Notice2026-06453
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Homer Harbor System Four Float Replacement Project
Primary source
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Published
April 2, 2026
Issuing agencies
Commerce DepartmentNational Oceanic and Atmospheric Administration
Abstract
NMFS has received a request from the City of Homer (Homer) for authorization to take marine mammals incidental to the Homer Harbor System Four Float Replacement Project in Homer, AK. 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.
Full Text
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<title>Federal Register, Volume 91 Issue 63 (Thursday, April 2, 2026)</title>
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[Federal Register Volume 91, Number 63 (Thursday, April 2, 2026)]
[Notices]
[Pages 16651-16670]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-06453]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XF550]
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to Homer Harbor System Four Float
Replacement Project
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental harassment authorization; request
for comments on proposed authorization and possible renewal.
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SUMMARY: NMFS has received a request from the City of Homer (Homer) for
authorization to take marine mammals incidental to the Homer Harbor
System Four Float Replacement Project in Homer, AK. 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 4,
2026.
ADDRESSES: Comments should be addressed to Permits and Conservation
Division, Office of Protected Resources, National Marine Fisheries
Service and should be submitted via email to <a href="/cdn-cgi/l/email-protection#9cd5c8ccb2fff3fff7eef9f0f0dcf2f3fdfdb2fbf3ea"><span class="__cf_email__" data-cfemail="8cc5d8dca2efe3efe7fee9e0e0cce2e3ededa2ebe3fa">[email protected]</span></a>.
Electronic copies of the application and supporting documents, as well
as a list of the references cited in this document, may be obtained
online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>. In
case of problems accessing these documents, please call the contact
listed below.
Instructions: NMFS is not responsible for comments sent by any
other method, to any other address or individual, or received after the
end of the comment period. Comments, including all attachments, must
not exceed a 25-megabyte file size. All comments received are a part of
the public record and will generally be posted online at <a href="https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act">https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act</a> without change. All personal identifying
information (e.g., name, address) voluntarily submitted by the
commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.
FOR FURTHER INFORMATION CONTACT: Craig Cockrell, Office of Protected
Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Background
The MMPA prohibits the ``take'' of marine mammals, with certain
exceptions. Section 101(a)(5)(D) of the MMPA (16 U.S.C. 1361 et seq.)
directs 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; 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 as ``mitigation'');
and requirements pertaining to the monitoring and reporting of the
takings. The definitions of all applicable MMPA statutory terms used
above are included in the relevant sections below (see also 16 U.S.C.
1362; 50 CFR 216.3 and 216.103).
National Environmental Policy Act
To comply with the National Environmental Policy Act of 1969 (NEPA;
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A,
NMFS must review our proposed action (i.e., the issuance of an IHA)
with respect to potential impacts on the human environment.
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 NAO 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.
Summary of Request
On November 13, 2025, NMFS received a request from Homer for an IHA
to take marine mammals incidental to the construction of the Homer
Harbor System Four Float Replacement Project in Homer, AK. Following
NMFS' review of the application, Homer submitted a revised version on
February 11, 2026. The application was deemed adequate and complete on
February 24, 2026. Homer's request is for take of six species of marine
mammals, by Level B harassment and, for harbor seals, Level A
harassment. Neither Homer nor NMFS expect serious injury or mortality
to result from this activity and, therefore, an IHA is appropriate.
Description of Proposed Activity
Overview
The purpose of the project is to repair and make improvements,
including the expansion of the current footprint of the dock system of
the Homer Small Boat Harbor. The location provides safe harbor for
boats of various sizes in the city of Homer. Takes of marine mammals by
Level A and Level B harassment are expected to occur due to impact and
vibratory pile driving and removal. The project would occur at the
entrance of Kachemak Bay which is located in off of a sandbar directly
south of Homer, AK. It is expected to take up to 75 non-consecutive
days to complete the pile driving and removal activities.
Dates and Duration
The proposed IHA would be valid for the statutory maximum of 1 year
from the date of effectiveness. It will become
[[Page 16652]]
effective upon written notification from the applicant to NMFS, but not
beginning later than 1 year from the date of issuance or extending
beyond 2 years from the date of issuance. Construction activities are
expected to occur over a 1-year period from August 2027 through July
2028. It is anticipated that the pile driving work would take 75 non-
consecutive days.
Specific Geographic Region
The project area is located within the Homer Small Boat Harbor,
within Kachemak Bay in Southcentral Alaska (figure 1). Kachemak Bay is
approximately 64 kilometers (km) long and empties into the lower Cook
Inlet. The bay is approximately 35 km wide at the mouth and narrows to
approximately 5 km wide at the end. The Homer Small Boat Harbor is
located near the end of Homer Spit, which extends 7 km into the mouth
of Kachemak Bay. Kachemak Bay is between 3 and 137 m deep in the
project area outside of Homer Harbor.
[GRAPHIC] [TIFF OMITTED] TN02AP26.015
Figure 1--Homer Small Boat Harbor Project Area
Detailed Description of the Specified Activity
Homer proposes to replace the gangway at Ramp Six and most of Float
System Four at the Homer Small Boat Harbor. In-water construction
activities associated with the project would include impact pile
driving and vibratory pile driving and removal. Pile removal may also
be completed using a ``dead pull'' method, where a pile is tethered to
a crane and is removed directly. Impact hammers operate by repeatedly
dropping a heavy piston onto a pile to drive the pile into the
substrate. Vibratory hammers install piles by vibrating them and
allowing the weight of the hammer to push them into the sediment.
The new dock system would be constructed in two units, unit one and
unit two to repair failing components of the dock system and expand the
footprint of the current dock configuration (see figure 7 and 8 in
Homer's application). During the construction of unit one Homer would
remove 56 steel and timber piles and install 76 steel piles of various
sizes. During the construction of unit two Homer would remove 46 steel
and timber piles and install 57 steel piles of various sizes (table 1).
Twenty-eight 16 inch (in) (41 centimeters (cm)) temporary steel piles
would only be used when needed and would not be driven to support the
installation of every permanent pile. Homer does not know the location
and number of the temporary piles in advance. Therefore, Homer is
estimating, based on similar previous projects, that temporary piles
would be installed in proportion to the number of permanent piles in
each unit. Unit 1 contains 57 percent of the permanent piles, and it is
assumed that 57 percent of temporary piles (16 piles) would be
installed and removed in unit one. Unit two would include 43 percent of
temporary piles (12 piles) would be installed and removed. Dead pull
methods would not have impacts on marine mammals; however, we assume
that all pile removal is conducted using vibratory hammer.
Table 1--Number and Types of Piles To Be Installed and Removed by
Construction Unit
------------------------------------------------------------------------
Number
Pile diameter and construction unit of piles
------------------------------------------------------------------------
Pile Installation
------------------------------------------------------------------------
12.75-in steel pipe piles (unit one).......................... 8
16-in steel pipe piles (unit one)............................. 42
18-in steel pipe piles (unit one)............................. 26
12.75-in steel pipe piles (unit two).......................... 6
16-in steel pipe piles (unit two)............................. 28
[[Page 16653]]
18-in steel pipe piles (unit two)............................. 3
24-in steel pipe piles (unit two)............................. 20
------------------------------------------------------------------------
Pile Removal
------------------------------------------------------------------------
12-in timber piles (unit one)................................. 16
12.75-in steel pipe piles (unit one).......................... 23
16-in steel pipe piles (unit one)............................. 17
12-in timber piles (unit two)................................. 20
12.75-in steel pipe piles (unit two).......................... 17
16-in steel pipe piles (unit two)............................. 9
------------------------------------------------------------------------
Above water construction would include the installation of
components on the new floats such as mooring cleats and bullrails,
electrical lines and power/light pedestals, fire suppression lines and
hydrants, water lines, and a new sewer remote pumping station and
safety equipment such as fire extinguishers, life rings, and safety
ladders. This above-water work is not expected to result in incidental
take of marine mammals. Noise generated above the water would not be
transmitted into the water and there are no major pinniped haulouts
located near the project area, therefore airborne noise is therefore
not considered further in this document.
Proposed mitigation, monitoring, and reporting measures are
described in detail later in this document (please see Proposed
Mitigation and Proposed Monitoring and Reporting).
Description of Marine Mammals in the Area of Specified Activities
Sections 3 and 4 of the application summarize available information
regarding status and trends, distribution and habitat preferences, and
behavior and life history of the potentially affected species. NMFS
fully considered all of this information, and we refer the reader to
these descriptions, instead of reprinting the information. Additional
information regarding population trends and threats may be found in
NMFS' Stock Assessment Reports (SARs; <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>) and
more general information about these species (e.g., physical and
behavioral descriptions) may be found on NMFS' website (<a href="https://www.fisheries.noaa.gov/find-species">https://www.fisheries.noaa.gov/find-species</a>).
Table 2 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 mortality and serious injury (M/
SI) 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 SARs. All values presented in table 2 are the most
recent available at the time of publication (including from the draft
2024 SARs) and are available online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>.
Table 2--Species, Stocks, and the Status of Marine Mammals With Estimated Take From the Specified Activities
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ESA/ MMPA status; Stock abundance (CV,
Common name Scientific name \1\ 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.................. Megaptera novaeangliae. Hawai[revaps]i......... -,-, N 11,278 (0.56, 7,265, 127 27.09
2020).
Mexico-North Pacific... T, D, Y N/A (N/A, N/A, 2006).. UND 0.57
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Odontoceti (toothed whales, dolphins, and porpoises)
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Family Delphinidae:
Killer whale.................... Orcinus orca........... Eastern North Pacific -, -, N 1,920 (N/A, 1,920, 19 1.3
Alaska Resident. 2019).
Eastern North Pacific -, -, N 587 (N/A, 587, 2012).. 5.9 0.8
Gulf of Alaska,
Aleutian Islands and
Bering Sea Transient.
Family Phocoenidae (porpoises):
Harbor porpoise................. Phocoena phocoena...... Gulf of Alaska......... -, -, Y 31,046 (0.21, N/A, UND 72
1998).
Dall's Porpoise................. Phocoenoides dalli..... Alaska................. -, -, N UND (UND, UND, 2015).. UND 37
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Order Carnivora--Pinnipedia
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Family Otariidae (eared seals and
sea lions):
Steller Sea Lion................ Eumetopias jubatus..... Western DPS............ E, D, Y 49,837 (N/A, 49,837, 299 267
2022).
Family Phocidae (earless seals):
[[Page 16654]]
Harbor Seal..................... Phoca vitulina......... Cook Inlet/Shelikof -, -, N 28,411 (N/A, 26,907, 807 107
Strait. 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
(<a href="https://www.marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/">https://www.marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/</a>).
\2\ ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or
designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or
which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is
automatically designated under the MMPA as depleted and as a strategic stock.
\3\ NMFS marine mammal stock assessment reports online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports/">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports/</a>. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.
\4\ These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g.,
commercial fisheries, vessel strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range.
