Take of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Hampton Roads Bridge-Tunnel Expansion Project, Hampton-Norfolk, Virginia, 48153-48179 [2020-17344]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 85, Number 154 (Monday, August 10, 2020)]
[Notices]
[Pages 48153-48179]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-17344]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XA122]


Take of Marine Mammals Incidental to Specified Activities; Taking 
Marine Mammals Incidental to the Hampton Roads Bridge-Tunnel Expansion 
Project, Hampton-Norfolk, Virginia

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

ACTION: Notice; issuance of an incidental harassment authorization.

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SUMMARY: In accordance with the regulations implementing the Marine 
Mammal Protection Act (MMPA) as amended, notification is hereby given 
that NMFS has issued an incidental harassment authorization (IHA) to 
the Hampton Roads Connector Partners (HRCP) to incidentally harass, by 
Level A and Level B harassment, marine mammals during pile driving and 
removal activities associated with the Hampton Roads Bridge-Tunnel 
(HRBT) Expansion Project, Hampton-Norfolk, Virginia.

DATES: This Authorization is effective for one year from July 10, 2020 
to July 9, 2021.

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: https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act. In case of problems accessing these 
documents, please call the contact listed above.

SUPPLEMENTARY INFORMATION:

Background

    The MMPA prohibits the ``take'' of marine mammals, with certain 
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to 
allow, upon request, the incidental, but not intentional, taking of 
small numbers of marine mammals by U.S. citizens who engage in a 
specified activity (other than commercial fishing) within a specified 
geographical region if certain findings are made and either regulations 
are issued or, if the taking is limited to harassment, a notice of a 
proposed incidental take authorization may be provided to the public 
for review. Under the MMPA, ``take'' is defined as meaning to harass, 
hunt, capture, or kill, or attempt to harass, hunt, capture, or kill 
any marine mammal.
    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.

Summary of Request

    On September 18, 2019, NMFS received a request from the HRCP for an 
IHA to take marine mammals incidental to impact and vibratory pile 
driving activities associated with the HRBT, in Hampton and Norfolk, 
Virginia for one year from the date of issuance. The application was 
deemed adequate and complete on February 4, 2020. The HRCP request is 
for take of a small number of five species of marine mammals by Level A 
and B harassment. Neither the HRCP nor NMFS expects injury, serious 
injury or mortality to result from this activity and, therefore, an IHA 
is appropriate. The planned activities are part of a larger project and 
the applicant has requested rulemaking and a letter of authorization 
for the other components of this project.

Description of Specified Activity

Overview

    The HRCP is working with the Virginia Department of Transportation 
(VDOT) and Federal and state agencies to advance the design, approvals, 
and multi-year construction of the Interstate (I)-64 HRBT Expansion 
project. The overall project will widen I-64 for approximately 15.93 
kilometer (km) (9.9 miles) along I-64 from Settlers Landing Road in 
Hampton, Virginia to the I-64/I-564 interchange in Norfolk, Virginia. 
The project will create an eight-lane facility with six consistent use 
lanes. The project will include full replacement of the North and South 
Trestle Bridges, two new parallel tunnels constructed using a Tunnel 
Boring Machine (TBM), expansion of the existing portal islands, and 
widening of the Willoughby Bay Trestle Bridges, Bay Avenue Trestle 
Bridges, and Oastes Creek Trestle Bridges. Also, upland portions of I-
64 will be widened to accommodate the additional lanes, the Mallory 
Street Bridge will be replaced, and the I-64 overpass bridges will be 
improved. The planned activities below are part of the overall project 
(see the application for additional details on the overall project). 
Only the activities relevant to the IHA requested by HRCP are discussed 
below. This includes the following components:
    [ssquf] TBM Platform at the South Island;
    [ssquf] Conveyor Trestle at the South Island;
    [ssquf] Temporary trestles for jet grouting at the South Island;
    [ssquf] Temporary trestle for bridge construction at the North 
Shore;
    [ssquf] Mooring piles at the South Trestle (located at the South 
Island), North Island, and Willoughby Bay; and
    [ssquf] Installation and removal of piles for test pile program.
    Pile installation methods will include impact and vibratory 
driving, jetting, and drilling with a down-the-hole (DTH) hammer. Pile 
removal techniques for temporary piles will include vibratory pile 
removal or cutting below the mud line. Installation of steel pipe piles 
could be 24-, 36-, or 42-inches (in) in diameter to support temporary 
work trestles, platforms, and moorings. Test piles would consist of 30-
in square concrete or 54-in concrete cylinder piles. Only load test 
piles will be removed under this IHA. In-water pile installation using 
impact and vibratory driving, and drilling with a DTH hammer, and pile 
removal using a vibratory hammer, have the potential to harass marine 
mammals acoustically and could result in incidental takes of individual 
marine mammals. Jetting is not likely to result in take.

Dates and Duration

    Work could occur at any point during the year, and will occur 
during the day. Pile installation may extend into

[[Page 48154]]

evening or nighttime hours as needed to accommodate pile installation 
requirements (e.g., once pile driving begins--a pile will be driven to 
design tip elevation). The overall number of anticipated days of pile 
installation is 312, based on a 6-day work week for one year. Pile 
installation can occur at variable rates, from a few minutes to several 
hours per pile. The HRCP anticipate that 1 to 10 piles could be 
installed per day. In order to account for inefficiencies and delays, 
the HRCP have estimated an average installation rate of six piles per 
day for most components.

Specific Geographic Region

    The HRBT is located in the waterway of Hampton Roads adjacent to 
the existing bridge and island structures of the HRBT in Virginia. 
Hampton Roads is located at the confluence of the James River, the 
Elizabeth River, the Nansemond River, Willoughby Bay, and the 
Chesapeake Bay (Figure 1). Hampton Roads is a wide marine channel that 
provides access to the Port of Virginia and several other deep water 
anchorages upstream of the project area (VDOT and Federal Highway 
Administration (FHWA) 2016). Navigational channels are maintained by 
the U. S. Army Corps of Engineers within Hampton Roads to provide 
transit to the many ports in the region.
[GRAPHIC] [TIFF OMITTED] TN10AU20.000

    Pile installation will occur in waters ranging in depth from less 
than 1 meter (m) (3.3 feet (ft)) near the shore to approximately 8 m 
(28 ft), depending on the structure and location. The majority of the 
piles will be in water depths of 3.6-4.6 m (12-15 ft).

Detailed Description of the Specific Activity

    Three methods of pile installation are anticipated and expected to 
result in take of marine mammals. These include use of vibratory, 
impact, and DTH hammers. More than one installation method will be used 
within a day. Most piles will be installed using a combination of 
vibratory (ICE 416L or similar) and impact hammers (S35 or similar). 
Overall, steel pipe piles at the North Shore Work Trestle, Jet Grouting 
Trestle, and TBM Platform would be installed using the vibratory hammer 
approximately 80 percent of the time and impact hammer approximately 20 
percent of the time, while all mooring piles and steel pipe piles at 
Conveyor Trestle would be installed using the

[[Page 48155]]

vibratory hammer approximately 90 percent and the impact hammer 
approximately 10 percent of the time. Depending on the location, the 
pile will be advanced using vibratory methods and then impact driven to 
final tip elevation. Where bearing layer sediments are deep, driving 
will be conducted using an impact hammer so that the structural 
capacity of the pile embedment can be verified. The pile installation 
methods used will depend on sediment depth and conditions at each pile 
location. Table 1 provides additional information on the pile driving 
operation including estimated pile driving times. The sum of the days 
of pile installation is greater than the anticipated number of days 
because more than one pile installation method will be used within a 
day.
    Prior to installing steel pipe piles near shorelines protected with 
rock armor and/or rip rap (e.g., South Island shorelines; North Shore 
shoreline), it will be necessary to temporarily shift the rock armoring 
that protects the shoreline to an adjacent area to allow for the 
installation of the piles. The rock armor should only be encountered at 
the shoreline and at relatively shallow depths below the mudline. The 
rock armor and/or rip rap will be moved and reinstalled near its 
original location following the completion of pile installation. 
Alternatively, the piles may be installed without moving the rock, by 
first drilling through the rock with a DTH hammer (e.g., Berminghammer 
BH 80 drill or equivalent) to allow for the installation of the piles. 
It is estimated that a down-the-hole hammer will be used for 
approximately 1 to 2 hours per pile, when necessary. It is anticipated 
that approximately 5 percent of the North Shore Work Trestle piles, 10 
percent of the Jet Grouting Trestle piles, 10 percent of the Conveyor 
Trestle piles, and 50 percent of the TBM Platform piles may require use 
of a down-the-hole hammer (Table 1).
    Detailed descriptions of the project components for this IHA 
request are explained below.
Project Segments
    The project design is divided into five segments (see also Figure 
2) as follows:
     Segment 1a (Hampton) begins at the northern terminus of 
the Project in Hampton and ends at the north end of the north approach 
slabs for the north tunnel approach trestles. This segment has two 
interchanges and also includes improvements along Mallory Street to 
accommodate the bridge replacement over I-64. This segment covers 
approximately 1.2 miles along I-64;
     Segment 1b (North Trestle-Bridges) includes the new and 
replacement north tunnel approach trestles, including any approach 
slabs. This segment covers approximately 1 km (0.6 mi) along I-64;
     Segment 2a (Tunnel) includes the new bored tunnels, the 
tunnel approach structures, buildings, the North Island improvements 
for tunnel facilities, and South Island improvements. This segment 
covers approximately 2.9 km (1.8 mi) along I-64;
     Segment 3a (South Trestle-Bridge) includes the new South 
Trestle-Bridge and any bridge elements that interface with the South 
Island to the south end of the south abutments at Willoughby Spit. This 
segment covers approximately 1.93 km (1.2 mi) along I-64;
     Segment 3b (Willoughby Spit) continues from the south end 
of the south approach slabs for the south trestle and ends at the north 
end of the north approach slabs for the Willoughby Bay trestles. This 
segment includes a modified interchange connection to Bayville Street, 
and has a truck inspection station for the westbound tunnels. This 
segment covers approximately 1 km (0.6 mi) along I-64;
     Segment 3c (Willoughby Bay Trestle-Bridges) includes the 
entire structures over Willoughby Bay, from the north end of the north 
approach slabs on Willoughby Spit to the south end of south approach 
slabs near the 4th View Street interchange. This segment covers 
approximately 1.6 km (1.0 mi) along I-64;
     Segment 3d (4th View Street Interchange) continues from 
the Willoughby Trestle-Bridges south, leading to the north end of the 
north approach slabs of I-64 bridges over Mason Creek Road along 
mainline I-64. This segment covers approximately 1.6 km (1.0 mi) along 
I-64;
     Segment 4a (Norfolk-Navy) goes from the I-64 north end of 
the north approach slabs at Mason Creek Road to the north end of the 
north approach slabs at New Gate/Patrol Road. There are three 
interchange ramps in this segment: Westbound I-64 exit ramp to Bay 
Avenue, eastbound I-64 entrance ramp from Ocean Avenue, and westbound 
I-64 entrance ramp from Granby Street. The ramps in this segment are 
all on structure. This segment covers approximately 2.4 km (1.5 mi) 
along I-64; and
     Segment 5a (I-564 Interchange) starts from the north end 
of the north approach slab of the New Gate/Patrol Road Bridge to the 
southern Project Limit. This segment runs along the Navy property and 
includes an entrance ramp from Patrol Road, access ramps to and from 
the existing I-64 Express Lanes, ramps to and from I-564, and an 
eastbound I-64 entrance ramp from Little Creek Road. This segment 
covers approximately 1.93 km (1.2 mi) along I-64.

[[Page 48156]]

[GRAPHIC] [TIFF OMITTED] TN10AU20.001

    However, the only planned in-water marine construction activities 
that have potential to affect marine mammals and result in take would 
occur at the following locations in the following segments:
    [ssquf] North Trestle-Bridges (Segment 1b);
    [ssquf] Tunnel--North Island and South Island (Segment 2a);
    [ssquf] South Trestle-Bridge (Segment 3a); and
    [ssquf] Willoughby Bay Trestle-Bridges (Segment 3c).
    Approximately, 1070 piles (of all sizes) would be installed (only 
some removed) under this IHA (Table 1). For 36-in steel piles, 698 
piles would be installed. For 42-in steel piles, 257 piles would be 
installed. For 24-in piles, 66 piles would be installed. For 54-in 
concrete cylinder piles, 33 piles would be installed. For 24-in or 30-
in concrete square piles, 16 piles would be installed. Removal would 
only occur for piles as part of the test pile program (Table 1).
Project Components That Are Likely To Result in Take of Marine Mammals
    Tunnel Boring Machine (TBM) Platform at the South Island (Segment 
2a)--The HRCP is constructing the temporary TBM Platform or ``quay'' at 
the South Island to allow for the delivery, unloading, and assembly of 
the TBM components from barges to the Island. The large TBM components 
will be delivered by barge and then transferred to the platform using a 
Self-

[[Page 48157]]

