25730 Federal Register / Vol. 75, No. 88 / Friday, May 7, 2010 / Notices 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

RIN 0648–XW14 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to an Exploration 

Drilling Program in the Chukchi Sea, 

AK 

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 Offshore 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 June 7, 2010. 

ADDRESSES: Comments on the 

application should be addressed to 

Michael Payne, Chief, Permits, 

Conservation and Education Division, 

Office of Protected Resources, National 

Marine Fisheries Service, 1315 EastWest Highway, Silver Spring, MD 

20910. The mailbox address for 

providing e-mail comments is PR1.0648- 

XW14@noaa.gov. NMFS is not 

responsible for e-mail comments sent to 

addresses other than the one provided 

here. Comments sent via e-mail, 

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 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. The 

following associated documents are also 

available at the same Internet address: 

Shell’s 2010 Exploration Drilling 

Communication Plan Chukchi Sea, 

Alaska, and Shell’s 2010 Plan of 

Cooperation (POC) Camden Bay, Alaska. 

Documents cited in this notice may also 

be viewed, by appointment, during 

regular business hours, at the 

aforementioned address. 

FOR FURTHER INFORMATION CONTACT: 

Candace Nachman, Office of Protected 

Resources, NMFS, (301) 713–2289, ext 

156. 

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. 

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.’’ 

Section 101(a)(5)(D) of the MMPA 

established an expedited process by 

which citizens of the U.S. can apply for 

an authorization to incidentally take 

small numbers of marine mammals by 

harassment. Section 101(a)(5)(D) 

establishes a 45-day time limit for 

NMFS review of an application 

followed by a 30-day public notice and 

comment period on any proposed 

authorizations for the incidental 

harassment of marine mammals. Within 

45 days of the close of the comment 

period, NMFS must either issue or deny 

the authorization. 

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 

NMFS received an application on 

May 26, 2009, from Shell for the taking, 

by harassment, of marine mammals 

incidental to offshore exploration 

drilling on OCS leases in the Chukchi 

Sea, Alaska. NMFS reviewed Shell’s 

application and identified a number of 

issues requiring further clarification. 

After addressing comments from NMFS, 

Shell modified its application and 

submitted a revised application on 

December 11, 2009. However, after some 

additional discussions regarding certain 

activities, NMFS determined that a 

second revision to the application was 

warranted. The latest revised 

application was submitted to NMFS on 

April 14, 2010. NMFS carefully 

evaluated Shell’s application, including 

their analyses, and determined that the 

application is complete and that it is 

appropriate to make the necessary 

preliminary determinations pursuant to 

the MMPA. The April 14, 2010, 

application is the one available for 

public comment (see ADDRESSES) and 

considered by NMFS for this proposed 

IHA. 

Shell intends to drill up to three 

exploration wells at five possible drill 

sites on seven leases at the prospects 

known as Burger, Crackerjack, and 

Southwest (SW) Shoebill on OCS leases 

offshore in the Chukchi Sea, Alaska, 

during the 2010 Arctic open-water 

season (July through October). Impacts 

to marine mammals may occur from 

noise produced by the drillship and 

supporting vessels and aircraft. 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 include: 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 


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seal (Erignathus barbatus); ringed seal 

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

and ribbon seal (Histriophoca fasciata). 

Description of the Specified Activity 

Shell plans to conduct an offshore 

exploration drilling program on U.S. 

Department of the Interior, Minerals 

Management Service (MMS) Alaska 

OCS leases located greater than 60 mi 

(97 km) from the Chukchi Sea coast 

during the 2010 open-water season. The 

leases were acquired during the 

Chukchi Sea Oil and Gas Lease Sale 193 

held in February 2008. During the 2010 

drilling program, Shell plans to drill up 

to three exploration wells at five 

possible drill sites on seven leases at the 

prospects known as Burger, Crackerjack, 

and SW Shoebill. See Figure 1–1 in 

Shell’s application for the lease block 

and drill site locations (see ADDRESSES). 

All drilling is planned to be vertical. 

All of the possible Chukchi Sea 

offshore drill sites are located between 

64 and 124 mi (103 and 200 km) from 

the Chukchi coast in water depths 

between 142 and 149 ft (43.3 and 45.4 

m). Table 2–1 in Shell’s application 

provides the coordinates for the drill 

sites (see ADDRESSES). Shell plans to 

commence drilling at the Burger 

prospect as soon as ice, weather, and 

other conditions allow for safe drilling 

operations. In the event ice and weather 

conditions prevent the Discoverer from 

reaching the Burger prospect, Shell 

intends to mobilize its exploration 

operations to one of the alternative drill 

sites in the SW Shoebill or Crackerjack 

prospects. 

The ice reinforced drillship 

Discoverer will be used to drill the 

wells. The Discoverer is 514 ft (156.7 m) 

long with a maximum height (above 

keel) of 274 ft (83.7 m). Additional rig 

specifications for the Discoverer can be 

found in Attachment A of Shell’s 

application (see ADDRESSES). While on 

location at the drill sites, the Discoverer 

will be affixed to the seafloor using 

eight 7-ton Stevpris anchors arranged in 

a radial array. 

During the 2010 drilling season, the 

Discoverer will be attended by a 

minimum of seven vessels that will be 

used for ice-management, anchor 

handling, oil spill response (OSR), 

refueling, resupply, and servicing of the 

drilling operations. The ice-management 

vessels will consist of an icebreaker and 

an anchor handler. Table 1–2 in Shell’s 

application provides a list of the 

support vessels that will be used during 

the drilling program, as well as 

information about trip frequency and 

duration for each vessel. 

Primary resupply between the drill 

sites and logistics facilities at Dutch 

Harbor will use a coastwise qualified 

offshore supply vessel. Some minor 

resupply is also planned to be 

conducted between the drill sites and 

Wainwright with a shallow water 

landing craft. An ice-capable OSR vessel 

will be dedicated to Chukchi Sea 

operations and remain in the vicinity of 

the drillship when drilling into liquid 

hydrocarbon zones. An OSR barge, with 

an associated tug, will be staged in the 

nearshore zone, and an OSR tanker will 

be staged to respond to a discharge and 

provide storage capability for recovered 

liquids, if necessary. 

Shell’s base plan is for the icemanagement vessel, the M/V Vladimir 

Ignatjuk, and the anchor handler, the M/ 

V Nordica, or similar vessels, to 

accompany the Discoverer traveling 

north from Dutch Harbor through the 

Bering Strait, on or about July 1, 2010, 

then into the Chukchi Sea, before 

arriving on location approximately July 

4. Exploration drilling is expected to be 

complete by October 31. At the 

completion of the drilling season, one or 

two ice-management vessels, along with 

various support vessels, such as the 

OSR fleet, will accompany the 

Discoverer as it travels south out of the 

Chukchi Sea and through the Bering 

Strait to Dutch Harbor. Subject to ice 

conditions, alternate exit routes may be 

considered. 

Shell plans to cease drilling on or 

before October 31, after which the 

Discoverer will exit the Alaskan 

Chukchi Sea. Shell anticipates that the 

exploration drilling program will 

require approximately 37 days per well, 

including mudline cellar construction. 

Therefore, if Shell is able to drill three 

exploration wells during the 2010 openwater season, it would require a total of 

111 days. These estimates do not 

include any downtime for weather or 

other operational delays. Shell also 

assumes approximately 10 additional 

days will be needed for transit, drillship 

mobilization and mooring, drillship 

moves between locations, and drillship 

demobilization. 

Activities associated with the 2010 

Chukchi Sea exploration drilling 

program include operation of the 

Discoverer, associated support vessels, 

crew change support, and resupply. The 

Discoverer 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 in accordance 

with Shell’s Ice-management Plan 

(IMP). The anchor handler and OSR 

vessels will remain in close proximity to 

the drillship during drilling operations. 

The ice-management vessel will 

generally be working upwind of the 

drillship from 3–25 mi (4.8–40.2 km) 

away. Helicopters would be used to 

provide support for crew change, 

provision resupply, and any search-andrescue operations during the drilling 

season. 

Shell recognizes that the 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 

has developed and will implement an 

IMP to ensure real-time ice and weather 

forecasting is conducted in order to 

identify conditions that might put 

operations at risk and will modify its 

activities accordingly. The IMP also 

contains ice threat classification levels 

depending on the time available to 

suspend drilling operations, secure the 

well, and escape from advancing 

hazardous ice. Real-time ice and 

weather forecasting will be available to 

operations personnel for planning 

purposes and to alert the fleet of 

impending hazardous ice and weather 

conditions. Ice and weather forecasting 

is provided by Shell’s Ice and Weather 

Advisory Center. The center is 

continuously manned by experienced 

personnel, who rely on a number of data 

sources for ice forecasting and tracking, 

including: 

• Radarsat and Envisat data— 

satellites with Synthetic Aperture 

Radar, providing all-weather imagery of 

ice conditions with very high 

resolution; 

• Moderate Resolution Imaging 

Spectroradiometer—a satellite 

providing lower resolution visual and 

near infrared imagery; 

• Aerial reconnaissance—provided 

by specially deployed fixed wing or 

rotary wing aircraft for confirmation of 

ice conditions and position; 

• Reports from ice specialists on the 

ice-management and anchor handling 

vessels and from the ice observer on the 

drillship; 

• Incidental ice data provided by 

commercial ships transiting the area; 

and 

• Information from NOAA ice centers 

and the University of Colorado. 

The ice-management/anchor handling 

vessels would manage the ice by 

deflecting any ice floes that could affect 

the Discoverer when it is drilling and 

would also handle the Discoverer’s 

anchors during connection to and 

separation from the seafloor. The ice 

floe frequency and intensity are 

unpredictable and could range from no 


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ice to ice sufficiently dense that the fleet 

has insufficient capacity to continue 

operating, and the Discoverer would 

need to disconnect from its anchors and 

move off site. If ice is present, icemanagement activities may be necessary 

in early July and towards the end of 

operations in late October, but it is not 

expected to be needed throughout the 

proposed drilling season. Shell has 

indicated that when ice is present at the 

drill site, ice disturbance will be limited 

to the minimum needed to allow 

drilling to continue. First-year ice will 

be the type most likely to be 

encountered. The ice-management 

vessels will be tasked with managing 

the ice so that it will flow easily around 

and past the Discoverer without 

building up in front of it. This type of 

ice is managed by the ice-management 

vessel continually moving back and 

forth across the drift line, directly updrift of the Discoverer and making turns 

at both ends. During ice-management, 

the vessel’s propeller is rotating at 

approximately 15–20 percent of the 

vessel’s propeller rotation capacity. Icemanagement 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, thereby reducing cavitation 

effects in the water. Occasionally, there 

may be multi-year ice ridges that would 

be managed at a much slower speed 

than that used to manage first-year ice. 

Shell has indicated that they do not 

have any intention of breaking ice with 

the ice-management vessels but, rather, 

intend to push it out of the area as 

described here. Should ice become so 

prevalent in the drilling area that it is 

difficult to continue operations without 

the breaking of ice, Shell has indicated 

that they would stop operations and 

move off site instead of breaking ice (S. 

Childs, Shell, 2010, pers. comm.). Shell 

has indicated that ice breaking would 

only be conducted if the ice poses an 

immediate safety hazard at the drill 

sites. 

Potential impacts to marine mammals 

could occur from the noise produced by 

the drillship and its support vessels and 

aircraft. The drillship produces 

continuous noise into the marine 

environment. NMFS currently uses a 

threshold of 120 dB re 1 μPa (rms) for 

the onset of Level B harassment from 

continuous sound sources. Sound 

measurements from the Discoverer have 

not previously been conducted in the 

Arctic or elsewhere; however, sounds 

from a similar drillship, the Northern 

Explorer II, were measured at two 

different times and locations in the 

Beaufort Sea (Miles et al., 1987; Greene, 

1987a,b). In both cases, a support vessel 

was present in the vicinity of the 

drillship, thus providing an aggregate 

source level for modeling the combined 

drilling activities. The underwater 

received sound pressure level (SPL) in 

the 20–1,000 Hz band for drilling 

activity by the Northern Explorer II, 

including a nearby support vessel, was 

134 dB re 1 μPa (rms) at 0.1 mi (0.2 km; 

Greene, 1987b). The back-propagated 

source levels (175 dB re 1 μPa at 1 m) 

from these measurements were used as 

a proxy for modeling the sounds likely 

to be produced by drilling activities 

from the Discoverer. NMFS has 

determined that the sound 

measurements for the Northern Explorer 

II constitute a good proxy for estimating 

sound radii for the Discoverer. Sound 

propagation measurements will be 

performed on the Discoverer in 2010 

once on location near the Chukchi Sea 

drill sites. The results of those 

measurements will be used during the 

drilling season to implement proposed 

mitigation measures described later in 

this document (see the ‘‘Proposed 

Mitigation’’ section). 

Although there will be several 

support vessels in the drilling 

operations area, NMFS considers the 

possibility of collisions with marine 

mammals highly unlikely. Once on 

location, the majority of the support 

vessels will remain in the area of the 

drillship throughout the 2010 drilling 

season and will not be making trips 

between the shorebase and the offshore 

vessels. Aircraft travel would be 

controlled by Federal Aviation 

Administration approved flight paths. 

Shell has agreed to a flight altitude of 

1,500 ft (457 m; except during takeoffs 

and landings or during emergencies) to 

minimize impacts on marine mammals. 

As the crew change/resupply activities 

are considered part of normal vessel 

traffic and are not anticipated to impact 

marine mammals in a manner that 

would rise to the level of taking, those 

activities are not considered further in 

this document. Additionally, icemanagement activities are not 

anticipated to impact marine mammals 

in a manner that would rise to the level 

of taking. This is based on the fact that 

the propeller rotation (i.e., cavitation) 

will be similar to that of vessels under 

normal operations and will not be used 

at 100 percent power as is the case in 

other situations rising to the level of 

taking (e.g., thruster use for dynamic 

positioning at terminals). 

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 3–1 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. 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. Additionally, the 

ribbon seal is considered a ‘‘species of 

concern’’ under the ESA, and the 

bearded and ringed seals are ‘‘candidate 

species’’ under the ESA, meaning they 

are currently being considered for 

listing. 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 include: 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 


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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, and abundance of 

each of the species under NMFS 

jurisdiction mentioned in this 

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 

2009 SAR is available at: http:// 

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

ak2009.pdf. 

Brief Background on Marine Mammal 

Hearing 

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 derived 

using auditory evoked potential 

techniques, 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 22 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; and 

• Pinnipeds in Water: functional 

hearing is estimated to occur between 

approximately 75 Hz and 75 kHz, with 

the greatest sensitivity between 

approximately 700 Hz and 20 kHz. 

As mentioned previously in this 

document, 12 marine mammal species 

(four pinniped and eight cetacean 

species) are likely to occur in the 

proposed drilling area. Of the eight 

cetacean species likely to occur in 

Shell’s project area, five are classified as 

low frequency cetaceans (i.e., bowhead, 

gray, humpback, minke, and fin 

whales), two are classified as midfrequency cetaceans (i.e., beluga and 

killer whales), and one is classified as 

a high-frequency cetacean (i.e., harbor 

porpoise) (Southall et al., 2007). 

