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Notice2026-03945

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

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Published

February 27, 2026

Issuing agencies

Commerce DepartmentNational Oceanic and Atmospheric Administration

Abstract

NMFS has received a request from the Hampton Roads Connector Partners (HRCP) for authorization to take marine mammals incidental to Hampton Roads Bridge-Tunnel Expansion Project (HRBT) in Norfolk, Virginia. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an incidental harassment authorization (IHA) to incidentally take marine mammals during the specified activities. NMFS is also requesting comments on a possible one-time, 1-year renewal that could be issued under certain circumstances and if all requirements are met, as described in Request for Public Comments at the end of this notice. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorization and agency responses will be summarized in the final notice of our decision.

Full Text

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[Federal Register Volume 91, Number 39 (Friday, February 27, 2026)]
[Notices]
[Pages 9815-9843]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-03945]

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XF531]

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

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

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

-----------------------------------------------------------------------

SUMMARY: NMFS has received a request from the Hampton Roads Connector
Partners (HRCP) for authorization to take marine mammals incidental to
Hampton Roads Bridge-Tunnel Expansion Project (HRBT) in Norfolk,
Virginia. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is
requesting comments on its proposal to issue an incidental harassment
authorization (IHA) to incidentally take marine mammals during the
specified activities. NMFS is also requesting comments on a possible
one-time, 1-year renewal that could be issued under certain
circumstances and if all requirements are met, as described in Request
for Public Comments at the end of this notice. NMFS will consider
public comments prior to making any final decision on the issuance of
the requested MMPA authorization and agency responses will be
summarized in the final notice of our decision.

DATES: Comments and information must be received no later than March
30, 2026.

ADDRESSES: Comments should be addressed to Permits and Conservation
Division, Office of Protected Resources, National Marine Fisheries
Service and should be submitted via email to <a href="/cdn-cgi/l/email-protection#1f564b4f316f7e6a7376717a5f71707e7e31787069"><span class="__cf_email__" data-cfemail="aae3fefa84dacbdfc6c3c4cfeac4c5cbcb84cdc5dc">[email&#160;protected]</span></a>.
Electronic copies of the application and supporting documents, as well
as a list of the references cited in this document, may be obtained
online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>. In
case of problems accessing these documents, please call the contact
listed below.

[[Page 9816]]

Instructions: NMFS is not responsible for comments sent by any
other method, to any other address or individual, or received after the
end of the comment period. Comments, including all attachments, must
not exceed a 25-megabyte file size. All comments received are a part of
the public record and will generally be posted online at <a href="https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act">https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act</a> without change. All personal identifying
information (e.g., name, address) voluntarily submitted by the
commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.

FOR FURTHER INFORMATION CONTACT: Robert Pauline, Office of Protected
Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Background

The MMPA prohibits the ``take'' of marine mammals, with certain
exceptions. Section 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et
seq.) directs the Secretary of Commerce (as delegated to NMFS) to
allow, upon request, the incidental, but not intentional, taking of
small numbers of marine mammals by U.S. citizens who engage in a
specified activity (other than commercial fishing) within a specified
geographical region if certain findings are made and either regulations
are proposed or, if the taking is limited to harassment, a notice of a
proposed IHA is provided to the public for review.
Authorization for incidental takings shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s) and will not have an unmitigable adverse impact on the
availability of the species or stock(s) for taking for subsistence uses
(where relevant). Further, NMFS must prescribe the permissible methods
of taking; other ``means of effecting the least practicable adverse
impact'' on the affected species or stocks and their habitat, paying
particular attention to rookeries, mating grounds, and areas of similar
significance, and on the availability of the species or stocks for
taking for certain subsistence uses (referred to as ``mitigation'');
and requirements pertaining to the monitoring and reporting of the
takings. The definitions of all applicable MMPA statutory terms used
above are included in the relevant sections below (see also 16 U.S.C.
1362; 50 CFR 216.3 and 216.103).

National Environmental Policy Act

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

Summary of Request

On August 8, 2025, NMFS received a request from HRCP for an IHA to
take marine mammals incidental to construction of the HRBT in Norfolk,
Virginia. The application was deemed adequate and complete on February
13, 2026. HRCP's request is for take of five species of marine mammals
by Level B harassment and, for a subset of these species, Level A
harassment. Neither HRCP nor NMFS expect serious injury or mortality to
result from this activity and, therefore, an IHA is appropriate.
NMFS initially issued an IHA to HRCP on August 10, 2020 (85 FR
48153) then promulgated regulations and issued a five-year Letter of
Authorization to HRCP for similar work (86 FR 17458, April 2, 2021).
HRCP complied with all the requirements (e.g., mitigation, monitoring,
and reporting) of the previous Letter of Authorization (LOA), and
information regarding their monitoring results may be found in the
Estimated Take of Marine Mammals section.
This proposed IHA would cover 1 year of a larger project for which
HRCP was issued the LOA. Barring any delays, the sixth year project
should result in the complete construction of the bridge-tunnel
project.

Description of Proposed Activity

Overview

HRCP is proposing to continue ongoing construction activities
associated with the HRBT project. This is a major road transport
infrastructure project along the existing I-64 highway in Virginia,
consisting of roadway improvements, trestle bridges, and bored tunnels
crossing Hampton Roads between Norfolk and Hampton. The Project will
address severe traffic congestion at the existing HRBT crossing by
increasing capacity. Due to unforeseen schedule delays, all in-water
pile installation which began in December 2020 under an IHA (85 FR
48153) will not be completed by the existing LOA's (86 FR 17458)
expiration (March 31, 2026) and therefore, HRCP has requested a 1-year
(IHA) to complete the outstanding construction components.
Given the proposed use of vibratory and impact pile driving and
vibratory pile removal, there is potential of the take of marine
mammals by Level B harassment and, for a subset of the species, Level A
harassment. No serious injury and/or mortality is expected or proposed
for this project.

Dates and Duration

The proposed IHA would be valid for the statutory maximum of 1 year
from the date of effectiveness. The IHA effective period would begin on
April 1, 2026 and end on March 31, 2027. The overall number of
anticipated days of pile installation and removal is 312 per year,
based on a 6-day work week for 1 year.

Specific Geographic Region

The Project is located in the waterway of Hampton Roads adjacent to
the existing bridge and island structures of the HRBT in Virginia
(figure 1). Hampton Roads is located at the confluence of the James
River, the Elizabeth River, the Nansemond River, Willoughby Bay, and
the Chesapeake Bay. Hampton Roads, one of the world's largest natural
harbors, is a wide marine channel that provides access to the Port of
Virginia and several other deep-water anchorages upstream of the
Project area. The Port of Virginia, located along the Elizabeth River,
is a naturally deep harbor. Navigational channels are maintained by the
U.S. Army Corps of Engineers (USACE) within Hampton Roads to provide
transit to the many ports in the region.
BILLING CODE 3510-22-P

[[Page 9817]]

[GRAPHIC] [TIFF OMITTED] TN27FE26.004

BILLING CODE 3510-22-C

Detailed Description of the Specified Activity

The HRBT project will widen I-64 for approximately 9.9 miles along
I-64 from Settlers Landing Road in Hampton, Virginia, to the I-64/I-564
interchange in Norfolk, Virginia and 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 Bridges, and Oastes Creek 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.
Two methods of pile installation are anticipated: vibratory hammer
and impact hammer. More than one installation method could be used
within a day and at each location. Most steel pipe piles will be
installed using a combination of vibratory (ICE 416L or similar) and
impact hammers (S35 or similar). Steel pipe piles will be installed
using the vibratory hammer approximately 80 percent of the time and
impact hammer approximately 20 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

[[Page 9818]]

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.
Permanent piles will be set using temporary steel templates.
Templates will be positioned and held in place using 36-inch steel pipe
piles, generally one at each corner of the template. As templates are
temporary and largely do not bear significant vertical loads,
installation (i.e., driving) and removal of template requires minimal
driving time, approximately 5 minutes per pile. Permanent concrete
piles will be installed using an impact hammer. Temporary steel sheet
piles and steel pipe piles will be removed using a vibratory hammer or
cut to approximately 2-3 feet (60.9-91.4 cm) below the mudline.
The HRBT project design is divided into five segments as shown in
table 1 and figure 1. Only the segments that have the potential to
affect marine mammals will be discussed further and are identified in
table 1. Table 2 shows the piles proposed for installation under the
proposed IHA.

Table 1--HRBT Expansion Project Design Segments
------------------------------------------------------------------------
In-water
Project design segment No. and activities that
name Construction area could result in
take
------------------------------------------------------------------------
Segment 1a (Hampton)............ Area 1............
Segment 1b (North Trestle- Area 2............ X.
Bridges).
Segment 2a (Tunnel)............. Area 3............ X.
Segment 3a (South Trestle- Area 2............ X.
Bridge).
Segment 3b (Willoughby Spit).... Area 4............ X.
Segment 3c (Willoughby Bay Area 2............ X.
Trestle-Bridges).
Segment 3d (4th View Street Area 4............
Interchange).
Segment 4a (Norfolk-Navy)....... Area 4............
------------------------------------------------------------------------

Table 2--Piles To Be Installed/Removed Under Proposed IHA
------------------------------------------------------------------------
Total number Total number
Pile size/type and material of piles to be of piles to be
installed removed
------------------------------------------------------------------------
AZ-19 Steel Sheet....................... 95 95
36-inch Steel Pipe...................... 642 1,074
36-inch Steel Pipe (Template Piles)..... 112 112
54-inch, Concrete Cylinder Pipe......... 130 0
12-inch Composite Pile.................. 42 42
------------------------------------------------------------------------

Segment 1b (North Trestle-Bridges)

Several temporary work trestles will support construction of the
permanent eastbound and westbound North Trestle-Bridges. The temporary
North Shore Work Trestle will support construction of the permanent
eastbound North Trestle-Bridge in the shallow water (<4 to 6 feet (1.2
to 1.8 m) Mean Low Water (MLW)) closer to the North Shore, avoiding the
need to dredge or deepen this area and minimizing potential impacts to
the adjacent submerged aquatic vegetation. The temporary North Shore
Work Trestle was installed under a separate IHA (85 FR 48153, August
10, 2020).
Additional temporary work trestles will support construction of the
permanent westbound North Trestle-Bridge in the shallow water near the
North Island. These work trestles will be the same or like the North
Shore Work Trestle, steel structures founded on 36-inch diameter steel
pipe piles with 30 to 40 feet (9.1 to 12.2 m) spans sized to
accommodate a 300-ton crane. One hundred and eighty-three 36-inch steel
piles will be installed to support these trestles using a combination
of vibratory and impact hammers.
Once that portion of the permanent eastbound and westbound North
Trestle-Bridge is complete, the temporary pile foundations will be
removed using a vibratory hammer and the work trestle reused for
similar purposes at a different location on the Project.
Jump Trestles at the North Trestle temporary heavy-duty platforms
used to support cranes and other equipment, will be used for
constructing trestle bridges (new permanent maintenance of traffic
(MOT) bridges). Jump trestles are built with a maximum of three spans
which are progressively removed and reinstalled one span at a time,
moving forward with the construction of the adjacent structure. Each
span is supported by six temporary 36-inch steel pipe piles. The steel
pipe piles will be installed, removed, and reinstalled as the spans
move forward using a combination of vibratory and impact hammers for
installation and vibratory hammers for removal. Approximately 140
individual pile installations and 140 removals will be needed to
support the Jump Trestle movement for construction of the permanent
westbound North Trestle-Bridge.
Temporary template piles will be used to guide installation of the
permanent concrete piles used to support the new North Trestle-Bridge.
The templates will be supported by four temporary steel piles up to 36-
inch in diameter, generally one at each corner of the template. A two-
tier template will be used to account for the batter of the permanent
piles. Each template will allow installation of multiple permanent
concrete piles. A vibratory hammer will be used to install and remove
the 30 temporary 36-inch steel piles supporting the template. Of the
562 permanent 54-inch concrete cylinder piles on the project, 30 remain
for installation on the North Trestle under this IHA request. These
piles are installed using an impact hammer and will remain in place at
the end of construction.
Steel sheet piles will be installed at the North Shore shoreline to
support excavation and construction of the North Shore Abutment.
Approximately 30 panels of AZ-700-19 sheet piles remain to be
temporarily installed using a vibratory hammer to form a continuous.
Sheet piles will be removed using a vibratory hammer.
A temporary dock consisting of 24 36-inch steel piles was
constructed on the

[[Page 9819]]

West side of the North Island to allow the circulation of equipment and
material around the Cell 1 and Cell 2 Shafts located in North Island.
The piles will be removed using a vibratory hammer or cut to
approximately 3 feet (91.4 cm) below the mudline.

Segment 2a

HRCP constructed 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 installation of the TBM
platform was performed under a separate IHA (85 FR 48153, August 10,
2020).
The TBM Platform is a steel structure founded on 136 36-inch
diameter steel piles. At the conclusion of the Project, the TBM
Platform piles will be removed using a vibratory hammer or cut to
approximately 2-3 feet (60.9-91.4 cm) below the mudline.
Tunnel boring spoils and other related materials were moved between
the South Island and barges via a conveyor belt and other equipment
inside the tunnel boring machine. The Conveyor Trestle was 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 10 36-inch diameter steel piles. The
installation of the Conveyor Trestle was performed under the previous
LOA. At the conclusion of the Project, the Conveyor Trestle piles will
be removed using a vibratory hammer or cut to approximately 3 feet
(91.4 cm) below the mudline.
Temporary moorings have been installed along the perimeter of the
South Island Expansion to support the construction of the island
expansion. Thirty-four 36-inch steel pipe piles remain to be removed
once the barges and vessels are no longer needed. They will be removed
using a vibratory hammer at the conclusion of the Project.

Segment 3a

Temporary template piles will be used to guide installation of the
permanent concrete piles used to support the new South Trestle-Bridge.
The templates will use four temporary steel piles 36-inch in diameter
as supports, generally one at each corner of the template. A two-tier
template will be used to account for the possible batter of the piles.
Each template will allow installation of multiple permanent concrete
piles. A vibratory hammer will be used to install and remove the
remaining 100 temporary 36-inch steel piles supporting the template.
Of the 810 permanent 54-inch concrete cylinder piles needed on the
South Trestle, only 100 piles will remain to be installed under the
requested IHA. These piles will be installed using an impact hammer and
will remain in place at the end of construction.
Temporary heavy duty moving platforms (Jump Trestles) will be used
for constructing trestle bridges (both new permanent and temporary MOT
bridges) at the South Trestle. A combination of jump trestles and
working from the existing trestles will be used to build the new
trestle bridges. Jump trestles are built with a maximum of three spans
which are progressively uninstalled and reinstalled one span at a time,
moving forward with the construction of the adjacent structure.
The 36-inch steel pipe piles will be installed, removed, and
reinstalled as the spans move forward using a combination of vibratory
and impact hammers for installation and vibratory hammers for removal.
To minimize hydroacoustic impacts caused by the impact hammer, a bubble
curtain will be used for installation of steel pipe piles in water
depths greater than 20 feet (6.1 m). Portions of the South Trestle Jump
Trestle in water depths less than 20 feet 6.1 m) will be installed
without a bubble curtain. Approximately 189 individual pile
installations and 189 removals will still be needed to support the jump
trestle movement for construction of the permanent westbound South
Trestle-Bridge.

Segment 3c

There are 40 remaining temporary moorings to be removed in
Willoughby Bay to support the construction of temporary work trestles
and permanent trestle bridges, and to provide a safe haven (harbor of
safe refuge) for vessels in the event of severe weather. The piles will
be removed using a vibratory hammer.
The existing fender was previously removed under the previous 5-
year LOA. The proposed fender will require 42 12-inch composite piles
that will be installed over a 4-month period. These will be permanent
piles that will not require removal.
There is currently an existing 36-inch stormwater outfall in this
location that will be replaced with a 42-inch pipe to increase the
capacity. This will require the installation of 65 PZ-19 sheet piles to
create coffer damns in order to protect the excavation, removal,
installation and backfill operations associated with replacing the
bulkhead. These piles will be installed and removed with a vibratory
hammer.

Segment 3b

HRCP was granted use of property on Willoughby Spit next to the
South Trestle-Bridge to be used for laydown areas and as a base for
marine operations. Two temporary piers were constructed to allow barge
access. At the conclusion of the project, under this IHA, there will be
the remaining six 36-inch steel piles that will need to be removed. The
temporary steel piles will be removed using a vibratory hammer.
Table 3 shows summary of all piles planned to be installed or
removed and their specific attributes.

Table 3--Numbers and Types of Piles To Be Installed and Removed Under IHA
[April 2026 through April 2027]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Number of
Installation/ Bubble Number of days per Number of days Anticipated
Pile location Pile function Pile type removal method curtain piles activity per activity (per installation date
yes/no below MHW (total) ** hammer type)
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Trestle...... Jump Trestle...... 36-inch Diameter Impact (Install). Yes....... 140 140 70 Days (2 piles/ 4/10-12/31/2026.
Hollow Steel Pipe Vibratory No........ Day).
Pile. (Removal). 70 Days (2 piles/
Day).
North Trestle...... Template Piles.... 36-inch Diameter Vibratory No........ 30 20 10Days (3Piles/ 4/16-8/1/2026.
Hollow Steel Pipe (Install & Day).
Pile. Removal). 10 Days (3 Piles/
Day).
North Trestle...... Permanent Piles... 54-inch, Concrete Impact (Install No........ 30 30 30 Days (1 Pile/ 4/16-8/1/2026.
Cylinder Pipe. Only). Day).

