Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to an Exploration Drilling Program Near Camden Bay, Beaufort Sea, AK;, 68974-69027 [2011-28641]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 76, Number 215 (Monday, November 7, 2011)]
[Notices]
[Pages 68974-69027]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-28641]



[[Page 68973]]

Vol. 76

Monday,

No. 215

November 7, 2011

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 Near 
Camden Bay, Beaufort Sea, AK; Notice

Federal Register / Vol. 76 , No. 215 / Monday, November 7, 2011 / 
Notices

[[Page 68974]]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XA804


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to an Exploration Drilling Program 
Near Camden Bay, Beaufort 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 Beaufort 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, eight species of marine mammals during the specified 
activity.

DATES: Comments and information must be received no later than December 
7, 2011.

ADDRESSES: Comments on the application should be addressed to Michael 
Payne, Chief, Permits and Conservation Division, Office of Protected 
Resources, National Marine Fisheries Service, 1315 East-West Highway, 
Silver Spring, MD 20910. The mailbox address for providing email 
comments is ITP.Nachman@noaa.gov. NMFS is not responsible for email 
comments sent to addresses other than the one provided here. Comments 
sent via email, including all attachments, must not exceed a 10-
megabyte file size.
    Instructions: All comments received are a part of the public record 
and will generally be posted to https://www.nmfs.noaa.gov/pr/permits/incidental.htm without change. All Personal Identifying Information 
(for example, name, address, etc.) voluntarily submitted by the 
commenter may be publicly accessible. Do not submit Confidential 
Business Information or otherwise sensitive or protected information.
    A copy of the application, which contains several attachments, 
including Shell's marine mammal mitigation and monitoring plan and Plan 
of Cooperation, used in this document may be obtained by writing to the 
address specified above, telephoning the contact listed below (see FOR 
FURTHER INFORMATION CONTACT), or visiting the Internet at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm. Documents cited in this 
notice may also be viewed, by appointment, during regular business 
hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Candace Nachman, Office of Protected 
Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION: 

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce to allow, upon request, the 
incidental, but not intentional, taking of small numbers of marine 
mammals by U.S. citizens who engage in a specified activity (other than 
commercial fishing) within a specified geographical region if certain 
findings are made and either regulations are issued or, if the taking 
is limited to harassment, a notice of a proposed authorization is 
provided to the public for review.
    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 10, 2011, from Shell for the 
taking, by harassment, of marine mammals incidental to offshore 
exploration drilling on OCS leases in the Beaufort 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 
September 2, 2011. NMFS carefully evaluated Shell's application, 
including their analyses, and determined that the application is 
complete. The September 2, 2011, application is the one available for 
public comment (see ADDRESSES) and considered by NMFS for this proposed 
IHA.
    Shell plans to drill two exploration wells at two drill sites in 
Camden Bay, Beaufort Sea, Alaska, during the 2012 Arctic open-water 
season (July through October). Impacts to marine mammals may occur from 
noise produced by the drillship, zero-offset vertical seismic profile 
(ZVSP) surveys, and supporting vessels (including icebreakers) and 
aircraft. Shell has requested an authorization to take 11 marine mammal 
species by Level B harassment. However, some of these species are not 
expected to be found in the activity area. Therefore, NMFS is proposing 
to authorize take of eight marine mammal species, by Level B 
harassment, incidental to Shell's offshore exploration drilling program 
in Camden Bay. These species include: Beluga whale (Delphinapterus 
leucas); bowhead whale (Balaena mysticetus); gray whale (Eschrichtius 
robustus); harbor porpoise (Phocoena phocoena); bearded seal 
(Erignathus barbatus); ringed seal (Phoca hispida); spotted seal (P. 
largha); and ribbon seal (Histriophoca fasciata).

Description of the Specified Activity and Specified Geographic Region

    Shell plans to conduct an offshore exploration drilling program on 
U.S. Department of the Interior, Bureau of Ocean Energy Management 
(BOEM, formerly the Minerals Management Service) Alaska OCS leases 
located north of Point Thomson near Camden Bay in the Beaufort Sea, 
Alaska, during the 2012 open-water season. During the 2012 drilling 
program, Shell plans to complete two exploration wells at two

[[Page 68975]]

drill sites, one well each on the Torpedo prospect (NR06-04 Flaxman 
Island lease block 6610, OCS-Y-1941 [Flaxman Island 6610--Torpedo ``H'' 
or ``J'' drill site]) and the Sivulliq prospect (NR06-04 Flaxman Island 
lease block 6658, OCS-Y 1805 [Flaxman Island 6658--Sivulliq ``N'' or 
``G'' drill sites]). 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.

