Notice2025-06593
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Construction of the Alaska Liquefied Natural Gas Project in Prudhoe Bay, Alaska
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
April 18, 2025
Issuing agencies
Commerce DepartmentNational Oceanic and Atmospheric Administration
Abstract
NMFS has received a request from the Alaska Gasline Development Corporation (AGDC) for authorization to take marine mammals incidental to construction of the Alaska Liquefied Natural Gas (AK LNG) Project in Prudhoe Bay, Alaska. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an incidental harassment authorization (IHA) to incidentally take marine mammals during the specified activities. NMFS is also requesting comments on a possible one-time, 1-year renewal that could be issued under certain circumstances and if all requirements are met, as described in Request for Public Comments at the end of this notice. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorization and agency responses will be summarized in the final notice of our decision.
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[Federal Register Volume 90, Number 74 (Friday, April 18, 2025)]
[Notices]
[Pages 16600-16637]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-06593]
[[Page 16599]]
Vol. 90
Friday,
No. 74
April 18, 2025
Part II
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 Construction of the Alaska Liquefied
Natural Gas Project in Prudhoe Bay, Alaska; Notice
Federal Register / Vol. 90, No. 74 / Friday, April 18, 2025 /
Notices
[[Page 16600]]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XE705]
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to Construction of the Alaska
Liquefied Natural Gas Project in Prudhoe Bay, Alaska
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental harassment authorization; request
for comments on proposed authorization and possible renewal.
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SUMMARY: NMFS has received a request from the Alaska Gasline
Development Corporation (AGDC) for authorization to take marine mammals
incidental to construction of the Alaska Liquefied Natural Gas (AK LNG)
Project in Prudhoe Bay, Alaska. Pursuant to the Marine Mammal
Protection Act (MMPA), NMFS is requesting comments on its proposal to
issue an incidental harassment authorization (IHA) to incidentally take
marine mammals during the specified activities. NMFS is also requesting
comments on a possible one-time, 1-year renewal that could be issued
under certain circumstances and if all requirements are met, as
described in Request for Public Comments at the end of this notice.
NMFS will consider public comments prior to making any final decision
on the issuance of the requested MMPA authorization and agency
responses will be summarized in the final notice of our decision.
DATES: Comments and information must be received no later than May 19,
2025.
ADDRESSES: Comments should be addressed to Jolie Harrison, Chief,
Permits and Conservation Division, Office of Protected Resources,
National Marine Fisheries Service and should be submitted via email to
<a href="/cdn-cgi/l/email-protection#c68f9296e88ca7a5a9a4b3b586a8a9a7a7e8a1a9b0"><span class="__cf_email__" data-cfemail="0e475a5e20446f6d616c7b7d4e60616f6f20696178">[email protected]</span></a>. Electronic copies of the application and
supporting documents, as well as a list of the references cited in this
document, may be obtained online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-other-energy-activities-renewable">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-other-energy-activities-renewable</a>. In case of problems accessing these
documents, please call the contact listed below.
Instructions: NMFS is not responsible for comments sent by any
other method, to any other address or individual, or received after the
end of the comment period. Comments, including all attachments, must
not exceed a 25-megabyte file size. All comments received are a part of
the public record and will generally be posted online at <a href="https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act">https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act</a> without change. All personal identifying
information (e.g., name, address) voluntarily submitted by the
commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.
FOR FURTHER INFORMATION CONTACT: Kristy Jacobus, Office of Protected
Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Background
The MMPA prohibits the ``take'' of marine mammals, with certain
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361
et seq.) direct the Secretary of Commerce (as delegated to NMFS) 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 proposed or, if the taking is limited to harassment, a notice of a
proposed IHA 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) and will not have an unmitigable adverse impact on the
availability of the species or stock(s) for taking for subsistence uses
(where relevant). Further, NMFS must prescribe the permissible methods
of taking and other ``means of effecting the least practicable adverse
impact'' on the affected species or stocks and their habitat, paying
particular attention to rookeries, mating grounds, and areas of similar
significance, and on the availability of the species or stocks for
taking for certain subsistence uses (referred to in shorthand as
``mitigation''); and requirements pertaining to the monitoring and
reporting of the takings. The definitions of all applicable MMPA
statutory terms cited above are included in the relevant sections below
and can be found in section 3 of the MMPA (16 U.S.C. 1362) and NMFS
regulations at 50 CFR 216.103.
National Environmental Policy Act
To comply with the National Environmental Policy Act of 1969 (NEPA;
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A,
NMFS must review our proposed action (i.e., the issuance of an IHA)
with respect to potential impacts on the human environment. NMFS
participated as a cooperating agency on the 2020 Alaska LNG Project
Environmental Impact Statement (EIS), which was finalized on March 6,
2020, and is available at <a href="https://www.ferc.gov/industries-data/natural-gas/environment/final-environmental-impact-statement-feis">https://www.ferc.gov/industries-data/natural-gas/environment/final-environmental-impact-statement-feis</a>.
When acting as a cooperating agency, as is the case with this
project, NMFS may satisfy its independent NEPA obligations by either
preparing a separate NEPA analysis for its issuance of an incidental
take authorization or, if appropriate, by adopting the NEPA analysis
prepared by the lead agency. NMFS independently reviewed and evaluated
the 2020 Alaska LNG Project EIS and determined that was adequate and
sufficient to meet our responsibilities under NEPA for the issuance of
the 2020 Prudhoe Bay IHA (86 FR 10658, February 22, 2021). NMFS
therefore adopted the 2020 Alaska LNG Project EIS on February 16, 2021.
Summary of Request
On June 21, 2024, NMFS received a request from AGDC for an IHA to
take marine mammals incidental to construction activities in Prudhoe
Bay, Alaska. The application was deemed adequate and complete on
February 11, 2025. AGDC's request is for take of six species of marine
mammals by Level B harassment and ringed seal, spotted seal, and
bearded seal, by Level A harassment. Neither AGDC nor NMFS expect
serious injury or mortality to result from this activity and,
therefore, an IHA is appropriate.
NMFS previously issued an IHA to AGDC for the same activities (86
FR 10658; February 22, 2021). However, no work was conducted under that
IHA.
This proposed IHA would authorize incidental take during one year
of the larger AK LNG project. The larger project involves a pipeline
that will span approximately 807 miles (mi) (1,299 kilometers (km))
from a gas treatment facility on Alaska's North Slope, which holds 35
trillion cubic feet (991 billion cubic meters) of proven gas reserves,
to a liquefaction and export facility in southcentral Alaska.
Description of Specified Activity
Overview
AGDC plans to construct an integrated liquefied natural gas (LNG)
project with
[[Page 16601]]
interdependent facilities to liquefy supplies of natural gas from
Alaska, in particular from the Point Thomson Unit and Prudhoe Bay Unit
production fields on the Alaska North Slope (North Slope), for export
in foreign commerce and for in-state deliveries of natural gas. AGDC
plans to construct an AK LNG Gas Treatment Plant (GTP), which they
would construct with large, pre-fabricated modules that can only be
transported to the North Slope with barges (sealifts).
AGDC is proposing to modify the existing West Dock causeway and
associated dock heads in Prudhoe Bay, Alaska in order to facilitate
offloading modular construction components and transporting them to the
GTP construction site. Vibratory and impact pile driving associated
with the work at West Dock would introduce underwater sound that may
result in take by Level A and Level B harassment of marine mammals in
Prudhoe Bay, Alaska. AGDC proposes to conduct pile driving up to 24
hours per day on approximately 123 days from July through October
during the open water (i.e., ice-free) season.
Dates and Duration
The proposed IHA would be effective for one year beginning June 1,
2027 or June 1, 2028, depending on the project schedule indicated by
the applicant. Work that may result in the take of marine mammals is
expected to occur during the open water season, between July and
October, and would be conducted up to 24 hours per day, six days a
week.
Several communities on the North Slope of Alaska engage in
subsistence hunting activities at varying times and in varying
locations. These subsistence hunts are further described below in the
Effects of Specified Activities on Subsistence Uses of Marine Mammals
section. The proposed construction activities would occur closest to
the marine subsistence use area used by the Native Village of Nuiqsut.
Their whaling season typically occurs August 25th to September 15th,
although the exact dates may change. AGDC will cease pile driving
during the Nuiqsut whaling season.
AGDC conservatively calculated that in-water construction would
last 164 days. However, they expect that different pile types would be
installed on the same day, which should reduce the overall number of
construction days to approximately 123 days of in-water work
considering the open water period, and the break in construction during
the whaling season. If AGDC is not able to complete the work during the
open water season construction period as planned, they will complete
the work during a contingency period from late February to April.
Specific Geographic Region
The specified activity (i.e., AK LNG construction activities) will
occur at West Dock in Prudhoe Bay, Alaska, on Alaska's North Slope (see
figure 1). West Dock is a multipurpose facility, commonly used to
offload marine cargo to support Prudhoe Bay oilfield development. West
Dock extends out from the shoreline 2.7 mi (4.3 km) and is within
shallow waters less than 14.2 feet (ft, 4.3 meters (m)) deep.
[[Page 16602]]
[GRAPHIC] [TIFF OMITTED] TN18AP25.000
Figure 1. Map of Project Location
Detailed Description of the Specified Activity
Below, we discuss the proposed activities in Prudhoe Bay, a portion
of the larger AK LNG project (which extends from the North Slope to
Cook Inlet). For information on other AK LNG project components, please
refer to Volume I, Chapter 2 of the Alaska LNG Project Final EIS.
AGDC is proposing to further develop the West Dock facility in
Prudhoe Bay, AK. West Dock is a multipurpose facility, commonly used to
offload marine cargo to support Prudhoe Bay oilfield development. The
West Dock causeway, which extends approximately 2.5 mi (4 km) into
Prudhoe Bay from the shoreline, is a solid-fill gravel causeway
structure. There are two existing loading docks along the causeway,
referred to as Dock Head 2 (DH2) and Dock Head 3 (DH3), and a seawater
treatment plant (STP) at the seaward terminus of the structure. A 650-
ft (198-m) breach with a single lane bridge was installed in the
causeway between DH2 and DH3 during 1995 and 1996 due to concerns that
the solid causeway was affecting coastal circulation and marine
resources.
Development of the dock facility would require constructing a new
dock head referred to as Dock Head 4 (DH4), widening the gravel
causeway between the proposed DH4 site and the onshore road system, and
installation of a
[[Page 16603]]
temporary barge bridge parallel to the existing bridge over the
aforementioned breach to accommodate transport of the modules over the
breach. The following describes these activities in detail.
DH4 Work Area and Bulkhead--AGDC will construct a new dock head
(DH4). DH4 would be a gravity-based structure, with a combi-wall (sheet
piles connected by H-piles) bulkhead or dock face back-filled with
gravel. The gravel dock head would provide a working area of
approximately 31 acres (0.13 km\2\) and would have five cargo berths.
Gravel would be hauled in by truck and deposited in place by shore-
based heavy equipment. Hauling and placement of gravel for construction
of DH4 would occur from June-September. Gravel requirements are
quantified in table 3 of AGDC's application.
Construction of DH4 would require the installation of over 1,080
linear ft (329 m) of combi-wall forming a bulkhead at the dock face,
and will require vibratory and impact pile driving. Noise generated by
pile driving is expected to result in the take of marine mammals. Other
margins of the dock head would be sloped and armored with sand bags.
Table 1 indicates the planned numbers and types of piles proposed for
installation, and the proposed installation method for DH4 work,
including the work area and bulkhead.
Table 1-Piles Planned for Installation at DH4
------------------------------------------------------------------------
Number of
Pile type/size Installation method piles
------------------------------------------------------------------------
11.5-inch (29 cm \a\) Steel H- Impact................. 212
Pile.
48-inch (122 cm) Steel Pipe Impact................. 12
Pile.
25-inch (64 cm) Steel Sheet Vibratory.............. 422
Pile.
14-inch (36 cm) Steel H-Pile Vibratory.............. 48
(temporary).
------------------------------------------------------------------------
\a\ cm = centimeter.
AGDC plans to construct DH4 from June-October (open water season).
Hauling and placing of the gravel will take place first. AGDC plans to
install the combi-wall mid-September-October (after the whaling season
and before ice). In the unlikely event AGDC is not able to complete the
DH4 construction during the open water season, they plan to complete
construction during a contingency period from February to April,
working off the ice. AGDC stated that it is highly motivated to
complete work during the open-water season, as work during the ice-
covered winter/spring contingency period would require additional
equipment and include other constraints. NMFS expects that if AGDC
works during the contingency period, it would be because of lost
construction days on which they were unable to work during their
planned open water work season.
DH4 Mooring Dolphins--AGDC plans to install twelve mooring dolphins
in the cargo berths at the proposed DH4 to hold the ballasted barges in
place. Figure 5 of AGDC's application shows the locations of the
proposed mooring dolphins. AGDC plans to install four temporary spuds
(14-inch (36 cm) steel H-piles) for support prior to the construction
of each mooring dolphin using a vibratory hammer. AGDC would extract
these piles immediately after completion of the dolphin. Noise
generated by pile driving is expected to result in the take of marine
mammals. Table 1 lists the proposed pile types, numbers, and driving
methods for DH4 work, including the mooring dolphins.
AGDC plans to install the mooring dolphins from September-October
(after the Nuiqsut whaling season and before ice cover). If AGDC is not
able to complete mooring dolphin construction during this time, they
plan to complete construction during a contingency period from late
February to April of the following year.
Barge Bridge Abutments--AGDC plans to construct a temporary barge
bridge, and NMFS does not expect take as a result of its construction
(see description of Barge Bridge installation below). AGDC plans to
construct approach abutments (gravel filled open-cell sheet pile
bulkheads) along the east side of the existing causeway on both ends of
the barge bridge, and take is expected as a result of this
construction. AGDC would place gravel bags for erosion control in
locations where there is no bulkhead. The bulkheads would be
approximately 420 ft (128 m) long (along the causeway) and 120 ft (36.6
m) across.
Much of the abutment sheet pile is for the tail walls that run from
the bulkhead into the gravel fill and terminate at an anchor pile (H-
pile). Noise generated by pile driving is expected to result in the
take of marine mammals. A large portion of this tail wall piling and
many of the tail wall anchor piles would be driven into dry ground and
are not included in the analysis for assessing in-water noise impacts
on marine mammals. Table 2 lists the numbers and types of pilings
planned for in-water installation for the barge bridge abutments.
Table 2--Piles Planned for In-Water Installation at the North and South
Barge Bridge Abutment Bulkheads
------------------------------------------------------------------------
Pile type and Number of
installation method piles
------------------------------------------------------------------------
South Abutment................. 19.69-inch (50.01 cm) 695
Steel Sheet Pile
(Vibratory).
14-inch (36 cm) Steel H- 4
Pile (Impact).
North Abutment................. 19.69-inch (50.01 cm) 609
Steel Sheet Pile
(Vibratory).
14-inch (36 cm) Steel H- 4
Pile (Impact).
------------------------------------------------------------------------
AGDC plans to install the sheet piles from land or barges on open
water, and potentially from the ice if the contingency period is
necessary.
Construction of the barge bridge abutments is scheduled for July-
August with a break in pile driving during the Nuiqsut whaling season
(approximately August 25-September 15) if activities overlap. If AGDC
is unable to complete construction during the open water period, they
plan to complete the work
[[Page 16604]]
during the contingency period from February to April.
Barge Bridge Mooring Dolphins--AGDC plans to install four mooring
dolphins at the barge bridge site to protect the current bridge from
the barges and hold the ballasted barges in place. Each mooring dolphin
consists of one 48-inch diameter (122 cm), 100 ft (30.5 m) long steel
pipe pile that AGDC will drive with an impact hammer to a minimum of 65
ft (19.8 m) into the seabed. As described above for the DH4 mooring
dolphins, AGDC plans to install four temporary spuds (14.5-inch (37 cm)
steel H-piles) with a vibratory hammer for support prior to the
construction of each barge bridge mooring dolphin. AGDC would extract
these temporary spuds immediately after completion of the dolphin.
Noise generated by pile driving is expected to result in the take of
marine mammals. Table 3 summarizes installation method and number of
piles.
AGDC plans to construct the barge bridge abutments, including the
mooring dolphins, in July and August, with a break in pile driving
during the Nuiqsut whaling season (approximately August 25-September
15). If AGDC is not able to complete the work during that period, they
will complete the dolphin installation during the contingency period
from February to April.
Table 4 summarizes the total number of piles by hammer type for all
project components.
Table 3--Piles Planned for Mooring Dolphin Installation at the Barge
Bridge Abutments
------------------------------------------------------------------------
Number of
Pile type Installation method piles
------------------------------------------------------------------------
48-inch (122 cm) Steel Pipe Pile.. Impact.............. 4
14-inch (36 cm) Steel H-Pile Vibratory........... \a\ 16
(Temporary).
------------------------------------------------------------------------
\a\ Each of these piles will be installed and later removed after
installation of mooring dolphin.
Table 4--Total Number of Piles Among All Prudhoe Bay Project Components
------------------------------------------------------------------------
Number of
Pile size and type Hammer type piles
------------------------------------------------------------------------
11.5-inch (29.2 cm) H-Pile........ Impact.............. 212
14.5-inch (35.8 cm) H-Pile........ Impact.............. 8
Vibratory........... 64
48-inch (122 cm) Pipe Pile........ Impact.............. 16
Sheet Piles (19.69-inch (50.01 cm) Vibratory........... 1726
and 25-inch (63.5 cm)).
------------------------------------------------------------------------
AGDC will only operate one hammer at a time during all pile
driving.
The below described activities are not expected to result in the
take of marine mammals.
Causeway Widening--AGDC will build a parallel causeway
approximately 100-125 ft (31-38 m) wide and 5,000 ft long (1,524 m) on
the east side of the existing causeway from DH 3 to DH 4. AGDC will
upgrade the other two existing segments of West Dock causeway to a
width of approximately 100-125 ft from the current width of 40-80 ft
(12-24 m). AGDC will conduct the widening on the east side of the
causeway because there is a pipeline along the west side. The widening
would occur along approximately 4,500 ft (1,372 m) from DH3 to DH2, and
3,800 ft (1,158 m) from DH2 to land. This causeway widening work would
be conducted during the summer (July-August). Gravel would be hauled in
by truck and deposited in place by shore-based heavy equipment.
Expected gravel requirements are indicated in table 2 of AGDC's
application. Gravel fill deposition would produce a continuous sound of
a relatively short duration, does not require seafloor penetration, and
would affect a very small portion of habitat for marine mammals and
their prey. Placement would occur in a controlled manner so as not to
compromise the newly installed piles. Gravel deposition is not expected
to result in marine mammal harassment and it is not discussed further.
Further, a portion of the gravel deposition will occur behind sheet
piles, which will act as an acoustic barrier which further supports the
conclusion that take from gravel deposition is unlikely to occur.
