to 60‐m

(148‐ to 197‐ft) bathymetric contours has potential for prehistoric sites dating after

12,000 years B.P.  Because of inherent uncertainties in both the depth of sea level and the entry

date of prehistoric man into North America, this Agency adopted the 60‐m (197‐ft) water depth

as the seaward extent for archaeological site potential in Gulf of Mexico region.

With water depths of 1,838 to 1,843 m (6,030 to 6,045 ft), the wellsites are well beyond the

60‐m (197‐ft) depth contour used by the BOEMRE as the seaward extent for prehistoric

archaeological site potential in the Gulf of Mexico.  Because prehistoric archaeological sites are

not found in the lease area, the only relevant IPF is a large oil spill (WCD).  A small diesel fuel

spill would not affect prehistoric archaeological resources because the oil would float and

dissipate on the sea surface.

Impacts of a Large Oil Spill (WCD)

Because prehistoric archaeological sites are not found in the lease area, they would not be

affected by the physical effects of a subsea blowout.  The MMS (2007b) estimates that a severe

subsurface blowout could resuspend and disperse sediments within a 300‐m (984‐ft) radius.

Along the northern Gulf Coast, prehistoric sites occur frequently along the barrier islands and

mainland coast and along the margins of bays and bayous (MMS, 2007b).  The revised OSRA

modeling summarized in Table 3 predicts that there is a 78% probability of oil from a spill in the

lease area reaching shorelines in Texas within 120 days and a 60% probability of oil reaching

Louisiana shorelines within 120 days.  If a  spill did reach a prehistoric site along these shorelines

it could coat fragile artifacts or site features and compromise the potential for radiocarbon

dating organic materials in a site (although other dating methods are available and it is possible

to decontaminate an oiled sample for radiocarbon dating).  Coastal prehistoric sites could also

be damaged by spill cleanup operations (e.g., by destroying fragile artifacts and disturbing the

provenance of artifacts and site features).
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C.7 Coastal Habitats and Protected Areas

Coastal habitats in the northeastern Gulf of Mexico that may be affected by oil and gas activities

are described in recent EISs (MMS, 2007b, 2008) and in a literature review by Collard and Way

(1997).  Coastal habitats inshore of the project area include barrier beaches and dunes,

wetlands, and submerged seagrass beds.  Generally, most of the northeastern Gulf is fringed by

barrier beaches, with wetlands and/or submerged seagrass beds occurring in sheltered areas

behind the barrier islands and in estuaries.

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

likely to affect beaches and dunes, wetlands, seagrass beds, coastal wildlife refuges, wilderness

areas, or any other managed or protected coastal area.  The support bases at Fourchon and

Houma are not in a wildlife refuge or a wilderness area.  Potential impacts of support vessel

traffic are addressed briefly below.

A small diesel fuel spill in the lease area would be unlikely to affect coastal habitats, as the lease

area is 68 mi (110 km) from the nearest shoreline.  As explained in Section A.9.2, a small diesel

fuel spill would break up before reaching shore.

Impacts of Support Vessel Traffic

For OCS activities in general, support operations, including crew boats and supply boats, may

have a minor incremental impact on coastal habitats.  Over time with a large number of vessel

trips, vessel wakes can erode shorelines along inlets, channels, and harbors.  Support

operations, including crew boats and supply boats as detailed in EP Section K, may have a minor

incremental impact on coastal habitats or protected areas.  Impacts will be minimized by

following the speed and wake restrictions in harbors and channels.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on coastal habitats are discussed in recent EISs (MMS, 2007b, 2008).  

Coastal habitats inshore of the project area include barrier beaches and dunes, wetlands, and

submerged seagrass beds.  For the EP associated with this EIA, there are no unique site‐specific

issues with respect to coastal habitats.

The revised OSRA modeling summarized in Table 3 predicts that there is a 78% probability of oil

from a spill in the lease area reaching shorelines in Texas within 120 days and a 60% probability

of oil reaching Louisiana shorelines within 120 days.

The shorelines within the geographic range predicted by the OSRA modeling (Table 3) include

extensive barrier beaches and wetlands, with submerged seagrass beds occurring in sheltered

areas behind the barrier islands and in estuaries.  National wildlife refuges and other protected

areas along the coast are discussed in the lease sale EIS (MMS, 2007b) and Noble’s OSRP.  

