Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Portsmouth Naval Shipyard Dry Dock 1 Modification and Expansion, 18244-18268 [2021-06782]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 86, Number 66 (Thursday, April 8, 2021)]
[Notices]
[Pages 18244-18268]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-06782]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XA918]


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to Portsmouth Naval Shipyard Dry Dock 
1 Modification and Expansion

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 Portsmouth Naval 
Shipyard Dry Dock 1 modification and expansion in Kittery, Maine. 
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

[[Page 18245]]

also requesting comments on a possible one-time, one-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 authorizations and 
agency responses will be summarized in the final notice of our 
decision.

DATES: Comments and information must be received no later than May 10, 
2021.

ADDRESSES: Comments should be addressed to Jolie Harrison, Chief, 
Permits and Conservation Division, Office of Protected Resources, 
National Marine Fisheries Service and should be sent by electronic mail 
to [email protected].
    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: Carter Esch, Office of Protected 
Resources, NMFS, (301) 427-8421. Electronic copies of the application 
and supporting documents, as well as a list of the references cited in 
this document, may be obtained online at: https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act. In case of problems accessing these 
documents, please call the contact listed above.

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 issued or, if the taking is limited to harassment, a notice of a 
proposed incidental take authorization may be 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 such 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 such takings are set forth. The definitions 
of all applicable MMPA 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 (IHA with no anticipated serious injury or 
mortality) of the Companion Manual for NOAA Administrative Order 216-
6A, which do not individually or cumulatively have the potential for 
significant impacts on the quality of the human environment and for 
which NMFS has 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.
    NMFS 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 October 22, 2020, NMFS received a request from the Navy for an 
IHA to take marine mammals incidental to modification and expansion of 
Dry Dock 1 at Portsmouth Naval Shipyard in Kittery, Maine. The Navy 
submitted revised versions of the application on December 30, 2020, and 
January 19 and February 11, 2021. The application was deemed adequate 
and complete on February 19, 2021. The Navy's request is for take of 
harbor porpoises, harbor seals, gray seals, harp seals, and hooded 
seals by Level B harassment and Level A harassment. Neither the Navy 
nor NMFS expects serious injury or mortality to result from this 
activity; therefore, an IHA is appropriate.
    NMFS previously issued three IHAs to the Navy for waterfront 
improvement work, in 2017 (81 FR 85525; November 28, 2016), 2018 (83 FR 
3318; January 24, 2018), 2019 (84 FR 24476, May 28, 2019), and a 
renewal of the 2019 IHA (86 FR 14598; March 17, 2021). As required, the 
applicant provided monitoring reports (available at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities) which confirm that the 
applicant has implemented the required mitigation and monitoring, and 
which also shows that no impacts of a scale or nature not previously 
analyzed or authorized have occurred as a result of the activities 
conducted. This proposed IHA (if issued) would cover the second year of 
a larger 5-year project, for which the Navy also intends to request 
take authorization for subsequent dock modification and expansion at 
the Portsmouth Naval Shipyard.

Description of Proposed Activity

Overview

    The purpose of the proposed action is to modernize and maximize dry 
dock capabilities for performing current and future missions 
efficiently and with maximum flexibility. The Navy plans to modify and 
expand Dry Dock 1 (DD1) at the Portsmouth Naval Shipyard (PNSY) by 
constructing two new dry docking positions capable of servicing 
Virginia class submarines within the super flood basin of the dry dock.
    The in-water portion of the dock modification and expansion work 
includes:
    [ssquf] Construction of the west closure wall;
    [ssquf] Construction of entrance structure closure walls; and
    [ssquf] Bedrock excavation.
    Construction activities that could affect marine mammals are 
limited to in-water pile driving and removal activities, rock drilling, 
and underwater blasting.

Dates and Duration

    In-water construction activities are expected to begin in spring 
2021, with an estimated total of 29 days for pile

[[Page 18246]]

driving and pile removal, 130 days for drilling of blast charge holes, 
and 130 days of blasting for bedrock excavation, for a total of 289 
construction days. Some of these activities would occur on the same 
day, resulting in 159 total construction days over 12 months. All in-
water construction work will be limited to daylight hours, with the 
exception of pre-dawn (beginning no earlier than 3:00 a.m.) drilling of 
blast charge holes; drilling would not occur from sunset to pre-dawn.

Specific Geographic Region

    The Shipyard is located in the Piscataqua River in Kittery, Maine. 
The Piscataqua River originates at the boundary of Dover, New 
Hampshire, and Elliot, Maine. The river flows in a southeasterly 
direction for 21 kilometers (km) before entering Portsmouth Harbor and 
emptying into the Atlantic Ocean. The lower Piscataqua River is part of 
the Great Bay Estuary system and varies in width and depth. Many large 
and small islands break up the straight-line flow of the river as it 
continues toward the Atlantic Ocean. Seavey Island, the location of the 
proposed action, is located in the lower Piscataqua River approximately 
500 meters (m) from its southwest bank, 200 m from its north bank, and 
approximately 4 km upstream from the mouth of the river.
    A map of the Portsmouth Naval Shipyard dock expansion action area 
is provided in Figure 1 below; additional maps are available in Figures 
1-1 to 1-6 in the IHA application.
    Water depths in the proposed project area range from 6.4 to 11.9 m, 
while water depths in the lower Piscataqua River near the proposed 
project area range from 4.5 m in the shallowest areas to 21 m in the 
deepest areas. The river is approximately 1 km wide near the proposed 
project area, measured from the Kittery shoreline north of Wattlebury 
Island to the Portsmouth shoreline west of Peirce Island. The furthest 
direct line of sight from the proposed project area would be 1.3 km to 
the southeast and 0.4 km to the northwest.
BILLING CODE 3510-22-P

[[Page 18247]]

[GRAPHIC] [TIFF OMITTED] TN08AP21.012

BILLING CODE 3510-22-C

Detailed Description of Specific Activity

    Under the proposed action, the expansion and modification would 
occur as multiple construction projects. Prior to the start of 
construction, the entrance to DD1would be dredged to previously 
permitted maintenance dredge limits. This dredging effort is required 
to support the projects; additional project-related dredging would 
occur intermittently throughout the proposed action. Since dredging and 
disposal activities would be slow-moving and generate continuous noise 
similar to other ongoing sources of industrial noise at PNSY, NMFS does 
not consider its effects as likely to rise to the level of take of 
marine mammals; therefore, these activities are not discussed further 
in this document.
    The proposed 2021 through 2022 construction activities include pile 
driving (vibratory and impact), rock drilling, and blasting associated 
with construction of the super flood basin. The action would take place 
in and adjacent to DD1 in the Controlled Industrial Area (CIA) that 
occupies the

[[Page 18248]]

western extent of the Portsmouth Naval Shipyard.
    Construction of the super flood basin phasing would be required to 
minimize impacts on critical dry dock operations. Six notional 
construction phases were identified of which the first three were 
completed under previous IHAs (84 FR 24476, May 28, 2019; 86 FR 10545, 
February 22, 2021). Phases 4, 5, and 6 would occur under this proposed 
IHA. This phasing schedule could change due to fleet mission 
requirements and boat schedules. The first phase of construction 
occurred when a boat was present and was limited to site 
reconnaissance, field measurements, contractor submittals and general 
mobilization activities. Phase 2 included construction of the southern 
closure wall and caisson seat foundation, Berth 1 and Berth 11 (A and 
B) improvements, DD1 utility improvements, and dredging. Phase 3 
includes construction of the temporary blast wall and completion of the 
caisson seat foundation, which comprise the entirety of activities to 
be completed under the renewal IHA. Phases 4 through 6, considered 
here, would include construction of the west closure wall and entrance 
structure closure walls, as well as bedrock excavation.
    The super flood basin would be created in front of the entrance of 
DD1 by constructing closure walls that span from Berth 1 to Berth 11. 
The super flood basin would operate like a navigation lock-type 
structure: Artificially raising the elevation of the water within the 
basin and dry dock above the tidally controlled river in order to lift 
the submarines to an elevation where they can be safely transferred 
into the dry dock without the use of buoyancy assist tanks. Located 
between Berths 1 and 11, the super flood basin would extend 
approximately 177 m from the existing outer seat of the dry dock 
(approximately 53 m beyond the waterside end of Berth 1), and would 
consist of three primary components: South closure wall, west closure 
wall, and entrance structure. Construction of the south closure wall 
was completed under the initial 2019 IHA, with only in-water 
construction for the west closure wall and the entrance structure 
scheduled to occur under the IHA proposed here.
    The west closure wall would consist of a cellular sheet pile wall 
with one full cell and a second partial cell. The cells would be filled 
with crushed stone fill and have a paved access way as a cap. 
Approximately 160, Z-shaped piles would be installed to construct the 
west closure wall. The closure wall would be connected to the entrance 
structure and existing Berth 11 structures, and would be in place for 
the remainder of the in-water construction activities.
    The entrance (i.e., caisson seat) will be constructed under the 
renewal IHA, including installation of six temporary dolphins, 
comprised of 12, 30-inch (in) diameter steel pipe piles, to assist with 
float-in and placement of the caisson seat. Under this proposed IHA, 
the temporary dolphins would be removed using vibratory extraction once 
installation of the caisson seat is completed under the renewal IHA 
(installation will be complete prior to initiation of the construction 
activities that are the subject of this proposed IHA).
    The Navy plans to remove approximately 16,056 cubic meters (m\3\) 
of sediment and 9,939 m\3\ of bedrock from the closure wall and Berth 
11 face to support increased flexibility within the basin (see Figure 
1-5 in the IHA application for more details). The current bedrock 
elevation at this location would limit submarine and tug movements 
within the super flood basin. While the super flood basin would be 
operational without bedrock removal, removing the bedrock would allow 
the Shipyard additional operational flexibility for using Berth 11 
while other aspects of the project are under construction. In addition, 
the added depth would increase ship clearances resulting in reduced 
sediment disturbance from boat propellers during docking operations.
    Bedrock would be removed by drilling and confined blasting methods, 
which involves drilling holes in the bedrock, placing the charges in 
the holes, and then stemming the charges. A barge-mounted rotary action 
drill would be used to bore into the bedrock to excavate the 4.5-inch 
diameter holes where the blasting charges would be placed. The drill 
would operate within a casing that would temporarily contain sediments 
disturbed during drilling. Air would be injected into the casing to 
lift sediments during drilling, providing a buffer to sound entering 
the water column. Charge holes would be approximately 3 to 11 m deep, 
depending on the depth of the rock that needs to be removed. Stemming 
is the packing of inert material, such as gravel, sand, or drill 
cuttings, on top of the charge to the top of the borehole, which 
confines the pressure and gasses created by the explosive. Confined 
blasting activities using stemmed charges would occur during an 
approximately 10 month window when DD1 is expected to be empty. It is 
anticipated that there would be approximately 130 blasting days, with 
one or two blast events (i.e., the detonation of multiple charges in 
sequence with a small delay between the detonations of each individual 
charge) each day. Production blasting would utilize a maximum of 120 
pounds (lbs) of explosives per charge. Depending on the rate of 
drilling achieved, 5 (minimum) to 30 (maximum) holes would be detonated 
per blast event. Each charge would be detonated with an approximately 
8-millisecond (ms) delay. Therefore, each blast event would only last a 
total duration of approximately 0.24 seconds (sec) for a 30-hole 
detonation. A bubble curtain will be deployed across the entrance to 
the basin during all blast events to reduce acoustics impacts outside 
of the blasting area. The Navy has not yet determined the exact 
configuration (single or double bubble curtain) that will be utilized.
    Blasting activities include the Navy's requirement to construct a 
temporary blast wall across the opening of the existing DD1, which will 
be completed under the renewal IHA prior to the construction activities 
described here. Following the completion of blasting activities, the 
blast wall would be removed by underwater torch cutting. Neither NMFS 
not the Navy anticipate take associated with removal of the blast wall; 
therefore, this activity is not discussed further.
    Overall, the construction work is estimated to take approximately 
12 months to complete. The number of construction days (289) does not 
account for the fact that blast-hole drilling and pile driving would 
occur concurrently. The proposed schedule, including overlapping 
activities, is anticipated to reduce the number of actual construction 
days from 289 days to 159 total days. However, as a conservative 
measure, construction days are accounted for as consecutive rather than 
concurrent activities in take estimates (see Estimated Take section).
    A summary of in-water pile driving activity is provided in Table 1. 
In addition, a total of 1,580, 4.5-in blast charge holes would be 
drilled at a rate of 12 holes per day over 130 days. The Navy is 
proposing one to two blast events per day, with a maximum of six blast 
events per week; a total of 150 blast events would occur over 130 days.

