UNITED STATES GOVERNMENT

MEMORANDUM

To: Public Information (MS 5030)

Plan Coordinator, FO, Plans Section (MS 

5231)

Public Information copy of plan

Control # - N-09781

Type - Initial Exploration Plan

Lease(s) - OCS-G32556 Block - 19 Atwater Valley Area

OCS-G33863 Block - 18 Atwater Valley Area

Operator - Anadarko Petroleum Corporation

Drill & Complete Wells CC, DD, GG, GV, QQ, EE, KK, KV

Not Found

Attached is a copy of the subject plan. 

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

Tonya Jez

Plan Coordinator

G33863/AT/18

G33863/AT/18

G32556/AT/19

G33863/AT/18

G33863/AT/18

G32556/AT/19

G32556/AT/19

G33863/AT/18

4267 FSL, 6783 FEL

7512 FSL, 3926 FEL

7452 FNL, 6272 FWL

2761 FNL, 2730 FEL

2820 FNL, 1653 FEL

705 FSL, 5349 FWL

1726 FSL, 5336 FWL

2055 FNL, 2638 FEL

G33863/AT/18

G33863/AT/18

G32556/AT/19

G33863/AT/18

G33863/AT/18

G32556/AT/19

G32556/AT/19

G33863/AT/18

WELL/CC

WELL/DD

WELL/EE

WELL/GG

WELL/GV

WELL/KK

WELL/KV

WELL/QQ

Site Type/Name Botm Lse/Area/Blk Surface Location Surf Lse/Area/Blk

Description -

Rig Type -

Subject:

From:

April 28, 2014
INITIAL EXPLORATION PLAN (N-9781) 

ANADARKO PETROLEUM CORPORATION 

ATWATER VALLEY BLOCK 18/19 

OCS-G 33863/32556 

PUBLIC COPY 

RECORD OF CHANGE LOG 

Submission Type Date Sent to 

BOEM 

Summary of Submission Page Numbers 

Initial 2/3/2014 Initial EP submission. All 

Amendment 3/10/2014 Submit PDF copy of OCD air modeling report (printed copy 

submitted with Initial EP submittal). 

N/A 

Amendment 4/11/2014 Submit CALPUFF air modeling protocol per BOEM/Fish & 

Wildlife request. 

N/A 

Final Copy of Plan 4/17/2014 Complete Initial EP submittal with amendments included. All 

Add Record of 

Change Log 

4/17/2014 Add record of change log. 1 
 

PUBLIC 

INITIAL EXPLORATION PLAN 

ATWATER VALLEY BLOCK 18/19 

OCS-G 33863/32556

OFFSHORE, LOUISIANA & MISSISSIPPI

 

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive 

The Woodlands, Texas 77380 

Contact: Bridget O’Farrell 

Bridget.OFarrell-Villarreal@anadarko.com 

(832) 636-1694 

1 – Hard Copy Confidential 

1 – CD Confidential 

1 – Hard Copy Public Information 

1 – CD Public Information

January 2014 
 

INITIAL EXPLORATION PLAN 

LEASE OCS-G 33863/32556

Atwater Valley Block 18/19 

 A. Plan Contents 

 B. General Information 

 C. Geological, Geophysical 

D. Hydrogen Sulfide Information 

 E. Biological, Physical and Socioeconomic Information 

F. Wastes and Discharge Information 

 G. Air Emissions Information 

 H. Oil Spill Information 

I. Environmental Monitoring Information 

 J. Lease Stipulations 

 K. Support Vessels and Aircraft Information 

 L. Onshore Support Facilities Information 

M. Coastal Zone Management Act Information 

N. Environmental Impact Analysis 

O. Administrative Information 
 

SECTION A 

PLAN CONTENTS

(a) Plan Information Form 

Under this Initial Exploration Plan (EP), Anadarko Petroleum Corporation (Anadarko) proposes 

to drill and complete eight wells total in Atwater Valley 18/19. 

 Five well locations will be in Atwater Valley 18: Location CC, DD, GG, GV and QQ. 

 Three well locations will be in Atwater Valley 19: Location EE, KK and KV. 

The wells will be drilled using a dynamically positioned (DP) drillship or DP semi-submersible 

drilling rig. Drilling and completion operations for all well locations will utilize a subsea BOP 

stack. OCS Plan Information Form BOEM-137 is enclosed as Attachment A-1.

(b) Location 

Enclosed as Attachment A-2 is a well location plat at a scale of 1 inch = 2,000 feet that depicts 

the surface locations and water depth of the proposed wells. 

(c) Safety and Pollution Prevention Features 

Safety features on the drilling rig will include well control, pollution prevention, safe welding 

procedures, and blowout prevention equipment as described in Title 30 CFR Part 250, Subparts 

C, D, E, G and O; and as further clarified by BOEM/BSEE Notices to Lessees, and applicable 

regulations of the Environmental Protection Agency and the U.S. Coast Guard. The appropriate 

life rafts, life jackets, ring buoys, etc., as prescribed by the U.S. Coast Guard, will be maintained 

on the facility at all times. 
 

(d) Storage Tanks and Production Vessels 

The proposed wells will be drilled with a DP drillship or DP semi-submersible drilling rig. 

Type of Facility Type Of Storage 

Tank 

Tank 

Capacity 

Number 

of Tanks 

Total 

Capacity 

Fluid 

Gravity 

(API) 

Total Capacity of all 

Tanks for Rig Type 

DP Drillship Fuel Oil Storage Tank 5,514 bbls 2 11,028 bbls No. 2 Diesel 12 tanks total= 

62,874 bbls 

Fuel Oil Storage Tank 12,458 bbls 2 24,916 bbls No. 2 Diesel 

Fuel Oil Storage Tank 12,065 bbls 2 24,130 bbls No. 2 Diesel 

Fuel Oil Settling 

Tanks 640 bbls 2 1,280 bbls No. 2 Diesel 

Fuel Oil Service 

Tanks 480 bbls 3 1,440 bbls No. 2 Diesel 

Fuel Oil Emergency 

Generator Tank 80 bbls 1 80 bbls No. 2 Diesel 

DP SemiSubmersible 

Fuel Oil Hull Tanks 4,541 bbls 2 9,082 bbls No. 2 Diesel 7 tanks total= 

16,689 bbls 

Fuel Oil Hull Tanks 3,392 bbls 2 6,784 bbls No. 2 Diesel 

Fuel Oil Deck Day 

Tank 

629 bbls 1 629 bbls No. 2 Diesel 

Fuel Oil Deck Settling 

Tank 

164 bbls 1 164 bbls No. 2 Diesel 

Fuel Oil Emergency 

Generator 

30 bbls 1 30 bbls No. 2 Diesel 
 

(e) Pollution Prevention Measures 

The drilling rig utilized for these operations will comply with all applicable regulations regarding 

pollution prevention and control. The rig has a Shipboard Oil Pollution Emergency Plan 

(SOPEP), which is reviewed and approved annually by the American Bureau of Shipping (ABS). 

The SOPEP is provided to assist employees in dealing with an unexpected discharge of oil. Its 

primary purpose is to set in motion the necessary actions to stop or minimize the discharge of oil 

and to mitigate its effects. Effective planning ensures that the necessary actions are taken in a 

structured, logical and timely manner. 

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

areas to collect all contaminants and debris. Most deck drains and some of the joints at the edge 

of the rig floor go overboard or into the moonpool, respectively. To prevent ocean discharge 

from the drains there is a dedicated drip pan under the rotary table. The pipe racks, mud pump 

room, sack store, and drill floor drains go to a holding tank, which is served by a dedicated oily 

water separator. The well test area, engine room, and other major machinery spaces drains all go 

to slops tanks, which are served by a large general-service, oily water separator. The containment 

devices are temporary. They are not meant for permanent storage of waste. On the rare occasion 

that they contain wastes, they are pumped, mopped, or cleaned within a short period of time. The 

chances of damage to a containment structure during such time as it contains wastes are 

exceedingly small. 

(f) Additional Pollution Prevention Measures 

No additional measures are proposed under this plan. The activities proposed in this plan are not 

located offshore Florida. 

(g) Description of Previously Approved Lease Activities 

Anadarko does not have previously approved well locations in Atwater Valley 18/19. 

BHP Billiton Petroleum (GOM) Inc. previously had an Initial Exploration Plan approved for 

Atwater Valley 18 only. Anadarko will not be revising or utilizing any of the well locations 

approved under Plan Control No.: N-7103. 

Control # Plan Type/Approval Well Location(s) Status of Well Location 

N-7103 Initial EP 

Approved 

A 

B 

C 

Previously permitted locations. AT 18 #001 was PA’d. 

Open location 

Open location 
U.S. Department of the Interior  20%&RQWURO1XPEHU

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OCS PLAN INFORMATION FORM 

General Information 

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Project and Worst Case Discharge (WCD) Information

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Description of Proposed Activities and Tentative Schedule (Mark all that apply) 

Proposed Activity Start Date End Date No. of Days 

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Description of Drilling Rig Description of Structure 

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Description of Lease Term Pipelines 

From (Facility/Area/Block) To (Facility/Area/Block) Diameter (Inches) Length (Feet) 

Form BOEM- 0137 'HFHPEHU- 6XSHUVHGHVDOOSUHYLRXVHGLWLRQVRIWKLVIRUPZKLFKPD\QRWEHXVHG

Exploration drilling, completion & installation of subsea wellhead and/or manifold-AT 18, CC

Exploration drilling, completion & installation of subsea wellhead and/or manifold-AT 19, KV

Attachment A-1

X

Anadarko Petroleum Corporation 00981

Bridget O'Farrell

1201 Lake Robbins Dr. 832-636-1694

The Woodlands, TX 77380 Bridget.OFarrell-Villarreal@anadarko.com

$29,384.00 Pay.gov: 25DV21AG, Agency: 74556983633

OCS-G33863/32556 AT 18/19 Stromboli

X X Fourchon (primary); Alt. Galveston, Cameron, Lake Charles, Houma, Pascagoula

GV (AT 18)/KV (AT 19) 63,744 bbls (AT 18) / 250,188 bbls (AT 19) 28.7

71 63,744 bbls (AT 18) / 250,188 bbls (AT 19)

X

X

X

X

6/24/2014 12/31/2014 190

3/1/2015 9/7/2015 190

4/25/2016 11/1/2016 190

11/4/2016 5/13/2017 190

9/6/2017 3/15/2018 190

7/10/2018 1/16/2019 190

1/1/2020 7/9/2020 190

7/1/2020 7/9/2021 190

X

X
OCS PLAN INFORMATION FORM (CONTINUED) 

Include one copy of this page for each proposed well/structure 

Proposed Well/Structure Location

Well or Structure Name/Number (If renaming well or 

structure, reference previous name): 

Previously reviewed under an approved EP or 

DOCD? S-7363

Yes No 

Is this an existing well 

or structure? 

Yes No If this is an existing well or structure, list the 

Complex ID or API No. 

Do you plan to use a subsea BOP or a surface BOP on a floating facility to conduct your proposed activities? Yes No 

WCD info For wells, volume of uncontrolled 

blowout (Bbls/day): 

For structures, volume of all storage and 

pipelines (Bbls): 

API Gravity of 

fluid 

Surface Location Bottom-Hole Location (For Wells) Completion (For multiple completions, 

enter separate lines) 

Lease No. OCS OCS OCS 

OCS 

Area Name 

Block No. 

Blockline 

Departures 

(in feet)

N/S Departure: F____ L N/S Departure: F____ L N/S Departure: F____ L 

N/S Departure: F____ L 

N/S Departure: F____ L 

E/W Departure: F____ L E/W Departure: F____ L E/W Departure: F____ L 

E/W Departure: F____ L 

E/W Departure: F____ L 

Lambert XY 

coordinates 

X: X: X: 

X: 

X: 

Y: Y: Y: 

Y: 

Y: 

Latitude/ 

Longitude

Latitude Latitude Latitude 

Latitude 

Latitude 

Longitude Longitude Longitude 

Longitude 

Longitude 

Water Depth (Feet): MD (Feet): TVD (Feet): 

Anchor Radius (if applicable) in feet: 

MD (Feet): 

MD (Feet): 

MD (Feet): 

TVD (Feet): 

TVD (Feet): 

TVD (Feet): 

Anchor Locations for Drilling Rig or Construction Barge (If anchor radius supplied above, not necessary) 

Anchor Name 

 or No. 

Area Block X Coordinate Y Coordinate Length of Anchor Chain on Seafloor 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

X = Y = 

 

Form BOEM- 0137 (December 2011- Supersedes all previous editions of this form which may not be used.) 







AT 18 “Gnome”

Stromboli Prospect

APC SL‐ AT 18 “DD”

X:978173 Y:10145103

Lat: 27.941 Lon: ‐89.052

7512’ FSL, 3926’ FEL

APC SL‐ AT 18 “CC”

X:975301 Y:10141870

Lat: 27.932 Lon: ‐89.060

4267’ FSL, 6783’ FEL

APC SL‐ AT 19 “EE”

X:988360 Y:10145062

Lat: 27.942  Lon: ‐89.020

7452’ FSL, 6272’ FWL

APC SL‐ AT 19 “KV”

X:987423 Y:10139337

Lat: 27.926  Lon: ‐89.023

1726’ FSL, 5336’ FWL

APC SL‐ AT 19 “KK”

X:987439 Y:10138306

Lat: 27.923 Lon: ‐89.023

705’ FSL, 5349’ FWL

SHL PLAT

18 19

APC SL‐ AT 18 “GV”

X:980582 Y:10150777

Lat: 27.597 Lon: ‐89.045

2820’ FNL, 1653’ FEL

APC SL‐ AT 18 “GG”

X:979365 Y:10150705

Lat: 27.957 Lon: ‐89.048

2761’ FNL, 2730’ FEL

APC SL‐ AT 18 “QQ”

X:979462 Y:10151381

Lat: 27.597 Lon: ‐89.048

2055’ FNL, 2638’ FEL
 

SECTION B 

GENERAL INFORMATION 

(a) Applications and Permits 

Prior to beginning exploration operations the following application(s) will be submitted for 

approval: 

Application/Permit Issuing Agency Status 

Permit to Drill Bureau of Safety and Environmental 

Enforcement (BSEE) 

To be submitted 

(b) Drilling Fluids 

Type of Drilling Fluid Estimated Volume Per Well 

Water-based (NaCl saturated, seawater, 

freshwater, barite) for Pump and Dump 

19,000 bbls 

Synthetic-based (internal olefin, ester) 18,500 bbls 

Oil-based N/A 

(c) Oils Characteristics 

Oil will not be produced under this Initial Exploration Plan. Therefore the oils characteristics 

information is not required per NTL 2008-G04 2(d), extended by NTL 2014-G03. 

(d) New or Unusual Technology 

Anadarko does not propose to use any new or unusual technology to drill the wells proposed in 

this plan. 

(e) Bonding Statement 

The bond requirements for the activities and facilities proposed in this EP are satisfied by an 

area-wide bond furnished and maintained according to 30 CFR Part 556, subpart I; NTL 2000-

G16, “Guidelines for General Lease Surety Bonds,” and National NTL 2008-N07, 

“Supplemental Bond Procedures”. 

(f) Oil Spill Financial Responsibility (OSFR) 

Anadarko Petroleum Corporation (Company Number 00981) has demonstrated oil spill financial 

responsibility for the facilities proposed in this EP according to 30 CFR Part 553, and NTL 

2008-N05, “Guidelines for Oil Spill Financial Responsibility for Covered Facilities”. 
 

(g) Deepwater Well Control Statement 

Anadarko Petroleum Corporation (Company Number 00981) has the financial capability to drill 

a relief well and conduct other emergency well control operations if required. 

(h) Blowout Scenario

Purpose 

This overview provides a generic blowout scenario, additional information regarding any 

potential oil spill, and the measures Anadarko will take to prevent a blowout and if necessary 

promptly respond to manage a blowout scenario if one occurs. The following overview is 

pursuant with 30 CFR 250.213(g), 250.219, 250.250 and NTL No. 2010-N06. 

Background 

The Atwater Valley 18, Location GG well is currently the primary drill location and is located 

2,735' FNL & 2,715' FEL (in Atwater Valley 18). This overview has been developed to 

document the additional information requirements for Exploration Plans as requested by NTL 

No. 2010-N06 

Information Requirements: 

Blowout Scenario 

The Atwater Valley 18, Location GG well is to be drilled utilizing a MODU rig with a marine 

riser and sub-sea BOP. A typical casing program will be used including a wellhead system, 

conductor casing, surface casing, intermediate casing, as well as two drilling liners to reach the 

planned total depth. 

The blowout scenario assumes that a hydrocarbon influx occurs followed by a well control event 

from the objective sands. The sub-sea BOP and marine riser subsequently fail followed by a 

blowout to the seabed. The worst case discharge (WCD) scenario assumes 8-1/2" open hole with 

a 9-7/8" drilling liner, an 11-7/8" drilling liner, and 14" intermediate casing string set. 

The WCD scenario for the Atwater Valley 18, Location GV (location with highest WCD flow 

rate in AT 18) assumes a 10-5/8" OH with an 11-7/8" drilling liner and 14" intermediate casing 

string. 

The WCD scenario for the Atwater Valley 19, Location KV (location with highest WCD flow 

rate in AT 19) assumes a 14" OH with a 14" intermediate casing string. 
 

Estimated flow rate of the potential blowout for Atwater Valley 18, Location GG 

(Primary drill location): 

Category Initial EP 

Type of Activity Exploration Drilling 

Facility Location (area/block) AT 18 

Facility Designation Location GG 

Distance to Nearest Shoreline (miles) 71 

Uncontrolled blowout (volume per day) 50,781 bbls 

Type of Fluid(s) Crude Oil 

Estimated flow rate of the potential blowout for Atwater Valley 18, Location GV: 

Category Initial EP 

Type of Activity Exploration Drilling 

Facility Location (area/block) AT 18 

Facility Designation Location GV 

Distance to Nearest Shoreline (miles) 71 

Uncontrolled blowout (volume per day) 63,744 bbls 

Type of Fluid(s) Crude Oil 

Estimated flow rate of the potential blowout for Atwater Valley 19, Location KV: 

Category Initial EP 

Type of Activity Exploration Drilling 

Facility Location (area/block) AT 19 

Facility Designation Location KV 

Distance to Nearest Shoreline (miles) 71 

Uncontrolled blowout (volume per day) 250,188 bbls 

Type of Fluid(s) Crude Oil 

a) Potential for the well to bridge over:

Discussions regarding geologic information are considered proprietary and have been 

omitted from this public copy of the EP. 
 

b) Likelihood and measures taken for surface and/or sub-sea intervention to stop the 

blowout: 

The likelihood of surface intervention to prevent, or stop, a blowout is high and is based 

on the following equipment specific to a capable MODU that will be contracted to do this 

drilling program: 

 ROV Secondary BOP Control System: The BOP will be confirmed to have 

an ROV Intervention Panel and circuits that have the following attributes: 

 Hot stab capable of closing one set of: 

 Blind-Shear Rams 

 Pipe Rams 

 Unlatch the Lower Marine Riser Package 

 Hot stab has been function tested in conjunction with the stump test 

and was tested at the same rate and pressure as the pump installed on 

the ROV used by the rig. 

The panel can also be operated by an ROV from an independent supply 

boat in the event of a loss of rig scenario. 

 Deadman/Autoshear function: The rig will be equipped with an 

automated sequence that closes the blind shear rams in the event of 

any of the following scenarios: 

 Inadvertent disconnect of the LMRP 

 Loss of both hydraulic pressure and electrical supply from the 

surface BOP control system 

No human interface is to be required once these systems are armed. 

c) Availability of a rig to drill a relief well: 

As per the Mutual Aid agreements between E&P Operators in the Gulf of Mexico, 

Anadarko will select from the best rig option available in the Gulf of Mexico fleet if, and 

when, it is required for relief well work. 

As of January 15, 2014 there were 14 additional rigs in the Gulf of Mexico which would 

be capable of operating under the conditions associated with drilling a relief well for this 

prospect. A rig which could be used to drill a relief well is the Discoverer India which is 

a dynamically positioned drillship capable of operating in the water depths, and drilling 

to the total well depths, associated with a relief well for this prospect. The rig is currently 

under contract to Chevron and is on location in Walker Ridge 143. 

There are no nearby platforms from which to drill a relief well. It is not feasible to drill a 

relief well from land. 
 

d) Rig constraints: 

A rig with a 15,000 psi BOP stack and capable of drilling in 5,000' of water is required 

for any relief well operations. 

e) Time taken to mobilize a rig and drill a relief well: 

An estimated 7-21 days is required to suspend operations on a deepwater GOM well, 

mobilize to a relief well location, and begin relief well drilling operations. This estimate 

includes 0-14 days to suspend current operations on an existing well and 7 days to 

mobilize to location and be ready to spud a relief well. The estimated time to drill the 

relief well and perform kill operations is 180 days for an estimated total of 187-201 days 

from time of blowout to completion of a relief well. 

The time estimate provided for the plan well is inclusive of 'both' drilling 'and' 

completion operations. As a completion is not typically part of relief well operations no 

time has been included for completion operations in the relief well estimate. Therefore 

the estimated time for a relief well should be less than for the plan well. In addition, 

information and learning from the drilling of the original well may provide opportunities 

to optimize drilling performance for relief well operations and thus reduce the required 

drilling time. 

f) Assumptions and calculations used in approved or proposed Oil Spill Response 

Plan: 

Regional OSRP–Green Canyon 683, Location G (Approved 9/25/13) 

 The Merlin reservoir simulator and Avalon nodal analysis programs were used to 

estimate the WCD. The estimated worst case discharge for Green Canyon 683 #002 

(Location G) is 403,608 bbls. (Plan Control No.: S-7623) 

 The maximum total volume during a blowout could potentially be 61,752,024 bbls 

assuming 153 days for the maximum duration of a blowout, multiplied by the worst 

case daily uncontrolled blowout volume of 403,608 bbls. 

 The volume denoted in the Regional OSRP is higher than the NTL 2010-N06 

(403,608 bopd) calculations submitted under the Supplemental EP. Anadarko elected 

to denote a higher volume (410,000 bbls) in the Regional OSRP for planning 

purposes to demonstrate additional equipment response capabilities per previous 

discussions with Mr. Mike Tolbert, OSRD. 
 

Initial EP–Atwater Valley 18, Location GG (WCD for Primary Drill Location) 

 Nodal analysis was performed to calculate worst case discharge volumes. The 

estimated worst case discharge for the well is 50,781 bopd. 

 The maximum total volume during a blowout at Atwater Valley 18, Location GG

could potentially be 10,206,981 bbls assuming 201 days for the maximum duration of 

a blowout, multiplied by the worst case daily uncontrolled blowout volume of 50,781 

bopd. 

Initial EP–Atwater Valley 18, Location GV (Highest WCD for AT 18) 

 Nodal analysis was performed to calculate worst case discharge volumes. The

estimated worst case discharge for the well is 63,744 bopd. 

 The maximum total volume during a blowout at Atwater Valley 18, Location GV

could potentially be 12,812,544 bbls assuming 201 days for the maximum duration of 

a blowout, multiplied by the worst case daily uncontrolled blowout volume of 63,744 

bopd. 

Initial EP–Atwater Valley 19, Location KV (Highest WCD for AT 19) 

 Nodal analysis was performed to calculate worst case discharge volumes. The 

estimated worst case discharge for the well is 250,188 bopd. 

 The maximum total volume during a blowout at Atwater Valley 19, Location KV

could potentially be 50,287,788 bbls assuming 201 days for the maximum duration of 

a blowout, multiplied by the worst case daily uncontrolled blowout volume of 

250,188 bopd. 
 

g) Measures taken to enhance the ability to prevent or reduce the likelihood of a 

blowout 

 Well design: Anadarko utilizes a systematic well design process for the planning and 

construction of a well operation. This process utilizes the depth of experience 

Anadarko possesses in the deepwater arena and involves a multi-disciplinary team 

peer review of the well design, shallow hazards, and formation pressure hazards 

expected during the drilling phase of the well. This process minimizes the potential 

for an unplanned well control event that could lead to a blowout. This process will 

also include Professional Engineer review and certification of the final casing design 

and cementing program. 

A detailed pre-drill assessment of formation pressure provided by Anadarko’s 

Geologic/Geophysical team, along with third party consultants, allows for 

development of a mud program that provides an overbalanced mud weight for the 

safe drilling of the well. For an exploration well this may also include taking 

formation pressures to confirm the actual formation pressure during the well 

construction process and minimize the risk of an unplanned well control event. 

The well construction process also requires a systematic review and management 

acceptance of the start-up preparation work for the rig and crews along with the third 

party technical audit work on the rig and the rig’s well control equipment. This 

review and audit process measures the rig’s ability to handle an unplanned well 

control event and provides assurance that the rig can successfully mitigate a loss of 

well control event and prevent it from becoming a blowout scenario. 

 Barrier Philosophy: For all well designs, Anadarko requires and uses a redundant 

barrier philosophy, that being two independent barriers for both internal and external 

flow paths in the final wellbore. It is also standard practice to conduct pressure 

testing, in accordance with the applicable regulations, to evaluate integrity on all 

relevant barriers. In addition, all intermediate and production casings returned to the 

wellhead will be locked down before subsequent wellbore construction proceeds. 

 BOP and well control equipment: The rig will have an 18-3/4" 15,000 psi BOP 

with primary and secondary BOP control systems. The BOP will have been 

completely recertified compliant to OEM specifications and all applicable federal 

regulations by a qualified third party. Prior to commencement of operations an 

independent third party verification will be obtained to verify that the subsea BOP is 

designed for the specific equipment on the rig and this specific well design. 
 

 BOP and well control equipment testing: To ensure effectiveness of the BOP and 

well control equipment, a testing program will be conducted prior to running the BOP 

and then during drilling operations as well. This testing program will be in 

compliance with applicable federal regulations for pressure and function testing and 

will also provide periodic assessment on the performance of both primary and 

secondary BOP control systems including actual interface operations with the ROV 

and the ROV panel. 

 Well control training and drills: Anadarko requires that key nominated onshore and 

offshore positions including rig contractor personnel to hold a WellCAP, or 

equivalent, well control training certificate, renewable every two years for the type of 

floating drilling operation being conducted. Anadarko also monitors compliance of 

its personnel with the applicable federal regulations, including those found in 30 CFR 

Part 250 Sub-Part O. 

A comprehensive program of well control drills will be conducted offshore to ensure 

readiness to identify and then manage a well control situation and thereby minimize 

the potential for a well control event to lead to a blowout scenario.

h) Arrangements for drilling a relief well 

 Anadarko maintains a master agreement with Wild Well Control for advice, 

management, engineering, well kick pre and post modeling, and resource support for 

an unplanned loss of well control event. In the event of any well control event, Wild 

Well Control would be contacted and mobilized if required to support Anadarko’s 

operational team both in the onshore and offshore locations. 

 The conceptual relief well design will be similar to the design of the Atwater Valley 

18, Location GG well in that casing weights, grades and setting points are anticipated 

to be identical or very similar. A finalized relief well design can be prepared within 

two days of initialization. 

 A block wide shallow hazard assessment has been completed for Atwater Valley 18 

and 19. Furthermore, the potential for high density chemo-synthetic communities in 

the study area are negligible. Depending on the nature of the blowout scenario, well 

geometry, and total depth required to intersect the blowout, the most suitable surface 

location will be chosen and submitted for approval as the location for the relief well. 
 

 Anadarko’s philosophy is to carry an adequate inventory of well construction 

equipment to drill a complete well(s) from surface to total depth. Back-up long lead 

equipment equivalent to the original well design will be carried in stock to allow a 

rapid response. This includes a spare deepwater sub-sea wellhead system and the 

large OD casing (36", 22", 18", 16", and 13-5/8") and connectors required for the first 

part of the well. Smaller OD casing is considered readily available on the ground in 

the GoM and would be resourced out of existing inventory or from suppliers as 

required. 

 Existing service agreements will be in place for support services including drilling 

fluids, casing running, cementing, ROV’s, solids control, mud logging, directional 

drilling, LWD/MWD, logging, boats and helicopters. 

 Specialist services for range finding to drill the relief well in close proximity to the 

original wellbore at the reservoir depth may potentially be provided through Vector 

Magnetics LLC. During drilling operations Anadarko maintains in-house directional 

drilling services personnel, (e.g. Schlumberger and/or Halliburton), to support and 

supplement Vector Magnetics under our existing directional drilling agreements. 
 

SECTION C 

GEOLOGICAL AND GEOPHYSICAL INFORMATION 

(a) Geological Description 

Discussions regarding geologic information are considered proprietary and have been omitted 

from this public copy of the EP, along with some of the associated geologic attachments. 

(b) Structure Contour Maps 

Current structure maps drawn to the top of each productive hydrocarbon sand showing the entire 

lease block, the surface locations of each well and locations of geological cross-sections, are 

enclosed as Attachment C-1. (Omitted from this public copy of the EP.) 

(c) Interpreted 2-D and/or 3-D Seismic Lines 

Interpreted seismic lines are enclosed as Attachment C-2. (Omitted from this public copy of the 

EP.) 

(d) Geological Structure Cross-Sections 

Interpreted geological structure cross-sections showing the location and depth of each proposed 

well are enclosed as Attachment C-3. (Omitted from this public copy of the EP.) 

(e) Shallow Hazards Report 

A Shallow Hazards Report for Atwater Valley 18/19 is being submitted with this EP. The data 

was provided within the geohazard report, “3D Geohazard Assessment-Gulf of Mexico-Atwater 

Valley-Blocks 018 and 019-Stromboli Prospect” (Gardline Report 9172).
 

(f) Shallow Hazards Assessment 

Site Clearance Letters for the proposed wellsites are included with this EP submittal and 

enclosed as Attachment C-4. 

(g) High-resolution Seismic Lines 

High resolution seismic lines are enclosed as Attachment C-5.

(h) Stratigraphic Column 

A generalized stratigraphic column depicting the wells from the seafloor to total depth is 

included as Attachment C-6. (Omitted from this public copy of the EP.)

(i) Time Vs. Depth Tables 

The proposed activities under this EP are not considered to be in areas where there is no well 

control. Therefore, a seismic travel time versus depth table is not required per NTL 2008-G04, 

extended by NTL 2014-G03. 
ANADARKO PETROLEUM CORPORATION

3D GEOHAZARD ASSESSMENT

GULF OF MEXICO

ATWATER VALLEY BLOCK AT018

STROMBOLI PROSPECT

AT018-CC PROPOSED WELL LOCATION

WELL CLEARANCE LETTER 

APRIL 2013

Gardline Project Ref. 9520

Report Status Final

Issue Date July 15, 2013

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

REPORT AUTHORIZATION AND DISTRIBUTION

Report Status Final 

Issue Date July 15, 2013

Compilation Geophysicist L Fuentes

Authorization Geophysics .....................

A R Haigh

Quality Assurance .....................

M DeLeon

Distribution 

6 copies 

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

For attention of:

Rick Kincaid

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

SERVICE WARRANTY

USE OF THIS REPORT

This report has been prepared with due care, diligence and with the skill reasonably expected of a 

reputable contractor experienced in the types of work, carried out under the contract. As such, the 

findings in this report are based on an interpretation of data which is a matter of opinion on which 

professionals may differ and, unless clearly stated, is not a recommendation of any course of action. 

Gardline Surveys, Inc. has prepared this report for the client identified on the front cover in fulfilment of 

its contractual obligations under the referenced contract, and the only liabilities Gardline Surveys, Inc. 

will accept are those contained therein.

Please be aware that further distribution of this report, in whole or part, or the use of the data for a 

purpose not expressly stated within the contractual work scope is at the client’s sole risk, and Gardline 

Surveys, Inc recommends that this disclaimer be included in any such distribution. 

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com

iii
Green Canyon Atwater Valley Lloyd Ridge

Mississippi Canyon

Destin Dome

De Soto Canyon

Mobile Pensacola

Ship Shoal Area

Eugene Island Area

Viosca Knoll

Viosca Knoll

Main Pass Area

Ewing Bank

South Timbalier Area

West Delta Area

Louisiana

Alabama Mississippi

Florida

Location Map

Study Area
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

TABLE OF CONTENTS

REPORT AUTHORIZATION AND DISTRIBUTION ii

SERVICE WARRANTY iii

LOCATION MAP iv

TABLE OF CONTENTS v

LIST OF FIGURES vi

LIST OF CHARTS vii

WELL CLEARANCE LETTER – PROPOSED AT018-CC WELL LOCATION 1

1. LOCATION COORDINATES 3

1.1 Proposed AT018-CC Well Location 3

2. VELOCITY DATA 4

2.1 Velocity Data 4

3. SEABED CONDITIONS 6

3.1 Bathymetry 6

3.2 Seafloor Morphology and Man Made Features 6

4. SUBSEABED CONDITIONS 7

4.1 Geology and Lithology 7

4.2 Unit A 7

4.3 Unit B 7

4.4 Unit C 7

4.5 Unit D 8

4.6 Shallow Gas Assessment 9

4.7 Shallow Water Flow Assessment 9

5. CONCLUSIONS AND RECOMMENDATIONS 10

APPENDIX A – Public Shallow Hazards Statements

APPENDIX B – Sensitive Sessile Benthic Community Statements

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

LIST OF FIGURES

Proposed AT018-CC Well Location

1 Seabed Depth Extract

2 Seabed Morphology Extract

3 Seabed Amplitude Extract

4 Geohazard Summary Extract

5 Sand Lithology Summary 

6 Inline Data Example

7 Crossline Data Example

8 Top Hole Prognosis

9 ROV Plat

10 Power Spectrum

11 Bathymetry Plat

12 Public Information Plat

13 Proprietary Information Plat

14 Vicinity Map

15 10-Mile Radius Plat

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

LIST OF CHARTS

The following chart at a scale of 1" = 2,000ft is enclosed:

Chart No Title Drawing No

1 Biological, Physical and Socio-Economic Map 9520.01

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

WELL CLEARANCE LETTER – PROPOSED AT018-CC WELL LOCATION 

July 15, 2013

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

Attention: Rick Kincaid

Well Clearance Letter

Proposed AT018-CC Well Location

Block 018, Atwater Valley Area

OCS- G33863

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Well Clearance 

Letter for the proposed AT018-CC well location in Block 018, Atwater Valley Area (OCS-G 33863). 

This letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this well clearance 

assessment is Top of Salt or -10,279ft below sea surface (6,112ft below seabed). We understand that 

Anadarko Petroleum Corporation plans to drill the proposed exploration well from a dynamically 

positioned drilling vessel; therefore, an anchoring assessment is not required. Relevant letter-size 

chart extracts, data examples, and a Top Hole Prognosis are presented with this Well Clearance 

Letter. This geohazard assessment is based on the interpretation of 3D seismic data. This site 

clearance letter is issued as a supplement to Gardline Report No.9172 entitled: 3D Geohazard 

Assessment, Atwater Valley Block 018, dated August 2012. 

Archaeological Survey. Anadarko Petroleum Corporation provided for review the complete 

archaeological survey report acquired by C&C Technologies Survey Services: Archaeological Survey 

Blocks 18 (OCS-G-33863) and 19 (OCS-G-32556) Atwater Valley Area for the Anadarko Stromboli 

Prospect. 

3D Geophysical Survey. Anadarko Petroleum Corporation provided the 3D dataset to Gardline 

Surveys Inc. on tape media in SEG-Y format for loading onto a Seismic Micro-Technology (SMT) 

workstation. The 3D data cube contains a survey with 4 millisecond sample rate data to a record 

length of 6.0 seconds TWT below sea surface. Inlines are oriented north to south, have a numerical 

increment of one, and exhibit a line spacing of 65.62ft. Crosslines are oriented west to east, have a 

numerical increment of one, and exhibit a line spacing of 41.01ft.

• The acquisition parameters are: 

o Atwater Valley (I) DW V

Shooting Direction: N/S

Configuration: 4 sources, 6-10 streamers

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

Maximum offset: 8000 m

Channels: 324 per streamer 

Shotpoint interval: 47.25 m per array 

Group interval: 25 m

CMP line spacing: 40 m 

CMP bin dimension: 12.5 m x 40 m 

Record Length: 9 s below sea bottom 

Nominal fold: 43

Vintage: April 1999

• The basic processing parameters are:

o Atwater Valley (I) DW V

480-m x 500-m velocity grid 

Demultiple 

3D DMO velocity and stacking technology 

One-pass 3D poststack migration 

12.5-m x 20-m final bin dimension

The data exhibits a good frequency response across the upper 1 second below seabed, with an 

effective frequency range of 5Hz to 60Hz. The data exhibits a dominant frequency of 

approximately 53Hz with significant higher usable frequencies. This frequency range results in a 

mean vertical resolvability of approximately 10m and a layer detectability of 5ft. 

In summary and with reference to NTL No. 2008-G04

a) The 3D data provides images of sufficient resolution of the shallow section allowing a 

clear analysis of the shallow conditions

b) The data can be loaded to a workstation at 16bit resolution or greater, and is un-scaled

c) There is no trace or sample decimation

d) The sample interval and bin size are maintained throughout the assessment area

e) The data possess a frequency content of 50Hz or higher across the first second below 

seabed (See Power Spectrum Diagram: Figure 10) 

f) Seabed reflection is free of gaps and defined by a wavelet of stable shape and phase, 

allowing auto-tracking of the seabed event with minimum user intervention and guidance

g) There are no significant acquisition artefacts throughout the dataset

h) There are no merge points in the data

i) Processed bin sizes are 65.62ft x 41.01ft

j) The sample rate of the data is 4ms

k) An accurate velocity model has been utilized in the shallow section allowing optimum 

structural and stratigraphy resolution with no evidence of under or over migration

l) There is no significant multiple energy

m) The proposed activities are not in an area of high archaeological potential.

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1. LOCATION COORDINATES

1.1 Proposed AT018-CC Well Location

Proposed AT 18 CC Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 55' 56.56” North Easting 975,301 US ft E

Longitude 89° 03’ 37.04” West Northing 10,141,870 US ft N

FEL of Atwater Valley 18 6,779 US ft Inline 5242

FSL of Atwater Valley 18 4,270 US ft Crossline 10492

Water Depth: -4,167 ft Slope: 1.3° NE

Nearest Shoreline 71 Miles @ 343° 

Port of Operation Fourchon 106 Miles @ 320° 

Nearest Manned Platform MC941-(Mirage/Titan) 7 Miles @ 341° 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

2. VELOCITY DATA 

2.1 Velocity Data

Time-to-depth conversion for the water column was derived using the Advocate and Hood 

(1993) polynomial.

Water Depth (ft) =

0.1105 – 5066.9193X + 468.6693X2 – 554.7107X3 + 340.7019X4 – 116.991X5 + 20.728X6 – 1.4658X7 

Where X = one way time in seconds to seabed. 

One Way Time To Seabed (s) Seabed Depth (ft) Seabed Depth (m) Vavg (m/s)

0.0 0 0 0

1.0 4910 1496 1496

1.1 5400 1646 1496

1.2 5892 1796 1496

1.3 6384 1946 1497

1.4 6877 2096 1497

1.5 7370 2246 1498

1.6 7865 2397 1498

1.7 8360 2548 1499

1.8 8856 2699 1499

1.9 9353 2851 1500

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Sub-seabed time to depth conversion was performed using a polynomial function 

successfully applied in an adjacent project and approved by Anadarko Petroleum 

Company: 

Vavg = = -45.841X5 + 190.08X4

 – 183.08X3 - 14.729X2 + 735.59X +4900

Where A = two way time in seconds below seabed. 

The resultant velocity was then multiplied by the time below seabed to produce depth below 

seabed; this horizon depth was summed with seabed depth to produce horizon depth below 

sea surface.

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

3. SEABED CONDITIONS 

3.1 Bathymetry

Seabed depth at the proposed AT018-CC well location is -4,167ft below sea surface (Figure 

1). The seafloor slopes to the NE at 1.3°.

3.2 Seafloor Morphology and Man Made Features

The proposed AT018-CC well location is in the south of Block AT018. The seabed at the 

proposed well location is smooth and featureless (Figure 2). Soft clays and silts are predicted 

at seabed. Sediments appear conducive for jetting of seabed casing with no hard layers 

predicted. 

The proposed well AT018-CC is located in a region with a number of seabed fault 

intersections with the nearest fault being located approximately 1,279ft to the southwest; 

this fault should not affect the proposed well. 

There is an existing well AT018-1 located 11,253ft to the northeast. The following are the 

coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

There are no anomalous seabed amplitudes indicative of hydrocarbon macroseep observed 

within a 2,000ft radius of the proposed location (Figure 3).

No items of archaeological significance were identified within 2,000ft of the proposed location

(archaeological report submitted under a separate cover). 

No other features are observed within a 2,000ft radius that could affect well emplacement or 

jetting of casing.

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

4. SUBSEABED CONDITIONS

4.1 Geology and Lithology

The sub-seabed geology has been divided into four units separated by four horizons (Figures 

6 through 8). A Geohazard Summary Extract and Sand Lithology Extract complete the well 

assessment (Figures 4 and 5). 

4.2 Unit A 

The uppermost interval within Unit A, from seabed to -4,428ft below sea surface (261ft below 

seabed), is interpreted as clays and silts with occasional minor coarser interbeds. 

The lower interval of Unit A, from -4,428ft to -4,802ft below sea surface (261ft to 635ft below 

seabed), is interpreted to comprise of clays and silts. 

No shallow gas or shallow water flow is predicted within Unit A at the proposed well location.

A vertical borehole will not penetrate any faults within Unit A. 

Horizon H10 marks the base of Unit A at -4,802ft below sea surface (635ft below seabed). 

4.3 Unit B 

The upper interval of Unit B, from -4,802t to -5,620ft below sea surface (635ft to 1,453ft below 

seabed), is expected to comprise slightly higher energy clays and silts with the possibility of 

several coarser interbeds. Due to the increased potential for some unconsolidated interbeds 

in this interval minor drilling fluid circulation and minor wellbore stability problems may occur

within this interval. 

The lower interval of Unit B, from -5,620ft to -5,714ft below sea surface (1,453ft to 1,547ft 

below seabed), is interpreted to consist of clays and silts with occasional coarser interbeds. 

No shallow gas or shallow water flow is predicted within Unit B at the proposed well location.

A vertical borehole will not penetrate any faults within Unit B.

Horizon H20 marks the base of Unit B at -5,714ft below sea surface (1,547ft below seabed).

4.4 Unit C 

Lithology within the upper interval of this unit, from -5,714ft to -6,313ft below sea surface 

(1,547ft to 2,146ft below sea surface), is interpreted as higher energy clays and silts with 

several coarser interbeds that may represent sands. The proposed well is located on the 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

southwest edge of a sand fairway package that extends from the southwest part of the 

adjacent Block AT019 into the northwest of Block AT018 (Figure 5). A number of highamplitude anomalies associated with this sand fairway package are located within 2,000ft 

around the proposed well location and have been assigned a high risk of gas. The vertical 

borehole will not intersect any of these anomalies; the closest being approximately 389ft to 

the southeast of the proposed well. However, given the location of the well on the periphery 

of this higher energy sand fairway, a Slight Risk of Gas is assigned to this interval. In 

addition to higher energy, the likely sandy nature of this interval is a favorable environment for 

the development of shallow water flow. A previously drilled well (AT063-2) located 3.8 miles 

to the southeast of the present well experienced a low shallow water flow event at -2,012ft 

below seabed which correlates with this interval. Given this drilling provenance and the 

relatively close association with possible gas anomalies in the sand fairway, a Moderate 

Shallow Water Flow Risk classification is assigned to this interval.

The lithology from -6,313ft to -6,575ft below sea surface (2,146ft to 2,408ft below seabed) is 

interpreted as clays and silts with several coarser interbeds that may represent sands. Minor 

drilling fluid circulation and wellbore stability problems may also occur. 

The lower interval within Unit C from -6,575ft to -6,846ft below sea surface (2,408ft to 2,679ft 

below seabed) is interpreted to comprise a further higher-energy package with indications of

clays and silts with several coarser interbeds that may represent sands. The well path is 

located outside the main cluster of high-amplitude anomalies, with the closest anomaly 

considered a significant risk of gas being over 1300ft to the southeast. However, due to the

higher energy interpreted sandy nature of this interval, and the overlying more clay prone 

interval, a Slight Shallow Water Flow Risk is assigned. Additionally, minor drilling fluid 

circulation and wellbore stability problems may also occur. 

A vertical borehole will not penetrate any faults within Unit C.

Horizon H30 marks the base of Unit C at -6,846ft below sea surface (2,679ft below seabed). 

4.5 Unit D 

The upper interval of Unit D from -6,846 ft to -7,520ft below sea surface (2,679ft to 3,353ft 

below seabed), is interpreted to consist of clays and silts with occasional coarser interbeds. 

From -7,520ft to -8,825ft below sea surface (3,353ft to 4,654ft below seabed) is interpreted as 

a higher energy package comprising clays and silts with numerous coarser interbeds. This 

interval exhibits character of shallow water flow, with potential for rapid deposition, and 

inadequate dewatering. As such, a Moderate Shallow Water Flow Risk is assigned to this 

interval. Downdip connectivity of these sandy interbeds is broken by a fault occurring to the 

southwest of the location, this could potentially limit the severity of any shallow water flow 

experienced. To the north, south and east, these sandy interbeds exhibit significant character 

of shallow gas, both up and downdip, and are considered a moderate risk of gas. At the 

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proposed location the amplitude is reduced and direct connectivity to the anomalies is broken 

by faulting. However, given the potential for shallow gas in the general vicinity, it is 

considered prudent to assign a Slight Risk of Gas to this interval. 

Within the interval from -8,825m to -10,279m below sea surface (4,658m to 6,112m below 

seabed) the stratigraphy is interpreted to consist of clays with occasional coarser interbeds 

that may represent sands. A possible <40ft thick sand interbed occurs just above the salt at -

10,068ft below sea surface (5,901ft below seabed). It remains possible that this reflectivity 

could be from the top salt surface, but it appears out of the general context and slightly 

anomalous. The reflection exhibits a moderate risk of gas character around 35ft to the east of 

the proposed location, but the location is downdip of this anomaly. As such, the close 

presence of better defined gas indicators results in a Slight Risk of Gas classification

assigned at the level of the interbed.

A vertical borehole will penetrate three faults within Unit D. The upper fault is interpreted at 

-7,056ft below sea surface (2,889ft below seabed) and extends back to seafloor. This fault 

presents a significant risk for drilling fluid circulation and wellbore stability problems, especially 

if pressures over hydrostatic are exerted by the drilling fluid column. The deeper two faults 

occur at -7,931ft and 8,825ft below sea surface (3,764ft and 4,658ft below seabed), and have

limited vertical extent. Minor drilling fluid circulation and wellbore stability problems may occur 

at the level of these faults if pressures over hydrostatic are exerted by the drilling fluid column.

Top of Salt marks the base of Unit D and the base of this interpretation at -10,279ft below sea 

surface (6,112ft below seabed).

4.6 Shallow Gas Assessment

Within Unit C, a Slight Risk of Gas is assigned from -5,714ft to -6,313ft below sea surface 

(1,547ft to 2,146ft below seabed). 

Within Unit D, a Slight Risk of Gas is assigned between -7,520ft to -8,825ft below sea 

surface (3,353ft to 4,658ft below seabed) and at the level of a <40ft thick sand interbed at 

-10,068ft below sea surface (5,901ft below seabed). 

4.7 Shallow Water Flow Assessment

Within Unit C, a Moderate Shallow Water Flow Risk is interpreted from -5,714ft to -6,313ft 

below sea surface (1,547ft to 2,146ft below seabed) and a Slight Shallow Water Flow Risk

is assigned from -6,575ft to -6,846ft below sea surface (2,408ft to 2,679ft below seabed). 

Within Unit D, a Moderate Shallow Water Flow Risk is assigned from -7,520ft to -8,825ft 

below sea surface (3,353ft to 4,658ft below seabed). 

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5. CONCLUSIONS AND RECOMMENDATIONS

• Seabed

No significant problems are anticipated at seabed. Shallow soils are expected to be 

conducive to the jetting of seabed casing with no hardgrounds predicted.

• Unit A 

No drilling hazards or problems are predicted.

• Unit B

Minor drilling and minor wellbore stability problems are possible from -4,802ft to -5,620ft 

below sea surface (635ft to 1,453ft below seabed). 

• Unit C 

Within Unit C, a Slight Risk of Gas and a Moderate Shallow Water Flow Risk is assigned 

to the interval from -5,714ft to -6,313ft below sea surface (1,547ft to 2,146ft below seabed). 

Drilling Caution is advised and appropriate drilling methodology is recommended to contain

a possible water flow event throughout this interval. Additionally, minor drilling fluid circulation 

and wellbore stability problems may also occur within this interval.

A Slight Shallow Water Flow Risk is also interpreted from -6,575ft to -6,846ft below sea 

surface (2,408ft to 2,679ft below seabed). Appropriate drilling methodology is recommended 

to contain a shallow water flow event through this interval. Additionally, minor drilling fluid 

circulation and wellbore stability problems may also occur within this interval.

Minor drilling and minor wellbore stability problems are possible from -6,313ft to -6,575ft 

below sea surface (2,146ft to 2,408ft below seabed).

• Unit D

Within Unit D, a Slight Risk of Gas and Moderate Shallow Water Flow Risk is assigned 

between -7,520ft to -8,825ft below sea surface (3,353ft to 4,658ft below seabed). Drilling 

Caution is advised and appropriate drilling methodology is recommended to contain a 

possible water flow event throughout this interval. Additionally, minor drilling fluid circulation 

and wellbore stability problems may also occur within this interval. 

A Slight Risk of Gas is assigned at the level of a <40ft thick sand interbed at -10,068ft below 

sea surface (5,901ft below seabed). Drilling Caution is advised; however, it is likely that full 

well control will have been established by this depth.

A vertical borehole will penetrate three faults within Unit D. The upper fault occurs at -7,056ft 

below sea surface (2,889ft below seabed); and extends to seabed. As such, drilling fluid 

circulation problems are considered possible at the level of this fault if pressures over 

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hydrostatic are exerted by the drilling fluid column. The two less extensive deeper faults 

occur at -7,931ft below sea surface (3,764ft below seabed) and at -8,825ft below sea surface 

(4,658ft below seabed). Minor drilling fluid circulation and wellbore stability problems may 

occur at the level of this fault. It is recommended that casing seats avoid the level of the faults 

as formation integrity could be compromised.

11
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

We appreciate the opportunity to work with you on this project, and look forward to continuing as 

your geohazards consultants. Please contact us if you have any questions or if we can be of 

further assistance.

Sincerely,

Gardline Surveys Inc.

Andrew Haigh Matilde DeLeon

Geophysical Manager Quality Assurance

Copies Submitted: 6 copies to Rick Kincaid at Anadarko Petroleum Corporation.

Attachments:

Proposed AT018 CC Well Location

Seabed Depth Extract

Seabed Morphology Extract

Seabed Amplitude Extract

Geohazard Summary Extract

Sand Lithology Summary

Inline Data Example

Crossline Data Example

Top Hole Prognosis

ROV Plat

Power Spectrum

Bathymetry Plat

Public Information Plat

Proprietary Information Plat

Vicinity Map

10-Mile Radius Plat

12
Top Hole Prognosis for Proposed AT018-CC Well Location

975,301ft E / 10,141,870ft N

Inline: 5242 / Crossline: 10492 Horizon

Subsea

Depth

(ft)

BML

Depth

(ft)

Horizon

TWT

(sec)

Lithology, Structure & Stratigraphy Potential Drilling Hazards & Constraints

Risk

of

Gas

SWF

Risk

Seabed -4,167 0 1.703 Seabed is smooth sloping to the northeast at 1.3°. Surficial sediments comprises of 

soft clays and silts, passing into clays and silts with occasional minor coarser 

interbeds.

Figure 8

Interface -6,313 2,146 2.492

Horizon H10 -4,802 635 1.953

Interface -6,575 2,408 2.579

None predicted

Unit A

Unit B

Horizon H20 -5,714 1,547 2.286

Interface -7,520 3,353 2.878

Horizon H30 -6,846 2,679 2.667

Top of Salt -10,279 6,112 3.627

Fault -7,056 2,889 2.734

Interface -5,620 1,453 2.253

Interface -4,428 261 1.808 None predicted

Vavg

BML

(m/s)

0

5,441

5,081

5,498

5,306

5,707

5,557

6,353

5,603

5,285

4,976 Clays and silts

Unit C

Unit D

Fault -7,931 3,764 3.001 5,800

Interface/Fault -8,825 4,658 3.253 6,010

Sand Interbed -10,068 5,901 3.575 6,305

Minor drilling fluid circulation and minor wellbore stability problems

possible within this interval

Clays and silts with several coarser interbeds

Clays and silts with occasional coarser interbeds None predicted

Clays and silts with several coarser interbeds that may represent sands Slight Risk of Gas and Moderate Shallow Water Flow Risk

Minor drilling fluid circulation and minor wellbore stability problems

possible within this interval

Clays and silts with several coarser interbeds that my represent sands

Slight Shallow Water Flow Risk. Minor drilling fluid circulation and

wellbore stability problems possible

Clays and silts with several coarser interbeds that may represent sands

Drilling fluid circulation problems may occur at the level of the fault if

pressures over hydrostatic are exerted by the drilling fluid column

Clays and silts with occasional coarser interbeds

Clay and silts with numerous coarser interbeds that may represent sands Slight Risk of Gas and Moderate Shallow Water Flow Risk

Drilling fluid circulation problems may occur at the level of the fault if

pressures over hydrostatic are exerted by the drilling fluid column

Clays with occasional coarser interbeds that may represent sands Slight Risk of Gas and Moderate Shallow Water Flow Risk

Slight Risk of Gas, Full well control should have been established 

at these depths

<40ft thick sand interbed

Base of interpretation
±

3® 3

3

3

Proposed AT018-CC Well

-4180

-4190

-4200

-4210

-4170

-4160

-4220

-4150

-4230

-4240

-4250

-4260

-4270

-4280

-4290

-4140

-4300

-4240

-4220

-4160

-4230

-4270

-4260

-4160

-4150

-4280

-4150

-4140

-4210

-4160

-4240

-4260

-4270

-4180

-4200

-4180

-4160

-4200

-4150

-4180

-4250

-4210

-4210

-4150

-4150

-4230

-4170

-4170 -4160

-4150

-4230

89°5'0"W89°4'0"W89°3'0"W

27°57'0"N

27°56'0"N

27°55'0"N

970,000975,000980,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1 = 2,000'

Bathymetry Plat Figure 11

2,000ft Radius

Proposed AT018-CC

Easting: 975,301ft E

Northing: 10,141,870ft N

FEL of AT018-CC: 6,779ft

FSL of AT018-CC: 4,270ft

ATWATER VALLEY 

BLOCK 18(OCS-G33863)

ATWATER VALLEY 

BLOCK 62(OCS-G32560)
±

3® 3

3

3

Proposed AT018-CC Well

89°5'0"W89°4'0"W89°3'0"W

27°57'0"N

27°56'0"N

27°55'0"N

970,000975,000980,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1" = 2,000'

Well Location Plat - Public Information Figure 12

ATWATER VALLEY 

BLOCK 18(OCS-G33863)

ATWATER VALLEY 

BLOCK 62(OCS-G32560)

Location Call N/S Call E/W X Coordinate Y Coordinate Latitude Longitude WD

AT018-CC SL 4,270ft FSL 6,779ft FEL 975,301 10,141,870 27° 55' 56.56'' N 89° 03' 37.04'' W -4,167

Proposed Location - AT018-CC
Nearest Shoreline

Range: 71mi

Bearing: 343°

Fourchon

Range: 106mi

Bearing: 320°

Lund

Henderson

Lloyd Ridge

Walker Ridge

Destin Dome

Atwater Valley Green Canyon

De Soto Canyon

The Elbow

Florida Plain

Vernon Basin

Apalachicola

Garden Banks

Keathley Canyon

Florida Middle Ground

Howell Hook

Lund South

Pensacola

Amery Terrace

Mobile

Viosca Knoll

Viosca Knoll

Sigsbee Escarpment

New Orleans

Baton Rouge

Pensacola

Lafayette

Gulfport Pascagoula

Vicinity Map - Atwater Valley Block 019

Figure 14
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-CC

APPENDIX A – Public Shallow Hazards Statements 

28
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-CC

Public Shallow Hazards Statement – AT018-CC

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213-2394

Attention: 

Reference: Shallow Hazards Analysis

Atwater Valley Block 018

OCS-(G 33863) 

Ladies/Gentlemen:

Anadarko Petroleum Corporation contracted Gardline Surveys, Inc. to prepare a Well Clearance Letter 

for the proposed AT018-CC well location in Block 018, Atwater Valley Area (OCS-G 33863). This 

letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this geohazard assessment 

is to Top of Salt at -10,279ft below sea surface (6,112ft below seabed).

This hazard summary letter is issued as a supplement to Gardline Report No.9172 entitled: 3D 

Geohazard Assessment, Atwater Valley Block 018, dated August 2012.

Seabed Hazards. 

The seabed is smooth and featureless. No problems are expected at the proposed AT018-CC well 

location.

There are no indications of seabed fluid seeps within 2,000ft of the well location.

No existing seabed infrastructure is located within 2,000ft of the proposed well. 

Sub-Seabed Hazards. 

Drilling Caution is indicated within Units C and D for a Slight Risk of Gas. 

Moderate Shallow Water Flow Risk is assigned to two intervals within Units C and D. A Slight 

Shallow Water Flow Risk is anticipated within an interval in Unit C. 

29
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-CC

Proposed AT 18 CC Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 55' 56.56” North Easting 975,301 US ft E

Longitude 89° 03’ 37.04” West Northing 10,141,870 US ft N

FEL of Atwater Valley 18 6,779 US ft Inline 5242

FSL of Atwater Valley 18 4,270 US ft Crossline 10492

Water Depth: -4,167 ft Slope: 1.3° NE

Nearest Shoreline 71.34 Miles @ 343° 25’ 48’’

Port of Operation Fourchon 106.42Miles @ 320° 36’ 0’’

Nearest Manned Platform MC941-(Mirage/Titan) 7.38 Miles @ 341° 31’ 18”

Conclusions and Recommendations. 

Drilling techniques will take into consideration the possibility of encountering possible gas within 

defined intervals in Unit C and in Unit D. Appropriate drilling methodology should be utilized to contain 

a potentially non-persistent Slight Shallow Water Flow Risk interpreted in Unit C. Appropriate drilling 

methodology should be utilized to contain a possible Moderate Shallow Water Flow Risk in the 

intervals within Unit C and within Unit D. 

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

PUBLIC INFORMATION

30
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-CC

APPENDIX B – Sensitive Sessile Benthic Community Statements

31
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-CC

Sensitive Sessile Benthic Community Statement – AT018-CC

Anadarko Petroleum Corporation

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213

Reference: Sensitive Sessile Benthic Community Summary

Atwater Valley, Block 018

OCS-(G 33863) 

Ladies/Gentlemen:

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Site Clearance 

Letter for the proposed AT018-CC well location in Atwater Valley, Block 018, Stromboli Prospect 

(OCS-G G 33863). This letter addresses location proximity to potential sensitive sessile benthic 

community sites. Anadarko Petroleum Corporation will be drilling this well from a dynamically 

positioned drilling module; therefore, no anchors will impact seabed.

This sensitive sessile benthic community summary letter is issued as a supplement to Gardline Report 

No.9172 entitled: 3D Geohazard Assessment, Atwater Valley Block 018, dated August 2012. A 

Biological, Physical and Socio-Economic Map is included at the end of this appendix illustrating the 

areas of potential seabed impact.

Potential Sensitive Sessile Benthic Communities. 

Features or areas that could support high density sensitive sessile benthic communities are not 

located within 2,000ft of any proposed mud and cuttings discharge location.

Proposed AT 18 CC Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 55' 56.56” North Easting 975,301 US ft E

Longitude 89° 03’ 37.04” West Northing 10,141,870 US ft N

FEL of Atwater Valley 18 6,779 US ft Inline 5242

FSL of Atwater Valley 18 4,270 US ft Crossline 10492

Water Depth: -4,167 ft Slope: 1.3° NE

Nearest Shoreline 71.34 Miles @ 343° 25’ 48’’

Port of Operation Fourchon 106.42Miles @ 320° 36’ 0’’

Nearest Manned Platform MC941-(Mirage/Titan) 7.38 Miles @ 341° 31’ 18”

32
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-CC

No potential sensitive sessile benthic community site is located within 2,000ft of the proposed 

location. 

Conclusions and Recommendations: 

The proposed AT018-CC well location will not impact any sites favorable for development of sensitive 

sessile benthic communities.

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

33
ANADARKO PETROLEUM CORPORATION

3D GEOHAZARD ASSESSMENT

GULF OF MEXICO

ATWATER VALLEY BLOCK AT018

STROMBOLI PROSPECT

AT018-DD PROPOSED WELL LOCATION

WELL CLEARANCE LETTER 

APRIL 2013

Gardline Project Ref. 9521

Report Status Final

Issue Date July 15, 2013

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

REPORT AUTHORIZATION AND DISTRIBUTION

Report Status Final

Issue Date July 15, 2013

Compilation Geophysicist L Fuentes

Authorization Geophysics .....................

A R Haigh

Quality Assurance .....................

M DeLeon

Distribution 

6 copies

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

For attention of:

Rick Kincaid

ii
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

SERVICE WARRANTY

USE OF THIS REPORT

This report has been prepared with due care, diligence and with the skill reasonably expected of a 

reputable contractor experienced in the types of work, carried out under the contract. As such, the 

findings in this report are based on an interpretation of data which is a matter of opinion on which 

professionals may differ and, unless clearly stated, is not a recommendation of any course of action. 

Gardline Surveys, Inc. has prepared this report for the client identified on the front cover in fulfilment of 

its contractual obligations under the referenced contract, and the only liabilities Gardline Surveys, Inc. 

will accept are those contained therein.

Please be aware that further distribution of this report, in whole or part, or the use of the data for a 

purpose not expressly stated within the contractual work scope is at the client’s sole risk, and Gardline 

Surveys, Inc recommends that this disclaimer be included in any such distribution. 

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com

iii
Green Canyon Atwater Valley Lloyd Ridge

Mississippi Canyon

Destin Dome

De Soto Canyon

Mobile Pensacola

Ship Shoal Area

Eugene Island Area

Viosca Knoll

Viosca Knoll

Main Pass Area

Ewing Bank

South Timbalier Area

West Delta Area

Louisiana

Alabama Mississippi

Florida

Location Map

Study Area
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

TABLE OF CONTENTS

REPORT AUTHORIZATION AND DISTRIBUTION ii

SERVICE WARRANTY iii

LOCATION MAP iv

TABLE OF CONTENTS v

LIST OF FIGURES vi

LIST OF CHARTS vii

WELL CLEARANCE LETTER – PROPOSED AT018-DD WELL LOCATION 1

1. LOCATION COORDINATES 3

1.1 Proposed AT018-DD Well Location 3

2. VELOCITY DATA 4

2.1 Velocity Data 4

3. SEABED CONDITIONS 6

3.1 Bathymetry 6

3.2 Seafloor Morphology and Man Made Features 6

4. SUBSEABED CONDITIONS 7

4.1 Geology and Lithology 7

4.2 Unit A 7

4.3 Unit B 7

4.4 Unit C 7

4.5 Unit D 8

4.6 Shallow Gas Assessment 9

4.7 Shallow Water Flow Assessment 9

5. CONCLUSIONS AND RECOMMENDATIONS 10

APPENDIX A – Public Shallow Hazards Statements

APPENDIX B – Sensitive Sessile Benthic Community Statements

v 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

LIST OF FIGURES

Proposed AT018-DD Well Location

1 Seabed Depth Extract

2 Seabed Morphology Extract

3 Seabed Amplitude Extract

4 Geohazard Summary Extract

5 Sand Lithology Summary 

6 Inline Data Example

7 Crossline Data Example

8 Top Hole Prognosis

9 ROV Plat

10 Power Spectrum

11 Bathymetry Plat

12 Public Information Plat

13 Proprietary Information Plat

14 Vicinity Map

15 10-Mile Radius Plat

vi
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

LIST OF CHARTS

The following chart at a scale of 1" = 2,000ft is enclosed:

Chart No Title Drawing No

1 Biological, Physical and Socio-Economic Map 9521.01

vii
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

WELL CLEARANCE LETTER – PROPOSED AT018-DD WELL LOCATION 

July 15, 2013

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

Attention: Rick Kincaid

Well Clearance Letter

Proposed AT018-DD Well Location

Block 018, Atwater Valley Area

OCS- G33863

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Well Clearance 

Letter for the proposed AT018-DD well location in Block 018, Atwater Valley Area (OCS-G 33863). 

This letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this well clearance 

assessment is Top of Salt or -10,071ft below sea surface (5,881ft below seabed). We understand that 

Anadarko Petroleum Corporation plans to drill the proposed exploration well from a dynamically 

positioned drilling vessel; therefore, an anchoring assessment is not required nor provided. Relevant 

letter-size chart extracts, data examples, and a Top Hole Prognosis are presented with this Well 

Clearance Letter. This geohazard assessment is based on the interpretation of 3D seismic data. This 

site clearance letter is issued as a supplement to Gardline Report No.9172 entitled: 3D Geohazard 

Assessment, Atwater Valley Block 018, dated August 2012. 

Archaeological Survey. Anadarko Petroleum Corporation provided for review the complete 

archaeological survey report acquired by C&C Technologies Survey Services: Archaeological Survey 

Blocks 18 (OCS-G-33863) and 19 (OCS-G-32556) Atwater Valley Area for the Anadarko Stromboli 

Prospect. 

3D Geophysical Survey. Anadarko Petroleum Corporation provided the 3D dataset to Gardline 

Surveys Inc. on tape media in SEG-Y format for loading onto a Seismic Micro-Technology (SMT) 

workstation. The 3D data cube contains a survey with 4 millisecond sample rate data to a record 

length of 6.0 seconds TWT below sea surface. Inlines are oriented north to south, have a numerical 

increment of one, and exhibit a line spacing of 65.62ft. Crosslines are oriented west to east, have a 

numerical increment of one, and exhibit a line spacing of 41.01ft.

• The acquisition parameters are: 

o Atwater Valley (I) DW V

Shooting Direction: N/S

Configuration: 4 sources, 6-10 streamers

1 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

Maximum offset: 8000 m

Channels: 324 per streamer 

Shotpoint interval: 47.25 m per array 

Group interval: 25 m

CMP line spacing: 40 m 

CMP bin dimension: 12.5 m x 40 m 

Record Length: 9 s below sea bottom 

Nominal fold: 43

Vintage: April 1999

• The basic processing parameters are:

o Atwater Valley (I) DW V

480-m x 500-m velocity grid 

Demultiple 

3D DMO velocity and stacking technology 

One-pass 3D poststack migration 

12.5-m x 20-m final bin dimension

The data exhibits a good frequency response across the upper one second below seabed, with an 

effective frequency range of 5Hz to 60Hz. The data exhibits a dominant frequency of 

approximately 53Hz with significant higher usable frequencies. This frequency range results in a 

mean vertical resolvability of approximately 10ft and a layer detectability of 5ft. 

In summary and with reference to NTL No. 2008-G04

a) The 3D data provides images of sufficient resolution of the shallow section allowing a 

clear analysis of the shallow conditions

b) The data can be loaded to a workstation at 16bit resolution or greater, and is un-scaled

c) There is no trace or sample decimation

d) The sample interval and bin size are maintained throughout the assessment area

e) The data possess a frequency content of 50Hz or higher across the first second below 

seabed (See Power Spectrum Diagram: Figure 10) 

f) Seabed reflection is free of gaps and defined by a wavelet of stable shape and phase, 

allowing auto-tracking of the seabed event with minimum user intervention and guidance

g) There are no significant acquisition artefacts throughout the dataset

h) There are no merge points in the data

i) Processed bin sizes are 65.62ft x 41.01ft

j) The sample rate of the data is 4ms

k) An accurate velocity model has been utilized in the shallow section allowing optimum 

structural and stratigraphy resolution with no evidence of under or over migration

l) There is no significant multiple energy

m) The proposed activities are not in an area of high archaeological potential.

2 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

1. LOCATION COORDINATES 

1.1 Proposed AT018-DD Well Location

Proposed AT 18-DD Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 56' 29.05” North Easting 978,173 US ft E

Longitude 89° 03’ 05.63” West Northing 10,145,103 US ft N

FEL of Atwater Valley 18 3,907 US ft Inline 5286

FSL of Atwater Valley 18 7,503 US ft Crossline 10571

Water Depth: -4,190 ft Slope: 3.5° SW

Nearest Shoreline 71 Miles @ 343° 

Port of Operation Fourchon 106 Miles @ 320° 

Nearest Manned Platform MC941-(Mirage/Titan) 7 Miles @ 356° 

3 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

2. VELOCITY DATA 

2.1 Velocity Data

Time-to-depth conversion for the water column was derived using the Advocate and Hood 

(1993) polynomial.

Water Depth (ft) =

0.1105 – 5066.9193X + 468.6693X2 – 554.7107X3 + 340.7019X4 – 116.991X5 + 20.728X6 – 1.4658X7 

Where X = one way time in seconds to seabed. 

One Way Time To Seabed (s) Seabed Depth (ft) Seabed Depth (m) Vavg (m/s)

0.0 0 0 0

1.0 4910 1496 1496

1.1 5400 1646 1496

1.2 5892 1796 1496

1.3 6384 1946 1497

1.4 6877 2096 1497

1.5 7370 2246 1498

1.6 7865 2397 1498

1.7 8360 2548 1499

1.8 8856 2699 1499

1.9 9353 2851 1500

4 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

Sub-seabed time to depth conversion was performed using a polynomial function 

successfully applied in an adjacent project and approved by Anadarko Petroleum 

Corporation: 

Vavg = = -45.841X5 + 190.08X4

 – 183.08X3 - 14.729X2 + 735.59X +4900

Where A = two way time in seconds below seabed. 

The resultant velocity was then multiplied by the time below seabed to produce depth below 

seabed; this horizon depth was summed with seabed depth to produce horizon depth below 

sea surface.

5 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

3. SEABED CONDITIONS 

3.1 Bathymetry

Seabed depth at the proposed AT018-DD well location is -4,190ft below sea surface (Figure 

1). The seafloor slopes to the SW at 3.5°.

3.2 Seafloor Morphology and Man Made Features

The proposed AT018-DD well location is in east-central Block AT018. The seabed at the 

proposed well location is smooth and featureless (Figure 2). Soft clays and silts are predicted 

at seabed. Sediments appear conducive for jetting of seabed casing with no hard layers 

predicted. 

The proposed AT018-DD well is located in an area of numerous seabed fault intersections. 

The seabed rendering illustrates a slight rise due to flexure or draping over an old surface, 

but no fault is observed at seabed at this location. Major structural faults are located

2,199ft to the southwest and 500ft to the east and north. These faults only affect the well

at depth (Figure 6). 

Existing well AT018-1 is located 7,130ft to the northeast. The following are the 

coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

BHP Billiton At018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

There are no anomalous seabed amplitudes indicative of hydrocarbon macroseep observed 

within 2,000ft radius of the proposed location (Figure 3).

No items of archaeological significance were identified within 2,000ft of the proposed location

(archaeological report submitted under a separate cover). 

No other features are observed within a 2,000ft radius that could affect well emplacement or 

jetting of casing.

6 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

4. SUBSEABED CONDITIONS

4.1 Geology and Lithology

The sub-seabed geology has been divided into four units separated by four horizons (Figures 

6 through 8). A Geohazard Extract and Sand Lithology Extract complete the well assessment 

(Figures 4 and 5). 

4.2 Unit A 

The uppermost interval within Unit A from seabed to -4,456ft below sea surface (266ft below 

seabed) is interpreted as clays and silts with occasional minor coarser interbeds. 

The lower interval of Unit A from -4,456ft to -4,788ft below sea surface (266ft to 598ft below 

seabed) is interpreted to comprise of clays and silts. 

No shallow gas or shallow water flow is predicted within Unit A at the proposed well location.

A vertical borehole will not penetrate any faults within Unit A. 

Horizon H10 marks the base of Unit A at -4,788ft below sea surface (598ft below seabed). 

4.3 Unit B 

The upper interval of Unit B from -4,788ft to -5,441ft below sea surface (598ft to 1,252ft below 

seabed) is interpreted to consist of clays and silts with several coarser interbeds. Due to the 

potential for possible poorly consolidated sediments in this interval, especially uppermost, 

minor drilling fluid circulation and wellbore stability problems may occur.

A vertical borehole will not penetrate any faults within Unit B.

Horizon H20 marks the base of Unit B at -5,441ft below sea surface (1,252ft below seabed).

4.4 Unit C 

The upper interval of Unit C from -5,441ft to -5,668ft below sea surface (1,252ft to 1,478ft 

below seabed) is interpreted as clays and silts with several coarser interbeds that may 

represent sands. Due to the potential for possible poorly consolidated sediments in this 

interval, minor drilling fluid circulation and wellbore stability problems may occur.

The lithology from -5,668ft to -6,887ft below sea surface (1,478ft to 2,697ft below sea surface)

is interpreted as higher energy clays and silts with numerous coarser interbeds that may 

represent sands. The proposed well is located within a sand fairway package that extends 

from the southwest of the adjacent Block AT019 into the northwest of Block AT018 (Figure 5). 

7 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

A number of high-amplitude anomalies are located within 2,000ft around the proposed well 

location and have been assigned a high risk of gas. The vertical borehole will not intersect 

any of these anomalies, the closest being approximately 592ft to the northeast of the

proposed location. However, given the location of the well within this higher energy sand 

fairway, and the possibility of connectivity a Slight Risk of Gas is assigned to this interval. In 

addition the higher energy, and frequently sandy component in this interval creates a 

favorable environment for the development of shallow water flow. A previously drilled well 

(AT063-2) located 3.8 miles to the southeast of the present well experienced a low shallow 

water flow event at -2,012ft below seabed which correlates with this interval. Given this 

drilling provenance and the relatively close association with possible gas anomalies in the 

sand fairway, a High Shallow Water Flow Risk classification is assigned to this interval.

The lower interval within Unit C from -6,887ft to -7,009ft below sea surface (2,697ft to 2,819ft 

below seabed) is interpreted to comprise a further higher-energy package with indications of

several coarser interbeds that may represent sands. Minor drilling fluid circulation and 

wellbore stability problems may occur. 

A vertical borehole will not penetrate any faults within Unit C.

Horizon H30 marks the base of Unit C at -7,009ft below sea surface (2,819ft below seabed). 

4.5 Unit D 

The upper interval of Unit D, from -7,009 ft to -7,503ft below sea surface (2,819ft to 3,313ft 

below seabed), is interpreted as clays and silts with occasional minor coarser interbeds. 

From -7,503ft to -8,686ft below sea surface (3,313ft to 4,497ft below seabed), the lithology is 

interpreted as a higher energy package comprising clays and silts with numerous coarser 

interbeds. This interval, with the potential for rapid deposition and inadequate dewatering, is 

assigned a Moderate Shallow Water Flow Risk. Within 2,000ft of the proposed location, 

amplitude anomalies occur in this interval that are classed as a Moderate Risk of Gas, the 

closest approach being 600ft to the northwest. Some of these interpreted sandy interbeds 

within which the anomalies occur exhibit connectivity to the wellbore and as such a Slight 

Risk of Gas is assigned. In addition due to the potential for poorly consolidated material 

within this interval minor drilling fluid circulation and wellbore stability problems could occur.

From -8,686ft to -9,753ft below sea surface (4,497ft to 5,563ft below seabed) is interpreted to 

consist of clays with occasional coarser interbeds that may represent sands. 

Within the interval, from -9,753m to -10,071m below sea surface (5,563m to 5,881m below 

seabed), the stratigraphy is interpreted to consist of clays with several coarser interbeds that 

may represent sands. A slight increase in amplitude is observed in this interval immediately 

above top of salt and there is considered the possibility that these may contain small volumes

of fluid; hence a Slight Risk of Gas is assigned.

8 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

A vertical borehole will penetrate a fault within Unit D. This fault occurs at -8,686ft below sea 

surface (4,497ft below seabed), and has a limited vertical extent. However, immediately north 

of the proposed well location an antithetic fault occurs that intersects the wellbore at the same 

level, this fault exhibits connectivity to seabed. It is therefore interpreted that drilling fluid 

circulation and wellbore stability problems could occur at this level, especially if pressures 

over hydrostatic are exerted by the wellbore.

Top of Salt marks the base of Unit D and the base of this interpretation at -10,071ft below sea 

surface (5,881ft below seabed).

4.6 Shallow Gas Assessment

Within Unit C, a Slight Risk of Gas is assigned from -5,668ft to -6,887ft below sea surface 

(1,478ft to 2,697ft below seabed). 

Within Unit D, a Slight Risk of Gas is assigned between -7,503ft to -8,686ft below sea 

surface (3,313ft to 4,497ft below seabed) and from -9,753ft to -10,071ft below sea surface 

(5,563ft to 5,881ft below seabed). 

4.7 Shallow Water Flow Assessment

Within Unit C, a High Shallow Water Flow Risk is interpreted from -5,668ft to -6,887ft below 

sea surface (1,478ft to 2,697ft below seabed). 

Within Unit D, a Moderate Shallow Water Flow Risk is assigned from -7,503ft to -8,686ft 

below sea surface (3,313ft to 4,497ft below seabed). 

9 
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

5. CONCLUSIONS AND RECOMMENDATIONS

• Seabed

No significant problems are anticipated at seabed. Shallow soils are expected to be 

conducive to the jetting of seabed casing with no hardgrounds predicted.

• Unit A 

No drilling hazards or problems are predicted.

• Unit B

Minor drilling fluid and wellbore stability problems are possible throughout this unit from -

4,788ft to -5,441ft below sea surface (598ft to 1,252ft below seabed). 

• Unit C 

Within Unit C, a Slight Risk of Gas and a High Shallow Water Flow Risk is assigned from 

-5,668ft to -6,887ft below sea surface (1,478ft to 2,697ft below seabed).Drilling Caution is 

advised and appropriate drilling methodology is recommended to contain a possible water 

flow event throughout this interval. Additionally, minor drilling fluid circulation and wellbore 

stability problems may also occur within this interval. Due to the potential for poorly 

consolidated material in this interval it is recommended casing seats avoid this section.

Minor drilling fluid and wellbore stability problems are possible from -5,441ft to -5,668ft below 

sea surface (1,252ft to 1,478ft below seabed) and from -6,887ft to -7,009ft below sea surface 

(2,697ft to 2,819ft below seabed). 

• Unit D

Within Unit D, a Slight Risk of Gas and Moderate Shallow Water Flow Risk is assigned 

between -7,503ft to -8,686ft below sea surface (3,313ft to 4,497ft below seabed). Drilling 

Caution is advised and appropriate drilling methodology is recommended to contain a 

possible water flow event throughout this interval. Additionally, minor drilling fluid circulation 

and wellbore stability problems may also occur within this interval. Due to the potential for 

poorly consolidated material in this interval it is recommended casing seats avoid this section.

Within Unit D, a Slight Risk of Gas is assigned within -9,753ft to -10,071ft below sea surface 

(5,563ft to 5,881ft below seabed. Drilling Caution is advised; however, it is likely that full 

well control will have been established by this depth.

A vertical borehole will penetrate a fault within Unit D at -8,686ft below sea surface (4,497ft 

below seabed). This fault extends to seafloor and therefore drilling fluid circulation and 

wellbore stability problems may occur if pressures over hydrostatic are exerted by the drilling 

fluid column. It is recommended that casing seats avoid the level of the fault as formation 

10
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

integrity could be compromised.

We appreciate the opportunity to work with you on this project, and look forward to continuing as 

your geohazards consultants. Please contact us if you have any questions or if we can be of 

further assistance.

Sincerely,

Gardline Surveys Inc.

Andrew Haigh Matilde DeLeon

Geophysical Manager Quality Assurance

Copies Submitted: 6 copies to Rick Kincaid at Anadarko Petroleum Corporation.

Attachments:

Proposed AT018 DD Well Location

Seabed Depth Extract

Seabed Morphology Extract

Seabed Amplitude Extract

Geohazard Summary Extract

Sand Lithology Summary

Inline Data Example

Crossline Data Example

Top Hole Prognosis

ROV Plat

Power Spectrum

Bathymetry Plat

Public Information Plat

Proprietary Information Plat

Vicinity Map

10-Mile Radius Plat

11
Top Hole Prognosis for Proposed AT018-DD Well Location

978,173ft E / 10,145,103ft N

Inline: 5286 / Crossline: 10571 Horizon

Subsea

Depth

(ft)

BML

Depth

(ft)

Horizon

TWT

(sec)

Lithology, Structure & Stratigraphy Potential Drilling Hazards & Constraints

Risk

of

Gas

SWF

Risk

Seabed -4,190 0 1.708 Seabed is smooth sloping to the southwest at 3.5°. Surficial sediments comprise of 

soft clays and silts. Underlying the seabed the lithology comprises of clays and silts 

with occasional minor coarser interbeds.

Figure 8

Interface -7,503 3,313 2.871

Horizon H20 -5,441 1,252 2.186

Interface/Fault -8,686 4,497 3.214

None predicted

Unit A

Unit B

Horizon H30 -7,009 2,819 2.717

Interface -6,887 2,697 2.678

Interface -4,456 266 1.815

Interface -5,668 1,478 2.267

Horizon H10 -4,788 598 1,944

None predicted

Vavg

BML

(m/s)

0

5,698

5,237

5,947

5,582

5,561

5,071

5,669

5,250

Clays and silts

Unit C

Unit D

Interface -9,753 5,563 3.495 6,225

Top of Salt -10,071 5,881 3.575 6300

Clays and silts with several coarser interbeds especially uppermost None predicted

Minor drilling fluid circulation and minor wellbore stability problems 

possible within this interval

Clays and silts with several coarser interbeds that may represent sands

Slight Risk of Gas and High Shallow Water Flow Risk.Minor drilling fluid 

circulation and minor wellbore stability problems possible within this 

interval

Clays and silts with numerous coarser interbeds that may represent sands

Minor drilling fluid circulation and minor wellbore stability problems

possible within this interval

Clays and silts with several coarser interbeds that may represent sands

Clays and silts with occasional coarser interbeds None predicted

Clays and silts with numerous coarser interbeds that may represent sands Slight Risk of Gas and Moderate Shallow Water Flow Risk

Drilling fluid circulation problems may occur at the level of the fault if 

pressures over hydrostatic are exerted by the drilling fluid column

Clays with occasional coarser interbeds that may represent sands

Clays with several coarser interbeds that may represent sands Slight Risk of Gas

Base of interpretation
±

3® 3

3

3

-4180

-4190

-4200

-4210

-4170

-4160

-4220

-4150

-4230

-4240

-4250

-4260

-4270

-4280

-4290

-4140

-4300

-4240

-4220

-4160

-4230

-4270

-4260

-4160

-4150

-4280

-4150

-4140

-4210

-4160

-4240

-4260

-4270

-4180

-4200

-4180

-4160

-4200

-4150

-4180

-4250

-4210

-4210

-4150

-4150

-4230

-4170

-4170 -4160

-4150

-4230

89°5'0"W89°4'0"W89°3'0"W

27°57'0"N

27°56'0"N

27°55'0"N

970,000975,000980,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1 = 2,000'

Bathymetry Plat Figure 11

2,000ft Radius

Proposed AT018-DD

Easting: 978,173ft E

Northing: 10,145,103ft N

FEL of AT018-DD: 3,907ft

FSL of AT018-DD: 7,503ft

ATWATER VALLEY 

BLOCK 18(OCS-G33863)

ATWATER VALLEY 

BLOCK 62(OCS-G32560)
± 6

3® 3

3

3

Proposed AT018-DD Well

AT018-001

89°5'0"W89°4'0"W89°3'0"W

27°57'0"N

27°56'0"N

27°55'0"N

970,000975,000980,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1" = 2,000'

Well Location Plat - Public Information Figure 12

ATWATER VALLEY 

BLOCK 18(OCS-G33863)

ATWATER VALLEY 

BLOCK 62(OCS-G32560)

Location Call N/S Call E/W X Coordinate Y Coordinate Latitude Longitude WD

AT018-DD SL 7,503ft FSL 3,907ft FEL 978,173 10,145,103 27° 56' 29.05"N 89° 03' 05.63"W -4,190

Proposed Location - AT018-DD
Nearest Shoreline

Range: 71mi

Bearing: 343°

Fourchon

Range: 106mi

Bearing: 320°

Lund

Henderson

Lloyd Ridge

Walker Ridge

Destin Dome

Atwater Valley Green Canyon

De Soto Canyon

The Elbow

Florida Plain

Vernon Basin

Apalachicola

Garden Banks

Keathley Canyon

Florida Middle Ground

Howell Hook

Lund South

Pensacola

Amery Terrace

Mobile

Viosca Knoll

Viosca Knoll

Sigsbee Escarpment

New Orleans

Baton Rouge

Pensacola

Lafayette

Gulfport Pascagoula

Vicinity Map - Atwater Valley Block 019

Figure 14
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

APPENDIX A – Public Shallow Hazards Statements 

28
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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

Public Shallow Hazards Statement – AT018-DD

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213-2394

Attention: 

Reference: Shallow Hazards Analysis

Atwater Valley Block 018

OCS-(G 33863) 

Ladies/Gentlemen:

Anadarko Petroleum Corporation contracted Gardline Surveys, Inc. to prepare a Well Clearance Letter 

for the proposed AT018-DD well location in Block 018, Atwater Valley Area (OCS-G 33863). This 

letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this geohazard assessment 

is to Top of Salt at -10,071ft below sea surface (5,881ft below seabed).

This hazard summary letter is issued as a supplement to Gardline Report No.9172 entitled: 3D 

Geohazard Assessment, Atwater Valley Block 018, dated August 2012.

Seabed Hazards. 

The seabed is smooth and featureless. No problems are expected at the proposed AT018-DD well 

location. 

There are no indications of seabed fluid seeps within 2,000ft of the well location.

No existing seabed infrastructure is located within 2,000ft of the proposed well. 

Sub-Seabed Hazards. 

Drilling Caution is indicated within Units C and D for a Slight Risk of Gas. 

High Shallow Water Flow Risk is assigned to an interval within Unit C. A Moderate Shallow Water 

Flow Risk is anticipated within an interval in Unit D. 

29
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

Proposed AT 18 DD Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 56' 29.05” North Easting 978,173. US ft E

Longitude 89° 03’ 05.63 West Northing 10,145,103 US ft N

FEL of Atwater Valley 18 3,907 US ft Inline 5286

FSL of Atwater Valley 18 7,503 US ft Crossline 10571

Water Depth: -4,190 ft Slope: 3.5° SW

Nearest Shoreline 71 Miles @ 343° 

Port of Operation Fourchon 106 Miles @ 320° 

Nearest Manned Platform MC941-(Mirage/Titan) 7 Miles @ 355° 

Conclusions and Recommendations. 

Drilling techniques will take into consideration the possibility of encountering possible gas within 

defined intervals in Unit C and in Unit D. Appropriate drilling methodology should be utilized to contain

a possible Moderate and High Shallow Water Flow Risk in the intervals within Unit C and within Unit 

D. 

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

PUBLIC INFORMATION

30
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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

APPENDIX B – Sensitive Sessile Benthic Community Statements

31
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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

Sensitive Sessile Benthic Community Statement – AT018-DD

Anadarko Petroleum Corporation

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213

Reference: Sensitive Sessile Benthic Community Summary

Atwater Valley, Block 018

OCS-(G 33863) 

Ladies/Gentlemen:

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Site Clearance 

Letter for the proposed AT018-DD well location in Atwater Valley, Block 018, Stromboli Prospect 

(OCS-G G 33863). This letter addresses location proximity to potential sensitive sessile benthic 

community sites. Anadarko Petroleum Corporation will be drilling this well from a dynamically 

positioned drilling module; therefore, no anchors will impact seabed.

This sensitive sessile benthic community summary letter is issued as a supplement to Gardline Report 

No.9172 entitled: 3D Geohazard Assessment, Atwater Valley Block 018, dated August 2012. A 

Biological, Physical and Socio-Economic Map is included at the end of this appendix illustrating the 

areas of potential seabed impact.

Potential Sensitive Sessile Benthic Communities. 

Features or areas that could support high density sensitive sessile benthic communities are not 

located within 2,000ft of any proposed mud and cuttings discharge location.

Proposed AT 18 DD Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 56' 29.05” North Easting 978,173. US ft E

Longitude 89° 03’ 05.63 West Northing 10,145,103 US ft N

FEL of Atwater Valley 18 3,907 US ft Inline 5286

FSL of Atwater Valley 18 7,503 US ft Crossline 10571

Water Depth: -4,190 ft Slope: 3.5° SW

Nearest Shoreline 71 Miles @ 343° 

Port of Operation Fourchon 106 Miles @ 320° 

Nearest Manned Platform MC941-(Mirage/Titan) 7.00 Miles @ 355° 

32
Anadarko Petroleum Corporation Gardline Report 9521

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-DD Well Location

No potential sensitive sessile benthic community site is located within 2,000ft of the proposed 

location. 

Conclusions and Recommendations: 

The proposed AT018-DD well location will not impact any sites favorable for development of sensitive 

sessile benthic communities.

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

33
ANADARKO PETROLEUM CORPORATION

3D GEOHAZARD ASSESSMENT

GULF OF MEXICO

ATWATER VALLEY BLOCK AT 18

STROMBOLI PROSPECT

AT018-GG PROPOSED WELL LOCATION

WELL CLEARANCE LETTER 

APRIL 2013

Gardline Project Ref. 9515

Report Status Final

Issue Date July 15, 2013

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

REPORT AUTHORIZATION AND DISTRIBUTION

Report Status Final 

Issue Date July 15, 2013

Compilation Geophysicist L Fuentes

Authorization Geophysics .....................

A R Haigh

Quality Assurance .....................

M DeLeon

Distribution 

6 copies

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

For attention of:

Rick Kincaid

ii
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

SERVICE WARRANTY

USE OF THIS REPORT

This report has been prepared with due care, diligence and with the skill reasonably expected of a 

reputable contractor experienced in the types of work, carried out under the contract. As such, the 

findings in this report are based on an interpretation of data which is a matter of opinion on which 

professionals may differ and, unless clearly stated, is not a recommendation of any course of action. 

Gardline Surveys, Inc. has prepared this report for the client identified on the front cover in fulfilment of 

its contractual obligations under the referenced contract, and the only liabilities Gardline Surveys, Inc. 

will accept are those contained therein.

Please be aware that further distribution of this report, in whole or part, or the use of the data for a 

purpose not expressly stated within the contractual work scope is at the client’s sole risk, and Gardline 

Surveys, Inc recommends that this disclaimer be included in any such distribution. 

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com

iii
Green Canyon Atwater Valley Lloyd Ridge

Mississippi Canyon

Destin Dome

De Soto Canyon

Mobile Pensacola

Ship Shoal Area

Eugene Island Area

Viosca Knoll

Viosca Knoll

Main Pass Area

Ewing Bank

South Timbalier Area

West Delta Area

Louisiana

Alabama Mississippi

Florida

Location Map

Study Area
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

TABLE OF CONTENTS

REPORT AUTHORIZATION AND DISTRIBUTION ii

SERVICE WARRANTY iii

LOCATION MAP iv

TABLE OF CONTENTS v

LIST OF FIGURES vi

LIST OF CHARTS vii

WELL CLEARANCE LETTER – PROPOSED AT 18 GG WELL LOCATION 1

1. LOCATION COORDINATES 4

1.1 Proposed AT 18 GG Well Location 4

2. VELOCITY DATA 5

2.1 Velocity Data 5

3. SEABED CONDITIONS 7

3.1 Bathymetry 7

3.2 Seafloor Morphology and Man Made Features 7

4. SUBSEABED CONDITIONS 8

4.1 Geology and Lithology 8

4.2 Unit A 8

4.3 Unit B 8

4.4 Unit C 8

4.5 Unit D 10

4.6 Shallow Gas Assessment 10

4.7 Shallow Water Flow Assessment 10

5. CONCLUSIONS AND RECOMMENDATIONS 11

APPENDIX A – Public Shallow Hazards Statements 29

APPENDIX B – Sensitive Sessile Benthic Community Statements 32

v 
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

LIST OF FIGURES

Proposed AT 18 GG Well Location

1 Seabed Depth Extract

2 Seabed Morphology Extract

3 Seabed Amplitude Extract

4 Geohazard Summary Extract

5 Sand Lithology Summary

6 Inline Data Example

7 Crossline Data Example

8 Tie Line to AT018-001

9 Top Hole Prognosis

10 ROV Plat

11 Power Spectrum

12 Bathymetry Plat

13 Public Information Plat

14 Proprietary Information Plat

15 Vicinity Map

16 10-Mile Radius Plat

vi
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

LIST OF CHARTS

The following chart at a scale of 1" = 2,000ft is enclosed:

Chart No Title Drawing No

1 Biological, Physical and Socio-Economic Map 9515.01

vii
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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

WELL CLEARANCE LETTER – PROPOSED AT018 GG WELL LOCATION 

July 15, 2013

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

Attention: Rick Kincaid

Well Clearance Letter

Proposed AT018 GG Well Location

Block 18, Atwater Valley Area

OCS- G 33863

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Well Clearance 

Letter for the proposed AT018 GG well location in Block 18, Atwater Valley Area (OCS-G 33863). This

letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this well clearance 

assessment is Top of Salt or -10,827ft below sea surface (6,587ft below seabed). We understand that 

Anadarko Petroleum Corporation plans to drill the proposed exploration well from a dynamically 

positioned drilling vessel; therefore, an anchoring assessment is not required nor provided. Relevant 

letter-size chart extracts, data examples, and a Top Hole Prognosis are presented with this Well 

Clearance Letter. This geohazard assessment is based on the interpretation of 3D seismic data. This 

site clearance letter is issued as a supplement to Gardline Report No.9172 entitled: 3D Geohazard 

Assessment, Atwater Valley Block 018 and 019, dated August 2012. 

Archaeological Survey. Anadarko Petroleum Corporation provided for review the complete 

archaeological survey report acquired by C&C Technologies Survey Services: Archaeological Survey 

Blocks 18 (OCS-G-33863) and 19 (OCS-G-32556) Atwater Valley Area for the Anadarko Stromboli 

Prospect. 

3D Geophysical Survey. Anadarko Petroleum Corporation provided the 3D dataset to Gardline 

Surveys Inc. on tape media in SEG-Y format for loading onto a Seismic Micro-Technology (SMT) 

workstation. The 3D data cube contains a survey with 4 millisecond sample rate data to a record 

length of 6.0 seconds TWT below sea surface. Inlines are oriented north to south, have a numerical 

increment of one, and exhibit a line spacing of 65.62ft. Crosslines are oriented west to east, have a 

numerical increment of one, and exhibit a line spacing of 41.01ft.

• The acquisition parameters are: 

o Atwater Valley (I) DW V

 

Shooting Direction: N/S

Configuration: 4 sources, 6-10 streamers

1 
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

Maximum offset: 8000 m

Channels: 324 per streamer 

Shotpoint interval: 47.25 m per array 

Group interval: 25 m

CMP line spacing: 40 m 

CMP bin dimension: 12.5 m x 40 m 

Record Length: 9 s below sea bottom 

Nominal fold: 43

Vintage: April 1999

• The basic processing parameters are:

o Atwater Valley (I) DW V

480-m x 500-m velocity grid 

Demultiple 

3D DMO velocity and stacking technology 

One-pass 3D poststack migration 

12.5-m x 20-m final bin dimension

. 

The data exhibits a good frequency response across the upper 1second below seabed, with an 

effective frequency range of 5 to 65Hz (Figure 11). The data exhibits a dominant frequency of 

approximately 53Hz with significant higher usable frequencies. This frequency range results in a 

mean vertical resolvability of approximately 10m and a layer detectability of 5ft. 

In summary and with reference to NTL No. 2008-G04: 

a) The 3D data provides images of sufficient resolution of the shallow section allowing a 

clear analysis of the shallow conditions

b) The data can be loaded to a workstation at 16bit resolution or greater, and is un-scaled

c) There is no trace or sample decimation

d) The sample interval and bin size are maintained throughout the assessment area

e) The data possess a frequency content of 50Hz or higher across the first second below 

seabed (See Power Spectrum Diagram: (Figure 11) 

f) Seabed reflection is free of gaps and defined by a wavelet of stable shape and phase, 

allowing auto-tracking of the seabed event with minimum user intervention and guidance

g) There are no significant acquisition artefacts throughout the dataset

h) There are no merge points in the data

i) Processed bin sizes are 65.62ft x 41.01ft

j) The sample rate of the data is 4ms

k) An accurate velocity model has been utilized in the shallow section allowing optimum 

structural and stratigraphy resolution with no evidence of under or over migration

l) There is no significant multiple energy

2 
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

m) The proposed activities are not in an area of high archaeological potential.

3 
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

1. LOCATION COORDINATES

1.1 Proposed AT018-GG Well Location

Proposed AT018-GG Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 57' 24.70” North Easting 979,365 US ft E

Longitude 89° 02’ 53.39” West Northing 10,150,705 US ft N

FEL of Atwater Valley 18 2,715 US ft Inline 5304

FNL of Atwater Valley 18 2,735 US ft Crossline 10707

Water Depth: -4,240 ft Slope: 1.5° NE

Nearest Shoreline 71 Miles @ 343° 

Port of Operation Fourchon 106 Miles @ 320° 

Nearest Manned Platform MC941-(Mirage/Titan) 6 Miles @ 328° 

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Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

2. VELOCITY DATA 

2.1 Velocity Data

Time-to-depth conversion for the water column was derived using the Advocate and Hood 

(1993) polynomial.

Water Depth (ft) =

0.1105 – 5066.9193X + 468.6693X2 – 554.7107X3 + 340.7019X4 – 116.991X5 + 20.728X6 – 1.4658X7 

Where X = one way time to seabed (in seconds)

One Way Time To Seabed (s) Seabed Depth (ft) Seabed Depth (m) Vavg (m/s)

0.0 0 0 0

1.0 4910 1496 1496

1.1 5400 1646 1496

1.2 5892 1796 1496

1.3 6384 1946 1497

1.4 6877 2096 1497

1.5 7370 2246 1498

1.6 7865 2397 1498

1.7 8360 2548 1499

1.8 8856 2699 1499

1.9 9353 2851 1500

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Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

Sub-seabed time to depth conversion was performed using a polynomial function 

successfully applied in an adjacent project and approved by Anadarko Petroleum 

Company: 

Vavg = = -45.841X5 + 190.08X4

 – 183.08X3 - 14.729X2 + 735.59X +4900

Where X = two way time in seconds below seabed. 

The resultant velocity was then multiplied by the time below seabed to produce depth below 

seabed; this was summed with seabed depth to produce horizon depth below sea surface.

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Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

3. SEABED CONDITIONS 

3.1 Bathymetry

Seabed depth at the proposed AT018-GG well location is -4,240ft below sea surface (Figure 

1). The seafloor slopes to the northeast at 1.5°.

3.2 Seafloor Morphology and Man Made Features

The proposed AT018-GG well location is in the northeast of Block AT18. The seabed is 

smooth and featureless at the proposed well location (Figure 2). Soft clays and silts are 

predicted at seabed. Sediments appear conducive for jetting of seabed casing with no hard 

layers predicted. 

An existing well AT018-001 is located 1,543ft to the northeast. The following are the 

coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

There are no anomalous seabed amplitudes indicative of hydrocarbon macroseep observed 

within a 2,000ft radius of the proposed location (Figure 3).

No items of archaeological significance were identified within 2,000ft of the proposed location

(archaeological report submitted under a separate cover).

No other features are observed within a 2,000ft radius that could affect well emplacement or 

jetting of casing.

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Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

4. SUBSEABED CONDITIONS

4.1 Geology and Lithology

The sub-seabed geology has been divided into four units separated by four horizons (Figures

6 through 9). A Geohazard Extract and Sand Lithology Extract complete the well assessment 

(Figures 4 and 5). 

4.2 Unit A 

The uppermost interval within Unit A from Seabed to -4,479ft below sea surface (238ft below 

seabed) is interpreted to consist of clays and silts with occasional minor coarser interbeds. 

The lower interval of Unit A from -4,479ft to -4,865ft below sea surface (238ft to 625ft below 

seabed) is interpreted to comprise of clays and silts. 

No shallow gas or shallow water flow is predicted within Unit A at the proposed well location.

A vertical borehole will not penetrate any faults within Unit A. 

Horizon H10 marks the base of Unit A at -4,865ft below sea surface (625ft below seabed). 

4.3 Unit B 

The upper interval of Unit B from -4,865ft to -5,176ft below sea surface (625ft to 936ft below 

seabed) is expected to comprise of clays and silts with occasional coarser interbeds. 

The lower interval of Unit B from -5,176ft to -5,425ft below sea surface (936ft to 1,185ft below 

seabed) is interpreted to consist of clays and silts with several coarser interbeds. The coarser 

interbeds in this lower interval of Unit B may cause minor drilling fluid circulation and minor 

wellbore stability problems.

No shallow gas or shallow water flow is predicted within Unit B at the proposed well location.

A vertical borehole will not penetrate any faults within Unit B.

Horizon H20 marks the base of Unit B at -5,425ft below sea surface (1,185ft below seabed). 

4.4 Unit C 

Lithology within the upper interval of Unit C from -5,425ft to -6,045ft below sea surface 

(1,185ft to 1,805ft below sea surface) is interpreted to consist of a clay-prone sequence with 

occasional coarser interbeds. 

 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

From -6,045ft to -6,282ft below sea surface (1,805ft to 2,042ft below seabed) the stratigraphy 

is interpreted as clays and silts with several coarser interbeds that possibly represent sands. 

The proposed well is located on the northeast edge of a sand fairway that extends from the 

southwest of the adjacent block (Block AT019) into the east-central part of Block AT018 and 

continues to cross the center of the block to the northwest (Figure 5). A cluster of high 

amplitude anomalies located around 600ft to the east and northeast of the proposed well are 

interpreted as a high risk of gas. The vertical borehole will not traverse any of these 

anomalies, with the nearest risk of gas anomaly being 312ft to the southeast. However, the 

sands within this package could possibly connect to the borehole, and as such a Slight Risk 

of Gas is assigned within this interval. In addition due to the sandy nature of this interval, 

potentially rapidly deposited with inadequate dewatering time, with a possible clay rich 

impermeable overburden forms a favorable setting for development of shallow water flow, and 

a Moderate Shallow Water Flow Risk is assigned to this interval. This interval did not 

present any reported drilling problems at the nearby offset well AT018-001.

The lithology from -6,282ft to -6,428ft below sea surface (2,042ft to 2,188ft below seabed) is 

interpreted to comprise of clays and silts with occasional coarser interbeds. 

The interval from -6,428ft to -7,170ft below sea surface (2,188ft to 2,930ft below seabed) is 

interpreted to consist of clays and silts with several coarser interbeds that may represent 

sands. The well path is located outside the main cluster of high amplitude anomalies that 

occur around 2,000ft to the southwest that are interpreted as fluid charged sands. A 

previously drilled well located 4.9 miles to the southeast (AT063-002) experienced a low 

volume shallow water flow event in sands at 2,012ft below seabed; correlating with this 

interval. The nearest offset well, AT018-001 did encounter some shallow gas shows and 

some ballooning of the wellbore through this interval. At the proposed location this interval is 

thicker and exhibits higher energy character than observed at the existing AT018-001 well. 

The proposed location is also more centrally placed within the Unit C sand fairways than the 

existing AT018-001well (Figure 5). However, the seismic over the existing AT018-001well 

does present an anomaly that could be the source of the gas shows observed (Figure 8) and 

this anomaly is not present at the proposed well location. Taking into account all these 

observations and the acoustic signature of the interval, suggestive of potentially rapidly 

deposited sandy interbeds that have may have experienced inadequate dewatering a Slight 

Risk of Gas and a Moderate Shallow Water Flow Risk is assigned to this interval.

A clay-rich sequence with occasional coarser-grained interbeds is interpreted from -7,170ft to 

-7,307ft below sea surface (2,930ft to 3,067ft below seabed). 

The lower interval within Unit C from -7,307ft to -7,639ft below sea surface (3,067ft to 3,398ft 

below seabed) is interpreted to comprise of clays with several coarser interbeds. The coarser 

interbeds within this package may induce minor drilling fluid circulation and wellbore stability 

problems. The existing well AT018-001 did encounter some minor shallow gas shows in this 

interval, but there is no clear indication of any anomalies on the seismic data to support any 

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Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

shallow gas occurrence at the proposed well location.

A vertical borehole will not penetrate any faults within Unit C.

Horizon H30 marks the base of Unit C at -7,639ft below sea surface (3,398ft below seabed).

4.5 Unit D 

The upper interval of Unit D, from -7,639ft to -8,041ft below sea surface (3,398ft to 3,802ft 

below seabed), is interpreted to consist of clays and silts with occasional coarser interbeds. 

No drilling hazards or problems are expected within this upper interval.

From -8,041ft to -8,653ft below sea surface (3,802ft to 4,413ft below seabed), is interpreted 

as a slightly higher-energy deposited package with clays and several coarser interbeds. This 

interval exhibits character of shallow water flow, with potential for rapid deposition, and 

inadequate dewatering. As such, a Slight Shallow Water Flow Risk is assigned to this 

interval. Due to the potential for coarser, potentially poorly consolidated sediments within this 

interval, minor drilling fluid circulation and wellbore stability problems may also occur. The 

nearby offset well AT018-001 did not report any problems from this interval, which is 

acoustically similar on the seismic data.

Stratigraphy from -8,653ft to -10,827ft below sea surface (4,413ft to 6,587ft below seabed) is 

interpreted to consist of clays with occasional coarser interbeds. 

No shallow gas is predicted within Unit D at the proposed well location. The risk of gas

anomaly is approximately 625ft WSW.

Top of Salt marks the base of Unit D and the Base of this interpretation at -10,827ft below sea 

surface (6,587ft below seabed). 

4.6 Shallow Gas Assessment

Within Unit C, a Slight Risk of Gas is assigned to the interval from -6,045ft to -6,282ft below 

sea surface (1,805ft to 2,042ft below seabed), and also from -6,428ft to -7,170ft below sea 

surface (2,188ft to 2,930ft below seabed).

4.7 Shallow Water Flow Assessment

Within Unit C, a Moderate Shallow Water Flow Risk is interpreted in the interval from -

6,045ft to -6,282ft below sea surface (1,805ft to 2,042ft below seabed) and from -6,428ft to 

-7,170ft below sea surface (2,188ft to 2,930ft below seabed). 

Within Unit D, a Slight Shallow Water Flow Risk is assigned from -8,041ft to -8,653ft below 

sea surface (3,802ft to 4,413ft below seabed). 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

5. CONCLUSIONS AND RECOMMENDATIONS

• Seabed

No significant problems are anticipated at seabed. Shallow soils are expected to be 

conducive to the jetting of seabed casing with no hardgrounds predicted.

• Unit A 

No drilling hazards or problems predicted.

• Unit B

Minor drilling and minor wellbore stability problems are possible from -5,176ft to -5,425ft 

below sea surface (936ft to 1,185ft below seabed). 

• Unit C 

Within Unit C, a Slight Risk of Gas and a Moderate Shallow Water Flow Risk is assigned 

to the interval from -6,045ft to -6,282ft below sea surface (1,805ft to 2,042ft below seabed), 

and from -6,428ft to -7,170ft below sea surface (2,188ft to 2,930ft below seabed). Drilling 

Caution is advised and appropriate drilling methodology is recommended to deal with a 

possible water flow event through this interval. The existing AT018-001 well, did encounter 

some shallow gas shows and minor drilling problems from the lower interval. 

Within Unit C, a Moderate Shallow Water Flow Risk is also interpreted from -6,428ft to 

-7,170ft below sea surface (2,188ft to 2,930ft below seabed). Appropriate drilling 

methodology is recommended to deal with a possible water flow event through this interval. 

Additionally, minor drilling fluid circulation and wellbore stability problems may also occur 

within this interval.

Minor drilling fluid circulation and wellbore stability problems may also occur from -7,307ft to 

-7,639ft below sea surface (3,067ft to 3,398ft below seabed). 

• Unit D

A Slight Shallow Water Flow Risk is interpreted in Unit D, from -8,041ft to -8,653ft below 

sea surface (3,802ft to 4,413ft below seabed). Appropriate drilling methodology should be 

utilized to contain a potentially non-persistent shallow water flow event within this interval. 

Minor drilling fluid circulation and wellbore stability problems may also occur within this 

interval.

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Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GG

We appreciate the opportunity to work with you on this project, and look forward to continuing as 

your geohazards consultants. Please contact us if you have any questions or if we can be of 

further assistance.

Sincerely,

Gardline Surveys Inc.

Andrew Haigh Matilde DeLeon

Geophysical Manager Quality Assurance

Copies Submitted: 6 copies to Rick Kincaid at Anadarko Petroleum Corporation.

Attachments:

Proposed AT018-GG Well Location

Seabed Depth Extract

Seabed Morphology Extract

Seabed Amplitude Extract

Geohazard Summary Extract

Sand Lithology Summary

Inline Data Example

Crossline Data Example

Arbitrary Line Data Example

Top Hole Prognosis

ROV Plat

Power Spectrum

Bathymetry Plat

Public Information Plat

Proprietary Information Plat

Vicinity Map

10-Mile Radius Plat

12
Top Hole Prognosis for Proposed AT18 GG Well Location

979,365ft E / 10,150,705ft N

Inline: 5304 / Crossline: 10707 Horizon

Subsea

Depth

(ft)

BML

Depth

(ft)

Horizon

TWT

(sec)

Lithology, Structure & Stratigraphy Potential Drilling Hazards & Constraints

Risk

of

Gas

SWF

Risk

Seabed -4,240 0 1.725 Seabed is smooth sloping to the northeast at 1.5°. Surficial sediments comprise of 

soft clays and silts. Underlying the seabed lithology comprises of clays and silts 

with occasional minor coarser interbeds

Figure 9

Interface -6,045 1,805 2.398

Horizon H10 -4,865 625 1.971

Interface -6,282 2,042 2.479

Clays and silts 

Clays and silts with occasional coarser interbeds

None predicted

None predicted

None predicted

Minor drilling fluid circulation and minor wellbore stability problems 

possible within this interval

Unit A

Unit B

Unit D

Interface -7,170 2,930 2.769

Horizon H20 -5,425 1,185 2.179

Interface -7,307 3,067 2.812

Horizon H30 -7,639 3,398 2.914

Interface -8,041 3,802 3.034

Top of Salt -10,827 6,587 3.765

Clay-prone sequence with occasional coarser interbeds

Clays and silts with several coarser interbeds that may represent sands

Clay-prone sequence with occasional coarser-grained interbeds

Clays with occasional coarser interbeds

None predicted

Unit C

Base of interpretation

Clays and silts with occasional coarser interbeds

Clays and silts with several coarser interbeds

Slight Risk of Gas. Moderate Shallow Water Flow Risk

None Predicted

Slight Risk of Gas and Moderate Shallow Water Flow Risk. Minor drilling 

fluid circulation and wellbore stability problems possible

None Predicted

Interface -6,428 2,188 2.528

Interface -8,653 4,413 3.208

Clays and silts with several coarser interbeds that may represent sands

Interface -5,176 936 2.088

Interface -4,479 238 1.821

Clays with several coarser interbeds Minor drilling fluid circulation and wellbore stability problems possible

Clays and silts with occasional coarser interbeds None Predicted

Clays with several coarser interbeds that may represent sands Slight Shallow Water Flow Risk. Minor drilling fluid circulation and 

wellbore stability problems possible

None Predicted

Vavg

BML

(m/s)

0

5,365

5,078

5,418

5,613

5,220

5,643

5,717

5,809

6,457

5,450

5,952

5,159

4,970
± 6

3® 3

3

3

-4210

-4180

-4200 -4190

-4170

-4220

-4160

-4230

-4240

-4150

-4250

-4260

-4270

-4280

-4290

-4300

-4310

-4140

-4320

-4330

-4150

-4150

-4150

-4240

-4150

-4280

-4260

-4170

-4210

-4270

-4250

-4230

-4140

-4200

-4220

-4200

-4240

-4260

-4180

-4270

-4160

-4180

-4210

-4160

-4170

-4210

-4210

-4180

-4160

-4160

-4230

-4230

-4160

-4150

-4150

AT018-001

89°5'0"W89°4'0"W89°3'0"W

27°57'0"N

27°56'0"N

27°55'0"N

970,000975,000980,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1 = 2,000'

Bathymetry Plat Figure 12

AT018-GG

Easting: 979,365ft E

Northing: 10,150,705ft N

FEL of AT018-GG: 2,715ft

FNL of AT018-GG: 2,735ft

2,000ft Radius

ATWATER VALLEY BLOCK 18(OCS-G33863)
± 6

3® 3

3

3

Proposed AT018-GG Well

AT018-001

89°5'0"W89°4'0"W89°3'0"W

27°57'0"N

27°56'0"N

27°55'0"N

970,000975,000980,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1" = 2,000'

Well Location Plat - Public Information Figure 13

ATWATER VALLEY BLOCK 18(OCS-G33863)

Location Call N/S Call E/W X Coordinate Y Coordinate Latitude Longitude WD

AT018-GG SL 2,735ft FNL 2,715ft FEL 979,365 10,150,705 27° 57' 24.70"N 89° 02' 53.39"W -4,240

Proposed Location - AT018-GG
Nearest Shoreline

Range: 71mi

Bearing: 343°

Fourchon

Range: 106mi

Bearing: 320°

Lund

Henderson

Lloyd Ridge

Walker Ridge

Destin Dome

Atwater Valley Green Canyon

De Soto Canyon

The Elbow

Florida Plain

Vernon Basin

Apalachicola

Garden Banks

Keathley Canyon

Florida Middle Ground

Howell Hook

Lund South

Pensacola

Amery Terrace

Mobile

Viosca Knoll

Viosca Knoll

Sigsbee Escarpment

New Orleans

Baton Rouge

Pensacola

Lafayette

Gulfport Pascagoula

Vicinity Map - Atwater Valley Block 018

Figure 15
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GG

APPENDIX A – Public Shallow Hazards Statements 

29
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GG

Public Shallow Hazards Statement – AT018-GG

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213-2394

Attention: 

Reference: Shallow Hazards Analysis

Atwater Valley Block 18

OCS-(G 33863) 

Ladies/Gentlemen:

Anadarko Petroleum Corporation contracted Gardline Surveys, Inc. to prepare a Well Clearance Letter 

for the proposed AT018-GG well location in Block 18, Atwater Valley Area (OCS-G 33863). This letter 

addresses seafloor and shallow geologic conditions that may impact exploratory drilling operations 

within 2,000ft of the proposed well location. The depth limit of this geohazard assessment is to Top of 

Salt at -10,827ft below sea surface (6,587ft below seabed).

This hazards summary letter is issued as a supplement to Gardline Report No.9172 entitled: 3D 

Geohazard Assessment, Atwater Valley Block 018and 019, dated August 2012.

Seabed Hazards. 

The seabed is smooth and featureless. No problems are expected at the proposed AT 18 GG well 

location.

There are no indications of seabed fluid seeps within 2,000ft of the well location.

No existing seabed infrastructure is located within 2,000ft of the proposed well. There is an existing 

well AT018-001 located 1,543ft to the northeast. The following are the coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

Two pipelines are located on the adjacent Block AT019 approximately 6,315ft and 5,335ft 

to the east and northeast. The following are detailed of the pipelines:

Pipeline Installations

Operator Area Block - Origin/Termination Outside Diameter (in) Product Status

ATP O&G AT063 / MC941 5 in BLKO ACT

ATP O&G MC941 / AT063 4in UBEH ACT

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Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GG

Sub-Seabed Hazards. 

Drilling Caution is indicated for a Slight Risk of Gas at the well location within two intervals of Unit C.

Moderate Shallow Water Flow Risk is assigned to two intervals within Unit C. A Slight Shallow 

Water Flow Risk is anticipated within an interval in Unit D. 

Proposed AT 18 GG Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 57' 24.70” North Easting 979,365 US ft E

Longitude 89° 02’ 53.39” West Northing 10,150,705 US ft N

FEL of Atwater Valley 18 2,715 US ft Inline 5304

FNL of Atwater Valley 18 2,735 US ft Crossline 10707

Water Depth: -4,240 ft Slope: 1.5° NE

Nearest Shoreline 71 Miles @ 343° 

Port of Operation Fourchon 106 Miles @ 320° 

Nearest Manned Platform MC941-(Mirage/Titan) 6 Miles @ 328° 

Conclusions and Recommendations. 

Drilling techniques will take into consideration the possibility of encountering possible gas within two 

interval of Unit C. Appropriate drilling methodology should be utilized to contain a potentially nonpersistent Slight Shallow Water Flow Risk interpreted in the lower interval of Unit D. Appropriate 

drilling methodology should be utilized to deal with a possible Moderate Shallow Water Flow Risk in 

the intervals within Unit C. 

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

PUBLIC INFORMATION

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GG

APPENDIX B – Sensitive Sessile Benthic Community Statements

32
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GG

Sensitive Sessile Benthic Community Statement – AT018-GG

Anadarko Petroleum Corporation

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213

Reference: Sensitive Sessile Benthic Community Summary

Atwater Valley, Block 18

OCS-(G 33863) 

Ladies/Gentlemen:

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Site Clearance 

Letter for the proposed AT018-GG well location in Atwater Valley, Block 18, Stromboli Prospect (OCSG G 33863). This letter addresses location proximity to potential sensitive sessile benthic community 

sites. Anadarko Petroleum Corporation will be drilling this well from a dynamically positioned drilling 

module; therefore, no anchors will impact seabed.

This sensitive sessile benthic community summary letter is issued as a supplement to Gardline Report 

No.9172 entitled: 3D Geohazard Assessment, Atwater Valley Block 018, dated August 2012. A 

Biological, Physical and Socio-Economic Map is included at the end of this appendix illustrating the 

areas of potential seabed impact.

Potential Sensitive Sessile Benthic Communities. 

Features or areas that could support high density sensitive sessile benthic communities are not 

located within 2,000ft of any proposed mud and cuttings discharge location.

Proposed AT018-GG Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 57' 24.70” North Easting 979,365 US ft E

Longitude 89° 02’ 53.39” West Northing 10,150,705 US ft N

FEL of Atwater Valley 18 2,715 US ft Inline 5304

FNL of Atwater Valley 18 2,735 US ft Crossline 10707

Water Depth: -4,240 ft Slope: 1.5° NE

Nearest Shoreline 71 Miles @ 343° 

Port of Operation Fourchon 106 Miles @ 320° 

Nearest Manned Platform MC941-(Mirage/Titan) 6 Miles @ 328° 

33
Anadarko Petroleum Corporation Gardline Report 9515

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GG

No potential sensitive sessile benthic community site is located within 2,000ft of the proposed 

location. 

Conclusions and Recommendations: 

The proposed AT018-GG well location will not impact any sites favorable for development of sensitive 

sessile benthic communities.

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

34
ANADARKO PETROLEUM CORPORATION

3D GEOHAZARD ASSESSMENT

GULF OF MEXICO

ATWATER VALLEY BLOCK AT018

STROMBOLI PROSPECT

AT018-GV PROPOSED WELL LOCATION

WELL CLEARANCE LETTER 

APRIL 2013

Gardline Project Ref. 9518

Report Status Final

Issue Date July 15, 2013

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

REPORT AUTHORIZATION AND DISTRIBUTION

Report Status Final

Issue Date July 15, 2013

Compilation Geophysicist L Fuentes

Authorization Geophysics .....................

A R Haigh

Quality Assurance .....................

M DeLeon

Distribution 

6 copies 

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

For attention of:

Rick Kincaid

ii
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

SERVICE WARRANTY

USE OF THIS REPORT

This report has been prepared with due care, diligence and with the skill reasonably expected of a 

reputable contractor experienced in the types of work, carried out under the contract. As such, the 

findings in this report are based on an interpretation of data which is a matter of opinion on which 

professionals may differ and, unless clearly stated, is not a recommendation of any course of action. 

Gardline Surveys, Inc. has prepared this report for the client identified on the front cover in fulfilment of 

its contractual obligations under the referenced contract, and the only liabilities Gardline Surveys, Inc. 

will accept are those contained therein.

Please be aware that further distribution of this report, in whole or part, or the use of the data for a 

purpose not expressly stated within the contractual work scope is at the client’s sole risk, and Gardline 

Surveys, Inc recommends that this disclaimer be included in any such distribution. 

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com

iii
Green Canyon Atwater Valley Lloyd Ridge

Mississippi Canyon

Destin Dome

De Soto Canyon

Mobile Pensacola

Ship Shoal Area

Eugene Island Area

Viosca Knoll

Viosca Knoll

Main Pass Area

Ewing Bank

South Timbalier Area

West Delta Area

Louisiana

Alabama Mississippi

Florida

Location Map

Study Area
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

TABLE OF CONTENTS

REPORT AUTHORIZATION AND DISTRIBUTION ii

SERVICE WARRANTY iii

LOCATION MAP iv

TABLE OF CONTENTS v

LIST OF FIGURES vi

LIST OF CHARTS vii

WELL CLEARANCE LETTER – PROPOSED AT018 GG WELL LOCATION 1

1. LOCATION COORDINATES 4

1.1 Proposed AT018-GV Well Location 4

2. VELOCITY DATA 5

2.1 Velocity Data 5

3. SEABED CONDITIONS 7

3.1 Bathymetry 7

3.2 Seafloor Morphology and Man Made Features 7

4. SUBSEABED CONDITIONS 8

4.1 Geology and Lithology 8

4.2 Unit A 8

4.3 Unit B 8

4.4 Unit C 8

4.5 Unit D 10

4.6 Shallow Gas Assessment 10

4.7 Shallow Water Flow Assessment 11

5. CONCLUSIONS AND RECOMMENDATIONS 12

APPENDIX A – Public Shallow Hazards Statements 29

APPENDIX B – Sensitive Sessile Benthic Community Statements 32

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

LIST OF FIGURES

Proposed AT 18 GV Well Location

1 Seabed Depth Extract

2 Seabed Morphology Extract

3 Seabed Amplitude Extract

4 Geohazard Summary Extract

5 Sand Lithology Summary

6 Inline Data Example

7 Crossline Data Example

8 Tie Line to AT018-001

9 Top Hole Prognosis

10 ROV Plat

11 Power Spectrum

12 Bathymetry Plat

13 Public Information Plat

14 Proprietary Information Plat

15 Vicinity Map

16 10-Mile Radius Plat

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Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

LIST OF CHARTS

The following chart at a scale of 1" = 2,000ft is enclosed:

Chart No Title Drawing No

1 Biological, Physical and Socio-Economic Map 9518.01

vii
Anadarko Petroleum Corporation Gardline Report 9520

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT018-CC Well Location

WELL CLEARANCE LETTER – PROPOSED AT018-CC WELL LOCATION 

July 15, 2013

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

Attention: Rick Kincaid

Well Clearance Letter

Proposed AT018-CC Well Location

Block 018, Atwater Valley Area

OCS- G33863

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Well Clearance 

Letter for the proposed AT018-CC well location in Block 018, Atwater Valley Area (OCS-G 33863). 

This letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this well clearance 

assessment is Top of Salt or -10,279ft below sea surface (6,112ft below seabed). We understand that 

Anadarko Petroleum Corporation plans to drill the proposed exploration well from a dynamically 

positioned drilling vessel; therefore, an anchoring assessment is not required. Relevant letter-size 

chart extracts, data examples, and a Top Hole Prognosis are presented with this Well Clearance 

Letter. This geohazard assessment is based on the interpretation of 3D seismic data. This site 

clearance letter is issued as a supplement to Gardline Report No.9172 entitled: 3D Geohazard 

Assessment, Atwater Valley Block 018, dated August 2012. 

Archaeological Survey. Anadarko Petroleum Corporation provided for review the complete 

archaeological survey report acquired by C&C Technologies Survey Services: Archaeological Survey 

Blocks 18 (OCS-G-33863) and 19 (OCS-G-32556) Atwater Valley Area for the Anadarko Stromboli 

Prospect. 

3D Geophysical Survey. Anadarko Petroleum Corporation provided the 3D dataset to Gardline 

Surveys Inc. on tape media in SEG-Y format for loading onto a Seismic Micro-Technology (SMT) 

workstation. The 3D data cube contains a survey with 4 millisecond sample rate data to a record 

length of 6.0 seconds TWT below sea surface. Inlines are oriented north to south, have a numerical 

increment of one, and exhibit a line spacing of 65.62ft. Crosslines are oriented west to east, have a 

numerical increment of one, and exhibit a line spacing of 41.01ft.

• The acquisition parameters are: 

o Atwater Valley (I) DW V

Shooting Direction: N/S

Configuration: 4 sources, 6-10 streamers

1 
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

Maximum offset: 8000 m

Channels: 324 per streamer 

Shotpoint interval: 47.25 m per array 

Group interval: 25 m

CMP line spacing: 40 m 

CMP bin dimension: 12.5 m x 40 m 

Record Length: 9 s below sea bottom 

Nominal fold: 43

Vintage: April 1999

• The basic processing parameters are:

o Atwater Valley (I) DW V

480-m x 500-m velocity grid 

Demultiple 

3D DMO velocity and stacking technology 

One-pass 3D poststack migration 

12.5-m x 20-m final bin dimension

. 

The data exhibits a good frequency response across the upper 1second below seabed, with an 

effective frequency range of 5 to 65Hz (Figure 11). The data exhibits a dominant frequency of 

approximately 53Hz with significant higher usable frequencies. This frequency range results in a 

mean vertical resolvability of approximately 10m and a layer detectability of 5ft. 

In summary and with reference to NTL No. 2008-G04: 

a) The 3D data provides images of sufficient resolution of the shallow section allowing a 

clear analysis of the shallow conditions

b) The data can be loaded to a workstation at 16bit resolution or greater, and is un-scaled

c) There is no trace or sample decimation

d) The sample interval and bin size are maintained throughout the assessment area

e) The data possess a frequency content of 50Hz or higher across the first second below 

seabed (See Power Spectrum Diagram: (Figure 10)

f) Seabed reflection is free of gaps and defined by a wavelet of stable shape and phase, 

allowing auto-tracking of the seabed event with minimum user intervention and guidance

g) There are no significant acquisition artefacts throughout the dataset

h) There are no merge points in the data

i) Processed bin sizes are 65.62ft x 41.01ft

j) The sample rate of the data is 4ms

k) An accurate velocity model has been utilized in the shallow section allowing optimum 

structural and stratigraphy resolution with no evidence of under or over migration

l) There is no significant multiple energy

2 
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

m) The proposed activities are not in an area of high archaeological potential.

3 
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

1. LOCATION COORDINATES

1.1 Proposed AT018-GV Well Location

Proposed AT 18 GV Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 57' 25.62” North Easting 980,582 US ft E

Longitude 89° 02’ 39.83” West Northing 10,150,777 US ft N

FEL of Atwater Valley 18 1,498 US ft Inline 5322

FNL of Atwater Valley 18 2,663 US ft Crossline 10709

Water Depth: -4,271 ft Slope: 1.5° NE

Nearest Shoreline 71.34 Miles @ 343° 25’ 48’’

Port of Operation Fourchon 106.42Miles @ 320° 36’ 0’’

Nearest Manned Platform MC941-(Mirage/Titan) 6.25 Miles @ 328° 17’ 24”

4 
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

2. VELOCITY DATA 

2.1 Velocity Data

Time-to-depth conversion for the water column was derived using the Advocate and Hood 

(1993) polynomial.

Water Depth (ft) =

0.1105 – 5066.9193X + 468.6693X2 – 554.7107X3 + 340.7019X4 – 116.991X5 + 20.728X6 – 1.4658X7 

Where X = one way time to seabed (in seconds)

One Way Time To Seabed (s) Seabed Depth (ft) Seabed Depth (m) Vavg (m/s)

0.0 0 0 0

1.0 4910 1496 1496

1.1 5400 1646 1496

1.2 5892 1796 1496

1.3 6384 1946 1497

1.4 6877 2096 1497

1.5 7370 2246 1498

1.6 7865 2397 1498

1.7 8360 2548 1499

1.8 8856 2699 1499

1.9 9353 2851 1500

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Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

Sub-seabed time to depth conversion was performed using a polynomial function 

successfully applied in an adjacent project and approved by Anadarko Petroleum 

Company: 

Vavg = = -45.841X5 + 190.08X4

 – 183.08X3 - 14.729X2 + 735.59X +4900

Where X = two way time in seconds below seabed. 

The resultant velocity was then multiplied by the time below seabed to produce depth below 

seabed; this was summed with seabed depth to produce horizon depth below sea surface.

6 
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

3. SEABED CONDITIONS 

3.1 Bathymetry

Seabed depth at the proposed AT018-GV well location is -4,271ft below sea surface (Figure 

1). The seafloor slopes to the northeast at 1.5°. 

3.2 Seafloor Morphology and Man Made Features

The proposed AT018-GV well location is in the northeast of Block AT18. The seabed is 

smooth and featureless at the proposed well location (Figure 2). Soft clays and silts are 

predicted at seabed. Sediments appear conducive for jetting of seabed casing with no hard 

layers predicted. 

An existing well AT018-001 is located 1,375ft to the northwest. The following are the 

coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

There are no anomalous seabed amplitudes indicative of hydrocarbon macroseep observed 

within a 2,000ft radius of the proposed location (Figure 3).

No items of archaeological significance were identified within 2,000ft of the proposed location

(archaeological report submitted under a separate cover).

