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Notice2022-04406

Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to U.S. Navy Construction of the Multifunctional Expansion of Dry Dock 1 at Portsmouth Naval Shipyard, Kittery, Maine

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Published

March 2, 2022

Issuing agencies

Commerce DepartmentNational Oceanic and Atmospheric Administration

Abstract

NMFS has received a request from the U.S. Navy (Navy) for authorization to take marine mammals incidental to construction activities associated with the multifunctional expansion of Dry Dock 1 at Portsmouth Naval Shipyard 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 will consider public comments prior to making any final decision on the issuance of the requested MMPA authorization and agency responses will be summarized in the final notice of our decision.

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[Federal Register Volume 87, Number 41 (Wednesday, March 2, 2022)]
[Notices]
[Pages 11860-11889]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2022-04406]

[[Page 11859]]

Vol. 87

Wednesday,

No. 41

March 2, 2022

Part II

Department of Commerce

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National Oceanic and Atmospheric Administration

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Takes of Marine Mammals Incidental to Specified Activities; Taking
Marine Mammals Incidental to U.S. Navy Construction of the
Multifunctional Expansion of Dry Dock 1 at Portsmouth Naval Shipyard,
Kittery, Maine; Notice

Federal Register / Vol. 87 , No. 41 / Wednesday, March 2, 2022 /
Notices

[[Page 11860]]

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XB652]

Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to U.S. Navy Construction of the
Multifunctional Expansion of Dry Dock 1 at Portsmouth Naval Shipyard,
Kittery, Maine

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.

ACTION: Notice; proposed incidental harassment authorization request
for comments.

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SUMMARY: NMFS has received a request from the U.S. Navy (Navy) for
authorization to take marine mammals incidental to construction
activities associated with the multifunctional expansion of Dry Dock 1
at Portsmouth Naval Shipyard 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
will consider public comments prior to making any final decision on the
issuance of the requested MMPA authorization and agency responses will
be summarized in the final notice of our decision.

DATES: Comments and information must be received no later than March
31, 2022.

ADDRESSES: Comments should be addressed to Jolie Harrison, Chief,
Permits and Conservation Division, Office of Protected Resources,
National Marine Fisheries Service. Written comments should be submitted
via email to <a href="/cdn-cgi/l/email-protection#347d60641a7153535146745a5b55551a535b42">[email&#160;protected]</a>.
Instructions: NMFS is not responsible for comments sent by any
other method, to any other address or individual, or received after the
end of the comment period. Comments, including all attachments, must
not exceed a 25-megabyte file size. All comments received are a part of
the public record and will generally be posted online at
<a href="http://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act">www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act</a> without change. All personal identifying
information (e.g., name, address) voluntarily submitted by the
commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.

FOR FURTHER INFORMATION CONTACT: Stephanie Egger, Office of Protected
Resources, NMFS, (301) 427-8401. Electronic copies of the application
and supporting documents, as well as a list of the references cited in
this document, may be obtained online at: <a href="https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act">https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act</a>. 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 September 2, 2021, NMFS received a request from the Navy for an
IHA to take marine mammals incidental to construction activities
associated with the multifunctional expansion of Dry Dock 1 project
(also referred to as P-831) at Portsmouth Naval Shipyard in Kittery,
Maine. The Navy submitted a revised version of the application on
December 21, 2021. The application was deemed adequate and complete on
February 10, 2022. The Navy's request is for take of harbor porpoises,
harbor seals, gray seals, harp seals, and hooded seals by Level A
harassment and Level B harassment. Neither the Navy nor NMFS expects
serious injury or mortality to result from this activity; therefore, an
IHA is appropriate.
NMFS previously issued IHAs and renewals to the Navy for waterfront
improvement work in Portsmouth, in 2017 (81 FR 85525; November 28,
2016), 2018 (83 FR 3318; January 24, 2018), 2019 (84 FR 24476, May 28,
2019), a renewal of the 2019 IHA (86 FR 14598; March 17, 2021), and a
2021 IHA (86 FR 30418; June 8, 2021) As required, the applicant
provided monitoring reports (available at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>) 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 would cover 1 year of a larger project for which
the Navy intends to request a take authorization for subsequent facets
of the project. The larger overall expansion

[[Page 11861]]

and modification of Dry Dock 1 project involves modification of the
super flood basin to create two additional dry docking positions (Dry
Dock 1 North and Dry Dock 1 West) in front of the existing Dry Dock 1
East. Year 1 construction activities will focus on the preparation of
the walls and floors of the super flood basin to support the placement
of the monoliths and the construction of the two dry dock positions.
The Navy complied with all the requirements (e.g., mitigation,
monitoring, and reporting) of the previous IHAs they provided for other
preparatory work related to the Dry Dock 1 project and information
regarding their monitoring results may be found in the Estimated Take
section.

Description of Proposed Activity

Overview

Multifunctional Expansion of Dry Dock 1 (P-381) is one of three
projects that support the overall expansion and modification of Dry
Dock 1, located in the western extent of the shipyard. The previous two
projects, construction of a super flood basin (P-310) and extension of
portal crane rail and utilities (P-1074) are currently under
construction. Work associated with P-310 and P-1074 has been and/or is
being completed under the separate IHAs issued by NMFS. The projects
have been phased to support Navy mission schedules. P-381 will be
constructed within the same footprint of the super flood basin over an
approximated 7-year period. In-water activities are expected to occur
within the first 5 years, between April 2022 and April 2027. This IHA
request is for the first year of in-water construction for P-381
occurring from April 2022 through April 2023. All work beyond year 1 is
anticipated to be requested in a rulemaking/Letter of Authorization
(LOA) application submission to NMFS.
The purpose of the proposed project, Multifunctional Expansion of
Dry Dock 1 (P-381), is to modify the super flood basin to create two
additional dry docking positions (Dry Dock 1 North and Dry Dock 1 West)
in front of the existing Dry Dock 1 East. The super flood basin
provides the starting point for the P-381 work (see Figure 1-2 of the
application).
Year 1 construction activities will focus on the preparation of the
walls and floors of the super flood basin to support the placement of
the monoliths and the construction of the two dry dock positions. The
primary work needed to prepare the super flood basin involves
structural reinforcement of the existing berths and floor within the
super flood basin, bedrock removal, and demolition of portions of the
super flood basin walls. Most of the preparatory work will occur behind
the existing super flood basin walls that would act as a barrier to
sound and would contain underwater noise to within a small portion of
the Piscataqua River (see Figure 1-3 of the application). Construction
activities that could affect marine mammals are limited to in-water
pile driving and removal activities, rock hammering, rotary drilling,
and down-the-hole (DTH) hammering.

Dates and Duration

The construction activities are anticipated to begin in March 2022
and proceed to March 2023. In-water construction activities would occur
for 365 days over a period of approximately 12 consecutive months. All
in-water work capable of producing noise harmful to marine mammals will
be limited to daylight hours. Pile driving days are not necessarily
consecutive and certain activities may occur at the same time,
decreasing the total number of in-water construction days. The
contractor could be working in more than one area of the berths at a
time. It is not possible to predict if and/or how often work will occur
simultaneously, but it is estimated that overlapping activities would
permit the work described in Table 1 to be completed within one
calendar year. Table 1 provides the estimated construction schedule and
production rates for P-381 Year 1 construction activities. Table 1
reflects the current pile driving, hammering, and drilling durations
for activities occurring in Year 1 included in this request for
incidental take authorization. Vibratory pile driving and extraction is
assumed to occur during 84 days of Year 1. Impact pile driving will
occur during 24 days in Year 1. DTH activities would occur for 919 days
and rotary drilling would occur for 282 days. Rock hammering would
occur for 252 days. Overlapping activities are estimated to reduce the
number of construction days by 1,172 days for a total of 365
construction days.

Table 1--Pile Driving and Drilling Durations
[March 2022-March 2023]
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Total
Activity Total amount and Activity component Method Daily production rate production
estimated dates days
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Center Wall--Install Foundation 38 drilled shafts, Mar- Install 102-inch Rotary Drill............... 1 shaft/day, 1 hour/day... 38
Support Piles. 22 to Mar-23. diameter outer casing.
Pre-drill 102-inch Rotary Drill............... 1 shaft/day, 9 hours/day.. 38
diameter socket.
Remove 102-inch outer Rotary Drill............... 1 casing/day, 15 minutes/ 38
casing. casing.
Drill 78-inch diameter Cluster drill DTH.......... 6.5 days/shaft, 10 hours/ 247
shaft. day.
Center Wall--Install Diving Board 18 drilled shafts, Mar- Install 102-inch Rotary Drill............... 1 shaft/day, 1 hour/day... 18
Shafts. 22 to Mar-23. diameter outer casing.
Pre-drill 102-inch Rotary Drill............... 1 shaft/day, 9 hours/day.. 18
diameter socket.
Remove 102-inch outer Rotary Drill............... 1 casing/day, 15 minutes/ 18
casing. casing.
Drill 78-inch diameter Cluster drill DTH.......... 6.5 days/shaft, 10 hours/ 117
shaft. day.
Center Wall--Access Platform 38 drilled shafts, Mar- Install 102-inch Rotary Drill............... 1 shaft/day, 1 hour/day... 38
Support. 22 to Mar-23. diameter outer casing.
Pre-drill 102-inch Rotary Drill............... 1 shaft/day, 9 hours/day.. 38
diameter socket.
Remove 102-inch outer Rotary Drill............... 1 casing/day, 15 minutes/ 38
casing. casing.
Drill 78-inch diameter Cluster drill DTH.......... 3.5 days/shaft, 10 hours/ 133
shaft. day.
Center Wall--Temporary Launching 6 drilled shafts, Mar- 42-inch diameter shaft Mono-hammer DTH............ 1 shaft/day, 10 hours/day. 6
Piles. 22 to Apr-22.

[[Page 11862]]

Center Wall Tie Downs.............. Install 36 rock 9-inch diameter holes. Mono-hammer DTH............ 2 holes/day, 5 hours/hole. 18
anchors, Mar-22 to
Mar-23.
Center Wall--Access Platform Tie Install 18 rock 9-inch diameter holes. Mono-hammer DTH............ 2 holes/day, 5 hours/hole. 9
Downs. anchors, Mar-22 to
Mar-23.
Center Wall--Install Tie-In to 16 sheet piles, Mar-22 28-inch wide Z-shaped Impact with initial 4 piles/day, 5 minutes and * 4
Existing West Closure Wall. to Mar-23\+\. sheets. vibratory set. 300 blows/pile.
Berth 11 End Wall--Install Secant 60 sheet piles, Feb-22 28-inch wide Z-shaped Impact with initial 8 piles/day, 5 minutes and 8
Pile Guide Wall. to Mar-23. sheets. vibratory set. 300 blows/pile.
Berth 1--Remove Granite Block Quay 610 cy, May-22 to Mar- Granite block Hydraulic rock hammering... 2.5 hours/day............. * 10
Wall. 23\+\. demolition.
P-310 West Closure Wall--Remove 238 sheet piles, Aug- 18-inch wide flat- Vibratory extraction....... 4 piles/day, 5 minutes/ 60
Closure Wall. 22 to Oct-22. sheets. pile.
P-310 West Closure Wall--Mechanical 985 cy, Nov-22 to Feb- Excavate bedrock...... Hydraulic rock hammering... 9 hours/day............... 77
Rock Excavation. 23.
P-310 West Closure Wall--Mechanical Drill 500 relief 4-6 inch holes........ Mono-hammer DTH............ 25 holes/day, 24 minutes/ 20
Rock Excavation. holes, Nov-22 to Feb- hole.
23.
Drill 46 rock borings 42-inch diameter Mono-hammer DTH............ 2 borings/day, 5 hours/ \1\ 24
(50 cy), May-22 to casing. boring.
Jun-22.
West closure wall--Berth 11 Drill 28 shafts, Aug- 42-inch diameter Mono-hammer DTH............ 1 shaft/day, 10 hours/day. 28
Abutment--Install Piles. 22 to Mar-23. casing.
Berth 11--Remove Shutter Panels.... 112 panels, Oct-22 to Demolish shutter Hydraulic rock hammering... 5 hours/day............... * 56
Mar-23\+\. panels.
Berth 11 Face--Mechanical Rock 3,500 cy, Oct-22 to Excavate Bedrock...... Hydraulic rock hammering... 12 hours/day.............. * 100
Removal at Basin Floor. Mar-23\+\.
Drill 2,201 relief 4-6 inch holes........ Mono-hammer DTH............ 27 holes/day, 22.2 minutes/ * 82
holes, Oct-22 to Mar- hole.
23\+\.
Berth 11 Face--Mechanical Rock at Drill 365 rock borings 42-inch diameter Mono-hammer DTH............ 2 borings/day, 5 hours/ 183
Abutment. (1,220 cy), Jul-22 to casing. boring.
Jan-23.
Dry Dock 1 North Entrance--Drill Drill 100 rock 9-inch holes.......... Mono-hammer DTH............ 2 holes/day, 2 hours/hole. \1\ 52
Tremie Tie Downs. anchors, Jan-23 to
Mar-23.
Dry Dock 1 North Entrance--Install Install 96 sheet 28-inch wide Z-shaped Impact with initial 8 sheets/day, 5 minutes 12
Temporary Cofferdam. piles, Dec-22 to Mar- sheets. vibratory set. and 300 blows/pile.
23.
Berth 1--Remove Sheet Piles........ Remove 12 sheet piles, 25-inch wide Z-shaped Hydraulic rock hammering... 6 hours/day............... * 3
Mar-23 \+\. sheets.
Berth 1 Top of Wall--Demolition For 30 lf\+\, Mar-23 \+\.. Mechanical concrete Hydraulic rock hammering... 10 hours/day.............. * 6
Waler Installation. demolition.
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Totals......................... 539 shafts/borings, ...................... ........................... .......................... 1,537
2,855 holes/
anchors,422 sheet
piles.
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\+\ These activities may continue into subsequent construction years pursuant to a proposed authorization.
* These activities will begin in year 1 of this IHA request and may continue into following construction years pursuant to a proposed authorization.
Only the number of production days occurring in year 1 are presented.

