[Federal Register Volume 75, Number 88 (Friday, May 7, 2010)]
[Notices]
[Pages 25730-25757]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-10880]



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Part III





Department of Commerce





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National Oceanic and Atmospheric Administration



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Takes of Marine Mammals Incidental to Specified Activities; Taking 
Marine Mammals Incidental to an Exploration Drilling Program in the 
Chukchi Sea, AK; Notice

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

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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.

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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 East-West 
Highway, Silver Spring, MD 20910. The mailbox address for providing e-
mail comments is <a href="/cdn-cgi/l/email-protection#39696b0817090f0d0114616e080d7957565858175e564f"><span class="__cf_email__" data-cfemail="df8f8deef1efe9ebe7f28788eeeb9fb1b0bebef1b8b0a9">[email protected]</span></a>. 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

[[Page 25731]]

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 ice-management 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 open-
water 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-
and-rescue 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:
    <bullet> Radarsat and Envisat data--satellites with Synthetic 
Aperture Radar, providing all-weather imagery of ice conditions with 
very high resolution;
    <bullet> Moderate Resolution Imaging Spectroradiometer--a satellite 
providing lower resolution visual and near infrared imagery;
    <bullet> Aerial reconnaissance--provided by specially deployed 
fixed wing or rotary wing aircraft for confirmation of ice conditions 
and position;
    <bullet> Reports from ice specialists on the ice-management and 
anchor handling vessels and from the ice observer on the drillship;
    <bullet> Incidental ice data provided by commercial ships 
transiting the area; and
    <bullet> 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

[[Page 25732]]

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, ice-management 
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 up-drift 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. Ice-management occurs with slow movements 
of the vessel using lower power and therefore slower propeller rotation 
speed (i.e., lower cavitation), allowing for fewer repositions of the 
vessel, 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 [mu]Pa (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 [mu]Pa (rms) at 0.1 
mi (0.2 km; Greene, 1987b). The back-propagated source levels (175 dB 
re 1 [mu]Pa 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, ice-management 
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 peer-reviewed 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):
    <bullet> Low frequency cetaceans (13 species of mysticetes): 
functional hearing is estimated to occur between approximately 7 Hz and 
22 kHz;
    <bullet> 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;
    <bullet> 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
    <bullet> 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 mid-frequency 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

[[Page 25734]]

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 ice-management 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 
industry-generated 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 ice-management, 
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-and-rescue operations 
that may be necessary. Under calm conditions, rotor and engine sounds 
are coupled into the water within a 26[deg] cone beneath the aircraft. 
Some of the sound will transmit beyond the immediate area, and some 
sound will enter the water outside the 26[deg] 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

[[Page 25735]]

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 high-frequency sounds to communicate and locate prey; therefore, 
masking by low-frequency sounds associated with drilling activities is 
not expected to occur (Gales, 1982, as cited in Shell, 2009). If the 
distance between communicating whales does not exceed their distance 
from the drilling activity, the likelihood of potential impacts from 
masking would be low (Gales, 1982, as cited in Shell, 2009). At 
distances greater than 660-1,300 ft (200-400 m), recorded sounds from 
drilling activities did not affect behavior of beluga whales, even 
though the sound energy level and frequency were such that it could be 
heard several kilometers away (Richardson et al., 1995b). This exposure 
resulted in whales being deflected from the sound energy and changing 
behavior. These minor changes are not expected to affect the beluga 
whale population (Richardson et al., 1991; Richard et al., 1998). 
Brewer et al. (1993) observed belugas within 2.3 mi (3.7 km) of the 
drilling unit Kulluk during drilling; however, the authors do not 
describe any behaviors that may have been exhibited by those animals. 
Please refer to the Arctic Multiple-Sale Draft Environmental Impact 
Statement (USDOI MMS, 2008), available on the Internet at: http://www.mms.gov/alaska/ref/EIS%20EA/ArcticMultiSale_209/_DEIS.htm, for 
more detailed information.
    There is evidence of other marine mammal species continuing to call 
in the presence of industrial activity. 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