[[Page 18249]]



                                                  Table 1--Summary of In-Water Pile Driving Activities
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                                                              Pile size
            Pile purpose                    Pile type           (inch)        Pile drive method             Total piles          Piles/day    Work days
--------------------------------------------------------------------------------------------------------------------------------------------------------
West closure wall template.........  Steel pipe............           30  Vibratory................  13 installed.............            3            5
                                                                                                     13 removed...............            3            5
West closure wall construction.....  Flat-webbed steel                18  Vibratory................  160......................           12           13
                                      sheet.                              Impact...................
Entrance structure temporary guide   Steel pipe............           30  Vibratory................  12.......................            8            2
 dolphin removal.
Entrance structure closure wall      Steel sheet...........           28  Vibratory................  44.......................           12            4
 construction.                                                            Impact...................
                                                            --------------------------------------------------------------------------------------------
    Total..........................  ......................  ...........  .........................  242......................  ...........           29
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    Proposed mitigation, monitoring, and reporting measures are 
described in detail later in this document (please see Proposed 
Mitigation and Proposed Monitoring and Reporting).

Description of Marine Mammals in the Area of Specified Activities

    Sections 3 and 4 of the application summarize available information 
regarding status and trends, distribution and habitat preferences, and 
behavior and life history, of the potentially affected species. 
Additional information regarding population trends and threats may be 
found in NMFS's 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's 
website (https://www.fisheries.noaa.gov/find-species).
    Table 2 lists all species with expected potential for occurrence in 
the Piscataqua River in Kittery, Maine, and summarizes information 
related to the population or stock, including regulatory status under 
the MMPA and ESA and potential biological removal (PBR), where known. 
For taxonomy, NMFS follows Committee on Taxonomy (2020). 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's SARs). While no mortality is 
anticipated or authorized here, PBR and annual serious injury and 
mortality from anthropogenic sources are included here as gross 
indicators of the status of the species 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's 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's U.S. Atlantic Marine Mammal SARs. All values presented in Table 
2 are the most recent available at the time of publication and are 
available in the final 2019 SARs (Hayes et al., 2020) and draft 2020 
SARs, available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports).

                                    Table 2--Marine Mammals With Potential Presence Within the Proposed Project Area
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                                                                                         ESA/ MMPA status;   Stock abundance (CV,
             Common name                  Scientific name               Stock             strategic (Y/N)      Nmin, most recent       PBR     Annual M/
                                                                                                \1\          abundance survey) \2\               SI \3\
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                                         Order Cetartiodactyla--Cetacea--Superfamily Odontoceti (toothed whales)
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Family Phocoenidae (porpoises):
    Harbor porpoise.................  Phocoena phocoena......  Gulf of Maine/Bay of     -; N                95,543 (0.31; 74,034;         851        217
                                                                Fundy.                                       2016).
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                                                         Order Carnivora--Superfamily Pinnipedia
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Family Phocidae (earless seals):
    Harbor seal.....................  Phoca vitulina.........  Western North Atlantic.  -; N                75,834 (0.15, 66,884;       2,006        350
                                                                                                             2012).
    Gray seal.......................  Halichoerus grypus.....  Western North Atlantic.  -; N                27,131 \4\ (0.19;           1,389      4,729
                                                                                                             23,158; 2016).
    Harp seal.......................  Pagophilus               Western North Atlantic.  -; N                Unknown (NA, NA)......        unk    232,422
                                       groenlandicus.
    Hooded seal.....................  Cystophora cristata....  Western North Atlantic.  -; N                Unknown (NA, NA)......        unk      1,680
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\1\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed
  under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality
  exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
  under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\2\ NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region#reports. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance.
\3\ 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.
\4\ NMFS stock abundance estimate applies to U.S. population only, actual stock abundance is approximately 505,000. The PBR value presented is in
  relation to the U.S. population, whereas the annual M/SI value is for the entire stock.


[[Page 18250]]

    All species that could potentially occur in the proposed action 
area are included in Table 2. More detailed descriptions of marine 
mammals in the PNSY project area are provided below.

Harbor Porpoise

    Harbor porpoises occur from the coastline to deep waters (>1,800 
meters (m); Westgate et al. 1998), although the majority of the 
population is found over the continental shelf (Hayes et al., 2020). In 
the project area, only the Gulf of Maine/Bay of Fundy stock of harbor 
porpoise may be present. This stock is found in U.S. and Canadian 
Atlantic waters and 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., 2016).
    Marine mammal monitoring was conducted during the Berth 11 
Waterfront Improvements project from April 2017 through December 2017 
(Cianbro 2018a) and through June 2018 (Cianbro 2018b). Harbor porpoises 
were observed traveling quickly through the river channel and past the 
proposed project area. A total of 5 harbor porpoises was sighted 
between April 2017 and June 2018. One harbor porpoise was sighted 
during the first year of expansion and modification of DD1.

Harbor Seal

    The harbor seal is found in all nearshore waters of the North 
Atlantic and North Pacific Oceans and adjoining seas above about 
30[deg] N (Burns, 2009). In the western North Atlantic, harbor seals 
are distributed from the eastern Canadian Arctic and Greenland south to 
southern New England and New York, and occasionally to the Carolinas 
(Hayes et al., 2020). Haulout and pupping sites are located off 
Manomet, MA and the Isles of Shoals, ME (Waring et al., 2016).
    Harbor seals are the most abundant pinniped in the Piscataqua 
River. They were commonly observed within the proposed project area 
between the months of April 2017 and June 2018 during the Berth 11 
Waterfront Improvements project (Cianbro 2018a, 2018b). The primary 
behaviors observed during monitoring were milling (diving), swimming, 
and traveling during nearly 60 percent, 29 percent and 12 percent of 
observations, respectively (Cianbro 2018a). Marine mammal surveys were 
conducted for one day of each month in 2017 (NAVFAC Mid-Atlantic 2018); 
harbor seals were commonly observed near the project area throughout 
the year, and did not show any seasonality in their presence. A total 
of 721 (including repeated sightings of individuals) sightings of 658 
harbor seals were documented from May through December during the first 
year of monitoring of construction activities for the expansion and 
modification of DD1 (Navy 2020). As anticipated, no harbor seal pups 
were observed during the surveys or monitoring, as known pupping sites 
are north of the Maine-New Hampshire border (Waring et al., 2016).

Gray Seal

    There are three major populations of gray seals found in the world; 
eastern Canada (western North Atlantic stock), northwestern Europe and 
the Baltic Sea. 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 Exclusive Economic Zone (EEZ) 
(Hayes et al., 2020). Although the rate of increase is unknown, surveys 
conducted since their arrival in the 1980s indicate a steady increase 
in abundance in both Maine and Massachusetts (Hayes et al., 2018). It 
is believed that recolonization by Canadian gray seals is the source of 
the U.S. population (Hayes et al., 2018).
    Twenty-four gray seals were observed within the proposed project 
area between the months of April and December 2017 (Cianbro 2018a), two 
during the months of January through June 2018 (Cianbro 2018b), and 12 
during a monitoring period from January 2018 through January 2019 (Navy 
2019). The primary behavior observed during surveys was milling at just 
over 60 percent of the time followed by swimming within and traveling 
through the proposed project area. Only approximately 5 percent of the 
time were gray seals observed foraging (Cianbro 2018a). Monthly one-day 
marine mammal surveys also took place during 2017 and 2018, during 
which six and three sightings of gray seal were recorded, respectively 
(NAVFAC Mid-Atlantic 2018). Forty-seven (including repeated sighting of 
individuals) observations of 34 individual gray seals were documented 
from May through December 2020 during the first year of construction 
activities for expansion and modification of DD1 (Navy 2020). No gray 
seal pups were observed during the surveys or monitoring, given known 
pupping sites for gray seals (like harbor seals) are north of the 
Maine-New Hampshire border (Waring et al., 2016).

Hooded Seal

    Hooded seals are also members of the true seal family (Phocidae) 
and are generally found in deeper waters or on drifting pack ice. The 
world population of hooded seals has been divided into three stocks, 
which coincide with specific breeding areas, as follows: (1) Northwest 
Atlantic, (2) Greenland Sea, and (3) White Sea (Waring et al., 2020). 
The hooded seal is a highly migratory species, and its range can extend 
from the Canadian arctic to Puerto Rico. In U.S. waters, the species 
has an increasing presence in the coastal waters between Maine and 
Florida (Waring et al., 2019). In the U.S., they are considered members 
of the western North Atlantic stock and generally occur in New England 
waters from January through May and further south in the summer and 
fall seasons (Waring et al., 2019).
    Population abundance of hooded seals in the western North Atlantic 
is derived from pup production estimates, which are developed from 
whelping pack surveys. The most recent population estimate in the 
western North Atlantic was derived in 2005. There have been no recent 
surveys conducted or population estimates developed for this species. 
The 2005 best population estimate for hooded seals is 593,500 
individuals, with a minimum population estimate of 543,549 individuals 
(Waring et al., 2019). Currently, not enough data are available to 
determine what percentage of this estimate may represent the population 
within U.S. waters. Hooded seals have been observed in the Piscataqua 
River; however, they are not as abundant as the more commonly observed 
harbor seal. Anecdotal sighting information indicates that two hooded 
seals were observed near the Shipyard in August 2009, but no other 
observations have been recorded (NAVFAC Mid-Atlantic 2018). Hooded 
seals were not observed in the proposed project area during marine 
mammal monitoring or survey events that took place in 2017, 2018, and 
2020 (Cianbro 2018a, b; NAVFAC Mid-Atlantic 2018, 2019b, Navy 2019, 
Stantec 2020).

Harp Seal

    The harp seal is a highly migratory species, its range extending 
throughout the Arctic and North Atlantic Oceans. The world's harp seal 
population is separated into three stocks, based on associations with 
specific locations of pagophilic breeding activities: (1) Off eastern 
Canada, (2) on the West Ice off eastern Greenland, and (3) in the White 
Sea off the coast of Russia. The largest stock, which includes two 
herds that breed either off the coast of Newfoundland/Labrador or near 
the Magdelan Islands in the Gulf of St.

[[Page 18251]]

Lawrence, is equivalent to the western North Atlantic stock. The best 
estimate of abundance for western North Atlantic harp seals, based on 
the last survey (in 2012) is 7.4 million, with a minimum estimate of 
6.9 million (Waring et al., 2020). In U.S. waters, the species has an 
increasing presence since the 1990s, evidenced by increasing numbers of 
sightings and strandings in the coastal waters between Maine and New 
Jersey (Waring et al., 2020). Harp seals that occur in the United 
States are considered members of the western North Atlantic stock and 
generally occur in New England waters from January through May (Waring 
et al., 2020).
    Harp seals have been observed in the Piscataqua River; however, 
they are not as abundant as the more commonly observed harbor seal. The 
most recent harp seal sightings in the river were of two single seals 
on separate days in mid-May 2020 (Stantec 2020). The last harp seal 
sighting prior to these observations was in 2016 (NAVFAC Mid-Atlantic 
2016).

Unusual Mortality Events (UMEs)

    Since July 2018, elevated numbers of harbor seal and gray seal 
mortalities have occurred across Maine, New Hampshire and 
Massachusetts. This event has been declared a UME. Additionally, 
stranded seals have shown clinical signs as far south as Virginia, 
although not in elevated number; therefore, the UME investigation now 
encompasses all seal strandings from Maine to Virginia. Full or partial 
necropsy examinations have been conducted on some of the seals and 
samples have been collected for testing. Based on tests conducted thus 
far, the main pathogen found in the seals is phocine distemper virus. 
NMFS is performing additional testing to identify any other factors 
that may be involved in this UME. Lastly, ice seals (harp and hooded 
seals) have also started stranding with clinical signs, although not in 
elevated numbers, and those two seal species have also been added to 
the UME investigation discussed above. Information on this UME is 
available online at: www.fisheries.noaa.gov/new-england-mid-atlantic/marine-life-distress/2018-2020-pinniped-unusual-mortality-event-along.