As indicated above, all six species (with eight managed stocks) in
table 2 temporally and spatially co-occur with the activity to the
degree that take is reasonably likely to occur. While gray whale
(Eschrichtius robustus), fin whale (Balaenoptera physalus), minke whale
(Balaenoptera acutorostrata), beluga whale (Delphinapterus leucas),
Pacific white-sided dolphin (Lagenorhynchus obliquidens), and northern
fur seals (Callorhinus ursinus) have been documented in the area in the
past, 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. Based on the applicants research
these species have not used the entrance of the Kachemak Bay and the
surrounding waters for a number of years. Although the entrance of the
Kachemak Bay is a designated critical habitat and a small and resident
population biologically important area (BIA) for Cook Inlet beluga
whale, sightings of beluga whale in the area have not occurred since
2001. Therefore, take of these species is not expected to occur.
Humpback Whale
Two stocks of humpback whales could be found in the project area.
These include the Hawai'i Stock (not ESA-listed) and the Mexico-North
Pacific Stock (ESA-threatened). Humpback whales are encountered
regularly in lower Cook Inlet, including Kachemak Bay. Since there are
multiple sightings of humpback whales every year, they are considered
frequent in the project area.
Within the project area, most humpback whales (89 percent) are
likely to be from the Hawaii DPS, approximately 11 percent are likely
to be from the threatened Mexico DPS.
Killer Whale
Two stocks of killer whales could occur in the project area. These
include the Eastern North Pacific Alaska Resident stock and the Gulf of
Alaska/Aleutian Islands/Bering Sea Transient stock. Killer whales have
been sighted near Homer and Port Graham in lower Cook Inlet (Shelden et
al., 2022, Shelden et al., 2003, Rugh et al., 2005). Resident killer
whales from pods often sighted near Kenai Fjords National Park and in
Prince William Sound have been occasionally photographed in lower Cook
Inlet (Shelden et al., 2003). The availability of salmon influences
when resident killer whales are more likely to be sighted in Cook
Inlet. Killer whales were observed in Kachemak and English Bay three
times during aerial surveys conducted between 1993 and 2004 (Rugh et
al., 2005).
Harbor Porpoise
The harbor porpoise frequents nearshore waters and coastal
embayments throughout their range, including bays, harbors, estuaries,
and fjords less than 198 meters (m) deep (NMFS 2022). A review of
marine mammal sighting databases (iNaturalist 2025, OBIS 2025),
indicates that harbor porpoises are infrequently observed throughout
Kachemak Bay during spring, summer, and fall. Anecdotal observations
also report infrequent sightings of harbor porpoises year-round in the
vicinity of the project area (SolsticeAK 2025).
Dall's Porpoise
Although Dall's porpoises generally prefer open water, they are
known to frequent nearshore habitats and areas of shallow water and
therefore may be found in Kachemak Bay (Moran et al., 2018). A review
of marine mammal sighting databases indicates that Dall's porpoises are
infrequently observed throughout Kachemak Bay during summer
(iNaturalist 2025). This is corroborated by anecdotal observations
reporting infrequent sightings in the vicinity of the project area
(SolsticeAK 2025).
Steller Sea Lion
Steller sea lions were partitioned into the western and eastern
distinct population segments (DPSs) in 1997 (62 FR 24345, May 5, 1997).
The western DPS (those individuals west of the 144[deg] W longitude or
Cape Suckling, Alaska) was also upgraded to endangered status during
the separation of the DPSs on May 5, 1997. Only individuals from the
western DPS are present in the project area. A review of marine mammal
sighting databases indicates that Steller sea lions are infrequently
recorded in Kachemak Bay during spring, summer, and fall (iNaturalist
2025) and anecdotal reports suggest they are occasionally observed near
the project area, primarily outside the harbor and during summer and
fall (SolsticeAK 2025). There are no Steller sea lion haulouts or
rookeries in Kachemak Bay.
Harbor Seal
Harbor seals are common in the project area and are frequently
observed within the Homer Small Boat Harbor. A review of marine mammal
sighting databases indicates that harbor seals are commonly recorded in
Kachemak Bay year-round (iNaturalist 2025). Anecdotal reports suggest
they are observed almost daily near the project area (SolsticeAK 2025).
There are no haulouts located within the vicinity of the project area
that would be affected by the construction activities.
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
[[Page 16655]]
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.). Generalized hearing ranges were chosen based on the 65
decibel (dB) threshold from composite audiograms, previous analyses in
NMFS (2018), and/or data from Southall et al. (2007) and Southall et
al. (2019). We note that the names of two hearing groups and the
generalized hearing ranges of all marine mammal hearing groups have
been recently updated (NMFS, 2024) as reflected below in table 3.
Table 3--Marine Mammal Hearing Groups
[NMFS, 2024]
------------------------------------------------------------------------
Hearing group Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen 7 Hz to 36 kHz.
whales).
High-frequency (HF) cetaceans 150 Hz to 160 kHz.
(dolphins, toothed whales, beaked
whales, bottlenose whales).
Very High-frequency (VHF) cetaceans 200 Hz to 165 kHz.
(true porpoises, Kogia, river
dolphins, Cephalorhynchid,
Lagenorhynchus cruciger & L.
australis).
Phocid pinnipeds (PW) (underwater) 40 Hz to 90 kHz.
(true seals).
Otariid pinnipeds (OW) (underwater) 60 Hz to 68 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 may not be as broad. Generalized hearing range
chosen based on approximately 65 dB threshold from composite
audiogram, previous analysis in NMFS (2018), and/or data from Southall
et al. (2007) and Southall et al. (2019). Additionally, animals are
able to detect very loud sounds above and below that ``generalized''
hearing range.
For more detail concerning these groups and associated frequency
ranges, please see NMFS (2024) for a review of available information.
Potential Effects of 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 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.
Acoustic effects on marine mammals during the specified activities
are expected to potentially occur from vibratory pile installation and
removal and impact pile driving. The effects of underwater noise from
Homer's proposed activities have the potential to result in Level B
harassment of marine mammals in the action area and, for harbor seals
as a result of certain activities, Level A harassment.
There are a variety of types and degrees of effects on marine
mammals and their habitat (including prey) that could occur as a result
of the specified activities. Below we provide a brief description of
the types of sound generated by specified activities, the general
impacts on marine mammals and their habitat from these types of
activities, and a related project-specific analysis with consideration
of the proposed mitigation measures.
Description of Sound Sources for the Specified Activities
Activities associated with the project that have the potential to
incidentally take marine mammals though exposure to sound include both
vibratory and impact hammers.
Impact hammers typically operate by repeatedly dropping and/or
pushing a heavy piston onto a pile to drive the pile into the
substrate. Sound generated by impact hammers is impulsive,
characterized by rapid rise times and high peak sound pressure levels,
a potentially injurious combination (Hastings and Popper, 2005).
Vibratory hammers install piles by vibrating them and allowing the
weight of the hammer to push them into the substrate, and extract piles
by using vibration to break the sediment friction and allow a crane to
pull the piles out. Vibratory hammers typically produce less sound
(i.e., lower sound pressure levels) than impact hammers. Peak sound
pressure levels (SPLs) may be 180 dB or greater, but are generally 10
to 20 dB lower than SPLs generated during impact pile driving of the
same-sized pile (Oestman et al., 2009; California Department of
Transportation (CALTRANS), 2015, 2020). Sounds produced by vibratory
hammers are non-impulsive; compared to sounds produced by impact
hammers, they have a slower rise time, reducing the probability and
severity of injury, and the sound energy is distributed over a greater
amount of time (Nedwell and Edwards, 2002; Carlson et al., 2005).
Potential Effects of Underwater Sound on Marine Mammals
The introduction of anthropogenic noise into the aquatic
environment from impact and vibratory hammers is the primary means by
which marine mammals may be harassed from the Homer's specified
activity. 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. Broadly, underwater sound from active acoustic sources,
such as those in the Project, 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., 2003; Nowacek et al.,
2007; Southall et al., 2007; G[ouml]tz et al., 2009).
We describe the more severe effects of certain non-auditory
physical or physiological effects only briefly as we do not expect that
the use of impact and vibratory hammers are reasonably likely to result
in such effects (see below for
[[Page 16656]]
further discussion). Potential effects from impulsive sound sources can
range in severity from effects such as behavioral disturbance or
tactile perception to physical discomfort, slight injury of the
internal organs and the auditory system, or mortality (Yelverton et
al., 1973). Non-auditory physiological effects or injuries that
theoretically might occur in marine mammals exposed to high level
underwater sound or as a secondary effect of extreme behavioral
reactions (e.g., change in dive profile as a result of an avoidance
reaction) caused by exposure to sound include neurological effects,
bubble formation, resonance effects, and other types of organ or tissue
damage (Cox et al., 2006; Southall et al., 2007; Zimmer and Tyack,
2007; Tal et al., 2015). The Project activities considered here do not
involve the use of devices such as explosives or mid-frequency tactical
sonar that are associated with these types of effects.
The degree of effect of an acoustic exposure on marine mammals is
dependent on several factors, including, but not limited to, sound type
(e.g., impulsive vs. non-impulsive), signal characteristics, the
species, age and sex class (e.g., adult male vs. mom with calf),
duration of exposure, the distance between the noise source and the
animal, received levels, behavioral state at time of exposure, and
previous history with exposure (Wartzok et al., 2004; Southall et al.,
2007). In general, sudden, high-intensity sounds can cause hearing loss
as can longer exposures to lower-intensity sounds. Moreover, any
temporary or permanent loss of hearing, if it occurs at all, will occur
almost exclusively for noise within an animal's hearing range. We
describe below the specific manifestations of acoustic effects that may
occur based on the activities proposed by Homer.
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. First (at the greatest distance) 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 (closer to the receiving animal) corresponds
with the area where the signal is audible to the animal and of
sufficient intensity to elicit behavioral or physiological
responsiveness. The 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.
Below, we provide additional details regarding potential impacts on
marine mammals and their habitat from noise in general, starting with
hearing impairment, as well as from the specific activities Homer plans
to conduct, to the degree it is available.
Hearing Threshold Shifts
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, 2024). The amount
of threshold shift is customarily expressed in dB. A TS can be
permanent or temporary. As described in NMFS (2018, 2024) there are
numerous factors to consider when examining the consequence of TS,
including, but not limited to, the signal temporal pattern (e.g.,
impulsive or non-impulsive), likelihood an individual would be exposed
for a long enough duration or to a high enough level to induce a TS,
the magnitude of the TS, time to recovery (seconds to minutes or hours
to days), the frequency range of the exposure (i.e., spectral content),
the hearing frequency range of the exposed species relative to the
signal's frequency spectrum (i.e., how animal uses sound within the
frequency band of the signal; e.g., Kastelein et al., 2014), and the
overlap between the animal and the source (e.g., spatial, temporal, and
spectral).
