[Federal Register Volume 90, Number 170 (Friday, September 5, 2025)]
[Notices]
[Pages 42937-42959]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-16993]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XE969]
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to the Pier 171 Repair and Replacement
Project in Newport, Rhode Island.
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental harassment authorization; request
for comments on proposed authorization and possible renewal.
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SUMMARY: NMFS has received a request from the U.S. Navy for
authorization to take marine mammals incidental to Pier 171 Repair and
Replacement Project in Newport, Rhode Island (RI). Pursuant to the
Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its
proposal to issue an incidental harassment authorization (IHA) to
incidentally take marine mammals during the specified activities. NMFS
is also requesting comments on a possible one-time, 1-year renewal that
could be issued under certain circumstances and if all requirements are
met, as described in Request for Public Comments at the end of this
notice. NMFS will consider public comments prior to making any final
decision on the issuance of the requested MMPA authorization and agency
responses will be summarized in the final notice of our decision.
DATES: Comments and information must be received no later than October
6, 2025.
ADDRESSES: Comments should be addressed to Permits and Conservation
[[Page 42938]]
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/permit/incidental-take-authorizations-under-marine-mammal-protection-act. 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) 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. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to
allow, upon request, the incidental, but not intentional, taking of
small numbers of marine mammals by U.S. citizens who engage in a
specified activity (other than commercial fishing) within a specified
geographical region if certain findings are made and either regulations
are proposed or, if the taking is limited to harassment, a notice of a
proposed IHA is provided to the public for review.
Authorization for incidental takings shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s) and will not have an unmitigable adverse impact on the
availability of the species or stock(s) for taking for subsistence uses
(where relevant). Further, NMFS must prescribe the permissible methods
of taking and other ``means of effecting the least practicable adverse
impact'' on the affected species or stocks and their habitat, paying
particular attention to rookeries, mating grounds, and areas of similar
significance, and on the availability of the species or stocks for
taking for certain subsistence uses (collectively 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
and can be found in section 3 of the MMPA (16 U.S.C. 1362) and NMFS
regulations at 50 CFR 216.103.
National Environmental Policy Act
To comply with the National Environmental Policy Act of 1969 (NEPA;
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A,
NMFS must review our proposed action (i.e., the issuance of an IHA)
with respect to potential impacts on the human environment.
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 February 27, 2025, NMFS received a request from U.S. Navy (Navy)
for an IHA to take marine mammals incidental to the Pier 171 Repair and
Replacement Project in Newport, RI. Following NMFS' review of the
application, the Navy submitted a revised version deemed adequate and
complete on June 23, 2025. The Navy is requesting incidental take of 7
species of marine mammals, by Level B harassment only. Neither the Navy
nor NMFS expect serious injury or mortality to result from this
activity and, therefore, an IHA is appropriate.
Description of Proposed Activity
Overview
The Navy is proposing the Stillwater Basin Upgrade Project
(project) located at Naval Station Newport (NAVSTA Newport), Stillwater
Basin in Coddington Cove, Newport, RI. The project consists of partial
demolition, repair, and replacement of the deteriorating and unstable
Pier 171. Pier 171 was originally constructed in 1943 and is primarily
used to berth Naval Undersea Warfare Center (NUWC) Division Newport
vessels. Figure 1 provides a site overview and the site location.
[[Page 42939]]
[GRAPHIC] [TIFF OMITTED] TN05SE25.000
Dates and Duration
The proposed IHA would be valid for the statutory maximum of 1 year
from the date of effectiveness, and would 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. Pier 171 is the northernmost pier within Stillwater
Basin and the Navy proposes to conduct in-water activities from March
1, 2026-February 28, 2027.
Specific Geographic Region
Coddington Cove, RI is a protected embayment on the western side of
Aquidneck Island in Narragansett Bay. The cove is protected immediately
north of Pier 171 by a 1.2 kilometer (km) (4,000 foot (ft)) long
rubble-mound breakwater, and to the south by the Coddington Point
peninsula (Figure 1). The cove covers an area of 5.5 square km (km\2\)
(1.6 square nautical miles) with water depths up to 15 m (50 ft). The
area is a restricted area and is closed to all commercial and
recreational vessel traffic, unless authorized by the appropriate
personnel (33 CFR 334.81). According to a 2015 bathymetric survey,
water depths in the proposed project area are less than 34 ft (10 m)
mean lower low water (NAVFAC 2015). Water depths in the pier are
maintained via periodic dredging to accommodate the berthing of large
ships.
Water temperature ranges from 36 degrees Fahrenheit ([deg]F; 2
degrees Celsius ([deg]C)) in winter to 68 [deg]F (20 [deg]C) in summer,
with salinity about 31 parts per thousand (ppt). Substrate surrounding
the timber piles of the pier include chunks of asphalt, sand, shell,
mud, silt, and natural fluvial deposits. Proposed repairs would occur
in these shallow nearshore waters (less than 34 ft; 10 m).
Detailed Description of the Specified Activity
This construction project involves the proposed repair and
replacement of Pier 171 within Coddington Cove (Figure 1) from March 1,
2026 through February 28, 2027. The Navy originally proposed the
Stillwater Basin Upgrade Project located at Naval Station Newport
(NAVSTA Newport) in 2023, but the project was postponed. The project
consists of partial demolition, repair, and replacement of the
deteriorating and unstable Pier 171, with approximately 37 total days
of pile driving. Pier 171 was originally constructed in 1943 and is
primarily used to berth Naval Undersea Warfare Center (NUWC) Division
Newport vessels. Upgrades to this L-shaped pier are necessary to
support the Large Displacement Unmanned Underwater Vehicle (LDUUV) and
the Extra Large Unmanned Underwater Vehicle (XLUUV) Programs. As part
of these program requirements, Pier 171 requires the ability to support
a gross vehicle weight limit of 20,000 pounds (lb; 9,072 kilograms
(kg)). The existing 166 12-inch (in) to 14-in (30-35 cm) timber piles
will be repaired and/or replaced
[[Page 42940]]
with approximately 165 12-in to 14-in (30-35 cm) timber piles, with
fender systems located along both the north and south sides of the
pier. Stressors that may cause incidental take during this project
would include vibratory pile driving, with the option for impact pile
driving if necessary. Table 1 presents a summary of the proposed
construction. Section 1 of the Navy's IHA application provides detailed
description of the treatments proposed to fortify this structure, along
with diagrams of two considered bid options. NMFS refers the reader to
this material for more description (https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities).
Table 1--Estimated Planned Construction
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Maximum number Maximum number
Approximate Pile-driving of piles of days of
Method of timber pile driving maximum number Pile strikes minutes per installed or pile-driving/
of piles per pile pile removed each removal
day required
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Removal Vibratory............... 166 NA 10 16 13
Installation Vibratory.......... 165 NA 1 8 24
Installation Impact............. 75 NA
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Proposed mitigation, monitoring, and reporting measures are
described in detail later in this document (please see Proposed
Mitigation and Proposed Monitoring and Reporting).
Description of Marine Mammals in the Area of Specified Activities
Information regarding population trends and threats for the
following species 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).
Sections 3 and 4 of the application summarize available information
regarding status and trends, distribution and habitat preferences, and
behavior and life history of the potentially affected species. NMFS
fully considered all of this information, and we refer the reader to
these descriptions, instead of reprinting the information.
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 serious injury and mortality (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. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments
2023 (Hayes et al. 2024). 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--Status of Marine Mammal Species \a\ Likely To Occur Near the Project Area
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ESA/ MMPA status; Stock abundance (CV,
Common name Scientific name Stock strategic (Y/N) Nmin, most recent PBR Annual M/
\b\ abundance survey) \c\ SI \d\
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Order Artiodactyla--Cetacea--Superfamily Odontoceti (toothed whales, dolphins, and porpoises
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Family Delphinidae:
Atlantic white-sided dolphin.... Leucopleurus \e\ acutus Western North Atlantic. -, -, N 93,233 (0.71, 54,443, 544 28
2021).
Common dolphin/Short beaked..... Delphinus delphis Western North Atlantic. -, -, N 93,100 (0.56, 59,897, 1,452 414
delphis. 2021).
Family Phocoenidae (porpoises):
Harbor porpoise................. Phocoena phocoena...... Gulf of Maine/Bay of -, -, N 85,765 (0.53, 56,420, 649 145
Fundy. 2021).
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Order Carnivora--Superfamily Pinnipedia
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Family Phocidae (earless seals):
Gray seal \f\................... Halichoerus grypus..... Western North Atlantic. -, -, N 27,911 (0.20, 23,624, 1,512 4,570
2021).
Harbor seal..................... Phoca vitulina......... Western North Atlantic. -, -, N 61,336 (0.08, 57,637, 1,729 339
2018).
Harp seal....................... Pagophilus Western North Atlantic. -, -, N 7.6 M (UNK, 7.1, 2019) 426,000 178,573
groenlandicus.
[[Page 42941]]
Hooded seal..................... Cystophora cristata.... Western North Atlantic. -, -, N 593,500 (UNK, UNK, UNK 1,680
2005).
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\a\ 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).
\b\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed
under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality
exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\c\ NMFS' marine mammal SARs can be found online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments.
CV is the coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.
\d\ These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g.,
commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range.
\e\ Genus Reclassification for Atlantic white-sided dolphins (Society for Marine Mammalogy, 2025). The Society for Marine Mammalogy (SMM) Taxonomy
Committee completed the annual 2025 Taxonomic review of the Official List of Marine Mammal Species and Subspecies, announcing reclassification updates
on July 21, 2025. Following work by Galatius et al. (2025) and Vollmer et al. (2019), the Committee implemented major revisions to the genera within
the subfamily Lissodelphininae. The Atlantic white-sided dolphin (formerly Lagenorhynchus acutus) has been reassigned to the genus Leucopleurus, now
Leucopleurus acutus. (Society for Marine Mammalogy (2025) List of Marine Mammal Species and Subspecies--Updated July 2025; available at https://marinemammalscience.org/; July 21, 2025).
