UNITED STATES GOVERNMENT MEMORANDUM

To: Public Information (MS 5030)

Plans Section, Office of Field 

Operations (MS 5231)

Public Information copy of Exploration Plan

Control # - S-07521

Type - Supplemental Exploration Plan

Lease(s) - OCS-G21811 Block - 679 Green Canyon Area

OCS-G21813 Block - 723 Green Canyon Area

Operator - Noble Energy, Inc.

Drill & complete Wells F, G, H, J, & K

DP SEMISUBMERSIBLE

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

should be addressed in an Environmental Assessment.

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

James Webb

Plan Coordinator

Description -

Rig Type -

Subject:

From:

February 2, 2012
WCD Discussion - Proprietary

OCSG-21813 # 2 Operator – Noble Energy, Inc.

GC 723, Deep Blue Prospect

1 of 5

Description of the Drilling Blowout Scenario

The worst case discharge (WCD) is based on a drilling blowout scenario whereby the well has

been drilled to depth of 26,200’ MD to the 9-7/8” liner depth and there is no drill pipe in the

well. At the time of the blowout, the well contains a 14” x 13-5/8” tapered long string that is

hung off in the wellhead, an 11-7/8” drilling liner below the long string, and approximately

2300’ of 12-1/4” x 10-5/8” open hole. The open hole section is assumed to produce both oil and

water from all the exposed reservoirs. Gas reservoirs are not expected in the sidetrack since the

original GC723 No. 1 exploration well did not encounter evidence of gas reservoirs. In this

WCD scenario, the assumption is that the highest unrestricted flow volumes from this well will

be encountered form the 12-1/4” x 10-5/8” open hole section and will flow against a seawater

gradient as back pressure at the wellhead. The WCD calculation assumes the absence of subsea

blowout preventers and riser.

Estimated Worst Case Discharge

The estimated calculated WCD for the GC 723 No. 2 is 249,052 BOPD and calculations are

based on the petrophysical and reservoir fluid data collected in the GC 723 No.1 well. These

calculations were performed using a well known industry nodal analysis program called Well

Evaluation Model (WEM). Assuming the well produces with a 5% decline /month for 143 days

(time to drill a relief well) the total volume of produced oil is 31.65 mmbo.

The GC 723 No. 2 is planned to be spudded from the “G” location on block GC 723, updip to the

GC 723 No. 1 well, and will encounter the same reservoirs. It is also assumed that any sand that

contained oil in the GC 723 No. 1 well would contain oil in the updip GC 723 No. 2 well and

any sand that was wet in the GC 723 No. 1 well would be wet in the updip GC 723 No. 2 well.

For example, the “A” Sand at 28,250’ MD contained 2’ of oil over water in the GC 723 No. 1

well and in the GC 723 No. 2 it is assumed that the sand completely fills with oil and will have

121’ of net TVD oil pay.

Duration of the Worst Case Discharge

The duration of the WCD is dependent on the characteristics of the blowout. The WCD will

persist until the well is contained, a relief well is drilled, or the well bridges over due to wellbore

instability.

Based upon the petrophysical and detailed rock stress analysis, the highest likelihood is the

wellbore will fail under WCD conditions. The primary wellbore failure mechanism is due to the

low bottomhole flowing pressures allowing the in situ rock stress to fail the exposed rock in the

open hole section. As a result, there is a strong possibility of the wellbore to bridge over where

the failed rock fragments lodge downhole to prevent the well discharge from continuing.

Scenarios exist in which the duration may be short lived to several weeks depending on the

condition of the well at the time of the discharge as outlined below:
WCD Discussion - Proprietary

OCSG-21813 # 2 Operator – Noble Energy, Inc.

GC 723, Deep Blue Prospect

2 of 5

 The well could bridge over due to wellbore instability which should happen relatively

early in the WCD scenario due to the highly fragile nature of the wellbore integrity.

 A 15K WP subsea well capping BOP could be installed will allow the well to be shut in

eliminating the discharge of well fluids. As a contingency, a 10k WP subsea well

capping BOP can be installed and the ROV can manually close vent valves allowing

capture and containment of the discharged fluids at surface under a dynamic controlled

situation.

 Twisted riser material may need to be removed prior to any containment equipment

installation, which could take a considerable time to eliminate fluid releases.

 If all intervention attempts were unsuccessful, the well could discharge until terminated

by a relief well intervention and the GC 723 No. 2 well is killed.

In summary, the WCD duration may be short lived if it bridges over, last several days until the

well is contained, or discharge for several months until the relief well kills the discharging well.

Potential of Open Hole to Bridge Over

Due to the unrestricted flow of a WCD scenario, it is expected that well will experience a

downhole rock failure. The primary failure mechanism is the wellbore instability cause by the

reduced wellbore pressure. The in situ stresses that exist in the reservoir rock are held in place

by the hydrostatic pressure of the weighted drilling fluid in the wellbore. If the wellbore

pressure is reduced, the high in situ stresses are no longer opposed by the weighted drilling fluid

and the in situ rock will fail and collapse into the wellbore. Based on sand strength analysis

calculations there are some portions of the open hole wellbore that will start to fail once the

wellbore pressure drops a small amount below the actual reservoir pressure. Since the estimated

downhole flowing reservoir pressure is calculated to be 3000 psi below the reservoir pressure

based on the submitted WEM model results, it is expected that all of the sands in the wellbore

would fail due to wellbore instability. The calculations support the conclusion that if the GC 723

No. 2 well were to encounter a worst case discharge scenario the wellbore would fail due to an in

situ stress induced failure event. In addition to the sands failing, the shales would also fail as a

result of the decreased borehole pressure. A separate wellbore instability study was conducted to

evaluate shale stability for the GC 723 No. 1 ST01. The calculations confirm that all of the

shales in the exposed wellbore, from TD back to the casing shoe, would fail and collapse in a

worst case discharge scenario. As a result, there is a high probability of the wellbore to “bridge

over” where the failed rock fragments accumulate and lodge downhole to prevent the well

discharge from continuing.
WCD Discussion - Proprietary

OCSG-21813 # 2 Operator – Noble Energy, Inc.

GC 723, Deep Blue Prospect

3 of 5

Likelihood for Surface Intervention to Stop Blowout

There is a high likelihood that a combined surface and subsea intervention would stop a blowout

of the GC 723 No. 2 well. Noble Energy has access to and can deploy surface and subsea

containment resources adequate to promptly respond to a blowout or loss of well control. The

GC 723 No. 2 well is designed to handle the worst-case shut in pressure and maintain full

integrity. This wellbore integrity will allow the 15K subsea capping stack to be utilized to its

fullest potential of shutting in the well eliminating the discharge. Clean Gulf Associates has the

capability to provide efficient mobilization of necessary equipment and procedures to effectively

mitigate numerous blowout scenarios.

Availability of Drilling Rig for a Relief Well

In the event of a WCD, Noble has identified several 5th generation DP rigs that are capable of

drilling the GC 723 No. 2 relief well to the appropriate depth and in 5,000’ of water. Depending

on the activity and location of the available rigs at the time of the worst case discharge, it may

require 1-2 weeks before the rig is on location ready to spud the relief well.

Estimated Time to Drill a Relief Well

The estimated time to drill a relief well is 133 days from the time the rig arrives on location to

intersection of the blowout wellbore. The estimated time to acquire the rig is 1-3 days after the

blowout and then 10 days or less to mobilize the rig on location. The relief well time estimate

assumes 25% NPT and 20 total ranging runs. The relief well surface location will be a

approximately 3,000’ away from the blowout well and drilled as a directional well designed to

intersect the blowout well above the 11-7/8” drilling liner shoe. Once intersected, the well can

be killed with kill weight mud and cemented as appropriate for permanently abandoning the

well. A deepwater drilling rig capable of drilling in 5,000’ of water must be utilized for a relief

well. In this scenario, drilling a relief well from a nearby platform is not feasible.

Measures for Blowout Prevention

Certain measures will be taken to prevent and reduce the likelihood of a blowout as described in

the WCD discharge scenario. The blowout prevention measures provide additional assurance in

improving the safety of offshore oil and gas drilling. Key measures taken for blowout prevention

include but are not limited to:

 Compliance with all Federal rules and regulations: CFRs, NTLs, and Final Rules.

 Follow provisions in API RP 65-Part 2 and API RP 53.

 Utilization of Noble’s management systems: Global Management System (GMS), Safety

and Environmental Management System (SEMS), Drilling Management System (DMS),

Management of Change (MOC), and/or appropriate bridging documents to contractor’s

Safety Management Systems.
WCD Discussion - Proprietary

OCSG-21813 # 2 Operator – Noble Energy, Inc.

GC 723, Deep Blue Prospect

4 of 5

 Utilize established well control practices, guidelines, and procedures.

 Ensure proper physical barriers are in place to prevent uncontrolled flow.

 Utilize established negative testing procedures and BOEMRE approved fluid

displacement procedures.

 Utilize experienced and fully trained personnel.

 Strict adherence to well monitoring.

 Certified BOPE that is fit for purpose.

 Utilize rig and equipment that is fit for purpose.

 Professionally certified and peer reviewed well design (casing and cementing).

 Contractor engagement meeting to gain alignment on well plan.

 Specific procedures to execute well plan.

Early Intervention In the Event of a Blowout

Noble Energy has access to and can deploy surface and subsea containment resources adequate

to promptly respond to a blowout or loss of well control. In the event that all attempts to shut-in

the well with the rig’s BOP fail, Noble plans to utilize the Helix Fast Response System (HFRS)

containment system for intervention. Procedures have been developed and equipment has been

identified for a fast deployment. Service companies who support the operation and their specific

equipment have been identified and documented during several technical sessions to mature the

well containment response. Procedures have been developed for: debris removal, BOP and/or

LMRP and/or riser removal, capping stack installation, well shut-in, and static top kill

operations. Noble has access to the following through the Clean Gulf Associates:

 Subsea containment and capture equipment.

 Subsea equipment to cut riser and perform various interventions.

 Dispersant injection equipment.

 Riser systems

 Remotely operated vehicles (ROVs)

 Capture vessels

 Support vessels

 Storage facilities

GC 723 #2 Containment:

In the event of a WCD scenario blowout, the GC 723 No. 2 well design will experience collapse

of the 11-7/8” liner and the lower section of the 13-5/8” long string which will expose the strata

below the 16” casing shoe. Upon shut in with a 15K capping stack, an underground flow (UGF)

will be initiated into the strata below the 16” casing shoe and continue until the flow is killed by

a relief well. A broaching study indicates that, upon shut-in below a capping stack, the exposed

strata will accept the UGF fluid volume without broaching to the seafloor until the relief well is

drilled and the well is killed, thereby, eliminating hydrocarbon discharge in the environment

once the capping stack rams are closed. The GC 723 No. 2 wellbore will retain integrity from
WCD Discussion - Proprietary

OCSG-21813 # 2 Operator – Noble Energy, Inc.

GC 723, Deep Blue Prospect

5 of 5

the capping stack to the 16” casing shoe during this shut-in and UGF period. Efficient

mobilization of necessary response equipment and procedures to effectively mitigate numerous

blowout scenarios is available through Clean Gulf Associates.

Relief Well Arrangements

Noble has taken additional measures for drilling a relief well to assist in conducting early and

effective intervention of a blowout. The Deep Blue team has selected two relief well locations

with notional well designs to intercept the last drilling liner set prior to drilling the production

hole section. The team has assessed the tangibles, equipment, and services necessary to drill a

relief well and can source all of those requirements in the event of a blowout.
Description of the Drilling Blowout Scenario

The worst case discharge (WCD) is based on a drilling blowout scenario whereby the

well has been drilled to depth of the 9-7/8” liner setting depth and there is no drill pipe in

the well. At the time of the blowout, the well contains a 14” x 13-5/8” tapered long string

that is hung off in the wellhead, an 11-7/8” drilling liner below the long string, and 12-

1/4” x 10-5/8” open hole. The open hole section is assumed to produce oil and/or water

from all the exposed reservoirs. In this WCD scenario, the assumption is that it will flow

against a seawater gradient as back pressure at the wellhead. The WCD calculation

assumes the absence of subsea blowout preventers and riser.

Estimated Worst Case Discharge

The estimated calculated WCD for the GC 723 No. 2 is 249,052 BOPD. The GC 723

No. 2 is planned to be spudded from the “G” location on block GC 723.

Duration of the Worst Case Discharge

The duration of the WCD is dependent on the characteristics of the blowout. The WCD

will persist until the well is contained, a relief well is drilled, or the well bridges over due

to wellbore instability.

Scenarios exist in which the duration may be short lived to several weeks depending on

the condition of the well at the time of the discharge as outlined below:

 The well could bridge over.

 A 15K WP subsea well capping BOP could be installed.

 Twisted riser material may need to be removed.

 If all intervention attempts were unsuccessful, the well could discharge until

terminated by a relief well intervention and the GC 723 No. 2 well is killed.

In summary, the WCD duration may be short lived if it bridges over, last several days

until the well is contained, or discharge for several months until the relief well kills the

discharging well.

Potential of Open Hole to Bridge Over

Due to the unrestricted flow of a WCD scenario, the well could experience downhole

rock failure. The wellbore could “bridge over” where the failed rock fragments

accumulate and lodge downhole to prevent the well discharge from continuing.
Likelihood for Surface Intervention to Stop Blowout

There is a high likelihood that a combined surface and subsea intervention would stop a

blowout of the GC 723 No. 2 well. Clean Gulf Associates has the capability to provide

efficient mobilization of necessary equipment and procedures to effectively mitigate

numerous blowout scenarios.

Availability of Drilling Rig for a Relief Well

In the event of a WCD, Noble has identified several 5th generation DP rigs that are

capable of drilling the GC 723 No. 2 relief well to the appropriate depth and in 5,000’ of

water. Depending on the activity and location of the available rigs at the time of the

worst case discharge, it may require 1-2 weeks before the rig is on location ready to spud

the relief well.

Estimated Time to Drill a Relief Well

The estimated time to drill a relief well is 143 days from mobilization of the rig to

intersection of the blowout wellbore. A deepwater drilling rig capable of drilling in

5,000’ of water must be utilized for a relief well. In this scenario, drilling a relief well

from a nearby platform is not feasible.

Measures for Blowout Prevention

Certain measures will be taken to prevent and reduce the likelihood of a blowout as

described in the WCD discharge scenario. The blowout prevention measures provide

additional assurance in improving the safety of offshore oil and gas drilling.

Early Intervention In the Event of a Blowout

Noble Energy has access to and can deploy surface and subsea containment resources to

promptly respond to a blowout or loss of well control.

GC 723 #2 Containment:

In the event of a WCD scenario blowout, it is Noble’s intent to contain the well.

Efficient mobilization of necessary response equipment and procedures to effectively

mitigate numerous blowout scenarios is available through Clean Gulf Associates.
Relief Well Arrangements

Noble has taken additional measures for drilling a relief well to assist in conducting early

and effective intervention of a blowout. Noble has selected two relief well locations with

well designs to intercept the blowout well.
PUBLIC COPY

October 31, 2011

Supplemental Exploration Plan

Lease OCS-G 21811 & 21813

Green Canyon 679 & 723

Prospect Name: Deep Blue

Offshore: Louisiana

Submitted by:

Noble Energy, Inc.

100 Glenborough Drive

Suite 100

Houston, Texas 77067

Estimated start-up date: April 1, 2012
Table of Contents

Noble Energy, Inc.

Supplemental Exploration Plan

Lease OCS-G 21811 & 21813

Green Canyon 679 & 723

A. Plan Contents

a. Plan Summary

b. Plan Information Form

c. Location

d. Safety and Pollution Prevention Features

e. Storage Tanks and/or Production Vessels

f. Additional Measures

B. General Information

a. Applications and Permits

b. Drilling Fluids

c. New or Unusual Technologies

d. Bonding Statement

e. Oil Spill Financial Responsibility (OSFR)

f. Deepwater Well Control Statement

g. Blowout Scenario

C. Geological and Geophysical Information

a. Geologic Description

b. Structure Contour Maps

c. Interpreted 3-D Seismic Lines

d. Geological Structure Cross Section

e. Shallow Hazards Report

f. Shallow Hazards Assessment

g. High Resolution Seismic Lines

h. Stratigraphic Column

i. Time vs. Depth Table

D. Hydrogen Sulfide (H2S) Information

a. Concentration

b. Classification

E. Biological, Physical, and Socioeconomic Information

a. Chemosynthetic Communities Report

b. Topographic Features Map

c. Topographic Features Statement (Shunting)

d. Live Bottoms (Pinnacle Trend) Map

e. Live Bottoms (Low Relief) Map

f. Potentially Sensitive Biological Features

g. Remotely Operated Vehicle (ROV) Monitoring Survey Plan

h. Threatened and Endangered Species Information, Critical Habitat, and Marine Mammal

Information

i. Archaeological Report
F. Waste and Discharge Information

a. Projected Generated Wastes & Projected Ocean Discharges

G. Air Emissions Information

H. Oil Spill Information

a. Oil Spill Response Planning

b. Spill Response Sites

c. OSRO Information

d. Worst-case Scenario Comparison

e. Oil Spill Response Discussion

I. Environmental Monitoring Information

a. Monitoring Systems

b. Incidental Takes

c. Flower Garden Banks National Marine Sanctuary

J. Lease Stipulation Information

K. Support Vessels and Aircraft Information

a. General

b. Diesel Oil Supply Vessels

c. Solid and Liquid Wastes Transportation

d. Vicinity Map

L. Onshore Support Facilities Information

a. General

b. Support Base Construction or Expansion

c. Waste Disposal

M. Coastal Zone Management Act (CZMA) Information

N. Environmental Impact Analysis (EIA)

O. Administrative Information

a. Exempted Information Description

b. Bibliography
Noble Energy, Inc. Page A-1

Supplemental Exploration Plan 10/31/2011

Green Canyon 679 & 723 (OCS-G 21811 & 21813)

Section A

Plan Contents

A. Plan Summary

Noble Energy, Inc. proposes to drill and complete four wells in Green Canyon 679 & 723 utilizing a

dynamically positioned semisubmersible rig and a subsea BOP. The anticipated spud date of the first well is

April 1, 2012. Noble anticipates it will take approximately 115 days to drill and 94 days to complete each

well. If commercial quantities of hydrocarbons are discovered, a Development Operations Coordination

Document will be submitted for approval.

B. Plan Information Form

See attached OCS Plan Information Form – Form MMS-137, included as Attachment A-1.

C. Location

Included as Attachment A-2 is a location map depicting the proposed surface locations of the new wells.

Attachment A-3 is a bathymetry map showing the water depths at the surface location of each proposed

well. Attachment A-4 is a regional seafloor rendering with bathymetry showing a 2000’ radius around the

proposed wellsites. No anchors will be used for the proposed operations.

D. Safety and Pollution Prevention Features

A description of the drilling unit is included on the OCS Plan Information Form. Rig specifications will be

made part of each Application for Permit to Drill.

Safety features on the drilling unit will include well control, pollution prevention, and blowout prevention

equipment as described in Title 30 CFR Part 250, Subparts C, D, E, and G; and as further clarified by

BOEMRE Notices to Lessees, and current policy making invoked by the BOEMRE, Environmental

Protection Agency and the U.S. Coast Guard. Appropriate life rafts, life jackets, ring buoys, etc., will be

maintained on the facility at all times.

Pollution prevention measures include installation of curbs, gutters, drip pans, and drains on drilling deck

areas to collect all contaminants and debris.

E. Storage Tanks and/or Production Vessels

All facility tanks of 25 barrels or more.

Type of Storage

Tank Type of Facility Tank Capacity(bbls)

Number

of Tanks

Total

Capacity

(bbls)

Fluid

Gravity

(API)

Fuel Oil (Marine

Diesel) DP Semisubmersible

3,461 2 6,922 32.4°

4,634 2 9,268 32.4°

Total 16,190

F. Additional Measures

Noble does not propose additional safety, pollution prevention, or early spill detection measures beyond

those required by 30 CFR 250.






OCS-G-21813

H

G

F 6

5124' 5364' 

6487'

LOCATION PLA

STAFF 

GREEN CANYON 6

X=2,280,960'

Y=9,884,160'

N

Lat. 27 14' 51.21"

Lon. 90 59' 57.54"

WD 4797'

"H" X= 2,291,676'

Y= 9,894,244'

Lat. 27 15' 07.27"

Lon. 90 59' 42.15"

WD 4845'

"J" X= 2,292,192'

Y= 9,895,591'

Lat. 27 15' 20.52"

Lon. 90 59' 36.20"

WD 4850'

"K" X= 2,290,165'

Y= 9,900,528'

Lat. 27 16' 09.73"

Lon. 90 59' 57.78"

WD 4662'

1ST1

M

 MD 30,121', TVD 29,20
OCS-G-21813

H

G

F

5124' 5364' 

6487'

BATHYMETRY PL

STAFF 

GREEN CANYON 6

X=2,280,960'

Y=9,884,160'

N

-51

-5000'

-4900'

-4800'

-4700'

-4400'

-4300'

-4400'

-4500'

-4600'

25'

1ST1

M

 MD 30,121', TVD 29,200
Geodetic Datum: NAD27

Projection: UTM

Zone: UTM 15N

Grid Unit: Feet

!(

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!

!(

!(

GC 678

G25184

GC 679

G21811

GC 680

G22987

GC 722

G27362

GC 723

G21813

GC 724

Not Leased

GC 766

G22994

GC 767

G24182

GC 768

G21817

GC 723-F

GC 723-G

GC 723-H

GC 723-J

GC 679 K

G24182 #1

G21813 #1

Inline 8350

Inline 8300

Inline 8250

Inline 8200

Inline 8150

Inline 8050

Inline 8000

Inline 8400

Inline 8100 Crossline 9900

Crossline 9950Crossline 10000Crossline 10050Crossline 10100Crossline 10150Crossline 10200Crossline 10250Crossline 10300Crossline 10350Crossline 10400

Interpretation By: Jennifer Weller

Cartography: Zach Metz

Project No.: 11-04-14

Date: September 2011

Map Prepared by:

Berger Geosciences, LLC.

Blocks 679 and 723

Green Canyon Area

Gulf of Mexico

Map 1-2

Seafloor Rendering

3

Legend

3D Seismic Inlines & Crosslines

Subsurface Study Area

!( Existing Wells

!( Proposed Wells

2,000 ft Radius Circle

(as per NTL 2009-G40)

Seafloor Features

! ! Seafloor Faults

(tics indicate downthrown direction)

Expulsion Mounds

Seafloor Slumps

Î Lat/Long Grid Points

0 1,000 2,000 3,000 4,000 500

Feet

Scale: 1:12,000

Green Canyon

Study Area

27°17'0"N, 91°1'0"W 27°17'0"N, 90°59'0"W

27°15'0"N, 91°1'0"W 27°15'0"N, 90°59'0"W

UTM Northing & Easting

2,285,000 E

2,295,000 E

9,895,000 N

9,905,000 N

Bathymetry

4,172 ft

5,623 ft

Rendering Illumination:

Azimuth: 330°

Altitude: 50°

V.E.: 4X

**IMPORTANT NOTICE**

This map is not intended for navigation purposes. 

Public information obtained from BOEMRE database (August 2011)

9,885,000 N

Expulsion Mounds

Seafloor Expression

of Buried Faults

Relict Slumps
Noble Energy, Inc. Page B-1

Supplemental Exploration Plan 10/31/2011

Green Canyon 697 & 698 (OCS-G 21811 & 21813)

Section B

General Information

A. Applications and Permits

No additional applications or permits are required to conduct the activities proposed herein.

B. Drilling Fluids –

Type of Drilling Fluid Estimated Volume of Drilling

Fluid to be used per Well

Water-based 75,000 bbls

Synthetic-based 21,564 bbls

C. New or Unusual Technology

Noble does not propose to use any new or unusual technology to carry out the proposed exploration

activities.

D. 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 256, subpart I; NTL No. 2000-G16, "Guidelines for

General Lease Surety Bonds;" and National NTL No. 2003-N06, "Supplemental Bond Procedures".

E. Oil Spill Financial Responsibility (OSFR)

Noble Energy, Inc., BOEMRE company number 02237, 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".

F. Deepwater Well Control Statement

Noble Energy, Inc., BOEMRE company number 02237, has the financial capability to drill a relief well and

conduct other emergency well control operations.

G. Blowout Scenario

The worst case discharge (WCD) is based on a drilling blowout scenario whereby the well has been drilled

to depth of the 9-7/8” liner setting depth and there is no drill pipe in the well. At the time of the blowout,

the well contains a 14” x 13-5/8” tapered long string that is hung off in the wellhead, an 11-7/8” drilling

liner below the long string, and 12-1/4” x 10-5/8” open hole. The open hole section is assumed to produce

oil and/or water from all the exposed reservoirs. In this WCD scenario, the assumption is that it will flow

against a seawater gradient as back pressure at the wellhead. The WCD calculation assumes the absence of

subsea blowout preventers and riser.
Noble Energy, Inc. Page C-1

Supplemental Exploration Plan 10/31/2011

Green Canyon 697 & 698 (OCS-G 21811 & 21813)

Section C

Geological and Geophysical Information

A. Geological Description

Proprietary Data

B. Structure Contour Map

Proprietary Data

C. Interpreted 3-D Seismic Lines

Proprietary Data

D. Geological Structure Cross-Section

Proprietary Data

E. Shallow Hazards Report

A shallow hazards survey was conducted over Green Canyon 679 & 723.

One copy of a combined Shallow Hazards Assessment, Benthic Communities Evaluation, and

Archeological Resource Survey is included with this Exploration Plan.

F. Shallow Hazards Assessment

Utilizing the 3D seismic exploration data, a shallow hazards assessment was prepared for the proposed

surface locations, and is included as Attachment C-4. The shallow hazards assessments of the proposed

well locations are also included in the “Wellsite Discussion” section of the combined Shallow Hazards

Assessment, Benthic Communities Evaluation, and Archeological Resource Survey being submitted with

this EP.

G. High-Resolution Seismic Lines

Proprietary Data

H. Stratigraphic Column

Proprietary Data

I. Time vs. Depth Table

Proprietary Data

.
Project No. 11-04-14

BERGER GEOSCIENCES, LLC E-MAIL: beinnovative@b-geo.com WEBSITE: b-geo.com

Wellsite Discussion

Green Canyon Area 

Blocks 679 (Lease No. G21811) 

and 723 (Lease No. G21813) 

Gulf of Mexico
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Table of Contents: Wellsite Discussion Page

LIST OF TABLES ........................................................................................................................ ii

LIST OF FIGURES ...................................................................................................................... ii

LIST OF MAPS............................................................................................................................. ii

SHALLOW HAZARDS ASSESSMENT FOR PROPOSED WELLS .................................... 1

Maximum Anchor Radius Criteria .......................................................................................... 1

Tophole and Potential Relief Well Zone Prognosis Criteria .................................................. 1

Proposed Well GC 723-F ........................................................................................................ 3

Power Spectrum Analysis ................................................................................................... 3

Maximum Anchor Radius ................................................................................................... 4

Muds and Cuttings Discharge Location .............................................................................. 4

Wellbore Location .............................................................................................................. 5

Proposed Well GC 723-G ....................................................................................................... 8

Power Spectrum Analysis ................................................................................................... 8

Maximum Anchor Radius ................................................................................................... 9

Muds and Cuttings Discharge Location .............................................................................. 9

Wellbore Location ............................................................................................................ 10

Proposed Well GC 723-H ..................................................................................................... 13

Power Spectrum Analysis ................................................................................................. 13

Maximum Anchor Radius ................................................................................................. 14

Muds and Cuttings Discharge Location ............................................................................ 14

Wellbore Location ............................................................................................................ 15

Proposed Well GC 723-J ...................................................................................................... 18

Power Spectrum Analysis ................................................................................................. 18

Maximum Anchor Radius ................................................................................................. 19

Muds and Cuttings Discharge Location ............................................................................ 19

Wellbore Location ............................................................................................................ 20

Proposed Well GC 679-K ..................................................................................................... 23

Power Spectrum Analysis ................................................................................................. 23

Maximum Anchor Radius ................................................................................................. 24

Muds and Cuttings Discharge Location ............................................................................ 24

Wellbore Location ............................................................................................................ 25
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List of Tables

Table W-1. Location, block calls, and seismic lines for Proposed Well GC 723-F 

Table W-2. Location, block calls, and seismic lines for Proposed Well GC 723-G 

Table W-3. Location, block calls, and seismic lines for Proposed Well GC 723-H 

Table W-4. Location, block calls, and seismic lines for Proposed Well GC 723-J 

Table W-5. Location, block calls, and seismic lines for Proposed Well GC 679-K 

List of Figures

Figure W-1. Seafloor rendering of seafloor assessment area

Figure W-2. Seismic sections with tophole prognosis for Proposed Well GC 723-F 

Figure W-3. Seismic sections with tophole prognosis for Proposed Well GC 723-G 

Figure W-4. Seismic sections with tophole prognosis for Proposed Well GC 723-H 

Figure W-5. Seismic sections with tophole prognosis for Proposed Well GC 723-J 

Figure W-6. Seismic sections with tophole prognosis for Proposed Well GC 679-K 

List of Maps

Map W-1. Bathymetry, Proposed Well GC 723-F 

Map W-2. Bathymetry, Proposed Well GC 723-G 

Map W-3. Bathymetry, Proposed Well GC 723-H 

Map W-4. Bathymetry, Proposed Well GC 723-J 

Map W-5. Bathymetry, Proposed Well GC 679-K 
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Shallow Hazards Assessment for Proposed Wells

This section contains an assessment of the shallow hazards and tophole prognoses for five

proposed wells in the subsurface study area. 

Maximum Anchor Radius Criteria

Noble anticipates using a dynamically positioned Mobile Offshore Drilling Unit (MODU) in 

the seafloor assessment area; therefore, no specific anchor pattern has been analyzed.

Tophole Prognosis Criteria 

The following sections specify the criteria used to develop the tophole prognosis for the 

proposed wells. The assessment is based on the review of existing interpretations, evaluation 

of 3-D seismic data, correlation to regional well log data, and comparison to regional 

stratigraphic units as available. The tophole assessment is restricted to the specific proposed 

well location. 

Gas Hydrates. The potential for solid gas hydrates was evaluated for each proposed well. 

The criteria used to evaluate each proposed well include:

• What is the depth to the base of the gas hydrate stability zone (BGHSZ) at the proposed 

well?

• Is a bottom-simulating reflector (BSR) present between the seafloor and BGHSZ? 

• Is a BSR present within 500 ft of the proposed well? 

• Does the proposed well intersect a BSR?

• Have gas hydrates been identified in the region of the proposed well? 

HIGH

MODERATE

LOW

NEGLIGIBLE
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Shallow Gas. The potential for shallow gas was evaluated for each proposed well. The 

criteria used to evaluate each proposed well include:

• Does an anomalous amplitude event exist within 500 ft of the proposed well? 

• Is there a phase reversal associated with the high-amplitude event? 

• Is the anomalous amplitude within a sequence that may be sand-prone? 

• Is there evidence of migration of fluid from depth, such as along a fault plane? 

• Does the sequence correlate to other wells within the area that encountered shallow gas? 

Shallow Water Flow. The potential for shallow water flow (SWF) was assessed for each 

proposed well. The potential for SWF is based on the following criteria: 

• Does the stratigraphic unit correlate to a regional sand-prone sequence?

• Is the area subject to high sedimentation rates and rapid overburden deposition? 

• Is the sequence composed of high-amplitude, chaotic reflectors indicative of sand? 

• Is there a potential seal (perhaps clay-prone) above the sand-prone sequence?

• Does the sequence correlate to other wells within the area that encountered SWF?

• Is the proposed well located in a frontier area with little or no offset well control?

HIGH

MODERATE

LOW

NEGLIGIBLE

HIGH

MODERATE

LOW

NEGLIGIBLE
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Proposed Well GC 723-F

The seafloor assessment considers seafloor conditions within a 2,000-ft radius from the 

proposed well. The subsurface assessment considers the conditions within a 500-ft radius 

from the seafloor to 1.2 seconds below the mudline (bml), approximately 3,735 ft bml. 

The proposed well GC 723-F location provided by Noble is as follows:

NAD27 UTM ZONE 15,US Survey ft Geographic Coordinates

X Y Latitude Longitude

2,290,718.00 9,889,524.00 27° 14' 20.689" -90° 59' 53.603" 

Block Calls

3-D Seismic Line Reference

Inline Crossline

6,082.00' FEL 5,364.00' FSL 8080 10195

Table W-1. Location, block calls, and seismic lines for proposed well GC 723-F 

Power Spectrum Analysis

The power spectrum for the proposed well was derived through the use of Seismic MicroTechnology’s trace calculations amplitude spectrum tool. The frequency content appears to 

meet or exceed the minimum 50 Hz within the upper 1.0 second below the seafloor set forth 

in NTL No. 2008-G04 (MMS, 2008a). 

Power spectrum at proposed well GC 723-F 
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Maximum Anchor Radius

Noble anticipates using a dynamically positioned (DP) MODU at this location; therefore, no 

specific anchor pattern has been analyzed. 

Muds and Cuttings Discharge Location

Seafloor Conditions. Proposed well GC 723-F is located in south-central GC 723

(Map 1-1). Water depths within the muds and cuttings discharge area for the proposed well 

range from 4,705 ft to 4,996 ft bsl (Map W-1). The water depth at the proposed well is 

4,891 ft bsl. The proposed well is located along the western margin of the basin, within the 

limits of a relict slump feature. The seafloor is slightly undulating near the proposed well 

and slopes to the southeast at 4.0° (Figure 1-4).

There are no seafloor faults within 2,000 ft of the proposed well (Map 1-2). 

Benthic Communities. There are no seafloor amplitude anomalies or expulsion mounds 

within 2,000 ft of the proposed well (Map 1-3). The nearest seafloor amplitude anomalies 

are about 6,300 ft west-southwest of the proposed location, associated with a large expulsion 

mound. There is no indication of hydrocarbon migration to the seafloor within 2,000 ft of the 

proposed well. 

Features or areas that could support high-density chemosynthetic or other benthic 

communities are not anticipated within 2,000 ft of the proposed well. 

Gas Hydrates. There are no seafloor amplitude anomalies within 2,000 ft of the proposed 

well (Map 1-4). There are no seismic indicators of gas hydrates within 2,000 ft of the 

proposed well. The nearest expulsion feature is located about 6,050 ft west-southwest of the 

proposed location. 

Gas hydrates are not anticipated at the seafloor within 2,000 ft of the proposed well. 

Man-Made Features. There are no pipelines or other apparent man-made features within 

2,000 ft of the proposed well (Map W-1; BOEMRE, 2011a). The nearest existing well is in 

east-central GC 723, approximately 5,510 ft east-northeast of the proposed well.

The seafloor assessment area is not located within an area of high archaeological potential as 

described in NTL No. 2005-G07 and supplemental NTLs; however, Noble contracted Fugro 

Geoservices, Inc. to conduct an archaeological resource survey (Fugro, 2011) over the blocks 

of interest to satisfy the recently issued Pre-Seabed Disturbance Survey Mitigation document 

published by the BOEMRE (2011c). 

Berger Geosciences reviewed data from the Fugro report (2011). Three sonar contacts were 

identified within 2,000 ft of the proposed well (Map 3-1). The closest observed sonar contact 

is about 1,100 ft south-southwest of proposed well GC 723-F. This sonar contact is less than 

10 ft long by less than 5 ft wide, and has no discernible height above the seafloor (Sonar 

Contact 143; Fugro, 2011). Sonar Contact 156 is located about 1,460 ft east of the proposed 

well. Sonar Contact 153 is located about 1,966 ft west-southwest of the proposed well. Both 

of these contacts are less than 10 ft long by less than 5 ft wide, and do not have any height 
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above the seafloor. All three of these contacts have been interpreted to be small debris 

targets that are not “deemed archaeologically significant” (Fugro, 2011). These contacts 

should be avoided by at least 100 ft as per MMS NTL 2008-G05 (MMS, 2008b). No other 

contacts were reported within 2,000 ft of the proposed well. 