Potential Effects of the Specified 

Activity on Marine Mammals 

Potential effects of Shell’s proposed 

drilling program in the Chukchi Sea on 

marine mammals would most likely be 

acoustic in nature. Petroleum 

development and associated activities 

introduce sound into the marine 

environment. Potential acoustic effects 

on marine mammals relate to sound 

produced by drilling activity, vessels, 

and aircraft. The potential effects of 

sound from the proposed exploratory 

drilling program 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). 

However, for reasons discussed later in 

this document, it is unlikely that there 

would be any cases of temporary, or 

especially permanent, hearing 

impairment resulting from these 

activities. As outlined in previous 

NMFS documents, the effects of noise 

on marine mammals are highly variable, 

and can be categorized as follows (based 

on Richardson et al., 1995a): 

(1) The noise may be too weak to be 

heard at the location of the animal (i.e., 

lower than the prevailing ambient noise 

level, the hearing threshold of the 

animal at relevant frequencies, or both); 

(2) The noise may be audible but not 

strong enough to elicit any overt 

behavioral response; 

(3) The noise may elicit reactions of 

variable conspicuousness and variable 

relevance to the well being of the 

marine mammal; these can range from 

temporary alert responses to active 

avoidance reactions such as vacating an 

area at least until the noise event ceases 

but potentially for longer periods of 

time; 

(4) Upon repeated exposure, a marine 

mammal may exhibit diminishing 

responsiveness (habituation), or 

disturbance effects may persist; the 

latter is most likely with sounds that are 

highly variable in characteristics, 

infrequent, and unpredictable in 

occurrence, and associated with 

situations that a marine mammal 

perceives as a threat; 

(5) Any anthropogenic noise that is 

strong enough to be heard has the 

potential to reduce (mask) the ability of 

a marine mammal to hear natural 

sounds at similar frequencies, including 

calls from conspecifics, and underwater 

environmental sounds such as surf 

noise; 

(6) If mammals remain in an area 

because it is important for feeding, 

breeding, or some other biologically 

important purpose even though there is 

chronic exposure to noise, it is possible 

that there could be noise-induced 

physiological stress; this might in turn 

have negative effects on the well-being 

or reproduction of the animals involved; 

and 

(7) Very strong sounds have the 

potential to cause a temporary or 

permanent reduction in hearing 

sensitivity. In terrestrial mammals, and 

presumably marine mammals, received 

sound levels must far exceed the 

animal’s hearing threshold for there to 

be any temporary threshold shift (TTS) 

in its hearing ability. For transient 

sounds, the sound level necessary to 

cause TTS is inversely related to the 

duration of the sound. Received sound 

levels must be even higher for there to 

be risk of permanent hearing 

impairment. In addition, intense 

acoustic or explosive events may cause 

trauma to tissues associated with organs 

vital for hearing, sound production, 

respiration and other functions. This 

trauma may include minor to severe 

hemorrhage. 

Drilling Sounds 

Exploratory drilling will be conducted 

from a vessel specifically designed for 

such operations in the Arctic. 

Underwater sound propagation results 

from the use of generators, drilling 

machinery, and the rig itself. Received 

sound levels during vessel-based 

operations may fluctuate depending on 

the specific type of activity at a given 


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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 558 ft (170 m) the 20–1000 

Hz band level was 122–125 dB for the 

drillship Explorer I. Underwater sound 

levels were slightly higher (134 dB) 

during drilling activity from the 

Northern Explorer II at a range of 656 ft 

(200 m), although tones were only 

recorded below 600 Hz. Underwater 

sound measurements from the Kulluk at 

0.62 mi (1 km) were higher (143 dB) 

than from the other two vessels. Shell 

used the measurements from the 

Northern Explorer II to model the 

various sound radii (which are 

discussed later in this document) for the 

Discoverer. Once on location at the drill 

sites in the Chukchi Sea, Shell plans to 

take measurements of the Discoverer to 

quantify the absolute sound levels 

produced by drilling and to monitor 

their variations with time, distance, and 

direction from the drillship. Based on 

the similarities of the two drillships, 

NMFS has preliminarily determined 

that the radii produced by the 

Discoverer would be similar to those 

recorded for the Northern Explorer II. 

Vessel Sounds 

In addition to the drillship, various 

types of vessels will be used in support 

of the operations, including icemanagement vessels, anchor handlers, 

and oil-spill response 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 (e.g., Aerts et al., 

2008; Hauser et al., 2008; Brueggeman, 

2009; Ireland et al., 2009). For example, 

Garner and Hannay (2009) estimated 

sound pressure levels of 100 dB at 

distances ranging from approximately 

1.5 to 2.3 mi (2.4 to 3.7 km) from 

various types of barges. MacDonald et 

al. (2008) estimated higher underwater 

SPLs from the seismic vessel Gilavar of 

120 dB at approximately 13 mi (21 km) 

from the source, although the sound 

level was only 150 dB at 85 ft (26 m) 

from the vessel. Like other industrygenerated sound, underwater sound 

from vessels is generally at relatively 

low frequencies. 

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. 

Sound levels during ice-management 

activities would not be as intense as 

during icebreaking, and the resulting 

effects to marine species would be less 

significant in comparison. During icemanagement, the vessel’s propeller is 

rotating at approximately 15–20 percent 

of the vessel’s propeller rotation 

capacity. Instead of actually breaking 

ice, during ice-management, the vessel 

redirects and repositions the ice by 

pushing it away from the direction of 

the drillship at slow speeds so that the 

ice floe does not slip past the vessel 

bow. Basically, ice-management occurs 

at slower speed, lower power, and 

slower propeller rotation speed (i.e., 

lower cavitation), allowing for fewer 

repositions of the vessel, thereby 

reducing cavitation effects in the water 

compared to those that would occur 

during icebreaking. Once on location at 

the drill sites in the Chukchi Sea, Shell 

plans to measure the sound levels 

produced by vessels operating in 

support of drilling operations. These 

vessels will include crew change 

vessels, tugs, ice-management vessels, 

and spill response vessels. 

Aircraft Sound 

Helicopters may be used for personnel 

and equipment transport to and from 

the drillship, as well as any search-andrescue operations that may be necessary. 

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 drillship will generally 

maintain straight-line routes at altitudes 

of at least 1,000 ft (305 m), thereby 

limiting the received levels at and below 

the surface. 

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). 

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 


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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). 

Masking 

The term ‘‘masking’’ refers to the 

obscuring of sounds of interest by 

interfering sounds, generally at similar 

frequencies. Masking effects of 

underwater sounds on marine mammal 

calls and other natural sounds are 

expected to be limited. For example, 

beluga whales primarily use highfrequency sounds to communicate and 

locate prey; therefore, masking by lowfrequency 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. For 

example, bowhead whale calls are 

frequently detected in the presence of 

seismic pulses, although the number of 

calls detected may sometimes be 

reduced (Richardson et al., 1986; Greene 

et al., 1999; Blackwell et al., 2009). 

Additionally, 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 nearly 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 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). 

Cummings et al. (1984) subjected 

breeding ringed seals to recordings of 

industrial sounds. The authors did not 

document any impacts to ringed seal 

vocalizations as a result of exposure to 

the recordings. 

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. If, as 

described later in this document, certain 

species avoid the proposed drilling 

locations, impacts from masking will be 

low. 

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 

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 provide an idea of the 

variability that would be expected given 

the different sensitivities of marine 


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mammal species to sound and the wide 

range of potential acoustic sources to 

which a marine mammal may be 

exposed. 

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). 

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 ice 

breaking 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 

other sightings were at much greater 

distances. Few bowheads were recorded 

near industrial activities by aerial 

observers, but observations by surface 

observers suggested that 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 whale 

reactions 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). Restriction 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 μPa (rms). Probability of 

avoidance and other behavioral effects 

increased when received levels were 

from 120–160 dB re 1 μPa (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 percent, 50 percent, and 90 percent 

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 

percent 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 


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between 120 and 130 dB re 1 μPa (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 Pt. 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 

(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. However, 

while the Vladimir Ignatjuk (an 

icebreaker) is anticipated to be one of 

the vessels attending the Discoverer, it 

will only be conducting icemanagement activities (which were 

described in the ‘‘Description of the 

Specified Activity’’ section earlier in 

this document) and not physical 

breaking of ice. Thus, NMFS does not 

anticipate that marine mammals would 

exhibit the types of behavioral reactions 

as those noted in the aforementioned 

studies. 

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 

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 to 120 dB, while 

others failed to exhibit such responses 

for exposure to received levels from 120 

to 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 ice-breaking ships. 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 ice-breaking 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 


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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. 

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 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’’). 

Harbor porpoise off Vancouver Island, 

British Columbia, were found to be 

sensitive to the simulated sound of a 2- 

megawatt offshore wind turbine 

(Koschinski et al., 2003). The porpoises 

remained significantly further away 

from the sound source when it was 

active, and this effect was seen out to a 

distance of 60 m (197 ft). The device 

used in that study produced sounds in 

the frequency range of 30 to 800 Hz, 

with peak source levels of 128 dB re 1 

μPa at 1 m at the 80- and 160-Hz 

frequencies. 

Kastelein et al. (2005) exposed two 

captive harbor porpoise (a highfrequency cetacean) to various nonpulse sounds in an approximately 111.5 

× 65.6 ft (34 × 20 m) enclosure. The 

frequency range of the four test sounds 

fell into the 1⁄3-octave bands 8, 10, 12.5, 

and 16 kHz, with a source level range 

of 116 to 130 [plus or minus 3] dB, 

depending on the sound source. Each 

session lasted for 30 minutes (15-min 

period of baseline [no sound emission] 

followed immediately by 15-min test 

period [sound emission]). The 

researchers measured the distance 

between the underwater transducer and 

the surfacing area of the porpoises to 

determine the deterrent effect and the 

number of respirations during the 

session to determine the level of 

agitation of the animals. Kastelein et al. 

(2005) found that one porpoise was 

displaced between 29.5 and 42.7 ft (9 

and 13 m), and the other one was 

displaced between 16.4 and 32.8 ft (5 

and 10 m). Additionally, the researchers 

found that both animals surfaced more 

during test periods than during baseline 

periods. The porpoises were not 

reinforced with food for remaining in 

the sound field. It should be noted, 

however, that the sounds used in this 

study produce frequencies much higher 

than those that will be produced by the 

drillship proposed to be used by Shell 

for this program. 

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 

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). 

Responses of pinnipeds to drilling 

noise have not been well studied. 

Richardson et al. (1995) summarizes the 

few available studies, which showed 

ringed and bearded seals in the Arctic 

to be rather tolerant of drilling noise. 

Seals were often seen near active 

drillships and approached, to within 50 

m (164 ft), a sound projector 

broadcasting low-frequency drilling 

sound. 

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 

<1.9 mi (3 km) 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 


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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. 

Reactions of harbor seals to the 

simulated noise of a 2-megawatt wind 

power generator were measured by 

Koschinski et al. (2003). Harbor seals 

surfaced significantly further away from 

the sound source when it was active and 

did not approach the sound source as 

closely. The device used in that study 

produced sounds in the frequency range 

of 30 to 800 Hz, with peak source levels 

of 128 dB re 1 μPa at 1 m at the 80- and 

160-Hz frequencies. 

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. The following subsections 

discuss in somewhat more detail the 

possibilities of TTS, permanent 

threshold shift (PTS), and non-auditory 

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. 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. 

Human non-impulsive noise exposure 

guidelines are based on exposures of 

equal energy (the same sound exposure 

level [SEL]) producing equal amounts of 

hearing impairment regardless of how 

the sound energy is distributed in time 

(NIOSH, 1998). Until recently, previous 

marine mammal TTS studies have also 

generally supported this equal energy 

relationship (Southall et al., 2007). 

Three newer studies, two by Mooney et 

al. (2009a,b) on a single bottlenose 

dolphin either exposed to playbacks of 

U.S. Navy mid-frequency active sonar or 

octave-band noise (4–8 kHz) and one by 

Kastak et al. (2007) on a single 

California sea lion exposed to airborne 

octave-band noise (centered at 2.5 kHz), 

concluded that for all noise exposure 

situations the equal energy relationship 

may not be the best indicator to predict 

TTS onset levels. Generally, with sound 

exposures of equal energy, those that 

were quieter (lower SPL) with longer 

duration were found to induce TTS 

onset more than those of louder (higher 

SPL) and shorter duration. Given the 

available data, the received level of a 

single seismic pulse (with no frequency 

weighting) might need to be 

approximately 186 dB re 1 μPa2.s (i.e., 

186 dB SEL) in order to produce brief, 

mild TTS. Exposure to several strong 

seismic pulses that each have received 

levels near 175–180 dB SEL might result 

in slight TTS in a small odontocete, 

assuming the TTS threshold is (to a first 

approximation) a function of the total 

received pulse energy. Given that the 

SPL is approximately 10–15 dB higher 

than the SEL value for the same pulse, 

an odontocete would need to be 

exposed to a sound level of 190 dB re 

1 μPa (rms) in order to incur TTS. 

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 lower than 

those to which odontocetes are most 

sensitive, and natural background noise 

levels at those low frequencies tend to 

be higher. Marine mammals can hear 

sounds at varying frequency levels. 

However, sounds that are produced in 

the frequency range at which an animal 

hears the best do not need to be as loud 

as sounds in less functional frequencies 

to be detected by the animal. 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., 


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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. Since current NMFS practice 

assumes the same thresholds for the 

onset of hearing impairment in both 

odontocetes and mysticetes, the 

threshold is likely conservative for 

mysticetes. 

In free-ranging 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). Kastak et al. (1999) 

reported TTS of approximately 4–5 dB 

in three species of pinnipeds (harbor 

seal, Californian sea lion, and northern 

elephant seal) after underwater 

exposure for approximately 20 minutes 

to noise with frequencies ranging from 

100 Hz to 2,000 Hz at received levels 

60–75 dB above hearing threshold. This 

approach allowed similar effective 

exposure conditions to each of the 

subjects, but resulted in variable 

absolute exposure values depending on 

subject and test frequency. Recovery to 

near baseline levels was reported within 

24 hours of noise exposure (Kastak et 

al., 1999). Kastak et al. (2005) followed 

up on their previous work using higher 

sensitive levels and longer exposure 

times (up to 50-min) and corroborated 

their previous findings. The sound 

exposures necessary to cause slight 

threshold shifts were also determined 

for two California sea lions and a 

juvenile elephant seal exposed to 

underwater sound for similar duration. 

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 μPa2.s; Bowles et al., 

unpub. data). 

NMFS (1995, 2000) concluded that 

cetaceans and pinnipeds should not be 

exposed to pulsed underwater noise at 

received levels exceeding, respectively, 

180 and 190 dB re 1 μPa (rms). The 

established 180- and 190-dB re 1 μPa 

(rms) criteria are not considered to be 

the levels above which TTS might 

occur. Rather, they are the received 

levels above which, in the view of a 

panel of bioacoustics specialists 

convened by NMFS before TTS 

measurements for marine mammals 

started to become available, one could 

not be certain that there would be no 

injurious effects, auditory or otherwise, 

to marine mammals. Based on the 

summary provided here and the fact 

that modeling indicates the backpropagated source level for the drillship 

to be 175 dB re 1 μPa at 1 m, 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. 

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. 

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. 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. PTS might occur at 

a received sound level at least several 

decibels above that inducing mild TTS. 

