Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Open Water Marine Survey Program in the Beaufort and Chukchi Seas, Alaska, 27708-27731 [2010-11860]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 75, Number 95 (Tuesday, May 18, 2010)]
[Notices]
[Pages 27708-27731]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-11860]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XV09


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to Open Water Marine Survey Program in 
the Beaufort and Chukchi Seas, Alaska

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 a proposed open water marine 
survey program in the Beaufort and Chukchi Seas, Alaska, between July 
and October 2010. 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 June 17, 
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 PR1.0648-XV09@noaa.gov. NMFS is not responsible for e-
mail comments sent to addresses other than the one provided here. 
Comments sent via e-mail, including all attachments, must not exceed a 
10-megabyte file size.
    Instructions: All comments received are a part of the public record 
and will

[[Page 27709]]

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 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: Shane Guan, Office of Protected 
Resources, NMFS, (301) 713-2289, ext 137.

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 December 24, 2009, from Shell for 
the taking, by harassment, of marine mammals incidental to several 
marine surveys designed to gather data relative to site clearance and 
shallow hazards, ice gouge, and strudel scour in selected areas of the 
Beaufort Sea and ice gouge in the Chukchi Sea, Alaska. These surveys 
are continuations of those performed by Shell in the Beaufort Sea 
beginning in 2006, and in the Chukchi Sea in 2008. After addressing 
comments from NMFS, Shell modified its application and submitted a 
revised application on April 19, 2010. The April 19, 2009, application 
is the one available for public comment (see ADDRESSES) and considered 
by NMFS for this proposed IHA.
    Site clearance and shallow hazards surveys will evaluate the 
seafloor, and shallow sub seafloor at prospective exploration drilling 
locations, focusing on the depth to seafloor, topography, the potential 
for shallow faults or gas zones, and the presence of archaeological 
features. The types of equipment used to conduct these surveys use low 
level energy sources focused on limited areas in order to characterize 
the footprint of the seafloor and shallow sub seafloor at prospective 
drilling locations. Ice gouge surveys will determine the depth and 
distribution of ice gouges into the seabed. Ice gouge surveys use low-
level energy sources similar to the site clearance and shallow hazards.
    Shell intends to conduct these marine surveys during the 2010 
Arctic open-water season (July through October). Impacts to marine 
mammals may occur from noise produced by various active acoustic 
sources used in the surveys.

Description of the Specified Activity

    Shell plans to complete the following surveys during the 2010 open-
water season:

 Beaufort Sea Site Clearance and Shallow Hazards Surveys
 Beaufort Sea Marine Surveys
[cir] Ice Gouge Survey
[cir] Strudel Scour Survey
 Chukchi Sea Marine Surveys
[cir] Ice Gouge Survey
    Each of these individual surveys will require marine vessels to 
accomplish the work. Shell states that these marine surveys will be 
conducted between July and October 2010, however, ice and weather 
conditions will influence the exact dates and locations marine vessel 
survey operations can be conducted.

1. Beaufort Sea Site Clearance and Shallow Hazards Surveys

    Shell's proposed site clearance and shallow hazards surveys are to 
gather data on: (1) Bathymetry, (2) seabed topography and other seabed 
characteristics (e.g., boulder patches), (3) potential geohazards 
(e.g., shallow faults and shallow gas zones), and (4) the presence of 
any archeological features (e.g., shipwrecks). Site clearance and 
shallow hazards surveys can be accomplished by one vessel with acoustic 
sources. No other vessels are necessary to accomplish the proposed 
work.
    The focus of this activity will be on Shell's existing leases in 
Harrison Bay in the central Beaufort Sea. Actual locations of site 
clearance and shallow hazards surveys within Harrison Bay have not been 
definitively set as of this date, although these will occur on the 
Outer Continental Shelf (OCS) lease blocks in Harrison Bay located in 
the Beaufort Sea shown on Figure 1 of Shell's IHA application. The site 
clearance and shallow hazards surveys will be conducted within an area 
of approximately 216 mi \2\ (558 km \2\) north of Thetis Island more 
than 3 mi (4.8 km) to approximately 20 mi (33 km) offshore. 
Approximately 63 mi (162.7 km) of the data acquisition is planned 
within this general area. The survey track line is approximately 351.5 
mi \2\ (565 km \2\). The average depth of the survey area ranges from 
35 to 85 ft (10.7 to 26 m).
    Ice and weather permitting, Shell is proposing to conduct site 
clearance and shallow hazards surveys within the timeframe of July 2010 
through October 2010. The actual survey time is expected to take 30 
days.
    The vessel that will be conducting this activity has not been 
determined at this point, but will be similar to the R/V Mt. Mitchell 
which is the vessel that was used for surveys in the Chukchi Sea in 
2009. The R/V Mt. Mitchell is a diesel powered-vessel, 70 m (231 ft) 
long, 12.7 m (42 ft) wide, with a 4.5 m (15 ft) draft.

[[Page 27710]]

