Notice2026-09046
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to S50S/LNG and S499 Bulkheads Replacement Project at Naval Station Newport, Rhode Island
Primary source
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Published
May 7, 2026
Issuing agencies
Commerce DepartmentNational Oceanic and Atmospheric Administration
Abstract
NMFS has received a request from the United States Navy (Navy) for authorization to take marine mammals incidental to construction activities associated with the S50S/LNG and S499 Bulkheads Replacement Project at Naval Station (NAVSTA) Newport, Rhode Island (RI). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue two consecutive 1-year incidental harassment authorizations (IHAs) to incidentally take marine mammals during the specified activities. NMFS is also requesting comments on possible one- time, 1-year renewals for each IHA that could be issued under certain circumstances and if all requirements are met, as described in the Request for Public Comments section at the end of this notice. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorizations.
Full Text
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<title>Federal Register, Volume 91 Issue 88 (Thursday, May 7, 2026)</title>
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[Federal Register Volume 91, Number 88 (Thursday, May 7, 2026)]
[Notices]
[Pages 24817-24842]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-09046]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XE974]
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to S50S/LNG and S499 Bulkheads
Replacement Project at Naval Station Newport, Rhode Island
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental harassment authorizations; request
for comments on proposed authorizations and possible renewals.
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SUMMARY: NMFS has received a request from the United States Navy (Navy)
for authorization to take marine mammals incidental to construction
activities associated with the S50S/LNG and S499 Bulkheads Replacement
Project at Naval Station (NAVSTA) Newport, Rhode Island (RI). Pursuant
to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments
on its proposal to issue two consecutive 1-year incidental harassment
authorizations (IHAs) to incidentally take marine mammals during the
specified activities. NMFS is also requesting comments on possible one-
time, 1-year renewals for each IHA that could be issued under certain
circumstances and if all requirements are met, as described in the
Request for Public Comments section at the end of this notice. NMFS
will consider public comments prior to making any final decision on the
issuance of the requested MMPA authorizations.
DATES: Comments and information must be received no later than June 8,
2026.
ADDRESSES: Comments should be addressed to the Permits and Conservation
Division, Office of Protected Resources, NMFS and should be submitted
via email to <a href="/cdn-cgi/l/email-protection#460f1216682335252e062829272768212930"><span class="__cf_email__" data-cfemail="662f3236480315050e260809070748010910">[email protected]</span></a>. Electronic copies of the application
and supporting documents, as well as a list of the references cited in
this document, may be obtained online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>. In case of problems
accessing these documents, please call the contact listed below.
Instructions: NMFS is not responsible for comments sent by any
other method, to any other address or individual, or received after the
end of the comment period. Comments, including all attachments, must
not exceed a 25-megabyte file size. All comments received are a part of
the public record and will generally be posted online at <a href="https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act">https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act</a> without change. All personal identifying
information (e.g., name, address) voluntarily submitted by the
commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.
FOR FURTHER INFORMATION CONTACT: Carter Esch, Office of Protected
Resources, NMFS (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Background
The MMPA prohibits the ``take'' of marine mammals, with certain
exceptions. Section 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et
seq.) directs the Secretary of Commerce (as delegated to NMFS) to
allow, upon request, the incidental, but not intentional, taking of
small numbers of marine mammals by U.S. citizens who engage in a
specified activity (other than commercial fishing) within a specified
geographical region if certain findings are made and either regulations
are proposed or, if the taking is limited to
[[Page 24818]]
harassment, a notice of a proposed IHA is provided to the public for
review.
Authorization for incidental takings shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s) and will not have an unmitigable adverse impact on the
availability of the species or stock(s) for taking for subsistence uses
(where relevant). Further, NMFS must prescribe the permissible methods
of taking; other ``means of effecting the least practicable adverse
impact'' on the affected species or stocks and their habitat, paying
particular attention to rookeries, mating grounds, and areas of similar
significance, and on the availability of the species or stocks for
taking for certain subsistence uses (referred to as ``mitigation'');
and requirements pertaining to the monitoring and reporting of the
takings. The definitions of all applicable MMPA statutory terms used
above are included in the relevant sections below (see also 16 U.S.C.
1362; 50 CFR 216.3, 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.
These actions are 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 IHAs
qualifies to be categorically excluded from further NEPA review.
Summary of Request
Bulkhead S50S/LNG and Bulkhead S499 were part of a previously
designed multi-section bulkhead repair/replacement project for which
NMFS issued incidental take regulations (ITRs) and a Letter of
Authorization (LOA) authorizing incidental take of marine mammals,
effective from May 15, 2022, through May 14, 2027 (86 FR 71162,
December 15, 2021). Subsequently, the Navy requested a modification to
the LOA, which was issued on January 25, 2023 (88 FR 5856, January 30,
2023). The Bulkhead S50S/LNG and Bulkhead S499 project has again been
redesigned, including addition of components that were not analyzed
under the currently effective ITRs and LOA, and construction is planned
to extend beyond the effective period of the LOA, from September 1,
2026, to May 31, 2029. Therefore, on March 21, 2025, the Navy submitted
a new request for incidental take authorization of marine mammals
incidental to construction activities supporting the redesigned S50S/
LNG and S499 Bulkheads Replacement Project at NAVSTA in Newport, RI,
over the course of approximately 2 years.
Following NMFS' review of the application draft and associated
discussions, the Navy submitted a revised version of the application on
August 21, 2025. NMFS coordinated with the Navy to conduct revised
modeling incorporating NMFS' updated source level proxy values for
construction activities and, on April 10, 2026, the application was
deemed adequate and complete. The Navy's request is for authorization
to take seven species of marine mammals by Level B harassment and, for
five of these species, Level A harassment. Neither the Navy nor NMFS
expect serious injury or mortality to result from this activity,
therefore, an IHA is appropriate.
NMFS previously issued other ITAs for similar activities at NAVSTA
Newport, including an IHA (87 FR 78072, December 21, 2022) and renewal
IHA (90 FR 11400, March 6, 2025) to the Navy on behalf of NOAA's Office
of Marine and Aviation Operations for a construction project associated
with the relocation of NOAA's research vessels to NAVSTA Newport. More
recently, NMFS issued an IHA to the Navy for the Pier 171 Repair and
Replacement project (90 FR 57953, December 15, 2025) and the USCG
Offshore Patrol Cutter Homeporting project (91 FR 16650. April 2,
2026). The Navy and associated parties have complied with all the
requirements (e.g., mitigation, monitoring, and reporting) of the
previous ITAs, and information regarding their monitoring results may
be found in the Potential Effects of Specified Activities on Marine
Mammals and their Habitat section.
Description of the Proposed Activity
Overview
The Navy proposes to replace or repair several sections of
deteriorating, unstable, hazardous, and eroding bulkhead, sheet pile,
and revetment (approximately 1,160 total linear feet (ft)) along the
Coddington Cove waterfront of NAVSTA Newport (figure 1). Over time, the
existing storm sewer systems and bulkheads along the Coddington Cove
waterfront have severely degraded due to erosion from under-capacity
stormwater system piping and aging infrastructure. This impacts the
ability of the installation to minimize shoreline erosion and minimize
safety risks from associated upland subsidence, while also maintaining
potential berthing space. To complete the necessary work to repair and
replace the bulkheads over a 2-year period, the Navy plans to use
impact pile driving, vibratory pile driving and removal, and down-the-
hole (DTH) methods--activities likely to result in the incidental take
of marine mammals by Level A harassment and Level B harassment.
BILLING CODE 3510-22-P
[[Page 24819]]
[GRAPHIC] [TIFF OMITTED] TN07MY26.000
BILLING CODE 3510-22-C
Dates and Duration
The Navy anticipates that the bulkhead repair project would occur
in two phases, Year 1 and Year 2, over 2 years. The proposed IHAs would
each be valid for the statutory maximum of 1 year from the date of
effectiveness and will become effective upon written notification from
the applicant to NMFS but not beginning later than 1 year from the date
of issuance or extending beyond 2 years from the date of issuance.
The specified activities could occur any time during each project
year. A total of 75 days and 57 non-consecutive days of in-water work
are planned for Year 1 and Year 2, respectively. The Navy anticipates
that all work would be limited to daylight hours (i.e., from 30 minutes
before civil dawn to 30 minutes after civil dusk). No in-water
activities with the potential to result in incidental take of marine
mammals would occur concurrently.
The Navy has requested issuance of two consecutive IHAs, one for
each year of construction activities. Given the similarities in
activities between project years, NMFS is issuing a single Federal
Register notice to solicit public comments on the issuance of the two
similar, but separate, IHAs.
Specific Geographic Region
Coddington Cove is a protected embayment on the western side of
[[Page 24820]]
Aquidneck Island in Narragansett Bay (figure 1). The cove covers an
area of approximately 395 acres (1.6 square kilometers (km\2\)),
receiving partial protection by the Coddington Point mass to the south
and a breakwater to the north; however, the northwestern section of the
cove is exposed to the open-water conditions of Narragansett Bay. The
tides in Coddington Cove are semi-diurnal, with two high tides and two
low tides per day.
Proposed specified activities would occur in shallow, near-shore
waters (less than 34 ft; 10 meters (m)). Based on a bathymetric survey
the Navy conducted between December 2023 and January 2024, water depths
generally range between -30 and -40 ft mean lower low water (MLLW) and
are, on average, approximately -5 ft MLLW at the proposed Bulkhead
S50S/LNG and Bulkhead S499 repair/replacement locations (Haley &
Aldrich, Inc., 2024). Water temperature in the Coddington Cove ranges
from 36 degrees Fahrenheit ([deg]F; 2 degrees Celsius ([deg]C)) in
winter to 68 [deg]F (20 [deg]C) in summer, and salinity in the
nearshore areas of Narragansett Bay at NAVSTA Newport ranges between
29.2 and 33.7 parts per thousand (Navy, 2017a). A benthic survey
conducted in 2024 indicated substrates primarily consist of mud or
gravelly mud, including varying amounts of cobble and shell debris
(Stantec Consulting Services Inc., 2024).
In addition to underwater noise-producing activities at NAVSTA
Newport, vessel noise from commercial shipping and recreational traffic
in Narragansett Bay contributes to the ambient underwater soundscape in
the proposed project area. Underwater noise data collected at the Naval
Undersea Warfare Center (NUWC) Division indicated that ambient noise in
the project area ranged from approximately 120 to 123 dB referenced to
a pressure of 1 micropascal (dB re 1 [mu]Pa) root mean square (RMS).
Detailed Description of the Action
The proposed activity would replace two unstable, deteriorating
sections of bulkhead--S50S/LNG and S499--along the Coddington Cove
waterfront at NAVSTA Newport, RI, thus reestablishing a secure barrier
to erosion and eliminating safety hazards. The Navy is required to
repair the bulkheads at the direction of the U.S. Environmental
Protection Agency to prevent further erosion and migration of
contaminated soils from entering Coddington Cove. The project will also
demolish the existing T-Pier (figure 1), which has deteriorated and
partially collapsed into the water, in its entirety by removing all
features and fill down to an elevation that will match the existing
ground line. In addition to the replacement bulkheads, existing
stormwater outfalls in the bulkhead repair areas will also be replaced
and improved in anticipation of future upgrades to the stormwater
system. Demolition of existing T-Pier and stormwater system upgrades
include activities that are not likely to result in take of marine
mammals; these and other activities such as barge repositioning and
grouting are not discussed further.
The activities that have the potential to take marine mammals, by
Level A harassment and Level B harassment, include impact pile driving,
vibratory pile driving and extraction, and DTH excavation. In total,
the Navy anticipates conducting 146 non-consecutive days of in-water
construction over approximately 2 years. This total includes 75 planned
construction days in Year 1 at the Bulkhead S50S/LNG site, 57 planned
construction days in Year 2 for Bulkhead S499 repairs, and
approximately 14 additional days to provide flexibility should
unexpected delays occur. All work will be limited to daylight
construction. Detailed descriptions follow table 1, which summarizes
in-water activities by year.