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 drillship 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 drillship, the levels immediately 

adjacent to the drillship may not be 

sufficient to induce PTS, even if the 

animals remain in the immediate 

vicinity of the activity. The modeled 

source level from a similar drillship 

(i.e., the Northern Explorer II) suggests 

that marine mammals located 

immediately adjacent to a drillship such 

as the Discoverer 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. 

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. 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. 

Until recently, it was assumed that 

diving marine mammals are not subject 

to the bends or air embolism. This 

possibility was first explored at a 

workshop (Gentry [ed.], 2002) held to 

discuss whether the stranding of beaked 

whales in the Bahamas in 2000 

(Balcomb and Claridge, 2001; NOAA 

and USN, 2001) might have been related 

to bubble formation in tissues caused by 

exposure to noise from naval sonar. 

However, the opinions were 

inconclusive. Jepson et al. (2003) first 

suggested a possible link between midfrequency sonar activity and acute and 

chronic tissue damage that results from 

the formation in vivo of gas bubbles, 

based on the beaked whale stranding in 

the Canary Islands in 2002 during naval 

exercises. Fernandez et al. (2005a) 

showed those beaked whales did indeed 

have gas bubble-associated lesions as 

well as fat embolisms. Fernandez et al. 

(2005b) also found evidence of fat 

embolism in three beaked whales that 

stranded 62 mi (100 km) north of the 

Canaries in 2004 during naval exercises. 

Examinations of several other stranded 

species have also revealed evidence of 

gas and fat embolisms (Arbelo et al., 

2005; Jepson et al., 2005a; Mendez et al., 

2005). Most of the afflicted species were 

deep divers. There is speculation that 

gas and fat embolisms may occur if 

cetaceans ascend unusually quickly 

when exposed to aversive sounds or if 

sound in the environment causes the 

destabilization of existing bubble nuclei 

(Potter, 2004; Arbelo et al., 2005; 

Fernandez et al., 2005a; Jepson et al., 

2005b). Even if gas and fat embolisms 

can occur during exposure to midfrequency sonar, there is no evidence 

that that type of effect occurs in 

response to the types of sound produced 

during the proposed exploratory 

activities. Also, most evidence for such 


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effects has been in beaked whales, 

which do not occur in the proposed 

survey area. 

The low levels of continuous sound 

that will be produced by the drillship 

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. 

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). Underwater sound from 

drilling and support activities is less 

energetic and has slower rise times, and 

there is no proof that they can cause 

serious injury, death, or stranding. 

However, the association of mass 

strandings of beaked whales with naval 

exercises and, in one case, a LamontDoherty Earth Observatory seismic 

survey, 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. The potential for 

stranding to result from exposure to 

strong pulsed sound suggests that 

caution be used when exposing marine 

mammals to pulsed or other underwater 

sound. Most of the stranding events 

associated with exposure of marine 

mammals to pulsed sound however, 

have involved beaked whales which do 

not occur in the proposed area. 

Additionally, the sound produced from 

the proposed activities will be at much 

lower levels than those reported during 

stranding events, as the source levels of 

the drillship are much lower than those 

other sources. Pulsed sounds, such as 

those produced by seismic airgun 

arrays, are transient and have rapid rise 

times, whereas the non-impulsive, 

continuous sounds produced by the 

drillship to be used by Shell do not have 

a rapid rise time. 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. 

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 Habitat 

The primary potential impacts to 

marine mammals and other marine 

species are associated with elevated 

sound levels produced by the 

exploratory drilling program. However, 

other potential impacts to the 

surrounding habitat from physical 

disturbance are also possible. 

Potential Impacts From Seafloor 

Disturbance 

There is a possibility of some seafloor 

disturbance or temporary increased 

turbidity in the seabed sediments during 

anchoring and excavation of the 

mudline cellars (MLCs). The amount 

and duration of disturbed or turbid 

conditions will depend on sediment 

material and consolidation of specific 

activity. 

Both the anchor and anchor chain 

will disturb sediments and create an 

‘‘anchor scar,’’ which is a depression in 

the seafloor caused by the anchor 

embedding. The anchor scar is a 

depression with ridges of displaced 

sediment, and the area of disturbance 

will often be greater than the size of the 

anchor itself because the anchor is 

dragged along the seafloor until it takes 

hold and sets. The drilling units will be 

stabilized and held in place with a 

system of eight 15,432 lbs (7,000 kg) 

anchors during operations, which are 

designed to embed into the seafloor. The 

area of seafloor that would be impacted 

by the setting of an anchor varies, but, 

on average, each anchor may impact an 

area of 2,124 ft2 (197 m2) of the seafloor, 

including the scar made when the 

anchor chain is dragged across the 

seafloor. Assuming eight anchors will be 

set for each well, mooring the 

Discoverer at three drill sites would 

disturb approximately 1.2 acres (4,736 

m2) of seafloor. This estimate assumes 

that the anchors are set only once and 

not moved by outside forces such as sea 

current. However, based on the vast size 

of the Chukchi Sea, the area of 

disturbance is not anticipated to 

adversely affect marine mammal use of 

the area. 

Once the drillship ends operation, the 

anchors will be retrieved. 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 5–10 

years after retrieval. Centaur Associates, 

Inc. (1984) reported that anchoring in 

sand or muddy sand sediments may not 

result in anchor scars or may result in 

scars that do not persist. Shallow 

hazards and geotechnical surveys 

conducted at the historic Burger, 

Crackerjack, and Tourmaline prospects 

indicate the surficial sediments in 

Shell’s Burger, Crackerjack, and SW 

Shoebill prospects consist of fine 

materials (clays and silts), which are 

reworked by currents, storms, and ice 

gouging. The physical effects of MLCs 

and anchor scars are expected to be 

obscured within 5–10 years. 

Vessel mooring and MLC construction 

would result in increased suspended 

sediment in the water column that 

could result in lethal effects on some 

zooplankton (food source for baleen 

whales). However, compared to the 

overall population of zooplankton and 

the localized nature of effects, any 

mortality that may occur would not be 

considered significant. Due to fast 

regeneration periods of zooplankton, 

populations are expected to recover 

quickly. 

Impacts on fish resulting from 

suspended sediments would be 

dependent upon the life stage of the fish 

(e.g., eggs, larvae, juveniles, or adults), 

the concentration of the suspended 

sediments, the type of sediment, and the 

duration of exposure (IMG Golder, 

2004). Eggs and larvae have been found 

to exhibit greater sensitivity to 

suspended sediments (Wilber and 

Clarke, 2001) and other stresses, which 

is thought to be related to their relative 

lack of motility (Auld and Schubel, 

1978). Sedimentation could affect fish 

by causing egg morbidity of demersal 

fish feeding near or on the ocean floor 

(Wilber and Clarke, 2001). Surficial 

membranes are especially susceptible to 

abrasion (Cairns and Scheier, 1968). 

Adhesive demersal eggs could be 

exposed to the sediments as long as the 

excavation activity continues, while 

exposure of pelagic eggs would be much 

shorter as they move with ocean 

currents (Wilber and Clarke, 2001). Most 

of the offshore demersal marine fish 

species in the northeastern Chukchi Sea 

(Shell’s proposed project area) spawn 

under the ice during the winter and 

therefore would not be affected by 

redeposition of sediments on the 

seafloor due to MLC construction since 

Shell has not scheduled any exploration 

drilling activities during the winter 

months. 

Most diadromous fish species 

expected to be present in the area of 

Shell’s drilling operations lay their eggs 

in freshwater or coastal estuaries. 

Therefore, only those eggs carried into 

the marine environment by winds and 

current would be affected by these 

operations. Because Shell’s proposed 


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drill sites occur 64 and 124 mi (103 and 

200 km) from the Chukchi coast, the 

statistical probability of diadromous fish 

eggs being present in the vicinity of 

Shell’s proposed operations is 

infinitesimally small. Thus, impacts on 

diadromous fish eggs due to abrasion, 

puncture, burial, or other effects 

associated with anchoring or MLC 

construction would be slight. Further, 

since most diadromous fish species 

produce eggs prolifically, even if a small 

number of eggs were impacted by these 

activities, the total species population 

would not be expected to be impacted. 

Suspended sediments, resulting from 

vessel mooring and MLC excavation, are 

not expected to result in permanent 

damage to habitats used by the marine 

mammal species in the proposed project 

area or on the food sources that they 

utilize. Rather, NMFS considers that 

such impacts will be temporary in 

nature and concentrated in the areas 

directly surrounding vessel mooring and 

MLC excavation activities—areas which 

are very small relative to the overall 

Chukchi Sea region. Less than 

0.0000001 percent of the fish habitat in 

the LS 193 area would be directly 

affected by the mooring and excavation 

activity. 

Potential Impacts From Sound 

Generation 

With regard to fish as a prey source 

for odontocetes and seals, fish are 

known to hear and react to sounds and 

to use sound to communicate (Tavolga 

et al., 1981) and possibly avoid 

predators (Wilson and Dill, 2002). 

Experiments have shown that fish can 

sense both the strength and direction of 

sound (Hawkins, 1981). Primary factors 

determining whether a fish can sense a 

sound signal, and potentially react to it, 

are the frequency of the signal and the 

strength of the signal in relation to the 

natural background noise level. 

The level of sound at which a fish 

will react or alter its behavior is usually 

well above the detection level. Fish 

have been found to react to sounds 

when the sound level increased to about 

20 dB above the detection level of 120 

dB (Ona, 1988); however, the response 

threshold can depend on the time of 

year and the fish’s physiological 

condition (Engas et al., 1993). In 

general, fish react more strongly to 

pulses of sound rather than a 

continuous signal (Blaxter et al., 1981), 

such as the type of sound that will be 

produced by the drillship, and a quicker 

alarm response is elicited when the 

sound signal intensity rises rapidly 

compared to sound rising more slowly 

to the same level. 

Investigations of fish behavior in 

relation to vessel noise (Olsen et al., 

1983; Ona, 1988; Ona and Godo, 1990) 

have shown that fish react when the 

sound from the engines and propeller 

exceeds a certain level. Avoidance 

reactions have been observed in fish 

such as cod and herring when vessels 

approached close enough that received 

sound levels are 110 dB to 130 dB 

(Nakken, 1992; Olsen, 1979; Ona and 

Godo, 1990; Ona and Toresen, 1988). 

However, other researchers have found 

that fish such as polar cod, herring, and 

capeline are often attracted to vessels 

(apparently by the noise) and swim 

toward the vessel (Rostad et al., 2006). 

Typical sound source levels of vessel 

noise in the audible range for fish are 

150 dB to 170 dB (Richardson et al., 

1995a). (Based on measurements from 

the Northern Explorer II, the 160 dB 

radius for the Discoverer was modeled 

by JASCO to be approximately 115 ft [35 

m]; therefore, fish would need to be in 

close proximity to the drillship for the 

noise to be audible). In calm weather, 

ambient noise levels in audible parts of 

the spectrum lie between 60 dB to 100 

dB. 

Sound will also occur in the marine 

environment from the various support 

vessels. Reported source levels for 

vessels during ice-management have 

ranged from 175 dB to 185 dB (Brewer 

et al., 1993, Hall et al., 1994). However, 

ice-management activities are not 

expected to be necessary throughout the 

entire drilling season, so impacts from 

that activity would occur less frequently 

than sound from the drillship. Sound 

pressures generated while drilling have 

been measured during past exploration 

in the Beaufort and Chukchi seas. 

Sounds generated by drilling and icemanagement are generally low 

frequency and within the frequency 

range detectable by most fish. 

Based on a sound level of 

approximately 140 dB, there may be 

some avoidance by fish of the area near 

the drillship while drilling, around icemanagement vessels in transit and 

during ice-management, and around 

other support and supply vessels when 

underway. Any reactions by fish to 

these sounds will last only minutes 

(Mitson and Knudsen, 2003; Ona et al., 

2007) longer than the vessel is operating 

at that location or the drillship is 

drilling. Any potential reactions by fish 

would be limited to a relatively small 

area within about 0.9 mi (1.4 km) of the 

drillship during drilling based on the 

modeled 120-dB isopleth. Avoidance by 

some fish or fish species could occur 

within portions of this area. No 

important spawning habitats are known 

to occur at or near the drilling locations. 

Additionally, impacts to fish as a prey 

species for odontocetes and seals are 

expected to be minor. 

Some mysticetes, including bowhead 

whales, feed on concentrations of 

zooplankton. Bowhead whales primarily 

feed off Point Barrow in September and 

October. Reactions of zooplankton to 

sound are, for the most part, not known. 

Their ability to move significant 

distances is limited or nil, depending on 

the type of zooplankton. A reaction by 

zooplankton to sounds produced by the 

exploratory drilling program would only 

be relevant to whales if it caused 

concentrations of zooplankton to scatter. 

Pressure changes of sufficient 

magnitude to cause that type of reaction 

would probably occur only very close to 

the sound source, if any would occur at 

all due to the low energy sounds 

produced by the drillship. However, 

Barrow is located 140 mi (225 km) east 

of Shell’s prospect areas. Impacts on 

zooplankton behavior are predicted to 

be inconsequential. Thus, bowhead 

whales feeding off Point Barrow would 

not be adversely affected. 

Gray whales are bottom feeders and 

suck sediment and the benthic 

amphipods that are their prey from the 

seafloor. The species primary feeding 

habitats are in the northern Bering Sea 

and Chukchi Sea (Nerini, 1984; Moore 

et al., 1986; Weller et al., 1999). In the 

northeastern Chukchi Sea, gray whales 

can be found feeding in the shallow 

offshore water area known as Hanna 

Shoals, which is located approximately 

25 mi (40 km) northeast from the 

proposed drill sites. This area lies 

outside of the 120-dB ensonified zone 

for all of Shell’s proposed Chukchi Sea 

drill sites. While some gray whales may 

migrate past or through Shell’s proposed 

drill sites, no impacts to gray whales 

feeding at Hanna Shoal are anticipated 

based on the distance from the proposed 

activity and the area of the ensonified 

zone. Additionally, Yazvenko et al. 

(2007) studied the impacts of seismic 

surveys off Sakhalin Island, Russia, on 

feeding gray whales and found that the 

seismic activity had no measurable 

effect on bottom feeding gray whales in 

the area. 

Potential Impacts From Drillship 

Presence 

The Discoverer is 514 ft (156.7 m) 

long. If an animal’s swim path is 

directly perpendicular to the drillship, 

the animal will need to swim around 

the ship in order to pass through the 

area. The length of the drillship 

(approximately one and a half football 

fields) is not significant enough to cause 

a large-scale diversion from the animals’ 

normal swim and migratory paths. 


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Additionally, the eastward spring 

bowhead whale migration will occur 

prior to the beginning of Shell’s 

proposed exploratory drilling program. 

Moreover, any deflection of bowhead 

whales or other marine mammal species 

due to the physical presence of the 

drillship or its support vessels would be 

very minor. The drillship’s physical 

footprint is small relative to the size of 

the geographic region it will occupy and 

will likely not cause marine mammals 

to deflect greatly from their typical 

migratory route. Also, even if animals 

may deflect because of the presence of 

the drillship, the Chukchi Sea is much 

larger in size than the length of the 

drillship (many dozens to hundreds of 

miles vs. less than two football fields), 

and animals would have other means of 

passage around the drillship. In sum, 

the physical presence of the drillship is 

not likely to cause a significant 

deflection to migrating marine 

mammals. 

