Billing Code 3510-22-P
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XD974]
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine
Mammals Incidental to the New London Pier Extension Project at the Naval
Submarine Base
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; issuance of an incidental harassment authorization.
SUMMARY: In accordance with the regulations implementing the Marine Mammal
Protection Act (MMPA) as amended, notification is hereby given that NMFS has issued
an incidental harassment authorization (IHA) to the U.S. Navy (Navy) to incidentally
harass marine mammals during construction activities associated with the New London
Pier Extension Project at Naval Submarine Base (SUBASE) New London in Groton,
Connecticut. There are no changes from the proposed authorization in this final
authorization.
DATES: This authorization is effective from December 1, 2024, through November 30,
2025.
ADDRESSES: Electronic copies of the application and supporting documents, as well as
a list of the references cited in this document, may be obtained online at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-takeauthorizations-construction-activities. In case of problems accessing these documents,
please call the contact listed below.
FOR FURTHER INFORMATION CONTACT: Rachel Wachtendonk, Office of
Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:
Background
The MMPA prohibits the “take” of marine mammals, with certain exceptions.
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) direct the Secretary
of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not
intentional, taking of small numbers of marine mammals by U.S. citizens who engage in
a specified activity (other than commercial fishing) within a specified geographical
region if certain findings are made and either regulations are proposed or, if the taking is
limited to harassment, a notice of a proposed IHA is provided to the public for review.
Authorization for incidental takings shall be granted if NMFS finds that the taking
will have a negligible impact on the species or stock(s) and will not have an unmitigable
adverse impact on the availability of the species or stock(s) for taking for subsistence
uses (where relevant). Further, NMFS must prescribe the permissible methods of taking
and other “means of effecting the least practicable adverse impact” on the affected
species or stocks and their habitat, paying particular attention to rookeries, mating
grounds, and areas of similar significance, and on the availability of the species or stocks
for taking for certain subsistence uses (referred to in shorthand as “mitigation”); and
requirements pertaining to the mitigation, monitoring and reporting of the takings are set
forth. The definitions of all applicable MMPA statutory terms cited above are included in
the relevant sections below.
Summary of Request
On August 21, 2023, NMFS received a request from the Navy for an IHA to take
marine mammals incidental to pile driving and removal activities associated with the
New London Pier Extension Project at SUBASE New London in Groton, Connecticut.
Following NMFS’ review of the application, the Navy submitted a revised version on
January 31, 2024. The application was deemed adequate and complete on February 2,

2024. The Navy’s request is for take of six species of marine mammals by Level B
harassment and for take of harbor seals, gray seals, and harp seals by Level A
harassment. Neither the Navy nor NMFS expects serious injury or mortality to result
from this activity; therefore, an IHA is appropriate.
There are no changes from the proposed IHA to the final IHA.
Description of Specified Activity
Overview
The Navy is planning the partial demolition and extension of pier 31 at SUBASE
New London in Groton, Connecticut (figure 1). The existing pier 31 will be partially
demolished and then an 81-foot (ft), or 24.7-meter (m), extension will be constructed.
This project will also include the demolition of an existing small access ramp for pier 17.
The project includes impact and vibratory pile installation and vibratory pile removal. For
a portion of the piles, an auger drill will be used inside the pipe casing to lift sediment.
The pier 31 extension will include the removal of 28 16-inch (in), or 0.41-m,
fiberglass reinforced plastic fender piles. The pier 17 demolition will include the removal
of 20 14-in (0.36-m) concrete encased steel H-piles and 10 timber piles. Existing piles
will be removed by the deadpull method, with timber piles being cut at the mudline and
all other piles being removed with the vibratory hammer if deadpull is unsuccessful.
Once the existing piles are removed, 20 36-in (0.91-m) steel pipe piles and 60 16-in
(0.41-m) fiberglass reinforced plastic fender piles will be installed to support the pier 31
extension and pier 17 quaywall. The installation and removal of a temporary work trestle
supported by 60 14-in (0.36-m) steel H-piles will be completed to support permanent pile
installation. Temporary and permanent piles will be initially installed with a vibratory
hammer followed by an impact hammer to embed them to their final depth. For a portion
of the piles, an auger drill will be used inside the pipe casing to lift sediment.

In order to maintain project schedules, it is possible that multiple pieces of
equipment will operate at the same time within the project area. Piles may be extracted
and installed on the same day, with a maximum of three vibratory hammers operating
simultaneously. The method of installation, and whether concurrent pile driving scenarios
will be implemented, will be determined by the construction crew once the project has
begun. Therefore, the total take estimate reflects the worst-case scenario for the project.
A further detailed description of the planned construction project is provided in
the Federal Register notice for the proposed IHA (89 FR 27717, April 18, 2024). Since
that time, no changes have been made to the planned activities. Therefore, a detailed
description is not provided here. Please refer to that Federal Register notice for the
description of the specified activity. Mitigation, monitoring, and reporting measures are
described in detail later in this document (please see Mitigation and Monitoring and
Reporting sections).
Comments and Responses
A notice of NMFS' proposal to issue an IHA to the Navy was published in the
Federal Register on April 18, 2024 (89 FR 27717). That notice described, in detail, the
Navy's activity, the marine mammal species that may be affected by the activity, and the
anticipated effects on marine mammals. In that notice, we requested public input on the
request for authorization described therein, our analyses, the proposed authorization, and
any other aspect of the notice of proposed IHA, and requested that interested persons
submit relevant information, suggestions, and comments. During the 30-day public
comment period, NMFS did not receive any substantive comments on the proposed IHA.
Changes from the Proposed IHA to Final IHA
Changes were made between publication of the notice of the proposed IHA and
this notice of the final IHA. The Hydroacoustic Monitoring section was updated for
clarification. We clarified that the monitoring should occur at 10 m (33 ft) from the

monitored pile; at a location intermediate of the pinniped and cetacean Level A
(permanent threshold shift (PTS) onset) zones; and occasionally near the predicted
harassment zones for Level B (behavioral) harassment. Additionally, table 11 was
updated to reflect that the measurements and acoustic monitoring would be conducted for
at least 10 percent and up to a maximum of 10 of each different type of pile and each
method of installation. We also added a requirement that all PSO data will be submitted
electronically with the draft marine mammal report in a format that can be queried, such
as a spreadsheet or database.
Description of Marine Mammals in the Area of Specified Activities
Sections 3 and 4 of the IHA application summarize available information
regarding status and trends, distribution and habitat preferences, and behavior and life
history of the potentially affected species. NMFS fully considered all of this information,
and we refer the reader to these descriptions, instead of reprinting the information.
Additional information regarding population trends and threats may be found in NMFS’
Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/national/marinemammal-protection/marine-mammal-stock-assessments) and more general information
about these species (e.g., physical and behavioral descriptions) may be found on NMFS’
website (https://www.fisheries.noaa.gov/find-species).
Table 1 lists all species or stocks for which take is expected and authorized for
this activity and summarizes information related to the population or stock, including
regulatory status under the MMPA and Endangered Species Act (ESA) and potential
biological removal (PBR), where known. PBR is defined by the MMPA as the maximum
number of animals, not including natural mortalities, that may be removed from a marine
mammal stock while allowing that stock to reach or maintain its optimum sustainable
population (as described in NMFS’ SARs). While no serious injury or mortality is
anticipated or authorized here, PBR and annual serious injury and mortality from

anthropogenic sources are included here as gross indicators of the status of the species or
stocks and other threats.
Marine mammal abundance estimates presented in this document represent the
total number of individuals that make up a given stock or the total number estimated
within a particular study or survey area. NMFS’ stock abundance estimates for most
species represent the total estimate of individuals within the geographic area, if known,
that comprises that stock. For some species, this geographic area may extend beyond U.S.
waters. All managed stocks in this region are assessed in NMFS’ U.S. 2022 SARs. All
values presented in table 1 are the most recent available at the time of publication
(including from the draft 2023 SARs) and are available online at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammalstock-assessments.
Table 1 -- Marine Mammal Species1 Likely Impacted by the Specified Activities

Common name

ESA/MMPA
status;
Stock abundance (CV, Nmin,
Scientific name
Stock
Strategic
most recent abundance survey)3
(Y/N)2
Order Odontoceti (toothed whales, dolphins, and porpoises)