    It is proposed that the following acoustic instrumentation, or 
something similar, be used.
     Deep Penetration Profiler, (40 cu-in airgun source with 
48-channel streamer) and Medium Penetration Profiler, (40 cu-in airgun 
source with 24-channel streamer):
    The deep and medium penetration profiler and the medium penetration 
profiler are the major active acoustic sources used in the site 
clearance and shallow hazards surveys. The modeled source level is 
estimated at 217 dB re 1 [mu]Pa rms. The 120, 160, 180, and 190 dB re 1 
[mu]Pa rms received level isopleths are estimated at 14,900 m, 1,220 m, 
125 m, and 35 m from the source, respectively.
     Dual-frequency side scan sonar, (100-400 kHz or 300-600 
kHz):
    Based on the 2006 Shell's 90-day report, the source level of this 
active acoustic source when operated at 190 and 240 kHz is 
approximately 225 dB re 1 [mu]Pa rms. Due to its high frequency range, 
NMFS does not consider its acoustic energy would be strong enough to 
cause impacts to marine mammals beyond a couple of hundred meters from 
the source.
     Single beam Echo Sounder, (high: 100-340 kHz, low: 24-50 
kHz):
    This echo sounder is a typical ``fathometer'' or ``fish-finder'' 
that is widely used in most recreational or fishing vessels. Source 
levels for these types of units are typically in the range of 180-200 
dB re 1 [mu]Pa rms. Using a spherical spreading model, the 160 dB 
isopleth is estimated at 100 m from the source for the lower range of 
the acoustic signals. For the higher range of the signal, due to the 
higher absorption coefficients, the 160 dB isopleth is expected to be 
under 100 m from the source.
     Multi-beam Echo Sounder, (240 kHz):
    Since the output frequency from this echo sounder is above the 
upper limit of marine mammal hearing range, NMFS does not believe this 
equipment would affect marine mammals.
     Shallow Sub-Bottom Profiler, (2-12 kHz):
    Information regarding this active acoustic source on two vessels 
(Alpha Helix and Henry C.) was provided in Shell's 2008 90-day open 
water marine survey monitoring report. For the Alpha Helix measurement, 
at 3.5 kHz, the source level for the shallow sub-bottom profiler was 
193.8 dB re 1 [mu]Pa rms, and its 120, 160, 180, and 190 dB re 1 [mu]Pa 
rms isopleths were determined to be 310 m, 14 m, 3 m, and 1 m from the 
source, respectively. For the Henry C. measurement, at 3.5 kHz, the 
source level of the similar profiler was measured at 167.2 dB re 1 
[mu]Pa rms, and its 120 and 160 dB re 1 [mu]Pa rms isopleths were 
determined to be 980 m and 3 m, respectively.

2. Beaufort Sea Marine Surveys

    Two marine survey activities are proposed for the Beaufort Sea: (1) 
Ice gouge survey, and (2) strudel scour survey. Shell continues to 
conduct these types of marine surveys annually over a few years to 
enhance baseline and statistical understanding of the formation, 
longevity, and temporal distribution of sea floor features and baseline 
environmental and biologic conditions. Marine surveys for ice gouge and 
strudel scour surveys can be accomplished by one vessel for each. No 
other vessels are necessary to accomplish the proposed work.
    The proposed ice gouge surveys will be conducted in both State of 
Alaska waters including Camden Bay, and the Federal waters of the OCS 
in the Beaufort Sea near Pt. Thomson ranging from near shore to 
approximately 37 mi (59.5 km) offshore. The water depth in the ice 
gouging survey area ranges between 15 to 120 ft (4.5 to 36.6 m), and 
the surveys will be conducted within an area of 1,950 mi \2\ (5,036 km 
\2\) with a survey track line of approximately 1,276 mi (2,050 km, See 
Figure 2 of Shell's IHA application).
    The proposed strudel scour survey will occur in State of Alaska 
waters in Pt. Thomson ranging from near shore to 3 mi (4.8 km) 
offshore. The water depth ranges from 3 to 20 ft (0.9 to 6.1 m). The 
strudel scour survey will be conducted in an area of approximately 140 
mi \2\ (361.5 km \2\). The survey track line is approximately 124 mi 
(200 km).
    Ice and weather permitting, Shell is proposing to conduct this work 
within the timeframe of July 2010 through October 2010. The actual 
survey time is expected to take 45 days.

Ice Gouge Survey

    As part of the feasibility study for Shell's Alaskan prospects a 
survey is required to identify and evaluate seabed conditions. Ice 
gouging is created by ice keels, which project from the bottom of 
moving ice and gouge into seafloor sediment. Ice gouge features are 
mapped, and by surveying each year, new gouges can be identified. The 
ice gouge information is used to aid in predicting the prospect of, 
orientation, depth, and frequency of future ice gouges. Ice gouge 
information is required for the design of potential pipelines and for 
the design of pipeline trenching and installation equipment.
    The 2010 ice gouge surveys will be conducted using the conventional 
survey method where the acoustic instrumentation will be towed behind 
the survey vessel, or possibly with the use of an Autonomous Underwater 
Vehicle (AUV). The same acoustic instrumentation will be used during 
both AUV and the conventional survey methods. The AUV is a self-
propelled autonomous vehicle that will be equipped with acoustic 
instrumentation and programmed for remote operation over the seafloor 
where the ice gouge survey is to be conducted, and the vehicle is 
launched and retrieved from a marine vessel.
    For the survey operations, the AUV will be launched from the stern 
of a vessel and will survey the seafloor close to the vessel. The 
vessel will transit an area, with the AUV surveying the area behind the 
vessel. The AUV also has a Collision Avoidance System and operates 
without a towline that reduces potential impact to marine mammals (such 
as entanglement). Using bathymetric sonar or multibeam echo sounder the 
AUV can record the gouges on the seafloor surface caused by ice keels. 
The sub-bottom profiler can record layers beneath the surface to about 
20 feet (6 m). The AUV is more maneuverable and able to complete 
surveys quicker than a conventional survey. This reduces the duration 
that vessels producing sound must operate. The proposed ice gouge 
survey in the Beaufort Sea is expected to last for 45 days.
    The vessel that will be used for ice gouging surveys has not been 
selected, but it is anticipated that the vessel would be similar to the 
R/V Mt. Mitchell, which is 70 m (231 ft) long, 12.7 m (42 ft) wide, and 
4.5 m (15 ft) draft.
    It is proposed that the following acoustic instrumentation, or 
something similar, be used.
     Dual Frequency subbottom profiler; (2 to 7 kHz or 8 to 23 
kHz):
    Information regarding this active acoustic source on Henry C. was 
provided in Shell's 2006 and 2007 90-day open water marine survey 
monitoring reports. In the 2006 report, at 2-7 and 8-23 kHz, the source 
level was estimated at 184.6 dB re 1 [mu]Pa rms, and its 120, 160, and 
180 dB re 1 [mu]Pa rms isopleths were determined to be 456 m, 7 m, and 
2 m from the source, respectively. In the 2007 report, at 2-7 kHz, the 
source level was estimated at 161.1 dB re 1 [mu]Pa rms, and its 120 and 
160 dB re 1 [mu]Pa rms isopleths were determined to be 260 m and 1 m, 
respectively.
     Multibeam Echo Sounder (240 kHz) and Side-scan sonar 
system (190 to 210 kHz):

