[Federal Register Volume 91, Number 57 (Wednesday, March 25, 2026)]
[Notices]
[Pages 14535-14556]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-05812]
-----------------------------------------------------------------------
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XF061]
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to Robert Storrs Harbor Floats A&B
Replacement Project in Unalaska, Alaska
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental harassment authorization; request
for comments.
-----------------------------------------------------------------------
SUMMARY: NMFS has received a request from the City of Unalaska (COU)
for authorization to take marine mammals incidental to the replacement
of the harbor floats in Unalaska, Alaska. Pursuant to the Marine Mammal
Protection Act (MMPA), NMFS is requesting comments on its proposal to
issue an incidental harassment authorization (IHA) to incidentally take
marine mammals during the specified activities. NMFS is also requesting
comments on a possible one-time, 1-year renewal that could be issued
under certain circumstances and if all requirements are met, as
described in the Request for Public Comments section 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 April
24, 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 [email protected].
Electronic copies of the application and supporting documents, as well
as a list of the references cited in this document, may be obtained
online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities. In
case of problems accessing these documents, please call the contact
listed 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 https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act without change. All personal identifying
information (e.g., name, address, etc.) 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: Jennifer Gatzke, 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 June 25, 2025, NMFS received a request from the COU for an IHA
to take marine mammals incidental to construction work involving pile
driving during a harbor replacement project on Unalaska Island, Alaska.
Following NMFS' review of the application, COU submitted a revised
version, which was deemed adequate and complete, on March 2, 2026.
COU's request is for take of five species of marine mammals by Level B
harassment and, for a subset of three of these species, Level A
harassment. Neither COU nor NMFS expect serious injury or mortality to
result from this activity and, therefore, an IHA is appropriate.
[[Page 14536]]
Description of Proposed Activity
Overview
COU plans to conduct construction, including pile driving,
associated with the Robert Storrs Harbor Floats A&B Replacement Project
in Unalaska, Alaska. The project includes the use of vibratory, impact
and down-the-hole (DTH) pile driving hammers, which may result in the
incidental take by Levels A and B harassment of marine mammals.
Unalaska, an island in the Aleutian Island chain, is west of the
Alaska Peninsula (figure 1). The Robert Storrs Harbor is a small
harbor, west-southwest (WSW) of Dutch Harbor, and the only recreational
vessel harbor used by residents of Unalaska.
[GRAPHIC] [TIFF OMITTED] TN25MR26.006
This project is designed to better serve the community, by removing
the current ailing infrastructure, and modernizing the docks to make
them more accessible. To support this expanded upland parking area,
rock fill will be placed below the high tide line to create an
embankment for this improvement. Construction will require removal of
piles and floats, as well as installation of new materials, which is
expected to take a maximum of 100 days of in-water work. Vibratory,
impact, and DTH hammer pile driving will be used to remove the existing
steel pipe piles and floats. This IHA would be effective for 1 year
within a maximum 2-year window of effectiveness from the date of
issuance.
No serious injury or mortality is anticipated to result from this
activity. A small number of incidental take by Level A harassment
(auditory injury) is proposed for authorization, as is incidental take
by Level B Harassment. The COU will implement mitigation measures and a
monitoring program that will reduce the likelihood of injurious
interaction. Multiple trained protected species observers (PSOs) in
strategic locations will monitor the project area and clearance zones.
The number and/or intensity of incidents of takes will be minimized
through the incorporation of the mitigation measures that were proposed
by COU or are the result of coordination between NMFS and COU. The COU
has agreed that all of the mitigation measures are practicable. As
required by the MMPA, we concurred that these measures are sufficient
to achieve the least practicable adverse impact on the affected marine
mammal species or stocks and their habitat and have included them in
the IHA as proposed mitigation requirements.
Dates and Duration
The proposed IHA would be valid for the statutory maximum of 1 year
from the date of effectiveness and will become 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. Due to weather considerations, most in-water work is
planned to occur between March and September, with the COU planning to
start work in July 2026. However, project delays may occur due to a
number of factors, such as project funding, availability of equipment
and/or materials, weather and tide-related delays, equipment
maintenance and/or repair, and other considerations. Pile driving will
consist of vibratory, impact and DTH drilling of steel piles no larger
than 24 inches (61 centimeters). Plans include: (1) the removal of
existing piles, installation and removal of temporary piles, and
installation of permanent piles; (2) no simultaneous pile driving; (3)
a maximum number of 100 pile driving days; and (4) 10- to 12-hour
daytime construction shifts.
Specific Geographic Region
Approximately 2,560 km (1,591 miles) WSW of Anchorage, AK, Robert
Storrs Harbor sits beside Iliuliuk Harbor, WSW of Dutch Harbor, and is
the only recreational harbor used by Unalaska residents, including a
small number of subsistence hunters (figure 2).
[[Page 14537]]
[GRAPHIC] [TIFF OMITTED] TN25MR26.007
Detailed Description of the Specified Activity
Pile removal and installation will involve vibratory, impact and
DTH drilling. The project will use a single crane barge with no
simultaneous pile driving. The project aims to replace most of the
infrastructure, removing and installing new piles, floats, gang/
walkways, bulkheads, below the high tide line rock armoring to support
a new upland parking area. Pile removal and driving are expected to
cause behavioral disturbance, temporary threshold shifts (TTS), or
auditory injury (AUD INJ), which includes but is not limited to
permanent threshold shifts (PTS).
There are components of this project that we do not expect to
impact marine mammals, their habitat, or their subsistence use. These
components include the work to expand the parking area, abutments, and
gravel fill. We do not expect any of these activities to result in
disturbance beyond the ambient noise and activity of a working harbor,
including both airborne and underwater sound, and these activities will
not be considered further.
The COU plans for 95 days of pile driving, with a maximum of 100
days. All in-water work is scheduled for 10-12 daytime hours per day: 6
days to remove existing piles, 6 days to install temporary template
piles, and 88 days to install permanent piles. In-water work, including
pile driving, needs to occur between March 15 and September 30 to avoid
hazardous weather conditions. Overall construction season includes an
allowance for weather delays and is subject to change.
Table 1--Pile Driving Activity Planned
--------------------------------------------------------------------------------------------------------------------------------------------------------
Project total Max piles per Min/strikes Average piles
Size steel pipe pile (inches) Construction method # piles day per pile Days of effort per day
--------------------------------------------------------------------------------------------------------------------------------------------------------
16.................................... Vibratory removal............... 33 15 15 6 7
24.................................... (Temporary) Vibratory 5 4 20 3 2
installation.
24.................................... (Temporary) Vibratory removal... 4 15 3 2
24.................................... Vibratory installation.......... 44 4 20 22 2
Impact installation............. 4 1,000 22 2
DTH installation................ 2 180 44 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 14538]]
Proposed mitigation, monitoring, and reporting measures are
described in detail later in this document (please see Proposed
Mitigation and Proposed Monitoring and Reporting sections).
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 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; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments) and
more general information about these species (e.g., physical and
behavioral descriptions) may be found on NMFS' website (https://www.fisheries.noaa.gov/find-species).
Table 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: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments.