Table 1--Summary of Planned Construction Activities by Year
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Duration of
vibratory Total number
Pile size Method of pile Total number of Maximum number of driving/ Number of strikes of
Activity Pile type (inches) driving/extraction piling events \1\ piles installed/ extracting or per pile construction
extracted per day DTH (minutes/ days
pile)
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YEAR 1
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Bulkhead S50S/LNG................. Steel sheet pile Z28 18 Vibratory/impact.... 228 (114 Pairs)..... 8 pairs/day......... 30 530 Strikes/pile.... 15
Steel pipe pile..... 18 Vibratory/impact.... 111................. 8 piles/day......... 30 1,000 strikes/pile.. 15
DTH \2\............. 11.................. 1 hole/day.......... 300 13 strikes/second... 11
(Template) steel 18 Vibratory 68 (4 x 17 moves)... 4 piles/day......... 30 N/A................. 34
pipe pile. installation/
extraction.
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YEAR 2
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Bulkhead S499..................... Steel Sheet Pile Z26 18 Vibratory/Impact.... 166 (83 Pairs)...... 8 pairs/day......... 30 530 strikes/pile.... 11
Steel Pipe Pile..... 18 Vibratory/Impact.... 84.................. 8 piles/day......... 30 1,000 strikes/pile.. 11
DTH \2\............. 9................... 1 hole/day.......... 300 13 strikes/second... 9
(Template) Steel 18 Vibratory 52 (4 x 13 moves)... 4 piles/day......... 30 N/A................. 26
pipe pile. Installation/
Extraction.
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Legend: N/A = not applicable for activity.
\1\ A piling event may be a pile installation or extraction.
\2\ DTH excavation may be used to clear boulders and other hard driving conditions for steel pipe piling. DTH excavation will only be used when an obstruction or pile refusal prevents the pile
from being advanced to the required penetration depth.
Bulkhead S50S/LNG (Year 1): In its current state, Bulkhead S50S/LNG
is heavily corroded, with extensive associated landside erosion. Repair
and replacement activities would be staged from the existing T-Pier
(figures 1-2 and
[[Page 24821]]
1-3 in the Navy's ITA application) prior to its demolition. The new
bulkhead will run from the return at the south end of the bulkhead
north to and across the T-Pier approach and will tie into the adjacent
Bulkhead S50N (constructed under a separate project).
Activities include excavation and repair of approximately 650
linear feet of bulkhead and installation of a new deadman-anchored
sheet-pipe pile combination wall bulkhead. The new structure would
consist of a system of 114 interlocking pairs of (18-in) Z-shaped steel
sheet piles (228 total sheet piles) and 111 (18-in) steel pipe piles,
permanently installed using a vibratory hammer, primarily, and an
impact hammer and DTH excavation if the Navy encounters obstructions
when attempting to install piles to the target penetration depth. A
preliminary drawing showing a typical bulkhead cross section for S50S/
LNG is depicted in figure 1-3 of Navy's ITA application. The Navy would
use a set of four (18-in) steel pipe piles as a template to assist with
installation of the permanent piles. All template piles would be
installed temporarily and subsequently removed using vibratory piling
methods. Installation of template guide piles, pipe piles, and sheet
piles will occur sequentially (not concurrently) in 40-linear foot
increments.
The Bulkhead S50S/LNG replacement process would also require
modification of existing structures using methods that are not expected
to result in harassment of marine mammals. The old bulkhead will be cut
down approximately one foot below the elevation of the proposed tie
rods. The sheet piles will be tied back laterally via tie rods to a
steel sheet pile deadman (i.e., sheet-pile wall and tie-back system)
placed landward of the existing sheet-pile wall and deadman system,
which will remain in place but will not be utilized by the new
construction. The rip rap revetment at the south end of Bulkhead S50S/
LNG will be cast aside to clear the drive line to install the
replacement bulkhead. After installation of the sheeting, the rip rap
will be brought back into place to rebuild the revetment.
Bulkhead S499 (Year 2): Currently, Bulkhead S499 has widespread
moderate-to-advanced corrosion across multiple zones, including steel
sheet pile and timber planking losses and failed protective coatings.
The southerly portion of the existing bulkhead runs beneath Pier 2,
thus, the Navy will employ a phased construction approach to maintain
utility services and pedestrian and vehicular access to the pier.
Repairs will be staged from a rock revetment north of the existing
bulkhead S499, to the south side of Pier 2 (figure 1). The Navy plans
to excavate and repair of approximately 510 linear feet of bulkhead,
replacing the existing bulkhead with the same type of structure as that
planned for Bulkhead S50S/LNG (i.e., steel sheet-pipe pile combination
wall bulkhead with a tie-back system) using the same methods (i.e.,
template-assisted installations using primarily a vibratory hammer, and
an impact hammer and DTH, where necessary). The new structure would
consist of a system of 83 interlocking pairs of (18-in) Z-shaped steel
sheet piles (166 total sheet piles) and 84 (18-in) steel pipe piles. A
preliminary drawing showing a typical bulkhead cross section for S499
is depicted in figure 1-4 of the Navy's ITA application.
In addition to permanent pile installations, the repair and
replacement process would require modifications of existing structures
using methods not likely to result in marine mammal harassment (i.e.,
like those described for Bulkhead S50S/LN). To limit the extent of
demolition, the existing bulkhead will only be cut down to the top of
an existing concrete repair at the face of the bulkhead. The
replacement tie-back system will be installed just above the existing
concrete face repair. Existing rip rap along the bulkhead north of Pier
2 will be removed to clear the drive line for installation of the
replacement bulkhead. After installation of the sheeting, the rip rap
will be brought back into place as toe protection. The pile-supported
North Marginal Wharf at Bulkhead S499 will be demolished in its
entirety by cutting off the piles below the existing ground line (i.e.,
using hydraulic cutting shears or similar), an activity that would not
produce underwater noise at levels that would rise to the level of take
of marine mammals.
Proposed mitigation, monitoring, and reporting measures are
described in detail later in this document (please see Proposed
Mitigation and Proposed Monitoring and Reporting sections).
Description of Marine Mammals in the Area of Specified Activities
Sections 3 and 4 of the ITA application summarize available
information regarding status and trends, distribution and habitat
preferences, and behavior and life history of the potentially affected
species. NMFS fully considered all this information, and we refer the
reader to these descriptions, instead of reprinting the information.
Information regarding population trends and threats for the following
species may be found in NMFS' Stock Assessment Reports (SARs; <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>) and more general information about these species
(e.g., physical and behavioral descriptions) may be found on NMFS'
website (<a href="https://www.fisheries.noaa.gov/find-species">https://www.fisheries.noaa.gov/find-species</a>).
Table 2 lists all species or stocks for which take is expected and
proposed to be authorized for this activity and summarizes information
related to the population or stock, including regulatory status under
the MMPA and Endangered Species Act (ESA) and potential biological
removal (PBR), where known. PBR is defined by the MMPA as the maximum
number of animals, not including natural mortalities, that may be
removed from a marine mammal stock while allowing that stock to reach
or maintain its optimum sustainable population (as described in NMFS'
SARs). While no mortality or serious injury is anticipated or proposed
to be authorized for the Navy's project, PBR and annual mortality and
serious injury (M/SI) from anthropogenic sources are included here as
gross indicators of the status of the species or stocks and other
threats.
Marine mammal abundance estimates presented in this document
represent the total number of individuals that make up a given stock or
the total number estimated within a particular study or survey area.
NMFS' stock abundance estimates for most species represent the total
estimate of individuals within the geographic area, if known, that
comprises that stock. For some species, this geographic area may extend
beyond U.S. waters. All managed stocks in this region are assessed in
NMFS' U.S. Atlantic and Gulf of America Marine Mammal Stock
Assessments. All values presented in table 2 are the most recent
available at the time of publication and are available online at:
<a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>.
[[Page 24822]]
Table 2--Species \1\ 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/
\2\ abundance survey) \3\ SI \4\
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Order Artiodactyla--Cetacea--Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Delphinidae:
Atlantic white-sided dolphin.... Leucopleurus \5\ 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
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Phocidae (earless seals):
Gray seal \6\................... 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.
Hooded seal..................... Cystophora cristata.... Western North Atlantic. -, -, N 593,500 (UNK, UNK, UNK 1,680
2005).
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\1\ Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy
(<a href="https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies">https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies</a>).
\2\ ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or
designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or
which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is
automatically designated under the MMPA as depleted and as a strategic stock.
\3\ NMFS' marine mammal SARs can be found online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>.
CV is the coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.
\4\ These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g.,
commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range.
\5\ Genus reclassification for Atlantic white-sided dolphins (Society for Marine Mammalogy). The Society for Marine Mammalogy 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 <a href="https://marinemammalscience.org/">https://marinemammalscience.org/</a>; July 21, 2025).
\6\ NMFS' stock abundance estimate (and associated PBR) 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 in table 2 temporally and
spatially co-occur with the activity to the extent that take is
reasonably likely to occur. While several large whale species 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 project within Coddington Cove
to construct a pier for NOAA ships included pile driving and removal
from June 2024 to 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) west-southwest 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).
Harbor seals are one of the most common marine mammal species in
Narragansett Bay, with over 22 documented haul-out sites. The Sisters
seal haul-out site is the closest to the project area, approximately 1
mile (1.6 km) south of the Navy's proposed construction site location,
on the open water edge of Coddington Cove. NAVSTA employees have
reported seals hauled out at The Sisters, particularly at low tide and,
in observations off the haul-out site gathered between 2011 and 2020,
the NUWC Division Newport noted a steady increase in wintertime harbor
seal occurrence (DeAngelis, 2020). During this period, harbor seals
were rarely observed at The Sisters haul-out site in the early fall
(i.e., September and October) but steadily increased in number to a
peak population size of 40-50 animals in March. The number of harbor
seals began to decline in April and the haul-out site was typically
abandoned for the season by mid-May (DeAngelis, 2020). 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 a count of 357 seals in 2021 and above the average of
427 seals calculated across years prior (Save the Bay, 2022). From
November 2024 through January 2025, harbor seals were the most
regularly occurring marine mammal species, accounting for 26 of the 31
total seal detections, and 80 of the 109 overall individual marine
mammal detections, with the first detection on November 1, 2024, with
regular occurrences through January 2025 (Werre 2025).
Marine Mammal Hearing
Hearing is the most important sensory modality for marine mammals
[[Page 24823]]
underwater, and exposure to anthropogenic sound can have deleterious
effects. To assess noise impacts, it is necessary to characterize
marine mammal hearing ranges. 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 marine mammal hearing groups (table 3). 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) and Southall et al
(2019). Of the species potentially present in the action area, Atlantic
white-sided and common dolphins are considered high-frequency (HF)
cetaceans, and harbor porpoise are considered very high-frequency (VHF)
cetaceans. Harbor, gray, hooded and harp seals are phocid pinnipeds
(PW).
Table 3--Marine Mammal Hearing Groups (NMFS, 2024)
------------------------------------------------------------------------
Hearing group Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen 7 Hz to 36 kHz.
whales).
High-frequency (HF) cetaceans (dolphins, 150 Hz to 160 kHz.
toothed whales, beaked whales, bottlenose
whales).
Very High-frequency (VHF) cetaceans (true 200 Hz to 165 kHz.
porpoises, Kogia, river dolphins,
Cephalorhynchid, Lagenorhynchus cruciger &
L. australis).
Phocid pinnipeds (PW) (underwater) (true 40 Hz to 90 kHz.
seals).
Otariid pinnipeds (OW) (underwater) (sea 60 Hz to 68 kHz.
lions and fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
composite (i.e., all species within the group), where individual
species' hearing ranges 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, 2019.
Additionally, animals are able to detect vCery loud sounds above and
below that ``generalized'' hearing range.
For more details concerning these groups and associated generalized
hearing ranges, please see (NMFS, 2024) for a review of available
information.
Potential Effects of Specified Activities on Marine Mammals and Their
Habitat
This section includes a summary and provides a discussion of the
ways in which components of the specified activity may impact marine
mammals and their habitat. The Estimated Take of Marine Mammals section
later in this document includes a quantitative analysis of the number
of individuals that are expected to be taken by 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 likely to
adversely affect the species or stock through effects on annual rates
of recruitment or survival.
Acoustic effects on marine mammals during the specified activities
are expected to potentially occur from impact pile driving, vibratory
pile driving and extraction, and DTH excavation. 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
and, for some species, Level A harassment.