No other features are observed within a 2,000ft radius that could affect well emplacement or 

jetting of casing.

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Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

4. SUBSEABED CONDITIONS

4.1 Geology and Lithology

The sub-seabed geology has been divided into four units separated by four horizons (Figures 

6 through 9). A Geohazard Extract and Sand Lithology Extract complete the well assessment 

(Figures 4 and 5). 

4.2 Unit A 

The uppermost interval within Unit A from Seabed to -4,479ft below sea surface (263ft below 

seabed) is interpreted to consist of clays and silts with occasional minor coarser interbeds. 

The lower interval of Unit A from -4,479ft to -4,848ft below sea surface (263ft to 577ft below 

seabed) is interpreted to comprise of clays and silts. 

No shallow gas or shallow water flow is predicted within Unit A at the proposed well location.

A vertical borehole will not penetrate any faults within Unit A. 

Horizon H10 marks the base of Unit A at -4,848ft below sea surface (577ft below seabed). 

4.3 Unit B 

The upper interval of Unit B from -4,848ft to -5,234ft below sea surface (577ft to 963ft below 

seabed) is expected to comprise of clays and silts with occasional coarser interbeds. 

The lower interval of Unit B from -5,234ft to -5,407ft below sea surface (963ft to 1,136ft below 

seabed) is interpreted to consist of clays and silts. 

No shallow gas or shallow water flow is predicted within Unit B at the proposed well location.

A vertical borehole will not penetrate any faults within Unit B.

Horizon H20 marks the base of Unit B at -5,407ft below sea surface (1,136ft below seabed). 

4.4 Unit C 

Lithology within the upper interval of Unit C from -5,407ft to -5,886ft below sea surface 

(1,136ft to 1,615ft below sea surface) is interpreted to consist of clays, silts, with occasional 

coarser interbeds. 

From -5,886ft to -6,299ft below sea surface (1,615ft to 2,028ft below seabed) is interpreted as

higher energy clays and silts with several coarser interbeds that possibly represent sands. 

8 
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

The proposed well is located on the northeast edge of a sand fairway that extends from the 

southwest of the adjacent block (Block AT019) into the east-central part of Block AT018 and 

continues to cross the center of the block to the northwest (Figure 5). A number of high 

amplitude anomalies located within 2,000ft to the west, northwest, south and southeast and 

north of the proposed well are interpreted as a high risk of gas. The vertical borehole will not 

traverse any of these anomalies, with the nearest risk of gas anomaly being 510ft to the west. 

However, these higher amplitude anomalies apperar possibly connected (downdip) to the 

proposed well location, and as such, even though there is not an anomalous response at the 

location, a Slight Risk of Gas is assigned within this interval. Due to the sandy nature of this 

interval, potentially rapidly deposited with inadequate dewatering time, with a likely clay rich 

impermeable overburden forms a favorable setting for development of shallow water flow, and 

a Moderate Shallow Water Flow Risk is assigned to this interval. This interval did not 

present any reported drilling problems at the nearby offset well AT018-001, however, this 

existing well is a little further away from the higher energy deposits.

The lithology from -6,299ft to -6,492ft below sea surface (2,028ft to 2,221ft below seabed) is 

interpreted to comprise of clays and silts with occasional coarser interbeds. 

The interval from -6,492ft to -7,175ft below sea surface (2,221ft to 2,904ft below seabed) is 

interpreted to consist of clays and silts with several coarser interbeds that may represent 

sands. The well path is located in the northeast edge of a package of northwest to southeast 

trending sands. A previously drilled well located 4.93 miles to the southeast (AT063-002) 

experienced a low volume shallow water flow event in sands at 2,012ft below seabed; 

correlating with this interval. The nearest offset well, AT018-001 did encounter some shallow 

gas shows and some ballooning of the wellbore through this interval. At the proposed 

location this interval is thicker than encountered at AT-018-001, and exhibits a similar higher 

energy character. The proposed location is also more centrally placed within the Unit C sand 

fairways than the existing AT018-001well (Figure 5). However, the seismic over the existing 

AT018-001well does present an anomaly that could be the source of the gas shows observed

(Figure 8) and although this interbed does extend to the proposed AT018-GV location the 

amplitude character is reduced. Taking into account all these observations and the acoustic 

signature of the interval, suggestive of potentially rapidly deposited sandy interbeds that have 

may have experienced inadequate dewatering a Slight Risk of Gas and a Moderate 

Shallow Water Flow Risk is assigned to this interval.

A clay-rich sequence with occasional coarser-grained interbeds is interpreted from -7,175ft to 

-7,325ft below sea surface (2,904ft to 3,054ft below seabed). 

The lower interval within Unit C from -7,325ft to -7,739ft below sea surface (3,054ft to 3,468ft 

below seabed) is interpreted to comprise of clays with several coarser interbeds. The coarser 

interbeds within this package may induce minor drilling fluid circulation and wellbore stability 

problems. The existing well AT018-001 did encounter some minor shallow gas shows in this 

interval and the character at the proposed well location is similar (Figure 8), but other than the 

9 
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

elevated amplitude character there are no other indicators of shallow gas, and therefore a 

Slight Risk of Gas is assigned to this interval. The existing AT-018-001 did not report any 

shallow water flow from this interval. Given the similarities in between the proposed and 

existing well locations at this level then no shallow water flow risk is assigned.

A vertical borehole will not penetrate any faults within Unit C.

Horizon H30 marks the base of Unit C at -7,739ft below sea surface (3,468ft below seabed).

4.5 Unit D 

The upper interval of Unit D, from -7,739ft to -7,977ft below sea surface (3,468ft to 3,707ft 

below seabed), is interpreted to consist of clays and silts with occasional coarser interbeds. 

No drilling hazards or problems are expected within this upper interval.

From -7,977ft to -8,848ft below sea surface (3,707ft to 4,577ft below seabed), is interpreted 

as a slightly higher-energy deposited package with clays and several coarser interbeds. This 

interval exhibits character of shallow water flow, with potential for rapid deposition, and 

inadequate dewatering. The nearby offset well AT018-001 did not report any problems from 

this interval, which is acoustically similar on the seismic data, with just a slight increase in 

energy character at the proposed well location. As such, a Slight Shallow Water Flow Risk

is assigned to this interval. Due to the potential for coarser, potentially poorly consolidated 

sediments within this interval, minor drilling fluid circulation and wellbore stability problems 

may also occur. 

Stratigraphy from -8,848ft to -10,717ft below sea surface (4,577ft to 6,447ft below seabed) is 

interpreted to consist of clays with occasional coarser interbeds. 

No shallow gas is predicted within Unit D at the proposed well location. The risk of gas 

anomaly is approximately 2,027ft WSW.

Top of Salt marks the base of Unit D and the Base of this interpretation at -10,717ft below sea 

surface (6,447ft below seabed). 

4.6 Shallow Gas Assessment

Within Unit C, a Slight Risk of Gas is assigned to the interval from -5,886ft to -6,299ft below 

sea surface (1,615ft to 2,028ft below seabed), from -6,492ft to -7,175ft below sea surface 

(2,221ft to 2,904ft), and also from -7,325ft to -7,739ft below sea surface (3,054ft to 3,468ft 

below seabed).

Within D, a Slight Risk of Gas -7,977ft to -8,848ft below surface (3,707ft to 4,577ft below 

seabed). 

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Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

4.7 Shallow Water Flow Assessment

Within Unit C, a Moderate Shallow Water Flow Risk is interpreted in the interval from -

5,886ft to -6,299ft below sea surface (1,615ft to 2,028ft below seabed), and from -6,492ft to -

7,175ft below sea surface (2,221ft to 2,904ft). 

Within Unit D, a Slight Shallow Water Flow Risk is assigned from -7,977ft to -8,848ft below 

sea surface (3,707ft to 4,577ft below seabed). 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

5. CONCLUSIONS AND RECOMMENDATIONS

• Seabed

No significant problems are anticipated at seabed. Shallow soils are expected to be 

conducive to the jetting of seabed casing with no hardgrounds predicted.

• Unit A 

No drilling hazards or problems predicted.

• Unit B

No drilling hazards or problems predicted.

• Unit C 

Within Unit C, a Slight Risk of Gas and a Moderate Shallow Water Flow Risk is assigned 

to the interval from -5,886ft to -6,299ft below sea surface (1,615ft to 2,028ft below seabed), 

and from -6,492ft to -7,175ft below sea surface (2,221ft to 2,904ft below seabed). Drilling 

Caution is advised and appropriate drilling methodology is recommended to deal with a 

possible water flow event through this interval. The existing AT018-001 well, did encounter 

some shallow gas shows and minor drilling problems from the lower interval. 

Within Unit C, a Slight Risk of Gas is assigned to the interval from -7,325ft to -7,739ft below 

sea surface (3,054ft to 3,468ft below seabed). Drilling Caution is advised. The existing 

AT018-001 well, did encounter some shallow gas shows from this interval.

Minor drilling fluid circulation and wellbore stability problems may also occur from -7,307ft to 

-7,639ft below sea surface (3,067ft to 3,398ft below seabed). 

• Unit D

Within Unit D, a Slight Shallow Water Flow Risk is assigned from -7,977ft to -8,848ft below 

sea surface (3,707ft to 4,577ft below seabed). Appropriate drilling methodology should be 

utilized to contain a potentially non-persistent shallow water flow event within this interval. 

Minor drilling fluid circulation and wellbore stability problems may also occur within this 

interval. The existing AT018-001 well did not report any problems from this interval.

12
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-GV

We appreciate the opportunity to work with you on this project, and look forward to continuing as 

your geohazards consultants. Please contact us if you have any questions or if we can be of

further assistance.

Sincerely,

Gardline Surveys Inc.

Andrew Haigh Matilde DeLeon

Geophysical Manager Quality Assurance

Copies Submitted: 6 copies to Rick Kincaid at Anadarko Petroleum Corporation.

Attachments:

Proposed AT018-GV Well Location

Seabed Depth Extract

Seabed Morphology Extract

Seabed Amplitude Extract

Geohazard Summary Extract

Sand Lithology Summary

Inline Data Example

Crossline Data Example

Arbitrary Line Data Example

Top Hole Prognosis

ROV Plat

Power Spectrum

Bathymetry Plat

Public Information Plat

Proprietary Information Plat

Vicinity Map

10-Mile Radius Plat

13
Top Hole Prognosis for Proposed AT018-GV Well Location

980,582ft E / 10,150,777ft N

Inline: 5322 / Crossline: 10709 Horizon

Subsea

Depth

(ft)

BML

Depth

(ft)

Horizon

TWT

(sec)

Lithology, Structure & Stratigraphy Potential Drilling Hazards & Constraints

Risk

of

Gas

SWF

Risk

Seabed -4,271 0 1.738 Seabed is smooth sloping to the northeast at 1.5°. Surficial sediments comprise of 

soft clays and silts.Underlying the seabed the lithology comprises of clays and silts 

with occasional minor coarser interbeds.

Figure 9

Interface -5,886 1,615 2.345

Horizon H10 -4,848 577 1.966

Interface -6,299 2,028 2.487

None predicted

Unit A

Unit B

Horizon H20 -5,407 1,136 2.174

Interface -7,175 2,904 2.774

Horizon H30 -7,739 3,468 2.948

Top of Salt -10,717 6,446 3.744 Base of interpretation

Interface -6,492 2,221 2.552

Interface -5,234 963 2.111

Interface -4,534 263 1.844 None predicted

Vavg

BML

(m/s)

0

5,322

5,065

5,415

5,209

5,607

5,733

6,427

5,457

5,166

4,977 Clays and silts

Unit C

Unit D

Interface -7,325 3,054 2.821 5,640

Interface -7,977 3,706 3.019 5,787

Interface -8,848 4,577 3.266 5,991

Clays and silts with occasional coarser interbeds None predicted

Clays and silts

Clay-prone sequence with occasional coarser interbeds

Clays and silts with several coarser interbeds that may represent sands

Clays and silts with occasional coarser interbeds

Clays and silts with several coarser interbeds that may represent sands

Clay-prone sequence with occasional coarser-grained interbeds

Clays with several coarser interbeds

Clays and silts with occasional coarser interbeds

Clays with several coarser interbeds that may represent sands

Clays with occasional coarser interbeds

None predicted

None predicted

Slight Risk of Gas and Moderate Shallow Water Flow Risk

None predicted

Slight Risk of Gas and Moderate Shallow Water Flow Risk

None predicted

Slight Risk of Gas.Minor drilling fluid circulation and wellbore stability 

problems possible

None predicted

Slight Shallow Water Flow Risk. Minor drilling fluid circulation and 

wellbore stability problems possible

None predicted
±

6

3® 3

3

3

-4210

-4180

-4200 -4190

-4170

-4220

-4160

-4230

-4240

-4150

-4250

-4260

-4270

-4280

-4290

-4300

-4310

-4320

-4140

-4330

-4340

-4280

-4200

-4150

-4230

-4220

-4160

-4200

-4150

-4200

-4240

-4150

-4240

-4180

-4190

-4160

-4210

-4170

-4270

-4250

-4140

-4150

-4230

-4180

-4260

-4270

-4210

-4220

-4220

-4160

-4210

-4210

-4160

-4170

-4230

-4160

-4150

-4150

-4260

AT018-001

89°5'0"W89°4'0"W89°3'0"W

27°58'0"N

27°57'0"N

27°56'0"N

970,000975,000980,000

27°55'0"N

10,140,000

10,145,000

10,150,000

10,155,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1 = 2,000'

Bathymetry Plat Figure 12

2,000ft Radius

Proposed AT018-GV

Easting: 980,582ft E

Northing: 10,150,777ft N

FEL of AT018-GV: 1,498ft

FNL of AT018-GV: 2,663ft

ATWATER VALLEY 

BLOCK 18(OCS-G33863)

2,000ft Radius

MISSISSIPPI CANYON

BLOCK 986(OCS-G33770)

ATWATER VALLEY 

BLOCK 62(OCS-G32560)
±

6

3® 3

3

3

Proposed AT018-GV Well

AT018-001

89°5'0"W89°4'0"W89°3'0"W

27°58'0"N

27°57'0"N

27°56'0"N

27°55'0"N

970,000975,000980,000

10,140,000

10,145,000

10,150,000

10,155,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1" = 2,000'

Well Location Plat - Public Information Figure 13

2,000ft Radius

Location Call N/S Call E/W X Coordinate Y Coordinate Latitude Longitude WD

AT018-GV SL 2,663ft FNL 1,498ft FEL 980,582 10,150,777 27° 57' 25.62''N 89° 02' 39.83''W -4,271

Proposed Location - AT018-GV

ATWATER VALLEY 

BLOCK 18(OCS-G33863)

MISSISSIPPI CANYON

BLOCK 986(OCS-G33770)

ATWATER VALLEY 

BLOCK 62(OCS-G32560)
Nearest Shoreline

Range: 71mi

Bearing: 343°

Fourchon

Range: 106mi

Bearing: 320°

Lund

Henderson

Lloyd Ridge

Walker Ridge

Destin Dome

Atwater Valley Green Canyon

De Soto Canyon

The Elbow

Florida Plain

Vernon Basin

Apalachicola

Garden Banks

Keathley Canyon

Florida Middle Ground

Howell Hook

Lund South

Pensacola

Amery Terrace

Mobile

Viosca Knoll

Viosca Knoll

Sigsbee Escarpment

New Orleans

Baton Rouge

Pensacola

Lafayette

Gulfport Pascagoula

Vicinity Map - Atwater Valley Block 018

Figure 15
Anadarko Petroleum Corporation Gardline Report 9518

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GV

APPENDIX A – Public Shallow Hazards Statements 

29
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Public Shallow Hazards Statement – AT018-GV

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213-2394

Attention: 

Reference: Shallow Hazards Analysis

Atwater Valley Block 18

OCS-(G 33863) 

Ladies/Gentlemen:

Anadarko Petroleum Corporation contracted Gardline Surveys, Inc. to prepare a Well Clearance Letter 

for the proposed AT018-GV well location in Block 18, Atwater Valley Area (OCS-G 33863). This letter 

addresses seafloor and shallow geologic conditions that may impact exploratory drilling operations 

within 2,000ft of the proposed well location. The depth limit of this geohazard assessment is to Top of 

Salt at -10,717ft below sea surface (6,447ft below seabed).

This hazards summary letter is issued as a supplement to Gardline Report No.9172 entitled: 3D 

Geohazard Assessment, Atwater Valley Block 018 and 019, dated August 2012.

Seabed Hazards. 

The seabed is smooth and featureless. No problems are expected at the proposed AT 18 GV well 

location.

There are no indications of seabed fluid seeps within 2,000ft of the well location.

No existing seabed infrastructure is located within 2,000ft of the proposed well. There is an existing 

well AT018-001 located 1,375ft to the northwest. The following are the coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

Two pipelines are located on the adjacent Block AT019 approximately 5,174ft and 5,353ft 

to the east and northeast. The following are detailed of the pipelines:

Pipeline Installations

Operator Area Block - Origin/Termination Outside Diameter (in) Product Status

ATP O&G AT063 / MC941 5 in BLKO ACT

ATP O&G MC941 / AT063 4in UBEH ACT

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GV

Sub-Seabed Hazards. 

Drilling Caution is indicated for a Slight Risk of Gas at the well location within two intervals of Unit C

and within an interval in Unit D. 

Moderate Shallow Water Flow Risk is assigned to two intervals within Unit C. A Slight Shallow 

Water Flow Risk is anticipated within an interval in Unit D. 

Proposed AT 18 GV Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 57' 25.62” North Easting 980,582 US ft E

Longitude 89° 02’ 39.83” West Northing 10,150,777 US ft N

FEL of Atwater Valley 18 1,498 US ft Inline 5322

FNL of Atwater Valley 18 2,663 US ft Crossline 10709

Water Depth: -4,271 ft Slope: 1.5° NE

Nearest Shoreline 71.34 Miles @ 343° 25’ 48’’

Port of Operation Fourchon 106.42Miles @ 320° 36’ 0’’

Nearest Manned Platform MC941-(Mirage/Titan) 6.25 Miles @ 328° 17’ 24”

Conclusions and Recommendations. 

Drilling techniques will take into consideration the possibility of encountering possible gas within two 

interval of Unit C and within an interval in Unit D. Appropriate drilling methodology should be utilized to 

deal with a possible Moderate Shallow Water Flow Risk in the intervals within Unit C. 

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

PUBLIC INFORMATION

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GV

APPENDIX B – Sensitive Sessile Benthic Community Statements

32
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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GV

Sensitive Sessile Benthic Community Statement – AT018-GV

Anadarko Petroleum Corporation

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213

Reference: Sensitive Sessile Benthic Community Summary

Atwater Valley, Block 18

OCS-(G 33863) 

Ladies/Gentlemen:

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Site Clearance 

Letter for the proposed AT018-GV well location in Atwater Valley, Block 18, Stromboli Prospect (OCSG G 33863). This letter addresses location proximity to potential sensitive sessile benthic community 

sites. Anadarko Petroleum Corporation will be drilling this well from a dynamically positioned drilling 

module; therefore, no anchors will impact seabed.

This sensitive sessile benthic community summary letter is issued as a supplement to Gardline Report 

No.9172 entitled: 3D Geohazard Assessment, Atwater Valley Block 018, dated August 2012. A 

Biological, Physical and Socio-Economic Map is included at the end of this appendix illustrating the 

areas of potential seabed impact.

Potential Sensitive Sessile Benthic Communities. 

Features or areas that could support high density sensitive sessile benthic communities are not 

located within 2,000ft of any proposed mud and cuttings discharge location.

Proposed AT 18 GV Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 57' 25.62” North Easting 980,582 US ft E

Longitude 89° 02’ 39.83” West Northing 10,150,777 US ft N

FEL of Atwater Valley 18 1,498 US ft Inline 5322

FNL of Atwater Valley 18 2,663 US ft Crossline 10709

Water Depth: -4,271 ft Slope: 1.5° NE

Nearest Shoreline 71.34 Miles @ 343° 25’ 48’’

Port of Operation Fourchon 106.42Miles @ 320° 36’ 0’’

Nearest Manned Platform MC941-(Mirage/Titan) 6.25 Miles @ 328° 17’ 24”

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 GV

No potential sensitive sessile benthic community site is located within 2,000ft of the proposed 

location. 

Conclusions and Recommendations: 

The proposed AT018-GV well location will not impact any sites favorable for development of sensitive 

sessile benthic communities.

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

34
ANADARKO PETROLEUM CORPORATION

3D GEOHAZARD ASSESSMENT

GULF OF MEXICO

ATWATER VALLEY BLOCK AT 018

STROMBOLI PROSPECT

AT018-QQ PROPOSED WELL LOCATION

WELL CLEARANCE LETTER 

Gardline Project Ref. 9648

Report Status Final

Issue Date July 30, 2013

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-QQ

ii

REPORT AUTHORIZATION AND DISTRIBUTION

Report Status Final

Issue Date July 30, 2013

Compilation Geophysicist L Fuentes

Authorization Geophysics .....................

A R Haigh

Quality Assurance .....................

M DeLeon

Distribution 

6 copies

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

For attention of:

Rick Kincaid
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SERVICE WARRANTY

USE OF THIS REPORT

This report has been prepared with due care, diligence and with the skill reasonably expected of a 

reputable contractor experienced in the types of work, carried out under the contract. As such, the 

findings in this report are based on an interpretation of data which is a matter of opinion on which 

professionals may differ and, unless clearly stated, is not a recommendation of any course of action. 

Gardline Surveys, Inc. has prepared this report for the client identified on the front cover in fulfilment of 

its contractual obligations under the referenced contract, and the only liabilities Gardline Surveys, Inc. 

will accept are those contained therein.

Please be aware that further distribution of this report, in whole or part, or the use of the data for a 

purpose not expressly stated within the contractual work scope is at the client’s sole risk, and Gardline 

Surveys, Inc recommends that this disclaimer be included in any such distribution. 

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
Green Canyon Atwater Valley Lloyd Ridge

Mississippi Canyon

Destin Dome

De Soto Canyon

Mobile Pensacola

Ship Shoal Area

Eugene Island Area

Viosca Knoll

Viosca Knoll

Main Pass Area

Ewing Bank

South Timbalier Area

West Delta Area

Louisiana

Alabama Mississippi

Florida

Location Map

Study Area
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TABLE OF CONTENTS

REPORT AUTHORIZATION AND DISTRIBUTION ii

SERVICE WARRANTY iii

LOCATION MAP iv

TABLE OF CONTENTS v

LIST OF FIGURES vi

LIST OF CHARTS vii

WELL CLEARANCE LETTER – PROPOSED AT018-QQ WELL LOCATION 1

1. LOCATION COORDINATES 4

1.1 Proposed AT018-QQ Well Location 4

2. VELOCITY DATA 5

2.1 Velocity Data 5

3. SEABED CONDITIONS 7

3.1 Bathymetry 7

3.2 Seafloor Morphology and Man Made Features 7

4. SUBSEABED CONDITIONS 8

4.1 Geology and Lithology 8

4.2 Unit A 8

4.3 Unit B 8

4.4 Unit C 8

4.5 Unit D 10

4.6 Shallow Gas Assessment 10

4.7 Shallow Water Flow Assessment 11

5. CONCLUSIONS AND RECOMMENDATIONS 12

APPENDIX A – Public Shallow Hazards Statements

APPENDIX B – Sensitive Sessile Benthic Community Statements
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LIST OF FIGURES

Proposed AT 018-QQ Well Location

1 Seabed Depth Extract

2 Seabed Morphology Extract

3 Seabed Amplitude Extract

4 Geohazard Summary Extract

5 Sand Lithology Summary

6 Inline Data Example

7 Crossline Data Example

8 Tie Line to AT018-001

9 Top Hole Prognosis

10 ROV Plat

11 Power Spectrum

12 Bathymetry Plat

13 Public Information Plat

14 Proprietary Information Plat

15 Vicinity Map

16 10-Mile Radius Plat
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LIST OF CHARTS

The following chart at a scale of 1" = 2,000ft is enclosed:

Chart No Title Drawing No

1 Biological, Physical and Socio-Economic Map 9648.01
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WELL CLEARANCE LETTER – PROPOSED AT018-QQ WELL LOCATION

July 30, 2013

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

Attention: Rick Kincaid

Well Clearance Letter

Proposed AT018-QQ Well Location

Block 018, Atwater Valley Area

OCS- G 33863

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Well Clearance 

Letter for the proposed AT018-QQ well location in Block 018, Atwater Valley Area (OCS-G 33863). 

This letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this well clearance 

assessment is Top of Salt or -10,858ft below sea surface (6,603ft below seabed). We understand that 

Anadarko Petroleum Corporation plans to drill the proposed exploration well from a dynamically 

positioned drilling vessel; therefore, an anchoring assessment is not required nor provided. Relevant 

letter-size chart extracts, data examples, and a Top Hole Prognosis are presented with this Well 

Clearance Letter. This geohazard assessment is based on the interpretation of 3D seismic data. This 

site clearance letter is issued as a supplement to Gardline Report No.9172 entitled: 3D Geohazard 

Assessment, Atwater Valley Block 018 and 019, dated August 2012. 

Archaeological Survey. Anadarko Petroleum Corporation provided for review the complete 

archaeological survey report acquired by C&C Technologies Survey Services: Archaeological Survey 

Blocks 18 (OCS-G-33863) and 19 (OCS-G-32556) Atwater Valley Area for the Anadarko Stromboli 

Prospect. 

3D Geophysical Survey. Anadarko Petroleum Corporation provided the 3D dataset to Gardline 

Surveys Inc. on tape media in SEG-Y format for loading onto a Seismic Micro-Technology (SMT) 

workstation. The 3D data cube contains a survey with 4 millisecond sample rate data to a record 

length of 6.0 seconds TWT below sea surface. Inlines are oriented north to south, have a numerical 

increment of one, and exhibit a line spacing of 65.6ft. Crosslines are oriented west to east, have a 

numerical increment of one, and exhibit a line spacing of 41.0ft.

• The acquisition parameters are: 

o Atwater Valley (I) DW V

 

Shooting Direction: N/S

Configuration: 4 sources, 6-10 streamers
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Maximum offset: 8000 m

Channels: 324 per streamer 

Shotpoint interval: 47.25 m per array 

Group interval: 25 m

CMP line spacing: 40 m 

CMP bin dimension: 12.5 m x 40 m 

Record Length: 9 s below sea bottom 

Nominal fold: 43

Vintage: April 1999

• The basic processing parameters are:

o Atwater Valley (I) DW V

480-m x 500-m velocity grid 

Demultiple 

3D DMO velocity and stacking technology 

One-pass 3D poststack migration 

12.5-m x 20-m final bin dimension

. 

The data exhibits a good frequency response across the upper one second below seabed, with an 

effective frequency range of 5 to 65Hz (Figure 11). The data exhibits a dominant frequency of 

approximately 53Hz with significant higher usable frequencies. This frequency range results in a 

mean vertical resolvability of approximately 10m and a layer detectability of 5ft. 

In summary and with reference to NTL No. 2008-G04: 

a) The 3D data provides images of sufficient resolution of the shallow section allowing a 

clear analysis of the shallow conditions

b) The data can be loaded to a workstation at 16bit resolution or greater, and is un-scaled

c) There is no trace or sample decimation

d) The sample interval and bin size are maintained throughout the assessment area

e) The data possess a frequency content of 50Hz or higher across the first second below 

seabed (See Power Spectrum Diagram: Figure 11) 

f) Seabed reflection is free of gaps and defined by a wavelet of stable shape and phase, 

allowing auto-tracking of the seabed event with minimum user intervention and guidance

g) There are no significant acquisition artefacts throughout the dataset

h) There are no merge points in the data

i) Processed bin sizes are 65.62ft x 41.01ft

j) The sample rate of the data is 4ms

k) An accurate velocity model has been utilized in the shallow section allowing optimum 

structural and stratigraphy resolution with no evidence of under or over migration

l) There is no significant multiple energy
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m) The proposed activities are not in an area of high archaeological potential.
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1. LOCATION COORDINATES

1.1 Proposed AT018-QQ Well Location

Proposed AT 018-QQ Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 57' 31.41” North Easting 979,462 US ft E

Longitude 89° 02’ 52.44” West Northing 10,151,381 US ft N

FEL of Atwater Valley 018 2,618 US ft Inline 5305

FNL of Atwater Valley 018 2,059 US ft Crossline 10724

Water Depth: -4,255 ft Slope: 2.1° NE

Nearest Shoreline 71 Miles @ 343° 

Port of Operation Fourchon 106 Miles @ 320° 

Nearest Manned Platform MC941-(Mirage/Titan) 6 Miles @ 300° 
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2. VELOCITY DATA

2.1 Velocity Data

Time-to-depth conversion for the water column was made using the Advocate and Hood 

(1993) polynomial.

Seabed Depth (ft) =

0.1105 – 5066.9193X + 468.6693X2 – 554.7107X3 + 340.7019X4 – 116.991X5 + 20.728X6 – 1.4658X7 

Where X = one way time to seabed in seconds.

One Way Time To Seabed (s) Seabed Depth (ft) Seabed Depth (m) Vavg (m/s)

0.0 0 0 0

1.0 4910 1496 1496

1.1 5400 1646 1496

1.2 5892 1796 1496

1.3 6384 1946 1497

1.4 6877 2096 1497

1.5 7370 2246 1498

1.6 7865 2397 1498

1.7 8360 2548 1499

1.8 8856 2699 1499

1.9 9353 2851 1500
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Sub-seabed time to depth conversion was performed using a polynomial function 

successfully applied in an adjacent project and approved by Anadarko Petroleum 

Company: 

Vavg = = -45.841X5 + 190.08X4

 – 183.08X3 - 14.729X2 + 735.59X +4900

Where X = two way time in seconds below seabed. 

The resultant velocity was then multiplied by the time below seabed to produce depth below 

seabed; this was summed with seabed depth to produce horizon depth below sea surface.
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3. SEABED CONDITIONS

3.1 Bathymetry

Seabed depth at the proposed AT018-QQ well location is -4,255ft below sea surface (Figure 

1). The seafloor slopes to the northeast at 2.1°.

3.2 Seafloor Morphology and Man Made Features

The proposed AT018-QQ well location is in the northeast of Block AT018. The seabed is 

smooth and featureless at the proposed well location (Figure 2). Soft clays and silts are 

predicted at seabed. Sediments appear conducive for jetting of seabed casing with no hard 

layers predicted. 

A seabed fault occurs 2,780ft to the southwest of the proposed well. The fault should not 

impact the proposed well. 

An existing well AT018-001 is located 949ft to the northeast. The following are the 

coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

There are no anomalous seabed amplitudes indicative of hydrocarbon macroseep observed 

within a 2,000ft radius of the proposed location (Figure 3).

No items of archaeological significance were identified within 2,000ft of the proposed location

(Archaeological report submitted under a separate cover). 

No other features are observed within a 2,000ft radius that could affect well emplacement or 

jetting of casing.
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4. SUBSEABED CONDITIONS

4.1 Geology and Lithology

The sub-seabed geology has been divided into four units separated by four horizons (Figures 

6 through 9). A Geohazard Extract and Sand-Prone Lithology Extract complete the well 

assessment (Figures 4 and 5). 

4.2 Unit A 

The uppermost interval within Unit A from seabed to -4,466ft below sea surface (211ft below 

seabed) is interpreted to consist of clays and silts with occasional minor coarser interbeds. 

The lower interval of Unit A from -4,466ft to -4,832ft below sea surface (211ft to 577ft below 

seabed) is interpreted to comprise of clays and silts. 

No shallow gas or shallow water flow is predicted within Unit A at the proposed well location.

A vertical borehole will not penetrate any faults within Unit A. 

Horizon H10 marks the base of Unit A at -4,832ft below sea surface (577ft below seabed). 

4.3 Unit B 

The upper interval of Unit B from -4,832ft to -5,281ft below sea surface (577ft to 1,026ft below 

seabed) is expected to comprise of clays and silts with occasional coarser interbeds. 

The lower interval of Unit B from -5,281ft to -5,465ft below sea surface (1,026ft to 1,210ft 

below seabed) is interpreted to consist of clays and silts with several coarser interbeds. The 

coarser interbeds in this lower interval of Unit B may cause minor drilling fluid circulation and 

minor wellbore stability problems.

No shallow gas or shallow water flow is predicted within Unit B at the proposed well location.

A vertical borehole will not penetrate any faults within Unit B.

Horizon H20 marks the base of Unit B at -5,465ft below sea surface (1,210ft below seabed). 

4.4 Unit C 

Lithology within the upper interval of Unit C from -5,465ft to -5,548ft below sea surface 

(1,210ft to 1,293ft below sea surface) is interpreted to consist of a clay-prone sequence with 

several coarser interbeds. Due to the potential for some possible poorly consolidated coarser 

material within this interval minor drilling fluid circulation and minor wellbore stability problems 
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may occur.

The stratigraphy from -5,548ft to -5,902ft below sea surface (1,293ft to 1,647ft below seabed) 

is interpreted to consist of clays and silts with several coarser interbeds that may represent 

sands. Due to the potential for some possible poorly consolidated coarser material within this 

interval minor drilling fluid circulation and minor wellbore stability problems may occur.. 

From -5,902ft to -6,494ft below sea surface (1,647ft to 2,239ft below seabed) is interpreted as

clays and silts with several coarser interbeds that possibly represent sands. The proposed 

well is located on the northeast edge of a sand fairway that extends from the southwest of the 

adjacent block (Block AT019) into the east-central part of Block AT018 and continues to cross 

the center of the block to the northwest (Figure 5). A cluster of high amplitude anomalies 

located approximately 250ft to the east and northeast of the proposed well are interpreted as

a high risk of gas. The vertical borehole will not intersect any of these anomalies; however, 

the sands within this package do exhibit a slight amplitude response. As such a Slight Risk 

of Gas is assigned within this interval. In addition, the combination of the sandy nature of this 

interval which was potentially rapidly deposited with inadequate dewatering time, plus a 

possible clay-rich impermeable overburden, combine to create a favorable setting for 

development of shallow water flow; a Moderate Shallow Water Flow Risk is assigned to this 

interval. This interval did not present any reported drilling problems at the nearby offset well 

AT018-001. However, AT018-001 presents a slight reduction in seismic amplitude perhaps 

indicating a reduced sandy content at that well.

The interval from -6,494ft to -7,200ft below sea surface (2,239ft to 2,946ft below seabed) is 

interpreted to consist of clays and silts with several coarser interbeds that may represent 

sands. The well path is located outside the main cluster of high amplitude anomalies that

occur around 2,000ft to the southwest that are interpreted as fluid-charged sands. A 

previously drilled well located 5.1 miles to the southeast (AT063-002) experienced a low 

volume shallow water flow event in sands at 2,012ft below seabed; correlating with this 

interval. The nearest offset well, AT018-001 did encounter some shallow gas shows and 

some ballooning of the wellbore through this interval. At the proposed location this interval is 

thicker and exhibits higher energy character than observed at the existing AT018-001 well. 

The proposed location is also more centrally placed within the Unit C sand fairways than the 

existing AT018-001well (Figure 5). However, the seismic profile over the existing AT018-001

well does present an anomaly that could be the source of the observed gas shows (Figure 8); 

this anomaly is considerably weaker at the proposed well location. Taking into account all 

these observations, plus the acoustic signature of the interval which is suggestive of 

potentially rapidly-deposited sandy interbeds that may have experienced inadequate 

dewatering, a Slight Risk of Gas and a High Shallow Water Flow Risk is assigned to this 

interval.

A clay-prone sequence with occasional coarser-grained interbeds is interpreted from -7,200ft 

to -7,335ft below sea surface (2,946ft to 3,080ft below seabed). 
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The lower interval within Unit C from -7,335ft to -7,644ft below sea surface (3,080ft to 3,389ft 

below seabed) is interpreted to comprise of clays with several coarser interbeds. The coarser 

interbeds within this package may induce minor drilling fluid circulation and wellbore stability 

problems. The existing well AT018-001 did encounter some minor shallow gas shows in this 

interval, but there is no clear indication of any anomalies on the seismic data to support any 

shallow gas occurrence at the proposed well location.

A vertical borehole will not penetrate any faults within Unit C.

Horizon H30 marks the base of Unit C at -7,644ft below sea surface (3,389ft below seabed).

4.5 Unit D 

The upper interval of Unit D from -7,644ft to -8,098ft below sea surface (3,389ft to 3,843ft 

below seabed) is interpreted as clays and silts with occasional coarser interbeds. No drilling 

hazards or problems are expected within this interval.

From -8,098ft to -8,715ft below sea surface (3,843ft to 4,460ft below seabed), is interpreted 

as a slightly higher-energy deposited package with clays and several coarser interbeds. This 

interval exhibits the characteristics of shallow water flow with the potential for rapid deposition, 

plus inadequate dewatering. As such, a Slight Shallow Water Flow Risk is assigned to this 

interval. Due to the potential for coarser and potentially poorly-consolidated sediments within 

this interval, minor drilling fluid circulation and wellbore stability problems may also occur. 

Additionally, these sand interbeds exhibit an increase in amplitude and these sands exhibit a 

risk of gas ~818ft to the west. Although we suspect the gas is being trapped by faults, we still 

consider a Slight Risk of Gas within this interval. The nearby offset well AT018-001 did not 

report any problems from this interval, which is acoustically similar on the seismic data.

Stratigraphy from -8,715ft to -10,858ft below sea surface (4,460ft to 6,603ft below seabed) is 

interpreted to consist of clays with occasional coarser interbeds. 

A vertical borehole will penetrate three faults within Unit D at -8,994ft, -9,972ft, and -10,562ft 

below sea surface (4,739ft, 5,717ft, and 6,307ft below seabed). Minor drilling fluid circulation 

and wellbore stability problems are possible at the level of these small-scale faults. 

Top of Salt marks the base of Unit D and the base of this interpretation at -10,858ft below sea 

surface (6,603ft below seabed). 

4.6 Shallow Gas Assessment

Within Unit C, a Slight Risk of Gas is assigned to the interval from -5,902ft to -6,494ft below 

sea surface (1,647ft to 2,239ft below seabed), and also from -6,494ft to -7,200ft below sea 

surface (2,239ft to 2,946ft below seabed).
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Within Unit D, a Slight Risk of Gas is assigned to the interval from -8,098ft to -8,715ft below 

sea surface (3,843ft to 4,460ft below seabed). 

4.7 Shallow Water Flow Assessment

Within Unit C, a High Shallow Water Flow Risk is interpreted in the interval from -6,494ft to 

-7,200ft below sea surface (2,239ft to 2,946ft below seabed). A Moderate Shallow Water 

Flow Risk is interpreted from -5,902ft to -6,494ft below sea surface (1,647ft to 2,239ft below 

seabed). 

Within Unit D, a Slight Shallow Water Flow Risk is assigned from -8,098ft to -8,715ft below 

sea surface (3,843ft to 4,460ft below seabed). 
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5. CONCLUSIONS AND RECOMMENDATIONS

• Seabed

No significant problems are anticipated at seabed. Shallow soils are expected to be 

conducive to the jetting of seabed casing with no hardgrounds predicted.

• Unit A 

No drilling hazards or problems predicted.

• Unit B

Minor drilling and minor wellbore stability problems are possible from -5,281ft to -5,465ft 

below sea surface (1,026ft to 1,210ft below seabed). 

• Unit C 

Within Unit C, a Slight Risk of Gas and a High Shallow Water Flow Risk is assigned to the 

interval from -6,494ft to -7,200ft below sea surface (2,239ft to 2,946ft below seabed). 

Drilling Caution is advised and appropriate drilling methodology is recommended to deal 

with a possible water flow event through this interval. The existing AT018-001 well did 

encounter some shallow gas shows and minor drilling problems from this interval. 

Within Unit C, a Slight Risk of Gas and a Moderate Shallow Water Flow Risk is also 

interpreted from -5,902ft to -6,494ft below sea surface (1,647ft to 2,239ft below seabed). 

Appropriate drilling methodology is recommended to deal with a possible water flow event 

through this interval. 

Minor drilling fluid circulation and wellbore stability problems may also occur from -5,465ft to 

-5,548ft below sea surface (1,210ft to 1,293ft below seabed), from -5,548ft to -5,902ft below 

sea surface (1,293ft to 1,647ft below seabed) and from -7,335ft to -7,644ft below sea surface 

(3,080ft to 3,389ft below seabed). 

• Unit D

Within Unit D, a Slight Risk of Gas and a Slight Shallow Water Flow Risk is assigned to 

the interval from -8,098ft to -8,715ft below sea surface (3,843ft to 4,460ft below seabed). 

Drilling Caution and appropriate drilling methodology should be utilized to contain a 

potentially non-persistent shallow water flow event within this interval. Minor drilling fluid 

circulation and wellbore stability problems may also occur within this interval.
Anadarko Petroleum Corporation Gardline Report 9648

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT018-QQ

13

We appreciate the opportunity to work with you on this project, and look forward to continuing as 

your geohazards consultants. Please contact us if you have any questions or if we can be of 

further assistance.

Sincerely,

Gardline Surveys Inc.

Andrew Haigh Matilde DeLeon

Geophysical Manager Quality Assurance

Copies Submitted: 6 copies to Rick Kincaid at Anadarko Petroleum Corporation.

Attachments:

Proposed AT018-QQ Well Location

Seabed Depth Extract

Seabed Morphology Extract

Seabed Amplitude Extract

Geohazard Summary Extract

Sand Lithology Summary

Inline Data Example

Crossline Data Example

Arbitrary Line Data Example

Top Hole Prognosis

ROV Plat

Power Spectrum

Bathymetry Plat

Public Information Plat

Proprietary Information Plat

Vicinity Map

10-Mile Radius Plat
Top Hole Prognosis for Proposed AT018-QQ Well Location

979,462ft E / 10,151,381ft N

Inline: 5305 / Crossline: 10724 Horizon

Subsea

Depth

(ft)

BML

Depth

(ft)

Horizon

TWT

(sec)

Lithology, Structure & Stratigraphy Potential Drilling Hazards & Constraints

Risk

of

Gas

SWF

Risk

Seabed -4,255 0 1.740 Seabed is smooth sloping to the northeast at 2.1°. Surficial sediments comprise of 

soft clays and silts. Underlaying the seabed the lithology comprises of clays and silts 

with occasional minor coarser interbeds

Figure 9

Interface -5,902 1,647 2.358

Horizon H20 -5,465 1,210 2.203

Interface -6,494 2,239 2.560

None predicted

Unit A

Unit B

Horizon H30 -7,644 3,389 2.962

Interface -5,548 1,293 2.233

Interface -4,466 211 1.825

Interface -5,281 1,026 2.136

Horizon H10 -4,832 577 1.968

None predicted

Vavg

BML

(m/s)

0

5,329

5,227

5,461

5,714

5,247

4,962

5,182

5,065

Clays and silts

Unit C

Unit D

Interface -7,200 2,946 2.789 5,616

Top of Salt -10,858 6,603 3.784 6,461

Interface -7,335 3,080 2.831 5,646

Interface -8,098 3,843 3.061 5,818

Interface -8,715 4,460 3.236 5,963

Fault -9,972 5,717 3.566 6,262

Fault -10,562 6,307 3.712 6,397

Fault -8,994 4,739 3.312 6,029

Clays and silts with occasional coarser interbeds None predicted

Minor drilling fluid circulation and minor wellbore stability problems

possible within this interval

Clays and silts with occasional coarser interbeds

Minor drilling fluid circulation and minor wellbore stability problems

possible within this interval

Clays and silts with several coarser interbeds

Clays and silts with several coarser interbeds that may represent sands Minor drilling fluid circulation and minor wellbore stability problems

possible within this interval

Clays and silts with several coarser interbeds that may represent sands Slight Risk of Gas and Moderate Shallow Water Flow Risk

Clays and silts with several coarser interbeds that may represent sands Slight Risk of Gas and High Shallow Water Flow Risk

Clay-prone sequence with occasional coarser-grained interbeds None predicted

Clays with several coarser interbeds Minor drilling fluid circulation and wellbore stability problems possible

Clays and silts with occasional coarser interbeds None predicted

Slight Risk of Gas and Slight Shallow Water Flow Risk. Minor drilling fluid 

circulation and wellbore stability problems possible

Clays with several coarser interbeds that may represent sands

Clays with occasional coarser interbeds

Minor drilling fluid circulation and wellbore stability problems possible at

faults

Base of Interpretation
±

6

3® 3

3

3

-4210

-4180

-4200 -4190

-4170

-4220

-4160

-4230

-4240

-4250

-4260

-4150

-4270

-4280

-4290

-4300

-4310

-4320

-4140

-4330

-4340

-4260

-4250

-4160

-4220

-4210

-4140

-4270

-4210

-4280

-4220

-4270

-4160

-4170

-4160

-4230

-4240

-4200

-4160

-4200

-4210

-4230

-4220

-4160

-4150

-4150

AT018-001

89°5'0"W89°4'0"W89°3'0"W

27°59'0"N

27°58'0"N

27°57'0"N

27°56'0"N

970,000975,000980,000

10,145,000

10,150,000

10,155,000

10,160,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1 = 2,000'

Bathymetry Plat Figure 12

2,000ft Radius

Proposed AT018-QQ

Easting: 979,462ft E

Northing: 10,151,381ft N

FEL of AT018-QQ: 2,618ft

FNL of AT018-QQ: 2,059ft

ATWATER VALLEY 

BLOCK 18(OCS-G33863)

MISSISSIPPI CANYON

BLOCK 986(OCS-G33770)
±

6

3® 3

3

3

Proposed AT018-QQ Well

AT018-001

89°5'0"W89°4'0"W89°3'0"W

27°59'0"N

27°58'0"N

27°57'0"N

27°56'0"N

970,000975,000980,000

10,145,000

10,150,000

10,155,000

10,160,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1" = 2,000'

Well Location Plat - Public Information Figure 13

ATWATER VALLEY 

BLOCK 18(OCS-G33863)

Location Call N/S Call E/W X Coordinate Y Coordinate Latitude Longitude WD

AT018-QQ SL 2,059ft FNL 2,618ft FEL 979,462 10,151,381 27° 57' 31.41'' N 89° 02' 52.44'' N -4,255

Proposed Location - AT018-QQ

MISSISSIPPI CANYON

BLOCK 986(OCS-G33770)
Nearest Shoreline

Range: 71mi

Bearing: 343°

Fourchon

Range: 106mi

Bearing: 320°

Lund

Henderson

Lloyd Ridge

Walker Ridge

Destin Dome

Atwater Valley Green Canyon

De Soto Canyon

The Elbow

Florida Plain

Vernon Basin

Apalachicola

Garden Banks

Keathley Canyon

Florida Middle Ground

Howell Hook

Lund South

Pensacola

Amery Terrace

Mobile

Viosca Knoll

Viosca Knoll

Sigsbee Escarpment

New Orleans

Baton Rouge

Pensacola

Lafayette

Gulfport Pascagoula

Vicinity Map - Atwater Valley Block 018

Figure 15
Anadarko Petroleum Corporation Gardline Report 9648

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 QQ

30

APPENDIX A – Public Shallow Hazards Statements 
Anadarko Petroleum Corporation Gardline Report 9648

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31

Public Shallow Hazards Statement – AT018-QQ

July 30, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213-2394

Attention: 

Reference: Shallow Hazards Analysis

Atwater Valley Block 18

OCS-(G 33863) 

Ladies/Gentlemen:

Anadarko Petroleum Corporation contracted Gardline Surveys, Inc. to prepare a Well Clearance Letter 

for the proposed AT018-QQ well location in Block 18, Atwater Valley Area (OCS-G 33863). This letter 

addresses seafloor and shallow geologic conditions that may impact exploratory drilling operations 

within 2,000ft of the proposed well location. The depth limit of this geohazard assessment is to Top of 

Salt at -10,858ft below sea surface (6,603ft below seabed).

This hazards summary letter is issued as a supplement to Gardline Report No.9172 entitled: 3D 

Geohazard Assessment, Atwater Valley Block 018and 019, dated August 2012.

Seabed Hazards. 

The seabed is smooth and featureless. No problems are expected at the proposed AT 18 QQ well 

location.

There are no indications of seabed fluid seeps within 2,000ft of the well location.

No existing seabed infrastructure is located within 2,000ft of the proposed well. There is an existing 

well AT018-001 located 949ft to the northeast. The following are the coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

Two pipelines are located on the adjacent Block AT019 approximately 6,113ft and 6,330ft 

to the east and northeast. The following are detailed of the pipelines:

Pipeline Installations

Operator Area Block - Origin/Termination Outside Diameter (in) Product Status

ATP O&G AT063 / MC941 5 in BLKO ACT

ATP O&G MC941 / AT063 4in UBEH ACT
Anadarko Petroleum Corporation Gardline Report 9648

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 QQ

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Sub-Seabed Hazards. 

Drilling Caution is indicated for a Slight Risk of Gas at the well location within two intervals of Unit C.

High and Moderate Shallow Water Flow Risk is assigned to two intervals within Unit C. A Slight 

Shallow Water Flow Risk is anticipated within an interval in Unit D. 

Proposed AT 18 QQ Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 57' 31.411” North Easting 979,462 US ft E

Longitude 89° 02’ 52.438” West Northing 10,151,381 US ft N

FEL of Atwater Valley 18 2,618 US ft Inline 5305

FNL of Atwater Valley 18 2,059 US ft Crossline 10724

Water Depth: -4,255 ft Slope: 2.1° NE

Nearest Shoreline 71.34 Miles @ 343° 25’ 48’’

Port of Operation Fourchon 106.42Miles @ 320° 36’ 0’’

Nearest Manned Platform MC941-(Mirage/Titan) 6.06 Miles @ 300° 06’ 0”

Conclusions and Recommendations. 

Drilling techniques will take into consideration the possibility of encountering possible gas within two 

interval of Unit C. Appropriate drilling methodology should be utilized to contain a potentially nonpersistent Slight Shallow Water Flow Risk interpreted in the lower interval of Unit D. Appropriate 

drilling methodology should be utilized to deal with a possible High and Moderate Shallow Water 

Flow Risk in the intervals within Unit C. 

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

PUBLIC INFORMATION
Anadarko Petroleum Corporation Gardline Report 9648

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 QQ

33

APPENDIX B – Sensitive Sessile Benthic Community Statements
Anadarko Petroleum Corporation Gardline Report 9648

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 QQ

34

Sensitive Sessile Benthic Community Statement – AT018-QQ

Anadarko Petroleum Corporation

July 30, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213

Reference: Sensitive Sessile Benthic Community Summary

Atwater Valley, Block 18

OCS-(G 33863) 

Ladies/Gentlemen:

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Site Clearance 

Letter for the proposed AT018-QQ well location in Atwater Valley, Block 18, Stromboli Prospect (OCSG G 33863). This letter addresses location proximity to potential sensitive sessile benthic community 

sites. Anadarko Petroleum Corporation will be drilling this well from a dynamically positioned drilling 

module; therefore, no anchors will impact seabed.

This sensitive sessile benthic community summary letter is issued as a supplement to Gardline Report 

No.9172 entitled: 3D Geohazard Assessment, Atwater Valley Block 018, dated August 2012. A 

Biological, Physical and Socio-Economic Map is included at the end of this appendix illustrating the 

areas of potential seabed impact.

Potential Sensitive Sessile Benthic Communities. 

Features or areas that could support high density sensitive sessile benthic communities are not 

located within 2,000ft of any proposed mud and cuttings discharge location.

Proposed AT 18 QQ Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 57' 31.411” North Easting 979,462 US ft E

Longitude 89° 02’ 52.438” West Northing 10,151,381 US ft N

FEL of Atwater Valley 18 2,618 US ft Inline 5305

FNL of Atwater Valley 18 2,059 US ft Crossline 10724

Water Depth: -4,255 ft Slope: 2.1° NE

Nearest Shoreline 71.34 Miles @ 343° 25’ 48’’

Port of Operation Fourchon 106.42Miles @ 320° 36’ 0’’

Nearest Manned Platform MC941-(Mirage/Titan) 6.06 Miles @ 300° 06’ 0”
Anadarko Petroleum Corporation Gardline Report 9648

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Locations AT018 QQ

35

No potential sensitive sessile benthic community site is located within 2,000ft of the proposed 

location. 

Conclusions and Recommendations: 

The proposed AT018-QQ well location will not impact any sites favorable for development of sensitive 

sessile benthic communities.

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations
ANADARKO PETROLEUM CORPORATION

3D GEOHAZARD ASSESSMENT

GULF OF MEXICO

ATWATER VALLEY BLOCK AT019

STROMBOLI PROSPECT

AT019-EE PROPOSED WELL LOCATION

WELL CLEARANCE LETTER 

APRIL 2013

Gardline Project Ref. 9522

Report Status Final

Issue Date July 17, 2013

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

ii

REPORT AUTHORIZATION AND DISTRIBUTION

Report Status Final

Issue Date July 17, 2013

Compilation Geophysicist L Fuentes

Authorization Geophysics .....................

A R Haigh

Quality Assurance .....................

M DeLeon

Distribution 

6 copies

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

For attention of:

Rick Kincaid
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

iii

SERVICE WARRANTY

USE OF THIS REPORT

This report has been prepared with due care, diligence and with the skill reasonably expected of a 

reputable contractor experienced in the types of work, carried out under the contract. As such, the 

findings in this report are based on an interpretation of data which is a matter of opinion on which 

professionals may differ and, unless clearly stated, is not a recommendation of any course of action. 

Gardline Surveys, Inc. has prepared this report for the client identified on the front cover in fulfilment of 

its contractual obligations under the referenced contract, and the only liabilities Gardline Surveys, Inc. 

will accept are those contained therein.

Please be aware that further distribution of this report, in whole or part, or the use of the data for a 

purpose not expressly stated within the contractual work scope is at the client’s sole risk, and Gardline 

Surveys, Inc recommends that this disclaimer be included in any such distribution. 

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
Green Canyon Atwater Valley Lloyd Ridge

Mississippi Canyon

Destin Dome

De Soto Canyon

Mobile Pensacola

Ship Shoal Area

Eugene Island Area

Viosca Knoll

Viosca Knoll

Main Pass Area

Ewing Bank

South Timbalier Area

West Delta Area

Louisiana

Alabama Mississippi

Florida

Location Map

Study Area
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

v 

TABLE OF CONTENTS

REPORT AUTHORIZATION AND DISTRIBUTION ii

SERVICE WARRANTY iii

LOCATION MAP iv

TABLE OF CONTENTS v

LIST OF FIGURES vi

LIST OF CHARTS vii

WELL CLEARANCE LETTER – PROPOSED AT019-EE WELL LOCATION 1

1. LOCATION COORDINATES 3

1.1 Proposed AT019-EE Well Location 3

2. VELOCITY DATA 4

2.1 Velocity Data 4

3. SEABED CONDITIONS 6

3.1 Bathymetry 6

3.2 Seafloor Morphology and Man Made Features 6

4. SUBSEABED CONDITIONS 7

4.1 Geology and Lithology 7

4.2 Unit A 7

4.3 Unit B 7

4.4 Unit C 8

4.5 Unit D 9

4.6 Shallow Gas Assessment 9

4.7 Shallow Water Flow Assessment 9

5. CONCLUSIONS AND RECOMMENDATIONS 10

APPENDIX A – Public Shallow Hazards Statements 28

APPENDIX B – Sensitive Sessile Benthic Community Statements 31
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

vi

LIST OF FIGURES

Proposed AT019-EE Well Location

1 Seabed Depth Extract

2 Seabed Morphology Extract

3 Seabed Amplitude Extract

4 Geohazard Summary Extract

5 Sand Lithology Summary

6 Inline Data Example

7 Crossline Data Example

8 Top Hole Prognosis

9 ROV Plat

10 Power Spectrum

11 Bathymetry Plat

12 Public Information Plat

13 Proprietary Information Plat

14 Vicinity Map

15 10-Mile Radius Plat
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

vii

LIST OF CHARTS

The following chart at a scale of 1" = 2,000ft is enclosed:

Chart No Title Drawing No

1 Biological, Physical and Socio-Economic Map 9522.01
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

1 

WELL CLEARANCE LETTER – PROPOSED AT019-EE WELL LOCATION

July 17, 2013

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

Attention: Rick Kincaid

Well Clearance Letter

Proposed AT019-EE Well Location

Block 019, Atwater Valley Area

OCS- G 32556

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Well Clearance 

Letter for the proposed AT019-EE well location in Block 019, Atwater Valley Area (OCS-G 32556). 

This letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this well clearance 

assessment is Top of Salt or -9,554ft below sea surface (5,250ft below seabed). We understand that 

Anadarko Petroleum Corporation plans to drill the proposed exploration well from a dynamically 

positioned drilling vessel; therefore, an anchoring assessment is not required nor provided. Relevant 

letter-size chart extracts, data examples, and a Top Hole Prognosis are presented with this Well 

Clearance Letter. This geohazard assessment is based on the interpretation of 3D seismic data. This 

site clearance letter is issued as a supplement to Gardline Report No.9172 entitled: 3D Geohazard 

Assessment, Atwater Valley Blocks 018 & 019, dated August 2012. 

Archaeological Survey. Anadarko Petroleum Corporation provided for review the complete 

archaeological survey report acquired by C&C Technologies Survey Services: Archaeological Survey 

Blocks 18 (OCS-G-33863) and 19 (OCS-G-32556) Atwater Valley Area for the Anadarko Stromboli 

Prospect. 

3D Geophysical Survey. Anadarko Petroleum Corporation provided the 3D dataset to Gardline 

Surveys Inc. on tape media in SEG-Y format for loading onto a Seismic Micro-Technology (SMT) 

workstation. The 3D data cube contains a survey with 4 millisecond sample rate data to a record 

length of 6.0 seconds TWT below sea surface. Inlines are oriented north to south, have a numerical 

increment of one, and exhibit a line spacing of 65.6ft. Crosslines are oriented west to east, have an 

numerical increment of one, and exhibit a line spacing of 41.0ft.

• The acquisition parameters are: 

o Atwater Valley (I) DW V

 

Shooting Direction: N/S

Configuration: 4 sources, 6-10 streamers
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

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Maximum offset: 8000 m

Channels: 324 per streamer 

Shotpoint interval: 47.25 m per array 

Group interval: 25 m

CMP line spacing: 40 m 

CMP bin dimension: 12.5 m x 40 m 

Record Length: 9 s below sea bottom 

Nominal fold: 43

Vintage: April 1999

• The basic processing parameters are:

o Atwater Valley (I) DW V

480-m x 500-m velocity grid 

Demultiple 

3D DMO velocity and stacking technology 

One-pass 3D poststack migration 

12.5-m x 20-m final bin dimension

The data exhibits a good frequency response across the upper one second below seabed, with an 

effective frequency range of 5 to 60Hz. The data exhibits a dominant frequency of approximately 

53Hz with significant higher usable frequencies. This frequency range results in a mean vertical 

resolvability of approximately 10m and a layer detectability of 5ft. 

In summary and with reference to NTL No. 2008-G04

a) The 3D data provides images of sufficient resolution of the shallow section allowing a 

clear analysis of the shallow conditions

b) The data can be loaded to a workstation at 16bit resolution or greater, and is un-scaled

c) There is no trace or sample decimation

d) The sample interval and bin size are maintained throughout the assessment area

e) The data possess a frequency content of 50Hz or higher across the first second below 

seabed (See Power Spectrum Diagram: Figure 10) 

f) Seabed reflection is free of gaps and defined by a wavelet of stable shape and phase, 

allowing auto-tracking of the seabed event with minimum user intervention and guidance

g) There are no significant acquisition artefacts throughout the dataset

h) There are no merge points in the data

i) Processed bin sizes are 65.62ft x 41.01ft

j) The sample rate of the data is 4ms

k) An accurate velocity model has been utilized in the shallow section allowing optimum 

structural and stratigraphy resolution with no evidence of under or over migration

l) There is no significant multiple energy

m) The proposed activities are not in an area of high archaeological potential.
Anadarko Petroleum Corporation Gardline Report 9522

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1. LOCATION COORDINATES

1.1 Proposed AT019-EE Well Location

Proposed AT 019 EE Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 56' 30.32” North Easting 988,360 US ft E

Longitude 89° 01’ 12.07” West Northing 10,145,062 US ft N

FWL of Atwater Valley 19 6,280 US ft Inline 5441

FSL of Atwater Valley 19 7,462 US ft Crossline 10570

Water Depth: -4,304 ft Slope: 1.4° NE

Nearest Shoreline 72 Miles @ 341° 

Port of Operation Fourchon 108 Miles @ 319° 

Nearest Manned Platform MC941-(Mirage/Titan) 8 Miles @ 326° 
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

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2. VELOCITY DATA

2.1 Velocity Data

Time-to-depth conversion for the water column was derived using the Advocate and Hood 

(1993) polynomial.

Seabed depth (ft) =

0.1105 – 5066.9193X + 468.6693X2 – 554.7107X3 + 340.7019X4 – 116.991X5 + 20.728X6 – 1.4658X7 

Where X = one way time in seconds to seabed 

One Way Time To Seabed (s) Seabed Depth (ft) Seabed Depth (m) Vavg (m/s)

0.0 0 0 0

1.0 4910 1496 1496

1.1 5400 1646 1496

1.2 5892 1796 1496

1.3 6384 1946 1497

1.4 6877 2096 1497

1.5 7370 2246 1498

1.6 7865 2397 1498

1.7 8360 2548 1499

1.8 8856 2699 1499

1.9 9353 2851 1500
Anadarko Petroleum Corporation Gardline Report 9522

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Sub-seabed time to depth conversion was performed using a polynomial function 

successfully applied in an adjacent project and approved by Anadarko Petroleum 

Company: 

Vavg = -45.841X5 + 190.08X4

 – 183.08X3 - 14.729X2 + 735.59X +4900

Where X = two way time in seconds below seabed. 

The resultant velocity was then multiplied by the time below seabed to produce depth below 

seabed; this horizon depth was summed with seabed depth to produce horizon depth below 

sea surface.
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

6 

3. SEABED CONDITIONS

3.1 Bathymetry

Seabed depth at the proposed AT019-EE well location is -4,304ft below sea surface (Figure 

1). The seafloor slopes to the northeast at 1.4°.

3.2 Seafloor Morphology and Man Made Features

The proposed AT019-EE well location is in the center of Block AT019. At the proposed well 

location the seabed appears to be smooth and featureless (Figure 2). Soft clays and silts are 

predicted at seabed. Sediments appear conducive for jetting of seabed casing with no hard 

layers predicted. 

The proposed AT019-EE well location is on a low-relief ridge. The ridge is the result of a 

slight uplift induced by the nearby faults and tectonic movement; no fluid venting is 

associated with this faulting. The nearest fault is located 2,938ft to the south of the 

proposed location; this fault should not impact the proposed well. 

There is an existing well, AT063-SS004, located approximately 19,500ft to the SSW. 

Additionally, there is an existing well, AT018-001, located approximately 10,960ft to the 

northwest. The following are the coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

ATP Oil & Gas AT063 SS004 608184004100 4,418 27,802 987,101 10,134,998 COM

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

Two pipelines traverse Block AT019, located approximately 581ft and 795ft to the east and 

northeast respectively. The following are details of the pipelines:

Pipeline Installations

Operator Area Block - Origin/Termination Outside Diameter (in) Product Status

ATP O&G AT063 / MC941 5 in BLKO ACT

ATP O&G MC941 / AT063 4in UBEH ACT

There are no anomalous seabed amplitudes indicative of hydrocarbon macroseep observed 

within a 2,000ft radius of the proposed location (Figure 3).

No items of archaeological significance were identified within 2,000ft of the proposed location.

No other features are observed within a 2,000ft radius that could affect well emplacement or 

jetting of casing.
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

7 

4. SUBSEABED CONDITIONS

4.1 Geology and Lithology

The sub-seabed geology has been divided into four units separated by four horizons (Figures 

6 through 8). A geohazard extract and sand lithology extract utilized to complete the well 

assessment are presented in Figures 4 and 5. 

4.2 Unit A 

The uppermost interval within Unit A from seabed to -4,502ft below sea surface (198ft below 

seabed) is interpreted to consist of clays and silts with occasional minor coarser interbeds. 

The lower interval of Unit A from -4,502ft to -4,744ft below sea surface (198ft to 440ft below 

seabed) is interpreted to comprise of clays and silts. 

No shallow gas or shallow water flow is predicted within Unit A at the proposed well location.

A vertical borehole will not penetrate any faults within Unit A. 

Horizon H10 marks the base of Unit A at -4,744ft below sea surface (440ft below seabed). 

4.3 Unit B 

The upper interval of Unit B from -4,744ft to -4,997ft below sea surface (440ft to 693ft below 

seabed) is expected to comprise of clays and silts with occasional coarser interbeds. A <40ft 

thick sand interbed occurs at -4,929ft below sea surface (625ft below seabed). Minor drilling 

fluid circulation and minor wellbore stability problems are possible at the level of the interbed. 