Berthing Basin--The proposed location of the DH4 bulkhead is
approximately 1,000 ft (305 m) beyond the end of the existing causeway
at the STP. This location was selected as it provides an existing
nominal water depth of -12 ft (-4 m) mean lower low water (MLLW) across
the length of the bulkhead, allowing for berthing of cargo barges at
their intended transit draft of 10 ft (3 m) without the exchange of
ballast water.
AGDC plans to conduct screeding over the seafloor within the
berthing area to a depth of -12 ft (-4 m) MLLW. Screeding would
redistribute the seabed materials to provide a flat and even surface on
which the module cargo barges can be grounded. The berthing area
encompasses approximately 13.7 acres (0.06 km\2\). In the screeding
process, a tug and/or barge pushes or drags a beam or blade across the
seafloor, removing high spots and filling local depressions. The
screeding operation is not intended to increase or decrease overall
seabed elevation so there would be no excavated materials requiring
disposal.
AGDC would conduct screeding in the summer immediately prior to
arrival of each sealift and as soon as sea ice conditions allow
mobilization of the screeding barge. Based on historical ice data, AGDC
anticipates screeding during July for a period of up to 14 days. AGDC
would conduct a multi-beam hydrographic survey to identify high and low
spots in the seabed prior to each season with equipment emitting sound
at frequencies above 200 kilohertz (kHz). Therefore, we do not expect
these surveys to take marine mammals, as marine mammals are unlikely to
hear the surveys, much less respond to them, and we do not discuss it
further in this notice. Additionally, we do not expect screeding to
result in take of marine mammals, given that it is a continuous noise
source comparable to other general construction activities. Further,
this proposed IHA requires AGDC to shut down at 215 m during screeding
operations, consistent with the 2020 Alaska LNG Biological
[[Page 16605]]
Opinion. AGDC has not requested, and NMFS does not propose to authorize
take incidental to the proposed screeding.
Barge Bridge--The existing bridge over the aforementioned 650 ft
(198 m) breach in the causeway is too narrow for module transport and
incapable of supporting the weight of the project modules. Therefore,
AGDC plans to construct a temporary barge bridge to accommodate
transport of the modules over the breach and to the onshore road
system. The first two barges to offload materials would be used to form
the temporary bridge, paralleling the existing weight-limited bridge,
and spanning the breach. AGDC would move these barges into place
against the mooring dolphins with tugs where they would be ballasted
and fastened to the causeway abutments and each other. The two
ballasted barges would be placed bow-to-bow when resting on the
seafloor. The barge rakes would angle upward and touch at their
adjoining point, leaving an approximately 52.5-ft (16-m) gap at the
seafloor between the barges. The stern of each barge would angle
sharply upward at each end of the bridge, leaving an additional 10-ft
(3.1-m) gap at the seafloor at each end.
Ramps would be installed to accommodate smooth transit of the self-
propelled module transporters (SPMTs) over the bridge. Modules would be
transported by SPMTs down the causeway and over the temporary bridge to
a staging pad at the base of West Dock. From there, they would be moved
southward over approximately 6 mi (9.7 km) of new and existing roads to
the GTP construction site.
AGDC expects construction of the temporary barge bridge will last 3
days. The temporary bridge would be held in place by the mooring
dolphins. AGDC expects the temporary bridge to be in place for 21 to 39
days, depending on weather conditions and logistics. At the conclusion
of each year's sealift, AGDC would de-ballast the barges and remove
them from the breach. Upon the subsequent summer season and the next
sealift, AGDC would position the barges back in the breach and re-
ballast them onto the barge pad for module transport operations. NMFS
does not expect placement or removal of the barge bridges to result in
take of marine mammals, and we do not discuss it further.
AGDC plans to leave West Dock modifications in place after modules
are offloaded, as their removal would result in greater disturbance to
the surrounding environment. AGDC also plans to leave the piling and
infrastructure forming the offshoot and ramp to the temporary barge
bridge in place, as removing it may result in erosion or weakening of
the existing causeway. AGDC would cut the mooring pilings below the
sediment surface, remove them, and cover the area with surrounding
sediment.
Sealifts--AGDC has proposed six sealifts, consisting of two
preliminary sealifts (NEG1 and NEG2) transporting materials (smaller
modules, equipment, and supplies) and four primary sealifts (Sealifts
1-4) carrying the GTP modules. AGDC identified the timing, numbers of
vessels, and numbers of modules associated with each of these six
sealifts in their application (See Tables 8 and 9 of AGDC's
application).
The barges will transport the modules from the manufacturing site
(likely in Asia) with first call being Dutch Harbor to clear customs.
The barges would then proceed to a designated Marine Transit Staging
Area (MTSA), with Port Clarence being the preferred location for the
MTSA at this time. The tug and barge will wait in a secure anchorage
there until sea ice conditions have improved to 3/10 ice cover or
better. The tow spread would be accompanied by a light aircraft which
would repeatedly fly along the tow route to give a detailed report on
sea and ice conditions. When such conditions are favorable, the tug and
barge would proceed to the Prudhoe Bay Offshore Staging Area (PBOSA)
located south (shoreward) of Reindeer Island and approximately 5 mi (8
km) north of DH4 to await berthing at DH4.
The sealift barges would be moved from the PBOSA to DH4 with the
shallow draft assist tugs. Offloading operations at DH4 would occur 24
hours a day during periods of favorable metocean and weather
conditions. Current North Slope sealift practices limit operations to
wind speed below 20 knots. The barges would be butted up against the
dock face and then ballasted down until they rest on the prepared barge
bearing pad. Ramps would be placed to connect the barge deck with the
dock so that the SPMTs are able to roll under the modules, lift them,
then roll out and transport them to the onshore module staging area.
The barges would be demobilized from the PBOSA by ocean-going tugs
using standard marine shipping routes. The barges would transit
individually through the Beaufort and Chukchi seas rather than in
groups, as occurred during their arrival into Prudhoe Bay. They would
be demobilized from Prudhoe Bay on or about mid-September. NMFS does
not expect take to occur associated with regular vessel transit, and
therefore the use of sealifts is not discussed further.
Sealifts and barge bridge installation and removal would occur each
of six consecutive years to accommodate the modules required for the
project. AGDC would construct the approach abutments and mooring
dolphins (as described above) in the first season, and would prepare
the seabed before installation of the barge bridge for the first
sealift. The barge bridge would be installed annually each sealift year
at the beginning of the open-water season, and would be removed each
fall prior to freeze-up. Seabed Preparation at the Barge Bridge- AGDC
will construct a level and stable barge pad to support the ballasted
barge at the proper horizontal and vertical location for successful
transit of modules across the breach. The pad would be designed to
support the fully loaded weight of the barge and the heaviest modules.
Pad construction would begin in February and would include an
initial through-ice bathymetric survey within the breach. AGDC would
conduct the through-ice survey by drilling or augering holes through
the ice and measuring the bottom elevations by a survey rod tied to the
local Global Positioning System--Real Time Kinematic (GPS-RTK) system
to provide the needed level of accuracy of horizontal positions and
vertical elevations. A grid of survey holes would be established over
the 710 ft (216 m) by 160 ft (48.8 m) dimensions (2.6 acres; 0.01
km\2\) of the breach barge pad to allow for determination of the bottom
bathymetry such that a plan can be developed accordingly to prepare the
barge pad surface. Cetaceans are not predicted to be present in the
area during these activities (Quakenbush et al., 2018, Citta et al.,
2017) and while ringed seals likely will be present, few, if any,
spotted or bearded seals are likely to be present during that time
(Bengston et al., 2005; Lowry et al., 1998; Simpkins et al., 2003).
Therefore, take of cetaceans from drilling/augering is not expected,
and take of spotted or bearded seals is so low as to be discountable.
Given that drilling/augering is expected to occur in February, prior to
ringed seals establishing lairs, we would not expect ringed seals to
build their lairs close enough to the project so as to be disturbed by
the drilling/augering during the activity. Although there is potential
that a seal might build its lair in an alternate location due to
drilling/augering, this disturbance is accounted for in the takes by
Level B harassment, which have considered all likely take by behavioral
disturbance, including that
[[Page 16606]]
which could influence lair location. Therefore, NMFS did not conduct
any further analysis of Level B harassment of ringed seals during the
drilling/augering.
Seabed preparation would consist of smoothing the seabed within the
pad area as necessary to level the seabed across the pad at an
elevation grade of approximately -7 ft (-2.1 m) MLLW. Some gravel fill
may be required at scour holes. Rock filled marine mattresses or
gabions approximately 1 ft (0.3 m) thick would then be placed across
the graded pad to provide a stable and low maintenance surface at -6 ft
(-1.8 m) MLLW on which the barges would be grounded. These mattresses
are gravel-filled containers constructed of high-strength geogrid, with
the geogrid panels laced together to form mattress-shaped baskets.
AGDC would conduct the seabed preparations through the ice during
winter using excavation equipment and ice excavation methods. Equipment
required for the grading work includes ice trenchers, excavators,
front-end loaders, man-lifts, haul trucks, survey equipment, and other
ancillary equipment necessary to support the operation. An equipment
spread includes a trencher for cutting ice, an excavator for removing
ice, a second excavator, and haul units. AGDC would initiate through-
ice grading efforts by cutting through the ice with trenchers.
Excavators would then proceed to remove the ice to expose the seafloor
bottom. Once a section has been exposed to the seafloor, the bottom
will be graded to -7 ft (-2.1 m) MLLW using the excavation equipment.
AGDC would then install marine mattresses on the graded pad, likely
requiring use of a crane. Grounded ice conditions are expected to occur
at the breach on or before February 1 of each year at the latest. AGDC
expects to conduct through-ice surveying and grading work immediately
after, if not sooner. AGDC expects the total construction duration will
be 45 to 60 days with construction complete by the end of March and
demobilization from the breach area in early April. NMFS expects these
activities to produce continuous noise similar to other standard
construction noise and does not expect seabed preparation to result in
take of marine mammals.
AGDC may conduct some screeding right before the barges are placed
in summer in an effort to achieve a surface that is near flush with
adjacent subsurface elevations. Any screeding at the barge bridge site
would be expected to take 14 days or less. As discussed previously,
NMFS does not expect screeding to result in marine mammal harassment,
therefore, screeding is not discussed further in this document.
NMFS is carrying forward impact and vibratory pile driving and
removal activities (piles indicated in table 4) for further analysis
because these activities are likely to result in the take of marine
mammals.
Proposed mitigation, monitoring, and reporting measures are
described in detail later in this document (please see Proposed
Mitigation and Proposed Monitoring and Reporting).
Description of Marine Mammals in the Area of Specified Activities
Sections 3 and 4 of the application summarize available information
regarding status and trends, distribution and habitat preferences, and
behavior and life history of the potentially affected species. NMFS
fully considered all of this information, and we refer the reader to
these descriptions, instead of reprinting the information. Additional
information regarding population trends and threats may be found in
NMFS' Stock Assessment Reports (SARs; <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>) and
more general information about these species (e.g., physical and
behavioral descriptions) may be found on NMFS' website (<a href="https://www.fisheries.noaa.gov/find-species">https://www.fisheries.noaa.gov/find-species</a>). Additional information may be
found in the Aerial Survey of Arctic Marine Mammals (ASAMM) reports,
which are available online at <a href="https://www.fisheries.noaa.gov/alaska/marine-mammal-protection/aerial-surveys-arctic-marine-mammals">https://www.fisheries.noaa.gov/alaska/marine-mammal-protection/aerial-surveys-arctic-marine-mammals</a>, with the
exception of the 2020 and 2021 reports, which are available in the NMFS
repository (<a href="https://repository.library.noaa.gov/">https://repository.library.noaa.gov/</a>).
Table 5 lists all species or stocks for which take is expected and
proposed to be authorized for this activity and summarizes information
related to the population or stock, including regulatory status under
the MMPA and Endangered Species Act (ESA) and potential biological
removal (PBR), where known. PBR is defined by the MMPA as the maximum
number of animals, not including natural mortalities, that may be
removed from a marine mammal stock while allowing that stock to reach
or maintain its optimum sustainable population (as described in NMFS'
SARs). While no serious injury or mortality is anticipated or proposed
to be authorized here, PBR and annual serious injury and mortality from
anthropogenic sources are included here as gross indicators of the
status of the species or stocks and other threats.
Marine mammal abundance estimates presented in this document
represent the total number of individuals that make up a given stock or
the total number estimated within a particular study or survey area.
NMFS' stock abundance estimates for most species represent the total
estimate of individuals within the geographic area, if known, that
comprises that stock. For some species, this geographic area may extend
beyond U.S. waters. All managed stocks in this region are assessed in
NMFS' U.S. Pacific and Alaska SARs. All values presented in table 5 are
the most recent available at the time of publication (including from
the 2023 SARs) and are available online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>.
Table 5--Marine Mammal Species \1\ Likely Impacted by the Specified Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stock abundance
(CV, Nmin, most Annual M/
Common name Scientific name Stock ESA/MMPA status; strategic (Y/N) \2\ recent abundance PBR SI \4\
survey) \3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Artiodactyla--Cetacea--Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Eschrichtiidae:
Gray Whale................ Eschrichtius Eastern N -, -, N 26,960 (0.05, 801 131
robustus. Pacific. 25,849, 2016).
Family Balaenidae:
Bowhead whale............. Balaena Western Arctic.. E, D, Y 15,227 (0.165, 133 57
mysticetus. 13,263, 2019).
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 16607]]
Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Monodontidae (white
whales):
Beluga Whale.............. Delphinapterus Beaufort Sea.... -, -, N 39,258 (0.229, N/ UND 104
leucas. A, 1992).
Beluga Whale.................. Delphinapterus Eastern Chukchi. -, -, N 13,305 (0.51, 178 56
leucas. 8,875, 2017).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Carnivora--Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Phocidae (earless
seals):
Bearded Seal.............. Erignathus Beringia........ T, D, Y UND (UND, UND, UND 6,709
barbatus. 2013) \5\.
Ringed Seal............... Pusa hispida.... Arctic.......... T, D, Y UND (UND, UND, UND 6,459
2013) \6\.
Spotted Seal.............. Phoca largha.... Bering.......... -, -, N 461,625 (N/A, 25,394 5,254
423,237, 2013).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy
(<a href="https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/">https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/</a>; Committee on Taxonomy (2022)).
\2\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed
under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality
exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\3\ NMFS marine mammal stock assessment reports online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region</a>. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance.
\4\ These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g.,
commercial fisheries, vessel strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A
CV associated with estimated mortality due to commercial fisheries is presented in some cases.
\5\ Reliable population estimate for the entire stock not available. PBR is based upon the negatively biased Nmin for bearded seals in the U.S. portion
of the stock.
\6\ A reliable population estimate for the entire stock is not available. Using a sub-sample of data collected from the U.S portion of the Bering Sea,
an abundace estimate of 171,418 ringed seals has been calculated, but this estimate does not account for availability bias due to seals in the water
or in the shorefast ice zone at the time of the survey. The actual number of ringed seals in the U.S. portion of the Bering Sea is likely much higher.
Using the Nmin based upon this negatively biased population estimate, the PBR is calculated to be 4,755 seals, although this is also a negatively
biased estimate.
As indicated above, all 6 species (with 7 managed stocks) in table
5 temporally and spatially co-occur with the activity to the degree
that take is reasonably likely to occur. While a harbor porpoise
(Phocoena phocoena) was sighted in the 2017 ASAMM survey (Clarke et
al., 2018) the spatial occurrence of harbor porpoise is such that take
is not expected to occur, and they are not discussed further beyond the
explanation provided here. Harbor porpoise are considered to be
extremely rare in the Beaufort Sea, particularly in the project area
(Megan Ferguson, pers. comm., November 2019).
In addition, the polar bear (Ursus maritimus) may be found in
Prudhoe Bay. However, polar bears are managed by the U.S. Fish and
Wildlife Service and are not considered further in this document.
Gray Whale
During the summer and fall, most whales in the Eastern North
Pacific (ENP) stock feed in the Chukchi, northwestern Bering Sea, and
extreme western Beaufort Sea (west of 155 degrees W) (Muto et al.,
2021, Clarke et al., 2015b). In the fall, ENP gray whales migrate south
to their wintering and calving grounds off the coast of Baja
California, Mexico. While gray whales are occasionally seen in the
Beaufort Sea, their occurrence there is considered extralimital, and
they are rarely seen east of 155 degrees West (Clarke et al., 2015b).
We expect that gray whales could occur within the project area during
the open water season, though occurrence is not likely. We would not
expect gray whales to be present during AGDC's winter/spring
contingency pile driving period.
Bowhead Whale
Bowhead whales belonging to the Western Arctic stock are
distributed seasonally in ice-covered waters of the Arctic and near-
Arctic, generally between 60 degrees and 75 degrees North latitude in
the Western Arctic Basin (Young et al., 2023). The majority of the
Western Arctic stock migrates annually from wintering areas (December
to March) in the central and northwestern Bering Sea, north through the
Chukchi seas (December to April), through the Chukchi Sea and Beaufort
Sea in the spring (April through May), to the eastern Beaufort Sea
where they spend much of the late spring and summer (May through
September). During late summer and fall (September through December),
individuals from this stock migrate back to the Chukchi Sea and then to
the Bering Sea (Young et al., 2023, Citta et al., 2021)
NMFS was petitioned in 2000 to consider designating the nearshore
areas from Utqia[gdot]vik east to the U.S.-Canada border as critical
habitat for the Western Arctic stock. In 2002, NMFS determined that a
critical habitat designation was not necessary as the population was
increasing and approaching the pre-commercial whaling size, there were
no known habitat issues slowing the population growth, and activities
that occurred in the petitioned area were already being managed to
minimize impacts to the population (67 FR 55767).
The annual migration of the Western Arctic stock to and from the
summer feeding grounds in the Beaufort Sea has been monitored by the
Bureau of Ocean Energy Management (BOEM) (and predecessor agencies),
NMFS, and/or industry since 1982 (Treacy et al. 2006; Blackwell et al.
2007; Ireland et al. 2009; Reiser et al. 2011; Bisson et al. 2013;
Clarke et al. 2014, 2020; Brower et al. 2022a, 2022b). Survey data
indicate that the fall migration off northern Alaska occurs primarily
over the continental shelf, generally 12-37 mi (19-60 km) offshore, in
waters 66-197 ft (11-60 m deep (Moore et al. 1989; Moore and Reeves
1993; Monnett and
[[Page 16608]]
Treacy 2005; Treacy et al. 2006). Waters less than 15 ft. (4.5 m) deep
are considered too shallow to support these whales, and in three
decades of aerial surveys by BOEM (ASAMM), no bowhead whale has been
recorded in waters less than 16.4 ft (5 m) deep (Clarke and Ferguson
2010).