There is a variety of types and degrees of effects on marine
mammals and their habitat (including prey) that could occur because of
the specified activities. Below, we provide a brief description of the
types of sound generated by specified activities, the general impacts
on marine mammals and their habitat from these types of activities, and
a related project-specific analysis, with consideration of the proposed
mitigation measures.
Description of Sound Sources for the Specified Activities
Activities associated with the project that have the potential to
incidentally take marine mammals though exposure to sound would include
impact pile installation, vibratory pile installation and extraction,
and DTH excavation. Impact hammers typically operate by repeatedly
dropping and/or pushing a heavy piston onto a pile to drive the pile
into the substrate. Sound generated by impact hammers is impulsive,
characterized by rapid rise times and high peak sound pressure levels
(SPLs), a potentially injurious combination (Hastings and Popper,
2005). Vibratory hammers install piles by vibrating them and allowing
the weight of the hammer to push them into the substrate. Vibratory
hammers typically produce less sound (i.e., lower SPLs) than impact
hammers. Peak SPLs may be 180 dB or greater but are generally 10 to 20
dB lower than SPLs generated during impact pile driving of the same-
sized pile (Oestman et al., 2009; California Department of
Transportation (Caltrans), 2015, 2020). Sounds produced by vibratory
hammers are non-impulsive and, compared to sounds produced by impact
hammers, have a slower rise time that reduces the probability and
severity of injury, given the sound energy is distributed over a
greater amount of time (Nedwell and Edwards, 2002; Carlson et al.,
2005).
DTH excavation uses a combination of drilling and impact hammering
mechanisms to advance development of a hole in rock, with or without
simultaneously advancing a pile/casing into that hole. DTH excavation
is accomplished by the efficient progression of a drill bit, rotated
under pressure while simultaneously hammered by a specialized
percussive hammer located within the drill string (i.e., ``behind'' the
bit), the combined forces moving the bit forward to fracture rock.
Traditional impact and vibratory pile driving involve a hammer striking
the top of the pile, causing the entire length of the submerged pile to
radiate sound as a linear source. However, the DTH hammering mechanism
is integrated into the drill itself, so the primary sound generation
point is at the interface of the drill bit and the substrate (i.e.,
rock) deep within the ground/seabed, radiating sound pressure more like
a point rather than linear source. DTH systems often involve a single
hammer (mono-hammer), but multi- or ``cluster'' hammer drills are also
used widely. For repair and replacement of Bulkhead S50S/LNG and
Bulkhead S499, the Navy anticipates that installation of approximately
9 percent of the 18-inch permanent steel pipe piles may require
[[Page 24824]]
DTH excavation using a mono-hammer. The sounds produced by the DTH
excavation methods simultaneously contain both a continuous non-
impulsive component from the drilling action and an impulsive component
from the hammering effect. Therefore, for purposes of evaluating Level
A harassment and Level B harassment under the MMPA, NMFS treats DTH
systems simultaneously as both impulsive (Level A harassment
thresholds) and continuous, non-impulsive (Level B harassment
thresholds) sound source types.
The likely or possible impacts of Navy's proposed activities on
marine mammals could be generated from both non-acoustic and acoustic
stressors. Potential non-acoustic stressors include the physical
presence of the equipment, vessels, and personnel; however, the closest
known haul-out site is located approximately 1 mi (1.6 km) from the
Bulkhead S50S/LNG and Bulkhead S499 locations, thus we expect that
visual and other non-acoustic stressors would be limited. Should any
animals approach the project site(s) close enough to be harassed due to
the presence of equipment or personnel, we expect they would have
already traveled through the Level B harassment and/or Level A
harassment zones for the specified in-water activities and, thus, would
already be considered taken by acoustic impacts. Therefore, any impacts
to marine mammals are expected to be primarily acoustic in nature.
Acoustic Effects
The introduction of anthropogenic noise into the aquatic
environment by impact pile driving, vibratory pile driving and
extraction, and DTH excavation is the means by which marine mammals may
be harassed by Navy's specified activities. In general, animals exposed
to natural or anthropogenic sound may experience behavioral,
physiological, and/or physical effects, ranging in magnitude from none
to severe (Southall et al., 2007, 2019). Generally, exposure to pile
driving and extraction and other construction noise has the potential
to result in auditory threshold shifts (TSs) and behavioral reactions
(e.g., avoidance, temporary cessation of foraging and vocalizing,
changes in dive behavior). Exposure to anthropogenic noise can also
lead to non-observable physiological responses such as 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 effects of pile
driving and demolition noise on marine mammals are dependent on several
factors, including, but not limited to, sound type (e.g., impulsive vs.
non-impulsive), the species, age and sex class (e.g., adult male vs.
mother with calf), duration of exposure, the distance between the pile
and the animal, received levels, behavior at time of exposure, and
previous history with exposure (Wartzok et al., 2003; Southall et al.,
2007). Here we discuss physical auditory effects (i.e., TSs) followed
by behavioral effects and potential impacts on habitat.
NMFS defines noise-induced TS as a change, usually an increase, in
the threshold of audibility at a specified frequency or portion of an
individual's hearing range above a previously established reference
level (NMFS, 2024). The amount of TS is customarily expressed in dB. A
TS can be permanent or temporary. As described in NMFS (2018, 2024),
there are numerous factors to consider when examining the consequence
of TS, including, but not limited to, the signal temporal pattern
(e.g., impulsive or non-impulsive), likelihood an individual would be
exposed for a long enough duration or to a high enough level to induce
a TS, the magnitude of the TS, time to recovery (seconds to minutes or
hours to days), the frequency range of the exposure (i.e., spectral
content), the hearing and vocalization frequency range of the exposed
species relative to the signal's frequency spectrum (i.e., how 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) and Permanent Threshold Shift (PTS)--NMFS
(2024) defines AUD INJ as damage to the inner ear that can result in
destruction of tissue, such as the loss of cochlear neuron synapses or
auditory neuropathy (Houser 2021; Finneran 2024). AUD INJ may or may
not result in a PTS. PTS is subsequently defined as a permanent,
irreversible increase in the threshold of audibility at a specified
frequency or portion of an individual's hearing range above a
previously established reference level (NMFS, 2024). PTS does not
generally affect more than a limited frequency range, and an animal
that has incurred PTS has some level of hearing loss at the relevant
frequencies; typically, animals with PTS or other AUD INJ are not
functionally deaf (Au and Hastings, 2008; Finneran, 2016). Available
data from humans and other terrestrial mammals indicate that a 40-dB TS
approximates AUD INJ onset (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 (Southall et al., 2007,
2019), a TTS of 6 dB is considered the minimum TS clearly larger than
any day-to-day or session-to-session variation in a subject's normal
hearing ability (Finneran et al., 2000, 2002; Schlundt et al., 2000).
As described in Finneran (2015), marine mammal studies have shown the
amount of TTS increases with the 24-hour cumulative sound exposure
level (SEL<INF>24</INF>) in an accelerating fashion: at low exposures
with lower SEL<INF>24</INF>, the amount of TTS is typically small and
the growth curves have shallow slopes. At exposures with higher
SEL<INF>24</INF>, the growth curves become steeper and approach linear
relationships with the sound exposure level (SEL).
Depending on the degree (elevation of threshold in dB), duration
(i.e., recovery time), and frequency range of TTS, and the context in
which it is experienced, TTS can have effects on marine mammals ranging
from discountable to more impactful (similar to those discussed in
auditory masking, below). For example, a marine mammal may be able to
readily compensate for a brief, relatively small amount of TTS in a
non-critical frequency range that takes place during a time when the
animal is traveling through the open ocean, where ambient noise is
lower and there are not as many competing sounds present.
Alternatively, a larger amount and longer duration of TTS sustained
during time when communication is critical for successful mother/calf
interactions could have more severe impacts. We note that reduced
hearing sensitivity as 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
[[Page 24825]]
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, and Yangtze finless porpoise
(Neophocoena asiaeorientalis) (Southall et al., 2019). For pinnipeds in
water, measurements of TTS are limited to harbor seals, elephant seals
(Mirounga angustirostris), bearded seals (Erignathus barbatus) and
California sea lions (Zalophus californianus) (Kastak et al., 1999,
2007; Kastelein et al., 2019b, 2019c, 2021, 2022a, 2022b; Reichmuth et
al., 2019; Sills et al., 2020). TTS was not observed in spotted (Phoca
largha) and ringed (Pusa hispida) seals exposed to single airgun
impulse sounds at levels matching previous predictions of TTS onset
(Reichmuth et al., 2016). These studies examine hearing thresholds
measured in marine mammals before and after exposure to intense or
long-duration sound exposures. The difference between the pre-exposure
and post-exposure thresholds can be used to determine the amount of
threshold shift at various post-exposure times.
The amount and onset of TTS depends on the exposure frequency.
Sounds below the region of best sensitivity for a species or hearing
group are less hazardous than those near the region of best sensitivity
(Finneran and Schlundt, 2013). At low frequencies, onset-TTS exposure
levels are higher compared to those in the region of best sensitivity
(i.e., a low frequency noise would need to be louder to cause TTS onset
when TTS exposure level is higher), as shown for harbor porpoises and
harbor seals (Kastelein et al., 2019a, 2019c). Note that in general,
harbor seals and harbor porpoises have a lower TTS onset than other
measured pinniped or cetacean species (Finneran, 2015). In addition,
TTS can accumulate across multiple exposures, but the resulting TTS
will be less than the TTS from a single, continuous exposure with the
same SEL (Mooney et al., 2009; Finneran et al., 2010; Kastelein et al.,
2014, 2015). This means that TTS predictions based on the total,
SEL<INF>24</INF> will overestimate the amount of TTS from intermittent
exposures, such as sonars and impulsive sources. Nachtigall et al.
(2018) describe measurements of hearing sensitivity of multiple
odontocete species (bottlenose dolphin, harbor porpoise, beluga, and
false killer whale (Pseudorca crassidens)) when a relatively loud sound
was preceded by a warning sound. These captive animals were shown to
reduce hearing sensitivity when warned of an impending intense sound.
Based on these experimental observations of captive animals, the
authors suggest that wild animals may dampen their hearing during
prolonged exposures or if conditioned to anticipate intense sounds.
Another study showed that echolocating animals (including odontocetes)
might have anatomical specializations that might allow for conditioned
hearing reduction and filtering of low-frequency ambient noise,
including increased stiffness and control of middle ear structures and
placement of inner ear structures (Ketten et al., 2021). Data available
on noise-induced hearing loss for mysticetes are currently lacking
(NMFS, 2024). Additionally, the existing marine mammal TTS data come
from a limited number of individuals within these species.
Relationships between TTS and AUD INJ thresholds have not been
studied in marine mammals, and there are no measured PTS data for
cetaceans, but such relationships are assumed to be similar to those in
humans and other terrestrial mammals. AUD INJ typically occurs at
exposure levels at least several dB above that inducing mild TTS (e.g.,
a 40-dB TS approximates AUD INJ onset (Kryter et al., 1966; Miller,
1974), while a 6-dB TS shift approximates TTS onset (Southall et al.,
2007, 2019). Based on data from terrestrial mammals, a precautionary
assumption is that the AUD INJ thresholds for impulsive sounds (such as
impact pile driving pulses as received close to the source) are at
least 6 dB higher than the TTS threshold on a peak-pressure basis and
AUD INJ cumulative SEL thresholds are 15 to 20 dB higher than TTS
cumulative SEL thresholds (Southall et al., 2007, 2019). Given the
higher level of sound or longer exposure duration necessary to cause
AUD INJ as compared with TTS, it is considerably less likely that AUD
INJ could occur.
Behavioral Effects--Exposure to noise (e.g., pile driving, DTH)
also has the potential to behaviorally disturb marine mammals to a
level that rises to the definition of harassment under the MMPA.