The lower interval of Unit B from -4,997ft to -5,620ft below sea surface (693ft to 1,316ft below 

seabed) is interpreted to consist of slightly higher energy clays and silts with occasional minor 

coarser interbeds that may represent sands. Due to the slightly elevated energy content 

within this interval, minor drilling fluid circulation and minor wellbore stability problems are 

predicted. 

No shallow gas or shallow water flow is predicted within Unit B at the proposed well location.

A vertical borehole will not penetrate any faults within Unit B.

Horizon H20 marks the base of Unit B at -5,620ft below sea surface (1,316ft below seabed). 
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

8 

4.4 Unit C 

The lithology within the upper interval from -5,620ft to -5,746ft below sea surface (1,316ft to 

1,442ft below seabed) is interpreted as clays and silts with the possibility of several minor 

coarser interbeds. Some minor drilling fluid circulation and minor wellbore stability problems 

are predicted within this interval. 

Lithology within the interval from -5,746ft to -6,597ft below sea surface (1,442ft to 2,293ft 

below sea surface) is interpreted to consist of higher energy clays and silts with numerous 

coarser interbeds that may represent sands. The proposed well is located at the edge of a 

sand fairway package that extends from south of the well to the northwest, and further to the 

north and northeast of the well (Figure 5). A cluster of high-amplitude anomalies located

generally to the south, west, and northwest of the proposed well at these depths have been 

assigned a high risk of gas. The vertical borehole will not traverse any of these anomalies

with the nearest risk of gas anomaly being ~550ft to the southwest. However, due to the 

close encroachment and general higher energy nature of this interval, a Slight Risk of Gas is 

assigned. This interval exhibits the characteristics of rapid high energy deposition plus a welldefined clay-prone overburden (Unit B); this combination present favorable conditions for the 

formation of shallow water flow. In addition, a previously drilled well (AT063-2) located 2.4 

miles to the south experienced a low shallow water flow event at 2,012ft below seabed; these 

sands correlate with this interval. As such, a Moderate Shallow Water Flow Risk is 

assigned to this interval.

From -6,597m to -7,769m below sea surface (2,293m to 3,415m below seabed) is interpreted 

to consist of further slightly higher energy clays and silts with several coarser interbeds that 

may represent sands. Due to the presence of several possible minor sand interbeds, 

suggestion of localized rapid deposition and encapsulation within clays and silts, this interval 

is considered a Slight Shallow Water Flow Risk.

The lower interval within Unit C from -7,769ft to -8,393ft below sea surface (3,415ft to 4,089ft 

below seabed) is interpreted to comprise of clays with numerous sands. The sand interbeds 

within this interval exhibit a high risk of gas 435ft to the southwest. At the proposed well 

location the amplitude response is diminished, and the location is downdip from the high risk 

of gas anomalies. However, there ramians a slightly elevated amplitude response at the 

wellbore, and as such a Slight Risk of Gas is assigned within this interval. The interpreted 

higher energy, sandy nature of this lower interval of Unit C and the more continuous sandy 

interbeds extending downdip is a favorable environment for the formation of shallow water 

flow, as such a Moderate Shallow Water Flow Risk is assigned to this interval. Minor 

drilling fluid circulation and minor wellbore stability problems are also considered possible

within this interval due to the increased potential for poorly consolidated material. 

Horizon H30 marks the base of Unit C occurring at -8,393ft below sea surface (4,089ft below 

seabed). 
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

9 

4.5 Unit D 

Unit D from -8,393ft to -9,554ft below sea surface (4,089ft to 5,250ft below seabed) is 

interpreted to consist of clays and silts with several coarser interbeds. Minor drilling fluid 

circulation and wellbore stability problems may occur.

Top of Salt marks the base of Unit D and the base of this interpretation, occurring at -9,554ft 

below sea surface (5,250ft below seabed). 

4.6 Shallow Gas Assessment

Within Unit C, a Slight Risk of Gas is assigned to the interval from -5,746ft to -6,597ft below 

sea surface (1,442ft to 2,293ft below seabed), and within the interval from -7,769ft to -8,393ft 

below sea surface (3,415ft to 4,089ft below seabed).

4.7 Shallow Water Flow Assessment

Within Unit C, a Moderate Shallow Water Flow Risk is assigned from -5,746ft to -6,597ft 

below sea surface (1,442ft to 2,293ft below seabed) and from -7,769ft to -8,393ft below sea 

surface (3,415ft to 4,089ft below seabed). A Slight Shallow Water Flow Risk is assigned 

from -6,597ft to -7,769ft below sea surface (2,293ft to 3,415ft below seabed). 
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

10

5. CONCLUSIONS AND RECOMMENDATIONS

• Seabed

No significant problems are anticipated at seabed. Shallow soils are expected to be 

conducive to the jetting of seabed casing with no hardgrounds predicted. An existing pipeline 

is located 581ft to the east of the proposed well location. 

• Unit A 

No drilling hazards or problems predicted.

• Unit B

Minor drilling and minor wellbore stability problems are possible from -4,997ft to -5,620ft

below sea surface (693ft to 1,316ft below seabed) and at the level of a <40ft thick sand 

interbed at -4,929ft below sea surface (625ft below seabed). 

• Unit C 

Unit C presents a potentially challenging section to drill, with numerous intervals considered a 

risk of gas and a shallow water flow risk.

Within Unit C, a Slight Risk of Gas and a Moderate Shallow Water Flow Risk is assigned 

to the interval from -5,746ft to -6,597ft below sea surface (1,442ft to 2,293ft below seabed)

and within the interval from -7,769ft to -8,393ft below sea surface (3,415ft to 4,089ft below 

seabed). Drilling Caution and appropriate drilling methodology is recommended to deal with 

a possible water flow event throughout these intervals. Sediments in these intervals are most 

probably poorly consolidated and as such may induce minor drilling fluid circulation and 

wellbore stability problems.

Within Unit C, a Slight Shallow Water Flow Risk is assigned from -6,597ft to -7,769ft below 

sea surface (2,293ft to 3,415ft below seabed). Appropriate drilling methodology is 

recommended to deal with a possible less-persistent water flow event through this interval. 

Additionally, minor drilling fluid circulation and wellbore stability problems may also occur 

within this interval. 

Minor drilling and minor wellbore stability problems are possible from -5,620ft to -5,746ft 

below sea surface (1,316ft to 1,442ft below seabed).

• Unit D

Minor drilling and minor wellbore stability problems are possible throughout Unit D. 
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019-EE Well Location

11

We appreciate the opportunity to work with you on this project, and look forward to continuing as 

your geohazards consultants. Please contact us if you have any questions or if we can be of 

further assistance.

Sincerely,

Gardline Surveys Inc.

Andrew Haigh Matilde DeLeon

Geophysical Manager Quality Assurance

Copies Submitted: 6 copies to Rick Kincaid at Anadarko Petroleum Corporation.

Attachments:

Proposed AT019 EE Well Location

Seabed Depth Extract

Seabed Morphology Extract

Seabed Amplitude Extract

Geohazard Summary Extract

Sand Lithology Summary

Inline Data Example

Crossline Data Example

Top Hole Prognosis

ROV Plat

Power Spectrum

Bathymetry Plat

Public Information Plat

Proprietary Information Plat

Vicinity Map

10-Mile Radius Plat
Top Hole Prognosis for Proposed AT019-EE Well Location

988,360ft E / 10,145,062ft N

Inline: 5441 / Crossline: 10570 Horizon

Subsea

Depth

(ft)

BML

Depth

(ft)

Horizon

TWT

(sec)

Lithology, Structure & Stratigraphy Potential Drilling Hazards & Constraints

Risk

of

Gas

SWF

Risk

Seabed -4,304 0 1.756 Seabed is sloping to the northeast at 1.4°. The proposed well is located on the 

low-relief ridge. Surficial sediments comprise of soft clays and silts with occasional 

minor coarser intebeds

Figure 8

Interface -5,746 1,442 2.302

Horizon H10 -4,744 440 1.931

Interface -6,597 2,293 2.594

Existing pipeline occurs 581ft to the east

Unit A

Unit B

Unit D

Interface -7,769 3,415 2.991

Horizon H20 -5,620 1,316 2.257

Horizon H30 -8,393 4,089 3.148

Top of Salt -9,554 5,250 3.463

Unit C

-4,929 625 2.002 Sand Interbed

Interface -4,997 693 2.028

Interface -4,502 198 1.836

Vavg

BML

(m/s)

0

5,282

5,027

5,473

5,721

5,252

5,876

6,152

5,078

5,096

4,959 Clays and silts None predicted

Clays and silts with occasional coarser interbeds

Minor drilling fluid circulation and minor wellbore stability problems

possible at the level of the interbed <40ft thick sand interbed

Clays and silts with occasional coarser interbeds that may represent sands Minor drilling fluid circulation and minor wellbore stability problems

possible

Clays and silts with several coarser interbeds Minor drilling fluid circulation and minor wellbore stability problems

possible within this interval

Clays and silts with numerous coarser interbeds that may represent sands Slight Risk of Gas and Moderate Shallow Water Flow Risk

Clays and silts with several sand interbeds Slight Shallow Water Flow Risk. Minor drilling fluid circulation and minor 

wellbore stability problems possible within this interval

Clays with numerous coarser interbeds that may represent sands Slight Risk of Gas and Moderate Shallow Water Flow Risk, minor drilling 

fluid circulation and wellbore stability problems possible

Clays and silts with several coarser interbeds Minor drilling fluid circulation and wellbore stability problems possible

Base of interpretation
±

6

3® 3

3

3

-4510

-4470

-4460

-4360

-4370

-4380

-4390

-4480

-4400

-4410

-4430

-4420

-4440

-4450

-4500

-4490

-4350

-4340

-4520

-4330

-4320

-4530

-4310

-4300

-4290

-4280

-4270

-4540

-4550

-4560

-4260

-4570

-4250

-4240

-4580

-4590

-4230

-4600

-4220

-4210

-4610

-4200

-4190

-4180

-4520

-4510

-4530

-4540

-4520

-4260

-4480

-4550

-4530

-4370

-4560

89°2'0"W89°1'0"W89°0'0"W

27°58'0"N

27°57'0"N

27°56'0"N

27°55'0"N

985,000990,000995,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1 = 2,000'

Bathymetry Plat Figure 11

Proposed AT019-EE

Easting: 988,360ft E

Northing: 10,145,062ft N

FWL of AT019-EE: 6,280ft

FSL of AT019-EE: 7,462ft

ATP 5'' OIL(16173)

ATP 4'' UMBILICAL(16181)

BPE&P 2 1/2''OR 2 7/8''CBLC(17364)

ATWATER VALLEY 

BLOCK 19(OCS-G32556)

ATWATER VALLEY BLOCK 63(OCS-G13198)

MISSISSIPPI CANYON BLOCK 987(OCS-G28032)
±

6

3® 3

3

3

Proposed AT019-EE

89°2'0"W89°1'0"W89°0'0"W

27°58'0"N

27°57'0"N

27°56'0"N

27°55'0"N

985,000990,000995,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1" = 2,000'

Well Location Plat - Public Information Figure 12

ATP 5'' OIL(16173)

BPE&P 2 1/2''OR 2 7/8''CBLC(17364)

ATP 4'' UMBILICAL(16181)

Location Call N/S Call E/W X Coordinate Y Coordinate Latitude Longitude WD

AT019-EE SL 7,462ft FSL 6,280ft FWL 988,360 10,145,062 27° 56' 30.32"N 89° 01' 12.07"W -4,304

Proposed Location - AT019-EE

ATWATER VALLEY 

BLOCK 19(OCS-G32556)

ATWATER VALLEY BLOCK 63(OCS-G13198)

MISSISSIPPI CANYON BLOCK 987(OCS-G28032)
Nearest Shoreline

Range: 72mi

Bearing: 341°

Fourchon

Range: 108mi

Bearing: 319°

Lund

Henderson

Lloyd Ridge

Walker Ridge

Destin Dome

Atwater Valley Green Canyon

De Soto Canyon

The Elbow

Florida Plain

Vernon Basin

Apalachicola

Garden Banks

Keathley Canyon

Florida Middle Ground

Howell Hook

Lund South

Pensacola

Amery Terrace

Mobile

Viosca Knoll

Viosca Knoll

Sigsbee Escarpment

New Orleans

Baton Rouge

Pensacola

Lafayette

Gulfport Pascagoula

Vicinity Map - Atwater Valley Block 019

Figure 14
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019 EE Well Location

28

APPENDIX A – Public Shallow Hazards Statements 
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019 EE Well Location

29

Public Shallow Hazards Statement – AT019 EE

July 17, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213-2394

Attention: 

Reference: Shallow Hazards Analysis

Atwater Valley Block 019

OCS-(G 32556) 

Ladies/Gentlemen:

Anadarko Petroleum Corporation contracted Gardline Surveys, Inc. to prepare a Well Clearance Letter 

for the proposed AT019 EE well location in Block 019, Atwater Valley Area (OCS-G 32556). This letter 

addresses seafloor and shallow geologic conditions that may impact exploratory drilling operations 

within 2,000ft of the proposed well location. The depth limit of this geohazard assessment is Top of 

Salt at -9,554ft below sea surface (5,250ft below seabed).

This hazards summary letter is issued as a supplement to Gardline Report No.9172 entitled: 3D 

Geohazard Assessment, Atwater Valley Blocks 018 and 019, dated August 2012.

Seabed Hazards. 

The seabed is smooth and featureless. No problems are expected at the proposed AT019 EE well 

location. There are no indications of seabed fluid seeps within 2,000ft of the well location.

There is an existing well, AT063-SS004, located approximately 19,500ft to the SSW. There is an 

existing well AT018-001 located approximately 10,960ft to the northwest. The following are the 

coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

ATP Oil & Gas AT063 SS004 608184004100 4,418 27,802 987,101 10,134,998 COM

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

Two pipelines are located in Block AT019, located approximately 581ft and 795ft to the east and 

northeast respectively. The following are details of the pipelines:

Pipeline Installations

Operator Area Block - Origin/Termination Outside Diameter (in) Product Status

ATP O&G AT063 / MC941 5 in BLKO ACT

ATP O&G MC941 / AT063 4in UBEH ACT
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019 EE Well Location

30

Sub-Seabed Hazards. 

Drilling Caution is indicated for a Slight Risk of Gas at the well location within Unit C.

Moderate, and Slight Shallow Water Flow Risk is assigned to some of the intervals within Unit C. 

Proposed AT 19 EE Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 56' 30.32” North Easting 988,360 US ft E

Longitude 89° 01’ 12.07” West Northing 10,145,062 US ft N

FWL of Atwater Valley 19 6,280 US ft Inline 5441

FSL of Atwater Valley 19 7,462 US ft Crossline 10570

Water Depth: -4,304 ft Slope: 1.4° NE

Nearest Shoreline 72 Miles @ 341° 

Port of Operation Fourchon 108 Miles @ 319° 

Nearest Manned Platform MC941-(Mirage/Titan) 8 Miles @ 326° 

Conclusions and Recommendations. 

Drilling techniques will take into consideration the possibility of encountering possible gas within the 

prescribed intervals within Unit C. Appropriate drilling methodology should be utilized to contain a 

potentially non-persistent Slight Shallow Water Flow Risk interpreted in Unit C. Appropriate drilling 

methodology should be utilized to deal with a possible Moderate Shallow Water Flow Risk within the 

prescribed intervals within Unit C. 

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

PUBLIC INFORMATION
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019 EE Well Location

31

APPENDIX B – Sensitive Sessile Benthic Community Statements
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019 EE Well Location

32

Sensitive Sessile Benthic Community Statement – AT019 EE

Anadarko Petroleum Corporation

July 17, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213

Reference: Sensitive Sessile Benthic Community Summary

Atwater Valley, Block 019

OCS-(G 32556) 

Ladies/Gentlemen:

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Site Clearance 

Letter for the proposed AT019 EE well location in Atwater Valley, Block 019, Stromboli Prospect 

(OCS-G G 32556). This letter addresses location proximity to potential sensitive sessile benthic 

community sites. Anadarko Petroleum Corporation will be drilling this well from a dynamically 

positioned drilling module, therefore no anchors will impact seabed.

This sensitive sessile benthic community summary letter is issued as a supplement to Gardline Report 

No.9172 entitled: 3D Geohazard Assessment, Atwater Valley Blocks 018 and 019, dated August 2012. 

A Biological, Physical and Socio-Economic Map is included at the end of this appendix illustrating the 

areas of potential seabed impact.

Potential Sensitive Sessile Benthic Communities. 

Features or areas that could support high density sensitive sessile benthic communities are not 

located within 2,000ft of any proposed mud and cuttings discharge location.

Proposed AT 19 EE Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 56' 30.32” North Easting 988,360 US ft E

Longitude 89° 01’ 12.07” West Northing 10,145,062 US ft N

FWL of Atwater Valley 19 6,280 US ft Inline 5441

FSL of Atwater Valley 19 7,462 US ft Crossline 10570

Water Depth: -4,304 ft Slope: 1.4° NE

Nearest Shoreline 72 Miles @ 341° 

Port of Operation Fourchon 108 Miles @ 319° 

Nearest Manned Platform MC941-(Mirage/Titan) 8 Miles @ 326° 
Anadarko Petroleum Corporation Gardline Report 9522

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed AT019 EE Well Location

33

No potential sensitive sessile benthic community site is located within 2,000ft of the proposed 

location. 

Conclusions and Recommendations: 

The proposed AT019 EE well location will not impact any sites favorable for development of sensitive 

sessile benthic communities.

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations
ANADARKO PETROLEUM CORPORATION

3D GEOHAZARD ASSESSMENT

GULF OF MEXICO

ATWATER VALLEY BLOCK AT019

STROMBOLI PROSPECT

AT019-KK PROPOSED WELL LOCATION

WELL CLEARANCE LETTER 

APRIL 2013

Gardline Project Ref. 9517

Report Status Final

Issue Date July 15, 2013 

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

REPORT AUTHORIZATION AND DISTRIBUTION

Report Status Final

Issue Date July 15, 2013 

Compilation Geophysicist L Fuentes

Authorization Geophysics .....................

A R Haigh

Quality Assurance .....................

M DeLeon

Distribution 

6 copies 

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

For attention of:

Rick Kincaid

ii
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

SERVICE WARRANTY

USE OF THIS REPORT

This report has been prepared with due care, diligence and with the skill reasonably expected of a 

reputable contractor experienced in the types of work, carried out under the contract. As such, the 

findings in this report are based on an interpretation of data which is a matter of opinion on which 

professionals may differ and, unless clearly stated, is not a recommendation of any course of action. 

Gardline Surveys, Inc. has prepared this report for the client identified on the front cover in fulfilment of 

its contractual obligations under the referenced contract, and the only liabilities Gardline Surveys, Inc. 

will accept are those contained therein.

Please be aware that further distribution of this report, in whole or part, or the use of the data for a 

purpose not expressly stated within the contractual work scope is at the client’s sole risk, and Gardline 

Surveys, Inc recommends that this disclaimer be included in any such distribution. 

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com

iii
Green Canyon Atwater Valley Lloyd Ridge

Mississippi Canyon

Destin Dome

De Soto Canyon

Mobile Pensacola

Ship Shoal Area

Eugene Island Area

Viosca Knoll

Viosca Knoll

Main Pass Area

Ewing Bank

South Timbalier Area

West Delta Area

Louisiana

Alabama Mississippi

Florida

Location Map

Study Area
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

TABLE OF CONTENTS

REPORT AUTHORIZATION AND DISTRIBUTION ii

SERVICE WARRANTY iii

LOCATION MAP iv

TABLE OF CONTENTS v

LIST OF FIGURES vi

LIST OF CHARTS vii

WELL CLEARANCE LETTER – PROPOSED AT019-KK WELL LOCATION 1

1. LOCATION COORDINATES 3

1.1 Proposed AT019-KK Well Location 3

2. VELOCITY DATA 4

2.1 Velocity Data 4

3. SEABED CONDITIONS 6

3.1 Bathymetry 6

3.2 Seafloor Morphology and Man Made Features 6

4. SUBSEABED CONDITIONS 7

4.1 Geology and Lithology 7

4.2 Unit A 7

4.3 Unit B 7

4.4 Unit C 7

4.5 Unit D 9

4.6 Shallow Gas Assessment 9

4.7 Shallow Water Flow Assessment 9

5. CONCLUSIONS AND RECOMMENDATIONS 10

APPENDIX A – Public Shallow Hazards Statements 28

APPENDIX B – Sensitive Sessile Benthic Community Statements 31

v 
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

LIST OF FIGURES

Proposed AT019-KK Well Location

1 Seabed Depth Extract

2 Seabed Morphology Extract

3 Seabed Amplitude Extract

4 Geohazard Summary Extract

5 Sand Lithology Summary

6 Inline Data Example

7 Crossline Data Example

8 Top Hole Prognosis

9 ROV Plat

10 Power Spectrum

11 Bathymetry Plat

12 Public Information Plat

13 Proprietary Information Plat

14 Vicinity Map

15 10-Mile Radius Plat

vi
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

LIST OF CHARTS

The following chart at a scale of 1" = 2,000ft is enclosed:

Chart No Title Drawing No

1 Biological, Physical and Socio-Economic Map 9517.01

vii
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

WELL CLEARANCE LETTER – PROPOSED AT019-KK WELL LOCATION 

July 15, 2013

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

Attention: Rick Kincaid

Well Clearance Letter

Proposed AT019-KK Well Location

Block 019, Atwater Valley Area

OCS- G 32556

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Well Clearance 

Letter for the proposed AT019-KK well location in Block 019, Atwater Valley Area (OCS-G 32556). 

This letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this well clearance 

assessment is Top of Salt or -9,893ft below sea surface (5,460ft below seabed). We understand that 

Anadarko Petroleum Corporation plans to drill the proposed exploration well from a dynamically 

positioned drilling vessel; therefore, an anchoring assessment is not required nor provided. Relevant 

letter-size chart extracts, data examples, and a Top Hole Prognosis are presented with this Well 

Clearance Letter. This geohazard assessment is based on the interpretation of 3D seismic data. This 

site clearance letter is issued as a supplement to Gardline Report No.9172 entitled: 3D Geohazard 

Assessment, Atwater Valley Blocks 018 & 019, dated August 2012. 

Archaeological Survey. Anadarko Petroleum Corporation provided for review the complete 

archaeological survey report acquired by C&C Technologies Survey Services: Archaeological Survey 

Blocks 18 (OCS-G-33863) and 19 (OCS-G-32556) Atwater Valley Area for the Anadarko Stromboli 

Prospect. 

3D Geophysical Survey. Anadarko Petroleum Corporation provided the 3D dataset to Gardline 

Surveys Inc. on tape media in SEG-Y format for loading onto a Seismic Micro-Technology (SMT) 

workstation. The 3D data cube contains a survey with 4 millisecond sample rate data to a record 

length of 6.0 seconds TWT below sea surface. Inlines are oriented north to south, have a numerical 

increment of one, and exhibit a line spacing of 65.6ft. Crosslines are oriented west to east, have a 

numerical increment of one, and exhibit a line spacing of 41.0ft.

• The acquisition parameters are: 

o Atwater Valley (I) DW V

 

Shooting Direction: N/S

Configuration: 4 sources, 6-10 streamers

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Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

Maximum offset: 8000 m

Channels: 324 per streamer 

Shotpoint interval: 47.25 m per array 

Group interval: 25 m

CMP line spacing: 40 m 

CMP bin dimension: 12.5 m x 40 m 

Record Length: 9 s below sea bottom 

Nominal fold: 43

Vintage: April 1999

• The basic processing parameters are:

o Atwater Valley (I) DW V

480-m x 500-m velocity grid 

Demultiple 

3D DMO velocity and stacking technology 

One-pass 3D poststack migration 

12.5-m x 20-m final bin dimension

The data exhibits a good frequency response across the upper one second below seabed, with an 

effective frequency range of 5 to 60Hz. The data exhibits a dominant frequency of approximately 

53Hz with significant higher usable frequencies. This frequency range results in a mean vertical 

resolvability of approximately 10m and a layer detectability of 5ft. 

In summary and with reference to NTL No. 2008-G04

a) The 3D data provides images of sufficient resolution of the shallow section allowing a 

clear analysis of the shallow conditions

b) The data can be loaded to a workstation at 16bit resolution or greater, and is un-scaled

c) There is no trace or sample decimation

d) The sample interval and bin size are maintained throughout the assessment area

e) The data possess a frequency content of 50Hz or higher across the first second below 

seabed (See Power Spectrum Diagram: Figure 10) 

f) Seabed reflection is free of gaps and defined by a wavelet of stable shape and phase, 

allowing auto-tracking of the seabed event with minimum user intervention and guidance

g) There are no significant acquisition artefacts throughout the dataset

h) There are no merge points in the data

i) Processed bin sizes are 65.62ft x 41.01ft

j) The sample rate of the data is 4ms

k) An accurate velocity model has been utilized in the shallow section allowing optimum 

structural and stratigraphy resolution with no evidence of under or over migration

l) There is no significant multiple energy

m) The proposed activities are not in an area of high archaeological potential.

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

1. LOCATION COORDINATES

1.1 Proposed AT019-KK Well Location

Proposed AT019-KK Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 55' 23.29” North Easting 987,439 US ft E

Longitude 89° 01’ 21.10” West Northing 10,138,306 US ft N

FWL of Atwater Valley 19 5,359 US ft Inline 5427

FSL of Atwater Valley 19 706 US ft Crossline 10405

Water Depth: -4,433 ft Slope: <1.0° SE

Nearest Shoreline 72 Miles @ 341° 

Port of Operation Fourchon 108 Miles @ 319° 

Nearest Manned Platform MC941-(Mirage/Titan) 9 Miles @ 328° 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

2. VELOCITY DATA 

2.1 Velocity Data

Time-to-depth conversion for the water column was derived using the Advocate and Hood 

(1993) polynomial.

Seabed depth (ft) =

0.1105 – 5066.9193X + 468.6693X2 – 554.7107X3 + 340.7019X4 – 116.991X5 + 20.728X6 – 1.4658X7 

Where X = one way time in seconds to seabed 

One Way Time To Seabed (s) Seabed Depth (ft) Seabed Depth (m) Vavg (m/s)

0.0 0 0 0

1.0 4910 1496 1496

1.1 5400 1646 1496

1.2 5892 1796 1496

1.3 6384 1946 1497

1.4 6877 2096 1497

1.5 7370 2246 1498

1.6 7865 2397 1498

1.7 8360 2548 1499

1.8 8856 2699 1499

1.9 9353 2851 1500

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

Sub-seabed time to depth conversion was performed using a polynomial function 

successfully applied in an adjacent project and approved by Anadarko Petroleum 

Company: 

Vavg = = -45.841X5 + 190.08X4

 – 183.08X3 - 14.729X2 + 735.59X +4900

Where A = two way time in seconds below seabed. 

The resultant velocity was then multiplied by the time below seafloor to produce depth below 

seabed; this horizon depth was summed with seabed depth to produce horizon depth below 

sea surface.

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

6 

3. SEABED CONDITIONS

3.1 Bathymetry

Seabed depth at the proposed AT019-KK well location is -4,433ft below sea surface (Figure 

1). The seafloor slopes to the southeast at <1.0°. 

3.2 Seafloor Morphology and Man Made Features

The proposed AT019-KK well location is in the south-central part of Block AT019. At the 

proposed well location the seabed appears to be smooth and featureless (Figure 2). Soft 

clays and silts are predicted at seabed. Sediments appear conducive for jetting of seabed 

casing with no hard layers predicted. 

The proposed well AT019-KK is located within a graben with the nearest fault occurring 

3,401ft to the north of the proposed well; this fault should not affect the proposed well. 

There is an existing well AT063-SS004 located approximately 3,325ft to the SSW. There 

is an existing well AT018-001 located approximately 15,588ft to the northwest. The 

following are the coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

ATP Oil & Gas AT063 SS004 608184004100 4,418 27,802 987,101 10,134,998 COM

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

Two pipelines are located in Block AT019, located approximately 996ft and 1,159ft to the 

east and southeast. The following are detailed of the pipelines:

Pipeline Installations

Operator Area Block - Origin/Termination Outside Diameter (in) Product Status

ATP O&G AT063 / MC941 5 in BLKO ACT

ATP O&G MC941 / AT063 4in UBEH ACT

There are no anomalous seabed amplitudes indicative of hydrocarbon macroseep observed 

within a 2,000ft radius of the proposed location (Figure 3).

No items of archaeological significance were identified within 2,000ft of the proposed location

(archaeological report submitted under a separate cover).

No other features are observed within a 2,000ft radius that could affect well emplacement or 

jetting of casing.
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

4. SUBSEABED CONDITIONS

4.1 Geology and Lithology

The sub-seabed geology has been divided into four units separated by four horizons (Figures 

6 through 8). A geohazard extract and sand lithology extract utilized to complete the well 

assessment are presented in Figures 4 and 5. 

4.2 Unit A 

The uppermost interval within Unit A from seabed to -4,727ft below sea surface (294ft below 

seabed) is interpreted to consist of clays and silts with occasional minor coarser interbeds. 

The lower interval of Unit A from -4,727ft to -5,003ft below sea surface (294ft to 570ft below 

seabed) is interpreted to comprise of clays and silts. 

No shallow gas or shallow water flow is predicted within Unit A at the proposed well location.

A vertical borehole will not penetrate any faults within Unit A. 

Horizon H10 marks the base of Unit A at -5,003ft below sea surface (570ft below seabed). 

4.3 Unit B 

The upper interval of Unit B from -5,003ft to -5,569ft below sea surface (570ft to 1,136ft below

seabed) is expected to comprise of clays and silts with occasional coarser interbeds. 

The lower interval of Unit B from -5,569ft to -6,143ft below sea surface (1,136ft to 1,710ft

below seabed) is interpreted to consist of slightly higher energy clays and silts with several

minor coarser interbeds. Due to the slightly elevated energy content of this interval minor 

drilling fluid circulation and minor wellbore stability problems are predicted within this interval. 

No shallow gas or shallow water flow is predicted within Unit B at the proposed well location.

A vertical borehole will not penetrate any faults within Unit B.

Horizon H20 marks the base of Unit B at -6,143ft below sea surface (1,710ft below seabed). 

4.4 Unit C 

Lithology within the upper interval of this unit from -6,143ft to -6,896ft below sea surface 

(1,710ft to 2,463ft below sea surface) is interpreted to consist of higher energy clays and silts 

with numerous coarser interbeds that may represent sands. The proposed well is located 

within a sand fairway package that extends from south of the well to the northwest (Figure 5). 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

A cluster of high-amplitude anomalies, located generally to the west of the proposed well, 

have been assigned a high risk of gas. The vertical borehole will not traverse any of these 

anomalies with the nearest risk of gas anomaly being approximately 365ft to the south. 

However, due to the close encroachment and general higher energy nature of this interval a 

Slight Risk of Gas is assigned. This interval exhibits character of rapid higher energy 

deposition and with a well defined clay prone overburden (Unit B) which are favorable 

conditions for the formation of shallow water flow. In addition a previously drilled well (AT063-

2) located 2.4 miles to the south experienced a low shallow water flow event at 2,012ft below 

seabed and these sands correlate with this interval. As such a High Shallow Water Flow 

Risk is assigned to this interval.

The lithology within the thin interval from -6,896ft to -7,025ft below sea surface (2,463ft to 

2,592ft below seabed) is interpreted as lower energy clays and silts with possibility of several

minor coarser interbeds. Some minor drilling fluid circulation and minor wellbore stability 

problems are predicted within this interval. 

From -7,025m to -7,766m below sea surface (2,592m to 3,333m below seabed) is interpreted 

to consist of further higher energy clays and silts with several coarser interbeds that may 

represent sands. A better defined <40ft thick sand interbed occurs at -7,071ft below sea 

surface (2,638ft below seabed). This sand interbed presents a slight increase in amplitude, 

and may contain small amounts of fluid; therefore, a Slight Risk of Gas is assigned. Due to 

the presence of numerous sand interbeds, suggestion of rapid deposition and encapsulation 

within clays and silts this interval is considered a Slight Shallow Water Flow Risk.

The lower interval within Unit C from -7,766ft to -8,529ft below sea surface (3,333ft to 4,096ft 

below seabed) is interpreted to comprise of clays with numerous sands. Even in this lower 

interval of Unit C the proposed well path is on the periphery of the sand fairway. A better

defined <40ft more aerially expansive thick sand interbed is identified at -8,015ft below sea 

surface (3,582ft below seabed). This sand interbed also exhibits slight elevated amplitude 

and the possibility for small amounts of gas to be present within this interbed is considered

possible, though no other direct hydrocarbon indicators are observed. As such a Slight Risk 

of Gas is assigned at the level of the interbed. Due to the interpreted sandy nature of this

lower interval of Unit C with further higher energy depositional character and the possibility of 

more continuous sandy interbeds a Moderate Shallow Water Flow Risk is assigned. Minor 

drilling fluid circulation and minor wellbore stability problems are also considered possible

within this interval. 

A vertical borehole will penetrate a fault within Unit C at -7,766ft below sea surface (3,333ft 

below seabed). This fault extends a significant amount into the shallower section into the 

overlying Unit B, and as such it is possible that drilling fluid circulation problems may occur at 

the level of the fault if pressures over background are exerted by the drilling fluid column. 

Horizon H30 marks the base of Unit C occurring at -8,529ft below sea surface (4,096ft below 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

seabed). 

4.5 Unit D 

Unit D from -8,529ft to -9,893ft below sea surface (4,096ft to 5,460ft below seabed), is 

interpreted to consist of clays and silts with several coarser interbeds. Minor drilling fluid 

circulation and wellbore stability problems may also occur.

A vertical borehole will penetrate a significant fault within Unit D at -9,120ft below sea surface 

(4,687ft below seabed). This fault extends upwards to sea surface. If this fault is not sealed 

then drilling fluid circulation problems are possible if pressures over hydrostatic are exerted by 

the drilling fluid column.

Top of Salt marks the base of Unit D and the base of this interpretation occurring at -9,893ft 

below sea surface (5,460ft below seabed). 

4.6 Shallow Gas Assessment

Within Unit C, a Slight Risk of Gas is assigned to the interval from 6,143ft to 6,896ft below 

sea surface (1,710ft to 2,463ft below seabed), and at the level of two <40ft thick sand 

interbeds at -7,071ft and -8,015ft below sea surface (2,638ft and 3,582ft below seabed). 

4.7 Shallow Water Flow Assessment

Within Unit C, a High Shallow Water Flow Risk is interpreted to the interval from -6,143ft to -

6,896ft below sea surface (1,710ft to 2,463ft below seabed). A Moderate Shallow Water 

Flow Risk is assigned from -7,766ft to -8,529ft below sea surface (3,333ft to 4,096ft below 

seabed). A Slight Shallow Water Flow Risk is assigned from -7,025ft to -7,766ft below sea 

surface (2,592ft to 3,333ft below seabed). 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

5. CONCLUSIONS AND RECOMMENDATIONS

• Seabed

No significant problems are anticipated at seabed. Shallow soils are expected to be 

conducive to the jetting of seabed casing with no hardgrounds predicted.

• Unit A 

No drilling hazards or problems predicted.

• Unit B

Minor drilling and minor wellbore stability problems are possible from -5,569ft to -6,143ft 

below sea surface (1,136ft to 1,710ft below seabed). 

• Unit C 

Unit C presents a potentially challenging section to drill, with numerous intervals considered a 

shallow water flow risk and additional complications with faulting.

A Slight Risk of Gas and a High Shallow Water Flow Risk is assigned to the interval from -

6,143ft to -6,896ft below sea surface (1,710ft to 2,463ft below seabed). Drilling Caution and 

appropriate drilling methodology is recommended to deal with a possible water flow event 

throughout this interval. Sediments in this interval are likely poorly consolidated and as such 

may induce minor drilling fluid circulation and wellbore stability problems.

Minor drilling and minor wellbore stability problems are possible from -6,896ft to -7,025ft 

below sea surface (2,463ft to 2,592ft below seabed).

Within Unit C, a Slight Shallow Water Flow Risk is also interpreted from -7,025ft to -7,766ft 

below sea surface (2,592ft to 3,333ft below seabed). Appropriate drilling methodology is 

recommended to deal with a possible less-persistent water flow event through this interval. 

Additionally, minor drilling fluid circulation and wellbore stability problems may also occur 

within this interval. A Slight Risk of Gas is assigned at the level of a better defined <40ft 

thick sand interbed at -7,071ft below sea surface (2,638ft below seabed). Drilling Caution is 

advised at the level of the interbed.

Within the lower section of Unit C, a Moderate Shallow Water Flow Risk is interpreted from 

-7,766ft to -8,529ft below sea surface (3,333ft to 4,096ft below seabed). Appropriate drilling 

methodology is recommended to deal with a possible water flow event through this interval. 

Additionally, due to the potentially poorly consolidated sediment through this interval, minor 

drilling fluid circulation and wellbore stability problems may also occur within this interval. A 

Slight Risk of Gas is assigned at the level of a better defined <40ft thick sand interbed at -

8,015ft below sea surface (3,582ft below seabed). Drilling Caution is advised at the level of 

the interbed. 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

A vertical borehole will penetrate a fault within Unit C at -7,766ft below sea surface (3,333ft 

below seabed). Drilling fluid circulation problems may occur at the level of the fault if 

pressures over background are exerted by the drilling fluid column. 

• Unit D

Minor drilling and minor wellbore stability problems are possible throughout Unit D. 

A vertical borehole will penetrate a fault within Unit D at -9,120ft below sea surface (4,687ft 

below seabed). This fault extends upwards to seabed. Drilling fluid circulation problems are 

possible at the level of the fault if pressures over hydrostatic are exerted by the drilling fluid 

column.

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Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019-KK

We appreciate the opportunity to work with you on this project, and look forward to continuing as 

your geohazards consultants. Please contact us if you have any questions or if we can be of 

further assistance.

Sincerely,

Gardline Surveys Inc.

Andrew Haigh Matilde DeLeon

Geophysical Manager Quality Assurance

Copies Submitted: 6 copies to Rick Kincaid at Anadarko Petroleum Corporation .

Attachments:

Proposed AT019 KK Well Location

Seabed Depth Extract

Seabed Morphology Extract

Seabed Amplitude Extract

Geohazard Summary Extract

Sand Lithology Summary

Inline Data Example

Crossline Data Example

Top Hole Prognosis

ROV Plat

Power Spectrum

Bathymetry Plat

Public Information Plat

Proprietary Information Plat

Vicinity Map

10-Mile Radius Plat

12
Top Hole Prognosis for Proposed AT019-KK Well Location

987,439ft E / 10,138,306ft N

Inline: 5427 / Crossline: 10405 Horizon

Subsea

Depth

(ft)

BML

Depth

(ft)

Horizon

TWT

(sec)

Lithology, Structure & Stratigraphy Potential Drilling Hazards & Constraints

Risk

of

Gas

SWF

Risk

Seabed -4,433 0 1.806 Seabed is smooth sloping to the southeast at <1.0°. Surficial sediments comprise of 

soft clays and silts. Underlying the seabed the lithology comprises of clays and silts 

with occasional minor coarser interbeds

Figure 8

Interface -6,896 2,463 2.700

Horizon H10 -5,003 570 2.031

Interface -7,025 2,592 2.742

Clays and silts 

Clays and silts with occasional coarser interbeds

None predicted

None predicted

None predicted

Minor drilling fluid circulation and wellbore stability problems possible

within this interval

Unit A

Unit B

Unit D

Interface/Fault -7,766 3,333 2.975

Horizon H20 -6,143 1,710 2.446

Sand Interbed -8,015 3,582 3.050

Horizon H30 -8,529 4,096 3.200

Fault -9,120 4,687 3.364

Top of Salt -9,893 5,460 3.567

Clays and silts with numerous coarser interbeds that may represent sands

Clays and silts with several coarser interbeds

<40ft thick sand interbed

Slight Risk of Gas and High Shallow Water Flow Risk. Minor drilling fluid 

circulation and wellbore stability problems possible

Unit C

Base of interpretation

Clays and silts with numerous sands

Clays and silts with several coarser interbeds

Minor drilling fluid circulation and minor wellbore stability problems

possible within this interval

Slight Risk of Gas and Slight Shallow Water Flow Risk in this interval. 

Minor drilling fluid circulation and wellbore stability problems possible 

within this interval.

Moderate Shallow Water Flow Risk. Minor drilling fluid circulation and 

wellbore stability problems possible within this interval and at the level of 

the fault if pressures over hydrostatic are exerted by the drilling fluid column

Sand Interbed -7,071 2,638 2.757 <40ft thick sand interbed

Interface -5,569 1,136 2.242

Interface -4,727 294 1.924

Clays and silts with several coarser interbeds Minor drilling fluid circulation and wellbore stability problems possible

Clays with numerous coarser interbeds that may represent sands

Slight Risk of Gas at the level of the sand interbed

Drilling fluid circulation problems may occur at the level of the fault if

 pressures over hydrostatic are exerted by the drilling fluid column

Vavg

BML

(m/s)

0

5,510

5,063

5,538

5,702

5,344

5,748

5,877

6,017

6,202

5,549

5,209

4,986
±

6

3® 3

3

3

AT063-SS004

-4510

-4500

-4490

-4480

-4520

-4470

-4460

-4340

-4330

-4350

-4370

-4360

-4380

-4390

-4400

-4410

-4450

-4440

-4430

-4420

-4320 -4310

-4530

-4300

-4290

-4540

-4280

-4270

-4550

-4560

-4260

-4570

-4250

-4240

-4580

-4590

-4230

-4600

-4220

-4210

-4610

-4200

-4190

-4180

-4530

-4510

-4560

-4540

-4550

-4520

-4370

-4260

89°2'0"W89°1'0"W89°0'0"W

27°57'0"N

27°56'0"N

27°55'0"N

985,000990,000995,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1 = 2,000'

Bathymetry Plat Figure 11

Proposed AT019-KK

Easting: 987,439ft E

Northing: 10,138,306ft N

FWL of AT019-KK: 5,359ft

FSL of AT019-KK: 706ft

2,000ft Radius

ATP 5'' OIL(16173)

ATP 4'' UMBILICAL(16181)

BPE&P 2 1/2''OR 2 7/8''CBLC(17364)

ATWATER VALLEY 

BLOCK 19(OCS-G32556)

ATWATER VALLEY 

BLOCK 63(OCS-G13198)
±

6

3® 3

3

3

AT063-SS004

Proposed AT019-KK Well

89°2'0"W89°1'0"W89°0'0"W

27°57'0"N

27°56'0"N

27°55'0"N

985,000990,000995,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1" = 2,000'

Well Location Plat - Public Information Figure 12

ATP 5'' OIL(16173)

BPE&P 2 1/2''OR 2 7/8''CBLC(17364)

ATP 4'' UMBILICAL(16181)

Location Call N/S Call E/W X Coordinate Y Coordinate Latitude Longitude WD

AT019-KK SL 706ft FSL 5,359ft FWL 987,439 10,138,306 27° 55' 23.29"N 89° 01' 21.10"W -4,433

Proposed Location - AT019-KK

ATWATER VALLEY 

BLOCK 19(OCS-G32556)

ATWATER VALLEY 

BLOCK 63(OCS-G13198)
Nearest Shoreline

Range: 72mi

Bearing: 341°

Fourchon

Range: 108mi

Bearing: 319°

Lund

Henderson

Lloyd Ridge

Walker Ridge

Destin Dome

Atwater Valley Green Canyon

De Soto Canyon

The Elbow

Florida Plain

Vernon Basin

Apalachicola

Garden Banks

Keathley Canyon

Florida Middle Ground

Howell Hook

Lund South

Pensacola

Amery Terrace

Mobile

Viosca Knoll

Viosca Knoll

Sigsbee Escarpment

New Orleans

Baton Rouge

Pensacola

Lafayette

Gulfport Pascagoula

Vicinity Map - Atwater Valley Block 019

Figure 14
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019 KK

APPENDIX A – Public Shallow Hazards Statements 

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019 KK

Public Shallow Hazards Statement – AT019 KK

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213-2394

Attention: 

Reference: Shallow Hazards Analysis

Atwater Valley Block 019

OCS-(G 32556) 

Ladies/Gentlemen:

Anadarko Petroleum Corporation contracted Gardline Surveys, Inc. to prepare a Well Clearance Letter 

for the proposed AT019 KK well location in Block 019, Atwater Valley Area (OCS-G 32556). This letter 

addresses seafloor and shallow geologic conditions that may impact exploratory drilling operations 

within 2,000ft of the proposed well location. The depth limit of this geohazard assessment is to Top of 

Salt at -9,893ft below sea surface (5,460ft below seabed).

This hazards summary letter is issued as a supplement to Gardline Report No.9172 entitled: 3D 

Geohazard Assessment, Atwater Valley Blocks 018 and 019, dated August 2012.

Seabed Hazards. 

The seabed is smooth and featureless. No problems are expected at the proposed AT019 KK well 

location.

There are no indications of seabed fluid seeps within 2,000ft of the well location.

No existing seabed infrastructure is located within 2,000ft of the proposed well. There is an existing 

well AT-18-1 located approximately 15,588ft to the northwest. The following are the coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

BHP Billiton At018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

Two pipelines are located on the adjacent Block AT019 approximately 996ft and 1,159ft to 

the east and southeast. The following are detailed of the pipelines. 

Pipeline Installations

Operator Area Block - Origin/Termination Outside Diameter (in) Product Status

ATP O&G AT063 / MC941 5 in BLKO ACT

ATP O&G MC941 / AT063 4in UBEH ACT

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019 KK

Sub-Seabed Hazards. 

Drilling Caution is indicated for a Slight Risk of Gas at the well location within Unit C.

High, Moderate, and Slight Shallow Water Flow Risk is assigned to some of the intervals within Unit 

C. 

Proposed AT 19 KK Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 55' 23.29” North Easting 987,439 US ft E

Longitude 89° 01’ 21.10” West Northing 10,138,306 US ft N

FWL of Atwater Valley 19 5,359 US ft Inline 5427

FSL of Atwater Valley 19 706 US ft Crossline 10550

Water Depth: -4,433 ft Slope: <1.0° SE

Nearest Shoreline 72.25 Miles @ 341° 07’ 48’’

Port of Operation Fourchon 108.35Miles @ 319° 22’ 12’’

Nearest Manned Platform MC941-(Mirage/Titan) 8.9 Miles @ 328° 48’ 00”

Conclusions and Recommendations. 

Drilling techniques will take into consideration the possibility of encountering possible gas within the 

interval in Unit C. Appropriate drilling methodology should be utilized to contain a potentially nonpersistent Slight Shallow Water Flow Risk interpreted in Unit C. Appropriate drilling methodology 

should be utilized to deal with a possible High and Moderate Shallow Water Flow Risk in the 

intervals within Unit C. 

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

PUBLIC INFORMATION

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Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019 KK

APPENDIX B – Sensitive Sessile Benthic Community Statements

31
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019 KK

Sensitive Sessile Benthic Community Statement – AT019 KK

Anadarko Petroleum Corporation

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213

Reference: Sensitive Sessile Benthic Community Summary

Atwater Valley, Block 018

OCS-(G 32556) 

Ladies/Gentlemen:

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Site Clearance 

Letter for the proposed AT019 KK well location in Atwater Valley, Block 019, Stromboli Prospect 

(OCS-G G 32556). This letter addresses location proximity to potential sensitive sessile benthic 

community sites. Anadarko Petroleum Corporation will be drilling this well from a dynamically 

positioned drilling module; therefore, no anchors will impact seabed.

This sensitive sessile benthic community summary letter is issued as a supplement to Gardline Report 

No.9172 entitled: 3D Geohazard Assessment, Atwater Valley Blocks 018 and 019, dated August 2012. 

A Biological, Physical and Socio-Economic Map is included at the end of this appendix illustrating the 

areas of potential seabed impact.

Potential Sensitive Sessile Benthic Communities. 

Features or areas that could support high density sensitive sessile benthic communities are not 

located within 2,000ft of any proposed mud and cuttings discharge location.

Proposed AT 19 KK Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 55' 23.29” North Easting 987,439 US ft E

Longitude 89° 01’ 21.10” West Northing 10,138,306 US ft N

FWL of Atwater Valley 19 5,359 US ft Inline 5427

FSL of Atwater Valley 19 706 US ft Crossline 10550

Water Depth: -4,433 ft Slope: <1.0° SE

Nearest Shoreline 72.25 Miles @ 341° 07’ 48’’

Port of Operation Fourchon 108.35Miles @ 319° 22’ 12’’

Nearest Manned Platform MC941-(Mirage/Titan) 8.9 Miles @ 328° 48’ 00”

32
Anadarko Petroleum Corporation Gardline Report 9517

Well Clearance Letters – Stromboli Prospect - Atwater Valley – Proposed Well Location AT019 KK

No potential sensitive sessile benthic community site is located within 2,000ft of the proposed 

location. 

Conclusions and Recommendations: 

The proposed AT019 KK well location will not impact any sites favorable for development of sensitive 

sessile benthic communities.

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

33
ANADARKO PETROLEUM CORPORATION

3D GEOHAZARD ASSESSMENT

GULF OF MEXICO

ATWATER VALLEY BLOCK AT019

STROMBOLI PROSPECT

PROPOSED AT019-KV WELL LOCATION

WELL CLEARANCE LETTER 

MAY 2013

Gardline Project Ref. 9519

Report Status Final 

Issue Date July 15, 2013

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

REPORT AUTHORIZATION AND DISTRIBUTION

Report Status Final 

Issue Date July 15, 2013

Compilation Geophysicist L Fuentes

Authorization Geophysics .....................

A R Haigh

Quality Assurance .....................

M DeLeon

Distribution 

6 copies 

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

For attention of:

Rick Kincaid

ii
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

SERVICE WARRANTY

USE OF THIS REPORT

This report has been prepared with due care, diligence and with the skill reasonably expected of a 

reputable contractor experienced in the types of work, carried out under the contract. As such, the 

findings in this report are based on an interpretation of data which is a matter of opinion on which 

professionals may differ and, unless clearly stated, is not a recommendation of any course of action. 

Gardline Surveys, Inc. has prepared this report for the client identified on the front cover in fulfilment of 

its contractual obligations under the referenced contract, and the only liabilities Gardline Surveys, Inc. 

will accept are those contained therein.

Please be aware that further distribution of this report, in whole or part, or the use of the data for a 

purpose not expressly stated within the contractual work scope is at the client’s sole risk, and Gardline 

Surveys, Inc recommends that this disclaimer be included in any such distribution. 

Gardline Surveys Inc

1500 Bingle Road, Houston, Texas 77055, USA

Telephone 713 481 4630 Fax 713 464 8275 www.gardline.com

iii
Green Canyon Atwater Valley Lloyd Ridge

Mississippi Canyon

Destin Dome

De Soto Canyon

Mobile Pensacola

Ship Shoal Area

Eugene Island Area

Viosca Knoll

Viosca Knoll

Main Pass Area

Ewing Bank

South Timbalier Area

West Delta Area

Louisiana

Alabama Mississippi

Florida

Location Map

Study Area
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

TABLE OF CONTENTS

REPORT AUTHORIZATION AND DISTRIBUTION ii

SERVICE WARRANTY iii

LOCATION MAP iv

TABLE OF CONTENTS v

LIST OF FIGURES vi

LIST OF CHARTS vii

WELL CLEARANCE LETTER – PROPOSED AT019-KV WELL LOCATION 1

1. LOCATION COORDINATES 3

1.1 Proposed AT019-KV Well Location 3

2. VELOCITY DATA 4

2.1 Velocity Data 4

3. SEABED CONDITIONS 6

3.1 Bathymetry 6

3.2 Seafloor Morphology and Man Made Features 6

4. SUBSEABED CONDITIONS 7

4.1 Geology and Lithology 7

4.2 Unit A 7

4.3 Unit B 7

4.4 Unit C 7

4.5 Unit D 9

4.6 Shallow Gas Assessment 9

4.7 Shallow Water Flow Assessment 9

5. CONCLUSIONS AND RECOMMENDATIONS 10

APPENDIX A – Public Shallow Hazards Statements 28

APPENDIX B – Sensitive Sessile Benthic Community Statements 31

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Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

LIST OF FIGURES

Proposed AT019 KK Well Location

1 Seabed Depth Extract

2 Seabed Morphology Extract

3 Seabed Amplitude Extract

4 Geohazard Summary Extract

5 Sand Lithology Summary

6 Inline Data Example

7 Crossline Data Example

8 Top Hole Prognosis

9 ROV Plat

10 Power Spectrum

11 Bathymetry Plat

12 Public Information Plat

13 Proprietary Information Plat

14 Vicinity Map

15 10-Mile Radius Plat

vi
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

LIST OF CHARTS

The following chart at a scale of 1" = 1,000ft is enclosed:

Chart No Title Drawing No

1 Biological, Physical and Socio-Economic Map 9519.01

vii
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

WELL CLEARANCE LETTER – PROPOSED AT019-KV WELL LOCATION 

July 15, 2013

Anadarko Petroleum Corporation 

1201 Lake Robbins Drive

The Woodlands, TX 77380

Attention: Rick Kincaid

Well Clearance Letter

Proposed AT019-KV Well Location

Block 019, Atwater Valley Area

OCS- G 32556

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Well Clearance 

Letter for the proposed AT019-KV well location in Block 019, Atwater Valley Area (OCS-G 32556). 

This letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this well clearance 

assessment is Top of Salt or -9,864ft below sea surface (5,449ft below seabed). We understand that 

Anadarko Petroleum Corporation plans to drill the proposed exploration well from a dynamically 

positioned drilling vessel; therefore, an anchoring assessment is not required nor provided. Relevant 

letter-size chart extracts, data examples, and a Top Hole Prognosis are presented with this Well 

Clearance Letter. This geohazard assessment is based on the interpretation of 3D seismic data. This 

site clearance letter is issued as a supplement to Gardline Report No.9172 entitled: 3D Geohazard 

Assessment, Atwater Valley Blocks 018 & 019, dated August 2012. 

Archaeological Survey. Anadarko Petroleum Corporation provided for review the complete 

archaeological survey report acquired by C&C Technologies Survey Services: Archaeological Survey 

Blocks 18 (OCS-G-33863) and 19 (OCS-G-32556) Atwater Valley Area for the Anadarko Stromboli 

Prospect. 

3D Geophysical Survey. Anadarko Petroleum Corporation provided the 3D dataset to Gardline 

Surveys Inc. on tape media in SEG-Y format for loading onto a Seismic Micro-Technology (SMT) 

workstation. The 3D data cube contains a survey with 4 millisecond sample rate data to a record 

length of 6.0 seconds TWT below sea surface. Inlines are oriented north to south, have a numerical 

increment of one, and exhibit a line spacing of 65.62ft. Crosslines are oriented west to east, have a 

numerical increment of one, and exhibit a line spacing of 41.01ft.

• The acquisition parameters are: 

o Atwater Valley (I) DW V

Shooting Direction: N/S

Configuration: 4 sources, 6-10 streamers

Maximum offset: 8000 m

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Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

Channels: 324 per streamer 

Shot-point interval: 47.25 m per array 

Group interval: 25 m

CMP line spacing: 40 m 

CMP bin dimension: 12.5 m x 40 m 

Record Length: 9 sec. below sea bottom 

Nominal fold: 43

Vintage: April 1999

• The basic processing parameters are:

o Atwater Valley (I) DW V

480-m x 500-m velocity grid 

Demultiple 

3D DMO velocity and stacking technology 

One-pass 3D poststack migration 

12.5-m x 20-m final bin dimension

. 

The data exhibits a good frequency response across the upper one second below seabed, with an 

effective frequency range of 5 to 60Hz. The data exhibits a dominant frequency of approximately 

53Hz with significant higher usable frequencies. This frequency range results in a mean vertical 

resolvability of approximately 30ft and a layer detectability of 5ft. 

In summary and with reference to NTL No. 2008-G04

a) The 3D data provides images of sufficient resolution of the shallow section allowing a 

clear analysis of the shallow conditions

b) The data can be loaded on a workstation at 16bit resolution or greater, and is un-scaled

c) There is no trace or sample decimation

d) The sample interval and bin size are maintained throughout the assessment area

e) The data possess a frequency content of 50Hz or higher across the first second below 

seabed. See Power Spectrum Diagram: Figure 10

f) Seabed reflection is free of gaps and defined by a wavelet of stable shape and phase, 

allowing auto-tracking of the seabed event with minimum user intervention and guidance

g) There are no significant acquisition artefacts throughout the dataset

h) There are no merge points in the data 

i) Processed bin sizes are 65.62ft x 41.01ft

j) The sample rate of the data is 4ms

k) An accurate velocity model has been utilized in the shallow section allowing optimum 

structural and stratigraphy resolution with no evidence of under or over migration

l) There is no significant multiple energy

m) The proposed activities are not in an area of high archaeological potential.

2 
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

1. LOCATION COORDINATES

1.1 Proposed AT019-KV Well Location

Proposed AT019-KV Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 55' 33.49” North Easting 987,423 US ft E

Longitude 89° 01’ 21.68” West Northing 10,139,337 US ft N

FWL of Atwater Valley 19 5,343 US ft Inline 5427

FSL of Atwater Valley 19 1737 US ft Crossline 10430

Water Depth: -4,415 ft Slope: 1.3° SE

Nearest Shoreline 72 Miles @ 341° 

Port of Operation Fourchon 108 Miles @ 319° 

Nearest Manned Platform MC941-(Mirage/Titan) 9 Miles @ 328° 

3 
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

2. VELOCITY DATA 

2.1 Velocity Data

Time-to-depth conversion for the seabed depth was made using the Advocate and Hood 

(1993) polynomial:

Seabed Depth (ft) =

0.1105 – 5066.9193X + 468.6693X2 – 554.7107X3 + 340.7019X4 – 116.991X5 + 20.728X6 – 1.4658X7 

Where X = one way time in seconds to seabed 

One Way Time To Seabed (s) Seabed Depth (ft) Seabed Depth (m) Vavg (m/s)

0.0 0 0 0

1.0 4910 1496 1496

1.1 5400 1646 1496

1.2 5892 1796 1496

1.3 6384 1946 1497

1.4 6877 2096 1497

1.5 7370 2246 1498

1.6 7865 2397 1498

1.7 8360 2548 1499

1.8 8856 2699 1499

1.9 9353 2851 1500

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Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

Sub-seabed time to depth conversion was performed using a formula successfully applied in 

an adjacent project and approved by Anadarko Petroleum Company: 

Vavg = -45.841X5 + 190.08X4

 – 183.08X3 - 14.729X2 + 735.59X +4900

Where X = two way time in seconds below seabed. 

The resultant velocity was then multiplied by the one way time below seabed to produce 

depth below seabed. This was summed with seabed depth to determine depth below sea 

surface.

5 
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

6 

3. SEABED CONDITIONS

3.1 Bathymetry

Seabed depth at the proposed AT019-KV well location is -4,415ft below sea surface (Figure 

1). The seafloor slopes to the southeast at 1.3°. 

3.2 Seafloor Morphology and Man Made Features

The proposed AT019-KV well location is in the south of Block AT019. At the proposed well 

location the seabed is smooth and featureless (Figure 2). Soft clays and silts are predicted at 

seabed. Sediments appear conducive for jetting of seabed casing with no hard layers 

predicted. 

The proposed well AT019-KV is located within a graben structure with the nearest fault 

located 2,817ft to the northeast of the proposed well. The fault should not affect the 

proposed well. 

There is an existing well AT063-SS004 located approximately 4,300ft to the south. There 

is an existing well AT018-001 located approximately 15,400ft to the northwest. The 

following are the coordinates:

Well Installation:

Operator Block Well No. API No. Depth (ft) TVD Easting Northing Status

ATP Oil & Gas AT063 SS004 608184004100 4,418 27,802 987,101 10,134,998 COM

BHP Billiton AT018 001 60 818 40024 00 4,266 28,651 980,051 10,152,077 PA

Two pipelines traverse Block AT019 and are located approximately 1,448ft and 1,627ft to 

the east and southeast of the proposed location. The following are details of the pipelines:

Pipeline Installations

Operator Area Block - Origin/Termination Outside Diameter (in) Product Status

ATP O&G AT063 / MC941 5 in BLKO ACT

ATP O&G MC941 / AT063 4in UBEH ACT

There are no anomalous seabed amplitudes indicative of hydrocarbon macroseep observed 

within a 2,000ft radius of the proposed location (Figure 3). 

No items of archaeological significance were identified within 2,000ft of the proposed location

(archaeological report submitted under a separate cover).

No other features are observed within a 2,000ft radius that could affect well emplacement or 

jetting of casing.
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

4. SUBSEABED CONDITIONS

4.1 Geology and Lithology

The sub-seabed geology has been divided into four units separated by four horizons (Figures 

6 through 8). A Geohazards Extract and Sand Lithology Extract complete the well 

assessment and are presented as Figures 4 and 5. 

4.2 Unit A 

The uppermost interval within Unit A from seabed to -4,697ft below sea surface (282ft below 

seabed) is interpreted to consist of clays and silts with occasional minor coarser interbeds. 

The lower interval of Unit A from -4,697ft to -4,951ft below sea surface (282ft to 536ft below 

seabed) is interpreted to comprise of clays and silts. 

No shallow gas or shallow water flow is predicted within Unit A at the proposed well location.

A vertical borehole will not penetrate any faults within Unit A. 

Horizon H10 marks the base of Unit A at -4,951ft below sea surface (536ft below seabed). 

4.3 Unit B 

The upper interval of Unit B from -4,951ft to -5,545ft below sea surface (536ft to 1,130ft below 

seabed) is expected to comprise of clays and silts with occasional coarser interbeds. 

The lower interval of Unit B from -5,545ft to -5,939ft below sea surface (1,130ft to 1,524ft 

below seabed) is interpreted as clays and silts with several coarser interbeds. Due to the 

slightly elevated energy content of this interval minor drilling fluid circulation and minor 

wellbore stability problems are predicted within this interval. 

No shallow gas or shallow water flow is predicted within Unit B at the proposed well location.

A vertical borehole will not penetrate any faults within Unit B.

Horizon H20 marks the base of Unit B at -5,939ft below sea surface (1,524ft below seabed). 

4.4 Unit C 

The upper interval of Unit C from -5,939ft to -6,267ft below sea surface (1,524ft to 1,852ft 

below seabed) is interpreted to consist of clays and silts with several coarser interbeds that 

may represent sands. Minor drilling fluid circulation and minor wellbore stability problems are 

predicted within this interval. 

7 
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

Lithology from -6,267ft to -6,729ft below sea surface (1,852ft to 2,314ft below sea surface) is 

interpreted as higher energy clays and silts with numerous coarser interbeds that may 

represent sands. The proposed well is located within a sand fairway that extends from the 

south and southeast of the well to the northeast (Figure 5). A cluster of high-amplitude 

anomalies located generally to the southwest of the proposed well have the potential for a 

high risk of gas; however, a vertical borehole will not intersect any of these polygons. The 

nearest risk of gas anomalies are located approximately 643ft to the northwest and 

southwest. These gas hazards illustrate possible connectivity to the borehole, and we have 

assigned a Slight Risk of Gas within this interval. This interval exhibits character of rapid 

higher energy deposition and with a well defined clay prone overburden (Unit B) which are 

favorable conditions for the formation of shallow water flow. In addition a previously drilled 

well (AT063-2) located 2.4 miles to the south experienced a low shallow water flow event at 

2,012ft below seabed and these sands correlate with this interval. However, the amplitude 

character of this interval is slightly reduced at the proposed location, and as such a Moderate 

Shallow Water Flow Risk is assigned to this interval.

The lithology within the this interval from -6,729ft to -6,992ft below sea surface (2,314ft to 

2,577ft below seabed) is interpreted to comprise of lower energy clays and silts with the 

possibility of several minor coarser interbeds. Some minor drilling fluid circulation and minor 

wellbore stability problems are predicted within this interval. 

From -6,992m to -7,830m below sea surface (2,577m to 3,415m below seabed) is interpreted 

to consist of clays and silts with several coarser interbeds that may represent sands. It is 

possible that the sand interbeds within this interval may contain small volumes of fluid and a 

Slight Risk of Gas is assigned. Due to the presence and rapid deposition of the sands within 

this interval plus the possibility for fluid to be present within some of these sands, and possible 

downdip connectivity to additional probable coarser deposits (Figure 7), that may have pore 

pressure connectivity to the well location, a Moderate Shallow Water Flow Risk is assigned. 

The lower interval within Unit C from -7,830ft to -8,400ft below sea surface (3,415ft to 3,985ft 

below seabed) is interpreted to comprise of clays with numerous sands. The well path is 

located within the main cluster of increased amplitude events indicative of sands. Due to this 

slightly elevated amplitude character a Slight Risk of Gas is assigned to this interval. Due to 

the sandy nature of this interval, and the possibility of relatively continuous sandy interbeds, 

that descend eastward, possibly linking the pore pressure regimen to deeper levels, we have 

assigned a Moderate Shallow Water Flow Risk.

