[Federal Register Volume 91, Number 22 (Tuesday, February 3, 2026)]
[Notices]
[Pages 4875-4904]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-02173]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XF037]
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to the Naval Base Point Loma Deperming
Pier Replacement Project and the Naval Base San Diego Chollas Creek
Quay Wall Repair Project in San Diego Bay, California
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; two proposed incidental harassment authorizations;
request for comments on two proposed authorizations and possible
renewals.
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SUMMARY: NMFS has received separate requests from the U.S. Navy (Navy)
for authorization to take marine mammals incidental to the Naval Base
Point Loma (NBPL) Deperming Pier Replacement Project and the Naval Base
San Diego (NBSD) Chollas Creek Quay Wall Repair Project, respectively,
both in San Diego Bay, California (CA). Pursuant to the Marine Mammal
Protection Act (MMPA), NMFS is requesting comments on its proposals to
issue separate incidental harassment authorizations (IHAs) to
incidentally take marine mammals during the specified activities. NMFS
is also requesting comments on a possible one-time, 1-year renewal for
each IHA that could be issued under certain circumstances, provided all
requirements are met, as described in Request for Public Comments at
the end of this notice. NMFS will consider public comments prior to
making any final decision on the issuance of the requested MMPA
authorizations. Agency responses will be summarized in the final notice
of our decision.
DATES: Comments and information must be received no later than March 5,
2026.
ADDRESSES: Comments should be addressed to the Permits and Conservation
Division, Office of Protected Resources, National Marine Fisheries
Service, and should be submitted via email to [email protected].
Electronic copies of the application and supporting documents, as well
as a list of the references cited in this document, may be obtained
online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities. In
case of problems accessing these documents, please call the contact
listed below.
Instructions: NMFS is not responsible for comments sent by any
other method, to any other address or individual, or received after the
end of the comment period. Comments, including all attachments, must
not exceed a 25-megabyte file size. All comments received are a part of
the public record and will generally be posted online at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act without change. All personal identifying
information (e.g., name, address) voluntarily submitted by the
commenter may be publicly accessible. Do not submit confidential
business information or otherwise sensitive or protected information.
FOR FURTHER INFORMATION CONTACT: Krista Graham, 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 (collectively 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 216.103).
[[Page 4876]]
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.
These actions are 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, for both proposed
IHAs, NMFS has preliminarily determined that the issuance of the
proposed IHA qualifies for categorical exclusion from further NEPA
review.
Summary of Request
On April 23, 2025, NMFS received a request from the Navy for an IHA
to authorize incidental take of marine mammals during the NBPL
Deperming Pier Replacement Project, which involves removing and
replacing damaged fender piles at three large piers at NBPL in San
Diego Bay, CA. Then, on April 30, 2025, NMFS received another request
from the Navy for an IHA to authorize incidental take during the NBSD
Chollas Creek Quay Wall Repair Project, which includes removing and
replacing the existing quay wall and dock pilings in Chollas Creek, San
Diego Bay, CA. Since both projects are proposed by the Navy and are
located in San Diego Bay, CA, and the Navy has requested the
authorizations be issued near concurrently, NMFS is announcing its
proposals of the two IHAs and soliciting public comment within this
single Federal Register notice.
Following NMFS' review of the applications, the Navy submitted a
revised version of both applications on November 13, 2025. Both
applications were deemed adequate and complete on November 19, 2025.
For the NBPL Deperming Pier Replacement Project, the Navy's request is
for the take of six species of marine mammals, by Level A harassment
and/or Level B harassment only; for the NBSD Chollas Creek Quay Wall
Repair Project, the Navy's request is for the take of three species of
marine mammals, by Level B harassment only. Neither the Navy nor NMFS
expects serious injury or mortality to result from either activity;
therefore, an IHA for each project is appropriate. Both IHAs would be
valid for the statutory maximum of 1 year from the date of
effectiveness, and would become effective upon written notification
from the Navy to NMFS, but not beginning later than 1 year from the
date of issuance or extending beyond 2 years from the date of issuance.
Description of Proposed Activity
Overview
The purpose of both Navy projects is to maintain structurally sound
and operational areas at both naval bases, to continue safely
supporting Pacific Fleet surface ships, and to allow berth-side repair,
maintenance, and storage of vessels. Both proposed projects are located
at naval bases within San Diego Bay, CA, either near the mouth of the
Bay at Point Loma (NBPL), or in the south-central part of the Bay, at
Chollas Creek (NBSD). The Navy would remove existing piles using a dead
pull, high-pressure water jetting, or a vibratory extractor, and
install permanent piles using high-pressure water jetting, vibratory
hammer, or an impact hammer to replace the existing piers. For the NBPL
Project, the proposed activities would result in removing 192 piles and
installing 192 piles over approximately 171 in-water work days. For the
NBSD Project, 190 in-water work days are estimated to remove 544 piles,
and 121 days to install 936 piles. Pile removal via vibratory extractor
and pile installation via vibratory hammer or impact hammer have the
potential to result in marine mammal harassment, and, therefore, IHAs
are warranted.
Dates and Duration
Each proposed IHA would be valid for the statutory maximum of 1
year from the date of effectiveness. They would become effective upon
written notification from the applicant to NMFS, but not beginning
later than 1 year from the date of issuance or extending beyond 2 years
from the date of issuance. Pile driving is expected to occur at NBPL
between June 1, 2026, and May 31, 2027, for 171 days. Pile driving is
expected to occur at NBSD between January 1, 2027, and December 31,
2027, for 190 days. However, project delays may occur due to several
factors, including project funding, permitting requirements, equipment
and/or material availability, weather-related delays, equipment
maintenance and/or repair, and other contingencies. For both projects,
pile removal and driving would occur only during daylight hours.
Specific Geographic Region
The NBPL Deperming Pier Replacement Project is located on the
peninsula of Point Loma near the mouth and along the northern edge of
San Diego Bay, CA. This area, known as North Bay, extends from the Bay
mouth to the area offshore Downtown San Diego.
The NBSD Chollas Creek Quay Wall Repair Project is located in the
San Diego Bay in an area known as South-Central Bay. Specifically, the
project is located at the mouth of Chollas Creek, a highly militarized
area on both sides of the Creek.
The U.S. Army Corps of Engineers dredges the main navigation
channel into and through San Diego Bay to maintain a depth of 47 feet
(ft) (14.3 meters (m)) below mean lower low water (MLLW), ensuring safe
passage for private, commercial, and military vessels within the Bay
(NOAA 2010). In North Bay, typical depths range from 36 to 38 ft (11.0
to 11.6 m) below MLLW to support large ship turning and anchorage
(Merkel & Associates, Inc., 2008, 2009). In Central Bay, typical depths
range from 11 to 12 m (35 to 38 ft) below MLLW (Merkel & Associates,
2009).
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Detailed Description of the Specified Activity
NBPL Deperming Pier Replacement Project
For the NBPL Project, the Navy proposes in-water construction work
at three piers: the two Magnetic Silencing Facility (MSF) piers (i.e.,
the Deperming Pier and the Electromagnetic Roll Garden (ERG) Pier), and
Pier 5002 North Inner Berth. Specifically, the Navy proposes to remove
and replace damaged piles at the Deperming Pier and the ERG Pier, and
replace plastic fender piles at Pier 5002. The MSF provides mission-
critical magnetic treatment (deperming) of Navy surface vessels, and
calibration and testing of magnetic signature reduction systems
(degaussing), thereby significantly reducing the risk to Navy ships
from magnetic mines. The project would maintain the Deperming Pier, ERG
Pier, and Pier 5002 in a structurally sound, operational condition so
that the Navy
[[Page 4880]]
may safely continue to support Pacific Fleet surface ships.
During construction activities at NBPL, 192 16-inch timber piles
would be removed via vibratory extraction over an estimated 86 days.
High-pressure water jetting or dead pull may also be used to remove
piles. The installation of the 192 16-inch round fiberglass-reinforced
plastic piles would be carried out using vibratory or impact hammers
over 85 days. High-pressure external water jetting may be used to
loosen the soil before vibratory or impact hammering. Two-inch pile
sleeves made of high-density polyethylene would be slipped onto the
outside of each 16-inch pile to minimize long-term pile degradation
(i.e., no pile driving is needed). Each sleeve would be bolted in place
to the steel pile above the waterline. Additionally, 8-ft (2.4 m) link
chains (one for each replaced piling) would be replaced to connect the
pier to the piling for extra support. High-pressure water jetting or
dead-pull removal methods are not likely to result in harassment and,
therefore, we do not discuss these action components further.
The Navy estimates that 171 days are needed to remove and install a
total of 384 piles. A floating barge secured directly to the pier would
remove and install between two and four piles per day. The sequence of
pile removal and installation involves removing three to four piles,
then installing three to four new piles. The barge would then move to
the next section and repeat the process.
The estimated time to remove each timber pile with a vibratory
hammer is up to 5 minutes. Installation is expected to take up to 5
minutes per plastic pile using vibratory pile driving, while impact
installation may require up to 600 strikes per plastic pile (see table
1). A bubble curtain or similar attenuation method is not proposed (see
Proposed Mitigation section below for rationale).
NBSD Chollas Creek Quay Wall Repair Project
For this project, the Navy plans to repair Quay Wall Segment B at
NBSD along Chollas Creek. This area experienced a catastrophic failure
in 2019 due to its age (82 years), which led to undermined sheet piles
and the deterioration of utility lines. The project includes
demolishing the existing quay wall and associated piles, then building
a new quay wall. Additionally, piles would be installed to support a
small craft floating dock in the same area as the old location (within
Chollas Creek) for berth-side repairs, maintenance, and vessel storage.
Repairs would span approximately 1,410 ft (430 m) along the quay wall
in about 30 ft (10 m) of water depth. Vibratory extraction would be
used to remove the 14-inch steel H piles, 18-inch square concrete
fender piles, 18-inch octagonal concrete fender piles, and 24-inch
steel sheet piles. Dead pulling would be used to remove the 13-inch
round plastic fender piles. Piles would only be removed if they
interfere with the installation of new piles. Vibratory pile driving,
impact pile driving, or high-pressure water jetting would be used to
install the 24-inch sheet piles, 18-inch square concrete fender piles,
18-inch octagonal concrete guide piles, and the 13-inch round plastic
fender piles. For reasons described for the NBPL project above, dead
pull and high-pressure water jetting are not expected to have the
potential to result in harassment and are not discussed further.
The Navy estimates 190 days of in-water work, conducted only during
daylight hours, are necessary for this project. Specifically, the Navy
estimates 69 days to remove 544 piles and 121 days to install 936
piles. The sequence of pile removal/installation for this project is
less certain but likely involves removing all piles, then installing
all new piles. However, the contractor may opt to remove and install
all piles of a similar nature (e.g., square and octagonal piles) before
moving on to another pile type (e.g., wall sheet piles).