Generally speaking, NMFS considers a behavioral disturbance that rises
to the level of harassment under the MMPA a non-minor response--in
other words, not every response qualifies as behavioral disturbance,
and for responses that do, those of a higher level, or accrued across a
longer duration, have the potential to affect foraging, reproduction,
or survival. Behavioral disturbance may include a variety of effects,
including subtle changes in behavior (e.g., minor or brief avoidance of
an area or changes in vocalizations), more conspicuous changes in
similar behavioral activities, and more sustained and/or potentially
severe reactions, such as displacement from or abandonment of high-
quality habitat. Behavioral responses may include changing durations of
surfacing and dives, changing direction and/or speed; reducing/
increasing vocal activities; changing/cessation of certain behavioral
activities (such as socializing or feeding); eliciting a visible
startle response or aggressive behavior (such as tail/fin slapping or
jaw clapping); and avoidance of areas where sound sources are located.
In addition, pinnipeds may increase their haul out time, possibly to
avoid in-water disturbance (Thorson and Reyff, 2006).
Behavioral responses to sound are highly variable and context-
specific and any reactions depend on numerous intrinsic and extrinsic
factors (e.g., species, state of maturity, experience, current
activity, reproductive state, auditory sensitivity, time of day), as
well as the interplay between factors (e.g., Richardson et al., 1995;
Wartzok et al., 2004; Southall et al., 2007, 2019; Weilgart, 2007;
Archer et al., 2010). Behavioral reactions can vary not only among
individuals but also within an individual, depending on previous
experience with a sound source, context, and numerous other factors
(Ellison et al., 2012), and can vary depending on characteristics
associated with the sound source (e.g., whether it is moving or
stationary, number of sources, distance from the source). In general,
pinnipeds seem more tolerant of, or at least habituate more quickly to,
potentially disturbing underwater sound than do cetaceans, and
generally seem to be less responsive to exposure to industrial sound
than most cetaceans. Please see Appendices B and C of Southall et al.
(2007) and Gomez et al. (2016), respectively, 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
[[Page 24826]]
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 (e.g., Richardson et al., 1995;
Morton and Symonds, 2002; Nowacek et al., 2007; Southall et al. 2023,
2024, 2025, 2026).
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; Southall et al., 2022, 2023, 2024, 2025).
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. However, during controlled exposure
experiments to very low-frequency sound produced by a marine vibrator,
Southall et al. (2026) observed that blue whales engaged in intensive
foraging in a dense prey field did not display broadscale avoidance
behavior compared to conspecifics engaged in different behaviors (i.e.,
opportunistic foraging in a more diffuse prey field). As for other
types of behavioral response, the frequency, duration, and temporal
pattern of signal presentation, as well as differences in species
sensitivity, are likely contributing factors to differences in response
in any given circumstance (e.g., Croll et al., 2001; Nowacek et al.,
2004; Madsen et al., 2006; Yazvenko et al., 2007). A determination of
whether foraging disruptions incur fitness consequences would require
information on or estimates of the energetic requirements of the
affected individuals and the relationship between prey availability,
foraging effort and success, and the life history stage of the animal.
Respiration rates vary naturally with different behaviors and
alterations to breathing rate as a function of acoustic exposure can be
expected to co-occur with other behavioral reactions, such as a flight
response or an alteration in diving. However, respiration rates in and
of themselves may be representative of annoyance or an acute stress
response. Various studies have shown that respiration rates may either
be unaffected or could increase, depending on the species and signal
characteristics, again highlighting the importance in understanding
species differences in the tolerance of underwater noise when
determining the potential for impacts resulting from anthropogenic
sound exposure (e.g., Kastelein et al., 2001; 2005; 2006; Gailey et
al., 2007). For example, harbor porpoise respiration rates increased in
response to pile driving sounds at and above a received broadband SPL
of 136 dB (zero-peak SPL: 151 dB re 1 [mu]Pa; SEL of a single strike
(SEL<INF>ss</INF>): 127 dB re 1 [mu]Pa\2\-s) (Kastelein et al., 2013).
Avoidance is the displacement of an individual from an area or
migration path as a result of the presence of a sound or other
stressors, and is one of the most obvious manifestations of disturbance
in marine mammals (Richardson et al., 1995). For example, gray whales
(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,
and minke whales have demonstrated avoidance in response to vessels
during line transect surveys (Palka and Hammond, 2001). In addition,
beluga whales in the St. Lawrence Estuary in Canada have been reported
to increase levels of avoidance with increased boat presence by way of
increased dive durations and swim speeds, decreased surfacing
intervals, and by bunching together into groups (Blane and Jaakson,
1994). Avoidance may be short-term, with animals returning to the area
once the noise has ceased (e.g., Bowles et al., 1994; Goold, 1996;
Stone et al., 2000; Morton and Symonds, 2002; Gailey et al., 2007).
Longer-term displacement is possible, however, which may lead to
changes in abundance or distribution patterns of the affected species
in the affected region if habituation to the presence of the sound does
not occur (e.g., Blackwell et al., 2004; Bejder et al., 2006; Teilmann
et al., 2006).
A flight response is a dramatic change in normal movement to a
directed and rapid movement away from the perceived location of a sound
source.
[[Page 24827]]
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 flight response induced by perception of a
predator's acoustic signal could range from brief, temporary exertion
and displacement from the area to, in extreme cases, marine mammal
strandings (e.g., England et al., 2001). However, it should be noted
that response to a perceived predator does not necessarily invoke
flight (e.g., Ford and Reeves, 2008; Southall et al., 2026), and
whether individuals are solitary or in groups may influence the
response (Southall et al., 2024).
Behavioral disturbance can also impact marine mammals in more
subtle ways. Increased vigilance may result in costs related to
diversion of focus and attention (i.e., when a response consists of
increased vigilance, it may come at the cost of decreased attention to
other critical behaviors such as foraging or resting). These effects
have generally not been demonstrated for marine mammals, but studies
involving fishes and terrestrial animals have shown that increased
vigilance may substantially reduce feeding rates (e.g., Beauchamp and
Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). In
addition, chronic disturbance can cause population declines through
reduction of fitness (e.g., decline in body condition) and subsequent
reduction in reproductive success, survival, or both (e.g., Harrington
and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). However,
Ridgway et al. (2006) reported that increased vigilance in bottlenose
dolphins exposed to sound over a 5-day period did not cause any sleep
deprivation or stress effects.
Many animals perform vital functions, such as feeding, resting,
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption
of such functions resulting from reactions to stressors such as sound
exposure are more likely to be significant if they last more than one
diel cycle or recur on subsequent days (Southall et al., 2007).
Consequently, a behavioral response lasting less than 1 day and not
recurring on subsequent days is not considered particularly severe
unless it could directly affect reproduction or survival (Southall et
al., 2007). Note that there is a difference between multi-day
substantive (i.e., meaningful) behavioral reactions and multi-day
anthropogenic activities. For example, just because an activity lasts
for multiple days does not necessarily mean that individual animals are
either exposed to activity-related stressors for multiple days or,
further, exposed in a manner resulting in sustained multi-day
substantive behavioral responses.
Physiological stress responses--An animal's perception of a threat
may be sufficient to trigger stress responses consisting of some
combination of behavioral responses, autonomic nervous system
responses, neuroendocrine responses, or immune responses (e.g., Selye,
1950; Moberg, 2000). In many cases, an animal's first and sometimes
most economical (in terms of energetic costs) response is behavioral
avoidance of the potential stressor. Autonomic nervous system responses
to stress typically involve changes in heart rate, blood pressure, and
gastrointestinal activity. These responses have a relatively short
duration and may or may not have a significant long-term effect on an
animal's fitness.
Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that
are affected by stress, including immune competence, reproduction,
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been
implicated in failed reproduction, altered metabolism, reduced immune
competence, and behavioral disturbance (e.g., Moberg, 1987; Blecha,
2000). Increases in the circulation of glucocorticoids are also equated
with stress (Romano et al., 2004).
The primary distinction between stress (which is adaptive and does
not normally place an animal at risk) and ``distress'' is the cost of
the response. During a stress response, an animal uses glycogen stores
that can be quickly replenished once the stress is alleviated. In such
circumstances, the cost of the stress response would not pose serious
fitness consequences. However, when an animal does not have sufficient
energy reserves to satisfy the energetic costs of a stress response,
energy resources must be diverted from other functions. This state of
distress will last until the animal replenishes its energetic reserves
sufficient to restore normal function.
Relationships between these physiological mechanisms, animal
behavior, and the costs of stress responses are well-studied through
controlled experiments and for both laboratory and free-ranging animals
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003;
Krausman et al., 2004; Lankford et al., 2005; Ayres et al., 2012; Yang
et al., 2022). Stress responses due to exposure to anthropogenic sounds
or other stressors and their effects on marine mammals have also been
reviewed (Fair and Becker, 2000; Romano et al., 2002b) and, more
rarely, studied in wild populations (e.g., Romano et al., 2002a). For
example, Rolland et al. (2012) found that noise reduction from reduced
ship traffic in the Bay of Fundy was associated with decreased stress
in North Atlantic right whales. In addition, Lemos et al. (2022)
observed a correlation between higher levels of fecal glucocorticoid
metabolite concentrations (indicative of a stress response) and vessel
traffic in gray whales. Yang et al. (2022) studied behavioral and
physiological responses in captive bottlenose dolphins exposed to
playbacks of ``pile-driving-like'' impulsive sounds, finding
significant changes in cortisol and other physiological indicators but
only minor behavioral changes. These and other studies lead to a
reasonable expectation that some marine mammals will experience
physiological stress responses upon exposure to acoustic stressors and
that it is possible that some of these would be classified as
``distress.'' In addition, any animal experiencing TTS would likely
also experience stress responses (NRC, 2005), however distress is an
unlikely result of this project based on observations of marine mammals
during previous, similar construction projects.
Vocalizations and Auditory Masking--Since many marine mammals rely
on sound to find prey, moderate social interactions, and facilitate
mating (Tyack, 2008), noise from anthropogenic sound sources can
interfere with these functions, but only if the noise spectrum overlaps
with the hearing sensitivity of the receiving marine mammal (Southall
et al., 2007; Clark et al., 2009; Hatch et al., 2012). Chronic exposure
to excessive, though not high-intensity, noise could cause masking at
particular frequencies for marine mammals that utilize sound for vital
biological functions (Clark et al., 2009). Acoustic masking is when
other noises such as from human sources interfere with an animal's
ability to detect, recognize, or discriminate between acoustic signals
of interest (e.g., those used for intraspecific communication and
social interactions, prey detection, predator avoidance, navigation)
(Richardson et al., 1995; Erbe et al., 2016). Therefore, under certain
circumstances, marine mammals whose acoustical sensors or
[[Page 24828]]
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 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 (e.g.,
Bowles et al., 1994; Wisniewska et al., 2018; Southall et al., 2026).
Under certain circumstances, marine mammals experiencing
significant masking could also be impaired from maximizing their
performance fitness in survival and reproduction. For example, King et
al. (2022) observed that bottlenose dolphins attempting to vocally
coordinate accomplishing a joint task could not overcome masking by
typical compensatory mechanisms (e.g., increasing whistle amplitude or
duration), thus, cooperative task success decreased in the presence of
noise. 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. Pile driving
sound energy is distributed over a broad frequency spectrum, within the
hearing range of marine mammals that may occur 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 75 days and 57 days in the Year 1
and Year 2 effective periods, respectively, 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.
Airborne Acoustic Effects--Phocid pinnipeds (i.e., seals) 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 seals that
are swimming or hauled out near the project site within the range of
noise levels elevated above airborne acoustic harassment criteria.
Although seals are known to haul out regularly on man-made objects
(e.g., pier), we believe that incidents of take resulting solely from
airborne sound are unlikely given the proximity of the proposed project
area to local haul-out sites, which we assume would be preferred
habitat. We do not anticipate that cetaceans would be exposed to
airborne sounds that would result in harassment, as defined under the
MMPA.
We recognize that seals 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
[[Page 24829]]
would cause behavioral responses similar to those discussed above in
relation to underwater sound. For instance, anthropogenic sound could
cause hauled-out seals to exhibit changes in their normal behavior,
such as reduction in vocalizations, or cause them to flush from haul-
out sites, temporarily abandon the area, and or move further from the
source. However, these animals would previously have been `taken'
because of exposure to underwater 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 seals 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 near 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 near-shore 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 extraction 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 because of in-water construction activities. Most of this
effect would occur during installation and extraction of piles, which
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 and
Hastings, 2009). Several studies have demonstrated that impulse sounds
might affect the distribution and behavior of some fishes, potentially
impacting foraging opportunities or increasing energetic costs (e.g.,
Fewtrell and McCauley, 2012; Pearson et al., 1992; Skalski et al.,
1992; Santulli et al., 1999; Paxton et al., 2017). However, some
studies have shown no or slight reaction to impulse sounds (e.g.,
Pe[ntilde]a et al., 2013; Wardle et al., 2001; Jorgenson and Gyselman,
2009; Cott et al., 2012). More commonly, though, the impacts of noise
on fishes are temporary.