Monitoring surveys have been conducted annually since 2001 at the
Northstar offshore oil and gas facility located just offshore of West
Dock. Over 95 percent of the bowheads observed during these fall
surveys occurred more than 13.9 mi (22.3 km) offshore in 2001, 14.2 mi
(22.9 km) in 2002, 8.4 mi (13.5 km) in 2003, and 10.1 mi (16.3 km) in
2004 (Blackwell et al. 2007). West Dock extends out from the shoreline
2.7 mi (4.3 km) and is within shallow waters less than 14.2 ft (4.3 m)
deep. The proposed project activities would occur primarily along the
West Dock causeway in an area developed for oil and gas with existing
vessel traffic. While a small number of bowhead whales have been seen
or heard offshore near Prudhoe Bay in late August (LGL and Greenridge
1996; Greene et al. 1999; Blackwell et al. 2007; Goetz et al. 2008),
bowheads are not likely to occur in the immediate vicinity of the
proposed activities.
Clarke et al. (2023) identify and score biologically important
areas (BIAs) in the Arctic, including areas of importance for
migration, reproduction, and feeding. However, none of these BIAs
overlap with the Level B harassment zones of the project. For example,
some of the feeding areas lie just north of the project area, the
spring (April-May) migratory corridor BIAs for bowheads are far
offshore from the Level B harassment zones for the project, and the
fall (August-October) migratory corridor BIAs are further inshore and
closer to the project site.
In summary, we expect that whales could occur within the project
area during the open water season. We would not expect bowhead whales
to be present during AGDC's winter/spring contingency pile driving
period.
Beluga Whale
Individuals of both the Beaufort Sea stock and the Eastern Chukchi
stock of beluga whale occur in the waters around the project area.
Beluga whales from the two stocks migrate between the Bering and
Beaufort Seas and are closely associated with open leads and polynyas.
The Beaufort Sea stock departs the Bering Sea in early spring,
migrating through the Chukchi Sea and into the Canadian Beaufort Sea
where they spend the summer and most of the fall, returning to the
Bering Sea in the late fall. The Eastern Chukchi stock remains in the
Bering Sea slightly longer, departing in the late spring and early
summer for the Chukchi Sea and western Beaufort Sea where they spend
the summer before returning to the Bering Sea in the fall (Muto et al.,
2021).
O'Corry-Crowe et al. (2018) studied genetic marker sets in 1,647
beluga whales. The data set was from over 20 years and encompassed all
of the whales' major coastal summering regions in the Pacific Ocean.
The genetic marker analysis of the migrating whales revealed that while
both the wintering and summering areas of the eastern Chukchi Sea and
eastern Beaufort Sea subpopulations may overlap, the timing of spring
migration differs such that the whales hunted at coastal sites in
Chukotka, the Bering Strait (i.e., Diomede), and northwest Alaska
(i.e., Point Hope) in the spring and off of Alaska's Beaufort Sea coast
in summer were predominantly from the eastern Beaufort Sea population.
Earlier genetic investigations and recent telemetry studies show that
the spring migration of eastern Beaufort whales occurs earlier and
through denser sea ice than eastern Chukchi Sea belugas. The discovery
that a few individual whales found at some of these spring locations
had a higher likelihood of having eastern Chukchi Sea ancestry or being
of mixed-ancestry, indicates that the Bering Strait region is also an
area where the stocks mix in spring. Citta et al. (2017) also observed
that tagged eastern Beaufort Sea whales migrated north in the spring
through the Bering Strait earlier than the eastern Chukchi belugas, so
they had to pass through the latter's primary wintering area.
Therefore, the Eastern Chukchi stock is unlikely to be present in the
action area at any time in general, particularly during summer and
fall, when most beluga takes would be anticipated for this project.
However, we conservatively assume that beluga whale takes during AGDC's
project could occur to either stock.
Most belugas recorded during aerial surveys conducted in the
Alaskan Beaufort Sea in the last two decades were found over 40 mi (65
km) from shore (Miller et al. 1999; Funk et al. 2008; Christie et al.
2010; Clarke and Ferguson 2010; Brandon et al. 2011). ASAMM 2016
surveys reported belugas along the continental slope with few sightings
nearshore in the western Beaufort Sea, and Clarke et al. (2017)
reported that distribution was similar to that documented in previous
years with light sea ice cover.
Surveys have recorded belugas close to shore and in the vicinity of
the activity area. Green and Negri (2005) reported small beluga groups
nearshore Cape Lonely (August 26) and in Smith Bay (September 4). Funk
et al. (2008) reported a group just offshore of the barrier islands
near Simpson Lagoon. Aerts et al. (2008) reported summer sightings of
three groups of eight animals inside the barrier islands near Prudhoe
Bay; and Lomac-MacNair (2014) recorded 15 beluga whales offshore of
Prudhoe Bay between July and August. While it is possible for belugas
to occur in the project area, nearshore sightings are unlikely.
Whales from both the Beaufort Sea and eastern Chukchi Sea stocks
overwinter in the Bering Sea. Belugas of the eastern Chukchi may winter
in offshore, although relatively shallow, waters of the western Bering
Sea (Richard et al., 2001), and the Beaufort Sea stock may winter in
more nearshore waters of the northern Bering Sea (R. Suydam, pers.
comm. 2012).
Clarke et al. (2023) designated feeding and migratory BIAs for
Beaufort Sea beluga whales, however, none of these BIAs overlap the
project area. The migratory corridors are far offshore from the project
area, while the West Beaufort North Chukchi feeding BIA lies just to
the north of the project area and extends from Cape Bathurt, Canada in
the east to north of Wrangel Island, Russia in the west. In summary, we
expect that beluga whales from either the Beaufort or Chukchi Sea stock
may occur within the project area during the open water season. We
would not expect belugas to be present during AGDC's winter/spring
contingency pile driving period.
Bearded Seal
The Beringia stock of bearded seals occur seasonally in the shallow
shelf waters of the Beaufort, Chukchi, and Bering Seas (Cameron et al.,
2010). Bearded seals are closely associated with ice and their
migration coincides with the sea ice retreat and advancement. Some
seals are found in the Beaufort Sea year-round; however, most prefer to
winter in the Bering Sea and summer in areas with high ice coverage
(70-90 percent) in the Chukchi and Beaufort seas (Simpkins et al.,
2003, Bengtson et al., 2005).
Aerial surveys conducted in the Beaufort Sea indicated that bearded
seals preferred water depths between 82-246 ft (25-75 m) and areas of
open ice cover (Cameron et al. 2010). ASAMM commonly observes bearded
seals offshore in the Beaufort Sea; however, no sightings have been
observed in the West Dock activity area. Based on bearded seal water
depth and ice coverage preferences, survey
[[Page 16609]]
observations in the Prudhoe Bay region, and the normal level of ongoing
industrial activity in the project area, only very small numbers of
bearded seals are expected near the project area.
Critical habitat for the Beringia DPS of the bearded seal was
designated in May 2022 (87 FR 19180). Essential features for
conservation designated by NMFS include (1) sea ice habitat suitable
for whelping and nursing, which is defined as areas with waters 200 m
or less in depth containing pack ice of at least 25 percent
concentration and providing bearded seal access to those waters from
the ice, (2) sea ice habitat suitable as a platform for molting, which
is defined as areas with waters 200 m or less in depth containing pack
ice of at least 15 percent concentration and providing bearded seals
access to those waters from the ice., and (3) primary prey resources to
support bearded seals: waters 200 m or less in depth containing benthic
organisms, including epifaunal and infaunal invertebrates, and demersal
fishes. This critical habitat is designated in specific areas of the
Bering, Chukchi, and Beaufort Seas. The Beaufort Sea section of the
critical habitat is relatively narrow band that lies to the north of
the project area and does not overlap with the project area.
Notwithstanding an earlier court decision vacating NMFS's critical
habitat designation, the underlying information regarding the
importance of the area and associated features to bearded seals and
their habitat remains relevant to the discussion here.
In summary, bearded seals may occur in the project area during the
open water season. Bearded seals could potentially occur in the project
area during AGDC's winter/spring contingency period; however, we would
expect very few, if any, bearded seals to be present during this time.
Ringed Seal
Ringed seals have a circumpolar distribution and are found in all
seasonally ice-covered seas of the Northern Hemisphere (Muto et al.,
2021). Ringed seals rely on the sea ice for key life history functions
and remain associated with the ice most of the year. They are well
adapted to inhabiting both shorefast and pack ice, and diminishing sea
ice and snow resulting from climate change is the primary concern for
this population. The ice provides a platform for pupping and nursing in
late winter and early spring, for molting in late spring to early
summer, and for resting during other times of the year. When sea ice is
at its maximal extent during the winter and early spring in Alaska
waters, ringed seal numbers are high in the northern Bering Sea, and
throughout the Chukchi and Beaufort Seas. The species is generally not
abundant south of Norton Sound, but animals have occurred as far south
as Bristol Bay in years of extensive ice coverage (Muto et al., 2021).
Seasonal movements have not been thoroughly documented; however,
most ringed seals that overwinter in the Bering and Chukchi seas are
thought to migrate north as the ice retreats in the spring. During the
summer, ringed seals feed in the pack ice of the northern Chukchi and
Beaufort seas, and in nearshore ice remnants of the Beaufort Sea. As
the ice advances with freeze-up in the fall, many seals move west and
south and disperse throughout the Chukchi and Bering seas while some
remain in the Beaufort Sea (Muto et al., 2021).
Critical habitat for the ringed seal was designated in May 2022 and
includes marine waters within one specific area in the Bering, Chukchi,
and Beaufort Seas (87 FR 19232, April 1, 2022). Essential features
established by NMFS for conservation of ringed seals are (1) snow-
covered sea ice habitat suitable for the formation and maintenance of
subnivean birth lairs used for sheltering pups during whelping and
nursing, which is defined as waters 3 m (9.8 ft) or more in depth
(relative to MLLW) containing areas of seasonal land-fast (shore-fast)
ice or dense, stable pack ice, that have undergone deformation and
contain snowdrifts of sufficient depth to form and maintain birth lairs
(typically at least 54 cm (21.3 in) deep); (2) sea ice habitat suitable
as a platform for basking and molting, which is defined as areas
containing sea ice of 15 percent or more concentration in waters 3 m
(9.8 ft) or more in depth (relative to MLLW); and (3) primary prey
resources to support Arctic ringed seals, which are defined to be
small, often schooling, fishes, in particular Arctic cod (Boreogadus
saida), saffron cod (Eleginus gracilis), and rainbow smelt (Osmerus
dentex); and small crustaceans, in particular, shrimps and amphipods.
The project area overlaps a very small portion of this large critical
habitat area. Notwithstanding an earlier court decision vacating NMFS's
critical habitat designation, the underlying information regarding the
importance of the area and associated features to ringed seals and
their habitat remains relevant to the discussion here.
Historically, ringed seal occurrence in or near the activity area
has been minimal, and large concentrations of seals are not expected
near West Dock during project operations. However, ringed seals may
occur in the project area during the open-water season or during AGDC's
winter/spring contingency period.
Spotted Seal
The Bering stock of the spotted seal is found along the continental
shelf of the Bering, Chukchi, and Beaufort Seas (Muto et al., 2020).
During the late fall through spring, when seals are hauled out on sea
ice, whelping, nursing, breeding, and molting occurs. After the sea ice
has melted, most spotted seals haul out on land in the summer and fall
(Boveng et al., 2009). Pupping occurs along the Bering Sea ice front
during March and April, followed by mating and molting in May and June
(Quakenbush, 1988). During the summer, the seals follow the retreating
ice north into the Chukchi and Beaufort seas, and haul out on lagoon
and river delta beaches during the open water period. The migration
back to the Bering Sea wintering grounds begins with sea ice
advancement, usually in October (Lowry et al., 1998).
Spotted seals were recorded during barging activities in the summer
and early fall of 2005 and 2007 between Prudhoe Bay and Cape Simpson
(Green et al., 2007, Green and Negri, 2006). Lomac-MacNair et al.
(2015) observed spotted seals in Prudhoe Bay, including several in the
immediate vicinity of West Dock, while monitoring July-August seismic
activity. Therefore, we expect that spotted seals could be present in
the project area during the summer months. However, spotted seals are
not expected in the area during AGDC's contingency period.
Marine Mammal Hearing
Hearing is the most important sensory modality for marine mammals
underwater, and exposure to anthropogenic sound can have deleterious
effects. To appropriately assess the potential effects of exposure to
sound, it is necessary to understand the frequency ranges marine
mammals are able to hear. Not all marine mammal species have equal
hearing capabilities (e.g., Au and Hastings, 2008, Richardson et al.,
1995, Wartzok and Ketten, 1999). To reflect this, (Southall et al.,
2007, 2019) recommended that marine mammals be divided into hearing
groups based on directly measured (behavioral or auditory evoked
potential techniques) or estimated hearing ranges (behavioral response
data, anatomical modeling, etc.). Generalized hearing ranges were
chosen based on the ~65 decibel (dB) threshold from composite
audiograms, previous analyses in NMFS (2018), and/or data from Southall
et al.
[[Page 16610]]
(2007) and Southall et al. (2019). We note that the names of two
hearing groups and the generalized hearing ranges of all marine mammal
hearing groups have been recently updated (NMFS, 2024) as reflected in
table 6.
Table 6--Marine Mammal Hearing Groups (NMFS, 2024)
------------------------------------------------------------------------
Generalized
Hearing group hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen whales)......... 7 Hz to 36 kHz.
High-frequency (HF) cetaceans (dolphins, toothed 150 Hz to 160
whales, beaked whales, bottlenose whales). kHz.
Very High-frequency (VHF) cetaceans (true porpoises, 200 Hz to 165
Kogia, river dolphins, Cephalorhynchid, kHz.
Lagenorhynchus cruciger & L. australis).
Phocid pinnipeds (PW) (underwater) (true seals)...... 40 Hz to 90 kHz.
Otariid pinnipeds (OW) (underwater) (sea lions and 60 Hz to 68 kHz.
fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
composite (i.e., all species within the group), where individual
species' hearing ranges may not be as broad. Generalized hearing range
chosen based on ~65 dB threshold from composite audiogram, previous
analysis in NMFS 2018, and/or data from Southall et al. 2007; Southall
et al. 2019. Additionally, animals are able to detect very loud sounds
above and below that ``generalized'' hearing range.
For more detail concerning these groups and associated frequency
ranges, please see NMFS (2024) for a review of available information.
Potential Effects of the Specified Activity on Marine Mammals and Their
Habitat
This section provides a discussion of the ways in which components
of the specified activity may impact marine mammals and their habitat.
The Estimated Take of Marine Mammals section later in this document
includes a quantitative analysis of the number of individuals that are
expected to be taken by this activity. The Negligible Impact Analysis
and Determination section considers the content of this section, the
Estimated Take of Marine Mammals section, and the Proposed Mitigation
section, to draw conclusions regarding the likely impacts of these
activities on the reproductive success or survivorship of individuals
and whether those impacts are reasonably expected to, or reasonably
likely to, adversely affect the species or stock through effects on
annual rates of recruitment or survival.
Description of Sound Sources
The marine soundscape is comprised of both ambient and
anthropogenic sounds. Ambient sound is defined as the all-encompassing
sound in a given place and is usually a composite of sound from many
sources both near and far. The sound level of an area is defined by the
total acoustical energy being generated by known and unknown sources.
These sources may include physical (e.g., waves, wind, precipitation,
earthquakes, ice, atmospheric sound), biological (e.g., sounds produced
by marine mammals, fish, and invertebrates), and anthropogenic sound
(e.g., vessels, dredging, aircraft, construction). The sum of the
various natural and anthropogenic sound sources at any given location
and time--which comprise ``ambient'' or ``background'' sound--depends
not only on the source levels (as determined by current weather
conditions and levels of biological and shipping activity) but also on
the ability of sound to propagate through the environment. In turn,
sound propagation is dependent on the spatially and temporally varying
properties of the water column and sea floor, and is frequency-
dependent. As a result of the dependence on a large number of varying
factors, ambient sound levels can be expected to vary widely over both
coarse and fine spatial and temporal scales. Sound levels at a given
frequency and location can vary by 10-20 dB from day to day (Richardson
et al., 1995). The result is that, depending on the source type and its
intensity, sound from the specified activity may be a negligible
addition to the local environment or could form a distinctive signal
that may affect marine mammals.
In-water construction activities associated with the project would
include vibratory pile driving and removal and impact pile driving. The
sounds produced by these activities fall into one of two general sound
types: Impulsive and non-impulsive. Impulsive sounds (e.g., explosions,
gunshots, sonic booms, impact pile driving) are typically transient,
brief (less than one second), broadband, and consist of high peak sound
pressure with rapid rise time and rapid decay (American National
Standards Institute (ANSI), 1986, National Institute for Occupational
Safety and Health (NIOSH), 1998, NMFS, 2024, ANSI, 2005). Non-impulsive
sounds (e.g., aircraft, machinery operations such as drilling or
dredging, vibratory pile driving, and active sonar systems) can be
broadband, narrowband or tonal, brief or prolonged (continuous or
intermittent), and typically do not have the high peak sound pressure
with raid rise/decay time that impulsive sounds do (ANSI, 1995, NIOSH,
1998, NMFS, 2024). The distinction between these two sound types is
important because they have differing potential to cause physical
effects, particularly with regard to hearing (e.g., Ward, 1997,
Southall et al., 2007).
Two types of pile hammers would be used on this project: Impact and
vibratory. Impact hammers operate by repeatedly dropping a heavy piston
onto a pile to drive the pile into the substrate. Sound generated by
impact hammers is characterized by rapid rise times and high peak
levels, a potentially injurious combination (Hastings and Popper,
2005). Vibratory hammers install piles by vibrating them and allowing
the weight of the hammer to push them into the sediment. Vibratory
hammers produce significantly less sound than impact hammers. Peak
sound pressure levels (SPLs) may be 180 dB or greater, but are
generally 10 to 20 dB lower than SPLs generated during impact pile
driving of the same-sized pile (Oestman et al., 2009). Rise time is
slower, reducing the probability and severity of injury, and sound
energy is distributed over a greater amount of time (Nedwell and
Edwards, 2002, Carlson et al., 2005).
The likely or possible impacts of AGDC's proposed activity on
marine mammals could involve both non-
[[Page 16611]]
acoustic and acoustic stressors. Potential non-acoustic stressors could
include the physical presence of the equipment and personnel; however,
any impacts to marine mammals are expected to primarily be acoustic in
nature. Acoustic stressors include effects of heavy equipment operation
during pile installation and removal.
Acoustic Impacts
The introduction of anthropogenic noise into the aquatic
environment from pile driving and removal is the primary means by which
marine mammals may be harassed from AGDC's specified activity. Animals
exposed to natural or anthropogenic sound may experience physical and
psychological effects, ranging in magnitude from none to severe
(Southall et al., 2007, 2019). Exposure to pile driving and removal
noise has the potential to result in auditory threshold shifts (TS) and
behavioral reactions (e.g., avoidance, temporary cessation of foraging
and vocalizing, changes in dive behavior). Exposure to anthropogenic
noise can also lead to non-observable physiological responses such as
an increase in stress hormones. Additional noise in a marine mammal's
habitat can mask acoustic cues used by marine mammals to carry out
daily functions such as communication and predator and prey detection.
