11726 Federal Register / Vol. 80, No. 42 / Wednesday, March 4, 2015 / Notices 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

RIN 0648–XD655 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to an Exploration 

Drilling Program in the Chukchi Sea, 

Alaska 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice; proposed incidental 

harassment authorization; request for 

comments. 

SUMMARY: NMFS received an 

application from Shell Gulf of Mexico 

Inc. (Shell) for an Incidental Harassment 

Authorization (IHA) to take marine 

mammals, by harassment, incidental to 

offshore exploration drilling on Outer 

Continental Shelf (OCS) leases in the 

Chukchi Sea, Alaska. Pursuant to the 

Marine Mammal Protection Act 

(MMPA), NMFS is requesting comments 

on its proposal to issue an IHA to Shell 

to take, by Level B harassment only, 12 

species of marine mammals during the 

specified activity. 

DATES: Comments and information must 

be received no later than April 3, 2015. 

ADDRESSES: Comments on the 

application should be addressed to Jolie 

Harrison, Chief, Permits and 

Conservation Division, Office of 

Protected Resources, National Marine 

Fisheries Service, 1315 East-West 

Highway, Silver Spring, MD 20910. The 

mailbox address for providing email 

comments is ITP.Guan@noaa.gov. 

NMFS is not responsible for email 

comments sent to addresses other than 

the one provided here. Comments sent 

via email, including all attachments, 

must not exceed a 10-megabyte file size. 

Instructions: All comments received 

are a part of the public record and will 

generally be posted to http://

www.nmfs.noaa.gov/pr/permits/

incidental.htm without change. All 

Personal Identifying Information (for 

example, name, address, etc.) 

voluntarily submitted by the commenter 

may be publicly accessible. Do not 

submit Confidential Business 

Information or otherwise sensitive or 

protected information. 

A copy of the application, which 

contains several attachments, including 

Shell’s marine mammal mitigation and 

monitoring plan (4MP) and Plan of 

Cooperation, used in this document may 

be obtained by writing to the address 

specified above, telephoning the contact 

listed below (see FOR FURTHER

INFORMATION CONTACT), or visiting the 

internet at: http://www.nmfs.noaa.gov/ 

pr/permits/incidental.htm. Documents 

cited in this notice may also be viewed, 

by appointment, during regular business 

hours, at the aforementioned address. 

FOR FURTHER INFORMATION CONTACT: 

Shane Guan, Office of Protected 

Resources, NMFS, (301) 427–8401. 

SUPPLEMENTARY INFORMATION: 

Background 

Sections 101(a)(5)(A) and (D) of the 

MMPA (16 U.S.C. 1361 et seq.) direct 

the Secretary of Commerce to allow, 

upon request, the incidental, but not 

intentional, taking of small numbers of 

marine mammals by U.S. citizens who 

engage in a specified activity (other than 

commercial fishing) within a specified 

geographical region if certain findings 

are made and either regulations are 

issued or, if the taking is limited to 

harassment, a notice of a proposed 

authorization is provided to the public 

for review. 

An authorization for incidental 

takings shall be granted if NMFS finds 

that the taking will have a negligible 

impact on the species or stock(s), will 

not have an unmitigable adverse impact 

on the availability of the species or 

stock(s) for subsistence uses (where 

relevant), and if the permissible 

methods of taking and requirements 

pertaining to the mitigation, monitoring 

and reporting of such takings are set 

forth. NMFS has defined ‘‘negligible 

impact’’ in 50 CFR 216.103 as ‘‘an 

impact resulting from the specified 

activity that cannot be reasonably 

expected to, and is not reasonably likely 

to, adversely affect the species or stock 

through effects on annual rates of 

recruitment or survival.’’ 

Except with respect to certain 

activities not pertinent here, the MMPA 

defines ‘‘harassment’’ as: any act of 

pursuit, torment, or annoyance which (i) 

has the potential to injure a marine 

mammal or marine mammal stock in the 

wild [Level A harassment]; or (ii) has 

the potential to disturb a marine 

mammal or marine mammal stock in the 

wild by causing disruption of behavioral 

patterns, including, but not limited to, 

migration, breathing, nursing, breeding, 

feeding, or sheltering [Level B 

harassment]. 

Summary of Request 

On September 18, 2014, Shell 

submitted an application to NMFS for 

the taking of marine mammals 

incidental to exploration drilling 

activities in the Chukchi Sea, Alaska. 

After receiving comments and questions 

from NMFS, Shell revised its IHA 

application and 4MP on December 17, 

2014. NMFS determined that the 

application was adequate and complete 

on January 5, 2015. 

The proposed activity would occur 

between July and October 2015. The 

following specific aspects of the 

proposed activities are likely to result in 

the take of marine mammals: 

Exploration drilling, supply and drilling 

support vessels using dynamic 

positioning, mudline cellar 

construction, anchor handling, ice 

management activities, and zero-offset 

vertical seismic profiling (ZVSP) 

activities. 

Shell has requested an authorization 

to take 13 marine mammal species by 

Level B harassment. However, the 

narwhal (Monodon monoceros) is not 

expected to be found in the activity 

area. Therefore, NMFS is proposing to 

authorize take of 12 marine mammal 

species, by Level B harassment, 

incidental to Shell’s offshore 

exploration drilling in the Chukchi Sea. 

These species are: beluga whale 

(Delphinapterus leucas); bowhead 

whale (Balaena mysticetus); gray whale 

(Eschrichtius robustus); killer whale 

(Orcinus orca); minke whale 

(Balaenoptera acutorostrata); fin whale 

(Balaenoptera physalus); humpback 

whale (Megaptera novaeangliae); harbor 

porpoise (Phocoena phocoena); bearded 

seal (Erignathus barbatus); ringed seal 

(Phoca hispida); spotted seal (P. largha); 

and ribbon seal (Histriophoca fasciata). 

In 2012, NMFS issued two IHAs to 

Shell to conducted two exploratory 

drilling activities at exploration wells in 

the Beaufort (77 FR 27284; May 9, 2012) 

and Chukchi (77 FR 27322; May 9, 

2012) Seas, Alaska, during the 2012 

Arctic open-water season (July through 

October). Shell’s proposed 2015 

exploration drilling program is similar 

to those conducted in 2012. In 

December 2012, Shell submitted two 

additional IHA applications to take 

marine mammals incidental to its 

proposed exploratory drilling in 

Beaufort and Chukchi Seas during the 

2013 open-water season. However, Shell 

withdrew its application in February 

2013. 

Description of the Specified Activity 

Overview 

Shell proposes to conduct exploration 

drilling at up to four exploration drill 

sites at Shell’s Burger Prospect on the 

OCS leases acquired from the U.S. 

Department of Interior, Bureau of Ocean 

Energy Management (BOEM). The 

exploration drilling planned for the 


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2015 season is a continuation of the 

Chukchi Sea exploration drilling 

program that began in 2012, and 

resulted in the completion of a partial 

well at the location known as Burger A. 

Exploration drilling will be done 

pursuant to Shell’s Chukchi Sea 

Exploration Plan, Revision 2 (EP). 

Shell plans to use two drilling units, 

the drillship Noble Discoverer 

(Discoverer) and semi-submersible 

Transocean Polar Pioneer (Polar 

Pioneer) to drill at up to four locations 

on the Burger Prospect. Both drilling 

units will be attended to by support 

vessels for the purposes of ice 

management, anchor handling, oil spill 

response (OSR), refueling, support to 

drilling units, and resupply. The 

drilling units will be accompanied by an 

expanded number of support vessels, 

aircraft, and oil spill response vessels 

(OSRV) greater than the number 

deployed during the 2012 drilling 

season. 

Dates and Duration 

Shell anticipates that its exploration 

drilling program will occur between 

July 1 and approximately October 31, 

2015. The drilling units will move 

through the Bering Strait and into the 

Chukchi Sea on or after July 1, 2015, 

and then onto the Burger Prospect as 

soon as ice and weather conditions 

allow. Exploration drilling activities 

will continue until about October 31, 

2015, the drilling units and support 

vessels will exit the Chukchi Sea at the 

conclusion of the exploration drilling 

season. Transit entirely out of the 

Chukchi Sea by all vessels associated 

with exploration drilling may take well 

into the month of November due to ice, 

weather, and sea states. 

Specified Geographic Region 

All drill sites at which exploration 

drilling would occur in 2015 will be at 

Shell’s Burger Prospect (see Figure 1–1 

on page 1–2 of Shell’s IHA application). 

Shell has identified a total of six 

Chukchi Sea lease blocks on the Burger 

Prospect. All six drill sites are located 

more than 64 mi (103 km) off the 

Chukchi Sea coast. During 2015, the 

Discoverer and Polar Pioneer will be 

used to conduct exploration drilling 

activities at up to four exploration drill 

sites. As with any Arctic exploration 

program, weather and ice conditions 

will dictate actual operations. 

Activities associated with the 

Chukchi Sea exploration drilling 

program and analyzed herein include 

operation of the Discoverer, Polar 

Pioneer, and associated support vessels. 

The drilling units will remain at the 

location of the designated exploration 

drill sites except when mobilizing and 

demobilizing to and from the Chukchi 

Sea, transiting between drill sites, and 

temporarily moving off location if it is 

determined ice conditions require such 

a move to ensure the safety of personnel 

and/or the environment. 

Detailed Description of Activities 

The specific activities that may result 

in incidental taking of marine mammals 

based on the IHA application are 

limited to Shell’s exploration drilling 

program and related activities. 

Activities include exploration drilling 

sounds, MLC construction, anchor 

handling while mooring a drilling unit 

at a drill site, vessels on DP when 

tending to a drilling unit, ice 

management, and zero-offset vertical 

seismic profile (ZVSP) surveys. 

(1) Exploration Drilling 

In 2015 Shell plans to continue its 

exploration drilling program on BOEM 

Alaska OCS leases at drill sites greater 

than 64 mi (103 km) from the Chukchi 

Sea coast during the 2015 drilling 

season. Shell plans to conduct 

exploration drilling activities at up to 

four drill sites at the Burger Prospect 

utilizing two drilling units, the drillship 

Discoverer and the semi-submersible 

Polar Pioneer. 

During 2012, Shell drilled a partial 

well at the Burger A drill site. Drilling 

at Burger A did not reach a depth at 

which a ZVSP survey would be 

conducted. Consequently one was not 

performed. 

A mudline cellar (MLC) will be 

constructed at each drill site. The MLCs 

will be constructed in the seafloor using 

a large diameter bit operated by 

hydraulic motors and suspended from 

the Discoverer or Polar Pioneer. 

(2) Support Vessels 

During exploration drilling, the 

Discoverer and Polar Pioneer will be 

supported by the types of vessels listed 

in Table 1–1 of Shell’s IHA application. 

These drilling units would be 

accompanied by greater number of 

support vessels and oil spill response 

vessels than were deployed by Shell 

during 2012 exploration drilling in the 

Chukchi Sea. 

Two ice management vessels will 

support the drilling units. These vessels 

will enter and exit the Chukchi Sea with 

or ahead of the drilling units, and will 

generally remain in the vicinity of the 

drilling units during the drilling season. 

Ice management and ice scouting is 

expected to occur at distances of 20 mi 

(32 km) and 30 mi (48 km) respectively 

from drill site locations. However, these 

vessels may have to range beyond these 

distances depending on ice conditions. 

Up to three anchor handlers will 

support the drilling units. These vessels 

will enter and exit the Chukchi Sea with 

or ahead of the drilling units, and will 

generally remain in the vicinity of the 

drilling units during the drilling season. 

When the vessels are not anchor 

handling, they will be available to 

provide other general support. Two of 

the three anchor handlers may be used 

to perform secondary ice management 

tasks if needed. 

The planned exploration drilling 

activities will use three offshore supply 

vessels (OSVs) for resupply of the 

drilling units and support vessels. 

Drilling materials, food, fuel, and other 

supplies will be picked up in Dutch 

Harbor (with possible minor resupply 

coming out of Kotzebue) and 

transported to the drilling units and 

support vessels. 

Shell plans to use up to two science 

vessels; one for each drilling unit, from 

which sampling of ocean water and 

sediments prior to and following 

drilling discharges would be conducted. 

The science vessel specifications are 

based on larger OSVs, but smaller 

vessels may be used. 

Two tugs will tow the Polar Pioneer 

from Dutch Harbor to the Burger 

Prospect. After the Polar Pioneer is 

moored, the tugs will remain in the 

vicinity of the drilling units to help 

move either drilling unit in the event 

they need to be moved off of a drilling 

site due to ice or any other event. 

Shell may deploy a MLC ROV system 

from an OSV type vessel that could be 

used to construct MLCs prior to a 

drilling units arriving. If used, this 

vessel would be located at a drill site on 

the Burger Prospect. When not in use, 

the vessel would be outside of the 

Chukchi Sea 

(3) Oil Spill Response Vessels 

The oil spill response (OSR) vessel 

types supporting the exploration 

drilling program are listed in Table 1.2 

of Shell’s IHA application. 

One dedicated OSR barge and on-site 

oil spill response vessel (OSRV) will be 

staged in the vicinity of the drilling 

unit(s) when drilling into potential 

liquid hydrocarbon bearing zones. This 

will enable the OSRV to respond to a 

spill and provide containment, 

recovery, and storage for the initial 

response period in the unlikely event of 

a well control incident. 

The OSR barge, associated tug, and 

OSRV possess sufficient storage 

capacity to provide containment, 

recovery, and storage for the initial 

response period. Shell plans to use two 


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oil storage tankers (OSTs). An OST will 

be staged at the Burger Prospect. The 

OST will hold fuel for Shell’s drilling 

units, support vessels, and have space 

for storage of recovered liquids in the 

unlikely event of a well control 

incident. A second OST will be 

stationed in the Chukchi Sea and sited 

such that it will be able to respond to 

a well control event before the first 

tanker reaches its recovered liquid 

capacity. 

The tug and barge will be used for 

nearshore OSR. The nearshore tug and 

barge will be moored near Goodhope 

Bay, Kotzebue Sound. The nearshore tug 

and barge will also carry response 

equipment, including one 47 ft. (14 m) 

skimming vessel, 34 ft. (10 m) 

workboats, mini-barges, boom and 

duplex skimming units for nearshore 

recovery and possibly support nearshore 

protection. The nearshore tug and barge 

will also carry designated response 

personnel and will mobilize to recovery 

areas, deploy equipment, and begin 

response operations. 

(4) Aircraft 

Offshore operations will be serviced 

by up to three helicopters operated out 

of an onshore support base in Barrow. 

The helicopters are not yet contracted. 

Sikorsky S–92s (or similar) will be used 

to transport crews between the onshore 

support base, the drilling units and 

support vessels with helidecks. The 

helicopters will also be used to haul 

small amounts of food, materials, 

equipment, samples and waste between 

vessels and the shorebase. 

Approximately 40 Barrow to Burger 

Prospect round trip flights will occur 

each week to support the additional 

crew change necessities for an 

additional drilling unit, support vessels, 

and required sampling. 

The route chosen will depend on 

weather conditions and whether 

subsistence users are active on land or 

at sea. These routes may be modified 

depending on weather and subsistence 

uses. 

Shell will also have a dedicated 

helicopter for Search and Rescue (SAR). 

The SAR helicopter is expected to be a 

Sikorsky S–92 (or similar). This aircraft 

will stay grounded at the Barrow shore 

base location except during training 

drills, emergencies, and other nonroutine events. The SAR helicopter and 

crew plan training flights for 

approximately 40 hr/month. 

A fixed wing propeller or turboprop 

aircraft, such as the Saab 340–B, 

Beechcraft 1900, or De Havilland Dash 

8, will be used to transport crews, 

materials, and equipment between 

Wainwright and hub airports such as 

Barrow or Fairbanks. It is anticipated 

that there will be one round trip flight 

every three weeks. 

A fixed wing aircraft, Gulfstream 

Aero-Commander (or similar), will be 

used for photographic surveys of marine 

mammals. These flights will take place 

daily depending on weather conditions. 

Flight paths are located in the Marine 

Mammal Monitoring and Mitigation 

Plan (4MP). 

An additional Gulfstream Aero 

Commander may be used to provide ice 

reconnaissance flights to monitor ice 

conditions around the Burger Prospect. 

Typically, the flights will focus on the 

ice conditions within 50 mi (80 km) of 

the drill sites, but more extensive ice 

reconnaissance may occur beyond 50 mi 

(80 km). 

These flights will occur at an altitude 

of approximately 3,000 ft. (915 m). 

(5) Vertical Seismic Profile 

Shell may conduct a geophysical 

survey referred to as a vertical seismic 

profile (VSP) survey at each drill site 

where a well is drilled in 2015. During 

VSP surveys, an airgun array is 

deployed at a location near or adjacent 

to the drilling units, while receivers are 

placed (temporarily anchored) in the 

wellbore. The sound source (airgun 

array) is fired, and the reflected sonic 

waves are recorded by receivers 

(geophones) located in the wellbore. 

The geophones, typically a string of 

them, are then raised up to the next 

interval in the wellbore and the process 

is repeated until the entire wellbore has 

been surveyed. The purpose of the VSP 

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 will be conducting a particular 

form of VSP referred to as a zero-offset 

VSP (ZVSP), in which the sound source 

is maintained at a constant location near 

the wellbore (Figure 1–2 in IHA 

application). Shell may use one of two 

typical sound sources: (1) A threeairgun array consisting of three, 150 

cubic inches (in3) (2,458 cm3) airguns, 

or (2) a two-airgun array consisting of 

two, 250 in3 (4,097 cm3) airguns. 

Typical receivers would consist of a 

standard wireline four-level vertical 

seismic imager (VSI) tool, which has 

four receivers 50 ft (15.2 m) apart. 

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 Discoverer or Polar 

Pioneer with a crane, the sound source 

will be 50–200 ft (15–61 m) from the 

wellhead depending on crane location, 

and reach a depth of approximately 10– 

23 ft (3–7 m) below the water surface. 

The VSI along with its four receivers 

will be temporarily anchored in the 

wellbore at depth. 

The sound source will be pressured 

up to 3,000 pounds per square inch 

(psi), and activated 5–7 times at 

approximately 20-second intervals. The 

VSI will then be moved to the next 

interval of the wellbore and reanchored, after which the airgun array 

will again be activated 5–7 times. This 

process will be repeated until the entire 

wellbore is surveyed. The interval 

between anchor points for the VSI is 

usually 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. 

(6) Ice Management and Forecasting 

The exploration drilling program is 

located in an area that is characterized 

by active sea ice movement, ice 

scouring, and storm surges. In 

anticipation of potential ice hazards that 

may be encountered, Shell will 

implement a Drilling Ice Management 

Plan (DIMP) to ensure real-time ice and 

weather forecasting that will identify 

conditions that could put operations at 

risk, allowing Shell to modify its 

activities accordingly. 

Shell’s ice management fleet will 

consist of four vessels: two ice 

management vessels and two anchor 

handler/icebreakers. Ice management 

that is necessary for safe operations 

during Shell’s planned exploration 

drilling program will occur far out in 

the OCS, remote from the vicinities of 

any routine marine vessel traffic in the 

Chukchi Sea, thereby resulting in no 

threat to public safety or services that 

occur near to shore. Shell vessels will 

also communicate movements and 

activities through the 2015 North Slope 

Communications Centers (Com Centers). 

Management of ice will occur during the 

drilling season predominated by open 

water, thus it will not contribute to ice 

hazards, such as ridging, override, or 

pileup in an offshore or nearshore 

environment. 

The ice-management/anchor handling 

vessels will manage the ice by deflecting 

any ice floes that could affect the 

Discoverer or Polar Pioneer when they 

are drilling or anchor mooring buoys 

even if the drilling units are not 

anchored at a drill site. When managing 

ice, the ice management vessels will 

generally operate upwind of the drilling 

units, since the wind and currents 

contribute to the direction of ice 


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movement. Ice reconnaissance or ice 

scouting forays may occur out to 48.3km 

(30mi) from the drilling units and are 

conducted by the ice management 

vessels into ice that may move into the 

vicinity of exploration drilling 

activities. This will provide the vessel 

and shore-based ice advisors with the 

information required to decide whether 

or not active ice management is 

necessary. The actual distances from the 

drilling units and the patterns of ice 

management (distances between vessels, 

and width of the swath in which ice 

management occurs) will be determined 

by the ice floe speed, size, thickness, 

and character, and wind forecast. 

Ice floe frequency and intensity is 

unpredictable and could range from no 

ice to ice densities that exceed icemanagement capabilities, in which case 

drilling activities might be stopped and 

the drilling units disconnected from 

their moorings and moved off site. The 

Discoverer was disconnected from its 

moorings once during the 2012 season 

to avoid a potential encounter with 

multi-year ice flows of sufficient size to 

halt activities. Advance scouting of ice 

primarily north and east of the Burger 

A well by the ice management vessels 

did not detect ice of sufficient size or 

thickness to warrant disconnecting the 

Discoverer from its moorings during the 

remainder of the 2012 season. If ice is 

present, ice management activities may 

be necessary in early July, at discrete 

intervals at other times during the 

season, and towards the end of 

operations in late October. However, 

data regarding historic ice patterns in 

the area of activities indicate that it will 

not be required throughout the planned 

2015 drilling season. 

During the 2012 drilling season, a 

total of seven days of active ice 

management by vessels occurred in 

support of Shell’s exploration drilling 

program in the Chukchi Sea. 

When ice is present at a drill site, ice 

disturbance will be limited to the 

minimum amount needed to allow 

drilling to continue. First-year ice will 

be the type most likely to be 

encountered. The ice-management 

vessel will be tasked with managing the 

ice so that it flows easily around the 

drilling units and their anchor moorings 

without building up in front of either. 

This type of ice is managed by the icemanagement vessel continually moving 

back and forth across the drift line, 

directly up drift of the drilling units and 

making turns at both ends, or in circular 

patterns. During ice-management, the 

vessel’s propeller is rotating at 

approximately 15 to 20% of the vessel’s 

propeller rotation capacity. Ice 

management occurs with slow 

movements of the vessel using lower 

power and therefore slower propeller 

rotation speed (i.e., lower cavitation), 

allowing for fewer repositions of the 

vessel, and thereby reducing cavitation 

effects in the water. Occasionally, there 

may be multi-year ice features that 

would be managed at a much slower 

speed than that used to manage firstyear ice. 

As detailed in Shell’s Drilling Ice 

Management Plan (DIMP), in 2012 

Shell’s ice management vessels 

conducted ice management to protect 

moorings for the Discoverer after the 

drilling unit was moved off of the 

Burger A well. This work consisted of 

re-directing flows as necessary to avoid 

potential impact with mooring buoys, 

without the necessity to break up multiyear ice flowbergs. Actual breaking of 

ice may need to occur in the event that 

ice conditions in the immediate vicinity 

of activities create a safety hazard for 

the drilling unit, or its moorings. In 

such a circumstance, operations 

personnel will follow the guidelines 

established in the DIMP to evaluate ice 

conditions and make the formal 

designation of a hazardous ice alert 

condition, which would trigger the 

procedures that govern any actual 

icebreaking operations. Despite Shell’s 

experience in 2012, historical data 

relative to ice conditions in the Chukchi 

Sea in the vicinity of Shell’s planned 

2015 activities, establishes that there is 

a low probability for the type of 

hazardous ice conditions that might 

necessitate icebreaking (e.g., records of 

the National Naval Ice Center archives; 

Shell/SIWAC). The probability could be 

greater at the beginning and/or the end 

of the drilling season (early July or late 

October). For the purposes of evaluating 

possible impacts of the planned 

activities, Shell has assumed 

icebreaking activities for a limited 

period of time, and estimated incidental 

exposures of marine mammals from 

such activities. 

Description of Marine Mammals in the 

Area of the Specified Activity 

The Chukchi Sea supports a diverse 

assemblage of marine mammals, 

including: Bowhead, gray, beluga, killer, 

minke, humpback, and fin whales; 

harbor porpoise; ringed, ribbon, spotted, 

and bearded seals; narwhals; polar bears 

(Ursus maritimus); and walruses 

(Odobenus rosmarus divergens; see 

Table 4–1 in Shell’s application). The 

bowhead, humpback, and fin whales are 

listed as ‘‘endangered’’ under the 

Endangered Species Act (ESA) and as 

depleted under the MMPA. The ringed 

seal is listed as ‘‘threatened’’ under the 

ESA. Certain stocks or populations of 

gray, beluga, and killer whales and 

spotted seals are listed as endangered or 

are proposed for listing under the ESA; 

however, none of those stocks or 

populations occur in the proposed 

activity area. Both the walrus and the 

polar bear are managed by the U.S. Fish 

and Wildlife Service (USFWS) and are 

not considered further in this proposed 

IHA notice. 

Of these species, 12 are expected to 

occur in the area of Shell’s proposed 

operations. These species are: The 

bowhead, gray, humpback, minke, fin, 

killer, and beluga whales; harbor 

porpoise; and the ringed, spotted, 

bearded, and ribbon seals. Beluga, 

bowhead, and gray whales, harbor 

porpoise, and ringed, bearded, and 

spotted seals are anticipated to be 

encountered more than the other marine 

mammal species mentioned here. The 

marine mammal species that is likely to 

be encountered most widely (in space 

and time) throughout the period of the 

proposed drilling program is the ringed 

seal. Encounters with bowhead and gray 

whales are expected to be limited to 

particular seasons, as discussed later in 

this document. Where available, Shell 

used density estimates from peerreviewed literature in the application. In 

cases where density estimates were not 

readily available in the peer-reviewed 

literature, Shell used other methods to 

derive the estimates. NMFS reviewed 

the density estimate descriptions and 

articles from which estimates were 

derived and requested additional 

information to better explain the density 

estimates presented by Shell in its 

application. This additional information 

was included in the revised IHA 

application. The explanation for those 

derivations and the actual density 

estimates are described later in this 

document (see the ‘‘Estimated Take by 

Incidental Harassment’’ section). 

The narwhal occurs in Canadian 

waters and occasionally in the Alaskan 

Beaufort Sea and the Chukchi Sea, but 

it is considered extralimital in U.S. 

waters and is not expected to be 

encountered. There are scattered records 

of narwhal in Alaskan waters, including 

reports by subsistence hunters, where 

the species is considered extralimital 

(Reeves et al., 2002). Due to the rarity 

of this species in the proposed project 

area and the remote chance it would be 

affected by Shell’s proposed Chukchi 

Sea drilling activities, this species is not 

discussed further in this proposed IHA 

notice. 

Shell’s application contains 

information on the status, distribution, 

seasonal distribution, abundance, and 

life history of each of the species under 

NMFS jurisdiction mentioned in this 


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document. When reviewing the 

application, NMFS determined that the 

species descriptions provided by Shell 

correctly characterized the status, 

distribution, seasonal distribution, and 

abundance of each species. Please refer 

to the application for that information 

(see ADDRESSES). Additional information 

can also be found in the NMFS Stock 

Assessment Reports (SAR). The Alaska 

2013 SAR is available at: http:// 

www.nmfs.noaa.gov/pr/sars/pdf/ 

ak2013_final.pdf. 

Table 1 lists the 12 marine mammal 

species or stocks under NMFS 

jurisdiction with confirmed or possible 

occurrence in the proposed project area. 

TABLE 1—MARINE MAMMAL SPECIES AND STOCKS WITH CONFIRMED OR POSSIBLE OCCURRENCE IN THE PROPOSED

EXPLORATION DRILLING AREA

Common name Scientific name Status Occurrence Seasonality Range Abundance 

Odontocetes: 

Beluga whale 

(Eastern 

Chukchi Sea 

stock).

Dephinapterus 

leucas.

............................... Common ............... Mostly spring and 

fall with some in 

summer.

Russia to Canada 3,710 

Beluga whale 

(Beaufort Sea 

stock).

Delphinapterus 

leucas.

............................... Common ............... Mostly spring and 

fall with some in 

summer.

Russia to Canada 39,258 

Killer whale ...... Orcinus orca ......... ............................... Occasional/

Extralimital.

Mostly summer 

and early fall.

California to Alaska 2,084 

Harbor porpoise Phocoena 

phocoena.

............................... Occasional/

Extralimital.

Mostly summer 

and early fall.

California to Alaska 48,215 

Mysticetes: 

Bowhead whale Balaena mysticetus Endangered; Depleted.Common ............... Mostly spring and 

fall with some in 

summer.

Russia to Canada 19,534 

Gray whale ...... Eschrichtius 

robustus.

............................... Somewhat common.Mostly summer ..... Mexico to the U.S. 

Arctic Ocean.

19,126 

Minke whale .... Balaenoptera 

acutorostrata.

............................... Rare ...................... Summer ................ North Pacific ......... 810–1,003 

Fin whale 

(North Pacific 

stock).

B. physalus ........... Endangered; Depleted.Rare ...................... Summer ................ North Pacific ......... 1,652 

Humpback 

whale (Central North Pacific stock).

Megaptera 

novaeangliae.

Endangered; Depleted.Rare ...................... Summer ................ Central to North 

Pacific.

20,800 

Pinnipeds: 

Bearded seal 

(Beringia distinct population segment).

Erigathus barbatus Candidate .............. Common ............... Spring and summer.Bering, Chukchi, 

and Beaufort 

Seas.

155,000 

Ringed seal 

(Arctic stock).

Phoca hispida ....... Threatened; Depleted.Common ............... Year round ............ Bering, Chukchi, 

and Beaufort 

Seas.

300,000 

Spotted seal .... Phoca largha ......... ............................... Common ............... Summer ................ Japan to U.S. Arctic Ocean.141,479 

Ribbon seal ..... Histriophoca 

fasciata.

Species of concern Occasional ............ Summer ................ Russia to U.S. Arctic Ocean.49,000 

Potential Effects of the Specified 

Activity on Marine Mammals 

This section includes a summary and 

discussion of the ways that the types of 

stressors associated with the specified 

activity (e.g., drilling, seismic airgun, 

vessel movement) have been observed to 

or are thought to impact marine 

mammals. This section is intended as a 

background of potential effects and does 

not consider either the specific manner 

in which this activity will be carried out 

or the mitigation that will be 

implemented or how either of those will 

shape the anticipated impacts from this 

specific activity. The ‘‘Estimated Take 

by Incidental Harassment’’ section later 

in this document will include a 

quantitative analysis of the number of 

individuals that are expected to be taken 

by this activity. The ‘‘Negligible Impact 

Analysis’’ section will include the 

analysis of how this specific activity 

will impact marine mammals and will 

consider the content of this section, the 

‘‘Estimated Take by Incidental 

Harassment’’ section, the ‘‘Mitigation’’ 

section, and the ‘‘Anticipated Effects on 

Marine Mammal Habitat’’ section to 

draw conclusions regarding the likely 

impacts of this activity on the 

reproductive success or survivorship of 

individuals and from that on the 

affected marine mammal populations or 

stocks. 

Background on Sound 

Sound is a physical phenomenon 

consisting of minute vibrations that 

travel through a medium, such as air or 

water, and is generally characterized by 

several variables. Frequency describes 

the sound’s pitch and is measured in 

hertz (Hz) or kilohertz (kHz), while 

sound level describes the sound’s 

intensity and is measured in decibels 

(dB). Sound level increases or decreases 

exponentially with each dB of change. 

The logarithmic nature of the scale 

means that each 10-dB increase is a 10- 

fold increase in acoustic power (and a 

20-dB increase is then a 100-fold 

increase in power). A 10-fold increase in 

acoustic power does not mean that the 


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sound is perceived as being 10 times 

louder, however. Sound levels are 

compared to a reference sound pressure 

(micro-Pascal) to identify the medium. 

For air and water, these reference 

pressures are ‘‘re 20 m Pa’’ and ‘‘re 1 

m Pa,’’ respectively. Root mean square 

(RMS) is the quadratic mean sound 

pressure over the duration of an 

impulse. RMS is calculated by squaring 

all of the sound amplitudes, averaging 

the squares, and then taking the square 

root of the average (Urick, 1983). RMS 

accounts for both positive and negative 

values; squaring the pressures makes all 

values positive so that they may be 

accounted for in the summation of 

pressure levels (Hastings and Popper, 

2005). This measurement is often used 

in the context of discussing behavioral 

effects, in part, because behavioral 

effects, which often result from auditory 

cues, may be better expressed through 

averaged units rather than by peak 

pressures. 

Exploration Drilling Program Sound 

Characteristics 

(1) Drilling Sounds 

Exploration drilling will be conducted 

from the drilling units Discoverer and 

Polar Pioneer. Underwater sound 

propagation during the activities results 

from the use of generators, drilling 

machinery, and the drilling units 

themselves. Sound levels during vesselbased operations may fluctuate 

depending on the specific type of 

activity at a given time and aspect from 

the vessel. Underwater sound levels 

may also depend on the specific 

equipment in operation. Lower sound 

levels have been reported during well 

logging than during drilling operations 

(Greene 1987b), and underwater sound 

appeared to be lower at the bow and 

stern aspects than at the beam (Greene 

1987a). 

Most drilling sounds generated from 

vessel-based operations occur at 

relatively low frequencies below 600 Hz 

although tones up to 1,850 Hz were 

recorded by Greene (1987a) during 

drilling operations in the Beaufort Sea. 

At a range of 0.17 km, the 20–1000 Hz 

band level was 122–125 dB re 1m Pa rms 

for the drillship Explorer I. Underwater 

sound levels were slightly higher (134 

db re 1m Pa rms) during drilling activity 

from the Explorer II at a range of 0.20 

km; although tones were only recorded 

below 600 Hz. Underwater sound 

measurements from the Kulluk in 1986 

at 0.98 km were higher (143 dB re 1m Pa 

rms) than from the other two vessels. 

Measurements of the Discoverer on the 

Burger prospect in 2012, without any 

support vessels operating nearby, 

showed received sound levels of 120 dB 

re 1 m Pa rms at 1.5 km. The Polar 

Pioneer, a semi-submersible drilling 

unit, is expected to introduce less sound 

into the water than the Discoverer 

during drilling and related activities. 

(2) Airgun Sounds 

Two sound sources have been 

proposed by Shell for the ZVSP surveys 

in 2015. The first is a small airgun array 

that consists of three 150 in3 (2,458 cm3) 

airguns for a total volume of 450 in3

(7,374 cm3). The second ZVSP sound 

source consists of two 250 in3 (4097 

cm3) airguns with a total volume of 500 

in3 (8,194 cm3). Typically, a single 

ZVSP survey will be performed when 

the well has reached PTD or final depth 

although, in some instances, a prior 

ZVSP will have been performed at a 

shallower depth. A typical survey, 

would last 10–14 hours, depending on 

the depth of the well and the number of 

anchoring points, and include firings of 

up to the full array, plus additional 

firing of the smallest airgun in the array 

to be used as a ‘‘mitigation airgun’’ 

while the geophones are relocated 

within the wellbore. 

Airguns function by venting highpressure air into the water. The pressure 

signature of an individual airgun 

consists of a sharp rise and then fall in 

pressure, followed by several positive 

and negative pressure excursions caused 

by oscillation of the resulting air bubble. 

The sizes, arrangement, and firing times 

of the individual airguns in an array are 

designed and synchronized to suppress 

the pressure oscillations subsequent to 

the first cycle. A typical high-energy 

airgun arrays emit most energy at 10– 

120 Hz. However, the pulses contain 

energy up to 500–1000 Hz and some 

energy at higher frequencies (Goold and 

Fish 1998; Potter et al. 2007). 

(3) Aircraft Noise 

Helicopters may be used for personnel 

and equipment transport to and from 

the drilling units and support vessels. 

Under calm conditions, rotor and engine 

sounds are coupled into the water 

within a 26° cone beneath the aircraft. 

Some of the sound will transmit beyond 

the immediate area, and some sound 

will enter the water outside the 26° area 

when the sea surface is rough. However, 

scattering and absorption will limit 

lateral propagation in the shallow water. 

Dominant tones in noise spectra from 

helicopters are generally below 500 Hz 

(Greene and Moore 1995). Harmonics of 

the main rotor and tail rotor usually 

dominate the sound from helicopters; 

however, many additional tones 

associated with the engines and other 

rotating parts are sometimes present. 

Because of doppler shift effects, the 

frequencies of tones received at a 

stationary site diminish when an aircraft 

passes overhead. The apparent 

frequency is increased while the aircraft 

approaches and is reduced while it 

moves away. 

Aircraft flyovers are not heard 

underwater for very long, especially 

when compared to how long they are 

heard in air as the aircraft approaches 

an observer. Helicopters flying to and 

from the drilling units will generally 

maintain straight-line routes at altitudes 

of 1,500 ft. (457 m) above sea level, 

thereby limiting the received levels at 

and below the surface. 

(4) Vessel Noise 

In addition to the drilling units, 

various types of vessels will be used in 

support of the operations including ice 

management vessels, anchor handlers, 

OSVs, and OSR vessels. Sounds from 

boats and vessels have been reported 

extensively (Greene and Moore 1995; 

Blackwell and Greene 2002, 2005, 

2006). Numerous measurements of 

underwater vessel sound have been 

performed in support of recent industry 

activity in the Chukchi and Beaufort 

Seas. Results of these measurements 

were reported in various 90-day and 

comprehensive reports since 2007. For 

example, Garner and Hannay (2009) 

estimated sound pressure levels of 100 

dB re 1 m Pa rms at distances ranging 

from ∼1.5 to 2.3 mi (∼2.4 to 3.7 km) from 

various types of barges. MacDonnell et 

al. (2008) estimated higher underwater 

sound pressure levels from the seismic 

vessel Gilavar of 120 dB re 1 m Pa rms 

at ∼13 mi (∼21 km) from the source, 

although the sound level was only 150 

dB re 1 m Pa rms at 85 ft (26 m) from 

the vessel. Like other industry-generated 

sound, underwater sound from vessels 

is generally at relatively low 

frequencies. During 2012, underwater 

sound from ten (10) vessels in transit, 

and in two instances towing or 

providing a tow-assist, were recorded by 

JASCO in the Chukchi Sea as a function 

of the sound source characterization 

(SSC) study required in the Shell 2012 

Chukchi Sea drilling IHA. SSC transit 

and tow results from 2012 include ice 

management vessels, an anchor handler, 

OSR vessels, the OST, support tugs, and 

OSVs. The recorded sound pressure 

levels to 120 dB re 1 m Pa rms for vessels 

in transit primarily range from ∼0.8–4.3 

mi (1.3–6.9 km), whereas the measured 

120 dB re 1 m Pa rms for the drilling unit 

Kulluk under tow by the Aiviq in the 

Chukchi Sea was approximately 11.8 mi 

(19 km) on its way to the Beaufort Sea 

(O’Neil and McCrodan 2012a, b). 

Measurements of vessel sounds from 


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Shell’s 2012 exploration drilling 

program in the Chukchi Sea are 

presented in detail in the 2012 

Comprehensive Monitoring Report (LGL 

2013). 

The primary sources of sounds from 

all vessel classes are propeller 

cavitation, propeller singing, and 

propulsion or other machinery. 

Propeller cavitation is usually the 

dominant noise source for vessels (Ross 

1976). Propeller cavitation and singing 

are produced outside the hull, whereas 

propulsion or other machinery noise 

originates inside the hull. There are 

additional sounds produced by vessel 

activity, such as pumps, generators, 

flow noise from water passing over the 

hull, and bubbles breaking in the wake. 

Icebreakers contribute greater sound 

levels during ice-breaking activities than 

ships of similar size during normal 

operation in open water (Richardson et 

al. 1995a). This higher sound 

production results from the greater 

amount of power and propeller 

cavitation required when operating in 

thick ice. 