[[Page 9820]]

North Trestle...... Sheet Pile PZ 19-Sheet....... Vibratory Install No........ 30 10 5 Days 6 Piles/ 4/1/2026-3/30/
Installation for & Removal). Day). 2027.
Shore 5 Days (6 Piles/
Stabilization. Day).
North Trestle...... Temporary Trestle. 36-inch Diameter Impact (Install). Yes....... 183 184 92 Days (2Piles/ 4/1-8/30/2026.
Hollow Steel Pipe Vibratory No........ Day).
Piles. (Removal). 92 Days (2 Piles/
Day).
North Island....... Circulation Dock.. 36-inch Diameter Vibratory No........ 24 12 12 Days (2 Piles/ 3/01-3/30/2027.
Hollow Steel Pipe (Removal Only). Day).
Piles.
South Trestle...... Temp MOT Trestle.. 36-inch Diameter Vibratory No........ 182 61 61 Days (3 Piles/ 4/1/2026-1/8/
Hollow Steel Pipe (Removal Only). Day). 2027.
Piles.
South Trestle...... Permanent Piles... 54-inch, Concrete Impact (Install No........ 100 100 100 Days (1 Pile/ 4/16-8/1/2026.
Cylinder Pipe. Only). Day).
South Island....... Template Piles.... 36-inch Diameter Vibratory No........ 100 56 28Days (3Piles/ 4/1/-3/30/2027.
Hollow Steel Pipe (Install & Day).
Piles. Removal). 28 Days (3 Piles/
Day).
South Island....... Temp/Jump Trestle. 36-inch Diameter Impact (Install). No........ 189 126 63Days (3Piles/ 4/1/-3/30/2027.
Hollow Steel Pipe Vibratory Yes....... Day).
Piles. (Removal). 63Days (3Piles/
Day).
South Island....... TBM Mooring Piles. 36-inch Diameter Vibratory No........ 34 17 17 Days (2 Piles/ 11/1-12/31/2026.
Hollow Steel Pipe (Removal Only). Day).
Piles.
South Island....... TBM Platform 36-inch Diameter Vibratory No........ 136 68 68 Days (2 Piles/ 1/1-3/30/2027.
(Quay). Hollow Steel Pipe (Removal Only). Day).
Piles.
South Island....... TBM Conveyor...... 36-inch Diameter Vibratory No........ 10 5 5 Days (2 Piles/ 4/15-5/15/2026.
Hollow Steel Pipe (Removal Only). Day).
Piles.
Willoughby Spit.... Temp Dock/Finger 36-inch Diameter Vibratory No........ 6 2 2Days (3 Piles/ 11/1-12/31/2026.
Piers. Hollow Steel Pipe (Removal Only). Day).
Piles.
Willoughby Bay..... Moorings (Safe 36-inch Diameter Vibratory No........ 40 10 10 Days (4Piles/ 11/1-12/31/2026.
Haven). Hollow Steel Pipe (Install & Day).
Piles. Removal). 10 Days (4 Piles/
Day).
Willoughby Bay..... Fender............ 12-inch Diameter Vibratory No........ 42 42 42 Days (1Pile/ 4/1-12/31/2027.
Composite Piles. (Install). Day).
Willoughby Bay..... Sheet Pile PZ 19-Sheet....... Vibratory No........ 65 22 11 Days (6Piles/ 4/1-5/1/2026.
Installation for (Install & Day).
Bulkhead Removal). 11 Days (6Piles/
Replacement. Day).
--------------------------------------------------------------------------------------------------------------------------------------------------------

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

Description of Marine Mammals in the Area of Specified Activities

Sections 3 and 4 of the application summarize available information
regarding status and trends, distribution and habitat preferences, and
behavior and life history of the potentially affected species. NMFS
fully considered all of this information, and we refer the reader to
these descriptions, instead of reprinting the information. Additional
information regarding population trends and threats may be found in
NMFS' Stock Assessment Reports (SARs; <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>) and
more general information about these species (e.g., physical and
behavioral descriptions) may be found on NMFS' website (<a href="https://www.fisheries.noaa.gov/find-species">https://www.fisheries.noaa.gov/find-species</a>).
Table 4 lists all species or stocks for which take is expected and
proposed to be authorized for this activity and summarizes information
related to the population or stock, including regulatory status under
the MMPA and Endangered Species Act (ESA) and potential biological
removal (PBR), where known. PBR is defined by the MMPA as the maximum
number of animals, not including natural mortalities, that may be
removed from a marine mammal stock while allowing that stock to reach
or maintain its optimum sustainable population (as described in NMFS'
SARs). While no serious injury or mortality is anticipated or proposed
to be authorized here, PBR and annual mortality and serious injury (M/
SI) from anthropogenic sources are included here as gross indicators of
the status of the species or stocks and other threats.
Marine mammal abundance estimates presented in this document
represent the total number of individuals that make up a given stock or
the total number estimated within a particular study or survey area.
NMFS' stock abundance estimates for most species represent the total
estimate of individuals within the geographic area, if known, that
comprises that stock. For some species, this geographic area may extend
beyond U.S. waters. All managed stocks in this region are assessed in
NMFS' U.S. U.S. Atlantic and Gulf of Mexico Marine Mammal Stock
Assessments 2023 (Hayes et al. 2024). All values presented in table 3
are the most recent available at the time of

[[Page 9821]]

publication (including from the draft 2024 SARs) and are available
online at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>.

Table 4--Species \a\ With Estimated Take From the Specified Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
ESA/MMPA status; Stock abundance (CV,
Common name Scientific name Stock strategic (Y/N) Nmin, most recent PBR Annual M/
\b\ abundance survey) \c\ SI \d\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Cetartiodactyla--Cetacea--Superfamily Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Balaenopteridae (rorquals):
Humpback Whale.................. Megaptera novaeangliae. Gulf of Maine.......... -,-; N 1,396 (0, 1,380; 2019) 22 12.15
--------------------------------------------------------------------------------------------------------------------------------------------------------
Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Delphinidae:.................
Bottlenose dolphin.............. Tursiops truncatus..... WNA Coastal, Northern -,-; Y 6,639 (0.41; 4,759; 48 12.2-21.5
Migratory. 2020).
WNA Coastal, Southern -,-; Y 3,751 (0.6; 2,353; 24 0-18.3
Migratory. 2020).
Northern North Carolina -,-; Y 823 (0.06; 782; 2020). 7.8 7.2-30
Estuarine System.
Family Phocoenidae (porpoises):
Harbor porpoise................. Phocoena phocoena...... Gulf of Maine/Bay of -, -; N 85,765 (0.53; 56,420; 649 145
Fundy. 2021).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Carnivora--Superfamily Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Phocidae (earless seals):
Harbor seal..................... Phoca vitulina......... WNA.................... -; N 61,336 (0.08; 57,637 1,729 339
2021)\e\.
Gray seal....................... Halichoerus grypus..... WNA.................... -; N 27,911 (0.20, 23,624, 1,512 4,570
2021).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy
(<a href="https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/">https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/</a>).
\b\ 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 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.
\c\ NMFS marine mammal stock assessment reports online at <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a> assessments. CV is the coefficient of variation; N min is the minimum estimate of stock abundance. In some cases, a CV is not applicable. N/A
indicates data are unknown. UND (undetermined) PBR indicates data are available to calculate a PBR level, but a determination has been made that
calculating a PBR level using those data is inappropriate (see the SAR for details).
\d\ 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 strikes). Annual M/SI often cannot be determined precisely and is sometimes presented as a minimum value or range.
\e\ NMFS' stock abundance estimate (and associated Potential Biological Removal value) applies to the U.S. population only. Total stock abundance
(including animals in Canada) is approximately 394,311. The annual M/SI value given is for the total stock.

As indicated above, all five species (with eight managed stocks) in
table 4 temporally and spatially co-occur with the activity to the
degree that take is reasonably likely to occur.

Humpback Whale

In the winter months, humpback whales from waters off New England,
Canada, Greenland, Iceland, and Norway, migrate to mate and calve
primarily in the West Indies, where spatial and genetic mixing among
these groups occurs. NMFS defines a humpback whale stock on the basis
of feeding location (i.e., Gulf of Maine). However, our reference to
humpback whales in this document refers to any individual of the
species that are found in the species geographic region. These
individuals may be from the same breeding population (e.g., West Indies
breeding population of humpback whales) but visit different feeding
areas.
Prior to 2016, humpback whales were listed under the ESA as an
endangered species worldwide. Following a 2015 global status review
(Bettridge et al., 2015), NMFS established 14 Distinct Population
Segments (DPSs) with different listing statuses (81 FR 62259, September
8, 2016) pursuant to the ESA. Humpback whales in the Project Area are
expected to be from the West Indies DPS, which consists of the whales
whose breeding range includes the Atlantic margin of the Antilles from
Cuba to northern Venezuela, and whose feeding range primarily includes
the Gulf of Maine, eastern Canada, and western Greenland. This DPS is
not ESA listed. Bettridge et al., (2003) estimated the size of the West
Indies DPS at 12,312 (95 percent confidence interval 8,688-15,954)
whales in 2004-05, which is consistent with previous population
estimates of approximately 10,000-11,000 whales (Stevick et al., 2003;
Smith et al., 1999) and the increasing trend for the West Indies DPS
(Bettridge et al., 2015).
Since January 2016, elevated humpback whale mortalities have
occurred along the Atlantic coast from Maine through Florida. This
event was declared an unusual mortality event (UME) in 2017. A portion
of the whales have shown evidence of pre-mortem vessel strike; however,
this finding is not consistent across all whales examined, and
additional research is needed. Since early 2026, over 240 mortalities
have been subject to the active UME. Additional information is
available at: <a href="https://www.fisheries.noaa.gov/national/marine-life-distress/2016-2026-humpback-whale-unusual-mortality-event-along-atlantic-coast">https://www.fisheries.noaa.gov/national/marine-life-distress/2016-2026-humpback-whale-unusual-mortality-event-along-atlantic-coast</a>.
Humpback whales are most likely to occur near the mouth of the
Chesapeake Bay and coastal waters of Virginia Beach between January and
March; however, they could be found in the area year-round, based on
shipboard sighting and stranding data (Barco and Swingle, 2014;
Aschettino et al., 2015; 2016; 2017; 2018). Photo-identification data
support the repeated use of the mid-Atlantic region by individual
humpback whales. Results of the vessel surveys show site fidelity in
the survey area for some individuals and a high level of occurrence
within shipping channels--an important high-use area by both the Navy
and commercial traffic (Aschettino et al., 2015; 2016; 2017; 2018).

[[Page 9822]]

Nearshore surveys conducted in early 2015 reported 61 individual
humpback whale sightings, and 135 individual humpback whale sightings
in late 2015 through May 2016 (Aschettino et al., 2016). Subsequent
surveys confirmed the occurrence of humpback whales in the nearshore
survey area: 248 individuals were detected in 2016-2017 surveys
(Aschettino et al., 2017), 32 individuals were detected in 2017-2018
surveys (Aschettino et al., 2018), and 80 individuals were detected in
2019 surveys (Aschettino et al., 2019). Sightings in the Hampton Roads
area in the vicinity of NAVSTA Norfolk were reported in nearshore
surveys and through tracking of satellite-tagged whales in 2016, 2017
and 2019. The numbers of whales detected, most of which were juveniles,
reflect the varying level of survey effort and changes in survey
objectives from year to year, and do not indicate abundance trends over
time. Recent monitoring reports from the Hampton Roads Bridge-Tunnel
Expansion Project and the Pier 3 Navy Construction Project did not
observe any humpback whales near the project sites. Monitoring for the
Hampton Roads Bridge-Tunnel Expansion Project spanned from September
2020 through July 2021 (over a 197-day period) and monitoring for the
Pier 3 Navy Construction Project spanned from August 2022 to December
2022 (i.e., over a 45-day period) (WF Magann 2023)

Bottlenose Dolphin

Along the U.S. East Coast and northern Gulf of Mexico, the
bottlenose dolphin stock structure is well studied. There are currently
54 management stocks identified by NMFS in the western North Atlantic
and Gulf of Mexico, including oceanic, coastal, and estuarine stocks
(Hayes et al., 2017; Waring et al., 2015, 2016).
Bottlenose dolphins inhabiting nearshore coastal and estuarine
waters between New York and Florida may be a separate species from
their offshore counterparts (Costa et al., 2022). The offshore form is
larger in total length and skull length and has wider nasal bones than
the coastal form. Both inhabit waters in the western North Atlantic
Ocean and Gulf of Mexico (Hersh and Duffield, 1990; Mead and Potter,
1995) along the U.S. Atlantic coast. The coastal species of bottlenose
dolphin is continuously distributed along the Atlantic coast south of
Long Island, New York, around the Florida peninsula, and along the Gulf
of Mexico coast. This type typically occurs in waters less than 25
meters deep (Waring et al., 2015). The range of the offshore bottlenose
dolphin includes waters beyond the continental slope (Kenney, 1990),
and offshore bottlenose dolphins may move between the Gulf of Mexico
and the Atlantic (Wells et al., 1999).
Two coastal stocks are likely to be present in the Project Area:
(1) the Western North Atlantic Northern Migratory Coastal stock; and
(2) the Western North Atlantic Southern Migratory Coastal stock.
Additionally, the Northern North Carolina Estuarine System (NNCES)
stock may occur in the Project Area.
Bottlenose dolphins are the most abundant marine mammal along the
Virginia coast and within the Chesapeake Bay, typically traveling in
groups of 2-15 individuals, but occasionally in groups of over 100
individuals (Engelhaupt et al., 2014; 2015; 2016). Bottlenose dolphins
of the Western North Atlantic Northern Migratory Coastal stock winter
along the coast of North Carolina and migrate as far north as Long
Island, New York, in the summer. The Western North Atlantic Southern
Migratory Coastal stock occurs in waters of southern North Carolina
from October to December, moving south during winter months and north
to North Carolina during spring months. During July and August, the
Western North Atlantic Southern Migratory Coastal stock is presumed to
occupy coastal waters north of Cape Lookout, North Carolina, to the
eastern shore of Virginia (NMFS, 2018). It is possible that these
animals also occur inside the Chesapeake Bay and in nearshore coastal
waters. The North Carolina Estuarine System stock dolphins may also
occur in the Chesapeake Bay during July and August (NMFS, 2018).
Vessel surveys conducted along coastal and offshore transects from
NAVSTA Norfolk to Virginia Beach in most months from August 2012 to
August 2015 reported bottlenose dolphins throughout the survey area,
including the vicinity of NAVSTA Norfolk (Engelhaupt et al., 2014;
2015; 2016). The final results from this project confirmed earlier
findings that bottlenose dolphins are common in the study area, with
highest densities in the coastal waters in summer and fall months.
However, bottlenose dolphins do not completely leave this area during
colder months, with approximately 200-300 individuals still present in
winter and spring months, which is commonly referred to as the
Chesapeake Bay resident dolphin population (Engelhaupt et al., 2016).
During monitoring of Pier 3 Navy Construction Project, 18 bottlenose
dolphins were observed over 45 days of construction (W.F. Magann
Corporation 2023). Over the 197 days of construction a total of 94
bottlenose dolphins were observed during the Hampton Roads Bridge-
Tunnel Expansion Project (Hampton Roads Connector Partners 2023). For
both projects bottlenose dolphins were the only marine mammal observed
while conducting monitoring activities.

Harbor Porpoise

Harbor porpoises inhabit cool temperate-to-subpolar waters, often
where prey aggregations are concentrated (Watts and Gaskin, 1985).
Thus, they are frequently found in shallow waters, most often near
shore, but they sometimes move into deeper offshore waters. Harbor
porpoises are rarely found in waters warmer than 63 degrees Fahrenheit
(17 degrees Celsius) and closely follow the movements of their primary
prey, Atlantic herring (Gaskin 1992).
In the western North Atlantic, harbor porpoise range from
Cumberland Sound on the east coast of Baffin Island, southeast along
the eastern coast of Labrador to Newfoundland and the Gulf of St.
Lawrence, then southwest to about 34 degrees North on the coast of
North Carolina (Waring et al., 2016). During winter (January to March),
intermediate densities of harbor porpoises can be found in waters off
New Jersey to North Carolina, and lower densities are found in waters
off New York to New Brunswick, Canada (Waring et al., 2016). Harbor
porpoises sighted off the mid-Atlantic during winter include porpoises
from other western North Atlantic populations (Rosel et al., 1999).
There does not appear to be a temporally coordinated migration or a
specific migratory route to and from the Bay of Fundy region (Waring et
al., 2016). During the fall (October to December) and the spring (April
to June), harbor porpoises are widely dispersed from New Jersey to
Maine, with lower densities farther north and south (LaBrecque et al.,
2015).
Based on stranding reports, passive acoustic recorders, and
shipboard surveys, harbor porpoise occur in coastal waters primarily in
winter and spring months, but there is little information on their
presence in the Chesapeake Bay. They do not appear to be abundant in
the NAVSTA Norfolk area in most years, but this is confounded by wide
variations in stranding occurrences over the past decade. There were no
harbor porpoise observed during construction activities for the Pier 3
Navy Construction Project or the Hampton Roads Bridge-Tunnel Expansion
Project (Hampton Roads

[[Page 9823]]

Connector Partners 2023; W.F. Magann Corporation 2023).