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 Eliot, Maine (see Figure 1 below). The river flows in a
southeasterly direction for 2,093 meters (m) (13 miles (mi)) 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 activities, is
located in the lower Piscataqua River approximately 500 m from its
southwest bank, 200 m from its north bank, and approximately 4,000 m
(2.5 mi) from the mouth of the river.
Water depths in the proposed project area range from 6.4 m (21 feet
(ft) to 11.9 m (39 ft) at Berths 11, 12, and 13. Water depths in the
lower Piscataqua River near the proposed project area range from 15 ft
in the shallowest areas to 69 ft in the deepest areas. The river is
approximately 914 m (3,300 ft) 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 1,287 m (0.8 mi) to the
southeast and 418 m (0.26 mi) to the northwest.
Much of the shoreline in the proposed project area is composed of
hard shores (rocky intertidal). In general, rocky intertidal areas
consist of bedrock that alternates between marine and terrestrial
habitats, depending on the tide (Department of the Navy 2013). Rocky
intertidal areas consist of ``bedrock, stones, or boulders that singly
or in combination cover 75 percent or more of an area that is covered
less than 30 percent by vegetation'' (Navy 2013).
The lower Piscataqua River is home to Portsmouth Harbor and is used
by commercial, recreational, and military vessels. Between 150 and 250
commercial shipping vessels transit the lower Piscataqua River each
year (Magnusson et al. June 2012). Commercial fishing vessels are also
very common in the river year-round, as are recreational vessels, which
are more common in the warmer summer months. The shipyard is a dynamic
industrial facility situated on an island with a narrow separation of
waterways between the installation and the communities of Kittery and
Portsmouth (see Figure 2). The predominant noise sources from Shipyard
industrial operations consist of dry dock cranes; passing vessels; and
industrial equipment (e.g., forklifts, loaders, rigs, vacuums, fans,
dust collectors, blower

[[Page 11863]]

belts, heating, air conditioning, and ventilation (HVAC) units, water
pumps, and exhaust tubes and lids). Other components such as
construction, vessel ground support equipment for maintenance purposes,
vessel traffic across the Piscataqua River, and vehicle traffic on the
shipyard's bridges and on local roads in Kittery and Portsmouth produce
noise, but such noise generally represents a transitory contribution to
the average noise level environment (Blue Ridge Research and Consulting
(BRRC) 2015; ESS Group 2015). Ambient sound levels recorded at the
shipyard are considered typical of a large outdoor industrial facility
and vary widely in space and time (ESS Group 2015).
BILLING CODE 3510-22-P

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[GRAPHIC] [TIFF OMITTED] TN02MR22.048

[[Page 11865]]

[GRAPHIC] [TIFF OMITTED] TN02MR22.049

BILLING CODE 3510-22-C

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Detailed Description of Specific Activity

Preparatory work for P-381 in Year 1 as proposed for this IHA can
be generally grouped into four categories: center wall support and tie-
in, structural reinforcement of super flood basin sidewalls and
entrance, mechanical bedrock removal, and demolition of super flood
basin wall components. Each category involves one or more activities
expected to result in harassment of marine mammals.
Center wall support and tie-in--The location of the future center
wall requires reinforcement to allow placement of the large pre-cast
monolith structures forming the separation between the two new dry
docking positions. Specifically, the floor of the existing basin must
be able to provide an adequate foundation for the pre-cast monoliths
that will make up the dry dock interiors and center wall. The basin
floor will be reinforced by 38, 84-inch (in) diameter shafts throughout
the footprint of the center wall that will be filled with concrete to
create the structural support piles for the center wall. The shafts
will be installed using a cluster drill consisting of multiple down-
the-hole (DTH) hammers.
Preparations for the center wall also require the installation of a
relatively short length of sheet pile wall to create a connection
between the existing west closure wall and the center wall. In
construction year 1, 16, 28-in wide, Z-shaped sheet piles would be
installed for the tie-in on the westerly end of the center wall
footprint where it will connect to the west closure wall structure. The
sheet piles will be installed using an initial vibratory set followed
by driving with impact hammers. The remaining sheet piles will be
proposed for installation in the following construction years and
described in the subsequent rulemaking/LOA application.
Structural reinforcement of super flood basin sidewalls and
entrance--The existing super flood basin walls must be reinforced to
allow adjacent bedrock removal and to provide support for the future
dry dock walls. Bedrock removal is required to establish the deeper
floor elevations needed for the project. The existing walls must be
reinforced to prevent undermining during rock removal which could cause
the walls to collapse.
Wall reinforcement activities will include the installation of a
sheet pile guide wall along the Berth 11 end wall. The guide wall will
support the installation of an adjacent secant pile structural support
wall that will be installed landside. In construction year 1, 24, 28-
in, Z-shaped sheet piles will be installed for the guide wall. The
guide wall sheet piles will be placed using an initial vibratory set
followed by driving with impact hammers. The remaining guide wall sheet
piles will be proposed for installation in the following construction
years and described in the subsequent rulemaking/LOA application.
The conversion of the existing west closure wall to the Dry Dock 1
North entrance requires reinforcement of the section of the west
closure wall that will become the new dry dock entrance. The existing
structure will be reinforced by drilling shafts through its interior
into the underlying bedrock. The shafts will be filled with concrete to
create structural piles. This activity will not occur in the water and
will not create underwater noise impacts. The structure will then be
surrounded by a temporary cofferdam. In construction Year 1, the
cofferdam base will be constructed with 24, 28-in wide, Z-shaped sheet
piles. The sheet piles will be installed using an initial vibratory set
followed by driving with impact hammers. The remainder of cofferdam
construction will be proposed in the following construction years and
described in the subsequent rulemaking/LOA application.
Additional preparatory work in the west closure wall area involves
the installation of support tie downs for future tremie concrete work.
The tie downs require the placement of an estimated 51 rock anchors
requiring 9-in diameter holes. The rock anchors will be installed using
a rotary drill.
Along the northern section of the west closure wall, at its
junction with Berth 11, reinforcement piles will be installed to
strengthen the abutment area. The reinforcement piles will be
constructed by drilling 28, 42-in diameter shafts that will be filled
with concrete to create a pile wall. The shafts will be constructed
using a DTH cluster drill.
Mechanical bedrock removal--Bedrock will be mechanically excavated
using various methods appropriate for the removal location and as
needed to avoid damage to adjacent structures. Bedrock removal is
required in several locations throughout the basin area. Three methods
of rock removal will be employed that may result in injury or
harassment of marine mammals:

[ssquf] Bedrock excavation with a hydraulic rock hammer (i.e., hoe ram
or breaker)
[ssquf] Installation of relief holes (4- to 6-in diameter) using a DTH
drill
[ssquf] Removal of rock using DTH drilling with 36-in cluster drill

Two primary areas of mechanical rock removal are scheduled for Year
1 of the project: The west closure wall footprint and the Berth 11
face. Both sites require the use of the three methods presented in the
bulleted list above.
Preparation of the west closure wall area requires the removal of
bedrock with a hydraulic hammer along with the DTH drilling 500, 4-6 in
diameter relief holes and the drilling of 19 rock borings with a 36-in
diameter DTH cluster drill. Approximately 905 cubic yards (cy) of
bedrock are anticipated to be removed from the west closure wall area.
Bedrock removal is also required along the Berth 11 face. Again,
the rock will be removed with a hydraulic hammer: By drilling 351, 4-6-
in diameter relief holes plus drilling 8 rock borings with 36-in
diameter DTH cluster drill. Approximately 415 cy of bedrock are
anticipated to be removed during construction Year 1. The remaining
bedrock will be proposed for removal in the following construction
years and described in the rulemaking/subsequent LOA application.
Demolition of super flood basin wall components--Demolition of
existing wall structures includes the removal of shutter panels,
granite quay walls, sheet piles, and concrete making up the super flood
basin. Demolition of existing wall structures would largely be
conducted using a rock hammer but some features would be removed by
torch cutting. Torch cutting would not generate noise that would be
harmful to marine mammals and therefore not discussed further.
Portions of the basin west closure wall will be demolished by
extracting the sheet piles with a vibratory hammer. 238, 18-in wide,
flat sheet piles will be removed.
Sections of the existing concrete shutter panels making up the face
of Berth 11 will be removed with a hydraulic rock hammer.
Approximately112 panels would be removed in construction Year 1. The
remaining shutter panels will be proposed for removal in the following
construction years and described in the rulemaking/subsequent LOA that
application.
Berth 1 demolition includes removal of the existing sheet pile wall
and portions of the underlying granite block quay wall. In construction
year 1, 12, 25-in wide, Z-shaped sheet piles and approximately 610 cy
of granite would be removed. The sheet piles and the granite block quay
wall will be removed with a hydraulic rock hammer with the remaining
sheet piles and granite blocks proposed for removal in the following
construction years and described in the subsequent rulemaking/LOA
application.

[[Page 11867]]

A section of Berth 1 requires the installation of a waler (steel
beam) for structural support. To accommodate the waler, about 9.144 m
(30 linear ft) of concrete wall will be removed using a hydraulic rock
hammer in construction Year 1 with the remaining concrete wall proposed
for removal in the following construction years and described in the
subsequent rulemaking/LOA application.

Overall Noise Producing Activities

Two types of piles will be installed or removed with pile driving
equipment during construction Year 1: 28-in wide, Z-shaped sheet piles
and 18-in wide, flat sheet piles. The installation of 28-in wide, Z-
shaped steel sheets would use a combination of vibratory and impact
hammers, whereas the removal of 18-in wide, flat sheet piles would use
only vibratory hammers.
Pile installation/removal would occur using barge mounted cranes
equipped with both vibratory and impact hammers. Piles would be
installed initially using vibratory means and then finished with impact
hammers, if necessary. Impact hammers would also be used to push
obstructions out of the way and where sediment conditions do not permit
the efficient use of vibratory hammers. To the extent practicable, it
is assumed that the piles installed for this project would be set with
a vibratory hammer and then finished with an impact hammer in order to
reach bearing depth or to have the required load-bearing capacity if
installed using vibratory methods only. Pile removal activities would
use vibratory hammers exclusively.
The removal of bedrock and the demolition of concrete shutter
panels and granite blocks during construction Year 1 would be by
mechanical means. These features would be demolished using a hydraulic
rock hammer or hoe ram (a portion of bedrock removal would also use DTH
mono hammers and cluster drilling).
Two methods of rock excavation would be used during construction
Year 1: rotary drill and DTH excavation. DTH excavation using mono-
hammers would be used for bedrock removal, to create shafts for support
piles and tie downs, and for the excavation of relief holes during
mechanical bedrock removal. For the largest shafts (greater than 42-in
in diameter) DTH excavation would use a cluster drill. A cluster drill
uses multiple mono-hammers within a single bit to efficiently break up
bedrock and create large diameter holes. Rotary drilling is considered
an intermittent, non-impulsive noise source, similar to vibratory pile-
driving.

Concurrent Activities

In order to maintain project schedules, it is likely that multiple
pieces of equipment would operate at the same time within the basin.
Given the spatial constraints of the project area, a maximum of five
pieces of equipment could potentially operate in the project area at a
single time. Table 2 provides a summary of possible equipment
combinations that could be used simultaneously over the course of the
construction year. An analysis of concurrent activities with respect to
noise generation from multiple sources is provided in the Estimated
Take section.

Table 2--Summary of Multiple Equipment Scenarios
------------------------------------------------------------------------
Quantity Equipment
------------------------------------------------------------------------
2............................... Rotary Drill (2).
2............................... Cluster Drill (1), Rotary Drill (1).
2............................... Cluster Drill (2).
3............................... Cluster Drill (2), Vibratory Hammer
(1).
5............................... Cluster Drill (2), Vibratory Hammer
(1), Mono-hammer DTH(1), Rotary Drill
(1).
4............................... Cluster Drill (1), Rock Hammering (1),
Mono-hammer DTH (1), Rotary Drill
(1).
2............................... Mono-hammer DTH (1), Rock Hammer (1).
3............................... Mono-hammer DTH (1), Rock Hammer (2).
------------------------------------------------------------------------
Source: 381 Constructors 2021.

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' Stock Assessment Reports (SARs; <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>) and more general information about these species
(e.g., physical and behavioral descriptions) may be found on NMFS'
website (<a href="https://www.fisheries.noaa.gov/find-species">https://www.fisheries.noaa.gov/find-species</a>).
Table 3 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 (2021). PBR is defined
by the MMPA as the maximum number of animals, not including natural
mortalities, that may be removed from a marine mammal stock while
allowing that stock to reach or maintain its optimum sustainable
population (as described in NMFS' SARs). While no mortality 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' stock abundance estimates for most species represent the total
estimate of individuals within the geographic area, if known, that
comprises that stock. For some species, this geographic area may extend
beyond U.S. waters. All managed stocks in this region are assessed in
NMFS' U.S. Atlantic Marine Mammal SARs. All values presented in Table 3
are the most recent available at the time of publication and are
available in the final 2020 SARs (Hayes et al., 2021) and draft 2021
SARs, available online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports">https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports</a>.

Table 3--Marine Mammals With Potential Presence Within the Proposed Project Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
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\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Cetartiodactyla--Cetacea--Superfamily Odontoceti (toothed whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Phocoenidae (porpoises):

[[Page 11868]]

Harbor porpoise................. Phocoena phocoena...... Gulf of Maine/Bay of -;N 95,543 (0.31; 74,034; 851 164
Fundy. 2016).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Carnivora--Superfamily Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Phocidae (earless seals):
Harbor seal..................... Phoca vitulina......... Western North Atlantic. -;N 61,336 (0.08, 57,637; 1,729 339
2018).
Gray seal....................... Halichoerus grypus..... Western North Atlantic. -;N 27,300 \4\ (0.22; 1,389 4,453
22,785; 2016).
Harp seal....................... Pagophilus Western North Atlantic. -;N 7,600,000 426,000 178,573
groenlandicus. (unk,7,100.000, 2019).
Hooded seal..................... Cystophora cristata.... Western North Atlantic. -;N 593,500............... Unknown 1,680
--------------------------------------------------------------------------------------------------------------------------------------------------------
\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: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region#reports">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region#reports</a>. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance.
\3\ These values, found in NMFS' 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\ This abundance value and the associated PBR value reflect the US population only. Estimated abundance for the entire Western North Atlantic stock,
including animals in Canada, is 451,600. The annual M/SI estimate is for the entire stock.

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 (>1800 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).
The Navy has been collecting data on marine mammals in the
Piscataqua River since 2017 through construction monitoring and non-
construction related monthly surveys (2017-2018). Three harbor
porpoises were observed travelling quickly through the river channel
during marine mammal monitoring conducted between April and December
2017 in support of the Berth 11 Waterfront Improvements Project
(Cianbro 2018a). Two harbor porpoises were observed during construction
monitoring that occurred between January 2018 and January 2019 (Cianbro
2018b; Navy 2019). One harbor porpoise was observed in March 2017
during non-construction related surveys conducted on 12 days (one per
month) in 2017, and two harbor porpoises (one in August and one in
November) were observed in monthly surveys conducted in 2018 (Naval
Facilities Engineering Systems Command (NAVFAC) Mid-Atlantic 2018,
2019b). There was one sighting of harbor porpoise during P-310 year 1
monitoring events (May through December 2020) (NAVFAC 2021). To date,
no harbor porpoise have been sighted in calendar year 2021 (Stantec
2021).

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[ordm] 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. The majority of harbor seals occur along the Maine coast with a
large portion of them hauling out at the Isles of Shoals (see Figure 4-
1 of the application). Pupping season for harbor seals is May to June.
No harbor seal pups were observed during the surveys (Cianbro 2018a, b)
as pupping sites are north of the Maine-New Hampshire border (Waring et
al. 2016). During construction monitoring between the months of April
and December 2017, 199 harbor seals were observed (Cianbro 2018a) in
the project area. A total of 249 harbor seals were observed during
construction monitoring between the months of January 2018 and January
2019 (Navy 2019). The primary behaviors observed during monitoring were
milling that occurred almost 60 percent of the time followed by
swimming and traveling by the proposed project area at 29 percent and
12 percent, respectively (Cianbro 2018a). A total of 17 and 83 harbor
seals were observed during the one-day monthly surveys conducted in
2017 and 2018, respectively (NAVFAC Mid-Atlantic 2018, 2019b). Between
May and December of 2020 (NAVFAC 2021), 721 harbor seals were sighted
during construction monitoring (NAVFAC 2021). A total of 302 harbor
seals have been observed during construction monitoring of the project
area between January 2021 and November 2021 (Stantec 2021).

