[Federal Register Volume 89, Number 76 (Thursday, April 18, 2024)]
[Notices]
[Pages 27717-27738]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-08284]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XD732]


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; proposed incidental harassment authorization; request 
for comments on proposed authorization and possible renewal.

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SUMMARY: NMFS has received a request from the U.S. Navy (Navy) for 
authorization to take marine mammals incidental to the New London Pier 
Extension Project at Naval Submarine Base (SUBASE) New London in 
Groton, Connecticut. Pursuant to the Marine Mammal Protection Act 
(MMPA), NMFS is requesting comments on its proposal to issue an 
incidental harassment authorization (IHA) to incidentally take marine 
mammals during the specified activities. NMFS is also requesting 
comments on a possible one-time, 1-year renewal that could be issued 
under certain circumstances and if all requirements are met, as 
described in Request for Public Comments at the end of this notice. 
NMFS will consider public comments prior to making any final decision 
on the issuance of the requested MMPA authorization and agency 
responses will be summarized in the final notice of our decision.

DATES: Comments and information must be received no later than May 20, 
2024.

ADDRESSES: Comments should be addressed to Jolie Harrison, Chief, 
Permits and Conservation Division, Office of Protected Resources, 
National Marine Fisheries Service and should be submitted via email to 
[email protected]. Electronic copies of the application and 
supporting documents, as well as a list of the references cited in this 
document, may be obtained online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities. In case of problems accessing these documents, 
please call the contact listed below.
    Instructions: NMFS is not responsible for comments sent by any 
other method, to any other address or individual, or received after the 
end of the comment period. Comments, including all attachments, must 
not exceed a 25-megabyte file size. All comments received are a part of 
the public record and will generally be posted online at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act without change. All personal identifying 
information (e.g., name, address) 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: 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

[[Page 27718]]

statutory terms cited above are included in the relevant sections 
below.

National Environmental Policy Act

    To comply with the National Environmental Policy Act of 1969 (NEPA; 
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, 
NMFS must review our proposed action (i.e., the issuance of an IHA) 
with respect to potential impacts on the human environment. This action 
is consistent with categories of activities identified in Categorical 
Exclusion B4 (IHAs with no anticipated serious injury or mortality) of 
the Companion Manual for NAO 216-6A, which do not individually or 
cumulatively have the potential for significant impacts on the quality 
of the human environment and for which we have not identified any 
extraordinary circumstances that would preclude this categorical 
exclusion. Accordingly, NMFS has preliminarily determined that the 
issuance of the proposed IHA qualifies to be categorically excluded 
from further NEPA review. We will review all comments submitted in 
response to this notice prior to concluding our NEPA process or making 
a final decision on the IHA request.

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.

Description of Proposed Activity

Overview

    The Navy is proposing the partial demolition and extension of pier 
31 at SUBASE New London in Groton, Connecticut (figure 1). The existing 
pier 31 would be partially demolished and then an 81-foot (ft), or 
24.7-meter (m), extension would be constructed. This project would also 
include the demolition of an existing small access ramp for pier 17. 
The proposed project includes impact and vibratory pile installation 
and vibratory pile removal. For a portion of the piles, an auger drill 
would be used inside the pipe casing to lift sediment.
    Sounds resulting from pile driving and removal may result in the 
incidental take of marine mammals by Level A and Level B harassment in 
the form of auditory injury or behavioral harassment. Underwater sound 
would be constrained to the Thames River and a small portion of the 
Long Island Sound and would be truncated by land masses in the river. 
The purpose of this project is to extend the existing pier 31 to 
provide two berths for a submarine platform that is approximately 80 ft 
(24.4 m) longer than the existing submarines. Construction activities 
would start in December 2024 and last 12 months.

Dates and Duration

    The proposed IHA would be effective from December 1, 2024, through 
November 30, 2025. Vibratory and impact pile driving and auger drilling 
are expected to start in December 2024 and take 242 days over a span of 
12 months. All pile driving and removal would be completed during 
daylight hours.

Specific Geographic Region

    The project is located at SUBASE New London in Groton, Connecticut, 
which is located approximately 6 miles (mi), or 9.5 kilometers (km), up 
the Thames River from Long Island Sound. Project activities would occur 
at the existing piers 31 and 17.
BILLING CODE 3510-22-P

[[Page 27719]]

[GRAPHIC] [TIFF OMITTED] TN18AP24.213

BILLING CODE 3510-22-C

Detailed Description of the Specified Activity

    The pier 31 extension would include the removal of 28 16-inch (in), 
or 0.41-m, fiberglass reinforced plastic fender piles. The pier 17 
demolition would include the removal of 20 14-in (0.36-m) concrete 
encased steel H-piles and 10 timber piles. Existing piles would 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 would 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 
would be completed to support permanent pile installation. Temporary 
and permanent piles would 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 would be used inside the 
pipe casing to lift sediment. Table 1

[[Page 27720]]

provides a summary of the pile driving activities.
    Concurrent Activities--In order to maintain project schedules, it 
is possible that multiple pieces of equipment would 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 proposed project. 
Table 2 provides a summary of concurrent pile driving scenarios.

                          Table 1--Number and Type of Piles To Be Installed and Removed
----------------------------------------------------------------------------------------------------------------
                                                          Number of                      Piles per
      Activity           Structure       Type and size      piles          Method           day       Total days
----------------------------------------------------------------------------------------------------------------
Demolition.........  Pier 31 partial   16-in fiberglass           28  Deadpull OR                 2           14
                      demo.             reinforced                     vibratory
                                        plastic fender.                extract.
                     Pier 17.........  14-in concrete             20  Vibratory                   5            4
                                        encased steel H-               extract.
                                        pile.
                                       Timber..........           10  Deadpull OR cut             5            2
                                                                       at mudline.
                     Temporary work    14-in steel H-             60  Vibratory                   5           12
                      trestle.          pile.                          extract.
Installation.......  Temporary work    14-in steel H-             60  Vibratory                   5           12
                      trestle.          pile.                          installation.              4           15
                                                                      Impact..........
                     Pier 31           36-in steel pipe           20  Vibratory            \a\ 0.17          120
                      extension.        pile.                          installation.            2.5            8
                                                                      Impact..........            1           20
                                                                      Auger drilling..
                     Piers 31 and 17   16-in fiberglass           60  Vibratory                   2           30
                      guaywall.         reinforced                     installation.            2.5           24
                                        plastic fender.               Impact..........
----------------------------------------------------------------------------------------------------------------
\a\ Assumes that each pile would be installed in increments of 0.17 per workday to allow for the welding,
  painting, and curing of pile sections and joins and repositioning of barges, resulting in a total installation
  rate of one pile per week.


                              Table 2--Potential Concurrent Pile Driving Scenarios
----------------------------------------------------------------------------------------------------------------
                                                                                                         Total
                                                                                                       potential
                Structure                          Type and size                    Method              days of
                                                                                                        overlap
----------------------------------------------------------------------------------------------------------------
Temporary work trestle installation and    14-in steel H-pile AND 14-in  Vibratory installation and            4
 pier 17 demolition.                        concrete encased steel H-     demolition.
                                            pile.
Temporary work trestle installation, pier  14-in steel H-pile AND 14-in  Vibratory installation and            4
 17 demolition, and pier 31 demolition.     concrete encased steel H-     demolition.
                                            pile AND 16-in fiberglass
                                            reinforced plastic fender.
Temporary work trestle installation and    14-in steel H-pile AND 16-in  Vibratory installation and           12
 pier 31 demolition.                        fiberglass reinforced         demolition.
                                            plastic fender.
----------------------------------------------------------------------------------------------------------------

    Proposed mitigation, monitoring, and reporting measures are 
described in detail later in this document (please see Proposed 
Mitigation and Proposed Monitoring and Reporting).

Description of Marine Mammals in the Area of Specified Activities

    Sections 3 and 4 of the 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/marine-mammal-protection/marine-mammal-stock-assessments) and more general information about these species 
(e.g., physical and behavioral descriptions) may be found on NMFS' 
website (https://www.fisheries.noaa.gov/find-species).
    Table 3 lists all species or stocks for which take is expected and 
proposed to be authorized for this activity and summarizes information 
related to the population or stock, including regulatory status under 
the MMPA and Endangered Species Act (ESA) and potential biological 
removal (PBR), where known. PBR is defined by the MMPA as the maximum 
number of animals, not including natural mortalities, that may be 
removed from a marine mammal stock while allowing that stock to reach 
or maintain its optimum sustainable population (as described in NMFS' 
SARs). While no serious injury or mortality is anticipated or proposed 
to be authorized here, PBR and annual serious injury and mortality 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 3 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-mammal-stock-assessments.