There is no evidence of anomalous man-made features from the 3-D seismic data; however, 

man-made features and other seafloor conditions may exist that are not detectable within the 

resolution limits of the 3-D seismic data used for this assessment.

No man-made potential seafloor hazards have been identified within 2,000 ft of the 

proposed well that could constrain drilling activities. 

Wellbore Location

Stratigraphy. Horizons 1, 2, 3, 4, 6, and 7 were interpreted at proposed well GC 723-F. A 

generalized description of the stratigraphic sequences can be found in Section 1.4 of this 

report. The following is an assessment of the conditions that will be encountered directly 

below the surface location. 

Seafloor to Horizon 1. The sediments between the seafloor and Horizon 1 are fine-grained 

hemipelagic drape overlying relict slump deposits that also contain clay sediments. This 

sequence is 226 ft thick at the proposed well (Figure W-2; Map 1-5).

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas. There is a negligible potential for SWF from this sequence. 

Horizon 1 to Horizon 2. The sequence between Horizons 1 and 2 contains three units at the 

proposed well. The upper unit contains low-amplitude, parallel reflectors representing claydominated turbidites that are about 248 ft thick. The middle unit contains low- to moderateamplitude, discontinuous reflectors that represent channelized basin fill deposits of silts and 

isolated sands. The middle unit is about 156 ft thick at the proposed well. The basal unit 

consists of ponded turbidites containing silts and clays. Horizon 2 marks the base of the finegrained turbidites at about 809 ft bml (Figure W-2; Map 1-6). The basal unit is about 179 ft 

thick at the proposed well. 

The nearest subsurface amplitude anomaly to the proposed well occurs within this sequence, 

approximately 275 ft to the north-northeast of the proposed well (Map 1-4). Two additional 

anomalies occur within this sequence, 375 ft southeast and 440 ft west-northwest of the 

proposed well. These anomalies are all within the middle unit and probably represent higher 

sand content rather than hydrocarbon accumulations.

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas from the upper unit (226 ft to 474 ft bml). There is a low potential for 

shallow gas from the middle unit, between 474 ft and 630 ft bml. There is a negligible

potential for shallow gas from the basal unit (630 ft to 809 ft bml). There is a negligible

potential for SWF from the upper unit (226 ft to 474 ft bml). There is a low potential for 

SWF from the middle unit, between 474 ft and 630 ft bml. There is a negligible potential for 

SWF from the basal unit (630 ft to 809 ft bml). 
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Horizon 2 to Horizon 3. The sequence between Horizons 2 and 3 contains low-amplitude, 

discontinuous reflectors that represent ponded turbidites of silts and clays. Horizon 3 is a 

prominent peak reflector at the base of this unit encountered at 1,016 ft bml (Figure W-2; 

Map 1-7). 

There is a low potential for gas hydrates in this sequence. There is a negligible potential for

shallow gas from this sequence. There is a negligible potential for SWF from this sequence. 

Horizon 3 to Horizon 4. The sequence between Horizons 3 and 4 contains two units. The 

upper unit contains low-amplitude, discontinuous reflectors that represent fine-grained 

deposits along the margin of the basin that are about 104 ft thick. The lower unit contains 

low-amplitude, parallel reflectors representing clay-dominated turbidites. The lower unit is 

about 161 ft thick at the proposed well. Horizon 4 is a prominent peak reflector encountered 

at 6,172 ft bsl (Figure W-2; Map 1-8). 

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit of this sequence (1,016 ft and 1,120 ft bml). There is a

negligible potential for shallow gas from the lower unit, between 1,120 ft and 1,281 ft bml. 

There is a low potential for SWF from the upper unit (1,016 ft to 1,120 ft bml). There is a

negligible potential for SWF from the lower unit, between 1,120 ft and 1,281 ft bml. 

Horizon 4 to Horizon 6. The sequence between Horizons 4 and 6 contains two units. The 

upper unit is about 345 ft thick and consists of low- to moderate-amplitude, parallel to 

slightly discontinuous reflectors that represent turbidites containing silts and clays. A 

prominent trough/peak pair at the base of this unit represents a layer of more coarse-grained 

turbidites. The lower unit contains low-amplitude, parallel reflectors representing claydominated turbidites. The lower unit is about 170 ft thick at the proposed well. Horizon 6 is 

a peak reflector that represents an erosional surface at the proposed well. It is encountered at 

1,796 ft bml (Figure W-2; Map 1-9). 

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit (1,281 ft to 1,626 ft bml). There is a negligible potential for 

shallow gas from the lower unit, between 1,626 ft and 1,796 ft bml. There is a low potential 

for SWF from the upper unit (1,281 ft to 1,626 ft bml). There is a negligible potential for 

SWF from the lower unit, between 1,626 ft and 1,796 ft bml. 

Horizon 6 to Horizon 7. The sequence between Horizons 6 and 7 contains three units of finegrained turbidites interbedded with sand-prone mass transport deposits. The upper turbidite 

unit contains low-amplitude, parallel reflectors. The upper unit is about 355 ft thick. The 

middle unit contains moderate-amplitude, discontinuous reflectors that represent the sandprone mass transport deposit. The middle unit is about 145 ft thick at the proposed well. The 

basal turbidite unit consists of low-amplitude, parallel reflectors representing silts and clays. 

Horizon 7 marks the base of the fine-grained turbidites at about 2,616 ft bml (Figure W-2; 

Map 1-10). The basal unit is about 320 ft thick at the proposed well. 

The BGHSZ is predicted at 2,135 ft bml based on the trend of an identified BSR in the basin. 

There is a low potential for gas hydrates within this sequence from Horizon 6 (1,796 ft bml) 
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to the BGHSZ (2,135 ft bml) and a negligible potential for gas hydrates between the BGHSZ 

(2,135 ft bml) and the base of this sequence (2,616 ft bml). There is a negligible potential for 

shallow gas from the upper unit (1,796 ft to 2,151 ft bml). There is a low potential for 

shallow gas from the middle unit, between 2,151 ft and 2,296 ft bml. There is a negligible

potential for shallow gas from the basal unit (2,296 ft to 2,616 ft bml). There is a negligible

potential for SWF from the upper unit (1,796 ft to 2,151 ft bml). There is a low potential for 

SWF from the middle unit, between 2,151 ft and 2,296 ft bml. There is a negligible potential 

for SWF from the basal unit (2,296 ft to 2,616 ft bml). 

Horizon 7 to Investigation Limit. The sediments below Horizon 7 are represented by 

alternating units of low-amplitude, parallel reflectors and low- to moderate-amplitude, 

chaotic reflectors (Figure W-2). The low-amplitude, parallel reflectors represent claydominated turbidites. The more chaotic reflectors probably represent mass transport deposits 

containing silts, clays, and isolated sand lenses. Salt is not present beneath the proposed well 

within the investigation limit. 

There is a negligible potential for gas hydrates in this sequence. There is a low potential for

shallow gas from this sequence. There is a low potential for SWF from this sequence. 

Faults. A vertical wellbore at proposed well GC 723-F will intersect one buried fault at 

about 1,378 ft bml (Figure W-2). This fault is a minor fracture that does not extend to the 

seafloor. The fault is downthrown to the southeast and only offsets Horizons 4 and 6. There 

is no evidence of fluid migration along this fault. 
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Proposed Well GC 723-G

The seafloor assessment considers seafloor conditions within a 2,000-ft radius from the 

proposed well. The subsurface assessment considers the conditions within a 500-ft radius 

from the seafloor to 1.2 seconds below the mudline (bml), approximately 3,735 ft bml. 

The proposed well GC 723-G location provided by Noble is as follows:

NAD27 UTM ZONE 15,US Survey ft Geographic Coordinates

X Y Latitude Longitude

2,290,313.00 9,892,600.00 27° 14' 51.208" -90° 59' 57.544" 

Block Calls

3-D Seismic Line Reference

Inline Crossline

6,487.00' FEL 7,400.00' FNL 8127 10186

Table W-2. Location, block calls, and seismic lines for proposed well GC 723-G 

Power Spectrum Analysis

The power spectrum for the proposed well was derived through the use of Seismic MicroTechnology’s trace calculations amplitude spectrum tool. The frequency content appears to 

meet or exceed the minimum 50 Hz within the upper 1.0 second below the seafloor set forth 

in NTL No. 2008-G04 (MMS, 2008a). 

Power spectrum at proposed well GC 723-G 
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Maximum Anchor Radius

Noble anticipates using a dynamically positioned (DP) MODU at this location; therefore, no 

specific anchor pattern has been analyzed. 

Muds and Cuttings Discharge Location

Seafloor Conditions. Proposed well GC 723-G is located in central GC 723 (Map 1-1). 

Water depths within the muds and cuttings discharge area for the proposed well range from 

4,521 ft to 4,918 ft bsl (Map W-2). The water depth at the proposed well is 4,794 ft bsl. The 

proposed well is located along the western margin of the basin, within the limits of a relict 

slump feature. The seafloor is slightly undulating near the proposed well and slopes to the 

southeast at 3.8° (Figure 1-4).

There are no seafloor faults within 2,000 ft of the proposed well (Map 1-2). 

Benthic Communities. There are no seafloor amplitude anomalies or expulsion mounds 

within 2,000 ft of the proposed well (Map 1-3). The nearest seafloor amplitude anomalies 

are about 8,225 ft southwest of the proposed location, associated with a large expulsion 

mound. There is no indication of hydrocarbon migration to the seafloor within 2,000 ft of the 

proposed well. 

Features or areas that could support high-density chemosynthetic or other benthic 

communities are not anticipated within 2,000 ft of the proposed well. 

Gas Hydrates. There are no seafloor amplitude anomalies within 2,000 ft of the proposed 

well (Map 1-4). There are no other seismic indicators of gas hydrates within 2,000 ft of the 

proposed well. The nearest expulsion feature is located about 7,850 ft southwest of the 

proposed location. 

Gas hydrates are not anticipated at the seafloor within 2,000 ft of the proposed well. 

Man-Made Features. There are no pipelines or other apparent man-made features within 

2,000 ft of the proposed well (Map W-2; BOEMRE, 2011a). The nearest existing well is in 

east-central GC 723, approximately 5,430 ft east-southeast of the proposed well. 

The seafloor assessment area is not located within an area of high archaeological potential as 

described in NTL No. 2005-G07 and supplemental NTLs; however, Noble contracted Fugro 

Geoservices, Inc. to conduct an archaeological resource survey (Fugro, 2011) over the blocks 

of interest to satisfy the recently issued Pre-Seabed Disturbance Survey Mitigation document 

published by the BOEMRE (2011c). 

Berger Geosciences reviewed data from the Fugro report (2011). Four sonar contacts were 

identified within 2,000 ft of the proposed well (Map 3-1). The closest observed sonar contact 

is about 565 ft south-southeast of proposed well GC 723-G. This sonar contact is less than 

10 ft long by less than 5 ft wide, and has no discernible height above the seafloor (Sonar 

Contact 196; Fugro, 2011). Sonar Contact 195 is located about 1,030 ft southwest of the 

proposed well. Sonar Contact 216 is located about 1,263 ft northeast of the proposed well. 

Sonar Contact 190 is located about 1,935 ft west-southwest of the proposed well. All of 
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these contacts are less than 10 ft long by less than 5 ft wide, and do not have any height 

above the seafloor. All four sonar contacts have been interpreted to be small debris targets 

that are not “deemed archaeologically significant” (Fugro, 2011). These contacts should be

avoided by at least 100 ft as per MMS NTL 2008-G05 (MMS, 2008b). No other contacts

were reported within 2,000 ft of the proposed well. 

There is no evidence of anomalous man-made features from the 3-D seismic data; however, 

man-made features and other seafloor conditions may exist that are not detectable within the 

resolution limits of the 3-D seismic data used for this assessment.

No man-made potential seafloor hazards have been identified within 2,000 ft of the 

proposed well that could constrain drilling activities. 

Wellbore Location

Stratigraphy. Horizons 1, 3, 4, 6, and 7 were interpreted at proposed well GC 723-G. 

Horizon 2 is not defined below this well location because of thinning of sediments along the 

salt uplift. A generalized description of the stratigraphic sequences can be found in 

Section 1.4 of this report. The following is an assessment of the conditions that will be 

encountered directly below the surface location. 

Seafloor to Horizon 1. The sediments between the seafloor and Horizon 1 are fine-grained 

hemipelagic drape overlying relict slump deposits that also contain clay sediments. This 

sequence is 207 ft thick at the proposed well (Figure W-3; Map 1-5).

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas from this sequence. There is a negligible potential for SWF from this 

sequence.

Horizon 1 to Horizon 3. The sequence between Horizons 1 and 3 contains three units at the 

proposed well. The upper unit contains low-amplitude, parallel reflectors representing claydominated turbidites that are about 200 ft thick. The middle unit contains low- to moderateamplitude, discontinuous to parallel reflectors that represent basin fill deposits of silts and 

isolated sands overlying ponded turbidites containing silts and clays. The middle unit is 

about 152 ft thick at the proposed well. The basal unit consists of low amplitude, parallel 

reflectors that represent clay-dominated turbidites, equivalent to the Horizons 2 to 3 

sequence. Horizon 3 marks the base of the fine-grained turbidites at about 742 ft bml 

(Figure W-3; Map 1-7). The basal unit is about 183 ft thick at the proposed well. 

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas from the upper unit (207 ft to 407 ft bml). There is a low potential for 

shallow gas from the middle unit, between 407 ft and 559 ft bml. There is a negligible

potential for shallow gas from the basal unit (559 ft to 742 ft bml). There is a negligible

potential for SWF from the upper unit (207 ft to 407 ft bml). There is a low potential for 

SWF from the middle unit, between 407 ft and 559 ft bml. There is a negligible potential for 

SWF from the basal unit (559 ft to 742 ft bml). 
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Horizon 3 to Horizon 4. The sequence between Horizons 3 and 4 contains two units. The 

upper unit contains low-amplitude, discontinuous reflectors that represent fine-grained 

deposits along the margin of the basin that are about 171 ft thick. The lower unit contains 

low-amplitude, parallel reflectors representing clay-dominated turbidites. The lower unit is 

about 195 ft thick at the proposed well. Horizon 4 is a prominent peak reflector encountered 

at 5,902 ft bsl (Figure W-3; Map 1-8). 

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit (742 ft bml to 913 ft bml). There is a negligible potential for 

shallow gas from the lower unit, between 913 ft and 1,108 ft bml. There is a low potential 

for SWF from the upper unit (742 ft bml to 913 ft bml). There is a negligible potential for 

SWF from the lower unit, between 913 ft and 1,108 ft bml. 

Horizon 4 to Horizon 6. The sequence between Horizons 4 and 6 contains two units. The 

upper unit is about 321 ft thick and consists of low- to moderate-amplitude, parallel to 

slightly discontinuous reflectors that represent turbidites containing silts and clays. A 

prominent trough/peak pair at the base of this unit, at about 1,429 ft bml, represents a layer of 

more coarse-grained turbidites. The lower unit contains low-amplitude, parallel to 

discontinuous reflectors representing clay-dominated turbidites with a reworked section of 

clays and silts. The lower unit is about 221 ft thick at the proposed well. Horizon 6 is a peak 

reflector that represents an erosional surface at the proposed well is encountered at 1,650 ft 

bml (Figure W-3; Map 1-9). 

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit (1,108 ft to 1,429 ft bml). There is a negligible potential for 

shallow gas from the lower unit, between 1,429 ft and 1,650 ft bml. There is a low potential 

for SWF from the upper unit (1,108 ft to 1,429 ft bml). There is a negligible potential for 

SWF from the lower unit, between 1,429 ft and 1,650 ft bml. 

Horizon 6 to Horizon 7. The sequence between Horizons 6 and 7 contains three units of finegrained turbidites interbedded with sand-prone mass transport deposits. The upper turbidite 

unit contains low-amplitude, parallel reflectors. The upper unit is about 383 ft thick. The 

middle unit contains moderate-amplitude, discontinuous reflectors that represent the sandprone mass transport deposit. The middle unit is about 208 ft thick at the proposed well. The 

basal turbidite unit consists of low-amplitude, parallel reflectors representing silts and clays. 

Horizon 7 marks the base of the fine-grained turbidites at about 2,622 ft bml (Figure W-3; 

Map 1-10). The basal unit is about 381 ft thick at the proposed well. 

The nearest subsurface amplitude anomaly to the proposed well occurs within this sequence, 

approximately 358 ft to the north-northwest of the proposed well (Figure W-3; Map 1-4). 

This anomaly is within the sand-prone mass transport deposits within this sequence and is 

grouped with several other anomalies north and west of the proposed well. These anomalies 

probably represent hydrocarbon accumulations within the sand-prone sediments. 

The BGHSZ is predicted at 2,077 ft bml based on the trend of an identified BSR in the basin. 

There is a low potential for gas hydrates within this sequence from Horizon 6 (1,650 ft bml) 

to the BGHSZ (2,077 ft bml) and a negligible potential for gas hydrates between the BGHSZ 
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(2,077 ft bml) and the base of this sequence (2,622 ft bml). There is a negligible potential for 

shallow gas from the upper unit (1,650 ft to 2,033 ft bml). There is a moderate potential for 

shallow gas from the middle unit, between 2,033 ft and 2,241 ft bml. There is a negligible

potential for shallow gas from the basal unit (2,241 ft to 2,622 ft bml). There is a negligible

potential for SWF from the upper unit (1,650 ft to 2,033 ft bml). There is a low potential for 

SWF from the middle unit, between 2,033 ft and 2,241 ft bml. There is a negligible potential 

for SWF from the basal unit (2,241 ft to 2,622 ft bml). 

Horizon 7 to Investigation Limit. The sediments below Horizon 7 are represented by 

alternating units of low-amplitude, parallel reflectors and low- to moderate-amplitude, 

chaotic reflectors (Figure W-3). The low-amplitude, parallel reflectors represent claydominated turbidites. The more chaotic reflectors probably represent mass transport deposits 

containing silts, clays, and isolated sand lenses. Salt is not present beneath the proposed well 

within the investigation limit. 

There is a negligible potential for gas hydrates in this sequence. There is a low potential for

shallow gas from this sequence. There is a low potential for SWF from this sequence.

Faults. A vertical wellbore at proposed well GC 723-G will not intersect any apparent faults 

within the investigation limit (Figure W-3). 
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Proposed Well GC 723-H

The seafloor assessment considers seafloor conditions within a 2,000-ft radius from the 

proposed well. The subsurface assessment considers the conditions within a 500-ft radius 

from the seafloor to 1.2 seconds below the mudline (bml), approximately 3,735 ft bml. 

The proposed well GC 723-H location provided by Noble is as follows:

NAD27 UTM ZONE 15,US Survey ft Geographic Coordinates

X Y Latitude Longitude

2,291,676.00 9,894,244.00 27° 15' 07.269" -90° 59' 42.154" 

Block Calls

3-D Seismic Line Reference

Inline Crossline

5,124.00' FEL 5,756.00' FNL 8152 10219

Table W-3. Location, block calls, and seismic lines for proposed well GC 723-H 

Power Spectrum Analysis

The power spectrum for the proposed well was derived through the use of Seismic MicroTechnology’s trace calculations amplitude spectrum tool. The frequency content appears to 

meet or exceed the minimum 50 Hz within the upper 1.0 second below the seafloor set forth 

in NTL No. 2008-G04 (MMS, 2008a). 

Power spectrum at proposed well GC 723-H 
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Maximum Anchor Radius

Noble anticipates using a dynamically positioned (DP) MODU at this location; therefore, no 

specific anchor pattern has been analyzed. 

Muds and Cuttings Discharge Location

Seafloor Conditions. Proposed well GC 723-H is located within the northeastern quadrant 

of GC 723 (Map 1-1). Water depths within the muds and cuttings discharge area for the 

proposed well range from 4,700 ft to 4,948 ft bsl (Map W-3). The water depth at the

proposed well is 4,841 ft bsl. The proposed well is located along the western margin of the 

basin, just north of the limits of a relict slump feature. The seafloor is relatively smooth near 

the proposed well and slopes to the south at 4.4° (Figure 1-4).

There are no seafloor faults within 2,000 ft of the proposed well (Map 1-2). 

Benthic Communities. There are no seafloor amplitude anomalies or expulsion mounds 

within 2,000 ft of the proposed well (Map 1-3). The nearest seafloor amplitude anomalies 

are about 10,320 ft southwest of the proposed location, associated with a large expulsion 

mound. There is no indication of hydrocarbon migration to the seafloor within 2,000 ft of the 

proposed well. 

Features or areas that could support high-density chemosynthetic or other benthic 

communities are not anticipated within 2,000 ft of the proposed well. 

Gas Hydrates. There are no seafloor amplitude anomalies within 2,000 ft of the proposed 

well (Map 1-4). There are no other seismic indicators of gas hydrates within 2,000 ft of the 

proposed well. The nearest expulsion feature is located about 9,970 ft southwest of the 

proposed location. 

Gas hydrates are not anticipated at the seafloor within 2,000 ft of the proposed well. 

Man-Made Features. There are no pipelines or other apparent man-made features within 

2,000 ft of the proposed well (Map W-2; BOEMRE, 2011a). The nearest existing well is in 

east-central GC 723, approximately 4,660 ft east-southeast of the proposed well. 

The seafloor assessment area is not located within an area of high archaeological potential as 

described in NTL No. 2005-G07 and supplemental NTLs; however, Noble contracted Fugro 

Geoservices, Inc. to conduct an archaeological resource survey (Fugro, 2011) over the blocks 

of interest to satisfy the recently issued Pre-Seabed Disturbance Survey Mitigation document 

published by the BOEMRE (2011c). 

Berger Geosciences reviewed data from the Fugro report (2011). Three sonar contacts were 

identified within 2,000 ft of the proposed well (Map 3-1). The closest observed sonar contact 

is about 834 ft northwest of proposed well GC 723-H. This sonar contact is less than 10 ft 

long by less than 5 ft wide, and has no discernible height above the seafloor (Sonar 

Contact 232; Fugro, 2011). Sonar Contact 219 is located about 915 ft southwest of the 

proposed well. Sonar Contact 209 is located about 1,472 ft southeast of the proposed well. 

All of these contacts are less than 10 ft long by less than 5 ft wide, and do not have any 
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height above the seafloor. All three sonar contacts have been interpreted to be small debris 

targets that are not “deemed archaeologically significant” (Fugro, 2011). These contacts 

should be avoided by at least 100 ft as per MMS NTL 2008-G05 (MMS, 2008b). No other 

contacts were reported within 2,000 ft of the proposed well. 

There is no evidence of anomalous man-made features from the 3-D seismic data; however, 

man-made features and other seafloor conditions may exist that are not detectable within the 

resolution limits of the 3-D seismic data used for this assessment.

No man-made potential seafloor hazards have been identified within 2,000 ft of the 

proposed well that could constrain drilling activities. 

Wellbore Location

Stratigraphy. Horizons 1, 2, 3, 4, 6, and 7 were interpreted at proposed well GC 723-H. A 

generalized description of the stratigraphic sequences can be found in Section 1.4 of this 

report. The following is an assessment of the conditions that will be encountered directly 

below the surface location. 

Seafloor to Horizon 1. The sediments between the seafloor and Horizon 1 are fine-grained 

hemipelagic drape. This sequence is 218 ft thick at the proposed well (Figure W-4; 

Map 1-5).

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas from this sequence. There is a negligible potential for SWF from this 

sequence.

Horizon 1 to Horizon 2. The sequence between Horizons 1 and 2 contains three units at the 

proposed well. The upper unit contains low-amplitude, parallel reflectors representing claydominated turbidites that are about 268 ft thick. The middle unit contains low- to moderateamplitude, discontinuous reflectors that represent channelized basin fill deposits of silts and 

isolated sands. The middle unit is about 136 ft thick at the proposed well. The basal unit 

consists of ponded turbidites containing silts and clays. Horizon 2 marks the base of the finegrained turbidites at about 774 ft bml (Figure W-4; Map 1-6). The basal unit is about 152 ft 

thick at the proposed well. 

The nearest subsurface amplitude anomaly to the proposed well occurs within this sequence, 

approximately 340 ft to the west of the proposed well (Map 1-4). Another anomaly occurs 

within this sequence, 430 ft west-southwest of the proposed well. These anomalies are 

within the middle unit and probably represent higher sand content rather than hydrocarbon 

accumulations.

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas from the upper unit (218 ft to 486 ft bml). There is a low potential for 

shallow gas from the middle unit, between 486 ft and 622 ft bml. There is a negligible

potential for shallow gas from the basal unit (622 ft to 774 ft bml). There is a negligible

potential for SWF from the upper unit (218 ft to 486 ft bml). There is a low potential for 
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SWF from the middle unit, between 486 ft and 622 ft bml. There is a negligible potential for 

SWF from the basal unit (622 ft to 774 ft bml). 

Horizon 2 to Horizon 3. The sequence between Horizons 2 and 3 contains low-amplitude, 

discontinuous reflectors that represent clay-dominated turbidites. Horizon 3 is a prominent 

peak reflector at the base of this unit encountered at 990 ft bml (Figure W-4; Map 1-7). 

There is a low potential for gas hydrates in this sequence. There is a negligible potential for

shallow gas this sequence. There is a negligible potential for SWF from this sequence. 

Horizon 3 to Horizon 4. The sequence between Horizons 3 and 4 contains two units. The 

upper unit contains low-amplitude, discontinuous reflectors that represent fine-grained 

deposits along the margin of the basin that are about 148 ft thick. The lower unit contains 

low-amplitude, parallel reflectors representing clay-dominated turbidites. The lower unit is 

about 177 ft thick at the proposed well. Horizon 4 is a prominent peak reflector encountered 

at 6,155 ft bsl (Figure W-4; Map 1-8). 

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit (990 ft bml to 1,138 ft bml). There is a negligible potential 

for shallow gas from the lower unit, between 1,138 ft and 1,314 ft bml. There is a low

potential for SWF from the upper unit (990 ft bml to 1,138 bml). There is a negligible

potential for SWF from the lower unit, between 1,138 ft and 1,314 ft bml. 

Horizon 4 to Horizon 6. The sequence between Horizons 4 and 6 contains two units. The 

upper unit is about 383 ft thick and consists of low- to moderate-amplitude, parallel to 

slightly discontinuous reflectors that represent turbidites containing silts and clays. A 

prominent trough/peak pair at the base of this unit represents a layer of more coarse-grained 

turbidites. The lower unit contains low-amplitude, parallel to discontinuous reflectors 

representing clay-dominated turbidites overlying a reworked section of similar clays and 

silts. The lower unit is about 253 ft thick at the proposed well. Horizon 6 is a peak reflector

that represents an erosional surface at the proposed well is encountered at 1,950 ft bml 

(Figure W-4; Map 1-9). 

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit (1,314 ft to 1,697 ft bml). There is a negligible potential for 

shallow gas from the lower unit, between 1,697 ft and 1,950 ft bml. There is a low potential 

for SWF from the upper unit (1,314 ft to 1,697 ft bml). There is a negligible potential for 

SWF from the lower unit, between 1,697 ft and 1,950 ft bml. 

Horizon 6 to Horizon 7. The sequence between Horizons 6 and 7 contains three units of finegrained turbidites interbedded with sand-prone mass transport deposits. The upper turbidite 

unit contains low-amplitude, parallel reflectors. The upper unit is about 534 ft thick. The 

middle unit contains moderate-amplitude, discontinuous reflectors that represent the sandprone mass transport deposit. The middle unit is about 248 ft thick at the proposed well. The 

basal turbidite unit consists of low-amplitude, parallel reflectors representing silts and clays. 

Horizon 7 marks the base of the fine-grained turbidites at about 2,997 ft bml (Figure W-4; 

Map 1-10). The basal unit is about 265 ft thick at the proposed well. 
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The BGHSZ is predicted at 2,212 ft bml based on the trend of an identified BSR in the basin. 

There is a low potential for gas hydrates within this sequence from Horizon 6 (1,950 ft bml) 

to the BGHSZ (2,212 ft bml) and a negligible potential for gas hydrates between the BGHSZ 

(2,212 ft bml) and the base of this sequence (2,997 ft bml). There is a negligible potential for 

shallow gas from the upper unit (1,950 ft to 2,484 ft bml). There is a low potential for 

shallow gas from the middle unit, between 2,484 ft and 2,732 ft bml. There is a negligible

potential for shallow gas from the basal unit (2,732 ft to 2,997 ft bml). There is a negligible

potential for SWF from the upper unit (1,950 ft to 2,484 ft bml). There is a low potential for 

SWF from the middle unit, between 2,484 ft and 2,732 ft bml. There is a negligible potential 

for SWF from the basal unit (2,732 ft to 2,997 ft bml). 

Horizon 7 to Investigation Limit. The sediments below Horizon 7 are represented by 

alternating units of low-amplitude, parallel reflectors and low- to moderate-amplitude, 

chaotic reflectors (Figure W-4). The low-amplitude, parallel reflectors represent claydominated turbidites. The more chaotic reflectors probably represent mass transport deposits 

containing silts, clays, and isolated sand lenses. Salt is not present beneath the proposed well 

within the investigation limit. 

There is a negligible potential for gas hydrates in this sequence. There is a low potential for

shallow gas from this sequence. There is a low potential for SWF from this sequence. 

Faults. A vertical wellbore at proposed well GC 723-H will not intersect any apparent faults 

within the investigation limit (Figure W-4). 
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Proposed Well GC 723-J

The seafloor assessment considers seafloor conditions within a 2,000-ft radius from the 

proposed well. The subsurface assessment considers the conditions within a 500-ft radius 

from the seafloor to 1.2 seconds below the mudline (bml), approximately 3,735 ft bml. 

The proposed well GC 723-J location provided by Noble is as follows:

NAD27 UTM ZONE 15,US Survey ft Geographic Coordinates

X Y Latitude Longitude

2,292,192.00 9,895,591.00 27° 15' 20.524" -90° 59' 36.199" 

Block Calls

3-D Seismic Line Reference

Inline Crossline

4,608.00' FEL 4,409.00' FNL 8172 10231

Table W-4. Location, block calls, and seismic lines for proposed well GC 723-J 

Power Spectrum Analysis

The power spectrum for the proposed well was derived through the use of Seismic MicroTechnology’s trace calculations amplitude spectrum tool. The frequency content appears to 

meet or exceed the minimum 50 Hz within the upper 1.0 second below the seafloor set forth 

in NTL No. 2008-G04 (MMS, 2008a). 

Power spectrum at proposed well GC 723-J 
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Maximum Anchor Radius

Noble anticipates using a dynamically positioned (DP) MODU at this location; therefore, no 

specific anchor pattern has been analyzed. 

Muds and Cuttings Discharge Location

Seafloor Conditions. Proposed well GC 723-J is located within the northeastern quadrant of 

GC 723 (Map 1-1). Water depths within the muds and cuttings discharge area for the 

proposed well range from 4,729 ft to 4,942 ft bsl (Map W-4). The water depth at the

proposed well is 4,845 ft bsl. The proposed well is located along the western margin of the 

basin. The seafloor is relatively smooth near the proposed well and slopes to the eastsoutheast at 3.1° (Figure 1-4).

There are no seafloor faults within 2,000 ft of the proposed well (Map 1-2). 

Benthic Communities. There are no seafloor amplitude anomalies or expulsion mounds 

within 2,000 ft of the proposed well (Map 1-3). The nearest seafloor amplitude anomalies 

are about 11,775 ft southwest of the proposed location, associated with a large expulsion 

mound. There is no indication of hydrocarbon migration to the seafloor within 2,000 ft of the 

proposed well. 

Features or areas that could support high-density chemosynthetic or other benthic 

communities are not anticipated within 2,000 ft of the proposed well. 

Gas Hydrates. There are no seafloor amplitude anomalies within 2,000 ft of the proposed 

well (Map 1-4). There are no other seismic indicators of gas hydrates within 2,000 ft of the 

proposed well. The nearest expulsion feature is located about 11,350 ft southwest of the 

proposed location. 

Gas hydrates are not anticipated at the seafloor within 2,000 ft of the proposed well. 

Man-Made Features. There are no pipelines or other apparent man-made features within 

2,000 ft of the proposed well (Map W-2; BOEMRE, 2011a). The nearest existing well is in 

east-central GC 723, approximately 5,100 ft southeast of the proposed well.

The seafloor assessment area is not located within an area of high archaeological potential as 

described in NTL No. 2005-G07 and supplemental NTLs; however, Noble contracted Fugro 

Geoservices, Inc. to conduct an archaeological resource survey (Fugro, 2011) over the blocks 

of interest to satisfy the recently issued Pre-Seabed Disturbance Survey Mitigation document 

published by the BOEMRE (2011c). 

Berger Geosciences reviewed data from the Fugro report (2011). Six sonar contacts were 

identified within 2,000 ft of the proposed well (Map 3-1). The closest observed sonar contact 

is about 1,125 ft southwest of proposed well GC 723-J. This sonar contact is less than 10 ft 

long by less than 5 ft wide, and has no discernible height above the seafloor (Sonar 

Contact 232; Fugro, 2011). Sonar Contacts 236, 239, and 247 are grouped together about 

1,500 ft east of the proposed well. All three of these contacts are less than 10 ft long by less 

than 5 ft wide, and do not have any height above the seafloor (Fugro, 2011). Sonar Contact 
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260 is located about 1,530 ft northwest of the proposed well. Sonar Contact 270 is located 

about 1,775 ft northeast of the proposed well. These contacts are also less than 10 ft wide 

and less than 5 ft long with no height above the seafloor. All six sonar contacts have been 

interpreted to be small debris targets that are not “deemed archaeologically significant” 

(Fugro, 2011). These contacts should be avoided by at least 100 ft as per MMS NTL 2008-

G05 (MMS, 2008b). No other contacts were reported within 2,000 ft of the proposed well. 

There is no evidence of anomalous man-made features from the 3-D seismic data; however, 

man-made features and other seafloor conditions may exist that are not detectable within the 

resolution limits of the 3-D seismic data used for this assessment.

No man-made potential seafloor hazards have been identified within 2,000 ft of the 

proposed well that could constrain drilling activities. 

Wellbore Location

Stratigraphy. Horizons 1, 2, 3, 4, 6, and 7 were interpreted at proposed well GC 723-J. A 

generalized description of the stratigraphic sequences can be found in Section 1.4 of this 

report. The following is an assessment of the conditions that will be encountered directly 

below the surface location. 

Seafloor to Horizon 1. The sediments between the seafloor and Horizon 1 are fine-grained 

hemipelagic drape. This sequence is 221 ft thick at the proposed well (Figure W-5; 

Map 1-5).

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas from this sequence. There is a negligible potential for SWF from this 

sequence.

Horizon 1 to Horizon 2. The sequence between Horizons 1 and 2 contains three units at the 

proposed well. The upper unit contains low-amplitude, parallel reflectors representing claydominated turbidites that are about 262 ft thick. The middle unit contains low- to moderateamplitude, discontinuous reflectors that represent channelized basin fill deposits of silts and 

isolated sands. The middle unit is about 173 ft thick at the proposed well. The basal unit 

consists of ponded turbidites containing silts and clays. Horizon 2 marks the base of the finegrained turbidites at about 817 ft bml (Figure W-5; Map 1-6). The basal unit is about 161 ft 

thick at the proposed well. 