Anywhere from 2 to 12 piles may be removed per day, during daylight
hours only, with 4 to 10 piles installed per day. Vibratory pile
removal is estimated to take approximately 20 minutes per pile for all
pile types; vibratory pile installation is estimated to take anywhere
from 1 to 20 minutes per pile, depending on the pile type, whereas
impact pile installation is estimated to take 600 strikes per pile (see
table 1).
Table 1--NBPL and NBSD Pile Removal and Installation Method, Pile Size/Type, Location, Number, and Duration
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Number of Number of
Method Pile size/type Pile location Piles/day piles days
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NBPL DEPERMING PIER
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Pile Removal \1\
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Vibratory Extraction............ 16-inch (41 cm) Deperming Pier 4 72 21
round timber. Edge.
Deperming Pier 2 51 26
Corners.
ERG Pier Dolphin 2 38 20
Clusters.
ERG Pier.......... 2 28 17
Pier 5002......... 2 3 2
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Total................................................................ 2-4 192 \2\ 86
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Pile Installation \1\
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Vibratory Hammer/Impact Hammer.. 16-inch (41 cm) Deperming Pier 3 72 24
round fiberglass- Edge. 2 51 26
reinforced plastic. Deperming Pier
Corners.
ERG Pier Dolphin 2 38 19
Clusters.
ERG Pier.......... 2 28 14
Pier 5002......... 2 3 2
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Totals............................................................... 2-3 192 85
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Total in-water pile extraction/installation days............................................... 171
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NBSD CHOLLAS CREEK
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Pile Removal \3\
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Vibratory Extraction............ 13-inch round Quay wall corner 7 14 2
plastic \4\. to channel.
18-inch square Quay wall......... 5 140 28
concrete.
[[Page 4881]]
14-inch steel H.... Quay wall......... 12 100 9
18-inch octagonal Small craft dock.. 2 2 1
concrete.
24-inch steel sheet Quay wall......... 10 288 29
\5\.
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Totals............................................................... 2-12 544 69
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Pile Installation \1\
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Vibratory/Impact Hammer......... 13-round plastic... Quay wall corner 5 14 3
to channel.
18-inch square Quay wall......... 6 155 26
concrete.
18-inch octagonal Small craft dock.. 4 23 6
concrete.
27.5-inch steel Quay wall......... 10 744 86
sheet \6\.
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Total................................................................ 4-10 936 121
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Total in-water pile extraction/installation days............................................... 190
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\1\ Vibratory pile removal/installation and impact pile installation may occur with or without high-pressure
water jetting occurring either simultaneously or separately.
\2\ Contractor added buffer days for some locations.
\3\ While other methods of pile extraction are possible, vibratory extraction is the most likely method that
would be used to extract piles. No Level A harassment or Level B harassment (take analysis) is conducted on
the other pile extraction methods (i.e., dead pull, water jetting).
\4\ These piles are anticipated to be dead pulled.
\5\ These piles are anticipated to be either vibratory extracted, dead pulled, or clipped at the mud-line and
removed. For this IHA, we are assuming vibratory extraction for the demolition of all existing sheet piles.
\6\ Includes extra days as a buffer.
For both projects, only in-water vibratory pile removal and
vibratory and impact pile installation are anticipated to result in
marine mammal harassment due to elevated underwater noise. Any above-
ground activities (e.g., repositioning equipment) are expected to
result in only in-air/in-ground construction noise below levels known
to affect marine mammals, and thus won't be discussed further. The
underwater sound generated by these in-water activities associated with
the NBPL Deperming Pier Replacement Project may result in Level A
harassment and/or Level B harassment of six marine mammal species,
comprising six stocks. For the NBSD Chollas Creek Quay Wall Repair
Project, underwater sound may result in Level B harassment of three
marine mammal species.
With respect to the ambient or background underwater sound levels
(SPL) for San Diego Bay, these levels are reported in the ``Compendium
of Underwater and Airborne Sound Data during Pile Installation and In-
Water Demolition Activities in San Diego Bay, California'' (NAVFAC SW,
2020). These sound levels were measured for the NBPL Fuel Pier
Replacement Project at two locations. The median background underwater
SPL in areas of the Bay subject to project construction noise at NBPL
averaged approximately 129.6 dB (referenced to 1 micropascal (re 1
[micro]Pa)). As described in the Estimated Take section, pile removal
and installation noise for the NBSD Project is likely to become
indistinguishable from background noise as it diminishes to 126 dB re 1
[mu]Pa with distance from the source (NBSD IHA application, citing Dahl
and Dall'Osto, 2019).
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 the 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 in the application instead of reprinting the
information. Additional information on population trends and threats
may be found in NMFS' Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments), and more general information about these species
(e.g., physical and behavioral descriptions) may be found on NMFS'
website (https://www.fisheries.noaa.gov/find-species). Furthermore,
information may be found in the ``U.S. Navy's Dive Distribution and
Group Size Parameters for Marine Species Occurring in the U.S. Navy's
Atlantic and Hawaii-California Training and Testing Study Areas''
(Navy, 2024), available online at https://www.nepa.navy.mil/Portals/20/Documents/Pacific%20Fleet/HSTTEIS/HCTT/DraftEIS/TechnicalReports/AFTTHCTTDiveProfile_TR12243A.pdf.
Table 2 lists all the species or stocks for which take is expected
and proposed to be authorized for these activities and summarizes
information related to the population or stock, including regulatory
status under the MMPA and Endangered Species Act (ESA), as well as the
potential biological removal (PBR), where known. The MMPA defines PBR
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 for either project, the 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 geographical area, if known, that
comprises that stock. For some species, this area may extend beyond
U.S. waters. All managed stocks in this region are assessed in NMFS'
U.S. Pacific SARs (Carretta et al., 2025). All values presented in
table 2 are the most recent available at the time of publication
(including from the draft 2024 SARs) and are available online at:
https://www.fisheries.noaa.gov/
[[Page 4882]]
national/marine-mammal-protection/marine-mammal-stock-assessments.
Table 2--Species, Stocks, and the Status of Marine Mammals With Estimated Take From the Specified NBPL and NBSD Activities
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ESA/ MMPA status; Stock abundance (CV,
Common name \1\ Scientific name Stock strategic (Y/N) Nmin, most recent PBR Annual M/
\2\ abundance survey) \3\ S \4\
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Order Artiodactyla--Infraorder Cetacea--Mysticeti (baleen whales)
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Family Eschrichtiidae:
Gray whale \5\.................. Eschrichtius robustus.. Eastern North Pacific.. -,-,N 25,960 (0.05, 25,849, 801 131
2016).
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Odontoceti (toothed whales, dolphins, and porpoises)
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Family Delphinidae:
Common dolphin (short-beaked) Delphinus delphis...... CA/OR/WA............... -,-,N 1,056,308 (0.21, 8,889 >=30.5
\5\. 888,971, 2018).
Common dolphin (long-beaked) \5\ Delphinus delphis CA..................... -,-,N 83,379 (0.216, 69,636, 668 >=29.7
bairdii. 2018).
Common bottlenose dolphin \5\ Tursiops truncatus CA coastal............. -,-,N 453 (0.6, 346, 2011).. 2.7 >=2.0
\6\. truncatus.
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Order Carnivora--Pinnipedia
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Family Otariidae (eared seals and
sea lions):
California sea lion \5\ \6\..... Zalophus californianus. U.S.................... -,-,N 257,606 (N/A, 233,515, 14,011 >321
2014).
Family Phocidae (earless seals):
Harbor seal \5\ \6\............. Phoca vitulina......... California............. -,-,N 30,968 (N/A, 27,348, 1,641 43
2012).
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\1\ Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy
(https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/).
\2\ 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 as depleted and as a strategic stock under the MMPA.
\3\ NMFS marine mammal stock assessment reports online at https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports. CV is the coefficient of variation; Nmin 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).
\4\ These values, found in NMFS' SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial
fisheries, ship strikes). Annual M/SI is often not precisely determined and is sometimes reported as a minimum value or a range.
\5\ Species occurs in the NBPL Project area; see the Marine Mammal Species at NBPL section and table 8 for further information.
\6\ Species occurs in the NBSD Project area; see the Marine Mammal Species at NBSD section and table 8 for further information.
As indicated above, table 2 lists all six species that temporally
and spatially co-occur during all or a portion of the in-water work
associated with the proposed activities at NBPL to the degree that
incidental take could potentially occur. Thus, the Navy has requested,
and NMFS proposes to authorize, the incidental take of these six
species. Table 2 also lists the three species that temporally and
spatially co-occur during all or a portion of the in-water work
associated with the proposed activities at NBSD to the degree that
incidental take could potentially occur. Thus, for the NBSD Project,
the Navy has requested, and NMFS proposes to authorize, the incidental
take of California sea lions, the California coastal stock of the
bottlenose dolphins, and harbor seals.
NMFS has previously authorized the incidental take of Risso's
dolphins (Grampus griseus), northern elephant seals (Mirounga
angustirostris), and Pacific white-sided dolphins (Lagenorhynchus
obliquidens) in past IHAs spanning over a decade for Navy projects in
San Diego Bay (see the NBPL Fuel Pier Replacement projects: 78 FR
44539, July 24, 2013 (Year 1 Project); 79 FR 65378, November 4, 2014;
(Year 2 Project); 80 FR 62032, October 15, 2015 (Year 3 Project); 81 FR
66628, September 28, 2016 (Year 4 Project); 82 FR 45811, and October 2,
2017 (Year 5 Project); 85 FR 33129, June 1, 2020 (NBPL Floating Dry
Dock Project); 86 FR 7993, February 3, 2021 (NBPL Pier 6 Replacement
Project), and 86 FR 48986, September 1, 2021 (NBPL Fuel Pier Inboard
Pile Removal Project) for examples). However, based on monitoring
reports for these projects, sightings of these species were rare or
occurred only during an El Ni[ntilde]o monitoring year and are not
considered representative of typical species occurrences (see 88 FR
6703, February 1, 2024). Therefore, because the temporal and/or spatial
occurrence of Risso's dolphins, northern elephant seals, and Pacific
white-sided dolphins during in-water activities for both projects is
such that incidental take is not expected to occur, the Navy did not
request, and NMFS is not proposing to authorize, the incidental take of
these three species, and these species are not discussed further (for
either the NBPL or NBSD projects).
