Revised Outer Continental Shelf Lease Exploration Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. May 2011 

Appendix D 

Marine Mammal Monitoring and Mitigation Plan 
Revised Outer Continental Shelf Lease Exploration Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. May 2011 

THIS PAGE 

INTENTIONALLY 

LEFT BLANK 

 
MARINE MAMMAL MONITORING 

AND MITIGATION PLAN 

for 

Exploration Drilling of Selected Lease Areas in 

the Alaskan Chukchi Sea

Shell Gulf of Mexico Inc. 

May 2011 

 REVISED AUGUST 2011
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. ii Revised August 2011 

TABLE OF CONTENTS 

ACRONYMS & ABBREVIATIONS ............................................................................ IV

INTRODUCTION............................................................................................................. 1

VESSEL-BASED MARINE MAMMAL MONITORING PROGRAM ..................... 2

INTRODUCTION ................................................................................................................... 2

MITIGATION MEASURES DURING EXPLORATION DRILLING ACTIVITIES AND 

ZERO-OFFSET VERTICAL SEISMIC PROFILE SURVEYS ....................................................... 3

Safety and Disturbance Zones............................................................................................ 3

Exploration Drilling Activities ........................................................................................... 4

ZVSP Surveys ..................................................................................................................... 5

MARINE MAMMAL OBSERVERS ......................................................................................... 6

Number of Observers ......................................................................................................... 6

Crew Rotation .................................................................................................................... 7

Observer Qualifications and Training ............................................................................... 7

MMO Handbook ................................................................................................................ 8

MONITORING METHODOLOGY ........................................................................................... 8

Monitoring At Night and In Poor Visibility ....................................................................... 9

Specialized Field Equipment ............................................................................................ 10

Field Data-Recording, Verification, Handling, and Security .......................................... 10

Field Reports.................................................................................................................... 10

REPORTING ....................................................................................................................... 11

ACOUSTIC MONITORING PLAN ............................................................................. 12

EXPLORATION DRILLING SOUND MEASUREMENTS ......................................................... 12

Objectives ........................................................................................................................ 12

Equipment ........................................................................................................................ 12

Vessel Sounds Monitoring ................................................................................................ 14

Zero Offset Vertical Seismic Profiling Sounds Monitoring .............................................. 14

Acoustic Data Analyses .................................................................................................... 16

Reporting of Results ......................................................................................................... 18

JOINT MONITORING PROGRAM ............................................................................ 18

CHUKCHI SEA COASTAL AERIAL SURVEY ....................................................................... 18

Objectives ........................................................................................................................ 19

Survey Considerations ..................................................................................................... 19

Survey Procedures ........................................................................................................... 19

Coordination with Other Aerial Surveys .......................................................................... 21

Analysis of Aerial Survey Data ........................................................................................ 22

ACOUSTIC “NET” ARRAY IN CHUKCHI SEA ..................................................................... 22

Background and Objectives ............................................................................................. 22

Technical Approach ......................................................................................................... 22

Analysis and Reporting .................................................................................................... 24

COMPREHENSIVE REPORT ON INDUSTRY ACTIVITIES AND 

MARINE MAMMAL MONITORING EFFORTS IN THE BEAUFORT 

AND CHUKCHI SEAS .................................................................................................. 24

LITERATURE CITED .................................................................................................. 25

 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. iii Revised August 2011

Figures 

Figure 1. Cabled hydrophone method for real time monitoring of drilling 

sound energy. ............................................................................................ 13

Figure 2. Hydrophone recording system being deployed at sea. The 

hydrophone system is an autonomous recorder with very high 

recording resolution. Acoustic data is stored internally on a harddrive. ......................................................................................................... 14

Figure 3. Schematic of ZVSP ................................................................................... 16

Figure 4. Lower: spectrogram of sound level measurements obtained from a 

hydrophone recording system. Upper: broadband and selected 

band level variation with time. .................................................................. 17

Figure 5. Upper: 1-hour Leq levels that will be calculated from acoustic 

measurements for use in correlating with bowhead whale 

deflection data. .......................................................................................... 17

Figure 6. Aerial survey transects location and general pattern for the eastern 

Chukchi Sea, 2012. Specific transect start-/end-points will be 

altered randomly from survey to survey, and hunting areas will be 

avoided when hunting is occurring. .......................................................... 20

Figure 7. Deployment locations of Hydrophones in acoustic arrays in the 

eastern Chukchi Sea, Alaska 2012. Depiction of hydrophone array 

at Burger is not scaled correctly based on description below (12 

km by 18 km) ............................................................................................ 23

Tables 

Table 1 Typical Sound Source (Airgun Array) Specifications for ZVSP 

Surveys ...................................................................................................... 15
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. iv Revised August 2011 

ACRONYMS & ABBREVIATIONS 

C degrees Celsius 

T degrees True North 

μPa micropascal(s) 

4MP Marine Mammal Monitoring and Mitigation Plan 

AEWC Alaska Eskimo Whaling Commission 

BOEMRE Bureau of Ocean Energy Management, Regulation and Enforcement 

dB decibel 

CDs compact discs 

cm3

 cubic centimeter(s) 

Com Center Communications and Call Center 

Discoverer Motor Vessel Noble Discoverer

GPS Global Positioning System 

ft feet 

ft2

 square feet 

Hz Hertz 

in3

 cubic inch(es) 

IHA Incidental Harassment Authorization 

JASCO JASCO Applied Sciences 

kHz kilohertz 

km kilometer(s) 

km2

 square kilometer(s) 

lb pound(s) 

Leq sound energy equivalent level 

LOA Letter of Authorization 

m meter(s) 

m2

 square meter(s) 

mi mile(s) 

mi2

 square mile(s) 

MMO Marine Mammal Observer 

MMPA Marine Mammal Protection Act 

MMS Minerals Management Service 

M/V Motor Vessel 

NMFS National Marine Fisheries Service 

Noble Noble Corporation 

NSB North Slope Borough 

NVD night-vision device 

psi pounds per square inch 

rms root mean squared 

Shell Shell Gulf of Mexico Inc. 

USB universal serial bus 

USFWS U.S. Fish and Wildlife Service 

VSI vertical seismic imager 

VSP vertical seismic profile 

ZVSP zero-offset vertical seismic profile 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 1 Revised August 2011 

INTRODUCTION 

Shell Gulf of Mexico Inc. (Shell) will conduct a Marine Mammal Monitoring and Mitigation Plan 

(4MP) for exploration drilling activities in the Chukchi Sea during the 2012 exploration drilling 

season. The 4MP developed for Shell’s exploration drilling program supports protection of the 

marine mammal resources in the area, fulfills reporting obligations to the Bureau of Ocean 

Energy Management, Regulation and Enforcement (BOEMRE), the National Marine Fisheries 

Service (NMFS), and the U.S. Fish and Wildlife Service (USFWS), and establishes a means for 

gathering additional data on marine mammals for future operations planning. 

Shell plans to conduct exploration drilling within existing lease holdings in the Chukchi Sea. 