Exploration Drilling

    Shell plans to drill the Torpedo prospect well (Torpedo ``H'' or 
``J'') first, followed by the Sivulliq well (Sivulliq ``N'' or ``G''), 
unless adverse surface conditions or other factors dictate a reversal 
of drilling sequence. In that case, Shell will mobilize to the Sivulliq 
prospect and drill there first. Because this is an Arctic program, 
weather and ice conditions will dictate actual operations. The Torpedo 
H and J drill sites are located 20.8 and 23.1 mi (33.5 and 37.2 km) 
from shore in water 120 and 124 ft (36.6 and 37.8 m) deep, 
respectively. The Sivulliq G and N drill sites are located 16.6 and 
16.2 mi (26.7 and 26.1 km) from shore in water 110 and 107 ft (33.5 and 
32.6 m) deep, respectively.
(1) Drilling Vessels
    Shell plans to use one of two drilling vessels for its proposed 
2012 Camden Bay exploratory drilling program: The Kulluk (owned by 
Shell and operated by Noble Drilling [Noble]); or the Discoverer (owned 
and operated by Noble). Only one of these drilling vessels would be 
used for the Camden Bay program, not both. Information on each vessel 
is provided next, and additional details can be found in Attachment A 
of Shell's IHA application (see ADDRESSES).
    The Kulluk has an Arctic Class IV hull design, is capable of 
drilling in up to 600 ft (182.9 m) of water and is moored using a 12-
point anchor system. The vessel is 266 ft (81 m) long. The Kulluk's 
mooring system consists of 12 Hepburn winches located on the outboard 
side of the main deck. Anchor wires lead off the bottom of each winch 
drum inboard for approximately 55 ft (16.8 m). The wire is then 
redirected by a sheave, down through a hawse pipe to an underwater, ice 
protected, swivel fairlead. The wire travels from the fairlead directly 
under the hull to the anchor system on the seafloor. The Kulluk would 
have an anchor radius maximum of 3,117 ft (950 m) for the Sivulliq and 
Torpedo drill sites. While on location at the drill sites, the Kulluk 
will be affixed to the seafloor using 12, 15 metric ton Stevpris 
anchors arranged in a radial array.
    The Kulluk is designed to maintain its location in drilling mode in 
moving ice with thickness up to 4 ft (1.2 m) without the aid of any 
active ice management. With the aid of the ice management vessels, the 
Kulluk would be able to withstand more severe ice conditions. In more 
open-water conditions, the Kulluk can maintain its drilling location 
during storm events with wave heights up to 18 ft (5.5 m) while 
drilling, and can withstand wave heights of up to 40 ft (12.2 m) when 
not drilling and disconnected (assuming a storm duration of 24 hours).
    The Discoverer is a true drillship and is a largely self-contained 
drillship that offers full accommodations for a crew of up to 140 
persons. The Discoverer is 514 ft (156.7 m) long with a maximum height 
(above keel) of 274 ft (83.7 m). It is an anchored drillship with an 8-
point anchored mooring system and would likely have a maximum anchor 
radius of 2,969-2,986 ft (905-910 m) at either the Sivulliq or Torpedo 
drill sites. While on location at the drill sites, the Discoverer will 
be affixed to the seafloor using eight 7,000 kg (7.7 ton) Stevpris 
anchors arranged in a radial array. The underwater fairleads prevent 
ice fouling of the anchor lines. Turret mooring allows orientation of 
the vessel's bow into the prevailing ice drift direction to present 
minimum hull exposure to drifting ice. The vessel is rotated around the 
turret by hydraulic jacks. Rotation can be augmented by the use of the 
fitted bow and stern thrusters. The hull has been reinforced for ice 
resistance. Ice-strengthened sponsons have been retrofitted to the 
ship's hull.
(2) Support Vessels
    During the 2012 drilling season, the Kulluk or Discoverer will be 
attended by 11 vessels that will be used for ice-management, anchor 
handling, oil spill response (OSR), refueling, resupply, drill mud/
cuttings and wastewater transfer, equipment and waste holding, and 
servicing of the drilling operations. Tables 1-1a and 1-1b in Shell's 
application provide lists of the support vessels to be used during the 
drilling program and OSR vessels. The workboats associated with OSR 
training (which are stored on an OSR barge) are not counted among the 
11 attending vessels. All vessels are intended to be either in transit 
or staged (i.e., on anchor) in the Beaufort Sea during the exploration 
drilling activities. The oil spill tanker (OST) would be staged such 
that it would arrive at a recovery site, if needed, within 24 hours of 
departure from the staging location. The purpose of the OST would be to 
provide a place to store large volumes of recovered crude oil, emulsion 
and free water in the unlikely event of a spill, and OSR operations. 
Additional information on Shell's fleet of oil spill response vessels 
can be found in the IHA application.
    The M/V Nordica (Nordica) or a similar vessel will serve as the 
primary ice management vessel in support of the Kulluk or Discoverer. 
Hull 247 or a similar vessel will provide anchor handling duties, serve 
as the berthing (accommodations) vessel for the OSR crew, and will also 
serve as a secondary ice management vessel by managing smaller ice 
floes that may pose a potential safety issue to the drillship and the 
support vessels servicing the drillship. This vessel will also provide 
supplemental oil recovery capability (Vessel of Opportunity Skimming 
System [VOSS]). When managing ice, the Nordica (or similar vessel) and 
Hull 247 will generally be confined to a 40[deg] arc up to 3.1 mi (4.9 
km) upwind originating at the drilling vessel (see Figure 1-3 in 
Shell's application). It is anticipated that the ice management vessels 
will be managing ice for up to 38% of the time when within 25 mi (40 
km) of the Kulluk or Discoverer. Active ice management involves using 
the ice management vessel to steer larger floes so that their path does 
not intersect with the drill site. Around-the-clock ice forecasting 
using real-time satellite coverage (available through Shell Ice and 
Weather Advisory Center [SIWAC]) will support the ice management 
duties. When the Nordica and Hull 247 are not needed for ice 
management, they will reside outside the 25 mi (40 km) radius from the 
Kulluk or Discoverer if it is safe to do so. These vessels will enter 
and exit the Beaufort Sea with the Kulluk or Discoverer.
    The exploration drilling operations will require the transfer of 
supplies between either the Deadhorse/West Dock shorebase or Dutch 
Harbor and the drillship (either the Kulluk or Discoverer). While the 
Kulluk or Discoverer is anchored at a drill site, Shell anticipates 24 
visits/tie-ups (if the Kulluk is the drilling vessel being used) or 8 
visits/tie-ups (if the Discoverer is being used) throughout the 
drilling season from support vessels. During resupply, mud/cuttings and 
other waste streams will be transferred to a deck barge or waste barge 
for temporary storage, which will be brought south for disposal at the 
end of the drilling season. Additional information on the resupply and 
waste removal vessels can be found in Shell's application. Removal of 
waste and resupply to the

