UNITED STATES GOVERNMENT MEMORANDUM

To: Public Information (MS 5030)

Plans Section, Office of Field 

Operations (MS 5231)

Public Information copy of Exploration Plan

Control # - R-05982

Type - Revised Exploration Plan

Lease(s) - OCS-G21849 Block - 143 Walker Ridge Area

Operator - Union Oil Company of California

Wells A and B

Not Found

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

should be addressed in an Environmental Assessment.

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

Chiquita Hill

Plan Coordinator

Description -

Rig Type -

Subject:

From:

November 21, 2013
Environmental Impact Analysis

REVISED EXPLORATION PLAN

Coronado Prospect

Walker Ridge Block 143 (OCSͲG 21849)

Offshore Louisiana

November 2013

Prepared for:

Philip A. Von Dullen III

Geophysical Technologist

Chevron U.S.A. Inc.

1500 Louisiana Street

Houston, Texas77002

Telephone: (832) 854Ͳ3644

Prepared by:

CSA Ocean Sciences Inc.

8502 SW Kansas Avenue

Stuart, Florida34997

Telephone: (772) 219Ͳ3000
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page ii

Contents

Page

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

A.ImpactͲProducing Factors .......................................................................................4

A.1 Drilling Rig Presence (including noise and lights)........................................................................... 4

A.2 Physical Disturbance to the Seafloor.............................................................................................. 4

A.3 Air Emissions...................................................................................................................................7

A.4 Effluent Discharges......................................................................................................................... 7

A.5 Seawater Intake.............................................................................................................................. 7

A.6 Onshore Waste Disposal................................................................................................................. 8

A.7 Marine Debris.................................................................................................................................8

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

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

A.9.1 Types of Accidents Evaluated ............................................................................................. 9

A.9.2 Small Fuel Spill .................................................................................................................... 9

A.9.3 Crude Oil Spill (Worst Case Discharge) ............................................................................. 10

A.9.4 Other Accidents Not Analyzed in Detail............................................................................ 12

B.Potentially Affected Environment .........................................................................14

C.Impact Analysis.....................................................................................................16

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

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

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

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

C.2.1 Soft Bottom Benthic Communities................................................................................... 20

C.2.2 HighͲDensity Deepwater Benthic Communities............................................................... 22

C.2.3 Designated Topographic Features.................................................................................... 24

C.2.4 Pinnacle Trend Area Live Bottoms.................................................................................... 24

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

C.3 Threatened, Endangered, and Protected Species and Critical Habitat........................................ 25

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

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

C.3.3 Endangered Mysticete Whales......................................................................................... 31

C.3.4 NonͲEndangered Marine Mammals (Protected).............................................................. 32

C.3.5 Sea Turtles (Endangered/Threatened) ............................................................................. 35

C.3.6 Piping Plover (Threatened) ............................................................................................... 38

C.3.7 Whooping Crane (Endangered) ........................................................................................ 40

C.3.8 Gulf Sturgeon (Threatened).............................................................................................. 41

C.3.9 Beach Mice (Endangered)................................................................................................. 41

C.4 Coastal and Marine Birds.............................................................................................................. 42

C.4.1 Marine and Pelagic Birds .................................................................................................. 42

C.4.2 Shorebirds and Coastal Nesting Birds............................................................................... 45

C.5 Fisheries Resources ...................................................................................................................... 47
Contents

(Continued)

Page

Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page iii

C.5.1 Pelagic Communities and Ichthyoplankton ...................................................................... 47

C.5.2 Essential Fish Habitat........................................................................................................ 50

C.6 Archaeological Resources............................................................................................................. 52

C.6.1 Shipwreck Sites................................................................................................................. 52

C.6.2 Prehistoric Archaeological Sites........................................................................................ 53

C.7 Coastal Habitats and Protected Areas.......................................................................................... 54

C.8 Socioeconomic and Other Resources........................................................................................... 57

C.8.1 Recreational and Commercial Fishing .............................................................................. 57

C.8.2 Public Health and Safety ................................................................................................... 58

C.8.3 Employment and Infrastructure ....................................................................................... 59

C.8.4 Recreation and Tourism.................................................................................................... 60

C.8.5 Land Use............................................................................................................................ 61

C.8.6 Other Marine Uses............................................................................................................ 61

D.Environmental Hazards.........................................................................................62

D.1 Geologic Hazards.......................................................................................................................... 62

D.2 Severe Weather............................................................................................................................ 62

D.3 Currents and Waves ..................................................................................................................... 62

E.Alternatives ..........................................................................................................63

F.Mitigation Measures.............................................................................................63

G.Consultation.........................................................................................................63

H.Preparers..............................................................................................................63

I.References.............................................................................................................63
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised 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) ............................................................................................................. 3

2 Matrix of impactͲproducing factors and potentially affected environmentalresources...............5

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

(From: Ji et al., 2004)........................................................................................................... 11

4 Benthic community data from stations near the lease area sampled during the

Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology Study

(From: Wei, 2006; Rowe and Kennicutt, 2009). .................................................................. 20

5 Federally listed endangered and threatened species potentially present in the

lease area and along the northern Gulf Coast .................................................................... 26

6 Coastal wildlife refuges, wilderness areas, and parks within the geographic range

of potential shoreline contacts within 30 days after an oil spill based on the OSRA

results summarized in Table 3............................................................................................. 56

List of Figures

Figure Page

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

2 Bathymetric map of the wellsite locations in Walker Ridge Block 143............................... 15

3 Location of selected environmental features in relation to the lease area........................ 39
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page v

Acronyms and Abbreviations

ADIOS Automated Data Inquiry for Oil Spills

BOEM Bureau of Ocean Energy Management

BOEMRE Bureau of Ocean Energy Management,

Regulation and Enforcement

BOP blowout preventer

BOPD barrels of oil per day

BPD barrels per day

BSEE Bureau of Safety and Environmental

Enforcement

Chevron Chevron U.S.A. Inc.

CO carbon monoxide

DP dynamic positioning

DPS Distinct Population Segment

EA Environmental Assessment

EFH Essential Fish Habitat

EIA Environmental Impact Analysis

EIS Environmental Impact Statement

EP Exploration Plan

ERMA Environmental Response Management

Application

ESA Endangered Species Act

FAA Federal Aviation Administration

FAD fishͲattracting device

Fugro Fugro GeoConsulting, Inc.

GEMS Geoscience Earth & Marine Services, Inc.

GMFMC Gulf of Mexico Fishery Management Council

GPM gallons per minute

H2S hydrogen sulfide

HAPC Habitat Area of Particular Concern

IPF impactͲproducing factor

MARPOL International Convention for the

Prevention of Pollution from Ships

MGD million gallons per day

MMC Marine Mammal Commission

MMPA Marine Mammal Protection Act

MMS Minerals Management Service

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

NRDA Natural Resource Damage Assessment

NTL Notice to Lessees and Operators

NWR National Wildlife Refuge

OCS Outer Continental Shelf

OSAT Operational Science Advisory Team

OSRA Oil Spill Risk Analysis

OSRP Oil Spill Response Plan

PAH polycyclic aromatic hydrocarbon

PM particulate matter

PSD Prevention of Significant Deterioration

ROV remotely operated vehicle

SBM syntheticͲbased mud

SOx sulfur oxides

USCG U.S. Coast Guard

USEPA U.S. Environmental Protection Agency

USFWS U.S. Fish and Wildlife Service

VOC volatile organic compound

WBM waterͲbased drilling mud

WCD worst case discharge

WR Walker Ridge
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 1

Introduction

This Environmental Impact Analysis (EIA) was prepared on behalf of Union Oil Company of

California, an affiliate of Chevron U.S.A. Inc. (Chevron) for submittal to the Bureau of Ocean

Energy Management (BOEM)1

.The EIA evaluates the impacts of drilling activities proposed by

Chevron in its Revised Exploration Plan (EP) for Walker Ridge (WR) Block 143.

Under the Revised EP, Chevron plans to drill two exploration wells (surface locations A and B) in

WR 143.Drilling is anticipated to begin in November 2013 and is expected to require

approximately 150 days per well.The lease area is 156 miles (251 km) from the nearest

shoreline (Texas) and 183 miles (294 km) from the onshore support base at Leeville, Louisiana

(Figure 1).Water depths at the wellsites range from 1,705 to 1,756 m (5,593 to 5,760 ft).

Chevron plans to use a dynamic positioning (DP) drillship to drill the wells.

This EIA is a projectͲand siteͲspecific analysis of Chevron’s planned activities prepared in

accordance with Federal regulations, including 30 CFR 550.212(o) and 550.227, as well as

Notices to Lessees and Operators (NTLs) 2008ͲG04 and 2013ͲG02.An EIA is a projectͲspecific

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 Programmatic Environmental Impact Statement

(EIS) for the Outer Continental Shelf (OCS) Oil and Gas Leasing Program (MMS, 2007a) and in

multiͲleaseͲsale EISs for the Western and Central Gulf of Mexico Planning Areas (MMS, 2007b;

BOEM, 2012, 2013a), as well as the Environmental Assessment (EA) for Gulf of Mexico

deepwater operations and activities (MMS, 2000).The most recent multiͲleaseͲsale EISs update

environmental baseline information in light of the Macondo (Deepwater Horizon) incident and

address potential impacts of a catastrophic spill (BOEM, 2012, 2013a).

All the proposed activities and facilities in Chevron’s plan will be covered by the Oil Spill

Response Plan (OSRP) filed by Chevron in accordance with 30 CFR 254 and approved

April 15, 2010.Chevron submitted a biannual update to the Regional OSRP on January 11, 2012.

An updated OSRP was received by the BSEE Oil Spill Response Planning Division on February 11,

2013, with a worst case discharge (WCD) certification date of February 12, 2013, along with a

letter certifying that Chevron continues to have the capability to respond to the maximum

extent practical to a worst case discharge from all Chevron facilities located in the Gulf of

Mexico.

Sections A through I of this EIA provide the information required by NTL 2008ͲG04.The main

impactͲrelated discussions are in Sections A (ImpactͲProducing Factors) and C (Impact Analysis).

Table 1 lists and summarizes the NTLs that are referenced in this EIA.



1

On October 1, 2011, the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE), formerly the Minerals

Management Service (MMS), was replaced by the BOEM and the Bureau of Safety and Environmental Enforcement (BSEE) as

part of a major reorganization.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 2

Figure 1. Vicinity map for the lease area.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 3

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

Impact Analysis (EIA).

NTL Title Summary

2013ͲG02 Extension of Prior Notices to Lessees Extends the effective date of NTL 2008ͲG04 (and two other NTLs)

until the end of the 2013 calendar year.

2012ͲN06

Guidance to Owners and Operators

of Offshore Facilities Seaward of the

Coast Line Concerning Oil Spill

Response Plans

Provides clarification, guidance, and information concerning the

preparation of Oil Spill Response Plans.

2012ͲBSEEͲG01 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.

2012ͲJOINTͲG01

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.

2011ͲJOINTͲG01

Revisions to the List of OCS Blocks

Requiring Archaeological Resource

Surveys and Reports

Provides new information on which OCS blocks require

archaeological surveys and reports and line spacing required in

each block.This NTL augments NTL 2005ͲG07.

2010ͲN10

Statement of Compliance with

Applicable Regulations and

Evaluation of Information

Demonstrating Adequate Spill

Response and Well Containment

Resources

Informs operators using subsea blowout preventers (BOPs) or

surface BOPs on floating facilities that applications for well permits

must include a statement signed by an authorized company official

stating that the operator will conduct all activities in compliance

with all applicable regulations, including the increased safety

measures regulations (75 FR 63346).Informs operators that the

BOEM will evaluate 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.

2010ͲN06

Information Requirements for

Exploration Plans, Development and

Production Plans, and Development

Operations Coordination Documents

on the OCS

Rescinds the limitations set forth in NTL 2008ͲG04 regarding a

blowout scenario and worst case discharge scenario, and provides

guidance for the information required in blowout scenario and

worst case discharge scenario descriptions.

2009ͲG40 Deepwater Benthic Communities

Provides guidance for avoiding and protecting highͲdensity

deepwater benthic communities (including chemosynthetic and

deepwater coral communities) from damage caused by Outer

Continental Shelf (OCS) oil and gas activities in water depths

greater than 300 m (984 ft).Prescribes separation distances of

610 m (2,000 ft) from each mud and cuttings discharge location

and 76 m (250 ft) from all other seafloor disturbances.

2009ͲG39 BiologicallyͲSensitive Underwater

Features and Areas

Provides guidance for avoiding and protecting biologically sensitive

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

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.

2008ͲG04

Information Requirements for

Exploration Plans and Development

Operations Coordination Documents

Provides 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.

2005ͲG07 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.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 4

A.ImpactͲProducing Factors

Table 2 is a matrix of impactͲproducing factors (IPFs) and potentially affected environmental

resources adapted from the worksheet referenced in NTL 2008ͲG04.An “X” indicates that an

IPF could reasonably be expected to affect a resource, and a dash (ͲͲ) indicates no impact or

negligible impact.Where there may be an impact, an analysis is provided in Section C.Potential

IPFs for the proposed activity are listed below and briefly discussed in the following subsections:

x Drilling rig presence (including noise and lights);

x Physical disturbance to the seafloor;

x Air emissions;

x Effluent discharges;

x Seawater intake;

x Onshore waste disposal;

x Marine debris;

x Support vessel and helicopter traffic; and

x Accidents.

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

The drilling rig will be a DP drillship.The rig will be on site for approximately 150 days per well.

The physical presence of a floating structure in the ocean can attract pelagic fishes and other

marine life, as discussed in Section C.5.1.A typical drillship would have hull dimensions of about

230 by 40 m (755 by 130 ft) and an operating draft of 12 m (40 ft).

Sound and vibration from rig generators and drilling machinery aboard a drillship are

transmitted through the hull, which is well coupled to the water (Richardson et al., 1995).

Drilling operations produce noise that is not particularly intense and is strongest at low

frequencies, averaging 10 to 500 Hz (Richardson et al., 1995; MMS, 2000).Nedwell and

Edwards (2004) report that the majority of noise from an operational drillship was found to be

in the 40Ͳto 600ͲHz band when measured at a range of 0.3 to 1.2 miles (0.5 to 2 km).At a range

of 3 miles (5 km), there was no perceptible noise above ambient.All drilling rigs maintain

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

A.2 Physical Disturbance to the Seafloor

Because a DP drillship will be used, there will be no physical disturbance to the seafloor from

anchoring during the drilling activities analyzed in this EIA.A very small area of seafloor would

be disturbed at the wellbore where the bottom template and blowout preventer (BOP) are

located.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 5

Table 2. Matrix of impactͲproducing factors and potentially affected environmentalresources. X = potential impact; dash (ͲͲ) = no impact or negligible impact.

Environmental Resources

ImpactͲproducing Factors

Drilling Rig Presence

(including noise and

lights)

Physical

Disturbance to

Seafloor

Air

Emissions

Effluent

Discharges

Seawater

Intake

Onshore

Waste

Disposal

Marine

Debris

Support

Vessel/Helo

Traffic

Accidents

Small Fuel

Spill

Oil Spill

(WCD)

Physical/Chemical Environment

Air quality and greenhouse gases ͲͲ ͲͲ X(9) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6) X(6)Water quality ͲͲ ͲͲ ͲͲ X ͲͲ ͲͲ ͲͲ ͲͲ X(6) X(6)

Seafloor Habitats and Biota

Soft bottom benthic communities ͲͲ ͲͲ ͲͲ X ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)HighͲdensity deepwater benthic communities ͲͲ ͲͲ(4) ͲͲ ͲͲ(4) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Designated topographic features ͲͲ ͲͲ(1) ͲͲ ͲͲ(1) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲPinnacle trend area live bottoms ͲͲ ͲͲ(2) ͲͲ ͲͲ(2) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲEastern Gulf live bottoms ͲͲ ͲͲ(3) ͲͲ ͲͲ(3) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ

Threatened, Endangered, and Protected Species and Critical Habitat

Sperm whale (endangered) X(8) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(8) X(6,8) X(6,8)Florida manatee (endangered) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(8) ͲͲ X(6,8)Endangered mysticete whales ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲNonͲendangeredmarinemammals(protected) X ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X X(6) X(6)Sea turtles (endangered/threatened) X(8) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(8) X(6,8) X(6,8)Piping Plover (threatened) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Whooping Crane (endangered) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Gulf sturgeon (threatened) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Beach mice (endangered) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)

Coastal and Marine Birds

Marine and pelagic birds X ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X X(6) X(6)Shorebirds and coastal nesting birds ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X ͲͲ X(6)

Fisheries Resources

Pelagic communities and ichthyoplankton X ͲͲ ͲͲ X X ͲͲ ͲͲ ͲͲ X(6) X(6)Essential Fish Habitat X ͲͲ ͲͲ X X ͲͲ ͲͲ ͲͲ X(6) X(6)

Archaeological Resources

Shipwreck sites ͲͲ ͲͲ(7) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Prehistoric archaeological sites ͲͲ ͲͲ(7) ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)

Coastal Habitats and Protected Areas

Beaches ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Wetlands and seagrass beds ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X ͲͲ X(6)Coastal wildlife refuges and wilderness areas ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)

Socioeconomic and Other Resources

Recreational and commercial fishing X ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6) X(6)Public health and safety ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Employment and infrastructure ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Recreation and tourism ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Land use ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)Other marine uses ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ ͲͲ X(6)

WCD = worst case discharge.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 6

Table 2 Footnotes and Applicability:

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

any anchors will be on the seafloor within the following:

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

(b) 1,000Ͳm, 1Ͳmile, or 3Ͳmile 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 noͲactivity zone; or

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

the Topographic Features Stipulation attached to an OCS lease.

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

noͲactivity zone.There are no submarine banks in the lease area.

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

Trend) Stipulation attached to an OCS lease.

x 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

(LowͲRelief) Stipulation attached to an OCS lease.

x The Live Bottom (LowͲRelief) Stipulation is not applicable to the lease area.

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

x No impacts on highͲdensity deepwater benthic communities are anticipated.There are no features

indicative of highͲdensity chemosynthetic communities or coral communities within 610 m (2,000 ft) of

any drilling mud/cuttings discharge locations.Because a dynamic positioning (DP) drillship will be used,

there will be no seafloor disturbances from the use of anchors.

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

x Not applicable.The Regional Supervisor has classified the area as “H2S absent” with the Initial EP

approval and subsequent Revised EP approvals.

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

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

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

x Accidental hydrocarbon spills could affect the resources marked (X) in the “Accidents” portion of the

matrix, and potential impacts are analyzed in Section C.

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

by the BOEM as having highͲprobability 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.

x No impacts on archaeological resources are expected.The lease area is not on the list of highͲprobability

blocks for shipwrecks and is well beyond the 60Ͳm (197Ͳft) depth contour used by the BOEM as the

seaward extent for prehistoric archaeological site potential in the Gulf of Mexico.Because a DP drillship

will be used, there will be no seafloor disturbances from the use of anchors.An archaeological

assessment of the proposed wellsites has been conducted, and no archaeological avoidance features

were detected.

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

or sea turtles or their critical habitats.

x IPFs that may affect marine mammals, sea turtles, or their critical habitats include drilling rig presence

and emissions; support vessel and helicopter traffic; and accidents.See Section C.

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

x Not applicable.

 
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 7

A.3 Air Emissions

Air emissions are estimated in Section G of the Revised EP.Offshore air emissions will result

from drilling rig operations, as well as service vessels and helicopters.These emissions occur

mainly from combustion of diesel fuel.The combustion of fuels occurs on dieselͲpowered

generators, pumps, or motors and from lighter fuel motors.Primary air emissions associated

with OCS activities typically include suspended particulate matter (PM), sulfur oxides (SOx),

nitrogen oxides (NOx), volatile organic compounds (VOCs), and carbon monoxide (CO).

The Air Quality Emissions Report prepared in accordance with BOEM requirements shows that

the projected emissions are below exemption levels.Therefore, no control measures are

required, and no significant onshore impacts are expected.

A.4 Effluent Discharges

Effluent discharges are summarized in Section F of the Revised EP.All discharges from the

drilling rig will be in accordance with the National Pollutant Discharge Elimination System

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

(USEPA).Discharges will be in accordance with and monitored as required by the permit.

Support vessel discharges are expected to be in accordance with U.S. Coast Guard (USCG)

regulations and, as applicable, the NPDES Vessel General Permit.

For each well, an estimated maximum of 110,003 bbl of waterͲbased drilling muds (WBMs) and

4,317 bbl of cuttings coated with WBMs will be released at the seafloor during the initial well

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

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

drilling operations.

A syntheticͲbased mud (SBM) system will be used after the riser is installed.The SBM will not be

discharged but will be recovered and transported to the shorebase for recycling by the mud

company.Treated SBM cuttings will be discharged overboard after treatment with a cuttings

dryer, which is expected to reduce retention on cuttings to well below the NPDES permit

requirement of 6.9%.The volume of treated SBM cuttings to be discharged per well is

estimated to be 5,062 bbl.

Other effluent discharges in accordance with the NPDES permit will include treated sanitary and

domestic wastes, deck drainage, desalination unit brine, BOP fluid, uncontaminated ballast

water, excess cement, uncontaminated water from testing of the firewater system, nonͲcontact

cooling water, and other miscellaneous discharges.

A.5 Seawater Intake

Seawater will be drawn from the ocean for onceͲthrough, nonͲcontact cooling of machinery on

the drilling rig.The estimated intake and discharge of cooling water is approximately

500,000 BPD (21 million gallons per day [MGD]).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 reduce the potential for adverse

environmental impacts from impingement and entrainment of aquatic organisms.All affected

intakes will be in accordance with the design, monitoring, and recordkeeping requirements of

the NPDES permit.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 8

A.6 Onshore Waste Disposal

Solid and liquid wastes generated during drilling are tabulated in Section F of the Revised EP.An

estimated 1,800 lb/day of trash and debris will be transported in storage bins to the shorebase

for landfill disposal.Approximately 3 BPD of chemical product wastes will be transported in

drums on the supply boat to the shorebase and then trucked to the disposal facility for

incineration or recycling.An estimated 17,000 bbl/well of spent SBM drilling fluids will be

transported to the shorebase and taken to Newpark Environmental Services for recycling.An

estimated 1,000 bbl of SBM cuttings will be transported to shore, treated, and landfilled.

A.7 Marine Debris

Chevron will adhere to the International Convention for the Prevention of Pollution from Ships

(MARPOL 73/78) Annex V requirements, USEPA and USCG regulations, and BOEM regulations

and NTLs regarding solid wastes.Regulations at 30 CFR 250.300(a) and (b)(6) prohibit operators

from deliberately discharging containers and other similar materials (i.e., trash and debris) into

the marine environment, and 30 CFR 250.300(c) requires durable identification markings on

equipment, tools and containers (especially drums), and other material.USCG and USEPA

regulations require operators to become proactive in avoiding accidental loss of solid waste

items by developing waste management plans, posting informational placards, manifesting trash

sent to shore, and using special precautions such as covering outside trash bins to prevent

accidental loss of solid waste.NTL 2012ͲBSEEͲG01, 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.Chevron’s compliance

with these laws, regulations, and NTL 2012ͲBSEEͲG01 will avoid or reduce the potential for

significant impacts on the environment.

A.8 Support Vessel and Helicopter Traffic

Chevron will use existing shorebase facilities at Leeville, Louisiana, for onshore support for water

and air transportation.No terminal expansion or construction is planned.

The project will be supported by two supply boats and one crew boat traveling between the

drilling rig and the onshore support base.The supply boats are expected to make round trips

every 2 to 3 days, and the crew boat will make one round trip per week.Typically, the boats will

move to the project area via the most direct route from the shorebase.

A helicopter will be used to transport personnel and small supplies between the drilling rig and

the heliport (estimated seven round trips per week).The helicopter normally will take the most

direct route between the shorebase and the lease area when air traffic and weather conditions

permit.Helicopters would be expected to follow Federal Aviation Administration (FAA) Advisory

Circular 91Ͳ36D (FAA, 2004), which recommends a minimum altitude of 610 m (2,000 ft) when

flying over noiseͲsensitive areas such as parks, wildlife refuges, and wilderness areas.Corporate

policies for all helicopter companies in the Gulf of Mexico require a minimum altitude of 213 m

(700 ft) during transit to and from the working area and a minimum altitude of about 152 m

(500 ft) while traveling between platforms (BOEM, 2012).
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 9

A.9 Accidents

A.9.1 Types of Accidents Evaluated

The analysis in this EIA focuses on two potential accidents:

x a small fuel spill, which is the most likely type of spill during OCS oil and gas activities; and

x the worst case discharge (WCD) for the Revised EP, 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 Chevron’s spill response plans.Potential impacts are analyzed in Section C.

The recent lease sale EIS (BOEM, 2012) analyzes four other types of accidents: loss of well

control, vessel collisions, chemical and drilling fluid spills, and pipeline failures.The plan does

not include any pipelines; the other accident types are discussed briefly in Section A.9.4.

A.9.2 Small Fuel Spill

Spill Size.The most likely type of small spill (<1,000 bbl) during OCS activities is a minor diesel

fuel spill (BOEM, 2012).Historically, most diesel spills have beenч1 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 (BOEM, 2012).The average size for spillsч1 bbl is

0.07 bbl, and the median size for spills of 1 to 10 bbl is 3 bbl (BOEM, 2012).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 a loss of contents (<3 bbl fuel) in the

fuel transfer hose.

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

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

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

opportunity for impacts to occur would be very brief.

The waterͲsoluble fractions of diesel are dominated by twoͲand threeͲringed polycyclic

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

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

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

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

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

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

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

and Atmospheric Administration [NOAA], 2006).

The fate of a small diesel fuel spill was estimated using NOAA’s Automated Data Inquiry for Oil

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

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

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

would be evaporated or dispersed within 24 hours.The estimated sea surface area that could

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

weather conditions.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 10

The ADIOS model outcomes, coupled with spill trajectory information discussed in the following

subsection for a large spill, indicate that a small fuel spill would not have any impacts on coastal

or shoreline resources.The lease area is 156 miles (251 km) from the nearest shoreline

(Louisiana).Modeling results discussed in the following subsection indicate that a spill in the

lease area would not contact any shorelines within 10 days after a spill.By that time, essentially

100% of a small fuel spill would have been dispersed or evaporated by natural processes,

without taking into account Chevron’s response measures.BOEM (2012) 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.

Spill Response.In the unlikely event that a fuel spill occurs, response equipment and trained

personnel would be available to act to localize the spill.Section H of the Revised EP provides a

detailed discussion of Chevron’s plans for responding to a spill.

A.9.3 Crude Oil Spill (Worst Case Discharge)

Spill Size.In accordance with requirements of NTL 2010ͲN06, Chevron has estimated a WCD for

the Revised EP.The initial flow rate is calculated to be 156,994 barrels of oil per day (BOPD).

Chevron estimates that it would take 153 days to mobilize a rig, drill a relief well, and conduct a

kill operation.During this time, the total potential spill volume is estimated at 22,137,417 bbl.

See Section H of the Revised EP for further information.

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 nonͲNorth 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.

On January 28, 2011, Chevron submitted additional information to the BOEM in response to

NTL 2010ͲN06, including descriptions of measures designed to prevent a blowout, reduce the

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

Chevron will also comply with NTL 2010ͲN10 and the Interim Final Drilling Safety Rule, which

specify additional safety measures for OCS activities.

Spill Trajectory.The fate of a large oil spill in the lease area would depend on meteorological

and oceanographic conditions at the time.The Oil Spill Risk Analysis (OSRA) model is a

computer simulation of oil spill transport that uses realistic data for winds and currents to

estimate spill fate.The OSRA report by Ji et al. (2004) provides conditional contact probabilities

for shoreline segments.The results for Launch Area 47 (where the lease area is located) are

presented in Table 3.The model predicts no shoreline contacts within 10 days after a spill.

After 30 days, four Texas counties and four Louisiana parishes may be contacted, ranging from

Matagorda County, Texas, to Plaquemines Parish, Louisiana.The greatest probability of

shoreline contact after 30 days is 3% for Cameron Parish, Louisiana.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 11

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

(From: Ji et al., 2004).Values are conditional probabilities that a hypothetical spill in

the lease area (represented by Oil Spill Risk Analysis Launch Area 47) could contact

shoreline segments within 3, 10, or 30 days.

Shoreline

Segment County or Parish and State Conditional Probability of Contacta (%)

3 Days 10 Days 30 Days

C08 Matagorda County, Texas ͲͲ ͲͲ 1

C09 Brazoria County, Texas ͲͲ ͲͲ 1

C10 Galveston County, Texas ͲͲ ͲͲ 2

C12 Jefferson County, Texas ͲͲ ͲͲ 1

C13 Cameron Parish, Louisiana ͲͲ ͲͲ 3

C14 Vermilion Parish, Louisiana ͲͲ ͲͲ 1

C17 Terrebonne Parish, Louisiana ͲͲ ͲͲ 1

C20 Plaquemines Parish, Louisiana ͲͲ ͲͲ 1

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

occurred (ͲͲindicates less than 0.5%).

The original OSRA modeling runs reported by Ji et al. (2004) did not evaluate the fate of a spill

over time periods longer than 30 days, nor did they estimate the fate of a release that continues

over a period of weeks or months.Also as noted by Ji et al. (2004), the OSRA model does not

take into account the chemical composition or biological weathering of oil spills, the spreading

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

spill size but has generally been used by the BOEM to evaluate contact probabilities for spills

greater than 1,000 bbl.

BOEM (2012) recently conducted additional OSRA modeling to simulate a spill that continues

over 90 consecutive days, with each trajectory tracked for 120 days during four seasons.The

spatial resolution is limited, with five launch points to represent the entire northern Gulf of

Mexico.The nearest launch point to the lease area is Launch Point #3.For this launch point,

potential shoreline contacts after 120 days range from Cameron County, Texas (at the

Texas/Mexico border) to Dade County in southeastern Florida.Based on statewide contact

probabilities after 120 days, Texas and Louisiana shorelines have the highest likelihood of

contact during all four seasons, with Louisiana having higher probabilities in spring (60%) and

Texas having higher probabilities during all other seasons (ranging from 41% to 78%).The

modeling predicts a 1% probability of a spill contacting Alabama and Mississippi shorelines, but

only during spring.The modeling predicts that Florida shorelines could be contacted in any

season, with statewide probabilities ranging from 1% to 4%.Based on the 120Ͳday trajectories,

counties, or parishes with greater than 10% contact probability during any season range from

Matagorda County, Texas, to Plaquemines Parish, Louisiana.

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,

thereby influencing its potential effects on marine organisms and ecosystems.The most

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

water column, formation of waterͲinͲoil emulsions, photochemical oxidation, microbial

degradation, adsorption to suspended particulate matter, and stranding on shore or

sedimentation to the seafloor (NRC, 2003).
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 12

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

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

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

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

the water surface and in the water column by marine bacteria removes first the nͲalkanes and

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

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

the water surface.

Spill Response.See Section H of the Revised EP for a detailed description of Chevron’s

siteͲspecific response to the WCD for this plan.These sections, along with Chevron’s OSRP, also

include a description of surface and subsea containment capabilities that could be implemented

in the event of the WCD for this plan.

All the proposed activities and facilities in Chevron’s plan will be covered by the OSRP filed by

Chevron in accordance with 30 CFR 254 and approved April 15, 2010.Chevron submitted a

biannual update to the Regional OSRP on January 11, 2012.An updated OSRP was received by

the BSEE Oil Spill Response Planning Division on February 11, 2013, with a WCD certification

date of February 12, 2013, along with a letter certifying that Chevron continues to have the

capability to respond to the maximum extent practical to a worst case discharge from all

Chevron facilities located in the Gulf of Mexico.

A.9.4 Other Accidents Not Analyzed in Detail

The recent lease sale EIS (BOEM, 2012) analyzes four other types of accidents: loss of well

control, vessel collisions, chemical and drilling fluid spills, and pipeline failures.The Revised EP

does not include any pipelines; the other accident types are discussed briefly in this subsection

along with hydrogen sulfide (H2S) release, and there are no other siteͲspecific issues for this

Revised EP.The analysis in the lease sale EIS for these topics is incorporated by reference.

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

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

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

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

human injury (MMS, 2007b).Loss of well control may result in the release of synthetic drilling

fluid or loss of oil.Chevron has a robust system in place designed to prevent loss of well control.

On January 28, 2011, Chevron submitted additional information to the BOEM in response to

NTL 2010ͲN06, including descriptions of measures designed to prevent a blowout, reduce the

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

Chevron will also comply with NTL 2010ͲN10 and the Interim Final Drilling Safety Rule, which

specify additional safety measures for OCS activities.

Vessel Collisions.As summarized in BOEM (2012), vessel collisions occasionally occur during

routine operations.Most collisions involve service vessels colliding with platforms or vessel

collisions with pipeline risers.Some of these collisions have caused spills of diesel fuel or

chemicals.Chevron will implement all applicable USCG and BOEMͲmandated safety

requirements to reduce the potential for vessel collisions.

Chemical and Drilling Fluid Spills.Chemicals used in drilling operations are required to

overcome technical issues in the drilling process, improve the efficiency and safety of drilling,
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 13

and protect associated equipment.To perform these tasks, a variety of chemicals may be mixed

together to develop the siteͲspecific properties required in drilling a well.Examples of

chemicals used to achieve these properties include surfactants, bentonite clays, olefins,

inorganic salts, nut shells, glycols, polymers, barite, and calcium carbonate.Supplies are

renewed on a regular basis by transfer in containers from supply boats (Boehm et al., 2001).

Other than chemicals used in drilling fluids, examples of chemicals that may be found on or

transported to the rig include ethylene glycol (BOP control fluid, closed cooling loops for crane

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

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

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

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

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

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

chloride (Boehm et al., 2001).The risk of a chemical spill is very low, and most chemicals are

either nontoxic or used in small quantities (BOEM, 2012).No significant impacts are expected

from chemical spills.

H2S Release.The Regional Supervisor has classified the area as “H2S absent” with the Initial EP

approval and subsequent Revised EP approvals.It is not expected that H2S will be encountered

or handled while conducting the proposed activities.Therefore, no impacts from an H2S release

are expected.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 14

B.Potentially Affected Environment

The lease area is 156 miles (251 km) from the nearest shoreline (Louisiana) and 183 miles

(294 km) from the onshore support base at Leeville, Louisiana (Figure 1).

Figure 2 shows a bathymetric map of the lease area.Water depths at the wellsites range from

1,705 to 1,756 m (5,593 to 5,760 ft).The seafloor at the proposed wellsites is generally smooth

and stable, but slightly undulatory.The seafloor gradient at both surface locations is about 6q to

the west.Surficial sediments are expected to be normally consolidated clays and silts.Visual

observations of the seafloor from a remotely operated vehicle (ROV) during the archaeological

survey identified scattered epibiota such as occasional solitary corals, sea fans, sea urchins,

sponges, starfish, eels, and unidentified animals on feathery stalks (possibly crinoids)

(Geoscience Earth & Marine Services, Inc. [GEMS], 2013).No highͲdensity benthic communities

were seen in the ROV observations.The site clearance letters by Fugro GeoConsulting, Inc.

(Fugro) concluded that there are no seafloor features that could support highͲdensity

deepwater benthic communities within 610 m (2,000 ft) of the proposed wellsites.

A detailed description of the regional potentially affected environment, 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, is provided in recent EISs (MMS, 2007b; BOEM, 2012, 2013a).

These regional descriptions are based on extensive literature reviews and are incorporated by

reference.General information is presented in the following paragraph, and brief descriptions

of each potentially affected resource are presented in Section C, including siteͲspecific and/or

new information if available.

The Macondo spill has resulted in environmental impacts to portions of the Gulf of Mexico.The

lease area is located approximately 226 miles (365 km) from the Macondo spill site.Based on

an analysis of satellite imagery (Environmental Response Management Application [ERMA] Gulf

Response, 2012), the surface slick did not extend over the lease area.Existing surface water

quality in the lease area therefore was not affected.Subsurface plumes were reported at a

water depth of about 1,100 m (3,609 ft), extending at least 22 miles (35 km) from the wellsite

and persisting for more than a month (Camilli et al., 2010).While the behavior and impacts of

subsurface plumes are not well known, impacts on water quality in the lease area are unlikely

because of the distance from the Macondo spill site.This is confirmed by the water and

sediment monitoring data reported by the Operational Science Advisory Team (OSAT, 2010).