[[Page 27721]]



                                     Table 3--Marine Mammal Species \1\ Likely Impacted by the Specified Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                        ESA/ MMPA  status;   Stock abundance  (CV,
             Common name                  Scientific name               Stock             strategic  (Y/N)     Nmin, most recent       PBR     Annual M/
                                                                                                \2\          abundance survey) \3\               SI \4\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                               Order Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Delphinidae:
    Atlantic White-Sided Dolphin....  Lagenorhynchus acutus..  Western N Atlantic.....  -, -, N             93,233 (0.71, 54,443,         544         28
                                                                                                             2021).
    Common Dolphin..................  Delphinus delphis......  Western N Atlantic.....  -, -, N             93,100 (0.56, 59,897,       1,452        414
                                                                                                             2021).
Family Phocoenidae (porpoises):
    Harbor Porpoise.................  Phocoena phocoena......  Gulf of Maine/Bay of     -, -, N             85,765 (0.53, 56,420,         649        145
                                                                Fundy.                                       2021).
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Order Carnivora--Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Phocidae (earless seals):
    Gray Seal.......................  Halichoerus grypus.....  Western N Atlantic \5\.  -, -, N             27,911 (0.20, 23,624,       1,512      4,570
                                                                                                             2021).
    Harbor Seal.....................  Phoca vitulina.........  Western N Atlantic.....  -, -, N             61,336 (0.08, 57,637,       1,729        339
                                                                                                             2018).
    Harp Seal.......................  Pagophilus               Western N Atlantic.....  -, -, N             7.6M (UNK, 7.1M, 2019)    426,000    178,573
                                       groenlandicus.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy
  (https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies; Committee on Taxonomy, 2022).
\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 online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region.
  CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable
\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. A CV
  associated with estimated mortality due to commercial fisheries is presented in some cases.
\5\ NMFS' 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.

    As indicated above, all six species (with six managed stocks) in 
table 3 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 proposed 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 the area, 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 would be 
ensonified, and therefore incidental take of these species are not 
anticipated.

Atlantic White-sided Dolphin

    White-sided dolphins of the Western North Atlantic Stock are found 
in temperate and sub-polar waters of the North Atlantic, primarily in 
continental shelf waters to the 100-m depth contour from central West 
Greenland to North Carolina (Hayes et al., 2019). The Gulf of Maine 
population of the Western North Atlantic Stock is most common in 
continental shelf waters from Hudson Canyon to Georges Bank, and in the 
Gulf of Maine and lower Bay of Fundy. Sighting data indicate seasonal 
shifts in distribution (Northridge et al., 1997). During January to 
May, low numbers of white-sided dolphins are found from Georges Bank to 
Jeffreys Ledge (off New Hampshire), with even lower numbers south of 
Georges Bank, as documented by a few strandings collected on beaches of 
Virginia to South Carolina. From June through September, large numbers 
of white-sided dolphins are found from Georges Bank to the lower Bay of 
Fundy. From October to December, white-sided dolphins occur at 
intermediate densities from southern Georges Bank to southern Gulf of 
Maine (Payne and Heinemann, 1990). Sightings south of Georges Bank, 
particularly around Hudson Canyon, occur year-round but at low 
densities. In the North Atlantic, Atlantic white-sided dolphins travel 
in pods with an average group size of 12 individuals (from AMAPPS 
(Palka et al., 2017 and 2021)).
    The Navy conducted a 3-year marine mammal survey from the mouth of 
Thames River to just north of SUBASE from 2017 through 2019, using 
line-transect methods. Atlantic white-sided dolphins were not 
documented (Tetra Tech, 2019) but are likely to occur near the mouth of 
the river and out into Long Island Sound during the fall, with peak 
abundance in October (Northeast Ocean Data, 2019).

Common Dolphin

    The common dolphin is found world-wide in temperate to subtropical 
seas. In the North Atlantic, common dolphins are found over the 
continental shelf between the 100-m and 2,000-m isobaths and over 
prominent underwater topography and east to the mid-Atlantic Ridge 
(Hayes et al., 2019), but may be found in shallower shelf waters as 
well. They can be found from Cape Hatteras northeast to Georges Bank 
from mid-January to May and in Gulf of Maine from mid-summer to autumn 
(Hayes et al., 2019). In the North Atlantic, common dolphins travel in 
pods with an average group size of 30 individuals (from AMAPPS (Palka 
et al., 2017 and 2021)).
    Common dolphins are expected to occur in the vicinity of the 
project area in Long Island Sound in moderate numbers but were not 
found in the Navy's Thames River study (Tetra Tech, 2019).

Harbor Porpoise

    Harbor porpoise occur along the US and Canadian east coast (Hayes 
et al., 2019). They rarely occur in waters warmer than 62.6 [deg]F (17 
[deg] Celsius; Read,

[[Page 27722]]

1990). The Gulf of Maine/Bay of Fundy stock is found is concentrated in 
the northern Gulf of Maine and southern Bay of Fundy region, generally 
in waters less than 150 m deep (Waring et al., 2017). During fall 
(October to December) and spring (April to June) harbor porpoises are 
widely dispersed from New Jersey to Maine. During winter (January to 
March), intermediate densities of harbor porpoises can be found in 
waters off New Jersey to North Carolina, and lower densities are found 
in waters off New York to New Brunswick, Canada. In the summer they are 
sighted primarily in the northern Gulf of Maine and southern Bay of 
Fundy. They are seen from the coastline to deep waters (>1,800 m; 
Westgate and Read, 1998), although the majority of the population is 
found over the continental shelf (Waring et al., 2017). In most areas, 
harbor porpoise occur in small groups of just a few individuals. Harbor 
porpoise must forage nearly continuously to meet their high metabolic 
needs (Wisniewska et al., 2016). They consume up to 550 small fish 
(1.2-3.9 in [3-10 cm]) per hour at a nearly 90 percent capture success 
rate (Wisniewska et al., 2016).
    Harbor porpoise have not been documented in the Thames River (Tetra 
Tech, 2019) but are likely to occur near the mouth of the river and out 
into Long Island Sound during the fall, with peak abundance in December 
(Northeast Ocean Data, 2019).

Gray Seal

    Gray seals in the project area belong to the western North Atlantic 
stock. The range for this stock is from New Jersey to Labrador. Current 
population trends show that gray seal abundance is likely increasing in 
the U.S. Atlantic EEZ (Hayes et al., 2019). In U.S. waters, year-round 
breeding of approximately 400 animals has been documented on areas of 
outer Cape Cod and Muskeget Island in Massachusetts. They are a coastal 
species that generally remains within the continental shelf region but 
do venture into deeper water to feed. Gray seals primarily feed on 
fish, squid, various crustacean species, and octopus.
    Monthly observations over the 3-year marine mammal survey yielded a 
total of three sightings of individual gray seals (Tetra Tech, 2019). 
No seals were observed hauled out onshore (Tetra Tech, 2019) and there 
are no known haulout areas within the Thames River (Navy, 2018). Gray 
seals are common in Long Island Sound from September through June 
(Medic, 2005).