Table 2--Species,1 Stocks, and the Status of Marine Mammals That Occur Near the Project Area and that May be Taken by the COU's Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
ESA/MMPA status; Stock abundance (CV;
Common name Scientific name Stock strategic (Y/N) Nmin; most recent PBR Annual M/
\2\ abundance survey) \3\ SI \4\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Artiodactyla--Cetacea--Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Balaenopteridae (rorquals):
Humpback Whale.................. Megaptera novaeangliae. Hawai[revaps]i......... -, -, N 11,278 (0.56, 7,265, 127 27.09
2020).
Humpback Whale.................. Megaptera novaeangliae. Mexico-North Pacific... T, D, Y N/A (N/A, N/A, 2006).. UND 0.57
Humpback Whale.................. Megaptera novaeangliae. Western N Pacific...... E, D, Y 1,084 (0.088, 1,007, 3.4 5.82
2006).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Delphinidae:.................
Killer Whale.................... Orcinus orca........... ENP Alaska Resident.... -, -, N 1,920 (N/A, 1,920, 19 1.3
2019).
Killer Whale.................... Orcinus orca........... ENP Gulf of Alaska, -, -, N 587 (N/A, 587, 2012).. 5.9 0.8
Aleutian Islands and
Bering Sea Transient.
Family Phocoenidae (porpoises):.....
Harbor Porpoise................. Phocoena phocoena...... Bering Sea............. -, -, N 4,130 (UNK, N/A, 2008) UND 0.4
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Artiodactyla--Order Carnivora--Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otariidae (eared seals and
sea lions):
Steller Sea Lion................ Eumetopias jubatus..... Western................ E, D, Y 49,837 (N/A, 73,211, 299 267
2022).
Family Phocidae (earless seals):
Harbor seal..................... Phoca vitulina......... Aleutian Islands....... -, -, N 5,588 (N/A, 5,366, 97 90
2018).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Information on the classification of marine mammal species can be found on the web page for the Society for Marine Mammalogy's Committee on Taxonomy
(https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/).
\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: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable
[explain if this is the case].
\4\ These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g.,
commercial fisheries, vessel strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A
CV associated with estimated mortality due to commercial fisheries is presented in some cases.
As indicated above, all five 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 other marine
mammal species, including sperm whales (Physeter macrocephalus), fin
whales (Balaenoptera physalus), North Pacific
[[Page 14539]]
right whales (Eubalaena japonica), minke whales (Balaenoptera
acutorostrata), and Dall's porpoise (Phocoenoides dalli) have been
documented in the waters surrounding Unalaska, we do not expect these
species to overlap in space and time with the project site and they
will not be discussed further. In addition, the northern sea otter
(Enhydra lutris kenyoni) is found in Unalaska. However, sea otters are
managed by the U.S. Fish and Wildlife Service and are not considered
further in this document.
Humpback whales--Waters surrounding Unalaska Island are designated
as a humpback whale feeding biologically important area (BIA) (Harrison
et al. 2023). Three stocks are found in the Aleutian Islands, with the
Hawaiian stock most heavily represented, followed by the Western North
Pacific and Mexico-North Pacific stocks. This humpback whale feeding
BIA is active from May through January when humpback whales congregate
in the bay to feed on spawning herring. Overall, humpback whales are
likely to be present during construction. The COU notified PND
Engineers, Inc., and NMFS that they received a January 2026 sighting of
a humpback whale in Expedition Inlet, indicating the likelihood that
humpback whales may be in the adjacent project area during construction
(personal communication, 2/18/26). The final monitoring report for the
UniSea G1 Dock Replacement Project (figure 2) noted three rare
sightings of humpback whales inside Iliuliuk Harbor in June and July of
2016. The first whale surfaced during construction at the center of
Iliuliuk Harbor on June 16 when construction was halted for an hour.
The remaining two humpback whales were sighted before entering the
observation zone and Iliuliuk Harbor (PND Engineers, Inc., 2017).
During the 2017 Unalaska Marine Center (UMC) Dock Replacement project
in nearby Dutch Harbor, approximately 9 humpback whales were observed
within estimated Level B harassment zones.
Killer whales--While killer whales are sighted in waters around
Unalaska, and there are food sources that might attract whales in the
harbors, monitoring reports from the UniSea and UMC projects reveal no
killer whale sightings in nearby harbors. Whales in this area could be
from either the Eastern North Pacific (ENP) Alaska Resident stock, or
the ENP Gulf of Alaska, Aleutian Islands, and Bering Sea Transient
stock. Resident killer whales are particularly common around Unalaska
and Umnak Islands (Zerbini et al., 2007), and they have been documented
predating on gray whales migrating through the nearby Unimak Pass
(Barrett-Lennard et al., 2011).
Harbor porpoises--During the UniSea G1 Dock Replacement Project in
Iliuliuk Harbor between March and October 2016, protected species
observers reported no sightings of harbor porpoises (PND Engineers,
Inc., 2017). While there are few reported sightings of harbor porpoises
in the general area of the harbor, there is potential for them to be
sighted during the project. Table 2 notes the most recent ship survey
for the Bering Sea stock of harbor porpoise was conducted in 2008.
Using that resulting partial population estimate of 5,713 and its
associated Coefficient of Variation (CV) of 0.4, NMIN for
the Bering Sea stock of harbor porpoise is 4,130. As this is an
underestimate for the entire stock because it is based on a survey that
covered only a small portion of the stock's range, and because the
survey data are more than 8 years old, NMIN is considered
unknown in the most recent SARs report. However, we use the 4,130
figure as the best available information to calculate the percentage of
take in table 3 in support of the small numbers determination.
Steller sea lions--Winter Steller eider surveys conducted by the
USACE regularly found Steller sea lions in Iliuliuk Harbor and in
Expedition Inlet, with a maximum of ten Steller sea lions within
Iliuliuk Harbor per survey (PND, 2026). Sea lions were frequently seen
on the southern side of Iliuliuk Bay, likely moving toward the entrance
channel of Iliuliuk Harbor, where they were commonly found (Chris
Hoffman, unpublished data). There are fish processing plants and an
anadromous river in the bay that draw pinnipeds and other marine life.
While critical habitat exists around Unalaska Island, the nearest
Steller sea lion haul-out site is 17 nautical miles (nmi) away, and the
nearest rookery is 20 nmi away. Due to the shape of the enclosed
harbor, and the resulting limit to the extent of acoustic noise,
project activities are not expected to affect critical habitat.
Harbor seals--The UniSea G1 Dock Replacement Project conducted
protected species observations between March and October of 2016 for
211 days in the Iliuliuk Harbor Area. The final monitoring report
totaled sightings of 200 individuals and indicated that harbor seals
remained relatively constant in their presence throughout the season,
but moved away from areas with the highest concentration of sea lions
(PND Engineers, Inc., 2017). There are no haul-out sites nearby that
would be a concern for dislocating seals during 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 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 or hear over the same frequency range (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.). Subsequently, NMFS (2018, 2024) described generalized
hearing ranges for these marine mammal hearing groups (table 3).
Generalized hearing ranges were chosen based on the approximately 65-
decibel (dB) threshold from composite audiograms, previous analyses in
NMFS (2018), and/or data from Southall et al. (2007, 2019). Of the
species potentially present in the action area, humpback whales
considered low-frequency (LF) cetaceans, killer whales are considered
high-frequency (HF) cetaceans, harbor porpoises are considered very
high-frequency (VHF) cetaceans, Steller sea lions are otariid
pinnipeds, and harbor seals are phocid pinnipeds.