The OSAT data show that after August 2010, waters and sediments in the deepwater

Gulf of Mexico beyond 1.8 miles (3 km) from the Macondo wellsite were below USEPA acute

and chronic benchmarks for PAHs and were not hypoxic.These observations indicate that

baseline environmental conditions in the lease area are unlikely to have been significantly

altered by the spill.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 15

Figure 2. Bathymetric map of the wellsite locations in Walker Ridge Block 143.Water depths are in

feet.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 16

C.Impact Analysis

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

Impacts have been analyzed extensively in multiͲleaseͲsale EISs for the Western and Central

Gulf of Mexico Planning Areas (MMS, 2007b; BOEM, 2012, 2013a) as well as in the EA for

Gulf of Mexico deepwater operations and activities (MMS, 2000).The most recent

multiͲleaseͲsale EISs update environmental baseline information in light of the Macondo

(Deepwater Horizon) incident and address potential impacts of a catastrophic spill (BOEM, 2012,

2013a).SiteͲspecific issues are addressed in this section as appropriate.

C.1 Physical/Chemical Environment

C.1.1 Air Quality

There are no siteͲspecific air quality data for the project area.Because of the distance from

shoreͲbased pollution sources, offshore air quality is expected to be good.The attainment

status of Federal OCS waters is unclassified because there is no provision in the Clean Air Act for

classification of areas outside State waters (BOEM, 2012).

All Alabama, Florida, and Mississippi coastal counties adjacent to the Central and Western

Planning Areas are currently in attainment of the National Ambient Air Quality Standards

(NAAQS) for all criteria pollutants (USEPA, 2013).Two metropolitan areas in Texas are

nonattainment areas for 8Ͳh ozone (DallasͲFort Worth and HoustonͲBrazoria), and

El Paso County, Texas, is a nonattainment area for PMͲ10 (USEPA, 2013).

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

(BOEM, 2012).The Gulf of Mexico is located to the southwest of this center of circulation,

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

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

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

IPFs potentially affecting air quality are air emissions and two types of accidents: a small fuel

spill and a large oil spill (WCD).

Potential Impacts of Air Emissions

Air emissions are the only routine IPF that could affect air quality.Offshore air emissions will

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

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

primarily on dieselͲpowered generators, pumps, or motors and from lighter fuel motors.

Primary air emissions typically associated with OCS activities are suspended PM, SOx, NOx, VOCs,

and CO.

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

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

the lease sale EIS (BOEM, 2012), emissions 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 coast.The Air Quality Emissions Report prepared in accordance with
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 17

BOEM requirements shows that projected emissions are below exemption levels.Therefore, no

control measures are required, and no significant onshore impacts are expected.

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

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

quality area.The BOEM 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 miles

(300 km) of the Breton Class I area that exceed emission limits agreed upon by the administering

agencies (NPS, 2010).The lease area is approximately 226 miles (363 km) from the

Breton Wilderness Area.Chevron does not anticipate any impact on the Class I area.

Potential Impacts from a Small Fuel Spill

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

and discussed in recent EISs (MMS, 2007b; BOEM, 2012, 2013a).The potential of a small spill

would be reduced by implementation of Chevron’s preventative measures during routine

operations, including fuel transfer.In the unlikely event of a spill, implementation of Chevron’s

OSRP will mitigate and reduce the potential for impacts.Given the open ocean location of the

lease area, the extent and duration of air quality impacts from a small spill would not be

significant.

A small fuel spill could affect air quality near the spill site by introducing VOCs through

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

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

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

weather conditions.Assuming the evaporated volume is 100% VOCs and assuming a diesel fuel

density of 7.08 lb/gal., the estimated VOC emissions would be 803 lb.This small volume of VOC

emissions would have no impact on coastal air quality.

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

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

Potential Impacts of a Large Oil Spill (WCD)

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

analyzed and discussed in recent EISs (MMS, 2007b; BOEM, 2012, 2013a).

A large oil spill (WCD) could affect air quality by introducing VOCs through evaporation from the

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

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

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

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

CO, and PM, as well as greenhouse gases.

Because of the lease area location, which is 156 miles (251 km) from the nearest shoreline, any

air quality impacts would likely occur in offshore waters.Depending on the spill trajectory,

meteorological and oceanographic conditions, and the effectiveness of spill response measures,

coastal air quality could also be affected.Based on the 30Ͳday OSRA modeling predictions

(Table 3), the coastal area most likely to be affected would be Cameron Parish, Louisiana.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 18

Air quality monitoring following the Macondo spill provides an indication of the potential for air

quality impacts from a large spill.The USEPA and the affected states conducted extensive air

quality monitoring along the Gulf Coast.The air quality monitoring indicated that the levels of

ozone and particulates were at levels well below those that would cause shortͲterm health

problems and did not detect any pollutants at levels expected to cause longͲterm harm

(BOEM, 2012).

C.1.2 Water Quality

There are no siteͲspecific water quality data for the lease area.Because of the lease location in

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

Deepwater areas in the northern Gulf of Mexico are relatively homogeneous with respect to

temperature, salinity, and oxygen (BOEM, 2012).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

nearͲsurface sediments and up through the water column.

The lease area is located approximately 226 miles (365 km) from the Macondo spill site.Based

on satellite imagery (ERMA Gulf Response, 2012), the surface slick did not extend over the lease

area.Existing surface water quality in the lease area therefore was not affected.Subsurface

plumes were reported at a water depth of about 1,100 m (3,609 ft), extending at least 22 miles

(35 km) from the wellsite and persisting for more than a month (Camilli et al., 2010).While the

behavior and impacts of subsurface plumes are not well known, impacts on water quality in the

lease area are unlikely because of the distance from the Macondo spill site.This is confirmed by

the water and sediment monitoring data reported by the OSAT (2010).The OSAT data show

that after August 2010, waters and sediments in the deepwater Gulf of Mexico beyond 1.8 miles

(3 km) from the Macondo wellsite were below USEPA acute and chronic benchmarks for PAHs

and were not hypoxic.

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

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

Potential Impacts of Effluent Discharges

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

solids in the water column around the drilling rig.In general, turbid water can be expected to

extend between a few hundred meters and several kilometers down current from the discharge

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

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

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

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

quality in the lease area.

Treated sanitary and domestic wastes may have 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.All NPDES permit limitations and requirements will be implemented,

and little or no impact on water quality is anticipated.

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

and drains, including drip pans in work areas.Rainwater that falls on uncontaminated areas of
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 19

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 will be separated to meet NPDES permit

requirements.Little or no impact on water quality is anticipated.

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

BOP fluid, uncontaminated ballast water, excess cement, uncontaminated water from testing of

the firewater system, and nonͲcontact cooling water, are expected to be diluted rapidly and

have little or no potential for impact on water quality.

Support vessels will discharge treated sanitary and domestic wastes.These will have little or no

potential for impact on water quality in the immediate vicinity of the discharges.Support vessel

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

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

Potential Impacts of a Small Fuel Spill

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

analyzed and discussed in recent EISs (MMS, 2007b; BOEM, 2012, 2013a).The risk of a small

spill would be reduced by Chevron’s preventative measures during routine operations, including

fuel transfer.In the unlikely event of a spill, implementation of Chevron’s OSRP will mitigate

and reduce the potential for impacts.Given the open ocean location of the lease area, the

extent and duration of water quality impacts from a small spill would not be significant.

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

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

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

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

90% of a small diesel spill would be evaporated or dispersed within 24 hours (see Section A.9.2).

The potential area of the sea surface with diesel fuel on it is estimated to range from 0.5 to 5 ha

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

The waterͲsoluble fractions of diesel are dominated by twoͲand threeͲringed PAHs, which are

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

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

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

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

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

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

by naturally occurring microbes (NOAA, 2006).

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

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

Potential Impacts of a Large Oil Spill (WCD)

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

analyzed and discussed in recent EISs (MMS, 2007b; BOEM, 2012, 2013a).A large spill could

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 any
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 20

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

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

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

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

(Camilli et al., 2010; Hazen et al., 2010; Joint Analysis Group, 2010a,b,c).Small droplets in the

water may adhere to suspended sediment and be removed from the water column.

Because the lease area location is 156 miles (251 km) from the nearest shoreline, any water

quality impacts would likely occur in offshore waters.Depending on the spill trajectory and the

effectiveness of spill response measures, coastal water quality could be affected.Based on the

30Ͳday OSRA modeling predictions (Table 3), nearshore waters and embayments of Cameron

Parish, Louisiana are the coastal areas with the most potential for water quality to be affected.

C.2 Seafloor Habitats and Biota

Water depths at the proposed wellsites range from 1,705 to 1,756 m (5,593 to 5,760 ft).The

seafloor in the lease area is expected to consist mainly of soft bottom communities.Visual

observations of the seafloor from an ROV during the archaeological survey identified scattered

epibiota such as occasional solitary corals, sea fans, sea urchins, sponges, starfish, eels, and

unidentified animals on feathery stalks (possibly crinoids) (GEMS, 2013).No highͲdensity

benthic communities were seen in the ROV observations.Based on the site clearance letters by

Fugro as summarized in Section C of the Revised EP, there are no seafloor features that could

support highͲdensity deepwater benthic communities within 610 m (2,000 ft) of the proposed

drilling discharge locations.

C.2.1 Soft Bottom Benthic Communities

There are no siteͲspecific benthic community data from the lease area.However, data from the

recent Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology Study

(Wei, 2006; Rowe and Kennicutt, 2009) can be used to describe typical benthic communities in

the area.Table 4 summarizes data from nearby stations in similar water depths.Table 4

summarizes data from nearby stations.Sediments at these stations were predominantly clay

(55% to 59%) and silt (32% to 41%).

Table 4. Benthic community data from stations near the lease area sampled during the

Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology Study

(From: Wei, 2006; Rowe and Kennicutt, 2009).

Station Water Depth

(m)

Abundance

Meiofauna

(individuals/m2)

Macroinfauna

(individuals/m2)

Megafauna

(individuals/ha)

B1 2,255 157,417 1,446 252

NB3 1,875 165,245 1,342 191

NB5 2,063 117,263 706 1,600

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

Meiofaunal (animals passing through a 0.3Ͳmm sieve but retained on a 0.062Ͳmm sieve)

densities in water depths representative of the lease area typically range from about 150,000 to

500,000 individuals/m2 (Rowe and Kennicutt, 2009).Nematodes, nauplii, and harpacticoid

copepods were the three dominant meiofaunal groups, accounting for 90% of total abundance.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 21

The benthic macroinfauna (animals retained on a 0.3Ͳmm sieve) 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 at nearby stations ranged

from 706 to 1,446 individuals/m2 (Table 4).

Polychaetes are typically the most abundant macroinfaunal group on the northern Gulf of

Mexico continental slope, followed by amphipods, tanaids, bivalves, and isopods.Wei (2006)

recognized four depthͲdependent faunal zones (1 through 4), two of which are divided

horizontally.The lease area is in Zone 3W, which consists of stations on the mid TexasͲLouisiana

Slope ranging in depth from 1,875 to 3,008 m (6,152 to 9,869 ft).The most abundant species in

this zone were the polychaetes Levinsenia uncinata, Paraonella monilaris, and

Tachytrypane sp. A; the bivalve Heterodonta sp. B; and the isopod Macrostylis sp.

Megafaunal densities from nearby stations ranged from 191 to 1,600 individuals/ha (Table 4).

Common megafauna included motile groups such as decapods, ophiuroids, holothurians, and

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

Bacteria are the foundation of deepͲsea chemosynthetic communities (Ross et al., 2012) and are

an important component in terms of biomass and cycling of organic carbon (CruzͲKaegi, 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 (6 in.) of sediments (Rowe and Kennicutt, 2009).

IPFs potentially affecting benthic communities are effluent discharges (drilling muds and

cuttings) and a large oil spill (WCD) from a well blowout at the seafloor.Because a DP drillship

will be used, there will be no seafloor disturbances from the use of anchors.A small fuel spill

would not affect benthic communities because the diesel fuel would float and dissipate on the

sea surface.

Potential Impacts of Effluent Discharges

Drilling muds and cuttings are the only effluents with the potential to affect benthic

communities.During initial well interval(s) before the marine riser is set, cuttings and

seawaterͲbased “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 WBMs (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 deepͲsea biota

grow and reproduce slowly, recovery may require several years.

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, treated 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 in

bottom sediments, benthic infaunal communities may be adversely affected because of 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
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 22

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 preͲdrilling

conditions.Disturbed sediments will be recolonized through larval settlement and migration

from adjacent areas.

The areal extent of impacts from drilling discharges will be relatively small.The Revised EP

includes a total of two wells to be drilled in the lease area.Based on the monitoring studies

discussed above, benthic community impacts are expected to be concentrated within about

500 m (1,640 ft) of each wellsite.

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

(Gallaway, 1988; Gallaway et al., 2003; Rowe and Kennicutt, 2009).Drilling discharges during

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

basis.

Potential 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.BOEM (2012) estimates that a severe subsurface blowout could

resuspend and disperse sediments within a 300Ͳm (984Ͳft) 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).

Additional benthic community impacts could extend beyond the immediate vicinity of the

wellhead, depending on the specific circumstances (BOEM, 2012).During the Macondo spill,

subsurface plumes were reported at a water depth of about 1,100 m (3,609 ft), extending at

least 22 miles (35 km) from the wellsite and persisting for more than a month (Camilli et al.,

2010).The subsurface plumes apparently resulted from the use of dispersants at the wellhead

(Joint Analysis Group, 2010c).While the behavior and impacts of subsurface plumes are not

well known, a subsurface plume could contact the seafloor and affect benthic communities

beyond the 300Ͳm (984Ͳft) radius estimated by BOEM (2012), depending on its extent,

trajectory, and persistence.This contact could result in smothering and/or toxicity to benthic

organisms.Any affected area would be recolonized by benthic organisms over a period of

months to years (NRC, 2003).

C.2.2 HighͲDensity Deepwater Benthic Communities

As defined by NTL 2009ͲG40, highͲdensity deepwater benthic communities are features or areas

that could support highͲdensity chemosynthetic communities, or features or areas that could

support highͲdensity deepwater corals and other associated highͲdensity 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.Based on a list of sites compiled by the

BOEM (2013b) and maps presented by the U.S. Geological Survey (2011), the nearest known

chemosynthetic or deepwater coral community site is in WR 269, located approximately

19 miles (31 km) from the lease area.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 23

Based on the site clearance letters by Fugro as summarized in Section C of the Revised EP, there

are no seafloor features that could support highͲdensity deepwater benthic communities within

610 m (2,000 ft) of the proposed drilling discharge locations.

A large oil spill (WCD) from a well blowout at the seafloor is the only IPF potentially affecting

highͲdensity deepwater benthic communities.A small fuel spill would not affect benthic

communities because the diesel fuel would float and dissipate on the sea surface.Because a

DP drillship will be used, there will be no physical disturbance to the seafloor from anchoring

during the drilling activities analyzed in this EIA.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).

Although small amounts of cuttings particles may reach areas inhabited by highͲdensity

deepwater benthic communities, the discharges are not expected to result in significant impacts

to these communities.

Potential Impacts of a Large Oil Spill (WCD)

A large oil spill caused by a seafloor blowout could cause direct impacts on benthic communities

within about 300 m (984 ft) of the wellhead (i.e., caused by the physical impacts of a blowout)

(BOEM, 2012).However, based on the site clearance letters by Fugro as summarized in

Section C of the Revised EP, there are no seafloor features that could support highͲdensity

deepwater benthic communities within 610 m (2,000 ft) of the proposed drilling discharge

locations.Therefore, this type of impact is expected to be avoided.

Additional benthic community impacts could extend beyond the immediate vicinity of the

wellhead, depending on the specific circumstances (BOEM, 2012).During the Macondo spill,

subsurface plumes were reported at a water depth of about 1,100 m (3,609 ft), extending at

least 22 miles (35 km) from the wellsite and persisting for more than a month

(Camilli et al., 2010).The subsurface plumes apparently resulted from the use of dispersants at

the wellhead (Joint Analysis Group, 2010c).While the behavior and impacts of subsurface

plumes are not well known, a subsurface plume could have the potential to contact highͲdensity

deepwater benthic communities beyond the 300Ͳm (984Ͳft) radius estimated by BOEM (2012),

depending on its extent, trajectory, and persistence.Potential impacts on sensitive resources

would be an integral part of the decision and approval process for the use of dispersants.

Potential impacts of oil on highͲdensity deepwater benthic communities are discussed by

MMS (2007b) and BOEM (2012).Although chemosynthetic communities live among

hydrocarbon seeps, natural seepage typically is constant and occurs at low rates as compared to

the potential rates of oil release from a blowout.In addition, seep organisms also require

unrestricted access to oxygenated water at the same time as exposure to hydrocarbon energy

sources (MacDonald, 2002).Oil droplets or oiled sediment particles could come into contact

with chemosynthetic organisms or deepwater corals.As discussed by MMS (2007b), impacts

could include loss of habitat, biodiversity, and live coral coverage; destruction of hard substrate;

change in sediment characteristics; and reduction or loss of one or more commercial and

recreational 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).
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 24

The potential for a spill to affect deepwater corals was observed during an October 2010 survey

of deepwater coral habitats near the Macondo spill site (BOEMRE, 2010; Fisher, 2010, 2011).

Scientists observed dead and dying corals with sloughing tissue and discoloration 7 miles

(11 km) from the Macondo wellhead at a depth of 1,400 m (4,600 ft).Much of the soft coral

observed in an area measuring about 15 by 40 m (50 by 130 ft) was covered by what appeared

to be a brown flocculent material with signs of widespread stress, including varying degrees of

tissue loss and excess mucous production (White et al., 2012a).Researchers concluded, based

on analysis of the flocculent material, that it contained oil from the Macondo spill (White et al.,

2012a,b).The injured and dead corals were in an area where a subsea plume of oil had been

documented during the spill in June 2010.The deepwater coral at this location showed signs of

tissue damage that was not observed elsewhere during those surveys or in previous deepwater

coral studies in the Gulf of Mexico.The research team concluded that the observed coral

injuries likely resulted from exposure to the subsurface oil plume (White et al., 2012a,b).

C.2.3 Designated Topographic Features

The block is not within or near a designated topographic feature or a noͲactivity zone as

identified in NTL 2009ͲG39.The nearest topographic feature is Jakkula Bank, located

approximately 76 miles (122 km) from the lease area.

There are no IPFs associated with either routine operations or accidents that could affect

designated topographic features because of the distance from the lease area.A small fuel spill

would float and dissipate on the surface and would not reach these seafloor features.

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

features.If a subsurface plume were to occur, impacts on these features would be unlikely

because of the distance of the spill from these features, the depth of the features, and the

currents that surround the features.NearͲbottom 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.According to the analysis by BOEM (2012), although there are

mechanisms that could result in oil contacting these features, it is expected that most of the oil

would rise to the surface and that the most heavily oiled sediments would likely be deposited

before reaching these features.Any contact with spilled oil would likely cause sublethal effects

to benthic organisms because the distance from the spill source would prevent contact with

concentrated oil (BOEM, 2012).

C.2.4 Pinnacle Trend Area Live Bottoms

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

pinnacle trend blocks, as defined by NTL 2009ͲG39, are about 245 miles (394 km) from the lease

area, along the shelf edge south of Alabama.

There are no IPFs associated with either routine operations or accidents that could affect

pinnacle trend area live bottoms because of the distance from the lease area.A small fuel spill

would float on the surface and would not reach these seafloor features.

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

features.If a subsurface plume were to occur, impacts on these features would be unlikely

because of the distance from the lease area and the difference in water depth.NearͲbottom

currents in the region are predicted to flow along the isobaths (Nowlin et al., 2001) and typically
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 25

would not carry a plume up onto the continental shelf edge.According to the analysis in the

most recent multiͲlease sale EISs, although there are mechanisms that could result in oil

contacting these features, it is expected that most of the oil would rise to the surface and that

the most heavily oiled sediments would likely be deposited before reaching these features

(BOEM, 2012).

C.2.5 Eastern Gulf Live Bottoms

The lease area is not covered by the Live Bottom (LowͲRelief) Stipulation, which applies mainly

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

nearest blocks covered by the live bottom stipulation, as defined by NTL 2009ͲG39, are about

284 miles (458 km) from the project area.

There are no IPFs associated with either routine operations or accidents that could affect

eastern Gulf live bottom areas because of the distance from the lease area.A small fuel spill

would float and dissipate on the surface and would not reach these seafloor features.

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

features.If a subsea plume were to occur, impacts on these features would be unlikely because

of the distance from the lease area and the difference in water depth.NearͲbottom 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.According to the analysis by BOEM (2012),

although there are mechanisms that could result in oil contacting these features, it is expected

that most of the oil would rise to the surface and that the most heavily oiled sediments would

likely be deposited before reaching these features.

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 5.The table also indicates the location of critical habitat (if

designated in the Gulf of Mexico).Critical habitat is defined as (1) specific areas within the

geographical area occupied by the species at the time of listing that contain physical or

biological features essential to conservation and 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 ESAͲlisted cetaceans, sea turtles,

and fishes in the Gulf of Mexico.The USFWS has jurisdiction for ESAͲlisted birds and the Florida

manatee.

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

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

species in the Gulf of Mexico.However, critical habitat has been proposed for the loggerhead

turtle as discussed in Section C.3.5.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 26

Table 5. Federally listed endangered and threatened species potentially present in the lease

area and along the northern Gulf Coast.

Species Scientific Name Status

Potential Presence Critical Habitat Designated

in Gulf of Mexico Lease

Area Coastal

Marine Mammals

Sperm whale Physeter macrocephalus E X ͲͲ None

Florida manatee Trichechus manatus latirostris E ͲͲ X Florida (Peninsular)

Blue whale Balaenoptera musculus E Xa ͲͲ None

Fin whale Balaenoptera physalus E Xa ͲͲ None

Humpback whale Megaptera novaeangliae E Xa ͲͲ None

NorthAtlanticrightwhale Eubalaena glacialis E Xa ͲͲ None

Sei whale Balaenoptera borealis E Xa ͲͲ None

Sea Turtles

Loggerhead turtle Caretta caretta T

b X X Proposedb

Green turtle Chelonia mydas T, E

c X X None

Leatherback turtle Dermochelys coriacea E X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Birds

Piping Plover Charadrius melodus T ͲͲ X

Coastal Texas, Louisiana,

Mississippi, Alabama, and

Florida (Panhandle)

Whooping Crane Grus americana E ͲͲ X Coastal Texas (Aransas

National Wildlife Refuge)

Fishes

Gulf sturgeon Acipenser oxyrinchus desotoi T ͲͲ X

Coastal Louisiana,

Mississippi, Alabama, and

Florida (Panhandle)

Terrestrial Mammals

Beachmice(Alabama,

Choctawhatchee,

PerdidoKey,St.Andrew)

Peromyscus polionotus E ͲͲ 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

In September 2011, NMFS and USFWS listed nine distinct population segments (DPS) of loggerhead turtles under

the Endangered Species Act.The Northwest Atlantic Ocean DPS was designated as threatened (76 FR 58868).The

NMFS and USFWS have proposed to designate critical habitat for this DPS, including beaches in Jackson County,

Mississippi; Baldwin County, Alabama; and Bay, Gulf, and Franklin Counties in the Florida panhandle, as well as

several counties in southwest Florida and the Florida Keys (78 FR 18000). c

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

Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic right

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

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

species in the Gulf of Mexico.

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

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

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

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

longer federally listed as endangered or threatened; these are discussed in Section C.4.2.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 27

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.

In 2007, the MMS conducted ESA consultation with NMFS and USFWS in conjunction with the

EIS for the FiveͲYear Leasing Plan for the Western and Central Planning Areas (MMS, 2007b).

The ESA consultation led to Biological Opinions by NMFS and USFWS.Following the Macondo

spill, on July 30, 2010, BOEM requested to reinitiate ESA consultation with NMFS and USFWS.

According to BOEM (2012), NMFS and USFWS have placed the consultation process on hold

because they believe the environmental baseline information needs to be updated for the

postͲMacondo spill environment based on the results of the Natural Resource Damage

Assessment (NRDA) process, which is still ongoing.Meanwhile, the existing consultation

remains in effect (BOEM, 2012).The existing consultation recognizes that mitigation measures

required by BOEM and BSEE should reduce the likelihood of impacts from all BOEMͲauthorized

activities in the Gulf of Mexico.These measures are taken into account in the impact analysis in

the following subsections.

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 recovery plan for this species

(NMFS, 2010a).Gulf of Mexico sperm whales are classified as an endangered species and a

“strategic stock” (defined as a stock that may have unsustainable humanͲcaused impacts) by

NOAA Fisheries (Waring et al., 2013).According to the recovery plan, the main threats to sperm

whale populations include collisions with vessels, direct harvest, loss of prey base because of

climate change, disturbance from anthropogenic noise, and possibly competition for resources

(NMFS, 2010a).

In March 2013, the NMFS began a status review to consider designating the Gulf of Mexico

population of the sperm whale as a Distinct Population Segment (DPS) under the ESA

(78 FR 19176).The designation would list the DPS as a separate endangered or threatened

population that is “significant to the species and faces additional unique threats to its survival.”

As part of the status review, the NMFS is also considering whether to designate sperm whale

critical habitat in the Gulf of Mexico (currently none has been designated).

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 northͲcentral Gulf of Mexico are present there throughout the

year (Davis et al., 2000).Results of a multiͲyear tracking study show female sperm whales

typically concentrated along the upper continental slope between the 200Ͳand 1,000Ͳm

(656Ͳand 3,280Ͳft) 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

MMSͲfunded Sperm Whale Seismic Study consisted of mixedͲsex groups comprising adult

females and immatures, and groups of bachelor males.The typical group size for mixed groups

was 10 individuals (Jochens et al., 2008).Study results showed that sperm whales transit

through the vicinity of the lease area.Movements of satelliteͲtracked 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).
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 28

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

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

(WCD).Effluent discharges are likely to have negligible impacts on sperm whales because of

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

the mobility of these marine mammals.Implementation of NTL 2012ͲBSEEͲG01 mitigation

measures will reduce the potential for marine debrisͲrelated impacts on sperm whales.

Potential 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 lowͲfrequency 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.Because of the limited scope and short duration of drilling activities,

this project would represent a small temporary contribution to the overall noise regime.

NMFS (2007) analyzed the potential for impacts of drillingͲrelated noise on sperm whales in its

Biological Opinion for the FiveͲYear Oil and Gas Leasing Program in the Central and Western

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

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

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

(NMFS, 2007).

Drilling rig lighting and rig presence are not identified as IPFs for sperm whales in recent lease

sale EISs (MMS, 2007b; BOEM, 2012, 2013a) or the NMFS (2007) Biological Opinion.

Potential 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 an “unknown but potentially low” threat in the recovery plan for

this species (NMFS, 2010a).Data concerning the frequency of vessel strikes are presented in the

lease sale EIS (BOEM, 2012).To reduce the potential for vessel strikes, BOEM and BSEE have

issued NTL 2012ͲJOINTͲG01, which recommends protected species identification training for

vessel operators and crews; recommends that they 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.When safety permits, 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.Implementation of this NTL’s mitigation

measures will reduce the potential of vessel strikes as well as reduce the chance for disturbing

sperm whales.

NMFS (2007) analyzed the potential for vessel strikes and harassment of sperm whales in its

Biological Opinion for the FiveͲYear Oil and Gas Leasing Program in the Central and Western

Planning Areas of the Gulf of Mexico.With implementation of the mitigation measures in

NTL 2012ͲJOINTͲG01, NMFS concluded that the likelihood of collisions between vessels and

sperm whales would be reduced to insignificant levels.NMFS concluded that the observed

avoidance of passing vessels by sperm whales is an advantageous response to avoid a potential
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 29

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, 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 fixedͲwing aircraft flying at an

altitude of 245 m (804 ft).A reaction to the initial pass of the aircraft was observed during

3 (12%) of 24 sightings.All three reactions consisted of a hasty dive and occurred at 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 shortͲterm and probably of no longͲterm 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 (BOEM, 2012).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, NMFS (2007) concluded that this altitude

would minimize the potential for disturbing sperm whales.Therefore, no significant impacts are

expected.

Potential Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals including sperm whales are discussed in recent EISs

(MMS, 2007b; BOEM, 2012, 2013a) and by NMFS (2007) in its Biological Opinion for the

FiveͲYear Oil and Gas Leasing Program in the Central and Western Planning Areas of the Gulf of

Mexico.Oil impacts on marine mammals are discussed by Geraci and St. Aubin (1990).For the

Revised EP, there are no unique siteͲspecific issues with respect to spill impacts on these

animals.

The probability of a fuel spill will be reduced by implementation of Chevron’s preventative

measures during routine operations, including fuel transfer.In the unlikely event of a spill,

implementation of Chevron’s OSRP will mitigate and reduce 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 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 any 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

estimated fate of a small fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.The estimated 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 oiled prey; and stress from the activities and noise of

response vessels and aircraft (Marine Mammal Commission [MMC], 2012).However, because
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 30

of the limited areal extent and short duration of water quality impacts from a small fuel spill as

well as the mobility of sperm whales, no significant impacts would be expected.

Potential Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine mammals including sperm whales are discussed in recent EISs

(MMS, 2007b; BOEM, 2012, 2013a) and by NMFS (2007) in its Biological Opinion for the

FiveͲYear Oil and Gas Leasing Program in the Central and Western Planning Areas of the Gulf of

Mexico.Oil impacts on marine mammals are discussed by Geraci and St. Aubin (1990).For the

Revised EP, there are no unique siteͲspecific issues with respect to spill impacts on these

animals.

Potential impacts of oil spills on sperm whales can include direct impacts from oil exposure, as

well as indirect impacts caused by response activities and materials (e.g., vessel traffic, noise,

and dispersants) (MMC, 2012).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 oiled 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, 2012).Ackleh et al. (2012) hypothesized that sperm whales may have

temporarily relocated away from areas near the Macondo spill in 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 include vessel strikes, entanglement, or other injury

or stress.Response vessels would operate in accordance with NTL 2012ͲJOINTͲG01 to reduce

the potential for striking or disturbing these animals.

C.3.2 Florida Manatee (Endangered)

Most of the manatee population is located in peninsular Florida (USFWS, 2001).Manatee

sightings in Louisiana have been increasing as manatees extend their presence farther west of

Florida in the warmer months (Wilson, 2003).A species description is presented in lease sale

EISs (MMS, 2007b; BOEM, 2012, 2013a) and in the recovery plan for this species (USFWS, 2001).

IPFs potentially affecting manatees include support vessel and helicopter traffic and a large oil

spill (WCD).A small fuel spill in the lease area would be unlikely to affect manatees, as the lease

area is approximately 156 miles (251 km) from the nearest shoreline (Texas).As explained in

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

prior to breaking up.Compliance with NTL 2012ͲBSEEͲG01 will minimize the potential for

marine debrisͲrelated impacts on manatees.

Potential 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, BOEM and BSEE have issued NTL 2012ͲJOINTͲG01,

which recommends protected species identification training for vessel operators and crews;

recommends that they maintain a vigilant watch for marine mammals and slow down or stop
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 31

their vessel to avoid striking protected species; and requires operators to report sightings of any

injured or dead protected species.Implementation of this NTL’s mitigation measures will

reduce the potential for 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 fixedͲwing 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

(BOEM, 2012).This mitigation measure will minimize the potential for disturbing manatees, and

no significant impacts are expected.

Potential Impacts of a Large Oil Spill (WCD)

The OSRA results summarized in Table 3 predict that some Texas and Louisiana shorelines could

be contacted by a spill within 30 days.There is no critical habitat designated in these areas, and

the number of manatees potentially present is a small fraction of the population in peninsular

Florida.

In the event that manatees were exposed to oil, effects could include direct impacts from oil

exposure, as well as indirect impacts caused by response activities and materials (e.g., vessel

traffic, noise, and dispersants) (MMC, 2012).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 oiled prey

(or 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, 2012).

In the event that a large spill reached coastal waters where manatees were present, the level of

vessel and aircraft activity associated with spill response could disturb manatees and potentially

include vessel strikes, entanglement, or other injury or stress.Response vessels would operate

in accordance with NTL 2012ͲJOINTͲG01 to reduce the potential for striking or disturbing these

animals, and therefore no significant impacts are expected.

C.3.3 Endangered Mysticete Whales

Five endangered mysticete whales (blue whale, fin whale, humpback whale, North Atlantic right

whale, and sei whale) have also 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.

Because of 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.NMFS (2007) did not

include any of these mysticete whales as affected species in its Biological Opinion for the
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 32

FiveͲYear Oil and Gas Leasing Program in the Central and Western Planning Areas of the

Gulf of Mexico.Potential impacts are analyzed in recent lease sale EISs (MMS, 2007b;

BOEM, 2012, 2013a), 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 in

Section C.3.4.

C.3.4 NonͲEndangered Marine Mammals (Protected)

All marine mammals are protected species under the MMPA.Excluding the 7 endangered

species that have been cited previously, there are 22 additional species of marine mammals that

may be found in the Gulf of Mexico.This includes 2 species of mysticete whales, the dwarf and

pygmy sperm whales, 4 species of beaked whales, and 14 species of delphinids.The most

common nonͲendangered cetaceans in the deepwater environment are odontocetes such as the

pantropical spotted dolphin, spinner dolphin, and Clymene dolphin.A brief summary is

presented in this subsection, and additional information on these groups is presented in recent

lease sale EISs (MMS, 2007b; BOEM, 2012, 2013a).

Mysticete whales.Two species of nonͲendangered mysticete whales are known from the

Gulf of Mexico.The Bryde’s whale (Balaenoptera edeni) has been sighted most frequently along

the 100Ͳm (328Ͳft) 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 westͲcentral 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.

Beaked whales.Four species of beaked whales are known from the Gulf of Mexico: 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.Because of the difficulties of atͲsea identification, beaked whales

in the Gulf of Mexico are identified as either Cuvier’s beaked whales or 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:

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), melonͲheaded whale (Peponocephala electra),

pantropical spotted dolphin (Stenella attenuata), pygmy killer whale (Feresa attenuata),

shortͲfinned pilot whale (Globicephala macrorhynchus), Risso’s dolphin (Grampus griseus),
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 33

roughͲtoothed dolphin (Steno bredanensis), spinner dolphin (Stenella longirostris), and

striped dolphin (Stenella coeruleoalba).The most common nonͲendangered cetaceans in the

deepwater environment are the pantropical spotted dolphin, spinner dolphin, and

Clymene dolphin.However, any of these species could occur in the lease area.

Bottlenose dolphin populations in the northern Gulf of Mexico are separated into

37 geographically distinct population units, or stocks, for management purposes by NMFS

(Waring et al., 2013).The 2012 stock assessment classifies the Gulf of Mexico Northern Coastal

Stock, Western Coastal Stock, and all 32 of the Bay, Sound, and Estuarine Stocks as strategic

stocks, based primarily on the occurrence of an “unusual mortality event” of unprecedented size

and duration (which began in February 2010 and is ongoing) that has affected these stock areas

(NMFS, 2013).Carmichael et al. (2012) hypothesized that the unusual number of bottlenose

dolphin strandings in the northern Gulf of Mexico during this time may have been associated

with environmental perturbations, including sustained cold weather and the Macondo spill in

2010, as well as large volumes of cold freshwater discharge in the early months of 2011.

IPFs potentially affecting nonͲendangered marine mammals include drilling rig presence, noise,

and lights; support vessel and helicopter traffic; and two types of accidents (a small fuel spill and

a large oil spill represented by the WCD for the Revised EP).Any impact on marine mammals is

expected to be negligible because of rapid dispersion, the small area of ocean affected, the

intermittent nature of the discharges, and the mobility of marine mammals.Implementation of

NTL 2012ͲBSEEͲG01 mitigation measures will reduce the potential for marine debrisͲrelated

impacts on marine mammals.