Exploration drilling will be conducted from the drillship Motor Vessel (M/V) Noble Discoverer

(Discoverer) owned and operated by Noble Corporation. The drillship is an ice-strengthened 

drilling vessel designed, engineered and constructed to safely operate in arctic waters like the 

Chukchi Sea. In addition to the drillship, several support vessels will be used. The support 

vessels will include tugs and barges, a primary ice management vessel, an anchor handler/ice 

management vessel, and oil spill response vessels. 

At, or near the end of each well, a zero-offset vertical seismic profile (ZVSP) likely will be 

conducted. During ZVSP surveys, an airgun array is deployed adjacent to the drillship, while 

receivers are placed (temporarily anchored) in the wellbore. The sound source (airgun array) is 

fired repeatedly, and the reflected sonic waves are recorded by receivers (geophones) located in 

the wellbore. The survey will last 10-14 hours as the receivers are moved through the length of 

the wellbore and the airguns are fired 5-7 times after each movement. The purpose of the ZVSP 

is to gather geophysical information at various depths, which can then be used to tie-in or groundtruth geophysical information from the previous seismic surveys with geological data collected 

within the wellbore. 

Shell’s 4MP is a combination of active monitoring of the area of operations and the implementation of 

mitigation measures designed to minimize project impacts to marine resources. Monitoring will 

provide information on the numbers of marine mammals potentially affected by the exploration 

operations and facilitate real time mitigation to prevent injury of marine mammals by industrial 

sounds or activities. These goals will be accomplished by conducting vessel-based, aerial, and 

acoustic monitoring programs to document the potential reactions of marine mammals in the area 

to the various sounds and activities and to characterize the sounds produced by the exploration 

drilling activities, support vessels, and ZVSP. 

Aerial monitoring and reconnaissance of marine mammals in coastal areas of the Chukchi Sea 

and recordings of ambient sound levels and vocalizations of marine mammals along the Chukchi 

Sea coast will be used to interpret potential impacts to marine mammals in subsistence use areas. 

Acoustic measurements will be made to establish safety radii for real time mitigation, if 

necessary, around the activities. These measurements will be used to determine the sound levels 

produced by various equipment and to establish any safety and disturbance radii if necessary. An 

initial sound source analysis will be supplied to NMFS within 120 hours of completion of the 

measurements, if possible. A detailed report will be issued to NMFS as part of the 90-day report 

following the end of the exploration drilling season. Shell will continue to measure the sound 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 2 Revised August 2011 

propagation of the drillship at various times or throughout the exploration drilling program. 

Sound energy from support vessels will also be measured. Bottom-founded hydrophones will 

also be placed in a large array across the Chukchi Sea to collect information on the use of the 

region by marine mammals and additional information on the propagation of sounds from human 

activities. 

VESSEL-BASED MARINE MAMMAL MONITORING PROGRAM 

Introduction 

The vessel-based operations of Shell’s 4MP are designed to meet the requirements of the 

Incidental Harassment Authorization (IHA) and the Letter of Authorization (LOA) which Shell 

requested from the NMFS and the USFWS, respectively, and to meet any other stipulated 

agreements between Shell and other agencies or groups. The objectives of the program will be to 

ensure that disturbance to marine mammals and subsistence hunts is minimized, that effects on 

marine mammals are documented, and to collect data on the occurrence and distribution of 

marine mammals in the project area. 

The 4MP will be implemented by a team of experienced marine mammal observers (MMOs). 

These MMOs will be trained, experienced field observers, including both biologists and Inupiat 

personnel. The MMOs will be stationed aboard the drillship and associated support vessels 

throughout the exploration drilling period. The duties of the MMOs will include watching for 

and identifying marine mammals; recording their numbers, distances, and reactions to the 

exploration drilling operations; initiating mitigation measures when appropriate; and reporting the 

results. Reporting of the results of the vessel-based monitoring program will include the 

estimation of the number of marine mammal “takes” as defined by the NMFS and stipulated in 

the IHA. 

The vessel-based operations of Shell’s 4MP will be required to support the vessel based 

exploration drilling activities in the Chukchi Sea. The dates and operating areas will depend upon 

ice and weather conditions, along with Shell’s arrangements with agencies and stakeholders. The 

Discoverer and associated support vessels will transit through the Bering Strait into the Chukchi 

Sea on or about July 1, arriving on location at the Burger Prospect as soon as ice and weather 

conditions allow. Exploration drilling will then commence on or about July 4, as ice, weather, 

and other conditions allow for safe exploration drilling operations, and may last until October 31. 

Vessel-based monitoring for marine mammals will be done throughout the period of exploration 

drilling operations to comply with provisions in the anticipated IHA and LOA from NMFS and 

USFWS, respectively. 

The vessel-based work will provide: 

 the basis for real-time mitigation, if necessary, as required by the various permits that 

Shell receives; 

 information needed to estimate the number of “takes” of marine mammals by harassment, 

which must be reported to NMFS and USFWS; 

 data on the occurrence, distribution, and activities of marine mammals in the areas where 

the exploration drilling program is conducted; 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 3 Revised August 2011 

 information to compare the distances, distributions, behavior, and movements of marine 

mammals relative to the drillship at times with and without exploration drilling activity; 

 a communication channel to coastal communities including Inupiat whalers; and 

 employment and capacity building for local residents, with one objective being to 

develop a larger pool of experienced Inupiat MMOs. 

The 4MP will be operated and administered consistent with monitoring programs conducted 

during seismic and shallow hazards surveys in 2006–2010 or such alternative requirements as 

may be specified in the IHA and LOA received from NMFS and USFWS, respectively for this 

project. Any other agreements between Shell and agencies or groups such as BOEMRE, the 

North Slope Borough (NSB), and the Alaska Eskimo Whaling Commission (AEWC) will also be 

fully incorporated. All MMOs will be provided training through a program approved by NMFS, 

USFWS (if so stipulated) and Shell, as described in the MMO section of this 4MP. At least one 

observer on each vessel will be an Inupiat who will have the additional responsibility of 

communicating with the Inupiat community and (during the various subsistence harvests) directly 

with Inupiat hunters and whalers. Details of the vessel-based marine mammal monitoring 

program are described below. 

Mitigation Measures During Exploration Drilling Activities and Zero-Offset 

Vertical Seismic Profile Surveys 

Shell’s planned exploration drilling program incorporates both design features and operational 

procedures for minimizing potential impacts on marine mammals and on subsistence hunts. The 

design features and operational procedures of the mitigation measures have been described in the 

IHA (Section 12 of the IHA application to which this 4MP is appended) and LOA applications 

submitted to NMFS and USFWS respectively, and are not repeated in entirety here. Survey 

design features include: 

 timing and locating exploration drilling and support activities to avoid interference with 

the annual subsistence hunting by the peoples of the Chukchi villages; 

 conducting pre-season acoustic modeling to establish the appropriate safety zones and 

behavioral or disturbance radii; 

 vessel-based monitoring to implement appropriate mitigation if necessary, and to 

determine the effects of project activities on marine mammals; 

 acoustic monitoring of drillship and vessel sounds and marine mammal vocalizations; 

and 

 seismic activity mitigation measures during performance of ZVSP surveys. 

