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 5 th 

### 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 5 th 

### 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.

## P UBLIC 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 (H 2 

### S) 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.

# 723

OCS-G-21813 K

J

H

G

F 6082'528'5756' 6635'4409'

4608'

5124'5364'7400'

6487'

1"=2000' 

### LOCATION PLAT

STAFF 10/2011 

## GREEN CANYON 679, 723 

# 679 OCS-G-21811X=2,280,960'

Y=9,884,160'X=2,296,800'

Y=9,900,000'



# N "F" X= 2,290,718' Y= 9,889,524' Lat. 27 14' 20.69" Lon. 90 59' 53.60" WD 4893'

"G" X= 2,290,313' Y= 9,892,600' 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' Coordinates 

### Public Information

1

1ST1 MD/TVD 32684

MD 30,121', TVD 29,200'

# 723

OCS-G-21813 K

J

H

G

F 6082'528'5756' 6635'4409'

4608'

5124'5364'7400'

6487'

1"=2000' 

### BATHYMETRY PLAT

STAFF 10/2011 

## GREEN CANYON 679, 723 

# 679 OCS-G-21811X=2,280,960'

Y=9,884,160'X=2,296,800'

Y=9,900,000'



# N -5200'

-5100' -5000' -4900' -4800' -4700' -4600' -4400' -4300'

-4300'

-4400'

-4300'

-4400' -4500' -4600' -4500'

25' 

### Public Information

1

1ST1 MD/TVD 32684

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 8100Crossline 10400Crossline 10350Crossline 10300Crossline 10250Crossline 10200Crossline 10150Crossline 10100Crossline 10050Crossline 10000Crossline 9950Crossline 9900 

## 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 

## 1:12,000 Scale: 

# 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 & Easting2,285,000 E2,295,000 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 MexicoProject No. 11

- 04

- 14

BERGER GEOSCIENCES, LLC E- MAIL: beinnovative@b

- geo.com WEBSITE: b

- geo.com 

### i 

## 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 Spect rum 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 Prop osed 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

............................................................................................................ 25Project No. 11

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### ii 

## 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
Fi gure 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 t ophole 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-KProject No. 11

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### 1 

## 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 potenti al 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

NEGLIGIBLEProject No. 11

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### 2 **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 anomalou s 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.** Th e 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

NEGLIGIBLEProject No. 11

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### 3 **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 1 5 ,US Survey ft Geographi c Coordinates

X Y Latitude Longitude

2,290,718.00 9,889,524.00 27° 1 4 ' 20.689 " -90 ° 59 ' 53.603 "

Block Calls 3- D Seismic Line Reference

Inline Crossline

6,082 .00' F EL 5,364 .00' FSL 8080 10195

Table W -1

. Location, block calls, and seismic lines for p roposed well GC 723 -F


### Power Spectrum Analysis

The power spectrum for the proposed well was derived through the use of Seismic Micro

Technology’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 -FProject No. 11

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### 4 **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 south east at 4.0° ( Figure 1-4 ).

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

Benthic Communities. T here 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, 30 0 ft west -sou thwest 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 ben thic 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, 201 1a ). The nearest existing well is in
east -central GC 723, approximately 5,51 0 ft east -northeast of the propose d 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 ( Fugr o, 2011) over the block s 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 wi thin 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 1,46 0 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 le ss than 10 ft long by less than 5 ft wide, and do not have any heightProject No. 11

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### 5 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 othe r 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 dri lling activities

.
**Wellbore Location**

**Stratigraphy.** Horizons 1, 2, 3, 4, 6, and 7 w ere 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 th at 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 r eflectors representing clay

dominated turbidites that are about 248 ft thick. The middle unit contains low- to moderate

amplitude, 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 fine

grained 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 th an 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).Project No. 11

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### 6 Horizon 2 to Horizon 3 . The sequence between Horizons 2 and 3 contains low- amplitude, discontin uous 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 h ydrates 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 b s l ( 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 p otential 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
uppe r 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 c oarse

- grained turbidites. The lower unit contains low

- amplitude, parallel reflectors representing clay

dominated 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 b m l ( 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 negli gible 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 fine

grained turbidites interbedded with sand

- prone mass transport deposit s . 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 sand

prone 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 ( Figu re 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 wit hin this sequence from Horizon 6 (1,796 ft bml )Project No. 11

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### 7 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

- ampl itude, parallel reflectors and low - to moderate -amplitude, chaotic reflectors ( Figure W -2 ). The low

- amplitude , parallel reflectors represent clay

dominated turbidites . The more chaoti c reflectors probably represent mass transport deposit s 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 interse ct 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.Project No. 11

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### 8 **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 t he 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 1 5 ,US Survey ft Geographic Coordinates

X Y Latitude Longitude

2,290,313 .00 9,892,600 .00 2 7° 14' 51.208" -90 ° 59 ' 57.544 "

Block Calls 3- D Seismic Line Reference

Inline Crossline

6,487 .00' FEL 7,400 .00' F NL 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 Micro

Technology’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 -GProject No. 11

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### 9 **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 4,9 18 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 w ell and slopes to the south east at 3.8° ( Figure 1-4 ).

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

Benthic Communities. T here 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. Th ere 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

.

Ga s 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, 201 1a ). 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

- Seab ed Disturbance Survey Mitigation document published by the BOEMRE (2011c). Berger Geosciences reviewed data from the Fugro report (2011). Four sonar contact s were identified within 2,000 ft of the proposed well ( Map 3 -1 ). The closest observed sonar contact is about 565 ft south-south ea st 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 ofProject No. 11

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### 10 these contacts are l ess 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 s eafloor 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 drilli ng activities.

**Wellbore Location**

**Stratigraphy.** Horizons 1, 3, 4, 6, and 7 w ere 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 bet ween 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 clay

dominated turbidites that are about 200 ft thick. The middle unit contains low - to moderate

amplitude, disc ontinuous 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 bm l) . 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)

.Project No. 11

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### 11 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 turb idites. The lower unit is about 195 ft thick at the proposed well. Horizon 4 is a prominent peak reflector encountered
at 5,902 ft b s l ( Figure W-3 ; Map 1-8 ).

There is a low poten tial 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 pot ential 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 un it 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, represen ts 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 propo sed well. Horizon 6 is a peak reflector that represents an erosional surface at the proposed well is encountered at 1, 650 ft bm l ( Figure W-3 ; Map 1-9 ).

There is a low potential fo r 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 potentia l 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 fine

grained turbidites interbedded with s and

- prone mass transport deposit s . 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 repre sent the sand

prone 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 -northwe st of the proposed well ( Figure W -3 ; Map 1 -4 ). This anomaly is within the sand

- prone mass transport deposits wi thin 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 BGHSZProject No. 11

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### 12 (2, 077 ft bml) and the base of this sequ ence (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 f or shallow gas from the basal unit ( 2, 241 ft to 2,6 22 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 n egligible 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 clay

dominated 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 ).Project No. 11

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### 13 **Proposed Well GC 723**  **-H**

The seafloor assessment considers s eafloor 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 1 5 ,US Survey ft Geographic Coordinates

X Y Latitude Longitude

2,29 1, 676.00 9,89 4, 244.00 27° 1 5 ' 07.269 " -90 ° 59 ' 42.154 "

Block Calls 3- D Seismic Line Reference

Inline Crossline

5,124 .00' FEL 5 ,756 .00' F NL 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 Micro

Technology’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 -HProject No. 11

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### 14 **Maximum Anchor Radius** 

Noble anticipate s 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 4,9 48 ft bsl ( Map W -3 ). The water depth at the proposed well is 4,841 ft b sl. 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° ( F igure 1-4 ).

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

Benthic Communities. T here 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 pr oposed 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, 201 1a ). The n earest 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).

Ber ger 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 we ll 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 anyProject No. 11

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### 15 height above the seafloor. All three sonar contacts have been interpreted to be small debris targets th at 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 anom alous 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 haza rds 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 w ere interpreted at proposed well GC 723 -H . A generalized description of the stratigrap hic 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 seafl oor 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 clay

dominated turbidites that are about 268 ft thick. The middle unit contains low - to moderate

amplitude, discontinuous reflectors that represent channelized basin fill deposits of silts an d isolated sands. The middle unit is about 136 ft thick at the proposed well. The basal unitconsists 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 -southwe st 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 (2 18 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 forProject No. 11

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### 16 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 -dominat ed 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

- amplitu de, 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 b s l ( Figure W-4 ; Map 1-8 ).

There is a low potential for gas hydrates within this seque nce. 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 consi sts 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 b m l ( Figure W-4 ; Map 1-9 ).