[[Page 27711]]

    Since the output frequencies from these acoustic instruments are 
above the upper-limits of marine mammal hearing range, NMFS does not 
believe they would affect marine mammals.
    Because of the low source levels of the sub-bottom profiler and the 
high-frequency nature of the multi-beam echo sounder used in the 
proposed ice gouge survey, NMFS believes it unlikely that a marine 
mammal would be taken by this activity.

Strudel Scour Survey

    During the early melt on the North Slope, the rivers begin to flow 
and discharge water over the coastal sea ice near the river deltas. 
That water flows down holes in the ice (``strudels'') and scours the 
seafloor. These areas are called ``strudel scours.'' Information on 
these features is required for prospective pipeline planning. Two 
proposed activities are required to gather this information: Aerial 
survey via helicopter overflights during the melt to locate the 
strudels; and strudel scour marine surveys to gather bathymetric data. 
The overflights investigate possible sources of overflood water and 
will survey local streams that discharge in the vicinity of Point 
Thomson including the Staines River, which discharges to the east into 
Flaxman Lagoon, and the Canning River, which discharges to the east 
directly into the Beaufort Sea. These helicopter overflights will occur 
during late May/early June 2010 and, weather permitting, should take no 
more than two days. There are no planned landings during these 
overflights other than at the Deadhorse or Kaktovik airports.
    Areas that have strudel scour identified during the aerial survey 
will be verified and surveyed with a marine vessel after the breakup of 
nearshore ice. The vessel has not been determined, however, it is 
anticipated that it will be the diesel-powered R/V Annika Marie which 
has been utilized 2006 through 2008 and measures 13.1 m (43 ft) long, 
or similar vessel.
    This proposed activity is not anticipated to take more than 5 days 
to conduct. The operation is conducted in the shallow water areas near 
the coast in the vicinity of Point Thomson. This vessel will use the 
following equipment:
     Multibeam Echo Sounder (240 kHz) and Side-scan sonar 
system (190 to 210 kHz):
    Since the output frequencies from these acoustic instruments are 
above the upper-limits of marine mammal hearing range, NMFS does not 
believe they would affect marine mammals.
     Single Beam Bathymetric Sonar:
    Source levels for these types of units are typically in the 180-230 
dB range, somewhat lower than multibeam or side scan sonars. A unit 
used during a previous survey had a source level (at high power) of 215 
dB re 1 [mu]Pa (0-peak) and a standard operating frequency of 200 kHz. 
Since the output frequencies from these acoustic instruments are above 
the upper-limits of marine mammal hearing range, NMFS does not believe 
they would affect marine mammals.

3. Chukchi Sea Marine Survey--Ice Gouge Survey

    Shell proposes one marine survey activity for the Chukchi Sea in 
2010. Shell intends to conduct ice gouge surveys annually over a few 
years to enhance baseline and statistical understanding of the 
formation, longevity, and temporal distribution of sea floor features 
and baseline environmental and biologic conditions. The ice gouge 
survey can be accomplished by one vessel. No other vessels are 
necessary to accomplish the proposed work.
    The proposed ice gouge surveys will be conducted in both State of 
Alaska waters and the Federal waters of the OCS in the Chukchi Sea. 
Actual locations of the ice gouge surveys have not been definitively 
set as of this date, although these will occur within the area outlined 
in Figure 4 of the IHA application. The water depth of the ice gouging 
survey ranges between 20 to 120 ft (6.1 to 36.6 m), and the surveys 
will take in an area of 21,954 mi \2\ (56,965 km \2\), with a survey 
track line of approximately 1,539 mi (2,473 km). This activity is 
proposed to be conducted within the timeframe of July through October 
2010. The total program will last a maximum of 60 days, excluding 
downtime due to ice, weather and other unforeseen delays, and should be 
complete by the end of October 2010.
    The equipment and method used to conduct the ice gouge survey in 
the Chukchi Sea will be the same as that used in the Beaufort Sea. 
Because of the low source levels of the sub-bottom profiler and the 
high-frequency nature of the multi-beam echo sounder used in the 
proposed ice gouge survey, NMFS believes it unlikely that a marine 
mammal would be taken by this activity.
Description of Marine Mammals in the Area of the Specified Activity
    Nine cetacean and four pinniped species under NMFS jurisdiction 
could occur in the general area of Shell's open water marine survey 
areas in the Beaufort and Chukchi Seas. The species most likely to 
occur in the general area near Harrison Bay in the Alaskan Beaufort Sea 
include two cetacean species: beluga (Delphinapterus leucas) and 
bowhead whales (Balaena mysticetus) and three seal species: ringed 
(Phoca hispida), spotted (P. largha), and bearded seals (Erignathus 
barbatus). Most encounters are likely to occur in nearshore shelf 
habitats or along the ice edge. The marine mammal species that is 
likely to be encountered most widely (in space and time) through-out 
the period of the planned shallow hazards surveys is the ringed seal. 
Encounters with bowhead and beluga whales are expected to be limited to 
particular regions and seasons, as discussed below.
    Other marine mammal species that have been observed in the Beaufort 
and Chukchi Seas but are less frequent or uncommon in the project area 
include harbor porpoise (Phocoena phocoena), narwhal (Monodon 
monoceros), killer whale (Orcinus orca), fin whale (Balaenoptera 
physalus), minke whale (B. acutorostrata), humpback whale (Megaptera 
novaeangliae), gray whale (Eschrichtius robustus), and ribbon seal 
(Histriophoca fasciata). 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 
proposed marine surveys. 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). 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). Monnett and Treacy (2005) did not report any harbor porpoise 
sightings during aerial surveys in the Beaufort Sea from 2002 through 
2004. Humpback, fin, 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

[[Page 27712]]

the Beaufort Sea in 2007 and 2008. Ribbon seals do not normally occur 
in the Beaufort Sea; however, two ribbon seal sightings were reported 
during vessel-based activities near Prudhoe Bay in 2008 (Savarese et 
al. 2009).
    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 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.
    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. 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: https://www.nmfs.noaa.gov/pr/pdfs/sars/ak2009.pdf.