Propelled Modular Transport, crawler crane, sheerleg crane and/or other 
suitable equipment. The TBM Platform will also allow barge delivery and 
storage of concrete tunnel segments as the boring operation progresses. 
The concrete tunnel segments will be offloaded and moved using a 
combination of crawler cranes and a gantry crane installed on the TBM 
Platform. The tunnel segments will be stored on the platform prior to 
delivery to the tunnel shaft for installation.
    The TBM Platform is a steel structure founded on (216) 36-in 
diameter steel piles, with an overall area of approximately 0.40 acres 
(approximately 50.6 m x 2.7 m). The piles will be installed using a 
combination of vibratory and impact hammers except along the perimeter 
where down-the-hole hammering may be needed to install piles through 
the rock armor stone. The piles are 47 m (154 ft) long and will have an 
average embedded length of approximately 42.7 m (140 ft). Table 1 
provides additional information on the pile driving operation including 
estimated pile installation times and number of strikes necessary to 
drive a pile to completion.
    The superstructure of the platform is set on top of the piles and 
consists of transverse and longitudinal beams below a 13/16-in-thick 
plate set on top of the beams. Rail beams will be installed on top of 
the plate and will support the gantry crane. A concrete slab may be 
placed on top of the steel plates or timber trusses.
    Dolphins will be installed along the shoreline of the South Island 
in the areas adjacent to the TBM Platform. Each dolphin will consist of 
36-in steel piles and will be installed with a combination of vibratory 
and impact hammers.
    Conveyor Trestle at the South Island (Segment 2a)--Tunnel boring 
spoils and other related materials will be moved between the South 
Island and barges via a conveyor belt and other equipment throughout 
tunnel boring. The Conveyor Trestle will also be used for maintenance 
and mooring of barges and vessels carrying TBM materials and other 
project related materials.
    The Conveyor Trestle is a steel structure founded on (84) 36-in 
diameter steel piles, with an overall area of approximately 0.42 acres 
(approximately 205 m x 8 m). The piles will be installed using a 
combination of vibratory (International Construction Equipment (ICE) 
416L or similar) and impact hammers (S35 or similar). The piles are 
approximately 42.7 m (140 ft) long and will have an average embedded 
length of approximately 30.5 m (100 ft). Table 1 provides additional 
information on the pile driving operation including estimated pile 
driving times and number of strikes necessary to drive a pile to 
completion.
    Additionally, mooring dolphins will be installed along the outside 
edge of the Conveyor Trestle. Each dolphin will consist of 36-in steel 
piles and will be installed with a combination of vibratory and impact 
hammers.
    Temporary Trestle for Bridge Construction at the North Shore Work 
Trestle (Segment 1b)--The temporary North Shore Work Trestle will 
support construction of the permanent eastbound North Trestle Bridge in 
the shallow water (<1.2-1.8 m (4-6 ft) MLW) closer to the North Shore, 
avoiding the need to dredge or deepen this area (which otherwise would 
have been required for barge access) and minimizing potential impacts 
to the adjacent submerged aquatic vegetation (SAV). The temporary North 
Shore Work Trestle is a steel structure founded on 194 36-in diameter 
steel piles with 9-12 m (30-40 ft) spans sized to accommodate a 300-ton 
crane. The main portion of the work trestle will be approximately 345 m 
long x 14 m wide (1,130 ft long by 45 ft wide), with three 
approximately 24.4 m x 9 m (80 ft x 30 ft) fingers and an additional 
landing area approximately 45.7 m x 14 m (150 ft x 45 ft), for a total 
overall approximate area of 0.006 km\2\ (1.49 acres).
    Dolphins will be installed at the southern end and along the 
outside edge of the work trestle. Each dolphin will consist of 24-in 
steel piles. In addition, 42-in steel pipe piles will be installed 
along the outer edge of the work trestle to provide additional single 
mooring points for barges and vessels delivering material and accessing 
the trestle. The mooring dolphin piles and the single mooring point 
piles will be installed using a vibratory hammer.
    Moorings at the North Island Expansion (Segment 2a)--Temporary 
moorings will be installed along the perimeter of the North Island 
Expansion area to support the construction of the Island expansion. 
Eighty 42-in steel pipe piles will be installed to provide mooring 
points for barges and vessels. The mooring point piles will be 
installed using a vibratory hammer.
    Temporary Trestles for Jet Grouting at the South Island (Segment 
2a)--Unconsolidated soil conditions at the western edge of the South 
Island--along the centerline and depth of the planned tunnel 
alignment--require ground improvements to allow tunnel boring to 
proceed safely and efficiently. Ground improvements will be achieved 
using deep injection or jet grouting to stabilize and consolidate the 
sediments along the planned tunnel alignment and tunnel depth.
    Two temporary work trestles will be constructed along either side 
of the planned tunnel alignment to support jet grouting activity. Each 
trestle will be approximately 12.2 m (40 ft) wide and extend 
approximately 305 m (1,000 ft) west of the South Island shoreline, for 
a total overall approximate area of 0.007 km\2\ (1.84 acres). Two 
temporary Jet Grouting Trestles will be constructed, each will be 
founded on (102) 36-in diameter steel piles (a total of 204 steel 
piles) with 7.6 m (25 ft) +/- spans sized to accommodate a 35-ton drill 
rig and support equipment.
    Moorings at the South Trestle (Segment 3a)--Temporary moorings will 
be installed in the area of the South Trestle to support the 
construction of temporary work trestles and permanent trestle bridges. 
Six mooring dolphins will be installed and each will consist of (3) 24-
in steel piles for a total of (18) 24-in piles. An additional (41) 42-
in steel pipe piles will be installed along what will become the outer 
edge of the work trestle to provide additional single mooring points 
for barges and vessels delivering material and accessing the trestle. 
The mooring dolphin piles and the single mooring point piles will be 
installed using a vibratory hammer.
    Mooring at Willoughby Bay (Segment 3c)--Temporary moorings will be 
installed in Willoughby Bay to support the construction of temporary 
work trestles and permanent trestle bridges. Six mooring dolphins will 
be installed--each consisting of (3) 24-in steel piles. An additional 
(50) 42-in steel pipe piles will be installed along what will become 
the outer edge of the work trestle to provide additional single mooring 
points for barges and vessels delivering material and accessing the 
trestle. The mooring dolphin piles and the single mooring point piles 
will be installed using a vibratory hammer. A total of 68 steel pipe 
piles will be driven, (50) 42-in piles and (18) 24-in piles.
    An additional (50) 42-in steel pipe piles will be installed in 
Willoughby Bay to create moorings for additional staging of barges and 
safe haven for vessels in the event of severe weather. The moorings 
will be configured as (2) 2,000-ft long lines with a 42-in mooring pile 
every 24.4 m (80 ft). The piles will be installed using a vibratory 
hammer.
Installation and Removal of Piles for Test Pile Program (Segments 1b, 
2a, 3a, and 3c)
    The HRCP will perform limited pile load testing to confirm 
permanent

[[Page 48158]]

concrete pile design at the start of the project. Test piles will be 
installed at the North Trestle (1 load test pile, 10 production test 
piles), South Trestle (2 load test piles, 20 production test piles) and 
at Willoughby Bay (1 load test pile, 15 production test piles)--test 
piles will be 30-in square concrete or 54-in concrete cylinder piles 
(see Table 1). Test piles will be set using temporary steel templates 
designed to support and position the test pile while being driven. 
Concrete test piles will be driven using an impact hammer. Test pile 
templates will be positioned and held in place using spuds (one at each 
corner of the template). The test pile templates and pile load test 
frame and supports will be installed using a vibratory hammer and 
proofed using an impact hammer to confirm sufficient load capacity. 
Test piles will be cut below the mudline and removed. The temporary 
test pile templates and load test frame and supports will be removed 
using a vibratory hammer.

                                   Table 1--Pile Driving and Removal Associated With the HRBT Project That Are Likely To Result in the Take of Marine Mammals
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                                                                                                       Average
                                                                                                      down-the-    Number of     Average    Approximate   Number of     Estimated
                                       Pile size)/ type and      Total      Embedment    Number of       hole        piles      vibratory    number of    piles per   total number    Number of
          Project component                  material          number of      length    piles down-    duration    vibrated/     duration      impact      day per     of hours of     days of
                                                                 piles        (feet)      the-hole     per pile     hammered     per pile   strikes per     hammer    installation  installation
                                                                                                      (minutes)                 (minutes)       pile
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                                                                                   North Trestle (Segment 1b)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
North Shore Work Trestle............  36-in Steel Pipe......          194          100           10          120          184           50           40            3           162            65
Moorings............................  42-in Steel Pipe......           36           60  ...........  ...........           36           30  ...........            6            18             6
Moorings............................  24-in Steel Pipe......           30           60  ...........  ...........           30           30  ...........            6            15             5
Test Pile Program (Load Test Piles).  54-in Concrete                    1          140  ...........  ...........            1  ...........        2,100            1             2             1
                                       Cylinder Pipe.
Test Pile Program (Production Piles)  54-in Concrete                   10          140  ...........  ...........           10  ...........        2,100            1            20            10
                                       Cylinder Pipe.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                    North Island (Segment 2a)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Moorings............................  42-in Steel Pipe......           80           60  ...........  ...........           80           30  ...........            6            40            13
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                   Willoughby Bay (Segment 3c)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Moorings............................  42-in Steel Pipe......           50           60  ...........  ...........           50           30  ...........            6            25             9
Moorings............................  24-in Steel Pipe......           18           60  ...........  ...........           18           30  ...........            6             9             3
Moorings (Safe Haven)...............  42-in Steel Pipe......           50           60  ...........  ...........           50           30  ...........            6            25             9
Test Pile Program (Load Test Piles).  24-in or 30-in                    1          140  ...........  ...........            1  ...........        2,100            1             2             1
                                       Concrete Square Pipe.
Test Pile Program (Production Piles)  24-in or 30-in                   15          140  ...........  ...........           15  ...........        2,100            1            30            15
                                       Concrete Square Pipe.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                   South Trestle (Segment 3a)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Moorings............................  42-in Steel Pipe......           41           60  ...........  ...........           41           30  ...........            6            21             7
Moorings............................  24-in Steel Pipe......           18           60  ...........  ...........           18           30  ...........            6             9             3
Test Pile Program (Load Test Piles).  54-in Concrete                    2          140  ...........  ...........            2  ...........        2,100            1             4             2
                                       Cylinder Pipe.
Test Pile Program (Production Piles)  54-in Concrete                   20          140  ...........  ...........           20  ...........        2,100            1            40            20
                                       Cylinder Pipe.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                    South Island (Segment 2a)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TBM Platform........................  36-in Steel Pipe......          216          140          108          120          108           60           60            2           216           108
Jet Grouting Trestle................  36-in Steel Pipe......          204          100           20          120          184           50           40            3           170            68
Conveyor Trestle....................  36-in Steel Pipe......           84          100            8          120           76           50           40            3            70            28
                                     -----------------------------------------------------------------------------------------------------------------------------------------------------------
    Total...........................  ......................        1,070  ...........  ...........  ...........  ...........  ...........  ...........  ...........  ............  ............
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    Planned in-water marine construction activities that have potential 
to affect marine mammals will occur at the following locations in 
Construction Areas 2 and 3 (Figure 2):
    [ssquf] North Trestle-Bridges (Segment 1b);
    [ssquf] Tunnel--North Island and South Island (Segment 2a);
    [ssquf] South Trestle-Bridge (Segment 3a); and
    [ssquf] Willoughby Bay Trestle-Bridges (Segment 3c).
    Mitigation, monitoring, and reporting measures are described in 
detail later in this document (please see Mitigation and Monitoring and 
Reporting section).
    A detailed description of the planned project is provided in the 
Federal Register notice for the proposed IHA (85 FR 16194; March 20, 
2020). Since that time, no changes have been made to the planned 
construction activities. Therefore, a detailed description is not 
provided here. Please refer to that Federal Register notice for the 
description of the specific activity.

Comments and Responses

    A notice of NMFS's proposal to issue an IHA to HRCP was published 
in the Federal Register on March 20, 2020 (85 FR 16194). That notice 
described, in detail, the project activity, the marine mammal species 
that may be affected by the activity, and the anticipated effects on 
marine mammals. During the 30-day public comment period, NMFS received 
comments from the Marine Mammal Commission (Commission). The 
Commission's letter is available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities. Please see the letter for 
full details of the recommendations and associated rationale.
    Comment: The Commission commented that NMFS used incorrect proxy 
source levels for impact installation of 30- and 54-in concrete piles 
based on MacGillivray et al. (2007) and therefore underestimated the 
various Level A and B harassment zones noted in Tables 11 and 12 of the 
Federal Register notice of proposed IHA and Tables 2 and 3 in the draft 
authorization. The Commission said that NMFS omitted the fact that 
source levels for impact installation of 36-in

[[Page 48159]]

concrete piles were used as a proxy for the 30- and 54-in concrete 
piles in the Federal Register notice (85 FR 16194; March 20, 2020).
    Response: NMFS revised the source levels for 30- and 54-in concrete 
piles to 193 dB SPLpeak (peak sound pressure level), 187 dB SPLrms 
(sound pressure level, root mean square), and 177 decibels (dB) SEL 
(sound exposure level) and therefore revised the Level A and Level B 
harassment zones accordingly. However, the source level of 36-in 
concrete piles were not used as a proxy for the 30- and 54-in concrete 
piles.
    Comment: The Commission stated that NMFS incorrectly noted that the 
source levels for unattenuated and attenuated impact installation of 
36-in piles originated from Chesapeake Tunnel Joint Venture (CTJV; 
2018) and Department of the Navy (2015) rather than California 
Department of Transportation (Caltrans; 2015) in Table 5 of the Federal 
Register notice (85 FR 16194; March 20, 2020).
    Response: NMFS recognizes this error and has made the correction in 
this notice.
    Comment: The Commission commented that NMFS indicated that three or 
more hammers could be used simultaneously in the proposed IHA (85 FR 
16194; March 20, 2020), but did not specify what the resulting source 
levels would be if up to four vibratory hammers were used, what the 
Level B harassment zone would be for the combined source level when 
four hammers are used, whether multiple hammers of the same type would 
be used at a given site, or what the worst-case scenario would be. The 
Commission stated that extents of the Level B harassment zones, similar 
to Table 3 in the draft authorization, must be specified to ensure the 
appropriate zones are used to extrapolate the number of Level B 
harassment takes during simultaneous use of vibratory hammers, 
particularly since the monitoring zones are much smaller than the Level 
B harassment zones.
    Response: NMFS did provide the worst-case scenarios for when 
multiple vibratory hammers (3) are used for 42-in steel piles. This was 
described in Table 7 and 11. Table 11 assumes the max number of 42-in 
steel piles that could be driven in a given day by multiple impact 
hammers for two scenarios, three piles or two piles driven 
simultaneously. It is not anticipated that four hammers would be used 
simultaneously so the wording ``or more'' was an error and has been 
omitted from the final notice. NMFS did not provide what the resulting 
source levels would be for four hammers as the applicant indicated 
three would be the maximum used. Therefore, no changes were made in 
Table 13 for the calculated distances for Level B harassment in this 
notice or Table 3 of the final IHA.
    Comment: The Commission recommended using 162 rather than 161 dB re 
1 [mu]Pa rms (1 micro Pascal, root mean square) at 10 m for vibratory 
installation of 24-in piles and to re-estimate the Level A and B 
harassment zones accordingly.
    Response: NMFS believes that 161 dB re 1 [mu]Pa rms remains 
appropriate for use in this circumstance and does not adopt the 
recommendation to re-estimate the Level A and B harassment zones. The 
source level is within 2 dB of the Commission's recommended 
source level.
    Comment: The Commission recommends that NMFS (1) have its experts 
in underwater acoustics and bioacoustics review and finalize in the 
next month its recommended proxy source levels for impact pile driving 
of the various pile types and sizes, (2) compile and analyze the source 
level data for vibratory pile driving of the various pile types and 
sizes in the near term, and (3) ensure action proponents use consistent 
and appropriate proxy source levels in all future rulemakings and 
proposed IHA. If a subset of source level data is currently available 
(i.e., vibratory pile driving of 24-in steel piles), those data should 
be reviewed immediately.
    Response: NMFS concurs with this recommendation and has prioritized 
this effort. NMFS will conclude the process as soon as possible.
    Comment: The Commission recommends that, for all authorizations 
involving DTH drilling including HRCP's final IHA and proposed 
rulemaking, NMFS use (1) source level data from Denes et al. (2019), 
the Level A harassment thresholds for impulsive sources, and the 
relevant expected operating parameters to estimate the extents of the 
Level A harassment zones and (2) source level data from Denes et al. 
(2016) and its Level B harassment threshold of 120-dB re 1 [mu]Pa rms 
for continuous sources to estimate the extents of the Level B 
harassment zones. If NMFS does not revise the Level B harassment zones 
based on a more appropriate proxy source level and the Level B 
harassment thresholds for continuous sources, the Commission recommends 
that NMFS justify its decision not consider a DTH hammer to be an 
impulsive, continuous sound source.
    Response: NMFS did use the source level data from Denes et al. 
(2019) and its Level A harassment thresholds for impulsive sources, and 
the relevant expected operating parameters to estimate the extents of 
the Level A harassment zones for DTH drilling in the proposed IHA (85 
FR 16194; March 20, 2020). For the calculation of the Level B 
harassment zone, NMFS concurs with the recommendation for this IHA and 
made the change using the threshold of 120-dB re 1 [mu]Pa rms for 
continuous sources to estimate the extents of the Level B harassment 
zones using source level data from Denes et al. (2016). However, NMFS 
does not agree that using Denes et al., 2019 as a source level is 
necessarily appropriate for ``all authorizations'' and will evaluate 
the best source level to use based on the operational details of future 
projects and the source level data available at that time.
    Comment: The Commission commented on the assumptions used by NMFS 
regarding the efficacy of bubble curtains and NMFS adoption of a 
standard 7 dB source level reduction when bubble curtains are use. The 
Commission recommends that NMFS (1) consult with acousticians, 
including those at University of Washington, Applied Physics Lab, 
regarding the appropriate source level reduction factor to use to 
minimize near-field (<100 m) and far-field (>100 m) effects on marine 
mammals or (2) use the data NMFS has compiled regarding source level 
reductions at 10 m for near-field effects and assume no source level 
reduction for far-field effects for all relevant incidental take 
authorizations. The Commission has made this recommendation, with 
supporting justification and responses to NMFS's previous responses, 
since mid-December 2019--NMFS has yet to address it. NMFS has directed 
the Commission to NMFS's response from before the Commission made this 
specific recommendation and to a Federal Register notice that does not 
even pertain to NMFS. The Commission explicitly requests a detailed 
response to both parts of this recommendation if NMFS does not follow 
or adopt it, as required under section 202(d) of the MMPA.
    Response: NMFS disagrees with the Commission regarding this issue, 
and does not adopt the recommendation. The Commission has raised this 
concern before and NMFS refers readers to our full response, which may 
be found in a previous notice of issuance of an IHA (84 FR 64833, 
November 25, 2019). NMFS will additionally provide a detailed 
explanation of its decision