[[Page 68976]]

drilling vessels will be conducted the same way regardless of drilling 
vessel.
(3) Aircraft
    An AW139 or Sikorsky S-92 helicopter based in Deadhorse will be 
used for flights between the shorebase and drill sites. It is expected 
that on average, up to two flights per day (approximately 12 flights 
per week) will be necessary to transport supplies and rotate crews. A 
Sikorsky S-92 based in Barrow will be used for search and rescue 
operations. Marine mammal monitoring flights will utilize a de 
Havilland Twin Otter aircraft. The de Havilland Twin Otter is expected 
to fly daily. Table 1-1c in Shell's application presents the aircraft 
planned to support the exploration drilling program.

Zero-Offset Vertical Seismic Profile

    At the end of each drill hole, Shell may conduct a geophysical 
survey referred to as ZVSP at each drill site where a well is drilled 
in 2012. During ZVSP surveys, an airgun array is deployed at a location 
near or adjacent to the drilling vessel, while receivers are placed 
(temporarily anchored) in the wellbore. The sound source (airgun array) 
is fired repeatedly, and the reflected sonic waves are recorded by 
receivers (geophones) located in the wellbore. The geophones, typically 
in a string, are then raised up to the next interval in the wellbore, 
and the process is repeated until the entire wellbore has been 
surveyed. The purpose of the ZVSP is to gather geophysical information 
at various depths, which can then be used to tie-in or ground-truth 
geophysical information from the previous seismic surveys with 
geological data collected within the wellbore.
    Shell intends to conduct a particular form of vertical seismic 
profile known as a ZVSP, in which the sound source is maintained at a 
constant location near the wellbore (see Figure 1-2 in Shell's 
application). A typical sound source that would be used by Shell in 
2012 is the ITAGA eight-airgun array, which consists of four 150 in\3\ 
airguns and four 40 in\3\ airguns. These airguns can be activated in 
any combination, and Shell intends to utilize the minimum airgun volume 
required to obtain an acceptable signal. Current specifications of the 
array are provided in Table 1-2 of Shell's application. The airgun 
array is depicted within its frame or sled, which is approximately 6 ft 
x 5 ft x 10 ft (1.8 m x 1.5 m x 3 m) (see photograph in Shell's 
application). Typical receivers would consist of a Schlumberger 
wireline four level Vertical Seismic Imager (VSI) tool, which has four 
receivers 50-ft (15-m) apart.
    A ZVSP survey is normally conducted at each well after total depth 
is reached but may be conducted at a shallower depth. For each survey, 
Shell plans to deploy the airgun array over the side of the Kulluk or 
Discoverer with a crane (sound source will be 50-200 ft [15-61 m] from 
the wellhead depending on crane location) to a depth of approximately 
10-23 ft (3-7 m) below the water surface. The VSI, with its four 
receivers, will be temporarily anchored in the wellbore at depth. The 
sound source will be pressured up to 2,000 pounds per square inch (psi) 
and activated 5-7 times at approximately 20-second intervals. The VSI 
will then be moved to the next interval of the wellbore and reanchored, 
after which the airgun array will again be activated 5-7 times. This 
process will be repeated until the entire well bore is surveyed in this 
manner. The interval between anchor points for the VSI usually is 
between 200 and 300 ft (61 and 91 m). A normal ZVSP survey is conducted 
over a period of about 10-14 hours, depending on the depth of the well 
and the number of anchoring points. Therefore, considering a few 
different scenarios, the airgun array could be fired between 117 and 
245 times during the 10-14 hour period. For example, a 7,000-ft 
(2,133.6-m) well with 200-ft (61-m) spacing and seven activations per 
station would result in the airgun array being fired 245 times to 
survey the entire well. That same 7,000-ft (2,133.6-m) well with 300-ft 
(91-m) spacing and five activations would result in the airgun array 
being fired 117 times to survey the entire well. The remainder of the 
time during those 10-14 hours when the airgun is not firing is used to 
move and anchor the geophone array.

Ice Management and Forecasting

    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 Ice Management 
Plan (IMP; see Attachment B in Shell's IHA application) 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 SIWAC. 
The center is continuously manned by experienced personnel, who rely on 
a number of data sources for ice forecasting and tracking, including:
     Radarsat and Envisat data--satellites with Synthetic 
Aperture Radar, providing all-weather imagery of ice conditions with 
very high resolution;
     Moderate Resolution Imaging Spectroradiometer--a satellite 
providing lower resolution visual and near infrared imagery;
     Aerial reconnaissance--provided by specially deployed 
fixed wing or rotary wing aircraft for confirmation of ice conditions 
and position;
     Reports from ice specialists on the ice management and 
anchor handling vessels and from the ice observer on the drillship;
     Incidental ice data provided by commercial ships 
transiting the area; and
     Information from NOAA ice centers and the University of 
Colorado.
    Drift ice will be actively managed by ice management vessels, 
consisting of an ice management vessel and an anchor handling vessel. 
Ice management for safe operation of Shell's planned exploration 
drilling program will occur far out in the OCS, remote from the 
vicinities of any routine marine vessel traffic in the Beaufort Sea 
causing no threat to public safety or services that occurs near to 
shore. Shell vessels will also communicate movements and activities 
through the 2012 North Slope Communications Centers. Management of ice 
by ice management vessels will occur during a drilling season 
predominated by open water and thus is not expected to contribute to 
ice hazards, such as ridging, override, or pileup in an offshore or 
nearshore environment.
    The ice-management/anchor handling vessels would manage the ice by 
deflecting any ice floes that could affect the Kulluk or Discoverer 
when it is drilling and would also handle the Kulluk's or Discoverer's 
anchors during connection to and separation from the seafloor. When 
managing ice, the ice management and anchor handling vessels will 
generally be operating at a 40[deg] arc up to 3.1 mi (4.9 km) upwind 
originating at the Kulluk or Discoverer (see Figure 1-3 in Shell's 
application).
    It is anticipated that the ice management vessels will be managing 
ice for 38% of the time when within 25 mi (40 km) of the Kulluk or 
Discoverer.