There is a low potential for gas hydrates within this sequence. There i s 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, 9 50 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 fine

grained turbidites interbedded with sand

- prone mass transport deposit s . 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 sand

prone 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.Project No. 11

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### 17 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 pote ntial for shallow gas from the upper unit (1, 9 50 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 ( Fi gure W -4 ). The low

- amplitude, parallel reflectors represent clay

dominated turbidites. The more chaotic reflectors probably represent mass transport deposits containing silts, clays, and isolated sand lenses. Salt is not present beneath the proposed we ll 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 propo sed well GC 723

- H will not intersect any apparent faults within the investigation limit ( Figure W-4 ).Project No. 11

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### 18 **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 1 5 ,US Survey ft Geographic Coordinates

X Y Latitude Longitude

2,29 2, 192.00 9,8 95
, 591.00 27° 1 5 ' 20.524 " -90 ° 59 ' 36.199 "

Block Calls 3- D Seismic Line Reference

Inline Crossline

4,608 .00' FEL 4,409 .00' F NL 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 Micro

Technology’s trace calculations amplitude spectrum tool . The frequency content appears to

mee t 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 -JProject No. 11

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### 19 **Maximum Anchor Radius** 

Noble anticipates using a dynamically positioned (DP) MODU at this lo cation ; 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 de pths within the muds and cuttings discharge area for the proposed well range from 4,729 ft to 4,9 42 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 east

southeast at 3.1° ( Figure 1-4 ).

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

Benthic Communities. T here 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. T here are no pipelines or other apparent man

- made features within 2,000 ft of the proposed well ( Map W -2 ; BOEMRE, 201 1a ). The nearest existing well is in
east -central GC 723, approximately 5,100 ft southeast of the propose d 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 ( Fugr o, 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 with in 2,000 ft of the proposed well ( Map 3 -1 ). The closest observed sonar contact is about 1,125 ft sou thwest 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 ContactProject No. 11

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### 20 260 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 20 08- 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 det ectable 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 w ere 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 clay

dominated turbidites that are about 262 ft thick. The middle unit contains low - to moderate

amplitude, 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 unitconsists 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.

Th ere 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)

.Project No. 11

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### 21 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 negli gible 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 reflector s 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 b s l ( Figure W-5 ; Map 1-8 ).

There is a low potential for gas hydrates within this sequence. There is a low potent ial 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 bm l) . 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

- amplit ude, 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 surfac e at the proposed well is encountered at 2,017 ft b m l ( Figure W-5 ; Map 1-9 ).

There is a low potential for gas hydrates within this sequence. There is a low potential for shallow g as 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 1,7 71 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 fine

grained turbidites interbedded with sand

- prone mass transport deposit s . 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 sand

prone 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 ( Figur e 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 with in this sequence from Horizon 6 (2,017 ft bml )Project No. 11

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### 22 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 clay

dominated 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 inte rsect any apparent faults within the investigation limit ( Figure W-5 ).Project No. 11

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### 23 **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 1 5 ,US Survey ft Geographic Coordinates

X Y Latitude Longitude

2,290, 165.00 9, 900
, 528.00 27° 1 6 ' 09.726 " -90 ° 59 ' 57. 778 "

Block Calls 3- D Seismic Line Reference

Inline Crossline

6,635 .00' FEL 528 .00' F SL 8248 10182

Table W -5

. Location, block calls, and seismic lines for prop osed well GC 679 -K


### Power Spectrum Analysis

The power spectrum for the proposed well was derived through the use of Seismic Micro

Technology’s trace calculations amplitude spectrum tool . The frequency content appears to meet or exceed the minimum 50 Hz wit hin the upper 1.0 second below the seafloor set forth in NTL No. 2008-G04 (MMS, 2008a).

Power spectrum at proposed well GC 679 -KProject No. 11

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### 24 **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 burie d 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. T here 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, 201 1a ). 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 resourc e 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 contact s were identified within 2,000 ft of the proposed well ( Map 3 -1 ). The closest observed sonar contact is about 739 ft e ast 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 Contact s 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 ofProject No. 11

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### 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 seaf loor. 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 w ere inte rpreted 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 sequ ence. 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 clay

dominated 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
seque nce. 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
sequen ce

.
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 isProject No. 11

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### 26 about 94 ft thick at the proposed well. Horizon 4 is a prominent peak reflector encountered at 5, 597 ft b s l ( Figure W-6 ; Map 1-8 ).

There is a low pot ential 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 pot ential for SWF from the upper unit (722 ft bml to 8 46 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 3 89 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 coar se

- 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 b m l ( Figure W-6 ; Map 1-9 ).

The nearest subsurface amplitude anomaly to the proposed well occurs within this sequence,
ap proximately 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 pote ntial 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 ) . Th ere 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 fine

grained turbidites interbedded with sand

- prone mass transport deposi ts . 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 sand

prone 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 shallo w 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

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### 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 clay

dominated 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 , 5 0 0 4 , 7 0 0

4 , 8 0 0 4 , 9 0 0

5 , 0 0 0 5 , 1 0 0 5 , 1 0 0GREENCANYONAREA4 , 8 0 0 5 , 0 0 0

5 , 1 0 0GREENCANYONAREA4 , 5 0 0 4 , 6 0 0 4 , 8 0 0

4 , 9 0 0 5 , 0 0 0 5 , 1 0 0GREENCANYONAREA4 , 5 0 0 4 , 8 0 0GREENCANYONAREAGREENCANYONAREAFigure W-1GC 679 & 723Seafloor rendering of seafloor assessment area1 MILEExisting4,1724,2504,7505,0005,2505,5005,623Seafloor assessment areaProposed wellCircle represents 2,000’radius around well (perNTL 2009-G40)Subsurface study areaWellsGreen CanyonBathymetry (ft)4,500RelictSlumpsGC723-HGC723-FGC 679GC 723GC679-KGC723-GG24182#1G21813#1GC679-JExpulsionMounds

### 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 H 2 

### S 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 H 2 

### S 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 Answe r 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 discharge

25% 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 = 3400D 2/3 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 H 2 S 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 Amounts 1 (tons) Calculated

Exemption Amounts 2 (tons) Calculated

Complex Total Emission Amounts 3 (tons) Carbon Monoxide (CO) 264.47 82717.95 264.47 Particular matter (PM) 35.26 3996.00 35.26 Sulphur dioxide (SO 2 ) 161.77 3996.00 161.77 Nitrogen oxides (NO x ) 1212.17 3996.00 1212.17 Volatile organic compounds (VOC) 36.37 3996.00 36.37

1 For activities proposed in your EP, list the projected emissions calculated from the worksheets.

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

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

### 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 todeploy 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 ourregional 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 Mana gement Act analysis, the largest spill volume originating from the proposed activity would be a well bl owout 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 BS EE 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% proba bility of impact to the s horelines of Cameron Parish, Louisiana within 30 days. Cameron Parish includes the east side of Sabine Lake, Sabine National Wildlife Refuge, Calcasieu Lake, Lacassine Nationa l 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 habita t for numerous birds, finf ish and other animals, including several rare, threat ened 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 e quipment under contract to contain and recover the Worst Case Discharge is shown in Figure 2.

Using the estimated chemical and physical charact eristics of crude oil, an ADIOS weathering model was run on a similar product from the ADIO S oil database. The results indicate 14% or approximately 34,867 barrels of crude oil would be evapor ated/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 sp ill of approximately 214,185 barrels. The volume accounts for the amount remaining after evaporatio n/dispersion at 24 hours. The list estimates

### Page 2 of 18 individual times needed for proc urement, 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. St rategies will be decided by Unified Command based on size of the spill, weather and potential impacts. If aerial dispersants are util ized, 8 sorties (9,600 gallons) from two of the DC-3 aircraft s and 4 sorties (8,000 gallons) from the Basler aircraft would provide a daily dispersant capab ility of 7,540 barrels. If the condi tions 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 imme diately called out and on-scene as soon as possible. Offshore response strategies may in clude 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, Te xas 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. Tempor ary storage associated with skimming equipment equals 274,300 barrels. If additiona l 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 barg e 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 monito ring will be accomplished and operations deemed safe prior to any containment/skimming attempts.

