Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the U.S. Army Corps of Engineers Unalaska (Dutch Harbor) Channel Deepening Project, 21630-21650 [2023-07561]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 88, Number 69 (Tuesday, April 11, 2023)]
[Notices]
[Pages 21630-21650]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-07561]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XC824]


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to the U.S. Army Corps of Engineers 
Unalaska (Dutch Harbor) Channel Deepening Project

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Notice; proposed incidental harassment authorization; request 
for comments.

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SUMMARY: NMFS has received a request from the United States Army Corps 
of Engineers (Alaska District) (USACE) for authorization to take marine 
mammals incidental to Unalaska (Dutch Harbor) Channel Deepening in 
Iliuliuk Bay, Unalaska, 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 11, 
2023.

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 
[email protected].
    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 
www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act 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: Cara Hotchkin, Office of Protected 
Resources, NMFS, (301) 427-8401. 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: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities. In case of problems 
accessing these documents, please call the contact listed above.

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.

[[Page 21631]]

    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 mitigation, 
monitoring and reporting of the takings are set forth. The definitions 
of all applicable MMPA statutory terms cited above are included in the 
relevant sections below.

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.
    This action is consistent with categories of activities identified 
in Categorical Exclusion B4 (IHAs with no anticipated serious injury or 
mortality) of the Companion Manual for NOAA Administrative Order 216-
6A, which do not individually or cumulatively have the potential for 
significant impacts on the quality of the human environment and for 
which we have not identified any extraordinary circumstances that would 
preclude this categorical exclusion. Accordingly, NMFS has 
preliminarily determined that the issuance of the proposed IHA 
qualifies to be categorically excluded from further NEPA review.
    We will review all comments submitted in response to this notice 
prior to concluding our NEPA process or making a final decision on the 
IHA request.

Summary of Request

    On October 31, 2022, NMFS received a request from the United States 
Army Corps of Engineers--Alaska District (USACE) for an IHA to take 
marine mammals incidental to deepening the entrance to Iliuliuk Bay, 
adjacent to Dutch Harbor, Alaska. Following NMFS' review of the 
application, USACE submitted supplemental information on November 28, 
2022 and January 5, 2023. The application was deemed adequate and 
complete on March 2, 2023. USACE's request is for take of harbor seals 
(Phoca vitulina richardsi), Steller sea lions (Eumetopias jubatus), 
harbor porpoise (Phocoena phocoena) and humpback whales (Megaptera 
novaengliae) by Level A harassment and Level B Harassment. Neither 
USACE nor NMFS expect serious injury or mortality to result from this 
activity and, therefore, an IHA is appropriate.

Description of Proposed Activity

Overview

    The USACE is proposing to deepen the entrance channel of Iliuliuk 
Bay by means of dredging and (if necessary) confined blasting of a 42-
foot (ft) (12.8 meter (m)) deep ``bar'' which currently restricts 
access to the port of Dutch Harbor, Alaska. Dutch Harbor is the only 
deep draft, year-round ice-free port along the 1,200-mile (1,931 km) 
Aleutian Island chain, providing vital services to vessels operating in 
both the North Pacific and the Bering Sea, and the depth of the bar 
currently restricts access for large vessels that may need to enter the 
port, particularly during extreme weather. The purpose of the project 
is to increase navigational safety and improve economic efficiencies 
into and out of Dutch Harbor via Iliuliuk Bay. As shown in Figure 1-1 
of the IHA application, the depth of the bar and entrance is 
approximately 42 ft (12.8 m) below mean lower low water (MLLW), which 
is shallower than the surrounding bathymetry (approximately 100 ft 
(33.3 m) below MLLW). The bar is the only constraint preventing safe 
and efficient access for the delivery of fuel, durable goods, and 
exports to and from Dutch Harbor. Deeper draft vessels are unable to 
safely cross the bar to seek refuge in Dutch Harbor, and if they have 
to conduct personnel evacuations, it must be done outside the bar in 
open waters. This presents risks to rescuers and vessel personnel. The 
need for the project is to reduce inefficiencies in cargo 
transportation and provide safer options in protected waters for vessel 
repairs and medical evacuations than currently exist due to draft 
restrictions at the bar.
    Sounds resulting from confined blasting may result in the 
incidental take of marine mammals by Level A and Level B harassment in 
the form of slight injury (auditory and non-auditory) and behavioral 
harassment. Dredging and disposal of dredged material are not expected 
to result in either Level A or Level B harassment due to the low source 
level and mid-channel location of the dredging activities. If dredging 
is sufficient to deepen the channel to the required depth, reduced or 
no blasting may be necessary. USACE proposes a conservative scenario 
requiring blasting approximately 50 percent of the bar area, resulting 
in approximately 1,800 drilled boreholes and up to 24 total blasting 
events.

Dates and Duration

    The proposed IHA would be effective from November 1, 2023 to 
October 31, 2024. The in-water work period for the proposed action will 
occur over approximately 150 to 200 days over 12 months, including a 
maximum of 24 non-consecutive days with confined blasting events. 
Dredging could occur for up to 10 hours per day; dredge disposal could 
occur for up to 1 hour per day. USACE proposes to conduct all work 
during daylight hours.

Specific Geographic Region

    This project is located at the entrance to Iliuliuk Bay on Amaknak 
Island in the Aleutian Islands of Alaska. Dutch Harbor is a port 
facility with the City of Unalaska, and is located on the northern side 
of Amaknak Island, some 800 air miles (1,288 km) from Anchorage. The 
port of Dutch Harbor opens onto Iliuliuk Bay, and from there into 
Unalaska Bay and the Pacific Ocean (Figure 1). This project would occur 
at the mouth of Iliuliuk Bay out to a distance of approximately 3.1 
miles (5 kilometers (km)).

[[Page 21632]]

[GRAPHIC] [TIFF OMITTED] TN11AP23.014

Figure 1--Map of Proposed Project Area Amaknack Island, Alaska

Detailed Description of the Specified Activity

    The USACE is proposing to deepen the entrance channel of Iliuliuk 
Bay by means of dredging and (if necessary) confined blasting of a 42-
foot (ft) (12.8 meter (m)) deep ``bar'' which currently restricts 
access to the port of Dutch Harbor, Alaska. The bar is likely a 
terminal moraine from when the area around Iliuliuk Bay was glaciated; 
such moraines are typically made up of a heterogeneous mixture of 
everything from sand to large boulders. Geophysical surveys of the site 
indicate that the sediment is highly compacted and may require the use 
of explosives to effectively remove the sediment down to the desired 
depth of 58 ft (17.7 m) below MLLW. Removal of the bar would involve 
dredging (via clamshell dredge or long-reach excavator) an area 
approximately 600 ft (182.9 m) by 600 ft (182.9 m), moving 
approximately 182,000 cubic yards (139,150 cubic meters) of sediment. 
Dredged material would be placed in the water immediately adjacent to 
the inside of the bar in approximately 100 ft (33.3 m) of water. If 
required to enable dredging, confined blasting (hereafter ``blasting'') 
involving drilled boreholes and multiple charges with microdelays 
between blasts will be used to break up the sediment. If dredging is 
sufficient to deepen the channel to the required depth, reduced or no 
blasting may be necessary. USACE proposes a conservative scenario 
requiring blasting approximately 50 percent of the bar area, resulting 
in approximately 1,800 drilled boreholes and up to 24 total blasting 
events.
    The proposed project may result in take of marine mammals by Level 
A and Level B harassment caused by sounds produced from underwater 
blasting activities. No Level A or Level B harassment is expected from 
the proposed dredging, dredged material disposal, or borehole drilling 
due to the low source levels, similarity to sound from passing vessels, 
and mid-channel location of the activities, and therefore none is 
proposed for authorization. Acoustic impacts from dredging and borehole 
drilling are not addressed further in this document.
    Blasting Plan--The blasting plan for this project would be based on 
initial dredging activity, but a reasonable scenario involves drilling 
boreholes for confined underwater blasting in a 10-ft (3 m) by 10-ft (3 
m) grid pattern over the dredge prism. While it is possible that 
dredging would be accomplished without any blasting at all, it is 
conservative to assume that up to 50 percent of the dredged area would 
need to be blasted to break up the hard crust and possibly large 
boulders encountered in the dredge prism. This would result in up to 
1,800 boreholes drilled up to 60 ft (18.3 m) below MLLW. Drilling to 60 
ft (18.3 m) below MLLW would ensure that everything down to the design 
depth of 58 ft (17.7 m) below MLLW is completely fractured. However, if 
just the crust needs to be broken up by blasting it is possible that 
charges will not need to be placed as deep as 60 ft (18.3 m) below 
MLLW. Drilling would likely take place from a jack-up barge with a 
drilling template. It is expected that after 75 holes are drilled they 
would be shot in a single blasting event (with delays between charges). 
Shooting 75 holes per event would lead to a maximum total of 24 
blasting events to blast all 1,800 holes. Each of these 24 blasting 
events, lasting just over 1 second, may induce take by Level A and 
Level B harassment.
    Although the desired outcome is to avoid all or at least a large 
portion of the blasting, USACE conservatively assumes blasting would be 
necessary for up to 50 percent of the entire area. The 600 ft (182.9 m) 
by 600 ft (182.9 m) dredged area is 360,000 sq. ft (33,445 square 
meters (m\2\)). Borehole spacing of 10 ft (3 m) would require a total 
of 3,600 boreholes, so 50 percent would be a maximum of 1,800 
boreholes. Boreholes would likely be blasted in groups of 75 holes with 
delays between charges in each hole. It is estimated that there could 
be up to 24 days of blasting with

[[Page 21633]]

one blasting event lasting just over 1 second each of those 24 days. 
These blasting days will not occur every day, but will occur as needed 
and be separated by the time it takes to drill the necessary holes. It 
is possible that drilling might occur on the 1st and 2nd of a given 
month and then charges are placed and shot on the third day of that 
month and then dredging might proceed for a week or two before drilling 
and blasting are needed again. The proposed IHA would authorize a 
maximum of 24 blasting events.
    All underwater blasting would incorporate stemmed charges (i.e., 
crushed rock packed at the top of the hole above the explosive charge). 
Stemming helps to reduce the impact from blasting above the surface and 
maximizes the ability of the charge to fracture rock without wasting 
energy. Charge sizes would be limited to no more than 93.5 pounds (lbs) 
(42.4 kilograms (kg)) placed in lined boreholes that would be about 
3.5-4.0 inches (in) (8.9-10.2 centimeters (cm)) in diameter. Smaller 
charge sizes could be used at the contractor's discretion. The charge 
detonation in subsequent boreholes would be separated by at least 15 
milliseconds (ms) to reduce the overall charge at one time while still 
retaining the effectiveness of the charges in the borehole.
    Safety restrictions impose some limits on blasting activity and 
potential mitigations available to protect marine mammals. The 
explosives cannot ``sleep'' after being placed for longer than 24 hours 
without becoming a risk to private property and human health, and they 
cannot be detonated in the dark. If a marine mammal enters the blast 
area following the emplacement of charges, detonation will be delayed 
as long as possible. All other legal measures to avoid injury will be 
utilized; however, the charges will be detonated when delay is no 
longer feasible. As discussed in the mitigation section, in order to 
minimize the chances the charges need to be detonated while animals are 
present in the vicinity, the IHA includes a mitigation measure 
requiring explosives to be set as early in the day as possible, and 
detonated as soon as the pre-clearance zone is clear for 30 minutes.
    In summary, the project period includes up to 24 days of confined 
underwater blasting activities for which incidental take authorization 
is requested, and up to 180 days of dredging activity for which no take 
of any marine mammal species is expected or proposed for authorization.
    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, incorporated here by reference, instead of 
reprinting the information. Additional information regarding population 
trends and threats may be found in NMFS' Stock Assessment Reports 
(SARs; www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments) and more general information about these 
species (e.g., physical and behavioral descriptions) may be found on 
NMFS' website (https://www.fisheries.noaa.gov/find-species).
    Table 1 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. Alaska and Pacific Ocean SARs. All values presented in Table 
1 are the most recent available at the time of publication (including 
from the draft 2022 SARs) and are available online at: 
www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments.
    On January 24, 2023, NMFS published the draft 2022 SARs (https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region). The Alaska and Pacific Ocean SARs 
include a proposed update to the humpback whale stock structure. The 
new structure, if finalized, would modify the MMPA-designated stocks to 
align more closely with the ESA-designated DPSs. Please refer to the 
draft 2022 Alaska and Pacific Ocean SARs for additional information.
    NMFS Office of Protected Resources, Permits and Conservation 
Division has generally considered peer-reviewed data in draft SARs 
(relative to data provided in the most recent final SARs), when 
available, as the best available science, and has done so in this IHA 
for all species and stocks, with the exception of a new proposal to 
revise humpback whale stock structure. Given that the proposed changes 
to the humpback whale stock structure involve application of NMFS's 
Guidance for Assessing Marine Mammal Stocks and could be revised 
following consideration of public comments, it is more appropriate to 
conduct our analysis in this notice based on the status quo stock 
structure identified in the most recent final SARs (2021; Carretta et 
al., 2022; Muto et al., 2022).