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas from the upper unit (221 ft to 483 ft bml). There is a low potential for 

shallow gas from the middle unit, between 483 ft and 656 ft bml. There is a negligible

potential for shallow gas from the basal unit (656 ft to 817 ft bml). There is a negligible

potential for SWF from the upper unit (221 ft to 483 ft bml). There is a low potential for 

SWF from the middle unit, between 483 ft and 656 ft bml. There is a negligible potential for 

SWF from the basal unit (656 ft to 817 ft bml). 
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Horizon 2 to Horizon 3. The sequence between Horizons 2 and 3 contains low-amplitude, 

discontinuous reflectors that represent clay-dominated turbidites. Horizon 3 is a prominent 

peak reflector at the base of this unit encountered at 1,099 ft bml (Figure W-5; Map 1-7). 

There is a low potential for gas hydrates in this sequence. There is a negligible potential for

shallow gas this sequence. There is a negligible potential for SWF from this sequence. 

Horizon 3 to Horizon 4. The sequence between Horizons 3 and 4 contains two units. The 

upper unit contains low-amplitude, discontinuous reflectors that represent fine-grained 

deposits along the margin of the basin that are about 137 ft thick. The lower unit contains 

low-amplitude, parallel reflectors representing clay-dominated turbidites. The lower unit is 

about 169 ft thick at the proposed well. Horizon 4 is a prominent peak reflector encountered 

at 6,250 ft bsl (Figure W-5; Map 1-8). 

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit (1,099 ft bml to 1,236 ft bml). There is a negligible potential 

for shallow gas from the lower unit, between 1,236 ft and 1,405 ft bml. There is a low

potential for SWF from the upper unit (1,099 ft bml to 1,236 bml). There is a negligible

potential for SWF from the lower unit, between 1,236 ft and 1,405 ft bml. 

Horizon 4 to Horizon 6. The sequence between Horizons 4 and 6 contains two units. The 

upper unit is about 366 ft thick and consists of low- to moderate-amplitude, parallel to 

slightly discontinuous reflectors that represent turbidites containing silts and clays. A 

prominent trough/peak pair at the base of this unit represents a layer of more coarse-grained 

turbidites. The lower unit contains low-amplitude, parallel to discontinuous reflectors 

representing clay-dominated turbidites overlying a reworked section of clays and silts. The 

lower unit is about 246 ft thick at the proposed well. Horizon 6 is a peak reflector that 

represents an erosional surface at the proposed well is encountered at 2,017 ft bml 

(Figure W-5; Map 1-9). 

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit (1,405 ft to 1,771 ft bml). There is a negligible potential for 

shallow gas from the lower unit, between 1,771 ft and 2,017 ft bml. There is a low potential 

for SWF from the upper unit (1,405 ft to 1,771 ft bml). There is a negligible potential for 

SWF from the lower unit, between 1,771 ft and 2,017 ft bml. 

Horizon 6 to Horizon 7. The sequence between Horizons 6 and 7 contains three units of finegrained turbidites interbedded with sand-prone mass transport deposits. The upper turbidite 

unit contains low-amplitude, parallel reflectors. The upper unit is about 599 ft thick. The 

middle unit contains moderate-amplitude, discontinuous reflectors that represent the sandprone mass transport deposit. The middle unit is about 256 ft thick at the proposed well. The 

basal turbidite unit consists of low-amplitude, parallel reflectors representing silts and clays. 

Horizon 7 marks the base of the fine-grained turbidites at about 3,122 ft bml (Figure W-5; 

Map 1-10). The basal unit is about 250 ft thick at the proposed well. 

The BGHSZ is predicted at 2,254 ft bml based on the trend of an identified BSR in the basin. 

There is a low potential for gas hydrates within this sequence from Horizon 6 (2,017 ft bml) 
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to the BGHSZ (2,254 ft bml) and a negligible potential for gas hydrates between the BGHSZ 

(2,254 ft bml) and the base of this sequence (3,122 ft bml). There is a negligible potential for 

shallow gas from the upper unit (2,017 ft to 2,616 ft bml). There is a low potential for 

shallow gas from the middle unit, between 2,616 ft and 2,872 ft bml. There is a negligible

potential for shallow gas from the basal unit (2,872 ft to 3,122 ft bml). There is a negligible

potential for SWF from the upper unit (2,017 ft to 2,616 ft bml). There is a low potential for 

SWF from the middle unit, between 2,616 ft and 2,872 ft bml. There is a negligible potential 

for SWF from the basal unit (2,872 ft to 3,122 ft bml). 

Horizon 7 to Investigation Limit. The sediments below Horizon 7 are represented by 

alternating units of low-amplitude, parallel reflectors and low- to moderate-amplitude, 

chaotic reflectors (Figure W-5). The low-amplitude, parallel reflectors represent claydominated turbidites. The more chaotic reflectors probably represent mass transport deposits 

containing silts, clays, and isolated sand lenses. Salt is not present beneath the proposed well 

within the investigation limit. 

There is a negligible potential for gas hydrates in this sequence. There is a low potential for

shallow gas from this sequence. There is a low potential for SWF from this sequence. 

Faults. A vertical wellbore at proposed well GC 723-J will not intersect any apparent faults 

within the investigation limit (Figure W-5). 
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Proposed Well GC 679-K

The seafloor assessment considers seafloor conditions within a 2,000-ft radius from the 

proposed well. The subsurface assessment considers the conditions within a 500-ft radius 

from the seafloor to 1.2 seconds below the mudline (bml), approximately 3,735 ft bml. 

The proposed well GC 679-K location provided by Noble is as follows:

NAD27 UTM ZONE 15,US Survey ft Geographic Coordinates

X Y Latitude Longitude

2,290,165.00 9,900,528.00 27° 16' 09.726" -90° 59' 57.778" 

Block Calls

3-D Seismic Line Reference

Inline Crossline

6,635.00' FEL 528.00' FSL 8248 10182

Table W-5. Location, block calls, and seismic lines for proposed well GC 679-K 

Power Spectrum Analysis

The power spectrum for the proposed well was derived through the use of Seismic MicroTechnology’s trace calculations amplitude spectrum tool. The frequency content appears to 

meet or exceed the minimum 50 Hz within the upper 1.0 second below the seafloor set forth 

in NTL No. 2008-G04 (MMS, 2008a). 

Power spectrum at proposed well GC 679-K 
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Maximum Anchor Radius

Noble anticipates using a dynamically positioned (DP) MODU at this location; therefore, no 

specific anchor pattern has been analyzed. 

Muds and Cuttings Discharge Location

Seafloor Conditions. Proposed well GC 679-K is located in south-central GC 679 

(Map 1-1). Water depths within the muds and cuttings discharge area for the proposed well 

range from 4,367 ft to 4,798 ft bsl (Map W-5). The water depth at the proposed well is 

4,657 ft bsl. The proposed well is located at the eastern edge of the uplifted salt ridge within 

an apparent buried slump scar. The seafloor is slightly undulating near the proposed well and 

slopes to the south-southeast at 5.1° (Figure 1-4).

There are no seafloor faults within 2,000 ft of the proposed well (Map 1-2). 

Benthic Communities. There are no seafloor amplitude anomalies or expulsion mounds 

within 2,000 ft of the proposed well (Map 1-3). The nearest seafloor amplitude anomalies 

are more than 15,000 ft south-southwest of the proposed location, associated with a large 

expulsion mound. There is no indication of hydrocarbon migration to the seafloor within 

2,000 ft of the proposed well. 

Features or areas that could support high-density chemosynthetic or other benthic 

communities are not anticipated within 2,000 ft of the proposed well. 

Gas Hydrates. There are no seafloor amplitude anomalies within 2,000 ft of the proposed 

well (Map 1-4). There are no other seismic indicators of gas hydrates within 2,000 ft of the 

proposed well. The nearest expulsion feature is located about 14,900 ft south-southwest of 

the proposed location. 

Gas hydrates are not anticipated at the seafloor within 2,000 ft of the proposed well. 

Man-Made Features. There are no pipelines or other apparent man-made features within 

2,000 ft of the proposed well (Map W-5; BOEMRE, 2011a). The nearest existing well is in 

east-central GC 723, approximately 10,260 ft southeast of the proposed well. 

The seafloor assessment area is not located within an area of high archaeological potential as 

described in NTL No. 2005-G07 and supplemental NTLs; however, Noble contracted Fugro 

Geoservices, Inc. to conduct an archaeological resource survey (Fugro, 2011) over the blocks 

of interest to satisfy the recently issued Pre-Seabed Disturbance Survey Mitigation document 

published by the BOEMRE (2011c). 

Berger Geosciences reviewed data from the Fugro report (2011). Eight sonar contacts were

identified within 2,000 ft of the proposed well (Map 3-1). The closest observed sonar contact 

is about 739 ft east of proposed well GC 679-K. This sonar contact is less than 10 ft long by 

less than 5 ft wide, and has no discernible height above the seafloor (Sonar Contact 340; 

Fugro, 2011). Sonar Contacts 343 and 349 are located northwest of the proposed well at a 

distance of 1,330 ft and 1,603 ft, respectively. Sonar Contact 331 is located about 1,430 ft 

west-southwest of the proposed well. Sonar Contacts 314 and 315 are located southwest of 
Project No. 11-04-14

BERGER GEOSCIENCES, LLC E-MAIL: beinnovative@b-geo.com WEBSITE: b-geo.com 25 

the proposed well at a distance of 1,619 ft and 1,550 ft, respectively. Sonar Contacts 343 and 

349 are located northwest of the proposed well at a distance of 1,330 ft and 1,603 ft, 

respectively. Sonar Contacts 357 and 362 are located northeast of the proposed well at a 

distance of 1,540 ft and 1,525 ft, respectively. All of these contacts are less than 10 ft long 

by less than 5 ft wide, and do not have any height above the seafloor. All eight sonar 

contacts have been interpreted to be small debris targets that are not “deemed 

archaeologically significant” (Fugro, 2011). These contacts should be avoided by at least 

100 ft as per MMS NTL 2008-G05 (MMS, 2008b). No other contacts were reported within 

2,000 ft of the proposed well. 

There is no evidence of anomalous man-made features from the 3-D seismic data; however, 

man-made features and other seafloor conditions may exist that are not detectable within the 

resolution limits of the 3-D seismic data used for this assessment.

No man-made potential seafloor hazards have been identified within 2,000 ft of the 

proposed well that could constrain drilling activities. 

Wellbore Location

Stratigraphy. Horizons 1, 3, 4, 6, and 7 were interpreted at proposed well GC 679-K. 

Horizon 2 is not defined below this well location because of thinning of sediments along the 

salt uplift. A generalized description of the stratigraphic sequences can be found in 

Section 1.4 of this report. The following is an assessment of the conditions that will be 

encountered directly below the surface location. 

Seafloor to Horizon 1. The sediments between the seafloor and Horizon 1 are fine-grained 

hemipelagic drape overlying relict slump deposits that also contain clay sediments. This 

sequence is 213 ft thick at the proposed well (Figure W-6; Map 1-5).

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas from this sequence. There is a negligible potential for SWF from this 

sequence.

Horizon 1 to Horizon 3. The sequence between Horizons 1 and 3 contains two units at the 

proposed well. The upper unit contains low-amplitude, parallel reflectors representing claydominated turbidites that are about 102 ft thick. The lower unit consists of low amplitude, 

parallel reflectors that represent clay-dominated turbidites, equivalent to the Horizons 2 to 3 

sequence. Horizon 3 marks the base of the fine-grained turbidites at about 722 ft bml 

(Figure W-6; Map 1-7). The basal unit is about 407 ft thick at the proposed well. 

There is a low potential for gas hydrates within this sequence. There is a negligible potential 

for shallow gas from this sequence. There is a negligible potential for SWF from this 

sequence. 

Horizon 3 to Horizon 4. The sequence between Horizons 3 and 4 contains two units. The 

upper unit contains low-amplitude, discontinuous reflectors that represent fine-grained 

deposits along the margin of the basin that are about 124 ft thick. The lower unit contains 

low-amplitude, parallel reflectors representing clay-dominated turbidites. The lower unit is 
Project No. 11-04-14

BERGER GEOSCIENCES, LLC E-MAIL: beinnovative@b-geo.com WEBSITE: b-geo.com 26 

about 94 ft thick at the proposed well. Horizon 4 is a prominent peak reflector encountered

at 5,597 ft bsl (Figure W-6; Map 1-8). 

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit (722 ft bml to 846 ft bml). There is a negligible potential for 

shallow gas from the lower unit, between 846 ft and 940 ft bml. There is a low potential for 

SWF from the upper unit (722 ft bml to 846 ft bml). There is a negligible potential for SWF

from the lower unit, between 846 ft and 940 ft ft bml. 

Horizon 4 to Horizon 6. The sequence between Horizons 4 and 6 contains two units. The 

upper unit is about 389 ft thick and consists of low- to moderate-amplitude, parallel to 

slightly discontinuous reflectors that represent turbidites containing silts and clays. A 

prominent trough/peak pair at the base of this unit represents a layer of more coarse-grained 

turbidites. The lower unit contains low-amplitude, parallel reflectors representing turbidites 

containing clays and silts. The lower unit is about 349 ft thick at the proposed well. 

Horizon 6 is a peak reflector that represents an erosional surface at the proposed well. It is 

encountered at 1,678 ft bml (Figure W-6; Map 1-9). 

The nearest subsurface amplitude anomaly to the proposed well occurs within this sequence, 

approximately 695 ft to the west-northwest of the proposed well (Map 1-4). This anomaly 

may represent fluid migration along a fault plane.

There is a low potential for gas hydrates within this sequence. There is a low potential for 

shallow gas from the upper unit (940 ft to 1,329 ft bml). There is a negligible potential for 

shallow gas from the lower unit, between 1,329 ft and 1,678 ft bml. There is a low potential 

for SWF from the upper unit (940 ft to 1,329 ft bml). There is a negligible potential for SWF

from the lower unit, between 1,329 ft and 1,678 ft bml. 

Horizon 6 to Horizon 7. The sequence between Horizons 6 and 7 contains three units of finegrained turbidites interbedded with sand-prone mass transport deposits. The upper turbidite 

unit contains low-amplitude, parallel reflectors. The upper unit is about 650 ft thick. The 

middle unit contains moderate-amplitude, discontinuous reflectors that represent the sandprone mass transport deposit. The middle unit is about 215 ft thick at the proposed well. The 

basal turbidite unit consists of low-amplitude, parallel reflectors representing silts and clays. 

Horizon 7 marks the base of the fine-grained turbidites at about 2,859 ft bml (Figure W-6; 

Map 1-10). The basal unit is about 316 ft thick at the proposed well. 

The BGHSZ is predicted at 1,988 ft bml based on the trend of an identified BSR in the basin. 

There is a low potential for gas hydrates within this sequence from Horizon 6 (1,678 ft bml) 

to the BGHSZ (1,988 ft bml) and a negligible potential for gas hydrates between the BGHSZ 

(1,988 ft bml) and the base of this sequence (2,859 ft bml). There is a negligible potential for 

shallow gas from the upper unit (1,678 ft to 2,328 ft bml). There is a low potential for 

shallow gas from the middle unit, between 2,328 ft and 2,543 ft bml. There is a negligible

potential for shallow gas from the basal unit (2,543 ft to 2,859 ft bml). There is a negligible

potential for SWF from the upper unit (1,678 ft to 2,328 ft bml). There is a low potential for 

SWF from the middle unit, between 2,328 ft and 2,543 ft bml. There is a negligible potential 

for SWF from the basal unit (2,543 ft to 2,859 ft bml). 
Project No. 11-04-14

BERGER GEOSCIENCES, LLC E-MAIL: beinnovative@b-geo.com WEBSITE: b-geo.com 27 

Horizon 7 to Investigation Limit. The sediments below Horizon 7 are represented by 

alternating units of low-amplitude, parallel reflectors and low- to moderate-amplitude, 

chaotic reflectors (Figure W-3). The low-amplitude, parallel reflectors represent claydominated turbidites. The more chaotic reflectors probably represent mass transport deposits 

containing silts, clays, and isolated sand lenses. Salt is not present beneath the proposed well 

within the investigation limit. 

There is a negligible potential for gas hydrates in this sequence. There is a low potential for

shallow gas from this sequence. There is a low potential for SWF from this sequence. 

Faults. A vertical wellbore at proposed well GC 679-K will intersect one buried fault at 

about 916 ft bml (Figure W-6). This fault is downthrown to the west and extends to the top 

of salt. This fault does not offset any sediment above Horizon 3. There are elevated 

amplitudes trapped along this fault at depth; however, there is no evidence of fluid migration 

above Horizon 6 at the proposed well. 
4,500

4,700

4,800

4,900

5,000

5,100

5,100
4,800

5,000

5,100
4,500

4,600

4,800

4,900

5,000

5,100
4,500

4,800

GC 679 & 723 Seafloor rendering of seafloor assessment area 

1 MILE

Existing

4,1724,2504,7505,0005,2505,5005,623

Seafloor assessment area

Proposed wellCircle represents 2,000’ radius around well (per NTL 2009-G40)

Subsurface study area

Wells

Green Canyon

Bathymetry (ft)

4,500

Reli

Slum

GC7

GC723-F

GC 679GC 723

GC679-K

GC723-G

G241

G

GC

Expulsion 

Mounds
Noble Energy, Inc. Page D-1

Supplemental Exploration Plan 10/31/2011

Green Canyon 697 & 698 (OCS-G 21811 & 21813)

Section D

Hydrogen Sulfide Information

A. Concentration

Noble Energy, Inc. does not anticipate encountering any H2S during the proposed operations.

B. Classification

In accordance with Title 30 CFR 250.490(c) and NTL No. 2003-G17, Noble requests that Green Canyon

679 & 723 be classified by the BOEMRE as H2S absent.
Noble Energy, Inc. Page E-1

Supplemental Exploration Plan 10/31/2011

Green Canyon 697 & 698 (OCS-G 21811 & 21813)

Section E

Biological, Physical and Socioeconomic Information

A. Chemosynthetic Communities Report

Activities proposed in this plan could disturb seafloor areas in deepwater, therefore, a report described in

Attachment A of NTL No. 2009-G40 "Deepwater Benthic Communities" is provided below:

MAPS

Submitted under separate cover are maps prepared using high resolution seismic information and/or 3-D

seismic data depicting bathymetry, seafloor and shallow geological features, surface location of proposed

well(s), and a radius circle of 2,000 feet around each such location.

ANALYSIS

Using high-resolution seismic information and/or 3-D seismic information, all seafloor features and areas

that could be disturbed by the activities proposed in this plan have been identified. The likelihood of these

proposed activities disturbing these seafloor and shallow geologic features is discussed in the following

summary statement:

No Associated Anchors – No Disturbances within 2,000 Feet of Chemosynthetic Communities

Well Locations F, G, H, J, K:

 Features or areas that could support high-density deepwater benthic communities are not located

within 2,000 feet of each proposed muds and cuttings discharge location.

1. Sensitive Underwater Features

The activities proposed in this plan will not take place within 500 feet of any identified topographic feature;

therefore topographic features information is not required.

2. Marine Sanctuaries

Green Canyon 679 & 723 is not located within 100 feet of any pinnacle trend feature with vertical relief

equal to or greater than 8 feet; therefore, live bottom information is not required.

B. Topographic Features Map

Activities proposed in this EP do not fall within 305 meters (1,000 feet) of the “no activity zone”, therefore

no map is required.

C. Topographic Features Statement (Shunting)

All activities proposed under this EP will be conducted outside all Topographic Feature Protective Zones,

therefore shunting of drill cuttings and drilling fluids is not required.

D. Live Bottoms (Pinnacle Trend) Map

Green Canyon 679 & 723 is not located within 61 meters (200 feet) of any pinnacle trend feature with

vertical relief equal to or greater than 8 feet; therefore, live bottom information is not required.

E. Live Bottoms (Low Relief) Map

Green Canyon 679 & 723 is not located within 100 feet of any pinnacle trend feature with vertical relief

equal to or greater than 8 feet; therefore, live bottom (low relief) maps are not required.

F. Potentially Sensitive Biological Features

Green Canyon 679 & 723 is not located within 30 meters (100 feet) of potentially sensitive biological

features; therefore, biologically sensitive area maps are not required.
Noble Energy, Inc. Page E-2

Supplemental Exploration Plan 10/31/2011

Green Canyon 697 & 698 (OCS-G 21811 & 21813)

G. Remotely Operated Vehicle (ROV) Monitoring Survey Plan

Green Canyon 679 & 723 falls within Grid No. 10, an area which BOEMRE classifies as having adequate

ROV survey coverage.

Pursuant to NTL No. 2008-G06, operators may be required to conduct remotely operated vehicle (ROV)

surveys during pre-spudding and post-drilling operations for the purpose of biological and physical

observations.

If required, surveys will be conducted immediately prior and upon completion of drilling operations.

A rig based ROV equipped with video imaging capabilities will be used. The survey pattern will consist of

six transects extending at least 100 meters from the launch point and where at least one transect passes

directly over or very near the well site. The seafloor will be videotaped continuously along each track.

Biological and physical observations as described in the subject NTL and Form BOEMRE-141 will be made

prior to commencing drilling operations and also following the completion of drilling operations, but prior

to moving the rig off location. The observations will be documented using Form BOEMRE-141 or a

facsimile and submitted to the BOEMRE within 60 days after the second survey is completed.

H. Threatened and Endangered Species Information, 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 our

operations.

I. Archaeological Report

Green Canyon 679 & 723 has been determined to have a high potential for containing archaeological

properties, therefore, an Archaeological Survey Report has been prepared in accordance with NTL 2005-

G07 "Archaeological Surveys and Reports".

One copy of a combined Shallow Hazards Assessment/ Benthic Communities Evaluation/ and

Archeological Resource Survey are included in this Exploration Plan submittal package.
Noble Energy, Inc. Page F-1

Supplemental Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

Section F

Waste and Discharge Information

A. Projected Generated Wastes & Projected Ocean Discharges

See Table 1 below

All discharges associated with operations proposed in this Exploration Plan will be in accordance with

regulations implemented by Bureau of Ocean Energy Management, Regulation and Enforcement

(BOEMRE), U. S. Coast Guard (USCG) and the U.S. Environmental Protection Agency (EPA).

Projected generated waste Projected ocean discharges

Projected

Downhole

Disposal

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

EXAMPLE: Cuttings wetted with

synthetic based fluid

Cuttings generated while

using synthetic based

drilling fluid. X bbl/well

X bbl/day/

well discharge overboard No

Water-based drilling fluid Seawater 75,000 10,700 Riserless at sea floor No

Cuttings wetted with water-based fluid

Cuttings generated while

using water based

drilling fluid. 3,500 500 Riserless at sea floor No

Cuttings wetted with synthetic-based fluid

Cutting generated while

using synthetic based

drilling fluid. 6,400 61 Discharge overboard No

Will humans be there? If yes, expect conventional waste

EXAMPLE: Sanitary waste water

Sanitary waste from living

quarters X bbl/well X bbl/hr/well

chlorinate and

discharge overboard No

Domestic waste – gray water Food waste disposal 100 lbs/day 10 lbs/min Discharge overboard No

Sanitary waste Human Waste

2,312

gal/day 96.3 GPH Chlorinated No

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

Deck Drainage Rain Water N/A N/A Closed loop system No

Will you conduct well treatment, completion, or workover?

Well treatment fluids

12.5 ppg sodium bromide

based well treatment

fluid

7,500

bbls/well

2,500 bbl

/treatment

(3

treatments) discharge overboard No

Well completion fluids

16.6 lb/gal Calcium

Bromide/ Zinc Bromide 12,000 bbls N/A

No ocean discharge25% lost to formation

during completion/

75% reclaimed and

sold back to vendor No

Workover 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 Seawater 46,656/day 1,950 GPH Discharge overboard No

Blowout prevent fluid Erifon

1,500 gal at

4% Stack No

Ballast water Seawater

72,000

gal/day 1,200 GPM Pump No

Bilge water N/A N/A N/A N/A No

Excess cement at seafloor Class A Portland Cement 50 BBLS 8 BPM Pump No

Fire water Seawater

0 bbls –

only use in

case of fire 800 GPM Discharge overboard No

Cooling water Seawater

5,760,000

gal/day

240,000

gal/hr Pump No

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

Produced water N/A N/A N/A N/A N/A

Will you be covered by an individual or general NPDES permit ? General
Noble Energy, Inc. Page G-1

Supplemental Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 21811 & 21813)

Section G

Air Emissions Information

A. Emissions Worksheets and Screening Questions

Screen Procedures for EP’s Yes No

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

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

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

(where D = distance to shore in miles)?

X

Do your emission calculations include any emission reduction measures or modified

emission factors?

X

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

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

(ppm)?

X

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

any proposed well?

X

Do you propose to burn produced hydrocarbon liquids? X

If you answer no to all of the above screening questions, then provide the following:

There are no existing facilities or activities co-located with the currently proposed activities, therefore the

Complex Total Emissions are the same as the Plan Emissions and are provided in the table below.

Air Pollutant

Plan

Emission

Amounts1

(tons)

Calculated

Exemption

Amounts2

(tons)

Calculated

Complex Total

Emission

Amounts3

(tons)

Carbon Monoxide (CO) 264.47 82717.95 264.47

Particular matter (PM) 35.26 3996.00 35.26

Sulphur dioxide (SO2) 161.77 3996.00 161.77

Nitrogen oxides (NOx) 1212.17 3996.00 1212.17

Volatile organic compounds (VOC) 36.37 3996.00 36.37

1For activities proposed in your EP, list the projected emissions calculated from the worksheets.

2List the exemption amounts for your proposed activities calculated by using the formulas in 30 CFR 250.303(d).

3List the complex total emissions associated with your proposed activities calculated from the worksheets.
Noble Energy, Inc. Page H-1

Initial Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

Section H

Oil Spill Information

A. Oil Spill Response Planning

Noble Energy, Inc.’s (BOEMRE Operator Number 02237) Regional Oil Spill Response Plan (OSRP) was

approved on December 7, 2009 and most recently updated on September 29, 2011. Activities proposed in

this EP will be covered by the Regional OSRP in accordance with 30 CFR 254.

Surface Containment – In the event of an oil spill, resources have been contracted and are available to

deploy ocean boom to collect product on the water and direct it to skimmers for recovery or to conduct insitu burn operations. By utilizing multiple contractors over 100,000 feet of ocean boom is available for use

within 48 hours.

If product continues to move closer to shore both collection and protection booming strategies can be

utilized to minimize impact to the Coastal Zone. In the near-shore environment over 250,000 feet of 18”

hard boom is available within 48 hours. The primary focus is to collect and/or remove the product from

the surface of the water via mechanical recovery and/or in-situ burning.

The final protection is beach boom and would need to be deployed very strategically based on the

conditions observed and the movement of the product. Utilizing the same 48 hour window of availability

5,000 feet is available. Based on the WCD information Cameron Parish has a 4% chance of impact within

the first 30 days. All other parishes on the coastline have a 2% or less chance in the same period.

Noble Energy has taken extra steps to ensure resources are available quickly from around the Gulf of

Mexico to respond to a release from GC 697 or GC 723 and to the extent possible minimize potential

impacts to the Coastal Zone by engaging the product early in the offshore and near-shore environments.

Based on the anticipated worst case discharge scenario, Noble Energy anticipates it can be onsite within an

estimated 48 hours with dedicated, contracted oil spill recovery equipment with adequate response capacity

to contain and recover surface hydrocarbons and prevent land impact, to the extent possible given the actual

conditions encountered upon arrival (based on the equipment’s Estimated Daily Response Capacity

(EDRC)). Noble Energy will continue to commit additional on-water mechanical recovery resources and

apply dispersants and engage in-situ burning if and to the extent appropriate and as approved by the Unified

Command, incorporating the direction of the U.S. Coast Guard Captain of the Port (COTP) and the

Regional Response Team.

The worst case discharge scenario is based on an uncontrolled continuous release. Containment of the

product to the greatest extent possible given the actual conditions is an ongoing objective and will continue

until the source is appropriately controlled.

B. Spill Response Sites

Primary Response Equipment Location Preplanned Staging Location

Houma/ Venice/ Belle Chasse, LA Houma/ Fourchon/ Venice, LA;

Theodore, AL

C. OSRO Information

Noble has two equipment providers, Clean Gulf Associates (CGA) and Marine Spill Response Corporation

(MSRC). The Marine Spill Response Corporation’s (MSRC) STARS network will provide closest available

personnel, as well as an MSRC supervisor to operate the equipment.
Noble Energy, Inc. Page H-2

Initial Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

D. Worst-Case Scenario Comparison

Category Regional OSRP

WCD

EP

WCD

Type of Activity Drilling Exploration

Facility Location

(Area/Block) MC 699 GC 723

Facility Designation Location D Location H

Distance to Nearest

Shoreline (miles) 80 120

Volume

Storage tanks (total)

Uncontrolled blowout

Total Volume 265,500 249,052

Type of Oil(s)

(crude, condensate, diesel) Crude Crude

API Gravity 30.95° 28.4°

Since Noble Energy Inc. has the capability to respond to the worst-case spill scenario included in our

regional OSRP approved on December 7, 2009 and updated on September 29, 2011, and since the worstcase scenario determined for our EP does not replace the appropriate worst-case scenario in our regional

OSRP, Noble Energy Inc. has certified that it 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 this EP.

The worst case discharge calculation for the regional OSRP was reviewed and accepted under plan R-5205.

E. Oil Spill Response Discussion

See attachment H-1.
Page 1 of 18 

SPILL RESPONSE DISCUSSION 

For the purpose of NEPA and Coastal Zone Management Act analysis, the largest spill volume 

originating from the proposed activity would be a well blowout during drilling operations, 

estimated to be 249,052 barrels of crude oil with an API gravity of 28.4°. 

Land Segment and Resource Identification

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

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

Western Gulf of Mexico available on the BSEE website. The results are shown in Figure 1. The 

BSEE OSRAM identifies a 4% probability of impact to the shorelines of Cameron Parish, 

Louisiana within 30 days. Cameron Parish includes the east side of Sabine Lake, Sabine National 

Wildlife Refuge, Calcasieu Lake, Lacassine National Wildlife Refuge (inland) and Grand Lake. 

Cameron Parish also includes the area along the coastline from Sabine Pass to Big Constance 

Lake in Rockefeller Wildlife Refuge. This region is composed of open public beaches, 

marshlands and swamps. It serves as a habitat for numerous birds, finfish and other animals, 

including several rare, threatened and endangered species. 

Response

Noble Energy, Inc. will make every effort to respond to the Worst Case Discharge as effectively 

as practicable. A description of the response equipment under contract to contain and recover 

the Worst Case Discharge is shown in Figure 2.

Using the estimated chemical and physical characteristics of crude oil, an ADIOS weathering 

model was run on a similar product from the ADIOS oil database. The results indicate 14% or 

approximately 34,867 barrels of crude oil would be evaporated/dispersed within 24 hours, with 

approximately 214,185 barrels remaining. 

Spill Response GC 723, Location H Barrels of Oil 

WCD Volume 249,052 

Less 14% natural evaporation/dispersion 34,867 

Remaining volume 214,185 

Daily dispersant capability 7,540 

Oil addressed by in-situ burning 10,709 

Figure 2 outlines equipment, personnel, materials and support vessels as well as temporary 

storage equipment available to respond to a spill of approximately 214,185 barrels. The volume 

accounts for the amount remaining after evaporation/dispersion at 24 hours. The list estimates 
Page 2 of 18 

individual times needed for procurement, load out, travel time to the site and deployment. Figure 

2 also indicates how operations will be supported. 

Noble Energy, Inc.’s Oil Spill Response Plan includes alternative response technologies such as 

dispersants and in-situ burn. Strategies will be decided by Unified Command based on size of 

the spill, weather and potential impacts. If aerial dispersants are utilized, 8 sorties (9,600 gallons) 

from two of the DC-3 aircrafts and 4 sorties (8,000 gallons) from the Basler aircraft would 

provide a daily dispersant capability of 7,540 barrels. If the conditions are favorable for in-situ 

burning, the proper approvals have been obtained and the proper planning is in place, in-situ 

burning of oil may be attempted. Using estimates based on the Deepwater Horizon spill of 2010, 

up to 5% or approximately 10,709 barrels of the total daily Worst Case Discharge volume could 

be burned. Slick containment boom would be immediately called out and on-scene as soon as 

possible. Offshore response strategies may include attempting to skim utilizing CGA’s HOSS 

Barge, nine Fast Response Units (FRUs), two Aqua Guard Triton RBS Skimmers and eleven sets 

of Koseq skimming arms, along with MSRC’s Louisiana Responder, Deep Blue Responder, 

Mississippi Responder, Gulf Coast Responder, Texas Responder, Southern Responder, MSRC 

Lightning, MSRC Quick Strike, MSRC 360 Offshore Barge, MSRC 402 Offshore Barge, MSRC 

403 Offshore Barge, MSRC 452 Offshore Barge, and MSRC 570 Offshore Barge, with a total 

derated skimming capacity of 480,987 barrels. Temporary storage associated with skimming 

equipment equals 274,300 barrels. If additional storage is needed, one 80,000 barrel storage 

barge, one 47,000 barrel storage barge, one 25,000 barrel storage barge, three 23,000 barrel 

storage barges, and one 20,000 barrel storage barge may be mobilized and centrally located to 

provide temporary storage allowing the skimmers to stay in the area of operations as much as 

possible. Safety is first priority. Air monitoring will be accomplished and operations 

deemed safe prior to any containment/skimming attempts. 

If the spill went unabated, shoreline impact in Cameron Parish, Louisiana would depend upon 

existing environmental conditions. Shoreline protection would include the use of CGA’s and 

MSRC’s near shore and shallow water skimmers with a totaled derated skimming capacity of 

75,854 barrels. Temporary storage associated with skimming equipment equals 5,136 barrels. If 

additional storage is needed, one 86,948 barrel storage barge and one 20,000 barrel storage barge 

may be mobilized and centrally located to provide temporary storage allowing the skimmers to 

stay in the area of operations as much as possible. Onshore response may include the deployment 

of shoreline boom on beach areas, or protection and sorbent boom on vegetated areas. A Master 

Service Agreement with Oil Mop will ensure access to 30,000 feet of 18” shoreline protection 

boom. Figure 2 outlines individual times needed for procurement, load out, travel time to the site 

and deployment. Strategies would be based upon surveillance and real time trajectories that 

depict areas of potential impact given actual sea and weather conditions. The State of Louisiana 

Initial Oil Spill Response Plan for Cameron Parish and Unified Command would be consulted to 

ensure that environmental and special economic resources would be correctly identified and 

prioritized to ensure optimal protection. Shoreline protection strategies depict the protection 

response modes applicable for oil spill clean-up operations. The State of Louisiana Initial Oil 

Spill Response Plan provides detailed shoreline protection strategies for this area, and it 

describes necessary action to keep the oil spill from entering Louisiana’s coastal wetlands, based 

on the assumption that removal of the released oil will be much easier and less damaging to 
Page 3 of 18 

fragile coastal ecosystems if done in the open waters of the Gulf of Mexico. Supervisory 

personnel have the option to modify the deployment and operation of equipment allowing a more 

effective response to site-specific circumstances. Noble Energy, Inc.’s contract Spill 

Management Team holds a copy of the State of Louisiana Initial Oil Spill Response Plan. 
Page 4 of 18 

Initial Response Considerations 

Actual actions taken during an oil spill response will be based on many factors to include but not 

be limited to: 

• Weather 

• Equipment and materials availability 

• Ocean currents and tides 

• Location of the spill 

• Product spilled 

• Amount spilled 

• Environmental risk assessments 

• Trajectory and product analysis 

• Well status, i.e., shut in or continual release 

Noble Energy, Inc. will take action to provide a safe, aggressive response to contain and recover 

as much of the spilled oil as quickly as it is safe to do so. In an effort to protect the environment, 

response actions will be designed to provide an “in-depth” protection strategy meant to recover 

as much oil as possible as far from environmentally sensitive areas as possible. Safety will take 

precedence over all other considerations during these operations. 