If the spill went unabated, s horeline impact in Cameron Pa rish, Louisiana would depend upon existing environmental conditions. Shoreline pr otection would include the use of CGA’s and MSRC’s near shore and shallow water skimmers w ith a totaled derated skimming capacity of 75,854 barrels. Temporary storage associated with skimming equipment e quals 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 ac cess to 30,000 feet of 18 ” shoreline protection boom. Figure 2 outlines individual times needed for procur ement, load out, travel time to the site and deployment. Strategies w ould be based upon surveillance an d real time trajectories that depict areas of potential impact given actual s ea 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 co rrectly identified and prioritized to ensure optimal protection. Shorel ine 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 deploym ent and operation of equipment allowing a more effective response to site-specific circumst ances. Noble Energy, Inc.’s contract Spill Management Team holds a copy of the State of Louisiana Initial O il 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 quick ly 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 environmenta lly 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 agen cies 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 situa tion and coordinated objectives

o Areas of responsibility esta blished for Source Control a nd each surface operational site

o On-site command and control established

Offshore Response Actions

Equipment Deployment Surveillance

• Surveillance Aircraft: within two hours of QI notificati on, or at first light

• Provide trained observer to pr ovide on site status reports

• Provide command and control platfo rm at the site if needed

• Continual surveillance of oil movement by remote sensing systems, aerial photography and visual confirm ation

• 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 determin e 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, ai rcraft, and support equipment and personnel

• Confirm dispersant availability fo r current and long range operations

• Start ordering dispersa nt 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 aer ial 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 boa t 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 ski mming assets to minimize offloading time

Vessels of Opportunity (VOO)

• Use Noble Energy, Inc.’s contract ed 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 sa fety training to be required

• Plan with the US Coast Guard for vessel inspections

In-situ Burn assets

• Determine appropriateness of in-situ burn ope ration 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 deploym ent 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 Re sponse Team level (Region 6)

Vessel Deployment Dedicated Near Shore skimming systems

• FRVs

• Egmopol and Marco SWS

• Operate with aerial spotter directi ng systems to observed oil slicks

VOO

• Use Noble Energy, Inc.’s contract ed 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 sa fety training to be required

• Plan with the US Coast Guard for vessel inspections

• Operate with aerial spotter d irecting 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 eq uipment and their availability

• Previous contingency planning contained in the appropriate Area Contingency Plan, and currently for Louisiana, The State of Loui siana 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 site s 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 respons e personnel as close to the job site as possible to maximize on-site work time

• Boom tending, repair, replacement and security (u se of local assets may be advantageous)

• Constant awareness of weather and oil moveme nt 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 se parate into distinct phases when left in a quiescent state. When separati on occurs, the relatively clean water phase can be siphoned or decanted back to the recovery point with minima l, if any, impact. Decan ting therefore increases the effective on-site oil storage capacity a nd 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 rela tion 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 a nd/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 opera tions ceased when seas reache d 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 wint er and easterly winds in the summer. Average wind speed is generally 14-15 mph along the coast. Wave he ights 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 temperatur e will range from 50 and 60  ̊ F.