[[Page 21634]]



                                            Table 1--Species Likely Impacted by the Specified Activities \1\
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                                                                                         ESA/MMPA  status;   Stock abundance (CV,
             Common name                  Scientific name               Stock             strategic (Y/N)      Nmin, most recent       PBR     Annual M/
                                                                                                \2\          abundance survey) \3\               SI \4\
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                                            Order Artiodactyla--Infraorder Cetacea--Mysticeti (baleen whales)
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Family Balaenopteridae (rorquals):
Humpback Whale \5\..................  Megaptera novaeangliae.  Central N Pacific......  -, -, Y             10,103 (0.3, 7,890,            83         26
                                                                                                             2006).
                                                               Western N Pacific......  E, D, Y             1,107 (0.3, 865, 2006)          3        2.8
                                                               CA/OR/WA...............  -, -, Y             4,973 (0.05, 4,776,          28.7     >=48.6
                                                                                                             2018).
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                                                  Odontoceti (toothed whales, dolphins, and porpoises)
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Family Phocoenidae (porpoises):
Harbor porpoise.....................  Phocoena phocoena......  Bering Sea \6\.........  -, -, Y             UNK (UNK, N/A, 2008)..        UND        0.4
                                                               Gulf of Alaska.........  -, -, Y             31,046 (0.21, N/A,            UND         72
                                                                                                             1998).
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                                                               Order Carnivora--Pinnipedia
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Family Otariidae (eared seals and
 sea lions):
Steller Sea Lion....................  Eumetopias jubatus.....  Western................  E, D, Y             52,932 (N/A, 52,932,          318        254
                                                                                                             2019).
                                                               Eastern................  -, -, N             43,201 (N/A, 43,201,         2592        112
                                                                                                             2017).
Family Phocidae (earless seals):
Harbor Seal.........................  Phoca vitulina.........  Aleutian Islands.......  -, -, N             5,588 (N/A, 5,366,             97         90
                                                                                                             2018).
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\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
  (https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/; 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: www.nmfs.noaa.gov/pr/sars/. CV is coefficient of variation; Nmin is the minimum estimate of
  stock abundance. In some cases, CV is not applicable due to lack of recent surveys allowing for accurate assessment 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, ship 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\ The two humpback whale Distinct Population Segments (DPSs) making up the California, Oregon, and Washington (CA/OR/WA) stock present in Southern
  California are the Mexico DPS, listed under the ESA as Threatened, and the Central America DPS, which is listed under the ESA as Endangered.
\6\ The best available abundance estimate and Nmin are likely an underestimate for the entire stock because it is based upon a survey that covered only
  a small portion of the stock's range. PBR for this stock is undetermined due to this estimate being older than 8 years.

    As indicated above, all four species (with eight managed stocks) in 
Table 1 temporally and spatially co-occur with the activity to the 
degree that take is reasonably likely to occur. All species that could 
potentially occur in the proposed survey areas are included in Table 3-
1 of the IHA application. While a biologically important area (BIA) for 
sperm whales (Physeter physeter) surrounds Amaknack Island (Brower et 
al., 2022), and killer whales (Orcinus orca) have been reported in the 
area, the temporal and/or spatial occurrence of these species is such 
that take is not expected to occur, and they are not discussed further 
beyond the explanation provided here. Previous monitoring for a 
construction project at Dutch Harbor, adjacent to Iliuliuk Bay, 
documented no sightings of any of these three species. Additionally, 
the shallow and confined nature of the bay makes it unsuitable habitat 
for sperm whales. Killer whales may occur within Iliuliuk Bay, but are 
infrequent and short-term visitors to the area and would be highly 
visible on approach.
    In addition, the northern sea otter (Enhydra lutris kenyoni) may be 
found in Iliuliuk Bay. However, northern sea otters are managed by the 
U.S. Fish and Wildlife Service and are not considered further in this 
document.

Humpback Whale

    The humpback whale is found worldwide in all oceans. Prior to 2016, 
humpback whales were listed under the ESA as an endangered species 
worldwide. Following a 2015 global status review (Bettridge et al., 
2015), NMFS established 14 Distinct Population Segments (DPS) with 
different listing statuses (81 FR 62259, September 8, 2016) pursuant to 
the ESA. Humpback whales found in the project area are predominantly 
from the three DPSs that are present in Alaska.
    Whales from the Western North Pacific (WNP), Mexico, and Hawaii 
DPSs overlap on feeding grounds off Alaska and are not visually 
distinguishable. Members of different DPSs are known to intermix on 
feeding grounds; therefore, all waters off the coast of Alaska should 
be considered to have ESA-listed humpback whales. Based on an analysis 
of migration between winter mating/calving areas and summer feeding 
areas using photo-identification, Wade et al. (2016) concluded that the 
humpback whales in the Aleutian Islands, Bering, Chukchi, and Beaufort 
Seas summer feeding areas are primarily from the recovered Hawaii DPS 
(91 percent), followed by the Mexico DPS (7 percent), and Western North 
Pacific DPS (2 percent).
    The DPSs of humpback whales that were identified through the ESA 
listing process do not equate to the existing MMPA stocks. The updated 
stock delineations for humpback whales under the MMPA are currently out 
for public review in the draft 2022 SARs, as mentioned above. Until 
this review is complete, NMFS considers humpback whales in the Aleutian 
Islands to be part of either the Central North Pacific stock or of the 
Western North Pacific stock (Muto et al., 2021).
    Humpback whales are found throughout the Aleutian Islands, Gulf of 
Alaska, and Bering Sea in a variety of marine environments, including 
open-ocean, near-shore waters, and areas within strong tidal currents 
(Dahlheim et al., 2009). Satellite tracking indicates humpbacks 
frequently congregate in

[[Page 21635]]

shallow, highly productive coastal areas of the North Pacific Ocean and 
Bering Sea (Kennedy et al., 2014). The waters surrounding the eastern 
Aleutian Islands are dominated by strong tidal currents, water-column 
mixing, and unique bathymetry. These factors are thought to concentrate 
the small fish and zooplankton that compose the typical humpback diet 
in Alaska, creating a reliable and abundant food source for whales. 
Unalaska Island is situated between Unimak and Umnak Passes, which are 
known to be important humpback whale migration routes and feeding areas 
(Kennedy et al., 2014). Humpback whales are often present near the 
project area during summer and show up in the larger area of Unalaska 
Bay beginning in April and are present well into October most years 
(USACE, 2019). Presence in Unalaska Bay and Iliuliuk Bay appears to be 
largely prey-driven, so large variations in abundance between months 
and years is common.
    The most common areas to see most humpback whales in Unalaska Bay 
is shown in the orange shading on Figure 4-3 of the IHA application. Up 
to 60 humpback whales at one time have been observed during USACE 2018 
surveys and use of this general area is supported by casual 
observations over the past 23 years of working in the area. Humpback 
whales have been seen in Captains Bay, Iliuliuk Bay, and inside Dutch 
Harbor, but are always in smaller numbers than the overall Unalaska Bay 
area.
    NMFS identified a portion of the area surrounding the Aleutian 
Islands as a Biologically Important Area (BIA) for humpback whales for 
feeding during the months of May through January (Brower et al. 2022). 
BIAs are spatial and temporal boundaries identified for certain marine 
mammal species where populations are known to concentrate for specific 
behaviors such as migration, feeding, or breeding. This BIA was 
identified based on tagging studies, visual observations, and acoustic 
detections of high numbers of humpback whales feeding in the area 
(Brower et al., 2022). Initial designation of humpback whale BIAs 
helped to inform the critical habitat designation finalized by NMFS in 
2021 (86 FR 21082, April 21, 2021).
    Critical habitat became effective on May 21, 2021 (86 FR 21082) for 
the Central America, Mexico, and Western North Pacific DPS of humpback 
whales. The nearshore boundaries of the critical habitat for Mexico and 
Western North Pacific DPS humpback whales in Alaska are defined by the 
1-meter isobath relative to MLLW. Additionally, on the north side of 
the Aleutian Islands, the seaward boundary is defined by a line 
extending from 55[deg]41' N, 162[deg]41' W to 55[deg]41' N, 169[deg]30' 
W, then southward through Samalga Pass to a boundary drawn along the 
2,000-meter isobath on the south side of the islands.
    The critical habitat does not include manmade structures (such as 
ferry docks or seaplane facilities) and the land on which they rest 
within the critical habitat boundaries. Sites owned or controlled by 
the Department of Defense (DoD) are also excluded from the critical 
habitat where they overlap. Essential features identified as essential 
to the conservation of the Mexico DPS and Western North Pacific DPS 
relevant to this IHA are the prey species of each (which are primarily 
euphausiids and small pelagic schooling fish) are of sufficient 
quality, abundance, and accessibility within humpback whale feeding 
areas to support feeding and population growth. Material and equipment 
barges' routes would transit through critical habitat on the way to the 
project site.

Harbor Porpoise

    Harbor porpoise range throughout the coastal waters of the North 
Pacific Ocean from Point Barrow along the Alaska Coast and throughout 
the Gulf of Alaska (Muto et al., 2021). While existing data suggests 
that the stock structure is likely more fine-scaled than current 
analyses have been able to describe, there are currently two defined 
stocks of harbor porpoise that may be present in the project area. 
These are the Bering Sea and Gulf of Alaska stocks. The Bering Sea 
stock occurs around the Aleutian Islands and northward, while the Gulf 
of Alaska Stock occurs south of the Aleutians and ranges throughout 
southcentral Alaskan coastal waters. There is likely some overlap in 
stocks around Unimak Pass (Muto et al., 2021), potentially including 
the action area. Harbor porpoise typically occur in waters less than 
100 m deep, tend to be solitary or occur in small groups, and can be 
difficult for observers to detect.
    Harbor porpoise tend to be short-term, infrequent visitors to 
Iliuliuk Bay. While there were no detections of this species during 
monitoring and survey efforts in 2017 and 2018, a group of 
approximately eight porpoises was spotted by USACE biologists during 
2017 project scoping efforts (USACE, 2019).