The most frequently observed marine mammal in San Diego Bay is the
California sea lion, which is considered abundant and often rests on
buoys and other man-made structures found throughout the North to North
Central Bay. Other species known to occur in San Diego Bay include the
California coastal stock of the common bottlenose dolphin, which is
seen year-round in the North Bay but sightings are sporadic and highly
variable, and the harbor seal, which is relatively uncommon in the
North Bay. Gray whales, which are occasionally sighted near the mouth
of San Diego Bay during their winter migration, are considered rare/
seasonal. Lastly, common dolphins (both short-beaked and long-beaked
are occasional visitors to San Diego Bay. Recently, the Committee on
Taxonomy (https://marinemammalscience.org/science-and-publications/
list-marine-mammal-
[[Page 4883]]
species-subspecies/) determined that both the short-beaked and long-
beaked common dolphin belong to the same species, and we adopt this
taxonomy. However, the SARs still describe the two as separate stocks,
and that stock information is presented in table 2.
Sightings of common dolphins (both short-beaked and long-beaked)
and gray whales are rare occurrences in San Diego Bay, especially in
South-Central San Diego Bay, where Chollas Creek is located. Based on
the lack of sightings as documented in the NBSD Pier 6 Replacement
Project's final report (NAVFAC SW, 2024) during 172 monitoring days,
the Navy is not requesting, and NMFS is not proposing to authorize, the
incidental take for these three species, and they are not discussed
further beyond the explanation provided here.
Finally, there are no known biologically important areas (BIAs) for
marine mammals near the project sites that would be relevant to the
Navy's proposed activities.
Marine Mammal Hearing
Hearing is the most vital sensory modality for marine mammals
underwater, and exposure to anthropogenic sound can have deleterious
effects. To appropriately assess the potential effects of sound
exposure, it is necessary to understand the frequency ranges that
marine mammals can hear. Not all marine mammal species have equal
hearing capabilities or hear over the same frequency range (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.). Subsequently, NMFS (2018, 2024) described generalized
hearing ranges for these marine mammal hearing groups. Generalized
hearing ranges were chosen based on the approximately 65-decibel (dB)
threshold from the normalized composite audiograms, with the exception
of lower limits for low-frequency cetaceans, where the lower bound was
deemed to be biologically implausible, and the lower bound from
Southall et al. (2007) was retained. In October 2024, NMFS published
its 2024 Updated Technical Guidance, which includes updated thresholds
and weighting functions to inform auditory injury estimates and
replaces the 2018 Technical Guidance referenced above. This 2024
Updated Technical Guidance represents the best available science.
Marine mammal hearing groups and their associated hearing ranges are
provided in table 3. Of the species potentially present in both
proposed action areas, gray whales are considered low-frequency (LF)
cetaceans; bottlenose dolphins and short- and long-beaked common
dolphins are considered high-frequency (HF) cetaceans; California sea
lions are otariid pinnipeds; and harbor seals are phocid pinnipeds.
Table 3--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 150 Hz to 160 kHz.
(dolphins, 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) 40 Hz to 90 kHz.
(true seals).
Otariid pinnipeds (OW) (underwater) 60 Hz to 68 kHz.
(sea lions and fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
composite (i.e., all species within the group), where individual
species' hearing ranges 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 can
detect very loud sounds above and below the ``generalized'' hearing
range.
Potential Effects of Specified Activities on Marine Mammals and Their
Habitat
This section includes a discussion of how components of the
specified activities for both the NBPL and NBSD projects may affect
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 both the NBPL
and NBSD activities. The Negligible Impact Analysis and Determination
section considers the content of this section, as well as the Estimated
Take of Marine Mammals section and the Proposed Mitigation section, to
draw conclusions regarding the likely impacts of both of the proposed
project 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 activities
for both projects are expected to result from vibratory removal/driving
and impact pile driving. While marine mammals in some cases have
exhibited little to no obviously detectable response to certain common
or routine industrialized activities (Cornick et al., 2011; Horley and
Larson, 2023) such as those that occur in San Diego Bay, it is possible
that some animals may, at times, be exposed to received levels of sound
above the auditory injury (AUD INJ; discussed later) and/or Level B
harassment thresholds during the proposed projects. This potential
exposure, in combination with the nature of planned activities (e.g.,
vibratory pile removal/driving and impact pile driving), means that
take by Level A harassment and/or Level B harassment could occur over
the total estimated period of activities. Therefore, NMFS, in response
to the Navy's NBPL Deperming Pier Replacement Project IHA application,
proposes to authorize take by Level A harassment and/or Level B
harassment from the proposed construction activities. Moreover, in
response to the Navy's NBSD Chollas Creek Quay Wall Repair Project IHA
application, NMFS proposes to authorize take by Level B harassment only
from the proposed construction activities.
NMFS has summarized a brief technical description of the physics of
sound and relevant measurement metrics (i.e., RMS, Peak, and SEL)
(NMFS, 2024), available online at https://www.fisheries.noaa.gov/
national/marine-mammal-protection/
[[Page 4884]]
marine-mammal-acoustic-technical-guidance. We refer readers to this
document for definitions of the measurement terms and metrics used
herein.
There are a variety of types and degrees of effects on marine
mammals, prey species, and habitats that could result from the
projects. Since both projects would use the same pile-driving and
removal methods, below is a brief description of the sound sources the
projects would generate, the general impacts of these activities, and
an analysis of the anticipated impacts on marine mammals from the
projects, with consideration of the proposed mitigation measures.
Description of Sound Sources for the Specified NBPL and NBSD Activities
Construction Activities
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 hammer's weight to
drive them into the substrate. Vibratory hammers typically produce less
sound (i.e., lower levels) than impact hammers. Peak 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 a greater amount of time (Nedwell and Edwards, 2002;
Carlson et al., 2005).
Potential Effects of Underwater Sound on Marine Mammals
The introduction of anthropogenic noise into the aquatic
environment from vibratory pile removal and vibratory and impact pile
installation is the primary means by which marine mammals may be
harassed from the Navy's specified activities at both NBPL and NBSD.
Anthropogenic sounds span a broad range of frequencies and sound levels
and can have highly variable impacts on marine life, from none or minor
to potentially severe responses, depending on received levels, duration
of exposure, behavioral context, and other factors. Broadly, underwater
sound from active acoustic sources, such as those in these projects,
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; G[ouml]tz et al., 2009).
We describe the more severe effects of certain non-auditory
physical or physiological effects only briefly, as we do not expect
that the use of impact/vibratory hammers is reasonably likely to result
in such effects (see below for further discussion). For non-auditory
physical effects, for the NBPL Project, abundant California sea lions
are known to haul out at docks associated with Pier 122 (~363 ft (110
m) to the north) and Pier 40 (~192 ft (58 m) to the south). They are
also known to haul out at barges associated with the Everingham
Brothers' Bait Barge Company that are from 541 ft to 1,003 ft (164 m to
304 m) east of the NBPL Project area. For the NBSD Project, the species
is known to haul out near the NBSD security fence and navigation
channel marker buoys. However, California sea lions exhibit a high
tolerance to human activity (Holcomb et al., 2009) and
opportunistically use almost any available structure as a haul out
(NAVFAC SW and POSD, 2013). As for the NBSD Project, the relatively
uncommon harbor seals also haul out on rocks, buoys, and other
structures. As stated above, the nearest pinniped haul outs are a pair
of active Navy docks to the north and the south of the Deperming Pier,
with a pair of bait barges to the east. Harbor seals are even more
uncommon with respect to the NBSD Project. Ultimately, we expect that
any visual and/or other non-acoustic stressors would be limited and
that any impacts on marine mammals would be acoustic in nature for both
projects.
Potential physiological effects from sound sources, particularly
impulsive sound, can range from behavioral disturbance or tactile
perception to physical discomfort, slight injury to 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; Tal et al., 2015).
However, the 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 can result in auditory threshold shifts and
behavioral responses (e.g., avoidance, temporary cessation of foraging
and vocalizing, changes in dive behavior). It can also lead to non-
observable physiological responses, such as increased stress hormone
levels. Additional noise in a marine mammal's habitat can mask acoustic
cues used in 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 from the specified activities.
Richardson et al. (1995) described zones of increasing effect
intensity that might be expected to occur with distance from a source,
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 to the area
where the signal is audible to the animal and sufficiently intense to
elicit behavioral or physiological responsiveness. The third is a zone
within which, for high-intensity signals, the received level is
sufficient to cause discomfort or tissue damage to auditory or other
systems. Overlaying these zones to some extent is the area within which
masking (i.e.,
[[Page 4885]]
when a sound interferes with or masks an animal's ability to detect a
signal of interest above the absolute hearing threshold) may occur; the
masking zone may vary widely in size.
Below, we provide additional detail regarding the potential impacts
on marine mammals and their habitat from noise in general, starting
with hearing impairment, as well as from the specific activities the
Navy plans to conduct at both project sites, to the extent available.
Hearing Threshold Shifts
NMFS defines a noise-induced threshold shift (TS) as a change,
usually an increase, in the audibility threshold 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. A 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), the likelihood an individual would be
exposed for a long enough duration or to a high enough level to induce
a TS, the magnitude of the TS, the 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 the 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).
Temporary Threshold Shift
A temporary threshold shift (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 that the amount of TTS increases with the 24-hour cumulative
sound exposure level (SEL24) in an accelerating fashion: at low
exposures with lower SEL24, the amount of TTS is typically small, and
the growth curves have shallow slopes. At higher SEL24
exposures, the growth curves become steeper and approach a linear
relationship 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 readily
compensate for a brief, relatively small amount of TTS in a non-
critical frequency range that occurs while the animal is traveling
through the open ocean, where ambient noise is lower and competing
sounds are fewer. Alternatively, a larger amount and longer duration of
TTS sustained during times 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 in humans and other
taxa (Southall et al., 2007), suggesting that strategies exist to cope
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, so a sound must be louder to be heard. In terrestrial
and marine mammals, TTS can last from minutes to hours (in cases of
strong TTS) (Finneran, 2015). 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 (Phocoena phocoena), and Yangtze finless porpoise
(Neophocoena asiaeorientalis) (Southall et al., 2019). For pinnipeds in
water, measurements of TTS are limited to harbor seals, northern
elephant seals, bearded seals (Erignathus barbatus), and California sea
lions (Kastak et al., 1999, 2007; Kastelein et al., 2019b, 2019c, 2021,
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 in marine mammals before and after exposure
to intense or long-duration sound. 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 depend 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 lower than that from a single, continuous exposure with the
same SEL (Mooney et al., 2009; Finneran et al., 2010; Kastelein et al.,
2014, 2015). This means that TTS predictions based on the total,
SEL24, will overestimate the amount of TTS from intermittent
exposures, such as sonars and impulsive sources. Nachtigall et al.
(2018) describe measurements of hearing sensitivity of multiple
odontocete species (bottlenose dolphin, harbor porpoise, beluga, and
false killer whale (Pseudorca crassidens)) when a warning sound
preceded a relatively loud 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 enable conditioned hearing
reduction and filtering of low-frequency ambient noise, including
increased stiffness and control of middle ear structures, as well as
placement of inner ear structures (Ketten et al., 2021). Data available
on 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
[[Page 4886]]
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.