Auditory Injury (AUD INJ)
NMFS (2024) defines AUD INJ as damage to the inner ear that can
result in destruction of tissue, such as the loss of cochlear neuron
synapses or auditory neuropathy (Houser 2021; Finneran 2024). AUD INJ
may or may not result in a permanent threshold shift (PTS). PTS is
subsequently defined as a permanent, irreversible increase in the
threshold of audibility at a specified frequency or portion of an
individual's hearing range above a previously established reference
level (NMFS, 2024). PTS does not generally affect more than a limited
frequency range, and an animal that has incurred PTS has some level of
hearing loss at the relevant frequencies; typically, animals with PTS
or other AUD INJ are not functionally deaf (Au and Hastings, 2008;
Finneran, 2016). Available data from humans and other terrestrial
mammals indicate that a 40-dB threshold shift approximates AUD INJ
onset (see Ward et al., 1958, 1959; Ward, 1960; Kryter et al., 1966;
Miller, 1974; Ahroon et al., 1996; Henderson et al., 2008). AUD INJ
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 AUD INJ in marine
mammals largely due to the fact that, for various ethical reasons,
experiments involving anthropogenic noise exposure at levels inducing
AUD INJ are not typically pursued or authorized (NMFS, 2024).
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,
2024), and is not considered an AUD INJ. Based on data from marine
mammal 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 (Finneran et al., 2000, 2002; Schlundt et al., 2000).
As described in Finneran (2015), marine mammal studies have shown the
amount of TTS increases with the 24-hour cumulative sound exposure
level (SEL<INF>24</INF>) in an accelerating fashion: at low exposures
with lower SEL<INF>24</INF>, the amount of TTS is typically small and
the growth curves have shallow slopes. At exposures with higher
SEL<INF>24</INF>, the growth curves become steeper and approach linear
relationships with the sound exposure level (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 more impactful (similar to those discussed in
auditory masking, below). For example, a marine mammal may be able to
readily compensate for a brief, relatively small amount of TTS in a
non-critical frequency range that takes place during a time when the
animal is traveling through the open ocean, where ambient noise is
lower and there are not as many competing sounds present.
Alternatively, a larger amount and longer duration of TTS sustained
during time when communication is critical for successful mother/calf
interactions could have more severe impacts. We note that reduced
hearing sensitivity as
[[Page 16657]]
a simple function of aging has been observed in marine mammals, as well
as humans and other taxa (Southall et al., 2007), so we can infer that
strategies exist for coping with this condition to some degree, though
likely not without cost.
Many studies have examined noise-induced hearing loss in marine
mammals (see Finneran (2015) and Southall et al. (2019) for summaries).
TTS is the mildest form of hearing impairment that can occur during
exposure to sound (Kryter, 2013). While experiencing TTS, the hearing
threshold rises, and a sound must be at a higher level in order to be
heard. In terrestrial and marine mammals, TTS can last from minutes or
hours to days (in cases of strong TTS) (Finneran, 2015). In many cases,
hearing sensitivity recovers rapidly after exposure to the sound ends.
For cetaceans, published data on the onset of TTS are limited to
captive bottlenose dolphin (Tursiops truncatus), beluga whale, harbor
porpoise, and Yangtze finless porpoise (Neophocoena asiaeorientalis)
(Southall et al., 2019). For pinnipeds in water, measurements of TTS
are limited to harbor seals, elephant seals (Mirounga angustirostris),
bearded seals (Erignathus barbatus) and California sea lions (Zalophus
californianus) (Kastak et al., 1999, 2007; Kastelein et al., 2019b,
2019c, 2021, 2022a, 2022b; Reichmuth et al., 2019; Sills et al., 2020).
TTS was not observed in spotted (Phoca largha) and ringed (Pusa
hispida) seals exposed to single airgun impulse sounds at levels
matching previous predictions of TTS onset (Reichmuth et al., 2016).
These studies examine hearing thresholds measured in marine mammals
before and after exposure to intense or long-duration sound exposures.
The difference between the pre-exposure and post-exposure thresholds
can be used to determine the amount of threshold shift at various post-
exposure times.
The amount and onset of TTS depends on the exposure frequency.
Sounds below the region of best sensitivity for a species or hearing
group are less hazardous than those 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, 2019c). Note that in general,
harbor seals and harbor porpoises have a lower TTS onset than other
measured pinniped or cetacean species (Finneran, 2015). In addition,
TTS can accumulate across multiple exposures, but the resulting TTS
will be less than the TTS from a single, continuous exposure with the
same SEL (Mooney et al., 2009; Finneran et al., 2010; Kastelein et al.,
2014, 2015). This means that TTS predictions based on the total,
SEL<INF>24</INF> will overestimate the amount of TTS from intermittent
exposures, such as sonars and impulsive sources. Nachtigall et al.
(2018) describe measurements of hearing sensitivity of multiple
odontocete species (bottlenose dolphin, harbor porpoise, beluga, and
false killer whale (Pseudorca crassidens)) when a relatively loud sound
was preceded by a warning sound. These captive animals were shown to
reduce hearing sensitivity when warned of an impending intense sound.
Based on these experimental observations of captive animals, the
authors suggest that wild animals may dampen their hearing during
prolonged exposures or if conditioned to anticipate intense sounds.
Another study showed that echolocating animals (including odontocetes)
might have anatomical specializations that might allow for conditioned
hearing reduction and filtering of low-frequency ambient noise,
including increased stiffness and control of middle ear structures and
placement of inner ear structures (Ketten et al., 2021). Data available
on noise-induced hearing loss for mysticetes are currently lacking
(NMFS, 2024). Additionally, the existing marine mammal TTS data come
from a limited number of individuals within these species.
Relationships between TTS and AUD INJ thresholds have not been
studied in marine mammals, and there are no measured PTS data for
cetaceans, but such relationships are assumed to be similar to those in
humans and other terrestrial mammals. AUD INJ typically occurs at
exposure levels at least several dB above that inducing mild TTS (e.g.,
a 40-dB threshold shift approximates AUD INJ onset (Kryter et al.,
1966; Miller, 1974), while a 6-dB threshold shift approximates TTS
onset (Southall et al., 2007, 2019). Based on data from terrestrial
mammals, a precautionary assumption is that the AUD INJ thresholds for
impulsive sounds (such as impact pile driving pulses as received close
to the source) are at least 6 dB higher than the TTS threshold on a
peak-pressure basis and AUD INJ cumulative sound exposure level
thresholds are 15 to 20 dB higher than TTS cumulative sound exposure
level thresholds (Southall et al., 2007, 2019). Given the higher level
of sound or longer exposure duration necessary to cause AUD INJ as
compared with TTS, it is considerably less likely that AUD INJ could
occur.
Behavioral Effects
Exposure to noise also has the potential to behaviorally disturb
marine mammals to a level that rises to the definition of harassment
under the MMPA. Generally speaking, NMFS considers a behavioral
disturbance that rises to the level of harassment under the MMPA a non-
minor response--in other words, not every response qualifies as
behavioral disturbance, and for responses that do, those of a higher
level, or accrued across a longer duration, have the potential to
affect foraging, reproduction, or survival. Behavioral disturbance may
include a variety of effects, including subtle changes in behavior
(e.g., minor or brief avoidance of an area or changes in
vocalizations), more conspicuous changes in similar behavioral
activities, and more sustained and/or potentially severe reactions,
such as displacement from or abandonment of high-quality habitat.
Behavioral responses may include changing durations of surfacing and
dives, changing direction and/or speed; reducing/increasing vocal
activities; changing/cessation of certain behavioral activities (such
as socializing or feeding); eliciting a visible startle response or
aggressive behavior (such as tail/fin slapping or jaw clapping); and
avoidance of areas where sound sources are located. In addition,
pinnipeds may increase their haul out time, possibly to avoid in-water
disturbance (Thorson and Reyff, 2006).
Behavioral responses to sound are highly variable and context-
specific and any reactions depend on numerous intrinsic and extrinsic
factors (e.g., species, state of maturity, experience, current
activity, reproductive state, auditory sensitivity, time of day), as
well as the interplay between factors (e.g., Richardson et al., 1995;
Wartzok et al., 2004; Southall et al., 2007, 2019; Weilgart, 2007;
Archer et al., 2010). 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). In general,
pinnipeds seem more tolerant of, or at least habituate more quickly to,
potentially disturbing underwater sound than do cetaceans, and
generally seem to be less responsive to exposure to
[[Page 16658]]
industrial sound than most cetaceans. Please see Appendices B and C of
Southall et al. (2007) and Gomez et al. (2016) for reviews of studies
involving marine mammal behavioral responses to sound.
Habituation can occur when an animal's response to a stimulus wanes
with repeated exposure, usually in the absence of unpleasant associated
events (Wartzok et al., 2004). Animals are most likely to habituate to
sounds that are predictable and unvarying. It is important to note that
habituation is appropriately considered as a ``progressive reduction in
response to stimuli that are perceived as neither aversive nor
beneficial,'' rather than as, more generally, moderation in response to
human disturbance (Bejder et al., 2009). The opposite process is
sensitization, when an unpleasant experience leads to subsequent
responses, often in the form of avoidance, at a lower level of
exposure.
As noted above, behavioral state may affect the type of response.
For example, animals that are resting may show greater behavioral
change in response to disturbing sound levels than animals that are
highly motivated to remain in an area for feeding (Richardson et al.,
1995; Wartzok et al., 2004; National Research Council (NRC), 2005).
Controlled experiments with captive marine mammals have shown
pronounced behavioral reactions, including avoidance of loud sound
sources (Ridgway et al., 1997; Finneran et al., 2003). Observed
responses of wild marine mammals to loud pulsed sound sources (e.g.,
seismic airguns) have been varied but often consist of avoidance
behavior or other behavioral changes (Richardson et al., 1995; Morton
and Symonds, 2002; Nowacek et al., 2007).
Available studies show wide variation in response to underwater
sound; therefore, it is difficult to predict specifically how any given
sound in a particular instance might affect marine mammals perceiving
the signal (e.g., Erbe et al., 2019). If a marine mammal does react
briefly to an underwater sound by changing its behavior or moving a
small distance, the impacts of the change are unlikely to be
significant to the individual, let alone the stock or population. If a
sound source displaces marine mammals from an important feeding or
breeding area for a prolonged period, impacts on individuals and
populations could be significant (e.g., Lusseau and Bejder, 2007;
Weilgart, 2007; NRC, 2005). However, there are broad categories of
potential response, which we describe in greater detail here, that
include alteration of dive behavior, alteration of foraging behavior,
effects to breathing, interference with or alteration of vocalization,
avoidance, and flight.
Avoidance and Displacement
Changes in dive behavior can vary widely and may consist of
increased or decreased dive times and surface intervals as well as
changes in the rates of ascent and descent during a dive (e.g., Frankel
and Clark, 2000; Costa et al., 2003; Ng and Leung, 2003; Nowacek et
al., 2004; Goldbogen et al., 2013a, 2013b; Blair et al., 2016).