Potential 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.Because of the limited scope and short duration of

drilling activities, this project would represent a small temporary contribution to the overall

noise regime, and any shortͲterm impacts are not expected to be biologically significant to

marine mammal populations.

Drilling rig lighting and rig presence are not identified as IPFs for marine mammals in recent

lease sale EISs (MMS, 2007b; BOEM, 2012, 2013a).

Potential 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 are presented in the lease sale EIS

(BOEM, 2012).To reduce the potential for vessel strikes, BOEM and BSEE have issued

NTL 2012ͲJOINTͲG01, which recommends protected species identification training for vessel

operators and crews; recommends that they 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
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 34

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.

Implementation of this NTL’s mitigation measures will reduce the potential 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 (BOEM, 2012).This altitude will minimize the potential for disturbing

marine mammals, and no significant impacts are expected.

Potential Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b;

BOEM, 2012, 2013a), and oil impacts on marine mammals in general are discussed by Geraci

and St. Aubin (1990).For this Revised EP, there are no unique siteͲspecific issues with respect to

spill impacts on these animals.

The probability of a fuel spill will be reduced by implementation of Chevron’s preventative

measures during fuel transfer.In the unlikely event of a spill, implementation of Chevron’s

OSRP is expected to mitigate and reduce the potential for impacts on marine mammals.Given

the open ocean location of the lease area, the duration of a small spill and opportunity for

impacts to occur would be very brief.

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

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

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

the time and the effectiveness of spill response measures.Section A.9.2 discusses the likely fate

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally

within 24 hours.The estimated 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 oiled prey; and stress from the activities and noise of

response vessels and aircraft (MMC, 2012).However, because of the limited areal extent and

short duration of water quality impacts from a small fuel spill, as well as the mobility of

marine mammals, no significant impacts would be expected.

Potential Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b;

BOEM, 2012, 2013a) and by Geraci and St. Aubin (1990).For this Revised EP, there are no

unique siteͲspecific issues.

Potential impacts of oil spills on marine mammals can include direct impacts from oil exposure,

as well as indirect impacts caused by response activities and materials (e.g., vessel traffic, noise,

and dispersants) (MMC, 2012).Direct physical and physiological effects can include skin
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 35

irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes;

inhalation of toxic fumes; ingestion of oil (and dispersants) directly or via oiled prey (or

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, 2012).

In the event of a large spill, the level of vessel and aircraft activity associated with spill response

could disturb marine mammals and potentially include vessel strikes, entanglement, or other

injury or stress.Response vessels would operate in accordance with NTL 2012ͲJOINTͲG01 to

reduce the potential for striking or disturbing these animals, and therefore no significant

impacts are expected.

Data from the Macondo spill indicate that numerous marine mammals could be affected by a

large spill.According to NMFS (2011a), through April 2011, 157 dead marine mammals were

reported, most of which were bottlenose dolphins.Other affected species included

dwarf/pygmy sperm whale, melonͲheaded whales, and spinner dolphins.Because of known low

detection rates of carcasses, it is possible that the number of marine mammal deaths is

significantly underestimated (Williams et al., 2011).Also, necropsies to confirm the cause of

death could not be conducted for many of these marine mammals, and it is possible that some

were not related to the Macondo spill.

C.3.5 Sea Turtles (Endangered/Threatened)

Five species of endangered or threatened sea turtles may be found near the lease area.The

leatherback (Dermochelys coriacea), Kemp's ridley (Lepidochelys kempii), and hawksbill

(Eretmochelys imbricata) turtles are endangered species.The loggerhead turtle

(Caretta caretta) is a threatened species.The green turtle (Chelonia mydas) is listed as

threatened, except for the Florida breeding population, which is listed as endangered.Species

descriptions are presented in recent lease sale EISs (MMS, 2007b; BOEM, 2012, 2013a).

In September 2011, NMFS and USFWS listed nine DPS for loggerhead turtles under the ESA.The

Northwest Atlantic Ocean DPS was designated as threatened (76 FR 58868).In March 2013, the

NMFS and USFWS proposed to designate critical habitat for this DPS including beaches in

Jackson County, Mississippi; Baldwin County, Alabama; and Bay, Gulf, and Franklin Counties in

the Florida panhandle, as well as several counties in southwest Florida and the Florida Keys

(78 FR 18000).

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:

x Loggerhead turtles – Loggerhead turtles nest in significant numbers along the Florida

Panhandle (Florida Fish and Wildlife Conservation Commission, 2013a) and, to a lesser
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 36

extent, from Texas through Alabama (NMFS and USFWS, 2008).The nearest significant

nesting area of loggerhead turtles is found in Louisiana, on beaches within the Breton NWR;

x Green and leatherback turtles – Green and leatherback turtles infrequently nest on

Florida Panhandle beaches (Florida Fish and Wildlife Conservation Commission, 2013b,c);

x Hawksbill turtles – Hawksbill turtles typically do not nest anywhere near the project area

(USFWS, 2011a); and

x 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 nesting in

Alabama (Share the Beach, 2012).

IPFs potentially affecting sea turtles include drilling rig presence, noise, and lights; support

vessel and helicopter traffic; and two types of accidents (a small fuel spill and a large oil spill

represented by the WCD for this Revised EP).Any impacts on sea turtles from effluent

discharges are expected to be negligible because of rapid dispersion, the small area of ocean

affected, and the intermittent nature of the discharges.Implementation of NTL 2012ͲBSEEͲG01

mitigation measures will reduce the potential for marine debrisͲrelated impacts on sea turtles.

Potential 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 because of

machinery noise and/or visual disturbances.Any impacts would likely be shortͲterm behavioral

changes, such as diving and evasive swimming, disruption of activities, or departure from the

area.Because of the limited scope and short duration of drilling activities, these shortͲterm

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).NMFS (2007) concluded that the effects of lighting from offshore structures

on sea turtles are insignificant.

Potential Impacts of 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, BOEM and BSEE have issued NTL 2012ͲJOINTͲG01, which recommends protected

species identification training for vessel operators and crews; recommends that they 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.Implementation of this NTL’s mitigation
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 37

measures will reduce the potential for vessel strikes as well as reduce the chance for disturbing

sea turtles (NMFS, 2007).

Helicopter traffic also has the potential to disturb sea turtles.However, while flying offshore,

helicopters maintain altitudes above 213 m (700 ft) during transit to and from the working area

(BOEM, 2012).This altitude will reduce the potential for disturbing sea turtles, and no

significant impacts are expected.

Potential Impacts of a Small Fuel Spill

Potential spill impacts on sea turtles are discussed in recent EISs (MMS, 2007b; BOEM, 2012,

2013a) and by NMFS (2007) in its Biological Opinion for the FiveͲYear Oil and Gas Leasing

Program in the Central and Western Planning Areas of the Gulf of Mexico.For the Revised EP,

there are no unique siteͲspecific issues with respect to spill impacts on these animals.

The probability of a fuel spill will be reduced by implementation of Chevron’s preventative

measures during fuel transfer.In the unlikely event of a spill, implementation of Chevron’s

OSRP is expected to mitigate and reduce the potential for impacts on sea turtles.Given the

open ocean location of the lease area, the duration of a small spill and opportunity for impacts

to occur would be very brief.

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

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

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

the time and the effectiveness of spill response measures.Section A.9.2 discusses the

estimated fate of a small fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.The estimated 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 oiled prey; and stress from the activities and noise of

response vessels and aircraft (MMC, 2012).However, because of the limited areal extent and

short duration of water quality impacts from a small fuel spill, no significant impacts would be

expected.

A small fuel spill in the lease area would be unlikely to affect sea turtle nesting beaches, as the

lease area is 156 miles (251 km) from the nearest shoreline (Louisiana).As explained in

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

prior to breaking up.

Potential 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 caused by 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 affected

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,
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 38

declining physical condition, and death.Behavioral responses can include displacement of

animals from prime habitat, disruption of social structure, changing food availability and

foraging distribution and/or patterns, changing reproductive behavior/productivity, and

changing movement patterns or migration (MMC, 2012).In the unlikely event of a spill,

implementation of Chevron’s OSRP is expected to mitigate and reduce the potential for these

types of impacts on sea turtles.Section H of the Revised EP provides detail on spill response.

Studies of oil effects on loggerheads in a controlled setting (Lutcavage et al., 1995) suggest that

sea turtles show no avoidance behavior when they encounter an oil slick, and any sea turtle in

an affected area would be expected to be exposed.Sea turtles’ diving behaviors also put them

at risk.Sea turtles rapidly inhale a large volume of air before diving and continually resurface

over time, which may result in repeated exposure to volatile vapors and oiling (NMFS, 2007).

The OSRA results summarized in Table 3 estimate that Texas and Louisiana shorelines that

support limited sea turtle nesting could be contacted within 30 days.The highest contact

probability for any shoreline segment after 30 days is 3% for Cameron Parish, Louisiana.The

modeling estimates no contacts within 30 days with Alabama and Florida Panhandle shorelines

that support significant loggerhead sea turtle nesting.The 120Ͳday OSRA predicts a maximum

contact probability of 1% for these areas (BOEM, 2012).

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 bodily functions (NMFS, 2007).

In the event of a large spill, 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 2012ͲJOINTͲG01 to reduce the

risk of 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).Species descriptions are presented in

recent lease sale EISs (MMS, 2007b; BOEM, 2012, 2013a).

A large oil spill (WCD) is the only IPF potentially affecting Piping Plovers.There are no IPFs

associated with routine project activities that could affect these birds.A small fuel spill in the

lease area would be unlikely to affect Piping Plovers because a small fuel spill would not be

expected to make landfall or reach coastal waters prior to breaking up (see explanation in

Section A.9.2).
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 39

Figure 3. Location of selected environmental features in relation to the lease area. Shown are Essential Fish Habitat (EFH) for coral and coral

reefs; Habitat Areas of Particular Concern (HAPCs) for northwestern Gulf of Mexico reefs and banks and spawning Atlantic bluefin

tuna; and critical habitat for beach mice, Gulf sturgeon, Piping Plover, and Whooping Crane.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 40

Potential Impacts of a Large Oil Spill (WCD)

The lease area is 156 miles (251 km) from the nearest shorelines inhabited by Piping Plovers.

The OSRA results summarized in Table 3 estimate that Texas and Louisiana shorelines

designated as critical habitat for the wintering Piping Plover could be contacted by a spill within

30 days.The highest probability of shoreline contact after 30 days is 3% for Cameron Parish,

Louisiana.

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 these birds are most common along the

coastal Gulf or if spills contacted their critical habitat.Impacts could also occur from vehicular

traffic on beaches and other activities associated with spill cleanup.Chevron has extensive

resources available designed 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.Two distinct migratory populations summer in northwestern Canada and central

Wisconsin and winter along the Gulf Coast of Texas and the southeastern United States,

respectively (International Crane Foundation, 2012).One of these populations 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 freeͲranging Whooping Cranes

and reached a record population of 278 at Aransas NWR in December 2011 (Whooping Crane

Eastern Partnership, 2012).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).

Species descriptions are presented in recent lease sale EISs (MMS, 2007b; BOEM, 2012, 2013a).

A large oil spill (WCD) is the only IPF potentially affecting Whooping Cranes.A small fuel spill in

the lease area would also be unlikely to affect Whooping Cranes, because of the distance from

Aransas NWR.As explained in Section A.9.2, a small fuel spill would not be expected to make

landfall or reach coastal waters prior to breaking up.

Potential Impacts of a Large Oil Spill (WCD)

A large oil spill is unlikely to affect Whooping Cranes as the lease area is approximately

327 miles (526 km) from its critical habitat (Aransas NWR).The OSRA modeling predicts no

contacts with shorelines of the Aransas NWR (Calhoun County, Texas) within 30 days.

Additional OSRA modeling by BOEM (2012) predicts contact probabilities for Calhoun County

ranging seasonally from <1% to 6% after 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 oiled shellfish, frogs,

and fishes.It is possible that some death of Whooping Cranes could occur.Chevron has
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 41

extensive resources available designed to protect and rehabilitate wildlife in the event of a spill

reaching the shoreline, as detailed in the OSRP.

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).Populations have been depleted or even extirpated

throughout the species’ historical 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 bestͲknown

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).Species descriptions are presented in recent lease sale EISs (MMS, 2007b;

BOEM, 2012, 2013a) 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 fuel spill in the

lease area would be unlikely to affect Gulf sturgeon, because a small fuel spill would not be

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

Potential Impacts of a Large Oil Spill (WCD)

Potential spill impacts on Gulf sturgeon are discussed in recent EISs (MMS, 2007b; BOEM, 2012,

2013a) and by NMFS (2007) in its Biological Opinion for the FiveͲYear Oil and Gas Leasing

Program in the Central and Western Planning Areas of the Gulf of Mexico.For the Revised EP,

there are no unique siteͲspecific issues with respect to this species.

The lease area is about 233 miles (375 km) from the nearest Gulf sturgeon critical habitat.The

OSRA modeling (Table 3) estimates no contacts with coastal areas inhabited by Gulf sturgeon

within 30 days.Based on additional OSRA modeling by BOEM (2012), contact probabilities after

120 days would be 1%.

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 Beach Mice (Endangered)

Four subspecies of endangered beach mouse (Peromyscus polionotus) occur on the barrier

islands of Alabama and the Florida Panhandle: the Alabama, Choctawhatchee, Perdido Key, and

St. Andrew beach mice.Critical habitat has been designated for all four subspecies and is shown
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 42

combined for all four subspecies in Figure 3.Species descriptions are provided in recent lease

sale EISs (MMS, 2007b; BOEM, 2012, 2013a).

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 because of the distance

from shore and the lack of any onshore support activities near their habitat.A small fuel spill in

the lease area would not affect beach mice because a small fuel spill would not be expected to

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

Potential Impacts of a Large Oil Spill (WCD)

Potential spill impacts on beach mice are discussed in recent EISs (MMS, 2007b; BOEM, 2012,

2013a).For the Revised EP, there are no unique siteͲspecific issues with respect to these

species.

The lease area is about 312 miles (502 km) from the nearest beach mouse critical habitat.The

OSRA modeling predicts no contacts with Alabama and Florida shorelines inhabited by beach

mice within 30 days.Based on additional OSRA modeling by BOEM (2012), contact probabilities

after 120 days would be 1%.

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

oiled 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.

C.4 Coastal and Marine Birds

C.4.1 Marine and Pelagic Birds

A variety of seabirds may occur in the pelagic environment of the project area (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 because of 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, stormͲpetrels, 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).
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 43

Common seabird species include Wilson’s StormͲPetrel (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’s Shearwater (Puffinus lherminieri).Seabirds

are distributed GulfͲwide and are not specifically associated with the lease area.

Relationships with hydrographic features were found for several seabird species, possibly

caused by 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

.

TransͲGulf migrant birds including shorebirds, wading birds, and terrestrial birds may also be

present in the lease area.Migrant birds may use offshore structures and platforms for resting,

feeding, or as temporary shelter from inclement weather (Russell, 2005).Some birds may be

attracted to offshore structures because of the lights and the fish populations that aggregate

around these structures.

IPFs potentially affecting marine and pelagic birds include drilling rig presence, noise, and lights;

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

spill represented by the WCD for the Revised EP).Any impacts on the birds from effluent

discharges is expected to be negligible because of rapid dispersion, the small area of ocean

affected, the intermittent nature of the discharges, and the mobility of these animals.

Implementation of NTL 2012ͲBSEEͲG01 mitigation measures will reduce the potential for marine

debrisͲrelated impacts on birds.

Potential Impacts of Drilling Rig Presence, Noise, and Lights

Birds that frequent platforms may be exposed to contaminants including air emissions and

routine discharges, but significant impacts are unlikely because of 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

landͲbased structures has been reviewed extensively, and the mechanisms involved in platform

collisions appear to be similar.In some cases, migrants simply do not see a part of the platform

until it is too late.In other cases, navigation may be disrupted by noise (Russell, 2005).On the

other hand, offshore structures are suitable stopover habitats for most transͲGulf migrant

species, and most of the migrants that stop over on platforms probably benefit from their stay,

particularly in spring (Russell, 2005).Because of the limited scope and short duration of drilling

activities in the Revised EP, any impacts on populations of either seabirds or transͲGulf migrant

birds are not expected to be significant.

A recent study in the North Sea indicated that platform lighting causes circling behavior in

various birds, especially on cloudy nights; apparently the birds’ geomagnetic compasses are

upset by the red part of the spectrum from the lights currently in use (Van de Laar, 2007; Poot

et al., 2008).The numbers varied greatly, from none at all to some tens of thousands of birds

per night per platform, with an apparent effect radius of up to 3 miles (5 km).A study in the

Gulf of Mexico also noted the phenomenon (Russell, 2005).Factors to consider in evaluating

this impact in the Gulf of Mexico would include the lower incidence of cloudy and foggy days in

the Gulf of Mexico versus the North Sea.Because of the limited scope and short duration of
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 44

drilling activities proposed in this plan, lighting impacts, collisions, or other adverse effects are

unlikely, and no significant impacts are expected.

Potential 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 shortͲterm

behavioral disruption, and the impact would not be significant.

Potential Impacts of a Small Fuel Spill

Potential spill impacts on marine birds are discussed in recent EISs (MMS, 2007b; BOEM, 2012,

2013a).For the Revised EP, there are no unique siteͲspecific issues with respect to spill impacts

on these animals.

The probability of a fuel spill will be reduced by implementation of Chevron’s preventative

measures during routine operations, including fuel transfer.In the unlikely event of a spill,

implementation of Chevron’s OSRP will mitigate and reduce the potential for impacts on marine

and pelagic birds.Given the open ocean location of the lease area, the duration of a small spill

and opportunity for impacts to occur would be very brief.

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

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

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

the time and the effectiveness of spill response measures.Section A.9.2 discusses the

estimated fate of a small fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.The area of the sea surface with diesel fuel on it would

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

Birds exposed to oil on the sea surface could experience direct physical and physiological effects

including skin irritation; chemical burns of skin, eyes, and mucous membranes; and inhalation of

toxic fumes.Because of the limited areal extent and short duration of water quality impacts

from a small fuel spill, secondary impacts caused by ingestion of oil via oiled prey or reductions

in prey abundance are unlikely.Because of 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.

Potential Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine and pelagic birds are discussed in recent EISs (MMS, 2007b;

BOEM, 2012, 2013a).For the Revised EP, there are no unique siteͲspecific 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, stormͲpetrels, 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.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 45

The recent Macondo spill provides relevant information about the species of pelagic birds that

may be affected in the event of a large oil spill.Oiled birds that were collected either alive or

dead following the spill included several pelagic species such as Audubon’s Shearwater, Greater

Shearwater, Leach’s Storm Petrel, Manx Shearwater, Northern Gannet, Magnificent Frigatebird,

and Masked Booby (USFWS, 2011b).The Northern Gannet was among the species with the

largest numbers of birds affected by the spill.

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 nonͲendangered 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, GullͲBilled

Tern, Laughing Gull, Least Tern, and Royal Tern (USFWS, 2010b).Additional information is

presented in recent lease sale EISs (MMS, 2007b; BOEM, 2012, 2013a).

The Eastern Brown Pelican (Pelecanus occidentalis) has been delisted from its endangered status

under the ESA (USFWS, 2010c).However, this species remains listed as endangered by both

Louisiana (Louisiana Department of Wildlife and Fisheries, 2013) and Mississippi (Mississippi

Natural Heritage Program, 2011), and is designated as a species of special concern by the State

of Florida (Florida Fish and Wildlife Conservation Commission, 2013d).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 fuel spill in the lease area would be unlikely

to affect shorebirds or coastal nesting birds, as the lease area is 156 miles (251 km) from the

nearest shoreline.As explained in Section A.9.2, a small fuel spill would not be expected to

make landfall or reach coastal waters prior to breaking up.Implementation of

NTL 2012ͲBSEEͲG01 mitigation measures will reduce the potential for marine debrisͲrelated

impacts on shorebirds.

Potential Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters will transit coastal areas near Leeville, 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).
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 46

Vessel traffic may disturb some foraging and resting birds.The disturbances will be limited to

flushing birds away from vessel pathways.Flushing distances vary among species and

individuals; 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 outboardͲpowered boat (Rodgers and Schwikert, 2002).

Flushing distances may be similar or less for the support vessels to be used for Chevron’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 disturbance 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.Because of the limited

scope and short duration of drilling activities, any shortͲterm impacts are not expected to be

biologically significant to coastal bird populations.

Aircraft traffic can cause some disturbance to birds on shore 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 compared to other human disturbances for some species

(Bélanger and Bédard, 1989).However, Federal Aviation Administration Advisory Circular

No. 91Ͳ36D recommends that pilots maintain a minimum altitude of 610 m (2,000 ft) when

flying over noiseͲsensitive 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 the implementation of these guidelines, it is likely that individual birds would

experience, at most, only shortͲterm behavioral disruption.

Potential Impacts of Large Oil Spill (WCD)

The OSRA results summarized in Table 3 estimate that shorelines of Texas and Louisiana that

include habitat for shorebirds and coastal nesting birds could be affected within 30 days.

Data from the Macondo spill provide additional information about the species of coastal birds

that may be affected in the event that a large oil spill reached coastal habitats.According to

USFWS (2011b), within approximately 1 year after the spill, about 6,400 dead birds had been

collected, and about 2,100 of the dead animals were visibly oiled.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 (USFWS, 2011b).There are

no reports of Bald Eagle oiling.Antonio et al. (2011) modeled bird mortality from the Macondo

spill showing cumulative carcass numbers and mortality rate increasing exponentially from the

start of the Macondo spill until the mortality rate began to decline after the 97th day of the spill.

Note that the collected animals would be a small subset of the total number of impacted birds;

therefore, the collected animals would represent an underestimated measure of the overall

impact of the Macondo event (BOEM, 2012).

In addition, over 2,000 oiled birds were collected alive, and about 1,200 birds were released

(NMFS, 2010c).According to the USFWS (2011b), birds collected alive but oiled after the spill

included the following species:

x American Coot

x American Oystercatcher

x American White Pelican

x Audubon’s Shearwater

x BlackͲcrowned Night Heron

x Black Skimmer

x Brown Pelican

x Bufflehead
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 47

x Canada Goose

x Caspian Tern

x Cattle Egret

x Clapper Rail

x Common Loon

x Common Tern

x DoubleͲcrested Cormorant

x European Starling

x Forster’s Tern

x Glossy Ibis

x Great Blue Heron

x Great Egret

x Greater Shearwater

x Grebe, unidentified

x Gull, unidentified

x Herring Gull

x Laughing Gull

x Least Tern

x Lesser BlackͲbacked Gull

x Loon, unidentified

x Magnificent Frigatebird

x Mallard

x Masked Booby

x Mourning Dove

x Northern Gannet

x Osprey

x Pelican, unidentified

x PiedͲbill Grebe

x Pigeon, unidentified

x RedͲbreasted Merganser

x Reddish Egret

x RingͲbilled Gull

x Rock Pigeon

x Roseate Spoonbill

x Royal Tern

x Ruddy Turnstone

x Sanderling

x Sandwich Tern

x Semipalmated Sandpiper

x Snowy Egret

x Sooty Tern

x Sora

x Surf Scoter

x Tern, unidentified

x Tricolored Heron

x White Ibis

x Willet

Coastal birds can be exposed to oil as they float on the water’s surface, dive during foraging, or

wade in oiled coastal waters.Oiled birds can lose the ability to fly, dive for food, or float on the

water, which could lead to drowning (USFWS, 2010d).Oil interferes with the water repellency

of feathers and can cause hypothermia in the right conditions.As birds groom themselves, they

can ingest and inhale the oil on their bodies.Scavengers such as Bald Eagles and gulls can be

exposed to oil by feeding on carcasses of oiled 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 harmed if an oiled adult sits on the nest.

As noted above, the Brown Pelican was recently removed from the endangered species list.

Over 500 dead Brown Pelicans were collected in the Gulf following the Macondo spill, of which

about 25% were visibly oiled (USFWS, 2011b).These data indicate that Brown Pelicans may be

particularly at risk of oiling in the event of a large spill reaching coastal waters.Potential

impacts to Brown Pelicans include direct contact with oil, disturbance by cleanup activities, and

longͲterm habitat impacts.

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 lowͲproductivity condition are

productive “hot spots” associated with entrainment of nutrientͲrich Mississippi River water and
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 48

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).These ichthyoplankton

become part of the planktonic community for various lengths of time (10 to 100 days,

depending on the species).Ichthyoplankton surveys such as the Southeast Area Monitoring and

Assessment Program (SEAMAP) reveal that larval fishes form crossͲshelf assemblages (inner,

midͲ, and outer shelf) similar to those observed in adult fishes (Ditty et al., 1988; Shaw et al.,

2002; Hernandez et al., 2003).Waters around oil and gas platforms had higher abundance and

diversity of postlarval and juvenile fishes than waters immediately downͲcurrent of the

platform.The reason is unknown, but possible contributing factors include increased feeding

opportunities and refuge from predation (Shaw et al., 2002).A study by Ross et al. (2012) on

midͲwater fauna to characterize vertical distribution of mesopelagic fishes in deepwater areas of

the Gulf of Mexico substantiated high species richness, but the community was dominated by

relatively few families and species.

IPFs potentially affecting pelagic communities and ichthyoplankton include drilling rig presence,

noise, and lights; effluent discharges; seawater intakes; and two types of accidents (a small fuel

spill and a large oil spill [WCD]).

Potential Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as a fishͲattracting

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).Positive fish

associations with offshore rigs and platforms in the Gulf of Mexico are well documented

(Gallaway and Lewbel, 1982; Wilson et al., 2003, 2006; Peabody and Wilson, 2006).This FAD

effect could possibly enhance the feeding of epipelagic predators by attracting and

concentrating smaller fishes.Because the drilling rig is a single, temporary structure, impacts on

fish populations, whether beneficial or adverse, are considered minor.

Potential Impacts of Effluent Discharges

Treated sanitary and domestic wastes will have little or no impact 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 will have little or no impact on the pelagic environment in the immediate vicinity

of these discharges.Deck drainage from oily areas will be passed through an oilͲandͲwater

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.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 49

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

BOP fluid, uncontaminated ballast water, excess cement, uncontaminated water from testing of

the firewater system, and nonͲcontact cooling water, are expected to be diluted rapidly and

have little or no potential for impact on water column biota.

Potential Impacts of Seawater Intakes

Seawater will be drawn from the ocean for onceͲthrough, nonͲcontact cooling of machinery

on the drilling rig.The estimated intake and discharge of cooling water is 500,000 BPD

(21 MGD).All affected cooling water intakes will be in compliance with the design, monitoring,

and recordkeeping requirements of the NPDES permit to comply with 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 strongͲswimming 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 fastͲswimming 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).Because of the limited scope and short duration of drilling activities,

any shortͲterm impacts of entrainment are not expected to be biologically significant to

plankton or ichthyoplankton populations.

Potential Impacts of a Small Fuel Spill

Potential spill impacts on fisheries resources are discussed in recent EISs (MMS, 2007b;

BOEM, 2012, 2013a).For the Revised EP, there are no unique siteͲspecific issues with respect to

spill impacts.

The probability of a fuel spill will be reduced by implementation of Chevron’s preventative

measures during routine operations, including fuel transfer.In the unlikely event of a spill,

implementation of Chevron’s OSRP will mitigate and reduce the potential for impacts on pelagic

communities, including ichthyoplankton.Given the open ocean location of the lease area, the

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

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

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

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

the time and the effectiveness of spill response measures.Section A.9.2 discusses the

estimated fate of a small fuel spill and indicates that over 90% would be evaporated or

dispersed naturally within 24 hours.The estimated area of the sea surface with diesel fuel on it

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

A small fuel spill could have localized impacts on phytoplankton, zooplankton, and nekton.

Because of the limited areal extent and short duration of water quality impacts, a small fuel spill

would be unlikely to produce detectable impacts on pelagic communities.

Potential 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
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 50

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 localͲscale 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 MagnusonͲStevens Fishery

Conservation and Management Act, as amended, Federal agencies are required to consult on

activities that may adversely affect EFH designated in Fishery Management Plans developed by

the regional Fishery Management Councils.

The Gulf of Mexico Fishery Management Council (GMFMC) has prepared Fishery Management

Plans for corals and coral reefs, shrimps, stone crab, spiny lobster, reef fishes, coastal migratory

pelagic fishes, and red drum.In 2005, the EFH for these managed species was redefined in

Generic Amendment No. 3 to the various Fishery Management Plans (GMFMC, 2005).The EFH

for most of these GMFMCͲmanaged 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 shelfͲedge topographic

features on the TexasͲLouisiana OCS, the nearest of which is approximately 76 miles (122 km)

from the lease area.

Highly migratory pelagic fishes, which occur as transients in the lease area, are the only

remaining group for which EFH has been identified in the deepwater Gulf of Mexico.Species in

this group, including tunas, swordfishes, billfishes, and sharks, are managed by NMFS.Highly

migratory species with EFH at or near the lease area include the following (NMFS, 2009):

x Blue marlin (juveniles, adults)

x White marlin (juveniles, adults)

x Sailfish (adult)

x Longbill spearfish (juveniles, adults)

x Swordfish (larvae, juveniles, adults)

x Atlantic bluefin tuna (spawn, eggs,

larvae, adults)

x Bigeye tuna (adults)

x Skipjack tuna (spawn, adults)

x Yellowfin tuna (spawn, juveniles,

adults)

x Bigeye thresher shark (all)

x Dusky shark (adult, juveniles)

x Longfin mako shark (all)

x Oceanic whitetip shark (all)

x Shortfin mako shark (all)

x Silky shark (all)

x Tiger shark (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 116,000 mi2

(300,000 km2).The prevailing assumption is that Atlantic bluefin tuna follow an annual cycle of

foraging in June through March off the eastern U.S. and Canadian coasts, followed by migration

to the Gulf of Mexico to spawn in April, May, and June (NMFS, 2009).The Atlantic bluefin tuna

has also been designated as a species of concern by NMFS (2011b).
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 51

Other HAPCs have been identified in the Gulf of Mexico by the GMFMC (2005).These include

the Florida Middle Grounds, MadisonͲSwanson Marine Reserve, Tortugas North and South

Ecological Reserves, Pulley Ridge, as well as the East and West Flower Garden Banks and several

other reefs and banks of the northwestern Gulf of Mexico (Figure 3).The nearest of these is

Jakkula Bank, located approximately 76 miles (123 km) from the lease area.

Routine IPFs potentially affecting EFH include drilling rig presence, noise, and lights; effluent

discharges; seawater intakes; and two types of accidents – a small fuel spill and a large oil spill

(WCD).

Potential Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as a FAD.

In oceanic waters, the FAD effect would be most pronounced for epipelagic fishes such as tunas,

dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting surface

structures (Holland et al., 1990; Higashi, 1994; Relini et al., 1994).This FAD effect would

possibly enhance feeding of epipelagic predators by attracting and concentrating smaller fish

species.Because the drilling rig is a single, temporary structure, any impacts on EFH for highly

migratory pelagic fishes are considered minor.

Potential 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.

Potential Impacts of Seawater Intakes

As noted previously, cooling water intake will entrain and impinge plankton, including fish eggs

and larvae (ichthyoplankton).Because of the limited scope and short duration of drilling

activities, any shortͲterm impacts on EFH for highly migratory pelagic fishes are not expected to

be biologically significant.

Potential Impacts of a Small Fuel Spill

The potential of a fuel spill will be reduced by implementation of Chevron’s preventative

measures during routine operations, including fuel transfer.In the unlikely event of a spill,

implementation of Chevron’s OSRP will mitigate and reduce the potential for impacts on EFH.

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; BOEM, 2012, 2013a).

For the Revised EP, there are no unique siteͲspecific issues with respect to spill impacts.

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

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

persistence of any 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

estimated fate of a small fuel spill and indicates that over 90% would be evaporated or
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 52

dispersed naturally within 24 hours.The estimated area of the sea surface with diesel fuel on it

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

A small fuel spill could have localized impacts on EFH for highly migratory pelagic fishes,

including tunas, swordfishes, billfishes, and sharks.These species occur as transients in the

lease area.A spill would also produce a shortͲterm impact on water quality in the HAPC for

spawning Atlantic bluefin tuna, which covers much of the deepwater Gulf of Mexico.The areal

extent of the affected area would represent a negligible portion of the HAPC.

A small fuel spill would not affect EFH for corals and coral reefs because it would float and

dissipate on the sea surface and would not contact these seafloor features.

Potential Impacts of a Large Oil Spill (WCD)

Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b; BOEM, 2012, 2013a).

For the Revised EP, there are no unique siteͲspecific issues with respect to EFH.

An oil spill in offshore waters would temporarily increase hydrocarbon concentrations on the

water surface and potentially in the subsurface as well.Given the extent of EFH designations in

the Gulf of Mexico (GMFMC, 2005; NMFS, 2009), some impact on EFH would be unavoidable.

A large spill could affect the EFH for many managed species including shrimps, stone crab, spiny

lobster, 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 oiled 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 by increasing 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 nearest area designated as EFH under the corals and coral reefs management plan is

Jakkula Bank, located approximately 76 miles (122 km) from the lease area.A floating oil slick

would be unlikely to affect this area because it is located on the seafloor.Although subsurface

plumes occurred during the Macondo spill (resulting from the use of subsea dispersants), the

distance and difference in water depth are factors that would make an impact unlikely.

NearͲbottom 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

The lease area is not on the list of blocks with a high potential for historic shipwrecks.It is not

expected that any shipwreck sites are present in the lease area.As required by

30 CFR 550.194(a)(2), an archaeological assessment has been performed, and no archaeological

avoidance features were detected around the proposed wellsites (GEMS, 2013).If potential

archaeological resources are detected during the activities proposed in the Revised EP, Chevron

would report the discovery to the BOEM Regional Director, who would provide instructions for
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 53

protecting the resource.Therefore, all impacts on shipwreck sites from routine activities are

expected to be avoided.A large oil spill (WCD) is the only IPF considered.A small fuel spill

would not affect shipwrecks because the oil would float and dissipate on the sea surface.

Potential Impacts of a Large Oil Spill (WCD)

A seafloor blowout could cause physical impacts on the seafloor within about 300 m (984 ft) of

the wellhead (BOEM, 2012).However, it is not expected that any shipwreck sites would be

present within this radius because of the archaeological assessment required by regulations and

BOEM’s requirements for avoiding such features.Therefore, this type of impact is expected to

be avoided.

Beyond this radius, there is the potential for impacts from oil, dispersants, and depleted oxygen

levels (BOEM, 2012).These impacts could include chemical contamination as well as alteration

of the rates of microbial activity (BOEM, 2012).During the Macondo spill, subsurface plumes

were reported at a water depth of about 1,100 m (3,609 ft), extending at least 22 miles (35 km)

from the wellsite and persisting for more than a month (Camilli et al., 2010).The subsurface

plumes apparently resulted from the use of dispersants at the wellhead (Joint Analysis Group,

2010c).While the behavior and impacts of subsurface plumes are not well known, a subsurface

plume could have the potential to contact shipwreck sites beyond the 300Ͳm (984Ͳft) radius

estimated by BOEM (2012), 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 2005ͲG07, Chevron will immediately

halt operations, take steps to not disturb the site, and contact the Regional Supervisor, Leasing

and Environment, within 48 hours of its discovery.Chevron would cease all operations within

305 m (1,000 ft) of the site until the Regional Supervisor provides instructions on steps to take

to assess the site’s potential historic significance and implement the steps designed to protect it.

A spill entering shallow coastal waters could conceivably affect an undiscovered shipwreck site.

The OSRA modeling summarized in Table 3 predicts that Texas and Louisiana shorelines could be

contacted by a spill within 30 days.Also, if an oil spill contacted a coastal historic site such as a

fort or a lighthouse, the main impact would be a temporary, reversible visual impact from oil

contact of the site and its environment (MMS, 2007b; BOEM, 2012).