Upon notification of a spill, the following actions will be taken: 

• Information will be confirmed 

• An assessment will be made and initial objectives set 

• OSROs and appropriate agencies will be notified 

• ICS 201, Initial Report Form completed 

• Initial Safety plan will be written and published 

• Unified Command will be established 

o Overall safety plan developed to reflect the operational situation and coordinated 

objectives 

o Areas of responsibility established for Source Control and each surface operational 

site 

o On-site command and control established 

Offshore Response Actions 

Equipment Deployment

Surveillance 

• Surveillance Aircraft: within two hours of QI notification, or at first light

• Provide trained observer to provide on site status reports 

• Provide command and control platform at the site if needed 

• Continual surveillance of oil movement by remote sensing systems, aerial photography 

and visual confirmation 

• Continual monitoring of vessel assets using vessel monitoring systems 
Page 5 of 18 

Dispersant application assets 

• Put ASI on standby 

• With the FOSC, conduct analysis to determine appropriateness of dispersant application 

• Gain FOSC approval for use of dispersants on the surface 

• Deploy aircraft in accordance with a plan developed for the actual situation 

• Coordinate movement of dispersants, aircraft, and support equipment and personnel 

• Confirm dispersant availability for current and long range operations 

• Start ordering dispersant stocks required for expected operations 

Containment boom 

• Call out early and expedite deployment to be on scene ASAP 

• Ensure boom handling and mooring equipment is deployed with boom 

• Provide continuing reports to vessels to expedite their arrival at sites that will provide for 

their most effective containment 

• Use Vessels of Opportunity (VOO) to deploy and maintain boom 

Dedicated off-shore skimming systems 

General 

• Deployed to the highest concentration of oil 

• Assets deployed at safe distance from aerial dispersant and in-situ burn operations 

CGA HOSS Barge 

• Use in areas with heaviest oil concentrations 

• Consider for use in areas of known debris (seaweed, and other floating materials) 

CGA FRUs 

• To the area of the thickest oil 

• Use as far off-shore as allowed 

MSRC OSRVs 

• Use in areas with heaviest oil concentrations 

• Use as far off-shore as allowed 

MSRC Responders 

• Use in areas with heaviest oil concentrations 

• Consider for use in areas of known debris (seaweed, and other floating materials) 

T&T Koseq Skimming Systems 

• To the area of the thickest oil 

• Use as far off-shore as allowed 

• VOOs with a minimum of 2,000 bbls storage capacity 
Page 6 of 18 

Storage Vessels 

• Establish availability of CGA contracted assets 

• Early call out (to allow for tug boat acquisition and deployment speeds) 

• Phase mobilization to allow storage vessels to arrive at the same time as skimming 

systems 

• Position as closely as possible to skimming assets to minimize offloading time 

Vessels of Opportunity (VOO) 

• Use Noble Energy, Inc.’s contracted resources as applicable 

• Industry vessels are usually best for deployment of Vessel of Opportunity Skimming 

Systems (VOSS) 

• Acquire additional resources as needed 

• Consider use of local assets, i.e. fishing and pleasure craft 

• Expect mission specific and safety training to be required 

• Plan with the US Coast Guard for vessel inspections 

In-situ Burn assets 

• Determine appropriateness of in-situ burn operation in coordination with the FOSC and 

affected SOSC 

• Determine availability of fire boom and selected ignition systems 

• Start ordering fire boom stocks required for expected operations 

• Contact boom manufacturer to provide training if required 

• Determine assets to perform on water operation 

• Build operations into safety plan 

• Conduct operations in accordance with an approved plan 
Page 7 of 18 

Near Shore Response Actions 

Timing 

• Put near shore assets on standby and deployment in accordance with planning based on 

the actual situation, actual trajectories and oil budgets 

• VOO identification and training in advance of spill nearing shoreline if possible 

• Outfitting of VOOs for specific missions 

• Deployment of assets based on actual movement of oil 

Considerations 

• Water depth, vessel draft 

• Shoreline gradient 

• State of the oil 

• Use of VOOs 

• Distance of surf zone from shoreline 

Equipment Deployment 

Surveillance 

• Provide trained observer to direct skimming operations 

• Continual surveillance of oil movement by remote sensing systems, aerial photography 

and visual confirmation 

• Continual monitoring of vessel assets 

Dispersant Use 

• Generally will not be approved within 3 miles of shore or with less than 10 meters of 

water depth 

• Approval would be at Regional Response Team level (Region 6) 

Vessel Deployment 

Dedicated Near Shore skimming systems 

• FRVs 

• Egmopol and Marco SWS 

• Operate with aerial spotter directing systems to observed oil slicks 

VOO 

• Use Noble Energy, Inc.’s contracted resources as applicable 

• Industry vessels are usually best for deployment of Vessel of Opportunity Skimming 

Systems (VOSS) 

• Acquire additional resources as needed 

• Consider use of local assets, i.e. fishing and pleasure craft 

• Expect mission specific and safety training to be required 

• Plan with the US Coast Guard for vessel inspections 

• Operate with aerial spotter directing systems to oil patches 
Page 8 of 18 

Shoreline Protection Operations 

Response Planning Considerations 

• Environmental risk assessments (ERA) to determine priorities for area protection 

• Time to acquire personnel and equipment and their availability 

• Previous contingency planning contained in the appropriate Area Contingency Plan, and 

currently for Louisiana, The State of Louisiana Initial Oil Spill Response Plan, Deep 

Water Horizon, dated 2 May 2010 (La. OSRP) 

Actions 

Placement of boom 

• Position boom in accordance with the ERA based on the actual situation or the 

appropriate ACP 

• Assess timing of booming operations to ensure it is where it needs to be at time of 

impact. Consider: 

o Trajectories 

o Weather forecast 

o Oil Impact forecast 

o Verified spill movement 

o Boom, manpower and vessel (shallow draft) availability 

o Near shore boom and support material, (stakes, anchors, line) 

Beach Preparation 

Considerations and Actions 

• Use of a 10 mile go/no go line to determine timing of beach cleaning 

• Shoreline Cleanup and Assessment Team Reports and recommendations 

• Determination of Archeological sites and gaining authority to enter 

• Monitoring of tide tables and weather to determine extent of high tides 

• Pre cleaning of beaches by moving waste above high time lines to minimize waste 

• Staging of equipment and housing of response personnel as close to the job site as 

possible to maximize on-site work time 

• Boom tending, repair, replacement and security (use of local assets may be advantageous) 

• Constant awareness of weather and oil movement for resource redeployment as necessary 

• In-situ burn may be considered when marshes have been impacted 

• Passive clean up of marshes should considered and appropriate stocks of sorbent boom 

and/or sweep obtained 

• Earthen berms and shoreline protection boom may be considered to protect sensitive 

inland areas 
Page 9 of 18 

Decanting Strategy 

Recovered oil and water mixtures will typically separate into distinct phases when left in a 

quiescent state. When separation occurs, the relatively clean water phase can be siphoned or 

decanted back to the recovery point with minimal, if any, impact. Decanting therefore increases 

the effective on-site oil storage capacity and equipment operating time. FOSC/SOSC approval 

will be requested prior to decanting operations. This practice is routinely used for oil spill 

recovery. 

CGA Equipment Limitations 

The capability for any spill response equipment, whether a dedicated or portable system, to 

operate in differing weather conditions will be directly in relation to the capabilities of the vessel 

the system in placed on. Most importantly, however, the decision to operate will be based on the 

judgment of the Unified Command and/or the Captain of the vessel, who will ultimately have the 

final say in terminating operations. Skimming equipment listed below may have operational 

limits which exceed those safety thresholds. As was seen in the Deepwater Horizon (DWH) oil 

spill response, vessel skimming operations ceased when seas reached 5-6 feet and vessels were 

often recalled to port when those conditions were exceeded. Systems below are some of the 

most up-to-date systems available and were employed during the DWH spill. 

Boom 3 foot seas, 20 knot winds 

Dispersants Winds more than 25 knots 

Visibility less than 3 nautical miles 

Ceiling less than 1,000 feet. 

FRU 8 foot seas 

HOSS Barge/OSRB 8 foot seas 

Koseq Arms 8 foot seas 

OSRV 4 foot seas 
Page 10 of 18 

Environmental Conditions in the GOM

Louisiana is situated between the easterly and westerly wind belts, and therefore, experiences 

westerly winds during the winter and easterly winds in the summer. Average wind speed is 

generally 14-15 mph along the coast. Wave heights average 4 and 5 feet. However, during 

hurricane season, Louisiana has recorded wave heights ranging from 40 to 50 feet high and 

winds reaching speeds of 100 mph. Because much of southern Louisiana lies below sea level, 

flooding is prominent. 

Surface water temperature ranges between 70 and 80 ̊F during the summer months. During the 

winter, the average temperature will range from 50 and 60 ̊F. 

The Atlantic and Gulf of Mexico hurricane season is officially from 1 June to 30 November. 

97% of all tropical activity occurs within this window. The Atlantic basin shows a very peaked 

season from August through October, with 78% of the tropical storm days, 87% of the minor 

(Saffir-Simpson Scale categories 1 and 2) hurricane days, and 96% of the major (Saffir-Simpson 

categories 3, 4 and 5) hurricane days occurring then. Maximum activity is in early to mid 

September. Once in a few years there may be a hurricane occurring "out of season" - primarily in 

May or December. Globally, September is the most active month and May is the least active 

month. 
Page 11 of 18 

FIGURE 1 

TRAJECTORY BY LAND SEGMENT 

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

utilizing Noble Energy, Inc.’s WCD and information in the BSEE Oil Spill Risk Analysis 

Model (OSRAM) for the Central and Western Gulf of Mexico available on the BSEE 

website using 30 day impact. The results are tabulated below. 

Area/Block OCS-G Launch 

Area 

Land Segment and/or 

Resource 

Conditional 

Probability (%) 

within 30 days 

Exploratory Drilling 

GC 723, Location H 

120 miles from shore 

G21813 C45 Calhoun County, TX 

Matagorda County, TX 

Brazoria County, TX 

Galveston County, TX 

Jefferson County, TX 

Cameron Parish, LA 

Vermilion Parish, LA 

Iberia Parish, LA 

Terrebonne Parish, LA 

Lafourche Parish, LA 

Plaquemines Parish, LA 

1 

1 

1 

2 

1 

4 

2 

1 

2 

1 

2 
Page 12 of 18 

WCD Scenario– BASED ON WELL BLOWOUT DURING DRILLING OPERATIONS (120 miles from s

214,185 bbls of crude oil (Volume considering natural weathering) API Gravity 28.4° 

FIGURE 2 – Equipment Response Time to GC 723, Location H 

Dispersants/Surveillance 

Dispersant/Surveillance Dispersant Capacity (gal) Storage Capacity Persons Req. From Hrs to Procure Hrs to Loadout Travel to site 

CGA 

Basler 67T 2000 NA 2 Houma 1 1 0.8 

ASI 

DC 3 1200 NA 2 Houma 1 1 1.1 DC 3 1200 NA 2 Houma 1 1 1.1 Aero Commander NA NA 2 Houma 1 1 0.8 

Offshore Response 

Offshore Equipment No 

Staging EDRC Storage Capacity VOO Persons Required From Hrs to Procure Hrs to Loadout Hrs to GOM 

CGA 

HOSS Barge 43000 4000 3 Tugs 8 Harvey 7 0 8 

T&T Marine Services LLC (available through contract with CGA) 

Koseq Skimming Arms (3) 53487 6000 3 Utility 18 Leeville 4 12 2 Koseq Skimming Arms (2) 35658 4000 2 Utility 12 Venice 4 12 2 Koseq Skimming Arms (1) 17829 2000 1 Utility 6 Fourchon 4 12 2 Koseq Skimming Arms (5) 89145 10000 5 Utility 30 Galveston 4 12 2 

K-Sea Operating (available through contract with CGA) 

Pacific 996165 NA 80000 1 Tug 6 Houma 4 12 2 

Enterprise Marine Services LLC (available through contract with CGA) 

CTCo 2603 NA 25000 1 Tug 6 Amelia 4 12 4 CTCo 2606 NA 20000 1 Tug 6 Amelia 4 12 4 CTCo 2607 NA 23000 1 Tug 6 Amelia 4 12 4 CTCo 2608 NA 23000 1 Tug 6 Amelia 4 12 4 CTCo 2609 NA 23000 1 Tug 6 Amelia 4 12 4 CTCo 5001 NA 47000 1 Tug 6 Amelia 4 12 4 
Page 13 of 18 

Offshore Equipment No 

Staging EDRC Storage Capacity VOO Persons Required From Hrs to Procure Hrs to Loadout Hrs to GOM 

MSRC 

MSRC Lightning + (2) LORI Brush Pack 5000 50 NA 4 Tampa 2 0 1 MSRC 360 Offshore Barge 1 Crucial Disk 88/30 1,540’ 44” Sea Sentry II Boom 

11122 36000 3 Tugs 6 Tampa 2 0 1 

Mississippi Responder Transrec 350 + OSRV 2,625’ 44” Sea Sentry II Boom 

10567 4000 NA 14 Pascagoula 2 0 1 

MSRC 402 Offshore Barge 2 Crucial Disk 88/30 330’ 44” Sea Sentry II Boom 

22244 40300 3 Tugs 6 Pascagoula 2 0 1 

Louisiana Responder Transrec 350 + OSRV 2,640’ 44” Sea Sentry II Boom 

10567 4000 NA 14 Fort Jackson 2 0 1 

MSRC 452 Offshore Barge 2 Crucial Disk 88/30 660’ 44” Sea Sentry II Boom 

22244 45000 3 Tugs 6 Fort Jackson 2 0 2 

Deep Blue Responder Transrec 350 + OSRV 2,640’ 44” Sea Sentry II Boom 

10567 4000 NA 14 Fourchon 2 0 1 

Gulf Coast Responder Transrec 350 + OSRV 2,640’ 44” Sea Sentry II Boom 

10567 4000 NA 14 Lake Charles 2 0 3.5 

Texas Responder Transrec 350 + OSRV 2,640’ 44” Sea Sentry II Boom 

10567 4000 NA 14 Galveston 2 0 1 

MSRC 570 Offshore Barge 2 Crucial Disk 88/30 770’ 44” Sea Sentry II Boom 

22244 56900 3 Tugs 6 Galveston 2 0 1 

MSRC Quick Strike + (2) LORI Brush Pack 5000 50 NA 4 Ingleside 2 0 1 Southern Responder Transrec 350 + OSRV 2,970’ 44” Sea Sentry II Boom 

10567 4000 NA 14 Ingleside 2 0 1 

MSRC 403 Offshore Barge 1 Crucial Disk 88/30 770’ 44” Sea Sentry II Boom 

11122 40300 3 Tugs 6 Ingleside 2 0 1 
Page 14 of 18 

Staging Area: Fourchon

Offshore Equipment With 

Staging EDRC Storage Capacity VOO Persons Req. From Hrs to Procure Hrs to Loadout Travel to Staging 

CGA 

FRU (1) + 100 bbl Tank (2) 3770 200 1 Utility 6 Belle Chasse 1 2 2.5 FRU (1) + 100 bbl Tank (2) 3770 200 1 Utility 6 Galveston 1 2 7 FRU (3) + 100 bbl Tank (5) 11310 500 1 Utility 6 Houma 1 2 1 FRU (1) + 100 bbl Tank (2) 3770 200 1 Utility 6 Ingleside 1 2 9.5 FRU (1) + 100 bbl Tank (2) 3770 200 1 Utility 6 Lake Charles 1 2 4 FRU (2) + 100 bbl Tank (4) 7540 400 1 Utility 6 Venice 1 2 4 

T&T Marine Services LLC (available through contract with CGA) 

Aqua Guard Triton RBS (2) 45560 4000 2 Utility 12 Galveston 4 12 7 
Page 15 of 18 

Offshore Equipment With 

Staging EDRC Storage Capacity VOO Persons Req. From Hrs to Procure Hrs to Loadout Travel to Staging 

CGA 

42” Auto Boom (5000’) NA NA 10 Crew 20 Belle Chasse 1 2 2.5 42” Auto Boom (5000’) NA NA 10 Crew 20 Galveston 1 2 7 42” Auto Boom (5000’) NA NA 10 Crew 20 Houma 1 2 1 42” Auto Boom (2500’) NA NA 6 Crew 12 Ingleside 1 2 9.5 42” Auto Boom (5000’) NA NA 10 Crew 20 Lake Charles 1 2 4 42” Auto Boom (2500’) NA NA 6 Crew 12 Pascagoula 1 2 4 1000’ Hydro-Fire Boom NA NA 8 Utility 20 Harvey 1 4 2.75 

MSRC 

44” Sea Sentry II Boom (2860’) NA NA 6 Crew 12 Ingleside 1 2 9.5 44” Sea Sentry II Boom (4290’) NA NA 10 Crew 20 Galveston 1 2 7 44” Sea Sentry II Boom (6679’) NA NA 10 Crew 20 Lake Charles 1 2 4 44” Sea Sentry II Boom (1980’) NA NA 6 Crew 12 Fort Jackson 1 2 2.5 44” Sea Sentry II Boom (3190’) NA NA 10 Crew 20 Pascagoula 1 2 4 1500’ Hydro-Fire Boom NA NA 12 Utility 60 Lake Charles 1 4 4 
Page 16 of 18 

Nearshore Response 

Nearshore Equipment No 

Staging EDRC Storage Capacity VOO Persons Required From Hrs to Procure Hrs to Loadout Hrs to GOM T

CGA 

46’ FRV 5000 65 NA 4 Houma 1 0 2 46’ FRV 5000 65 NA 4 Venice 1 0 1 46’ FRV 5000 65 NA 4 Lake Charles 1 0 1 46’ FRV 5000 65 NA 4 Galveston 0 0 1 

Enterprise Marine Services LLC (available through contract with CGA) 

CTCo 2604 NA 20000 1 Tug 6 Amelia 4 12 4 

K-Sea Operating (available through contract with CGA) 

DBL 82 1137538 NA 86948 1 Tug 6 Venice 4 12 2 

Staging Area: Cameron 

Nearshore Equipment With Staging EDRC Storage Capacity VOO Persons Req. From Hrs to Procure Hrs to Load Out Travel to Staging 

CGA 

SWS Egmopol 3000 100 NA 3 Galveston 1 2 3.5 SWS Egmopol 3000 100 NA 3 Houma 1 2 4 SWS Marco 3588 34 NA 3 Venice 1 2 6.25 SWS Marco 3588 34 NA 3 Houma 1 2 4 SWS Marco 3588 20 NA 3 Lake Charles 1 2 1 Foilex Skim Package (TDS 150) 891 45 NA 3 Lake Charles 1 2 1 Foilex Skim Package (TDS 150) 891 45 NA 3 Houma 1 2 4 4 Drum Skimmer (Magnum 100) 686 NA NA 3 Lake Charles 1 2 1 4 Drum Skimmer (Magnum 100) 686 NA NA 3 Houma 1 2 4 2 Drum Skimmer (TDS 118) 240 NA NA 3 Lake Charles 1 2 1 2 Drum Skimmer (TDS 118) 240 NA NA 3 Houma 1 2 4 Rope Mop 77 2 0 3 Belle Chasse 1 2 4.5 RO Storage Barge NA 249 Towed 0 Galveston 1 2 3.5 RO Storage Barge NA 249 Towed 0 Houma 1 2 4 RO Storage Barge NA 249 Towed 0 Lake Charles 1 2 1 RO Storage Barge NA 249 Towed 0 Venice 1 2 6.25 
Page 17 of 18 

Staging Area: Cameron 

Nearshore Equipment With 

Staging EDRC Storage Capacity VOO Persons Req. From Hrs to Procure Hrs to Load Out Travel to Staging 

MSRC 

GT 185 with Adaptor (1) 1371 400 1 Utility 3 Ingleside 2 .5 6 GT 185 with Adaptor (2) 2742 800 2 Utility 6 Galveston 2 .5 3.5 GT 185 with Adaptor (1) 1371 400 1 Utility 3 Port Arthur 2 .5 1.25 GT 185 with Adaptor (1) 1371 400 1 Utility 3 Baton Rouge 2 .5 3 GT 185 with Adaptor (1) 1371 400 1 Utility 3 Fort Jackson 2 .5 4.5 GT 185 with Adaptor (1) 1371 400 1 Utility 3 Pascagoula 2 .5 5.5 Foilex 250 Skimmer 3977 400 1 Crew 3 Fort Jackson 2 .5 4.5 Foilex 250 Skimmer 3977 100 1 Crew 3 Lake Charles 2 .5 1 Foilex 250 Skimmer 3977 100 1 Crew 3 Galveston 2 .5 3.5 Foilex 250 Skimmer 3977 100 1 Crew 3 Ingleside 2 .5 6 WP-1 Skimmer 3017 NA 1 Utility 3 Ingleside 2 .5 6 WP-1 Skimmer 3017 NA 1 Utility 3 Pascagoula 2 .5 5.5 Aardvac 800 Skimmer 3840 NA NA 3 Pascagoula 2 .5 5.5 
Page 18 of 18 

Shoreline Protection 

Staging Area: Cameron 

Shoreline 

Protection Boom VOO Persons Req. Storage/Warehouse Location Hrs to Procure Hrs to Loadout Travel to Staging Travel to Deployment Site 

Oil Mop (available through MSA) 

10,000’ 18” Boom 4 10 New Iberia 1 1 2.5 2 10,000’ 18” Boom 4 10 Houston 1 1 2.5 2 

10,000 18” Boom 4 10 Port Arthur 1 1 1.25 2 

Beach Boom EDRC Storage Capacity VOO Persons Req. From Hrs to Procure Hrs to Loadout Travel to Staging Tra

Deplo

CGA 

Beach Boom (2000’) NA NA NA 6 Galveston 1 2 3.5 Beach Boom (1000’) NA NA NA 4 Ingleside 1 2 6 Beach Boom (2000’) NA NA NA 6 Pascagoula 1 2 5.5 

Wildlife Response EDRC Storage Capacity VOO Persons Req. From Hrs to Procure Hrs to Loadout Travel to Staging T

De

CGA 

Wildlife Support Trailer NA NA NA 2 Houma 1 2 4 Bird Scare Guns (24) NA NA NA 2 Belle Chasse 1 2 4.5 Bird Scare Guns (12) NA NA NA 2 Galveston 1 2 3.5 Bird Scare Guns (24) NA NA NA 2 Houma 1 2 4 Bird Scare Guns (12) NA NA NA 2 Ingleside 1 2 6 Bird Scare Guns (24) NA NA NA 2 Lake Charles 1 2 1 Bird Scare Guns (24) NA NA NA 2 Pascagoula 1 2 5.5 

Response Asset Total 

Offshore EDRC (bbls) 480,987 Offshore Recovered Oil Storage (bbls) 515,300 Nearshore / Shallow Water EDRC (bbls) 75,854 Nearshore / Shallow Water Recovered Oil Storage (bbls) 112,084 
Noble Energy, Inc. Page I-1

Initial Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

Section I

Environmental Monitoring and Mitigation Information

A. Monitoring Systems

There are no environmental monitoring systems currently in place or planned for the proposed activities.

B. Incidental Takes

There is no reason to believe that protected species may be incidentally taken by the activities proposed in

this Supplemental Exploration Plan. However, Noble will comply with NTL 2007-G04 “Vessel Strike

Avoidance and Injured/Dead Protected Species Reporting” and NTL 2007-G03 “Marine Trash and Debris

Awareness and Elimination”.

C. Flower Garden Banks National Marine Sanctuary

Green Canyon 679 & 723 is not located in the Flower Garden Banks National Marine Sanctuary; therefore,

the requested information is not required in this EP.
Noble Energy, Inc. Page J-1

Initial Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

Section J

Lease Stipulations Information

Exploration activities are subject to the following stipulation attached to Lease OCS-G 21811 & 21813,

Green Canyon 679 & 723.

1. Military Warning Area (MWA)

Green Canyon 679 & 723 is located within designated Elgin Water Test Area (EWTA-1). The Air

Armament Center will be contacted in order to coordinate and control the electromagnetic emissions during

the proposed operations.
Noble Energy, Inc. Page K-1

Initial Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

Section K

Support Vessels and Aircraft Information

A. General

The most practical, direct route from the shorebase as permitted by weather and traffic conditions will be

utilized.

Type Maximum Fuel

Tank Capacity

Maximum

Number in Area

at Any Time

Trip Frequency

or Duration

Supply Boat 9,588 bbls 2 2 trips per week

Supply Boat 7,082 bbls 1 4 trips per week

Crew Boat 809 bbls 1 4 trips per week

Helicopter S-92 764 gals 1 4 trips per week

B. Diesel Oil Supply Vessels

Size of Fuel Supply Vessel Capacity of Fuel

Supply Vessel

Frequency of Fuel

Transfers

Route Fuel Supply

Vessel Will Take

Norbert Bouziga - 280 Feet 310,000 gals Once a month From the shore base in

Fourchon, LA to MC

679 & 723 Field, then

to Fourchon, La

Gary Chouest - 276 Feet 300,000 gals Once every 3

months

From the shore base in

Fourchon, LA to MC

679 & 723 Field, then

to Fourchon, La

C. Solid and Liquid Wastes Transportation

See section F, Waste and Discharge Information and Section L, Onshore Support Facilities Information,

Waste Disposal.

D. Vicinity Map

Enclosed as Attachment K-1 is a vicinity map showing the location of the activities proposed herein

relative to the shoreline with the distance of the proposed activities from the shoreline and the primary

route(s) of the support vessels and aircraft that will be used when traveling between the onshore support

facilities and the drilling unit.
GREEN CANYON 

FOURCHON ISLE GRAND VENICE 

ON OPER. BASE 679, 723 

Distance from Deep Blue to Fourchon (roughy) 215 km 133 mi 116 nmi 

re 
Noble Energy, Inc. Page L-1

Supplemental Exploration Plan 10/31/2011

Green Canyon 679 & 723 (OCS-G 21811 & 21813)

Section L

Onshore Support Facilities Information

A. General

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

support for the proposed activities:

Name of Shorebase Location Existing/New/Modified

C Port 1 Slip 4 Port Fourchon, LA Existing

B. Support Base Construction or Expansion

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

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

Initial Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

C. Waste Disposal

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

solid and liquid wastes generated by the proposed activities.

Type of Waste Composition

Solid and Liquid

Wastes Transport

Method

Name/Location

of Facility Amount Disposal Method

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

EXAMPLE: Synthetic-based

drilling fluid or mud internal olefin, ester

Below deck storage

tanks on offshore

support vessels

Newport

Environmental

Services Inc.,

Ingleside, TX X bbl/well Recycled

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

Synthetic-based drilling fluid or

mud Internal Olefin 25 bbl transport

US Fluids

Port Fourchon 150 bbls Injection

Cuttings wetted with Waterbased fluid Seawater Seafloor N/A N/A N/A

Cuttings wetted with Syntheticbased fluid

Interfaces, cement

contamination Cutting boxes

Newpark

Environmental

Fourchon, LA 300 bbls Injection

Cuttings wetted with oil-based

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

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

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

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

fill in the appropriate rows.

Lbs/

month

Recylables

Plastic, paper,

aluminum

Approved

Compactor Bags

Tech Oil, New

Iberia, LA 1,000 lbs Recycled

Trash and debris Household Debris

Approved

Compactor Bags

C Port 1

Fourchon, LA 46,000 lbs Landfill/Disposal

Used oil 40 wt, 90 wt & hyd

DOT approved tote

tank

American

Recovery

Houma, LA 4,000 gals Recycled

Scrap Irons

Iron, Copper, Brass &

Stainless

4’ x 8’ Solid Bin

Basket

C Port

Chouest

Offshore

Fourchon, LA 26,000 lbs Recycled

Chemical product wastes

Paint, Oily Rags,

Gloves & Tyvek Suits

DOT approved

drum

American

Recovery

Houma, LA 4,800 lbs

Processed,

Recycled/Disposed

Spent, dirty completion fluid

Zinc

Bromide/Calcium

Bromide

Offshore Support

Vessels

Newpark

Environmental

Fourchon,LA 2,200 bbls Injection

Completion fluid filtration

media & wash water

Diatomaceous Earth

and Water

25-bbl Cuttings

Boxes

Newpark

Environmental

Fourchon, LA 900 bbls Injection
Noble Energy, Inc. Page M-1

Initial Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

Section M

Coastal Zone Management Act (CZMA) Information

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

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

Noble Energy, Inc. Page N-1

Initial Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

Section N

Environmental Impact Analysis (EIA)

See attachment N – 1.
Environmental Impact Analysis

REVISED EXPLORATION PLAN

Green Canyon Block 679 (OCS-G 21811) and

Green Canyon Block 723 (OCS-G 21813) 

Offshore Louisiana

October 2011

Prepared for:

Noble Energy

100 Glenborough Drive, Suite 100

Houston, Texas 77067

Telephone: (381) 872-3100

Prepared by:

CSA International, Inc.

8502 SW Kansas Avenue

Stuart, Florida 34997

Telephone: (772) 219-3000
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page ii

Contents

Page

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

A. Impact-Producing Factors .......................................................................................5

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

C.1.2 Water Quality ..................................................................................................................21

C.2 Seafloor Habitats and Biota.........................................................................................................23

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

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

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

C.2.4 Pinnacle Trend Area Live Bottoms...................................................................................29

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

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

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

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

C.3.3 Endangered Mysticete Whales........................................................................................35

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

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

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

C.3.7 Whooping Crane (Endangered).......................................................................................42

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

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

C.3.10 Beach Mice (Endangered)................................................................................................45

C.3.11 Elkhorn Coral (Endangered).............................................................................................46
Contents

(Continued)

Page

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Environmental Impact Analysis for Revised Exploration Plan Page iii

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

C.4.1 Marine Birds....................................................................................................................46

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

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

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

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

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

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

C.6.2 Prehistoric Archaeological Sites ......................................................................................58

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

C.8 Socioeconomic and Other Resources..........................................................................................61

C.8.1 Recreational and Commercial Fishing .............................................................................61

C.8.2 Public Health and Safety..................................................................................................63

C.8.3 Employment and Infrastructure......................................................................................64

C.8.4 Recreation and Tourism ..................................................................................................65

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

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

D. Environmental Hazards.........................................................................................67

D.1 Geologic Hazards.........................................................................................................................67

D.2 Severe Weather...........................................................................................................................67

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

E. Alternatives ..........................................................................................................67

F. Mitigation Measures.............................................................................................67

G. Consultation .........................................................................................................68

H. Preparers..............................................................................................................68

I. References.............................................................................................................68
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Environmental Impact Analysis for Revised Exploration Plan Page iv

List of Tables

Table Page

1 Notices to Lessees and Operators (NTLs) applicable to this Environmental Impact 

Analysis (EIA) .........................................................................................................................3

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

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

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

120 days (Adapted from: BOEMRE, 2011a,b Appendix C) ..................................................12

4 Estimated air pollutant emissions in Green Canyon Blocks 679 and 723 over the 

life of the project.................................................................................................................20

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

depths sampled during the Northern Gulf of Mexico Continental Slope Habitats 

and Benthic Ecology Study (From: Rowe and Kennicutt, 2009)..........................................24

6 Federally listed endangered and threatened species potentially occurring in the 

lease area and along the northern Gulf Coast ....................................................................30

7 Wildlife refuges, wilderness areas, and State and National parks within the 

geographic range of the potential shoreline contacts after 120 days................................59

List of Figures 

Figure Page

1 Distance of lease area from nearest shoreline (Louisiana), onshore support base 

at Port Fourchon, and helicopter base at Houma, Louisiana................................................2

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

3 Location of selected environmental features in relation to the lease area........................43
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page v 

Acronyms and Abbreviations

ADIOS Automated Data Inquiry for Oil Spills

bbl barrel

B-Geo Berger Geosciences, LLC 

BHL bottom hole location

BOEM Bureau of Ocean Energy Management

BOEMRE Bureau of Ocean Energy Management, 

Regulation and Enforcement 

BOP blowout preventer

B.P. Before Present

CEI Coastal Environments, Inc.

CFR Code of Federal Regulations

CGA Clean Gulf Associates

CH4 methane

CO carbon monoxide

CO2 carbon dioxide

DOCD Development Operations Coordination 

Documents

DP dynamically positioned

DPP Development & Production Plan

EEZ Exclusive Economic Zone

EFH Essential Fish Habitat

EIA Environmental Impact Analysis

EIS Environmental Impact Statement

EP Exploration Plan

ESA Endangered Species Act

EW Ewing Bank

FAD fish-attracting device

FR Federal Register

GC Green Canyon

GMFMC Gulf of Mexico Fishery Management 

Council

GPS global positioning system

H2S hydrogen sulfide

HAPC Habitat Area of Particular Concern

HOSS high-volume open sea skimmer

IPF impact-producing factor

MARPOL International Convention for the 

Prevention of Pollution from Ships

MMC Marine Mammal Commission

MMPA Marine Mammal Protection Act

MMS Minerals Management Service

MSRC Marine Spill Response Corporation

NAAQS National Ambient Air Quality Standards

NMFS National Marine Fisheries Service

NOAA National Oceanic and Atmospheric 

Administration

Noble Noble Energy, Inc.

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

NWR National Wildlife Refuge

OBM oil-based mud

OCS Outer Continental Shelf

OSAT Operational Scientific Advisory Team

OSRA Oil Spill Risk Analysis

OSRP Oil Spill Response Plan

OSRV oil spill response vessel

PAH polycyclic aromatic hydrocarbon

PM particulate matter

PSD Prevention of Significant Deterioration

SBF synthetic-based fluid

SBM synthetic-based mud

SHL surface hole location

SOx sulfur oxides

SWSS Sperm Whale Seismic Study

UHF ultra high frequency

USCG U.S. Coast Guard

USEPA U.S. Environmental Protection Agency

USFWS U.S. Fish and Wildlife Service

VHF very high frequency

VOC volatile organic compound

WCD worst case discharge
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 1 

Introduction

Noble Energy, Inc. (Noble) is submitting a revised Exploration Plan (EP) for Green Canyon Blocks 

679 and 723 (GC 679 and 723). Noble proposes to drill four exploratory wells in GC 723 and one 

exploratory well in GC 679 using a dynamically positioned (DP) semisubmersible drilling rig. It is 

anticipated to take approximately 190 days to drill and complete each well. All surface hole 

locations (SHLs) and bottom hole locations (BHLs) will be located in GC 723 and 679 respectively. 

This Environmental Impact Analysis (EIA) information provides an analysis of all five well 

locations.

The lease area is 120 miles (193 km) south of the nearest shoreline (Louisiana), 135 miles 

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

from the helicopter base at Houma, Louisiana (Figure 1). Water depths in the assessment area 

range from 1,272 to 1,714 m (4,172 to 5,623 ft). This EIA was prepared for submittal to the 

Bureau of Ocean Energy Management (BOEM) in accordance with applicable regulations,

including 30 Code of Federal Regulations (CFR) 250.212(o) and 250.227—it is a project- and 

site-specific analysis of Noble’s planned activities. As specified in the Notice to Lessees and 

Operators (NTL) 2008-G04, an EIA is a project-specific analysis that focuses on the impacts of a 

specific plan to the extent feasible. Potential impacts have been analyzed at a broader level in 

the Programmatic Environmental Impact Statement (EIS) for the Outer Continental Shelf (OCS) 

Oil and Gas Leasing Program (MMS, 2007a) and in lease sale EISs for the Western and Central 

Gulf of Mexico Planning Areas (MMS, 2007b, 2008). The analyses from these documents are 

incorporated here by reference. Also incorporated are the post-Macondo incident Draft 

Supplemental EISs for the Central and Western Planning Area lease sales (BOEMRE, 2011a,b), 

which present updated environmental baseline information relative to the Macondo incident. 