[[Page 68977]]

The ice floe frequency and intensity are unpredictable and could range 
from no ice to ice sufficiently dense that the fleet has insufficient 
capacity to continue operating, and the Kulluk or 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 (i.e., ice that formed in the most recent autumn-winter period) 
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 Kulluk or Discoverer without building up in 
front of or around 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 Kulluk or 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 (i.e., ice that has survived at least one summer melt 
season) ridges that would be managed at a much slower speed than that 
used to manage first-year ice.
    During Camden Bay exploration drilling operations, Shell has 
indicated that they do not intend to conduct any icebreaking 
activities; rather, Shell would deploy its support vessels to manage 
ice as described here. As detailed in Shell's IMP (see Attachment B of 
Shell's IHA application), actual breaking of ice would occur only in 
the unlikely event that ice conditions in the immediate vicinity of 
operations create a safety hazard for the drilling vessel. In such a 
circumstance, operations personnel will follow the guidelines 
established in the IMP to evaluate ice conditions and make the formal 
designation of a hazardous, ice alert condition, which would trigger 
the procedures that govern any actual icebreaking operations. 
Historical data relative to ice conditions in the Beaufort Sea in the 
vicinity of Shell's planned operations, and during the timeframe for 
those operations, establish that there is a very low probability (e.g., 
minimal) for the type of hazardous ice conditions that might 
necessitate icebreaking (e.g., records of the National Naval Ice Center 
archives). This probability could be greater at the shoulders of the 
drilling season (early July or late October); therefore, for purposes 
of evaluating possible impacts of the planned activities, Shell has 
assumed limited icebreaking activities for a very limited period of 
time, and estimated incidental takes of marine mammals from such 
activities.

Timeframe of Activities

    Shell's base plan is for the Kulluk or Discoverer and the 
associated support vessels to transit through the Bering Strait, after 
July 1, 2012, then through the Chukchi Sea, around Pt. Barrow, and east 
through the Alaskan Beaufort Sea, before arriving on location at the 
Torpedo ``H'' location on or about July 10, or Sivulliq ``N'' if 
adverse surface conditions or other factors dictate a reversal of 
drilling sequence. At the completion of the drilling season on or 
before October 31, 2012, one or two ice management vessels, along with 
various support vessels, such as the OSR fleet, will accompany the 
Kulluk or Discoverer as it travels west through the Beaufort Sea, then 
south through the Chukchi Sea and the Bering Strait. Subject to ice 
conditions, alternate exit routes may be considered. Shell has planned 
a suspension of all operations beginning on August 25 for the Nuiqsut 
(Cross Island) and Kaktovik subsistence bowhead whale hunts. During the 
suspension for the whale hunts, the drilling fleet will leave the 
Camden Bay project area, will move to a location at or north of 71.25 
[deg] N. latitude and at or west of 146.4 [deg] W. longitude and will 
return to resume activities after the Nuiqsut (Cross Island) and 
Kaktovik subsistence bowhead whale hunts conclude. Shell will consult 
with the Whaling Captain's Associations of Kaktovik and Nuiqsut to 
ascertain the conclusion of their respective fall subsistence bowhead 
whale hunts.
    Shell will cease drilling on or before October 31, after which the 
Kulluk or Discoverer will exit the Alaskan Beaufort Sea. In total, 
Shell anticipates that the exploration drilling program will require 
approximately 78 drilling days, excluding weather delays, the shutdown 
period to accommodate the fall bowhead whale harvests at Kaktovik and 
Cross Island (Nuiqsut), or other operational delays. Time to conduct 
the ZVSP surveys is included in the 78 drilling days. Shell assumes 
approximately 11 additional days will be needed for drillship 
mobilization, drillship moves between locations, and drillship 
demobilization.
    Activities associated with the 2012 Camden Bay, Beaufort Sea, 
exploration drilling program include operation of the drillship (either 
the Kulluk or Discoverer), associated support vessels, crew change 
support, and re-supply, ZVSP surveys, and icebreaking. The Kulluk or 
Discoverer will remain at the location of the designated exploration 
drill sites except when mobilizing and demobilizing to and from Camden 
Bay, 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 IMP. Ice management vessels, anchor tenders, and OSR 
vessels will remain in close proximity to the drillship during drilling 
operations.