Acoustic Impacts 

When considering the influence of 

various kinds of sound on the marine 

environment, it is necessary to 

understand that different kinds of 

marine life are sensitive to different 

frequencies of sound. Based on available 

behavioral data, audiograms have been 

derived using auditory evoked 

potentials, anatomical modeling, and 

other data, Southall et al. (2007) 

designate ‘‘functional hearing groups’’ 

for marine mammals and estimate the 

lower and upper frequencies of 

functional hearing of the groups. The 

functional groups and the associated 

frequencies are indicated below (though 

animals are less sensitive to sounds at 

the outer edge of their functional range 

and most sensitive to sounds of 

frequencies within a smaller range 

somewhere in the middle of their 

functional hearing range): 

• Low frequency cetaceans (13 

species of mysticetes): functional 

hearing is estimated to occur between 

approximately 7 Hz and 30 kHz; 

• Mid-frequency cetaceans (32 

species of dolphins, six species of larger 

toothed whales, and 19 species of 

beaked and bottlenose whales): 

functional hearing is estimated to occur 

between approximately 150 Hz and 160 

kHz; 

• High frequency cetaceans (eight 

species of true porpoises, six species of 

river dolphins, Kogia, the franciscana, 

and four species of cephalorhynchids): 

functional hearing is estimated to occur 

between approximately 200 Hz and 180 

kHz; 

• Phocid pinnipeds in Water: 

functional hearing is estimated to occur 

between approximately 75 Hz and 100 

kHz; and 

• Otariid pinnipeds in Water: 

functional hearing is estimated to occur 

between approximately 100 Hz and 40 

kHz. 

As mentioned previously in this 

document, 12 marine mammal species 

or stocks (nine cetaceans and four 

phocid pinnipeds) may occur in the 

proposed seismic survey area. Of the 

nine cetacean species or stocks likely to 

occur in the proposed project area and 

for which take is requested, two are 

classified as low-frequency cetaceans 

(i.e., bowhead and gray whales), two are 

classified as mid-frequency cetaceans 

(i.e., both beluga stocks and killer 

whales), and one is classified as a highfrequency cetacean (i.e., harbor 

porpoise) (Southall et al., 2007). A 

species functional hearing group is a 

consideration when we analyze the 

effects of exposure to sound on marine 

mammals. 

(1) Tolerance 

Numerous studies have shown that 

underwater sounds from industry 

activities are often readily detectable by 

marine mammals in the water at 

distances of many kilometers. 

Numerous studies have also shown that 

marine mammals at distances more than 

a few kilometers away often show no 

apparent response to industry activities 

of various types (Miller et al., 2005; Bain 

and Williams, 2006). This is often true 

even in cases when the sounds must be 

readily audible to the animals based on 

measured received levels and the 

hearing sensitivity of that mammal 

group. Although various baleen whales, 

toothed whales, and (less frequently) 

pinnipeds have been shown to react 

behaviorally to underwater sound such 

as airgun pulses or vessels under some 

conditions, at other times mammals of 

all three types have shown no overt 

reactions (e.g., Malme et al., 1986; 

Richardson et al., 1995; Madsen and 

Mohl, 2000; Croll et al., 2001; Jacobs 

and Terhune, 2002; Madsen et al., 2002; 

Miller et al., 2005). In general, 

pinnipeds and small odontocetes seem 

to be more tolerant of exposure to some 

types of underwater sound than are 

baleen whales. Richardson et al. (1995a) 

found that vessel noise does not seem to 

strongly affect pinnipeds that are 

already in the water. Richardson et al. 

(1995a) went on to explain that seals on 

haul-outs sometimes respond strongly to 

the presence of vessels and at other 

times appear to show considerable 

tolerance of vessels, and Brueggeman et 

al. (1992, cited in Richardson et al., 

1995a) observed ringed seals hauled out 

on ice pans displaying short-term 

escape reactions when a ship 

approached within 0.25–0.5 mi (0.4–0.8 

km). 

(2) Masking 

Masking is the obscuring of sounds of 

interest by other sounds, often at similar 

frequencies. Marine mammals are 

highly dependent on sound, and their 

ability to recognize sound signals amid 

other noise is important in 

communication, predator and prey 

detection, and, in the case of toothed 

whales, echolocation. Even in the 

absence of manmade sounds, the sea is 

usually noisy. Background ambient 

noise often interferes with or masks the 

ability of an animal to detect a sound 

signal even when that signal is above its 

absolute hearing threshold. Natural 

ambient noise includes contributions 

from wind, waves, precipitation, other 

animals, and (at frequencies above 30 

kHz) thermal noise resulting from 

molecular agitation (Richardson et al., 

1995a). Background noise also can 

include sounds from human activities. 

Masking of natural sounds can result 

when human activities produce high 

levels of background noise. Conversely, 

if the background level of underwater 

noise is high (e.g., on a day with strong 

wind and high waves), an 

anthropogenic noise source will not be 

detectable as far away as would be 

possible under quieter conditions and 

will itself be masked. 

Although some degree of masking is 

inevitable when high levels of manmade 

broadband sounds are introduced into 

the sea, marine mammals have evolved 

systems and behavior that function to 

reduce the impacts of masking. 

Structured signals, such as the 

echolocation click sequences of small 

toothed whales, may be readily detected 

even in the presence of strong 

background noise because their 

frequency content and temporal features 

usually differ strongly from those of the 

background noise (Au and Moore, 1988, 

1990). The components of background 

noise that are similar in frequency to the 

sound signal in question primarily 

determine the degree of masking of that 

signal. 

Redundancy and context can also 

facilitate detection of weak signals. 

These phenomena may help marine 

mammals detect weak sounds in the 

presence of natural or manmade noise. 

Most masking studies in marine 

mammals present the test signal and the 

masking noise from the same direction. 

The sound localization abilities of 


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marine mammals suggest that, if signal 

and noise come from different 

directions, masking would not be as 

severe as the usual types of masking 

studies might suggest (Richardson et al., 

1995a). The dominant background noise 

may be highly directional if it comes 

from a particular anthropogenic source 

such as a ship or industrial site. 

Directional hearing may significantly 

reduce the masking effects of these 

noises by improving the effective signalto-noise ratio. In the cases of highfrequency hearing by the bottlenose 

dolphin, beluga whale, and killer whale, 

empirical evidence confirms that 

masking depends strongly on the 

relative directions of arrival of sound 

signals and the masking noise (Penner et 

al., 1986; Dubrovskiy, 1990; Bain et al., 

1993; Bain and Dahlheim, 1994). 

Toothed whales, and probably other 

marine mammals as well, have 

additional capabilities besides 

directional hearing that can facilitate 

detection of sounds in the presence of 

background noise. There is evidence 

that some toothed whales can shift the 

dominant frequencies of their 

echolocation signals from a frequency 

range with a lot of ambient noise toward 

frequencies with less noise (Au et al., 

1974, 1985; Moore and Pawloski, 1990; 

Thomas and Turl, 1990; Romanenko 

and Kitain, 1992; Lesage et al., 1999). A 

few marine mammal species are known 

to increase the source levels or alter the 

frequency of their calls in the presence 

of elevated sound levels (Dahlheim, 

1987; Au, 1993; Lesage et al., 1993, 

1999; Terhune, 1999; Foote et al., 2004; 

Parks et al., 2007, 2009; Di Iorio and 

Clark, 2009; Holt et al., 2009). 

These data demonstrating adaptations 

for reduced masking pertain mainly to 

the very high frequency echolocation 

signals of toothed whales. There is less 

information about the existence of 

corresponding mechanisms at moderate 

or low frequencies or in other types of 

marine mammals. For example, Zaitseva 

et al. (1980) found that, for the 

bottlenose dolphin, the angular 

separation between a sound source and 

a masking noise source had little effect 

on the degree of masking when the 

sound frequency was 18 kHz, in contrast 

to the pronounced effect at higher 

frequencies. Directional hearing has 

been demonstrated at frequencies as low 

as 0.5–2 kHz in several marine 

mammals, including killer whales 

(Richardson et al., 1995a). This ability 

may be useful in reducing masking at 

these frequencies. In summary, high 

levels of noise generated by 

anthropogenic activities may act to 

mask the detection of weaker 

biologically important sounds by some 

marine mammals. This masking may be 

more prominent for lower frequencies. 

For higher frequencies, such as that 

used in echolocation by toothed whales, 

several mechanisms are available that 

may allow them to reduce the effects of 

such masking. 

Masking effects of underwater sounds 

from Shell’s proposed activities on 

marine mammal calls and other natural 

sounds are expected to be limited. For 

example, beluga whales primarily use 

high-frequency sounds to communicate 

and locate prey; therefore, masking by 

low-frequency sounds associated with 

drilling activities is not expected to 

occur (Gales, 1982, as cited in Shell, 

2009). If the distance between 

communicating whales does not exceed 

their distance from the drilling activity, 

the likelihood of potential impacts from 

masking would be low (Gales, 1982, as 

cited in Shell, 2009). At distances 

greater than 660–1,300 ft (200–400 m), 

recorded sounds from drilling activities 

did not affect behavior of beluga whales, 

even though the sound energy level and 

frequency were such that it could be 

heard several kilometers away 

(Richardson et al., 1995b). This 

exposure resulted in whales being 

deflected from the sound energy and 

changing behavior. These minor 

changes are not expected to affect the 

beluga whale population (Richardson et 

al., 1991; Richard et al., 1998). Brewer 

et al. (1993) observed belugas within 2.3 

mi (3.7 km) of the drilling unit Kulluk 

during drilling; however, the authors do 

not describe any behaviors that may 

have been exhibited by those animals. 

Please refer to the Arctic Multiple-Sale 

Draft Environmental Impact Statement 

(USDOI MMS, 2008), available on the 

Internet at: http://www.mms.gov/alaska/ 

ref/EIS%20EA/ArcticMultiSale_209/ 

_DEIS.htm, for more detailed 

information. 

There is evidence of other marine 

mammal species continuing to call in 

the presence of industrial activity. 

Annual acoustical monitoring near BP’s 

Northstar production facility during the 

fall bowhead migration westward 

through the Beaufort Sea has recorded 

thousands of calls each year (for 

examples, see Richardson et al., 2007; 

Aerts and Richardson, 2008). 

Construction, maintenance, and 

operational activities have been 

occurring from this facility for over 10 

years. To compensate and reduce 

masking, some mysticetes may alter the 

frequencies of their communication 

sounds (Richardson et al., 1995a; Parks 

et al., 2007). Masking processes in 

baleen whales are not amenable to 

laboratory study, and no direct 

measurements on hearing sensitivity are 

available for these species. It is not 

currently possible to determine with 

precision the potential consequences of 

temporary or local background noise 

levels. However, Parks et al. (2007) 

found that right whales (a species 

closely related to the bowhead whale) 

altered their vocalizations, possibly in 

response to background noise levels. For 

species that can hear over a relatively 

broad frequency range, as is presumed 

to be the case for mysticetes, a narrow 

band source may only cause partial 

masking. Richardson et al. (1995a) note 

that a bowhead whale 12.4 mi (20 km) 

from a human sound source, such as 

that produced during oil and gas 

industry activities, might hear strong 

calls from other whales within 

approximately 12.4 mi (20 km), and a 

whale 3.1 mi (5 km) from the source 

might hear strong calls from whales 

within approximately 3.1 mi (5 km). 

Additionally, masking is more likely to 

occur closer to a sound source, and 

distant anthropogenic sound is less 

likely to mask short-distance acoustic 

communication (Richardson et al., 

1995a). 

Although some masking by marine 

mammal species in the area may occur, 

the extent of the masking interference 

will depend on the spatial relationship 

of the animal and Shell’s activity. 

Almost all energy in the sounds emitted 

by drilling and other operational 

activities is at low frequencies, 

predominantly below 250 Hz with 

another peak centered around 1,000 Hz. 

Most energy in the sounds from the 

vessels and aircraft to be used during 

this project is below 1 kHz (Moore et al., 

1984; Greene and Moore, 1995; 

Blackwell et al., 2004b; Blackwell and 

Greene, 2006). These frequencies are 

mainly used by mysticetes but not by 

odontocetes. Therefore, masking effects 

would potentially be more pronounced 

in the bowhead and gray whales that 

might occur in the proposed project 

area. If, as described later in this 

document, certain species avoid the 

proposed drilling locations, impacts 

from masking are anticipated to be low. 

(3) Behavioral Disturbance Reactions 

Behavioral responses to sound are 

highly variable and context-specific. 

Many different variables can influence 

an animal’s perception of and response 

to (in both nature and magnitude) an 

acoustic event. An animal’s prior 

experience with a sound or sound 

source affects whether it is less likely 

(habituation) or more likely 

(sensitization) to respond to certain 

sounds in the future (animals can also 

be innately pre-disposed to respond to 


asabaliauskas on DSK5VPTVN1PROD with NOTICES
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certain sounds in certain ways; Southall 

et al., 2007). Related to the sound itself, 

the perceived nearness of the sound, 

bearing of the sound (approaching vs. 

retreating), similarity of a sound to 

biologically relevant sounds in the 

animal’s environment (i.e., calls of 

predators, prey, or conspecifics), and 

familiarity of the sound may affect the 

way an animal responds to the sound 

(Southall et al., 2007). Individuals (of 

different age, gender, reproductive 

status, etc.) among most populations 

will have variable hearing capabilities 

and differing behavioral sensitivities to 

sounds that will be affected by prior 

conditioning, experience, and current 

activities of those individuals. Often, 

specific acoustic features of the sound 

and contextual variables (i.e., proximity, 

duration, or recurrence of the sound or 

the current behavior that the marine 

mammal is engaged in or its prior 

experience), as well as entirely separate 

factors such as the physical presence of 

a nearby vessel, may be more relevant 

to the animal’s response than the 

received level alone. 

Exposure of marine mammals to 

sound sources can result in (but is not 

limited to) no response or any of the 

following observable responses: 

Increased alertness; orientation or 

attraction to a sound source; vocal 

modifications; cessation of feeding; 

cessation of social interaction; alteration 

of movement or diving behavior; 

avoidance; habitat abandonment 

(temporary or permanent); and, in 

severe cases, panic, flight, stampede, or 

stranding, potentially resulting in death 

(Southall et al., 2007). On a related note, 

many animals perform vital functions, 

such as feeding, resting, traveling, and 

socializing, on a diel cycle (24-hr cycle). 

Behavioral reactions to noise exposure 

(such as disruption of critical life 

functions, displacement, or avoidance of 

important habitat) are more likely to be 

significant if they last more than one 

diel cycle or recur on subsequent days 

(Southall et al., 2007). Consequently, a 

behavioral response lasting less than 

one day and not recurring on 

subsequent days is not considered 

particularly severe unless it could 

directly affect reproduction or survival 

(Southall et al., 2007). 

Detailed studies regarding responses 

to anthropogenic sound have been 

conducted on humpback, gray, and 

bowhead whales and ringed seals. Less 

detailed data are available for some 

other species of baleen whales, sperm 

whales, small toothed whales, and sea 

otters. The following sub-sections 

provide examples of behavioral 

responses that demonstrate the 

variability in behavioral responses that 

would be expected given the different 

sensitivities of marine mammal species 

to sound. 

Baleen Whales—Richardson et al. 

(1995b) reported changes in surfacing 

and respiration behavior and the 

occurrence of turns during surfacing in 

bowhead whales exposed to playback of 

underwater sound from drilling 

activities. These behavioral effects were 

localized and occurred at distances up 

to 1.2–2.5 mi (2–4 km). 

Some bowheads appeared to divert 

from their migratory path after exposure 

to projected icebreaker sounds. Other 

bowheads however, tolerated projected 

icebreaker sound at levels 20 dB and 

more above ambient sound levels. The 

source level of the projected sound 

however, was much less than that of an 

actual icebreaker, and reaction distances 

to actual icebreaking may be much 

greater than those reported here for 

projected sounds. 

Brewer et al. (1993) and Hall et al. 

(1994) reported numerous sightings of 

marine mammals including bowhead 

whales in the vicinity of offshore 

drilling operations in the Beaufort Sea. 

One bowhead whale sighting was 

reported within approximately 1,312 ft 

(400 m) of a drilling vessel although 

most other bowhead sightings were at 

much greater distances. Few bowheads 

were recorded near industrial activities 

by aerial observers. After controlling for 

spatial autocorrelation in aerial survey 

data from Hall et al. (1994) using a 

Mantel test, Schick and Urban (2000) 

found that the variable describing 

straight line distance between the rig 

and bowhead whale sightings was not 

significant but that a variable describing 

threshold distances between sightings 

and the rig was significant. Thus, 

although the aerial survey results 

suggested substantial avoidance of the 

operations by bowhead whales, 

observations by vessel-based observers 

indicate that at least some bowheads 

may have been closer to industrial 

activities than was suggested by results 

of aerial observations. 

Richardson et al. (2008) reported a 

slight change in the distribution of 

bowhead whale calls in response to 

operational sounds on BP’s Northstar 

Island. The southern edge of the call 

distribution ranged from 0.47 to 1.46 mi 

(0.76 to 2.35 km) farther offshore, 

apparently in response to industrial 

sound levels. This result however, was 

only achieved after intensive statistical 

analyses, and it is not clear that this 

represented a biologically significant 

effect. 

Patenaude et al. (2002) reported fewer 

behavioral responses to aircraft 

overflights by bowhead compared to 

beluga whales. Behaviors classified as 

reactions consisted of short surfacings, 

immediate dives or turns, changes in 

behavior state, vigorous swimming, and 

breaching. Most bowhead reaction 

resulted from exposure to helicopter 

activity and little response to fixed-wing 

aircraft was observed. Most reactions 

occurred when the helicopter was at 

altitudes ≤492 ft (150 m) and lateral 

distances ≤820 ft (250 m; Nowacek et 

al., 2007). 

During their study, Patenaude et al. 

(2002) observed one bowhead whale 

cow-calf pair during four passes totaling 

2.8 hours of the helicopter and two pairs 

during Twin Otter overflights. All of the 

helicopter passes were at altitudes of 

49–98 ft (15–30 m). The mother dove 

both times she was at the surface, and 

the calf dove once out of the four times 

it was at the surface. For the cow-calf 

pair sightings during Twin Otter 

overflights, the authors did not note any 

behaviors specific to those pairs. Rather, 

the reactions of the cow-calf pairs were 

lumped with the reactions of other 

groups that did not consist of calves. 

Richardson et al. (1995b) and Moore 

and Clarke (2002) reviewed a few 

studies that observed responses of gray 

whales to aircraft. Cow-calf pairs were 

quite sensitive to a turboprop survey 

flown at 1,000 ft (305 m) altitude on the 

Alaskan summering grounds. In that 

survey, adults were seen swimming over 

the calf, or the calf swam under the 

adult (Ljungblad et al., 1983, cited in 

Richardson et al., 1995b and Moore and 

Clarke, 2002). However, when the same 

aircraft circled for more than 10 minutes 

at 1,050 ft (320 m) altitude over a group 

of mating gray whales, no reactions 

were observed (Ljungblad et al., 1987, 

cited in Moore and Clarke, 2002). 

Malme et al. (1984, cited in Richardson 

et al., 1995b and Moore and Clarke, 

2002) conducted playback experiments 

on migrating gray whales. They exposed 

the animals to underwater noise 

recorded from a Bell 212 helicopter 

(estimated altitude=328 ft [100 m]), at 

an average of three simulated passes per 

minute. The authors observed that 

whales changed their swimming course 

and sometimes slowed down in 

response to the playback sound but 

proceeded to migrate past the 

transducer. Migrating gray whales did 

not react overtly to a Bell 212 helicopter 

at greater than 1,394 ft (425 m) altitude, 

occasionally reacted when the 

helicopter was at 1,000–1,198 ft (305– 

365 m), and usually reacted when it was 

below 825 ft (250 m; Southwest 

Research Associates, 1988, cited in 

Richardson et al., 1995b and Moore and 

Clarke, 2002). Reactions noted in that 

study included abrupt turns or dives or 


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both. Green et al. (1992, cited in 

Richardson et al., 1995b) observed that 

migrating gray whales rarely exhibited 

noticeable reactions to a straight-line 

overflight by a Twin Otter at 197 ft (60 

m) altitude. Restrictions on aircraft 

altitude will be part of the proposed 

mitigation measures (described in the 

‘‘Proposed Mitigation’’ section later in 

this document) during the proposed 

drilling activities, and overflights are 

likely to have little or no disturbance 

effects on baleen whales. Any 

disturbance that may occur would likely 

be temporary and localized. 

Southall et al. (2007, Appendix C) 

reviewed a number of papers describing 

the responses of marine mammals to 

non-pulsed sound, such as that 

produced during exploratory drilling 

operations. In general, little or no 

response was observed in animals 

exposed at received levels from 90–120 

dB re 1 mPa (rms). Probability of 

avoidance and other behavioral effects 

increased when received levels were 

from 120–160 dB re 1 mPa (rms). Some 

of the relevant reviews contained in 

Southall et al. (2007) are summarized 

next. 

Baker et al. (1982) reported some 

avoidance by humpback whales to 

vessel noise when received levels were 

110–120 dB (rms) and clear avoidance at 

120–140 dB (sound measurements were 

not provided by Baker but were based 

on measurements of identical vessels by 

Miles and Malme, 1983). 

Malme et al. (1983, 1984) used 

playbacks of sounds from helicopter 

overflight and drilling rigs and 

platforms to study behavioral effects on 

migrating gray whales. Received levels 

exceeding 120 dB induced avoidance 

reactions. Malme et al. (1984) calculated 

10%, 50%, and 90% probabilities of 

gray whale avoidance reactions at 

received levels of 110, 120, and 130 dB, 

respectively. Malme et al. (1986) 

observed the behavior of feeding gray 

whales during four experimental 

playbacks of drilling sounds (50 to 315 

Hz; 21-min overall duration and 10% 

duty cycle; source levels of 156–162 

dB). In two cases for received levels of 

100–110 dB, no behavioral reaction was 

observed. However, avoidance behavior 

was observed in two cases where 

received levels were 110–120 dB. 

Richardson et al. (1990) performed 12 

playback experiments in which 

bowhead whales in the Alaskan Arctic 

were exposed to drilling sounds. Whales 

generally did not respond to exposures 

in the 100 to 130 dB range, although 

there was some indication of minor 

behavioral changes in several instances. 

McCauley et al. (1996) reported 

several cases of humpback whales 

responding to vessels in Hervey Bay, 

Australia. Results indicated clear 

avoidance at received levels between 

118 to 124 dB in three cases for which 

response and received levels were 

observed/measured. 

Palka and Hammond (2001) analyzed 

line transect census data in which the 

orientation and distance off transect line 

were reported for large numbers of 

minke whales. The authors developed a 

method to account for effects of animal 

movement in response to sighting 

platforms. Minor changes in locomotion 

speed, direction, and/or diving profile 

were reported at ranges from 1,847 to 

2,352 ft (563 to 717 m) at received levels 

of 110 to 120 dB. 

Biassoni et al. (2000) and Miller et al. 

(2000) reported behavioral observations 

for humpback whales exposed to a lowfrequency sonar stimulus (160- to 330- 

Hz frequency band; 42-s tonal signal 

repeated every 6 min; source levels 170 

to 200 dB) during playback experiments. 

Exposure to measured received levels 

ranging from 120 to 150 dB resulted in 

variability in humpback singing 

behavior. Croll et al. (2001) investigated 

responses of foraging fin and blue 

whales to the same low frequency active 

sonar stimulus off southern California. 

Playbacks and control intervals with no 

transmission were used to investigate 

behavior and distribution on time scales 

of several weeks and spatial scales of 

tens of kilometers. The general 

conclusion was that whales remained 

feeding within a region for which 12 to 

30 percent of exposures exceeded 140 

dB. 

Frankel and Clark (1998) conducted 

playback experiments with wintering 

humpback whales using a single speaker 

producing a low-frequency ‘‘Msequence’’ (sine wave with multiplephase reversals) signal in the 60 to 90 

Hz band with output of 172 dB at 1 m. 

For 11 playbacks, exposures were 

between 120 and 130 dB re 1 mPa (rms) 

and included sufficient information 

regarding individual responses. During 

eight of the trials, there were no 

measurable differences in tracks or 

bearings relative to control conditions, 

whereas on three occasions, whales 

either moved slightly away from (n = 1) 

or towards (n = 2) the playback speaker 

during exposure. The presence of the 

source vessel itself had a greater effect 

than did the M-sequence playback. 

Finally, Nowacek et al. (2004) used 

controlled exposures to demonstrate 

behavioral reactions of northern right 

whales to various non-pulse sounds. 

Playback stimuli included ship noise, 

social sounds of conspecifics, and a 

complex, 18-min ‘‘alert’’ sound 

consisting of repetitions of three 

different artificial signals. Ten whales 

were tagged with calibrated instruments 

that measured received sound 

characteristics and concurrent animal 

movements in three dimensions. Five 

out of six exposed whales reacted 

strongly to alert signals at measured 

received levels between 130 and 150 dB 

(i.e., ceased foraging and swam rapidly 

to the surface). Two of these individuals 

were not exposed to ship noise, and the 

other four were exposed to both stimuli. 

These whales reacted mildly to 

conspecific signals. Seven whales, 

including the four exposed to the alert 

stimulus, had no measurable response 

to either ship sounds or actual vessel 

noise. 

Toothed Whales—Most toothed 

whales have the greatest hearing 

sensitivity at frequencies much higher 

than that of baleen whales and may be 

less responsive to low-frequency sound 

commonly associated with oil and gas 

industry exploratory drilling activities. 

Richardson et al. (1995b) reported that 

beluga whales did not show any 

apparent reaction to playback of 

underwater drilling sounds at distances 

greater than 656–1,312 ft (200–400 m). 

Reactions included slowing down, 

milling, or reversal of course after which 

the whales continued past the projector, 

sometimes within 164–328 ft (50–100 

m). The authors concluded (based on a 

small sample size) that the playback of 

drilling sounds had no biologically 

significant effects on migration routes of 

beluga whales migrating through pack 

ice and along the seaward side of the 

nearshore lead east of Point Barrow in 

spring. 

At least six of 17 groups of beluga 

whales appeared to alter their migration 

path in response to underwater 

playbacks of icebreaker sound in the 

Arctic (Richardson et al., 1995b). 

Received levels from the icebreaker 

playback were estimated at 78–84 dB in 

the 1/3-octave band centered at 5,000 

Hz, or 8–14 dB above ambient. If beluga 

whales reacted to an actual icebreaker at 

received levels of 80 dB, reactions 

would be expected to occur at distances 

on the order of 6.2 mi (10 km). Finley 

et al. (1990) also reported beluga 

avoidance of icebreaker activities in the 

Canadian High Arctic at distances of 

22–31 mi (35–50 km). In addition to 

avoidance, changes in dive behavior and 

pod integrity were also noted. 

Patenaude et al. (2002) reported that 

beluga whales appeared to be more 

responsive to aircraft overflights than 

bowhead whales. Changes were 

observed in diving and respiration 

behavior, and some whales veered away 

when a helicopter passed at ≤820 ft (250 

m) lateral distance at altitudes up to 492 


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ft (150 m). However, some belugas 

showed no reaction to the helicopter. 

Belugas appeared to show less response 

to fixed-wing aircraft than to helicopter 

overflights. 

In reviewing responses of cetaceans 

with best hearing in mid-frequency 

ranges, which includes toothed whales, 

Southall et al. (2007) reported that 

combined field and laboratory data for 

mid-frequency cetaceans exposed to 

non-pulse sounds did not lead to a clear 

conclusion about received levels 

coincident with various behavioral 

responses. In some settings, individuals 

in the field showed profound 

(significant) behavioral responses to 

exposures from 90–120 dB, while others 

failed to exhibit such responses for 

exposure to received levels from 120– 

150 dB. Contextual variables other than 

exposure received level, and probable 

species differences, are the likely 

reasons for this variability. Context, 

including the fact that captive subjects 

were often directly reinforced with food 

for tolerating noise exposure, may also 

explain why there was great disparity in 

results from field and laboratory 

conditions—exposures in captive 

settings generally exceeded 170 dB 

before inducing behavioral responses. A 

summary of some of the relevant 

material reviewed by Southall et al. 

(2007) is next. 

LGL and Greeneridge (1986) and 

Finley et al. (1990) documented belugas 

and narwhals congregated near ice 

edges reacting to the approach and 

passage of icebreaking ships in the 

Arctic. Beluga whales responded to 

oncoming vessels by (1) fleeing at 

speeds of up to 12.4 mi/hr (20 km/hr) 

from distances of 12.4–50 mi (20–80 

km), (2) abandoning normal pod 

structure, and (3) modifying vocal 

behavior and/or emitting alarm calls. 

Narwhals, in contrast, generally 

demonstrated a ‘‘freeze’’ response, lying 

motionless or swimming slowly away 

(as far as 23 mi [37 km] down the ice 

edge), huddling in groups, and ceasing 

sound production. There was some 

evidence of habituation and reduced 

avoidance 2 to 3 days after onset. 

The 1982 season observations by LGL 

and Greeneridge (1986) involved a 

single passage of an icebreaker with 

both ice-based and aerial measurements 

on June 28, 1982. Four groups of 

narwhals (n = 9 to 10, 7, 7, and 6) 

responded when the ship was 4 mi (6.4 

km) away (received levels of 

approximately 100 dB in the 150- to 

1,150-Hz band). At a later point, 

observers sighted belugas moving away 

from the source at more than 12.4 mi (20 

km; received levels of approximately 90 

dB in the 150- to 1,150-Hz band). The 

total number of animals observed 

fleeing was about 300, suggesting 

approximately 100 independent groups 

(of three individuals each). No whales 

were sighted the following day, but 

some were sighted on June 30, with ship 

noise audible at spectrum levels of 

approximately 55 dB/Hz (up to 4 kHz). 

Observations during 1983 (LGL and 

Greeneridge, 1986) involved two 

icebreaking ships with aerial survey and 

ice-based observations during seven 

sampling periods. Narwhals and belugas 

generally reacted at received levels 

ranging from 101 to 121 dB in the 20- 

to 1,000-Hz band and at a distance of up 

to 40.4 mi (65 km). Large numbers 

(100s) of beluga whales moved out of 

the area at higher received levels. As 

noise levels from icebreaking operations 

diminished, a total of 45 narwhals 

returned to the area and engaged in 

diving and foraging behavior. During the 

final sampling period, following an 8-h 

quiet interval, no reactions were seen 

from 28 narwhals and 17 belugas (at 

received levels ranging up to 115 dB). 

The final season (1984) reported in 

LGL and Greeneridge (1986) involved 

aerial surveys before, during, and after 

the passage of two icebreaking ships. 

During operations, no belugas and few 

narwhals were observed in an area 

approximately 16.8 mi (27 km) ahead of 

the vessels, and all whales sighted over 

12.4–50 mi (20–80 km) from the ships 

were swimming strongly away. 

Additional observations confirmed the 

spatial extent of avoidance reactions to 

this sound source in this context. 

Buckstaff (2004) reported elevated 

dolphin whistle rates with received 

levels from oncoming vessels in the 110 

to 120 dB range in Sarasota Bay, Florida. 

These hearing thresholds were 

apparently lower than those reported by 

a researcher listening with towed 

hydrophones. Morisaka et al. (2005) 

compared whistles from three 

populations of Indo-Pacific bottlenose 

dolphins. One population was exposed 

to vessel noise with spectrum levels of 

approximately 85 dB/Hz in the 1- to 22- 

kHz band (broadband received levels 

approximately 128 dB) as opposed to 

approximately 65 dB/Hz in the same 

band (broadband received levels 

approximately 108 dB) for the other two 

sites. Dolphin whistles in the noisier 

environment had lower fundamental 

frequencies and less frequency 

modulation, suggesting a shift in sound 

parameters as a result of increased 

ambient noise. 

Morton and Symonds (2002) used 

census data on killer whales in British 

Columbia to evaluate avoidance of nonpulse acoustic harassment devices 

(AHDs). Avoidance ranges were about 

2.5 mi (4 km). Also, there was a 

dramatic reduction in the number of 

days ‘‘resident’’ killer whales were 

sighted during AHD-active periods 

compared to pre- and post-exposure 

periods and a nearby control site. 

Monteiro-Neto et al. (2004) studied 

avoidance responses of tucuxi (Sotalia 

fluviatilis) to Dukane® Netmark acoustic 

deterrent devices. In a total of 30 

exposure trials, approximately five 

groups each demonstrated significant 

avoidance compared to 20 pinger off 

and 55 no-pinger control trials over two 

quadrats of about 0.19 mi2 (0.5 km2). 

Estimated exposure received levels were 

approximately 115 dB. 

Awbrey and Stewart (1983) played 

back semi-submersible drillship sounds 

(source level: 163 dB) to belugas in 

Alaska. They reported avoidance 

reactions at 984 and 4,921 ft (300 and 

1,500 m) and approach by groups at a 

distance of 2.2 mi (3.5 km; received 

levels were approximately 110 to 145 

dB over these ranges assuming a 15 log 

R transmission loss). Similarly, 

Richardson et al. (1990) played back 

drilling platform sounds (source level: 

163 dB) to belugas in Alaska. They 

conducted aerial observations of eight 

individuals among approximately 100 

spread over an area several hundred 

meters to several kilometers from the 

sound source and found no obvious 

reactions. Moderate changes in 

movement were noted for three groups 

swimming within 656 ft (200 m) of the 

sound projector. 

Two studies deal with issues related 

to changes in marine mammal vocal 

behavior as a function of variable 

background noise levels. Foote et al. 

(2004) found increases in the duration 

of killer whale calls over the period 

1977 to 2003, during which time vessel 

traffic in Puget Sound, and particularly 

whale-watching boats around the 

animals, increased dramatically. 

Scheifele et al. (2005) demonstrated that 

belugas in the St. Lawrence River 

increased the levels of their 

vocalizations as a function of the 

background noise level (the ‘‘Lombard 

Effect’’). 

Several researchers conducting 

laboratory experiments on hearing and 

the effects of non-pulse sounds on 

hearing in mid-frequency cetaceans 

have reported concurrent behavioral 

responses. Nachtigall et al. (2003) 

reported that noise exposures up to 179 

dB and 55-min duration affected the 

trained behaviors of a bottlenose 

dolphin participating in a TTS 

experiment. Finneran and Schlundt 

(2004) provided a detailed, 

comprehensive analysis of the 

behavioral responses of belugas and 


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bottlenose dolphins to 1-s tones 

(received levels 160 to 202 dB) in the 

context of TTS experiments. Romano et 

al. (2004) investigated the physiological 

responses of a bottlenose dolphin and a 

beluga exposed to these tonal exposures 

and demonstrated a decrease in blood 

cortisol levels during a series of 

exposures between 130 and 201 dB. 

Collectively, the laboratory observations 

suggested the onset of a behavioral 

response at higher received levels than 

did field studies. The differences were 

likely related to the very different 

conditions and contextual variables 

between untrained, free-ranging 

individuals vs. laboratory subjects that 

were rewarded with food for tolerating 

noise exposure. 

Pinnipeds—Pinnipeds generally seem 

to be less responsive to exposure to 

industrial sound than most cetaceans. 

Pinniped responses to underwater 

sound from some types of industrial 

activities such as seismic exploration 

appear to be temporary and localized 

(Harris et al., 2001; Reiser et al., 2009). 

Blackwell et al. (2004) reported little 

or no reaction of ringed seals in 

response to pile-driving activities 

during construction of a man-made 

island in the Beaufort Sea. Ringed seals 

were observed swimming as close as 

151 ft (46 m) from the island and may 

have been habituated to the sounds 

which were likely audible at distances 

<9,842 ft (3,000 m) underwater and 0.3 

mi (0.5 km) in air. Moulton et al. (2003) 

reported that ringed seal densities on ice 

in the vicinity of a man-made island in 

the Beaufort Sea did not change 

significantly before and after 

construction and drilling activities. 

Southall et al. (2007) reviewed 

literature describing responses of 

pinnipeds to non-pulsed sound and 

reported that the limited data suggest 

exposures between approximately 90 

and 140 dB generally do not appear to 

induce strong behavioral responses in 

pinnipeds exposed to non-pulse sounds 

in water; no data exist regarding 

exposures at higher levels. It is 

important to note that among these 

studies, there are some apparent 

differences in responses between field 

and laboratory conditions. In contrast to 

the mid-frequency odontocetes, captive 

pinnipeds responded more strongly at 

lower levels than did animals in the 

field. Again, contextual issues are the 

likely cause of this difference. 

Jacobs and Terhune (2002) observed 

harbor seal reactions to AHDs (source 

level in this study was 172 dB) 

deployed around aquaculture sites. 

Seals were generally unresponsive to 

sounds from the AHDs. During two 

specific events, individuals came within 

141 and 144 ft (43 and 44 m) of active 

AHDs and failed to demonstrate any 

measurable behavioral response; 

estimated received levels based on the 

measures given were approximately 120 

to 130 dB. 

Costa et al. (2003) measured received 

noise levels from an Acoustic 

Thermometry of Ocean Climate (ATOC) 

program sound source off northern 

California using acoustic data loggers 

placed on translocated elephant seals. 

Subjects were captured on land, 

transported to sea, instrumented with 

archival acoustic tags, and released such 

that their transit would lead them near 

an active ATOC source (at 939-m depth; 

75-Hz signal with 37.5- Hz bandwidth; 

195 dB maximum source level, ramped 

up from 165 dB over 20 min) on their 

return to a haul-out site. Received 

exposure levels of the ATOC source for 

experimental subjects averaged 128 dB 

(range 118 to 137) in the 60- to 90-Hz 

band. None of the instrumented animals 

terminated dives or radically altered 

behavior upon exposure, but some 

statistically significant changes in 

diving parameters were documented in 

nine individuals. Translocated northern 

elephant seals exposed to this particular 

non-pulse source began to demonstrate 

subtle behavioral changes at exposure to 

received levels of approximately 120 to 

140 dB. 

Kastelein et al. (2006) exposed nine 

captive harbor seals in an approximately 

82 × 98 ft (25 × 30 m) enclosure to nonpulse sounds used in underwater data 

communication systems (similar to 

acoustic modems). Test signals were 

frequency modulated tones, sweeps, and 

bands of noise with fundamental 

frequencies between 8 and 16 kHz; 128 

to 130 [± 3] dB source levels; 1- to 2-s 

duration [60–80 percent duty cycle]; or 

100 percent duty cycle. They recorded 

seal positions and the mean number of 

individual surfacing behaviors during 

control periods (no exposure), before 

exposure, and in 15-min experimental 

sessions (n = 7 exposures for each sound 

type). Seals generally swam away from 

each source at received levels of 

approximately 107 dB, avoiding it by 

approximately 16 ft (5 m), although they 

did not haul out of the water or change 

surfacing behavior. Seal reactions did 

not appear to wane over repeated 

exposure (i.e., there was no obvious 

habituation), and the colony of seals 

generally returned to baseline 

conditions following exposure. The 

seals were not reinforced with food for 

remaining in the sound field. 

Potential effects to pinnipeds from 

aircraft activity could involve both 

acoustic and non-acoustic effects. It is 

uncertain if the seals react to the sound 

of the helicopter or to its physical 

presence flying overhead. Typical 

reactions of hauled out pinnipeds to 

aircraft that have been observed include 

looking up at the aircraft, moving on the 

ice or land, entering a breathing hole or 

crack in the ice, or entering the water. 

Ice seals hauled out on the ice have 

been observed diving into the water 

when approached by a low-flying 

aircraft or helicopter (Burns and Harbo, 

1972, cited in Richardson et al., 1995a; 

Burns and Frost, 1979, cited in 

Richardson et al., 1995a). Richardson et 

al. (1995a) note that responses can vary 

based on differences in aircraft type, 

altitude, and flight pattern. 

Additionally, a study conducted by 

Born et al. (1999) found that wind chill 

was also a factor in level of response of 

ringed seals hauled out on ice, as well 

as time of day and relative wind 

direction. 

Blackwell et al. (2004a) observed 12 

ringed seals during low-altitude 

overflights of a Bell 212 helicopter at 

Northstar in June and July 2000 (9 

observations took place concurrent with 

pipe-driving activities). One seal 

showed no reaction to the aircraft while 

the remaining 11 (92%) reacted either 

by looking at the helicopter (n=10) or by 

departing from their basking site (n=1). 

Blackwell et al. (2004a) concluded that 

none of the reactions to helicopters were 

strong or long lasting, and that seals 

near Northstar in June and July 2000 

probably had habituated to industrial 

sounds and visible activities that had 

occurred often during the preceding 

winter and spring. There have been few 

systematic studies of pinniped reactions 

to aircraft overflights, and most of the 

available data concern pinnipeds hauled 

out on land or ice rather than pinnipeds 

in the water (Richardson et al., 1995a; 

Born et al., 1999). 