\f\ NMFS' stock abundance estimate (and associated Potential Biological Removal value) applies to the U.S. population only. Total stock abundance
(including animals in Canada) is approximately 394,311. The annual M/SI value given is for the total stock.
As indicated above, all seven species (with seven managed stocks)
in Table 2 temporally and spatially co-occur with the activity to the
degree that take is reasonably likely to occur. While several species
of whales have been documented seasonally in New England waters, the
spatial occurrence of these species is such that take is not expected
to occur, and they are not discussed further beyond the explanation
provided here. The humpback (Megaptera novaeangliae), fin (Balaenoptera
physalus), sei (Balaenoptera borealis), sperm (Physeter macrocephalus)
and North Atlantic right whales (Eubaleana glacialis) occur seasonally
in the Atlantic Ocean, offshore of RI. However, due to the relatively
shallow depths of Narragansett Bay and nearshore location of the
project area, these marine mammals are unlikely to occur in the project
area. Therefore, the Navy did not request, and NMFS is not proposing to
authorize takes of these species.
Marine mammal observation data is available from previous projects
in and around NAVSTA Newport. A recent construction project within
Coddington Cove to build a pier for NOAA ships included pile driving
and removal from June 2024-January 2025. The monitoring report included
3 sightings of unidentified dolphins, including a pod of 5 animals on
August 28, 2024, 10 animals on November 4, 2024 off Taylor Point (about
3 miles (4.8 km) WSW of the pier), and 1 animal on November 25, 2024
(Werre, 2025). The report also included a detection of 12 common
dolphins off Taylor Point on November 1, 2024 (Werre 2025). Monitoring
did not result in any confirmed harbor porpoise, gray seal, harp seal,
or hooded seal sightings (Werre 2025). However, harbor seals were the
most prevalent observed protected species, accounting for 26 of the 31
total seal detections and 80 of the 109 total individual protected
species detected, with the first detection on November 1, 2024 and
regular occurrences through January 2025 (Werre 2025).
Harbor seals are also common in Narragansett Bay, with over 22
documented haul-out sites. Results from the bay-wide count for 2019
recorded 572 harbor seals, which also included counts from Block Island
(DeAngelis 2020). During a 1-day Narragansett Bay-wide count in 2025,
there were at least 551 seals observed with all 22 haul-out sites
represented (The Jamestown Press 2025). This is an increase from 2021
when 357 seals were counted and above the average of 427 calculated for
years prior (Save the Bay 2022).
The Three Sisters seal haulout is the closest to the project area,
just over 1 mile (1.6 km) south of the pier on the open water edge of
Coddington Cove. In RI waters, harbor seals prefer to haul out on
isolated intertidal rock ledges and outcrops. Numerous Naval Station
employees have reported seals hauled out on The Sisters haulout, which
is approximately 1,066.8 m (3,500 ft) from the proposed project area
(see Figure 4-1 of the application) (NUWC Division, 2011). This haulout
site has been studied by the NUWC Division Newport since 2011 and has
demonstrated a steady increase in use during winter months when harbor
seals are present in the Bay. Harbor seals are rarely observed at The
Sisters haulout in the early fall (September-October) but sighted in
consistent numbers in mid-November (0-10 animals) and are regularly
observed with a gradual increase of more than 20 animals until numbers
peak in the upper 40s during March, typically at low tide. The number
of harbor seals begins to decline in April, and by mid-May are no
longer observed hauled out (DeAngelis, 2020).
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. Generalized
hearing ranges were chosen based on the approximately 65-decibel (dB)
threshold from the composite audiograms, previous analyses in NMFS
(2018), and/or data from Southall et al. (2007, 2019). We note the
names of two hearing groups and the generalized hearing ranges of all
marine mammal hearing groups have been recently updated (NMFS, 2024) as
reflected below in table 3. Of the species potentially present in the
action area, white-sided and common dolphins are considered high-
frequency (HF) cetaceans, and harbor porpoise are considered very high-
[[Page 42942]]
frequency (VHF) cetaceans. Harbor, gray, hooded and harp seals are
phocid pinnipeds.
Table 3--Marine Mammal Hearing Groups
[NMFS, 2024]
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Hearing group Generalized hearing range *
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Low-frequency (LF) cetaceans (baleen 7 Hz to 36 kHz.
whales).
High-frequency (HF) cetaceans 150 Hz to 160 kHz.
(dolphins, toothed whales, beaked
whales, bottlenose whales).
Very High-frequency (VHF) cetaceans 200 Hz to 165 kHz.
(true porpoises, Kogia, river
dolphins, Cephalorhynchid,
Lagenorhynchus cruciger & L.
australis).
Phocid pinnipeds (PW) (underwater) 40 Hz to 90 kHz.
(true seals).
Otariid pinnipeds (OW) (underwater) 60 Hz to 68 kHz.
(sea lions and fur seals).
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* Represents the generalized hearing range for the entire group as a
composite (i.e., all species within the group), where individual
species' hearing ranges may not be as broad. Generalized hearing range
chosen based on ~65 dB threshold from composite audiogram, previous
analysis in NMFS 2018, and/or data from Southall et al. 2007; Southall
et al. 2019. Additionally, animals are able to detect very loud sounds
above and below that ``generalized'' hearing range.
For more detail concerning these groups and associated 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 this activity. The
Negligible Impact Analysis and Determination section considers the
content of this section, the Estimated Take of Marine Mammals section,
and the Proposed Mitigation section, to draw conclusions regarding the
likely impacts of these activities on the reproductive success or
survivorship of individuals and whether those impacts are reasonably
expected to, or reasonably likely to, adversely affect the species or
stock through effects on annual rates of recruitment or survival.
Acoustic effects on marine mammals during the specified activity
are expected to potentially occur from impact and vibratory pile
installation and removal. The effects of underwater noise from the
Navy's proposed activities have the potential to result in Level B
harassment of marine mammals in the action area.
The proposed activities would result in the construction and
placement of up to 331 pilings, 166 of which will be temporary. There
are a variety of types and degrees of effects to marine mammals, prey
species, and habitat that could occur as a result of the Project. Below
we provide a brief description of the types of sound sources that would
be generated by the project, the general impacts from these types of
activities, and an analysis of the anticipated impacts on marine
mammals from the project, with consideration of the proposed mitigation
measures.
Underwater noise data collected at NUWC during testing indicated
that true ambient conditions (without static from the source) of
underwater noise are approximately 120 to 123 decibels (dB) referenced
to a pressure of 1 micropascal (re 1 [micro]Pa) root mean square (RMS)
(Iafrate, 2017). The test site was directly adjacent to the wharf at
Stillwater and 1.5 m (5 ft) below the surface. NUWC personnel indicated
that a recording in the open water and at greater depth would likely be
less (Iafrate, 2017). Because the proposed repairs would occur in
shallow nearshore waters, for purposes of this analysis, ambient
underwater noise in the project area is considered to be 120 dB RMS.
Description of Sound Sources for the Specified Activities
Activities associated with the project that have the potential to
incidentally take marine mammals though exposure to sound would include
impact and vibratory hammering. 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 levels, a
potentially injurious combination (Hastings and Popper, 2005).
Vibratory hammers install piles by vibrating them and allowing the
weight of the hammer to push them into the substrate. Vibratory hammers
typically produce less sound (i.e., lower levels) than impact hammers.
Peak sound pressure levels (SPLs) may be 180 dB or greater but are
generally 10 to 20 dB lower than SPLs generated during impact pile
driving of the same-sized pile (Oestman et al., 2009; California
Department of Transportation (CALTRANS), 2015, 2020). Sounds produced
by vibratory hammers are non-impulsive; compared to sounds produced by
impact hammers, the rise time is slower, 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).
The likely or possible impacts of the Navy'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 within one mile of the pier, 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 impact and vibratory hammering is the primary means by
which marine mammals may be harassed from the Navy'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
[[Page 42943]]
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 impact and vibratory hammers are 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.
In general, animals exposed to natural or anthropogenic sound may
experience physical and psychological effects, ranging in magnitude
from none to severe (Southall et al., 2007, 2019). Exposure to
anthropogenic noise has the potential to result in auditory threshold
shifts and behavioral reactions (e.g., avoidance, temporary cessation
of foraging and vocalizing, changes in dive behavior). It can also lead
to non-observable physiological responses, such an increase in stress
hormones. Additional noise in a marine mammal's habitat can mask
acoustic cues used by marine mammals to carry out daily functions, such
as communication and predator and prey detection.
The 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 the Navy.
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 detail regarding potential impacts on
marine mammals and their habitat from noise in general, starting with
hearing impairment, as well as from the specific activities the Navy
plans to conduct, to the degree it is available.
Hearing Threshold Shifts. NMFS defines a noise-induced threshold
shift (TS) as a change, usually an increase, in the threshold of
audibility at a specified frequency or portion of an individual's
hearing range above a previously established reference level (NMFS,
2018, 2024). The amount of threshold shift is customarily expressed in
dB. A TS can be permanent or temporary. As described in NMFS (2018,
2024) there are numerous factors to consider when examining the
consequence of TS, including, but not limited to, the signal temporal
pattern (e.g., impulsive or non-impulsive), likelihood an individual
would be exposed for a long enough duration or to a high enough level
to induce a TS, the magnitude of the TS, time to recovery (seconds to
minutes or hours to days), the frequency range of the exposure (i.e.,
spectral content), the hearing frequency range of the exposed species
relative to the signal's frequency spectrum (i.e., how animal uses
sound within the frequency band of the signal; e.g., Kastelein et al.,
2014), and the overlap between the animal and the source (e.g.,
spatial, temporal, and spectral).