Variations in dive behavior may reflect interruptions in biologically
significant activities (e.g., foraging) or they may be of little
biological significance. The impact of an alteration to dive behavior
resulting from an acoustic exposure depends on what the animal is doing
at the time of the exposure and the type and magnitude of the response.
Disruption of feeding behavior can be difficult to correlate with
anthropogenic sound exposure, so it is usually inferred by observed
displacement from known foraging areas, the appearance of secondary
indicators (e.g., bubble nets or sediment plumes), or changes in dive
behavior. Acoustic and movement bio-logging tools also have been used
in some cases to infer responses to anthropogenic noise. 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.
Respiration rates vary naturally with different behaviors and
alterations to breathing rate as a function of acoustic exposure can be
expected to co-occur with other behavioral reactions, such as a flight
response or an alteration in diving. However, respiration rates in and
of themselves may be representative of annoyance or an acute stress
response. Various studies have shown that respiration rates may either
be unaffected or could increase, depending on the species and signal
characteristics, again highlighting the importance in understanding
species differences in the tolerance of underwater noise when
determining the potential for impacts resulting from anthropogenic
sound exposure (e.g., Kastelein et al., 2001; 2005; 2006; Gailey et
al., 2007). For example, harbor porpoise respiration rates increased in
response to pile driving sounds at and above a received broadband SPL
of 136 dB (zero-peak SPL: 151 dB re 1 [mu]Pa; SEL of a single strike
(SEL<INF>ss</INF>): 127 dB re 1 [mu]Pa\2\-s) (Kastelein et al., 2013).
Avoidance is the displacement of an individual from an area or
migration path as a result of the presence of a sound or other
stressors, and is one of the most obvious manifestations of disturbance
in marine mammals (Richardson et al., 1995). For example, gray whales
are known to change direction--deflecting from customary migratory
paths--in order to avoid noise from seismic surveys (Malme et al.,
1984). Avoidance may be short-term, with animals returning to the area
once the noise has ceased (e.g., Bowles et al., 1994; Goold, 1996;
Stone et al., 2000; Morton and Symonds, 2002; Gailey et al., 2007).
Longer-term displacement is possible, however, which may lead to
changes in abundance or distribution patterns of the affected species
in the affected region if habituation to the presence of the sound does
not occur (e.g., Blackwell et al., 2004; Bejder et al., 2006; Teilmann
et al., 2006).
A flight response is a dramatic change in normal movement to a
directed and rapid movement away from the perceived location of a sound
source. The flight response differs from other avoidance responses in
the intensity of the response (e.g., directed movement, rate of
travel). Relatively little information on flight responses of marine
mammals to anthropogenic signals exist, although observations of flight
responses to the presence of predators have occurred (Connor and
Heithaus, 1996; Bowers et al., 2018). The result of a flight response
could range from brief, temporary exertion and displacement from the
area where the signal provokes flight to, in extreme cases, marine
mammal strandings (England et al., 2001). However, it should be noted
that response to a perceived predator does not necessarily invoke
flight (Ford and Reeves, 2008), and whether individuals are solitary or
in groups may influence the response.
Behavioral disturbance can also impact marine mammals in more
subtle ways. Increased vigilance may result in costs related to
diversion of focus and attention (i.e., when a response consists of
increased vigilance, it may come at the cost of decreased attention to
other critical behaviors such as foraging or resting). These effects
have generally not been demonstrated for marine mammals, but studies
involving fishes and terrestrial animals have shown that
[[Page 16659]]
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 one day and not
recurring on subsequent days is not considered particularly severe
unless it could directly affect reproduction or survival (Southall et
al., 2007). Note that there is a difference between multi-day
substantive (i.e., meaningful) behavioral reactions and multi-day
anthropogenic activities. For example, just because an activity lasts
for multiple days does not necessarily mean that individual animals are
either exposed to activity-related stressors for multiple days or,
further, exposed in a manner resulting in sustained multi-day
substantive behavioral responses.
Physiological Stress Responses
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., Selye, 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; Ayres et al., 2012; Yang
et al., 2022). 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. In addition, Lemos et al. (2022)
observed a correlation between higher levels of fecal glucocorticoid
metabolite concentrations (indicative of a stress response) and vessel
traffic in gray whales. Yang et al. (2022) studied behavioral and
physiological responses in captive bottlenose dolphins exposed to
playbacks of ``pile-driving-like'' impulsive sounds, finding
significant changes in cortisol and other physiological indicators but
only minor behavioral changes. 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, 2005), however distress is an
unlikely result of this project based on observations of marine mammals
during previous, similar construction projects.
Auditory Masking
Since many marine mammals rely on sound to find prey, moderate
social interactions, and facilitate mating (Tyack, 2008), noise from
anthropogenic sound sources can interfere with these functions, but
only if the noise spectrum overlaps with the hearing sensitivity of the
receiving marine mammal (Southall et al., 2007; Clark et al., 2009;
Hatch et al., 2012). Chronic exposure to excessive, though not high-
intensity, noise could cause masking at particular frequencies for
marine mammals that utilize sound for vital biological functions (Clark
et al., 2009). Acoustic masking is when other noises such as from human
sources interfere 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; Erbe et al.,
2016). Therefore, under certain circumstances, marine mammals whose
acoustical sensors or environment are being severely masked could also
be impaired from maximizing their performance fitness in survival and
reproduction. 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 (Hotchkin and Parks, 2013).
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) or vocalizations (Foote et al., 2004),
respectively, while
[[Page 16660]]
North Atlantic 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., 2007). Fin whales have also been documented lowering the
bandwidth, peak frequency, and center frequency of their vocalizations
under increased levels of background noise from large vessels
(Castellote et al., 2012). Other alterations to communication signals
have also been observed. For example, gray whales, in response to
playback experiments exposing them to vessel noise, have been observed
increasing their vocalization rate and producing louder signals at
times of increased outboard engine noise (Dahlheim and Castellote,
2016). Alternatively, in some cases, animals may cease sound production
during production of aversive signals (Bowles et al., 1994, Wisniewska
et al., 2018).
Under certain circumstances, marine mammals experiencing
significant masking could also be impaired from maximizing their
performance fitness in survival and reproduction. Therefore, when the
coincident (masking) sound is human-made, it may be considered
harassment when disrupting or altering critical behaviors. It is
important to distinguish TTS and PTS, which persist after the sound
exposure, from masking, which occurs during the sound exposure. Because
masking (without resulting in TS) is not associated with abnormal
physiological function, it is not considered a physiological effect,
but rather a potential behavioral effect (though not necessarily one
that would be associated with harassment).
The frequency range of the potentially masking sound is important
in determining any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation
sounds produced by odontocetes but are more likely to affect detection
of mysticete communication calls and other potentially important
natural sounds such as those produced by surf and some prey species.
The masking of communication signals by anthropogenic noise may be
considered as a reduction in the communication space of animals (e.g.,
Clark et al., 2009) and may result in energetic or other costs as
animals change their vocalization behavior (e.g., Miller et al., 2000;
Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2010; Holt
et al., 2009). Masking can be reduced in situations where the signal
and noise come from different directions (Richardson et al., 1995),
through amplitude modulation of the signal, or through other
compensatory behaviors, including modifications of the acoustic
properties of the signal or the signaling behavior (Hotchkin and Parks,
2013). Masking can be tested directly in captive species (e.g., Erbe,
2008), but in wild populations it must be either modeled or inferred
from evidence of masking compensation. There are few studies addressing
real-world masking sounds likely to be experienced by marine mammals in
the wild (e.g., Branstetter et al., 2013).
Masking occurs in the frequency band that the animals utilize, and
is more likely to occur in the presence of broadband, relatively
continuous noise sources such as vibratory hammers. Energy distribution
of construction sound covers a broad frequency spectrum, and is
anticipated to be within the audible range of marine mammals present in
the proposed action area. Since noises generated from the proposed
construction activities are mostly concentrated at low frequencies (< 2
kHz), these activities likely have less effect on mid-frequency
echolocation sounds produced by odontocetes (toothed whales). However,
lower frequency noises are more likely to affect detection of
communication calls and other potentially important natural sounds such
as surf and prey noise. Low-frequency noise may also affect
communication signals when they occur near the frequency band for noise
and thus reduce the communication space of animals (e.g., Clark et al.,
2009) and cause increased stress levels (e.g., Holt et al., 2009).
Unlike TS, masking, which can occur over large temporal and spatial
scales, can potentially affect the species at population, community, or
even ecosystem levels, in addition to individual levels. Masking
affects both senders and receivers of the signals, and at higher levels
for longer durations, could have long-term chronic effects on marine
mammal species and populations. However, the noise generated by the
Homer's proposed activities will only occur intermittently, across an
estimated 75 days during the authorization period in a relatively small
area focused around the proposed construction site. Thus, while the
Homer's proposed activities may mask some acoustic signals that are
relevant to the daily behavior of marine mammals, the short-term
duration and limited areas affected make it very unlikely that the
fitness of individual marine mammals would be impacted.
Potential Effects on Marine Mammal Habitat
The Homer's proposed activities could have localized, temporary
impacts on marine mammal habitat, including prey, by increasing in-
water SPLs. Increased noise levels may affect acoustic habitat and
adversely affect marine mammal prey in the vicinity of the project
areas (see discussion below). Elevated levels of underwater noise would
ensonify the project areas where both fishes and mammals occur and
could affect foraging success. Additionally, marine mammals may avoid
the area during the proposed construction activities; however,
displacement due to noise is expected to be temporary and is not
expected to result in long-term effects to the individuals or
populations.
The total area likely impacted by the Homer's activities is
relatively small compared to the available habitat in the Kachemak Bay,
AK. Avoidance by potential prey (i.e., fish) of the immediate area due
to increased noise is possible. The duration of fish and marine mammal
avoidance of this area after the in-water construction stops is
unknown, but a rapid return to normal recruitment, distribution, and
behavior is anticipated. Any behavioral avoidance by fish or marine
mammals of the disturbed area would still leave significantly large
areas of fish and marine mammal foraging habitat in the nearby
vicinity.
The proposed project would occur within the same footprint as
existing marine infrastructure. The nearshore and intertidal habitat
where the proposed project would occur is an area of relatively high
marine vessel traffic. Most marine mammals do not generally use the
area within the footprint of the project area. Temporary, intermittent,
and short-term habitat alteration may result from increased noise
levels during the proposed construction activities. Effects on marine
mammal habitat would be limited to pile installation and removal noise,
and effects on prey species would be similarly limited in time and
space.