Born et al. (1999) determined that 49 

percent of ringed seals escaped (i.e., left 

the ice) as a response to a helicopter 

flying at 492 ft (150 m) altitude. Seals 

entered the water when the helicopter 

was 4,101 ft (1,250 m) away if the seal 

was in front of the helicopter and at 

1,640 ft (500 m) away if the seal was to 

the side of the helicopter. The authors 

noted that more seals reacted to 

helicopters than to fixed-wing aircraft. 

The study concluded that the risk of 

scaring ringed seals by small-type 

helicopters could be substantially 

reduced if they do not approach closer 

than 4,921 ft (1,500 m). 

Spotted seals hauled out on land in 

summer are unusually sensitive to 

aircraft overflights compared to other 

species. They often rush into the water 

when an aircraft flies by at altitudes up 

to 984–2,461 ft (300–750 m). They 


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occasionally react to aircraft flying as 

high as 4,495 ft (1,370 m) and at lateral 

distances as far as 1.2 mi (2 km) or more 

(Frost and Lowry, 1990; Rugh et al., 

1997). 

(4) Hearing Impairment and Other 

Physiological Effects 

Temporary or permanent hearing 

impairment is a possibility when marine 

mammals are exposed to very strong 

sounds. Non-auditory physiological 

effects might also occur in marine 

mammals exposed to strong underwater 

sound. Possible types of non-auditory 

physiological effects or injuries that 

theoretically might occur in mammals 

close to a strong sound source include 

stress, neurological effects, bubble 

formation, and other types of organ or 

tissue damage. It is possible that some 

marine mammal species (i.e., beaked 

whales) may be especially susceptible to 

injury and/or stranding when exposed 

to strong pulsed sounds. However, as 

discussed later in this document, there 

is no definitive evidence that any of 

these effects occur even for marine 

mammals in close proximity to 

industrial sound sources, and beaked 

whales do not occur in the proposed 

activity area. Additional information 

regarding the possibilities of TTS, 

permanent threshold shift (PTS), and 

non-auditory physiological effects, such 

as stress, is discussed for both 

exploratory drilling activities and ZVSP 

surveys in the following section 

(‘‘Potential Effects from Zero-Offset 

Vertical Seismic Profile Activities’’). 

Potential Effects From Zero-Offset 

Vertical Seismic Profile Activities 

(1) Tolerance 

Numerous studies have shown that 

pulsed sounds from airguns are often 

readily detectable in the water at 

distances of many kilometers. Weir 

(2008) observed marine mammal 

responses to seismic pulses from a 24 

airgun array firing a total volume of 

either 5,085 in3 or 3,147 in3 in Angolan 

waters between August 2004 and May 

2005. Weir recorded a total of 207 

sightings of humpback whales (n = 66), 

sperm whales (n = 124), and Atlantic 

spotted dolphins (n = 17) and reported 

that there were no significant 

differences in encounter rates 

(sightings/hr) for humpback and sperm 

whales according to the airgun array’s 

operational status (i.e., active versus 

silent). For additional information on 

tolerance of marine mammals to 

anthropogenic sound, see the previous 

subsection in this document (‘‘Potential 

Effects from Exploratory Drilling 

Activities’’). 

(2) Masking 

As stated earlier in this document, 

masking is the obscuring of sounds of 

interest by other sounds, often at similar 

frequencies. For full details about 

masking, see the previous subsection in 

this document (‘‘Potential Effects from 

Exploratory Drilling Activities’’). Some 

additional information regarding pulsed 

sounds is provided here. 

There is evidence of some marine 

mammal species continuing to call in 

the presence of industrial activity. 

McDonald et al. (1995) heard blue and 

fin whale calls between seismic pulses 

in the Pacific. Although there has been 

one report that sperm whales cease 

calling when exposed to pulses from a 

very distant seismic ship (Bowles et al., 

1994), a more recent study reported that 

sperm whales off northern Norway 

continued calling in the presence of 

seismic pulses (Madsen et al., 2002). 

Similar results were also reported 

during work in the Gulf of Mexico 

(Tyack et al., 2003). Bowhead whale 

calls are frequently detected in the 

presence of seismic pulses, although the 

numbers of calls detected may 

sometimes be reduced (Richardson et 

al., 1986; Greene et al., 1999; Blackwell 

et al., 2009a). Bowhead whales in the 

Beaufort Sea may decrease their call 

rates in response to seismic operations, 

although movement out of the area 

might also have contributed to the lower 

call detection rate (Blackwell et al., 

2009a,b). Additionally, there is 

increasing evidence that, at times, there 

is enough reverberation between airgun 

pulses such that detection range of calls 

may be significantly reduced. In 

contrast, Di Iorio and Clark (2009) found 

evidence of increased calling by blue 

whales during operations by a lowerenergy seismic source, a sparker. 

There is little concern regarding 

masking due to the brief duration of 

these pulses and relatively longer 

silence between airgun shots (9–12 

seconds) near the sound source. 

However, at long distances (over tens of 

kilometers away) in deep water, due to 

multipath propagation and 

reverberation, the durations of airgun 

pulses can be ‘‘stretched’’ to seconds 

with long decays (Madsen et al., 2006; 

Clark and Gagnon, 2006). Therefore it 

could affect communication signals 

used by low frequency mysticetes when 

they occur near the noise band and thus 

reduce the communication space of 

animals (e.g., Clark et al., 2009a,b) and 

cause increased stress levels (e.g., Foote 

et al., 2004; Holt et al., 2009). 

Nevertheless, the intensity of the noise 

is also greatly reduced at long distances. 

Therefore, masking effects are 

anticipated to be limited, especially in 

the case of odontocetes, given that they 

typically communicate at frequencies 

higher than those of the airguns. 

(3) Behavioral Disturbance Reactions 

As was described in more detail in the 

previous sub-section (‘‘Potential Effects 

of Exploratory Drilling Activities’’), 

behavioral responses to sound are 

highly variable and context-specific. 

Summaries of observed reactions and 

studies related to seismic airgun activity 

are provided next. 

Baleen Whales—Baleen whale 

responses to pulsed sound (e.g., seismic 

airguns) have been studied more 

thoroughly than responses to 

continuous sound (e.g., drillships). 

Baleen whales generally tend to avoid 

operating airguns, but avoidance radii 

are quite variable. Whales are often 

reported to show no overt reactions to 

pulses from large arrays of airguns at 

distances beyond a few kilometers, even 

though the airgun pulses remain well 

above ambient noise levels out to much 

greater distances (Miller et al., 2005). 

However, baleen whales exposed to 

strong noise pulses often react by 

deviating from their normal migration 

route (Richardson et al., 1999). 

Migrating gray and bowhead whales 

were observed avoiding the sound 

source by displacing their migration 

route to varying degrees but within the 

natural boundaries of the migration 

corridors (Schick and Urban, 2000; 

Richardson et al., 1999; Malme et al., 

1983). Baleen whale responses to pulsed 

sound however may depend on the type 

of activity in which the whales are 

engaged. Some evidence suggests that 

feeding bowhead whales may be more 

tolerant of underwater sound than 

migrating bowheads (Miller et al., 2005; 

Lyons et al., 2009; Christie et al., 2010). 

Results of studies of gray, bowhead, 

and humpback whales have determined 

that received levels of pulses in the 

160–170 dB re 1 mPa rms range seem to 

cause obvious avoidance behavior in a 

substantial fraction of the animals 

exposed. In many areas, seismic pulses 

from large arrays of airguns diminish to 

those levels at distances ranging from 

2.8–9 mi (4.5–14.5 km) from the source. 

For the much smaller airgun array used 

during the ZVSP survey (total discharge 

volume of 760 in3), distances to 

received levels in the 170–160 dB re 1 

mPa rms range are estimated to be 1.44– 

2.28 mi (2.31–3.67 km). Baleen whales 

within those distances may show 

avoidance or other strong disturbance 

reactions to the airgun array. Subtle 

behavioral changes sometimes become 

evident at somewhat lower received 

levels, and recent studies have shown 


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that some species of baleen whales, 

notably bowhead and humpback 

whales, at times show strong avoidance 

at received levels lower than 160–170 

dB re 1 mPa rms. Bowhead whales 

migrating west across the Alaskan 

Beaufort Sea in autumn, in particular, 

are unusually responsive, with 

avoidance occurring out to distances of 

12.4–18.6 mi (20–30 km) from a 

medium-sized airgun source (Miller et 

al., 1999; Richardson et al., 1999). 

However, more recent research on 

bowhead whales (Miller et al., 2005) 

corroborates earlier evidence that, 

during the summer feeding season, 

bowheads are not as sensitive to seismic 

sources. In summer, bowheads typically 

begin to show avoidance reactions at a 

received level of about 160–170 dB re 1 

mPa rms (Richardson et al., 1986; 

Ljungblad et al., 1988; Miller et al., 

2005). 

Malme et al. (1986, 1988) studied the 

responses of feeding eastern gray whales 

to pulses from a single 100 in3 airgun off 

St. Lawrence Island in the northern 

Bering Sea. They estimated, based on 

small sample sizes, that 50% of feeding 

gray whales ceased feeding at an average 

received pressure level of 173 dB re 1 

mPa on an (approximate) rms basis, and 

that 10% of feeding whales interrupted 

feeding at received levels of 163 dB. 

Those findings were generally 

consistent with the results of 

experiments conducted on larger 

numbers of gray whales that were 

migrating along the California coast and 

on observations of the distribution of 

feeding Western Pacific gray whales off 

Sakhalin Island, Russia, during a 

seismic survey (Yazvenko et al., 2007). 

Data on short-term reactions (or lack 

of reactions) of cetaceans to impulsive 

noises do not necessarily provide 

information about long-term effects. 

While it is not certain whether 

impulsive noises affect reproductive 

rate or distribution and habitat use in 

subsequent days or years, certain 

species have continued to use areas 

ensonified by airguns and have 

continued to increase in number despite 

successive years of anthropogenic 

activity in the area. Gray whales 

continued to migrate annually along the 

west coast of North America despite 

intermittent seismic exploration and 

much ship traffic in that area for 

decades (Appendix A in Malme et al., 

1984). Bowhead whales continued to 

travel to the eastern Beaufort Sea each 

summer despite seismic exploration in 

their summer and autumn range for 

many years (Richardson et al., 1987). 

Populations of both gray whales and 

bowhead whales grew substantially 

during this time. Bowhead whales have 

increased by approximately 3.4% per 

year for the last 10 years in the Beaufort 

Sea (Allen and Angliss, 2011). In any 

event, the brief exposures to sound 

pulses from the proposed airgun source 

(the airguns will only be fired for a 

period of 10–14 hours for each of the 

three, possibly four, wells) are highly 

unlikely to result in prolonged effects. 

Toothed Whales—Few systematic 

data are available describing reactions of 

toothed whales to noise pulses. Few 

studies similar to the more extensive 

baleen whale/seismic pulse work 

summarized earlier in this document 

have been reported for toothed whales. 

However, systematic work on sperm 

whales is underway (Tyack et al., 2003), 

and there is an increasing amount of 

information about responses of various 

odontocetes to seismic surveys based on 

monitoring studies (e.g., Stone, 2003; 

Smultea et al., 2004; Moulton and 

Miller, 2005). 

Seismic operators and marine 

mammal observers sometimes see 

dolphins and other small toothed 

whales near operating airgun arrays, 

but, in general, there seems to be a 

tendency for most delphinids to show 

some limited avoidance of seismic 

vessels operating large airgun systems. 

However, some dolphins seem to be 

attracted to the seismic vessel and 

floats, and some ride the bow wave of 

the seismic vessel even when large 

arrays of airguns are firing. Nonetheless, 

there have been indications that small 

toothed whales sometimes move away 

or maintain a somewhat greater distance 

from the vessel when a large array of 

airguns is operating than when it is 

silent (e.g., Goold, 1996a,b,c; 

Calambokidis and Osmek, 1998; Stone, 

2003). The beluga may be a species that 

(at least at times) shows long-distance 

avoidance of seismic vessels. Aerial 

surveys during seismic operations in the 

southeastern Beaufort Sea recorded 

much lower sighting rates of beluga 

whales within 6.2–12.4 mi (10–20 km) 

of an active seismic vessel. These results 

were consistent with the low number of 

beluga sightings reported by observers 

aboard the seismic vessel, suggesting 

that some belugas might be avoiding the 

seismic operations at distances of 6.2– 

12.4 mi (10–20 km) (Miller et al., 2005). 

Captive bottlenose dolphins and (of 

more relevance in this project) beluga 

whales exhibit changes in behavior 

when exposed to strong pulsed sounds 

similar in duration to those typically 

used in seismic surveys (Finneran et al., 

2002, 2005). However, the animals 

tolerated high received levels of sound 

(pk–pk level >200 dB re 1 mPa) before 

exhibiting aversive behaviors. 

Reactions of toothed whales to large 

arrays of airguns are variable and, at 

least for delphinids, seem to be confined 

to a smaller radius than has been 

observed for mysticetes. However, based 

on the limited existing evidence, 

belugas should not be grouped with 

delphinids in the ‘‘less responsive’’ 

category. 

Pinnipeds—Pinnipeds are not likely 

to show a strong avoidance reaction to 

the airgun sources proposed for use. 

Visual monitoring from seismic vessels 

has shown only slight (if any) avoidance 

of airguns by pinnipeds and only slight 

(if any) changes in behavior. Ringed 

seals frequently do not avoid the area 

within a few hundred meters of 

operating airgun arrays (Harris et al., 

2001; Moulton and Lawson, 2002; 

Miller et al., 2005). Monitoring work in 

the Alaskan Beaufort Sea during 1996– 

2001 provided considerable information 

regarding the behavior of seals exposed 

to seismic pulses (Harris et al., 2001; 

Moulton and Lawson, 2002). These 

seismic projects usually involved arrays 

of 6 to 16 airguns with total volumes of 

560 to 1,500 in3. The combined results 

suggest that some seals avoid the 

immediate area around seismic vessels. 

In most survey years, ringed seal 

sightings tended to be farther away from 

the seismic vessel when the airguns 

were operating than when they were not 

(Moulton and Lawson, 2002). However, 

these avoidance movements were 

relatively small, on the order of 328 ft 

(100 m) to a few hundreds of meters, 

and many seals remained within 328– 

656 ft (100–200 m) of the trackline as 

the operating airgun array passed by. 

Seal sighting rates at the water surface 

were lower during airgun array 

operations than during no-airgun 

periods in each survey year except 1997. 

Similarly, seals are often very tolerant of 

pulsed sounds from seal-scaring devices 

(Mate and Harvey, 1987; Jefferson and 

Curry, 1994; Richardson et al., 1995a). 

However, initial telemetry work 

suggests that avoidance and other 

behavioral reactions by two other 

species of seals to small airgun sources 

may at times be stronger than evident to 

date from visual studies of pinniped 

reactions to airguns (Thompson et al., 

1998). Even if reactions of the species 

occurring in the present study area are 

as strong as those evident in the 

telemetry study, reactions are expected 

to be confined to relatively small 

distances and durations, with no longterm effects on pinniped individuals or 

populations. Additionally, the airguns 

are only proposed to be used for a short 

time during the exploration drilling 

program (approximately 10–14 hours for 


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each well, for a total of 40–56 hours, 

and more likely to be 30–42 hours if the 

fourth well is not completed, over the 

entire open-water season, which lasts 

for approximately 4 months). 

(4) Hearing Impairment and Other 

Physiological Effects 

TTS—TTS is the mildest form of 

hearing impairment that can occur 

during exposure to a strong sound 

(Kryter, 1985). While experiencing TTS, 

the hearing threshold rises, and a sound 

must be stronger in order to be heard. 

At least in terrestrial mammals, TTS can 

last from minutes or hours to (in cases 

of strong TTS) days, can be limited to 

a particular frequency range, and can be 

in varying degrees (i.e., a loss of a 

certain number of dBs of sensitivity). 

For sound exposures at or somewhat 

above the TTS threshold, hearing 

sensitivity in both terrestrial and marine 

mammals recovers rapidly after 

exposure to the noise ends. Few data on 

sound levels and durations necessary to 

elicit mild TTS have been obtained for 

marine mammals, and none of the 

published data concern TTS elicited by 

exposure to multiple pulses of sound. 

Marine mammal hearing plays a 

critical role in communication with 

conspecifics and in interpretation of 

environmental cues for purposes such 

as predator avoidance and prey capture. 

Depending on the degree (elevation of 

threshold in dB), duration (i.e., recovery 

time), and frequency range of TTS and 

the context in which it is experienced, 

TTS can have effects on marine 

mammals ranging from discountable to 

serious. For example, a marine mammal 

may be able to readily compensate for 

a brief, relatively small amount of TTS 

in a non-critical frequency range that 

takes place during a time when the 

animal is traveling through the open 

ocean, where ambient noise is lower 

and there are not as many competing 

sounds present. Alternatively, a larger 

amount and longer duration of TTS 

sustained during a time when 

communication is critical for successful 

mother/calf interactions could have 

more serious impacts if it were in the 

same frequency band as the necessary 

vocalizations and of a severity that it 

impeded communication. The fact that 

animals exposed to levels and durations 

of sound that would be expected to 

result in this physiological response 

would also be expected to have 

behavioral responses of a comparatively 

more severe or sustained nature is also 

notable and potentially of more 

importance than the simple existence of 

a TTS. 

Researchers have derived TTS 

information for odontocetes from 

studies on the bottlenose dolphin and 

beluga. For the one harbor porpoise 

tested, the received level of airgun 

sound that elicited onset of TTS was 

lower (Lucke et al., 2009). If these 

results from a single animal are 

representative, it is inappropriate to 

assume that onset of TTS occurs at 

similar received levels in all 

odontocetes (cf. Southall et al., 2007). 

Some cetaceans apparently can incur 

TTS at considerably lower sound 

exposures than are necessary to elicit 

TTS in the beluga or bottlenose dolphin. 

For baleen whales, there are no data, 

direct or indirect, on levels or properties 

of sound that are required to induce 

TTS. The frequencies to which baleen 

whales are most sensitive are assumed 

to be lower than those to which 

odontocetes are most sensitive, and 

natural background noise levels at those 

low frequencies tend to be higher. As a 

result, auditory thresholds of baleen 

whales within their frequency band of 

best hearing are believed to be higher 

(less sensitive) than are those of 

odontocetes at their best frequencies 

(Clark and Ellison, 2004), meaning that 

baleen whales require sounds to be 

louder (i.e., higher dB levels) than 

odontocetes in the frequency ranges at 

which each group hears the best. From 

this, it is suspected that received levels 

causing TTS onset may also be higher in 

baleen whales (Southall et al., 2007). 

Since current NMFS practice assumes 

the same thresholds for the onset of 

hearing impairment in both odontocetes 

and mysticetes, NMFS’ onset of TTS 

threshold is likely conservative for 

mysticetes. For this proposed activity, 

Shell expects no cases of TTS given the 

strong likelihood that baleen whales 

would avoid the airguns before being 

exposed to levels high enough for TTS 

to occur. The source levels of the 

drilling units are far lower than those of 

the airguns. 

In pinnipeds, TTS thresholds 

associated with exposure to brief pulses 

(single or multiple) of underwater sound 

have not been measured. However, 

systematic TTS studies on captive 

pinnipeds have been conducted (Bowles 

et al., 1999; Kastak et al., 1999, 2005, 

2007; Schusterman et al., 2000; 

Finneran et al., 2003; Southall et al., 

2007). Initial evidence from more 

prolonged (non-pulse) exposures 

suggested that some pinnipeds (harbor 

seals in particular) incur TTS at 

somewhat lower received levels than do 

small odontocetes exposed for similar 

durations (Kastak et al., 1999, 2005; 

Ketten et al., 2001; cf. Au et al., 2000). 

The TTS threshold for pulsed sounds 

has been indirectly estimated as being a 

sound exposure level (SEL) of 

approximately 171 dB re 1 mPa2·s 

(Southall et al., 2007) which would be 

equivalent to a single pulse with a 

received level of approximately 181 to 

186 dB re 1 mPa (rms), or a series of 

pulses for which the highest rms values 

are a few dB lower. Corresponding 

values for California sea lions and 

northern elephant seals are likely to be 

higher (Kastak et al., 2005). For harbor 

seal, which is closely related to the 

ringed seal, TTS onset apparently 

occurs at somewhat lower received 

energy levels than for odonotocetes. The 

sound level necessary to cause TTS in 

pinnipeds depends on exposure 

duration, as in other mammals; with 

longer exposure, the level necessary to 

elicit TTS is reduced (Schusterman et 

al., 2000; Kastak et al., 2005, 2007). For 

very short exposures (e.g., to a single 

sound pulse), the level necessary to 

cause TTS is very high (Finneran et al., 

2003). For pinnipeds exposed to in-air 

sounds, auditory fatigue has been 

measured in response to single pulses 

and to non-pulse noise (Southall et al., 

2007), although high exposure levels 

were required to induce TTS-onset 

(SEL: 129 dB re: 20 mPa2.s; Bowles et al., 

unpub. data). 

NMFS has established acoustic 

thresholds that identify the received 

sound levels above which hearing 

impairment or other injury could 

potentially occur, which are 180 and 

190 dB re 1 mPa (rms) for cetaceans and 

pinnipeds, respectively (NMFS 1995, 

2000). The established 180- and 190-dB 

criteria were established before 

additional TTS measurements for 

marine mammals became available, and 

represent the received levels above 

which one could not be certain there 

would be no injurious effects, auditory 

or otherwise, to marine mammals. TTS 

is considered by NMFS to be a type of 

Level B (non-injurious) harassment. The 

180- and 190-dB levels are also typically 

used as shutdown criteria for mitigation 

applicable to cetaceans and pinnipeds, 

respectively, as specified by NMFS 

(2000) and are used to establish 

exclusion zones (EZs), as appropriate. 

Additionally, based on the summary 

provided here and the fact that 

modeling indicates the back-propagated 

source level for the Discoverer to be 

between 177 and 185 dB re 1 mPa at 1 

m (Austin and Warner, 2010), TTS is 

not expected to occur in any marine 

mammal species that may occur in the 

proposed drilling area since the source 

level will not reach levels thought to 

induce even mild TTS. While the source 

level of the airgun is higher than the 

190-dB threshold level, an animal 

would have to be in very close 


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proximity to be exposed to such levels. 

Additionally, the 180- and 190-dB radii 

for the airgun are 0.8 mi (1.24 km) and 

0.3 mi (524 m), respectively, from the 

source. Because of the short duration 

that the airguns will be used (no more 

than 30–56 hours throughout the entire 

open-water season) and mitigation and 

monitoring measures described later in 

this document, hearing impairment is 

not anticipated. 

PTS—When PTS occurs, there is 

physical damage to the sound receptors 

in the ear. In some cases, there can be 

total or partial deafness, whereas in 

other cases, the animal has an impaired 

ability to hear sounds in specific 

frequency ranges (Kryter, 1985). 

There is no specific evidence that 

exposure to underwater industrial 

sound associated with oil exploration 

can cause PTS in any marine mammal 

(see Southall et al., 2007). However, 

given the possibility that mammals 

might incur TTS, there has been further 

speculation about the possibility that 

some individuals occurring very close to 

such activities might incur PTS (e.g., 

Richardson et al., 1995, p. 372ff; 

Gedamke et al., 2008). Single or 

occasional occurrences of mild TTS are 

not indicative of permanent auditory 

damage in terrestrial mammals. 

Relationships between TTS and PTS 

thresholds have not been studied in 

marine mammals but are assumed to be 

similar to those in humans and other 

terrestrial mammals (Southall et al., 

2007; Le Prell, in press). PTS might 

occur at a received sound level at least 

several decibels above that inducing 

mild TTS. Based on data from terrestrial 

mammals, a precautionary assumption 

is that the PTS threshold for impulse 

sounds (such as airgun pulses as 

received close to the source) is at least 

6 dB higher than the TTS threshold on 

a peak-pressure basis and probably 

greater than 6 dB (Southall et al., 2007). 

It is highly unlikely that marine 

mammals could receive sounds strong 

enough (and over a sufficient duration) 

to cause PTS during the proposed 

exploratory drilling program. As 

mentioned previously in this document, 

the source levels of the drilling units are 

not considered strong enough to cause 

even slight TTS. Given the higher level 

of sound necessary to cause PTS, it is 

even less likely that PTS could occur. In 

fact, based on the modeled source levels 

for the drilling units, the levels 

immediately adjacent to the drilling 

units may not be sufficient to induce 

PTS, even if the animals remain in the 

immediate vicinity of the activity. The 

modeled source level from the 

Discoverer suggests that marine 

mammals located immediately adjacent 

to a drilling unit would likely not be 

exposed to received sound levels of a 

magnitude strong enough to induce 

PTS, even if the animals remain in the 

immediate vicinity of the proposed 

activity location for a prolonged period 

of time. Because the source levels do not 

reach the threshold of 190 dB currently 

used for pinnipeds and is at the 180 dB 

threshold currently used for cetaceans, 

it is highly unlikely that any type of 

hearing impairment, temporary or 

permanent, would occur as a result of 

the exploration drilling activities. 

Additionally, Southall et al. (2007) 

proposed that the thresholds for injury 

of marine mammals exposed to 

‘‘discrete’’ noise events (either single or 

multiple exposures over a 24-hr period) 

are higher than the 180- and 190-dB re 

1 mPa (rms) in-water threshold currently 

used by NMFS. 

Non-auditory Physiological Effects— 

Non-auditory physiological effects or 

injuries that theoretically might occur in 

marine mammals exposed to strong 

underwater sound include stress, 

neurological effects, bubble formation, 

and other types of organ or tissue 

damage (Cox et al., 2006; Southall et al., 

2007). Studies examining any such 

effects are limited. If any such effects do 

occur, they probably would be limited 

to unusual situations when animals 

might be exposed at close range for 

unusually long periods. It is doubtful 

that any single marine mammal would 

be exposed to strong sounds for 

sufficiently long that significant 

physiological stress would develop. 

Classic stress responses begin when 

an animal’s central nervous system 

perceives a potential threat to its 

homeostasis. That perception triggers 

stress responses regardless of whether a 

stimulus actually threatens the animal; 

the mere perception of a threat is 

sufficient to trigger a stress response 

(Moberg, 2000; Sapolsky et al., 2005; 

Seyle, 1950). Once an animal’s central 

nervous system perceives a threat, it 

mounts a biological response or defense 

that consists of a combination of the 

four general biological defense 

responses: behavioral responses; 

autonomic nervous system responses; 

neuroendocrine responses; or immune 

responses. 

In the case of many stressors, an 

animal’s first and most economical (in 

terms of biotic costs) response is 

behavioral avoidance of the potential 

stressor or avoidance of continued 

exposure to a stressor. An animal’s 

second line of defense to stressors 

involves the sympathetic part of the 

autonomic nervous system and the 

classical ‘‘fight or flight’’ response, 

which includes the cardiovascular 

system, the gastrointestinal system, the 

exocrine glands, and the adrenal 

medulla to produce changes in heart 

rate, blood pressure, and gastrointestinal 

activity that humans commonly 

associate with ‘‘stress.’’ These responses 

have a relatively short duration and may 

or may not have significant long-term 

effects on an animal’s welfare. 

An animal’s third line of defense to 

stressors involves its neuroendocrine or 

sympathetic nervous systems; the 

system that has received the most study 

has been the hypothalmus-pituitaryadrenal system (also known as the HPA 

axis in mammals or the hypothalamuspituitary-interrenal axis in fish and 

some reptiles). Unlike stress responses 

associated with the autonomic nervous 

system, virtually all neuroendocrine 

functions that are affected by stress— 

including immune competence, 

reproduction, metabolism, and 

behavior—are regulated by pituitary 

hormones. Stress-induced changes in 

the secretion of pituitary hormones have 

been implicated in failed reproduction 

(Moberg, 1987; Rivier, 1995), altered 

metabolism (Elasser et al., 2000), 

reduced immune competence (Blecha, 

2000), and behavioral disturbance. 

Increases in the circulation of 

glucocorticosteroids (cortisol, 

corticosterone, and aldosterone in 

marine mammals; see Romano et al., 

2004) have been equated with stress for 

many years. 

The primary distinction between 

stress (which is adaptive and does not 

normally place an animal at risk) and 

distress is the biotic cost of the 

response. During a stress response, an 

animal uses glycogen stores that can be 

quickly replenished once the stress is 

alleviated. In such circumstances, the 

cost of the stress response would not 

pose a risk to the animal’s welfare. 

However, when an animal does not have 

sufficient energy reserves to satisfy the 

energetic costs of a stress response, 

energy resources must be diverted from 

other biotic functions, which impair 

those functions that experience the 

diversion. For example, when mounting 

a stress response diverts energy away 

from growth in young animals, those 

animals may experience stunted growth. 

When mounting a stress response 

diverts energy from a fetus, an animal’s 

reproductive success and fitness will 

suffer. In these cases, the animals will 

have entered a pre-pathological or 

pathological state which is called 

‘‘distress’’ (sensu Seyle, 1950) or 

‘‘allostatic loading’’ (sensu McEwen and 

Wingfield, 2003). This pathological state 

will last until the animal replenishes its 

biotic reserves sufficient to restore 

normal function. Note that these 


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examples involved a long-term (days or 

weeks) stress response exposure to 

stimuli. 

Relationships between these 

physiological mechanisms, animal 

behavior, and the costs of stress 

responses have also been documented 

fairly well through controlled 

experiment; because this physiology 

exists in every vertebrate that has been 

studied, it is not surprising that stress 

responses and their costs have been 

documented in both laboratory and freeliving animals (for examples see, 

Holberton et al., 1996; Hood et al., 1998; 

Jessop et al., 2003; Krausman et al., 

2004; Lankford et al., 2005; Reneerkens 

et al., 2002; Thompson and Hamer, 

2000). Although no information has 

been collected on the physiological 

responses of marine mammals to 

anthropogenic sound exposure, studies 

of other marine animals and terrestrial 

animals would lead us to expect some 

marine mammals to experience 

physiological stress responses and, 

perhaps, physiological responses that 

would be classified as ‘‘distress’’ upon 

exposure to anthropogenic sounds. 

For example, Jansen (1998) reported 

on the relationship between acoustic 

exposures and physiological responses 

that are indicative of stress responses in 

humans (e.g., elevated respiration and 

increased heart rates). Jones (1998) 

reported on reductions in human 

performance when faced with acute, 

repetitive exposures to acoustic 

disturbance. Trimper et al. (1998) 

reported on the physiological stress 

responses of osprey to low-level aircraft 

noise while Krausman et al. (2004) 

reported on the auditory and physiology 

stress responses of endangered Sonoran 

pronghorn to military overflights. Smith 

et al. (2004a, 2004b) identified noiseinduced physiological transient stress 

responses in hearing-specialist fish (i.e., 

goldfish) that accompanied short- and 

long-term hearing losses. Welch and 

Welch (1970) reported physiological 

and behavioral stress responses that 

accompanied damage to the inner ears 

of fish and several mammals. 

Hearing is one of the primary senses 

marine mammals use to gather 

information about their environment 

and communicate with conspecifics. 

Although empirical information on the 

relationship between sensory 

impairment (TTS, PTS, and acoustic 

masking) on marine mammals remains 

limited, it seems reasonable to assume 

that reducing an animal’s ability to 

gather information about its 

environment and to communicate with 

other members of its species would be 

stressful for animals that use hearing as 

their primary sensory mechanism. 

Therefore, we assume that acoustic 

exposures sufficient to trigger onset PTS 

or TTS would be accompanied by 

physiological stress responses because 

terrestrial animals exhibit those 

responses under similar conditions 

(NRC, 2003). More importantly, marine 

mammals might experience stress 

responses at received levels lower than 

those necessary to trigger onset TTS. 

Based on empirical studies of the time 

required to recover from stress 

responses (Moberg, 2000), NMFS also 

assumes that stress responses could 

persist beyond the time interval 

required for animals to recover from 

TTS and might result in pathological 

and pre-pathological states that would 

be as significant as behavioral responses 

to TTS. However, as stated previously in 

this document, the source levels of the 

drilling units are not loud enough to 

induce PTS or likely even TTS. 

Resonance effects (Gentry, 2002) and 

direct noise-induced bubble formations 

(Crum et al., 2005) are implausible in 

the case of exposure to an impulsive 

broadband source like an airgun array. 

If seismic surveys disrupt diving 

patterns of deep-diving species, this 

might result in bubble formation and a 

form of the bends, as speculated to 

occur in beaked whales exposed to 

sonar. However, there is no specific 

evidence of this upon exposure to 

airgun pulses. Additionally, no beaked 

whale species occur in the proposed 

exploration drilling area. 

In general, very little is known about 

the potential for strong, anthropogenic 

underwater sounds to cause nonauditory physical effects in marine 

mammals. Such effects, if they occur at 

all, would presumably be limited to 

short distances and to activities that 

extend over a prolonged period. The 

available data do not allow 

identification of a specific exposure 

level above which non-auditory effects 

can be expected (Southall et al., 2007) 

or any meaningful quantitative 

predictions of the numbers (if any) of 

marine mammals that might be affected 

in those ways. The low levels of 

continuous sound that will be produced 

by the drilling units are not expected to 

cause such effects. Additionally, marine 

mammals that show behavioral 

avoidance of the proposed activities, 

including most baleen whales, some 

odontocetes (including belugas), and 

some pinnipeds, are especially unlikely 

to incur auditory impairment or other 

physical effects. 

(5) Stranding and Mortality 

Marine mammals close to underwater 

detonations of high explosives can be 

killed or severely injured, and the 

auditory organs are especially 

susceptible to injury (Ketten et al., 1993; 

Ketten, 1995). However, explosives are 

no longer used for marine waters for 

commercial seismic surveys; they have 

been replaced entirely by airguns or 

related non-explosive pulse generators. 

Underwater sound from drilling, 

support activities, and airgun arrays is 

less energetic and has slower rise times, 

and there is no proof that they can cause 

serious injury, death, or stranding, even 

in the case of large airgun arrays. 

However, the association of mass 

strandings of beaked whales with naval 

exercises involving mid-frequency 

active sonar, and, in one case, 

coinciding with a Lamont-Doherty Earth 

Observatory (L–DEO) seismic survey 

(Malakoff, 2002; Cox et al., 2006), has 

raised the possibility that beaked whales 

exposed to strong pulsed sounds may be 

especially susceptible to injury and/or 

behavioral reactions that can lead to 

stranding (e.g., Hildebrand, 2005; 

Southall et al., 2007). 

Specific sound-related processes that 

lead to strandings and mortality are not 

well documented, but may include: 

(1) Swimming in avoidance of a 

sound into shallow water; 

(2) A change in behavior (such as a 

change in diving behavior) that might 

contribute to tissue damage, gas bubble 

formation, hypoxia, cardiac arrhythmia, 

hypertensive hemorrhage or other forms 

of trauma; 

(3) A physiological change, such as a 

vestibular response leading to a 

behavioral change or stress-induced 

hemorrhagic diathesis, leading in turn 

to tissue damage; and 

(4) Tissue damage directly from sound 

exposure, such as through acousticallymediated bubble formation and growth 

or acoustic resonance of tissues. 

Some of these mechanisms are 

unlikely to apply in the case of impulse 

sounds. However, there are indications 

that gas-bubble disease (analogous to 

‘‘the bends’’), induced in supersaturated 

tissue by a behavioral response to 

acoustic exposure, could be a pathologic 

mechanism for the strandings and 

mortality of some deep-diving cetaceans 

exposed to sonar. However, the 

evidence for this remains circumstantial 

and is associated with exposure to naval 

mid-frequency sonar, not seismic 

surveys or exploratory drilling programs 

(Cox et al., 2006; Southall et al., 2007). 

Both seismic pulses and continuous 

drillship sounds are quite different from 

mid-frequency sonar signals, and some 

mechanisms by which sonar sounds 

have been hypothesized to affect beaked 

whales are unlikely to apply to airgun 

pulses or drillships. Sounds produced 

by airgun arrays are broadband impulses 


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with most of the energy below 1 kHz, 

and the low-energy continuous sounds 

produced by drillships have most of the 

energy between 20 and 1,000 Hz. 

Additionally, the non-impulsive, 

continuous sounds produced by the 

drilling units proposed to be used by 

Shell do not have rapid rise times. Rise 

time is the fluctuation in sound levels 

of the source. The type of sound that 

would be produced during the proposed 

drilling program will be constant and 

will not exhibit any sudden fluctuations 

or changes. Typical military midfrequency sonar emits non-impulse 

sounds at frequencies of 2–10 kHz, 

generally with a relatively narrow 

bandwidth at any one time. A further 

difference between them is that naval 

exercises can involve sound sources on 

more than one vessel. Thus, it is not 

appropriate to assume that there is a 

direct connection between the effects of 

military sonar and oil and gas industry 

operations on marine mammals. 

However, evidence that sonar signals 

can, in special circumstances, lead (at 

least indirectly) to physical damage and 

mortality (e.g., Balcomb and Claridge, 

2001; NOAA and USN, 2001; Jepson et 

al., 2003; Ferna ́ndez et al., 2004, 2005; 

Hildebrand, 2005; Cox et al., 2006) 

suggests that caution is warranted when 

dealing with exposure of marine 

mammals to any high-intensity 

‘‘pulsed’’ sound. 

There is no conclusive evidence of 

cetacean strandings or deaths at sea as 

a result of exposure to seismic surveys, 

but a few cases of strandings in the 

general area where a seismic survey was 

ongoing have led to speculation 

concerning a possible link between 

seismic surveys and strandings. 

Suggestions that there was a link 

between seismic surveys and strandings 

of humpback whales in Brazil (Engel et 

al., 2004) were not well founded (IAGC, 

2004; IWC, 2007). In September 2002, 

there was a stranding of two Cuvier’s 

beaked whales in the Gulf of California, 

Mexico, when the L–DEO vessel R/V 

Maurice Ewing was operating a 20 

airgun (8,490 in3) array in the general 

area. The link between the stranding 

and the seismic surveys was 

inconclusive and not based on any 

physical evidence (Hogarth, 2002; 

Yoder, 2002). Nonetheless, the Gulf of 

California incident, plus the beaked 

whale strandings near naval exercises 

involving use of mid-frequency sonar, 

suggests a need for caution in 

conducting seismic surveys in areas 

occupied by beaked whales until more 

is known about effects of seismic 

surveys on those species (Hildebrand, 

2005). No injuries of beaked whales are 

anticipated during the proposed 

exploratory drilling program because 

none occur in the proposed area. 

Potential Impacts From Drilling Wastes 

Shell will discharge drilling wastes to 

the Chukchi Sea. These discharges will 

be authorized under the EPA’s National 

Pollutant Discharge Elimination System 

(NPDES) General Permit for Oil and Gas 

Exploration Activities on the Outer 

Continental Shelf in the Chukchi Sea 

(AKG–28–8100; ‘‘NPDES exploration 

facilities GP’’). This permit establishes 

various limits and conditions on the 

authorized discharges, and the EPA has 

determined that with these limits and 

conditions the discharges will not result 

in any unreasonable degradation of 

ocean waters. 

Under the NPDES exploration 

facilities GP, drilling wastes to be 

discharged must have a 96-hr Lethal 

Concentration 50 percent (LC50) 

toxicity of 30,000 parts per million or 

greater at the point of discharge. Both 

modeling and field studies have shown 

that discharged drilling wastes are 

diluted rapidly in receiving waters 

(Ayers et al. 1980a, 1980b, Brandsma et 

al. 1980, NRC 1983, O’Reilly et al. 1989, 

Nedwed et al. 2004, Smith et al. 2004; 

Neff 2005). The dilution is strongly 

affected by the discharge rate. The 

NPDES exploration facilities GP limits 

the discharge of drilling wastes to 1,000 

bbl/hr (159 m3/hr). For example, 

TetraTech (2011) modeled hypothetical 

1,000 bbl/hr (159 m3/hr) discharges of 

drilling wastes in water depths of 131– 

164 ft (40–50 m) in the Beaufort and 

Chukchi Seas for the EPA and predicted 

dilution factors of 950–17,500 at a 

distance of 330 ft (100 m) from the 

discharge point. 