Exploratory Drilling Program Sound Characteristics

    Potential impacts to marine mammals could occur from the noise 
produced by the drillship and its support vessels (including the 
icebreakers), aircraft, and the airgun array during ZVSP surveys. The 
drillship produces continuous noise into the marine environment. NMFS 
currently uses a threshold of 120 dB re 1 [micro]Pa (rms) for the onset 
of Level B harassment from continuous sound sources. This 120 dB 
threshold is also applicable for the icebreakers when actively managing 
or breaking ice. The drilling vessel to be used will be either the 
Kulluk or the Discoverer. The two vessels are likely to introduce 
somewhat different levels of sound into the water during the 
exploration drilling activities. The airgun array proposed to be used 
by Shell for the ZVSP surveys produces pulsed noise into the marine 
environment. NMFS currently uses a threshold of 160 dB re 1 [micro]Pa 
(rms) for the onset of Level B harassment from pulsed sound sources.
(1) Drilling Sounds
    Exploratory drilling will be conducted from the Kulluk or 
Discoverer, vessels 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 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

[[Page 68978]]

(Greene, 1987b), and underwater sound levels 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. Sounds from the Kulluk were measured in the Beaufort Sea in 
1986 and reported by Greene (1987a). The back propagated broadband 
source level from the measurements (185.5 dB re 1 [micro]Pa at 1 m 
(rms); reported from the 1/3-octave band levels), which included sounds 
from a support vessel operating nearby, were used to model sound 
propagation at the Sivulliq prospect near Camden Bay.
    Sound measurements from the Discoverer have not previously been 
conducted in the Arctic. However, measurements of sounds produced by 
the Discoverer were made in the South China Sea in 2009 (Austin and 
Warner, 2010). The results of those measurements were used to model the 
sound propagation from the Discoverer (including a nearby support 
vessel) at planned exploration drilling locations in the Beaufort Sea 
(Warner and Hannay, 2011). Broadband source levels of sounds produced 
by the Discoverer varied by activity and direction from the ship but 
were generally between 177 and 185 dB re 1 [mu]Pa at 1 m (rms) (Austin 
and Warner, 2010). Once on location at the drill sites in Camden Bay, 
Shell plans to take measurements of the drillship (either the Kulluk or 
Discoverer) to quantify the absolute sound levels produced by drilling 
and to monitor their variations with time, distance, and direction from 
the drilling vessel.
(2) 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, offshore supply vessels, barges and tugs, and OSR vessels. 
Sounds from boats and vessels have been reported extensively (Greene 
and Moore, 1995; Blackwell and Greene, 2002, 2005, 2006). Numerous 
measurements of underwater vessel sound have been performed in support 
of recent industry activity in the Chukchi and Beaufort Seas. Results 
of these measurements were reported in various 90-day and comprehensive 
reports since 2007 (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 sound 
pressure levels (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 icebreaking 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.
    Measurements of the icebreaking supply ship Robert Lemeur pushing 
and breaking ice during exploration drilling operations in the Beaufort 
Sea in 1986 resulted in an estimated broadband source level of 193 dB 
re 1 [mu]Pa at 1 m (Greene, 1987a; Richardson et al., 1995a).
    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 than would occur during icebreaking. Once on location at the 
drill sites in Camden Bay, 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 OSR vessels.
(3) Aircraft Sound
    Helicopters may be used for personnel and equipment transport to 
and from the drillship. 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 1,500 ft (457 m) above sea level, thereby limiting the 
received levels at and below the surface. Aircraft travel would be 
controlled by Federal Aviation Administration approved flight paths.
(4) Vertical Seismic Profile Sound
    A typical eight airgun array (4 x 40 in\3\ airguns and 4 x 150 
in\3\ airguns, for a total discharge volume of 760 in\3\) would be used 
to perform ZVSP surveys, if conducted after the completion of each 
exploratory well. Typically, a single ZVSP survey will be performed 
when the well has reached proposed total depth or final depth; 
although, in some instances, a prior ZVSP will have been performed at a

[[Page 68979]]

shallower depth. A typical survey will last 10-14 hours, depending on 
the depth of the well and the number of anchoring points, and include 
firings of the full array, plus additional firing of a single 40-in\3\ 
airgun to be used as a ``mitigation airgun'' while the geophones are 
relocated within the wellbore. The source level for the airgun array 
proposed for use by Shell will differ based on source depth. At a depth 
of 9.8 ft (3 m), the SPL is 238 dB re 1 [mu]Pa at 1 m, and at a depth 
of 16.4 ft (5 m), the SPL is 241 dB re 1 [mu]Pa at 1 m, with most 
energy between 20 and 140 Hz.
    Airguns function by venting high-pressure air into the water. The 
pressure signature of an individual airgun consists of a sharp rise and 
then fall in pressure, followed by several positive and negative 
pressure excursions caused by oscillation of the resulting air bubble. 
The sizes, arrangement, and firing times of the individual airguns in 
an array are designed and synchronized to suppress the pressure 
oscillations subsequent to the first cycle. Typical high-energy airgun 
arrays emit most energy at 10-120 Hz. However, the pulses contain 
significant energy up to 500-1,000 Hz and some energy at higher 
frequencies (Goold and Fish, 1998; Potter et al., 2007).
    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 
2012 drilling season and will not be making trips between the shorebase 
and the offshore vessels. When not needed for ice management/
icebreaking operations, the icebreaker and anchor handler will remain 
approximately 25 mi (40 km) upwind and upcurrent of the drillship. Any 
ice management/icebreaking activity would be expected to occur at a 
distance of 0.6-12 mi (1-19 km) upwind and upcurrent of the drillship. 
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.