Auditory Injury (AUD INJ). NMFS (2024) defines AUD INJ as damage to
the inner ear that can result in destruction of tissue, such as the
loss of cochlear neuron synapses or auditory neuropathy (Houser 2021;
Finneran 2024). AUD INJ may or may not result in a permanent threshold
shift (PTS). PTS is subsequently defined as a permanent, irreversible
increase in the threshold of audibility at a specified frequency or
portion of an individual's hearing range above a previously established
reference level (NMFS, 2024). PTS does not generally affect more than a
limited frequency range, and an animal that has incurred PTS has some
level of hearing loss at the relevant frequencies; typically, animals
with PTS or other AUD INJ are not functionally deaf (Au and Hastings,
2008; Finneran, 2016). Available data from humans and other terrestrial
mammals indicate that a 40-dB threshold shift approximates AUD INJ
onset (see Ward et al., 1958, 1959; Ward, 1960; Kryter et al., 1966;
Miller, 1974; Ahroon et al., 1996; Henderson et al., 2008). AUD INJ
levels for marine mammals are estimates, as with the exception of a
single study unintentionally inducing PTS in a harbor seal (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).
Temporary Threshold Shift (TTS). TTS is a temporary, reversible
increase in the threshold of audibility at a specified frequency or
portion of an individual's hearing range above a previously established
reference level (NMFS, 2024), and is not considered an AUD INJ. Based
on data from marine mammal TTS measurements (see Southall et al., 2007,
2019), a TTS of 6 dB is considered the minimum threshold shift clearly
larger than any day-to-day or session-to-session variation in a
subject's normal hearing ability (Finneran et al., 2000, 2002; Schlundt
et al., 2000). As described in Finneran (2015), marine mammal studies
have shown the amount of TTS increases with the 24-hour cumulative
sound exposure level (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
[[Page 42944]]
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 in order to be
heard. In terrestrial and marine mammals, TTS can last from minutes or
hours to days (in cases of strong TTS) (Finneran 2015). In many cases,
hearing sensitivity recovers rapidly after exposure to the sound ends.
For cetaceans, published data on the onset of TTS are limited to
captive bottlenose dolphin (Tursiops truncatus), beluga whale
(Delphinapterus leucas), harbor porpoise (Phocoena phocoena), and
Yangtze finless porpoise (Neophocoena asiaeorientalis) (Southall et
al., 2019). For pinnipeds in water, measurements of TTS are limited to
harbor seals (Phoca vitulina), elephant seals (Mirounga
angustirostris), bearded seals (Erignathus barbatus) and California sea
lions (Zalophus californianus) (Kastak et al., 1999, 2007; Kastelein et
al., 2019b, 2019c, 2021, 2022a, 2022b; Reichmuth et al., 2019; Sills et
al., 2020). TTS was not observed in spotted (Phoca largha) and ringed
(Pusa hispida) seals exposed to single airgun impulse sounds at levels
matching previous predictions of TTS onset (Reichmuth et al., 2016).
These studies examine hearing thresholds measured in marine mammals
before and after exposure to intense or long-duration sound exposures.
The difference between the pre-exposure and post-exposure thresholds
can be used to determine the amount of threshold shift at various post-
exposure times.
The amount and onset of TTS depends on the exposure frequency.
Sounds below the region of best sensitivity for a species or hearing
group are less hazardous than those near the region of best sensitivity
(Finneran and Schlundt, 2013). At low frequencies, onset-TTS exposure
levels are higher compared to those in the region of best sensitivity
(i.e., a low frequency noise would need to be louder to cause TTS onset
when TTS exposure level is higher), as shown for harbor porpoises and
harbor seals (Kastelein et al., 2019a, 2019c). Note that in general,
harbor seals and harbor porpoises have a lower TTS onset than other
measured pinniped or cetacean species (Finneran, 2015). In addition,
TTS can accumulate across multiple exposures, but the resulting TTS
will be less than the TTS from a single, continuous exposure with the
same SEL (Mooney et al., 2009; Finneran et al., 2010; Kastelein et al.,
2014, 2015). This means that TTS predictions based on the total,
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 low-frequency ambient noise,
including increased stiffness and control of middle ear structures and
placement of inner ear structures (Ketten et al., 2021). Data available
on noise-induced hearing loss for mysticetes are currently lacking
(NMFS, 2024). Additionally, the existing marine mammal TTS data come
from a limited number of individuals within these species.
Relationships between TTS and AUD INJ thresholds have not been
studied in marine mammals, and there are no measured PTS data for
cetaceans, but such relationships are assumed to be similar to those in
humans and other terrestrial mammals. AUD INJ typically occurs at
exposure levels at least several dB above that inducing mild TTS (e.g.,
a 40-dB threshold shift approximates AUD INJ onset (Kryter et al.,
1966; Miller, 1974), while a 6-dB threshold shift approximates TTS
onset (Southall et al., 2007, 2019). Based on data from terrestrial
mammals, a precautionary assumption is that the AUD INJ thresholds for
impulsive sounds (such as impact pile driving pulses as received close
to the source) are at least 6 dB higher than the TTS threshold on a
peak-pressure basis and AUD INJ cumulative sound exposure level
thresholds are 15 to 20 dB higher than TTS cumulative sound exposure
level thresholds (Southall et al., 2007, 2019). Given the higher level
of sound or longer exposure duration necessary to cause AUD INJ as
compared with TTS, it is considerably less likely that AUD INJ could
occur.
Behavioral Effects. Exposure to noise also has the potential to
behaviorally disturb marine mammals to a level that rises to the
definition of harassment under the MMPA. Generally speaking, NMFS
considers a behavioral disturbance that rises to the level of
harassment under the MMPA a non-minor response--in other words, not
every response qualifies as behavioral disturbance, and for responses
that do, those of a higher level, or accrued across a longer duration,
have the potential to affect foraging, reproduction, or survival.
Behavioral disturbance may include a variety of effects, including
subtle changes in behavior (e.g., minor or brief avoidance of an area
or changes in vocalizations), more conspicuous changes in similar
behavioral activities, and more sustained and/or potentially severe
reactions, such as displacement from or abandonment of high-quality
habitat. Behavioral responses may include changing durations of
surfacing and dives, changing direction and/or speed; reducing/
increasing vocal activities; changing/cessation of certain behavioral
activities (such as socializing or feeding); eliciting a visible
startle response or aggressive behavior (such as tail/fin slapping or
jaw clapping); and avoidance of areas where sound sources are located.
In addition, pinnipeds may increase their haul out time, possibly to
avoid in-water disturbance (Thorson and Reyff, 2006).
Behavioral responses to sound are highly variable and context-
specific and
[[Page 42945]]
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 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 micropascal ([mu]Pa); SEL of a
single strike (SELss): 127 dB re 1 [mu]Pa\2\-s) (Kastelein
et al., 2013).
Avoidance is the displacement of an individual from an area or
migration path as a result of the presence of a sound or other
stressors, and is one of the most obvious manifestations of disturbance
in marine mammals (Richardson et al., 1995). For example, gray whales
(Eschrictius robustus) are known to change direction--deflecting from
customary migratory paths--in order to avoid noise from seismic surveys
(Malme et al., 1984). Harbor porpoises, Atlantic white-sided dolphins
(Leukopleurus 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
[[Page 42946]]
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 one day and not
recurring on subsequent days is not considered particularly severe
unless it could directly affect reproduction or survival (Southall et
al., 2007). Note that there is a difference between multi-day
substantive (i.e., meaningful) behavioral reactions and multi-day
anthropogenic activities. For example, just because an activity lasts
for multiple days does not necessarily mean that individual animals are
either exposed to activity-related stressors for multiple days or,
further, exposed in a manner resulting in sustained multi-day
substantive behavioral responses.
Physiological stress responses. An animal's perception of a threat
may be sufficient to trigger stress responses consisting of some
combination of behavioral responses, autonomic nervous system
responses, neuroendocrine responses, or immune responses (e.g., Selye,
1950; Moberg, 2000). In many cases, an animal's first and sometimes
most economical (in terms of energetic costs) response is behavioral
avoidance of the potential stressor. Autonomic nervous system responses
to stress typically involve changes in heart rate, blood pressure, and
gastrointestinal activity. These responses have a relatively short
duration and may or may not have a significant long-term effect on an
animal's fitness.
Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that
are affected by stress, including immune competence, reproduction,
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been
implicated in failed reproduction, altered metabolism, reduced immune
competence, and behavioral disturbance (e.g., Moberg, 1987; Blecha,
2000). Increases in the circulation of glucocorticoids are also equated
with stress (Romano et al., 2004).
The primary distinction between stress (which is adaptive and does
not normally place an animal at risk) and ``distress'' is the cost of
the response. During a stress response, an animal uses glycogen stores
that can be quickly replenished once the stress is alleviated. In such
circumstances, the cost of the stress response would not pose serious
fitness consequences. However, when an animal does not have sufficient
energy reserves to satisfy the energetic costs of a stress response,
energy resources must be diverted from other functions. This state of
distress will last until the animal replenishes its energetic reserves
sufficient to restore normal function.
Relationships between these physiological mechanisms, animal
behavior, and the costs of stress responses are well-studied through
controlled experiments and for both laboratory and free-ranging animals
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003;
Krausman et al., 2004; Lankford et al., 2005; Ayres et al., 2012; Yang
et al., 2022). Stress responses due to exposure to anthropogenic sounds
or other stressors and their effects on marine mammals have also been
reviewed (Fair and Becker, 2000; Romano et al., 2002b) and, more
rarely, studied in wild populations (e.g., Romano et al., 2002a). For
example, Rolland et al. (2012) found that noise reduction from reduced
ship traffic in the Bay of Fundy was associated with decreased stress
in North Atlantic right whales. In addition, Lemos et al. (2022)
observed a correlation between higher levels of fecal glucocorticoid
metabolite concentrations (indicative of a stress response) and vessel
traffic in gray whales. Yang et al. (2022) studied behavioral and
physiological responses in captive bottlenose dolphins exposed to
playbacks of ``pile-driving-like'' impulsive sounds, finding
significant changes in cortisol and other physiological indicators but
only minor behavioral changes. These and other studies lead to a
reasonable expectation that some marine mammals will experience
physiological stress responses upon exposure to acoustic stressors and
that it is possible that some of these would be classified as
``distress.'' In addition, any animal experiencing TTS would likely
also experience stress responses (NRC, 2005), however distress is an
unlikely result of this project based on observations of marine mammals
during previous, similar construction projects.