The potential disturbance of marine mammals during operations will be minimized further 

through the implementation of several vessel-based mitigation measures (see Section 12 of the 

IHA application to which this 4MP is appended) if mitigation becomes necessary. 

Safety and Disturbance Zones 

Under current NMFS guidelines (e.g., NMFS 2000), “safety radii” for marine mammals around 

industrial sound sources are customarily defined as the distances within which received pulse 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 4 Revised August 2011 

levels are ≥180 decibels (dB) re 1micropascal (μPa) root mean squared (rms) for cetaceans and 

≥190 dB re 1 μPa (rms) for pinnipeds. These safety criteria are based on an assumption that 

sound energy received at lower levels will not injure these animals or impair their hearing 

abilities, but that higher received levels might have some such effects. Disturbance or behavioral 

effects to marine mammals from underwater sound may occur after exposure to sound at 

distances greater than the safety radii (Richardson et al. 1995). NMFS assumes that marine 

mammals exposed to underwater impulsive sounds at received levels 160 dB (rms) have the 

potential to exhibit behavioral reactions great enough to meet the definition of “harassment” in 

the MMPA. For continuous sounds NMFS has established a similar disturbance threshold at 

≥120 dB (rms). 

Exploration Drilling Activities 

Expected safety and disturbance radii based on sound propagation from the drillship Discoverer

were modeled by JASCO Applied Sciences (JASCO) at the three potential drill sites (JASCO 

2009). Changes in the water column of the Chukchi Sea through the course of the exploration 

drilling season will likely affect the propagation of sounds produced by drilling activities, so 

models were run for expected oceanographic conditions in July and October to bracket the 

seasonal variability. These radii will be used for mitigation purposes, should they be necessary, 

until direct measurements are available early during the exploration drilling activities. Shell will 

measure the received levels of underwater sound versus distance and direction from the sound 

sources using calibrated hydrophones. The acoustic data will be analyzed as quickly as 

reasonably practicable in the field and used to verify (and if necessary adjust) the safety and 

disturbance radii. 

Sounds from the Discoverer have not previously been measured in the Arctic. However, 

measurements of sounds produced by the Discoverer were made in the South China Sea in 2009 

(Austin and Warner 2010). The results of those measurements were used to model the sound 

propagation from the Discoverer (including a nearby support vessel) at planned drilling locations 

in the Chukchi and Beaufort seas (Warner and Hannay 2011). Broadband source levels of sounds 

produced by the Discoverer varied by activity and direction from the ship, but were generally 

between 177 and 185 dB re 1 μPa @ 1 m rms (Austin and Warner 2010). Propagation modeling 

at the Burger prospect resulted in an estimated distance of 0.814 miles (mi) (1.31 kilometers 

[km]) to the point at which drillings sounds would likely fall below 120 dB. The estimated 0.814 

mi (1.31 km) distance was multiplied by 1.5 (= 1.22 mi [1.97 km]) as a further precautionary 

measure before calculating the total area that may be exposed to continuous sounds ≥120 dB re 1 

μPa rms by the Discoverer at each drill site on the Burger prospect. Assuming one well will be 

drilled in each season (summer and fall), the total area of water ensonified to ≥120 dB rms in 

each season is estimated to be 4.6 square miles (mi2

) (12 square kilometers [km2]). As noted 

above, broadband source levels from the Discoverer generally were close to 180 dB rms (Austin 

and Warner 2010). Source levels by definition are measured at a 1 m distance. Therefore the 180 

dB rms distance is 1 m. The distance to which sounds ≥160 are expected to propagate are 

estimated to be less than 33 feet (ft) (10 meters [m]) from the vessel and were not included in 

modeling results. 

The source levels noted above for exploration drilling activities are not high enough to cause a 

temporary reduction in hearing sensitivity or permanent hearing damage to marine mammals. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 5 Revised August 2011 

Consequently, mitigation as described for seismic activities including ramp ups, power downs, 

and shut downs should not be necessary for exploration drilling activities, but will be employed 

during the ZVSP survey described below. Shell plans to use MMOs onboard the drillship and the 

various support vessels to monitor marine mammals and their responses to industry activities and 

to initiate mitigation measures should in-field measurements of the operations indicate conditions 

represent a threat to the health and well-being of marine mammals. 

ZVSP Surveys 

The sound source likely to be used by Shell for the ZVSP survey in 2012 will be similar to the 

ITAGA eight-airgun array, which consists of four 150 cubic inches (in.3

) (2,458 cubic centimeters 

[cm3

]) airguns and four 40 in.3 (655 cm3) airguns. These airguns can be activated in any 

combination and Shell would utilize the minimum airgun volume required to obtain an acceptable 

signal. A similar airgun source was used in the region in 2008 during the BP Liberty seismic 

survey. Preseason estimates of the propagation of airgun sounds from the ITAGA vertical 

seismic profile (VSP) sound source have been estimated based on the measurements of the 

seismic source reported in BP’s 90-day report (Aerts et al. 2008). The BP liberty source was also 

an eight-airgun array, but had a slightly larger total volume of 880 in.3

 (14,421 cm3). Because the 

number of airguns is the same, and the difference in total volume only results in an estimated 0.4 

dB decrease in the source level of the ZVSP source, the 100th percentile propagation model from 

the measurements of the BP Liberty source is almost directly applicable. However, the BP 

Liberty source was towed at a depth of 5.9 ft (1.8 m), while the ZVSP source will be lowered to a 

target depth of 13 ft (4 m) (from 10-23 ft [3-7 m]). The lower depth of the ZVSP source has the 

potential to increase the source strength by as much as 6 dB. Thus, the constant term in the 

propagation equation from the BP Liberty source has been increased from 235.4 to 241.4 while 

the remainder of the equation (-18*LogR – 0.0047*R) has been left unchanged. This equation 

results in the following estimated distances to maximum received levels: 190 dB = 1,719 ft (524 

m); 180 dB = 4,068 ft (1,240 m); 160 dB = 12,041 ft (3,670 m); 120 dB = 34,449 ft (10,500 m). 

MMOs on the drillship will initially use these estimated safety radii for monitoring and mitigation 

purposes. An acoustics contractor will perform direct measurements of the received levels of 

underwater sound versus distance and direction from the ZVSP array using calibrated 

hydrophones. The acoustic data will be analyzed as quickly as reasonably practicable (within 5 

days) in the field and used to verify (and if necessary adjust) the safety distances. The mitigation 

measures to be implemented will include pre-ramp up watches, ramp ups, power downs and shut 

downs as described below. 

Ramp Ups 

A ramp up of an airgun array provides a gradual increase in sound levels, and involves a stepwise increase in the number and total volume of airguns firing until the full volume is achieved. 

The purpose of a ramp up (or “soft start”) is to “warn” cetaceans and pinnipeds in the vicinity of 

the airguns and to provide the time for them to leave the area and thus avoid any potential injury 

or impairment of their hearing abilities. 