Table 3--Marine Mammal Hearing Groups (NMFS, 2024)
------------------------------------------------------------------------
Hearing group Generalized hearing range *
------------------------------------------------------------------------
LF cetaceans (baleen whales)......... 7 Hz to 36 kHz.
HF cetaceans (dolphins, toothed 150 Hz to 160 kHz.
whales, beaked whales, bottlenose
whales).
VHF cetaceans (true porpoises, Kogia, 200 Hz to 165 kHz.
river dolphins, Cephalorhynchid,
Lagenorhynchus cruciger & L.
australis).
Phocid pinnipeds (PW) (underwater) 40 Hz to 90 kHz.
(true seals).
[[Page 14540]]
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 ~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 details concerning these groups and associated generalized
hearing ranges, please see NMFS (2024) for a review of available
information.
Potential Effects of Specified Activities on Marine Mammals and Their
Habitat
This section includes a summary and 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 the specified
activities. 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, impact pile driving, DTH systems, and rock hammering. The
effects of underwater noise from COU's proposed activities have the
potential to result in Level B harassment of marine mammals in the
action area and, for some species 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 Specified Activities
Activities associated with the project that have the potential to
incidentally take marine mammals though exposure to sound include pile
driving activity using vibratory, impact, and DTH drilling.
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
(SPLs), 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 SPLs) than impact hammers. Peak 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, 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).
DTH systems use a combination of drilling and percussive mechanisms
to advance a hole into the rock, with or without simultaneously
advancing a pile/casing into that hole. Drill cuttings and debris at
the rock face are removed by an air-lift exhaust through the inside of
the pile (Guan and Miner, 2020). Unlike other pile installation
methods, at least one sound source during DTH is found at the
intersection of the drill tip and the substrate and is often more
characteristically a point source rather than a linear source, as in
impact and vibratory pile driving. A DTH system is essentially a drill
bit that drills through the bedrock using a rotating function like a
normal drill integrated with a hammering mechanism to increase speed of
progress through the substrate (i.e., it is similar to a ``hammer
drill'' hand tool). DTH systems typically involve a single hammer
(mono-hammer), but multi- or ``cluster'' hammer drills may also be
used.
DTH systems include both DTH drilling and DTH driving techniques.
During DTH pile drilling, the DTH hammer does not make direct contact
with the pile; rather, the hammer acts as a percussive drill to advance
a hole through the substrate within a casing (casing is driven through
overburden using impact or vibratory methods). After the hole is
drilled to the desired depth, the casing is removed, and the production
pile is placed inside the hole. Often, an impact hammer is then used to
confirm the pile has reached load-bearing capacity (i.e., proof). If
needed, a tension anchor can be drilled following these same methods
within the production pile to add lateral support to the pile.
During DTH pile driving, the DTH hammer directly strikes a
specially designed shoe located at the bottom of the pile, which has
wings that have a slightly larger diameter than the pile (i.e., the
hammer directly strikes the production pile itself; no pile casing is
used). The drill head locks into the bottom of the pile, and then the
drill head and pile advance simultaneously into the substrate to the
desired depth. Often, the production pile is then proofed with an
impact hammer. If needed, a tension anchor can be drilled using DTH
drilling methods within the production pile to add lateral support to
the pile.
The sounds produced by the DTH methods simultaneously contain both
a continuous non-impulsive component from the drilling action and an
impulsive component from the hammering effect. Therefore, for purposes
of evaluating Level A and Level B harassment under the MMPA, NMFS
treats DTH systems as both impulsive (Level A harassment thresholds)
and continuous, non-impulsive (Level B harassment thresholds) sound
source types simultaneously.
[[Page 14541]]
Typical activities for which DTH systems are used include rock
socketing and tension or rock anchoring. Rock socketing involves using
DTH techniques to create a hole in the bedrock inside which a pile is
placed to give it lateral and longitudinal strength as described in DTH
drilling, above. Rock sockets are made in bedrock when the overlaying
sediments are too shallow to adequately secure the bottom portion of a
pile using other methods.
The purpose of a tension anchor is to secure a pile to the bedrock
to withstand uplift forces. Tension anchors are installed within
production piles that are installed into the substrate below the
elevation of the pile tip after the pile has been driven through the
sediment layer to refusal. Typically, a small- diameter casing (e.g.,
6- to 8-inch (15.24- to 20.32-centimeter) steel pipe casing) is
inserted into a larger- diameter production pile. A rock drill is then
inserted into the casing, and a small (e.g., 6- to 10-inch; 15.24- to
25.4-centimeter) diameter hole is drilled into bedrock with rotary and
percussion drilling methods (using DTH drilling methods). The drilling
activity is contained within the steel pile casing and the steel pipe
pile. The typical depth of the drilled tension anchor hole varies, but
a 6- to 9-meter (m) depth is common. A steel rod is then grouted into
the drilled hole and affixed to the top of the pile.
Hydraulic rock hammers would be used for removal and demolition
purposes. These tools are impact devices designed to break rock or
concrete. A rock hammer operates by using a chisel-like hammer to
rapidly strike an exposed surface to break it up into smaller pieces
that would be removed by a clamshell dredge or bucket excavator, as
appropriate. Few data exist regarding the underwater sounds produced by
rock hammers. Data reported by Escude (2012), however, suggest that the
sounds produced by hoe rams are comparable to impact hammers.
Therefore, for the purposes of this analysis, it is assumed that
hydraulic rock hammers act as an impulsive source characterized by
rapid rise times and high peak levels.
The likely or possible impacts of the COU's proposed activities on
marine mammals could involve both non-acoustic and acoustic stressors.
Potential non-acoustic stressors could result from the physical
presence of the equipment and personnel; however, given there are no
known pinniped haul-out sites in the vicinity of the Robert Storrs
Harbor, visual and other non-acoustic stressors would be limited, and
any impacts to marine mammals are expected to primarily be acoustic in
nature.
Potential Effects of Underwater Sound on Marine Mammals
The introduction of anthropogenic noise into the aquatic
environment from vibratory and impact hammers is the primary means by
which marine mammals may be harassed from the COU'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
use of rock fill is reasonably likely to result in such effects (see
below for 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 COU.
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 COU plans
to conduct, to the degree it is available.
Hearing Threshold Shifts (TSs). NMFS defines a noise-induced TS as
a change, usually an increase, in the threshold of audibility at a
specified frequency or portion of an individual's hearing range above a
previously established reference level (NMFS, 2018, 2024). The amount
of TS 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
[[Page 14542]]
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).
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 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 (Phoca vitulina) (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).
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 (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 (SEL24) in an accelerating fashion: at low exposures
with lower SEL24, the amount of TTS is typically small and
the growth curves have shallow slopes. At exposures with higher
SEL24, 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 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 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 (Delphinapterus
leucas), harbor porpoise, and Yangtze finless porpoise (Neophocoena
asiaeorientalis) (Southall et al., 2019). For pinnipeds in water,
measurements of TTS are limited to harbor seals, elephant seals
(Mirounga angustirostris), bearded seals (Erignathus barbatus) and
California sea lions (Zalophus californianus) (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 seals
(Phoca largha) and ringed seals (Pusa hispida) 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 depend 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 LF 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
SEL24 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 LF 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.