Harbor Seal

    Harbor seals are found in all nearshore waters of the North 
Atlantic Ocean and adjoining seas above about lat. 30 [deg] N (Burns, 
2009). In the western North Atlantic, harbor seals are distributed from 
the eastern Canadian Arctic and Greenland down the east coast of the 
United States (Hayes et al., 2019). They occur seasonally along the 
coasts from southern New England to New Jersey from September through 
late May. Haulout and pupping sites are located off Manomet, MA, and 
the Isles of Shoals, ME (Waring et al., 2016).
    Harbor seals are central-place foragers (Orians and Pearson, 1979) 
and tend to exhibit strong site fidelity within season and across 
years, generally forage close to haulout sites, and repeatedly visit 
specific foraging areas (Grigg et al., 2012; Suryan and Harvey, 1998; 
Thompson et al., 1998). Harbor seals tend to forage at night and haul 
out during the day (Grigg et al., 2012; London et al., 2001; Stewart 
and Yochem, 1994; Yochem et al., 1987). Tide levels affect the maximum 
number of seals hauled out, with the largest number of seals hauled out 
at low tide, but time of day and season have the greatest influence on 
haul out behavior (Manugian et al., 2017; Patterson and Acevedo-
Guti[eacute]rrez, 2008; Stewart and Yochem, 1994). Harbor seals molt 
from May through June. Peak numbers of harbor seals haul out in late 
May to early June, which coincides with the peak molt. During both 
pupping and molting seasons, the number of seals and the length of time 
hauled out per day increase, from an average of 7 to 10-12 hours per 
day (Harvey and Goley, 2011; Huber et al., 2001; Stewart and Yochem, 
1994).
    Harbor seals are the most commonly observed marine mammals in the 
Thames River. Monthly observations over the 3-year marine mammal survey 
yielded a total of 12 sightings of individual harbor seals (Tetra Tech, 
2019). Most of the sightings were in the inner portion of the river, 
north of the I-95 Bridge. No seals were observed hauled out onshore 
(Tetra Tech, 2019), and there are no known haulout areas within the 
Thames River (Navy, 2018). Harbor seal populations have increased in 
Connecticut since the 1980s and they are common in Long Island Sound 
from September through June (Medic, 2005).

Harp Seal

    Harp seals are highly migratory and occur throughout much of the 
North Atlantic and Arctic Oceans (Hayes et al., 2019). Breeding occurs 
between late-February and April and adults then assemble on suitable 
pack ice to undergo the annual molt. The migration then continues north 
to Arctic summer feeding grounds. Harp seal occurrence in the project 
area is considered rare. However, since the early 1990s, numbers of 
sightings and strandings have been increasing off the east coast of the 
United States from Maine to New Jersey (Hayes et al., 2019). These 
appearances usually occur in January through May (Harris et al., 2002), 
when the western North Atlantic stock is at its most southern point of 
migration.
    Harp seals are not known to regularly occur in the Thames River as 
previous surveys have not recorded their presence (Tetra Tech, 2019). 
However, two harp seals were identified in March and one harp seal in 
April 2019 by Mystic Aquarium staff. On both occasions they were 
observed hauled out on the finger piers of the marina at SUBASE (Navy, 
2019a). Harp seals are also expected to occur within Long Island Sound 
from January through May (Hayes et al., 2019).

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 4.

[[Page 27723]]



                  Table 4--Marine Mammal Hearing Groups
                              [NMFS, 2018]
------------------------------------------------------------------------
               Hearing group                 Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen         7 Hz to 35 kHz.
 whales).
Mid-frequency (MF) cetaceans (dolphins,      150 Hz to 160 kHz.
 toothed whales, beaked whales, bottlenose
 whales).
High-frequency (HF) cetaceans (true          275 Hz to 160 kHz.
 porpoises, Kogia, river dolphins,
 Cephalorhynchid, Lagenorhynchus cruciger &
 L. australis).
Phocid pinnipeds (PW) (underwater) (true     50 Hz to 86 kHz.
 seals).
Otariid pinnipeds (OW) (underwater) (sea     60 Hz to 39 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 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 
(Hemil[auml] 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

    This section provides a discussion of the ways in which components 
of the specified activity may impact marine mammals and their habitat. 
The Estimated Take of Marine Mammals section later in this document 
includes a quantitative analysis of the number of individuals that are 
expected to be taken by this activity. The Negligible Impact Analysis 
and Determination section considers the content of this section, the 
Estimated Take of Marine Mammals section, and the Proposed Mitigation 
section, to draw conclusions regarding the likely impacts of these 
activities on the reproductive success or survivorship of individuals 
and whether those impacts are reasonably expected to, or reasonably 
likely to, adversely affect the species or stock through effects on 
annual rates of recruitment or survival.

Description of Sound Sources

    The marine soundscape is comprised of both ambient and 
anthropogenic sounds. Ambient sound is defined as the all-encompassing 
sound in a given place and is usually a composite of sound from many 
sources both near and far. The sound level of an area is defined by the 
total acoustical energy being generated by known and unknown sources. 
These sources may include physical (e.g., waves, wind, precipitation, 
earthquakes, ice, atmospheric sound), biological (e.g., sounds produced 
by marine mammals, fish, and invertebrates), and anthropogenic sound 
(e.g., vessels, dredging, aircraft, construction).
    The sum of the various natural and anthropogenic sound sources at 
any given location and time--which comprise ``ambient'' or 
``background'' sound--depends not only on the source levels (as 
determined by current weather conditions and levels of biological and 
shipping activity) but also on the ability of sound to propagate 
through the environment. In turn, sound propagation is dependent on the 
spatially and temporally varying properties of the water column and sea 
floor, and is frequency-dependent. As a result of the dependence on a 
large number of varying factors, ambient sound levels can be expected 
to vary widely over both coarse and fine spatial and temporal scales. 
Sound levels at a given frequency and location can vary by 10 to 20 dB 
from day to day (Richardson et al., 1995). The result is that, 
depending on the source type and its intensity, sound from the 
specified activity may be a negligible addition to the local 
environment or could form a distinctive signal that may affect marine 
mammals.
    In-water construction activities associated with the project would 
include vibratory pile removal, impact and vibratory pile driving, and 
auger drilling within pipe casings. The sounds produced by these 
activities fall into one of two general sound types: impulsive and non-
impulsive. Impulsive sounds (e.g., explosions, gunshots, sonic booms, 
impact pile driving) are typically transient, brief (less than 1 
second), broadband, and consist of high peak sound pressure with rapid 
rise time and rapid decay (ANSI, 1986; NIOSH, 1998; ANSI, 2005; NMFS, 
2018). Non-impulsive sounds (e.g., aircraft, machinery operations such 
as drilling or dredging, vibratory pile driving, and active sonar 
systems) can be broadband, narrowband or tonal, brief or prolonged 
(continuous or intermittent), and typically do not have the high peak 
sound pressure with raid rise/decay time that impulsive sounds do 
(ANSI, 1995; NIOSH, 1998; NMFS, 2018). The distinction between these 
two sound types is important because they have differing potential to 
cause physical effects, particularly with regard to hearing (e.g., 
Ward, 1997 in Southall et al., 2007).
    Impact hammers operate by repeatedly dropping a heavy piston onto a 
pile to drive the pile into the substrate. Sound generated by impact 
hammers is characterized by rapid rise times and high peak levels, a 
potentially injurious combination (Hastings and Popper, 2005). 
Vibratory hammers install piles by vibrating them and allowing the 
weight of the hammer to push them into the sediment. The vibrations 
produced also cause liquefaction of the substrate surrounding the pile, 
enabling the pile to be extracted or driven into the ground more 
easily. Vibratory hammers produce significantly less sound than impact 
hammers. Peak sound pressure levels (SPLs) may be 180 dB or greater, 
but are generally 10 to 20 dB lower than SPLs generated during impact 
pile driving of the same-sized pile (Oestman et al., 2009). Rise time 
is slower, reducing the probability and severity of injury, and sound 
energy is distributed over a greater amount of time (Nedwell and 
Edwards, 2002; Carlson et al., 2005). For a portion of the piles, an 
auger drill (rotary drill with a spiral shaft that drills through loose 
rock or soft sediment) would be used inside the pipe casing to lift 
sediment; no rock drilling would be required.
    The likely or possible impacts of the Navy's proposed activity on 
marine mammals could involve both non-acoustic and acoustic stressors. 
Potential non-acoustic stressors could result from the physical 
presence of the equipment and personnel; however, any impacts to marine 
mammals are

[[Page 27724]]

expected to be primarily acoustic in nature. Acoustic stressors include 
effects of heavy equipment operation during pile installation and 
removal, and sediment removal during auger drilling.