Harbor Seal

The Western North Atlantic stock of harbor seals occurs in the
Project Area. Harbor seal distribution along the U.S. Atlantic coast
has shifted in recent years, with an increased number of seals reported
from southern New England to the mid-Atlantic region (DiGiovanni et
al., 2011; Hayes et al., 2021). Regular sightings of seals in Virginia
have become a common occurrence in winter and early spring (Costidis et
al., 2019). Winter haulout sites for harbor seals have been documented
in the Chesapeake Bay at the Chesapeake Bay Bridge Tunnel (CBBT), on
the Virginia Eastern Shore, and near Oregon Inlet, North Carolina
(Waring et al., 2016; Rees et al., 2016; Jones et al., 2018).
Harbor seals regularly haul out on rocks around the portal islands
of the CBBT and on mud flats on the nearby southern tip of the Eastern
Shore from December through April (Rees et al., 2016; Jones et al.,
2018). Seals captured in 2018 on the Eastern Shore and tagged with
satellite-tracked tags that lasted from 2 to 5 months spent at least 60
days in Virginia waters before departing the area. All tagged seals
returned regularly to the capture site while in Virginia waters, but
individuals utilized offshore and Chesapeake Bay waters to different
extents (Ampela et al., 2019). The area that was utilized most heavily
was near the Eastern Shore capture site, but some seals ranged into the
Chesapeake Bay. To supplement this information, there were no harbor
seals observed during construction activities for the Pier 3 Navy
Construction Project or the Hampton Roads Bridge-Tunnel Expansion
Project (Hampton Roads Connector Partners 2023; W.F. Magann Corporation
2023).

Gray Seal

The Western North Atlantic stock of gray seal occurs in the project
area. The western North Atlantic stock is centered in Canadian waters,
including the Gulf of St. Lawrence and the Atlantic coasts of Nova
Scotia, Newfoundland, and Labrador, Canada, and the northeast U.S.
continental shelf (Hayes et al., 2021). Gray seals range south into the
northeastern United States, with strandings and sightings as far south
as North Carolina (Waring et al., 2004). Gray seal distribution along
the U.S. Atlantic coast has shifted in recent years, with an increased
number of seals reported in southern New England (Kenney R.D., 2019;
Waring et al., 2016). Recent sightings included a gray seal in the
lower Chesapeake Bay during the winter of 2014 to 2015 (Rees et al.,
2016). Along the coast of the United States, gray seals are known to
pup at three or more colonies in Massachusetts and Maine.

Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals
underwater, and exposure to anthropogenic sound can have deleterious
effects. To appropriately assess the potential effects of exposure to
sound, it is necessary to understand the frequency ranges marine
mammals are able to hear. Not all marine mammal species have equal
hearing capabilities (e.g., Richardson et al., 1995; Wartzok and
Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al.
(2007; 2019) recommended that marine mammals be divided into hearing
groups based on directly measured (behavioral or auditory evoked
potential techniques) or estimated hearing ranges (behavioral response
data, anatomical modeling, etc.). Generalized hearing ranges were
chosen based on the approximately 65 decibel (dB) threshold from
composite audiograms, previous analyses in NMFS (2018), and/or data
from Southall et al. (2007) and Southall et al. (2019). We note that
the names of two hearing groups and the generalized hearing ranges of
all marine mammal hearing groups have been recently updated (NMFS,
2024) as reflected below in table 5.

Table 5--Marine Mammal Hearing Groups
[NMFS, 2024]
------------------------------------------------------------------------
Hearing group Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen 7 Hz to 36 kHz.
whales).
High-frequency (HF) cetaceans (dolphins, 150 Hz to 160 kHz.
toothed whales, beaked whales,
bottlenose whales).
Very High-frequency (VHF) cetaceans 200 Hz to 165 kHz.
(true porpoises, Kogia, river dolphins,
Cephalorhynchid, Lagenorhynchus
cruciger & L. australis).
Phocid pinnipeds (PW) (underwater) (true 40 Hz to 90 kHz.
seals).
Otariid pinnipeds (OW) (underwater) (sea 60 Hz to 68 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 may not be as broad. Generalized hearing range
chosen based on approximately 65 dB threshold from composite
audiogram, previous analysis in NMFS (2018), and/or data from Southall
et al. (2007) and Southall et al. (2019). Additionally, animals are
able to detect very loud sounds above and below that ``generalized''
hearing range.

For more details concerning these groups and associated frequency
ranges, please see NMFS (2024) for a review of available information.

Potential Effects of Specified Activities on Marine Mammals and Their
Habitat

This section provides a discussion of the ways in which components
of the specified activity may impact marine mammals and their habitat.
The Estimated Take of Marine Mammals section later in this document
includes a quantitative analysis of the number of individuals that are
expected to be taken by this activity. The Negligible Impact Analysis
and Determination section considers the content of this section, the
Estimated Take of Marine Mammals section, and the Proposed Mitigation
section, to draw conclusions regarding the likely impacts of these
activities on the reproductive success or survivorship of individuals
and whether those impacts are reasonably expected to, or reasonably
likely to, adversely affect the species or stock through effects on
annual rates of recruitment or survival.
Acoustic effects on marine mammals during the specified activity
are expected to potentially occur from impact and vibratory pile
installation and removal. The effects of underwater noise from HRCP's
proposed activities have the potential to result in Level B harassment
of marine mammals in the action area and, for some species as a result
of certain activities, Level A harassment.
Below we provide a brief description of the types of sound sources
that would be generated by the project, the general impacts from these
types of activities, and an analysis of the anticipated impacts on
marine mammals from the

[[Page 9824]]

project, with consideration of the proposed mitigation measures.

Description of Sound Sources for the Specified Activities

Activities associated with the project that have the potential to
incidentally take marine mammals though exposure to sound would include
impact pile driving for installation, and vibratory pile driving for
installation and removal. Impact hammers typically operate by
repeatedly dropping and/or pushing a heavy piston onto a pile to drive
the pile into the substrate. Sound generated by impact hammers is
impulsive, characterized by rapid rise times and high peak levels, a
potentially injurious combination (Hastings and Popper, 2005).
Vibratory hammers install piles by vibrating them and allowing the
weight of the hammer to push them into the substrate. Vibratory hammers
typically produce less sound (i.e., lower levels) than impact hammers.
Peak sound pressure levels (SPLs) may be 180 dB or greater but are
generally 10 to 20 dB lower than SPLs generated during impact pile
driving of the same-sized pile (Oestman et al., 2009; California
Department of Transportation (CALTRANS), 2015, 2020). Sounds produced
by vibratory hammers are non-impulsive; compared to sounds produced by
impact hammers, the rise time is slower, reducing the probability and
severity of injury, and the sound energy is distributed over more time
(Nedwell and Edwards, 2002; Carlson et al., 2005).
The likely or possible impacts of HRCP's proposed activities on
marine mammals could involve both non-acoustic and acoustic stressors.
Potential non-acoustic stressors could result from the physical
presence of the equipment and personnel. However, given there are no
known pinniped haulout sites in the vicinity of the project site,
visual and other non-acoustic stressors would be limited, and any
impacts to marine mammals are expected to primarily be acoustic in
nature.

Potential Effects of Underwater Sound on Marine Mammals

The introduction of anthropogenic noise into the aquatic
environment from impact and vibratory pile driving is the primary means
by which marine mammals may be harassed from HRCP's specified activity.
Anthropogenic sounds cover a broad range of frequencies and sound
levels and can have a range of highly variable impacts on marine life
from none or minor to potentially severe responses depending on
received levels, duration of exposure, behavioral context, and various
other factors. Broadly, underwater sound from active acoustic sources,
such as those in the project, can potentially result in one or more of
the following: temporary or permanent hearing impairment, non-auditory
physical or physiological effects, behavioral disturbance, stress, and
masking (Richardson et al., 1995; Gordon et al., 2003; Nowacek et al.,
2007; Southall et al., 2007).
We describe the more severe effects of certain non-auditory
physical or physiological effects only briefly as we do not expect that
use of impact and vibratory hammers are reasonably likely to result in
such effects (see below for further discussion). Potential effects from
impulsive sound sources can range in severity from effects such as
behavioral disturbance or tactile perception to physical discomfort,
slight injury of the internal organs and the auditory system, or
mortality (Yelverton et al., 1973). Non-auditory physiological effects
or injuries that theoretically might occur in marine mammals exposed to
high level underwater sound or as a secondary effect of extreme
behavioral reactions (e.g., change in dive profile as a result of an
avoidance reaction) caused by exposure to sound include neurological
effects, bubble formation, resonance effects, and other types of organ
or tissue damage (Cox et al., 2006; Southall et al., 2007; Zimmer and
Tyack, 2007). The proposed project activities considered here do not
involve the use of devices such as explosives or mid-frequency tactical
sonar that are associated with these types of effects.
In general, animals exposed to natural or anthropogenic sound may
experience physical and psychological effects, ranging in magnitude
from none to severe (Southall et al., 2007, 2019). Exposure to
anthropogenic noise has the potential to result in auditory threshold
shifts and behavioral reactions (e.g., avoidance, temporary cessation
of foraging and vocalizing, changes in dive behavior). It can also lead
to non-observable physiological responses, such an increase in stress
hormones. Additional noise in a marine mammal's habitat can mask
acoustic cues used by marine mammals to carry out daily functions, such
as communication and predator and prey detection.
The degree of effect of an acoustic exposure on marine mammals is
dependent on several factors, including, but not limited to, sound type
(e.g., impulsive vs. non-impulsive), signal characteristics, the
species, age and sex class (e.g., adult male vs. mom with calf),
duration of exposure, the distance between the noise source and the
animal, received levels, behavioral state at time of exposure, and
previous history with exposure (Wartzok et al., 2004; Southall et al.,
2007). In general, sudden, high-intensity sounds can cause hearing
loss, as can longer exposures to lower-intensity sounds. Moreover, any
temporary or permanent loss of hearing, if it occurs at all, would
occur almost exclusively for noise within an animal's hearing range. We
describe below the specific manifestations of acoustic effects that may
occur based on the activities proposed by HRCP.
Richardson et al. (1995) described zones of increasing intensity of
effect that might be expected to occur in relation to distance from a
source and assuming that the signal is within an animal's hearing
range. First (at the greatest distance) is the area within which the
acoustic signal would be audible (potentially perceived) to the animal
but not strong enough to elicit any overt behavioral or physiological
response. The next zone (closer to the receiving animal) corresponds
with the area where the signal is audible to the animal and of
sufficient intensity to elicit behavioral or physiological
responsiveness. The third is a zone within which, for signals of high
intensity, the received level is sufficient to potentially cause
discomfort or tissue damage to auditory or other systems. Overlaying
these zones to a certain extent is the area within which masking (i.e.,
when a sound interferes with or masks the ability of an animal to
detect a signal of interest that is above the absolute hearing
threshold) may occur; the masking zone may be highly variable in size.
Below, we provide additional detail regarding potential impacts on
marine mammals and their habitat from noise in general, starting with
hearing impairment, as well as from the specific activities HRCP plans
to conduct, to the degree it is available.
Hearing Threshold Shifts--NMFS defines a noise-induced threshold
shift (TS) as a change, usually an increase, in the threshold of
audibility at a specified frequency or portion of an individual's
hearing range above a previously established reference level (NMFS,
2018, 2024). The amount of threshold shift is customarily expressed in
dB. TS can be permanent or temporary. As described in NMFS (2018, 2024)
there are numerous factors to consider when examining the consequence
of TS, including, but not limited to, the signal temporal pattern
(e.g., impulsive or non-impulsive), likelihood an individual would be
exposed for a long enough duration or to a high enough level to

[[Page 9825]]

induce a TS, the magnitude of the TS, time to recovery (seconds to
minutes or hours to days), the frequency range of the exposure (i.e.,
spectral content), the hearing frequency range of the exposed species
relative to the signal's frequency spectrum (i.e., how animal uses
sound within the frequency band of the signal; e.g., Kastelein et al.,
2014), and the overlap between the animal and the source (e.g.,
spatial, temporal, and spectral).
Auditory Injury (AUD INJ)--NMFS (2024) defines AUD INJ as damage to
the inner ear that can result in destruction of tissue, such as the
loss of cochlear neuron synapses or auditory neuropathy (Houser, 2021;
Finneran, 2024). AUD INJ may or may not result in a permanent threshold
shift (PTS). PTS is subsequently defined as a permanent, irreversible
increase in the threshold of audibility at a specified frequency or
portion of an individual's hearing range above a previously established
reference level (NMFS, 2024). PTS does not generally affect more than a
limited frequency range, and an animal that has incurred PTS has some
level of hearing loss at the relevant frequencies; typically, animals
with PTS or other AUD INJ are not functionally deaf (Au and Hastings,
2008; Finneran, 2016). Available data from humans and other terrestrial
mammals indicate that a 40-dB threshold shift approximates AUD INJ
onset (see Ward et al., 1958, 1959; Ward, 1960; Kryter et al., 1966;
Miller, 1974; Ahroon et al., 1996; Henderson et al., 2008). AUD INJ
levels for marine mammals are estimates, as with the exception of a
single study unintentionally inducing PTS in a harbor seal (Kastak et
al., 2008), there are no empirical data measuring AUD INJ in marine
mammals largely due to the fact that, for various ethical reasons,
experiments involving anthropogenic noise exposure at levels inducing
AUD INJ are not typically pursued or authorized (NMFS, 2024).
Temporary Threshold Shift (TTS)--TTS is a temporary, reversible
increase in the threshold of audibility at a specified frequency or
portion of an individual's hearing range above a previously established
reference level (NMFS, 2024), and is not considered an AUD INJ. Based
on data from marine mammal TTS measurements (see Southall et al., 2007,
2019), a TTS of 6 dB is considered the minimum threshold shift clearly
larger than any day-to-day or session-to-session variation in a
subject's normal hearing ability (Finneran et al., 2000, 2002; Schlundt
et al., 2000). As described in Finneran (2015), marine mammal studies
have shown the amount of TTS increases with the 24-hour cumulative
sound exposure level (SEL<INF>24</INF>) in an accelerating fashion: at
low exposures with lower SEL<INF>24</INF>, the amount of TTS is
typically small and the growth curves have shallow slopes. At exposures
with higher SEL<INF>24</INF>, the growth curves become steeper and
approach linear relationships with the sound exposure level (SEL).
Depending on the degree (elevation of threshold in dB), duration
(i.e., recovery time), and frequency range of TTS, and the context in
which it is experienced, TTS can have effects on marine mammals ranging
from discountable to more impactful (similar to those discussed in
auditory masking, below). For example, a marine mammal may be able to
readily compensate for a brief, relatively small amount of TTS in a
non-critical frequency range that takes place during a time when the
animal is traveling through the open ocean, where ambient noise is
lower and there are not as many competing sounds present.
Alternatively, a larger amount and longer duration of TTS sustained
during time when communication is critical for successful mother/calf
interactions could have more severe impacts. We note that reduced
hearing sensitivity as a simple function of aging has been observed in
marine mammals, as well as humans and other taxa (Southall et al.,
2007), so we can infer that strategies exist for coping with this
condition to some degree, though likely not without cost.
Many studies have examined noise-induced hearing loss in marine
mammals (see Finneran (2015) and Southall et al. (2019) for summaries).
TTS is the mildest form of hearing impairment that can occur during
exposure to sound (Kryter, 2013). While experiencing TTS, the hearing
threshold rises, and a sound must be at a higher level in order to be
heard. In terrestrial and marine mammals, TTS can last from minutes or
hours to days (in cases of strong TTS). In many cases, hearing
sensitivity recovers rapidly after exposure to the sound ends. For
cetaceans, published data on the onset of TTS are limited to captive
bottlenose dolphin (Tursiops truncatus), beluga whale (Delphinapterus
leucas), harbor porpoise, and Yangtze finless porpoise (Neophocoena
asiaeorientalis) (Southall et al., 2019). For pinnipeds in water,
measurements of TTS are limited to harbor seals, elephant seals
(Mirounga angustirostris), bearded seals (Erignathus barbatus) and
California sea lions (Zalophus californianus) (Kastak et al., 1999,
2007; Kastelein et al., 2019b, 2019c, 2022a, 2022b; Reichmuth et al.,
2019; Sills et al., 2020). TTS was not observed in spotted (Phoca
largha) and ringed (Pusa hispida) seals exposed to single airgun
impulse sounds at levels matching previous predictions of TTS onset
(Reichmuth et al., 2016). These studies examine hearing thresholds
measured in marine mammals before and after exposure to intense or
long-duration sound exposures. The difference between the pre-exposure
and post-exposure thresholds can be used to determine the amount of
threshold shift at various post-exposure times.
The amount and onset of TTS depends on the exposure frequency.
Sounds below the region of best sensitivity for a species or hearing
group are less hazardous than those near the region of best sensitivity
(Finneran and Schlundt, 2013). At low frequencies, onset-TTS exposure
levels are higher compared to those in the region of best sensitivity
(i.e., a low frequency noise would need to be louder to cause TTS onset
when TTS exposure level is higher), as shown for harbor porpoises and
harbor seals (Kastelein et al., 2019a, 2019c). Note that in general,
harbor seals and harbor porpoises have a lower TTS onset than other
measured pinniped or cetacean species (Finneran, 2015). In addition,
TTS can accumulate across multiple exposures, but the resulting TTS
would be less than the TTS from a single, continuous exposure with the
same SEL (Mooney et al., 2009; Finneran et al., 2010; Kastelein et al.
2015). This means that TTS predictions based on the total,
SEL<INF>24</INF> would overestimate the amount of TTS from intermittent
exposures, such as sonars and impulsive sources. Nachtigall et al.
(2018) describe measurements of hearing sensitivity of multiple
odontocete species (bottlenose dolphin, harbor porpoise, beluga, and
false killer whale (Pseudorca crassidens)) when a relatively loud sound
was preceded by a warning sound. These captive animals were shown to
reduce hearing sensitivity when warned of an impending intense sound.
Based on these experimental observations of captive animals, the
authors suggest that wild animals may dampen their hearing during
prolonged exposures or if conditioned to anticipate intense sounds.
Another study showed that echolocating animals (including odontocetes)
might have anatomical specializations that might allow for conditioned
hearing reduction and filtering of low-frequency ambient noise,
including increased stiffness and control of middle ear structures and
placement of inner ear structures (Ketten et al., 2021). Data available
on