Steller Sea Lion

    Steller sea lions were listed as threatened range-wide under the 
ESA on November 26, 1990 (55 FR 49204). Steller sea lions were 
subsequently partitioned into the western and eastern Distinct 
Population Segments (DPSs; western and eastern stocks) in 1997 (62 FR 
24345, May 5, 1997). The eastern DPS remained classified as threatened 
until it was delisted in November 2013. The western DPS (those 
individuals west of the 144[deg] W longitude or Cape Suckling, Alaska) 
was upgraded to endangered status following separation of the DPSs, and 
it remains endangered today. There is regular movement of both DPSs 
across this 144[deg] W longitude boundary (Jemison et al., 2013) 
however, due to the distance from this DPS boundary, it is likely that 
only western DPS Steller sea lions are present in the project area. 
Therefore, animals potentially affected by the project are assumed to 
be part of the western DPS. Sea lions from the eastern DPS, are not 
likely to be affected by the proposed activity and are not discussed 
further.
    Steller sea lions do not follow traditional migration patterns, but 
will move from offshore rookeries in the summer to more protected 
haulouts closer to shore in the winter. They use rookeries and haulouts 
as resting spots as they follow prey movements and take foraging trips 
for days, usually within a few miles of their rookery or haulout. They 
are generalist marine predators and opportunistic feeders based on 
seasonal abundance and location of prey. Steller sea lions forage in 
nearshore as well as offshore areas, following prey resources. They are 
highly social and are often observed in large groups while hauled out, 
but alone or in small groups when at sea (NMFS, 2022).
    Steller sea lions are distributed throughout the Aleutian Islands, 
occurring year-round in the proposed action area. Steller sea lions are 
drawn to fish processing plants and high forage value areas, such as 
anadromous streams. Dutch Harbor is one of the busiest commercial 
fishing ports in the United States, with consistent fishing vessel 
traffic in and out of Iliuliuk Bay. Steller sea lions were common 
during periodic USACE winter surveys in Dutch Harbor between 2000 and 
2016, but they were not abundant near the proposed project area. Single 
marine mammals were observed on occasion outside the Dutch Harbor spit. 
In past years during winter surveys during 2000 to 2006, there were two 
areas outside of Iliuliuk Bay where large aggregations of 50 to 60 
Steller sea lions were common (USACE, unpublished data; see Figure 4-5 
of the IHA application for further detail).
    Critical habitat for Steller sea lions was designated by NMFS in 
1993 based on the following essential physical and

[[Page 21636]]

biological habitat features: terrestrial habitat (including rookeries 
and haulouts important for rest, reproduction, growth, social 
interactions) and aquatic habitat (including nearshore waters around 
rookeries and haulouts, free passage for migration, prey resources, and 
foraging habitats) (58 FR 45269).
    There are three major haulouts and one major rookery within 20 
nautical miles of the Proposed Project site (see Figure 4-6 in the IHA 
application). The major haulouts include Old Man Rocks and Unalaska/
Cape Sedanka (approximately 15 nautical miles southeast straight-line 
distance from the project site) and Akutan/Lava Reef (approximately 19 
nautical miles northeast straight-line distance from the project site). 
The closest rookery is Akutan/Cape Morgan (approximately 19 nautical 
miles east straight-line distance from the project site). Another major 
rookery is located approximately 19 nmi from the project location 
(straight line distance over mountains) at Akutan/Lava Reef. As of 
2014, the number of adult Steller sea lions using these sites was: 
1,129 (Akutan/Cape Morgran rookery); 182 (Akutan/Lava Reef haulout); 15 
(Old Man Rocks haulout); and 0 (Unalaska/Cape Sedanka haulout) (NMFS, 
2021).
    In addition to major rookery and haulout locations, there are three 
special aquatic foraging areas in Alaska for the Steller sea lion 
(Shelikof Strait area, Bogoslof area, and Seguam Pass area). The 
project site is within the outer limits of the Bogoslof foraging area 
(Figure 4-7 in the IHA application).
    Since the ensonified action area is within 20 nmi of major haulouts 
and a major rookery, it would intersect Steller sea lion designated 
critical habitat. Additionally, since Iliuliuk Bay is within Steller 
sea lion critical habitat, material and equipment barges' routes would 
transit through critical habitat on the way to the project site.

Harbor Seal

    Harbor seals inhabit coastal and estuarine waters off Alaska and 
are one of the most common marine mammals in Alaska. They haul out on 
rocks, reefs, beaches, and drifting glacial ice. They are opportunistic 
feeders and often adjust their distribution to take advantage of 
locally and seasonally abundant prey, feeding in marine, estuarine, and 
occasionally fresh waters (Womble et al., 2009, Allen and Angliss, 
2015). Harbor seals are generally non-migratory, with local movements 
associated with such factors as tide, weather, season, food 
availability and reproduction. They deviate from other pinniped species 
in that pupping may occur on a wide variety of haulout sites rather 
than particular major rookeries (ADF&G, 2022).
    There are 12 distinct stocks of harbor seals in Alaska. A 1996 to 
2018 survey resulted in an estimated 243,938 harbor seals throughout 
Alaska. The Aleutian Island Stock is the only stock that occurs within 
the project area and is estimated to consist of 5,588 harbor seals. The 
ability to obtain data on the Aleutian Island Stock is limited due to 
the region's size and weather; in addition, it is difficult to acquire 
the logistics to conduct aerial surveys in the region.
    In skiff-based surveys conducted in the western Aleutians from 1977 
to 1982, 1,619 harbor seals were observed. Compared to an aerial survey 
conducted in 1999 resulting in 884 harbor seals being observed, there 
was a 45 percent decrease in harbor seal population (Small et al., 
2008). Figure 4-1 in the IHA applications shows the locations where 
these surveys were conducted in the Fox Islands. The Fox Islands 
includes Unalaska Island, which had a multitude of locations surveyed.
    Harbor seals occur throughout Unalaska Bay. They are usually 
observed as single individuals in the water, but often in groups when 
hauled out. They occasionally haul out in three locations when in 
Iliuliuk Bay (Figure 4-2 in the IHA application). They typically haul 
out in groups of 1 to 10 individuals during calm conditions. Around 40 
harbor seals can haul out near Ulakta Head when the tide is at lower 
levels in calm seas. Additionally, although they can be found anywhere 
along the shoreline, they are more commonly seen routinely foraging at 
the kelp beds along the shoreline.

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., Richardson et al., 1995; Wartzok and 
Ketten, 1999; Au and Hastings, 2008). 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.). Note that no direct measurements of 
hearing ability have been successfully completed for mysticetes (i.e., 
low-frequency cetaceans). Subsequently, NMFS (2018) described 
generalized hearing ranges for these marine mammal hearing groups. 
Generalized hearing ranges were chosen based on the approximately 65 
decibel (dB) threshold from the normalized composite audiograms, with 
the exception for lower limits for low-frequency cetaceans where the 
lower bound was deemed to be biologically implausible and the lower 
bound from Southall et al. (2007) retained. Marine mammal hearing 
groups and their associated hearing ranges are provided in Table 2.

                  Table 2--Marine Mammal Hearing Groups
                              [NMFS, 2018]
------------------------------------------------------------------------
               Hearing group                 Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen        7 Hz to 35 kHz.
 whales).
Mid-frequency (MF) cetaceans (dolphins,     150 Hz to 160 kHz.
 toothed whales, beaked whales, bottlenose
 whales).
High-frequency (HF) cetaceans (true         275 Hz to 160 kHz.
 porpoises, Kogia, river dolphins,
 Cephalorhynchid, Lagenorhynchus cruciger
 & L. australis).
Phocid pinnipeds (PW) (underwater) (true    50 Hz to 86 kHz.
 seals).
Otariid pinnipeds (OW) (underwater) (sea    60 Hz to 39 kHz.
 lions and 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 are typically not as broad. Generalized
  hearing range chosen based on ~65 dB threshold from normalized
  composite audiogram, with the exception for lower limits for LF
  cetaceans (Southall et al., 2007) and PW pinniped (approximation).

    The pinniped functional hearing group was modified from Southall et 
al. (2007) on the basis of data indicating that phocid species have 
consistently demonstrated an extended frequency range of hearing 
compared to otariids, especially in the higher frequency range 
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth et al., 
2013).
    For more detail concerning these groups and associated frequency 
ranges, please see NMFS (2018) for a review of available information.

Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat

    This section provides a discussion of the ways in which components 
of the specified activity may impact marine

[[Page 21637]]

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

    Sound-producing in-water construction activities associated with 
the project would include confined blasting. The sounds produced by 
confined blasting are considered impulsive (as compared to non-
impulsive, defined below). The distinction between the two sound types 
is important because they have differing potential to cause 
physiological effects, particularly with regard to hearing (e.g., Ward 
1997 in Southall et al., 2007). Please see Southall et al. (2007) for 
an in-depth discussion of these concepts.
    Impulsive sound sources (e.g., explosions, gunshots, sonic booms, 
impact pile driving) produce signals that are brief (typically 
considered to be less than 1 second), broadband, atonal transients 
(ANSI 1986; Harris 1998; NIOSH 1998; ISO 2003; ANSI 2005) and occur 
either as isolated events or repeated in some succession. Impulsive 
sounds are all characterized by a relatively rapid rise from ambient 
pressure to a maximal pressure value followed by a rapid decay period 
that may include a period of diminishing, oscillating maximal and 
minimal pressures, and generally have an increased capacity to induce 
physical injury as compared with sounds that lack these features.
    Non-impulsive sounds can be tonal, narrowband, or broadband, brief 
or prolonged, and may be either continuous or non-continuous (ANSI 
1995; NIOSH 1998). Some of these non-impulsive sounds can be transient 
signals of short duration but without the essential properties of 
impulses (e.g., rapid rise time). Examples of non-impulsive sounds 
include those produced by vessels, aircraft, machinery operations such 
as drilling, vibratory pile driving, and active sonar systems. The 
duration of such sounds, as received at a distance, can be greatly 
extended in a highly reverberant environment.

Acoustic Impacts

    Anthropogenic sounds cover a broad range of frequencies and sound 
levels and can have a range of highly variable impacts on marine life, 
from none or minor to potentially severe responses, depending on 
received levels, duration of exposure, behavioral context, and various 
other factors. The potential effects of underwater sound from active 
acoustic sources can potentially result in one or more of the 
following; temporary or permanent hearing impairment, non-auditory 
physical or physiological effects, behavioral disturbance, stress, and 
masking (Richardson et al., 1995; Gordon et al., 2004; Nowacek et al., 
2007; Southall et al., 2007; Gotz et al., 2009). The degree of effect 
is intrinsically related to the signal characteristics, received level, 
distance from the source, and duration of the sound exposure. In 
general, sudden, high level sounds can cause hearing loss, as can 
longer exposures to lower level sounds. Temporary or permanent loss of 
hearing will occur almost exclusively for noise within an animal's 
hearing range. Specific manifestations of acoustic effects are first 
described before providing discussion specific to the USACE's blasting 
activities.
    Richardson et al. (1995) described zones of increasing intensity of 
effect that might be expected to occur, in relation to distance from a 
source and assuming that the signal is within an animal's hearing 
range. The first zone is the area within which the acoustic signal 
would be audible (potentially perceived) to the animal, but not strong 
enough to elicit any overt behavioral or physiological response. The 
next zone corresponds with the area where the signal is audible to the 
animal and of sufficient intensity to elicit behavioral or 
physiological responsiveness. Third is a zone within which, for signals 
of high intensity, the received level is sufficient to potentially 
cause discomfort or tissue damage to auditory or other systems. 
Overlaying these zones to a certain extent is the area within which 
masking (i.e., when a sound interferes with or masks the ability of an 
animal to detect a signal of interest that is above the absolute 
hearing threshold) may occur; the masking zone may be highly variable 
in size.
Hearing Threshold Shift
    NMFS defines a noise-induced threshold shift (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 
threshold shift is customarily expressed in decibels (dB). A TS can be 
permanent or temporary. As described in NMFS (2018), 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).
    Permanent Threshold Shift (PTS)--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 2018). Available data from 
humans and other terrestrial mammals indicate that a 40 dB threshold 
shift approximates PTS onset (see Ward et al., 1958, 1959; Ward 1960; 
Kryter et al., 1966; Miller 1974; Ahroon et al., 1996; Henderson et 
al., 2008). PTS levels for marine mammals are estimates, as with the 
exception of a single study unintentionally inducing PTS in a harbor 
seal (Kastak et al., 2008), there are no empirical data measuring PTS 
in marine mammals 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)--TTS is 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 threshold shift clearly larger than any day-to-
day or session-to-session variation in a subject's normal hearing 
ability (Schlundt et al., 2000; Finneran et al., 2000, 2002). As 
described in Finneran (2015), marine mammal studies have shown the 
amount of TTS increases with cumulative sound exposure level (SELcum) 
in an