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. Current data indicate that 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) recommended that marine mammals be divided 
into functional hearing groups based on directly measured or estimated 
hearing ranges on the basis of available behavioral response data, 
audiograms derived using auditory evoked potential techniques, 
anatomical modeling, and other data. 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 3.

                  Table 3--Marine Mammal Hearing Groups
                              [NMFS, 2018]
------------------------------------------------------------------------
                                                    Generalized hearing
                  Hearing group                           range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen whales)....  7 Hz to 35 kHz.
Mid-frequency (MF) cetaceans (dolphins, toothed   150 Hz to 160 kHz.
 whales, beaked whales, bottlenose whales).
High-frequency (HF) cetaceans (true porpoises,    275 Hz to 160 kHz.
 Kogia, river dolphins, cephalorhynchid,
 Lagenorhynchus cruciger & L. australis).
Phocid pinnipeds (PW) (underwater) (true seals).  50 Hz to 86 kHz.
Otariid pinnipeds (OW) (underwater) (sea lions    60 Hz to 39 kHz.
 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 and Holt, 
2013).
    For more detail concerning these groups and associated frequency 
ranges, please see NMFS (2018) for a review of available information. 
Five marine mammal species (one cetacean and four pinniped (all phocid) 
species) have the reasonable potential to co-occur with the proposed 
survey activities. Please refer to Table 2. The only cetacean species 
that may be present, the harbor porpoise, is classified as a high-
frequency cetacean.

Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat

    This section includes a summary and discussion of the ways that 
components of the specified activity may impact marine mammals and 
their habitat. The Estimated Take 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 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 how those 
impacts on individuals are likely to impact marine mammal species or 
stocks.

Description of Sound

    Sound travels in waves, the basic components of which are 
frequency, wavelength, velocity, and amplitude. Frequency is the number 
of pressure waves that pass by a reference point per unit of time and 
is measured in hertz (Hz) or cycles per second. Wavelength is the 
distance between two peaks of a sound wave; lower frequency sounds

[[Page 18252]]

have longer wavelengths than higher frequency sounds. Amplitude is the 
height of the sound pressure wave or the `loudness' of a sound and is 
typically measured using the dB scale. A dB is the ratio between a 
measured pressure (with sound) and a reference pressure (sound at a 
constant pressure, established by scientific standards). It is a 
logarithmic unit that accounts for large variations in amplitude; 
therefore, relatively small changes in dB ratings correspond to large 
changes in sound pressure. When referring to sound pressure levels 
(SPLs) (the sound force per unit area), sound is referenced in the 
context of underwater sound pressure to one microPascal ([mu]Pa). One 
pascal is the pressure resulting from a force of one newton exerted 
over an area of one square meter. The source level (SL) represents the 
sound level at a distance of 1 m from the source (referenced to 1 
[mu]Pa). The received level is the sound level at the listener's 
position. Note that all underwater sound levels in this document are 
referenced to a pressure of 1 [micro]Pa and all airborne sound levels 
in this document are referenced to a pressure of 20 [micro]Pa.
    Root mean square (rms) is the quadratic mean sound pressure over 
the duration of an impulse. Rms is calculated by squaring all of the 
sound amplitudes, averaging the squares, and then taking the square 
root of the average (Urick 1983). Rms accounts for both positive and 
negative values; squaring the pressures makes all values positive so 
that they may be accounted for in the summation of pressure levels 
(Hastings and Popper 2005). This measurement is often used in the 
context of discussing behavioral effects, in part because behavioral 
effects, which often result from auditory cues, may be better expressed 
through averaged units than by peak pressures.
    When underwater objects vibrate or activity occurs, sound-pressure 
waves are created. These waves alternately compress and decompress the 
water as the sound wave travels. Underwater sound waves radiate in all 
directions away from the source (similar to ripples on the surface of a 
pond), except in cases where the source is directional. The 
compressions and decompressions associated with sound waves are 
detected as changes in pressure by aquatic life and man-made sound 
receptors such as hydrophones.
    Even in the absence of sound from the specified activity, the 
underwater environment is typically loud due to ambient sound. Ambient 
sound is defined as environmental background sound levels lacking a 
single source or point (Richardson et al., 1995), and the sound level 
of a region is defined by the total acoustical energy being generated 
by known and unknown sources. These sources may include physical (e.g., 
waves, earthquakes, ice, atmospheric sound), biological (e.g., sounds 
produced by marine mammals, fish, and invertebrates), and anthropogenic 
sound (e.g., vessels, dredging, aircraft, construction). A number of 
sources contribute to ambient sound, including the following 
(Richardson et al., 1995):
     Wind and waves: The complex interactions between wind and 
water surface, including processes such as breaking waves and wave-
induced bubble oscillations and cavitation, are a main source of 
naturally occurring ambient noise for frequencies between 200 Hz and 50 
kilohertz (kHz) (Mitson 1995). In general, ambient sound levels tend to 
increase with increasing wind speed and wave height. Surf noise becomes 
important near shore, with measurements collected at a distance of 8.5 
km from shore showing an increase of 10 dB in the 100 to 700 Hz band 
during heavy surf conditions;
     Precipitation: Sound from rain and hail impacting the 
water surface can become an important component of total noise at 
frequencies above 500 Hz, and possibly down to 100 Hz during quiet 
times;
     Biological: Marine mammals can contribute significantly to 
ambient noise levels, as can some fish and shrimp. The frequency band 
for biological contributions is from approximately 12 Hz to over 100 
kHz; and
     Anthropogenic: Sources of ambient noise related to human 
activity include transportation (surface vessels and aircraft), 
dredging and construction, oil and gas drilling and production, seismic 
surveys, sonar, explosions, and ocean acoustic studies. Shipping noise 
typically dominates the total ambient noise for frequencies between 20 
and 300 Hz. In general, the frequencies of anthropogenic sounds are 
below 1 kHz and, if higher frequency sound levels are created, they 
attenuate rapidly (Richardson et al., 1995). Sound from identifiable 
anthropogenic sources other than the activity of interest (e.g., a 
passing vessel) is sometimes termed background sound, as opposed to 
ambient sound.
    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 10-20 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.
Description of Sounds Sources
    In-water construction activities associated with the project would 
include impact and vibratory pile installation and removal, drilling, 
and blasting. The sounds produced by these activities fall into one of 
two general sound types: Impulsive and non-impulsive (defined below). 
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). Please 
see Southall et al. (2007) for an in-depth discussion of these 
concepts.
    Impulsive sound sources (e.g., explosions, gunshots, sonic booms, 
impact pile driving) produce signals that are brief (typically 
considered to be less than one second), broadband, atonal transients 
(ANSI 1986; Harris 1998; NIOSH 1998; ISO 2003; ANSI 2005) and occur 
either as isolated events or repeated in some succession. Impulsive 
sounds are all characterized by a relatively rapid rise from ambient 
pressure to a maximal pressure value followed by a rapid decay period 
that may include a period of diminishing, oscillating maximal and 
minimal pressures, and generally have an increased capacity to induce 
physical injury as compared with sounds that lack these features.
    Non-impulsive sounds can be tonal, narrowband, or broadband, brief 
or prolonged, and may be either continuous or non-continuous (ANSI 
1995; NIOSH 1998). Some of these non-impulsive sounds can be transient 
signals of short duration but without the essential properties of 
impulses (e.g., rapid rise time). Examples of non-impulsive sounds 
include those produced by vessels, aircraft, machinery operations such 
as drilling or dredging, vibratory pile driving, and active sonar 
systems. The duration of such sounds,

[[Page 18253]]

as received at a distance, can be greatly extended in a highly 
reverberant environment.

Acoustic Impacts

    Anthropogenic sounds cover a broad range of frequencies and sound 
levels and can have a range of highly variable impacts on marine life, 
from none or minor to potentially severe responses, depending on 
received levels, duration of exposure, behavioral context, and various 
other factors. The potential effects of underwater sound from active 
acoustic sources can potentially result in one or more of the 
following; temporary or permanent hearing impairment, non-auditory 
physical or physiological effects, behavioral disturbance, stress, and 
masking (Richardson et al., 1995; Gordon et al., 2004; Nowacek et al., 
2007; Southall et al., 2007; Gotz et al., 2009). The degree of effect 
is intrinsically related to the signal characteristics, received level, 
distance from the source, and duration of the sound exposure. In 
general, sudden, high level sounds can cause hearing loss, as can 
longer exposures to lower level sounds. Temporary or permanent loss of 
hearing will occur almost exclusively for noise within an animal's 
hearing range. Specific manifestations of acoustic effects are first 
described before providing discussion specific to the Navy's 
construction activities.
    Richardson et al. (1995) described zones of increasing intensity of 
effect that might be expected to occur, in relation to distance from a 
source and assuming that the signal is within an animal's hearing 
range. The first zone is the area within which the acoustic signal 
would be audible (potentially perceived) to the animal, but not strong 
enough to elicit any overt behavioral or physiological response. The 
next zone corresponds with the area where the signal is audible to the 
animal and of sufficient intensity to elicit behavioral or 
physiological responsiveness. Third is a zone within which, for signals 
of high intensity, the received level is sufficient to potentially 
cause discomfort or tissue damage to auditory or other systems. 
Overlaying these zones to a certain extent is the area within which 
masking (i.e., when a sound interferes with or masks the ability of an 
animal to detect a signal of interest that is above the absolute 
hearing threshold) may occur; the masking zone may be highly variable 
in size.
    The potential for more severe effects (i.e., permanent hearing 
impairment, certain non-auditory physical or physiological effects) is 
considered here, although NMFS does not expect that there is a 
reasonable likelihood that the Navy's activities may result in such 
effects (see below for further discussion). Marine mammals exposed to 
high-intensity sound, or to lower-intensity sound for prolonged 
periods, can experience hearing threshold shift (TS), which is the loss 
of hearing sensitivity at certain frequency ranges (Kastak et al., 
1999; Schlundt et al., 2000; Finneran et al., 2003, 2005). TS can be 
permanent (PTS), in which case the loss of hearing sensitivity is not 
fully recoverable, or temporary (TTS), in which case the animal's 
hearing threshold would recover over time (Southall et al., 2007). 
Repeated sound exposure that leads to TTS could cause PTS. In severe 
cases of PTS, there can be total or partial deafness, while in most 
cases the animal has an impaired ability to hear sounds in specific 
frequency ranges (Kryter 1985).
    When PTS occurs, there is physical damage to the sound receptors in 
the ear (i.e., tissue damage), whereas TTS represents primarily tissue 
fatigue and is reversible (Southall et al., 2007). In addition, other 
investigators have suggested that TTS is within the normal bounds of 
physiological variability and tolerance and does not represent physical 
injury (e.g., Ward 1997). Therefore, NMFS does not consider TTS to 
constitute auditory injury.
    Relationships between TTS and PTS thresholds have not been studied 
in marine mammals--PTS data exists only for a single harbor seal 
(Kastak et al., 2008)--but are assumed to be similar to those in humans 
and other terrestrial mammals. PTS typically occurs at exposure levels 
at least several dB above that which induces mild TTS: A 40-dB 
threshold shift approximates PTS onset; e.g., Kryter et al., 1966; 
Miller, 1974), whereas a 6-dB threshold shift) approximates TTS onset 
(e.g., Southall et al., 2007). Based on data from terrestrial mammals, 
a precautionary assumption is that the PTS thresholds for impulsive 
sounds (such as bombs) 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). 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.
    TTS is the mildest form of hearing impairment that can occur during 
exposure to sound (Kryter 1985). 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. Few data 
on sound levels and durations necessary to elicit mild TTS have been 
obtained for marine mammals.
    Marine mammal hearing plays a critical role in communication with 
conspecifics, and interpretation of environmental cues for purposes 
such as predator avoidance and prey capture. 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. 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 occurs during a time 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.
    Currently, TTS data only exist for four species of cetaceans 
(bottlenose dolphin (Tursiops truncatus), beluga whale (Delphinapterus 
leucas), harbor porpoise, and Yangtze finless porpoise (Neophocoena 
asiaeorientalis) and three species of pinnipeds (northern elephant seal 
(Mirounga angustirostris), harbor seal, and California sea lion 
(Zalophus californianus)) exposed to a limited number of sound sources 
(i.e., mostly tones and octave-band noise) in laboratory settings 
(e.g., Finneran et al., 2002; Nachtigall et al., 2004; Kastak et al., 
2005; Lucke et al., 2009). In general, harbor seals (Kastak et al., 
2005; Kastelein et al., 2012a) and harbor porpoises (Lucke et al., 
2009; Kastelein et al., 2012b) have a lower TTS onset than other 
measured pinniped or cetacean species. Additionally, the existing 
marine mammal TTS data come from a limited number of individuals within 
these species. There are no data available on noise-induced hearing 
loss for mysticetes. For summaries of data on TTS in marine mammals or 
for further discussion of TTS onset thresholds, please see Southall et 
al. (2007) and Finneran and Jenkins (2012).
    In addition to PTS and TTS, there is a potential for non-auditory 
physiological effects or injuries that theoretically might occur in 
marine mammals exposed to high level underwater sound or as a secondary 
effect of extreme behavioral reactions (e.g., change in dive profile as 
a result