[[Page 9826]]

noise-induced hearing loss for mysticetes are currently lacking (NMFS,
2024). Additionally, the existing marine mammal TTS data come from a
limited number of individuals within these species.
Relationships between TTS and AUD INJ thresholds have not been
studied in marine mammals, and there are no measured PTS data for
cetaceans, but such relationships are assumed to be similar to those in
humans and other terrestrial mammals. AUD INJ typically occurs at
exposure levels at least several dB above that inducing mild TTS (e.g.,
a 40-dB threshold shift approximates AUD INJ onset (Kryter et al.,
1966; Miller, 1974), while a 6-dB threshold shift approximates TTS
onset (Southall et al., 2007, 2019). Based on data from terrestrial
mammals, a precautionary assumption is that the AUD INJ thresholds for
impulsive sounds (such as impact pile driving pulses as received close
to the source) are at least 6 dB higher than the TTS threshold on a
peak-pressure basis and AUD INJ cumulative sound exposure level
thresholds are 15 to 20 dB higher than TTS cumulative sound exposure
level thresholds (Southall et al., 2007, 2019). Given the higher level
of sound or longer exposure duration necessary to cause AUD INJ as
compared with TTS, it is considerably less likely that AUD INJ could
occur. Given the stationary nature of the construction activities, the
fact that HRBT is relatively sheltered (i.e., not located in the open
ocean), and the fact that many marine mammals are likely moving through
the project areas and not remaining in ensonified areas for extended
periods of time, the potential for threshold shift is low for most
species.
Behavioral Effects--Exposure to noise also has the potential to
behaviorally disturb marine mammal response--in other words, not every
response qualifies as behavioral disturbance, and for responses that
do, those of a higher level, or accrued across a longer duration, have
the potential to affect foraging, reproduction, or survival. Behavioral
disturbance may include a variety of effects, including subtle changes
in behavior (e.g., minor or brief avoidance of an area or changes in
vocalizations), more conspicuous changes in similar behavioral
activities, and more sustained and/or potentially severe reactions,
such as displacement from or abandonment of high-quality habitat.
Behavioral responses may include changing durations of surfacing and
dives, changing direction and/or speed; reducing/increasing vocal
activities; changing/cessation of certain behavioral activities (such
as socializing or feeding); eliciting a visible startle response or
aggressive behavior (such as tail/fin slapping or jaw clapping); and
avoidance of areas where sound sources are located. In addition,
pinnipeds may increase their haul out time, possibly to avoid in-water
disturbance (Thorson and Reyff, 2006).
Behavioral responses to sound are highly variable and context-
specific and any reactions depend on numerous intrinsic and extrinsic
factors (e.g., species, state of maturity, experience, current
activity, reproductive state, auditory sensitivity, time of day), as
well as the interplay between factors (e.g., Richardson et al., 1995;
Wartzok et al., 2004; Southall et al., 2007, 2019; Weilgart, 2007;
Archer et al., 2010). Behavioral reactions can vary not only among
individuals but also within an individual, depending on previous
experience with a sound source, context, and numerous other factors
(Ellison et al., 2012), and can vary depending on characteristics
associated with the sound source (e.g., whether it is moving or
stationary, number of sources, distance from the source). In general,
pinnipeds seem more tolerant of, or at least habituate more quickly to
potentially disturbing underwater sound than do cetaceans, and
generally seem to be less responsive to exposure to industrial sound
than most cetaceans. Please see appendices B and C of Southall et al.
(2007) and Gomez et al. (2016) for reviews of studies involving marine
mammal behavioral responses to sound.
Habituation can occur when an animal's response to a stimulus wanes
with repeated exposure, usually in the absence of unpleasant associated
events (Wartzok et al., 2004). Animals are most likely to habituate to
sounds that are predictable and unvarying. It is important to note that
habituation is appropriately considered as a ``progressive reduction in
response to stimuli that are perceived as neither aversive nor
beneficial,'' rather than as, more generally, moderation in response to
human disturbance (Bejder et al., 2009). The opposite process is
sensitization, when an unpleasant experience leads to subsequent
responses, often in the form of avoidance, at a lower level of
exposure.
As noted above, behavioral state may affect the type of response.
For example, animals that are resting may show greater behavioral
change in response to disturbing sound levels than animals that are
highly motivated to remain in an area for feeding (Richardson et al.,
1995; Wartzok et al., 2004; National Research Council (NRC), 2005).
Controlled experiments with captive marine mammals have shown
pronounced behavioral reactions, including avoidance of loud sound
sources (Ridgway et al., 1997; Finneran et al., 2003). Observed
responses of wild marine mammals to loud-pulsed sound sources (e.g.,
seismic airguns) have been varied but often consist of avoidance
behavior or other behavioral changes (Richardson et al., 1995; Morton
and Symonds, 2002; Nowacek et al., 2007).
Available studies show wide variation in response to underwater
sound; therefore, it is difficult to predict specifically how any given
sound in a particular instance might affect marine mammals perceiving
the signal (e.g., Erbe et al., 2019). If a marine mammal does react
briefly to an underwater sound by changing its behavior or moving a
small distance, the impacts of the change are unlikely to be
significant to the individual, let alone the stock or population. If a
sound source displaces marine mammals from an important feeding or
breeding area for a prolonged period, impacts on individuals and
populations could be significant (e.g., Lusseau and Bejder, 2007;
Weilgart, 2007; NRC, 2005). However, there are broad categories of
potential response, which we describe in greater detail here, that
include alteration of dive behavior, alteration of foraging behavior,
effects to breathing, interference with or alteration of vocalization,
avoidance, and flight.
Avoidance and displacement--Changes in dive behavior can vary
widely and may consist of increased or decreased dive times and surface
intervals as well as changes in the rates of ascent and descent during
a dive (e.g., Frankel and Clark, 2000; Costa et al., 2003; Ng and
Leung, 2003; Nowacek et al., 2004; Goldbogen et al., 2013a, 2013b,
Blair et al., 2016). Variations in dive behavior may reflect
interruptions in biologically significant activities (e.g., foraging)
or they may be of little biological significance. The impact of an
alteration to dive behavior resulting from an acoustic exposure depends
on what the animal is doing at the time of the exposure and the type
and magnitude of the response.
Disruption of feeding behavior can be difficult to correlate with
anthropogenic sound exposure, so it is usually inferred by observed
displacement from known foraging areas, the appearance of secondary
indicators (e.g., bubble nets or sediment plumes), or changes in dive
behavior. Acoustic and movement bio-logging tools also have been used
in some cases to infer responses to anthropogenic noise. For example,
Blair et al. (2015) reported significant effects on humpback whale
foraging behavior in Stellwagen Bank in response to ship

[[Page 9827]]

noise including slower descent rates, and fewer side-rolling events per
dive with increasing ship nose. In addition, Wisniewska et al. (2018)
reported that tagged harbor porpoises demonstrated fewer prey capture
attempts when encountering occasional high-noise levels resulting from
vessel noise as well as more vigorous fluking, interrupted foraging,
and cessation of echolocation signals observed in response to some
high-noise vessel passes. As for other types of behavioral response,
the frequency, duration, and temporal pattern of signal presentation,
as well as differences in species sensitivity, are likely contributing
factors to differences in response in any given circumstance (e.g.,
Croll et al., 2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko
et al., 2007). A determination of whether foraging disruptions incur
fitness consequences would require information on or estimates of the
energetic requirements of the affected individuals and the relationship
between prey availability, foraging effort and success, and the life
history stage of the animal.
Respiration rates vary naturally with different behaviors and
alterations to breathing rate as a function of acoustic exposure can be
expected to co-occur with other behavioral reactions, such as a flight
response or an alteration in diving. However, respiration rates in and
of themselves may be representative of annoyance or an acute stress
response. Various studies have shown that respiration rates may either
be unaffected or could increase, depending on the species and signal
characteristics, again highlighting the importance in understanding
species differences in the tolerance of underwater noise when
determining the potential for impacts resulting from anthropogenic
sound exposure (e.g., Kastelein et al., 2001; 2005; 2006; Gailey et
al., 2007). For example, harbor porpoise respiration rates increased in
response to pile driving sounds at and above a received broadband SPL
of 136 dB (zero-peak SPL: 151 dB re 1 [mu]Pa; SEL of a single strike
(SEL<INF>ss</INF>): 127 dB re 1 [mu]Pa\2\-s) (Kastelein et al., 2013).
Avoidance is the displacement of an individual from an area or
migration path as a result of the presence of a sound or other
stressors, and is one of the most obvious manifestations of disturbance
in marine mammals (Richardson et al., 1995). For example, gray whales
are known to change direction--deflecting from customary migratory
paths--in order to avoid noise from seismic surveys (Malme et al.,
1984). Harbor porpoises, Atlantic white-sided dolphins (Lagenorhynchus
actusus), and minke whales (Balaenoptera acutorostrata) have
demonstrated avoidance in response to vessels during line transect
surveys (Palka and Hammond, 2001). In addition, beluga whales in the
St. Lawrence Estuary in Canada have been reported to increase levels of
avoidance with increased boat presence by way of increased dive
durations and swim speeds, decreased surfacing intervals, and by
bunching together into groups (Blane and Jaakson, 1994). Avoidance may
be short-term, with animals returning to the area once the noise has
ceased (e.g., Bowles et al., 1994; Goold, 1996; Stone et al., 2000;
Morton and Symonds, 2002; Gailey et al., 2007). Longer-term
displacement is possible, however, which may lead to changes in
abundance or distribution patterns of the affected species in the
affected region if habituation to the presence of the sound does not
occur (e.g., Bejder et al., 2006).
A flight response is a dramatic change in normal movement to a
directed and rapid movement away from the perceived location of a sound
source. The flight response differs from other avoidance responses in
the intensity of the response (e.g., directed movement, rate of
travel). Relatively little information on flight responses of marine
mammals to anthropogenic signals exist, although observations of flight
responses to the presence of predators have occurred (Connor and
Heithaus, 1996; Bowers et al., 2018). The result of a flight response
could range from brief, temporary exertion and displacement from the
area where the signal provokes flight to, in extreme cases, marine
mammal strandings (England et al., 2001). However, it should be noted
that response to a perceived predator does not necessarily invoke
flight (Ford and Reeves, 2008), and whether individuals are solitary or
in groups may influence the response.
Behavioral disturbance can also impact marine mammals in more
subtle ways. Increased vigilance may result in costs related to
diversion of focus and attention (i.e., when a response consists of
increased vigilance, it may come at the cost of decreased attention to
other critical behaviors such as foraging or resting). These effects
have generally not been demonstrated for marine mammals, but studies
involving fishes and terrestrial animals have shown that increased
vigilance may substantially reduce feeding rates (e.g., Beauchamp and
Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). In
addition, chronic disturbance can cause population declines through
reduction of fitness (e.g., decline in body condition) and subsequent
reduction in reproductive success, survival, or both (e.g., Harrington
and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). However,
Ridgway et al. (2006) reported that increased vigilance in bottlenose
dolphins exposed to sound over a 5-day period did not cause any sleep
deprivation or stress effects.
Many animals perform vital functions, such as feeding, resting,
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption
of such functions resulting from reactions to stressors such as sound
exposure are more likely to be significant if they last more than one
diel cycle or recur on subsequent days (Southall et al., 2007).
Consequently, a behavioral response lasting less than 1 day and not
recurring on subsequent days is not considered particularly severe
unless it could directly affect reproduction or survival (Southall et
al., 2007). Note that there is a difference between multi-day
substantive (i.e., meaningful) behavioral reactions and multi-day
anthropogenic activities. For example, just because an activity lasts
for multiple days does not necessarily mean that individual animals are
either exposed to activity-related stressors for multiple days or,
further, exposed in a manner resulting in sustained multi-day
substantive behavioral responses.
Physiological stress responses--An animal's perception of a threat
may be sufficient to trigger stress responses consisting of some
combination of behavioral responses, autonomic nervous system
responses, neuroendocrine responses, or immune responses (e.g., Selye,
1950; Moberg, 2000). In many cases, an animal's first and sometimes
most economical (in terms of energetic costs) response is behavioral
avoidance of the potential stressor. Autonomic nervous system responses
to stress typically involve changes in heart rate, blood pressure, and
gastrointestinal activity. These responses have a relatively short
duration and may or may not have a significant long-term effect on an
animal's fitness.
Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that
are affected by stress--including immune competence, reproduction,
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been
implicated in failed reproduction, altered metabolism, reduced immune
competence, and behavioral disturbance (e.g., Moberg, 1987; Blecha,
2000). Increases in the circulation of

[[Page 9828]]

glucocorticoids are also equated with stress (Romano et al., 2004).
The primary distinction between stress (which is adaptive and does
not normally place an animal at risk) and ``distress'' is the cost of
the response. During a stress response, an animal uses glycogen stores
that can be quickly replenished once the stress is alleviated. In such
circumstances, the cost of the stress response would not pose serious
fitness consequences. However, when an animal does not have sufficient
energy reserves to satisfy the energetic costs of a stress response,
energy resources must be diverted from other functions. This state of
distress would last until the animal replenishes its energetic reserves
sufficient to restore normal function.
Relationships between these physiological mechanisms, animal
behavior, and the costs of stress responses are well studied through
controlled experiments and for both laboratory and free-ranging animals
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003;
Krausman et al., 2004; Lankford et al., 2005; Ayres et al., 2012; Yang
et al., 2022). Stress responses due to exposure to anthropogenic sounds
or other stressors and their effects on marine mammals have also been
reviewed (Fair and Becker, 2000; Romano et al., 2002b) and, more
rarely, studied in wild populations (e.g., Romano et al., 2002a). For
example, Rolland et al. (2012) found that noise reduction from reduced
ship traffic in the Bay of Fundy was associated with decreased stress
in North Atlantic right whales. In addition, Lemos et al. (2022)
observed a correlation between higher levels of fecal glucocorticoid
metabolite concentrations (indicative of a stress response) and vessel
traffic in gray whales. Yang et al. (2022) studied behavioral and
physiological responses in captive bottlenose dolphins exposed to
playbacks of ``pile-driving-like'' impulsive sounds, finding
significant changes in cortisol and other physiological indicators but
only minor behavioral changes. These and other studies lead to a
reasonable expectation that some marine mammals would experience
physiological stress responses upon exposure to acoustic stressors and
that it is possible that some of these would be classified as
``distress.'' In addition, any animal experiencing TTS would likely
also experience stress responses (NRC, 2005), however distress is an
unlikely result of this project based on observations of marine mammals
during previous, similar construction projects.
Vocalizations and Auditory Masking--Since many marine mammals rely
on sound to find prey, moderate social interactions, and facilitate
mating (Tyack, 2008), noise from anthropogenic sound sources can
interfere with these functions, but only if the noise spectrum overlaps
with the hearing sensitivity of the receiving marine mammal (Southall
et al., 2007; Clark et al., 2009; Hatch et al., 2012). Chronic exposure
to excessive, though not high-intensity, noise could cause masking at
particular frequencies for marine mammals that utilize sound for vital
biological functions (Clark et al., 2009). Acoustic masking is when
other noises such as from human sources interfere with an animal's
ability to detect, recognize, or discriminate between acoustic signals
of interest (e.g., those used for intraspecific communication and
social interactions, prey detection, predator avoidance, navigation)
(Richardson et al., 1995; Erbe et al., 2016). Therefore, under certain
circumstances, for marine mammals whose acoustic sensors or environment
are being severely masked could also be impaired from maximizing their
performance fitness in survival and reproduction. The ability of a
noise source to mask biologically important sounds depends on the
characteristics of both the noise source and the signal of interest
(e.g., signal-to-noise ratio, temporal variability, direction), in
relation to each other and to an animal's hearing abilities (e.g.,
sensitivity, frequency range, critical ratios, frequency
discrimination, directional discrimination, age or TTS hearing loss),
and existing ambient noise and propagation conditions (Hotchkin and
Parks, 2013).
Marine mammals vocalize for different purposes and across multiple
modes, such as whistling, echolocation click production, calling, and
singing. Changes in vocalization behavior in response to anthropogenic
noise can occur for any of these modes and may result from a need to
compete with an increase in background noise or may reflect increased
vigilance or a startle response. For example, in the presence of
potentially masking signals, humpback whales and killer whales have
been observed to increase the length of their songs (Miller et al.,
2000; Fristrup et al., 2003) or vocalizations (Foote et al., 2004),
respectively, while North Atlantic right whales (Eubalaena glacialis)
have been observed to shift the frequency content of their calls upward
while reducing the rate of calling in areas of increased anthropogenic
noise (Parks et al., 2007). Fin whales (Balaenoptera physalus) have
also been documented lowering the bandwidth, peak frequency, and center
frequency of their vocalizations under increased levels of background
noise from large vessels (Castellote et al. 2012). Other alterations to
communication signals have also been observed. For example, gray
whales, in response to playback experiments exposing them to vessel
noise, have been observed increasing their vocalization rate and
producing louder signals at times of increased outboard engine noise
(Dahlheim and Castellote, 2016). Alternatively, in some cases, animals
may cease sound production during production of aversive signals
(Bowles et al., 1994, Wisniewska et al., 2018).
Under certain circumstances, marine mammals experiencing
significant masking could also be impaired from maximizing their
performance fitness in survival and reproduction. Therefore, when the
coincident (masking) sound is human-made, it may be considered
harassment when disrupting or altering critical behaviors. It is
important to distinguish TTS and PTS, which persist after the sound
exposure, from masking, which occurs during the sound exposure. Because
masking (without resulting in TS) is not associated with abnormal
physiological function, it is not considered a physiological effect,
but rather a potential behavioral effect (though not necessarily one
that would be associated with harassment).
The frequency range of the potentially masking sound is important
in determining any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation
sounds produced by odontocetes but are more likely to affect detection
of mysticete communication calls and other potentially important
natural sounds such as those produced by surf and some prey species.
The masking of communication signals by anthropogenic noise may be
considered as a reduction in the communication space of animals (e.g.,
Clark et al., 2009) and may result in energetic or other costs as
animals change their vocalization behavior (e.g., Miller et al., 2000;
Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2010; Holt
et al., 2009). Masking can be reduced in situations where the signal
and noise come from different directions (Richardson et al., 1995),
through amplitude modulation of the signal, or through other
compensatory behaviors, including modifications of the acoustic
properties of the signal or the signaling behavior (Hotchkin and Parks,
2013). Masking can be tested directly in captive species (e.g., Erbe,
2008), but in