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

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

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

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

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

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

blowout per 200 well starts (MMS, 2000). More recently in its Draft Supplemental EIS for the 

Central Gulf of Mexico Planning Area, BOEMRE confirmed that “significant changes to the spill 

rates for the entire OCS are not anticipated” (BOEMRE, 2011a).

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

Mexico from 1971 to 1995, only 18 (12%) resulted in oil spills, with a total combined volume of

1,000 barrels (bbl) of crude oil and condensate released (MMS, 2000). Between 1964 and 1999, 

almost all offshore spills (94%) from drilling and production-related operations on the OCS were 

less than or equal to 1 bbl in size (Anderson and LaBelle, 2000). According to BOEMRE’s Interim 

Final Drilling Safety Rule (75 Federal Register (FR) 63365 dated 10 October 2010) issued 

following the Macondo incident, the baseline risk of a catastrophic blowout is estimated to be 

about once every 26 years. 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 2 

Figure 1. Distance of lease area from nearest shoreline (Louisiana), onshore support base at Port Fourchon, and helicopter base at Houma, 

Louisiana.
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 3 

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

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

The OSRP details Noble’s plan for response to rapidly and to effectively manage oil spills that 

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

based on a regional capability of response to spills ranging from small operational spills to a 

worst discharge (WCD) from a well blowout. Noble’s spill response program meets the response 

planning requirements of the relevant coastal states and applicable Federal oil spill planning 

regulations and also includes information regarding Noble’s regional oil spill organization and 

dedicated response assets, potential spill risks, and local environmental sensitivities. The OSRP 

describes personnel and equipment mobilization, the incident management team organization, 

and an overview of actions and notifications to be taken in the event of a spill. All activities 

planned for GC 679 and 723 are covered under this regional OSRP in accordance with 

30 CFR 254.

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

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

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

this EIA.

Table 1. Notices to Lessees and Operators (NTLs) applicable to this Environmental Impact 

Analysis (EIA). 

NTL Title Summary

2010-N10 

Statement of Compliance with 

Applicable Regulations and 

Evaluation of Information 

Demonstrating Adequate Spill 

Response and Well Containment 

Resources

Informs operators using subsea blowout preventers (BOPs) or 

surface BOPs on floating facilities that applications for well 

permits must include a statement signed by an authorized 

company official stating that the operator will conduct all 

activities in compliance with all applicable regulations, 

including the increased safety measures regulations 

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

evaluating whether each operator has submitted adequate 

information demonstrating that it has access to and can 

deploy containment resources to promptly respond to a 

blowout or other loss of well control.

2010-N06 

Information Requirements for 

Exploration Plans, Development 

and Production Plans, and 

Development Operations 

Coordination Documents on the 

OCS

Rescinds the limitations set forth in NTL 2008-G04 regarding 

a blowout scenario and worst case discharge scenario, and 

provides guidance regarding the information required in 

blowout scenario and worst case discharge scenario 

descriptions.

2009-G40 Deepwater Benthic Communities

Guidance for avoiding and protecting high-density deepwater 

benthic communities (including chemosynthetic and 

deepwater coral communities) from damage caused by 

OCS oil and gas activities in water depths greater than 300 m 

(984 ft). Prescribes separation distances of 610 m (2,000 ft) 

from each mud and cuttings discharge location and 76 m 

(250 ft) from all other seafloor disturbances.

2009-G39 Biologically Sensitive Underwater 

Features and Areas

Guidance for avoiding and protecting biologically sensitive 

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

relief live bottom areas, and other potentially sensitive 

biological features) when conducting OCS operations in water 

depths less than 300 m (984 ft) in the Gulf of Mexico.
Table 1. (Continued.)

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Environmental Impact Analysis for Revised Exploration Plan Page 4 

NTL Title Summary

2009-G06 Military Warning and Water Test 

Areas

Provides contact links to individual command headquarters 

for the military warning and water test areas in the Gulf of 

Mexico. Lease stipulations require lessees or designated 

operators to enter into an agreement with the appropriate 

individual military command headquarters concerning the 

control of electromagnetic emissions and use of boats and 

aircraft in the applicable warning area or water test area 

before commencing such traffic.

2008-G04 

Information Requirements for 

Exploration Plans and 

Development Operations 

Coordination Documents

Guidance on the information requirements for OCS plans, 

including EIA requirements and information regarding 

compliance with the provisions of the Endangered Species 

Act and Marine Mammal Protection Act.

2007-G04 

Vessel Strike Avoidance and 

Injured/Dead Protected Species 

Reporting

Recommends protected species identification training, 

recommends that vessel operators and crews maintain a 

vigilant watch for marine mammals and slow down or stop 

their vessel to avoid striking protected species, and requires 

operators to report sightings of any injured or dead protected 

species.

2007-G03 Marine Trash and Debris 

Awareness and Elimination

Instructs operators to exercise caution in the handling and 

disposal of small items and packaging materials; requires the 

posting of placards at prominent locations on offshore 

vessels and structures; and mandates a yearly marine trash 

and debris awareness training and certification process.

2005-G07 Archaeological Resource Surveys 

and Reports

Provides guidance on regulations regarding archaeological 

discoveries, specifies requirements for archaeological 

resource surveys and reports, and outlines options for 

protecting archaeological resources.
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 5 

A. Impact-Producing Factors

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

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

expected to affect a certain resource, and a dash (--) indicates no impact or negligible impact. 

Where there may be an effect, an analysis is provided in Section C. Potential IPFs for the 

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

• Drilling rig presence (including noise and lights);

• Physical disturbance to the seafloor;

• Air pollutant emissions;

• Effluent discharges;

• Water intake;

• Onshore waste disposal; 

• Marine debris;

• Support vessel and helicopter traffic; and

• Accidents.

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

The drilling rig proposed for this Revised EP is a DP semisubmersible. DP semisubmersibles use 

a geographic positioning system (GPS) and sensors in conjunction with their own propellers and 

thrusters to maintain position. Essentially, through satellite navigation, the location of the 

vessel is precisely monitored, and thrusters positioned at various locations about the vessel’s 

hull are activated to provide any required stationkeeping adjustment. This allows operations at 

sea where mooring or anchoring is not feasible.

The drilling rig for the wells proposed in this EP will be on site for an estimated 190 days for each 

well drilled. The physical presence of the drilling rig in the ocean can attract pelagic fishes and 

other marine life, as discussed in Section C.5.1. 

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

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

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

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

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

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

regulations.
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 6 

Table 2. Matrix of impact-producing factors and affected environmental resources. X = potential impact; dash (--) = no impact or negligible impact.

Environmental Resources

Impact-producing Factors

Drilling Rig 

Presence (incl. 

noise & lights)

Physical 

Disturbance 

to Seafloor

Air 

Pollutant 

Emissions

Effluent 

Discharges

Water 

Intake

Onshore 

Waste 

Disposal

Marine 

Debris

Support 

Vessel/Helo 

Traffic

Accidents

Small Fuel 

Spill

Oil Spill 

(WCD)

Physical/Chemical Environment

Air quality and greenhouse gases -- -- X(9) -- -- -- -- -- X(6) X(6)

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

Seafloor Habitats and Biota

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

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

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

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

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

Threatened, Endangered, and Protected Species and Critical Habitat

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

West Indian manatee (endangered) -- -- -- -- -- -- -- X(8) -- X(6,8)

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

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

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

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

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

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

Smalltooth sawfish (endangered) X(6)

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

Elkhorn coral (endangered) X(6)

Coastal and Marine Birds

Marine birds X -- -- -- -- -- -- X X(6) X(6)

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

Fisheries Resources

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

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

Archaeological Resources

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

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

Coastal Habitats and Protected Areas

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

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

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

Socioeconomic and Other Resources

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

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

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

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

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

Other marine uses -- -- -- -- -- -- -- -- -- X(6)

WCD = worst case discharge.
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 7 

Table 2 Footnotes and Applicability:

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

anchors will be on the seafloor within the following:

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

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

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

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

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

the Topographic Features Stipulation attached to an OCS lease.

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

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

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

(Pinnacle Trend) Stipulation attached to an OCS lease.

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

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

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

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

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

• No impacts on high-density deepwater benthic communities are anticipated. There are no features 

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

any drilling mud/cuttings discharge location. 

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

• Based on CFR 250.490(c), Noble is requesting that BOEM classify the area as “H2S absent.” 

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

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

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

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

analyzed in Section C. 

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

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

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

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

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

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

blocks for shipwrecks and is well beyond the 60-m depth contour used by the BOEM as the seaward 

extent for prehistoric archaeological site potential in the Gulf of Mexico.

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

or sea turtles or their critical habitats. 

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

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

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

• Not applicable.
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 8 

A.2 Physical Disturbance to the Seafloor

In water depths of 600 m (1,969 ft) or greater, DP semisubmersibles disturb only a very small 

area of the seafloor around the wellbore (SHL) where the bottom template and blowout 

preventer (BOP) are located. Depending on the specific well configuration, this area is generally 

about 0.25 ha (0.62 ac) (MMS 2007b). 

A.3 Air Pollutant Emissions

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

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

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

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

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

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

monoxide (CO).

The Air Quality Emissions Report prepared in accordance with BOEM requirements 

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

regulations in 30 CFR 250.303. Based on this and the distance to shore, it can be concluded that

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

criteria pollutants. No further analysis or control measures are required.

A.4 Effluent Discharges

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

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

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

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

permit.

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

intervals before the marine riser that allows their return to the surface is set. Excess cement 

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

the drilling operations. Synthetic-based drilling muds (SBMs) will be collected on the rig and 

transported to Port Fourchon for disposal at an approved facility. Cuttings wetted with SBMs 

will be discharged to the seafloor in accordance with the NPDES permit.

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

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

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

A.5 Water Intake

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

the drilling rig. Section 316(b) of the Clean Water Act requires NPDES permits to ensure that the 

location, design, construction, and capacity of cooling water intake structures reflect the best 

technology available to minimize adverse environmental impact from impingement and 

entrainment of aquatic organisms. The current NPDES General Permit No. GMG290000 does 

not specify requirements for existing facilities (those that started construction before 

16 July 2006). The rig being considered for use for activities described in this EP is not a “new” 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 9 

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

regulations.

A.6 Onshore Waste Disposal

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

will be generated each month due to operations, or a total of 190 bbl per well for each of the 

three wells proposed under this EP. This trash will be transported in disposal bags to shore, 

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

regulations. 

A.7 Marine Debris

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

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

requirements and USEPA and U.S. Coast Guard (USCG) regulations, as well as those of BOEM. 

For example, BOEM regulations at 30 CFR 250.300(a) and (b)(6) prohibit operators from 

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

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

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

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

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

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

bins to prevent accidental loss of solid waste. In addition to the regulations in 30 CFR 250, 

MMS issued NTL 2007-G03, which instructs operators to exercise caution in the handling and 

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

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

awareness training and certification process.

A.8 Support Vessel and Helicopter Traffic

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

vessel activities. Air transportation (helicopters) will be based at facilities in Houma, Louisiana. 

No terminal expansion or construction is planned at either location.

The project will be supported by one crew boat and two supply vessels. The crew vessel will 

make four round-trips per week and supply vessels will make a total of six round-trips per week. 

The boats typically will move to the project area via the most direct route from the shorebase.

A helicopter will make an estimated four round-trips per week between the drilling rig and the 

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

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

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

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

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

park properties. 
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A.9 Accidents 

A.9.1 Types of Accidents Evaluated

The analysis in this EIA focuses on two potential accidents:

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

• the WCD for this 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 Noble’s spill response plans. Impacts are analyzed in Section C. 

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

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

These accidents are discussed briefly in Section A.9.4. 

A.9.2 Small Fuel Spill

Spill Size. According to analyses in MMS (2007b) and BOEMRE (2011a,b), the most likely type of 

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

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

future OCS activities in the Western and Central Gulf of Mexico Planning Areas. As spill size 

increases the incident rate declines dramatically (MMS, 2007b; BOEMRE, 2011a,b). The average 

size for spills <1 bbl is 0.07 bbl, and the median size for spills of 1 to 10 bbl is 3 bbl 

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

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

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

Spill Fate

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

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

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

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

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

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

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

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

and Atmospheric Administration [NOAA], 2006).

. 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 and response actions, it is expected 

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

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

Automated Data Inquiry for Oil Spills 2 (ADIOS2) model. This model uses the physical properties 

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

changes in the density, viscosity, and water content of the product spilled. It is estimated that 

over 90% of a small diesel spill would be evaporated or dispersed within 24 hours. The area of 

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

(1.2 to 12 ac) depending on sea state and weather conditions.
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The ADIOS2 results, coupled with spill trajectory information discussed below for a large spill,

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

The lease area is 120 miles (193 km) south of the nearest shoreline. Modeling results discussed 

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

coastline within 10 days after a spill. By that time, essentially 100% of a small fuel spill would 

have been dispersed or evaporated by natural processes, without taking into account Noble’s 

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

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

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

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

and historical records of spill incidents.

Spill Response

A.9.3 Crude Oil Spill (Worst Case Discharge)

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

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

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

EP Section H – Attachment H-1 provides a detailed discussion of Noble’s response to a spill.

Spill Size

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

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

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

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

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

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

of updating these spill frequency estimates to include the recent Macondo event; however, 

significant changes to the spill rates for the entire OCS are not anticipated (BOEMRE, 2011a,b). 

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

every 26 years (BOEMRE Interim Final Drilling Safety Rule, 75 FR 63365 – 10 October 2010).

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

this EP as 249,052 barrels of oil (EP Section H).

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

including descriptions of measures to prevent a blowout, reduce the likelihood of a blowout, 

and conduct effective and early intervention in the event of a blowout. Noble will also comply 

with NTL 2010-N10 and the Interim Final Drilling Safety Rule, which specifies additional safety 

measures for OCS activities.

Spill Trajectory

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

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

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

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

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

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

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

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

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

it is still the most widely scientifically accepted model for estimating the fate of small fuel spills. 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 12 

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

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

probabilities for spills greater than 1,000 bbl.

To address this criticism a special OSRA run was conducted for the recent BOEMRE Western Gulf 

of Mexico Planning Area Supplemental EIS (BOEMRE, 2011a,b) in order to estimate the impacts 

of a possible future catastrophic long-duration oil spill. In this OSRA model run, a hypothetical 

high-volume, long-duration oil spill was assumed to have occurred, and the analysis emphasized 

modeling a spill that continued for 90 consecutive days, with each trajectory tracked for up to 

120 days. 

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

Central and Western Gulf of Mexico Planning Areas. These launch points were deliberately 

located in areas identified as having a high possibility of containing large oil reserves. 

The five launch point areas were as follows:

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

92.17851 W longitude; 

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

88.15338 W longitude; 

3. Central Gulf of Mexico slope area—27.31998 N latitude, 90.22203 W longitude; 

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

5. Western Gulf of Mexico slope area—27.51367 N latitude, 94.51836 W longitude. 

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

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

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

(Adapted from: BOEMRE, 2011a,b, Appendix C).

Season Winter Spring Summer Fall

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

County or Parish Percent Chance

Cameron, Texas -- -- -- 2 -- -- -- -- -- -- -- 2 -- -- -- 2

Willacy, Texas -- -- -- 3 -- -- -- -- -- -- -- 2 -- -- -- 3 

Kenedy, Texas -- -- -- 8 -- -- -- 1 -- -- -- 9 -- -- -- 5

Kleberg, Texas -- -- 1 6 -- -- -- -- -- -- -- 4 -- -- 1 6 

Nueces, Texas -- -- 1 6 -- -- -- -- -- -- -- 2 -- -- 1 2

Aransas, Texas -- -- -- 5 -- -- -- 1 -- -- -- 3 -- -- -- 2 

Calhoun, Texas -- -- 1 6 -- -- -- -- -- -- -- 6 -- -- 1 4

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

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

Galveston, Texas -- -- 3 10 -- -- 3 6 -- -- 2 5 -- -- -- 4 

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

Cameron, Louisiana -- -- 1 4 -- -- 11 12 -- 1 1 4 -- -- -- 4 

Vermilion, Louisiana -- -- 1 2 -- -- 5 6 -- 1 1 2 -- -- -- --

Iberia, Louisiana -- -- -- 1 -- -- 4 4 -- -- -- -- -- -- -- --

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

Lafourche, Louisiana -- -- 1 1 -- 2 8 10 -- -- 1 2 -- -- -- --

Jefferson, Louisiana -- -- -- 1 -- -- 2 2 -- -- 1 1 -- -- -- --

Plaquemines, Louisiana -- -- -- 1 -- 2 10 12 -- -- 1 2 -- -- -- --

Jackson, Mississippi -- -- -- -- -- -- 1 1 -- -- -- -- -- -- -- --

Baldwin, Alabama -- -- -- -- -- -- 1 1 -- -- -- -- -- -- -- --
Table 3. (Continued.)

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Season Winter Spring Summer Fall

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

County or Parish Percent Chance

Bay, Florida -- -- -- -- -- -- -- 1 -- -- -- -- -- -- -- --

Franklin, Florida -- -- -- 1 -- -- -- -- -- -- -- -- -- -- -- --

Monroe, Florida -- -- -- -- -- -- -- -- -- -- -- 1 -- -- -- 1

Dade, Florida -- -- -- -- -- -- -- -- -- -- -- 1 -- -- -- --

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

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

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

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

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

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

major spill or uncontrolled release. 

Weathering

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

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

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

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

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

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

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

water surface.

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

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

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

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

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

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

seafloor (NRC, 2003).

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

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

spill-response-related NTLs are listed in Table 1 and the guidance documents are as follows: 

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

Information Demonstrating Adequate Spill Response and Well Containment Resources

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

using subsea or surface BOPs on floating facilities. It explains that lessees and operators 

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

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

compliance with all applicable regulations, including the Increased Safety Measures 

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

whether or not each operator has submitted adequate information demonstrating that 

it has access to and can deploy surface and subsea containment resources that would be 

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

: 
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Environmental Impact Analysis for Revised Exploration Plan Page 14 

notifies the operator that BOEM intends to evaluate the adequacy of each operator to 

comply in the operator’s current OSRP; therefore, there is an incentive for voluntary 

compliance.

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

Production Plans, and Development Operations Coordination Documents on the OCS

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

submit supplemental information for new or previously submitted EPs, Development 

and Production Plan (DPPs), or Development Operations Coordination Documents 

(DOCDs). The required supplemental information includes the following: (1) a 

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

(2) a description of their assumptions and calculations used in determining the volume 

of the worst-case discharge required by 30 CFR 250.219(a)(2)(iv) (for EPs) or 

30 CFR 250.250(a)(2)(iv) (for DPPs and DOCDs); and (3) a description of the measures 

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

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

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

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

surface and subsea containment resources that BOEM announced in NTL 2010-N10, 

which states that BOEM will begin reviewing to ensure that the measures are adequate 

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

:

Noble submitted an updated Gulf of Mexico Regional OSRP to BOEMRE on 4 May 2011. The 

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

spills that may result from drilling and production operations.

In the event of a WCD, Noble has access to surface and subsea response/containment 

capabilities that could be implemented through various organizations under contract. Noble's 

primary spill response equipment provider is Clean Gulf Associates (CGA). 

CGA has four skimming vessels capable of operating in shallow waters and offshore/nearshore 

areas. These vessels have oleophilic brush pack skimming systems operating in troughs built 

into the hulls; below deck storage; and marine electronics packages including marine, aircraft 

and company frequency radios, radar, moving map plotters (GPS), satellite phone, and depth 

finders. CGA also offers nine Fast Response Systems staged throughout the Gulf of Mexico 

available for offshore use. 

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

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

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

room overlooking the skimmer deck. The estimated daily recovery capacity for the HOSS barge 

is approximately 43,000 bbl. 

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

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

is on order.
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Environmental Impact Analysis for Revised Exploration Plan Page 15 

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

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

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

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

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

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

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

barges. 

In addition to these 15 oil spill response vessels, MSRC is outfitted with other specialized 

response vessels and support equipment, including: 

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

• 68 shallow water barges; 

• 600,000 feet of boom; 

• Over 240 skimming systems; 

• Six self-propelled skimming vessels 10 to 18 m (32 to 58 ft); 

• Seven mobile communications suites comprising telephone and computer connections and 

ultra high frequency (UHF) and very high frequency (VHF) marine, aviation, and business 

band radios; 

• Various small crafts and shallow-water vessels; 

• One C-130 dispersant aircraft; and 

• One King Air dispersant/spotter aircraft. 

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

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

and Theodore, Louisiana.

See EP Section H (Attachment H-1) for a detailed description of Noble’s site-specific response to 

the WCD for this plan.

A.9.4 Other Accidents Not Analyzed in Detail

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

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

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

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

by drilling the wells proposed in this EP.

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

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

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

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

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

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

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

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

processing (BOEMRE, 2011a,b). 
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Synthetic-based Fluid Spills. In deepwater drilling, SBMs are preferred over petroleum oil-based 

muds (OBMs) due to their superior environmental properties. Synthetic-based fluids (SBFs) 

used in SBMs are less toxic to the marine environment and have the potential to biodegrade. 

SBMs have been used since the mid 1990s. Three SBF spills >1,000 bbl occurred between 

2001 and 2004. Between 5 and 20 SBF releases are anticipated each year as a result of offshore 

drilling programs; the majority of these releases are <50 bbl in size. The volume of the synthetic 

portion of the drill fluid rather than the total volume of the drill fluid is now used to describe 

spill size. Accidental riser disconnects could result in the release of large quantities of drilling 

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

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

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

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

the OCS resulted in diesel spills, and in several collision incidents, fires resulted from 

hydrocarbon releases. To date, the largest diesel spill associated with a collision occurred in 

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

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

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

of vessel collisions. Human error accounts for approximately half of all reported vessel collisions 

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

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

diesel fuel or chemicals. Noble will comply with all USCG and BOEM-mandated safety 

requirements to minimize the potential for vessel collisions.

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

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

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

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

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

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

to prevent a blowout, reduce the likelihood of a blowout, and conduct effective and early 

intervention in the event of a blowout are described in EP Section H as required by NTL 2010-06. 

The potential for a loss-of-well-control event will be minimized by adhering to the requirements 

of applicable regulations such as the Interim Final Drilling Safety Rule and NTL 2010-N10, which 

specify additional safety measures for OCS activities. 

H2S Release. Pursuant to 30 CFR 250.490(c), Noble is requesting in the EP that the BOEM

Regional Supervisor, Field Operations, classify the area in the proposed drilling operations as 

"H2S absent." H2S is not known or anticipated to occur in the objective Miocene-age section. 

H2S was not present in the analogous Miocene section as penetrated in Noble Energy GC 723, 

Well No. 1 (OCS-G 21813), at a depth range of 5,008 to 9,475 m (16,430 to 31,085 ft). Several 

additional wells in GC 640 and 727 drilled middle and lower Miocene-age objective sections also 

failed to show signs of H2S. 
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Environmental Impact Analysis for Revised Exploration Plan Page 17 

B. Affected Environment

The lease area is in the north-central Gulf of Mexico, 120 miles (193 km) south of the nearest 

shoreline (Louisiana) and 135 miles (217 km) from the onshore support base at Port Fourchon, 

Louisiana (Figure 1). Based on the 2011 Shallow Hazards Assessment, Benthic Communities

Evaluation, and Archaeological Resources Survey by Berger Geosciences, Inc. (B-Geo), water 

depths at the wellsites range from 1,272 to 1,714 m (4,172 to 5,623 ft) (Figure 2). Benthic or 

chemosynthetic communities may occur on or near two expulsion mounds seen in the 

southwestern quadrant of GC 723, but there is no evidence of features that may support 

chemosynthetic or other benthic communities within 610 m (2,000 ft) of any of the proposed 

wells in GC 679 and 723 (B-Geo, 2011). 

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

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 (MMS, 2007b, 2008). These regional 

descriptions remain valid and are incorporated by reference. General background information is 

presented below, and brief descriptions of each potentially affected resource, including 

site-specific and/or new information if available, are presented in Section C. 

The Macondo spill resulted in impacts to water quality in the area of the spill. In addition to the 

oil slick on the sea surface, plumes of submerged oil droplets were produced when subsea 

dispersants were applied at the wellhead (Camilli et al., 2010; Hazen et al., 2010; Joint Analysis 

Group, 2010a,b,c). Despite limited information on the water quality of deep water, it is clear 

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

event. Various monitoring efforts and environmental studies are in progress, but it is not 

currently possible to precisely estimate the long-term impacts the spill will have on offshore 

water quality (BOEMRE, 2011a,b).

The lease area is located approximately 187 miles (302 km) west-southwest of the Macondo spill 

site. Based on an analysis of satellite imagery (ESRI, 2010), the surface slick extended over the 

lease area. With the current information available, there is evidence to suggest that water 

quality in the lease area was temporarily affected by the Macondo incident. Prior to the 

Macondo incident, water quality in deep, offshore waters of the Gulf of Mexico was expected to 

be good, with low levels of contaminants (Kennicutt, 2000). Based on the information currently 

available, there is no reason to expect any long-term change in water quality conditions in the 

lease area from those predicted in the recent lease sale EISs (MMS 2007b, 2008; BOEMRE, 

2011a,b). 
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Environmental Impact Analysis for Revised Exploration Plan Page 18 

Figure 2. Bathymetric map of the lease area showing proposed well surface locations. (Water depth in meters.)
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 19 

C. Impact Analysis

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

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

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

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

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

section.

C.1 Physical/Chemical Environment

C.1.1 Air Quality

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

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

quality at the wellsites is expected to be good. The attainment status of Federal OCS waters is 

unclassified because there is no provision in the Clean Air Act for classification of areas outside 

state waters (MMS, 2007b). 

As noted earlier, all Louisiana, Mississippi, Alabama, and Florida coastal counties and parishes 

were in attainment of the National Ambient Air Quality Standards (NAAQS) for all criteria 

pollutants (USEPA, 2011). Two metropolitan areas in Texas are nonattainment areas for 

8-h ozone (Dallas-Fort Worth and Houston-Brazoria), and El Paso County is a nonattainment 

area for PM10 (USEPA, 2011).

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

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

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

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

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

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

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

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

large oil spill (WCD).

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

additional information and in consideration of the Macondo oil spill event. No substantial new 

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

lease sale EISs (BOEMRE, 2011a,b).

Impacts of Air Pollutant Emissions

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

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

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

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

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

and CO. Emissions of pollutants into the atmosphere from these activities are not projected to 
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Environmental Impact Analysis for Revised Exploration Plan Page 20 

have significant effects on onshore air quality because of the prevailing atmospheric conditions, 

emission rates and heights, and resulting pollutant concentrations. As the BOEM found in 

lease sale EISs, the incremental contribution of activities similar to Noble’s proposed activities to 

the cumulative impacts is not significant and will not cause or contribute to a violation of any 

national ambient air quality standard (MMS, 2007b, 2008). Since the BOEMRE completed the 

lease sale EISs, the USEPA adopted a new short-term NAAQS for nitrogen dioxide. The standard 

has not yet been implemented in the Gulf Coast states, but given the levels of expected 

emissions and the distance of the project from shore, emissions from the activities described in 

Noble’s proposed EP are not likely to contribute to violations of any NAAQS onshore.

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

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

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

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

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

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

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

proposed project represent a negligible contribution to the total greenhouse gas emissions from 

reasonably foreseeable activities in the Gulf of Mexico area and would not significantly alter any 

of the climate change impacts evaluated in the lease sale EIS (MMS, 2007b) or Programmatic EIS 

(MMS, 2007a).

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

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

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

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

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

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

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

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

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

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

Table 4. Estimated air pollutant emissions in Green Canyon Blocks 679 and 723 over the life of 

the project.

Air Pollutant

Plan Emission 

Amounts

(tons)

Calculated Exemption 

Amounts

(tons)

Calculated Complex 

Total Emission 

Amounts

(tons)

Carbon Monoxide (CO) 264.47 82,717.95 264.47

Particular matter (PM) 35.26 3,996.00 35.26

Sulphur dioxide (SO2) 161.77 3,996.00 161.77

Nitrogen oxides (NOx) 1,212.17 3,996.00 1,212.17

Volatile organic compounds (VOC) 36.37 3,996.00 36.37
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 21 

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

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

quality area. The 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 185 miles (296 km) from the Breton 

Wilderness Area, and air quality impacts on the Wilderness Area are not expected.

Impacts of a Small Fuel Spill

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

and discussed in EISs prepared for recent lease sales (MMS, 2007b, 2008; BOEMRE 2011a,b). 

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

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

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

the spill response measures that would be employed (see Attachment H-1). Given the open 

ocean location of the lease area, the extent and duration of air quality impacts from a small spill 

would not be significant.

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

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

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

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

conditions.

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

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

Impacts of a Large Oil Spill (WCD)

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

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

A large oil spill (WCD) could potentially affect air quality by introducing VOCs through 

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

meteorological and oceanographic conditions at the time and the effectiveness of spill response 

measures. Real time wind and current data from the project area would be available at the time 

of a spill and would be used to assess the fate and effects of VOCs released. Additional air 

quality impacts could occur if response measures included in situ burning of the floating oil. 

Burning would generate a plume of black smoke and result in emissions of NOx, SOx, CO, and 

PM, as well as greenhouse gases. However, in situ burning would occur only after authorization 

from the USEPA.

Due to the lease area location (120 miles [193 km]) from the nearest shoreline, most air quality 

impacts would occur in offshore waters with minimal chance to affect onshore air quality.

C.1.2 Water Quality

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

deep, offshore waters, water quality is expected to be good, with low levels of contaminants. As 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 22 

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

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

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

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

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

The lease area is located approximately 187 miles (302 km) from the Macondo spill site. Based 

on the general circulation pattern seen in the Gulf of Mexico and on satellite imagery

(ESRI, 2010), the surface slick from that discharge extended over the lease area during the spill. 

The existing water quality in the lease area is not expected to have been affected by the 

Macondo release. 

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

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

Impacts of Effluent Discharges

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

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

SBMs will be collected on the rig and transported to Port Fourchon for recycling and/or disposal 

at an approved facility. Cuttings wetted with SBMs will be discharged to the seafloor in 

accordance with the NPDES permit. There will be no persistent impacts on water quality in the 

lease area (NRC, 1983; Neff, 1987; Neff et al., 2000).

Treated sanitary and domestic wastes, including those from support vessels, may have a slight 

transient effect on water quality in the immediate vicinity of these discharges. All NPDES permit 

limitations and requirements and USCG regulations (as applicable) will be met, therefore, little 

or no impact on water quality is anticipated.

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

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

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

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

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

Based on adherence to permit limits and applicable regulations, little or no impact on water 

quality is anticipated.

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

uncontaminated cooling water, fire water, and ballast water are expected to be diluted rapidly, 

resulting in little or no impact on water quality.

Impacts of a Small Fuel Spill

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

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

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

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

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

addition to the summary information provided in this EIA. Given the open ocean location of the 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 23 

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

significant.

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

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

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

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

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

The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha (1.2 to 12 ac) 

depending on sea state and weather conditions.

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

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

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

such that it will not sink and pool on the seafloor. Diesel dispersed in the water column can 

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

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

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

by naturally occurring microbes (NOAA, 2006).

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

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

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

Impacts of a Large Oil Spill (WCD)

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

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

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

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

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

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

the surface, although new information from the Macondo 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;). However, dispersants 

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

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

Team [OSAT] 2010).

Due to the lease area location (120 miles or 193 km from the nearest shoreline), it is expected

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

lasting less than 30 days.

C.2 Seafloor Habitats and Biota

Water depths at the proposed SHLs range from 1,272 to 1,714 m (4,172 to 5,623 ft). The 

seafloor is relatively smooth and expected to be composed of stable marine clays. No areas of 

possible hard bottom or microseepages were seen within 610 m (2,000 ft) of either wellsite 

(B-Geo, 2011). 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 24 

Based on the 2011 shallow hazard assessment by (B-Geo, 2011), benthic or chemosynthetic 

communities may occur on or near two expulsion mounds in the southwestern quadrant of 

GC 723, but there is no evidence of features that may support chemosynthetic or other benthic 

communities within 610 m (2,000 ft) of any of the proposed wells in GC 679 and 723 

(B GEO, 2008).

C.2.1 Soft Bottom Benthic Communities

There are no site-specific 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 region. Table 5 summarizes data from several nearby stations in similar water depths.

Table 5. Benthic community data from stations near the lease area and in similar water depths 

sampled during the Northern Gulf of Mexico Continental Slope Habitats and Benthic 

Ecology Study (From: Rowe and Kennicutt, 2009).

Station Water Depth

(m)

Abundance

Meiofauna

(no./m2)

Macroinfauna

(no./m2)

Megafauna

(no./hectare)

WC12 1,166 218,447 1,787 2,941

NB2 1,530 168,276 1,700 570

C4 1,463 273,585 3,045 743

Meiofaunal and megafaunal abundance from Rowe and Kennicutt (2009); macroinfaunal abundance from Wei 

(2006). 

Meiofauna (animals passing through a 0.5-mm sieve but retained on a 0.062-mm sieve) 

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

400,000 individuals/m2 (Rowe and Kennicutt, 2009). Data from nearby stations (Table 5) are 

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

meiofauna, accounting for about 90% of total abundance.

The benthic macroinfauna is characterized by small mean individual sizes and low densities, 

both of which are a reflection of the meager primary production in Gulf of Mexico surface 

waters (Wei, 2006). Densities decrease exponentially with water depth. Based on an equation 

presented by Wei (2006), macroinfaunal densities in the water depth of the lease area are 

expected to range from about 2,000 to 2,600 individuals/m2

. However, actual densities are 

highly variable. Macroinfaunal densities at the stations listed in Table 5 range from 

1,700 to 3,045 individuals/m2

. 

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

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

recognized four depth-dependent faunal zones (1 through 4), two of which are divided 

horizontally. GC 723 is near the boundary between Zones 2W and 3W; both zones are on the 

mid Texas-Louisiana Slope, with Zone 2W stations ranging in depth from 863 to 1,620 m and 

Zone 3W from 1,875 to 3,008 m. The most abundant species in Zone 2W were all polychaetes 

(Tharyx marioni, Paraonella monilaris, Levinsenia uncinata, Macrochaeta clavicornis, and

Aricidea suecica). The five most abundant species in Zone 3W were the polychaetes Levinsenia 

uncinata, Paraonella monilaris, and Tachytrypane sp. A, the bivalve Heterodonta sp. B, and the 

isopod Macrostylis sp. 256. 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 25 

Megafaunal densities from nearby stations ranged from 570 to 2,941 individuals/hectare 

(Table 5). Common megafauna included motile groups such as decapods, ophiuroids, 

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

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

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

1 to 2 g C/m2 in the top 15 cm of sediments (Rowe and Kennicutt, 2009).

Physical Disturbance to the Seafloor

In water depths such as those that are encountered in the lease area, DP semisubmersibles 

disturb the seafloor only around the wellbore (SHL) where the bottom template and blowout 

preventer are located. Depending upon the specific well configuration, this area is generally 

about 0.25 ha (0.62 ac). 

The areal extent of these impacts from a DP drilling rig will be small compared to the lease area 

itself, and these types of soft bottom communities are ubiquitous along the northern Gulf of 

Mexico continental slope (Gallaway, 1988; Gallaway et al., 2003; Rowe and Kennicutt, 2009). 

Impacts from the physical disturbance of the seafloor during the project will have no significant 

impact on soft bottom benthic communities in the region. 

Impacts of Effluent Discharges

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

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

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

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

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

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

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

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

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

reproduce slowly, recovery may require several years.