[[Page 48160]]

within 120 days, as required by section 202(d) of the MMPA.
    Comment: The Commission recommends that NMFS require HRCP to (1) 
conduct hydroacoustic monitoring (a) during impact installation of 54-
in concrete piles, (b) when multiple vibratory hammers are used 
simultaneously and multiple DTH hammers are used simultaneously, (c) 
when only one DTH hammer is used, and (d) when 36-in steel piles are 
installed both with and without the bubble curtain, (2) ensure that 
signal processing is conducted appropriately 28 for DTH drilling, and 
(3) adjust the Level A and B harassment zones accordingly.
    Response: The Commission states that it is ``apparent'' that HRCP 
``should be'' conducting hydroacoustic monitoring, but fails to justify 
the necessity of this recommended requirement, and does not address the 
practicability of such a requirement. The Commission's recommendation 
is based on the fact that source levels for 36-in piles are used as a 
proxy for 54-in piles, as well as the following assertions: (1) Source 
levels for DTH drilling have yet to be analyzed appropriately and (2) 
the presumed 7-dB source level reduction associated with use of a 
bubble curtain has yet to be proven. In addition, the Commission states 
that the extents of the Level B harassment zones ``have not been 
substantiated.'' NMFS disagrees with these points and does not adopt 
the recommendation. It is common practice to use the best available 
proxy data when data are not available for a particular pile type or 
size and, while additional data may be useful, the use of a proxy does 
not alone justify a requirement to conduct hydroacoustic monitoring. 
Moreover, the Commission's assumption that source levels are 
underestimated does not ultimately lead to a conclusion that the 
evaluation of potential effects is similarly underestimated, given the 
simple and conservative assumptions made in relation to expected 
transmission loss. The source levels for DTH drilling are provided 
through a hydroacoustic monitoring study for a similar project at a 
nearby location. The Commission does not further explain its reasoning 
on this point. The assumed 7-dB source level reduction attributed to 
use of the bubble curtain was developed as a generic standard through 
review of a large amount of data relating to use of bubble curtains 
and, therefore, the Commission's suggestion that this reduction ``has 
yet to be proven'' is incorrect. Further, the suggestion to conduct 
this type of testing is inconsistent with the Commission's own 
insistence that no reduction should be applied in any circumstances. 
Finally, the suggestion that the size of the Level B harassment zones 
has ``yet to be substantiated'' is nonsensical, as the project has yet 
to begin, and is inconsistent with typical practice. The vast majority 
of projects proceed with assumptions regarding zone size, and the 
Commission does not adequately explain why the cost and logistical 
considerations associated with hydroacoustic monitoring are warranted 
in this case to ``substantiate'' the zone sizes.
    The Commission points out that the HRCP plans to conduct more than 
5 years of activities. This IHA only pertains to one year of those 
activities. The applicant has requested a rulemaking/Letter of 
Authorization for another 5 years of work to complete the overall 
project. NMFS will consider the potential need for hydroacoustic 
monitoring with the applicant as part of the rulemaking/Letter of 
Authorization process.
    Comment: The Commission noted its understanding that NMFS has 
formed an internal committee to address perceived issues with 
estimating Level A harassment zone sizes and is consulting with 
external acousticians and modelers as well. In the absence of relevant 
recovery time data for marine mammals, the Commission continues to 
believe that animat modeling that considers various operational and 
animal scenarios should be used to inform the appropriate accumulation 
time and could be incorporated into NMFS's user spreadsheet that 
currently estimates the Level A harassment zones. The Commission 
recommends that NMFS continue to make this issue a priority to resolve 
in the near future and consider incorporating animat modeling into its 
user spreadsheet.
    Response: NMFS concurs with this recommendation and has prioritized 
the issue.
    Comment: The Commission recommends that NMFS increase the number of 
takes from 261 to at least 3,588 takes of harbor seals, equating to at 
least 753 Level A harassment and 2,835 Level B harassment takes of 
harbor seals.
    Response: NMFS disagrees with the Commission's recommendation and 
does not adopt it. In the proposed IHA, NMFS proposed 55 takes by Level 
A harassment and 206 takes by Level B harassment. During the comment 
period, NMFS informally discussed with the Commission increasing harbor 
seals takes using 8 seals/day multiplied by 156 days for a total of 
1,248 takes. The Commission did not indicate any opposition to this new 
estimate. That said, NMFS has determined that it will use the average 
5-year daily count of 13.6 seals (Jones et al., 2020) in its take 
estimate to be more conservative than the proposed IHA as fully 
described in the Estimated Take section.
    Comment: The Commission recommends that NMFS use the Chesapeake Bay 
density of 1.38 dolphins/square kilometer (km\2\) from Engelhaupt et 
al. (2016) and (1) the Level B harassment ensonified area of 131.4 
km\2\ west of the HRBT and 312 days of activities, (2) the Level B 
harassment ensonified area of 221.46 km\2\ for vibratory installation 
of 42-in steel piles at the South Trestle and 7 days of activities, (3) 
the Level B harassment ensonified area associated of 27.65 km\2\ for 
vibratory installation of 24-in steel piles at the South Trestle and 3 
days of activities, and (4) the Level B harassment ensonified area 
associated of 0.87 km\2\ for impact installation of 54-in concrete 
piles at the South Trestle and 22 days of activities to increase the 
numbers of Level B harassment takes of bottlenose dolphins from 6,343 
to 58,856.
    Response: NMFS has accepted the Commission's recommendation and 
will use the dolphin density of 1.38 dolphins/km\2\ from Engelhaupt et 
al. (2016) to estimate take of bottlenose dolphins as described in the 
Estimated Take section. However, NMFS notes the Commission's statement 
that the use of bottlenose dolphin data in the notice of proposed IHA 
``appears to be an attempt to reduce the number of takes rather than an 
effort to use the best available data.'' The Commission's statement is 
both inappropriate and incorrect, and NMFS strongly objects to the 
Commission's attempt to interpret intent.
    Comment: The Commission recommends that NMFS ensure HRCP keeps a 
running tally of the total takes, based on observed and extrapolated 
takes, for Level A and B harassment.
    Response: We agree that HRCP must ensure they do not exceed 
authorized takes, but do not concur with the recommendation. NMFS is 
not responsible for ensuring that HRCP does not operate in violation of 
an issued IHA.
    Comment: The Commission recommends that NMFS require HRCP to use at 
least (1) one protected species observer (PSO) to monitor the shut-down 
zones for each hammer that is in use at each site, (2) one PSO to 
monitor the Level B harassment zones during vibratory installation of 
piles at Willoughby Bay and to be located near the entrance of the Bay 
to observe

[[Page 48161]]

animals entering and exiting the Level B harassment zone, (3) one PSO 
to monitor the Level A and B harassment zones during impact 
installation of 30- and 54-in piles at North and South Trestle, (4) 
three PSOs to monitor the Level B harassment zones during vibratory 
pile driving of 24-in piles at South Trestle, one PSO on the Hampton 
side and one on the Norfolk side of Chesapeake Bay to the east of HRBT 
and one PSO on the Hampton side to the west of HRBT, (5) four PSOs to 
monitor the Level B harassment zones during vibratory pile driving of 
42-in piles at South Trestle, one on the Hampton side and one on the 
Norfolk side of Chesapeake Bay to the east of HRBT and one on the 
Hampton side and one on the Norfolk side to the west of HRBT, and (6) 
four PSOs to monitor the Level B harassment zones during vibratory pile 
driving and/or DTH drilling of 36- and 42-in piles and during 
simultaneous use of multiple hammers at North Trestle, North Island, 
and South Island, two on the Hampton side and two on the Norfolk side 
to the west of HRBT.
    Response: NMFS appreciates the Commission's recommendations for PSO 
locations. As previously described in the proposed IHA, monitoring 
locations will provide an unobstructed view of all water within the 
shutdown zone and as much of the Level B harassment zone as possible 
for pile driving activities. However, after further discussion with the 
applicant, HRCP will station between one and four PSOs at locations 
offering the best available views of the Level A and Level B monitoring 
zones during in-water pile driving at the North Trestle, North Island, 
South Trestle, and South Island. When and where able, as determined by 
the PSO or Lead PSO when multiple observers are required, Level A and 
Level B harassment zones may be monitored for multiple pile driving 
locations by the same individual PSO. HRCP will be required to station 
between one and two PSOs at locations offering the best available views 
of the Level A and Level B monitoring zones during in-water pile 
driving at Willoughby Bay.
    Comment: The Commission recommends that NMFS include in (1) section 
3 of the final authorization the requirement that HRCP conduct pile-
driving activities during daylight hours only and (2) section 4 of the 
final authorization the requirement that, if the entire shut-down 
zone(s) is not visible due to fog or heavy rain, HRCP delay or cease 
pile-driving and -removal activities until the zone(s) is visible.
    Response: NMFS does not concur and does not adopt the 
recommendation. The work is anticipated to be conducted during daylight 
hours. However, if work needs to extend into the night, work may only 
be conducted under conditions where there is full visibility of the 
shutdown zone or where stopping ongoing work would otherwise create an 
unsafe work condition. In addition, the IHA requires that work must be 
conducted during conditions of good visibility. If poor environmental 
conditions restrict full visibility of the shutdown zone, pile 
installation must be delayed. Poor visibility implies a condition that 
would occur under fog or heavy rain.
    Comment: The Commission recommends that NMFS include in all draft 
and final IHA the explicit requirements to cease activities if a marine 
mammal is injured or killed during the specified activities until NMFS 
reviews the circumstances involving any injury or death that is likely 
attributable to the activities and determines what additional measures 
are necessary to minimize additional injuries or deaths.
    Response: NMFS concurs with the Commission's recommendation as it 
relates to this IHA and has added the referenced language to the 
Monitoring and Reporting section of this notice and the Reporting 
section of the issued IHA. We will continue to evaluate inclusion of 
this language in future IHAs.
    Comment: The Commission reiterates programmatic recommendations 
regarding NMFS' potential use of the renewal mechanism for one-year 
IHAs.
    Response: NMFS does not agree with the Commission and, therefore, 
does not adopt the Commission's recommendation. NMFS will provide a 
detailed explanation of its decision within 120 days, as required by 
section 202(d) of the MMPA.
    Comment: The Commission recommends that NMFS (1) publish a revised 
proposed authorization for public comment, (2) consult with HRCP 
regarding the numerous issues raised in this letter and direct the 
applicant to revise its letter of authorization application 
accordingly, and (3) refrain from publishing for public comment 
proposed IHAs and proposed rules based on underlying applications that 
contain omissions, errors, and inconsistencies and instead return such 
applications to action proponents as incomplete.
    Response: NMFS does not agree with the Commission and does not 
adopt the recommendation. NMFS disagrees that the information presented 
in association with the proposed IHA was insufficient to facilitate 
public review and comment, as the Commission states. What the 
Commission claims are ``omissions, errors, and inconsistencies'' are, 
for the most part, differences of opinion on how available data should 
be applied to our analysis and, in each case, we have presented reasons 
why we disagree with specific recommendations. If we did agree that 
there actually was an error or that the Commission's logic is more 
appropriate to implement, we have made the recommended changes. We note 
many of the recommendations by the Commission are detail-oriented and, 
in NMFS' view, do not provide additional conservation value or 
meaningfully influence any of the analyses underlying the necessary 
findings. NMFS strongly disagrees with the Commission's suggestion that 
NMFS' negligible impact and least practicable adverse impact 
determinations may be invalid, and we note that the Commission does not 
provide any information supporting this comment, whether NMFS retained 
the take numbers and mitigation requirements from the proposed IHA or 
adopted those recommended by the Commission. Overall, there are no 
substantial changes or new information that would lead us to reach any 
other conclusions regarding the impact to marine mammals. For these 
reasons, NMFS is not republishing a notice of proposed IHA.

Changes From the Proposed IHA to the Final IHA

    Changes were made to the source level for 30- and 54-in concrete 
piles during impact pile driving. Therefore, Level A and Level B 
harassment zones were recalculated and corrected in Tables 11 and 12 
and in the final authorization. The Level B harassment zone was also 
recalculated for DTH drilling for 36-in piles, reflecting use of the 
continuous noise, 120-dB threshold. Appropriate corrections were made 
to Table 12 and in the final authorization. Changes to the estimated 
take numbers for harbor seals and bottlenose dolphins were made, as 
recommended by the Commission. For mitigation and monitoring, 
clarification of the timing of the work as well as PSO locations were 
also made.