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).
There were 24 gray seals observed within the proposed project area
between the months of April and December 2017 (Cianbro 2018a) and a
total of 12 observed during the January 2018 to January 2019
construction monitoring period (Navy 2019). Ten of

[[Page 11869]]

the 12 observation occurred during the winter months. (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. Gray seals were observed foraging
approximately 5 percent of the time (Cianbro 2018a). The one-day
monthly marine mammal surveys during 2017 and 2018 recorded six and
three sightings, respectively, of gray seal (NAVFAC Mid-Atlantic 2018,
2019b). A total of 47 gray seals were observed during P-310 Year 1
monitoring events from May through December 2020 (NAVFAC 2021). Pupping
season for gray seals is December through February. No gray seal pups
were observed during the surveys (Cianbro 2018a, b) as pupping sites
for gray seals (like harbor seals) are north of Maine-New Hampshire
border (Waring et al. 2016). In 2021, monitoring activities have
sighted 9 gray seals thus far (Stantec 2021).

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).
Hooded seals are known to occur 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 from the Shipyard in August 2009, but no other observations
have been recorded (Trefry November 20, 2015). Hooded seals were not
observed 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; NAVFAC 2021). To date no hooded seals have been
sighted in 2021 (Stantec 2021).

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. Lawrence, is equivalent to the
western North Atlantic stock. 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 are known to occur in the Piscataqua River; however,
they are not as abundant as the more commonly observed harbor seal and
were last documented in the river in May of 2020 (Stantec 2020). Two
harp seals were sighted on two separate occasions (on May 12 and May
14, 2020) during construction monitoring for P-310 (NAVFAC 2021). No
pile driving was occurring at the time of the sighting. Previous to
that, the last harp seal sighting was in 2016 (NAVFAC Mid-Atlantic
2016; NMFS 2016b). Harp seals were not observed during marine mammal
monitoring or survey events that took place in 2017 and 2018 (Cianbro
2018a, b; NAVFAC Mid-Atlantic 2018, 2019b; Navy 2019). To date no harp
seals have been sighted in 2021 (Stantec 2021).

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 was declared a UME, but it is now considered
non-active and pending closing. Information on this UME is available
online at: <a href="https://www.fisheries.noaa.gov/new-england-mid-atlantic/marine-life-distress/2018-2020-pinniped-unusual-mortality-event-along">https://www.fisheries.noaa.gov/new-england-mid-atlantic/marine-life-distress/2018-2020-pinniped-unusual-mortality-event-along</a>.

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 4.

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

[[Page 11870]]

Otariid pinnipeds (OW) (underwater) 60 Hz to 39 kHz.
(sea lions and fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
composite (i.e., all species within the group), where individual
species' hearing ranges are typically not as broad. Generalized
hearing range chosen based on ~65 dB threshold from normalized
composite audiogram, with the exception for lower limits for LF
cetaceans (Southall et al. 2007) and PW pinniped (approximation).

The pinniped functional hearing group was modified from Southall et
al. (2007) on the basis of data indicating that phocid species have
consistently demonstrated an extended frequency range of hearing
compared to otariids, especially in the higher frequency range
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth 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 3. 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 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):
<bullet> 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;
<bullet> 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;
<bullet> 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
<bullet> 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

[[Page 11871]]

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, rotary
drilling, DTH, and rock hammering. 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
(American National Standards Institute standards (ANSI) 1986; Harris
1998; National Institute for Occupational Safety and Health (NIOSH)
1998; International Organization for Standardization (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, as received at a distance, can be
greatly extended in a highly reverberant environment.

Acoustic Impacts

The introduction of anthropogenic noise into the aquatic
environment from pile driving or drilling is the primary means by which
marine mammals may be harassed from the Navy's specified activity. In
general, animals exposed to natural or anthropogenic sound may
experience physical and psychological effects, ranging in magnitude
from none to severe (Southall et al., 2007). In general, exposure to
pile driving or drilling noise has the potential to result in auditory
threshold shifts and behavioral reactions (e.g., avoidance, temporary
cessation of foraging and vocalizing, changes in dive behavior).
Exposure to anthropogenic noise can also lead to non-observable
physiological responses such an increase in stress hormones. Additional
noise in a marine mammal's habitat can mask acoustic cues used by
marine mammals to carry out daily functions such as communication and
predator and prey detection. The effects of pile driving or drilling
noise on marine mammals are dependent on several factors, including,
but not limited to, sound type (e.g., impulsive vs. non-impulsive), the
species, age and sex class (e.g., adult male vs. mom with calf),
duration of exposure, the distance between the pile and the animal,
received levels, behavior at time of exposure, and previous history
with exposure (Wartzok et al., 2004; Southall et al., 2007). Here we
discuss physical auditory effects (threshold shifts) followed by
behavioral effects and potential impacts on habitat.
NMFS defines a noise-induced threshold shift (TS) as a change,
usually an increase, in the threshold of audibility at a specified
frequency or portion of an individual's hearing range above a
previously established reference level (NMFS 2018). The amount of
threshold shift is customarily expressed in decibels (dB). A TS can be
permanent or temporary.
As described in NMFS (2018), there are numerous factors to consider
when examining the consequence of TS, including, but not limited to,
the signal temporal pattern (e.g., impulsive or non-impulsive),
likelihood an individual would be exposed for a long enough duration or
to a high enough level to induce a TS, the magnitude of the TS, time to
recovery (seconds to minutes or hours to days), the frequency range of
the exposure (i.e., spectral content), the hearing and vocalization
frequency range of the exposed species relative to the signal's
frequency spectrum (i.e., how an animal uses sound within the frequency
band of the signal; e.g., Kastelein et al., 2014), and the overlap
between the animal and the source (e.g., spatial, temporal, and
spectral).
Permanent Threshold Shift (PTS)--NMFS defines PTS as a permanent,
irreversible increase in the threshold of audibility at a specified
frequency or portion of an individual's hearing range above a
previously established reference level (NMFS 2018). Available data from
humans and other terrestrial mammals indicate that a 40 dB threshold
shift approximates PTS onset (see Ward et al., 1958, 1959; Ward 1960;
Kryter et al., 1966; Miller 1974; Ahroon et al., 1996; Henderson et
al., 2008). PTS levels for marine mammals are estimates, as with the
exception of a single study unintentionally inducing PTS in a harbor
seal (Kastak et al., 2008), there are no empirical data measuring PTS
in marine mammals largely due to the fact that, for various ethical
reasons, experiments involving anthropogenic noise exposure at levels
inducing PTS are not typically pursued or authorized (NMFS 2018).
Temporary Threshold Shift (TTS)--TTS is a temporary, reversible
increase in the threshold of audibility at a specified frequency or
portion of an individual's hearing range above a previously established
reference level (NMFS 2018). Based on data from cetacean TTS
measurements (see Southall et al., 2007), a TTS of 6 dB is considered
the minimum threshold shift clearly larger than any day-to-day or
session-to-session variation in a subject's normal hearing ability

[[Page 11872]]

(Schlundt et al., 2000; Finneran et al., 2000, 2002). As described in
Finneran (2015), marine mammal studies have shown the amount of TTS
increases with cumulative sound exposure level (SELcum) in an
accelerating fashion: At low exposures with lower SELcum, the amount of
TTS is typically small and the growth curves have shallow slopes. At
exposures with higher SELcum, the growth curves become steeper and
approach linear relationships with the noise SEL.
Depending on the degree (elevation of threshold in dB), duration
(i.e., recovery time), and frequency range of TTS, and the context in
which it is experienced, TTS can have effects on marine mammals ranging
from discountable to serious (similar to those discussed in auditory
masking, below). For example, a marine mammal may be able to readily
compensate for a brief, relatively small amount of TTS in a non-
critical frequency range that takes place during a time when the animal
is traveling through the open ocean, where ambient noise is lower and
there are not as many competing sounds present. Alternatively, a larger
amount and longer duration of TTS sustained during a time when
communication is critical for successful mother/calf interactions could
have more serious impacts. We note that reduced hearing sensitivity as
a simple function of aging has been observed in marine mammals, as well
as humans and other taxa (Southall et al., 2007), so we can infer that
strategies exist for coping with this condition to some degree, though
likely not without cost.
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 five species of pinnipeds exposed to a limited
number of sound sources (i.e., mostly tones and octave-band noise) in
laboratory settings (e.g., Finneran 2015). TTS was not observed in
trained spotted (Phoca largha) and ringed (Pusa hispida) seals exposed
to impulsive noise at levels matching previous predictions of TTS onset
(Reichmuth et al., 2016). 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 (Finneran 2015). 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), Finneran and Jenkins (2012) and
Finneran (2015).
Behavioral Harassment--Exposure to noise from pile driving and
removal also has the potential to behaviorally disturb marine mammals.
Available studies show wide variation in response to underwater sound;
therefore, it is difficult to predict specifically how any given sound
in a particular instance might affect marine mammals perceiving the
signal. If a marine mammal does react briefly to an underwater sound by
changing its behavior or moving a small distance, the impacts of the
change are unlikely to be significant to the individual, let alone the
stock or population. However, if a sound source displaces marine
mammals from an important feeding or breeding area for a prolonged
period, impacts on individuals and populations could be significant
(e.g., Lusseau and Bejder 2007; Weilgart 2007; NRC 2005).
Disturbance may result in changing durations of surfacing and
dives, number of blows per surfacing, or moving direction and/or speed;
reduced/increased vocal activities; changing/cessation of certain
behavioral activities (such as socializing or feeding); visible startle
response or aggressive behavior (such as tail/fluke slapping or jaw
clapping); avoidance of areas where sound sources are located.
Pinnipeds may increase their haul out time, possibly to avoid in-water
disturbance (Thorson and Reyff 2006). Behavioral responses to sound are
highly variable and context-specific and any reactions depend on
numerous intrinsic and extrinsic factors (e.g., species, state of
maturity, experience, current activity, reproductive state, auditory
sensitivity, time of day), as well as the interplay between factors
(e.g., Richardson et al., 1995; Wartzok et al., 2003; Southall et al.,
2007; Weilgart 2007; Archer et al., 2010). Behavioral reactions can
vary not only among individuals but also within an individual,
depending on previous experience with a sound source, context, and
numerous other factors (Ellison et al., 2012), and can vary depending
on characteristics associated with the sound source (e.g., whether it
is moving or stationary, number of sources, distance from the source).
In general, pinnipeds seem more tolerant of, or at least habituate more
quickly to, potentially disturbing underwater sound than do cetaceans,
and generally seem to be less responsive to exposure to industrial
sound than most cetaceans. Please see Appendices B-C of Southall et
al., (2007) for a review of studies involving marine mammal behavioral
responses to sound.
Disruption of feeding behavior can be difficult to correlate with
anthropogenic sound exposure, so it is usually inferred by observed
displacement from known foraging areas, the appearance of secondary
indicators (e.g., bubble nets or sediment plumes), or changes in dive
behavior. As for other types of behavioral response, the frequency,
duration, and temporal pattern of signal presentation, as well as
differences in species sensitivity, are likely contributing factors to
differences in response in any given circumstance (e.g., Croll et al.,
2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko et al.,
2007). A determination of whether foraging disruptions incur fitness
consequences would require information on or estimates of the energetic
requirements of the affected individuals and the relationship between
prey availability, foraging effort and success, and the life history
stage of the animal.
Stress responses--An animal's perception of a threat may be
sufficient to trigger stress responses consisting of some combination
of behavioral responses, autonomic nervous system responses,
neuroendocrine responses, or immune responses (e.g., Seyle 1950; Moberg
2000). In many cases, an animal's first and sometimes most economical
(in terms of energetic costs) response is behavioral avoidance of the
potential stressor. Autonomic nervous system responses to stress
typically involve changes in heart rate, blood pressure, and
gastrointestinal activity. These responses have a relatively short
duration and may or may not have a significant long-term effect on an
animal's fitness.
Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that
are affected by stress--including immune 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

[[Page 11873]]

replenished once the stress is alleviated. In such circumstances, the
cost of the stress response would not pose serious fitness
consequences. However, when an animal does not have sufficient energy
reserves to satisfy the energetic costs of a stress response, energy
resources must be diverted from other functions. This state of distress
will last until the animal replenishes its energetic reserves
sufficient to restore normal function.
Relationships between these physiological mechanisms, animal
behavior, and the costs of stress responses are well studied through
controlled experiments and for both laboratory and free-ranging animals
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003;
Krausman et al., 2004; Lankford et al., 2005). Stress responses due to
exposure to anthropogenic sounds or other stressors and their effects
on marine mammals have also been reviewed (Fair and Becker 2000; Romano
et al., 2002b) and, more rarely, studied in wild populations (e.g.,
Romano et al., 2002a). For example, Rolland et al., (2012) found that
noise reduction from reduced ship traffic in the Bay of Fundy was
associated with decreased stress in North Atlantic right whales. These
and other studies lead to a reasonable expectation that some marine
mammals will experience physiological stress responses upon exposure to
acoustic stressors and that it is possible that some of these would be
classified as ``distress.'' In addition, any animal experiencing TTS
would likely also experience stress responses (NRC, 2003), however
distress is an unlikely result of this project based on observations of
marine mammals during previous, similar projects in the area.
Masking--Sound can disrupt behavior through masking, or interfering
with, an animal's ability to detect, recognize, or discriminate between
acoustic signals of interest (e.g., those used for intraspecific
communication and social interactions, prey detection, predator
avoidance, navigation) (Richardson et al., 1995). Masking occurs when
the receipt of a sound is interfered with by another coincident sound
at similar frequencies and at similar or higher intensity, and may
occur whether the sound is natural (e.g., snapping shrimp, wind, waves,
precipitation) or anthropogenic (e.g., pile driving, shipping, sonar,
seismic exploration) in origin. The ability of a noise source to mask
biologically important sounds depends on the characteristics of both
the noise source and the signal of interest (e.g., signal-to-noise
ratio, temporal variability, direction), in relation to each other and
to an animal's hearing abilities (e.g., sensitivity, frequency range,
critical ratios, frequency discrimination, directional discrimination,
age or TTS hearing loss), and existing ambient noise and propagation
conditions. Masking of natural sounds can result when human activities
produce high levels of background sound at frequencies important to
marine mammals. Conversely, if the background level of underwater sound
is high (e.g. on a day with strong wind and high waves), an
anthropogenic sound source would not be detectable as far away as would
be possible under quieter conditions and would itself be masked.
Airborne Acoustic Effects--Although pinnipeds are known to haul-out
regularly on man-made objects, we believe that incidents of take
resulting solely from airborne sound are unlikely due to the sheltered
proximity between the proposed project area and the haulout sites (on
the opposite side of the island where activities are occuring). There
is a possibility that an animal could surface in-water, but with head
out, within the area in which airborne sound exceeds relevant
thresholds and thereby be exposed to levels of airborne sound that we
associate with harassment, but any such occurrence would likely be
accounted for in our estimation of incidental take from underwater
sound. Therefore, authorization of incidental take resulting from
airborne sound for pinnipeds is not warranted, and airborne sound is
not discussed further here. Cetaceans are not expected to be exposed to
airborne sounds that would result in harassment as defined under the
MMPA.