Potential Impacts From Ice-management 

Ice-management activities include the 

physical pushing or moving of ice to 

create more open-water in the proposed 

drilling area and to prevent ice floes 

from striking the drillship. Ringed, 

bearded, spotted, and ribbon seals 

(along with the walrus) 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. Should icemanagement activities be necessary 

during the proposed drilling program, 

Shell would only manage pack ice in 

either early to mid-July or mid- to late 

October. Landfast ice would not be 

present during Shell’s proposed 

operations. 

The ringed seal is the most common 

pinniped species in the proposed 

project area. While ringed seals use ice 

year-round, they do not construct lairs 

for pupping until late winter/early 

spring on the landfast ice. Therefore, 

since Shell plans to conclude drilling on 

October 31, Shell’s activities would not 

impact ringed seal lairs or habitat 

needed for breeding and pupping in the 

Chukchi Sea. Aerial surveys in the 

eastern Chukchi Sea conducted in late 

May–early June 1999–2000 found that 

ringed seals were four to ten times more 

abundant in nearshore fast and pack ice 

environments than in offshore pack ice 

(Bengtson et al., 2005). Ringed seals can 

be found on the pack ice surface in the 

late spring and early summer in the 

northern Chukchi Sea, the latter part of 

which may overlap with the start of 

Shell’s proposed drilling activities. If an 

ice floe is pushed into one that contains 

hauled out seals, the animals may 

become startled and enter the water 

when the two ice floes collide. Bearded 

seals breed in the Bering and Chukchi 

Seas from mid-March through early May 

(several months prior to the start of 

Shell’s operations). Bearded seals 

require sea ice for molting during the 

late spring and summer period. Because 

this species feeds on benthic prey, 

bearded seals occur over the pack ice 

front over the Chukchi Sea shelf in 

summer (Burns and Frost, 1979) but 

were not associated with the ice front 

when it receded over deep water 

(Kingsley et al., 1985). The spotted seal 

does not breed in the Chukchi Sea. 

Spotted seals molt most intensely 

during May and June and then move to 

the coast after the sea ice has melted. 

Ribbon seals are not known to breed in 

the Chukchi Sea. From July–October, 

when sea ice is absent, the ribbon seal 

is entirely pelagic, and its distribution is 

not well known (Burns, 1981; Popov, 

1982). Therefore, ice used by bearded, 

spotted, and ribbon seals needed for life 

functions such as breeding and molting 

would not be impacted as a result of 

Shell’s drilling program since these life 

functions do not occur in the proposed 

project area or occur prior to the start of 

Shell’s operations. For ringed seals, icemanagement would occur during a time 

when life functions such as breeding, 

pupping, and molting do not occur in 

the proposed activity area. Additionally, 

these life functions normally occur on 

landfast ice, which will not be impacted 

by Shell’s activity. 

In conclusion, NMFS has 

preliminarily determined that Shell’s 

proposed exploration drilling program 

in the Chukchi Sea, Alaska, is not 

expected to have any habitat-related 

effects that could cause significant or 

long-term consequences for individual 

marine mammals or on the food sources 

that they utilize. 

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). 

Mitigation Measures Proposed in Shell’s 

IHA Application 

Shell submitted a Marine Mammal 

Monitoring and Mitigation Plan (4MP) 

as part of its application (Attachment B; 

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 design features 

and operational procedures have been 

described in the IHA and LOA 

applications submitted to NMFS and 

USFWS, respectively, and are 

summarized here. Survey design 

features include: 

• Timing and locating drilling and 

support activities to avoid interference 

with the annual subsistence hunts by 

the peoples of the Chukchi villages; 

• Identifying transit routes and timing 

to avoid other subsistence use areas and 

communicating with coastal 

communities before operating in or 

passing through these areas; and 

• Conducting pre-season sound 

propagation modeling to establish the 

appropriate safety and behavioral radii. 

Shell indicates that the potential 

disturbance of marine mammals during 

operations will be minimized further 

through the implementation of several 

ship-based mitigation measures, which 

include establishing and monitoring 

safety and disturbance zones. 

Safety radii for marine mammals 

around sound sources are customarily 

defined as the distances within which 

received sound levels are greater than or 

equal to 180 dB re 1 μPa (rms) for 

cetaceans and greater than or equal to 

190 dB re 1 μPa (rms) for pinnipeds. 

These safety criteria are based on an 

assumption that sounds at lower 

received levels will not injure these 

animals or impair their hearing abilities, 

but that higher received levels might 

have such effects. It should be 

understood that marine mammals inside 

these safety zones will not necessarily 

be injured, seriously injured, or killed, 

as the received sound thresholds which 

determine these zones were established 

prior to the current understanding that 

significantly higher levels of sound 

would be required before injury, serious 

injury, or mortality could occur (see 

Southall et al., 2007). With respect to 

Level B harassment, NMFS’ practice has 

been to apply the 120 dB re 1 μPa (rms) 

received level threshold for underwater 

continuous sound levels. 

Initial safety and behavioral radii for 

the sound levels produced by the 

drilling activities have been modeled. 

These radii will be used for mitigation 

purposes, should they be necessary, 


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until direct measurements are available 

early during the exploration activities. 

However, it is not anticipated that 

source levels from the Discoverer will 

reach the 180- or 190-dB (rms) levels. 

Sounds from the Discoverer have not 

previously been measured in the Arctic 

or elsewhere, but sounds from a similar 

drillship, Explorer II, were measured in 

the Beaufort Sea (Greene, 1987; Miles et 

al., 1987). The underwater received SPL 

in the 20 to 1,000 Hz band for drilling 

activity by the Explorer II, including a 

nearby support vessel, was 134 dB re 1 

μPa (rms) at 0.1 mi (0.2 km; Greene 

1987). The back-propagated source 

levels (175 dB re 1 μPa at 1 m) from 

these measurements were used as a 

proxy for modeling the sounds likely to 

be produced by drilling activities from 

the Discoverer. Based on the models, 

source levels from drilling are not 

expected to reach the 180-dB (rms) level 

and are expected to fall below 160 dB 

rms at 328 ft (100 m) from the drillship. 

The 120-dB (rms) radius is expected to 

be 0.85 mi (1.36 km) from the drillship 

at the Burger prospect, 0.35 mi (0.57 

km) at the SW Shoebill prospect, and 

0.37 mi (0.59 km) at the Crackerjack 

prospect. These estimated source 

measurements were used to model the 

expected sounds produced at the 

exploratory well sites by the Discoverer. 

Based on the best available scientific 

literature, the source levels noted above 

for exploration drilling are not high 

enough to cause a temporary reduction 

in hearing sensitivity or permanent 

hearing damage to marine mammals. 

Consequently, Shell believes that 

mitigation as described for seismic 

activities including ramp ups, power 

downs, and shutdowns should not be 

necessary for drilling activities. NMFS 

has also preliminarily determined that 

these types of mitigation measures, 

traditionally required for seismic survey 

operations, are not practical or 

necessary for this proposed drilling 

activity. Seismic airgun arrays can be 

turned on slowly (i.e., only turning on 

one or some guns at a time) and 

powered down quickly. The types of 

sound sources used for exploratory 

drilling have different properties and 

are unable to be ‘‘powered down’’ like 

airgun arrays or shutdown 

instantaneously without posing other 

risks. However, Shell plans to use 

marine mammal observers (MMOs) 

onboard the drillship and the various 

support vessels to monitor marine 

mammals and their responses to 

industry activities and to initiate 

mitigation measures should in-field 

measurements of the operations indicate 

that such measures are necessary. 

Additional details on the MMO program 

are described in the ‘‘Proposed 

Monitoring and Reporting’’ section 

found later in this document. 

Drilling sounds are expected to vary 

significantly with time due to variations 

in the level of operations and the 

different types of equipment used at 

different times onboard the drillship. 

Once on location in the Chukchi Sea, 

Shell will conduct sound source 

verification (SSV) tests to establish 

safety zones for the previously 

mentioned sound level criteria. The 

objectives of the SSV tests are: (1) To 

quantify the absolute sound levels 

produced by drilling and to monitor 

their variations with time, distance, and 

direction from the drillship; and (2) to 

measure the sound levels produced by 

vessels operating in support of drilling 

operations, which include crew change 

vessels, tugs, ice-management vessels, 

and spill response vessels. The 

methodology for conducting the SSV 

tests is fully described in Shell’s 4MP 

(see ADDRESSES). Please refer to that 

document for further details. Upon 

completion of the SSV tests, the new 

radii will be established and monitored, 

and mitigation measures will be 

implemented in accordance with Shell’s 

4MP. 

Additional mitigation measures 

proposed by Shell include: (1) Reducing 

speed and/or changing course if a 

marine mammal is sighted from a vessel 

in transit (NMFS has proposed a 

specific distance in the next subsection); 

(2) resuming full activity (e.g., full 

support vessel speed) only after marine 

mammals are confirmed to be outside 

the safety zone; (3) implementing flight 

restrictions prohibiting aircraft from 

flying below 1,500 ft (457 m) altitude 

(except during takeoffs and landings or 

in emergency situations); and (4) 

keeping vessels anchored when 

approached by marine mammals to 

avoid the potential for avoidance 

reactions by such animals. 

Shell has also proposed additional 

mitigation measures to ensure no 

unmitigable adverse impact on the 

availability of affected species or stocks 

for taking for subsistence uses. Those 

measures are described in the ‘‘Impact 

on Availability of Affected Species or 

Stock for Taking for Subsistence Uses’’ 

section found later in this document. 

Additional Mitigation Measures 

Proposed by NMFS 

In addition to the mitigation measures 

proposed in Shell’s IHA application, 

NMFS proposes the following measures 

be included in the IHA, if issued, in 

order to ensure the least practicable 

impact on the affected species or stocks: 

(1) All vessels should reduce speed 

when within 300 yards (274 m) of 

whales. The reduction in speed will 

vary based on the situation but must be 

sufficient to avoid interfering with the 

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; 

(2) Avoid multiple changes in 

direction and speed when within 300 

yards (274 m) of whales; and 

(3) 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. 

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. 

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 mammal 

species or stocks and their habitat, 

paying particular attention to rookeries, 

mating grounds, and areas of similar 

significance. 

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, where 

applicable, 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 


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populations of marine mammals that are 

expected to be present in the proposed 

action area. 

Monitoring Measures Proposed in 

Shell’s IHA Application 

The monitoring plan proposed by 

Shell can be found in the 4MP 

(Attachment B of Shell’s application; 

see ADDRESSES). 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). 

A summary of the primary components 

of the plan follows. 

(1) Vessel-Based MMOs 

Vessel-based monitoring for marine 

mammals will be done by trained 

MMOs throughout the period of drilling 

operations. MMOs will monitor the 

occurrence and behavior of marine 

mammals near the drillship during all 

daylight periods during operation and 

during most daylight periods when 

drilling operations are not occurring. 

MMO duties will include watching for 

and identifying marine mammals, 

recording their numbers, distances, and 

reactions to the drilling operations. A 

sufficient number of MMOs will be 

required onboard each vessel to meeting 

the following criteria: (1) 100 percent 

monitoring coverage during all periods 

of drilling operations in daylight; (2) 

maximum of 4 consecutive hours on 

watch per MMO; and (3) maximum of 

12 hours of watch time per day per 

MMO. Shell anticipates that there will 

be provision for crew rotation at least 

every 3–6 weeks to avoid observer 

fatigue. 

Biologist-observers will have previous 

marine mammal observation experience, 

and field crew leaders will be highly 

experienced with previous vessel-based 

marine mammal monitoring projects. 

Resumes for those individuals will be 

provided to NMFS so that NMFS can 

review and accept their qualifications. 

Inupiat observers will be experienced in 

the region, familiar with the marine 

mammals of the area, and complete a 

NMFS approved observer training 

course designed to familiarize 

individuals with monitoring and data 

collection procedures. A MMO 

handbook, adapted for the specifics of 

the planned Shell drilling program, will 

be prepared and distributed beforehand 

to all MMOs. 

MMOs will watch for marine 

mammals from the best available 

vantage point on the drillship and 

support vessels. MMOs will scan 

systematically with the unaided eye and 

7 x 50 reticle binoculars, supplemented 

with ‘‘Big-eye’’ binoculars and nightvision equipment when needed. 

Personnel on the bridge will assist the 

MMOs in watching for marine 

mammals. 

Information to be recorded by MMOs 

will include the same types of 

information that were recorded during 

recent monitoring programs associated 

with industry activity in the Arctic (e.g., 

Ireland et al., 2009). When a mammal 

sighting is made, the following 

information about the sighting will be 

recorded: 

(A) 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 MMO, apparent 

reaction to activities (e.g., none, 

avoidance, approach, paralleling, etc.), 

closest point of approach, and 

behavioral pace; 

(B) Time, location, speed, activity of 

the vessel, sea state, ice cover, visibility, 

and sun glare; and 

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

the vicinity of the MMO location. 

The ship’s position, speed, 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. 

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. MMOs may use a laser 

rangefinder to test and improve their 

abilities for visually estimating 

distances to objects in the water. 

However, previous experience showed 

that a Class 1 eye-safe device was not 

able to measure distances to seals more 

than about 230 ft (70 m) away. The 

device was very useful in improving the 

distance estimation abilities of the 

observers at distances up to about 1,968 

ft (600 m)—the maximum range at 

which the device could measure 

distances to highly reflective objects 

such as other vessels. Humans observing 

objects of more-or-less known size via a 

standard observation protocol, in this 

case from a standard height above water, 

quickly become able to estimate 

distances within about ±20 percent 

when given immediate feedback about 

actual distances during training. 

(2) Aerial Survey Program 

Recent aerial surveys of marine 

mammals in the Chukchi Sea were 

conducted over coastal areas to 

approximately 23 mi (37 km) offshore in 

2006–2008 in support of Shell’s summer 

seismic exploration activities. These 

surveys were designed to provide data 

on the distribution and abundance of 

marine mammals in nearshore waters of 

the Chukchi Sea. Shell proposes to 

conduct an aerial survey program in the 

Chukchi Sea in 2010 that would be 

similar to the 2006–2008 program. 

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. Shell’s objectives for this 

program include: 

(A) To address data deficiencies in the 

distribution and abundance of marine 

mammals in coastal areas of the eastern 

Chukchi Sea; and 

(B) To collect and report data on the 

distribution, numbers, orientation and 

behavior of marine mammals, 

particularly beluga whales, near 

traditional hunting areas in the eastern 

Chukchi Sea. 

With agreement from hunters in the 

coastal villages, aerial surveys of coastal 

areas to approximately 23 mi (37 km) 

offshore between Point Hope and Point 

Barrow will begin in early to mid-July 

and will continue until drilling 

operations in the Chukchi Sea are 

completed. Weather and equipment 

permitting, surveys will be conducted 

twice per week during this time period. 

In addition, during the 2010 drilling 

season, aerial surveys will be 

coordinated in cooperation with the 

aerial surveys funded by MMS and 

conducted by NMFS and any other 

groups conducting surveys in the 

region. A full description of Shell’s 

survey procedures can be found in the 

4MP of Shell’s application (see 

ADDRESSES). A summary follows next. 

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 (see Figure 6 of Shell’s 4MP). This 

design will permit completion of the 

survey in one to two days and will 

provide representative coverage of the 

nearshore region. The surveyed area 

will include waters where belugas are 

normally available to subsistence 

hunters. Survey altitude will be at least 

1,000 ft (305 m) with an average survey 

speed of 110–120 knots. 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. 