[[Page 18254]]

of an avoidance reaction) caused by exposure to sound. These impacts 
can include neurological effects, bubble formation, resonance effects, 
and other types of organ or tissue damage (Cox et al., 2006; Southall 
et al., 2007; Zimmer and Tyack 2007). The Navy's activities involve the 
use of explosives, which has been associated with these types of 
effects. The underwater explosion will send a shock wave and blast 
noise through the water, release gaseous by-products, create an 
oscillating bubble, and cause a plume of water to shoot up from the 
water surface. The shock wave and blast noise are of most concern to 
marine animals. The effects of an underwater explosion on a marine 
mammal depends on many factors, including the size, type, and depth of 
both the animal and the explosive charge; the depth of the water 
column; and the standoff distance between the charge and the animal, as 
well as the sound propagation properties of the environment. Potential 
impacts can range from brief effects (such as behavioral disturbance), 
tactile perception, physical discomfort, slight injury of the internal 
organs and the auditory system, to death of the animal (Yelverton et 
al., 1973; DoN, 2001). Non-lethal injury includes slight injury to 
internal organs and the auditory system; however, delayed lethality can 
be a result of individual or cumulative sublethal injuries (DoN, 2001). 
Immediate lethal injury would be a result of massive combined trauma to 
internal organs as a direct result of proximity to the point of 
detonation (DoN 2001). Generally, the higher the level of impulse and 
pressure level exposure, the more severe the impact to an individual.
    Injuries resulting from a shock wave take place at boundaries 
between tissues of different density. Different velocities are imparted 
to tissues of different densities, and this can lead to their physical 
disruption. Blast effects are greatest at the gas-liquid interface 
(Landsberg 2000). Gas-containing organs, particularly the lungs and 
gastrointestinal (GI) tract, are especially susceptible (Goertner 1982; 
Hill 1978; Yelverton et al., 1973). In addition, gas-containing organs 
including the nasal sacs, larynx, pharynx, trachea, and lungs may be 
damaged by compression/expansion caused by the oscillations of the 
blast gas bubble. Intestinal walls can bruise or rupture, with 
subsequent hemorrhage and escape of gut contents into the body cavity. 
Less severe GI tract injuries include contusions, petechiae (small red 
or purple spots caused by bleeding in the skin), and slight 
hemorrhaging (Yelverton et al., 1973).
    Because the ears are the most sensitive to pressure, they are the 
organs most sensitive to injury (Ketten 2000). Sound-related damage 
associated with blast noise can be theoretically distinct from injury 
from the shock wave, particularly farther from the explosion. If an 
animal is able to hear a noise, at some level it can damage its hearing 
by causing decreased sensitivity (Ketten 1995). Sound-related trauma 
can be lethal or sub-lethal. Lethal impacts are those that result in 
immediate death or serious debilitation in or near an intense source 
and are not, technically, pure acoustic trauma (Ketten 1995). Sub-
lethal impacts include hearing loss, which is caused by exposures to 
perceptible sounds. Severe damage (from the shock wave) to the ears 
includes tympanic membrane rupture, fracture of the ossicles, damage to 
the cochlea, hemorrhage, and cerebrospinal fluid leakage into the 
middle ear. Moderate injury implies partial hearing loss due to 
tympanic membrane rupture and blood in the middle ear. Permanent 
hearing loss also can occur when the hair cells are damaged by one very 
loud event, as well as by prolonged exposure to a loud noise or chronic 
exposure to noise. The level of impact from blasts depends on both an 
animal's location and, at outer zones, on its sensitivity to the 
residual noise (Ketten 1995).
    The above discussion concerning underwater explosions only pertains 
to open water detonations in a free field without mitigation. 
Therefore, given the proposed monitoring and mitigation measures 
discussed below, the Navy's blasting events are not likely to have 
injury or mortality effects on marine mammals in the project vicinity. 
Instead, NMFS considers that the Navy's blasts are most likely to cause 
behavioral harassment and may cause TTS or, in some cases PTS, in a few 
individual marine mammals, as discussed below.

Behavioral Effects

    Behavioral disturbance may include a variety of effects, including 
subtle changes in behavior (e.g., minor or brief avoidance of an area 
or changes in vocalizations), more conspicuous changes in similar 
behavioral activities, and more sustained and/or potentially severe 
reactions, such as displacement from or abandonment of high-quality 
habitat. Behavioral responses 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). Please see Appendices B-C of 
Southall et al. (2007) for a review of studies involving marine mammal 
behavioral responses to sound.
    Habituation can occur when an animal's response to a stimulus wanes 
with repeated exposure, usually in the absence of unpleasant associated 
events (Wartzok et al., 2003). Animals are most likely to habituate to 
sounds that are predictable and unvarying. It is important to note that 
habituation is appropriately considered as a ``progressive reduction in 
response to stimuli that are perceived as neither aversive nor 
beneficial,'' rather than as, more generally, moderation in response to 
human disturbance (Bejder et al., 2009). The opposite process is 
sensitization, when an unpleasant experience leads to subsequent 
responses, often in the form of avoidance, at a lower level of 
exposure. As noted, behavioral state may affect the type of response. 
For example, animals that are resting may show greater behavioral 
change in response to disturbing sound levels than animals that are 
highly motivated to remain in an area for feeding (Richardson et al., 
1995; NRC 2003; Wartzok et al., 2003). Controlled experiments with 
captive marine mammals have showed pronounced behavioral reactions, 
including avoidance of loud sound sources (Ridgway et al., 1997; 
Finneran et al., 2003). Observed responses of wild marine mammals to 
loud-impulsive sound sources (typically seismic airguns or acoustic 
harassment devices) have been varied but often consist of avoidance 
behavior or other behavioral changes suggesting discomfort (Morton and 
Symonds 2002; see also Richardson et al., 1995; Nowacek et al., 2007).
    Available studies show wide variation in response to underwater 
sound; therefore, it is difficult to predict specifically how any given 
sound in a particular instance might affect marine mammals perceiving 
the signal. If a marine mammal does react briefly to an underwater 
sound by changing its behavior or moving a small distance, the

[[Page 18255]]

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). 
This highlights the importance of assessing the context of the acoustic 
effects alongside the received levels anticipated. Severity of effects 
from a response to an acoustic stimuli can likely vary based on the 
context in which the stimuli was received, particularly if it occurred 
during a biologically sensitive temporal or spatial point in the life 
history of the animal. There are broad categories of potential 
response, described in greater detail here, that include alteration of 
dive behavior, alteration of foraging behavior, effects to breathing, 
interference with or alteration of vocalization, avoidance, and flight.
    Changes in dive behavior can vary widely, and may consist of 
increased or decreased dive times and surface intervals as well as 
changes in the rates of ascent and descent during a dive (e.g., Frankel 
and Clark 2000; Costa et al., 2003; Ng and Leung 2003; Nowacek et al., 
2004; Goldbogen et al., 2013a,b). Variations in dive behavior may 
reflect interruptions in biologically significant activities (e.g., 
foraging) or they may be of little biological significance. The impact 
of an alteration to dive behavior resulting from an acoustic exposure 
depends on what the animal is doing at the time of the exposure and the 
type and magnitude of the response.
    Disruption of feeding behavior can be difficult to correlate with 
anthropogenic sound exposure, so it is usually inferred by observed 
displacement from known foraging areas, the appearance of secondary 
indicators (e.g., bubble nets or sediment plumes), or changes in dive 
behavior. 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.
    Variations in respiration naturally vary with different behaviors 
and alterations to breathing rate as a function of acoustic exposure 
can be expected to co-occur with other behavioral reactions, such as a 
flight response or an alteration in diving. However, respiration rates 
in and of themselves may be representative of annoyance or an acute 
stress response. Various studies have shown that respiration rates may 
either be unaffected or could increase, depending on the species and 
signal characteristics, again highlighting the importance in 
understanding species differences in the tolerance of underwater noise 
when determining the potential for impacts resulting from anthropogenic 
sound exposure (e.g., Kastelein et al., 2001, 2005b, 2006; Gailey et 
al., 2007).
    Marine mammals vocalize for different purposes and across multiple 
modes, such as whistling, echolocation click production, calling, and 
singing. Changes in vocalization behavior in response to anthropogenic 
noise can occur for any of these modes and may result from a need to 
compete with an increase in background noise or may reflect increased 
vigilance or a startle response. For example, in the presence of 
potentially masking signals, humpback whales and killer whales have 
been observed to increase the length of their songs (Miller et al., 
2000; Fristrup et al., 2003; Foote et al., 2004), while right whales 
(Eubalaena glacialis) have been observed to shift the frequency content 
of their calls upward while reducing the rate of calling in areas of 
increased anthropogenic noise (Parks et al., 2007b). In some cases, 
animals may cease sound production during production of aversive 
signals (Bowles et al., 1994).
    Avoidance is the displacement of an individual from an area or 
migration path because of the presence of a sound or other stressors, 
and is one of the most obvious manifestations of disturbance in marine 
mammals (Richardson et al., 1995). For example, gray whales 
(Eschrictius robustus) are known to change direction--deflecting from 
customary migratory paths--in order to avoid noise from seismic surveys 
(Malme et al., 1984). Avoidance may be short-term, with animals 
returning to the area once the noise has ceased (e.g., Bowles et al., 
1994; Goold, 1996; Stone et al., 2000; Morton and Symonds, 2002; Gailey 
et al., 2007). Longer-term displacement is possible, however, which may 
lead to changes in abundance or distribution patterns of the affected 
species in the affected region if habituation to the presence of the 
sound does not occur (e.g., Blackwell et al., 2004; Bejder et al., 
2006; Teilmann et al., 2006).
    A flight response is a dramatic change in normal movement to a 
directed and rapid movement away from the perceived location of a sound 
source. The flight response differs from other avoidance responses in 
the intensity of the response (e.g., directed movement, rate of 
travel). Relatively little information on flight responses of marine 
mammals to anthropogenic signals exist, although observations of flight 
responses to the presence of predators have occurred (Connor and 
Heithaus 1996). The result of a flight response could range from brief, 
temporary exertion and displacement from the area where the signal 
provokes flight to, in extreme cases, marine mammal strandings (Evans 
and England 2001). However, it should be noted that response to a 
perceived predator does not necessarily invoke flight (Ford and Reeves 
2008), and whether individuals are solitary or in groups may influence 
the response.
    Behavioral disturbance can also impact marine mammals in more 
subtle ways. Increased vigilance may result in costs related to 
diversion of focus and attention (i.e., when a response consists of 
increased vigilance, it may come at the cost of decreased attention to 
other critical behaviors such as foraging or resting). These effects 
have generally not been demonstrated for marine mammals, but studies 
involving fish and terrestrial animals have shown that increased 
vigilance may substantially reduce feeding rates (e.g., Beauchamp and 
Livoreil 1997; Fritz et al., 2002; Purser and Radford 2011). In 
addition, chronic disturbance can cause population declines through 
reduction of fitness (e.g., decline in body condition) and subsequent 
reduction in reproductive success, survival, or both (e.g., Harrington 
and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). However, 
Ridgway et al. (2006) reported that increased vigilance in bottlenose 
dolphins exposed to sound over a 5 day period did not cause any sleep 
deprivation or stress effects.
    Many animals perform vital functions, such as feeding, resting, 
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption 
of such functions resulting from reactions to stressors such as sound 
exposure are more likely to be significant if they last more than one 
diel cycle or recur on subsequent days (Southall et al., 2007). 
Consequently, a behavioral response lasting less than one day and not 
recurring on subsequent days is not considered particularly severe 
unless it could directly affect reproduction or

[[Page 18256]]

survival (Southall et al., 2007). Note that there is a difference 
between multi-day substantive behavioral reactions and multi-day 
anthropogenic activities. For example, just because an activity lasts 
for multiple days does not necessarily mean that individual animals are 
either exposed to activity-related stressors for multiple days or, 
further, exposed in a manner resulting in sustained multi-day 
substantive behavioral responses.