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

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

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

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

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

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

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

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

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

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

as opportunistic species that tolerate low oxygen and high H2S predominate (Continental Shelf 

Associates, Inc., 2006). As the base synthetic fluid is decomposed by microbes, the area will 

gradually return to pre-drilling conditions. Disturbed sediments will be recolonized through 

larval settlement and migration from adjacent areas.
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 26 

The areal extent of impacts from drilling discharges will be small. Assuming a typical effect 

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

seafloor within a lease block. Soft bottom communities are ubiquitous along the northern Gulf 

of Mexico continental slope (Gallaway, 1988; Gallaway et al., 2003; Rowe and Kennicutt, 2009). 

Impacts from drilling discharges during this project will have no significant impact on soft

bottom benthic communities in the region.

Impacts of a Large Oil Spill (WCD)

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

hundred meters of the wellsite. MMS (2007b) estimated that a severe subsurface blowout 

could resuspend and disperse sediments within a 300-m (984-ft) radius. While coarse sediments 

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

sediments (silts and clays) could be resuspended for more than 30 days and dispersed over a 

much wider area. Based on previous studies, surface sediments at the project area are assumed 

to largely be silt and clay (Rowe and Kennicutt, 2009).

Recent lease sale EISs (MMS, 2007a, 2008) indicated that oil spills would be unlikely to affect 

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

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

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

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

persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently 

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). While the 

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

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

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

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

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

C.2.2 High-Density Deepwater Benthic Communities

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

that could support high-density chemosynthetic communities, or features or areas that could 

support high-density deepwater corals and other associated high-density hard bottom 

communities. Chemosynthetic communities were discovered in the central Gulf of Mexico in 

1984 and have been studied extensively (MacDonald, 2002). Deepwater coral communities are 

also known from numerous locations in the Gulf of Mexico (Brooke and Schroeder, 2007; 

CSA International, Inc., 2007). These communities occur almost exclusively on authigenic 

carbonates created by chemosynthetic communities.

The nearest known chemosynthetic community site is approximately 28 miles (45 km)

north-northeast of the lease area in GC 287. The nearest identified deep water coral 

communities are in GC 852, 13 miles (22 km) southwest of GC 723. 

The geohazards assessment of the lease area did not identify any features that could support 

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

mud/cuttings discharge locations. Benthic or chemosynthetic communities may occur on or 

near two expulsion mounds and associated seafloor anomalies in the southwestern quadrant of 

GC 723, but these areas are well away from the proposed drillsites. 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 27 

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

of the seafloor, effluent discharges (drilling muds and cuttings), and a large oil spill (WCD) from a 

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

the diesel fuel would float and dissipate on the sea surface. 

Physical Disturbance to the Seafloor

In water depths such as those that are encountered in the lease area, DP semisubmersibles 

disturb the seafloor only around the wellbore (SHL) where the bottom template and blowout 

preventer are located. Depending upon the specific well configuration, this area is generally 

about 0.25 ha (0.62 ac). 

The areal extent of these impacts will be small, and NTL 2009-G40 requires that high-density 

deepwater benthic communities and features or areas that could support high-density 

chemosynthetic communities, or deepwater corals communities be avoided. Impacts from the 

physical disturbance of the seafloor during this project should have no impact on 

chemosynthetic or deepwater coral communities in the region. 

Impacts of Effluent Discharges

The shallow hazards assessment did not identify any features that could support high-density 

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

the presence of chemosynthetic communities in the lease area is considered remote. 

Monitoring programs on the Gulf of Mexico continental slope have shown that benthic impacts 

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

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

Inc., 2004, 2006; Neff et al., 2005). Because of the water depth of the lease area, drilling 

discharges would be expected to result in thinner, more diffuse accumulations on the seafloor 

than those documented in the literature. Although small amounts of cuttings particles may 

reach areas inhabited by high-density deepwater benthic communities, the discharges are not 

expected to result in significant impacts to these communities.

Impacts of a Large Oil Spill (WCD)

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

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

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

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

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

persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently 

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). While the 

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

the potential to contact high-density deepwater benthic communities beyond the 300-m 

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

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

and approval process for the use of dispersants, and such approval would be obtained from the 

USEPA prior to the use of dispersants. 

The biological effects and expected fate of the oil remaining in the Gulf of Mexico from the 

Deepwater Horizon blowout are still unknown due to the depth and magnitude of this event. 

Hazen et al. (2010) reported changes in plume hydrocarbon composition with distance from the 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 28 

source. Incubation experiments with environmental isolates demonstrated faster than expected 

hydrocarbon biodegradation rates at 5°C. Based on these results, Hazen et al. (2010) suggested 

the potential exists for intrinsic bioremediation of the oil plume in the deep-water column 

without substantial oxygen drawdown.

Potential impacts of oil on high-density deepwater benthic communities are discussed in 

MMS (2007b). Although chemosynthetic communities live among hydrocarbon seeps, natural 

seepage is very constant and occurs at low rates compared to the potential rates of oil release 

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).

The potential for a spill to affect deepwater corals is indicated by preliminary findings from a 

recent (October 2010) survey of deepwater coral habitats near the Macondo spill site 

(BOEMRE, 2010). Government and academic researchers were working at a site 1,400 m 

(4,600 ft) deep and approximately 7 miles (11 km) southwest of the Macondo wellhead when 

they visually observed dead and dying corals with sloughing tissue and discoloration. Much of 

the soft coral observed in an area measuring about 15 to 40 m (50 to 130 ft) was covered by 

what appeared to be a brown substance. Ninety percent of 40 large corals were heavily 

affected and showed dead and dying parts and discoloration. Another site 400 m (1,312 ft) 

away had a colony of stony corals similarly affected and partially covered with a similar brown 

substance. Until laboratory analyses are conducted, scientists cannot be certain what caused 

the impacts. Sediment and coral samples were collected with a remotely operated vehicle and 

brought to the surface for analyses. Further testing will also determine if the substance is oil, 

and if so, whether it is consistent with the release from the Macondo spill. Charles Fisher, a 

Penn State biological oceanographer, anticipated publishing the results of this sampling effort in 

March of 2011, but these results have not yet appeared in press.

C.2.3 Designated Topographic Features

GC 679 and 723 are not within or near a designated topographic feature or a no-activity zone as 

identified in NTL 2009-G39. The nearest designated topographic feature is Ship Shoal South in 

Ewing Bank (EW) Block 945, located 50 miles (80 km) north of the lease area. 

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

impacts to designated topographic features due to the distance from the lease area. A small 

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

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

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

to the distance and the difference in water depth. Near-bottom currents in the region are 

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume 

up onto the continental shelf edge. 
Green Canyon Blocks 679 and 723 October 2011 

Environmental Impact Analysis for Revised Exploration Plan Page 29 

C.2.4 Pinnacle Trend Area Live Bottoms

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

NTL 2009-G39, the nearest pinnacle trend block is Main Pass Block 290, which lies 203 miles 

(327 km) to the northeast of GC 679. 

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

impacts to pinnacle trend area live bottoms due to the distance from the lease area. A small 

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

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

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

to the distance and the difference in water depth. Near-bottom currents in the region are 

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume 

up onto the continental shelf edge. 

C.2.5 Eastern Gulf Live Bottoms

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

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

nearest block covered by the live bottom stipulation, as defined by NTL 2009-G39, is 

Destin Dome Block 573, approximately 243 miles (392 km) northeast of the lease area.

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

impacts to eastern Gulf live bottom areas due to the distance from the lease area. A small fuel 

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

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

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

to the distance and the difference in water depth. Near-bottom currents in the region are 

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume 

up onto the continental shelf. 

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

This section discusses species listed as endangered or threatened under the Endangered Species 

Act (ESA). In addition, it includes all marine mammal species in the region, which are protected 

under the Marine Mammal Protection Act (MMPA). 

Endangered or threatened species that may occur in the project area and/or along the northern 

Gulf Coast are listed in Table 6. The table also indicates the location of critical habitat 

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

geographical area occupied by the species at the time of listing, if they contain physical or 

biological features essential to conservation, and those features may require special 

management considerations or protection; and 2) specific areas outside the geographical area 

occupied by the species if the agency determines that the area itself is essential for 

conservation. The National Marine Fisheries Service (NMFS) has jurisdiction for ESA-listed 

cetaceans, sea turtles, and fishes in the Gulf of Mexico. The USFWS has jurisdiction for 

ESA-listed birds and the West Indian manatee.
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Table 6. Federally listed endangered and threatened species potentially occurring in the lease 

area and along the northern Gulf Coast. 

Species Scientific Name Status

Potential Presence Critical Habitat 

Designated in

Gulf of Mexico

Lease 

Area Coastal

Marine Mammals

Sperm whale Physeter macrocephalus E X -- None

West Indian manatee Trichechus manatus latirostris E -- X Florida (Peninsular)

Blue whale Balaenoptera musculus E Xa -- None

Fin whale Balaenoptera physalus E Xa -- None

Humpback whale Megaptera novaeangliae E Xa -- None

North Atlantic right whale Eubalaena glacialis E Xa -- None

Sei whale Balaenoptera borealis E Xa -- None

Sea Turtles

Loggerhead turtle Caretta caretta T X X None

Green turtle Chelonia mydas T, Eb X X None

Leatherback turtle Dermochelys coriacea E X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Birds

Piping Plover Charadrius melodus T -- X 

Coastal Texas, Louisiana, 

Mississippi, Alabama, 

and Florida (Panhandle)

Whooping Crane Grus americana E -- X 

Coastal Texas 

(Aransas National 

Wildlife Refuge)

Fishes

Gulf sturgeon Acipenser oxyrinchus desotoi T -- X 

Coastal Louisiana, 

Mississippi, Alabama, 

and Florida (Panhandle)

Smalltooth sawfish Pristis pectinata E -- X Southwest Florida and 

the Florida Keys

Invertebrates

Elkhorn coral Acropora palmata E -- X Flower Garden Banks

Terrestrial Mammals

Beach mice (Alabama, 

Choctawhatchee, 

Perdido Key, St. Andrew)

Peromyscus polionotus E -- X Alabama and Florida 

(Panhandle) beaches

Abbreviations: E = endangered; T = threatened. a

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

to be present in the lease area. b

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

As mandated by the ESA, BOEMRE consulted NMFS and the USFWS on possible and potential 

impacts from the proposed leasing in the Gulf of Mexico on endangered/threatened species and 

their designated critical habitat (MMS, 2007a,b). A Biological Assessment was prepared for each 

consultation. The formal ESA consultation with NMFS was concluded with receipt of the 

Biological Opinion on 3 July 2007 (NMFS, 2007). The Biological Opinion concludes that the 

proposed lease sales and associated activities in the Five-Year Leasing Plan for Western and 

Central Planning Areas 2007-2012 are not likely to jeopardize the continued existence of 

threatened and endangered species under NMFS jurisdiction or destroy or adversely modify 

designated critical habitat. The informal ESA consultation with USFWS was concluded with a 

letter dated 14 September 2007. The USFWS concurred with MMS’s determination that 

proposed actions of the current Five-Year Leasing Plan were not likely to adversely affect 

threatened/endangered species or designated critical habitat under USFWS jurisdiction. 

Following the Macondo spill, BOEMRE requested to reinitiate an ESA consultation with both 
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NMFS and USFWS on 30 July 2010. The NMFS responded with a letter to BOEMRE on 

24 September 2010, and the USFWS responded with a letter to BOEMRE on 27 September 2010. 

At present, the NMFS and USFWS have placed the consultation process on hold because they 

feel the environmental baseline information needs to be updated for the post-Macondo spill 

environment based on the results of the Natural Resource Damage Assessment (NRDA) process. 

The NRDA data have yet to be released, and the existing consultation remains in effect

(BOEMRE, 2011a). The existing consultation recognizes that BOEM-required mitigations and 

other reasonable and prudent measures should reduce the likelihood of impacts from all 

BOEM-authorized activities in the Gulf of Mexico.

Coastal endangered or threatened species that may occur along the northern Gulf Coast include 

the West Indian manatee, Piping Plover, Whooping Crane, Gulf sturgeon, the smalltooth 

sawfish, and four subspecies of beach mice. Critical habitat has been designated for all of these 

species as indicated in Table 6 and discussed in individual sections. 

Two other coastal species (Bald Eagle and Brown Pelican) discussed in the MMS lease sale 

EIS (2007b) are no longer listed as endangered or threatened. These are discussed under 

Coastal and Marine Birds.

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

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

species in the Gulf of Mexico.

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

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

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

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

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

be affected.

C.3.1 Sperm Whale (Endangered)

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

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

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

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

as a stock that may have unsustainable human-caused impacts) by NOAA Fisheries (Waring 

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

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

features such as eddies associated with the Gulf of Mexico Loop Current (Jochens et al., 2008). 

Sperm whale populations in the north-central Gulf of Mexico are present there throughout the 

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

typically concentrated along the upper continental slope between the 200- and 1,000-m 

(656- and 3,280-ft) depth contours (Jochens et al., 2008). Male sperm whales were more 

variable in their movements and were documented in water depths greater than 3,000 m 

(9,843 ft). Generally, groups of sperm whales sighted in the Gulf of Mexico during the 

MMS-funded Sperm Whale Seismic Study (SWSS) consisted of mixed-sex groups comprising 

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

groups was 10 individuals (Jochens et al., 2008). SWSS results show that sperm whales transit 
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through the vicinity of the lease area. Movements of satellite-tracked individuals suggest that 

this area of the Gulf continental slope is within the home range of the Gulf of Mexico population 

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

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

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

(WCD). Effluent discharges are likely to have negligible impacts on sperm whales due to rapid 

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

mobility of these marine mammals. Compliance with NTL 2007-G03 will minimize the potential 

for marine debris-related impacts on sperm whales. 

Current threats to sperm whale populations worldwide are discussed in a final recovery plan for 

the sperm whale recently published by NOAA (NMFS, 2010a). Threats are defined as “any factor 

that could represent an impediment to recovery,” and include fisheries interactions, 

anthropogenic noise, vessel interactions, contaminants and pollutants, disease, injury from 

marine debris, research, predation and natural mortality, direct harvest, competition for 

resources, loss of prey base due to climate change and ecosystem change, and cable laying. In 

the Gulf of Mexico, the impacts from many of these threats are identified as either low or 

unknown (BOEMRE, 2011a,b). 

Impacts of Drilling Rig Presence, Noise, and Lights

Noise from routine drilling activities has the potential to disturb sperm whales. Sperm whales 

appear to have good low-frequency hearing, but the available data do not indicate a consistent 

response to anthropogenic noise (Jochens et al., 2008). Noise associated with drilling is 

relatively weak in intensity, and an individual animal’s noise exposure would be transient. There 

are other OCS facilities and activities near the lease area, and the region as a whole has a large 

number of similar sources. Due to the limited scope and short duration of drilling activities, this 

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

NMFS analyzed the potential for impacts of drilling-related noise on sperm whales in its 

Biological Opinion for the Gulf of Mexico Oil and Gas Activities: Five-Year Leasing Plan for 

Western and Central Planning Areas 2007-2012 (NMFS, 2007). The analysis noted that 

semisubmersible drilling rigs emit low sound source levels and concluded that drilling is not 

expected to produce amplitudes sufficient to cause hearing or behavioral effects in sperm 

whales; therefore, these effects are insignificant (NMFS, 2007).

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

sale EISs (MMS, 2007b, 2008) or the NMFS (2007) Biological Opinion.

Impacts of Support Vessel and Helicopter Traffic

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

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

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

To reduce the potential for vessel strikes, MMS issued NTL 2007-G04, which recommends 

protected species identification training and that vessel operators and crews maintain a vigilant 

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

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

When whales are sighted, vessel operators and crews are required to attempt to maintain a 
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distance of 91 m (300 ft) or greater whenever possible. Vessel operators are required to reduce 

vessel speed to 10 knots or less when mother/calf pairs, pods, or large assemblages of 

cetaceans are observed near an underway vessel when safety permits. Compliance with this 

NTL will minimize the likelihood of vessel strikes as well as reduce the chance for disturbing 

sperm whales.

NMFS (2007) analyzed the potential for vessel strikes and harassment of sperm whales. With 

implementation of the mitigation measures in NTL 2007-G04, NMFS concluded that the 

likelihood of collisions between vessels and sperm whales would be reduced to insignificant 

levels. NMFS concluded that the observed avoidance of passing vessels by sperm whales is an 

advantageous response to avoid a potential threat and is not expected to result in any 

significant effect on migration, breathing, nursing, breeding, feeding, or sheltering to individuals, 

or have any consequences at the level of the population. With implementation of the vessel 

strike avoidance measures requirement to maintain a distance of 90 m (295 ft) from sperm 

whales, the NMFS concluded that the potential for harassment of sperm whales would be 

reduced to discountable levels.

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

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

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

3 (12%) of 24 sightings. All three reactions consisted of a hasty dive and occurred at less than 

360 m (1,180 ft) lateral distance from the aircraft. Additional reactions were seen when aircraft 

circled certain whales to make further observations. Based on other studies of cetacean 

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

the aircraft were short-term and probably of no long-term biological significance.

While flying offshore in the Gulf of Mexico, helicopters maintain altitudes above 213 m (700 ft) 

during transit to and from the working area. In the event that a whale is seen during transit, the 

helicopter will not approach or circle the animals. Although responses are possible based on the 

Smultea et al. (2008) study, the NMFS (2007) concluded that this altitude would minimize the 

potential for disturbing sperm whales. Therefore, no significant impacts are expected. 

Impacts of a Small Fuel Spill

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

sale EISs (MMS, 2007b, 2008) and by NMFS (2007). Oil impacts on marine mammals are 

discussed by Geraci and St. Aubin (1990). For this EP, there are no unique site-specific issues 

with respect to spill impacts on these animals that were not analyzed in the previous 

documents. 

The probability of a fuel spill will be minimized by Noble’s preventative measures during routine 

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

OSRP will mitigate and lessen the potential for impacts on sperm whales. Given the open ocean 

location of the lease area, the duration of a small spill and opportunity for impacts to occur 

would be very brief.

A small 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 
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of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha 

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and 

noise of response vessels and aircraft (Marine Mammal Commission [MMC], 2010). However, 

due to the limited areal extent and short duration of water quality impacts from a small fuel 

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

Impacts of a Large Oil Spill (WCD)

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

(MMS, 2007b, 2008) and by NMFS (2007). For this EP, there are no unique site-specific issues 

with respect to spill impacts on these animals.

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

indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and 

dispersants) (MMC, 2010). Direct physical and physiological effects can include skin irritation, 

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 

toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey; and stress from 

the activities and noise of response vessels and aircraft. Complications of the above may lead to 

dysfunction of immune and reproductive systems, physiological stress, declining physical 

condition, and death. Behavioral responses can include displacement of animals from prime 

habitat, disruption of social structure, changing prey availability and foraging distribution and/or 

patterns, changing reproductive behavior/productivity, and changing movement patterns or 

migration (MMC, 2010).

In the event of a large spill, the level of vessel and aircraft activity associated with spill response 

could disturb sperm whales and potentially result in vessel strikes, entanglement, or other injury 

or stress. Response vessels would operate in accordance with NTL 2007-G04 to reduce the 

potential for striking or disturbing these animals.

C.3.2 West Indian Manatee (Endangered)

Most of the manatee population is located in peninsular Florida (USFWS, 2001). Manatee 

sightings in Louisiana have been increasing as the species extends its presence farther west of 

Florida in the warmer months (Wilson, 2003). A species description is presented in a recent

lease sale EIS (MMS, 2007b) and in the recovery plan for this species (USFWS, 2001).

IPFs potentially affecting manatees include support vessel and helicopter traffic and a large oil 

spill (WCD). A small fuel spill in the lease area would be unlikely to affect manatees, as the lease 

area is approximately 120 miles (193 km) from the nearest shoreline (Louisiana). As explained in 

Section A.9.2, a small fuel spill would not be expected to make landfall or reach coastal waters 

prior to breaking up. Compliance with NTL 2007-G03 will minimize the potential for marine 

debris-related impacts on manatees.
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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, MMS issued NTL 2007-G04, which recommends 

protected species identification training and that vessel operators and crews maintain a vigilant 

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

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

Compliance with this NTL will minimize the likelihood of vessel strikes, and no significant 

impacts on manatees are expected.

Helicopter traffic also has the potential to disturb manatees. Rathbun (1988) reported that 

manatees were disturbed more by helicopters than by fixed-wing aircraft; however, the 

helicopter was flown at a relatively low altitude of 20 to 160 m (66 to 525 ft). Helicopters used 

in support operations maintain a minimum altitude of 213 m (700 ft) while in transit offshore, 

305 m (1,000 ft) over unpopulated areas or across coastlines, and 610 m (2,000 ft) over 

populated areas and sensitive habitats such as wildlife refuges and park properties. This 

mitigation measure will minimize the potential for disturbing manatees, and no significant 

impacts are expected.

Impacts of a Large Oil Spill (WCD)

In the event that manatees were exposed to oil, effects could include direct impacts from oil 

exposure, as well as indirect impacts due to response activities and materials (e.g., vessel traffic, 

noise, and dispersants) (MMC, 2010). Direct physical and physiological effects can include skin 

irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; 

inhalation of toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey 

(or contaminated vegetation, in the case of manatees); and stress from the activities and noise 

of response vessels and aircraft. Complications of the above may lead to dysfunction of immune 

and reproductive systems, physiological stress, declining physical condition, and death. 

Behavioral responses can include displacement of animals from prime habitat, disruption of 

social structure, changing prey availability and foraging distribution and/or patterns, changing 

reproductive behavior/productivity, and changing movement patterns or migration 

(MMC, 2010).

In the event that a large oil spill reached coastal waters where manatees were present, the level 

of vessel and aircraft activity associated with spill response could disturb manatees and 

potentially result in vessel strikes, entanglement, or other injury or stress. Response vessels 

would operate in accordance with NTL 2007-G04 to reduce the potential for striking or 

disturbing these animals, and therefore no significant impacts are expected. 

C.3.3 Endangered Mysticete Whales

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

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

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

species in the Gulf of Mexico.
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Due to the rare occurrence of these whales in the Gulf of Mexico and the limited scope and 

duration of the project, it is highly unlikely that any endangered mysticete would come into 

contact with any project activities, either routine operations or accidents. NMFS did not include 

any of these mysticete whales as affected species in its Biological Opinion (NMFS, 2007). 

Potential impacts are analyzed in recent lease sale EISs (MMS, 2007b, 2008), and those analyses 

are incorporated by reference. If any of these whales were present in the area, potential 

impacts would be the same as those discussed below in Section C.3.4. 

C.3.4 Non-Endangered Marine Mammals (Protected)

Excluding the seven endangered species that have been cited previously, there are 22 additional 

species of marine mammals that may be found in the Gulf of Mexico. This includes two 

mysticete whales, the dwarf and pygmy sperm whales, 4 species of beaked whales, and 

14 species of delphinids. The most common non-endangered cetaceans in the deepwater 

environment are odontocetes such as the pantropical spotted dolphin, spinner dolphin, and 

clymene dolphin. A brief summary is presented below, and additional information on these 

groups is presented in a recent lease sale EIS (MMS, 2007b).

Mysticete whales. Two non-endangered mysticete whales are known from the Gulf of Mexico. 

The Bryde’s whale (Balaenoptera edeni) has been sighted most frequently along the 100-m 

(328-ft) isobath (Davis and Fargion, 1996; Davis et al., 2000). Most sightings have been made in 

the DeSoto Canyon region and off western Florida, although there have been some in the 

west-central portion of the northeastern Gulf. The minke whale (Balaenoptera acutorostrata) is 

considered rare in the Gulf of Mexico, with the only confirmed records coming from strandings 

(Würsig et al., 2000). Based on the available data, it is possible that Bryde’s whales could occur 

in the lease area.

Dwarf and pygmy sperm whales. At sea, it is difficult to differentiate dwarf sperm whales 

(Kogia sima) from pygmy sperm whales (Kogia breviceps), and sightings are often grouped 

together as Kogia spp. Both species have a worldwide distribution in temperate to tropical 

waters. In the Gulf of Mexico, both species occur primarily along the continental shelf edge and 

in deeper waters off the continental shelf (Mullin et al., 1991). Either species could occur in the 

lease area.

Beaked whales. Four species of beaked whales are known from the Gulf of Mexico. They are 

Blainville’s beaked whale (Mesoplodon densirostris), Cuvier’s beaked whale (Ziphius cavirostris), 

Sowerby’s beaked whale (Mesoplodon bidens), and Gervais’ beaked whale (Mesoplodon 

europaeus). Stranding records in the Gulf of Mexico suggest that Gervais’ beaked whale is the 

most common and Sowerby’s is extralimital. Due to the difficulties of at-sea identification, 

beaked whales in the Gulf of Mexico are identified either as Cuvier’s beaked whales or are 

grouped into an undifferentiated complex (Mesoplodon spp. and Ziphius spp.). In the northern 

Gulf of Mexico, they are broadly distributed in water depths greater than 1,000 m (3,281 ft) over 

lower slope and abyssal landscapes (Davis et al., 2000). Any of these species could occur in the 

lease area.

Delphinids. Fourteen species of delphinids are known from the Gulf of Mexico, including 

Atlantic spotted dolphin (Stenella frontalis), bottlenose dolphin (Tursiops truncatus), clymene 

dolphin (Stenella clymene), false killer whale (Pseudorca crassidens), Fraser’s dolphin

(Lagenodelphis hosei), killer whale (Orcinus orca), melon-headed whale (Peponocephala electra), 
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pantropical spotted dolphin (Stenella attenuata), pygmy killer whale (Feresa attenuata), 

short-finned pilot whale (Globicephala macrorhynchus), Risso’s dolphin (Grampus griseus), 

rough-toothed dolphin (Steno bredanensis), spinner dolphin (Stenella longirostris), and striped 

dolphin (Stenella coeruleoalba). Any of these species could occur in the lease area. The most 

common non-endangered cetaceans in the deepwater environment are the pantropical spotted 

dolphin, spinner dolphin, and clymene dolphin. 

IPFs potentially affecting non-endangered marine mammals include drilling rig presence, noise, 

and lights; support vessel and helicopter traffic; and two types of accidents (a small fuel spill and 

a large oil spill represented by the WCD for this EP). Effluent discharges are likely to have 

negligible impacts on marine mammals due to rapid dispersion, the small area of ocean 

affected, the intermittent nature of the discharges, and the mobility of marine mammals. 

Compliance with NTL 2007-G03 will minimize the potential for marine debris-related impacts on 

marine mammals.

Impacts of Drilling Rig Presence, Noise, and Lights

Noise from routine drilling activities has the potential to disturb marine mammals. Most 

odontocetes (toothed whales and dolphins) use higher frequency sounds than the dominant low 

frequencies produced by OCS drilling activities (Richardson et al., 1995). Noise associated with 

drilling is relatively weak in intensity, and an individual animal’s noise exposure would be 

transient. There are other OCS facilities and activities near the lease area, and the region as a 

whole has a large number of similar sources. Due to the limited scope and short duration of 

drilling activities, this project would represent a small temporary contribution to the overall 

noise regime, and any short-term impacts are not expected to be biologically significant to 

marine mammal populations.

Drilling rig lighting and rig presence are not identified as IPFs for marine mammals in lease sale 

EISs (MMS, 2007b, 2008).

Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb marine mammals, and there is also a risk of 

vessel strikes. Data concerning the frequency of vessel strikes is presented in a recent lease sale 

EIS (MMS, 2007b). To reduce the potential for vessel strikes, MMS issued NTL 2007-G04, which 

recommends protected species identification training and that vessel operators and crews 

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

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

protected species. Vessel operators and crews are required to attempt to maintain a distance of 

91 m (300 ft) or greater when whales are sighted and 45 m (150 ft) when small cetaceans are 

sighted. When cetaceans are sighted while a vessel is underway, vessels must attempt to 

remain parallel to the animal’s course and avoid excessive speed or abrupt changes in direction 

until the cetacean has left the area. Vessel operators are required to reduce vessel speed to 

10 knots or less when mother/calf pairs, pods, or large assemblages of cetaceans are observed 

near an underway vessel, when safety permits. Compliance with NTL 2007-G04 will minimize 

the likelihood of vessel strikes as well as reduce the chance for disturbing marine mammals, and 

therefore no significant impacts are expected. 
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Aircraft traffic also has the potential to disturb marine mammals (Würsig et al., 1998). However, 

while flying offshore, helicopters maintain altitudes above 213 m (700 ft) during transit to and 

from the working area. This altitude will minimize the potential for disturbing marine mammals, 

and no significant impacts are expected (MMS, 2007b).

Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals are discussed in recent EISs (MMS, 2007b, 2008), 

and oil impacts on marine mammals in general are discussed by Geraci and St. Aubin (1990). For 

this EP, there are no unique site-specific issues with respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by Noble’s preventative measures during fuel 

transfer. In the unlikely event of a spill, implementation of Noble’s OSRP is expected to lessen 

the potential for impacts on marine mammals. EP Section H provides detail on spill response 

measures, along with a summary of those measures in this EIA. Given the open ocean location 

of the lease area, the limited duration of a small spill and response efforts, it is expected that 

any impacts would be brief and minimal. 

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

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

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

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate 

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha 

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and 

noise of response vessels and aircraft (MMC, 2010). However, due to the limited areal extent 

and short duration of water quality impacts from a small fuel spill, as well as the mobility of 

marine mammals, no significant impacts would be expected.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine mammals are discussed in MMS, 2000; 2007b; and 2008. For 

this EP, there are no unique site-specific issues. Impacts of oil spills on marine mammals can 

include direct impacts from oil exposure, as well as indirect impacts due to response activities 

and materials (e.g., vessel traffic, noise, and dispersants) (MMC, 2010). Direct physical and 

physiological effects can include skin irritation, inflammation, or necrosis; chemical burns of 

skin, eyes, and mucous membranes; inhalation of toxic fumes; ingestion of oil (and dispersants) 

directly or via contaminated prey (or contaminated vegetation, in the case of manatees); and 

stress from the activities and noise of response vessels and aircraft. Complications of the above 

may lead to dysfunction of immune and reproductive systems, physiological stress, declining 

physical condition, and death. Behavioral responses can include displacement of animals from 

prime habitat, disruption of social structure, changing prey availability and foraging distribution 

and/or patterns, changing reproductive behavior/productivity, and changing movement 

patterns or migration (MMC, 2010).
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In the event of a large spill, the level of vessel and aircraft activity associated with spill response 

could disturb marine mammals and potentially result in vessel strikes, entanglement, or other 

injury or stress. Response vessels would operate in accordance with NTL 2007-G04 to reduce 

the potential for striking or disturbing these animals, and therefore no significant impacts are 

expected. 

C.3.5 Sea Turtles (Endangered/Threatened)

Five species of endangered or threatened sea turtles may be found near the lease area. 

Leatherback (Dermochelys coriacea), Kemp's ridley (Lepidochelys kempii), and hawksbill 

(Eretmochelys imbricata) turtles are endangered. The loggerhead turtle (Caretta caretta) is a 

threatened species. The green turtle (Chelonia mydas) is listed as threatened, except for the 

Florida and Pacific Coast of Mexico breeding populations, which are listed as endangered. 

Species descriptions are presented in the MMS (2007b).

BOEM has reexamined the impacts analysis presented in MMS 2007b and 2008 for the five sea 

turtles species that inhabit the Gulf of Mexico based on additional information and in 

consideration of the Macondo oil spill event. Information from the 5-year status reviews for 

federally listed sea turtles in the Gulf of Mexico has been incorporated in the 2011 Draft 

Supplemental EIS for the Western Gulf of Mexico Planning Area Lease Sale 218 (BOEMRE, 

2011a,b). However, no new information from previous EISs was found that would alter the 

potential impacts on sea turtles. In most foreseeable cases, exposure to hydrocarbons 

persisting in the sea following the dispersal of an oil slick will result in sublethal impacts 

(e.g., decreased health, reproductive fitness, and longevity; and increased vulnerability to 

disease) to sea turtles.

Leatherbacks and loggerheads are the most likely species to be present near the lease area as 

adults. Green, hawksbill, and Kemp’s ridley turtles are typically inner shelf and nearshore 

species, unlikely to occur near the lease area as adults. Hatchlings or juveniles of any of the sea 

turtle species may be present in deepwater areas, including the lease area, where they may be 

associated with Sargassum and other flotsam.

Sea turtle nesting in the northern Gulf of Mexico can be summarized by species as follows:

• Loggerhead turtles – Loggerheads nest in significant numbers along the Florida Panhandle 

and, to a lesser extent, from Texas through Alabama (MMS, 2007b). The nearest significant 

nesting area of loggerhead turtles is found in Louisiana, on beaches within the Breton NWR; 

• Green and leatherback turtles – Green and leatherback turtles infrequently nest on Florida 

Panhandle beaches (Florida Fish and Wildlife Conservation Commission, 2011);

• Kemp’s ridley turtles – The main Kemp’s ridley nesting site is Rancho Nuevo beach, 

Tamaulipas, Mexico (NMFS et al., 2011). Kemp’s ridley turtles typically do not nest 

anywhere near the project area, although there have been occasional reports of 

Kemp’s ridleys nesting in Alabama (Share the Beach, 2010); and

• Hawksbill turtles – Hawksbills typically do not nest anywhere near the project area.

IPFs potentially affecting sea turtles include drilling rig presence, noise, and lights; support 

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

represented by the WCD for this EP). Effluent discharges are likely to have negligible impacts on 

sea turtles due to rapid dispersion, the small area of ocean affected, and the intermittent nature 

of the discharges. Compliance with NTL 2007-G03 will minimize the potential for marine 

debris-related impacts on sea turtles.
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Impacts of Drilling Rig Presence, Noise, and Lights 

Offshore drilling activities produce a broad array of sounds at frequencies and intensities that 

may be detected by sea turtles (Geraci and St. Aubin, 1987). Potential impacts may include 

behavioral disruption and temporary or permanent displacement from the area near the sound 

source. Certain sea turtles, especially loggerheads, may be attracted to offshore structures 

(Lohoefener et al., 1990) and, thus, may be more susceptible to impacts from sounds produced 

during routine operations. Helicopters and service vessels may also affect sea turtles due to 

machinery noise and/or visual disturbances. The most likely impacts would be short-term 

behavioral changes such as diving and evasive swimming, disruption of activities, or departure 

from the area. Due to the limited scope and short duration of drilling activities, these 

short-term impacts are not expected to be biologically significant to sea turtle populations.

Artificial lighting can disrupt the nocturnal orientation of sea turtle hatchlings (Witherington, 

1997; Tuxbury and Salmon, 2005). However, hatchlings may rely less on light cues when they 

are offshore than when they are emerging on the beach (Salmon and Wyneken, 1990). The 

NMFS (2007) concluded that the effects of lighting from offshore structures on sea turtles are 

insignificant.

Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb sea turtles, and there is also a risk of vessel 

strikes. Data show that vessel traffic is one cause of sea turtle mortality in the Gulf of Mexico 

(Lutcavage et al., 1997). While adult sea turtles are visible at the surface during the day and in 

clear weather, they can be difficult to spot from a moving vessel when resting below the water 

surface, during nighttime, or during periods of inclement weather. To reduce the potential for 

vessel strikes, MMS issued NTL 2007-G04, which recommends protected species identification 

training and that vessel operators and crews maintain a vigilant watch for sea turtles and slow 

down or stop their vessel to avoid striking protected species, and requires operators to report 

sightings of any injured or dead protected species. When sea turtles are sighted, vessel 

operators and crews are required to attempt to maintain a distance of 45 m (150 ft) or greater 

whenever possible. Compliance with this NTL will minimize the likelihood of vessel strikes as 

well as reduce the chance for disturbing sea turtles (NMFS, 2007).