Description of Marine Mammals in the Area of the Specified Activity

    The Beaufort Sea supports a diverse assemblage of marine mammals, 
including: bowhead, gray, beluga, killer (Orcinus orca), minke 
(Balaenoptera acutorostrata), and humpback (Megaptera novaeangliae) 
whales; harbor porpoises; ringed, ribbon, spotted, and bearded seals; 
narwhal (Monodon monoceros); polar bears (Ursus maritimus); and 
walruses (Odobenus rosmarus divergens; see Table 4-1 in Shell's 
application). The bowhead and humpback 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. On December 10, 2010, 
NMFS published a notice of proposed threatened status for subspecies of 
the ringed seal (75 FR 77476) and a notice of proposed threatened and 
not warranted status for subspecies and distinct population segments of 
the bearded seal (75 FR 77496) in the Federal Register. Neither of 
these two ice seal species is considered depleted under the MMPA. 
Additionally, the ribbon seal is considered a ``species of concern'' 
under the ESA. 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 Notice of Proposed IHA.
    Of these species, eight are expected to occur in the area of 
Shell's proposed operations. These species include: The bowhead, gray, 
and beluga whales, harbor porpoise, and the ringed, spotted, bearded, 
and ribbon seals. 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. Bowhead whales are 
also anticipated to occur in the proposed project area more frequently 
than the other cetacean species; however, their occurrence is not 
expected until later in the season. Even though harbor porpoise and 
ribbon seals are not typically sighted in Camden Bay, there have been 
recent sightings in the Beaufort Sea near the Prudhoe Bay area, so 
their occurrence could not be completely ruled out. Point Barrow, 
Alaska, is the approximate northeastern extent of the harbor porpoise's 
regular range (Suydam and George, 1992), though there are extralimital 
records east to the mouth of the Mackenzie River in the Northwest 
Territories, Canada, and recent sightings in the Beaufort Sea in the 
vicinity of Prudhoe Bay during surveys in 2007 and 2008 (Christie et 
al., 2009). Two ribbon seal sightings were reported during vessel-based 
activities near Prudhoe Bay in 2008 (Savarese et al., 2009). 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 document (see the 
``Estimated Take by Incidental Harassment'' section).
    Other cetacean species that have been observed in the Beaufort Sea 
but are uncommon or rarely identified in the project area include 
narwhal and killer, minke, and humpback whales. These species could 
occur in the project area, but each of these species is uncommon or 
rare in the area and relatively few encounters with these species are 
expected during the exploration drilling program. The narwhal occurs in 
Canadian waters and occasionally in the Beaufort Sea, but it is rare 
there 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). Humpback and minke whales have recently been sighted in the 
Chukchi Sea but very rarely in the Beaufort Sea. Greene et al. (2007) 
reported and photographed a humpback whale cow/calf pair east of Barrow 
near Smith Bay in 2007, which is the first known occurrence of 
humpbacks in the Beaufort Sea. Savarese et al. (2009) reported one 
minke whale sighting in the Beaufort Sea in 2007 and 2008. Due to the 
rarity of these species in the proposed project area and the remote 
chance they would be affected by Shell's proposed Beaufort Sea drilling 
activities, these species are not discussed further in this proposed 
IHA notice.
    Shell's application contains information on the status, 
distribution, seasonal distribution, abundance, and life history of 
each of the species under NMFS jurisdiction mentioned in this 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

[[Page 68980]]