C.6.2 Prehistoric Archaeological Sites

Water depths at the proposed wellsites range from 1,705 to 1,756 m (5,593 to 5,760 ft), and,

therefore, prehistoric archaeological sites are unlikely to occur there.As required by

30 CFR 550.194(a)(2), an archaeological assessment has been performed, and no archaeological

avoidance features were detected around the proposed wellsites (GEMS, 2013).If potential

archaeological resources are detected during the activities proposed in the Revised EP, Chevron

would report the discovery to the BOEM Regional Supervisor, who would provide instructions

for protecting the resource.Therefore, routine activities are not expected to have any impacts

on prehistoric archaeological sites.The only relevant IPF is a large oil spill (WCD).A small fuel

spill would not affect prehistoric archaeological resources because the oil would float and

dissipate on the sea surface.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 54

Potential Impacts of a Large Oil Spill (WCD)

Because of the water depth, it is not expected that any prehistoric archaeological sites are

present in the lease area.Therefore, it is highly unlikely that any such resources would be

affected by the physical effects of a subsea blowout, which are limited to an estimated radius of

300 m (984 ft) (BOEM, 2012).If a subsurface plume from a large spill were to reach lease blocks

in water depths less than 60 m (197 ft), there would be the potential for impacts from oil,

dispersants, and depleted oxygen levels (BOEM, 2012).These impacts could include chemical

contamination as well as alteration of the rates of microbial activity (BOEM, 2012).

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; BOEM, 2012).The

OSRA modeling summarized in Table 3 estimates that Texas and Louisiana shorelines could be

contacted by a spill within 30 days.A spill reaching a prehistoric site along these shorelines

could coat fragile artifacts or site features and compromise the potential for radiocarbon dating

organic materials in a site (although other dating methods are available and it is possible to

decontaminate an oiled sample for radiocarbon dating).Coastal prehistoric sites could also be

affected by spill cleanup operations (e.g., by damaging fragile artifacts and disturbing the

provenance of artifacts and site features).

C.7 Coastal Habitats and Protected Areas

Coastal habitats in the northern Gulf of Mexico that may be affected by oil and gas activities are

described in recent EISs (MMS, 2007b; BOEM, 2012, 2013a).Sensitive coastal habitats are also

tabulated in the OSRP.Coastal habitats inshore of the project area include barrier beaches and

dunes, wetlands, and submerged seagrass beds.Generally, most of the northeastern Gulf is

fringed by barrier beaches, with wetlands and/or submerged seagrass beds occurring in

sheltered areas behind the barrier islands and in estuaries.

Because of the distance from shore, there are no IPFs associated with routine offshore 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 base at Leeville

is not in a wildlife refuge or a wilderness area.Potential impacts of support vessel traffic are

briefly addressed in this subsection.

A large oil spill is the only accidental impact analyzed.A small fuel spill in the lease area would

be unlikely to affect coastal habitats, as the lease area is 156 miles (251 km) from the nearest

shoreline.As explained in Section A.9.2, a small fuel spill would not be expected to make

landfall or reach coastal waters prior to breaking up.

Potential Impacts of Support Vessel Traffic

For OCS activities in general, support vessel operations 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 vessel traffic may have a minor

incremental impact on coastal habitats or protected areas.Impacts will be reduced by following

the speed and wake restrictions in harbors and channels.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 55

Potential Impacts of a Large Oil Spill (WCD)

Potential spill impacts on coastal habitats are discussed in recent EISs (MMS, 2007b;

BOEM, 2012, 2013a).Coastal habitats inshore of the project area include barrier beaches and

dunes, wetlands, and submerged seagrass beds.For the Revised EP, there are no unique

siteͲspecific issues with respect to coastal habitats.

The 30Ͳday OSRA results (Table 3) predict that shorelines of Texas and Louisiana could be

affected within 30 days.The highest probability of shoreline contact after 30 days is 3% for

Cameron Parish, Louisiana.After 30 days, 4 Texas counties and 4 Louisiana parishes may be

contacted, ranging from Matagorda County, Texas, to Plaquemines Parish, Louisiana.The

shorelines within this geographic range include extensive barrier beaches and wetlands, with

submerged seagrass beds occurring in sheltered areas behind the barrier islands and in

estuaries.NWRs and other protected areas along the coast are discussed in the lease sale EISs

(MMS, 2007b; BOEM, 2012, 2013a) and Chevron’s OSRP.Coastal wildlife refuges, wilderness

areas, and parks within the geographic range of the potential shoreline contacts after 30 days

are listed in Table 6.

Additional coastal areas could be contacted in the event of a spill persisting for more than

30 days.In the 120Ͳday OSRA modeling (BOEM, 2012), potential shoreline contacts after

120 days ranged from Cameron County, Texas (at the Texas/Mexico border) to Dade County in

southeastern Florida.However, in the 120Ͳday OSRA modeling, counties or parishes with

greater than 10% contact probability during any season ranged from Matagorda County, Texas

to Plaquemines Parish, Louisiana, which is identical to the geographic range identified in the

30Ͳday OSRA modeling.These areas include habitats such as barrier beach and dune systems,

wetlands, and submerged seagrass beds that support diverse wildlife, including endangered or

threatened species.

The level of potential impacts from oil spills on coastal habitats depends on many factors,

including oil characteristics, the geographic location of the landfall, and the weather and

oceanographic conditions at the time (MMS, 2007b; BOEM, 2012).Oil that makes it to beaches

may be either liquid weathered oil, an oilͲandͲwater mousse, or tarballs.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 (MMS, 2007b; BOEM, 2012).
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 56

Table 6. Coastal wildlife refuges, wilderness areas, and parks within the geographic range of

potential shoreline contacts within 30 days after an oil spill based on the OSRA results

summarized in Table 3.

County or Parish Wildlife Refuge, Wilderness Area, or Park

Matagorda County, Texas

Big Boggy National Wildlife Refuge

Mad Island Wildlife Management Area

San Bernard National Wildlife Refuge

Brazoria County, Texas

San Bernard National Wildlife Refuge

Peach Point Wildlife Management Area

Brazoria National Wildlife Refuge

Christmas Bay Coastal Preserve and Christmas Bay State Park

Galveston County, Texas

Brazoria National Wildlife Refuge

Galveston Island State Park

Apffel East Beach Park

Seawolf Park

Fort Travis Seashore Park

Atkinson Island Wildlife Management Area

Anahuac National Wildlife Refuge

McFaddin National Wildlife Refuge

Jefferson County, Texas

McFaddin National Wildlife Refuge

J.D. Murphree Wildlife Management Area

Sea Rim State Park

Texas Point National Wildlife Refuge

Cameron Parish, Louisiana

Sabine National Wildlife Refuge

Little Pecan Island Preserve

Peveto Woods Sanctuary

Rockefeller State Wildlife Refuge and Game Preserve

Vermilion Parish, Louisiana

Rockefeller State Wildlife Refuge and Game Preserve

Paul J. Rainey Wildlife Management Area

State Wildlife Refuge and Game Preserve

Terrebonne Parish, Louisiana Isles Dernieres Barrier Island Refuge

Pointe Aux Chenes Wildlife Management Area

Plaquemines Parish, Louisiana

Delta National Wildlife Refuge

PassͲaͲLoutre Wildlife Management Area

Breton National Wildlife Refuge

Coastal wetlands are highly sensitive to oiling and can be significantly affected because of the

inherent toxicity of hydrocarbon and nonͲhydrocarbon components of the spilled substances

(Beazley et al., 2012; Lin and Mendelssohn, 2012; Mendelssohn et al., 2012).The MMS (2007b)

estimated 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 affected 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 openͲwater habitat.The critical

concentration of oil is that concentration above which impacts to wetlands will be longͲterm

and recovery will take longer than two growing seasons, and which causes plant mortality and

some permanent wetland loss.Critical concentrations of various oils are expected to vary

broadly for wetland types and wetland plant species (Lin and Mendelssohn, 2012).Louisiana

wetlands are assumed to be more sensitive to oil contact than those elsewhere in the Gulf

because of high cumulative stress (MMS, 2007b).In addition to the direct impacts of oil,
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 57

cleanup activities in marshes may accelerate rates of erosion and retard recovery rates, which

have been reported to require from years to decades following a spill (MMS, 2007b).

C.8 Socioeconomic and Other Resources

C.8.1 Recreational and Commercial Fishing

The main commercial fishing activity in deep waters of the northern Gulf of Mexico is pelagic

longlining for tunas, swordfishes, and other billfishes (Continental Shelf Associates, Inc., 2002).

Pelagic longlining has occurred historically in the project area, primarily during spring and

summer.

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 onͲboard

temperature sensors, depth finders, and positioning equipment.Longlining vessels are 10 to

30 m (33 to 98 ft) long, and trips typically last from about 1 to 3 weeks.The main homeports for

Gulf longlining vessels are in Louisiana (Dulac and Venice) and Florida (Destin, Madeira Beach,

and Panama City).

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

project area.Benthic species targeted by commercial fishers occur on the upper continental

slope, well inshore of the project area.Royal red shrimp are caught by trawlers in water depths

of about 250 to 550 m (820 to 1,804 ft).Tilefish are caught by bottom longlining in water

depths from about 165 to 450 m (540 to 1,476 ft) (Continental Shelf Associates, Inc., 2002).

Most recreational fishing activity in the region occurs in water depths less than 200 m (656 ft)

(Continental Shelf Associates, Inc., 1997, 2002).In deeper water, the main attraction to

recreational fishers would be petroleum platforms offshore Texas and Louisiana.Because of the

distance from shore and existing platforms, 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 potential accidents are also addressed in this subsection – a small fuel spill and a

large oil spill (WCD).

Potential Impacts of Drilling Rig Presence, Noise, and Lights

There is a slight possibility of pelagic longlines becoming entangled in the drilling rig.For

example, in January 1999 a portion of a pelagic longline snagged on the acoustic Doppler

current profiler of a drillship working in the Gulf of Mexico (Continental Shelf Associates, Inc.,

2002).The line was removed without incident.Generally, longline fishers use radar and are

aware of offshore structures and ships when placing their sets.Therefore, little or no impact on

pelagic longlining is expected.

Because it is unlikely that any recreational fishing activity is occurring in the project area, no

adverse impacts are anticipated.Other factors such as effluent discharges are likely to have
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 58

negligible impacts on commercial or recreational fisheries because of rapid dispersion, the small

area of ocean affected, and the intermittent nature of the discharges.

Potential Impacts of a Small Fuel Spill

The potential for a fuel spill will be reduced by implementation of Chevron’s preventative

measures during routine operations, including fuel transfer.In the unlikely event of a spill,

implementation of Chevron’s OSRP will mitigate and reduce the potential for impacts.Given the

open ocean location of the lease area, the duration of a small spill and opportunity for impacts

to occur would be very brief.

Pelagic longlining activities in the lease area, if any, could be interrupted in the event of a small

fuel spill.The estimated 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 because of the activities of response vessels operating in the lease area.

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

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

Potential Impacts of a Large Oil Spill (WCD)

Potential spill impacts on fishing activities are discussed in recent EISs (MMS, 2007b;

BOEM, 2012, 2013a).For the Revised EP, there are no unique siteͲspecific 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.Commercial fishermen

would be expected to avoid the area of an oil spill.A spill may or may not result in fishery

closures, depending on the duration of the spill, the oceanographic and meteorological

conditions at the time, and the effectiveness of spill response measures.The recent Macondo

spill provides information about the maximum potential extent of fishery closures in the event

of a large oil spill in the Gulf of Mexico (NMFS, 2011c).At its peak on June 2, 2010, closures

encompassed 88,522 mi2 (229,270 km2

), or 36.6% of the U.S. Exclusive Economic Zone in the

Gulf of Mexico.BOEM (2012) notes that fisheries closures from a large spill event could have a

negative effect on shortͲterm fisheries catch and/or marketability.

According to BOEM (2012), the potential impacts on commercial and recreational fishing

activities from an accidental oil spill are anticipated to be minimal because the potential for oil

spills is very low, the most typical events are small and of short duration, and the effects are so

localized that fishes are typically able to avoid the affected area.Fish populations may be

affected by an oil spill event should it occur, but they would be primarily affected if the oil

reaches the productive shelf and estuarine areas where many fishes spend a portion of their life

cycle.The probability of an offshore spill affecting these nearshore environments is also low.

BOEM (2012) concludes that impacts on catch or value of catch would be insignificant compared

with natural variability and other pressures affecting the resource.

C.8.2 Public Health and Safety

There are no IPFs associated with routine operations that are expected to affect public health

and safety.A small fuel spill would not have any impacts on public health and safety, because it

would occur in a small area of the open ocean 156 miles (251 km) from the nearest shoreline,

and nearly all of the diesel fuel would evaporate or disperse naturally within 24 hours.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 59

Response crews would be equipped with appropriate safety equipment designed to avoid injury

and health impacts.A small fuel spill would not be expected to make landfall or reach coastal

waters prior to breaking up (see Section A.9.2).Any potential impacts of a large oil spill (WCD)

are addressed in the following subsections.

Potential Impacts of a Large Oil Spill (WCD)

In the event of a large spill from a blowout, the main safety and health concerns are those of the

offshore personnel involved in the incident and those responding to the spill.The proposed

activities will be covered by the OSRP, and, in addition, the drilling rig maintains a Shipboard Oil

Pollution Emergency Plan as required under MARPOL 73/78.

Depending on the spill rate and duration, the physical/chemical characteristics of the oil, the

meteorological and oceanographic conditions at the time, and the effectiveness of spill response

measures, the public could be exposed to oil on the water and along the shoreline, including

skin contact or breathing VOCs.Crude oil is a highly flammable material; any smoke or vapors

from a crude oil fire can cause irritation, and in large quantities, may pose a health hazard.

Data from the recent Macondo spill provide relevant information about the types of health

issues that may occur in the event of a large oil spill.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).Wildlife cleaning and rehabilitation workers reported concerns

including scrapes and cuts, itchy or red skin or rash, and symptoms of headache or feeling faint,

dizzy, or fatigued (King and Gibbins, 2011).Hand, shoulder, or back pain was also reported by

some wildlife cleaning workers.Awkward postures, repetitive motions, and heavy lifting tasks

were noted by investigators as contributing to musculoskeletal symptoms.However, the most

common occupational hazard identified for spill response workers was heat stress from work in

a hot and humid environment (King and Gibbins, 2011).

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.Therefore, any impacts 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

will be negligible.A small fuel spill that is dissipated within a few days would have little or no

economic impact, as the spill response would use existing facilities, resources, and personnel.

Impacts of a large oil spill (WCD) are addressed in the following subsections.

Potential Impacts of a Large Oil Spill (WCD)

Potential socioeconomic impacts of an oil spill are discussed in recent EISs (MMS, 2007b;

BOEM, 2012, 2013a).For the Revised EP, there are no unique siteͲspecific issues with respect to

employment and coastal infrastructure.A large spill could include economic impacts such as

fishery closures; temporary employment as part of the response effort; adverse publicity that

affects employment in coastal recreation and tourism industries; and suspension of OCS drilling
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 60

activities, including service and support operations that are an important part of local

economies.

The lease area is 156 miles (251 km) from the nearest shoreline.Based on the 30Ͳday

OSRA modeling as summarized in Table 3, as well as the 120Ͳday modeling by BOEM (2012),

Texas and Louisiana coastal areas have the most potential to be affected by a spill.Potential

shoreline contacts after 120 days range from Cameron County, Texas (at the Texas/Mexico

border) to Dade County in southeastern Florida (BOEM, 2012).

A recent study explored the economic impacts of the Macondo spill on oil and gas industry

employment caused by suspension of deepwater drilling (InterͲAgency 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 that the moratorium 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 6Ͳmonth 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 (InterͲAgency

Economic Report, 2010).

As noted by BOEM (2012), the shortͲterm social and economic consequences for the Gulf Coast

region should a large spill occur include the opportunity cost of employment and expenditures

that could have gone to production or consumption rather the spill cleanup efforts.Nonmarket

effects such as traffic congestion, strains on public services, shortages of commodities or

services, and disruptions to the normal patterns of activities or expectations could also occur in

the short term.These negative, shortͲterm social and economic consequences of a spill are

expected to be modest in terms of projected cleanup expenditures and the number of people

employed in cleanup and remediation activities (BOEM, 2012).Net employment impacts from a

spill would not be expected to exceed 1% of baseline employment in any given year

(BOEM, 2012).

C.8.4 Recreation and Tourism

There are no known recreational uses of the lease area.Recreational resources and tourism in

coastal areas would not be affected by any routine activities because of the distance from shore.

Implementation of NTL 2012ͲBSEEͲG01 mitigation measures will reduce the potential for trash

or debris to be lost overboard from the drilling rig and subsequently wash up on beaches.

A small fuel spill in the lease area would be unlikely to affect recreation and tourism because, as

explained in Section A.9.2, it would not be expected to make landfall or reach coastal waters

prior to breaking up.Impacts of a large oil spill (WCD) are discussed below.

Potential Impacts of a Large Oil Spill (WCD)

Potential impacts of an oil spill on recreation and tourism are discussed in recent EISs

(MMS, 2007b; BOEM, 2012, 2013a).For the Revised EP, there are no unique siteͲspecific issues

with respect to these impacts.

Any 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
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 61

30Ͳday OSRA modeling as summarized in Table 3, as well as the 120Ͳday OSRA modeling by

BOEM (2012), Texas and Louisiana shorelines are the areas with the most potential to be

contacted by a spill.However, potential shoreline contacts after 120 days range from Cameron

County, Texas (at the Texas/Mexico border) to Dade County in southeastern Florida (BOEM,

2012).

According to BOEM (2012), should an oil spill occur and contact a beach area or other

recreational resource, it would cause some disruption during the impact and cleanup phases of

the spill.However, these effects are also likely to be small in scale and of short duration, in part

because the probability of an offshore spill contacting most beaches is small.In the unlikely

event that a spill occurs that is sufficiently large to affect large areas of the coast and, through

public perception, have effects that reach beyond the damaged area, effects to recreation and

tourism could be significant (BOEM, 2012).

In addition to the analysis presented by MMS (2007b) and BOEM (2012), recent and ongoing

studies have explored the economic impacts of the Macondo spill including tourism and “brand”

damage (IEM, 2010; Oxford Economics, 2010).The U.S. Travel Association has estimated the

economic impact of the Macondo spill on tourism across the Gulf Coast over a 3Ͳyear 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;

BOEM, 2012, 2013a).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 site 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 shorebase.

A large oil spill (WCD) is the only relevant IPF.A small fuel spill would not have any impacts on

land use, as the response would be staged out of existing shorebases and facilities.

Potential Impacts of a Large Oil Spill (WCD)

The initial response for a large oil spill would be staged out of existing facilities, with no effect on

land use.A large spill could have limited temporary impacts on land use along the coast if

additional staging areas were needed.For example, during the Macondo spill, temporary

staging areas were established in Louisiana, Mississippi, Alabama, and Florida for spill response

and cleanup efforts.In the event of a large spill in the lease area, similar temporary staging

areas could be needed.These areas would eventually return to their original use as the

response is demobilized.

According to BOEM (2012), an accidental oil spill is not likely to significantly affect land use and

coastal infrastructure in the region, in part because an offshore spill would have a small

probability of contacting onshore resources.

C.8.6 Other Marine Uses

The lease area is not within any USCGͲdesignated fairway or shipping lane, and is not within a

Military Warning Area.There are no other known marine uses of the lease area.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 62

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 fuel spill would not have any

impacts on other marine uses, as spill response activities would be mainly within the lease area

and the duration would be brief.

Potential 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 USCGͲdesignated 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.Chevron will comply with BOEM requirements and lease stipulations

to avoid impacts on uses of the area by military vessels and aircraft.

D.Environmental Hazards

D.1 Geologic Hazards

Based on the site clearance letters by Fugro as summarized in Section C of the Revised EP, the

proposed drillsites are free of any significant geological hazards and are suitable for the

proposed activities.

D.2 Severe Weather

Under most circumstances, weather is not expected to have an effect on the proposed activities.

Extreme weather, including high winds, strong currents, and large waves, was considered in the

design criteria for the drilling rig.High winds and limited visibility during a severe storm could

disrupt support activities (vessel and helicopter traffic) and make it necessary to suspend some

activities on the drilling rig for safety reasons until the storm or weather event passes.In the

event of a hurricane, procedures as outlined in the Hurricane Evacuation Plan would be

adhered to.

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 an 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.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 63

E.Alternatives

No formal alternatives were evaluated in this EIA.However, various technical and operational

options, including the location of the proposed wellsites and the selection of a drilling unit, were

considered by Chevron in developing the proposed action.

F.Mitigation Measures

The proposed action includes numerous mitigation measures required by laws, regulations, and

BOEM lease stipulations and NTLs.The project will comply with all applicable Federal, State,

and local requirements concerning air emissions, discharges to water, and solid waste disposal.

All of the proposed activities will be covered by Chevron’s OSRP, which includes the measures

described in Section H of the Revised EP.Chevron has a robust Health, Environment, and Safety

system with a focus on injuryͲand incidentͲfree operations.Chevron’s operations have been,

and will continue to be, the focus of numerous hazard assessments and mitigations to reduce

the risk of accidents and incidents, including pollution.

G.Consultation

No persons or agencies were consulted during the preparation of this EIA.

H.Preparers

The EIA was prepared by CSA Ocean Sciences Inc.Contributors included

x Neal Phillips, Ph.D. (Senior Scientist);

x Stephen Viada (Senior Scientist);

x Keith VanGraafeiland (Geospatial Manager); and

x Melody Powell (Technical Editor).

I.References

Ackleh, A., G.E. Loup, J.W. Loup, B. Ma, J.J. Newcomb, N. Pal, N.A. Sidorovskaia, and C. Tiemann.2012.Assessing

the Deepwater Horizon oil spill impact on marine mammal population through acoustics: Endangered sperm

whales.J. Acoust. Soc. Am. 131(3): 2,306Ͳ2,314.

Antonio, F.J., R.S. Mendes, and S.M. Thomaz.2011.Identifying and modeling patterns of tetrapod vertebrate

mortality rates in the Gulf of Mexico oil spill.Aquatic Toxicology 105(1Ͳ2):177Ͳ179.

Barkuloo, J.M.1988.Report on the conservation status of the Gulf of Mexico sturgeon, Acipenser oxyrinchus

desotoi.U.S. Department of the Interior, U.S. Fish Wildlife Service, Panama City, FL.33 pp.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 64

Beazley, M.J., R.J. Martinez, S. Rajan, J. Powell , Y.M. Piceno, L.M. Tom, G.L. Anderson, T.C. Hazen, J.D. Van

Nostrand, J. Zhou, B. Mortazavi, and P.A. Sobecky.2012.Microbial community analysis of a coastal salt marsh

affected by the Deepwater Horizon oil spill. PLoS ONE 7(7): e41305. doi:10.1371/journal.pone.0041305.

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041305

Bélanger, L. and J. Bédard.1989.Responses of staging Greater Snow Geese to human disturbance.

J. Wildl. Manage. 53:713Ͳ719.

Biggs, D.C. and P.H. Ressler.2000.Water column biology, pp. 141Ͳ187.In: Continental Shelf Associates, Inc.

Deepwater Program: Gulf of Mexico Deepwater Information Resources Data Search and Literature Synthesis.

Volume I: Narrative Report.U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico

OCS Region, New Orleans, LA.OCS Study MMS 2000Ͳ049.

Boehm, P., D. Turton, A. Raval, D. Caudle, D. French, N. Rabalais, R. Spies, and J. Johnson.2001.Deepwater

program: Literature review, environmental risks of chemical products used in Gulf of Mexico deepwater oil

and gas operations.Volume I: Technical report.U.S. Department of the Interior, Minerals Management

Service, Gulf of Mexico OCS Region, New Orleans, LA.OCS Study MMS 2001Ͳ011.326 pp.

Brooke, S. and W.W. Schroeder.2007.State of deep coral ecosystems in the Gulf of Mexico region: Texas to the

Florida Straits, pp. 271Ͳ306.In: S.E. Lumsden, T.F. Hourigan, A.W. Bruckner, and G. Dorr (eds.), The State of

Deep Coral Ecosystems of the United States.NOAA Tech. Memo. CRCPͲ3.Silver Spring, MD.365 pp.

Bureau of Ocean Energy Management (BOEM).2012.Gulf of Mexico OCS Oil and Gas Lease Sales: 2012Ͳ2017.

Western Planning Area Lease Sales 229, 233, 238, 246, and 248; Central Planning Area Lease Sales 227, 231,

235, 241, and 247.Final Environmental Impact Statement.OCS EIS/EA BOEM 2012Ͳ019.July 2012.

http://www.boem.gov/EnvironmentalͲStewardship/EnvironmentalͲAssessment/NEPA/BOEMͲ2012Ͳ

019_v1.aspx

Bureau of Ocean Energy Management (BOEM).2013a.Gulf of Mexico OCS Oil and Gas Lease Sales: 2013Ͳ2014.

Western Planning Area Lease Sale 233.Central Planning Area Lease Sale 231.Final Supplemental

Environmental Impact Statement.

http://www.boem.gov/uploadedFiles/BOEM/BOEM_Newsroom/Library/Publications/2013/BOEM%202013Ͳ

0118.pdf

Bureau of Ocean Energy Management (BOEM).2013b.Chemosynthetic communities in the Gulf of Mexico.

http://www.boem.gov/EnvironmentalͲStewardship/EnvironmentalͲStudies/GulfͲofͲMexicoͲ

Region/chemo/Chemosynthetic_Metazoan_SitesͲpdf.aspx

Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE).2010.Federal & Academic

Scientists Return from DeepͲsea Research Cruise in Gulf of Mexico: Scientists Observe Damage to DeepͲsea

Corals.Press release dated 4 November 2010.http://www.BOEMRE.gov/ooc/press/2010/press1104a.htm

Camilli, R., C.M. Reddy, D.R. Yoerger, B.A.S. Van Mooy, M.V. Jakuba, J.C. Kinsey, C.P. McIntyre, S.P. Sylva, and

J.V. Maloney.2010.Tracking hydrocarbon plume transport and biodegradation at Deepwater Horizon.

Science DOI: 10.1126/science.1195223.

Carmichael, R.H., W.M. Graham, A. Aven, G.Worthy, and S. Howden.2012.Were multiple stressors a ‘perfect

storm’ for northern Gulf of Mexico bottlenose dolphins (Tursiops truncatus) in 2011?PLoS ONE 7(7): e41155.

doi:10.1371/journal.pone.0041155.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0041155

Carr, A.1996.Suwannee River sturgeon, pp. 73Ͳ83.In: M.H. Carr (ed.), A Naturalist in Florida.Yale University

Press, New Haven, CT.

Clapp, R.B., R.C. Banks, D. MorganͲJacobs, and W.A. Hoffman.1982a.Marine birds of the southeastern United

States and Gulf of Mexico.Part I.Gaviiformes through Pelicaniformes.U.S. Fish and Wildlife Service, Office of

Biological Services, Washington, DC.FWS/OBSͲ82/01.637 pp.

Clapp, R.B., D. MorganͲJacobs, and R.C. Banks.1982b.Marine birds of the southeastern United States and Gulf of

Mexico.Part II.Anseriformes.U.S. Fish and Wildlife Service, Office of Biological Services, Washington, DC.

FWS/OBSͲ82/20.492 pp.

Clapp, R.B., D. MorganͲJacobs, and R.C. Banks.1983.Marine birds of the southeastern United States and

Gulf of Mexico.Part III.Charadriiformes.U.S. Fish and Wildlife Service, Office of Biological Services,

Washington, DC.FWS/OBSͲ83/30.853 pp.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 65

Continental Shelf Associates, Inc.1997.Characterization and trends of recreational and commercial fishing from

the Florida panhandle.U.S. Department of Interior, Minerals Management Service, Gulf of Mexico

OCS Region, New Orleans, LA.USGS/BRD/CRͲ1997Ͳ0001 and OCS Study MMS 97Ͳ0020.333 pp.

Continental Shelf Associates, Inc.2002.Deepwater Program: Bluewater fishing and OCS activity, interactions

between the fishing and petroleum industries in deepwaters of the Gulf of Mexico.U.S. Department of the

Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA.OCS Study

MMS 2002Ͳ078.

Continental Shelf Associates, Inc.2004.Final Report: Gulf of Mexico Comprehensive Synthetic Based Muds

Monitoring Program.Report prepared for SBM Research Group, Houston, TX.October 2004.3 volumes.

Continental Shelf Associates, Inc.2006.Effects of oil and gas exploration and development at selected continental

slope sites in the Gulf of Mexico.Volume II: Technical report.U.S. Department of the Interior, Minerals

Management Service, Gulf of Mexico OCS Region, New Orleans, LA.OCS Study MMS 2006Ͳ045.

CruzͲKaegi, M.E.1998.Latitudinal variations in biomass and metabolism of benthic infaunal communities.

Ph.D. dissertation, Texas A&M University, College Station, TX.

CSA International, Inc.2007.Characterization of northern Gulf of Mexico deepwater hardͲbottom communities

with emphasis on Lophelia coral.U.S. Department of the Interior, Minerals Management Service,

Gulf of Mexico OCS Region, New Orleans, LA.OCS Study MMS 2007Ͳ044.169 pp. + app.

Davis, R.W. and G.S. Fargion.1996.Distribution and abundance of cetaceans in the northͲcentral and western

Gulf of Mexico: Final report.U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico

OCS Region, New Orleans, LA.http://www.getcited.org/pub/100201353

Davis, R.W., J.G. OrtegaͲOrtiz, C.A. Ribic, W.E. Evans, D.C. Biggs, P.H. Ressler, J.H. Wormuth, R.R. Leben, K.D. Mullin,

and B. Würsig.2000.Cetacean habitat in the northern Gulf of Mexico, pp. 217Ͳ253.In: R.W. Davis,

W.E. Evans, and B. Würsig (eds.), Cetaceans, sea turtles, and seabirds in the northern Gulf of Mexico:

Distribution, abundance and habitat associations.Volume II: Technical report.U.S. Geological Survey,

Biological Resources Division, USGS/BRD/CRͲ1999Ͳ0006 and U.S. Department of the Interior, Minerals

Management Service, Gulf of Mexico OCS Region, New Orleans, LA.OCS Study MMS 2000Ͳ003.346 pp.

http://www.tamug.edu/marb/davisdocs/DeepͲSea%20Res%202001%20Davis%20etal.pdf

Ditty, J.G.1986.Ichthyoplankton in neretic waters of the northern Gulf of Mexico off Louisiana: Composition,

relative abundance, and seasonality.Fish. Bull. 84(4):935Ͳ946.

Ditty, J.G., G.G. Zieske, and R.F. Shaw.1988.Seasonality and depth distribution of larval fishes in the northern

Gulf of Mexico above 26°00’N.Fish. Bull. 86:811Ͳ823.

Efroymson, R.A., W.H. Rose, S. Nemeth, and G.W. Suter II.2000.Ecological risk assessment framework for low

altitude overflights by fixedͲwing and rotaryͲwing military aircraft.Report prepared by Oak Ridge National

Laboratory, Oak Ridge, TN.ORNL/TMͲ2000/289: ESͲ5048.

Ehrlich, P.R., D.S. Dobkin, and D. Wheye.1992.Birds in Jeopardy: The Imperiled and Extinct Birds of the United

States and Canada, including Hawaii and Puerto Rico.Stanford University Press, Palo Alto, CA.261 pp.

Environmental Response Management Application (ERMA) Gulf Response.2012.Potential Oiling

FootprintͲNOAA/NESDIS (RADARSATͲ2 ScanSAR).http://gomex.erma.noaa.gov/erma.html#x=Ͳ

90.85693&y=27.57159&z=8&layers=17846

Federal Aviation Administration (FAA).2004.Advisory Circular 91Ͳ36D.Visual flight rules (VFR) flight near

noiseͲsensitive areas.September 17, 2004.2 pp.

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2091Ͳ36D/$FILE/AC91Ͳ

36d.pdf.

Fisher, C.2010.The final dive. Lophelia II: Oil seeps and deep reefs.November 3, 2010, dive log.NOAA Ocean

Explorer.http://oceanexplorer.noaa.gov/explorations/10lophelia/logs/nov3/nov3.html

Fisher, C.2011.Oil spill impact on deepͲwater coral communities and future directions.Presentation given at the

TwentyͲSixth Gulf of Mexico Information Transfer Meeting, March 22Ͳ24, 2011.Sponsored by the

U.S. Department of the Interior, Bureau of Ocean Energy Management, Regulation and Enforcement,

Gulf of Mexico OCS Region, New Orleans, LA.

Florida Fish and Wildlife Conservation Commission.2013a.Loggerhead nesting in Florida.

http://myfwc.com/research/wildlife/seaͲturtles/nesting/loggerhead/

Florida Fish and Wildlife Conservation Commission.2013b.Green turtle nesting in Florida.

http://myfwc.com/research/wildlife/seaͲturtles/nesting/greenͲturtle/
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 66

Florida Fish and Wildlife Conservation Commission.2013c.Leatherback nesting in Florida.

http://myfwc.com/research/wildlife/seaͲturtles/nesting/leatherback/

Florida Fish and Wildlife Conservation Commission.2013d.Florida's endangered species, threatened species, and

species of special concern.Updated January, 2013.

http://myfwc.com/media/1515251/Threatened_Endangered_Species.pdf

Fox, D.A., J.E. Hightower, and F.M. Paruka.2000.Gulf sturgeon spawning migration and habitat in the

Choctawhatchee River system, AlabamaͲFlorida.Trans. Am. Fish. Soc. 129:811Ͳ826.

Fritts, T.H. and R.P. Reynolds.1981.Pilot study of the marine mammals, birds, and turtles in OCS areas of the Gulf

of Mexico.U.S. Department of the Interior, Fish and Wildlife Service, Biological Services Program.

FWS/OBSͲ81/36.

Gallaway, B. (ed.).1988.Northern Gulf of Mexico continental slope study, final report: Year 4.Volume II:

Synthesis report.Final report submitted to the Minerals Management Service, New Orleans, LA.

Contract No. 14Ͳ12Ͳ0001Ͳ30212.

Gallaway, B.J. and G.S. Lewbel.1982.The ecology of petroleum platforms in the northwestern Gulf of Mexico: a

community profile.U.S. Fish and Wildlife Service, Washington, DC, FWS/OBSͲ82/27.U.S. Department of the

Interior, Bureau of Land Management, Metairie, LA, Open File Report 82Ͳ03.92 pp.

http://www.nwrc.usgs.gov/techrpt/82Ͳ27text.pdf

Gallaway, B.J., J.G. Cole, and R.G. Fechhelm.2003.Selected aspects of the ecology of the continental slope fauna

of the Gulf of Mexico: A synopsis of the Northern Gulf of Mexico Continental Slope Study, 1983Ͳ1988.

U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA.

OCS Study MMS 2003Ͳ072.

Geoscience Earth & Marine Services, Inc. (GEMS).2013.Archaeological ROV Survey, Coronado Prospect,

Block 143, Walker Ridge Area, Gulf of Mexico.Report for Chevron U.S.A. Inc., Houston, TX.Project No. 0613Ͳ

2251.August 2013.

Geraci, J.R. and D.J. St. Aubin.1987.Effects of offshore oil and gas development on marine mammals and turtles,

pp. 587Ͳ617.In: D.F. Boesch and N.N. Rabalais (eds.), Long Term Environmental Effects of Offshore Oil and

Gas Development.Elsevier Applied Science Publ. Ltd., London and New York.

Geraci, J.R. and D.J. St. Aubin.1990.Sea Mammals and Oil: Confronting the Risks.Academic Press, San Diego.

Gulf of Mexico Fishery Management Council (GMFMC).2005.Generic Amendment Number 3 for addressing

Essential Fish Habitat Requirements, Habitat Areas of Particular Concern, and adverse effects of fishing in the

following Fishery Management Plans of the Gulf of Mexico: Shrimp fishery of the Gulf of Mexico, United States

waters red drum fishery of the Gulf of Mexico, reef fish fishery of the Gulf of Mexico coastal migratory pelagic

resources (mackerels) in the Gulf of Mexico and South Atlantic, stone crab fishery of the Gulf of Mexico, spiny

lobster in the Gulf of Mexico and South Atlantic, coral and coral reefs of the Gulf of Mexico.Gulf of Mexico

Fishery Management Council, Tampa, FL.