[[Page 21638]]

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 a 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). 
For cetaceans, published data on the onset of TTS are limited to the 
captive bottlenose dolphin (Tursiops truncatus), beluga whale 
(Delphinapterus leucas), 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) (Reichmuth et al., 2019; 
Sills et al., 2020; Kastak et al., 1999, 2007; Kastelein et al., 
2019a,b, 2021, 2022). These studies examine hearing thresholds measured 
in marine mammals before and after exposure to intense sounds. 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, 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., 2019a, 
2019b). 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., 
2014; Kastelein et al., 2015a; 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 the 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).
Behavioral Effects
    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 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., 2003; Southall et al., 2007; Weilgart, 2007; Archer et 
al., 2010). Behavioral reactions can vary not only among individuals 
but also within an individual, depending on previous experience with a 
sound source, context, and numerous other factors (Ellison et al., 
2012), and can vary depending on characteristics associated with the 
sound source (e.g., whether it is moving or stationary, number of 
sources, distance from the source). Please see Appendices B-C of 
Southall et al. (2007) for a review 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., 2003). 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 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, 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; NRC, 2003; Wartzok et al., 2003). 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-impulsive sound sources (typically seismic airguns or acoustic 
harassment devices) have been varied but often consist of avoidance 
behavior or other behavioral changes suggesting discomfort (Morton and 
Symonds, 2002; see also Richardson et al., 1995; 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. 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

[[Page 21639]]

mammals from an important feeding or breeding area for a prolonged 
period, impacts on individuals and populations could be significant 
(e.g., Lusseau and Bejder, 2007; Weilgart, 2007; NRC, 2005). This 
highlights the importance of assessing the context of the acoustic 
effects alongside the received levels anticipated. Severity of effects 
from a response to an acoustic stimuli can likely vary based on the 
context in which the stimuli was received, particularly if it occurred 
during a biologically sensitive temporal or spatial point in the life 
history of the animal. There are broad categories of potential 
response, described 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,b). 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. 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 relationship between 
prey availability, foraging effort and success, and the life history 
stage 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, 2005b, 2006; Gailey et 
al., 2007).
    Marine mammals vocalize for different purposes and across multiple 
modes, such as whistling, echolocation click production, calling, and 
singing. Changes in vocalization behavior in response to anthropogenic 
noise can occur for any of these modes and may result from a need to 
compete with an increase in background noise or may reflect increased 
vigilance or a startle response. For example, in the presence of 
potentially masking signals, humpback whales and killer whales have 
been observed to increase the length of their songs (Miller et al., 
2000; Fristrup et al., 2003; Foote et al., 2004), while right whales 
(Eubalaena glacialis) have been observed to shift the frequency content 
of their calls upward while reducing the rate of calling in areas of 
increased anthropogenic noise (Parks et al., 2007b). In some cases, 
animals may cease sound production during production of aversive 
signals (Bowles et al., 1994).
    Avoidance is the displacement of an individual from an area or 
migration path because 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 
(Eschrictius robustus) are known to change direction--deflecting from 
customary migratory paths--in order to avoid noise from seismic surveys 
(Malme et al., 1984). 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). 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 
(Evans and England, 2001). However, it should be noted that response to 
a 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 fish 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 behavioral reactions and multi-day anthropogenic 
activities. For example, just because an activity lasts

[[Page 21640]]

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.
    With blasting activities, it is likely that the onset of sound 
sources could result in temporary, short-term changes in an animal's 
typical behavior and/or avoidance of the affected area. These 
behavioral changes may include (Richardson et al., 1995): changing 
durations of surfacing and dives, number of blows per surfacing, or 
moving direction and/or speed; reduced/increased vocal activities; 
changing/cessation of certain behavioral activities (such as 
socializing or feeding); visible startle response or aggressive 
behavior (such as tail/fluke slapping or jaw clapping); avoidance of 
areas where sound sources are located; and/or flight responses (e.g., 
pinnipeds flushing into water from haulouts or rookeries). Pinnipeds 
may increase their haulout time, possibly to avoid in-water disturbance 
(Thorson and Reyff, 2006). If a marine mammal responds to a stimulus by 
changing its behavior (e.g., through relatively minor changes in 
locomotion direction/speed or vocalization behavior), the response may 
or may not constitute taking at the individual level, and is unlikely 
to affect the stock or the species as a whole. However, if a sound 
source displaces marine mammals from an important feeding or breeding 
area for a prolonged period, impacts on animals, and if so potentially 
on the stock or species, could potentially be significant (e.g., 
Lusseau and Bejder, 2007; Weilgart, 2007). Given the nature of the 
proposed blasting activities (single, short-duration blasts on non-
consecutive days), and the monitoring and mitigation measures described 
below, NMFS considers the most likely impact to marine mammals to be a 
short-term, temporary behavioral disturbance such as a startle or 
change in orientation. It is expected that animals would return to 
their normal behavioral patterns within a few minutes after the 
blasting event, and that no habitat abandonment is likely as a result 
of the proposed construction activities.
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., Seyle, 1950; Moberg, 2000). 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 and 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 (Fair and Becker, 2000; 
Romano et al., 2002b) 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 ship traffic in the Bay of Fundy was 
associated with decreased stress in North Atlantic right 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 (NRC, 2003).
Auditory 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., 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. Given the short duration (approximately 1 second each) and 
non-consecutive nature of the blasting events proposed, it is unlikely 
that masking would occur for any marine mammal species.

Non-Auditory Physiological Effects From Explosive Detonations

    In addition to PTS and TTS, there is a potential for non-auditory 
physiological effects that could result from exposure to the detonation 
of explosives, which the USACE's activities include. Underwater 
explosions will send a shock wave and blast noise through the water, 
release gaseous by-products, create an oscillating bubble, and cause a 
plume of water to shoot up from the water surface. The shock wave and 
blast noise are of most concern to marine animals. The effects of an 
underwater explosion on a marine mammal depends on many factors, 
including the size, type, and depth of both the animal and the 
explosive charge; the depth of the water column; and the standoff 
distance between the charge and the animal, as well as the sound 
propagation properties of the environment. Potential impacts can range 
from brief effects

[[Page 21641]]

(such as behavioral disturbance), tactile perception, physical 
discomfort, slight injury of the internal organs and the auditory 
system, to death of the animal (Yelverton et al., 1973; DoN, 2001). 
Non-lethal injury includes slight injury to internal organs and the 
auditory system; however, delayed lethality can be a result of 
individual or cumulative sublethal injuries (DoN, 2001). Immediate 
lethal injury would be a result of massive combined trauma to internal 
organs as a direct result of proximity to the point of detonation (DoN, 
2001). Generally, the higher the level of impulse and pressure level 
exposure, the more severe the impact to an individual.
    Injuries resulting from a shock wave take place at boundaries 
between tissues of different density. Different velocities are imparted 
to tissues of different densities, and this can lead to their physical 
disruption. Blast effects are greatest at the gas-liquid interface 
(Landsberg, 2000). Gas-containing organs, particularly the lungs and 
gastrointestinal (GI) tract, are especially susceptible (Goertner, 
1982; Hill, 1978; Yelverton et al., 1973). In addition, gas-containing 
organs including the nasal sacs, larynx, pharynx, trachea, and lungs 
may be damaged by compression/expansion caused by the oscillations of 
the blast gas bubble. Intestinal walls can bruise or rupture, with 
subsequent hemorrhage and escape of gut contents into the body cavity. 
Less severe GI tract injuries include contusions, petechiae (small red 
or purple spots caused by bleeding in the skin), and slight 
hemorrhaging (Yelverton et al., 1973).
    Because the ears are the most sensitive to pressure, they are the 
organs most sensitive to injury (Ketten, 2000). Sound-related damage 
associated with blast noise can be theoretically distinct from injury 
from the shock wave, particularly farther from the explosion. If an 
animal is able to hear a noise, at some level it can damage its hearing 
by causing decreased sensitivity (Ketten, 1995). Sound-related trauma 
can be lethal or sub-lethal. Lethal impacts are those that result in 
immediate death or serious debilitation in or near an intense source 
and are not, technically, pure acoustic trauma (Ketten, 1995). Sub-
lethal impacts include hearing loss, which is caused by exposures to 
perceptible sounds. Severe damage (from the shock wave) to the ears 
includes tympanic membrane rupture, fracture of the ossicles, damage to 
the cochlea, hemorrhage, and cerebrospinal fluid leakage into the 
middle ear. Moderate injury implies partial hearing loss due to 
tympanic membrane rupture and blood in the middle ear. Permanent 
hearing loss also can occur when the hair cells are damaged by one very 
loud event, as well as by prolonged exposure to a loud noise or chronic 
exposure to noise. The level of impact from blasts depends on both an 
animal's location and, at outer zones, on its sensitivity to the 
residual noise (Ketten, 1995).
    The above discussion concerning underwater explosions only pertains 
to open water detonations in a free field without mitigation. Given the 
proposed monitoring and mitigation measures discussed below, the size 
of the explosives used, and the environment, the USACE's blasting 
events are not likely to have non-auditory injury or mortality effects 
on marine mammals in the project vicinity. Instead, NMFS considers that 
the USACE's blasts are most likely to cause Level B harassment, 
including behavioral harassment and TTS, or in some cases PTS, in a few 
individual marine mammals. Neither NMFS nor the USACE anticipates non-
auditory injuries of marine mammals as a result of the proposed 
construction activities.

Potential Effects on Marine Mammal Habitat

    Water quality--Temporary and localized reduction in water quality 
will occur as a result of dredging, dredge disposal, and blasting when 
bottom sediments are disturbed. Effects to turbidity and sedimentation 
are expected to be short-term, minor, and localized. Currents are 
strong in the area and, therefore, suspended sediments in the water 
column should dissipate and quickly return to background levels. 
Following the completion of sediment-disturbing activities, the 
turbidity levels are expected to return to normal ambient levels 
following the end of construction. Turbidity within the water column 
has the potential to reduce the level of oxygen in the water and 
irritate the gills of prey fish species in the proposed project area. 
However, turbidity plumes associated with the project would be 
temporary and localized, and fish in the proposed project area would be 
able to move away from and avoid the areas where plumes may occur. It 
is expected that the impacts on prey fish species from turbidity and, 
therefore, on marine mammals, would be minimal and temporary. In 
general, the area likely impacted by the project is relatively small 
compared to the available habitat in Iliuliuk Bay and the greater 
Unalaska Bay. While the project area occurs within a humpback whale 
feeding BIA, the area impacted by the blasting activities is very small 
relative to the available foraging habitat, and blasting would occur 
for a single second on non-consecutive days in an area that is already 
highly trafficked by vessels. As a result, activity at the project site 
would be inconsequential in terms of its effects on marine mammal 
foraging.
    Effects to Prey--Sound may affect marine mammals through impacts on 
the abundance, behavior, or distribution of prey species (e.g., 
crustaceans, cephalopods, fish, zooplankton). Marine mammal prey varies 
by species, season, and location and, for some, is not well documented. 
Studies regarding the effects of noise on known marine mammal prey are 
described here.
    Fish utilize the soundscape and components of sound in their 
environment to perform important functions such as foraging, predator 
avoidance, mating, and spawning (e.g., Zelick et al., 1999; Fay, 2009). 
Depending on their hearing anatomy and peripheral sensory structures, 
which vary among species, fishes hear sounds using pressure and 
particle motion sensitivity capabilities and detect the motion of 
surrounding water (Fay et al., 2008). The potential effects of noise on 
fishes depends on the overlapping frequency range, distance from the 
sound source, water depth of exposure, and species-specific hearing 
sensitivity, anatomy, and physiology. Key impacts to fishes may include 
behavioral responses, hearing damage, barotrauma (pressure-related 
injuries), and mortality.
    Fish react to sounds that are especially strong and/or intermittent 
low-frequency sounds, and behavioral responses, such as flight or 
avoidance are the most likely effects. Short duration, sharp sounds can 
cause overt or subtle changes in fish behavior and local distribution. 
The reaction of fish to noise depends on the physiological state of the 
fish, past exposures, motivation (e.g., feeding, spawning, migration), 
and other environmental factors. 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., Scholik and Yan, 
2001, 2002; Popper and Hastings, 2009). Several studies have 
demonstrated that impulse sounds might affect the distribution and 
behavior of some fishes, potentially impacting foraging opportunities 
or increasing energetic costs (e.g., Fewtrell and McCauley, 2012; 
Pearson et al., 1992; Skalski et al., 1992; Santulli et al., 1999; 
Paxton et al., 2017). However, some studies have shown no or slight 
reaction to impulse