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 bedrock
removal when bottom sediments are disturbed. The installation of piles
and bedrock removal an will disturb bottom sediments and may cause a
temporary increase in suspended sediment in the project area. Using
available information collected from a project in the Hudson River,
pile driving activities are anticipated to produce total suspended
sediment (TSS) concentrations of approximately 5.0 to 10.0 mg/L above
background levels within approximately 300 feet (91 meters) of the pile
being driven (Federal Highway Administration (FHWA) 2012). During pile
extraction, sediment attached to the pile moves vertically through the
water column until gravitational forces cause it to slough off under
its own weight. The small resulting sediment plume is expected to
settle out of the water column within a few hours. Studies of the
effects of turbid water on fish (marine mammal prey) suggest that
concentrations of suspended sediment can reach thousands of milligrams
per liter before an acute toxic reaction is expected (Burton 1993). The
TSS levels expected for pile driving or removal (5.0 to 10.0 mg/L) are
below those shown to have adverse effects on fish (580.0 mg/L for the
most sensitive species, with 1,000.0 mg/L more typical) and benthic
communities (390.0 mg/L (Environmental Protection Agency 1986)).
Impacts to water quality from DTH mono-hammers are expected to be
similar to those described for pile driving. Impacts to water quality
would be localized and temporary and would have negligible impacts on
marine mammal habitat. The cluster drill system and rotary drilling of
shafts would have negligible impacts on water quality from sediment
resuspension because the system would operate within a casing set into
the bedrock. The cluster drill would collect excavated material inside
of the apparatus where it would be lifted to the surface and placed
onto a barge for subsequent disposal.
Turbidity within the water column has the potential to reduce the
level of oxygen in the water and irritate the gills of prey fish
species in the proposed project area. However, turbidity plumes
associated with the project would be temporary and localized, and fish
in the proposed project area would be able to move away from and avoid
the areas where plumes may occur. Therefore, it is expected that the
impacts on prey fish species from turbidity, and therefore on marine
mammals, would be minimal and temporary.
Overall effects of 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. In
general, the area likely impacted by the project is relatively small
compared to the available habitat in Great Bay Estuary.
Effects on Potential Prey--Sound may affect marine mammals through
impacts

[[Page 11874]]

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 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).
The greatest potential impact to fish during construction would
occur during impact pile driving, rock hammering, and DTH excavation
(DTH mono-hammer and cluster drill). However, the duration of impact
pile driving would be limited to the final stage of installation
(``proofing'') after the pile has been driven as close as practicable
to the design depth with a vibratory driver. Vibratory pile driving and
rock hammering would possibly elicit behavioral reactions from fish
such as temporary avoidance of the area but is unlikely to cause
injuries to fish or have persistent effects on local fish populations.
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.

In-Water Construction Effects on Potential Foraging Habitat

The proposed activities would not result in permanent impacts to
habitats used directly by marine mammals. The total seafloor area
affected by pile installation and removal is a very small area compared
to the vast foraging area available to marine mammals outside this
project area. 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 (14,164 square m) of benthic habitat from construction of the
super flood basin. The water surface of Great Bay Estuary extends
approximately 4.45 square miles (124,000,000 sf) at low tide (Mills No
date). Therefore, the loss of 152,000 sf would represent approximately
one-tenth of one percent of the benthic habitat in the estuary at low
tide. 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 project are not likely to have adverse
effects on marine mammal foraging habitat in the proposed project area.
The impacts will be temporary and highly localized, and no habitat will
be permanently impacted by construction. Therefore, it is expected that
impacts on foraging opportunities for marine mammals due to the project
would be minimal.
The area impacted by the project is relatively small compared to
the available habitat just outside the project area, and there are no
areas of particular importance that would be impacted by this project.
Any behavioral avoidance by fish of the disturbed area would still
leave significantly large areas of fish and marine mammal foraging
habitat in the nearby vicinity. As described in the preceding, the
potential for the Navy's construction to affect the availability of
prey to marine mammals or to meaningfully impact the quality of
physical or acoustic habitat is considered to be insignificant.

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, in the
form of behavioral disturbance, masking, and potential TTS, with a
smaller amount of Level A harassment in the form of PTS. As described
previously, no mortality is anticipated or proposed to be authorized

[[Page 11875]]

for this activity. Below we describe how the take is estimated.
Generally speaking, we estimate take by considering: (1) Acoustic
thresholds above which NMFS believes the best available science
indicates marine mammals will be behaviorally harassed or incur some
degree of permanent hearing impairment; (2) the area or volume of water
that will be ensonified above these levels in a day; (3) the density or
occurrence of marine mammals within these ensonified areas; and (4) the
number of days of activities. We note that while these factors can
contribute to a basic calculation to provide an initial prediction of
takes, additional information that can qualitatively inform take
estimates is also sometimes available (e.g., previous monitoring
results or average group size). Below, we describe the factors
considered here in more detail and present the 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).
Level B Harassment--Though significantly driven by received level,
the onset of behavioral disturbance from anthropogenic noise exposure
is also informed to varying degrees by other factors related to the
source (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 we consider 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, DTH) sources. The Navy's construction includes the use of
continuous and impulsive sources, and therefore the level of 120 and
160 dB re 1 [mu]Pa (RMS) is applicable.
Level A harassment--NMFS' Technical Guidance for Assessing the
Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0)
(Technical Guidance, 2018) identifies dual criteria to assess auditory
injury (Level A harassment) to five different marine mammal groups
(based on hearing sensitivity) as a result of exposure to noise. The
technical guidance identifies the received levels, or thresholds, above
which individual marine mammals are predicted to experience changes in
their hearing sensitivity for all underwater anthropogenic sound
sources, and reflects the best available science on the potential for
noise to affect auditory sensitivity. The technical guidance does this
by identifying threshholds in the follow manner:
<bullet> Dividing sound sources into two groups (i.e., impulsive
and non-impulsive) based on their potential to affect hearing
sensitivity;
<bullet> Choosing metrics that best address the impacts of noise on
hearing sensitivity, i.e., sound pressure level (peak SPL) and sound
exposure level (SEL) (also accounting for duration of exposure); and
<bullet> Dividing marine mammals into hearing groups and developing
auditory weighting functions based on the science supporting the fact
that not all marine mammals hear and use sound in the same manner.
These thresholds were developed by compiling and synthesizing the
best available science and are provided in Table 5 below. The
references, analysis, and methodology used in the development of the
thresholds are described in NMFS 2018 Technical Guidance, which may be
accessed at <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection">https://www.fisheries.noaa.gov/national/marine-mammal-protection</a>.
As mentioned previously, the Navy's modification and expansion of
Dry Dock 1 includes the use of impulsive (i.e., impact pile driving,
DTH) and non-impulsive (i.e., drilling, vibratory pile driving)
sources.

Table 5--Thresholds Identifying the Onset of Permanent Threshold Shift for High Frequency Ceteaceans and
Pinnipeds
----------------------------------------------------------------------------------------------------------------
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 [mu]Pa, and cumulative sound exposure level (LE) has
a reference value of 1[mu]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.

Ensonified Area

Here, we describe operational and environmental parameters of the
activity that will feed into identifying the area ensonified above the
acoustic thresholds, which include source levels transmission loss
coefficient.
Transmission loss (TL) is the decrease in acoustic intensity as an
acoustic pressure wave propagates out from a source. TL parameters vary
with frequency, temperature, sea conditions, current, source and
receiver depth, water depth, water chemistry, and bottom composition
and topography. The general formula for underwater TL is:

[[Page 11876]]

TL = B * log<INF>10</INF>(R<INF>1</INF>/R<INF>2</INF>),

where

B = transmission loss coefficient (assumed to be 15)
R<INF>1</INF> = the distance of the modeled SPL from the driven
pile, and
R<INF>2</INF> = the distance from the driven pile of the initial
measurement.

This formula neglects loss due to scattering and absorption, which
is assumed to be zero here. The degree to which underwater sound
propagates away from a sound source is dependent on a variety of
factors, most notably the water bathymetry and presence or absence of
reflective or absorptive conditions, including in-water structures and
sediments. Spherical spreading occurs in a perfectly unobstructed
(free-field) environment not limited by depth or water surface,
resulting in a 6 dB reduction in sound level for each doubling of
distance from the source (20*log(range)). Cylindrical spreading occurs
in an environment in which sound propagation is bounded by the water
surface and sea bottom, resulting in a reduction of 3 dB in sound level
for each doubling of distance from the source (10*log(range)). As is
common practice in coastal waters, here we assume practical spreading
(4.5 dB reduction in sound level for each doubling of distance).
Practical spreading is a compromise that is often used under conditions
where water depth increases as the receiver moves away from the
shoreline, resulting in an expected propagation environment that would
lie between spherical and cylindrical spreading loss conditions.
Practical spreading was used to determine sound propagation for this
project.
The intensity of pile driving sounds is greatly influenced by
factors such as the type of piles, hammers, and the physical
environment in which the activity takes place. There are sound source
level (SSL) measurements available for certain pile types and sizes
from the similar environments from other Navy pile driving projects
that were evaluated and used as proxy sound source levels to determine
reasonable sound source levels likely to result from the pile driving
and removal activities (Table 6). Some of the proxy source levels are
expected to be more conservative, as the values are from larger pile
sizes. Acoustic monitoring results and associated monitoring reports
from past projects conducted at the shipyard and elsewhere were
reviewed. Projects reviewed were those most similar to the specified
activity in terms of drilling and rock hammering activities, type and
size of piles installed, method of pile installation, and substrate
conditions.

Table 6--Summary of In-Water Pile Driving Source Levels (at 10 m From Source)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Peak (dB re 1
Pile type Installation method Pile diameter [mu]Pa) RMS (dB re 1 [mu]Pa) SEL (dB re 1 [mu]Pa\2\ sec)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Casing/Socket................... Rotary Drill....... 102-inch \1\.......... NA 154 m....................... NA
Shaft........................... DTH Cluster Drill.. 78-inch \2\........... NA 195.2 (Level A)............. 181
167 dB (Level B)............
Casing.......................... DTH mono-hammer.... 42-inch \1\........... 194 167......................... 164
Rock anchor..................... DTH mono-hammer.... 9-inch \1\............ 172 167......................... 146
Relief hole..................... DTH mono-hammer.... 4 to 6-inch \1\....... 170 167......................... 144
Z-shaped Sheet.................. Impact............. 28-inch \3\........... 211 196......................... 181
Vibratory.......... 28-inch \4\........... NA 167......................... 167
Flat sheet...................... Vibratory.......... 18-inch \5\........... NA 163......................... 163
Bedrock and concrete demolition. Rock Hammer \6 7\.. NA.................... 197 184......................... 175
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Egger 2021a.
\2\ Egger 2021b.
\3\ A proxy value for impact pile driving 28-inch steel sheet piles could not be found so the proxy for a 30-inch steel pipe pile has been used (NAVFAC
SW 2020 [p. A-4]).
\4\ A proxy value for vibratory pile driving 28-inch steel sheet piles could not be found so a proxy for a 30-inch steel pipe pile has been used (Navy
2015 [p. 14]).
\5\ NMFS 2019 (p. 24484, Table 5).
\6\ Reyff 2018a.
\7\ Reyff 2018b.
Notes: All SPLs are unattenuated; dB = decibels; NA = Not applicable; single strike SEL are the proxy sources levels presented for impact pile driving
and were used to calculate distances to PTS.
dB re 1 [mu]Pa = dB referenced to a pressure of 1 microPascal, measures underwater SPL. dB re 1 [mu]Pa\2\-sec = dB referenced to a pressure of 1
microPascal squared per second, measures underwater SEL.
All recordings were made at 10 meters unless noted otherwise.

With regards to the proxy values summarized in Table 6, very little
information is available regarding source levels for in-water rotary
drilling activities. As a conservative measure and to be consistent
with previously issued IHAs for similar projects in the region (Egger
2021a; Dazey 2012), a proxy of 154 dB RMS is proposed for all rotary
drilling activities.
Rock hammering is analyzed as an impulsive noise source. For
purposes of this analysis, it is assumed that the hammer would have a
maximum strike rate of 460 strikes per minute and would operate for a
maximum duration of 15 minutes before needing to reposition or stop to
check progress. Therefore, noise impacts for rock hammering activities
are assessed using the number of blows per 15-minute interval (6,900
blows) and the number of 15-minute intervals anticipated over the
course of the day based on the durations provided in Table 2-1 and
Table 6-5. As with rotary drilling, very little information is
available regarding source levels associated with nearshore rock
hammering. Measurements taken for this activity as part of the Tappan
Zee Bridge replacement project recorded sound levels as follows:

<bullet> 197 dBpk, 184 dB RMS, 175 dB SEL (Reyff 2108a, 2018b)

Since no other comparable proxy values were identified in the
literature, the Navy is proposing to use the same proxy values for rock
hammering activities associated with P-381.
The Navy consulted with NMFS to obtain the appropriate proxy values
for DTH mono-hammers. With regards to DTH mono-hammers, NMFS provided
proxy values of 170 dBpk, 167 RMS, and 144 dB single strike SEL for
holes 8-inches in diameter or less (Reyff 2020); 172 dBpk, 167 RMS, and
146 dB single strike SEL for holes 8- to 18

[[Page 11877]]

inches in diameter (Guan and Miner 2020); and 194 dBpk, 167 RMS, and
164 dB single strike SEL for holes 24- to 42-inches in diameter (Reyff
2020, Denes et al 2019 as cited in NMFS 2021a). For the 78-inch DTH
cluster drill, NMFS provided an RMS value of 195.2 based off of
regression and extrapolation calculations of existing data. Because of
the high number of hammers and strikes for this system, cluster drills
were treated as a continuous sound source for the time component of
Level A harassment but still used the impulsive thresholds. The Level B
harassment sound source level at 10 m remained at 167 dB RMS (Heyvaert
and Reyff, 2021 as cited in NMFS 2021b).
In conjunction with the NMFS Technical Guidance (2018), in
recognition of the fact that 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. We note
that, because of some of the assumptions included in the methods used
for these tools, we anticipate that isopleths produced are typically
going to be overestimates of some degree, which may result in some
degree of overestimation 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 from impact and vibratory pile driving), the NMFS User
Spreadsheet (2020) predicts the closest distance at which, if a marine
mammal remained at that distance the whole duration of the activity, it
would not incur PTS. Inputs used in the User Spreadsheet can be found
in Appendix A of the Navy's application and the resulting isopleths are
reported below (Tables 7 and 8).
Calculated distances to Level A harassment (PTS Onset) and Level B
harassment thresholds are large, especially for DTH and rock hammering
activities. However, the full distance of sound propagation would not
be reached due to the presence of land masses and anthropogenic
structures that would prevent the noise from reaching nearly the full
extent of the larger harassment isopleths. Refer to Figure 2 for the
region of influence, which illustrates that the land masses preclude
the sound from traveling more than approximately 870 m (3,000 ft) from
the source, at most.
Maximum distances are provided for the behavioral thresholds for
in-water construction activities. Areas encompassed within the
threshold (harassment zones) were calculated by using a Geographical
Information System to clip the maximum calculated distances to the
extent of the region of influence (ROI) (refer to Figure 2 for the
ROI).
Table 7 summarizes the calculated maximum distances corresponding
to the underwater marine mammal harassment zones from impulsive (impact
pile driving, rock hammering, DTH) and Table 8 for non-impulsive noise
(vibratory pile driving, rotary drilling, etc.) and the area of the
harassment zone within the ROI. The distances do not take the land
masses into consideration, but the ensonified areas do. Neither
consider the reduction that will be achieved by the required use of a
bubble curtain and therefore all take estimates are considered
conservative. Refer to Figures 6-9 through 6-11 of the application for
the calculated maximum distances corresponding to the underwater marine
mammal harassment zones from impulsive (impact pile driving, rock
hammering, DTH) and non-impulsive noise (vibratory pile driving, rotary
drilling) and the corresponding area of the harassment zone within the
ROI.