Auditory Injury
NMFS (2024) defines AUD INJ as damage to the inner ear that can
result in tissue destruction, such as 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 generally affects only a limited frequency range, and
animals with PTS have 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 the onset of PTS (see Ward et al., 1958,
1959; Ward, 1960; Kryter et al., 1966; Miller, 1974; Ahroon et al.,
1996; Henderson et al., 2008). However, a variety of terrestrial and
marine mammal studies (see Ward et al., 1958; Ward et al., 1959; Ward,
1960; Miller et al., 1963; Kryter et al., 1966; Finneran et al., 2007;
Kastelein et al., 2013) indicate that threshold shifts of up to 40 to
50 dB (measured a few minutes after exposure) may be induced without
resulting in PTS. PTS levels for marine mammals are estimates; with the
exception of a single study unintentionally inducing PTS in a harbor
seal (Phoca vitulina) (Kastak et al., 2008), no empirical data measure
PTS 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).
NMFS has set the PTS onset as a threshold shift of 40 dB.
However, after sound exposure ceases or between successive sound
exposures, the potential for recovery from hearing loss exists. Thus,
because a threshold shift is measured a few minutes after noise
exposure does not mean that those initial shifts are persistent (i.e.,
no recovery). When initial threshold shifts fully recover back to
baseline hearing levels, these are considered TTS. PTS indicates there
is no full recovery back to baseline hearing levels; however, it does
not mean there is no recovery. Rather, PTS indicates incomplete
recovery of hearing. Recovery depends on the initial threshold shift
amount, the frequency at which the shift occurred, the temporal pattern
of exposure (e.g., exposure duration; continuous vs. intermittent
exposure), and the physiological mechanisms underlying the shift (e.g.,
mechanical vs. metabolic). Since recovery is complicated, our current
AUD INJ onset criteria do not account for the potential for recovery.
Behavioral Effects
Exposure to noise can also behaviorally disturb marine mammals to a
level that rises to the definition of harassment under the MMPA.
Generally speaking, NMFS considers a behavioral disturbance that rises
to the level of harassment under the MMPA a non-minor response. In
other words, not every response qualifies as a behavioral disturbance,
and for responses that do, those of higher level or longer duration
have the potential to affect foraging, reproduction, or survival.
Behavioral disturbance may include subtle changes (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
predictable, unvarying sounds. 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, in which
an unpleasant experience leads to subsequent responses, often in the
form of avoidance, at lower levels of exposure.
As noted above, behavioral state may affect the type of response.
For example, resting animals may show greater behavioral change in
response to disturbing sound levels than highly motivated 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
[[Page 4887]]
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 briefly reacts
to an underwater sound by changing its behavior or moving a small
distance, the resulting change is 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 on 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 in dive behavior
resulting from acoustic exposure depends on what the animal is doing at
the time of exposure and on the type and magnitude of the response.
Disruption of feeding behavior can be difficult to correlate with
anthropogenic sound exposure, so it is usually inferred by observed
displacement from known foraging areas, the appearance of secondary
indicators (e.g., bubble nets or sediment plumes), or changes in dive
behavior. As for other types of behavioral response, the frequency,
duration, and temporal pattern of signal presentation, as well as
differences in species sensitivity, are likely contributing factors to
differences in response in any given circumstance (e.g., Croll et al.,
2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko et al.,
2007). A determination of whether foraging disruptions incur fitness
consequences would require information on, or estimates of, the
energetic requirements of the affected individuals, the relationship
between prey availability, foraging effort, and success, and the
animal's life history stage.
Respiration rates vary naturally with different behaviors, and
alterations in 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 of
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
(SELss): 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 due to 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). 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 the abundance or distribution
patterns of the affected species in the affected region if habituation
to the sound does not occur (e.g., Blackwell et al., 2004; Bejder et
al., 2006; Teilmann et al., 2006).
A flight response is a dramatic change in normal movement, with
directed, rapid movement away from the perceived location of a sound
source. The flight response differs from other avoidance responses in
its intensity (e.g., directed movement and travel rate). Relatively
little information exists on the flight responses of marine mammals to
anthropogenic signals, although observations of flight responses to the
presence of predators have been made (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 affect marine mammals in more
subtle ways. Increased vigilance may incur costs from the diversion of
attention (i.e., when a response requires heightened vigilance, it may
come at the expense of reduced attention to other critical behaviors,
such as foraging or resting). These effects have generally not been
demonstrated in marine mammals, but studies of 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 reductions in fitness (e.g., declines in
body condition) and subsequent reductions 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 result in sleep deprivation or stress.
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, is more likely to be significant if it lasts more than one
diel cycle or recurs on subsequent days (Southall et al., 2007).
Consequently, a behavioral response lasting less than one day and not
recurring on subsequent days is not considered particularly severe
unless it could directly affect reproduction or 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
multiple days does not necessarily mean that individual animals are
exposed to activity-related stressors for multiple days, or, further,
exposed in a manner that results in sustained, multi-day, substantive
behavioral responses.
Physiological Stress Responses
An animal's perception of a threat may be sufficient to trigger
stress responses that include some
[[Page 4888]]
combination of behavioral, autonomic nervous system, neuroendocrine,
and immune responses (e.g., Selye, 1950; Moberg, 2000). In many cases,
an animal's first and sometimes most economical response (in terms of
energetic costs) 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 pituitary hormone secretion have been implicated in
reproductive failure, altered metabolism, reduced immune competence,
and behavioral disturbances (e.g., Moberg, 1987; Blecha, 2000).
Increases in glucocorticoid levels are also associated 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 its glycogen
stores, which can be quickly replenished once the stress is alleviated.
In such circumstances, the cost of the stress response would not pose
serious fitness consequences. However, when an animal does not have
sufficient energy reserves to satisfy the energetic costs of a stress
response, energy resources must be diverted from other functions. This
state of distress will last until the animal replenishes its energy
reserves to a sufficient level 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 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 will experience
physiological stress responses upon exposure to acoustic stressors, and
that some of these responses may be classified as ``distress.'' In
addition, any animal experiencing TTS would likely also experience
stress responses (NRC, 2005); however, distress is unlikely to result
from these projects based on observations of marine mammals during
previous, similar construction projects in San Diego Bay.
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 specific frequencies for marine
mammals that rely on 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).
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 the
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 wild populations it must be either modeled or inferred
from evidence of masking compensation. Few studies have addressed 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 use, and is
more likely to occur in the presence of broadband, relatively
continuous noise sources such as vibratory pile removal or
installation. The energy distribution of pile-driving sound spans a
broad frequency spectrum and is expected to fall within the audible
range of marine mammals present in the project areas. Since noises
generated from the proposed construction activities are mostly
concentrated at low frequencies (<2 kHz), 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 the 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 noise band, thereby reducing the communication space of
animals (e.g., Clark et al., 2009) and increasing 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
signals, and at higher levels and for longer durations could have long-
term chronic effects on marine mammal species and populations. However,
the noise generated by the Navy's proposed activities would occur only
intermittently, across an estimated 171 and 190 days, respectively, at
both proposed activity locations (NBPL and NBSD) during the
authorization periods,
[[Page 4889]]
in a relatively small area focused around the proposed construction
sites. Thus, while the Navy's proposed activities may mask some
acoustic signals 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 affected.
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 across any of these modes and may result from a need to
compete with increased background noise, or may reflect increased
vigilance or a startle response. For example, in the presence of
potentially masking signals, humpback whales (Megaptera novaeangliae)
and killer whales (Orcinus orca) 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 physalus) have also been documented
to lower the bandwidth, peak frequency, and center frequency of their
vocalizations in the presence of increased 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 that exposed them to vessel noise, have been
observed to increase their vocalization rate and produce louder signals
during periods of increased outboard engine noise (Dahlheim and
Castellote, 2016). Alternatively, in some cases, animals may cease
sound production during the production of aversive signals (Bowles et
al., 1994; Wisniewska et al., 2018).
Under certain circumstances, marine mammals that experience
significant masking could also be impaired in maximizing their
performance fitness for survival and reproduction. Therefore, when the
coincident (masking) sound is human-made, it may be considered
harassment if it disrupts or alters 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 associated with
harassment). Therefore, under certain circumstances, marine mammals
whose acoustic sensors or environment are severely masked could also be
impaired in maximizing their performance fitness for survival and
reproduction.
Airborne Acoustic Effects
Pinnipeds occurring near either project site could be exposed to
airborne sounds associated with construction activities, depending on
their distance from these activities, which could cause behavioral
harassment. Airborne noise would primarily be an issue for pinnipeds
that are swimming or hauled out near either project site, within the
range of noise levels elevated above the airborne acoustic harassment
criteria. 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 proximity between the proposed
project areas and the known haul out sites (e.g., on docks associated
with Pier 122 and Pier 40 for the NBPL project, and on the security
fencing and barges associated with the Everingham Brothers' Bait Barge
Company for the NBSD project) in San Diego Bay. 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 may be exposed to airborne
sound that could result in behavioral harassment when they lift their
heads above the water or when they haul out. 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 a reduction in vocalizations, or to flush from
haulouts, temporarily abandon the area, and/or move further from the
source. However, these animals previously would 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 additional incidental take
resulting from airborne sound for pinnipeds is warranted for either
project, and airborne sound is not discussed further here.
Potential Effects on Marine Mammal Habitat
The Navy's proposed activities for both projects could have
localized, temporary impacts on marine mammal habitat, including prey,
due to increased in-water noise levels. Increased noise levels may
affect the 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, any displacement due to noise is
expected to be temporary and not to result in long-term effects on
individuals or populations.
The total area likely impacted by the Navy's proposed activities at
NBPL and NBSD is relatively small compared to the available habitat
within and outside of San Diego Bay. Avoidance by potential prey (i.e.,
fish) of the immediate areas due to increased noise is possible. The
duration of fish and marine mammal avoidance of this area after
construction stops is unknown, but a rapid return to normal
recruitment, distribution, and behavior is anticipated. Any behavioral
avoidance by fish or marine mammals of either disturbed area would
still leave significantly large areas of fish and marine mammal
foraging habitat in the nearby vicinity.
The proposed projects would occur within the same footprint as
existing marine infrastructure. The nearshore and intertidal habitats
where the proposed projects would occur are in industrialized areas
with relatively high marine vessel traffic. Temporary, intermittent,
and short-term habitat alteration may result from increased noise
levels during the proposed construction activities. Effects on marine
mammal habitat would be limited to temporary displacement from pile
removal and installation noise, and effects on prey species would be
similarly limited in time and space.
[[Page 4890]]
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 removal and installation of piles, when bottom
sediments are disturbed, and may temporarily increase suspended
sediment in the project area. During pile extraction, sediment attached
to the pile moves vertically through the water column causing a
sediment plume. However, since currents are so strong in the area,
following the completion of sediment-disturbing activities, suspended
sediment in the water column should dissipate and quickly return to
background levels across all construction scenarios.