During the proposed ZVSP surveys, the operator will ramp up the airgun arrays slowly. Full 

ramp ups (i.e., from a cold start when no airguns have been firing) will begin by firing a single 

airgun in the array. A full ramp up will not begin until there has been a minimum of 30 minutes 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 6 Revised August 2011 

of observation of the safety zone by MMOs to assure that no marine mammals are present. The 

entire safety zone must be visible during the 30-minute lead-in to a full ramp up. If the entire 

safety zone is not visible, then ramp up from a cold start cannot begin. If a marine mammal(s) is 

sighted within the safety zone during the 30-minute watch prior to ramp up, ramp up will be 

delayed until the marine mammal(s) is sighted outside of the safety zone or the animal(s) is not 

sighted for at least 15-30 minutes: 15 minutes for small odontocetes and pinnipeds, or 30 minutes 

for baleen whales and large odontocetes. 

Power Downs and Shut Downs 

A power down is the immediate reduction in the number of operating energy sources from all 

firing to some smaller number. A shut down is the immediate cessation of firing of all energy 

sources. The arrays will be immediately powered down whenever a marine mammal is sighted 

approaching close to or within the applicable safety zone of the full arrays, but is outside the 

applicable safety zone of the single source. If a marine mammal is sighted within the applicable 

safety zone of the single energy source, the entire array will be shut down (i.e., no sources firing). 

Marine Mammal Observers 

Vessel-based monitoring for marine mammals will be done by trained MMOs throughout the 

period of exploration drilling operations to comply with expected provisions in the IHA and LOA 

that Shell receives. The observers will monitor the occurrence and behavior of marine mammals 

near the drillship and support vessels during all daylight periods during the exploration drilling 

operation, and during most periods when exploration drilling is not being conducted. MMO 

duties will include watching for and identifying marine mammals; recording their numbers, 

distances, and reactions to the exploration drilling operations; and documenting “take by 

harassment” as defined by NMFS. 

Number of Observers 

A sufficient number of MMOs will be onboard each vessel to meet the following criteria: 

 100 percent monitoring coverage during all periods of exploration drilling operations in 

daylight; 

 maximum of four consecutive hours on watch per MMO; and 

 maximum of approximately 12 hours on watch per day per MMO. 

MMO teams will consist of trained Inupiat and field biologist observers. An experienced field 

crew leader will be a member of every MMO team aboard the drillship and each support vessel 

during the exploration drilling program. The total number of MMOs aboard may decrease later in 

the season as the duration of daylight decreases assuming NMFS does not require continuous 

nighttime monitoring. Inupiat MMOs will also function as Native language communicators with 

hunters and whaling crews and with the Communications and Call Centers (Com Centers) in 

Native villages along the Chukchi Sea coast. 
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Shell Gulf of Mexico, Inc. 7 Revised August 2011 

Crew Rotation 

Shell anticipates that there will be provision for crew rotation at least every three to six weeks to 

avoid observer fatigue. During crew rotations detailed hand-over notes will be provided to the 

incoming crew leader by the outgoing leader. Other communications such as email, fax, and/or 

phone communication between the current and oncoming crew leaders during each rotation will 

also occur when possible. In the event of an unexpected crew change Shell will facilitate such 

communications to insure monitoring consistency among shifts. 

Observer Qualifications and Training 

Crew leaders and most other biologists serving as observers in 2012 will be individuals with 

experience as observers during one or more of the 2006–2010 monitoring projects for Shell or recent 

experience with other operators in Alaska or the Canadian Beaufort. 

Biologist-observers will have previous marine mammal observation experience, and field crew 

leaders will be highly experienced with previous vessel-based marine mammal monitoring 

projects. Resumés for those individuals will be provided to NMFS so that NMFS (and USFWS if so 

stipulated) can review and accept their qualifications. All observers will be trained and familiar with 

the marine mammals of the area. A MMO handbook, adapted for the specifics of the planned Shell 

exploration drilling program will be prepared and distributed beforehand to all MMOs (see below). 

Most observers will also complete a two-day training and refresher session on marine mammal 

monitoring, to be conducted shortly before the anticipated start of the 2012 exploration drilling season. 

Any exceptions will have or receive equivalent experience or training. The training session(s) will be 

conducted by marine mammalogists with extensive crew-leader experience during previous vesselbased seismic monitoring programs. 

Primary objectives of the training include: 

 review of the marine mammal monitoring plan for this project, including any amendments adopted, or specified by NMFS or USFWS in the IHA or LOA, by BOEMRE, or 

other agreements in which Shell may elect to participate; 

 review of marine mammal sighting, identification, (photographs and videos) and distance 

estimation methods, including any amendments specified by NMFS or USFWS in the 

2012 IHA or LOA; 

 review of operation of specialized equipment (reticle binoculars, night vision devices, 

and global positioning system [GPS] system); 

 review of, and classroom practice with, data recording and data entry systems, including 

procedures for recording data on mammal sightings, exploration drilling and monitoring 

operations, environmental conditions, and entry error control. These procedures will be 

implemented through use of a customized computer database and laptop computers; and 

 review of specific tasks of the Inupiat communicator. 
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Shell Gulf of Mexico Inc. 8 Revised August 2011 

MMO Handbook 

A MMO Handbook will be prepared for Shell’s monitoring program. The Handbook will contain 

maps, illustrations, and photographs as well as copies of important documents and descriptive 

text and are intended to provide guidance and reference information to trained individuals who 

will participate as MMOs. The following topics will be covered in the MMO Handbook: 

 summary overview descriptions of the project, marine mammals and underwater sound 

energy, the 4MP (vessel-based, aerial, acoustic measurements, special studies), the 

NMFS IHA and USFWS LOA and other regulations/permits/agencies, the Marine 

Mammal Protection Act (MMPA); 

 monitoring and mitigation objectives and procedures, including initial safety radii, 

 responsibilities of staff and crew regarding the 4MP; 

 instructions for ship crew regarding the 4MP; 

 data recording procedures: codes and coding instructions, common coding mistakes, 

electronic database; navigational, marine physical, and exploration drilling data 

recording, field data sheet; 

 use of specialized field equipment: reticle binoculars, Big-eye binoculars, night vision 

devices (NVDs), laser rangefinders; 

 reticle binocular distance scale; 

 table of wind speed, Beaufort wind force, and sea state codes; 

 data storage and backup procedures; 

 list of species that might be encountered: identification, natural history; 

 safety precautions while onboard; 

 crew and/or personnel discord; conflict resolution among MMOs and crew; 

 drug and alcohol policy and testing; 

 scheduling of cruises and watches; 

 communications; 

 list of field gear provided; 

 suggested list of personal items to pack; 

 suggested literature, or literature cited; and 

 copies of the NMFS IHA and USFWS LOA will be made available. 