[[Page 14543]]
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 SEL thresholds are 15 to 20
dB higher than TTS cumulative SEL 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 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. For example,
Blair et al. (2015) reported significant effects on humpback whale
foraging behavior in Stellwagen Bank in response to ship noise
including slower descent rates, and fewer side-rolling events per dive
with increasing ship nose. In addition, Wisniewska et al. (2018)
reported that tagged harbor porpoises demonstrated fewer prey capture
attempts when encountering occasional high-noise levels resulting from
vessel noise as well as more vigorous fluking, interrupted foraging,
and cessation of echolocation signals observed in
[[Page 14544]]
response to some high-noise vessel passes. 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:
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 because of the presence of a sound or other stressors,
and is one of the most obvious manifestations of disturbance in marine
mammals (Richardson et al., 1995). For example, gray whales
(Eschrictius robustus) are known to change direction--deflecting from
customary migratory paths--to avoid noise from seismic surveys (Malme
et al., 1984). Harbor porpoises, Atlantic white-sided dolphins
(Lagenorhynchus actusus), and minke whales have demonstrated avoidance
in response to vessels during line transect surveys (Palka and Hammond,
2001). In addition, beluga whales in the St. Lawrence Estuary in Canada
have been reported to increase levels of avoidance with increased boat
presence by way of increased dive durations and swim speeds, decreased
surfacing intervals, and by bunching together into groups (Blane and
Jaakson, 1994). 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 increased
vigilance may substantially reduce feeding rates (e.g., Beauchamp and
Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). In
addition, chronic disturbance can cause population declines through
reduction of fitness (e.g., decline in body condition) and subsequent
reduction in reproductive success, survival, or both (e.g., Harrington
and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). However,
Ridgway et al. (2006) reported that increased vigilance in bottlenose
dolphins exposed to sound over a 5-day period did not cause any sleep
deprivation or stress effects.
Many animals perform vital functions, such as feeding, resting,
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption
of such functions resulting from reactions to stressors such as sound
exposure are more likely to be significant if they last more than one
diel cycle or recur on subsequent days (Southall et al., 2007).
Consequently, a behavioral response lasting less than 1 day and not
recurring on subsequent days is not considered particularly severe
unless it could directly affect reproduction or survival (Southall et
al., 2007). Note that there is a difference between multi-day
substantive (i.e., meaningful) behavioral reactions and multi-day
anthropogenic activities. For example, just because an activity lasts
for multiple days does not necessarily mean that individual animals are
either exposed to activity-related stressors for multiple days or,
further, exposed in a manner resulting in sustained multi-day
substantive behavioral responses.
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
[[Page 14545]]
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.
Vocalizations and 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 acoustic 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 (Orcinus
orca) 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 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 (Balaenoptera
physalus) 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, LF
signals may have less effect on HF 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.
[[Page 14546]]
Energy distribution of vibratory hammer sounds cover 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. LF 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
COU's proposed activities will only occur intermittently, across an
estimated 100 days during the authorization period in a relatively
small area focused around the proposed construction site. Thus, while
the COU'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.
Airborne Acoustic Effects. Pinnipeds that occur near the project
site could be exposed to airborne sounds associated with construction
activities that have the potential to cause behavioral harassment,
depending on their distance from these activities. Airborne noise would
primarily be an issue for pinnipeds that are swimming or hauled out
near the project site within the range of noise levels elevated above
airborne acoustic harassment criteria. Although pinnipeds are known to
haul out regularly on man-made objects, we believe that incidents of
take resulting solely from airborne sound are unlikely due to the
proximity between the proposed project area and the known haul-out
sites (e.g., Steller sea lions are known to haul out on a buoy in
Iliuliuk Bay, and pinniped rookeries and haul-out sites exist around
Unalaska Island). Cetaceans are not expected to be exposed to airborne
sounds that would result in harassment as defined under the MMPA.
We recognize that pinnipeds in the water could be exposed to
airborne sounds that may result in behavioral harassment when looking
with their heads above water. Most likely, airborne sounds would cause
behavioral responses similar to those discussed above in relation to
underwater sound. For instance, anthropogenic sound could cause hauled-
out pinnipeds to exhibit changes in their normal behavior, such as
reduction in vocalizations, or cause them to flush from haul-out sites,
temporarily abandon the area, and or move further from the source.
However, these animals would previously have been `taken' because of
exposure to underwater sounds above the behavioral harassment
thresholds, which are in all cases larger than those associated with
airborne sound. Thus, the behavioral harassment of these animals is
already accounted for in these estimates of potential take. Therefore,
we do not believe that authorization of additional incidental take
resulting from airborne sound for pinnipeds is warranted, and airborne
sound is not discussed further here.
Potential Effects on Marine Mammal Habitat
The COU'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, any
displacement due to noise is expected to be temporary and is not
expected to result in long-term effects to the individuals or
populations.
The total area likely impacted by the COU's activities is
relatively small compared to the available habitat in Iliuliuk Harbor.
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 construction activity 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 temporary 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 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).
Impacts to water quality from DTH are expected to be similar to
those described for pile driving. Impacts to water quality would be
localized and temporary and would have negligible impacts on marine
mammal habitat. Drilling would have negligible impacts on water quality
from sediment resuspension because the system would operate within a
casing set into the bedrock. The drill would collect excavated material
inside of the apparatus where it would be lifted to the surface and
placed onto a barge for subsequent disposal.
Effects to turbidity and sedimentation are expected to be short-
term, minor, and localized. 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
[[Page 14547]]
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 Iliuliuk Harbor.
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 depend 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
LF 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 is likely 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 cause death, and it 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, rock hammering,
and DTH excavation. However, the duration of impact pile driving would
be limited 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 and rock hammering 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.
Potential Effects on Foraging Habitat
The Robert Storrs Harbor Floats A&B 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
[[Page 14548]]
significantly large areas of fish and marine mammal foraging habitat in
the nearby vicinity. As described in the preceding, the potential for
the COU'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 COU'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
preliminarily 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 acoustic (i.e., pile driving hammers) has the potential to
result in disruption of behavioral patterns for individual marine
mammals. There is also some potential for AUD INJ (Level A harassment)
to result, primarily for VHF species and phocids because predicted AUD
INJ zones are relatively large and these species are often difficult to
detect. In addition, AUD INJ is anticipated for otariids due to their
common occurrence in the immediate vicinity of the project area. AUD
INJ is unlikely to occur for LF or HF species due to the anticipated
low likelihood of occurrence and relative ease of detection. 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). In this particular
case, we did not use density or ensonified area to calculate take, but
relied heavily upon the number of days marine mammal groups would be
exposed to different underwater sound regimes within the highly
constrained harbor environment, and previous monitoring results
(pinnipeds) and average group size (cetaceans). 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). Criteria have also been developed to identify the
pressure levels above which animals may incur different types of tissue
damage (non-acoustic Level A harassment or mortality) from exposure to
pressure waves from explosive detonation. We note that the criteria for
AUD INJ, as well as the names of two hearing groups, have been recently
updated (NMFS, 2024) as reflected below in the Level A harassment
section.
Level B Harassment. Though significantly driven by received level,
the onset of behavioral disturbance from anthropogenic noise exposure
is also informed to varying degrees by other factors related to the
source or exposure context (e.g., frequency, predictability, duty
cycle, duration of the exposure, signal-to-noise ratio, distance to the
source), the environment (e.g., bathymetry, other noises in the area,
predators in the area), and the receiving animals (hearing, motivation,
experience, demography, life stage, depth) and can be difficult to
predict (e.g., Southall et al., 2007; 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 (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.