The primary effect of the drilling 

waste discharges will be increases in 

total suspended solids (TSS) in the 

water column and localized increase in 

sedimentation on the sea floor. Shell 

conducted dispersion modeling of the 

drilling waste discharges using the 

Offshore Operators Committee Mud and 

Produced Water Discharge (OOC) model 

(Fluid Dynamix 2014). Simulations 

were performed for each of the six 

discrete drilling intervals with two 

discharge locations: Seafloor and sea 

surface. The Burger Prospect wells are 

all very similar in well design and site 

conditions so the simulation 

approximates the results for the all drill 

sites. The model results indicate that 

most of the increase in TSS will be 

ameliorated within 984 ft (300 m) of the 

discharge locations through settling and 

dispersion. Impacts to water quality will 

cease when the discharge is concluded. 

Modeling of similar discharges 

offshore of Sakhalin Island predicted a 

1,000-fold dilution within 10 minutes 

and 330 ft (100 m) of the discharge. In 

a field study (O’Reilly et al. 1989) of a 

drilling waste discharge offshore of 

California, a 270 bbl (43 m3) discharge 

of drilling wastes was found to be 

diluted 183-fold at 33 ft (10 m) and 

1,049-fold at 330 ft (100 m). Neff (2005) 

concluded that concentrations of 

discharged drilling waste would 

diminish to levels that would have no 

effect within about two minutes of 

discharge and within 16 ft (5 m) of the 

discharge location. 

Discharges of drilling wastes could 

potentially displace marine mammals a 

short distance from a drilling location. 

However, it is likely that marine 

mammals will have already avoided the 

area due to sound energy generated by 

the drilling activities. 

Baleen whales, such as bowheads, 

tend to avoid drilling units at distances 

up to 12 mi (20 km). Therefore, it is 

highly unlikely that the whales will 

swim or feed in close enough proximity 

of discharges to be affected. The levels 

of drilling waste discharges are 

regulated by the NPDES exploration 

facilities GP. The impact of drilling 

waste discharges would be localized 

and temporary. Drilling waste 

discharges could displace endangered 

whales (bowhead and humpback 

whales) a short distance from a drill 

site. Effects on the whales present 

within a few meters of the discharge 

point would be expected, primarily due 

to sedimentation. However, endangered 

whales are not likely to have long-term 

exposures to drilling wastes because of 

the episodic nature of discharges 

(typically only a few hours in duration). 

Like other baleen whales, gray whales 

will more than likely avoid drilling 

activities and therefore not come into 

close contact with drilling wastes. Gray 

whales are benthic feeders and the 

seafloor area covered by accumulations 

of discharged drilling wastes will be 

unavailable to the whales for foraging 

purposes, and represents an indirect 

impact on these animals. Such indirect 

impacts are negligible resulting in little 

effect on individual whales and no 

effect on the population, because such 

areas of disturbance will be few and in 

total will occur over a very small area 

representing an extremely small portion 

of available foraging habitat in the 

Chukchi Sea. Other baleen whales such 

as the minke whale, which could be 

found near the drill site, would not be 

expected to be affected. 

Discharges of drilling wastes are not 

likely to affect beluga whales and other 

odontocetes such as harbor porpoises 


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and killer whales. These marine 

mammals will likely avoid the 

immediate areas where drilling wastes 

will be discharged. Discharge modeling 

performed for both the Discoverer and 

the Polar Pioneer based on maximum 

prevailing current speeds of 9.84 in/s 

(25 cm/s), shows that sedimentation 

depth of drilling wastes at greater than 

0.4 in (1 cm) thickness will occur within 

approximately 1,641 (500 m) of the 

drilling unit discharge point (Fluid 

Dynamix, 2014b). Concentrations of 

TSS, a transient feature of the discharge, 

are modeled to be below 15 mg/L at 

distances approximately 3,281 ft (1,000 

m) from the drilling unit discharge 

point. Therefore, it is highly unlikely 

that beluga whales will come into 

contact with any drilling discharge and 

impacts are not expected. 

Seals are also not expected to be 

impacted by the discharges of drilling 

wastes. It is highly unlikely that a seal 

would remain within 330 ft (100 m) of 

the discharge source for any extended 

period of time but if they were to remain 

within 330 ft (100 m) of the discharge 

source for an extended period of time, 

it is possible that physiological effects 

due to toxins could impact the animal. 

Potential Impacts From Drilling Units’ 

Presence 

The length of the Discoverer at 514 ft 

(156.7 m) and Polar Pioneer at 279 ft 

(85m) are not large enough to cause 

large-scale diversions from the animals’ 

normal swim and migratory paths. The 

drilling units’ physical footprints are 

small relative to the size of the 

geographic region either would occupy, 

and will likely not cause marine 

mammals to deflect greatly from their 

typical migratory routes. 

Any deflection of bowhead whales or 

other marine mammal species due to the 

physical presence of the drilling units or 

support vessels would be extremely 

small. Even if animals may deflect 

because of the presence of the drilling 

units, the Chukchi Sea’s migratory 

corridor is much larger in size than the 

length of the drilling units, and animals 

would have other means of passage 

around the drilling units. In sum, the 

physical presence of the drilling units is 

not likely to cause a material deflection 

to migrating marine mammals. 

Moreover, any impacts would last only 

as long as the drilling units are actually 

present. 

Seal species which may be 

encountered during ice management 

activities include ringed seals, bearded 

seals, spotted seals, and the much less 

common ribbon seal. Ringed seals are 

found in the activity area year-around. 

Bearded seals spend the winter season 

in the Bering Sea, and then follow the 

ice edge as it retreats in spring. Spotted 

seals are found in the Bering Sea in 

winter and spring where they breed, 

molt, and pup in large groups. Few 

spotted seals are expected to be 

encountered in the Chukchi Sea until 

July. Even then, they are rarely seen on 

pack ice but are commonly observed 

hauled out on land or swimming in 

open water. 

Based on extensive analysis of digital 

imagery taken during aerial surveys in 

support of Shell’s 2012 operations in the 

Chukchi and Beaufort Seas, ice seals are 

very infrequently observed hauled out 

on the ice in groups of greater than one 

individual. Tens of thousands of images 

from 17 flights that took place from July 

through October were reviewed in 

detail. Of 107 total observations of 

spotted or ringed seals on ice, only three 

of those sightings were of a group of two 

or more individuals. Since seals are 

found as individuals or in very small 

groups when they are in the activity 

area, the chance of a stampede event is 

very unlikely. Finally, ice seals are well 

adapted to move between ice and water 

without injury, including ‘‘escape 

reactions’’ to avoid predators. 

Exploratory Drilling Program and 

Potential for Oil Spill 

As noted above, the specified activity 

involves the drilling of exploratory 

wells and associated activities in the 

Chukchi Sea during the 2015 openwater season. The impacts to marine 

mammals that are reasonably expected 

to occur will be behavioral in nature. 

The likelihood of a large or very large 

(i.e., ≥1,000 barrels or ≥150,000 barrels, 

respectively) oil spill occurring during 

Shell’s proposed program has been 

estimated to be low. A total of 35 

exploration wells have been drilled 

between 1982 and 2003 in the Chukchi 

and Beaufort seas, and there have been 

no blowouts. In addition, no blowouts 

have occurred from the approximately 

98 exploration wells drilled within the 

Alaskan OCS (MMS, 2007a). Based on 

modeling conducted by Bercha (2008), 

the predicted frequency of an 

exploration well oil spill in waters 

similar to those in the Chukchi Sea, 

Alaska, is 0.000612 per well for a 

blowout sized between 10,000 barrels 

(bbl) to 149,000 bbl and 0.000354 per 

well for a blowout greater than 150,000 

bbl. 

Shell has implemented several design 

standards and practices to reduce the 

already low probability of an oil spill 

occurring as part of its operations. The 

wells proposed to be drilled in the 

Arctic are exploratory and will not be 

converted to production wells; thus, 

production casing will not be installed, 

and the well will be permanently 

plugged and abandoned once 

exploration drilling is complete. Shell 

has also developed and will implement 

the following plans and protocols: 

Shell’s Critical Operations Curtailment 

Plan; DIMP; Well Control Plan; and Fuel 

Transfer Plan. Many of these safety 

measures are required by the 

Department of the Interior’s interim 

final rule implementing certain 

measures to improve the safety of oil 

and gas exploration and development 

on the Outer Continental Shelf in light 

of the Deepwater Horizon event (see 75 

FR 63346, October 14, 2010). 

Operationally, Shell has committed to 

the following to help prevent an oil spill 

from occurring in the Chukchi Sea: 

• Shell’s Blow Out Preventer (BOP) 

was inspected and tested by an 

independent third party specialist; 

• Further inspection and testing of 

the BOP have been performed to ensure 

the reliability of the BOP and that all 

functions will be performed as 

necessary, including shearing the drill 

pipe; 

• Shell will conduct a function test of 

annular and ram BOPs every 7 days 

between pressure tests; 

• A second set of blind/shear rams 

will be installed in the BOP stack; 

• Full string casings will typically not 

be installed through high pressure 

zones; 

• Liners will be installed and 

cemented, which allows for installation 

of a liner top packer; 

• Testing of liners prior to installing 

a tieback string of casing back to the 

wellhead; 

• Utilizing a two-barrier policy; and 

• Testing of all casing hangers to 

ensure that they have two independent, 

validated barriers at all times. 

NMFS has considered Shell’s 

proposed action and has concluded that 

there is no reasonable likelihood of 

serious injury or mortality of marine 

mammals from the proposed 2015 

Chukchi Sea exploration drilling 

program. NMFS has consistently 

interpreted the term ‘‘potential,’’ as used 

in 50 CFR 216.107(a), to only include 

impacts that have more than a 

discountable probability of occurring, 

that is, impacts must be reasonably 

expected to occur. Hence, NMFS has 

regularly issued IHAs in cases where it 

found that the potential for serious 

injury or mortality was ‘‘highly 

unlikely’’ (See 73 FR 40512, 40514, July 

15, 2008; 73 FR 45969, 45971, August 7, 

2008; 73 FR 46774, 46778, August 11, 

2008; 73 FR 66106, 66109, November 6, 

2008; 74 FR 55368, 55371, October 27, 


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2009; 77 FR 27322, May 9, 2012; and 77 

FR 27284, May 9, 2012). 

Interpreting ‘‘potential’’ to include 

impacts with any probability of 

occurring (i.e., speculative or extremely 

low probability events) would nearly 

preclude the issuance of IHAs in every 

instance. For example, NMFS would be 

unable to issue an IHA whenever 

vessels were involved in the marine 

activity since there is always some, 

albeit remote, possibility that a vessel 

could strike and seriously injure or kill 

a marine mammal. This would also be 

inconsistent with the dual-permitting 

scheme Congress created and 

undesirable from a policy perspective, 

as limited agency resources would be 

used to issue regulations that provide no 

additional benefit to marine mammals 

beyond what is proposed in this IHA. 

Despite concluding that the risk of 

serious injury or mortality from an oil 

spill in this case is extremely remote, 

NMFS has nonetheless evaluated the 

potential effects of an oil spill on marine 

mammals. While an oil spill is not a 

component of Shell’s specified activity, 

potential impacts on marine mammals 

from an oil spill are discussed in more 

detail below and will be addressed in 

the Environmental Assessment. 

Potential Effects of Oil on Cetaceans 

The specific effects an oil spill would 

have on cetaceans are not well known. 

While mortality is unlikely, exposure to 

spilled oil could lead to skin irritation, 

baleen fouling (which might reduce 

feeding efficiency), respiratory distress 

from inhalation of hydrocarbon vapors, 

consumption of some contaminated 

prey items, and temporary displacement 

from contaminated feeding areas. Geraci 

and St. Aubin (1990) summarize effects 

of oil on marine mammals, and Bratton 

et al. (1993) provides a synthesis of 

knowledge of oil effects on bowhead 

whales. The number of cetaceans that 

might be contacted by a spill would 

depend on the size, timing, and 

duration of the spill and where the oil 

is in relation to the animals. Whales 

may not avoid oil spills, and some have 

been observed feeding within oil slicks 

(Goodale et al., 1981). These topics are 

discussed in more detail next. 

In the case of an oil spill occurring 

during migration periods, disturbance of 

the migrating cetaceans from cleanup 

activities may have more of an impact 

than the oil itself. Human activity 

associated with cleanup efforts could 

deflect whales away from the path of the 

oil. However, noise created from 

cleanup activities likely will be short 

term and localized. Moreover, whale 

avoidance of clean-up activities may 

benefit whales by displacing them from 

the oil spill area. 

There is no direct evidence that oil 

spills, including the much studied Santa 

Barbara Channel and Exxon Valdez 

spills, have caused any deaths of 

cetaceans (Geraci, 1990; Brownell, 1971; 

Harvey and Dahlheim, 1994). It is 

suspected that some individually 

identified killer whales that disappeared 

from Prince William Sound during the 

time of the Exxon Valdez spill were 

casualties of that spill. However, no 

clear cause and effect relationship 

between the spill and the disappearance 

could be established (Dahlheim and 

Matkin, 1994). The AT–1 pod of 

transient killer whales that sometimes 

inhabits Prince William Sound has 

continued to decline after the Exxon 

Valdez Oil Spill. Matkin et al. (2008) 

tracked the AB resident pod and the 

AT–1 transient group of killer whales 

from 1984 to 2005. The results of their 

photographic surveillance indicate a 

much higher than usual mortality rate 

for both populations the year following 

the spill (33% for AB Pod and 41% for 

AT–1 Group) and lower than average 

rates of increase in the 16 years after the 

spill (annual increase of about 1.6% for 

AB Pod compared to an annual increase 

of about 3.2% for other Alaska killer 

whale pods). In killer whale pods, 

mortality rates are usually higher for 

non-reproductive animals and very low 

for reproductive animals and 

adolescents (Olesiuk et al., 1990, 2005; 

Matkin et al., 2005). No effects on 

humpback whales in Prince William 

Sound were evident after the Exxon 

Valdez Oil Spill (von Ziegesar et al., 

1994). There was some temporary 

displacement of humpback whales out 

of Prince William Sound, but this could 

have been caused by oil contamination, 

boat and aircraft disturbance, 

displacement of food sources, or other 

causes. 

Migrating gray whales were 

apparently not greatly affected by the 

Santa Barbara spill of 1969. There 

appeared to be no relationship between 

the spill and mortality of marine 

mammals. The higher than usual counts 

of dead marine mammals recorded after 

the spill likely represented increased 

survey effort and therefore cannot be 

conclusively linked to the spill itself 

(Brownell, 1971; Geraci, 1990). The 

conclusion was that whales were either 

able to detect the oil and avoid it or 

were unaffected by it (Geraci, 1990). 

(1) Oiling of External Surfaces 

Whales rely on a layer of blubber for 

insulation, so oil would have little if 

any effect on thermoregulation by 

whales. Effects of oiling on cetacean 

skin appear to be minor and of little 

significance to the animal’s health 

(Geraci, 1990). Histological data and 

ultrastructural studies by Geraci and St. 

Aubin (1990) showed that exposures of 

skin to crude oil for up to 45 minutes 

in four species of toothed whales had no 

effect. They switched to gasoline and 

applied the sponge up to 75 minutes. 

This produced transient damage to 

epidermal cells in whales. Subtle 

changes were evident only at the cell 

level. In each case, the skin damage 

healed within a week. They concluded 

that a cetacean’s skin is an effective 

barrier to the noxious substances in 

petroleum. These substances normally 

damage skin by getting between cells 

and dissolving protective lipids. In 

cetacean skin, however, tight 

intercellular bridges, vital surface cells, 

and the extraordinary thickness of the 

epidermis impeded the damage. The 

authors could not detect a change in 

lipid concentration between and within 

cells after exposing skin from a whitesided dolphin to gasoline for 16 hours 

in vitro. 

Bratton et al. (1993) synthesized 

studies on the potential effects of 

contaminants on bowhead whales. They 

concluded that no published data 

proved oil fouling of the skin of any 

free-living whales, and conclude that 

bowhead whales contacting fresh or 

weathered petroleum are unlikely to 

suffer harm. Although oil is unlikely to 

adhere to smooth skin, it may stick to 

rough areas on the surface (Henk and 

Mullan, 1997). Haldiman et al. (1985) 

found the epidermal layer to be as much 

as seven to eight times thicker than that 

found on most whales. They also found 

that little or no crude oil adhered to 

preserved bowhead skin that was 

dipped into oil up to three times, as 

long as a water film stayed on the skin’s 

surface. Oil adhered in small patches to 

the surface and vibrissae (stiff, hairlike 

structures), once it made enough contact 

with the skin. The amount of oil 

sticking to the surrounding skin and 

epidermal depression appeared to be in 

proportion to the number of exposures 

and the roughness of the skin’s surface. 

It can be assumed that if oil contacted 

the eyes, effects would be similar to 

those observed in ringed seals; 

continued exposure of the eyes to oil 

could cause permanent damage (St. 

Aubin, 1990). 

(2) Ingestion 

Whales could ingest oil if their food 

is contaminated, or oil could also be 

absorbed through the respiratory tract. 

Some of the ingested oil is voided in 

vomit or feces but some is absorbed and 

could cause toxic effects (Geraci, 1990). 


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When returned to clean water, 

contaminated animals can depurate this 

internal oil (Engelhardt, 1978, 1982). Oil 

ingestion can decrease food assimilation 

of prey eaten (St. Aubin, 1988). 

Cetaceans may swallow some oilcontaminated prey, but it likely would 

be only a small part of their food. It is 

not known if whales would leave a 

feeding area where prey was abundant 

following a spill. Some zooplankton 

eaten by bowheads and gray whales 

consume oil particles and 

bioaccumulation can result. Tissue 

studies by Geraci and St. Aubin (1990) 

revealed low levels of naphthalene in 

the livers and blubber of baleen whales. 

This result suggests that prey have low 

concentrations in their tissues, or that 

baleen whales may be able to metabolize 

and excrete certain petroleum 

hydrocarbons. Whales exposed to an oil 

spill are unlikely to ingest enough oil to 

cause serious internal damage (Geraci 

and St. Aubin, 1980, 1982) and this kind 

of damage has not been reported 

(Geraci, 1990). 

(3) Fouling of Baleen 

Baleen itself is not damaged by 

exposure to oil and is resistant to effects 

of oil (St. Aubin et al., 1984). Crude oil 

could coat the baleen and reduce 

filtration efficiency; however, effects 

may be temporary (Braithwaite, 1983; 

St. Aubin et al., 1984). If baleen is 

coated in oil for long periods, it could 

cause the animal to be unable to feed, 

which could lead to malnutrition or 

even death. Most of the oil that would 

coat the baleen is removed after 30 min, 

and less than 5% would remain after 24 

hr (Bratton et al., 1993). Effects of oiling 

of the baleen on feeding efficiency 

appear to be minor (Geraci, 1990). 

However, a study conducted by 

Lambertsen et al. (2005) concluded that 

their results highlight the uncertainty 

about how rapidly oil would depurate at 

the near zero temperatures in arctic 

waters and whether baleen function 

would be restored after oiling. 

(4) Avoidance 

Some cetaceans can detect oil and 

sometimes avoid it, but others enter and 

swim through slicks without apparent 

effects (Geraci, 1990; Harvey and 

Dahlheim, 1994). Bottlenose dolphins in 

the Gulf of Mexico apparently could 

detect and avoid slicks and mousse but 

did not avoid light sheens on the surface 

(Smultea and Wursig, 1995). After the 

Regal Sword spill in 1979, various 

species of baleen and toothed whales 

were observed swimming and feeding in 

areas containing spilled oil southeast of 

Cape Cod, MA (Goodale et al., 1981). 

For months following Exxon Valdez Oil 

Spill, there were numerous observations 

of gray whales, harbor porpoises, Dall’s 

porpoises, and killer whales swimming 

through light-to-heavy crude-oil sheens 

(Harvey and Dalheim, 1994, cited in 

Matkin et al., 2008). However, if some 

of the animals avoid the area because of 

the oil, then the effects of the oiling 

would be less severe on those 

individuals. 

(5) Factors Affecting the Severity of 

Effects 

Effects of oil on cetaceans in open 

water are likely to be minimal, but there 

could be effects on cetaceans where 

both the oil and the whales are at least 

partly confined in leads or at ice edges 

(Geraci, 1990). In spring, bowhead and 

beluga whales migrate through leads in 

the ice. At this time, the migration can 

be concentrated in narrow corridors 

defined by the leads, thereby creating a 

greater risk to animals caught in the 

spring lead system should oil enter the 

leads. This situation would only occur 

if there were an oil spill late in the 

season and Shell could not complete 

cleanup efforts prior to ice covering the 

area. The oil would likely then be 

trapped in the ice until it began to thaw 

in the spring. 

In fall, the migration route of 

bowheads can be close to shore 

(Blackwell et al., 2009c). If fall migrants 

were moving through leads in the pack 

ice or were concentrated in nearshore 

waters, some bowhead whales might not 

be able to avoid oil slicks and could be 

subject to prolonged contamination. 

However, the autumn migration through 

the Chukchi Sea extends over several 

weeks, and some of the whales travel 

along routes north or inland of the area, 

thereby reducing the number of whales 

that could approach patches of spilled 

oil. Additionally, vessel activity 

associated with spill cleanup efforts 

may deflect whales traveling near the 

Burger prospect in the Chukchi Sea, 

thereby reducing the likelihood of 

contact with spilled oil. 

Bowhead and beluga whales 

overwinter in the Bering Sea (mainly 

from November to March). In the 

summer, the majority of the bowhead 

whales are found in the Canadian 

Beaufort Sea, although some have 

recently been observed in the U.S. 

Beaufort and Chukchi Seas during the 

summer months (June to August). Data 

from the Barrow-based boat surveys in 

2009 (George and Sheffield, 2009) 

showed that bowheads were observed 

almost continuously in the waters near 

Barrow, including feeding groups in the 

Chukchi Sea at the beginning of July. 

The majority of belugas in the Beaufort 

stock migrate into the Beaufort Sea in 

April or May, although some whales 

may pass Point Barrow as early as late 

March and as late as July (Braham et al., 

1984; Ljungblad et al., 1984; Richardson 

et al., 1995a). Therefore, a spill in 

summer would not be expected to have 

major impacts on these species. 

Additionally, humpback and fin whales 

are only sighted in the Chukchi Sea in 

small numbers in the summer, as this is 

thought to be the extreme northern edge 

of their range. Therefore, impacts to 

these species from an oil spill would be 

extremely limited. 

Potential Effects of Oil on Pinnipeds 

Ice seals are present in open-water 

areas during summer and early autumn. 

Externally oiled phocid seals often 

survive and become clean, but heavily 

oiled seal pups and adults may die, 

depending on the extent of oiling and 

characteristics of the oil. Prolonged 

exposure could occur if fuel or crude oil 

was spilled in or reached nearshore 

waters, was spilled in a lead used by 

seals, or was spilled under the ice when 

seals have limited mobility (NMFS, 

2000). Adult seals may suffer some 

temporary adverse effects, such as eye 

and skin irritation, with possible 

infection (MMS, 1996). Such effects may 

increase stress, which could contribute 

to the death of some individuals. Ringed 

seals may ingest oil-contaminated foods, 

but there is little evidence that oiled 

seals will ingest enough oil to cause 

lethal internal effects. There is a 

likelihood that newborn seal pups, if 

contacted by oil, would die from oiling 

through loss of insulation and resulting 

hypothermia. These potential effects are 

addressed in more detail in subsequent 

paragraphs. 

Reports of the effects of oil spills have 

shown that some mortality of seals may 

have occurred as a result of oil fouling; 

however, large scale mortality had not 

been observed prior to the Exxon Valdez 

Oil Spill (St. Aubin, 1990). Effects of oil 

on marine mammals were not well 

studied at most spills because of lack of 

baseline data and/or the brevity of the 

post-spill surveys. The largest 

documented impact of a spill, prior to 

Exxon Valdez Oil Spill Exxon Valdez 

Oil Spill, was on young seals in January 

in the Gulf of St. Lawrence (St. Aubin, 

1990). Brownell and Le Boeuf (1971) 

found no marked effects of oil from the 

Santa Barbara oil spill on California sea 

lions or on the mortality rates of 

newborn pups. 

Intensive and long-term studies were 

conducted after the Exxon Valdez Oil 

Spill in Alaska. There may have been a 

long-term decline of 36% in numbers of 

molting harbor seals at oiled haul-out 

sites in Prince William Sound following 


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Exxon Valdez Oil Spill Exxon Valdez 

Oil Spill (Frost et al., 1994a). However, 

in a reanalysis of those data and 

additional years of surveys, along with 

an examination of assumptions and 

biases associated with the original data, 

Hoover-Miller et al. (2001) concluded 

that the Exxon Valdez Oil Spill effect 

had been overestimated. The decline in 

attendance at some oiled sites was more 

likely a continuation of the general 

decline in harbor seal abundance in 

Prince William Sound documented 

since 1984 (Frost et al., 1999) rather 

than a result of Exxon Valdez Oil Spill. 

The results from Hoover-Miller et al. 

(2001) indicate that the effects of Exxon 

Valdez Oil Spill were largely 

indistinguishable from natural decline 

by 1992. However, while Frost et al. 

(2004) concluded that there was no 

evidence that seals were displaced from 

oiled sites, they did find that aerial 

counts indicated 26% fewer pups were 

produced at oiled locations in 1989 than 

would have been expected without the 

oil spill. Harbor seal pup mortality at 

oiled beaches was 23% to 26%, which 

may have been higher than natural 

mortality, although no baseline data for 

pup mortality existed prior to Exxon 

Valdez Oil Spill (Frost et al., 1994a). 

There was no conclusive evidence of 

spill effects on Steller sea lions (Calkins 

et al., 1994). Oil did not persist on sea 

lions themselves (as it did on harbor 

seals), nor did it persist on sea lion 

haul-out sites and rookeries (Calkins et 

al., 1994). Sea lion rookeries and haul 

out sites, unlike those used by harbor 

seals, have steep sides and are subject 

to high wave energy (Calkins et al., 

1994). 

(1) Oiling of External Surfaces 

Adult seals rely on a layer of blubber 

for insulation, and oiling of the external 

surface does not appear to have adverse 

thermoregulatory effects (Kooyman et 

al., 1976, 1977; St. Aubin, 1990). 

Contact with oil on the external surfaces 

can potentially cause increased stress 

and irritation of the eyes of ringed seals 

(Geraci and Smith, 1976; St. Aubin, 

1990). These effects seemed to be 

temporary and reversible, but continued 

exposure of eyes to oil could cause 

permanent damage (St. Aubin, 1990). 

Corneal ulcers and abrasions, 

conjunctivitis, and swollen nictitating 

membranes were observed in captive 

ringed seals placed in crude oil-covered 

water (Geraci and Smith, 1976) and in 

seals in the Antarctic after an oil spill 

(Lillie, 1954). 

Newborn seal pups rely on their fur 

for insulation. Newborn ringed seal 

pups in lairs on the ice could be 

contaminated through contact with 

oiled mothers. There is the potential 

that newborn ringed seal pups that were 

contaminated with oil could die from 

hypothermia. 

(2) Ingestion 

Marine mammals can ingest oil if 

their food is contaminated. Oil can also 

be absorbed through the respiratory tract 

(Geraci and Smith, 1976; Engelhardt et 

al., 1977). Some of the ingested oil is 

voided in vomit or feces but some is 

absorbed and could cause toxic effects 

(Engelhardt, 1981). When returned to 

clean water, contaminated animals can 

depurate this internal oil (Engelhardt, 

1978, 1982, 1985). In addition, seals 

exposed to an oil spill are unlikely to 

ingest enough oil to cause serious 

internal damage (Geraci and St. Aubin, 

1980, 1982). 

(3) Avoidance and Behavioral Effects 

Although seals may have the 

capability to detect and avoid oil, they 

apparently do so only to a limited extent 

(St. Aubin, 1990). Seals may abandon 

the area of an oil spill because of human 

disturbance associated with cleanup 

efforts, but they are most likely to 

remain in the area of the spill. One 

notable behavioral reaction to oiling is 

that oiled seals are reluctant to enter the 

water, even when intense cleanup 

activities are conducted nearby (St. 

Aubin, 1990; Frost et al., 1994b, 2004). 

(4) Factors Affecting the Severity of 

Effects 

Seals that are under natural stress, 

such as lack of food or a heavy 

infestation by parasites, could 

potentially die because of the additional 

stress of oiling (Geraci and Smith, 1976; 

St. Aubin, 1990; Spraker et al., 1994). 

Female seals that are nursing young 

would be under natural stress, as would 

molting seals. In both cases, the seals 

would have reduced food stores and 

may be less resistant to effects of oil 

than seals that are not under some type 

of natural stress. Seals that are not 

under natural stress (e.g., fasting, 

molting) would be more likely to 

survive oiling. In general, seals do not 

exhibit large behavioral or physiological 

reactions to limited surface oiling or 

incidental exposure to contaminated 

food or vapors (St. Aubin, 1990; 

Williams et al., 1994). Effects could be 

severe if seals surface in heavy oil slicks 

in leads or if oil accumulates near haulout sites (St. Aubin, 1990). An oil spill 

in open-water is less likely to impact 

seals. 

The potential effects to marine 

mammals described in this section of 

the document do not take into 

consideration the proposed monitoring 

and mitigation measures described later 

in this document (see the ‘‘Proposed 

Mitigation’’ and ‘‘Proposed Monitoring 

and Reporting’’ sections). 

Anticipated Effects on Marine Mammal 

Habitat 

The primary potential impacts to 

marine mammals and other marine 

species are associated with elevated 

sound levels produced by the 

exploratory drilling program (i.e. the 

drilling units and the airguns). 

However, other potential impacts are 

also possible to the surrounding habitat 

from physical disturbance and an oil 

spill (should one occur). This section 

describes the potential impacts to 

marine mammal habitat from the 

specified activity. Because the marine 

mammals in the area feed on fish and/ 

or invertebrates there is also information 

on the species typically preyed upon by 

the marine mammals in the area. 

Potential Impacts on Habitat From 

Seafloor Disturbance (Mooring and MLC 

Construction) 

Mooring of the drilling units and 

construction of MLCs will result in 

some seafloor disturbance and 

temporary increases in water column 

turbidity. 

The drilling units would be held in 

place during operations with systems of 

eight anchors for each unit. The 

embedment type anchors are designed 

to embed into the seafloor thereby 

providing the required resistance. The 

anchors will penetrate the seafloor on 

contact and may drag 2–3 or more times 

their length while being set. Both the 

anchor and anchor chain will disturb 

sediments in this process creating a 

trench or depression with surrounding 

berms where the displaced sediment is 

mounded. Some sediments will be 

suspended in the water column during 

the setting and subsequent removal of 

the anchors. The depression with 

associated berm, collectively known as 

an anchor scar, remains when the 

anchor is removed. 

Dimensions of future anchor scars can 

be estimated based on the dimensions of 

the anchor. Shell estimates that each 

anchor may impact a seafloor area of up 

to about 2,510 ft2 (233m2). Impact 

estimates associated with mooring a 

drilling unit by its eight anchors is 

20,078 ft2 (1,865 m2) of seafloor 

assuming that the 15 metric ton anchors 

are used and set only once. Shell plans 

to pre-set anchors and deploy mooring 

lines at each drill site prior to arrival of 

the drilling units. Unless moved by an 

outside force such as sea current, 

anchors should only need to be set once 

per drill site. 


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Once the drilling units end operation, 

the Polar Pioneer anchors will be 

retrieved and the Discoverer anchors 

may be left on site for wet storage. Over 

time the anchor scars will be filled 

through natural movement of sediment. 

The duration of the scars depends upon 

the energy of the system, water depth, 

ice scour, and sediment type. Anchor 

scars were visible under low energy 

conditions in the North Sea for five to 

ten years after retrieval. Scars typically 

do not form or persist in sandy mud or 

sand sediments but may last for nine 

years in hard clays (Centaur Associates, 

Inc 1984). Surficial sediments in Shell’s 

Burger Prospect consist of soft sandy 

mud (silt and clay) with lesser amounts 

of gravel (Battelle Memorial Institute 

2010; Blanchard et al. 2010a, b). The 

energy regime, plus possible effects of 

ice gouge in the Chukchi Sea suggests 

that anchor scars would be refilled 

faster than in the North Sea. 

Excavation of each MLC by the 

drilling units using a large diameter 

drill bit will displace about 589m3 of 

seafloor sediments and directly disturb 

approximately 1,075 ft2 (100 m2) of 

seafloor. Pressurized air and seawater 

(no drilling mud used) will be used to 

assist in the removal of the excavated 

materials from the MLC. Some of the 

excavated sediments will be displaced 

to adjacent seafloor areas and some will 

be pumped and discharged on the 

seafloor away from the MLC. These 

excavated materials will also have some 

indirect effects as they are suspended in 

the water and deposited on the seafloor 

in the vicinity of the MLCs. Direct and 

indirect effects would include slight 

changes in seafloor relief and sediment 

consistency, and smothering of benthic 

organisms. 

Potential Impacts on Habitat From 

Sound Generation 

Underwater noise generated from 

Shell’s proposed exploration drilling 

activity may potentially affect marine 

mammal prey species, which are fish 

species and various invertebrates in the 

action area. 

(1) Zooplankton 

Zooplankton are food sources for 

several endangered species, including 

bowhead, fin, and humpback whales. 

The primary generators of sound energy 

associated with the exploration drilling 

program are the airgun array during the 

conduct of ZVSPs, the drilling units 

during drilling, and marine vessels, 

particularly during ice management and 

DP. Sound energy generated by these 

activities will not negatively impact the 

diversity and abundance of 

zooplankton, and will therefore have no 

direct effect on marine mammals. 

Sound energy generated by the airgun 

arrays to be used for the ZVSPs will 

have no more than negligible effects on 

zooplankton. Studies on euphausiids 

and copepods, which are some of the 

more abundant and biologically 

important groups of zooplankton in the 

Chukchi Sea, have documented the use 

of hearing receptors to maintain 

schooling structures (Wiese 1996) and 

detection of predators (Hartline et al. 

1996, Wong 1996) respectively, and 

therefore have some sensitivity to 

sound; however any effects of airguns 

on zooplankton would be expected to be 

restricted to the area within a few feet 

or meters of the airgun array and would 

likely be sublethal. Studies on brown 

shrimp in the Wadden Sea (Webb and 

Kempf 1998) revealed no particular 

sensitivity to sounds generated by 

airguns at sound levels of 190 dB re 1 

mPa rms at 3.3 ft. (1.0 m) in water depths 

of 6.6 ft. (2.0 m). Koshleva (1992) 

reported no detectable effects on the 

amphipod (Gammarus locusta) at 

distances as close as 0.5 m from an 

airgun with a source level of 223 dB re 

1 mPa rms. A recent Canadian 

government review of the impacts of 

seismic sound on invertebrates and 

other organisms (CDFO 2004) included 

similar findings; this review noted 

‘‘there are no documented cases of 

invertebrate mortality upon exposure to 

seismic sound under field operating 

conditions’’ (CDFO 2004). Some 

sublethal effects (e.g., reduced growth, 

behavioral changes) were noted (CDFO 

2004). 

The energy from airguns has 

sometimes been shown to damage eggs 

and fry of some fish. Eggs and larvae of 

some fish may apparently sustain 

sublethal to lethal effects if they are 

within very close proximity to the 

seismic-energy-discharge point. These 

types of effects have been demonstrated 

by some laboratory experiments using 

single airguns (e.g., Kosheleva 1992, 

Matishov 1992, Holliday et al. 1987), 

while other similar studies have found 

no material increases in mortality or 

morbidity due to airgun exposure (Dalen 

and Knutsen 1986, Kostyuvchenko 

1973). The effects, where they do occur, 

are apparently limited to the area within 

3–6 ft. (1–2 m) from the airgundischarge ports. In their detailed review 

of studies on the effects of airguns on 

fish and fisheries, Dalen et al. (1996) 

concluded that airguns can have 

deleterious effects on fish eggs and 

larvae out to a distance of 16 ft (5.0 m), 

but that the most frequent and serious 

injuries are restricted to the area within 

5.0 ft (1.5 m) of the airguns. Most 

investigators and reviewers (Gausland 

2003, Thomson and Davis 2001, Dalen 

et al. 1996) have concluded that even 

seismic surveys with much larger airgun 

arrays than are used for shallow hazards 

and site clearance surveys, have no 

impact to fish eggs and larvae 

discernible at the population or fisheries 

level. 

These studies indicate that some 

zooplankton within a distance of about 

16 ft. (5.0 m) or less from the airgun 

array may sustain sublethal or lethal 

injuries but there would be no 

population effects even over small areas. 

Therefore there would be no indirect 

effect on marine mammals. 

Ice management is likely to be the 

most intense sources of sound 

associated with the exploration drilling 

program Richardson et al. (1995a). Ice 

management vessels, during active ice 

management, may have to adjust course 

forward and astern while moving ice 

and thereby create greater variability in 

propeller cavitation than other vessels 

that maintain course with less 

adjustment. The drilling units maintain 

station during drilling without 

activation of propulsion propellers. 

Richardson (et al.1995a) reported that 

the noise generated by an icebreaker 

pushing ice was 10–15 dB re 1 mPa rms 

greater than the noise produced by the 

ship underway in open water. It is 

expected that the lower level of sound 

produced by the drilling units, ice 

management, or other vessels would 

have less impact on zooplankton than 

would 3D seismic (survey) sound. 

No appreciable adverse impact on 

zooplankton populations will occur due 

in part to large reproductive capacities 

and naturally high levels of predation 

and mortality of these populations. Any 

mortality or impacts on zooplankton as 

a result of Shell’s operations is 

immaterial as compared to the naturally 

occurring reproductive and mortality 

rates of these species. This is consistent 

with previous conclusions that 

crustaceans (such as zooplankton) are 

not particularly sensitive to sound 

produced by seismic sounds (Wiese 

1996). Impact from sound energy 

generated by an ice breaker, other 

marine vessels, and drill ships would 

have less impact, as these activities 

produce lower sound energy levels 

(Burns 1993). Historical sound 

propagation studies performed on the 

Kulluk by Hall et al. (1994) also indicate 

the Kulluk and similar drilling units 

would have lower sound energy output 

than three-dimensional seismic sound 

sources (Burns et al. 1993). The drilling 

units Discoverer and Polar Pioneer 

would emit sounds at a lower level than 

the Kulluk and therefore the impacts 


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due to drilling noise would be even 

lower than the Kulluk. Therefore, 

zooplankton organisms would not likely 

be affected by sound energy levels by 

the vessels to be used during Shell’s 

exploration drilling activities in the 

Chukchi Sea. 

(2) Benthos 

There was no indication from postdrilling benthic biomass or density 

studies that previous drilling activities 

at the Hammerhead Prospect have had 

a measurable impact on the ecology of 

the immediate local area. To the 

contrary, the abundance of benthic 

communities in the Sivulliq area would 

suggest that the benthos were actually 

thriving there (Dunton et al. 2008). 

Sound energy generated by 

exploration drilling and ice 

management activities will not 

appreciably affect diversity and 

abundance of plants or animals on the 

seafloor. The primary generators of 

sound energy are the drilling units and 

marine vessels. Ice management vessels 

are likely to be the loudest sources of 

sounds associated with the exploration 

drilling program (Richardson et al. 

1995a). Ice management vessels, during 

active ice management, may have to 

adjust course forward and astern while 

moving ice and thereby create greater 

variability in propeller cavitation than 

other vessels that maintain course with 

less adjustment. The drilling units 

maintain station during drilling without 

activation of propulsion propellers. 

Richardson et al. (1995a) reported that 

the noise generated by an icebreaker 

pushing ice was 10–15 dB re 1 mPa rms 

greater than the noise produced by the 

ship underway in open water. The 

lower level of sound produced by the 

drilling units, ice management vessels, 

or other vessels will have less impact on 

bottom-dwelling organisms than would 

3D seismic (survey) sound. 

No appreciable adverse impacts on 

benthic populations would be expected 

due in part to large reproductive 

capacities and naturally high levels of 

predation and mortality of these 

populations. Any mortalities or impacts 

that might occur as a result of Shell’s 

operations is immaterial compared to 

the naturally occurring high 

reproductive and mortality rates. This is 

consistent with previous BOEM 

conclusions that the effect of seismic 

exploration on benthic organisms 

probably would be immeasurable 

(USDI/MMS 2007). Impacts from sound 

energy generated by ice breakers, other 

marine vessels, and drilling units would 

have less impact, as these activities 

produce much lower sound energy 

levels (Burns et al. 1993). 