Monitoring Methodology 

The observer(s) will watch for marine mammals from the best available vantage point on the 

drillship and support vessels. Ideally this vantage point is an elevated stable platform from which 

the MMO has an unobstructed 360-degree view of the water. The observer(s) will scan 

systematically with the naked eye and 7  50 reticle binoculars, supplemented with Big-eye 

binoculars and night-vision equipment when needed (see below). Personnel on the bridge will 

assist the MMO(s) in watching for pinnipeds and whales. New or inexperienced MMOs will be 

paired with an experienced MMO or experienced field biologist so that the quality of marine 

mammal observations and data recording is kept consistent. 
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Shell Gulf of Mexico, Inc. 9 Revised August 2011 

Information to be recorded by MMOs will include the same types of information that were 

recorded during previous monitoring projects (e.g., Moulton and Lawson 2002). When a 

mammal sighting is made, the following information about the sighting will be carefully and 

accurately recorded: 

 species, group size, age/size/sex categories (if determinable); 

 physical description of features that were observed or determined not to be present in the 

case of unknown or unidentified animals; 

 behavior when first sighted and after initial sighting; 

 heading (if consistent), bearing and distance from observer; 

 apparent reaction to activities (e.g., none, avoidance, approach, paralleling, etc.); 

 closest point of approach and behavioral pace; 

 time, location, speed, and activity of the vessel, sea state, ice cover, visibility, and sun 

glare; on support ships the distance and bearing to the drillship will also be recorded; and 

 positions of other vessel(s) in the vicinity of the observer location. 

The ship’s position, speed, water depth, sea state, ice cover, visibility, and sun glare will also be 

recorded at the start and end of each observation watch, every 30 minutes during a watch, and 

whenever there is a change in any of those variables. 

Distances to nearby marine mammals will be estimated with binoculars (Fujinon 7  50 

binoculars) containing a reticle to measure the vertical angle of the line of sight to the animal 

relative to the horizon. 

Observers may use a laser rangefinder to test and improve their abilities for visually estimating 

distances to objects in the water. However, previous experience showed that a Class 1 eye-safe 

device was not able to measure distances to seals more than about 230 ft (70 m) away. The 

device was very useful in improving the distance estimation abilities of the observers at distances 

up to about 1,968 ft (600 m)—the maximum range at which the device could measure distances 

to highly reflective objects such as other vessels. Humans observing objects of more-or-less 

known size via a standard observation protocol, in this case from a standard height above water, 

quickly become able to estimate distances within about ±20 percent when given immediate 

feedback about actual distances during training. 

Monitoring At Night and In Poor Visibility 

Night-vision equipment (“Generation 3” binocular image intensifiers, or equivalent units) will be 

available for use when needed. However, past experience with NVDs in the Beaufort Sea and 

elsewhere indicates that NVDs are not nearly as effective as visual observation during daylight 

hours (e.g., Harris et al. 1997, 1998; Moulton and Lawson 2002). 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 10 Revised August 2011 

Specialized Field Equipment 

Shell will provide or arrange for the following specialized field equipment for use by the onboard 

MMOs: reticle binoculars, Big-eye binoculars, GPS unit, laptop computers, night vision 

binoculars, and possibly digital still and digital video cameras. 

Field Data-Recording, Verification, Handling, and Security 

The observers on the drillship and support vessels will record their observations onto datasheets 

or directly into handheld computers. During periods between watches and periods when 

operations are suspended, those data will be entered into a laptop computer running a custom 

computer database. The accuracy of the data entry will be verified in the field by computerized 

validity checks as the data are entered, and by subsequent manual checking of the database 

printouts. These procedures will allow initial summaries of data to be prepared during and 

shortly after the field season, and will facilitate transfer of the data to statistical, graphical or other 

programs for further processing. Quality control of the data will be facilitated by (1) the start-ofseason training session, (2) subsequent supervision by the onboard field crew leader, and 

(3) ongoing data checks during the field season. 

The data will be backed up regularly onto compact discs (CDs) and/or universal serial bus (USB) 

disks, and stored at separate locations on the vessel. If possible, data sheets will be photocopied 

daily during the field season. Data will be secured further by having data sheets and backup data 

CDs carried back to the Anchorage office during crew rotations. 

In addition to routine MMO duties, observers will be encouraged to record comments about their 

observations into the “comment” field in the database. Copies of these records will be available 

to the observers for reference if they wish to prepare a statement about their observations. If 

prepared, this statement would be included in the 90-day and final reports documenting the 

monitoring work. 

Both Inupiat and trained-biologist observers will be encouraged to record comments about their 

observations into the “comment” field in the marine mammal sightings database. Observer 

training will emphasize the use of “comments” for sightings that may be considered unique or not 

fully captured by standard data codes. 

In addition to the standard marine mammal sightings forms, a specialized form was developed for 

recording traditional knowledge and natural history observations. MMOs will be encouraged to 

use this form to capture observations related to any aspect of the arctic environment and the 

marine mammals found within it. Examples might include relationships between ice and marine 

mammal sightings, marine mammal behaviors, comparisons of observations among different 

years/seasons, etc. Copies of these records will be available to all observers for reference if they 

wish to prepare a statement about their observations for reporting purposes. If prepared, this 

statement would be included in the 90-day and final reports documenting the monitoring work. 

Field Reports 

Throughout the exploration drilling program, the observers will prepare a report each day or at 

such other interval as required summarizing the recent results of the monitoring program. The 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 11 Revised August 2011 

reports will summarize the species and numbers of marine mammals sighted. These reports will 

be provided to NMFS, USFWS, BOEMRE, and Shell as required. 

Reporting 

The results of the 2012 vessel-based monitoring, including estimates of “take by harassment”, 

will be presented in the 90-day and final technical report(s). Reporting will address the 

requirements established by NMFS in the IHA, and USFWS in the LOA (if so stipulated). 

The technical report(s) will include: 

 summaries of monitoring effort: total hours, total distances, and distribution of marine 

mammals through study period for sea state, and other factors affecting visibility and 

detectability of marine mammals; 

 analyses of the effects of various factors influencing detectability of marine mammals: 

sea state, number of observers, and fog/glare; 

 species composition, occurrence, and distribution of marine mammal sightings including 

date, water depth, numbers, age/size/gender categories (when discernable), group sizes, 

and ice cover; and 

 analyses of the effects of exploration drilling operations: 

- sighting rates of marine mammals during periods with and without exploration 

drilling activities (and other variables that could affect detectability), 

- initial sighting distances versus drilling state, 

- closest point of approach versus drilling state, 

- observed behaviors and types of movements versus drilling state, 

- numbers of sightings/individuals seen versus drilling state, 

- distribution around the drillship and support vessels versus drilling state, and 

- estimates of “take by harassment”. 

Data will be visualized by plotting sightings relative to the position of the drillship. We will also 

overlay the sightings data with acoustic data that indicates the sound levels associated with the 

exploration drilling activity and with maps of call locations determined by the seafloor recorders. 

Additionally, sightings data will be incorporated into animations of the call locations around the 

exploration drilling activity. Seafloor recorders used in the Chukchi Sea do not have the ability to 

localize calls. Larger groups of recorders, however, can localize calls using arrival times of the 

calls captured on several nearby recorders.