A vertical borehole will penetrate a fault within Unit C at -7,830ft below sea surface (3,415ft 

below seabed). This fault extends upwards to seabed, and as such if the fault is not sealed 

then some drilling fluid circulation problems may occur at the level of the fault if pressures 

over hydrostatic are exerted by the drilling fluid column. Wellbore stability problems could 

also occur.

8 
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

Horizon H30 marks the base of Unit C at -8,400ft below sea surface (3,985ft below seabed). 

4.5 Unit D 

Unit D from -8,400ft to -9,864ft below sea surface (3,985ft to 5,449ft below seabed) is 

interpreted to consist of clays and silts with several coarser interbeds. Minor drilling fluid 

circulation and wellbore stability problems may also occur.

A vertical borehole will not penetrate any faults within Unit D. 

Top of Salt marks the base of Unit D and the base of this interpretation at -9,864ft below sea 

surface (5,449ft below seabed). 

4.6 Shallow Gas Assessment

Within Unit C, a Slight Risk of Gas is assigned to the interval from -6,267ft to -6,729ft below 

sea surface (1,852ft to 2,314ft below seabed), from -6,992ft to -7,830ft below sea surface 

(2,577ft to 3,415ft below seabed), and from -7,830ft to -8,400ft below sea surface (3,415ft to 

3,985ft below seabed). 

4.7 Shallow Water Flow Assessment

Within Unit C, a Moderate Shallow Water Flow Risk is assigned to the interval from -6,267ft 

to -6,729ft below sea surface (1,852ft to 2,314ft below seabed), from -6,992ft to -7,830ft 

below sea surface (2,577ft to 3,415ft below seabed), and from -7,830ft to -8,400ft below sea 

surface (3,415ft to 3,985ft below seabed).

9 
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

5. CONCLUSIONS AND RECOMMENDATIONS

• Seabed

No significant problems are anticipated at seabed. Shallow soils are expected to be 

conducive to the jetting of seabed casing with no hardgrounds predicted.

• Unit A 

No drilling hazards or problems predicted.

• Unit B

Minor drilling and minor wellbore stability problems are possible from -5,545ft to -5,939ft 

below sea surface (1,130ft to 1,524ft below seabed). 

• Unit C 

Unit C presents a potentially challenging section to drill, with numerous intervals considered a 

shallow water flow risk and additional complications with faulting.

Within Unit C, a Slight Risk of Gas and a Moderate Shallow Water Flow Risk is assigned 

to the interval from -6,267ft to -6,729ft below sea surface (1,852ft to 2,314ft below seabed), 

from -6,992ft to -7,830ft below sea surface (2,577ft to 3,415ft below seabed), and from 

-7,830ft to -8,400ft below sea surface (3,415ft to 3,985ft below seabed). Drilling Caution is 

advised and appropriate drilling methodology is recommended to deal with a possible water 

flow event through this interval. Sediments in this interval are likely poorly consolidated and 

as such may induce minor drilling fluid circulation and wellbore stability problems.

Minor drilling fluid circulation and wellbore stability problems may also occur from -6,729ft to -

6,992ft below sea surface (2,314ft to 2,577ft below seabed). 

Minor drilling and minor wellbore stability problems are possible from -5,939ft to -6,267ft 

below sea surface (1,524ft to 1,852ft below seabed).

A vertical borehole will penetrate a fault within Unit C at -7,830ft below sea surface (3,415ft 

below seabed). Drilling fluid circulation problems may occur at the level of the fault if 

pressures over hydrostatic are exerted by the drilling fluid column.

 

• Unit D

Minor drilling and minor wellbore stability problems are possible within Unit D. 

10
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

We appreciate the opportunity to work with you on this project, and look forward to continuing as 

your geohazards consultants. Please contact us if you have any questions or if we can be of 

further assistance.

Sincerely,

Gardline Surveys Inc.

Andrew Haigh Matilde DeLeon

Geophysical Manager Quality Assurance

Copies Submitted: 6 copies to Rick Kincaid at Anadarko Petroleum Corporation.

Attachments:

Proposed AT019-KV Well Location

Seabed Depth Extract

Seabed Morphology Extract

Seabed Amplitude Extract

Geohazard Summary Extract

Sand Lithology Summary

Inline Data Example

Crossline Data Example

Top Hole Prognosis

ROV Plat

Power Spectrum

Bathymetry Plat

Public Information Plat

Proprietary Information Plat

Vicinity Map

10-Mile Radius Plat

11
Top Hole Prognosis for Proposed AT019-KV Well Location

987,423ft E / 10,139,337ft N

Inline: 5427 / Crossline: 10430 Horizon

Subsea

Depth

(ft)

BML

Depth

(ft)

Horizon

TWT

(sec)

Lithology, Structure & Stratigraphy Potential Drilling Hazards & Constraints

Risk

of

Gas

SWF

Risk

Seabed -4,415 0 1.797 Seabed is smooth sloping to the southeast at 1.3°. Surficial sediments comprise of 

soft clays and silts.Underlying the seabed the lithology comprises of clays and silts 

with occasional minor coarser interbeds

Figure 8

Interface -6,267 1,852 2.486

Horizon H10 -4,951 536 2.009

Interface -6,729 2,314 2.642

Clays and silts with occasional coarser interbeds

None predicted

None predicted

Minor drilling fluid circulation and minor wellbore stability problems 

possible within this interval

Unit A

Unit B

Horizon H20 -5,939 1,524 2.372

Interface/Fault -7,830 3,415 2.991

Horizon H30 8,400 3,985 3.159

Top of Salt -9,864 5,449 3.555

Clays and silts with several coarser interbeds that represent sands

Clays and silts with minor numerous coarser interbeds that may represent sands

Clays with numerous coarser interbeds that may represent sands

Minor drilling fluid circulation and minor wellbore stability problems 

possible within this interval

Base of interpretation

Clays and silts with minor coarser interbeds that may represent sands

Clays and silts with several coarser interbeds

Slight Risk of Gas and Moderate Shallow Water Flow Risk

Minor drilling fluid circulation and wellbore stability problems possible

Slight Risk of Gas and Moderate Shallow Water Flow Risk. Interface -6,992 2,577 2.728

Interface -5,545 1,130 2.231

Interface -4,697 282 1.910

Clays and silts with several coarser interbeds Minor drilling fluid circulation and wellbore stability problems possible

Clays and silts with several sand interbeds

Slight Risk of Gas and Moderate Shallow Water Flow Risk

Drilling fluid circulation problems may occur at the level of the fault if 

pressures over hydrostatic are exerted by drilling fluid column

None predicted

Vavg

BML

(m/s)

0

5,376

5,054

5,478

5,301

5,721

5,851

6,199

5,535

5,208

4,983 Clays and silts

Unit C

Unit D
±

6

3® 3

3

3

AT063-SS004

-4510

-4500

-4490

-4480

-4520

-4470

-4460

-4340

-4330

-4350

-4370

-4360

-4380

-4390

-4400

-4410

-4450

-4440

-4430

-4420

-4320 -4310

-4530

-4300

-4290

-4540

-4280

-4270

-4550

-4560

-4260

-4570

-4250

-4240

-4580

-4590

-4230

-4600

-4220

-4210

-4610

-4200

-4190

-4180

-4530

-4510

-4560

-4540

-4550

-4520

-4370

-4260

89°2'0"W89°1'0"W89°0'0"W

27°57'0"N

27°56'0"N

27°55'0"N

985,000990,000995,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1 = 2,000'

Bathymetry Plat Figure 11

2,000ft Radius

ATP 5'' OIL(16173)

ATP 4'' UMBILICAL(16181)

BPE&P 2 1/2''OR 2 7/8''CBLC(17364)

ATWATER VALLEY 

BLOCK 19(OCS-G32556)

ATWATER VALLEY 

BLOCK 63(OCS-G13198)

Proposed AT019-KV

Easting: 987,423ft E

Northing: 10,139,337ft N

FWL of AT019-KV: 5,343ft

FSL of AT019-KV: 1,737ft
±

6

3® 3

3

3

AT063-SS004

Proposed AT019-KV Well

89°2'0"W89°1'0"W89°0'0"W

27°57'0"N

27°56'0"N

27°55'0"N

985,000990,000995,000

10,135,000

10,140,000

10,145,000

10,150,000

0 1,000 2,000 500 Feet

0 250 500 125 Meters

Chart scale 1" = 2,000'

Well Location Plat - Public Information Figure 12

ATP 5'' OIL(16173)

BPE&P 2 1/2''OR 2 7/8''CBLC(17364)

ATP 4'' UMBILICAL(16181)

ATWATER VALLEY 

BLOCK 19(OCS-G32556)

ATWATER VALLEY 

BLOCK 63(OCS-G13198)

Location Call N/S Call E/W X Coordinate Y Coordinate Latitude Longitude WD

AT019-KV SL 1,737ft FSL 5,343ft FWL 987,423 10,139,337 27° 55' 33.49'' N 89° 01' 21.68'' -4,415

Proposed Location - AT019-KV
Nearest Shoreline

Range: 72mi

Bearing: 341°

Fourchon

Range: 108mi

Bearing: 319°

Lund

Henderson

Lloyd Ridge

Walker Ridge

Destin Dome

Atwater Valley Green Canyon

De Soto Canyon

The Elbow

Florida Plain

Vernon Basin

Apalachicola

Garden Banks

Keathley Canyon

Florida Middle Ground

Howell Hook

Lund South

Pensacola

Amery Terrace

Mobile

Viosca Knoll

Viosca Knoll

Sigsbee Escarpment

New Orleans

Baton Rouge

Pensacola

Lafayette

Gulfport Pascagoula

Vicinity Map - Atwater Valley Block 019

Figure 14
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

APPENDIX A – Public Shallow Hazards Statements 

28
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

Public Shallow Hazards Statement – AT019-KV

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213-2394

Attention: 

Reference: Shallow Hazards Analysis

Atwater Valley Block 019

OCS-(G 32556) 

Ladies/Gentlemen:

Anadarko Petroleum Corporation contracted Gardline Surveys, Inc. to prepare a Well Clearance Letter 

for the proposed AT019-KV well location in Block 019, Atwater Valley Area (OCS-G 32556). This 

letter addresses seafloor and shallow geologic conditions that may impact exploratory drilling 

operations within 2,000ft of the proposed well location. The depth limit of this geohazard assessment 

is Top of Salt at -9,864ft below sea surface (5,449ft below seabed).

This hazards summary letter is issued as a supplement to Gardline Report No.9172 entitled: 3D 

Geohazard Assessment, Atwater Valley Blocks 018 and 019, dated August 2012.

Seabed Hazards. 

The seabed is smooth and featureless. No problems are expected at the proposed AT019-KV well 

location.

There are no indications of seabed fluid seeps within 2,000ft of the well location.

Sub-Seabed Hazards. 

Drilling Caution is indicated for a Slight Risk of Gas at the well location within Unit C.

Moderate and Slight Shallow Water Flow Risk is assigned to sand intervals within Unit C. 

29
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

Proposed AT019-KV Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 55' 33.49” North Easting 987,423 US ft E

Longitude 89° 01’ 21.68” West Northing 10,139,337 US ft N

FWL of Atwater Valley 19 5,343 US ft Inline 5427

FSL of Atwater Valley 19 1737 US ft Crossline 10430

Water Depth: -4,415 ft Slope: 1.3° SE

Nearest Shoreline 72 Miles @ 341° 

Port of Operation Fourchon 108 Miles @ 319° 

Nearest Manned Platform MC941-(Mirage/Titan) 9 Miles @ 328° 

Conclusions and Recommendations. 

Drilling techniques will take into consideration the possibility of encountering possible gas within Unit 

C. 

Appropriate drilling methodology will be utilized to contain a potentially non-persistent Slight Shallow 

Water Flow Risk within Unit C. Appropriate drilling methodology will be utilized to deal with a possible 

Moderate Shallow Water Flow Risk in the sand intervals within Unit C. 

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

PUBLIC INFORMATION

30
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

APPENDIX B – Sensitive Sessile Benthic Community Statements

31
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

Sensitive Sessile Benthic Community Statement – AT019-KV

Anadarko Petroleum Corporation

July 15, 2013

US Department of the Interior

Bureau of Energy, Management, Regulation and Enforcement

1201 Elmwood Park Blvd.

New Orleans, LA 70213

Reference: Sensitive Sessile Benthic Community Summary

Atwater Valley, Block 018

OCS-(G 32556) 

Ladies/Gentlemen:

Gardline Surveys Inc was contracted by Anadarko Petroleum Corporation to prepare a Site Clearance 

Letter for the proposed AT019-KV well location in Atwater Valley, Block 019, Stromboli Prospect 

(OCS-G G 32556). This letter addresses location proximity to potential sensitive sessile benthic 

community sites. Anadarko Petroleum Corporation will be drilling this well from a dynamically 

positioned drilling module; therefore, no anchors will impact seabed.

This sensitive sessile benthic community summary letter is issued as a supplement to Gardline Report 

No.9172 entitled: 3D Geohazard Assessment, Atwater Valley Blocks 018 and 019, dated August 2012. 

A Biological, Physical and Socio-Economic Map is included at the end of this appendix illustrating the 

areas of potential seabed impact.

Potential Sensitive Sessile Benthic Communities. 

Features or areas that could support high density sensitive sessile benthic communities are not 

located within 2,000ft of any proposed mud and cuttings discharge location.

Proposed AT 19 KV Location (Surface)

Location Coordinates

NAD 27 Datum - Clarke 1866 Ellipsoid UTM Zone 16N - CM 93° West

Latitude 27° 55' 33.49” North Easting 987,423 US ft E

Longitude 89° 01’ 21.68” West Northing 10,139,337 US ft N

FWL of Atwater Valley 19 5,343 US ft Inline 5427

FSL of Atwater Valley 19 1737 US ft Crossline 10430

Water Depth: -4,415 ft Slope: 1.3° SE

Nearest Shoreline 72 Miles @ 341° 

Port of Operation Fourchon 108 Miles @ 319° 

Nearest Manned Platform MC941-(Mirage/Titan) 9 Miles @ 328° 

32
Anadarko Petroleum Corporation Gardline Report 9519

Well Clearance Letter – Stromboli Prospect - Atwater Valley – Proposed Well Location AT 019 KV

No potential sensitive sessile benthic community site is located within 2,000ft of the proposed 

location. 

Conclusions and Recommendations: 

The proposed AT019-KV well location will not impact any sites favorable for development of sensitive 

sessile benthic communities.

Sincerely,

Anadarko Petroleum Corporation

Rick Kincaid

Leader-Geologic Operations

33
 

SECTION D 

HYDROGEN SULFIDE INFORMATION 

Discussions regarding geologic information are considered proprietary and have been omitted from 

this public copy of the EP. 

Anadarko requests the area be classified as a “zone where the absence of H2S has been 

confirmed.” 
 

SECTION E 

BIOLOGICAL, PHYSICAL, AND SOCIOECONOMIC INFORMATION 

(a) Chemosynthetic Communities Report 

The seafloor disturbing activities proposed in this plan are in approximately 4,167'-4,433' of 

water. The wells will be drilled with a DP drillship or DP semi-submersible. 

Maps 

A map prepared using 3-D seismic data to depict bathymetry, seafloor and shallow geological 

features, and surface locations of the proposed wells is included in Section A. 

Analysis 

Features or areas that could support high-density chemosynthetic communities are not located 

within 2,000' of each proposed muds and cuttings discharge location. 

Features or areas that could support high-density chemosynthetic communities are not located 

within 250' of any seafloor disturbances. 

(b) Topographic Features Map 

The proposed activities are not within 1,000' of a no-activity zone or within the 3-mile radius 

zone of an identified topographic feature. Therefore, no map is required per NTL 2008-G04, 

extended by NTL 2014-G03. 

(c) Topographic Features Statement (Shunting) 

Anadarko does not plan to drill more than two wells from the same surface location within the 

Protective Zone of an identified topographic feature. Therefore, the topographic features 

statement required by NTL 2008-G04, extended by NTL 2014-G03, is not applicable. 

(d) Live Bottoms (Pinnacle Trend) Map 

The activities proposed in this plan are not within 200' of any pinnacle trend feature with vertical 

relief equal to or greater than 8'. Therefore, no map is required per NTL 2008-G04, extended by 

NTL 2014-G03. 

(e) Live Bottoms (Low Relief) Map 

The activities proposed in this plan are not within 100' of any live bottom low relief features. 

Therefore, no map is required per NTL 2008-G04, extended by NTL 2014-G03. 
 

(f) Potentially Sensitive Biological Features 

The activities proposed in this plan are not within 200' of any potentially sensitive biological 

features. Therefore, no map is required per NTL 2008-G04, extended by NTL 2014-G03. 

(g) Remotely Operated Vehicle (ROV) Monitoring Survey Plan 

Atwater Valley 18/19 is located within Deepwater Grid Area 13. This grid is considered to have 

“adequate ROV survey coverage”, and, therefore, under the guidance set out in NTL 2008-G06, 

a Remotely Operated Vehicle Monitoring Survey Plan is not required. 

Pursuant to NTL 2008-G06, operators may be required to conduct remotely operated vehicle 

(ROV) surveys during the proposed operations for the purpose of biological and physical 

observations. 

Anadarko is familiar with the ROV survey and reporting provisions of NTL 2008-G06; and if 

required, will conduct a survey. 

Anadarko will utilize ROV equipped with video imaging capabilities. The survey pattern will 

consist of six transects centered on the well location with tracks extending approximately 100 

meters away from the well on bearings of 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 

degrees and 330 degrees. The seafloor will be videotaped continuously along each track. 

Anadarko will make biological and physical observations as described in the subject NTL and 

Form BOEM-141 prior to commencing operations and prior to moving off location. The 

observations will be documented using Form BOEM-141, or a facsimile and submitted along 

with videotapes, and any other imagery obtained, to the BOEM/BSEE within 60 days after 

completion of the final ROV survey. 

(h) Threatened and Endangered Species 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 550, Subpart B, effective May 14, 2007, and further outlined in 

Notice to Lessees (NTL) 2008-G04 (extended by NTL 2014-G03), 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. 
 

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. The following table reflects the Federally-listed endangered and 

threatened species in the lease area and along the northern Gulf coast: 

Species Scientific Name Status 

Potential Presence Critical Habitat 

Designated in 

Gulf of Mexico 

Lease 

Area Coastal 

Marine Mammals 

Sperm whale Physeter macrocephalus E X -- None

Florida manatee Trichechus manatus 

latirostris E -- X Florida 

(Peninsular)

Blue whale Balaenoptera musculus E Xa -- None

Fin whale Balaenoptera physalus E Xa -- None

Humpback whale Megaptera novaeangliae E Xa -- None

North Atlantic right whale Eubalaena glacialis E Xa -- None

Sei whale Balaenoptera borealis E Xa -- None

Sea Turtles 

Loggerhead turtle Caretta caretta T X X None

Green turtle Chelonia mydas T, Eb X X None

Leatherback turtle Dermochelys coriacea E X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Birds 

Piping Plover Charadrius melodus T -- X 

Coastal Texas, 

Louisiana, Mississippi, 

Alabama, and Florida 

(Panhandle) 

Whooping Crane Grus americana E -- X 

Coastal Texas 

(Aransas National 

Wildlife Refuge)

Fishes 

Gulf sturgeon Acipenser oxyrinchus desotoi T -- X 

Coastal Louisiana, 

Mississippi, Alabama, 

and Florida (Panhandle)

Terrestrial Mammals 

Beach mice (Alabama, 

Choctawhatchee, Perdido 

Key, St. Andrew)

Peromyscus polionotus E -- X Alabama and Florida 

(Panhandle) beaches 

Abbreviations:  E = Endangered; T = Threatened.   a

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

unlikely to be present in the lease area. b

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

The Environmental Impact Analysis in Section N of this plan further discusses potential impacts 

and mitigation measures related to threatened and endangered species. 

(i) Archaeological Report 

Atwater Valley 18/19 is not in an area designated as an area of high archaeological potential and, 

as such, as such, an Archaeological Report is not required per NTL 2008-G04, extended 

by extended by NTL 2014-G03. However an “Archaeological Assessment Report” prepared by 

C & C Technologies Survey Services (Project #120015) is being submitted with this EP for 

reference. 
 

(j) Air and Water Quality Information

This EP does not propose activities for which the State of Florida is an affected State. Therefore, 

the discussion required per NTL 2008-G04, extended by NTL 2014-G03, is not applicable to this 

EP. 

(k) Socioeconomic Information 

The activities proposed in this plan are not located offshore Florida. Therefore, socioeconomic 

information required per NTL 2008-G04, extended by NTL 2014-G03, is not applicable to this 

EP. 
 

SECTION F 

WASTE AND DISCHARGE INFORMATION 

The following estimates were prepared utilizing Anadarko’s experience with similar drilling operations. 

Estimated maximum discharge rates are reflected below. 

(a) Projected Generated Wastes 

Type of Waste Composition Projected Amount Treatment/Storage/Disposal 

Synthetic-based drilling 

fluids 

Synthetic-based 

drilling muds 

18,500 bbls/well Re-use and/or transport to shore in 

DOT approved containers to 

Fourchon, Louisiana and on to 

base/transfer station. If recycled, 

returned to vendor (Baroid or MI.) 

Cuttings wetted with 

synthetic-based muds 

Cuttings coated with 

synthetic drilling 

muds/fluids, 

including drilled out 

cement. 

6,500 bbls/well Treated and discharged overboard. 

*Note, an estimated 5-10% of 

cuttings may be transported to shore 

in tanks and/or cutting boxes and on 

to the base/transfer station if oil still 

remains. 

Water-based drilling 

fluids 

Water-based drilling 

muds (NaCl 

saturated, seawater, 

freshwater, barite) 

43,000 bbls/well Discharge overboard or at seafloor. 

Cuttings wetted with 

water-based fluids 

Cuttings coated with 

water-based drilling 

muds/fluids 

2,400 bbls/well Discharge overboard or at seafloor. 

Chemical product waste 

(well treatment fluids) 

Ethylene glycol 

Methanol 

100 bbls/month 

25 bbls/month 

Transport to shore in DOT approved 

containers to Fourchon, Louisiana 

for pick up. 

Completion Fluids Brine, spent acid, 

prop sand, debris 

3,000 bbls/well Transport to shore in DOT approved 

containers to Fourchon, Louisiana 

and on to Newpark Base. 

Non-pollutant 

completion fluids 

Low density 

uninhibited 

completion brines 

5,000 bbls/well Discharge overboard. 

Workover fluids Brine, spent acid, 

prop sand, debris 

3,000 bbls/well Transport to shore in DOT approved 

containers to Fourchon, Louisiana 

and on to Newpark Base. 

Trash and debris Refuse generated 

during operations 

2,850 bbls total Transport to shore in disposal bags 

by vessel to shorebase for pickup by 

municipal operations. 

*Sanitary Wastes Treated human body 

waste 

7,600,000 gals total Chlorinate and discharge overboard. 

*Domestic Waste Gray water 7,600,000 gals total Chlorinate and discharge overboard. 

Deck drainage Platform washings 

and rainwater 

5,320,000 bbls total Treat for oil and grease and 

discharge overboard. 

Produced water N/A N/A N/A 

Desalinization Unit Seawater 532,000 bbls total Discharge overboard. 

Wash water Drill water (fresh) 85,500 bbls total Discharge overboard. 

Blowout preventer fluid Blend (3% Stack 

Magic & Filtered 

Fresh Water) 

200,857 gals total Discharge at seafloor. 

Ballast water Seawater 47,650 m3/year Discharge overboard. 
 

Cont. 

Type of Waste Composition Projected Amount Treatment/Storage/Disposal 

Bilge water Seawater 542,070 bbls total Discharge overboard through 15 

ppm equipment 

Excess cement at the 

seafloor 

Nitrified cement 

slurry 

524 bbls/well Discharge at seafloor 

Fire water Seawater 137,142 bbls/day/well Discharge overboard 

Cooling water Seawater 137,142 bbls/day/well Discharge overboard 

Produced Sand N/A N/A N/A 

Used oil Excess oil from 

engines 

6,128 bbls total Transport in DOT approved 

containers to shore for recycling 

(b) Projected Ocean Discharges

Type of Waste Total Amount to 

be Discharged 

Disch6arge Rate Discharge Method 

*Sanitary Wastes 7,600,000 gals 25 gals per person daily Chlorinate and discharge 

overboard 

*Domestic waste 7,00,000 gals 25 gals per person daily Chlorinate and discharge 

overboard 

Deck drainage 5,320,000 bbls 3,500 bbls/day Treat for oil and grease and 

discharge 

Blowout preventer fluid 200,857 gals 925 gals/week/well 

Vents on weekly basis 

Discharge at seafloor 

Desalinization Unit 532,000 bbls 350 bbls/day Discharge overboard 

Wash water 85,500 bbls 50 bbls/day Discharge overboard 

Ballast water As needed Not continuous Discharge overboard 

Bilge water 542,070 bbls 317 bbls/day Discharge overboard through 

15 ppm equipment 

Excess cement at the 

seafloor 

4,192 bbls 20 bbls/min Discharge at seafloor 

Fire water 234,512,820 bbls 137,142 bbls/day Discharge overboard 

Cooling water 234,512,820 bbls 137,142 bbls/day Discharge overboard 

Cuttings wetted with 

water-based fluids 

19,200 bbls 1,000 bbls/hr max Discharge overboard or at seafloor 

Water-based drilling 

fluids 

344,000 bbls** 1,000 bbls/hr max Discharge overboard or at seafloor 

Cuttings wetted with 

synthetic-based fluids 

52,000 bbls 1,000 bbls/hr max*** Treated and discharge overboard 

*Note, an estimated 5-10% of cuttings may 

be transported to shore in tanks and/or 

cutting boxes and on to the base/transfer 

station if oil still remains. 

Non-pollutant 

completion fluids 

40,000 bbls 100 bbls/hour Discharge overboard 

*The rig is designed for maximum personnel capacity of 200 people. The discharge rates are based off of maximum personnel capacity but will generally 

not have this many personnel onboard during drilling and/or completion operations. 

**The volume ordered out will be an estimated 19,000 bbls/well of mud. Once on location this volume will be cut back and mixed with seawater to 

different desired mud weights which will increase the volume that is discharged at the seafloor. The estimated volume that will be discharged at the 

seafloor will be approximately 43,000 bbls/well. (43,000 bbls x 8 wells=344,000 bbls) 

***The rate for cuttings wetted with synthetic-based fluids varies depending on the hole section and the stage of the actual drilling process. 

(c) Modeling Report 

The proposed activities under this plan do not meet the U.S. Environmental Protection Agency 

requirements for an individual NPDES permit. Therefore, modeling report requirements per 

NTL 2008-G04, extended by NTL 2014-G03, is not applicable to this EP. 
 

SECTION G 

AIR EMISSIONS INFORMATION 

(a) Screening Questions 

Screening Questions for EP’s Yes No

Is any calculated Complex Total (CT) Emission amount (in tons) associated with your 

proposed exploration activities more than 90% of the amounts calculated using the 

following formulas: CT = 3400D2/3 for CO, and CT = 33.3D for the other air pollutants 

(where D = distance to shore in miles)? 

Yes 

Do your emission calculations include any emission reduction measures or modified 

emission factors? 

Yes 

Are your proposed exploration activities located east of 87.5 W longitude? No 

Do you expect to encounter H2S at concentrations greater than 20 parts per million (ppm)? No 

Do you propose to flare or vent natural gas for more than 48 continuous hours from any 

proposed well? 

 No 

Do you propose to burn produced hydrocarbon liquids? No 

(b) Emissions Worksheets 

Air emission worksheets have been prepared utilizing the maximum horsepower rating from an 

Anadarko contracted DP drillship, the Noble Bob Douglas. The Noble Bob Douglas has six 

main engines. The average number of engines on-line at once will be four engines. Rigs typically 

do not operate at maximum horsepower capacity or engine load, therefore Anadarko has opted to 

calculate the plan emission amounts based on the total horsepower rating and 50% average 

engine load. A different rig may be utilized (DP drillship or DP semi-submersible); but the 

horsepower rating, average engine load, and air emissions will be equal to, or less than, the 

calculated plan emission amounts shown on the following pages. Air emission worksheets are 

enclosed as Attachment G-1. 

Based on the attached Air Quality Review (AQR) spreadsheet, projected potential emissions of 

nitrogen oxides (NOx) are above the corresponding exemption threshold estimated for 

2016/2017/2018, therefore, Trinity Consultants performed an air quality modeling analysis for 

NOx. Submitted along with this EP are two copies of Trinity Consultants’ “Offshore and 

Coastal Dispersion Modeling Analysis Report” for Atwater Valley 18/19 (Project No. 

131901.0103). Potential emissions of all other pollutants included in the AQR are below the 

corresponding exemption thresholds; therefore modeling has not been performed for any other 

pollutant(s). 
 

(c) Summary Information 

If drilled with a DP Drillship 

Air Pollutant Plan Emission 

Amounts1

 (tons) 

Calculated Exemption 

Amounts2 (tons)

Calculated Complex 

Total Emission Amounts3

(tons) 

Particulate matter (PM) 72.23 2,364.30 72.23 

Sulphur dioxide (SO2) 331.34 2,364.30 331.34 

Nitrogen oxides (NOx) 2,482.82 2,364.30 2,482.82 

Volatile organic compounds (VOC) 74.48 2,364.30 74.48 

Carbon monoxide (CO) 541.71 58,297.66 541.71 

If drilled with a DP Semi-submersible 

Air Pollutant Plan Emission 

Amounts1

 (tons) 

Calculated Exemption 

Amounts2 (tons)

Calculated Complex 

Total Emission Amounts3

(tons) 

Particulate matter (PM) 68.90 2,364.30 68.90 

Sulphur dioxide (SO2) 316.09 2,364.30 316.09 

Nitrogen oxides (NOx) 2,368.54 2,364.30 2,368.54 

Volatile organic compounds (VOC) 71.06 2,364.30 71.06 

Carbon monoxide (CO) 516.77 58,297.66 516.77 

*Plan emissions amounts (tons) are based on 248 days. 

**Calculated complex total emission amounts (tons) are based on 248 days. 

The air emission calculations were calculated by: 

Bridget O’Farrell 

Regulatory Analyst 

(832) 636-1694 

Bridget.OFarrell-Villarreal@anadarko.com
COMPANY Anadarko Petroleum Corporation

AREA ATBLOCK 18/19LEASE OCS-G 33863, G-32556PLATFORMWELL AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KVCOMPANY CONTACT Bridget O'FarrellTELEPHONE NO. 832-636-1694REMARKS Drill and complete 8 wellsDrillship

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 1 of 11

EXPLORATION PLAN (EP)

AIR QUALITY SCREENING CHECKLIST

OMB 
EMISSIONS FACTORS

Fuel Usage Conversion Factors Natural Gas Turbines Natural Gas Engines Diesel Recip. Engine R

SCF/hp-hr 9.524 SCF/hp-hr 7.143 GAL/hp-hr 0.0483 AP4

Equipment/Emission Factors units PM SOx NOx VOC CO RNG Turbines gms/hp-hr 0.00247 1.3 0.01 0.83 AP42 3NG 2-cycle lean gms/hp-hr 0.00185 10.9 0.43 1.5 AP4NG 4-cycle lean gms/hp-hr 0.00185 11.8 0.72 1.6 AP4NG 4-cycle rich gms/hp-hr 0.00185 10 0.14 8.6 AP4

Diesel Recip. < 600 hp. gms/hp-hr 1 1.468 14 1.12 3.03 AP4

Diesel Recip. > 600 hp. gms/hp-hr 0.32 1.468 11 0.33 2.4 AP4Diesel Boiler lbs/bbl 0.084 2.42 0.84 0.008 0.21 AP42 NG Heaters/Boilers/Burners lbs/mmscf 7.6 0.593 100 5.5 84 P42 1.4-NG Flares lbs/mmscf 0.593 71.4 60.3 388.5 AP4Liquid Flaring lbs/bbl 0.42 6.83 2 0.01 0.21 AP42 1Tank Vapors lbs/bbl 0.03 E&P Fugitives lbs/hr/comp. 0.0005 APGlycol Dehydrator Vent lbs/mmscf 6.6 LaGas Venting lbs/scf 0.0034

Sulfur Content Source Value Units

Fuel Gas 3.33 ppm

Diesel Fuel 0.4 % weight

Produced Gas( Flares) 3.33 ppm

Produced Oil (Liquid Flaring) 1 % weight

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 2 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 64,370 3109.071 50% 37308.85 24 190 45.37 208.14 1559.63 46.79 340.28 51.72 

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 81 10.44 47.87 358.71 10.76 78.26 2.55 

2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 54 6.53 29.96 224.51 6.74 48.98 1.06 

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

MISC. BPD SCF/HR COUNTTANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2014 YEAR TOTAL 62.34 285.97 2142.84 64.29 467.53 55.34 

EXEMPTION 

CALCULATION DISTANCE FROM LAND IN MILES 2364.30 

71.0

Average 

Engine 

Load %

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 3 of 11

EMISSIONS CALCULATIONS 1ST YEAR
EMISSIONS CALCULATIONS 2ND YEAR

COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corpo AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 64,370 3109.071 50% 37308.85 24 190 45.37 208.14 1559.63 46.79 340.28 51.72 Drillship PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 81 10.44 47.87 358.71 10.76 78.26 2.55 2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 54 6.53 29.96 224.51 6.74 48.98 1.06 

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

MISC. BPD SCF/HR COUNTTANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2015 YEAR TOTAL 62.34 285.97 2142.84 64.29 467.53 55.34 

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 2364.30 

71.0

Average 

Engine 

Load %

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 4 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO P

DRILLING PRIME MOVER>600hp diesel 64,370 3109.071 50% 37308.85 24 248 45.37 208.14 1559.63 46.79 340.28 67Drillship PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 106 10.44 47.87 358.71 10.76 78.26 3.

2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 71 6.53 29.96 224.51 6.74 48.98 1.

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.

MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2016 YEAR TOTAL 62.34 285.97 2142.84 64.29 467.53 72

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 236

71.0

Average 

Engine Load %

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 5 of 11

EMISSIONS CALCULATIONS 3RD YEAR
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum CorpAT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 64,370 3109.071 50% 37308.85 24 248 45.37 208.14 1559.63 46.79 340.28 67.5Drillship PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 106 10.44 47.87 358.71 10.76 78.26 3.32 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 71 6.53 29.96 224.51 6.74 48.98 1.3

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0MISC. BPD SCF/HR COUNTTANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2017 YEAR TOTAL 62.34 285.97 2142.84 64.29 467.53 72.2

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 2364

71.0

Average 

Engine 

Load %

EMISSIONS CALCULATIONS 4TH YEAR

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 6 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum CorpAT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 64,370 3109.071 50% 37308.85 24 248 45.37 208.14 1559.63 46.79 340.28 67.5Drillship PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 106 10.44 47.87 358.71 10.76 78.26 3.32 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 71 6.53 29.96 224.51 6.74 48.98 1.3

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0

Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2018 YEAR TOTAL 62.34 285.97 2142.84 64.29 467.53 72.2

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 2364

71.0

Average 

Engine 

Load %

EMISSIONS CALCULATION STH YEAR

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 7 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum CorpAT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 64,370 3109.071 50% 37308.85 24 16 45.37 208.14 1559.63 46.79 340.28 4.3Drillship PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 7 10.44 47.87 358.71 10.76 78.26 0.2

2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 5 6.53 29.96 224.51 6.74 48.98 0.0

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0

Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2019 YEAR TOTAL 62.34 285.97 2142.84 64.29 467.53 4.6

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 2364

71.0

Average 

Engine 

Load %

EMISSIONS CALCULATIONS 6TH YEAR

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 8 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 64,370 3109.071 50% 37308.85 24 190 45.37 208.14 1559.63 46.79 340.28 51.7Drillship PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 81 10.44 47.87 358.71 10.76 78.26 2.5

2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 54 6.53 29.96 224.51 6.74 48.98 1.0

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0MISC. BPD SCF/HR COUNTTANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2020 YEAR TOTAL 62.34 285.97 2142.84 64.29 467.53 55.3

EXEMPTION 

CALCULATION DISTANCE FROM LAND IN MILES 2364

71.0

Average 

Engine Load 

%

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 9 of 11

EMISSIONS CALCULATIONS 9TH YEAR
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 64,370 3109.071 50% 37308.85 24 190 45.37 208.14 1559.63 46.79 340.28 51.72 Drillship PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

AUXILIARY EQUIP<600hp diese 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 81 10.44 47.87 358.71 10.76 78.26 2.55 2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 54 6.53 29.96 224.51 6.74 48.98 1.06 

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 MISC. BPD SCF/HR COUNTTANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2021 YEAR TOTAL 62.34 285.97 2142.84 64.29 467.53 55.34 

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 2364.30 

71.0

Average 

Engine 

Load %

EMISSIONS CALCULATIONS 10TH YEAR

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 10 of 11
SUMMARY

COMPANY AREA BLOCK LEASE PLATFORM WELL

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 

AT 18:CGV, QQ/KK, KV

Emitted Substance

Year

 PM SOx NOx VOC 

2014 55.34 253.85 1902.16 57.06 4

2015 55.34 253.85 1902.16 57.06 4

2016 72.23 331.34 2482.82 74.48 5

2017 72.23 331.34 2482.82 74.48 5

2018 72.23 331.34 2482.82 74.48 5

2019 4.66 21.38 160.18 4.81 3

2020 55.34 253.85 1902.16 57.06 4

2021 55.34 253.85 1902.16 57.06 4

Allowable 2364.30 2364.30 2364.30 2364.30 58

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 11 of 11
A

COMPANY Anadarko Petroleum CorporationAREA ATBLOCK 18/19LEASE OCS-G 33863, G-32556PLATFORMWELL AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KVCOMPANY CONTACT Bridget O'FarrellTELEPHONE NO. 832-636-1694REMARKS Drill and complete 9 wellsDP Semi-Submersible

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 1 of 11

EXPLORATION PLAN (EP)

AIR QUALITY SCREENING CHECKLIST

OMB 
EMISSIONS FACTORS

Fuel Usage Conversion Factors Natural Gas Turbines Natural Gas Engines Diesel Recip. Engine R

SCF/hp-hr 9.524 SCF/hp-hr 7.143 GAL/hp-hr 0.0483 AP4

Equipment/Emission Factors units PM SOx NOx VOC CO RNG Turbines gms/hp-hr 0.00247 1.3 0.01 0.83 AP42 3NG 2-cycle lean gms/hp-hr 0.00185 10.9 0.43 1.5 AP4NG 4-cycle lean gms/hp-hr 0.00185 11.8 0.72 1.6 AP4NG 4-cycle rich gms/hp-hr 0.00185 10 0.14 8.6 AP4

Diesel Recip. < 600 hp. gms/hp-hr 1 1.468 14 1.12 3.03 AP4

Diesel Recip. > 600 hp. gms/hp-hr 0.32 1.468 11 0.33 2.4 AP4Diesel Boiler lbs/bbl 0.084 2.42 0.84 0.008 0.21 AP42 NG Heaters/Boilers/Burners lbs/mmscf 7.6 0.593 100 5.5 84 P42 1.4-NG Flares lbs/mmscf 0.593 71.4 60.3 388.5 AP4Liquid Flaring lbs/bbl 0.42 6.83 2 0.01 0.21 AP42 1Tank Vapors lbs/bbl 0.03 E&P Fugitives lbs/hr/comp. 0.0005 APGlycol Dehydrator Vent lbs/mmscf 6.6 LaGas Venting lbs/scf 0.0034

Sulfur Content Source Value Units

Fuel Gas 3.33 ppm

Diesel Fuel 0.4 % weight

Produced Gas( Flares) 3.33 ppm

Produced Oil (Liquid Flaring) 1 % weight

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 2 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 61,200 2955.96 50% 35471.52 24 190 43.14 197.89 1482.82 44.48 323.52 49.18 

DP Semi-Submersible PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 81 10.44 47.87 358.71 10.76 78.26 2.55 

2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 54 6.53 29.96 224.51 6.74 48.98 1.06 

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

MISC. BPD SCF/HR COUNTTANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2014 YEAR TOTAL 60.10 275.72 2066.04 61.98 450.77 52.79 

EXEMPTION 

CALCULATION DISTANCE FROM LAND IN MILES 2364.30 

71.0

Average 

Engine 

Load %

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 3 of 11

EMISSIONS CALCULATIONS 1ST YEAR
EMISSIONS CALCULATIONS 2ND YEAR

COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO P

DRILLING PRIME MOVER>600hp diesel 61,200 2955.96 50% 35471.52 24 190 43.14 197.89 1482.82 44.48 323.52 49DP Semi-Submersible PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 81 10.44 47.87 358.71 10.76 78.26 2.2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 54 6.53 29.96 224.51 6.74 48.98 1.

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0MISC. BPD SCF/HR COUNTTANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2015 YEAR TOTAL 60.10 275.72 2066.04 61.98 450.77 52

EXEMPTION 

CALCULATION DISTANCE FROM LAND IN MILES 236

71.0

Average 

Engine Load %

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 4 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO P

DRILLING PRIME MOVER>600hp diesel 61,200 2955.96 50% 35471.52 24 248 43.14 197.89 1482.82 44.48 323.52 64DP Semi-Submersible PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0

AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 106 10.44 47.87 358.71 10.76 78.26 32 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 71 6.53 29.96 224.51 6.74 48.98 1

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2016 YEAR TOTAL 60.10 275.72 2066.04 61.98 450.77 68

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 236

71.0

Average 

Engine Load %

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 5 of 11

EMISSIONS CALCULATIONS 3RD YEAR
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO P

DRILLING PRIME MOVER>600hp diesel 61,200 2955.96 50% 35471.52 24 248 43.14 197.89 1482.82 44.48 323.52 64DP Semi-Submersible PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.

AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 106 10.44 47.87 358.71 10.76 78.26 3.

2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 71 6.53 29.96 224.51 6.74 48.98 1.

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.

Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2017 YEAR TOTAL 60.10 275.72 2066.04 61.98 450.77 68

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 236

71.0

Average 

Engine Load %

EMISSIONS CALCULATIONS 4TH YEAR

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 6 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO P

DRILLING PRIME MOVER>600hp diesel 61,200 2955.96 50% 35471.52 24 248 43.14 197.89 1482.82 44.48 323.52 64DP Semi-Submersible PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0

AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 106 10.44 47.87 358.71 10.76 78.26 3

2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 71 6.53 29.96 224.51 6.74 48.98 1

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0

Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2018 YEAR TOTAL 60.10 275.72 2066.04 61.98 450.77 68

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 236

71.0

Average 

Engine 

Load %

EMISSIONS CALCULATION STH YEAR

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 7 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO P

DRILLING PRIME MOVER>600hp diesel 61,200 2955.96 50% 35471.52 24 16 43.14 197.89 1482.82 44.48 323.52 4DP Semi-Submersible PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0

AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 7 10.44 47.87 358.71 10.76 78.26 02 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 5 6.53 29.96 224.51 6.74 48.98 0

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0

MISC. BPD SCF/HR COUNT

TANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0

Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2019 YEAR TOTAL 60.10 275.72 2066.04 61.98 450.77 4

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 236

71.0

Average 

Engine 

Load %

EMISSIONS CALCULATIONS 6TH YEAR

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 8 of 11
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KK, KV Bridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 61,200 2955.96 50% 35471.52 24 190 43.14 197.89 1482.82 44.48 323.52 49.1DP Semi-Submersible PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.0BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0AUXILIARY EQUIP<600hp diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 81 10.44 47.87 358.71 10.76 78.26 2.52 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 54 6.53 29.96 224.51 6.74 48.98 1.0

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.0MISC. BPD SCF/HR COUNTTANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.0Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2020 YEAR TOTAL 60.10 275.72 2066.04 61.98 450.77 52.7

EXEMPTION 

CALCULATION DISTANCE FROM LAND IN MILES 2364

71.0

Average 

Engine Load 

%

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 9 of 11

EMISSIONS CALCULATIONS 9TH YEAR
COMPANY AREA BLOCK LEASE PLATFORM WELL CONTACT PHONE REMARKS

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 AT 18:CC, DD, GG, GV, QQ/AT 19:EE, KKBridget O'Farrell 832-636-1694 0

OPERATIONS EQUIPMENT RATING MAX. FUEL ACT. FUEL RUN TIME MAXIMUM POUNDS PER HOUR 

Diesel Engines HP GAL/HR GAL/D

Nat. Gas Engines HP SCF/HR SCF/D

Burners MMBTU/HR SCF/HR SCF/D HR/D DAYS PM SOx NOx VOC CO PM 

DRILLING PRIME MOVER>600hp diesel 61,200 2955.96 50% 35471.52 24 190 43.14 197.89 1482.82 44.48 323.52 49.18 DP Semi-Submersible PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

PRIME MOVER>600hp diesel 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

BURNER diesel 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

AUXILIARY EQUIP<600hp diese 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

3 trips/week VESSELS>600hp diesel(crew) 14805 715.0815 17161.96 6 81 10.44 47.87 358.71 10.76 78.26 2.55 2 trips/week VESSELS>600hp diesel(supply) 9266 447.5478 10741.15 6 54 6.53 29.96 224.51 6.74 48.98 1.06 

VESSELS>600hp diesel(tugs) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

FACILITY DERRICK BARGE diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 INSTALLATION MATERIAL TUG diesel 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 

VESSELS>600hp diesel(crew) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 VESSELS>600hp diesel(supply) 0 0 0.00 0 0 0.00 0.00 0.00 0.00 0.00 0.00 MISC. BPD SCF/HR COUNTTANK- 0 0 0 0.00 

Flowback After OIL BURN 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 Completion GAS FLARE 0 0.00 0.00 0.00 0.00 

2021 YEAR TOTAL 60.10 275.72 2066.04 61.98 450.77 52.79 

EXEMPTION 

CALCULATION

DISTANCE FROM LAND IN 

MILES 2364.30 

71.0

Average 

Engine 

Load %

EMISSIONS CALCULATIONS 10TH YEAR

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 10 of 11
SUMMARY

COMPANY AREA BLOCK LEASE PLATFORM WELL

Anadarko Petroleum Corporation AT 18/19 G33863/G32556 

AT 18:CGV, QQ/KK, KV

Emitted Substance

Year

 PM SOx NOx VOC 

2014 52.79 242.17 1814.60 54.44 3

2015 52.79 242.17 1814.60 54.44 3

2016 68.90 316.09 2368.54 71.06 5

2017 68.90 316.09 2368.54 71.06 5

2018 68.90 316.09 2368.54 71.06 5

2019 4.45 20.39 152.81 4.58 3

2020 52.79 242.17 1814.60 54.44 3

2021 52.79 242.17 1814.60 54.44 3

Allowable 2364.30 2364.30 2364.30 2364.30 58

FORM BOEM-0138 (December 2011 - Supersedes all previous versions of this form which may not be used). Page 11 of 11
 

SECTION H 

OIL SPILL INFORMATION 

(a) Oil Spill Response Planning 

(i) OSRP Information 

All the proposed activities and facilities in this EP are covered by the Regional Oil Spill 

Response Plan (OSRP) last approved on September 25, 2013 for Anadarko Petroleum 

Corporation and its subsidiaries, Anadarko US Offshore Corporation and Anadarko E&P 

Company L.P. (Company Numbers 00981, 02219 and 00148, respectively) in accordance with 

30 CFR Part 254. 

(ii) Spill Response Sites 

Primary Response Equipment Location(s) Preplanned Staging Location(s) 

Galveston, Texas 

Harvey, Louisiana 

Houma, Louisiana 

Lake Charles, Louisiana 

Leeville, Louisiana 

Venice, Louisiana 

Galveston, Texas 

Harvey, Louisiana 

Fourchon, Louisiana 

Cameron, Louisiana 

Leeville, Louisiana 

Venice, Louisiana 

(iii) OSRO Information 

Anadarko maintains a contract with Clean Gulf Associates (CGA) for spill response equipment. 

Various equipment locations are staged throughout the Gulf of Mexico. CGA equipment can be 

referenced on their website: http://www.cleangulfassoc.com/. Personnel would be obtained from 

the Marine Spill Response Corporation’s (MSRC) STARS network, including a supervisor to 

operate the equipment. 

In addition Anadarko has a contract with the Marine Spill Response Corporation (MSRC) for 

spill response equipment. MSRC stages equipment throughout the Gulf of Mexico and has 

recently completed a large expansion of its resources, with particular focus on deepwater. The expansion 

is known as “Deep Blue”. MSRC capabilities and a complete equipment listing are available online at: http://www.msrc.org/. 

Anadarko is a member of the Marine Well Containment Company (MWCC), which provides 

access to containment response capabilities and includes subsea dispersant injection equipment. 
 

(iv) Worst-Case Scenario Determination 

Category Regional OSRP EP EP 

Type of Activity Exploratory Exploratory Exploratory 

Facility Location (area/block) GC 683 AT 18 AT 19 

Facility Designation* Location G Location GV Location KV 

Distance to Nearest Shoreline 120 Miles 71 miles 71 miles 

 Storage Tanks (total) N/A N/A N/A 

 Flowlines (on facility) N/A N/A N/A 

 Pipelines N/A N/A N/A 

 Uncontrolled Blowout 410,000 bopd* 63,744 bopd 250,188 bopd 

Type of Oil(s) Crude Oil Crude Oil Crude Oil 

API Gravity 28.9o 21.9o 28.7o

* The volume recently denoted in the Regional OSRP (410,000 bopd) is higher than the NTL 2010-N06 (403,608 bopd) calculations 

associated with the GC 683, Location G and GG Supplemental EP. (Plan Control No: S-7623). Anadarko elected to denote a higher volume 

in the Regional OSRP for planning purposes to demonstrate equipment response capabilities per previous discussions with 

Mr. Mike Tolbert. 

Anadarko has determined that the worst-case scenario from the activities proposed in this Initial 

EP does not supersede the worst-case scenario for Green Canyon 683 as previously filed in the 

Regional OSRP. 

Since Anadarko has the capability to respond to the worst-case spill scenario included in our 

Regional OSRP, and since the worst-case scenarios determined for our EP does not replace the 

worst-case scenario in our Regional OSRP last approved on September 25, 2013, I hereby certify 

that Anadarko has the capability to respond, to the maximum extent practicable, to a worst-case 

discharge, or a substantial threat of such a discharge, resulting from the activities proposed in our 

EP. 

(b) Worst-Case Discharge Volume Assumptions 

Worst-case discharge (WCD) calculations and assumptions within this section utilized guidelines 

and requirements pursuant with NTL 2010-N06. Discussions regarding geologic information are 

considered proprietary and have been omitted from this public copy of the EP. 

(c) Oil Spill Response Discussion

For the purpose of NEPA analysis, the largest spill volume originating from the proposed 

activity in Atwater Valley 19 would be an uncontrolled blowout during drilling operations at 

250,188 barrels of crude oil with an API gravity of 28.7o

. A discussion of the blowout scenario 

from this proposed activity is included within this Initial EP in accordance with NTL 2010-N06. 
 

Land Segment and Resource Identification Modeling

Trajectory of a spill and the probability of its impacting a land segment have been projected 

utilizing information in the Oil Spill Risk Analysis Model (OSRAM) for the Central Gulf of 

Mexico. Additional information may be referenced in the “Oil-Spill Risk Analysis: Contingency 

Planning Statistics for Gulf of Mexico OCS Activities” (OCS Report MMS 2004-026), using the 

average conditional probability for 3, 10, and 30 day impacts. 

Atwater Valley 19 is located within Launch Area 60. According to the OSRAM, the trajectory 

indicates a 4% probability of potential impact to the shoreline in Plaquemines Parish, Louisiana. 

The results are shown in Table H-2. Plaquemines Parish is identified as the most probable 

potential impacted parish or county within the Gulf of Mexico for this operation. 

Response 

Anadarko will make every effort to respond to the worst-case discharge as effectively as 

possible. Response equipment available to respond to the worst-case discharge and the estimated 

time of a spill response from oil spill detection to equipment deployment on-site is included in 

Table H-3. The table estimates individual times needed for procurement, load out, travel time to 

the site and deployment. In the event of an actual incident equipment and times can vary. 

For the purpose of response scenario discussion, an uncontrolled blowout would be considered 

the largest potential spill volume at 250,188 barrels of crude oil. An ADIOS weathering model 

was run based on a similar type of oil expected to be produced from this well. Based on this 

information, approximately 12% (30,023 bbls) of the initial volume would be 

evaporated/dispersed within 24 hours. 

If approved and appropriate, 4 sorties (8,000 gallons) from the Basler aircraft and 8 sorties 

(9,600 gallons) from two DC-3 aircrafts could disperse approximately 7,540 barrels of oil. 

If the conditions are appropriate, and the necessary approvals and permits have been obtained, 

in-situ burning may be utilized. Based on in-situ burn operations during Deepwater Horizon, 

approximately 5% (11,008 bbls) of the worst case discharge volume after natural 

evaporation/dispersion after 24 hours could potentially be burned. 

Although unlikely in a spill lasting 30 days, potential shoreline impact in Plaquemines Parish, 

Louisiana could occur depending on environmental conditions (wind, currents and temperature) 

at the time of an incident. Nearshore response may include the use of shoreline boom on beach 

areas, or protection/sorbent boom on vegetated areas. Surveillance and real time trajectories 

would aide in determining the most appropriate strategies to respond to a spill. 

Table H.3 provides an example of offshore and nearshore equipment, response times, and 

personnel to respond to a spill of 220,165 bbls, which is the estimated amount that would remain 

considering natural evaporation/dispersion at 24 hours. This amount could be further reduced 

through the application of aerial and subsea dispersants, provided such applications were 

approved. 
 

Anadarko’s contingency plan for dealing with this worst-case discharge would be to activate 

its Spill Management Team and equipment resources as described in its Gulf of Mexico 

Regional Oil Spill Response Plan (OSRP) and provide continuous support for the duration of the 

event. Response resources are activated and supplemented according to need. These resources 

would remain engaged in the response until the incident is deemed complete or until released by 

Unified Command. 

Anadarko is a member of the Marine Well Containment Company (MWCC), which provides 

access to containment response capabilities and includes subsea dispersant injection equipment. 

In the event of a blowout, Anadarko may: 

 1. Evacuate personnel, if necessary. Deploy emergency responders in an effort to preserve 

human life, if necessary. 

 2. Assess the damage and attempt to stop the flow at the source, if safe to do so, to reduce 

the amount of oil discharged. 

 3. Notify agencies. 

 4. Assess the amount of oil that has been spilled and calculate additional potential of oil 

flow. A continuous aerial surveillance program would be used to assess the growth of the 

slick and the volume of oil on the water. Observations of the size of the slick on the 

water, combined with observations at the source, would be used to provide a constant 

update. Additional potential to release fuel from the remaining tanks onboard the 

appropriate DP drillship or DP semi-submersible drilling rig would be determined by 

marine surveyors. Operations and Unified Command would continue to assess the 

adequacy of response equipment capacities based on this continually updated mass 

balance. 

 5. Convene the Spill Management Team (SMT). Organize Unified Command and establish 

objectives and priorities. 

 6. Monitor the oil spill with aerial surveillance and obtain trajectories. If oil is seaward 

bound, going away from land, discuss additional strategies with Unified Command. 

 7. If oil is moving in the direction of a shoreline and weather conditions are favorable, 

request approval to utilize dispersants. 

 a. Prior to commencing application operations, conduct an on-site survey in consultation 

with natural resource specialists to determine if any threatened or endangered species 

are present in the projected application area or otherwise at risk from dispersant 

application. 
 

 b. Upon approval, mobilize one Basler aircraft and two DC-3 aircrafts from Houma if 

needed, with surveillance aircraft and spotter. Rotate aircraft, spraying the leading 

edge of the spill and working back to the source. Monitor/sample for effectiveness 

(USCG SMART Team). Truck additional dispersants from CGA or MSRC stockpile, 

if necessary. 

 c. Dispersants are most effective when applied as soon after discharge as possible, since 

weathering of the oil decreases dispersant effectiveness. The estimated window of 

opportunity for most effective use of dispersants is within 48-72 hours post-release. 

The oil may still be dispersible after 72 hours on the water surface, but the 

effectiveness of dispersant use would likely be diminished after the oil has been on the 

water for more than three days. Ultimately, the USCG SMART monitoring protocol 

will be used to determine whether or not dispersant operations are effective. 

 d. Once the CGA HOSS barge is on location and in the skimming mode, dispersants 

would only be used if required and approved. 

 8. Deploy offshore mechanical oil containment and recovery equipment. Attempt to recover 

as much oil at sea as possible, utilizing: 

 a. The CGA HOSS barge, will be positioned in a stationary mode, will be situated downwind and down-current from location for long-duration, high-volume skimming. 

Based on average travel times, the HOSS barge could be on location within 

approximately 51 hours of the release. The de-rated skimming capacity of the HOSS 

barge is 43,000 bbls per day. However, only the oil encountered by a skimmer can be 

recovered. In order to maximize oil encounter rate, boom will be deployed in a 

V-configuration in front of the HOSS barge to funnel oil to the skimmers. If 

necessary, temporary barges can be activated to support continuous skimming 

operations. (These barges arrive on-site at approximately the same time as the HOSS 

barge.) For an on-going release, multiple barges are deployed to provide for 

continuous off-loading of skimmer storage vessels and shuttling of recovered oil to an 

onshore waste handling facility. Sufficient barges are available to provide enough 

temporary storage for continuous recovery operations. 

 b. CGA’s Fast Response Units (FRU) could arrive on-scene between approximately 

13.75-28.5 hours of the initial release. These skimmers operate downstream of the 

HOSS barge and are used to recover pockets and streamers of oil that may move past 

the large stationary skimmer. FRUs have approximately 200 barrels of on-board 

storage. Approval will be requested to decant water after gravity separation, through a 

hose forward of the skimmer, to optimize temporary storage capacity. Auto boom will 

be utilized to concentrate oil so that it is thick enough to be skimmed. 
 

 9. Dispersants, Fast Response Units (FRU), Oil Spill Response Vessels (OSRV or R/V) 

would typically work daylight hours only. The HOSS barge can operate continuously, 

including night operations. Available technology will be considered such as remote 

sensing devices that will enable 24 hour surveillance, trajectories, and planning. All 

response vessels are designed to be able to remain offshore continuously throughout the 

response. Even if sea conditions prohibit effective skimming, these resources would 

remain offshore until skimming operations could be commenced again. Safety would 

remain the first priority. 

 10. Prepare site-specific Waste Management Plan, Site Safety Plan, Decontamination Plans, 

Communications and Medical Plans. 

 11. If oil becomes a threat to any shoreline, data from the aerial surveillance, weather reports, 

and trajectories would be used to direct onshore teams to deploy protection/containment 

boom with reference to Area Contingency Plans and in coordination with State and 

Federal On-Scene Coordinators. 

 a. Implement pre-designated strategies. 

 b. Identify resources at risk in spill vicinity. 

 c. Develop/implement appropriate protection tactics. 

 12. Establish site-specific Wildlife Rescue and Rehabilitation Plan. 

The following types of additional support may be required for a blowout lasting 120 days. 

 Additional Oil Spill Removal Organization (OSRO) personnel to relieve equipment 

operators 

 Vessels for supporting offshore operations 

 Field safety personnel 

 Continued surveillance and monitoring of oil movement 

 Helicopter, video cameras 

 Infra red (night time spill tracking) capabilities, X-band radar 

 Barge to transport recovered oil from offshore skimming system, and temporary 

storage barges to onshore disposal sites that are identified in Area Contingency Plans 

(ACP) 

 Logistics needed to support equipment: 

- Staging areas 

- Parts, trailers, and mechanics to maintain skimmers and boom 

- Fueling facilities 

- Decontamination stations 

- Dispersant stockpile transported from Houston to Houma or other potential 

command post locations 

- Communications equipment and technicians 
 

 Logistics needed to support responder personnel 

- Medical aid stations 

- Safety personnel

- Food 

- Berthing 

- Additional clothing/safety supplies 

- Decontamination stations 

Anadarko has the capability to respond and contain, to the maximum extent practicable as 

defined in 30 CFR 254.6 and 30 CFR 250.26(d)(1), to the estimated worst case discharge (WCD) 

associated with the proposed activity within 30 days. Deployment time for surface containment 

equipment is subject to availability and location, weather conditions, potential security zones 

around the spill site, and site/well specific assessment data. Personnel safety is always first and 

foremost. Refer to further details on equipment and timing provided in Section H–Oil Spill 

Information and Table H-3 of the EP. 

The potential WCD will be further evaluated during the Application for Permit to Drill (APD) 

process, including the Well Containment Screening Tool (WCST) and associated subsea 

containment plan for enhanced planning purposes. 

There will be no new or unusual technology deployed that has not been previously deployed for 

Gulf of Mexico oil spill prevention, control, and/or cleanup. 
 

Table H-1 

Worst Case Discharge Calculation 

(Based on an Uncontrolled Blowout)

Calculations for an Uncontrolled Blowout: Block 19 

 i. Type of Oil (crude, condensate, diesel) Crude Oil 

 ii. API Gravity 28.7 ̊

 iii. EP Location Used for NTL 2010-N06 WCD for AT 19 Location KV 

 iv. Largest Anticipated WCD Rate during blowout 250,188 bbls 

 v. WCD Total for Drilling Operations for AT 19 (> 10 miles from shore): 250,188 bbls 
 

Table H-2 

Trajectory by Land Segment 

Following are the average conditional probabilities (expressed as percent chance) that an oil spill starting at a 

particular launch area will contact a land segment as included in the Oil Spill Risk Analysis Model (OSRAM) for 

the Central Gulf of Mexico. This information can be found on the BOEM website using 3/10/30 day potential 

impact, as applicable. The results are listed below. 

Area/Block/ 

Location OCS-G Launch Area Land Segment and/or Resource 

Conditional Probability (%) 

3 

days 

10 

days 

30 

days 

Atwater Valley 19, 

Location KV 

Drilling 

(71 miles from 

shore) 

G 32556 Launch 

Area 60 

Central 

Planning 

Area 

Galveston County, TX 

Jefferson County, TX 

Cameron Parish, LA 

Vermilion Parish, LA 

Terrebonne Parish, LA 

Lafourche Parish, LA 

Plaquemines Parish, LA 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

1 

1 

1 

2 

1 

2 

1 

4 
Table H-3 

WCD Scenario Drilling Activities – Based on an uncontrolled blowout (71 miles from shore) Atwater Valley 19, Location KV 250,188 bbls of crude (initial volume) 220,165 bbls (after evaporation/dispersion) API Gravity 28.7o 

Offshore Equipment from Spill Detection to Equipment Deployment Response Time: Atwater Valley 19, Loca

Offshore Equipment 

Owner/Location Initial Staging 

Hours to 

Staging 

Area 

Time to 

Procure 

(1) 

Time 

to 

Load Out 

(2) 

Tra

Tim

(Stag

Spi

(3

Type 

Derated 

Capacity 

(bbls) 

Storage 

(bbls) 

No. of 

Units/ 

Persons 

Basler Spray Aircraft DC 3 Spray Aircraft Aero Commander 

-- -- 

-- -- 

1 2 2 

ASI/Houma Houma 

0 0 1 1 1 1.

HOSS Barge Operators Tugs 

43,000 4,000 1 

8 3 

CGA/Harvey STARS VOO 

Harvey 

1 2 4 4 0 46 

Texas Responder Transrec 350 + OSRV 4,620' 44" Sea Sentry Boom 3,300' 67" LAMOR 

10,567 4,000 1 

1 

14 crew MSRC/Galveston Galveston 

0 2 2 2 2 0 9.2

Gulf Coast Responder Transrec 350 + OSRV 5,280' 44" Sea Sentry Boom 2,640' 67" LAMOR 

10,567 4,000 1 

1 

14 crew MSRC/Lake Charles Lake Charles 

0 2 2 2 2 0 14.

Deep Blue Responder LFF 100 Brush + OSRV 6,600' 44" Sea Sentry Boom 660' 67" LAMOR 

18,086 4,000 1 

1 

14 crew MSRC/Fourchon Fourchon 

0 2 2 2 2 0 19

FRU Operators Utility Boat 

4,251 200 1 

6 1 

CGA/Ingleside STARS VOO 

Ingleside 

0 2 2 1 2 12.

FRU Operators Utility Boat 

4,251 200 1 

6 1 

CGA/Galveston STARS VOO 

Galveston 

0 2 2 1 2 9.7

FRU Operators Utility Boat 

4,251 200 1 

6 1 

CGA/Lake Charles STARS VOO 

Cameron 

.5 

2 2 1 2 15.

FRU Operators Utility Boat 

4,251 200 1 

6 1 

CGA/Morgan City STARS VOO 

Morgan City 

.5 

2 2 1 2 17 

FRU Operators Utility Boat 

8,502 400 2 

12 

2 

CGA/Leeville STARS VOO 

Leeville 

0 2 2 1 2 20 

FRU Operators Utility Boat 

8,502 400 2 

12 

2 

CGA/Venice STARS VOO 

Venice 

.5 

2 2 1 2 24

Spill Team Area Responders (STARS) called out by Marine Spill Response Corporation (MSRC) Vessel of Opportunity=VOO EMS=Enterprise Marine Services
Offshore Equipment, cont. 