Helicopter traffic also has the potential to disturb sea turtles. However, while flying offshore, 

helicopters maintain altitudes above 213 m (700 ft) during transit to and from the working area. 

This altitude will minimize the potential for disturbing sea turtles, and no significant impacts are 

expected.

Impacts of a Small Fuel Spill

Potential spill impacts on sea turtles are discussed in recent EISs (MMS, 2007b, 2008) and the 

NMFS Biological Opinion (2007). For this EP, there are no unique site-specific issues with 

respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by Noble’s preventative measures during fuel 

transfer. In the unlikely event of a spill, implementation of Noble’s OSRP is expected to

minimize potential impacts on sea turtles. EP Section H provides detail on spill response 

measures. Given the open ocean location of the lease area, the duration of a small spill and 

opportunity for impacts to occur would be very brief.
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A small fuel spill in offshore waters would produce a slick on the water surface and increase the 

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

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

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate 

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha 

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and 

noise of response vessels and aircraft. However, due to the limited areal extent and short 

duration of water quality impacts from a small fuel spill, no significant impacts would be 

expected.

A small fuel spill in the lease area would be unlikely to affect sea turtle nesting beaches, as the 

lease area is 120 miles (193 km) from the nearest shoreline (Louisiana). As explained in 

Section A.9.2, a small fuel spill would not be expected to make landfall or reach coastal waters 

prior to breaking up. 

Impacts of a Large Oil Spill (WCD)

Impacts of oil spills on sea turtles can include direct impacts from oil exposure, as well as 

indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and 

dispersants). Direct physical and physiological effects can include skin irritation, inflammation, 

or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes and 

smoke (e.g., from in situ burning of oil); ingestion of oil (and dispersants) directly or via 

contaminated food; and stress from the activities and noise of response vessels and aircraft. 

Complications of the above may lead to dysfunction of immune and reproductive systems, 

physiological stress, declining physical condition, and death. Behavioral responses can include 

displacement of animals from prime habitat, disruption of social structure, changing food 

availability and foraging distribution and/or patterns, changing reproductive 

behavior/productivity, and changing movement patterns or migration. In the unlikely event of a 

spill, implementation of Noble’s OSRP is expected to minimize the potential for these types of 

impacts on sea turtles. EP Section H provides detail on spill response measures.

Studies of oil effects on loggerheads in a controlled setting (Lutcavage et al., 1995) suggest that 

sea turtles show no avoidance behavior when they encounter an oil slick, and any sea turtle in 

an affected area would be expected to be exposed. Sea turtles’ diving behaviors also put them 

at risk. Sea turtles rapidly inhale a large volume of air before diving and continually resurface 

over time, which may result in repeated exposure to volatile vapors and oiling (NMFS, 2007).

Spilled oil reaching sea turtle nesting beaches could have effects on nesting sea turtles and egg 

development (NMFS, 2007). An oiled beach could affect nest site selection or result in no 

nesting at all (e.g., false crawls). Upon hatching and successfully reaching the water, hatchlings 

are subject to the same types of oil spill exposure hazards as adults. Hatchlings that contact oil 

residues while crossing a beach can exhibit a range of effects, from acute toxicity to impaired 

movement and normal bodily functions (NMFS, 2007).

In the event of a large spill, the level of vessel and aircraft activity associated with spill response 

could disturb sea turtles and potentially result in vessel strikes, entanglement, or other injury or 
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stress. Response vessels would operate in accordance with NTL 2007-G04 to reduce the 

potential for striking or disturbing these animals, and therefore no significant impacts are 

expected. 

C.3.6 Piping Plover (Threatened)

The Piping Plover (Charadrius melodus) is a migratory shorebird that overwinters along the 

southeastern U.S. and Gulf of Mexico coasts. This threatened species is in decline as a result of 

hunting, habitat loss and modification, predation, and disease (USFWS, 2003). Critical 

overwintering habitat has been designated, including beaches in Texas, Louisiana, Mississippi, 

Alabama, and Florida (Figure 3). Piping Plovers inhabit coastal sandy beaches and mudflats, 

feeding by probing for invertebrates at or just below the surface. They use beaches adjacent to 

foraging areas for roosting and preening (USFWS, 2010a). A species description is presented in a 

recent lease sale EIS (MMS, 2007b).

A large oil spill (WCD) is the only IPF potentially affecting Piping Plovers. There are no IPFs 

associated with routine project activities that could affect these birds. A small fuel spill in the 

lease area would be unlikely to affect Piping Plovers because a small fuel spill would not be 

expected to make landfall or reach coastal waters prior to breaking up (see explanation in 

Section A.9.2). 

Impacts of a Large Oil Spill (WCD)

The lease area is 121 miles (194 km) from the nearest shorelines inhabited by Piping Plovers. 

The revised OSRA results (BOEMRE, 2011a,b) summarized in Section A.9.3 (Table 3) predict 

there is a 4% probability that in spring, an oil spill in the lease area would reach a shoreline 

designated as critical habitat for the wintering Piping Plover within 10 days. Plovers could 

physically oil themselves while foraging on oiled shores or secondarily contaminate themselves 

through ingestion of oiled intertidal sediments and prey (MMS, 2007b). Plovers congregate and 

feed along tidally exposed banks and shorelines, following the tide out and foraging at the 

water’s edge. It is possible that some deaths of Piping Plovers could occur, especially if spills 

occur during winter months when plovers are most common along the coastal Gulf or if spills 

contacted critical habitat. Impacts could also occur from vehicular traffic on beaches and other 

activities associated with spill cleanup. Noble has extensive resources available to protect and 

rehabilitate wildlife in the event of a spill reaching the shoreline, as detailed in the OSRP.

C.3.7 Whooping Crane (Endangered)

The Whooping Crane (Grus americana) is an omnivorous wading bird and an endangered 

species. There are three wild populations in North America (Whooping Crane Eastern 

Partnership, 2010). One population winters along the Texas coast at Aransas NWR and 

summers at Wood Buffalo National Park in Canada; this population represents the majority of 

the world’s population of free-ranging Whooping Cranes and reached a record population of 

270 at Aransas NWR in December 2008 (Whooping Crane Eastern Partnership, 2010). 

A non-migrating population has been re-introduced in central Florida, and another 

re-introduced population summers in Wisconsin and migrates to the southeastern U.S. for the 

winter. Whooping Cranes breed, migrate, winter, and forage in a variety of habitats, including 

coastal marshes and estuaries, inland marshes, lakes, ponds, wet meadows and rivers, and 

agricultural fields (USFWS, 2007). About 9,000 ha (22,240 ac) of salt flats on Aransas NWR and 

adjacent islands comprise the principal wintering grounds of the Whooping Crane. Aransas 

NWR is designated as critical habitat for the species (Figure 3). A species description is 

presented in a recent lease sale EIS (MMS, 2007b).
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Figure 3. Location of selected environmental features in relation to the lease area.
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A large oil spill (WCD) is the only IPF potentially affecting Whooping Cranes. A small fuel spill in 

the lease area would also be unlikely to affect Whooping Cranes, due to the distance from 

Aransas NWR. As explained in Section A.9.2, a small fuel spill would not be expected to make 

landfall or reach coastal waters prior to breaking up. 

Impacts of a Large Oil Spill (WCD)

A large oil spill is unlikely to affect Whooping Cranes as the lease area is approximately 

341 miles (549 km) from its critical habitat (Aransas NWR). The revised OSRA modeling 

(BOEMRE, 2011a,b) predicts a 3% probability that an oil spill originating in the lease area would 

reach the Matagorda Island area of the Aransas NWR in Calhoun County, Texas, within 30 days 

and an 17% probability of oil reaching that area in 120 days.

In the event of oil exposure, Whooping Cranes could physically oil themselves while foraging in 

oiled areas or secondarily contaminate themselves through ingestion of contaminated shellfish, 

frogs, and fishes. It is possible that some Whooping Crane deaths could occur. In the event of a 

spill, Noble would work with the applicable State and Federal agencies to prevent impacts from 

a spill. 

C.3.8 Gulf Sturgeon (Threatened)

The Gulf sturgeon (Acipenser oxyrinchus desotoi) is a threatened fish species that inhabits major 

rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida 

(Barkuloo, 1988; Wakeford, 2001). An anadromous fish that migrates from the sea upstream 

into coastal rivers to spawn in freshwater, it historically ranged from the Mississippi River to 

Charlotte Harbor, Florida (Wakeford, 2001). Today, this range has contracted to encompass 

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida. 

Populations have been depleted or even extirpated throughout this range by fishing, shoreline 

development, dam construction, water quality changes, and other factors (Barkuloo, 1988; 

Wakeford, 2001). These declines prompted the listing of the Gulf sturgeon as a threatened 

species in 1991. The best known populations occur in the Apalachicola and Suwannee Rivers in 

Florida (Carr, 1996; Sulak and Clugston, 1998), the Choctawhatchee River in Alabama (Fox et al., 

2000), and the Pearl River in Mississippi/Louisiana (Morrow et al., 1998). Critical habitat in the 

Gulf extends from Lake Borgne, Louisiana (St. Bernard Parish) to Suwannee Sound, Florida 

(Levy County) (NMFS, 2010b) (Figure 3). A species description is presented in a recent lease sale 

EIS (MMS, 2007b) and in the recovery plan for this species (USFWS and Gulf States Marine 

Fisheries Commission, 1995). 

A large oil spill (WCD) is the only IPF potentially affecting Gulf sturgeon. There are no IPFs 

associated with routine project activities that could affect these fish. A small fuel spill in the 

lease area would be unlikely to affect Gulf sturgeon because a small fuel spill would not be 

expected to make landfall or reach coastal waters prior to breaking up (see explanation in 

Section A.9.2). 

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on Gulf sturgeon are discussed in recent lease sale EISs (MMS, 2007b, 

2008) and by NMFS (2007). For this EP, there are no unique site-specific issues with respect to 

this species.
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The lease area is approximately 195 miles (313 km) from the nearest Gulf sturgeon critical 

habitat. The revised OSRA modeling (BOEMRE, 2011a,b) predicts that a spill in the lease area 

has 1% or less probability of contacting coastal areas inhabited by Gulf sturgeon within 

30 or 120 days.

In the event of oil reaching Gulf sturgeon habitat, the fish could be affected by direct ingestion, 

ingestion of oiled prey, or the absorption of dissolved petroleum products through the gills. 

Based on the life history of this species, subadult and adult Gulf sturgeon would be most 

vulnerable to an estuarine or marine oil spill, and would be vulnerable only during winter 

months (from 1 September through 30 April) when this species is foraging in estuarine and 

marine habitats (NMFS, 2007).

C.3.9 Smalltooth Sawfish (Endangered)

Smalltooth sawfish (Pristis pectinata) are found in the tropical and subtropical Atlantic Ocean. 

In the Western Atlantic they have historically ranged from New York to Brazil, including the Gulf 

of Mexico and Caribbean Sea. This sawfish primarily occurs in estuarine and coastal habitats 

such as bays, lagoons, and rivers. The smalltooth sawfish was listed as endangered on 

1 April 2003, under the ESA. Its critical habitat consists of two units: the Charlotte Harbor 

Estuary Unit, which comprises approximately 89,621 ha (221,459 ac) of coastal habitat; and the 

Ten Thousand Islands/Everglades Unit, which comprises approximately 250,506 ha (619,013 ac) 

of coastal habitat. The two units are located along the southwestern coast of Florida between 

Charlotte Harbor and Florida Bay.

A large oil spill (WCD) is the only IPF potentially affecting smalltooth sawfish. There are no IPFs 

associated with routine project activities that could affect these fishes. A small fuel spill in the 

lease area would be unlikely to affect smalltooth sawfish 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).

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on smalltooth sawfish are similar to those discussed for other coastal and 

estuarine species in recent lease sale EISs (MMS, 2000, 2007b, 2008) and by NMFS (2007) in its 

Biological Opinion. For this EP, there are no unique site-specific issues with respect to this 

species. 

In the event of oil reaching smalltooth sawfish habitat, the fish could be affected by direct 

ingestion, ingestion of oiled prey, or the absorption of dissolved petroleum products through 

the gills.

C.3.10 Beach Mice (Endangered)

Four subspecies of endangered beach mice (Peromyscus polionotus) occur on the barrier islands 

of Alabama and the Florida Panhandle. They are the Alabama, Choctawatchee, Perdido Key, and 

St. Andrew beach mice. Critical habitat has been designated for all four subspecies; Figure 3

shows the critical habitat combined for all four subspecies. Species descriptions are provided in 

a recent lease sale EIS (MMS, 2007b).

A large oil spill (WCD) is the only IPF potentially affecting beach mice. There are no IPFs 

associated with routine project activities that could affect these animals due to the distance 

from shore and the lack of any onshore support activities near their habitat. A small fuel spill in 
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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). 

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on beach mice are discussed in recent lease sale EISs (MMS, 2007b, 

2008). For this EP, there are no unique site-specific issues with respect to these species that 

were not analyzed in these documents.

The lease area is about 271 miles (435 km) southwest from the nearest beach mouse critical 

habitat. The revised OSRA modeling summarized in Section A.9.3 predicts that a spill in the 

lease area has a 1% or less probability of reaching either the Alabama or Florida shorelines 

inhabited by beach mice within 120 days.

In the event of oil contacting these beaches, beach mice could experience several types of direct 

and indirect impacts. Contact with spilled oil could cause skin and eye irritation and subsequent 

infection; matting of fur; irritation of sweat glands, ear tissues, and throat tissues; disruption of 

sight and hearing; asphyxiation from inhalation of fumes; and toxicity from ingestion of oil and 

contaminated food. Indirect impacts could include reduction of food supply, destruction of 

habitat, and fouling of nests. Impacts could also occur from vehicular traffic and other activities 

associated with spill cleanup. However, any such impacts are unlikely due to the distance from 

shore and response actions that would occur in the event of a spill.

C.3.11 Elkhorn Coral (Endangered) 

Elkhorn coral (Acropora palmata) is found primarily in shallow waters with temperatures ranging 

between 26°C and 30°C (79°F and 86°F) and significant water movement. Elkhorn coral was 

once one of the most abundant species in waters ranging from 1 to 5 m (3.3 to 16 ft) deep in 

tropical and subtropical waters. In the northern Gulf, elkhorn coral has been found within the 

coral cap region of the Flower Garden Banks National Marine Sanctuary (Flower Garden Banks 

National Marine Sanctuary, 2011).

There are no IPFs associated with routine project activities that could affect this species in the 

northern Gulf. A small fuel spill would not affect elkhorn coral colonies because the oil would 

float and dissipate on the sea surface. A WCD would be unlikely to affect the coral cap region of 

the Flower Gardens Bank because of the water depth of the area. Although subsurface plumes 

were reported following the Macondo spill, these plumes resulted from the use of subsea 

dispersants at the seafloor.

C.4 Coastal and Marine Birds

C.4.1 Marine Birds

Marine birds include seabirds and other species that may occur in the pelagic environment of 

the project 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 due to the distance from shore. For a discussion of shorebirds 

and coastal nesting birds, see Section C.4.2. 
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Seabirds of the northern Gulf of Mexico were surveyed from ships during the GulfCet II program. 

Hess and Ribic (2000) reported that terns, storm-petrels, shearwaters, and jaegers were the 

most frequently sighted seabirds in the deepwater area. From these surveys, four ecological 

categories of seabirds were documented in the deepwater areas of the Gulf: summer migrants 

(shearwaters, storm petrels, boobies); summer residents that breed in the Gulf (Sooty Tern, 

Least Tern, Sandwich Tern, Magnificent Frigatebird); winter residents (gannets, gulls, jaegers); 

and permanent resident species (Laughing Gulls, Royal Terns, Bridled Terns) (Hess and Ribic, 

2000).

Common seabird species include Wilson’s Storm-Petrel (Oceanites oceanicus), Magnificent 

Frigatebird (Fregata magnificens), Northern Gannet (Morus bassanus), Masked Booby 

(Sula dactylatra), Brown Booby (Sula leucogaster), Cory’s Shearwater (Calonectris diomedea), 

Greater Shearwater (Puffinus gravis), and Audubon’s Shearwater (Puffinus lherminieri). Seabirds 

are distributed Gulf-wide and are not specifically associated with the lease area.

Relationships with hydrographic features were found for several seabird species, possibly due to 

effects of hydrography on nutrient levels and productivity of surface waters where birds forage. 

The GulfCet II study did not estimate bird densities; however, Powers (1987) indicates that 

seabird densities over the open ocean typically are <10 birds/km2

. 

Trans-Gulf migrant birds including shorebirds, wading birds, and terrestrial birds may also be 

present in the lease area. Migrant birds may use offshore structures and rigs for resting, 

feeding, or as temporary shelter from inclement weather (Russell, 2005). Some birds may be 

attracted to offshore structures because of the lights and the fish populations that aggregate 

around these structures.

IPFs potentially affecting marine and pelagic birds include drilling rig presence, noise, and lights; 

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

spill represented by the WCD for this EP). Effluent discharges are likely to have negligible 

impacts on the birds due to rapid dispersion, the small area of ocean affected, the intermittent 

nature of the discharges, and the mobility of these animals. Compliance with NTL 2007-G03 will 

minimize the potential for marine debris-related impacts on birds.

Impacts of Drilling Rig Presence, Noise, and Lights

Birds that frequent rigs may be exposed to contaminants including air pollutants and routine 

discharges, but significant impacts are unlikely due to rapid dispersion. Birds migrating over 

water have been known to strike offshore structures, resulting in death or injury (Wiese et al., 

2001; Russell, 2005). Mortality of migrant birds at tall towers and other land-based structures 

has been reviewed extensively, and the mechanisms involved in rig collisions appear to be 

similar. In some cases, migrants simply do not see a part of the rig until it is too late. In other 

cases, navigation may be disrupted by noise (Russell, 2005). On the other hand, offshore 

structures are suitable stopover habitats for most trans-Gulf migrant species, and most of the 

migrants that stop over on rigs probably benefit from their stay, particularly in spring 

(Russell, 2005). Due to the limited scope and short duration of drilling activities described in this 

EP, any impacts on populations of either seabirds or trans-Gulf migrant birds are not expected 

to be significant.
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A recent study in the North Sea indicated that rig lighting causes circling behavior in various 

birds, especially on cloudy nights; apparently the birds’ geomagnetic compass is upset by the 

red part of the spectrum from the lights currently in use (Nederlandse Aardolie Maatschappij, 

2007). The numbers varied greatly, from none at all to some tens of thousands of birds per 

night per rig, with an apparent effect radius of up to 3 miles (5 km). A study in the Gulf of 

Mexico also noted the phenomenon, but did not recommend mitigation (Russell, 2005). Factors 

to consider in evaluating this impact in the Gulf of Mexico would include the lower incidence of 

cloudy and foggy days in the Gulf of Mexico versus the North Sea. Due to the limited scope and 

short duration of drilling activities proposed in this EP, lighting impacts, collisions, or other 

adverse effects are unlikely, and no significant impacts are expected.

Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters are unlikely to significantly disturb pelagic birds in open, 

offshore waters. It is likely that individual birds would experience, at most, only short-term 

behavioral disruption, and the impact would not be significant.

Impacts of a Small Fuel Spill

Potential spill impacts on marine birds are discussed in recent EISs (MMS, 2007b, 2008). For this 

EP, there are no unique site-specific issues with respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by Noble’s preventative measures during routine 

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

OSRP will reduce the potential for impacts on marine and pelagic birds. EP Section H provides 

detail on spill response measures. Given the open ocean location of the lease area, the duration 

of a small spill and opportunity for impacts to occur would be very brief.

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

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

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

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate 

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha 

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

Birds exposed to oil on the sea surface could experience direct physical and physiological effects 

including skin irritation; chemical burns of skin, eyes, and mucous membranes; and inhalation of 

toxic fumes. Due to the limited areal extent and short duration of water quality impacts from a 

small fuel spill, secondary impacts due to ingestion of oil via contaminated prey or reductions in 

prey abundance are unlikely. Due to the low densities of birds in open ocean areas, the small 

area affected, and the brief duration of the surface slick, no significant impacts on pelagic birds 

would be expected.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine and pelagic birds are discussed in recent EISs (MMS, 2007b, 

2008). For this EP, there are no unique site-specific issues with respect to spill impacts on these 

animals.
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BOEM has reexamined the analyses for coastal and marine birds presented in MMS (2007b, 

2008) and determined that no new information was found that would alter the potential 

impacts on marine and pelagic birds (BOEMRE, 2011a,b).

Pelagic seabirds could be exposed to oil from a spill at the project area. Hess and Ribic (2000) 

reported that terns, storm-petrels, shearwaters, and jaegers were the most frequently sighted 

seabirds in the deepwater Gulf of Mexico (>200 m). Powers (1987) indicates that seabird 

densities over the open ocean typically are <10 birds/km2

. The number of pelagic birds that 

could be affected in open, offshore waters would depend on the extent and persistence of the 

oil slick.

The recent Macondo spill provides relevant information about the species of pelagic birds that 

may be affected in the event of a large oil spill. Birds that have been treated for oiling include 

several pelagic species such as the Northern Gannet, Magnificent Frigatebird, and Masked 

Booby (USFWS, 2011). The Northern Gannet is 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 non-endangered birds are also found 

along the northern Gulf Coast, including diving birds, shorebirds, marsh birds, wading birds, and 

waterfowl. Gulf Coast marshes and beaches also provide important feeding grounds and 

nesting habitats. Species that breed on beaches, flats, dunes, bars, barrier islands, and similar 

habitats include the Sandwich Tern, Wilson’s Plover, Black Skimmer, Forster’s Tern, Gull-Billed 

Tern, Laughing Gull, Least Tern, and Royal Tern (USFWS, 2010b). Additional information is 

presented in recent lease sale EISs (MMS, 2007b, 2008).

The Brown Pelican (Pelecanus occidentalis) was delisted from Federal endangered status in 2009 

(USFWS, 2010c). However, this species is listed as a species of greatest conservation need by 

the State of Mississippi (Mississippi Department of Wildlife, Fisheries and Parks, 2011) and as a 

species of special concern by the State of Florida (Florida Fish and Wildlife Conservation 

Commission, 2011). Brown Pelicans inhabit coastal habitats and forage within both coastal 

waters and waters of the inner continental shelf. Aerial and shipboard surveys, including 

GulfCet and GulfCet II, indicate that Brown Pelicans do not occur in deep offshore waters 

(Fritts and Reynolds, 1981; Peake, 1996; Hess and Ribic, 2000). Nearly half the southeastern 

population of Brown Pelicans lives 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 28 June 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 120 miles (193 km) from the 

nearest shoreline. As explained in Section A.9.2, a small fuel spill would not be expected to 
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make landfall or reach coastal waters prior to breaking up. Compliance with NTL 2007-G03 will 

minimize the potential for marine debris-related impacts on shorebirds.

Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters will transit coastal areas near Port Fourchon and Houma, 

Louisiana, where shorebirds and coastal nesting birds may be found. These activities could 

periodically disturb individuals or groups of birds within sensitive coastal habitats (e.g., wetlands 

that may support feeding, resting, or breeding birds).

Vessel traffic may disturb some foraging and resting birds. Flushing distances vary between 

species and between individuals (Rodgers and Schwikert, 2002). The disturbances will be 

limited to flushing birds away from vessel pathways; known distances are from 20 to 49 m 

(65 to 160 ft) for personal watercraft and 23 to 58 m (75 to 190 ft) for an outboard-powered 

boat (Rodgers and Schwikert, 2002). Flushing distances may be similar or less for the support 

vessels to be used for Noble’s project, and some species such as gulls are attracted to boats. 

Support vessels will not approach nesting or breeding areas on the shoreline, so disturbances to 

nesting birds, eggs, and chicks is not expected. Vessel operators will use designated navigation 

channels and comply with posted speed and wake restrictions while transiting sensitive inland 

waterways. Due to the limited scope and short duration of drilling activities, any short-term 

impacts are not expected to be biologically significant to coastal bird populations.

Aircraft traffic can cause some disturbance to birds onshore and offshore. Responses are highly 

dependent on the type of aircraft, the bird species, the activities that animals were previously 

engaged in, and previous exposures to overflights (Efroymson et al., 2000). Helicopters seem to 

cause the most intense responses over other human disturbances for some species (Bélanger 

and Bédard, 1989). However, Federal Aviation Administration Advisory Circular No. 91-36D 

recommends that pilots maintain a minimum altitude of 610 m (2,000 ft) when flying over 

noise-sensitive areas such as wildlife refuges, parks, and areas with wilderness characteristics. 

This is greater than the distance (slant range) at which aircraft overflights have been reported to 

cause behavioral effects on most species of birds studied (Efroymson et al., 2000). With these 

guidelines in effect, it is likely that individual birds would experience, at most, only short-term 

behavioral disruption.

Impacts of Large Oil Spill (WCD)

Data from the Macondo spill provide additional information about the species of coastal birds 

that may be affected in the event of a catastrophic spill of a similar nature and duration. This 

information supplements the analysis presented in the lease sale EIS (MMS, 2007b). According 

to USFWS (2010d) and based on the latest reports, about 5,000 dead birds have been collected 

since the spill began, and about 1,900 of the dead animals were visibly oiled. In addition, over 

2,000 oiled birds have been collected alive and about 1,200 released (NMFS, 2010c). According 

to the USFWS (2011), bird species that have been treated for oiling include the following:

• Brown Pelican

• White Pelican

• Masked Booby

• Magnificent Frigatebird

• Laughing Gull

• Herring Gull

• Northern Gannet

• Black Crowned Night Heron

• Tri-colored Heron

• Green Heron

• Cattle Egret

• Snowy Egret
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• Reddish Egret

• Least Bittern

• Common Tern

• Royal Tern

• Caspian Tern

• Sandwich Tern

• Forsters Tern

• Black Tern

• Gull-billed Tern

• Least Tern

• Black Skimmer

• Black Oystercatcher

• White Ibis

• Roseate Spoonbill

• Willet

• Sanderling

• Dunlin

• Semipalmated Sandpiper

• Killdeer

• King Rail

• Clapper Rail

• Virginia Rail

According to the USFWS (2010d), species with the largest numbers of dead, oiled birds were 

Laughing Gull, Northern Gannet, Brown Pelican, Royal Tern, Black Skimmer, Least Tern, 

unidentified Gull, and unidentified Tern. There are no reports of Bald Eagle oiling.

Coastal birds can be exposed to oil as they float on the water’s surface, dive during foraging, or 

wade in oiled coastal waters. Oiled birds can lose the ability to fly, dive for food, or float on the 

water, which could lead to drowning (USFWS, 2010e). Oil interferes with the water repellency 

of feathers and can cause hypothermia in the right conditions. As birds groom themselves, they 

can ingest and inhale the oil on their bodies. Scavengers such as Bald Eagles and gulls can be 

exposed to oil by feeding on carcasses of contaminated fish and wildlife. While ingestion can kill 

animals immediately, more often it results in lung, liver, and kidney damage, which can lead to 

death. Bird eggs may be damaged if an oiled adult sits on the nest.

As noted above, the Brown Pelican was recently removed from the Federal endangered species 

list. Over 300 dead Brown Pelicans were collected in the Gulf following the Macondo spill, 

(USFWS, 2010d). These data indicate that Brown Pelicans may be particularly at risk of oiling in 

the event of a catastrophic spill reaching coastal waters. Issues for Brown Pelicans include direct 

contact with oil, disturbance by cleanup activities, and long-term habitat contamination.

C.5 Fisheries Resources

C.5.1 Pelagic Communities and Ichthyoplankton

Biggs and Ressler (2000) reviewed the biology of pelagic communities in the deepwater 

environment of the northern Gulf of Mexico. The biological oceanography of the region is 

dominated by the influence of the Loop Current, whose surface waters are among the most 

oligotrophic in the world’s oceans. Superimposed on this low-productivity condition are 

productive “hot spots” associated with entrainment of nutrient-rich Mississippi River water and 

mesoscale oceanographic features. Anticyclonic and cyclonic hydrographic features play an 

important role in determining biogeographic patterns and controlling primary productivity in the 

northern Gulf of Mexico (Biggs and Ressler, 2000).

Most fishes inhabiting shelf or oceanic waters of the Gulf of Mexico have planktonic eggs and 

larvae (Ditty, 1986; Ditty et al., 1988; Richards et al., 1989, 1993). Pelagic eggs and larvae 

become part of the planktonic community for various lengths of time (10 to 100 days, 

depending on the species) (MMS, 2007b).
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IPFs potentially affecting pelagic communities and ichthyoplankton include drilling rig presence, 

noise, and lights; effluent discharges; water intakes; and two types of accidents (a small fuel spill 

and a large oil spill [WCD]).

Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as a fish-attracting 

device (FAD). In oceanic waters, the FAD effect would be most pronounced for epipelagic fishes 

such as tunas, dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting 

surface structures (e.g., Holland et al., 1990; Higashi, 1994; Relini et al., 1994 MMS 2000, 2007b, 

2008). This FAD effect could possibly enhance the feeding of epipelagic predators by attracting 

and concentrating smaller fish species. Because the drilling rig is a single, temporary structure, 

impacts on fish populations, whether beneficial or adverse, are considered minor.

Impacts of Effluent Discharges

Treated sanitary and domestic wastes may have a slight effect on the pelagic environment in the 

immediate vicinity of these discharges. These wastes may have elevated levels of nutrients, 

organic matter, and chlorine, but should be diluted rapidly to undetectable levels within tens to 

hundreds of meters from the source. Minimal impacts on water quality, plankton, and nekton 

are anticipated.

Deck drainage may have a slight effect on the pelagic environment in the immediate vicinity of 

these discharges. Deck drainage from contaminated areas will be passed through an 

oil-and-water separator prior to release, and discharges will be monitored for visible sheen. The 

discharges may have slightly elevated levels of hydrocarbons but should be diluted rapidly to 

undetectable levels within tens to hundreds of meters from the source. Minimal impacts on 

water quality, plankton, and nekton are anticipated.

Other discharges in accordance with the NPDES permit, such as water-based muds and cuttings, 

desalination unit brine and uncontaminated cooling water, fire water, and ballast water, are 

expected to be diluted rapidly and have little or no impact on water column biota.

Impacts of Water Intakes

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

on the drilling rig. The rig considered for use in this EP is not a “new” facility as defined by the 

NPDES permit and therefore is not subject to the cooling water intake regulations for Phase III 

facilities under Section 316(b) of the Clean Water Act. 

The intake of seawater for cooling water will entrain plankton. The low intake velocity should 

allow most strong swimming juvenile fishes and smaller adults to escape entrainment or 

impingement. However, drifting plankton would not be able to escape entrainment with the 

exception of a few fast swimming larvae of certain taxonomic groups. Those organisms 

entrained may be stressed or killed, primarily through changes in water temperature during the 

route from cooling intake structure to discharge structure and mechanical damage (turbulence 

in pumps and condensers). Due to the limited scope and short duration of drilling activities, any 

short-term impacts of entrainment are not expected to be biologically significant to plankton or 

ichthyoplankton populations.
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Impacts of a Small Fuel Spill

Potential spill impacts on fisheries resources are discussed in recent EISs (MMS, 2007b, 2008). 

For this EP, there are no unique site-specific issues with respect to spill impacts.

The probability of a fuel spill will be minimized by Noble’s preventative measures during routine 

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

OSRP will mitigate the potential for impacts on pelagic communities, including ichthyoplankton. 

EP Section H provides detail on spill response measures. Given the open ocean location of the 

lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.

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

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

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

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate 

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha 

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

A small fuel spill could have localized impacts on phytoplankton, zooplankton, and nekton. Due 

to the limited areal extent and short duration of water quality impacts, a small fuel spill would 

be unlikely to produce detectable impacts on pelagic communities.

Impacts of a Large Oil Spill (WCD)

A large oil spill could affect water column biota including phytoplankton, zooplankton, 

ichthyoplankton, and nekton. A large spill that persisted for weeks or months would be more 

likely to affect these communities. While adult and juvenile fishes may actively avoid a large 

spill, planktonic eggs and larvae would be unable to avoid contact. Eggs and larvae of fishes are 

especially vulnerable to oiling because they inhabit the upper layers of the water column, and 

they will die if exposed to certain toxic fractions of spilled oil. Impacts potentially would be 

greater if local scale currents retained planktonic larval assemblages (and the floating oil slick) 

within the same water mass.

C.5.2 Essential Fish Habitat

Essential Fish Habitat (EFH) is defined as those waters and substrate necessary to fish for 

spawning, breeding, feeding, and growth to maturity. Under the Magnuson-Stevens Fishery 

Conservation and Management Act, as amended, Federal agencies are required to consult on 

activities that may adversely affect EFH designated in Fishery Management Plans developed by 

the regional Fishery Management Councils.

The Gulf of Mexico Fishery Management Council (GMFMC) has prepared Fishery Management 

Plans for corals and coral reefs, shrimps, stone crab, spiny lobster, reef fishes, coastal migratory 

pelagic fishes, and red drum. In 2005, the EFH for these managed species was redefined in 

Generic Amendment No. 3 to the various Fishery Management Plans (GMFMC, 2005). The EFH 

for most of these GMFMC-managed species is on the continental shelf in waters shallower than 

183 m (600 ft). The shelf edge is the outer boundary for coastal migratory pelagic fishes, reef 

fishes, and shrimps. EFH for corals and coral reefs includes some shelf-edge topographic 

features on the Texas-Louisiana OCS, the nearest of which are in EW 945, located approximately 

50 miles (80 km) north of the lease area along the shelf edge south of Louisiana.
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Highly migratory pelagic fishes, which occur as transients in the lease area, are the only 

remaining group for which EFH has been identified in the deepwater Gulf of Mexico. Species in 

this group, including tunas, swordfishes, billfishes, and sharks, are managed by NMFS. Highly 

migratory species with EFH at or near the lease area include the following species and life 

stages: 

• Blue marlin (juveniles, adults)

• White marlin (juveniles, adults) 

• Skipjack tuna (spawn, adult) 

• Yellowfin tuna (spawn, juveniles, 

adults)

• Bigeye thresher shark (all)

• Bigeye tuna (juveniles) 

• Bluefin tuna (spawn, eggs, larvae, 

adults) 

• Common thresher shark (all)

• Great hammerhead shark (all)

• Longbill spearfish (adults, juveniles)

• Longfin mako shark (all)

• Oceanic whitetip shark (all)

• Sailfish (juveniles, adults)

• Shortfin mako shark (all)

• Silky shark (all)

• Swordfish (larvae, juveniles, adults)

• Tiger shark (adult)

• Whale shark (all)

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 15,000 mi2 (300,000 km2

). The 

prevailing assumption is that Atlantic bluefin tuna follow an annual cycle of foraging in June 

through March off the eastern U.S. and Canadian coasts, followed by migration to the Gulf of 

Mexico to spawn in April, May, and June (NMFS, 2009).

On 27 May 2011 after an extensive scientific review, NOAA announced that Atlantic bluefin tuna 

currently do not warrant species protection under the ESA. NOAA said the species would be 

classified as a species of concern; however, effectively placing bluefin on a watch list as the 

agency awaits new data on the impact of a stricter international management regimen.

A new amendment to the original EFH Generic Amendment was finalized in 2005 (GMFMC, 

2005). One of the most significant proposed changes in this amendment reduced the extent of 

EFH relative to the 1998 Generic Amendment by removing the EFH description and 

identification from waters between 100 fathoms and the seaward limit of the Exclusive 

Economic Zone (EEZ). The Highly Migratory Species Fisheries Management Plan was amended 

in 2009 to update EFH and HAPC to include the bluefin tuna spawning area (NMFS, 2009). 