Hazen, T.C., E.A. Dubinsky, T.Z. DeSantis, G.L. Andersen, Y.M. Piceno, N. Singh, J.K. Jansson, A. Probst, S.E. Borglin,

J.L. Fortney, W.T. Stringfellow, M. Bill, M.S. Conrad, L.M. Tom, K.L. Chavarria, T.R. Alusi, R. Lamendella,

D.C. Joyner, C. Spier, J. Baelum, M. Auer, M.L. Zemla, R. Chakraborty, E.L. Sonnenthal, P. D’haeseleer,

H.N. Holman, S. Osman, Z. Lu, J.D. Van Nostrand, Y. Deng, J. Zhou, and O.U. Mason.2010.DeepͲsea oil plume

enriches indigenous oilͲdegrading bacteria.Science DOI: 10.1126/science.1195979.

Hernandez, F.J., R.F. Shaw, J.S. Cope, J.G. Ditty, T. Farooqi., M.C. Benfield.2003.The acrossͲshelf larval, postlarval,

and juvenile fish assemblages collected at offshore oil and gas platforms west of the Mississippi River Delta.

American Fisheries Society Symposium 36:39–72.

http://www.usm.edu/gcrl/cv/hernandez.frank/docs/Hernandez.et.al.2003.across.shelf.fish.assemblages.pdf

Hess, N.A. and C.A. Ribic.2000.Seabird ecology, pp. 275Ͳ315.In: R.W. Davis, W.E. Evans, and B. Würsig (eds.),

Cetaceans, sea turtles, and seabirds in the northern Gulf of Mexico: Distribution, abundance and habitat

associations.Volume II: Technical report.U.S. Geological Survey, Biological Resources Division,

USGS/BRD/CRͲ1999Ͳ0006 and U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico

OCS Region, New Orleans, LA.OCS Study MMS 2000Ͳ003.346 pp.

Higashi, G.R.1994.Ten years of fish aggregating device (FAD) design and development in Hawaii.Bull. Mar. Sci.

55(2Ͳ3):651Ͳ666.

Holand, P.1997.Offshore Blowouts: Causes and Control.Gulf Publishing Co., Houston, TX.ISBN 0884155145.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 67

Holland, K.R., R.W. Brill, and R.K.C. Chang.1990.Horizontal and vertical movements of yellowfin and bigeye tuna

associated with fish aggregating devices.Fish. Bull. 88:493Ͳ507.

IEM.2010.A Study of the Economic Impact of the Deepwater Horizon Oil Spill.Prepared for Greater

New Orleans, Inc.October 2010.http://gnoinc.org/wpͲcontent/uploads/Economic_Impact_Study_Part_I_Ͳ

_Full_Report1.pdf

InterͲAgency Economic Report.2010.Estimating the effects of the deepwater drilling moratorium on the Gulf

coast economy.September 2010.

http://www.esa.doc.gov/sites/default/files/reports/documents/drillingmoratorium.pdf

International Association of Oil & Gas Producers.2010.Risk assessment data directory: Blowout frequencies.

IAGP Report No. 434Ͳ2.March 2010.http://www.ogp.org.uk/pubs/434Ͳ02.pdf

International Crane Foundation.2012.Whooping crane.https://www.savingcranes.org/whoopingͲcrane.html

Ji, ZͲG., W.R. Johnson, C.F. Marshall, and E.M. Lear.2004.OilͲSpill Risk Analysis: Contingency Planning Statistics

for Gulf of Mexico OCS Activities.U.S. Department of the Interior, Minerals Management Service, Gulf of

Mexico OCS Region.OCS Report MMS 2004Ͳ026.

Jochens, A., D. Biggs, K. BenoitͲBird, D. Engelhaupt, J. Gordon, C. Hu, N. Jaquet, M. Johnson, R. Leben, B. Mate,

P. Miller, J. OrtegaͲOrtiz, A. Thode, P. Tyack, and B. Würsig.2008.Sperm whale seismic study in the

Gulf of Mexico: Synthesis report.U.S. Department of the Interior, Minerals Management Service,

Gulf of Mexico OCS Region, New Orleans, LA.OCS Study MMS 2008Ͳ006.341 pp.

Johnsgard, P.A.1990.Hawks, Eagles, and Falcons of North America; Biology and Natural History.Smithsonian

Institute Press, Washington.403 pp.

Joint Analysis Group.2010a.Joint Analysis Group (JAG) review of preliminary data to examine subsurface oil in

the vicinity of MC252#1 May 19 to June 19, 2010.

http://gomex.erma.noaa.gov/layerfiles/7229/files/JAG_Data_Report_2_Subsurface%20Oil_Final.pdf

Joint Analysis Group.2010b.Joint Analysis Group (JAG) review of R/V Brooks McCall data to examine subsurface

oil.http://www.noaa.gov/sciencemissions/PDFs/JAG_Report_1_BrooksMcCall_Final_June20.pdf

Joint Analysis Group.2010c.Joint Analysis Group (JAG) review of preliminary data to examine oxygen levels in the

vicinity of MC252#1 May 8 to August 9, 2010.

http://www.noaa.gov/sciencemissions/PDFs/JAG_Oxygen_Report%20%28FINAL%20090410%29.pdf

Kennicutt, M.C. II.2000.Chemical Oceanography, pp. 123Ͳ139.In: Continental Shelf Associates, Inc.Deepwater

Program: Gulf of Mexico deepwater information resources data search and literature synthesis.Volume I:

Narrative report.U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region,

New Orleans, LA.OCS Study MMS 2000Ͳ049.

King, B.S. and J.D. Gibbins.2011.Health hazard evaluation of Deepwater Horizon response workers.Centers for

Disease Control and Prevention, National Institute for Occupational Safety and Health.Health Hazard

Evaluation Report HETA 2010Ͳ0115 & 2010Ͳ0129Ͳ3138.August 2011.

http://www.cdc.gov/niosh/hhe/reports/pdfs/2010Ͳ0115Ͳ0129Ͳ3138.pdf

Lin, Q. and I.A. Mendelssohn.2012.Impacts and recovery of the Deepwater Horizon oil spill on vegetation

structure and function of coastal salt marshes in the northern Gulf of Mexico.Environ. Sci. Technol.

46(7): 3,737Ͳ3,743.

Lohoefener, R., W. Hoggard, K. Mullin, C. Roden, and C. Rogers.1990.Association of sea turtles with petroleum

platforms in the northͲcentral Gulf of Mexico.U.S. Department of the Interior, Minerals Management Service,

Gulf of Mexico OCS Region, New Orleans, LA.OCS Study MMS 90Ͳ0025.90 pp.

Louisiana Department of Wildlife and Fisheries.2013.Tracking List and Fact Sheets.Website accessed

25 July 2013.http://www.wlf.louisiana.gov/wildlife/rareͲanimalsͲfactͲsheets.

Lutcavage, M.E., P.L. Lutz, G.D. Bossart, and D.M. Hudson.1995.Physiologic and clinicopathologic effects of crude

oil on loggerhead sea turtles.Arch. Environ. Contam. Toxicol. 28:417Ͳ422.

Lutcavage, M.E., P. Plotkin, B. Witherington, and P.L. Lutz.1997.Human impacts on sea turtle survival,

pp. 387Ͳ409.In: Lutz, P.L. and J.A. Musick (eds.), The Biology of Sea Turtles. CRC Press, Boca Raton, FL.

MacDonald, I.R. (ed.).2002.Stability and Change in Gulf of Mexico Chemosynthetic Communities.Volume II:

Technical Report.U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region,

New Orleans, LA.OCS Study MMS 2002Ͳ036.456 pp.

Marine Mammal Commission (MMC).2012.The Deepwater Horizon Oil Spill and Marine Mammals.

http://www.mmc.gov/oil_spill/welcome.shtml
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 68

Mendelssohn, I.A., G.L. Andersen, D.M. Baltz, R.H. Caffey, K.R. Carman, J.W. Fleeger, S.B. Joye, Q. Lin, E. Maltby,

E.B. Overton, and L. P. Rozas.2012.Oil Impacts on Coastal Wetlands: Implications for the Mississippi River

Delta Ecosystem after the Deepwater Horizon Oil Spill.BioScience, 62(6):562Ͳ574.

http://www.jstor.org/discover/10.1525/bio.2012.62.6.7?uid=3739600&uid=2129&uid=2&uid=70&uid=4&uid=

3739256&sid=21102052664157

Minerals Management Service (MMS).2000.Gulf of Mexico Deepwater Operations and Activities: Environmental

Assessment.U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region,

New Orleans, LA.OCS EIS/EA MMS 2000Ͳ001.

Minerals Management Service (MMS).2007a.Outer Continental Shelf Oil & Gas Leasing Program: 2007Ͳ2012

Final Environmental Impact Statement.U.S. Department of the Interior, Minerals Management Service,

Herndon, VA.OCS EIS/EA MMS 2007Ͳ003.April 2007.

Minerals Management Service (MMS).2007b.Gulf of Mexico OCS Oil and Gas Lease Sales: 2007Ͳ2012.Western

Planning Area Sales 204, 207, 210, 215, and 218; Central Planning Area Sales 205, 206, 208, 213, 216, and 222.

Final Environmental Impact Statement.U.S. Department of the Interior, Minerals Management Service,

Gulf of Mexico OCS Region.OCS EIS/EA MMS 2007Ͳ018.April 2007.

Mississippi Natural Heritage Program.2011.Listed species of Mississippi: 2011.

http://www.mdwfp.com/media/127066/endangered_species_list.pdf.

Morrow, J.V., Jr., J.P. Kirk, K.J. Killgore, H. Rugillio, and C. Knight.1998.Status and recovery of Gulf sturgeon in the

Pearl River system, LouisianaͲMississippi.North American Journal of Fisheries Management 18:798Ͳ808.

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers, and B. Taggart.1991.Cetaceans on the upper

continental slope in the northͲcentral Gulf of Mexico.OCS Study/MMS 910027.U.S. Department of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, LA.108 pp.

National Marine Fisheries Service (NMFS).2007.Endangered Species Act, Section 7 Consultation – Biological

Opinion.Gulf of Mexico Oil and Gas Activities: FiveͲYear Leasing Plan for Western and Central Planning Areas

2007Ͳ2012.29 June 2007.

National Marine Fisheries Service (NMFS).2009.Final Amendment 1 to the Consolidated Atlantic Highly

Migratory Species Fishery Management Plan Essential Fish Habitat.Highly Migratory Species Management

Division, Office of Sustainable Fisheries, Silver Spring, MD.June 2009.

http://www.nmfs.noaa.gov/sfa/hms/EFH/Final/FEIS_Amendment_Total.pdf

National Marine Fisheries Service (NMFS).2010a.Final recovery plan for the sperm whale

(Physeter macrocephalus).Silver Spring, MD.165 pp.

http://www.nmfs.noaa.gov/pr/pdfs/recovery/final_sperm_whale_recovery_plan_21dec.pdf

National Marine Fisheries Service (NMFS).2010b.Gulf sturgeon (Acipenser oxyrinchus desotoi).

http://www.nmfs.noaa.gov/pr/species/fish/gulfsturgeon.htm

National Marine Fisheries Service (NMFS).2010c.Deepwater Horizon Response Consolidated Fish and Wildlife

Collection Report, November 2, 2010.

http://www.restorethegulf.gov/sites/default/files/documents/pdf/Consolidated%20Wildlife%20Table%20110

210.pdf

National Marine Fisheries Service (NMFS).2011a.Sea turtles, dolphins, and whales and the Gulf of Mexico oil

spill.http://www.nmfs.noaa.gov/pr/health/oilspill.htm

National Marine Fisheries Service (NMFS).2011b.Species of concern:Atlantic bluefin tuna, Thunnus thynnus.

16 November 2011.http://www.nmfs.noaa.gov/pr/pdfs/species/bluefintuna_detailed.pdf

National Marine Fisheries Service (NMFS).2011c.Deepwater Horizon/BP oil spill: size and percent coverage of

fishing area closures due to BP oil spill.http://sero.nmfs.noaa.gov/ClosureSizeandPercentCoverage.htm

National Marine Fisheries Service (NMFS).2013.Draft marine mammal stock assessment reports (SARs).Updated

January 23, 2013.http://www.nmfs.noaa.gov/pr/sars/draft.htm

National Marine Fisheries Service (NMFS) and U.S. Fish and Wildlife Service (USFWS).2008.Recovery plan for the

Northwest Atlantic population of the loggerhead sea turtle (Caretta caretta), second revision.National

Marine Fisheries Service, Silver Spring, MD.

http://www.nmfs.noaa.gov/pr/pdfs/recovery/turtle_loggerhead_atlantic.pdf

National Marine Fisheries Service (NMFS), U.S. Fish and Wildlife Service (USFWS), and SEMARNAT.2010.

BiͲNational Recovery Plan for the Kemp‘s Ridley Sea Turtle (Lepidochelys kempii), Second Revision.National

Marine Fisheries Service.Silver Spring, Maryland.http://www.fws.gov/kempsridley/pdfs/DraftKRRP.pdf
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 69

National Oceanic and Atmospheric Administration (NOAA).2006.Fact Sheet: Small Diesel Spills

(500Ͳ5,000 gallons).NOAA Scientific Support Team, Hazardous Materials Response and Assessment Division,

National Oceanic and Atmospheric Administration.Seattle, Washington.2 pp.

National Park Service (NPS).2010.Breton Wilderness 300 km Radius.

http://www.fws.gov/refuges/AirQuality/docs/Breton_WA300km.pdf

National Research Council (NRC).1983.Drilling Discharges in the Marine Environment.National Academy Press,

Washington, DC.180 pp.

National Research Council (NRC).2003.Oil in the Sea III: Inputs, Fates, and Effects.National Academies Press,

Washington, DC.182 pp. + app.

Nedwell, J. and B. Edwards.2004.A review of the measurements of underwater manͲmade noise carried out by

Subacoustech Ltd, 1993Ͳ2003.Subacoustech Report 534R0109.

http://www.subacoustech.com/information/downloads/reports/534R0109.pdf

Neff, J.M.1987.Biological effects of drilling fluids, drill cuttings and produced waters, pp. 469Ͳ538.

In: D.F. Boesch and N.N. Rabalais (eds.), LongͲTerm Effects of Offshore Oil and Gas Development.Elsevier

Applied Science Publishers, London.

Neff, J.M., S. McKelvie, and R.C. Ayers, Jr.2000.Environmental impacts of synthetic based drilling fluids.

Prepared by Robert Ayers & Associates, Inc.U.S. Department of the Interior, Minerals Management Service,

Gulf of Mexico OCS Region, New Orleans, LA.OCS Study MMS 2000Ͳ064.118 pp.

Neff, J.M., A.D. Hart, J.P. Ray, J.M. Limia, and T.W. Purcell.2005.An assessment of seabed impacts of

syntheticͲbased drillingͲmud cuttings in the Gulf of Mexico.2005 SPE/EPA/DOE Exploration and Production

Environmental Conference, 7Ͳ9 March 2005, Galveston, Texas, USA.SPE 94086.

Nowlin, W.D., Jr., A.E. Jochens, S.F. DiMarco, R.O. Reid, and M.K. Howard.2001.Deepwater Physical

Oceanography Reanalysis and Synthesis of Historical Data: Synthesis Report.U.S. Department of the Interior,

Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA.OCS Study MMS 2001Ͳ064.

528 pp.

Operational Science Advisory Team (OSAT).2010.Summary report for subͲsurface and subͲsea oil and dispersant

detection: Sampling and monitoring.Prepared for Paul F. Zukunft, U.S. Coast Guard Federal OnͲScene

Coordinator, Deepwater Horizon MC252.December 17, 2010.

http://www.restorethegulf.gov/sites/default/files/documents/pdf/OSAT_Report_FINAL_17DEC.pdf

Oxford Economics.2010.Potential impact of the Gulf oil spill on tourism.Report prepared for the U.S. Travel

Association.http://www.ustravel.org/sites/default/files/page/2009/11/Gulf_Oil_Spill_Analysis_Oxford_Economics_710.pdf

Peabody, M.B. and C.A. Wilson.2006.Fidelity of red snapper (Lutjanus campechanus) to petroleum platforms and

artificial reefs in the northern Gulf of Mexico.U.S. Department of the Interior, Minerals Management Service,

Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2006Ͳ005. 66 pp.

http://www.data.boem.gov/PI/PDFImages/ESPIS/3/3413.pdf

Peake, D.E.1996.Bird surveys, pp. 271Ͳ304.In: R.W. Davis and G.S. Fargion (eds.), Distribution and abundance of

cetaceans in the northͲcentral and western Gulf of Mexico, Final report.Volume II: Technical report.

Prepared by the Texas Institute of Oceanography and the National Marine Fisheries Service.U.S. Department

of the Interior, Minerals Management Service, Gulf of Mexico OCS Region Office, New Orleans, LA.OCS Study

MMS 96Ͳ0027.357 pp.

Poot, H., B.J. Ens, H. de Vries, M.A.H. Donners, M.R. Wernand, and J.M. Marquenie.2008.Green light for

nocturnally migrating birds.Ecology and Society 13(2):47.

http://www.ecologyandsociety.org/vol13/iss2/art47

Powers, K.1987.Seabirds, pp. 194Ͳ201.In: J.D. Milliman and W.R. Wright (eds.), The Marine Environment of the

U.S. Atlantic Continental Slope and Rise.Jones and Bartlett Publ., Inc. Boston/Woods Hole, MA.275 pp.

Rathbun, G.B.1988.FixedͲwing airplane versus helicopter surveys of manatees.Mar. Mamm. Sci. 4(1):71Ͳ75.

Relini, M., L.R. Orsi, and G. Relini.1994.An offshore buoy as a FAD in the Mediterranean.Bull. Mar. Sci.

55(2Ͳ3):1,099Ͳ1,105.

Richards, W.J., T. Leming, M.F. McGowan, J.T. Lamkin, and S. KelleyͲFarga.1989.Distribution of fish larvae in

relation to hydrographic features of the Loop Current boundary in the Gulf of Mexico.Rapp. P.Ͳv. Reun. Cons.

Int. Explor. Mer. 191:169Ͳ176.

Richards, W.J., M.F. McGowan, T. Leming, J.T. Lamkin, and S. Kelley.1993.Larval fish assemblages at the Loop

Current boundary in the Gulf of Mexico.Bull. Mar. Sci. 53(2):475Ͳ537.
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 70

Richardson, W.J., C.R. Greene, Jr., C.I. Malme, and D.H. Thomson.1995.Marine Mammals and Noise.Academic

Press, San Diego.576 pp.

Rodgers, J., Jr. and S. Schwikert.2002.Buffer Zone Distances to Protect Foraging and Loafing Waterbirds from

Disturbances by Personal Watercraft and OutboardͲPowered Boats.Conservation Biology 16:216Ͳ224.

Ross, S.W., A.W.J. Demopoulos, C.A. Kellogg, C.L. Morrison, M.S. Nizinski, C.L. Ames, T.L. Casazza, D. Gualtieri,

K. Kovacs, J.P. McClain, A.M. Quattrini, A.Y. RoaͲVarón, and A.D. Thaler.2012.Deepwater Program: Studies of

Gulf of Mexico lower continental slope communities related to chemosynthetic and hard substrate habitats.

U.S. Geological Survey OpenͲFile Report 2012Ͳ1032.301 pp.

http://pubs.usgs.gov/of/2012/1032/pdf/USGS_CHEMOIII_Report.pdf

Rowe, G.T. and M.C. Kennicutt II.2009.Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology

Study.Final Report.U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico

OCS Region, New Orleans, LA.OCS Study MMS 2009Ͳ039.456 pp.

Russell, R.W.2005.Interactions between migrating birds and offshore oil and gas platforms in the northern

Gulf of Mexico: Final Report.U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico

OCS Region, New Orleans, LA.OCS Study MMS 2005Ͳ009.348 pp.

Salmon, M. and J. Wyneken.1990.Do swimming loggerhead sea turtles (Caretta caretta) use light cues for

offshore orientation?Mar. Freshw. Behav. Phy. 17(4): 233Ͳ246.

Share the Beach.2012.Nesting season statistics.http://www.alabamaseaturtles.com/nestingͲseasonͲstatistics

Shaw, R.F., D.C. Lindquist, M.C. Benfield, T. Farooqi, and J.T. Plunket.2002.Offshore petroleum platforms:

functional significance for larval fish across longitudinal and latitudinal gradients.Prepared by Coastal

Fisheries Institute, Louisiana State University.U.S. Department of the Interior, Minerals Management Service,

Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2002Ͳ077.107 pp.

http://www.data.boem.gov/PI/PDFImages/ESPIS/3/3092.pdf

Smultea, M.A., J.R. Mobley, Jr., D. Fertl, and G.L. Fulling.2008.An unusual reaction and other observations of

sperm whales near fixed wing aircraft.Gulf Carib. Res. 20:75Ͳ80.

Solomon, G.M. and S. Janssen.2010.Health effects of the Gulf oil spill.J. Amer. Med. Assoc.

http://www.asquifyde.es/uploads/documentos/HealthͲEffectsͲofͲtheͲGulfͲOilͲSpill.pdf

Sulak, K.J. and J.P. Clugston.1998.Early life history stages of Gulf sturgeon in the Suwannee River, Florida.Trans.

Am. Fish. Soc. 127:758Ͳ771.

Tuxbury, S.M. and M. Salmon.2005.Competitive interactions between artificial lighting and natural cues during

seafinding by hatchling marine turtles.Biol. Conserv. 121: 311Ͳ316.

U.S. Environmental Protection Agency (USEPA).2013.The green book nonattainment areas for criteria pollutants.

http://www.epa.gov/air/oaqps/greenbk.

U.S. Fish and Wildlife Service (USFWS).2001.Florida manatee recovery plan (Trichechus manatus latirostris),

Third Revision.U.S. Fish and Wildlife Service, Southeast Region, Atlanta, GA.

U.S. Fish and Wildlife Service (USFWS).2003.Recovery plan for the Great Lakes Piping Plover (Charadrius

melodus).Fort Snelling, Minnesota.September 2003.

U.S. Fish and Wildlife Service (USFWS).2007.International Recovery Plan: Whooping Crane (Grus americana),

Third Revision.Albuquerque, New Mexico.March 2007.

U.S. Fish and Wildlife Service (USFWS).2010a.All about piping plovers.http://www.fws.gov/plover/facts.html

U.S. Fish and Wildlife Service (USFWS).2010b.FWS Deepwater Horizon oil spill response.

http://www.fws.gov/home/dhoilspill/pdfs/DHBirdsOfTheGulf.pdf

U.S. Fish and Wildlife Service (USFWS).2010c.Species information, threatened and endangered animals and

plants.http://www.fws.gov/endangered/

U.S. Fish and Wildlife Service (USFWS).2010d.Effects of oil on wildlife and habitat.

http://www.fws.gov/home/dhoilspill/pdfs/DHJICFWSOilImpactsWildlifeFactSheet.pdf

U.S. Fish and Wildlife Service (USFWS).2011a.Hawksbill sea turtle (Eretmochelys imbricata).

http://www.fws.gov/northflorida/SeaTurtles/Turtle%20Factsheets/hawksbillͲseaͲturtle.htm

U.S. Fish and Wildlife Service (USFWS).2011b.Bird impact data and consolidated wildlife reports.Last updated

May 12, 2011.http://www.fws.gov/home/dhoilspill/collectionreports.html

U.S. Fish and Wildlife Service (USFWS) and Gulf States Marine Fisheries Commission.1995.Gulf Sturgeon

Recovery Plan.Atlanta, Georgia.170 pp.http://www.nmfs.noaa.gov/pr/pdfs/recovery/sturgeon_gulf.pdf
Walker Ridge Block 143 November 2013

Environmental Impact Analysis for Revised Exploration Plan Page 71

U.S. Geological Survey.2011.ColdͲwater coral ecosystem studies: U.S. Gulf of Mexico.

http://fl.biology.usgs.gov/pdf/20100504Gulf_corals_v1.pdf

Van de Laar, F.2007.Green light to birds: Investigation into the effect of birdͲfriendly lighting.NAM Locatie

L15ͲFAͲ1.December 2007.

http://www.waddenzee.nl/fileadmin/content/Dossiers/Energie/pdf/green_light_to_birdsNAM.pdf

Wakeford, A.2001.State of Florida conservation plan for Gulf sturgeon (Acipencer oxyrinchus desotoi).Florida

Marine Research Institute Technical Report TRͲ8.St. Petersburg, FL.

Waring, G.T., E. Josephson, K. MazeͲFoley, and P.E. Rosel (eds.).2013.U.S. Atlantic and Gulf of Mexico Marine

Mammal Stock Assessments – 2012.March 2013.http://www.nmfs.noaa.gov/pr/sars/pdf/ao2012.pdf

Wei, CͲL.2006.The bathymetric zonation and community structure of deepͲsea macrobenthos in the northern

Gulf of Mexico.M.S. thesis, Texas A&M University.http://repository.tamu.edu/handle/1969.1/4927

White, H.K., P. Hsing, W. Cho, T.M. Shank, E.E. Cordes, A.M. Quattrini, R.K. Nelson, R. Camilli, A.W.J. Demopoulous,

C.R. German, J.M. Brooks, H.H. Roberts, W. Shedd, C.M. Reddy, and C.R. Fisher.2012a.Impact of the

Deepwater Horizon oil spill on a deepͲwater coral community in the Gulf of Mexico.Proc. Nat. Acad. Sci. Early

Edition. doi:10.1073/pnas.1118029109.http://www.pnas.org/content/early/2012/03/23/1118029109.full.pdf

White, H.K., P. Hsing, W. Cho, T.M. Shank, E.E. Cordes, A.M. Quattrini, R.K. Nelson, R. Camilli, A.W.J. Demopoulous,

C.R. German, J.M. Brooks, H.H. Roberts, W. Shedd, C.M. Reddy, and C.R. Fisher.2012b.Reply to Boehm and

Carragher: Multiple lines of evidence link deepͲwater coral damage to Deepwater Horizon oil spill.Proc.Nat.

Acad. Sci. 109 (40): E2648.doi/10.1073/pnas.1210413109.

Whooping Crane Eastern Partnership.2012.Whooping crane numbers, 2002 thru 2011.

http://www.bringbackthecranes.org/technicaldatabase/recovery/wc_nos_02to11.html

Wiese, F.K., W.A. Montevecchi, G.K. Davoren, F. Huettmann, A.W. Diamond, and J. Linke.2001.Seabirds at risk

around offshore oil platforms in the northͲwest Atlantic.Mar. Poll. Bull. 42(12):1,285Ͳ1,290.

Williams, R., S. Gero, L. Bejder, J. Calambokidis, S.D. Krauss, D. Lusseau, A.J. Read, and J. Robbins.2011.

Underestimating the damage: Interpreting cetacean carcass recoveries in the context of the Deepwater

Horizon BP incident.Conservation Letters 0:1Ͳ6.

Wilson, J.2003.Manatees in Louisiana. Louisiana Conservationist.July/August 2003, pp. 4Ͳ7.

http://www.lamer.lsu.edu/pdfs/Manatees_LaConservArticle.pdf

Wilson, C.A., A. Pierce, and M.W. Miller.2003.Rigs and reefs: A comparison of the fish communities at two

artificial reefs, a production platform, and a natural reef in the northern Gulf of Mexico.U.S. Department of

the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS Study

MMS 2003Ͳ009.95 pp.http://www.data.boem.gov/PI/PDFImages/ESPIS/0/176.pdf

Wilson, C.A., M.W. Miller, Y.C. Allen, K.M. Boswell, and D.L. Nieland.2006.Effects of depth, location, and habitat

type on relative abundance and species composition of fishes associated with petroleum platforms and

Sonnier Bank in the northern Gulf of Mexico.U.S. Department of the Interior, Minerals Management Service,

Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2006Ͳ037.85 pp.

http://www.data.boem.gov/PI/PDFImages/ESPIS/3/3603.pdf

Witherington, B.E.1997.The problem of photopollution for sea turtles and other nocturnal animals, pp. 303Ͳ328.

In: J.R. Clemmons and R. Buchholz (eds.), Behavioral Approaches to Conservation in the Wild.Cambridge

University Press, Cambridge, England.

Würsig, B., S.K. Lynn, T.A. Jefferson, and K.D. Mullin.1998.Behaviour of cetaceans in the northern Gulf of Mexico

relative to survey ships and aircraft.Aquat. Mamm. 24: 41Ͳ50.

Würsig, B., T.A. Jefferson, and D.J. Schmidly.2000.The Marine Mammals of the Gulf of Mexico.Texas A&M

University Press, College Station, TX.232 pp.


September 24, 2013 Public Information

REVISED EXPLORATION PLAN 

UNION OIL COMPANY OF CALIFORNIA

(An Affiliate of CHEVRON U.S.A. INC.)

WALKER RIDGE BLOCK 143

OCS-G 21849

OFFSHORE LOUISIANA

“CORONADO” PROSPECT

SECTION A PLAN CONTENTS 

SECTION B GENERAL INFORMATION 

SECTION C GEOLOGICAL AND GEOPHYSICAL INFORMATION 

SECTION D HYDROGEN SULFIDE (H2S) INFORMATION

SECTION E BIOLOGICAL, PHYSICAL, AND SOCIOECONOMIC INFORMATION

SECTION F WASTE AND DISCHARGE INFORMATION

SECTION G AIR EMISSIONS INFORMATION

SECTION H OIL SPILLS INFORMATION

SECTION I ENVIRONMENTAL MONITORING INFORMATION

SECTION J LEASE STIPULATIONS INFORMATION

SECTION K ENVIRONMENTAL MITIGATION MEASURES INFORMATION

SECTION L SUPPORT VESSELS AND AIRCRAFT INFORMATION

SECTION M ONSHORE SUPPORT FACILITIES INFORMATION

SECTION N COASTAL ZONE MANAGEMENT ACT (CZMA) INFORMATION

SECTION O ENVIRONMENTAL IMPACT ANALYSIS (EIA)

SECTION P ADMINISTRATIVE INFORMATION
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION A PLAN CONTENTS

(a) PLAN INFORMATION FORM

Union Oil Company of California, an affiliate of Chevron U.S.A. Inc. (Chevron), plans to use a Subsea BOP in the 

drilling of the wells proposed in this plan.

The Worst Case Discharge number for this plan was previously reviewed in Revised Plan R-5084 and approved on 

June 16, 2011.

This Revised Exploration Plan (REP) revises the location of the two remaining approved wells, WR 143 “G” and “H”

in plan R-5084 by moving them more than 500 feet. The revised locations are renamed WR 143 “A” and “B”.

Well location “J”, approved in plan R-5084, was drilled and permanently abandoned in 2011.

Proposed Schedule

Proposed Activity Estimated 

Start Date

Estimated 

End Date

Estimated 

No. of Days

Drill and temporarily abandon well location A 11/15/2013 04/13/2014 150

Drill and temporarily abandon well location B 1/1/2015 05/30/2015 150

Included as attachment A-1 at the end of this section is Form BOEM-0137 “OCS Plan Information Form”.

(b) LOCATION / BATHYMETRY MAP

Included as attachments A-2 and A-3 are a location map at a scale of 1”=2,000’ showing the surface locations for the 

proposed wells and a bathymetry map of the area at a scale of 1”=2,000’ with the surface locations of the proposed 

wells.

(c) SAFETY and POLLUTION PREVENTION FEATURES 

Chevron plans to use a dynamically positioned drillship to drill the wells proposed in this plan. The wells will be 

drilled using a Subsea BOP system. Rig specifications will be provided with the Applications for Permit to Drill. If 

another rig type is used, any differences regarding air emissions, safety, drilling or pollution control equipment will be 

addressed in a revised Exploration Plan. 

In accordance with 30 CFR 250.406, safety features will include well control, pollution prevention, welding procedure, 

and blowout prevention equipment and as further clarified by the Bureau of Safety and Environmental Enforcement 

(BSEE) and the Bureau of Ocean Energy Management (BOEM) Notices to Lessees (NTL’s) and current policy 

making invoked by BSEE and BOEM.

The rig will be monitored daily by a Chevron drilling representative and any waste or fuel resulting in pollution of the 

Gulf waters will be reported to the representative in charge for immediate isolation and correction of the problem. 

Any spill will be reported to governmental agencies. Chevron will comply with all BSEE and BOEM regulations 

during the course of the activities. 

The rig is equipped with safety, fire fighting, and lifesaving equipment required for compliance with USCG, ABS, 

SOLAS, and IMO code requirements.
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

Chevron will comply with all pertinent regulations in 30 CFR 250.203, NTL’s, and all applicable federal and state 

requirements. Chevron will maintain compliance with the EPA NPDES Permit and lease agreement during these 

proposed activities.

(d) TABLE of STORAGE TANKS and PRODUCTION VESSELS

Information regarding the storage tanks that will be used to conduct the proposed activities in this plan that will store 

oil, as defined at 30 CFR 254.6, is provided in the table below. Only those tanks with a capacity of 25 barrels or 

more are included.

Type of Storage 

Tank

Type of 

Facility

Tank Capacity 

(bbls)

Number of 

Tanks

Total Capacity 

(bbls)

Fluid Gravity 

(API)

Main Fuel Oil

Drillship

18,000 2 36,000

No. 2 diesel

Diesel Settling 837 2 1674

Diesel Day 837 2 1674

Emergency Diesel 100 1 100

Diesel Overflow 823 1 823

Diesel Oil Drain Aft 42 1 42

Engine Oil Storage 182 1 182 26.2

Gear Oil Aft 62 1 62 27

Gear Oil Fwd 176 1 176 27

Hydraulic Oil Aft 84 1 84 31

Hydraulic Oil Fwd 87 1 87 31

(f) MEASURES to PREVENT DISCHARGE of OILS and GREASES DURING RAINFALL and ROUTINE 

OPERATIONS

The drillship is equipped with a comprehensive network of piping, drains and scuppers to minimize the risk that no 

pollutants are discharged into the marine environment.

All drains and drain material are collected in various holding tanks and located in the ship and then processed by the 

oily water separator systems. Clean water, either from hazardous or nonhazardous sources, may be directed 

overboard according to regulatory requirements if the effluent discharge is within the environmental limits. Any 

remaining sludge and oil are directed to the necessary holding tanks for proper disposal according to regulatory 

requirements.

(g) ADDITIONAL SAFETY, POLLUTION PREVENTION, and EARLY SPILL DETECTION MEASURES BEYOND 

THOSE REQUIRED IN 30 CFR 250

In addition to pollution prevention measures utilized by Chevron, the drill ship has a comprehensive, proactive plan to 

address emergency situations that could result in an unanticipated oil/chemical release. The “Shipboard Oil Pollution 

Emergency Plan” has specific checklists and procedures to address accidental releases due to fuel/oil transfer, tank 

overflow, hull leakage, fire, explosion, collision and grounding. This plan is reviewed annually and oil pollution 

prevention drills are conducted as specified by MARPOL regulations. There is a fully stocked environmental 

equipment locker located on the main deck, forward of the Moon-pool and numerous spill kits located throughout the 

main deck. The decks of the drillship are fully contained, a comprehensive scupper management plan in place, and 

any spills on the deck would be immediately cleaned up using absorbents or permitted solvents.

ATTACHMENTS TO SECTION A

• A-1- Form BOEM-0137 “OCS Plan Information Form” Public Information Copy

• A-2- Location Plat, Scale: 1”=2,000’

• A-3- Bathymetry Plat, Scale: 1”=2,000’
U.S. Department of the Interior OMB Control Number: 1010-0151

Bureau of Ocean Energy Management OMB Approval Expires: 12/31/14

OCS PLAN INFORMATION FORM 

General Information 

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

Company Name: BOEM Operator Number: 

Address: Contact Person:

Phone Number:

E-Mail Address: 

If a service fee is required under 30 CFR 550.125(a), provide the Amount paid Receipt No. 