Turbidity in the water column can reduce dissolved oxygen levels
and irritate the gills of prey fish in the proposed project areas.
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). However, turbidity plumes associated with the projects
would be temporary and localized, and fish in the proposed project
areas would be able to move away from and avoid the areas where plumes
may occur.
Overall, the water quality in the immediate area that is likely
impacted by the proposed construction activities for both projects is
relatively small compared to the available marine mammal habitat within
and surrounding San Diego Bay. Therefore, it is expected that water
quality impacts on prey fish species due to turbidity, and therefore on
marine mammals, would be minimal and temporary.
Potential Effects on Prey
Sound may affect marine mammals by altering 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, it is not well documented.
Studies regarding the effects of noise on known marine mammal prey are
described here.
Fishes use 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 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 on fishes may include behavioral responses,
hearing damage, barotrauma (pressure-related injuries), and mortality.
Fish react to 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 their physiological state, 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.
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
4-6 dB was recoverable within 24 hours in one species. Impacts would be
most severe when the individual fish is near the source, and the
exposure duration 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 prey
for marine mammals could be temporarily affected by noise from pile
removal and installation. 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 in response to strong and/or intermittent sounds
that could harm fish. 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 indirectly affect
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 sound levels from pile driving, seismic activity,
or other human-made sources would have physiological effects on
invertebrates. Any such effects would be limited to the area very near
(1 to 5 m) 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 from the specified activities, due
in part to their large reproductive capacity and naturally high levels
of predation and mortality. Any mortalities or impacts that might occur
would be negligible.
The greatest potential impact on marine mammal prey during
construction would occur during impact pile driving. Vibratory pile
removal/installation may elicit behavioral responses in fishes, such as
temporary avoidance of the area, but is unlikely to cause injuries to
fishes or have persistent effects on local fish populations. In-water
construction activities would only occur during daylight hours,
allowing fish to forage and transit the project area in the evening.
Construction would also have minimal permanent and temporary impacts on
benthic invertebrate species, a marine mammal prey source.
Additionally, the proposed project areas are low-quality habitats, as
both areas are already highly developed and experience high levels of
anthropogenic
[[Page 4891]]
noise from regular naval operations and other vessel traffic.
Potential Effects on Foraging Habitat
The proposed projects are 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
removal and installation of in-water piles would be temporary and
intermittent. The areas affected by these projects are relatively small
compared to the available habitat just outside the project areas, and
neither project would affect any areas of particular importance. Any
behavioral avoidance by fish of the disturbed areas would still leave
significantly large areas of fish and marine mammal foraging habitat in
the nearby vicinity. As described in the preceding, the potential for
the Navy's construction at NBPL or NBSD to affect the availability of
prey to marine mammals or to meaningfully impact the quality of
physical or acoustic habitat is considered to be insignificant.
Therefore, the impacts of the projects are not likely to adversely
affect marine mammal foraging habitat in the proposed project areas.
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 the Navy's NBPL or
NBSD activities on prey habitat or prey populations are expected to be
minor and temporary. The most likely impact on fishes at the project
sites would be temporary avoidance of the area. Any behavioral
avoidance by fish of the disturbed areas would still leave
significantly large areas of fish and marine mammal foraging habitat in
the nearby vicinity. Thus, we preliminarily conclude that the impacts
of the specified activities at both the NBPL and NBSD are not likely to
have more than short-term adverse effects on any prey habitat or
populations of prey species. Further, any impacts on 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 under both IHAs, 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 for 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 disrupting behavioral patterns, including, but not limited
to, migration, breathing, nursing, breeding, feeding, or sheltering
(Level B harassment).
Authorized takes would predominantly be by Level B harassment for
both the NBPL and NBSD Projects, as using acoustic sources (i.e.,
vibratory and impact pile driving) can potentially disrupt behavioral
patterns for individual marine mammals. There is also some potential
for AUD INJ (Level A harassment) to result for six species of marine
mammals incidental to the NBPL Project. As for the NBSD Project, due to
the location within South-Central San Diego Bay in Chollas Creek, AUD
INJ is not anticipated to occur for any of the three species for which
harassment is proposed for authorization due to the low noise energy
marine mammals may be exposed (resulting in very small distances to the
Level A harassment threshold as described below). The proposed
mitigation and monitoring measures for both projects are expected to
minimize the amount and severity of the taking to the extent
practicable.
As previously described, no serious injury or mortality is
anticipated or proposed to be authorized for either proposed 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 the best
available science indicates that 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 would 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. 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 reasonably expect to be behaviorally harassed (equated to Level B
harassment) or incur AUD INJ of some degree (equated to Level A
harassment). Below, we describe the thresholds used by the Navy and
NMFS for this analysis.
Level B Harassment
Though significantly driven by the received level, the onset of
behavioral disturbance from anthropogenic noise exposure is also
informed to varying degrees by other factors. These factors are 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; Ellison et al.,
2012). Based on available science and the practical need to use a
threshold based on a predictable, measurable metric for most
activities, NMFS typically uses a generalized acoustic threshold based
on the 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 re 1 [mu]Pa for continuous
(e.g., vibratory pile driving, drilling) and above RMS SPL 160 dB re 1
[mu]Pa for non-explosive impulsive (e.g., seismic airguns) or
intermittent (e.g., scientific sonar) sources. Level B harassment take
estimates based on these behavioral harassment thresholds potentially
include TTS, as, in most cases, TTS likely occurs at distances from the
source less than those at which behavioral harassment may occur. TTS of
sufficient degree can manifest as behavioral harassment and reduced
hearing sensitivity, and the potential reduction in opportunities to
detect important signals (conspecific communication, predators, prey)
may result in behavior patterns that would not otherwise occur.
The Navy's proposed activities for projects at NBPL and NBSD
include continuous (vibratory pile driving) and impulsive (impact pile
driving) sources. As previously discussed, the Navy has
[[Page 4892]]
measured and reported background noise in San Diego Bay (NAVFAC SW,
2020) above 120 dB re 1 [mu]Pa. Therefore, the RMS SPL thresholds of
129.6 dB and 160 dB re 1 [mu]Pa are applicable to the NBPL Project, and
the thresholds of 126 dB and 160 dB re 1 [mu]Pa are applicable to the
NBSD Project.
Level A Harassment
NMFS' Updated Technical Guidance for Assessing the Effects of
Anthropogenic Sound on Marine Mammal Hearing (Version 3.0) (NMFS, 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). It includes updated thresholds
and updated weighting functions for each hearing group, provided in
table 4 below. The references, analysis, and methodology used to
develop the criteria are described in NMFS' 2024 Updated Technical
Guidance, available at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-
acoustic-tools.
Table 4--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 criterion 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
better reflect International Organization for Standardization (ISO) standards (ISO, 2017). The subscript
``flat'' is being included to indicate that peak sound pressures 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, action proponents should indicate the conditions
under which these criteria would be exceeded.
Ensonified Area
Here, we describe the operational and environmental parameters of
the activity used to estimate the area ensonified above the acoustic
thresholds, including source levels and the transmission loss
coefficient.
The sound field in the project areas 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., vibratory pile removal,
vibratory pile driving, and impact pile driving). The source levels
assumed for both removal and installation activities are based on
reviews of measurements of piles of the same or similar types and
dimensions available in the scientific literature and from similar
coastal construction projects. The source level for the piles and
activities (i.e., installation or removal) at both NBPL and NBSD is
presented in table 5.
Table 5--Proxy Sound Source Levels for Pile Sizes and Driving Methods
--------------------------------------------------------------------------------------------------------------------------------------------------------
Peak SPL (dB re RMS SPL (dB re SEL (dB re
Method Pile size/type 1[micro]Pa) \1\ 1[micro]Pa) \1\ 1[micro]Pa) \1\ Source
--------------------------------------------------------------------------------------------------------------------------------------------------------
NBPL DEPERMING PIER REPLACEMENT PROJECT
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pile Removal Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory Extraction..................... 16-inch round timber........ ............... 162 ............... Naval Submarine Base New
London Monitoring Report
(NAVFAC Mid-Atlantic,
2022); NMFS interim proxy
level (2024).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pile Installation Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory Pile Driving................... 16-inch round plastic....... ............... 162 ............... Naval Submarine Base New
London Monitoring Report
(NAVFAC Mid-Atlantic,
2022); NMFS interim proxy
level (2024).
Impact Hammer............................ 196 182 170
--------------------------------------------------------------------------------------------------------------------------------------------------------
NBSD CHOLLAS CREEK QUAY WALL REPAIR PROJECT
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pile Removal Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory Extraction..................... 14-inch steel H............. ............... 150 ............... California Department of
Transportation (Caltrans,
2020); Chevron Long Wharf
(Richmond, CA).
24-inch steel sheet......... ............... 160 ............... Caltrans (2020); Berth 23
(Port of Oakland).
18-inch square concrete..... ............... 155 ............... NAVFAC SW (2024); NBSD Pier
6 Pier Replacement.\2\
[[Page 4893]]
18-inch octagonal concrete.. ............... 155 ............... NAVFAC SW (2024); NBSD Pier
6 Pier Replacement.\2\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pile Installation Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory Pile Driving................... 13-inch round plastic....... ............... 159 ............... NAVFAC SW (2024); NBSD Pier
6 Pier Replacement.\3\
18-inch octagonal concrete.. ............... 155 ............... NAVFAC SW (2024); NBSD Pier
6 Replacement.\2\
27.5-inch steel sheet....... ............... 160 ............... Caltrans (2020); Berth 23
(Port of Oakland).
Impact Hammer............................ 18-inch octagonal concrete.. 185 170 160 NMFS Interim Proxy Level
based on Caltrans
(2020).\2\
18-inch square concrete..... 185 170 160 NMFS Interim Proxy Level
based on Caltrans (2020).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ As measured, or calculated, at 10 m (33 ft).
\2\ 20-inch square concrete piles used as a proxy; based on the maximum value between 56-61 m of 149.5 dB (rounded to 150 dB) @61 m, and back-calculated
to the source (10 m).
\3\ 12-inch round plastic piles used as a proxy; based on an RMS average of 159.4 dB and back-calculated to the source (10 m). Data show that the 12-
inch plastic proxy source level is louder than the 20-inch concrete pile proxy source due to reverberation from the lighter plastic pile.
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, bottom composition, and
topography. The general formula for underwater TL is:
TL = B * Log10 (R1/R2),
where:
TL = transmission loss in dB
B = transmission loss coefficient; for practical spreading equals 15
R1 = the distance of the modeled SPL from the driven
pile, and
R2 = the distance from the driven pile of the initial
measurement.