2010 SAR is available at: https://www.nmfs.noaa.gov/pr/pdfs/sars/ak2010.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 have been derived using 
auditory evoked potentials, anatomical modeling, and other data, 
Southall et al. (2007) designate ``functional hearing groups'' for 
marine mammals and estimate the lower and upper frequencies of 
functional hearing of the groups. The functional groups and the 
associated frequencies are indicated below (though animals are less 
sensitive to sounds at the outer edge of their functional range and 
most sensitive to sounds of frequencies within a smaller range 
somewhere in the middle of their functional hearing range):
     Low frequency cetaceans (13 species of mysticetes): 
Functional hearing is estimated to occur between approximately 7 Hz and 
22 kHz (however, a study by Au et al. (2006) of humpback whale songs 
indicate that the range may extend to at least 24 kHz);
     Mid-frequency cetaceans (32 species of dolphins, six 
species of larger toothed whales, and 19 species of beaked and 
bottlenose whales): Functional hearing is estimated to occur between 
approximately 150 Hz and 160 kHz;
     High frequency cetaceans (eight species of true porpoises, 
six species of river dolphins, Kogia, the franciscana, and four species 
of cephalorhynchids): Functional hearing is estimated to occur between 
approximately 200 Hz and 180 kHz; and
     Pinnipeds in Water: Functional hearing is estimated to 
occur between approximately 75 Hz and 75 kHz, with the greatest 
sensitivity between approximately 700 Hz and 20 kHz.
    As mentioned previously in this document, six marine mammal species 
(three cetacean and three pinniped species) are likely to occur in the 
proposed exploratory drilling area. Of the three cetacean species 
likely to occur in Shell's proposed project area, two are classified as 
low frequency cetaceans (i.e., bowhead and gray whales) and one is 
classified as a mid-frequency cetacean (i.e., beluga whales) (Southall 
et al., 2007).
    Underwater audiograms have been obtained using behavioral methods 
for four species of phocinid seals: The ringed, harbor, harp, and 
northern elephant seals (reviewed in Richardson et al., 1995a; Kastak 
and Schusterman, 1998). Below 30-50 kHz, the hearing threshold of 
phocinids is essentially flat down to at least 1 kHz and ranges between 
60 and 85 dB re 1 [mu]Pa. There are few published data on in-water 
hearing sensitivity of phocid seals below 1 kHz. However, measurements 
for one harbor seal indicated that, below 1 kHz, its thresholds 
deteriorated gradually to 96 dB re 1 [mu]Pa at 100 Hz from 80 dB re 1 
[mu]Pa at 800 Hz and from 67 dB re 1 [mu]Pa at 1,600 Hz (Kastak and 
Schusterman, 1998). More recent data suggest that harbor seal hearing 
at low frequencies may be more sensitive than that and that earlier 
data were confounded by excessive background noise (Kastelein et al., 
2009a,b). If so, harbor seals have considerably better underwater 
hearing sensitivity at low frequencies than do small odontocetes like 
belugas (for which the threshold at 100 Hz is about 125 dB).
    Pinniped call characteristics are relevant when assessing potential 
masking effects of man-made sounds. In addition, for those species 
whose hearing has not been tested, call characteristics are useful in 
assessing the frequency range within which hearing is likely to be most 
sensitive. The three species of seals present in the study area, all of 
which are in the phocid seal group, are all most vocal during the 
spring mating season and much less so during late summer. In each 
species, the calls are at frequencies from several hundred to several 
thousand hertz--above the frequency range of the dominant noise 
components from most of the proposed oil exploration activities.
    Cetacean hearing has been studied in relatively few species and 
individuals. The auditory sensitivity of bowhead, gray, and other 
baleen whales has not been measured, but relevant anatomical and 
behavioral evidence is available. These whales appear to be specialized 
for low frequency hearing, with some directional hearing ability 
(reviewed in Richardson et al., 1995a; Ketten, 2000). Their optimum 
hearing overlaps broadly with the low frequency range where exploration 
drilling activities, airguns, and associated vessel traffic emit most 
of their energy.
    The beluga whale is one of the better-studied species in terms of 
its hearing ability. As mentioned earlier, the auditory bandwidth in 
mid-frequency odontocetes is believed to range from 150 Hz to 160 kHz 
(Southall et al., 2007); however, belugas are most sensitive above 10 
kHz. They have relatively poor sensitivity at the low frequencies 
(reviewed in Richardson et al., 1995a) that dominate the sound from 
industrial activities and associated vessels. Nonetheless, the noise 
from strong low frequency sources is detectable by belugas many 
kilometers away (Richardson and Wursig, 1997). Also, beluga hearing at 
low frequencies in open-water conditions is apparently somewhat better 
than in the captive situations where most hearing studies were 
conducted (Ridgway and Carder, 1995; Au, 1997). If so, low frequency 
sounds emanating from drilling activities may be detectable somewhat 
farther away than previously estimated.
    Call characteristics of cetaceans provide some limited information 
on their hearing abilities, although the auditory range often extends 
beyond the range of frequencies contained in the calls. Also, 
understanding the frequencies at which different marine mammal species 
communicate is relevant for the assessment of potential impacts from 
manmade sounds. A summary of the call characteristics for bowhead, 
gray, and beluga whales is provided next.
    Most bowhead calls are tonal, frequency-modulated sounds at 
frequencies of 50-400 Hz. These calls overlap broadly in frequency with 
the underwater sounds emitted by many of the activities to be performed 
during Shell's proposed exploration drilling program (Richardson et 
al., 1995a). Source levels are quite variable, with the stronger calls 
having source levels up to about 180 dB re 1 [mu]Pa at 1 m. Gray whales 
make a wide variety of calls at frequencies from <100-2,000 Hz (Moore 
and Ljungblad, 1984; Dalheim, 1987).
    Beluga calls include trills, whistles, clicks, bangs, chirps and 
other sounds (Schevill and Lawrence, 1949; Ouellet, 1979; Sjare and 
Smith, 1986a). Beluga whistles have dominant frequencies in the 2-6 kHz 
range (Sjare and Smith, 1986a). This is above the frequency range of 
most of the sound energy produced by the proposed exploratory drilling 
activities and associated vessels. Other beluga call types reported by 
Sjare and Smith (1986a,b) included sounds at mean frequencies ranging 
upward from 1 kHz.
    The beluga also has a very well developed high frequency 
echolocation system, as reviewed by Au (1993). Echolocation signals 
have peak frequencies from 40-120 kHz and broadband source levels of up 
to 219 dB re 1 [mu]Pa-m (zero-peak). Echolocation calls are far above 
the frequency range of the sounds produced by the devices proposed for 
use during Shell's Camden Bay exploratory drilling program. Therefore, 
those industrial sounds are

[[Page 68981]]

not expected to interfere with echolocation.

Potential Effects of the Specified Activity on Marine Mammals

    The likely or possible impacts of the proposed exploratory drilling 
program in Camden Bay on marine mammals could involve both non-acoustic 
and acoustic effects. Potential non-acoustic effects could result from 
the physical presence of the equipment and personnel. Petroleum 
development and associated activities introduce sound into the marine 
environment. Impacts to marine mammals are expected to primarily be 
acoustic in nature. Potential acoustic effects on marine mammals relate 
to sound produced by drilling activity, vessels, and aircraft, as well 
as the ZVSP airgun array. 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.