SPLs of sufficient strength have been known to cause injury to
fishes and fish mortality (summarized in Popper et al., 2014). However,
in most fish species, hair cells in the ear continuously regenerate and
loss of auditory function is likely restored when damaged cells are
replaced with new cells. Halvorsen et al. (2012b) showed that a TTS of
4 to 6 dB was recoverable within 24 hours for one species. Impacts
would be most severe when the individual fish is close to the source
and when the duration of exposure is long. Injury caused by barotrauma
can range from slight to severe and can cause death and is most likely
for fish with swim bladders. Barotrauma injuries have been documented
during controlled exposure
[[Page 24830]]
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 extraction. The frequency range in which fishes
generally perceive underwater sounds is 50 to 2,000 Hz, with peak
sensitivities below 800 Hz (Popper and Hastings, 2009). Fish behavior
or distribution may change, especially with strong and/or intermittent
sounds that could harm fishes. High underwater SPLs have been
documented to alter behavior, cause hearing loss, and injure or kill
individual fish by causing serious internal injury (Hastings and
Popper, 2005).
Zooplankton is a food source for several marine mammal species, as
well as a food source for fish that are then preyed upon by marine
mammals. Population effects on zooplankton could have indirect effects
on marine mammals. Data are limited on the effects of underwater sound
on zooplankton species, particularly sound from construction (Erbe et
al., 2019). Popper and Hastings (2009) reviewed information on the
effects of human-generated sound and concluded that no substantive data
are available on whether the sound levels from pile driving, seismic
activity, or any human-made sound would have physiological effects on
invertebrates. Any such effects would be limited to the area very near
(1 to 5 m) the sound source and would result in no population effects
because of the relatively small area affected at any one time and the
reproductive strategy of most zooplankton species (short generation,
high fecundity, and very high natural mortality). No adverse impact on
zooplankton populations is expected to occur from the specified
activity due in part to large reproductive capacities and naturally
high levels of predation and mortality of these populations. Any
mortalities or impacts that might occur would be negligible.
The greatest potential impact to marine mammal prey during
construction would occur during impact pile driving, vibratory pile
driving and extraction, and DTH excavation. However, the duration of
impact pile driving would be limited to the final stage of installation
(``proofing'') after the pile has been driven as close as practicable
to the design depth with a vibratory driver. In-water construction
activities would only occur during daylight hours, allowing fish to
forage and transit the project area in the evening. Vibratory pile
driving could 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 relatively low-quality
habitat, given it is already highly developed and regularly 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 extraction of many in-water piles would be temporary and
intermittent. The total seafloor area affected by pile installation and
extraction 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 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 IHAs, which will inform NMFS'
consideration of ``small numbers,'' the negligible impact
determinations, and impacts on subsistence uses.
Harassment is the only type of take expected to result from these
activities. Except with respect to certain activities not pertinent
here, section 3(18) of the MMPA defines ``harassment'' as any act of
pursuit, torment, or annoyance, which (i) has the potential to injure a
marine mammal or marine mammal stock in the wild (Level A harassment);
or (ii) has the potential to disturb a marine mammal or marine mammal
stock in the wild by causing disruption of behavioral patterns,
including, but not limited to, migration, breathing, nursing, breeding,
feeding, or sheltering (Level B harassment).
Authorized takes would primarily be by Level B harassment, as use
of the acoustic sources (i.e., impact pile driving, vibratory
installation and extraction, DTH excavation) has the potential to
result in disruption of behavioral patterns for individual marine
mammals. There is also some potential for Level A harassment (AUD INJ/
PTS) to result, primarily for harbor porpoises and seals, because
predicted AUD INJ zones are larger for these species than the analogous
zones for dolphins, and harbor porpoises and seals are smaller and,
thus, can be more difficult to sight. However, the proposed mitigation
and monitoring measures are expected to minimize the severity of the
taking to the extent practicable.
As described previously, no serious injury or mortality is
anticipated or proposed to be authorized for this activity. Below we
describe how the proposed take numbers are estimated.
For acoustic impacts, generally speaking, we estimate take by
considering: (1) acoustic criteria above which NMFS believes there is
some reasonable potential for marine mammals to be behaviorally
harassed or incur some degree of AUD INJ; (2) the area or volume of
water that will be ensonified above these levels in a day; (3) the
density or occurrence of marine mammals within these ensonified areas;
and, (4) the number of days of activities. We note that while these
factors can contribute to a basic calculation to provide an initial
prediction of potential takes, additional information that can
[[Page 24831]]
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. 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.
Navy's proposed activity includes the use of continuous (i.e.,
vibratory pile driving and DTH drilling) and impulsive (i.e., impact
pile driving and DTH hammering) sources, therefore the RMS SPL
thresholds of 120 and 160 dB re 1 [mu]Pa, respectively, are applicable
when assessing the potential for Level B harassment.
Level A harassment--NMFS' 2024 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) as a result of exposure
to noise from two different types of sources (impulsive or non-
impulsive) for five different underwater marine mammal groups (based on
hearing sensitivity) (table 4). Navy's proposed activity includes the
use of impulsive (impact pile driving and DTH hammering) and non-
impulsive (vibratory pile driving and DTH drilling) sources. The 2024
Updated Technical Guidance criteria include both updated thresholds and
updated weighting functions for each hearing group (table 4). These
thresholds criteria thresholds are provided in the table below. The
references, analysis, and methodology used in the development of the
criteria thresholds, as well as the detailed description of the updated
weighting functions, are described in NMFS' 2024 Updated Technical
Guidance, which may be accessed at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools</a>.
Table 4--Thresholds Identifying the Onset of Auditory Injury (AUD INJ)
----------------------------------------------------------------------------------------------------------------
AUD INJ onset thresholds * (received level)
Hearing group ------------------------------------------------------------------------
Impulsive Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans........... Cell 1: L0-pk,flat: 222 Cell 2: LE, LF,24h: 197 dB.
dB; LE, LF,24h: 183 dB.
High-Frequency (HF) Cetaceans.......... Cell 3: L0-pk,flat: 230 Cell 4: LE, HF,24h: 201 dB.
dB; LE, HF,24h: 193 dB.
Very High-Frequency (VHF) Cetaceans.... Cell 5: L0-pk,flat: 202 Cell 6: LE, VHF,24h: 181 dB.
dB; LE,VHF,24h: 159 dB.
Phocid Pinnipeds (PW) (Underwater)..... Cell 7: L0-pk,flat: 223 Cell 8: LE,PW,24h: 195 dB.
dB; LE,PW,24h: 183 dB.
Otariid Pinnipeds (OW) (Underwater).... Cell 9: L0-pk,flat: 230 Cell 10: LE,OW,24h: 199 dB.
dB; LE,OW,24h: 185 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating AUD
INJ onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds
associated with impulsive sounds, these thresholds are recommended for consideration.
Note: Peak sound pressure level (L0-pk) has a reference value of 1 [micro]Pa, and weighted cumulative sound
exposure level (LE,) has a reference value of 1[micro]Pa\2\s. In this table, thresholds are abbreviated to be
more reflective of International Organization for Standardization standards (ISO 2017). The subscript ``flat''
is being included to indicate peak sound pressure are flat weighted or unweighted within the generalized
hearing range of marine mammals (i.e., 7 Hz to 165 kHz). The subscript associated with cumulative sound
exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, HF, and VHF
cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The weighted
cumulative sound exposure level thresholds could be exceeded in a multitude of ways (i.e., varying exposure
levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the
conditions under which these thresholds will be exceeded.
As described previously, DTH systems have both continuous, non-
impulsive, and impulsive components as discussed in the Description of
Sound Sources section above. When evaluating Level B harassment, NMFS
recommends treating DTH as a continuous source and applying RMS SPL
thresholds of 120 dB re 1 [mu]Pa. When evaluating Level A harassment,
NMFS recommends treating DTH as an impulsive source, applying the
thresholds in the second column of table 4. NMFS (2022) guidance on DTH
systems recommends source levels for DTH systems (<a href="https://media.fisheries.noaa.gov/2022-11/PUBLIC%20DTH%20Basic%20Guidance_November%202022.pdf">https://media.fisheries.noaa.gov/2022-11/PUBLIC%20DTH%20Basic%20Guidance_November%202022.pdf</a>). NMFS has applied
those
[[Page 24832]]
levels in our analysis (see table 5 for NMFS' proposed source levels)
of potential acoustic impacts from the DTH excavation that might be
required to complete installation of a small number of piles.
Ensonified Area
Here, we describe operational and environmental parameters of the
activity that are used in estimating the area ensonified above the
acoustic thresholds, including source levels and transmission loss
coefficient.
The sound field in the project area is the existing background
noise plus additional construction noise from the proposed project.
Marine mammals are expected to be affected via sound generated by the
primary components of the project (i.e., vibratory pile driving and
extraction, impact pile driving, DTH).
Source levels for vibratory pile installation and extraction,
impact pile driving, and DTH are based on reviews of measurements of
the same or similar types and dimensions of pile available in the
literature. Source levels for vibratory installation and extraction of
the 18-in template steel pipe piles are assumed equal. Table 5 presents
source levels for in-water construction activities, which apply to both
Year 1 and Year 2.
Table 5--Source Levels for Proposed Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Peak SPL (dB
Pile type Installation/extraction re 1 RMS SPL (dB re SEL (dB re 1 Reference
method [micro]Pa) 1 [micro]Pa) [micro]Pa 2-s)
--------------------------------------------------------------------------------------------------------------------------------------------------------
18'' Steel Pipe (permanent)............. DTH (Level A)............. 172 N/A 146 NMFS 2022.
DTH (Level B)............. N/A 167 N/A NMFS 2022.
Impact.................... 203 190 177 Caltrans 2020.
Vibratory................. N/A 158 N/A Caltrans 2020.
18'' Steel pipe pile (temporary/ Vibratory................. N/A 158 N/A Caltrans 2020.
template).
18'' Steel Sheet (permanent)............ Impact.................... 205 190 180 Caltrans 2015.
Vibratory................. N/A 160 N/A Caltrans 2015.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Transmission loss (TL) is the decrease in acoustic intensity as an
acoustic pressure wave propagates out from a source in the acoustic
field. TL parameters vary with frequency, temperature, sea conditions,
current, source and receiver depth, water depth, water chemistry, and
bottom composition and topography. The general formula for underwater
TL is:
TL = B x Log10 (R<INF>1</INF>/R<INF>2</INF>),
Where:
TL = transmission loss in dB
B = transmission loss coefficient
R<INF>1</INF> = the distance of the modeled SPL from the driven
pile, and
R<INF>2</INF> = the distance from the driven pile of the initial
measurement
Absent site-specific acoustical monitoring with differing measured
TL, a practical spreading loss value of 15 is used as the TL
coefficient in the above formula for nearshore environments. Site-
specific TL data for Coddington Cove are not available; therefore, the
default coefficient of 15 is used to determine the distances to the
Level A harassment and Level B harassment thresholds.
The TL model described above was used to calculate the expected
noise propagation from impact pile driving, vibratory pile driving and
extraction, and DTH excavation using representative source levels to
estimate the harassment zones or area exceeding the noise criteria,
resulting in the maximum distances to the Level B harassment isopleths
shown in table 6. Using these maximum distance values, the areas
ensonified above the Level B harassment thresholds were calculated and
truncated to account for landmass interference, where applicable, using
a Geographic Information System. Sound source locations were chosen to
model the greatest possible affected areas from a representative
notional pile location. For both Year 1 and Year 2, the largest
calculated distance to the Level B harassment isopleth is 13,594 m,
which would be produced during DTH excavation of the 18-in steel pipe
piles and would result in a 580.26 square kilometer ensonified area.