Table 7--Calculated Distance and Areas of Level A and Level B Harassment for Impulsive Noise
[DTH, impact pile driving, hydraulic rock hammering]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Level A harassment (PTS onset) * Level B harassment
Total ------------------------------------------ *
Activity Purpose Count and size/ production High frequency --------------------
duration days cetaceans (harbor Phocid pinnipeds Harbor porpoise and
porpoise) phocids
--------------------------------------------------------------------------------------------------------------------------------------------------------
DTH Cluster Drill................ Foundation Support 38, 78-inch shafts. 247 84,380.4 m/0.417 37,909.7 m/0.417 13,594 m/0.417
Piles for Center km\2\. km\2\. km\2\.
Wall.
DTH Cluster Drill................ Foundation Leveling 18, 78-inch shafts. 117 84,380.4 m/0.417 37,909.7 m/0.417 13,594 m/0.417
Piles for Center km\2\. km\2\. km\2\.
Wall.
DTH Cluster Drill................ Center Wall--Access 38, 78-inch shafts. 133 84,380.4 m/0.417 37,909.7 m/0.417 13,594 m/0.417
Support Platform. km\2\. km\2\. km\2\.
DTH Mono-hammer.................. Center Wall-- 6, 42-inch shafts.. 6 3,880.3 m/0.417 1,743.3 m/0417km\2\ 13,594 m/0.417
Temporary Launching km\2\. km\2\.
Piles.
DTH Mono-hammer.................. Center Wall Tie- 36, 9-inch holes... 18 244.8 m/0.074 km\2\ 110 m/0.0229 km\2\. 13,594 m/0.417
Downs. km\2\.
DTH Mono-hammer.................. Center Wall--Access 18, 9-inch holes... 9 244.8 m/0.0741 110 m/0.0229 km\2\. 13,594 m/0.417
Platform Tie-Downs. km\2\. km\2\.
Impact Pile Driving.............. West Closure Wall 16, ** 28-inch Z- ** 4 988.2 m/0.4034 444.0 m/0.2012 2,512 m/0.417
Tie-In to Existing shaped sheets. km\2\. km\2\. km\2\.
Wall.
Impact Pile Driving.............. Berth 11 End Wall 60, 28-inch Z- 7 1,568.6 m/0.417 704.7 m/0.365 km\2\ 2,512 m/0.417
Secant Pile Guide shaped sheets. km\2\. km\2\.
Wall.
DTH Mono-hammer.................. Relief Holes Under 500, 4-6 inch holes 20 180.1 m/0.0481 80.9 m/0.015 km\2\. 13,594 m/0. 417
West Closure Cell. km\2\. km\2\.
DTH Mono-hammer.................. Mechanical Rock 46, 42-inch casing 24 3,880.3 m/0.417 1,743.3 m/0.417 13,594 m/0.417
Removal Along Face advancements. km\2\. km\2\. km\2\.
of Existing
Abutment.
DTH Mono-hammer.................. Install Piles for 28, 42-inch shafts. 28 3,880.3 m/0.417 1,743.3 m/0.417 13,594 m/0.417
Dry Dock 1 North km\2\. km\2\. km\2\.
Entrance Abutment.
DTH Mono-hammer.................. Relief Holes Under 2,201, ** 4-6 inch ** 82 180.1 m/0.0481km\2\ 80.9 m/0.015 km\2\. 13,594 m/0.417
West Closure Cell. holes. km\2\.
DTH Mono-hammer.................. Mechanical Rock 365, 42-inch casing 183 3,880.3 m/0.417 1,743.3 m/0.417 13,594 m/0.417
Removal Along Face advancements. km\2\. km\2\. km\2\.
of Existing
Abutment.
DTH Mono-hammer.................. Dry Dock 1 Entrance 100, 9-inch holes.. 52 132.9 m/0.0303 59.7 m/0.009km\2\.. 13,594 m/0.417
Tremie Tie Downs. km\2\. km\2\.

[[Page 11878]]

Impact Pile Driving.............. Install Sheet Piles 96, 28-inch Z- 12 1,568.6 m/0.417 704.7 m/0.365km\2\. 2,512 m/0.417
for Dry Dock 1 shaped sheets. km\2\. km\2\.
North Entrance and
Temporary Cofferdam.
Hydraulic Rock Hammer............ Removal of Sheetpile 2.5 hours.......... ** 10 5,860.0 m/0.417 2,633 m/0.4174km\2\ 398 m/0.165 km\2\.
and Granite Quay km\2\.
Wall (610 cy).
Hydraulic Rock Hammer............ Mechanical Rock 9 hours............ 77 13,766 m/0.417 6,184.7 m/0.417 398 m/0.165 km\2\.
Removal (985 cy) km\2\. km\2\.
Under West Closure
Cell.
Hydraulic Rock Hammer............ Shutter Panel 5 hours............ ** 56 9,303.1 m/0.417 4,179.6 m/0.417 398 m/0.165 km\2\.
Demolition. km\2\. km\2\.
Hydraulic Rock Hammer............ Mechanical Rock 12 hours........... ** 100 16,676.3 m/0.417 7,492.2 m/0.417 398 m/0.165 km\2\.
Removal (3,500 cy) km\2\. km\2\.
Along Face of
Existing Berth 11
at Basin Floor.
Hydraulic Rock Hammer............ P-310 Sheet Pile 12, 25-inch Z- ** 3 10,505.4 m/0.417 4,719.8 m/0.417 398 m/0.1652 km\2\.
Removal--Berth 1. shaped sheets, 6 km\2\. km\2\.
hours.
Hydraulic Rock Hammer............ Berth 1 Top of Wall 10 hours........... ** 6 14,767.7 m/0.417 6,634.7 m/0.417 398 m/0.165km\2\.
Demolition for km\2\. km\2\.
Waler Install.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: Kiewit 2021.
Notes:
* To determine underwater harassment zones, ensonified areas from the source were clipped along the shoreline using Geographical Information Systems
(GIS).
** These activities will continue into the following construction years and the remaining construction days and activities will be included in a
subsequent LOA. The construction days and activities represented in this table account ONLY for year 1 activities.
lf = linear feet; N/A = Not Applicable.
Proxy sources used were unattenuated SPLs.

Table 8--Calculated Distance and Areas of Level A and Level B Harassment for Non-Impulsive Noise
[Vibratory pile driving, rotary drilling]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Level A harassment (PTS onset) Level B harassment
Total --------------------------------------------------------------
Activity Purpose Count and size production High frequency
days cetaceans harbor Phocid pinnipeds Harbor porpoise and
porpoise phocids
--------------------------------------------------------------------------------------------------------------------------------------------------------
Rotary Drill..................... Center Wall 38, 102-inch 38 2.1 m/0.000014 1.3 m/0.000005 1,848 m/0.417
Foundation Pile-- Borings. km\2\. km\2\. km\2\.
Install Outer
Casing.
Rotary Drill..................... Center Wall 38, 102-inch 38 8.9 m/0.000248 5.4 m/0.000091 1,848 m/0.417
Foundation Pile-- Borings. km\2\. km\2\. km\2\.
Pre-Drill Socket.
Rotary Drill..................... Center Wall 38, 102-inch 38 0.8 m/0.000002 0.5 m/0.000001 1,848 m/0.417
Foundation Pile-- Borings. km\2\. km\2\. km\2\.
Remove Outer Casing.
Rotary Drill..................... Center Wall Leveling 18, 102-inch 18 2.1 m/0.000014 1.3 m/0.000005 1,848 m/0.417
Piles--Install Borings. km\2\. km\2\. km\2\.
Outer Casing.
Rotary Drill..................... Center Wall Leveling 18, 102-inch 18 8.9 m/0.000248 5.4 m/0.000091 1,848 m/0.417
Piles--Pre-Drill Borings. km\2\. km\2\. km\2\.
Socket.
Rotary Drill..................... Center Wall Leveling 18, 102-inch 18 0.8 m/0.000002 0.5 m/0.000001 1,848 m/0.417
Piles--Remove Outer Borings. km\2\. km\2\. km\2\.
Casing.
Rotary Drill..................... Center Wall Access 38, 102-inch 38 2.1 m/0.000014 1.3 m/0.000005 1,848 m/0.417
Platform Support-- Borings. km\2\. km\2\. km\2\.
Install Outer
Casing.
Rotary Drill..................... Center Wall Access 38, 102-inch 38 8.9 m/0.000248 5.4 m/0.000091 1,848 m/0.417
Platform Support-- Borings. km\2\. km\2\. km\2\.
Pre-Drill Socket.
Rotary Drill..................... Center Wall Access 38, 102-inch 38 0.8 m/0.000002 0.5 m/0.000001 1,848 m/0.417
Platform Support -- Borings. km\2\. km\2\. km\2\.
Remove Outer Casing.
Vibratory Pile Driving........... Tie-In to Existing 16, ** 28-inch Z- ** 4 12.2 m/0.000454 5.0 m/0.000078 13,594 m/0.417
West Closure Wall. Shaped Sheets. km\2\. km\2\. km\2\.
Vibratory Pile Driving........... Berth 11 End Wall 60, 28-inch Z- 7 19.4 m/0.001041 8.0 m/0.0002 km\2\. 13,594 m/0.417
Secant Pile Guide Shaped Sheets. km\2\. km\2\.
Wall.
Vibratory Extraction............. Remove P-310 West 238, 18-inch Flat 60 6.6 m/0.000136 2.7 m/0.000023 7,356 m/0.417
Closure Wall. Sheets. km\2\. km\2\. km\2\.
Vibratory Pile Driving........... Install Sheet Piles 96, 28-inch Z- 12 19.4 m/0.001041 8.0 m/0.0002 km\2\. 13,594 m/0.417
for Dry Dock 1 Shaped Sheets. km\2\. km\2\.
North Entrance and
Temporary Cofferdam.
--------------------------------------------------------------------------------------------------------------------------------------------------------
** These activities will continue into the following construction years and the remaining construction days and activities will be included in a
subsequent LOA. The construction days and activities represented in this table account ONLY for year 1 activities.
lf = linear feet; N/A = Not Applicable.
Proxy sources used were unattenuated SPLs.

[[Page 11879]]

Concurrent Activities
Simultaneous use of pile drivers, hammers, and drills could result
in increased SPLs and harassment zone sizes given the proximity of the
component sites and the rules of decibel addition (see Table 9 below).
Due to the relatively small size of the ROI, the use of a single DTH
cluster drill or rock hammer would ensonify the entire ROI to the Level
A harassment thresholds (PTS Onset) (refer to Table 7). Therefore, when
this equipment is operated in conjunction with other noise generating
equipment, there would be no change in the size of the harassment zone.
The entire ROI would remain ensonified to the Level A harassment
thresholds for the duration of the activity and there would be no Level
B harassment zone. However, when DTH cluster drills or rock hammers are
not in use, increased SPLs and harassment zone sizes within the ROI
could result. Due to the large amount of bedrock excavation required
for the construction of the multifunctional expansion of Dry Dock 1,
the only scenario identified in which DTH cluster drills and/or rock
hammers would not be in operation would be at the beginning of the
project when two rotary drills could be used simultaneously (refer to
Table 2).
According to recent, project specific, guidance provided by NMFS to
the Navy, when two noise sources have overlapping sound fields, there
is potential for higher sound levels than for non-overlapping sources
because the isopleth of one sound source encompasses the sound source
of another isopleth. In such instances, the sources are considered
additive and combined using the rules of decibel addition, presented in
Table 9 below.

Table 9--Adjustments for Sound Exposure Level Criterion
------------------------------------------------------------------------
Adjustments to
Difference in sound specifications for
Source types level (at specified Level A harassment
meters) RMS/SELss*
calculations
------------------------------------------------------------------------
Non-impulsive, continuous/ 0 or 1 dB........... Add 3 dB to the
Non-impulsive, continuous highest sound level
OR Impulsive source (at specified
(multiple strikes per meters) AND adjust
second)/Impulsive source number of piles per
(multiple strikes per day to account for
second. overlap (space and
time).
2 or 3 dB........... Add 2 dB to the
highest sound level
(at specified
meters) AND adjust
number of piles per
day to account for
overlap (space and
time).
4 to 9 dB........... Add 1 dB to the
highest sound level
(at specified
meters) AND adjust
number of piles per
day to account for
overlap (space and
time).
10 dB or more Add 0 dB to the
highest sound level
(at specified
meters) AND adjust
number of piles per
day to account for
overlap (space and
time).
------------------------------------------------------------------------
* RMS level for vibratory pile driving/rotary hammer and single strike
SEL (SELss) level for DTH/rock hammer.

For simultaneous usage of three or more continuous sound sources,
the three overlapping sources with the highest sound source levels are
identified. Of the three highest sound source levels, the lower two are
combined using the above rules, then the combination of the lower two
is combined with the highest of the three. For example, with
overlapping isopleths from 24-, 36-, and 42-inch diameter steel pipe
piles with sound source levels of 161, 167, and 168 dB RMS
respectively, the 24- and 36-inch would be added together; given that
167-161 = 6 dB, then 1 dB is added to the highest of the two sound
source levels (167 dB), for a combined noise level of 168 dB. Next, the
newly calculated 168 dB is added to the 42-inch steel pile with sound
source levels of 168 dB. Since 168-168 = 0 dB, 3 dB is added to the
highest value, or 171 dB in total for the combination of 24-, 36-, and
42-inch steel pipe piles (NMFS, 2021 unpublished). By using this
method, a revised proxy source for Level A and Level B analysis was
determined for the use of two, 102-inch diameter rotary drills. The
revised proxy value is presented in Table 10 and the resulting
harassment zones are summarized in Table 11 (depicted in Figure 6-13 in
the Navy's application).