Description of Marine Mammals in the Area of Specified Activities

    Sections 3 and 4 of the application summarize available information 
regarding status and trends, distribution and habitat preferences, and 
behavior and life history, of the potentially affected species. 
Additional information regarding population trends and threats may be 
found in NMFS's Stock Assessment Reports (SARs; https://

[[Page 48162]]

www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-
stock-assessments) and more general information about these species 
(e.g., physical and behavioral descriptions) may be found on NMFS's 
website (https://www.fisheries.noaa.gov/find-species).
    Table 2 lists all species or stocks for which take is expected and 
authorized for this action, 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, we 
follow Committee on Taxonomy (2019). PBR is defined by the MMPA as the 
maximum number of animals, not including natural mortalities, that may 
be removed from a marine mammal stock while allowing that stock to 
reach or maintain its optimum sustainable population (as described in 
NMFS's SARs). While no mortality is anticipated or authorized here, PBR 
and annual serious injury and mortality from anthropogenic sources are 
included here as gross indicators of the status of the species and 
other threats.
    Marine mammal abundance estimates presented in this document 
represent the total number of individuals that make up a given stock or 
the total number estimated within a particular study or survey area. 
NMFS's stock abundance estimates for most species represent the total 
estimate of individuals within the geographic area, if known, that 
comprises that stock. For some species, this geographic area may extend 
beyond U.S. waters. All managed stocks in this region are assessed in 
NMFS's United States Atlantic and Gulf of Mexico Marine Mammal SARs. 
All values presented in Table 2 are the most recent available at the 
time of publication and are available in the draft 2019 SARs (https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports).

                                          Table 2--Marine Mammal Species Likely To Occur Near the Project Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                             Stock abundance  (CV,
             Common name                  Scientific name               Stock           ESA/MMPA  status;      Nmin, most recent       PBR     Annual M/
                                                                                       strategic (Y/N) \1\   abundance survey) \2\               SI \3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                          Order Cetartiodactyla--Cetacea--Superfamily Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Balaenopteridae (rorquals):
    Humpback whale \4\..............  Megaptera novaeangliae.  Gulf of Maine.........  -,-; N               896 (.42; 896; 2012)..       14.6        9.7
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                            Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Delphinidae:
    Bottlenose dolphin..............  Tursiops spp...........  Western North Atlantic  -,-; Y               6,639 (0.41; 4,759;            48   6.1-13.2
                                                                (WNA) Coastal,                               2011).
                                                                Northern Migratory.
                                                               WNA Coastal, Southern   -,-; Y               3,751 (0.06; 2,353;            23     0-14.3
                                                                Migratory.                                   2011).
                                                               Northern North          -,-; Y               823 (0.06; 782; 2013).        7.8   0.8-18.2
                                                                Carolina Estuarine
                                                                System (NNCES).
Family Phocoenidae (porpoises):
    Harbor porpoise.................  Phocoena phocoena......  Gulf of Maine/Bay of    -, -; N              79,833 (0.32; 61,415;         706        256
                                                                Fundy.                                       2011).
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Order Carnivora--Superfamily Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Phocidae (earless seals):
    Harbor seal.....................  Phoca vitulina.........  WNA...................  -; N                 75,834 (0.1; 66,884,        2,006        345
                                                                                                             2012).
    Gray seal.......................  Halichoerus grypus.....  WNA...................  -; N                 27,131 (0.19, 23,158,       1,359      5,688
                                                                                                             2016).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed
  under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality
  exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
  under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\2\ NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.
\3\ These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g.,
  commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV
  associated with estimated mortality due to commercial fisheries is presented in some cases.
\4\ 2018 U.S. Atlantic SAR for the Gulf of Maine feeding population lists a current abundance estimate of 896 individuals. However, we note that the
  estimate is defined on the basis of feeding location alone (i.e., Gulf of Maine) and is therefore likely an underestimate.

    As indicated above, all five species (with seven managed stocks) in 
Table 2, temporally and spatially co-occur with the activity to the 
degree that take is reasonably likely to occur, and therefore 
authorized. All species that could potentially occur in the planned 
project area are included in Table 3-1 of the application. While North 
Atlantic right whales (Eubalaena glacialis), minke whales (Balaenoptera 
acutorostrata acutorostrata), and fin whales (Balaenoptera physalus) 
have been documented in the area, the temporal and/or spatial 
occurrence of these whales is such that take is not expected to occur, 
and they are not discussed further. Detailed descriptions of marine 
mammals in the project area were provided in the Federal Register 
notice for the proposed IHA (85 FR 16194; March 20, 2020).

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

[[Page 48163]]

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 dB 
threshold from the normalized composite audiograms, with the exception 
for lower limits for low-frequency cetaceans where the lower bound was 
deemed to be biologically implausible and the lower bound from Southall 
et al. (2007) retained. Marine mammal hearing groups and their 
associated hearing ranges are provided in Table 3.

                  Table 3--Marine Mammal Hearing Groups
                              [NMFS, 2018]
------------------------------------------------------------------------
               Hearing group                 Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen         7 Hz to 35 kHz.
 whales).
Mid-frequency (MF) cetaceans (dolphins,      150 Hz to 160 kHz.
 toothed whales, beaked whales, bottlenose
 whales).
High-frequency (HF) cetaceans (true          275 Hz to 160 kHz.
 porpoises, Kogia, river dolphins,
 cephalorhynchid, Lagenorhynchus cruciger &
 L. australis).
Phocid pinnipeds (PW) (underwater) (true     50 Hz to 86 kHz.
 seals).
Otariid pinnipeds (OW) (underwater) (sea     60 Hz to 39 kHz.
 lions and fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
  composite (i.e., all species within the group), where individual
  species' hearing ranges are typically not as broad. Generalized
  hearing range chosen based on ~65 dB threshold from normalized
  composite audiogram, with the exception for lower limits for LF
  cetaceans (Southall et al. 2007) and PW pinniped (approximation).

    The pinniped functional hearing group was modified from Southall et 
al. (2007) on the basis of data indicating that phocid species have 
consistently demonstrated an extended frequency range of hearing 
compared to otariids, especially in the higher frequency range 
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth 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 (three cetacean and two phocid pinniped) 
have the reasonable potential to co-occur with the planned survey 
activities. Please refer to Table 2. Of the cetacean species that may 
be present, one is classified as low-frequency (humpback whale), one is 
classified as mid-frequency (bottlenose dolphin) and one is classified 
as high-frequency (harbor porpoise).

Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat

    The effects from underwater noise from the planned pile driving and 
removal activities have the potential to result in Level A and Level B 
harassment of marine mammals in the vicinity of the project area. The 
Federal Register notice for the proposed IHA (85 FR 16194; March 20, 
2020) included a discussion of the effects of anthropogenic noise on 
marine mammals and their habitat, therefore that information is not 
repeated here; please refer to that Federal Register notice (85 FR 
16194; March 20, 2020) for that information.

Estimated Take

    This section provides an estimate of the number of incidental takes 
authorized through this IHA, which will inform both NMFS' consideration 
of ``small numbers'' and the negligible impact determinations.
    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).
    Take of marine mammals incidental to HRCP's pile driving and 
removal activities could occur by Level A and Level B harassment, as 
pile driving has the potential to result in disruption of behavioral 
patterns for individual marine mammals. The planned mitigation and 
monitoring measures are expected to minimize the severity of such 
taking to the extent practicable. As described previously, no mortality 
is anticipated or authorized 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) 
and the number of days of activities. We note that while these basic 
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 authorized take 
estimates for the IHA.

Acoustic Thresholds

    Using the best available science, NMFS has developed 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 
permanent threshold shift (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

[[Page 48164]]

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 non-explosive 
impulsive (e.g., impact pile driving seismic airguns) or intermittent 
(e.g., scientific sonar) sources. The planned activities include the 
use of continuous, non-impulsive (vibratory pile driving) and impulsive 
(impact pile driving) sources and therefore, the 120 and 160 dB re 1 
[mu]Pa (rms) are applicable. The DTH hammer is considered a continuous 
noise source for purposes of evaluating potential behavioral impacts.
    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 by:
    [ssquf] Dividing sound sources into two groups (i.e., impulsive and 
non- impulsive) based on their potential to affect hearing sensitivity;
    [ssquf] 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 accounts for duration of exposure); and
    [ssquf] Dividing marine mammals into hearing groups and developing 
auditory weighting functions based on the science supporting 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 4 below. The 
references, analysis, and methodology used in the development of the 
thresholds are described in NMFS 2018 Technical Guidance, which may be 
accessed at https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technicalguidance. The planned 
activity includes the use of impulsive (impact pile driving) and non-
impulsive (vibratory pile driving) sources. The DTH hammer is 
considered an impulsive noise source for purposes of evaluating 
potential auditory impacts.

                     Table 4--Thresholds Identifying the Onset of Permanent Threshold Shift
----------------------------------------------------------------------------------------------------------------
                                                    PTS onset acoustic thresholds *  (received level)
             Hearing group              ------------------------------------------------------------------------
                                                  Impulsive                         Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans...........  Cell 1: Lpk,flat: 219 dB;   Cell 2: LE,LF,24h: 199 dB.
                                          LE,LF,24h: 183 dB.
Mid-Frequency (MF) Cetaceans...........  Cell 3: Lpk,flat: 230 dB;   Cell 4: LE,MF,24h: 198 dB.
                                          LE,MF,24h: 185 dB.
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.
Otariid Pinnipeds (OW) (Underwater)....  Cell 9: Lpk,flat: 232 dB;   Cell 10: LE,OW,24h: 219 dB.
                                          LE,OW,24h: 203 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for
  calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level
  thresholds associated with impulsive sounds, these thresholds should also be considered.
Note: Peak sound pressure (Lpk) has a reference value of 1 [micro]Pa, and cumulative sound exposure level (LE)
  has a reference value of 1[micro]Pa\2\s. In this Table, thresholds are abbreviated to reflect American
  National Standards Institute standards (ANSI 2013). However, peak sound pressure is defined by ANSI as
  incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript
  ``flat'' is being included to indicate peak sound pressure should be flat weighted or unweighted within the
  generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates
  the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW 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 and transmission loss 
coefficient.
Sound Propagation
    Transmission loss (TL) is the decrease in acoustic intensity as an 
acoustic pressure wave propagates out from a source. TL parameters vary 
with frequency, temperature, sea conditions, current, source and 
receiver depth, water depth, water chemistry, and bottom composition 
and topography. The general formula for underwater TL is:

TL = B * log10(R1/R2),

Where:

B = transmission loss coefficient (assumed to be 15)
R1 = the distance of the modeled SPL from the driven 
pile, and
R2 = the distance from the driven pile of the initial 
measurement.

    This formula neglects loss due to scattering and absorption, which 
is assumed to be zero here. The degree to which underwater sound 
propagates away from a sound source is dependent on a variety of 
factors, most notably the water bathymetry and presence or absence of 
reflective or absorptive conditions including in-water structures and 
sediments. Spherical spreading occurs in a perfectly unobstructed 
(free-field) environment not limited by depth or water surface, 
resulting in a 6 dB reduction in sound level for each doubling of 
distance from the source (20*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 
loss (4.5 dB reduction in sound level for each doubling of distance). 
Practical spreading is a compromise that is often

[[Page 48165]]

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.
Sound Source Levels
    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 source level 
measurements available for certain pile types and sizes from the 
similar environments recorded from underwater pile driving projects 
(e.g., Caltrans 2015) that were used to determine reasonable sound 
source levels likely result from the HRCP's pile driving and removal 
activities (Table 5). Bubble curtains will be used during impact pile 
driving of 36-in steel piles at the Jet Grouting Trestle in water 
depths greater than 6 m (20 ft). Therefore, a 7dB reduction of the 
sound source level will be implemented (Table 5).

                            Table 5--Predicted Sound Source Levels for All Pile Types
----------------------------------------------------------------------------------------------------------------
         Method and pile type                   Sound source level at 10 meters
---------------------------------------------------------------------------------------          Source
           Vibratory hammer                                 dB rms
----------------------------------------------------------------------------------------------------------------
42-in steel pile......................                                        \a\ 168   City and Borough of
                                                                                         Sitka Department of
                                                                                         Public Works 2017.
36-in steel pile......................                                        \b\ 167   DoN 2015.
24-in steel pile......................                                         \c\161   DoN 2015.
----------------------------------------------------------------------------------------------------------------


 
        Down-the-hole hammer               dB rms           dB SEL          dB peak
----------------------------------------------------------------------------------------------------------------
All pile sizes......................             180              164              190   Denes et al., 2019.
----------------------------------------------------------------------------------------------------------------


 
            Impact hammer                  dB rms           dB SEL          dB peak
----------------------------------------------------------------------------------------------------------------
36-in steel pile....................             193              183              210   Caltrans, 2015.
36-in steel pile, attenuated *......             186              176              203   Caltrans, 2015.
54-in concrete cylinder pile........             187              177              193   MacGillivray et al.,
                                                                                          2007.
30-in concrete square pile..........             187              177              193   MacGillivray et al.,
                                                                                          2007.
24-in concrete square pile..........             176              166              188   Caltrans, 2015.
----------------------------------------------------------------------------------------------------------------
SEL = sound exposure level; dB peak = peak sound level; rms = root mean square; DoN = Department of the Navy.
* Sound source levels (SSLs) are a 7 dB reduction for the usage of a bubble curtain.
\a\ The SPL rms value of 168 dB is within 2 dB of Caltrans (2015) at 170 dB rms for 42-in piles.
\b\ The SPL rms value of 167 is within 3 dB of Caltrans (2015) at 170 dB rms; however, the DoN (2015)
  incorporates a larger dataset and is better suited to this project.
\c\ There is no Caltrans (2015) data available for this pile size. Caltrans is 155 dB rms for 12-in pipe pile or
  170 dB rms for 36-in steel piles. The value of 161 dB rms has been also used in previous IHAs (e.g., 82 FR
  31400, July 6, 2017; 83 FR 12152, March 20, 2018; 84 FR 22453, May 17, 2019; and 84 FR 34134, July 17, 2019).

    During pile driving installation activities, there may be times 
when multiple construction sites are active and hammers are used 
simultaneously. For impact hammering, it is unlikely that the two 
hammers would strike at the same exact instant, and therefore, the 
sound source levels will not be adjusted regardless of the distance 
between the hammers. For this reason, multiple impact hammering is not 
discussed further. For simultaneous vibratory hammering, the likelihood 
of such an occurrence is anticipated to be infrequent and would be for 
short durations on that day. In-water pile installation is an 
intermittent activity, and it is common for installation to start and 
stop multiple times as each pile is adjusted and its progress is 
measured. When two continuous noise sources, such as vibratory hammers, 
have overlapping sound fields, there is potential for higher sound 
levels than for non-overlapping sources. When two or more vibratory 
hammers are used simultaneously, and the sound field of one source 
encompasses the sound field of another source, the sources are 
considered additive and combined using the following rules (see Table 
6): For addition of two simultaneous vibratory hammers, the difference 
between the two SSLs is calculated, and if that difference is between 0 
and 1 dB, 3 dB are added to the higher SSL; if difference is between 2 
or 3 dB, 2 dB are added to the highest SSL; if the difference is 
between 4 to 9 dB, 1 dB is added to the highest SSL; and with 
differences of 10 or more decibels, there is no addition.