Water Quality
Temporary and localized reduction in water quality would occur as a
result of in-water construction activities. Most of this effect would
occur during the installation and removal of piles when bottom
sediments are disturbed. The installation and removal of piles would
disturb bottom sediments and may cause a temporary increase in
suspended sediment in the project area. During pile extraction,
sediment
[[Page 16661]]
attached to the pile moves vertically through the water column until
gravitational forces cause it to slough off under its own weight. The
small resulting sediment plume is expected to settle out of the water
column within a few hours. Studies of the effects of turbid water on
fish (marine mammal prey) suggest that concentrations of suspended
sediment can reach thousands of milligrams per liter before an acute
toxic reaction is expected (Burton, 1993).
Since the currents are so strong in the area, following the
completion of sediment-disturbing activities, suspended sediments in
the water column should dissipate and quickly return to background
levels in all construction scenarios. 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.
Therefore, 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 proposed
construction activities is relatively small compared to the available
marine mammal habitat in the Homer Harbor System Four Float Replacement
Project.
Potential Effects on Prey
Sound may affect marine mammals through impacts on the abundance,
behavior, or distribution of prey species (e.g., crustaceans,
cephalopods, fishes, 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.
Fishes 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 fishes (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 sounds (e.g.,
Pe[ntilde]a et al., 2013; Wardle et al., 2001; Jorgenson and Gyselman,
2009; Cott et al., 2012). More commonly, though, the impacts of noise
on fishes are temporary.
SPLs of sufficient strength have been known to cause injury to
fishes and fish mortality (summarized in Popper et al., 2014). 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. (2012b) showed that a TTS of
4 to 6 dB was recoverable within 24 hours for one species. Impacts
would be most severe when the individual fish is close to the source
and when the duration of exposure is long. 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 impact pile driving (Halvorsen et al.,
2012a; Casper et al., 2013, 2017).
Fish populations in the proposed project area that serve as marine
mammal prey could be temporarily affected by noise from pile
installation and removal. The frequency range in which fishes generally
perceive underwater sounds is 50 to 2,000 Hz, with peak sensitivities
below 800 Hz (Popper and Hastings, 2009). Fish behavior or distribution
may change, especially with strong and/or intermittent sounds that
could harm fishes. High underwater SPLs have been documented to alter
behavior, cause hearing loss, and injure or kill individual fish by
causing serious internal injury (Hastings and Popper, 2005).
Zooplankton is a food source for several marine mammal species, as
well as a food source for fish that are then preyed upon by marine
mammals. Population effects on zooplankton could have indirect effects
on marine mammals. Data are limited on the effects of underwater sound
on zooplankton species, particularly sound from construction (Erbe et
al., 2019). Popper and Hastings (2009) reviewed information on the
effects of human-generated sound and concluded that no substantive data
are available on whether the sound levels from pile driving, seismic
activity, or any human-made sound would have physiological effects on
invertebrates. Any such effects would be limited to the area very near
(1 to 5 m) the sound source and would result in no population effects
because of the relatively small area affected at any one time and the
reproductive strategy of most zooplankton species (short generation,
high fecundity, and very high natural mortality). No adverse impact on
zooplankton populations is expected to occur from the specified
activity due, in part, to large reproductive capacities and naturally
high levels of predation and mortality of these populations. Any
mortalities or impacts that might occur would be negligible.
The greatest potential impact to marine mammal prey during
construction would occur during impact pile driving. However, the
duration of impact pile driving would be limited to two piles and to
the final stage of installation (``proofing'') after the pile has been
driven as close as practicable to the design depth with a vibratory
driver. In-water construction activities would only occur during
daylight hours, allowing fish to forage and transit the project area in
the evening. Vibratory pile driving would possibly elicit behavioral
reactions from fishes such as temporary avoidance of the area but is
unlikely to cause injuries to fishes or have persistent effects on
local fish populations. Construction also would have minimal permanent
and temporary impacts on benthic invertebrate species, a marine mammal
prey source. In addition, it should be noted that the area in question
is low-quality habitat since it is already highly developed and
experiences a high level of anthropogenic noise from normal operations
and other vessel traffic.
[[Page 16662]]
Potential Effects on Foraging Habitat
The Homer Harbor System Four Float Replacement Project is not
expected to result in any habitat-related effects that could cause
significant or long-term negative consequences for individual marine
mammals or their populations, since installation and removal of in-
water piles would be temporary and intermittent. The total seafloor
area affected by pile installation and removal is a very small area
compared to the vast foraging area available to marine mammals outside
this project area. The area impacted by the project is relatively small
compared to the available habitat just outside the project area, and
there are no areas of particular importance that would be impacted by
this project. Any behavioral avoidance by fish of the disturbed area
would still leave significantly large areas of fish and marine mammal
foraging habitat in the nearby vicinity. As described in the preceding,
the potential for the Homer's construction to affect the availability
of prey to marine mammals or to meaningfully impact the quality of
physical or acoustic habitat is considered to be insignificant.
Therefore, impacts of the project are not likely to have adverse
effects on marine mammal foraging habitat in the proposed project area.
In summary, given the relatively small areas being affected, as
well as the temporary and mostly transitory nature of the proposed
construction activities, any adverse effects from the Homer's
activities on prey habitat or prey populations are expected to be minor
and temporary. The most likely impact to fishes at the project site
would be temporary avoidance of the area. Any behavioral avoidance by
fish of the disturbed area would still leave significantly large areas
of fish and marine mammal foraging habitat in the nearby vicinity.
Thus, we conclude that impacts of the specified activities are not
likely to have more than short-term adverse effects on any prey habitat
or populations of prey species. Further, any impacts to marine mammal
habitat are not expected to result in significant or long-term
consequences for individual marine mammals, or to contribute to adverse
impacts on their populations.
Estimated Take of Marine Mammals
This section provides an estimate of the number of incidental takes
proposed for authorization through the IHA, which will inform NMFS'
consideration of ``small numbers,'' the negligible impact
determinations, and impacts on subsistence uses.
Harassment is the only type of take expected to result from these
activities. Except with respect to certain activities not pertinent
here, section 3(18) of the MMPA defines ``harassment'' as any act of
pursuit, torment, or annoyance, which (i) has the potential to injure a
marine mammal or marine mammal stock in the wild (Level A harassment);
or (ii) has the potential to disturb a marine mammal or marine mammal
stock in the wild by causing disruption of behavioral patterns,
including, but not limited to, migration, breathing, nursing, breeding,
feeding, or sheltering (Level B harassment).
Authorized takes would primarily be by Level B harassment, as use
of the construction equipment (i.e., impact and vibratory hammers) has
the potential to result in disruption of behavioral patterns for
individual marine mammals. There is also some potential for auditory
injury (AUD INJ) (Level A harassment) to result, primarily for harbor
seals because predicted AUD INJ zones are larger and this species may
be present in the project area. AUD INJ is unlikely to occur for all
other species where take is proposed due to in-water sound not leaving
the confines of the harbor. The proposed mitigation and monitoring
measures are expected to minimize the severity of the taking to the
extent practicable.
As described previously, no serious injury or mortality is
anticipated or proposed to be authorized for this activity. Below we
describe how the proposed take numbers are estimated.
For acoustic impacts, generally speaking, we estimate take by
considering: (1) acoustic criteria above which NMFS believes there is
some reasonable potential for marine mammals to be behaviorally
harassed or incur some degree of AUD INJ; (2) the area or volume of
water that will be ensonified above these levels in a day; (3) the
density or occurrence of marine mammals within these ensonified areas;
and, (4) the number of days of activities. We note that while these
factors can contribute to a basic calculation to provide an initial
prediction of potential takes, additional information that can
qualitatively inform take estimates is also sometimes available (e.g.,
previous monitoring results or average group size). Below, we describe
the factors considered here in more detail and present the proposed
take estimates.
Acoustic Criteria
NMFS recommends the use of acoustic criteria that identify the
received level of underwater sound above which exposed marine mammals
would be reasonably expected to be behaviorally harassed (equated to
Level B harassment) or to incur AUD INJ of some degree (equated to
Level A harassment).
Level B Harassment--Though significantly driven by received level,
the onset of behavioral disturbance from anthropogenic noise exposure
is also informed to varying degrees by other factors related to the
source or exposure context (e.g., frequency, predictability, duty
cycle, duration of the exposure, signal-to-noise ratio, distance to the
source), the environment (e.g., bathymetry, other noises in the area,
predators in the area), and the receiving animals (hearing, motivation,
experience, demography, life stage, depth) and can be difficult to
predict (e.g., Southall et al., 2007; Southall et al., 2021; Ellison et
al., 2012). Based on what the available science indicates and the
practical need to use a threshold based on a metric that is both
predictable and measurable for most activities, NMFS typically uses a
generalized acoustic threshold based on received level to estimate the
onset of behavioral harassment. NMFS generally predicts that marine
mammals are likely to be behaviorally harassed in a manner considered
to be Level B harassment when exposed to underwater anthropogenic noise
above root-mean-squared sound pressure levels (RMS SPL) of 120 dB
(referenced to 1 micropascal (re 1 [mu]Pa)) for continuous (e.g.,
vibratory pile driving, drilling) and above RMS SPL 160 dB re 1 [mu]Pa
for non-explosive impulsive (e.g., seismic airguns) or intermittent
(e.g., scientific sonar) sources. Generally speaking, Level B
harassment take estimates based on these behavioral harassment
thresholds are expected to include any likely takes by TTS as, in most
cases, the likelihood of TTS occurs at distances from the source less
than those at which behavioral harassment is likely. TTS of a
sufficient degree can manifest as behavioral harassment, as reduced
hearing sensitivity and the potential reduced opportunities to detect
important signals (conspecific communication, predators, prey) may
result in changes in behavior patterns that would not otherwise occur.
Homer's proposed activity includes the use of continuous (vibratory
hammers) and impulsive (impact hammers) sources, and therefore the RMS
SPL thresholds of 120 and 160 dB re 1 [mu]Pa, respectively, are
applicable.
Level A harassment--NMFS' Updated Technical Guidance for Assessing
the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version
3.0) (Updated Technical Guidance, 2024) identifies dual criteria to
assess AUD
[[Page 16663]]
INJ (Level A harassment) to five different underwater marine mammal
groups (based on hearing sensitivity) as a result of exposure to noise
from two different types of sources (impulsive or non-impulsive).
Homer's proposed activity includes the use of impulsive (impact
hammers) and non-impulsive (vibratory hammers) sources.
The 2024 Updated Technical Guidance criteria include both updated
thresholds and updated weighting functions for each hearing group. The
thresholds are provided in the table below. The references, analysis,
and methodology used in the development of the criteria are described
in NMFS' 2024 Updated Technical Guidance, which may be accessed at:
<a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools</a>.
Table 4--Thresholds Identifying the Onset of Auditory Injury
----------------------------------------------------------------------------------------------------------------
AUD INJ onset acoustic thresholds * (received level)
Hearing group ------------------------------------------------------------------------
Impulsive Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans........... Cell 1: Lpk,flat: 222 dB; Cell 2: LE,LF,24h: 197 dB.
LE,LF,24h: 183 dB.