Project and Worst Case Discharge (WCD) Information

Lease(s): Area: Block(s): Project Name (If Applicable): 

Objective(s) Oil Gas Sulphur Salt Onshore Support Base(s): 

Platform/Well Name: Total Volume of WCD: API Gravity: 

Distance to Closest Land (Miles): Volume from uncontrolled blowout: 

Have you previously provided information to verify the calculations and assumptions for your WCD? Yes No 

If so, provide the Control Number of the EP or DOCD with which this information was provided 

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

Do you propose to use a vessel with anchors to install or modify a structure? Yes No 

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

Description of Proposed Activities and Tentative Schedule (Mark all that apply) 

Proposed Activity Start Date End Date No. of Days 

Exploration drilling 

Development drilling 

Well completion 

Well test flaring (for more than 48 hours) 

Installation or modification of structure 

Installation of production facilities 

Installation of subsea wellheads and/or manifolds 

Installation of lease term pipelines 

Commence production 

Other (Specify and attach description) 

Description of Drilling Rig Description of Structure 

Jackup Drillship Caisson Tension leg platform

Gorilla Jackup Platform rig Fixed platform Compliant tower 

Semisubmersible Submersible Spar Guyed tower

DP Semisubmersible Other (Attach Description) 

Drilling Rig Name (If Known): 

Floating production 

system 

Other (Attach Description) 

Description of Lease Term Pipelines 

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

Form BOEM- 0137 (December 2011- Supersedes all previous editions of this form which may not be used.) Page 1 of 4

X

Union Oil Company Of California 00003

1500 Louisiana St. Phil Von Dullen

Houston TX 77002 (832) 854-3644

pvondullen@chevron.com

N/A

OCS -G 21849 WR 143 Coronado

X X Leeville, LA

WR 143 J 22,137,417 bbls 28

156 156,994 bopd

X

R-5084

X

X

X

11/15/2013 05/30/2015 Well A, 150 days

Well B, 150 days

300 Total Drilling Days

X
OCS PLAN INFORMATION FORM (CONTINUED)

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

Proposed Well/Structure Location

Well or Structure Name/Number (If renaming well or 

structure, reference previous name): 

Previously reviewed under an approved EP or 

DOCD? 

Yes No 

Is this an existing well 

or structure? 

Yes No If this is an existing well or structure, list the 

Complex ID or API No. 

Do you plan to use a subsea BOP or a surface BOP on a floating facility to conduct your proposed activities? Yes No 

WCD info For wells, volume of uncontrolled 

blowout (Bbls/day): 

For structures, volume of all storage and 

pipelines (Bbls):

API Gravity of 

fluid

Surface Location Bottom-Hole Location (For Wells) Completion (For multiple completions, 

enter separate lines) 

Lease No. OCS OCS OCS

OCS

Area Name 

Block No. 

Blockline

Departures 

(in feet)

N/S Departure: F____ L N/S Departure: F____ L N/S Departure: F____ L

N/S Departure: F____ L 

N/S Departure: F____ L 

E/W Departure: F____ L E/W Departure: F____ L E/W Departure: F____ L 

E/W Departure: F____ L 

E/W Departure: F____ L 

Lambert XY

coordinates 

X: X: X: 

X:

X:

Y: Y: Y:

Y:

Y:

Latitude/

Longitude

Latitude Latitude Latitude 

Latitude

Latitude

Longitude Longitude Longitude 

Longitude

Longitude

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

Anchor Radius (if applicable) in feet: 

MD (Feet): 

MD (Feet): 

MD (Feet): 

TVD (Feet): 

TVD (Feet): 

TVD (Feet): 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor Chain on Seafloor 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

Form BOEM- 0137 (December 2011- Supersedes all previous editions of this form which may not be used.) Page 2 of 4

WR 143 A X

X

X

G 21849

WR

143

N

660 W

586

2154826

9740940

N 26° 50' 8.469"

W 91° 25' 19.596"

5760
OCS PLAN INFORMATION FORM (CONTINUED)

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

Proposed Well/Structure Location

Well or Structure Name/Number (If renaming well or 

structure, reference previous name): 

Previously reviewed under an approved EP or 

DOCD? 

Yes No 

Is this an existing well 

or structure? 

Yes No If this is an existing well or structure, list the 

Complex ID or API No. 

Do you plan to use a subsea BOP or a surface BOP on a floating facility to conduct your proposed activities? Yes No 

WCD info For wells, volume of uncontrolled 

blowout (Bbls/day): 

For structures, volume of all storage and 

pipelines (Bbls):

API Gravity of 

fluid

Surface Location Bottom-Hole Location (For Wells) Completion (For multiple completions, 

enter separate lines) 

Lease No. OCS OCS OCS

OCS

Area Name 

Block No. 

Blockline

Departures 

(in feet)

N/S Departure: F____ L N/S Departure: F____ L N/S Departure: F____ L

N/S Departure: F____ L 

N/S Departure: F____ L 

E/W Departure: F____ L E/W Departure: F____ L E/W Departure: F____ L 

E/W Departure: F____ L 

E/W Departure: F____ L 

Lambert XY

coordinates 

X: X: X: 

X:

X:

Y: Y: Y:

Y:

Y:

Latitude/

Longitude

Latitude Latitude Latitude 

Latitude

Latitude

Longitude Longitude Longitude 

Longitude

Longitude

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

Anchor Radius (if applicable) in feet: 

MD (Feet): 

MD (Feet): 

MD (Feet): 

TVD (Feet): 

TVD (Feet): 

TVD (Feet): 

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

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor Chain on Seafloor 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

Form BOEM- 0137 (December 2011- Supersedes all previous editions of this form which may not be used.) Page 2 of 4

WR 143 B X

X

X

G 21849

WR

143

N

2831 W

727

2154967

9738769

N 26° 49' 49.950"

W 91° 25' 18.337"

5593


Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION B GENERAL INFORMATION 

(a) APPLICATIONS AND PERMITS

In the table below, information is provided on the filing or approval status of the Federal, State, and local application 

approvals or permits that must be obtained to conduct the proposed activities. Only those individual or site-specific 

application approvals that must be obtained are listed.

Application/Permit Issuing Agency Status

NPDES Permit EPA Approved

EEP U.S. Coast Guard To be submitted

APD BSEE To be submitted

(b) DRILLING FLUIDS

(1) Information on the types (including chemical constituents) and amounts of the drilling fluids planned for use in 

drilling the proposed wells: 

Type of Drilling Fluid Est. Volume of Drilling Fluid

(bbls/well)

Water based (seawater, brine, freshwater) 110,003

Synthetic based (internal olefin, ester) 25,000

Oil based (diesel, mineral oil) 0

(2) Major Components of Synthetic-based drilling fluid listed above:

Product Name Amount to be Used Reference Number MSDS No.

Lime (Calcium Hydroxide) 2,700 50-lb bags CAS # 1302-78-9 10046

Calcium Chloride 26,200 50-lb bags CAS # 10043-52-4 10109

VG Plus 1,000 50-lb bags CAS # 68153-30-0 10128

VG Supreme 500 50-lb bags CAS # 14808-60-7 12207

Rheflat 7,000 gals CAS # 68855-60-7 12246

Rhethik 4,000 gals CAS # 111-46-6 12247

Rheduce 1,500 gals 12248

Suremul 32,000 gals CAS#111-76-2,112-34-5 12243

Surewet 11,000 gals CAS # 112-80-1 12245

M-I BAR 4,500 tons CAS # 7727-43-7 10617

Synthetic B 15,700 bbls 12269

G Seal Plus 2,000 50-lb bags CAS # 7782-42-5 10391

Safe Carb 8,000 50-lb bags CAS # 471-34-1 10337
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

(e) NEW OR UNUSUAL TECHNOLOGY

No new or unusual technology will be used to carry out the activities proposed in this plan.

(f) BONDING STATEMENT

The bond requirements for the activities and facilities proposed in this EP are satisfied by an area-wide bond, 

furnished and maintained according to 30 CFR part 256, subpart I; NTL No. 2000-G16, “Guidelines for General 

Lease Surety Bonds;” and a current MMS-approved deferment from providing additional security under 30 CFR 

256.53(d) and National NTL No. 2003-N06, “Supplemental Bond Procedures. If, any point, Chevron no longer 

qualifies for a supplemental bonding deferment, Chevron will either provide the required additional security or a third 

party guarantee within 60 days after such disqualification.

(g) OIL SPILL FINANCIAL RESPONSIBILITY (OSFR)

Chevron U.S.A. Inc., MMS company number 00078, has demonstrated oil spill financial responsibility for the facilities 

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

Responsibility for Covered Facilities.”

(h) DEEPWATER WELL CONTROL STATEMENT

Chevron U.S.A. Inc., MMS company number 00078, has the financial capability to drill a relief well and conduct other 

emergency well control operations.
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

(j) BLOWOUT SCENARIO

The WCD number was reviewed and approved in Revised Plan R-5084, July 16, 2011. No change in the 

approved WCD number is necessary for this revised plan. Below is the WCD information approved in plan 

R-5084:

Estimated flow rate

Systems analysis indicates that an uncontrolled blowout in the 10-5/8” open hole section will lead to a maximum 

Worst Case Discharge Scenario initial flow rate of 156,994 barrels of oil per day (bopd). This rate is based on 

transient nodal analysis and does not include the effects of heavy fluid unloading or filter cake cleanup. Assuming a 

500 acre drainage volume, the production rate would stabilize in about 40 days at 144,689 bopd

Total volume and maximum duration of the potential blowout

Modeling indicates that the well could sustain the stabilized rate until a relief well could be drilled. The estimated total 

time required to drill the relief well and conduct the kill operation is 153 days. Production decline due to reservoir 

depletion and sand bridging are assumed not to occur. Using rate profiles resulting from well test data in correlative 

sands, the Total Potential Spill Volume is estimated at 22,137,417 bbls.

Potential for well to bridge over

Although it is highly likely that some sand would be produced under a blowout scenario, Chevron expects that the 

amount of sand is small enough to be lifted to the seafloor without bridging.

Likelihood for surface intervention to stop the blowout

The likelihood of surface intervention to stop a blowout is based on the equipment specific to the MODU(s) or drill 

ships that will drill the well(s). Chevron’s contracted drill ships and personnel have the following methods and 

equipment available to minimize the risk of an incident occurring:

• Maintaining well control

• Deadman / Autoshear functions on the BOP

• Permanently fixed ROV panels on the BOP to allow an ROV to function the BOP via standard hot stab 

interfaces

• Acoustic Pods on the BOP to function the BOP in the event the primary BOP control system is compromised

In the event of a well blowout, Chevron will act as soon as practical to reduce the overall risk of injury to personnel 

and damage to the environment and may consider potential actions that may have short term increases in effluent 

flow in the interest of reducing overall environmental impact or incident escalation. One such action that Chevron 

would consider is removal of any compromised or damaged equipment that may be restricting our ability to control 

the effluent flow (a BOP, LMRP, and / or riser) and to allow for installation of the appropriate response equipment (an 

alternate BOP or capping stack) to assist in controlling the well.

Initial response actions could include, but are not limited to: 

• Actions necessary for personnel safety, including evacuation. 

• ROV mobilization and tactics, including: 

o Identify the source(s) of hydrocarbon release

o Assess the post incident geometry of equipment

• Identify existing BOP / LMRP options and / or take action: 

o Status 

o Functionality 

o Actuate rams 

o Disconnection of existing BOP / LMRP / Riser to affect an appropriate connection point for capping 

/ intervention options 
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

There are multiple capping stack alternatives that Chevron will consider to cap and contain a well during a loss of 

well control event. As a member of the Marine Well Containment Company (MWCC), Chevron has access to 

MWCC’s Interim Containment System. This system can handle pressure up to 15k psi. The Single Ram Capping 

Stack can cap a well in deepwater depths up to 10,000 feet. It is engineered to “cap and flow” a well in deepwater 

depths up to 8,000 feet. The system has the capacity to contain 60,000 barrels per day (and 120 million standard 

cubic feet of gas per day) with potential for expansion and has dispersant injection capability. Through mutual aid 

agreement by members of MWCC, the interim containment system includes capture vessels under contract to 

member companies that would be deployed to assist in surface processing and storage of hydrocarbons captured 

during the event.

In addition to MWCC’s capping stacks, Chevron has access to additional capping options through the immediate 

availability of two complete 18 3⁄4” 15k BOP stacks, which are held as permanent secondary stacks located on two of 

Chevron’s contracted drill ships operating in the Gulf of Mexico. Access to both the MWCC and Chevron specific 

equipment provides Chevron with increased flexibility in capping and containing a well blowing out. The selection of 

the appropriate capping method will be dependent upon the incident circumstances.

Time to contract rig, move it onsite and drill relief well

Chevron estimates that it would take ten (10) days to acquire and demobilize a rig, four (4) days to move the rig 

onsite, and 139 days to drill the relief well, intersect the blowout well, and conduct a kill operation for a total of 153 

days. 

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

Chevron plans to drill Coronado with one of the three Enterprise-Class drillships under contract. At any given time, 

Chevron also plans to have at least two other similar drillships that could drill a relief well. These drillships do not 

have any equipment constraints with respect to drilling a relief well for the Coronado project. The 11-7/8” casing point 

is selected as the intervention point for the relief well; Chevron estimates that it would take 153 days to mobilize a rig, 

drill relief well, intersect that blowout well and conduct a kill operation. This estimate includes NPT time and a 30% 

contingency factor. 

There are no nearby platforms or other infrastructure nearby that would hamper relief well operations. Site surveys 

have been conducted near the current drilling location to identify surface hazards that might impact the selection of a 

relief well location. Selection of the actual location would be constrained by typical parameters such as planned 

inclination, benign water-bottom and salt entry/exit points, wind and current direction and subsurface hazard 

avoidance. Directional plans for a relief well would be a simple build and hold with less than 40 degrees hole angle. 

Casing design for the relief well will be similar to that proposed for the Coronado well.

Measures to enhance the ability to prevent a blowout, reduce the likelihood of a blowout, and conduct 

effective and early intervention in the event of a blowout

In order for Chevron to address its ability to prevent blowouts, reduce the likelihood of blowouts, and conduct 

effective/early intervention in the event of a blowout, Chevron has developed standards for well control, personnel 

safety, and emergency response plans. Chevron has also entered into agreements with industry Subject Matter 

Experts (SME).

At all times from planning through execution, Chevron takes the necessary steps to maintain primary well control to 

prevent the occurrence of blowouts as outlined in the Chevron Well Control Guide.

The drilling team works in conjunction with the geological and geophysical operations team and the exploration 

project team to use their knowledge and good judgment to create best possible well plans and program for any 

particular prospect. All relevant geological information is used to understand the risks and uncertainties that are 

unique to the location. Appropriate plans are then generated to eliminate or mitigate the identified risks. Special 

equipment for contingency plans is sourced and qualified personnel are identified for conducting the various tasks. 
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

Prior to the execution phase, all the well control equipment on the rig undergoes a rigorous inspection and 

acceptance process/procedure by the Chevron Global Well Intervention group.

To reduce the likelihood of a blowout, appropriate offset information is used to generate pore pressure models that 

predict localized area pore pressure. Maximum Anticipated Surface Pressure (MASP) is calculated to ensure that the 

working pressure of the BOP equipment is not exceeded at any time during well construction. Pressure While Drilling 

(PWD) and Log While Drilling (LWD) data, such as gamma ray, resistivity, sonic, are used during the drilling 

operation to monitor real time pore pressure variances. 

Adjustments can then be made to the mud system to maintain the appropriate overbalance on the pore pressure. 

Mud tank volumes and trip tank volumes are monitored while drilling for early detection of changes in anticipated 

trends. Routine maintenance and testing of blowout prevention equipment helps to ensure the equipment is in good 

working condition during operations. Data sheets and critical wellbore information which are needed in well control 

situations are maintained at the well site.

There shall be two (2) barriers available during all normal well activities, operations, suspensions, and abandonments 

to prevent uncontrolled flow from the wellbore to the environment. Prior to removing the Blowout Preventer (BOP) 

from a well which has hydrocarbons, there will be two mechanical barriers in place.

Preliminary plans are developed for potential relief well locations(s) during the planning phase for the primary well(s). 

These preliminary plans can be used to develop detailed relief well drilling plans as needed in a timely manner. Two 

relief well locations have been identified for the primary well location.

In addition to Chevron’s contracted resources to assist in the event of a blowout, Chevron is a founding member of 

the Marine Well Containment Company (“MWCC”), currently has access to MWCC’s Interim Containment Response 

System (“ICRS”), and will have full access to MWCC’s Expanded Containment Response System when it is 

available. These resources, along with Chevron’s own well containment and emergency response planning, give 

Chevron a high probability of regaining control of a blown out well.

Chevron maintains the “Chevron Interim Well Containment Plan (0128-OFGN-RGL-PLN-DGM-0000-00001)” which 

guides Chevron’s procedures and plans for well containment until the expanded Marine Well Containment System is 

in place. Additional details for each component of well containment planning can be found in the Chevron Interim 

Well Containment Plan (“IWCP”), which is available upon request.

Assumptions and calculations used in the determination of the Worst Case Discharge Information to comply 

with NTL No. 2010-N06 were reviewed and approved in Revised Plan R-5084, July 16, 2011.
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION C GEOLOGICAL AND GEOPHYSICAL INFORMATION 

(a) GEOLOGICAL DESCRIPTION

Proprietary Information

(b) STRUCTURE CONTOUR MAPS

Proprietary Information

(c) INTERPRETED 2-D AND/OR 3-D SEISMIC LINES

Proprietary Information

(d) GEOLOGICAL STRUCTURE CROSS-SECTION

Proprietary Information

(e) SHALLOW HAZARDS REPORT

A Shallow Hazard Report was prepared by Fugro Geoservices, Inc. (Fugro) in August 2003 based on a review of 

proprietary exploration 3-D seismic data. Fugro Report No. 2400-2073, “Shallow Hazards Assessment, Coronado 

Prospect, Blocks 98, 99, 142, and 143, OCS-G-21841, OCS-G--21842, OCS-G-21848, and OCS-G-21849, Walker 

Ridge Area, Gulf of Mexico”, was submitted as an enclosure with Initial Plan N-8136.

(f) SHALLOW HAZARDS ASSESSMENT

Site specific shallow hazard clearance letters for the proposed wellsites were prepared by Fugro complying with 

Notice to Lessees (NTL’s) 2008-G05, and 2009-G40. The site specific clearance letters are based on findings 

provided in the main body of the Shallow Hazards Assessment, (Fugro Report No. 2400-2073). The site clearance 

letters supplement the hazard report with details pertaining directly to the proposed drill locations. Seismic 

acquisition and processing details are included in the Site Clearance Letters.

A non-proprietary copy of the site specific shallow hazard clearance letters from the GEMS report for the proposed 

well locations is included below:
FUGRO GEOCONSULTING, INC. 

Letter Report No. 27.2013-2655-A 

19 September 2013 

Chevron U.S.A., Inc. 

1500 Louisiana St. 

Houston, Texas 77002 

Attention: Mr. Philip Von Dullen III

Site Clearance Letter 

Proposed Wellsite WR 143 A 

Block 143, Walker Ridge Area 

OCS-G-21849 

Introduction. Chevron U.S.A., Inc. (Chevron) contracted Fugro GeoConsulting, Inc. (Fugro) to 

complete a wellsite clearance assessment for proposed wellsite WR 143 A in Block 143, Walker Ridge 

(WR) Area (OCS-G-21849). The primary scope of this assessment is to identify and assess potential 

seafloor and shallow drilling hazards within 2,000 ft of the proposed wellsite to a depth limit of 3,000 ft 

below the seafloor (~0.936 seconds two-way-travel time BML), and to meet current Bureau of Ocean 

Energy Management (BOEM) regulations for shallow hazards and deepwater benthic communities. 

Anchor locations are not assessed in this letter report because a dynamically-positioned (DP) vessel will be 

used to drill the proposed wellbore. 

Shallow geologic conditions at the proposed wellsite are summarized on the attached 

Tophole Prognosis Chart. The nearest inline and crossline from the 3-D seismic data 

are attached to illustrate shallow geologic conditions in the vicinity of the proposed wellsite. Page-size 

Water Depth and Seafloor Features, Seafloor Amplitude, and Subsurface Geologic Features Maps

presented at 1:12,000 scale showing the proposed wellsite are also attached. A power spectrum chart for 

the 3-D seismic data set in the vicinity of the proposed wellsite is also included. Please refer to Fugro 

Report No. 2400-2073, “Shallow Hazards Assessment, Coronado Prospect, Blocks 98, 99, 142, and 143, 

OCS-G-21841, OCS-G-21842, OCS-G-21848, and OCS-G-21849, Walker Ridge Area, Gulf of Mexico”, 

published by Fugro GeoServices, Inc., in August 2003, for a comprehensive assessment of shallow 

hazards within Walker Ridge Blocks 98, 99, 142 and 143. This wellsite clearance assessment meets the 

requirements set forth in BOEM Notices to Lessees (NTLs) 2008-G05 and 2009-G40 (published as 

Minerals Management Service, 2008 and 2009). 

3-D Seismic Survey Parameters. This assessment is based on interpretation of a reprocessed 

3-D seismic exploration data set that covers an approximate 4-block area (about 36 mi2

). The 3-D data set 

was provided to Fugro on tape media in SEG-Y format for loading onto a PC-based Seismic 

Micro-Technology (SMT) workstation. The 3-D data cube contains short-offset 2-millisecond sample rate 

data to a record length of 6 seconds TWT below sea surface (BSS). The 3-D cube encompasses all of 

Blocks 98, 99, 142 and 143. The inlines are oriented east-west, have a numerical increment of 5, and 

exhibit a line spacing of 65.6 ft (~20 m). Crosslines are oriented north-south, have a numerical increment 

of 1, and exhibit a line spacing of 41 ft (~12.5 m). The data, as originally provided, did not display a 

balanced zero-phase wavelet in the shallow section. Fugro rotated the data phase by 90° to approximate a 

zero-phase wavelet at the seafloor and top of salt interface over much of its extent. 

The 3-D seismic exploration survey was collected by Digicon Geophysical Corporation between 

April 1997 and January 1998. The acquisition vessels Polar Princess and Polar Search collected the data 

along an east-west azimuth (090°/270°), with positioning provided by redundant wide area differential 

global positioning system (WADGPS). The data were acquired at 2-msec sample rate, 12.5-sec record 

A Member of the Fugro group of companies with offices throughout the world.

6100 Hillcroft (77081)

P.O. Box 740010

Houston, TX 77274

Phone: 713-369-5600

Fax: 713-778-6816
Letter Report No. 27.2013-2655-A 2

length, with dual alternating point-source tuned airgun arrays of 27 guns per array. Each airgun provides a 

source volume of 4,140 cu. in. at a pressure of 2,000 p.s.i. The source array was towed at a nominal depth 

of 7.6 m +/- 1 m, source separation of 80 m, and was fired on an alternating basis every 37.5 m of travel. 

The streamer array had an active group length of 7,200 m, consists of 288 groups of 3-4 receivers each at 

25 m separation. Each streamer was towed at a nominal depth of 9.1 m +/- 1.5 m, and the streamer 

separation distance was nominally 160 m. The data were collected in SEG-D format. 

Survey processing steps include the following: 

• reformat 

• anti-alias filter (minimum phase, out - 90 Hz) 

• adjustment for differences in recording systems 

• trace edits 

• merge navigation with seismic 

• SPHDIV correction (V2T) 

• mute – first break suppression 

• gap deconvolution based on water bottom 

• operator length: 240 msec 

• predictive gap: 24 msec 

• 15-trace average 

• multiple attenuation, radon transform algorithm 

• DMO velocity analysis (2 km grid) 

• bin offset regularization (utilizing 2 km grid) 

• 3-D dip moveout correction on common offsets (V(Z)) 

• bin fold normalization 

• INTERP to 12.5 X 20 m bins on each common offset 

• one-pass phase shift migration of each offset (V(Z)) 

• migration velocity analysis (moves velocity analysis) 0.5 km grid 

• 3-D normal moveout correction (moves velocity field) 

• offset weighting – based on water bottom 

• mute – based on water bottom 

• common mid-point stack 12.5 X 20 m bins 

• inverse migration of MOVES stack, (V(Z)) 

• one-pass migration with velocity model generated from inversion of moves velocities 

(GLINVEL) 

• datum correction to sea level +10 msec 

3-D Seismic Frequency. Based on power spectrum analysis of the 3-D seismic data, at 50% 

power (within the upper second two-way travel time below the seafloor), the frequency bandwidth at the 

proposed wellsite ranges between about 6 and 65 Hz. This bandwidth corresponds to a local limit of 

separability (using the λ/4 approximation) of about 76 ft, assuming a dominant frequency of 38 Hz and an 

average seismic velocity of 5,800 ft/sec in the shallow section. 

Offset Well Data. Chevron provided offset well information for the WR 98 #1 and WR 143 #1 well 

locations. Information includes daily drilling reports and electric log curves for the two previously drilled 

wellsites. These data were used to augment our stratigraphic and geohazards assessments where 

possible.
Letter Report No. 27.2013-2655-A 3

Depth Conversions. Water column time-to-depth conversions are based on a harmonic mean 

velocity function for the northern deepwater Gulf of Mexico reported by Advocate and Hood (1993). 

This function is based upon an average of fourteen velocity profiles in water depths up to 6,000 ft: 

D = 0.1105 - 5066.9193T + 468.6693T2

- 554.7107T3+ 340.7019T4 - 116.9910T5 + 20.7280T6 - 1.4658T7 

in which D = water depth (in subsea feet) and T = one-way travel time (in seconds). 

Subsurface depths cited in this letter are based on a 3rd order polynomial equation derived from 

velocity data originally supplied by Unocal. The velocity data was an average of six different points and 

was acquired from prestack depth migration velocity analysis of the 3-D data reported by Unocal. 

The 3rd order polynomial equation is as follows: 

Vavg (BML) = -101.7 (T3

)+ 63.6765 (T2)+ 1539.9776681(T) + 5000 

where Vavg is average sediment column velocity (ft/sec) BML and T is two-way travel time (sec) BML.

Proposed Well Location. Proposed Wellsite WR 143 A is located in the northwestern portion of 

Walker Ridge Block 143 as follows: 

Proposed Wellsite WR 143 A 

Block 143, Walker Ridge Area 

UTM Zone 15, NAD 1927 

 586' FWL 660’ FNL 

X = 2,154,826 ft Y = 9,740,940 ft 

Latitude: 26° 50’ 8.469” N Longitude: 91° 25’ 19.596” W 

3-D Inline: 29705 3-D Crossline: 4408 

Water Depth and Seafloor Gradient. The water depth at the proposed wellsite is about 5,760 ft 

with zero datum at sea surface. The seafloor at the proposed wellsite is generally smooth and stable, but 

slightly undulatory due to seafloor faults in the vicinity. The seafloor gradient at the proposed wellsite is 

about 5.9° (~10.3 %) to the west. 

Seafloor Features. The proposed wellsite is on the western flank of a topographic high, related to 

salt withdrawal and subsequent subsidence, which failed to the north as a massive slope failure. Locally, 

multiple seafloor faults create an irregular, low-relief seafloor. The nearest is a north-dipping fault, 

approximately 320 ft to the northeast of the proposed wellsite. The activity of this and other seafloor faults 

cannot be determined with the 3-D seismic data; however, even active faults are not expected to pose a 

hazard to temporary occupation drilling activities. Although there are no indications of recent or incipient 

slope instability at or upslope of the proposed wellsite, slopes in excess of 6° are present upslope and in 

association with nearby seafloor fault scarps. While not suggestive of potential large-scale slope instability, 

small-scale instability may occur under natural conditions or upon disturbance. Such small-scale slope 

failures would likely be localized, and are not expected to affect temporary occupation drilling activities. No 

evidence of hydrocarbon seepage features, such as seafloor mounds, pockmarks, gas hydrates, or 

authigenic carbonates are found in the area. 

Impact to Potential High-Density Benthic Communities. There is no geophysical evidence of 

hydrocarbon seepage sites within 2,000 ft of proposed wellsite. Therefore, there is a negligible potential for 

high-density benthic communities of chemosynthetic organisms and other associated organisms within 

2,000 ft of the proposed wellsite, in accordance with NTL 2009-G40. 
Letter Report No. 27.2013-2655-A 4

Man-Made Obstructions. According to the Fugro database of man-made facilities and seafloor 

obstructions, no man-made features are identified in the study area. However, seafloor debris and most 

man-made obstructions cannot be identified within the vertical resolution limits of conventional 3-D seismic 

data. We recommend that an ROV be used to inspect the seafloor at the proposed wellsite immediately 

before spud-in to confirm that there are no seafloor obstructions. No other seafloor conditions that may 

adversely affect exploratory drilling from a DP vessel were identified in the vicinity of the proposed wellsite. 

Stratigraphy. The seafloor and six subsurface horizons (Horizons 10, 20, 30, 40, 50, and 60) 

were mapped to divide the tophole section into seven stratigraphic sequences (Sequence 1 through 7) in 

the study area. At the proposed wellsite, Horizon 60 is below the depth limit of investigation, so there are 

only six sequences shown on the Tophole Prognosis Chart. Chevron provided offset well data to assist 

with stratigraphic correlation into the study area. Predicted depths and thicknesses associated with each of 

the mapped horizons and sequences are displayed on the attached Tophole Prognosis Chart for the 

proposed wellsite location. 

The thickness and compositions of each sequence varies along the WR 143 A wellbore. 

Sequence 1 is interpreted to be comprised of 303 ft of stratified marine clays interlayered with thin, finegrained mass transport deposits (MTDs). Sequences 2 sediments are characterized as well-defined, 

laterally continuous, mud-rich sediments with some possible MTDs present, and is 428 ft thick at the 

proposed wellbore. Sequence 3 is comprised of about 503 ft of interlayered stratified marine clays and 

thin, fine-grained MTDs. Sequences 4, 5, 6 are 398 ft, 688 ft, and 682 ft thick, respectively, and are 

interpreted to be comprised of fine-grained MTDs interlayered with stratified marine clays and possible 

coarse-grained sediments. 

Fault Penetrations. A vertical wellbore at the proposed wellsite will penetrate three buried faults 

within the depth limit of investigation. The first is a northeast-dipping normal fault at about 6,319 ft BSS 

(559 ft BML) in Sequence 2. The second dips to the north and is at 6,618 ft BSS (858 ft BML). The third is 

a north-dipping fault at about 7,392 ft BSS (1,632 ft BML) at the top of Sequence 5 (Horizon 40). The level 

of current fault activity cannot be determined with the available data. However, none of these faults are 

expected to affect exploratory drilling operations with the exception of fault-related permeability, which may 

allow the loss of drilling fluids to formation. 

Assessment of Shallow Drilling Hazards. The following assessment of shallow hazards 

assumes open-hole drilling conditions in the tophole section, without regard to specific casing and mud 

programs that Chevron may be planning. Also, this assessment indicates the probability of encountering a 

particular hazardous condition along the proposed wellbore, but does not provide any prediction of the 

potential severity of the hazard. 

Gas Hydrate/Shallow Gas Hazards. In the water depths associated with the study area, it is 

possible for escaping methane gas (or a mixture of gases) to produce hydrates at or near the seafloor. 

Hydrates can, in many circumstances, be recognized or inferred by subtle mounding of the seafloor 

surrounding fluid expulsion vents. Since no such features are present near the proposed well location, the 

likelihood of gas hydrates at the seafloor is negligible. 

The interval in which gas hydrates may form below mudline is the gas hydrate stability zone 

(GHSZ). Zones of hydrates have been drilled through in various places throughout the world without 

causing drilling problems. Gas hydrates do pose a possible concern, especially in terms of the structural 

stability of production wells; however, they are generally not considered to be a drilling hazard. A vague 

bottom-simulating reflector (BSR) is present across portions of the Coronado study area and at the 

proposed location is estimated to be at a depth of 1,535 ft BML within Sequence 4. For the remainder of 
Letter Report No. 27.2013-2655-A 5

the area, the base of gas hydrate stability (BGHS) is estimated by extrapolating the BSR to the study area 

extents. If hydrates are present, they would likely be localized and disseminated within the predominantly 

fine-grained sediments in the form of small crystals, small to large nodules, lenses and partings, or thin 

veins. 

No high-amplitude anomalies interpreted to represent shallow gas will be penetrated in the tophole 

section by a vertical wellbore at the proposed wellsite, and none are located in the vicinity. The nearest 

amplitude anomaly was identified approximately 990 ft east-southeast of the proposed wellsite in 

Sequence 6 and is not considered a drilling hazard. 

Shallow-Water-Flow (SWF). Sequences 1 through 5 are assessed a negligible potential for SWF. 

Offset well data from two nearby wells, WR 98 #1 and WR 143 #1, were provided by Chevron to assist with 

stratigraphic correlation into the study area. Well drilling activity reports for the WR 98 #1 well report a 

drilling fluid loss at a depth of 7,271 ft MD at that site. This depth is within Sequence 1 at that wellbore, but 

the sediments potentially associated with this flow are not present at the WR 143 A wellsite, as they pinchout before reaching the study area. Well drilling activity reports for the WR 143 #1 well report a shallowwater-flow incident at a depth of 8,076 ft MD at that site. This occurs at the base of a package of 

sediments that exhibit relatively higher amplitudes, interpreted to be a mix of sands and silts, in upper 

Sequence 6. At WR 143 A, an interval 216 ft thick immediately below Horizon 50, from 2,320 ft to 2,536 ft 

BML, is assigned a moderate potential for encountering shallow-water-flow. 

We appreciate the opportunity to work with you on this project and look forward to continuing as 

your geohazards consultants. If you have any questions concerning this assessment, please call Fred 

Muñoz at (713) 369-5843. 

Sincerely, 

FUGRO GEOCONSULTING, INC. 

Fred Muñoz 

Staff Geoscientist 

Daniel Ruberg, P.G. 

Supervising Geoscientist 
Letter Report No. 27.2013-2655-A 6

Attachments: 

Water Depth and Seafloor Features Map, Coronado Prospect, Block 143, Walker Ridge Area, 

Proposed Wellsite WR 143 A (1:12,000 scale) 

Seafloor Amplitude Map, Coronado Prospect, Block 143, Walker Ridge Area, Proposed Wellsite WR 

143 A (1:12,000 scale) 

Subsurface Geologic Features Map, Coronado Prospect, Block 143, Walker Ridge Area, Proposed 

Wellsite WR 143 A (1:12,000 scale) 

Tophole Prognosis Chart, Proposed Wellsite WR 143 A, Block 143, Walker Ridge Area, Gulf of Mexico 

3-D Seismic Record, Inline 29705, Showing Tophole Conditions At Proposed Wellsite WR 143 A, 

Block 143, Walker Ridge Area, Gulf of Mexico 

3-D Seismic Record, Crossline 4408, Showing Tophole Conditions At Proposed Wellsite WR 143 A, 

Block 143, Walker Ridge Area, Gulf of Mexico 

3-D Seismic Data Set Power Spectrum, Proposed Wellsite WR 143 A, Block 143, Walker Ridge Area, 

Gulf of Mexico 

References: 

Advocate, D.M. and Hood, K.C. (1993), “An Empirical Time-Depth Model for Calculating Water Depth, 

Northwest Gulf of Mexico,” Geo-Marine Letters, vol. 13, 207-211. 

Chevron (2011), DWEP Drilling Activity Reports, WR 98 #1 Wellsite, 5/4-5/8 and 6/4-6/15, 2012. 

Chevron (2012), DWEP Drilling Activity Reports, WR 143 #1 Wellsite, 10/4-10/16, 2012. 

Fugro GeoServices, Inc. (2003), "Shallow Hazards Assessment, Coronado Prospect, Blocks 98, 99, 142, 

and 143, OCS-G-21841, OCS-G-21842, OCS-G-21848, and OCS-G-21849, Walker Ridge Area, Gulf of 

Mexico", published to Union Oil Company of California, August 2003 as Report No. 2400-2073. Published 

with one wellsite assessment addendum in June 2004 as Report No. 2404-2073. 