Family Delphinidae
Atlantic WhiteLagenorhynchus acutus
Sided Dolphin
Common Dolphin
Delphinus delphis
Family Phocoenidae (porpoises)
Harbor Porpoise

Phocoena phocoena

Western N Atlantic
Western N Atlantic

PBR

Annual
M/SI4

-, -, N

93,233 (0.71, 54,443, 2021)

28

-, -, N

93,100 (0.56, 59,897, 2021)

1,452

85,765 (0.53, 56,420, 2021)

145

Gulf of Maine/ Bay
-, -, N
of Fundy
Order Carnivora – Pinnipedia

Family Phocidae (earless seals)
Gray Seal
Halichoerus grypus
Western N Atlantic5
-, -, N
27,911 (0.20, 23,624, 2021)
1,512
Harbor Seal
Phoca vitulina
Western N Atlantic
-, -, N
61,336 (0.08, 57,637, 2018)
1,729
Harp Seal
Pagophilus groenlandicus Western N Atlantic
-, -, N
7.6M (UNK, 7.1M, 2019)
426,000
1Information on the classification of marine mammal species can be found on the web page for The Society for Marine
Mammalogy's Committee on Taxonomy (https://marinemammalscience.org/science-and-publications/list-marinemammal-species-subspecies; Committee on Taxonomy, 2022).
2ESA 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.
3NMFS marine mammal SARs online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marinemammal-stock-assessment-reports-region. CV is coefficient of variation; Nmin is the minimum estimate of stock
abundance. In some cases, CV is not applicable.
4These values, found in NMFS’s SARs, represent annual levels of human-caused mortality plus serious injury from all
sources combined (e.g., commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in
some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial
fisheries is presented in some cases.
5NMFS' stock abundance estimate (and associated PBR value) applies to the U.S. population only. Total stock
abundance (including animals in Canada) is approximately 394,311. The annual M/SI value given is for the total stock.

4,570
339
178,573

As indicated above, all six species (with six managed stocks) in table 1 temporally
and spatially co-occur with the activity to the degree that take is reasonably likely to
occur. All species that could potentially occur in the project area are included in table 3-1
of the IHA application. While North Atlantic right whale (Eubalaena glacialis), common
minke whale (Balaenoptera acutorostrata), fin whale (Balaenoptera physalus), and
humpback whale (Megaptera novaeangliae) have been documented in Long Island
Sound, the spatial and temporal occurrence of these species is such that take is not
expected to occur, and they are not discussed further beyond the explanation provided
here. These species occur at low densities at the mouth of the Thames River, extending
into Long Island Sound, and do not occur in the Thames River. Sound from the project is
only expected to propagate into the Long Island Sound during the vibratory driving of the
36-in steel pipe piles. Only a small portion of the Long Island Sound will be ensonified,
and therefore incidental take of these species is not anticipated.
A detailed description of the species likely to be affected by the Navy's
construction project, including brief introductions to the species and relevant stocks as
well as available information regarding population trends and threats, and information
regarding local occurrence, were provided in the Federal Register notice for the
proposed IHA (89 FR 27717, April 18, 2024); since that time, we are not aware of any
changes in the status of these species and stocks; therefore, detailed descriptions are not
provided here. Please refer to that Federal Register notice for these descriptions. Please
also refer to the NMFS website (https://www.fisheries.noaa.gov/find-species) for
generalized species accounts.
Marine Mammal Hearing
Hearing is the most important sensory modality for marine mammals underwater,
and exposure to anthropogenic sound can have deleterious effects. To appropriately
assess the potential effects of exposure to sound, it is necessary to understand the

frequency ranges marine mammals are able to hear. Not all marine mammal species have
equal hearing capabilities (e.g., Richardson et al., 1995; Wartzok and Ketten, 1999; Au
and Hastings, 2008). To reflect this, Southall et al. (2007, 2019) recommended that
marine mammals be divided into hearing groups based on directly measured (behavioral
or auditory evoked potential techniques) or estimated hearing ranges (behavioral response
data, anatomical modeling, etc.). Note that no direct measurements of hearing ability
have been successfully completed for mysticetes (i.e., low-frequency cetaceans).
Subsequently, NMFS (2018) described generalized hearing ranges for these marine
mammal hearing groups. Generalized hearing ranges were chosen based on the
approximately 65-decibel (dB) threshold from the normalized composite audiograms,
with the exception for lower limits for low-frequency cetaceans where the lower bound
was deemed to be biologically implausible and the lower bound from Southall et al.
(2007) retained. Marine mammal hearing groups and their associated hearing ranges are
provided in table 2.
Table 2 -- Marine Mammal Hearing Groups (NMFS, 2018)
Hearing Group
Low-frequency (LF) cetaceans
(baleen whales)
Mid-frequency (MF) cetaceans
(dolphins, toothed whales, beaked whales, bottlenose whales)
High-frequency (HF) cetaceans
(true porpoises, Kogia, river dolphins, Cephalorhynchid,
Lagenorhynchus cruciger & L. australis)
Phocid pinnipeds (PW) (underwater)
(true seals)
Otariid pinnipeds (OW) (underwater)
(sea lions and fur seals)

Generalized Hearing
Range*
7 Hz to 35 kHz
150 Hz to 160 kHz
275 Hz to 160 kHz
50 Hz to 86 kHz
60 Hz to 39 kHz

* Represents the generalized hearing range for the entire group as a composite (i.e., all species within
the group), where individual species’ hearing ranges are typically not as broad. Generalized hearing
range chosen based on ~65-dB threshold from normalized composite audiogram, with the exception
for lower limits for LF cetaceans (Southall et al., 2007) and PW pinniped (approximation).

The pinniped functional hearing group was modified from Southall et al. (2007)
on the basis of data indicating that phocid species have consistently demonstrated an
extended frequency range of hearing compared to otariids, especially in the higher

frequency range (Hemilä et al., 2006; Kastelein et al., 2009; Reichmuth et al., 2013).
This division between phocid and otariid pinnipeds is now reflected in the updated
hearing groups proposed in Southall et al. (2019).
For more detail concerning these groups and associated frequency ranges, please
see NMFS (2018) for a review of available information.
Potential Effects of Specified Activities on Marine Mammals and Their Habitat
The effects of underwater noise from the Navy's pile driving activities have the
potential to result in behavioral harassment of marine mammals in the vicinity of the
project area. The notice of the proposed IHA (89 FR 27717, April 18, 2024) included a
discussion of the effects of anthropogenic noise on marine mammals and the potential
effects of underwater noise from the Navy's pile driving activities on marine mammals
and their habitat. That information and analysis is incorporated by reference into this final
IHA determination and is not repeated here; please refer to the notice of the proposed
IHA (89 FR 27717, April 18, 2024).
Estimated Take of Marine Mammals
This section provides an estimate of the number of incidental takes authorized
through the IHA, which will inform NMFS’ consideration of “small numbers,” the
negligible impact determinations, and impacts on subsistence uses.
Harassment is the only type of take expected to result from these activities.
Except with respect to certain activities not pertinent here, section 3(18) of the MMPA
defines “harassment” as any act of pursuit, torment, or annoyance, which: (i) has the
potential to injure a marine mammal or marine mammal stock in the wild (Level A
harassment); or (ii) has the potential to disturb a marine mammal or marine mammal
stock in the wild by causing disruption of behavioral patterns, including, but not limited
to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment).