Table 10--Revised Proxy Values for Simultaneous Use of Non-Impulsive
Sources
------------------------------------------------------------------------

------------------------------------------------------------------------
Equipment Rotary drill
------------------------------------------------------------------------
RMS 154
Rotary Drill...................... 154 157
------------------------------------------------------------------------

Table 11--Level A and Level B Harassment Zones Resulting From the Simultaneous Use of Two, 102-in Diameter
Rotary Drill
----------------------------------------------------------------------------------------------------------------
Level A harassment (PTS Onset) Level B harassment
--------------------------------------------------------------------------
Harbor porpoise Harbor porpoise and
Multiple source scenario distance to 155 dB Phocids distance to 185 phocids distance to 120
SELcum threshold/area dB SELcum threshold/ dB (DTH) threshold/area
of harassment zone area of harassment zone of harassment zone
----------------------------------------------------------------------------------------------------------------
2 Rotary Drills...................... 23.6 m/0.002 km\2\..... 9.7 m/0.0002 km\2\..... 2,929 m/0.417 km\2\.
----------------------------------------------------------------------------------------------------------------

[[Page 11880]]

Marine Mammal Occurrence and Take Calculation and Estimation

In this section we provide the information about the presence,
density, or group dynamics of marine mammals that will inform the take
calculations. Potential exposures to impact pile and vibratory pile
driving, rotary drilling, DTH, and rock hammering noise for each
acoustic threshold were estimated using marine mammal density estimates
(N) from the Navy Marine Species Density Database (NMSDD) (Navy 2017)
or from monitoring reports from the Berth 11 Waterfront Improvements
and P-310 construction projects. Specifically, where monitoring data
specific to the project area were available, they were used, and the
NMSDD data were used when there were no monitoring data available. The
take estimate was determined using the following equation take estimate
= N * days of activity * area of harassment. The pile type, size, and
installation method that produce the largest zone of influence (ZOI)
were used to estimate exposure of marine mammals to noise impacts. We
describe how the information provided above is brought together to
produce a quantitative take estimate in the species sections below.
Harbor Porpoise
Harbor porpoises may be present in the proposed project area during
spring, summer, and fall, from April to December. Based on density data
from the Navy Marine Species Density Database, their presence is
highest in spring, decreases in summer, and slightly increases in fall.
During previous monitoring of construction projects in the area, three
harbor porpoise were sighted between April and December of 2017; two
harbor porpoise were sighted in early August of 2018; and one harbor
porpoise was sighted in 2020 (Cianbro 2018a, b; Navy 2019; NAVFAC
2021). Using the 2017 and 2018 data from construction monitoring for
the Berth 11 Waterfront Improvements project, the density of harbor
porpoise for the largest harassment zone was determined to be 0.04/
km\2\.
Estimated take was calculated by density * harassment zone * days
for each activity (see Table 12). Note that where the Level A
harassment zone is as large as the Level B harassment zone and fills
the entire ensonified area, the enumerated takes in the Level A
harassment column may be in the form of Level A harassment and/or Level
B harassment.

Table 12--Calculated Proposed Take by Level A and Level B Harassment of Harbor Porpoise by Project Activity
----------------------------------------------------------------------------------------------------------------
Level A Level B
harassment Number of Take by harassment Take by
Project activity Density zone days Level A zone Level B
(km\2\) harassment (km\2\) harassment
----------------------------------------------------------------------------------------------------------------
Center Wall--Install Foundation: 0.04 0.417 247 4 0.417 0
38 drilled shafts: Cluster drill
DTH (Drill) 78-inch diameter
casing...........................
Center Wall--Install Diving Board 0.04 0.417 117 2 0.417 0
Shafts: 18 drilled shafts:
Cluster drill DTH (Drill) 78-inch
diameter socket..................
Center Wall--Access Platform 0.04 0.417 133 2 0.417 0
Support: 38 drilled shafts:
Cluster Drill DTH (Drill) 78-inch
outer casing.....................
Mechanical Rock Excavation, 0.04 0.417 77 1 0.165 0
Hydraulic rock hammering (985 cy)
Remove Shutter Panels: 112 panels, 0.04 0.417 56 1 0.165 0
Demolish shutter panels,
Hydraulic rock hammering.........
Mechanical Rock Removal at Basin 0.04 0.417 100 2 0.165 0
Floor: Excavate Bedrock,
Hydraulic rock hammering.........
Mechanical Rock at Abutment: Drill 0.04 0.417 183 3 0.417 0
365 rock borings (1,220 cy), 42-
inch diameter casing, Mono-hammer
DTH..............................
Center Wall--Install Foundation: 0.04 0.00001 38 0 0.417 1
38 drilled shafts: Rotary Drill
(Install) 102-inch diameter outer
casing...........................
Center Wall--Install Foundation: 0.04 0.00001 38 0 0.417 1
38 drilled shafts: Rotary Drill
(Pre-drill) 102-inch diameter
socket,..........................
Center Wall--Install Foundation: 0.04 0.00001 38 0 0.417 1
38 drilled shafts: Rotary Drill
(Remove) 102-inch outer casing...
Center Wall--Access Platform 0.04 0.00001 38 0 0.417 1
Support: 38 drilled shafts:
Rotary Drill (Install) 102-inch
diameter outer casing............
Center Wall--Access Platform 0.04 0.00001 38 0 0.417 1
Support: 38 drilled shafts:
Rotary Drill (Pre-drill) 102-inch
diameter socket..................
Center Wall--Access Platform 0.04 0.0000002 38 0 0.417 1
Support: 38 drilled shafts:
Rotary Drill (Remove) 102-inch
outer casing,....................
Remove Wall: 238 sheet piles, 18- 0.04 0.000136 60 0 0.417 1
inch wide flatwebbed, Vibratory
Extraction.......................
Mechanical Rock Removal at Basin 0.04 0.048109 82 0 0.417 1
Floor: Drill 2,201 relief holes,
4-6 holes, Mono-hammer DTH,......
Drill Tremie Ties Downs: Drill 100 0.04 0.0303 52 0 0.417 1
rock anchors, 9-inch holes, Mono-
hammer DTH.......................
-----------------------------------------------------------------------------
Total Estimated Take.......... ........... ........... ........... 15 ........... 9
----------------------------------------------------------------------------------------------------------------

In summary, we estimate that up to 15 takes in the form of Level A
harassment and/or Level B harassment could occur during DTH excavation
(DTH mono-hammer and cluster drill), impact pile driving, and rock
hammering activities. In addition, DTH mono-hammer excavation could
result in 2 takes by Level B harassment and vibratory installing/
extracting and rotary drilling activities could result in 7 takes by
Level B harassment (Table 12).
Harbor Seal
Harbor seals may be present year-round in the project vicinity,
with constant densities throughout the year. Harbor seals are the most
common pinniped in the Piscataqua River near the Shipyard. Harbor seal
sightings were recorded during monthly surveys conducted in 2017 and
2018 (NAVFAC Mid-Atlantic 2018, 2019b) as well as during Berth 11 and
P-310 construction monitoring in 2017, 2018, 2020 and 2021 (Cianbro
2018a, b; Navy 2019; Stantec 2020, Stantec 2021). Estimated take by
Level B harassment has been calculated by multiplying the average
number of harbor seals sighted per day from May 2020 through October
2021 by the number of actual in-water

[[Page 11881]]

construction days (375 days (159 during P-310 year 1 and 216 during P-
310 year 2). Over the course of this time period, there have been 1,023
harbor seal observations equating to equating to 3 harbor seal
sightings per day. Initially, takes were calculated for Level A and
Level B harassment for harbor seals where the density of animals (2.48
harbor seals/km\2\, rounded to 3) was multiplied by the harassment zone
and the number of days per construction activity. However, using that
method produced take numbers for Level B harassment that were lower
than the number of harbor seals that has been previously observed in
the Navy's monitoring reports. Therefore, NMFS is proposing (and the
Navy agrees), to increase the take by Level B harassment to more
accurately reflect harbor seal observations in the monitoring reports,
by using the value of three harbor seals a day multiplied by the total
number of construction days resulting in 1,125 takes by Level B
harassment proposed for authorization. Take by Level A harassment of
1,269 harbor seals is shown in Table 13 below. Note that where the
Level A harassment zone is as large as the Level B harassment zone and
fills the entire ensonified area, the enumerated takes in the Level A
harassment column may be in the form of Level A harassment and/or Level
B harassment. The proposed takes by Level B harassment were not
included in Table 13 as they were calculated by a different method.

Table 13--Calculated Proposed Take by Level A Harassment of Harbor Seal by Project Activity
----------------------------------------------------------------------------------------------------------------
Level A
Project activity Harbor seals harassment Number of days Take by Level
density zone (km\2\) A harassment
----------------------------------------------------------------------------------------------------------------
Center Wall--Install Foundation: 38 drilled 3 0.417 247 309
shafts: Cluster drill DTH (Drill) 78-inch
diameter casing................................
Center Wall--Install Diving Board Shafts: 18 3 0.417 117 146
drilled shafts: Cluster drill DTH (Drill) 78-
inch diameter socket...........................
Center Wall--Access Platform Support: 38 drilled 3 0.417 133 166
shafts: Cluster Drill DTH (Drill) 78-inch outer
casing.........................................
Center Wall--Temp Launching Piles: 6 drilled 3 0.417 6 8
shafts: 42-inch diameter shaft, Mono-hammer DTH
Center Wall Tie Downs: 36 Rock Anchors 3 0.023 18 1
(Install): 9-inch diameter holes, Mono-hammer
DTH............................................
Center Wall--Access Platform Tie Downs: 18 Rock 3 0.023 9 1
Anchors (Install): 9-inch diameter holes, Mono-
hammer DTH.....................................
Center Wall-Install Tie-In to Existing West 3 0.201 4 2
Closure Wall: 16 sheet piles: 28-inch wide Z-
shaped sheets--IMPACT Install..................
Berth 11 End Wall--Install Secant Pile Guide 3 0.417 7 8
Wall: 60 sheets piles: 28-inch wide Z-shaped
sheets--IMPACT Install.........................
Berth 1--Remove Granite Block Quay Wall: 610 cy, 3 0.417 10 13
Granite block demo, Hydraulic Rock hammering...
P310 West Closure Wall--Mechanical Rock 3 0.417 77 96
Excavation: 985 cy, Excavated bedrock,
Hydraulic rock hammering.......................
P310 West Closure Wall--Mechanical Rock 3 0.015 20 1
Excavation: Drill 500 relief holes, 4-6 inch
holes, Mono-hammer DTH.........................
P310 West Closure Wall--Mechanical Rock 3 0.417 24 30
Excavation: Drill 46 rock borings (50 cy), 42-
inch diameter casing, Mono-hammer DTH..........
West Closure well--Berth 11 Abutment- Install 3 0.417 28 35
Piles: Drill 28 shafts, 42-inch diameter
casing, Mono-hammer DTH........................
Berth 11--Remove Shutter Panels: 112 panels, 3 0.417 56 70
Demolish shutter panels, Hydraulic rock
hammering......................................
Berth 11 Face--Mechanical Rock Removal at Basin 3 0.417 100 125
Floor: 3,500 cy, Excavate Bedrock, Hydraulic
rock hammering.................................
Berth 11 Face--Mechanical Rock Removal at Basin 3 0.015 82 4
Floor: Drill 2,201 relief holes, 4-6 holes,
Mono-hammer DTH................................
Berth 11 Face--Mechanical Rock at Abutment: 3 0.417 183 229
Drill 365 rock borings (1,220 cy), 42-inch
diameter casing, Mono-hammer DTH...............
Dry Dock 1 North Entrances--Install Temporary 3 0.365 12 13
Cofferdam: Install 96 sheet piles, 28-inch wide
Z-shaped sheets, IMPACT Install................
Berth 1--Remove sheet piles: Remove 12 sheet 3 0.417 3 4
piles, 25-inch wide Z-shaped sheets, Hydraulic
rock hammering.................................
Berth 1 Top of Wall--Demolition for Waler 3 0.417 6 8
Installation: 30 lf, Mechanical concrete
demolition, Hydraulic rock hammering...........
---------------------------------------------------------------
Total Estimated Take........................ .............. .............. .............. 1,269
----------------------------------------------------------------------------------------------------------------

Gray Seal
Gray seals may be present year-round in the project vicinity, with
constant densities throughout the year. Gray seals are less common in
the Piscataqua River than the harbor seal. Sightings of gray seals were
recorded during P-310 construction monitoring in 2020 and 2021 (Stantec
2020; Stantec 2021). Estimated take by Level B harassment has been
calculated by multiplying the average number of gray seal observations
per day from May 2020 through October 2021 (47 during year 1 P-310
monitoring and 9 during year 2 P-310 monitoring (to date)) over the
course of 337 monitoring days (Stantec 2020; 2021). Over the course of
this time period, there have been 56 gray seal observations equating to
equating to 0.2 gray seal sightings per day. Initially, takes were
calculated for Level A and Level B harassment for gray seals where

[[Page 11882]]

the density was multiplied by the harassment zone and the number of
days per construction activity. However, using that method produced
take numbers for Level B harassment that were fewer than the number of
gray seals that has been previously observed in the Navy's monitoring
reports. Therefore, NMFS is proposing (and the Navy agrees), to
increase the take by Level B harassment to more accurately reflect gray
seal observations in the monitoring reports, by using the value of 0.2
gray seals multiplied by the total number of construction days
resulting in 75 takes by Level B harassment proposed for authorization.
Initially takes were calculated for Level A and Level B harassment for
gray seals in a similar manner where takes were determined by
individual activity. However, NMFS is proposing (and Navy agrees) to
increase the take by Level B harassment by using the value of 0.2 gray
seals which were then multiplied by the number of total construction
days resulting in 75 takes by Level B harassment proposed for
authorization. Take by Level A harassment of 85 gray seals is shown in
Table 14 below. Note that where the Level A harassment zone is as large
as the Level B harassment zone and fills the entire ensonified area,
the enumerated takes in the Level A harassment column may be in the
form of Level A harassment and/or Level B harassment. The proposed
takes by Level B harassment were not included in Table 14 as they were
calculated by a different method.

Table 14--Calculated Proposed Take by Level A Harassment of Gray Seal by Project Activity
----------------------------------------------------------------------------------------------------------------
Level A
Project activity Gray seal harassment Number of days Take by Level
density zone (km\2\) A harassment
----------------------------------------------------------------------------------------------------------------
Center Wall--Install Foundation: 38 drilled 0.2 0.417 247 21
shafts: Cluster drill DTH (Drill) 78-inch
diameter casing................................
Center Wall--Install Diving Board Shafts: 18 0.2 0.417 117 10
drilled shafts: Cluster drill DTH (Drill) 78-
inch diameter socket...........................
Center Wall--Access Platform Support: 38 drilled 0.2 0.417 133 11
shafts: Cluster Drill DTH (Drill) 78-inch outer
casing.........................................
Center Wall--Temp Launching Piles: 6 drilled 0.2 0.417 6 1
shafts: 42-inch diameter shaft, Mono-hammer DTH
Berth 11 End Wall--Install Secant Pile Guide 0.2 0.417 7 1
Wall: 60 sheets piles: 28-inch wide Z-shaped
sheets--IMPACT Install.........................
Berth 1--Remove Granite Block Quay Wall: 610 cy, 0.2 0.417 10 1
Granite block demo, Hydraulic Rock hammering...
P310 West Closure Wall--Mechanical Rock 0.2 0.417 77 6
Excavation: 985 cy, Excavated bedrock,
Hydraulic rock hammering.......................
P310 West Closure Wall--Mechanical Rock 0.2 0.417 24 2
Excavation: Drill 19 rock borings (50 cy), 42-
inch diameter casing, Mono-hammer DTH..........
West Closure well--Berth 11 Abutment- Install 0.2 0.417 28 2
Piles: Drill 28 shafts, 42-inch diameter
casing, Mono-hammer DTH........................
Berth 11--Remove Shutter Panels: 112 panels, 0.2 0.417 56 5
Demolish shutter panels, Hydraulic rock
hammering......................................
Berth 11 Face--Mechanical Rock Removal at Basin 0.2 0.417 3 8
Floor: 1,020 cy, Excavate Bedrock, Hydraulic
rock hammering.................................
Berth 11 Face--Mechanical Rock at Abutment: 0.2 0.417 24 15
Drill 192 rock borings (610 cy), 42-inch
diameter casing, Mono-hammer DTH...............
Dry Dock 1 North Entrances--Install Temporary 0.2 0.365 12 1
Cofferdam: Install 96 sheet piles, 28-inch wide
Z-shaped sheets, IMPACT Install................
Berth 1 Top of Wall--Demolition for Waler 0.2 0.417 6 1
Installation: 30 lf, Mechanical concrete
demolition, Hydraulic rock hammering...........
---------------------------------------------------------------
Total Estimated Take........................ .............. .............. .............. 85
----------------------------------------------------------------------------------------------------------------