Owner/Location Initial Staging 

Hours to 

Staging 

Area 

Time to 

Procure 

(1) 

Time 

to 

Load Out 

(2) 

Trav

Tim

(Stagi

Spil

(3) 

Type 

Derated 

Capacity 

(bbls) 

Storage 

(bbls) 

No. of 

Units/ 

Persons 

FRU Operators Utility Boat 

4,251 100 1 

6 1 

CGA/Harvey STARS VOO 

Harvey 

.5 

2 2 1 2 22 

Koseq Skimming Arms,1 set Vessel w/ storage/hull 

17,830 

10,000 

2 1 

CGA/Galveston VOO Galveston 0 2 1 12 9.75 

MSRC 570 Offshore Barge Tugs 2 Crucial Disk 88/30 2,640' 44" Sea Sentry II Boom 

22,244 56,900 1 

3 1 

6 crew 

MSRC/Galveston VOO 

Galveston 0 

2 2 2 2 0 17.2

CTCo2603 Operators Tug 

-- 25,000 1 

6 1 

EMS/Amelia STARS VOO 

Amelia 

0 2 4 4 0 37 

CTCo2604 Operators Tug 

-- 20,000 1 

6 1 

EMS/Amelia STARS VOO 

Amelia 

0 2 4 4 0 37 

CTCo2605 Operators Tug 

-- 20,000 1 

6 1 

EMS/Amelia STARS VOO 

Amelia 

0 2 4 4 0 37 

CTCo 5001 Operators Tug 

-- 45,000 1 

6 1 

EMS/Amelia STARS VOO 

Amelia 

0 2 4 4 0 37 

10,000' 42" Auto Boom VOO 

-- -- 20 

10 crew 

CGA/Harvey STARS Harvey .5 2 1 2 22 

5,000' 42" Auto Boom VOO 

-- -- 20 

10 crew 

CGA/Lake Charles STARS Cameron .5 2 1 2 15.7

5,000' 42" Auto Boom VOO 

-- -- 20 

10 crew 

CGA/Galveston STARS Galveston 0 2 1 2 9.75 

2,500' 42" Auto Boom VOO 

-- -- 12 

6 crew 

CGA/Ingleside STARS Ingleside 0 2 1 2 12.7

2,500' 42" Auto Boom VOO 

-- -- 12 

6 crew 

CGA/Pascagoula STARS Pascagoula 0 2 1 2 27.7

22,400' 42" Boom VOO 

-- -- 80 

25 crew AMPOL/New Iberia New Iberia 0 2 1 2 16.5 

4,800' 42" Boom VOO 

-- -- 18 

9 crew AMPOL/Harvey Harvey 0 2 1 2 22 

Spotter Helo Surveillance Helo Hand Held Radios 

-- -- -- 

-- -- -- 

1 1 

30 

PHI/Galveston PHI/Galveston STARS 

Spill Site Spill Site Galveston 

1 1 

1.5 

1 1 

1.5 

-- -- -- 

1.5 1.5 

3 

Total 160,553 194,600 
Nearshore Equipment from Spill Detection to Equipment Deployment Response Time: Atwater Valley 19, Loca

Nearshore Equipment* 

Owner/Location Initial Staging 

Hours to 

Staging 

Area 

Time to 

Procure 

(1) 

Time 

to 

Load Out 

(2) 

Trave

Time 

(Stagin

Spill) 

(3) 

Type 

Derated 

Capacity 

(bbls) 

Storage 

(bbls) 

No. of 

Units/ 

Persons 

Basler Spray Aircraft DC 3 Spray Aircraft Aero Commander 

-- -- 1 

2 2 

ASI/Houma Houma 

0 0 1 1 1 1.5 

Trinity SWS Operators 

21,500 249 1 

4 

CGA/Galveston STARS Galveston 0 2 1 2 9.25 

SWS Egmopol Operators 

3,000 100 1 

3 

CGA/Galveston STARS Galveston 0 2 1 2 4.5 

SWS Egmopol Operators 

3,000 100 1 

3 

CGA/Morgan City STARS Morgan City .5 2 1 2 8 

SWS Marco Operators 

3,588 34 1 

3 

CGA/Venice STARS Venice .5 2 1 2 9.5 

SWS Marco Operators 

3,588 34 1 

3 

CGA/Leeville STARS Leeville .5 2 1 2 8.5 

SWS Marco Operators 

3,588 20 1 

3 

CGA/Lake Charles STARS Cameron .5 2 1 2 6 

R/V Grand Bay Operators 

5,000 65 1 

3 

CGA/Venice STARS Venice .5 2 2 .5 4.75 

R/V RW Armstrong Operators 

5,000 65 1 

3 

CGA/Leeville STARS Leeville .5 2 2 .5 12.75 

R/V Bastian Bay Operators 

5,000 65 1 

3 

CGA/Lake Charles STARS Cameron .5 2 2 .5 10.25 

R/V Timbalier Bay Operators 

5,000 65 1 

3 

CGA/Galveston STARS Galveston 0 2 2 .5 6 

CTCo 2606 Operators Tugs 

-- 20,000 1 

6 1 

EMS/Amelia Amelia 

0 2 4 4 0 20 

CTCo 2607 Operators Tugs 

-- 23,000 1 

6 1 

EMS/Amelia Amelia 

0 2 4 4 0 20 

CTCo 2608 Operators Tugs 

-- 23,000 1 

6 1 

EMS/Amelia Amelia 

0 2 4 4 0 20 

CTCo 2609 Operators Tugs 

-- 23,000 1 

6 1 

EMS/Amelia Amelia 

0 2 4 4 0 20 

2,000' Beach Boom -- -- 6 CGA/Galveston Galveston 0 1 2 1.5 1,000' Beach Boom -- -- 4 CGA/Ingleside Ingleside 0 1 2 3 2,000' Beach Boom -- -- 6 CGA/Pascagoula Pascagoula 0 1 2 4 
Nearshore Equipment, cont. 

Owner/Location Initial Staging 

Hours to 

Staging 

Area 

Time to 

Procure 

(1) 

Time 

to 

Load Out 

(2) 

Trave

Time 

(Stagin

Spill) 

(3) 

Type 

Derated 

Capacity 

(bbls) 

Storage 

(bbls) 

No. of 

Units/ 

Persons 

10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/New Iberia New Iberia 0 2 1 1 7 

10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/Houston Houston 1 2 1 1 2.5 

10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/Port Arthur Port Arthur 0 2 1 1 2.5 

10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/Houma Fourchon .5 2 1 1 6 

10,000' 18" Boom VOO 

-- -- 10 

4 crew Oil Mop/Port Allen Port Allen 0 2 1 1 6.25 

20,000' 18" Boom VOO 

-- -- 20 

8 crew Oil Mop/Belle Chasse Venice .5 2 1 1 7 

15,000' 18" Boom VOO 

-- -- 14 

6 crew Oil Mop/Gretna Gretna 0 2 1 1 8 

Wildlife Support Trailer -- -- 1/ 2 crew CGA/Harvey Harvey .5 1 2 1.5 Bird Scare Cannons -- -- 2 CGA/Venice Venice .5 1 2 2 Bird Scare Cannons -- -- 1 CGA/Galveston Galveston 0 1 2 1 Bird Scare Cannons -- -- 1 CGA/Ingleside Ingleside 0 1 2 2.5 Bird Scare Cannons -- -- 2 CGA/Harvey Harvey .5 1 2 1.5 Bird Scare Cannons -- -- 2 CGA/Lake Charles Cameron .5 1 2 3.5 Bird Scare Cannons -- -- 2 CGA/Pascagoula Pascagoula 0 1 2 4.5 Spotter Helo Surveillance Helo Hand Held Radios 

-- -- -- 

-- -- -- 

1 1 

30 

PHI/Galveston PHI/Galveston STARS 

Spill Site Spill Site Galveston 

1 1 

1.5 

1 1 

1.5 

-- -- -- 

1.5 1.5 

3 

Total 58,264 89,797 

*Some equipment may be used offshore up to approximately 25 miles from shore 
 

H-3 (continued) 

Operational Limitations of Response Equipment 

 HOSS Barge–8 foot seas 

 Fast Response Unit (FRU)–8 foot seas 

 Oil Spill Response Vessel (OSRV and R/V)–4 foot seas 

 Boom–3 foot seas, 20 knot winds 

 Dispersants–winds more than 25 knots, visibility less than 3 nautical miles or ceiling less than 

1,000 feet 
 

SECTION I 

Environmental Monitoring and Environmental Mitigation Measures 

(a) Monitoring 

If required, Anadarko will monitor loop currents per NTL 2009-G02. 

Anadarko subscribes to Wilkins Weather Service which provides real-time weather 

conditions such as tropical depressions, storms and/or hurricanes entering the Gulf of 

Mexico. 

Additional measures to avoid, minimize, and mitigate environmental impacts is included 

in Section N–Environmental Impact Analysis. 

(b) Incidental Takes 

Although marine mammals may be seen in the area, Anadarko does not believe that its 

operations proposed under this EP will result in the harassment, capture, collection or 

killing of any mammals covered by the Marine Mammal Protection Act. 

Anadarko will operate in accordance with applicable regulations in order to avoid or 

minimize incidental takes of marine mammals and other species, including: 

 Joint NTL 2012-G02 “Implementation of Seismic Survey Mitigation Measures 

and Protected Species Observer Program” 

 BSEE NTL 2012-G01 “Marine Trash and Debris Awareness and Elimination”, 

and 

 Joint NTL 2012-G01 “Vessel Strike Avoidance and Injured/Dead Protected 

Species Reporting” 
 

SECTION J 

LEASE STIPULATIONS INFORMATION 

Stipulation No.8–Protected Species (Lease Sale 213-AT 18, Lease Sale 206-AT 19) 

This stipulation is meant to reduce the potential taking of federally protected species. The 

stipulation requires seismic surveys employ mitigation measures including the use of a 

500 meter “exclusion zone”. 

Anadarko will operate in accordance with Joint NTL 2012-G01 to minimize the risk of 

vessel strikes to protected species and will report observations of injured or dead 

protected species. Anadarko will operate in accordance with BSEE NTL 2012-G01 to 

prevent intentional and/or accidental introduction of debris into the marine environment. 
 

SECTION K 

Support Vessels and Aircraft Information 

(a) General 

Type Max. Total Fuel 

Tank Storage 

Capacity 

Max. No. in Area 

at any Time 

Trip Frequency or 

Duration 

Supply Vessel 336,227 gallons 1 2 trips/week 

Helicopter 735.3 gallons 1 10 trips/week 

Crew Vessel 50,000 gallons 1 3 trips/week 

Tug Boats 218,300 gallons 1-2 Duration of operation 

Anchor Handling Vessel 450,698 gallons 1-2 Duration of operation 

(b) Diesel Oil Supply Vessels 

Fuel for the rig will be transported via a supply vessel as follows: 

a. Size of fuel supply vessel: 230 feet 

b. Carrying capacity of fuel supply vessel: 336,227 gallons 

c. Frequency that fuel supply vessel will visit the 

facilities: once per week 

d. Routes the fuel supply vessel will use to travel 

between the onshore support base and proposed 

facility: 

6 miles from Port Fourchon to the mouth 

of Bayou Lafourche, then approximately 

71 miles to AT 18/19. 

(c) Drilling Fluids Transportation 

The following estimates were prepared utilizing Anadarko’s experience with similar drilling 

operations. Estimated quantities are reflected in the table below.

Type of Material Quantity Being Transported Transportation Method 

Water-based drilling fluid 

(NaCl saturated, seawater, 

freshwater, barite) for Pump 

and Dump 

13 gallon tote tanks (liquids) 

40-63 sacks on pallet (sack 

chemicals)* 

Supply boat 

Synthetic-based drilling fluid 

(internal olefin, ester) 

13 gallon tote tanks (liquids) 

40-63 sacks on pallet (sack 

chemicals)** 

Supply boat 

Oil-based drilling fluid N/A N/A 

* Estimate 19,000 bbls/well 

** Estimate 18,500 bbls/well 

Note: The estimated amount of tote tanks and size of sacks may vary during drilling operations. 
 

(d) Solid and Liquid Wastes Transportation 

Type of 

Waste 

Composition Total 

Projected 

Amount 

Rate Transport 

Method 

Name/Location of 

Facility 

Disposal 

Method 

Syntheticbased drilling 

fluid or muds 

Synthetic-based 

drilling muds 

148,000 bbls 

total 

18,500 bbls/well Re-use 

and/or 

transport to 

shore in 

DOT 

approved 

containers. 

Waste - Port Fourchon, 

LA and on to Newpark 

Fourchon Transfer Station 

#1 & #2. Newpark 

Transfer Station Morgan 

City. Newpark Transfer 

Station Port Arthur. USLL 

Galveston and Fourchon 

Transfer Station. If 

recycled, returned to 

vendor (Bariod or MI). 

Re-used and/or 

recycled; if can’t 

be reused and/or 

recycled the 

waste is disposed 

of at Newpark 

(injection 

disposal facility) 

or USLL 

(landfarm). 

Cuttings 

wetted with 

syntheticbased muds 

Cuttings coated 

with synthetic 

drilling muds, 

including 

drilled out 

cement 

800-1,600 

bbls total 

100-200 

bbls/well* 

*An estimated 

5-10% of 

cuttings may be 

transported to 

shore 

Re-use 

and/or 

transport to 

shore in 

DOT 

approved 

containers. 

Waste - Port Fourchon, 

LA and on to Newpark 

Fourchon Transfer Station 

#1 & #2. Newpark 

Transfer Station Morgan 

City. Newpark Transfer 

Station Port Arthur. USLL 

Galveston and Fourchon 

Transfer Station. If 

recycled, returned to 

vendor (Bariod or MI). 

Re-used and/or 

recycled; if can’t 

be reused and/or 

recycled the 

waste is disposed 

of at Newpark 

(injection 

disposal facility) 

or USLL 

(landfarm). 

Chemical 

product waste 

(well 

treatment 

fluids) 

Ethylene glycol 

Methanol 

5,700 bbls 

total 

1,425 bbls 

total 

100 

bbls/month/well 

25 

bbls/month/well 

Transport to 

shore in 

DOT 

approved 

containers 

for pick up 

Chemwaste in Sulphur, 

LA and Veolia Port 

Arthur, TX or to Newpark, 

Port Arthur as nonhazardous waste. 

Can be returned 

to vendor and/or 

used at another 

facility; MEG is 

solidified and 

disposed of in a 

landfill. 

Methanol is 

incinerated or 

used for fuels 

blending. 

Completion 

fluids 

Brine, spent 

acid, prop sand, 

debris 

24,000 bbls 

total 

3,000 bbls/well Transport to 

shore in 

DOT 

approved 

containers 

and/or vessel 

tanks for 

pick up. 

Sent to Port Fourchon, LA 

and on to Newpark 

Fourchon Transfer Station 

#1 & #2. Newpark 

Transfer Station Morgan 

City. Newpark Transfer 

Station Port Arthur. USLL 

Galveston and Fourchon 

Transfer Station 

Unused brine can 

be returned to 

vendor and/or 

stored for use on 

another job. 

Used brine and 

spent acid is 

transferred to 

Newpark's 

Processing & 

Transfer facility 

for injection. 

Workover 

fluids 

Brine, spent 

acid, prop sand, 

debris 

24,000 bbls 

total 

3,000 bbls/well Transport to 

shore in 

DOT 

approved 

containers, 

and/or vessel 

tanks for 

pick up. 

Sent to Port Fourchon, LA 

and on to Newpark 

Fourchon Transfer Station 

#1 & #2. Newpark 

Transfer Station Morgan 

City. Newpark Transfer 

Station Port Arthur. USLL 

Galveston and Fourchon 

Transfer Station 

Unused brine can 

be returned to 

vendor and/or 

stored for use on 

another job. 

Used brine and 

spent acid is 

transferred to 

Newpark's 

Processing & 

Transfer facility 

for injection. 
 

Trash and 

debris 

Refuse 

generated 

during 

operations 

2,850 bbls 

total 

50 

bbls/month/well 

Transport to 

shore in 

disposal 

bags by 

vessel to 

shorebase 

for pickup 

by municipal 

operations. 

Recycled Material in 

ARC, New Iberia, LA. 

Trash disposed of at 

SWDI landfill. 

Recycled and/or 

disposed in 

landfill. 

Used oil Excess oil from 

engines 

6,128 bbls 

total 

430 bbls/120 

days/well 

Transport in 

DOT 

approved 

containers to 

shore for 

pick up. 

American Recovery 

Fourchon, LA 

Recycled 

*Total projected amount assumes 8 wells at 190 days/well 

**Rate per day is an estimated max.average and may vary during drilling operational phases. The total 

amount is rounded to nearest whole number. 

(e) Vicinity Map 

A vicinity map is included in this section as Attachment K-1. 
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan

Figure 1. Location of Atwater Valley Blocks 18 and 19. 
 

SECTION L 

ONSHORE SUPPORT FACILITIES INFORMATION

(a) General 

Per NTL 2008-G04, extended by NTL 2014-G03, the following tables reflect the onshore 

facilities Anadarko will utilize to provide supplies and service support for the activities 

proposed in this Exploration Plan. 

 

Name Primary Location Existing/New/Modified 

Anadarko Service Base Fourchon, LA Existing 

Name *Alternate Locations Existing/New/Modified 

Anadarko Service Base Galveston, TX Existing 

Anadarko Service Base Cameron, LA Existing 

Anadarko Service Base Lake Charles, LA Existing 

Anadarko Service Base Houma, LA Existing 

Anadarko Service Base Pascagoula, MS Existing 

*In the unlikely event Anadarko’s primary service base cannot be utilized Anadarko will exercise the 

use of an alternate service base during drilling and/or completion operations. 

(b) Support Base Construction or Expansion 

No onshore support base construction or expansion is planned for these activities. 

Therefore dredging or filling activities associated with construction or expansion of 

facilities will not be applicable. 

(c) Support Base Construction or Expansion Timetable 

Since no onshore support base construction or expansion is planned for these activities, a 

timetable for land acquisition and construction or expansion is not applicable. 

(d) Waste Disposal 

Disposed wastes describe those wastes generated by the proposed activity that are 

disposed of by means other than by release into the water of the GOM at the site where 

they are generated. These wastes can be disposed of by offsite release, injection, 

encapsulation, or placement at either onshore or offshore permitted locations for the 

purposes of returning them back to the environment. 
 

Type of 

Waste 

Composition Total 

Projected 

Amount 

Rate Transport 

Method 

Name/Location of 

Facility 

Disposal 

Method 

Syntheticbased drilling 

fluid or muds 

Synthetic-based 

drilling muds 

148,000 bbls 

total 

18,500 

bbls/well 

Re-use 

and/or 

transport to 

shore in 

DOT 

approved 

containers. 

Waste - Port Fourchon, LA 

and on to Newpark 

Fourchon Transfer Station 

#1 & #2. Newpark 

Transfer Station Morgan 

City. Newpark Transfer 

Station Port Arthur. USLL 

Galveston and Fourchon 

Transfer Station. If 

recycled, returned to 

vendor (Bariod or MI). 

Re-used and/or 

recycled; if can’t 

be reused and/or 

recycled the 

waste is disposed 

of at Newpark 

(injection 

disposal facility) 

or USLL 

(landfarm). 

Cuttings 

wetted with 

syntheticbased muds 

Cuttings coated 

with synthetic 

drilling muds, 

including drilled 

out cement 

800-1,600 

bbls total 

100-200 

bbls/well* 

*An estimated 

5-10% of 

cuttings may be 

transported to 

shore 

Re-use 

and/or 

transport to 

shore in 

DOT 

approved 

containers. 

Waste - Port Fourchon, LA 

and on to Newpark 

Fourchon Transfer Station 

#1 & #2. Newpark 

Transfer Station Morgan 

City. Newpark Transfer 

Station Port Arthur. USLL 

Galveston and Fourchon 

Transfer Station. If 

recycled, returned to 

vendor (Bariod or MI). 

Re-used and/or 

recycled; if can’t 

be reused and/or 

recycled the 

waste is disposed 

of at Newpark 

(injection 

disposal facility) 

or USLL 

(landfarm). 

Chemical 

product waste 

(well 

treatment 

fluids) 

Ethylene glycol 

Methanol 

5,700 bbls 

total 

1,425 bbls 

total 

100 

bbls/month/well 

25 

bbls/month/well 

Transport to 

shore in 

DOT 

approved 

containers 

for pick up. 

Chemwaste in Sulphur, LA 

and Veolia Port Arthur, 

TX or to Newpark, Port 

Arthur as non-hazardous 

waste. 

Can be returned 

to vendor and/or 

used at another 

facility; MEG is 

solidified and 

disposed of in a 

landfill. 

Methanol is 

incinerated or 

used for fuels 

blending. 

Completion 

fluids 

Brine, spent 

acid, prop sand, 

debris 

24,000 bbls 

total 

3,000 bbls/well Transport to 

shore in 

DOT 

approved 

containers 

and/or vessel 

tanks for 

pick up. 

Sent to Port Fourchon, LA 

and on to Newpark 

Fourchon Transfer Station 

#1 & #2. Newpark 

Transfer Station Morgan 

City. Newpark Transfer 

Station Port Arthur. USLL 

Galveston and Fourchon 

Transfer Station. 

Unused brine can 

be returned to 

vendor and/or 

stored for use on 

another job. Used 

brine and spent 

acid is 

transferred to 

Newpark's 

Processing & 

Transfer facility 

for injection. 

Workover 

fluids 

Brine, spent 

acid, prop sand, 

debris 

24,000 bbls 

total 

3,000 bbls/well Transport to 

shore in 

DOT 

approved 

containers 

and/or vessel 

tanks for 

pick up. 

Sent to Port Fourchon, LA 

and on to Newpark 

Fourchon Transfer Station 

#1 & #2. Newpark 

Transfer Station Morgan 

City. Newpark Transfer 

Station Port Arthur. USLL 

Galveston and Fourchon 

Transfer Station. 

Unused brine can 

be returned to 

vendor and/or 

stored for use on 

another job. Used 

brine and spent 

acid is 

transferred to 

Newpark's 

Processing & 

Transfer facility 

for injection. 
 

Trash and 

debris 

Refuse 

generated during 

operations 

2,850 bbls 

total 

50 

bbls/month/well 

Transport to 

shore in 

disposal 

bags by 

vessel to 

shorebase 

for pickup 

by municipal 

operations. 

Recycled Material in ARC, 

New Iberia, LA. Trash 

disposed of at SWDI 

landfill. 

Recycled and/or 

disposed in 

landfill. 

Used oil Excess oil from 

engines 

6,128 bbls 

total 

430 bbls/120 

days/well 

Transport in 

DOT 

approved 

containers to 

shore for 

pick up. 

American Recovery 

Fourchon, LA 

Recycled 

*Total projected amount assumes 8 wells at 190 days/well 

**Rate per day is an estimated max.average and may vary during drilling operational phases. The total 

amount is rounded to nearest whole number. 
 

SECTION M 

COASTAL ZONE MANAGEMENT ACT INFORMATION 

Alabama and Florida are not affected states. 
 

Texas 

The following is an evaluation that includes findings relating the coastal effects of the 

proposed activities and associated facilities to the relevant enforceable policies of the 

Texas’ Coastal Management Program (TCMP), Title 31, Part 16, Chapter 501, 

Subchapter B:

(Category 2) 

Construction, Operation & Maintenance of Oil & Gas Exploration & Production 

Facilities 

No operations are proposed in or near any critical areas. The proposed activities are 

explorative in nature, so no facility construction is proposed. The proposed activities are 

located approximately 350 miles from the Texas shoreline; therefore we expect no 

adverse impacts to CNRAs or beach access and use rights of the public. All activities 

shall be conducted in a manner that minimizes significant impacts to coastal resources. 

No adverse effects to Texas’ coastal area are expected in association with the proposed 

activities. 

(Category 3) 

Discharges of Wastewater and Disposal of Waste from Oil and Gas Exploration and 

Production Activities 

No discharge of wastewater or disposal of waste from the proposed activities will occur 

in the Texas’ coastal zone; therefore no impact to Texas’ coastal waters is expected. 

(Category 4) 

Construction and Operation of Solid Waste Treatment, Storage, and Disposal 

Facilities 

No construction of solid waste facilities or expansion of existing facilities in the coastal 

zone are proposed in the attached plan, therefore, no adverse effects on any features of 

Texas’ coastal cone are expected. 

(Category 5) 

Prevention, Response, and Remediation of Oil Spills 

The proposed activities will be covered under the Regional Oil Spill Response Plan. The 

plan is in place, practiced, and updated as necessary. The best practical techniques shall 

be utilized to prevent the release of pollutants or toxic substances into the environment. 

All involved vessels and facilities are designed to be capable of prompt response and 

adequate removal of accidental discharges of oil. In addition, the proposed activities are 

350 miles from shore; therefore no damages to natural resources are expected as the 

result of an unauthorized discharge of oil into coastal waters. 
 

(Category 6) 

Discharge of Municipal and Industrial Waste Water to Coastal Waters 

No discharges from the proposed activities will occur in coastal waters. The proposed 

activities are 350 miles from shore; therefore there will be no effect on coastal waters. 

(Category 8) 

Development in Critical Areas 

None of the proposed activities will occur in a critical area; therefore no effects to Texas’ 

coastal zone are expected. The activity will not jeopardize the continued existence of 

species listed as endangered or threatened, and will not result in likelihood of the 

destruction or adverse modification of a habitat determined to be a critical habitat under 

the Endangered Species Act. The activity will not cause or contribute to violation of any 

applicable surface water quality standards. The activity will not violate any requirement 

imposed to protect a marine sanctuary. 

(Category 9) 

Construction of Waterfront Facilities and Other Structures on Submerged lands 

No waterfront facilities or other structures are proposed on submerged lands in the Texas 

coastal zone, therefore the proposed activities are not expected to have any adverse 

impacts on submerged lands. 

(Category 10) 

Dredging and Dredged Material Disposal and Placement 

No dredging or disposal/placement of dredged material is proposed; therefore no adverse 

effects to coastal waters, submerged lands, critical areas, coastal shore areas, or Gulf 

beaches are expected. 

(Category 11) 

Construction in the Beach / Dune System 

The proposed activities do not include any construction projects in critical dune areas or 

areas adjacent to or on Gulf beaches, therefore, no impact to Texas’ beach or dune 

systems are expected. 

(Category 15) 

Alteration of Coastal Historic Areas 

The proposed activities do not include any alteration or disturbance of a coastal historic 

area; therefore, no impacts are expected to adversely affect any historical, architectural, 

or archaeological site in Texas’ coastal zone. 
 

(Category 16) 

Transportation 

The proposed activities do not include any transportation construction projects within the 

coastal zone; therefore, no impacts to Texas’ coastal zone are expected. 

(Category 17) 

Emission of Air Pollutants 

The proposed activities shall be carried out in conformance with applicable air quality 

laws, standards, and regulations. Emissions from the proposed activities are not expected 

to have significant impacts on onshore air quality because of the prevailing atmospheric 

conditions, emission heights, emission rates, and the distance of these emissions from the 

coastline. The proposed activities will occur approximately 350 miles from shore and will 

be within the exemption limits set by BOEM, therefore, no impacts to Texas’ coastal 

zone is expected. 

(Category 18) 

Appropriations of Water 

The proposed activities do not include the impoundment or diversion of state water, 

therefore, no impacts to Texas’ coastal zone is expected. 

(Category 20) 

Marine Fishery Management 

The proposed activities are located approximately 350 miles from shore and are not 

expected to have any effect on marine fishery management or fishery migratory patterns 

within waters in the coastal zone of Texas. 

(Category 22) 

Administrative Policies 

The necessary information for applicable agencies to make an informed decision on the 

proposed activities has been provided In conclusion, all activities shall be consistent with 

Texas’ coastal management program and shall comply with all relevant rules and 

regulations. No activities are planned within any critical areas. Activities will be carried 

out avoiding unnecessary conflicts with other uses of the vicinity. 

 

LOUISIANA 

Issues identified in the Louisiana Coastal Zone Management Program include the 

following: general coastal use guidelines, levees, linear facilities (pipelines); dredged soil 

deposition; shoreline modifications, surface alterations, hydrologic and sediment 

transport modifications, waste disposal; uses that result in the alteration of waters 

draining into coastal waters; oil, gas, or other mineral activities; and air and water quality. 

Relevant enforceable policies were considered in certifying consistency for Louisiana. 

 

MISSISSIPPI 

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

Mississippi developed a Coastal Management Program (CMP) to allow for the review of 

proposed Federal license and permit activities affecting any coastal use or resources, in or 

outside of the Mississippi Coastal Zone. 

The OCS related oil and gas exploratory and development activities having potential 

impact on the Mississippi Coastal Zone are based on the location of the proposed 

facilities, access to those sites, best practical techniques for drilling locations, drilling 

equipment guidelines for the prevention of adverse environmental effects, effective 

environmental protection, emergency plans and contingency plans. 

Below are goals identified by the State of Mississippi and our comments and/or 

corresponding cross references: 

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

ensure the efficient utilization of waterfront industrial sites so that suitable sites are 

conserved for water dependent industry. 

The activities proposed in this plan are based out of Fourchon, Louisiana. The activities 

will not provide any industrial expansion on the coastal area of Mississippi. Therefore 

Mississippi coastal areas will be conserved for water dependent industry. 

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

where a specific alteration of specific coastal wetlands would serve a higher public 

interest in compliance with the public purposes of the public trust in which the 

coastal wetlands are held. 

Goal 2 is addressed in Section N–Environmental Impact Analysis. The nearest 

proposed activities will be 110 miles from the Mississippi coast. 

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

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

Goal 3 is addressed in Section N–Environmental Impact Analysis. Little impact to the 

seafood industry can be expected due to the activities occurring 110 miles from the 

Mississippi coast. 

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

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

aquatic life, and for domestic, agricultural, industrial, recreational and other 

legitimate beneficial uses. 

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

Information, and Section N–Environmental Impact Analysis. 
 

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

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

unreasonable method of use of water. 

The activities proposed in this plan are based in Fourchon, Louisiana. As such, 

Mississippi’s water resources should not be impacted by the proposed activities. 

Activities occurring at the sites in the OCS will be conducted in accordance with our 

Regional Oil Spill Response Plan referenced in Section H of this plan. 

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

their destruction, and to enhance these resources wherever possible. 

Goal 6 is addressed in Section B–General Information, and Section N–Environmental 

Impact Analysis. 

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

Goal 7 is addressed in Section F–Wastes and Discharge Information, Section H–Oil Spill 

Information, Section G–Air Emissions Information, and Section N–Environmental 

Impact Analysis. 

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

manner consistent with the coastal program. 

As the proposed activities are located 110 miles from the Mississippi coast and are based 

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

 

SECTION N

ENVIRONMENTAL IMPACT ANALYSIS 
Environmental Impact Analysis

INITIAL EXPLORATION PLAN

for

Atwater Valley Block 18 (OCS-G 33863)

Atwater Valley Block 19 (OCS-G 32556)

Offshore Louisiana and Mississippi

December 2013

Prepared for:

Bridget O’Farrell

Regulatory Analyst

Anadarko Petroleum Corporation

1201 Lake Robbins Drive 

The Woodlands, Texas 77380

Telephone: (832) 636-1554

Prepared by:

CSA Ocean Sciences Inc.

8502 SW Kansas Avenue

Stuart, Florida 34997

Telephone: (772) 219-3000
Atwater Valley Blocks 18 and 19 December 2013

Environmental Impact Analysis for Initial Exploration Plan Page ii

Contents

Page

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

A. Impact-Producing Factors .......................................................................................5

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

A.2 Physical Disturbance to the Seafloor..............................................................................................5

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

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

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

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

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

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

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

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

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

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

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

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

C. Impact Analysis.....................................................................................................17

C.1 Physical/Chemical Environment...................................................................................................17

C.1.1 Air Quality .........................................................................................................................17

C.1.2 Water Quality....................................................................................................................20

C.2 Seafloor Habitats and Biota..........................................................................................................22

C.2.1 Soft Bottom Benthic Communities...................................................................................23

C.2.2 High-Density Deepwater Benthic Communities...............................................................25

C.2.3 Designated Topographic Features....................................................................................27

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

C.2.5 Eastern Gulf Live Bottoms................................................................................................. 28

C.3 Threatened, Endangered, and Protected Species and Critical Habitat........................................28

C.3.1 Sperm Whale (Endangered)..............................................................................................30

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

C.3.3 Endangered Mysticete Whales.........................................................................................35

C.3.4 Non-Endangered Marine Mammals (Protected)..............................................................35

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

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

C.3.7 Whooping Crane (Endangered) ........................................................................................44

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

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

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

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

(Continued)

Page

Atwater Valley Blocks 18 and 19 December 2013

Environmental Impact Analysis for Initial Exploration Plan Page iii

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

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

C.4.2 Shorebirds and Coastal Nesting Birds...............................................................................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........................................................................................57

C.7 Coastal Habitats and Protected Areas..........................................................................................58

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

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

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

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

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

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

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

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

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

D.2 Severe Weather............................................................................................................................69

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

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

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

G. Consultation .........................................................................................................70

H. Preparers..............................................................................................................70

I. References.............................................................................................................70
Atwater Valley Blocks 18 and 19 December 2013

Environmental Impact Analysis for Initial 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 percent chance that an oil spill starting at 

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

(Modified from: BOEM, 2012b, Appendix C)........................................................................13

4 Benthic community data from stations near the lease area and in similar water 

depths sampled during the Northern Gulf of Mexico Continental Slope Habitats 

and Benthic Ecology Study (Adapted from: Wei, 2006; Rowe and Kennicutt, 2009)...........23

5 Federally listed endangered and threatened species potentially occurring in the 

lease area and along the northern Gulf Coast......................................................................29

6 Wildlife refuges, wilderness areas, and State and National parks within the 

geographic range of the potential shoreline contacts after 120 days (From: BOEM, 

2012b)...................................................................................................................................59

List of Figures 

Figure Page

1. Location of Atwater Valley Blocks 18 and 19 .........................................................................2

2. Bathymetric map of the lease area showing the surface hole locations of the 

proposed wellsites................................................................................................................18

3. Location of selected environmental features in relation to the lease area. ........................43
Atwater Valley Blocks 18 and 19 December 2013

Environmental Impact Analysis for Initial Exploration Plan Page v 

Acronyms and Abbreviations

ac acre

Anadarko Anadarko Petroleum Corporation

ADIOS2 Automated Data Inquiry for Oil Spills 2 

AT Atwater Valley

bbl barrel

BML below mud line

BOEM Bureau of Ocean Energy Management

BOEMRE Bureau of Ocean Energy Management, 

Regulation and Enforcement

BOP blowout preventer

B.P. Before Present

BSEE Bureau of Safety and Environmental 

Enforcement

CFR Code of Federal Regulations

CH4 methane

CO carbon monoxide

CO2 carbon dioxide

CGA Clean Gulf Associates

DP dynamic positioning

EEZ Exclusive Economic Zone

EFH Essential Fish Habitat

EIA Environmental Impact Analysis

EIS Environmental Impact Statement

EP Exploration Plan

ESA Endangered Species Act

FAD fish-attracting device

FR Federal Register

Gardline Gardline Surveys, Inc.

GMFMC Gulf of Mexico Fishery Management 

Council

GPS global positioning system

H2S hydrogen sulfide

ha hectare

HAPC Habitat Area of Particular Concern

HOSS high-volume open sea skimmer

IPF impact-producing factor

MC Mississippi Canyon

MARPOL International Convention for the 

Prevention of Pollution from Ships

MMC Marine Mammal Commission

MMPA Marine Mammal Protection Act

MMS Minerals Management Service

MSRC Marine Spill Response Corporation

NAAQS National Ambient Air Quality 

Standards

NMFS National Marine Fisheries Service

NOAA National Oceanic and Atmospheric 

Administration

NO2 nitrogen dioxide

NOx nitrogen oxides

NPDES National Pollutant Discharge 

Elimination System

NPS National Park Service

NRDA Natural Resource Damage Assessment

NTL Notice to Lessees and Operators

NWR National Wildlife Refuge

OBM oil-based mud

OCS Outer Continental Shelf

OSAT Operational Scientific Advisory Team

OSRA Oil Spill Risk Analysis

OSRP Oil Spill Response Plan

PAH polycyclic aromatic hydrocarbon

PM particulate matter

PSD Prevention of Significant Deterioration

SBM synthetic-based mud

SHL surface hole location

SOx sulfur oxides

SWSS Sperm Whale Seismic Study

USCG U.S. Coast Guard

USEPA U.S. Environmental Protection Agency

USFWS U.S. Fish and Wildlife Service

VOC volatile organic compound

WCD worst case discharge
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 1 

Introduction

Anadarko Petroleum Corporation (Anadarko) is submitting an Initial Exploration Plan (EP) for 

Atwater Valley (AT) Blocks 18 (AT 18) and 19 (AT 19). The EP includes eight exploratory well 

locations: AT 18-CC, AT 18-DD, AT 18-GG, AT 18-GV, AT 18-QQ, AT 19-EE, AT 19-KK, and 

AT 19-KV. All surface hole locations (SHLs) and bottom hole locations (BHLs) will be in the same 

block. This Environmental Impact Analysis (EIA) provides information on the exploratory wells 

based on the SHLs.

The lease area is 71 miles (114 m) from the nearest shoreline, 108 miles (172 km) from the 

onshore support base at Port Fourchon, Louisiana, and 152 miles (243 km) from the helicopter 

support base at Houma, Louisiana (Figure 1). Water depths at the wellsites range from 1,270 to 

1,351 m (4,167 to 4,433 ft). The drilling rig is yet to be determined, but will be either a dynamic 

positioning (DP) drillship or a DP semisubmersible rig. The expected timeframe to conduct the 

operations proposed in this EP has not yet been determined. Each of the eight proposed wells 

will take approximately 190 days to drill and complete, for a total of 1,520 days on site.

This EIA was prepared for submittal to the Bureau of Ocean Energy Management (BOEM) in 

accordance with applicable regulations, including 30 Code of Federal Regulations (CFR) 

550.212(o) and 550.227. The EIA is a project- and site-specific analysis of Anadarko’s planned 

activities under this EP. This EIA complies with guidance provided in existing Notices to Lessees 

and Operators (NTLs) issued by the former Minerals Management Service (MMS) and Bureau of 

Ocean Energy Management, Regulation and Enforcement (BOEMRE), including NTL 2008-G04

and NTL 2013-G02. Potential impacts have been analyzed at a broader level in the 

Programmatic Environmental Impact Statement (EIS) for the Outer Continental Shelf (OCS) Oil 

and Gas Leasing Program (MMS, 2007a; BOEM, 2012a) and in multi-lease-sale EISs for the 

Western and Central Gulf of Mexico Planning Areas (MMS, 2007b; BOEM, 2012b). The analyses 

from these documents are incorporated here by reference.

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

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

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

U.S. Gulf of Mexico is 0.00593 blowouts per well drilled, or one blowout per 169 exploration 

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

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

blowout per 200 well starts (MMS, 2000). More recently, in its Final Supplemental EIS for the 

Central Gulf of Mexico Planning Area, BOEM confirmed that "significant changes to the spill 

rates for the entire OCS are not anticipated" (BOEM, 2012b).

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

Mexico from 1971 to 1995, only 18 (12%) resulted in oil spills, with a total combined volume of 

1,000 barrels (bbl) of crude oil and condensate released (MMS, 2000). Between 1964 and 1999, 

almost all offshore spills (94%) from drilling and production-related operations on the OCS were 

less than or equal to 1 bbl in size (Anderson and LaBelle, 2000). According to the Bureau of 

Safety and Environmental Enforcement’s (BSEE’s) Final Drilling Safety Rule (75 Federal Register

[FR] 63365) issued following the Macondo incident, the baseline risk of a catastrophic blowout is 

estimated to be about once every 26 years.
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 2 

Figure 1. Location of Atwater Valley Blocks 18 and 19. 
Atwater Valley Blocks 18 and 19 December 2013

Environmental Impact Analysis for Initial Exploration Plan Page 3 

All the proposed activities and facilities discussed in this EP are covered by the Regional Oil Spill 

Response Plan (OSRP) approved on 25 September 2013 for Anadarko and its subsidiaries, 

Anadarko U.S. Offshore Corporation and Anadarko E&P Company L.P. (Company Numbers 

00981, 02219, and 00148, respectively), in accordance with 30 Code of Federal Regulations 

(CFR) Part 254. 

The OSRP details Anadarko’s plan for response to rapidly and effectively manage oil spills that 

may result from drilling and production operations. Anadarko has designed its response 

program based on a regional capability of response to spills ranging from small operational spills 

to a worst case discharge (WCD) from a well blowout. Anadarko’s spill response program meets 

the response planning requirements of the relevant coastal states and applicable Federal oil spill 

planning regulations and also includes information regarding Anadarko’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.

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

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

and Section C (Impact Analysis). Table 1 lists and summarizes the NTLs applicable to this EIA.

Table 1. Notices to Lessees and Operators (NTLs) applicable to this Environmental Impact 

Analysis (EIA). 

NTL Title Summary

2013-G02 Extension of Prior Notices to 

Lessees

Extends the effective date of NTL 2008-G04 (and two other 

NTLs) until the end of the 2013 calendar year. 

2012-N06

Guidance to Owners and Operators 

of Offshore Facilities Seaward of 

the Coast Line Concerning Regional 

Oil Spill Response Plans 

Provides clarification, guidance, and information for 

preparation of regional Oil Spill Response Plans. 

Recommends description of response strategy for worst 

case discharge (WCD) scenarios to ensure capability to 

respond to oil discharges is both efficient and effective. 

2012-BSEE-G01 Marine Trash and Debris 

Awareness and Elimination

Instructs operators to exercise caution in the handling and 

disposal of small items and packaging materials; requires the 

posting of placards at prominent locations on offshore 

vessels and structures; and mandates a yearly marine trash 

and debris awareness training and certification process.

2012-JOINT-G01

Vessel Strike Avoidance and 

Injured/Dead Protected Species 

Reporting

Recommends protected species identification guides be 

carried on all Gulf of Mexico petroleum vessels and that 

vessel operators and crews maintain a vigilant watch for 

marine mammals. Vessels are to slow down or stop to avoid 

striking protected species, and operators are required to 

report sightings of any injured or dead protected species.

2011-JOINT-G01

Revisions to the List of OCS Blocks 

Requiring Archaeological Resource 

Surveys and Reports

Provides new information of which Outer Continental Shelf

(OCS) blocks require archaeological surveys and reports and 

required survey line spacing in each block. This 

NTL augments NTL 2005-G07. 
Table 1. (Continued).

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Environmental Impact Analysis for Initial Exploration Plan Page 4 

NTL Title Summary

2010-N10

Statement of Compliance with 

Applicable Regulations and 

Evaluation of Information 

Demonstrating Adequate Spill 

Response and Well Containment 

Resources

Informs operators using subsea blowout preventers (BOPs) 

or surface BOPs on floating facilities that applications for 

well permits must include a statement signed by an 

authorized company official stating that the operator will 

conduct all activities in compliance with all applicable 

regulations, including the increased safety measures 

regulations (75 FR 63346). Informs operators that BOEM

will be evaluating whether each operator has submitted 

adequate information demonstrating that it has access to 

and can deploy containment resources to promptly respond 

to a blowout or other loss of well control.

2010-N06

Information Requirements for 

Exploration Plans, Development 

and Production Plans, and 

Development Operations 

Coordination Documents on the 

OCS 

Rescinds the limitations set forth in NTL 2008-G04 regarding 

a blowout scenario and worst case discharge scenario, and 

provides guidance regarding the information required in 

blowout scenario and worst case discharge scenario 

descriptions.

2009-G40 Deepwater Benthic Communities

Provides 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

Provides guidance for avoiding and protecting biologically 

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

pinnacles, low relief live bottom areas, and other potentially 

sensitive biological features) when conducting OCS 

operations in water depths less than 300 m (984 ft) in the 

Gulf of Mexico.

2009-G06 Military Warning and Water Test 

Areas

Provides contact links to individual command headquarters 

for the military warning and water test areas in the Gulf of 

Mexico. Lease stipulations require lessees or designated 

operators to enter into an agreement with the appropriate 

individual military command headquarters concerning the 

control of electromagnetic emissions and use of boats and 

aircraft in the applicable warning area or water test area 

before commencing such traffic.

2008-G04

Information Requirements for 

Exploration Plans and Development 

Operations Coordination 

Documents

Provides guidance on the information requirements for OCS 

plans, including EIA requirements and information regarding 

compliance with the provisions of the Endangered Species 

Act and Marine Mammal Protection Act.

2005-G07 Archaeological Resource Surveys 

and Reports

Provides guidance on regulations regarding archaeological 

discoveries, specifies requirements for archaeological 

resource surveys and reports, and outlines options for 

protecting archaeological resources.
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Environmental Impact Analysis for Initial Exploration Plan Page 5 

A. Impact-Producing Factors

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

resources adapted from Form BOEM-0142. 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 sections. 

• 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

• Accidents

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

The wells proposed in this EP will be drilled using either a DP drillship or a DP semisubmersible 

rig. DP drillships and DP semisubmersible rigs use a global positioning system (GPS), specific 

computer software, and sensors in conjunction with and 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 station-keeping adjustment. This allows operations at sea where mooring 

or anchoring is not feasible.

The drilling rig for the wells proposed in this EP will be on site for an estimated 1,520 days 

(190 days per well). 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 DP drillships and DP 

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

10 to 500 Hz (Richardson et al., 1995). From a drilling rig, sound and vibration paths to the 

water flow 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.

A.2 Physical Disturbance to the Seafloor

In water depths of 600 m (1,969 ft) or greater, DP drilling vessels disturb only a very small area 

of the seafloor around the wellbore (SHL) where the bottom template and blowout preventer 

(BOP) are located. Depending on the specific well configuration, this area is generally about 

0.25 hectare ([ha]; 0.62 acre [ac] (MMS, 2007a).
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Environmental Impact Analysis for Initial Exploration Plan Page 6 

Table 2. Matrix of impact-producing factors and affected environmental resources. X = potential impact; dash (--) = no impact or negligible impact.

Environmental Resources

Impact-producing Factors

Drilling Rig 

Presence (incl. 

noise & lights)

Physical 

Disturbance 

to Seafloor

Air 

Pollutant 

Emissions

Effluent 

Discharges

Water 

Intake

Onshore 

Waste 

Disposal

Marine 

Debris

Support 

Vessel/Helo 

Traffic

Accidents

Small Fuel 

Spill

Oil Spill 

(WCD)

Physical/Chemical Environment

Air quality and greenhouse gases -- -- --X(9) -- -- -- -- -- X(6) X(6)

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

Seafloor Habitats and Biota

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

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

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

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

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

Threatened, Endangered, and Protected Species and Critical Habitat

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

West Indian manatee (endangered) -- -- -- -- -- -- -- X(8) -- X(6,8)

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

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

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

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

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

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

Smalltooth sawfish (endangered) -- -- -- -- -- -- -- -- -- X(6)

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

Elkhorn coral (endangered) -- -- -- -- -- -- -- -- -- X(6)

Coastal and Marine Birds

Marine birds X -- -- -- -- -- -- X X(6) X(6)

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

Fisheries Resources

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

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

Archaeological Resources

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

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

Coastal Habitats and Protected Areas

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

Wetlands and seagrass beds -- -- -- -- -- -- -- -- -- X(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.
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Environmental Impact Analysis for Initial Exploration Plan Page 7 

Table 2 Footnotes and Applicability:

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

anchors will be on the seafloor within the following:

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

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

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

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

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

the Topographic Features Stipulation attached to an OCS lease.

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

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

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

(Pinnacle Trend) Stipulation attached to an OCS lease.

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

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

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

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

(4) Activities on blocks designated by the BOEM as being in water depths 400 m or greater.

• No impacts on high-density deepwater benthic communities are anticipated. There are no features 

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

any drilling mud/cuttings discharge location. 

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

• Based on 30 CFR 250.490(c), Anadarko is proposing that BOEM classify the lease area as a zone where 

the absence of H2S has been confirmed. 

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

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

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

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

analyzed in Section C. 

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

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

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

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

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

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

survey blocks (BOEM, 2012c) and is well beyond the 60-m depth contour used by the BOEM as the 

seaward extent for prehistoric archaeological site potential in the Gulf of Mexico. The geohazards and 

archaeological assessments indicate multiple sonar contacts in the lease area, but none are interpreted 

to be historic shipwrecks. A dynamic positioning (DP) drilling vessel will be used; therefore, seafloor 

disturbances due to anchoring will not occur.

(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, 

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.
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Environmental Impact Analysis for Initial Exploration Plan Page 8 

A.3 Air Pollutant Emissions

Air pollutant emissions are calculated in EP Section G and are estimated to be insignificant. 

Offshore air pollutant emissions will result from drilling rig operations, as well as service vessels 

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

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

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

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

monoxide (CO).

The Air Quality Emissions Report prepared in accordance with BOEM requirements 

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

regulations in 30 CFR 250.303. Based on this and the distance to shore, it can be concluded that 

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

criteria pollutants. No further analysis or control measures are required.

A.4 Effluent Discharges

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

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

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

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

permit.

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

intervals before the marine riser that allows their return to the surface is set. Excess cement 

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

the drilling operations. Synthetic-based drilling muds (SBMs) will be collected on the rig and 

either reused by the vendor, or transported to Port Fourchon, Louisiana, 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.

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

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

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

A.5 Water Intake

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

the drilling rig. Section 316(b) of the Clean Water Act requires NPDES permits to ensure that the 

location, design, construction, and capacity of cooling water intake structures reflect the best 

technology available to minimize adverse environmental impact from impingement and 

entrainment of aquatic organisms. The current NPDES General Permit No. GMG290000 does 

not specify requirements for existing facilities (those that started construction before 

16 July 2006). The drilling vessel ultimately selected for this project will be in compliance with 

all cooling water intake structure requirements.
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Environmental Impact Analysis for Initial Exploration Plan Page 9 

A.6 Onshore Waste Disposal

Wastes generated during drilling are tabulated in EP Section F. A total of approximately

2,333 bbl of trash will be generated over the life of this project. The 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

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

including the International Convention for the Prevention of Pollution from Ships 

(MARPOL 73/78) Annex V requirements and USEPA and U.S. Coast Guard (USCG) regulations, as 

well as those of the BOEM. For example, BOEM regulations at 30 CFR 250.300(a) and

(b)(6) prohibit operators from deliberately discharging containers and other similar materials 

(i.e., trash and debris) into the marine environment, and 30 CFR 250.300(c) requires durable 

identification markings on equipment, tools, and containers (especially drums), and other 

material. USEPA and USCG regulations require operators to become proactive in avoiding 

accidental loss of solid waste items by developing waste management plans, posting 

informational placards, manifesting trash sent to shore, and using special precautions such as 

covering outside trash bins to prevent accidental loss of solid waste. In addition to the 

regulations in 30 CFR 250, BSEE issued NTL 2012-BSEE-G01, which instructs operators to exercise 

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

of placards at prominent locations on offshore vessels and structures, and mandates a yearly 

marine trash and debris awareness training and certification process.

A.8 Support Vessel and Helicopter Traffic

Anadarko 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 one supply vessel. The crew boat will make

three round-trips per week, and the supply vessels will make two round-trips per week. The 

boats typically will move to the project area via the most direct route from the shorebase. Up to 

two tugboats and anchor handling vessels may be in the project area at any time for the 

duration of the operation.

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

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

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

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

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

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

park properties. Additional guidelines and regulations specify that helicopters maintain an 

altitude of 305 m (1,000 ft) within 91 m (300 ft) of marine mammals (BOEM, 2012d).
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 10 

A.9 Accidents 

A.9.1 Types of Accidents Evaluated

The analysis in this EIA focuses on two potential accidents:

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

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

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

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

MMS (2007b) and BOEM (2012b) analyzed three other types of accidents: chemical spills, vessel 

collisions, and loss of well control. These types of accidents are discussed briefly in 

Section A.9.4. 

A.9.2 Small Fuel Spill

Spill Size. According to the analyses in MMS (2007b) and BOEM (2012a), the most likely type of 

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

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

future OCS activities in the Western and Central Gulf of Mexico Planning Areas. As the spill size 

increases, the incident rate declines dramatically (MMS, 2007b; BOEMRE, 2011a; BOEM, 2012b). 

The median size for spills <1 bbl is 0.024 bbl, and the median size for spills of 1 to 10 bbl is 3 bbl 

(BOEM, 2012a). For this analysis, a small diesel fuel spill of 3 bbl is assumed. Operational 

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

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

Spill Fate

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

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

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

readily degraded by aerobic microbial oxidation. Due to its light density, diesel will not sink to 

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

generally occurs only in coastal areas with high suspended solids loads (National Research 

Council, 2003a) and would not be expected to occur to any appreciable degree in offshore 

waters of the Gulf of Mexico. Diesel oil is readily and completely degraded by naturally 

occurring microbes (National Oceanic and Atmospheric Administration [NOAA], 2006).

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

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

However, given the open ocean location of the lease area and response actions, it is expected 

that impacts from a small spill would be minimal (BOEMRE, 2011a; BOEM, 2012b).

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

Automated Data Inquiry for Oil Spills 2 (ADIOS2) model. This model uses the physical properties 

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

changes in the density, viscosity, and water content of the product spilled. It is estimated that 

over 90% of a small diesel spill would be evaporated or dispersed within 24 hours. The sea 

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

(1.2 to 12 ac) depending on sea state and weather conditions.
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Environmental Impact Analysis for Initial Exploration Plan 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 71 miles (114 km) from the nearest shoreline. Modeling results discussed 

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

coastal areas of Louisiana within 10 days after a spill. By that time, essentially 100% of a small 

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

account Anadarko’s response measures. Slicks from spills are expected to persist for relatively 

short periods of time ranging from minutes (<1 bbl) to hours (<10 bbl) to a few days (10 to 

1,000 bbl) and rapidly spread out, evaporate and disperse into the water column (BOEM, 

2012b). Because of the distance of these potential spills on the OCS and their lack of 

persistence, it is unlikely that a spill would make landfall prior to dissipation (BOEM, 2012b).

Spill Response

A.9.3 Crude Oil Spill (Worst Case Discharge)

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

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

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

EP Section 9b provides a detailed discussion of Anadarko’s response to a spill.

Spill Size

An estimated 7-21 days is required to suspend operations on a deepwater Gulf of Mexico well, 

mobilize to a relief well location, and begin relief well drilling operations. This estimate includes 

0 to 14 days to suspend current operations on an existing well and 7 days to mobilize to location 

and be ready to spud a relief well. The estimated time to drill the relief well and perform kill 

operations is 180 days for an estimated total of 187 to 201 days from time of blowout to 

completion of a relief well. The detailed analysis of this calculation can be found in 

EP Section H. 

. AT 19-KV has the highest WCD for the entire Initial Exploration Plan at 250,199 bbl per 

day. AT 18-GV has the highest WCD for AT 18 with a potential maximum discharge of 63,744 bbl 

per day. The maximum total volume during a blowout at AT 19-KV could potentially be 

50,287,788 bbl assuming 201 days for the maximum duration of a blowout, multiplied by the 

worst case daily uncontrolled blowout volume of 250,188 bbl per day.

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

estimated a probability of 0.0021 for a deep drilling blowout during exploration drilling based on 

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

frequency of 0.0017 per exploratory well for non-North Sea locations (International Association 

of Oil & Gas Producers, 2010). As noted by MMS (2007b), from 1992 to 2005, half of blowouts 

lasted less than half a day, and fewer than 10% of blowouts resulted in spilled oil. BOEM is in 

the process of updating these spill frequency estimates to include the Macondo event; however, 

significant changes to the spill rates for the entire OCS are not anticipated (BOEMRE, 2011a; 

BOEM, 2012d). As noted in the Introduction, the baseline risk of a catastrophic blowout is 

estimated to be once every 26 years (BSEE Final Drilling Safety Rule, 75 FR 63365).

Included in EP Section H are Anadarko’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. Anadarko 

will also comply with NTL 2010-N10 and the Final Drilling Safety Rule, which specifies additional

safety measures for OCS activities.
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Environmental Impact Analysis for Initial Exploration Plan Page 12 

Spill Trajectory

To address this criticism, a special OSRA run was conducted for the recent BOEM Western and 

Central Gulf of Mexico Planning Area Supplemental EISs (BOEMRE, 2011a; BOEM, 2012b) in 

order to estimate the impacts of a possible future catastrophic long-duration oil spill. In this 

OSRA model run a hypothetical high volume, long-duration oil spill was assumed to have 

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

with each trajectory tracked for up to 120 days.

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

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

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

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

it is still the most widely scientifically accepted model for estimating the fate of small fuel spills. 

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

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

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

incident. Also as noted by Ji et al. (2004), the OSRA model does not take into account the 

chemical composition or biological weathering of oil spills, the spreading and splitting of oil 

spills, or spill response activities. The model does not assume a particular spill size but has 

generally been used by the BOEM to evaluate contact probabilities for spills greater than 

1,000 bbl.

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

in the Central and Western Gulf of Mexico Planning Areas. These launch points were 

deliberately located in areas identified as having a high possibility of containing large oil 

reserves.

The five launch point areas were as follows:

1. Central Gulf of Mexico shelf area west of the Mississippi River (28.98660° N latitude, 

92.17851° W longitude);

2. Central Gulf of Mexico shelf area east of the Mississippi River (29.91388° N latitude, 

88.15338° W longitude);

3. Central Gulf of Mexico slope area (27.31998° N latitude, 90.22203° W longitude);

4. Western Gulf of Mexico shelf area (27.55423° N latitude, 96.76627° W longitude); and

5. Western Gulf of Mexico slope area (27.51367° N latitude, 94.51836° W longitude).

The results for Launch Point 3, the launch point nearest to the project area, are presented in 

Table 3. 

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

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

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

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

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

major spill or uncontrolled release. 
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Environmental Impact Analysis for Initial Exploration Plan Page 13 

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

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

(Modified from: BOEM, 2012b, 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, State Percent Chance

Cameron, TX -- -- -- 2 -- -- -- -- -- -- -- 2 -- -- -- 2 

Willacy, TX -- -- -- 3 -- -- -- -- -- -- -- 2 -- -- -- 3 

Kenedy, TX -- -- -- 8 -- -- -- 1 -- -- -- 9 -- -- -- 5 

Kleberg, TX -- -- 1 6 -- -- -- -- -- -- -- 4 -- -- 1 6 

Nueces, TX -- -- 1 6 -- -- -- -- -- -- -- 2 -- -- 1 2 

Aransas, TX -- -- -- 5 -- -- -- 1 -- -- -- 3 -- -- -- 2 

Calhoun, TX -- -- 1 6 -- -- -- -- -- -- -- 6 -- -- 1 4 

Matagorda, TX -- -- 2 17 -- -- 3 4 -- -- -- 11 -- -- 1 6 

Brazoria, TX -- -- 3 12 -- -- 1 3 -- -- 2 8 -- -- 1 5 

Galveston, TX -- -- 3 10 -- -- 3 6 -- -- 2 5 -- -- 1 4 

Jefferson, TX -- -- 1 4 -- -- 7 9 -- -- 1 1 -- -- -- 2 

Cameron, TX -- -- 1 4 -- -- 11 12 -- 1 1 4 -- -- -- 4 

Vermilion, LA -- -- 1 2 -- -- 5 6 -- 1 1 2 -- -- -- --

Iberia, LA -- -- -- 1 -- -- 4 4 -- -- -- -- -- -- -- --

Terrebonne, LA -- 1 2 3 -- 4 12 14 -- -- -- 2 -- -- -- --

Lafourche, LA -- -- 1 1 -- 2 8 10 -- -- 1 2 -- -- -- --

Jefferson, LA -- -- -- 1 -- -- 2 2 -- -- 1 1 -- -- -- --

Plaquemines, LA -- -- -- 1 -- 2 10 12 -- -- 1 2 -- -- -- --

Jackson, MS -- -- -- -- -- -- 1 1 -- -- -- -- -- -- -- --

Baldwin, AL -- -- -- -- -- -- 1 1 -- -- -- -- -- -- -- --

Bay, FL -- -- -- -- -- -- -- 1 -- -- -- -- -- -- -- --

Franklin, FL -- -- -- 1 -- -- -- -- -- -- -- -- -- -- -- --

Monroe, FL -- -- -- -- -- -- -- -- -- -- -- 1 -- -- -- 1 

Miami-Dade, FL -- -- -- -- -- -- -- -- -- -- -- 1 -- -- -- --

"—" = Values <1.0%. Areas where there is <0.5% chance of contact within 120 days are not shown.

Weathering

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

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

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

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

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

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

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

water surface.

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

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

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

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

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

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

seafloor (National Research Council, 2003a).
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 14 

Spill Response. BOEM has issued recent NTLs following the Macondo spill that clarify additional 

oil-spill prevention and response planning requirements. These NTLs are summarized in Table 1, 

and additional BOEM (2012b) guidance is provided below.

NTL 2012-N06 – Guidance to Owners and Operators of Offshore Facilities Seaward of the 

Coast Line Concerning Regional Oil Spill Response Plans: This NTL, effective 10 August 2012, 

provides clarification, guidance, and information on the preparation and submittal of 

regional OSRPs for owners and operators of oil handling, storage, or transportation facilities, 

inclusive of pipelines, located seaward of the coastline. It states that lessees, designated 

operators, and pipeline right-of-way holders are responsible for preparation and submission 

of these plans. Some of the clarifications and recommended practices in the NTL are based 

on lessons learned from the Macondo oil spill response.

NTL 2010-N10 – Statement of Compliance with Applicable Regulations and Evaluation of 

Information Demonstrating Adequate Spill Response and Well Containment Resources: This 

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

subsea or surface BOPs on floating facilities. It requires that lessees and operators must 

submit a statement signed by an authorized company official with each well permit 

application indicating that they will conduct all of their authorized activities in compliance 

with all applicable regulations, including the Increased Safety Measures Regulations at 

75 FR 63346. The NTL also informs lessees that BOEMRE will evaluate whether the operator 

has submitted adequate information demonstrating that it has access to and can deploy 

surface and subsea containment resources that would be adequate to promptly respond to 

a blowout or other loss of well control. The NTL notifies the operator that BOEMRE intends 

to evaluate the adequacy of each operator to comply in the operator’s current OSRP; 

therefore, there is an incentive for voluntary compliance.

NTL 2010-N06 – Information Requirements for Exploration Plans, Development and 

Production Plans, and Development Operations Coordination Documents on the OCS

Anadarko’s Regional OSRP was last approved on 25 September 2013. The OSRP provides a 

detailed plan for Anadarko to respond to rapidly and effectively manage oil spills that may result 

from drilling and production operations. The OSRP contains detailed information on "Quick 

Response" procedures, including:

: 

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 Plans, or Development Operations Coordination Documents. The required 

supplemental information includes the following: (1) a description of the blowout scenario 

as required by 30 CFR 254(b) and 254(h); (2) a description of their assumptions and 

calculations used in determining the volume of the WCD required by 30 CFR 254.26; and 

(3) a description of the measures proposed that would enhance the ability to prevent a 

blowout, to reduce the likelihood of a blowout, and to conduct effective and early 

intervention in the event of a blowout, including the arrangements for drilling relief wells 

and any other measures proposed. The early intervention methods of the third 

requirement could actually include the surface and subsea containment resources that 

BOEM announced in NTL 2010-N10, which states that BOEM will review to ensure that the 

measures are adequate to promptly respond to a blowout or other loss of well control.
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 15 

• responsibilities of all Anadarko and contract personnel to report any observed discharge 

from known or unknown sources;

• procedures to locate and determine the size of a discharge; and 

• contact information for alerting the spill management team complete with names, phone 

numbers, and locations.

In the event of a WCD, Anadarko has access to surface and subsea response/containment 

capabilities that could be implemented through various organizations under contract. 

Anadarko’s primary spill response equipment provider is Clean Gulf Associates (CGA).

CGA has four skimming vessels capable of operating in shallow waters and offshore/nearshore 

areas. These vessels have oleophilic brush pack skimming systems operating in troughs built 

into the hulls, below-deck storage, and marine electronics packages including marine, aircraft 

and company-frequency radios; radar; moving map plotters; GPS; satellite phones; and depth 

finders. CGA also offers nine Fast Response Systems staged throughout the Gulf of Mexico 

available for offshore use.

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

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

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

room overlooking the skimmer deck. The estimated daily recovery capacity for the HOSS barge 

is approximately 43,000 bbl. 

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

arms and two Aqua Guard skimmers. In addition, an x-band radar/infrared tracking system is 

installed on the HOSS barge. Additional CGA equipment can be referenced on their website at

http://www.cleangulfassoc.com/equipment.