Coastal and near‐coastal wildlife refuges, wilderness areas, and state and national parks within

Counties or Parishes that have a greater than 1% probability of potential shoreline contact after

120 days are listed in Table 8.
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Table 8. Wildlife refuges, wilderness areas, and state and national parks within the geographic

range of the potential shoreline contacts after 120 days.   

County or Parish Wildlife Refuge, Wilderness Area, or

State/National Park

Cameron County, Texas

Lower Rio Grande Valley National Wildlife Refuge

Laguna Atascosa National Wildlife Refuge

Padre Island National Seashore

Isla Blanca Park

Andy Bowie County Park  

Laguna Madre Estuarine and Coastal Marine Area

Willacy County, Texas

Lower Rio Grande Valley National Wildlife Reserve

Laguna Atascosa National Wildlife Reserve  

Padre Island National Seashore

Laguna Madre Estuarine And Coastal Marine Area

Kenedy County, Texas Padre Island National Seashore

Laguna Madre Estuarine and Coastal Marine Area

Kleberg County, Texas Padre Island National Seashore

Laguna Madre Estuarine and Coastal Marine Area

Nueces County, Texas

Laguna Madre Estuarine and Coastal Marine Area

Mustang Island State Park

Lake Corpus Christi State Park

Port Aransas Park

Mission‐Aransas National Estuarine Research Reserve

Aransas County, Texas  

Mission‐Aransas National Estuarine Research Reserve

Aransas National Wildlife Refuge

Goose Island State Park

Calhoun County, Texas

Mission‐Aransas National Estuarine Research Reserve

Aransas National Wildlife Refuge

Matagorda Island State Park

Guadalupe Delta Wildlife Management Area

Welder Flats Coastal Preserve

Matagorda County, Texas  

Big Boggy National Wildlife Reserve

Aransas National Wildlife Reserve

Mad Island Wildlife Management Area

San Bernard National Wildlife Reserve

Brazoria County, Texas

San Bernard National Wildlife Reserve

Peach Point Wildlife Management Area

Brazoria National Wildlife Reserve

Christmas Bay Coastal Preserve and Christmas Bay State Park  

Galveston County, Texas

Galveston Island State Park

Brazoria National Wildlife Reserve

Apffel Park

Seawolf Park

Old Fort Travis Park

Atkinson Island Wildlife Management Area

Ft. Anahuc Park

Anahuac National Wildlife Reserve

Mcfaddin National Wildlife Reserve

Jefferson County, Texas  

Mcfaddin National Wildlife Reserve

Sea Rim State Park

Murphree Wildlife Management Area

Texas Point National Wildlife Reserve
Table 8.  (Continued.)

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County or Parish Wildlife Refuge, Wilderness Area, or

State/National Park

Cameron Parish, Louisiana  

Sabine National Wildlife Reserve

Cameron Prairie National Wildlife Reserve

Lacassine National Wildlife Reserve

Little Pecan Island Natural Area

Peveto Woods Natural Area

Lower Neches Wildlife Management Area

Rockefeller Wildlife Management Area

Vermilion Parish, Louisiana Louisiana Rockefeller Wildlife Management Area

Paul J. Rainey Wildlife Management Area

Terrebonne Parish, Louisiana

Atchafalaya Delta Wildlife Management Area

Mandalay National Wildlife Reserve

Isles Dernieres Barrier Islands Refuge

Pointe Au Chein Wildlife Management Area

Lafourche Parish Louisiana Louisiana Pointe Au Chein Wildlife Management Area

Wisner Wildlife Management Area

Plaquemines Parish, Louisiana  

Salvador Wildlife Management Area

Jean Lafitte National Historical Park and Preserve

Delta National Wildlife Reserve

Pass A Loutre Wildlife Management Area

Breton National Wildlife Reserve

St. Bernard State Park

The level of impacts from oil spills on coastal habitats depends on many factors, including the oil

characteristics, the geographic location of the landfall, and the weather and oceanographic

conditions at the time (MMS, 2007b).  Oil that makes it to beaches may be either liquid

weathered oil, an oil‐and‐water mousse, or tarballs (MMS, 2007b).  Oil is generally deposited on

beaches in lines defined by wave action at the time of landfall.  Oil that remains on the beach

will thicken as its volatile components are lost.  Thickened oil may form tarballs or aggregations

that incorporate sand, shell, and other materials into its mass.  Tar may be buried to varying

depths under the sand.  On warm days, both exposed and buried tarballs may liquefy and ooze.  