                  Table 6--Rules for Combining Sound Levels Generated During Pile Installation
----------------------------------------------------------------------------------------------------------------
             Hammer types                 Difference in SSL          Level A zones            Level B zones
----------------------------------------------------------------------------------------------------------------
Vibratory, Impact....................  Any....................  Use impact zones.......  Use vibratory zone.
Impact, Impact.......................  Any....................  Use zones for each pile  Use zone for each pile
                                                                 size and number of       size.
                                                                 strikes.
Vibratory, Vibratory.................  0 or 1 dB..............  Add 3 dB to the higher   Add 3 dB to the higher
                                                                 source level.            source level.
                                       2 or 3 dB..............  Add 2 dB to the higher   Add 2 dB to the higher
                                                                 source level.            source level.
                                       4 to 9 dB..............  Add 1 dB to the higher   Add 1 dB to the higher
                                                                 source level.            source level.
                                       10 dB or more..........  Add 0 dB to the higher   Add 0 dB to the higher
                                                                 source level.            source level.
----------------------------------------------------------------------------------------------------------------
Source: Modified from USDOT 1995, WSDOT 2018, and NMFS 2018b.
Note: dB = decibels; SSL = sound source level.


[[Page 48166]]

    For simultaneous usage of three or more continuous sound sources, 
such as vibratory hammers, the three overlapping sources with the 
highest SSLs are identified. Of the three highest SSLs, 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-in diameter steel pipe 
piles with SSLs of 161, 167, and 168 dB rms respectively, the 24- and 
36-inwould be added together; given that 167-161 = 6 dB, then 1 dB is 
added to the highest of the two SSLs (167 dB), for a combined noise 
level of 168 dB. Next, the newly calculated 168 dB is added to the 42-
in steel pile with SSL 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-in steel pipe piles (NMFS 2018b; WSDOT 2018). As described 
in Table 6, decibel addition calculations were carried out for all 
possible combinations of vibratory installation of 24-, 36- and 42-in 
steel pipe piles throughout the project area (Table 7).
[GRAPHIC] [TIFF OMITTED] TN10AU20.002

Level A Harassment
    When the NMFS Technical Guidance (2016) was published, 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, we 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 
overestimate of Level A harassment take. However, these tools offer the 
best way to predict appropriate isopleths when more sophisticated 3D 
modeling methods are not available, and NMFS continues to develop ways 
to quantitatively refine these tools, and will qualitatively address 
the output where appropriate. For stationary sources (such as from 
vibratory pile driving), NMFS User Spreadsheet predicts the closest 
distance at which, if a marine mammal remained at that distance the 
whole duration of the activity, it would incur PTS. Inputs used in the 
User Spreadsheet (Tables 8 through 10), and the resulting isopleths are 
reported below (Table 11).
    In the chance that multiple vibratory hammers would be operated 
simultaneously, to simplify implementation of Level A harassment zones, 
the worst-case theoretical scenarios were calculated for the longest 
anticipated duration of the largest pile size (42-in steel pile) that 
could be installed within a day (see Table 8). However, it would be 
unlikely that six sets of three piles could be installed in synchrony, 
but more likely that installations of piles would overlap by a few 
minutes at the beginning or end, throughout the day, so that during a 
12-hour construction shift, there would be periods of time when zero, 
one, two, three, or more hammers would be working.

         Table 8--NMFS Technical Guidance (2018) User Spreadsheet Input To Calculate PTS Isopleths for Vibratory Pile Driving for All Locations
                            [User spreadsheet input--vibratory pile driving spreadsheet tab A.1 vibratory pile driving used]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                           42-in steel piles        42-in steel piles
                                         24-in steel     36-in steel     36-in steel     42-in steel   (multiple hammer  event--     (multiple hammer
                                            piles           piles      piles  (at TBM       piles              3 hammers             event--2 hammers
                                                                          platform)                         simultaneously)          simultaneously)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Level (RMS SPL)...............             161             167             167             168  173.....................  171.
Weighting Factor Adjustment (kHz)....             2.5             2.5             2.5             2.5  2.5.....................  2.5.
Number of piles within 24-hr period..               6               3               2               6  6.......................  9.
                                                                                                       (3 piles installed        (2 piles installed
                                                                                                        simultaneously, 6         simultaneously, 9
                                                                                                        piling events).           piling events).
Duration to drive a single pile (min)              30              50              60              30  30......................  30.
Propagation (xLogR)..................              15              15              15              15  15......................  15.

[[Page 48167]]

 
Distance of source level measurement               10              10              10              10  10......................  10.
 (meters).
--------------------------------------------------------------------------------------------------------------------------------------------------------


    Table 9--NMFS Technical Guidance (2018) User Spreadsheet Input To
  Calculate PTS Isopleths for Impact Pile Driving for the Jet Grouting
                Trestle With and Without a Bubble Curtain
   [User spreadsheet input--impact pile driving spreadsheet tab E.1-2
           impact pile driving used for jet grouting trestle]
------------------------------------------------------------------------
                                                            36-in steel
                                            36-in steel        piles
                                               piles       (attenuated)
------------------------------------------------------------------------
Source Level (SEL)......................             183           * 176
Weighting Factor Adjustment (kHz).......               2               2
Number of piles within 24-hr period.....               3               3
Number of strikes per pile..............              40              40
Propagation (xLogR).....................              15              15
Distance of source level measurement                  10              10
 (meters)+..............................
------------------------------------------------------------------------
* The attenuated piles account for a 7dB reduction from the use of a
  bubble curtain.


                               Table 10--NMFS Technical Guidance (2018) User Spreadsheet Input To Calculate PTS Isopleths for Impact Pile Driving and DTH Drilling
                                                     [User spreadsheet input--impact pile driving spreadsheet tab E.1-2 impact pile driving]
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   North       North trestle, willoughby bay, and         South island                                DTH
                                                                  trestle       south trestle test pile program    -----------------------------------------------------------------------------
                                                               ----------------------------------------------------                                        North shore      Jet
                                                                                                                        TBM        Conveyor       TBM          work       grouting     Conveyor
                                                                36-in steel     24-in        30-in        54-in       platform   trestle  36-   platform   trestle  36- trestle  36- trestle  36-
                                                                   piles       concrete     concrete     concrete   36-in steel    in steel   36-in steel    in steel     in steel     in steel
                                                                                square       square      cylinder      piles        piles        piles        piles        piles        piles
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Source Level (SEL)............................................          183          166          177          177          183          183          164          164          164          164
Weighting Factor Adjustment (kHz).............................            2            2            2            2            2            2            2            2            2            2
Number of piles within 24-hr period...........................            3            1            1            1            2            3            2            3            3            3
Number of strikes per pile....................................           40        2,100        2,100        2,100           60           40       50,400       50,400       50,400       50,400
Propagation (xLogR)...........................................           15           15           15           15           15           15           15           15           15           15
Distance of source level measurement (meters)+................           10           10           10           10           10           10           10           10           10           10
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


                                    Table 11--Level A Harassment Isopleths for Both Vibratory and Impact Pile Driving
--------------------------------------------------------------------------------------------------------------------------------------------------------
             User spreadsheet output                            PTS isopleths  (meters)                             PTS isopleths  (km\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                  Level A harassment                                  Level A harassment
                                                 -------------------------------------------------------------------------------------------------------
      Pile type/activity          Sound source        Low-         Mid-        High-                      Low-         Mid-        High-
                                  level at 10 m    frequency    frequency    frequency      Phocid     frequency    frequency    frequency      Phocid
                                                   cetaceans    cetaceans    cetaceans                 cetaceans    cetaceans    cetaceans
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 Vibratory Pile Driving
--------------------------------------------------------------------------------------------------------------------------------------------------------
24-in steel pile installation   161 dB SPL......           15            2           21            9                         <0.01
 (All Locations).
                                                                                                     ---------------------------------------------------
36-in steel pile installation   167 dB SPL......           32            3           47           20                         <0.01
 (All Locations).
                                                                                                     ---------------------------------------------------
36-in steel pile installation   167 dB SPL......           28            3           41           17                         <0.01
 (TMB Platform).
                                                                                                     ---------------------------------------------------
42-in steel pile installation   168 dB SPL......           42            4           62           26                         <0.10
 (All Locations).
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        Impact Pile for the Jet Grouting Trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
36-in steel pile installation.  183 dB SEL/193            243            9          290          130         0.11        <0.01         0.16        <0.10
                                 SPL.
36-in steel pile installation   176 dB SEL/186             83            3           99           45        0.014       <0.001         0.20        <0.01
 (attenuated).                   SPL.
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 48168]]

 
                                                            Impact Pile Driving North Trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
36-in steel pile installation   183 dB SEL/193            243            9          290          130         0.19       <0.001         0.26         0.05
 (North Shore Work Trestle).     SPL.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                               Impact Pile Driving for North Trestle, Willoughby Bay, and South Trestle Test Pile Program
--------------------------------------------------------------------------------------------------------------------------------------------------------
24-in concrete square pile      166 dB SEL/190            121            5          144           65         0.05       <0.001         0.07         0.01
 installation/removal.           SPL.
30-in concrete square pile      177 dB SEL/187            652         23.2        776.6        348.9        1.335        0.002       1.8947       0.3824
 installation/removal.           SPL.
54-in concrete square pile      177 dB SEL/187            652         23.2        776.6        348.9        1.335        0.002       1.8947       0.3824
 installation/removal.           SPL.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Impact Pile Driving for South Island
--------------------------------------------------------------------------------------------------------------------------------------------------------
36-in steel pile installation   183 dB SEL/193            243            9          290          130         0.11       <0.001         0.16        <0.10
 (TBM Platform).                 SPL.
36-in steel pile installation   183 dB SEL/193            243            9          290          130         0.11       <0.001         0.16        <0.10
 (Conveyor Trestle).             SPL.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      DTH Drilling
--------------------------------------------------------------------------------------------------------------------------------------------------------
36-in steel pile installation   164 SEL/180 dB          1,171           42        1,395          627        2.437        <0.01        3.446        0.704
 (TBM Platform).                 SPL.
36-in steel pile installation   164 SEL/180 dB          1,534           55        1,827          821        3.615        <0.01        4.790        1.548
 (North Shore Work Trestle).     SPL.
36-in steel pile installation   164 SEL/180 dB          1,534           55        1,827          821        3.615        <0.01        5.908        1.548
 (Jet Grouting Trestle).         SPL.
36-in steel pile installation   164 SEL/180 dB          1,534           55        1,827          821        3.615        <0.01        5.908        1.548
 (Conveyor Trestle).             SPL.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                 Multiple Hammers--Vibratory Pile Driving (if occurs) *
--------------------------------------------------------------------------------------------------------------------------------------------------------
42-in steel pile installation   173 dB SPL......         89.6          7.9        132.5         54.5        0.025       0.0001        0.055        0.009
 (assumes 3 piles installed
 simultaneously, 6 piling
 events * 30 minutes each
 event in a 24-hr period).
42-in steel pile installation   171 dB SPL......         86.4          7.7        127.8         52.5        0.023       0.0001        0.051        0.009
 (assumes 2 piles installed
 simultaneously, 9 piling
 events * 30 minutes each
 event in a 24-hr period).
--------------------------------------------------------------------------------------------------------------------------------------------------------
* SPLs were calculated by decibel addition as presented in Table 6 using the largest pile size (42-in steel piles) and possible combinations of two and
  three multiple hammer events. Please note: smaller piles may also have multiple hammer events; however, their SPLs would be smaller than the 42-in
  steel pipe pile scenarios so they are not presented here. The HRCP will be using the largest Level A isopleths calculated regardless of pile size
  during multiple hammering events.

    For multiple hammering of 42-in steel pipe piles with a vibratory 
hammer on a single day, the calculated Level A harassment isopleth for 
the functional hearing groups would remain smaller than 100 m except 
for high-frequency cetaceans (i.e., harbor porpoise). The Level A 
harassment isopleth for harbor porpoises would be 132.5 m and 127.8 m 
for the two scenarios (Table 11). It is unlikely that a harbor porpoise 
could accumulate enough sound from the installation of multiple piles 
in multiple locations for the duration required to meet these Level A 
harassment thresholds. Additionally, other combinations of pile sizes 
under multiple hammering with a vibratory hammer would result in Level 
A harassment thresholds smaller than 100 m. To be precautionary, a 
shutdown zone of 100 m would be implemented for all species for each 
vibratory hammer on days when it is anticipated that multiple vibratory 
hammers will be used regardless of pile size.
Level B Harassment
    Utilizing the practical spreading loss model, underwater noise will 
fall below the behavioral effects threshold of 120 and 160 dB rms for 
marine mammals at the distances shown in Table 12 for vibratory and 
impact pile driving, respectively. Table 12 below provides all Level B 
harassment radial distances (m) and their corresponding areas (km\2\) 
during HRCP's planned activities.

[[Page 48169]]



  Table 12--Radial Distances (meters) to Relevant Behavioral Isopleths and Associated Ensonified Areas (km\2\)
                                       Using the Practical Spreading Model
----------------------------------------------------------------------------------------------------------------
                                                                                    Distance to
                                                                                      level B         Level B
            Location and component                    Method and pile type          harassment      harassment
                                                                                     zone  (m)     zone  (km\2\)
----------------------------------------------------------------------------------------------------------------
                                  Vibratory Hammer (Level B Isopleth = 120 dB)
                                                  North Trestle
----------------------------------------------------------------------------------------------------------------
Moorings......................................  42-in steel piles...............          15,849          96.781
North Shore Work Trestle......................  36-in steel piles...............          13,594          85.525
Moorings......................................  24-in steel piles...............           5,412          25.335
----------------------------------------------------------------------------------------------------------------
                                                  North Island
----------------------------------------------------------------------------------------------------------------
Moorings......................................  42-in steel piles...............          15,849         100.937
----------------------------------------------------------------------------------------------------------------
                                                  South Island
----------------------------------------------------------------------------------------------------------------
TBM Platform..................................  36-in steel piles...............          13,594          81.799
Conveyor Trestle..............................  36-in steel piles...............          13,594          81.799
Jet Grouting Trestle..........................  36-in steel piles...............          13,594          81.799
----------------------------------------------------------------------------------------------------------------
                                                  South Trestle
----------------------------------------------------------------------------------------------------------------
Moorings......................................  42-in steel piles...............          15,849         305.343
Moorings......................................  24-in steel piles...............           5,412          55.874
----------------------------------------------------------------------------------------------------------------
                                                 Willoughby Bay
----------------------------------------------------------------------------------------------------------------
Moorings......................................  42-in steel piles...............          15,849           5.517
Moorings......................................  24-in steel piles...............           5,412           5.517
----------------------------------------------------------------------------------------------------------------
                                Down-the-Hole Hammer (Level B Isopleth = 120 dB)
----------------------------------------------------------------------------------------------------------------
North Shore Work Trestle......................  36-in steel piles...............          11,659         427.044
TBM Platform..................................  36-in steel piles...............          11,659         427.044
Jet Grouting Trestle..........................  36-in steel piles...............          11,659         427.044
Conveyor Trestle..............................  36-in steel piles...............          11,659         427.044
----------------------------------------------------------------------------------------------------------------
                                    Impact Hammer (Level B Isopleth = 160 dB)
                                                  North Trestle
----------------------------------------------------------------------------------------------------------------
North Shore Work Trestle......................  36-in steel piles...............           1,585           3.806
----------------------------------------------------------------------------------------------------------------
                                                  South Island
----------------------------------------------------------------------------------------------------------------
TBM Platform..................................  36-in steel piles...............           1,585           0.087
Conveyor Trestle..............................  36-in steel piles...............           1,585           0.087
Jet Grouting Trestle with Bubble Curtain......  36-in steel piles...............           * 541         * 0.012
----------------------------------------------------------------------------------------------------------------
                                  North Trestle, South Trestle, Willoughby Bay
----------------------------------------------------------------------------------------------------------------
Test Pile Program.............................  54-in concrete cylinder piles...             631          1.2509
Test Pile Program.............................  30-in concrete square piles.....             631          1.2509
Test Pile Program.............................  24-in concrete square piles.....             117            0.04
----------------------------------------------------------------------------------------------------------------
dB = decibels; km\2\ = square kilometers; TBM = Tunnel Boring Machine.
* Values smaller than other 36-in steel piles due to usage of a bubble curtain, resulting in a 7 dB reduction in
  dB rms, dB peak, and dB SEL.