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
[[Page 42947]]
al., 2012). Chronic exposure to excessive, though not high-intensity,
noise could cause masking at particular frequencies for marine mammals
that utilize sound for vital biological functions (Clark et al., 2009).
Acoustic masking is when other noises such as from human sources
interfere with an animal's ability to detect, recognize, or
discriminate between acoustic signals of interest (e.g., those used for
intraspecific communication and social interactions, prey detection,
predator avoidance, navigation) (Richardson et al., 1995; Erbe et al.,
2016). Therefore, under certain circumstances, marine mammals whose
acoustical sensors or environment are being severely masked could also
be impaired from maximizing their performance fitness in survival and
reproduction. The ability of a noise source to mask biologically
important sounds depends on the characteristics of both the noise
source and the signal of interest (e.g., signal-to-noise ratio,
temporal variability, direction), in relation to each other and to an
animal's hearing abilities (e.g., sensitivity, frequency range,
critical ratios, frequency discrimination, directional discrimination,
age or TTS hearing loss), and existing ambient noise and propagation
conditions (Hotchkin and Parks, 2013).
Marine mammals vocalize for different purposes and across multiple
modes, such as whistling, echolocation click production, calling, and
singing. Changes in vocalization behavior in response to anthropogenic
noise can occur for any of these modes and may result from a need to
compete with an increase in background noise or may reflect increased
vigilance or a startle response. For example, in the presence of
potentially masking signals, humpback whales and killer whales (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, low-
frequency signals may have less effect on high-frequency echolocation
sounds produced by odontocetes but are more likely to affect detection
of mysticete communication calls and other potentially important
natural sounds such as those produced by surf and some prey species.
The masking of communication signals by anthropogenic noise may be
considered as a reduction in the communication space of animals (e.g.,
Clark et al., 2009) and may result in energetic or other costs as
animals change their vocalization behavior (e.g., Miller et al., 2000;
Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2010; Holt
et al., 2009). Masking can be reduced in situations where the signal
and noise come from different directions (Richardson et al., 1995),
through amplitude modulation of the signal, or through other
compensatory behaviors, including modifications of the acoustic
properties of the signal or the signaling behavior (Hotchkin and Parks,
2013). Masking can be tested directly in captive species (e.g., Erbe,
2008), but in wild populations it must be either modeled or inferred
from evidence of masking compensation. There are few studies addressing
real-world masking sounds likely to be experienced by marine mammals in
the wild (e.g., Branstetter et al., 2013).
Masking occurs in the frequency band that the animals utilize, and
is more likely to occur in the presence of broadband, relatively
continuous noise sources such as vibratory pile driving. Energy
distribution of pile driving sound covers a broad frequency spectrum,
and is anticipated to be within the audible range of marine mammals
present in the proposed action area. Since noises generated from the
proposed construction activities are mostly concentrated at low
frequencies (< 2 kHz), these activities likely have less effect on mid-
frequency echolocation sounds produced by odontocetes (toothed whales).
However, lower frequency noises are more likely to affect detection of
communication calls and other potentially important natural sounds such
as surf and prey noise. Low-frequency noise may also affect
communication signals when they occur near the frequency band for noise
and thus reduce the communication space of animals (e.g., Clark et al.,
2009) and cause increased stress levels (e.g., Holt et al., 2009).
Unlike TS, masking, which can occur over large temporal and spatial
scales, can potentially affect the species at population, community, or
even ecosystem levels, in addition to individual levels. Masking
affects both senders and receivers of the signals, and at higher levels
for longer durations, could have long-term chronic effects on marine
mammal species and populations. However, the noise generated by the
Navy's proposed activities will only occur intermittently, across an
estimated 37 days during the authorization period in a relatively small
area focused around the proposed construction site. Thus, while the
Navy'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.
While in some cases marine mammals have exhibited little to no
obviously detectable response to certain common or routine
industrialized activities (Cornick et al., 2011; Horley and Larson,
2023), it is possible some animals may at times be exposed to received
levels of sound above the Level B harassment thresholds during the
proposed project. This potential exposure in combination with the
nature of planned activity (e.g., vibratory pile driving, impact pile
driving) means it is possible that take by Level B harassment could
occur over the total estimated period of activities; therefore, NMFS in
response to the Navy's IHA application proposes to authorize take by
Level B harassment
[[Page 42948]]
from the Navy's proposed construction activities.
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 haulout sites
(Figure 4-1 of application). 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 sound that may result in behavioral harassment when looking
with their heads above water. Most likely, airborne sound 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 haulouts,
temporarily abandon the area, and or move further from the source.
However, these animals would previously have been `taken' because of
exposure to underwater sound 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 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 Navy's proposed activities could have localized, temporary
impacts on marine mammal habitat, including prey, by increasing in-
water SPLs. Increased noise levels may affect acoustic habitat and
adversely affect marine mammal prey in the vicinity of the project
areas (see discussion below). Elevated levels of underwater noise would
ensonify the project areas where both fishes and mammals occur and
could affect foraging success. Additionally, marine mammals may avoid
the area during the proposed construction activities; however,
displacement due to noise is expected to be temporary and is not
expected to result in long-term effects to the individuals or
populations.
The total area likely impacted by the Navy's activities is
relatively small compared to the available habitat in Narragansett Bay.
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 tugging 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 will occur within the same footprint as
existing marine infrastructure. The nearshore and intertidal habitat
where the proposed project will 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
mammals will be limited to temporary displacement from pile
installation and removal noise, and effects on prey species will be
similarly limited in time and space.
Water quality--Temporary and localized reduction in water quality
will 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).
Effects to turbidity and sedimentation are expected to be short-
term, minor, and localized. Turbidity within the water column has the
potential to reduce the level of oxygen in the water and irritate the
gills of prey fish species in the proposed project area. However,
turbidity plumes associated with the project would be temporary and
localized, and fish in the proposed project area would be able to move
away from and avoid the areas where plumes may occur. Therefore, it is
expected that the impacts on prey fish species from turbidity, and
therefore on marine mammals, would be minimal and temporary. In
general, the area likely impacted by the proposed construction
activities is relatively small compared to the available marine mammal
habitat in Narragansett Bay.
Potential Effects on Prey. Sound may affect marine mammals through
impacts on the abundance, behavior, or distribution of prey species
(e.g., crustaceans, cephalopods, fishes, zooplankton). Marine mammal
prey varies by species, season, and location and, for some, is not well
documented. Studies regarding the effects of noise on known marine
mammal prey are described here.
Fishes utilize the soundscape and components of sound in their
environment to perform important functions such as foraging, predator
avoidance, mating, and spawning (e.g., Zelick et al., 1999; Fay, 2009).
Depending on their hearing anatomy and peripheral sensory structures,
which vary among species, fishes hear sounds using pressure and
particle motion sensitivity capabilities and detect the motion of
surrounding water (Fay et al., 2008). The potential effects of noise on
fishes depends on the overlapping frequency range, distance from the
sound source, water depth of exposure, and species-specific hearing
sensitivity, anatomy, and physiology. Key impacts to fishes may include
behavioral responses, hearing damage, barotrauma (pressure-related
injuries), and mortality.
Fish react to sounds that are especially strong and/or intermittent
low-frequency sounds, and behavioral responses such as flight or
avoidance are the most likely effects. Short duration, sharp sounds can
cause overt or subtle changes in fish behavior and local distribution.
The reaction of fish to noise depends on the physiological state of the
fish, past exposures, motivation (e.g., feeding, spawning, migration),
and other environmental factors. (Hastings and Popper, 2005) identified
several studies that suggest fish may relocate to avoid certain areas
of sound energy. Additional studies have documented effects of pile
driving on fishes (e.g. Scholik and Yan, 2001, 2002; Popper
[[Page 42949]]
and Hastings, 2009). Several studies have demonstrated that impulse
sounds might affect the distribution and behavior of some fishes,
potentially impacting foraging opportunities or increasing energetic
costs (e.g., Fewtrell and McCauley, 2012; Pearson et al., 1992; Skalski
et al., 1992; Santulli et al., 1999; Paxton et al., 2017). However,
some studies have shown no or slight reaction to impulse sounds (e.g.,
Pe[ntilde]a et al., 2013; Wardle et al., 2001; Jorgenson and Gyselman,
2009; Cott et al., 2012). More commonly, though, the impacts of noise
on fishes are temporary.
SPLs of sufficient strength have been known to cause injury to
fishes and fish mortality (summarized in Popper et al., 2014). However,
in most fish species, hair cells in the ear continuously regenerate and
loss of auditory function likely is restored when damaged cells are
replaced with new cells. Halvorsen et al. (2012b) showed that a TTS of
4 to 6 dB was recoverable within 24 hours for one species. Impacts
would be most severe when the individual fish is close to the source
and when the duration of exposure is long. Injury caused by barotrauma
can range from slight to severe and can cause death, and is most likely
for fish with swim bladders. Barotrauma injuries have been documented
during controlled exposure to impact pile driving (Halvorsen et al.,
2012a; Casper et al., 2013, 2017).