Oozing may also serve to expand the size of a mass as it incorporates beach materials.  Oil on

beaches may be cleaned up manually, mechanically, or both.  Some oil can remain on the beach

at varying depths and may persist for several years as it slowly biodegrades and volatilizes.

Wetlands are highly sensitive to oiling.  The MMS (2007b) predicted that for every 50 bbl of oil

contacting wetlands, approximately 2.7 ha (6.7 ac) of wetland vegetation will experience

dieback.  Thirty percent of these damaged wetlands are assumed to recover within 4 years, and

85% within 10 years.  About 15% of the contacted wetlands are expected to be converted

permanently to open‐water habitat.  The critical concentration of oil is that concentration above

which impacts to wetlands will be long‐term and recovery will take longer than two growing

seasons, and that 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,
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which have been reported to require from years to decades following a spill (MMS, 2007b;

BOEMRE, 2011a,b).

C.8 Socioeconomic and Other Resources

C.8.1 Recreational and Commercial Fishing

BOEMRE has reexamined the analysis for recreational and commercial fishing presented in

MMS 2007b and 2008 based on additional information and in consideration of the Macondo

incident.  However, no additional information obtained after the previous EISs was found that

would alter the potential impacts on commercial and recreational fishing discussed in those EISs

(BOEMRE, 2011a,b).

The main commercial fishing activity in deep waters of the northern Gulf of Mexico is pelagic

longlining for tunas, swordfishes, and other billfishes (Continental Shelf Associates, Inc., 2002).  

Pelagic longlining has occurred historically in the project area, primarily during spring and

summer.  In August 2000, the Federal government closed two areas in the northeastern Gulf of

Mexico to longline fishing (65 Federal Register 47,214, 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

(33 to 98 ft) long, and their trips last from about 1 to 3 weeks.  The main homeports for

longlining vessels are in Louisiana (Dulac and Venice) and Florida (Destin, Madeira Beach, and

Panama City).

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

project area.  Benthic species targeted by commercial fishers occur on the upper continental

slope, well inshore of the project area.  Royal red shrimp are caught by trawlers in water depths

of about 250 to 550 m (820 to 1,804 ft).  Tilefish are caught by bottom longlining in water

depths from about 165 to 450 m (540 to 1,476 ft) (Continental Shelf Associates, Inc., 2002).

Most recreational fishing activity in the region occurs in water depths less than 200 m (656 ft)

(Continental Shelf Associates, Inc., 1997, 2002).  In deeper water, the main attraction to

recreational fishers would be petroleum rigs offshore Texas and Louisiana.  Due to the distance

from shore, it is unlikely that recreational fishing activity is occurring in the lease area.

The only routine IPF potentially affecting fisheries is drilling rig presence (including noise and

lights).  Two (2) potential accidents are also addressed below – a small diesel fuel spill and a

large oil spill (WCD).

Impacts of Drilling Rig Presence

There is a slight possibility of pelagic longlines becoming entangled in the drilling rig.  For

example, in January 1999 a portion of a pelagic longline snagged on the acoustic Doppler

current profiler of a drillship working in the Gulf of Mexico (Continental Shelf Associates, Inc.,
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Environmental Impact Analysis for Initial Exploration Plan Page 64

2002).  The line was removed without incident.  Generally, longline fishers use radar and are

aware of offshore structures and ships when placing their sets.  Therefore, little or no impact on

pelagic longlining is expected.

Because it is unlikely that any recreational fishing activity is occurring in the project area, no

adverse impacts are anticipated.  Other factors such as effluent discharges are likely to have

negligible impacts on commercial or recreational fisheries due to rapid dispersion, the small

area of ocean affected, and the intermittent nature of the discharges.

Impacts of a Small Fuel Spill

The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

routine operations including diesel fuel transfer.  In the unlikely event of a spill, implementation

of Noble’s OSRP will potentially mitigate and reduce the potential for impacts.  EP Section H

provides 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

diesel fuel spill.  The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha

(1.2 to 12 ac), depending on sea state and weather conditions.  Fishing activities could be

interrupted due to the activities of response vessels operating in the lease area.  A small diesel

fuel spill would not affect coastal water quality because the spill would not be expected to make

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

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on fishing activities are discussed in recent EISs (MMS, 2007b, 2008).  For

the EP associated with this EIA, there are no unique site‐specific issues with respect to this

activity.