The Atlantic and Gulf of Mexico hurricane seas on is officially from 1 June to 30 November. 97% of all tropical activity occurs within this window. The Atlant ic 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 occurri ng then. Maximum activity is in early to mid September. Once in a few years there may be a hurri cane occurring "out of season" - primarily in May or December. Globally, September is the mo st 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 inform ation in the BSEE Oil Spill Risk Analysis Model (OSRAM) for the Central and Western Gulf of Mexico av ailable 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 2Page 12 of 18WCD Scenario– BASED ON WELL BLOWOUT DURING DRILLING OPERATIONS(120 miles from shore)214,185 bbls of crude oil (Volume considering natural weathering)API Gravity 28.4°FIGURE 2 – Equipment ResponseTime to GC 723, Location HDispersants/SurveillanceDispersant/SurveillanceDispersantCapacity (gal)StorageCapacityPersonsReq.FromHrs toProcureHrs toLoadoutTravel tositeTotal HrsCGABasler 67T2000NA 2 Houma 1 1 0.82.8ASIDC 31200NA 2 Houma 1 1 1.13.1DC 31200NA 2 Houma 1 1 1.13.1Aero CommanderNANA 2 Houma 1 1 0.82.8Offshore ResponseOffshore Equipment NoStagingEDRCStorageCapacityVOOPersonsRequiredFromHrs toProcureHrs toLoadoutHrs toGOMTravel toSpill SiteHrs toDeployTotalHrsCGAHOSS Barge43000 4000 3 Tugs 8Harvey7 0 8 15 1 31T&T Marine Services LLC (available through contract with CGA)Koseq Skimming Arms (3) 53487 6000 3 Utility 18 Leeville 4 12 2 11.5 2 31.5Koseq Skimming Arms (2) 35658 4000 2 Utility 12Venice4 12 2 13.3 2 33.3Koseq Skimming Arms (1) 17829 2000 1 Utility 6 Fourchon 4 12 2 11.5 2 31.5Koseq Skimming Arms (5) 89145 10000 5 Utility 30 Galveston 4 12 2 22.5 2 42.5K-Sea Operating (available through contract with CGA)Pacific 996165NA 80000 1 Tug 6Houma4 12 2 15 1 34Enterprise Marine Services LLC (available through contract with CGA)CTCo 2603NA 25000 1 Tug 6Amelia4 12 4 17.5 1 38.5CTCo 2606NA 20000 1 Tug 6Amelia4 12 4 17.5 1 38.5CTCo 2607NA 23000 1 Tug 6Amelia4 12 4 17.5 1 38.5CTCo 2608NA 23000 1 Tug 6Amelia4 12 4 17.5 1 38.5CTCo 2609NA 23000 1 Tug 6Amelia4 12 4 17.5 1 38.5CTCo 5001NA 47000 1 Tug 6Amelia4 12 4 17.5 1 38.5Page 13 of 18Offshore Equipment NoStagingEDRCStorageCapacityVOOPersonsRequiredFromHrs toProcureHrs toLoadoutHrs toGOMTravel toSpill SiteHrs toDeployTotalHrsMSRCMSRC Lightning +(2)LORI Brush Pack5000 50 NA 4 Tampa 2 0 1 20.4 1 24.4MSRC 360 Offshore Barge1 Crucial Disk 88/301,540’ 44” Sea SentryII Boom11122 36000 3 Tugs 6 Tampa 2 0 1 72.9 1 76.9Mississippi ResponderTransrec 350 + OSRV2,625’ 44” Sea SentryII Boom10567 4000 NA 14 Pascagoula 2 0 1 10.4 1 14.4MSRC 402 Offshore Barge2 Crucial Disk 88/30330’ 44” Sea SentryII Boom22244 40300 3 Tugs 6 Pascagoula 2 0 1 37.1 1 41.1Louisiana ResponderTransrec 350 + OSRV2,640’ 44” Sea SentryII Boom10567 4000 NA 14 Fort Jackson 2 0 1 6.4 1 10.4MSRC 452 Offshore Barge2 Crucial Disk 88/30660’ 44” Sea SentryII Boom22244 45000 3 Tugs 6 Fort Jackson 2 0 2 22.8 1 27.8Deep Blue ResponderTransrec 350 + OSRV2,640’ 44” Sea SentryII Boom10567 4000 NA 14 Fourchon 2 0 1 5.5 1 9.5Gulf Coast ResponderTransrec 350 + OSRV2,640’ 44” Sea SentryII Boom10567 4000 NA 14 Lake Charles 2 0 3.5 8.8 1 15.3Texas ResponderTransrec 350 + OSRV2,640’44” Sea SentryII Boom10567 4000 NA 14 Galveston 2 0 1 10.8 1 14.8MSRC 570 Offshore Barge2 Crucial Disk 88/30770’ 44” Sea SentryII Boom22244 56900 3 Tugs 6 Galveston 2 0 1 38.6 1 42.6MSRC Quick Strike +(2)LORI Brush Pack5000 50 NA 4 Ingleside 2 0 1 14.8 1 18.8Southern ResponderTransrec 350 + OSRV2,970’ 44” Sea SentryII Boom10567 4000 NA 14 Ingleside 2 0 1 14.8 1 18.8MSRC 403 Offshore Barge1 Crucial Disk 88/30770’ 44” Sea SentryII Boom11122 40300 3 Tugs 6 Ingleside 2 0 1 52.9 1 56.9Page 14 of 18Staging Area: FourchonOffshore Equipment WithStagingEDRCStorageCapacityVOOPersonsReq.FromHrs toProcureHrs toLoadoutTravel toStagingTravel toSiteHrs toDeployTotalHrsCGAFRU (1) + 100 bbl Tank (2) 3770 200 1 Utility 6 Belle Chasse 1 22.5 11.5 1 18FRU (1) + 100 bbl Tank (2) 3770 200 1 Utility 6Galveston 1 27 11.5 1 22.5FRU (3) + 100 bbl Tank (5) 11310 500 1 Utility 6Houma1 21 11.5 1 16.5FRU (1) + 100 bbl Tank (2) 3770 200 1 Utility 6Ingleside1 29.5 11.5 1 25FRU (1) + 100 bbl Tank (2) 3770 200 1 Utility 6 Lake Charles 1 24 11.5 1 19.5FRU (2) + 100 bbl Tank (4) 7540 400 1 Utility 6Venice1 24 11.5 1 19.5T&T Marine Services LLC (available through contract with CGA)Aqua Guard Triton RBS (2) 45560 4000 2 Utility 12 Galveston 4 127 11.5 2 36.5Page 15 of 18Offshore Equipment WithStagingEDRCStorageCapacityVOOPersonsReq.FromHrs toProcureHrs toLoadoutTravel toStagingTravel toSiteHrs toDeployTotalHrsCGA42” Auto Boom (5000’)NA NA 10 Crew20 Belle Chasse 1 2 2.5 11.5 1 18.042” Auto Boom (5000’)NA NA 10 Crew 20 Galveston 1 27 11.5 1 22.542” Auto Boom (5000’)NA NA 10 Crew 20Houma1 21 11.5 1 16.542” Auto Boom (2500’)NA NA 6 Crew 12 Ingleside 1 2 9.5 11.5 1 25.042” Auto Boom (5000’)NA NA 10 Crew 20 Lake Charles 1 24 11.5 1 19.542” Auto Boom (2500’)NA NA 6 Crew 12 Pascagoula 1 24 11.5 1 19.51000’ Hydro-Fire BoomNA NA 8 Utility 20Harvey1 4 2.75 11.5 6 25.25MSRC44” Sea Sentry II Boom(2860’)NA NA 6 Crew 12 Ingleside 1 2 9.5 11.5 1 2544” Sea Sentry II Boom(4290’)NA NA 10 Crew 20 Galveston 1 2 7 11.5 1 22.544” Sea Sentry II Boom(6679’)NA NA 10 Crew 20 Lake Charles 1 2 4 11.5 1 19.544” Sea Sentry II Boom(1980’)NA NA 6 Crew 12 Fort Jackson 1 2 2.5 11.5 1 1844” Sea Sentry II Boom(3190’)NA NA 10 Crew 20 Pascagoula 1 2 4 11.5 1 19.51500’ Hydro-Fire BoomNA NA 12 Utility 60 Lake Charles 1 44 11.5 6 26.5Page 16 of 18Nearshore ResponseNearshore Equipment NoStagingEDRCStorageCapacityVOOPersonsRequiredFromHrs toProcureHrs toLoadoutHrs toGOMTravel toSiteHrs toDeployTotalHrsCGA46’ FRV5000 65 NA 4 Houma 1 0 2 2.8 0 5.846’ FRV5000 65 NA 4 Venice 1 0 1 2 0 446’ FRV5000 65 NA 4 Lake Charles 1 0 1 9.6 0 11.646’ FRV5000 65 NA 4 Galveston 0 0 1 13.2 0 14.2Enterprise Marine Services LLC (available through contract with CGA)CTCo 2604NA 20000 1 Tug 6Amelia4 12 4 25.63 1 46.63K-Sea Operating (available through contract with CGA)DBL 82 1137538NA 86948 1 Tug 6Venice4 12 2 9.38 1 28.38Staging Area: CameronNearshore Equipment With Staging EDRCStorageCapacityVOOPersonsReq.FromHrs toProcureHrs toLoad OutTravel toStagingTravel toDeploymentHrs toDeployTotalHrsCGASWS Egmopol3000 100 NA 3 Galveston 1 2 3.52 0 8.5SWS Egmopol3000 100 NA 3 Houma 1 2 4 2 0 9SWS Marco3588 34 NA 3 Venice 1 2 6.25 2 0 11.25SWS Marco3588 34 NA 3Houma1 242 0 9SWS Marco3588 20 NA 3 Lake Charles 1 212 0 6Foilex Skim Package (TDS 150)891 45 NA 3 Lake Charles 1 212 0 6Foilex Skim Package (TDS 150)891 45 NA 3Houma1 242 0 94 Drum Skimmer (Magnum 100)686 NA NA 3 Lake Charles 1 212 0 64 Drum Skimmer (Magnum 100)686 NA NA 3Houma1 242 0 92 Drum Skimmer (TDS 118)240 NA NA 3 Lake Charles 1 212 0 62 Drum Skimmer (TDS 118)240 NA NA 3Houma1 242 0 9Rope Mop77 2 0 3 Belle Chasse 1 2 4.52 0 9.5RO Storage BargeNA 249 Towed 0 Galveston 1 2 3.52 0 8.5RO Storage BargeNA 249 Towed 0Houma1 242 0 9RO Storage BargeNA 249 Towed 0 Lake Charles 1 212 0 6RO Storage BargeNA 249 Towed 0Venice1 2 6.252 0 11.25Page 17 of 18Staging Area: CameronNearshore Equipment WithStagingEDRCStorageCapacityVOOPersonsReq.FromHrs toProcureHrs toLoad OutTravel toStagingTravel toDeploymentHrs toDeployTotalHrsMSRCGT 185 with Adaptor (1)1371 400 1 Utility 3 Ingleside 2 .562 .5 11GT 185 with Adaptor (2)2742 800 2 Utility 6 Galveston 2 .5 3.52 .5 8.5GT 185 with Adaptor (1)1371 400 1 Utility 3 Port Arthur 2 .5 1.252 .5 6.25GT 185 with Adaptor (1)1371 400 1 Utility 3 Baton Rouge 2 .532 .5 8GT 185 with Adaptor (1)1371 400 1 Utility 3 Fort Jackson 2 .5 4.52 .5 9.5GT 185 with Adaptor (1)1371 400 1 Utility 3 Pascagoula 2 .5 5.52 .5 10.5Foilex 250 Skimmer3977 400 1 Crew 3 Fort Jackson 2 .5 4.52 .5 9.5Foilex 250 Skimmer3977 100 1 Crew 3 Lake Charles 2 .512 .5 6Foilex 250 Skimmer3977 100 1 Crew 3 Galveston 2 .5 3.52 .5 8.5Foilex 250 Skimmer3977 100 1 Crew 3 Ingleside 2 .562 .5 11WP-1 Skimmer3017 NA 1 Utility 3 Ingleside 2 .562 .5 11WP-1 Skimmer3017 NA 1 Utility 3 Pascagoula 2 .5 5.52 .5 10.5Aardvac 800 Skimmer3840 NA NA 3 Pascagoula 2 .5 5.52 .5 10.5Page 18 of 18Shoreline ProtectionStaging Area: CameronShorelineProtection BoomVOOPersonsReq.Storage/WarehouseLocationHrs toProcureHrs toLoadoutTravel toStagingTravel toDeployment SiteHrs toDeployTotal HrsOil Mop (available through MSA)10,000’ 18” Boom 4 10New Iberia1 1 2.5239.510,000’ 18” Boom 4 10Houston1 1 2.5239.510,000 18” Boom 4 10Port Arthur1 1 1.25238.25Beach Boom EDRCStorageCapacityVOOPersonsReq.FromHrs toProcureHrs toLoadoutTravel toStagingTravel toDeploymentHrs toDeployTotalHrsCGABeach Boom (2000’) NA NA NA 6 Galveston 1 2 3.512 9.5Beach Boom (1000’) NA NA NA 4 Ingleside 1 2612 12Beach Boom (2000’) NA NA NA 6 Pascagoula 1 2 5.512 11.5Wildlife Response EDRCStorageCapacityVOOPersonsReq.FromHrs toProcureHrs toLoadoutTravel toStagingTravel toDeploymentHrs toDeployTotalHrsCGAWildlife Support Trailer NA NA NA 2Houma1 2412 10Bird Scare Guns (24)NA NA NA 2 Belle Chasse 1 2 4.512 10.5Bird Scare Guns (12)NA NA NA 2 Galveston 1 2 3.512 9.5Bird Scare Guns (24)NA NA NA 2Houma1 2412 10Bird Scare Guns (12)NA NA NA 2 Ingleside 1 2612 12Bird Scare Guns (24)NA NA NA 2 Lake Charles 1 2112 7Bird Scare Guns (24)NA NA NA 2 Pascagoula 1 2 5.512 11.5Response AssetTotalOffshore EDRC (bbls)480,987Offshore Recovered Oil Storage (bbls)515,300Nearshore / Shallow Water EDRC (bbls)75,854Nearshore / 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 67 9 & 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 CANYONCITYINTRACOASTALCITYFRESHWATERCAMERONFOURCHONISLEGRANDVENICE679/723GREEN CANYONOPER. BASE679, 723PublicInformationDistance fromDeep Blue toFourchon(roughy)215 km133 mi116 nmiDistance fromDeep Blue to shore(roughy)194 km120 mi105 nmi