High-Frequency (HF) Cetaceans.......... Cell 3: Lpk,flat: 230 dB; Cell 4: LE,HF,24h: 201 dB.
LE,HF,24h: 193 dB.
Very High-Frequency (VHF) Cetaceans.... Cell 5: Lpk,flat: 202 dB; Cell 6: LE,VHF,24h: 181 dB.
LE,VHF,24h: 159 dB.
Phocid Pinnipeds (PW) (Underwater)..... Cell 7: Lpk,flat: 223 dB; Cell 8: LE,PW,24h: 195 dB.
LE,PW,24h: 183 dB.
Otariid Pinnipeds (OW) (Underwater).... Cell 9: Lpk,flat: 230 dB; Cell 10: LE,OW,24h: 199 dB.
LE,OW,24h: 185 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric criteria for impulsive sounds: Use whichever criteria results in the larger isopleth for
calculating AUD INJ onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure
level criteria associated with impulsive sounds, the PK SPL criteria are recommended for consideration for non-
impulsive sources.
Note: Peak sound pressure level (Lp,0-pk) has a reference value of 1 [micro]Pa, and weighted cumulative sound
exposure level (LE,p) has a reference value of 1 [mu]Pa\2\s. In this table, criteria are abbreviated to be
more reflective of International Organization for Standardization standards (ISO, 2017). The subscript
``flat'' is being included to indicate peak sound pressure are flat weighted or unweighted within the
generalized hearing range of marine mammals underwater (i.e., 7 Hz to 165 kHz). The subscript associated with
cumulative sound exposure level criteria indicates the designated marine mammal auditory weighting function
(LF, HF, and VHF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours.
The weighted cumulative sound exposure level criteria could be exceeded in a multitude of ways (i.e., varying
exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate
the conditions under which these criteria will be exceeded.
Ensonified Area
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.
The sound field in the project area is the existing background
noise plus additional construction noise from the proposed project.
Marine mammals are expected to be affected via sound generated by the
primary components of the project (i.e., vibratory pile removal,
vibratory pile driving, and impact pile driving). The source levels
assumed for both removal and installation activities are based on
reviews of measurements of piles of the same or similar types and
dimensions available in the scientific literature and from similar
coastal construction projects. The source level for the piles and
activities (i.e., installation or removal) are presented in table 5.
Table 5--Proxy Sound Source Levels for Pile Sizes and Driving Methods
----------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------
Activity Proxy sound source level at 10 m Reference
----------------------------------------------------------------------------------------------------------------
12-in timber piles.................... 162 Caltrans 2020.
12.75-in steel piles.................. 163 NMFS 2023.
16-in steel piles.
18-in steel piles.
24-in steel piles.
----------------------------------------------------------------------------------------------------------------
Impact pile driving dB SEL dB RMS dB Peak
----------------------------------------------------------------------------------------------------------------
In-air; all pile sizes................ .............. 109 .............. NAVFAC SW 2020.
18-in steel piles..................... 175 185 200 Caltrans 2020.
----------------------------------------------------------------------------------------------------------------
Transmission loss (TL) is the decrease in acoustic intensity as an
acoustic pressure wave propagates out from a source. TL parameters vary
with frequency, temperature, sea conditions, current, source and
receiver depth, water depth, water chemistry, bottom composition, and
topography. The general formula for underwater TL is:
TL = B * Log<INF>10</INF> (R<INF>1</INF>/R<INF>2</INF>),
Where:
TL = transmission loss in dB
B = transmission loss coefficient; for practical spreading equals 15
R<INF>1</INF> = the distance of the modeled SPL from the driven
pile, and
R<INF>2</INF> = the distance from the driven pile of the initial
measurement.
This formula neglects loss due to scattering and absorption, which
is assumed to be zero here. The degree to which underwater sound
propagates away from a sound source depends on various factors, most
notably the water bathymetry and the presence or absence of reflective
or absorptive conditions, including in-water structures and sediments.
Spherical spreading occurs in a perfectly unobstructed (free-field)
environment not limited by depth or water surface, resulting in a 6 dB
reduction in sound level for each doubling of distance from the source
(20*log[range]). Cylindrical spreading occurs in an environment in
which sound propagation is bounded by the
[[Page 16664]]
water surface and sea bottom, resulting in a reduction of 3 dB in sound
level for each doubling of distance from the source (10*log[range]). A
practical spreading value of 15 is often used in shallow-water coastal
conditions, such as those found in the NBPL and NBSD projects. In these
environments, sound waves repeatedly reflect off the surface and
bottom, reflecting an expected propagation environment between
spherical and cylindrical spreading-loss conditions. Therefore, the
default coefficient of 15 is used to calculate distances to the Level A
harassment and Level B harassment thresholds.
Assuming practicable spreading and other assumptions regarding the
source characteristics and operational logistics (e.g., source level,
number of strikes per pile, number of piles per day), Homer calculated
distances to the Level A harassment and Level B harassment thresholds
and associated ensonified areas. Because an ensonified area associated
with Level A harassment is more technically challenging to predict
given the accounting for a cumulative energy component that changes
over time, to assist applicants in assessing the potential for Level A
harassment without the need for complex modeling, NMFS developed an
optional User Spreadsheet tool to accompany the 2024 Updated Technical
Guidance (see <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools</a>). This relatively simple tool can be used to calculate a Level A
harassment isopleth distance for use in conjunction with marine mammal
density or occurrence data to predict the amount of take that may occur
incidental to an activity. We note that, because of some of the
assumptions in the methods underlying this spreadsheet tool, we
anticipate that the resulting isopleths would typically be
overestimates, which may lead to an overestimate of potential exposures
from Level A harassment. However, this optional tool offers a practical
alternative for estimating isopleth distances when more sophisticated
modeling methods are unavailable or are impractical. For stationary
sources such as impact or vibratory pile driving and removal, the
optional User Spreadsheet tool predicts the distance at which, if a
marine mammal remained at that distance for the duration of the
activity within 24 hours, it would be expected to incur AUD INJ. Inputs
used in the optional User Spreadsheet tool are contained within table
6.
Table 6--User Spreadsheet Input Parameters Used for Calculating Level A Harassment Isopleths
--------------------------------------------------------------------------------------------------------------------------------------------------------
Existing pile removal Temporary pile Permanent pile installation
--------------------------------------- installation and removal ---------------------------------------------------
---------------------------
12-in 12.75-in 16-in 16-in 16-in 12.75-in 16-in 18-in 24-in
Installation Removal
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pile Material..................... Timber Steel Steel Steel Steel Steel Steel Steel Steel
Total Number of Piles............. 36 40 26 28 28 14 70 29 20
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory Pile Driving
--------------------------------------------------------------------------------------------------------------------------------------------------------
Max # of Piles Vibrated per Day... 20 20 20 2 2 10 10 10 10
Vibratory Time per Pile (mins).... 10 10 10 10 10 15 15 20 30
Estimated Number of Days.......... 4 4 3 14 14 4 18 8 5
Vibratory Time Total (mins)....... 360 400 260 280 280 210 1,050 580 600
--------------------------------------------------------------------------------------------------------------------------------------------------------
Impact Pile Driving
--------------------------------------------------------------------------------------------------------------------------------------------------------
Number of Piles................... 0 0 0 0 0 0 0 2 0
Max # of Piles Impacted per Day... ........... ........... ........... ............ ........... ........... ........... 2 ...........
Number of Strikes per Pile........ ........... ........... ........... ............ ........... ........... ........... 240 ...........
Number of Days.................... ........... ........... ........... ............ ........... ........... ........... 1 ...........
--------------------------------------------------------------------------------------------------------------------------------------------------------
Using the practical spreading model and source assumptions
identified in table 5 and the user spreadsheet inputs in table 6, Homer
calculated, and NMFS has carried forward into this analysis the
distances to the Level A harassment and Level B harassment thresholds
for marine mammals of this project (table 7). It should be noted that
the Level B harassment zones during the construction of unit two of the
project presented in the table below result in a narrow beam of sound
outside the harbor entrance. In past IHAs, NMFS had determined that
take from similar narrow harassment zones may not result in take of
marine mammals given that many animals pass through the area in a short
amount of time. Here NMFS does expect take of a limited number of
marine mammals during the construction of unit two based on the
analysis provided by the applicant.
Table 7--Calculated Distances to the Level A Harassment and Level B Harassment Thresholds by Marine Mammal Hearing Group and Activity
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Calculated distances for acoustic thresholds in M \a\ (ensonified area in square km)
------------------------------------------------------------------------------------------
Pile size and material Activity Level A Level B (all
------------------------------------------------------------------------------------------ species)
LF cetaceans HF cetaceans VHF cetaceans Phocids Otariids
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
12-in timber.................................... Existing pile removal............. 24.0 9.2 19.6 30.9 10.4 6,309.6
(0.014; \b\ (0.006) (0.012; \b\ (0.017; \b\ (0.0005) (0.244; \b\
0.016 \c\) 0.013 \c\) 0.021 \c\) 1.024 \c\)
12.75-in steel.................................. Existing pile removal............. 28.0 10.7 22.9 36.0 12.1 7,356.4
(0.016; \b\ (0.007) (0.013; \b\ (0.020; \b\ (0.008) (0.244; \b\
0.019 \c\) 0.015 \c\) 0.025 \c\) 1.326 \c\)
Permanent pile installation....... 23.1 8.9 18.9 29.7 10.0 7,356.4
(0.013; \b\ (0.006) (0.011; \b\ (0.017; \b\ (0.007; \b\ (0.244; \b\
0.015 \c\) 0.012 \c\) 0.020 \c\) 0.006 \c\) 1.326 \c\)
[[Page 16665]]
16-in steel..................................... Existing pile removal............. 28.0 10.7 22.9 36.0 12.1 7,356.4
(0.016; \b\ (0.007) (0.013; \b\ (0.020; \b\ (0.008) (0.244; \b\
0.019 \c\) 0.015 \c\) 0.025 \c\) 1.326 \c\)
Temporary pile installation....... 6.0 2.3 4.9 7.8 2.6 7,356.4
(0.004) (0.001) (0.003) (0.005) (0.002) (0.244; \b\
1.326 \c\)
Temporary pile removal............ 6.0 2.3 4.9 7.8 2.6 7,356.4
(0.004) (0.001) (0.003) (0.005) (0.002) (0.244; \b\
1.326 \c\)
Permanent pile installation....... 23.1 8.9 18.9 29.7 10.0 7,356.4
(0.013; \b\ (0.006) (0.011; \b\ (0.017; \b\ (0.007; \b\ (0.244; \b\
0.015 \c\) 0.012 \c\) 0.020 \c\) 0.006 \c\) 1.326 \c\)
18-in steel..................................... Permanent pile installation....... 28.0 10.7 22.9 36.0 12.1 7,356.4
(0.016; \b\ (0.007) (0.013b; 0.015c) (0.020; \b\ (0.008) (0.244; \b\
0.019 \c\) 0.025 \c\) 1.326 \c\)
24-in steel..................................... Permanent pile installation....... 36.7 14.1 29.9 47.2 15.9 7,356.4
(0.020; \b\ (0.009) (0.017; \b\ (0.026; \b\ (0.010) (0.244; \b\
0.026 \c\) 0.021 \c\) 0.035 \c\) 1.326 \c\)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Impact
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
18-in steel..................................... Permanent pile installation....... 178.6 22.8 276.4 158.7 59.2 464.2
(0.104 \b\) (0.013 \b\) (0.013 \b\) (0.091 \b\) (0.032 \b\) (0.195 \b\)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Distances refer to the maximum radius of the zone. The actual zone may be truncated by landforms. The values provided for Level A calculated distances represent the distance at which an
animal may incur AUD INJ if that animal remained at that distance for the entire duration of the activity within a 24-hour period.