Authorized takes will primarily be by Level B harassment, as use of the acoustic
(i.e., pile driving) has the potential to result in disruption of behavioral patterns for
individual marine mammals. There is also some potential for auditory injury (Level A
harassment) to result, primarily for phocids because no other species have been observed
within the Thames River adjacent to the project site, and the Level A harassment
isopleths do not extend to the Long Island Sound. The mitigation and monitoring
measures are expected to minimize the severity of the taking to the extent practicable. As
described previously, no serious injury or mortality is anticipated or authorized for this
activity. 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 is authorized.
For acoustic impacts, generally speaking, we estimate take by considering: (1)
acoustic thresholds above which NMFS believes the best available science indicates
marine mammals will be behaviorally harassed or incur some degree of permanent
hearing impairment; (2) the area or volume of water that will be ensonified above these
levels in a day; (3) the density or occurrence of marine mammals within these ensonified
areas; and (4) the number of days of activities. We note that while these factors can
contribute to a basic calculation to provide an initial prediction of potential takes,
additional information that can qualitatively inform take estimates is also sometimes
available (e.g., previous monitoring results or average group size). Below, we describe
the factors considered here in more detail and present the authorized take numbers.
Acoustic Thresholds
NMFS recommends the use of acoustic thresholds that identify the received level
of underwater sound above which exposed marine mammals would be reasonably
expected to be behaviorally harassed (equated to Level B harassment) or to incur a PTS
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 micropascal (re 1 μPa)) for continuous
(e.g., vibratory pile driving, drilling) and above RMS SPL 160 dB re 1 μPa for nonexplosive impulsive (e.g., seismic airguns) or intermittent (e.g., scientific sonar) sources.
Generally speaking, Level B harassment take estimates based on these behavioral
harassment thresholds are expected to include any likely takes by temporary threshold
shift (TTS) as, in most cases, the likelihood of TTS occurs at distances from the source
less than those at which behavioral harassment is likely. TTS of a sufficient degree can
manifest as behavioral harassment, as reduced hearing sensitivity and the potential
reduced opportunities to detect important signals (conspecific communication, predators,
prey) may result in changes in behavior patterns that would not otherwise occur.
The Navy’s activity includes the use of continuous (vibratory pile driving and
auger drilling) and impulsive (impact pile driving) sources, and therefore the RMS SPL
thresholds of 120 and 160 dB re 1 μPa are applicable.

Level A harassment – NMFS’ Technical Guidance for Assessing the Effects of
Anthropogenic Sound on Marine Mammal Hearing (Version 2.0; Technical Guidance,
2018) identifies dual criteria to assess auditory injury (Level A harassment) to five
different marine mammal groups (based on hearing sensitivity) as a result of exposure to
noise from two different types of sources (impulsive or non-impulsive). The Navy’s
activity includes the use of impulsive (impact pile driving) and non-impulsive (vibratory
pile driving and auger drilling) sources.
These thresholds are provided in the table below. The references, analysis, and
methodology used in the development of the thresholds are described in NMFS’ 2018
Technical Guidance, which may be accessed at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammalacoustic-technical-guidance.

Table 3 -- Thresholds Identifying the Onset of Permanent Threshold Shift

Hearing Group
Low-Frequency (LF)
Cetaceans
Mid-Frequency (MF)
Cetaceans
High-Frequency (HF)
Cetaceans
Phocid Pinnipeds (PW)
(Underwater)
Otariid Pinnipeds (OW)
(Underwater)

PTS Onset Thresholds*
(Received Level)
Impulsive
Non-impulsive
Cell 1
Cell 2
Lp,0-pk,flat: 219 dB
LE,p,LF,24h: 199 dB
LE,p,LF,24h: 183 dB
Cell 3
Cell 4
Lp,0-pk,flat: 230 dB
LE,p,MF,24h: 198 dB
LE,p,MF,24h: 185 dB
Cell 5
Cell 6
Lp,0-pk,flat: 202 dB
LE,p,HF,24h: 173 dB
LE,p,HF,24h: 155 dB
Cell 7
Cell 8
Lp,0-pk,flat: 218 dB
LE,p,PW,24h: 201 dB
LE,p,PW,24h: 185 dB
Cell 9
Cell 10
Lp,0-pk,flat: 232 dB
LE,p,OW,24h: 219 dB
LE,p,OW,24h: 203 dB

* Dual metric thresholds for impulsive sounds: Use whichever results in the largest isopleth for
calculating PTS 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 (Lp,0-pk) has a reference value of 1 µPa, and weighted cumulative sound
exposure level (LE,p) has a reference value of 1µPa2s. 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 to 160 kHz). The subscript associated with cumulative sound
exposure level thresholds indicates the designated marine mammal auditory weighting function (LF,
MF, and HF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is
24 hours. The 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.

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 project. Pile driving generates underwater noise
that can potentially result in disturbance to marine mammals in the project area. The
maximum (underwater) area ensonified is determined by the topography of the Thames
River, including intersecting land masses that will reduce the overall area of potential
impact. Additionally, vessel traffic, including large vessels and ferries, in the project area

may contribute to elevated background noise levels, which may mask sounds produced
by the project.
Transmission loss (TL) is the decrease in acoustic intensity as an acoustic pressure
wave propagates out from a source. TL parameters vary with frequency, temperature, sea
conditions, current, source and receiver depth, water depth, water chemistry, and bottom
composition and topography. The general formula for underwater TL is:
TL = B × Log10 (R1 /R2), where
TL = transmission loss in dB;
B = transmission loss coefficient; for practical spreading equals 15;
R1 = the distance of the modeled SPL from the driven pile; and,
R2 = the distance from the driven pile of the initial measurement.
This formula neglects loss due to scattering and absorption, which is assumed to
be zero here. The degree to which underwater sound propagates away from a sound
source is dependent on a variety of factors, most notably the water bathymetry and
presence or absence of reflective or absorptive conditions including in-water structures
and sediments. Spherical spreading occurs in a perfectly unobstructed (free-field)
environment not limited by depth or water surface, resulting in a 6-dB reduction in sound
level for each doubling of distance from the source (20×log10[range]). Cylindrical
spreading occurs in an environment in which sound propagation is bounded by the water
surface and sea bottom, resulting in a reduction of 3 dB in sound level for each doubling
of distance from the source (10×log10[range]). A practical spreading value of 15 is often
used under conditions, such as the project site, where water increases with depth as the
receiver moves away from the shoreline, resulting in an expected propagation
environment that would lie between spherical and cylindrical spreading loss conditions.
Practical spreading loss is assumed here.

The intensity of pile driving sounds is greatly influenced by factors such as the
type of piles, hammers, and the physical environment in which the activity takes place. In
order to calculate the distances to the Level A harassment and the Level B harassment
sound thresholds for the methods and piles being used in this project, NMFS used
acoustic monitoring data from other locations to develop proxy source levels for the
various pile types, sizes and methods (table 4). Generally, we choose source levels from
similar pile types from locations (e.g., geology, bathymetry) similar to the project.

Table 4 -- Proxy Sound Source Levels for Pile Sizes, Driving Methods, and Auger
Drilling
Pile type

Pile size

Peak SPL (re 1

RMS SPL (re 1

SEL (re 1 μPa

μPa (rms))

μPa (rms))

(rms))

Vibratory

NA

158

Navy, 2019b

Impact

177

Navy, 2019b

Vibratory

NA

168

Navy, 2018

Impact

198

Navy, 2019b

NA

NA

Dazey et al., 2012

Vibratory

162

Caltrans, 2020

Vibratory

NA

NA

Method

Source

14-in H-pile

Steel
36-in pipe pile
Auger
drilling
Concrete encased
14-in H-pile
steel
Illingworth and Rodkin,
Fiberglass
16-in fender
reinforced plastic

California Department
Impact

165

157
of Transportation, 2015

For this project, up to three vibratory hammers may operate simultaneously.
When two noise sources have overlapping sound fields, there is potential for higher
sound levels than for non-overlapping sources because the isopleth of one sound source
encompasses the sound source of another isopleth. In such instances, the sources are

considered additive and combined using the rules of decibel addition. For addition of two
simultaneous sources, the difference between the two sound source levels is calculated,
and if that difference is between 0 and 1 dB, 3 dB are added to the higher sound source
levels; if the difference is between 2 and 3 dB, 2 dB are added to the highest sound
source levels; if the difference is between 4 and 9 dB, 1 dB is added to the highest sound
source levels; and with differences of 10 or more dB, there is no addition. For
simultaneous usage of three or more continuous sound sources, the three overlapping
sources with the highest sound source levels are identified. Of the three highest sound
source levels, the lower two are combined using the above rules; then, the combination of
the lower two is combined with the highest of the three. The calculated proxy source
levels for the different potential concurrent pile driving scenarios are shown in table 5.