[[Page 25736]]

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 [mu]Pa (rms). Probability of avoidance and 
other behavioral effects increased when received levels were from 120-
160 dB re 1 [mu]Pa (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 low-frequency 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 ``M-sequence'' (sine wave with multiple-phase reversals) 
signal in the 60 to 90 Hz band with output of 172 dB at 1 m. For 11 
playbacks, exposures were

[[Page 25737]]

between 120 and 130 dB re 1 [mu]Pa (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 ice-management 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 
ice-breaking 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

[[Page 25738]]

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 non-pulse 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 [micro]Pa at 1 m at the 80- and 160-Hz 
frequencies.
    Kastelein et al. (2005) exposed two captive harbor porpoise (a 
high-frequency cetacean) to various non-pulse sounds in an 
approximately 111.5 x 65.6 ft (34 x 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

[[Page 25739]]

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 x 98 ft (25 x 30 m) enclosure to non-pulse 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 [<plus-
minus> 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 [micro]Pa 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 [micro]Pa\2.\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 
[micro]Pa (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.,

[[Page 25740]]

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 [micro]Pa<SUP>2.</SUP>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 [micro]Pa (rms). The established 180- 
and 190-dB re 1 [micro]Pa (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 
back-propagated source level for the drillship to be 175 dB re 1 
[micro]Pa 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 mid-frequency 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 
mid-frequency 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

[[Page 25741]]

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 
Lamont-Doherty 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 ft\2\ (197 m\2\) 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 m\2\) 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

[[Page 25742]]

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 ice-management 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 
ice-management 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.

[[Page 25743]]

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 ice-management 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, ice-management 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:
    <bullet> Timing and locating drilling and support activities to 
avoid interference with the annual subsistence hunts by the peoples of 
the Chukchi villages;
    <bullet> 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
    <bullet> 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 [micro]Pa (rms) for cetaceans 
and greater than or equal to 190 dB re 1 [micro]Pa (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 [micro]Pa 
(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,

[[Page 25744]]

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 [micro]Pa (rms) at 0.1 mi (0.2 km; Greene 1987). The back-
propagated source levels (175 dB re 1 [micro]Pa 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:
    <bullet> The manner in which, and the degree to which, the 
successful implementation of the measure is expected to minimize 
adverse impacts to marine mammals;
    <bullet> The proven or likely efficacy of the specific measure to 
minimize adverse impacts as planned; and
    <bullet> 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

[[Page 25745]]

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 night-vision 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 <plus-minus>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 saw-toothed 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.

[[Page 25746]]

    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)

[[Page 25747]]

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 vessel-based 
and aerial monitoring.
    Analysis of all acoustic data will be prioritized to address the 
primary questions, which are to: (a) Determine when, where, and what 
species of animals are acoustically detected on each 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; non-auditory 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 [mu]Pa (rms), no injury or 
mortality of marine mammals is

[[Page 25748]]

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
----------------------------------------------------------------------------------------------------------------
                                                            Open water                      Ice margin
                                                 ---------------------------------------------------------------
                                                      Average         Maximum         Average         Maximum
                     Species                          density         density         density         density
                                                    (<greek-i>/     (<greek-i>/     (<greek-i>/     (<greek-i>/
                                                      km\2\)          km\2\)          km\2\)          km\2\)
----------------------------------------------------------------------------------------------------------------
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

[[Page 25749]]

 
        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
----------------------------------------------------------------------------------------------------------------
                                                            Open water                      Ice margin
                                                 ---------------------------------------------------------------
                                                      Average         Maximum         Average         Maximum
                     Species                          density         density         density         density
                                                    (<greek-i>/     (<greek-i>/     (<greek-i>/     (<greek-i>/
                                                      km\2\)          km\2\)          km\2\)          km\2\)
----------------------------------------------------------------------------------------------------------------
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