Anadarko also has a contract with the Marine Spill Response Corporation (MSRC) for additional 

spill response equipment. MSRC has a dedicated fleet for the Atlantic/Gulf of Mexico region and 

additional available equipment staged throughout the U.S. MSRC equipment staged throughout 

the Gulf of Mexico includes seven oil spill response vessels, two fast response vessels, five oil 

spill response barges, five platform supply vessels, and 15 shallow water barges. Various 

equipment is outfitted with x-band and infrared technology.

MSRC recently completed a large expansion of its resources and capability in the Gulf of Mexico, 

with particular focus on deepwater. The expansion is known as "Deep Blue." Additional MSRC 

capabilities and a complete equipment listing are available on-line at 

http://www.msrc.org/services/oil-spill-response. 

Anadarko also is a member of the Marine Well Containment Company (MWCC). In the event of 

an incident, MWCC can provide a 15,000-psi single ram capping stack and dispersant injection 

capability. MWCC can also install and operate the interim containment system, including subsea 

flowlines, manifold, and risers. The interim system is engineered to be used in depths up to 

3,048 m (10,000 ft) and has the capacity to contain 60,000 barrels of liquid per day (BLPD) 

(and 120 million standard cubic feet per day [MMSCFD] of gas) with potential for expansion.

See EP Section H for a detailed description of Anadarko’s site-specific response to the WCD for 

this plan.
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 16 

A.9.4 Other Accidents Not Analyzed in Detail

BOEM (2012b) discusses three other types of accidents: chemical spills, vessel collisions, and 

loss of well control. The information from the EIS on these topics remains valid and is 

incorporated by reference into this document. These accidents are discussed briefly below 

along with a hydrogen sulfide (H2S) release. There are no other site-specific issues for the 

drilling of the wells proposed in this EP.

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

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

use is reflected in the largest volumes spilled. Completion fluids are the largest quantity used 

and comprise the largest releases. Between 5 and 15 chemical spills are anticipated each year, 

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

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

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

same, but spill frequency can be expected to decrease because of advances in subsea processing 

(BOEMRE, 2011a; BOEM, 2012b). 

Riser Disconnect SBM Spills. In deepwater drilling, SBMs are preferred over petroleum oil-based 

muds (OBMs) due to the superior environmental properties of SBMs. The synthetic base fluids 

used in SBMs are less toxic to the marine environment and have the potential to biodegrade. 

SBMs have been used in the Gulf of Mexico since the mid-1990s, and between 5 and 20 SBM 

releases are anticipated each year as a result of offshore drilling programs. The majority of 

these releases are <50 bbl in size, but accidental riser disconnects may result in the release of 

medium (238 to 2,380 bbl) to large (>2,380 bbl) quantities of drilling fluids. Riser disconnect 

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

Vessel Collisions. BOEM data show that from 1996 to 2009 there were 226 OCS-related 

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

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

the OCS resulted in diesel spills, and in several collision incidents, fires resulted from 

hydrocarbon releases. To date, the largest diesel spill associated with a collision occurred in 

1979 when an anchor-handling boat collided with a drilling platform in the Main Pass lease area, 

spilling 1,500 bbl. Diesel fuel is the product most frequently spilled, but oil, natural gas, 

corrosion inhibitor, hydraulic fluid, and lube oil have also been released as the result of vessel 

collisions. Human error accounted for approximately half of all reported vessel collisions from 

2006 to 2009. As summarized in MMS (2007b) and BOEM (2012b), vessel collisions occasionally 

occur during routine operations. Some of these collisions have caused spills of diesel fuel or 

chemicals. Anadarko will comply with all USCG and BOEM mandated safety requirements to 

minimize the potential for vessel collisions.

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

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

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

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

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

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

Measures to prevent a blowout, reduce the likelihood of a blowout, and conduct effective and 

early intervention in the event of a blowout are described in the NTL 2010-06 package 
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 17 

submitted with the exploration plan, as required. The potential for a loss-of-well-control event 

will be minimized by adhering to the requirements of applicable regulations such as the Final 

Drilling Safety Rule and NTL 2010-N10, which specify additional safety measures for 

OCS activities.

H2S Release. Pursuant to 30 CFR 250.490(c), Anadarko is proposing that the lease area be 

classified as a zone where the absence of H2S has been confirmed.

B. Affected Environment

Based on the site clearance survey conducted by Gardline Surveys, Inc (Gardline, 2013), water 

depths at the wellsites are anticipated to range from 1,270 to 1,351 m (4,167 to 4,433 ft). 

(Figure 2). The seafloor at all of the proposed wellsites appears to be smooth and featureless.

No anomalous seabed amplitudes indicative of hydrocarbon macroseeps, items of 

archaeological significance, or other features that could affect the well emplacements, jettings, 

or casings were identified within 610 m (2,000 ft) of the proposed wellsites (Gardline, 2013).

A detailed description of the regional affected environment, including meteorology, 

oceanography, geology, air and water quality, benthic communities, threatened and 

endangered species, biologically sensitive resources, archaeological resources, socioeconomic 

conditions, and other marine uses is provided in MMS (2007b) and BOEM (2012b). These 

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

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

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

C. Impact Analysis

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

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

of Mexico Planning Areas (MMS, 2007b; BOEM, 2012b). The information in these documents is 

incorporated by reference. Potential site-specific issues are addressed in this section.

C.1 Physical/Chemical Environment

C.1.1 Air Quality

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

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

quality at the wellsites is expected to be good. The attainment status of Federal OCS waters is 

unclassified because there is no provision in the Clean Air Act for classification of areas outside 

State waters (MMS, 2007b). 
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Environmental Impact Analysis for Initial Exploration Plan Page 18 

Figure 2. Bathymetric map of the lease area showing the surface hole locations of the proposed wellsites.
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 19 

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

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

Therefore, the only potential effects to air quality would be from routine air pollutant emissions, 

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

BOEM has reexamined the analysis for air quality presented in MMS (2007b, 2008) based on 

additional information and in consideration of the Macondo oil spill event. No substantial new 

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

BOEMRE (2011a) and BOEM (2012b).

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 and helicopters and service vessels. These 

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

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

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

and CO. Emissions of pollutants into the atmosphere from these activities are not projected to 

have significant effects on onshore air quality because of the prevailing atmospheric conditions, 

emission rates and heights, and resulting pollutant concentrations. The incremental 

contribution to cumulative impacts from activities similar to Anadarko’s proposed activities is 

not significant and will not cause or contribute to a violation of any National Ambient Air Quality 

Standard (NAAQS) (MMS, 2007b, 2008). Since the BOEM completed the lease sale EISs, the 

USEPA has adopted a new short-term NAAQS for nitrogen dioxide (NO2). The standard has not 

yet been implemented in the Gulf Coast states, but given the levels of expected emissions and 

the distance of the project from shore, emissions from the activities described in Anadarko’s 

proposed EP are not likely to contribute to violations of any NAAQS onshore.

Carbon dioxide (CO2) and methane (CH4) emissions from the project would constitute a small 

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

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

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

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

impacts 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 MMS (2007a,b). Because of 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 MMS (2007b), emissions 

of air pollutants from routine activities in the Central and Western Gulf of Mexico Planning Area

are projected to have minimal impacts to onshore air quality because of the prevailing 

atmospheric conditions, emission heights, emission rates, and the distance of these emissions 

from the coastline. The Air Quality Emissions Report (see EP Section G) prepared in accordance 

with BOEM requirements shows that the projected emissions are below exemption levels; 

therefore, according to 30 CFR 250.303, the emissions will not significantly affect the air quality 

of the onshore area for any of the criteria pollutants. No further analysis or control measures 

are required. 
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 20 

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

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

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

Wildlife Service (USFWS) if emissions from proposed projects may affect the Breton Class I area. 

Additional review and mitigation measures may be required for sources within 186 miles 

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

agencies (NPS, 2010). The lease area is approximately 105 miles (169 km) from the Breton 

Wilderness Area, and no air quality impacts on the Wilderness Area are expected. Anadarko will 

comply with all BOEM requirements regarding air emissions.

Impacts of a Small Fuel Spill

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

and discussed in MMS (2007b) and BOEM (2012b,d). The probability of a small spill would be 

minimized by Anadarko’s preventative measures during routine operations including fuel 

transfer. In the unlikely event of a spill, implementation of Anadarko’s OSRP could reduce the

potential impacts. EP Section H includes a detailed discussion of the spill response measures

that would be employed. Given the open ocean location of the lease area, the extent and 

duration of air quality impacts from a small spill would not be significant.

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

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

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

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

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

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

Impacts of a Large Oil Spill (WCD)

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

analyzed and discussed in MMS (2007b) and BOEM (2012b,d).

A large oil spill (WCD) could potentially affect air quality by introducing VOCs through 

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

meteorological and oceanographic conditions at the time and the effectiveness of spill response 

measures. Real-time wind and current data from the project area would be available at the 

time of a spill and would be used to assess the fate and effects of VOCs released. Additional air 

quality impacts could occur if response measures included in situ burning of the floating oil. 

Burning would generate a plume of black smoke and result in emissions of NOx, SOx, CO, and 

PM, as well as greenhouse gases. However, in situ burning would occur only after authorization 

from the USEPA.

Due to the lease area’s distance from the nearest shoreline, most air quality impacts would 

occur in offshore waters with minimal chances to affect onshore air quality.

C.1.2 Water Quality

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

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

As noted in MMS (2007b), deepwater areas in the northern Gulf of Mexico are relatively 
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 21 

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

the deepwater region has little evidence of contaminants in the dissolved or particulate phases 

of the water column. However, there are localized occurrences of natural seepage of oil, gas, 

and brines in near-surface sediments and up through the water column.

The lease area is located approximately 68 miles (109 km) from the Macondo spill site. Based 

on the general circulation pattern seen in the Gulf of Mexico and satellite imagery, the surface 

slick from that discharge did extend over the lease area during the spill, and there is the 

possibility that water quality in the lease area was briefly affected.

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

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

Impacts of Effluent Discharges

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

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

SBMs will be collected on the rig and either reused by the vendor, or transported to 

Port Fourchon, Louisiana for recycling and/or disposal in an approved facility. Cuttings wetted 

with SBMs will be discharged to the seafloor in accordance with the NPDES permit. All NPDES 

permit limitations and requirements will be met. There will be no persistent impacts on water 

quality in the lease area (National Research Council, 1983; Neff, 1987; Neff et al., 2000).

Treated sanitary and domestic wastes, including those from support vessels, may have a slight 

transient effect on water quality in the immediate vicinity of these discharges. All NPDES permit 

limitations and requirements and USCG regulations (as applicable) will be met, therefore, little 

or no impact on water quality is anticipated.

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

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

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

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

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

Based on adherence to permit limits and applicable regulations, little or no impact on water 

quality is anticipated.

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

uncontaminated cooling water, fire water, and ballast water are expected to be diluted rapidly, 

resulting in little or no impact on water quality.

Impacts of a Small Fuel Spill

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

analyzed and discussed in MMS (2007b) and BOEM (2012a,b). The probability of a small spill 

would be minimized by Anadarko’s preventative measures during routine operations including 

fuel transfer. In the unlikely event of a spill, implementation of Anadarko’s OSRP could 

potentially help mitigate and reduce the impacts. EP Section H provides detail on spill response 

measures in addition to the summary information provided in this EIA. Given the open ocean 

location of the lease area, the extent and duration of water quality impacts from a small spill 

would not be significant.
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 22 

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

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

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

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

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

The sea surface area with diesel fuel on it would range from 0.5 to 5 ha (1.2 to 12 ac) depending 

on sea state and weather conditions.

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

moderately volatile (National Research Council, 2003a). The constituents of these oils are light 

to intermediate in molecular weight and can be readily degraded by aerobic microbial oxidation. 

Because the density of diesel is less than the density of seawater, diesel 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 (National Research 

Council, 2003a) and would not be expected to occur to any appreciable degree in offshore 

waters of the Gulf of Mexico. Diesel oil is readily and completely degraded by naturally 

occurring microbes (NOAA, 2006).

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

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

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

Impacts of a Large Oil Spill (WCD)

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

analyzed and discussed in MMS (2007b) and BOEM (2012b,d). A large spill would affect water 

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

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

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

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

although new information from the Macondo spill indicates that plumes of submerged oil 

droplets can be produced when subsea dispersants are applied at the wellhead (Camilli et al., 

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

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

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

Team [OSAT], 2010).

Because of the lease area’s distance to 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 (Table 3). 

C.2 Seafloor Habitats and Biota

Water depths at the proposed project area range from 1,270 to 1,351 m (4,167 to 4,433 ft). The 

seafloor at the proposed wellsites is smooth and featureless. No anomalous seabed amplitudes 

indicative of hydrocarbon macroseeps were seen within 610 m (2,000 ft) of any of the wellsites

(Gardline, 2013).

Based on the absence of hard bottom areas detected by side-scan sonar during the site 

clearance survey, the seafloor within 610 m (2,000 ft) of the wellsites is expected to consist 
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 23 

mainly of soft bottom communities. The site clearance survey did not identify any features that 

could support high-density deepwater benthic communities within 610 m (2,000 ft) of the 

wellsites, and the presence of chemosynthetic communities is considered negligible (Gardline, 

2013).

C.2.1 Soft Bottom Benthic Communities

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

Northern Gulf of Mexico Continental Slope Habitats and Benthic Ecology Study (Wei, 2006; 

Rowe and Kennicutt, 2009) can be used to describe typical benthic communities in the area. 

Table 4 summarizes data collected at stations in water depths similar to the proposed drilling 

area.

Table 4. Benthic community data from stations near the lease area and in similar water depths 

sampled during the Northern Gulf of Mexico Continental Slope Habitats and Benthic 

Ecology Study (Adapted from: Wei, 2006; Rowe and Kennicutt, 2009).

Station Water Depth

(m)

Abundance

Meiofauna

(individuals/m2) 

Macroinfauna

(individuals/m2) 

Megafauna

(individuals/ha)

MT4 1,401 246,058 3,262 1,548

C4 1,463 273,585 3,045 743

Meiofaunal and megafaunal abundances from Rowe and Kennicutt (2009); macroinfaunal abundance from 

Wei (2006). 

Densities of meiofauna (animals passing through a 0.5-mm sieve but retained on a 0.062-mm 

sieve) in water depths representative of the lease area (1,270 to 1,351 m [4,167 to 4,433 ft]) 

typically range from approximately 185,000 to 285,000 individuals/m2 (Rowe and 

Kennicutt, 2009). Nematodes, nauplii, and harpacticoid copepods were the three dominant 

meiofaunal groups, accounting for about 90% of total abundance.

The benthic macroinfauna is characterized by small mean individual sizes and low densities, 

both of which reflect the meager primary production in Gulf of Mexico surface waters 

(Wei, 2006). Densities decrease exponentially with water depth. Based on an equation 

presented by Wei (2006), macroinfaunal densities in the water depths of the lease area are 

expected to be about 2,652 individuals/m2

. 

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

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

recognized four depth-dependent faunal zones (1 through 4), two of which are divided 

horizontally. The lease area is in Zone 2E, which includes parts of the mid Texas-Louisiana slope, 

the west flank of the Mississippi Fan, the mid Mississippi Canyon, the head of De Soto Canyon, 

and the mid West Florida Terrace, with stations ranging in depth from 625 to 1,828 m (2,051 to 

5,997 ft). The most abundant species in Zone 2E were the polychaetes Litocorsa antennata, 

Aricidea suecica, Tharyx marioni, Paralacydonia paradoxa, and the bivalve Heterodonta sp. D 

(Wei, 2006).
Atwater Valley Blocks 18 and 19 December 2013 

Environmental Impact Analysis for Initial Exploration Plan Page 24 

Megafaunal densities from nearby stations ranged from 625 to 1,548 individuals/ha. Common 

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

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

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

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

1 to 2 g C/m2 in the top 15 cm (6 in.) of sediments (Rowe and Kennicutt, 2009).

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

discharges (drilling muds and cuttings), and a large oil spill (WCD) resulting from a well blowout 

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

would float and dissipate on the sea surface.

Physical Disturbance to the Seafloor

In water depths such as those encountered in the lease area, the areal extent of seafloor 

impacts will be small compared to the lease area itself.These types of soft bottom communities 

are ubiquitous along the northern Gulf of Mexico continental slope (Gallaway, 1988; Gallaway et 

al., 2003; Rowe and Kennicutt, 2009) and impacts from the physical disturbance of the seafloor 

during this project will have no significant impact on soft bottom benthic communities in the 

region.

Impacts of Effluent Discharges

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

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

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

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

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

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

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

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

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

reproduce slowly, recovery may require several years.

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

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

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

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

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

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

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

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

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

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

as opportunistic species that tolerate low oxygen and high H2S predominate (Continental Shelf 

Associates, Inc., 2006). As the base synthetic fluid is decomposed by microbes, the area will 

gradually return to pre-drilling conditions. Disturbed sediments will be recolonized through 

larval settlement and migration from adjacent areas.
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Environmental Impact Analysis for Initial Exploration Plan Page 25 

The areal extent of impacts from drilling discharges will be small. Assuming a typical effect 

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

the seafloor within a lease block. Soft bottom communities are ubiquitous along the northern 

Gulf of Mexico continental slope (Gallaway, 1988; Gallaway et al., 2003; Rowe and 

Kennicutt, 2009). Impacts from drilling discharges during this project will have no significant 

impact on soft bottom benthic communities in the region.

Impacts of a Large Oil Spill (WCD)

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

hundred meters of the wellsite. The MMS (2007b) estimated that a severe subsurface blowout 

could resuspend and disperse sediments within a 300-m (984-ft) radius. While coarse sediments 

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

sediments (silts and clays) could be resuspended for more than 30 days and dispersed over a 

much wider area. Based on previous studies, surface sediments at the project area are assumed 

to largely be silt and clay (Rowe and Kennicutt, 2009).

Discussions in MMS (2007a, 2008) indicated that oil spills would be unlikely to affect benthic 

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

blowout) because the oil would rise quickly to the sea surface directly over the spill location. 

However, during the Macondo spill, subsurface plumes were reported at a water depth of about 

1,100 m (3,600 ft), extending at least 22 miles (35 km) from the wellsite and persisting for more 

than a month (Camilli et al., 2010). The subsurface plumes apparently resulted from the use of 

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

subsurface plumes are not well known, a subsurface plume could contact the seafloor and affect 

benthic communities beyond the 300-m (984-ft) radius estimated by MMS (2007a, 2008), 

depending on its extent, trajectory, and persistence. This contact could result in smothering 

and/or toxicity to benthic organisms. The affected area would be recolonized by benthic 

organisms over a period of months to years (National Research Council, 2003a).

C.2.2 High-Density Deepwater Benthic Communities

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

that could support high-density chemosynthetic communities, or features or areas that could 

support high-density deepwater corals and other associated high-density hard bottom 

communities. Chemosynthetic communities were discovered in the central Gulf of Mexico in 

1984 and have been studied extensively (MacDonald, 2002). Deepwater coral communities are 

also known from numerous locations in the Gulf of Mexico (Brooke and Schroeder, 2007; 

CSA International, Inc., 2007). These communities occur almost exclusively on authigenic 

carbonates created by chemosynthetic communities. 

The nearest known chemosynthetic community site is approximately 51 miles (82 km) west of 

the lease area in Mississippi Canyon (MC) Block 969. The nearest identified deepwater coral 

communities are in MC 943, 8 miles (13 km) north-northeast of the lease area. 

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 (Gardline, 2013). 
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Environmental Impact Analysis for Initial Exploration Plan Page 26 

IPFs potentially affecting high-density deepwater benthic communities include physical 

disturbance of the seafloor, effluent discharges (drilling muds and cuttings), and a large oil spill 

(WCD) from a well blowout at the seafloor. A small fuel spill would not affect benthic 

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

Physical Disturbance to the Seafloor

In water depths such as are encountered in the lease area, DP semisubmersibles disturb the 

seafloor only around the wellbore (SHL) where the bottom template and BOP are located. 

Depending upon the specific well configuration, this area is generally about 0.25 ha (0.62 ac).

The areal extent of these impacts from the DP rig will be small, and NTL 2009-G40 requires that 

high-density deepwater benthic communities and features or areas that could support 

high-density chemosynthetic communities, or deepwater corals communities be avoided. Based 

on the Gardline (2013) report, there will be no impacts on chemosynthetic or deepwater coral 

communities from this project.

Impacts of Effluent Discharges

The site clearance survey (Gardline, 2013) did not identify any features that could support 

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

locations, and the presence of chemosynthetic communities in the lease area is considered 

negligible. Monitoring programs on the Gulf of Mexico continental slope have shown that 

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

of the wellsite, although detectable deposits may extend beyond this distance (Continental Shelf 

Associates, Inc., 2004, 2006; Neff et al., 2005). Because of the water depth of the lease area, 

drilling discharges would be expected to result in thinner, more diffuse accumulations on the 

seafloor than those documented in the literature. Although small amounts of cuttings particles 

may reach areas inhabited by high-density deepwater benthic communities, the discharges are 

not expected to result in significant impacts to these communities.

Impacts of a Large Oil Spill (WCD)

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

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

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

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

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

persisting for more than a month (Camilli et al., 2010). The subsurface plumes apparently 

resulted from the use of dispersants at the wellhead (Joint Analysis Group, 2010c). While the 

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

the potential to contact high-density deepwater benthic communities beyond the 300-m 

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

persistence. Oil plumes that contact sensitive benthic communities before degrading could 

potentially impact the resource (BOEM, 2012b). 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 

blowout are still unknown due to the depth and the magnitude of this event. Hazen et al. (2010) 
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Environmental Impact Analysis for Initial Exploration Plan Page 27 

reported changes in plume hydrocarbon composition with distance from the source. Incubation 

experiments with environmental isolates demonstrated faster than expected hydrocarbon 

biodegradation rates at 5°C. Based on these results, Hazen et al. (2010) suggested the potential 

exists for intrinsic bioremediation of the oil plume in the deep water column without substantial 

oxygen drawdown.

Potential impacts of oil on high-density deepwater benthic communities are discussed in 

MMS (2007b). Although chemosynthetic communities live among hydrocarbon seeps, natural 

seepage is very constant and occurs at low rates compared to the potential rates of oil release 

from a blowout. In addition, seep organisms also require unrestricted access to oxygenated 

water at the same time as exposure to hydrocarbon energy sources (MacDonald, 2002). Oil 

droplets or oiled sediment particles could come into contact with chemosynthetic organisms or 

deepwater corals. As discussed by MMS (2007b), impacts could include loss of habitat, 

biodiversity, and live coral coverage; destruction of hard substrate; change in sediment 

characteristics; and reduction or loss of one or more commercial and recreational fishery 

habitats. Sublethal effects could be long-lasting and affect the resilience of coral colonies to 

natural disturbances (e.g., elevated water temperature and diseases) (BOEM, 2012d). 

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 observed dead and dying corals with sloughing tissue and discoloration. Much of the soft 

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

appeared to be a brown flocculent substance (floc). Out of 40 large corals, 90% were heavily 

affected and showed dead and dying parts and discoloration. Another site 400 m (1,312 ft) 

farther away had a colony of stony corals similarly affected and partially covered with a similar 

brown substance. Based on hopanoid petroleum biomarkers from the floc, researchers 

concluded that it contained oil from the Macondo spill. The injured and dead corals were in an 

area where a subsea plume of oil had been documented during the spill in June, 2010; corals 

elsewhere in the Gulf of Mexico outside the area affected by the plume did not appear to be 

experiencing higher mortality. The research team concluded that the observed coral injuries 

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

C.2.3 Designated Topographic Features

The lease blocks are not within or near a designated topographic feature or a no-activity zone as 

identified in NTL 2009-G39. The nearest designated topographic feature is Sackett Bank, located 

in West Delta Block 147, 55 miles (89 km) north-northwest of the lease area.

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

impacts to designated topographic features due to the distance from the lease area. A small 

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

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

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

to the distance and the difference in water depth. Near-bottom currents in the region are 

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume 

up onto the continental shelf edge. 
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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 is Main Pass Block 290, 97 miles (156 km) 

north-northeast of the lease area.

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

impacts to pinnacle trend area live bottoms due to the distance from the lease area. A small 

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

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

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

to the distance and the difference in water depth. Near-bottom currents in the region are 

predicted to flow along the isobaths (Nowlin et al., 2001) and typically would not carry a plume 

up onto the continental shelf edge. 

C.2.5 Eastern Gulf Live Bottoms

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

seagrass communities and low-relief hard-bottom reef within the Eastern Gulf of Mexico

Planning Area blocks in water depths of 100 m (328 ft) or less and portions of Pensacola and 

Destin Dome Area blocks in the Central Gulf of Mexico Planning Area. The nearest block

covered by the live bottom stipulation, as defined by NTL 2009-G39, is Destin Dome Block 573, 

approximately 128 miles (206 km) 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 5. The table also indicates the location of critical habitat 

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

geographical area occupied by the species at the time of listing, 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 
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Environmental Impact Analysis for Initial Exploration Plan Page 29 

cetaceans, sea turtles, and fishes in the Gulf of Mexico. The USFWS has jurisdiction for 

ESA-listed birds and the West Indian manatee.

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

area and along the northern Gulf Coast.

Species Scientific Name Status

Potential Presence Critical Habitat Designated 

in Gulf of Mexico Lease 

Area Coastal

Marine Mammals

Sei whale Balaenoptera borealis E Xa -- None

Blue whale Balaenoptera musculus E Xa -- None

Fin whale Balaenoptera physalus E Xa -- None

North Atlantic right whale Eubalaena glacialis E Xa -- None

Humpback whale Megaptera novaeangliae E Xa -- None

Sperm whale Physeter macrocephalus E X -- None

West Indian manatee Trichechus manatus 

latirostris E -- X Florida (Peninsular)

Sea Turtles

Loggerhead turtle Caretta caretta T X X None

Green turtle Chelonia mydas T, Eb X X None

Leatherback turtle Dermochelys coriacea E X X None

Hawksbill turtle Eretmochelys imbricata E X X None

Kemp’s ridley turtle Lepidochelys kempii E X X None

Birds

Piping Plover Charadrius melodus T -- X 

Coastal Texas, Louisiana, 

Mississippi, Alabama, and 

Florida (Panhandle)

Whooping Crane Grus americana E -- X 

Coastal Texas 

(Aransas National Wildlife 

Refuge)

Fishes

Gulf sturgeon Acipenser oxyrinchus desotoi T -- X 

Coastal Louisiana, 

Mississippi, Alabama, and 

Florida (Panhandle)

Smalltooth sawfish Pristis pectinata E -- X Southwest Florida and the 

Florida Keys

Invertebrates

Elkhorn coral Acropora palmata E -- X Flower Garden Banks

Terrestrial Mammals

Beach mice (Alabama, 

Choctawhatchee, 

Perdido Key, 

St. Andrew)

Peromyscus polionotus E -- X Alabama and Florida 

(Panhandle) beaches

Abbreviations: E = endangered; T = threatened. a

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

to be present in the lease area. b

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

As mandated by the ESA, MMS consulted NMFS and the USFWS on possible and potential 

impacts from the proposed leasing in the Gulf of Mexico on endangered/threatened species and 

their designated critical habitat (MMS, 2007a,b). A Biological Assessment was prepared for each 

consultation. The formal ESA consultation with NMFS was concluded with receipt of the 

Biological Opinion on 3 July 2007 (NMFS, 2007). The Biological Opinion concludes that the 

proposed lease sales and associated activities in the Five-Year Leasing Plan for Western and 

Central Planning Areas 2007-2012 are not likely to jeopardize the continued existence of 
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Environmental Impact Analysis for Initial Exploration Plan Page 30 

threatened and endangered species under NMFS jurisdiction or destroy or adversely modify 

designated critical habitat. The informal ESA consultation with USFWS was concluded with a 

letter dated 14 September 2007. The USFWS concurred with MMS’s determination that 

proposed actions of the Five-Year Leasing Plan were not likely to adversely affect 

threatened/endangered species or designated critical habitat under USFWS jurisdiction. 

Following the Macondo spill, BOEMRE requested to reinitiate an ESA consultation with both 

NMFS and USFWS on 30 July 2010. The NMFS responded with a letter to BOEMRE on 

24 September 2010, and the USFWS responded with a letter to BOEMRE on 27 September 2010. 

At present, the NMFS and USFWS have placed the consultation process on hold because they 

feel the environmental baseline information needs to be updated for the post-Macondo spill 

environment based on the results of the Natural Resource Damage Assessment (NRDA) process. 

The NRDA data have yet to be released, and the existing consultation remains in effect

(BOEM, 2012b). The existing consultation recognizes that BOEM-required mitigations and other 

reasonable and prudent measures should reduce the likelihood of impacts from all 

BOEM-authorized activities in the Gulf of Mexico.

Coastal endangered or threatened species that may occur along the northern Gulf Coast include 

the West Indian manatee, Piping Plover, Whooping Crane, Gulf sturgeon, and four subspecies of 

beach mouse. Critical habitat has been designated for all of these species as indicated in Table 5

and discussed in individual sections.

Two other coastal species (Bald Eagle and Brown Pelican) discussed in MMS (2007b) and BOEM 

(2012b) are no longer federally listed as endangered or threatened. These are discussed in 

Section C.4.2. 

There are five sea turtle and six marine mammal species that are currently listed as endangered 

and threatened by the ESA and known to occur within OCS and slope waters of the Gulf of 

Mexico. The listed sea turtles include the leatherback turtle, Kemp's ridley turtle, hawksbill

turtle, loggerhead turtle, and green turtle. Listed marine mammal species include one 

odontocete (toothed) whale (sperm whale) and five mysticete (baleen) whales (blue whale, fin 

whale, humpback whale, North Atlantic right whale, and sei whale)(Pritchard, 1997; Würsig et 

al., 2000). No critical habitat has been designated for these species in the Gulf of Mexico.

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

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

species in the Gulf of Mexico.

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

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

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

species in the Gulf of Mexico.

C.3.1 Sperm Whale (Endangered)

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

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

Gulf of Mexico; a species description is presented in 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., 2012). No 

critical habitat for the sperm whale has been designated in the Gulf of Mexico.
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Environmental Impact Analysis for Initial Exploration Plan Page 31 

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

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

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

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

concentrated along the upper continental slope between the 200- and 1,000-m (656- and 

3,280-ft) depth contours (Jochens et al., 2008). Male sperm whales were more variable in their 

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

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

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

and groups of bachelor males. Typical group size for mixed groups was 10 individuals 

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

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

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

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

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

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

(WCD). Effluent discharges are likely to have negligible impacts on sperm whales due to rapid 

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

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

potential for marine debris-related impacts on sperm whales. 

Current threats to sperm whale populations worldwide are discussed in a final recovery plan for 

the sperm whale recently published by NOAA (NMFS, 2010a). Threats are defined as "any factor 

that could represent an impediment to recovery," and include fisheries interactions, 

anthropogenic noise, vessel interactions, contaminants and pollutants, disease, injury from 

marine debris, research, predation and natural mortality, direct harvest, competition for 

resources, loss of prey base due to climate change and ecosystem change, and cable laying. 

In the Gulf of Mexico, the impacts from many of these threats are identified as either low or 

unknown (BOEMRE, 2011a; BOEM, 2012b). 

Impacts of Drilling Rig Presence, Noise, and Lights

Noise generated from the drilling rig and from routine drilling activities may be audible to sperm 

whales and so has the potential to disturb individuals near the lease area. The drilling rig used 

during the proposed activity will be located within a deepwater, open ocean environment and 

will remain stationary during drilling operations. Sounds generated by the rig and by drilling 

operations will be generally continuous (with some variability in sound level, considering 

thruster activity). This analysis assumes that the continuous nature of sounds produced by the 

drilling rig will provide individual whales with cues relative to the direction and relative distance 

(sound intensity) of the sound source, and the fixed position of the drilling rig will provide 

multiple options for active avoidance of potential physical impacts. NMFS analyzed the potential 

for impacts of drilling-related noise on sperm whales in its Biological Opinion for the Gulf of 

Mexico Oil and Gas Activities: Five-Year Leasing Plan for Western and Central Planning Areas 

2007-2012 (NMFS, 2007). The analysis noted that semisubmersible drilling rigs emit low sound 

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

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

(NMFS, 2007). 
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Environmental Impact Analysis for Initial Exploration Plan Page 32 

In addition, there are other OCS facilities and activities near the lease area, and the region as a 

whole has a large number of similar noise sources. Drilling-related noise associated with this 

project will contribute to increases in the ambient noise environment of the Gulf of Mexico, but 

it is not expected in amplitudes sufficient to cause either hearing or behavioral effects to sperm 

whales.

Drilling rig lighting and rig presence are not identified as IPFs for sperm whales (MMS, 2007b; 

BOEM, 2012a,b,d; NMFS, 2007) 

Impacts of Support Vessel and Helicopter Traffic

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

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

concerning the frequency of vessel strikes are presented in MMS (2007b). To reduce the 

potential for vessel strikes, the BSEE and BOEM issued NTL 2012-JOINT-G01, which recommends 

protected species identification training and that vessel operators and crews maintain a vigilant 

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

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

When whales are sighted, vessel operators and crews are required to attempt to maintain a 

distance of 91 m (300 ft) or greater whenever possible. Vessel operators are required to reduce 

vessel speed to 10 knots or less, when safety permits, when mother/calf pairs, pods, or large 

assemblages of cetaceans are observed near an underway vessel. Compliance with this NTL will 

minimize the likelihood of vessel strikes as well as reduce the chance for disturbing sperm 

whales.

NMFS (2007) analyzed the potential for vessel strikes and harassment of sperm whales. With 

implementation of the mitigation measures in NTL 2012-JOINT-G01, NMFS concluded that the 

likelihood of collisions between vessels and sperm whales would be reduced to insignificant 

levels. NMFS concluded that the observed avoidance of passing vessels by sperm whales is an 

advantageous response to avoid a potential threat and is not expected to result in any 

significant effect on migration, breathing, nursing, breeding, feeding, or sheltering to individuals, 

or have any consequences at the population level. With implementation of the vessel strike 

avoidance measures requirement to maintain a distance of 91 m (300 ft) from sperm whales, 

the NMFS concluded that the potential for harassment of sperm whales would be reduced to 

discountable levels.

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

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

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

3 (12%) of 24 sightings. All three reactions consisted of a hasty dive and occurred at less than 

360 m (1,180 ft) lateral distance from the aircraft. Additional reactions were seen when aircraft 

circled certain whales to make further observations. Based on other studies of cetacean 

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

the aircraft were short-term and probably of no long-term biological significance.

While flying offshore in the Gulf of Mexico, helicopters maintain altitudes above 213 m (700 ft) 

during transit to and from the working area. In the event that a whale is seen during transit, the 

helicopter will not approach or circle the animal. Although responses are possible (Smultea 
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Environmental Impact Analysis for Initial Exploration Plan Page 33 

et al., 2008), the NMFS (2007) and BOEM (2012d) concluded that this altitude would minimize 

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

Impacts of a Small Fuel Spill

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

(2007b), BOEM (2012a,b,d), and NMFS (2007). Oil impacts on marine mammals are discussed 

by Geraci and St. Aubin (1990). For this EP, there are no unique site-specific issues with respect 

to spill impacts on these animals that were not analyzed in the previous documents. 

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during 

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

Anadarko’s OSRP could mitigate and lessen the potential for impacts on sperm whales. Given 

the open ocean location of the lease area, the duration of a small spill and opportunity for 

impacts to occur would be very brief.

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

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

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

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The sea surface area with diesel fuel on it would range from 0.5 to 5 ha (1.2 to 

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and 

noise of response vessels and aircraft (Marine Mammal Commission [MMC], 2011). However, 

due to the limited areal extent and short duration of water quality impacts from a small fuel 

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

Impacts of a Large Oil Spill (WCD)

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

(2007b), BOEM (2012a,b,d), and NMFS (2007). For this EP, there are no unique site-specific 

issues with respect to spill impacts on these animals.

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

indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and 

dispersants) (MMC, 2011). Direct physical and physiological effects can include skin irritation, 

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 

toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey; and stress from 

the activities and noise of response vessels and aircraft. Complications of the above may lead to 

dysfunction of immune and reproductive systems, physiological stress, declining physical 

condition, and death. Behavioral responses can include displacement of animals from prime 

habitat, disruption of social structure, changing prey availability and foraging distribution and/or 

patterns, changing reproductive behavior/productivity, and changing movement patterns or 

migration (MMC, 2011). Ackleh et al. (2012) hypothesized that sperm whales may have 

temporarily relocated away from areas near the Macondo spill in 2010.
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Environmental Impact Analysis for Initial Exploration Plan Page 34 

In the event of a large spill, the level of vessel and aircraft activity associated with spill response 

could disturb sperm whales and potentially result in vessel strikes, entanglement, or other injury 

or stress. Response vessels would operate in accordance with NTL 2012-JOINT-G01 to reduce 

the potential for striking or disturbing these animals.

C.3.2 West Indian Manatee (Endangered)

Most of the Gulf of Mexico manatee population is located in peninsular Florida (USFWS, 2001). 

Manatee sightings in Louisiana have increased as the species extends its presence farther west 

of Florida in the warmer months (Wilson, 2003). A species description is presented in a MMS 

(2007b) and in the recovery plan for this species (USFWS, 2001).

IPFs potentially affecting manatees include support vessel and helicopter traffic and a large oil 

spill (WCD). A small fuel spill in the lease area would be unlikely to affect manatees due to the 

distance to the nearest shoreline. As explained in Section A.9.2, a small fuel spill would not be 

expected to make landfall or reach coastal waters prior to breaking up. Compliance with 

NTL 2012-BSEE-G01 will minimize the potential for marine debris-related impacts on manatees.

Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb manatees, and there is also a risk of vessel 

strikes, which are identified as a threat in the recovery plan for this species (USFWS, 2001). 

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

recommends protected species identification training and that vessel operators and crews 

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

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

protected species. Compliance with this NTL will minimize the likelihood of vessel strikes, and 

no significant impacts on manatees are expected.

Helicopter traffic also has the potential to disturb manatees. Rathbun (1988) reported that 

manatees were disturbed more by helicopters than by fixed-wing aircraft; however, the 

helicopter was flown at relatively low altitudes of 20 to 160 m (66 to 525 ft). Helicopters used in 

support operations maintain a minimum altitude of 213 m (700 ft) while in transit offshore, 

305 m (1,000 ft) over unpopulated areas or across coastlines, and 610 m (2,000 ft) over 

populated areas and sensitive habitats such as wildlife refuges and park properties. In addition, 

guidelines and regulations specify that helicopters maintain an altitude of 305 m (1,000 ft) 

within 91 m (300 ft) of marine mammals (BOEM, 2012a,d). This mitigation measure will 

minimize the potential for disturbing manatees, and no significant impacts are expected.

Impacts of a Large Oil Spill (WCD)

In the event that manatees were exposed to oil, effects could include direct impacts from oil 

exposure, as well as indirect impacts due to response activities and materials (e.g., vessel traffic, 

noise, and dispersants) (MMC, 2011). Direct physical and physiological effects can include skin 

irritation, inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; 

inhalation of toxic fumes; ingestion of oil (and dispersants) directly or via contaminated prey 

(or contaminated vegetation, in the case of manatees); and stress from the activities and noise 

of response vessels and aircraft. Complications of the above may lead to dysfunction of immune 

and reproductive systems, physiological stress, declining physical condition, and death. 

Behavioral responses can include displacement of animals from prime habitat, disruption of 
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Environmental Impact Analysis for Initial Exploration Plan Page 35 

social structure, changing prey availability and foraging distribution and/or patterns, changing 

reproductive behavior/productivity, and changing movement patterns or migration 

(MMC, 2011).

In the event that a large spill reached coastal waters where manatees were present, the level of 

vessel and aircraft activity associated with spill response could disturb manatees and potentially 

result in vessel strikes, entanglement, or other injury or stress. Response vessels would operate 

in accordance with NTL 2012-JOINT-G01 to reduce the potential for striking or disturbing these 

animals, and therefore no significant impacts are expected. 

C.3.3 Endangered Mysticete Whales

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

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

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

species in the Gulf of Mexico.

Because of the rare occurrence of these whales in the Gulf of Mexico and the limited scope and 

duration of the project, it is highly unlikely that any endangered mysticete would come into 

contact with any project activities, either routine operations or accidents. NMFS did not include 

any of these mysticete whales as affected species in its Biological Opinion (NMFS, 2007). 

Potential impacts are analyzed in MMS (2007b) and BOEM (2012a,b,d), and those analyses are 

incorporated by reference. If any of these whales were present in the area, potential impacts 

would be the same as those discussed below in Section C.3.4. 

C.3.4 Non-Endangered Marine Mammals (Protected)

Excluding the seven endangered species that have been cited previously, there are 22 additional 

species of marine mammals that may be found in the Gulf of Mexico, including 2 species of 

mysticete whales, dwarf and pygmy sperm whales, 4 species of beaked whales, and 14 species 

of delphinids. All marine mammals are protected species under the MMPA. The most common 

non-endangered cetaceans in the deepwater environment are odontocetes such as the 

pantropical spotted dolphin, spinner dolphin, and Clymene dolphin. A brief summary is 

presented below, and additional information on these groups is presented in MMS (2007b).

Mysticete whales. Two species of non-endangered mysticete whales are known from the Gulf 

of Mexico. The Bryde’s whale (Balaenoptera edeni) has been sighted most frequently along the 

100-m (328-ft) isobath (Davis and Fargion, 1996; Davis et al., 2000). Most sightings have been 

made in the DeSoto Canyon region and off western Florida, although there have been some in 

the west-central portion of the northeastern Gulf. The minke whale (Balaenoptera 

acutorostrata) is considered rare in the Gulf of Mexico, with the only confirmed records coming 

from strandings (Würsig et al., 2000). Based on the available data, it is possible that Bryde’s 

whales could occur in the lease area.

Dwarf and pygmy sperm whales. At sea, it is difficult to differentiate dwarf sperm whales 

(Kogia sima) from pygmy sperm whales (Kogia breviceps), and sightings are often grouped 

together as Kogia spp. Both species have a worldwide distribution in temperate to tropical 

waters. In the Gulf of Mexico, both species occur primarily along the continental shelf edge and 

in deeper waters off the continental shelf (Mullin et al., 1991). Either species could occur in the 

lease area.
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Environmental Impact Analysis for Initial Exploration Plan Page 36 

Beaked whales. Four species of beaked whales are known from the Gulf of Mexico. They are 

Blainville’s beaked whale (Mesoplodon densirostris), Cuvier’s beaked whale (Ziphius cavirostris), 

Sowerby’s beaked whale (Mesoplodon bidens), and Gervais’ beaked whale (Mesoplodon 

europaeus). Stranding records in the Gulf of Mexico suggest that Gervais’ beaked whale is the 

most common and Sowerby’s is extralimital. Due to the difficulties of at-sea identification, 

beaked whales in the Gulf of Mexico are identified either as Cuvier’s beaked whales or are 

grouped into an undifferentiated complex (Mesoplodon spp. and Ziphius spp.). In the northern 

Gulf of Mexico, they are broadly distributed in water depths greater than 1,000 m (3,281 ft) over 

lower slope and abyssal landscapes (Davis et al., 2000). Any of these species could occur in the 

lease area.

Delphinids. Fourteen species of delphinids are known from the Gulf of Mexico, including 

Atlantic spotted dolphin (Stenella frontalis), bottlenose dolphin (Tursiops truncatus), Clymene

dolphin (Stenella clymene), false killer whale (Pseudorca crassidens), Fraser’s dolphin

(Lagenodelphis hosei), killer whale (Orcinus orca), melon-headed whale (Peponocephala electra), 

pantropical spotted dolphin (Stenella attenuata), pygmy killer whale (Feresa attenuata), 

short-finned pilot whale (Globicephala macrorhynchus), Risso’s dolphin (Grampus griseus), 

rough-toothed dolphin (Steno bredanensis), spinner dolphin (Stenella longirostris), and striped 

dolphin (Stenella coeruleoalba). Any of these species could occur in the lease area. The most 

common non-endangered cetaceans in the deepwater environment are the pantropical spotted 

dolphin, spinner dolphin, and Clymene dolphin.

Bottlenose dolphins

• for which the level of direct human-caused mortality exceeds the potential biological 

removal level;

. The bottlenose dolphin (Tursiops truncatus) is a common inhabitant of the 

northern Gulf of Mexico, particularly within continental shelf waters. There are two ecotypes of 

bottlenose dolphins, a coastal form and an offshore form, which are genetically isolated from 

each other (Waring et al., 2012). The offshore form of the bottlenose dolphin may occur within 

the lease area. Inshore populations of coastal bottlenose dolphins in the northern Gulf of 

Mexico are separated into 37 geographically distinct population units, or stocks, for 

management purposes by the NMFS (Waring et al., 2012). NMFS (2013) has proposed to classify 

the Gulf of Mexico Northern Coastal Stock, Western Coastal Stock, and all 32 of the Bay, Sound, 

and Estuarine Stocks as strategic stocks. A “strategic” stock is defined by the MMPA as a marine 

mammal stock

• which, based on the best available scientific information, is declining and is likely to be listed 

as a threatened species under the ESA within the foreseeable future; or

• which is listed as a threatened or endangered species under the ESA, or is designated as 

depleted under the MMPA.

The strategic stock designation in this case was based primarily on the occurrence of an 

“unusual mortality event” of unprecedented size and duration that has affected these stock 

areas. This unusual mortality event began in February 2010 and is ongoing. Carmichael et al. 

(2012) hypothesized that the unusual number of bottlenose dolphin strandings in the northern 

Gulf of Mexico during this time may have been associated with environmental perturbations 

including sustained cold weather and the Macondo spill in 2010 as well as large volumes of cold 

freshwater discharge in the early months of 2011.
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Environmental Impact Analysis for Initial Exploration Plan Page 37 

IPFs potentially affecting non-endangered marine mammals include drilling rig presence, noise, 

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

and a large oil spill (WCD). Effluent discharges are likely to have negligible impacts due to rapid 

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

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

potential for marine debris-related impacts.

Impacts of Drilling Rig Presence, Noise, and Lights

Noise from routine drilling activities has the potential to disturb marine mammals. Most 

odontocetes (toothed whales and dolphins) use higher frequency sounds than those produced 

by OCS drilling activities (Richardson et al., 1995). Noise generated during drilling operations is 

generally continuous and fixed in location. Noise intensity associated with these operations is 

relatively weak. Stronger noise levels will occur during thruster use in dynamic positioning. 

Thruster noise impacts would be expected at greater distances than vessel noise alone 

(LGL Ecological Research Associates, Ltd., 2006) but are dependent on variables relating to 

thruster type and usage. It is expected that marine mammals within or near the lease area 

would be able to detect the presence of the drilling rig and avoid exposure to higher energy 

sounds, particularly within an open ocean environment. Some odontocetes have shown 

increased feeding activity around lighted platforms at night (Todd et al., 2009). Even temporary 

drill rigs present an attraction to pelagic food sources that may attract both cetaceans and sea 

turtles. Therefore, prey congregation could pose an attraction to protected species that 

exposes them to higher levels or longer durations of noise that might otherwise be avoided. 

There are other OCS facilities and activities near the lease area, and the region as a whole has a 

large number of similar sources. Species in the northern Gulf of Mexico have been exposed to 

noise from anthropogenic sources for a long period of time and over large geographic areas and 

likely do not represent a naïve population with regard to sound (National Research Council, 

2003b). Due to the limited duration of drilling activities, this project would represent a 

temporary contribution to the overall noise regime within the lease area, and potential impacts 

are expected to be biologically insignificant to marine mammal populations.

Drilling rig lighting and rig presence are not identified as IPFs for marine mammals (MMS, 

2007b, 2008; BOEMRE, 2011a; BOEM, 2012a,b).

Impacts of Support Vessel and Helicopter Traffic

Support vessel traffic has the potential to disturb marine mammals, and there is also a risk of 

vessel strikes. Data concerning the frequency of vessel strikes are presented in MMS (2007b). 

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

recommends protected species identification training and that vessel operators and crews 

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

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

protected species. Vessel operators and crews are required to attempt to maintain a distance of 

91 m (300 ft) or greater when whales are sighted and 45 m (150 ft) when small cetaceans are 

sighted. When cetaceans are sighted while a vessel is underway, vessels must attempt to 

remain parallel to the animal’s course and avoid excessive speed or abrupt changes in direction 

until the cetacean has left the area. Vessel operators are required to reduce vessel speed to 

10 knots or less when mother/calf pairs, pods, or large assemblages of cetaceans are observed 

near an underway vessel, when safety permits. Compliance with NTL 2012-JOINT-G01 will 
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Environmental Impact Analysis for Initial Exploration Plan Page 38 

minimize the likelihood of vessel strikes as well as reduce the chance for disturbing marine 

mammals, and therefore no significant impacts are expected. 

Aircraft traffic also has the potential to disturb marine mammals (Würsig et al., 1998). However, 

while flying offshore, helicopters maintain altitudes above 213 m (700 ft) during transit to and 

from the working area. In addition, guidelines and regulations specify that helicopters maintain 

an altitude of 305 m (1,000 ft) within 91 m (300 ft) of marine mammals (BOEM, 2012a,d). 

Maintaining this altitude will minimize the potential for disturbing marine mammals, and no 

significant impacts are expected (BOEM, 2012a,d).

Impacts of a Small Fuel Spill

Potential spill impacts on marine mammals are discussed in MMS (2007b) and BOEM (2012a,b); 

oil impacts on marine mammals in general are discussed by Geraci and St. Aubin (1990). For this 

EP, there are no unique site-specific issues with respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by Anadarko’s preventative measures including

fuel transfer. In the unlikely event of a spill, implementation of Anadarko’s OSRP is expected to 

lessen the potential for impacts on marine mammals. EP Section H provides detail on spill 

response measures, along with a summary of those measures in this EIA. Given the open ocean 

location of the lease area, the limited duration of a small spill and response efforts, it is 

expected that any impacts would be brief and minimal. 

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

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

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

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate 

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The sea surface area with diesel fuel on it would range from 0.5 to 5 ha (1.2 to 

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

Direct physical and physiological effects of exposure to diesel fuel could include skin irritation, 

inflammation, or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of 

toxic fumes; ingestion of oil directly or via contaminated prey; and stress from the activities and 

noise of response vessels and aircraft (MMC, 2011). However, due to the limited areal extent 

and short duration of water quality impacts from a small fuel spill, as well as the mobility of 

marine mammals, no significant impacts would be expected.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine mammals are discussed in MMS (2007b) and BOEM (2012a,b). 

For this EP, there are no unique site-specific issues. Impacts of oil spills on marine mammals can 

include direct impacts from oil exposure, as well as indirect impacts due to response activities 

and materials (e.g., vessel traffic, noise, and dispersants) (MMC, 2011). Direct physical and 

physiological effects can include skin irritation, inflammation, or necrosis; chemical burns of 

skin, eyes, and mucous membranes; inhalation of toxic fumes; ingestion of oil (and dispersants) 

directly or via contaminated prey (or contaminated vegetation, in the case of manatees); and 

stress from the activities and noise of response vessels and aircraft. Complications of the above 

may lead to dysfunction of immune and reproductive systems, physiological stress, declining 

physical condition, and death. Behavioral responses can include displacement of animals from 
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Environmental Impact Analysis for Initial Exploration Plan Page 39 

prime habitat, disruption of social structure, changing prey availability and foraging distribution 

and/or patterns, changing reproductive behavior/productivity, and changing movement 

patterns or migration (MMC, 2011).

In the event of a large spill, the level of vessel and aircraft activity associated with spill response 

could disturb marine mammals and potentially result in vessel strikes, entanglement, or other 

injury or stress. Response vessels would operate in accordance with NTL 2012-JOINT-G01 to 

reduce the potential for striking or disturbing these animals, and therefore no significant 

impacts are expected. 

C.3.5 Sea Turtles (Endangered/Threatened) 

Five species of endangered or threatened sea turtles may be found near the lease area. 

Leatherback turtle (Dermochelys coriacea), Kemp's ridley turtle (Lepidochelys kempii), and 

hawksbill turtle (Eretmochelys imbricata) turtles are endangered. The loggerhead turtle 

(Caretta caretta) is currently a threatened species; however, in March 2010, NMFS and USFWS 

proposed to list the Northwest Atlantic Ocean population of loggerhead turtles as endangered 

(75 FR 12598). The green turtle (Chelonia mydas) is listed as threatened, except for the Florida

and Pacific coast of Mexico breeding populations, which are listed as endangered. Species 

descriptions are presented in MMS (2007b).

Leatherback and loggerhead turtles are the most likely species to be present near the lease area 

as adults. Green, hawksbill, and Kemp’s ridley turtles are typically inner shelf and nearshore 

species, unlikely to occur near the lease area as adults. Hatchlings or juveniles of any of the sea 

turtle species may be present in deepwater areas, including the lease area, where they may be 

associated with Sargassum and other flotsam.

Sea turtle nesting on the northern Gulf of Mexico coast can be summarized by species as 

follows:

• Loggerhead turtles – Loggerheads nest in significant numbers along the Florida Panhandle 

and, to a lesser extent, from Texas through Alabama (MMS, 2007b). The nearest significant 

nesting area of loggerhead turtles is found in Louisiana, on beaches within the Breton NWR;

• Green and leatherback turtles – Green and leatherback turtles infrequently nest on Florida 

Panhandle beaches (Florida Fish and Wildlife Conservation Commission, 2012);

• Kemp’s ridley turtles – The main Kemp’s ridley nesting site is Rancho Nuevo beach, 

Tamaulipas, Mexico (NMFS et al., 2011). Kemp’s ridley turtles typically do not nest 

anywhere near the project area, although there have been occasional reports of Kemp’s 

ridleys nesting in Alabama (Share the Beach, 2010); and

• Hawksbill turtles – Hawksbills typically do not nest anywhere near the project area.

IPFs potentially affecting sea turtles include drilling rig presence, noise, and lights; support 

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

(WCD). Effluent discharges are likely to have negligible impacts on sea turtles due to rapid 

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

Compliance with NTL 2012-BSEE-G01 will minimize the potential for marine debris-related 

impacts on sea turtles.
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Environmental Impact Analysis for Initial Exploration Plan Page 40 

Impacts of Drilling Rig Presence, Noise, and Lights

Offshore drilling activities produce a broad array of sounds at frequencies and intensities that 

may be detected by sea turtles (Geraci and St. Aubin, 1987). Potential impacts may include 

behavioral disruption and temporary or permanent displacement from the area near the sound 

source. Certain sea turtles, especially loggerheads, may be attracted to offshore structures 

(Lohoefener et al., 1990) and, thus, may be more susceptible to impacts from sounds produced 

during routine operations. The most likely impacts would be short-term behavioral changes 

such as diving and evasive swimming, disruption of activities, or departure from the area. Due 

to the limited scope and short duration of drilling activities, these short-term impacts are not 

expected to be biologically significant to sea turtle populations.

Artificial lighting can disrupt the nocturnal orientation of sea turtle hatchlings (Witherington, 

1997; Tuxbury and Salmon, 2005). However, hatchlings may rely less on light cues when they 

are offshore than when they are emerging on the beach (Salmon and Wyneken, 1990). The 

NMFS (2007) concluded that the effects of lighting from offshore structures on sea turtles are 

insignificant.

Impacts of Support Vessel and Helicopter Traffic

Noise generated from support vessel traffic has the potential to disturb sea turtles, and there is 

also a risk of vessel strikes. Data show that vessel strike 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, BSEE and BOEM issued NTL 2012-JOINT-G01, which 

recommends protected species identification training and that vessel operators and crews 

maintain a vigilant watch for sea turtles and slow down or stop their vessel to avoid striking 

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

species. When sea turtles are sighted, vessel operators and crews are required to attempt to 

maintain a distance of 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).

Noise generated from support helicopter traffic also has the potential to disturb sea turtles. 

However, while flying offshore, helicopters maintain altitudes above 213 m (700 ft) during 

transit to and from the working area. This altitude will minimize the potential for disturbing sea 

turtles, and no significant impacts are expected.

Impacts of a Small Fuel Spill

Potential spill impacts on sea turtles are discussed in MMS (2007b), BOEM (2012a,b), and the 

NMFS Biological Opinion (NMFS, 2007). For this EP, there are no unique site-specific issues with 

respect to spill impacts on these animals.

The probability of a fuel spill will be minimized by Anadarko’s preventative measures including

fuel transfer. In the unlikely event of a spill, implementation of Anadarko’s OSRP is expected to

minimize potential impacts on sea turtles. EP Section H provides detail on spill response 

measures. Given the open ocean location of the lease area, the duration of a small spill and 

opportunity for impacts to occur would be very brief.
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Environmental Impact Analysis for Initial 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 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 sea surface area 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 (MMS, 2007b; NMFS, 2010b; BOEM, 2012b,d). 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 due to 

the distance to nearest shoreline. As explained in Section A.9.2, a small fuel spill would not be 

expected to make landfall or reach coastal waters prior to breaking up. 

Impacts of a Large Oil Spill (WCD)

Impacts of oil spills on sea turtles can include direct impacts from oil exposure, as well as 

indirect impacts due to response activities and materials (e.g., vessel traffic, noise, and 

dispersants). Direct physical and physiological effects can include skin irritation, inflammation, 

or necrosis; chemical burns of skin, eyes, and mucous membranes; inhalation of toxic fumes and 

smoke (e.g., from in situ burning of oil); ingestion of oil (and dispersants) directly or via 

contaminated food; and stress from the activities and noise of response vessels and aircraft. 

Complications of the above may lead to dysfunction of immune and reproductive systems, 

physiological stress, declining physical condition, and death. Behavioral responses can include 

displacement of animals from prime habitat, disruption of social structure, changing food 

availability and foraging distribution and/or patterns, changing reproductive 

behavior/productivity, and changing movement patterns or migration. In the unlikely event of a 

spill, implementation of Anadarko’s OSRP is expected to minimize the potential for these types 

of impacts on sea turtles. EP Section H provides detail on spill response measures.

Studies of oil effects on loggerheads in a controlled setting (Lutcavage et al., 1995) suggest that 

sea turtles show no avoidance behavior when they encounter an oil slick, and any sea turtle in 

an affected area would be expected to be exposed. Sea turtles’ diving behaviors also put them 

at risk. Sea turtles rapidly inhale a large volume of air before diving and continually resurface 

over time, which may result in repeated exposure to volatile vapors and oiling (NMFS, 2007).

Spilled oil reaching sea turtle nesting beaches could have effects on nesting sea turtles and egg 

development (NMFS, 2007). An oiled beach could affect nest site selection or result in no 

nesting at all (e.g., false crawls). Upon hatching and successfully reaching the water, hatchlings 

are subject to the same types of oil spill exposure hazards as adults. Hatchlings that contact oil 

residues while crossing a beach can exhibit a range of effects, from acute toxicity to impaired 

movement and normal bodily functions (NMFS, 2007).
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Environmental Impact Analysis for Initial Exploration Plan Page 42 

In the event of a large spill, the level of vessel and aircraft activity associated with spill response 

could disturb sea turtles and potentially result in vessel strikes, entanglement, or other injury or 

stress. Response vessels would operate in accordance with NTL 2012-JOINT-G01 to reduce the 

potential for striking or disturbing these animals, and therefore no significant impacts are 

expected. 

The extent and scope of the Macondo spill represents new information not assessed in the 

existing ESA Section 7 consultation under the current Five-Year Program. As a result of this new 

information, BOEMRE reinitiated ESA Section 7 consultation on the existing Gulf of Mexico lease 

sale EIS with NMFS and the USFWS on 30 July 2010. The NMFS responded with a letter to 

BOEMRE on 24 September 2010, and the USFWS responded with a letter to BOEMRE on 

27 September 2010. However, NMFS and the USFWS have placed the consultation process on 

hold pending the results of the NRDA post-Macondo spill data review, which has yet to be 

released. The existing consultation currently remains in effect (BOEM, 2012b). 

BOEMRE (2011a) and BOEM (2012b) reexamined the impacts analyses presented in MMS 

(2007b, 2008) for the five sea turtle species that inhabit the Gulf of Mexico based on additional 

information and in consideration of the Macondo spill. No new information was found that 

would alter the potential impacts on sea turtles described in previous EISs. 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.

C.3.6 Piping Plover (Threatened)

The Piping Plover (Charadrius melodus) is a migratory shorebird that overwinters along the 

southeastern U.S. and Gulf of Mexico coasts. This threatened species is in decline as a result of 

hunting, habitat loss and modification, predation, and disease (USFWS, 2003). Critical 

overwintering habitat has been designated, including beaches in Texas, Louisiana, Mississippi, 

Alabama, and Florida (Figure 3). Piping Plovers inhabit coastal sandy beaches and mudflats, 

feeding by probing for invertebrates at or just below the surface. They use beaches adjacent to 

foraging areas for roosting and preening (USFWS, 2010a). A species description is presented in 

MMS (2007b).

A large oil spill (WCD) is the only IPF potentially affecting Piping Plovers. There are no IPFs 

associated with routine project activities that could affect these birds. A small fuel spill in the 

lease area would be unlikely to affect Piping Plovers because a small fuel spill would not be 

expected to make landfall or reach coastal waters prior to breaking up (see explanation in 

Section A.9.2). 
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Figure 3. Location of selected environmental features in relation to the lease area.
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Impacts of a Large Oil Spill (WCD)

The lease area is 73 miles (117 km) from the nearest shorelines inhabited by Piping Plovers 

(Figure 3). The revised OSRA results (BOEMRE, 2011a; BOEM, 2012b) summarized in 

Section A.9.3 (Table 3) predict that during the spring there is a 4% probability that an oil spill 

from the lease area would reach a shoreline designated as critical habitat for the Piping Plover 

within 10 days. Plovers could physically oil themselves while foraging on oiled shores or 

secondarily contaminate themselves through ingestion of oiled intertidal sediments and prey 

(MMS, 2007b). Plovers congregate and feed along tidally exposed banks and shorelines, 

following the tide out and foraging at the water’s edge. It is possible that some deaths of Piping 

Plovers could occur, especially if spills occur during winter months when plovers are most 

common along the coastal Gulf or if spills contacted critical habitat. Impacts could also occur 

from vehicular traffic on beaches and other activities associated with spill cleanup. Anadarko 

has extensive resources available to protect and rehabilitate wildlife in the event of a spill 

reaching the shoreline, as detailed in the OSRP.

C.3.7 Whooping Crane (Endangered)

The Whooping Crane (Grus americana) is an omnivorous wading bird and an endangered 

species. There are three wild populations in North America (Whooping Crane Eastern 

Partnership, 2010). One population winters along the Texas coast at Aransas NWR and 

summers at Wood Buffalo National Park in Canada; this population represents the majority of 

the world’s population of free-ranging Whooping Cranes and reached a record population of 

270 at Aransas NWR in December 2008 (Whooping Crane Eastern Partnership, 2010). 

A nonmigrating population has been reintroduced in central Florida, and another reintroduced 

population summers in Wisconsin and migrates to the southeastern U.S. for the winter. 

Whooping Cranes breed, migrate, winter, and forage in a variety of habitats, including coastal 

marshes and estuaries, inland marshes, lakes, ponds, wet meadows and rivers, and agricultural 

fields (USFWS, 2007). About 9,000 ha (22,240 ac) of salt flats on Aransas NWR and adjacent 

islands comprise the principal wintering grounds of the Whooping Crane. Aransas NWR is 

designated as critical habitat for the species. A species description is presented in MMS (2007b) 

and BOEM (2012a). A large oil spill (WCD) is the only IPF potentially affecting Whooping Cranes. 

A small fuel spill in the lease area would 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

451 miles (726 km) from its critical habitat designated in the Aransas NWR. The revised 

OSRA modeling (BOEM, 2012b) predicts that there is a 0.5% or less probability that an oil spill 

originating in the lease area would reach the Aransas NWR within 30 days and a 5% probability 

of oil reaching that area in 120 days.

In the event of oil exposure, Whooping Cranes could physically oil themselves while foraging in 

oiled areas or secondarily contaminate themselves through ingestion of contaminated shellfish, 

frogs, and fishes. It is possible that some Whooping Crane deaths could occur. In the event of a 

spill, Anadarko would work with the applicable State and Federal agencies to prevent impacts 

from a spill. 
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C.3.8 Gulf Sturgeon (Threatened)

The Gulf sturgeon (Acipenser oxyrinchus desotoi) is a threatened fish species that inhabits major 

rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida 

(Barkuloo, 1988; Wakeford, 2001). An anadromous fish that migrates from the sea upstream 

into coastal rivers to spawn in freshwater, it historically ranged from the Mississippi River to 

Charlotte Harbor, Florida (Wakeford, 2001). Today, this range has contracted to encompass 

major rivers and inner shelf waters from the Mississippi River to the Suwannee River, Florida. 