This formula neglects loss due to scattering and absorption, which
is assumed to be zero here. The degree to which underwater sound
propagates away from a sound source 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[range]). Cylindrical spreading occurs in an environment in
which sound propagation is bounded by the water surface and sea bottom,
resulting in a reduction of 3 dB in sound level for each doubling of
distance from the source (10*log[range]). A practical spreading value
of 15 is often used in shallow-water coastal conditions, such as those
found in the NBPL and NBSD projects. In these environments, sound waves
repeatedly reflect off the surface and bottom, reflecting an expected
propagation environment between spherical and cylindrical spreading-
loss conditions. Therefore, the default coefficient of 15 is used to
calculate distances to the Level A harassment and Level B harassment
thresholds.
Assuming practicable spreading and other assumptions regarding the
source characteristics and operational logistics (e.g., source level,
number of strikes per pile, number of piles per day), the Navy
calculated distances to the Level A harassment and Level B harassment
thresholds and associated ensonified areas. Because an ensonified area
associated with Level A harassment is more technically challenging to
predict given the accounting for a cumulative energy component that
changes over time, to assist applicants in assessing the potential for
Level A harassment without the need for complex modeling, NMFS
developed an optional User Spreadsheet tool to accompany the 2024
Updated Technical Guidance (see https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools). This relatively simple tool can be used
to calculate a Level A harassment isopleth distance for use in
conjunction with marine mammal density or occurrence data to predict
the amount of take that may occur incidental to an activity. We note
that, because of some of the assumptions in the methods underlying this
spreadsheet tool, we anticipate that the resulting isopleths would
typically be overestimates, which may lead to an overestimate of
potential exposures from Level A harassment. However, this optional
tool offers a practical alternative for estimating isopleth distances
when more sophisticated modeling methods are unavailable or are
impractical. For stationary sources such as impact or vibratory pile
driving and removal, the optional User Spreadsheet tool predicts the
distance at which, if a marine mammal remained at that distance for the
duration of the activity within 24 hours, it would be expected to incur
AUD INJ. Inputs used in the optional User Spreadsheet tool are
contained within table 6.
[[Page 4894]]
Table 6--User Spreadsheet Input Parameters Used for Calculating Level A Harassment Isopleths
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Vibratory pile removal Vibratory pile installation Impact pile installation
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
18''
Equipment type 13'' round 13'' round octagonal 18'' square 18''
16'' round plastic \2\ 18'' square 18'' octagonal 14'' steel H 24'' steel 16'' round plastic \2\ concrete 27.5'' steel 16'' round concrete \2\ octagonal
timber \1\ \3\ concrete \2\ concrete \2\ \2\ sheet \2\ \4\ plastic \1\ \5\ (small float) sheet \2\ plastic \1\ \5\ concrete \2\
\2\ \5\ \5\
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Spreadsheet Tab Used......... A.1) Vibratory pile driving.
A.1) Vibratory pile driving.
E.1) Impact pile driving.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Source Level (dB re: 1 162 RMS....... Dead pull..... 155 RMS....... 155 RMS....... 150 RMS....... 160 RMS....... 162 RMS....... 159 RMS....... 155 RMS...... 160 RMS...... 196 Peak..... 185 Peak..... 185 Peak
[micro]Pa. 182 RMS...... 170 RMS...... 170 RMS
170 SEL...... 160 SEL...... 160 SEL.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Weighting Factor Adjustment 2.5
(kH).
2.5
2
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Activity Duration within 24 5 min/pile.... .............. 20 min/....... 20 min/....... 20 min/....... 20 min/....... 5 min/........ 1 min/........ 20 min/...... 20 min/......
Hours. *............ pile *........ pile *........ pile *........ pile *........ pile *........ pile *........ pile *....... pile *.......
4 piles =..... 5 piles =..... 2 piles =..... 12 piles =.... 10 piles =.... 4 piles =..... 5 piles =..... 4 piles =.... 10 piles =...
20 min........ 100 min....... 40 min........ 240 min....... 200 min....... 20 min........ 5 min......... 80 min....... 200 min......
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Strikes per Second........... .............. .............. .............. .............. .............. .............. .............. .............. ............. ............. 0.01......... 0.01
Number of strikes per pile... .............. .............. .............. .............. .............. .............. .............. .............. ............. ............. 600.......... 600
-----------------------------
Number of piles per day...... 4............. 7............. 5............. 2............. 12............ 10............ 3............. 5............. 4............ 10........... 3............ 6............ 4
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Propagation (xLogR).......... 15
15
15
Distance of SPL Measurement.. 10
10
10
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Acoustic threshold (dB RMS).. 129.6 dB...... .............. 126 dB 129.6 dB...... 126 dB
160 dB.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ NBPL Deperming Pier Replacement Project. See table 6-4 in the application.
\2\ NBSD Chollas Creek Quay Wall Repair Project. See table 1-4 in the application.
\3\ These piles are anticipated to be dead pulled.
\4\ These piles are anticipated to be either vibratory extracted, dead pulled, or clipped at the mud-line and removed. For this IHA, we are assuming vibratory extraction for the demolition of all existing sheet piles.
\5\ Vibratory and/or impact pile driving are the most likely methods that would be used to install piles. High-pressure water jetting may be used either separately from or in conjunction with impact pile installation.
[[Page 4895]]
Using the practical spreading model and source assumptions
identified in table 6, the Navy calculated, and NMFS has carried
forward into this analysis, the distances to the Level A harassment and
Level B harassment thresholds for marine mammals for both the NBPL and
the NBSD projects (table 7).
Table 7--Calculated Distances to the Level A Harassment and Level B Harassment Thresholds by Marine Mammal
Hearing Group and Activity
----------------------------------------------------------------------------------------------------------------
All marine mammals Level B harassment zone (m)
-------------------------------------------------------------------
Level A HFC
Site, activity, pile size/type harassment bottlenose,
zone (m) LFC Gray whales common OW CSL PW Harbor seals
dolphins
----------------------------------------------------------------------------------------------------------------
NBPL DEPERMING PIER
----------------------------------------------------------------------------------------------------------------
Pile Removal Activities
----------------------------------------------------------------------------------------------------------------
Vibratory Extraction 16'' 5.2 2.0 2.2 6.7 1,445
round timber.................
----------------------------------------------------------------------------------------------------------------
Pile Installation Activities
----------------------------------------------------------------------------------------------------------------
Vibratory Hammer 16'' round 5.2 2.0 6.7 2.2 1,455
plastic......................
Impact Hammer 16'' round 242.5 30.9 80.3 215.4 293
plastic......................
----------------------------------------------------------------------------------------------------------------
NBSD CHOLLAS CREEK \1\
----------------------------------------------------------------------------------------------------------------
Pile Removal Activities
----------------------------------------------------------------------------------------------------------------
Vibratory Extraction 14'' ............ 1.6 1.9 5.5 398
steel H......................
Vibratory Extraction 18'' ............ 1.1 1.2 3.6 858
octagonal concrete...........
Vibratory Extraction 18'' ............ 2.0 2.2 6.6 858
square concrete..............
Vibratory Extraction 24-steel ............ 6.8 7.6 22.7 1,848
sheet........................
----------------------------------------------------------------------------------------------------------------
Pile Installation Activities
----------------------------------------------------------------------------------------------------------------
Vibratory Driving 13'' round ............ 0.5 0.6 1.8 1,685
plastic......................
Vibratory Driving 18'' ............ 1.1 1.2 3.6 858
octagonal concrete (small
float).......................
Vibratory Driving 27.5'' steel ............ 6.8 7.6 22.7 1,848
sheet........................
Impact Driving 18'' octagonal ............ 6.7 17.3 46.4 46
concrete.....................
Impact Driving 18'' square ............ 8.7 22.7 60.8 46
concrete.....................
----------------------------------------------------------------------------------------------------------------
Abbreviations: LCF = Low-Frequency Cetacean; HFC = High-Frequency Cetacean; OW = Otariid; PW = Phocid; CSL =
California sea lions.
Marine Mammal Occurrence
In this section, we provide information on the anticipated
occurrence of marine mammals present in the project areas during the
proposed NBPL and NBSD Projects. This occurrence information then
informs the take calculations in the following section (see Take
Estimation and table 9).
For all species, the best available scientific information was
considered to estimate occurrence. First, the Navy considered density
data contained within the U.S. Navy Marine Species Density Database for
the Hawaii-Southern California Training and Testing Study Area
technical report (U.S. Navy, 2024), which includes San Diego Bay.
However, the Navy determined that a density-based approach would
overestimate take as evidenced in previous monitoring reports (NAVFAC
SW 2016, 2017a, 2017b, 2018a, 2018b).
To more accurately inform take estimates, the Navy reviewed IHA
applications and monitoring reports for previous projects at both NBPL
and NBSD to develop more site-specific occurrence estimates for each
species. Except for California sea lions, the average number of
observations of marine mammals during the NBPL Fuel Pier Replacement
Project monitoring periods, years 2-5 (2015-2018), was used by the Navy
to estimate the expected average number of individuals observed daily
for the current NBPL Project (NAVFAC SW 2016, 2017a, 2017b, 2018a,
2018b). The Navy also used observations presented in the final
monitoring report for the NBSD Pier 6 Replacement Project (NAVFAC SW,
2024) to estimate the expected average number of individuals observed
daily for the current NBSD Project. Except for California sea lions,
the average daily occurrence per species over the NBPL Fuel Pier's 4
years was deemed to provide a reasonably representative daily
occurrence estimate. As for California sea lions, due to the close
proximity of the NBPL Project to the Everingham Brothers' Bait Barge,
which sea lions regularly use as a haul-out location, the Navy used the
highest number of individuals observed per day (from the NBPL Fuel Pier
monitoring period year 2, 2015) to estimate the expected number of
individuals observed per day for the current NBPL Project (i.e., 25.09
sea lions expected to be observed daily).
[[Page 4896]]
Table 8--Estimated Occurrence of Marine Mammal Species
------------------------------------------------------------------------
Relative occurrence Expected number of
Species/location in north and south- individuals
central San Diego Bay observed/day
------------------------------------------------------------------------
Naval Base Point Loma
------------------------------------------------------------------------
California sea lion.......... Abundant............. 25.09
Harbor seal.................. Relatively Uncommon.. 0.56
Bottlenose dolphin........... Sporadic............. 1.29
Short-beaked common dolphin.. Occasional........... 0.10
Long-beaked common dolphin... Occasional........... ..................
gray whale................... Rare/Seasonal........ 0.02
------------------------------------------------------------------------
Naval Base San Diego
------------------------------------------------------------------------
California sea lion.......... Abundant............. 1.38
Harbor seal.................. Relatively Uncommon.. 0.01
Bottlenose dolphin........... Sporadic............. 0.5
------------------------------------------------------------------------
Take Estimation
In this section, we describe how the project scope, ensonified
area, and species occurrence information provided above are used to
produce a quantitative estimate of the take that could occur and is
proposed for authorization. We first describe the take estimation
process for the NBPL Project, then for the NBSD Project.