Pelagic longlining activities in the lease area and other fishing activities in the northern Gulf of

Mexico could be interrupted in the event of a large oil spill.  A spill may or may not result in

fishery closures, depending on the duration of the spill, the oceanographic and meteorological

conditions at the time, and the effectiveness of spill response measures.  The recent Macondo

incident provides information about the maximum 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 217,821 km2 (84,101 mi2

), or 34.8% of the U.S. Exclusive Economic Zone

(EEZ) in the Gulf of Mexico.

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 diesel fuel spill and a large oil spill (WCD) are addressed below.

Impacts of a Small Fuel Spill

The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

routine operations including diesel fuel transfer.  In the unlikely event of a spill, implementation

of Noble’s OSRP will potentially alleviate the potential for impacts.  EP Section H provides detail

on spill response measures.
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A small diesel fuel spill would not have any impacts on public health and safety because it would

affect only a small area of the open ocean 68 mi (110 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 diesel fuel spill would not be expected to make landfall or reach coastal waters prior to

breaking up (see Section A.9.2).

Impacts of a Large Oil Spill (WCD)

In the event of a large spill from a blowout, the main safety and health concerns are those of the

offshore personnel involved in the incident and those responding to the spill.  The drilling rig

maintains a Shipboard Oil Pollution Emergency Plan as required under MARPOL 73/78.

Depending on the spill rate and duration, the physical/chemical characteristics of the oil, the

meteorological and oceanographic conditions at the time, and the effectiveness of spill response

measures, the public could be exposed to oil on the water and along the shoreline, including

skin contact or breathing VOCs.  Crude oil is a highly flammable material, and any smoke or

vapors from a crude oil fire can cause irritation, and in large quantities may pose a health

hazard.

Data from the recent Macondo incident provide relevant information about the types of health

issues that may occur in the event of a large oil spill (Centers for Disease Control and Prevention,

2010a).  Wildlife cleaning  and rehabilitation workers have reported concerns including scrapes

and cuts, itchy or red skin or rash, and symptoms of headache or feeling faint, dizzy, or fatigued.  

Hand, shoulder, or back pain was also reported by some wildlife‐cleaning workers.  Personnel

working on offshore vessels or providing direct oversight to offshore vessels, including

USCG personnel, civilian contractors, and other responders who were exposed to oil and

dispersants, had a 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 in general was heat stress from work in a hot and

humid environment.  Initial symptoms from cleanup workers who sought medical care in

Louisiana were typical of acute exposure to hydrocarbons or H2S such as headaches, dizziness,

nausea, vomiting, cough, respiratory distress, and chest pain (Solomon and Janssen, 2010).

C.8.3 Employment and Infrastructure

There are no IPFs associated with routine operations that are expected to affect employment

and infrastructure.  The project involves drilling with support from existing shorebase facilities in

Louisiana.  No new or expanded facilities will be constructed, and no new employees are

expected to move permanently into the area.  The project will have a negligible impact on

socioeconomic conditions such as local employment, existing offshore and coastal infrastructure

(including major sources of supplies, services, energy, and water), and minority and lower

income groups.  Impacts of a small diesel fuel spill and a large oil spill (WCD) are addressed

below.

Impacts of a Small Fuel Spill

The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

routine operations including diesel fuel transfer.  In the unlikely event of a spill, implementation

of Noble’s OSRP will potentially mitigate and reduce the potential for impacts.  EP Section H
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Environmental Impact Analysis for Initial Exploration Plan Page 66

provides 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 diesel fuel spill that is dissipated within a few days would have little or no economic

impact, as the spill response would use existing facilities, resources, and personnel.

Impacts of a Large Oil Spill (WCD)

Potential socioeconomic impacts of an oil spill are discussed in recent EISs (MMS, 2007b, 2008).  

For the EP associated with this EIA, there are no unique site‐specific issues with respect to

employment and coastal infrastructure.  A large spill could cause economic impacts in several

ways: it could result in extensive fishery closures that put fishermen out of work; it could result

in temporary employment as part of the response effort; it could result in adverse publicity that

affects employment in coastal recreation and tourism industries; and it could result in another

suspension of OCS drilling activities, including service and support operations that are an

important part of local economies.