Stress Response

    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 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).

Acoustic Effects, Underwater

    The effects of sounds from the Navy's proposed activities might 
include one or more of the following: Temporary or permanent hearing 
impairment, non-auditory physical or physiological effects, behavioral 
disturbance, and masking (Richardson et al., 1995; Gordon et al., 2003; 
Nowacek et al., 2007; Southall et al., 2007). The effects of pile 
driving, drilling, and blasting on marine mammals are dependent on 
several factors, including the type and depth of the animal; the pile 
size and type, and the intensity and duration of the pile driving, 
drilling, or blasting sound; the substrate; the standoff distance 
between the pile and the animal; and the sound propagation properties 
of the environment. Impacts to marine mammals from pile driving, 
drilling, and blasting activities are expected to result primarily from 
acoustic propagation pathways. As such, the degree of effect is 
intrinsically related to the frequency, received level, and duration of 
the sound exposure, which are in turn influenced by the distance 
between the animal and the source. The further away from the source, 
the less intense the exposure should be. The substrate and depth of the 
habitat affect the sound propagation properties of the environment. In 
addition, substrates that are soft (e.g., mud) would absorb or 
attenuate the sound more readily than hard substrates (e.g., rock), 
which may reflect the acoustic wave. Soft porous substrates would also 
likely require less time to install or extract a pile, and possibly 
less forceful equipment, which would ultimately decrease the intensity 
of the acoustic source.
    In the absence of mitigation, impacts to marine species could be 
expected to include physiological and behavioral responses to the 
acoustic signature (Viada et al., 2008). Potential impacts from 
impulsive sound sources like blasting can range in severity from 
effects such as behavioral disturbance to temporary or permanent 
hearing impairment (Yelverton et al., 1973). Due to the characteristics 
of the sounds involved in the project, behavioral disturbance is the 
most likely effect from the proposed activity. Marine mammals exposed 
to high intensity sound repeatedly or for prolonged periods can 
experience hearing threshold shifts. PTS constitutes injury, but TTS 
does not (Southall et al., 2007). Due to the use mitigation measures 
discussed in detail in the Proposed Mitigation section, it is unlikely 
but possible that PTS or TTS could occur from blasting. Neither NMFS 
nor the Navy anticipates non-auditory injuries of marine mammals as a 
result of the proposed construction activities.

Disturbance Reactions

    With pile removal as well as drilling activities, it is likely that 
the onset of sound sources could result in temporary, short-term 
changes in an animal's typical behavior and/or avoidance of the 
affected area. These behavioral changes may include (Richardson et al., 
1995): 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); avoidance of 
areas where sound sources are located; and/or flight responses (e.g., 
pinnipeds flushing into water from haulouts or rookeries). Pinnipeds 
may increase their haul-out time, possibly to avoid in-water 
disturbance (Thorson and Reyff 2006). If a marine mammal responds to a 
stimulus by changing its behavior (e.g., through relatively minor 
changes in locomotion direction/speed or vocalization behavior), the 
response may or may not constitute taking at the individual level, and 
is unlikely to affect the stock or the species as a whole. However, if 
a sound source displaces marine mammals from an important feeding or 
breeding area for a prolonged period, impacts on animals, and if so 
potentially on the stock or

[[Page 18257]]

species, could potentially be significant (e.g., Lusseau and Bejder 
2007; Weilgart 2007).
    The biological significance of many of these behavioral 
disturbances is difficult to predict, especially if the detected 
disturbances appear minor. However, the consequences of behavioral 
modification could be biologically significant if the change affects 
growth, survival, or reproduction. Significant behavioral modifications 
that could potentially lead to effects on growth, survival, or 
reproduction include:
     Drastic changes in diving/surfacing patterns (such as 
those thought to cause beaked whale stranding due to exposure to 
military mid-frequency tactical sonar);
     Longer-term habitat abandonment due to loss of desirable 
acoustic environment; and
     Longer-term cessation of feeding or social interaction.
    The onset of behavioral disturbance from anthropogenic sound 
depends on both external factors (characteristics of sound sources and 
their paths) and the specific characteristics of the receiving animals 
(hearing, motivation, experience, demography) and is difficult to 
predict (Southall et al., 2007).

Auditory 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., 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.
    Under certain circumstances, marine mammals experiencing 
significant masking could also be impaired from maximizing their 
performance fitness in survival and reproduction. Therefore, when the 
coincident (masking) sound is man-made, it may be considered harassment 
when disrupting or altering critical behaviors. It is important to 
distinguish TTS and PTS, which persist after the sound exposure, from 
masking, which occurs during the sound exposure. Because masking 
(without resulting in TS) is not associated with abnormal physiological 
function, it is not considered a physiological effect, but rather a 
potential behavioral effect.
    The frequency range of the potentially masking sound is important 
in determining any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation 
sounds produced by odontocetes but are more likely to affect detection 
of mysticete communication calls and other potentially important 
natural sounds such as those produced by surf and some prey species. 
The masking of communication signals by anthropogenic noise may be 
considered as a reduction in the communication space of animals (e.g., 
Clark et al., 2009) and may result in energetic or other costs as 
animals change their vocalization behavior (e.g., Miller et al., 2000; 
Foote et al., 2004; Parks et al., 2007b; Di Iorio and Clark 2009; Holt 
et al., 2009). Masking can be reduced in situations where the signal 
and noise come from different directions (Richardson et al., 1995), 
through amplitude modulation of the signal, or through other 
compensatory behaviors (Houser and Moore 2014). Masking can be tested 
directly in captive species (e.g., Erbe 2008), but in wild populations 
it must be either modeled or inferred from evidence of masking 
compensation. There are few studies addressing real-world masking 
sounds likely to be experienced by marine mammals in the wild (e.g., 
Branstetter et al., 2013).
    Masking affects both senders and receivers of acoustic signals and 
can potentially have long-term chronic effects on marine mammals at the 
population level as well as at the individual level. Low-frequency 
ambient sound levels have increased by as much as 20 dB (more than 
three times in terms of SPL) in the world's ocean from pre-industrial 
periods, with most of the increase from distant commercial shipping 
(Hildebrand 2009). All anthropogenic sound sources, but especially 
chronic and lower-frequency signals (e.g., from vessel traffic), 
contribute to elevated ambient sound levels, thus intensifying masking.

Potential Effects on Marine Mammal Habitat

    Water quality--Temporary and localized reduction in water quality 
will occur as a result of in-water construction activities. Most of 
this effect will occur during the installation of piles and blasting 
when bottom sediments are disturbed. Effects to turbidity and 
sedimentation are expected to be short-term, minor, and localized. 
Currents are strong in the area and, therefore, suspended sediments in 
the water column should dissipate and quickly return to background 
levels. Following the completion of sediment-disturbing activities, the 
turbidity levels are expected to return to normal ambient levels 
following the end of construction. Turbidity within the water column 
has the potential to reduce the level of oxygen in the water and 
irritate the gills of prey fish species in the proposed project area. 
However, turbidity plumes associated with the project would be 
temporary and localized, and fish in the proposed project area would be 
able to move away from and avoid the areas where plumes may occur. It 
is expected that the impacts on prey fish species from turbidity and, 
therefore, on marine mammals, would be minimal and temporary. In 
general, the area likely impacted by the project is relatively small 
compared to the available habitat in Great Bay Estuary, and there is no 
biologically important area for marine mammals that could be affected. 
As a result, activity at the project site would be inconsequential in 
terms of its effects on marine mammal foraging.
    Effects to Prey--Sound may affect marine mammals through impacts on 
the abundance, behavior, or distribution of prey species (e.g., 
crustaceans, cephalopods, fish, zooplankton). Marine mammal prey varies 
by species, season, and location and, for some, is not well documented. 
Studies regarding the effects of noise on known marine mammal prey are 
described here.
    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

[[Page 18258]]

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). More commonly, though, the impacts of noise on fish are 
temporary.
    SPLs of sufficient strength have been known to cause injury to fish 
and fish mortality. 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. (2012a) showed that a TTS of 4-6 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., 2012b; Casper et al., 2013).
    Construction activities would produce continuous (i.e., vibratory 
pile driving and removal, and drilling) and impulsive (i.e., impact 
pile driving and blasting) sounds. The duration of impact pile driving 
for the proposed project 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. Vibratory pile 
driving and drilling would possibly elicit behavioral reactions from 
fish, such as temporary avoidance of the area, but are unlikely to 
cause injuries to fish or have persistent effects on local fish 
populations. The duration of fish avoidance of this area after pile 
driving and drilling stop is unknown, but a return to normal 
recruitment, distribution and behavior is anticipated. While impacts 
from blasting to fish are more severe, including barotrauma and 
mortality, the blast will last less than one second for each blast 
event, making the duration of this acoustic impact short term. 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 Shipyard operations and other 
vessel traffic. In general, impacts on marine mammal prey species are 
expected to be minor and temporary.
    Construction may have temporary impacts on benthic invertebrate 
species, another marine mammal prey source. Direct benthic habitat loss 
would result with the permanent loss of approximately 3.5 acres of 
benthic habitat from construction of the super flood basin. However, 
the areas to be permanently removed are beneath and adjacent to the 
existing berths along the Shipyard's industrial waterfront and are 
regularly disturbed as part of the construction dredging to maintain 
safe navigational depths at the berths. Further, vessel activity at the 
berths creates minor disturbances of benthic habitats (e.g., vessel 
propeller wakes) during waterfront operations. Therefore, impacts of 
the proposed project are not likely to have adverse effects on marine 
mammal foraging habitat in the proposed project area.
    All marine mammal species using habitat near the proposed project 
area are primarily transiting the area; no known foraging or haulout 
areas are located within 1.5 miles of the proposed project area. The 
most likely impacts on marine mammal habitat for the project are from 
underwater noise, bedrock removal, turbidity, and potential effects on 
the food supply. However, it is not expected that any of these impacts 
would be significant.

Estimated Take

    This section provides an estimate of the number of incidental takes 
proposed for authorization through this IHA, which will inform both 
NMFS' consideration of ``small numbers'' and the negligible impact 
determination.
    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 noise 
generated from in-water pile driving (vibratory and impact), drilling, 
and blasting has the potential to result in disruption of behavioral 
patterns for individual marine mammals. The use of the explosive source 
(i.e., blasting) for a very short period each day has the potential to 
result in TTS. The primary relevant mitigation measure is avoiding 
blasting when any marine mammal is observed in the PTS zones. While 
this measure should avoid all take by Level A harassment, NMFS is 
authorizing takes by Level A harassment to account for the possibility 
that marine mammals escape observation in the PTS zone. Additionally, 
the distances to thresholds for slight lung injury for harbor porpoises 
(5 m) and phocids (9 m) are small enough that the mitigation and 
monitoring measures are expected to minimize the potential for such 
taking to the extent practicable. Therefore the potential for non-
auditory physical injury is considered discountable, and all takes by 
Level A harassment are expected to occur due to PTS.
    As described previously, no mortality is anticipated or proposed to 
be authorized for these activities. The method by which take is 
estimated is described below.
    Generally speaking, NMFS estimates take by considering: (1) 
Acoustic thresholds above which NMFS believes 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) and the number of days 
of activities. NMFS notes that while these basic factors can contribute 
to a basic calculation to provide an initial prediction of takes, 
additional information that can qualitatively

[[Page 18259]]

inform take estimates is also sometimes available (e.g., previous 
monitoring results or average group size). Below, the factors 
considered here are described in more detail and present the proposed 
take estimate.