Potential Effects of the Specified Activity on Marine Mammals

    Operating a variety of active acoustic sources such as airguns, 
side-scan sonars, echo-sounders, and sub-bottom profilers for site 
clearance and shallow hazard surveys, ice gouge, and strudel surveys 
can impact marine mammals in a variety of ways.

Potential Effects of Airgun Sounds on Marine Mammals

    The effects of sounds from airgun pulses might include one or more 
of the following: tolerance, masking of natural sounds, behavioral 
disturbance, and temporary or permanent hearing impairment or non-
auditory effects (Richardson et al. 1995). 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. 1995):
(1) Tolerance
    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
Numerous studies have also shown that marine mammals at distances more 
than a few kilometers from operating seismic vessels often show no 
apparent response. That is often true even in cases when the pulsed 
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 airgun pulses under 
some conditions, at other times, mammals of all three types have shown 
no overt reactions. In general, pinnipeds and small odontocetes seem to 
be more tolerant of exposure to airgun pulses than baleen whales.
(2) Behavioral Disturbance
    Marine mammals may behaviorally react to sound when exposed to 
anthropogenic noise. These behavioral reactions are often shown as: 
changing durations of surfacing and dives, number of blows per 
surfacing, or moving direction and/or speed; reduced/increased vocal 
activities; changing/cessation of certain behavioral activities (such 
as socializing or feeding); visible startle response or aggressive 
behavior (such as tail/fluke slapping or jaw clapping); avoidance of 
areas where noise sources are located; and/or flight responses (e.g., 
pinnipeds flushing into water from haulouts or rookeries).
    The biological significance of many of these behavioral 
disturbances is difficult to predict, especially if the detected 
disturbances appear minor. However, the consequences of behavioral 
modification could be expected to be biologically significant if the 
change affects growth, survival, and reproduction. Some of these 
significant behavioral modifications include:
     Drastic change in diving/surfacing patterns (such as those 
thought to be causing beaked whale stranding due to exposure to 
military mid-frequency tactical sonar);
     Habitat abandonment due to loss of desirable acoustic 
environment; and
     Cease feeding or social interaction.
    For example, at the Guerreo Negro Lagoon in Baja California, 
Mexico, which is one of the important breeding grounds for Pacific gray 
whales, shipping and dredging associated with a salt works may have 
induced gray whales to abandon the area through most of the 1960s 
(Bryant et al. 1984). After these activities stopped, the lagoon was 
reoccupied, first by single whales and later by cow-calf pairs.
    The onset of behavioral disturbance from anthropogenic noise 
depends on both external factors (characteristics of noise sources and 
their paths) and the receiving animals (hearing, motivation, 
experience, demography) and is also difficult to predict (Southall et 
al. 2007).
    Currently NMFS uses 160 dB re 1 [mu]Pa at received level for 
impulse noises (such as airgun pulses) as the onset of marine mammal 
behavioral harassment.
(3) Masking
    Chronic exposure to excessive, though not high-intensity, noise 
could cause masking at particular frequencies for marine mammals that 
utilize sound for vital biological functions. Masking can interfere 
with detection of acoustic signals such as communication calls, 
echolocation sounds, and environmental sounds important to marine 
mammals. Since marine mammals depend on acoustic cues for vital 
biological functions, such as orientation, communication, finding prey, 
and avoiding predators, marine mammals that experience severe acoustic 
masking will have reduced fitness in survival and reproduction.
    Masking occurs when noise and signals (that the animal utilizes) 
overlap at both spectral and temporal scales. For the airgun noise 
generated from the proposed site clearance and shallow hazards surveys, 
noise will consist of low frequency (under 1 kHz) pulses with extremely 
short durations (in the scale of milliseconds). Lower frequency man-
made noises are more likely to affect detection of communication calls 
and other potentially important natural sounds such as surf and prey 
noise. There is little concern regarding masking near the noise source 
due to the brief duration of these pulses and relatively longer silence 
between airgun shots (9-12 seconds). However, at long distances (over 
tens of kilometers away), due to multipath propagation and 
reverberation, the durations of airgun pulses can be ``stretched'' to 
seconds with long decays (Madsen et al. 2006). Therefore it could 
affect communication signals used by low frequency mysticetes when they 
occur near the noise band and thus reduce the communication space of 
animals (e.g., Clark et al. 2009) and cause increased stress levels 
(e.g., Foote et al. 2004; Holt et al. 2009). Nevertheless, the 
intensity of the noise is also greatly reduced at such long distances 
(for example, the modeled received level drops below 120 dB re 1 [mu]Pa 
rms at 14,900 m from the source).
    Marine mammals are thought to be able to compensate for masking by 
adjusting their acoustic behavior such as shifting call frequencies, 
increasing call volume and vocalization rates. For example, blue whales 
are found to increase call rates when exposed to seismic survey noise 
in the St. Lawrence

[[Page 27713]]