(3) Fish 

Fish react to sound and use sound to 

communicate (Tavolga et al. 1981). 

Experiments have shown that fish can 

sense both the intensity and direction of 

sound (Hawkins 1981). Whether or not 

fish can hear a particular sound 

depends upon its frequency and 

intensity. Wavelength and the natural 

background sound also play a role. The 

intensity of sound in water decreases 

with distance as a result of geometrical 

spreading and absorption. Therefore, the 

distance between the sound source and 

the fish is important. Physical 

conditions in the sea, such as 

temperature thermoclines and seabed 

topography, can influence transmission 

loss and thus the distance at which a 

sound can be heard. 

The impact of sound energy from 

exploration drilling and ice 

management activities will be negligible 

and temporary. Fish typically move 

away from sound energy above a level 

that is at 120 dB re 1 mPa rms or higher 

(Ona 1988). 

Drilling unit sound source levels 

during drilling can range from 90 dB re 

1 mPa rms within 31 mi (50 km) of the 

drilling unit to 138 dB re 1 mPa rms 

within a distance of 0.06 mi (0.01 km) 

from the drilling unit (Greene 1985, 

1987b). These are predicted sound 

levels at various distances based on 

modeled transmission loss equations in 

the literature (Greene 1987b). Ice 

management vessel sound source levels 

can range from 174–184 dB re 1 mPa 

rms. At these intensity levels, fish may 

avoid the drilling unit, ice management 

vessels, or other large support vessels. 

This avoidance behavior is temporary 

and limited to periods when a vessel is 

underway or drilling. There have been 

no studies of the direct effects of ice 

management vessel sounds on fish. 

However, it is known that the ice 

management vessels produce sounds 

generally 10–15 dB re 1 mPa rms higher 

when moving through ice rather than 

open water (Richardson et al. 1995b). In 

general, fish show greater reactions to a 

spike in sound energy levels, or impulse 

sounds, rather than a continuous high 

intensity signal (Blaxter et al. 1981). 

Fish sensitivity to impulse sound 

such as that generated by ZVSPs varies 

depending on the species of fish. Cod, 

herring and other species of fish with 

swim bladders have been found to be 

relatively sensitive to sound, while 

mackerel, flatfish, and many other 

species that lack swim bladders have 

been found to have poor hearing 

(Hawkins 1981, Hastings and Popper 

2005). An alarm response in these fish 

is elicited when the sound signal 

intensity rises rapidly compared to 

sound rising more slowly to the same 

level (Blaxter et al. 1981). Any such 

effects on fish would be negligible and 

have no indirect effect on marine 

mammals. 

Potential Impacts on Habitat From 

Drilling Wastes 

Discharges of drilling wastes must be 

authorized by the NPDES exploration 

facilities GP, and this GP places 

numerous conditions and limitations on 

such discharges. The EPA (2012) has 

determined that with these limits and 

conditions in place, the discharges will 

not result in any unreasonable 

degradation of ocean waters. The 

primary impacts of the discharges are 

increases in TSS in the water column 

and the deposition of drilling wastes on 

the seafloor. These impacts would be 

localized to the drill sites and 

temporary. 

(1) Zooplankton 

Reviews by EPA (2006) and Neff 

(2005) indicate that though planktonic 

organisms are sensitive to 

environmental conditions (e.g., 

temperature, light, availability of 

nutrients, and water quality), there is 

little or no evidence of effects from 

drilling waste discharges on plankton in 

the ocean. In the laboratory, high 

concentrations of drilling wastes have 

been shown to have lethal or sublethal 

effects on zooplankton due to toxicity 

and abrasion by suspended sediments. 

These effects are minimized at the drill 

site by limits and conditions placed on 

the discharges by the NPDES 

exploration facilities GP, which include 

discharge rate limits and toxicity limits. 

Any impact by drilling waste 

discharges on zooplankton would be 

localized and temporary. Fine-grained 

particulates and other solids in drilling 

wastes could cause sublethal effects to 

organisms in the water column. 

Responses observed in the laboratory 

following exposure to drilling mud 

include alteration of respiration and 

filtration rates and altered behavior. 

Zooplankton in the immediate area of 

discharge from drilling operations could 

potentially be adversely impacted by 

sediments in the water column, which 

could clog respiratory and feeding 

structures, cause abrasions to gills and 

other sensitive tissues, or alter behavior 

or development. However, the 

planktonic organisms are not likely to 

have long-term exposures to the drilling 

waste because of the episodic nature of 

discharges (typically only a few hours in 

duration), the small area affected, and 

the movement of the organisms with the 

ocean currents. The discharged waste 


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must have low toxicities to meet permit 

requirements and modeling studies 

indicate dilution factors of >1,000 

within 328 ft (100 m). Modeling and 

monitoring studies have demonstrated 

that increased TSS in the water column 

from the discharges would largely be 

limited to the area within 984 ft (300 m) 

from the discharge. This impact would 

likely not have more than a short-term 

impact on zooplankton and no effect on 

zooplankton populations, and therefore 

no indirect effects on marine mammals. 

(2) Benthos 

Benthic organisms would primarily be 

affected by the discharges through the 

deposition of the discharged drilling 

waste on the seafloor resulting in the 

smothering of organisms, changes in the 

consistency of sediments on the 

seafloor, and possible elevation in heavy 

metal concentrations in the 

accumulations. 

Drilling waste discharges are 

regulated by the EPA’s NPDES 

exploration facilities GP. The impact of 

drilling waste discharges would be 

localized and temporary. Effects on 

benthic organisms present within a few 

meters of the discharge point would be 

expected, primarily due to 

sedimentation. However, benthic 

animals are not likely to have long-term 

exposures to drilling wastes because of 

the episodic nature of discharges 

(typically only a few hours in duration). 

Shell conducted dispersion modeling 

of the drilling waste discharges using 

the Offshore Operators Committee Mud 

and Produced Water Discharge (OOC) 

model (Fluid Dynamix 2014a, b). The 

modeling effort provided predictions of 

the area and thickness of accumulations 

of discharged drilling waste on the 

seafloor. The USA EPA has performed 

an evaluation of drilling waste in 

support of the issuance of NPDES GP 

AKG–28–8100 for exploration facilities 

(EPA, 2012b) (October 2012), and 

determined these accumulations will 

not result in any unreasonable 

degradation of the marine environment. 

Heavy metal contamination of 

sediments and resulting effects on 

benthic organisms is not expected. The 

NPDES exploration facilities GP 

contains stringent limitations on the 

concentrations of mercury, cadmium, 

chromium, silver, and thallium allowed 

in discharged drilling waste. Additional 

limitations are placed on free oil, diesel 

oil, and total aromatic hydrocarbons 

allowed in discharged drilling waste. 

Discharge rates are also controlled by 

the permit. Baseline studies at the 1985 

Hammerhead drill site (Trefry and 

Trocine 2009) detected background 

levels Al, Fe, Zn, Cd and Hg in all 

surface and subsurface sediment 

samples. Considering the relatively 

small area that drilling waste discharges 

will be deposited, no material impacts 

on sediment are expected to occur. The 

expected increased concentrations of 

Zn, Cd, and Cr in sediments near the 

drill site due to the discharge are in the 

range where no or low effects would 

result. 

Studies in the 1980s, 1999, 2000, and 

2002 (Brown et al. 2001 in USDI/MMS 

2003) also found that benthic organism 

near drill sites in the Beaufort Sea have 

accumulated neither petroleum 

hydrocarbon nor heavy metals. In 2008 

Shell investigated the benthic 

communities (Dunton et al. 2008) and 

sediments (Trefry and Trocine 2009) 

around the Sivulliq Prospect including 

the location of the historical 

Hammerhead drill site that was drilled 

in 1985. Benthic communities at the 

historical Hammerhead drill site were 

found not to differ statistically in 

abundance, community structure, or 

diversity, from benthic communities 

elsewhere in this portion of the Beaufort 

Sea, indicating that there was no long 

term effect. 

Sediment samples taken in the 

Chukchi Sea Environmental Studies 

Program Burger Study Area were 

analyzed for metal and hydrocarbon 

concentrations (Neff et al. 2010). 

Concentrations of all measured 

hydrocarbon types were found to be 

well within the range of non-toxic 

background concentrations reported by 

other Alaskan and Arctic coastal and 

shelf sediment studies (Neff et al. 2010, 

Dunton et al. 2012). Metal 

concentrations were found to be quite 

variable. Average concentrations of all 

metals except for arsenic and barium 

were found to be lower than those 

reported for average marine sediment. 

Trefry et al. (2012) confirmed findings 

by Neff et al. 2010 that concentrations 

of all measured hydrocarbon types were 

well within the range of non-toxic 

background concentrations reported by 

other Alaskan and Arctic coastal and 

shelf sediment studies. 

Neff et al. (2010) assessed the 

concentrations of metals and various 

hydrocarbons in sediments at the 

historic Burger and Klondike wells in 

the Chukchi Sea, which were drilled in 

1989–1990. Surface and subsurface 

sediments collected in 2008 at the 

historic drill sites contained higher 

concentrations of all types of analyzed 

hydrocarbon in comparison to the 

surrounding area. The same pattern was 

found for the metal barium, with 

concentrations 2–3 times greater at the 

historic drill sites (mean = 1,410 m/g and 

1,300 m/g) than in the surrounding areas 

(639 m/g and 595 m/g). Concentrations of 

copper, mercury, and lead, were 

elevated in a few samples from the 

historic drill sites where barium was 

also elevated. All observed 

concentrations of hydrocarbons or 

metals in the sediment samples from the 

historic drill sites were below levels 

(below ERL or Effects Range Low of 

Long 1995) believed to have adverse 

ecological effects (Neff et al. 2010). 

Similar results were reported by Trefry 

and Trocine (2009) for the historic 

Hammerhead drill sites in the Beaufort 

Sea. 

These data show that the potential 

accumulation of heavy metals in 

discharged drilling waste on the 

Chukchi seafloor associated with 

drilling exploration wells is very limited 

and does not pose a threat. Impacts to 

seafloor sediments from the discharge of 

drilling wastes will be minor, as they 

would be restricted to a very small 

portion of the activity area and will not 

result in contamination. 

The drilling waste discharges will be 

conducted as authorized by the EPA’s 

NPDES exploration facilities GP, which 

limits the metal content and flow rate 

for such discharges. The EPA (2012b) 

analyzed the effects of these types of 

discharges, including potential transport 

of pollutants such as metals by 

biological, physical, or chemical 

processes, and has concluded that these 

types of discharges do not result in 

unreasonable degradation of ocean 

waters. The physical effects of mooring 

and MLC construction would be 

restricted to a very small portion of the 

Chukchi Sea seafloor (15.7–33.2 ac in 

total for the exploration program) which 

represents less than 0.000011%– 

0.000024% of the seafloor of the 

Chukchi Sea. However, the predicted 

small increases in concentrations of 

metals will likely be evident for a 

number of years until gouged by ice, 

redistributed by currents, or buried 

under natural sedimentation. 

There is relatively little information 

on the effects of various deposition 

depths on arctic biota (Hurley and Ellis 

2004); most such studies have 

investigated the effects of deposition of 

dredged materials (Wilbur 1992). Burial 

depths as low as 1.0 in (2.54 cm) have 

been found to be lethal for some benthic 

organisms (Wilbur 1992, EPA 2006). 

Accumulations of drilling waste to 

depths > 1.0 in (>2.54 cm) will be 

restricted to very small areas of the 

seafloor around each drill site and in 

total represent an extremely small 

portion of the Chukchi Sea. These areas 

would be re-colonized by benthic 

organisms rather quickly. Impacts to 

benthic organisms are therefore 


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considered to be negligible with no 

indirect effects on marine mammals. As 

required by the NPDES exploration 

facilities GP, Shell will implement an 

environmental monitoring program 

(EMP), to assess the recovery of the 

benthos from impacts drilling waste 

discharges. 

(3) Fish 

Drilling waste discharges are 

regulated by the NPDES exploration 

facilities GP. The impact of drilling 

waste discharges would be localized 

and temporary. Drilling waste 

discharges could displace fish a short 

distance from a drill site. Effects on fish 

and fish larvae present within a few 

meters of the discharge point would be 

expected, primarily due to 

sedimentation. However, fish and fish 

larvae that live in the water column are 

not likely to have long-term exposures 

to drilling wastes because of the 

episodic nature of the discharges 

(typically only a few hours in duration). 

Although unlikely at deeper offshore 

drilling locations, demersal fish eggs 

could be smothered if discharges occur 

in a spawning area during the period of 

egg production. No specific demersal 

fish spawning locations have been 

identified at the Burger drill site 

locations. The most abundant and 

trophically important marine fish, the 

Arctic cod, spawns with planktonic eggs 

and larvae under the sea ice during 

winter and will therefore have little 

exposure to discharges. 

Habitat alteration concerns apply to 

special or relatively uncommon 

habitats, such as those important for 

spawning, nursery, or overwintering. 

Important fish overwintering habitats 

are located in coastal rivers and 

nearshore coastal waters, but are not 

found in the proposed exploration 

drilling areas. Important spawning areas 

have not been identified in the Chukchi 

Sea. Impacts on fish will be negligible, 

with no indirect effects on marine 

mammals. 

Potential Impacts on Habitat From Ice 

Management/Icebreaking Activities 

Ice management or icebreaking 

activities include the physical pushing 

or moving of ice in the proposed 

exploration drilling area and to prevent 

ice floes from striking the drilling unit. 

Ringed, bearded, spotted, and ribbon 

seals) are dependent on sea ice for at 

least part of their life history. Sea ice is 

important for life functions such as 

resting, breeding, and molting. These 

species are dependent on two different 

types of ice: Pack ice and landfast ice. 

Shell does not expect to have to manage 

pack ice during the majority of the 

drilling season. The majority of the ice 

management or icebreaking should 

occur in the early and latter portions of 

the drilling season. Landfast ice would 

not be present during Shell’s proposed 

operations. 

The ringed seal is the most common 

pinniped species in the Chukchi Sea 

activity area. While ringed seals use ice 

year-round, they do not construct lairs 

for pupping until late winter/early 

spring on the landfast ice. Shell plans to 

conclude drilling on or before 31 

October, therefore Shell’s activities 

would not impact ringed seal lairs or 

habitat needed for breeding and 

pupping in the Chukchi Sea. Ringed 

seals can be found on the pack ice 

surface in the late spring and early 

summer in the Chukchi Sea, the latter 

part of which may overlap with the start 

of Shell’s planned exploration drilling 

activities. Management of pack ice that 

contains hauled out seals may result in 

the animals becoming startled and 

entering the water, but such effects 

would be brief. 

Ice management or icebreaking would 

occur during a time when ringed seal 

life functions such as breeding, 

pupping, and molting do not occur in 

the proposed project area. Additionally, 

these life functions occur more 

commonly on landfast ice, which will 

not be impacted by Shell’s activity. 

Bearded seals breed in the Bering and 

Chukchi Seas, but would not be 

plentiful in the area of the Chukchi Sea 

exploration drilling program. Spotted 

seals are even less common in the 

Chukchi Sea activity area. Ice is used by 

bearded and spotted seals for critical life 

functions such as breeding and molting, 

but it is unlikely these life functions 

would occur in the proposed project 

area, during the time in which drilling 

activities will take place. The 

availability of ice would not be 

impacted as a result of Shell’s 

exploration drilling program. 

Ice-management or icebreaking 

related to Shell’s planned exploration 

drilling program in the Chukchi Sea is 

not expected to have any habitat-related 

effects that could cause material or longterm consequences for individual 

marine mammals or on the food sources 

that they utilize. 

Potential Impacts From an Oil Spill 

Lower trophic organisms and fish 

species are primary food sources for 

Arctic marine mammals. However, as 

noted earlier in this document, the 

offshore areas of the Chukchi Sea are 

not primary feeding grounds for many of 

the marine mammals that may pass 

through the area. Therefore, impacts to 

lower trophic organisms (such as 

zooplankton) and marine fishes from an 

oil spill in the proposed drilling area 

would not be likely to have long-term or 

significant consequences to marine 

mammal prey. Impacts would be greater 

if the oil moves closer to shore, as many 

of the marine mammals in the area have 

been seen feeding at nearshore sites 

(such as bowhead whales). Gray whales 

do feed in more offshore locations in the 

Chukchi Sea; therefore, impacts to their 

prey from oil could have some impacts. 

Due to their wide distribution, large 

numbers, and rapid rate of regeneration, 

the recovery of marine invertebrate 

populations is expected to occur soon 

after the surface oil passes. Spill 

response activities are not likely to 

disturb the prey items of whales or seals 

sufficiently to cause more than minor 

effects. Spill response activities could 

cause marine mammals to avoid the 

disturbed habitat that is being cleaned. 

However, by causing avoidance, animals 

would avoid impacts from the oil itself. 

Additionally, the likelihood of an oil 

spill is expected to be very low, as 

discussed earlier in this document. 

Proposed Mitigation 

In order to issue an incidental take 

authorization (ITA) under Sections 

101(a)(5)(A) and (D) of the MMPA, 

NMFS must, where applicable, set forth 

the permissible methods of taking 

pursuant to such activity, and other 

means of effecting the least practicable 

impact on such species or stock and its 

habitat, paying particular attention to 

rookeries, mating grounds, and areas of 

similar significance, and on the 

availability of such species or stock for 

taking for certain subsistence uses 

(where relevant). This section 

summarizes the contents of Shell’s 

Marine Mammal Monitoring and 

Mitigation Plan (4MP). Later in this 

document in the ‘‘Proposed Incidental 

Harassment Authorization’’ section, 

NMFS lays out the proposed conditions 

for review, as they would appear in the 

final IHA (if issued). 

Shell submitted a 4MP as part of its 

application (see ADDRESSES). Shell’s 

planned offshore drilling program 

incorporates both design features and 

operational procedures for minimizing 

potential impacts on marine mammals 

and on subsistence hunts. The 4MP is 

a combination of active monitoring in 

the area of operations and the 

implementation of mitigation measures 

designed to minimize project impacts to 

marine resources. Monitoring will 

provide information on marine 

mammals potentially affected by 

exploration activities, in addition to 

facilitating real time mitigation to 


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prevent injury of marine mammals by 

industrial sounds or activities. 

Vessel Based Marine Mammal 

Monitoring for Mitigation 

The objectives of the vessel based 

marine mammal monitoring are to 

ensure that disturbance to marine 

mammals and subsistence hunts is 

minimized, that effects on marine 

mammals are documented, and that data 

is collected on the occurrence and 

distribution of marine mammals in the 

project area. 

The marine mammal monitoring will 

be implemented by a team of 

experienced protected species observers 

(PSOs). The PSOs will be experienced 

biologists and Alaska Native personnel 

trained as field observers. PSOs will be 

stationed on both drilling units, ice 

management vessels, anchor handlers 

and other drilling support vessels 

engaged in transit to and between drill 

sites to monitor for marine mammals. 

The duties of the PSOs will include; 

watching for and identifying marine 

mammals, recording their numbers, 

recording distances and reactions of 

marine mammals to exploration drilling 

activities, initiating mitigation measures 

when appropriate, and reporting results 

of the vessel based monitoring program, 

which will include the estimation of the 

number of marine mammal ‘‘exposures’’ 

as defined by the NMFS and stipulated 

in the IHA. 

The vessel based work will provide: 

• The basis for initiating real-time 

mitigation, if necessary, as required by 

the various permits that Shell receives; 

• Information needed to estimate the 

number of ‘‘exposures’’ of marine 

mammals to sound levels that may 

result in harassment, which must be 

reported to NMFS; 

• Data on the occurrence, 

distribution, and activities of marine 

mammals in the areas where drilling 

activity is conducted; 

• Information to compare the 

distances, distributions, behavior, and 

movements of marine mammals relative 

to the drilling unit during times with 

and without drilling activity occurring; 

• A communication channel to 

coastal communities including whalers; 

and 

• Employment and capacity building 

for local residents, with one objective 

being to develop a larger pool of 

experienced Alaska Native PSOs. 

The vessel based monitoring will be 

operated and administered consistent 

with monitoring programs conducted 

during past exploration drilling 

activities, seismic and shallow hazards 

surveys, or alternative requirements 

stipulated in permits issued to Shell. 

Agreements between Shell and other 

agencies will also be fully incorporated. 

PSOs will be provided training through 

a program approved by the NMFS. 

Mitigation Measures During the 

Exploration Drilling Program 

Shell’s planned exploration drilling 

activities incorporate design features 

and operational procedures aimed at 

minimizing potential impacts on marine 

mammals and subsistence hunts. Some 

of the mitigation design features 

include: 

• Conducting pre-season acoustic 

modeling to establish the appropriate 

exclusion and disturbance zones; 

• Vessel based PSO monitoring to 

implement appropriate mitigation if 

necessary, and to determine the effects 

of the drilling program on marine 

mammals; 

• Passive acoustic monitoring of 

drilling and vessel sounds and marine 

mammal vocalizations; and 

• Aerial surveys with photographic 

equipment over operations and in 

coastal and nearshore waters with 

photographic equipment to help 

determine the effects of project activities 

on marine mammals; and seismic 

activity mitigation measures during 

acquisition of the ZVSP surveys. 

The potential disturbance of marine 

mammals during drilling activities will 

be mitigated through the 

implementation of several vessel based 

mitigation measures as necessary. 

(1) Exclusion and Disturbance Zones 

Mitigation for NMFS’ incidental take 

authorizations typically includes ‘‘safety 

radii’’ or ‘‘exclusion zones’’ for marine 

mammals around airgun arrays and 

other impulsive industrial sound 

sources where received levels are ≥180 

dB re 1 mPa (rms) for cetaceans and ≥190 

dB re 1 mPa (rms) for pinnipeds. These 

zones are based on a cautionary 

assumption that sound energy at lower 

received 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 from 

exposure to sound at distances greater 

than these zones (Richardson et al. 

1995). The NMFS assumes that marine 

mammals exposed to pulsed airgun 

sounds with received levels ≥160 dB re 

1 mPa (rms) or continuous sounds from 

vessel activities with received levels 

≥120 dB re 1 mPa (rms) have the 

potential to be disturbed. These sound 

level thresholds are currently used by 

NMFS to define acoustic disturbance 

(harassment) criteria. 

(A) Exploration Drilling Activities 

The areas exposed to sounds 

produced by the drilling units 

Discoverer and Polar Pioneer were 

determined by measurements from 

drilling in 2012 or were modeled by 

JASCO Applied Sciences. The 2012 

measurement of the distance to the 120 

dB (rms) threshold for normal drilling 

activity by the Discoverer was 0.93 mi 

(1.5 km) while the distance of the ≥120 

dB (rms) radius during MLC 

construction was 5.1 mi (8.2 km). 

Measured sound levels for the Polar 

Pioneer were not available. Its sound 

footprint was estimated with JASCOs 

Marine Operations Noise Model 

(MONM) using an average source level 

derived from a number of reported 

acoustic measurements of comparable 

semi-submersible drill units, including 

the Ocean Bounty (Gales, 1982), SEDCO 

708 (Greene, 1986), and Ocean General 

(McCauley, 1998). The model yielded a 

propagation range of 0.22 mi (0.35 km) 

for rms sound pressure levels of 120 dB 

for the Polar Pioneer while drilling at 

the Burger Prospect. 

In addition to drilling and MLC 

construction, numerous activities in 

support of exploration drilling produce 

continuous sounds above 120 dB (rms). 

These activities in direct support of the 

moored drilling units include ice 

management, anchor handling, and 

supply/discharge sampling vessels 

using DP thrusters. Detailed sound 

characterizations for each of these 

activities are presented in the 2012 

Comprehensive Report for NMFS’ 2012 

IHA (LGL et al. 2013). 

The source levels for exploration 

drilling and related support activities 

are not high enough to cause temporary 

reduction in hearing sensitivity or 

permanent hearing damage to marine 

mammals. Consequently, mitigation as 

described for seismic activities 

including ramp ups, power downs, and 

shut downs should not be necessary for 

exploration drilling activities. However, 

Shell plans to use PSOs onboard the 

drilling units, ice management, and 

anchor handling vessels to monitor 

marine mammals and their responses to 

industry activities, in addition to 

initiating mitigation measures should 

in-field measurements of the activities 

indicate conditions that may present a 

threat to the health and well-being of 

marine mammals. 

(B) ZVSP Surveys 

Two sound sources have been 

proposed by Shell for the ZVSP surveys. 

The first is a small airgun array that 

consists of three 150 in3 (2,458 cu cm3) 

airguns for a total volume of 450 in3


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(7,374 cm3). The second ZVSP sound 

source consists of two 250 in3 (4,097 

cm3) airguns with a total volume of 500 

in3 (8,194 cm3). Sound footprints of the 

ZVSP airgun array configurations were 

estimated using JASCO Applied 

Sciences’ Marine Operations Noise 

Model (MONM). The model results were 

maximized over all water depths 

between 9.9 and 23 ft (3 and 7 m) to 

yield sound level isopleths as a function 

of range and direction from the source. 

The 450 in3 airgun array at a source 

depth of 23 ft (7 m) yielded the 

maximum ranges to the ≥190, ≥180, and 

≥160 dB (rms) isopleths. The estimated 

95th percentile distances to these 

thresholds were: 190 dB = 558 ft (170 

m), 180 dB = 3,018 ft (920 m), and 160 

dB = 39,239 ft (11,960 m). These 

distances were multiplied by 1.5 as a 

conservative measure, and the resulting 

radii are shown in Table 1. 

PSOs on the drilling units will 

initially use the radii in Table 1 for 

monitoring and mitigation purposes 

during ZVSP surveys. 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 and used to 

verify (and if necessary adjust) the 

threshold radii distances during later 

ZVSP surveys. The mitigation measures 

to be implemented will include preramp up watches, ramp ups, power 

downs and shut downs as described 

below. 

TABLE 1—ESTIMATED DISTANCES OF

THE ≥190, 180, AND 160, dB (rms) 

ISOPLETHS TO BE USED FOR MITIGATION PURPOSES DURING ZVSP 

SURVEYS UNTIL SSV RESULTS ARE

AVAILABLE

Threshold levels in dB re 1 μPa 

(rms) 

Estimated 

distance 

(m) 

≥190 .......................................... 255 

≥180 .......................................... 1,380 

≥160 .......................................... 11,960 

(2) Ramp Ups 

A ramp up of an airgun array provides 

a gradual increase in sound levels, and 

involves a step-wise 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 time for them to leave 

the area, thus avoiding 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 

observation of the exclusion zone by 

PSOs for a minimum of 30 minutes to 

ensure that no marine mammals are 

present. The entire exclusion zones 

must be visible during the 30 minutes 

leading into to a full ramp up. If the 

entire exclusion zone is not visible, a 

ramp up from a cold start cannot begin. 

If a marine mammal is sighted within 

the relevant exclusion zone during the 

30 minutes prior to ramp up, ramp up 

will be delayed until the marine 

mammal is sighted outside of the 

exclusion zone or 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. 

(3) 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 

exclusion zone of the full arrays, but is 

outside the applicable exclusion zone of 

the single source. If a marine mammal 

is sighted within the applicable 

exclusion zone of the single energy 

source, the entire array will be shut 

down (i.e., no sources firing). 

Mitigation Conclusions 

NMFS has carefully evaluated the 

applicant’s proposed mitigation 

measures and considered a range of 

other measures in the context of 

ensuring that NMFS prescribes the 

means of effecting the least practicable 

impact on the affected marine mammal 

species and stocks and their habitat. Our 

evaluation of potential measures 

included consideration of the following 

factors in relation to one another: 

• The manner in which, and the 

degree to which, the successful 

implementation of the measure is 

expected to minimize adverse impacts 

to marine mammals, 

• The proven or likely efficacy of the 

specific measure to minimize adverse 

impacts as planned, and 

• The practicability of the measure 

for applicant implementation. 

Any mitigation measure(s) prescribed 

by NMFS should be able to accomplish, 

have a reasonable likelihood of 

accomplishing (based on current 

science), or contribute to the 

accomplishment of one or more of the 

general goals listed below: 

1. Avoidance or minimization of 

injury or death of marine mammals 

wherever possible (goals 2, 3, and 4 may 

contribute to this goal). 

2. A reduction in the numbers of 

marine mammals (total number or 

number at biologically important time 

or location) exposed to received levels 

of noises generated from exploration 

drilling and associated activities, or 

other activities expected to result in the 

take of marine mammals (this goal may 

contribute to 1, above, or to reducing 

harassment takes only). 

3. A reduction in the number of times 

(total number or number at biologically 

important time or location) individuals 

would be exposed to received levels of 

noises generated from exploration 

drilling and associated activities, or 

other activities expected to result in the 

take of marine mammals (this goal may 

contribute to 1, above, or to reducing 

harassment takes only). 

4. A reduction in the intensity of 

exposures (either total number or 

number at biologically important time 

or location) to received levels of noises 

generated from exploration drilling and 

associated activities, or other activities 

expected to result in the take of marine 

mammals (this goal may contribute to a, 

above, or to reducing the severity of 

harassment takes only). 

5. Avoidance or minimization of 

adverse effects to marine mammal 

habitat, paying special attention to the 

food base, activities that block or limit 

passage to or from biologically 

important areas, permanent destruction 

of habitat, or temporary destruction/ 

disturbance of habitat during a 

biologically important time. 

6. For monitoring directly related to 

mitigation—an increase in the 

probability of detecting marine 

mammals, thus allowing for more 

effective implementation of the 

mitigation. 

Based on our evaluation of the 

applicant’s proposed measures, as well 

as other measures considered by NMFS, 

NMFS has preliminarily determined 

that the proposed mitigation measures 

provide the means of effecting the least 

practicable impact on marine mammals 

species or stocks and their habitat, 

paying particular attention to rookeries, 

mating grounds, and areas of similar 

significance. 

Proposed measures to ensure 

availability of such species or stock for 


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taking for certain subsistence uses are 

discussed later in this document (see 

‘‘Impact on Availability of Affected 

Species or Stock for Taking for 

Subsistence Uses’’ section). 

Proposed Monitoring and Reporting 

In order to issue an ITA for an 

activity, section 101(a)(5)(D) of the 

MMPA states that NMFS must set forth, 

‘‘requirements pertaining to the 

monitoring and reporting of such 

taking.’’ The MMPA implementing 

regulations at 50 CFR 216.104(a)(13) 

indicate that requests for ITAs must 

include the suggested means of 

accomplishing the necessary monitoring 

and reporting that will result in 

increased knowledge of the species and 

of the level of taking or impacts on 

populations of marine mammals that are 

expected to be present in the proposed 

action area. Shell submitted a marine 

mammal monitoring plan as part of the 

IHA application. It can be found in 

Appendix B of the Shell’s IHA 

application. The plan may be modified 

or supplemented based on comments or 

new information received from the 

public during the public comment 

period or from the peer review panel 

(see the ‘‘Monitoring Plan Peer Review’’ 

section later in this document). 

Monitoring measures prescribed by 

NMFS should accomplish one or more 

of the following general goals: 

1. An increase in the probability of 

detecting marine mammals, both within 

the mitigation zone (thus allowing for 

more effective implementation of the 

mitigation) and in general to generate 

more data to contribute to the analyses 

mentioned below; 

2. An increase in our understanding 

of how many marine mammals are 

likely to be exposed to levels of noises 

generated from exploration drilling and 

associated activities that we associate 

with specific adverse effects, such as 

behavioral harassment, TTS, or PTS; 

3. An increase in our understanding 

of how marine mammals respond to 

stimuli expected to result in take and 

how anticipated adverse effects on 

individuals (in different ways and to 

varying degrees) may impact the 

population, species, or stock 

(specifically through effects on annual 

rates of recruitment or survival) through 

any of the following methods: 

D Behavioral observations in the 

presence of stimuli compared to 

observations in the absence of stimuli 

(need to be able to accurately predict 

received level, distance from source, 

and other pertinent information); 

D Physiological measurements in the 

presence of stimuli compared to 

observations in the absence of stimuli 

(need to be able to accurately predict 

received level, distance from source, 

and other pertinent information); 

D Distribution and/or abundance 

comparisons in times or areas with 

concentrated stimuli versus times or 

areas without stimuli; 

4. An increased knowledge of the 

affected species; and 

5. An increase in our understanding 

of the effectiveness of certain mitigation 

and monitoring measures. 

Proposed Monitoring Measures 

1. Protected Species Observers 

Vessel based monitoring for marine 

mammals will be done by trained PSOs 

on both drilling units and ice 

management and anchor handler vessels 

throughout the exploration drilling 

activities. The observers will monitor 

the occurrence and behavior of marine 

mammals near the drilling units, ice 

management and anchor handling 

vessels, during all daylight periods 

during the exploration drilling 

operation, and during most periods 

when exploration drilling is not being 

conducted. PSO duties will include 

watching for and identifying marine 

mammals; recording their numbers, 

distances, and reactions to the 

exploration drilling activities; and 

documenting exposures to sound levels 

that may constitute harassment as 

defined by NMFS. PSOs will help 

ensure that the vessel communicates 

with the Communications and Call 

Centers (Com Centers) in Native villages 

along the Chukchi Sea coast. 

(A) Number of Observers 

A sufficient number of PSOs will be 

onboard 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 PSO; and 

• Maximum of approximately 12 

hours on watch per day per PSO. 

PSO teams will consist of trained 

Alaska Natives and field biologist 

observers. An experienced field crew 

leader will be on every PSO team aboard 

the drilling units, ice management and 

anchor handling vessels, and other 

support vessels during the exploration 

drilling program. The total number of 

PSOs aboard may decrease later in the 

season as the duration of daylight 

decreases. 

(B) Crew Rotation 

Shell anticipates that there will be 

provisions for crew rotation at least 

every three to six weeks to avoid 

observer fatigue. During crew rotations 

detailed notes will be provided to the 

incoming crew 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 necessary. In the event of an 

unexpected crew change Shell will 

facilitate such communications to 

insure monitoring consistency among 

shifts. 

(C) Observer Qualifications and 

Training 

Crew leaders serving as PSOs will 

have experience from one or more 

projects with operators in Alaska or the 

Canadian Beaufort. 

Biologist-observers will have previous 

PSO experience, and crew leaders will 

be highly experienced with previous 

vessel based marine mammal 

monitoring projects. Resumes for those 

individuals will be provided to the 

NMFS for approval. All PSOs will be 

trained and familiar with the marine 

mammals of the area. A PSO handbook, 

adapted for the specifics of the planned 

Shell drilling program, will be prepared 

and distributed beforehand to all PSOs. 

PSOs will also complete a two-day 

training and refresher session on marine 

mammal monitoring, to be conducted 

shortly before the anticipated start of the 

drilling season. The training sessions 

will be conducted by marine 

mammalogists with extensive crew 

leader experience from previous vessel 

based seismic monitoring programs in 

the Arctic. 

Primary objectives of the training 

include: 

• Review of the 4MP for this project, 

including any amendments adopted or 

specified by NMFS in the final IHA 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 in the IHA (if issued); 

• Review operation of specialized 

equipment (e.g., reticle binoculars, big 

eye binoculars, night vision devices, 

GPS system); and 

• Review of data recording and data 

entry systems, including procedures for 

recording data on mammal sightings, 

exploration drilling and monitoring 

activities, environmental conditions, 

and entry error control. These 

procedures will be implemented 

through use of a customized computer 

databases and laptop computers. 

(D) PSO Handbook 

A PSO Handbook will be prepared for 

Shell’s monitoring program. The 


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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 PSOs. The following 

topics will be covered in the PSO 

Handbook: 

• Summary overview descriptions of 

the project, marine mammals and 

underwater sound energy, the 4MP 

(vessel-based, aerial, acoustic 

measurements, special studies), the IHA 

(if issued) and other regulations/ 

permits/agencies, the Marine Mammal 

Protection Act; 

• Monitoring and mitigation 

objectives and procedures, including 

initial exclusion and disturbance zones; 

• Responsibilities of staff and crew 

regarding the 4MP; 

• Instructions for staff and crew 

regarding the 4MP; 

• Data recording procedures: codes 

and coding instructions, common 

coding mistakes, electronic database; 

navigational, marine physical, and 

drilling data recording, field data sheet; 

• Use of specialized field equipment 

(e.g., reticle binoculars, Big-eye 

binoculars, 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 PSOs 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; 

• Field reporting requirements and 

procedures; 

• Copies of the IHA will be made 

available; and 

• Areas where vessels need 

permission to operate such as the 

Ledyard Bay Critical Habitat Unit 

(LBCHU). 

2. Vessel-Based Monitoring 

Methodology 

The observer(s) will watch for marine 

mammals from the best available 

vantage point on the drilling units and 

support vessels. Ideally this vantage 

point is an elevated stable platform from 

which the PSO has an unobstructed 

360o view of the water. The observer(s) 

will scan systematically with the naked 

eye and 7 x 50 reticle binoculars, 

supplemented with Big-eye binoculars 

and night-vision equipment when 

needed. Personnel on the bridge will 

assist the marine mammal observer(s) in 

watching for pinnipeds and cetaceans. 

New or inexperienced PSOs will be 

paired with an experienced PSO or 

experienced field biologist so that the 

quality of marine mammal observations 

and data recording is kept consistent. 

Information to be recorded by marine 

mammal observers will include the 

same types of information that were 

recorded during previous monitoring 

projects (e.g., Moulton and Lawson 

2002; Reiser et al. 2010, 2011; Bisson et 

al. 2013). 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 

vessels the distance and bearing to the 

drilling unit will also be recorded; and 

• Positions of other vessel(s) in the 

vicinity of the observer location. 

The vessel’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 x 50 binoculars) containing 

a reticle to measure the vertical angle of 

the line of sight to the animal relative 

to the horizon. 

An electronic database will be used to 

record and collate data obtained from 

visual observations during the vesselbased study. The PSOs will enter the 

data into the custom data entry program 

installed on field laptops. The data 

entry program automates the data entry 

process and reduces data entry errors 

and maximizes PSO time spent looking 

at the water. PSOs also have voice 

recorders available to them. This is 

another tool that will allow PSOs to 

maximize time spent focused on the 

water. 

PSO’s are instructed to identify 

animals as unknown when appropriate 

rather than strive to identify an animal 

when there is significant uncertainty. 

PSOs should also provide any sightings 

cues they used and any distinguishable 

features of the animal even if they are 

not able to identify the animal and 

record it as unidentified. Emphasis will 

also be placed on recording what was 

not seen, such as dorsal features. 

(A) 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 night-vision devices (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; Hartin et al. 2013). 

(B) Specialized Field Equipment 

Shell will provide the following 

specialized field equipment for use by 

the onboard PSOs: reticle binoculars, 

Big-eye binoculars, GPS unit, laptop 

computers, night vision binoculars, and 

possibly digital still and digital video 

cameras. Big eye binoculars will be 

mounted and used on key monitoring 

vessels including the drilling units, ice 

management vessels and the anchor 

handler. 

(C) Field Data-Recording, Verification, 

Handling, and Security 

The observers on the drilling units 

and support vessels will record their 

observations directly into computers 

using a custom software package. 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. 

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-of-season training session, (2) 

subsequent supervision by the onboard 

field crew leader, and (3) ongoing data 

checks during the field season. 

The data will be sent off of the vessel 

to Anchorage on a daily basis and 

backed up regularly onto storage devices 

on the vessel, and stored at separate 

locations on the vessel. If practicable, 

hand-written data sheets will be 

photocopied daily during the field 

season. Data will be secured further by 


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having data sheets and backup data 

devices carried back to the Anchorage 

office during crew rotations. 

In addition to routine PSO 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 

comprehensive reports documenting the 

monitoring work. 

PSOs will be able to plot sightings in 

near real-time for their vessel. 

Significant sightings from key vessels 

including drilling units, ice 

management, anchor handlers and 

aircraft will be relayed between 

platforms to keep observers aware of 

animals that may be in or near the area 

but may not be visible to the observer 

at any one time. Emphasis will be 

placed on relaying sightings with the 

greatest potential to involve mitigation 

or reconsideration of a vessel’s course 

(e.g., large group of bowheads). 