### 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 Housto n, Texas 77067 Telephone : (381) 872

- 3100

Prepared by:

CSA International, Inc. 8502 SW Kansas Avenue

Stuart, Florida 34997 Telephone: (772) 219

- 3000Green Canyon Block s 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 E missions

.................................................................................................................. 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 Ben thic Communities

.................................................................................. 24 C.2.2 High

- Density Deepwater Benthic Communities

.............................................................. 26 C.2.3 Designated Topographic Features

................................................................................... 28 C.2 .4 P innacle 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 Sawfi sh (Endangered)

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

................................................................................................ 45 C.3.11 Elkhorn Coral (Endangered)

............................................................................................. 46

## Contents (C ontinued)

Page

Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page iii C.4 Coastal and Marine Birds

............................................................................................................ 46 C.4.1 Marine B irds

.................................................................................................................... 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

............................................................................................................. 68Green Canyon Blocks 679 and 723 October 2011 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 Estimat ed 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 Co ntinental 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 W ildlife 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

........................ 43Green 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 Be rger Geosciences, LL C BHL bottom hole location BOEM Bureau of Ocean Energy Management BOEMRE Bureau of Ocean Energy Managem ent, Regulation and Enforcement BOP blowout preventer
B.P. Before Present CEI Coastal Environments, Inc. CFR Code of Federal Regulations CGA Clean Gulf Associates CH 4 methane CO carbon monoxide CO 2 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 Anal ysis 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
H 2 S hydrogen s ulfide 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 Miner als 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. NO x nitrogen oxides NPDES Nati onal 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 Sc ientific 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

- ba sed mud SHL su r face hole location SO x 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 c ompound WCD worst case dischargeGreen 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 Block s 679 and 723 (GC 679 and 723) . Noble proposes to drill four exploratory wells in GC 723 and one exploratory we ll 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 En ergy 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 Op erators ( 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 O uter 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 incorpor ated 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. Gul f of Mexico is 0.00593 blowouts per well s 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 start s, or one blowout per 200 well starts ( MMS, 2000 ). More recently in its Draft S upplemental 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, 201 1a ).

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, 200 0 ). 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 Rul e ( 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 Ex ploration 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. T he OSRP detail s 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 respon se 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 F ederal 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.

Th is 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 O perators (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 Infor ms 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 dep loy 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 C ommunities 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.)

Green Canyon Blocks 679 and 723 October 2011 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 Requirement s 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 M ammal 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 Archa eological 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. Impac t- 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 an choring 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). S ound and vibration s 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 Analys is for Revised E xploration P lan Page 6 Table 2. Matrix of impact

- producing factors and affected environmental resources. X = potential impact; dash (

-- ) = no impact or negligible impact.

Environmental Resou rces 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 Smal l 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 bo ttoms

-- -- (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) Endange red 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 (endang ered) 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) E ssential 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 Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan 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 fol lowing: ( 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) l ease; (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 l ease.

• 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 L ive 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 (L ow

- 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 H 2 S concentrations greater than 500 ppm might be encountered.

• Based on CFR 250.490 (c), Noble is requesting that BOEM classify the area as “H 2 S 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 se award 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 Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan 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 t he 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 Sectio n 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 (SO x ), nitrogen oxides (NO x ), 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 con cluded 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 d ischarges will be in complianc e 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 thei r return to the surface is set. Excess cemen t 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, unco ntaminated fresh water and sea water, and ballast water.



## A.5 Water Intake

Seawater will be drawn from the ocean for once

- through, non

- contact cooling of machinery on the drilling rig. Section 316(b) of th e 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 a quatic organisms. The current NPDES General P ermit No. GMG 290000 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 “n ew”Green Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan 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 ea ch 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 regu lations 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 USE PA 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

m arine environment, and 30 CFR 250.300(c) requires durable identification markings on equipment, tools and containers (especially drums), and other material. US EPA and US CG regulations require operators to become proactive in avoiding accidental loss of so lid 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 regulati ons 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 m andates 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

- trip s per week and supply vessel s 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 typic ally 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

.Green Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan Page 10 

## A.9 Accidents

A.9.1 Types of Accidents Evaluated

The analysis in this EIA focuses on two potential accidents:

• a s mall fuel spill, which is the most likely type of spill during OCS exploration activities; and

• t he WCD for this EP, which is an oil spill resulting from an uncontrolled blowout.

The following subsections summarize assumptions about the size s and fate s 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 a nalys e s 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 a nd 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, 2011 a,b ). The average size for spills < 1 bbl is 0.07 bbl, and the median size for spil ls 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 (PAH s ), 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 t o 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 w aters 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, g iven the o pen 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, t he 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. I t 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) dependi ng on sea state and weather conditions.Green Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan Page 11 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 m iles (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 th at 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 shor t- 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 bl owouts 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 I ntroduction , the baseline risk of a catastrophic blowout is estimated to be once every 26 years (BOEMRE Interim Final Drilling Safety Rule
, 75 F R 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 als o comply with NTL 2010 -N 10 and the Interim Final Drilling Safety Rule, which specif ies 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 p eriods 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 th e 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 condit ions 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 Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan 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 proba bilities 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, 2011 a,b ) in order to estimate the impacts of a possible future catas trophic 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 fo r up to 120 days.

The OSRA model run for this analysis was conducted for five hypothetical launch points in the C entral and W estern Gulf of Mexico Planning Areas. These launch point s were deliberately locat ed in area s identified as having a high possibil ity 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 —2 9.91388 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. We stern Gulf of Mexico slope area

— 27.51367 N latitude
, 9 4.51836 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 f rom: BOEMRE, 2011 a,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 Aran sas, 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.)

Green Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan Page 13 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 uncontroll ed 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 hydr ocarbons 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 i n 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 ma tter, and stranding on shore or sedimentation to the seafloor (NRC, 2003).

Spill Response

. The BOEMRE has issued re c ent 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

— Statemen t 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 BOP s on floating facilities. It explains that lessees and operators submit a statement signed by an authorized company official with each application for a well permit indicating that they will conduct all of their authorized activities in compliance with al l 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 :Green Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan 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 supplement al 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 25 0.219(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 ea rly 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 t hat 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

c apabilities 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/nearsh ore

areas. These vessels have o leophilic 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 ( G PS), 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 bar ge. 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 HO SS barge is approximately 43,000 b bl

. 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.Green Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan Page 15 Noble also has a n agreement with the Marine Spill Response Corporation (MSRC) as a secondary spill response equipment provider (s ee 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 us ing 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 vesse ls and support equipment, including:

• 19 o il s pill r esponse b arges with storage capacities between 12,000 and 68,000 bbl ;

• 68 shallow water barges;

• 600,000 f ee t 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 dis persant 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 T heodore, Louisiana.

See EP Section H ( A ttachment H -1 ) f or 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 acciden ts: 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 ( H 2 S) release . T here 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 procedu res. 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 ma jority 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, 2011 a,b ).Green Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan Page 16 Synthetic

- based Fluid Spills

. In deepwater drilling, SBMs a re preferred over petroleum oil

- based muds (OBMs) due to the ir superior e nvironmental properties. S ynthetic

- base d fluid s (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. Betw een 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 no w used to describe spill size. Accidental riser disconnects could result in the release of large quantities of drilling fluids and are of particular concern w hen SB M s are in use (BOEMRE, 2011a,b ).

Vessel Collisions

. BOEMRE data show that from 1996 to 200 9 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 spil ls , 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 collision s

. Human error accounts for approximately half of all reported vessel collisions from 2006 to 2009. As summarized in MMS (2007b ; BOEMRE, 2011 a,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 i njury (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 con duct 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 th e Interim Final Drilling Safety Rule and NTL 2010

- N10 , which specify additional safety measures for OCS activities.