[[Page 9829]]

wild populations it must be either modeled or inferred from evidence of
masking compensation. There are few studies addressing real-world
masking sounds likely to be experienced by marine mammals in the wild
(e.g., Branstetter et al., 2013).
Masking occurs in the frequency band that the animals utilize and
is more likely to occur in the presence of broadband, relatively
continuous noise sources such as vibratory pile driving. Energy
distribution of vibratory pile driving sound covers a broad frequency
spectrum and is anticipated to be within the audible range of marine
mammals present in the proposed action area. Since noises generated
from the proposed construction activities are mostly concentrated at
low frequencies (<2 kHz (kilohertz)), these activities likely have less
effect on mid-frequency echolocation sounds produced by odontocetes
(toothed whales). However, lower frequency noises are more likely to
affect detection of communication calls and other potentially important
natural sounds such as surf and prey noise. Low-frequency noise may
also affect communication signals when they occur near the frequency
band for noise and thus reduce the communication space of animals
(e.g., Clark et al., 2009) and cause increased stress levels (e.g.,
Holt et al., 2009). Unlike TS, masking, which can occur over large
temporal and spatial scales, can potentially affect the species at
population, community, or even ecosystem levels, in addition to
individual levels. Masking affects both senders and receivers of the
signals, and at higher levels for longer durations, could have long-
term chronic effects on marine mammal species and populations. However,
the noise generated by HRCP's proposed activities would only occur
intermittently, across an estimated 231 (not necessarily consecutive)
days during the proposed authorization period in a relatively small
area focused around the proposed construction site. Thus, while the
HRCP's proposed activities may mask some acoustic signals that are
relevant to the daily behavior of marine mammals, the short-term
duration and limited areas affected make it very unlikely that the
fitness of individual marine mammals would be impacted.
While in some cases marine mammals have exhibited little to no
obviously detectable response to certain common or routine
industrialized activities (Cornick et al., 2011; Horsley and Larson,
2023), it is possible some animals may at times be exposed to received
levels of sound above the AUD INJ and Level B harassment thresholds
during the proposed project. This potential exposure in combination
with the nature of planned activity (e.g., vibratory pile driving,
impact pile driving) means it is possible that take by Level A and
Level B harassment could occur over the total estimated period of
activities; therefore, NMFS, in response to HRCP's IHA application,
proposes to authorize take by Level A and Level B harassment from
HRCP's proposed construction activities.
Airborne Acoustic Effects--Pinnipeds that occur near the project
site could be exposed to airborne sounds associated with construction
activities that have the potential to cause behavioral harassment,
depending on their distance from these activities. Airborne noise would
primarily be an issue for pinnipeds that are swimming or hauled out
near the project site within the range of noise levels elevated above
airborne acoustic harassment criteria. As described above in
Description of Sound Sources for the Specified Activities, although
pinnipeds are known to haul-out regularly on man-made objects, we
believe that incidents of take resulting solely from airborne sound are
unlikely due to the distance between the proposed project area and the
known haulout sites. Cetaceans are not expected to be exposed to
airborne sounds that would result in harassment as defined under the
MMPA.
We recognize that pinnipeds in the water could be exposed to
airborne sound that may result in behavioral harassment when looking
with their heads above water. Most likely, airborne sound would cause
behavioral responses similar to those discussed above in relation to
underwater sound. For instance, anthropogenic sound could cause hauled
out pinnipeds to exhibit changes in their normal behavior, such as
reduction in vocalizations, or cause them to flush from haulouts,
temporarily abandon the area, and or move further from the source.
However, these animals would previously have been ``taken'' because of
exposure to underwater sound above the behavioral harassment
thresholds, which are in all cases larger than those associated with
airborne sound. Thus, the behavioral harassment of these animals is
already accounted for in these estimates of potential take. Therefore,
we do not believe that authorization of incidental take resulting from
airborne sound for pinnipeds is warranted, and airborne sound is not
discussed further here.

Potential Effects on Marine Mammal Habitat

HRCP's proposed activities could have localized, temporary impacts
on marine mammal habitat, including prey, by increasing in-water SPLs.
Increased noise levels may affect acoustic habitat and adversely affect
marine mammal prey in the vicinity of the project areas (see discussion
below). Elevated levels of underwater noise would ensonify the project
areas where both fishes and mammals occur and could affect foraging
success. Additionally, marine mammals may avoid the area during the
proposed construction activities; however, displacement due to noise is
expected to be temporary and is not expected to result in long-term
effects to the individuals or populations.
The total area likely impacted by HRCP's activities is relatively
small compared to the available habitat in and around the Chesapeake
Bay and Atlantic Ocean. Avoidance by potential prey (i.e., fish) of the
immediate area due to increased noise is possible. The duration of fish
and marine mammal avoidance of this area after tugging stops is
unknown, but a rapid return to normal recruitment, distribution, and
behavior is anticipated. Any behavioral avoidance by fish or marine
mammals of the disturbed area would still leave significantly large
areas of fish and marine mammal foraging habitat in the nearby
vicinity.
The proposed project would occur within the same general footprint
as the existing marine infrastructure. The nearshore and intertidal
habitat where the proposed project would occur is an area of relatively
high marine vessel traffic. Most marine mammals do not generally use
the area within the footprint of the project area. Temporary,
intermittent, and short-term habitat alteration may result from
increased noise levels during the proposed construction activities.
Effects on marine mammals would be limited to temporary displacement
from pile installation and removal noise, and effects on prey species
would be similarly limited in time and space.
Water quality--Temporary and localized reduction in water quality
would occur as a result of in-water construction activities. Most of
this effect would occur during the installation and removal of piles
when bottom sediments are disturbed. The installation and removal of
piles would disturb bottom sediments and may cause a temporary increase
in suspended sediment in the project area. During pile extraction,
sediment attached to the pile moves vertically through the water column
until gravitational forces cause it to slough off under its own weight.
The small resulting sediment plume is expected to settle out of the
water column within a

[[Page 9830]]

few hours. Studies of the effects of turbid water on fish (marine
mammal prey) suggest that concentrations of suspended sediment can
reach thousands of milligrams per liter before an acute toxic reaction
is expected (Burton, 1993).
Effects to turbidity and sedimentation are expected to be short-
term, minor, and localized. Turbidity within the water column has the
potential to reduce the level of oxygen in the water and irritate the
gills of prey fish species in the proposed project area. However,
turbidity plumes associated with the project would be temporary and
localized, and fish in the proposed project area would be able to move
away from and avoid the areas where plumes may occur. Therefore, it is
expected that the impacts on prey fish species from turbidity, and
therefore on marine mammals, would be minimal and temporary. In
general, the area likely impacted by the proposed construction
activities is relatively small compared to the available marine mammal
habitat in the Chesapeake Bay and Atlantic Ocean.
Potential Effects on Prey--Sound may affect marine mammals through
impacts on the abundance, behavior, or distribution of prey species
(e.g., crustaceans, cephalopods, fishes, zooplankton). Marine mammal
prey varies by species, season, and location and, for some, is not well
documented. Studies regarding the effects of noise on known marine
mammal prey are described here.
Fishes utilize the soundscape and components of sound in their
environment to perform important functions such as foraging, predator
avoidance, mating, and spawning (e.g., Zelick et al., 1999; Fay, 2009).
Depending on their hearing anatomy and peripheral sensory structures,
which vary among species, fishes hear sounds using pressure and
particle motion sensitivity capabilities and detect the motion of
surrounding water (Fay et al., 2008). The potential effects of noise on
fishes depends on the overlapping frequency range, distance from the
sound source, water depth of exposure, and species-specific hearing
sensitivity, anatomy, and physiology. Key impacts to fishes may include
behavioral responses, hearing damage, barotrauma (pressure-related
injuries), and mortality.
Fish react to sounds that are especially strong and/or intermittent
low-frequency sounds, and behavioral responses such as flight or
avoidance are the most likely effects. Short duration, sharp sounds can
cause overt or subtle changes in fish behavior and local distribution.
The reaction of fish to noise depends on the physiological state of the
fish, past exposures, motivation (e.g., feeding, spawning, migration),
and other environmental factors. (Hastings and Popper, 2005) identified
several studies that suggest fish may relocate to avoid certain areas
of sound energy. Additional studies have documented effects of pile
driving on fishes (e.g., Scholik and Yan, 2001, 2002; Popper and
Hastings, 2009). Several studies have demonstrated that impulse sounds
might affect the distribution and behavior of some fishes, potentially
impacting foraging opportunities or increasing energetic costs (e.g.,
Fewtrell and McCauley, 2012; Pearson et al., 1992; Skalski et al.,
1992; Santulli et al., 1999; Paxton et al., 2017). However, some
studies have shown no or slight reaction to impulse sounds (e.g.,
Pe[ntilde]a et al., 2013; Wardle et al., 2001; Jorgenson and Gyselman,
2009; Cott et al., 2012). More commonly, though, the impacts of noise
on fishes are temporary. For example, during the Port of Alaska's
Marine Terminal Redevelopment Project, the effects of impact and
vibratory installation of 30-inch (76-cm (centimeter)) steel sheet
piles at the POA on 133 caged juvenile coho salmon (Oncorhynchus
kisutc) in Knik Arm were studied (Hart Crowser Incorporated et al.,
2009; Houghton et al., 2010). Acute or delayed mortalities, or
behavioral abnormalities were not observed in any of the coho salmon.
Furthermore, results indicated that the pile driving had no adverse
effect on feeding ability or the ability of the fish to respond
normally to threatening stimuli (Hart Crowser Incorporated et al.,
2009; Houghton et al., 2010).
SPLs of sufficient strength have been known to cause injury to
fishes and fish mortality (summarized in Popper et al., 2014). However,
in most fish species, hair cells in the ear continuously regenerate and
loss of auditory function is likely restored when damaged cells are
replaced with new cells. Halvorsen et al. (2012b) showed that a TTS of
4 to 6 dB was recoverable within 24 hours for one species. Impacts
would be most severe when the individual fish is close to the source
and when the duration of exposure is long. Injury caused by barotrauma
can range from slight to severe and can cause death, and is most likely
for fish with swim bladders. Barotrauma injuries have been documented
during controlled exposure to impact pile driving (Halvorsen et al.,
2012a; Casper et al., 2013, 2017).
Fish populations in the proposed project area that serve as marine
mammal prey could be temporarily affected by noise from pile
installation and removal. The frequency range in which fishes generally
perceive underwater sounds is 50 to 2,000 Hz, with peak sensitivities
below 800 Hz (Popper and Hastings, 2009). Fish behavior or distribution
may change, especially with strong and/or intermittent sounds that
could harm fishes. High underwater SPLs have been documented to alter
behavior, cause hearing loss, and injure or kill individual fish by
causing serious internal injury (Hastings and Popper, 2005).
Zooplankton is a food source for several marine mammal species, as
well as a food source for fish that are then preyed upon by marine
mammals. Population effects on zooplankton could have indirect effects
on marine mammals. Data are limited on the effects of underwater sound
on zooplankton species, particularly sound from construction (Erbe et
al., 2019). Popper and Hastings (2009) reviewed information on the
effects of human-generated sound and concluded that no substantive data
are available on whether the sound levels from pile driving, seismic
activity, or any human-made sound would have physiological effects on
invertebrates. Any such effects would be limited to the area very near
(1 to 5 meters (m) (3.28 to 16.4 feet (ft))) to the sound source and
would result in no population effects because of the relatively small
area affected at any one time and the reproductive strategy of most
zooplankton species (short generation, high fecundity, and very high
natural mortality). No adverse impact on zooplankton populations is
expected to occur from the specified activity due in part to large
reproductive capacities and naturally high levels of predation and
mortality of these populations. Any mortalities or impacts that might
occur would be negligible.
The greatest potential impact to marine mammal prey during
construction would occur during impact pile driving. However, in most
cases, the duration of impact pile driving would be limited to the
final stage of installation (proofing) after the pile has been driven
as close as practicable to the design depth with a vibratory driver.
In-water construction activities would only occur during daylight
hours, allowing fish to forage and transit the project area in the
evening. Vibratory pile driving could possibly elicit behavioral
reactions from fishes, such as temporary avoidance of the area, but is
unlikely to cause injuries to fishes or have persistent effects on
local fish populations. Construction also would have minimal permanent
and temporary impacts on benthic invertebrate species, a marine mammal
prey source. In

[[Page 9831]]

addition, it should be noted that the area in question is low-quality
habitat since it is already highly developed and experiences a high
level of anthropogenic noise from normal operations and other vessel
traffic.

Potential Effects on Foraging Habitat

The proposed project is not expected to result in any habitat
related effects that could cause significant or long-term negative
consequences for individual marine mammals or their populations, since
installation and removal of in-water piles would be temporary and
intermittent. The total seafloor area affected by pile installation and
removal is a very small area compared to the vast foraging area
available to marine mammals outside this project area. For marine
mammals, while the area is commonly used or traversed by some species,
the proposed project area does not contain any particularly high-value
habitat and is not usually important to any of the other species
potentially affected by HRCP's proposed activities. While opportunistic
foraging could occur, more foraging habitat is available outside the
Bay, in more open ocean waters. Overall, the area impacted by the
project is relatively small compared to the available habitat just
outside the project area, and there are no areas of particular
importance that would be impacted by this project during the period
planned for activities to occur. Any behavioral avoidance by fish of
the disturbed area would still leave significantly large areas of fish
and marine mammal foraging habitat in the nearby vicinity. As described
in the preceding, the potential for the HRCP's construction to affect
the availability of prey to marine mammals or to meaningfully impact
the quality of physical or acoustic habitat is considered
insignificant. Therefore, impacts of the project are not likely to have
adverse effects on marine mammal foraging habitat in the proposed
project area.
In summary, given the relatively small areas being affected, as
well as the temporary and mostly transitory nature of the proposed
construction activities, any adverse effects from HRCP's activities on
prey habitat or prey populations are expected to be minor and
temporary. The most likely impact to fishes at the project site would
be temporary avoidance of the area. Any behavioral avoidance by fish of
the disturbed area would still leave significantly large areas of fish
and marine mammal foraging habitat in the nearby vicinity. Thus, we
preliminarily conclude that impacts of the specified activities are not
likely to have more than short-term adverse effects on any prey habitat
or populations of prey species. Further, any impacts to marine mammal
habitat are not expected to result in significant or long-term
consequences for individual marine mammals, or to contribute to adverse
impacts on their populations.