Hooded Seal
Hooded seals may be present in the project vicinity from January
through May, though their exact seasonal densities are unknown. In
general, hooded seals are much rarer than the harbor seal and gray seal
in the Piscataqua River. One take per month from January to May from
Level B harassment of a hooded seal for the Berth 11 Waterfront
Improvements Construction project (NMFS 2018b) and for Year 1
construction activities for Dry Dock 1 (NMFS, 2019) was previously
authorized. To date, the monitoring for that project and for the
density surveys have not recorded a sighting of hooded seal in the
project area (Cianbro 2018a, b; NAVFAC Mid-Atlantic 2018, 2019b; Navy
2019; Stantec 2020; Stantec 2021). In order to guard against
unauthorized take, the Navy is requesting and NMFS is proposing one
take by Level B harassment of hooded seal per month (between the months
of January and May) resulting in five total takes of Level B
harassment. No take by Level A harassment is anticipated or proposed
for authorization.
Harp Seal
Harp seals may be present in the project vicinity January through
May. In general, harp seals are much rarer than the harbor seal and
gray seal in the Piscataqua River. As discussed above for hooded seals,
one take by Level B harassment during each month of construction for
the Berth 11 Waterfront Improvements Project (NMFS 2018b) and for year
1 construction activities for Dry Dock 1 (NMFS, 2019) was previously
authorized. The monitoring for the Berth 11 Waterfront Improvements
Construction and P-310 projects did not record any sightings of harp
seal in the project area (Cianbro 2018a, b; NAVFAC Mid-Atlantic 2018,
2019b; Navy 2019; Stantec 2020; Stantec 2021). However, it should be
noted that two harp seals (one on 5/12/2020 and one on 5/14/2020) were
observed when pile driving activities were not

[[Page 11883]]

occurring (Stantec 2020). In order to guard against unauthorized take,
the Navy is requesting and NMFS is proposing one take by Level B
harassment of harp seal per month (between the months of January and
May) resulting in five total takes of Level B harassment. No take by
Level A harassment is anticipated or proposed for authorization.
Table 15 below summarizes the authorized take for all the species
described above as a percentage of stock abundance.

Table 15--Proposed Take Estimates as a Percentage of Stock Abundance
----------------------------------------------------------------------------------------------------------------
Proposed Level Proposed Level
Species Stock (NEST) A harassment B harassment Percent of stock
----------------------------------------------------------------------------------------------------------------
Harbor porpoise.............. Gulf of Maine/ 15 9 Less than 1 percent.
Bay of Fundy
(95,543).
Harbor seal.................. Western North 1,269 1,125 Less than 3 percent.
Atlantic
(61,336).
Gray seal.................... Western North 85 75 Less than 1 percent.
Atlantic
(451,600).
Hooded seal.................. Western North 0 5 Less than 1 percent.
Atlantic
(593,500).
Harp seal.................... Western North 0 5 Less than 1 percent.
Atlantic (7.6
million).
----------------------------------------------------------------------------------------------------------------

Proposed Mitigation

Under section 101(a)(5)(D) of the MMPA, NMFS must set forth the
permissible methods of taking pursuant to the activity, and other means
of effecting the least practicable impact on the species or stock and
its habitat, paying particular attention to rookeries, mating grounds,
areas of similar significance, and on the availability of the species
or stock for taking for certain subsistence uses (latter not applicable
for this action). NMFS regulations require applicants for incidental
take authorizations to include information about the availability and
feasibility (economic and technological) of equipment, methods, and
manner of conducting the activity or other means of effecting the least
practicable adverse impact upon the affected species or stocks and
their habitat (50 CFR 216.104(a)(11)).
In evaluating how mitigation may or may not be appropriate to
ensure the least practicable adverse impact on species or stocks and
their habitat, we carefully consider 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.
Based on our evaluation of the applicant's proposed measures, as
well as other measures considered by NMFS, NMFS has preliminarily
determined that the proposed mitigation measures provide the means
effecting the least practicable impact on the affected species or
stocks and their habitat, paying particular attention to rookeries,
mating grounds, and areas of similar significance.

General

The Navy shall follow mitigation procedures as described below. In
general, if poor environmental conditions restrict full visibility of
the shutdown zone, pile driving activities would be delayed.

Training

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

Avoiding Direct Physical Interaction

The Navy shall avoid direct physical interaction with marine
mammals during construction activity. If a marine mammal comes within
10 m of such activity, operations shall cease and vessels will reduce
speed to the minimum level required to maintain steerage and safe
working conditions, as necessary to avoid direct physical interaction.

Shutdown Zones

The Navy will establish shutdown zones for all pile driving
activities. The purpose of a shutdown zone is generally to define an
area within which shutdown of the activity would occur upon sighting of
a marine mammal (or in anticipation of an animal entering the defined
area). Shutdown zones will vary based on the activity type and marine
mammal hearing group (Table 16).

Table 16--Pile Driving Shutdown Zone and Monitoring Zones During Project Activities
----------------------------------------------------------------------------------------------------------------
Shutdown zone (m) Level B
----------------------------------- harassment \1\
P-381 Year 1 activity description monitoring zone
Harbor porpoise Phocids (m)
----------------------------------------------------------------------------------------------------------------
78-inch cluster drill..................................... \2\ 200 \2\ 50 ROI.
DTH monohammer--42-inch................................... \2\ 200 \2\ 50 ROI.
DTH monohammer--9-inch Center wall tie downs.............. \2\ 200 \2\ 50 ROI.
DTH monohammer--9-inch tremie tie-downs................... \2\ 200 \2\ 50 ROI.
DTH monohammer--4-6-inch (500)............................ \2\ 200 \2\ 50 ROI.
Impact install of sheet piles (16) West Closure Wall Tie- \2\ 200 \2\ 50 ROI.
in.......................................................
Impact install of sheet piles (60) Secant pile guide wall; \2\ 200 \2\ 50 ROI.
(96) temporary coffer dam................................

[[Page 11884]]

Rock hammering--all durations............................. \2\ 200 \2\ 50 ROI.
Rotary drilling--Install 102-inch casing.................. 10 10 ROI.
Rotary drilling--Predrill 102-inch socket................. 10 10 ROI.
Rotary drilling--Remove 102-inch casing................... 10 10 ROI.
Vibratory pile driving (16) 28-inch sheets................ 20 10 ROI.
Vibratory pile driving (60) and (96) 28-inch sheets....... 20 10 ROI.
Vibratory extraction (238) 28-inch sheets................. 10 10 ROI.
----------------------------------------------------------------------------------------------------------------
Notes:
\1\ In instances where the harassment zone is larger than the ROI, the entire ROI is indicated as the limit of
monitoring.
\2\ Reduced Monitoring area distance negotiated with NMFS.
Key: ROI--region of influence.

Soft Start

The Navy shall use soft start techniques when impact pile driving.
Soft start requires contractors to provide an initial set of three
strikes from the hammer at reduced energy, followed by a 30-second
waiting period. Then two subsequent reduced-energy strike sets would
occur. A 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. Soft start is not
required during vibratory pile driving activities.

Bubble Curtain

A bubble curtain shall be installed across any openings at the
entrance of super flood basin to attenuate sound for the sound sources
that encompass the entire ROI. The Navy will record hydroacoustic
measurements inside and outside of the bubble curtain. Should the
results of the recordings inside the bubble curtain show that
thresholds are not being exceeded by the activity occurring, that upon
review of the data by NMFS, Navy may discontinue use of the bubble
curtain for those activities that are not actually exceeding
thresholds.
Based on our evaluation of the applicant's planned measures, NMFS
has preliminarily determined that the mitigation measures provide the
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.

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
action area. Effective reporting is critical both to compliance as well
as for 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:
[ssquf] Occurrence of marine mammal species or stocks in the area
in which take is anticipated (e.g., presence, abundance, distribution,
density);
[ssquf] 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);
[ssquf] Individual marine mammal responses (behavioral or
physiological) to acoustic stressors (acute, chronic, or cumulative),
other stressors, or cumulative impacts from multiple stressors;
[ssquf] How anticipated responses to stressors impact either: (1)
Long-term fitness and survival of individual marine mammals; or (2)
populations, species, or stocks;
[ssquf] Effects on marine mammal habitat (e.g., marine mammal prey
species, acoustic habitat, or other important physical components of
marine mammal habitat); and
[ssquf] Mitigation and monitoring effectiveness.
The Navy shall submit a Marine Mammal Monitoring Plan to NMFS for
approval in advance of the start of construction.

Monitoring Zones

The Navy shall conduct monitoring to include the area within the
Level B harassment zones (areas where SPLs are equal to or exceed the
160 dB RMS threshold for impact driving and the 120 dB RMS threshold
during vibratory pile driving) (see Table 16 above). These monitoring
zones provide utility for monitoring conducted for mitigation purposes
(i.e., shutdown zone monitoring) by establishing monitoring protocols
for areas adjacent to the shutdown zones. Monitoring of the disturbance
zones enables observers to be aware of and communicate the presence of
marine mammals in the project area, but outside the shutdown zone, and
thus prepare for potential shutdowns of activity.

Visual Monitoring

Monitoring shall take place from 30 minutes (min) prior to
initiation of pile driving activity (i.e., pre-start clearance
monitoring) through 30 min post-completion of pile driving activity. If
a marine mammal is observed entering or within the shutdown zones, pile
driving shall be delayed or halted. If pile driving is delayed or
halted due to the presence of a marine mammal, the activity may not
commence or resume until either the animal has voluntarily exited and
been visually confirmed beyond the shutdown zone or 15 min have passed
without re-detection of the animal. Pile driving activity shall be
halted upon observation of either a species for which incidental take
is not authorized or a species for which incidental take has been
authorized but the authorized number of takes has been

[[Page 11885]]

met, entering or within the disturbance zone.

Protected Species Observer (PSO) Monitoring Requirements and Locations

PSOs shall be responsible for monitoring, the shutdown zones, the
disturbance zones and the pre-clearance zones, as well as effectively
documenting Level A and B harassment take. As described in more detail
in the Reporting section below, they shall also (1) document the
frequency at which marine mammals are present in the project area, (2)
document behavior and group composition, (3) record all construction
activities, and (4) document observed reactions (changes in behavior or
movement) of marine mammals during each sighting. The PSOs shall
monitor for marine mammals during all in-water pile activities
associated with the project. The Navy shall monitor the project area to
the extent possible based on the required number of PSOs, required
monitoring locations, and environmental conditions. Visual monitoring
shall be conducted by three PSOs. It is assumed that three PSOs shall
be located on boats, docks, or piers sufficient to monitor the
respective ROIs given the abundance of suitable vantage points (see
Figure 11-1 of the application). The PSOs must record all observations
of marine mammals, regardless of distance from the pile being driven.
In addition, PSOs shall work in shifts lasting no longer than 4 hrs
with at least a 1-hr break between shifts and will not perform duties
as a PSO for more than 12 hrs in a 24[hyphen]hr period (to reduce PSO
fatigue).
Monitoring of pile driving shall be conducted by qualified, PSOs.
The Navy shall adhere to the following conditions when selecting PSOs:
[ssquf] PSOs must be independent (i.e., not construction personnel)
and have no other assigned tasks during monitoring periods;
[ssquf] At least one PSO must have prior experience performing the
duties of a PSO during construction activities pursuant to a NMFS-
issued incidental take authorization;
[ssquf] Other PSOs may substitute other relevant experience,
education (degree in biological science or related field), or training;
[ssquf] Where a team of three PSOs are required, a lead observer or
monitoring coordinator shall be designated. The lead observer must have
prior experience performing the duties of a PSO during construction
activity pursuant to a NMFS-issued incidental take authorization; and
[ssquf] PSOs must be approved by NMFS prior to beginning any
activity subject to this rule.
The Navy will ensure that the PSOs have the following additional
qualifications:
[ssquf] Visual acuity in both eyes (correction is permissible)
sufficient for discernment of moving targets at the water's surface
with ability to estimate target size and distance; use of binoculars
may be necessary to correctly identify the target;
[ssquf] Experience and ability to conduct field observations and
collect data according to assigned protocols;
[ssquf] Experience or training in the field identification of
marine mammals, including the identification of behaviors;
[ssquf] Sufficient training, orientation, or experience with the
construction operation to provide for personal safety during
observations;
[ssquf] Writing skills sufficient to prepare a report of
observations including but not limited to the number and species of
marine mammals observed; dates and times when in-water construction
activities were conducted; dates, times, and reason for implementation
of mitigation (or why mitigation was not implemented when required);
and marine mammal behavior; and
[ssquf] Ability to communicate orally, by radio or in person, with
project personnel to provide real-time information on marine mammals
observed in the area as necessary.

Hydroacoustic Monitoring

The Navy shall conduct a sound source verification (SSV) study for
all pile types and will follow accepted methodological standards to
achieve their objectives. The Navy shall submit an acoustic monitoring
plan to NMFS for approval prior to the start of construction. The Navy
will collect and evaluate acoustic sound record levels for 10 percent
of the new rotary drilling, DTH excavation (DTH mono-hammer and cluster
drill), and rock hammering activities conducted as part of P-381 (Table
15). Hydrophones would be placed at locations 10 m (33 ft) from the
noise source and, where the potential for Level A harassment exists, at
a second representative monitoring location at an intermediate distance
between the cetacean and phocid shutdown zones. For the 10 percent of
rotary drilling, DTH excavation (DTH mono-hammer and cluster drill),
and rock hammering events acoustically measured, 100 percent of the
data will be analyzed.
At a minimum, the methodology includes:
[ssquf] For underwater recordings, a stationary hydrophone system
with the ability to measure SPLs will be placed in accordance with NMFS
most recent guidance for the collection of source levels.
[ssquf] Hydroacoustic monitoring will be conducted for 10 percent
of each different type of activity not previously monitored as part of
P-310 (Table 15). Monitoring will occur from the same locations
approved by NMFS for P-310 construction activities. The resulting data
set will be analyzed to examine and confirm sound pressure levels and
rates of transmission loss for each separate in-water construction
activity. With NMFS concurrence, these metrics will be used to
recalculate the limits of shutdown and Level B (Behavioral) harassment
zones, and to make corresponding adjustments in marine mammal
monitoring of these zones for use in the forthcoming rulemaking/LOA
application. Hydrophones will be placed in the same manner as for P-310
construction activities. Locations of hydroacoustic recordings will be
collected via GPS. A depth sounder and/or weighted tape measure will be
used to determine the depth of the water. The hydrophone will be
attached to a-weighted nylon cord to maintain a constant depth and
distance from the pile/drill/hammer location. The nylon cord or chain
will be attached to a float or tied to a static line.
[ssquf] Each hydrophone (underwater) will be calibrated at the
start of each action and will be checked frequently to the applicable
standards of the hydrophone manufacturer.
[ssquf] For each monitored location, a single hydrophone will be
suspended midway in the water column in order to evaluate site-specific
attenuation and propagation characteristics that may be present
throughout the water column.
[ssquf] Environmental data will be collected, including but not
limited to, the following: Wind speed and direction, air temperature,
humidity, surface water temperature, water depth, wave height, weather
conditions, and other factors that could contribute to influencing the
airborne and underwater sound levels (e.g., aircraft, boats, etc.).
[ssquf] The chief inspector will supply the acoustics specialist
with the substrate composition, hammer/drill model and size, hammer/
drill energy settings, depth of drilling, and boring rates and any
changes to those settings during the monitoring.
[ssquf] For acoustically monitored construction activities, data
from the continuous monitoring locations will be post-processed to
obtain the following sound measures:

[[Page 11886]]

[cir] Maximum peak pressure level recorded for all activities,
expressed in dB re 1 [mu]Pa. This maximum value will originate from the
phase of drilling/hammering during which drill/hammer energy was also
at maximum (referred to as Level 4).
[cir] From all activities occurring during the Level 4 phase these
additional measures will be made, as appropriate:

[ssquf] Mean, median, minimum, and maximum RMS pressure level in (dB re
1 [mu]Pa)
[ssquf] mean duration of a pile strike (based on the 90 percent energy
criterion)
[ssquf] number of hammer strikes
[ssquf] mean, median, minimum, and maximum single strike SEL (dB re
[mu]Pa\2\ sec)

[cir] Cumulative SEL as defined by the mean single strike SEL +
10*log (number of hammer strikes) (dB re [mu]Pa\2\ sec).
[cir] Median integration time used to calculate SPL RMS.
[cir] A frequency spectrum (pressure spectral density) (dB re
[mu]Pa\2\ per Hz) based on the average of up to eight successive
strikes with similar sound. Spectral resolution will be 1 Hz, and the
spectrum will cover nominal range from 7 Hz to 20 kHz.
[cir] Finally, the cumulative SEL will be computed from all the
strikes associated with each pile occurring during all phases, i.e.,
soft start, Level 1 to Level 4. This measure is defined as the sum of
all single strike SEL values. The sum is taken of the antilog, with
log<INF>10</INF> taken of result to express (dB re [mu]Pa\2\ sec).