\b\ Ensonifed area for Unit 1.
\c\ Ensonifed area for Unit 2.
Marine Mammal Occurrence
In this section we provide information about the occurrence of
marine mammals, including density or other relevant information which
will inform the take calculations.
The applicant used survey data from the Cook Inlet Beluga Whale
surveys over several years to estimate average group sizes for all of
the marine mammal species where take is proposed outside the harbor
(Sheldon et al., 2013, 2015, 2017, 2022; Sheldon and Wade 2019).
Average group sizes from within the harbor were derived by local
observations (SolsticeAK 2025). The frequency of occurrence (e.g.,
monthly or daily) was determined by local observations within and
outside the Homer Small Boat Harbor. Humpback whales and killer whales
are expected to frequent the area four times a month. Dall's porpoise,
harbor porpoise, and Steller sea lions are less frequent, only
occurring once a month. Harbor seals are the most common marine mammal
expected to be present daily during the project. Both Steller sea lions
and harbor seals are the only marine mammals expected to occur within
and outside the harbor and take could occur during both unit one and
unit two. All other species are expected to occur outside the harbor
and would only be taken during the construction of unit two. The table
below summarizes the average group sizes calculated from the Cook Inlet
Beluga Whale survey for each species where take is proposed.
Table 8--Average Group Size of Marine Mammals Occurring in the Project
Area
------------------------------------------------------------------------
Group size Group size
Species within harbor outside harbor
------------------------------------------------------------------------
Humpback whale.......................... N/A 2
Killer whale............................ N/A 7
Dall's porpoise......................... N/A 3
Harbor porpoise......................... N/A 3
Harbor seal............................. 2 (9 \1\) 12
Steller sea lion........................ 1 5
------------------------------------------------------------------------
\1\ A group size of nine harbor seals was used for take by Level A
harassment estimates. While harbor seals are most commonly seen in
groups of one to two individuals, groups as large as nine have been
observed. A larger group was used for the take by Level A harassment
calculations if a large group is in the harbor on the single day of
impact pile driving.
Take Estimation
Here we describe how the information provided above is synthesized
to produce a quantitative estimate of the take that is reasonably
likely to occur and proposed for authorization.
To calculate the estimated take that may occur incidental to the
Homer Small Boat Harbor project, the applicant used the following
methods below, and NMFS has carried them forward in the analysis below.
Each estimate of take was rounded up to the highest whole number. Homer
used the following equation to estimate exposures during each unit of
construction:
Occurrence by day or times per month x average group size of marine
mammal species x days of activity on a given unit
For example for humpback whales take by Level B harassment is only
expected during construction of unit two. The following equation was
used to estimate the incidental take of humpbacks:
4 groups per month x 2 whales per group x 32 days in unit 2/30 days per
month = 9 humpback whale takes by Level B harassment
Additional information related to the take calculations for each
marine mammal species by construction unit and construction method
(i.e., vibratory and impact) can be found in section 6.1 of Homer's
application. It is expected
[[Page 16666]]
that in the project area incidental take of humpback whales would be
split between both the Hawaii stock and the Mexico-North Pacific stock
by 89 percent and 11 percent respectively (Wade 2021). NMFS estimates
that incidental take from both stocks of killer whales present in the
project area could occur at an equal probability from either stock. The
total incidental take by Level A and Level B harassment proposed for
authorization under this IHA can be found in table 9.
Table 9--Proposed Authorized Take by Level A Harassment and Level B Harassment and as a Percentage of Stock
Abundance
----------------------------------------------------------------------------------------------------------------
Stock Percent of
Species Stock (Nest) Level A Level B Total abundance stock
----------------------------------------------------------------------------------------------------------------
Humpback Whale............... Hawaii.......... 0 8 8 11,278 <0.1
Mexico North 0 1 1 \1\ 918 0.1
Pacific.
Killer Whale................. ENP Alaska 0 30 30 1,920 1.6
Resident.
ENP Gulf of 0 587 5.1
Alaska,
Aleutian
Islands, and
Bering Sea.
Dall's Porpoise.............. Alaska.......... 0 4 4 \2\ 13,110 <0.1
Harbor Porpoise.............. Gulf of Alaska.. 0 4 4 31,046 <0.1
Harbor Seal.................. Cook Inlet/ 9 854 863 28,411 3.0
Shelikof Strait.
Steller Sea Lion............. Western DPS..... 0 8 8 49,837 <0.1
----------------------------------------------------------------------------------------------------------------
\1\ Population estimate based on surveys in Alaskan waters, as abundance estimates for the Mexico-North Pacific
stock are more than eight years old and no longer considered reliable (Young et al. 2024).
\2\ Population estimation based on surveys from the Gulf of Alaska only, as abundance estimates for the Alaska
stock are more than 25 years old and no longer considered reliable (Young et al. 2025).
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. 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.
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, impact on
operations.
The mitigation requirements described in the following were
proposed by Homer in its adequate and complete application. Homer has
agreed that all of the mitigation measures are practicable. NMFS has
fully reviewed the specified activities and the mitigation measures to
determine if the mitigation measures would result in the least
practicable adverse impact on marine mammals and their habitat, as
required by the MMPA, and has determined the proposed measures are
appropriate. NMFS describes these below as proposed mitigation
requirements, and has included them in the proposed IHA.
Establishment of Shutdown Zones--Homer would establish shutdown
zones with radial distances as identified in table 10 for all
construction activities. The purpose of a shutdown zone is generally to
define an area within which shutdown of the activity would occur upon
sighting of a marine mammal (or in anticipation of an animal entering
the defined area). If a marine mammal is observed entering or within
the shutdown zones indicated in table 10, pile driving activity must be
delayed or halted. If pile driving is delayed or halted due to the
presence of a marine mammal, the activity may not commence or resume
until either the animal has voluntarily exited and been visually
confirmed beyond the shutdown zones or 15 minutes have passed without
re-detection of the animal. If a marine mammal comes within or
approaches the shutdown zone indicated in table 10, such operations
must cease. Shutdown zones would vary based on the activity type and
marine mammal hearing group.
Table 10--Proposed Shutdown Zones During Project Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Distance (m) to Level A shutdown zones
Pile size and material Activity -------------------------------------------------------------------------------
LF cetaceans HF cetaceans VHF cetaceans PW OW
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory Pile Driving
--------------------------------------------------------------------------------------------------------------------------------------------------------
12-in timber.............................. Existing pile removal....... 25 10 20 35 15
12.75-in steel............................ Existing pile removal....... 30 15 25 40 15
Permanent pile installation. 25 10 20 30 10
16-in steel............................... Existing pile removal....... 30 15 25 40 15
[[Page 16667]]
Temporary pile installation. 10 10 10 10 10
Temporary pile removal...... 10 10 10 10 10
Permanent pile installation. 25 10 20 30 10
18-in steel............................... Permanent pile installation. 30 15 25 40 15
24-in steel............................... Permanent pile installation. 40 15 30 50 20
--------------------------------------------------------------------------------------------------------------------------------------------------------
Impact Pile Driving
--------------------------------------------------------------------------------------------------------------------------------------------------------
18-in steel............................... Permanent pile installation. 180 25 280 50 60
--------------------------------------------------------------------------------------------------------------------------------------------------------
Monitoring the Level B Harassment Zones--Homer has identified the
Level B harassment zones for each proposed activity. These zones
provide utility for observing by establishing monitoring protocols for
areas adjacent to the shutdown zones. The Level B harassment zones
enable observers to be aware of and communicate the presence of marine
mammals in the project area outside the shutdown zone and thus prepare
for a potential cessation of activity should the animal enter the
shutdown zone. Protected Species Observers (PSOs) would monitor the
entire area to the extent practicable defined in tables 11.
Table 11--Level B Harassment Zones
------------------------------------------------------------------------
Level B
Pile size and material Activity harassment
zone
------------------------------------------------------------------------
Vibratory Pile Driving
------------------------------------------------------------------------
12-in timber...................... Existing pile 6,310
removal.
12.75-in steel.................... Existing pile 7,360
removal.
Permanent pile 7,360
installation.
16-in steel....................... Existing pile 7,360
removal.
Temporary pile 7,360
installation.
Temporary pile 7,360
removal.
Permanent pile 7,360
installation.
18-in steel....................... Permanent pile 7,360
installation.
24-in steel....................... Permanent pile 7,360
installation.
------------------------------------------------------------------------
Impact Pile Driving
------------------------------------------------------------------------
18-in steel....................... Permanent pile 470
installation.
------------------------------------------------------------------------
Pre- and Post-Activity Monitoring--Monitoring would take place from
30 minutes prior to initiation of pile driving activity (i.e., pre-
start clearance monitoring) through 30 minutes post-completion of pile
driving activity. In addition, monitoring for 30 minutes would take
place whenever a break in the specified activity (i.e., impact pile
driving or vibratory pile driving) of 30 minutes or longer occurs. Pre-
start clearance monitoring would be conducted during periods of
visibility sufficient for the lead PSO to determine that the shutdown
zones indicated in table 10 are clear of marine mammals. Pile driving
may commence following 30 minutes of observation when the determination
is made that the shutdown zones are clear of marine mammals.
Soft Start--Homer would use soft-start techniques when impact pile
driving. Soft-start requires contractors to provide an initial set of
three strikes at reduced energy, followed by a 30-second waiting
period, then two subsequent reduced-energy strike sets. A soft-start
would be implemented at the start of each day's impact pile driving and
at any time following cessation of impact pile driving for a period of
30 minutes or longer. Soft-start procedures are used to provide
additional protection to marine mammals by providing a warning and/or
giving marine mammals a chance to leave the area prior to the hammer
operating at full capacity.
In summary, based on our evaluation of the Homer's proposed
mitigation measures for the Homer Small Boat Harbor project, 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, with particular focus on
rookeries, mating grounds, and similar areas of significance.
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.