Minerals Management Service (2008), "Notice to Lessees and Operators of Federal Oil, Gas, and Sulphur 

Leases in the Outer Continental Shelf, Gulf of Mexico OCS Region, Shallow Hazards Program", United 

States Department of the Interior, Minerals Management Service, Gulf of Mexico, NTL 2008-G05. 

Minerals Management Service (2009), "Notice to Lessees and Operators of Federal Oil, Gas, and Sulphur 

Leases in the Outer Continental Shelf, Gulf of Mexico OCS Region, Deepwater Benthic Communities", 

United States Department of the Interior, Minerals Management Service, Gulf of Mexico, NTL 2009-G40. 
WATER DEPTH AND SEAFLOOR FEATURES

CORONADO PROSPECT, BLOCK 143, WALKER RIDGE AREA

PROPOSED WELLSITE WR 143 A
SEAFLOOR AMPLITUDE

CORONADO PROSPECT, BLOCK 143, WALKER RIDGE AREA

PROPOSED WELLSITE WR 143 A

RELATIVE AMPLITUDE
SUBSURFACE GEOLOGIC FEATURES

CORONADO PROSPECT, BLOCK 143, WALKER RIDGE AREA

PROPOSED WELLSITE WR 143 A

HIGH-AMPLITUDE ANOMALIES
FUGRO GEOCONSULTING, INC. 

Letter Report No. 27.2013-2655-B 

19 September 2013 

Chevron U.S.A., Inc. 

1500 Louisiana St. 

Houston, Texas 77002 

Attention: Mr. Philip Von Dullen III 

Site Clearance Letter 

Proposed Wellsite WR 143 B 

Block 143, Walker Ridge Area 

OCS-G-21849 

Introduction. Chevron U.S.A., Inc. (Chevron) contracted Fugro GeoConsulting, Inc. (Fugro) to 

complete a wellsite clearance assessment for proposed wellsite WR 143 B in Block 143, Walker Ridge 

(WR) Area (OCS-G-21849). The primary scope of this assessment is to identify and assess potential 

seafloor and shallow drilling hazards within 2,000 ft of the proposed wellsite to a depth limit of 3,000 ft 

below the seafloor (~0.936 seconds two-way-travel time BML), and to meet current Bureau of Ocean 

Energy Management (BOEM) regulations for shallow hazards and deepwater benthic communities. 

Anchor locations are not assessed in this letter report because a dynamically-positioned (DP) vessel will be 

used to drill the proposed wellbore. 

Shallow geologic conditions at the proposed wellsite are summarized on the 

attached Tophole Prognosis Chart. The nearest inline and crossline from the 3-D seismic data 

are attached to illustrate shallow geologic conditions in the vicinity of the proposed wellsite Page-size 

Water Depth and Seafloor Features, Seafloor Amplitude, and Subsurface Geologic Features Maps

presented at 1:12,000 scale showing the proposed wellsite are also attached. A power spectrum chart for 

the 3-D seismic data set in the vicinity of the proposed wellsite is also included. Please refer to Fugro 

Report No. 2400-2073, “Shallow Hazards Assessment, Coronado Prospect, Blocks 98, 99, 142, and 143, 

OCS-G-21841, OCS-G-21842, OCS-G-21848, and OCS-G-21849, Walker Ridge Area, Gulf of Mexico”, 

published by Fugro GeoServices, Inc., in August 2003, for a comprehensive assessment of shallow 

hazards within Walker Ridge Blocks 98, 99, 142 and 143. This wellsite clearance assessment meets the 

requirements set forth in BOEM Notices to Lessees (NTLs) 2008-G05 and 2009-G40 (published as 

Minerals Management Service, 2008 and 2009). 

3-D Seismic Survey Parameters. This assessment is based on interpretation of a reprocessed 

3-D seismic exploration data set that covers an approximate 4-block area (about 36 mi2

). The 3-D data set 

was provided to Fugro on tape media in SEG-Y format for loading onto a PC-based Seismic 

Micro-Technology (SMT) workstation. The 3-D data cube contains short-offset 2-millisecond sample rate 

data to a record length of 6 seconds TWT below sea surface (BSS). The 3-D cube encompasses all of 

Blocks 98, 99, 142 and 143. The inlines are oriented east-west, have a numerical increment of 5, and 

exhibit a line spacing of 65.6 ft (~20 m). Crosslines are oriented north-south, have a numerical increment 

of 1, and exhibit a line spacing of 41 ft (~12.5 m). The data, as originally provided, did not display a 

balanced zero-phase wavelet in the shallow section. Fugro rotated the data phase by 90° to approximate a 

zero-phase wavelet at the seafloor and top of salt interface over much of its extent. 

The 3-D seismic exploration survey was collected by Digicon Geophysical Corporation between 

April 1997 and January 1998. The acquisition vessels Polar Princess and Polar Search collected the data 

along an east-west azimuth (090°/270°), with positioning provided by redundant wide area differential 

global positioning system (WADGPS). The data were acquired at 2-msec sample rate, 12.5-sec record 

A Member of the Fugro group of companies with offices throughout the world.

6100 Hillcroft (77081)

P.O. Box 740010

Houston, TX 77274

Phone: 713-369-5600

Fax: 713-778-6816
Letter Report No. 27.2013-2655-B 2

length, with dual alternating point-source tuned airgun arrays of 27 guns per array. Each airgun provides a 

source volume of 4,140 cu. in. at a pressure of 2,000 p.s.i. The source array was towed at a nominal depth 

of 7.6 m +/- 1 m, source separation of 80 m, and was fired on an alternating basis every 37.5 m of travel. 

The streamer array had an active group length of 7,200 m, consists of 288 groups of 3-4 receivers each at 

25 m separation. Each streamer was towed at a nominal depth of 9.1 m +/- 1.5 m, and the streamer 

separation distance was nominally 160 m. The data were collected in SEG-D format. 

Survey processing steps include the following: 

• reformat 

• anti-alias filter (minimum phase, out - 90 Hz) 

• adjustment for differences in recording systems 

• trace edits 

• merge navigation with seismic 

• SPHDIV correction (V2T) 

• mute – first break suppression 

• gap deconvolution based on water bottom 

• operator length: 240 msec 

• predictive gap: 24 msec 

• 15-trace average 

• multiple attenuation, radon transform algorithm 

• DMO velocity analysis (2 km grid) 

• bin offset regularization (utilizing 2 km grid) 

• 3-D dip moveout correction on common offsets (V(Z)) 

• bin fold normalization 

• INTERP to 12.5 X 20 m bins on each common offset 

• one-pass phase shift migration of each offset (V(Z)) 

• migration velocity analysis (moves velocity analysis) 0.5 km grid 

• 3-D normal moveout correction (moves velocity field) 

• offset weighting – based on water bottom 

• mute – based on water bottom 

• common mid-point stack 12.5 X 20 m bins 

• inverse migration of MOVES stack, (V(Z)) 

• one-pass migration with velocity model generated from inversion of moves velocities 

(GLINVEL) 

• datum correction to sea level +10 msec 

3-D Seismic Frequency. Based on power spectrum analysis of the 3-D seismic data, at 50% 

power (within the upper second two-way travel time below the seafloor), the frequency bandwidth at the 

proposed wellsite ranges between about 6 and 65 Hz. This bandwidth corresponds to a local limit of 

separability (using the λ/4 approximation) of about 76 ft, assuming a dominant frequency of 38 Hz and an 

average seismic velocity of 5,800 ft/sec in the shallow section. 

Offset Well Data. Chevron provided offset well information for the WR 98 #1 and WR 143 #1 well 

locations. Information includes daily drilling reports and electric log curves for the two previously drilled 

wellsites. These data were used to augment our stratigraphic and geohazards assessments where 

possible.
Letter Report No. 27.2013-2655-B 3

Depth Conversions. Water column time-to-depth conversions are based on a harmonic mean 

velocity function for the northern deepwater Gulf of Mexico reported by Advocate and Hood (1993). 

This function is based upon an average of fourteen velocity profiles in water depths up to 6,000 ft: 

D = 0.1105 - 5066.9193T + 468.6693T2

- 554.7107T3+ 340.7019T4 - 116.9910T5 + 20.7280T6 - 1.4658T7 

in which D = water depth (in subsea feet) and T = one-way travel time (in seconds). 

Subsurface depths cited in this letter are based on a 3rd order polynomial equation derived from 

velocity data originally supplied by Unocal. The velocity data was an average of six different points and 

was acquired from prestack depth migration velocity analysis of the 3-D data reported by Unocal. 

The 3rd order polynomial equation is as follows: 

Vavg (BML) = -101.7 (T3

)+ 63.6765 (T2)+ 1539.9776681(T) + 5000 

where Vavg is average sediment column velocity (ft/sec) BML and T is two-way travel time (sec) BML.

Proposed Well Location. Proposed Wellsite WR 143 B is located in the northwestern portion of 

Walker Ridge Block 143 follows: 

Proposed Wellsite WR 143 B 

Block 143, Walker Ridge Area 

UTM Zone 15, NAD 1927 

 727' FWL 2,831’ FNL 

X = 2,154,967 ft Y = 9,738,769 ft 

Latitude: 26° 49’ 49.950” N Longitude: 91° 25’ 18.337” W 

3-D Inline: 29540 3-D Crossline: 4412 

Water Depth and Seafloor Gradient. The water depth at the proposed wellsite is about 5,593 ft 

with zero datum at sea surface. The seafloor at the proposed wellsite is generally smooth and stable, but 

slightly undulatory due to seafloor faults in the vicinity. The seafloor gradient at the proposed wellsite is 

about 6.4° (~11.2 %) to the west. 

Seafloor Features. The proposed wellsite is on the western flank of a topographic high, related to 

salt withdrawal and subsequent subsidence, which failed to the north as a massive slope failure. Locally, 

multiple seafloor faults create an irregular, low-relief seafloor. The nearest is a north-dipping fault, 

approximately 285 ft to the northeast of the proposed wellsite. The activity of this and other seafloor faults 

cannot be determined with the 3-D seismic data; however, even active faults are not expected to pose a 

hazard to temporary occupation drilling activities. Although there are no indications of recent or incipient 

slope instability at or upslope of the proposed wellsite, slopes in excess of 6° are present at the wellsite in 

association with nearby seafloor fault scarps. While not suggestive of potential large-scale slope instability, 

small-scale instability may occur under natural conditions or upon disturbance. Such small-scale slope 

failures would likely be localized, and are not expected to affect temporary occupation drilling activities. No 

evidence of hydrocarbon seepage features, such as seafloor mounds, pockmarks, gas hydrates, or 

authigenic carbonates are identified in the area. 

Impact to Potential High-Density Benthic Communities. There is no geophysical evidence of 

hydrocarbon seepage sites within 2,000 ft of proposed wellsite. Therefore, there is a negligible potential for 
Letter Report No. 27.2013-2655-B 4

high-density benthic communities of chemosynthetic organisms and other associated organisms within 

2,000 ft of the proposed wellsite, in accordance with NTL 2009-G40. 

Man-Made Obstructions. According to the Fugro database of man-made facilities and seafloor 

obstructions, no man-made features are identified in the study area. However, seafloor debris and most 

man-made obstructions cannot be identified within the vertical resolution limits of conventional 3-D seismic 

data. We recommend that an ROV be used to inspect the seafloor at the proposed wellsite immediately 

before spud-in to confirm that there are no seafloor obstructions. No other seafloor conditions that may 

adversely affect exploratory drilling from a DP vessel were identified in the vicinity of the proposed wellsite. 

Stratigraphy. The seafloor and six subsurface horizons (Horizons 10, 20, 30, 40, 50, and 60) 

were mapped to divide the tophole section into seven stratigraphic sequences (Sequence 1 through 7) in 

the study area. At the proposed wellsite, Horizon 60 is below the depth limit of investigation, so there are 

only six sequences shown on the tophole prognosis chart. Chevron provided offset well data to assist with 

stratigraphic correlation into the study area. Predicted depths and thicknesses associated with each of the 

mapped horizons and sequences are displayed on the attached Tophole Prognosis Chart for the proposed 

wellsite location. 

The thickness and compositions of each sequence varies along the WR 143 B wellbore. 

Sequence 1 is interpreted to be comprised of 333 ft of stratified marine clays interlayered with thin, finegrained mass transport deposits (MTDs). Sequences 2 sediments are characterized as well-defined, 

laterally continuous, mud-rich sediments with some possible MTDs present, and is 478 ft thick at the 

proposed wellbore. Sequence 3 is comprised of about 590 ft of interlayered stratified marine clays and 

thin, fine-grained MTDs. Sequences 4, 5, 6 are 359 ft, 658 ft, and 584 ft thick, respectively, and are 

interpreted to be comprised of fine-grained MTDs interlayered with stratified marine clays and possible 

coarse-grained sediments. 

Fault Penetrations. A vertical wellbore at the proposed wellsite will penetrate one buried fault 

within the depth limit of investigation. It is a northeast-dipping normal fault at about 7,808 ft BSS (2,215 ft 

BML) in Sequence 5. The level of current fault activity cannot be determined with the available data. 

However, none of these faults are expected to affect exploratory drilling operations with the exception of 

fault-related permeability, which may allow the loss of drilling fluids to formation. 

Assessment of Shallow Drilling Hazards. The following assessment of shallow hazards 

assumes open-hole drilling conditions in the tophole section, without regard to specific casing and mud 

programs that Chevron may be planning. Also, this assessment indicates the probability of encountering a 

particular hazardous condition along the proposed wellbore, but does not provide any prediction of the 

potential severity of the hazard. 

Gas Hydrate/Shallow Gas Hazards. In the water depths associated with the study area, it is 

possible for escaping methane gas (or a mixture of gases) to produce hydrates at or near the seafloor. 

Hydrates can, in many circumstances, be recognized or inferred by subtle mounding of the seafloor 

surrounding fluid expulsion vents. Since no such features are present near the proposed well location, the 

likelihood of gas hydrates at the seafloor is negligible. 

The interval in which gas hydrates may form below mudline is the gas hydrate stability zone 

(GHSZ). Zones of hydrates have been drilled through in various places throughout the world without 

causing drilling problems. Gas hydrates do pose a possible concern, especially in terms of the structural 

stability of production wells; however, they are generally not considered to be a drilling hazard. A vague 

bottom-simulating reflector (BSR) is present across portions of the Coronado study area and at the 

proposed location is estimated to be at a depth of 1,632 ft BML within Sequence 4. For the remainder of 

the area, the base of gas hydrate stability (BGHS) is estimated by extrapolating the BSR to the study area 
Letter Report No. 27.2013-2655-B 5

extents. If hydrates are present, they would likely be localized and disseminated within the predominantly 

fine-grained sediments in the form of small crystals, small to large nodules, lenses and partings, or thin 

veins.

No high-amplitude anomalies interpreted to represent shallow gas will be penetrated in the tophole 

section by a vertical wellbore at the proposed wellsite, and none are located in the vicinity. The nearest 

amplitude anomaly (above the depth limit) was identified approximately 2,210 ft west of the proposed 

wellsite in the upper portion of Sequence 6 and is not considered a drilling hazard. 

Shallow-Water-Flow (SWF). Sequences 1 through 5 are assessed a negligible potential for SWF. 

Offset well data from two nearby wells, WR 98 #1 and WR 143 #1, were provided by Chevron to assist with 

stratigraphic correlation into the study area. Well drilling activity reports for the WR 98 #1 well report a 

drilling fluid loss at a depth of 7,271 ft MD at that site. This depth is within Sequence 1 at that wellbore, but 

the sediments potentially associated with this flow are not present at the WR 143 A wellsite, as they pinchout before reaching the study area. Well drilling activity reports for the WR 143 #1 well report a shallowwater-flow incident at a depth of 8,076 ft MD at that site. This occurs at the base of a package of 

sediments that exhibit relatively higher amplitudes, interpreted to be a mix of sands and silts, in upper 

Sequence 6. At WR 143 B, an interval 219 ft thick immediately below Horizon 50, from 2,418 ft to 2,636 ft 

BML, is assigned a moderate potential for encountering shallow-water-flow. 

We appreciate the opportunity to work with you on this project and look forward to continuing as 

your geohazards consultants. If you have any questions concerning this assessment, please call Fred 

Muñoz at (713) 369-5843. 

Sincerely, 

FUGRO GEOCONSULTING, INC. 

Fred Muñoz 

Staff Geoscientist 

Daniel Ruberg, P.G. 

Supervising Geoscientist 
Letter Report No. 27.2013-2655-B 6

Attachments: 

Water Depth and Seafloor Features Map, Coronado Prospect, Block 143, Walker Ridge Area, 

Proposed Wellsite WR 143 B (1:12,000 scale) 

Seafloor Amplitude Map, Coronado Prospect, Block 143, Walker Ridge Area, Proposed Wellsite WR 

143 B (1:12,000 scale) 

Subsurface Geologic Features Map, Coronado Prospect, Block 143, Walker Ridge Area, Proposed 

Wellsite WR 143 B (1:12,000 scale) 

Tophole Prognosis Chart, Proposed Wellsite WR 143 B, Block 143, Walker Ridge Area, Gulf of Mexico 

3-D Seismic Record, Inline 29540, Showing Tophole Conditions At Proposed Wellsite WR 143 B, 

Block 143, Walker Ridge Area, Gulf of Mexico 

3-D Seismic Record, Crossline 4412, Showing Tophole Conditions At Proposed Wellsite WR 143 B, 

Block 143, Walker Ridge Area, Gulf of Mexico 

3-D Seismic Data Set Power Spectrum, Proposed Wellsite WR 143 B, Block 143, Walker Ridge Area, 

Gulf of Mexico 

References: 

Advocate, D.M. and Hood, K.C. (1993), “An Empirical Time-Depth Model for Calculating Water Depth, 

Northwest Gulf of Mexico,” Geo-Marine Letters, vol. 13, 207-211. 

Chevron (2011), DWEP Drilling Activity Reports, WR 98 #1 Wellsite, 5/4-5/8 and 6/4-6/15, 2012. 

Chevron (2012), DWEP Drilling Activity Reports, WR 143 #1 Wellsite, 10/4-10/16, 2012. 

Fugro GeoServices, Inc. (2003), "Shallow Hazards Assessment, Coronado Prospect, Blocks 98, 99, 142, 

and 143, OCS-G-21841, OCS-G-21842, OCS-G-21848, and OCS-G-21849, Walker Ridge Area, Gulf of 

Mexico", published to Union Oil Company of California, August 2003 as Report No. 2400-2073. Published 

with one wellsite assessment addendum in June 2004 as Report No. 2404-2073. 

Minerals Management Service (2008), "Notice to Lessees and Operators of Federal Oil, Gas, and Sulphur 

Leases in the Outer Continental Shelf, Gulf of Mexico OCS Region, Shallow Hazards Program", United 

States Department of the Interior, Minerals Management Service, Gulf of Mexico, NTL 2008-G05. 

Minerals Management Service (2009), "Notice to Lessees and Operators of Federal Oil, Gas, and Sulphur 

Leases in the Outer Continental Shelf, Gulf of Mexico OCS Region, Deepwater Benthic Communities", 

United States Department of the Interior, Minerals Management Service, Gulf of Mexico, NTL 2009-G40. 
WATER DEPTH AND SEAFLOOR FEATURES

CORONADO PROSPECT, BLOCK 143, WALKER RIDGE AREA

PROPOSED WELLSITE WR 143 B
SEAFLOOR AMPLITUDE

CORONADO PROSPECT, BLOCK 143, WALKER RIDGE AREA

PROPOSED WELLSITE WR 143 B

RELATIVE AMPLITUDE
SUBSURFACE GEOLOGIC FEATURES

CORONADO PROSPECT, BLOCK 143, WALKER RIDGE AREA

PROPOSED WELLSITE WR 143 B

HIGH-AMPLITUDE ANOMALIES
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

(g) HIGH RESOLUTION SEISMIC LINES

Proprietary Information

(h) STRATIGRAPHIC COLUMN

Proprietary Information

(i) TIME vs. DEPTH TABLE

Due to adequate well control in the area, Chevron feels that a time vs. depth table is not required.

ATTACHMENTS TO SECTION C (Proprietary Information)

• C-1 - Depth Structure Contour Maps with Lines of Cross Section, 1”=2,000’

• C-2, 4 - Schematic Cross Section

• C-3, 5– Interpreted 3- D Seismic Line 

• C-6 - Stratigraphic Column

PROPRIETARY ENCLOSURE TO PLAN

• Site Clearance Letter, Proposed Wellsite WR 143 A, Block 143, Walker Ridge Area, OCS-G-21849, Fugro 

GeoConsulting, Inc., Report Number 27.2013-2655-A, 19 September 2013

• Site Clearance Letter, Proposed Wellsite WR 143 B, Block 143, Walker Ridge Area, OCS-G-21849, Fugro 

GeoConsulting, Inc., Report Number 27.2013-2655-B, 19 September 2013
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION D HYDROGEN SULFIDE (H2S) INFORMATION

(a) CONCENTRATION

It is not expected that H2S will be encountered or handled while conducting the activities proposed in this plan.

(b) CLASSIFICATION

The Regional Supervisor has classified the area as H2S absent with the initial EP approval. We do not have any 

reason to request a change in this classification. No Hydrogen Sulfide has been produced or encountered in the 

closest wells to the area.

(c) H2S CONTINGENCY PLAN

Should the Regional Supervisor not classify the activities proposed in this plan as being situated in an area 

designated as “H2S absent” - an H2S contingency plan will be proposed and submitted for approval. This proposed 

contingency plan would accompany the Application for Permit to Drill (APD) for the respective proposed well(s).

(d) MODELING REPORT

H2S concentrations greater than 500 parts per million (ppm) have not been determined or estimated to be 

encountered or handled while conducting the activities proposed in this plan, therefore a modeling report is not 

required for this plan based on the guidelines provided in NTL No. 2008-G04.
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION E BIOLOGICAL, PHYSICAL, AND SOCIOECONOMIC INFORMATION

(a) HIGH-DENSITY DEEPWATER BENTHIC COMMUNITIES INFORMATION

Fugro was contracted by Chevron to prepare Site Clearance Letters for the proposed locations in this plan. The site 

clearance letters address specific seafloor and subsurface geologic conditions near the proposed locations to the 

Top of Salt along with containing Deepwater benthic community reviews. The report complies with the various 

Bureau of Ocean Energy Management (BOEM) Notice to Lessees (NTL’s) 2008-G05 and 2009-G40. The proposed 

wellsites will be required to follow NTL 2008-G06 with respect to pre- and post-spud ROV visual inspection surveys.

The proposed wells in this plan will be drilled with a dynamically positioned drillship, so there are no associated 

anchors, anchor chain or wire ropes.

High-Density Deepwater Benthic Communities Summary Statement for the proposed locations:

WR 143 A:

There is no geophysical evidence of hydrocarbon seepage within 2,000 ft of the proposed wellsite. Therefore, there 

is a negligible potential for high-density benthic communities of chemosynthetic organisms and other associated 

organisms within 2,000 ft of the proposed wellsite, in accordance with NTL No. 2009-G40.

WR 143 B:

There is no geophysical evidence of hydrocarbon seepage within 2,000 ft of the proposed wellsite. Therefore, there 

is a negligible potential for high-density benthic communities of chemosynthetic organisms and other associated 

organisms within 2,000 ft of the proposed wellsite, in accordance with NTL No. 2009-G40.

(b) TOPOGRAPHIC FEATURES MAP

The proposed bottom disturbing activity is greater than 305 meters (1,000 feet) from the “No Activity Zone” of an 

identified topographic feature; therefore the map described in Attachment 2, Section A, Item No. 1 of NTL No. 2004-

G05 is not required for this plan based on the guidelines provided in NTL No. 2008-G04.

(c) TOPOGRAPHIC FEATURES STATEMENT (SHUNTING)

Chevron does not propose to drill two wells from the same surface location outside the 1-mile Zone but within the 

Protective Zone of an identified topographic feature. The statement described in Attachment 2, Section A, Item No.2 

of NTL No. 2004-G05 is not required for this plan based on the guidelines provided in NTL No. 2008-G04.

(d) LIVE BOTTOMS (PINNACLE TREND) MAP

The leases in this proposed plan do not have the Live Bottoms (Pinnacle Trend) stipulation.

(e) LIVE BOTTOMS (LOW RELIEF) MAP

The leases in this proposed plan do not have the Live Bottoms (Low Relief) stipulation.

(f) POTENTIALLY SENSITIVE BIOLOGICAL FEATURES

No bottom disturbing activities will be within 30 meters (100 feet) of potentially sensitive biological features. 

Therefore the map described in Attachment 8, Section A of NTL No. 2004-G05 is not required for this plan based on 

the guidelines provided in NTL No. 2008-G04.

(g) REMOTELY OPERATED VEHICLE (ROV) MONITORING SURVEY PLAN

Chevron is aware of the requirements of NTL No. 2008-G06 to conduct remotely operated vehicle (ROV) surveys 

and report findings from same in grid areas of inadequate ROV survey coverage as determined by the BOEM 

GOMR. 

Walker Ridge Block 143 is located in Grid 10 where there is adequate ROV survey coverage. A plan for an ROV 

monitoring survey does not need to be submitted per NTL No. 2008-G04.
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

(h) THREATENED OR ENDANGERED SPECIES, CRITICAL HABITAT, AND MARINE MAMMAL INFORMATION

Under Section 7 of the Endangered Species Act (ESA) all federal agencies must ensure that any actions they 

authorize, fund, or carry out are not likely to jeopardize the continued existence of a listed species, or destroy or 

adversely modify its designated critical habitat.

In accordance with the 30 CFR 250, Subpart B, effective May 14, 2007, and further outlined in Notice to Lessees 

(NTL) 2008-G04, lessees/operators are required to address site-specific information on the presence of federally 

listed threatened or endangered species and critical habitat designated under the ESA and marine mammals 

protected under the Marine Mammal Protection Act (MMPA) in the area of proposes activities under this plan.

NOAA Fisheries currently lists the Sperm Whale, Leatherback Turtle, Green Turtle, Hawksbill Turtle, and the Kemp’s 

Ridley Turtle as endangered and the Loggerhead Turtle and Gulf Sturgeon as threatened. Currently there are no 

designated critical habitats for the listed species in the Gulf of Mexico Outer Continental Shelf; however, it is possible 

that one or more of these species could be seen in the area of Chevron’s operations.

(i) ARCHAEOLOGICAL REPORT

Walker Ridge Block 143 does not fall within a previously identified “high probability” archaeology block per the BOEM 

Notice-to-Lessees (NTLs) 2005-G07 and 2008-G20. Recent mitigation guidelines, however, released by BOEM in 

March 2011 entitled “Pre-Seabed Disturbance Survey Mitigation” requires an archaeological assessment of the 

surveyed blocks prior to Chevron undertaking any bottom disturbing activities in the Area. 

Geoscience Earth & Marine Services, Inc. ® (GEMS) was contracted by Chevron to provide a survey methodology, 

archaeologists on the ROV vessel during the archaeological survey, and an assessment of the ROV survey findings 

for the proposed Coronado well sites in Block 143, Walker Ridge Area, Gulf of Mexico. The ROV investigation 

methodology complying with the “Remotely Operated Vehicle (ROV) Investigations of Unidentified Magnetic 

Anomalies and/or Sidescan Sonar Targets: Methodological Guidelines” (MMS 2005b), and the “Pre-Seabed 

Disturbance Survey Mitigation” (BOEM 2011a) was submitted to the BOEM on 19 June 2013 and subsequently 

approved on 24 June 2013 by the Archaeological Unit of the BOEM. Following notice to BOEM, the ROV 

investigation project mobilized on 6 July 2013. Survey of the proposed locations took place on July 9 and 10, 2013.

The survey utilized a Schilling Heavy-Duty 26 ROV operated by C-Innovation. The Schilling HD 26 unit is rated to 

9,800 feet and can deploy up to 1,350 feet from its Tether Management System. A dynamic positioning system keeps 

the HD ROV stable during data acquisition. The HD unit has a five-function, Rigmaster 2TM slave arm on the port 

side and a seven-function, Titan 4TM manipulator arm on the starboard side. A Kongsberg Mesotech MS1000 sector 

scanning sonar was mounted on the ROV during the survey. The unit was mobilized from the M/V Juan C Chouest, a 

299-foot-long vessel with dynamic positioning capabilities. The Schilling HD 26 ROV is permanently mobilized aboard 

the vessel with C-Innovation providing ROV support. For this survey, Fugro Chance provided survey support. 

RESULTS and RECOMMENDATIONS

Review of all available ROV data for the study area delineated no historically significant submerged cultural 

resources in the Coronado Prospect of Block 143, Walker Ridge Area, Gulf of Mexico. 

Results

• Water depths over the three proposed well sites range from 5,579 ft. (1,700 m) to 5,760 ft. (1756 m) below 

mean sea level. 

• Thirty-one (31) man-made objects were encountered and investigated during the ROV survey, including 

aluminum cans, line, glass bottles, and metal, plastic, wooden, and textile debris. Two 55-gallon steel drums 

were found, but no labels were observable. All objects appear to be modern, and none were found to represent 

culturally- or historically-significant materials. 
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

• The seafloor environment in the survey areas was found to be smooth and largely barren with occasional 

shallow depressions. A few sporadic examples of possible seafloor expulsion features were observed. 

• Observable marine life in the surveyed areas consisted mostly of animals on stalks, deepwater coral, starfish, 

sponges, and possible bacterial mats. 

Recommendations

• All 31 of the targets encountered during the survey operation represent modern debris. None are 

recommended for further archaeological investigation or archaeological avoidance. 

• If any wood, ceramics, textiles or ferrous objects become exposed during the course of bottom-founded 

operations all activities must be halted and BOEM must be notified within 48 hours. 

PROPRIETARY ENCLOSURE TO PLAN

• Archaeological ROV Survey, Coronado Prospect, Block 143, Walker Ridge Area, Gulf of Mexico, Geoscience 

Earth & Marine Services, Inc.®, August 26, 2013 (GEMS Project No. 0613-2251) (Two Hard Copies and Two 

Digital Copies of the report)

• Portable Hard Drive containing the digital field data from the Archaeological ROV Survey for WR Block 143
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION F WASTE AND DISCHARGE INFORMATION

(a) PROJECTED GENERATED WASTES

(b) PROJECTED OCEAN DISCHARGES

Water Quality Spreadsheets, included below, replace the Projected Generated Wastes and the Projected Generated 

Ocean Discharges Tables.
please specify if the amount reported is a total or per well amount

Projected generated waste Projected ocean discharges 

Type of Waste Composition Projected Amount Discharge rate Discharge Method Answer yes or no

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

Water-based drilling fluid Water-based drilling muds 110,003 bbls/well 7,857 bbls/day Discharge at mudline prior to riser installation. No

Cuttings wetted with water-based fluid Cuttings coated with water-based drilling 

muds

4,317 bbls/well 308 bbls/day Discharge at mudline prior to riser installation. No

Cuttings wetted with synthetic-based fluid Cuttings coated with Synthetic drilling 

muds, including drilled out cement

5,062 bbls/well 43 bbls/day Treated cuttings will be discharged overboard 

during drilling of SBM interval. Cuttings will pass 

through curttings dryer substantially reducing 

ROC percentage from worst case quoted below. 

Or stored in cutting boxes and transported to 

shore.

No

Will humans be there? If yes, expect conventional waste

Domestic waste Gray water from living quarters,control 

 

50,550 bbls/well 377 bbls/day Food grinder. Starboard Caisson. No

Sanitary waste Sanitary waste from living 

quarters,control rooms, and common 

28,050 bbls/well 187 bbls/day USCG-approved MSD with chlorination. 

Starboard Caisson.

No

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

Deck Drainage Deck drainage from drilling floor, 

 

170,550 bbls/well 1,137 bbls/day Hull discharge overboard. No

Will you conduct well treatment, completion, or workover? 

Well completion fluids N/A N/A N/A N/A N/A

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

Desalinization unit discharge Rejected water from watermaker unit 274,050 bbls/well 1,827 bbls/day Hull discharge overboard. No

Blowout prevent fluid Stackmagic 200/0/5% glycol based on 

2% mixture with potable water

312 bbls/well 2.08 bbls/day discharge at sea floor, or w/ deck drainage 

when tested on the surface

No

Ballast water Uncontaminated seawater used to 

maintain proper draft

760,200bbls/well 5,068 bbls/day Hull discharge overboard. No

Excess cement Cement,Fluid Loss Additive,Cement 

Retarder,Free Water Control 

Additive,Defoamer,Surfacant

800 bbls/well 800 bbls/well Discharged at seafloor during riserless drilling No

Fire water Seawater with no addition of chemicals 51,428 bbls/day when 

flaring

51,428 bbls/day when 

flaring

Hull discharge overboard. No

Cooling water Seawater with no addition of chemicals 750,000,000 bbls/well 500,000 bbls/day Hull discharge overboard. No

Hydrate control fluid Glycol 25 gals/well 25 gals/well Discharge at seafloor No

Sub sea wellhead preservation fluid Sub sea wellhead preservation fluid 2 bbls/well 2 bbls/well Discharge at seafloor No

Leak tracer dye Lignite 21,000 lbs/well 21,000 lbs/well Discharge at seafloor No

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

Will you be covered by an individual or general NPDES permit ? General

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

TABLE 1. WASTES YOU WILL GENERATE, TREAT AND DOWNHOLE DISPOSE OR DISCHARGE TO THE 

GOM ~ Coronado

Projected 

Downhole 

Disposal
please specify whether the amount reported is a total or per well

Projected 

generated waste

Solid and Liquid Wastes 

transportation 

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

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

EXAMPLE: 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 Synthetic-based drilling muds Internal mud tanks on motor vessel Newpark, Port Fourchon, LA 17,000 bbls/well Transport by boat in cutting 

bins to shorebase; truck to 

disposal facility. Recycled

Cuttings wetted with Water-based fluid N/A N/A N/A N/A N/A

Cuttings wetted with Synthetic-based fluid Cuttings coated with 

Synthetic drilling muds, 

including drilled out cement

Cuttings box on workboat/crewboat Newpark, Port Fourchon, LA 1,000 bbs/well Transport by boat in cutting 

bins to shorebase; truck to 

disposal facility. Treated and 

landfilled.

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

EXAMPLE: trash and debris (recylables) Plastic, paper, aluminum barged in a storage bin ARC, New Iberia, LA X lb/well Recycled

Trash and debris Plastic, paper, aluminum, 

glass, and other refuse

Storage bins on crew boat SWIDI, Leeville, LA 1,800 lbs/day Transport by boat in storage 

bins to shorebase. Landfilled.

Wash water Transport by boat in tanks to shorebase Newpark, Port Fourchon, LA 2-5 bbls/day Transport by boat in cutting 

bins to shorebase; truck to 

disposal facility. Injected.

Chemical product wastes Used oil, hazardous waste Drums on crew boat Chemical Waste Management, 

Sulfur, La; WMI Woodside, 

Walker, LA

3 bbls/day Transport in drums on crew 

boat to shorebase; truck to 

disposal facility. Recycled or 

incinerated.

Completion Fluids N/A N/A N/A N/A N/A

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

Waste Disposal

TABLE 2. WASTES YOU WILL TRANSPORT AND /OR DISPOSE OF ONSHORE 

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

yes, fill in the appropriate rows. 
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION G AIR EMISSIONS INFORMATION

EMISSIONS WORKSHEETS AND SCREENING QUESTIONS

The Complex Total Emissions are the same as the Plan Emissions, and therefore only one set of emissions 

calculations is included. Emissions from the proposed location are estimated using the EPA Publications referenced 

in the tables. 

All calculations are based on worst possible situations. Actual emissions are expected to be considerably below 

those estimated.

Included in this section as attachment G-1 is the Projected Air Quality Emissions Report worksheets (Form MMS138).

SCREENING QUESTIONS FOR EP’S YES NO

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

exploration activities more than 90% of the amounts calculated using the following formulas: CT = 

3400D2/3 for CO, and CT = 33.3D for the other pollutants (where D = distances to shore in miles)?

