[Federal Register Volume 88, Number 225 (Friday, November 24, 2023)]
[Notices]
[Pages 82326-82336]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-25934]


-----------------------------------------------------------------------

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XC980]


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; issuance of an incidental harassment authorization.

-----------------------------------------------------------------------

SUMMARY: In accordance with the regulations implementing the Marine 
Mammal Protection Act (MMPA) as amended, notification is hereby given 
that NMFS has issued an incidental harassment authorization (IHA) to 
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.

DATES: This Authorization is effective from January 1, 2024 through 
December 31, 2024.

ADDRESSES: 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/action/incidental-take-authorization-us-army-corps-engineers-unalaska-dutch-harbor-channel. In case of problems accessing these documents, please 
call the contact listed below.

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

SUPPLEMENTARY INFORMATION:

Background

    The MMPA prohibits the ``take'' of marine mammals, with certain 
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to 
allow, upon request, the incidental, but not intentional, taking of 
small numbers of marine mammals by U.S. citizens who engage in a 
specified activity (other than commercial fishing) within a specified 
geographical region if certain findings are made and either regulations 
are proposed or, if the taking is limited to harassment, a notice of a 
proposed IHA is provided to the public for review.
    Authorization for incidental takings shall be granted if NMFS finds 
that the taking will have a negligible impact on the species or 
stock(s) and will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for taking for subsistence uses 
(where relevant). Further, NMFS must prescribe the permissible methods 
of taking and other ``means of effecting the least practicable adverse 
impact'' on the affected species or stocks and their habitat, paying 
particular attention to rookeries, mating grounds, and areas of similar 
significance, and on the availability of the species or stocks for 
taking for certain subsistence uses (referred to in shorthand as 
``mitigation''); and requirements pertaining to the 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.

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. The notice of the proposed IHA and request 
for comments was published on April 11, 2023 (88 FR 21630). 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 the Specified Activity

    The USACE plans 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.
    Removal of the bar will 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 will 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.
    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.
    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. The notice for the proposed IHA (88 FR 
21630, April 11, 2023) analyzed a conservative scenario requiring 
blasting approximately 50 percent of the bar area, resulting in

[[Page 82327]]

approximately 1,800 drilled boreholes and up to 24 total blasting 
events.
    A detailed description of the planned project is provided in the 
Federal Register notice for the proposed IHA (88 FR 21630, April 11, 
2023). Since that time, no changes have been made to the planned 
activities. Therefore, a detailed description is not provided here. 
Please refer to that Federal Register notice for the detailed 
description of the specific activity.

Comments and Responses

    A notice of NMFS' proposal to issue an IHA to the USACE was 
published in the Federal Register on April 11, 2023 (88 FR 21630). That 
notice described, in detail, USACE's planned activities, the marine 
mammal species that may be affected by the activities, and the 
anticipated effects on marine mammals. In that notice, we requested 
public input on the request for authorization described therein, our 
analyses, the proposed authorization, and any other aspect of the 
notice of proposed IHA, and requested that interested persons submit 
relevant information, suggestions, and comments. This proposed notice 
was available for a 30-day public comment period.
    NMFS received two non-substantive comments on the proposed IHA: one 
from the U.S. Geological Survey stating no objections to the project, 
and one from a private citizen opposed to offshore wind, which is not 
related to this action.

Changes From the Proposed IHA to Final IHA

    Since the Federal Register notice of the proposed IHA was published 
(88 FR 21630, April 11, 2023), NMFS published the final 2022 Alaska and 
Pacific Stock Assessment Reports (SARs), which describe revised stock 
structures under the MMPA for humpback whales. In the notice of 
proposed IHA, we explained that although we typically consider updated 
peer-reviewed data provided in draft SARs to be the best available 
science, and use the information accordingly, we make exception for 
proposed revised stock structures. Upon finalization of these revised 
stock structures, we have made appropriate updates, including 
description of the potentially affected stocks (see table 1), 
attribution of take numbers to stock (see Estimated Take), and by 
updating our analyses to ensure the necessary determinations are made 
for the new stocks (see Negligible Impact Analysis and Determination 
and Small Numbers).
    Additionally, between the publication of the proposed IHA (88 FR 
21630, April 11, 2023) and this notice, the USACE requested that the 
effective dates of the authorization be shifted from November 1, 2023 
through October 31, 2024 to January 1, 2024 through December 31, 2024 
due to logistical constraints. The analysis presented in the proposed 
IHA remains valid because the estimated takes were based on year-round 
monitoring data at the project location. The change to the effective 
dates of the authorization is reflected in the Dates section, above.

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 
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 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 and are 
available online at: www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments.