Estimated Take of Marine Mammals

This section provides an estimate of the number of incidental takes
proposed for authorization through the IHA, which will inform NMFS'
consideration of ``small numbers,'' the negligible impact
determinations, and impacts on subsistence uses.
Harassment is the only type of take expected to result from these
activities. Except with respect to certain activities not pertinent
here, section 3(18) of the MMPA defines ``harassment'' as any act of
pursuit, torment, or annoyance, which (i) has the potential to injure a
marine mammal or marine mammal stock in the wild (Level A harassment);
or (ii) has the potential to disturb a marine mammal or marine mammal
stock in the wild by causing disruption of behavioral patterns,
including, but not limited to, migration, breathing, nursing, breeding,
feeding, or sheltering (Level B harassment).
Authorized takes would primarily be by Level B harassment, as use
of the acoustic source's (i.e., impact pile driving, vibratory pile
driving) has the potential to result in disruption of behavioral
patterns for individual marine mammals. There is also some potential
for auditory injury (AUD INJ) (Level A harassment) to result, primarily
for very high frequency species, high frequency species and/or phocids.
The large number of dolphins that are proposed for take increases the
likelihood that some could enter in the Level A harassment zone. The
cryptic nature of porpoises and seals means that some animals could
enter into the Level A harassment zone unseen by observers. AUD INJ is
unlikely to occur for low-frequency cetaceans since they are likely to
be uncommon and unlikely to remain in the AUD INJ zone long enough to
experience injury. The proposed mitigation and monitoring measures are
expected to minimize the severity of the taking to the extent
practicable.
As described previously, no serious injury or mortality is
anticipated or proposed to be authorized for this activity. Below we
describe how the proposed take numbers are estimated.
For acoustic impacts, generally speaking, we estimate take by
considering: (1) acoustic criteria above which NMFS believes there is
some reasonable potential for marine mammals to be behaviorally
harassed or incur some degree of AUD INJ; (2) the area or volume of
water that will be ensonified above these levels in a day; (3) the
density or occurrence of marine mammals within these ensonified areas;
and, (4) the number of days of activities. We note that while these
factors can contribute to a basic calculation to provide an initial
prediction of potential takes, additional information that can
qualitatively inform take estimates is also sometimes available (e.g.,
previous monitoring results or average group size). Below, we describe
the factors considered here in more detail and present the proposed
take estimates.

Acoustic Criteria

NMFS recommends the use of acoustic criteria 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 AUD INJ of some degree (equated to
Level A harassment). We note that the criteria for AUD INJ, as well as
the names of two hearing groups, have been recently updated (NMFS,
2024) as reflected below in the Level A harassment section.
Level B Harassment--Though significantly driven by received level,
the onset of behavioral disturbance from anthropogenic noise exposure
is also informed to varying degrees by other factors related to the
source or exposure context (e.g., frequency, predictability, duty
cycle, duration of the exposure, signal-to-noise ratio, distance to the
source), the environment (e.g., bathymetry, other noises in the area,
predators in the area), and the receiving animals (hearing, motivation,
experience, demography, life stage, depth) and can be difficult to
predict (e.g., Southall et al., 2007; Southall et al., 2021; Ellison et
al., 2012). Based on what the available science indicates and the
practical need to use a threshold based on a metric that is both
predictable and measurable for most activities, NMFS typically uses a
generalized acoustic threshold based on received level to estimate the
onset of behavioral harassment. NMFS generally predicts that marine
mammals are likely to be behaviorally harassed in a manner considered
to be Level B harassment when exposed to underwater anthropogenic noise
above root-mean-squared sound pressure levels (RMS SPL) of 120 dB
(referenced to 1 micropascal (re 1 [mu]Pa)) for continuous (e.g.,
vibratory pile driving, drilling) and above RMS SPL 160 dB re 1 [mu]Pa
for non-

[[Page 9832]]

explosive impulsive (e.g., seismic airguns) or intermittent (e.g.,
scientific sonar) sources. Generally speaking, Level B harassment take
estimates based on these behavioral harassment thresholds are expected
to include any likely takes by TTS as, in most cases, the likelihood of
TTS occurs at distances from the source less than those at which
behavioral harassment is likely. TTS of a sufficient degree can
manifest as behavioral harassment, as reduced hearing sensitivity and
the potential reduced opportunities to detect important signals
(conspecific communication, predators, prey) may result in changes in
behavior patterns that would not otherwise occur.
HRCP's proposed pile driving includes the use of continuous
(vibratory hammer) and impulsive (impact hammer) sources, and therefore
the RMS SPL thresholds of 120 AND/OR 160 dB re 1 [mu]Pa are applicable.
Level A harassment--NMFS' Updated Technical Guidance for Assessing
the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version
3.0) (Updated Technical Guidance, 2024) identifies dual criteria to
assess AUD INJ (Level A harassment) to five different underwater marine
mammal groups (based on hearing sensitivity) as a result of exposure to
noise from two different types of sources (impulsive or non-impulsive).
HRCP's proposed pile driving includes the use of impulsive (impact
hammer) and non-impulsive (vibratory hammer) sources.
The 2024 Updated Technical Guidance criteria include both updated
thresholds and updated weighting functions for each hearing group
(table 6). The thresholds are provided in the table below. The
references, analysis, and methodology used in the development of the
criteria are described in NMFS' 2024 Updated Technical Guidance, which
may be accessed at: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools</a>.

Table 6--Thresholds Identifying the Onset of Auditory Injury
----------------------------------------------------------------------------------------------------------------
AUD INJ onset acoustic thresholds * (received level)
Hearing group ------------------------------------------------------------------------
Impulsive Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans........... Cell 1: Lpk,flat: 222 dB; Cell 2: LE,LF,24h: 197 dB.
LE,LF,24h: 183 dB.
High-Frequency (HF) Cetaceans.......... Cell 3: Lpk,flat: 230 dB; Cell 4: LE,HF,24h: 201 dB.
LE,HF,24h: 193 dB.
Very High-Frequency (VHF) Cetaceans.... Cell 5: Lpk,flat: 202 dB; Cell 6: LE,VHF,24h: 181 dB.
LE,VHF,24h: 159 dB.
Phocid Pinnipeds (PW) (Underwater)..... Cell 7: Lpk,flat: 223 dB; Cell 8: LE,PW,24h: 195 dB.
LE,PW,24h: 183 dB.
Otariid Pinnipeds (OW) (Underwater).... Cell 9: Lpk,flat: 230 dB; Cell 10: LE,OW,24h: 199 dB.
LE,OW,24h: 185 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric criteria for impulsive sounds: Use whichever criteria results in the larger isopleth for
calculating AUD INJ onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure
level criteria associated with impulsive sounds, the PK SPL criteria are recommended for consideration for non-
impulsive sources.
Note: Peak sound pressure level (Lp,0-pk) has a reference value of 1 [micro]Pa, and weighted cumulative sound
exposure level (LE,p) has a reference value of 1 [micro]Pa\2\s. In this table, criteria are abbreviated to be
more reflective of International Organization for Standardization standards (ISO, 2017). The subscript
``flat'' is being included to indicate peak sound pressure are flat weighted or unweighted within the
generalized hearing range of marine mammals underwater (i.e., 7 Hz to 165 kHz). The subscript associated with
cumulative sound exposure level criteria indicates the designated marine mammal auditory weighting function
(LF, HF, and VHF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours.
The weighted cumulative sound exposure level criteria 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 criteria will be exceeded.

Ensonified Area

Here, we describe operational and environmental parameters of the
activity that are used in estimating the area ensonified above the
acoustic thresholds, including source levels and transmission loss
coefficient.
The sound field in the project area is the existing background
noise plus additional construction noise from the proposed project.
Marine mammals are expected to be affected via sound generated by the
primary components of the project (i.e., impact pile driving and
vibratory pile driving). The source levels assumed for both removal and
installation activities are based on reviews of measurements of the
same or similar types and dimensions of piles available in the
scientific literature and from similar coastal construction projects.
Derived by the applicant using Geographic Information System software,
the source levels for the piles and activities (i.e., installation and/
or removal), and the information and literature used to determine
appropriate proxy sources, where applicable, are presented in table 7.
The source levels for vibratory removal and installation of piles of
the same material and diameter are assumed to be the same.

Table 7--Estimates of Underwater Sound Source Levels Generated During Vibratory and Impact Pile Installation and
Vibratory Removal
----------------------------------------------------------------------------------------------------------------
Pile type rms SEL dB peak Reference
----------------------------------------------------------------------------------------------------------------
Vibratory Hammer
----------------------------------------------------------------------------------------------------------------
36-inch steel pile................... 170 ......... 180 Caltrans 2015.
AZ 700 steel sheet pile.............. 160 ......... 175 Caltrans 2020.
----------------------------------------------------------------------------------------------------------------
Impact Hammer
----------------------------------------------------------------------------------------------------------------
12-inch Composite pile *............. 153 143 177 Caltrans 2015.
36-inch steel pile................... 193 183 210 Caltrans 2020.
36-inch steel pile, attenuated **.... 188 178 205 Caltrans 2020.

[[Page 9833]]

54-inch concrete cylinder pile ***... 183 170 192 MacGillivray et al. 2007.
----------------------------------------------------------------------------------------------------------------
Note: It is assumed that noise levels during pile installation and removal are similar. dB = decibel: SEL =
sound exposure level; dB peak = peak sound level; rms = root mean square; DoN = Department of the Navy; CCA =
Chromated Copper Arsenate, Caltrans = California Department of Transportation.
* SSL taken from 16-inch composite.
** SSLs taken from 36-inch concrete square piles, no project specific information provided.

Level B Harassment

Transmission Loss (TL) is the decrease in acoustic intensity as an
acoustic pressure wave propagates out from a source. TL parameters vary
with frequency, temperature, sea conditions, current, source and
receiver depth, water depth, water chemistry, and bottom composition
and topography. The general formula for underwater TL is:

TL = B x Log10(R1/R2),

Where:

TL = transmission loss in dB,
B = transmission loss coefficient,
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 in this case. The degree to which underwater
sound propagates away from a sound source depends on various factors,
most notably the water bathymetry and the 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<INF>10</INF>[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<INF>10</INF>[range]). A practical spreading value of 15 is
often used under conditions where water increases with depth as the
receiver moves away from the shoreline, resulting in an expected
propagation environment that would lie between spherical and
cylindrical spreading loss conditions. Absent site-specific acoustic
monitoring with differing measured TL, practical spreading is used.
Site-specific TL data for HRB is not available; therefore, the default
coefficient of 15 is used to determine the distances to the Level A
harassment and Level B harassment thresholds.
Level A Harassment
The ensonified area associated with Level A harassment is more
technically challenging to predict due to the need to account for a
duration component. Therefore, NMFS developed an optional User
Spreadsheet tool to accompany the 2024 Updated Technical Guidance that
can be used to relatively simply predict an isopleth distance for use
in conjunction with marine mammal density or occurrence to help predict
potential takes. We note that because of some of the assumptions
included in the methods underlying this optional tool, we anticipate
that the resulting isopleth estimates are typically going to be
overestimates of some degree, which may result in an overestimate of
potential take by Level A harassment. However, this optional tool
offers a practical, alternative way to estimate isopleth distances when
more sophisticated modeling methods are not available or practical. For
stationary sources[such as pile driving, the optional User Spreadsheet
tool predicts the distance at which, if a marine mammal remained at
that distance for the duration of the activity, it would be expected to
incur AUD INJ. Inputs used in the optional User Spreadsheet tool (table
8), and the resulting estimated isopleths (table 9, table 10) are
reported below.

Table 8--User Spreadsheet Inputs
--------------------------------------------------------------------------------------------------------------------------------------------------------
Steel 12-in 36-in steel pipe 54-in
sheet comp ---------------------------------------------------------- concrete
Model parameter ---------------- -----------
Vib Vib Vib Vib Vib Imp Imp--Bubble Imp--Bubble Imp
--------------------------------------------------------------------------------------------------------------------------------------------------------
Spreadsheet Tab................................................... A.1 A.1 A.1 A.1 A.1 E.1 E.1 E.1 E.1
Weighting Factor Adjustment (kHz)................................. 2.5 2.5 2.5 2.5 2.5 2 2 2 2
Sound Pressure Level (SPLrms)..................................... 160 153 170 170 170 193 188 188 183
SELss (LE, p, single strike) at 10 meters......................... ...... ...... ...... ...... ...... 183 178 178 170
Lp, 0-pk at 10 meters............................................. ...... ...... ...... ...... ...... 210 205 205 192
Number of piles within 24-hour period............................. 6 4 4 3 2 ...... 2 3 1
Estimated Duration to drive a single pile (min)................... 30 30 30 30 30 ...... ........... ........... ..........
Duration to drive a single pile (min)............................. 30 30 30 30 30 ...... ........... ........... ..........
Transmission loss coefficient..................................... 15 15 15 15 15 15 15 15 15
Distance from sound pressure level (SPLrms) measurement (m)....... 10 10 10 10 10 10 10 10 10
Strikes per pile.................................................. ...... ...... ...... ...... ...... 40 40 40 2,100
Estimated Strikes per pile........................................ ...... ...... ...... ...... ...... 40 40 40 2,100
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 9834]]

Table 9--Calculated Distances to Level A and Level B Harassment Isopleths During Vibratory Pile Installation and Removal With No Attenuation
--------------------------------------------------------------------------------------------------------------------------------------------------------
Level B Level B
Project component Size/type Minutes Piles LF * HF * VHF * PW * isopleth area
per pile per day (m) (km\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
Template Piles.................. 36-inch Pipe, Steel........... 30 3 48 19 40 62 21,544 390
North Shore Work & Jump Trestle. 36-inch Pipe, Steel........... 30 3 48 19 40 62 21,544 390
North Shore abutment Island..... Steel sheet................... 30 6 17 7 14 22 4,642 39
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Island
--------------------------------------------------------------------------------------------------------------------------------------------------------
Circulation Dock................ 36-inch Pipe, Steel........... 15 2 37 15 30 48 21,544 399
--------------------------------------------------------------------------------------------------------------------------------------------------------
South Island
--------------------------------------------------------------------------------------------------------------------------------------------------------
TBM Platform & Conveyor......... 36-inch Pipe, Steel........... 30 3 48 19 40 62 21,544 504
Moorings........................ 36-inch Pipe, Steel........... 30 4 59 23 48 75 21,544 504
--------------------------------------------------------------------------------------------------------------------------------------------------------
South Trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
Template Piles.................. 36-inch Pipe, Steel........... 30 3 48 19 40 62 21,544 408
Work Trestle, Jump Trestle, 36-inch Pipe, Steel........... 30 2 37 15 30 48 21,544 408
Demolition Trestle, Temporary
MOT Trestle.
Moorings........................ 36-inch Pipe, Steel........... 30 4 59 23 48 75 21,544 408
--------------------------------------------------------------------------------------------------------------------------------------------------------
Willoughby Bay
--------------------------------------------------------------------------------------------------------------------------------------------------------
Moorings (Safe Haven)........... 36-inch Pipe, Steel........... 30 4 59 23 48 75 21,544 32
Fender.......................... 12-inch Composite............. 30 4 5 2 4 6 1,585 7
Bulkhead Replacement............ Steel sheet................... 30 6 17 7 14 22 4,642 5
--------------------------------------------------------------------------------------------------------------------------------------------------------
Willoughby Split Laydown area
Temp Dock/Finger Piers.......... 36-inch Pipe, Steel........... 30 3 48 19 40 62 21,544 156
--------------------------------------------------------------------------------------------------------------------------------------------------------
* All ensonified areas are <=0.02 km\2\.

Table 10--Calculated Distances to Level A and Level B Harassment Isopleths (m) and areas (km\2\) During Impact Installation With Attenuation (5 dB) From
Bubble Curtain
--------------------------------------------------------------------------------------------------------------------------------------------------------
Level A harassment isopleth (area) Level B
Strikes Piles ------------------------------------------------ harassment
Project component Size/type per pile per day isopleth
LF HF VHF PW (area)
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
Permanent piles.................. 54-inch Pipe, Concrete......... 2,100 1 222 (0.2) 28 (<0.01) 343 (0.4) 197 (0.12) 342 (0.4)
Work Trestle, Jump Trestle, 36-inch Pipe, Steel............ 40 2 86 (0.02) 11 (<0.01) 133 (0.06) 77 (0.02) 736 (1.6)
Demolition Trestle.
--------------------------------------------------------------------------------------------------------------------------------------------------------
South Island
--------------------------------------------------------------------------------------------------------------------------------------------------------
TBM Platform..................... 36-inch Pipe, Steel............ 40 3 113 (0.04) 15 (<0.01) 174 (0.1) 100 (0.03) 736 (1.6)
--------------------------------------------------------------------------------------------------------------------------------------------------------
South Trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
Work Trestle, Jump Trestle, 36-inch Pipe, Steel............ 40 3 522 (0.9) 67 (0.02) 808 (2) 464 (0.69) 736 (1.6)
Demolition Trestle, Temporary
MOT Trestle.
Permanent Piles.................. 54-inch Pipe, Concrete......... 2,100 1 222 (0.2) 28 (<0.01) 343 (0.4) 197 (0.12) 342 (0.4)
--------------------------------------------------------------------------------------------------------------------------------------------------------

Note that to minimize hydroacoustic impacts caused by the impact
hammer, a bubble curtain will be used for installation of steel pipe
piles in water depths greater than 20 feet. Portions of the South
Trestle Jump Trestle in water depths less than 20 feet will be
installed without a bubble curtain. Additionally, HRCP may employ more
than one hammer operating simultaneously. However, separate pile
driving actions will not be conducted in close proximity to each other.
Therefore, there is no need to apply decibel addition when calculating
isopleths given that the sources will be well separated.

Marine Mammal Occurrence and Take Estimation

In this section, we provide information about the occurrence of
marine mammals, including density or other relevant information, which
will inform the take calculations. Then, we describe how all of the
information detailed above is synthesized to produce a quantitative
estimate of the take that is reasonably likely to occur and proposed
for authorization.
In the preceding LOA, NMFS and HRCP estimated potential exposure
using daily sighting data for areas west of the HRBT area and within
the Core Monitoring Area (CMA). The CMA encompasses the area south of
the HRBT and north of the Hampton Roads Monitor-Merrimac Memorial
Bridge-Tunnel (Interstate 664). This is the area that will be
ensonified during most of the pile installation and removal activities.