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Aerial surveys at an altitude of 1,000 

ft (305 m) do not provide much 

information about seals but are suitable 

for bowhead, beluga, and gray whales. 

The need for a 1,000+ ft (305+ m) cloud 

ceiling will limit the dates and times 

when surveys can be flown. Selection of 

a higher altitude for surveys would 

result in a significant reduction in the 

number of days during which surveys 

would be possible, impairing the ability 

of the aerial program to meet its 

objectives. If large concentrations of 

belugas are encountered during the 

survey, the survey may be interrupted to 

photograph the groups to obtain better 

counts of the number of animals 

present. If whales are photographed in 

lagoons or other shallow-water 

concentration areas, the aircraft will 

climb to approximately 10,000 ft (3,050 

m) altitude to avoid disturbing the 

whales and causing them to leave the 

area. If whales are in offshore areas, the 

aircraft will climb high enough to 

include all whales within a single 

photograph; typically about 3,000 ft 

(914 m) altitude. 

Three MMOs will be aboard the 

aircraft during surveys. Two observers 

will be looking for marine mammals 

within 1.6 mi (2.5 km) of the survey 

track line; one each at bubble windows 

on either side of the aircraft. The third 

person will record data. When sightings 

are made, observers will notify the data 

recorder of the species or species class 

of the animal(s) sighted, the number of 

animals present, and the lateral distance 

(inclinometer angle) of the animals from 

the flight path of the aircraft. Data on 

location and conditions will also be 

recorded. 

(3) Acoustic Monitoring 

As discussed earlier in this document, 

Shell will conduct SSV tests to establish 

the isopleths for the applicable safety 

radii. In addition, Shell proposes to use 

an acoustic ‘‘net’’ array to accomplish 

two main objectives: 

(A) To collect information on the 

occurrence and distribution of marine 

mammals that may be available to 

subsistence hunters near villages 

located on the Chukchi Sea coast and to 

document their relative abundance, 

habitat use, and migratory patterns; and 

(B) To measure the ambient 

soundscape throughout the eastern 

Chukchi Sea and to record received 

levels of sound from industry and other 

activities further offshore in the 

Chukchi Sea. 

The net array configuration used in 

2007–2009 is again proposed for 2010. 

The basic components of this effort 

consist of 30 hydrophone systems 

placed widely across the U.S. Chukchi 

Sea and a prospect specific array of 12 

hydrophones capable of localization of 

marine mammal calls. The net array 

configuration will include hydrophone 

systems distributed at each of the four 

primary transect locations: Cape 

Lisburne; Point Hope; Wainwright; and 

Barrow. The systems comprising the 

regional array will be placed at locations 

shown in Figure 7 of the 4MP in Shell’s 

application (see ADDRESSES). These 

offshore systems will capture 

exploration drilling sounds, if present, 

over large distances to help characterize 

the sound transmission properties in the 

Chukchi Sea and will also provide a 

large amount of information related to 

marine mammals in the Chukchi Sea. 

The regional acoustic monitoring 

program will be augmented in 2010 by 

an array of 12 additional acoustic 

recorders to be deployed on a grid 

pattern over a 7.2 mi (12 km) by 10.8 mi 

(18 km) area extending over several of 

Shell’s lease blocks near locations of 

highest interest for drilling in 2010. The 

cluster array will operate at a sampling 

frequency of 16 kHz, which is sufficient 

to capture vocalizations from bowhead, 

beluga, gray, fin, humpback, and killer 

whales, walrus, and most other marine 

mammals known to be present in the 

Chukchi Sea. The cluster deployment 

configuration was defined to allow 

tracking of vocalizing animals that pass 

through the immediate area of these 

lease blocks. Maximum separation 

between adjacent recorders is 3.6 mi 

(5.8 km). At this spacing, Shell expects 

that individual whale calls will be 

detected on at least three different 

recorders when the calling animals are 

within the boundary of the deployment 

pattern. Bowhead and other mysticete 

calls should be detectable 

simultaneously on more than three 

recorders due to their relatively higher 

sound source levels compared to other 

marine mammals. In calm weather 

conditions, when ambient underwater 

sound levels are low, Shell expects to 

detect most other marine mammal calls 

on more than three recorders. The goal 

of simultaneous detection on multiple 

recorders is to allow for triangulation of 

the call positions, which also requires 

accurate time synchronization of the 

recorders. When small numbers of 

whales are vocalizing, Shell hopes to be 

able to identify and track the 

movements of specific individuals 

within the deployment area. It will not 

be possible to track individual whales if 

many whales are calling due to 

abundant overlapping calls. In this case, 

analyses will show the general 

distribution of calls in the vicinity of the 

recorders. 

Additional details on data analysis for 

the types of monitoring described here 

(i.e., vessel-based, aerial, and acoustic) 

can be found in the 4MP in Shell’s 

application (see ADDRESSES). 

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 convened an independent peer 

review panel to review Shell’s 4MP for 

Exploration Drilling of Selected Lease 

Areas in the Alaskan Chukchi Sea in 

2010. The panel met in late March 2010, 

and provided comments to NMFS in 

late April 2010. 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 preliminary results of 

the acoustic verification measurements, 

including as a minimum the measured 

190-, 180-, 160-, and 120-dB (rms) radii, 

if source levels are high enough for all 

of these radii to be reached, of the 

drillship and the support vessels, will 

be submitted within 120 hr after 

collection and analysis of those 

measurements at the start of the field 

season. This report will specify the 

distances of the safety zones that were 

adopted for the exploratory drilling 

program. 

(2) Technical Reports 

The results of Shell’s 2010 offshore 

Chukchi Sea exploratory drilling 

monitoring program (i.e., vessel-based, 

aerial, and acoustic) will be presented in 

the ‘‘90-day’’ and Final Technical 

reports, as required by NMFS under 

IHAs. 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) 


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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 drillship and support vessels 

versus drilling state; and (10) estimates 

of take by harassment. This information 

will be reported for both the vesselbased 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 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 noise; and (d) measure 

received levels of drillship 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 exploratory 

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. 

(3) Comprehensive Report 

In November, 2007, Shell (in 

coordination and cooperation with other 

Arctic seismic IHA holders) released a 

final, peer-reviewed edition of the 2006 

Joint Monitoring Program in the 

Chukchi and Beaufort Seas, July– 

November 2006 (LGL, 2007). This report 

is available on the NMFS Protected 

Resources Web site (see ADDRESSES). In 

March, 2009, Shell released a final, 

peer-reviewed edition of the Joint 

Monitoring Program in the Chukchi and 

Beaufort Seas, Open Water Seasons, 

2006–2007 (Ireland et al., 2009). This 

report is also available on the NMFS 

Protected Resources Web site (see 

ADDRESSES). A draft of the final 

comprehensive report for 2008 (Funk et 

al., 2009), which incorporated 

comments from several agencies, was 

provided to NMFS and other 

government agencies in March 2010. 

The 2008 report provides data and 

analyses from a number of industry 

monitoring and research studies carried 

out in the Chukchi and Beaufort Seas 

during the 2008 open-water season with 

comparison to data collected in 2006 

and 2007. Once Shell is able to 

incorporate reviewer comments, the 

final 2008 report will be made available 

to the public. The 2009 draft 

comprehensive report is due to NMFS 

by mid-April 2010. NMFS will make 

this report available to the public upon 

receipt. 

Following the 2010 drilling season a 

comprehensive report describing the 

vessel-based, aerial, and acoustic 

monitoring programs will be prepared. 

The comprehensive report will describe 

the methods, results, conclusions and 

limitations of each of the individual 

data sets in detail. The report will also 

integrate (to the extent possible) the 

studies into a broad based assessment of 

industry activities, and other activities 

that occur in the Beaufort and/or 

Chukchi seas, and their impacts on 

marine mammals during 2010. The 

report will help to establish long-term 

data sets that can assist with the 

evaluation of changes in the Chukchi 

and Beaufort Sea ecosystems. The report 

will attempt to provide a regional 

synthesis of available data on industry 

activity in offshore areas of northern 

Alaska that may influence marine 

mammal density, distribution and 

behavior. The comprehensive report 

will be due to NMFS within 240 days 

of the date of issuance of the IHA (if 

issued). 

(4) Notification of Injured or Dead 

Marine Mammals 

Shell will notify NMFS’ Office of 

Protected Resources and NMFS’ 

Stranding Network within 48 hours of 

sighting an injured or dead marine 

mammal in the vicinity of drilling 

operations. 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). 

In the event that an injured or dead 

marine mammal is found by Shell that 

is not in the vicinity of the proposed 

drilling program, Shell will report the 

same information listed above to NMFS 

as soon as operationally feasible. 

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. Anticipated impacts to marine 

mammals are associated with noise 

propagation from the drillship and 

associated support vessels. Additional 

disturbance to marine mammals may 

result from aircraft overflights and 

visual disturbance of the drillship 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 

might include one or more of the 

following: tolerance; masking of natural 

sounds; behavioral disturbance; nonauditory physical effects; and, at least in 

theory, temporary or permanent hearing 

impairment (Richardson et al., 1995a). 

As discussed earlier in this document, 

the most common impact will likely be 

from behavioral disturbance, including 

avoidance of the ensonified area or 

changes in speed, direction, and/or 

diving profile of the animal. For reasons 

discussed previously in this document, 

hearing impairment (TTS and PTS) are 

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. 

Additionally, non-auditory 

physiological effects are anticipated to 

be minor, if any would occur at all. 

Finally, based on the proposed 

mitigation and monitoring measures 

described earlier in this document and 

the fact that the back-propagated source 

level for the drillship is estimated to be 

175 dB re 1 μPa (rms), no injury or 

mortality of marine mammals is 


jlentini on DSKJ8SOYB1PROD with NOTICES2
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anticipated as a result of Shell’s 

proposed exploratory drilling program. 

For continuous sounds, such as those 

produced by drilling operations, NMFS 

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

indicate the onset of Level B 

harassment. Shell provided calculations 

for the 120-dB isopleths produced by 

the Discoverer and then used those 

isopleths to estimate takes by 

harassment. Shell also included 

modeling results of the 160-dB isopleths 

for the Discoverer and associated 

estimated takes by harassment. 

However, NMFS has used the 120-dB 

calculations to make the necessary 

MMPA preliminary findings. 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. However, this 

document only discusses the take 

estimates at the 120 dB level. Please 

refer to Shell’s application for the full 

explanation and estimates at the 160 dB 

level. 

Shell has requested authorization for 

bowhead, gray, fin, humpback, minke, 

killer, and beluga whales, harbor 

porpoise, and ringed, spotted, bearded, 

and ribbon seals. 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 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 

sound levels of ≥120 dB. NMFS 

evaluated and critiqued the methods 

provided in Shell’s application and 

determined that they were appropriate 

in order to make the necessary 

preliminary MMPA findings. 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 

‘‘Potential Number of Takes by 

Harassment’’ subsection. 

Marine mammal densities near the 

operation are likely to vary by season 

and habitat. 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 operations are 

occurring: Open water or ice margin. 

More ice is likely to be present in the 

area of operations during the summer 

period, so summer ice-margin densities 

have been applied to 50 percent of the 

area that may be exposed to sounds 

from drilling. 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 fall 

season, so fall ice-margin densities have 

been applied to only 20 percent of the 

area that may be exposed to sounds 

from drilling. Fall open-water densities 

were applied to the remaining 80 

percent of the area. 

Shell notes that 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, and in those 

cases the mean and maximum estimates 

were determined from the survey data. 

In other cases, no applicable estimate 

(or perhaps a single estimate) was 

available, so correction factors were 

used to arrive at ‘‘average’’ and 

‘‘maximum’’ estimates. These are 

described in detail in the following 

subsections. Table 6–6 in Shell’s 

application indicates that the ‘‘average 

estimate’’ for every species but one, the 

ringed seal, is zero. Therefore, to 

account for the fact that the 12 species 

listed as being potentially taken by 

harassment in this document may occur 

in Shell’s proposed drilling sites during 

active operations, NMFS either used the 

‘‘maximum estimates’’ or made an 

estimate based on typical group size for 

a particular species. 

Detectability bias, quantified in part 

by f(0), is associated with diminishing 

sightability with increasing lateral 

distance from the trackline. Availability 

bias [g(0)] refers to the fact that there is 

<100 percent probability of sighting an 

animal that is present along the survey 

trackline. Some sources of densities 

used below included these correction 

factors in their reported densities (e.g., 

ringed seals in Bengtson et al., 2005). In 

other cases the best available correction 

factors were applied to reported results 

when they had not been included in the 

reported data (e.g., Moore et al., 2000). 

Estimated densities of marine 

mammals in the Chukchi Sea project 

area during the summer period (July– 

August) are presented in Table 6–1 in 

Shell’s application and Table 1 here, 

and estimated fall densities (September– 

October) are presented in Table 6–2 in 

Shell’s application and Table 2 here. 

Descriptions of the individual density 

estimates shown in the tables are 

presented next. 