                        Table 1--Species Likely Impacted by the Specified Activities \1\
----------------------------------------------------------------------------------------------------------------
                                                                                 Stock abundance
                                                                     ESA/MMPA    (CV, Nmin, most          Annual
         Common name            Scientific name        Stock         status;    recent abundance   PBR     M/SI
                                                                    strategic      survey) \3\             \4\
                                                                    (Y/N) \2\
----------------------------------------------------------------------------------------------------------------
                        Order Artiodactyla--Infraorder Cetacea--Mysticeti (baleen whales)
----------------------------------------------------------------------------------------------------------------
Family Balaenopteridae
 (rorquals):
    Humpback Whale \5\.......  Megaptera         Hawai[revaps]i..  -, -, N      11,278 (0.56,       127    27.09
                                novaeangliae.    Mexico--North     T, D, Y       7,265, 2020).      UND     0.57
                                                  Pacific.         E, D, Y      918 (0.217, UNK,    3.4     5.82
                                                 Western North                   2006).
                                                  Pacific.                      1,084 (0.088,
                                                                                 1,007, 2021).
----------------------------------------------------------------------------------------------------------------
                              Odontoceti (toothed whales, dolphins, and porpoises)
----------------------------------------------------------------------------------------------------------------
Family Phocoenidae
 (porpoises):
    Harbor porpoise..........  Phocoena          Bering Sea \5\..  -, -, Y      UNK (UNK, N/A,      UND      0.4
                                phocoena.        Gulf of Alaska..  -, -, Y       2008).             UND       72
                                                                                31,046 (0.21, N/
                                                                                 A, 1998).
----------------------------------------------------------------------------------------------------------------

[[Page 82328]]

 
                                           Order Carnivora--Pinnipedia
----------------------------------------------------------------------------------------------------------------
Family Otariidae (eared seals
 and sea lions):
    Steller Sea Lion.........  Eumetopias        Western.........  E, D, Y      52,932 (N/A,        318      254
                                jubatus.         Eastern.........  -, -, N       52,932, 2019).    2592      112
                                                                                43,201 (N/A,
                                                                                 43,201, 2017).
Family Phocidae (earless
 seals):
    Harbor Seal..............  Phoca vitulina..  Aleutian Islands  -, -, N      5,588 (N/A,          97       90
                                                                                 5,366, 2018).
----------------------------------------------------------------------------------------------------------------
\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 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.

    A detailed description of the of the species likely to be affected 
by the Unalaska Channel Deepening project, including brief 
introductions to the species and relevant stocks as well as available 
information regarding population trends and threats, and information 
regarding local occurrence, were provided in the Federal Register 
notice for the proposed IHA (88 FR 21630, April 11, 2023); since that 
time, we are not aware of any changes in the status of these species 
and stocks; therefore, detailed descriptions are not provided here. 
Please refer to that Federal Register notice for these descriptions. 
Please also refer to NMFS' website (https://www.fisheries.noaa.gov/find-species) for generalized species accounts.

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            150 Hz to 160 kHz.
 (dolphins, 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)      50 Hz to 86 kHz.
 (true seals).
Otariid pinnipeds (OW) (underwater)     60 Hz to 39 kHz.
 (sea 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

    The effects of underwater noise from USACE's construction 
activities have the potential to result in behavioral harassment of 
marine mammals in the vicinity of the blasting area. The notice

[[Page 82329]]

of proposed IHA (88 FR 21630, April 11, 2023) included a discussion of 
the effects of anthropogenic noise on marine mammals and the potential 
effects of underwater noise from confined blasting activities on marine 
mammals and their habitat. That information and analysis is 
incorporated by reference into this final IHA determination and is not 
repeated here; please refer to the notice of proposed IHA (88 FR 21630, 
April 11, 2023).

Estimated Take of Marine Mammals

    This section provides an estimate of the number of incidental takes 
authorized through this IHA, which informs 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 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 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 take numbers were 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 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 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 
planned 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 a 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 disturbance 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 (multiple
          Hearing group                thresholds           thresholds                  detonations)
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans....  Cell 1: Lp,0-        Cell 2: Lp,0-        Cell 3: LE,LF,24h: 163 dB.
                                   pk,flat: 219 dB;     pk,flat: 213 dB;
                                   LE,LF,24h: 183 dB.   LE,LF,24h: 168 dB.
Mid-Frequency (MF) Cetaceans....  Cell 4: Lp,0-        Cell 5: Lp,0-        Cell 6: LE,MF,24h: 165 dB.
                                   pk,flat: 230 dB;     pk,flat: 224 dB;
                                   LE,MF,24h: 185 dB.   LE,MF,24h: 170 dB.
High-Frequency (HF) Cetaceans...  Cell 7: Lp,0-        Cell 8: Lp,0-        Cell 9: LE,HF,24h: 135 dB.
                                   pk,flat: 202 dB;     pk,flat: 196 dB;
                                   LE,HF,24h: 155 dB.   LE,HF,24h: 140 dB.
Phocid Pinnipeds (PW)             Cell 10: Lp,0-       Cell 11: Lp,0-       Cell 12: LE,PW,24h: 165 dB.
 (Underwater).                     pk,flat: 218 dB;     pk,flat: 212 dB;
                                   LE,PW,24h: 185 dB.   LE,PW,24h: 170 dB.