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. PSOs 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. Voice recorders will also be 

available for observers to use during 

periods when large numbers of animals 

may be present and it is difficult to 

capture all of the sightings on written or 

digital forms. These recorders can also 

be used to capture traditional 

knowledge and natural history 

observations should individuals feel 

more comfortable using the recorders 

rather than writing down their 

comments. 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. 

3. Acoustic Monitoring Plan 

Exploration Drilling, ZVSP, and Vessel 

Noise Measurements 

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 drilling units. 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 

drilling unit; 

• To measure the sound levels 

produced by vessels while operating in 

direct support of exploration drilling 

operations. These vessels will include 

crew change vessels, tugs, icemanagement vessels, and spill response 

vessels not measured in 2012; and 

• To measure the sound levels 

produced by an end-of-hole zero-offset 

vertical seismic profile (ZVSP) survey 

using a stationary sound source. 

Sound characterization and 

measurements of all exploration drilling 

activities will be performed using five 

Autonomous Multichannel Acoustic 

Recorders (AMAR) deployed on the 

seabed along the same radial at 

distances of 0.31, 0.62, 1.2, 2.5 and 5 mi 

(0.5,1, 2, 4 and 8 km) from each drilling 

unit. All five recording stations will 

sample at least at 32 kHz, providing 

calibrated acoustic measurements in the 

5 Hz to 16 kHz frequency band. The 

logarithmic spacing of the recorders is 

designed to sample the attenuation of 

drilling unit sounds with distance. The 

autonomous recorders will sample 

through completion of the first well, to 

provide a detailed record of sounds 

emitted from all activities. These 

recorders will be retrieved and their 

data analyzed and reported in the 

project’s 90-day report. 

The deployment of drilling sound 

monitoring equipment will occur before, 

or as soon as possible after the 

Discoverer and the Polar Pioneer are on 

site. Activity logs of exploration drilling 

operations and nearby vessel activities 

will be maintained to correlate with 

these acoustic measurements. All 

results, including back-propagated 

source levels for each operation, will be 

reported in the 90-day report. 

(A) Vessel Sound Characterization 

Vessel sound characterizations will be 

performed using dedicated recorders 

deployed at sufficient distances from 

exploration drilling operations so that 

sound produced by those activities does 

not interfere. Three AMAR acoustic 

recorders will be deployed on and 

perpendicular to a sail track on which 

all Shell contracted vessels will transit. 

This geometry is designed to obtain 

sound level measurements as a function 

of distance and direction. The fore and 

aft directions are sampled continuously 

over longer distances to 3 and 6 miles 

(5 and 10 km) respectively, while 

broadside and other directions are 

sampled as the vessels pass closer to the 

recorders. 

Vessel sound measurements will be 

processed and reported in a manner 

similar to that used by Shell and other 

operators in the Beaufort and Chukchi 

Seas during seismic survey operations. 

The measurements will further be 

analyzed to calculate source levels. 

Source directivity effects will be 

examined and reported. Preliminary 

vessel characterization measurements 

will be reported in a field report to be 

delivered 120 hours after the recorders 

are retrieved and data downloaded. 

Those results will include sound level 

data but not source level calculations. 

All vessel characterization results, 

including source levels, will be reported 

in 1/3-octave bands in the project 90- 

day report. 

(B) Zero-Offset Vertical Seismic 

Profiling Sound Monitoring 

Shell states that it may conduct a 

geophysical survey referred to as a zerooffset vertical seismic profile, or ZVSP, 

at two drill sites in 2015. During ZVSP 

surveys, an airgun array, which is much 

smaller than those used for routine 

seismic surveys, is deployed at a 

location near or adjacent to the drilling 

unit, 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 geophones, typically a string of 

them, are then raised up to the next 

interval in the wellbore and the process 

is repeated until the entire wellbore has 

been surveyed. The purpose of the 

ZVSP survey is to gather geophysical 

information at various depths in the 

wellbore, which can then be used to tiein or ground truth geophysical 

information from the previously 

collected 2D and 3D seismic surveys 

with geological data collected within 

the wellbore. 

Shell will conduct a ZVSP surveys in 

which the sound source is maintained at 

a constant location near the wellbore. 

Two sound sources have been proposed 

by Shell for the ZVSP surveys in 2015. 

The first is a small airgun array that 

consists of three 150 in3 (2,458 cu cm3) 

airguns for a total volume of 450 in3

(7,374 cm3). The second ZVSP sound 


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source consists of two 250 in3 (4,097 cu 

cm3) airguns with a total volume of 500 

in3 (8,194 cm3). 

A ZVSP survey is typically conducted 

at each well after total depth is reached 

but may be conducted at a shallower 

depth. For each survey, the sound 

source (airgun array) would be deployed 

over the side of the Discoverer or the 

Polar Pioneer with a crane. The sound 

source will be positioned 50–200ft (15– 

61 m) from the wellhead (depending on 

crane location), at a depth of ∼10–23ft 

(3–7 m) below the water surface. 

Receivers will be temporarily anchored 

in the wellbore at depth. The sound 

source will be pressured up to 3,000 

pounds per square inch (psi), and 

activated 5–7 times at approximately 20- 

second intervals. The receivers 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 has been 

surveyed in this manner. The interval 

between anchor points for the receiver 

array is usually 200–300ft (61–91 m). A 

typical ZVSP survey takes about 10–14 

hours to complete per well (depending 

on the depth of the well and the number 

of anchoring points in each well). 

ZVSP sound verification 

measurements will be performed using 

either the AMARs that are deployed for 

drilling unit sound characterizations, or 

by JASCO Ocean Bottom Hydrophone 

(OBH) recorders. The use of AMARS or 

OBHs depends on the specific timing 

these measurements will be required by 

NMFS; the AMARs will not be retrieved 

until several days after the ZVSP as they 

are intended to monitor during 

retrievals of drilling unit anchors and 

related support activities. If the ZVSP 

acoustic measurements are required 

sooner, four OBH recorders would be 

deployed at the same locations and 

those could be retrieved immediately 

following the ZVSP measurement. The 

ZVSP measurements can be delivered 

within 120 hours of retrieval and 

download of the data from either 

instrument type. 

(C) 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. These results are 

useful for correlating measured sound 

energy events with specific survey 

operations. 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. The analyses will 

also consider sound level integrated 

through 1-hour durations (referred to as 

sound energy equivalent level Leq (1- 

hour). Similar graphs for long time 

periods will be generated as part of the 

data analysis performed for indicating 

drilling sound variation with time in 

selected frequency bands. 

(D) 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 drilling 

units and all drilling support vessels; 

• Spectrogram and band level versus 

time plots computed from the 

continuous recordings obtained from 

the hydrophone systems; 

• Hourly 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 

drilling sound associated with 

differences in drilling unit activities as 

indicated in detailed drilling unit logs. 

Acoustic ‘‘Net’’ Array in Chukchi Sea 

This section describes acoustic 

studies that were undertaken from 2006 

through 2013 in the Chukchi Sea as part 

of the Joint Monitoring Program and that 

will be continued by Shell during 

exploration drilling activities. The 

acoustic ‘‘net’’ array used during the 

2006–2013 field seasons 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 other species) that may be 

available to subsistence hunters near 

villages along 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. 

A net array configuration similar to 

that deployed in 2007–2013 is again 

proposed. The basic components of this 

effort consist of autonomous acoustic 

recorders deployed widely across the 

U.S. Chukchi Sea during the open water 

season and then more limited arrays 

during the winter season. These 

calibrated systems sample at 16 kHz 

with 24-bit resolution, and are capable 

of recording marine mammal sounds 

and making anthropogenic noise 

measurements. The net array 

configuration will include a regional 

array of 23 AMAR recorders deployed 

July–October off the four main transect 

locations: Cape Lisburne, Point Lay, 

Wainwright and Barrow. All of these 

offshore systems will capture sounds 

associated with exploration drilling, 

where present, over large distances to 

help characterize the sound 

transmission properties in the Chukchi 

Sea. Six additional summer AMAR 

recorders will be deployed around the 

Burger drill sites to monitor directional 

variations and longer-range propagation 

of drilling-related sounds. These 

recorders will also be used to examine 

marine mammal vocalization patterns in 

vicinity of exploration drilling 

activities. The regional recorders will be 

retrieved in early October 2015; acoustic 

monitoring will continue through the 

winter with 8 AMAR recorders 

deployed October 2015–August 2016. 

The winter recorders will sample at 16 

kHz on a 17% duty cycle (40 minutes 

every 4 hours). The winter recorders 

deployed in previous years have 

provided important information about 

fall and spring migrations of bowhead, 

beluga, walrus and several seal species. 

The Chukchi acoustic net array 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 that have been developed 

over several years. 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 provides 

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 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 sound propagation 

over a very large area. It is expected that 

sounds from exploratory drilling 

activities will be detectable on 

hydrophone systems within 

approximately 30 km of the drilling 

units when ambient sound energy 

conditions are low. The 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 


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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 

drilling unit 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 drilling or vessel 

sound levels). 

4. Chukchi Offshore Aerial 

Photographic Monitoring Program 

Shell has been reticent to conduct 

manned aerial surveys in the offshore 

Chukchi Sea because conducting those 

surveys puts people at risk. There is a 

strong desire, however, to obtain data on 

marine mammal distribution in the 

offshore Chukchi Sea and Shell will 

conduct a photographic aerial survey 

that would put fewer people at risk as 

an alternative to the fully-manned aerial 

survey. The photographic survey would 

reduce the number of people on board 

the aircraft from six persons to two 

persons (the pilot and copilot) and 

would serve as a pilot study for future 

surveys that would use an Unmanned 

Aerial System (UAS) to capture the 

imagery. 

Aerial photographic surveys have 

been used to monitor distribution and 

estimate densities of marine mammals 

in offshore areas since the mid-1980s, 

and before that, were used to estimate 

numbers of animals in large 

concentration areas. Digital photographs 

provide many advantages over 

observations made by people if the 

imagery has sufficient resolution (Koski 

et al. 2013). With photographs there is 

constant detectability across the 

imagery, whereas observations by 

people decline with distance from the 

center line of the survey area. 

Observations at the outer limits of the 

transect can decline to 5–10% of the 

animals present for real-time 

observations by people during an aerial 

survey. The distance from the trackline 

of sightings is more accurately 

determined from photographs; group 

size can be more accurately determined; 

and sizes of animals can be measured, 

and hence much more accurately 

determined, in photographs. As a result 

of the latter capability, the presence or 

absence of a calf can be more accurately 

determined from a photograph than by 

in-the-moment visual observations. 

Another benefit of photographs over 

visual observations is that photographs 

can be reviewed by more than one 

independent observer allowing 

quantification of detection, 

identification and group size biases. 

The proposed photographic survey 

will provide imagery that can be used to 

evaluate the ability of future studies to 

use the same image capturing systems in 

an UAS where people would not be put 

at risk. Although the two platforms are 

not the same, the slower airspeed and 

potentially lower flight altitude of the 

UAS would mean that the data quality 

would be better from the UAS. Initial 

comparisons have been made between 

data collected by human observers on 

board both the Chukchi and Beaufort 

aerial survey aircraft and the digital 

imagery collected in 2012. Overall, the 

imagery provided better estimates of the 

number of large cetaceans and 

pinnipeds present but fewer sightings 

were identified to species in the imagery 

than by PSOs, because the PSOs had 

sightings in view for a longer period of 

time and could use behavior to 

differentiate species. The comparisons 

indicated that some cetaceans that were 

not seen by PSOs were detected in the 

imagery; errors in identification were 

made by the PSOs during the survey 

that could be resolved from examination 

of the imagery; cetaceans seen by PSOs 

were visible in the imagery; and during 

periods with large numbers of sightings, 

the imagery provided much better 

estimates of numbers of sightings and 

group size than the PSO data. 

Photographic surveys would start as 

soon as the ice management, anchor 

handler and drilling units are at or near 

the first drill site and would continue 

throughout the drilling period and until 

the drilling related vessels have left the 

exploration drilling area. Since the 

current plans are for vessels to enter the 

Chukchi Sea on or about 1 July, surveys 

would be initiated on or about 3 July. 

This start date differs from past 

practices of beginning five days prior to 

initiation of an activity and continuing 

until five days after cessation of the 

activity because the presence of vessels 

with helidecks in the area where 

overflights will occur is one of the main 

mitigations that will allow for safe 

operation of the overflight program this 

far offshore. The surveys will be based 

out of Barrow and the same aircraft will 

conduct the offshore surveys around the 

drilling units and the coastal saw-tooth 

pattern. The surveys of offshore areas 

around the drilling units will take 

precedence over the sawtooth survey, 

but if weather does not permit surveying 

offshore, the nearshore survey will be 

conducted if weather permits. 

The aerial survey grids are designed 

to maximize coverage of the sound level 

fields of the drilling units during the 

different exploratory drilling activities. 

The survey grids can be modified as 

necessary based on weather and 

whether a noisy activity or quiet activity 

is taking place. The intensive survey 

design maximizes the effort over the 

area where sound levels are highest. The 

outer survey grid covers an elliptical 

area with a 45 km radius near the center 

of the ellipse. The spacing of the outer 

survey lines is 10 km, and the spacing 

between the intensive and outer lines is 

5 km. The expanded survey grid covers 

a larger survey area, and the design is 

based on an elliptical area with a 50 km 

radius centered on the well sties. For 

both survey designs the main transects 

will be spaced 10 km apart which will 

allow even coverage of the survey area 

during a single flight if weather 

conditions permit completion of a 

survey. A random starting point will be 

selected for each survey and the evenly 

spaced lines will be shifted NE or SW 

along the perimeter of the elliptical 

survey area based on the start point. The 

total length of survey lines will be about 

1,000 km and the exact length will 

depend on the location of the randomly 

selected start point. 

Following each survey, the imagery 

will be downloaded from the memory 

card to a portable hard drive and then 

backed up on a second hard drive and 

stored at accommodations in Barrow 

until the second hard drive can be 

transferred to Anchorage. In Anchorage, 

the imagery will be processed through a 

computer-assisted analysis program to 

identify where marine mammal 

sightings might be located among the 

many images obtained. A team of 

trained photo analysts will review the 

photographs identified as having 

potential sightings and record the 

appropriate data on each sighting. If 

time permits, a second review of some 

of the images will be conducted while 

in the field, but the sightings recorded 

during the second pass will be 

identified in the database as secondary 

sightings, so that biases associated with 

the detection in the imagery can be 

quantified. If time does not permit that 

review to be conducted while in the 

field, the review will be conducted by 

personnel in the office during or after 

the field season. A sample of images 

that are not identified by the computerassisted analysis program will be 

examined in detail by the image 

analysts to determine if the program has 

missed marine mammal sightings. If the 

analysis program has missed mammal 


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sightings, these data will be to develop 

correction factors to account for these 

missed sightings among the images that 

were not examined. 

5. Chukchi Sea Coastal Aerial Survey 

Nearshore aerial surveys of marine 

mammals in the Chukchi Sea were 

conducted over coastal areas to 

approximately 23 miles (mi) [37 

kilometers (km)] offshore in 2006–2008 

and in 2010 in support of Shell’s 

summer seismic exploration activities. 

In 2012 these surveys were flown when 

it was not possible to fly the 

photographic transects out over the 

Burger well site due to weather or 

rescue craft availability. These surveys 

provided data on the distribution and 

abundance of marine mammals in 

nearshore waters of the Chukchi Sea. 

Shell plans to conduct these nearshore 

aerial surveys in the Chukchi Sea as 

opportunities unfold and surveys will 

be similar to those conducted during 

previous years except that no PSOs will 

be onboard the aircraft. As noted above, 

the first priority will be to conduct 

photographic surveys around the 

offshore exploration drilling activities, 

but nearshore surveys will be conducted 

whenever weather does not permit 

flying offshore. As in past years, surveys 

in the southern part of the nearshore 

survey area will depend on the end of 

the beluga hunt near Point Lay. In past 

years, Point Lay has requested that 

aerial surveys not be conducted until 

after the beluga hunt has ended and so 

the start of surveys has been delayed 

until mid-July. 

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. Gray 

whale and harbor porpoise are expected 

to be the most numerous cetacean 

species encountered during the 

proposed aerial survey; although harbor 

porpoise are abundant they are difficult 

to detect from aircraft because of their 

small size and brief surfacing. 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 and harbor porpoises 

because they are not reliably detectable 

during review of the collected images 

unless a third camera with a 50 mm or 

similar lens is deployed. 

Transects will be flown in a sawtoothed pattern between the shore and 

23 mi (37 km) offshore as well as along 

the coast from Point Barrow to Point 

Hope. This design will permit 

completion of the survey in one to two 

days and will provide representative 

coverage of the nearshore region. 

Sawtooth 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. 

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). 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) or 

1,500+ ft (454+ 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. 

The surveyed area will include waters 

where belugas are usually available to 

subsistence hunters. If large 

concentrations of belugas are 

encountered during the survey, the 

aircraft will climb to ∼10,000 ft (3,050 

m) altitude to avoid disturbing the 

cetaceans. If cetaceans are in offshore 

areas, the aircraft will climb high 

enough to include all cetaceans 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 

over flights 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. 

Monitoring Plan Peer Review 

The MMPA requires that monitoring 

plans be independently peer reviewed 

‘‘where the proposed activity may affect 

the availability of a species or stock for 

taking for subsistence uses’’ (16 U.S.C. 

1371(a)(5)(D)(ii)(III)). Regarding this 

requirement, NMFS’ implementing 

regulations state, ‘‘Upon receipt of a 

complete monitoring plan, and at its 

discretion, [NMFS] will either submit 

the plan to members of a peer review 

panel for review or within 60 days of 

receipt of the proposed monitoring plan, 

schedule a workshop to review the 

plan’’ (50 CFR 216.108(d)). 

NMFS has established an 

independent peer review panel to 

review Shell’s 4MP for Exploration 

Drilling of Selected Lease Areas in the 

Alaskan Chukchi Sea in 2015. The panel 

is scheduled to meet in early March 

2015, and will provide comments to 

NMFS shortly after they meet. After 

completion of the peer review, NMFS 

will consider all recommendations 

made by the panel, incorporate 

appropriate changes into the monitoring 

requirements of the IHA (if issued), and 

publish the panel’s findings and 

recommendations in the final IHA 

notice of issuance or denial document. 

Reporting Measures 

(1) SSV Report 

A report on the results of the acoustic 

verification measurements, including at 

a minimum the measured 190-, 180-, 

160-, and 120-dB (rms) radii of the 

drilling units, and support vessels, will 

be reported in the 90-day report. A 

report of the acoustic verification 

measurements of the ZVSP airgun array 

will be submitted within 120 hr after 

collection and analysis of those 

measurements once that part of the 

program is implemented. The ZVSP 

acoustic array report will specify the 

distances of the exclusion zones that 

were adopted for the ZVSP program. 

Prior to completion of these 

measurements, Shell will use the radii 

outlined in their application and 

proposed in Tables 2 and 3 of this 

document. 


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(2) Field Reports 

Throughout the exploration drilling 

program, the biologists will prepare a 

report each day or at such other interval 

as required summarizing the recent 

results of the monitoring program. The 

reports will summarize the species and 

numbers of marine mammals sighted. 

These reports will be provided to NMFS 

as required. 

(3) Technical Reports 

The results of Shell’s 2015 Chukchi 

Sea exploratory drilling monitoring 

program (i.e., vessel-based, aerial, and 

acoustic) will be presented in the ‘‘90- 

day’’ and Final Technical reports under 

the proposed IHA. Shell proposes that 

the Technical Reports will include: (1) 

Summaries of monitoring effort (e.g., 

total hours, total distances, and marine 

mammal distribution through study 

period, accounting for sea state and 

other factors affecting visibility and 

detectability of marine mammals); (2) 

analyses of the effects of various factors 

influencing detectability of marine 

mammals (e.g., sea state, number of 

observers, and fog/glare); (3) species 

composition, occurrence, and 

distribution of marine mammal 

sightings, including date, water depth, 

numbers, age/size/gender categories (if 

determinable), group sizes, and ice 

cover; (4) sighting rates of marine 

mammals during periods with and 

without drilling activities (and other 

variables that could affect detectability); 

(5) initial sighting distances versus 

drilling state; (6) closest point of 

approach versus drilling state; (7) 

observed behaviors and types of 

movements versus drilling state; (8) 

numbers of sightings/individuals seen 

versus drilling state; (9) distribution 

around the drilling units and support 

vessels versus drilling state; and (10) 

estimates of take by harassment. This 

information will be reported for both the 

vessel-based and aerial monitoring. 

Analysis of all acoustic data will be 

prioritized to address the primary 

questions, which are to: (a) Determine 

when, where, and what species of 

animals are acoustically detected on 

each AMAR ; (b) analyze data as a 

whole to determine offshore bowhead 

distributions as a function of time; (c) 

quantify spatial and temporal variability 

in the ambient noise; and (d) measure 

received levels of drilling unit activities. 

The detection data will be used to 

develop spatial and temporal animal 

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, time of season, environmental 

conditions, ambient noise, vessel type, 

operation conditions). 

The initial technical report is due to 

NMFS within 90 days of the completion 

of Shell’s Chukchi Sea exploration 

drilling program. The ‘‘90-day’’ report 

will be subject to review and comment 

by NMFS. Any recommendations made 

by NMFS must be addressed in the final 

report prior to acceptance by NMFS. 

(4) Notification of Injured or Dead 

Marine Mammals 

Shell will be required to notify NMFS’ 

Office of Protected Resources and 

NMFS’ Stranding Network of any 

sighting of an injured or dead marine 

mammal. Based on different 

circumstances, Shell may or may not be 

required to stop operations upon such a 

sighting. Shell will provide NMFS with 

the species or description of the 

animal(s), the condition of the animal(s) 

(including carcass condition if the 

animal is dead), location, time of first 

discovery, observed behaviors (if alive), 

and photo or video (if available). The 

specific language describing what Shell 

must do upon sighting a dead or injured 

marine mammal can be found in the 

‘‘Proposed Incidental Harassment 

Authorization’’ section later in this 

document. 

Estimated Take by Incidental 

Harassment 

Except with respect to certain 

activities not pertinent here, the MMPA 

defines ‘‘harassment’’ as: Any act of 

pursuit, torment, or annoyance which (i) 

has the potential to injure a marine 

mammal or marine mammal stock in the 

wild [Level A harassment]; or (ii) has 

the potential to disturb a marine 

mammal or marine mammal stock in the 

wild by causing disruption of behavioral 

patterns, including, but not limited to, 

migration, breathing, nursing, breeding, 

feeding, or sheltering [Level B 

harassment]. Only take by Level B 

behavioral harassment is anticipated as 

a result of the proposed drilling 

program. Noise propagation from the 

drilling units, associated support vessels 

(including during icebreaking if 

needed), and the airgun array are 

expected to harass, through behavioral 

disturbance, affected marine mammal 

species or stocks. Additional 

disturbance to marine mammals may 

result from aircraft overflights and 

visual disturbance of the drilling units 

or support vessels. However, based on 

the flight paths and altitude, impacts 

from aircraft operations are anticipated 

to be localized and minimal in nature. 

The full suite of potential impacts to 

marine mammals from various 

industrial activities was described in 

detail in the ‘‘Potential Effects of the 

Specified Activity on Marine Mammals’’ 

section found earlier in this document. 

The potential effects of sound from the 

proposed exploratory drilling program 

without any mitigation might include 

one or more of the following: tolerance; 

masking of natural sounds; behavioral 

disturbance; non-auditory physical 

effects; and, at least in theory, 

temporary or permanent hearing 

impairment (Richardson et al., 1995a). 

As discussed earlier in this document, 

NMFS estimates that Shell’s activities 

will most likely result in behavioral 

disturbance, including avoidance of the 

ensonified area or changes in speed, 

direction, and/or diving profile of one or 

more marine mammals. For reasons 

discussed previously in this document, 

hearing impairment (TTS and PTS) is 

highly unlikely to occur based on the 

fact that most of the equipment to be 

used during Shell’s proposed drilling 

program does not have source levels 

high enough to elicit even mild TTS 

and/or the fact that certain species are 

expected to avoid the ensonified areas 

close to the operations. Additionally, 

non-auditory physiological effects are 

anticipated to be minor, if any would 

occur at all. 

For continuous sounds, such as those 

produced by drilling operations and 

during icebreaking activities, NMFS 

uses a received level of 120-dB (rms) to 

indicate the onset of Level B 

harassment. For impulsive sounds, such 

as those produced by the airgun array 

during the ZVSP surveys, NMFS uses a 

received level of 160-dB (rms) to 

indicate the onset of Level B 

harassment. Shell provided calculations 

for the 120-dB isopleths produced by 

aggregate sources and then used those 

isopleths to estimate takes by 

harassment. Additionally, Shell 

provided calculations for the 160-dB 

isopleth produced by the airgun array 

and then used that isopleth to estimate 

takes by harassment. Shell provides a 

full description of the methodology 

used to estimate takes by harassment in 

its IHA application (see ADDRESSES), 

which is also provided in the following 

sections. 

Shell has requested authorization to 

take bowhead, gray, fin, humpback, 

minke, killer, and beluga whales, harbor 

porpoise, and ringed, spotted, bearded, 

and ribbon seals incidental to 

exploration drilling, ice management/

icebreaking, and ZVSP activities. 

Additionally, Shell provided exposure 

estimates and requested takes of 

narwhal. However, as stated previously 

in this document, sightings of this 

species are rare, and the likelihood of 

occurrence of narwhals in the proposed 


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drilling area is minimal. Therefore, 

NMFS is not proposing to authorize take 

of this species. 

Basis for Estimating ‘‘Take by 

Harassment’’ 

‘‘Take by Harassment’’ is described in 

this section and was calculated in 

Shell’s application by multiplying the 

expected densities of marine mammals 

that may occur near the exploratory 

drilling operations by the area of water 

likely to be exposed to continuous, nonpulse sounds ≥120 dB re 1 mPa (rms) 

during drilling unit operations or 

icebreaking activities and impulse 

sounds ≥160 dB re 1 mPa (rms) created 

by seismic airguns during ZVSP 

activities. NMFS evaluated and 

critiqued the methods provided in 

Shell’s application and determined that 

they were appropriate to conduct the 

requisite MMPA analyses. This section 

describes the estimated densities of 

marine mammals that may occur in the 

project area. The area of water that may 

be ensonified to the above sound levels 

is described further in the ‘‘Estimated 

Area Exposed to Sounds >120 dB or 

>160 dB re 1 mPa rms’’ subsection. 

Marine Mammal Density Estimates 

Marine mammal density estimates in 

the Chukchi Sea have been derived for 

two time periods, the summer period 

covering July and August, and the fall 

period including September and 

October. Animal densities encountered 

in the Chukchi Sea during both of these 

time periods will further depend on the 

habitat zone within which the activities 

are occurring: open water or ice margin. 

More ice is likely to be present in the 

area of activities during the July–August 

period, so summer ice-margin densities 

have been applied to 50% of the area 

that may be ensonified from drilling and 

ZVSP activities in those months. Open 

water densities in the summer were 

applied to the remaining 50 percent of 

the area. Less ice is likely to be present 

during the September–October period, 

so fall ice-margin densities have been 

applied to only 20% of the area that 

may be ensonified from drilling and 

ZVSP activities in those months. Fall 

open-water densities were applied to 

the remaining 80 percent of the area. 

Since ice management activities would 

only occur within ice-margin habitat, 

the entire area potentially ensonified by 

ice management activities has been 

multiplied by the ice-margin densities 

in both seasons. 

There is some uncertainty about the 

representativeness of the data and 

assumptions used in the calculations. 

To provide some allowance for the 

uncertainties, ‘‘maximum estimates’’ as 

well as ‘‘average estimates’’ of the 

numbers of marine mammals potentially 

affected have been derived. For a few 

marine mammal species, several density 

estimates were available. In those cases, 

the mean and maximum estimates were 

determined from the reported densities 

or survey data. In other cases only one 

or no applicable estimate was available, 

so correction factors were used to arrive 

at ‘‘average’’ and ‘‘maximum’’ estimates. 

These are described in detail in the 

following subsections. 

Detectability bias, quantified in part 

by f(0), is associated with diminishing 

sightability with increasing lateral 

distance from the survey trackline. 

Availability bias, g(0), refers to the fact 

that there is <100% probability of 

sighting an animal that is present along 

the survey trackline. Some sources 

below included these correction factors 

in the reported densities (e.g. ringed 

seals in Bengtson et al. 2005) and the 

best available correction factors were 

applied to reported results when they 

had not already been included (e.g. 

Moore et al. 2000). 

(1) Cetaceans 

Eight species of cetaceans are known 

to occur in the activity area. Three of the 

nine species, bowhead, fin, and 

humpback whales, are listed as 

‘‘endangered’’ under the ESA. 

(a) Beluga Whales 

Summer densities of beluga whales in 

offshore waters are expected to be low, 

with somewhat higher densities in icemargin and nearshore areas. Past aerial 

surveys have recorded few belugas in 

the offshore Chukchi Sea during the 

summer months (Moore et al. 2000). 

More recent aerial surveys of the 

Chukchi Sea from 2008–2012 flown by 

the NMML as part of the COMIDA 

project, now part of the Aerial Surveys 

of Arctic Marine Mammals (ASAMM) 

project, reported 10 beluga sightings (22 

individuals) in offshore waters during 

22,154 km of on-transect effort. Larger 

groups of beluga whales were recorded 

in nearshore areas, especially in June 

and July during the spring migration 

(Clarke et al. 2012, 2013). Additionally, 

only one beluga sighting was recorded 

during >80,000 km of visual effort 

during good visibility conditions from 

industry vessels operating in the 

Chukchi Sea in September–October of 

2006–2010 (Hartin et al. 2013). If 

belugas are present during the summer, 

they are more likely to occur in or near 

the ice edge or close to shore during 

their northward migration. Effort and 

sightings reported by Clarke et al. (2012, 

2013) were used to calculate the average 

open-water density estimate. The mean 

group size of the sightings was 2.2. A 

f(0) value of 2.841 and g(0) value of 0.58 

from Harwood et al. (1996) were also 

used in the density calculation resulting 

in an average open-water density of 

0.0024 belugas/km2 (Table 6–1 of 

Shell’s IHA application). The highest 

density from the reported survey 

periods (0.0049 belugas/km2, in 2012) 

has been used as the maximum density 

that may occur in open-water habitat 

(Table 6–1 in Shell’s IHA application). 

Specific data on the relative abundance 

of beluga in open-water versus icemargin habitat during the summer in the 

Chukchi Sea is not available. However, 

belugas are commonly associated with 

ice, so an inflation factor of four was 

used to estimate the ice-margin 

densities from the open-water densities. 

Very low densities observed from 

vessels operating in the Chukchi Sea 

during non-seismic periods and 

locations in July–August of 2006–2010 

(0.0–0.0003/mi2, 0.0–0.0001/km2; 

Hartin et al. 2013), also suggest the 

number of beluga whales likely to be 

present near the planned activities will 

not be large. 

In the fall, beluga whale densities 

offshore in the Chukchi Sea are 

expected to be somewhat higher than in 

the summer because individuals of the 

eastern Chukchi Sea stock and the 

Beaufort Sea stock will be migrating 

south to their wintering grounds in the 

Bering Sea (Allen and Angliss 2012). 

Densities derived from survey results in 

the northern Chukchi Sea in Clarke and 

Ferguson (in prep, cited in Shell 2014) 

and Clarke et al. (2012, 2013) were used 

as the average density for open-water 

season estimates (Table 6–2 in Shell’s 

IHA application). Clarke and Ferguson 

(in prep, cited in Shell 2014) and Clarke 

et al. (2012, 2013) reported 17 beluga 

sightings (28 individuals) during 22,255 

km of on-transect effort in water depths 

36–50 m during the months of July 

through September. The mean group 

size of those three sightings was 1.6. A 

f(0) value of 2.841 and a g(0) value of 

0.58 from Harwood et al. (1996) were 

used to calculate the average open-water 

density of 0.0031 belugas/km2 (Table 6– 

2 in Shell IHA application). The highest 

density from the reported periods 

(0.0053 belugas/km2, in 2012) was again 

used as the maximum density that may 

occur in open-water habitat. Moore et al. 

(2000) reported lower than expected 

beluga sighting rates in open-water 

during fall surveys in the Beaufort and 

Chukchi seas, so an inflation value of 

four was used to estimate the ice-margin 

densities from the open-water densities. 

Based on the few beluga sightings from 

vessels operating in the Chukchi Sea 


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during non-seismic periods and 

locations in September–November of 

2006–2010 (Hartin et al. 2013), the 

relatively low densities shown in Table 

6–2 in Shell’s IHA application are 

consistent with what is likely to be 

observed form vessels during the 

planned exploration drilling activities. 

(b) Bowhead Whales 

By July, most bowhead whales are 

northeast of the Chukchi Sea, within or 

migrating toward their summer feeding 

grounds in the eastern Beaufort Sea. No 

bowheads were reported during 10,686 

km of on-transect effort in the Chukchi 

Sea by Moore et al. (2000). Bowhead 

whales were also rarely sighted in JulyAugust of 2006–2010 during aerial 

surveys of the Chukchi Sea coast 

(Thomas et al. 2011). This is consistent 

with movements of tagged whales 

(ADFG 2010), all of which moved 

through the Chukchi Sea by early May 

2009, and tended to travel relatively 

close to shore, especially in the northern 

Chukchi Sea. 

The estimate of the July–August openwater bowhead whale density in the 

Chukchi Sea was calculated from the 

three bowhead sightings (3 individuals) 

and 22,154 km of survey effort in waters 

36–50 m deep in the Chukchi Sea 

during July–August reported in Clarke 

and Ferguson (in prep, cited in Shell 

2014) and Clarke et al. (2012, 2013). The 

mean group size from those sightings 

was 1. The group size value, along with 

a f(0) value of 2 and a g(0) value of 0.07, 

both from Thomas et al. (2002) were 

used to estimate a summer density of 

0.0019 bowheads/km2 (Table 6–1 in 

Shell’s IHA application). The two 

sightings recorded during 4,209 km of 

survey effort in 2011 (Clarke et al. 2012) 

produced the highest annual bowhead 

density during July–August (0.0068 

bowheads/km2) which was used as the 

maximum open-water density (Table 6– 

1 in Shell’s IHA application). Bowheads 

are not expected to be encountered in 

higher densities near ice in the summer 

(Moore et al. 2000), so the same density 

estimates have been used for open-water 

and ice-margin habitats. Densities from 

vessel based surveys in the Chukchi Sea 

during non-seismic periods and 

locations in July–August of 2006–2010 

(Hartin et al. 2013) ranged from 0.0002– 

0.0008/km2 with a maximum 95% CI of 

0.0085/km2. This suggests the densities 

used in the calculations and shown in 

Table 6–1 in Shell’s IHA application are 

similar to what are likely to be observed 

from vessels near the area of planned 

exploration drilling activities. 

During the fall, bowhead whales that 

summered in the Beaufort Sea and 

Amundsen Gulf migrate west and south 

to their wintering grounds in the Bering 

Sea, making it more likely those 

bowheads will be encountered in the 

Chukchi Sea at this time of year. Moore 

et al. (2000) reported 34 bowhead 

sightings during 44,354 km of ontransect survey effort in the Chukchi Sea 

during September–October. Thomas et 

al. (2011) also reported increased 

sightings on coastal surveys of the 

Chukchi Sea during October and 

November of 2006–2010. GPS tagging of 

bowheads appear to show that migration 

routes through the Chukchi Sea are 

more variable than through the Beaufort 

Sea (Quakenbush et al. 2010). Some of 

the routes taken by bowheads remain 

well north of the planned drilling 

activities while others have passed near 

to or through the area. Kernel densities 

estimated from GPS locations of whales 

suggest that bowheads do not spend 

much time (e.g. feeding or resting) in the 

north-central Chukchi Sea near the area 

of planned activities (Quakenbush et al. 

2010). However, tagged whales did 

spend a considerable amount of time in 

the north-central Chukchi Sea in 2012, 

despite ongoing industrial activities in 

the region (ADFG 2012). Clarke and 

Ferguson (in prep, cited in Shell 2014) 

and Clarke et al. (2012, 2013) reported 

72 sightings (86 individuals) during 

22,255 km of on-transect aerial survey 

effort in waters 36–50 m deep in 2008– 

2012, the majority of which (53 

sightings) were recorded in 2012. The 

mean group size of the 72 sightings was 

1.2. The same f(0) and g(0) values that 

were used for the summer estimates 

above were used for the fall estimates 

resulting in an average September– 

October estimate of 0.0552 bowheads/

km2 (Table 6–2 in Shell’s IHA 

application). The highest density form 

the survey periods (0.1320 bowheads/

km2; in 2012) was used as the maximum 

open-water density during the fall 

period. Moore et al. (2000) found that 

bowheads were detected more often 

than expected in association with ice in 

the Chukchi Sea in September–October, 

so the ice-margin densities that are used 

are twice the open-water densities. 

Densities from vessel based surveys in 

the Chukchi Sea during non-seismic 

periods and locations in September– 

November of 2006–2010 (Hartin et al. 

2013) ranged from 0.0003 to 0.0052/km2

with a maximum 95 percent CI of 0.051/ 

km2. This suggests the densities used in 

the calculations and shown in Table 6– 

2 in Shell’s IHA application are 

somewhat higher than are likely to be 

observed from vessels near the area of 

planned exploration drilling activities. 

(c) Gray Whales 

Gray whale densities are expected to 

be much higher in the summer months 

than during the fall. Moore et al. (2000) 

found the distribution of gray whales in 

the planned operational area was 

scattered and limited to nearshore areas 

where most whales were observed in 

water less than 35 m deep. Thomas et 

al. (2011) also reported substantial 

declines in the sighting rates of gray 

whales in the fall. The average openwater summer density (Table 6–1 in 

Shell’s IHA application) was calculated 

from 2008–2012 aerial survey effort and 

sightings in Clarke and Ferguson (in 

prep, cited in Shell 2014) and Clarke et 

al. (2012, 2013) for water depths 36–50 

m including 98 sightings (137 

individuals) during 22,154 km of ontransect effort. The average group size of 

those sightings was 1.4. Correction 

factors f(0) = 2.49 (Forney and Barlow 

1998) and g(0) = 0.30 (Forney and 

Barlow 1998, Mallonee 1991) were used 

to calculate and average open-water 

density of 0.0253 gray whales/km2 

(Table 6–1 in Shell’s IHA application). 

The highest density from the survey 

periods reported in Clarke and Ferguson 

(in prep, cited in Shell 2014) and Clarke 

et al. (2012, 2013) was 0.0268 gray 

whales/km2 in 2012 and this was used 

as the maximum open-water density. 

Gray whales are not commonly 

associated with sea ice, but may be 

present near it, so the same densities 

were used for ice-margin habitat as were 

derived for open-water habitat during 

both seasons. Densities from vessel 

based surveys in the Chukchi Sea 

during non-seismic periods and 

locations in July–August of 2006–2010 

(Hartin et al. 2013) ranged from 0.0008/ 

km2 to 0.0085/km2 with a maximum 95 

percent CI of 0.0353 km2. 

In the fall, gray whales may be 

dispersed more widely through the 

northern Chukchi Sea (Moore et al. 

2000), but overall densities are likely to 

be decreasing as the whales begin 

migrating south. A density calculated 

from effort and sightings (46 sightings 

[64 individuals] during 22,255 km of ontransect effort) in water 36–50 m deep 

during September–October reported by 

Clarke and Ferguson (in prep, cited in 

Shell 2014) and Clarke et al. (2012, 

2013) was used as the average estimate 

for the Chukchi Sea during the fall 

period (0.0118 gray whales/km2; Table 

6–2 in Shell’s IHA application). The 

corresponding group size value of 1.39, 

along with the same f(0) and g(0) values 

described above were used in the 

calculation. The maximum density from 

the survey periods (0.0248 gray whales/ 

km2) was reported in 2011 (Clarke et al. 


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2012) and used as the maximum fall 

open-water density (Table 6–2 in Shell’s 

IHA application). Densities from vessel 

based surveys in the Chukchi Sea 

during non-seismic periods and 

locations in September–November of 

2006–2010 (Hartin et al. 2013) ranged 

from 0.0/km2 to 0.0044/km2 with a 

maximum 95% CI of 0.0335 km2. 