[[Page 21642]]

sounds (e.g., Pena et al., 2013; Wardle et al., 2001; Jorgenson and 
Gyselman, 2009; Cott et al., 2012). More commonly, though, the impacts 
of noise on fish are temporary.
    Regarding impacts from explosive detonations, SPLs of sufficient 
strength have been known to cause injury to fish and fish mortality 
(Dahl et al., 2020). However, in most fish species, hair cells in the 
ear continuously regenerate and loss of auditory function likely is 
restored when damaged cells are replaced with new cells. Halvorsen et 
al. (2012a) showed that a TTS of 4-6 dB was recoverable within 24 hours 
for one species. Smith et al. (2022) found that damage to the inner 
ears of fishes at up to 400 m away from an open-water explosion, but 
noted that the damage present was not linearly related to the distance 
from the blast. They also did not examine the potential time to 
recovery from these injuries. Impacts would be most severe when the 
individual fish is close to the source. Injury caused by barotrauma can 
range from slight to severe and can cause death, and is most likely for 
fish with swim bladders. Barotrauma injuries have been documented 
during controlled exposure to explosions and impact pile driving, but 
the relationships between severity of injury and location of the fish 
relative to the sound source are not well understood (Halvorsen et al., 
2012b; Casper et al., 2013; Dahl et al., 2020). While physical impacts 
from blasting to fish are potentially severe, including barotrauma and 
mortality, the geographic range for these potential impacts from the 
explosion is likely to be limited. Given the other activity occurring 
within the blast zone (dredging and drilling), it is unlikely that many 
fishes would remain in a highly disturbed area with extensive 
construction operations occurring. NMFS therefore believes that the 
likelihood of injury and mortality to fishes from explosives will be 
minimized, and that any injurious effects would accrue only to 
individuals, with no overall impact to fish populations in and around 
the action area. With respect to non-injurious acoustic impacts, 
including TTS and behavioral disturbance, the blasting events will last 
less than 1 second each blast event, making the duration of potential 
acoustic impacts short term and temporary.
    Construction activities would also produce continuous (i.e., 
dredging and drilling) sounds. Sounds from dredging and drilling 
activities are unlikely to elicit behavioral reactions from fish due to 
their similarity to sounds from vessel passages, which are common in 
the area. These sounds are unlikely to cause injuries to fish or have 
persistent effects on local fish populations. The duration of possible 
fish avoidance of this area after dredging or drilling stops is 
unknown, but a return to normal recruitment, distribution and behavior 
is anticipated. In addition, it should be noted that the area in 
question experiences a high level of anthropogenic noise from normal 
port operations and other vessel traffic.
    The most likely impacts to fishes from the proposed project are 
behavioral disturbances, with some potential for TTS or non-auditory 
injury (ranging from superficial to serious); in general, impacts to 
fishes are expected to be minor and temporary.
    Construction may have temporary impacts on benthic invertebrate 
species, another possible marine mammal prey source. Direct benthic 
habitat loss would result with the permanent loss of 0.03 km\2\ of 
benthic habitat from deepening of the bar. However, the shallow habitat 
in the middle of the channel is not of high value to marine mammals, 
which are typically observed foraging either at the shoreline or 
further into open water, and represents a minimal portion of the 
available habitat. Further, vessel activity during passages in and out 
of Iliuliuk Bay creates minor disturbances of benthic habitats (e.g., 
vessel propeller wakes). The most likely impacts on marine mammal 
habitat for the project are from underwater noise, bedrock removal, and 
turbidity, all of which may have impacts on marine mammal prey species. 
However, as described in the analysis, any impacts to fish and 
invertebrates are expected to be relatively short term and localized, 
and would be inconsequential to the fish and invertebrate populations, 
as well as the marine mammals that use them as prey.

Estimated Take of Marine Mammals

    This section provides an estimate of the number of incidental takes 
proposed for authorization through this IHA, which will inform both 
NMFS' consideration of ``small numbers,'' and the negligible impact 
determinations.
    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).
    Authorized takes would primarily be by Level B harassment, as use 
of the explosive source (i.e., confined blasting) has the potential to 
result in disruption of behavioral patterns for individual marine 
mammals. There is also some potential for auditory injury and tissue 
damage (Level A harassment) to result, primarily for cetaceans 
(humpback whale and harbor porpoise) and phocids because predicted 
auditory injury zones are larger than for otariids. 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. While 
blasting has the potential to result in mortality, when the isopleths 
within which mortality could occur were calculated, the zones were 
sufficiently small that the risk of mortality is considered 
discountable. Below we describe how the proposed take numbers are 
estimated.
    For acoustic impacts, generally speaking, we estimate take by 
considering: (1) acoustic thresholds above which NMFS believes the best 
available science indicates marine mammals will be behaviorally 
harassed or incur some degree of permanent hearing impairment; (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 Thresholds

    NMFS recommends the use of acoustic thresholds 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 PTS of some degree (equated to Level A 
harassment). Thresholds have also been developed to identify the 
pressure levels above which animals may incur different types of tissue 
damage (non-acoustic Level A harassment or mortality) from exposure

[[Page 21643]]

to pressure waves from explosive detonation.
    Level A harassment--NMFS' Technical Guidance for Assessing the 
Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0) 
(Technical Guidance, 2018) identifies dual criteria to assess auditory 
injury (Level A harassment) to five different marine mammal groups 
(based on hearing sensitivity) as a result of exposure to noise from 
two different types of sources (impulsive (including explosives) or 
non-impulsive). These thresholds are provided in Table 3, below. The 
references, analysis, and methodology used in the development of the 
thresholds are described in NMFS' 2018 Technical Guidance, which may be 
accessed at: www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.
    Explosive sources--Based on the best available science, NMFS uses 
the acoustic and pressure thresholds indicated in Tables 3 and 4 to 
predict the onset of behavioral harassment, PTS, TTS, tissue damage, 
and mortality.
    For explosive activities using single detonations (i.e., no more 
than one detonation within a day), such as those described in the 
proposed activity, NMFS uses TTS onset thresholds to assess the 
likelihood of behavioral harassment, rather than the Level B Harassment 
threshold for multiple detonations indicated in Table 3. While marine 
mammals may also respond behaviorally to single explosive detonations, 
these responses are expected to typically be in the form of startle 
reaction, rather than a more meaningful disruption of a behavioral 
pattern. On the rare occasion that a single detonation might result in 
a behavioral response that qualifies as Level B harassment, it would be 
expected to be in response to a comparatively higher received level. 
Accordingly, NMFS considers the potential for these responses to be 
quantitatively accounted for through the application of the TTS 
threshold, which, as noted above, is 5 dB higher than the behavioral 
harassment threshold for multiple explosives.

                   Table 3--Explosive Thresholds for Marine Mammals for PTS, TTS, and Behavior
                                             [Multiple detonations]
----------------------------------------------------------------------------------------------------------------
                                            PTS impulsive            TTS impulsive         Behavioral threshold
            Hearing group                     thresholds               thresholds         (multiple detonations)
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans.........  Cell 1: L,0-pk,flat:     Cell 2: L,0-pk,flat:     Cell 3: LE,LF,24h: 163
                                        219 dB; LE,LF,24h: 183   213 dB; LE,LF,24h: 168   dB.
                                        dB.                      dB.
Mid-Frequency (MF) Cetaceans.........  Cell 4: L,0-pk,flat:     Cell 5: L,0-pk,flat:     Cell 6: LE,MF,24h: 165
                                        230 dB; LE,MF,24h: 185   224 dB; LE,MF,24h: 170   dB.
                                        dB.                      dB.
High-Frequency (HF) Cetaceans........  Cell 7: L,0-pk,flat:     Cell 8: L,0-pk,flat:     Cell 9: LE,HF,24h: 135
                                        202 dB; LE,HF,24h: 155   196 dB; LE,HF,24h: 140   dB.
                                        dB.                      dB.
Phocid Pinnipeds (PW) (Underwater)...  Cell 10: L,0-pk,flat:    Cell 11: L,0-pk,flat:    Cell 12: LE,PW,24h: 165
                                        218 dB; LE,PW,24h: 185   212 dB; LE,PW,24h: 170   dB.
                                        dB.                      dB.
Otariid Pinnipeds (OW) (Underwater)..  Cell 13: L,0-pk,flat:    Cell 14: L,0-pk,flat:    Cell 15: LE,OW,24h: 183
                                        232 dB; LE,OW,24h: 203   226 dB; LE,OW,24h: 188   dB.
                                        dB.                      dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for
  calculating PTS/TTS onset. Note: Peak sound pressure (Lpk) has a reference value of 1 [micro]Pa, and
  cumulative sound exposure level (LE) has a reference value of 1[micro]Pa\2\s. In this Table, thresholds are
  abbreviated to reflect American National Standards Institute standards (ANSI 2013). However, ANSI defines peak
  sound pressure as incorporating frequency weighting, which is not the intent for this Technical Guidance.
  Hence, the subscript ``flat'' is being included to indicate peak sound pressure should be flat weighted or
  unweighted within the overall marine mammal generalized hearing range. The subscript associated with
  cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function
  (LF, MF, and HF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours.
  The cumulative sound exposure level thresholds 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 acoustic thresholds will be exceeded.