Table 5 -- Calculated Proxy Sound Source Levels for Potential Concurrent Pile
Driving Scenarios
Structure

Pile type and proxy

Calculated proxy
sound source level

Vibratory installation of 14-in steel
H-pile: 158 dB RMS
Temporary work trestle installation
and pier 17 demolition

Temporary work trestle installation,
pier 17 demolition, and pier 31
demolition

Vibratory demolition of 14-in
concrete encased steel H-pile: 162 dB
RMS
Vibratory installation of 14-in steel
H-pile: 158 dB RMS
Vibratory demolition of 14-in
concrete encased steel H-pile: 162 dB
RMS

163 dB RMS

165 dB RMS

Vibratory demolition of 16-in
fiberglass reinforced plastic fender:
158 dB RMS
Vibratory installation of 14-in steel
H-pile: 158 dB RMS
Temporary work trestle installation
and pier 31 demolition

Vibratory demolition of 16-in
fiberglass reinforced plastic fender:
158 dB RMS

161 dB RMS

The ensonified area associated with Level A harassment is more technically
challenging to predict due to the need to account for a duration component. Therefore,

NMFS developed an optional User Spreadsheet tool to accompany the Technical
Guidance that can be used to relatively simply predict an isopleth distance for use in
conjunction with marine mammal density or occurrence to help predict potential takes.
We note that because of some of the assumptions included in the methods underlying this
optional tool, we anticipate that the resulting isopleth estimates are typically going to be
overestimates of some degree, which may result in an overestimate of potential take by
Level A harassment. However, this optional tool offers the best way to estimate isopleth
distances when more sophisticated modeling methods are not available or practical. For
stationary sources, like pile driving, 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 PTS. Inputs used in the optional User Spreadsheet
tool, and the resulting estimated isopleths, are reported below.

Table 6 -- NMFS User Spreadsheet Inputs

Method

Vibratory

Pile size and type
16-in fiberglass
reinforced plastic fender
piles install and removal
14-in steel H-pile
(temporary) install and
removal
14-in concrete encased
steel H-pile removal
36-in steel pipe pile
install
16-in fiberglass
reinforced plastic fender
piles

Impact

14-in steel H-pile
(temporary) install
36-in steel pipe pile
install

Auger
drilling

36-in steel pipe pile
install

Spreadsheet
tab used
A.1.
Vibratory
pile driving
A.1.
Vibratory
pile driving
A.1.
Vibratory
pile driving
A.1
Vibratory
pile driving
E.1.
Impact pile
driving
E.1.
Impact pile
driving
E.1.
Impact pile
driving
A.
Stationary
source: nonimpulsive,
continuous

Weighting
factor
adjustment
(kHz)

Number
of piles
per day

Duration of
sound
production
within 24-h
period (sec)

Number
of strikes
per pile

2.5

2400

NA

2.5

6000

NA

2.5

6000

NA

2.5

0.17

428.4

NA

2.5

NA

2

NA

2

2.5

NA

2

28800

NA

Concurrent
pile
driving

14-in steel H-pile AND
14-in concrete encased
steel H-pile
14-in steel H-pile AND
14-in concrete encased
steel H-pile AND 16-in
fiberglass reinforced
plastic fender
14-in steel H-pile AND
16-in fiberglass
reinforced plastic fender

A.1.
Vibratory
pile driving

2.5

6000

NA

A.1.
Vibratory
pile driving

2.5

6000

NA

A.1.
Vibratory
pile driving

2.5

8400

NA

Table 7 -- Calculated Level A and Level B Harassment Isopleths
Method

Vibratory

Impact

Auger
drilling

Concurrent
pile
driving

Pile size
and type
16-in
fiberglass
reinforced
plastic
fender piles
install and
removal
14-in steel
H-pile
(temporary)
install and
removal
14-in
concrete
encased
steel H-pile
removal
36-in steel
pipe pile
install
16-in
fiberglass
reinforced
plastic
fender piles
14-in steel
H-pile
(temporary)
install
36-in steel
pipe pile
install
36-in steel
pipe pile
install
14-in steel
H-pile
AND 14-in
concrete
encased
steel H-pile
14-in steel
H-pile
AND 14-in
concrete
encased
steel H-pile
AND 16-in
fiberglass

Level A harassment zone (m/km2)
MF- cetaceans

HF- cetaceans

Phocid

0.3/0

4.9/0.000075

2.0/0.00013

Level B
harassment zone
(m/km2)

3,415/2.47916

0.5/0.000001

9.0/0.000253

3.7/0.000043

1.0/0.000003

16.5/0.000851

6.8/0.000145

6,310/2.620145

0.4/0.000001

7.2/0.000162

2.9/0.00026

15,849/3.435273

1.2/0.00005

40.5/0.005136

18.2/0.001035

22/0.001513

3.6/0.000041

119.3/0.044565

53.6/0.009004

136/0.056637

65.4/0.01341

2,191/1.588304

984.4/0.86872

3,415/2.620145

0.1/0

0.8/0.000002

0.5/0.000001

1,848/1.359058

1.2/0.000005a,b

19.3/0.001164a
19.3/0.001134b

7.9/0.000195a,b

7,356/3.121835a
7,356/0.205166b

1.6/0.000008a,b,c

26.2/0.002146a,c
26.2/0.001807b

10.8/0.000365a,b,c

10,000/3.197942a
10,000/0.205166b
10,000/2.822399c

reinforced
plastic
fender
14-in steel
H-pile
AND 16-in
fiberglass
1.1/0.000004a,b
17.8/0.00099a,b
7.3/0.000167a,b
reinforced
plastic
fender
aHarassment zones mapped from pier 31
bHarassment zones mapped from pier 17
cHarassment zones mapped from existing pier 31 for fender pile extraction

5,412/3.078261a
5,412/2.822399b

Marine Mammal Occurrence and Take Estimation
In this section we provide information about the occurrence of marine mammals,
including density or other relevant information which will inform the take calculations.
Density estimates come from Northeast Ocean Data (2023) for cetaceans and from the
U.S. Navy Marine Species Density Database (Navy, 2017) for pinnipeds. To determine
the incidental take estimate within each harassment zone, the following equation was
used:
Incidental take estimate = (harassment zone [km2] × estimated density
[individuals/km2]) × days of pile driving activity
A subset of the species (Atlantic white-sided dolphin, common dolphin, and
harbor porpoise) do not occur within the Thames River and have only been observed in
the Long Island Sound. For these species, the area from the mouth of the Thames River to
the furthest extent of the harassment zone in the Long Island Sound was used to
determine the incidental take estimate within that zone.
Atlantic White-Sided Dolphin
Atlantic white-sided dolphins do not occur within the Thames River but they
occur occasionally in the Long Island Sound. Monthly surveys conducted in the Thames
River from 2017 through 2019 did not record the presence of Atlantic white-sided
dolphins (Tetra Tech, 2019). The average density of Atlantic white-sided dolphins in the
Long Island Sound is 0.022 individuals per square kilometer (km2). Only vibratory pile
driving activities will generate a harassment zone that extends into the Long Island Sound

so for those activities the area from the mouth of the Thames River to the furthest extent
in the Long Island Sound (0.24 km2) was used to calculate take (table 8). Therefore, using
the equation given above, the calculated estimated take by Level B harassment for
Atlantic white-sided dolphins would be one. However, Atlantic white-sided dolphins
typically travel in pods, so the estimated take by Level B harassment was increased to the
average group size of 12 (NMFS, 2023b).
The largest Level A harassment zone for Atlantic white-sided dolphins extends 65
m from the sound source (table 9) and is entirely contained within the Thames River.
Therefore, no take by Level A harassment is anticipated or authorized.
Common Dolphin
Common dolphins do not occur within the Thames River but they occur
occasionally in the Long Island Sound. Monthly surveys conducted in the Thames River
from 2017 through 2019 did not record the presence of common dolphins (Tetra Tech,
2019). The average density of common dolphins in the Long Island Sound is 0.15
individuals per km2. Only vibratory pile driving activities will generate a harassment
zone that extends into the Long Island Sound so for those activities the area from the
mouth of the Thames River to the furthest extent in the Long Island Sound (0.24 km2)
was used to calculate take (table 8). Therefore, using the equation given above, the
calculated estimate of take by Level B harassment for common dolphins would be four.
However, common dolphins generally travel in pods, so the estimated take by Level B
harassment was increased to an assumed average group size of 30 (NMFS, 2023b).
The largest Level A harassment zone for common dolphins extends 65 m from the
sound source (table 7) and is entirely contained within the Thames River. Therefore, no
take by Level A harassment is anticipated or authorized.
Harbor Porpoise