NBPL Deperming Pier Replacement Project
To calculate the estimated take that may occur incidental to the
NBPL Project, the Navy used the following methods, and we have carried
them forward in this analysis. In summary, the Navy calculated
estimated exposures at each pier for each activity using the following
equation:
# of individuals/day x days per pier and activity x ensonified area
The number of individuals per day used in the calculations is found
in table 8. The number of days used in the calculations is as follows:
Vibratory pile extraction: Deperming Pier 47 days, ERG Pier 37
days, and Pier 5002 2 days;
Vibratory pile driving: Deperming Pier 50 days, ERG Pier 33 days,
and Pier 5002 2 days; and
Impact pile driving: Deperming Pier 50 days, ERG Pier 33 days, and
Pier 5002 2 days. The Navy then summed the exposure estimates across
the three piers to obtain a total exposure estimate for each species.
Please see section 6.9 and Appendix B of the NBPL IHA application
for a detailed description of exposure estimates and take calculations,
and tables of all of the calculations for each species, at each pier,
and for each pile method (vibratory pile extraction, vibratory pile
driving, and impact pile driving).
Because take by both behavioral harassment and AUD INJ could occur
incidentally to impact pile driving, the Navy allocated the total
exposures for this activity by Level A harassment and Level B
harassment at each of the three piers. To do so, the Navy identified
the Level A harassment area percentage relative to the Level B
harassment area at each pier for impact pile driving using the
following equation:
Level A harassment ensonified area (km2)/Level B harassment ensonified
area (km2) = Level A harassment ensonified area percentage
Using impact pile driving for California sea lions at the Deperming
Pier as an example, the Level A harassment ensonified area (0.025390
km\2\) divided by the Level B harassment ensonified area (0.201349
km\2\) equals 10.61 percent.
The Navy then multiplied each species' total impact pile driving
exposure estimates at each pier by the Level A harassment ensonified
area percentage:
Impact pile driving exposure estimate at each pier x Level A harassment
ensonified area percentage = Level A take at each pier
Again, using impact pile driving on California sea lions at the
Deperming Pier as an example, the exposure estimate for the species
(1,254.50 individuals) multiplied by the Level A harassment ensonified
area percentage (10.61 percent) equals 158.19 Level A takes.
The Navy then summed the results from all three piers to obtain the
total requested amount of Level A harassment take. Using the example
above, 159.18 + 106.46 + 5.04 equals 270 California sea lion Level A
harassment takes.
To calculate Level B harassment for each species at each pier, the
Navy conducted a similar process, accounting for the ensonified area
already considered in the Level A harassment calculations. The Navy
used the following formula to estimate the Level B harassment
ensonified area percentage:
Level B harassment ensonified area (km2)-Level A harassment ensonified
area (km2)/Level B harassment ensonified area (km2) = Level B
harassment ensonified area percentage
Again, using impact pile driving on California sea lions at the
Deperming Pier as an example, the Level B harassment ensonified area
(0.201349 km\2\) minus the Level A harassment ensonified area (0.025390
km\2\) divided by the Level B harassment ensonified area (0.201349
km\2\) equals 87.39 percent.
The Navy then multiplied the total species' impact pile driving
exposure estimates by the Level B harassment ensonified area percentage
for each species at each pier to obtain the requested amount of takes
by Level B harassment using the following formula:
Exposure estimate per pier x Level B harassment ensonified area
percentage = Level B take per pier
Again, using impact pile driving on California sea lions at the
Deperming Pier as an example, the exposure estimate for the species
(1,254.50) multiplied by the Level B harassment ensonified area (87.39
percent) equals 1,096 takes of Level B harassment.
The Navy then summed the takes by Level B harassment per species at
each of the three piers. (see table 9).
Of note, for the NBPL Project, the Navy combined sighting
information/species occurrence for the short- and long-beaked common
dolphins, as both
[[Page 4897]]
species are difficult to differentiate in the wild. For the take
estimates, we have authorized a single amount of take for both species
combined. We also note a minor discrepancy in the calculations for the
combined short- and long-beaked common dolphins, specifically for
impact pile driving at the ERG Pier. We calculated 0.08 Level A
harassment exposures for the species, whereas the application shows
1.00 Level A harassment exposure; and we calculated 3.22 Level B
harassment exposures, whereas the application shows 2.30 Level B
harassment exposures. This error, when carried through and using
standard rounding at the end (i.e., where a number of five or greater
is rounded up), resulted in the Navy calculating 2 takes by Level A
harassment and 18 takes by Level B harassment for the combined short-
and long-beaked common dolphins, whereas we calculated 0 takes by Level
A harassment and 18 takes by Level B harassment for the combined
species. NMFS confirmed with the Navy that our calculations are correct
(K. LeRoy, pers. comm., January 16, 2026); therefore, they are applied
in this proposed IHA. See table 9 below for the estimated takes by
Level A harassment and Level B harassment proposed to be authorized for
the NBPL Project.
NBSD Chollas Creek Quay Wall Repair Project
To calculate the estimated takes by Level B harassment that may
occur incidental to the NBSD Project, the Navy used the following
formula, and we have carried forward this analysis:
N x D = Estimated takes by Level B Exposure
Where:
N = the average number of individuals observed/day, and
D = the total days of pile extraction/installation (190 days).
See table 9 for the number of takes by Level B harassment proposed
to be authorized.
As described above, the Navy did not request, and NMFS does not
propose, to authorize take by Level A harassment for any of the three
species that may occur in the NBSD Chollas Creek area--California sea
lions, bottlenose dolphins, and harbor seals.
Based on the best available science, NMFS generally finds the
Navy's estimates of the types and amounts of take for each species and
each project to be a reasonable representation of the amount of take
that could occur from the project. NMFS has identified the minor
discrepancy in the NBPL Project take estimation section for short- and
long-beaked common dolphins discussed above and has carried forward our
calculations. Table 9 below summarizes the number of takes by Level A
harassment and/or Level B harassment, and the total proposed take per
stock as a percentage of stock abundance for both projects.
[[Page 4898]]
Table 9--Proposed Authorized Take by Level A Harassment and Level B Harassment and as a Percentage of Stock Abundance for the NBPL Project and NBSD Project
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Avg. number of indiv./ NBPL IHA proposed take NBSD IHA proposed take
Stock day --------------------------------------- ---------------------------------------
Common name Stock abundance -------------------------- Total Percent of Total Percent of
\1\ Level A Level B proposed stock Level A Level B proposed stock
NBPL NBSD take take
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
CA sea lion................... CA breeding 257,606 25.09 1.38 270 4,291 4,561 \1\ 1.77 0 262 262 0.10
stock.
Bottlenose dolphin............ CA coastal stock 453 1.29 0.5 3 221 224 \1\ \2\ 0 95 95 20.97
49.39
Harbor seal................... CA stock........ 30,968 0.56 0.01 30 96 106 \1\ 0.41 0 2 2 0.00
Short-beaked common dolphin... CA/OR/WA stock.. 1,056,308 0.10 ........... 0 18 18 0.00 ........... ........... ........... ...........
Long-beaked common dolphin.... CA stock........ 83,379 ...........
Gray whale.................... Eastern N 25,960 0.02 ........... 0 4 4 0.02 ........... ........... ........... ...........
Pacific.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ The values presented here are based on if all takes were to a different individual. This is not likely the case, however, for California sea lions, harbor seals, and bottlenose dolphins
due to their presumed persistence at a location (i.e., repeated takes of the same individual may occur across multiple days).
\2\ The percentage of the stock for the California coastal stock of bottlenose dolphins presented here is a simplistic calculation that considers each take is of a unique individual, which is
not likely the case. Please see the Small Numbers section for more rationale.
[[Page 4899]]
Proposed Mitigation
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 (ITA)
to include information about the availability and feasibility (economic
and technological) of equipment, methods, and the 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) How and to what degree the successful implementation of the
measure(s) is expected to reduce impacts on marine mammal species or
stocks and their habitat. This considers the nature of the potential
adverse impact being mitigated (its likelihood, scope, and range). It
further considers the likelihood that the measure would be effective if
implemented (probability of accomplishing the mitigating result if
implemented as planned), the likelihood of effective implementation
(probability of implementation as planned); and
(2) The practicability of the measures for applicant
implementation, which may consider such things as cost and impact on
operations.
The number and/or intensity of takes would be minimized by
incorporating the mitigation measures proposed by the Navy in its
adequate and complete applications for both the NBPL Project and the
NBSD Project. The Navy has agreed that all of the mitigation measures
are practicable. As required by the MMPA, we concurred that these
measures are sufficient to achieve the least practicable adverse impact
on the affected marine mammal species or stocks and their habitat. NMFS
describes these below and has included them as proposed mitigation
requirements in each of the proposed IHAs.
Establishment of Shutdown Zones
The Navy proposed, and NMFS would require, the establishment of
shutdown zones with radial distances, as identified in table 10, for
all construction activities. The purpose of a shutdown 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) to minimize potential instances of AUD INJ and more
severe behavioral disturbances by delaying the start of an activity if
marine mammals are near the activity. Additionally, the Navy would be
required to shut down in the event that an unauthorized species is
present to avoid taking that unauthorized species. Shutdown zones would
be cleared before activities begin, and would vary by activity type and
marine mammal hearing group.
The placement of up to three PSOs during all pile-driving
activities for both projects (as described in the Proposed Monitoring
and Reporting section) would ensure that the entire shutdown zone is
visible. Should environmental conditions deteriorate to the point that
the entire shutdown zone is not visible (e.g., fog, heavy rain), pile
driving would be delayed until the PSO is confident that marine mammals
within the shutdown zone can be detected. Limiting construction
activities to daylight hours only for both projects would also increase
the detectability of marine mammals in the area.
If a marine mammal is observed entering or within the shutdown
zones indicated in table 10, pile-driving activity must be delayed or
halted, unless in the case of human safety concerns or pile refusal/
instability.
If pile driving is delayed or halted due to the presence of a
marine mammal, the activity may not begin or resume until either the
animal has voluntarily exited and been visually confirmed beyond the
shutdown zone, or 15 minutes have passed without re-detection of the
animal.
During all in-water pile-driving activities for both projects, the
Navy would implement a minimum 20 m (66 ft) shutdown zone for
activities where the calculated Level A harassment distances were less
than 20 m (66 ft). For activities where the calculated Level A
harassment distance was greater than 20 m (66 ft), these distances were
rounded up to the nearest 10 m (33 ft) (e.g., a calculated Level A
harassment distance of 46 m would correspond to a 50 m shutdown zone).
The Navy must also avoid direct physical interaction with marine
mammals during construction activity through the implementation of a 10
m shutdown zone for activities other than pile driving. Adherence to
these shutdown zones would minimize the potential number and intensity
of Level A harassment during impact pile driving for the NBPL and NBSD
Projects. See table 10 below for shutdown zones and Level B harassment
zones.