                     Table 4--Lung and GI Tract Injury Thresholds for Underwater Explosives
----------------------------------------------------------------------------------------------------------------
                                        Mortality (severe lung
            Hearing group                     injury) *           Slight lung injury *       GI tract injury
----------------------------------------------------------------------------------------------------------------
All Marine Mammals...................  Cell 1: Modified         Cell 2: Modified         Cell 3: L,0-pk,flat:
                                        Goertner model;          Goertner model;          237 dB.
                                        Equation 1.              Equation 2.
----------------------------------------------------------------------------------------------------------------
* Lung injury (severe and slight) thresholds are dependent on animal mass (Recommendation: Table C.9 from DON
  2017 based on adult and/or calf/pup mass by species).
Note: Peak sound pressure (Lpk) has a reference value of 1 [micro]Pa. In this Table, thresholds are abbreviated
  to reflect American National Standards Institute standards (ANSI 2013). However, ANSI defines peak sound
  pressure as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the
  subscript ``flat'' is being included to indicate peak sound pressure should be flat weighted or unweighted
  within the overall marine mammal generalized hearing range.
Modified Goertner Equations for severe and slight lung injury (pascal-second)
Equation 1: 103M\1/3\(1 + D/10.1)\1/6\ Pa-s
Equation 2: 47.5M\1/3\(1 + D/10.1)\1/6\ Pa-s
M animal (adult and/or calf/pup) mass (kg) (Table C.9 in DoN 2017)
D animal depth (meters)

Ensonified Area

    Here, 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.
    NMFS computed cumulative sound exposure impact zones from the 
blasting information provided by the USACE. Peak source levels of the 
confined blasts were calculated based on Hempen et al. (2007), and 
scaled using a distance of 10 ft (3 m) and a weight of 95 lbs (43.1 kg) 
for a single charge. The total charge weight is defined as the product 
of the single charge weight and the number of charges. In this case, 
the number of charges is 75. Explosive energy was then

[[Page 21644]]

computed from peak pressure of the single maximum charge, using the 
pressure and time relationship of a shock wave (Urick, 1983). Due to 
time and spatial separation of each single charge by a distance of 10 
ft (3m), the accumulation of acoustic energy is added sequentially, 
assuming the transmission loss follows cylindrical spreading within the 
matrix of charges. The sound exposure level (SEL) from each charge at 
its source can then be calculated, followed by the received SEL from 
each charge. Since the charges will be deployed in a grid of 10 ft (3 
m) by 10 ft (3 m) apart, the received SELs from different charges to a 
given point will vary depending on the distance of the charges from the 
receiver. Without specific information regarding the layout of the 
charges, the modeling assumes a grid of 8 by 9 charges with an 
additional three charges located in three peripheral locations. Among 
the various total SELs calculated (one at a receiver location 
corresponding to each perimeter charge), the largest value, SELtotal 
(max) is selected to calculate the impact range. Using the pressure 
versus time relationship above, the frequency spectrum of the explosion 
can be computed by taking the Fourier transform of the pressure 
(Weston, 1960), and subsequently be used to produce hearing range 
weighted metrics.
    Frequency specific transmission loss of acoustic energy due to 
absorption is computed using the absorption coefficient, [alpha] (dB/
km), summarized by Fran[ccedil]ois and Garrison (1982a, b). Seawater 
properties for computing sound speed and absorption coefficient were 
based on NMFS Alaska Fisheries Science Center report of mean 
measurements in Auke Bay (Sturdevant and Landingham, 1993) and the 2022 
average seawater temperature from Unalaska (NOAA, 2023). Transmission 
loss was calculated using the sonar equation:

TL = SELtotal(m)-SELthreshold

where SELthreshold is the Level A harassment threshold. The 
distances, R, where such transmission loss is achieved were computed 
numerically by combining both geometric transmission loss, and 
transmission loss due to frequency-specific absorption. A spreading 
coefficient of 20 is assumed to account for acoustic energy loss from 
the sediment into the water column. The outputs from this model are 
summarized in Table 5, below.

                                            Table 5--Model Results of Impact Zones for Blasting in Meters (m)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Slight lung
                 Species                     Mortality        injury         GI tract       PTS: SELcum     PTS: SPLpk      TTS: SELcum     TTS: SPLpk
--------------------------------------------------------------------------------------------------------------------------------------------------------
Low frequency cetacean..................             4.0             9.2            25.8        * 344.66          205.29         * 1,918          409.62
High frequency cetacean.................            20.3            47.5            25.8        1,213.79      * 1,453.37      * 4,435.57        2,899.86
Otariid.................................            13.8            32.3            25.8           40.00         * 91.92        * 249.76          183.40
Phocid..................................            18.2            42.5            25.8          164.84        * 230.34        * 909.10          459.60
--------------------------------------------------------------------------------------------------------------------------------------------------------
* For the dual criteria of SELcum and SPLpk, the largest of the two calculated distances for each species group was used in our analysis. The PTS and
  TTS distances for Steller sea lions resulting from the model seemed uncharacteristically small when compared to the other thresholds resulting from
  the model and were doubled to 92 m and 230 m respectively for take estimation, mitigation, and monitoring.

Marine Mammal Occurrence

    In this section, we provide information about the occurrence of 
marine mammals, including density or other relevant information that 
will inform the take calculations. Reliable densities are not available 
for Iliuliuk Bay, and generalized densities for the North Pacific are 
not applicable given the high variability in occurrence and density at 
specific areas around the Aleutian Island chain. Therefore, the USACE 
consulted previous survey data in and around Iliuliuk Bay and Dutch 
Harbor to arrive at a number of animals expected to occur within the 
project area per day. Figure 4-8 and Table 4-3 in the IHA application 
provide further detail on observations of humpback whales, Steller sea 
lions, and harbor seals in and around Iliuliuk Bay. Harbor porpoise 
were not addressed in the IHA application; however, NMFS proposes 
authorization of harbor porpoise take out of an abundance of caution, 
based on the 2017 sighting of porpoises in the action area by USACE 
biologists.

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.
    Since reliable densities are not available, the USACE has requested 
take based on the maximum number of animals that may occur in the 
blasting area per day multiplied by the number of days of the activity. 
The applicant varied these calculations based on certain factors. 
Because of the nature of the proposed blasting (i.e., no more than one 
blasting event per day), the behavioral thresholds associated with the 
activity are the same as for the onset of TTS for all species. Both 
behavioral disturbance and TTS may occur.
    Humpback whale--Humpback whales are commonly sighted outside the 
mouth of Iliuliuk Bay, and were most common in August and September 
between 2 and 8 km from the survey site outside the mouth of the bay. 
Humpbacks were also spotted within Iliuliuk Bay in much lower numbers 
(maximum daily sightings within the bay: 4; outside the bay: 47) (USACE 
2022). Based on the previous monitoring efforts in and around Iliuliuk 
Bay, USACE and NMFS estimate that a maximum of two animals may be 
present within the Level B harassment threshold for each blasting 
event. While NMFS expects that the monitoring and mitigation described 
later in this document will be effective at preventing injurious take 
of marine mammals, we recognize that humpback whales are common in the 
area, that animals may enter the blasting area after charges have been 
set, and that there is a limit on the amount of time detonation may be 
safely delayed. Humpback whales are highly visible, and their presence 
would likely be known before charges are laid on a blasting day. We 
therefore conservatively estimate up to 10 percent of the blasting 
events may include a humpback whale within the Level A harassment 
isopleth. With a maximum take of 2 animals per day, multiplied by a 
maximum of 24 days of blasting, we propose authorization of 48 takes by 
Level B harassment and up to 3 takes by Level A harassment of humpback 
whales.
    Harbor porpoise--Harbor porpoise were not included in the IHA 
application. This species typically travels alone or in pairs, but may 
occasionally be sighted in larger groups. Based on the USACE's 
observation of a

[[Page 21645]]

group of eight individuals in the project area in 2017, and other 
infrequent sightings of harbor porpoise in and around Iliulliuk Bay, 
NMFS conservatively proposes an estimate of two animals within the 
Level B harassment threshold on up to 25 percent of blasting days. Out 
of an abundance of caution, and because this species is both very 
sensitive to noise (meaning the Level A harassment zone is 
comparatively larger), including explosions (von Benda-Beckmann et al., 
2015), and difficult to see in the field, NMFS also proposes that up to 
two harbor porpoise could be within the Level A harassment threshold 
for up to 10 percent of the blasting events. Given 24 days of blasting, 
we propose authorization of up to 12 harbor porpoise takes by Level B 
harassment, and up to 5 harbor porpoise takes by Level A harassment 
over the course of the activity.
    Steller sea lion--During previous monitoring efforts, Steller sea 
lions were sighted most frequently inside of Iliuliuk Bay, within 4 km 
of the proposed project area. The maximum number of sightings in a 
single day was 32, though it is unclear whether this includes multiple 
sightings of the same large group of 10 to 12 individuals (USACE 2022). 
Steller sea lions in this area are known to congregate around and 
follow fishing vessels that regularly transit into and out of Dutch 
Harbor. Given the previous monitoring data, USACE and NMFS 
conservatively estimate that a maximum of two animals may be within the 
Level B harassment threshold for each blast. While NMFS expects that 
the monitoring and mitigation described later in this document will be 
effective at preventing injurious take of marine mammals, we recognize 
that Steller sea lions are common in the area, that animals may enter 
the blasting area after charges have been set, and that there is a 
limit on the amount of time detonation may be safely delayed. Steller 
sea lions may be difficult for observers to detect before charges are 
laid on a blasting day, and we therefore conservatively estimate up to 
two Steller sea lions may be within the Level A harassment isopleth for 
up to 20 percent of the blasting events. With a maximum take of 2 
animals per day, multiplied by a maximum of 24 days of blasting, the 
applicant requests authorization of 48 takes by Level B harassment and 
up to 5 takes by Level A harassment of Steller sea lions.
    Harbor seal--Previous monitoring efforts documented harbor seals 
close to the shoreline Ulatka Head, on the northeastern side of 
Iliuliuk Bay between 1 and 4 km from the proposed project area, but 
were sighted throughout Iliuliuk Bay in all survey months (April-
October) (USACE 2022). They were most frequently sighted in the summer 
months, with up to 43 sightings on a single day. Based on the high rate 
of sightings within a few hundred meters of the Level B harassment 
isopleth in the previous data, USACE and NMFS conservatively assume a 
maximum of 10 seals within the Level B harassment threshold for each 
blast. While NMFS expects that the monitoring and mitigation described 
later in this document will be effective at preventing injurious take 
of marine mammals, we recognize that harbor seals are common in the 
area, that animals may enter the blasting area after charges have been 
set, and that there is a limit on the amount of time detonation may be 
safely delayed. Harbor seals were frequently sighted close to the Level 
B threshold distance and may be difficult for observers to detect 
before charges are laid on a blasting day. We therefore conservatively 
estimate up to two harbor seals may be within the Level A harassment 
isopleth for up to 20 percent of the blasting events. With a maximum 
take of 10 animals per day, multiplied by a maximum of 24 days of 
blasting, the applicant requests authorization of 240 takes by Level B 
harassment and up to 5 takes by Level A harassment of harbor seals.

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 species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of the species or stock for taking for certain 
subsistence uses. NMFS regulations require applicants for incidental 
take authorizations to include information about the availability and 
feasibility (economic and technological) of equipment, methods, and 
manner of conducting the activity or other means of effecting the least 
practicable adverse impact upon the affected species or stocks, and 
their habitat (50 CFR 216.104(a)(11)).
    In evaluating how mitigation may or may not be appropriate to 
ensure the least practicable adverse impact on species or stocks and 
their habitat, as well as subsistence uses where applicable, NMFS 
considers two primary factors:
    (1) The manner in which, and the degree to which, the successful 
implementation of the measure(s) is expected to reduce impacts to 
marine mammals, marine mammal species or stocks, and their habitat, as 
well as subsistence uses. This considers the nature of the potential 
adverse impact being mitigated (likelihood, scope, range). It further 
considers the likelihood that the measure will be effective if 
implemented (probability of accomplishing the mitigating result if 
implemented as planned), the likelihood of effective implementation 
(probability implemented as planned), and;
    (2) The practicability of the measures for applicant 
implementation, which may consider such things as cost and impact on 
operations.
    In addition to the measures described later in this section, the 
USACE will employ the following standard mitigation measures:
     Conduct a briefing between construction supervisors and 
crews and the marine mammal monitoring team prior to the start of 
construction, and when new personnel join the work, to explain 
responsibilities, communication procedures, marine mammal monitoring 
protocol, and operational procedures;
     For in-water and over-water heavy machinery work, if a 
marine mammal comes within 10 m, operations must cease and vessels must 
reduce speed to the minimum level required to maintain steerage and 
safe working conditions;
     Work may only occur during daylight hours, when visual 
monitoring of marine mammals can be conducted; and
     If take reaches the authorized limit for an authorized 
species, the blasting activity will be stopped as these species 
approach the Monitoring zones (Table 6) to avoid additional take of 
them.