Harbor porpoises do not occur within the Thames River but they occur
occasionally in the Long Island Sound. Monthly surveys conducted in the Thames River
from 2017 through 2019 did not record the presence of harbor porpoises (Tetra Tech,
2019). The average density of harbor porpoises in the Long Island Sound is 0.32
individuals per km2. Only vibratory pile driving activities will generate a harassment
zone that extends into the Long Island Sound so for those activities the area from the
mouth of the Thames River to the furthest extent in the Long Island Sound (0.24 km2)
was used to calculate take (table 8). Therefore, using the equation given above, the
estimated take by Level B harassment for harbor porpoises would be nine.
The largest Level A harassment zone for harbor porpoises extends 2,191 m from
the sound source (table 7) and is entirely contained within the Thames River. Therefore,
no take by Level A harassment is anticipated or authorized.
Table 8 -- Estimated Take by Level B Harassment for species observed only in the
Long Island Sound portion of the project area
Calculated
Ensonfied area
Total
Pile size and
Method

Density

estimated

(individuals/

take by

km2)

Level B

Total authorized

within the Long
ensonified

type

Species

Group size

take by Level B

Island Sound
area (km2)

harassment

(km2)
harassment
Atlantic
white-sided

0.022

12

0.15

30

0.32

3

dolphin
36-in steel pipe
Impact

3.435273

0.24

Common

pile install
dolphin
Harbor
porpoise

Harbor Seal

Harbor seals are present in the project vicinity including the Thames River from
September through May. Monthly surveys conducted in the Thames River from 2017
through 2019 recorded 12 sightings of individual harbor seals (Tetra Tech, 2019). Seals
were not observed on the shore and there are no harbor seal haulouts within the project
vicinity. Two different density estimates were used to calculate harbor seal take. A
density of 0.049 individuals per km2 was used in the Thames River and a density of 0.07
individuals per km2 was used in the Long Island Sound (Navy, 2017). Therefore, using
the equation given above, the estimated number of takes by Level B harassment for
harbor seals would be 44.
The largest Level A harassment zone for harbor seals extends 984 m from the
sound source (table 7). Using the equation given above, the calculated estimated take by
Level A harassment for harbor seals would be 1. However, due to the consistent presence
of phocid pinnipeds at the SUBASE over the last several years, NMFS conservatively
authorizes increasing the estimated take by Level A harassment to one per 30 days of pile
driving resulting in an estimated 8 harbor seals by Level A harassment over the course of
the project.
Gray Seal
Gray seals are present in the project vicinity including the Thames River from
March through June. Monthly surveys conducted in the Thames River from 2017 through
2019 recorded three sightings of individual gray seals (Tetra Tech, 2019). Seals were not
observed on the shore and there are no gray seal haulouts within the project vicinity. Two
different density estimates were used to calculate take of gray seals. A density of 0.049
individuals per km2 was used in the Thames River and a density of 0.07 individuals per
km2 was used in the Long Island Sound (Navy, 2017). Therefore, using the equation
given above, the calculated estimated take by Level B harassment for gray seals would be
44.

The largest Level A harassment zone for gray seals extends 984 m from the sound
source (table 7). Using the equation given above, the calculated estimated take by Level
A harassment for gray seals would be one. However, due to the consistent presence of
phocid pinnipeds at the SUBASE over the last several years, NMFS conservatively
authorized increasing the estimated take by Level A harassment to one per 30 days of pile
driving resulting in an estimate of 8 takes of harbor seals by Level A harassment over the
course of the project.
Harp Seal
Harp seals are present in the project vicinity from January through May and are
much rarer in the Thames River then the other two seal species. Harp seals were not
observed during monthly surveys conducted in the Thames River from 2017 through
2019 (Tetra Tech, 2019). However, two harp seals were identified in March 2019 and one
harp seal in April 2019 by Mystic Aquarium staff. On both occasions they were hauled
out on the finger piers of the marina at SUBASE (Navy, 2019a). The average density of
harp seals in the Long Island Sound is 0.278 individuals per km2. Only vibratory pile
driving activities will generate a harassment zone that extends into the Long Island Sound
so for those activities the area from the mouth of the Thames River to the furthest extent
in the Long Island Sound was used to calculate take. Therefore, using the equation given
above, the estimated take by Level B harassment for harp seals would be seven.
However, it was determined that up to one take by Level B harassment of harp seals
could occur within the Thames River during each month they are present (January to
May) resulting in an estimate of 12 takes of harp seals by Level B harassment.
The largest Level A harassment zone for harp seals extends 984 m from the sound
source (table 7) and is entirely contained within the Thames River. Harp seals do not
have a density estimate for within the Thames River; therefore, given the sightings of this
species hauled out at SUBASE, NMFS authorized increasing the estimated take by Level

A harassment to one per 30 days of pile driving during the period in which harp seals
could occur in the river. This results in an estimate of 5 takes of harp seals by Level A
harassment over the course of the project.
Table 9 -- Estimated Take by Level A and Level B Harassment
Common
name

Stock

Stock
abundance1

Level A
harassment

Level B
harassment

Atlantic
white-sided
dolphin

Total
authorized
take

Western
2 12
North
93,233
0
12
Atlantic
Western
Common
2 30
North
93,100
0
30
dolphin
Atlantic
Gulf of
Harbor
Maine/Bay of
87,765
0
9
9
porpoise
Fundy
Western
Harbor seal
North
61,336
8
44
52
Atlantic
Western
Gray seal
North
27,911
8
44
52
Atlantic
Western
Harp seal
North
7,600,000
5
12
17
Atlantic
1Stock size is N
best according to NMFS 2023a draft SARs.
2Authorized take increased to mean group size from AMAPPS (Palka et al., 2017 and 2021).

Authorized
take as a
percentage of
stock
0.01
0.03
0.01
0.08
0.19
0.00002

Mitigation
In order to issue an IHA under section 101(a)(5)(D) of the MMPA, NMFS must
set forth the permissible methods of taking pursuant to the activity, and other means of
effecting the least practicable impact on the species or stock and its habitat, paying
particular attention to rookeries, mating grounds, and areas of similar significance, and on
the availability of the species or stock for taking for certain subsistence uses (latter not
applicable for this action). NMFS regulations require applicants for incidental take
authorizations to include information about the availability and feasibility (economic and
technological) of equipment, methods, and manner of conducting the activity or other
means of effecting the least practicable adverse impact upon the affected species or
stocks, and their habitat (see 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.
In addition to the measures described later in this section, the Navy will employ
the following mitigation measures:
•

The Navy will ensure that construction supervisors and crews, the
monitoring team, and relevant Navy staff are trained prior to the start of
activities subject to the IHA, so that responsibilities, communication
procedures, monitoring protocols, and operational procedures are clearly
understood. New personnel joining during the project must be trained
prior to commencing work.

•

For those marine mammals for which incidental take has not been
authorized, in-water pile installation/removal will shut down immediately
if such species are observed within or entering the Level B harassment
zone.

•

If take reaches the authorized limit for any species, pile
installation/removal will shut down immediately if these species approach
the Level B harassment zone to avoid additional take.

The following mitigation measures will apply to the Navy's in-water construction
activities:
Shutdown and Monitoring Zones
The Navy must establish shutdown zones and Level B harassment monitoring
zones for all pile driving activities. The purpose of a shutdown zone is generally to define
an area within which shutdown of the activity will occur upon sighting of a marine
animal (or in anticipation of an animal entering the defined area). Shutdown zones are
based on the largest Level A harassment zone for each pile size/type and driving method,
and behavioral monitoring zones are meant to encompass Level B harassment zones for
each pile size/type and driving method, as shown in table 10. A minimum shutdown zone
of 10 m will be required for all in-water construction activities to avoid physical
interaction with marine mammals. Shutdown zones for each activity type are shown in
table 10.
Prior to pile driving, shutdown zones and monitoring zones will be established
based on zones represented in table 7. Protected Species Observers (PSOs) will survey
the shutdown zones and surrounding areas for at least 30 minutes before pile driving
activities start. If marine mammals are found within the shutdown zone, pile driving will
be delayed until the animal has moved out of the shutdown zone, either verified by an
observer or by waiting until 15 minutes has elapsed without a sighting. If a marine
mammal approaches or enters the shutdown zone during pile driving, the activity will be
halted. Pile driving may resume after the animal has moved out of and is moving away
from the shutdown zone or after at least 15 minutes has passed since the last observation
of the animal.