COU's proposed project includes the use of continuous (vibratory
and DTH) and intermittent (impact and DTH) sources, and therefore the
RMS SPL thresholds of 120 and 160 dB re 1 [micro]Pa are applicable.
Level A harassment. NMFS' Updated Technical Guidance for Assessing
the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version
3.0) (Updated Technical Guidance, 2024)
[[Page 14549]]
identifies dual criteria to assess AUD INJ (Level A harassment) to five
different underwater marine mammal groups (based on hearing
sensitivity) as a result of exposure to noise from two different types
of sources (impulsive or non-impulsive). COU's proposed activity
includes the use of impulsive (impact hammer and DTH) and non-impulsive
(vibratory hammer and DTH) 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:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools.
Table 4--Thresholds Identifying the Onset of Auditory Injury
----------------------------------------------------------------------------------------------------------------
AUD INJ onset acoustic thresholds * (received level)
Hearing group ------------------------------------------------------------------------
Impulsive Non-impulsive
----------------------------------------------------------------------------------------------------------------
LF Cetaceans........................... Cell 1: Lpk,flat: 222 dB; Cell 2: LE,LF,24h: 197 dB.
LE,LF,24h: 183 dB.
HF Cetaceans........................... Cell 3: Lpk,flat: 230 dB; Cell 4: LE,HF,24h: 201 dB.
LE,HF,24h: 193 dB.
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 SPL criteria
associated with impulsive sounds, the peak SPL criteria are recommended for consideration for non-impulsive
sources.
Note: Peak SPL (Lp,0-pk) has a reference value of 1 [micro]Pa, and weighted cumulative SEL (LE,p) has a
reference value of 1 [micro]Pa\2\s. In this table, criteria are abbreviated to be more reflective of
International Organization for Standardization 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 SEL 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 SEL 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 Zone
Here, we describe operational and environmental parameters of the
activity that are used in estimating the zone ensonified above the
acoustic thresholds, including source levels and transmission loss
coefficient. The ensonified space is truncated by land features that
restrict the lineal distance of sound travel from the source to about
1000 m (figure 3).
BILLING CODE 3510-22-P
[[Page 14550]]
[GRAPHIC] [TIFF OMITTED] TN25MR26.008
BILLING CODE 3510-22-C
The ensonified zone associated with Level A harassment is more
technically challenging to predict due to the need to account for a
duration component. Therefore, NMFS developed an optional User
Spreadsheet tool to accompany the 2024 Updated Technical Guidance that
can be used to relatively predict an isopleth distance for use in
conjunction with marine mammal density or occurrence to help predict
potential takes. We note that because of some of the assumptions
included in the methods underlying this optional tool, we anticipate
that the resulting isopleth estimates are typically going to be
overestimates of some degree, which may result in an overestimate of
potential take by Level A harassment. However, this optional tool
offers a practical, alternative way to estimate isopleth distances when
more sophisticated modeling methods are not available or practical. For
stationary sources, the optional User Spreadsheet tool predicts the
distance at which, if a marine mammal remained at that distance for the
duration of the activity, it would be expected to incur AUD INJ. Inputs
used in the optional User Spreadsheet tool (table 5), and the resulting
estimated isopleths (table 6), are reported below.
Table 5--User Spreadsheet Inputs for the Robert Storrs Harbor Floats Project
--------------------------------------------------------------------------------------------------------------------------------------------------------
Predicted
source Peak source Distance Max piles Minutes
Source (steel pipe piles; inches) Source type level (SPL SEL level (SPL (m) WFA (kHz) per day (strikes)
RMS) RMS) per pile
--------------------------------------------------------------------------------------------------------------------------------------------------------
16................................... V, R...................... 163 153 181 10 2.5 15 15
24................................... V, I...................... 163 153 181 10 2.5 4 20
V, R...................... 163 153 181 10 2.5 4 15
24................................... V, I&R.................... 163 153 181 10 2.5 4 20
Impact.................... 190 177 203 10 2 4 1,000
DTH....................... 167 159 184 10 2 2 180
--------------------------------------------------------------------------------------------------------------------------------------------------------
V = Vibratory; R = Removal; I = Installation; DTH = Down-the-hole.
[[Page 14551]]
Table 6--Calculated Isopleths; Underwater Sources Using the NMFS 2024 Acoustic Tools and Technical Guidance
--------------------------------------------------------------------------------------------------------------------------------------------------------
PTS thresholds (m) Level A Level B
Max ------------------------------------------------------------ behavioral
Source (steel pipe piles; inches) Source type piles Strikes (PW) (OW) disturbance
per day per pile LF HF VHF phocid otariid isopleth
cetaceans cetaceans cetaceans pinnipeds pinnipeds (m)
--------------------------------------------------------------------------------------------------------------------------------------------------------
16................................ V, R................... 15 15 30.3 11.6 24.7 39.0 13.1 7,356.4
24................................ V, I................... 4 20 15.2 5.8 12.4 19.5 6.6 7,356.4
V, R................... 4 15 12.5 4.8 10.2 16.1 5.4 7,356.4
24................................ V, I&R................. 4 20 15.2 5.8 12.4 19.5 6.6 7,356.4
Impact................. 4 1000 998.2 127.4 1544.6 886.7 330.5 1,000.0
DTH.................... 2 180 899.8 114.8 1392.4 799.3 297.9 13,594
--------------------------------------------------------------------------------------------------------------------------------------------------------
V = Vibratory; R = Removal; I = Installation; DTH = Down-the-hole.
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools.
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.
For humpback whales and killer whales, no Level A harassment is
anticipated or proposed for authorization due to the likelihood that
these species would not linger in the ensonified zone, and there is a
duration element to Level A harassment. If encountered, these species
are thought to be brief visitors to the area and traveling through to
other portions of the island. PSOs would also likely be able to more
easily detect these large species, noting presence and behaviors for
the monitoring report. Therefore, all pile driving days would be
assumed to result in no worse than Level B harassment for these
species.
As noted previously, the constrained harbor environment means that
the largest attainable harassment zone distance is approximately 1,000
m. Therefore, due to the relatively large estimated Level A harassment
zones associated with impact driving and DTH installation for harbor
seal and harbor porpoise, all days of impact driving and DTH
installation are assumed to result in Level A harassment for these
species, while all days of vibratory driving would result in Level B
harassment only. However, for Steller sea lions, the Level A harassment
zone for both impact driving and DTH installation is approximately one-
third of this maximum harassment zone distance. Therefore, for Steller
sea lions, we assume that one-third of takes on days when impact
driving and DTH installation occur would result in Level A harassment.
The remaining takes on these days, and all takes of Steller sea lions
on vibratory driving days, are assumed to result in Level B harassment.
While no harbor porpoises were sighted during the UniSea project in
2016, COU proposed a monthly estimate of 10 harbor porpoise to account
for potential occurrence of this species. For humpback whales and
killer whales, COU proposed to assume that two and three individuals
may occur within the project area per month, respectively. Note that,
for humpback whale, given the low total estimated take, all humpback
whale takes are assumed to be of Hawaii stock. Similarly, for the low
total estimated take of killer whales, all are assumed to be of ENP
Alaska resident stock. For Steller sea lion and harbor seal, we assume
average occurrence of 9.4 and 0.95 individuals per day, respectively,
on the basis of past monitoring data. The UniSea G1 Dock Replacement
monitoring report from 2016 noted sightings of 1,987 individual Steller
sea lions and 200 harbor seals over 211 days of monitoring.