Acoustic Impacts

    The introduction of anthropogenic noise into the aquatic 
environment from pile driving is the primary means by which marine 
mammals may be harassed from the proposed activity. In general, animals 
exposed to natural or anthropogenic sound may experience physical and 
psychological effects, ranging in magnitude from none to severe 
(Southall et al., 2007). In general, exposure to pile driving noise has 
the potential to result in auditory threshold shifts and behavioral 
reactions (e.g., avoidance, temporary cessation of foraging and 
vocalizing, changes in dive behavior). 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 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. mom 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., 2004; 
Southall et al., 2007). Here we discuss physical auditory effects 
(threshold shifts) followed by behavioral effects and potential impacts 
on habitat.
    NMFS defines a noise-induced threshold shift (TS) as a change, 
usually an increase, in the threshold of audibility at a specified 
frequency or portion of an individual's hearing range above a 
previously established reference level (NMFS, 2018). The amount of 
threshold shift is customarily expressed in dB. A TS can be permanent 
or temporary. As described in NMFS (2018), there are numerous factors 
to consider when examining the consequence of TS, including, but not 
limited to, the signal temporal pattern (e.g., impulsive or non-
impulsive), likelihood an individual would be exposed for a long enough 
duration or to a high enough level to induce a TS, the magnitude of the 
TS, time to recovery (seconds to minutes or hours to days), the 
frequency range of the exposure (i.e., spectral content), the hearing 
frequency range of the exposed species relative to the signal's 
frequency spectrum (i.e., how an 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).
    Permanent Threshold Shift (PTS)--NMFS defines PTS 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, 2018). Available data 
from humans and other terrestrial mammals indicate that a 40-dB 
threshold shift approximates PTS onset (see Ward et al., 1958, 1959; 
Ward, 1960; Kryter et al., 1966; Miller, 1974; Ahroon et al., 1996; 
Henderson et al., 2008). PTS levels for marine mammals are estimates, 
as with the exception of a single study unintentionally inducing PTS in 
a harbor seal (Kastak et al., 2008), there are no empirical data 
measuring PTS in marine mammals largely due to the fact that, for 
various ethical reasons, experiments involving anthropogenic noise 
exposure at levels inducing PTS are not typically pursued or authorized 
(NMFS, 2018).
    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, 2018). Based on data from cetacean TTS 
measurements (Southall et al., 2007, 2019), a TTS of 6 dB is considered 
the minimum threshold shift clearly larger than any day-to-day or 
session-to-session variation in a subject's normal hearing ability 
(Schlundt et al., 2000; Finneran et al., 2000, 2002). As described in 
Finneran (2015), marine mammal studies have shown the amount of TTS 
increases with cumulative sound exposure level (SELcum) in 
an accelerating fashion: At low exposures with lower SELcum, 
the amount of TTS is typically small and the growth curves have shallow 
slopes. At exposures with higher SELcum, the growth curves 
become steeper and approach linear relationships with the noise 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 serious (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 a time when 
communication is critical for successful mother/calf interactions could 
have more serious impacts. We note that reduced hearing sensitivity as 
a simple function of aging has been observed in marine mammals, as well 
as humans and other taxa (Southall et al., 2007), so we can infer that 
strategies exist for coping with this condition to some degree, though 
likely not without cost.
    Many studies have examined noise-induced hearing loss in marine 
mammals (see Finneran (2015) and Southall et al. (2019) for summaries). 
TTS is the mildest form of hearing impairment that can occur during 
exposure to sound (Kryter, 2013). While experiencing TTS, the hearing 
threshold rises, and a sound must be at a higher level in order to be 
heard. In terrestrial and marine mammals, TTS can last from minutes or 
hours to days (in cases of strong TTS). 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). These studies examined 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 at low frequencies, well below the region of best sensitivity 
for a species or hearing group, are less hazardous than those at higher 
frequencies, 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

[[Page 27725]]

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, SELcum 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, 2018). Additionally, the existing marine 
mammal TTS data come from a limited number of individuals within these 
species.
    Relationships between TTS and PTS thresholds have not been studied 
in marine mammals, and there is no PTS data for cetaceans, but such 
relationships are assumed to be similar to those in humans and other 
terrestrial mammals. PTS typically occurs at exposure levels at least 
several decibels above that inducing mild TTS (e.g., a 40-dB threshold 
shift approximates PTS onset (Kryter et al., 1966; Miller, 1974), while 
a 6-dB threshold shift approximates TTS onset (Southall et al., 2007; 
2019). Based on data from terrestrial mammals, a precautionary 
assumption is that the PTS 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 
PTS cumulative sound exposure level thresholds are 15 to 20 dB higher 
than TTS cumulative sound exposure level thresholds (Southall et al., 
2007; 2019). Given the higher level of sound or longer exposure 
duration necessary to cause PTS as compared with TTS, it is 
considerably less likely that PTS could occur.
    Installing piles for this project requires either impact pile 
driving or vibratory pile driving. For this project, these activities 
could occur at the same time, and there would be pauses in activities 
producing the sound during each day. Given these pauses, and that many 
marine mammals are likely moving through the ensonified area and not 
remaining for extended periods of time, the potential for TS declines.
    Behavioral Harassment--Exposure to noise from pile driving and 
removal also has the potential to behaviorally disturb marine mammals. 
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. 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. However, 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).
    Disturbance may result in changing durations of surfacing and 
dives, number of blows per surfacing, or moving direction and/or speed; 
reduced/increased vocal activities; changing/cessation of certain 
behavioral activities (such as socializing or feeding); visible startle 
response or aggressive behavior (such as tail/fluke slapping or jaw 
clapping); or avoidance of areas where sound sources are located. 
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., 2003; Southall et al., 
2007; 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-C of Southall et al. 
(2007) for a review of studies involving marine mammal behavioral 
responses to sound.
    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. 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.
    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., Seyle, 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

[[Page 27726]]

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). 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. 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, 2003), however 
distress is an unlikely result of this project based on observations of 
marine mammals during previous, similar projects in the area.
    Masking--Sound can disrupt behavior through masking, or interfering 
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). Masking occurs when 
the receipt of a sound is interfered with by another coincident sound 
at similar frequencies and at similar or higher intensity, and may 
occur whether the sound is natural (e.g., snapping shrimp, wind, waves, 
precipitation) or anthropogenic (e.g., pile driving, shipping, sonar, 
seismic exploration) in origin. 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. Masking of natural sounds can result when human activities 
produce high levels of background sound at frequencies important to 
marine mammals. Conversely, if the background level of underwater sound 
is high (e.g., on a day with strong wind and high waves), an 
anthropogenic sound source would not be detectable as far away as would 
be possible under quieter conditions and would itself be masked.
    Airborne Acoustic Effects--Although pinnipeds are known to haul out 
regularly on manmade objects, we believe that incidents of take 
resulting solely from airborne sound are unlikely because there are no 
known haulouts in the Thames River. The closest haulout site for harbor 
and gray seals is 10 miles south of pier 31 at Fishers Island in Long 
Island Sound. There is a possibility that an animal could surface in-
water, but with head out, within the area in which airborne sound 
exceeds relevant thresholds and thereby be exposed to levels of 
airborne sound that we associate with harassment, but any such 
occurrence would likely be accounted for in our estimation of 
incidental take from underwater sound. Therefore, authorization of 
incidental take resulting from airborne sound for pinnipeds is not 
warranted, and airborne sound is not discussed further here.

Marine Mammal Habitat Effects

    The Navy's construction activities could have localized, temporary 
impacts on marine mammal habitat by increasing in-water sound pressure 
levels and slightly decreasing water quality. However, since the focus 
of the proposed action is pile driving, a minimal amount of net habitat 
loss is expected, as pier 31 would only be extended 87 ft (26.5 m). 
Construction activities are localized and would likely have temporary 
impacts on marine mammal habitat through increases in underwater 
sounds. Increased noise levels may affect acoustic habitat (see masking 
discussion above) and adversely affect marine mammal prey in the 
vicinity of the project area (see discussion below). During pile 
driving activities, elevated levels of underwater noise would ensonify 
the project area where both fishes and marine mammals may occur and 
could affect foraging success. Additionally, marine mammals may avoid 
the area during construction; 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.
    Temporary and localized reduction in water quality would occur 
because of in-water construction activities as well. Most of this 
effect would occur during the installation and removal of piles when 
bottom sediments are disturbed. The installation of piles would disturb 
bottom sediments and may cause a temporary increase in suspended 
sediment in the project area. In general, turbidity associated with 
pile installation is localized to about 25-ft (7.6-m) radius around the 
pile (Everitt et al., 1980). Pinnipeds are not expected to be close 
enough to the pile driving areas to experience effects of turbidity, 
and could avoid localized areas of turbidity. Therefore, we expect the 
impact from increased turbidity levels to be discountable to marine 
mammals and do not discuss it further.