There are current NTLs (2009-G39 and 2009-G40) that provide guidance and clarification of the 

regulations with respect to biologically sensitive underwater features and areas and benthic 

communities that are considered EFH (MMS, 2009a,b). A new EFH consultation has been 

initiated between BOEMRE’s Gulf of Mexico Region and NOAA’s Southeastern Region. Some 

EFH requirements may change with the new agreement. Until the new agreement is in place, 

the 1999 Programmatic Consultation with the elements described above will be followed 

(BOEMRE, 2011a,b).

There are Fishery Management Plans in the Gulf of Mexico OCS region for shrimps, red drum, 

reef fishes, coastal migratory pelagics, stone crab, spiny lobster, corals and coral reefs, billfishes, 

and highly migratory species. The Highly Migratory Species Fisheries Management Plan was 
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recently amended to update EFH and habitat areas of particular concern for the bluefin tuna 

spawning area (NMFS, 2009).

Other HAPCs have been identified in the Gulf of Mexico by the GMFMC (2005). These include 

the Florida Middle Grounds, Madison-Swanson Marine Reserve, Tortugas North and South 

Ecological Reserves, Pulley Ridge, and several individual reefs and banks of the northwestern 

Gulf of Mexico (Figure 3). The nearest of these is Jakkula Bank, located approximately 57 miles 

(92 km) from the lease area. 

Routine IPFs potentially affecting EFH include drilling rig presence, noise, and lights; effluent 

discharges; water intakes; and two types of accidents – a small fuel spill and a large oil spill 

(WCD).

Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as an FAD. In 

oceanic waters, the FAD effect would be most pronounced for epipelagic fishes such as tunas, 

dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting surface 

structures (Holland et al., 1990; Higashi, 1994; Relini et al., 1994; MMS 2000, 2007b, 2008). This 

FAD effect would possibly enhance feeding of epipelagic predators by attracting and 

concentrating smaller fish species. Because the drilling rig is a single, temporary structure, any 

impacts on EFH for highly migratory pelagic fishes are considered minor.

Impacts of Effluent Discharges

Other effluent discharges affecting EFH by diminishing ambient water quality include drilling 

muds and cuttings, treated sanitary and domestic wastes, deck drainage, and miscellaneous 

discharges such as desalination unit brine and uncontaminated cooling water, fire water, and 

ballast water. Impacts on water quality have been discussed previously. No significant impacts 

on EFH for highly migratory pelagic fishes are expected from these discharges.

Impacts of Water Intakes

As noted previously, cooling water intake will cause entrainment and impingement of plankton, 

including fish eggs and larvae (ichthyoplankton). Due to the limited scope and short duration of 

drilling activities, any short-term impacts on EFH for highly migratory pelagic fishes are not 

expected to be biologically significant.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Noble’s preventative measures during routine 

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

OSRP will help diminish the potential for impacts on EFH. EP Section H provides detail on spill 

response measures. Given the open ocean location of the lease area, the duration of a small 

spill and opportunity for impacts to occur would be very brief.

Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008). For this EP, 

there are no unique site-specific issues with respect to spill impacts.

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

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

persistence of impacts would depend on the meteorological and oceanographic conditions at 
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the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate 

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha 

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

A small fuel spill could have localized impacts on EFH for highly migratory pelagic fishes, 

including tunas, swordfishes, billfishes, and sharks. These species occur as transients in the 

lease area. A spill would also produce short-term impact on water quality in the HAPC for 

spawning Atlantic bluefin tuna, which covers much of the deepwater Gulf of Mexico. The 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, the nearest EFH being the 

topographic features located approximately 50 miles (80 km) from the lease area along the shelf 

edge south of Louisiana. A small fuel spill would float and dissipate on the sea surface and 

would not contact these features.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on EFH are discussed in recent EISs (MMS, 2007b, 2008). For this EP, 

there are no unique site-specific issues with respect to EFH.

An oil spill in offshore waters would temporarily increase hydrocarbon concentrations on the 

water surface and potentially the subsurface as well. Given the extent of EFH designations in 

the Gulf of Mexico (GMFMC, 2005; NMFS, 2009), some impact on EFH would be unavoidable.

A 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 contaminated and result in persistent 

degradation of the seafloor habitat for managed demersal fish and shellfish species.

The lease area is within the HAPC for spawning Atlantic bluefin tuna (NMFS, 2009). A large spill 

could temporarily degrade the HAPC due to increased hydrocarbon concentrations in the water 

column, with the potential for lethal or sublethal impacts on spawning tuna. Potential impacts 

would depend in part on the timing of a spill, as this species migrates to the Gulf of Mexico to 

spawn in April, May, and June (NMFS, 2009).

Topographic features (Ship Shoal south) located in EW 945, 50 miles (80 km) north of the lease 

area, are designated as EFH under the corals and coral reefs management plan. An accidental 

spill would be unlikely to affect this area, since a surface slick would not reach these features

due to their depth.

C.6 Archaeological Resources

C.6.1 Shipwreck Sites

BOEMRE (2011a,b) has reexamined the analyses for archaeological resources presented in 

MMS (2007b, 2008), based on additional information available since the publication of these 

two documents and in consideration of the Macondo oil spill event. Substantial new 

information that alters the impact conclusion for archaeological resources presented in

MMS (2007b, 2008) has come to light as a result of BOEMRE-sponsored studies and industry 
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surveys. Specifically, evidence of damage to significant cultural resources (i.e., historic 

shipwrecks) has been shown to have occurred because of an incomplete knowledge of seafloor 

conditions in lease areas >200 m (656 ft) deep that have been exempted from high-resolution

surveys. Since significant historic shipwrecks have recently been discovered outside the 

previously designated high-probability areas (some of which show evidence of impacts from 

permitted activities prior to their discovery), beginning in 2011 a survey will be required for 

exploration and development projects.

The lease area is not on the list of leases with a high potential for historic shipwrecks. There 

were no indications of wrecks or other archaeological resources detected near the proposed 

wellsites during the shallow hazards assessment (B-Geo, 2011). Noble will abide by the 

applicable requirements of NTL 2005-G07, which stipulate that work be stopped at the project 

site should any previously undetected archaeological resource be discovered after work has 

begun until appropriate surveys and evaluations have been completed.

Because there are no known or indicated shipwreck sites in the lease area, there are no routine 

IPFs that are likely to affect shipwrecks. Impacts of a large oil spill (WCD) are the only IPFs 

considered. A small fuel spill would not affect shipwrecks because the oil would float and 

dissipate on the sea surface.

Impacts of a Large Oil Spill (WCD)

The MMS (2007b) estimated that a severe subsurface blowout could resuspend and disperse 

sediments within a 300-m (984-ft) radius. Because there are no historic shipwrecks in the lease 

area, this impact would not be relevant.

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

archaeological sites beyond the immediate vicinity of the wellhead (i.e., due to physical impacts 

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

However, during the Macondo spill, subsurface plumes were reported at a water depth of about 

1,100 m (3,600 ft), extending at least 22 miles (35 km) from the wellsite and persisting for more 

than a month (Camilli et al., 2010). The subsurface plumes apparently resulted from the use of 

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

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

shipwreck sites beyond the 300-m (984-ft) radius estimated by MMS (2007a, 2008), depending 

on its extent, trajectory, and persistence. If oil from a subsea spill should come into contact with 

wooden shipwrecks on the seafloor it could adversely affect their condition or preservation. 

Should there be any indication that potential shipwreck sites could be affected, in accordance 

with NTL 2005-G07 Noble will immediately halt operations, take steps to ensure that the site is 

not disturbed in any way, and contact the Regional Supervisor, Leasing and Environment, within 

48 hours of its discovery. Noble would cease all operations within 305 m (1,000 ft) of the site 

until the Regional Director provides instructions on steps to take to assess the site’s potential 

historic significance and protect it.

A spill entering shallow coastal waters could conceivably contaminate an undiscovered 

shipwreck site. As noted by MMS (2007b), should an oil spill contact a coastal historic site, such 

as a fort or a lighthouse, the major impact would be a temporary, reversible visual impact from 

oil contact and contamination of the site and its environment.
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C.6.2 Prehistoric Archaeological Sites

Available evidence suggests that sea level in the northern Gulf of Mexico was at least 90 m 

(295 ft), and possibly as much as 130 m (427 ft), lower than present sea level during the period 

20,000 to 17,000 years Before Present (B.P.) (Nelson and Bray, 1970). Sea level in the northern 

Gulf reached its present stand around 3,500 years B.P. (Pearson et al., 1986).

During periods that the continental shelf was exposed above sea level, the area was open to 

habitation by prehistoric peoples. The advent of early man into the Gulf of Mexico region is 

currently accepted to be around 12,000 years B.P. (Aten, 1983). The sea-level curve for the 

northern Gulf of Mexico proposed by Coastal Environments, Inc. (CEI) suggests that sea level at 

12,000 years B.P. would have been approximately 45-60 m (148-197 ft) below the present-day 

sea level (CEI, 1977, 1982). On this basis, the continental shelf shoreward of the 45- to 60-m 

(148- to 197-ft) bathymetric contours has potential for prehistoric sites dating after 

12,000 years B.P. Because of inherent uncertainties in both the depth of sea level and the entry 

date of prehistoric man into North America, the MMS adopted the 60-m (197-ft) water depth as 

the seaward extent for archaeological site potential in Gulf of Mexico region.

With water depths of 1,272 to 1,714 m (4,172 to 5,623 ft), the wellsites are well beyond the 

60-m (197-ft) depth contour used by the BOEM as the seaward extent for prehistoric 

archaeological site potential in the Gulf of Mexico. Because prehistoric archaeological sites are 

not found in the lease area, the only relevant IPF is a large oil spill (WCD). A small fuel spill 

would not affect prehistoric archaeological resources because the oil would float and dissipate 

on the sea surface.

Impacts of a Large Oil Spill (WCD)

Because prehistoric archaeological sites are not found in the lease area, they would not be 

affected by the physical effects of a subsea blowout. The MMS (2007b) estimates that a severe 

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

Along the northern Gulf Coast, prehistoric sites occur frequently along the barrier islands and 

mainland coast and along the margins of bays and bayous (MMS, 2007b). If a spill did reach a 

prehistoric site along these shorelines it could coat fragile artifacts or site features and 

compromise the potential for radiocarbon dating organic materials in a site (although other 

dating methods are available and it is possible to decontaminate an oiled sample for 

radiocarbon dating). Coastal prehistoric sites could also be damaged by spill cleanup operations 

(e.g., by destroying fragile artifacts and disturbing the provenance of artifacts and site features).

C.7 Coastal Habitats and Protected Areas

Coastal habitats in the northeastern Gulf of Mexico that may be affected by oil and gas activities 

are described in recent EISs (MMS, 2007b, 2008) and in a literature review by Collard and Way 

(1997). Coastal habitats inshore of the project area include barrier beaches and dunes, 

wetlands, and submerged seagrass beds. Generally, most of the northeastern Gulf is fringed by 

barrier beaches, with wetlands and/or submerged seagrass beds occurring in sheltered areas 

behind the barrier islands and in estuaries.

Due to the distance from shore, there are no IPFs associated with routine activities that are 

likely to affect beaches and dunes, wetlands, seagrass beds, coastal wildlife refuges, wilderness 
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areas, or any other managed or protected coastal area. The support bases at Port Fourchon and 

Houma are not in a wildlife refuge or a wilderness area. Potential impacts of support vessel 

traffic are addressed briefly below.

A small fuel spill in the lease area would be unlikely to affect coastal habitats, as the lease area is 

120 miles (193 km) from the nearest shoreline. As explained in Section A.9.2, a small fuel spill 

would break up before reaching shore.

Impacts of Support Vessel Traffic

For OCS activities in general, support operations, including crew boats and supply boats, may 

have a minor incremental impact on coastal habitats. Over time with a large number of vessel 

trips, vessel wakes can erode shorelines along inlets, channels, and harbors. Support 

operations, including crew boats and supply boats as detailed in EP Section K, may have a minor 

incremental impact on coastal habitats or protected areas. Impacts will be minimized by 

following the speed and wake restrictions in harbors and channels.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on coastal habitats are discussed in recent EISs (MMS, 2007b, 2008). 

Coastal habitats inshore of the project area include barrier beaches and dunes, wetlands, and 

submerged seagrass beds. For this EP, there are no unique site-specific issues with respect to 

coastal habitats.

The shorelines within the geographic range predicted by the OSRA modeling (Table 3) include 

extensive barrier beaches and wetlands, with submerged seagrass beds occurring in sheltered 

areas behind the barrier islands and in estuaries. NWRs and other protected areas along the 

coast are discussed in a recent lease sale EIS (MMS, 2007b) and Noble’s OSRP. Coastal and 

near-coastal wildlife refuges, wilderness areas, and State and National parks within the 

geographic range of potential shoreline contacts after 120 days are listed in Table 7. 

Table 7. Wildlife refuges, wilderness areas, and State and National parks within the geographic 

range of the potential shoreline contacts after 120 days. 

County or Parish Wildlife Refuge, Wilderness Area, 

or State/National Park

Cameron County, Texas

Lower Rio Grande Valley National Wildlife Refuge

Laguna Atascosa National Wildlife Refuge

Padre Island National Seashore

Isla Blanca Park

Andy Bowie County Park 

Laguna Madre Estuarine and Coastal Marine Area

Willacy County, Texas

Lower Rio Grande Valley National Wildlife Reserve

Laguna Atascosa National Wildlife Reserve 

Padre Island National Seashore

Laguna Madre Estuarine And Coastal Marine Area

Kenedy County, Texas Padre Island National Seashore

Laguna Madre Estuarine and Coastal Marine Area

Kleberg County, Texas Padre Island National Seashore

Laguna Madre Estuarine and Coastal Marine Area

Nueces County, Texas

Laguna Madre Estuarine and Coastal Marine Area

Mustang Island State Park

Lake Corpus Christi State Park

Port Aransas Park
Table 7. (Continued.) 

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County or Parish Wildlife Refuge, Wilderness Area, 

or State/National Park

Mission-Aransas National Estuarine Research Reserve

Aransas County, Texas 

Mission-Aransas National Estuarine Research Reserve

Aransas National Wildlife Refuge

Goose Island State Park

Calhoun County, Texas

Mission-Aransas National Estuarine Research Reserve

Aransas National Wildlife Refuge

Matagorda Island State Park

Guadalupe Delta Wildlife Management Area

Welder Flats Coastal Preserve

Matagorda County, Texas 

Big Boggy National Wildlife Refuge

Aransas 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

Galveston Island State Park

Brazoria National Wildlife Refuge

Apffel Park

Seawolf Park

Old Fort Travis Park

Atkinson Island Wildlife Management Area

Ft. Anahuc Park

Anahuac National Wildlife Refuge

Mcfaddin National Wildlife Refuge

Jefferson County, Texas 

Mcfaddin National Wildlife Refuge

Sea Rim State Park

Murphree Wildlife Management Area

Texas Point National Wildlife Refuge

Cameron Parish, Louisiana 

Sabine National Wildlife Refuge

Cameron Prairie National Wildlife Refuge

Lacassine National Wildlife Refuge

Little Pecan Island Natural Area

Peveto Woods Natural Area

Lower Neches Wildlife Management Area

Rockefeller Wildlife Management Area

Vermilion Parish, Louisiana Louisiana Rockefeller Wildlife Management Area

Paul J. Rainey Wildlife Management Area

Terrebonne Parish, Louisiana

Atchafalaya Delta Wildlife Management Area

Mandalay National Wildlife Refuge

Isles Dernieres Barrier Islands Refuge

Pointe Au Chein Wildlife Management Area

Lafourche Parish Louisiana Louisiana Pointe Au Chein Wildlife Management Area

Wisner Wildlife Management Area

Plaquemines Parish, Louisiana 

Salvador Wildlife Management Area

Jean Lafitte National Historical Park and Preserve

Delta National Wildlife Refuge

Pass-a-Loutre Wildlife Management Area

Breton National Wildlife Refuge

St. Bernard State Park
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The level of impacts from oil spills on coastal habitats depends on many factors, including the oil 

characteristics, the geographic location of the landfall, and the weather and oceanographic 

conditions at the time (MMS, 2007b). Oil that makes it to beaches may be either liquid 

weathered oil, an oil-and-water mousse, or tarballs (MMS, 2007b). Oil is generally deposited on 

beaches in lines defined by wave action at the time of landfall. Oil that remains on the beach 

will thicken as its volatile components are lost. Thickened oil may form tarballs or aggregations 

that incorporate sand, shell, and other materials into its mass. Tar may be buried to varying 

depths under the sand. On warm days, both exposed and buried tarballs may liquefy and ooze. 

Oozing may also serve to expand the size of a mass as it incorporates beach materials. Oil on 

beaches may be cleaned up manually, mechanically, or both. Some oil can remain on the beach 

at varying depths and may persist for several years as it slowly biodegrades and volatilizes.

Wetlands are highly sensitive to oiling. The MMS (2007b) predicted that for every 50 bbl of oil 

contacting wetlands, approximately 2.7 ha (6.7 ac) of wetland vegetation will experience 

dieback. Thirty percent of these damaged wetlands are assumed to recover within 4 years, and 

85% within 10 years. About 15% of the contacted wetlands are expected to be converted 

permanently to open-water habitat. The critical concentration of oil is that concentration above 

which impacts to wetlands will be long-term and recovery will take longer than two growing 

seasons, and that causes plant mortality and some permanent wetland loss. Critical 

concentrations of various oils are expected to vary broadly for wetland types and wetland plant 

species. Louisiana wetlands are assumed to be more sensitive to oil contact than elsewhere in 

the Gulf because of high cumulative stress (MMS, 2007b). In addition to the direct impacts of 

oil, cleanup activities in marshes may accelerate rates of erosion and retard recovery rates, 

which have been reported to require from years to decades following a spill (MMS, 2007b; 

BOEMRE, 2011a,b).

C.8 Socioeconomic and Other Resources

C.8.1 Recreational and Commercial Fishing

BOEMRE has reexamined the analysis for recreational and commercial fishing presented in 

MMS 2007b and 2008 based on additional information and in consideration of the Macondo oil 

spill event. However, no additional information obtained after the previous EISs was found that 

would alter the potential impacts on commercial and recreational fishing discussed in those EISs 

(BOEMRE, 2011a,b). 

The main commercial fishing activity in deep waters of the northern Gulf of Mexico is pelagic 

longlining for tunas, swordfishes, and other billfishes (Continental Shelf Associates, Inc., 2002). 

Pelagic longlining has occurred historically in the project area, primarily during spring and 

summer. In August 2000, the Federal government closed two areas in the northeastern Gulf of 

Mexico to longline fishing (65 Federal Register 47214, 1 August 2000). The lease is outside of 

the closure areas.

Longline gear consists of monofilament line deployed from a moving vessel and generally 

allowed to drift for 4 to 5 hours (Continental Shelf Associates, Inc., 2002). As the mainline is put 

out, baited leaders and buoys are clipped in place at regular intervals. It takes 8 to 10 hours to 

deploy a longline and about the same time to retrieve it. Longlines are often set near 

oceanographic features such as fronts or downwellings, with the aid of sophisticated on-board 

temperature sensors, depth finders, and positioning equipment. Vessels typically are 10 to 30 m 
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(33 to 98 ft) long, and their trips last from about 1 to 3 weeks. The main Gulf of Mexico 

homeports for longlining vessels are in Louisiana (Dulac and Venice) and Florida (Destin, 

Madeira Beach, and Panama City).

It is unlikely that any commercial fishing activity other than longlining occurs at or near the 

project area. Benthic species targeted by commercial fishers occur on the upper continental 

slope, well inshore of the project area. Royal red shrimp are caught by trawlers in water depths 

of about 250 to 550 m (820 to 1,804 ft). Tilefish are caught by bottom longlining in water 

depths from about 165 to 450 m (540 to 1,476 ft) (Continental Shelf Associates, Inc., 2002).

Most recreational fishing activity in the region occurs in water depths less than 200 m (656 ft) 

(Continental Shelf Associates, Inc., 1997, 2002). In deeper water, the main attraction to 

recreational fishers would be petroleum rigs offshore Texas and Louisiana. Due to the distance 

from shore, it is unlikely that recreational fishing activity is occurring in the lease area.

The only routine IPF potentially affecting fisheries is drilling rig presence (including noise and 

lights). Two potential accidents are also addressed below – a small fuel spill and a large oil spill 

(WCD).

Impacts of Drilling Rig Presence

There is a slight possibility of pelagic longlines becoming entangled in the drilling rig. For 

example, in January 1999 a portion of a pelagic longline snagged on the acoustic Doppler 

current profiler of a drillship working in the Gulf of Mexico (Continental Shelf Associates, Inc., 

2002). The line was removed without incident. Generally, longline fishers use radar and are 

aware of offshore structures and ships when placing their sets. Therefore, little or no impact on 

pelagic longlining is expected.

Because it is unlikely that any recreational fishing activity is occurring in the project area, no 

adverse impacts are anticipated. Other factors such as effluent discharges are likely to have 

negligible impacts on commercial or recreational fisheries due to rapid dispersion, the small 

area of ocean affected, and the intermittent nature of the discharges.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Noble’s preventative measures during routine 

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

OSRP will potentially mitigate and reduce the potential for impacts. EP Section H provides detail 

on spill response measures. Given the open ocean location of the lease area, the duration of a 

small spill and opportunity for impacts to occur would be very brief.

Pelagic longlining activities in the lease area, if any, could be interrupted in the event of a small 

fuel spill. The area of the sea surface with diesel fuel on it would range from 0.5 to 5 ha 

(1.2 to 12 ac), depending on sea state and weather conditions. Fishing activities could be 

interrupted due to the activities of response vessels operating in the lease area. A small fuel 

spill would not affect coastal water quality because the spill would not be expected to make 

landfall or reach coastal waters prior to breaking up (see Section A.9.2).
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Impacts of a Large Oil Spill (WCD)

Potential spill impacts on fishing activities are discussed in recent EISs (MMS, 2007b, 2008). For 

this EP, there are no unique site-specific issues with respect to this activity.

Pelagic longlining activities in the lease area and other fishing activities in the northern Gulf of 

Mexico could be interrupted in the event of a large oil spill. A spill may or may not result in 

fishery closures, depending on the duration of the spill, the oceanographic and meteorological 

conditions at the time, and the effectiveness of spill response measures. The recent Macondo 

spill provides information about the maximum potential extent of fishery closures in the event 

of a large oil spill in the Gulf of Mexico (NMFS, 2010d). At its peak on 12 July 2010, closures 

encompassed 84,101 mi2

 (217,821 km2), or 34.8% of the U.S. EEZ in the Gulf of Mexico.

C.8.2 Public Health and Safety

There are no IPFs associated with routine operations that are expected to affect public health 

and safety. Impacts of a small fuel spill and a large oil spill (WCD) are addressed below.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Noble’s preventative measures during routine 

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

OSRP will potentially alleviate the potential for impacts. EP Section H provides detail on spill 

response measures.

A small fuel spill would not have any impacts on public health and safety because it would affect 

only a small area of the open ocean 120 miles (193 km) from the nearest shoreline and nearly all 

of the diesel fuel would evaporate or disperse naturally within 24 hours. Response crews would 

be equipped with appropriate safety equipment to avoid injury and health effects. A small fuel 

spill would not be expected to make landfall or reach coastal waters prior to breaking up

(see Section A.9.2).

Impacts of a Large Oil Spill (WCD)

In the event of a large spill from a blowout, the main safety and health concerns are those of the 

offshore personnel involved in the incident and those responding to the spill. The 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,

meteorological and oceanographic conditions at the time, and the effectiveness of spill response 

measures, the public could be exposed to oil on the water and along the shoreline, including 

skin contact or breathing VOCs. Crude oil is a highly flammable material, and any smoke or 

vapors from a crude oil fire can cause irritation, and in large quantities may pose a health 

hazard.

Data from the recent Macondo spill provide relevant information about the types of health 

issues that may occur in the event of a large oil spill (Centers for Disease Control and Prevention, 

2010a). Wildlife cleaning and rehabilitation workers have reported concerns including scrapes 

and cuts, itchy or red skin or rash, and symptoms of headache or feeling faint, dizzy, or fatigued. 

Hand, shoulder, or back pain was also reported by some wildlife-cleaning workers. Personnel 

working on offshore vessels or providing direct oversight to offshore vessels, including 
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USCG personnel, civilian contractors, and other responders who were exposed to oil and 

dispersants, had a 7 to 12 times higher prevalence of upper respiratory symptoms and cough 

than those not exposed (Centers for Disease Control and Prevention, 2010b). Another potential 

occupational hazard for spill response workers in general was heat stress from work in a hot and 

humid environment. Initial symptoms from cleanup workers who sought medical care in 

Louisiana were typical of acute exposure to hydrocarbons or H2S such as headaches, dizziness, 

nausea, vomiting, cough, respiratory distress, and chest pain (Solomon and Janssen, 2010).

C.8.3 Employment and Infrastructure

There are no IPFs associated with routine operations that are expected to affect employment 

and infrastructure. The project involves drilling with support from existing shorebase facilities in 

Louisiana. No new or expanded facilities will be constructed, and no new employees are 

expected to move permanently into the area. The project will have a negligible impact on 

socioeconomic conditions such as local employment, existing offshore and coastal infrastructure 

(including major sources of supplies, services, energy, and water), and minority and lower 

income groups. Impacts of a small fuel spill and a large oil spill (WCD) are addressed below.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Noble’s preventative measures during routine 

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

OSRP will potentially mitigate and reduce the potential for impacts. EP Section H provides detail 

on spill response measures. Given the open ocean location of the lease area, the duration of a 

small spill and opportunity for impacts to occur would be very brief.

A small fuel spill that is dissipated within a few days would have little or no economic impact, as 

the spill response would use existing facilities, resources, and personnel.

Impacts of a Large Oil Spill (WCD)

Potential socioeconomic impacts of an oil spill are discussed in recent EISs (MMS, 2007b, 2008). 

For this EP, there are no unique site-specific issues with respect to employment and coastal 

infrastructure. A large spill could cause economic impacts in several ways: it could result in 

extensive fishery closures that put fishermen out of work; it could result in temporary 

employment as part of the response effort; it could result in adverse publicity that affects 

employment in coastal recreation and tourism industries; and it could result in another 

suspension of OCS drilling activities, including service and support operations that are an 

important part of local economies.

In addition to the analysis presented by MMS (2007b, 2008; BOEMRE, 2011a,b), a recent study 

explored the economic impacts of the Macondo spill on oil and gas industry employment due to 

suspension of deepwater drilling (Inter-Agency Economic Report, 2010). The study indicates

that during the moratorium, the number of oil industry workers in the Gulf of Mexico fell by 

about 2,000 and may have indirectly caused a temporary loss of 8,000 to 12,000 jobs along the 

Gulf Coast. Total spending by drilling operators is estimated to have declined by $1.8 billion 

over a 6-month period; this direct reduction in spending affected employment in the industries 

that supply the Gulf drilling industry and in all other industries affected by declines in consumer 

and business spending (Inter-Agency Economic Report, 2010). 
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C.8.4 Recreation and Tourism

BOEMRE has reexamined the analyses for recreation and tourism presented in MMS (2007b, 

2008) based on additional information and in consideration of the Macondo oil spill event. 

No new information was found that would alter the potential impacts on recreation and tourism 

(BOEMRE, 2011a,b).

There are no known recreational uses of the lease area. Recreational resources and tourism in 

coastal areas would not be affected by any routine activities due to the distance from shore. 

Compliance with NTL 2007-G03 will minimize the chance of trash or debris being lost overboard 

from the drilling rig and subsequently washing up on beaches.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Noble’s preventative measures during routine 

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

OSRP will potentially help mitigate and reduce the potential for impacts. EP Section H provides 

detail on spill response measures. Given the open ocean location of the lease area, the duration 

of a small spill and opportunity for impacts to occur would be very brief.

A small fuel spill in the lease area would be unlikely to affect recreation and tourism. There are 

no known recreational or tourism activities occurring in the lease area, and as explained in 

Section A.9.2, a small fuel spill would not be expected to make landfall or reach coastal waters 

prior to breaking up.

Impacts of a Large Oil Spill (WCD)

Potential impacts of an oil spill on recreation and tourism are discussed in recent EISs 

(MMS, 2007b, 2008, BOEMRE 2011a,b). For this EP, there are no unique site-specific issues with 

respect to these impacts.

Impacts on recreation and tourism would vary depending on the duration of the spill and its fate 

including the effectiveness of response measures. A large spill that reached coastal waters and 

shorelines could adversely affect recreation and tourism by contaminating beaches and 

wetlands, resulting in negative publicity that encourages people to stay away.

In addition to the analysis presented by MMS (2007b, 2008), recent and ongoing studies have 

explored the economic impacts of the Macondo spill including tourism and “brand” damage 

(IEM, 2010; Oxford Economics, 2010). The U.S. Travel Association has estimated the economic 

impact of the Macondo spill on tourism across the Gulf Coast over a 3-year period at 

$22.7 billion (Oxford Economics, 2010). 

C.8.5 Land Use

Land use along the northern Gulf Coast is discussed in recent lease sale EISs (MMS, 2007b, 

2008). There are no routine IPFs potentially affecting land use. The project will use existing 

onshore support facilities in Louisiana. The land use at the existing shorebase sites is industrial. 

The project will not involve any new construction or changes to existing land use and, therefore, 

will not have any impacts. Levels of boat and helicopter traffic, as well as demand for goods and 

services including scarce coastal resources, will represent a small fraction of the level of activity 

occurring at the shorebases. 
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A large oil spill (WCD) is the only relevant IPF. A small fuel spill would not have any impacts on 

land use, as the response would be staged out of existing shorebases and facilities.

Impacts of a Large Oil Spill (WCD)

The initial response for a large oil spill would be staged out of existing facilities, with no effect on 

land use. A large spill could have limited temporary impacts on land use along the coast if 

additional staging areas were needed. For example, during the Macondo spill, temporary 

staging areas were established in Louisiana, Mississippi, Alabama, and Florida for spill response 

and cleanup efforts. In the event of a large spill in the lease area, similar temporary staging 

areas could be established (see EP Section H). These areas would eventually return to their 

original use as the response is demobilized.

C.8.6 Other Marine Uses

The lease area is not located within any USCG-designated fairway or shipping lane, but it is 

located within the W-92 Military Warning Area. Noble will coordinate with the Air Armament 

Center to control electromagnetic emissions during operations and will comply with all BOEM

requirements and lease stipulations to avoid impacts on uses of the area by military vessels and 

aircraft.

There are two existing wells near the proposed wellsites, one in east-central GC 723 and 

one in northern GC 767. There are no wells, pipelines or flowlines, or other subsea facilities 

within 609 m (2,000 ft) of the wellsites in GC 679 and 723. There are no other known marine 

uses of the lease area.

There are no IPFs from routine project activities that are likely to affect other marine uses of the 

lease area. A large oil spill (WCD) is the only relevant accident IPF. A small fuel spill would not 

have any impacts on other marine uses, as spill response activities would be mainly within the 

lease area and the duration would be brief.

Impacts of a Large Oil Spill (WCD)

An accidental spill would be unlikely to significantly affect shipping or other marine uses. The 

blocks are not located within any USCG-designated fairway or shipping lane or Military Warning 

Area. In the event of a large spill requiring numerous response vessels, coordination would be 

required to manage the vessel traffic for safe operations. Noble will comply with BOEM

requirements and lease stipulations to avoid impacts on uses of the area by military vessels and 

aircraft.

In the event of a large spill requiring numerous vessels in the area, coordination would be 

required to ensure that no anchoring or seafloor-disturbing activities occur near the existing 

pipelines and flowlines.
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D. Environmental Hazards

D.1 Geologic Hazards

The shallow hazards assessment by B-Geo (2011) concluded that the wellsites are free of any 

significant geological hazards and are suitable for the proposed activities. See EP Section C for 

supporting geological and geophysical information.

D.2 Severe Weather

Under most circumstances, weather is not expected to have any effect on the proposed 

activities. Extreme weather, including high winds, strong currents, and large waves, was 

considered in the design criteria for the drilling rig under consideration for this project. 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 any effect on the proposed activities. Strong currents (e.g., caused by Loop Current eddies 

and intrusions) and large waves were considered in the design criteria for the drilling rig under 

consideration for this project. High waves during a severe storm could disrupt support activities 

(i.e., vessel and helicopter traffic) and make it necessary to suspend some activities on the 

drilling rig for safety reasons until the storm or weather event passes.

E. Alternatives

No formal alternatives were evaluated in this EIA for an EP. However, various technical and 

operational options, including the location of the wellsites and the selection of a drilling unit, 

were considered by Noble in developing the proposed action.

F. Mitigation Measures

The proposed action includes numerous mitigation measures required by laws, regulations, and 

BOEM lease stipulations and NTLs. The project will comply with all applicable Federal, State, 

and local requirements concerning air pollutant emissions, discharges to water, and solid waste 

disposal. All project activities will be conducted under guidance by Noble’s OSRP and will 

include the measures described in EP Section H. 
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Environmental Impact Analysis for Revised Exploration Plan Page 68 

G. Consultation

No persons or agencies were consulted during the preparation of this EIA.

H. Preparers

The EIA was prepared by CSA International, Inc. Contributors included

• M. John Thompson (Senior Scientist);

• Neal Phillips, Ph.D. (Senior Scientist);

• Luis Lagera, Jr., Ph.D. (Senior Scientist);

• Keith VanGraafeiland (GIS/Remote Sensing Specialist);

• Kristen L. Metzger (Library and Information Services Director); and

• Kim Dunleavy (Technical Editor).

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Aten, L.E. 1983. Indians of the upper Texas coast. New York, NY: Academic Press. 370 pp.

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.

Bélanger, L. and J. Bédard. 1989. Responses of staging Greater Snow Geese to human disturbance. Journal of 

Wildlife Management 53:713-719.

Berger Geosciences, LLC (B-Geo). 2011. Shallow hazards assessment, benthic communities evaluation and 

archaeological resources survey Green Canyon Area Block 679 (Lease No. G21811) and 723 (Lease No. 

G21813) Gulf of Mexico.

Biggs, D.C. and P.H. Ressler. 2000. Water column biology, pp. 141-187. In: Continental Shelf Associates, Inc. 

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Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE). 2010. Federal and academic 

scientists return from deep-sea research cruise in Gulf of Mexico: Scientists observe damage to deep-sea 

corals. Press release dated 4 November 2010. Accessed 28 July 2011. 

http://www.BOEM.gov/ooc/press/2010/press1104a.htm
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Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE). 2011a. Gulf of Mexico OCS Oil 

and Gas Lease Sale: 2011. Central Planning Area Lease Sale 218. Draft Supplemental Environmental Impact 

Statement. U.S. Department of the Interior, Bureau of Ocean Energy Management, Regulation and 

Enforcement Gulf of Mexico OCS Region. OCS EIS/EA BOEMRE 2011-027. 

Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE). 2011b. Gulf of Mexico OCS Oil 

and Gas Lease Sale: 2011. Western Planning Area Lease Sale 218 Final Supplemental Environmental Impact 

Statement. U.S. Department of the Interior, Bureau of Ocean Energy Management, Regulation and 

Enforcement Gulf of Mexico OCS Region. OCS EIS/EA BOEMRE 2011-018. 

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.

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Noble Energy, Inc. Page O-1

Initial Exploration Plan 10/31/2011

Mississippi Canyon 697 & 698 (OCS-G 28021 & 28022)

Section O

Administrative Information

A. Exempted Information Description

The proposed bottom-hole locations of the planned wells have been removed from the public information

copy of the EP as well as any discussions of the target objectives, geologic or geophysical data, and any

interpreted geology.

B. Bibliography

Not applicable.