Humpback Whale

Humpback whales are relatively rare in the Project area and density
data for

[[Page 9835]]

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. Humpback whale sighting data collected by the
U.S. Navy near Naval Station Norfolk and Virginia Beach from 2012 to
2022 (Engelhaupt et al. 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021
and 2022) and in the mid-Atlantic (including the Chesapeake Bay) from
2012 to 2022. Based on these data, and the known movement of humpback
whales from November through April at the mouth of the Chesapeake Bay,
HRCP is requesting two takes every month from May to October and three
to four each month from November through April for the duration of in-
water pile installation and removal as shown in table 11. A total of 37
takes of humpback whale by Level B harassment is proposed. Take by
Level A is not proposed since there were zero takes of humpback whale
according to the HRBT marine mammal monitoring reports from 2021
through 2024. This is the same total number of takes requested under
the previous LOA.

Table 11--Estimated Numbers of Humpback Whales Potentially Exposed to Level A and Level B Harassment Sound Levels per Month
--------------------------------------------------------------------------------------------------------------------------------------------------------
Yr April M J J A S O N D J F Mar Total
--------------------------------------------------------------------------------------------------------------------------------------------------------
26-27........................................... 3 2 2 2 2 2 2 4 4 4 4 2 37
--------------------------------------------------------------------------------------------------------------------------------------------------------

Bottlenose Dolphin

Estimated take of bottlenose dolphins was derived using daily
sighting rates within the CMA from 2012 through 2016 by Engelhaupht et
al. (2016). . Seasonal density data was also used to establish
estimated take for areas northeast of the HRBT Project and outside the
CMA. However, the incorporation of the density data outside of the CMA
produced take estimates that were unrealistically high, based on the
monitoring results of the project, as shown in reports submitted by
HRCP (and available online at: <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-hampton-roads-bridge-tunnel-expansion-project-hampton-0">https://www.fisheries.noaa.gov/action/incidental-take-authorization-hampton-roads-bridge-tunnel-expansion-project-hampton-0</a>). Therefore, NMFS has not used these data for
estimating take for this proposed IHA.
To estimate potential exposure west of the Project site and within
the CMA, sighting rates (numbers of dolphins per day) were determined
for each of the four seasons from sightings located in the inshore
Chesapeake Bay zone (the Chesapeake Bay waters near Naval Station
Norfolk). Sighting data were used to calculate the number of dolphins/
day that could be anticipated to occur in the Project area for each of
the four seasons. The number of anticipated days of in-water pile
installation and removal for each activity was multiplied by the
average daily sighting rate (table 12) to estimate the number of
dolphins per month that could be exposed to Project noise. For most
piles, the ensonified area is contained within the surrounding land
features and cannot extend out into Chesapeake Bay. Therefore, this
method is sufficient to calculate potential exposure. Table 13 shows
the total annual proposed takes. HRCP and NMFS will assume that 1
percent of the total tales would be by Level A harassment since Level A
harassment takes were recorded in monitoring reports submitted under
the previous LOA. According to the HRBT marine mammal monitoring
reports from 2021 through 2024 annual dolphin takes ranged from 0 to 2
by Level A harassment and 9 to 92 by Level B harassment per year.

Table 12--Average Daily Sighting Rates Within Core Monitoring Area
------------------------------------------------------------------------
Average
Season sighted
per day
------------------------------------------------------------------------
Spring, March-May............................................. 17.33
Summer, June-August........................................... 16.43
Fall, Sept-Nov................................................ 27.22
Winter, Dec-Feb............................................... 0
------------------------------------------------------------------------

Table 13--Total Estimated Takes Shown by Month
--------------------------------------------------------------------------------------------------------------------------------------------------------
Month Apr M J J A S O N D J F M
--------------------------------------------------------------------------------------------------------------------------------------------------------
Daily avg.......................... 17.33 17.33 16.43 16.43 16.43 27.22 27.22 27.22 0 0 0 17.33 .......
Total.......................... 519.9 537.23 492.9 509.33 509.33 816.6 843.82 816.6 0 0 0 537.23 5,583
--------------------------------------------------------------------------------------------------------------------------------------------------------

The total number of bottlenose dolphin takes by Level A and Level B
harassment is expected to be split between three bottlenose dolphin
stocks: Western North Atlantic Southern Migratory Coastal; Western
North Atlantic Northern Migratory Coastal; and NNCES. There is
insufficient data available to apportion the requested takes precisely
to each of these three stocks present in the project area. Given that
most of the NNCES stock are found in the Pamlico Sound Estuarine
System, HRCP and NMFS will assume that no more than 200 of the
requested takes will be from this stock. Since members of the Western
North Atlantic Northern Migratory Coastal and Western North Atlantic
Southern Migratory Coastal stocks are thought to occur in or near the
Project area in greater numbers, HRCP and NMFS will conservatively
assume that half of the remaining animals will belong to either of
these stocks. The breakout of Level A and Level B harassment by dolphin
stock is shown in table 16.

Harbor Porpoise

Harbor porpoises are rarely seen in the project area although they
are known to occur in the coastal waters near Virginia Beach (Hayes et
al. 2020). They have been sighted on rare occasions in the Chesapeake
Bay closer to Norfolk. Density data does not exist for this species
within the project area and 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 high enough sample
sizes to calculate densities. One group of two harbor porpoises was
seen during spring 2015 (Engelhaupt et al. 2016). There were no
recorded take of harbor porpoise reported in the HRBT annual marine
mammal monitoring reports from 2021 through 2024.
HRCP estimated that one group of two harbor porpoises could be
exposed to project-related underwater noise each month during the
spring (March-May) for a total of six harbor porpoises takes

[[Page 9836]]

(i.e., one group of two individuals per month x 3 months per year = six
harbor porpoises). Given that porpoises are known to be cryptic animals
it is possible, if unlikely, that porpoises could enter into the Level
A harassment zone. HRCP has requested limited take by Level A
harassment. While NMFS does not agree that take by Level A harassment
is likely, due to the duration of time a harbor porpoise would be
required to remain within the Level A zone to accumulate enough energy
to experience AUD INJ, we nevertheless propose to authorize limited
take. It is anticipated that no more than two individuals may enter the
Level A harassment zone during pile installation and removal.
Therefore, NMFS is authorizing four takes by Level B harassment and two
Level A harassment takes.

Harbor Seal

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 November
2014 through April 2024 (Rees et al. 2016; Jones et al. 2018; Jones and
Rees 2020,2024). The number of harbor seals sighted by month from 2014
through 2024, in the Chesapeake Bay waters, in the vicinity (lower
Chesapeake Bay along the CBBT) of the Project, ranged from 0 to 170
individuals.
The estimated total number of harbor seals potentially exposed
during the Project to in-water noise is 11.8 per day (the average of
the 10-year average daily harbor seal count) (table 14) for 156 days
based on a 6-day work week from mid-November to mid-May. Seals are not
expected to be present in the Chesapeake Bay from June through October.
In the event that unanticipated Level A take does occur, HRCP assumed
it would not exceed 10 percent of total takes. Therefore, NMFS is
proposing to authorize 187 Level A harassment takes of harbor seals and
1,685 Level B harassment takes of harbor seal (1,872 total takes-187
Level A harassment takes = 1,685 Level B harassment takes). Note that
no harbor seals takes were reported in HRBT annual marine mammal
monitoring reports from 2021 through 2024.

Table 14--Harbor Seal Survey Effort, Total Count, Max Count, and the Average Number of Seals Observed per Survey
Day at the Chesapeake Bay Bridge Tunnel Survey Area
----------------------------------------------------------------------------------------------------------------
Number survey Total seal Average seal Max daily
Year days count 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
2018-2019....................................... 10 82 8 17
2019-2020....................................... 6 29 5 6
2020-2021....................................... 11 137 12 32
2021-2022....................................... 10 98 10 25
2022-2023....................................... 11 110 10 31
2023-2024....................................... 7 92 13 38
Average......................................... 11.7 149.6 11.8 30.6
----------------------------------------------------------------------------------------------------------------

Gray Seal

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 2019 (Rees et al. 2016; Jones et al.
2018; Jones and Rees 2020). Seasonal numbers of gray seals in the
Chesapeake Bay waters in the vicinity of the Project area in previous
years have been low as shown in table 15. Gray seals are not expected
to be present in the Chesapeake Bay during the months of June through
October. There were zero takes of gray seal reported in HRBT annual
marine mammal monitoring reports from 2021 through 2024.
Gray seals are expected to be very uncommon in the Project area. It
was assumed that three gray seals could be exposed to Level B
harassment during each of the winter months (December through
February). Therefore, HRCP conservatively requested and NMFS proposes
that nine gray seals could be exposed to harassment (three gray seals
per month x 3 months per year = nine gray seals). Given their cryptic
nature, a small number of Level A harassment takes (two) were also
requested by HRCP and are proposed by NMFS resulting in seven takes by
Level B harassment and two takes by Level A harassment.

Table 15--Average Number of Individual Gray Seal Sightings Summarized by
Season
[2014-2019]
------------------------------------------------------------------------

------------------------------------------------------------------------
Spring (March-May)...................................... 0
Summer (June-August).................................... 0
Fall (September-November)............................... 0
Winter (December-February).............................. 1
------------------------------------------------------------------------

Table 16 summarizes proposed take by Level A and/or Level B
harassment by stock, harassment type, and total proposed takes and as a
percentage of stock abundance.

[[Page 9837]]

Table 16--Proposed Take by Stock, Harassment Type, and as a Percentage of Stock Abundance
----------------------------------------------------------------------------------------------------------------
Level A Level B
Species Stock Stock harassment harassment Percentage
abundance take take
----------------------------------------------------------------------------------------------------------------
Humpback whale................ Gulf of Maine... 1,396 0 37 2.6
Bottlenose Dolphin............ Western North 3,751 27 2,664 71.7
Atlantic
Southern
Migratory
Coastal.
Western North 6,639 27 2,665 40.5
Atlantic
Northern
Migratory
Coastal.
Northern North 823 2 198 24.3
Carolina
Estuarine
System.
Harbor porpoises.............. Gulf of Maine- 85,765 2 4 <0.01
Bay of Fundy.
Harbor seals.................. Western North 61,336 184 1,647 0.30
Atlantic.
Gray seals.................... Western North 27,911 2 7 0.03
Atlantic.
----------------------------------------------------------------------------------------------------------------

Proposed Mitigation

In order to issue an IHA under section 101(a)(5)(D) of the MMPA,
NMFS must set forth the permissible methods of taking pursuant to the
activity, and other means of effecting the least practicable impact on
the species or stock and its habitat, paying particular attention to
rookeries, mating grounds, and areas of similar significance, and on
the availability of the species or stock for taking for certain
subsistence uses (latter not applicable for this action). NMFS
regulations require applicants for incidental take authorizations to
include information about the availability and feasibility (economic
and technological) of equipment, methods, and manner of conducting the
activity or other means of effecting the least practicable adverse
impact upon the affected species or stocks, and their habitat (50 CFR
216.104(a)(11)).
In evaluating how mitigation may or may not be appropriate to
ensure the least practicable adverse impact on species or stocks and
their habitat, as well as subsistence uses where applicable, NMFS
considers two primary factors:
(1) The manner in which, and the degree to which, the successful
implementation of the measure(s) is expected to reduce impacts to
marine mammals, marine mammal species or stocks, and their habitat.
This considers the nature of the potential adverse impact being
mitigated (likelihood, scope, range). It further considers the
likelihood that the measure will be effective if implemented
(probability of accomplishing the mitigating result if implemented as
planned), the likelihood of effective implementation (probability
implemented as planned); and
(2) The practicability of the measures for applicant
implementation, which may consider such things as cost, impact on
operations,
The mitigation requirements described in the following were
proposed by HRCP in its adequate and complete application or are the
result of subsequent coordination between NMFS and HRCP. HRCP has
agreed that all of the mitigation measures are practicable. NMFS has
fully reviewed the specified activities and the mitigation measures to
determine if the mitigation measures would result in the least
practicable adverse impact on marine mammals and their habitat, as
required by the MMPA, and has determined the proposed measures are
appropriate. NMFS describes these below as proposed mitigation
requirements and has included them in the proposed IHA.
In addition to the measures described later in this section, HRCP
would be required to follow these general mitigation measures:
<bullet> Takes proposed for authorization, by Level A harassment
and Level B harassment only, would be limited to the species and
numbers listed in table 16. Construction activities would be required
to be halted upon observation of either a species for which incidental
take was not authorized or for a species for which incidental take has
been authorized but the number of takes has been met, entering or is
within the harassment zone, if the IHA is issued.
<bullet> The taking by serious injury or death of any of the
species listed in table 16 or any taking of any other species of marine
mammal would be prohibited and would result in the modification,
suspension, or revocation of the IHA, if issued. Any taking exceeding
the amounts proposed for authorization listed in table 16 would be
prohibited and would result in the modification, suspension, or
revocation of the IHA, if issued;
<bullet> Ensure that construction supervisors and crews, the marine
mammal monitoring team, and relevant HRCP staff are trained prior to
the start of all construction activities, so that responsibilities,
communication procedures, marine mammal monitoring protocol, and
operational procedures are clearly understood. New personnel joining
during the project must be trained prior to commencing work;
<bullet> HRCP, construction supervisors and crews, protected
species observers PSOs, and relevant HRCP staff must avoid direct
physical interaction with marine mammals during construction activity.
If a marine mammal comes within 10 meters of such activity, operations
must cease and vessels must reduce speed to the minimum level required
to maintain steerage and safe working conditions, as necessary to avoid
direct physical interaction
<bullet> Employ PSOs and establish monitoring locations as
described in the Marine Mammal Monitoring and Mitigation Plan (MMMMP)
(see NMFS' website). HRCP must monitor the project area to the maximum
extent possible based on the required number of PSOs, required
monitoring locations, and environmental conditions.
Additionally, the following mitigation measures apply to HRCP's in-
water construction activities.

Pre- and Post-Activity Monitoring

HRCP would be required to establish pre- and post-monitoring zones
with radial distances (based on the distances to the Level B harassment
threshold and feasibility for PSOs in the field) for all construction
activities. Monitoring would take place from 30 minutes prior to
initiation of any pile driving activity (i.e., pre-start clearance
monitoring) through 30 minutes post-completion of pile driving
activity. In addition, monitoring for 30 minutes would take place
whenever a break in the specified activity (i.e., impact pile driving,
vibratory pile driving) of 30 minutes or longer occurs. Pre-start
clearance monitoring would be conducted during periods of visibility
sufficient for the Lead PSO to determine that the shutdown zones
(indicated further below) are clear of marine mammals. Pile driving may
commence following 30 minutes of observation when the determination is
made that the shutdown zones are clear of marine mammals.

Soft-Start

HRCP would use soft start techniques when impact pile driving.
Soft-start requires contractors to provide an initial set of three
strikes at reduced energy, followed by a 30-second waiting period, then
two subsequent reduced-energy

[[Page 9838]]

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. Soft-start
procedures are used to provide additional protection to marine mammals
by providing warning and/or giving marine mammals a chance to leave the
area prior to the hammer operating at full capacity.

Establishment of Shutdown Zones

HRCP would be required to establish shutdown zones with radial
distances, as identified in table 17 and table 18 for all construction
activities. The purpose of a shutdown zone is generally to define an
area within which shutdown of the activity would occur upon sighting of
a marine mammal (or in anticipation of an animal entering the defined
area). Additionally, HRCP would be required to shutdown in the event an
unauthorized species is present, to avoid take of that unauthorized
species. Shutdown zones would vary based on the activity type and
marine mammal hearing group.
If a marine mammal is observed entering or within the shutdown
zones indicated in table 17 or table 18, pile driving activities must
be delayed or halted. If pile driving is delayed or halted due to the
presence of a marine mammal, the activity may not commence or resume
until either the animal has voluntarily exited and been visually
confirmed beyond the shutdown zones or a specific time period has
passed without re-detection of the animal (i.e., 15 minutes). If a
marine mammal comes within or approaches the shutdown zone indicated in
table 16 or table 17 such operations must cease. Should environmental
conditions deteriorate such that marine mammals within the entire
shutdown zone would not be visible (e.g., fog, heavy rain), HRCP shall
delay pile driving and removal until observers are confident marine
mammals within the shutdown zone could be detected.