    For the test pile program, in some cases, the calculated Level A 
harassment isopleths are larger than the Level B harassment zones. This 
has occurred due to the conservative assumptions going into calculation 
of the Level A harassment isopleths. Animals will most likely respond 
behaviorally before they are injured, especially at greater distances 
and unlikely to accumulate noise levels over a certain period of time 
that would likely lead to PTS.
    When multiple vibratory hammers are used simultaneously, the 
calculated Level B harassment zones (Table 13) would be larger than the 
Level B harassment zones reported in above in Table 12 depending on the 
combination of sound sources due to decibel addition of multiple 
vibratory hammers as discussed earlier (see Table 7). Table 13 shows 
the calculated distances to the Level B harassment zone for decibel 
levels resulting from the simultaneous installation of piles with 
multiple vibratory hammers using the data provided in Table 7. However, 
the actual monitoring zones applied during multiple vibratory hammer 
use are discussed in the Monitoring and Reporting section.

[[Page 48170]]



 Table 13--Calculated Distances to Level B Harassment Zones for Multiple
                            Hammer Additions
------------------------------------------------------------------------
                                                            Distance to
                                                              level B
                   Combined SSL  (dB)                       harassment
                                                             zone  (m)
------------------------------------------------------------------------
163.....................................................           7,356
164.....................................................           8,577
165.....................................................          10,000
166.....................................................          11,659
167.....................................................          13,594
168.....................................................          15,849
169.....................................................          18,478
170.....................................................          21,544
171.....................................................          25,119
172.....................................................          29,286
173.....................................................          34,145
------------------------------------------------------------------------
Note: dB = decibels; SSL = sound source level.

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 and vibratory pile driving 
and removal for each acoustic threshold were estimated using local 
observational data. Authorized take by Level A and B harassment is also 
described.
Humpback Whales
    Humpback whales are more rare in the project area and density data 
for this species within the project vicinity are not available. 
Humpback whale sighting data collected by the U.S. Navy near Naval 
Station Norfolk and Virginia Beach from 2012 to 2015 (Engelhaupt et al. 
2014, 2015, 2016) and in the mid-Atlantic (including the Chesapeake 
Bay) from 2015 to 2018 (Aschettino et al. 2015, 2016, 2017a, 2018) did 
not produce large enough sample sizes to calculate densities, or survey 
data were not collected during systematic line-transect surveys. 
Humpback whale densities have been calculated for populations off the 
coast of New Jersey, resulting in a density estimate of 0.000130 
animals per square kilometer or one humpback whale within the area on 
any given day of the year (Whitt et al., 2015), which may be similar to 
the density of whales in the project area. Aschettino et al. (2018) 
observed and tracked two individual humpback whales in the Hampton 
Roads area of the project area (Movebank, 2019). The HRCP is estimating 
up to two whales may be exposed to project-related noise every two 
months. Pile installation/removal is expected to occur over a 12-month 
period; therefore, a total of 12 instances of take by Level B 
harassment of humpback whales is authorized. Due to the low occurrence 
of humpback whales and because large whales are easier to sight from a 
distance, we do not anticipate or propose take of humpback whales by 
Level A harassment.
Bottlenose Dolphin
    The expected number of bottlenose dolphins in the project area was 
estimated using inshore seasonal densities provided in Engelhaupt et 
al. (2016) from vessel line-transect surveys near Naval Station Norfolk 
and adjacent areas near Virginia Beach, Virginia, from August 2012 
through August 2015 (Engelhaupt et al., 2016). NMFS used the density of 
1.38 dolphins/km\2\ and (1) the Level B harassment ensonified area of 
131.4 km\2\ west of the HRBT multiplied by 312 days of activities, plus 
(2) the Level B harassment ensonified area of 221.46 km\2\ for 
vibratory installation of 42-in steel piles at the South Trestle 
multiplied by 7 days of activities, plus (3) the Level B harassment 
ensonified area associated of 27.65 km\2\ for vibratory installation of 
24-in steel piles at the South Trestle multiplied by 3 days of 
activities, and plus (4) the Level B harassment ensonified area 
associated of 0.87 km\2\ for impact installation of 54-in concrete 
piles at the South Trestle multiplied 22 days of activities to increase 
the numbers of Level B harassment takes of bottlenose dolphins from 
6,343 to 58,856. (Table 14).

                                                                          Table 14--Authorized Bottlenose Dolphin Take
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                             24-in                                  54-in                                  42-in
                                                     Level B                                 piles:                                 piles:                                 piles:
                                                    harassment    Dolphin     Days 24-in    level B      Dolphin     Days 54-in    level B      Dolphin     Days 42-in    level B      Dolphin
                Total project days                 west of the    density        pile      harassment    density        pile      harassment    density        pile      harassment    density
                                                   HRBT  (km2)   (animals/     driving      at South    (animals/     driving      at South    (animals/     driving      at South    (animals/
                                                                    km2)                    Trestle        km2)                    Trestle        km2)                    Trestle        km2)
                                                                                             (km2)                                  (km2)                                  (km2)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
312..............................................        131.4         1.38            3        27.65         1.38           22         0.87         1.38            7       221.46         1.38
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                 56,575.584                       114.471
                                                                  26.4132
                                                                 2,139.3036
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Total Authorized Takes of Bottlenose Dolphin 58,855.77 (rounded to 58,856).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Source: Engelhaupt et al., 2016.

    Because the Level A harassment zones are relatively small (a 55-m 
isopleth is the largest during DTH drilling of 36-in piles) and we 
believe the PSO will be able to effectively monitor the Level A 
harassment zones, we do not anticipate take by Level A harassment of 
bottlenose dolphins.
Harbor Seals
    The expected number of harbor seals in the project area was 
estimated using systematic, land- and vessel-based survey data for in-
water and hauled-out seals collected by the U.S. Navy at the Chesapeake 
Bay Bridge Tunnel (CBBT) rock armor and portal islands from 2014 
through 2019 (Jones et al., 2020). The average daily seal count from 
the 2014 through 2019 field seasons ranged from 8 to 23 for an average 
of 13.6 harbor seals across all the field seasons (Table 15).

                          Table 15--Harbor Seal Counts at Chesapeake Bay Bridge Tunnel
----------------------------------------------------------------------------------------------------------------
                                                   ``In season''    Total seal    Average  daily     Max daily
                  Field season                      survey days        count        seal count      seal count
----------------------------------------------------------------------------------------------------------------
2014-2015.......................................              11             113              10              33
2015-2016.......................................              14             187              13              39
2016-2017.......................................              22             308              14              40
2017-2018.......................................              15             340              23              45

[[Page 48171]]

 
2018-2019.......................................              10              82               8              17
                                                 ---------------------------------------------------------------
    Average.....................................  ..............  ..............            13.6            34.8
----------------------------------------------------------------------------------------------------------------
Source: Jones et al., 2020.

    NMFS estimated take using the average daily seal count over five 
field seasons (2014-2019) (Jones et al., 2020). This average count is 
13.6 seals (rounded up to 14 seals). Fourteen seals/day multiplied by 
156 days (number of days of activities when the seals are present, 
December to May) equals 2,184 takes. The takes by Level A harassment 
were calculated from approximately 21 percent of the pile-driving days 
during DTH drilling when the Level A harassment zone is fairly large 
(821 m) for a total of 459 takes. Therefore, 1,725 takes by Level B 
harassment and 459 takes by Level A harassment are being authorized for 
this IHA.
Gray Seals
    The expected number of gray seals in the project area was estimated 
using systematic, land- and vessel-based survey data for in-water and 
hauled out seals collected by the U.S. Navy at the CBBT rock armor and 
portal islands from 2014 through 2018 (Rees et al., 2016; Jones et al., 
2018). Seasonal numbers of gray seals in the Chesapeake Bay waters in 
the vicinity of the project area in previous years have been low (Table 
16). Gray seals are not expected to be present in the Chesapeake Bay 
during the months of June through October (Table 16 and Table 17).

                 Table 16--Summary of Historical Gray Seal Sightings by Month From 2014 to 2018
----------------------------------------------------------------------------------------------------------------
                                         Number of individual gray seals
-----------------------------------------------------------------------------------------------------------------
                                                                                                       Monthly
               Month                    2014         2015         2016         2017         2018       average
----------------------------------------------------------------------------------------------------------------
January...........................  ...........            0            0            0            0            0
February..........................  ...........            1            1            0            1          0.8
March.............................  ...........            0            0            0            0            0
April.............................  ...........            0            0            0            0            0
May...............................  ...........            0            0            0            0            0
                                   -----------------------------------------------------------------
June..............................                 Seals not expected to be present.                           0
                                   -----------------------------------------------------------------
July..............................                 Seals not expected to be present.                           0
                                   -----------------------------------------------------------------
August............................                 Seals not expected to be present.                           0
                                   -----------------------------------------------------------------
September.........................                 Seals not expected to be present.                           0
                                   -----------------------------------------------------------------
October...........................                 Seals not expected to be present.                           0
                                   -----------------------------------------------------------------
November..........................            0            0            0            0  ...........            0
December..........................            0            0            0            0  ...........            0
----------------------------------------------------------------------------------------------------------------
Source: Rees et al., 2016; Jones et al., 2018.


Table 17--Average Number of Individual Gray Seal Sightings Summarized by
                                 Season
------------------------------------------------------------------------
                                                              Average
                                                             number of
                         Season                             individuals
                                                            per season
------------------------------------------------------------------------
Spring (March-May)......................................               0
Summer (June-August)....................................               0
Fall (September-November)...............................               0
Winter (December-February)..............................               1
------------------------------------------------------------------------
Note: Data generated from Table 16.

    Gray seals are expected to be very uncommon in the project area. 
The historical data indicate that approximately one gray seal has been 
seen per year. To be conservative, HRCP requests three instances of 
take by Level B harassment of gray seals during each winter month 
(December through February). Therefore, HRCP estimated and NMFS is 
authorizing nine instances of take by Level B harassment of gray seals 
(three gray seals per month multiple by three months = nine gray 
seals). Because of the unlikely to low occurrence of gray seals in the 
project area, we do not anticipate and are not authorizing take by 
Level A harassment of gray seals.

[[Page 48172]]

Harbor Porpoise
    Harbor porpoises are known to occur in the coastal waters near 
Virginia Beach (Hayes et al. 2019), and although they have been 
reported on rare occasions in the Chesapeake Bay, closer to Norfolk, 
they are rarely seen in the project area. Density data for this species 
within the Project vicinity do not exist or were not calculated because 
sample sizes were too small to produce reliable estimates of density. 
Harbor porpoise sighting data collected by the U.S. Navy near Naval 
Station Norfolk and Virginia Beach from 2012 to 2015 (Engelhaupt et 
al., 2014; 2015; 2016) did not produce enough sightings to calculate 
densities. One group of two harbor porpoises was seen during spring 
2015 (Engelhaupt et al., 2016). Based on this data, it estimated that 
one group of two harbor porpoises could be exposed to project-related 
in-water noise each month during the spring (March-May) for a total of 
six instances of take by Level B harassment (i.e., one group of two 
individuals per month multiplied by three months = six harbor 
porpoises).
    The largest calculated Level A harassment isopleth for high 
frequency cetaceans (i.e., harbor porpoises) extends 1,827 m during DTH 
drilling of 36-in steel pipe piles. Because harbor porpoises are 
relatively difficult to observe, it is possible they may occur within 
the calculated Level A harassment zone without detection. As such, HRCP 
requested a small number of takes by Level A harassment for harbor 
porpoises during the project. Therefore, we authorize a total of two 
instances of take by Level A harassment, the number requested by HRCP.
    Table 18 below summarizes the authorized take for all the species 
described above as a percentage of stock abundance.

          Table 18--Authorized Take by Level A and B Harassment and as a Percentage of Stock Abundance
----------------------------------------------------------------------------------------------------------------
                                                   Authorized      Authorized
                                                     level A         level B       Total takes    Percentage of
           Species                   Stock         harassment      harassment     authorization       stock
                                                      takes           takes
----------------------------------------------------------------------------------------------------------------
Humpback whale...............  Gulf of Maine...               0              12              12  Less than 2
                                                                                                  percent.
Harbor porpoise..............  Gulf of Maine/                 2               4               6  Less than 1
                                Bay of Fundy.                                                     percent.
Bottlenose dolphin...........  WNA Coastal,                   0          29,320          29,320  Less than 33. *
                                Northern
                                Migratory \a\.
                               WNA Coastal,                   0          29,320          29,320  Less than 33. *
                                Southern
                                Migratory \a\.
                               NNCES \a\.......               0             216             216  26.25.
Harbor seal..................  Western North                459           1,725           2,184  Less than 1
                                Atlantic.                                                         percent.
Gray seal....................  Western North                  0               9               9  Less than 1
                                Atlantic.                                                         percent.
----------------------------------------------------------------------------------------------------------------
\a\ Take estimates are weighted based on calculated percentages of population for each distinct stock, assuming
  animals present would follow same probability of presence in project area.
* Assumes multiple repeated takes of same individuals from small portion of each stock as well as repeated takes
  of Chesapeake Bay resident population (size unknown).

Mitigation

    In order to issue an IHA under section 101(a)(5)(D) of the MMPA, 
NMFS must set forth the permissible methods of taking pursuant to such 
activity, and other means of effecting the least practicable impact on 
such species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of such species or stock for taking for certain 
subsistence uses (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 such 
activity or other means of effecting the least practicable adverse 
impact upon the affected species or stocks and their habitat (50 CFR 
216.104(a)(11)).
    In evaluating how mitigation may or may not be appropriate to 
ensure the least practicable adverse impact on species or stocks and 
their habitat, as well as subsistence uses where applicable, 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 
proposed), the likelihood of effective implementation (probability 
implemented as proposed), 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.
    The following mitigation measures are included in the IHA:

Timing Restrictions

    HRCP would conduct work during daylight hours, and if poor 
environmental conditions restrict full visibility of the shutdown zone, 
pile installation must be delayed. However, work may extend into the 
night as necessary under conditions where there is full visibility of 
the shutdown zone or where stopping ongoing work would otherwise create 
an unsafe work condition.