The effects of pile driving and removal noise on marine mammals are
dependent on several factors, including, but not limited to, sound type
(e.g., impulsive vs. non-impulsive), the species, age and sex class
(e.g., adult male vs. mom with calf), duration of exposure, the
distance between the pile and the animal, received levels, behavior at
time of exposure, and previous history with exposure (Wartzok et al.,
2004, Southall et al., 2007). Here we discuss physical auditory effects
(TS) followed by behavioral effects and potential impacts on habitat.
NMFS defines a noise-induced TS as a change, usually an increase,
in the threshold of audibility at a specified frequency or portion of
an individual's hearing range above a previously established reference
level (NMFS, 2018). The amount of TS is customarily expressed in dB. TS
can be permanent or temporary. As described by NMFS (2024), there are
numerous factors to consider when examining the consequence of TS,
including, but not limited to, the signal temporal pattern (e.g.,
impulsive or non-impulsive), likelihood an individual would be exposed
for a long enough duration or to a high enough level to induce a TS,
the magnitude of the TS, time to recovery (seconds to minutes or hours
to days), the frequency range of the exposure (i.e., spectral content),
the hearing and vocalization frequency range of the exposed species
relative to the signal's frequency spectrum (i.e., how an animal uses
sound within the frequency band of the signal (e.g, Kastelein et al.,
2014)), and the overlap between the animal and the source (e.g.,
spatial, temporal, and spectral).
Auditory Injury (AUD INJ) and Permanent Threshold Shift (PTS)
NMFS defines AUD INJ as ``damage to the inner ear that can result
in destruction of tissue . . . which may or may not result in PTS''
(NMFS, 2024). NMFS defines PTS as a permanent irreversible increase in
the threshold of audibility at a specified frequency or portion of an
individual's hearing range above a previously established reference
level (NMFS, 2024). PTS does not generally affect more than a limited
frequency range, and an animal that has incurred PTS has incurred some
level of hearing loss at the relevant frequencies; typically, animals
with PTS are not functionally deaf (Au and Hastings, 2008, Finneran,
2016). Available data from humans and other terrestrial mammals
indicate that a 40 dB TS approximates PTS onset (see Ahroon et al.,
1996, Kryter et al., 1966, Miller, 1974, Ward et al., 1958, Ward, 1960,
Ward et al., 1959, Henderson et al., 2008). PTS levels for marine
mammals are estimates, because there are limited empirical data
measuring PTS in marine mammals (e.g., Kastak et al., 2008), largely
due to the fact that, for various ethical reasons, experiments
involving anthropogenic noise exposure at levels inducing PTS are not
typically pursued or authorized (NMFS, 2018).
Temporary Threshold Shift (TTS)
NMFS defines TTS as a temporary, reversible increase in the
threshold of audibility at a specified frequency or portion of an
individual's hearing range above a previously established reference
level (NMFS, 2018). Based on data from cetacean TTS measurements (see
Southall et al., 2007, 2019), a TTS of 6 dB is considered the minimum
TS clearly larger than any day-to-day or session-to-session variation
in a subject's normal hearing ability (Finneran et al., 2000, 2002;
Schlundt et al., 2000,). As described in Finneran (2015), marine mammal
studies have shown the amount of TTS increases with cumulative sound
exposure level (SELcum) in an accelerating fashion: At low exposures
with lower SELcum, the amount of TTS is typically small and the growth
curves have shallow slopes. At exposures with higher SELcum, the growth
curves become steeper and approach linear relationships with the noise
SEL.
Depending on the degree (elevation of threshold in dB), duration
(i.e., recovery time), and frequency range of TTS, and the context in
which it is experienced, TTS can have effects on marine mammals ranging
from discountable to serious (similar to those discussed in auditory
masking, below). For example, a marine mammal may be able to readily
compensate for a brief, relatively small amount of TTS in a non-
critical frequency range that takes place during a time when the animal
is traveling through the open ocean, where ambient noise is lower and
there are not as many competing sounds present. Alternatively, a larger
amount and longer duration of TTS sustained during time when
communication is critical for successful mother/calf interactions could
have more serious impacts. We note that reduced hearing sensitivity as
a simple function of aging has been observed in marine mammals, as well
as humans and other taxa (Southall et al., 2007), so we can infer that
strategies exist for coping with this condition to some degree, though
likely not without cost.
Many studies have examined noise-induced hearing loss in marine
mammals (see Finneran (2015) and Southall et al. (2019) for summaries).
TTS is the mildest form of hearing impairment that can occur during
exposure to sound (Kryter, 2013). While experiencing TTS, the hearing
threshold rises, and a sound must be at a higher level in order to be
heard. In terrestrial and marine mammals, TTS can last from minutes or
hours to days (in cases of strong TTS). In many cases, hearing
sensitivity recovers rapidly after exposure to the sound ends. For
cetaceans, published data on the onset of TTS are limited to captive
bottlenose dolphin (Tursiops truncatus), beluga whale, harbor porpoise,
and Yangtze finless porpoise (Neophocoena asiaeorientalis) (Southall et
al., 2019). For pinnipeds in water, measurements of TTS are limited to
harbor seals, elephant seals (Mirounga angustirostris), bearded seals
(Erignathus barbatus) and California sea lions (Zalophus californianus)
(Kastak et al., 1999, 2007; Kastelein et al., 2019b, 2019c, 2021,
2022a, 2022b; Reichmuth et al., 2019; Sills et al., 2020). TTS was not
observed in spotted (Phoca largha) and ringed (Pusa hispida) seals
exposed to single airgun impulse sounds at levels matching previous
predictions of TTS onset (Reichmuth et al., 2016). These studies
examine hearing thresholds
[[Page 16612]]
measured in marine mammals before and after exposure to intense or
long-duration sound exposures. The difference between the pre-exposure
and post-exposure thresholds can be used to determine the amount of
threshold shift at various post-exposure times.
The amount and onset of TTS depends on the exposure frequency.
Sounds at low frequencies, well below the region of best sensitivity
for a species or hearing group, are less hazardous than those at higher
frequencies, near the region of best sensitivity (Finneran and
Schlundt, 2013). At low frequencies, onset-TTS exposure levels are
higher compared to those in the region of best sensitivity (i.e., a low
frequency noise would need to be louder to cause TTS onset when TTS
exposure level is higher), as shown for harbor porpoises and harbor
seals (Kastelein et al., 2020a, 2020b, Kastelein et al., 2019a, 2019b).
Note that in general, harbor seals and harbor porpoises have a lower
TTS onset than other measured pinniped or cetacean species (Finneran,
2015). In addition, TTS can accumulate across multiple exposures, but
the resulting TTS will be less than the TTS from a single, continuous
exposure with the same SEL (Finneran et al., 2010, Kastelein et al.,
2015, Kastelein et al., 2014, Mooney et al., 2009). This means that TTS
predictions based on the total, cumulative SEL will overestimate the
amount of TTS from intermittent exposures such as sonars and impulsive
sources.
Nachtigall et al. (2018) describe measurements of hearing
sensitivity of multiple odontocete species (bottlenose dolphin, harbor
porpoise, beluga, and false killer whale (Pseudorca crassidens)) when a
relatively loud sound was preceded by a warning sound. These captive
animals were shown to reduce hearing sensitivity when warned of an
impending intense sound. Based on these experimental observations of
captive animals, the authors suggest that wild animals may dampen their
hearing during prolonged exposures or if conditioned to anticipate
intense sounds. Another study showed that echolocating animals
(including odontocetes) might have anatomical specializations that
might allow for conditioned hearing reduction and filtering of low-
frequency ambient noise, including increased stiffness and control of
middle ear structures and placement of inner ear structures (Ketten et
al., 2021). Data available on noise-induced hearing loss for mysticetes
are currently lacking (NMFS, 2018). Additionally, the existing marine
mammal TTS data come from a limited number of individuals within these
species.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals, and there is no PTS data for cetaceans. However,
such relationships are assumed to be similar to those in humans and
other terrestrial mammals. PTS typically occurs at exposure levels at
least several dB above that inducing mild TTS (e.g., a 40-dB threshold
shift approximates PTS onset (Kryter et al., 1966; Miller, 1974), while
a 6-dB threshold shift approximates TTS onset (Southall et al., 2007,
2019). Based on data from terrestrial mammals, a precautionary
assumption is that the PTS thresholds for impulsive sounds (such as
impact pile driving pulses as received close to the source) are at
least 6 dB higher than the TTS threshold on a peak-pressure basis, and
PTS cumulative sound exposure level thresholds are 15 to 20 dB higher
than TTS cumulative sound exposure level thresholds (Southall et al.,
2007, 2019). Given the higher level of sound or longer exposure
duration necessary to cause PTS as compared with TTS, it is
considerably less likely that PTS could occur.
This project would install piles using vibratory and impact pile
driving. There would likely be pauses in activities producing the sound
during each day. Given these pauses and that many marine mammals are
likely moving through the ensonified area and not remaining for
extended periods of time, the potential for TS declines.
Behavioral Harassment
Exposure to noise from pile driving and removal also has the
potential to behaviorally disturb marine mammals to a level that rises
to the definition of harassment under the MMPA. Generally speaking,
NMFS considers a behavioral disturbance that rises to the level of
harassment under the MMPA a non-minor response--in other words, not
every response qualifies as behavioral disturbance, and for responses
that do, those of a higher level, or accrued across a longer duration,
have the potential to affect foraging, reproduction, or survival.
Behavioral disturbance may include a variety of effects, including
subtle changes in behavior (e.g., minor or brief avoidance of an area
or changes in vocalizations), more conspicuous changes in similar
behavioral activities, and more sustained and/or potentially severe
reactions, such as displacement from or abandonment of high-quality
habitat. Behavioral responses may include changing durations of
surfacing and dives; changing direction and/or speed; reducing/
increasing vocal activities; changing/cessation of certain behavioral
activities (such as socializing or feeding); eliciting a visible
startle response or aggressive behavior (such as tail/fin slapping or
jaw clapping); avoidance of areas where sound sources are located.
Pinnipeds may increase their haul out time, possibly to avoid in-water
disturbance (Thorson and Reyff, 2006).
Behavioral responses to sound are highly variable and context-
specific and any reactions depend on numerous intrinsic and extrinsic
factors (e.g., species, state of maturity, experience, current
activity, reproductive state, auditory sensitivity, time of day), as
well as the interplay between factors (e.g., Richardson et al., 1995;
Wartzok et al., 2004; Southall et al., 2007, 2019; Weilgart, 2007;
Archer et al., 2010, Erbe et al., 2019). Individuals (of different age,
gender, reproductive status, etc.) among most populations will have
variable hearing capabilities, and differing behavioral sensitivities
to sounds that will be affected by prior conditioning, experience, and
current activities of those individuals. Southall et al. (2007) and
Southall et al. (2021) have developed and subsequently refined methods
developed to categorize and assess the severity of acute behavioral
responses, considering impacts to individuals that may consequently
impact populations. Often, specific acoustic features of the sound and
contextual variables (i.e., proximity, duration, or recurrence of the
sound or the current behavior that the marine mammal is engaged in or
its prior experience), as well as entirely separate factors, such as
the physical presence of a nearby vessel, may be more relevant to the
animal's response than the received level alone. In general, pinnipeds
seem more tolerant of, or at least habituate more quickly to,
potentially disturbing underwater sound than do cetaceans and generally
seem to be less responsive to exposure to industrial sound than most
cetaceans. Please see appendices B and C of Southall et al. (2007) and
Gomez et al. (2016) for reviews of studies involving marine mammal
behavioral responses to sound.
Habituation can occur when an animal's response to a stimulus wanes
with repeated exposure, usually in the absence of unpleasant associated
events (Wartzok et al., 2004). Animals are most likely to habituate to
sounds that are predictable and unvarying. It is important to note that
habituation is appropriately considered as a ``progressive reduction in
response to stimuli that are perceived as neither
[[Page 16613]]
aversive nor beneficial,'' rather than as, more generally, moderation
in response to human disturbance (Bejder et al., 2009). The opposite
process is sensitization, when an unpleasant experience leads to
subsequent responses, often in the form of avoidance, at a lower level
of exposure.
As noted above, behavioral state may affect the type of response.
For example, animals that are resting may show greater behavioral
change in response to disturbing sound levels than animals that are
highly motivated to remain in an area for feeding (Richardson et al.,
1995; Wartzok et al., 2004; National Research Council (NRC), 2005).
Controlled experiments with captive marine mammals have showed
pronounced behavioral reactions, including avoidance of loud sound
sources (Ridgway et al., 1997; Finneran et al., 2003). Observed
responses of wild marine mammals to loud pulsed sound sources (e.g.,
seismic airguns) have been varied but often consist of avoidance
behavior or other behavioral changes (Richardson et al., 1995; Morton
and Symonds, 2002; Nowacek et al., 2007).
Available studies show wide variation in response to underwater
sound; therefore, it is difficult to predict specifically how any given
sound in a particular instance might affect marine mammals perceiving
the signal (e.g., Erbe et al., 2019). If a marine mammal does react
briefly to an underwater sound by changing its behavior or moving a
small distance, the impacts of the change are unlikely to be
significant to the individual, let alone the stock or population.
However, if a sound source displaces marine mammals from an important
feeding or breeding area for a prolonged period, impacts on individuals
and populations could be significant (Lusseau and Bejder, 2007,
Weilgart, 2007, National Research Council, 2005). However, there are
broad categories of potential response, which we describe in greater
detail here, that include alteration of dive behavior, alteration of
foraging behavior, effects to breathing, interference with or
alteration of vocalization, avoidance, and flight.
Changes in dive behavior can vary widely and may consist of
increased or decreased dive times and surface intervals as well as
changes in the rates of ascent and descent during a dive (e.g., Frankel
and Clark, 2000; Costa et al., 2003; Ng and Leung, 2003; Nowacek et
al., 2004; Goldbogen et al., 2013a, 2013b, Blair et al., 2016).
Variations in dive behavior may reflect interruptions in biologically
significant activities (e.g., foraging) or they may be of little
biological significance. The impact of an alteration to dive behavior
resulting from an acoustic exposure depends on what the animal is doing
at the time of the exposure and the type and magnitude of the response.
Disruption of feeding behavior can be difficult to correlate with
anthropogenic sound exposure, so it is usually inferred by observed
displacement from known foraging areas, the appearance of secondary
indicators (e.g., bubble nets or sediment plumes), or changes in dive
behavior. However, acoustic and movement bio-logging tools have been
used in some cases, to infer responses of feeding to anthropogenic
noise. For example, Blair et al. (2016) reported significant effects on
humpback whale foraging behavior in Stellwagen Bank in response to ship
noise including slower descent rates, and fewer side-rolling events per
dive with increasing ship nose. In addition, Wisniewska et al. (2018)
reported that tagged harbor porpoises demonstrated fewer prey capture
attempts when encountering occasional high-noise levels resulting from
vessel noise as well as more vigorous fluking, interrupted foraging,
and cessation of echolocation signals observed in response to some
high-noise vessel passes.
In response to playbacks of vibratory pile driving sounds, captive
bottlenose dolphins showed changes in target detection and number of
clicks used for a trained echolocation task (Branstetter et al. 2018).
Similarly, harbor porpoises trained to collect fish during playback of
impact pile driving sounds also showed potential changes in behavior
and task success, though individual differences were prevalent
(Kastelein et al. 2019d). As for other types of behavioral response,
the frequency, duration, and temporal pattern of signal presentation,
as well as differences in species sensitivity, are likely contributing
factors to differences in response in any given circumstance (e.g.,
Croll et al., 2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko
et al., 2007). A determination of whether foraging disruptions incur
fitness consequences would require information on or estimates of the
energetic requirements of the affected individuals and the
relationships among prey availability, foraging effort and success, and
the life history stage(s) of the animal.
Variations in respiration naturally vary with different behaviors
and alterations to breathing rate as a function of acoustic exposure
can be expected to co-occur with other behavioral reactions, such as a
flight response or an alteration in diving. However, respiration rates
in and of themselves may be representative of annoyance or an acute
stress response. Various studies have shown that respiration rates may
either be unaffected or could increase, depending on the species and
signal characteristics, again highlighting the importance in
understanding species differences in the tolerance of underwater noise
when determining the potential for impacts resulting from anthropogenic
sound exposure (e.g., Kastelein et al., 2001, 2005, 2006; Gailey et
al., 2007). For example, harbor porpoise' respiration rate increased in
response to pile driving sounds at and above a received broadband SPL
of 136 dB (zero-peak SPL: 151 dB re 1 [mu]Pa; SEL of a single strike:
127 dB re 1 [mu]Pa\2\ -s) (Kastelein et al., 2013).
Avoidance is the displacement of an individual from an area or
migration path as a result of the presence of a sound or other
stressors, and is one of the most obvious manifestations of disturbance
in marine mammals (Richardson et al., 1995). For example, gray whales
are known to change direction--deflecting from customary migratory
paths--in order to avoid noise from seismic surveys (Malme et al.,
1984). In response to construction noise from offshore wind farms,
harbor porpoises and harbor seals have demonstrated avoidance on the
scale of hours to weeks (Brandt et al., 2018; Russell et al., 2016).
Avoidance may be short-term, with animals returning to the area once
the noise has ceased (e.g., Bowles et al., 1994; Goold, 1996; Stone et
al., 2000; Morton and Symonds, 2002; Gailey et al., 2007). Longer-term
displacement is possible, however, which may lead to changes in
abundance or distribution patterns of the affected species in the
affected region if habituation to the presence of the sound does not
occur (e.g., Blackwell et al., 2004; Bejder et al., 2006; Teilmann et
al., 2006).
A flight response is a dramatic change in normal movement to a
directed and rapid movement away from the perceived location of a sound
source. The flight response differs from other avoidance responses in
the intensity of the response (e.g., directed movement, rate of
travel). Relatively little information on flight responses of marine
mammals to anthropogenic signals exist, although observations of flight
responses to the presence of predators have occurred (Connor and
Heithaus, 1996; Bowers et al., 2018). The result of a flight response
could range from brief, temporary exertion and displacement from the
area where the signal provokes flight to, in extreme cases, marine
mammal strandings (England et al., 2001). However, it should be noted
that response to a
[[Page 16614]]
perceived predator does not necessarily invoke flight (Ford and Reeves,
2008), and whether individuals are solitary or in groups may influence
the response.
Behavioral disturbance can also impact marine mammals in more
subtle ways. Increased vigilance may result in costs related to
diversion of focus and attention (i.e., when a response consists of
increased vigilance, it may come at the cost of decreased attention to
other critical behaviors such as foraging or resting). These effects
have generally not been demonstrated for marine mammals, but studies
involving fishes and terrestrial animals have shown that increased
vigilance may substantially reduce feeding rates (e.g., Beauchamp and
Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). In
addition, chronic disturbance can cause population declines through
reduction of fitness (e.g., decline in body condition) and subsequent
reduction in reproductive success, survival, or both (e.g., Harrington
and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). However,
Ridgway et al. (2006) reported that increased vigilance in bottlenose
dolphins exposed to sound over a 5-day period did not cause any sleep
deprivation or stress effects.