In-Water Construction Effects on Potential Foraging Habitat

    The proposed activities would not result in permanent impacts to 
habitats used directly by marine mammals outside of the actual 
footprint of the extended pier 31. The total seafloor area affected by 
pile installation and removal is a very small area compared to the vast 
foraging area available to marine mammals in the Thames River and Long 
Island Sound. Pile extraction and installation may have impacts on 
benthic invertebrate species primarily associated with disturbance of 
sediments that may cover or displace some invertebrates. The impacts 
would be temporary and highly localized, and no habitat would be 
permanently displaced by construction. Therefore, it is expected that 
impacts on foraging opportunities for marine mammals due to the 
demolition and expansion of pier 31 would be minimal.
    It is possible that avoidance by potential prey (i.e., fish) in the

[[Page 27727]]

immediate area may occur due to temporary loss of this foraging 
habitat. The duration of fish avoidance of this area after pile driving 
stops is unknown, but we anticipate a rapid return to normal 
recruitment, distribution and behavior. Any behavioral avoidance by 
fish of the disturbed area would still leave large areas of fish and 
marine mammal foraging habitat in the nearby vicinity in the in the 
project area, Thames River, and Long Island Sound.

Effects on Potential Prey

    Sound may affect marine mammals through impacts on the abundance, 
behavior, or distribution of prey species (e.g., fish). Marine mammal 
prey varies by species, season, and location. Here, we describe studies 
regarding the effects of noise on known marine mammal prey.
    Fish 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 which 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 fish, although several are 
based on studies in support of large, multiyear bridge construction 
projects (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., Pena 
et al., 2013; Wardle et al., 2001; Jorgenson and Gyselman, 2009; Cott 
et al., 2012).
    SPLs of sufficient strength have been known to cause injury to 
fishes and fish mortality (summarized in Popper et al., (2014)). 
However, in most fish species, hair cells in the ear continuously 
regenerate and loss of auditory function likely is restored when 
damaged cells are replaced with new cells. Halvorsen et al. (2012b) 
showed that a TTS of 4 to 6 dB was recoverable within 24 hours for one 
species. Impacts would be most severe when the individual fish is close 
to the source and when the duration of exposure is long. Injury caused 
by barotrauma can range from slight to severe and can cause death, and 
is most likely for fish with swim bladders. Barotrauma injuries have 
been documented during controlled exposure to impact pile driving 
(Halvorsen et al., 2012a; Casper et al., 2013; 2017).
    Fish populations in the proposed project area that serve as marine 
mammal prey could be temporarily affected by noise from pile 
installation and removal. The frequency range in which fishes generally 
perceive underwater sounds is 50 to 2,000 Hz, with peak sensitivities 
below 800 Hz (Popper and Hastings, 2009). Fish behavior or distribution 
may change, especially with strong and/or intermittent sounds that 
could harm fishes. High underwater SPLs have been documented to alter 
behavior, cause hearing loss, and injure or kill individual fish by 
causing serious internal injury (Hastings and Popper, 2005).
    The greatest potential impact to fishes during construction would 
occur during impact pile driving. However, the duration of impact pile 
driving would be limited to the final stage of installation 
(``proofing'') after the pile has been driven as close as practicable 
to the design depth with a vibratory driver. In-water construction 
activities would only occur during daylight hours, allowing fish to 
forage and transit the project area in the evening. Vibratory pile 
driving and auger drilling could elicit behavioral reactions from 
fishes such as temporary avoidance of the area but is unlikely to cause 
injuries to fishes or have persistent effects on local fish 
populations. Construction also would have minimal permanent and 
temporary impacts on benthic invertebrate species, a marine mammal prey 
source. In addition, it should be noted that the area in question is 
low-quality habitat since it is already highly developed and 
experiences a high level of anthropogenic noise from normal SUBASE 
operations and other vessel traffic.
    The area impacted by the project is relatively small compared to 
the available habitat in the remainder of the Thames River and Long 
Island Sound, and there are no areas of particular importance that 
would be impacted by this project. Any behavioral avoidance by fish of 
the disturbed area would still leave significantly large areas of fish 
and marine mammal foraging habitat in the nearby vicinity. As described 
in the preceding, the potential for the Navy's construction to affect 
the availability of prey to marine mammals or to meaningfully impact 
the quality of physical or acoustic habitat is considered to be 
insignificant.

Estimated Take of Marine Mammals

    This section provides an estimate of the number of incidental takes 
proposed for authorization through the IHA, which will inform NMFS' 
consideration of ``small numbers,'' the negligible impact 
determinations, and impacts on subsistence uses.
    Harassment is the only type of take expected to result from these 
activities. Except with respect to certain activities not pertinent 
here, section 3(18) of the MMPA defines ``harassment'' as any act of 
pursuit, torment, or annoyance, which: (i) has the potential to injure 
a marine mammal or marine mammal stock in the wild (Level A 
harassment); or (ii) has the potential to disturb a marine mammal or 
marine mammal stock in the wild by causing disruption of behavioral 
patterns, including, but not limited to, migration, breathing, nursing, 
breeding, feeding, or sheltering (Level B harassment).
    Authorized takes would primarily be by Level B harassment, as use 
of the acoustic (i.e., pile driving 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 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

[[Page 27728]]

activity. Below we describe how the proposed take numbers are 
estimated.
    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 proposed take estimates.

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 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 [mu]Pa)) for continuous (e.g., vibratory pile 
driving, drilling) and above RMS SPL 160 dB re 1 [mu]Pa for non-
explosive impulsive (e.g., seismic airguns) or intermittent (e.g., 
scientific sonar) sources. Generally speaking, Level B harassment take 
estimates based on these behavioral harassment thresholds are expected 
to include any likely takes by TTS as, in most cases, the likelihood of 
TTS occurs at distances from the source less than those at which 
behavioral harassment is likely. TTS of a sufficient degree can 
manifest as behavioral harassment, as reduced hearing sensitivity and 
the potential reduced opportunities to detect important signals 
(conspecific communication, predators, prey) may result in changes in 
behavior patterns that would not otherwise occur.
    The Navy's proposed 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 [mu]Pa 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 
proposed 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-mammal-acoustic-technical-guidance.

                     Table 5--Thresholds Identifying the Onset of Permanent Threshold Shift
----------------------------------------------------------------------------------------------------------------
                                                         PTS onset thresholds *  (received level)
             Hearing group              ------------------------------------------------------------------------
                                                  Impulsive                         Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans...........  Cell 1: Lp,0-pk,flat: 219   Cell 2: LE,p,LF,24h: 199 dB.
                                          dB; LE,p,LF,24h: 183 dB.
Mid-Frequency (MF) Cetaceans...........  Cell 3: Lp,0-pk,flat: 230   Cell 4: LE,p,MF,24h: 198 dB.
                                          dB; LE,p,MF,24h: 185 dB.
High-Frequency (HF) Cetaceans..........  Cell 5: Lp,0-pk,flat: 202   Cell 6: LE,p,HF,24h: 173 dB.
                                          dB; LE,p,HF,24h: 155 dB.
Phocid Pinnipeds (PW) (Underwater).....  Cell 7: Lp,0-pk,flat: 218   Cell 8: LE,p,PW,24h: 201 dB.
                                          dB; LE,p,PW,24h: 185 dB.
Otariid Pinnipeds (OW) (Underwater)....  Cell 9: Lp,0-pk,flat: 232   Cell 10: LE,p,OW,24h: 219 dB.
                                          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 [mu]Pa, and weighted cumulative sound
  exposure level (LE,p) has a reference value of 1[mu]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 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 proposed project. 
Pile driving generates

[[Page 27729]]

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 x 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 x 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 x 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 6). Generally, we choose source levels from similar pile types 
from locations (e.g., geology, bathymetry) similar to the project.

                                 Table 6--Proxy Sound Source Levels for Pile Sizes, Driving Methods, and Auger Drilling
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                   Peak SPL  (re 1   RMS SPL  (re 1     SEL  (re 1
            Pile type                     Pile size                 Method          [mu]Pa (rms))    [mu]Pa (rms))    [mu]Pa (rms))         Source
--------------------------------------------------------------------------------------------------------------------------------------------------------
Steel...........................  14-in H-pile............  Vibratory............               NA              158              158  Navy, 2019b.
                                                            Impact...............              194              177              162  Navy, 2019b.
                                  36-in pipe pile.........  Vibratory............               NA              168              168  Navy, 2018.
                                                            Impact...............              209              198              183  Navy, 2019b.
                                                            Auger drilling.......               NA              154               NA  Dazey et al.,
                                                                                                                                       2012.
Concrete encased steel..........  14-in H-pile............  Vibratory............              185              162              157  Caltrans, 2020.
Fiberglass reinforced plastic...  16-in fender............  Vibratory............               NA              158               NA  Illingworth and
                                                                                                                                       Rodkin, 2017.
                                                            Impact...............              177              165              157  California
                                                                                                                                       Department 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 7.