All marine mammals will be monitored in the Level B harassment to the extent of
visibility for the on-duty PSOs. If a marine mammal for which take is authorized enters
the Level B harassment zone, in-water activities would continue and PSOs will document
the animal's presence within the estimated harassment zone.
If a species for which authorization has not been granted, or for which the
authorized takes are met, is observed approaching or within the Level B harassment zone,
pile driving activities will be shut down immediately. Activities will not resume until the
animal has been confirmed to have left the area or 15 minutes has elapsed with no
sighting of the animal.
Table 10 –Shutdown and Level B Monitoring Zones by Activity
Method

Vibratory

Impact

Auger
drilling

Concurrent
pile
driving

Pile size and type
16-in fiberglass
reinforced plastic fender
piles install and removal
14-in steel H-pile
(temporary) install and
removal
14-in concrete encased
steel H-pile removal
36-in steel pipe pile
install
16-in fiberglass
reinforced plastic fender
piles
14-in steel H-pile
(temporary) install
36-in steel pipe pile
install
36-in steel pipe pile
install
14-in steel H-pile AND
14-in concrete encased
steel H-pile
14-in steel H-pile AND
14-in concrete encased
steel H-pile AND 16-in
fiberglass reinforced
plastic fender
14-in steel H-pile AND
16-in fiberglass
reinforced plastic fender

Protected Species Observers

Minimum shutdown zone (m)
MFHFPhocid
cetaceans
cetaceans
10

Level B
monitoring
zone (m)

10
3,415

10

10

15

6,310

10

15,849

45

22

120

136

200

3,415

10

1,848

35

7,356

30

10,000

20

5,412

The placement of PSOs during all pile driving and removal activities (described in
detail in the Monitoring and Reporting section) will ensure that the Thames River and
portion of the Long Island Sound is visible during pile installation.
Pre- and Post-Activity Monitoring
Monitoring must take place from 30 minutes prior to initiation of pile driving
activities (i.e., pre-clearance monitoring) through 30 minutes post-completion of pile
driving. Prior to the start of daily in-water construction activity, or whenever a break in
pile driving of 30 minutes or longer occurs, PSOs will observe the shutdown and
monitoring zones for a period of 30 minutes. The shutdown zone will be considered
cleared when a marine mammal has not been observed within the zone for a 30-minute
period. If a marine mammal is observed within the shutdown zones, pile driving activity
will be delayed or halted. If work ceases for more than 30 minutes, the pre-activity
monitoring of the shutdown zones will commence. A determination that the shutdown
zone is clear must be made during a period of good visibility (i.e., the entire shutdown
zone and surrounding waters must be visible to the naked eye).
Soft Start
Soft-start procedures are believed to provide additional protection to marine
mammals by providing warning and/or giving marine mammals a chance to leave the
area prior to the impact hammer operating at full capacity. For impact driving, an initial
set of three strikes will be made by the hammer at reduced energy, followed by a 30second waiting period, then two subsequent three-strike sets before initiating continuous
driving. Soft start will 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.
Based on our evaluation of the applicant’s planned measures, NMFS has
determined that the mitigation measures provide the means of effecting the least

practicable impact on the affected species or stocks and their habitat, paying particular
attention to rookeries, mating grounds, and areas of similar significance.
Monitoring and Reporting
In order to issue an IHA for an activity, section 101(a)(5)(D) of the MMPA states
that NMFS must set forth requirements pertaining to the monitoring and reporting of such
taking. The MMPA implementing regulations at 50 CFR 216.104(a)(13) indicate that
requests for authorizations must include the suggested means of accomplishing the
necessary monitoring and reporting that will result in increased knowledge of the species
and of the level of taking or impacts on populations of marine mammals that are expected
to be present while conducting the activities. Effective reporting is critical both to
compliance as well as ensuring that the most value is obtained from the required
monitoring.
Monitoring and reporting requirements prescribed by NMFS should contribute to
improved understanding of one or more of the following:
●

Occurrence of marine mammal species or stocks in the area in which take

is anticipated (e.g., presence, abundance, distribution, density);
●

Nature, scope, or context of likely marine mammal exposure to potential

stressors/impacts (individual or cumulative, acute or chronic), through better
understanding of: (1) action or environment (e.g., source characterization, propagation,
ambient noise); (2) affected species (e.g., life history, dive patterns); (3) co-occurrence of
marine mammal species with the activity; or (4) biological or behavioral context of
exposure (e.g., age, calving or feeding areas);
●

Individual marine mammal responses (behavioral or physiological) to

acoustic stressors (acute, chronic, or cumulative), other stressors, or cumulative impacts
from multiple stressors;

●

How anticipated responses to stressors impact either: (1) long-term fitness

and survival of individual marine mammals; or (2) populations, species, or stocks;
●

Effects on marine mammal habitat (e.g., marine mammal prey species,

acoustic habitat, or other important physical components of marine mammal habitat); and
●

Mitigation and monitoring effectiveness.

Visual Monitoring
Marine mammal monitoring must be conducted in accordance with the
Monitoring Plan and section 5 of the IHA. Marine mammal monitoring during pile
driving and removal must be conducted by NMFS-approved PSOs in a manner consistent
with the following:
•

PSOs must 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 must have prior experience performing the duties of a
PSO during construction activity pursuant to a NMFS-issued incidental
take authorization;

•

Other PSOs may substitute education (degree in biological science or
related field) or training for experience; and

•

The Navy must submit PSO Curriculum Vitae for approval by NMFS
prior to the onset of pile driving.

PSOs must have the following additional qualifications:
•

Ability to conduct field observations and collect data according to
assigned protocols;

•

Experience or training in the field identification of marine mammals,
including the identification of behaviors;

•

Sufficient training, orientation, or experience with the construction
operation to provide for personal safety during observations;

•

Writing skills sufficient to prepare a report of observations including but
not limited to the number and species of marine mammals observed; dates
and times when in-water construction activities were conducted; dates,
times, and reason for implementation of mitigation (or why mitigation was
not implemented when required); and marine mammal behavior; and

•

Ability to communicate orally, by radio or in person, with project
personnel to provide real-time information on marine mammals observed
in the area as necessary. The Navy will employ up to five PSOs. PSO
locations will provide an unobstructed view of all water within the
shutdown zone(s), and as much of the Level A harassment and Level B
harassment zones as possible. PSO locations may include the pile
installation/extraction barge, shore-based locations (such as pier 17 or pier
32), small boats, and the mouth of the Thames River.

Monitoring will be conducted 30 minutes before, during, and 30 minutes after pile
driving/removal activities. In addition, observers shall record all incidents of marine
mammal occurrence, regardless of distance from activity, and shall document any
behavioral reactions in concert with distance from piles being driven or removed. Pile
driving/removal activities include the time to install or remove a single pile or series of
piles, as long as the time elapsed between uses of the pile driving equipment is no more
than 30 minutes.
Data Collection
PSOs will use approved data forms to record the following information:
•

Dates and times (beginning and end) of all marine mammal monitoring.

•

PSO locations during marine mammal monitoring.

Construction activities occurring during each daily observation period, including
how many and what type of piles were driven or removed and by what method (i.e.,
vibratory, impact, or auger drilling).
•

Weather parameters and water conditions.

•

The number of marine mammals observed, by species, relative to the pile location
and if pile driving or removal was occurring at time of sighting.

•

Distance and bearings of each marine mammal observed to the pile being driven
or removed.

•

Description of marine mammal behavior patterns, including direction of travel.

•

Age and sex class, if possible, of all marine mammals observed.

•

Detailed information about implementation of any mitigation triggered (such as
shutdowns and delays), a description of specific actions that ensued, and resulting
behavior of the animal if any.

Hydroacoustic Monitoring
The Navy plans to conduct hydroacoustic monitoring, or sound source
verification (SSV), of all pile installation and removal methods. Hydroacoustic
monitoring results may be used to adjust the size of the Level A and Level B harassment
and monitoring zones after a request is made and approved by NMFS. At minimum, the
methodology includes:
•

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.