Fish populations in the proposed project area that serve as marine
mammal prey could be temporarily affected by noise from pile
installation and removal. The frequency range in which fishes generally
perceive underwater sounds is 50 to 2,000 Hz, with peak sensitivities
below 800 Hz (Popper and Hastings, 2009). Fish behavior or distribution
may change, especially with strong and/or intermittent sounds that
could harm fishes. High underwater SPLs have been documented to alter
behavior, cause hearing loss, and injure or kill individual fish by
causing serious internal injury (Hastings and Popper, 2005).
Zooplankton is a food source for several marine mammal species, as
well as a food source for fish that are then preyed upon by marine
mammals. Population effects on zooplankton could have indirect effects
on marine mammals. Data are limited on the effects of underwater sound
on zooplankton species, particularly sound from construction (Erbe et
al., 2019). Popper and Hastings (2009) reviewed information on the
effects of human-generated sound and concluded that no substantive data
are available on whether the sound levels from pile driving, seismic
activity, or any human-made sound would have physiological effects on
invertebrates. Any such effects would be limited to the area very near
(1 to 5 m) the sound source and would result in no population effects
because of the relatively small area affected at any one time and the
reproductive strategy of most zooplankton species (short generation,
high fecundity, and very high natural mortality). No adverse impact on
zooplankton populations is expected to occur from the specified
activity due in part to large reproductive capacities and naturally
high levels of predation and mortality of these populations. Any
mortalities or impacts that might occur would be negligible.
The greatest potential impact to marine mammal prey during
construction would occur during impact and vibratory pile driving.
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 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 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 many in-water piles would be temporary and intermittent.
The total seafloor area affected by pile installation and removal is a
very small area compared to the vast foraging area available to marine
mammals outside this project area. The area impacted by the project is
relatively small compared to the available habitat just outside the
project area, and there are no areas of particular importance that
would be impacted by this project. Any behavioral avoidance by fish of
the disturbed area would still leave significantly large areas of fish
and marine mammal foraging habitat in the nearby vicinity. As described
in the preceding, the potential for the Navy'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 Navy'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 be by Level B harassment only, as use of the
acoustic source (i.e., pile driving) has the potential to result in
disruption of behavioral patterns for individual marine mammals.
Auditory injury (AUD INJ) (Level A harassment) is unlikely to
[[Page 42950]]
occur due to mitigation measures. Based on the nature of the activity
and the anticipated effectiveness of the mitigation measures (i.e.,
shutdown) discussed in detail below in the Proposed Mitigation section,
Level A harassment is neither anticipated nor proposed to be
authorized.
As described previously, no serious injury or mortality is
anticipated or proposed to be authorized for this activity. Below we
describe how the proposed take numbers are estimated.
For acoustic impacts, generally speaking, we estimate take by
considering: (1) acoustic criteria above which NMFS believes there is
some reasonable potential for marine mammals to be behaviorally
harassed or incur some degree of AUD INJ; (2) the area or volume of
water that will be ensonified above these levels in a day; (3) the
density or occurrence of marine mammals within these ensonified areas;
and, (4) the number of days of activities. We note that while these
factors can contribute to a basic calculation to provide an initial
prediction of potential takes, additional information that can
qualitatively inform take estimates is also sometimes available (e.g.,
previous monitoring results or average group size). Below, we describe
the factors considered here in more detail and present the proposed
take estimates.
Acoustic Criteria
NMFS recommends the use of acoustic criteria that identify the
received level of underwater sound above which exposed marine mammals
would be reasonably expected to be behaviorally harassed (equated to
Level B harassment) or to incur AUD INJ of some degree (equated to
Level A harassment).
Level B Harassment--Though significantly driven by received level,
the onset of behavioral disturbance from anthropogenic noise exposure
is also informed to varying degrees by other factors related to the
source or exposure context (e.g., frequency, predictability, duty
cycle, duration of the exposure, signal-to-noise ratio, distance to the
source), the environment (e.g., bathymetry, other noises in the area,
predators in the area), and the receiving animals (hearing, motivation,
experience, demography, life stage, depth) and can be difficult to
predict (e.g., Southall et al., 2007, 2021, Ellison et al., 2012).
Based on what the available science indicates and the practical need to
use a threshold based on a metric that is both predictable and
measurable for most activities, NMFS typically uses a generalized
acoustic threshold based on received level to estimate the onset of
behavioral harassment. NMFS generally predicts that marine mammals are
likely to be behaviorally harassed in a manner considered to be Level B
harassment when exposed to underwater anthropogenic noise above root-
mean-squared pressure received levels (RMS SPL) of 120 dB (referenced
to 1 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, estimates of take by Level B
harassment 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.
The Navy's proposed activity includes the use of continuous
(vibratory hammer) and impulsive (impact hammer) sources, and therefore
the RMS SPL thresholds of 120 and 160 dB re 1 [mu]Pa are applicable.
Level A harassment--NMFS' Updated Technical Guidance for Assessing
the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version
3.0) (Updated Technical Guidance, 2024) identifies dual criteria to
assess AUD INJ (Level A harassment) to five different underwater marine
mammal groups (based on hearing sensitivity) as a result of exposure to
noise from two different types of sources (impulsive or non-impulsive).
The 2024 Updated Technical Guidance criteria include both updated
thresholds and updated weighting functions for each hearing group. The
thresholds are provided in table 3 above. 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.
Ensonified Area
Here, we describe operational and environmental parameters of the
activity that are used in estimating the area ensonified above the
acoustic thresholds, including source levels and transmission loss
coefficient.
To estimate the sound levels during installation and removal of the
proposed piles in the project area, proxy source levels for the piles
were identified from the literature. Vibratory source levels were based
on the data from vibratory pile-driving of timber piles at Norfolk
NAVSTA (Illingworth and Rodkin, 2017). Impact pile-driving source
levels for timber piles was based on the summary of data for timber
piles provided by Caltrans (2020). Table 4 describes the modeled source
levels for both types of pile driving proposed for the project
activities.
Table 4--Underwater Noise Source Levels Modeled for Impact and Vibratory Pile-Driving
--------------------------------------------------------------------------------------------------------------------------------------------------------
SPLs or SEL at 10 meters distance
Source for proxy values --------------------------------------------------------
Pile type Method used Average Peak SPL, Average RMS SPL, Average SEL, dB
dB re 1 [mu]Pa dB re 1 [mu]Pa re 1 [mu]Pa2-sec
--------------------------------------------------------------------------------------------------------------------------------------------------------
Timber Pile............................ Impact.................... Caltrans (2020)........... 180 170 160
Timber Pile............................ Vibratory................. Illingworth and Rodkin NA 162 NA
(2017).
--------------------------------------------------------------------------------------------------------------------------------------------------------
SPL = Sound Pressure Levels; SEL = Sound Exposure Level; RMS = root mean square; dB re 1 [mu]Pa = decibels referenced to 1 micropascal; dB re 1
[mu]Pa\2\-sec = decibels referenced to 1 micropascal squared second; NA = not applicable. All SPLs and SELs are unattenuated.
Pile-driving will generate underwater noise that potentially could
result in harassment to marine mammals swimming by the proposed project
area. Transmission loss (TL) underwater is the decrease in acoustic
intensity as an acoustic pressure wave propagates out from a source
until the source becomes indistinguishable from ambient sound. TL
parameters vary with frequency, temperature, sea conditions, current,
source and receiver depth, water depth,
[[Page 42951]]
water chemistry, and bottom composition and topography. A ``Practical
Spreading'' value of 15 (referred to as ``practical spreading loss'')
is widely used for intermediate or spatially varying conditions when
actual values for TL are unknown. This value was used to model the
estimated range from pile-driving activity to various expected SPLs at
potential project structures. This model follows a geometric
propagation loss based on the distance from the driven pile, resulting
in a 4.5 dB reduction in level for each doubling of distance from the
source. In this model, the SPL at some distance away from the source
(e.g., driven pile) is governed by a measured source level, minus the
TL of the energy as it dissipates with distance. The TL equation is:
TL = 15 log10 (R1/R2)
Where:
TL is the transmission in dB,
R1 is the distance of the modeled SPL from the driven
pile, and
R2 is the distance (usually 10 m) from the driven pile of
the initial measurement.
The degree to which underwater noise propagates away from a noise
source is dependent on a variety of factors, most notably by bathymetry
and the presence or absence of reflective or absorptive conditions,
including the water surface and sediment type. The TL model described
above was used to calculate the expected noise propagation from both
impact and vibratory pile-driving using representative source levels to
estimate the harassment or area exceeding the noise criteria. These
zones are based on the pile location within the construction area with
the greatest anticipated noise propagation.
The Navy used NMFS Technical Guidance, revised in 2024 (NMFS 2024a)
to calculate the maximum distance to AUD INJ onset and behavioral onset
associated with vibratory and impact pile-driving. The NMFS Multi-
species calculator tool was used to calculate the distances to the AUD
INJ isopleth based on the SEL24 thresholds and the
behavioral thresholds for the three hearing groups are provided in
Table 5 and Table 6 for vibratory and impact pile removal and
installation activities, respectively. Calculated distances to Level B
(behavioral) thresholds are large but do not account for attenuation
from intersecting landmasses, which would reduce the overall area of
potential impact to the Region of Influence (ROI). Level A (AUD INJ
onset) and Level B (behavioral) thresholds have the potential to be
exceeded within the entire ROI.
Adjusted maximum distances are provided for the behavioral
thresholds where the extent of noise reaches land prior to reaching the
calculated radial distance to the threshold. Areas encompassed within
the threshold (harassment zone) were calculated using the location of a
representative pile. Sound source locations were chosen to model the
greatest possible affected areas.