Populations have been depleted or even extirpated throughout this range by fishing, shoreline 

development, dam construction, water quality changes, and other factors (Barkuloo, 1988; 

Wakeford, 2001). These declines prompted the listing of the Gulf sturgeon as a threatened 

species in 1991. The best known populations occur in the Apalachicola and Suwannee Rivers in 

Florida (Carr, 1996; Sulak and Clugston, 1998), the Choctawhatchee River in Alabama (Fox et al., 

2000), and the Pearl River in Mississippi/Louisiana (Morrow et al., 1998). Critical habitat in the 

Gulf extends from Lake Borgne, Louisiana (St. Bernard Parish) to Suwannee Sound, Florida 

(Levy County) (NMFS, 2010b) (Figure 3). A species description is presented 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 MMS (2007b) and BOEM (2012a,b) and 

by NMFS (2007). For this EP, there are no unique site-specific issues with respect to this species.

The lease area is approximately 137 miles (220 km) from the nearest Gulf sturgeon critical 

habitat. The revised OSRA modeling (BOEM, 2012b) predicts that a spill in the lease area has 

1% or less probability of contacting any 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, sub-adult and adult Gulf sturgeon would be most 

vulnerable to an estuarine or marine oil spill, and would be vulnerable only from 

1 September through 30 April when this species is foraging in estuarine and shallow marine 

habitats (NMFS, 2007).

C.3.9 Smalltooth Sawfish (Endangered)

Smalltooth sawfish (Pristis pectinata) are found in the tropical and subtropical Atlantic Ocean. 

In the Western Atlantic they have historically ranged from New York to Brazil, including the Gulf 

of Mexico and Caribbean Sea. This sawfish primarily occurs in estuarine and coastal habitats 

such as bays, lagoons, and rivers. The smalltooth sawfish was listed as endangered under the 

ESA on 1 April 2003. Its critical habitat consists of two units: the Charlotte Harbor Estuary Unit, 

which comprises approximately 89,621 ha (221,459 ac) of coastal habitat; and the Ten Thousand 

Islands/Everglades Unit, which comprises approximately 250,506 ha (619,013 ac) of coastal 
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habitat. The two units are located along the southwestern coast of Florida between Charlotte 

Harbor and Florida Bay.

A large oil spill (WCD) is the only IPF potentially affecting smalltooth sawfish. There are no IPFs 

associated with routine project activities that could affect these fish. A small fuel spill in the 

lease area would be unlikely to affect smalltooth sawfish because a small fuel spill would not be 

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

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on smalltooth sawfish are similar to those discussed for other coastal and 

estuarine species in MMS (2007b), BOEM (2012a), and by the NMFS (2007) in its Biological 

Opinion. For this EP, there are no unique site-specific issues with respect to smalltooth sawfish. 

In the event of oil reaching smalltooth sawfish habitat, the fish could be affected by direct 

ingestion, ingestion of oiled prey, or the absorption of dissolved petroleum products through 

the gills.

C.3.10 Beach Mice (Endangered)

Four subspecies of endangered beach mouse (Peromyscus polionotus) occur on the barrier 

islands of Alabama and the Florida Panhandle. They are the Alabama, Choctawhatchee, 

Perdido Key, and St. Andrew beach mice. Critical habitat has been designated for all four 

subspecies; Figure 3 shows the critical habitat combined for all four subspecies. Species 

descriptions are provided in MMS (2007b).

A large oil spill (WCD) is the only IPF potentially affecting beach mice. There are no IPFs 

associated with routine project activities that could affect these animals due to the distance 

from shore and the lack of any onshore support activities near their habitat. A small fuel spill in 

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 MMS (2007b, 2008), BOEMRE (2011a), 

and BOEM (2012a). For this EP, there are no unique site-specific issues with respect to these 

species that were not analyzed in these documents. 

The beach mouse habitat is 169 miles (272 km) from the lease area. The revised OSRA modeling 

summarized in Section A.9.3 predicts that a spill in the lease area has a 1% or less probability of 

reaching either the Alabama or Florida shorelines inhabited by beach mice within 120 days.

In the event of oil contacting these beaches, beach mice could experience several types of direct 

and indirect impacts. Contact with spilled oil could cause skin and eye irritation and subsequent 

infection; matting of fur; irritation of sweat glands, ear tissues, and throat tissues; disruption of 

sight and hearing; asphyxiation from inhalation of fumes; and toxicity from ingestion of oil and 

contaminated food. Indirect impacts could include reduction of food supply, destruction of 

habitat, and fouling of nests. Impacts could also occur from vehicular traffic and other activities 

associated with spill cleanup. However, any such impacts are unlikely due to the distance from 

shore and response actions that would occur in the event of a spill.
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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 coral species in waters ranging from 1 to 5 m (3.3 to 16 ft) deep

in tropical and subtropical waters. In the northern Gulf of Mexico, elkhorn coral has been found 

within the coral cap region of the Flower Garden Banks National Marine Sanctuary (Flower 

Garden Banks National Marine Sanctuary, 2011).

There are no IPFs associated with routine project activities that could affect this species in the 

northern Gulf of Mexico. 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 Garden Banks because of the water depth of the area. Although 

subsurface plumes were reported following the Macondo spill, these plumes resulted from the 

use of subsea dispersants at the seafloor.

C.4 Coastal and Marine Birds

C.4.1 Marine Birds

Marine birds include seabirds and other species that may occur in the pelagic environment of 

the project area (Clapp et al., 1982a,b, 1983; Peake, 1996; Hess and Ribic, 2000). Seabirds spend 

much of their lives offshore over the open ocean, except during breeding season when they nest 

along the coast. In addition, other birds such as waterfowl, marsh birds, and shorebirds may 

occasionally be present over open ocean areas. No endangered or threatened bird species are 

likely to occur at the project area due to the distance from shore. For a discussion of shorebirds 

and coastal nesting birds, see Section C.4.2. 

Seabirds of the northern Gulf of Mexico were surveyed from ships during the GulfCet II program. 

Hess and Ribic (2000) reported that terns, storm-petrels, shearwaters, and jaegers were the 

most frequently sighted seabirds in the deepwater area. From these surveys, four ecological 

categories of seabirds were documented in the deepwater areas of the Gulf: summer migrants 

(shearwaters, storm petrels, boobies); summer residents that breed in the Gulf (Sooty Tern, 

Least Tern, Sandwich Tern, Magnificent Frigatebird); winter residents (gannets, gulls, jaegers); 

and permanent resident species (Laughing Gulls, Royal Terns, Bridled Terns) (Hess and Ribic, 

2000). The GulfCet II study did not estimate bird densities; however, Powers (1987) indicates 

that seabird densities over the open ocean typically are <10 birds/km2

. 

The distributions and relative densities of seabirds within the deepwater areas of the Gulf of 

Mexico, including the project area, vary temporally (i.e., seasonally) and spatially. In GulfCet II 

studies, species diversity and densities varied by hydrographic environment and by the presence 

and relative location of mesoscale features such as Loop Current eddies that may enhance

nutrient levels and productivity of surface waters where these seabird species forage (Hess and 

Ribic, 2000). 

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.
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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 (WCD). Effluent discharges are likely to have negligible impacts on the birds due to rapid 

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

mobility of these animals. Compliance with NTL 2012-BSEE-G01 will minimize the potential for 

marine debris-related impacts on birds.

Impacts of Drilling Rig Presence, Noise, and Lights

Birds that frequent rigs may be exposed to contaminants including air pollutants and routine 

discharges, but significant impacts are unlikely due to rapid dispersion. Birds migrating over 

water have been known to strike offshore structures, resulting in death or injury (Wiese et al., 

2001; Russell, 2005). Mortality of migrant birds at tall towers and other land-based structures 

has been reviewed extensively, and the mechanisms involved in rig collisions appear to be 

similar. In some cases, migrants simply do not see a part of the rig until it is too late. In other 

cases, navigation may be disrupted by noise (Russell, 2005). On the other hand, offshore 

structures are suitable stopover habitats for most trans-Gulf migrant species, and most of the 

migrants that stop over on rigs probably benefit from their stay, particularly in spring 

(Russell, 2005). Due to the limited scope and short duration of drilling activities described in this 

EP, any impacts on populations of either seabirds or trans-Gulf migrant birds are not expected 

to be significant.

Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters are unlikely to significantly disturb pelagic birds in open, 

offshore waters. It is likely that individual birds would experience, at most, only short-term 

behavioral disruption, and the impact would not be significant.

Impacts of a Small Fuel Spill

Potential spill impacts on marine birds are discussed in MMS (2007b) and BOEM (2012 a,b,d). 

For this EP, there are no unique site-specific issues with respect to spill impacts on these 

animals.

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during 

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

Anadarko’s OSRP could 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 sea surface area with diesel fuel on it would range from 0.5 to 5 ha (1.2 to 

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

Birds exposed to oil on the sea surface could experience direct physical and physiological effects 

including skin irritation; chemical burns of skin, eyes, and mucous membranes; and inhalation of 

toxic fumes. Due to the limited areal extent and short duration of water quality impacts from a 
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small fuel spill, secondary impacts due to ingestion of oil via contaminated prey or reductions in 

prey abundance are unlikely. Due to the low densities of birds in open ocean areas, the small 

area affected, and the brief duration of the surface slick, no significant impacts on pelagic birds 

would be expected.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on marine and pelagic birds are discussed in MMS (2007b) and BOEM 

(2012 a,b,d). For this EP, there are no unique site-specific issues with respect to spill impacts on 

these animals.

BOEM has reexamined the analyses for coastal and marine birds presented in MMS 

(2007b, 2008) and determined that no new information was found that would alter the 

potential impacts on marine and pelagic birds (BOEMRE, 2011a; BOEM, 2012b).

Pelagic seabirds could be exposed to oil from a spill at the project area. Hess and Ribic (2000) 

reported that terns, storm-petrels, shearwaters, and jaegers were the most frequently sighted 

seabirds in the deepwater Gulf of Mexico (>200 m [<656 ft]). Powers (1987) indicates that 

seabird densities over the open ocean typically are <10 birds/km2

. The number of pelagic birds 

that could be affected in open, offshore waters would depend on the extent and persistence of 

the oil slick.

The Macondo spill provides relevant information about the species of pelagic birds that may be 

affected in the event of a large oil spill. Birds that have been treated for oiling include several 

pelagic species such as the Northern Gannet, Magnificent Frigatebird, and Masked Booby 

(USFWS, 2011). The Northern Gannet is among the species with the largest numbers of birds 

affected by the spill.

C.4.2 Shorebirds and Coastal Nesting Birds

Threatened and endangered bird species (Piping Plover and Whooping Crane) have been 

discussed previously in Section C.3. Various species of non-endangered birds are also found 

along the northern Gulf Coast, including diving birds, shorebirds, marsh birds, wading birds, and 

waterfowl. Gulf Coast marshes and beaches also provide important feeding grounds and 

nesting habitats. Species that breed on beaches, flats, dunes, bars, barrier islands, and similar 

habitats include the Sandwich Tern, Wilson’s Plover, Black Skimmer, Forster’s Tern, Gull-Billed 

Tern, Laughing Gull, Least Tern, and Royal Tern (USFWS, 2010b). Additional information is 

presented in MMS (2007b) and BOEM (2012a).

The Brown Pelican (Pelecanus occidentalis) was delisted from Federal endangered status in 2009 

(USFWS, 2010c). However, this species remains listed as endangered on the Louisiana list of 

Endangered Species (Louisiana Department of Wildlife and Fisheries, 2013), is listed as a species 

of greatest conservation need by the State of Mississippi (Mississippi Department of Wildlife, 

Fisheries and Parks, 2005), and as a species of special concern by the State of Florida (Florida 

Fish and Wildlife Conservation Commission, 2012). Brown Pelicans inhabit coastal habitats and 

forage within both coastal waters and waters of the inner continental shelf. Aerial and 

shipboard surveys, including GulfCet and GulfCet II, indicate that Brown Pelicans do not occur in 

deep offshore waters (Fritts and Reynolds, 1981; Peake, 1996; Hess and Ribic, 2000). Nearly half 

the southeastern population of Brown Pelicans lives in the northern Gulf Coast, generally 

nesting on protected islands (USFWS, 2010b).
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The Southern Bald Eagle (Haliaeetus leucocephalus) was delisted from its threatened status in 

the lower 48 states on 28 June 2007. The Bald Eagle is a terrestrial raptor widely distributed 

across the southern U.S., including coastal habitats along the Gulf of Mexico. The Gulf Coast is 

inhabited by both wintering migrant and resident Bald Eagles (Johnsgard, 1990; Ehrlich et al., 

1992).

IPFs potentially affecting shorebirds and coastal nesting birds include support vessel and 

helicopter traffic and a large oil spill (WCD). A small fuel spill in the lease area would be unlikely 

to affect shorebirds or coastal nesting birds, due to the lease area’s distance from the nearest 

shoreline.As explained in Section A.9.2, a small fuel spill would not be expected to make landfall 

or reach coastal waters prior to breaking up. Compliance with NTL 2012-BSEE-G01 will minimize 

the potential for marine debris-related impacts on shorebirds.

Impacts of Support Vessel and Helicopter Traffic

Support vessels and helicopters will transit coastal areas near Port Fourchon and Houma, 

Louisiana, where shorebirds and coastal nesting birds may be found. These activities could 

periodically disturb individuals or groups of birds within sensitive coastal habitats (e.g., wetlands 

that may support feeding, resting, or breeding birds).

Vessel traffic may disturb some foraging and resting birds. Flushing distances vary between 

species and between individuals (Rodgers and Schwikert, 2002). The disturbances will be 

limited to flushing birds away from vessel pathways; known distances are from 20 to 49 m 

(65 to 160 ft) for personal watercraft and 23 to 58 m (75 to 190 ft) for an outboard-powered 

boat (Rodgers and Schwikert, 2002). Flushing distances may be similar or less for the support 

vessels to be used for Anadarko’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 are not expected. Vessel operators will use designated navigation 

channels and comply with posted speed and wake restrictions while transiting sensitive inland 

waterways. Due to the limited scope and short duration of drilling activities, any short-term 

impacts are not expected to be biologically significant to coastal bird populations.

Aircraft traffic can cause some disturbance to birds onshore and offshore. Responses are highly 

dependent on the type of aircraft, the bird species, the activities that animals were previously 

engaged in, and previous exposures to overflights (Efroymson et al., 2000). Helicopters seem to 

cause the most intense responses over other human disturbances for some species (Bélanger 

and Bédard, 1989). However, Federal Aviation Administration Advisory Circular No. 91-36D 

recommends that pilots maintain a minimum altitude of 610 m (2,000 ft) when flying over 

noise-sensitive areas such as wildlife refuges, parks, and areas with wilderness characteristics. 

This is greater than the distance (slant range) at which aircraft overflights have been reported to 

cause behavioral effects on most species of birds studied (Efroymson et al., 2000). With these 

guidelines in effect, it is likely that individual birds would experience, at most, only short-term 

behavioral disruption.

Impacts of Large Oil Spill (WCD)

Coastal birds can be exposed to oil as they float on the water surface, dive during foraging, or 

wade in oiled coastal waters. Oiled birds can lose the ability to fly, dive for food, or float on the 

water, which could lead to drowning (USFWS, 2010d). Oil interferes with the water repellency 

of feathers and can cause hypothermia in the right conditions. As birds groom themselves, they 
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can ingest and inhale the oil on their bodies. Scavengers such as Bald Eagles and gulls can be 

exposed to oil by feeding on carcasses of contaminated fish and wildlife. While ingestion can kill 

animals immediately, more often it results in lung, liver, and kidney damage, which can lead to 

death. Bird eggs may be damaged if an oiled adult sits on the nest.

As noted above, the Brown Pelican was removed from the Federal endangered species list. 

Brown Pelicans are especially at risk from direct and indirect impacts from spilled oil within 

inner shelf and inshore waters, such as embayments. The range of this species is generally 

limited to these waters and surrounding coastal habitats. Brown Pelicans feed on mid-sized fish 

that they capture by diving from above (“plunge diving”) and then scooping the fish into their 

expandable gular pouch. This behavior makes them susceptible to plumage oiling if they feed in 

areas with surface oil or an oil sheen. They may also capture prey that has been physically 

contaminated with oil or has ingested oil. Issues for Brown Pelicans include direct contact with 

oil, disturbance by cleanup activities, and long-term habitat contamination. The Bald Eagle may 

also be at risk from direct and indirect impacts from spilled oil. This species often captures fish 

within shallow water areas (snatching prey from the surface or wading into shallow areas to 

capture prey with their bill) and so may be susceptible to plumage oiling and, as with the Brown 

Pelican, they may also capture prey that has been physically contaminated with oil or has 

ingested oil.

C.5 Fisheries Resources

C.5.1 Pelagic Communities and Ichthyoplankton

Biggs and Ressler (2000) reviewed the biology of pelagic communities in the deepwater 

environment of the northern Gulf of Mexico. The biological oceanography of the region is 

dominated by the influence of the Loop Current, whose surface waters are among the most 

oligotrophic in the world’s oceans. Superimposed on this low-productivity condition are 

productive "hot spots" associated with entrainment of nutrient-rich Mississippi River water and 

mesoscale oceanographic features. Anticyclonic and cyclonic hydrographic features play an 

important role in determining biogeographic patterns and controlling primary productivity in the 

northern Gulf of Mexico (Biggs and Ressler, 2000).

Most fishes inhabiting shelf or oceanic waters of the Gulf of Mexico have planktonic eggs and 

larvae (Ditty, 1986; Ditty et al., 1988; Richards et al., 1989, 1993). Pelagic eggs and larvae 

become part of the planktonic community for various lengths of time (10 to 100 days, 

depending on the species) (MMS, 2007b).

IPFs potentially affecting pelagic communities and ichthyoplankton include drilling rig presence, 

noise, and lights; effluent discharges; water intakes; and two types of accidents – a small fuel 

spill and a large oil spill (WCD).

Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as a fish-attracting 

device (FAD). In oceanic waters, the FAD effect would be most pronounced for epipelagic fishes 

such as tunas, dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting 

surface structures (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 
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and concentrating smaller fish species. Because the drilling rig is a single, temporary structure, 

impacts on fish populations, whether beneficial or adverse, are considered minor.

Impacts of Effluent Discharges

Treated sanitary and domestic wastes may have a slight effect on the pelagic environment in the 

immediate vicinity of these discharges. These wastes may have elevated levels of nutrients, 

organic matter, and chlorine, but should be diluted rapidly to undetectable levels within tens to 

hundreds of meters from the source. Minimal impacts on water quality, plankton, and nekton 

are anticipated.

Deck drainage may have a slight effect on the pelagic environment in the immediate vicinity of 

these discharges. Deck drainage from contaminated areas will be passed through an 

oil-and-water separator prior to release, and discharges will be monitored for visible sheen. The 

discharges may have slightly elevated levels of hydrocarbons but should be diluted rapidly to 

undetectable levels within tens to hundreds of meters from the source. Minimal impacts on 

water quality, plankton, and nekton are anticipated.

Other discharges in accordance with the NPDES permit, such as 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 drilling rig ultimately chosen for this project will be in compliance with all 

cooling water intake requirements. 

The intake of seawater for cooling water will entrain plankton. The low intake velocity should 

allow most strong-swimming juvenile fishes and smaller adults to escape entrainment or 

impingement. However, drifting plankton would not be able to escape entrainment with the 

exception of a few fast-swimming larvae of certain taxonomic groups. Those organisms 

entrained may be stressed or killed, primarily through changes in water temperature during the 

route from cooling intake structure to discharge structure and mechanical damage (turbulence 

in pumps and condensers). Due to the limited scope and short duration of drilling activities, any 

short-term impacts of entrainment are not expected to be biologically significant to plankton or 

ichthyoplankton populations.

Impacts of a Small Fuel Spill

Potential spill impacts on fisheries resources are discussed in MMS (2007b) and

BOEM (2012a,d). For this EP, there are no unique site-specific issues with respect to spill 

impacts.

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during 

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

Anadarko’s OSRP could 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.
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A small fuel spill in offshore waters would produce a slick on the water surface and increase the 

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

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

the time and the effectiveness of spill response measures. Section A.9.2 discusses the likely fate 

of a small fuel spill and indicates that over 90% would be evaporated or dispersed naturally 

within 24 hours. The sea surface area with diesel fuel on it would range from 0.5 to 5 ha (1.2 to 

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

A small fuel spill could have localized impacts on phytoplankton, zooplankton, and nekton. 

Due to the limited areal extent and short duration of water quality impacts, a small fuel spill 

would be unlikely to produce detectable impacts on pelagic communities.

Impacts of a Large Oil Spill (WCD)

A large oil spill could affect water column biota including phytoplankton, zooplankton, 

ichthyoplankton, and nekton. A large spill that persisted for weeks or months would be more 

likely to affect these communities. While adult and juvenile fishes may actively avoid a large 

spill, planktonic eggs and larvae would be unable to avoid contact. Eggs and larvae of fishes are 

especially vulnerable to oiling because they inhabit the upper layers of the water column, and 

they will die if exposed to certain toxic fractions of spilled oil. Impacts potentially would be 

greater if local-scale currents retained planktonic larval assemblages (and the floating oil slick) 

within the same water mass.

C.5.2 Essential Fish Habitat

Essential Fish Habitat (EFH) is defined as those waters and substrate necessary to fish for 

spawning, breeding, feeding, and growth to maturity. Under the Magnuson-Stevens Fishery 

Conservation and Management Act, as amended, Federal agencies are required to consult on 

activities that may adversely affect EFH designated in Fishery Management Plans developed by 

the regional Fishery Management Councils.

The BOEM (2012b) has reexamined the analysis for fish resources and EFH presented in MMS 

(2007a,b) in consideration of the Macondo event. No substantial new information was found 

that would alter the impact conclusions for fish resources and EFH presented in MMS (2007a,b). 

The Gulf of Mexico Fishery Management Council (GMFMC) has prepared Fishery Management 

Plans for corals and coral reefs, shrimps, stone crab, spiny lobster, reef fishes, coastal migratory 

pelagic fishes, and red drum. In 2005, the EFH for these managed species was redefined in 

Generic Amendment No. 3 to the various Fishery Management Plans (GMFMC, 2005). The EFH 

for most of these GMFMC-managed species is on the continental shelf in waters shallower than 

183 m (600 ft). The shelf edge is the outer boundary for coastal migratory pelagic fishes, reef 

fishes, and shrimps. EFH for corals and coral reefs includes some shelf-edge topographic 

features on the Texas-Louisiana OCS, the nearest of which are located approximately 56 miles 

(90 km) north-northwest of the lease area.

Highly migratory pelagic fishes, which occur as transients in the lease area, are the only 

remaining group for which EFH has been identified in the deepwater Gulf of Mexico. Species in 

this group, including tunas, swordfishes, billfishes, and sharks, are managed by NMFS. Highly 

migratory species with EFH at or near the lease area include the following species and life stages 

(NMFS, 2009):
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• Atlantic bluefin tuna (spawn, eggs, 

larvae, adults) 

• Bigeye tuna (juveniles, adults) 

• Bigeye thresher shark (all)

• Blue marlin (juveniles, adults)

• Longbill spearfish (juveniles, adults)

• Longfin mako shark (all)

• Oceanic whitetip shark (all)

• Sailfish (adult)

• Silky shark (all)

• Skipjack tuna (spawn, adults) 

• Swordfish (larvae, juveniles, adults)

• White marlin (juveniles, adults)

• Yellowfin tuna (spawn, juveniles, 

adults)

Recent research indicates the central and western Gulf of Mexico may be important spawning 

habitat for Atlantic bluefin tuna, and NMFS (2009) has designated a Habitat Area of Particular 

Concern (HAPC) for this species. The HAPC covers much of the deepwater Gulf of Mexico, 

including the lease area (Figure 3). The areal extent of the HAPC is approximately 300,000 km2 

(15,000 mi2). The prevailing assumption is that Atlantic bluefin tuna follow an annual cycle of 

foraging in June through March off the eastern U.S. and Canadian coasts, followed by migration 

to the Gulf of Mexico to spawn in April, May, and June (NMFS, 2009).

On 27 May 2011, after an extensive scientific review, NOAA announced that Atlantic bluefin 

tuna currently do not warrant species protection under the ESA. However, NOAA did classify 

the bluefin tuna as a species of concern, effectively placing the species on a watch list as the 

agency awaits new data on the impact of a stricter international management regimen. 

A new amendment to the original EFH Generic Amendment was finalized in 2005

(GMFMC, 2005). One of the most significant proposed changes in this amendment reduced the 

extent of EFH relative to the 1998 Generic Amendment by removing the EFH description and 

identification from waters between 100 fathoms and the seaward limit of the Exclusive 

Economic Zone (EEZ). The Highly Migratory Species Fisheries Management Plan was amended 

in 2009 to update EFH and HAPC to include the bluefin tuna spawning area (NMFS, 2009).

There are current NTLs (2009-G39 and 2009-G40) that provide guidance and clarification of the 

regulations with respect to biologically sensitive underwater features and areas and benthic 

communities that are considered EFH (MMS, 2009a,b). A new EFH consultation has been 

initiated between BOEM’s Gulf of Mexico Region and NOAA’s Southeastern Region. Some 

EFH requirements may change with the new agreement. Until the new agreement is in place, 

the 1999 Programmatic Consultation with the elements described above will be followed 

(BOEMRE, 2011a; BOEM, 2012b).

Other HAPCs have been identified by the GMFMC (2005). These include the Florida Middle 

Grounds, Madison-Swanson Marine Reserve, Tortugas North and South Ecological Reserves, 

Pulley Ridge, and several individual reefs and banks of the northwestern Gulf of Mexico

(Figure 3). The nearest HAPC is Jakkula Bank, located approximately 153 miles (246 km) west of 

the lease area.

IPFs potentially affecting EFH include drilling rig presence, noise, and lights; effluent discharges; 

water intakes; and two types of accidents – a small fuel spill and a large oil spill (WCD).
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Impacts of Drilling Rig Presence, Noise, and Lights

The drilling rig, as a floating structure in the deepwater environment, will act as an FAD. In 

oceanic waters, the FAD effect would be most pronounced for epipelagic fishes such as tunas, 

dolphin, billfishes, and jacks, which are commonly attracted to fixed and drifting surface 

structures (Holland et al., 1990; Higashi, 1994; Relini et al., 1994; MMS, 2000, 2007b, 2008). 

This FAD effect would possibly enhance feeding of epipelagic predators by attracting and 

concentrating smaller fish species. Because the drilling rig is a single, temporary structure, any 

impacts on EFH for highly migratory pelagic fishes are considered minor.

Impacts of Effluent Discharges

Other effluent discharges affecting EFH by diminishing ambient water quality include drilling 

muds and cuttings, treated sanitary and domestic wastes, deck drainage, and miscellaneous 

discharges such as desalination unit brine and uncontaminated cooling water, fire water, and 

ballast water. Impacts on water quality have been discussed previously. No significant impacts 

on EFH for highly migratory pelagic fishes are expected from these discharges.

Impacts of Water Intakes

As noted previously, cooling water intake will cause entrainment and impingement of plankton, 

including fish eggs and larvae (ichthyoplankton). Due to the limited scope and short duration of 

drilling activities, any short-term impacts on EFH for highly migratory pelagic fishes are not 

expected to be biologically significant.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during 

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

Anadarko’s OSRP could 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 MMS (2007b) and BOEM (2012a,d). For this EP, 

there are no unique site-specific issues with respect to spill impacts.

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

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

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

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 sea surface area with diesel fuel on it would range from 0.5 to 5 ha (1.2 to 

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

A small fuel spill could have localized impacts on EFH for highly migratory pelagic fishes, 

including tunas, swordfishes, billfishes, and sharks. These species occur as transients in the 

lease area. A spill would also produce short-term impact on water quality in the HAPC for 

spawning bluefin tuna, which covers much of the deepwater Gulf of Mexico. The areal extent of 

the affected area would represent a negligible portion of the HAPC.
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A small fuel spill would not affect EFH for corals and coral reefs, as the nearest EFH is located 

approximately 56 miles (90 km) from the lease area. A small fuel spill would float and dissipate 

on the sea surface and would not contact these features.

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on EFH are discussed in MMS (2007b) and BOEM (2012a,d). 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 in the subsurface as well. Given the extent of EFH designations in 

the Gulf of Mexico (GMFMC, 2005; NMFS, 2009), some impact on EFH would be unavoidable.

A large spill could affect the EFH for many managed species including shrimps, stone crab, spiny 

lobster, reef fishes, coastal migratory pelagic fishes, and red drum. It would result in adverse 

impacts on water quality and water column biota including phytoplankton, zooplankton, and 

nekton. In coastal waters, sediments could be contaminated and result in persistent 

degradation of the seafloor habitat for managed demersal fish and shellfish species.

The lease area is within the HAPC for spawning Atlantic bluefin tuna (NMFS, 2009). A large spill 

could temporarily degrade the HAPC due to increased hydrocarbon concentrations in the water 

column, with the potential for lethal or sublethal impacts on spawning tuna. Potential impacts 

would depend in part on the timing of a spill, as this species migrates to the Gulf of Mexico to 

spawn in April, May, and June (NMFS, 2009).

The topographic features, located 56 miles (90 km) north-northwest of the lease area, are 

designated as EFH under the corals and coral reefs management plan. An accidental spill would 

be unlikely to affect this area, since a surface slick would not reach these features due to their 

depth. 

C.6 Archaeological Resources

C.6.1 Shipwreck Sites

The BOEM (2012b) reexamined the analyses for archaeological resources presented in 

MMS (2007b, 2008), based on additional information available since the publication of these 

two documents and in consideration of the Macondo oil spill. Substantial new information that 

alters the impact conclusion for archaeological resources presented in MMS (2007b, 2008) has 

come to light as a result of BOEM-sponsored studies and industry surveys. Specifically, evidence 

of damage to significant cultural resources (i.e., historic shipwrecks) has been shown to have 

occurred because of an incomplete knowledge of seafloor conditions in lease areas >200 m 

(656 ft) deep that have been exempted from high-resolution surveys. Since significant historic 

shipwrecks have recently been discovered outside the previously designated high-probability 

areas (some of which show evidence of impacts from permitted activities prior to their 

discovery), a survey is now required for exploration and development projects.

The lease area is not on the list of OCS blocks with a high potential for historic shipwrecks 

(BOEM, 2012c). The site clearance surveys conducted by Gardline (2013) found no items of 

archaeological significance within 610 m (2,000 ft) of any of the proposed wellsites. Anadarko

will abide by the applicable requirements of NTL 2005-G07, which stipulate that work be 
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stopped at the project site if any previously undetected archaeological resource is discovered 

after work has begun until appropriate surveys and evaluations have been completed.

Because there are no shipwreck sites in the lease area, there are no routine IPFs that are likely 

to affect shipwrecks. Impacts of a large oil spill (WCD) are the only IPFs considered. A small fuel 

spill would not affect shipwrecks because the oil would float and dissipate on the sea surface.

Impacts of a Large Oil Spill (WCD)

MMS (2007b) estimated that a severe subsurface blowout could resuspend and disperse 

sediments within a 300-m (984-ft) radius. Because there are no historic shipwrecks in the lease 

area, this impact would not be relevant.

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

archaeological sites beyond the immediate vicinity of the wellhead (i.e., due to physical impacts 

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

However, during the Macondo spill, subsurface plumes were reported at a water depth of about 

1,100 m (3,600 ft), extending at least 22 miles (35 km) from the wellsite and persisting for more 

than a month (Camilli et al., 2010). The subsurface plumes apparently resulted from the use of 

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

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

shipwreck sites beyond the 300-m (984-ft) radius estimated by MMS (2007a, 2008), depending 

on its extent, trajectory, and persistence. If oil from a subsea spill should come into contact with 

wooden shipwrecks on the seafloor, it could adversely affect their condition or preservation. 

Should there be any indication that potential shipwreck sites could be affected, in accordance 

with NTL 2005-G07 Anadarko will immediately halt operations, take steps to ensure that the site 

is not disturbed in any way, and contact the BOEM Regional Supervisor, Leasing and 

Environment, within 48 hours of its discovery. Anadarko would cease all operations within 

305 m (1,000 ft) of the site until the Regional Supervisor provides instructions on steps to take 

to assess the site’s potential historic significance and protect it.

A spill entering shallow coastal waters could conceivably contaminate an undiscovered 

shipwreck site. As noted by MMS (2007b), should an oil spill contact a coastal historic site, such 

as a fort or a lighthouse, the major impact would be a temporary, reversible visual impact from 

oil contact and contamination of the site and its environment.

C.6.2 Prehistoric Archaeological Sites

Available evidence suggests that sea level in the northern Gulf of Mexico was at least 91 m 

(300 ft), and possibly as much as 130 m (427 ft), lower than present sea level during the period 

20,000 to 17,000 years Before Present (B.P.) (Nelson and Bray, 1970). Sea level in the northern 

Gulf reached its present stand around 3,500 years B.P. (Pearson et al., 1986).

During periods that the continental shelf was exposed above sea level, the area was open to 

habitation by prehistoric peoples. The advent of early man into the Gulf of Mexico region is 

currently accepted to be around 12,000 years B.P. (Aten, 1983). The sea-level curve for the 

northern Gulf of Mexico proposed by Coastal Environments, Inc. suggests that sea level at 

12,000 years B.P. would have been approximately 45 to 60 m (148 to 197 ft) below the 

present-day sea level (Coastal Environments, Inc., 1977, 1982). On this basis, the continental 

shelf shoreward of the 45- to 60-m (148- to 197-ft) bathymetric contours has potential for 
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prehistoric sites dating after 12,000 years B.P. Because of inherent uncertainties in both the 

depth of sea level and the entry date of prehistoric man into North America, the MMS adopted 

the 60-m (197-ft) water depth as the seaward extent for archaeological site potential in Gulf of 

Mexico region. 

With a water depth between 1,270 and 1,351 m (4,167 and 4,433 ft), the lease area is well 

beyond the 60-m (197-ft) depth contour used by the BOEM as the seaward extent for 

prehistoric archaeological site potential in the Gulf of Mexico. Because prehistoric 

archaeological sites are not found in the lease area, the only relevant IPF is a large oil spill 

(WCD). A small fuel spill would not affect prehistoric archaeological resources because the oil 

would float and dissipate on the sea surface.

Impacts of a Large Oil Spill (WCD)

Because prehistoric archaeological sites are not found in the lease area, they would not be 

affected by the physical effects of a subsea blowout. The MMS (2007b) estimates that a severe 

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

Along the northern Gulf Coast, prehistoric sites occur frequently along the barrier islands and 

mainland coast and along the margins of bays and bayous (MMS, 2007b). If a spill did reach a 

prehistoric site along these shorelines it could coat fragile artifacts or site features and 

compromise the potential for radiocarbon dating organic materials in a site (although other 

dating methods are available and it is possible to decontaminate an oiled sample for 

radiocarbon dating). Coastal prehistoric sites could also be damaged by spill cleanup operations 

(e.g., by destroying fragile artifacts and disturbing the provenance of artifacts and site features).

C.7 Coastal Habitats and Protected Areas

Coastal habitats in the northeastern Gulf of Mexico that may be affected by oil and gas activities 

are described in MMS (2007b), BOEM (2012a,b,d), and in a literature review by Collard and Way 

(1997). Coastal habitats inshore of the project area include barrier beaches and dunes, 

wetlands, and submerged seagrass beds. Generally, most of the northeastern Gulf is fringed by 

barrier beaches, with wetlands and/or submerged seagrass beds occurring in sheltered areas 

behind the barrier islands and in estuaries.

Due to the distance from shore, the only IPF associated with routine activities in the lease area 

that potentially may affect beaches and dunes, wetlands, seagrass beds, coastal wildlife refuges, 

wilderness areas, or any other managed or protected coastal area relate to support vessel 

traffic. The support bases at Port Fourchon and Houma, Louisiana, are not in wildlife refuges or 

wilderness areas. 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 due to the lease 

area’s distance from the nearest shoreline. As explained in Section A.9.2, a small fuel spill 

would not be expected to make landfall or reach coastal waters prior to breaking up.

Impacts of Support Vessel Traffic

For OCS activities in general, support operations, including crew boats and supply boats, may 

have a minor incremental impact on coastal habitats. Over time with a large number of vessel 

trips, vessel wakes can erode shorelines along inlets, channels, and harbors. Support 

operations, including crew boats and supply boats as detailed in EP Section K, may have a minor 
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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 MMS (2007b) and BOEM (2012a,b,d). 

Coastal habitats inshore of the project area include barrier beaches and dunes, wetlands, and 

submerged seagrass beds. For this EP, there are no unique site-specific issues with respect to 

coastal habitats.

The revised OSRA modeling summarized in Table 3 predicts that there is a 17% probability of oil 

from a spill in the lease area reaching shorelines in Texas within 120 days, a 14% probability of 

oil reaching Louisiana shorelines within 120 days, and a 1% chance of oil from a spill from the 

lease area reaching Mississippi shorelines within 120 days. 

The shorelines within the geographic range predicted by the OSRA modeling (Table 3) include 

extensive barrier beaches and wetlands, with submerged seagrass beds occurring in sheltered 

areas behind the barrier islands and in estuaries. NWRs and other protected areas along the 

coast are discussed in MMS (2007b), BOEM (2012b), and Anadarko’s OSRP. Coastal and near 

coastal wildlife refuges, wilderness areas, and State and National parks within the geographic 

range of the potential shoreline contacts after 120 days are presented in Table 6. 

Table 6. Wildlife refuges, wilderness areas, and State and National parks within the geographic 

range of the potential shoreline contacts after 120 days (From: BOEM, 2012b). 

County or Parish, State Wildlife Refuge, Wilderness Area, or

State/National Park

Kenedy County, Texas Padre Island National Seashore

Laguna Madre Estuarine And Coastal Marine Area

Kleberg County, Texas Padre Island National Seashore

Laguna Madre Estuarine And Coastal Marine Area

Nueces County, Texas

Laguna Madre Estuarine And Coastal Marine Area

Mustang Island State Park

Lake Corpus Christi State Park

Port Aransas Park

Mission-Aransas National Estuarine Research Reserve

Aransas County, Texas

Mission-Aransas National Estuarine Research Reserve

Aransas National Wildlife Refuge

Goose Island State Park

Calhoun County, Texas

Mission-Aransas National Estuarine Research Reserve

Aransas National Wildlife Refuge

Matagorda Island State Park

Guadalupe Delta Wildlife Management Area

Welder Flats Coastal Preserve

Matagorda County, Texas

Aransas National Wildlife Refuge

Mad Island Wildlife Management Area

Big Boggy National Wildlife Refuge

San Bernard National Wildlife Refuge
Table 6. (Continued).

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County or Parish, State Wildlife Refuge, Wilderness Area, or

State/National Park

Brazoria County, Texas

San Bernard National Wildlife Refuge

Peach Point Wildlife Management Area

Brazoria National Wildlife Refuge

Christmas Bay State Park 

Christmas Bay Coastal Preserve 

Galveston County, Texas

Brazoria National Wildlife Refuge 

Galveston Island State Park

Apffel Park

Seawolf Park

Old Fort Travis Park 

Atkinson Island Wildlife Management Area 

Ft. Anahuac Park

Anahuac National Wildlife Refuge 

McFaddin National Wildlife Refuge

Candy Abshier Wildlife Management Area

Atkinson Island Wildlife Management Area

Chambers County, Texas Anahuac National Wildlife Refuge

McFaddin National Wildlife Refuge

Jefferson County, Texas

McFaddin National Wildlife Refuge

Sea Rim State Park 

Murphree Wildlife Management Area 

Texas Point National Wildlife Refuge 

Cameron Parish, Louisiana

Sabine National Wildlife Refuge 

Cameron Prairie National Wildlife Refuge 

Lacassine National Wildlife Refuge 

Little Pecan Island Natural Area 

Peveto Woods Natural Area

Lower Neches Wildlife Management Area 

Rockefeller Wildlife Management Area 

Vermilion Parish, Louisiana Rockefeller Wildlife Management Area 

Paul J. Rainey Wildlife Management Area

Iberia Parish, Louisiana

Marsh Island Wildlife Management Area

Cypremort Point State Park

Shell Keys National Wildlife Refuge

St. Mary Parish, Louisiana Atchafalaya Delta Wildlife Management Area

Bayoue Teche National Wildlife Refuge

Terrebonne Parish, Louisiana

Atchafalaya Delta Wildlife Management Area

Mandalay National Wildlife Refuge

Isles Dernieres Barrier Islands Refuge

Point Au Chein Wildlife Management Area

Lafourche Parish, Louisiana Point Au Chein Wildlife Management Area

Wisner Wildlife Management Area

Jefferson Parish, Louisiana

Grand Isle State Park

Salvador Wildlife Management Area

Jean Lafitte National Historical Park and Preserve

Lafitte Woods Natural Area
Table 6. (Continued).

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County or Parish, State Wildlife Refuge, Wilderness Area, or

State/National Park

Plaquemines Parish, Louisiana

Salvador Wildlife Management Area

Jean Lafitte National Historical Park and Preserve

Delta National Wildlife Refuge

Pass A Loutre Wildlife Management Area

Breton National Wildlife Refuge

St. Bernard State Park

St. Bernard Parish, Louisiana

Breton National Wildlife Refuge

St. Bernard State Park

Biloxi Wildlife Management Area

Bayou Sauvage National Wildlife Refuge

Hancock and Harrison Counties, Mississippi

Hancock County Coastal Marsh Reserve

Buccaneer State Park

Jourdan River Coastal Reserve

Biloxi River Coastal Reserve

Gulf Islands National Seashore

Bayou Sauvage National Wildlife Refuge

Big Branch Marsh National Wildlife Refuge

Pearl River Wildlife Management Area

Wolf River Coastal Reserve

Grand Bayou Coastal Preserve

Bayou Portage Coastal Reserve

Biloxi Marshes State Coastal Preserve

Deer Island State Coastal Preserve

Jackson County, Mississippi

Gulf Islands National Seashore

Davis Bayou Coastal Preserve

Mississippi Sandhill Crane National Wildlife Refuge

Pascagoula River Coastal Reserve

Grand Bay National Estuarine Research Reserve

Grand Bay National Wildlife Refuge

Grand Bay Savannah Coastal Preserve

Deer Island State Coastal Preserve

Old Fort Bayou Coastal Reserve

Bellefontaine Point Coastal Reserve

Graveline Bay Coastal Reserve

Mobile County, Alabama

Grand Bay National Wildlife Refuge

The Grand Bay Savanna Tract

Penalver State Park

Bon Secour National Wildlife Refuge

W.L. Holland Wildlife Management Area

Baldwin County, Alabama

Bon Secour National Wildlife Refuge

Meaher State Park

Weeks Bay National Estuarine Research Reserve

Gulf State Park

Lillian Swamp Mitigation Area

Tarklin Bayou State Preserve

W.L. Holland Wildlife Management Area
Table 6. (Continued).

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County or Parish, State Wildlife Refuge, Wilderness Area, or

State/National Park

Escambia County, Florida

Perdido Key State Recreation Area

Big Lagoon State Recreation Area

Fort Pickens State Park Aquatic Preserve

Gulf Islands National Seashore

Pensacola Bay SWIM Area

Yellow River Wildlife Management Area

Okaloosa County, Florida

Gulf Islands National Seashore

Pensacola Bay SWIM Area

Choctawatchee Bay SWIM Area

Walton County, Florida

Choctawatchee Bay SWIM Area

Henderson State Park

Point Washington Outstanding Florida Water

Deer Lake State Park

Grayton Beach State Park Outstanding Florida Water

St. Andrew Bay Watershed SWIM Area

Bay County, Florida

Point Washington Outstanding Florida Water

St. Andrew Bay Watershed SWIM Area

St. Andrews State Park Aquatic Preserve

St. Andrews State Park

Gulf County, Florida

St. Andrew Bay Watershed SWIM Area

St. Joseph Peninsula State Park

St. Joseph Bay State Buffer Preserve

Franklin County, Florida

St. Vincent National Wildlife Refuge

Apalachicola National Estuarine Research Reserve

Apalachicola Bay Aquatic Preserve Outstanding Florida Water

Apalachicola River and Bay SWIM Area

Apalachicola River Wildlife and Environmental Area

St. George Island State Park

The level of impacts from oil spills on coastal habitats depends on many factors, including the oil 

characteristics, the geographic location of the landfall, and the weather and oceanographic 

conditions at the time (MMS, 2007b). Oil that makes it to beaches may be either liquid 

weathered oil, an oil-and-water mousse, or tarballs (MMS, 2007b). Oil is generally deposited on 

beaches in lines defined by wave action at the time of landfall. Oil that remains on the beach 

will thicken as its volatile components are lost. Thickened oil may form tarballs or aggregations 

that incorporate sand, shell, and other materials into its mass. Tar may be buried to varying 

depths under the sand. On warm days, both exposed and buried tarballs may liquefy and ooze. 

Oozing may also serve to expand the size of a mass as it incorporates beach materials. Oil on 

beaches may be cleaned up manually, mechanically, or both. Some oil can remain on the beach 

at varying depths and may persist for several years as it slowly biodegrades and volatilizes.

Wetlands are highly sensitive to oiling. The MMS (2007b) predicted that for every 50 bbl of oil 

contacting wetlands, approximately 2.7 ha (6.7 ac) of wetland vegetation will experience 

dieback. Thirty percent of these damaged wetlands are assumed to recover within 4 years, and 

85% within 10 years. About 15% of the contacted wetlands are expected to be converted 

permanently to open-water habitat. The critical concentration of oil is that concentration above 
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which impacts to wetlands will be long-term and recovery will take longer than two growing 

seasons, and which causes plant mortality and some permanent wetland loss. Critical 

concentrations of various oils are expected to vary broadly for wetland types and wetland plant 

species. Louisiana wetlands are assumed to be more sensitive to oil contact than elsewhere in 

the Gulf because of high cumulative stress (MMS, 2007b). In addition to the direct impacts of 

oil, cleanup activities in marshes may accelerate rates of erosion and retard recovery rates, 

which have been reported to require from years to decades following a spill (MMS, 2007b; 

BOEMRE, 2011a; BOEM, 2012b).

C.8 Socioeconomic and Other Resources

C.8.1 Recreational and Commercial Fishing

BOEM has reexamined the analysis for recreational and commercial fishing presented in 

MMS (2007b, 2008) based on additional information and in consideration of the Macondo spill. 

No new information was found that would alter the potential impacts on commercial fishing

(BOEMRE, 2011a; BOEM, 2012b). 

The main commercial fishing activity in deep waters of the northern Gulf of Mexico is pelagic 

longlining for tunas, swordfishes, and other billfishes (Continental Shelf Associates, Inc., 2002). 

Pelagic longlining has occurred historically in the project area, primarily during spring and 

summer. 

Longline gear consists of monofilament line deployed from a moving vessel and generally 

allowed to drift for 4 to 5 hours (Continental Shelf Associates, Inc., 2002). As the mainline is put 

out, baited leaders and buoys are clipped in place at regular intervals. It takes 8 to 10 hours to 

deploy a longline and about the same time to retrieve it. Longlines are often set near 

oceanographic features such as fronts or downwellings, with the aid of sophisticated onboard 

temperature sensors, depth finders, and positioning equipment. Vessels typically are 10 to 30 m 

(33 to 98 ft) long, and their trips last from about 1 to 3 weeks. The main Gulf of Mexico

homeports for longlining vessels are in Louisiana (Dulac and Venice) and Florida (Destin, 

Madeira Beach, and Panama City).

It is unlikely that any commercial fishing activity other than longlining occurs at or near the 

project area. Benthic species targeted by commercial fishers occur on the upper continental 

slope, well inshore of the project area. Royal red shrimp (Pleoticus robustus) are caught by 

trawlers in water depths of about 250 to 550 m (820 to 1,804 ft). Tilefishes (primarily 

Lophalotilus chamaeleonticeps) are caught by bottom longlining in water depths from about 

165 to 450 m (540 to 1,476 ft) (Continental Shelf Associates, Inc., 2002).

Most recreational fishing activity in the region occurs in water depths less than 200 m (656 ft) 

(Continental Shelf Associates, Inc., 1997, 2002). In deeper water, the main attraction to 

recreational fishers would be petroleum rigs offshore Texas and Louisiana. Due to the distance 

from shore, it is unlikely that recreational fishing activity is occurring in the lease area.

The only routine IPF potentially affecting fisheries is drilling rig presence (including noise and 

lights). Two types of potential accidents are also addressed below – a small fuel spill and a large 

oil spill (WCD).
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Impacts of Drilling Rig Presence

There is a slight possibility of pelagic longlines becoming entangled in the drilling rig. For 

example, in January 1999, a portion of a pelagic longline snagged on the acoustic Doppler 

current profiler of a drillship working in the Gulf of Mexico (Continental Shelf Associates, Inc., 

2002). The line was removed without incident. Generally, longline fishers use radar and are 

aware of offshore structures and ships when placing their sets. Therefore, little or no impact on 

pelagic longlining is expected.

Because it is unlikely that any recreational fishing activity is occurring in the project area, no 

adverse impacts are anticipated. Other factors such as effluent discharges are likely to have 

negligible impacts on commercial or recreational fisheries due to rapid dispersion, the small 

area of ocean affected, and the intermittent nature of the discharges.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during 

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

Anadarko’s OSRP could potentially mitigate and reduce the potential for impacts. EP Section H

provides detail on spill response measures. Given the open ocean location of the lease area, the 

duration of a small spill and opportunity for impacts to occur would be very brief.

Pelagic longlining activities in the lease area, if any, could be interrupted in the event of a small 

fuel spill. The sea surface area with diesel fuel on it would range from 0.5 to 5 ha (1.2 to 12 ac), 

depending on sea state and weather conditions. Fishing activities could be interrupted due to 

the activities of response vessels operating in the lease area. A small fuel spill would not affect 

coastal water quality because the spill would not be expected to make landfall or reach coastal 

waters prior to breaking up (see Section A.9.2).

Impacts of a Large Oil Spill (WCD)

Potential spill impacts on fishing activities are discussed in MMS (2007b) and BOEM (2012b,d). 

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 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, 2010c). At its peak on 12 July 2010, closures 

encompassed 217,821 km2 (84,101 mi2

), or 34.8% of the U.S. Gulf of Mexico EEZ.

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 Anadarko’s preventative measures during 

routine operations including fuel transfer. In the unlikely event of a spill, implementation of 
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Environmental Impact Analysis for Initial Exploration Plan Page 65 

Anadarko’s OSRP could potentially alleviate the potential for impacts. EP Section H provides 

detail on spill response measures.

A small fuel spill would not have any impacts on public health and safety because it would affect 

only a small area of the open ocean 71 miles (114 km) from the nearest shoreline, and nearly all 

of the diesel fuel would evaporate or disperse naturally within 24 hours. Response crews would 

be equipped with appropriate safety equipment to avoid injury and health effects. A small fuel 

spill would not be expected to make landfall or reach coastal waters prior to breaking up

(see Section A.9.2).

Impacts of a Large Oil Spill (WCD)

In the event of a large spill from a blowout, the main safety and health concerns are those of the 

offshore personnel involved in the incident and those responding to the spill. The drilling rig 

maintains a Shipboard Oil Pollution Emergency Plan as required under MARPOL 73/78.

Depending on the spill rate and duration, the physical/chemical characteristics of the oil, 

meteorological and oceanographic conditions at the time, and the effectiveness of spill response 

measures, the public could be exposed to oil on the water and along the shoreline, including 

skin contact or breathing VOCs. Crude oil is a highly flammable material, and any smoke or 

vapors from a crude oil fire can cause irritation, and in large quantities may pose a health 

hazard.

Data from the Macondo spill provide relevant information about the types of health issues that 

may occur in the event of a large oil spill (Centers for Disease Control and Prevention, 2010a). 

Wildlife cleaning and rehabilitation workers have reported concerns including scrapes and cuts, 

itchy or red skin or rash, and symptoms of headache or feeling faint, dizzy, or fatigued. Hand, 

shoulder, or back pain was also reported by some wildlife-cleaning workers. Personnel working 

on offshore vessels or providing direct oversight to offshore vessels, including USCG personnel, 

civilian contractors, and other responders who were exposed to oil and dispersants, had a 7 to 

12 times higher prevalence of upper respiratory symptoms and cough than those not exposed 

(Centers for Disease Control and Prevention, 2010b). Another potential occupational hazard for 

spill response workers in general was heat stress from work in a hot and humid environment. 

Initial symptoms from cleanup workers who sought medical care in Louisiana were typical of 

acute exposure to hydrocarbons or H2S, e.g., headaches, dizziness, nausea, vomiting, cough, 

respiratory distress, and chest pain (Solomon and Janssen, 2010).

C.8.3 Employment and Infrastructure

There are no IPFs associated with routine operations that are expected to affect employment 

and infrastructure. The project involves drilling with support from existing shorebase facilities in 

Louisiana. No new or expanded facilities will be constructed, and no new employees are 

expected to move permanently into the area. The project will have a negligible impact on 

socioeconomic conditions such as local employment, existing offshore and coastal infrastructure 

(including major sources of supplies, services, energy, and water), and minority and lower 

income groups. Impacts of a small fuel spill and a large oil spill (WCD) are addressed below.

Impacts of a Small Fuel Spill

The probability of a fuel spill will be minimized by Anadarko’s preventative measures during 

routine operations including fuel transfer. In the unlikely event of a spill, implementation of 
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Environmental Impact Analysis for Initial Exploration Plan Page 66 

Anadarko’s OSRP could potentially mitigate and reduce the potential for impacts. EP Section H

provides detail on spill response measures. Given the open ocean location of the lease area, the 

duration of a small spill and opportunity for impacts to occur would be very brief.

A small fuel spill that is dissipated within a few days would have little or no economic impact, as 

the spill response would use existing facilities, resources, and personnel.

Impacts of a Large Oil Spill (WCD)

Potential socioeconomic impacts of an oil spill are discussed in MMS (2007b) and

BOEM (2012a,b,d). For this EP, there are no unique site-specific issues with respect to 

employment and coastal infrastructure. A large spill could cause economic impacts in several 

ways: it could result in extensive fishery closures that put fishermen out of work; it could result 

in temporary employment as part of the response effort; it could result in adverse publicity that 

affects employment in coastal recreation and tourism industries; and it could result in another 

suspension of OCS drilling activities, including service and support operations that are an 

important part of local economies.

In addition to the analyses presented by MMS (2007b, 2008) and BOEM (2012b), a recent study 

explored the economic impacts of the Macondo spill on oil and gas industry employment due to 

suspension of deepwater drilling (Inter-Agency Economic Report, 2010). The study indicates 

that during the moratorium, the number of oil industry workers in the Gulf of Mexico fell by 

about 2,000 and may have indirectly caused a temporary loss of 8,000 to 12,000 jobs along the 

Gulf Coast. Total spending by drilling operators is estimated to have declined by $1.8 billion 

over a six-month period; this direct reduction in spending affected employment in the industries 

that supply the Gulf drilling industry and in all other industries affected by declines in consumer 

and business spending (Inter-Agency Economic Report, 2010). 

C.8.4 Recreation and Tourism

BOEM has reexamined the analyses for recreation and tourism presented in MMS (2007b, 2008) 

based on additional information and in consideration of the Macondo oil spill event. No new 

information was found that would alter the potential impacts on recreation and tourism 

(BOEMRE, 2011a; BOEM, 2012b).

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 2012-BSEE-G01 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 Anadarko’s preventative measures during 

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

Anadarko’s OSRP could potentially help mitigate and reduce the potential for impacts. 

EP Section H provides detail on spill response measures. Given the open ocean location of the 

lease area, the duration of a small spill and opportunity for impacts to occur would be very brief.
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Environmental Impact Analysis for Initial Exploration Plan Page 67 

A small fuel spill in the lease area would be unlikely to affect recreation and tourism. There are 

no known recreational or tourism activities occurring in the lease area, and as explained in 

Section A.9.2, a small fuel spill would not be expected to make landfall or reach coastal waters 

prior to breaking up.

Impacts of a Large Oil Spill (WCD)

Potential impacts of an oil spill on recreation and tourism are discussed in MMS( 2007b) and

BOEM (2012a,b,d). For this EP, there are no unique site-specific issues with respect to these 

impacts.

Impacts on recreation and tourism would vary depending on the duration of the spill and its fate 

including the effectiveness of response measures. A large spill that reached coastal waters and 

shorelines could adversely affect recreation and tourism by contaminating beaches and 

wetlands, resulting in negative publicity that encourages people to stay away. Based on the 

revised OSRA modeling (BOEM, 2012b) as summarized in Section A.9.3 (Table 3), there is a 

12% probability of oil from a spill in the lease area reaching shorelines in Louisiana within 30 

days and a 17% chance of oil contacting shorelines in Texas within 120 days.

In addition to the analysis presented by MMS (2007b; BOEMa,b,d), recent and ongoing studies 

have explored the economic impacts of the Macondo spill including tourism and "brand" 

damage (IEM, 2010; Oxford Economics, 2010). The U.S. Travel Association has estimated the 

economic impact of the Macondo spill on tourism across the Gulf Coast over a three-year period 

at $22.7 billion (Oxford Economics, 2010). 

C.8.5 Land Use

Land use along the northern Gulf Coast is discussed in MMS (2007b) and BOEM (2012a,b,d). 

There are no routine IPFs potentially affecting land use. The project will use existing onshore 

support facilities in Louisiana. The land use at the existing shorebase sites is industrial. The 

project will not involve any new construction or changes to existing land use and, therefore, will 

not have any impacts. Levels of boat and helicopter traffic, as well as demand for goods and 

services including scarce coastal resources, will represent a small fraction of the level of activity 

occurring at the shorebases. 

A large oil spill (WCD) is the only relevant IPF. A small fuel spill would not have any impacts on 

land use, as the response would be staged out of existing shorebases and facilities.

Impacts of a Large Oil Spill (WCD)

The initial response for a large oil spill would be staged out of existing facilities, with no effect on 

land use. A large spill could have limited temporary impacts on land use along the coast if 

additional staging areas were needed. For example, during the Macondo spill, temporary 

staging areas were established in Louisiana, Mississippi, Alabama, and Florida for spill response 

and cleanup efforts. In the event of a large spill in the lease area, similar temporary staging 

areas could be needed. These areas would eventually return to their original use as the 

response is demobilized.
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Environmental Impact Analysis for Initial Exploration Plan Page 68 

C.8.6 Other Marine Uses

The lease area is not located within any USCG-designated fairway or shipping lane or Military 

Warning Area. Anadarko will comply with BOEM requirements and lease stipulations to avoid 

impacts on uses of the area by military vessels and aircraft.

Existing seafloor pipelines are present within 610 m (2,000 ft) of proposed wellsites AT 19-KV, 

AT 19-EE, and AT 19-KK. Existing wells are present within 610 m (2,000 ft) of proposed wellsites 

AT 18-GG, AT 18-GV, and AT 18-QQ. Anadarko will avoid existing infrastructure during the 

proposed exploratory drilling operations. 

There are no IPFs from routine project activities that are likely to affect other marine uses of the 

lease area. A large oil spill (WCD) is the only relevant accident IPF. A small fuel spill would not 

have any impacts on other marine uses because spill response activities would be mainly within 

the lease area and the duration would be brief.

Impacts of a Large Oil Spill (WCD)

An accidental spill would be unlikely to significantly affect shipping or other marine uses. In the 

event of a large spill requiring numerous response vessels, coordination would be required to 

manage the vessel traffic for safe operations and to ensure that no anchoring or 

seafloor-disturbing activities occur near the existing pipelines and flowlines. 

D. Environmental Hazards

D.1 Geologic Hazards

The site clearance surveys conducted by Gardline (2013) found a slight risk of shallow gas and a 

slight-to-moderate risk of shallow water flow across the lease area. A high risk for shallow water 

flow was identified at proposed wellsite AT 18-DD between 450 and 1,127 m (1,478 and 

2,697 ft) below mud line (BML). Gardline also identified a high risk for shallow water flow at 

proposed wellsite AT 19-KK between 521 and 751 m (1,710 and 2,463 ft BML), and for proposed 

wellsite AT 18-QQ between 683 and 898 m (2,239 and 2,946 ft BML). Gardline recommended 

drilling with caution and implementing appropriate drilling methodologies to contain possible 

shallow water flow events in these two intervals (Gardline, 2013). 

There are several seafloor faults in the vicinity of the proposed wellsites. A vertical wellbore at 

AT 19-DD will penetrate a fault at 4,497 ft BML. This fault appears to exhibit connectivity to the 

seabed and could cause drilling fluid circulation and wellbore stability problems, especially if 

pressures over hydrostatic are exerted by the wellbore. A vertical wellbore at AT 19-KK will 

penetrate a fault at 1,016 m (3,333 ft) BML. Gardline (2013) concluded that drilling fluid 

circulation problems could occur as a result of this fault penetration, if pressures over 

background level are exerted by the drilling fluid column. 

A vertical wellbore will penetrate three faults at well AT 18-CC. The upper fault is located at 

881 m (2,889 ft) BML and extends back to the seafloor; thereby representing a significant risk 

for drilling fluid recirculation and wellbore stability. The risk can be mitigated by preventing 

pressures exerted by the drilling fluid column from exceeding hydrostatic. The deeper two 
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Environmental Impact Analysis for Initial Exploration Plan Page 69 

faults occur at 1,147 and 1,420 m (3,764 and 4,658 ft) BML, respectively. These two faults have 

a limited vertical extent and could cause minor drilling fluid circulation and wellbore stability 

problems if pressures exerted by the drilling fluid column exceed hydrostatic. Vertical wellbores 

at all other proposed wellsites will not penetrate any seafloor faults (Gardline, 2013).

Gardline (2013) concluded that the wellsites are suitable for the proposed activities. 

See EP Section C for supporting geological and geophysical information.

D.2 Severe Weather

Under most circumstances, weather is not expected to have any effect on the proposed 

activities. Extreme weather, including high winds, strong currents, and large waves, was 

considered in the design criteria for the drilling rigs under consideration for this project. High 

winds and limited visibility during a severe storm could disrupt support activities (vessel and 

helicopter traffic) and make it necessary to suspend some activities on the drilling rig for safety 

reasons until the storm or weather event passes. In the event of a hurricane, procedures as 

outlined in the Hurricane Evacuation Plan would be adhered to.

D.3 Currents and Waves

Metocean conditions such as sea states, wind speed, ocean currents, etc., will be continuously 

monitored. Under most circumstances, physical oceanographic conditions are not expected to 

have any effect on the proposed activities. Strong currents (e.g., caused by Loop Current eddies 

and intrusions) and large waves were considered in the design criteria for the drilling rig under 

consideration for this project. High waves during a severe storm could disrupt support activities 

(i.e., vessel and helicopter traffic) and make it necessary to suspend some activities on the 

drilling rig for safety reasons until the storm or weather event passes.

E. Alternatives

No formal alternatives were evaluated in this EIA for an EP. However, various technical and 

operational options, including the location of the wellsites and the selection of a drilling unit, 

were considered by Anadarko in developing the proposed action.

F. Mitigation Measures

The proposed action includes numerous mitigation measures required by laws, regulations, and 

BOEM lease stipulations and NTLs. The project will comply with all applicable Federal, State, 

and local requirements concerning air pollutant emissions, discharges to water, and solid waste 

disposal. All project activities will be conducted under guidance by Anadarko’s OSRP and will 

include the measures described in EP Section H. 
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Environmental Impact Analysis for Initial Exploration Plan Page 70 

G. Consultation

No persons or agencies were consulted during the preparation of this EIA.

H. Preparers

The EIA was prepared by CSA Ocean Sciences Inc. Contributors included: 

• M. John Thompson (Senior Scientist);

• John M. Tiggelaar II (Project Scientist);

• Keith VanGraafeiland (Geospatial Manager);

• Kevin Noack (Geospatial Coordinator);

• Kristen L. Metzger (Library and Information Services Director);

• LeslieAnn Weekes (Technical Editor).

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SECTION O 

ADMINISTRATIVE INFORMATION 

(a) Proprietary Information 

Proprietary copies of this plan contain information not available to the public and include 

structure maps, seismic information, cross sections, depths of wells, etc. 

(b) Bibliography 

 Shallow Hazards Reports included with this EP 

 Site Clearance Letters included with this EP 

 Final Sale Packages for Central Gulf of Mexico Lease Sale 213 (AT 18) and 206 

(AT 19)
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Transaction Date and Time: 01/15/2014 16:44 EST

Payment Summary

Address Information

Account Holder 

Name: Jill Fowler 

Billing Address:

1201 Lake 

Robbins Dr. 

Billing Address 

2:

City: The Woodlands 

State / Province: TX 

Zip / Postal 

Code: 77380 

Country: USA 

Account Information

Card Type: Visa 

Card 

Number: ************1715 

Region: Gulf of Mexico

Contact:

Bridget O'Farrell 832-

636-1694

Company 

Name/No:

Anadarko Petroleum 

Corporation, 00981

Lease 

Number(s): 33863, 32556, , , 

Area-Block:

Atwater Valley AT, 

18: Atwater Valley 

AT, 19: , : , : , 

Surface 

Locations: 8

Payment Information

Payment Amount: $29,384.00

Transaction Date 

and Time:

01/15/2014 

16:44 EST

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