The project is expected to require approximately 100 days of pile
driving and DTH activity, with approximately two-thirds of this time
potentially involving impact driving or DTH installation. We therefore
multiply the monthly occurrence estimates by 3.3 months and, for harbor
porpoise, assume that two-thirds of the resulting estimated takes would
be by Level A harassment. For the species for which we use daily
occurrence estimates, we multiple those estimates by 100 days, and
assume proportional take by Level A and Level B harassment as described
above.
Table 7--Common Names for Species of Marine Mammals With Proposed Take From the Specified Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Maximum #
days Maximum #
exposure to days Min Proposed
Common name Estimated take impact exposure to Level A Level B Total IT abundance take as %
hammer & vibratory of stock
DTH hammer
--------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale....................... 2/mo...................... 66 34 * 0 7 7 11,278 .1
Killer whale......................... 3/mo...................... * 0 10 10 1920 .5
Harbor porpoise...................... 10/mo **.................. 22 11 33 4130 .8
Steller sea lion..................... 9.4/day ***............... 205 735 940 49837 1.8
Harbor seal.......................... .95/day ***............... 63 32 95 5366 1.8
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Level B only; easy sight-ability for shutdown in exclusion zones if needed.
** Different monthly rate than used by applicants, but using group size data used in their application.
*** Applicant presented site-specific monitoring data for pinnipeds, so are using daily sighting data as opposed to monthly estimates.
Proposed Mitigation
In order to issue an IHA under section 101(a)(5)(D) of the MMPA,
NMFS must set forth the permissible methods of taking pursuant to the
activity, and other means of effecting the least practicable impact on
the species or stock and its habitat, paying particular attention to
rookeries, mating grounds, and areas of similar significance, and on
the availability of the species or stock for taking for certain
subsistence uses.
[[Page 14552]]
NMFS regulations require applicants for incidental take authorizations
(ITAs) to include information about the availability and feasibility
(economic and technological) of equipment, methods, and manner of
conducting the activity or other means of effecting the least
practicable adverse impact upon the affected species or stocks, and
their habitat (50 CFR 216.104(a)(11)).
In evaluating how mitigation may or may not be appropriate to
ensure the least practicable adverse impact on species or stocks and
their habitat, as well as subsistence uses where applicable, NMFS
considers two primary factors:
(1) The manner in which, and the degree to which, the successful
implementation of the measure(s) is expected to reduce impacts to
marine mammals, marine mammal species or stocks, and their habitat, as
well as subsistence uses. This considers the nature of the potential
adverse impact being mitigated (likelihood, scope, range). It further
considers the likelihood that the measure will be effective if
implemented (probability of accomplishing the mitigating result if
implemented as planned), the likelihood of effective implementation
(probability implemented as planned), and;
(2) The practicability of the measures for applicant
implementation, which may consider such things as cost and impact on
operations.
The mitigation requirements described in the following were
proposed by COU in its adequate and complete application or are the
result of subsequent coordination between NMFS and COU. COU has agreed
that all 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.
In addition to the measures described later in this section, the
IHA would include these general mitigation measures:
Construction activities must be halted upon observation of
either a species for which incidental take is not authorized or a
species for which incidental take has been authorized but the
authorized number of takes has been met, entering or is within the
harassment zone.
Ensure that construction supervisors and crews, the marine
mammal monitoring team, and relevant COU staff are trained prior to the
start of all construction activities, so that responsibilities,
communication procedures, marine mammal monitoring protocol, and
operational procedures are clearly understood. New personnel joining
during the project must be trained prior to commencing work.
The COU, construction supervisors and crews, PSOs, and
relevant COU staff must avoid direct physical interaction with marine
mammals during construction activity. If a marine mammal comes within
10 m of such activity, operations must cease and vessels must reduce
speed to the minimum level required to maintain steerage and safe
working conditions, as necessary to avoid direct physical interaction.
Employ PSOs and establish monitoring locations as
described in the COU's Marine Mammal Monitoring and Mitigation Plan
(see appendix 3 of the COU's application). The COU must monitor the
project area to the maximum extent possible based on the required
number of PSOs, required monitoring locations, and environmental
conditions.
Additionally, the following mitigation measures apply to the COU's
in-water construction activities.
Establishment of Shutdown Zones. The COU would establish shutdown
zones with radial distances as identified in table 8 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 8, 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 8, such operations must
cease. Shutdown zones would vary based on the activity type and marine
mammal hearing group.
During the impact and DTH pile driving of 24-inch steel pipe piles,
the shutdown zone for Steller sea lions would be established at 60 m
rather than the larger Level A harassment isopleths (340 and 300 m,
respectively) due to practicability; local conditions indicate that
Steller sea lions are frequently present near the project site, likely
due to nearby docks that accommodate fishing vessels. The Level A
harassment zones for harbor porpoises and harbor seals are nearly or
equal to the size of the Level B harassment zones. As with the Steller
sea lion, harbor seals may be drawn to the project site, and the
shutdown zone is established at 130 m. The harbor porpoise shutdown
zone is established at 300 m, rather than the Level A harassment zone
of 1000 m (equal to the Level B zone).
Table 8--Proposed Shutdown Zones During Project Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Shutdown zone (m)
Activity Pile type/size (cm) -------------------------------------------------------------------------------
LF cetaceans HF cetaceans VHF cetaceans PW OW
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory Removal......................... steel 41 (16 inch).......... 40 20 30 40 20
Vibratory Removal......................... steel 61 (24 inch).......... 20 10 20 20 10
Vibratory Installation.................... steel 61 (24 inch).......... 20 10 20 20 10
Impact Installation....................... steel 61 (24 inch).......... 1000 130 300 130 60
Down-the-hole............................. steel 61 (24 inch).......... 900 120 300 130 60
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pre- and Post-Activity Monitoring. Monitoring would take place 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,
[[Page 14553]]
monitoring for 30 minutes would take place whenever a break in the
specified activity (i.e., impact pile driving, 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 4 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. The COU 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.
NMFS conducted an independent evaluation of the proposed measures
and has preliminarily determined that the proposed mitigation measures
provide the means of effecting the least practicable impact on the
affected species or stocks and their habitat, paying particular
attention to rookeries, mating grounds, and areas of similar
significance.
Proposed Monitoring and Reporting
In order to issue an IHA for an activity, section 101(a)(5)(D) of
the MMPA states that NMFS must set forth requirements pertaining to the
monitoring and reporting of such taking. The MMPA implementing
regulations at 50 CFR 216.104(a)(13) indicate that requests for
authorizations must include the suggested means of accomplishing the
necessary monitoring and reporting that will result in increased
knowledge of the species and of the level of taking or impacts on
populations of marine mammals that are expected to be present while
conducting the activities. Effective reporting is critical both to
compliance as well as ensuring that the most value is obtained from the
required monitoring.