Estuary (Di Iorio and Clark 2010). The North Atlantic right whales 
(Eubalaena glacialis) exposed to high shipping noise increase call 
frequency (Parks et al. 2007), while some humpback whales respond to 
low-frequency active sonar playbacks by increasing song length (Miller 
el al. 2000).
(4) Hearing Impairment
    Marine mammals exposed to high intensity sound repeatedly or for 
prolonged periods can experience hearing threshold shift (TS), which is 
the loss of hearing sensitivity at certain frequency ranges (Kastak et 
al. 1999; Schlundt et al. 2000; Finneran et al. 2002; 2005). TS can be 
permanent (PTS), in which case the loss of hearing sensitivity is 
unrecoverable, or temporary (TTS), in which case the animal's hearing 
threshold will recover over time (Southall et al. 2007). Just like 
masking, marine mammals that suffer from PTS or TTS will have reduced 
fitness in survival and reproduction, either permanently or 
temporarily. Repeated noise exposure that leads to TTS could cause PTS. 
For transient sounds, the sound level necessary to cause TTS is 
inversely related to the duration of the sound.
    Experiments on a bottlenose dolphin (Tursiops truncates) and beluga 
whale showed that exposure to a single watergun impulse at a received 
level of 207 kPa (or 30 psi) peak-to-peak (p-p), which is equivalent to 
228 dB re 1 [mu]Pa (p-p), resulted in a 7 and 6 dB TTS in the beluga 
whale at 0.4 and 30 kHz, respectively. Thresholds returned to within 2 
dB of the pre-exposure level within 4 minutes of the exposure (Finneran 
et al. 2002). No TTS was observed in the bottlenose dolphin. Although 
the source level of pile driving from one hammer strike is expected to 
be much lower than the single watergun impulse cited here, animals 
being exposed for a prolonged period to repeated hammer strikes could 
receive more noise exposure in terms of SEL than from the single 
watergun impulse (estimated at 188 dB re 1 [mu]Pa\2\-s) in the 
aforementioned experiment (Finneran et al. 2002).
    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 ambient noise levels at 
those low frequencies tend to be higher (Urick 1983). 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). 
From this, it is suspected that received levels causing TTS onset may 
also be higher in baleen whales. However, no cases of TTS are expected 
given the small size of the airguns proposed to be used and the strong 
likelihood that baleen whales (especially migrating bowheads) would 
avoid the approaching airguns (or vessel) before being exposed to 
levels high enough for there to be any possibility of TTS.
    In pinnipeds, TTS thresholds associated with exposure to brief 
pulses (single or multiple) of underwater sound have not been measured. 
Initial evidence from prolonged exposures suggested that some pinnipeds 
may incur TTS at somewhat lower received levels than do small 
odontocetes exposed for similar durations (Kastak et al. 1999, 2005; 
Ketten et al. 2001). However, more recent indications are that TTS 
onset in the most sensitive pinniped species studied (harbor seal, 
which is closely related to the ringed seal) may occur at a similar SEL 
as in odontocetes (Kastak et al., 2004).
    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. As 
summarized above, data that are now available to imply that TTS is 
unlikely to occur unless bow-riding odontocetes are exposed to airgun 
pulses much stronger than 180 dB re 1 [micro]Pa rms (Southall et al. 
2007).
    No cases of TTS are expected as a result of Shell's proposed 
activities given the small size of the source, the strong likelihood 
that baleen whales (especially migrating bowheads) would avoid the 
approaching airguns (or vessel) before being exposed to levels high 
enough for there to be any possibility of TTS, and the mitigation 
measures proposed to be implemented during the survey described later 
in this document.
    There is no empirical evidence that exposure to pulses of airgun 
sound can cause PTS in any marine mammal, even with large arrays of 
airguns (see Southall et al., 2007). However, given the possibility 
that mammals close to an airgun array might incur TTS, there has been 
further speculation about the possibility that some individuals 
occurring very close to airguns 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. That is, PTS might 
occur at a received sound level magnitudes higher than the level of 
onset TTS, or by repeated exposure to the levels that cause TTS. 
Therefore, by means of preventing the onset of TTS, it is highly 
unlikely that marine mammals could receive sounds strong enough (and 
over a sufficient duration) to cause permanent hearing impairment 
during the proposed marine surveys in the Beaufort and Chukchi Seas.
(5) Non-auditory Physical Effects
    Non-auditory physical effects might occur in marine mammals exposed 
to strong underwater pulsed 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. 
Some marine mammal species (i.e., beaked whales) may be especially 
susceptible to injury and/or stranding when exposed to strong pulsed 
sounds. However, there is no definitive evidence that any of these 
effects occur even for marine mammals in close proximity to large 
arrays of airguns, and beaked whales do not occur in the proposed 
project area. In addition, marine mammals that show behavioral 
avoidance of seismic vessels, including most baleen whales, some 
odontocetes (including belugas), and some pinnipeds, are especially 
unlikely to incur non-auditory impairment or other physical effects. 
The small airgun array proposed to be used by Shell would only have 190 
and 180 dB distances of 35 and 125 m (115 and 410 ft), respectively.
    Therefore, it is unlikely that such effects would occur during 
Shell's proposed surveys given the brief duration of exposure and the 
planned monitoring and mitigation measures described later in this 
document.
(6) Stranding and Mortality
    Marine mammals close to underwater detonations of high explosive 
can be killed or severely injured, and the auditory organs are 
especially susceptible to injury (Ketten et al. 1993;

[[Page 27714]]