[[Page 21646]]



     Table 6--Monitoring and Pre-Clearance Zones for Blasting Activities for Species With Take Proposed for
                                                  Authorization
----------------------------------------------------------------------------------------------------------------
                                                                      Pre-Clearance zones (m)
                                                                 --------------------------------
                                                                      Level A         Level B       Monitoring
                                                                    harassment      harassment       zones (m)
                                                                    thresholds      thresholds
                                                                       (PTS)           (TTS)
----------------------------------------------------------------------------------------------------------------
Humpback whale..................................................             345           1,918           2,500
Harbor Porpoise.................................................           1,214           4,500           5,000
Steller sea lion................................................              92             250           2,500
Harbor seal.....................................................             231             910           2,500
----------------------------------------------------------------------------------------------------------------

    The USACE would be required to implement the following mitigation 
requirements:
    Establishment of Pre-Clearance and Monitoring Zones--The USACE and 
NMFS have identified pre-clearance zones associated with the distances 
within which Level A harassment and Level B harassment are expected to 
occur. Additionally, monitoring zones that extend beyond the pre-
clearance zones have been established. Monitoring zones provide utility 
for observing by establishing monitoring protocols for areas adjacent 
to the pre-clearance zones. Monitoring zones enable observers to be 
aware of and communicate the presence of marine mammals in the project 
area outside the Level B harassment pre-clearance zone and thus prepare 
for a potential cessation of activity should the animal enter the Level 
A harassment zone (Table 6).
    Pre-monitoring and Delay of Activities--Prior to the start of daily 
in-water activity, or whenever a break in activity of 30 minutes or 
longer occurs, the observers will observe the pre-clearance and 
monitoring zones for a period of 30 minutes. Pre-clearance zones will 
be considered cleared when a marine mammal has not been observed within 
the zone for that 30-minute period. If any marine mammal is observed 
within the Level A pre-clearance zone, activity cannot proceed until 
the animal has left the zone or has not been observed for 15 minutes. 
If marine mammals are observed within the Level B pre-clearance or 
monitoring zones but outside of the Level A pre-clearance zones, work 
may proceed in good visibility conditions. If work ceases for more than 
30 minutes, the pre-activity monitoring of both the monitoring zone and 
shutdown zone will commence.
    In the event that a large whale for which take is not authorized is 
sighted within either the monitoring or the Level A or Level B pre-
clearance zones during monitoring prior to placement of charges on a 
planned blast day, USACE will evaluate whether environmental conditions 
allow for blasting to be delayed to the following day. If charges have 
already been laid before the whale is sighted, blasting would not 
commence until the whale has been positively observed outside of the 
monitoring zone, subject to the safety restrictions discussed below.
    Charges for blasting will not be laid if marine mammals are within 
the Level A pre-clearance zone or appear likely to enter the Level A 
pre-clearance zone. However, once charges are placed, they cannot be 
safely left undetonated for more than 24 hours. For blasting, the 
monitoring and pre-clearance zones will be monitored for a minimum of 
30 minutes prior to detonating the blasts. If a marine mammal is 
sighted within the Level A or Level B pre-clearance zones following the 
emplacement of charges, detonation will be delayed until the zones are 
clear of marine mammals for 30 minutes. This will continue as long as 
practicable within the constraints of the blasting design but not 
beyond sunset on the same day as the charges cannot lay dormant for 
more than 24 hours, which may force the detonation of the blast in the 
presence of marine mammals. All other legal measures to avoid injury 
will be utilized; however, the charges will be detonated when delay is 
no longer feasible.
    Charges will be laid as early as possible in the morning and 
stemming procedures will be used to fill the blasting holes to 
potentially reduce the noise from the blasts. Blasting will only be 
planned to occur in good visibility conditions, and at least 30 minutes 
after sunrise and at least one hour prior to sunset. The zones will 
also be monitored for 1 hour post-blasting.
    If a detonation occurs when a marine mammal is known to be within 
the Level A or Level B pre-clearance zones, USACE will observe the 
blast area for two hours after the blasting event, or until visibility 
or safety conditions decline to the point that monitoring is no longer 
feasible, to determine as much as possible about the behavior and 
physical status of the marine mammal affected by the blasting event.
    Based on our evaluation of the applicant's proposed measures, as 
well as other measures considered by NMFS, NMFS has preliminarily 
determined that the proposed mitigation measures provide the means of 
effecting the least practicable impact on 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 such species or stock for subsistence uses.

Proposed Monitoring and Reporting

    In order to issue an IHA for an activity, section 101(a)(5)(D) of 
the MMPA states that NMFS must set forth requirements pertaining to the 
monitoring and reporting of such taking. The MMPA implementing 
regulations at 50 CFR 216.104(a)(13) indicate that requests for 
authorizations must include the suggested means of accomplishing the 
necessary monitoring and reporting that will result in increased 
knowledge of the species and of the level of taking or impacts on 
populations of marine mammals that are expected to be present while 
conducting the activities. Effective reporting is critical both to 
compliance as well as ensuring that the most value is obtained from the 
required monitoring.
    Monitoring and reporting requirements prescribed by NMFS should 
contribute to improved understanding of one or more of the following:
     Occurrence of marine mammal species or stocks in the area 
in which take is anticipated (e.g., presence, abundance, distribution, 
density);
     Nature, scope, or context of likely marine mammal exposure 
to potential stressors/impacts (individual or cumulative, acute or 
chronic), through better understanding of: (1) action or environment 
(e.g., source

[[Page 21647]]

characterization, propagation, ambient noise); (2) affected species 
(e.g., life history, dive patterns); (3) co-occurrence of marine mammal 
species with the activity; or (4) biological or behavioral context of 
exposure (e.g., age, calving or feeding areas);
     Individual marine mammal responses (behavioral or 
physiological) to acoustic stressors (acute, chronic, or cumulative), 
other stressors, or cumulative impacts from multiple stressors;
     How anticipated responses to stressors impact either: (1) 
long-term fitness and survival of individual marine mammals; or (2) 
populations, species, or stocks;
     Effects on marine mammal habitat (e.g., marine mammal prey 
species, acoustic habitat, or other important physical components of 
marine mammal habitat); and,
     Mitigation and monitoring effectiveness.

Visual Monitoring

    Monitoring will be conducted 30 minutes before, during, and 30 
minutes after construction activities. In addition, observers must 
record all incidents of marine mammal occurrence, regardless of 
distance from activity, and must document any behavioral reactions in 
concert with distance from construction activities.
    Protected Species Observers (PSOs) will be land- and boat-based. 
For blasting, three PSOs will be required (two land-based and one boat-
based). Observers will be stationed at locations that provide adequate 
visual coverage for shutdown and monitoring zones. Potential 
observation locations are depicted in Figure 3-1 of the applicant's 
Marine Mammal Monitoring and Mitigation Plan. During blasting, pre-
blast monitoring, and post-blast monitoring, three observers will be on 
duty. Optimal observation locations will be selected based on 
visibility and the type of work occurring. All PSOs will be trained in 
marine mammal identification and behaviors and are required to have no 
other project-related tasks while conducting monitoring. In addition, 
monitoring will be conducted by qualified observers, who will be placed 
at the best vantage point(s) practicable to monitor for marine mammals 
and implement shutdown/delay procedures when applicable. Monitoring of 
construction activities must be conducted by qualified PSOs (see 
below), who must have no other assigned tasks during monitoring 
periods. The applicant must adhere to the following conditions when 
selecting observers:
     Independent PSOs must be used (i.e., not construction 
personnel);
     At least one PSO must have prior experience working as a 
marine mammal observer during construction activities;
     Other PSOs may substitute education (degree in biological 
science or related field) or training for experience;
     Where a team of three or more PSOs are required, a lead 
observer or monitoring coordinator must be designated. The lead 
observer must have prior experience working as a marine mammal observer 
during construction; and
     The applicant must submit PSO curriculum vitaes for 
approval by NMFS.
    The applicant must ensure that observers have the following 
additional qualifications:
     Ability to conduct field observations and collect data 
according to assigned protocols;
     Experience or training in the field identification of 
marine mammals, including the identification of behaviors;
     Sufficient training, orientation, or experience with the 
construction operation to provide for personal safety during 
observations;
     Writing skills sufficient to prepare a report of 
observations including, but not limited to, the number and species of 
marine mammals observed; dates and times when in-water construction 
activities were conducted; dates, times, and reason for implementation 
of mitigation (or why mitigation was not implemented when required); 
and marine mammal behavior; and
     Ability to communicate orally, by radio or in person, with 
project personnel to provide real-time information on marine mammals 
observed in the area as necessary.
    At least 24 hours prior to blasting, the USACE will notify the 
Office of Protected Resources, NMFS Alaska Regional Office, and the 
Alaska Regional Stranding Coordinator that blasting is planned to 
occur, as well as notify these parties within 24 hours after blasting 
that blasting actually occurred. If a marine mammals is known to be 
within the Level A or Level B pre-clearance zones during a detonation, 
USACE will report the following information within 24 hours of the 
blasting event:
     Description of the blasting event;
     PSO positions and monitoring effort for the 24 hours 
preceding the blast;
     Environmental conditions (e.g., Beaufort sea state, 
visibility);
     Description of all marine mammal observations in the 24 
hours preceding the incident;
     Species identification or description of the animal(s) 
involved;
     Fate of the animal(s); and
     Photographs or video footage of the animal(s) (if 
equipment is available).
    A draft marine mammal monitoring report will be submitted to NMFS 
within 90 days after the completion of construction activities. It will 
include an overall description of work completed, a narrative regarding 
marine mammal sightings, and associated PSO data sheets. Specifically, 
the report must include:
     Date and time that monitored activity begins or ends;
     Construction activities occurring during each observation 
period;
     Weather parameters (e.g., percent cover, visibility);
     Water conditions (e.g., sea state, tide state);
     Species, numbers, and, if possible, sex and age class of 
marine mammals;
     Description of any observable marine mammal behavior 
patterns, including bearing and direction of travel and distance from 
construction activity;
     Distance from construction activities to marine mammals 
and distance from the marine mammals to the observation point;
     Locations of all marine mammal observations; and
     Other human activity in the area.
    If no comments are received from NMFS within 30 days, the draft 
final report will constitute the final report. If comments are 
received, a final report addressing NMFS comments must be submitted 
within 30 days after receipt of comments.
    In the unanticipated event that the specified activity likely 
causes the take of a marine mammal in a manner prohibited by the IHA 
(if issued), such as a serious injury or mortality, the USACE will 
immediately cease the specified activities and report the incident to 
the Office of Protected Resources, NMFS Alaska Regional Office, and the 
Alaska Regional Stranding Coordinator. The report will include the 
following information:
     Description of the incident;
     Environmental conditions (e.g., Beaufort sea state, 
visibility);
     Description of all marine mammal observations in the 24 
hours preceding the incident;
     Species identification or description of the animal(s) 
involved;
     Fate of the animal(s); and
     Photographs or video footage of the animal(s) (if 
equipment is available).
    Activities will not resume until NMFS is able to review the 
circumstances of

[[Page 21648]]

the prohibited take. NMFS will work with the USACE to determine what is 
necessary to minimize the likelihood of further prohibited take and 
ensure MMPA compliance. The USACE will not be able to resume their 
activities until notified by NMFS via letter, email, or telephone.
    In the event that the USACE discovers an injured or dead marine 
mammal, and the lead PSO determines that the cause of the injury or 
death is unknown and the death is relatively recent (e.g., in less than 
a moderate state of decomposition as described in the next paragraph), 
the USACE will immediately report the incident to the Office of 
Protected Resources, NMFS Alaska Regional Office, and the Alaska 
Regional Stranding Coordinator. The report will include the same 
information identified in the paragraph above. Activities will be able 
to continue while NMFS reviews the circumstances of the incident. NMFS 
will work with the USACE to determine whether modifications in the 
activities are appropriate.
    In the event that the USACE discovers an injured or dead marine 
mammal and the lead PSO determines that the injury or death is not 
associated with or related to the activities authorized in the IHA 
(e.g., previously wounded animal, carcass with moderate to advanced 
decomposition, or scavenger damage), the USACE will report the incident 
to the Office of Protected Resources, NMFS Alaska Regional Office, and 
the NMFS Alaska Stranding Hotline and/or by email to the Alaska 
Regional Stranding Coordinator, within 24 hours of the discovery. The 
USACE will provide photographs, video footage (if available), or other 
documentation of the stranded animal sighting to NMFS and the Marine 
Mammal Stranding Coordinator.