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). Thresholds have also been developed to identify the 
pressure levels above which animals may incur different types of tissue 
damage from exposure to pressure waves from explosive detonations.
    Level B Harassment for non-explosive sources--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 (e.g., frequency, predictability, 
duty cycle), the environment (e.g., bathymetry), and the receiving 
animals (hearing, motivation, experience, demography, behavioral 
context) and can be difficult to predict (Southall et al., 2007, 
Ellison et al., 2012). Based on what the available science indicates 
and the practical need to use a threshold based on a factor that is 
both predictable and measurable for most activities, NMFS uses a 
generalized acoustic threshold based on received level to estimate the 
onset of behavioral harassment. NMFS predicts that marine mammals are 
likely to be behaviorally harassed in a manner NMFS considers Level B 
harassment when exposed to underwater anthropogenic noise above 
received levels of 120 dB re 1 [mu]Pa (rms) for continuous (e.g., 
vibratory pile-driving, drilling) and above 160 dB re 1 [mu]Pa (rms) 
for impulsive and/or intermittent (e.g., impact pile driving) sources.
    Level A harassment for non-explosive sources--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). As mentioned previously, the Navy's 
Portsmouth Naval Shipyard modification and expansion includes the use 
of impulsive (i.e., impact pile driving) and non-impulsive (i.e., 
drilling, vibratory pile driving) sources.
    These thresholds are provided in Table 4. 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 4--Thresholds Identifying the Onset of Permanent Threshold Shift
----------------------------------------------------------------------------------------------------------------
                                                     PTS onset acoustic thresholds * (received level)
             Hearing group              ------------------------------------------------------------------------
                                                  Impulsive                         Non-impulsive
----------------------------------------------------------------------------------------------------------------
High-Frequency (HF) Cetaceans..........  Cell 5: Lpk,flat: 202 dB;   Cell 6: LE,HF,24h: 173 dB.
                                          LE,HF,24h: 155 dB.
Phocid Pinnipeds (PW) (Underwater).....  Cell 7: Lpk,flat: 218 dB;   Cell 8: LE,PW,24h: 201 dB.
                                          LE,PW,24h: 185 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric acoustic 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 should also be considered.
Note: Peak sound pressure (Lpk) has a reference value of 1[micro]Pa, and cumulative sound exposure level (LE)
  has a reference value of 1[micro]Pa\2\s. In this Table, thresholds are abbreviated to reflect American
  National Standards Institute standards (ANSI 2013). However, peak sound pressure is defined by ANSI as
  incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript
  ``flat'' is being included to indicate peak sound pressure should be flat weighted or unweighted within the
  generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates
  the designated marine mammal auditory weighting function (HF cetaceans and PW pinnipeds) and that the
  recommended accumulation period is 24 hours. The 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 acoustic thresholds will be
  exceeded.

    Explosive sources--Based on the best available science, NMFS uses 
the acoustic and pressure thresholds indicated in Table 5 to predict 
the onset of behavioral harassment, PTS, non-auditory impacts, and 
mortality. Because of the nature of blasting, there is no established 
Level B behavioral harassment threshold associated with the activity, 
but TTS, which is a form of Level B harassment take, may occur. The 
behavioral threshold used in analyses for multiple explosive events is 
determined relative to (5 dB less than) the TTS onset threshold (DoN 
2017). 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.nmfs.noaa.gov/pr/acoustics/guidelines.htm.

                                         Table 5--Explosive Acoustic and Pressure Thresholds for Marine Mammals
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                           Level B harassment            Level A harassment                Non-auditory
                                -----------------------------------------------------------------------------------------------------
             Group                   Behavioral                                                                                            Mortality
                                      (multiple              TTS                 PTS           Gastrointestinal          Lung
                                    detonations)                                                    tract
--------------------------------------------------------------------------------------------------------------------------------------------------------
High-Frequency (HF) Cetaceans..  135 dB SEL........  140 dB SEL or 196   155 dB SEL or 202   237 dB SPLpk.......  39.1M\1/3\ (1+[D/   91.4M\1/3\ (1+[D/
                                                      dB SPLpk.           dB SPLpk.                                10.081])\1/2\ Pa-   10.081])\1/2\ Pa-
                                                                                                                   sec.                sec
                                                                                                                  where: M = mass of  where: M = mass of
                                                                                                                   the animals in      the animals in
                                                                                                                   kg;.                kg;
                                                                                                                  D = depth of        D = depth of
                                                                                                                   animal in m.        animal in m.

[[Page 18260]]

 
Phocid Pinnipeds (PW)            165 dB SEL........  170 dB SEL or 212   185 dB SEL or 218
 (Underwater).                                        dB SPLpk.           dB SPLpk.
--------------------------------------------------------------------------------------------------------------------------------------------------------

Ensonified Area

    The operational and environmental parameters of the activity that 
will feed into identifying the area ensonified above the acoustic 
thresholds are described below.

Source Levels

    The project includes impact pile driving, vibratory pile driving 
and pile removal, drilling, and blasting. Source levels of pile driving 
activities are based on reviews of measurements of the same or similar 
types and dimensions of piles available in the literature. Based on 
this review, the sources levels in Table 6 are assumed for the pile 
driving and drilling underwater noise produced by construction 
activities.

                             Table 6--Summary of In-Water Pile Driving Source Levels
                                              [at 10 m from source]
----------------------------------------------------------------------------------------------------------------
                                  Installation/
           Pile type               extraction      Pile diameter  SPLpk, dB re 1   SPLrms, dB re   SEL, dB re 1
                                     method           (inch)         [micro]Pa      1 [micro]Pa   [micro]Pa\2\-s
----------------------------------------------------------------------------------------------------------------
Z-shaped steel sheet 1 3......  Vibratory.......              28              NA             167             167
                                Impact..........              28             211             196             181
Flat-webbed steel sheet 1 3...  Vibratory.......              18              NA             163             163
                                Impact..........              18             205             190             180
Steel pipe \2\................  Vibratory.......              30              NA             167             167
Blast holes \4\...............  Drilling........             4.5              NA           166.2           166.2
----------------------------------------------------------------------------------------------------------------
Key: dB = decibels; NA = Not applicable; dB re 1 [mu]Pa = dB referenced to a pressure of 1 micropascal, measures
  underwater SPL. dB re 1 [mu]Pa2-s = dB referenced to a pressure of 1 micropascal squared per second, measures
  underwater SEL.
\1\ = A proxy value for 28-inch sheet piles could not be found for impact and vibratory driving so the proxy for
  a 30-inch steel pipe pile has been used. A proxy value for 18-inch flat-webbed sheet piles could not be found
  for impact and vibratory driving so the proxy for a 24-inch Z-shaped sheet pile has been used (NAVFAC MIDLANT
  2019a).
Sources: Navy 2015 \2\; CALTRANS 2015 \3\; Denes et al, 2016.

    The proxy source level for drilling of blast-charge holes is 
derived from Denes et al. (2016), which reports sound pressure levels 
measured during rock socket drilling at Kodiak Ferry Terminal in 
Alaska. The size of the blast-charge holes considered here (4.5-inch) 
is much smaller than the size of the drilled holes (24-inch) in Denes 
et al. (2016), making the use of 166.2 dB re 1[micro]Pa conservative.
    There are no data on sound source levels from explosives used under 
circumstances identical to the proposed activity (e.g., charge 
composition and weight, bathymetry, substrate composition, and the 
dimensions of holes for stemmed charge placement). Therefore, the Navy 
made approximations by reference to mathematical models that have been 
empirically validated, under roughly comparable circumstances, to 
estimate source levels both in terms of absolute peak sound pressure 
level (SPL in units of dB re 1[micro]Pa) and sound exposure level (SEL 
in units of dB re 1[micro]Pa\2\-s) (Table 7). The peak source level 
calculation of a confined blast follows Cole's (1948) equation and a 
regression curve from the Miami Harbor Deepening Project (Hempen et al. 
2007), using a distance of 2.4 m and a weight of 120 lbs for a single 
charge. Based on this approach, the peak source level for the proposed 
project is estimated to be 257 dB re 1 [micro]Pa for a 120 lb charge. 
Following Urick (1983), the Navy estimated the SEL for 30, 120 pound 
charges at 1 m by first calculating the instantaneous pressure 
following the onset of a shock wave, as a relationship between peak 
pressure and time. Blasting operations would involve detonating 120 
pounds up to 30 times in rapid succession, with a split second delay 
between each detonation. Without specific information regarding the 
layout of the charges, the modeling assumes a grid of 2.4 m by 2.4 m 
charges for the majority of the superflood basin, and 1.5 m by 1.8 m 
for the rows closest to Berth 11. Due to time and spatial separation of 
each single charge by a distance of 2.4 m, the accumulation of acoustic 
energy is added sequentially, assuming the transmission loss follows 
cylindrical spreading within the matrix of charges. Using this approach 
for multiple confined charges, the modeled source SEL for 30, 120 pound 
charges at 1 m is estimated to be 227 dB re 1[micro]Pa\2\-s. Please see 
the Navy's IHA application for more details regarding these 
calculations.

                     Table 7--Blasting Source Levels
------------------------------------------------------------------------
                                     SPLpk, (dB re 1      SEL (dB re 1
         Explosive charge               [micro]Pa)      [micro]Pa\2\-s)
------------------------------------------------------------------------
30 x 120 lb charge................               257                227
------------------------------------------------------------------------

    These source levels for pile driving, drilling, and blasting are 
used to estimate the Level A harassment and Level B harassment zones. 
For all construction activities, cumulative SEL values are used to 
calculate distances to

[[Page 18261]]

the Level A harassment thresholds using the NMFS acoustic guidance 
(NMFS 2018) because they were larger than the values calculated against 
the SPLpeak criteria.
    The Level B harassment distances for construction activities are 
calculated using geometric spreading with the source levels provided in 
Tables 6 and 7.
    Ensonified areas (A) are calculated using the following equation.

A = [pi]R\2\ (1)

where R is the harassment distance.

    However, the maximum distance from the source is capped due to 
landmass interception in the surrounding area. For this reason, the 
maximum area that could be ensonified by noise from construction 
activities is an estimated 0.418 km\2\ (0.16 square miles). Therefore, 
all harassment zones that are larger than 0.418 km\2\ are corrected to 
this maximum value. The maximum ensonified area for blasting is smaller 
(0.335 km\2\) because, prior to the removal of bedrock, a portion of 
the west closure wall will be installed, providing an additional 
boundary between noise produced within the superflood basin and the 
surrounding environment.
    When the original NMFS Technical Guidance (2016) was published, in 
recognition of the fact that the ensonified area/volume could be more 
technically challenging to predict because of the duration component in 
the new thresholds, NMFS developed a User Spreadsheet that includes 
tools to help predict a simple isopleth that can be used in conjunction 
with marine mammal density or occurrence to help predict takes. NMFS 
notes that because of some of the assumptions included in the methods 
used for these tools, NMFS anticipates that isopleths produced are 
typically going to be overestimates of some degree, which may result in 
some degree of overestimate of Level A harassment take. However, these 
tools offer the best way to predict appropriate isopleths when more 
sophisticated 3D modeling methods are not available, and NMFS continues 
to develop ways to quantitatively refine these tools, and will 
qualitatively address the output where appropriate. For stationary 
sources such as in-water vibratory and impact pile driving, NMFS User 
Spreadsheet predicts the closest distance at which, if a marine mammal 
remained at that distance the entire duration of the activity, it would 
not incur PTS. The Level A harassment areas are calculated using the 
same Equation (1), with corrections to reflect the largest possible 
area of 0.418 km\2\ if the calculation value was larger.
    The modeled distances to Level A harassment and Level B harassment 
isopleths for the marine mammal species likely to be affected by the 
proposed activities are provided in Tables 8 and 9. As discussed above, 
the only marine mammals that could occur in the vicinity of the project 
area are harbor porpoise (high-frequency cetacean) and four species of 
true seals (phocid).