Many animals perform vital functions, such as feeding, resting,
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption
of such functions resulting from reactions to stressors such as sound
exposure are more likely to be significant if they last more than one
diel cycle or recur on subsequent days (Southall et al., 2007).
Consequently, a behavioral response lasting less than 1 day and not
recurring on subsequent days is not considered particularly severe
unless it could directly affect reproduction or survival (Southall et
al., 2007). Note that there is a difference between multi-day
substantive (i.e., meaningful) behavioral reactions and multi-day
anthropogenic activities. For example, just because an activity lasts
for multiple days does not necessarily mean that individual animals are
either exposed to activity-related stressors for multiple days or,
further, exposed in a manner resulting in sustained multi-day
substantive behavioral responses.
Stress Response
An animal's perception of a threat may be sufficient to trigger
stress responses consisting of some combination of behavioral
responses, autonomic nervous system responses, neuroendocrine
responses, or immune responses (e.g., Moberg, 2000, Selye, 1950). In
many cases, an animal's first and sometimes most economical (in terms
of energetic costs) response is behavioral avoidance of the potential
stressor. Autonomic nervous system responses to stress typically
involve changes in heart rate, blood pressure, and gastrointestinal
activity. These responses have a relatively short duration and may or
may not have a significant long-term effect on an animal's fitness.
Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that
are affected by stress--including immune competence, reproduction,
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been
implicated in failed reproduction, altered metabolism, reduced immune
competence, and behavioral disturbance (e.g., Moberg, 1987, Blecha,
2000). Increases in the circulation of glucocorticoids are also equated
with stress (Romano et al., 2004).
The primary distinction between stress (which is adaptive and does
not normally place an animal at risk) and ``distress'' is the cost of
the response. During a stress response, an animal uses glycogen stores
that can be quickly replenished once the stress is alleviated. In such
circumstances, the cost of the stress response would not pose serious
fitness consequences. However, when an animal does not have sufficient
energy reserves to satisfy the energetic costs of a stress response,
energy resources must be diverted from other functions. This state of
distress will last until the animal replenishes its energetic reserves
sufficient to restore normal function.
Relationships between these physiological mechanisms, animal
behavior, and the costs of stress responses are well-studied through
controlled experiments for both laboratory and free-ranging animals
(e.g., Holberton et al., 1996, Hood et al., 1998, Jessop et al., 2003,
Krausman et al., 2004, Lankford et al., 2005). Stress responses due to
exposure to anthropogenic sounds or other stressors and their effects
on marine mammals have also been reviewed (Romano et al., 2002b, Fair
and Becker, 2000) and, more rarely, studied in wild populations (e.g.,
Romano et al., 2002a). For example, Rolland et al. (2012) found that
noise reduction from reduced vessel traffic in the Bay of Fundy was
associated with decreased stress in North Atlantic right whales. In
addition, Lemos et al. (2022) observed a correlation between higher
levels of fecal glucocorticoid metabolite concentrations (indicative of
a stress response) and vessel traffic in gray whales. These and other
studies lead to a reasonable expectation that some marine mammals will
experience physiological stress responses upon exposure to acoustic
stressors and that it is possible that some of these would be
classified as ``distress.'' In addition, any animal experiencing TTS
would likely also experience stress responses (National Research
Council, 2005), however distress is an unlikely result of these
projects based on observations of marine mammals during previous,
similar projects in the area.
Masking
Sound can disrupt behavior through masking, or interfering with, an
animal's ability to detect, recognize, or discriminate between acoustic
signals of interest (e.g., those used for intraspecific communication
and social interactions, prey detection, predator avoidance,
navigation) (Richardson et al., 1995). Masking occurs when the receipt
of a sound is interfered with by another coincident sound at similar
frequencies and at similar or higher intensity, and may occur whether
the sound is natural (e.g., snapping shrimp, wind, waves,
precipitation) or anthropogenic (e.g., pile driving, shipping, sonar,
seismic exploration) in origin. The ability of a noise source to mask
biologically important sounds depends on the characteristics of both
the noise source and the signal of interest (e.g., signal-to-noise
ratio, temporal variability, direction), in relation to each other and
to an animal's hearing abilities (e.g., sensitivity, frequency range,
critical ratios, frequency discrimination, directional discrimination,
age or TTS hearing loss), and existing ambient noise and propagation
conditions. Masking of natural sounds can result when human activities
produce high levels of background sound at frequencies important to
marine mammals. Conversely, if the background level of underwater sound
is high (e.g. on a day with strong wind and high waves), an
anthropogenic sound source would not be detectable as far away as would
be possible under quieter conditions and would itself be masked.
Airborne Acoustic Effects
There are no known pinniped haulouts near the project location.
Therefore, it is unlikely that pinnipeds would be taken by exposure to
in-air noise during the open water season. While there is a chance that
a pinniped could swim by the construction site with its head out of the
water during on-land construction such as pile driving, and be taken by
Level B harassment, the
[[Page 16615]]
likelihood of that occurring is so low as to be discountable.
Additionally, there is a small chance that an individual animal could
haul out in an area that is not a normal haulout site, but the chance
of that occurring is also discountable. Further, if AGDC must work
during their contingency period, they will begin pile driving prior to
March 1 (see Proposed Mitigation Measures), so we would not expect
ringed seals to build their lairs close enough to the project site to
be taken by in-air sound during the contingency period, other than
potentially by building their lair in an alternate location due to
construction noise.
While the presence of non-acoustic stressors could affect
pinnipeds, a pinniped in the water that is close enough to be disturbed
by a non-acoustic (i.e., visual) stressor is likely to have already
been counted as taken due to in-water noise from activities occurring
in the water. As noted above, while there is a chance that a pinniped
could swim by the construction site with its head out of the water, or
haul out in an area that is not a normal haulout site, and be taken by
Level B harassment due to non-acoustic stressors, it is so unlikely as
to be considered discountable. Therefore, while a pinniped could be
taken due to disturbance from in-air or non-acoustic stressors during
construction, we would expect very few of these takes, if any. Further,
any such takes would be within the margin of error in the take estimate
and their potential effects fully considered in the analysis.
In-air stressors and non-acoustic stressors, such as the physical
presence of land-based equipment and personnel, are not expected to
affect cetaceans, given that cetaceans are present only in the water at
some distance from shore and the activity and remain under water the
majority of the time, and therefore are not expected to be exposed to
these stressors. While AGDC may use barges to stage land-based
equipment during some activities, these barges would be stationary, and
at the project site where the water is extremely shallow (less than
14.2 ft. (4.3 m) at West Dock); therefore, we do not expect bowhead
whales to occur close enough to the barge or equipment to be disturbed
by its presence. Given the rare occurrence of beluga whales within the
barrier islands, as evidenced by Block 1a ASAMM survey data, we expect
the potential for beluga whales to be disturbed by barges to be so low
as to be discountable. (Block 1a encompasses the area between the
shoreline and the barrier islands, including Prudhoe Bay. ASAMM reports
include just one beluga whale was observed in survey Block 1a in 2018.)
We also do not expect gray whales to occur close enough to the barge or
equipment to be disturbed by its presence, as gray whales rarely occur
within the barrier islands, as also evidenced by Block 1A ASAMM
surveys.
Given the factors above, we do not believe that authorization of
incidental take resulting from airborne sound is warranted, and
airborne sound is not discussed further.
Marine Mammal Habitat Effects
AGDC's construction activities could have localized, temporary
impacts on marine mammal habitat by increasing in-water sound pressure
levels, disturbing benthic habitat, and increased turbidity.
Construction activities are of short duration and would likely have
temporary impacts on marine mammal habitat through increases in
underwater sound. Increased noise levels may affect acoustic habitat
(see masking discussion above) and adversely affect marine mammal prey
in the vicinity of the project area (see discussion below). During
vibratory pile driving, elevated levels of underwater noise would
ensonify the area where both fish and mammals may occur and could
affect foraging success. Additionally, marine mammals may avoid the
area during construction; any displacement due to noise is expected to
be temporary and is not expected to result in long-term effects to the
individuals or populations.
Additionally, winter construction activities, including through-ice
surveying and through-ice grading could potentially disturb ice
habitat, as ice will be cut and removed to facilitate grading the
seafloor. Work is expected to begin immediately after the ice becomes
grounded, which typically occurs in the work area on or before February
1. These activities could affect available ringed seal habitat,
however, ringed seal density is low in areas with water depths less
than 10 ft (3 meters) (Moulton et al., 2005), and the grounded ice
conditions suitable for construction activities are not preferred
habitat for ringed seals. Additionally, winter construction activities
would begin prior to March 1, further reducing the potential for
disturbance to ringed seal birth lairs.
In-Water Construction Effects on Potential Foraging Habitat
Potential prey (i.e., fish) may avoid the immediate area due to the
temporary loss of this foraging habitat during pile driving activities.
The duration of fish avoidance of this area after pile driving stops is
unknown, but we anticipate a rapid return to normal recruitment,
distribution and behavior. Any behavioral avoidance by fish of the
disturbed area would still leave large areas of fish and marine mammal
foraging habitat in the nearby vicinity.
Additionally, a small amount of seafloor habitat will be disturbed
as a result of pile driving, gravel deposition, screeding, and other
seabed preparation. Benthic infauna abundance and diversity are very
low in this area, likely due to the shallow water depth (<16 ft (5 m)),
run-off from adjacent rivers, and ice related stress (Carey et al.,
1984). Freezing and thawing sea ice and river runoff during the summer
melting season significantly affect the coastal water mass
characteristics and decrease the salinity. River outflow and coastal
erosion also transport significant amounts of suspended sediments. Sea
ice pressure ridges scour and gouge the seafloor and move sediments,
creating natural, seasonal disruptions of the seafloor. These factors
result in a less than favorable habitat for benthic organisms in the
activity area. Bottom disturbance is a natural and frequent occurrence
in this nearshore region resulting in benthic communities with patchy
distributions (Carey et al., 1984). Given the low nearshore densities
of benthic prey items, we do not expect screeding, pile driving, or
related construction activities to have significant impacts on marine
mammal foraging habitat. Additionally, installation of the new DH4 and
barge bridge abutments will cover the associated seafloor; however, the
total seafloor area affected from installing the structures is a very
small area compared to the vast foraging area available to marine
mammals in the Beaufort Sea, particularly given the limited prey
expected to be in the West Dock area.
In addition to ensonification and seafloor disturbance, a temporary
and localized increase in turbidity near the seafloor would occur
immediately surrounding the area where piles are installed and removed,
and where screeding and seabed preparation will take place. The
screeding process redistributes seabed materials to create a flat even
seafloor surface without the need for excavation or disposal of
materials. Screeding would occur each summer immediately prior to the
arrival of the first cargo barge, and would likely increase turbidity
in the immediate area around West Dock. Turbidity and sedimentation
rates are naturally high in this region due to ice scouring and gouging
of the seafloor and significant amounts of suspended sediments from
river outflow and coastal erosion.
[[Page 16616]]
Therefore, the additional turbidity resulting from screeding activities
is not anticipated to have a significant impact. The sediments on the
sea floor will also be disturbed during pile driving; however, like
during screeding, sediment suspension will be brief and localized and
is unlikely to measurably affect marine mammals or their prey in the
area. In general, turbidity associated with pile installation is
localized to about a 25-ft (7.6 m) radius around the pile (Everitt et
al., 1980). Cetaceans are not expected to be close enough to the
project pile driving areas to experience effects of turbidity, and any
pinnipeds are able to easily avoid localized areas of turbidity.
Therefore, the impact from increased turbidity levels is expected to be
discountable to marine mammals. Furthermore, pile driving and removal
at the project site would not obstruct movements or migration of marine
mammals. Impacts to potential foraging habitat are expected to be
temporary and minimal based on the short duration of activities.
In-Water Construction Effects on Potential Prey
Numerous fish and invertebrate species occur in Prudhoe Bay and the
Beaufort Sea and could be affected by the construction activities that
would produce continuous (i.e., vibratory pile driving) and impulsive
(i.e., impact pile driving) sounds. Fish react to sounds that are
especially strong and/or intermittent low-frequency sounds. Short
duration, sharp sounds can cause overt or subtle changes in fish
behavior and local distribution. Hastings and Popper (2005) identified
several studies that suggest fish may relocate to avoid certain areas
of sound energy. Additional studies have documented effects of pile
driving on fish, although several are based on studies in support of
large, multiyear bridge construction projects (e.g., Popper and
Hastings, 2009, Scholik and Yan, 2001, Scholik and Yan, 2002). Sound
pulses at received levels of 160 dB may cause subtle changes in fish
behavior. SPLs of 180 dB may cause noticeable changes in behavior
(Pearson et al., 1992, Skalski et al., 1992). SPLs of sufficient
strength have been known to cause injury to fish and fish mortality.
The most likely impact to fish from pile driving activities at the
project site would be temporary behavioral avoidance of the area. The
duration of fish avoidance of this area after pile driving stops is
unknown, but as noted above, a rapid return to normal recruitment,
distribution and behavior is anticipated.
In addition to fish, prey sources such as marine invertebrates
could potentially be impacted by noise stressors as a result of the
proposed activities. However, most marine invertebrates' ability to
sense sounds is limited. Invertebrates appear to be able to detect
sounds (Pumphrey, 1950; Frings and Frings, 1967) and are most sensitive
to low-frequency sounds (Packard et al., 1990; Budelmann and
Williamson, 1994; Lovell et al., 2005; Mooney et al., 2010). Data on
response of invertebrates such as squid, another marine mammal prey
species, to anthropogenic sound is more limited (de Soto, 2016; Sole et
al., 2017). Data suggest that cephalopods are capable of sensing the
particle motion of sounds and detect low frequencies up to 1-1.5 kHz,
depending on the species, and so are likely to detect airgun noise
(Kaifu et al., 2008; Hu et al., 2009; Mooney et al., 2010; Samson et
al., 2014). Sole et al. (2017) reported physiological injuries to
cuttlefish in cages placed at-sea when exposed during a controlled
exposure experiment to low-frequency sources (315 Hz, 139 to 142 dB re
1m Pa\2\ and 400 Hz, 139 to 141 dB re 1m Pa\2\). Fewtrell and McCauley
(2012) reported squids maintained in cages displayed startle responses
and behavioral changes when exposed to seismic airgun sonar (136-162 re
1m Pa\2\[middot]s). Jones et al. (2020) found that when squid
(Doryteuthis pealeii) were exposed to impulse pile driving noise, body
pattern changes, inking, jetting, and startle responses were observed
and nearly all squid exhibited at least one response. However, these
responses occurred primarily during the first eight impulses and
diminished quickly, indicating potential rapid, short-term habituation.
Cephalopods have a specialized sensory organ inside the head called
a statocyst that may help an animal determine its position in space
(orientation) and maintain balance (Budelmann, 1992). Packard et al.
(1990) showed that cephalopods were sensitive to particle motion, not
sound pressure, and Mooney et al. (2010) demonstrated that squid
statocysts act as an accelerometer through which particle motion of the
sound field can be detected (Budelmann, 1992). Auditory injuries
(lesions occurring on the statocyst sensory hair cells) have been
reported upon controlled exposure to low-frequency sounds, suggesting
that cephalopods are particularly sensitive to low-frequency sound
(Andre et al., 2011; Sole et al., 2013). Behavioral responses, such as
inking and jetting, have also been reported upon exposure to low-
frequency sound (McCauley et al., 2000; Samson et al., 2014). Squids,
like most fish species, are likely more sensitive to low frequency
sounds and may not perceive mid- and high-frequency sonars.
With regard to potential impacts on zooplankton, McCauley et al.
(2017) found that exposure to airgun noise resulted in significant
depletion for more than half the taxa present and that there were two
to three times more dead zooplankton after airgun exposure compared
with controls for all taxa, within 1 km (0.6 mi) of the airguns.
However, the results of this study are inconsistent with a large body
of research that generally finds limited spatial and temporal impacts
to zooplankton as a result of exposure to airgun noise (e.g., Dalen and
Knutsen, 1987; Payne, 2004; Stanley et al., 2011). Most prior research
on this topic, which has focused on relatively small spatial scales,
has showed minimal effects (e.g., Kostyuchenko, 1973; Booman et al.,
1996; S[aelig]tre and Ona, 1996; Pearson et al., 1994; Bolle et al.,
2012).
Notably, a more recent study produced results inconsistent with
those of McCauley et al. (2017). Researchers conducted a field and
laboratory study to assess if exposure to airgun noise affects
mortality, predator escape response, or gene expression of the copepod
Calanus finmarchicus (Fields et al., 2019). There were no sublethal
effects on the escape performance or the sensory threshold needed to
initiate an escape response at any of the distances from the airgun
that were tested. Whereas McCauley et al. (2017) reported an SEL of 156
dB at a range of 509-658 m (1,670-2,159 ft), with zooplankton mortality
observed at that range, Fields et al. (2019) reported an SEL of 186 dB
at a range of 25 m (82 ft), with no reported mortality at that
distance.
As noted above, due to the limited presence of benthic
invertebrates in the West Dock area, we do not expect screeding and
seafloor preparation activities to result in a significant loss of
benthic prey availability, particularly in comparison to the vast
foraging area available to marine mammals in the Beaufort Sea.
In summary, given the short daily duration of sound associated with
individual pile driving events and the relatively small areas being
affected, pile driving activities associated with the proposed action
are not likely to have a permanent, adverse effect on any fish or
invertebrate habitat, or populations of fish or invertebrate species.
Thus, we conclude that impacts of the specified activity are not likely
to
[[Page 16617]]
have more than short-term adverse effects on any prey habitat or
populations of prey species. Further, any impacts to marine mammal
habitat are not expected to result in significant or long-term
consequences for individual marine mammals, or to contribute to adverse
impacts on their populations.
Estimated Take of Marine Mammals
This section provides an estimate of the number of incidental takes
proposed for authorization through the IHA, which will inform NMFS'
consideration of ``small numbers,'' the negligible impact
determinations, and impacts on subsistence uses.
Harassment is the only type of take expected to result from these
activities. Except with respect to certain activities not pertinent
here, section 3(18) of 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).
Proposed takes would primarily be by Level B harassment, as
vibratory and impact pile driving has the potential to result in
disruption of behavioral patterns for individual marine mammals. There
is some potential for AUD INJ (Level A harassment) to result from
impact pile driving, primarily for phocids, due to the size of the
Level A harassment zones and the difficulty in being detected by
observers. Auditory injury is unlikely to occur to cetaceans. The
proposed mitigation and monitoring measures are expected to minimize
the severity of the taking to the extent practicable.
As described previously, no serious injury or mortality is
anticipated or proposed to be authorized for this activity. Below we
describe how the proposed take numbers are estimated.