Ketten 1995). Airgun pulses are less energetic and their peak 
amplitudes have slower rise times. To date, there is no evidence that 
serious injury, death, or stranding by marine mammals can occur from 
exposure to airgun pulses, even in the case of large airgun arrays.
    However, in numerous past IHA notices for seismic surveys, 
commenters have referenced two stranding events allegedly associated 
with seismic activities, one off Baja California and a second off 
Brazil. NMFS has addressed this concern several times, and, without new 
information, does not believe that this issue warrants further 
discussion. For information relevant to strandings of marine mammals, 
readers are encouraged to review NMFS' response to comments on this 
matter found in 69 FR 74905 (December 14, 2004), 71 FR 43112 (July 31, 
2006), 71 FR 50027 (August 24, 2006), and 71 FR 49418 (August 23, 
2006). In addition, a May-June 2008, stranding of 100-200 melon-headed 
whales (Peponocephala electra) off Madagascar that appears to be 
associated with seismic surveys is currently under investigation (IWC 
2009).
    It should be noted that strandings related to sound exposure have 
not been recorded for marine mammal species in the Beaufort and Chukchi 
seas. NMFS notes that in the Beaufort Sea, aerial surveys have been 
conducted by MMS and industry during periods of industrial activity 
(and by MMS during times with no activity). No strandings or marine 
mammals in distress have been observed during these surveys and none 
have been reported by North Slope Borough inhabitants. As a result, 
NMFS does not expect any marine mammals will incur serious injury or 
mortality in the Arctic Ocean or strand as a result of proposed seismic 
survey.

Potential Effects From Active Sonar Equipment on Marine Mammals

    Several active acoustic sources other than the 40 cu-in airgun have 
been proposed for Shell's 2010 open water marine surveys in the 
Beaufort and Chukchi Seas. The specifications of these sonar equipments 
(source levels and frequency ranges) are provided above. In general, 
the potential effects of these equipments on marine mammals are similar 
to those from the airgun, except the magnitude of the impacts is 
expected to be much less due to the lower intensity and higher 
frequencies. Estimated source levels and zones of influence from sonar 
equipment are discussed above. In some cases, due to the fact that the 
operating frequencies of some of this equipment (e.g., Multi-beam echo 
sounder: frequency at 240 kHz) are above the hearing ranges of marine 
mammals, they are not expected to have any impacts to marine mammals.

Vessel Sounds

    In addition to the noise generated from seismic airguns and active 
sonar systems, various types of vessels will be used in the operations, 
including source vessels and support 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. Compared to airgun pulses, 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. 1995). This higher 
sound production results from the greater amount of power and propeller 
cavitation required when operating in thick ice. Source levels from 
various vessels would be empirically measured before the start of 
marine surveys.

Anticipated Effects on Habitat

    The primary potential impacts to marine mammals and other marine 
species are associated with elevated sound levels produced by airguns 
and other active acoustic sources. However, other potential impacts to 
the surrounding habitat from physical disturbance are also possible.

Potential Impacts on Prey Species

    With regard to fish as a prey source for cetaceans and pinnipeds, 
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), 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. 1995).
    Some mysticetes, including bowhead whales, feed on concentrations 
of zooplankton. Some feeding bowhead whales may occur in the Alaskan 
Beaufort Sea in July and August, and others feed intermittently during 
their westward migration in September and October (Richardson and 
Thomson [eds.] 2002; Lowry et al. 2004). Reactions of zooplanktoners to 
sound are, for the most part, not known. Their abilities to move 
significant distances

[[Page 27715]]

are limited or nil, depending on the type of animal. A reaction by 
zooplankton to sounds produced by the marine survey 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 near the airgun source, which is 
expected to be a very small area. Impacts on zooplankton behavior are 
predicted to be negligible, and that would translate into negligible 
impacts on feeding mysticetes.

Proposed Mitigation

    In order to issue an incidental take authorization under Section 
101(a)(5)(D) of the MMPA, NMFS must set forth the permissible methods 
of taking pursuant to such activity, and other means of effecting the 
least practicable adverse 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.
    For the proposed Shell open water marine surveys in the Beaufort 
and Chukchi Sea, Shell worked with NMFS and proposed the following 
mitigation measures to minimize the potential impacts to marine mammals 
in the project vicinity as a result of the marine survey activities.
    As part of the application, Shell submitted to NMFS a Marine Mammal 
Monitoring and Mitigation Program (4MP) for its shallow hazards survey 
activities in the Beaufort Sea during the 2010 open-water season. The 
objectives of the 4MP are:
     To ensure that disturbance to marine mammals and 
subsistence hunts is minimized and all permit stipulations are 
followed,
     To document the effects of the proposed survey activities 
on marine mammals, and
     To collect baseline data on the occurrence and 
distribution of marine mammals in the study area.
    The 4MP 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).