TABLE 1—EXPECTED DENSITIES OF CETACEANS AND SEALS IN AREAS OF THE CHUKCHI SEA, ALASKA, FOR THE PLANNED

SUMMER (JULY–AUGUST) PERIOD. SPECIES LISTED UNDER THE ESA ARE IN ITALICS

Species 

Open water Ice margin 

Average 

density 

(#/km2) 

Maximum 

density 

(#/km2) 

Average 

density 

(#/km2) 

Maximum 

density 

(#/km2) 

Odontocetes: 

Monodontidae: 

Beluga ............................................................................................... 0.0033 0.0066 0.0162 0.0324 

Narwhal ............................................................................................. 0.0000 0.0000 0.0000 0.0001

Delphinidae: 

Killer whale ........................................................................................ 0.0001 0.0004 0.0001 0.0004

Phocoenidae: 

Harbor porpoise ................................................................................. 0.0011 0.0016 0.0011 0.0016 

Mysticetes: 

Bowhead whale ................................................................................. 0.0018 0.0036 0.0018 0.0036 

Fin whale ........................................................................................... 0.0001 0.0004 0.0001 0.0004 


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TABLE 1—EXPECTED DENSITIES OF CETACEANS AND SEALS IN AREAS OF THE CHUKCHI SEA, ALASKA, FOR THE PLANNED

SUMMER (JULY–AUGUST) PERIOD. SPECIES LISTED UNDER THE ESA ARE IN ITALICS—Continued 

Species 

Open water Ice margin 

Average 

density 

(#/km2) 

Maximum 

density 

(#/km2) 

Average 

density 

(#/km2) 

Maximum 

density 

(#/km2) 

Gray whale ........................................................................................ 0.0081 0.0162 0.0081 0.0162 

Humpback whale ............................................................................... 0.0001 0.0004 0.0001 0.0004 

Minke whale ...................................................................................... 0.0001 0.0004 0.0001 0.0004 

Pinnipeds: 

Bearded seal ..................................................................................... 0.0107 0.0203 0.0142 0.0270 

Ribbon seal ....................................................................................... 0.0003 0.0012 0.0003 0.0012 

Ringed seal ....................................................................................... 0.3668 0.6075 0.4891 0.8100 

Spotted seal ...................................................................................... 0.0073 0.0122 0.0098 0.0162 

TABLE 2—EXPECTED DENSITIES OF CETACEANS AND SEALS IN AREAS OF THE CHUKCHI SEA, ALASKA, FOR THE PLANNED

FALL (SEPTEMBER–OCTOBER) PERIOD. SPECIES LISTED UNDER THE ESA ARE IN ITALICS

Species 

Open water Ice margin 

Average 

density 

(#/km2) 

Maximum 

density 

(#/km2) 

Average 

density 

(#/km2) 

Maximum 

density 

(#/km2) 

Odontocetes: 

Monodontidae: 

Beluga ............................................................................................... 0.0162 0.0324 0.0324 0.0648 

Narwhal ............................................................................................. 0.0000 0.0000 0.0000 0.0001

Delphinidae: 

Killer whale ........................................................................................ 0.0001 0.0004 0.0001 0.0004

Phocoenidae: 

Harbor porpoise ................................................................................. 0.0010 0.0013 0.0010 0.0013 

Mysticetes: 

Bowhead whale ................................................................................. 0.0174 0.0348 0.0348 0.0696 

Fin whale ........................................................................................... 0.0001 0.0004 0.0001 0.0004 

Gray whale ........................................................................................ 0.0062 0.0124 0.0062 0.0124 

Humpback whale ............................................................................... 0.0001 0.0004 0.0001 0.0004 

Minke whale ...................................................................................... 0.0001 0.0004 0.0001 0.0004 

Pinnipeds: 

Bearded seal ..................................................................................... 0.0107 0.0203 0.0142 0.0270 

Ribbon seal ....................................................................................... 0.0003 0.0012 0.0003 0.0012 

Ringed seal ....................................................................................... 0.2458 0.4070 0.3277 0.5427 

Spotted seal ...................................................................................... 0.0049 0.0081 0.0065 0.0108 

(1) Cetaceans 

Beluga Whales—Summer densities of 

belugas in offshore waters are expected 

to be low. Aerial surveys have recorded 

few belugas in the offshore Chukchi Sea 

during the summer months (Moore et 

al., 2000). Aerial surveys of the Chukchi 

Sea in 2008–2009 flown by NMFS’ 

National Marine Mammal Laboratory 

(NMML) as part of the Chukchi Offshore 

Monitoring in Drilling Area project 

(COMIDA) have only reported five 

beluga sightings during more than 8,700 

mi (14,001 km) of on-transect effort, 

only two of which were offshore 

(NMML, 2009). Additionally, only one 

beluga sighting was recorded during 

more than 37,900 mi (60,994 km) of 

visual effort during good visibility 

conditions from industry vessels 

operating in the Chukchi Sea in 

September-October of 2006–2008 (Haley 

et al., 2009b). 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. Expected densities were 

calculated from data in Moore et al. 

(2000). Data from Moore et al. (2000; 

Figure 6 and Table 6) used in the 

average open-water density estimate 

included two on-transect beluga 

sightings during 6,640 mi (10,686 km) of 

on-transect effort in the Chukchi Sea 

during summer. A mean group size of 

7.1 (Coefficient of Variation [CV]=1.7) 

was calculated from 10 Chukchi Sea 

summer sightings present in the 

Bowhead Whale Aerial Survey Program 

(BWASP) database. A f(0) value of 2.841 

and g(0) value of 0.58 from Harwood et 

al. (1996) were also used in the 

calculation. The CV associated with 

group size was used to select an 

inflation factor of 2 to estimate the 

maximum density that may occur in 

both open-water and ice-margin 

habitats. Specific data on the relative 

abundance of beluga in open-water 

versus ice-margin habitat during the 

summer in the Chukchi Sea is not 

available. However, Moore et al. (2000) 

reported higher than expected beluga 

sighting rates in open-water during fall 

surveys in the Beaufort and Chukchi 

seas. This would suggest that densities 

near ice may actually be lower than 

open water, but belugas are commonly 

associated with ice, so an inflation 

factor of only 2 (instead of 4) was used 

to estimate the average ice-margin 

density from the open-water density. 

In the fall, beluga whale densities 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 

(Angliss and Allen, 2009). Consistent 

with this, the number of on-effort beluga 


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sightings reported during COMIDA 

flights in September–October of 2008– 

2009 was over three times more (n=17) 

than during July–August with a very 

similar amount of on-transect effort 

(NMML, 2009). However, there were no 

beluga sightings reported during more 

than 11,200 mi (18,025 km) of vessel 

based effort in good visibility conditions 

during 2006–2008 industry operations 

in the Chukchi Sea. Densities derived 

from survey results in the northern 

Chukchi Sea in Moore et al. (2000) were 

used as the average density for openwater and ice-margin fall season 

estimates (see Table 6–2 in Shell’s 

application and Table 2 here). Data from 

Moore et al. (2000; Table 8) used in the 

average open-water density estimate 

included 123 beluga sightings and 

27,560 mi (44,354 km) of on-transect 

effort in water depths 118–164 ft (36–50 

m). A mean group size of 2.39 (CV=0.92) 

came from the average group size of 82 

Chukchi Sea fall sightings in waters 

115–164 ft (35–50 m) deep present in 

the BWASP database. A f(0) value of 

2.841 and g(0) value of 0.58 from 

Harwood et al. (1996) were used in the 

calculation. The CV associated with 

group size was used to select an 

inflation factor of 2 to estimate the 

maximum density that may occur in 

both open-water and ice-margin 

habitats. Moore et al. (2000) reported 

higher than expected beluga sighting 

rates in open-water during fall surveys 

in the Beaufort and Chukchi seas, so an 

inflation value of only 2 was used to 

estimate the average ice-margin density 

from the open-water density. 

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 6,640 mi (10,686 

km) of on-transect effort in the Chukchi 

Sea by Moore et al. (2000). Aerial 

surveys in 2008–2009 by NMML as part 

of the COMIDA project reported only 

four sightings during more than 8,700 

mi (14,001 km) of on-transect effort. 

Two of the four sightings were offshore, 

both of which occurred near the end of 

August. Bowhead whales were also 

rarely reported in July–August of 2006– 

2008 during aerial surveys of the 

Chukchi Sea coast (Thomas et al., 2009). 

This is consistent with movements of 

tagged whales (see ADFG, 2009; 

Quakenbush et al., 2009), 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 bowhead whale density in the 

Chukchi Sea was calculated by 

assuming there was one bowhead 

sighting during the 6,640 mi (10,686 

km) of survey effort in the Chukchi Sea 

during the summer months reported in 

Moore et al. (2000) although no 

bowheads were actually observed 

during those surveys. The more recent 

COMIDA data were not used as NMML 

has not released a report summarizing 

the data so they are not considered final. 

Only two sightings are present in the 

BWASP database during July and 

August in the Chukchi Sea, both of 

which were of individual whales. The 

mean group size from combined July– 

August sightings in the BWASP, 

COMIDA, and 2006–2008 industry 

database is 1.33 (CV=0.58). This 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 bowhead whales. The CV of 

group size and standard errors reported 

in Thomas et al. (2002) for f(0) and g(0) 

correction factors suggest that an 

inflation factor of 2 is appropriate for 

estimating the maximum density from 

the average density. Bowheads are not 

expected to be encountered in higher 

densities near ice in the summer (Moore 

et al., 2000), so the same density 

estimates are 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 2006–2008 

(Haley et al., 2009b) ranged from 

0.0003–0.0013/mi2 (0.0001–0.0005/km2) 

with a maximum 95 percent confidence 

interval (CI) of 0.0049/mi2 (0.0019 km2). 

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 that 

bowheads will be encountered in the 

Chukchi Sea at this time of year. Moore 

et al. (2002; Table 8) reported 34 

bowhead sightings during 27,560 mi 

(44,354 km) of on-transect survey effort 

in the Chukchi Sea during September– 

October. Thomas et al. (2009) also 

reported increased sightings on coastal 

surveys of the Chukchi Sea during 

September and October of 2006–2008. 

Aerial surveys in 2008–2009 (NMML, 

2009) reported 20 bowhead sightings 

during 8,803 mi (14,167 km) of ontransect effort, eight of which were 

offshore. GPS tagging of bowheads 

appear to show that migration routes 

through the Chukchi Sea are more 

variable than through the Beaufort Sea 

(ADFG, 2009; Quakenbush et al., 2009). 

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., 2009). 

Most spent no more than 1 week in the 

general LS 193 area. The mean group 

size from September–October Chukchi 

Sea bowhead sightings in the BWASP 

database is 1.59 (CV=1.08). This is 

slightly below the mean group size of 

1.85 from all the preliminary COMIDA 

sightings during the same months, but 

above the value of 1.13 from only oneffort COMIDA sightings (NMML, 2009). 

The same f(0) and g(0) values that were 

used for the summer estimates above 

were used for the fall estimates. As with 

the summer estimates, an inflation 

factor of 2 was used to estimate the 

maximum density from the average 

density in both habitat types. 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 a density of 

twice the average open-water density 

was used as the average ice-margin 

density. Densities from vessel based 

surveys in the Chukchi Sea during nonseismic periods and locations in July– 

August of 2006–2008 (Haley et al., 

2009b) ranged from 0.0003 to 0.0129/ 

mi2 (0.0001–0.0050/km2) with a 

maximum 95 percent CI of 0.1243/mi2

(0.0480 km2). 

Gray Whales—Gray whales 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 115 ft (35 m) deep. With similar 

amounts of on-transect effort between 

the two seasons in the preliminary 

COMIDA data from aerial surveys in 

2008–2009, there were 3 times as many 

gray whale sightings in July–August 

than September–October, five times as 

many if you consider all effort and 

sightings. Thomas et al. (2009) also 

reported substantial declines in the 

sighting rates of gray whales in the fall. 

The average open-water summer density 

was calculated from effort and sightings 

in Moore et al. (2000; Table 6) for water 

depths 118–164 ft (36–50 m), including 

4 sightings during 3,901 mi (6,278 km) 

of on-transect effort. An average group 

size of 3.11 (CV=0.97) was calculated 

from all July–August Chukchi Sea gray 

whale sightings in the BWASP database 

and used in the summer density 

estimate. This value was higher than the 

average group size in the preliminary 


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COMIDA data (1.71; NMML, 2009) and 

from coastal aerial surveys in 2006– 

2008 (1.27; Thomas et al., 2009). 

Correction factors f(0) = 2.49 (Forney 

and Barlow, 1998) and g(0) = 0.30 

(Forney and Barlow, 1998; Mallonee, 

1991) were also used in the density 

calculation because the group size used 

in the average density estimate was 

relatively high compared to other data 

sources and the CV near one, an 

inflation factor of 2 was used to estimate 

the maximum densities from average 

densities in both habitat types. Gray 

whales are not commonly associated 

with sea ice, but may be present near it, 

so the same densities were used for icemargin habitat as were derived for openwater habitat during both seasons. 

Densities from vessel based surveys in 

the Chukchi Sea during non-seismic 

periods and locations in July–August of 

2006–2008 (Haley et al., 2009b) ranged 

from 0.0023/mi2 to 0.0088/mi2 (0.0009/ 

km2 to 0.0034/km2) with a maximum 95 

percent CI of 0.0378 mi2 (0.0146 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 (27 sightings 

during 27,559 mi [44,352 km] of ontransect effort) in water 118–164 ft (36– 

50 m) deep during autumn in Moore et 

al. (2000; Table 12) was used as the 

average estimate for the Chukchi Sea 

during the fall period. A group size 

value of 2.49 (CV=1.37) calculated from 

the BWASP database was used in the 

density calculation, along with the same 

f(0) and g(0) values described above. 

The group size value of 2.49 was again 

higher than the average group size 

calculated from preliminary COMIDA 

data (1.24; NMML, 2009) and reported 

from coastal aerial surveys in 2006– 

2008 (1.12; Thomas et al., 2009). 

Densities from vessel based surveys in 

the Chukchi Sea during non-seismic 

periods and locations in July–August of 

2006–2008 (Haley et al., 2009b) ranged 

from 0.0028/mi2 to 0.0062/mi2 (0.0011/ 

km2 to 0.0024/km2) with a maximum 95 

percent CI of 0.0474 mi2 (0.0183 km2). 

Harbor Porpoise—Harbor porpoise 

densities were estimated from industry 

data collected during 2006–2008 

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 2006–2008, however, recorded 

sightings throughout the Chukchi Sea 

during the summer and early fall 

months. Density estimates from 2006– 

2008 observations during non-seismic 

periods and locations in July–August 

ranged from 0.0023/mi2 to 0.0041/mi2

(0.0009/km2 to 0.0016/km2) with a 

maximum 95 percent CI of 0.0016/mi2

(0.0041/km2) (Haley et al., 2009b). The 

median value from the summer season 

of those three years (0.0028/mi2/0.0011/ 

km2) was used as the average openwater density estimate while the high 

value (0.0041/mi2/0.0016/km2) was 

used as the maximum estimate (see 

Table 6–1 in Shell’s application and 

Table 1 here). 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– 

2008 were slightly lower and ranged 

from 0.0005/mi2 to 0.0034/km2 (0.0002/ 

km2 to 0.0013/km2) with a maximum 95 

percent CI of 0.0114/mi2 (0.0044/km2). 

The median value 0.0026/mi2 (0.0010/ 

km2) was again used as the average 

density estimate and the high value 

0.0034/mi2 (0.0013/km2) was used as 

the maximum estimate (see Table 6–2 in 

Shell’s application and Table 2 here). 

Other Cetaceans—The remaining four 

cetacean species that could be 

encountered in the Chukchi Sea during 

Shell’s planned exploration drilling 

program include the humpback, killer, 

minke, and fin whales. Although there 

is evidence of the occasional occurrence 

of these animals in the Chukchi Sea, it 

is unlikely that more than a few 

individuals will be encountered during 

the planned drilling program. George 

and Suydam (1998) reported killer 

whales, Brueggeman et al. (1990) and 

Haley et al. (2009b) reported minke 

whale, Suydam and George (1992) and 

Haley et al. (2009b) reported harbor 

porpoise, and NMML (2009) and Haley 

et al. (2009b) reported fin whales off of 

Ledyard Bay in the Chukchi Sea. 

(2) Pinnipeds 

Four species of pinnipeds may be 

encountered in the Chukchi Sea area of 

Shell’s proposed drilling program: 

Ringed, bearded, spotted, and ribbon 

seals. Each of these species, except the 

spotted seal, is associated with both the 

ice margin and the nearshore area. The 

ice margin is considered preferred 

habitat (as compared to the nearshore 

areas) 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, before they move to shore. 

However, satellite tagging has shown 

that they sometimes undertake long 

excursions into offshore waters, as far as 

74.6 mi (120 km) off the Alaskan coast 

in the eastern Chukchi Sea, 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; Haley et al., 

2009b). 

Ringed and Bearded Seals—Ringed 

and bearded seals ‘‘average’’ and 

‘‘maximum’’ summer ice-margin 

densities (see Table 6–1 in Shell’s 

application and Table 1 here) were 

available in Bengtson et al. (2005) from 

spring surveys in the offshore pack ice 

zone of the northern Chukchi Sea. 

However, corrections for bearded seal 

availability, g(0), based on haul-out 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 the ice 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 2006–2008 industry 

operations ranged from 0.0212/mi2 to 

0.0572/mi2 (0.0082/km2 to 0.0221/km2) 

with a maximum 95 percent CI of 

0.1494/mi2 (0.0577/km2) (Haley et al., 

2009b). These estimates are lower than 

those made by Bengtson et al. (2005), 

which is not surprising given the 

different survey methods and timing. 