•

Hydroacoustic monitoring will be successfully conducted for at least 10
percent and up to a maximum of 10 of each different type of pile and each
method of installation (table 11). Monitoring will occur at 33 ft (10 m)
from the noise; at a location intermediate of the pinniped and cetacean

Level A (PTS onset) zones; and occasionally near the predicted
harassment zones for Level B (Behavioral) harassment. The resulting data
set will be analyzed to examine and confirm SPLs and rates of TL for each
separate in-water construction activity. With NMFS concurrence, these
metrics may be used to recalculate the limits of the shutdown, Level A
(PTS onset), and Level B (Behavioral) disturbance zones, and to make
corresponding adjustments in marine mammal monitoring of these zones.
Hydrophones will be placed using a static line deployed from a stationary
(temporarily moored) vessel. Locations of hydroacoustic recordings will
be collected via global positioning system. A depth sounder and/or
weighted tape measure will be used to determine the depth of the water.
The hydrophone will be attached to a weighted nylon cord or chain to
maintain a constant depth and distance from the pile area. The nylon cord
or chain will be attached to a float or tied to a static line.
•

Each hydrophone will be calibrated at the start of each action and will be
checked frequently to the applicable standards of the hydrophone
manufacturer.

•

Environmental data will 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 sound levels (e.g., aircraft, boats, etc.).

•

The chief inspector will supply the acoustics specialist with the substrate
composition, hammer/drill model and size, hammer/drill 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 will be post-processed to obtain the
following sound measures:
o Maximum peak pressure level recorded for all activities, expressed
in dB re 1 μPa.
â–ª

Mean, median, minimum, and maximum RMS pressure
level in [dB re 1 μPa].

â–ª

Mean duration of a pile strike (based on 90 percent energy
criterion).

â–ª

Number of hammer strikes.

â–ª

Mean, median, minimum, and maximum single strike
sound exposure level (SEL) in [dB re μPa2 sec].

o Cumulative SEL as defined by the mean single strike SEL +
10*log10 (number of hammer strikes) (dB re μPa2 sec).
o Median integration time used to calculate RMS SPL.
o A frequency spectrum (pressure spectral density) (dB re μPa2 per
Hz) based on the average of up to eight successive strikes with
similar sound. Spectral resolution will be 1 Hz, and the spectrum
will cover nominal range from 7 Hz to 20 kHz.
o Finally, the cumulative SEL will 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 single strike SEL
values. The sum is taken of the antilog, with log10 taken of result to
express (dB re μPa2 sec).
•

For vibratory driving/extraction/drilling: duration and frequency spectrum
of vibratory driving per pile; mean, median, and maximum sound levels

(dB re: 1 µPa): root mean square sound pressure level (SPLrms), SELcum
(and timeframe over which the sound is averaged).
Table 11 – Hydroacoustic Monitoring Summary
Pile type
Count
Method of install/extract
Number monitored1
14-in steel H-pile
60
Impact
6-10
14-in steel H-pile
60
Vibratory
6-10
36-in steel pipe pile
20
Impact
2-10
36-in steel pipe pile
20
Vibratory
2-10
36-in steel pipe pile
20
Auger (rotary) drill
2-10
16-in fiberglass reinforced
60
Impact
6-10
plastic fender pile
16-in fiberglass reinforced
60
Vibratory
6-10
plastic fender pile
14-in concrete encased
20
Vibratory
2-10
steel H-pile
1Hydroacoustic monitoring would be successfully conducted for at least 10 percent and up to 10 of each different type
of pile and each method of installation.

Reporting
A draft marine mammal monitoring report will be submitted to NMFS within 90
days after the completion of pile driving and removal activities. It will include an overall
description of work completed, a narrative regarding marine mammal sightings, and
associated PSO data sheets. Specifically, the report must include:
● Dates and times (begin and end) of all marine mammal monitoring.
● Construction activities occurring during each daily observation period, including
the number and type of piles driven or removed and by what method (i.e.,
vibratory driving) and the total equipment duration for cutting for each pile.
● PSO locations during marine mammal monitoring.
● 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: (1) name of
PSO who sighted the animal(s) and PSO location and activity at time of sighting;

(2) time of sighting; (3) 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; (4) distance and bearing
of each marine mammal observed relative to the pile being driven for each
sighting (if pile driving was occurring at time of sighting); (5) estimated number
of animals (min/max/best estimate); (6) estimated number of animals by cohort
(adults, juveniles, neonates, group composition, etc.); (7) animal’s closest point of
approach and estimated time spent within the harassment zone; and (8)
description of any marine mammal behavioral observations (e.g., observed
behaviors such as feeding or traveling), including an assessment of behavioral
responses thought to have resulted from the activity (e.g., no response or changes
in behavioral state such as ceasing feeding, changing direction, flushing, or
breaching).
● Number of marine mammals detected within the harassment zones, by species.
● Detailed information about any implementation of any mitigation triggered (e.g.,
shutdowns and delays), a description of specific actions that ensued, and resulting
changes in behavior of the animal(s), if any.
● All PSO data will be submitted electronically in a format that can be queried such
as a spreadsheet or database and would be submitted with the draft marine
mammal report.
If no comments are received from NMFS within 30 days, the draft final report
will constitute the final report. If comments are received, a final report addressing NMFS
comments must be submitted within 30 days after receipt of comments.
Reporting of Hydroacoustic Monitoring
The Navy shall also submit a draft hydroacoustic monitoring report to NMFS
within 90 days of the completion of required monitoring at the end of the project,

including data in a tabular spreadsheet format (Microsoft Excel or similar). The report
will detail the hydroacoustic monitoring protocol and summarize the data recorded during
monitoring. The final report must be prepared and submitted within 30 days following
resolution of any NMFS comments on the draft report. If no comments are received from
NMFS within 30 days of receipt of the draft report, the report shall be considered final. If
comments are received, a final report addressing NMFS comments must be submitted
within 30 days after receipt of comments. All draft and final hydroacoustic monitoring
reports must be submitted to PR.ITP.MonitoringReports@noaa.gov and
ITP.Wachtendonk@noaa.gov. The hydroacoustic monitoring report will contain the
informational elements described in the Hydroacoustic Monitoring Plan and, at
minimum, will include:
•

Hydrophone equipment and methods: recording device, sampling rate, distance
(m) from the pile where recordings were made; depth of recording device(s).

•

Type and size of pile being driven, substrate type, method of driving during
recordings (e.g., hammer model and energy), and total pile driving duration.

•

Whether a sound attenuation device is used and, if so, a detailed description of the
device used and the duration of its use per pile.

•

For impact pile driving: number of strikes and strike rate; depth of substrate to
penetrate; pulse duration and mean, median, and maximum sound levels (dB re: 1
μPa); SPLrms; SELcum; peak sound pressure level (SPLpeak); and single-strike
sound exposure level (SELss).

•

For vibratory driving/extraction/drilling: duration and frequency spectrum of
vibratory driving per pile; mean, median, and maximum sound levels (dB re: 1
μPa): SPLrms, SELcum (and timeframe over which the sound is averaged).

•

One-third octave band spectrum and power spectral density plot.

•

General Daily Site Conditions

o Date and time of activities.
o Water conditions (e.g., sea state, tidal state).
o Weather conditions (e.g., percent cover, visibility).
Reporting Injured or Dead Marine Mammals
In the event that personnel involved in the construction activities discover an
injured or dead marine mammal, the Navy shall report the incident to the Office of
Protected Resources (OPR), NMFS and to the regional stranding coordinator as soon as
feasible. If the death or injury was clearly caused by the specified activity, the Navy must
immediately cease the specified activities until NMFS is able to review the circumstances
of the incident and determine what, if any, additional measures are appropriate to ensure
compliance with the terms of the IHA. The IHA-holder must not resume their activities
until notified by NMFS. The report must include the following information:
•

Time, date, and location (latitude/longitude) of the first discovery (and
updated location information if known and applicable);

•

Species identification (if known) or description of the animal(s) involved;

•

Condition of the animal(s) (including carcass condition if the animal is
dead);

•

Observed behaviors of the animal(s), if alive;

•

If available, photographs or video footage of the animal(s); and

•

General circumstances under which the animal was discovered.