As shown in Table 5, the maximum radial distance (which would occur
from the removal/installation of the outermost pile) to the Level A
harassment isopleth (AUD INJ onset) for non-impulsive noise (vibratory
pile-driving) would be approximately 16.9 m (55.4 ft) for harbor
porpoise, 7.9 m (25.9 ft) for Atlantic white-sided and short-beaked
common dolphins, and 87.3 ft (26.6 m) for seals. The maximum radial
distance to the Level B harassment isopleth for all marine mammals
would be 3.9 mi (6.31 km).
Table 5--Calculated Maximum Distances Corresponding to MMPA Thresholds for Underwater Sound From Non-Impulsive
Noise
[Vibratory pile] \1\
----------------------------------------------------------------------------------------------------------------
Injury (AUD INJ onset) Level A Behavioral
------------------------------------------------------------ disturbance Level
B
High-frequency Very high- -------------------
Timber pile cetaceans 201 dB frequency Phocid pinnipeds All marine mammals
SELCUM threshold cetaceans 181 dB 195 dB SELCUM 120 dB RMS
radial distance/ SELCUM threshold threshold radial threshold baseline
area radial distance/ distance/area radial distance/
area area \1\
----------------------------------------------------------------------------------------------------------------
Removal......................... 7.9 m/196.1 m\2\.. 16.9 m/897.2 m\2\. 26.6 m/2,222.3 6,310 m/7,810
m\2\. m\2\.
Installation.................... 1.1 m/3.8 m\2\.... 2.3 m/16.6 m\2\... 3.6 m/40.7 m\2\... 6,310 m/7,810
m\2\.
----------------------------------------------------------------------------------------------------------------
As shown in Table 6, the maximum distance to AUD INJ onset for
impact pile-driving would be approximately 32.1 m (105.3 ft) for harbor
porpoise, 2.6 m (8.5 ft) for Atlantic white-sided and short-beaked
common dolphins, and 18.4 m (60.4 ft) for seals. The maximum radial
distance to the impulsive behavioral disturbance threshold (160 dB RMS)
would be approximately 46 m (150 ft) for all marine mammals.
Table 6--Calculated Maximum Distances Corresponding to MMPA Thresholds for Underwater Sound From Impulsive Noise
[Impact pile-driving] \1\
----------------------------------------------------------------------------------------------------------------
Injury (AUD INJ onset) Level A Behavioral
------------------------------------------------------------ disturbance Level
Very high- B
High-frequency frequency Phocid pinnipeds -------------------
Timber pile cetaceans 193 dB cetaceans 159 dB 183 dB SELCUM All marine mammals
SELCUM threshold SELCUM threshold threshold radial 160 dB RMS
radial distance/ radial distance/ distance/area threshold radial
area area distance/area
----------------------------------------------------------------------------------------------------------------
Installation.................... 2.6 m/21.2 m\2\... 32.1 m/3,237 m\2\. 18.4 m/1,063.6 46 m/6,647 m\2\.
m\2\.
----------------------------------------------------------------------------------------------------------------
[[Page 42952]]
Marine Mammal Occurrence and Take Estimation
In this section we provide information about the occurrence of
marine mammals, including density or other relevant information which
will inform the take calculations.
Here we describe how the information provided above is synthesized
to produce a quantitative estimate of the take that is reasonably
likely to occur and proposed for authorization.
To determine the number of animals potentially exposed, the
following equation was used:
Exposure estimate = (N x harassment zone) x days of pile-driving
Where:
N = density estimate used for each species
Harassment zone = the area where noise exceeds the noise threshold
value
The exposure estimate was then rounded to a whole number at the end
of the calculation.
The following assumptions were used to calculate potential
exposures to impact and vibratory pile removal and installation noise
for each threshold:
Each animal can be taken via Level B harassment once every
24 hrs.
The installation method that produces the largest
harassment zone was used to estimate exposure of marine mammals to
noise impacts.
Days of pile removal/installation were based on the
standard average daily production rates, but actual daily production
rates may vary. Production rates would be maximized to the extent
possible.
All piles will have an underwater noise disturbance
distance equal to the pile that causes the greatest noise disturbance
(that is, the pile farthest from shore) installed with the method that
has the largest harassment zone. The largest Level B harassment zone
will be produced by vibratory driving. In this case, the harassment
zone for an impact hammer will be encompassed by the larger behavioral
harassment zone from the vibratory driver.
The best available marine mammal density data for the U.S. western
North-Atlantic region is the Navy Marine Species Density Database
(NMSDD). These values reflect data collected during offshore sightings,
so they must be adjusted for inshore waters. Where cetacean density
calculations produced a value greater than one but less than the
average group size for cetacean species (Oliveira et al. 2024), the
take estimate was adjusted to that higher value. As cetaceans travel in
groups, average group sizes were used as a minimum value to estimate
take. NMFS proposes using the average group size for Atlantic white-
sided dolphins and common dolphins.
The NMSDD models harbor and gray seals as a guild due to the
difficulty in distinguishing these species at sea (Roberts et al.
2023). Harbor seals are expected to be the most common pinniped sighted
in Narragansett Bay, with a haulout known as The Sisters only 0.9 mi
(1.5 km) away from the project site. Harbor seals are rarely observed
at The Sisters haul-out from September to October, however, they are
regular visitors in mid-November (up to 10 seals per day). These
numbers gradually increase, peaking in March (less than 50 individuals
per day), and typically at low tide (DeAngelis 2023; Moll et al. 2017;
Moll 2016). The maximum guild density (0.439 seals/km\2\) was
determined to be appropriate for estimating takes of harbor seal since
they are the most common in the Narragansett Bay.
Gray seals are the second most common seal at the project site and,
based on stranding records, are commonly observed during spring to
early summer and occasionally observed during other months of the year
(Kenney, 2020). Therefore, the average density (0.306 species/km\2\)
for the harbor-gray seal guild was used for gray seal occurrence in
Narragansett Bay.
Harp seals and hooded seals are considered occasional visitors in
Narragansett Bay but much rarer than harbor and gray seals (Kenney,
2015), so the minimum guild density was used to estimate take (0.127
species/km\2\) for the harp seal. Hooded seals are the rarest pinniped
species that is reasonably likely to occur within Narragansett Bay. The
Navy proposes, and NMFS concurs, that one hooded seal may occur within
the project area over the course of the 37 days of pile driving.
Densities used for calculating take are shown in Table 7, while
proposed incidental take for the Pier 171 construction activity,
including percentage of each stock is represented below in table 8.
Table 7--Proposed Seasonal Densities for Species in Narragansett Bay
----------------------------------------------------------------------------------------------------------------
Relative and seasonal Average
Species occurrence in Narragansett Density in the project \1\ group size
Bay \2\ area (animals/km\2\) \2\
----------------------------------------------------------------------------------------------------------------
Atlantic white-sided dolphin............ Occasional Summer and Fall. Winter: 0.000.............. 13
Spring: 0.0000.............
Summer: 0.0001.
Fall: 0.0001...............
Common dolphin/Short-beaked............. Occasional Winter and Fall. Winter: 0.003.............. 31
Spring: 0.002..............
Summer: 0.0004.
Fall: 0.004................
Harbor porpoise......................... Occasional Winter and Winter: 0.014.............. 3
Spring. Spring: 0.008..............
Summer: 0.0001.
Fall: 0.0001...............
Harbor seal............................. Common Winter, Spring, and Winter: 0.439.............. 1
Fall. Spring: 0.364..............
Summer: 0.395.
Fall: 0.402................
Gray seal............................... Occasional Spring and Winter: 0.262.............. 1
Summer. Spring: 0.230..............
Summer: 0.295.
Fall: 0.306................
Harp seal............................... Rare Winter and Spring..... Winter: 0.131.............. 1
Spring: 0.127..............
Summer: 0.
Fall: 0....................
[[Page 42953]]
Hooded seal............................. Rare Winter and Spring..... Winter: 0.0000............. 1
Spring: 0.0000.............
Summer: 0.0000.
Fall: 0.0000...............
----------------------------------------------------------------------------------------------------------------
\1\ Density calculations used the highest seasonal density for cetaceans, maximum density for harbor seals,
average for gray seals, and minimum for harp and hooded seals.
\2\ The average group size according to summarized AMAPPS data.
Table 8--Proposed Take of Marine Mammals by Level B Harassment by Species, and Percent of Stock
----------------------------------------------------------------------------------------------------------------
Proposed
Level A Level B Total take as
Species name Stock Stock abundance (AUD INJ) (behavioral) proposed percentage
take of stock
----------------------------------------------------------------------------------------------------------------
Atlantic white-sided dolphin Western North 93,233 (CV = 0 16 16 .017
(Leucopleurus acutus). Atlantic Stock. 0.71).
Short-beaked common dolphin Western North 93,100 (CV = 0 31 31 .033
(Delphinus delphis delphis). Atlantic Stock. 0.56).
Harbor porpoise (Phocoena Gulf of Maine/ 85,765 (CV = 0 4 4 .005
phocoena). Bay of Fundy. 0.53).
Harbor seal (Phoca vitulina Western North 61, 336 (CV = 0 127 127 .207
vitulina). Atlantic Stock. 0.08).
Gray seal (Halichoerus Western North 27,911 (CV = 0 88 88 .315
grypus atlantica). Atlantic Stock. 0.20).
Harp seal (Pagophilus Western North 7,600,000 (CV = 0 38 38 .001
groenlandicus). Atlantic Stock. UKN).
Hooded seal (Cystophora Western North UKN (CV = UKN). 0 1 1 NA
cristata). Atlantic Stock.
----------------------------------------------------------------------------------------------------------------
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 (latter not applicable for this action). NMFS
regulations require applicants for incidental take authorizations to
include information about the availability and feasibility (economic
and technological) of equipment, methods, and manner of conducting the
activity or other means of effecting the least practicable adverse
impact upon the affected species or stocks, and their habitat (50 CFR
216.104(a)(11)).