Shell will consider requests for data collected during the marine mammal monitoring only after 

the data have been put through a quality control/quality assurance program. Such requests may 

include incorporating the data with other companies’ data and/or integrating the raw data with 

data from other marine mammal studies. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 12 Revised August 2011 

ACOUSTIC MONITORING PLAN 

Exploration Drilling Sound Measurements 

Objectives 

Exploration drilling sounds are expected to vary significantly with time due to variations in the 

level of operations and the different types of equipment used at different times onboard the 

drillship. The goals of these measurements are: 

 to quantify the absolute sound levels produced by exploration drilling and to monitor 

their variations with time, distance and direction from the drillship. 

 to measure the sound levels produced by vessels operating in support of exploration 

drilling operations. These vessels will include crew change vessels, tugs, icemanagement vessels, and spill response vessels. 

 to measure the sound levels produced by an end-of-hole ZVSP survey using a stationary 

sound source. 

Equipment 

The drillship, support vessels, and ZVSP sound measurements will be performed using one of 

two methods, both of which involve real-time monitoring. The first method would involve use of 

bottom-founded hydrophones cabled back to the drillship (Figure 1). These hydrophones weigh 

approximately 88 pounds (lb) (40 kilograms) with a footprint of approximately 2.7 square feet 

(ft2

) (0.25 square meters [m2]) and would be positioned between 1,640 ft (500 m) and 3,281 ft 

(1,000 m) from the drillship, depending on the final positions of the anchors used to hold the 

drillship in place. Hydrophone cables would be fed to real-time digitization systems on board. In 

addition to the cabled system, a separate set of bottom-founded hydrophones (Figure 2) may be 

deployed at various distances from the exploration drilling operation for storage of acoustic data 

to be retrieved and processed at a later date. 

As an alternative to the cabled hydrophone system (and possible inclusion of separate bottomfounded hydrophones), the second (or alternative) monitoring method would involve a radio buoy 

approach deploying four spar buoys 4-5 mi (6-8 km) from the drillship. Additional hydrophones 

may be deployed closer to the drillship if necessary to better determine sound source levels. 

Monitoring personnel and recording/receiving equipment would be onboard one of the support 

vessels with 24-hour monitoring capacity. The system would allow for collection and processing 

of real-time data similar to that provided by the cabled system but from a wider range of 

locations. Processing would provide real-time localization of sound sources including seals and 

whales. 

Sound level monitoring with either method will occur on a continuous basis throughout all 

exploration drilling activities. Both types of systems will be set to record digital acoustic data at 

sample rate 32 kilohertz (kHz), providing useful acoustic bandwidth to at least 15 kHz. Both the 

hydrophone systems use Reson TC4032 hydrophones with sensitivity -170 dB re V/Pa. These 

systems are capable of measuring absolute broadband sound levels between 90 and 180 dB re 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 13 Revised August 2011 

Pa. The long duration recordings will capture many different operations performed from the 

drillship. Retrieval of these systems will occur following completion of the exploration drilling 

activities. 

These recorders will provide a capability to examine sound levels produced by different 

exploration drilling activities and practices and possibly to develop real time noise reduction 

measures. This system will not have the capability to locate calling marine mammals and will 

indicate only relative proximity. The system will be evaluated during operations for its potential 

to improve MMO observations through notification of MMOs on vessel and aircraft of high 

levels of call detections and their general locations. 

The deployment of exploration drilling sound monitoring equipment will occur as soon as 

possible once the drillship is on site at any of the prospects where Shell intends to drill an 

exploration well. Retrieval of these systems will occur following completion of the exploration 

drilling activities. The long duration recordings will capture many different operations performed 

at the drillship. Accurate activity logs of exploration drilling operations and nearby vessel 

activities will be maintained to correlate with these acoustic measurements. 

Hydrophone

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Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 15 Revised August 2011 

Schlumberger wireline four level vertical seismic imager (VSI) tool, which has four receivers 50-

ft (15.2-m) apart. 

Photograph of ITAGA 8-airgun Array in Sled 

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A ZVSP survey is normally conducted at each well after total depth is reached but may be 

conducted at a shallower depth. For each survey, Shell would deploy the sound source (airgun 

array) over the side of the drillship Discoverer with a crane (sound source will be 50-200 ft / 15-

61 m from the wellhead depending on crane location), to a depth of approximately 10-23 ft (3-7 

m) below the water surface. The VSI with its four receivers will be temporarily anchored in the 

wellbore at depth. The sound source will be pressured up to 2,000 pounds per square inch (psi) 

(138 bar), and activated 5-7 times at approximately 20-second intervals. The VSI will then be 

moved to the next interval of the wellbore and re-anchored, after which the airgun array will 

again be activated 5-7 times. This process will be repeated until the entire wellbore is surveyed in 

this manner. The interval between anchor points for the VSI is usually between 200-300 ft (61-

91 m). A normal ZVSP survey is conducted over a period of about 10-14 hours depending on the 

depth of the well and the number of anchoring points. 

. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 16 Revised August 2011 

Figure 3. Schematic of ZVSP 

Acoustic Data Analyses 

Exploration drilling sound data will be analyzed to extract a record of the frequency-dependent 

sound levels as a function of time. Figure 4 shows the results of this type of analysis. These 

results are useful also for correlating measured sound energy events with specific survey 

operations and capturing marine mammal vocalizations. The analysis provides absolute sound 

levels in finite frequency bands that can be tailored to match the highest-sensitivity hearing 

ranges for species of interest. For example, bowhead hearing is thought to be most acute in the 

100 Hertz (Hz) - 1000 Hz frequency range that corresponds with the blue dotted line in the upper 

plot of Figure 4. 

The analyses will also consider sound level integrated through 1-hour durations (referred to as 

sound energy equivalent level Leq (1-hour). Figure 5 (upper) shows an example of a Leq 

analysis of hydrophone data. Similar graphs for long time periods will be generated as part of the 

data analysis performed for indicating exploration drilling sound variation with time in selected 

frequency bands. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 17 Revised August 2011 

Figure 4. Lower: spectrogram of sound level measurements obtained from a hydrophone 

recording system. Upper: broadband and selected band level variation with time. 

Figure 5. Upper: 1-hour Leq levels that will be calculated from acoustic measurements for 

use in correlating with bowhead whale deflection data. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 18 Revised August 2011 

Reporting of Results 

Acoustic sound level results will be reported in the 90-day and comprehensive reports for this 

program. The results reported will include: 

 sound source levels for the drillship and all exploration drilling support vessels; 

 spectrogram and band level versus time plots computed from the continuous recordings 

obtained from the hydrophone systems; 

 hourly sound energy equivalent (Leq) levels at the hydrophone locations; and 

 correlation of exploration drilling source levels with the type of exploration drilling 

operation being performed. These results will be obtained by observing differences in 

exploration drilling sound associated with differences in the drill rig activity as indicated 

in detailed drillship logs. 

JOINT MONITORING PROGRAM 

This section describes studies that were undertaken in the Chukchi Sea from 2006 through 2010, 

will be undertaken again in 2011, and will be conducted during exploration drilling operations in 

2012. Shell plans to conduct aerial surveys consistent with the previous 2006–2008 and 2010 

programs along the Chukchi Sea coast. Additionally, an acoustic net array similar to the one 

deployed in 2010 is planned for 2011 and 2012 will be used to monitor industry and marine 

mammal sounds across the Chukchi Sea and along coast. Additional recorders will be deployed 

in the area around prospects where Shell intends to drill. 