Negligible Impact Analysis and Determination
NMFS has defined negligible impact as an impact resulting from the specified
activity that cannot be reasonably expected to, and is not reasonably likely to, adversely
affect the species or stock through effects on annual rates of recruitment or survival (50
CFR 216.103). A negligible impact finding is based on the lack of likely adverse effects
on annual rates of recruitment or survival (i.e., population-level effects). An estimate of

the number of takes alone is not enough information on which to base an impact
determination. In addition to considering estimates of the number of marine mammals
that might be “taken” through harassment, NMFS considers other factors, such as the
likely nature of any impacts or responses (e.g., intensity, duration), the context of any
impacts or responses (e.g., critical reproductive time or location, foraging impacts
affecting energetics), as well as effects on habitat, and the likely effectiveness of the
mitigation. We also assess the number, intensity, and context of estimated takes by
evaluating this information relative to population status. Consistent with the 1989
preamble for NMFS’ implementing regulations (54 FR 40338, September 29, 1989), the
impacts from other past and ongoing anthropogenic activities are incorporated into this
analysis via their impacts on the baseline (e.g., as reflected in the regulatory status of the
species, population size and growth rate where known, ongoing sources of human-caused
mortality, or ambient noise levels).
To avoid repetition, the discussion of our analysis applies to all the species listed
in table 1, given that the anticipated effects of this activity on these different marine
mammal stocks are expected to be similar. There is little information about the nature or
severity of the impacts, or the size, status, or structure of any of these species or stocks
that would lead to a different analysis for this activity.
Pile driving activities have the potential to disturb or displace marine mammals.
Specifically, the project activities may result in take, in the form of Level A harassment
and Level B harassment from underwater sounds generated from pile driving and
removal. Potential takes could occur if individuals are present in the ensonified zone
when these activities are underway.
Estimated takes by Level B harassment would be due to potential behavioral
disturbance, and TTS. Take by Level A harassment would be due to PTS. No mortality or
serious injury is anticipated given the nature of the activity, even in the absence of the

required mitigation, and therefore none is authorized. The potential for harassment is
minimized through the construction method and the implementation of the mitigation
measures (see Mitigation section).
Take would occur within a limited, confined area (the Thames River and a small
section of the Long Island Sound) of the stocks’ ranges. Take by Level A and Level B
harassment would be reduced to the level of least practicable adverse impact through use
of mitigation measures described herein. Further, the amount of take authorized is
extremely small when compared to stock abundance, and the project is not anticipated to
impact any known important habitat areas for any marine mammal species.
Take by Level A harassment is authorized to account for the potential that an
animal could enter and remain within the area between a Level A harassment zone and
the shutdown zone for a duration long enough to be taken by Level A harassment. Any
take by Level A harassment is expected to arise from, at most, a small degree of PTS
because animals would need to be exposed to higher levels and/or longer duration than
are expected to occur here in order to incur any more than a small degree of PTS.
Additionally, and as noted previously, some subset of the individuals that are
behaviorally harassed could simultaneously incur some small degree of TTS for a short
duration of time. Because of the small degree anticipated, though, any PTS or TTS
potentially incurred here would not be expected to adversely impact individual fitness, let
alone annual rates of recruitment or survival.
Behavioral responses of marine mammals to pile driving at the project site, if any,
are expected to be mild and temporary. Marine mammals within the Level B harassment
zone may not show any visual cues they are disturbed by activities or could become alert,
avoid the area, leave the area, or display other mild responses that are not observable
such as changes in vocalization patterns. Given the limited number of piles to be installed

or extracted per day and that pile driving and removal will occur across a maximum of
242 days within the 12-month authorization period, any harassment will be temporary.
Any impacts on marine mammal prey that would occur during the Navy's activity
would have, at most, short-term effects on foraging of individual marine mammals, and
likely no effect on the populations of marine mammals as a whole. Indirect effects on
marine mammal prey during the construction are expected to be minor, and these effects
are unlikely to cause substantial effects on marine mammals at the individual level, with
no expected effect on annual rates of recruitment or survival.
In addition, it is unlikely that minor noise effects in a small, localized area of
habitat would have any effect on the stocks' annual rates of recruitment or survival. In
combination, we believe that these factors, as well as the available body of evidence from
other similar activities, demonstrate that the potential effects of the specified activities
will have only minor, short-term effects on individuals. The specified activities are not
expected to impact rates of recruitment or survival and will therefore not result in
population-level impacts.
In summary and as described above, the following factors primarily support our
determination that the impacts resulting from this activity are not expected to adversely
affect any of the species or stocks through effects on annual rates of recruitment or
survival:
●

No serious injury or mortality is anticipated or authorized;

●

The intensity of anticipated takes by Level B harassment is relatively low

for all stocks and would not be of a duration or intensity expected to result in impacts on
reproduction or survival;
●

No important habitat areas have been identified within the project area;

●

For all species, the Thames River and Long Island Sound are a very small

and peripheral part of their range and anticipated habitat impacts are minor; and

●

The Navy will implement mitigation measures, such as soft-starts for

impact pile driving and shut downs to minimize the numbers of marine mammals
exposed to injurious levels of sound, and to ensure that take by Level A harassment, is at
most, a small degree of PTS.
Based on the analysis contained herein of the likely effects of the specified
activity on marine mammals and their habitat, and taking into consideration the
implementation of the monitoring and mitigation measures, NMFS finds that the total
marine mammal take from the activity will have a negligible impact on all affected
marine mammal species or stocks.
Small Numbers
As noted previously, only take of small numbers of marine mammals may be
authorized under sections 101(a)(5)(A) and (D) of the MMPA for specified activities
other than military readiness activities. The MMPA does not define small numbers and
so, in practice, where estimated numbers are available, NMFS compares the number of
individuals taken to the most appropriate estimation of abundance of the relevant species
or stock in our determination of whether an authorization is limited to small numbers of
marine mammals. When the predicted number of individuals to be taken is fewer than
one-third of the species or stock abundance, the take is considered to be of small
numbers. Additionally, other qualitative factors may be considered in the analysis, such
as the temporal or spatial scale of the activities.
Table 9 demonstrates the number of animals that could be exposed to received
noise levels that could cause take by Level A and Level B harassment for the work at
SUBASE. Our analysis shows that less than 1 percent of each affected stock could be
taken by harassment. The numbers of animals authorized to be taken for these stocks is
considered small relative to the relevant stock's abundances, even if each estimated taking
occurred to a new individual—an extremely unlikely scenario.

Based on the analysis contained herein of the activity (including the mitigation
and monitoring measures) and the anticipated take of marine mammals, NMFS finds that
small numbers of marine mammals would be taken relative to the population size of the
affected species or stocks.
Unmitigable Adverse Impact Analysis and Determination
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 will 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 insure that any action it authorizes, funds, or carries out is not likely to
jeopardize the continued existence of any endangered or threatened species or result in
the destruction or adverse modification of designated critical habitat. To ensure ESA
compliance for the issuance of IHAs, NMFS consults internally whenever we authorize
take for endangered or threatened species.
No incidental take of ESA-listed species is authorized 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.
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
evaluate our action (i.e., the issuance of an IHA) and alternatives with respect to potential
impacts on the human environment.
This action is consistent with categories of activities identified in Categorical
Exclusion B4 (IHAs with no anticipated serious injury or mortality) of the Companion

Manual for NAO 216–6A, which do not individually or cumulatively have the potential
for significant impacts on the quality of the human environment and for which we have
not identified any extraordinary circumstances that would preclude this categorical
exclusion. Accordingly, NMFS has determined that the issuance of this IHA qualifies to
be categorically excluded from further NEPA review.
Authorization
NMFS has issued an IHA to the Navy for the potential harassment of small
numbers of six marine mammal species incidental to the New London Pier Extension
Project at SUBASE in Groton, Connecticut, that includes the previously explained
mitigation, monitoring and reporting requirements.
Dated: June 11, 2024.
Angela Somma,
Acting Director, Office of Protected Resources,
National Marine Fisheries Service.

[FR Doc. 2024-13169 Filed: 6/13/2024 8:45 am; Publication Date: 6/14/2024]