H 2 S Release . Pursuant to 30 CFR 250.490(c), Noble is request ing in the EP that the BOEM Regional Supervisor, Field Operations, classify the area in the proposed drilling operations as "H 2 S absent. " H 2 S is not known or anticipated to occur in the objective Miocene

- age section. H 2 S 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 G C 640 and 727 drilled middle and lower Miocene

- age objective sections also failed to show signs of H 2 S.Green Ca nyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised E xploration P lan Page 17 

## B. Affected Environment

The lease area is in the north

- cen tral 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 Hazard s Assessment, Benthic Communit ies Evaluation, a nd Arch a eological Resources Survey by Berger Geosciences, Inc. (B

- Geo) , w ater depths at the wellsite s 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

s outhwestern 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, socioeconom ic 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, includin g 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 produc ed when subsea dispersants we re 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 t he 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 th e 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. P rior to the Macondo incident, water quality in deep, offshore waters of the Gulf of Mexico was expected to be good, with low levels of co ntaminants (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 s ale EISs (MMS 2007b, 2008; BOEMRE, 2011a, b)

.Green Canyon Blocks 679 and 723 October 2011 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 analy z es the potential direct and indirect impacts of routine activities and accidents. Impacts have be en 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 t hese documents is incorporated by reference. Potential s ite

- 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

s tate 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
po llutants (USEPA, 201 1 ). 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 PM 10 (USEPA, 201 1 ).

Winds in the region are driven by the clockwise circ ulation 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 presente d 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 impact s on air quality presented in recent lease sale EIS s (BOEMRE, 2011 a, 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 m ainly 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, SO x , NO x , VOCs, and CO. Emissions of pollutants into the atmosphere from these activities are not projected toGreen Canyon Blocks 679 and 723 October 2011 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 a ir 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

em issions and the distance of the project from shore, emissions from the activities described in Noble’s propose d EP are not likely to contribute to violations of any NAAQS onshore.

Carbon dioxide (CO 2 ) and methane ( CH 4 ) emissions from the project w ill const itute a small incremental contribution to greenhouse gas emissions from all OCS activities. According to the Programmatic EIS (MMS, 2007a), estimated CO 2 emissions from all OCS activities in the 2007

- 2012 leasing program are about 0.08% to 0.016% of the global CO 2 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 prevail ing 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. Es timated air pollutant emissions in Green Canyon Block s 679 and 723 over the life of th e 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 (SO 2 ) 161.77 3
, 996.00 161.77 Nitrogen oxides (NO x ) 1
, 212.17 3
, 996.00 1
, 212.17 Volatile organic compounds (VOC) 36.37 3,996.00 36.37Green 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 Servic e ( 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 adm inistering agencies (NPS, 2010). The lease area is approximately 185 miles (296 km) from the Breton Wilderness Area
, and air quality impact s on the Wilderness Area are not expected.


### Impacts of a Small Fuel Spill
Potential impacts o f a small spill on air quality are expected to be consistent with th os e 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 operatio ns, 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 )

. Give n 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 mo del ( 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

con ditions.

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 th os e analyzed and discussed in recent lease sale EISs (MMS, 2007b, 2008 ; BOEMRE, 2011 a,b ).

A large oil spill (WCD) could potentially affect air quality by introducing VOCs through evaporation from t he 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 e missions of NO x , SO x , 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 occ ur 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 l ow levels of contaminants. AsGreen 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 l ocated 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 extend ed over the lease area during the s pill

. 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).



### I mpacts of Effluent Discharges
In general, turbid water can be expected to extend between a few hundred meters and several kilometers down c urrent from the discharge point for water

- based drilling muds and cuttings

. SBMs will be collected on the rig and tr ansported 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 (NR C, 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 requir ements and USCG regulations (as applicable) will be met , therefore, l ittle 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 pan s 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 e xposed 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 w ate r quality are expected to be consistent with th os e 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 l ocation of theGreen 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 dies el 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 die sel are dominated by two - and three

- ringed PAH s , 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 a ppreciable 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 ma ke 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 wate r quality are expected to be cons istent with th os e analyzed and discussed in the lease sale EISs (MMS, 2007b, 2008). A large spill w ould affect water quality by producing a slick on the water surface and increasing the concentrations of petroleum hydrocarbons and their degradation produc ts. 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 app lied 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

W ater depths at the proposed SHLs range from 1,272 to 1,714 m (4,1 72 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 ), b enthic or chemosynthetic communities may occur on or near two expulsion mounds in the southwestern quadrant of GC 723 , but t here is no evidence of features that may support chemosynthetic or other benthic communities within 61 0 m ( 2,000 ft ) of any of the pr oposed 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 Slo pe 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 fr om 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

. /m 2 ) Macroi nfau na (no

. /m 2 ) 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 pa ssing 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 1 50,000 to 400,000 individuals/m 2 (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 s mall mean individual size s and low densities
, both of which are a reflection of t he 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/m 2 . However, actual densities are highly variable. Macroinfaunal densities at the stations listed in Table 5 range from 1,700 to 3,045 individuals/m 2

. 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 Zon es 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
, L evinsenia 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 a nd anemones.

B acteria are also an important component in terms of biomass and cycling of organic carbon (Cruz

- Kaegi, 1998). B a cterial biomass at the depth range of the lease area typically is about
1 to 2 g C/m 2 in the top 15 cm of sediments (Rowe and Ken nicutt, 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).

T he areal extent of these impacts from a DP drilling rig will be small compared to the lease area itself, and these type s of s oft bottom communities are ubiqu itous 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 th e project will have no significant impact on soft bottom benthic co mmunities 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 chem icals 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 (Con tinental 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 H 2 S predominate (Continental Shelf Associates, Inc., 2006). As the base synthetic fluid is decompos ed 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 T he 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 represent s about 3% of the seafloor within a lease block. Soft bottom communities are ubiquitous along the northern Gulf of Mexico continental slope ( Gallaway, 1988; Gallaw ay 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 blowo ut on benthic communities would be within a few hundred meters of the wellsite. MMS (2007b) estimate d that a severe subsurface blowout could resuspend and disperse sediments within a 300

- m (984

- ft) radius. While coarse sediments (sands) would probably se ttle 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 assu med to largely be silt and clay ( Rowe and Kennicutt, 2009 ).

Recent lease sale EIS s (MMS, 2007a, 2008) in dicat ed 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 th e 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 f eatures 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 t he 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

- north east of the lease area in GC 287 . The nearest identified deep water cora l communities are in GC 852
, 13 miles ( 22 km) south west 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 poten tially 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 b enthic 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 wel lbore (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).

T he areal extent of these impacts will be small , and NTL 2009

- G40 requires that high

- density deepwater benthic communities and f eatures 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 i mpact 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 p roposed drilling locations, and the presence of chemosynthetic communities in the lease area is considered remote. Mo nitoring programs on the Gulf of Mexico continental slope have shown that benthic impacts from drilling discharges typically are concentra ted 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 no t 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 wellhea d (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), extendi ng 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 persisten ce. 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 theGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 28 source . I ncub ation 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 -w ater 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 oc curs 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 o r 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 sedim ent 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 disea ses).

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 t his 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 n earest designated topographic feature is Ship Shoal South in Ewing Bank ( EW ) Block 94 5 , 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 seaf loor 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 sm all 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 featu res 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 stipu lation, 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 m anatee.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 30 Table 6. Federally listed endangered and thre atened 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 macrocep halus E X

-- None West Indian manatee Trichechus manatus latirostris E

-- X Florida (Peninsular) Blue whale Balaenoptera musculus E X a

-- None Fin whale Balaenoptera physalus E X a

-- None Humpback whale Megaptera novaeangliae E X a

-- None North Atlant ic right whale Eubalaena glacialis E X a

-- None Sei whale Balaenoptera borealis E X a

-- None Sea Turtles

Loggerhead turtle Caretta caretta T X X None Green turtle Chelonia mydas T, E b X X None Leatherback turtle Dermochelys coriacea E X X None Hawksb ill 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 s awfish Pristis pectinata E

-- X Southwest Florida and the Florida Keys Invertebrates

Elkhorn coral Acropora palmata E

-- X Flower Garden Banks Terrestrial Mammals

Beach mice (A labama, Choctawhatchee, Perdido Key, St. Andrew) Peromyscus polionotus E

-- X Alabama and Florida (Panhandle) beaches

Abbreviations: E = e ndanger ed; T = t hreatened.

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 (M MS
, 2007a
, b)

. A B iological A ssessment was prepared for each consultation. The formal ESA consultation with NMFS was concluded with receipt of the Biological Opinion on 3 July 2 007 (NMFS, 2007). The Biological Opinion concludes that the proposed lease sa les 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 de signated 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 reinitiat e an ESA consultation with bothGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 31 NMFS and USFWS on 30 July 2010. The NMFS responded with a letter to B OEMRE on 24 September 2010 , and t he USFWS responded with a letter to BOEMRE on 27 September 2010. At present, the NMFS and US FWS have placed th e 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 remain s 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 Coa st 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 . T hese 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 cerv icornis ), 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 ar ea is the sperm whale ( Physeter macrocephalus )

. Resident populations of s perm 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 wh ales 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
y ear (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 w ere 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 transitGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 32 through the vicinity of the lease area. Movements of satelli te

- 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 sma ll 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

.