For acoustic impacts, generally speaking, we estimate take by
considering: (1) acoustic criteria above which NMFS believes the best
available science indicates marine mammals will likely be behaviorally
harassed or incur some degree of AUD INJ; (2) the area or volume of
water that will be ensonified above these levels in a day; (3) the
density or occurrence of marine mammals within these ensonified areas;
and, (4) the number of days of activities. We note that while these
factors can contribute to a basic calculation to provide an initial
prediction of potential takes, additional information that can
qualitatively inform take estimates is also sometimes available (e.g.,
previous monitoring results or average group size). Below, we describe
the factors considered here in more detail and present the proposed
take estimates.
Acoustic Criteria
NMFS recommends the use of acoustic criteria that identify the
received level of underwater sound above which exposed marine mammals
would be reasonably expected to be behaviorally harassed (equated to
Level B harassment) or to incur AUD INJ of some degree (equated to
Level A harassment). We note that the criteria for AUD INJ, as well as
the names of two hearing groups, have been recently updated (NMFS 2024)
as reflected below in the Level A Harassment section.
Level B Harassment--Though significantly driven by received level,
the onset of behavioral disturbance from anthropogenic noise exposure
is also informed to varying degrees by other factors related to the
source or exposure context (e.g., frequency, predictability, duty
cycle, duration of the exposure, signal-to-noise ratio, distance to the
source), the environment (e.g., bathymetry, other noises in the area,
predators in the area), and the receiving animals (hearing, motivation,
experience, demography, life stage, depth) and can be difficult to
predict (e.g., Southall et al., 2007, 2021, Ellison et al., 2012).
Based on what the available science indicates and the practical need to
use a threshold based on a metric that is both predictable and
measurable for most activities, NMFS typically uses a generalized
acoustic threshold based on received level to estimate the onset of
behavioral harassment. NMFS generally predicts that marine mammals are
likely to be behaviorally harassed in a manner considered to be Level B
harassment when exposed to underwater anthropogenic noise above root-
mean-squared pressure received levels (RMS SPL) of 120 dB (referenced
to 1 micropascal (re 1 [mu]Pa)) for continuous (e.g., vibratory pile
driving, drilling) and above RMS SPL 160 dB re 1 [mu]Pa for non-
explosive impulsive (e.g., seismic airguns) or intermittent (e.g.,
scientific sonar) sources. Generally speaking, Level B harassment take
estimates based on these behavioral harassment thresholds are expected
to include any likely takes by TTS as, in most cases, the likelihood of
TTS occurs at distances from the source less than those at which
behavioral harassment is likely. TTS of a sufficient degree can
manifest as behavioral harassment, as reduced hearing sensitivity and
the potential reduced opportunities to detect important signals
(conspecific communication, predators, prey) may result in changes in
behavior patterns that would not otherwise occur.
AGDC's proposed construction activity includes the use of
continuous (vibratory pile driving) and impulsive (impact pile driving)
sources, and therefore the RMS SPL thresholds of 120 and/or 160 dB re 1
[mu]Pa are applicable.
Level A harassment--NMFS' Updated Technical Guidance for Assessing
the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version
3.0) (Updated Technical Guidance, 2024) identifies dual criteria to
assess AUD INJ (Level A harassment) to five different underwater marine
mammal groups (based on hearing sensitivity) as a result of exposure to
noise from two different types of sources (impulsive or non-impulsive).
AGDC's proposed construction includes the use of impulsive (impact pile
driving) and non-impulsive (vibratory pile driving) sources.
The 2024 Updated Technical Guidance criteria include both updated
thresholds and updated weighting functions for each hearing group. The
thresholds are provided in table 7. The references, analysis, and
methodology used in the development of the criteria are described in
NMFS' 2024 Updated Technical Guidance, which may be accessed at <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools</a>.
[[Page 16618]]
Table 7--Thresholds Identifying the Onset of Auditory Injury
----------------------------------------------------------------------------------------------------------------
AUD INJ onset acoustic thresholds * (received level)
Hearing group ------------------------------------------------------------------------
Impulsive Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans........... Cell 1: Lpk,flat: 222 dB; Cell 2: LE,LF,24h: 197 dB.
LE,LF,24h: 183 dB.
High-Frequency (HF) Cetaceans.......... Cell 3: Lpk,flat: 230 dB; Cell 4: LE,HF,24h: 201 dB.
LE,HF,24h: 193 dB.
Very High-Frequency (VHF) Cetaceans.... Cell 5: Lpk,flat: 202 dB; Cell 6: LE,VHF,24h: 181 dB.
LE,VHF,24h: 159 dB.
Phocid Pinnipeds (PW) (Underwater)..... Cell 7: Lpk,flat: 223 dB; Cell 8: LE,PW,24h: 195 dB.
LE,PW,24h: 183 dB.
Otariid Pinnipeds (OW) (Underwater).... Cell 9: Lpk,flat: 230 dB; Cell 10: LE,OW,24h: 199 dB.
LE,OW,24h: 185 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric criteria for impulsive sounds: Use whichever criteria results in the larger isopleth for
calculating AUD INJ onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure
level criteria associated with impulsive sounds, the PK SPL criteria are recommended for consideration for non-
impulsive sources.
Note: Peak sound pressure level (Lp,0-pk) has a reference value of 1 [micro]Pa, and weighted cumulative sound
exposure level (LE,p) has a reference value of 1 [micro]Pa\2\s. In this table, criteria are abbreviated to be
more reflective of International Organization for Standardization (ISO) standards (ISO 2017; ISO 2020). The
subscript ``flat'' is being included to indicate peak sound pressure are flat weighted or unweighted within
the generalized hearing range of marine mammals underwater (i.e., 7 Hz to 165 kHz). The subscript associated
with cumulative sound exposure level criteria indicates the designated marine mammal auditory weighting
function (LF, HF, and VHF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is
24 hours. The weighted cumulative sound exposure level criteria could be exceeded in a multitude of ways
(i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents
to indicate the conditions under which these criteria will be exceeded.
Ensonified Area
In this section we describe operational and environmental
parameters of the activity that are used in estimating the area
ensonified above the acoustic thresholds, including source levels and
transmission loss coefficient.
The sound field in the project area is the existing background
noise plus additional construction noise from the proposed project.
Marine mammals are expected to be affected via sound generated by the
primary components of the project (i.e., pile driving and removal). The
maximum (underwater) area ensonified above the thresholds for
behavioral harassment referenced above is 67.7 km\2\ (26.1 mi\2\), and
the calculated distance to the farthest behavioral isopleth is
approximately 4.6 km (2.9 mi).
The project includes vibratory pile installation and removal and
impact pile installation. Source levels for these activities are based
on reviews of measurements of the same or similar types and dimensions
of piles available in the literature. Source levels for each pile size
and activity are presented in table 8. Source levels for vibratory
installation and removal of piles of the same diameter are assumed to
be the same.
Table 8--Sound Source Levels for Pile Driving
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source level (at 10 m)
---------------------------------------
Pile size and type Hammer type SEL (dB re Literature source
Peak (dB re RMS (dB re 1 [mu]Pa2
1 [mu]Pa) 1 [mu]Pa) sec)
--------------------------------------------------------------------------------------------------------------------------------------------------------
11.5-inch (29.2 cm) H-Pile.............. Impact..................... 200 183 170 Caltrans (2015) (12-inch (30 cm) H-Pile).
14-inch (122 cm) H-Pile................. Impact..................... 200 183 170 Caltrans (2015) (12-inch (30 cm) H-Pile).
Vibratory.................. 165 150 150 Caltrans (2015) (12- to 16-inch (30 to 40
cm) H-Pile).
48-Inch (122 cm) Pipe Pile.............. Impact..................... 213 192 179 Caltrans (2020) (40-48-inch (102 to 122
cm) Steel Pipe Pile).
Sheet Piles (19.69 and 25-inch (50.01 Vibratory.................. 175 160 160 Caltrans (2015) (AZ Steel Sheet).
and 64 cm).
--------------------------------------------------------------------------------------------------------------------------------------------------------
--Transmission loss (TL) is the decrease in acoustic intensity as an
acoustic pressure wave propagates out from a source. TL parameters vary
with frequency, temperature, sea conditions, current, source and
receiver depth, water depth, water chemistry, and bottom composition
topography. The general formula for underwater TL is:
TL = B * Log10 (R<INF>1</INF>/R<INF>2</INF>),
where
TL = transmission loss in dB;
B = transmission loss coefficient;
R<INF>1</INF> = the distance of the modeled SPL from the driven
pile; and
R<INF>2</INF> = the distance from the driven pile of the initial
measurement.
Absent site-specific acoustical monitoring with differing measured
transmission loss, a practical spreading value of 15 is used as the
transmission loss coefficient in the above formula. Project and site-
specific transmission loss data for the Prudhoe Bay portion of AGDC's
AK LNG project are not available; therefore, the default coefficient of
15 is used to determine the distances to the Level A and Level B
harassment thresholds. However, as discussed in the Proposed Monitoring
and Reporting section, AGDC would conduct SSV for pile driving.
Following the analysis of SSV results, AGDC may propose adjusted
shutdown zones and revised Level A and Level B harassment zones (for
the purpose of monitoring and reporting) for NMFS review and approval.
All Level B harassment isopleths are reported in table 10. The maximum
(underwater) area ensonified above the thresholds for behavioral
harassment is 67.7 km\2\ (42 mi\2\).
The ensonified area associated with Level A harassment is more
technically
[[Page 16619]]
challenging to predict due to the need to account for a duration
component. Therefore, NMFS developed an optional User Spreadsheet tool
to accompany the 2024 Updated Technical Guidance that can be used to
relatively simply predict an isopleth distance for use in conjunction
with marine mammal density or occurrence to help predict potential
takes. We note that because of some of the assumptions included in the
methods underlying this optional tool, we anticipate that the resulting
isopleth estimates are typically going to be overestimates of some
degree, which may result in an overestimate of potential take by Level
A harassment. However, this optional tool offers the best way to
estimate isopleth distances when more sophisticated modeling methods
are not available or practical. For stationary sources, such as pile
driving, the optional User Spreadsheet tool predicts the distance at
which, if a marine mammal remained at that distance for the duration of
the activity, it would be expected to incur AUD INJ. Inputs used in the
optional User Spreadsheet tool are provided in table 9, and the
resulting estimated isopleths, are reported in table 10.
Table 9--User Spreadsheet Input Parameters Used for Calculating Level A Harassment Isopleths
[Source levels provided in table 8]
----------------------------------------------------------------------------------------------------------------
Duration to Weighting
Pile size Piles per day Strikes per drive pile factor
\a\ pile (min) adjustment
----------------------------------------------------------------------------------------------------------------
Impact
----------------------------------------------------------------------------------------------------------------
11.5-inch (29.2 cm) H-Pile...................... \b\ 26.09 1,000 N/A 2
14-inch (36 cm) H-Pile.......................... 4 1,000 N/A 2
48-inch (122 cm) Pipe Pile...................... 1.25 1,000 N/A 2
----------------------------------------------------------------------------------------------------------------
Vibratory
----------------------------------------------------------------------------------------------------------------
14-inch (36 cm) H-Pile.......................... 8 N/A 15 2.5
19.69-inch (50.01 cm) Sheet Pile................ \b\ 15.24 N/A 18.9 2.5
25-inch (64 cm) Sheet Pile...................... 12 N/A 24 2.5
----------------------------------------------------------------------------------------------------------------
\a\ These estimates include contingencies for weather, equipment, workflow, and other factors that affect the
number of piles per day, and are assumed to be a maximum anticipated per day. Given that AGDC plans to pile
drive up to 24 hours per day, it is appropriate to assume that the number of piles installed within the 24-
hour period may not be a whole number.
\b\ These averages assume that AGDC will drive 11.5-inch (29.2-cm) H-piles and sheet piles at a rate of 25 ft
(7.6 m) per day.
Table 10--Calculated Distances to Level A and Level B Harassment Isopleths
----------------------------------------------------------------------------------------------------------------
Level A harassment zone (m) Level B
Pile type Hammer type ------------------------------------------------ harassment
LF cetaceans HF cetaceans Phocids zone (m)
----------------------------------------------------------------------------------------------------------------
11.5-Inch (29.2 cm) H-Pile.... Impact.......... 1,190 152 1,057 342
14-Inch (36 cm) H-Pile........ Impact.......... 341 44 303 341
Vibratory....... 3 1 4 1,000
48-Inch (122 cm) Pipe Pile.... Impact.......... 625 80 555 1,359
19.69-Inch (50.01 cm) Sheet Vibratory....... 23 9 29 4,642
Pile.
25-Inch (64 cm) Sheet Pile.... Vibratory....... 23 9 29 4,642
----------------------------------------------------------------------------------------------------------------
Level A harassment zones are typically smaller than Level B
harassment zones. However, in rare cases such as the impact pile
driving of the 11.5-inch (29.2 cm) H-piles herein, the calculated Level
A harassment isopleth is greater than the calculated Level B harassment
isopleth for LF cetaceans and phocids. Calculation of Level A
harassment isopleths include a duration component, which in the case of
impact pile driving, is estimated through the total number of daily
strikes and the associated pulse duration. For a stationary sound
source such as impact pile driving, we assume here that an animal is
exposed to all of the strikes expected within a 24-hour period.
Calculation of a Level B harassment zone does not include a duration
component. Depending on the duration included in the calculation, the
calculated Level A harassment isopleths can be larger than the
calculated Level B harassment isopleth for the same activity.
Marine Mammal Occurrence
In this section, we provide information about the occurrence of
marine mammals, including density or other relevant information which
will inform the take calculations.
From 2011-2019, each fall and summer, NMFS and BOEM conducted
aerial surveys in the Arctic, the ASAMM surveys (Clarke et al., 2012,
2013, 2014, 2015a, 2017a, 2017b, 2018, 2019, and 2020). The goal of
these surveys was to document the distribution and relative abundance
of bowhead, gray, right, fin, and beluga whales and other marine
mammals in area of potential oil and natural gas exploration,
development, and production activities in the Alaskan Beaufort and
northeastern Chukchi Seas. In 2020 and 2021, NMFS conducted aerial
surveys during the fall in the western Beaufort Sea focusing on Point
Barrow to Prudhoe Bay (Brower et al., 2022a, Brower et al., 2022b).
These surveys were conducted within blocks that overlay the Beaufort
and Chukchi Seas oil and gas lease sale areas offshore of Alaska
(Figure 16 in AGDC's application), and provide sighting data for
bowhead, gray, and beluga whales. NMFS used data from these surveys
from 2011-2021 to estimate seasonal densities of cetaceans in the
project area. During the summer, NMFS observed for marine mammals on
effort
[[Page 16620]]
for 15,127 km from 2011-2019 and 15,968 km during the fall from 2011 to
2021. We note that the proposed Prudhoe Bay portion of the AK LNG
project is in ASAMM survey block 1; the inshore boundary of this block
terminates at the McClure Island group. It was not until 2016 that on-
effort surveys began inside the McClure Island group (including Prudhoe
Bay) since bowhead whales, the focus of the surveys, are not likely to
enter this area, given its shallow depth. However, no bowheads and only
one beluga whale have been observed in block 1a (including Prudhoe
Bay). Therefore, the density estimates provided here are likely an
overestimate because they rely on offshore surveys where marine mammals
are more likely to be present.
Cetaceans
AGDC calculated summer and fall density estimates for bowhead
whale, gray whale, and beluga whale by dividing the average number of
whales observed per km of transect effort in ASAMM Block 1 by two times
the effective strip width (ESW) to encompass both sides of the transect
line (whales per km/(2xESW) (table 11 and table 12). The ESW for
bowhead whale, gray whale, and beluga whale from the Aero Commander
aircraft are 1.15 km (0.71 mi), 1.2 km (0.75 mi), and 0.613 km (0.38
mi), respectively (Ferguson and Clarke, 2013). Fall sighting data is
available from 2011-2021. Surveys were not conducted in the summer of
2020 and 2021, and therefore sighting data for the summer is only
available from 2011-2019. Additionally, although beluga whale sighting
data was available from 2011-2013, it was only summarized by depth
zone, rather than by survey block. Therefore, and given that more
recent data is available, data from 2011-2013 was excluded for beluga
whales.
Table 11 and table 12, below, include calculated summer and fall
densities for each species. All resulting densities are expected to be
overestimates for the AK LNG analysis because the data are based on
sighting effort outside of the barrier islands and these species rarely
occur within the barrier islands. To estimate take of each cetacean
species, AGDC used the higher density in an effort to avoid
underestimating take. Therefore, NMFS estimated take of gray whale and
beluga whale using the summer densities, 0.00003 and 0.009 whales/km\2\
respectively, and estimated take using the fall density of 0.017
whales/km\2\ for bowhead whale.
As noted in the Description of Marine Mammals in the Area of
Specified Activities section, we do not expect cetaceans to be present
during AGDC's winter/spring contingency pile driving period.
Table 11--Summer Sighting and Density Data
----------------------------------------------------------------------------------------------------------------
Number sightings
Year Transect (km) -----------------------------------------------
Bowhead whale Gray whale Beluga whale
----------------------------------------------------------------------------------------------------------------
2011.............................. 346 1 0 \a\ N/A
2012.............................. 1493 5 0 \a\ N/A
2013.............................. 1582 21 0 \a\ N/A
2014.............................. 1393 17 0 13
2015.............................. 1262 15 0 37
2016.............................. 1914 97 1 0
2017.............................. 3003 8 0 4
2018.............................. 2491 2 0 6
2019.............................. 1643 6 0 63
-----------------------------------------------------------------------------
Total......................... 15127 172 1 123
-----------------------------------------------------------------
Encounter Rate (whales/km)...................................... 0.01137 0.00007 \b\ 0.01051
-----------------------------------
Density (whales/km\2\) \c\...................................... 0.0049 0.00003 0.009
----------------------------------------------------------------------------------------------------------------
\a\ Beluga sighting data from 2011 to 2013 was only summarized by depth zone, rather than by survey block.
Therefore, data from 2011-2013 was excluded for beluga whales.
\b\ Encounter rate for beluga whales was calculated using total transect from 2014-2019, which was 11,706 km.
\c\ Density was calculated with the formula of Encounter rate/(2xESW). ESW for each species are as follows:
Bowhead whale: 1.15, Gray whale: 1.201, Beluga whale: 0.614 (Ferguson and Clarke, 2013).