However, when accounting for attenuation from landmass interference,
activities in Year 1 would generate an estimated maximum Level B
harassment ensonified area of approximately 6.37 km\2\ in Year 1 and
9.67 km\2\ in Year 2 (tables 6-9). Although the Navy would install the
same pile types and sizes using the same methods both years, the
ensonified zone sizes differ because the bulkheads are located at
different sites, thus, sound propagation would be differentially
intercepted by land (figure 1).
The ensonified area associated with Level A harassment (AUD INJ) is
more technically challenging to predict due to the need to account for
a duration component. Therefore, NMFS developed an optional User
Spreadsheet tool to accompany the 2024 Updated Technical Guidance that
can be used to predict an isopleth distance for use in conjunction with
marine mammal density or occurrence to help predict potential takes. We
note that because of some of the assumptions included in the methods
underlying this optional tool, we anticipate that the resulting
isopleth estimates are typically going to be overestimates of some
degree, which may result in an overestimate of potential take by Level
A harassment (AUD INJ). However, this optional tool offers the best way
to estimate isopleth distances when more sophisticated modeling methods
are not available or practical. For stationary sources such as pile
driving and DTH, the optional User Spreadsheet tool predicts the
distance at which, if a marine mammal remained at that distance for the
duration of the activity, it would be expected to incur AUD INJ, which
includes but is not limited to PTS.
The Navy used NMFS' 2024 Updated Technical Guidance and optional
User Spreadsheet to calculate the maximum distances to Level A
harassment (AUD INJ onset) thresholds for all in-water construction
activities in Year 1 and Year 2 (i.e., impact pile driving, vibratory
installation and extraction, and DTH excavation). Inputs used in the
optional User Spreadsheet tool include values in table 1 (e.g., number
of piles per day, duration, and/or strikes per pile) and table 5 (i.e.,
source levels). Sound source locations were chosen to model the
greatest possible affected area from the representative notional pile
location. The resulting estimated distances to Level A harassment
threshold isopleths and total ensonified areas are reported below in
tables 6 and 7 for Bulkhead S50S/LNG activities (Year 1) and tables 8
and 9 for Bulkhead
[[Page 24833]]
499 activities (Year 2). As described for the maximum calculated areas
based on the Level B harassment isopleths, areas ensonified above the
Level A harassment thresholds were calculated and truncated to account
for landmass interference, where applicable (tables 6-9).
Table 6--Year 1 Bulkhead S50S/LNG Calculated Maximum Distances to Harassment Thresholds From Impulsive Underwater Sound
[Impact pile driving and DTH mono-hammer component]
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Level A (AUD INJ) harassment Level B
------------------------------------------------------------ (behavioral)
HF cetacean VHF cetacean Phocid harassment
-------------------------------------------------------------------------------
All marine mammals
Total Maximum distance Maximum distance Maximum distance -------------------
Structure Pile size and type Activity production to 193 dB SELcum to 159 dB SELcum to 183 dB SELcum Maximum distance
days threshold (m)/ threshold (m)/ threshold (m)/ 160 dB RMS SPL
area of harassment area of harassment area of harassment (120 dB DTH)
zone (sq km) zone (sq km) zone (sq km) threshold (m)/
area of harassment
zone (sq km) *
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Bulkhead S50S/LNG....................... 18-in Steel Sheet Pile Impact Install............ 15 209.8/0.09092 2,545.1/3.7036 1,461/1.856 1,000/0.9718
(permanent).
18-in Steel Pipe Pile Impact Install............ 15 202.2/0.06965 2,452.0/2.957 1,407.6/1.4031 1,000/0.9718
(permanent).
18'' Steel Pipe Pile Mono-hammer DTH........... 11 16.5/0.000647 199.6/0.06104 114.6/0.02866 13,594/6.3678
(template, temporary).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* The calculated area based on the maximum distance to the harassment isopleth from the Bulkhead S50S/LNG location is truncated due to land interference, resulting in a maximum ensonified zone
of approximately 6.37 km\2\ in Year 1.
Table 7--Year 1 Bulkhead S50S/LNG Calculated Maximum Distances to Harassment Thresholds From Non-Impulsive Underwater Sound
[Vibratory pile driving/extracting, DTH continuous component]
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Level A (AUD INJ) harassment Level B
------------------------------------------------------------ (behavioral)
HF cetacean VHF cetacean Phocid harassment
-------------------------------------------------------------------------------
Total All marine mammals
Structure Pile size and type Activity production Maximum distance Maximum distance Maximum distance -------------------
days to 201 dB SELcum to 181 dB SELcum to 195 dB SELcum Maximum distance
threshold (m)/ threshold (m)/ threshold (m)/ 120 dB RMS SPL
area of harassment area of harassment area of harassment threshold (m)/
zone (sq km) zone (sq km) zone (sq km) area of harassment
zone (sq km) *
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Bulkhead S50S/LNG....................... 18-in Steel Sheet Pile Vibratory Install......... 15 7.7/0.00015 16.3/0.00065 25.7/0.00168 4,641.6/6.3678
(permanent).
18-in Steel Pipe Pile Vibratory Install......... 15 5.6/0.000078 12/0.000346 18.9/0.000852 3,415/4.35
(permanent).
18'' Steel Pipe Pile Vibratory Installation/ 34 3.5/0.000033 7.5/0.000138 11.9/0.000341 3,415/4.35
(template, temporary). Extraction.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* The calculated area based on the maximum distance to the harassment isopleth from the Bulkhead S50S/LNG location is truncated due to land interference, resulting in a maximum ensonified zone
of approximately 6.37 km\2\ in Year 1.
Table 8--Year 2 Bulkhead S499 Calculated Maximum Distances to Harassment Thresholds From Impulsive Underwater Sound
[Impact pile driving and DTH mono-hammer component]
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Level A (AUD INJ) harassment Level B
------------------------------------------------------------ (behavioral)
HF cetacean VHF cetacean Phocid harassment
-------------------------------------------------------------------------------
Total All marine mammals
Structure Pile size and type Activity production Maximum distance Maximum distance Maximum distance -------------------
days to 201 dB SELcum to 181 dB SELcum to 195 dB SELcum Maximum distance
threshold (m)/ threshold (m)/ threshold (m)/ 120 dB RMS SPL
area of harassment area of harassment area of harassment threshold (m)/
zone (sq km) zone (sq km) zone (sq km) area of harassment
zone (sq km) *
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Bulkhead S499........................... 18-in Steel Sheet Pile Impact Install............ 11 209.8/0.09092 2,545/4.706 1,461.0/2.813 1,000/1.69
(permanent).
18-in Steel Pipe Pile Impact Install............ 11 202.2/0.0819 2,452/4.177 1,407.6/2.21816 1,000/1.69
(permanent).
[[Page 24834]]
18'' Steel Pipe Pile Mono-hammer DTH........... 9 16.5/0.000634 199.6/0.07893 114.6/0.027161 13,594/9.4398
(template, temporary).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* The calculated area based on the maximum distance to the harassment isopleth from the Bulkhead S499 location is truncated due to land interference, resulting in a maximum ensonified zone of
approximately 9.44 km\2\ in Year 2.
Table 9--Year 2 Bulkhead S499 Calculated Maximum Distances to Harassment Thresholds From Non-Impulsive Underwater Sound
[Vibratory pile driving/extracting, DTH continuous component]
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Level A (AUD INJ) harassment Level B
------------------------------------------------------------ (behavioral)
HF cetacean VHF cetacean Phocid harassment
-------------------------------------------------------------------------------
Total All marine mammals
Structure Pile size and type Activity production Maximum distance Maximum distance Maximum distance -------------------
days to 201 dB SELcum to 181 dB SELcum to 195 dB SELcum Maximum distance
threshold (m)/ threshold (m)/ threshold (m)/ 120 dB RMS SPL
area of harassment area of harassment area of harassment threshold (m)/
zone (sq km) zone (sq km) zone (sq km) area of harassment
zone (sq km) *
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Bulkhead S499........................... 18-in Steel Sheet Pile Vibratory Install......... 11 7.7/0.000186 16.3/0.000651 25.7/0.001573 4,641.6/9.43
(permanent).
18-in Steel Pipe Pile Vibratory Install......... 11 5.6/0.000078 12/0.000346 18.9/0.000852 3,415/4.35
(permanent).
18'' Steel Pipe Pile Vibratory Installation/ 26 3.5/0.000033 7.5/0.000138 11.9/0.000341 3,415/4.35
(template, temporary). Extraction.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* The calculated area based on the maximum distance to the harassment isopleth from the Bulkhead S499 location is truncated due to land interference, resulting in a maximum ensonified zone of
approximately 9.44 km\2\ in Year 2.
For a given activity (e.g., pile driving), Level A harassment zones
are typically smaller than Level B harassment zones. However, in rare
cases, the maximum calculated distance to the Level A harassment
threshold isopleth is greater than the maximum calculated distance to
the Level B harassment threshold isopleth (e.g., values for impact pile
driving of 18-inch steel pipe piles in Year 2 for very high-frequency
(VHF) cetaceans and phocids (PW)) (table 8). Calculations of Level A
harassment isopleths include a duration component that, in the case of
impact pile driving and DTH methods, is estimated through the total
number of expected daily strikes within a 24-hour period and the
associated pulse duration. When analyzing potential acoustic impacts
for a stationary sound source such as impact pile driving or DTH, we
assume that an animal would be exposed to all of the strikes expected
for that activity within that 24-hour period. In contrast, calculation
of Level B harassment isopleths does not include a duration component.
Due to differences in the parameters that characterize each form of
harassment, it is assumed that Level B harassment occur instantaneously
rather than building through exposure to a series of hammer strikes
over a longer duration. Thus, depending on the duration included in the
calculation, the calculated radii to Level A harassment isopleths can
be larger than the calculated radii to the Level B harassment isopleth
for the same activity.
Marine Mammal Occurrence and Take Estimation
In this section, we provide information about the occurrence of
marine mammals, including density or other relevant information that
will inform the take calculations.
Marine Mammal Occurrence
Potential exposures to construction noise for each acoustic
threshold were estimated using marine mammal density estimates from the
Navy Marine Species Density Database (NMSDD) (Navy, 2017a) (table 10).
Monthly densities of species were evaluated in terms of minimum,
maximum, and average annual densities within Narragansett Bay. Average
densities were used for all cetaceans. The average densities were
calculated using all data records provided for each cetacean, where
density survey data was available over a 12-month survey period.
The NMSDD models densities for harbor and gray seals as a harbor-
gray seal guild due to difficulty in distinguishing these two species
at sea. Given records of its year-round occurrence in Narragansett Bay,
the harbor seal is expected to be the most commonly occurring phocid
pinniped
[[Page 24835]]
species in the project area (Kenney and Vigness-Raposa, 2010); thus,
take estimation for the harbor seal incorporates the maximum (i.e.,
versus minimum or average) density estimate for the harbor-gray seal
guild. Based on stranding records, gray seals are the second most
commonly occurring phocid species in Rhode Island waters and,
particularly during spring and early summer and occasionally during
other months of the year (Kenney, 2020). Therefore, the average density
for the pooled harbor-gray seal guild was used for gray seal take
estimation.
Unlike the pooled harbor-gray seal density model, the NMSDD
includes models specific to the hooded seal and the harp seal that are
separate from each other (and from the pooled harbor-gray seal density
model). Both species are considered only occasional visitors in
Narragansett Bay. Sightings of either species, either live or stranded,
are considered rare--particularly compared to harbor and gray seal
sighting frequencies (Kenney, 2015). Thus, take estimation for the
hooded seal considers only the minimum density estimate available for
the hooded seal density model (versus the average or maximum).
Similarly, take estimation for the harp seal considers only the minimum
density estimate available for the harp seal density model (versus the
average or maximum).