 Table 7--Calculated Proxy Sound Source Levels for Potential Concurrent
                         Pile Driving Scenarios
------------------------------------------------------------------------
                                                            Calculated
                                                            proxy sound
           Structure               Pile type and proxy     source level
                                                             (dB RMS)
------------------------------------------------------------------------
Temporary work trestle           Vibratory installation              163
 installation and pier 17         of 14-in steel H-pile:
 demolition.                      158 dB RMS.
                                 Vibratory demolition of
                                  14-in concrete encased
                                  steel H-pile: 162 dB
                                  RMS.
Temporary work trestle           Vibratory installation              165
 installation, pier 17            of 14-in steel H-pile:
 demolition, and pier 31          158 dB RMS.
 demolition.                     Vibratory demolition of
                                  14-in concrete encased
                                  steel H-pile: 162 dB
                                  RMS.
                                 Vibratory demolition of
                                  16-in fiberglass
                                  reinforced plastic
                                  fender: 158 dB RMS.

[[Page 27730]]

 
Temporary work trestle           Vibratory installation              161
 installation and pier 31         of 14-in steel H-pile:
 demolition.                      158 dB RMS.
                                 Vibratory demolition of
                                  16-in fiberglass
                                  reinforced plastic
                                  fender: 158 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 8--NMFS User Spreadsheet Inputs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                  Duration
                                                                                                       Weighting                  of sound
                                                                                                         factor     Number  of   production   Number  of
                  Method                        Pile size and type          Spreadsheet  tab used      adjustment   piles  per  within 24-h    strikes
                                                                                                         (kHz)         day         period      per pile
                                                                                                                                   (sec)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory................................  16-in fiberglass reinforced   A.1. Vibratory pile driving          2.5            2         2400           NA
                                            plastic fender piles
                                            install and removal.
                                           14-in steel H-pile            A.1. Vibratory pile driving          2.5            5         6000           NA
                                            (temporary) install and
                                            removal.
                                           14-in concrete encased steel  A.1. Vibratory pile driving          2.5            5         6000           NA
                                            H-pile removal.
                                           36-in steel pipe pile         A.1 Vibratory pile driving.          2.5         0.17        428.4           NA
                                            install.
Impact...................................  16-in fiberglass reinforced   E.1. Impact pile driving...            2          2.5           NA         1000
                                            plastic fender piles.
                                           14-in steel H-pile            E.1. Impact pile driving...            2            4           NA         1000
                                            (temporary) install.
                                           36-in steel pipe pile         E.1. Impact pile driving...            2          2.5           NA         1000
                                            install.
Auger drilling...........................  36-in steel pipe pile         A. Stationary source: non-             2            1        28800           NA
                                            install.                      impulsive, continuous.
Concurrent pile driving..................  14-in steel H-pile AND 14-in  A.1. Vibratory pile driving          2.5            5         6000           NA
                                            concrete encased steel H-
                                            pile.
                                           14-in steel H-pile AND 14-in  A.1. Vibratory pile driving          2.5            5         6000           NA
                                            concrete encased steel H-
                                            pile AND 16-in fiberglass
                                            reinforced plastic fender.
                                           14-in steel H-pile AND 16-in  A.1. Vibratory pile driving          2.5            7         8400           NA
                                            fiberglass reinforced
                                            plastic fender.
--------------------------------------------------------------------------------------------------------------------------------------------------------


                                              Table 9--Calculated Level A and Level B Harassment Isopleths
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                      Level A harassment zone  (m/km\2\)                    Level B
                  Method                         Pile size  and type     ------------------------------------------------------------   harassment zone
                                                                             MF-cetaceans        HF-cetaceans           Phocid             (m/km\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory.................................  16-in fiberglass reinforced                0.3/0        4.9/0.000075         2.0/0.00013       3,415/2.47916
                                             plastic fender piles
                                             install and removal.
                                            14-in steel H-pile                  0.5/0.000001        9.0/0.000253        3.7/0.000043  ..................
                                             (temporary) install and
                                             removal.
                                            14-in concrete encased steel        1.0/0.000003       16.5/0.000851        6.8/0.000145      6,310/2.620145
                                             H-pile removal.
                                            36-in steel pipe pile               0.4/0.000001        7.2/0.000162         2.9/0.00026     15,849/3.435273
                                             install.
Impact....................................  16-in fiberglass reinforced          1.2/0.00005       40.5/0.005136       18.2/0.001035         22/0.001513
                                             plastic fender piles.
                                            14-in steel H-pile                  3.6/0.000041      119.3/0.044565       53.6/0.009004        136/0.056637
                                             (temporary) install.
                                            36-in steel pipe pile               65.4/0.01341      2,191/1.588304       984.4/0.86872      3,415/2.620145
                                             install.
Auger drilling............................  36-in steel pipe pile                      0.1/0        0.8/0.000002        0.5/0.000001      1,848/1.359058
                                             install.
Concurrent pile driving...................  14-in steel H-pile AND 14-in    a b 1.2/0.000005   \a\ 19.3/0.001164    a b 7.9/0.000195  \a\ 7,356/3.121835
                                             concrete encased steel H-                         \b\ 19.3/0.001134                      \b\ 7,356/0.205166
                                             pile.
                                            14-in steel H-pile AND 14-in  a b c 1.6/0.000008   a c 26.2/0.002146         a b c 10.8/         \a\ 10,000/
                                             concrete encased steel H-                         \b\ 26.2/0.001807            0.000365            3.197942
                                             pile AND 16-in fiberglass                                                                       \b\ 10,000/
                                             reinforced plastic fender.                                                                         0.205166
                                                                                                                                             \c\ 10,000/
                                                                                                                                                2.822399
                                            14-in steel H-pile AND 16-in     a b 1.10.000004     a b 7.8/0.00099    a b 7.3/0.000167  \a\ 5,412/3.078261
                                             fiberglass reinforced                                                                    \b\ 5,412/2.822399
                                             plastic fender.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Harassment zones mapped from pier 31.
\b\ Harassment zones mapped from pier 17.
\c\ Harassment zones mapped from existing pier 31 for fender pile extraction.


[[Page 27731]]

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, and describe how the information 
provided is synthesized to produce a quantitative estimate of the take 
that is reasonably likely to occur and proposed for authorization. 
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 [km\2\] x estimated density 
[individuals/km\2\]) x 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 km\2\. Only vibratory pile driving 
activities would 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 
km\2\) was used to calculate take (table 10). Therefore, using the 
equation given above, the calculated estimate take by Level B 
harassment for Atlantic white-sided dolphins would be one. However, a 
solitary dolphin is unlikely to be encountered, 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 proposed for authorization.

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 km\2\. Only 
vibratory pile driving activities would 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 km\2\) was used to calculate take (table 10). 
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 9) and is entirely contained within the 
Thames River. Therefore, no take by Level A harassment is anticipated 
or proposed for authorization.

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 km\2\. Only 
vibratory pile driving activities would 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 km\2\) was used to calculate take (table 10). 
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 9) and is entirely contained 
within the Thames River. Therefore, no take by Level A harassment is 
anticipated or proposed for authorization.
    For concurrent activities, the largest Level A harassment zone for 
harbor porpoises extends 26.2 m from the sound source and the largest 
Level B harassment zone extends 10,000 m from the sound source (table 
9), and is contained within the Thames River. Therefore, no take by 
Level A or Level B harassment is anticipated or proposed for 
authorization from concurrent activities.