Potential Acoustic Effects From Exploratory Drilling Activities

(1) Tolerance
    Numerous studies have shown that underwater sounds from industry 
activities are often readily detectable by marine mammals in the water 
at distances of many kilometers. Numerous studies have also shown that 
marine mammals at distances more than a few kilometers away often show 
no apparent response to industry activities of various types (Miller et 
al., 2005; Bain and Williams, 2006). This is often true even in cases 
when the sounds must be readily audible to the animals based on 
measured received levels and the hearing sensitivity of that mammal 
group. Although various baleen whales, toothed whales, and (less 
frequently) pinnipeds have been shown to react behaviorally to 
underwater sound such as airgun pulses or vessels under some 
conditions, at other times mammals of all three types have shown no 
overt reactions (e.g., Malme et al., 1986; Richardson et al., 1995; 
Madsen and Mohl, 2000; Croll et al., 2001; Jacobs and Terhune, 2002; 
Madsen et al., 2002; Miller et al., 2005). In general, pinnipeds and 
small odontocetes seem to be more tolerant of exposure to some types of 
underwater sound than are baleen whales. Richardson et al. (1995a) 
found that vessel noise does not seem to strongly affect pinnipeds that 
are already in the water. Richardson et al. (1995a) went on to explain 
that seals on haul-outs sometimes respond strongly to the presence of 
vessels and at other times appear to show considerable tolerance of 
vessels, and Brueggeman et al. (1992, cited in Richardson et al., 
1995a) observed ringed seals hauled out on ice pans displaying short-
term escape reactions when a ship approached within 0.25-0.5 mi (0.4-
0.8 km).
(2) Masking
    Masking is the obscuring of sounds of interest by other sounds, 
often at similar frequencies. Marine mammals are highly dependent on 
sound, and their ability to recognize sound signals amid other noise is 
important in communication, predator and prey detection, and, in the 
case of toothed whales, echolocation. Even in the absence of manmade 
sounds, the sea is usually noisy. Background ambient noise often 
interferes with or masks the ability of an animal to detect a sound 
signal even when that signal is above its absolute hearing threshold. 
Natural ambient noise includes contributions from wind, waves, 
precipitation, other animals, and (at frequencies above 30 kHz) thermal 
noise resulting from molecular agitation (Richardson et al., 1995a). 
Background noise also can include sounds from human activities. Masking 
of natural sounds can result when human activities produce high levels 
of background noise. Conversely, if the background level of underwater 
noise is high (e.g., on a day with strong wind and high waves), an 
anthropogenic noise source will not be detectable as far away as would 
be possible under quieter conditions and will itself be masked.
    Although some degree of masking is inevitable when high levels of 
manmade broadband sounds are introduced into the sea, marine mammals 
have evolved systems and behavior that function to reduce the impacts 
of masking. Structured signals, such as the echolocation click 
sequences of small toothed whales, may be readily detected even in the 
presence of strong background noise because their frequency content and 
temporal features usually differ strongly from those of the background 
noise (Au and Moore, 1988, 1990). The components of background noise 
that are similar in frequency to the sound signal in question primarily

[[Page 68982]]

determine the degree of masking of that signal.
    Redundancy and context can also facilitate detection of weak 
signals. These phenomena may help marine mammals detect weak sounds in 
the presence of natural or manmade noise. Most masking studies in 
marine mammals present the test signal and the masking noise from the 
same direction. The sound localization abilities of marine mammals 
suggest that, if signal and noise come from different directions, 
masking would not be as severe as the usual types of masking studies 
might suggest (Richardson et al., 1995a). The dominant background noise 
may be highly directional if it comes from a particular anthropogenic 
source such as a ship or industrial site. Directional hearing may 
significantly reduce the masking effects of these noises by improving 
the effective signal-to-noise ratio. In the cases of high-frequency 
hearing by the bottlenose dolphin, beluga whale, and killer whale, 
empirical evidence confirms that masking depends strongly on the 
relative directions of arrival of sound signals and the masking noise 
(Penner et al., 1986; Dubrovskiy, 1990; Bain et al., 1993; Bain and 
Dahlheim, 1994). Toothed whales, and probably other marine mammals as 
well, have additional capabilities besides directional hearing that can 
facilitate detection of sounds in the presence of background noise. 
There is evidence that some toothed whales can shift the dominant 
frequencies of their echolocation signals from a frequency range with a 
lot of ambient noise toward frequencies with less noise (Au et al., 
1974, 1985; Moore and Pawloski, 1990; Thomas and Turl, 1990; Romanenko 
and Kitain, 1992; Lesage et al., 1999). A few marine mammal species are 
known to increase the source levels or alter the frequency of their 
calls in the presence of elevated sound levels (Dahlheim, 1987; Au, 
1993; Lesage et al., 1993, 1999; Terhune, 1999; Foote et al., 2004; 
Parks et al., 2007, 2009; Di Iorio and Clark, 2009; Holt et al., 2009).
    These data demonstrating adaptations for reduced masking pertain 
mainly to the very high frequency echolocation signals of toothed 
whales. There is less information about the existence of corresponding 
mechanisms at moderate or low frequencies or in other types of marine 
mammals. For example, Zaitseva et al. (1980) found that, for the 
bottlenose dolphin, the angular separation between a sound source and a 
masking noise source had little effect on the degree of masking when 
the sound frequency was 18 kHz, in contrast to the pronounced effect at 
higher frequencies. Directional hearing has been demonstrated at 
frequencies as low as 0.5-2 kHz in several marine mammals, including 
killer whales (Richardson et al., 1995a). This ability may be useful in 
reducing masking at these frequencies. In summary, high levels of noise 
generated by anthropogenic activities may act to mask the detection of 
weaker biologically important sounds by some marine mammals. This 
masking may be more prominent for lower frequencies. For higher 
frequencies, such as that used in echolocation by toothed whales, 
several mechanisms are available that may allow them to reduce the 
effects of such masking.
    Masking effects of underwater sounds from Shell's proposed 
activities on marine mammal calls and other natural sounds are expected 
to be limited. For example, beluga whales primarily use high-frequency 
sounds to communicate and locate prey; therefore, masking by low-
frequency sounds associated with drilling activities is not expected to 
occur (Gales, 1982, as cited in Shell, 2009). If the distance between 
communicating whales does not exceed their distance from the drilling 
activity, the likelihood of potential impacts from masking would be low 
(Gales, 1982, as cited in Shell, 2009). At distances greater than 660-
1,300 ft (200-400 m), recorded sounds from drilling activities did not 
affect behavior of beluga whales, even though the sound energy level 
and frequency were such that