                                    Table 8--Distances and Areas of Harassment Zones for Pile Driving and Drilling *
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                            Level A harassment                     Level B harassment
                                                                           -----------------------------------------------------------------------------
                                        Pile size, type, and    Number of          HF cetacean                 Phocid
              Activity                          rate               days    ----------------------------------------------------                  Area
                                                                                           Area  (m                  Area  (m    Dist.  (m)     (m\2\)
                                                                             Dist.  (m)      \2\)      Dist.  (m)      \2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Impulsive
--------------------------------------------------------------------------------------------------------------------------------------------------------
Construct west closure wall.........  18 flat-               13        1,763          418          792          380        1,000          405
                                       webbed sheet pile (12
                                       pile/day).
Entrance structure closure walls....  28 Z-shaped             4        2,056          418          923          395        2,512          418
                                       sheet pile (12 pile/
                                       day).
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Non-impulsive
--------------------------------------------------------------------------------------------------------------------------------------------------------
Construct west closure wall.........  18 flat-               13         13.7        0.556          5.6        0.098        7,356          418
                                       webbed sheet pile (13
                                       pile/day).
Install west closure wall template..  30 steel                5         10.1        0.319          4.1        0.053       13,594          418
                                       pipe pile (3 pile/day).
Remove west closure wall template...  30 steel                5         10.1        0.319          4.1        0.053       13,594          418
                                       pipe pile (3 pile/day).
Remove temporary dolphins...........  30 steel                2         66.1         10.7         27.2          2.0       46,416          418
                                       pipe pile (8 pile/day).
Entrance structure closure walls....  28 Z-shaped             4         25.4         1.75         10.4        0.338       13,594          418
                                       sheet pile (12 pile/
                                       day).
Bedrock drilling for blast charges..  4.5 (1,580            130            7        0.153          4.3        0.058       12,023          418
                                       holes).
--------------------------------------------------------------------------------------------------------------------------------------------------------
* 418 m\2\ is the maximum ensonified area in the project area due to landmass interception of sound propagation.


                                             Table 9--Distances and Areas of Harassment Zones for Blasting*
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Level A (PTS onset) harassment          Level B (behavioral) harassment        Non-auditory
                                                     --------------------------------------------------------------------------------       injury
                                                                                                                                     -------------------
                                                        Harbor porpoise    Phocids distance     Harbor porpoise    Phocids distance      Phocid/harbor
   Blasting events and charge        Blasting days     distance to  155    to  185 dB SELcum   distance to  135    to 165 dB SELcum    porpoise distance
                                                           dB SELcum       threshold/area of       dB SELcum       threshold/area of    to 243 dB  peak
                                                       threshold/area of          ZOI          threshold/area of          ZOI         pressure threshold/
                                                              ZOI                                     ZOI                                 area of ZOI
--------------------------------------------------------------------------------------------------------------------------------------------------------
5-30 blasts per event, 120-lb     130 (1-2 events/    1,007 m/335 m\2\..  110 m/9.78 m\2\...  2,131 m/335 m\2\..  577 m/276.36 m\2\.  5 m/0.08 m\2\.
 charge per blast event, 150       day).
 blast events.
--------------------------------------------------------------------------------------------------------------------------------------------------------
* 335 m\2\ is the maximum ensonified area in the project area due to landmass interception of sound propagation.


[[Page 18262]]

Marine Mammal Occurrence

    Marine mammal density estimates for the harbor porpoise, harbor 
seal, and gray seal are based on marine mammal monitoring observations 
during 2017 and 2018 (CIANBRO 2018a,b). Density values were calculated 
from visual sightings of all marine mammals divided by the monitoring 
days (a total of 154 days) and the total ensonified area in which the 
sightings occurred in the 2017 and 2018 activities (0.8401 km\2\). 
Details used for calculations are provided in Table 10 and described 
below.

  Table 10--Marine Mammal Sightings and Resulting Density in the Vicinity of Portsmouth Naval Shipyard Project
                                                      Area
----------------------------------------------------------------------------------------------------------------
                                                                                                      Density
                     Species                       2017 sighting   2018 sighting  Total sighting   (animal/day/
                                                     (96 days)       (58 days)                        km\2\)
----------------------------------------------------------------------------------------------------------------
Harbor porpoise.................................               3               2               5            0.04
Harbor seal.....................................             199             122             321            2.48
Gray seal.......................................              24               2              26            0.20
----------------------------------------------------------------------------------------------------------------

    Hooded and harp seals are much rarer than the harbor and gray seals 
in the Piscataqua River, and no density information for these two 
species is available. To date, marine mammal monitoring for the Berth 
11 Waterfront Improvements Construction project has not recorded a 
sighting of a hooded or harp seal in the project area (Cianbro 2018ab; 
NAVFAC Mid-Atlantic 2018, 2019b; Navy 2019; Stantec 2020); however, two 
harp seals were observed outside of Berth 11 pile-driving activities, 
one on May 12, 2020 and one on May 14, 2020 (Stantec 2020). The Navy 
requested authorization of take for these two species and NMFS is 
acting on that request.

Take Calculation and Estimation

    The approach by which the information provided above is brought 
together to produce a quantitative take estimate is described here.
    For marine mammals with known density information (i.e., harbor 
porpoise, harbor seal, and gray seal), estimated harassment take 
numbers are calculated using the following equation:

Estimated take = animal density x ensonified area x operating days (2)

    However, in consideration of the prevalence of seals in the project 
area and in accordance with the approach utilized in IHAs previously 
issued to the Navy for expansion and modification of DD1, NMFS has 
determined that it is appropriate to increase the number of proposed 
harbor seal and gray seal Level B behavioral harassment takes. Proposed 
harbor seal Level B behavioral harassment takes have been adjusted 
upwards by multiplying the average number of harbor seals sighted per 
day from May through December 2020 (721 sightings divided by 150 days 
of monitoring, or 5 harbor seals/day) by the number of proposed actual 
construction days (159), resulting in 795 proposed Level B behavioral 
harassment takes. Gray seal proposed Level B harassment takes have been 
increased utilizing the same approach (47 sightings divided by 150 days 
of monitoring, or 0.31 gray seals/day), resulting in 50 Level B 
behavioral harassment takes.
    NMFS authorized one Level B harassment take per month each of a 
hooded seal and a harp seal for the Berth 11 Waterfront Improvements 
Construction project in both 2018 and 2019. The Navy is requesting 
authorization of one Level B harassment take each of hooded seal and 
harp seal per month of construction from January through May when these 
species may occur (Total of 5 Level B harassment takes for each 
species).
    A summary of estimated and proposed takes is presented in Table 11. 
Non-auditory take estimates were zero for all species and are, 
therefore, not included in Table 11.
BILLING CODE 3510-22-P

[[Page 18263]]

[GRAPHIC] [TIFF OMITTED] TN08AP21.013


[[Page 18264]]


BILLING CODE 3510-22-C

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 such 
activity, and other means of effecting the least practicable impact on 
such species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of such species or stock for taking for certain 
subsistence uses. 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 such activity or other means of effecting the 
least practicable adverse impact upon the affected species or stocks 
and their habitat (50 CFR 216.104(a)(11)).
    In evaluating how mitigation may or may not be appropriate to 
ensure the least practicable adverse impact on species or stocks and 
their habitat, as well as subsistence uses where applicable, NMFS 
carefully 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, impact on 
operations, and, in the case of a military readiness activity, 
personnel safety, practicality of implementation, and impact on the 
effectiveness of the military readiness activity.
    In addition to the measures described later in this section, the 
Navy will employ the following standard mitigation measures:
     The Navy must employ Protected Species Observers (PSOs), 
establish monitoring locations, and monitor the project area to the 
maximum extent possible based on the required number of PSOs, required 
monitoring locations, and environmental conditions;
     Monitoring must take place from 30 minutes prior to 
initiation of construction activities through 30 minutes post-
completion of construction activities;
     The Navy must conduct a briefing between construction 
supervisors and crews and the marine mammal monitoring team prior to 
the start of construction, and when new personnel join the work, to 
explain responsibilities, communication procedures, marine mammal 
monitoring protocol, and operational procedures;
     For in-water and over-water heavy machinery work, if a 
marine mammal comes within 10 m, operations shall cease and vessels 
shall reduce speed to the minimum level required to maintain steerage 
and safe working conditions;
     With the exception of pre-dawn drilling, work may only 
occur during daylight hours, when visual monitoring of marine mammals 
can be conducted;
     For those marine mammals for which take has not been 
requested, pile removal, drilling, and blasting will shut down 
immediately when the animals are sighted approaching the harassment 
zones;
     If take reaches the authorized limit for an authorized 
species, activity for which take is authorized will be stopped as these 
species approach the Level B harassment zone to avoid additional take;
     Blasting would not begin until at least one sheet pile 
face of the west closure wall has been installed; and
     A bubble curtain would be installed across the DD1 
entrance openings to mitigate underwater noise impacts outside of the 
basin during pre-dawn drilling of blast-charge holes, and blasting 
events.
    The following measures would apply to the Navy's mitigation 
requirements:
    Monitoring Harassment Zones--Before the commencement of in-water 
construction activities (i.e., impact pile driving, vibratory pile 
driving and pile removal, drilling, and blasting), harassment zones 
must be established for purposes of monitoring. Monitoring zones enable 
observers to be aware of and communicate the presence of marine mammals 
in the project area outside of the shutdown zone (see below) and thus 
prepare for a potential cease of activity should the animal enter the 
shutdown zone. All Level B harassment monitoring zones for the proposed 
activities are equivalent to the maximum ensonified zone, adjusted for 
landmass interception, or 0.418 km\2\ (0.16 square miles). Similarly, 
harassment monitoring zones must be established for the PTS isopleths 
associated with each functional hearing group.
    Shutdown Zones--The Navy will implement shutdown zones for all pile 
driving and extraction, drilling, and blasting activities. The purpose 
of a shutdown is to prevent some undesirable outcome, such as auditory 
injury or severe behavioral disturbance of sensitive species, by 
halting the activity. If a marine mammal is observed entering or within 
the respective shutdown zone (Table 12) after a construction activity 
has begun, the PSO will request a temporary cessation of the 
construction activity. On days when multiple activities are occurring 
concurrently, the largest shutdown zone between/among the activities 
will be implemented. The shutdown zone for blasting would be the entire 
region of influence (ROI), equivalent to the maximum ensonified zone 
adjusted for landmass interception (0.418 km\2\). If shutdown zones are 
obscured by fog or poor lighting conditions, pile-driving and blasting 
will not be initiated until the entire shutdown zones are visible.
    Although drilling activities may occur during pre-dawn hours in 
order to maintain the project schedule, the shutdown distance for 
drilling is small (10 m) and will likely be entirely visible for 
monitoring despite visibility limitations during this timeframe. As 
mentioned previously, drilling will not occur between sunset and pre-
dawn hours.
    Shutdown zones typically vary based on the activity type and marine 
mammal hearing group. A summary of the shutdown zones is provided in 
Table 12.

[[Page 18265]]



 Table 12--Shutdown Zones Distances for Various Pile Driving Activities
                    and Marine Mammal Hearing Groups
------------------------------------------------------------------------
                                                Shutdown distance  (m)
      Pile type, size & driving method       ---------------------------
                                               HF cetacean     Phocid
------------------------------------------------------------------------
Vibratory drive 30-inch steel pipe piles....            70            30
Vibratory extraction 30-inch steel pipe                 70            30
 piles......................................
Impact drive 28-inch steel sheet piles......           110            50
Vibratory drive 28-inch steel sheet piles...            25            10
Impact drive 18-inch sheet piles............           110            50
Vibratory drive 18-inch sheet piles.........            15            10
Drilling 4.5-inch blast charge holes........            10            10
Blasting 120 lb. charge.....................    Entire ROI    Entire ROI
                                                       \1\
------------------------------------------------------------------------
\1\ Region of influence (ROI) is the maximum ensonified area (0.418
  km\2\).