Do your emissions calculations include any emission reduction measures or modified emissions 

factors?

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

Do you expect to encounter H2S at concentrations greater than 20 parts per million (ppm)?

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

well?

Do you propose to burn produced hydrocarbon liquids?

CONTACT INFORMATION

Philip Von Dullen

Chevron U.S.A. Inc.

1500 Louisiana Street

Houston, Texas 77002

(832) 854-3644

pvondullen@chevron.com

MODELING REPORT

A Modeling Report is not required for activities proposed in this plan.

ATTACHMENTS TO SECTION G

• G-1 – Form MMS-138 “Projected Air Quality Emissions Report”
EXPLORATION PLAN (EP)

AIR QUALITY SCREENING CHECKLIST

OMB Control No. 1010-0151

OMB Approval Expires: 12/31/2011

MMS FORM MMS-138 (December 2008 - Supersedes all previous versions of form MMS-138 which may not be used). Page 1 of 6

COMPANY Union Oil Company of California (Affiliate of Chevron U.S.A. Inc. )

AREA Walker Ridge

BLOCK 143

LEASE OCS-G 21849

PLATFORM DP DrillShip 

WELL 2-Wells - A and B

COMPANY CONTACT Phili Von Dullen

TELEPHONE NO. 832-854-3644

REMARKS Revised Exploration Plan 9/2013
EMISSIONS FACTORS

MMS FORM MMS-138 (December 2008 - Supersedes all previous versions of form MMS-138 which may not be used). Page 2 of 6

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

SCF/hp-hr 9.524 SCF/hp-hr 7.143 GAL/hp-hr 0.0483 AP42 3.2-1 4/76 & 8/84

Equipment/Emission Factors units PM SOx NOx VOC CO REF. DATE

NG Turbines gms/hp-hr 0.00247 1.3 0.01 0.83 AP42 3.2-1& 3.1-1 10/96

NG 2-cycle lean gms/hp-hr 0.00185 10.9 0.43 1.5 AP42 3.2-1 10/96

NG 4-cycle lean gms/hp-hr 0.00185 11.8 0.72 1.6 AP42 3.2-1 10/96

NG 4-cycle rich gms/hp-hr 0.00185 10 0.14 8.6 AP42 3.2-1 10/96

Diesel Recip. < 600 hp. gms/hp-hr 1 1.468 14 1.12 3.03 AP42 3.3-1 10/96

Diesel Recip. > 600 hp. gms/hp-hr 0.32 1.468 11 0.33 2.4 AP42 3.4-1 10/96

Diesel Boiler lbs/bbl 0.084 2.42 0.84 0.008 0.21 AP42 1.3-12,14 9/98

NG Heaters/Boilers/Burners lbs/mmscf 7.6 0.593 100 5.5 84 P42 1.4-1, 14-2, & 14 7/98

NG Flares lbs/mmscf 0.593 71.4 60.3 388.5 AP42 11.5-1 9/91

Liquid Flaring lbs/bbl 0.42 6.83 2 0.01 0.21 AP42 1.3-1 & 1.3-3 9/98

Tank Vapors lbs/bbl 0.03 E&P Forum 1/93

Fugitives lbs/hr/comp. 0.0005 API Study 12/93

Glycol Dehydrator Vent lbs/mmscf 6.6 La. DEQ 1991

Gas Venting lbs/scf 0.0034

Sulphur Content Source Value Units

Fuel Gas 3.33 ppm

Diesel Fuel 0.4 % weight

Produced Gas( Flares) 3.33 ppm

Produced Oil (Liquid Flaring) 1 % weight
EMISSIONS CALCULATIONS 1ST YEAR

MMS FORM MMS-138 (December 2008 - Supersedes all previous versions of form MMS-138 which may not be used). Page 3 of 6

COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Union Oil Company of Ca Walker Ridge 143 OCS-G 21849 DP DrillShip 2-Wells - A and B Phili Von Dullen 832-854-3644

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR ESTIMATED TONS

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

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

DRILLING PRIME MOVER>600hp diesel* 61800 2984.94 71638.56 24 47 43.56 199.83 1497.36 44.92 326.70 24.57 112.70 844.51 25.34 184.26

PRIME MOVER>600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

PRIME MOVER>600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

PRIME MOVER>600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

VESSELS>600hp diesel(crew) 5200 251.16 6027.84 16 7 3.67 16.81 125.99 3.78 27.49 0.21 0.94 7.06 0.21 1.54

VESSELS>600hp diesel(supply) 7200 347.76 8346.24 16 47 5.07 23.28 174.45 5.23 38.06 1.91 8.75 65.59 1.97 14.31

VESSELS>600hp diesel(supply) 7200 347.76 8346.24 16 47 5.07 23.28 174.45 5.23 38.06 1.91 8.75 65.59 1.97 14.31

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 0.00

DRILLING OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

WELL TEST GAS FLARE 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2013 YEAR TOTAL 57.37 263.21 1972.25 59.17 430.31 28.59 131.15 982.75 29.48 214.42

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 5194.80 5194.80 5194.80 5194.80 98528.53

156.0
EMISSIONS CALCULATIONS 2ND YEAR

MMS FORM MMS-138 (December 2008 - Supersedes all previous versions of form MMS-138 which may not be used). Page 4 of 6

COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Union Oil Company of Ca Walker Ridge 143 OCS-G 21849 DP DrillShip 2-Wells - A and B Phili Von Dullen 832-854-3644

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR ESTIMATED TONS

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

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

DRILLING PRIME MOVER>600hp diesel* 61800 2984.94 71638.56 24 103 43.56 199.83 1497.36 44.92 326.70 53.84 246.99 1850.73 55.52 403.80

PRIME MOVER>600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

PRIME MOVER>600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

PRIME MOVER>600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

VESSELS>600hp diesel(crew) 5200 251.16 6027.84 16 15 3.67 16.81 125.99 3.78 27.49 0.44 2.02 15.12 0.45 3.30

VESSELS>600hp diesel(supply) 7200 347.76 8346.24 16 103 5.07 23.28 174.45 5.23 38.06 4.18 19.18 143.75 4.31 31.36

VESSELS>600hp diesel(supply) 7200 347.76 8346.24 16 103 5.07 23.28 174.45 5.23 38.06 4.18 19.18 143.75 4.31 31.36

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

VESSELS>600hp diesel(crew) 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

VESSELS>600hp diesel(supply) 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 0.00

DRILLING OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

WELL TEST GAS FLARE 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2014 YEAR TOTAL 57.37 263.21 1972.25 59.17 430.31 62.64 287.37 2153.34 64.60 469.82

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 5194.80 5194.80 5194.80 5194.80 98528.53

156.0

*BOEM default value for drillships
EMISSIONS CALCULATIONS 3RD YEAR

MMS FORM MMS-138 (December 2008 - Supersedes all previous versions of form MMS-138 which may not be used). Page 5 of 6

COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Union Oil Company of Ca Walker Ridge 143 OCS-G 21849 DP DrillShip 2-Wells - A and B Phili Von Dullen 832-854-3644

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR ESTIMATED TONS

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

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

DRILLING PRIME MOVER>600hp diesel* 61800 2984.94 71638.56 24 150 43.56 199.83 1497.36 44.92 326.70 78.41 359.69 2695.24 80.86 588.05

PRIME MOVER>600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

PRIME MOVER>600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

PRIME MOVER>600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

VESSELS>600hp diesel(crew) 5200 251.16 6027.84 16 22 3.67 16.81 125.99 3.78 27.49 0.65 2.96 22.17 0.67 4.84

VESSELS>600hp diesel(supply) 7200 347.76 8346.24 16 150 5.07 23.28 174.45 5.23 38.06 6.09 27.94 209.34 6.28 45.67

VESSELS>600hp diesel(supply) 7200 347.76 8346.24 16 150 5.07 23.28 174.45 5.23 38.06 6.09 27.94 209.34 6.28 45.67

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 0.00

DRILLING OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

WELL TEST GAS FLARE 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2015 YEAR TOTAL 57.37 263.21 1972.25 59.17 430.31 91.23 418.53 3136.10 94.08 684.24

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 5194.80 5194.80 5194.80 5194.80 98528.53

156.0

*BOEM default value for drillships
SUMMARY

MMS FORM MMS-138 (December 2008 - Supersedes all previous versions of form MMS-138 which may not be used). Page 6 of 6

COMPANY AREA BLOCK LEASE PLATFORM WELL

Union Oil Company of Ca Walker Ridge 143 OCS-G 21849 DP DrillShip 2-Wells - A and B

Emitted Substance

Year

PM SOx NOx VOC CO

2013 28.59 131.15 982.75 29.48 214.42

2014 62.64 287.37 2153.34 64.60 469.82

2015 91.23 418.53 3136.10 94.08 684.24

2016 0.00 0.00 0.00 0.00 0.00

2017 0.00 0.00 0.00 0.00 0.00

2018 0.00 0.00 0.00 0.00 0.00

2019 0.00 0.00 0.00 0.00 0.00

2020 0.00 0.00 0.00 0.00 0.00

2021 0.00 0.00 0.00 0.00 0.00

2022 0.00 0.00 0.00 0.00 0.00

Allowable 5194.80 5194.80 5194.80 5194.80 98528.53
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION H OIL SPILLS INFORMATION

(a) OIL SPILL RESPONSE PLANNING

REGIONAL OSRP INFORMATION 

All the proposed activities and facilities in this plan will be covered by the Oil Spill Response Plan (OSRP), filed by 

Chevron Corporation, BOEM company number 02335, in accordance with 30 CFR 254. Chevrons current approved 

plan is dated April 15, 2010. Chevron submitted a biannual update to the Regional Oil Spill Response Plan on 

January 11, 2012. An updated OSRP was received by BSEE Oil Spill Response Planning Division on February 11, 

2013, with a WCD Certification date of February 12, 2013, along with a letter certifying that Chevron continues to 

have the capability to respond to the maximum extent practical to a worst case discharge from all Chevron facilities 

located in the Gulf of Mexico.

SPILL RESPONSE SITES

In the table below, information is provided on the location of the primary spill response equipment and the location of 

the planned staging area(s) that would be used should an oil spill occur resulting from activities proposed in this plan.

Primary Response Equipment Location Preplanned Staging Location(s)

Leeville, LA Leeville, LA

OIL SPILL REMOVAL ORGANIZATION (OSRO) INFORMATION

Chevron has service contracts with the following oil spill response organizations:

Marine Spill Response Corporation, Clean Gulf Associates Services, The Response Group, The O’Brien’s Group, 

AMPOL, Oil Mop, USES, ES&H, Clean Caribbean Associates, Oil Spill Response, LTD, Marine Well Containment 

Company, Airborne Support, Inc. and T&T Marine. 

Chevron’s primary staging areas, marine transportation facilities and helicopter bases are located in Intracoastal City, 

Leeville, and Venice Louisiana. Chevron also can contract for additional staging areas throughout Gulf of Mexico 

coastal ports. 

Chevron’s primary command post for an oil spill is located in Covington, LA; however, Chevron has the ability to set 

up and effectively manage spills at each shorebase as well as Chevron facilities located in Lafayette, LA and 

Houston, TX. 

Chevron, through service contracts with Clean Gulf Associates Services, T&T Marine, Marine Spill Response 

Corporation, American Pollution Control Corporation, U.S. Environmental Services, Oil Mop, Incorporated, ES&H 

Environmental Service and Airborne Support Incorporated has oil spill response equipment located throughout the 

Gulf coast with a heavy concentration located in Louisiana. Equipment includes offshore and shallow water 

skimmers, protective boom, oil-water separators, aerial dispersant equipment and in-situ burn equipment. Response 

technicians and supervisors are also located throughout Louisiana. 

Offshore recovery equipment is primarily staged at the following locations:

Ingleside, TX; Sugarland, TX; Galveston, TX; Port Arthur, TX; Intercoastal City, LA; Lake Charles, LA; New Iberia, 

LA; Houma, LA; Venice, LA; New Orleans, LA; Leeville, LA; Fort Jackson, LA; Fourchon, LA; Baton Rouge, LA; 

Pascagoula, MS; and Mobile, AL
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

WORST CASE DISCHARGE COMPARISON TABLE

The table below provides a comparison of the worst-case scenario from Chevron’s Regional OSRP with the worstcase scenario from the proposed activities in this plan.

The Regional OSRP calculations and assumptions used to calculate the WCD volume from a blowout was submitted 

to the BOEM in accordance with NTL No. 2010-N06 with Revised Exploration Plan R-05825.

Category

Regional OSRP 

“Drilling > 10 miles”

Worst-Case Discharge 

Scenario

EP

Type of Activity (Types of activities 

include pipeline, platform, caisson, subsea 

completion or manifold, and mobile drilling 

rig)

Exploratory Drilling Exploratory Drilling

Facility Location (area/block) Green Canyon Block 640 Walker Ridge Block 143

Facility Designation (e.g., Well No. 2, 

Platform JA, Pipeline Segment No. 6373)

GC 641 IS004 WR 143 “J”

Distance to Nearest Shoreline 119 miles 156 miles

Volume

Uncontrolled blowout (volume per day) 220,332 barrels 156,994 barrels

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

diesel)

Crude Oil Crude Oil

Gravity(s) API - (Provide API gravity of 

all oils given under “Type of Oil(s)” above.

Estimate for EP’s)

29.5o 28o

Chevron has the capability to respond to the appropriate worst-case spill scenario included in its revised Regional 

OSRP received by BSEE on February 11, 2013 with a WCD Certification date of February 12, 2013. The worst-case 

scenario determined for this EP does not replace the appropriate worst-case scenario in our Regional OSRP. 

Therefore, Chevron hereby certifies that Chevron has the capability to respond, to the maximum extent practicable, 

to a worst case discharge, or a substantial threat of such a discharge, resulting from the activities proposed in our 

Plan.1

 

1 This certification is provided as required by NTL No. 2008-G04 at page 19.
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

(b) OIL SPILL RESPONSE DISCUSSION

A discussion of the response to an oil spill resulting from the activities proposed in this plan. Included is all the 

applicable information described in 30 CFR 254.26(b), (c), (d), and (e).

Oil spill response related activities for facilities included in this document are governed by the Chevron Gulf of Mexico 

Business Unit Regional Oil Spill Response Plan (OSRP). This OSRP meets all requirements contained in 30 CFR 

250. The existing Chevron Regional OSRP was approved by BOEM on April 15, 2010. Chevron submitted several 

OSRP revisions with the current OSRP dated February 12, 2013. The below information is from this Chevron revised 

OSRP. The Chevron Gulf of Mexico Business Unit Regional OSRP encompasses all facilities operated by Chevron 

U.S.A. Inc. and, herein the jurisdiction of the BOEM. 

Chevron has multiple oil spill response assets under contract to rapidly contain a major oil spill in the Walker Ridge

area. Chevron has five (5) offshore dual purpose vessels (offshore supply vessels outfitted with ocean boom, 

skimming systems and onboard storage tanks) that are permanently assigned in the Gulf of Mexico. These vessels 

will be immediately deployed to Walker Ridge to contain the oil slick and to recover oil. Arrival times will vary on the 

vessel location but all five (5) vessels can be on-scene within 18 hours. In addition to these five (5) dual purpose 

vessels, Chevron has assets that can contain a worst case discharge at Walker Rdige, to the maximum extent 

practicable within 48 hours by deploying the following resources:

• 36,000’ of ocean boom

• Deepwater skimming vessels and systems capable of collecting 530,000 barrels of oil per day (EDRC)

• Dispersant aircraft capable of dispersing over 6,000 barrels of oil per day

These assets are listed in the Chevron Oil Spill Response Plan that was submitted to the BOEM on July 12, 2013.

The following paragraphs provide information required by 30 CFR 254.26. 

Trajectory Analysis (§ 254.26 (b))

Land areas that could be potentially impacted by an oil spill were determined using the BOEMRE Oil Spill Risk 

Analysis Model (OSRAM) trajectory results. The OSRAM estimates the probability that oil spills from designated 

locations would contact shoreline and offshore natural resources. These probabilities indicate, in terms of 

percentage, the chance that an oil spill occurring in a particular launch area will contact a certain county or parish 

within 3, 10, and 30 days. OCS Launch Area C50 was used as the point of origin for Walker Ridge Block 143. Land 

segments identified by the model are listed below:

Land Segment chance of contacting within 

3 days

chance of contacting within 

10 days

chance of contacting within 

30 days

C08 Matagorda, TX 0 0 1 %

C10 Galveston, TX 0 0 1 %

C13 Cameron, LA 0 0 1 %

C14 Vermillion, LA 0 0 1 %

C20 Plaquemines, LA 0 0 1 %

Resource Identification (§ 256.26 (c))

Resources of special economic or environmental importance found in land segments identified in the above 

paragraph can be found in the NOAA ESI Coastal Sensitivity Atlas (Maps). These maps can be accessed through 

NOAA and will be used during any spill occurring from the locations listed in this document. 

Additionally, information on environmental sensitivities is contained in the below Coast Guard Area Contingency 

Plans which will be accessed and followed during an oil spill that threatens the Gulf of Mexico shoreline. 
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

• Corpus Christi, TX Area Contingency Plan

• Port Arthur, TX Area Contingency Plan

• Houston-Galveston, TX Area Contingency Plan

• Southeast Louisiana Area Contingency Plan

• Sector New Orleans, LA Area Contingency Plan

• Mobile, AL Area Contingency Plan

• St. Petersburg, FL Area Contingency Plan

Response Discussion (§ 254.26 (d))

Chevron maintains numerous resources, equipment and expertise to respond to an oil spill in the Gulf of Mexico. 

Chevron has oil spill response service contracts with both local and international companies and cooperatives, and 

has a large corps of dedicated Chevron emergency responders that can work in the Gulf of Mexico. Chevron has 

contracts with the following oil spill response service providers.

Oil Spill Removal Organizations (OSRO). These companies have on-hand shoreline protection and cleanup 

equipment to respond to a spill in the Gulf of Mexico. 

• Oil Mop LLC

• U.S. Environmental Services

• ES&H Consulting

• American Pollution Control

• T&T Marine

Oil Spill Cooperatives (OSC). OSCs have equipment pre-staged in the Gulf of Mexico including Lake Charles, 

Intracoastal City, Houma, Grand Isle, Fort Jackson and Venice, Louisiana; Galveston, Texas; and Pascagoula, 

Mississippi. OSCs provide resources to respond to offshore incidents including areas identified in this plan.

• Clean Gulf Associates Services (CGAS) – This major cooperative strictly dedicated to Gulf of Mexico oil and 

gas developers and producers. 

• Marine Spill Response Corporation (MSRC) – This national cooperative has extensive dedicated offshore 

resource located in the Gulf of Mexico

• Clean Caribbean and Associates (CCA) – This is a major cooperative located in the Caribbean. 

• Oil Spill Response, Ltd. (OSR) – This one of the largest international cooperatives operating out of the UK, 

Bahrain and Singapore. 

Well Control Emergency Response Companies

• Wild Well Control Inc.

• Boots & Coots 

• IWC Services, Inc.

Oil Spill Management and Response Consultants 

• O’Brien’s Oil Pollution Services

• The Response Group (TRG) 

Chemical Dispersant Companies (capable of delivering air and vessel dispersants) 

• Airborne Support, Inc 

• MSRC

• CCA

• OSRL

Chevron has numerous staging areas in the Gulf of Mexico including Chevron’s three shorebases located in 

Intracoastal City, Leeville and Venice, Louisiana. Other staging areas will be pursued as warranted by any specific 

response. Chevron primary equipment locations are located Leeville, Houma, Fourchon, Venice, Lake Charles, LA 

and Pascagoula, MS. 
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

Chevron will use a layered approach to respond to a worst case discharge from the area by conducting simultaneous 

response operations at the well site, in the offshore environment and in nearshore and shoreline areas. Plans 

will be implemented, resources deployed and response operations established within these environmental areas to 

accomplish the following objectives:

• Provide for the safety of responders and the general public

• Intervene at the well site to stop the flow of oil 

• Minimize the spread of oil at the surface 

• Minimize encroachment to the coastline environment

• Protect coastal and natural resources 

Upon notification of a worst case discharge oil spill at the locations listed in this plan Chevron will mobilize resources 

listed in the attached enclosures. This information comes directly from the Chevron Gulf of Mexico Business Unit 

Regional Oil Spill Response Plan and applies to a worst case discharge volume of 220,332 barrels per day that could 

occur at a Chevron facility located in Green Canyon 641. These same assets would be mobilized to all sites 

contained in this plan. The on water recovery vessels, barges and systems listed below have an effective daily 

recovery capacity of 816,651 barrels per day. 

• Aerial Surveillance Equipment

• Offshore Recovery Equipment

• Nearshore Recovery Equipment

• In-Situ Burn Equipment

• Aerial Dispersant Equipment

• Shoreline Protection Equipment

• Offshore Storage Equipment

Chevron will also take the following general actions to mobilize and coordinate response operations:

• Set up and staff its command center in Covington, LA

• Set up a source control group in Houston, TX, or Covington, LA

• Mobilize well site resources to cap, contain and disperse oil at the well head

• Mobilize assets to drill relief wells

• Mobilize assets to contain and collect surface oil at the well site and in the offshore environment

• Mobilize assets to disperse and burn surface oil at the well site and in the offshore environment

• Establish a deepwater staging area from a LA port or location

• Deploy assets to track the movement of oil on the surface

Follow up actions will include the following:

• Locate, monitor, track and project the movement of the oil spill

• Mobilize nearshore skimming and booming vessels, barges and systems to shorebase locations for rapid 

deployment in the nearshore environment

• Mobilize oil spill removal organization (OSRO) resources and assets to staging areas for rapid deployment 

of shoreline protection resources

• Mobilize wildlife protection and rehabilitation resources to staging areas for rapid deployment of resources

• Determine Incident Command Post (ICP) locations based on intervention operations and results and surface 

oil spill trajectories

• Determine ICP Operations Branch locations based on intervention operations and results and surface oil 

spill trajectories

• Determine additional staging areas based on the spill trajectory
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

Spill Response Resources and Deployment Time to Walker Ridge Block 143

Offshore Response: Offshore response operations will integrate simultaneous containment booming, mechanical 

recovery, aerial dispersants and in-situ burning. Response objectives within the offshore layer are to:

• Provide for the safety of responders and the general public

• Minimize wide-scale spread of oil

• Minimize encroachment to coastline environment

The strategy for offshore response will be to:

• Station mechanical recovery vessels and barges that are outfitted with ocean boom systems closest to the 

source to contain and collect as much oil as possible.

• Station mechanical recovery vessels and barges that deploy skimming systems on vessels of opportunity 

close to the source to rapidly contain and collect oil that strays from the main oil slick.

• Station in-situ burn assets closets to the source to burn as much oil as possible.

• Aerially disperse oil that cannot be mechanically recovered.

Simultaneous implementation of these strategies will effectively contain and recover an oil spill well offshore to 

minimize the potential impacts to public health, wildlife and the environment. Separate and distinct resources will be 

assigned for each operation. The following sections provide more information on each operation to respond to and 

contain a worst case discharge to the maximum extent possible.

(1) Mechanical Recovery and Slick Containment. Offshore skimming and booming vessels, barges and systems will 

be deployed to the source of the spill and stationed in the thickest parts of the spill to enhance the encounter rate, 

collect and contain the oil. VHF radio communications will be established between skimming vessels and barges and 

spotter aircraft and surveillance systems to direct vessels to coordinates of thickest oil to maximize the effectiveness 

and efficiency of on water recovery resources. Vessels operating in oil will relay spill characteristics (thickness, 

trajectory) to the Forward Operating Branch and Chevron Decision Support Center to station additional vessels and 

barges that are equipped with night sensing systems in areas of recoverable oil prior to nightfall. This will again 

maximize the oil recovery encounter rate. MSRC Responder Class vessels, the CGA Hoss barge, Production 

Support Vessels, Dual Purpose Vessels and vessels of opportunity outfitted with KOSEQ skimming systems will 

deploy J-boom or U-boom configurations that will maximize containment of oil to collect using skimmers. These 

vessels will work in tandem to cover as large of a geographic area as possible at the location of the surface spill 

where oil is the thickest. 

Vessels deployed with MSRC and CGA Fast Response Units and CGA Fast Response Vessels will be stationed to 

collect oil that moves past the front line mechanical assets. These units will deploy a J-boom configuration because it 

only requires one support vessel. Oil that escapes the above assets and moves shoreward will be collected by 

vessels of opportunity that deploy sorbent boom, collection nets or other types of equipment that absorbs surface oil. 

These assets will be deployed as task forces that can rapidly respond to light oil.

Depending on the location of Chevron contracted Dual Purpose Vessels 20,000’ of deepwater containment boom 

could be deployed to the Walker Ridge area within 6 hours of a spill. An additional 15,800’ of offshore boom located 

on deepwater skimming vessels could be deployed within 36 hours. And finally 36,000’ of offshore boom could be 

deployed from barges within 36 hours. Deepwater skimming vessels and barges could be deployed within 6 to 36 

hours that could effectively skim over 300,000 barrels of oil per day. Offshore storage barges will arrive within 18 

hours and will be able to store over 300,000 of barrels of oil per day. 

(2) In-Situ Burning. Offshore in-situ burn assets will be deployed as primary response resources for all locations 

within federal waters. Vessels of opportunity that can operate near the spill site will be used to deploy fire boom and 

trained in-situ burn responders. Fire boom will be configured in a “U” shape or similar to the NOFI Ocean Buster 
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

design. First fire boom assets will arrive on scene within 17 hours and can have 5,500’ of fire boom deployed within 

66 hours. 

(3) Aerial Dispersants. Aerial dispersants will be deployed as primary response resources for all locations that fall 

within the FOSC pre-approval process and applied on oil that cannot be mechanically recovered or burned. 

Dispersant aircraft that arrive on-scene before mechanical recovery or in-situ burn resources will apply dispersants to 

areas until relieved by a different asset. First dispersants can be applied within 4 hours of notification of a spill in the 

Walker Ridge area. 

Vessel radar systems and infrared cameras will be used to detect and mechanically collect oil at night. This will allow 

surveillance operations to continue both day and night and through inclement weather. These systems also will be 

used to track the movement of oil which will assist with shoreline response planning.

Louisiana resources potentially at risk may include but are not limited to the following:

Marine sensitivities, Beaches, Waterfowl, Shoreline resources, Marshes, Marinas/Piers, Populated areas, and 

Environmental sensitivities

The BOEM oil spill trajectory model indicates that LA parishes could be impacted by an oil spill from areas listed in 

this plan. LA parishes are dominated by fine sand beaches, coarse sand beaches, swamps and salt water marshes. 

The below summarizes potential concerns with each environment. This information is taken from various Coast 

Guard Area Contingency Plans.

Fine Sand Beach Environment

• Sensitivity: Fine sand beaches have a low sensitivity to oil spill impacts and cleanup methods.

• Oil Behavior: Oil typically stains and covers the beach sands with low permeability.

• Cleanup: The penetration is low to moderate depending on the water table and the position of the oiling on 

the shoreline. A major environmental concern during beach cleanup is the protection of the dune habitat 

from the cleanup operations. Fine sand beaches typically have poor access, but good transportation ability. 

Fine sand beaches are relatively easier to clean in contrast to marshes. Large volumes of stained sand and 

debris can be generated by beach cleanup.

Coarse Sand Beach Environment

• Sensitivity: The environmental sensitivity of coarse sand beaches is low due to the limited animal and 

vegetation population.

• Oil Behavior: Spilled oil typically stains and coats coarse grain beach sands with moderate to high 

permeability.

• Cleanup: Sediment penetration on coarse grain beaches is moderate/high depending on the water table and 

the location of oil deposition. A major environmental concern is the protection of the dune habitat from 

cleanup operations. The transit ability of this shoreline type is less than fine sand beaches because the 

bearing strength is lower and this type of sand builds steep beach faces. Access is typically poor.

Swamp Environment

• Sensitivity: The environmental sensitivity is high for swamps because of the presence of wetland habitat.

• Oil Behavior: Oil usually coats and covers the sediment and vegetation with low sediment penetration.

• Cleanup: The sediment penetration potential is low due to the high water table and the water content of the 

sediments. A major environmental concern is that the cleanup may be more damaging than the oil itself. 

The access to swamps is poor due to the soft sediment and the presence of dense tree growth.

Salt Marsh Environment

• Sensitivity: The environmental sensitivity is high for salt marsh because of the presence of wetland habitat.
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

• Oil Behavior: Oil usually coats and covers the sediment and vegetation with low sediment penetration.

• Cleanup: The sediment penetration potential is low/moderate due to the high water table and water content 

of the sediment. A major environmental concern is that the cleanup may be more damaging than the oil 

itself. Access is typically poor in Louisiana.

The protection of waterfowl and wildlife during the course of an oil release is an essential element in every spill 

response operation. Federal and state natural resource trustees will be notified in the event that a wildlife habitat 

may be affected by a spill event. Information concerning methods to protect waterfowl and wildlife are contained in 

the Chevron OSRP. For fish and wildlife resources, the emphasis is on habitats where:

• Large numbers of animals are concentrated in small areas, such as bays where waterfowl concentrate 

during migration or over wintering

• Early life stages are present in somewhat restricted areas or in shallow water, such as anadromous fish 

streams and turtle nesting beaches

• Habitats are very important to specific life stages or migration patterns such as foraging or overwintering

• Specific areas are known to be vital sources for seed or propagation

• The species are on Federal or state threatened or endangered lists

• A significant percentage of the population is likely to be exposed to oil.

Human-use resources of concern are listed in the Chevron OSRP. Areas of economic importance, like waterfront 

hotels, should also be considered when establishing resource protection priorities. Human-use resources are most 

sensitive when:

• Archaeological and cultural sites are located in the intertidal zones

• Oiling can result in significant commercial losses through fouling, tainting, or avoidance because of public 

perception of a problem

• The resource is unique, such as a historical site

• Oiling can result in human health concerns, such as tainting of water intakes and/or subsistence fisheries

Suitability of Resources (§ 254.26 (e)). All response equipment, materials, support vessels and strategies listed in 

this document and the Chevron Gulf of Mexico Business Unit Regional Oil Spill Response Plan have proven suitable 

for the many environmental conditions existing at the locations listed in this plan. Chevron additionally conducts 

annual oil spill response training, drills and exercises and validates the content of the Oil Spill Response Plan. The 

Chevron Gulf of Mexico Business Unit Regional Oil Spill Response Plan is maintained by the Chevron Greater Gulf 

of Mexico Emergency Management Coordinator who can be contacted at DouglasBlakemore@Chevron.com.
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION I ENVIRONMENTAL MONITORING INFORMATION

(a) MONITORING SYSTEMS

The Drillship is installed with surface current monitoring equipment. This equipment is a 75 kHz Acoustic Doppler 

Current Profile (ADCP) unit. This unit monitors current to a depth of 603 meters / 1,978’. The data from this meter is 

reported to the BOEM via the NDBC website.

(b) INCIDENTAL TAKES

There is no reason to believe that any of the endangered species or marine mammals as listed in the ESA will be 

“taken” as a result of the operations proposed under this plan.

(c) FLOWER GARDEN BANKS NATIONAL MARINE SANCTUARY

No activities proposed in this plan will be conducted within the Protective Zones of the Flower Garden Banks and 

Stetson Bank.

SECTION J LEASE STIPULATIONS INFORMATION

Not applicable. No stipulations assigned to this lease.

SECTION K ENVIRONMENTAL MITIGATION MEASURES INFORMATION

(b) INCIDENTAL TAKES

Chevron will adhere to the requirements as set forth in the following documents, as applicable, to avoid or minimize 

impacts to any of the species listed in the ESA as a result of the operations conducted herein:

NTL No. 2012-Joint-G02, “Vessel Strike Avoidance and Injured/Dead Protected Species Reporting

NTL No. 2012-BSEE-G01, “Marine Trash and Debris Awareness and Elimination”

NTL No. 2012-Joint-G01, “Implementation of Seismic Survey Mitigation Measures and Protected Species Observer 

Program”
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION L SUPPORT VESSELS AND AIRCRAFT INFORMATION

(a) GENERAL 

In the table below, information is provided regarding the vessels (e.g., tug boats, anchor-handling vessels, 

construction barges, lay barges, supply boats, crew boats) and aircraft you will use to support your proposed 

activities. If specific vessels have not yet been determined, use the maximum capacities, numbers, and trip 

frequencies for the types of vessels you will use.

Type Maximum Fuel Tank 

Storage Capacity

Maximum No. in Area at 

Any Time

Trip Frequency or 

Duration

Crew Boat 47,382 gals. One Once per week

Supply Boat 303,093 gals. Two Every 2 to 3 days

Helicopter 2,800 lbs. / 430 gals. One 7 trips per week

(b) DIESEL OIL SUPPLY VESSELS

Information on the vessels used to supply diesel oil. Any vessels that will transfer diesel oil you will use for purposes 

other than fuel.

Size of Fuel Supply 

Vessel

Capacity of Fuel Supply 

Vessel

Frequency of Fuel 

Transfers

Route Fuel Supply 

Vessel Will Take

280 foot 860,000 gals quarterly From shore base to block

280 foot 275,000 gals 4-6 weeks From shore base to block

(d) SOLID AND LIQUID WASTES TRANSPORTATION

Water Quality Spreadsheets replace the Solid and Liquid Wastes Transportation Table.

(e) VICINITY MAP

A map showing the location of the proposed activities relative to the shoreline, the distance of the proposed activities 

from the shoreline, and the primary route(s) of the support vessels and aircraft you will use when traveling between 

the onshore support facilities and the drilling unit is provided as attachment L-1 at the end of this section.

Included in Initial Exploration Plan, N-08136, Section B, Attachment B-1
Union Oil Company of California Revised Exploration Plan

Walker Ridge Block 143 Public Information

SECTION M ONSHORE SUPPORT FACILITIES INFORMATION

(a) GENERAL

The table below provides a listing of the onshore facilities that will be used to provide supply and service support for 

the proposed activities.

Name Location Existing/New/Modified

Chevron’s Leeville Shore Base Leeville, Louisiana Existing

C-Port Shorebase- Port Fourchon Fourchon, Louisiana Existing

(b) SUPPORT BASE CONSTRUCTION OR EXPANSION

Chevron will use its existing onshore base facility located in Leeville, Louisiana. The base has adequate facilities for 

marine and air transportation to accommodate the activities proposed in this plan. The proposed operations do not 

require expansion or modifications to the base.

(d) WASTE DISPOSAL

Water Quality Spreadsheets replace the Waste Disposal Table.

SECTION N COASTAL ZONE MANAGEMENT ACT (CZMA) INFORMATION

No significant changes in impacts previously identified and evaluated are expected due to the revisions in this plan. 

SECTION O ENVIRONMENTAL IMPACT ANALYSIS (EIA)

A project-specific EIA was attached to Initial Exploration Plan, N-08136, as Appendix H.

SECTION P ADMINISTRATIVE INFORMATION

(a) EXEMPTED INFORMATION

Proprietary information included in the proprietary copy of this EP.

• BHL, TVD, MD on Form BOEM-0137 (OCS Plan Information Form)

• Correlative well names in H2S Classification

• All items and enclosures under Geological and Geophysical Information

• Archaeological Survey Report and Hard Drive with Archaeological Survey data

(b) BIBLIOGRAPHY

Any previously submitted EP, DPP, or DOCD; study report; survey report; or other material referenced in this EP or 

its accompanying information, is listed below:

• Initial Exploration Plan, N-8136, Walker Ridge Blocks 142 and 143, submitted July 6, 2004, approved August 

16, 2004.

• Revised Exploration Plan, R-5084, WR Block 143, submitted October 29, 2010, approved June 16, 2011.

• Chevron’s Regional Oil Spill Response Plan

• Fugro Report No. 2400-2073, “Shallow Hazard Assessment, Coronado Prospect, Blocks 98, 99, 142 and 143, 

(OCS-G 21841, 21842, 21848, and 21849), Walker Ridge Area, Gulf of Mexico”