Table 17--Hydroacoustic Monitoring Summary
----------------------------------------------------------------------------------------------------------------
Number
Size Count Activity monitored
----------------------------------------------------------------------------------------------------------------
102-inch......................... 94............................. Rotary Drill................ 9
78-inch.......................... 94............................. DTH Cluster Drill........... 9
42-inch.......................... 445............................ DTH Mono-hammer............. 10
9-inch........................... 154............................ DTH Mono-hammer............. 10
4 to 6-inch...................... 2,701.......................... DTH Mono-hammer............. 10
NA............................... 252 days....................... Rock Hammering.............. 10
----------------------------------------------------------------------------------------------------------------

Marine Mammal Monitoring Reporting

The Navy shall submit a draft report to NMFS within 90 calendar
days of the completion of monitoring or 60 calendar days prior to the
requested issuance of any subsequent IHA for construction activity at
the same location, whichever comes first. The report will detail the
monitoring protocol and summarize the data recorded during monitoring.
The final report must be prepared and submitted within 30 days
following resolution of any NMFS comments on the draft report. If no
comments are received from NMFS within 30 days of receipt of the draft
report, the report shall be considered final. If comments are received,
a final report addressing NMFS comments must be submitted within 30
days after receipt of comments. All draft and final marine mammal
monitoring reports must be submitted to
<a href="/cdn-cgi/l/email-protection#3363611d7a67631d7e5c5d5a475c415a5d546156435c414740735d5c52521d545c45">[email&#160;protected]</a> and <a href="/cdn-cgi/l/email-protection#48011c18660d2f2f2d3a0826272929662f273e">[email&#160;protected]</a>. The report
must contain the following informational elements, at minimum, (and be
included in the Marine Mammal Monitoring Plan), including:
[ssquf] Dates and times (begin and end) of all marine mammal
monitoring;
[ssquf] Construction activities occurring during each daily
observation period, including:
[cir] How many and what type of piles were driven and by what
method (e.g., impact or vibratory); and
[cir] Total duration of driving time for each pile (vibratory
driving) and number of strikes for each pile (impact driving);
[ssquf] PSO locations during marine mammal monitoring;
[ssquf] Environmental conditions during monitoring periods (at
beginning and end of PSO shift and whenever conditions change
significantly), including Beaufort sea state and any other relevant
weather conditions including cloud cover, fog, sun glare, and overall
visibility to the horizon, and estimated observable distance;
[ssquf] Upon observation of a marine mammal, the following
information:
[cir] PSO who sighted the animal and PSO location and activity at
time of sighting;
[cir] Time of sighting;
[cir] Identification of the animal (e.g., genus/species, lowest
possible taxonomic level, or unidentified), PSO confidence in
identification, and the composition of the group if there is a mix of
species;
[cir] Distance and bearing of each marine mammal observed to the
pile being driven for each sighting (if pile driving was occurring at
time of sighting);
[cir] Estimated number of animals (minimum/maximum/best);
[cir] Estimated number of animals by cohort (adults, juveniles,
neonates, group composition, etc.;
[cir] Animal's closest point of approach and estimated time spent
within the harassment zone; and
[cir] Description of any marine mammal behavioral observations
(e.g., observed behaviors such as feeding or traveling), including an
assessment of behavioral responses to the activity (e.g., no response
or changes in behavioral state such as ceasing feeding, changing
direction, flushing, or breaching);
[ssquf] Detailed information about implementation of any mitigation
(e.g., shutdowns and delays), a description of specific actions that
ensued, and resulting changes in behavior of the animal, if any; and
[ssquf] All PSO datasheets and/or raw sightings data.

Reporting of Hydroacoustic Monitoring

The Navy shall also submit a draft hydroacoustic monitoring report
to NMFS within 60 workdays of the completion of required monitoring at
the end of the project. The report will detail the hydroacoustic
monitoring protocol and summarize the data recorded during monitoring.
The final report must be prepared and submitted within 30 days
following resolution of any NMFS comments on the draft report. If no
comments are received from NMFS within 30 days of receipt of the draft
report, the report shall be considered final. If comments are received,
a final report addressing NMFS comments must be submitted within 30
days after receipt of comments. All draft and final hydroacoustic
monitoring reports must be submitted to
<a href="/cdn-cgi/l/email-protection#efbfbdc1a6bbbfc1a28081869b809d868188bd8a9f809d9b9caf81808e8ec1888099">[email&#160;protected]</a> and <a href="/cdn-cgi/l/email-protection#3e776a6e107b59595b4c7e50515f5f10595148">[email&#160;protected]</a>. The
hydroacoustic monitoring report will contain the informational elements
described in the Hydroacoustic Monitoring Plan and, at minimum, will
include:
[ssquf] Hydrophone equipment and methods: Recording device,
sampling

[[Page 11887]]

rate, distance (m) from the pile where recordings were made; depth of
water and recording device(s);
[ssquf] Type and size of pile being driven, substrate type, method
of driving during recordings (e.g., hammer model and energy), and total
pile driving duration;
[ssquf] Whether a sound attenuation device is used and, if so, a
detailed description of the device used and the duration of its use per
pile;
[ssquf] For impact pile driving and/or DTH excavation (DTH mono-
hammer and cluster drill) (per pile): Number of strikes and strike
rate; depth of substrate to penetrate; pulse duration and mean, median,
and maximum sound levels (dB re: 1 [micro]Pa): Root mean square sound
pressure level (SPLrms); cumulative sound exposure level (SELcum), peak
sound pressure level (SPLpeak), and single-strike sound exposure level
(SELs-s);
[ssquf] For vibratory driving/removal and/or DTH excavation (DTH
mono-hammer and cluster drill) (per pile): Duration of driving per
pile; mean, median, and maximum sound levels (dB re: 1 [micro]Pa): Root
mean square sound pressure level (SPLrms), cumulative sound exposure
level (SELcum) (and timeframe over which the sound is averaged); and
[ssquf] One-third octave band spectrum and power spectral density
plot.
[ssquf] General Daily Site Conditions.
[cir] Date and time of activities.
[cir] Water conditions (e.g., sea state, tidal state).
[cir] Weather conditions (e.g., percent cover, visibility).

Reporting of Injured or Dead Marine Mammals

In the event that personnel involved in the construction activities
discover an injured or dead marine mammal, the Navy shall report the
incident to NMFS Office of Protected Resources (OPR)
(<a href="/cdn-cgi/l/email-protection#0e5e5c20475a5e20436160677a617c6760695c6b7e617c7a7d4e60616f6f20696178">[email&#160;protected]</a>), NMFS (301-427-8401) and to the
Greater Atlantic Region New England/Mid-Atlantic Stranding Coordinator
(866-755-6622) as soon as feasible. If the death or injury was clearly
caused by the specified activity, the Navy must immediately cease the
specified activities until NMFS OPR is able to review the circumstances
of the incident and determine what, if any, additional measures are
appropriate to ensure compliance with the terms of this rule. The Navy
shal not resume their activities until notified by NMFS. The report
must include the following information:
[ssquf] Time, date, and location (latitude/longitude) of the first
discovery (and updated location information if known and applicable);
[ssquf] Species identification (if known) or description of the
animal(s) involved;
[ssquf] Condition of the animal(s) (including carcass condition if
the animal is dead);
[ssquf] Observed behaviors of the animal(s), if alive;
[ssquf] If available, photographs or video footage of the
animal(s); and
[ssquf] General circumstances under which the animal was
discovered.

Negligible Impact Analysis and Determination

NMFS has defined negligible impact as an impact resulting from the
specified activity that cannot be reasonably expected to, and is not
reasonably likely to, adversely affect the species or stock through
effects on annual rates of recruitment or survival (50 CFR 216.103). A
negligible impact finding is based on the lack of likely adverse
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough
information on which to base an impact determination. In addition to
considering estimates of the number of marine mammals that might be
taken through harassment, NMFS considers other factors, such as the
likely nature of any 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. We also assess the number, intensity, and context of
estimated takes by evaluating this information relative to population
status. Consistent with the 1989 preamble for NMFS' implementing
regulations (54 FR 40338; September 29, 1989), the impacts from other
past and ongoing anthropogenic activities are incorporated into this
analysis via their impacts on the 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).
To avoid repetition, this introductory discussion of our analyses
applies to all of the species listed in Table 3, given that many of the
anticipated effects of this project on different marine mammal stocks
are expected to be relatively similar in nature. Where there are
meaningful differences between species or stocks in anticipated
individual responses to activities, impacts of expected take on the
population due to differences in population status, or impacts on
habitat, they are described independently in the analysis below.
Construction activities associated with the project, as outlined
previously, have the potential to disturb or displace marine mammals.
Specifically, the specified activities may result in take, in the form
of Level A and Level B harassment from underwater sounds generated by
pile driving activities, rotary drilling, rock hammering, and DTH.
Potential takes could occur if marine mammals are present in zones
ensonified above the thresholds for Level A and Level B harassment,
identified above, while activities are underway.
No serious injury or mortality would be expected even in the
absence of the proposed mitigation measures. A bubble curtain shall be
installed across any openings at the entrance of super flood basin to
attenuate sound for the sound sources that encompass the entire ROI
(Figure 2). During all impact driving, implementation of soft start
procedures and monitoring of established shutdown zones will be
required, significantly reducing the possibility of injury. Given
sufficient notice through use of soft start (for impact driving),
marine mammals are expected to move away from an irritating sound
source prior to it becoming potentially injurious. In addition, PSOs
will be stationed within the action area whenever pile driving, rotary
drilling, rock hammering and DTH activities are underway. The Navy
shall employ the use of three PSOs to ensure all monitoring and
shutdown zones are properly observed. For hooded and harp seals which
are a rare species in within the project area, we do not anticipate any
take by Level A harassment.
The Navy's proposed activities and associated impacts will occur
within a limited area. Most of the work will occur behind the existing
super flood basin walls that would act as a barrier to sound and would
contain underwater noise to within a small portion of the Piscataqua
River. Exposures to elevated sound levels produced during pile driving
activities may cause behavioral disturbance of some individuals, but
they are expected to be mild and temporary and further minimized by the
use of a bubble curtain and soft starts. As described previously, the
mitigation and monitoring measures are expected to further reduce the
likelihood of injury as well as reduce behavioral disturbances.
Effects on individuals that are taken by Level B harassment, as
enumerated in the Estimated Take section, on the basis of reports in
the literature as well as monitoring from other similar activities,
will likely be limited to reactions such as increased swimming

[[Page 11888]]

speeds, increased surfacing time, or decreased foraging (if such
activity were occurring) (e.g., Thorson and Reyff 2006). Most likely,
individual animals will simply move away from the sound source and be
temporarily displaced from the area, although even this reaction has
been observed primarily only in association with impact pile driving.
The activities analyzed here are similar to numerous other construction
activities conducted along both Atlantic and Pacific coasts, which have
taken place with no known long-term adverse consequences from
behavioral harassment. These reactions and behavioral changes are
expected to subside quickly when the exposures cease. Level B
harassment will be minimized through use of mitigation measures
described herein. including the soft starts and the use of the bubble
curtain, which was not quantitatively factored into the take estimates.
Regarding Level A harassment particularly for harbor seals and gray
seals, monitoring and shutdown protocols, and a bubble curtain
implemented during DTH excavation (DTH mono-hammer and cluster drill)
and hydraulic rock hammering would minimize potential for take by Level
A harassment. For pinnipeds, the calculated Level A harassment likely
overestimates PTS exposure because: (1) Seals are unlikely to remain in
the Level A harassment zone underwater long enough to accumulate
sufficient exposure to noise resulting in PTS, and (2) the estimate
assumes that new seals are in the Level A harassment zone every day
during pile driving. Further as discussed above, take by Level A
harassment would be minimized due to implementation of monitoring,
shutdown procedures and a bubble curtain. Nonetheless, we have
considered the potential impacts of these PTS takes occurring in this
analysis. The degree of PTS that may incur from the Navy's activities
are not expected to impact marine mammals such that their reproduction
or survival could be affected. Similarly, data do not suggest that a
single instance in which an animal accrues PTS (or TTS) and is subject
to behavioral disturbance would result in impacts to reproduction or
survival. If PTS were to occur, it would be at a lower level likely to
accrue to a relatively small portion of the population by being a
stationary activity in one particular location.
The project is also not expected to have significant adverse
effects on any marine mammal habitat. The project activities will not
modify existing marine mammal habitat since the project will occur
within the same footprint as existing marine infrastructure. Impacts to
the immediate substrate are anticipated, but these would be limited to
minor, temporary suspension of sediments, which could impact water
quality and visibility for a short amount of time but which would not
be expected to have any effects on individual marine mammals. The
nearshore and intertidal habitat where the project will occur is an
area of consistent vessel traffic from Navy and non-Navy vessels, and
some local individuals would likely be somewhat habituated to the level
of activity in the area, further reducing the likelihood of more severe
impacts. The closest pinniped haulout used by harbor and gray seals is
2,414 m (1.5 mi) away on the opposite side of the island and not within
the ensonified area. There are no other biologically important areas
for marine mammals near the project area.
In addition, impacts to marine mammal prey species are expected to
be minor and temporary. Overall, the area impacted by the project is
very small compared to the available surrounding habitat. The most
likely impact to prey will be temporary behavioral avoidance of the
immediate area. During construction activities, it is expected that
some fish and marine mammals would temporarily leave the area of
disturbance, thus impacting marine mammals' foraging opportunities in a
limited portion of the foraging range. But, because of the relatively
small area of the habitat that may be affect

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