Mitigation Measures Proposed in Shell's IHA Application

    For the proposed mitigation measures, Shell listed the following 
protocols to be implemented during its marine surveys in the Beaufort 
Sea.
(1) Sound Source Measurements
    As described above, previous measurements of airguns in the 
Harrison Bay area were used to model the distances at which received 
levels are likely to fall below 160, 180, and 190 dB re 1 [mu]Pa (rms) 
from the planned airgun sources. These modeled distances will be used 
as temporary safety radii until measurements of the airgun sound source 
are conducted. The measurements will be made at the beginning of the 
field season and the measured radii used for the remainder of the 
survey period.
    The objectives of the sound source verification measurements 
planned for 2010 in the Beaufort Sea will be (1) to measure the 
distances in the broadside and endfire directions at which broadband 
received levels reach 190, 180, 170, 160, and 120 dB re 1 [mu]Pa (rms) 
for the energy source array combinations that may be used during the 
survey activities. The configurations will include at least the full 
array and the operation of a single source that will be used during 
power downs. The measurements of energy source array sounds will be 
made at the beginning of the survey and the distances to the various 
radii will be reported as soon as possible after recovery of the 
equipment. The primary radii of concern will be the 190 and 180 dB 
safety radii for pinnipeds and cetaceans, respectively, and the 160 dB 
disturbance radii. In addition to reporting the radii of specific 
regulatory concern, nominal distances to other sound isopleths down to 
120 dB re 1 [mu]Pa (rms) will be reported in increments of 10 dB.
    Data will be previewed in the field immediately after download from 
the ocean bottom hydrophone (OBH) instruments. An initial sound source 
analysis will be supplied to NMFS and the airgun operators within 120 
hours of completion of the measurements, if possible. The report will 
indicate the distances to sound levels between 190 dB re 1 [mu]Pa (rms) 
and 120 dB re 1 [mu]Pa (rms) based on fits of empirical transmission 
loss formulae to data in the endfire and broadside directions. The 120-
hour report findings will be based on analysis of measurements from at 
least three of the OBH systems. A more detailed report including 
analysis of data from all OBH systems will be issued to NMFS as part of 
the 90-day report following completion of the acoustic program.
    Airgun pressure waveform data from the OBH systems will be analyzed 
using JASCO's suite of custom signal processing software that 
implements the following data processing steps:
     Energy source pulses in the OBH recordings are identified 
using an automated detection algorithm. The algorithm also chooses the 
90% energy time window for rms sound level computations.
     Waveform data is converted to units of [mu]Pa using the 
calibrated acoustic response of the OBH system. Gains for frequency-
dependent hydrophone sensitivity, amplifier and digitizer are applied 
in this step.
     For each pulse, the distance to the airgun array is 
computed from GPS deployment positions of the OBH systems and the time 
referenced DGPS navigation logs of the survey vessel.
     The waveform data are processed to determine flat-weighted 
peak sound pressure level (PSPL), rms SPL and SEL.
     Each energy pulse is Fast Fourier Transformed (FFT) to 
obtain 1-Hz spectral power levels in 1-second steps.
     The spectral power levels are integrated in standard 1/3-
octave bands to obtain band sound pressure levels (BSPL) for bands from 
10 Hz to 20 kHz. Both un-weighted and M-weighted (frequency weighting 
based on hearing sensitivities of four marine mammal functional hearing 
groups, see Southall et al. (2007) for a review) SPL's for each airgun 
pulse may be computed in this step for species of interest.
    The output of the above data processing steps includes listings and 
graphs of airgun array narrow band and broadband sound levels versus 
range, and spectrograms of shot waveforms at specified ranges. Of 
particular importance are the graphs of level versus range that are 
used to compute representative radii to specific sound level 
thresholds.
(2) Safety and Disturbance Zones
    Under current NMFS guidelines, ``safety radii'' for marine mammals 
exposure to impulse sources are customarily defined as the distances 
within which received sound levels are >=180 dB re 1 [mu]Pa (rms) for 
cetaceans and >=190 dB re 1 [mu]Pa (rms) for pinnipeds. These safety 
criteria are based on an assumption that SPL received at levels lower 
than these will not injure these animals or impair their hearing 
abilities, but that SPL received at higher levels might have some such 
effects. Disturbance or behavioral effects to marine mammals from 
underwater sound may occur after exposure to sound at distances greater 
than the safety radii (Richardson et al. 1995).
    Initial safety and disturbance radii for the sound levels produced 
by the survey activities have been modeled. These

[[Page 27716]]

radii will be used for mitigation purposes until results of direct 
measurements are available early during the exploration activities. The 
planned survey will use an airgun source composed of either 40 in \3\ 
airguns or 1 x 20-in \3\ plus 2 x 10-in \3\ airguns. The total source 
volume will be 4 x 10 in \3\. Measurements of a 2 x 10-in \3\ airgun 
array used in 2007 were reported by Funk et al. (2008). These 
measurements were used as the basis for modeling both of the potential 
airgun arrays that may be used in 2010. The modeling results showed 
that the 40 in \3\ array is likely to produce sounds that propagate 
further than the alternative array, so those results were used to 
estimate ``takes by harassment'' in Shell's IHA application and will 
also be used during initial survey activities prior to in-field sound 
source measurements. The modeled 190 and 180 dB distances from a 40 
cubic inch array were 35 and 125 m, respectively. Because this is a 
modeled estimate, but based on similar measurements at the same 
location, the estimated distances for initial safety radii were only 
increased by a factor of 1.25 instead of a typical 1.5 factor. This 
results in a 190-dB distance of 44 m and a 180-dB distance of 156 m.
    A single 10-in \3\ airgun will be used as a mitigation gun during 
turns or if a power down of the full array is necessary due to the 
presence of a marine mammal close to the vessel. Underwater sound 
propagation of a 10-in \3\ airgun was measured near Harrison Bay in 
2007 and results were reported in Funk et al. (2008). The 190 dB and 
180 dB distances from those measurements, 5 m and 20 m respectively, 
will be used as the pre-sound source measurement safety zones during 
use of the single mitigation gun.
    An acoustics contractor will perform the direct measurements of the 
received levels of underwater sound versus distance and direction from 
the energy source arrays using calibrated hydrophones. The acoustic 
data will be analyzed as quickly as reasonably practicable in the field 
and used to verify (and if necessary adjust) the safety distances. The 
mitigation measures to be implemented at the 190 and 180 dB sound 
levels will include power downs and shut downs as described below.
(3) Power Downs and Shut Downs
    A power-down is the immediate reduction in the number of operating 
energy sources from all firing to some smaller number. A shutdown is 
the immediate cessation of firing of all energy sources. The arrays 
will be immediately powered down whenever a marine mammal is sighted 
approaching close to or within the applicable safety zone of the full 
arrays but is outside or about to enter the applicable safety zone of 
the single mitigation source. If a marine mammal is sighted within the 
applicable safety zone of the single mitigation airgun, the entire 
array will be shut down (i.e., no sources firing). Although MMOs will 
be located on the bridge ahead of the center of the airgun array, the 
shutdown criterion for animals ahead of the vessel will be based on the 
distance from the bridge (vantage point for MMOs) rather than from the 
airgun array--a precautionary approach. For marine mammals sighted 
alongside or behind the airgun array, the distance is measured from the 
array.
    Following a power-down or shutdown, operation of the airgun array 
will not resume until the marine mammal has cleared the applicable 
safety zone. The animal will be considered to have cleared the safety 
zone if it:
     Is visually observed to have left the safety zone;
     Has not been seen within the zone for 15 min in the case 
of small odontocetes and pinnipeds; or
     Has not been seen within the zone for 30 min in the case 
of mysticetes.
(4) Ramp Ups
    A ramp up of an airgun array provides a gradual increase in sound 
levels, and involves a stepwise increase in the number and total volume 
of airguns firing until the full volume is achieved.
    The purpose of a ramp up (or ``soft start'') is to ``warn'' 
cetaceans and pinnipeds in the vicinity of the airguns and to provide 
the time for them to leave the area and thus avoid any potential injury 
or impairment of their hearing abilities.
    During the proposed shallow hazards survey program, the seismic 
operator will ramp up the airgun arrays slowly. Full ramp ups (i.e., 
from a cold start after a shut down, when no airguns have been firing) 
will begin by firing a single airgun in the array. The minimum duration 
of a shut-down period, i.e., without air guns firing, which must be 
followed by a ramp up typically is the amount of time it would take the 
source vessel to cover the 180-dB safety radius. The actual time period 
depends on ship speed and the size of the 180-dB safety radius. That 
period is estimated to be about 1-2 minutes based on the modeling 
results described above and a survey speed of 4 knots.
    A full ramp up, after a shut down, will not begin until there has 
been a minimum of 30 min of observation of the safety zone by MMOs to 
assure that no marine mammals are present. The entire safety zone must 
be visible during the 30-minute lead-in to a full ramp up. If the 
entire safety zone is not visible, then ramp up from a cold start 
cannot begin. If a marine mammal(s) is sighted within the safety zone 
during the 30-minute watch prior to ramp up, ramp up will be delayed 
until the marine mammal(s) is sighted outside of the safety zone or the 
animal(s) is not sighted for at least 15-30 minutes: 15 minutes for 
small odontocetes and pinnipeds, or 30 minutes for baleen whales and 
large odontocetes.
    During turns and transit between seismic transects, at least one 
airgun will remain operational. The ramp-up procedure still will be 
followed when increasing the source levels from one airgun to the full 
arrays. However, keeping one airgun firing will avoid the prohibition 
of a cold start during darkness or other periods of poor visibility. 
Through use of this approach, seismic operations can resume upon entry 
to a new transect without a full ramp up and the associated 30-minute 
lead-in observations. MMOs will be on duty whenever the airguns are 
firing during daylight, and during the 30-min periods prior to ramp-ups 
as well as during ramp-ups. Daylight will occur for 24 h/day until mid-
August, so until that date MMOs will automatically be observing during 
the 30-minute period preceding a ramp up. Later in the season, MMOs 
will be called out at night to observe prior to and during any ramp up. 
The seismic operator and MMOs will maintain records of the times when 
ramp-ups start, and when the airgun arrays reach full power.