C urrent threats to sperm whale popu lations worldwide are discussed in a final recovery plan for the sperm whale recently published by NOAA (NMFS, 2010 a ). Threats are defined as “any factor that could represent an impediment to recovery
, ” and include fisheries interactions, anthropogenic no ise, 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 G ulf of Mexico , the impacts from many of these threats are identified as either low or unknown ( BOEMRE, 2011 a,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 d rilling activities, this project woul d 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 We stern 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 IPF s for sperm whales in recent lease sale EISs (MMS, 2007b, 2008) or the NMFS (2007) Biological Opinion.


### Impacts of Sup port 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 freq uency 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 vi gilant 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 aGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 33 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 w hen 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 . Wi th implementatio n 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

a dvantageous 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 imple mentation 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 h as 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 ot her studies of cetacean responses to sound, the authors concluded that the observed reactions to brief overflights by the air craft were short

- term and probably of no long

- term biological significance.

W hile flying offshore in the Gulf of Mexico , helicopte rs 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 wh ales 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 a nimals 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 effectivene ss of spill response measures. Section A.9.2 discusses the likely fateGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 34 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 t o 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 (MM S, 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 t o 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; inhalatio n 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, physi ological 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)

M ost of the manatee population is located in peninsular Florida (USFWS, 2001). Manatee sightings in Louisiana have been increasing as the species e xtend s its presence farther west of Florida in the warmer months (Wilson, 2003). A species description is presented in a recent lease sale EIS (MMS, 200 7b) 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 l ease 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.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 35 

### 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 thre at 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 marin e 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 signific ant 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 are as 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 wer e 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 includ e skin irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes; ingestion of oil (and dispersants) direct ly or via contaminated prey (or contaminated vegetation, in the case of manatees); and str ess 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 dis placement 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 even t 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 wh ale, 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 th e Gulf of Mexico.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 36 Due to the rare occurrence of these whales in the Gulf of Mexico and the limited sco pe and duration of the project, it is highly unlikely that any endangered mysticete would come into contact with any project activities, either routine op erations 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 refe rence. 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 ceta ceans in the deepwater environment are odontocetes such as the pantropical spotted dolphin, spinner dolphin, and clymene dolphin. A brief summary is presented below, and a dditional information on these
groups is presented in a recent lease sale EIS (MMS, 2007b).

Mysticete whale s . 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 wha les ( 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 c ontinental 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 co mmon 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.

D elphinids . 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 ), f alse killer whale ( Pseudorca crassidens )

, Fraser’s dolphin ( Lagenodelphis hosei ) , k iller whale ( Orcinus orca ) , m elon

- headed whale ( Peponocephala electra )

,Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 37 p antropical spotted dolphin ( Stenella attenuata )

, p ygmy killer whale ( Feresa attenuata )

, short

- finned pilot whale ( Globicephala macrorhynchus ) , R isso’s dolphin ( Grampus griseu s )

, r ough

- toothed dolphin ( Steno bredanensis ) , s pinner dolphin ( Stenella longirostris ) , and s triped 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 smal l 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 t he 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 di sturb 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 intensi ty, 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 ide ntified as IPF s 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 s peed 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 s afety 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

.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 38 Aircraft traffic also has the potential to disturb marine mammals (W ü rsig 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 significa nt 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
t his 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 N oble ’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 durat ion 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 indica tes 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 a nd 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.



### Impac ts 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 exposu re, 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 structur e, changing prey availability and foraging distribution and/or patterns

, changing reproductive behavior/productivity, and changing movement patterns or migration (MMC, 2010).Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 39 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)

F ive species of endangered or threatened sea turtles may be found near the lease area. L eatherback ( Dermochelys coriacea ), Kemp's ridley ( Lepidochelys ke mpii ), 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 population s , 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 addition al information and in consideration of the Macondo oil spill event. I nformation 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 P lanning Area Lease Sale 218 (BOEMRE, 2011 a,b ). However, no new information from previous EISs was found that would alter the potential impact s 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 near shore species, unlikely to occur near the lease area as adults. Hatchlings or juveniles of any of the sea turtle specie s may be present in deepwater areas, incl uding 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 P anhandle and, to a lesser extent, from Texas through Alabama (MMS, 2007 b) . 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 in frequently nest on Florida Panhandle beaches (Florida Fish and Wildlife Conservation Commission, 201 1 );

• Kemp’s ridley turtles – The main Kemp’s ridley nesting site is Rancho Nuevo beach, Tamaulipas, Mexico (NMFS et al., 201 1 ). Kemp’s ridley turtles typica lly do not nest anywhere near the project area, although there have be en 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 potentia lly 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.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 40 

### Imp acts 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 disrup tion 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 prod uced 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 t hat 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 vigila nt 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 impac ts 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 impac ts 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 Se ction 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.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 41 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 respo nse 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., fro m 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 syste ms, 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 expec ted 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 e ffects 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 orGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 42 stress. Response vessels w ould 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 shorebi rd 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 designat ed, 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 act ivities 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, 2011 a,b ) summarized in Section A.9.3 ( Table 3 ) predict there is a 4% probability that in spring, an oil spill in th e 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 themsel ves 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 ; t his 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 centr al 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 marshe s, lakes, ponds, wet meadows and rivers, and agricultural fie lds (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).Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 43 Fi gure 3. Location of selected environmental features in relation to the lease area.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 44 A large oil spill (WCD) is the only IPF potentially affecting Whooping Cranes. A small fuel spill in the lease area would also be unlikely to affect Whooping Cranes, due to the distance from Aransas NWR. As explained in Section A.9.2 , a small fuel spill would not be expected to make landfall or reach coastal waters prior to breaking up

. 

### Impacts of a Large Oil Spill (WCD)
A large oil spill is unlikely to affect Whooping Cranes as the lease area is approximately 341 miles (549 km) from its critical habitat (Aransas NWR). T he 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 even t 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 death s could occ ur. 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 majo r 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 extirpate d 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 kno wn 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) t o Suwannee Sound, Florida (Levy County) (NMFS, 2010 b) ( 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.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 45 The lease area is a pproximately 195 miles (313 km) from the nearest Gulf stur geon 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 ( P ristis pectinata ) are found in the tropical and subtropical Atlantic Ocean. In the W estern 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 ( 221,45 9 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 s malltooth s awfish. 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 s malltooth s awf ish 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 s malltooth s awfish are similar to those discussed for othe r 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 s malltooth sa wfish habitat, the fish could be affected by direct ingestion, ingestion of oiled prey, or the absorption of dissolved petrole um products through the gills.



### C.3. 10 Beach Mice (Endangered)
Four subspecies of endangered beach mice ( Peromyscus polionotus ) occ ur 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 al l four subspecies. Species descriptions are provided in a recent lease sale EIS (MM S, 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 a nimals due to the distance from shore and the lack of any onshore support activities near their habitat. A small fuel spill inGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 46 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

co ntaminated 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 unl ikely 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 , e lkhorn coral has been found within the

cor al 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. A lthough subsurface plumes

wer e reported following the Macondo spill, these plumes resulted from the use of subsea dispersant s 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
t he 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 shorebird s 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 shorebird s and coastal nesting birds, see S ection C.4.2

.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 47 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 are a. From these surveys, f our 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, j aegers); and permanent resident species (Laughing Gulls, Royal Terns, Bridled Terns) (Hess and Ribic, 2000).

Common seabird species include Wilson’s S torm -P etrel ( Oceanites oceanicus ) , Magnificent Frig atebird ( 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 su rface 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/km 2

.

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 mob ility 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 rig s may be exposed to contaminants including air pollutan ts and routine discharges, but significant impacts are unlikely due to rapid dispersion. Birds migrating over water have been known to strike offshore structures, resulti ng in death or injury (Wiese et al., 2001; Russell, 2005). Mortality of migrant bird s 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, navigati on 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 spri ng (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.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 48 A recent study in the North Sea indi cated 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 fogg y 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 i n 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 r ecent EISs (MMS, 2007b, 2008) . F or 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 fue l 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 experi ence 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 spil l, 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 i mpacts on these animals.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 49 BOEM has reexamined the analys e s for coastal and marine birds presented in MMS (2007b, 2008) and determined that no new information was found that would alter the potential impact s on marine and pelagic birds (BOEMRE, 2011a,b).

P el agic 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/km 2 . 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 ( US FWS, 2011 ). The Northern Gannet is among the species with the largest numbers of birds affected by the spill.