Table 17--Shutdown and Monitoring Zones During Vibratory Pile Installation and Removal
--------------------------------------------------------------------------------------------------------------------------------------------------------
Level B
isopleth
Project component Size/type Piles LF HF VHF PW (m)
per day monitoring
zone
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
Template Piles.................................. 36-inch Pipe, Steel............... 3 50 20 40 65 21,544
North Shore Work & Jump Trestle................. 36-inch Pipe, Steel............... 3 50 20 40 65 21,544
North Shore abutment Island..................... Steel sheet....................... 6 20 20 20 25 4,642
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Island
--------------------------------------------------------------------------------------------------------------------------------------------------------
Circulation Dock................................ 36-inch Pipe, Steel............... 2 40 20 30 50 21,544
--------------------------------------------------------------------------------------------------------------------------------------------------------
South Island
--------------------------------------------------------------------------------------------------------------------------------------------------------
TBM Platform & Conveyor......................... 36-inch Pipe, Steel............... 3 50 20 40 65 21,544
Moorings........................................ 36-inch Pipe, Steel............... 4 60 25 50 75 21,544
--------------------------------------------------------------------------------------------------------------------------------------------------------
South Trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
Template Piles.................................. 36-inch Pipe, Steel............... 3 50 20 40 65 21,544
Work Trestle, Jump Trestle, Demolition Trestle, 36-inch Pipe, Steel............... 2 40 20 30 50 21,544
Temporary MOT Trestle.
Moorings........................................ 36-inch Pipe, Steel............... 4 60 25 50 75 21,544
--------------------------------------------------------------------------------------------------------------------------------------------------------
Willoughby Bay
--------------------------------------------------------------------------------------------------------------------------------------------------------
Moorings (Safe Haven)........................... 36-inch Pipe, Steel............... 4 60 25 50 75 21,544
Fender.......................................... 12-inch Comp...................... 4 20 20 20 20 1,585
Bulkhead Replacement............................ Steel sheet....................... 6 20 20 20 25 4,642
--------------------------------------------------------------------------------------------------------------------------------------------------------
Willoughby Split Laydown area
--------------------------------------------------------------------------------------------------------------------------------------------------------
Temp Dock/Finger Piers.......................... 36-inch Pipe, Steel............... 3 50 20 40 65 21,544
--------------------------------------------------------------------------------------------------------------------------------------------------------

Table 18--Shutdown and Monitoring Zones During Impact Installation With Attenuation
--------------------------------------------------------------------------------------------------------------------------------------------------------
Level B
isopleth
Project component Size/type Piles LF HF VHF PW (m)
per day monitoring
zone
--------------------------------------------------------------------------------------------------------------------------------------------------------
North trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
Permanent piles................................. 54-inch Pipe, Concrete Cylinder... 1 225 30 350 200 158
Work Trestle, Jump Trestle, Demolition Trestle.. 36-inch Pipe, Steel............... 2 90 20 140 80 736
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 9839]]

South Island
--------------------------------------------------------------------------------------------------------------------------------------------------------
TBM Platform.................................... 36-inch Pipe, Steel............... 3 120 20 175 100 736
--------------------------------------------------------------------------------------------------------------------------------------------------------
South Trestle
--------------------------------------------------------------------------------------------------------------------------------------------------------
Work Trestle, Jump Trestle, Demolition Trestle, 36-inch Pipe, Steel............... 3 120 20 175 100 736
Temporary MOT Trestle.
Permanent Piles................................. 54-inch Pipe, Concrete Cylinder... 1 225 30 350 200 158
--------------------------------------------------------------------------------------------------------------------------------------------------------

Bubble Curtain

A bubble curtain must be employed during all impact pile driving. A
noise attenuation device would not be required during vibratory pile
driving. The bubble curtain must distribute air bubbles around 100
percent of the piling circumference for the full depth of the water
column. The lowest bubble ring must be in contact with the mudline for
the full circumference of the ring. The weights attached to the bottom
ring must ensure 100 percent substrate contact. No parts of the ring or
other objects may prevent full substrate contact. Air flow to the
bubblers must be balanced around the circumference of the pile.

Proposed Monitoring and Reporting

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

Visual Monitoring

All PSOs must be NMFS-approved. PSOs would be independent of the
activity contractor (for example, employed by a subcontractor) and have
no other assigned tasks during monitoring periods. At least one PSO
would have prior experience performing the duties of a PSO during an
activity pursuant to a NMFS-issued ITA. Other PSOs may substitute other
relevant experience, education (degree in biological science or related
field), or training for prior experience performing the duties of a PSO
during construction activity pursuant to a NMFS-issued ITA.
Additionally, PSOs would be required to meet the following
qualifications:
<bullet> The ability to conduct field observations and collect data
according to assigned protocols;
<bullet> Experience or training in the field identification of
marine mammals, including the identification of behaviors;
<bullet> Sufficient training, orientation, or experience with the
construction operation to provide for personal safety during
observations;
<bullet> Writing skills sufficient to prepare a report of
observations including but not limited to:
(1) Number and species of marine mammals observed;
(2) Dates and times when in-water construction activities were
conducted;
(3) Dates, times, and reason for implementation of mitigation (or
why mitigation was not implemented when required); and
(4) Marine mammal behavior.
<bullet> The 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.
HRCP must establish monitoring locations, as described in MMMMP
(see NMFS' website). Where a team of three or more PSOs is required, a
lead observer (``Lead PSO'') or monitoring coordinator would be
designated. The lead observer must have prior experience performing the
duties of a PSO during construction activity pursuant to a NMFS-issued
ITA.
For all pile driving activities, a minimum of two PSOs must be
assigned. PSOs will be positioned at the best practical vantage
point(s). The position(s) may vary based on construction activity and
location of

[[Page 9840]]

piles or equipment. At least one of the monitoring locations will have
an unobstructed view of the pile being driven and unobstructed view of
the CMA, Level A harassment shutdown zone, and Level B harassment
shutdown. Given the maximum effective observation distance, PSOs would
be required to continuously monitor the entirety of the shutdown zones
and as much as possible of the Level B harassment zones given
visibility constraints, using binoculars and other resources to aid in
observation. PSOs would be required to record all observations of
marine mammals, regardless of distance from the pile being driven.

Proposed Reporting

HRCP would be required to submit an annual draft summary report on
all construction activities and marine mammal monitoring results to
NMFS within 90 days following the end of construction or 60 calendar
days prior to the requested issuance of any subsequent IHA for similar
activity at the same location, whichever comes first. The draft summary
report would include an overall description of construction work
completed, a narrative regarding marine mammal sightings, and
associated raw PSO data sheets (in electronic spreadsheet format).
Specifically, the report must include:
<bullet> Dates and times (begin and end) of all marine mammal
monitoring;
<bullet> Construction activities occurring during each daily
observation period, including: (a) how many and what type of piles were
driven or removed and the method (i.e., impact and vibratory); and (b)
the total duration of time for each pile (vibratory driving) or number
of strikes for each pile (impact driving);
<bullet> PSO locations during marine mammal monitoring; and
<bullet> Environmental conditions during monitoring periods (at
beginning and end of PSO shift and whenever conditions change
significantly), including Beaufort sea state and any other relevant
weather conditions including cloud cover, fog, sun glare, and overall
visibility to the horizon, and estimated observable distance.
Upon observation of a marine mammal, the following information must
be reported:
<bullet> Name of PSO who sighted the animal(s) and PSO location and
activity at the time of the sighting;
<bullet> Time of the sighting;
<bullet> Identification of the animal(s) (e.g., genus/species,
lowest possible taxonomic level, or unidentified), PSO confidence in
identification, and the composition of the group if there is a mix of
species;
<bullet> Distance and bearing of each observed marine mammal
relative to the pile being driven or removed for each sighting;
<bullet> Estimated number of animals (min/max/best estimate);
<bullet> Estimated number of animals by cohort (e.g., adults,
juveniles, neonates, group composition, etc.);
<bullet> Animal's closest point of approach and estimated time
spent within the estimated harassment zone(s);
<bullet> Description of any marine mammal behavioral observations
(e.g., observed behaviors such as feeding or traveling), including an
assessment of behavioral responses thought to have resulted from the
activity (e.g., no response or changes in behavioral state such as
ceasing feeding, changing direction, flushing, or breaching);
<bullet> Description of any actions implemented in response to the
sighting (e.g., delays, shutdown) and time and location of the action.
If no comments are received from NMFS within 30 days after the
submission of the draft summary report, the draft report would
constitute the final report. If HRCP received comments from NMFS, a
final summary report addressing NMFS' comments would be submitted
within 30 days after receipt of comments.

Reporting Injured or Dead Marine Mammals

In the event that personnel involved in HRCP activities discover an
injured or dead marine mammal, HRCP would report the incident to the
NMFS Office of Protected Resources (OPR)
(<a href="/cdn-cgi/l/email-protection#164644385f4246385b79787f6279647f787144736679646265567879777738717960"><span class="__cf_email__" data-cfemail="98c8cab6d1ccc8b6d5f7f6f1ecf7eaf1f6ffcafde8f7eaecebd8f6f7f9f9b6fff7ee">[email&#160;protected]</span></a>, <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="d29b8682fc82b3a7bebbbcb792bcbdb3b3fcb5bda4">[email&#160;protected]</a>) and to the
Greater Atlantic Region New England/Mid-Atlantic Regional Stranding
Coordinator (978-282-8478 or 978-281-9291) as soon as feasible. If the
death or injury was clearly caused by the specified activity, HRCP
would 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 IHA.
HRCP would not resume their activities until notified by NMFS. The
report would include the following information:
<bullet> Time, date, and location (latitude/longitude) of the first
discovery (and updated location information if known and applicable);
<bullet> Species identification (if known) or description of the
animal(s) involved;
<bullet> Condition of the animal(s) (including carcass condition if
the animal is dead);
<bullet> Observed behaviors of the animal(s), if alive;
<bullet> If available, photographs or video footage of the
animal(s); and
<bullet> General circumstances under which the animal was
discovered.

Negligible Impact Analysis and Determination

NMFS has defined negligible impact as an impact resulting from the
specified activity that cannot be reasonably expected to, and is not
reasonably likely to, adversely affect the species or stock through
effects on annual rates of recruitment or survival (50 CFR 216.103). A
negligible impact finding is based on the lack of likely adverse
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough
information on which to base an impact determination. In addition to
considering estimates of the number of marine mammals that might be
``taken'' through harassment, NMFS considers other factors, such as the
likely nature of any impacts or responses (e.g., intensity, duration),
the context of any impacts or responses (e.g., critical reproductive
time or location, foraging impacts affecting energetics), as well as
effects on habitat, and the likely effectiveness of the mitigation. We
also assess the number, intensity, and context of estimated takes by
evaluating this information relative to population status. Consistent
with the 1989 preamble for NMFS' implementing regulations (54 FR 40338,
September 29, 1989), the impacts from other past and ongoing
anthropogenic activities are incorporated into this analysis via their
impacts on the baseline (e.g., as reflected in the regulatory status of
the species, population size and growth rate where known, ongoing
sources of human-caused mortality, or ambient noise levels).
To avoid repetition, the discussion of our analysis applies to all
the species listed in table 15, given that the anticipated effects of
this activity on these different marine mammal stocks are expected to
be similar. There is little information about the nature or severity of
the impacts, or the size, status, or structure of any of these species
or stocks that would lead to a different analysis for this activity.
Impact pile driving for installation and vibratory pile driving for
installation and/or removal activities associated with the proposed
project, as outlined previously, have the potential

[[Page 9841]]

to disturb or displace marine mammals. Specifically, the specified
activities may result in take in the form of Level A harassment and/or
Level B harassment from underwater sounds generated from pile driving
installation and removal. Potential takes could occur if individuals of
these species are present in zones ensonified above the thresholds for
Level A harassment or Level B harassment identified above when these
activities are underway.
Given the nature of the proposed activities, NMFS does not
anticipate serious injury or mortality due to HRCP's proposed project,
even in the absence of required mitigation. The Level A harassment
zones are based upon an animal exposed to vibratory pile driving and/or
impact pile driving for periods ranging from 30 to 180 minutes for in-
water pile driving per day. Overall, construction activities are not
expected to exceed 12 hours per day (likely ranging between 10-12 hours
but not all of that would be spent actively pile driving). Exposures of
this length are, however, unlikely for vibratory driving for
installation and/or removal, given marine mammal movement throughout
the area. Even during impact driving scenarios, an animal exposed to
the accumulated sound energy would likely only experience limited AUD
INJ at the lower frequencies where pile driving energy is concentrated.
As stated in the Proposed Mitigation section, HRCP would implement
shutdown zones that equal or exceed many of the Level A harassment
isopleths shown in table 16 and table 17. Take by Level A harassment is
proposed for four marine mammal species/stocks. This is precautionary
to account for the potential that an animal could enter and remain
within the area between a Level A harassment zone and the shutdown zone
for long enough to be taken by Level A harassment. Additionally, in
some cases, this precaution would account for the possibility that an
animal could enter a shutdown zone without detection and remain in the
Level A harassment zone for a duration long enough to be taken by Level
A harassment before being observed and a shutdown occurring. That said,
any take by Level A harassment is expected to arise from, at most, a
small degree of AUD INJ because animals would need to be exposed to
higher levels and/or longer duration than are expected to occur here to
incur any more than a small degree of AUD INJ. Additionally, some
subset of the individuals that are behaviorally harassed could also
simultaneously incur some small degree of TTS for a short duration of
time. Because of the small degree anticipated, any AUD INJ or TTS
potentially incurred here is not expected to adversely affect an
animal's individual fitness, let alone annual rates of recruitment or
survival.
For all species and stocks, take is expected to occur within a
limited, confined area (adjacent to the project site) of the stock's
range. The intensity and duration of take by Level A harassment and
Level B harassment would be expected to be minimized through the
proposed mitigation measures described herein.
Behavioral responses of marine mammals to pile driving for pile
installation and/or pile removal at the project site, if any, are
expected to be mild, short-term, and temporary. Marine mammals within
the Level B harassment zones may not show any visual cues if they are
disturbed by activities or they could become alert, avoid the area,
leave the area, or display other mild responses that are not
observable, such as changes in vocalization patterns. Additionally,
many of the species present in this region would only be present
temporarily based on seasonal patterns or during active transit between
other habitats. Most likely, during pile driving, individuals would be
expected to move away from the sound source and be temporarily
displaced from the areas of pile driving throughout the duration of
pile driving activities. However, this reaction has been observed
primarily associated with impact pile driving. While vibratory driving
associated with the proposed project may produce sound at distances of
many kilometers across the Chesapeake Bay from the site, the majority
of sound fields produced by the specified activities are constrained by
land masses to the north, south, and east of the site.
The potential for harassment is minimized by implementing the
proposed mitigation measures. During all impact driving, implementation
of soft-start procedures, use of bubble curtains, and monitoring of
established shutdown zones by trained and qualified PSOs shall be
required, significantly reducing any possibility of injury. Given
sufficient notice through soft-start (for impact driving), marine
mammals are expected to move away from an irritating sound source
before it becomes potentially injurious.
Any impacts on marine mammal prey that would occur during HRCP's
proposed activities would have, at most, short-term effects on foraging
of individual marine mammals, and likely no effect on the populations
of marine mammals as a whole. Indirect effects on marine mammal prey
during the construction are expected to be minor, and these effects are
unlikely to cause substantial effects on marine mammals at the
individual level, with no expected effect on annual rates of
recruitment or survival.
The project is also not expected to have significant adverse
effects on affected marine mammals' habitats. The project activities
will not modify existing marine mammal habitat. The activities may
cause some fish to leave the area of disturbance, thus temporarily
impacting marine mammals' foraging opportunities in a limited portion
of the foraging range; but, because of the relatively small area of the
habitat that may be affected (with no known particular importance to
marine mammals), the impacts to marine mammal habitat are not expected
to cause significant or long-term negative consequences. Furthermore,
there are no known biologically important areas (BIAs), or ESA-
designated critical habitat.
With regard to the humpback whale UME, there is currently no cause
for concern regarding population-level impacts. Despite the UME, the
relevant population of humpback whales (the West Indies breeding
population, or distinct population segment (DPS)) remains healthy.
Although NMFS is proposing to authorize limited take by Level B
harassment (37) since the whales have been observed in the Chesapeake
Bay, there have been no reported takes of humpback whales in the HRBT
monitoring reports from 2021 through 2024.
HRCP's proposed pile driving activities and associated impacts will
occur within a limited portion of the confluence of the Chesapeake Bay
area. It is unlikely that minor noise effects in a small, localized
area of habitat would have any effect on the reproduction or survival
of any individuals, much less the stocks' annual rates of recruitment
or survival.
In summary and as described above, the following factors primarily
support our preliminary determination that the impacts resulting from
this activity are not expected to adversely affect any of the species
or stocks through effects on annual rates of recruitment or survival:
<bullet> No serious injury or mortality is anticipated or proposed
for authorization;
<bullet> Any Level A harassment exposures are anticipated to result
in slight AUD INJ (i.e., of a few decibels) within the lower
frequencies associated with pile driving;
<bullet> The anticipated incidents of Level B harassment would
consist of, at worst,

[[Page 9842]]

temporary modifications in behavior that would not result in fitness
impacts to individuals;
<bullet> The area affected by the specified activity is very small
relative to the overall habitat ranges of all species and does not
include (BIAs) or ESA-designated critical habitat.
<bullet> Effects on species that serve as prey for marine mammals
are expected to be short-term and, therefore, any associated impacts on
marine mammal feeding are not expected to result in significant or
long-term consequences for individuals, or to accrue to adverse impacts
on their populations; and
<bullet> The proposed mitigation measures, such as employing
vibratory driving to the maximum extent practicable, soft-starts,
bubble curtains, and shutdowns, are expected to reduce the effects of
the specified activity to the least practicable adverse impact level.
Based on the analysis contained herein of the likely effects of the
specified activity on marine mammals and their habitat, and taking into
consideration the implementation of the proposed monitoring and
mitigation measures, NMFS preliminarily finds that the total marine
mammal take from the proposed activity will have a negligible impact on
all affected marine mammal species or stocks.

Small Numbers

As noted previously, only take of small numbers of marine mammals
may be authorized under section 101(a)(5)(A) and (D) of the MMPA for
specified activities other than military readiness activities. The MMPA
does not define small numbers and so, in practice, where estimated
numbers are available, NMFS compares the number of individuals taken to
the most appropriate estimation of abundance of the relevant species or
stock in our determination of whether an authorization is limited to
small numbers of marine mammals. When the predicted number of
individuals to be taken is fewer than one-third of the species or stock
abundance, the take

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