Little information on spotted seal 

densities in offshore areas of the 

Chukchi Sea is available. 

Spotted Seals—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 percent 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, 2010), and that the 

population of ringed seals in the 

Alaskan Chukchi Sea is greater than 

208,000 animals (Bengtson et al., 2005). 

In the fall, spotted seals show increased 

use of coastal haul-outs so densities 


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were estimated to be 2⁄3 of the summer 

densities. 

Ribbon Seals—Two ribbon seal 

sightings were reported during industry 

vessel operations in the Chukchi Sea in 

2006–2008 (Haley et al. 2009b). The 

resulting density estimate of 0.0008/mi2

(0.0003/km2) was used as the average 

density and 4 times that was used as the 

maximum for both seasons and habitat 

zones. 

As described earlier in this document, 

Shell’s proposed start date for the 

exploration drilling program in the 

Chukchi Sea is July 4. Up to three wells 

may be drilled, with an average of 37 

days at each drill site, including five 

days of MLC excavation. Shell’s 

preferred order in which the wells will 

be drilled, ice permitting, will likely be 

Burger, SW Shoebill, and Crackerjack. 

Drilling operations are expected to be 

completed on or before October 31. 

Expected sound propagation from the 

drillship Discoverer was modeled at the 

three possible drill sites. Changes in the 

water column of the Chukchi Sea 

through the course of the drilling season 

will likely affect the propagation of 

sounds produced by drilling activities, 

so models were run for expected 

oceanographic conditions in July and 

October to bracket the seasonal 

variability. As stated previously in this 

document, sounds from the Discoverer 

have not previously been measured in 

the Arctic or elsewhere, but sounds 

from a similar drillship, Explorer II, 

were measured twice in the Beaufort 

Sea (Greene, 1987a,b; Miles et al., 1987). 

The back-propagated source levels from 

these measurements (175 dB re 1 μPa 

rms), which included sounds from a 

support vessel operating nearby, were 

used as a proxy for modeling the sounds 

likely to be produced by drilling 

activities from the Discoverer. Results of 

sound propagation modeling that were 

used in the calculations of areas 

exposed to various levels of received 

sounds are summarized in Table 6–3 of 

Shell’s application and Table 3 here. 

TABLE 3—THE 120 dB re 1 μPA (rms) SOUND PROPAGATION MODELING RESULTS OF DRILLING ACTIVITIES AT THREE

LOCATIONS IN THE CHUKCHI SEA. THE VALUES USED IN CALCULATIONS INCLUDE A 50 PERCENT INFLATION FACTOR. 

Location Modeling results 

(km) 

Used in 

calculations 

(km) 

Burger (Summer) ............................................................................................................................................. 1.36 2.04 

SW Shoebill (Summer) .................................................................................................................................... 0.51 0.77 

SW Shoebill (Fall) ............................................................................................................................................ 0.57 0.86 

Crackerjack (Fall) ............................................................................................................................................. 0.59 0.89 

Potential Number of Takes by 

Harassment 

(1) Estimates of the Number of 

Individuals That may be Exposed to 

Sounds ≥120 dB 

Just because a marine mammal is 

exposed to drilling sounds ≥120 dB 

(rms), this does not mean that it will 

actually exhibit a disruption of 

behavioral patterns in response to the 

sound source. Rather, the estimates 

provided here are simply the best 

estimates of the number of animals that 

potentially could have a behavioral 

modification due to the noise. However, 

not all animals react to sounds at this 

low level, and many will not show 

strong reactions (and in some cases any 

reaction) until sounds are much 

stronger. There are several variables that 

determine whether or not an individual 

animal will exhibit a response to the 

sound, such as the age of the animal, 

previous exposure to this type of 

anthropogenic sound, habituation, etc. 

Numbers of marine mammals that 

might be present and potentially 

disturbed (i.e., Level B harassment) are 

estimated below based on available data 

about mammal distribution and 

densities at different locations and times 

of the year as described previously. 

Exposure estimates are based on a single 

drillship (Discoverer) drilling up to 

three wells in the Chukchi Sea from July 

4–October 31. Actual drilling may occur 

on approximately 11 days while the 

Discoverer is in the Chukchi Sea. 

The number of different individuals 

of each species potentially exposed to 

received levels ≥120 dB re 1 μPa within 

each season and habitat zone was 

estimated by multiplying: 

• The anticipated area to be 

ensonified to the specified level in the 

time period and habitat zone to which 

a density applies, by 

• the expected species density. 

The numbers of exposures were then 

summed for each species across the 

seasons and habitat zones. 

(2) Estimated Area Exposed to Sounds 

≥120 dB 

Distances shown in Table 6–3 in 

Shell’s application and Table 3 here 

were used to estimate the area 

ensonified to ≥120 dB (rms) around the 

drillship in summer and fall seasons. As 

noted earlier in this document, drilling 

activities at the SW Shoebill location 

may occur in both seasons, so the entire 

area that may be exposed to sounds by 

operations at the SW Shoebill location 

have been included in calculations for 

both seasons. The area of water 

potentially exposed to received sound 

levels ≥120 dB (rms) by exploration 

drilling operations was estimated to be 

5.8 mi2 (14.9 km2) in the summer for the 

Burger and SW Shoebill prospects 

combined and 1.9 mi2 (4.8 km2) in the 

fall at the SW Shoebill and Crackerjack 

prospects combined. 

Cetaceans—Cetacean species 

estimates of the average and maximum 

number of individual cetaceans that 

would be exposed to received sound 

levels ≥120 dB are shown in Table 6–6 

in Shell’s application. Based on the 

calculations, all species have an 

estimated average number of 

individuals exposed to ≥120 dB of less 

than one. However, chance encounters 

with individuals of any species are 

possible. To account for chance 

encounters with the cetacean species 

that possibly may occur in the proposed 

drilling area (i.e., beluga, killer, 

bowhead, fin, gray, humpback, and 

minke whales and harbor porpoise), 

Shell provided minimal estimates for 

the number of each marine mammal 

species or stock that may experience 

Level B harassment (see Table 6–6 in 

Shell’s application). Shell proposed five 

exposures to sounds ≥120 dB for each of 

the cetacean species. The estimates 

show that three endangered cetacean 

species (the bowhead, fin, and 

humpback whales) are expected to be 

exposed to sounds ≥120 dB unless they 

avoid the area around the drill sites. 

Migrating bowheads are likely to do so 

to some extent, though many of the 

bowheads engaged in other activities, 

particularly feeding and socializing, 

probably will not (Richardson, 2004). 

Some of the other cetacean species are 

likely to avoid the immediate area 

around the drilling vessel due to the 


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vessel traffic; however, not all cetaceans 

will change their behavior when 

exposed to these sound levels. 

Pinnipeds—The ringed seal is the 

most widespread and abundant 

pinniped in ice-covered arctic waters, 

and there appears to be a great deal of 

year-to-year variation in abundance and 

distribution of these marine mammals. 

Ringed seals account for a large number 

of marine mammals expected to be 

encountered during the exploration 

drilling program, and hence exposed to 

sounds with received levels ≥120 dB. 

The average (and maximum) estimate is 

that 8 (13) ringed seals might be 

exposed to sounds with received levels 

≥120 dB from the exploration drilling 

program. 

Two additional seal species are 

expected to be encountered: Bearded 

and spotted seals. Additionally, there is 

a slight possibility that ribbon seals may 

occur in the project area. Based on the 

calculations, all species have an 

estimated average number of 

individuals exposed to ≥120 dB of less 

than one. However, chance encounters 

with individuals of any species are 

possible. To account for chance 

encounters with these three pinniped 

species, Shell provided minimal 

estimates for the number of each marine 

mammal species or stock that may 

experience Level B harassment (see 

Table 6–6 in Shell’s application). Shell 

proposed five exposures each to sounds 

≥120 dB for bearded, spotted, and 

ribbon seals. 

Estimated Take Conclusions 

As stated previously, NMFS’ practice 

has been to apply the 120 dB re 1 μPa 

(rms) received level threshold for 

underwater continuous sound levels to 

determine whether take by Level B 

harassment occurs. However, not all 

animals react to sounds at this low 

level, and many will not show strong 

reactions (and in some cases any 

reaction) until sounds are much 

stronger. Southall et al. (2007) provide 

a severity scale for ranking observed 

behavioral responses of both freeranging marine mammals and laboratory 

subjects to various types of 

anthropogenic sound (see Table 4 in 

Southall et al. (2007)). Tables 15, 17, 19 

and 21 in Southall et al. (2007) outline 

the numbers of low-frequency, midfrequency, and high-frequency 

cetaceans and pinnipeds in water, 

respectively, reported as having 

behavioral responses to non-pulses in 

10-dB received level increments. These 

tables illustrate, especially for low- and 

mid-frequency cetaceans, that more 

intense observed behavioral responses 

did not occur until sounds were higher 

than 120 dB (rms). Many of the animals 

had no observable response at all when 

exposed to anthropogenic sound at 

levels of 120 dB (rms) or even higher. 

Although the 120-dB isopleth for the 

drillship may seem slightly expansive 

(i.e., 1.27 mi [2.04 km], which includes 

the 50 percent inflation factor), the zone 

of ensonification begins to shrink 

dramatically with each 10–dB increase 

in received sound level to where the 

160-dB isopleth is only about 328 ft (100 

m) from the drillship. As stated 

previously, source levels are expected to 

be 175 dB (rms). For an animal to 

receive a sound at this level, it would 

have to be within several meters of the 

vessel, which is unlikely, especially 

given the fact that certain species are 

likely to avoid the area (as described 

earlier in this document). 

NMFS is proposing to authorize the 

maximum take estimates provided in 

Table 6–6 of Shell’s application. The 

only exception to this is for the beluga 

whale to account for group size, as 

belugas typically occur in groups of 10 

to several hundred individuals. 

Therefore, NMFS proposes to authorize 

the take of 20 beluga whales, 13 ringed 

seals, and 5 individuals each of killer, 

bowhead, fin, gray, humpback, and 

minke whales, harbor porpoise, and 

bearded, ribbon, and spotted seals. 

Table 4 outlines the abundance, 

proposed take, and percentage of each 

stock or population for the 12 species 

that may be exposed to sounds ≥120 dB 

in Shell’s proposed Chukchi Sea drilling 

area. Less than 1 percent of each species 

or stock would potentially be exposed to 

sounds above the Level B harassment 

threshold. 

TABLE 4—ABUNDANCE ESTIMATES, TOTAL PROPOSED TAKE ESTIMATES, AND PERCENTAGE OF STOCK OR POPULATION

THAT MAY BE TAKEN FOR SPECIES THAT MAY OCCUR IN SHELL’S PROPOSED CHUKCHI SEA DRILLING AREA

Species Abundance1 Total proposed 

take 

Percentage of 

stock or population 

Beluga Whale ...................................................................................................................... 39,258 20 0.05 

Killer Whale .......................................................................................................................... 656 5 0.76 

Harbor Porpoise ................................................................................................................... 48,215 5 0.01 

Bowhead Whale ................................................................................................................... 2 14,247 5 0.04 

Fin Whale ............................................................................................................................. 5,700 5 0.09 

Gray Whale .......................................................................................................................... 17,752 5 0.03 

Humpback Whale ................................................................................................................ 2,256 5 0.22 

Minke Whale ........................................................................................................................ 810–1,003 5 0.62 

Bearded Seal ....................................................................................................................... 3 4,863 5 0.1 

Ribbon Seal ......................................................................................................................... 49,000 5 0.01 

Ringed Seal ......................................................................................................................... 208,000–252,000 13 0.01 

Spotted Seal ........................................................................................................................ 59,214 5 0.01 

1 Unless stated otherwise, abundance estimates are taken from the 2009 Alaska SAR. 

2Assumes 3.4 percent annual growth from the 2001 estimate of 10,545 individuals (Zeh and Punt, 2005). 

3Eastern Chukchi Sea population (NMML, unpublished data). 

Lastly, even though Shell has 

indicated that the Chukchi Sea drilling 

program will occur for approximately 

111 days between July 4 and October 31, 

2010, Shell has requested that the IHA 

(if issued) be valid for a full year. NMFS 

is proposing to grant this request in the 

event that Shell is unable to conduct 

active operations for the full 111 days. 

Therefore, depending on the expiration 

date of the IHA (if issued), Shell could 

potentially work early in the 2011 openwater season. The take numbers 

presented here (and in Shell’s 

application) are based on 111 days of 

active operations. Therefore, these 

numbers account for this situation. In 

fact, these numbers may then be an 

overestimate, as fewer animals, 

especially bowhead and beluga whales, 

would be expected at the drill sites in 

early July 2011. 


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Negligible Impact and Small Numbers 

Analysis and Preliminary Determination 

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.’’ 

In making a negligible impact 

determination, NMFS considers a 

variety of factors, including but not 

limited to: (1) The number of 

anticipated mortalities; (2) the number 

and nature of anticipated injuries; (3) 

the number, nature, intensity, and 

duration of Level B harassment; and (4) 

the context in which the takes occur. 

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. Additionally, animals 

in the area are not expected to incur 

hearing impairment (i.e., TTS or PTS) or 

non-auditory physiological effects. 

Takes will be limited to Level B 

behavioral harassment. 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 (ADF&G, 2009). 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 

ensonified area 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 is not 

expected to result in more than Level B 

harassment and is anticipated to have 

no more than a negligible impact on the 

affected species or stock. 

Few seals are expected to occur in the 

proposed project area, as several of the 

species prefer more nearshore waters. 

NMFS has preliminarily determined 

that the exposure of pinnipeds to 

sounds produced by exploratory drilling 

operations is not expected to result in 

more than Level B harassment and is 

anticipated to have no more than a 

negligible impact on the animals. 

Of the 12 marine mammal species 

likely to occur in the proposed drilling 

area, three are listed as endangered 

under the ESA: the bowhead, 

humpback, and fin whales. All three 

species are also designated as ‘‘depleted’’ 

under the MMPA. Despite these 

designations, the Bering-ChukchiBeaufort stock of bowheads has been 

increasing at a rate of 3.4 percent 

annually for nearly a decade (Allen and 

Angliss, 2010). Additionally, during the 

2001 census, 121 calves were counted, 

which was the highest yet recorded. The 

calf count provides corroborating 

evidence for a healthy and increasing 

population (Allen and Angliss, 2010). 

An annual increase of 4.8 percent 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, 2010). Zeribini et al. 

(2006, cited in Allen and Angliss, 2010) 

noted an increase of 6.6 percent for the 

Central North Pacific stock of humpback 

whales in Alaska waters. There is no 

critical habitat designated in the U.S. 

Arctic for any of these three whale 

species. The ribbon seal is a ‘‘species of 

concern,’’ and bearded and ringed seals 

are ‘‘candidate species’’ under the ESA, 

meaning they are currently being 

considered for listing but are not 

designated as depleted under the 

MMPA. None of the other three species 

that may occur in the project area are 

listed as threatened or endangered 

under the ESA or designated as depleted 

under the MMPA. 

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 

enough as to not affect rates of 

recruitment or survival of marine 

mammals in the area. 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 minor 

based on the fact that other feeding 

grounds exist elsewhere. 