Monitoring and reporting requirements prescribed by NMFS should
contribute to improved understanding of one or more of the following:
Occurrence of marine mammal species or stocks in the area
in which take is anticipated (e.g., presence, abundance, distribution,
density);
Nature, scope, or context of likely marine mammal exposure
to potential stressors/impacts (individual or cumulative, acute or
chronic), through better understanding of: (1) action or environment
(e.g., source characterization, propagation, ambient noise); (2)
affected species (e.g., life history, dive patterns); (3) co-occurrence
of marine mammal species with the activity; or (4) biological or
behavioral context of exposure (e.g., age, calving or feeding areas);
Individual marine mammal responses (behavioral or
physiological) to acoustic stressors (acute, chronic, or cumulative),
other stressors, or cumulative impacts from multiple stressors;
How anticipated responses to stressors impact either: (1)
long-term fitness and survival of individual marine mammals; or (2)
populations, species, or stocks;
Effects on marine mammal habitat (e.g., marine mammal prey
species, acoustic habitat, or other important physical components of
marine mammal habitat); and,
Mitigation and monitoring effectiveness.
The monitoring and reporting requirements described in the
following were proposed by COU in its adequate and complete application
and/or are the result of subsequent coordination between NMFS and COU.
COU has agreed to the requirements. NMFS describes these below as
requirements and has included them in the proposed IHA.
The COU would abide by all monitoring and reporting measures
contained within the IHA, if issued, and their Marine Mammal Monitoring
and Mitigation Plan (see appendix 3 of The COUs application). A summary
of those measures and additional requirements proposed by NMFS is
provided below.
Visual Monitoring. A minimum of two NMFS-approved protected species
observers (PSOs) must be stationed at the project site for the entirety
of active construction operations. PSOs would be independent of the
activity contractor (for example, employed by a subcontractor) and have
no other assigned tasks during monitoring periods. At least one PSO
would have prior experience performing the duties of a PSO during an
activity pursuant to a NMFS-issued ITA or Letter of Concurrence (LOC).
Other PSOs may substitute other relevant experience (including relevant
Alaska Native traditional knowledge), education (degree in biological
science or related field), or training for prior experience performing
the duties of a PSO during construction activity pursuant to a NMFS-
issued ITA. Where a team of three or more PSOs is required, a lead
observer or monitoring coordinator would be designated. The lead
observer must have prior experience performing the duties of a PSO
during construction activity pursuant to a NMFS-issued ITA or LOC.
PSOs should also have the following additional qualifications:
The ability to conduct field observations and collect data
according to assigned protocols;
Experience or training in field identification of marine
mammals, including the identification of behaviors;
Sufficient training, orientation, or experience with the
construction operation to provide for personal safety during
observations;
Writing skills sufficient to prepare a report of
observations including but not limited to: (1) the number and species
of marine mammals observed; (2) dates and times when in-water
construction activities were conducted; (3) dates, times, and reason
for implementation of mitigation (or why mitigation was not implemented
when required); and (4) marine mammal behavior; and
The ability to communicate orally, by radio or in person,
with Project personnel to provide real-time information on marine
mammals observed in the area, as necessary.
The COU must establish monitoring locations as described in the
Marine Mammal Monitoring and Mitigation Plan (see appendix 3 of the
COU's application). For all pile driving activities, a minimum of one
PSO must be assigned to each active pile driving location to monitor
the shutdown zones. PSOs would record all observations of marine
mammals, regardless of distance from the pile being driven, as well as
the additional data indicated below.
Reporting. The COU would be required to submit an annual draft
summary report on all construction activities and marine mammal
monitoring results to NMFS within 90 days following the end of
construction or 60 calendar days prior to the requested issuance of any
subsequent IHA for similar activity at the same location, whichever
comes first. The draft summary report would include an overall
description of construction work completed, a narrative regarding
marine mammal sightings, and associated raw PSO data sheets (in
electronic
[[Page 14554]]
spreadsheet format). Specifically, the report must include:
Dates and times (begin and end) of all marine mammal
monitoring;
Construction activities occurring during each daily
observation period, including: (a) how many and what type of piles were
driven or removed and the method (i.e., impact or vibratory); and (b)
the total duration of time for each pile (vibratory driving) or number
of strikes for each pile (impact driving);
PSO locations during marine mammal monitoring; and
Environmental conditions during monitoring periods (at
beginning and end of PSO shift and whenever conditions change
significantly), including Beaufort sea state and any other relevant
weather conditions including cloud cover, fog, sun glare, and overall
visibility to the horizon, and estimated observable distance.
Upon observation of a marine mammal the following information must
be reported:
Name of PSO who sighted the animal(s) and PSO location and
activity at the time of the sighting;
Time of the sighting;
Identification of the animal(s) (e.g., genus/species,
lowest possible taxonomic level, or unidentified), PSO confidence in
identification, and the composition of the group if there is a mix of
species;
Distance and bearing of each observed marine mammal
relative to the pile being driven or removed for each sighting;
Estimated number of animals (min/max/best estimate);
Estimated number of animals by cohort (e.g., adults,
juveniles, neonates, group composition, etc.);
Animal's closest point of approach and estimated time
spent within the estimated harassment zone(s);
Description of any marine mammal behavioral observations
(e.g., observed behaviors such as feeding or traveling), including an
assessment of behavioral responses thought to have resulted from the
activity (e.g., no response or changes in behavioral state such as
ceasing feeding, changing direction, flushing, or breaching);
Number of marine mammals detected within the estimated
harassment zones, by species; and
Detailed information about implementation of any
mitigation (e.g., shutdowns and delays), a description of specified
actions that ensued, and resulting changes in behavior of the
animal(s), if any.
If no comments are received from NMFS within 30 days after the
submission of the draft summary report, the draft report would
constitute the final report. If the COU received comments from NMFS, a
final summary report addressing NMFS' comments would be submitted
within 30 days after receipt of comments.
Reporting Injured or Dead Marine Mammals. In the event that
personnel involved in the COU's activities discover an injured or dead
marine mammal, the COU would report the incident to the NMFS Office of
Protected Resources ([email protected],
[email protected]) and to the Alaska Regional Stranding Coordinator
as soon as feasible. If the death or injury was clearly caused by the
specified activity, the COU 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. The COU would not resume
their activities until notified by NMFS. The report would include the
following information:
Description of the incident;
Environmental conditions (e.g., Beaufort sea state,
visibility);
Description of all marine mammal observations in the 24
hours preceding the incident;
Photographs or video footage of the animal(s) (if
equipment is available).
Time, date, and location (latitude/longitude) of the first
discovery (and updated location information if known and applicable);
Species identification (if known) or description of the
animal(s) involved;
Condition of the animal(s) (including carcass condition if
the animal is dead);
Observed behaviors of the animal(s), if alive; and
General circumstances under which the animal was
discovered.
NMFS conducted an independent evaluation of the proposed measures,
and has preliminarily determined that the proposed mitigation measures
provide the means of effecting the least practicable impact on the
affected species or stocks and their habitat, paying particular
attention to rookeries, mating grounds, and areas of similar
significance, and on the availability of such species or stock for
subsistence uses.
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 2, given that the anticipated effects of
this activity on these different marine mammal stocks are expected to
be similar. There is little information about the nature or severity of
the impacts, or the size, status, or structure of any of these species
or stocks that would lead to a different analysis for this activity.