(d) Harbor Porpoises 

Harbor Porpoise densities were 

estimated from industry data collected 

during 2006–2010 activities in the 

Chukchi Sea. Prior to 2006, no reliable 

estimates were available for the Chukchi 

Sea and harbor porpoise presence was 

expected to be very low and limited to 

nearshore regions. Observers on 

industry vessels in 2006–2010, however, 

recorded sightings throughout the 

Chukchi Sea during the summer and 

early fall months. Density estimates 

from 2006–2010 observations during 

non-seismic periods and locations in 

July-August ranged from 0.0013/km2 to 

0.0029/km2 with a maximum 95% CI of 

0.0137/km2 (Hartin et al. 2013). The 

average density from the summer season 

of those three years (0.0022/km2) was 

used as the average open-water density 

estimate while the high value (0.0029/ 

km2) was used as the maximum 

estimate (Table 6–1 in Shell’s IHA 

application). Harbor porpoise are not 

expected to be present in higher 

numbers near ice, so the open-water 

densities were used for ice-margin 

habitat in both seasons. Harbor porpoise 

densities recorded during industry 

operations in the fall months of 2006– 

2010 were slightly lower and ranged 

from 0.0/km2 to 0.0044/km2 with a 

maximum 95% CI of 0.0275/km2. The 

average of those years (0.0021/km2) was 

again used as the average density 

estimate and the high value (0.0044/

km2) was used as the maximum 

estimate (Table 6–2 in Shell’s IHA 

application). 

(e) Other Whales 

The remaining five cetacean species 

that could be encountered in the 

Chukchi Sea during Shell’s planned 

exploration drilling program include the 

humpback whale, killer whale, minke 

whale, and fin whale. Although there is 

evidence of the occasional occurrence of 

these five cetacean species in the 

Chukchi Sea, it is unlikely that more 

than a few individuals will be 

encountered during the planned 

exploration drilling program and 

therefore minimum densities have been 

assigned to these species (Tables 6–1 

and 6–2 in Shell’s IHA application). 

Clarke et al. (2011, 2013) and Hartin et 

al. (2013) reported humpback whale 

sightings; George and Suydam (1998) 

reported killer whales; Brueggeman et 

al. (1990), Hartin et al. (2013), Clarke et 

al. (2012, 2013), and Reider et al. (2013) 

reported minke whales; and Clarke et al. 

(2011, 2013) and Hartin et al. (2013) 

reported fin whales. With regard to 

humpback and fin whales, NMFS (2013) 

recently concluded these whales occur 

in very low numbers in the project area, 

but may be regular visitors. 

Of these uncommon cetacean species, 

minke whale has the potential to be the 

most common based on recent industry 

surveys. Reider et al. (2013) reported 13 

minke whale sightings in the Chukchi 

Sea in 2013 during Shell’s marine 

survey program. All but one minke 

whale sighting in 2013, however, were 

observed in nearshore areas despite only 

minimal monitoring effort in nearshore 

areas compared to more offshore 

locations near the Burger prospect 

(Reider et al. 2013). 

(2) Pinnipeds 

Three species of pinnipeds under 

NMFS jurisdiction are likely to be 

encountered in the Chukchi Sea during 

Shell’s planned exploration drilling 

program: Ringed seal, bearded seal, and 

spotted seal. Ringed and bearded seals 

are associated with both the ice margin 

and the nearshore area. The ice margin 

is considered preferred habitat (as 

compared to the nearshore areas) for 

ringed and bearded seals during most 

seasons. Spotted seals are often 

considered to be predominantly a 

coastal species except in the spring 

when they may be found in the southern 

margin of the retreating sea ice. 

However, satellite tagging has shown 

that they sometimes undertake long 

excursions into offshore waters during 

summer (Lowry et al. 1994, 1998). 

Ribbon seals have been reported in very 

small numbers within the Chukchi Sea 

by observers on industry vessels 

(Patterson et al. 2007, Hartin et al. 

2013). 

(a) Ringed and Bearded Seals 

Ringed seal and bearded seals 

‘‘average’’ and ‘‘maximum’’ summer icemargin densities were available in 

Bengtson et al. (2005) from spring 

surveys in the offshore pack ice zone 

(zone 12P) of the northern Chukchi Sea. 

However, corrections for bearded seal 

availability, g(0), based on haulout and 

diving patterns were not available. 

Densities of ringed and bearded seals in 

open water are expected to be somewhat 

lower in the summer when preferred 

pack ice habitat may still be present in 

the Chukchi Sea. Average and 

maximum open-water densities have 

been estimated as 3/4 of the ice margin 

densities during both seasons for both 

species. The fall density of ringed seals 

in the offshore Chukchi Sea has been 

estimated as 2/3 the summer densities 

because ringed seals begin to reoccupy 

nearshore fast ice areas as it forms in the 

fall. Bearded seals may also begin to 

leave the Chukchi Sea in the fall, but 

less is known about their movement 

patterns so fall densities were left 

unchanged from summer densities. For 

comparison, the ringed seal density 

estimates calculated from data collected 

during summer 2006–2010 industry 

operations ranged from 0.0138/km2 to 

0.0464/km2 with a maximum 95 percent 

CI of 0.1581/km2 (Hartin et al. 2013). 

(b) Spotted Seals 

Little information on spotted seal 

densities in offshore areas of the 

Chukchi Sea is available. Spotted seal 

densities in the summer were estimated 

by multiplying the ringed seal densities 

by 0.02. This was based on the ratio of 

the estimated Chukchi populations of 

the two species. Chukchi Sea spotted 

seal abundance was estimated by 

assuming that 8% of the Alaskan 

population of spotted seals is present in 

the Chukchi Sea during the summer and 

fall (Rugh et al. 1997), the Alaskan 

population of spotted seals is 59,214 

(Allen and Angliss 2012), and that the 

population of ringed seals in the 

Alaskan Chukchi Sea is ∼208,000 

animals (Bengtson et al. 2005). In the 

fall, spotted seals show increased use of 

coastal haulouts so densities were 

estimated to be 2/3 of the summer 

densities. 

(c) Ribbon Seals 

Four ribbon seal sightings were 

reported during industry vessel 

operations in the Chukchi Sea in 2006– 

2010 (Hartin et al. 2013). The resulting 

density estimate of 0.0007/km2 was 

used as the average density and 4 times 

that was used as the maximum for both 

seasons and habitat zones. 

Individual Sound Sources and Level B 

Radii 

The assumed start date of Shell’s 

exploration drilling program in the 

Chukchi Sea using the drilling units 

Discoverer and Polar Pioneer with 

associated support vessels is 4 July. 

Shell may conduct exploration drilling 

activities at up to four drill sites at the 

prospect known as Burger. Drilling 

activities are expected to be conducted 

through approximately 31 October 2015. 

Previous IHA applications for offshore 

Arctic exploration programs estimated 

areas potentially ensonified to ≥120 or 

≥160 dB re 1 mPa rms independently for 

each continuous or pulsed sound 


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source, respectively (e.g., drilling, 

ZVSP, etc.). The primary method used 

in this IHA application for estimating 

areas ensonified to continuous sound 

levels ≥120 dB re 1 mPa rms by drillingrelated activities involved sound 

propagation modeling of a variety of 

scenarios consisting of multiple, 

concurrently-operating sound sources. 

These ‘‘activity scenarios’’ consider 

additive acoustic effects from multiple 

sound sources at nearby locations, and 

more closely capture the nature of a 

dynamic acoustic environment where 

numerous activities are taking place 

simultaneously. The area ensonified to 

≥160 dB re 1 mPa rms from ZVSP, a 

pulsed sound source, was treated 

independently from the activity 

scenarios for continuous sound sources. 

The continuous sound sources used 

for sound propagation modeling of 

activity scenarios included (1) drilling 

unit and drilling sounds, (2) supply and 

drilling support vessels using DP when 

tending to a drilling unit, (3) MLC 

construction, (4) anchor handling in 

support of mooring a drilling unit, and 

(5) ice management activities. The 

information used to generate sound 

level characteristics for each continuous 

sound source is summarized below to 

provide background on the model 

inputs. A ‘‘safety factor’’ of 1.3 dB re 1 

mPa rms was added to the source level 

for each sound source prior to modeling 

activity scenarios to account for 

variability across the project area 

associated with received levels at 

different depths, geoacoustical 

properties, and sound-speed profiles. 

The addition of the 1.3 dB re 1 mPa rms 

safety factor to source levels resulted in 

an approximate 20 percent increase in 

the distance to the 120 dB re 1 mPa rms 

threshold for each continuous source. 

Table 2 summarizes the 120 dB re 1 

mPa rms radii for individual sound 

sources, both the ‘‘original’’ radii as 

measured in the field, and the 

‘‘adjusted’’ values that were calculated 

by adding the ‘‘safety factor’’ of 1.3 dB 

re 1 mPa rms to each source. The 

adjusted source levels were then used in 

sound propagation modeling of activity 

scenarios to estimate ensonified areas 

and associated marine mammal 

exposure estimates. Additional details 

for each of the continuous sound 

sources presented in Table 2 are 

discussed below. 

The pulsed sound sources used for 

sound propagation modeling of activity 

scenarios consisted of two small airgun 

arrays proposed for ZVSP activities. All 

possible array configurations and 

operating depths were modeled to 

identify the arrangement with the 

greatest sound propagation 

characteristics. The resulting ≥160 dB re 

1 mPa rms radius was multiplied by 1.5 

as a conservative measure prior to 

estimating exposed areas, which is 

discussed in greater detail below. 

TABLE 2—MEASURED AND ADJUSTED 120 dB re 1 μPa RADII FOR INDIVIDUAL, CONTINUOUS SOUND SOURCES

Activity/continuous sound source 

Radii of 120 dB re 1 μPa (rms) 

isopleth 

(meters) 

Original 

measurement 

With 1.3 dB 

correction 

factor 

Drilling at 1 site ............................................................................................................................................ 1,500 1,800 

Vessel in DP ................................................................................................................................................ 4,500 5,500 

Mudline cellar construction at 1 site ............................................................................................................ 8,200 9,300 

Anchor handling at 1 site (assumed to be 2 vessels) ................................................................................. 19,000 22,000 

Single vessel ice management .................................................................................................................... 9,600 11,000 

Two sound sources have been 

proposed by Shell for the ZVSP surveys 

in 2015. The first is a small airgun array 

that consists of three 150 in3 (2,458 

cm3) airguns for a total volume of 450 

in3 (7,374 cm3). The second ZVSP 

sound source consists of two 250 in3

(4,097 cm3) airguns with a total volume 

of 500 in3 (8,194 cm3). Sound footprints 

for each of the two proposed ZVSP 

airgun array configurations were 

estimated using JASCO Applied 

Sciences’ MONM. The model results 

were maximized over all water depths 

from 9.8 to 23 ft (3 to 7 m) to yield 

precautionary sound level isopleths as a 

function of range and direction from the 

source. The 450 in3 airgun array at a 

source depth of 7 m yielded the 

maximum ranges to the ≥190, ≥180, and 

≥160 dB re 1 mPa rms isopleths. 

There are two reasons that the radii 

for the 450 in3 airgun array are larger 

than those for the 500 in3 array. First, 

the sound energy does not scale linearly 

with the airgun volume, rather it is 

proportional to the cube root of the 

volume. Thus, the total sound energy 

from three airguns is larger than the 

total energy from two airguns, even 

though the total volume is smaller. 

Second, larger volume airguns emit 

more low-frequency sound energy than 

smaller volume airguns, and lowfrequency airgun sound energy is 

strongly attenuated by interaction with 

the surface reflection. Thus, the sound 

energy for the larger-volume array 

experiences more reduction and results 

in shorter sound threshold radii. 

The estimated 95th percentile 

distances to the following thresholds for 

the 450 in3 airgun array were: ≥190 dB 

re 1 mPa rms = 170 m, ≥180 dB re 1 mPa 

rms = 920 m, and ≥160 dB re 1 mPa rms 

= 7,970 m. The ≥160 dB re 1 mPa rms 

distance was multiplied by 1.5 for a 

distance of 11,960 m. This radius was 

used for estimating areas ensonified by 

pulsed sounds to ≥160 dB re 1 mPa rms 

during a single ZVSP survey. ZVSP 

surveys may occur at up to two different 

drill sites during Shell’s planned 2015 

exploration drilling program in the 

Chukchi Sea. 

As noted above, previous IHA 

applications for Arctic offshore 

exploration programs estimated areas 

potentially ensonified to continuous 

sound levels ≥120 dB re 1 mPa rms 

independently for each sound source. 

This method was appropriate for 

assessing a small number of continuous 

sound sources that did not consistently 

overlap in time and space. However, 

many of the continuous sound sources 

described above will operate 

concurrently at one or more nearby 

locations in 2015 during Shell’s planned 

exploration drilling program in the 

Chukchi Sea. It is therefore appropriate 

to consider the concurrent operation of 

numerous sound sources and the 

additive acoustic effects from combined 

sound fields when estimating areas 

potentially exposed to levels ≥120 dB re 

1 mPa rms. 

A range of potential ‘‘activity 

scenarios’’ was derived from a realistic 

operational timeline by considering the 


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various combinations of different 

continuous sound sources that may 

operate at the same time at one or more 

locations. The total number of possible 

activity combinations from all sources at 

up to four different drill sites would not 

be practical to assess or present in a 

meaningful way. Additionally, 

combinations such as concurrent 

drilling and anchor handling in close 

proximity do not add meaning to the 

analysis given the negligible 

contribution of drilling sounds to the 

total area ensonified by such a scenario. 

For these reasons, various combinations 

of similar activities were grouped into 

representative activity scenarios shown 

in Table 3. Ensonified areas for these 

representative activity scenarios were 

estimated through sound propagation 

modeling. Activity scenarios were 

modeled for different drill site 

combinations and, as a conservative 

measure, the locations corresponding to 

the largest ensonified area were chosen 

to represent the given activity scenario. 

In other words, by binning all potential 

scenarios into the most conservative 

representative scenario, the largest 

possible ensonified areas for all 

activities were identified for analysis. A 

total of nine representative activity 

scenarios were modeled to estimate 

areas exposed to continuous sounds 

≥120 dB re 1 mPa rms for Shell’s 

planned 2015 exploration drilling 

program in the Chukchi Sea (Table 3). 

A tenth scenario was included for the 

ZVSP activities. 

TABLE 3—SOUND PROPAGATION MODELING RESULTS OF REPRESENTATIVE DRILLING RELATED ACTIVITY SCENARIOS AND

ESTIMATES OF THE TOTAL AREA POTENTIALLY ENSONIFIED ABOVE THRESHOLD LEVELS AT THE BURGER PROSPECT

IN THE CHUKCHI SEA, ALASKA, DURING SHELL’S PROPOSED 2015 EXPLORATION DRILLING PROGRAM

Activity scenario description Threshold level 

(dB re 1 μPa rms) 

Area potentially ensonified 

(km2) 

Summer Fall 

Drilling at 1 site .......................................................................................................... 120 10.2 10.2 

Drilling and DP vessel at 1 site ................................................................................. 120 111.8 111.8 

Drilling and DP vessel (1 site) + drilling and DP vessel (2nd site) ........................... 120 295.5 295.5 

Mudline cellar construction at 2 different sites .......................................................... 120 575.5 575.5 

Anchor handling at 1 site ........................................................................................... 120 1,534.9 1,534.9 

Drilling and DP vessel at 1 site + anchor handling at 2nd site ................................. 120 1,759.2 1,759.2 

Mudline cellar construction at 2 different sites + anchor handling at 3rd site .......... 120 2,046.3 2,046.3 

Two-vessel ice management ..................................................................................... 120 937.4 937.4 

Four-vessel ice management .................................................................................... 120 1,926.0 1,926.0 

ZVSP at 2 different sites ........................................................................................... 160 0.0 898.0 

Potential Number of ‘‘Takes by 

Harassment’’ 

This section provides estimates of the 

number of individuals potentially 

exposed to continuous sound levels 

≥120 dB re 1 mPa rms from exploration 

drilling related activities and pulsed 

sound levels ≥160 dB re 1 mPa rms by 

ZVSP activities. The estimates are based 

on a consideration of the number of 

marine mammals that might be affected 

by operations in the Chukchi Sea during 

2015 and the anticipated area exposed 

to those sound levels. 

To account for different densities in 

different habitats, Shell has assumed 

that more ice is likely to be present in 

the area of operations during the July– 

August period than in the September– 

October period, so summer ice-margin 

densities have been applied to 50% of 

the area that may be exposed to sounds 

from exploration drilling activities in 

those months. Open water densities in 

the summer were applied to the 

remaining 50% of the area. 

Less ice is likely to be present during 

the September–October period than in 

the July–August period, so fall icemargin densities have been applied to 

only 20% of the area that may be 

exposed to sounds from exploration 

drilling activities in those months. Fall 

open-water densities were applied to 

the remaining 80% of the area. Since 

icebreaking activities would only occur 

within ice-margin habitat, the entire 

area potentially ensonified by 

icebreaking activities has been 

multiplied by the ice-margin densities 

in both seasons. 

Estimates of the numbers of marine 

mammals potentially exposed to 

continuous sounds ≥120 dB re 1 mPa 

rms or pulsed sounds ≥160 dB re 1 mPa 

rms are based on assumptions that 

include upward scaling of source levels 

for all sound sources, no avoidance of 

activities/sounds by individual marine 

mammals, and 100% turnover of 

individuals in ensonified areas every 24 

hours (except for bowhead whales, as 

discussed below). NMFS considers that 

these assumptions are overly 

conservative, especially for nonmigratory species/periods and for 

cetaceans in particular, which are 

known to avoid anthropogenic activities 

and associated sounds at varying 

distances depending on the context in 

which activities and sounds are 

encountered (Koski and Miller 2009; 

Moore 2000; Moore et al. 2000; Treacy 

et al. 2006). Although we recognize 

these assumptions may be overly 

conservative, it is difficult to scale 

variables in a more precise fashion until 

recent evidence can be incorporated 

into newer estimation methods. 

The following sections present a range 

of exposure estimates for bowhead 

whales and ringed seals. Estimates were 

generated based on an evaluation of the 

best available science and a 

consideration of the assumptions 

surrounding avoidance behavior and the 

frequency of turnover. In addition to 

demonstrating the sensitivity of 

exposure estimates to variable 

assumptions, the wide range of 

estimates is more informative for 

assessing negligible impact compared to 

a single estimated value with a high 

degree of uncertainty. 

It is difficult to determine an 

appropriate, precise average turnover 

time for a population of animals in a 

particular area of the Chukchi Sea. 

Reasons for this include differences in 

residency time for migratory and nonmigratory species, changes in 

distribution of food and other factors 

such as behavior that influence animal 

movement, variation among individuals 

of the same species, etc. Complete 

turnover of individual bowhead whales 

in the project area each 24-hour period 

may occur during fall migration when 

bowheads are traveling through the area. 

Even during this fall period, bowheads 

often move in pulses with one to several 

days between major pulses of whales 

(Miller et al. 2002). Gaps between 

groups of whales can probably be 


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accounted for partially by bowhead 

whales stopping to feed 

opportunistically when food is 

encountered. The extent of feeding by 

bowhead whales during fall migration 

across the Beaufort and Chukchi Seas 

varies greatly from year to year based on 

the location and abundance of prey 

(Shelden and Mocklin 2013). For 

example, if a turnover rate of 48 hours 

to account for intermittent periods of 

migrating and feeding individuals is 

assumed, then the number of bowhead 

whale being exposed would be reduced 

accordingly by 50%. Due to changes in 

the turnover rate across time, a 

conservative turnover rate of 24 hours 

has been selected to estimate the 

number of bowhead whales exposed. 

During the summer, relatively few 

bowhead or beluga whales are present 

in the Chukchi Sea and in most cases, 

given that the operations area is not 

known to be a critical feeding area (Citta 

et al. 2014; Allen and Angliss 2014), 

whales would be likely to simply avoid 

the area of operations (Schick and 

Urban 2000; Richardson et al. 1995a). 

Similarly, during migration many 

whales would likely travel around the 

area (i.e., avoid it) as it is not known to 

be important habitat for either 

bowheads or belugas during any portion 

of the year (Citta et al. 2014; Allen and 

Angliss 2014). There is a large body of 

evidence indicating that bowhead 

whales avoid anthropogenic activities 

and associated underwater sounds 

depending on the context in which 

these activities are encountered (LGL et 

al. 2014; Koski and Miller 2009; Moore 

2000; Moore et al. 2000; Treacy et al. 

2006). Increasing evidence suggests that 

proximity to an activity or sound 

source, coupled with an individual’s 

behavioral state (e.g., feeding vs 

traveling) among other contextual 

variables, as opposed to received sound 

level alone, strongly influences the 

degree to which an individual whale 

demonstrates aversion or other 

behaviors (reviewed in Richardson et al. 

1995b; Gordon et al. 2004; Koski and 

Miller 2009). 

Several historical studies provide 

valuable information on the distribution 

and behavior of bowhead whales 

relative to drilling activities in the 

Alaskan Arctic offshore. One is a 1986 

study by Shell at Hammerhead and 

Corona prospects (Davis 1987) and 

another is an analysis by Schick and 

Urban (2000) of 1993 aerial survey data 

collected by Coastal Offshore and 

Pacific Corporation. Both studies 

suggest that few whales approached 

within ∼18 km of an offshore drilling 

operation in the Beaufort Sea. Davis 

(1987) reported that the surfacing and 

respiration variables that are often used 

as indicators of behavioral disturbance 

seemed normal when whales were >18.5 

km from the active drill site and as they 

circumnavigated the drilling operation. 

The Schick and Urban (2000) study 

found whales as close as 18.5–20.3 km 

in all directions around the active 

operation, suggesting that whales that 

had diverted returned to their normal 

migration routes shortly after passing 

the operation. 

If bowhead whales avoid drilling and 

related support activities at distances of 

approximately 20 km in 2015, as was 

noted consistently by Davis (1987) and 

Schick and Urban (2002), this would 

preclude exposure of the vast majority 

of individuals to continuous sounds 

≥120 dB re 1 mPa rms or pulsed sounds 

≥160 dB re 1 mPa rms. The largest 

ensonified areas during Shell’s 2012 

exploration drilling program were 

produced by mudline cellar 

construction, ice management, and 

anchor handling (JASCO Applied 

Sciences and Greeneridge Sciences 

2014). Only anchor handling is expected 

to result in the lateral propagation of 

continuous sound levels ≥120 dB re 1 

mPa rms to distances of 20 km or greater 

from the source. 

By assuming half of the individual 

bowhead whales would avoid areas 

with sounds at or above Level B 

thresholds, the exposure estimate would 

be reduced accordingly by 50% even if 

100% turnover of migrating whales was 

still assumed to take place every 24 

hours. Taking into consideration what is 

known from studies documenting 

temporary diversion around drilling 

activities, and conservative assumptions 

with regards to turnover rates, NMFS 

considers the conservative estimate 

associated with a 24 hour turnover and 

50% avoidance to be the most 

reasonable estimate of individual 

exposures. 

Table 4 presents the exposure 

estimates for Shell’s proposed 2015 

exploration drilling program in the 

Chukchi Sea. The table also summarizes 

abundance estimates for each species 

and the corresponding percent of each 

population that may be exposed to 

continuous sounds ≥120 dB re 1 mPa 

rms or pulsed sounds ≥160 dB re 1 mPa 

rms. With the exception of the exposure 

estimate for bowhead whales described 

above, estimates for all other species 

assumed 100% daily turnover and no 

avoidance of activities or ensonified 

areas. 

TABLE 4—THE TOTAL NUMBER OF POTENTIAL EXPOSURES OF MARINE MAMMALS TO SOUND LEVELS ≥120 dB re 1 μPa 

rms OR ≥160 dB re 1 μPa rms DURING THE SHELL’S PROPOSED DRILLING ACTIVITIES IN THE CHUKCHI SEA, ALASKA, 2015 

[Estimates are also shown as a percent of each population] 

Species Abundance 

Number 

potential 

exposure 

Percent 

estimated 

population 

Beluga .......................................................................................................................................... 42,968 974 2.3 

Killer whale .................................................................................................................................. 2,084 14 0.8 

Harbor porpoise ........................................................................................................................... 48,215 294 0.6 

Bowhead whale ........................................................................................................................... 19,534 2,582 13.2 

Fin whale ..................................................................................................................................... 1,652 14 0.8 

Gray whale ................................................................................................................................... 19,126 2,581 13.5 

Humpback whale ......................................................................................................................... 20,800 14 0.1 

Minke whale ................................................................................................................................. 810 41 5.1 

Bearded seal ................................................................................................................................ 155,000 1,722 1.1 

Ribbon seal .................................................................................................................................. 49,000 96 0.2 

Ringed seal .................................................................................................................................. 300,000 50,433 16.8 

Spotted seal ................................................................................................................................. 141,479 1,007 0.7 


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In summary, several precautionary 

methods were applied when calculating 

exposure estimates. These conservative 

methods and related considerations 

include: 

• Application of a 1.3 dB re 1 mPa rms 

safety factor to the source level of each 

continuous sound source prior to sound 

propagation modeling of areas exposed 

to Level B thresholds; 

• Binning of similar activity scenarios 

into a representative scenario, each of 

which reflected the largest exposed area 

for a related group of activities; 

• Modeling numerous iterations of 

each activity scenario at different drill 

site locations to identify the spatial 

arrangement with the largest exposed 

area for each; 

• Assuming 100 percent daily 

turnover of populations, which likely 

overestimates the number of different 

individuals that would be exposed, 

especially during non-migratory 

periods; 

• Expected marine mammal densities 

assume no avoidance of areas exposed 

to Level B thresholds (with the 

exception of bowhead whale, for which 

50% of individuals were assumed to 

demonstrate avoidance behavior); and 

• Density estimates for some 

cetaceans include nearshore areas where 

more individuals would be expected to 

occur than in the offshore Burger 

Prospect area (e.g., gray whales). 

Additionally, post-season estimates of 

the number of marine mammals 

exposed to Level B thresholds per Shell 

90-Day Reports from the 2012 IHA 

consistently support the methods used 

in Shell’s IHA applications as 

precautionary. Most recently, exposure 

estimates reported by Reider et al. 

(2013) from Shell’s 2012 exploration 

activities in the Chukchi Sea were 

considerably lower than those requested 

in Shell’s 2012 IHA application. The 

following summary of the numbers of 

cetaceans and pinnipeds that may be 

exposed to sounds above Level B 

thresholds is best interpreted as 

conservatively high, particularly the 

larger value for each species that 

assumes a new population of 

individuals each day. 

Analysis and Preliminary 

Determinations 

Negligible Impact 

Negligible impact is ‘‘an impact 

resulting from the specified activity that 

cannot be reasonably expected to, and is 

not reasonably likely to, adversely affect 

the species or stock through effects on 

annual rates of recruitment or survival’’ 

(50 CFR 216.103). A negligible impact 

finding is based on the lack of likely 

adverse effects on annual rates of 

recruitment or survival (i.e., populationlevel effects). An estimate of the number 

of Level B harassment takes, alone, is 

not enough information on which to 

base an impact determination. In 

addition to considering estimates of the 

number of marine mammals that might 

be ‘‘taken’’ through behavioral 

harassment, NMFS must consider other 

factors, such as the likely nature of any 

responses (their intensity, duration, 

etc.), the context of any responses 

(critical reproductive time or location, 

migration, etc.), as well as the number 

and nature of estimated Level A 

harassment takes, the number of 

estimated mortalities, effects on habitat, 

and the status of the species. 

No injuries or mortalities are 

anticipated to occur as a result of Shell’s 

proposed Chukchi Sea exploratory 

drilling program, and none are proposed 

to be authorized. Injury, serious injury, 

or mortality could occur if there were a 

large or very large oil spill. However, as 

discussed previously in this document, 

the likelihood of a spill is extremely 

remote. Shell has implemented many 

design and operational standards to 

mitigate the potential for an oil spill of 

any size. NMFS does not propose to 

authorize take from an oil spill, as it is 

not part of the specified activity. 

Additionally, animals in the area are not 

expected to incur hearing impairment 

(i.e., TTS or PTS) or non-auditory 

physiological effects. Instead, any 

impact that could result from Shell’s 

activities is most likely to be behavioral 

harassment and is expected to be of 

limited duration. Although it is possible 

that some individuals may be exposed 

to sounds from drilling operations more 

than once, during the migratory periods 

it is less likely that this will occur since 

animals will continue to move across 

the Chukchi Sea towards their wintering 

grounds. 

Bowhead and beluga whales are less 

likely to occur in the proposed project 

area in July and August, as they are 

found mostly in the Canadian Beaufort 

Sea at this time. The animals are more 

likely to occur later in the season (midSeptember through October), as they 

head west towards Russia or south 

towards the Bering Sea. Additionally, 

while bowhead whale tagging studies 

revealed that animals occurred in the LS 

193 area, a higher percentage of animals 

were found outside of the LS 193 area 

in the fall (Quakenbush et al., 2010). 

Bowhead whales are not known to feed 

in areas near Shell’s leases in the 

Chukchi Sea. The closest primary 

feeding ground is near Point Barrow, 

which is more than 150 mi (241 km) 

east of Shell’s Burger prospect. 

Therefore, if bowhead whales stop to 

feed near Point Barrow during Shell’s 

proposed operations, the animals would 

not be exposed to continuous sounds 

from the drilling units or icebreaker 

above 120 dB or to impulsive sounds 

from the airguns above 160 dB, as those 

sound levels only propagate 1.8 km, 11 

km, and 11.9 km, respectively, which 

includes the inflation factor. Therefore, 

sounds from the operations would not 

reach the feeding grounds near Point 

Barrow. 

Gray whales occur in the northeastern 

Chukchi Sea during the summer and 

early fall to feed. Hanna Shoals, an area 

northeast of Shell’s proposed drill sites, 

is a common gray whale feeding ground. 

This feeding ground lies outside of the 

120-dB and 160-dB ensonified areas 

from Shell’s activities. While some 

individuals may swim through the area 

of active drilling, it is not anticipated to 

interfere with their feeding at Hanna 

Shoals or other Chukchi Sea feeding 

grounds. Other cetacean species are 

much rarer in the proposed project area. 

The exposure of cetaceans to sounds 

produced by exploratory drilling 

operations (i.e., drilling units, ice 

management/icebreaking, and airgun 

operations) is not expected to result in 

more than Level B harassment. 

Few seals are expected to occur in the 

proposed project area, as several of the 

species prefer more nearshore waters. 

Additionally, as stated previously in 

this document, pinnipeds appear to be 

more tolerant of anthropogenic sound, 

especially at lower received levels, than 

other marine mammals, such as 

mysticetes. Shell’s proposed activities 

would occur at a time of year when the 

ice seal species found in the region are 

not molting, breeding, or pupping. 

Therefore, these important life functions 

would not be impacted by Shell’s 

proposed activities. The exposure of 

pinnipeds to sounds produced by 

Shell’s proposed exploratory drilling 

operations in the Chukchi Sea is not 

expected to result in more than Level B 

harassment of the affected species or 

stock. 

Of the 12 marine mammal species or 

stocks likely to occur in the proposed 

drilling area, four are listed as 

endangered under the ESA: the 

bowhead, humpback, fin whales, and 

ringed seal. All four species are also 

designated as ‘‘depleted’’ under the 

MMPA. Despite these designations, the 

Bering-Chukchi-Beaufort stock of 

bowheads has been increasing at a rate 

of 3.4% annually for nearly a decade 

(Allen and Angliss, 2011), even in the 

face of ongoing industrial activity. 

Additionally, during the 2001 census, 

121 calves were counted, which was the 


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highest yet recorded. The calf count 

provides corroborating evidence for a 

healthy and increasing population 

(Allen and Angliss, 2011). An annual 

increase of 4.8% was estimated for the 

period 1987–2003 for North Pacific fin 

whales. While this estimate is consistent 

with growth estimates for other large 

whale populations, it should be used 

with caution due to uncertainties in the 

initial population estimate and about 

population stock structure in the area 

(Allen and Angliss, 2011). Zeribini et al. 

(2006, cited in Allen and Angliss, 2011) 

noted an increase of 6.6% for the 

Central North Pacific stock of humpback 

whales in Alaska waters. Certain stocks 

or populations of gray and beluga 

whales and spotted seals are listed as 

endangered or are proposed for listing 

under the ESA; however, none of those 

stocks or populations occur in the 

proposed activity area. Ringed seals 

were recently listed under the ESA as 

threatened species, and are considered 

depleted under the MMPA. On July 25, 

2014, the U.S. District Court for the 

District of Alaska vacated NMFS’ rule 

listing the Beringia bearded seal DPS as 

threatened and remanded the rule to 

NMFS to correct the deficiencies 

identified in the opinion. None of the 

other species that may occur in the 

project area is listed as threatened or 

endangered under the ESA or 

designated as depleted under the 

MMPA. There is currently no 

established critical habitat in the 

proposed project area for any of these 12 

species. 

Potential impacts to marine mammal 

habitat were discussed previously in 

this document (see the ‘‘Anticipated 

Effects on Habitat’’ section). Although 

some disturbance is possible to food 

sources of marine mammals, the 

impacts are anticipated to be minor. 

Based on the vast size of the Arctic 

Ocean where feeding by marine 

mammals occurs versus the localized 

area of the drilling program, any missed 

feeding opportunities in the direct 

project area would be of little 

consequence, as marine mammals 

would have access to other feeding 

grounds. 

Based on the analysis contained 

herein of the likely effects of the 

specified activity on marine mammals 

and their habitat, and taking into 

consideration the implementation of the 

proposed monitoring and mitigation 

measures, NMFS preliminarily finds 

that the total marine mammal take from 

Shell’s proposed 2015 open-water 

exploration drilling program in the 

Chukchi Sea will have a negligible 

impact on the affected marine mammal 

species or stocks. 

Small Numbers 

The estimated takes proposed to be 

authorized represent less than 1% of the 

affected population or stock for 6 of the 

species and less than 5.5% for three 

additional species. The estimated takes 

for bowhead and gray whales and for 

ringed seals are 13.2%, 13.5%, and 

16.8%, respectively. These estimates 

represent the percentage of each species 

or stock that could be taken by Level B 

behavioral harassment if each animal is 

taken only once. 

The estimated take numbers are likely 

somewhat of an overestimate for several 

reasons. First, an application of a 1.3 dB 

safety factor to the source level of each 

continuous sound source prior to sound 

propagation modeling of areas exposed 

to Level B thresholds, which make the 

effective zones for take calculation 

larger than they likely would be. In 

addition, Shell applied binning of 

similar activity scenarios into a 

representative scenario, each of which 

reflected the largest exposed area for a 

related group of activities. Further, the 

take estimates assume 100% daily 

turnover of populations, which likely 

overestimates the number of different 

individuals that would be exposed, 

especially during non-migratory 

periods. In addition, the take estimates 

assume no avoidance of marine 

mammals in areas exposed to Level B 

thresholds (with the exception of 

bowhead whale, for which 50% of 

individuals were assumed to 

demonstrate avoidance behavior). 

Finally, density estimates for some 

cetaceans include nearshore areas where 

more individuals would be expected to 

occur than in the offshore Burger 

Prospect area (e.g., gray whales). 

Based on the analysis contained 

herein of the likely effects of the 

specified activity on marine mammals 

and their habitat, and taking into 

consideration the implementation of the 

mitigation and monitoring measures, 

NMFS preliminarily finds that small 

numbers of marine mammals will be 

taken relative to the populations of the 

affected species or stocks. 

Impact on Availability of Affected 

Species or Stock for Taking for 

Subsistence Uses 

Relevant Subsistence Uses 

The disturbance and potential 

displacement of marine mammals by 

sounds from drilling activities are the 

principal concerns related to 

subsistence use of the area. Subsistence 

remains the basis for Alaska Native 

culture and community. Marine 

mammals are legally hunted in Alaskan 

waters by coastal Alaska Natives. In 

rural Alaska, subsistence activities are 

often central to many aspects of human 

existence, including patterns of family 

life, artistic expression, and community 

religious and celebratory activities. 

Additionally, the animals taken for 

subsistence provide a significant portion 

of the food that will last the community 

throughout the year. The main species 

that are hunted include bowhead and 

beluga whales, ringed, spotted, and 

bearded seals. The importance of each 

of these species varies among the 

communities and is largely based on 

availability. 

The subsistence communities in the 

Chukchi Sea that have the potential to 

be impacted by Shell’s offshore drilling 

program include Point Hope, Point Lay, 

Wainwright, Barrow, and possibly 

Kotzebue and Kivalina (however, these 

two communities are much farther to 

the south of the proposed project area). 

(1) Bowhead Whales 

Sound energy and general activity 

associated with drilling and operation of 

vessels and aircraft have the potential to 

temporarily affect the behavior of 

bowhead whales. Monitoring studies 

(Davis 1987, Brewer et al. 1993, Hall et 

al. 1994) have documented temporary 

diversions in the swim path of migrating 

bowheads near drill sites; however, the 

whales have generally been observed to 

resume their initial migratory route 

within a distance of 6–20 mi (10–32 

km). Drilling noise has not been shown 

to block or impede migration even in 

narrow ice leads (Davis 1987, 

Richardson et al. 1991). 

Behavioral effects on bowhead whales 

from sound energy produced by drilling, 

such as avoidance, deflection, and 

changes in surface/dive ratios, have 

generally been found to be limited to 

areas around the drill site that are 

ensonified to >160 dB re 1 mPa rms, 

although effects have infrequently been 

observed out as far as areas ensonified 

to 120 dB re 1 mPa rms. Ensonification 

by drilling to levels >120 dB re 1 mPa 

rms will be limited to areas within 

about 0.93 mi (1.5 km) of either drilling 

units during Shell’s exploration drilling 

program. Shell’s proposed drill sites are 

located more than 64 mi (103 km) from 

the Chukchi Sea coastline, whereas 

mapping of subsistence use areas 

indicates bowhead hunts are conducted 

within about 30 mi (48 km) of shore; 

there is therefore little or no opportunity 

for the proposed exploration drilling 

activities to affect bowhead hunts. 

Vessel traffic along planned travel 

corridors between the drill sites and 

marine support facilities in Barrow and 

Wainwright would traverse some areas 

used during bowhead harvests by 


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Chukchi villages. Bowhead hunts by 

residents of Wainwright, Point Hope 

and Point Lay take place almost 

exclusively in the spring prior to the 

date on which Shell would commence 

the proposed exploration drilling 

program. From 1984 through 2009, all 

bowhead harvests by these Chukchi Sea 

villages occurred only between April 14 

and June 24 (George and Tarpley 1986; 

George et al. 1987, 1988, 1990, 1992, 

1995, 1998, 1999, 2000; Philo et al. 

1994; Suydam et al. 1995, 1996, 1997, 

2001, 2002, 2003, 2004, 2005, 2006, 

2007, 2008, 2009, 2010), while Shell 

will not enter the Chukchi Sea prior to 

July 1. However, fall whaling by some 

of these Chukchi Sea villages has 

occurred since 2010 and is likely to 

occur in the future, particularly if 

bowhead quotas are not completely 

filled during the spring hunt, and fall 

weather is accommodating. A 

Wainwright whaling crew harvested the 

first fall bowhead for these villages in 90 

years or more on October 7, 2010, and 

another in October of 2011 (Suydam et 

al. 2011, 2012, 2013). No bowhead 

whales were harvested during fall in 

2012, but 3 were harvested by 

Wainwright in fall 2013. 

Barrow crews have traditionally 

hunted bowheads during both spring 

and fall; however spring whaling by 

Barrow crews is normally finished 

before the date on which Shell 

operations would commence. From 

1984 through 2011 whales were 

harvested in the spring by Barrow crews 

only between April 23 and June 15 

(George and Tarpley 1986; George et al. 

1987, 1988, 1990, 1992, 1995, 1998, 

1999, 2000; Philo et al. 1994; Suydam et 

al. 1995, 1996, 1997, 2001, 2002, 2003, 

2004, 2005, 2006, 2007, 2008, 2009, 

2010, 2011, 2012, 2103). Fall whaling by 

Barrow crews does take place during the 

time period when vessels associated 

with Shell’s exploration drilling 

program would be in the Chukchi Sea. 