         Table 10--Estimated Take by Level B Harassment for Species Observed Only in the Long Island Sound Portion of the Proposed Project Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                    Calculated                  Total
                                                Total     Ensonfied area                               Density      estimated                  proposed
      Method           Pile size and type     ensonified    within the            Species           (individuals/    take by     Group size    take by
                                                 area       Long Island                                km\2\)        Level B                   Level B
                                               (km\2\)    Sound  (km\2\)                                            harassment                harassment
--------------------------------------------------------------------------------------------------------------------------------------------------------
Impact............  36-in steel pipe pile       3.435273            0.24  Atlantic white-sided              0.022            1           12           12
                     install.                                              dolphin.
                                                                          Common dolphin.........            0.15            4           30           30
                                                                          Harbor porpoise........            0.32            9            3            9
--------------------------------------------------------------------------------------------------------------------------------------------------------

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 km\2\ was used in the 
Thames River and a density of 0.07 individuals per km\2\ 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.

[[Page 27732]]

    The largest Level A harassment zone for harbor seals extends 984 m 
from the sound source (table 9). 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 proposed 
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 km\2\ was used in the Thames River 
and a density of 0.07 individuals per km\2\ 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 9). Using the equation given above, the 
calculated estimated take by Level A harassment for gray seals would be 
1. However, due to the consistent presence of phocid pinnipeds at the 
SUBASE over the last several years, NMFS conservatively proposed 
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 
km\2\. Only vibratory pile driving activities would 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 months 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 9) 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 proposes 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 11--Estimated Take by Level A and Level B Harassment
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                               Proposed
                                                                                           Stock        Level A      Level B       Total      take as a
                   Common name                                   Stock                 abundance \a\   harassment   harassment    proposed    percentage
                                                                                                                                    take       of stock
--------------------------------------------------------------------------------------------------------------------------------------------------------
Atlantic white-sided dolphin....................  Western North Atlantic............          93,233            0       \2\ 12           12         0.01
Common dolphin..................................  Western North Atlantic............          93,100            0       \2\ 30           30         0.03
Harbor porpoise.................................  Gulf of Maine/Bay of Fundy........          87,765            0            9            9         0.01
Harbor seal.....................................  Western North Atlantic............          61,336            8           44           52         0.08
Gray seal.......................................  Western North Atlantic............          27,911            8           44           52         0.19
Harp seal.......................................  Western North Atlantic............       7,600,000            5           12           17      0.00002
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Stock size is Nbest according to NMFS 2023a draft SARs.
\2\ Proposed take increased to mean group size from AMAPPS (Palka et al., 2017 and 2021).

Proposed Mitigation

    In order to issue an IHA under section 101(a)(5)(D) of the MMPA, 
NMFS must set forth the permissible methods of taking pursuant to the 
activity, and other means of effecting the least practicable impact on 
the species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of the species or stock for taking for certain 
subsistence uses (latter not applicable for this action). NMFS 
regulations require applicants for incidental take authorizations to 
include information about the availability and feasibility (economic 
and technological) of equipment, methods, and manner of conducting the 
activity or other means of effecting the least practicable adverse 
impact upon the affected species or stocks, and their habitat (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 proposes to employ the following mitigation measures:
     The Navy would ensure that construction supervisors and 
crews, the monitoring team, and relevant Navy staff are trained prior 
to the start of activities subject to the proposed IHA,

[[Page 27733]]

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 would 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 proposed mitigation measures would apply to the 
Navy's in-water construction activities:

Proposed 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 would 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 12. A minimum shutdown zone of 10 m would be 
required for all in-water construction activities to avoid physical 
interaction with marine mammals. Proposed shutdown zones for each 
activity type are shown in table 12.
    Prior to pile driving, shutdown zones and monitoring zones would be 
established based on zones represented in table 9. Protected Species 
Observers (PSOs) would 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 would 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 would 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 would 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 would 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 would be shut down 
immediately. Activities would 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 12--Proposed Shutdown and Level B Monitoring Zones by Activity
----------------------------------------------------------------------------------------------------------------
                                                              Minimum shutdown zone (m)               Level B
             Method              Pile size and type ---------------------------------------------   monitoring
                                                      MF-cetaceans    HF-cetaceans      Phocid       zone (m)
----------------------------------------------------------------------------------------------------------------
Vibratory......................  16-in fiberglass                10              10           10           3,415
                                  reinforced
                                  plastic fender
                                  piles install and
                                  removal.
                                 14-in steel H-pile              10              10           10
                                  (temporary)
                                  install and
                                  removal.
                                 14-in concrete                  10              25           15           6,310
                                  encased steel H-
                                  pile removal.
                                 36-in steel pipe                10              10           10          15,849
                                  pile install.
Impact.........................  16-in fiberglass                10              40           20              22
                                  reinforced
                                  plastic fender
                                  piles.
                                 14-in steel H-pile              10             120           55             136
                                  (temporary)
                                  install.
                                 36-in steel pipe                70             200          200           3,415
                                  pile install.
Auger drilling.................  36-in steel pipe                10              10           10           1,848
                                  pile install.
Concurrent pile driving........  14-in steel H-pile              10              35           15           7,356
                                  AND 14-in
                                  concrete encased
                                  steel H-pile.
                                 14-in steel H-pile              10              30           15          10,000
                                  AND 14-in
                                  concrete encased
                                  steel H-pile AND
                                  16-in fiberglass
                                  reinforced
                                  plastic fender.
                                 14-in steel H-pile              10              20           10           5,412
                                  AND 16-in
                                  fiberglass
                                  reinforced
                                  plastic fender.
----------------------------------------------------------------------------------------------------------------

Protected Species Observers

    The placement of PSOs during all pile driving and removal 
activities (described in detail in the Proposed 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 would observe the shutdown and 
monitoring zones for a period of 30 minutes. The shutdown zone would 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 would be delayed or halted. 
If work ceases for more than 30 minutes, the pre-activity monitoring of 
the shutdown zones would 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 30-second 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 proposed measures, NMFS 
has preliminarily determined that the proposed mitigation measures 
provide the means of effecting the least

[[Page 27734]]

practicable impact on the affected species or stocks and their habitat, 
paying particular attention to rookeries, mating grounds, and areas of 
similar significance.

Proposed Monitoring and Reporting

    In order to issue an IHA for an activity, section 101(a)(5)(D) of 
the MMPA states that NMFS must set forth requirements pertaining to the 
monitoring and reporting of such taking. The MMPA implementing 
regulations at 50 CFR 216.104(a)(13) indicate that requests for 
authorizations must include the suggested means of accomplishing the 
necessary monitoring and reporting that will result in increased 
knowledge of the species and of the level of taking or impacts on 
populations of marine mammals that are expected to be present while 
conducting the activities. Effective reporting is critical both to 
compliance as well as ensuring that the most value is obtained from the 
required monitoring.
    Monitoring and reporting requirements prescribed by NMFS should 
contribute to improved understanding of one or more of the following:
     Occurrence of marine mammal species or stocks in the area 
in which take is anticipated (e.g., presence, abundance, distribution, 
density);
     Nature, scope, or context of likely marine mammal exposure 
to potential stressors/impacts (individual or cumulative, acute or 
chronic), through better understanding of: (1) action or environment 
(e.g., source characterization, propagation, ambient noise); (2) 
affected species (e.g., life history, dive patterns); (3) co-occurrence 
of marine mammal species with the activity; or (4) biological or 
behavioral context of exposure (e.g., age, calving or feeding areas);
     Individual marine mammal responses (behavioral or 
physiological) to acoustic stressors (acute, chronic, or cumulative), 
other stressors, or cumulative impacts from multiple stressors;
     How anticipated responses to stressors impact either: (1) 
long-term fitness and survival of individual marine mammals; or (2) 
populations, species, or stocks;
     Effects on marine mammal habitat (e.g., marine mammal prey 
species, acoustic habitat, or other important physical components of 
marine mammal habitat); and,
     Mitigation and monitoring effectiveness.