Table 12--Fall Sighting and Density Data
----------------------------------------------------------------------------------------------------------------
Number sightings
Year Transect (km) -----------------------------------------------
Bowhead whale Gray whale Beluga whale
----------------------------------------------------------------------------------------------------------------
2011............................................ 1130 24 0 \a\ N/A
2012............................................ 1696 17 0 \a\ N/A
2013............................................ 1121 21 0 \a\ N/A
2014............................................ 1538 79 1 9
2015............................................ 1663 17 0 3
2016............................................ 2360 23 0 1
2017............................................ 1803 255 0 0
2018............................................ 1535 69 0 0
2019............................................ 2055 45 0 1
2020............................................ 379 54 0 0
2021............................................ 668 15 0 3
---------------------------------------------------------------
[[Page 16621]]
Total....................................... 15968 619 1 17
-------------------------------------------------
Encounter Rate (whales/km)...................................... 0.03877 0.00006 \b\ 0.00141
-------------------------------------------------
Density (whales/km\2\) \c\...................................... 0.017 0.00002 0.00115
----------------------------------------------------------------------------------------------------------------
\a\ Beluga sighting data from 2011 to 2013 was only summarized by depth zone, rather than by survey block.
Therefore, data from 2011-2013 was excluded for beluga whales.
\b\ Encounter rate for beluga whales was calculated using total transect from 2014-2021, which was 12,021 km.
\c\ Density was calculated with the formula of Encounter rate/(2xESW). ESW for each species are as follows:
Bowhead whale--1.15, Gray whale--1.201, Beluga whale--0.614 (Ferguson and Clarke, 2013).
Ringed Seal
Ringed seals are the most abundant species in the project area.
They haul out on the ice to molt between late May and early June, and
spring aerial surveys provide the most comprehensive density estimates
available. Spring surveys are expected to provide the best ringed seal
density information, as the greatest percentage of seals have abandoned
their lairs and are hauled out on the ice (Kelly et al., 2010). Spring
aerial surveys conducted in the central Beaufort Sea from 1996-1999
(Frost et al., 2004) and around the West Dock area as part of industry
monitoring programs for the construction of the Northstar production
facility from 1997-2002 (Richardson and Williams, 2003, Richardson and
Williams, 2002) were considered the best data available to determine
spring density in the area of the project. The yearly densities from
these spring aerial surveys were averaged to determine spring ringed
seal density. The average observed spring ringed seal density from this
monitoring effort was 0.634 seals/km\2\ (table 13). While more recent
ASAMM surveys have been conducted in the project area, these surveys
did not identify observed pinnipeds to species, and therefore these
data are not included.
Table 13--Ringed Seal Densities Estimated Using Spring Aerial Surveys
Conducted From 1996 to 2002
------------------------------------------------------------------------
Density (seals/
Survey year km\2\) Reference
------------------------------------------------------------------------
1996.............................. 0.81 Frost et al. (2004).
1997.............................. 0.73 Frost et al. (2004).
1997.............................. 0.43 Richardson and
Williams (2002).
1998.............................. 0.64 Frost et al. (2004).
1998.............................. 0.39 Richardson and
Williams (2002).
1999.............................. 0.87 Frost et al. (2004).
1999.............................. 0.63 Richardson and
Williams (2002).
2000.............................. 0.47 Richardson and
Williams (2002).
2001.............................. 0.54 Richardson and
Williams (2002).
2002.............................. 0.83 Richardson and
Williams (2003).
Average....................... 0.634
------------------------------------------------------------------------
In order to generate a summer density, as AGDC expects that the
majority of their work will occur during the summer, we first begin
with the spring density. Summer densities in the project area are
expected to significantly decrease as ringed seals range considerable
distances during the open water season. Summer density was estimated to
be 50 percent of the spring density (0.634 seals/km\2\), resulting in a
summer density of 0.317 seals/km\2\. Given that AGDC will only pile
drive during the winter if they are unable to complete the work during
the summer and fall open water season, NMFS estimated ringed seal takes
using the summer density of 0.317 seals/km\2\ rather than winter.
Spotted Seal
The spotted seal occurs in the Beaufort Sea in small numbers during
the summer open water period. At the onset of freeze-up in the fall,
spotted seals return to the Chukchi Sea and then Bering Sea to spend
the winter and spring. As such, AGDC does not expect spotted seals to
occur in the project area during AGDC's winter/spring contingency
period, and NMFS concurs.
Only a few of the studies referenced in calculating the ringed seal
densities also include data for spotted seals. Given the limited
spotted seal data, NMFS expects that relying on this data may result in
an underestimate, and that it is more appropriate to calculate the
spotted seal density as a percentage of ringed seal density. Therefore,
summer spotted seal density was estimated as a percentage of ringed
seal sightings observed during monitoring during seismic exploration in
this area from 2006-2008 (Funk et al., 2010). Spotted seals comprised
34.8 percent of ringed seal sightings during these monitoring efforts.
Therefore, summer spotted seal density was calculated as 34.8 percent
of the ringed seal density of 0.317 seals/km\2\, which results in an
estimated spotted seal summer density of 0.11 seals/km\2\. This density
will be used to estimate take of spotted seal.
Bearded Seal
The majority of bearded seals spend the winter and spring in the
Chukchi and Bering Seas; however, some remain in the Beaufort Sea year-
round. A reliable population estimate for the bearded seal stock is not
available, and occurrence in the Beaufort Sea is less known than in the
Bering Sea. Spring
[[Page 16622]]
aerial surveys conducted as part of industry monitoring for the
Northstar production facility provide limited sighting numbers from
1999-2002 (Richardson and Williams, 2002, 2003).
Bearded seals occur in the Beaufort Sea more frequently during the
open water season, rather than other parts of the year. They prefer
water farther offshore. Only a few of the studies referenced in
calculating the ringed seal densities also include data for bearded
seals. Given the limited bearded seal data, NMFS expects that relying
on this data may result in an underestimate, and that it is more
appropriate to calculate the bearded seal density as a proportion of
the ringed seal density. Therefore, summer bearded seal density was
estimated as a percentage of ringed seal sightings observed during
seismic exploration in this area from 2006-2008 (Funk et al., 2010).
Bearded seals comprised 21.3 percent of ringed seal sightings during
these monitoring efforts. Therefore, summer bearded seal density was
calculated as 21.3 percent of the summer ringed seal density of 0.317
seals/km\2\, which results in an estimated bearded seal density of
0.068 seals/km\2\. NMFS used this density to estimate take of bearded
seal.
As noted in the Description of Marine Mammals in the Area of
Specified Activities section, bearded seals could potentially occur in
the project area during AGDC's winter/spring contingency period.
However, we would expect very few, if any bearded seals to be present
during this time. In consideration of this species presence information
and AGDC's plan to conduct most construction during the open-water
season, NMFS estimated take of bearded seal using the summer density.
Take Estimation
Here we describe how the information provided above is synthesized
to produce a quantitative estimate of the take that is reasonably
likely to occur and proposed for authorization.
To estimate take by Level A and Level B harassment, AGDC multiplied
the area (km\2\) estimated to be ensonified above the Level A or Level
B harassment (table 14 and table 15) thresholds for each species,
respectively, for pile driving (and removal) of each pile size and
hammer type by the duration (days) of that activity in that season by
the seasonal density for each species (number of animals/km\2\). NMFS
generally concurs with, and has adopted this method, with the exception
of the estimated duration of the activity (described below). NMFS also
used updated densities as described in the Marine Mammal Occurrence
section.
Table 14--Level B Harassment Zones
------------------------------------------------------------------------
Pile type Area (km\2\)
------------------------------------------------------------------------
Impact
------------------------------------------------------------------------
11.5-Inch (29.2 cm) H-Pile.............................. 0.37
14-Inch (36 cm) H-Pile.................................. 0.37
48-Inch (122 cm) Pipe Pile.............................. 5.8
------------------------------------------------------------------------
Vibratory
------------------------------------------------------------------------
14-Inch (36 cm) H-Pile.................................. 3.14
Sheet Piles (19.69- and 25-Inch (50.01 and 64 cm))...... 67.7
------------------------------------------------------------------------
Table 15--Level A Harassment Zones
----------------------------------------------------------------------------------------------------------------
Area (km\2\)
Pile type -----------------------------------------------
LF cetacean HF cetacean Phocids
----------------------------------------------------------------------------------------------------------------
Impact
----------------------------------------------------------------------------------------------------------------
11.5-Inch (29.2 cm) H-Pile...................................... 4.45 0.073 3.51
14-Inch (36 cm) H-Pile.......................................... 0.37 0.006 0.29
48-Inch (122 cm) Pipe Pile...................................... 1.23 0.020 0.97
----------------------------------------------------------------------------------------------------------------
Vibratory
----------------------------------------------------------------------------------------------------------------
14-Inch (36 cm) H-Pile.......................................... 0.00 0.00 0.00
19.69-Inch (50.01 cm) Sheet Pile................................ 0.00 0.00 0.00
25-Inch (64 cm) Sheet Pile...................................... 0.00 0.00 0.00
----------------------------------------------------------------------------------------------------------------
NMFS calculated take using summer densities for all species except
for bowhead whale (tables 16, 17, 18, and 19). For bowhead whales, NMFS
conservatively calculated take using the fall density.
Table 16--Marine Mammal Densities Used To Estimate Take
------------------------------------------------------------------------
Density (animals/
Species km\2\) Season
------------------------------------------------------------------------
Bowhead whale................... 0.017 Fall (September-
October).
Gray whale...................... 0.00003 Summer (July-
August).
Beluga whale.................... 0.009 Summer (July-
August).
Ringed seal..................... 0.317 Summer (July-
August).
Spotted seal.................... 0.11 Summer (July-
August).
Bearded seal.................... 0.068 Summer (July-
August).
------------------------------------------------------------------------
[[Page 16623]]
Table 17--Estimated Take by Level B Harassment by Species, Pile Size and Type, and Installation/Removal Method
--------------------------------------------------------------------------------------------------------------------------------------------------------
Estimated
Activity duration Bowhead whale Gray whale Beluga whale Ringed seal Spotted seal Bearded seal
(days)
--------------------------------------------------------------------------------------------------------------------------------------------------------
DH4
--------------------------------------------------------------------------------------------------------------------------------------------------------
Anchor Pile (11.5-inch (29.2 cm) H-Pile) 9 0.06 0.00 0.03 1.04 0.36 0.22
(impact)...............................
25-inch (64 cm) Sheet Pile (Vibratory).. 36 41.43 0.07 21.93 772.54 268.07 165.72
Mooring Dolphins (48-inch (122 cm) Pipe 10 0.99 0.00 0.52 18.39 6.38 3.95
Pile) (Impact).........................
Spud Piles (14-inch (36 cm) H-Pile) 12 0.64 0.00 0.34 11.95 4.15 2.56
(vibratory)............................
--------------------------------------------------------------------------------------------------------------------------------------------------------
South Bridge Abutment
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dock Face (19.69-inch (50.01 cm) Sheet 23 26.47 0.05 14.01 493.57 171.27 105.88
Pile) (Vibratory)......................
Tailwall (19.69-inch (50.01 cm) Sheet 23 26.47 0.05 14.01 493.57 171.27 105.88
Pile) (Vibratory)......................
Anchor Pile (14-inch (36 cm) H-Pile) 1 0.01 0.00 0.00 0.12 0.04 0.02
(Impact)...............................
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Bridge Abutment
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dock Face (19.69-inch (50.01 cm) Sheet 24 27.62 0.05 14.62 515.03 178.72 110.48
Pile) (Vibratory)......................
Tailwall (19.69-inch (50.01 cm) Sheet 17 19.56 0.03 10.36 364.81 126.59 78.26
Pile) (Vibratory)......................
Anchor Pile (14-inch (36 cm) H-Pile 1 0.01 0.00 0.00 0.12 0.04 0.02
(Impact)...............................
--------------------------------------------------------------------------------------------------------------------------------------------------------
Barge Bridge
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mooring Dolphins (48-inch (122 cm) Pipe 4 0.39 0.00 0.21 7.36 2.55 1.58
Pile) (Impact).........................
Spud Pile (14-inch (36 cm) H-Pile) 4 0.21 0.00 0.11 3.98 1.38 0.85
(vibratory)............................
---------------------------------------------------------------------------------------------------------------
Total............................... 164 143.86 0.25 76.16 2,682.48 930.83 575.42
75 percent of Total..................... 123 107.89 0.19 57.12 2,011.86 698.12 431.57
Proposed take by Level B Harassment..... .............. 108 * 2 57 2,012 698 432
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Although 75 percent of the calculated total is 0.2, in order to account for group size (Clarke et al., 2017b), NMFS is proposing to authorize two
takes by Level B harassment of gray whale.
AGDC expects that construction will likely be completed during the
open-water construction season. AGDC calculated that the construction
would require approximately 164 days of in-water work; however, this
estimate does not take into account that different pile types would be
installed on the same day, therefore reducing the total number of pile
driving days. Therefore, NMFS expects that the take calculation using
the method described above overestimates take. Taking into
consideration the number of calendar days, construction occurring 6
days per week, and no work occurring on days during the whaling season,
there are 123 days in the months of July through October on which the
work is expected to occur (75 percent of the 164 days estimated by
AGDC). As such, for each species, NMFS is proposing to authorize 75
percent of the take estimate calculated using the estimated 164 work
days (except for Level A harassment take of bowhead whales and beluga
whales, and Level B harassment of gray whales as noted below).
NMFS recognizes that AGDC may work outside of this period in their
February to April contingency period; however, we expect that if AGDC
works during the contingency period, it would be because of
construction delays (and therefore, days on which they did not work)
during their planned open water work season. Additionally, we recognize
that ringed seals may be present in ice lairs during the contingency
period. However, AGDC must initiate pile driving prior to March 1, as
described in the Proposed Mitigation section. Initiating pile driving
before March 1 is expected to discourage seals from establishing
birthing lairs near pile driving. As such, we expect that this measure
will eliminate the potential for physical injury to ringed seals during
this period. Therefore, NMFS expects that the take estimates described
herein are reasonable even if AGDC must pile drive during their
contingency period.
Table 18--Estimated Take by Level A Harassment by Species, Pile Size and Type, and Installation/Removal Method
--------------------------------------------------------------------------------------------------------------------------------------------------------
Estimated
Activity duration Bowhead whale Gray whale Beluga whale Ringed seal Spotted seal Bearded seal
(days)
--------------------------------------------------------------------------------------------------------------------------------------------------------
DH4
--------------------------------------------------------------------------------------------------------------------------------------------------------
Anchor Pile (11.5-inch (29.2 cm) H-Pile) 9 0.68 0.00 0.01 10.01 3.47 2.15
(impact)...............................
25-inch (64 cm) Sheet Pile (Vibratory).. 36 0.00 0.00 0.00 0.03 0.01 0.01
[[Page 16624]]
Mooring Dolphins (48-inch (122 cm) Pipe 10 0.21 0.00 0.00 3.07 1.06 0.66
Pile) (Impact).........................
Spud Piles (14-inch (36 cm) H-Pile) 12 0.00 0.00 0.00 0.00 0.00 0.00
(vibratory)............................
--------------------------------------------------------------------------------------------------------------------------------------------------------
South Bridge Abutment
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dock Face (19.69-inch (50.01 cm) Sheet 23 0.00 0.00 0.00 0.02 0.01 0.00
Pile) (Vibratory)......................
Tailwall (19.69-inch (50.01 cm) Sheet 23 0.00 0.00 0.00 0.02 0.01 0.00
Pile) (Vibratory)......................
Anchor Pile (14-inch (36 cm) H-Pile) 1 0.01 0.00 0.00 0.09 0.03 0.02
(Impact)...............................
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Bridge Abutment
--------------------------------------------------------------------------------------------------------------------------------------------------------
Dock Face (19.69-inch (50.01 cm) Sheet 24 0.00 0.00 0.00 0.02 0.01 0.00
Pile) (Vibratory)......................
Tailwall (19.69-inch (50.01 cm) Sheet 17 0.00 0.00 0.00 0.01 0.00 0.00
Pile) (Vibratory)......................
Anchor Pile (14-inch (36 cm) H-Pile 1 0.01 0.00 0.00 0.09 0.03 0.02
(Impact)...............................
--------------------------------------------------------------------------------------------------------------------------------------------------------
Barge Bridge
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mooring Dolphins (48-inch (122 cm) Pipe 4 0.08 0.00 0.00 1.23 0.43 0.26
Pile) (Impact).........................
Spud Pile (14-inch (36 cm) H-Pile) 4 0.00 0.00 0.00 0.00 0.00 0.00
(vibratory)............................
---------------------------------------------------------------------------------------------------------------
Total............................... 164 0.99 0.00 0.01 14.59 5.06 3.13
75 percent of Total..................... 123 0.74 0.00 0.01 10.95 3.8 2.35
Proposed Take by Level A Harassment..... .............. * 0 0 0 11 4 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
* NMFS does not expect bowhead whales to occur within the Level A harassment zone, and therefore NMFS does not propose to authorize take by Level A
harassment of bowhead whales.
NMFS does not expect bowhead whales to occur within the Level A
harassment zones due to the shallow waters (approximately 19ft in depth
at the isopleth), lack of historic sightings, and required mitigation.
Waters less than 15 ft deep are considered too shallow to support these
whales, and in three decades of aerial surveys by BOEM (ASAMM), no
bowhead whale has been recorded in waters less than 16.4 ft (5 m) deep
(Clarke and Ferguson 2010). Further, no bowhead whales have been
observed during ASAMM surveys in Block 1a (which encompasses the Level
A harassment zone) when surveys were conducted in Block 1a (Clarke et
al., 2017b, 2018, 2019, 2020). Shutdown requirements within designated
shutdown zones for LF cetaceans (which includes bowhead whales) are
expected to prevent take by Level A harassment given the large size and
visibility of bowhead whales. Additionally, Level A harassment zones
are calculated with an associated duration component based on the
amount of pile driving expected to occur within one day. Therefore, a
marine mammal is not taken by Level A harassment instantaneously when
it enters the Level A harassment zone, and given the shallow depths,
even if a bowhead did enter the Level A harassment zone, we would not
expect it to remain within the zone for a long enough period to incur
AUD INJ. Therefore, we do not expect Level A harassment of bowhead
whales to occur, and are not proposing to authorize Level A harassment
take of bowheads.
The likelihood of gray whales occurring in the Level A harassment
zone is extremely low, as evidenced by the very low densities included
in the Marine Mammal Occurrence section and the lack of modeled takes
in table 18. Further, shutdown requirements within designated shutdown
zones for LF cetaceans (which include gray whales) are expected to
prevent take by Level A harassment given the large size and visibility
of gray whales, and the duration component associated with the Level A
harassment zones. Even if a gray whale did enter the Level A harassment
zone, NMFS would not expect it to remain within the zone for a long
enough period to incur AUD INJ, given the mitigation and visibility.
Therefore, NMFS does not expect Level A harassment of gray whales to
occur, and is not proposing to authorize Level A harassment take of the
gray whale.
The largest Level A harassment zone for high-frequency cetaceans
(including the beluga whale) extends 152 m from the source during
impact driving of the 11.5-inch (29.2 cm) H pile (table 10).
Considering the small size of the Level A harassment zones, and the low
likelihood that a beluga whale will occur in this area, as evidenced by
the estimated values in table 18, Level A harassment is unlikely to
occur. Additionally, AGDC is planning to implement a 150 m shutdown
zone during this activity. NMFS expects shutdown zones (table 20) will
eliminate the potential for Level A harassment take of the beluga
whale. Therefore, NMFS is not proposing to authorize takes of beluga
whale by Level A harassment.