Shutdown Zone for In-Water Heavy Machinery Work

    For in-water heavy machinery work other than pile driving, if a 
marine mammal comes within 10 m of such operations, operations will 
cease and vessels will reduce speed to the minimum level required to 
maintain steerage and safe working conditions.

Shutdown Zones

    For all pile driving activities, HRCP will establish shutdown zones 
for a marine mammal (see Table 19 below). 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). HRCP will 
maintain a minimum 10 m shutdown zone for all pile driving activities 
where the

[[Page 48173]]

calculated PTS Isopleth is less than 10 m as described in Table 11.
    If multiple vibratory hammering occurs, a shutdown zone of 100 m 
will be implemented for all species for each vibratory hammer on days 
when it is anticipated that multiple vibratory hammers will be used 
regardless of pile size.
    During DTH drilling, a shutdown zone of 100 m for harbor seals will 
be implemented to reduce unnecessary shutdowns.

                                            Table 19--Shutdown Zones
----------------------------------------------------------------------------------------------------------------
                                                               Level a harassment shutdown zone (m)
                                                 ---------------------------------------------------------------
      Pile type/activity          Sound source         Low-            Mid-            High-
                                  level at 10 m      frequency       frequency       frequency        Phocid
                                                     cetaceans       cetaceans       cetaceans
----------------------------------------------------------------------------------------------------------------
                                             Vibratory Pile Driving
----------------------------------------------------------------------------------------------------------------
24-in steel pile installation   161 dB SPL......              15              10              21              10
 (All Locations).
36-in steel pile installation   167 dB SPL......              32              10              47              20
 (All Locations).
36-in steel pile installation   167 dB SPL......              28              10              41              17
 (TMB Platform).
42-in steel pile installation   168 dB SPL......              42              10              62              26
 (All Locations).
----------------------------------------------------------------------------------------------------------------
                                     Impact Pile for the Jet Grouting Trestle
----------------------------------------------------------------------------------------------------------------
36-in steel pile installation.  183 dB SEL/193               243              10             290             130
                                 SPL.
36-in steel pile installation   176 dB SEL/186                83              10              99              45
 (attenuated).                   SPL.
----------------------------------------------------------------------------------------------------------------
                                        Impact Pile Driving North Trestle
----------------------------------------------------------------------------------------------------------------
36-in steel pile installation   183 dB SEL/193               243              10             290             130
 (North Shore Work Trestle).     SPL.
----------------------------------------------------------------------------------------------------------------
           Impact Pile Driving for North Trestle, Willoughby Bay, and South Trestle Test Pile Program
----------------------------------------------------------------------------------------------------------------
24-in concrete square pile      166 dB SEL/190               121              10             144              65
 installation/removal.           SPL.
30-in concrete square pile      177 dB SEL/187               652              24             777             349
 installation/removal.           SPL.
54-in concrete square pile      177 dB SEL/187               652              24             777             349
 installation/removal.           SPL.
----------------------------------------------------------------------------------------------------------------
                                      Impact Pile Driving for South Island
----------------------------------------------------------------------------------------------------------------
36-in steel pile installation   183 dB SEL/193               243              10             290             130
 (TBM Platform).                 SPL.
36-in steel pile installation   183 dB SEL/193               243              10             290             130
 (Conveyor Trestle).             SPL.
----------------------------------------------------------------------------------------------------------------
                                                  DTH Drilling
----------------------------------------------------------------------------------------------------------------
36-in steel pile installation   164SEL/180 dB              1,171              42           1,395             100
 (TBM Platform).                 SPL.
36-in steel pile installation   164 SEL/180 dB             1,534              55           1,827             100
 (North Shore Work Trestle).     SPL.
36-in steel pile installation   164 SEL/180 dB             1,534              55           1,827             100
 (Jet Grouting Trestle).         SPL.
36-in steel pile installation   164 SEL/180 dB             1,534              55           1,827             100
 (Conveyor Trestle).             SPL.
----------------------------------------------------------------------------------------------------------------
                             Multiple Hammers--Vibratory Pile Driving (if occurs) *
----------------------------------------------------------------------------------------------------------------
42-in steel pile installation   173 dB SPL......             100             100             100             100
 (assumes 3 piles installed
 simultaneously, 6 piling
 events * 30 minutes each
 event in a 24-hr period).
42-in steel pile installation   171 dB SPL......             100             100             100             100
 (assumes 2 piles installed
 simultaneously, 9 piling
 events * 30 minutes each
 event in a 24-hr period).
----------------------------------------------------------------------------------------------------------------
* These zones are applicable for any multiple hammer events of any pile size where sound fields overlap.


[[Page 48174]]

Bubble Curtain

    HRCP will use an air bubble curtain system during impact pile 
driving of 36-in steel pipe piles for the Jet Grouting Trestle. Bubble 
curtains would meet the following requirements:
    The bubble curtain must distribute air bubbles around 100 percent 
of the piling perimeter for the full depth of the water column. The 
lowest bubble ring must be in contact with the mudline and/or rock 
bottom for the full circumference of the ring, and the weights attached 
to the bottom ring will ensure 100 percent mudline and/or rock bottom 
contact. No parts of the ring or other objects will prevent full 
mudline and/or rock bottom contact. The bubble curtain must be operated 
such that there is proper (equal) balancing of air flow to all 
bubblers. HRCP would employ the bubble curtain during impact pile 
driving in water depths greater than 6 m (20 ft) at the Jet Grouting 
Trestle.

Soft Start

    HRCP would use soft start techniques when impact pile driving. Soft 
start requires contractors to provide an initial set of strikes at 
reduced energy, followed by a 30-second waiting period, then two 
subsequent reduced energy strike sets. A soft start would be 
implemented at the start of each day's impact pile driving and at any 
time following cessation of impact pile driving for a period of 30 
minutes or longer.

Non-Authorized Take Prohibited

    If a species enters or approaches the Level B harassment zone and 
that species is either not authorized for take or its authorized takes 
are met, pile driving and removal activities must shut down immediately 
using delay and shutdown procedures. Activities must not resume until 
the animal has been confirmed to have left the area or an observation 
time period of 15 minutes has elapsed.
    Based on our evaluation of the HRCP's planned measures, NMFS has 
determined that the 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.

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 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.

Pre-Activity Monitoring

    Prior to the start of daily in-water construction activity, or 
whenever a break in pile driving of 30 min or longer occurs, PSOs will 
observe the shutdown and monitoring zones for a period of 30 min. The 
shutdown zone will be cleared when a marine mammal has not been 
observed within the zone for that 30-min period. If a marine mammal is 
observed within the shutdown zone, pile driving activities will not 
begin until the animal has left the shutdown zone or has not been 
observed for 15 min. If the Level B harassment zone (i.e., the 
monitoring zone) has been observed for 30 min and no marine mammals 
(for which take has not been authorized) are present within the zone, 
work can continue even if visibility becomes impaired within the 
monitoring zone. When a marine mammal for which Level B harassment take 
has been authorized is present in the monitoring zone, piling 
activities may begin and Level B harassment take will be recorded.

Monitoring Zones

    The HRCP will establish monitoring zones for Level B harassment as 
presented in Table 12. The monitoring zones for this project are areas 
where SPLs are equal to or exceed 120 dB rms (for vibratory pile 
driving/removal and DTH drilling) or 160 dB rms (for impact pile 
driving). These 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 Level B harassment zones enables observers to be 
aware of and communicate the presence of marine mammals in the project 
area, and thus prepare for potential shutdowns of activity. The HRCP 
will also be gathering information to help better understand the 
impacts of their planned activities on species and their behavioral 
responses. If the entire Level B harassment zone is not visible, Level 
B harassment takes will be extrapolated based upon the number of 
observed takes and the percentage of the Level B harassment zone that 
is not visible.
Multiple Hammer Level B Harassment Zones
    Due to the likelihood of multiple active construction sites across 
the project area, it is possible that multiple vibratory hammers with 
overlapping sound fields may be in operation simultaneously during 
certain times throughout the duration of the project. As described in 
the Estimated Take section, the decibel addition of continuous noise 
sources results in much larger zone sizes than a single vibratory 
hammer. Decibel addition is not a consideration when sound fields do 
not overlap. Willoughby Bay is largely surrounded by land, and sound 
will be prevented from propagating to other project construction sites 
(see Figure 1-1 and Figure 6-1 of the application). Therefore, 
Willoughby Bay will be treated as an independent site with its own 
sound isopleths and observer requirements when construction is taking 
place within the bay. Willoughby Bay is relatively small

[[Page 48175]]

and will be monitored from the construction site by a single observer.
    Additionally, the South Trestle is the only site where the sound 
will propagate into Chesapeake Bay (see Figure 6-1 of the application). 
Sound from other construction sites will not overlap with South Trestle 
and will not propagate into Chesapeake Bay. Therefore, the South 
Trestle also will be treated as an independent site with its own sound 
isopleths and observer requirements when construction is taking place. 
When the South Trestle site is active, an observer will be positioned 
on land to view as much of the Level B harassment zone as possible. If 
the entire Level B harassment zone is not visible, Level B harassment 
takes will be extrapolated based upon the number of observed takes and 
the percentage of the Level B harassment zone that is not visible.
    If two or more vibratory hammers at the other three project sites 
(North Trestle, North Shore, South Island) are installing piles, there 
is potential for the sound fields to overlap when installation occurs 
simultaneously. If two piles that are 36-in or larger in diameter are 
simultaneously installed with vibratory hammers, the Level B Harassment 
zone can extend up to a 25 km radius to the southwest (see Figure 6-1, 
171 dB isopleth of the application). However, the Level B harassment 
zones resulting from simultaneous use of multiple vibratory hammers are 
truncated in nearly all directions by the mainland and islands, which 
prevent propagation of sound beyond the confines of a core area (see 
Figure 11-1 (area outlined in red) of the application). The largest 
ensonified radii extend to the south into the James and Nansemond 
rivers, areas where marine mammal abundance is anticipated to be low 
and approaching zero. Therefore, HRCP will monitor a core area, called 
the Core Monitoring Area, during times when two or more vibratory 
hammers are simultaneously active at the other three project 
construction sites (North Trestle, North Shore, South Island). The Core 
Monitoring Area would encompass the area between the two bridge/
tunnels, with observers positioned at key areas to monitor the 
geographic area between the bridges (see Figure 11-1 (area outlined in 
red) of the application). Depending on placement, the observers will be 
able to view west/southwest towards Batten Bay and the mouth of the 
Nansemond River. Marine mammals transiting the area will be located and 
identified as they move in and out of the Chesapeake Bay.

Visual Monitoring

    Monitoring would be conducted 30 minutes before, during, and 30 
minutes after all pile driving/removal activities. In addition, PSOs 
will record all incidents of marine mammal occurrence, regardless of 
distance from activity, and will document any behavioral reactions in 
concert with distance from piles being driven/removed. Pile driving/
removal activities include the time to install, remove a single pile or 
series of piles, as long as the time elapsed between uses of the pile 
driving equipment is no more than 30 minutes.
    Monitoring will be conducted by PSOs from land. The number of PSOs 
will vary from one or more, depending on the type of pile driving, 
method of pile driving and size of pile, all of which determines the 
size of the harassment zones. Monitoring locations will be selected to 
provide an unobstructed view of all water within the shutdown zone and 
as much of the Level B harassment zone as possible for pile driving 
activities. Monitoring locations may vary based on construction 
activity and location of piles or equipment. HRCP will station between 
one and four PSOs at locations offering the best available views of the 
Level A and Level B monitoring zones during in-water pile driving at 
the North Trestle, North Island, South Trestle, and South Island. When 
and where able, as determined by the PSO or Lead PSO when multiple 
observers are required, Level A and Level B harassment zones may be 
monitored for multiple pile driving locations by the same individual 
PSO. HRCP will be required to station between one and two PSOs at 
locations offering the best available views of the Level A and Level B 
monitoring zones during in-water pile driving at Willoughby Bay. If any 
entire Level B monitoring zone is not visible, pile driving activities 
may continue, and the number of individual animals within the Level B 
zone will be estimated and recorded. Estimated numbers of individuals 
will be extrapolated by dividing the number of observed individuals by 
the percentage of the monitoring zone that was visible.
    In addition, PSOs will work in shifts lasting no longer than 4 
hours with at least a 1-hour break between shifts, and will not perform 
duties as a PSO for more than 12 hours in a 24[hyphen]hour period (to 
reduce PSO fatigue).
    Monitoring of pile driving will be conducted by qualified, NMFS-
approved PSOs, who will have no other assigned tasks during monitoring 
periods. The HRCP will adhere to the following conditions when 
selecting PSOs:
    [ssquf] Independent PSOs will be used (i.e., not construction 
personnel);
    [ssquf] At least one PSO must have prior experience working as a 
marine mammal observer during construction activities;
    [ssquf] Other PSOs may substitute education (degree in biological 
science or related field) or training for experience;
    [ssquf] Where a team of three or more PSOs are required, a lead 
observer or monitoring coordinator will be designated. The lead 
observer must have prior experience working as a marine mammal observer 
during construction; and
    [ssquf] The HRCP will submit PSO curriculum vitaes for approval by 
NMFS for all observers prior to monitoring.
    The HRCP 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;
    [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; and
    [ssquf] Sufficient training, orientation, or experience with the 
construction operations to provide for personal safety during 
observations.

Reporting of Injured or Dead Marine Mammals

    In the event that personnel involved in the construction activities 
discover an injured or dead marine mammal, HRCP will report the 
incident to the

[[Page 48176]]

Office of Protected Resources (OPR), NMFS and to the Greater Atlantic 
Region New England/Mid-Atlantic Regional Stranding Coordinator as soon 
as feasible. If the death or injury was clearly caused by the specified 
activity, the HRCP must immediately cease the specified activities 
until NMFS is able to review the circumstances of the incident and 
determine what, if any, additional measures are appropriate to ensure 
compliance with the terms of the IHA. HRCP must 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.