Table 10--Densities Used in Exposure Analysis, by Species
----------------------------------------------------------------------------------------------------------------
Density model output used Density in
Density model strategy for for take estimation project area
Species species (individual or (minimum, average, or (species per
grouped) maximum) km\2\)
----------------------------------------------------------------------------------------------------------------
Atlantic white-sided dolphin............ Individual................ Average................... 0.003
Common dolphin.......................... Individual................ Average................... 0.011
Harbor porpoise......................... Individual................ Average................... 0.012
Harbor seal \1\......................... Grouped................... Maximum................... 0.623
Gray seal \1\........................... Average................... 0.131
Harp seal \2\........................... Individual................ Minimum................... 0.05
Hooded seal \2\......................... Individual................ Minimum................... 0.001
----------------------------------------------------------------------------------------------------------------
\1\ The NMSDD models density (i.e., minimum, average, and maximum estimates) for harbor and gray seals as a
combined harbor-gray seal guild, due to difficulty in distinguishing these two species at sea. Harbor seals
are more common than gray seals in Narragansett Bay; thus, of the three density estimates produced by the
model, take estimation used the maximum and average density estimates for harbor and gray seals, respectively.
\2\ Harp seal occurrence in Narragansett Bay is rare, thus, take estimation is based on the minimum density
estimate produced by the density model for this species. For the same reason, this approach was used for the
hooded seal, another infrequent visitor to Narragansett Bay.
Take Estimation
Here we describe how the information provided above is synthesized
to produce a quantitative estimate of the take that is reasonably
likely to occur and proposed for authorization.
For each species, Navy multiplied the density (N) by the largest
ensonified area (tables 6-9) and the maximum days of activity (table 1)
(take estimate = N x ensonified area x days of pile driving/extraction
and DTH) in order to calculate estimated take by Level A harassment and
Level B harassment. The Navy used the pile type, size, and construction
method that produce the largest isopleth to estimate exposure of marine
mammals to noise impacts. The exposure estimate was rounded to the
nearest whole number at the end of the calculation. Estimated exposures
by activity type for each species are shown in table 6-12 in the
application.
For each species, tables 11 and 12 show the total requested number
of takes by Level A harassment and Level B harassment for all
activities for Year 1 and Year 2, respectively. For Year 1, the Navy is
requesting incidental take by Level B harassment of 7 species (Atlantic
white-sided dolphin, common dolphin, harbor porpoise, harbor seal, gray
seal, harp seal, and hooded seal) and 5 species (harbor porpoise and
all phocid species) by Level A harassment. When determining sufficient
numbers of take to request for authorization (relative to the number
estimated through exposure analysis), the Navy increased the estimated
take by Level B harassment for Atlantic white-sided dolphins from 2 to
16 takes in Year 1 and Year 2, as the estimated take was less than the
documented average group size (NUWC, 2017). A similar adjustment was
made for common dolphins, resulting in an increase from estimated to
requested take by Level B harassment from 5 to 30 takes in Year 1 and
Year 2. NMFS concurs with the Navy's approach and, for each IHA, is
proposing to authorize 16 takes of Atlantic white-sided dolphins by
Level B harassment and 30 takes of common dolphins by Level B
harassment.
Table 11--Proposed Take by Stock and Harassment Type and as a Percentage of Stock Abundance
[Year 1]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Proposed Proposed take
Species name Stock Stock Level A (AUD Level B maximum annual as percentage
abundance INJ/PTS) (behavioral) take of stock
--------------------------------------------------------------------------------------------------------------------------------------------------------
Atlantic white-sided dolphin \1\.......... Western North Atlantic...... 93,233 0 16 16 0.02
Common dolphin \1\........................ Western North Atlantic...... 93,100 0 30 30 0.03
Harbor porpoise........................... Gulf of Maine/Bay of Fundy.. 85,765 1 6 7 0.01
Harbor seal............................... Western North Atlantic...... 61,336 31 298 329 0.54
Gray seal................................. Western North Atlantic...... 27,911 7 63 70 0.25
Harp seal................................. Western North Atlantic...... 7,600,000 3 24 27 <0.001
[[Page 24836]]
Hooded seal............................... Western North Atlantic...... Unknown 1 1 2 N/A
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Requested take by Level B harassment has been increased to mean group size (NUWC, 2017). Mean group size was not used for those take estimates that
exceeded the mean group size.
Table 12--Proposed Take of Marine Mammals by Level B Harassment by Species, and Percent of Stock
[Year 2]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Proposed Proposed take
Species name Stock Stock Level A (AUD Level B maximum annual as percentage
abundance INJ/PTS) (behavioral) take of stock
--------------------------------------------------------------------------------------------------------------------------------------------------------
Atlantic white-sided dolphin \1\.......... Western North Atlantic...... 93,233 0 16 16 0.02
Common dolphin \1\........................ Western North Atlantic...... 93,100 0 30 30 0.03
Harbor porpoise........................... Gulf of Maine/Bay of Fundy.. 85,765 2 8 10 0.01
Harbor seal............................... Western North Atlantic...... 61,336 42 394 436 0.71
Gray seal................................. Western North Atlantic...... 27,911 7 71 78 0.28
Harp seal................................. Western North Atlantic...... 7,600,000 3 27 30 <0.001
Hooded seal............................... Western North Atlantic...... Unknown 1 1 2 N/A
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Requested take by Level B harassment has been increased to mean group size (NUWC, 2017). Mean group size was not used for those take estimates that
exceeded the mean group size.
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 ITAs to include information about
the availability and feasibility (economic and technological) of
equipment, methods, and manner of conducting the activity or other
means of effecting the least practicable adverse impact upon the
affected species or stocks, and their habitat (50 CFR 216.104(a)(11)).
In evaluating how mitigation may or may not be appropriate to
ensure the least practicable adverse impact on species or stocks and
their habitat, as well as subsistence uses where applicable, NMFS
considers two primary factors:
(1) The manner in which, and the degree to which, the successful
implementation of the measure(s) is expected to reduce impacts to
marine mammals, marine mammal species or stocks, and their habitat.
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 sections
were either 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 measures below as
proposed mitigation requirements (see section 11 of the Navy's
application for more detail) and has included them in both of the
proposed IHAs.
In addition to the measures described later in this section, the
Navy would follow these general mitigation measures:
<bullet> Authorized take, by Level A harassment and Level B
harassment, would be limited to the species and numbers listed in
tables 11 (Year 1) and 12 (Year 2). 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.
<bullet> The taking by serious injury or death of any of the
species listed in tables 11 and 12 or taking of any species of marine
mammal other than those listed in tables 11 and 12, would be prohibited
and would result in the modification, suspension, or revocation of the
IHAs, if issued. Exceeding the numbers of incidental take for a given
species that are proposed for authorization (tables 11 and 12) would be
prohibited and would result in the modification, suspension, or
revocation of the IHAs, if issued.
<bullet> The Navy must 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 procedures, marine mammal monitoring
protocol, and operational procedures are clearly understood. New
personnel joining during the project must be trained prior to
commencing work.
[[Page 24837]]
<bullet> 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 mof 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.
<bullet> The Navy must employ PSOs and establish monitoring
locations as described in section 5 of the IHAs 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 to
monitor for marine mammals during vibratory pile installations and
extractions; a minimum of three PSOs would be required to monitor for
marine mammals during impact pile driving and use of DTH methods.
Additionally, the following mitigation measures apply to the Navy's
in-water construction activities:
Establishment of Shutdown Zones--The purpose of a shutdown zone is
generally to define an area within which shutdown of the activity would
occur upon sighting a marine mammal (or in anticipation of an animal
entering the defined area). The Navy proposes shutdown zones with
radial distances identified in table 13 for all construction activities
(i.e., pile driving or extraction, and DTH). To prevent injury from
physical interaction with construction equipment, the Navy proposes a
minimum of a 10-m shutdown be implemented during all in-water
construction activities having the potential to affect marine mammals
to ensure marine mammals are not present within this zone and to
protect marine mammals from collisions with project vessels during pile
driving and other construction activities. These activities could
include, but are not limited to, barge positioning, drilling, or pile
driving. The other shutdown zones proposed by the Navy are based on the
size of the Level A harassment zone for each pile size/type and driving
method, although some of the zones are too large to monitor completely
(e.g., for VHFC and PW during impact pile driving and DTH); in these
cases, the Navy proposes to maintain a 200-m shutdown zone for that
activity. NMFS concurs with this approach.
If an activity is delayed or halted due to the presence of a marine
mammal, the activity may not commence or resume until the animal has
voluntarily exited and been visually confirmed beyond the relevant
shutdown zone indicated in table 13, or 15 minutes have passed without
re-detection of the animal. If a marine mammal species not covered
under these IHAs enters a harassment zone, all in-water activities must
cease and remain shut down until the animal leaves the harassment zone
or has not been observed for a minimum of 15 minutes. However, if a
marine mammal enters the Level B harassment zone, in-water work would
proceed and PSOs would document the marine mammal's presence and
behavior.
Table 13--Proposed Shutdown Zones for Project Activities
----------------------------------------------------------------------------------------------------------------
Shutdown zone (m) Level B
-------------------------------- harassment zone
(m)
Pile type Activity -----------------
Seals (PW) Cetaceans All marine
(HFC, VHFC) mammal species
\1\
----------------------------------------------------------------------------------------------------------------
18'' Steel sheet..................... Vibratory Install...... 50 50 4,642
18'' Steel pipe (template)........... Vibratory Install/ 50 50 7,356
Extract.
18'' Steel pipe (permanent).......... Vibratory Install...... 85 55 7,356
Impact Install \2\..... * 200 * 200 1,585
DTH \2\................ * 200 * 200 13,593
----------------------------------------------------------------------------------------------------------------
\1\ Harassment zones may not reach the maximum distance due to the presence of intersecting land masses. Refer
to figures 6-1 through 6-12 of Navy's IHA application for visual depictions of the truncated harassment zones
PSOs will monitor.
\2\ At least three PSOs must be assigned to monitor during impact pile driving and use of DTH methods.
\*\ Based on practicable shutdown zone distance implemented for other similar projects in the region (e.g., 87
FR 11860, March 2, 2022).
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 following 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 or extraction, DTH) 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 13 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 that provides access to the
bulkhead sites.
Based on our evaluation of the applicant's proposed measures, as
well as other measures we considered, NMFS has preliminarily
determined, for both proposed IHAs, 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
[[Page 24838]]
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 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:
<bullet> Occurrence of marine mammal species or stocks in the area
in which take is anticipated (e.g., presence, abundance, distribution,
density);
<bullet> Nature, scope, or context of likely marine mammal exposure
to potential stressors/impacts (individual or cumulative, acute or
chronic), through better understanding of: (1) action or environment
(e.g., source characterization, propagation, ambient noise); (2)
affected species (e.g., life history, dive patterns); (3) co-occurrence
of marine mammal species with the activity; or (4) biological or
behavioral context of exposure (e.g., age, calving or feeding areas);
<bullet> Individual marine mammal responses (behavioral or
physiological) to acoustic stressors (acute, chronic, or cumulative),
other stressors, or cumulative impacts from multiple stressors;
<bullet> How anticipated responses to stressors impact either: (1)
long-term fitness and survival of individual marine mammals; or (2)
populations, species, or stocks;
<bullet> Effects on marine mammal habitat (e.g., marine mammal prey
species, acoustic habitat, or other important physical components of
marine mammal habitat); and,
<bullet> Mitigation and monitoring effectiveness.
The monitoring and reporting requirements described in the
following were proposed by the Navy in its adequate and complete
application and/or are the result of subsequent coordination between
NMFS and Navy has agreed to the requirements. NMFS describes these
below as requirements and has included them in the proposed IHAs.
The Navy would abide by all monitoring and reporting measures
contained within the IHAs, 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 or three NMFS-approved PSOs
must be stationed at strategic vantage points for the entirety of
vibratory (i.e., vibratory pile driving/extraction) or impact (i.e.,
impact pile driving and DTH) installation methods, respectively. PSOs
would be independent of the activity contractor (for example, employed
by a subcontractor) and have no other assigned tasks during monitoring
periods. At least one PSO would have prior experience performing the
duties of a PSO during an activity pursuant to a NMFS-issued ITA or
Letter of Concurrence (LOC). Other PSOs may substitute other relevant
experience, education (degree in biological science or related field),
or training for prior experience performing the duties of a PSO during
construction activity pursuant to a NMFS-issued ITA.
<bullet> 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:
<bullet> The ability to conduct field observations and collect data
according to assigned protocols;
<bullet> Experience or training in the field identification of
marine mammals, including the identification of behaviors;
<bullet> Sufficient training, orientation, or experience with the
construction operation to provide for personal safety during
observations;
<bullet> 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
<bullet> 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).