Specified activities associated with the Robert Storrs Harbor
Project, as outlined previously, have the potential to disturb or
displace as well as cause AUD INJ to marine mammals. Specifically, the
specified activities may result in take, in the form of Level B
harassment and Level A harassment, from underwater sounds generated by
pile driving. Potential takes could occur if marine mammals are present
in zones ensonified above the thresholds for Level B harassment or
Level A harassment, identified above, while activities are underway.
No serious injury or mortality would be expected, even in the
absence of required mitigation measures, given the nature of the
activities. The potential for harassment would be minimized through the
implementation of planned
[[Page 14555]]
mitigation measures (see Proposed Mitigation section).
Take by Level A harassment is proposed for five species (harbor
porpoise, Steller sea lion, and harbor seal) as the size of the
estimated Level A harassment zone relative to the shutdown zone means
that it is possible that these species could enter the Level A
harassment zone and remain within the zone for a duration long enough
to incur AUD INJ before being detected.
Any take by Level A harassment is expected to arise from, at most,
a small degree of AUD INJ (i.e., minor degradation of hearing
capabilities within regions of hearing that align most completely with
the energy produced by impact pile driving such as the LF region below
2 kHz), not severe hearing impairment or impairment within the ranges
of greatest hearing sensitivity. Animals would need to be exposed to
higher levels and/or longer duration than are expected to occur here in
order to incur any more than a small degree of AUD INJ. COU would also
shut down pile-driving activities if marine mammals enter the shutdown
zones (table 4) further minimizing the likelihood and degree of AUD INJ
that would be incurred. Given the small degree anticipated, any AUD INJ
potential incurred would not be expected to affect the reproductive
success or survival of any individual, much less result in adverse
impacts on the species or stock.
Additionally, some subset of the individuals that are behaviorally
harassed could also simultaneously incur some small degree of TTS for a
short duration of time. However, since the hearing sensitivity of
individuals that incur TTS is expected to recover completely within
minutes to hours, it is unlikely that the brief hearing impairment
would affect the individual's long-term ability to forage and
communicate with conspecifics, and would therefore not likely impact
reproduction or survival of any individual marine mammal, let alone
adversely affect rates of recruitment or survival of the species or
stock.
As described above, NMFS expects that marine mammals would likely
move away from an aversive stimulus, especially at levels that would be
expected to result in AUD INJ, given sufficient notice through use of
soft start.
Effects on individuals that are taken by Level B harassment in the
form of behavioral disruption, on the basis of reports in the
literature as well as monitoring from other similar activities, would
likely be limited to reactions such as avoidance, increased swimming
speeds, increased surfacing time, or decreased foraging (if such
activity were occurring) (e.g., Thorson and Reyff, 2006). Most likely,
individuals would simply move away from the sound source and
temporarily avoid the area where pile driving is occurring. If sound
produced by pile removal and installation activities is sufficiently
disturbing, animals are likely to simply avoid the area while the
activities are occurring. We expect that any avoidance of the project
area by marine mammals would be temporary in nature and that any marine
mammals that avoid the project area during pile removal and
installation activities would not be permanently displaced. Short-term
avoidance of the project area and energetic impacts of interrupted
foraging or other important behaviors is unlikely to affect the
reproduction or survival of individual marine mammals, and the effects
of behavioral disturbance on individuals is not likely to accrue in a
manner that would affect the rates of recruitment or survival of any
affected stock.
The Robert Storrs Harbor Project is also not expected to have
significant adverse effects on affected marine mammals' habitats. The
pile removal and installation activities would not modify existing
marine mammal habitat for a significant amount of time. The activities
may cause some fish to leave the area of disturbance, thus temporarily
impacting marine mammals' foraging opportunities in a limited portion
of the foraging range. We do not expect pile-driving activities to have
significant consequences to marine invertebrate populations. Given the
short duration of the activities and the relatively small area of the
habitat that may be affected, the impacts to marine mammal habitat,
including fish and invertebrates, are not expected to cause significant
or long-term negative consequences. With the exception of some below
high tide line fill to support the upland parking area embankment, the
new improvements to the Robert Storrs Harbor would be contained within
the footprint of the existing harbor so no permanent impacts to habitat
are expected to occur.
In summary and as described above, the following factors primarily
support our preliminary determination that the impacts resulting from
this activity are not expected to adversely affect any of the species
or stocks through effects on annual rates of recruitment or survival:
No serious injury or mortality is anticipated or
authorized;
Level A harassment of three species proposed for
authorization are expected to be of a small degree;
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
to adverse impacts on their populations;
The lack of anticipated significant or long-term negative
effects to marine mammal habitat; and
The efficacy of the mitigation measures in reducing the
effects of the specified activities on all species and stocks.
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 (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.
The instances of take that NMFS proposes to authorize are below
one-third of the estimated stock abundance for all stocks (table 3).
The number of animals that we expect to authorize to be taken from
these stocks would be considered small relative to the relevant stocks'
abundances even if each estimated taking occurred to a new individual,
which is an 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,
[[Page 14556]]
NMFS preliminarily finds that small numbers of marine mammals would be
taken relative to the population size of the affected species or
stocks.
Unmitigable Adverse Impact Analysis and Determination
In order to issue an IHA, NMFS must find that the specified
activity will not have an ``unmitigable adverse impact'' on the
subsistence uses of the affected marine mammal species or stocks by
Alaskan Natives. NMFS has defined ``unmitigable adverse impact'' in 50
CFR 216.103 as an impact resulting from the specified activity: (1)
That is likely to reduce the availability of the species to a level
insufficient for a harvest to meet subsistence needs by (i) causing the
marine mammals to abandon or avoid hunting areas, (ii) directly
displacing subsistence users, or (iii) placing physical barriers
between the marine mammals and the subsistence hunters; and (2) That
cannot be sufficiently mitigated by other measures to increase the
availability of marine mammals to allow subsistence needs to be met.
Harbor seals and Steller sea lions are the only two species under
review that have recently been hunted for subsistence purposes in
Unalaska, with harbor seals being most recent in 2020 with 35 seals
harvested (Keating et al., 2022). While it appears that the percentage
of the Unalaskan subsistence hunters has recently been declining from
1994 to 2020 (less than 4 percent according to PND (2026)), and
acknowledging a gap in data collection from 2008 to 2020, there is also
trade in subsistence goods.
This harbor enhancement project does not overlap in space and time
with local Alaskan subsistence hunting, and when completed, will
provide improved water quality and accessibility for hunters to more
fully use this harbor. The proposed improvements to the harbor are
essential to support subsistence users in Unalaska. 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 COU'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 ITAs, NMFS
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 Steller Sea lions, which are
listed under the ESA. The NMFS Office of Protected Resources has
requested initiation of section 7 consultation with 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 the COU for conducting construction including pile
driving at Robert Storrs Harbor in Unalaska, Alaska, provided the
previously mentioned mitigation, monitoring, and reporting requirements
are incorporated. A draft of the proposed IHA can be found at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities.
Request for Public Comments
We request comment on our analyses, the proposed authorization, and
any other aspect of this notice of proposed IHA for the proposed Robert
Storrs Harbor Float A&B Replacement Project. 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:
A request for renewal is received no later than 60 days
prior to the needed renewal IHA effective date (recognizing that the
renewal IHA expiration date cannot extend beyond 1 year from expiration
of the initial IHA).
The request for renewal must include the following:
[cir] 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).
[cir] 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 23, 2026.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2026-05812 Filed 3-24-26; 8:45 am]
BILLING CODE 3510-22-P