Visual Monitoring

    Marine mammal monitoring must be conducted in accordance with the 
Monitoring Plan and section 5 of the IHA. A Marine Mammal Monitoring 
Plan would be submitted to NMFS for approval prior to commencement of 
project activities. 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 would 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 would 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 proposes to conduct hydroacoustic monitoring, or sound 
source verification (SSV), of all pile installation and removal 
methods. Data will be collected for a representative number of piles 
(at least 10 percent and up to 10 of each different type of pile) for 
each installation or removal method. Hydrophones would be placed at 
locations 10 m (33 ft) from the noise source and, where the potential 
for Level A harassment exists, at a second representative monitoring 
location at an intermediate distance between the cetacean and phocid 
shutdown zones. 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

[[Page 27735]]

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 would be successfully conducted 
for at least 10 percent and up to 10 of each different type of pile and 
each method of installation (table 13). Monitoring would occur at 33 
feet (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 would be analyzed to examine and confirm SPLs and 
rates of transmission loss 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 would be placed 
using a static line deployed from a stationary (temporarily moored) 
vessel. Locations of hydroacoustic recordings would be collected via 
global positioning system. A depth sounder and/or weighted tape measure 
would be used to determine the depth of the water. The hydrophone would 
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 would be 
attached to a float or tied to a static line.
     Each hydrophone (underwater) 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:
    [cir] Maximum peak pressure level recorded for all activities, 
expressed in dB re 1 [mu]Pa.
    [ssquf] Mean, median, minimum, and maximum RMS pressure level in 
[dB re 1 [mu]Pa].
    [ssquf] Mean duration of a pile strike (based on 90 percent energy 
criterion).
    [ssquf] Number of hammer strikes
    [ssquf] Mean, median, minimum, and maximum single strike SEL in [dB 
re [mu]Pa\2\ sec].
    [cir] Cumulative SEL as defined by the mean single strike SEL + 
10*log10 (number of hammer strikes) (dB re [mu]Pa\2\ sec).
    [cir] Median integration time used to calculate SPL RMS.
    [cir] A frequency spectrum (pressure spectral density) (dB re 
[mu]Pa\2\ 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.
    [cir] Finally, the cumulative SEL will be computed from all the 
strikes associated with each pile occurring during all phases, i.e., 
soft start, Level 1 to Level 4. 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 [mu]Pa\2\ sec).
     For vibratory driving/extraction/drilling: duration and 
frequency spectrum of vibratory driving per pile; mean, median, and 
maximum sound levels (dB re: 1 [micro]Pa): root mean square sound 
pressure level (SPLrms), SELcum (and timeframe 
over which the sound is averaged).

                                   Table 13--Hydroacoustic Monitoring Summary
----------------------------------------------------------------------------------------------------------------
                                                                                                      Number
                   Pile type                         Count          Method of install/extract        monitored
----------------------------------------------------------------------------------------------------------------
14-in steel H-pile............................              60  Impact..........................              10
14-in steel H-pile............................              60  Vibratory.......................              10
36-in steel pipe pile.........................              20  Impact..........................              10
36-in steel pipe pile.........................              20  Vibratory.......................              10
36-in steel pipe pile.........................              20  Auger (rotary) drill............              10
16-in fiberglass reinforced plastic fender                  60  Impact..........................              10
 pile.
16-in fiberglass reinforced plastic fender                  60  Vibratory.......................              10
 pile.
14-in concrete encased steel H-pile...........              20  Vibratory.......................              10
----------------------------------------------------------------------------------------------------------------

Reporting

    A draft marine mammal monitoring report would be submitted to NMFS 
within 90 days after the completion of pile driving and removal 
activities. It would 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

[[Page 27736]]

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.
    If no comments are received from NMFS within 30 days, the draft 
final report would 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 
[email protected] and [email protected]. 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 [mu]Pa); SPLrms; 
SELcum; peak sound pressure level (SPLpeak); and 
single-strike sound exposure level (SELs-s).
     For vibratory driving/extraction/drilling: duration and 
frequency spectrum of vibratory driving per pile; mean, median, and 
maximum sound levels (dB re: 1 [mu]Pa): SPLrms, 
SELcum (and timeframe over which the sound is averaged).
     One-third octave band spectrum and power spectral density 
plot.
     General Daily Site Conditions
    [cir] Date and time of activities.
    [cir] Water conditions (e.g., sea state, tidal state).
    [cir] 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 3, 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.
    The takes from Level B harassment would be due to potential 
behavioral disturbance, and TTS. Level A harassment takes 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. The 
potential for harassment is minimized through the

[[Page 27737]]

construction method and the implementation of the proposed mitigation 
measures (see Proposed 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. 
Level A harassment 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 proposed to be 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 also 
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 would occur across a maximum of 242 days within the 12-month 
authorization period, any harassment would be temporary.
    Any impacts on marine mammal prey that would occur during the 
Navy's proposed 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 preliminary determination that the impacts resulting from 
this activity are not expected to adversely affect any of the species 
or stocks through effects on annual rates of recruitment or survival:
     No serious injury or mortality is anticipated or 
authorized;
     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 would 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 proposed monitoring and 
mitigation measures, NMFS preliminarily finds that the total marine 
mammal take from the proposed activity will have a negligible impact on 
all affected marine mammal species or stocks.

Small Numbers

    As noted previously, only take of small numbers of marine mammals 
may be authorized under sections 101(a)(5)(A) and (D) of the MMPA for 
specified activities other than military readiness activities. The MMPA 
does not define small numbers and so, in practice, where estimated 
numbers are available, NMFS compares the number of individuals taken to 
the most appropriate estimation of abundance of the relevant species or 
stock in our determination of whether an authorization is limited to 
small numbers of marine mammals. When the predicted number of 
individuals to be taken is fewer than one-third of the species or stock 
abundance, the take is considered to be of small numbers. Additionally, 
other qualitative factors may be considered in the analysis, such as 
the temporal or spatial scale of the activities.
    Table 11 demonstrates the number of animals that could be exposed 
to received noise levels that could cause Level B harassment for the 
proposed work at SUBASE. Our analysis shows that less than 1 percent of 
each affected stock could be taken by harassment. The numbers of 
animals proposed to be taken for these stocks would be considered small 
relative to the relevant stock's abundances, even if each estimated 
taking occurred to a new individual--an extremely unlikely scenario.
    Based on the analysis contained herein of the proposed activity 
(including the proposed mitigation and monitoring measures) and the 
anticipated take of marine mammals, NMFS preliminarily finds that small 
numbers of marine mammals would be 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 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 Endangered Species Act of 1973 (ESA; 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 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.

[[Page 27738]]

Therefore, NMFS has determined that formal consultation under section 7 
of the ESA is not required for this action.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to the Navy for conducting the New London Pier Extension 
Project at SUBASE in Groton, Connecticut, between December 1, 2024, and 
November 30, 2025, provided the previously mentioned mitigation, 
monitoring, and reporting requirements are incorporated. A draft of the 
proposed IHA can be found at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities.

Request for Public Comments

    We request comment on our analyses, the proposed authorization, and 
any other aspect of this notice of proposed IHA for the proposed New 
London Pier Extension Project. We also request comment on the potential 
renewal of this proposed IHA as described in the paragraph below. 
Please include with your comments any supporting data or literature 
citations to help inform decisions on the request for this IHA or a 
subsequent renewal IHA.
    On a case-by-case basis, NMFS may issue a one-time, 1-year renewal 
IHA following notice to the public providing an additional 15 days for 
public comments when: (1) up to another year of identical or nearly 
identical activities as described in the Description of Proposed 
Activity section of this notice is planned; or (2) the activities as 
described in the Description of Proposed Activity section of this 
notice would not be completed by the time the IHA expires and a renewal 
would allow for completion of the activities beyond that described in 
the Dates and Duration section of this notice, provided all of the 
following conditions are met:
     A request for renewal is received no later than 60 days 
prior to the needed renewal IHA effective date (recognizing that the 
renewal IHA expiration date cannot extend beyond 1 year from expiration 
of the initial IHA).
     The request for renewal must include the following:
    (1) An explanation that the activities to be conducted under the 
requested renewal IHA are identical to the activities analyzed under 
the initial IHA, are a subset of the activities, or include changes so 
minor (e.g., reduction in pile size) that the changes do not affect the 
previous analyses, mitigation and monitoring requirements, or take 
estimates (with the exception of reducing the type or amount of take).
    (2) A preliminary monitoring report showing the results of the 
required monitoring to date and an explanation showing that the 
monitoring results do not indicate impacts of a scale or nature not 
previously analyzed or authorized.
     Upon review of the request for renewal, the status of the 
affected species or stocks, and any other pertinent information, NMFS 
determines that there are no more than minor changes in the activities, 
the mitigation and monitoring measures will remain the same and 
appropriate, and the findings in the initial IHA remain valid.

    Dated: April 11, 2024.
Catherine Marzin,
Deputy Director, Office of Protected Resources, National Marine 
Fisheries Service.
[FR Doc. 2024-08284 Filed 4-17-24; 8:45 am]
BILLING CODE 3510-22-P