    Pre-start Clearance Monitoring--Prior to the start of daily in-
water construction activity, or whenever a break in pile driving/
removal or drilling of 30 minutes or longer occurs, PSOs will observe 
the shutdown zones for a period of 30 minutes. The shutdown zone will 
be considered cleared when a marine mammal has not been observed within 
the zone for that 30-minute period. If a marine mammal is observed 
within the shutdown zone, no construction activity, including soft-
start (see below), can proceed until the animal has voluntarily left 
the zone or has not been observed for 15 minutes. When a marine mammal 
for which Level B harassment take is authorized is present in the Level 
B harassment zone, activities may begin. If the entire Level B 
harassment zone is not visible at the start of construction, pile 
driving activities can begin. If work ceases for more than 30 minutes, 
the pre-activity monitoring of the shutdown zones will commence.
    Soft Start--The use of a soft start procedure is believed to 
provide additional protection to marine mammals by warning marine 
mammals or providing them with a chance to leave the area prior to the 
hammer operating at full capacity, and typically involves a requirement 
to initiate sound from the hammer at reduced energy followed by a 
waiting period. The Navy will provide an initial set of strikes from 
the impact hammer at reduced energy, followed by a 30 second waiting 
period, and then two subsequent sets. NMFS notes that it is difficult 
to specify the reduction in energy for any given hammer because of 
variation across drivers and, for impact hammers, the actual number of 
strikes at reduced energy will vary because operating the hammer at 
less than full power results in ``bouncing'' of the hammer as it 
strikes the pile, resulting in multiple ``strikes''. 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 required measures, NMFS has 
preliminarily determined that the prescribed mitigation measures 
provide the means 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.

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 in the 
proposed action area. 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 action; 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.

Proposed Monitoring Measures

    The Navy shall employ trained PSOs to conduct marine mammal 
monitoring for its PNSY modification and expansion project. The 
purposes of marine mammal monitoring are to implement mitigation 
measures and learn more about impacts to marine mammals from the Navy's 
construction activities.
Protected Species Observer Qualifications
    NMFS-approved PSOs shall meet the following requirements:
    1. Independent observers (i.e., not construction personnel) are 
required;
    2. At least one observer must have prior experience working as an 
observer;
    3. Other observers may substitute education (undergraduate degree 
in biological science or related field) or training for experience;
    4. Where a team of three or more observers are required, one 
observer should be designated as lead observer or monitoring 
coordinator. The lead

[[Page 18266]]

observer must have prior experience working as an observer; and
    5. NMFS will require submission and approval of observer curricula 
vitae.
Marine Mammal Monitoring Protocols
    The Navy will monitor all Level A harassment zones and Level B 
harassment zones before, during, and after pile driving activities. The 
Marine Mammal Monitoring Plan would include the following procedures:
     At least two (3) PSOs shall be posted to monitor marine 
mammals during in-water pile driving and pile removal, blasting, and 
drilling;
     PSOs will be primarily located at the best vantage 
point(s) in order to properly see the entire shutdown zone(s) and zones 
associated with behavioral impact thresholds;
     PSOs must record all observations of marine mammals, 
regardless of distance from the construction activity;
     During all observation periods, PSOs will use high-
magnification (25X), as well as standard handheld (7X) binoculars, and 
the naked eye to search continuously for marine mammals;
     Monitoring distances will be measured with range finders. 
Distances to animals will be based on the best estimate of the PSO, 
relative to known distances to objects in the vicinity of the PSO;
     Pile driving, drilling, and blasting will only take place 
when the shutdown zones are visible and can be adequately monitored. If 
conditions (e.g., fog) prevent the visual detection of marine mammals, 
activities with the potential to result in Level A harassment shall not 
be initiated. If such conditions arise after the activity has begun, 
blasting and impact pile driving would be halted but drilling and 
vibratory pile driving or extraction would be allowed to continue;
    Information Collection:
    PSOs shall collect the following information during marine mammal 
monitoring:
    [cir] PSO locations during monitoring
    [cir] Date and time that monitored activity begins and ends for 
each day conducted (monitoring period);
    [cir] Construction activities occurring during each daily 
observation period, including how many and what type of piles driven, 
number of blast holes drilled, and number or blast events;
    [cir] 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 
estimated observable distance;
    [cir] For each marine mammal sighting:
     Name of PSO who sighted the animal(s) and PSO location and 
activity at time of sighting;
     Time of sighting;
     Species, numbers, and, if possible, sex and age class of 
marine mammals;
     Description of any observable marine mammal behavior 
patterns, including bearing and direction of travel and distance from 
construction activity;
     Location, distance, and bearing from pile driving, 
drilling, and blasting activities to marine mammals and distance from 
the marine mammals to the observation point; and
     Animal's closet point of approach and estimated amount of 
time that the animals remained in the Level B harassment zone; and
     Detailed information about implementation of any 
mitigation (e.g., shutdowns or delays), a description of specific 
actions that ensued, and resulting changes in behavior of the 
animal(s), if any.
Hydroacoustic Monitoring
    The Navy must conduct hydroacoustic monitoring of in-water 
construction activities, including the installation of (10) Z-shaped 
sheet piles for both impact and vibratory pile driving, (4) steel piles 
for vibratory pile driving, (10) blasting event, and (10) blast-charge 
hole drilling events.

Reporting Measures

    The Navy is required to submit a draft monitoring report (including 
all PSO data sheets and/or raw sighting data) within 90 days after 
completion of the construction work or the expiration of the IHA (if 
issued), whichever comes earlier. If Navy intends to request a renewal 
of the IHA (if issued) in a subsequent year, a monitoring report should 
be submitted no less than 60 days before the expiration of the current 
IHA (if issued). This report would detail the monitoring protocol, 
summarize the data recorded during monitoring, and estimate the number 
of marine mammals that may have been harassed. The acoustic monitoring 
report must contain the informational elements described in the 
hydroacoustic monitoring plan. NMFS would have an opportunity to 
provide comments on the report, and if NMFS has comments, The Navy 
would address the comments and submit a final report to NMFS within 30 
days.
    In addition, NMFS would require the Navy to notify NMFS' Office of 
Protected Resources and NMFS' Greater Atlantic Stranding Coordinator 
within 48 hours of sighting an injured or dead marine mammal in the 
construction site. The Navy shall provide NMFS and the Stranding 
Network with the species or description of the animal(s), the condition 
of the animal(s) (including carcass condition, if the animal is dead), 
location, time of first discovery, observed behaviors (if alive), and 
photo or video (if available).
    In the event that the Navy finds an injured or dead marine mammal 
that is not in the construction area, the Navy would report the same 
information as listed above to NMFS as soon as operationally feasible.

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 responses (e.g., intensity, duration), the context 
of any responses (e.g., critical reproductive time or location, 
migration), as well as effects on habitat, and the likely effectiveness 
of the mitigation. NMFS also assesses the number, intensity, and 
context of estimated takes by evaluating this information relative to 
population status. Consistent with the 1989 preamble for NMFS's 
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 environmental 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).
    Pile driving, drilling, and blasting activities associated with the 
proposed project, as described previously, have the potential to 
disturb or temporarily displace marine mammals. The specified 
activities may result in take, in the form of Level A harassment 
(potential injury; from impact pile driving or blasting) or Level B 
harassment (potential behavioral disturbance or TTS) from underwater 
sounds generated from pile driving

[[Page 18267]]

(impact and vibratory), drilling and blasting. Potential takes could 
occur if individual marine mammals are present in the ensonified zone 
when pile driving, drilling, or blasting activities are occurring.
    To avoid repetition, this introductory discussion of our analysis 
applies to all of the species listed in Table 2, given that the 
anticipated effects of the Navy's PNSY modification and expansion 
construction project activities on marine mammals are expected to be 
relatively similar in nature. There is no information about the nature 
or severity of the impacts, or the size, status, or structure of any 
species or stock that would lead to a different analysis by species for 
this activity, or else species-specific factors would be identified and 
analyzed.
    Although some individual harbor porpoises and harbor and gray seals 
are estimated to experience Level A harassment in the form of PTS if 
they remain within the impact pile driving Level A harassment zone for 
an entire day, or are present within the Level A harassment zone during 
a blasting event, the degree of injury is expected to be mild and is 
not likely to affect the reproduction or survival of the individual 
animals. It is expected that, if hearing impairments occurs as a result 
of impact pile driving or blasting, most likely the affected animal 
would lose a few dB in its hearing sensitivity, which in most cases is 
not likely to affect its survival and recruitment. Hearing impairment 
that might occur for these individual animals would be limited to the 
dominant frequency of the noise sources, i.e., in the low-frequency 
region below 2 kHz. Nevertheless, as for all marine mammal species, it 
is anticipated that, in general, these pinnipeds will avoid areas where 
sound levels could cause hearing impairment. Therefore it is not likely 
that an animal would stay in an area with intense noise that could 
cause severe levels of hearing damage.
    Under the majority of the circumstances, anticipated takes are 
expected to be limited to short-term Level B behavioral harassment or 
TTS. Marine mammals present in the vicinity of the action area and 
taken by Level B harassment would most likely show overt brief 
disturbance (startle reaction) from blasting events and avoidance of 
the area impacted by elevated noise levels during pile driving (and 
removal). Given the limited estimated number of predicted incidents of 
Level A harassment and Level B harassment and the limited, short-term 
nature of the responses by the individuals, the impacts of the 
estimated take cannot be reasonably expected to, and are not reasonably 
likely to, rise to the level that they would adversely affect the 
species considered here at the population level, through effects on 
annual rates of recruitment or survival. There are no known important 
habitats, such as rookeries or haulouts, in the vicinity of the Navy's 
proposed PNSY DD1 modification and expansion construction project. The 
project also is not expected to have significant adverse effects on 
affected marine mammals' habitat, including prey, as analyzed in detail 
in the Potential Effects of Specified Activities on Marine Mammals and 
their Habitat section.
    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 the species or stock 
through effects on annual rates of recruitment or survival:
     No mortality is anticipated or authorized;
     Some individual marine mammals might experience a mild 
level of PTS, but the degree of PTS is not expected to affect their 
survival;
     Most adverse effects to marine mammals are likely to be 
temporary behavioral harassment or TTS; and
     No biologically important area is present in or near the 
proposed construction area.
    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 above, only small numbers of incidental take may be 
authorized under section 101(a)(5)(A) and (D) of the MMPA for specified 
activities other than military readiness activities. The MMPA does not 
define small numbers and so, in practice, 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 less 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.
    NMFS proposes to authorize incidental take of 5 marine mammal 
stocks. The total amount of taking proposed for authorization is three 
percent or less for all five of these stocks, (Table 11).
    Based on the analysis contained herein of the proposed activity 
(including the prescribed mitigation and monitoring measures) and the 
anticipated take of marine mammals, NMFS preliminarily finds that small 
numbers of marine mammals will 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 (ESA)

    No incidental take of ESA-listed species is proposed for 
authorization or expected to result from this activity. Therefore, NMFS 
has determined that formal consultation under section 7 of the ESA is 
not required for this action.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to the Navy for the taking of marine mammals incidental to 
modification and expansion of the Portsmouth Naval Shipyard Dry Dock 1 
in Kittery, Maine, effective for one year from the date of issuance, 
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/permit/incidental-take-authorizations-under-marine-mammal-protection-act.

Request for Public Comments

    NMFS requests comment on these analyses, the proposed 
authorization, and any other aspect of this Notice of Proposed IHA for 
the proposed issuance of an IHA to the Navy for the taking of marine 
mammals incidental to modification and expansion of the Portsmouth 
Naval Shipyard Dry Dock 1 in Kittery, Maine, effective for one year 
from the date of issuance. NMFS also requests comment on the potential 
for a renewal of this proposed IHA as described in the paragraph below.

[[Page 18268]]

Please include with your comments any supporting data or literature 
citations to help inform NMFS' final decision on the request for MMPA 
authorization.
    On a case-by-case basis, NMFS may issue a one-time, 1-year IHA 
renewal with an expedited public comment period (15 days) when: (1) 
Another year of identical or nearly identical activities as described 
in the Specified Activities section is planned or (2) the activities 
would not be completed by the time the IHA expires and a second IHA 
would allow for completion of the activities beyond that described in 
the Dates and Duration section, provided all of the following 
conditions are met:
     A request for renewal is received no later than 60 days 
prior to expiration of the current IHA;
     The request for renewal must include the following:
    (1) An explanation that the activities to be conducted under the 
proposed renewal 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 
because only a subset of the initially analyzed activities remain to be 
completed under the renewal); and
    (2) A preliminary monitoring report showing the results of the 
required impacts of a scale or nature not previously analyzed or 
authorized;
     Upon review of the request for renewal, the status of the 
affected species or stocks, and any other pertinent information, NMFS 
determines that there are no more than minor changes in the activities, 
the mitigation and monitoring measures will remain the same and 
appropriate, and the findings in the initial IHA remain valid.

    Dated: March 29, 2021.
Donna S. Wieting,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2021-06782 Filed 4-7-21; 8:45 am]
BILLING CODE 3510-22-P