The estimated takes proposed to be 

authorized represent less than 1 percent 

of the affected population or stock for 

all 12 species. 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. Additionally, these 

numbers are likely an overestimate, as 

these take numbers were calculated 

using a 50 percent inflation factor of the 

120-dB radius, which is a conservative 

approach recommended by some 

acousticians when modeling a new 

sound source in a new location. This is 

fairly conservative given the fact that 

the radii were based on results from a 

similar drillship (i.e., the Northern 

Explorer II). SSV tests may reveal that 

the Level B harassment zone may in fact 

be smaller than that used to estimate 

take. If the SSV tests reveal that the 

Level B harassment zone is slightly 

larger than that of the Northern Explorer 

II, the 50 percent inflation factor should 

cover the discrepancy. Moreover, the 

mitigation and monitoring measures 

(described previously in this document) 

proposed for inclusion in the IHA (if 

issued) are expected to reduce even 

further any potential disturbance to 

marine mammals. 

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 Shell’s 

proposed Chukchi Sea exploratory 

drilling program may result in the 

incidental take of small numbers of 

marine mammals, by Level B 

harassment only, and that the total 

taking from the exploratory drilling 

program will have a negligible impact 

on 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 


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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, walruses, and polar bears. 

(As mentioned previously in this 

document, both the walrus and the 

polar bear are under the USFWS’ 

jurisdiction.) 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 (however, this community is 

much farther to the south of the 

proposed project area). Wainwright is 

the coastal village closest to the 

proposed drill sites. It is located 78 mi 

(125.5 km) from Shell’s prospects. Point 

Lay, Barrow, and Point Hope are 92, 

140, and 180 mi (148, 225.3, and 290 

km), respectively, from Shell’s 

prospects. 

Point Hope residents subsistence hunt 

for bowhead and beluga whales, polar 

bears, and walrus. Bowhead and beluga 

whales are hunted in the spring and 

early summer along the ice edge. Beluga 

whales may also be hunted later in the 

summer along the shore. Walrus are 

harvested in late spring and early 

summer, and polar bears are hunted 

from October to April (MMS, 2007). 

Seals are available from October through 

June, but are harvested primarily during 

the winter months, from November 

through March, due to the availability of 

other resources during the other periods 

of the year (MMS, 2007). 

With Point Lay situated near 

Kasegaluk Lagoon, the community’s 

main subsistence focus is on beluga 

whales. Each year, hunters from Point 

Lay drive belugas into the lagoon to a 

traditional hunting location. The 

belugas have been predictably sighted 

near the lagoon from late June through 

mid- to late July (Suydam et al., 2001). 

Seals are available year-round, and 

polar bears and walruses are normally 

hunted in the winter. Hunters typically 

travel to Barrow, Wainwright, or Point 

Hope to participate in bowhead whale 

harvest, but there is interest in 

reestablishing a local Point Lay harvest. 

Wainwright residents subsist on both 

beluga and bowhead whales in the 

spring and early summer. During these 

two seasons the chances of landing a 

whale are higher than during other 

seasons. Seals are hunted by this 

community year-round, and polar bears 

are hunted in the winter. 

Barrow residents’ main subsistence 

focus is concentrated on biannual 

bowhead whale hunts. They hunt these 

whales during the spring and fall. 

Westbound bowheads typically reach 

the Barrow area in mid-September and 

are in that area until late October 

(Brower, 1996). Autumn bowhead 

whaling near Barrow normally begins in 

mid-September to early October but may 

begin as early as late-August if whales 

are observed and ice conditions are 

favorable (USDI/BLM, 2005). Whaling 

near Barrow can continue into October, 

depending on the quota and conditions. 

Other animals, such as seals, walruses, 

and polar bears are hunted outside of 

the whaling season, but they are not the 

primary source of the subsistence 

harvest (URS Corporation, 2005). 

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. 

Plan of Cooperation (POC) 

Regulations at 50 CFR 216.104(a)(12) 

require IHA applicants for activities that 

take place in Arctic waters to provide a 

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 

developed a Draft POC for its 2010 

Chukchi Sea, Alaska, exploration 

drilling program to minimize any 

adverse impacts on the availability of 

marine mammals for subsistence uses. A 

copy of the Draft POC was distributed 

to the communities, subsistence user 

groups, NMFS, and other Federal and 

State agencies in May 2009. An updated 

Communications Plan was then 

submitted to NMFS as an attachment to 

the POC in early 2010. Shell conducted 

POC meetings throughout 2009 

regarding its planned 2010 activities in 

both the Beaufort and Chukchi Seas. 

During these meetings, Shell focused on 

lessons learned from prior years’ 

activities and presented mitigation 

measures for avoiding potential 

conflicts, which are outlined in the 2010 

POC and this document. Shell’s POC 

addresses issues of vessel transit, 

drilling, and associated activities. 

Communities that were consulted 

regarding Shell’s 2010 Arctic Ocean 

operations include: Barrow, Kaktovik, 

Wainwright, Kotzebue, Kivalina, Point 

Lay, and Point Hope. Attempts were 

made to meet individually with whaling 

captains and to hold a community 

meeting in Nuiqsut; however, after 

receipt of a request by the Mayor, the 

scheduled meeting was cancelled. Shell 

subsequently sent correspondence to all 

post office box holders in Nuiqsut on 

February 26, 2009, indicating its 

willingness to visit and have dialogue 

on the proposed plans. 

Beginning in early January 2009, Shell 

held one-on-one meetings with 

representatives from the North Slope 

Borough (NSB) and Northwest Arctic 

Borough (NWAB), subsistence-user 

group leadership, and Village Whaling 

Captain Association representatives. 

Shell’s primary purpose in holding 

individual meetings was to inform and 

prepare key leaders, prior to the public 

meetings, so that they would be 

prepared to give appropriate feedback 

on planned activities. 

Shell presented the proposed project 

to the NWAB Assembly on January 27, 

2009, to the NSB Assembly on February 

2, 2009, and to the NSB and NWAB 

Planning Commissions in a joint 

meeting on March 25, 2009. Meetings 

were also scheduled with 

representatives from the Alaska Eskimo 

Whaling Commission (AEWC), and 

presentations on proposed activities 

were given to the Inupiat Community of 

the Arctic Slope, and the Native Village 

of Barrow. A full list of POC meetings 

conducted by Shell between January 

and April 2009 can be found in Table 

4.2–1 of Shell’s POC. Shell has 

successfully completed additional POC 

meetings with several communities 

since submitting the Draft POC, 

including: 


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• June 1, 2009: NSB Assembly 

meeting; 

• June 2, 2009: Point Lay meeting 

with village leadership; 

• June 3, 2009: Kaktovik meeting with 

village leadership; 

• June 17, 2009: Point Hope meeting 

with village leadership; 

• August 5, 2009: NWAB Assembly 

meeting; and 

• August 27, 2009: NSB Planning 

Commission meeting. 

On December 8, 2009, Shell held 

consultation meetings with 

representatives from the various marine 

mammal commissions. Prior to drilling 

in 2010, Shell will also hold additional 

consultation meetings with the affected 

communities and subsistence user 

groups, NSB, and NWAB to discuss the 

mitigation measures included in the 

POC. 

The following mitigation measures, 

plans and programs, are integral to the 

POC and were developed during 

consultation with potentially affected 

subsistence groups and communities. 

These measures, plans, and programs 

will be implemented by Shell during its 

2010 exploration drilling operations in 

both the Beaufort and Chukchi Seas to 

monitor and mitigate potential impacts 

to subsistence users and resources. The 

mitigation measures Shell has adopted 

and will implement during its 2010 

Chukchi Sea offshore exploration 

drilling operations are listed and 

discussed below. This most recent 

version of Shell’s planned mitigation 

measures was presented to community 

leaders and subsistence user groups 

starting in January of 2009 and has 

evolved since in response to 

information learned during the 

consultation process. 

To minimize any cultural or resource 

impacts to subsistence activities from its 

exploration operations, Shell will 

implement the following additional 

measures to ensure coordination of its 

activities with local subsistence users to 

minimize further the risk of impacting 

marine mammals and interfering with 

the subsistence hunts for marine 

mammals: 

(1) The drillship and support vessels 

will not enter the Chukchi Sea before 

July 1 unless authorized by the USFWS 

based upon a review of seasonal ice 

conditions and other factors to 

minimize effects on marine mammals 

that frequent open leads and to 

minimize effects on spring bowhead or 

beluga whale hunts. 

(2) To minimize impacts on marine 

mammals and subsistence hunting 

activities, vessels that can safely travel 

outside of the polynya zone will do so. 

In the event the transit outside of the 

polynya zone results in Shell having to 

break ice (as opposed to managing ice 

by pushing it out of the way), the 

drillship and support vessels will enter 

into the polynya zone far enough so that 

ice breaking is not necessary. If it is 

necessary to move into the polynya 

zone, Shell will notify the local 

communities of the change in the transit 

route through the Communication 

Centers (Com Centers); 

(3) Shell has developed a 

Communication Plan and will 

implement the plan before initiating 

exploration drilling operations to 

coordinate activities with local 

subsistence users as well as Village 

Whaling Associations in order to 

minimize the risk of interfering with 

subsistence hunting activities and keep 

current as to the timing and status of the 

bowhead whale migration, as well as the 

timing and status of other subsistence 

hunts. The Communication Plan 

includes procedures for coordination 

with Com and Call Centers to be located 

in coastal villages along the Chukchi 

and Beaufort Seas during Shell’s 

proposed activities in 2010; 

(4) Shell will employ local 

Subsistence Advisors from the Beaufort 

and Chukchi Sea villages to provide 

consultation and guidance regarding the 

whale migration and subsistence hunt. 

There will be a total of nine subsistence 

advisor-liaison positions (one per 

village), to work approximately 8-hours 

per day and 40-hour weeks through 

Shell’s 2010 exploration project. The 

subsistence advisor will use local 

knowledge (Traditional Knowledge) to 

gather data on subsistence lifestyle 

within the community and advise as to 

ways to minimize and mitigate potential 

impacts to subsistence resources during 

the drilling season. Responsibilities 

include reporting any subsistence 

concerns or conflicts; coordinating with 

subsistence users; reporting subsistencerelated comments, concerns, and 

information; and advising how to avoid 

subsistence conflicts. A subsistence 

advisor handbook will be developed 

prior to the operational season to 

specify position work tasks in more 

detail; 

(5) Shell will recycle drilling muds 

(e.g., use those muds on multiple wells), 

to the extent practicable based on 

operational considerations (e.g., 

whether mud properties have 

deteriorated to the point where they 

cannot be used further), to reduce 

discharges from its operations. At the 

end of the season excess water base 

fluid will be pre-diluted to a 30:1 ratio 

with seawater and then discharged; 

(6) Shell will implement flight 

restrictions prohibiting aircraft from 

flying within 1,000 ft (305 m) of marine 

mammals or below 1,500 ft (457 m) 

altitude (except during takeoffs and 

landings or in emergency situations) 

while over land or sea; and 

(7) Vessels within 900 ft (274 m) of 

marine mammals will reduce speed, 

avoid separating members from a group, 

and avoid multiple changes in direction. 

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. Vessel 

and aircraft traffic associated with 

Shell’s proposed 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 traffic 

corridors do not traverse areas indicated 

in recent mapping as utilized by 

Barrow, Point Lay, or Point Hope for 

beluga hunts. The corridor avoids 

important beluga hunting areas in 

Kasegaluk Lagoon. 

For several years, a Conflict 

Avoidance Agreement (CAA) has been 

negotiated between the AEWC, affected 

whaling captains’ associations, and the 

oil and gas industry to avoid conflicts 

between industry activity and bowhead 

whale subsistence hunts. While the 

signing of a CAA is not a requirement 

to obtain an IHA, the CAA often 

contains measures that help NMFS 

make its no unmitigable adverse impact 

determination for bowhead whales. 

Shell reviewed the draft 2010 CAA and 

made some revisions to the CAA before 

signing the document. 

Unmitigable Adverse Impact Analysis 

and Preliminary Determination 

NMFS has preliminarily determined 

that Shell’s proposed Chukchi Sea 

offshore exploration drilling program 

will not have an unmitigable adverse 

impact on the availability of species or 

stocks for taking for subsistence uses. 

This preliminary determination is 

supported by information contained in 

this document and Shell’s POC. Shell 

has adopted a spatial and temporal 

strategy for its Chukchi Sea operations 

that should minimize impacts to 

subsistence hunters. Shell will enter the 

Chukchi Sea far offshore, so as to not 

interfere with July hunts in the Chukchi 

Sea villages and will communicate with 

the Com Centers to notify local 

communities of any changes in the 

transit route. After the close of the July 


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beluga whale hunts in the Chukchi Sea 

villages, very little whaling occurs in 

Wainwright, Point Hope, and Point Lay. 

Although the fall bowhead whale hunt 

in Barrow will occur while Shell is still 

operating (mid- to late September to 

October), Barrow is located 140 mi (225 

km) east of the proposed drill sites. 

Based on these factors, Shell’s Chukchi 

Sea survey is not expected to interfere 

with the fall bowhead harvest in 

Barrow. In recent years, bowhead 

whales have occasionally been taken in 

the fall by coastal villages along the 

Chukchi coast, but the total number of 

these animals has been small. 

Adverse impacts are not anticipated 

on sealing activities since the majority 

of hunts for seals occur in the winter 

and spring, when Shell will not be 

operating. Additionally, most sealing 

activities occur much closer to shore 

than Shell’s proposed drill sites. 

Shell will also support the village 

Com Centers in the Arctic communities 

and employ local Subsistence Advisors 

from the Beaufort and Chukchi Sea 

villages to provide consultation and 

guidance regarding the whale migration 

and subsistence hunt. The Subsistence 

Advisors will provide advice to Shell on 

ways to minimize and mitigate potential 

impacts to subsistence resources during 

the drilling season. Support activities, 

such as helicopter flights, could impact 

nearshore subsistence hunts. However, 

Shell will use flight paths to avoid 

adverse impacts to hunts and will 

communicate regularly with the Com 

Centers. 

Based on the measures described in 

Shell’s Draft POC, the proposed 

mitigation and monitoring measures 

(described earlier in this document), 

and the project design itself, NMFS has 

determined preliminarily that there will 

not be an unmitigable adverse impact on 

subsistence uses from Shell’s Chukchi 

Sea offshore exploration drilling 

activities. 

Endangered Species Act (ESA) 

There are three 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. NMFS’ Permits, Conservation 

and Education Division has initiated 

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 currently preparing an 

Environmental Assessment, pursuant to 

NEPA, to determine whether or not this 

proposed activity may have a significant 

effect on the human environment. This 

analysis will be completed prior to the 

issuance or denial of the IHA. 

Proposed Authorization 

As a result of these preliminary 

determinations, NMFS proposes to 

authorize the take of marine mammals 

incidental to Shell’s 2010 Chukchi Sea, 

Alaska, exploration drilling program, 

provided the previously mentioned 

mitigation, monitoring, and reporting 

requirements are incorporated. 

Dated: May 3, 2010. 

Helen M. Golde, 

Deputy Director, Office of Protected 

Resources, National Marine Fisheries Service. 

[FR Doc. 2010–10880 Filed 5–6–10; 8:45 am] 

BILLING CODE 3510–22–P 


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