In evaluating how mitigation may or may not be appropriate to
ensure the least practicable adverse impact on species or stocks and
their habitat, as well as subsistence uses where applicable, NMFS
considers two primary factors:
(1) The manner in which, and the degree to which, the successful
implementation of the measure(s) is expected to reduce impacts to
marine mammals, marine mammal species or stocks, and their habitat.
This considers the nature of the potential adverse impact being
mitigated (likelihood, scope, range). It further considers the
likelihood that the measure will be effective if implemented
(probability of accomplishing the mitigating result if implemented as
planned), the likelihood of effective implementation (probability
implemented as planned), and;
(2) The practicability of the measures for applicant
implementation, which may consider such things as cost and impact on
operations.
The mitigation requirements described in the following were
proposed by the Navy in its adequate and complete application or are
the result of subsequent coordination between NMFS and the Navy. The
Navy has agreed that all of the mitigation measures are practicable.
NMFS has fully reviewed the specified activities and the mitigation
measures to determine if the mitigation measures would result in the
least practicable adverse impact on marine mammals and their habitat,
as required by the MMPA, and has determined the proposed measures are
appropriate. NMFS describes these below as proposed mitigation
requirements (see section 11 of the Navy's application for more detail)
and has included them in the proposed IHA.
In addition to the measures described later in this section, the
Navy would follow these general mitigation measures:
Authorized take, by Level A and Level B harassment only,
would be limited to the species and numbers listed in Table 8.
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.
The taking by serious injury or death of any of the
species listed in Table 8 or any taking of any other species of marine
mammal would be prohibited and would result in the modification,
suspension, or revocation of the IHA, if issued. Any taking exceeding
the authorized amounts listed in Table 8 would be prohibited and would
result in the modification, suspension, or revocation of the IHA, if
issued.
Ensure that construction supervisors and crews, the marine
mammal monitoring team, and relevant Navy staff are trained prior to
the start of all construction activities, so that responsibilities,
communication
[[Page 42954]]
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 Navy, construction supervisors and crews, Protected
Species Observers (PSOs), and relevant Navy staff must avoid direct
physical interaction with marine mammals during construction activity.
If a marine mammal comes within 10 meters 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 Section 5 of the IHA and the Navy's Marine Mammal
Monitoring and Mitigation Plan, which would be submitted to NMFS for
approval no later than 30 days in advance of construction work. The
Navy must monitor the project area to the maximum extent possible based
on the required number of PSOs, required monitoring locations, and
environmental conditions. A minimum of two PSOs would be required for
all activities; when zones exceed 1,000 m, a minimum of three PSOs
would be required.
Additionally, the following mitigation measures apply to the Navy's
in-water construction activities:
Establishment of Shutdown Zones--To prevent injury from physical
interaction with construction equipment, the Navy proposes a minimum
shutdown zone of 10 m (33 ft) be implemented during all in-water
construction activities having the potential to affect marine mammals.
The Navy would establish shutdown zones with radial distances as
identified in Table 9 for all construction activities involving pile
driving. If a marine mammal is observed entering or within the shutdown
zone indicated in Table 9, 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 9, such operations must cease. 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). Shutdown zones
would vary based on the activity type and marine mammal hearing group.
Table 9--Proposed Shutdown Zones During Project Activities
----------------------------------------------------------------------------------------------------------------
Shutdown zone (m)
Activity Pile type/size --------------------------------------------------------
HF cetaceans VHF cetaceans PW
----------------------------------------------------------------------------------------------------------------
Impact and vibratory Installation 30-35 cm (12-14 in). 35 m (115 ft).
and removal.
----------------------------------------------------------------------------------------------------------------
Notes: cm = centimeter(s), m = meter(s).
Pre- and Post-Activity Monitoring--Monitoring would take place from
30 minutes prior to initiation of pile driving activity (i.e., pre-
start clearance monitoring) through 30 minutes post-completion of pile
driving activity. In addition, monitoring for 30 minutes would take
place whenever a break in the specified activity (i.e., impact pile
driving, 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 9 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 Navy 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 warning and/or
giving marine mammals a chance to leave the area prior to the hammer
operating at full capacity.
NMFS also considered the use of bubble curtains as a mitigation
measure. Bubble curtains were deemed not practicable, as they would not
be effective in the limited working area of Pier 171. Based on our
evaluation of the applicant's proposed measures, as well as other
measures considered by NMFS, NMFS has preliminarily determined that the
proposed mitigation measures provide the means of effecting the least
practicable impact on the affected species or stocks and their habitat,
paying particular attention to rookeries, mating grounds, and areas of
similar significance.
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
[[Page 42955]]
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 Navy would abide by all monitoring and reporting measures
contained within the IHA, if issued, and their Marine Mammal Monitoring
and Mitigation Plan (to be submitted for NMFS approval no later than 30
days prior to the start of construction). A summary of those measures
and additional requirements proposed by NMFS is provided below.
Visual Monitoring--A minimum of two NMFS-approved PSOs must be
stationed at strategic vantage points 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 Incidental Take Authorization (ITA) or Letter
of Concurrence (LOC). Other PSOs may substitute other relevant
experience, 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 incidental take
authorization.
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 would also have the following additional qualifications:
The ability to conduct field observations and collect data
according to assigned protocols;
Experience or training in the field identification of
marine mammals, including the identification of behaviors;
Sufficient training, orientation, or experience with the
construction operation to provide for personal safety during
observations;
Writing skills sufficient to prepare a report of
observations including but not limited to: (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 Navy must establish monitoring locations as described in the
approved Marine Mammal Monitoring and Mitigation Plan (see figure 11-1
of the Navy's IHA application for map indicating potential locations).
For all pile driving activities, a minimum of two PSOs must be assigned
to each active pile driving location to monitor the shutdown zones. In
order to effectively monitor a zone of 1000 m or more, at least three
PSOs would be required. PSOs would record all observations of marine
mammals, regardless of distance from the pile being driven, as well as
the additional data indicated below and in section 6 of the IHA, if
issued.
Acoustic Monitoring
The Navy must establish acoustic monitoring procedures as described
in the Acoustic Monitoring Plan (see summary in section 13.4 of the
Navy's application) to verify the sound source levels predicted. An
acoustic monitoring plan would be submitted to NMFS no later than 60
days prior to the beginning of in-water construction for approval. The
Navy proposes to monitor a minimum of 10 percent and up to 16 of each
type of piling with at least 2 hydrophones, 1 placed approximately 10 m
from the incident pile, and 1 further away in accordance with a
hydroacoustic monitoring plan that would be approved by NMFS in advance
of construction. The estimated harassment and/or shutdown zones may be
modified with NMFS' approval following NMFS' acceptance of an acoustic
monitoring report. See section 13 of the Navy's IHA application for
more detail.
At minimum, the methodology would include:
For underwater recordings, a stationary hydrophone system
with the ability to measure SPLs will be placed in accordance with
NMFS' most recent guidance for the collection of source levels (NMFS,
2012).
A close-range hydrophone placed at a horizontal distance
of 10 m from the pile. Additional hydrophones would be placed at (1) a
horizontal distance no less than three times the water depth and (2) in
the far field, well away from the source. Hydrophones would be placed
at a depth of half the water depth at each measurement location. Exact
positioning of the hydrophone(s) would ensure a direct, unobstructed
path between the sound source and the hydrophone(s);
Measurement systems would be deployed using configurations
which minimize self or platform noise and ensure stable positioning
throughout the recordings;
The recordings would be continuous throughout each
acoustic event for which monitoring is required;
The SSV measurement systems would have a sensitivity
appropriate for the expected SPLs. The frequency range of SSV
measurement systems would cover the range of at least 20 Hz to 20 kHz.
The dynamic range of the measurement system would be sufficient such
that at each location, the signals would avoid poor signal-to-noise
ratios for low amplitude signals, and would avoid clipping,
nonlinearity, and saturation for high amplitude signals;
All hydrophones used in SSV measurements systems would be
required to have undergone a full system laboratory calibration
conforming to a recognized standard procedure, from a factory or
accredited source to ensure the hydrophone(s) receives accurate SPLs,
at a date not to exceed 2 years before deployment.
Environmental data would be collected, including but not
limited to, the following: wind speed and direction, air temperature,
humidity, surface water temperature, water depth, wave height, weather
conditions, and other factors that could contribute to influencing the
airborne and underwater SPLs (e.g., aircraft, boats, etc.); and
The project engineer would supply the acoustics specialist
with the substrate composition, hammer model and size, hammer energy
settings, depth of drilling, and boring rates and any changes to those
settings during the monitoring.
For acoustically monitored construction activities, data from the
continuous monitoring locations would be post-processed to obtain the
following sound measures:
Maximum peak sound pressure level recorded for all
activities, expressed in dB re 1 [mu]Pa. This maximum value will
originate from the phase of hammering during which hammer energy was
also at maximum.
From all activities occurring during the time that the
hammer was at maximum energy, these additional measures will be made,
as appropriate:
[[Page 42956]]
[cir] mean, median, minimum, and maximum RMS SPL (dB re 1 [mu]Pa);
[cir] mean duration of a pile strike (based on the 90 percent
energy criterion);
[cir] number of hammer strikes;
[cir] mean, median, minimum, and maximum SELss (dB re
[mu]Pa\2\ sec);
[cir] Median integration time used to calculate RMS SPL (for
vibratory monitoring, the time period selected is 1-second intervals.
For impulsive monitoring, the time period is 90% of the energy pulse
duration);
[cir] A frequency spectrum (power spectral density) (dB re
[mu]Pa\2\ per Hz) based on all strikes with similar sound;
[cir] Finally, the SEL24 would be computed from all the
strikes associated with each pile occurring during all phases, i.e.,
soft start. This measure is defined as the sum of all SELss
values. The sum is taken of the antilog, with log10 taken of
result to express (dB re [mu]Pa\2\ sec).
Reporting--The Navy 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 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 ensured, and resulting changes in behavior of the
animal(s), if any.