The lease area is 68 mi (110 km) from the nearest shoreline.  Based on revised OSRA modeling

(BOEMRE, 2011a,b) as summarized in Section A.9.3 (Table 3), there is a 78% chance that oil

from a spill in this lease area would reach shorelines in Texas and a 60% chance of contacting

shorelines in Louisiana within 120 days.  In addition to the analysis presented by MMS (2007b,

2008; BOEMRE, 2011a,b), a recent study explored the economic impacts of the Macondo

incident on oil and gas industry employment due to suspension of deepwater drilling

(Inter‐Agency Economic Report, 2010).  The study indicates that during the moratorium, the

number of oil industry workers in the Gulf of Mexico fell by about 2,000 and may have indirectly

caused a temporary loss of 8,000 to 12,000 jobs along the Gulf Coast.  Total spending by drilling

operators is estimated to have declined by $1.8 billion over a 6‐month period.  This direct

reduction in spending by the rigs affected employment in the industries that supply the Gulf

drilling industry and in all other industries affected by declines in consumer and business

spending (Inter‐Agency Economic Report, 2010).

C.8.4 Recreation and Tourism

BOEMRE has reexamined the analysis for recreation and tourism presented in MMS 2007b and

2008 based on additional information and in consideration of the Macondo incident.  However,

no new information available since the publication of those EISs would alter the potential

impacts on recreation and tourism (BOEMRE, 2011a,b).

There are no known recreational uses of the lease area.  Recreational resources and tourism in

coastal areas would not be affected by any routine activities due to the distance from shore.  

Compliance with NTL 2007‐G03 will minimize the chance of trash or debris being lost overboard

from the drilling rig and subsequently washing up on beaches.

Impacts of a Small Fuel Spill

The probability of a diesel fuel spill will be minimized by Noble’s preventative measures during

routine operations including diesel fuel transfer.  In the unlikely event of a spill, implementation

of Noble’s OSRP will potentially help mitigate and reduce the potential for impacts.  

EP Section H provides detail on spill response measures.  Given the open ocean location of the

lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.
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Environmental Impact Analysis for Initial Exploration Plan Page 67

A small diesel 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 diesel fuel spill would not be expected to make landfall or

reach coastal waters prior to breaking up.

Impacts of a Large Oil Spill (WCD)

Potential impacts of an oil spill on recreation and tourism are discussed in recent EISs

(MMS, 2007b, 2008; BOEMRE, 2011a,b).  For the EP associated with this EIA, 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 the

revised OSRA modeling (BOEMRE, 2011a,b) as summarized in Section A.9.3 (Table 3), there is a

78% chance that oil from a spill in this lease area would reach shorelines in Texas and a

60% chance of contacting shorelines in Louisiana within 120 days.

In addition to the analysis presented by MMS (2007b, 2008), recent and ongoing studies have

explored the economic impacts of the Macondo incident including tourism and “brand” damage

(IEM, 2010; Oxford Economics, 2010).  The U.S. Travel Association has estimated the economic

impact of the Macondo incident on tourism across the Gulf Coast over a 3‐year period at

$22.7 billion (Oxford Economics, 2010).  

C.8.5 Land Use

Land use along the northern Gulf Coast is discussed in recent lease sale EISs (MMS, 2007b,

2008).  There are no routine IPFs potentially affecting land use.  The project will use existing

onshore support facilities in Louisiana.  The land use at the existing shorebase sites is industrial.  

The project will not involve any new construction or changes to existing land use and, therefore,

will not have any impacts.  Levels of boat and helicopter traffic, as well as demand for goods and

services including scarce coastal resources, will represent a small fraction of the level of activity

occurring at the shorebases.

A large oil spill (WCD) is the only relevant IPF.  A small diesel fuel spill would not have any

impacts on land use, as the response would be staged out of existing shorebases and facilities.

Impacts of a Large Oil Spill (WCD)

The initial response for a large oil spill would be staged out of existing facilities, with no effect on

land use.  A large spill could have limited temporary impacts on land use along the coast if

additional staging areas were needed.  For example, during the Macondo incident, 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 established (see EP Section H).  These areas would eventually return to their

original use as the response is demobilized.
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Environmental Impact Analysis for Initial Exploration Plan Page 68

C.8.6 Other Marine Uses

The lease area is not located within any Military Warning Area or USCG‐designated fairway or

shipping lane.