[[Page 16668]]
Monitoring and reporting requirements prescribed by NMFS should
contribute to improved understanding of one or more of the following:
<bullet> Occurrence of marine mammal species or stocks in the area
in which take is anticipated (e.g., presence, abundance, distribution,
density);
<bullet> 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);
<bullet> Individual marine mammal responses (behavioral or
physiological) to acoustic stressors (acute, chronic, or cumulative),
other stressors, or cumulative impacts from multiple stressors;
<bullet> How anticipated responses to stressors impact either: (1)
long-term fitness and survival of individual marine mammals; or (2)
populations, species, or stocks;
<bullet> Effects on marine mammal habitat (e.g., marine mammal prey
species, acoustic habitat, or other important physical components of
marine mammal habitat); and
<bullet> Mitigation and monitoring effectiveness.
The monitoring and reporting requirements described in the
following were proposed by Homer in its adequate and complete
application. Homer has agreed to the requirements. NMFS describes these
below as requirements and has included them in the proposed IHA.
Homer would abide by all monitoring and reporting measures
contained within the IHA, if issued, and their Protected Species
Monitoring Plans (see NMFS' website at <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>). NMFS describes these below as requirements
and has included them in the proposed IHA.
Visual Monitoring
All PSOs must be NMFS-approved and have no other assigned tasks
during monitoring periods. Homer would have between one and three PSOs
actively monitoring on-site at all times during pile-driving
activities. Where a team of three or more PSOs is required, a lead
observer or monitoring coordinator would be designated. The lead PSO
would be required to have prior experience working as a PSO during a
NMFS-issued ITA or Letter of Concurrence. PSOs would be placed in
locations as specified in the marine mammal monitoring plan.
Reporting
Homer would be required to submit a draft report(s) on all
construction activities and marine mammal monitoring results to NMFS
within 90 days of the completion of monitoring, or 60 days prior to the
requested issuance of any subsequent IHAs or similar activity at the
same location, whichever comes first. The information required to be
collected and reported to NMFS is included in the draft IHA available
at <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>. In summary, the
report would include, but not be limited to, information regarding
activities that occurred, marine mammal sighting data, and whether
mitigative actions were taken or could not be taken. Homer would also
be required to submit reports on any observed injured or dead marine
mammals. If the death or injury was clearly caused by the specified
activity, Homer would immediately cease the specified activities until
NMFS is able to review the circumstances of the incident and determine
what, if any, additional measures are appropriate to ensure compliance
with the terms of the IHA. Homer would not resume its activities until
notified by NMFS.
Reporting Injured or Dead Marine Mammals --In the event that
personnel involved in Homer's activities discover an injured or dead
marine mammal, Homer would report the incident to the NMFS Office of
Protected Resources (<a href="/cdn-cgi/l/email-protection#abfbf985e2fffb85e6c4c5c2dfc4d9c2c5ccf9cedbc4d9dfd8ebc5c4caca85ccc4dd"><span class="__cf_email__" data-cfemail="e8b8bac6a1bcb8c6a58786819c879a81868fba8d98879a9c9ba886878989c68f879e">[email protected]</span></a>,
<a href="/cdn-cgi/l/email-protection#206974700e434f434b52454c4c604e4f41410e474f56"><span class="__cf_email__" data-cfemail="b3fae7e39dd0dcd0d8c1d6dfdff3dddcd2d29dd4dcc5">[email protected]</span></a>) and to the Alaska Regional Stranding Coordinator
as soon as feasible. If the death or injury was clearly caused by the
specified activity, the Homer would immediately cease the specified
activities until NMFS is able to review the circumstances of the
incident and determine what, if any, additional measures are
appropriate to ensure compliance with the IHA. Homer would not resume
their activities until notified by NMFS. The report would include the
following information:
<bullet> Description of the incident;
<bullet> Environmental conditions (e.g., Beaufort sea state,
visibility);
<bullet> Description of all marine mammal observations in the 24
hours preceding the incident;
<bullet> Photographs or video footage of the animal(s) (if
equipment is available).
<bullet> Time, date, and location (latitude/longitude) of the first
discovery (and updated location information if known and applicable);
<bullet> Species identification (if known) or description of the
animal(s) involved;
<bullet> Condition of the animal(s) (including carcass condition if
the animal is dead);
<bullet> Observed behaviors of the animal(s), if alive; and
<bullet> General circumstances under which the animal was
discovered.
Specific proposed mitigation, monitoring, and reporting
requirements can be found in the draft IHAs found at <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>.
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 9, given that the
[[Page 16669]]
anticipated effects of this activity on these different marine mammal
stocks are expected to be similar. Where there are meaningful
differences between species or stocks, or groups of species, in
anticipated individual responses to activities, impact of expected take
on the population due to differences in population status, or impacts
on habitat, they are described independently in the analysis below.
Pile driving and removal activities associated with the project as
outlined previously, have the potential to disturb or displace marine
mammals. Specifically, the specified activities may result in take, in
the form of Level A harassment and Level B harassment from underwater
sounds generated from pile driving and removal. Potential takes could
occur if individuals of these species are present in zones ensonified
above the thresholds for Level A or Level B harassment identified above
when these activities are underway.
Take by Level A and Level B harassment would be due to potential
behavioral disturbance, TTS, and PTS. No serious injury or mortality is
anticipated or proposed for authorization given the nature of the
activity and measures designed to minimize the possibility of injury to
marine mammals. Take by Level A harassment is only anticipated for
harbor seals. Impacts to affected individuals of harbor seals are not
expected to result in population-level impacts. The potential for
harassment is minimized through the construction method (i.e. use of
direct pull removal or vibratory methods to the extent practical) and
the implementation of the planned mitigation measures (see Proposed
Mitigation section).
In addition to the expected effects resulting from Level B
harassment, we anticipate that harbor porpoises, Steller sea lions, and
harbor seals may sustain some limited Level A harassment in the form of
auditory injury. However, animals in these locations that experience
PTS would likely only receive slight PTS, i.e., minor degradation of
hearing capabilities within regions of hearing that align most
completely with the energy produced by pile driving, i.e., the low-
frequency region below 2 kHz, not severe hearing impairment or
impairment in the regions of greatest hearing sensitivity. If hearing
impairment occurs, it is most likely that the affected animal would
lose a few decibels in its hearing sensitivity, which in most cases is
not likely to meaningfully affect its ability to forage and communicate
with conspecifics. As described above, we expect that marine mammals
would be likely to move away from a sound source that represents an
aversive stimulus, especially at levels that would be expected to
result in PTS, given sufficient notice through use of soft start.
The project also is not expected to have significant adverse
effects on affected marine mammals' habitat. The project activities
would not modify existing marine mammal habitat for a significant
amount of time. The activities may cause some fish or invertebrates to
leave the area of disturbance, thus temporarily impacting marine
mammals' foraging opportunities in a limited portion of the foraging
range; but, because of the short duration of the activities, the
relatively small area of the habitat that may be affected, and the
availability of nearby habitat of similar or higher value, the impacts
to marine mammal habitat are not expected to cause significant or long-
term negative consequences. There are no known haulouts for Steller sea
lions or harbor seals within the project area. Repeated exposures of
individuals to this pile driving activity could cause Level A and Level
B harassment but are unlikely to considerably disrupt foraging behavior
or result in significant decrease in fitness, reproduction, or survival
for the affected individuals.
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:
<bullet> No serious injury or mortality is anticipated or
authorized;
<bullet> Any Level A harassment (AUD INJ) is anticipated to be
slight AUD INJ (i.e., of a few decibels) within the lower frequencies
associated with pile driving and not encompassing a species' full
hearing range;
<bullet> The anticipated incidents of Level B harassment would
consist of, at worst, temporary modifications in behavior that would
not result in fitness impacts on individuals;
<bullet> The area affected by the specified activity is very small
relative to the overall habitat ranges of all species, does not include
any rookeries, does not include ESA-designated critical habitat, and
does not include any BIAs;
<bullet> Effects on species that serve as prey for marine mammals
from the activities are expected to be short-term and, therefore, any
associated impacts on marine mammal feeding are not expected to result
in significant or long-term consequences for individuals, or to accrue
adverse impacts on their populations;
<bullet> The project area is located in a highly active harbor;
therefore, species are likely acclimated to anthropogenic activities
and behavioral reactions are expected to be minor (if at all); and
<bullet> The proposed mitigation measures, such as soft-starts, and
shutdowns, are expected to reduce the effects of the specified activity
to the least practicable adverse impact level.
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 section 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 (see 86 FR
5322, January 19, 2021). Additionally, other qualitative factors may be
considered in the analysis, such as the temporal or spatial scale of
the activities.
Table 9 demonstrates the number of animals that could be exposed to
the received noise levels that could cause harassment for the proposed
work in Homer, AK. Our analysis shows that less than 5.1 percent of
each affected stock could be taken by harassment. The numbers of
animals proposed to be taken for these stocks would be considered small
relative to the relevant stock's abundances, even if each estimated
taking occurred to a new individual, an extremely unlikely scenario.
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
[[Page 16670]]
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.
There have been no harvest of marine mammals in the Homer area
since 2014. The project area has never been used for subsistence hunts
by the surrounding communities of Seldovia Village Tribe, the Native
Village of Port Graham, the Native Village of Nanwalek (also known as
English Bay), and Ninilchik Village. Given the lack of overlap with
current subsistence hunting areas and the proposed project area there
are no relevant subsistence uses of marine mammals adversely impacted
by this action. The proposed project is not likely to adversely impact
the availability of any marine mammal species or stocks that are
commonly used for subsistence purposes or to impact subsistence harvest
of marine mammals in the region.
Based on the description of the specified activity, the measures
described to minimize adverse effects on the availability of marine
mammals for subsistence purposes, and the proposed mitigation and
monitoring measures, NMFS has preliminarily determined that there will
not be an unmitigable adverse impact on subsistence uses from Homer's
proposed activities.
Endangered Species Act
Section 7(a)(2) of the ESA of 1973 (16 U.S.C. 1531 et seq.)
requires that each Federal agency ensures 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 incidental take
authorizations, NMFS Office of Protected Resources (OPR) consults
internally whenever we propose to authorize take for ESA-listed
species, in this case with the NMFS Alaska Regional Office (AKRO).
NMFS is proposing to authorize take of Mexico-North Pacific DPS of
humpback whales and the Western DPS of Steller sea lions, which are
listed under the ESA.
OPR has requested initiation of section 7 consultation with the
AKRO 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 Homer for conducting construction of the Homer Harbor
System Four Float Replacement Project in Homer, AK, provided the
previously mentioned mitigation, monitoring, and reporting requirements
are incorporated. A draft of the proposed IHA can be found at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>.
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
construction of the Homer Harbor System Four Float Replacement Project
in Homer, AK. We also request comment on the potential 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:
<bullet> 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).
<bullet> 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: March 31, 2026.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2026-06453 Filed 4-1-26; 8:45 am]
BILLING CODE 3510-22-P
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</html>Indexed from Federal Register on April 2, 2026.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.