Final Report

    The HRCP will submit a draft report to NMFS no later than 90 days 
following the end of construction activities or 60 days prior to the 
issuance of any subsequent IHA for the project. PSO datasheets/raw 
sightings data would be required to be submitted with the reports. The 
HRCP will provide a final report within 30 days following resolution of 
NMFS' comments on the draft report. Reports will contain, at minimum, 
the following:
    [ssquf] Dates and times (begin and end) of all marine mammal 
monitoring;
    [ssquf] Construction activities occurring during each daily 
observation period, including how many and what type of piles were 
driven or removed and by what method (i.e., impact or vibratory);
    [ssquf] Weather parameters and water conditions during each 
monitoring period (e.g., wind speed, percent cover, visibility, sea 
state);
    [ssquf] The number of marine mammals observed, by species, relative 
to the pile location and if pile driving or removal was occurring at 
time of sighting;
    [ssquf] Age and sex class, if possible, of all marine mammals 
observed;
    [ssquf] PSO locations during marine mammal monitoring;
    [ssquf] Distances and bearings of each marine mammal observed to 
the pile being driven or removed for each sighting (if pile driving or 
removal was occurring at time of sighting);
    [ssquf] Description of any marine mammal behavior patterns during 
observation, including direction of travel and estimated time spent 
within the Level A and Level B harassment zones while the source was 
active;
    [ssquf] Number of individuals of each species (differentiated by 
month as appropriate) detected within the monitoring zone, and 
estimates of number of marine mammals taken, by species (a correction 
factor may be applied to total take numbers, as appropriate);
    [ssquf] Detailed information about any implementation of any 
mitigation triggered (e.g., shutdowns and delays), a description of 
specific actions that ensued, and resulting behavior of the animal, if 
any;
    [ssquf] Description of attempts to distinguish between the number 
of individual animals taken and the number of incidences of take, such 
as ability to track groups or individuals;
    [ssquf] An extrapolation of the estimated takes by Level B 
harassment based on the number of observed exposures within the Level B 
harassment zone and the percentage of the Level B harassment zone that 
was not visible; and
    [ssquf] Submit all PSO datasheets and/or raw sighting data (in a 
separate file from the Final Report referenced immediately above).

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's implementing 
regulations (54 FR 40338; September 29, 1989), the impacts from other 
past and ongoing anthropogenic activities are incorporated into this 
analysis via their impacts on the environmental baseline (e.g., as 
reflected in the regulatory status of the species, population size and 
growth rate where known, ongoing sources of human-caused mortality, or 
ambient noise levels). Of note, is the significant increase of takes by 
Level B harassment for bottlenose dolphins compared with what was 
evaluated in the notice of proposed IHA. Despite the increase in take 
numbers, our determination remains the same. There could be multiple 
takes of individual animals but without any long-term adverse effects. 
Take by Level B harassment of bottlenose dolphins will be minimized 
through use of mitigation measures.
    Pile driving activities associated with the planned HRCP project, 
as outlined previously, have the potential to disturb or displace 
marine mammals. The specified activities may result in take, in the 
form of Level B harassment (behavioral disturbance) or Level A 
harassment (auditory injury), incidental to underwater sounds generated 
from pile driving. Potential takes could occur if individuals are 
present in the ensonified zone when pile driving occurs. Level A 
harassment is only anticipated and authorized for harbor porpoises and 
harbor seals.
    No serious injury or mortality is anticipated given the nature of 
the activities and measures designed to minimize the possibility of 
injury to marine mammals. The potential for these outcomes is minimized 
through the construction method and the implementation of the 
mitigation measures. When impact pile driving is used, implementation 
of bubble curtains (during 36-in steel piles at the Jet Grouting 
Trestle in water depths greater than 6 m (20 ft)), soft start and 
shutdown zones significantly reduce the possibility of injury. Given 
sufficient notice through use of soft starts (for impact driving), 
marine mammals are expected to move away from a sound source that is 
annoying prior to it becoming potentially injurious.
    HRCP will use qualified PSOs stationed strategically to increase 
detectability of marine mammals, enabling a high rate of success in 
implementation of shutdowns to avoid injury for most species. PSOs will 
be stationed to provide a relatively clear view of the shutdown zones 
and monitoring zones. These factors will limit exposure of animals to 
noise levels that could result in injury.

[[Page 48177]]

    HRCP's planned pile driving activities are highly localized. Only a 
relatively small portion of the Chesapeake Bay may be affected. 
Localized noise exposures produced by project activities may cause 
short-term behavioral modifications in affected cetaceans and 
pinnipeds. Moreover, 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, 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 speeds, increased surfacing time, or decreased 
foraging (if such activity were occurring) (e.g., Thorson and Reyff 
2006). Individual animals, even if taken multiple times, will most 
likely move away from the sound source and be temporarily displaced 
from the areas of pile driving, although even this reaction has been 
observed primarily only in association with impact pile driving. The 
pile driving activities analyzed here are similar to, or less impactful 
than, 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. Furthermore, many 
projects similar to this one are also believed to result in multiple 
takes of individual animals without any documented long-term adverse 
effects. Level B harassment will be minimized through use of mitigation 
measures described herein and, if sound produced by project activities 
is sufficiently disturbing, animals are likely to simply avoid the area 
while the activity is occurring.
    In addition to the expected effects resulting from authorized Level 
B harassment, we anticipate that small numbers of harbor porpoises and 
some harbor seals may enter the Level A harassment zones undetected, 
particularly during times of DTH drilling when the Level A harassment 
zones are large. It is unlikely that the animals would remain in the 
area long enough for PTS to occur. If any animals did experience PTS, 
it would likely only receive slight PTS, i.e. minor degradation of 
hearing capabilities within regions of hearing that align most 
completely with the energy produced by pile driving (i.e., the low-
frequency region below 2 kHz), not severe hearing impairment or 
impairment in the regions of greatest hearing sensitivity. If hearing 
impairment occurs, it is most likely that the affected animal's 
threshold would increase by a few dBs, which is not likely to 
meaningfully affect its ability to forage and communicate with 
conspecifics. As described above, we expect that marine mammals would 
be likely to move away from a sound source that represents an aversive 
stimulus, especially at levels that would be expected to result in PTS, 
given sufficient notice through use of soft start.
    The project is not expected to have significant adverse effects on 
marine mammal habitat. No important feeding and/or reproductive areas 
for marine mammals are known to be near the project area. Project 
activities would not permanently modify existing marine mammal habitat. 
The activities may cause some fish to leave the area of disturbance, 
thus temporarily impacting marine mammal foraging opportunities in a 
limited portion of the foraging range. However, because of the 
relatively small area of the habitat that may be affected, the impacts 
to marine mammal habitat are not expected to cause significant or long-
term negative consequences.
    In summary and as described above, the following factors primarily 
support our determination that the impacts resulting from this activity 
are not expected to adversely affect the species or stock through 
effects on annual rates of recruitment or survival:
     No mortality is anticipated or authorized;
     Limited Level A harassment exposures (harbor porpoises and 
harbor seals) are anticipated;
     The anticipated incidents of Level B harassment consist 
of, at worst, temporary modifications in behavior that would not result 
in fitness impacts to individuals;
     The specified activity and associated ensonifed areas are 
very small relative to the overall habitat ranges of all species and 
does not include habitat areas of special significance (Biologically 
Important Areas or ESA-designated critical habitat); and
     The presumed efficacy of the mitigation measures in 
reducing the effects of the specified activity.
    Based on the analysis contained herein of the likely effects of the 
specified activity on marine mammals and their habitat, and taking into 
consideration the implementation of the monitoring and mitigation 
measures, NMFS finds that the total marine mammal take from the 
activity will have a negligible impact on all affected marine mammal 
species or stocks.

Small Numbers

    As noted above, only small numbers of incidental take may be 
authorized under sections 101(a)(5)(A) and (D) of the MMPA for 
specified activities other than military readiness activities. The MMPA 
does not define small numbers and so, in practice, where estimated 
numbers are available, NMFS compares the number of individuals taken to 
the most appropriate estimation of abundance of the relevant species or 
stock in our determination of whether an authorization is limited to 
small numbers of marine mammals. Additionally, other qualitative 
factors may be considered in the analysis, such as the temporal or 
spatial scale of the activities.
    The authorized take of four of the five marine mammal species/
stocks comprises less than one-third of the best available stock 
abundance, with the exception of the bottlenose dolphin stocks. There 
are three bottlenose dolphin stocks that could occur in the project 
area. Therefore, the estimated dolphin takes by Level B harassment 
would likely be portioned among the western North Atlantic northern 
migratory coastal stock, western North Atlantic southern migratory 
coastal stock, and NNCES stock. Based on the stocks' respective 
occurrence in the area, NMFS estimated that there would be 216 takes 
from the NNCES stock, with the remaining takes evenly split between the 
northern and southern migratory coastal stocks. Based on consideration 
of various factors described below, we have determined the numbers of 
individuals taken would likely comprise less than one-third of the best 
available population abundance estimate of either coastal migratory 
stock.
    Both the northern migratory coastal and southern migratory coastal 
stocks have expansive ranges and they are the only dolphin stocks 
thought to make broad-scale, seasonal migrations in coastal waters of 
the western North Atlantic. Given the large ranges associated with 
these two stocks it is unlikely that large segments of either stock 
would approach the project area and enter into the Chesapeake Bay. The 
majority of both stocks are likely to be found widely dispersed across 
their respective habitat ranges and unlikely to be concentrated in or 
near the Chesapeake Bay.
    Furthermore, the Chesapeake Bay and nearby offshore waters 
represent the boundaries of the ranges of each of the two coastal 
stocks during migration. The northern migratory coastal stock is found 
during warm water months from

[[Page 48178]]

coastal Virginia, including the Chesapeake Bay and Long Island, New 
York. The stock migrates south in late summer and fall. During cold 
water months dolphins may be found in coastal waters from Cape Lookout, 
North Carolina, to the North Carolina/Virginia. During January-March, 
the southern migratory coastal stock appears to move as far south as 
northern Florida. From April to June, the stock moves back north to 
North Carolina. During the warm water months of July-August, the stock 
is presumed to occupy coastal waters north of Cape Lookout, North 
Carolina, to Assateague, Virginia, including the Chesapeake Bay. There 
is likely some overlap between the northern and southern migratory 
stocks during spring and fall migrations, but the extent of overlap is 
unknown.
    The Chesapeake Bay and waters offshore of the mouth are located on 
the periphery of the migratory ranges of both coastal stocks (although 
during different seasons). Additionally, each of the migratory coastal 
stocks are likely to be located in the vicinity of the Chesapeake Bay 
for relatively short timeframes. Given the limited number of animals 
from each migratory coastal stock likely to be found at the seasonal 
migratory boundaries of their respective ranges, in combination with 
the short time periods (~two months) animals might remain at these 
boundaries, it is reasonable to assume that takes are likely to occur 
only within some small portion of either of the migratory coastal 
stocks.
    Both migratory coastal stocks likely overlap with the NNCES stock 
at various times during their seasonal migrations. The NNCES stock is 
defined as animals that primarily occupy waters of the Pamlico Sound 
estuarine system (which also includes Core, Roanoke, and Albemarle 
sounds, and the Neuse River) during warm water months (July-August). 
Members of this stock also use coastal waters (<=1 km from shore) of 
North Carolina from Beaufort north to Virginia Beach, Virginia, 
including the lower Chesapeake Bay. Comparison of dolphin photo-
identification data confirmed that limited numbers of individual 
dolphins observed in Roanoke Sound have also been sighted in the 
Chesapeake Bay (Young, 2018). Like the migratory coastal dolphin 
stocks, the NNCES stock covers a large range. The spatial extent of 
most small and resident bottlenose dolphin populations is on the order 
of 500 km\2\, while the NNCES stock occupies over 8,000 km\2\ 
(LeBrecque et al., 2015). Given this large range, it is again unlikely 
that a preponderance of animals from the NNCES stock would depart the 
North Carolina estuarine system and travel to the northern extent of 
the stock's range. However, recent evidence suggests that there is 
likely a small resident community of NNCES dolphins of indeterminate 
size that inhabits the Chesapeake Bay year-round (E. Patterson, NMFS, 
pers. comm.).
    Many of the dolphin observations in the Bay are likely repeated 
sightings of the same individuals. The Potomac-Chesapeake Dolphin 
Project has observed over 1,200 unique animals since observations began 
in 2015. Re-sightings of the same individual can be highly variable. 
Some dolphins are observed once per year, while others are highly 
regular with greater than 10 sightings per year (J. Mann, Potomac-
Chesapeake Dolphin Project, pers. comm.). Similarly, using available 
photo-identification data, Engelhaupt et al. (2016) determined that 
specific individuals were often observed in close proximity to their 
original sighting locations and were observed multiple times in the 
same season or same year. Ninety-one percent of re-sighted individuals 
(100 of 110) in the study area were recorded less than 30 km from the 
initial sighting location. Multiple sightings of the same individual 
would considerably reduce the number of individual animals that are 
taken by Level B harassment. Furthermore, the existence of a resident 
dolphin population in the Bay would increase the percentage of dolphin 
takes that are actually re-sightings of the same individuals.
    In summary and as described above, the following factors primarily 
support our determination regarding the incidental take of small 
numbers of the affected stocks of bottlenose dolphin:
     Potential bottlenose dolphin takes in the project area are 
likely to be allocated among three distinct stocks;
     Bottlenose dolphin stocks in the project area have 
extensive ranges and it would be unlikely to find a high percentage of 
any one stock concentrated in a relatively small area such as the 
project area or the Chesapeake Bay;
     The Chesapeake Bay represents the migratory boundary for 
each of the specified dolphin stocks and it would be unlikely to find a 
high percentage of any stock concentrated at such boundaries; and
     Many of the takes would likely be repeats of the same 
animals and likely from a resident population of the Chesapeake Bay.
    Based on the analysis contained herein of the planned activity 
(including the mitigation and monitoring measures) and the anticipated 
take of marine mammals, NMFS finds that small numbers of marine mammals 
will be taken relative to the population size of the affected species 
or stocks.

Unmitigable Adverse Impact Analysis and Determination

    There are no relevant subsistence uses of the affected marine 
mammal stocks or species implicated by this action. Therefore, NMFS has 
determined that the total taking of affected species or stocks would 
not have an unmitigable adverse impact on the availability of such 
species or stocks for taking for subsistence purposes.

National Environmental Policy Act

    To comply with the National Environmental Policy Act of 1969 (NEPA; 
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, 
NMFS must evaluate our proposed action (i.e., the promulgation of 
regulations and subsequent issuance of incidental take authorization) 
and alternatives with respect to potential impacts on the human 
environment. This action is consistent with categories of activities 
identified in Categorical Exclusion B4 of the Companion Manual for NAO 
216-6A, which do not individually or cumulatively have the potential 
for significant impacts on the quality of the human environment and for 
which we have not identified any extraordinary circumstances that would 
preclude this categorical exclusion. Accordingly, NMFS determined that 
the action qualified to be categorically excluded from further NEPA 
review.

Endangered Species Act (ESA)

    Section 7(a)(2) of the Endangered Species Act of 1973 (ESA: 16 
U.S.C. 1531 et seq.) requires that each Federal agency insure that any 
action it authorizes, funds, or carries out is not likely to jeopardize 
the continued existence of any endangered or threatened species or 
result in the destruction or adverse modification of designated 
critical habitat. No incidental take of ESA-listed marine mammals are 
expected or authorized. Therefore, NMFS determined that consultation 
under section 7 of the ESA was not required for this action.

Authorization

    As a result of these determinations, NMFS has issued an IHA to the 
HRCP for pile driving activities associated with the HRBT Expansion 
Project in Hampton-Norfolk, Virginia for a period of one year provided 
the previously mentioned mitigation, monitoring, and reporting 
requirements are incorporated.


[[Page 48179]]


    Dated: August 4, 2020.
Donna S. Wieting,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2020-17344 Filed 8-7-20; 8:45 am]
BILLING CODE 3510-22-P