Chukchi Sea Coastal Aerial Survey 

Nearshore aerial surveys of marine mammals in the Chukchi Sea were conducted over coastal 

areas to approximately 23 mi (37 km) offshore in 2006–2008 and 2010 in support of Shell’s 

open-water marine survey exploration activities. These surveys provided data on the distribution 

and abundance of marine mammals in nearshore waters of the Chukchi Sea. Shell plans to 

conduct an aerial survey program in the Chukchi Sea in 2012 that will be similar to the previous 

programs. 

Alaskan Natives from villages along the east coast of the Chukchi Sea hunt marine mammals 

during the summer and Native communities are concerned that offshore oil and gas exploration 

activities may negatively impact their ability to harvest marine mammals. Of particular concern 

are potential impacts on the beluga harvest at Point Lay and on future bowhead harvests at Point 

Hope, Point Lay, Wainwright and Barrow. Other species of concern in the Chukchi Sea include 

the gray whale, bearded, ringed, and spotted seals, and walrus. Gray whale and harbor porpoise 

are expected to be the most numerous cetacean species encountered during the proposed aerial 

survey, although harbor porpoise are difficult to detect from aircraft. Beluga whales may occur in 

high numbers early in the season. The ringed seal is likely to be the most abundant pinniped 

species. The current aerial survey program will be designed to collect distribution data on 

cetaceans but will be limited in its ability to collect similar data on pinnipeds. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 19 Revised August 2011 

Objectives 

The aerial survey program objectives in 2012 will be: 

 to collect data on the distribution and abundance of marine mammals in coastal areas of 

the eastern Chukchi Sea; and 

 to collect and report data on the distribution, numbers, orientation and behavior of marine 

mammals, particularly beluga whales, near traditional hunting areas in the eastern 

Chukchi Sea. 

Survey Considerations 

With agreement from hunters in the coastal villages, aerial surveys of coastal areas to 

approximately 23 mi (37 km) offshore between Point Hope and Point Barrow will begin in early 

to mid-July and will continue until exploration drilling operations in the Chukchi Sea are 

completed. Weather and equipment permitting, surveys will be conducted twice per week during 

this time period. In addition, during the 2012 exploration drilling season, aerial surveys will be 

coordinated in cooperation with the aerial surveys funded by BOEMRE and conducted by NMFS 

and any other groups conducting surveys in the region. 

Survey Procedures 

Transects will be flown in a saw-toothed pattern between the shore and 23 mi (37 km) offshore as 

well as along the coast from Point Barrow to Point Hope (Figure 6). This design will permit 

completion of the survey in one to two days and will provide representative coverage of the 

nearshore region. Saw-tooth transects were designed by placing transect start/end points every 34 

mi (55 km) along the offshore boundary of this 23 mi (37 km) wide nearshore zone, and at 

midpoints between those points along the coast. The transect line start/end points will be shifted 

along both the coast and the offshore boundary for each survey based upon a randomized starting 

location, but overall survey distance will not vary substantially. The coastline transect will 

simply follow the coastline or barrier islands. As with past surveys of the Chukchi Sea coast, 

coordination with coastal villages to avoid disturbance of the beluga whale subsistence hunt will 

be extremely important. “No-fly” zones around coastal villages or other hunting areas established 

during communications with village representatives will be in place until the end of the hunting 

season. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 20 Revised August 2011 

Figure 6. Aerial survey transects location and general pattern for the eastern Chukchi Sea, 

2012. Specific transect start-/end-points will be altered randomly from survey to survey, 

and hunting areas will be avoided when hunting is occurring. 

Standard aerial survey procedures used in previous marine mammal projects (by Shell as well as 

by others) will be followed. This will facilitate comparisons and (as appropriate) pooling with 

other data, and will minimize controversy about the chosen survey procedures. The aircraft will 

be flown at 110–120 knots ground speed and usually at an altitude of 1,000 ft (305 m). In 

accordance with anticipated stipulations in the LOA, survey aircraft will be flown at 1,500 ft (457 

m) over the Ledyard Bay spectacled eider habitat after 1 July. Aerial surveys at an altitude of 

1,000 ft (305 m) do not provide much information about seals but are suitable for bowhead, 

beluga, and gray whales. The need for a 1,000+ ft (305+ m) cloud ceiling will limit the dates and 

times when surveys can be flown. Selection of a higher altitude for surveys would result in a 

significant reduction in the number of days during which surveys would be possible, impairing 

the ability of the aerial program to meet its objectives. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 21 Revised August 2011 

The surveyed area will include waters where belugas are normally available to subsistence 

hunters. If large concentrations of belugas are encountered during the survey, the survey may be 

interrupted to photograph the groups to obtain better counts of the number of animals present. If 

whales are photographed in lagoons or other shallow-water concentration areas, the aircraft will 

climb to ~10,000 ft (3,048 m) altitude to avoid disturbing the whales and causing them to leave 

the area. If whales are in offshore areas, the aircraft will climb high enough to include all whales 

within a single photograph; typically about 3,000 ft (914 m) altitude. When in shallow water, 

belugas and other marine mammals are more sensitive to aircraft overflights and other forms of 

disturbance than when they are offshore (see Richardson et al. 1995 for a review). They 

frequently leave shallow estuaries when over flown at altitudes of 2,000–3,000 ft (610-904 m), 

whereas they rarely react to aircraft at 1,500 ft (457 m) when offshore in deeper water. 

Additionally, if large groups of other marine mammals are encountered on the surveys, such as 

the large aggregations of walruses seen in 2007 and 2010, we will attempt to photograph the 

animals and provide location information to interested stakeholders. 

Two primary observers will be seated at bubble windows on either side of the aircraft and a third 

observer will observe part-time and record data the rest of the time. All observers need bubble 

windows to facilitate downward viewing. For each marine mammal sighting, the observer will 

dictate the species, number, size/age/sex class when determinable, activity, heading, swimming 

speed category (if traveling), sighting cue, ice conditions (type and percentage), and inclinometer 

reading to the marine mammal into a digital recorder. The inclinometer reading will be taken 

when the animal’s location is 90° to the side of the aircraft track, allowing calculation of lateral 

distance from the aircraft trackline. 

Transect information, sighting data and environmental data will be entered into a GPS-linked 

computer by the third observer, and simultaneously recorded on digital voice recorders for 

backup and validation. At the start of each transect, the observer recording data will record the 

transect start time and position, ceiling height (ft), cloud cover (in 10ths), wind speed (knots), 

wind direction degrees True North (T) and outside air temperature degrees Celsius (C). In 

addition, each observer will record the time, visibility (subjectively classified as excellent, good, 

moderately impaired, seriously impaired or impossible), sea state (Beaufort wind force), ice cover 

(in 10ths) and sun glare (none, moderate, severe) at the start and end of each transect, and at 

2-minute intervals along the transect. This will provide data in units suitable for statistical 

summaries and analyses of effects of these variables (and position relative to the drillship) on the 

probability of detecting animals (Davis et al. 1982; Miller et al. 1999; Thomas et al. 2002). The 

data logger will automatically record time and aircraft position (latitude and longitude) for 

sightings and transect waypoints, and at pre-selected intervals along the transects. 