From 1984 through 2011, whales were 

harvested in the fall by Barrow crews 

between August 31 and October 30, 

indicating that there is potential for 

vessel traffic to affect these hunts. Most 

fall whaling by Barrow crews, however, 

takes place east of Barrow along the 

Beaufort Sea coast, therefore providing 

little opportunity for vessel traffic 

associated with Shell’s exploration 

drilling program to affect them. For 

example, Suydam et al. (2008) reported 

that in the previous 35 years, Barrow 

whaling crews harvested almost all their 

whales in the Beaufort Sea to the east of 

Point Barrow. Shell’s mitigation 

measures, which include a system of 

Subsistence Advisors (SAs), Community 

Liaisons, and Com Centers, will be 

implemented to avoid any effects from 

vessel traffic on fall whaling in the 

Chukchi Sea by Barrow and 

Wainwright. 

Aircraft traffic (helicopters and small 

fixed wing airplanes) between the drill 

sites and facilities in Wainwright and 

Barrow would also traverse these 

subsistence areas. Flights between the 

drill sites and Wainwright or other 

shoreline locations would take place 

after the date on which spring bowhead 

whaling out of Point Hope, Point Lay, 

and Wainwright is typically finished for 

the year; however, Wainwright has 

harvested bowheads in the fall since 

2010 and aircraft may traverse areas 

sometimes utilized for these fall hunts. 

Aircraft overflights between the drill 

sites and Barrow or other shoreline 

locations could also occur over areas 

used by Barrow crews during fall 

whaling, but again, most fall whaling by 

Barrow crews takes place to the east of 

Barrow in the Beaufort Sea. The most 

commonly observed reactions of 

bowheads to aircraft traffic are hasty 

dives, but changes in orientation, 

dispersal, and changes in activity are 

sometimes noted. Such reactions could 

potentially affect subsistence hunts if 

the flights occurred near and at the same 

time as the hunt, but Shell has 

developed and proposes to implement a 

number of mitigation measures to avoid 

such impacts. These mitigation 

measures include minimum flight 

altitudes, employment of SAs, and Com 

Centers. Twice-daily calls are held 

during the exploration drilling program 

and are attended by operations staff, 

logistics staff, and SAs. Vessel 

movements and aircraft flights are 

adjusted as needed and planned in a 

manner that avoids potential impacts to 

bowhead whale hunts and other 

subsistence activities. 

(2) Beluga Whale 

Beluga whales typically do not 

represent a large proportion of the 

subsistence harvests by weight in the 

communities of Wainwright and 

Barrow, the nearest communities to 

Shell’s planned exploration drilling 

program. Barrow residents hunt beluga 

in the spring (normally after the 

bowhead hunt) in leads between Point 

Barrow and Skull Cliffs in the Chukchi 

Sea, primarily in April–June and later in 

the summer (July–August) on both sides 

of the barrier island in Elson Lagoon/

Beaufort Sea (Minerals Management 

Service [MMS] 2008), but harvest rates 

indicate the hunts are not frequent. 

Wainwright residents hunt beluga in 

April–June in the spring lead system, 

but this hunt typically occurs only if 

there are no bowheads in the area. 

Communal hunts for beluga are 

conducted along the coastal lagoon 

system later in July–August. 

Belugas typically represent a much 

greater proportion of the subsistence 

harvest in Point Lay and Point Hope. 

Point Lay’s primary beluga hunt occurs 

from mid-June through mid-July, but 

can sometimes continue into August if 

early success is not sufficient. Point 

Hope residents hunt beluga primarily in 

the lead system during the spring (late 

March to early June) bowhead hunt, but 

also in open water along the coastline in 

July and August. Belugas are harvested 

in coastal waters near these villages, 

generally within a few miles from shore. 

Shell’s proposed drill sites are located 

more than 60 mi (97 km) offshore, 

therefore proposed exploration drilling 

in the Burger Prospect would have no or 

minimal impacts on beluga hunts. 

Aircraft and vessel traffic between the 

drill sites and support facilities in 

Wainwright, and aircraft traffic between 

the drill sites and air support facilities 

in Barrow, would traverse areas that are 

sometimes used for subsistence hunting 

of belugas. 

Disturbance associated with vessel 

and aircraft traffic could therefore 

potentially affect beluga hunts. 

However, all of the beluga hunt by 

Barrow residents in the Chukchi Sea, 

and much of the hunt by Wainwright 

residents, would likely be completed 

before Shell activities would commence. 

Additionally, vessel and aircraft traffic 

associated with Shell’s planned 

exploration drilling program will be 

restricted under normal conditions to 

designated corridors that remain 

onshore or proceed directly offshore 

thereby minimizing the amount of 

traffic in coastal waters where beluga 

hunts take place. The designated vessel 

and aircraft traffic corridors do not 

traverse areas indicated in recent 

mapping as utilized by Point Lay or 

Point Hope for beluga hunts, and avoids 

important beluga hunting areas in 

Kasegaluk Lagoon that are used by 

Wainwright. Shell has developed and 

proposes to implement a number of 

mitigation measures, e.g., PSOs on 

board vessels, minimum flight altitudes, 

and the SA and Com Center programs, 

to ensure that there is no impact on the 

availability of the beluga whale as a 

subsistence resource. 

(3) Pinnipeds 

Seals are an important subsistence 

resource and ringed seals make up the 

bulk of the seal harvest. Most ringed and 

bearded seals are harvested in the 

winter or in the spring before Shell’s 

exploration drilling program would 


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commence, but some harvest continues 

during open water and could possibly 

be affected by Shell’s planned activities. 

Spotted seals are also harvested during 

the summer. Most seals are harvested in 

coastal waters, with available maps of 

recent and past subsistence use areas 

indicating seal harvests have occurred 

only within 30–40 mi (48–64 km) of the 

coastline. Shell’s planned drill sites are 

located more than 64 statute mi (103 

km) offshore, so activities within the 

Burger Prospect, such as drilling, would 

have no impact on subsistence hunting 

for seals. Helicopter traffic between land 

and the offshore exploration drilling 

operations could potentially disturb 

seals and, therefore, subsistence hunts 

for seals, but any such effects would be 

minor and temporary lasting only 

minutes after the flight has passed due 

to the small number of flights and the 

altitude at which they typically fly, and 

the fact that most seal hunting is done 

during the winter and spring when the 

exploration drilling program is not 

operational. Mitigation measures to be 

implemented by Shell include 

minimum flight altitudes, employment 

of subsistence advisors in the villages, 

and operation of Com Centers. 

Potential Impacts to Subsistence Uses 

NMFS has defined ‘‘unmitigable 

adverse impact’’ in 50 CFR 216.103 as: 

‘‘an impact resulting from the specified 

activity: (1) That is likely to reduce the 

availability of the species to a level 

insufficient for a harvest to meet 

subsistence needs by: (i) Causing the 

marine mammals to abandon or avoid 

hunting areas; (ii) Directly displacing 

subsistence users; or (iii) Placing 

physical barriers between the marine 

mammals and the subsistence hunters; 

and (2) That cannot be sufficiently 

mitigated by other measures to increase 

the availability of marine mammals to 

allow subsistence needs to be met. 

Noise and general activity during 

Shell’s proposed drilling program have 

the potential to impact marine mammals 

hunted by Native Alaskans. In the case 

of cetaceans, the most common reaction 

to anthropogenic sounds (as noted 

previously in this document) is 

avoidance of the ensonified area. In the 

case of bowhead whales, this often 

means that the animals divert from their 

normal migratory path by several 

kilometers. Helicopter activity also has 

the potential to disturb cetaceans and 

pinnipeds by causing them to vacate the 

area. Additionally, general vessel 

presence in the vicinity of traditional 

hunting areas could negatively impact a 

hunt. Native knowledge indicates that 

bowhead whales become increasingly 

‘‘skittish’’ in the presence of seismic 

noise. Whales are more wary around the 

hunters and tend to expose a much 

smaller portion of their back when 

surfacing (which makes harvesting more 

difficult). Additionally, natives report 

that bowheads exhibit angry behaviors 

in the presence of seismic activity, such 

as tail-slapping, which translate to 

danger for nearby subsistence 

harvesters. Only limited seismic activity 

is planned in the vicinity of the drill 

units in 2015. 

Plan of Cooperation or Measures To 

Minimize Impacts to Subsistence Hunts 

Regulations at 50 CFR 216.104(a)(12) 

require IHA applicants for activities that 

take place in Arctic waters to provide a 

Plan of Cooperation (POC) or 

information that identifies what 

measures have been taken and/or will 

be taken to minimize adverse effects on 

the availability of marine mammals for 

subsistence purposes. 

Shell has prepared and will 

implement a POC pursuant to BOEM 

Lease Sale Stipulation No. 5, which 

requires that all exploration operations 

be conducted in a manner that prevents 

unreasonable conflicts between oil and 

gas activities and the subsistence 

activities and resources of residents of 

the North Slope. This stipulation also 

requires adherence to USFWS and 

NMFS regulations, which require an 

operator to implement a POC to mitigate 

the potential for conflicts between the 

proposed activity and traditional 

subsistence activities (50 CFR 

18.124(c)(4) and 50 CFR 216.104(a)(12)). 

A POC was prepared and submitted 

with the initial Chukchi Sea EP that was 

submitted to BOEM in May 2009, and 

approved on 7 December 2009. 

Subsequent POC Addendums were 

submitted in May 2011 with a revised 

Chukchi Sea EP and the IHA application 

for the 2012 exploration drilling 

program. For this IHA application, Shell 

has again updated the POC Addendum. 

The POC Addendum has been updated 

to include documentation of meetings 

undertaken to specifically gather 

feedback from stakeholder communities 

on Shell’s implementation of the 

Chukchi Sea exploration drilling 

program during 2012, plus inform and 

obtain their input regarding the 

continuation of the program with the 

addition of a second drilling unit, 

additional vessels and aircraft. 

The POC Addendum identifies the 

measures that Shell has developed in 

consultation with North Slope 

subsistence communities to minimize 

any adverse effects on the availability of 

marine mammals for subsistence uses 

and will implement during its planned 

Chukchi Sea exploration drilling 

program for the summer of 2015. In 

addition, the POC Addendum details 

Shell’s communications and 

consultations with local subsistence 

communities concerning its planned 

exploration drilling program, potential 

conflicts with subsistence activities, and 

means of resolving any such conflicts 

(50 CFR 18.128(d) and 50 CFR 

216.104(a) (12) (i), (ii), (iv)). Shell has 

documented its contacts with the North 

Slope subsistence communities, as well 

as the substance of its communications 

with subsistence stakeholder groups. 

The POC Addendum report 

(Attachment C of the IHA application) 

provides a list of public meetings 

attended by Shell since 2012 to develop 

the POC and the POC Addendum. The 

POC Addendum is updated through July 

2015, and includes sign-in sheets and 

presentation materials used at the POC 

meetings held in 2014 to present the 

2015 Chukchi Sea exploration drilling 

information. Comment analysis tables 

for numerous meetings held during 

2014 summarize feedback from the 

communities on Shell’s 2015 

exploration drilling and planned 

activities beginning in the summer of 

2015. 

The following mitigation measures, 

plans and programs, are integral to this 

POC and were developed during Shell’s 

consultation with potentially affected 

subsistence groups and communities. 

These measures, plans, and programs to 

monitor and mitigate potential impacts 

to subsistence users and resources will 

be implemented by Shell during its 

exploration drilling operations in the 

Chukchi Sea. The mitigation measures 

Shell has adopted and will implement 

during its Chukchi Sea exploration 

drilling operations are listed and 

discussed below. These mitigation 

measures reflect Shell’s experience 

conducting exploration activities in the 

Alaska Arctic OCS since the 1980s and 

its ongoing efforts to engage with local 

subsistence communities to better 

understand their concerns and develop 

appropriate and effective mitigation 

measures to address those concerns. 

This most recent version of Shell’s 

planned mitigation measures was 

presented to community leaders and 

subsistence user groups starting in 

January 2009 and has evolved since in 

response to information learned during 

the consultation process. 

To minimize any cultural or resource 

impacts from its exploration operations, 

Shell will continue to implement the 

following additional measures to ensure 

coordination of its activities with local 

subsistence users to minimize further 

the risk of impacting marine mammals 


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and interfering with the subsistence 

hunt: 

(1) Communications 

• Shell has developed a 

Communication Plan and will 

implement this plan before initiating 

exploration drilling operations to 

coordinate activities with local 

subsistence users, as well as Village 

Whaling Captains’ Associations, to 

minimize the risk of interfering with 

subsistence hunting activities, and keep 

current as to the timing and status of the 

bowhead whale hunt and other 

subsistence hunts. The Communication 

Plan includes procedures for 

coordination with Com Centers to be 

located in coastal villages along the 

Chukchi Sea during Shell’s proposed 

exploration drilling activities. 

• Shell will employ local SAs from 

the Chukchi Sea villages that are 

potentially impacted by Shell’s 

exploration drilling activities. The SAs 

will provide consultation and guidance 

regarding the whale migration and 

subsistence activities. There will be one 

per village, working approximately 8-hr 

per day and 40-hr per week during each 

drilling season. The subsistence advisor 

will use local knowledge (Traditional 

Knowledge) to gather data on 

subsistence lifestyle within the 

community and provide advice on ways 

to minimize and mitigate potential 

negative impacts to subsistence 

resources during each drilling season. 

Responsibilities include reporting any 

subsistence concerns or conflicts; 

coordinating with subsistence users; 

reporting subsistence-related comments, 

concerns, and information; coordinating 

with the Com and Call Center 

personnel; and advising how to avoid 

subsistence conflicts. 

(2) Aircraft Travel 

• Aircraft over land or sea shall not 

operate below 1,500 ft. (457 m) altitude 

unless engaged in marine mammal 

monitoring, approaching, landing or 

taking off, in poor weather (fog or low 

ceilings), or in an emergency situation. 

• Aircraft engaged in marine mammal 

monitoring shall not operate below 

1,500 ft. (457 m) in areas of active 

whaling; such areas to be identified 

through communications with the Com 

Centers. 

(3) Vessel Travel 

• The drilling unit(s) and support 

vessels will enter the Chukchi Sea 

through the Bering Strait on or after 1 

July, minimizing effects on marine 

mammals and birds that frequent open 

leads and minimizing effects on spring 

and early summer bowhead whale 

hunting. 

• The transit route for the drilling 

unit(s) and drilling support fleets will 

avoid known fragile ecosystems and the 

Ledyard Bay Critical Habitat Unit 

(LBCHU), and will include coordination 

through Com Centers. 

• PSOs will be aboard the drilling 

unit(s) and transiting support vessels. 

• When within 900 ft (274 m) of 

whales, vessels will reduce speed, avoid 

separating members from a group and 

avoid multiple changes of direction. 

• Vessel speed will be reduced during 

inclement weather conditions in order 

to avoid collisions with marine 

mammals. 

• Shell will communicate and 

coordinate with the Com Centers 

regarding all vessel transit. 

(4) ZVSP 

• Airgun arrays will be ramped up 

slowly during ZVSPs to warn cetaceans 

and pinnipeds in the vicinity of the 

airguns and provide time for them to 

leave the area and avoid potential injury 

or impairment of their hearing abilities. 

Ramp ups from a cold start when no 

airguns have been firing will begin by 

firing a single airgun in the array. A 

ramp up to the required airgun array 

volume will not begin until there has 

been a minimum of 30 min of 

observation of the safety zone by PSOs 

to assure that no marine mammals are 

present. The safety zone is the extent of 

the 180 dB radius for cetaceans and 190 

dB re 1 mPa rms for pinnipeds. The 

entire safety zone must be visible during 

the 30-min lead-into an array ramp up. 

If a marine mammal(s) is sighted within 

the safety zone during the 30-min 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 min: 15 min for small odontocetes 

and pinnipeds, or 30 min for baleen 

whales and large odontocetes. 

(5) Ice Management 

• Real time ice and weather 

forecasting will be from SIWAC. 

(6) Oil Spill Response 

• Pre-booming is required for all fuel 

transfers between vessels. 

The potentially affected subsistence 

communities, identified in BOEM Lease 

Sale, that were consulted regarding 

Shell’s exploration drilling activities 

include: Barrow, Wainwright, Point Lay, 

Point Hope, Kotzebue, and Deering. 

Additionally, Shell has met with 

subsistence groups including the Alaska 

Eskimo Whaling Commission (AEWC), 

Inupiat Community of the Arctic Slope 

(ICAS), and the Native Village of 

Barrow, and presented information 

regarding the proposed activities to the 

North Slope Borough (NSB) and 

Northwest Arctic Borough (NWAB) 

Assemblies, and NSB and NWAB 

Planning Commissions during 2014. In 

July 2014, Shell conducted POC 

meetings in Chukchi villages to present 

information on the proposed 2015 

drilling season. Shell has supplemented 

the IHA application with a POC 

addendum to incorporate these POC 

visits. Throughout 2014 and 2015 Shell 

anticipates continued engagement with 

the marine mammal commissions and 

committees active in the subsistence 

harvests and marine mammal research. 

Shell continues to meet each year 

with the commissioners and committee 

heads of AEWC, Alaska Beluga Whale 

Committee, the Nanuuq Commission, 

Eskimo Walrus Commission, and Ice 

Seal Committee jointly in comanagement meetings. Shell held 

individual consultation meetings with 

representatives from the various marine 

mammal commissions to discuss the 

planned Chukchi exploration drilling 

program. Following the drilling season, 

Shell will have a post-season comanagement meeting with the 

commissioners and committee heads to 

discuss results of mitigation measures 

and outcomes of the preceding season. 

The goal of the post-season meeting is 

to build upon the knowledge base, 

discuss successful or unsuccessful 

outcomes of mitigation measures, and 

possibly refine plans or mitigation 

measures if necessary. 

Shell attended the 2012–2014 Conflict 

Avoidance Agreement (CAA) 

negotiation meetings in support of 

exploration drilling, offshore surveys, 

and future drilling plans. Shell will do 

the same for the upcoming 2015 

exploration drilling program. Shell 

states that it is committed to a CAA 

process and will make a good-faith 

effort to negotiate an agreement every 

year it has planned activities. 

Unmitigable Adverse Impact Analysis 

and Preliminary Determination 

NMFS considers that these mitigation 

measures including measures to reduce 

overall impacts to marine mammals in 

the vicinity of the proposed exploration 

drilling area and measures to mitigate 

any potential adverse effects on 

subsistence use of marine mammals are 

adequate to ensure subsistence use of 

marine mammals in the vicinity of 

Shell’s proposed exploration drilling 

program in the Chukchi Sea. 

Based on the description of the 

specified activity, the measures 

described to minimize adverse effects 


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on the availability of marine mammals 

for subsistence purposes, and the 

proposed mitigation and monitoring 

measures, NMFS has preliminarily 

determined that there will not be an 

unmitigable adverse impact on 

subsistence uses from Shell’s proposed 

activities. 

Endangered Species Act (ESA) 

There are four marine mammal 

species listed as endangered under the 

ESA with confirmed or possible 

occurrence in the proposed project area: 

The bowhead, humpback, and fin 

whales, and ringed seals. NMFS’ 

Permits and Conservation Division will 

initiate consultation with NMFS’ 

Endangered Species Division under 

section 7 of the ESA on the issuance of 

an IHA to Shell under section 

101(a)(5)(D) of the MMPA for this 

activity. Consultation will be concluded 

prior to a determination on the issuance 

of an IHA. 

National Environmental Policy Act 

(NEPA) 

NMFS is preparing an Environmental 

Assessment (EA), pursuant to NEPA, to 

determine whether the issuance of an 

IHA to Shell for its 2015 drilling 

activities may have a significant impact 

on the human environment. NMFS has 

released a draft of the EA for public 

comment along with this proposed IHA. 

Proposed Authorization 

As a result of these preliminary 

determinations, NMFS proposes to issue 

an IHA to Shell for conducting an 

exploration drilling program in the 

Chukchi Sea during the 2015 Arctic 

open-water season, provided the 

previously mentioned mitigation, 

monitoring, and reporting requirements 

are incorporated. The proposed IHA 

language is provided next. 

This section contains a draft of the 

IHA itself. The wording contained in 

this section is proposed for inclusion in 

the IHA (if issued). 

(1) This Authorization is valid from 

July 1, 2015, through October 31, 2015. 

(2) This Authorization is valid only 

for activities associated with Shell’s 

2015 Chukchi Sea exploration drilling 

program. The specific areas where 

Shell’s exploration drilling program will 

be conducted are within Shell lease 

holdings in the Outer Continental Shelf 

Lease Sale 193 area in the Chukchi Sea. 

(3)(a) The incidental taking of marine 

mammals, by Level B harassment only, 

is limited to the following species: 

bowhead whale; gray whale; beluga 

whale; minke whale; fin whale; 

humpback whale; killer whale; harbor 

porpoise; ringed seal; bearded seal; 

spotted seal; and ribbon seal. 

(3)(b) The taking by injury (Level A 

harassment), serious injury, or death of 

any of the species listed in Condition 

3(a) or the taking of any kind of any 

other species of marine mammal is 

prohibited and may result in the 

modification, suspension or revocation 

of this Authorization. 

(4) The authorization for taking by 

harassment is limited to the following 

acoustic sources (or sources with 

comparable frequency and intensity) 

and from the following activities: 

(a) a three-airgun array consisting of 

three 150 in3 airguns, or a two-airgun 

array consisting of two 250 in3 airguns; 

(b) continuous drilling unit and 

associated dynamic positioning sounds 

during active drilling operations; 

(c) vessel sounds generated during 

active ice management or icebreaking; 

(d) mudline cellar construction during 

the exploration drilling program; 

(e) anchor handling during the 

exploration drilling program, and 

(f) aircraft associated with marine 

mammal monitoring and support 

operations, 

(5) The taking of any marine mammal 

in a manner prohibited under this 

Authorization must be reported 

immediately to the Chief, Permits and 

Conservation Division, Office of 

Protected Resources, NMFS or her 

designee. 

(6) The holder of this Authorization 

must notify the Chief of the Permits and 

Conservation Division, Office of 

Protected Resources, at least 48 hours 

prior to the start of exploration drilling 

activities (unless constrained by the 

date of issuance of this Authorization in 

which case notification shall be made as 

soon as possible). 

(7) General Mitigation and Monitoring 

Requirements: The Holder of this 

Authorization is required to implement 

the following mitigation and monitoring 

requirements when conducting the 

specified activities to achieve the least 

practicable impact on affected marine 

mammal species or stocks: 

(a) All vessels shall reduce speed to 

a maximum of 5 knots when within 900 

ft (300 yards/274 m) of whales. Those 

vessels capable of steering around such 

groups should do so. Vessels may not be 

operated in such a way as to separate 

members of a group of whales from 

other members of the group; 

(b) Avoid multiple changes in 

direction and speed when within 900 ft 

(300 yards/274 m) of whales; 

(c) When weather conditions require, 

such as when visibility drops, support 

vessels must reduce speed and change 

direction, as necessary (and as 

operationally practicable), to avoid the 

likelihood of injury to whales; 

(d) Aircraft shall not fly within 1,000 

ft (305 m) of marine mammals or below 

1,500 ft (457 m) altitude (except during 

takeoffs, landings, or in emergency 

situations) while over land or sea; 

(e) Utilize two, NMFS-approved, 

vessel-based Protected Species 

Observers (PSOs) (except during meal 

times and restroom breaks, when at least 

one PSO shall be on watch) to visually 

watch for and monitor marine mammals 

near the drilling units or support vessel 

during active drilling or airgun 

operations (from nautical twilight-dawn 

to nautical twilight-dusk) and before 

and during start-ups of airguns day or 

night. The vessels’ crew shall also assist 

in detecting marine mammals, when 

practicable. PSOs shall have access to 

reticle binoculars (7x50 Fujinon), bigeye binoculars (25x150), and night 

vision devices. PSO shifts shall last no 

longer than 4 consecutive hours and 

shall not be on watch more than 12 

hours in a 24-hour period. PSOs shall 

also make observations during daytime 

periods when active operations are not 

being conducted for comparison of 

animal abundance and behavior, when 

feasible; 

(f) When a mammal sighting is made, 

the following information about the 

sighting will be recorded by the PSOs: 

(i) Species, group size, age/size/sex 

categories (if determinable), behavior 

when first sighted and after initial 

sighting, heading (if consistent), bearing 

and distance from the PSO, apparent 

reaction to activities (e.g., none, 

avoidance, approach, paralleling, etc.), 

closest point of approach, and 

behavioral pace; 

(ii) Time, location, speed, activity of 

the vessel, sea state, ice cover, visibility, 

and sun glare; and 

(iii) The positions of other vessel(s) in 

the vicinity of the PSO location. 

(iv) The ship’s position, speed of 

support vessels, and water temperature, 

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. 

(g) PSO teams shall consist of Alaska 

Native observers and experienced field 

biologists. An experienced field crew 

leader will supervise the PSO team 

onboard the survey vessel. New 

observers shall be paired with 

experienced observers to avoid 

situations where lack of experience 

impairs the quality of observations; 

(h) PSOs will complete a two or threeday training session on marine mammal 

monitoring, to be conducted shortly 


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before the anticipated start of the 2015 

open-water season. The training 

session(s) will be conducted by 

qualified marine mammalogists with 

extensive crew-leader experience during 

previous vessel-based monitoring 

programs. A marine mammal observers’ 

handbook, adapted for the specifics of 

the planned program, will be reviewed 

as part of the training; 

(i) PSO training that is conducted 

prior to the start of the survey activities 

shall be conducted with both Alaska 

Native PSOs and biologist PSOs being 

trained at the same time in the same 

room. There shall not be separate 

training courses for the different PSOs; 

and 

(j) PSOs shall be trained using visual 

aids (e.g., videos, photos), to help them 

identify the species that they are likely 

to encounter in the conditions under 

which the animals will likely be seen. 

(8) ZVSP Mitigation and Monitoring 

Measures: The Holder of this 

Authorization is required to implement 

the following mitigation and monitoring 

requirements when conducting the 

specified activities to achieve the least 

practicable impact on affected marine 

mammal species or stocks: 

(a) PSOs shall conduct monitoring 

while the airgun array is being deployed 

or recovered from the water; 

(b) PSOs shall visually observe the 

entire extent of the exclusion zone (EZ) 

(180 dB re 1 mPa [rms] for cetaceans and 

190 dB re 1 mPa [rms] for pinnipeds) 

using NMFS-qualified PSOs, for at least 

30 minutes (min) prior to starting the 

airgun array (day or night). If the PSO 

finds a marine mammal within the EZ, 

Shell must delay the seismic survey 

until the marine mammal(s) has left the 

area. If the PSO sees a marine mammal 

that surfaces then dives below the 

surface, the PSO shall continue the 

watch for 30 min. If the PSO sees no 

marine mammals during that time, they 

may assume that the animal has moved 

beyond the EZ. If for any reason the 

entire radius cannot be seen for the 

entire 30 min period (i.e., rough seas, 

fog, darkness), or if marine mammals are 

near, approaching, or in the EZ, the 

airguns may not be ramped-up. If one 

airgun is already running at a source 

level of at least 180 dB re 1 mPa (rms), 

the Holder of this Authorization may 

start the second airgun without 

observing the entire EZ for 30 min prior, 

provided no marine mammals are 

known to be near the EZ; 

(c) Establish and monitor a 180 dB re 

1 mPa (rms) and a 190 dB re 1 mPa (rms) 

EZ for marine mammals before the 

airgun array is in operation. Before the 

field verification tests, described in 

condition 10(c)(i) below, the 180 dB 

radius is temporarily designated to be 

1.28 km and the 190 dB radius is 

temporarily designated to be 255 m; 

(d) Implement a ‘‘ramp-up’’ procedure 

when starting up at the beginning of 

seismic operations. During ramp-up, the 

PSOs shall monitor the EZ, and if 

marine mammals are sighted, a powerdown, or shut-down shall be 

implemented as though the full array 

were operational. Therefore, initiation 

of ramp-up procedures from shut-down 

requires that the PSOs be able to view 

the full EZ; 

(e) Power-down or shutdown the 

airgun(s) if a marine mammal is 

detected within, approaches, or enters 

the relevant EZ. A shutdown means all 

operating airguns are shutdown (i.e., 

turned off). A power-down means 

reducing the number of operating 

airguns to a single operating airgun, 

which reduces the EZ to the degree that 

the animal(s) is no longer in or about to 

enter it; 

(f) Following a power-down, if the 

marine mammal approaches the smaller 

designated EZ, the airguns must then be 

completely shutdown. Airgun activity 

shall not resume until the PSO has 

visually observed the marine mammal(s) 

exiting the EZ and is not likely to 

return, or has not been seen within the 

EZ for 15 min for species with shorter 

dive durations (small odontocetes and 

pinnipeds) or 30 min for species with 

longer dive durations (mysticetes); 

(g) Following a power-down or shutdown and subsequent animal departure, 

airgun operations may resume following 

ramp-up procedures described in 

Condition 8(d) above; 

(h) ZVSP surveys may continue into 

night and low-light hours if such 

segment(s) of the survey is initiated 

when the entire relevant EZs are visible 

and can be effectively monitored; and 

(i) No initiation of airgun array 

operations is permitted from a 

shutdown position at night or during 

low-light hours (such as in dense fog or 

heavy rain) when the entire relevant EZ 

cannot be effectively monitored by the 

PSO(s) on duty. 

(9) Subsistence Mitigation Measures: 

To ensure no unmitigable adverse 

impact on subsistence uses of marine 

mammals, the Holder of this 

Authorization shall: 

(b) Not enter the Bering Strait prior to 

July 1 to minimize effects on spring and 

early summer whaling; 

(c) Implement the Communication 

Plan before initiating exploration 

drilling operations to coordinate 

activities with local subsistence users 

and Village Whaling Associations in 

order to minimize the risk of interfering 

with subsistence hunting activities; 

(d) Participate in the Com Center 

Program. The Com Centers shall operate 

24 hours/day during the 2015 bowhead 

whale hunt; 

(e) Employ local Subsistence Advisors 

(SAs) from the Chukchi Sea villages to 

provide consultation and guidance 

regarding the whale migration and 

subsistence hunt; 

(f) Not operate aircraft below 1,500 ft 

(457 m) unless engaged in marine 

mammal monitoring, approaching, 

landing or taking off, or unless engaged 

in providing assistance to a whaler or in 

poor weather (low ceilings) or any other 

emergency situations; 

(10) Monitoring Measures: 

(a) Vessel-based Monitoring: The 

Holder of this Authorization shall 

designate biologically-trained PSOs to 

be aboard the drilling units and all 

transiting support vessels. The PSOs are 

required to monitor for marine 

mammals in order to implement the 

mitigation measures described in 

conditions 7 and 8 above; 

(b) Aerial Survey Monitoring: The 

Holder of this Authorization must 

implement the aerial survey monitoring 

program detailed in its Marine Mammal 

Mitigation and Monitoring Plan (4MP); 

and 

(c) Acoustic Monitoring: 

(i) Field Source Verification: the 

Holder of this Authorization is required 

to conduct sound source verification 

tests for the drilling units, support 

vessels, and the airgun array not 

measured in previous seasons. Sound 

source verification shall consist of 

distances where broadside and endfire 

directions at which broadband received 

levels reach 190, 180, 170, 160, and 120 

dB re 1 mPa (rms) for all active acoustic 

sources that may be used during the 

activities. For the airgun array, the 

configurations shall include at least the 

full array and the operation of a single 

source that will be used during power 

downs. The test results for the airgun 

array shall be reported to NMFS within 

5 days of completing the test. 

A report of the acoustic verification 

measurements of the ZVSP airgun array 

will be submitted within 120 hr after 

collection and analysis of those 

measurements once that part of the 

program is implemented. The ZVSP 

acoustic array report will specify the 

distances of the exclusion zones that 

were adopted for the ZVSP program. 

Prior to completion of these 

measurements, Shell will use the radii 

in condition 8(c). 

(ii) Acoustic ‘‘Net’’ Array: Deploy 

acoustic recorders widely across the 

U.S. Chukchi Sea and on the prospect 

in order to gain information on the 

distribution of marine mammals in the 


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region. This program must be 

implemented as detailed in the 4MP. 

(11) Reporting Requirements: The 

Holder of this Authorization is required 

to: 

(a) Within 5 days of completing the 

sound source verification tests for the 

airguns, the Holder shall submit a 

preliminary report of the results to 

NMFS. A report on the results of the 

acoustic verification measurements of 

the drilling units and support vessels, 

not recorded in previous seasons, will 

be reported in the 90-day report. The 

report should report down to the 120-dB 

radius in 10-dB increments; 

(b) Submit a draft report on all 

activities and monitoring results to the 

Office of Protected Resources, NMFS, 

within 90 days of the completion of the 

exploration drilling program. This 

report must contain and summarize the 

following information: 

(i) Summaries of monitoring effort 

(e.g., total hours, total distances, and 

marine mammal distribution through 

the study period, accounting for sea 

state and other factors affecting 

visibility and detectability of marine 

mammals); 

(ii) Sound source verification results 

for drilling units and vessels recorded in 

2015; 

(iii) Analyses of the effects of various 

factors influencing detectability of 

marine mammals (e.g., sea state, number 

of observers, and fog/glare); 

(iv) Species composition, occurrence, 

and distribution of marine mammal 

sightings, including date, water depth, 

numbers, age/size/gender categories (if 

determinable), group sizes, and ice 

cover; 

(v) Sighting rates of marine mammals 

during periods with and without 

exploration drilling activities (and other 

variables that could affect detectability), 

such as: (A) Initial sighting distances 

versus drilling state; (B) closest point of 

approach versus drilling state; (C) 

observed behaviors and types of 

movements versus drilling state; (D) 

numbers of sightings/individuals seen 

versus drilling state; (E) distribution 

around the survey vessel versus drilling 

state; and (F) estimates of take by 

harassment; 

(v) Reported results from all 

hypothesis tests should include 

estimates of the associated statistical 

power when practicable; 

(vi) Estimate and report uncertainty in 

all take estimates. Uncertainty could be 

expressed by the presentation of 

confidence limits, a minimummaximum, posterior probability 

distribution, etc.; the exact approach 

will be selected based on the sampling 

method and data available; 

(vii) The report should clearly 

compare authorized takes to the level of 

actual estimated takes; 

(viii) If, changes are made to the 

monitoring program after the 

independent monitoring plan peer 

review, those changes must be detailed 

in the report. 

(c) The draft report will be subject to 

review and comment by NMFS. Any 

recommendations made by NMFS must 

be addressed in the final report prior to 

acceptance by NMFS. The draft report 

will be considered the final report for 

this activity under this Authorization if 

NMFS has not provided comments and 

recommendations within 90 days of 

receipt of the draft report. 

(d) A draft comprehensive report 

describing the aerial, acoustic, and 

vessel-based monitoring programs will 

be prepared and submitted within 240 

days of the date of this Authorization. 

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 

all industry activities and their impacts 

on marine mammals in the Arctic Ocean 

during 2015. 

(e) The draft comprehensive report 

will be subject to review and comment 

by NMFS, the Alaska Eskimo Whaling 

Commission, and the North Slope 

Borough Department of Wildlife 

Management. The draft comprehensive 

report will be accepted by NMFS as the 

final comprehensive report upon 

incorporation of comments and 

recommendations. 

(12)(a) In the unanticipated event that 

the drilling program operation clearly 

causes the take of a marine mammal in 

a manner prohibited by this 

Authorization, such as an injury (Level 

A harassment), serious injury or 

mortality (e.g., ship-strike, gear 

interaction, and/or entanglement), Shell 

shall immediately cease operations and 

immediately report the incident to the 

Chief of the Permits and Conservation 

Division, Office of Protected Resources, 

NMFS, by phone or email and the 

Alaska Regional Stranding Coordinators. 

The report must include the following 

information: (i) Time, date, and location 

(latitude/longitude) of the incident; (ii) 

the name and type of vessel involved; 

(iii) the vessel’s speed during and 

leading up to the incident; (iv) 

description of the incident; (v) status of 

all sound source use in the 24 hours 

preceding the incident; (vi) water depth; 

(vii) environmental conditions (e.g., 

wind speed and direction, Beaufort sea 

state, cloud cover, and visibility); (viii) 

description of marine mammal 

observations in the 24 hours preceding 

the incident; (ix) species identification 

or description of the animal(s) involved; 

(x) the fate of the animal(s); (xi) and 

photographs or video footage of the 

animal (if equipment is available). 

Activities shall not resume until 

NMFS is able to review the 

circumstances of the prohibited take. 

NMFS shall work with Shell to 

determine what is necessary to 

minimize the likelihood of further 

prohibited take and ensure MMPA 

compliance. Shell may not resume their 

activities until notified by NMFS via 

letter, email, or telephone. 

(b) In the event that Shell discovers an 

injured or dead marine mammal, and 

the lead PSO determines that the cause 

of the injury or death is unknown and 

the death is relatively recent (i.e., in less 

than a moderate state of decomposition 

as described in the next paragraph), 

Shell will immediately report the 

incident to the Chief of the Permits and 

Conservation Division, Office of 

Protected Resources, NMFS, by phone 

or email and the NMFS Alaska 

Stranding Hotline and/or by email to the 

Alaska Regional Stranding Coordinators. 

The report must include the same 

information identified in Condition 

12(a) above. Activities may continue 

while NMFS reviews the circumstances 

of the incident. NMFS will work with 

Shell to determine whether 

modifications in the activities are 

appropriate. 

(c) In the event that Shell discovers an 

injured or dead marine mammal, and 

the lead PSO determines that the injury 

or death is not associated with or related 

to the activities authorized in Condition 

2 of this Authorization (e.g., previously 

wounded animal, carcass with moderate 

to advanced decomposition, or 

scavenger damage), Shell shall report 

the incident to the Chief of the Permits 

and Conservation Division, Office of 

Protected Resources, NMFS, by phone 

or email and the NMFS Alaska 

Stranding Hotline and/or by email to the 

Alaska Regional Stranding Coordinators, 

within 24 hours of the discovery. Shell 

shall provide photographs or video 

footage (if available) or other 

documentation of the stranded animal 

sighting to NMFS and the Marine 

Mammal Stranding Network. Activities 

may continue while NMFS reviews the 

circumstances of the incident. 

(13) Activities related to the 

monitoring described in this 

Authorization do not require a separate 

scientific research permit issued under 

section 104 of the Marine Mammal 

Protection Act. 

(14) The Plan of Cooperation 

outlining the steps that will be taken to 


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Federal Register / Vol. 80, No. 42 / Wednesday, March 4, 2015 / Notices 11775 

cooperate and communicate with the 

native communities to ensure the 

availability of marine mammals for 

subsistence uses must be implemented. 

(15) Shell is required to comply with 

the Terms and Conditions of the 

Incidental Take Statement (ITS) 

corresponding to NMFS’s Biological 

Opinion issued to NMFS’s Office of 

Protected Resources. 

(16) A copy of this Authorization and 

the ITS must be in the possession of all 

contractors and PSOs operating under 

the authority of this Incidental 

Harassment Authorization. 

(17) Penalties and Permit Sanctions: 

Any person who violates any provision 

of this Incidental Harassment 

Authorization is subject to civil and 

criminal penalties, permit sanctions, 

and forfeiture as authorized under the 

MMPA. 

(18) This Authorization may be 

modified, suspended or withdrawn if 

the Holder fails to abide by the 

conditions prescribed herein or if the 

authorized taking is having more than a 

negligible impact on the species or stock 

of affected marine mammals, or if there 

is an unmitigable adverse impact on the 

availability of such species or stocks for 

subsistence uses. 

Request for Public Comment 

As noted above, NMFS requests 

comment on our analysis, the draft 

authorization, and any other aspect of 

the Notice of Proposed IHA for Shell’s 

2015 Chukchi Sea exploratory drilling 

program. Please include, with your 

comments, any supporting data or 

literature citations to help inform our 

final decision on Shell’s request for an 

MMPA authorization. 

Dated: February 26, 2015. 

Donna S. Wieting, 

Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2015–04427 Filed 3–3–15; 8:45 am] 

BILLING CODE 3510–22–P 


asabaliauskas on DSK5VPTVN1PROD with NOTICES