### C.4.2 Shorebird s and Coastal Nesting Birds
Threatened and endangered bird species (Piping Plover and Whooping Crane) have been discussed previous ly in Section C.3 . Various species of non

- endangered birds are also found along the northern Gulf Coast , including diving birds, shorebird s, marsh birds, wading birds, and waterfowl. Gulf Coast marshes and beaches also provide important feeding grounds a nd 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, 20 10b). Additional information is presented in recent lease sale EISs (MMS, 2007b, 2008).

The Brown Pelican ( Pelecanus occidentalis ) was delisted from F ederal 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, 201 1 ). Brown Pelicans inhabit coastal habitats and forage within both coastal waters and waters of the inner continental shelf. Aerial and shipboard surveys, including GulfCet and GulfCet II, indicate that Brown Pelicans do not occur in deep offshore waters (Fritts and Reynolds, 1981; Peake, 1996; Hess and Ribic, 2000). Nearly half the southeastern population of Brown Pelicans live s in the northern Gulf Coast , generally nesting on protected islands (USFWS, 2010 b ).

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 shorebird s 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 shorebird s 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 toGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 50 make landfall or reach coastal waters prior to breaking up. Com pliance 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, wher e 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 dis turb 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 an d 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). Helicop ters 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 USF WS (2010d) and based on the latest reports, about 5,000 dead birds ha ve 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 (N MFS, 2010 c ). According to the USFWS (201 1 ), 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

- co lored Heron

• Green Heron

• Cattle Egret

• Snowy EgretGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 51 • 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

• Sander ling

• 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 Te rn, 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 le ad 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, an d 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 ocean ography 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 (B iggs 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 f or various lengths of time (10 to 100 days, depending on the species) (MMS, 2007b).Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 52 IPFs potentially affecting pelagic communities and ichthyoplankton include drilling rig presence, noise, and lights; effluent discharges; water intakes; and two types of ac cidents (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 ef fect 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 c onsidered 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 wat er

- 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 th e 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 biolo gically significant to plankton or ichthyoplankton populations.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 53 

### Impacts of a Small Fuel Spill
Potential spill impacts on fisheries resource s are discussed in recent EISs (MMS, 2007b, 2008)

. F or 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 sma ll 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 larv ae 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 Counci ls.

The Gulf of Mexico Fishery Management Council (GMFMC) has prepared Fishery Management Plans for corals and coral reefs, shrimp s , 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). T he 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 boun dary 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 94 5, located approximately 50 miles (80 km) north of the lease area along the shelf edge south of Louisiana.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 54 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 )

• Skipj ack 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 mi 2 ( 300,000 km 2 ). 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 s pawn 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 in ternational 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 ( E EZ ) . 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 NTL s (2009

- G39 and 2009

- G40) that provide guidance and clarification of the

re gulations with respect to biologically sensitive underwater features and areas and benthic communities that are considered EFH (MMS, 2009 a,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 a bove will be followed ( BOEMRE, 2011a,b ).

There are Fishery Management Plans in the Gulf of Mexico OCS region for shrimp s , red drum, reef fishes, coastal migratory pelagics, stone crab, spiny lobster , coral s and coral reefs, billfish es , and highly migratory species. The Highly Migratory Species Fisheries Management Plan wasGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 55 recently amended to updat e 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 N orth 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 potenti ally 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 a n 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 surfac e 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 s anitary 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 E FH 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 N oble ’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)

. F or this EP
, there are no unique sit e- 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 impac ts would depend on the meteorological and oceanographic conditions atGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 56 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 nat urally 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 fish es, 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 deepwate r 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 rece nt 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. Give n the extent of EFH designations in the Gulf of Mexico (GMFMC, 2005; NMFS, 2009), some impact on EFH would be unavoidable.

A large spill could affect the EFH for many managed species including shrimp s , 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.

T he 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 feature s (Ship Shoal south) located in EW 94 5, 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 thes e 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 t hese 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 industryGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 57 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 detect ed near the proposed wellsites during the shallow hazards assessment (B- Geo , 20 11 ). Noble will abide by the appl icable requirements of NTL 2005

- G07, which stipulate that work be stopped at the project site should any previously undetected archaeological r esource be discovered after work has begun until appropriate surveys and evaluations have been completed.

Because there are no know n or indicated shipwreck sites in the lease area, there are no routine IPFs that are likely to affect shipwrecks. I mpacts 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) estimate d that a severe subsurface blowo ut 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 af fect 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 plum es 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 s ites 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 conc eivably 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 contamin ation of the site and its environment.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 58 

### 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 En vironments, Inc. (CEI) suggests that sea level at 12,000 years B.P. wo uld 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) ba thymetric 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, th e 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 prehistori c 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 a vailable 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 fe atures).



## 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). Coas tal 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, wildernessGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 59 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 gen eral, 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 operat ions, 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 , ther e 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

a reas 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 S tate and N ational parks within the geographic range of potential shoreline contact s after 120 days are listed in Table 7

.
Table 7. W ildlife refuges, wilderness areas, and S tate and N ational parks within the geographic range of the potential shoreline contacts after 120 days

.

County or Parish Wildlife Refuge, Wilderness Are a,

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 Marin e 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 ParkTable 7. (Continued. )

Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 60 County or Parish Wildlife Refuge, Wilderness Are a,

or State/National Park
Mission

- Aransas National Estuarine Research Reserve

Aransas County, Texas Mission

- Aransas National Estuarine Research Reserve Aransas National W ildlife 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
Texa s 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 Wildl ife 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 Mand alay 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, Louisian a 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 ParkGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 61 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 weathe red 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 s ize 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 w ill 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, 2011 a,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, n o additional information obtained after the previous EISs was found that would alter the potential impact s on commercial and recreational fishing discussed in those EISs (BOEMRE, 2011 a,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. I n 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 le ase 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
tem perature sensors, depth finders, and positioning equipment. Vessels typically are 10 to 30 mGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 62 (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) an d 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 ins hore 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, I nc., 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 rig s offshore Te xas 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 p elagic 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 offsho re 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 pro bability 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 provide s 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, co uld 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 activ ities 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 ).Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 63 

### 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, 2010 d ). At its peak on 12 July 2010, c losures encompassed 84,101 mi 2 ( 217,821 km 2 ), 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, i mplementation of Noble ’s OSRP will potentially alleviate the potential for impacts. EP Section H provide s 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 are a 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 effect s. 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 o f 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 fai nt, 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 o ffshore vessels, includingGreen Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 64 USCG personnel, civilian contractors, and other r esponders 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 H 2 S such as headaches, dizziness, nausea, vomi ting, 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 provide s 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 r ecent 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 dril ling 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, 2011 a,b ), a recent study explored the economic impacts of the Macondo spill on oil a nd 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 c aused 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 ; t his direct reduction in spending affected employment in the industries that sup ply the Gulf drilling industry and in all other industries affected by declines in consumer and business spending (Inter

- Agency Economic Report, 2010)

.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 65 

### C.8.4 Recreation and Tourism

BOEMRE has reexamined the analys e s 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 impact s on recreation and tourism ( BOEMRE, 2011 a,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, implem entation of Noble ’s OSRP will potentially help mitigate and reduce the potential for impacts. EP Section H provide s detail on spill response measures. Given the open ocean location of the lease area, the duration of a small spill and opportunity for impa cts 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 s pill 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 2011 a,b ). For t his 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 C oast over a 3- year period at $22.7 billion (Oxford Economics, 2010)

.


### C.8.5 Land Use

Land use along the northern Gulf C oast is discussed in recent lease sale EISs (MMS, 2007b, 2008). There are no routine IPFs potential ly 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 shorebase s.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 66 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 effec t 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 demobi lized.



### 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 emissi ons 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 wellsite s in GC 679 and 723 . There are no other known marine uses of the lease area.

There are no IPFs from routine project activities t hat 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 are a 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 b locks are not located within any USCG

- designated fairway or shipping lane or Military W arning 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 t he 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.Green Canyon Blocks 679 and 723 October 2011 Environmental Impact Analysis for Revised Exploration Plan Page 67 

## D . Environmental Hazards

D.1 Geologic Hazards

The shallow hazards assessment by B- Geo ( 2011 ) conclude d that the wellsites are free of any significant geological hazards and are suitable for the proposed activities. See EP Section C for supporting geologic al 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 crite ria 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 drill ing rig for safety reasons until the storm or weather event passes.



## E. Alternatives

N o formal alternatives we re evaluated in this EIA for an EP . However, various technical and operational options
, including the location of the wellsite s and the selectio n 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 comp ly with all applicable F ederal, S tate, 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

.Green Canyon Blocks 679 and 723 October 2011 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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### 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.