[[Page 16625]]
Table 19--Take by Level A and Level B Harassment, by Species and Stock, Proposed for Authorization
--------------------------------------------------------------------------------------------------------------------------------------------------------
Total
Species Stock Level A Level B instances of Stock Percent of
harassment harassment take abundance stock
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bowhead Whale............................. Western Arctic.............. 0 108 108 15,227 0.7
Gray Whale................................ Eastern North Pacific....... 0 2 2 26,960 0.01
Beluga Whale *............................ Beaufort Sea................ 0 57 57 39,258 0.145
Eastern Chukchi............. 0 57 57 13,305 0.43
Ringed Seal............................... Arctic...................... 11 2,012 2,023 UND N/A
Spotted Seal.............................. Bering...................... 4 698 702 461,625 0.15
Bearded Seal.............................. Beringia.................... 2 432 434 UND N/A
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Beluga whales in the project area are likely to be from the Beaufort Sea stock. However, NMFS has conservatively attributed all takes to each stock
for their analysis.
Effects of Specified Activities on Subsistence Uses of Marine Mammals
The availability of the affected marine mammal stocks or species
for subsistence uses may be impacted by this activity. The subsistence
uses that may be affected and the potential impacts of the activity on
those uses are described below. Measures included in this IHA to reduce
the impacts of the activity on subsistence uses are described in the
Proposed Mitigation section. Last, the information from this section
and the Proposed Mitigation section is analyzed to determine whether
the necessary findings may be made in the Unmitigable Adverse Impact
Analysis and Determination section.
The communities of Nuiqsut, Utqia[gdot]vik and Kaktovik engage in
subsistence harvests off the North Slope of Alaska. Alaska Native
communities have harvested bowhead whales for subsistence and cultural
purposes with oversight and quotas regulated by the International
Whaling Commission (IWC). The North Slope Borough (NSB) Department of
Wildlife Management has been conducting bowhead whale subsistence
harvest research since the early 1980's to collect the data needed by
the IWC to set harvest quotas. Bowhead whale harvest (percent of total
marine mammal harvest), harvest weight, and percent of households using
bowhead whale are presented in table 25 of AGDC's application.
Due to ongoing oil and gas activities in the North Slope, the
Department of the Interior funded a subsistence mapping study conducted
in 2004 (Stephen R. Braund & Associates, 2010) and the Alaska LNG
Project funded a study, conducted by the Alaska Department of Fish &
Game in 2014 (Brown et al., 2016), to characterize and describe the
harvests and uses of wild foods by subsistence communities on the North
Slope. These are the most recent and applicable studies that NMFS is
aware of and will be used to describe the harvests of Utqia[gdot]vik,
Kaktovik, and Nuiqsut below.
Most of the Beaufort Sea population of beluga whales migrate from
the Bering Sea into the Beaufort Sea in April or May. The spring
migration routes through ice leads are similar to those of the bowhead
whale. Fall migration through the western Beaufort Sea occurs in
September or October. Surveys of the fall distribution strongly
indicate that most belugas migrate offshore along the pack ice front
beyond the reach of subsistence harvesters. Beluga whales are harvested
opportunistically during the bowhead harvest and throughout ice-free
months. No beluga whale harvests were reported in 2006 survey
interviews conducted by Stephen R. Braund & Associates in any community
(Stephen R. Braund & Associates, 2010). Beluga harvests were also not
reported in Nuiqsut and Kaktovik, although households did report using
beluga whale, likely through sharing from other communities (Brown et
al., 2016). We do not expect the planned activities at the AK LNG
project site to affect beluga whale subsistence harvests, as none are
expected.
Gray whale harvests were not reported by any of the communities
surveyed by Stephen R. Braund & Associates (2010) or Brown et al.
(2016) in any of the survey years, and therefore are not included as an
important subsistence species and are not further discussed.
Utqia[gdot]vik
Utqia[gdot]vik (formerly known as Barrow) is the northernmost
community on the North Slope and the United States, and is
approximately 320 km (200 mi) northwest of Prudhoe Bay. According to
Brown et al. (2016), 71 percent of households reported using marine
mammals as a resource. Of the marine mammals harvested, bowhead whale
made up the largest composition of marine mammals harvested at 54
percent by weight, while bearded seals represented 30 percent, ringed
seals 2 percent, and beluga whale 2 percent of total marine mammal
weight harvested (Brown et al., 2016). Bowhead whale was reported as a
resource used in 70 percent of households, bearded seal in 44 percent
of households, ringed seal in 19 percent of households, beluga whale in
15 percent of households, and spotted seals in 5 percent.
The spring hunt of bowhead whales occurs while bowheads are making
their migration east toward the eastern Beaufort Sea. Crews begin to
camp on the ice in mid- to late-April and stay out on the edge of the
ice for about 2-6 weeks, depending on the condition of the ice (Brown
et al., 2016). During the fall bowhead migration west, crews travel on
open boat, making day trips from the community. During the summer
months of July and August, bearded seals and ringed seals are targeted
offshore near ice floes (Brown et al., 2016).
The community of Utqia[gdot]vik's subsistence activities occur
outside of the area impacted by activities considered in this
authorization. We do not expect impacts to Utqia[gdot]vik's subsistence
activities, and they are not discussed further beyond the explanation
provided here. Impacts to marine mammals from the planned construction
would mostly include limited, temporary behavioral disturbances of
seals, however, some slight AUD INJ within the lower frequencies
associated with pile driving is possible. Additionally a small number
of takes of bowhead whales, by Level B harassment only, are predicted
to occur in the vicinity of AGDC's activity. Even if some subset of
taken individuals deflected farther offshore near the project site, it
is reasonable to predict that most individuals would likely resume a
more typical migration path by the time they reach the Utqia[gdot]vik
hunting area, and therefore, significant impacts to the Utqia[gdot]vik
hunt would be unlikely.
[[Page 16626]]
The planned activities and associated harassment of marine mammals
are not expected to impact marine mammals in numbers or locations
sufficient to render them unavailable for Utqia[gdot]vik subsistence
harvest given the short-term, temporary, and localized nature of
construction activities, and the planned mitigation measures.
Additionally, no serious injury or mortality of marine mammals is
expected or proposed for authorization, and the activities are not
expected to have any impacts on reproductive or survival rates of any
marine mammal species.
Kaktovik
Kaktovik is the easternmost village in the NSB. Kaktovik is located
on the north shore of Barter Island, situated between the Okpilak and
Jago rivers on the Beaufort Sea coast. Kaktovik's subsistence-harvest
areas are to the east of the project area and target marine mammal
species migrating eastward during spring and summer occur seaward of
the project area and westward in the fall.
Bowhead whale hunters report traveling between Camden Bay to the
west and Nuvagapak Lagoon to the east. This range does not include the
project area impacted by the activities analyzed for this IHA. The
small number of takes of bowhead whales, by Level B harassment only,
predicted to occur in the vicinity of AGDC's activity are not expected
to have any impacts on the fitness of any bowhead whales. Further, we
do not expect construction activities to deflect the bowhead whale
migration offshore in the Kaktovik hunting area, given the distance
from the western extent of the hunting area (Camden Bay) to the
predicted Level B harassment isopleths. Even if some subset of taken
individuals deflected farther offshore near the project site, it is
reasonable to predict that most individuals would likely resume a more
typical migration path by the time they reach the Kaktovik hunting area
during the eastbound migration, and during the westbound migration, a
bowhead exposed to construction noise would have already passed the
hunting area prior to exposure. Significant impacts to the Kaktovik
hunt would be unlikely, and Kaktovik bowhead whale hunting is not
discussed further. Please refer to AGDC's application for additional
information.
Ringed, spotted and bearded seals are harvested by the community of
Kaktovik. Residents hunt seals in rivers during ice-free months,
primarily July-August. Ringed seals are an important subsistence
resource for Native Alaskans living in communities along the Beaufort
Sea coast. Kaktovik hunters travel by boat to look for ringed seals on
floating ice (often while also hunting for bearded seal) or sometimes
along the ice edge by snow machine before break-up, during the spring
(Stephen R. Braund & Associates 2010). In 2006, 7 people (18 percent of
survey respondents) indicated that they had recently hunted for ringed
seals in Kaktovik (Stephen R. Braund & Associates, 2010). Residents
reported looking for ringed seal, usually while also searching for
bearded seal, offshore between Prudhoe Bay to the west and Demarcation
Bay to the east (Stephen R. Braund & Associates, 2010). Ringed seal
hunting typically peaks between March and August but continues into
September, as well (Stephen R. Braund & Associates. 2010). Although
residents reported hunting ringed seals up to approximately 30 mi (48
km) from shore, the highest numbers of overlapping use areas generally
occur within a few miles from shore (Stephen R. Braund & Associates,
2010). The total use area for ringed seal from 1995-2006 encompassed
approximately 2,139 mi\2\ (5540 km\2\). Harvest of ringed seals by
Kaktovik hunters does not typically occur to the west of Camden Bay.
Additionally, impacts to ringed seals are expected to include temporary
behavioral disturbances and some slight PTS within the lower
frequencies associated with pile driving. Serious injury or mortality
of ringed seals is not anticipated from the planned activities, and the
activities are not expected to have any impacts on ringed seal
reproductive or survival rates, or to impact availability of ringed
seals. Therefore, AK LNG project activities are not expected to impact
Kaktovik ringed seal harvests.
Kaktovik hunters harvested 126 pounds of spotted seals in 1992
(ADF&G Community Subsistence Information System (CSIS); retrieved and
analyzed August 15, 2018). Spotted seals were not reported harvested in
2006 survey interviews conducted in Nuiqsut (Stephen R. Braund &
Associates, 2010).
Hunting of bearded seals is more common than that of ringed seals
by Kaktovik residents, with 68 percent of respondents reporting the
hunting of bearded seals over the previous 10 years (Stephen R. Braund
& Associates, 2010). Kaktovik bearded seal hunting occurs along the
coast as far west as Prudhoe Bay and as far east as the United States/
Canada border (Stephen R. Braund & Associates, 2010). Residents
reported looking for bearded seal as far as approximately 30 mi (48 km)
from shore, but generally hunt them closer to shore, up to 5 mi (8 km;
Stephen R. Braund & Associates 2010). Between 1994-2003, 29 bearded
seals were taken in Kaktovik. Bearded seal hunting activities, like
ringed seal, begin in March, peaking in July and August, and then
conclude in September (Stephen R. Braund & Associate, 2010).
The community of Kaktovik is approximately 100 (direct) mi (161 km)
from the planned project at Prudhoe Bay; subsistence activities for
these communities primarily occur outside of the project construction
area and the associated Level A and Level B harassment zones. The
planned construction and use of improvements to West Dock would occur
in Prudhoe Bay, adjacent to existing oil and gas infrastructures, and
in an area that is not typically used for subsistence other than
extremely limited bearded seal hunting by residents of Kaktovik.
Because of the distance from Kaktovik, and Kaktovik's very limited
use of waters offshore of Prudhoe Bay, and because the planned
activities would occur in an already-developed area, it is unlikely
that the planned activities would have any effects on the use of marine
mammals for subsistence by residents of Kaktovik. Further, the planned
activities are not expected to impact marine mammals in numbers or
locations sufficient to render them unavailable for subsistence harvest
given the short-term, temporary, and localized nature of construction
activities, and the planned mitigation measures. Impacts to marine
mammals would mostly include limited, temporary behavioral disturbances
of seals, with limited AUD INJ associated with pile driving. Serious
injury or mortality of marine mammals is not anticipated from the
planned activities, and the activities are not expected to have any
impacts on reproductive or survival rates of any marine mammal species.
Therefore, we do not discuss Kaktovik's subsistence activities further.
Nuiqsut
The proposed construction activities would occur closest to the
marine subsistence use area used by the Native Village of Nuiqsut.
Nuiqsut is located on the west bank of the Nechelik Channel on the
lower Colville River, about 25 mi (40 km) from the Arctic Ocean and
approximately 150 mi (242 km) southeast of Utqia[gdot]vik. Nuiqsut
subsistence hunters utilize an extensive search area, spanning 16,322
mi\2\ (km\2\) across the central Arctic Slope (see Figure 19 of AGDC's
application, Brown et al., 2016). Marine mammal hunting is primarily
concentrated in two areas: (1) Harrison Bay, between Atigaru Point and
Oliktok Point, including a northward extent of approximately 50
[[Page 16627]]
mi (80 km) beyond the Colville River Delta (Brown et al., 2016); and
(2) east of the Colville River Delta between Prudhoe and Foggy Island
bays, which includes an area of approximately 100 square mi surrounding
the Midway Islands, McClure Island and Cross Island (Brown et al.,
2016). The community of Nuiqsut uses subsistence-harvest areas adjacent
to the proposed construction area; however, West Dock is not a common
hunting area, nor is it visited regularly by Nuiqsut subsistence
hunters primarily because of its industrial history.
The most important seal hunting area for Nuiqsut hunters is off the
Colville Delta, an area extending as far west as Fish Creek and as far
east as Pingok Island. Seal hunting search areas by Nuiqsut hunters
also included Harrison Bay, and a 30-mi (48-km) stretch northeast of
Nuiqsut between the Colville and Kuparuk rivers, near Simpson Lagoon
and Jones Islands (Brown et al., 2016). Cross Island is a productive
area for seals, but is too far from Nuiqsut to be used on a regular
basis. Seal subsistence use areas of Nuiqsut from 1995 through 2006 are
depicted in Figure 21 of AGDC's application.
Ringed seals are an important subsistence resource for Native
Alaskans living in communities along the Beaufort Sea coast. Nuiqsut
residents commonly harvest ringed seal in the Beaufort Sea during the
summer months (Stephen R. Braund & Associates, 2010). There are a
higher number of use areas extending east and west of the Colville
River delta. Residents reported traveling as far as Cape Halkett to the
west and Camden Bay to the east in search of ringed seal. Survey
respondents reported traveling offshore up to 30 mi (48 km; Stephen R.
Braund & Associates, 2010). Residents reported hunting ringed seals
throughout the late spring, summer, and early fall with a higher number
of use areas reported in June, July, and August (Stephen R. Braund &
Associates, 2010). In 2006, 12 people (36 percent of survey
respondents) indicated that they had recently hunted for ringed seals
in Nuiqsut (Stephen R. Braund & Associates, 2010).
Nuiqsut bearded seal use areas extend as far west as Cape Halkett,
as far east as Camden Bay, and offshore up to 40 mi (64 km). In 2006,
12 people (69 percent of survey respondents) indicated that they had
recently hunted for bearded seals in Nuiqsut (SRBA 2010). Nuiqsut
hunters reported hunting bearded seal during the summer season in open
water as the seals are following the ice pack. Residents reported
hunting bearded seal between June and September, although a small
number of use areas were reportedly used in May and October (SRBA
2010). The number of reported bearded seal use areas peak in July and
August, when the majority of seals are available along the ice pack
(SRBA 2010).
Nuiqsut's bowhead whale hunt occurs in the fall at Cross Island, a
barrier island located approximately 12 mi (19 km) northwest of West
Dock. Nuiqsut whalers base their activities from Cross Island
(Galginaitis 2014), and the whaling search and the harvest areas
typically are concentrated north of the island. Hunting activities
between 1997 and 2006 occurred almost as far west as Thetis Island, as
far east as Barter Island (Kaktovik), and up to approximately 50 mi (80
km) offshore (Stephen R Braund & Associates, 2010). Harvest locations
in 1973-2011 and GPS tracks of 2001-2011 whaling efforts are shown in
Figure 19 of AGDC's application.
Bowhead whales are harvested by Nuiqsut whalers during the fall
whaling season. Nuiqsut residents typically hunt bowhead whales in
September, although a small number of use areas were reported in August
and extending into October (Stephen R. Braund & Associates, 2010). Pile
driving would not occur during Nuiqsut whaling.
Nuiqsut subsistence hunting crews operating from Cross Island have
harvested three to four bowhead whales per year (Bacon et al., 2009;
Galginaitis 2014). In 2014, the Alaska Eskimo Whaling Commission (AEWC)
allocated Nuiqsut a quota of four bowhead whales each year; however,
through transfers of quota from other communities, in 2015 Nuiqsut was
able to harvest five whales (Brown et al., 2016). In 2006, 10 people
(30 percent of survey respondents) in Nuiqsut indicated that they had
recently hunted for bowhead whales (Stephen R. Braund & Associates,
2010). In 2016, Nuiqsut whaling crews harvested four bowhead whales
(Suydam et al., 2017).
Nuiqsut is 70 mi (112 km) away from the proposed project, and is
likely to be the community that has the greatest potential to
experience any impacts to subsistence practices. The primary potential
for AK LNG project impacts to Nuiqsut's subsistence use of marine
mammals is associated with barge activity, which could interfere with
summer seal and fall bowhead whale hunting (Alaska LNG 2016). Barge
activity is beyond the scope of this IHA, but noise associated with
barging could deflect bowhead whales as they migrate through Nuiqsut's
fall whaling grounds or cause temporary disturbances of seals, making
successful harvests more difficult. Barge traffic would occur from July
through September. Although barging activities would not cease during
Nuiqsut's fall bowhead whale hunting activities, the AGDC plans to keep
vessels landward of Cross Island during the August 25-September 15
period, avoiding the high use areas offshore of the island during the
entire whaling season in most years and greatly reducing the impact to
the whale hunt (Alaska LNG 2016, 2017).
Pile driving associated with construction at West Dock could also
affect subsistence hunting of bowhead whales, as the Level B harassment
zones extend up to 4.6 km from the pile driving site for some pile and
hammer type combinations. As such, AGDC will not pile drive during the
Nuiqsut whaling season (see Proposed Mitigation). AGDC has consulted
with AEWC and NSB on mitigation measures to limit impacts (Alaska LNG
2016), and has continued to provide formal and informal project updates
to these groups, as recently as July 2023.
The proposed activities are not expected to impact marine mammals
in numbers or locations sufficient to render them unavailable for
subsistence harvest given the short-term, temporary, and localized
nature of construction activities, and the proposed mitigation
measures. Impacts to marine mammals would mostly include limited,
temporary behavioral disturbances of seals, however, some PTS is
possible. Serious injury or mortality of marine mammals is not
anticipated from the proposed activities, and the activities are not
expected to have any impacts on reproductive or survival rates of any
marine mammal species.
In summary, impacts to subsistence hunting are not expected due to
the distance between West Dock construction and primary seal hunting
areas, and proposed mitigation during the Nuiqsut bowhead whale hunt.
Proposed Mitigation
In order to issue an IHA under section 101(a)(5)(D) of the MMPA,
NMFS must set forth the permissible methods of taking pursuant to the
activity, and other means of effecting the least practicable impact on
the specie
[…truncated; see source link]Indexed from Federal Register on April 18, 2025.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.