Additional Mitigation Measures Proposed by NMFS

    Besides Shell's proposed mitigation measures discussed above, NMFS 
proposes the following additional protective measures to address some 
uncertainties regarding the impacts to bowhead cow-calf pairs and 
aggregations of whales from seismic surveys. Specifically, NMFS 
proposes that:
     For seismic activities (including shallow hazards and site 
clearance and other marine surveys where active acoustic sources will 
be employed) in the Beaufort Sea after August 25, a 120-dB monitoring 
(safety) zone for bowhead whales will be established and monitored for 
the next 24 hours if four or more bowhead whale cow/calf pairs are 
observed at the surface during an aerial monitoring program within the 
area where an ensonified 120-dB zone around the vessel's track is 
projected. To the extent practicable, such

[[Page 27717]]

monitoring should focus on areas upstream (eastward) of the bowhead 
migration. No seismic surveying shall occur within the 120-dB safety 
zone around the area where these whale cow-calf pairs were observed, 
until two consecutive surveys (aerial or vessel) indicate they are no 
longer present within the 120-dB safety zone of seismic-surveying 
operations.
     A 160-dB vessel monitoring zone for bowhead and gray 
whales will be established and monitored in the Chukchi Sea and after 
August 25 in the Beaufort Sea during all seismic surveys. Whenever an 
aggregation of bowhead whales or gray whales (12 or more whales of any 
age/sex class that appear to be engaged in a nonmigratory, significant 
biological behavior (e.g., feeding, socializing)) are observed during 
an aerial or vessel monitoring program within the 160-dB safety zone 
around the seismic activity, the seismic operation will not commence or 
will shut down, until two consecutive surveys (aerial or vessel) 
indicate they are no longer present within the 160-dB safety zone of 
seismic-surveying operations.
     Survey information, especially information about bowhead 
whale cow-calf pairs or feeding bowhead or gray whales, shall be 
provided to NMFS as required in MMPA authorizations, and will form the 
basis for NMFS determining whether additional mitigation measures, if 
any, will be required over a given time period.
    Furthermore, 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, and 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 adjust speed accordingly to avoid the likelihood 
of injury to whales.

Mitigation Conclusions

    NMFS has carefully evaluated the applicant's proposed mitigation 
measures and considered a range of other measures in the context of 
ensuring that NMFS prescribes the means of effecting the least 
practicable impact on the affected marine mammal species and stocks and 
their habitat. Our evaluation of potential measures included 
consideration of the following factors in relation to one another:
     The manner in which, and the degree to which, the 
successful implementation of the measure is expected to minimize 
adverse impacts to marine mammals;
     The proven or likely efficacy of the specific measure to 
minimize adverse impacts as planned; and
     The practicability of the measure for applicant 
implementation.
    Based on our evaluation of the applicant's proposed measures, as 
well as other measures considered by NMFS, NMFS has preliminarily 
determined that the proposed mitigation measures provide the means of 
effecting the least practicable impact on marine mammal species or 
stocks and their habitat, paying particular attention to rookeries, 
mating grounds, and areas of similar significance.

Proposed Monitoring and Repor