Coordination with Other Aerial Surveys

The BOEMRE, the NMFS, the NSB, or other organizations may also conduct aerial surveys in 

the Chukchi Sea during the exploration drilling season. Shell will consult with any groups or 

organizations conducting aerial surveys along the eastern Chukchi Sea coast regarding 

coordination during the exploration drilling season. The objectives will be: 

 to ensure aircraft separation when both crews conduct surveys in the same general region; 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 22 Revised August 2011 

 to coordinate the 2012 aerial survey projects in order to maximize consistency and 

minimize duplication; and 

 to maximize consistency with previous years’ efforts insofar as feasible. 

Analysis of Aerial Survey Data 

During the field program, preliminary maps and summaries of the daily surveys will be provided 

to NMFS as normally required by the terms of the IHA. While in the field data will be checked 

for entry errors and files will be backed up to CDs or portable memory drives. Reporting of 

results will focus on the distribution of the observed species along the coast and the seasonal 

timing (if any) of the observed species. 

Acoustic “Net” Array in Chukchi Sea 

Background and Objectives 

The acoustic “net” array used during the 2006–2010 field seasons is again proposed for 2011 and 

2012 in the Chukchi Sea was designed to accomplish two main objectives. The first was to 

collect information on the occurrence and distribution of marine mammals (including beluga 

whale, bowhead whale, and walrus) that may be available to subsistence hunters near villages 

located on the Chukchi Sea coast and to document their relative abundance, habitat use, and 

migratory patterns. The second objective was to measure the ambient soundscape throughout the 

eastern Chukchi Sea and to record received levels of sounds from industry and other activities 

further offshore in the Chukchi Sea. 

Technical Approach 

The net array configuration used in 2007–2010 is again proposed for 2011 and 2012. The basic 

components of this effort consist of 30 hydrophone systems placed widely across the U.S. 

Chukchi Sea and a prospect specific array of 12 hydrophones capable of localization of mammal 

calls. The net array configuration will include hydrophone systems distributed at each of the four 

primary transect locations: Cape Lisburne, Point Hope, Wainwright and Barrow. The systems 

comprising the regional array will be placed at locations shown in Figure 7. These offshore 

systems will capture exploration drilling sounds, if present, over large distances to help 

characterize the sound transmission properties in the Chukchi Sea. They will also provide a large 

amount of information related to marine mammals in the Chukchi Sea. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 23 Revised August 2011 

Figure 7. Deployment locations of Hydrophones in acoustic arrays in the eastern Chukchi 

Sea, Alaska 2012. Depiction of hydrophone array at Burger is not scaled correctly based 

on description below (12 km by 18 km) 

The regional acoustic monitoring program, will be augmented in 2012 by an array of additional 

acoustic recorders to be deployed on a grid pattern over a 7.2 mi (12 km) by 10.8 mi (17.4 km) 

area extending over several of Shell’s lease blocks near locations of highest interest for 

exploration drilling in 2012. The cluster array will operate at a sampling frequency of 16 kHz, 

which is sufficient to capture vocalizations from bowhead, beluga, walrus, gray whale, fin whale, 

humpback, killer whale and most other marine mammals known to be present in the Chukchi Sea. 

The cluster deployment configuration was defined to allow tracking of vocalizing animals that 

pass through the immediate area of these lease blocks. Maximum separation between adjacent 

recorders is 3.6 mi (5.8 km). At this spacing we expect that individual whale calls will be 

detected on at least 3 different recorders when the calling animals are within the boundary of the 

deployment pattern. Bowhead and other mysticete calls should be detectable simultaneously on 

more than 3 recorders due to their relatively higher sound source levels compared to other marine 

mammals. In calm weather conditions, when ambient underwater sound levels are low, we 

expect to have detection of most other marine mammal calls on more than three recorders. The 

goal of simultaneous detection on multiple recorders is to allow for triangulation of the call 

positions, which also requires accurate time synchronization of the recorders. When small 

numbers of whales are vocalizing Shell hopes to be able to identify and track the movements of 

specific individuals within the deployment area. It will not be possible to track individual whales 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico Inc. 24 Revised August 2011 

if many whales are calling due to abundant overlapping calls. In this case analyses will show the 

general distribution of calls in the vicinity of the recorders. 

Analysis and Reporting 

The Chukchi Net Arrays and Cluster Array, deployed for up to 3 months, will produce an 

extremely large dataset comprising several Terabytes of acoustic data. The analyses of these data 

require identification of marine mammal vocalizations. Because of the very large amount of data 

to be processed, the analysis methods will incorporate automated vocalization detection 

algorithms. While the hydrophones used in the net array are not directional, and therefore not 

capable of accurate localization of detections, the number of vocalizations detected on each of the 

sensors may provide a measure of the relative spatial distribution of some marine mammal 

species, assuming that vocalization patterns are consistent within a species across the spatial and 

geographic distribution of the hydrophone array. These results may therefore provide 

information such as timing of migrations and routes of migration for belugas and bowheads. 

A second purpose of the Chukchi net array is to monitor the amplitude of exploration drilling 

sounds reaching the near-shore region. It is expected that sounds from exploration drilling 

activities will be detectable on hydrophone systems when ambient sound energy conditions are 

low. The exploration drilling sound levels at recorder locations will be quantified and reported. 

Analysis of all acoustic data will be prioritized to address the primary questions. The primary 

data analysis questions are to (a) determine when, where, and what species of animals are 

acoustically detected on each recorder (b) analyze data as a whole to determine offshore 

distributions as a function of time, (c) quantify spatial and temporal variability in the ambient 

sound energy, and (d) measure received levels of exploration drilling survey events and drillship 

activities. The detection data will be used to develop spatial and temporal animal detection 

distributions. Statistical analyses will be used to test for changes in animal detections and 

distributions as a function of different variables (e.g., time of day, season, environmental 

conditions, ambient sound energy, and exploration drilling or vessel sound levels). 

COMPREHENSIVE REPORT ON INDUSTRY ACTIVITIES AND 

MARINE MAMMAL MONITORING EFFORTS IN THE 

BEAUFORT AND CHUKCHI SEAS 

Following the 2012 exploration drilling season a comprehensive report describing the acoustic, 

vessel-based, and aerial monitoring programs will be prepared. The comprehensive report will 

describe the methods, results, conclusions and limitations of each of the individual data sets in 

detail. The report will also integrate (to the extent possible) the studies into a broad based 

assessment of industry activities and their impacts on marine mammals in the Chukchi Sea. The 

report will help to establish long term data sets that can assist with the evaluation of changes in 

the Chukchi Sea ecosystems. The report will attempt to provide a regional synthesis of available 

data on industry activity in offshore areas of northern Alaska that may influence marine mammal 

density, distribution and behavior. 
Marine Mammal Monitoring and Mitigation Plan Chukchi Sea, Alaska 

Shell Gulf of Mexico, Inc. 25 Revised August 2011 

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