[[Page 25750]]

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 open-water 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/
mi\2\ (0.0001-0.0005/km\2\) with a maximum 95 percent confidence 
interval (CI) of 0.0049/mi\2\ (0.0019 km\2\).
    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 on-transect 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 on-effort 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 non-seismic periods and locations in July-
August of 2006-2008 (Haley et al., 2009b) ranged from 0.0003 to 0.0129/
mi\2\ (0.0001-0.0050/km\2\) with a maximum 95 percent CI of 0.1243/
mi\2\ (0.0480 km\2\).
    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

[[Page 25751]]

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 
ice-margin habitat as were derived for open-water habitat during both 
seasons. Densities from vessel based surveys in the Chukchi Sea during 
non-seismic periods and locations in July-August of 2006-2008 (Haley et 
al., 2009b) ranged from 0.0023/mi\2\ to 0.0088/mi\2\ (0.0009/km\2\ to 
0.0034/km\2\) with a maximum 95 percent CI of 0.0378 mi\2\ (0.0146 
km\2\).
    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 on-transect 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/mi\2\ to 0.0062/mi\2\ (0.0011/
km\2\ to 0.0024/km\2\) with a maximum 95 percent CI of 0.0474 mi\2\ 
(0.0183 km\2\).
    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/mi\2\ to 0.0041/mi\2\ (0.0009/km\2\ to 0.0016/km\2\) 
with a maximum 95 percent CI of 0.0016/mi\2\ (0.0041/km\2\) (Haley et 
al., 2009b). The median value from the summer season of those three 
years (0.0028/mi\2\/0.0011/km\2\) was used as the average open-water 
density estimate while the high value (0.0041/mi\2\/0.0016/km\2\) 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/mi\2\ to 0.0034/km\2\ (0.0002/km\2\ to 0.0013/
km\2\) with a maximum 95 percent CI of 0.0114/mi\2\ (0.0044/km\2\). The 
median value 0.0026/mi\2\ (0.0010/km\2\) was again used as the average 
density estimate and the high value 0.0034/mi\2\ (0.0013/km\2\) 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/mi\2\ to 0.0572/mi\2\ (0.0082/km\2\ to 0.0221/km\2\) with a 
maximum 95 percent CI of 0.1494/mi\2\ (0.0577/km\2\) (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

[[Page 25752]]

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/mi\2\ (0.0003/
km\2\) 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 [micro]Pa 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 [mu]Pa (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.
------------------------------------------------------------------------
                                                             Used in
              Location                Modeling results    calculations
                                             (km)             (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 [mu]Pa within each season and 
habitat zone was estimated by multiplying:
    <bullet> The anticipated area to be ensonified to the specified 
level in the time period and habitat zone to which a density applies, 
by
    <bullet> 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 mi\2\ (14.9 km\2\) in the summer for the Burger 
and SW Shoebill prospects combined and 1.9 mi\2\ (4.8 km\2\) 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

[[Page 25753]]

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 [micro]Pa (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 free-ranging 
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, mid-frequency, 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
----------------------------------------------------------------------------------------------------------------
                                                                                                   Percentage of
                           Species                               Abundance\1\     Total proposed     stock or
                                                                                       take         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.
\2\ Assumes 3.4 percent annual growth from the 2001 estimate of 10,545 individuals (Zeh and Punt, 2005).
\3\ Eastern 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 open-water 
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.

[[Page 25754]]

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 (mid-September 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-Chukchi-Beaufort 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

[[Page 25755]]

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:

[[Page 25756]]

    <bullet> June 1, 2009: NSB Assembly meeting;
    <bullet> June 2, 2009: Point Lay meeting with village leadership;
    <bullet> June 3, 2009: Kaktovik meeting with village leadership;
    <bullet> June 17, 2009: Point Hope meeting with village leadership;
    <bullet> August 5, 2009: NWAB Assembly meeting; and
    <bullet> 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 subsistence-
related 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

[[Page 25757]]

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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