Man‐made features identified within MC 948 during the site clearance survey (GEMS, 2011)

include two existing Noble exploration wellsites, a 2‐in. fiber‐optic cable, an 8‐in. pipeline, and a

3‐in. umbilical.  Noble exploration well MC 948‐1 is approximately 985 m (3,230 ft)

south‐southwest of the proposed wellsites and exploration well MC 948‐2 is approximately

1,013 m (3,325 ft) south‐southwest of the proposed wellsites.  The BP fiber‐optic cable runs

northeast‐southwest crossing the northwest corner of MC 948 and is approximately 4,168 m

(13,675 ft) from the proposed wellsites.  The Mariner pipeline and umbilical, running

north‐south, occur approximately 1,745 m (5,725 ft) east of the proposed wellsites within

MC 949.

There are no IPFs from routine project activities that are likely to affect other marine uses.  A

large oil spill (WCD) is the only relevant accident IPF.  A small diesel fuel spill would not have any

impacts on other marine uses, as spill response activities would take place mainly within the

lease area and the duration would be brief.

Impacts of a Large Oil Spill (WCD)

An accidental spill would be unlikely to significantly affect shipping or other marine uses.  The

block is not located within any USCG‐designated fairway or shipping lane.  In the event of a large

spill requiring numerous response vessels, coordination would be required to manage the vessel

traffic for safe operations.  Noble will comply with BOEMRE requirements and lease stipulations

to avoid impacts on uses of the area by military vessels and aircraft.

In the event of a large spill requiring numerous vessels in the area, coordination would be

required to ensure that no anchoring or seafloor‐disturbing activities occur near the existing

pipelines and flowlines.

D.  Environmental Hazards

D.1 Geologic Hazards

The shallow hazards assessment conducted by GEMS (2011) concludes that the wellsites

generally appear suitable for exploration drilling operations, but the engineers should be aware

that the area has potential for overpressured sand layers.  See EP Section C 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 support activities (vessel and helicopter traffic) and make it

necessary to suspend some activities on the drilling rig for safety reasons until the storm or
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Environmental Impact Analysis for Initial Exploration Plan Page 69

weather event passes.  In the event of a hurricane, procedures as outlined in the Hurricane

Evacuation Plan would be adhered to.

D.3 Currents and Waves

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

monitored.  Under most circumstances, physical oceanographic conditions are not expected to

have any effect on the proposed activities.  Strong currents (e.g., caused by Loop Current eddies

and intrusions) and large waves were considered in the design criteria for the drilling rig.  High

waves during a severe storm could disrupt support activities (i.e., vessel and helicopter traffic)

and make it necessary to suspend some activities on the drilling rig for safety reasons until the

storm or weather event passes.

E.  Alternatives

No formal alternatives were evaluated in this EIA for an EP.  However, various technical and

operational options, including the location of the wellsites and the selection of a drilling unit,

were considered by Noble in developing the proposed action.  

F.  Mitigation Measures

The proposed action includes numerous mitigation measures required by laws, regulations, and

BOEMRE lease stipulations and NTLs.  The project will comply with all applicable Federal, State,

and local requirements concerning air pollutant emissions, discharges to water, and solid waste

disposal.  All project activities will be conducted under guidance by Noble’s OSRP and will

include the measures described in EP Section H.

G.  Consultation

No persons or agencies were consulted during the preparation of this EIA.

H.  Preparers

The EIA was prepared by CSA International, Inc.  Contributors included

 M. John Thompson (Senior Scientist);

 Neal Phillips, Ph.D. (Senior Scientist);

 Luis Lagera, Jr., Ph.D. (Senior Scientist);

 Deborah K. Fawcett, M.S. (Project Scientist 2);
Mississippi Canyon Blocks 948 and 949 August 2011

Environmental Impact Analysis for Initial Exploration Plan Page 70

 Keith VanGraafeiland (GIS/Remote Sensing Specialist);

 Kristen  L. Metzger (Library and Information Services Director); and

 Kim Dunleavy (Technical Editor).

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Noble Energy, Inc. Page O-1

Revised Exploration Plan 10/6/2011

Mississippi Canyon 948 & 949 (OCS-G 28030 & 32363)

Section O

Administrative Information

A. Exempted Information Description

The proposed bottom-hole locations of the planned wells have been removed from the public

information copy of the EP as well as any discussions of the target objectives, geologic or geophysical

data, and any interpreted geology.

B. Bibliography

Not applicable.