Negligible Impact Analysis and Determination

    NMFS has defined negligible impact as an impact resulting from the 
specified activity that cannot be reasonably expected to, and is not 
reasonably likely to, adversely affect the species or stock through 
effects on annual rates of recruitment or survival (50 CFR 216.103). A 
negligible impact finding is based on the lack of likely adverse 
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough 
information on which to base an impact determination. In addition to 
considering estimates of the number of marine mammals that might be 
``taken'' through harassment, NMFS considers other factors, such as the 
likely nature of any impacts or responses (e.g., intensity, duration), 
the context of any impacts or responses (e.g., critical reproductive 
time or location, foraging impacts affecting energetics), as well as 
effects on habitat, and the likely effectiveness of the mitigation. We 
also assess the number, intensity, and context of estimated takes by 
evaluating this information relative to population status. Consistent 
with the 1989 preamble for NMFS' implementing regulations (54 FR 40338, 
September 29, 1989), the impacts from other past and ongoing 
anthropogenic activities are incorporated into this analysis via their 
impacts on the baseline (e.g., as reflected in the regulatory status of 
the species, population size and growth rate where known, ongoing 
sources of human-caused mortality, or ambient noise levels).
    To avoid repetition, the discussion of our analysis applies to all 
the species listed in Table 1, given that the anticipated effects of 
this activity on these different marine mammal stocks are expected to 
be similar. There is little information about the nature or severity of 
the impacts, or the size, status, or structure of any of these species 
or stocks that would lead to a different analysis for this activity.
    As stated in the mitigation section, pre-clearance zones equal to 
or exceeding Level A isopleths shown in Table 6 for blasting will be 
implemented for all species. Serious injury or mortality is not 
anticipated nor authorized.
    Behavioral disturbances of marine mammals to blasting, if any, are 
expected to be mild and temporary due to the short-term duration of the 
noise produced by the source and the fact that only a single blasting 
event will occur on a given day. Additionally, blasting events will not 
occur on consecutive days. Given the short duration of noise-generating 
activities per day and that blasting events would occur on a maximum of 
24 days, any harassment would be temporary. For all species except 
humpbacks, there are no known biologically important areas near the 
project zone that would be impacted by the construction activities. The 
proposed project area occupies a small percentage of the humpback whale 
feeding BIA and Critical Habitat areas, and there is sufficient similar 
habitat nearby. Acoustic impacts will be short-term and temporary in 
duration. The region of Iliuliuk Bay where the project will take place 
is located in a highly trafficked commercial port area with regular 
marine vessel traffic.
    In summary and as described above, the following factors primarily 
support our preliminary determination that the impacts resulting from 
this activity are not expected to adversely affect any of the species 
or stocks through effects on annual rates of recruitment or survival:
     No serious injury or mortality is anticipated or 
authorized;
     Authorized Level A harassment will be very small amounts 
and of low degree;
     The intensity of anticipated takes by Level B harassment 
is relatively low for all stocks. Level B harassment will be primarily 
in the form of behavioral disturbance, resulting in avoidance of the 
project areas around where blasting is occurring, with some TTS that 
may limit the detection of acoustic cues for relatively brief amounts 
of time;
     While a feeding BIA and Critical Habitat for humpback 
whales exist in the action area, the proposed activity occupies a small 
percentage of the total BIA and of the Critical Habitat, and would 
occur on a short term, temporary basis.
     The USACE will implement mitigation measures, such as pre-
clearance zones, for all in-water and over-water activities; and
     Monitoring reports from similar work in Alaska have 
documented little to no effect on individuals of the same species 
impacted by the specified activities (USACE, 2020).
    Based on the analysis contained herein of the likely effects of the 
specified activity on marine mammals and their habitat, and taking into 
consideration the implementation of the proposed monitoring and 
mitigation measures, NMFS preliminarily finds that the total marine 
mammal take from the proposed activity will have a negligible impact on 
all affected marine mammal species or stocks.

Small Numbers

    As noted previously, only take of small numbers of marine mammals 
may be authorized under sections 101(a)(5)(A) and (D) of the MMPA for 
specified activities other than military readiness activities. The MMPA 
does not define small numbers and so, in practice, where estimated 
numbers are available, NMFS compares the number of individuals taken to 
the most appropriate estimation of abundance of the relevant species or 
stock in our determination of whether an authorization is limited to 
small numbers of marine mammals. When the predicted number of 
individuals to be taken is fewer than one-third of the species or stock 
abundance, the take is considered to be of small numbers. Additionally, 
other qualitative factors may be considered in the analysis, such

[[Page 21649]]

as the temporal or spatial scale of the activities.
    Table 7 below shows take as a percent of population for each of the 
species listed above.

                   Table 7--Summary of Authorized Instances of Level A and Level B Harassment
----------------------------------------------------------------------------------------------------------------
                                                     Number of       Number of
                                                  takes by level  takes by level       Stock        Percent of
            Species                 DPS/stock      B harassment    A harassment      abundance      population
                                                     by stock        by stock
----------------------------------------------------------------------------------------------------------------
Humpback whale................  Western North               0.96               0           1,107             0.1
                                 Pacific DPS.
                                Mexico DPS......            3.36               0           4,973             0.1
                                Hawaii DPS......           43.68               3          10,103             0.5
Harbor seal...................  Aleutian Island              240               5           5,588             4.4
                                 Stock.
Harbor porpoise \1\...........  Bering Sea......              12               5          31,046            0.05
                                Gulf of Alaska..
Steller sea lion..............  Western DPS.....              48               5          52,932             0.1
----------------------------------------------------------------------------------------------------------------
\1\ There is not enough information available to determine takes for separate stocks for harbor porpoise.
  Calculations have been based on the best available stock abundance for the Gulf of Alaska stock, as there are
  no available data for the Bering Sea stock. This number is conservative, because it represents a minimum value
  of both stocks.

    Table 7 presents the number of animals that could be exposed to 
received noise levels that may result in take by Level A or Level B 
harassment for the construction at Iliuliuk Bay, Unalaska. Our analysis 
shows that less than one-third of the best available population 
estimate of each affected stock could be taken. Therefore, the numbers 
of animals authorized to be taken for all species would be considered 
small relative to the relevant stocks or populations even if each 
estimated taking occurred to a new individual--an extremely unlikely 
scenario. For harbor seals and Steller sea lions occurring in the 
vicinity of the project site, there will almost certainly be some 
overlap in individuals present day-to-day, and these takes are likely 
to occur only within some small portion of the overall regional stock.
    Based on the analysis contained herein of the proposed activity 
(including the proposed mitigation and monitoring measures) and the 
anticipated take of marine mammals, NMFS preliminarily finds that small 
numbers of marine mammals would be taken relative to the population 
size of the affected species or stocks.

Unmitigable Adverse Impact Analysis and Determination

    In order to issue an IHA, NMFS must find that the specified 
activity will not have an ``unmitigable adverse impact'' on the 
subsistence uses of the affected marine mammal species or stocks by 
Alaskan Natives. NMFS has defined ``unmitigable adverse impact'' in 50 
CFR 216.103 as an impact resulting from the specified activity: (1) 
That is likely to reduce the availability of the species to a level 
insufficient for a harvest to meet subsistence needs by: (i) Causing 
the marine mammals to abandon or avoid hunting areas; (ii) Directly 
displacing subsistence users; or (iii) Placing physical barriers 
between the marine mammals and the subsistence hunters; and (2) That 
cannot be sufficiently mitigated by other measures to increase the 
availability of marine mammals to allow subsistence needs to be met.
    Subsistence activities in Unalaska have historically included the 
harvest of pinnipeds and sea otters. However, subsistence harvests of 
marine mammals declined between 1994 and 2008 (the last year for which 
data are available) (ADF&G 2022b). Additionally, a ban on firearm 
discharge within the city limits of the City of Unalaska means that 
current subsistence harvesting typically occurs from skiffs in areas 
outside of Dutch Harbor and Iliuliuk Bay, including Wide Bay, Kalekta 
Bay, Bishop Point, Wislow Island, and Beaver Inlet. The proposed 
activity would not impact these areas.
    Any impacts to marine mammals from the proposed activity are likely 
to be short-term and temporary, and limited to the area around the 
proposed blasting site. While a limited number of individuals may 
experience PTS, there are no expected impacts to the availability of 
marine mammals for subsistence uses due to the proposed activity.
    Based on the description of the specified activity, and the 
proposed mitigation and monitoring measures, NMFS has preliminarily 
determined that there will not be an unmitigable adverse impact on 
subsistence uses from USACE's proposed activities.

Endangered Species Act

    Section 7(a)(2) of the Endangered Species Act of 1973 (ESA; 16 
U.S.C. 1531 et seq.) requires that each Federal agency insure that any 
action it authorizes, funds, or carries out is not likely to jeopardize 
the continued existence of any endangered or threatened species or 
result in the destruction or adverse modification of designated 
critical habitat. To ensure ESA compliance for the issuance of IHAs, 
NMFS consults internally whenever we propose to authorize take for 
endangered or threatened species, in this case with NMFS Alaska 
Regional Office.
    NMFS is proposing to authorize take of the Mexico and Western North 
Pacific DPSs of humpback whales, and the western DPS of Steller sea 
lion, which are listed under the ESA. The Permits and Conservation 
Division has requested initiation of section 7 consultation with the 
NMFS Alaska Regional Office for the issuance of this IHA. NMFS will 
conclude the ESA consultation prior to reaching a determination 
regarding the proposed issuance of the authorization.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to the USACE for conducting confined blasting in Iliuliuk 
Bay, Unalaska between November 1, 2023 and October 31, 2024, provided 
the previously mentioned mitigation, monitoring, and reporting 
requirements are incorporated. A draft of the proposed IHA can be found 
at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities.

Request for Public Comments

    We request comment on our analyses, the proposed authorization, and 
any other aspect of this notice of proposed IHA for the proposed 
Unalaska (Dutch Harbor) Channel Deepening Project. We also request 
comment on the potential

[[Page 21650]]

renewal of this proposed IHA as described in the paragraph below. 
Please include with your comments any supporting data or literature 
citations to help inform decisions on the request for this IHA or a 
subsequent renewal IHA.
    On a case-by-case basis, NMFS may issue a one-time, 1-year renewal 
IHA following notice to the public providing an additional 15 days for 
public comments when (1) up to another year of identical or nearly 
identical activities as described in the Description of Proposed 
Activity section of this notice is planned or (2) the activities as 
described in the Description of Proposed Activity section of this 
notice would not be completed by the time the IHA expires and a renewal 
would allow for completion of the activities beyond that described in 
the Dates and Duration section of this notice, provided all of the 
following conditions are met:
     A request for renewal is received no later than 60 days 
prior to the needed renewal IHA effective date (recognizing that the 
renewal IHA expiration date cannot extend beyond 1 year from expiration 
of the initial IHA).
     The request for renewal must include the following:
    (1) An explanation that the activities to be conducted under the 
requested renewal IHA are identical to the activities analyzed under 
the initial IHA, are a subset of the activities, or include changes so 
minor (e.g., reduction in pile size) that the changes do not affect the 
previous analyses, mitigation and monitoring requirements, or take 
estimates (with the exception of reducing the type or amount of take).
    (2) A preliminary monitoring report showing the results of the 
required monitoring to date and an explanation showing that the 
monitoring results do not indicate impacts of a scale or nature not 
previously analyzed or authorized.
    Upon review of the request for renewal, the status of the affected 
species or stocks, and any other pertinent information, NMFS determines 
that there are no more than minor changes in the activities, the 
mitigation and monitoring measures will remain the same and 
appropriate, and the findings in the initial IHA remain valid.

    Dated: April 6, 2023.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2023-07561 Filed 4-10-23; 8:45 am]
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