Acoustic monitoring report(s) must be submitted on the same
schedule as visual monitoring reports (i.e., within 90 days following
the completion of construction). The acoustic monitoring report must
contain the informational elements described in the Acoustic Monitoring
Plan (see summary in section 13.4 of the Navy's application) and, at
minimum, must include:
Hydrophone equipment and methods: (1) recording device,
sampling rate, calibration details, distance (m) from the pile where
recordings were made; and (2) the depth of water and recording
device(s);
Location, identifier, orientation (e.g., vertical,
battered), material, and geometry (shape, diameter, thickness, length)
of pile being driven, substrate type, method of driving during
recordings (e.g., hammer model and energy), and total pile driving
duration;
Whether a sound attenuation device is used and, if so, a
detailed description of the device used, its distance from the pile and
hydrophone, and the duration of its use per pile;
For impact pile driving: (1) number of strikes per day and
per pile and strike rate; (2) depth of substrate to penetrate; (3)
decidecade (one-third octave) band spectra in tabular and figure
formats computed on a per-pulse basis, including the arithmetic mean or
median for all computed spectra; (4) pulse duration and median, mean,
maximum, minimum, and number of samples (where relevant) of the
following sound level metrics: (5) RMS SPL; (6) SEL24, Peak
(PK) SPL, and SELss; and
For vibratory driving/removal: (1) duration of driving per
pile; (2) vibratory hammer operating frequency; (3) decidecade (one-
third octave) band spectra in tabular and figure formats for 1-second
windows, including the arithmetic mean or median for all computed
spectra; and (4) median, mean, maximum, minimum, and number of samples
(where relevant) of the following sound level metrics: 1-sec RMS SPL,
SEL24 (and timeframe over which the sound is averaged).
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 Navy 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 Navy's activities discover an injured or dead
marine mammal, the Navy would report the incident to the NMFS Office of
Protected Resources (OPR) ([email protected],
[email protected]) and to the Greater Atlantic Region Regional
Stranding Coordinator as soon as feasible. If the death or injury was
clearly caused by the specified activity, the Navy 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 Navy
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;
[[Page 42957]]
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.
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 majority of our analysis applies to all
the species listed in table 2, given that many of the anticipated
effects of this project on different marine mammal stocks are expected
to be relatively similar in nature. Where there are meaningful
differences between species or stocks, or groups of species, in
anticipated individual responses to activities, impact of expected take
on the population due to differences in population status, or impacts
on habitat, they are described independently in the analysis below.
Pile driving activities associated with the Navy's construction
project has the potential to disturb or displace marine mammals.
Project activities may result in take, in the form of Level B
harassment, from underwater sounds generated from pile driving and
removal. Potential takes could occur if individuals are present in the
ensonified zone when these 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. Further, no take by Level A harassment is anticipated due
to the application of proposed mitigation measures, such as shutdown
zones that encompass the Level A harassment zones. The potential for
harassment would be minimized through the construction method and the
implementation of the planned mitigation measures (see Proposed
Mitigation section).
Proposed takes by Level B harassment would be due to potential
behavioral disturbance and TTS. A 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.
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 project 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 areas by marine mammals would
be temporary in nature and that any marine mammals that avoid the
project areas during construction would not be permanently displaced.
Short-term avoidance of the project areas 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 project is also not expected to have significant adverse
effects on affected marine mammals' habitats. No ESA-designated
critical habitat or biologically important areas (BIAs) are located
within the project area. The project activities would not modify
existing marine mammal habitat for a significant amount of time. The
activities may cause a low level of turbidity in the water column and
some fish may leave the area of disturbance, thus temporarily impacting
marine mammals' foraging opportunities in a limited portion of the
foraging range; but, because of the short duration of the activities
and the relatively small area of the habitat that may be affected (with
no known particular importance to marine mammals), the impacts to
marine mammal habitat are not expected to cause significant or long-
term negative consequences. Seasonal nearshore marine mammal surveys
were conducted at NAVSTA Newport from May 2016 to February 2017, and
several harbor seal haul outs were identified in Narragansett Bay, but
no pupping was observed.
For all species and stocks, take would occur within a limited,
relatively confined area (Coddington Cove) of the stock's range. Given
the availability of suitable habitat nearby, any displacement of marine
mammals from the project areas is not expected to affect marine
mammals' fitness, survival, and reproduction due to the limited
geographic area that would be affected in comparison to the much larger
habitat for marine mammals within Narragansett Bay and outside the bay
along the Rhode Island coasts. Level B harassment would be reduced to
the level of least practicable adverse impact to the marine mammal
species or stocks and their habitat through use of mitigation measures
described herein.
Some individual marine mammals in the project area, such as harbor
seals, may be present and be subject to repeated exposure to sound from
pile driving activities on multiple days. However, pile driving and
extraction is not expected to occur on every day, and these individuals
would likely return to normal behavior during gaps in pile driving
activity within each day of construction and in between work days. As
discussed above, there is similar transit and haul out habitat
available for marine mammals within and outside of the Narragansett Bay
along the Rhode Island coast, outside of the project area,
[[Page 42958]]
where individuals could temporarily relocate during construction
activities to reduce exposure to elevated sound levels from the
project. Therefore, any behavioral effects of repeated or long duration
exposures are not expected to negatively affect survival or
reproductive success of any individuals. Thus, even repeated Level B
harassment of some small subset of an overall stock is unlikely to
result in any effects on rates of reproduction and survival of the
stock.
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 proposed
for authorization;
No Level A harassment is anticipated or proposed for
authorization;
The intensity of anticipated takes by Level B harassment
is relatively low for all stocks. Level B harassment would be primarily
in the form of behavioral disturbance, resulting in avoidance of the
project areas around where impact or vibratory pile driving is
occurring, with some low-level TTS that may limit the detection of
acoustic cues for relatively brief amounts of time in relatively
confined footprints of the activities;
Nearby areas of similar habitat value (e.g., transit and
haul out habitats) within and outside of Narragansett Bay are available
for marine mammals that may temporarily vacate the project area during
construction activities;
The specified activity and associated ensonifed areas do
not include habitat areas known to be of special significance (BIAs or
ESA-designated critical habitat);
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 ensonified areas are very small relative to the
overall habitat ranges of all species and stocks, and would not
adversely affect ESA-designated critical habitat for any species or any
areas of known biological importance;
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 sections 101(a)(5)(A) and (D) of the MMPA for
specified activities other than military readiness activities. The MMPA
does not define small numbers and so, in practice, where estimated
numbers are available, NMFS compares the number of individuals taken to
the most appropriate estimation of abundance of the relevant species or
stock in our determination of whether an authorization is limited to
small numbers of marine mammals. When the predicted number of
individuals to be taken is fewer than one-third of the species or stock
abundance, the take is considered to be of small numbers (see 86 FR
5322, January 19, 2021). Additionally, other qualitative factors may be
considered in the analysis, such as the temporal or spatial scale of
the activities.
Table 8 demonstrates the number of instances in which individuals
of a given species could be exposed to received noise levels that could
cause take of marine mammals. The instances of take NMFS proposes to
authorize is below one-third of the estimated stock abundance for all
impacted stocks (table 8). In fact, take of individuals is less than 1
percent of the abundance for all affected stocks. The number of animals
that we expect to authorize to be taken would be considered small
relative to the relevant stocks or populations, even if each estimated
take occurred to a new individual. Furthermore, these takes are likely
to only occur within a small portion of the stock's range and the
likelihood that each take would occur to a new individual is low.
Based on the analysis contained herein of the proposed activity
(including the proposed mitigation and monitoring measures) and the
anticipated take of marine mammals, NMFS preliminarily finds that small
numbers of marine mammals would be taken relative to the population
size of the affected species or stocks, with no species take exceeding
0.32 of the best available population abundance estimate.
Unmitigable Adverse Impact Analysis and Determination
There are no relevant subsistence uses of the affected marine
mammal stocks or species implicated by this action. Therefore, NMFS has
determined that the total taking of affected species or stocks would
not have an unmitigable adverse impact on the availability of such
species or stocks for taking for subsistence purposes.
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 IHAs, NMFS
consults internally whenever we propose to authorize take for
endangered or threatened species.
No incidental take of ESA-listed species is proposed for
authorization or expected to result from this activity. Therefore, NMFS
has determined that formal consultation under section 7 of the ESA is
not required for this action.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
issue an IHA to the Navy for conducting pile driving activity in
Newport RI, 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 IHA.
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
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Proposed Activity section of this notice is planned or (2) the
activities as described in the Description of Proposed Activity section
of this notice would not be completed by the time the IHA expires and a
renewal would allow for completion of the activities beyond that
described in the Dates and Duration section of this notice, provided
all of the following conditions are met:
A request for renewal is received no later than 60 days
prior to the needed renewal IHA effective date (recognizing that the
renewal IHA expiration date cannot extend beyond 1 year from expiration
of the initial IHA).
The request for renewal must include the following:
1. An explanation that the activities to be conducted under the
requested renewal IHA are identical to the activities analyzed under
the initial IHA, are a subset of the activities, or include changes so
minor (e.g., reduction in pile size) that the changes do not affect the
previous analyses, mitigation and monitoring requirements, or take
estimates (with the exception of reducing the type or amount of take).
2. A preliminary monitoring report showing the results of the
required monitoring to date and an explanation showing that the
monitoring results do not indicate impacts of a scale or nature not
previously analyzed or authorized.
Upon review of the request for renewal, the status of the
affected species or stocks, and any other pertinent information, NMFS
determines that there are no more than minor changes in the activities,
the mitigation and monitoring measures will remain the same and
appropriate, and the findings in the initial IHA remain valid.
Dated: September 2, 2025.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2025-16993 Filed 9-4-25; 8:45 am]
BILLING CODE 3510-22-P