During vibratory pile installations and extractions, a minimum of two
PSOs must be assigned to each activity location to monitor the shutdown
zones. At least three PSOs must be assigned to monitor shutdown zones
during impact pile driving and use of DTH methods, activities producing
the largest Level A harassment zones. PSOs would record all
observations of marine mammals, regardless of distance from the pile
being driven, as well as the additional data indicated below and in
section 6 of the IHAs, if issued.
Acoustic Monitoring
The Navy must establish acoustic monitoring procedures as described
in a NMFS-approved Acoustic Monitoring Plan (see summary in section
13.2 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 of each type of
pile and method installation method combination listed in table 13-1 of
the application 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:
<bullet> 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).
<bullet> 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
[[Page 24839]]
between the sound source and the hydrophone(s);
<bullet> Measurement systems would be deployed using configurations
which minimize self or platform noise and ensure stable positioning
throughout the recordings;
<bullet> The recordings would be continuous throughout each
acoustic event for which monitoring is required;
<bullet> The sound source verification (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;
<bullet> 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.
<bullet> 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.).
<bullet> 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:
<bullet> Maximum peak SPL 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.
<bullet> From all activities occurring during the time that the
hammer was at maximum energy, these additional measures will be made,
as appropriate:
[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 SEL<INF>ss</INF> (dB re
[mu]Pa\2\ sec);
[cir] Median integration time used to calculate RMS SPL (for
vibratory monitoring, the period selected is 1-second intervals. For
impulsive monitoring, the period is 90 percent 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; and
[cir] Finally, the SEL<INF>24</INF> 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 SEL<INF>ss</INF>
values. The sum is taken of the antilog, with log<INF>10</INF> 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 for each IHA (i.e., Year 1 IHA, Year 2 IHA) 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:
<bullet> Dates and times (begin and end) of all marine mammal
monitoring;
<bullet> 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, DTH); and
(b) the total duration of time for each pile (vibratory driving) or
number of strikes for each pile (impact driving);
<bullet> PSO locations during marine mammal monitoring; and
<bullet> 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:
<bullet> Name of PSO who sighted the animal(s) and PSO location and
activity at the time of the sighting;
<bullet> Time of the sighting;
<bullet> 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;
<bullet> Distance and bearing of each observed marine mammal
relative to the pile being driven or removed for each sighting;
<bullet> Estimated number of animals (min/max/best estimate);
<bullet> Estimated number of animals by cohort (e.g., adults,
juveniles, neonates, group composition, etc.);
<bullet> Animal's closest point of approach and estimated time
spent within the estimated harassment zone(s);
<bullet> 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);
<bullet> Number of marine mammals detected within the harassment
zones, by species; and
<bullet> 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 13.2 of the Navy's application) and, at
minimum, must include:
<bullet> 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);
<bullet> 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;
<bullet> 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;
<bullet> 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,
[[Page 24840]]
maximum, minimum, and number of samples (where relevant) of the
following sound level metrics: (5) RMS SPL; (6) SEL<INF>24</INF>, Peak
(PK) SPL, and SEL<INF>ss</INF>; and
<bullet> For vibratory driving/extraction: (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, SEL<INF>24</INF> (and timeframe over which the sound is
averaged).
If no comments were 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 (<a href="/cdn-cgi/l/email-protection#7020225e3924205e3d1f1e19041f02191e172215001f020403301e1f11115e171f06"><span class="__cf_email__" data-cfemail="28787a06617c7806654746415c475a41464f7a4d58475a5c5b6846474949064f475e">[email protected]</span></a>,
<a href="/cdn-cgi/l/email-protection#9bd2cfcbb5fee8f8f3dbf5f4fafab5fcf4ed"><span class="__cf_email__" data-cfemail="86cfd2d6a8e3f5e5eec6e8e9e7e7a8e1e9f0">[email protected]</span></a>) 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:
<bullet> Description of the incident;
<bullet> Environmental conditions (e.g., Beaufort sea state,
visibility);
<bullet> Description of all marine mammal observations in the 24
hours preceding the incident;
<bullet> Photographs or video footage of the animal(s) (if
equipment is available);
<bullet> Time, date, and location (latitude/longitude) of the first
discovery (and updated location information if known and applicable);
<bullet> Species identification (if known) or description of the
animal(s) involved;
<bullet> Condition of the animal(s) (including carcass condition if
the animal is dead);
<bullet> Observed behaviors of the animal(s), if alive; and
<bullet> General circumstances under which the animal was
discovered.
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
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.
Noise associated with the Navy's Bulkhead Repair and Replacement
construction project has the potential to disturb or displace marine
mammals. Specifically, underwater sounds generated during impact pile
driving, vibratory pile installation and extraction, and DTH excavation
may result in take of seven species (i.e., Atlantic white-sided
dolphin, common dolphin, harbor porpoise, harbor seal, gray seal, harp
seal, and hooded seal) by Level B harassment and five these seven
species (i.e., harbor porpoise, harbor seal, gray seal, harp seal, and
hooded seal) by Level A harassment, in the form of PTS.
No serious injury or mortality would be expected, even in the
absence of required mitigation measures, given the nature of the
activities. No take by Level A harassment is anticipated for other
cetaceans 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).
As discussed previously, take by Level A harassment is proposed for
authorization for five species (i.e., harbor porpoise, harbor seal,
gray seal, harp seal, and hooded seal) in, as the Level A harassment
zones exceed the size of the shutdown zones for specific construction
scenarios. Therefore, there is the possibility that an animal could
enter a Level A harassment zone without being detected, and remain
within that zone for a duration long enough to incur AUD INJ in the
form of PTS (i.e., minor degradation of hearing capabilities within
regions of hearing that align most completely with the energy produced
by impact pile driving such as the low-frequency region below 2 kHz),
Any take by Level A harassment is expected to arise from, at most, a
small degree of PTS, not severe hearing impairment or impairment within
the ranges of greatest hearing sensitivity. Animals would have to be
exposed to higher levels and/or longer duration than are expected to
occur here in order to incur any more than a small degree of PTS.
Further, the amount of take by Level A harassment proposed for
authorization is very low for all species. For the harbor seals, the
species with the largest number of take proposed for authorization,
NMFS anticipates and proposes to authorize no more than 54 Level A
harassment takes over the duration of Navy's planned activities. If
hearing impairment occurs, it is most likely that the affected animal
would lose only a few dBs in its hearing sensitivity. Due to the small
degree anticipated, any PTS potential incurred would not be expected to
affect the reproductive success or survival of any individuals, much
less result in adverse impacts on the species or stock.
[[Page 24841]]
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.
As described above, NMFS expects that marine mammals would likely
move away from an aversive stimulus, especially at levels that would be
expected to result in PTS, given sufficient notice through use of soft
start. The Navy would also shut down pile driving activities if marine
mammals enter the shutdown zones (tables 10 and 11) further minimizing
the likelihood and degree of PTS that would be incurred.
Effects on individuals that are taken by Level B harassment in the
form of behavioral disruption, based on 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 simply to
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 are unlikely to affect the reproduction or
survival of individual marine mammals, and the effects of behavioral
disturbance on individuals are 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) associated with
feeding or reproduction (i.e., pupping) are located within the project
area. For example, while seasonal nearshore marine mammal surveys
conducted at NAVSTA Newport from May 2016 to February 2017 help
identify several harbor seal haul-out sites in Narragansett Bay, no
pupping was observed.
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.
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 area is not expected to affect marine mammals'
fitness, survival, and reproduction due to the limited geographic area
that would be ensonified and affected in comparison to the much larger
habitat for marine mammals within Narragansett Bay and outside the bay
along the RI coasts. Level A harassment and 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
construction activities occurring on multiple days. However, specified
activities like pile driving are not expected to occur every day, and
these individuals would likely return to normal behavior during gaps in
activity both within a given day and between workdays. As discussed
above, there is similar transit and haul-out habitat available for
marine mammals within and outside of the Narragansett Bay along the RI
coast, outside of the project area, 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 affect survival
or reproductive success of any individuals negatively. 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:
<bullet> No serious injury or mortality is anticipated or proposed
for authorization;
<bullet> No Level A harassment of any cetacean is proposed for
authorization;
<bullet> The low numbers of take by Level A harassment for harbor
seals, gray seals, hooded seals, and harp seals proposed for
authorization are expected to be of a small degree;
<bullet> The intensity of anticipated takes by Level B harassment
is expected to be relatively low for all stocks. Level B harassment
would primarily occur in the form of behavioral disturbance,
potentially resulting in avoidance of the project areas around where
pile driving (vibratory or impact) and/or DTH excavation is occurring.
Some low-level TTS may limit the detection of acoustic cues for some
individual marine mammals for relatively brief amounts of time in the
relatively confined footprints of the activities;
<bullet> The ensonified areas are very small relative to the
overall habitat ranges of all species and stocks;
<bullet> 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;
<bullet> The specified activity and associated ensonifed areas do
not overlap habitat areas known to be of special significance (BIAs or
ESA-designated critical habitat);
<bullet> Effects from the activities on species that serve as prey
for marine mammals 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;
<bullet> The lack of anticipated significant or long-term negative
effects to marine mammal habitat; and
<bullet> 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
[[Page 24842]]
specified activity on marine mammals and their habitat, and taking into
consideration the implementation of the proposed monitoring and
mitigation measures, NMFS preliminarily finds, for both proposed IHAs,
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 (86 FR 5322,
January 19, 2021). Additionally, other qualitative factors may be
considered in the analysis, such as the temporal or spatial scale of
the activities.
The instances of take NMFS proposes to authorize are below one-
third of the estimated stock abundance for all impacted stocks (tables
11 and 12). In fact, take of individuals is 1 percent or less of the
abundance for all affected stocks. Indeed, even if each take NMFS
proposes to authorize occurred to a new individual, the number of
animals would be considered small relative to the size of the relevant
stocks or populations. Furthermore, the takes proposed for
authorization would be limited to individuals occurring local to the
Navy's construction activities, an area that represents a small portion
of the range for any of the seven species considered here. Thus, the
likelihood that each take would occur to a new individual is low and,
while some individuals may return multiple times in a day, PSOs would
count them as separate takes if the individuals are not identifiable.
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, for both
proposed IHAs, 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 1 percent 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 two consecutive IHAs to the Navy for conducting the S50S/LNG and
S499 Bulkheads Replacement Project in Newport, RI, provided the
previously mentioned mitigation, monitoring, and reporting requirements
are incorporated. Drafts of the proposed IHAs can be found at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>.
Request for Public Comments
We request comment on our analyses, the proposed authorizations,
and any other aspect of this notice of proposed IHAs for the proposed
construction project. We also request comment on the potential renewal
of these proposed IHAs 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 these IHAs or a subsequent
renewal IHA.
On a case-by-case basis, NMFS may issue a one-time, 1-year renewal
IHA following notice to the public providing an additional 15 days for
public comments when (1) up to another year of identical or nearly
identical activities as described in the Description of Proposed
Activity section of this notice is planned or (2) the activities as
described in the Description of Proposed Activity section of this
notice would not be completed by the time the IHA expires and a renewal
would allow for completion of the activities beyond that described in
the Dates and Duration section of this notice, provided all of the
following conditions are met:
<bullet> A request for renewal is received no later than 60 days
prior to the needed renewal IHA effective date (recognizing that the
renewal IHA expiration date cannot extend beyond 1 year from expiration
of the initial IHA).
<bullet> The request for renewal must include the following:
1. An explanation that the activities to be conducted under the
requested renewal IHA are identical to the activities analyzed under
the initial IHA, are a subset of the activities, or include changes so
minor (e.g., reduction in pile size) that the changes do not affect the
previous analyses, mitigation and monitoring requirements, or take
estimates (with the exception of reducing the type or amount of take).
2. A preliminary monitoring report showing the results of the
required monitoring to date and an explanation showing that the
monitoring results do not indicate impacts of a scale or nature not
previously analyzed or authorized.
<bullet> 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: May 4, 2026.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2026-09046 Filed 5-6-26; 8:45 am]
BILLING CODE 3510-22-P
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