[[Page 82330]]

 
Otariid Pinnipeds (OW)            Cell 13: Lp,0-       Cell 14: Lp,0-       Cell 15: LE,OW,24h: 183 dB.
 (Underwater).                     pk,flat: 232 dB;     pk,flat: 226 dB;
                                   LE,OW,24h: 203 dB.   LE,OW,24h: 188 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: Lp,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: 103M1/3(1 + D/10.1)1/6 Pa-s.
Equation 2: 47.5M1/3(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 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.

[[Page 82331]]



                                            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 
informed 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 has authorized 
takes 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.
    Since reliable densities are not available, the USACE 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 planned 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 estimated 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 have authorized up to 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 group of eight individuals in the project area in 
2017, and other infrequent sightings of harbor porpoise in and around 
Iliulliuk Bay, NMFS conservatively estimated that two animals may occur 
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 proposed 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 have authorized 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 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 
estimated 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 estimated 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, we 
have authorized up to 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 project area, but they 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

[[Page 82332]]

meters of the Level B harassment isopleth in the previous data, USACE 
and NMFS conservatively assumed 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 estimated 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, we have authorized up to 240 takes 
by Level B harassment and up to 5 takes by Level A harassment of harbor 
seals.

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.

      Table 6--Monitoring and Pre-Clearance Zones for Blasting Activities for Species With Authorized Take
----------------------------------------------------------------------------------------------------------------
                                                                     Pre-clearance zones (m)
                                                                   --------------------------
                                                                      Level A      Level B     Monitoring zones
                                                                     harassment   harassment          (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 will 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 zones 
and pre-clearance zones 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

[[Page 82333]]

conditions allow for blasting to be delayed to the following day. If 
charges have already been laid before the whale is sighted, blasting 
will 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 planned measures, as 
well as other measures considered by NMFS, NMFS has determined that the 
listed 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.

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 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

[[Page 82334]]

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 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

[[Page 82335]]

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 will be impacted by the construction activities. The 
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 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 planned 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 monitoring and mitigation 
measures, NMFS finds that the total marine mammal take from the planned 
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 as 
the temporal or spatial scale of the activities.
    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.

                   Table 7--Summary of Authorized Instances of Level A and Level B Harassment
----------------------------------------------------------------------------------------------------------------
                                                               Number of    Number of
                                                                takes by     takes by
               Species                       DPS/stock          Level B      Level A       Stock      Percent of
                                                               harassment   harassment   abundance    population
                                                                by stock     by stock
----------------------------------------------------------------------------------------------------------------
Humpback whale......................  Western North Pacific.         0.96            0        1,107          0.1
                                      Mexico--North Pacific.         3.36            0        4,973          0.1
                                      Hawaii................        43.68            3       10,103          0.5
Harbor seal.........................  Aleutian Island Stock.          240            5        5,588          4.4
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.

    Based on the analysis contained herein of the planned activity 
(including the mitigation and monitoring measures) and the anticipated 
take of marine mammals, NMFS 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''

[[Page 82336]]

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 2022). 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 planned 
activity would not impact these areas.
    Any impacts to marine mammals from the planned activity are likely 
to be short-term and temporary, and limited to the area around the 
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 blasting activity.
    Based on the description of the specified activity, and the 
mitigation and monitoring measures, NMFS has determined that there will 
not be an unmitigable adverse impact on subsistence uses from USACE's 
construction 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.
    There are two marine mammal species (western DPS Steller sea lion 
and humpback whale (Mexico and Western North Pacific DPSs)) with 
confirmed occurrence in the project area that are listed as endangered 
under the ESA. The NMFS Alaska Regional Office Protected Resources 
Division issued a Biological Opinion on November 16, 2023 under section 
7 of the ESA, on the issuance of an IHA to USACE under section 
101(a)(5)(D) of the MMPA by the NMFS Permits and Conservation Division. 
The Biological Opinion concluded that the action is not likely to 
jeopardize the continued existence of Western DPS Steller sea lions or 
humpback whales from either the Mexico or Western North Pacific DPSs, 
and is not likely to destroy or adversely modify humpback whale 
critical habitat.

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 determined 
that the issuance of the IHA qualifies to be categorically excluded 
from further NEPA review.

Authorization

    As a result of these determinations, NMFS has issued an IHA to the 
USACE for conducting confined blasting in Iliuliuk Bay, Unalaska 
between January 1, 2024 and December 31, 2024, incorporating the 
previously mentioned mitigation, monitoring, and reporting 
requirements. The IHA can be found at: https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-army-corps-engineers-unalaska-dutch-harbor-channel.

    Dated: November 20, 2023.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2023-25934 Filed 11-22-23; 8:45 am]
BILLING CODE 3510-22-P