Table 10--Shutdown Zones and Level B Harassment Zones for the NBPL Deperming Pier Replacement Project and NBSD
Chollas Creek Quay Wall Project
----------------------------------------------------------------------------------------------------------------
Shutdown zone (m) \1\ All marine
--------------------------------------------------------------- mammals Level B
Site, activity, pile size/type LFC Gray HFC bottlenose, PW Harbor harassment zone
whales common dolphins OW CSL seals (m)
----------------------------------------------------------------------------------------------------------------
NBPL DEPERMING PIER IHA
----------------------------------------------------------------------------------------------------------------
Pile Removal Activities
----------------------------------------------------------------------------------------------------------------
Vibratory Extraction 16'' 20 20 20 20 1,450
round timber.................
----------------------------------------------------------------------------------------------------------------
Pile Installation Activities
----------------------------------------------------------------------------------------------------------------
Vibratory Hammer 16'' round 20 20 20 20 1,450
plastic......................
Impact Hammer 16'' round 250 40 90 220 300
plastic......................
----------------------------------------------------------------------------------------------------------------
[[Page 4900]]
NBSD CHOLLAS CREEK IHA
----------------------------------------------------------------------------------------------------------------
Pile Removal Activities
----------------------------------------------------------------------------------------------------------------
Vibratory Extraction 14'' ............ 20 20 20 400
steel H......................
Vibratory Extraction 18'' ............ 20 20 20 860
octagonal concrete...........
Vibratory Extraction 18'' ............ 20 20 20 860
square concrete..............
Vibratory Extraction 24-steel ............ 20 20 30 1,850
sheet........................
----------------------------------------------------------------------------------------------------------------
Pile Installation Activities
----------------------------------------------------------------------------------------------------------------
Vibratory Driving 13'' round ............ 20 20 20 1,690
plastic......................
Vibratory Driving 18'' ............ 20 20 20 860
octagonal concrete (small
float).......................
Vibratory Driving 27.5'' steel ............ 20 20 30 1,850
sheet........................
Impact Driving 18'' octagonal ............ 20 20 50 50
concrete.....................
Impact Driving 18'' square ............ 20 30 70 50
concrete.....................
----------------------------------------------------------------------------------------------------------------
\1\ The shutdown zone must be clear of marine mammals 30 minutes prior to commencing pile removal or
installation. If a marine mammal is observed entering or within the shutdown zone during pile removal or
installation, pile driving must cease until the animal has cleared the zone or not been re-sighted within 15
minutes. NMFS recognizes that pile driving may not cease in the case of safety concerns or pile refusal/
instability.
Abbreviations: LFC = Low-Frequency Cetacean; HFC = High-Frequency Cetacean; OW = Otariid; PW = Phocid; CSL =
California sea lions.
Pre- and Post-Activity Marine Mammal Monitoring
Monitoring would take place from 30 minutes prior to initiation of
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 sufficient visibility for the lead PSO to
determine that the shutdown zones indicated in table 10 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. If a marine mammal is observed entering or
within the shutdown zones, pile driving activity 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 zone, or 15 minutes have passed without re-detection of the
animal. Finally, if a shutdown and/or clearance procedure would result
in an imminent safety concern, as determined by the Navy, the in-water
activity would be allowed to continue until the safety concern has been
addressed, and the animal would be continuously monitored. The Navy
Point of Contact would be consulted before resuming any activities.
Soft-Start
The Navy would use soft-start techniques when impact pile driving.
Soft-start procedures are used to provide additional protection to
marine mammals by issuing a warning and/or giving them a chance to
leave the area before the hammer operates at full capacity. 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 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.
Bubble Curtain
The Navy has not proposed to use a bubble curtain to attenuate in-
water construction noise during any of the proposed pile driving
activities presented herein for either project. The Navy asserted that
due to strong tidal fluctuations and associated currents in San Diego
Bay, bubble curtains would not be effective in this environment (Navy
pers. comm., September 3, 2025). NMFS agrees that the use of a bubble
curtain would not appreciably decrease noise levels such that impacts
on marine mammals would be reduced.
In summary, based on our evaluation of the Navy's proposed
mitigation measures for both the NBPL and NBSD projects, NMFS has
preliminarily determined that the proposed mitigation measures provide
the means of effecting the least practicable impact on the affected
species or stocks and their habitat, with particular focus on
rookeries, mating grounds, and similar areas of significance.
Proposed Monitoring and Reporting
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 to both
compliance and ensuring the most value is obtained from the required
monitoring.
Monitoring and reporting requirements prescribed by NMFS should
help improve the understanding of one or more of the following:
Occurrence of marine mammal species or stocks in the area
in which take is anticipated (e.g., presence, abundance, distribution,
density);
Nature, scope, or context of likely marine mammal exposure
to potential
[[Page 4901]]
stressors/impacts (individual or cumulative, acute or chronic), through
better understanding of: (1) action or environment (e.g., source
characterization, propagation, ambient noise); (2) affected species
(e.g., life history, dive patterns); (3) co-occurrence of marine mammal
species with the activity; or (4) biological or behavioral context of
exposure (e.g., age, calving or feeding areas);
Individual marine mammal responses (behavioral or
physiological) to acoustic stressors (acute, chronic, or cumulative),
other stressors, or cumulative impacts from multiple stressors;
How anticipated responses to stressors impact either: (1)
long-term fitness and survival of individual marine mammals; or (2)
populations, species, or stocks;
Effects on marine mammal habitat (e.g., marine mammal prey
species, acoustic habitat, or other important physical components of
marine mammal habitat); and
Mitigation and monitoring effectiveness.
The Navy would abide by all monitoring and reporting measures
contained within the IHA, if issued, and their Protected Species
Monitoring Plans (see NMFS' website at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities). NMFS describes these below as requirements
and has included them in the proposed IHA.
Visual Monitoring
All PSOs must be NMFS-approved and have no other assigned tasks
during monitoring periods. At least one PSO would have prior experience
performing the duties of a PSO during construction activity pursuant to
a NMFS-issued ITA. The Navy would have between one and three PSOs
actively monitoring on-site at all times during pile-driving
activities. Where a team of three or more PSOs is required, a lead
observer or monitoring coordinator would be designated. The lead
observer would be required to have prior experience working as a marine
mammal observer during construction. Additional PSOs may be employed
during periods of low or obstructed visibility to ensure the entirety
of the shutdown zone is monitored.
Reporting
The Navy would be required to submit a draft report(s) on all
construction activities and marine mammal monitoring results to NMFS
within 90 days of the completion of monitoring, or 60 days prior to the
requested issuance of any subsequent IHAs or similar activity at the
same location, whichever comes first. The information required to be
collected and reported to NMFS is included in the draft IHA available
at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities. In summary, the
report would include, but not be limited to, information regarding
activities that occurred, marine mammal sighting data, and whether
mitigative actions were taken or could not be taken. The Navy would
also be required to submit reports on any observed injured or dead
marine mammals. If the death or injury was clearly caused by the
specified activity, the Navy 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 terms of the IHA. The Navy
would not resume its activities until notified by NMFS.
Specific proposed mitigation, monitoring, and reporting
requirements can be found in the draft IHAs found at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities.
Negligible Impact Analysis and Determination
NMFS defines negligible impact as an effect of the specified
activity that cannot reasonably be 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 absence of likely adverse effects on
annual recruitment or survival rates (i.e., population-level effects).
An estimate of the number of takes alone is insufficient to support 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), effects on habitat, and the likely
effectiveness of the mitigation. We also assess the number, intensity,
and context of estimated takes by evaluating them against population
status. Consistent with the 1989 preamble to NMFS' implementing
regulations (54 FR 40338, September 29, 1989), impacts from other past
and ongoing anthropogenic activities are incorporated into this
analysis via their effects 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
species listed in table 9 and to both projects, given that the
anticipated effects of the NBPL and NBSD Project activities on these
different marine mammal stocks are expected to be similar. There is
little information on the nature or severity of the impacts, or on the
size, status, or structure of any of these species or stocks, that
would lead to a different analysis for this activity.
Pile driving and removal associated with the project, as outlined
previously, have the potential to disturb or displace marine mammals.
Specifically, the specified activities may result in take in the form
of Level A harassment (NBPL Project only) and/or Level B harassment
from underwater sounds generated from pile driving and removal.
Potential takes could occur if individuals of these species are present
in zones ensonified above the thresholds for Level A harassment and/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 the Navy's proposed
projects, even in the absence of required mitigation. The Level A
harassment zones identified in table 7 are based upon an animal exposed
to vibratory pile driving/removal and/or impact pile driving for
periods ranging from 20 to 240 minutes of vibratory pile removal/
installation, and impact pile driving of 3 to 6 piles per day.
Exposures of this length are, however, unlikely for vibratory driving/
removal scenarios, given marine mammal movement throughout the area.
Even during impact driving scenarios, an animal exposed to the
accumulated sound energy would likely only experience a small degree of
AUD INJ at the lower frequencies where pile driving energy is
concentrated. Moreover, an individual may recover from hearing loss
after exposure to the sound has ceased. The level of recovery is based
on the initial threshold shift amount, the frequency at which the shift
occurred, and the duration of exposure. While not able to be
quantified, as described in the Effects to Marine Mammal and Their
Habitat section, some recovery is expected to occur.
As stated in the Proposed Mitigation section, the Navy would
implement shutdown zones that equal or exceed
[[Page 4902]]
many of the Level A harassment isopleths shown in table 7. Take by
Level A harassment is proposed for three of the six marine mammal
species during construction activities associated with the project at
the NBPL; no take by Level A harassment for species that occur at the
NBSD site is anticipated or proposed for authorization. The proposed
take by Level A harassment for species at the NBPL site 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, given the various obstructions along the shoreline, 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. Given the proximity to the shore, exposure over extended time
periods is unlikely to occur before the animal is observed by PSOs, and
before the proposed mitigation measures are implemented. Additionally,
as noted previously, some subset of individuals who are behaviorally
harassed during the activities could also simultaneously incur some
small degree of TTS for a short duration. However, because of the
anticipated small degree of possible overlap of sound exposure,
duration, and hearing frequency with species occurrence, 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. No AUD INJ for the NBSD Chollas Creek project is expected or
proposed to be authorized.
For all species and stocks, take is expected to occur within a
limited, confined area (adjacent to the project sites) of the species'
range. The intensity and duration of take by Level A harassment and/or
Level B harassment would be minimized through the proposed mitigation
measures described herein. Furthermore, the amount of take proposed for
authorization is small compared to the relative stock's abundance, even
assuming that every take for any particular species could wholly occur
to individuals of an individual stock.
Behavioral responses of marine mammals to pile driving and removal
at the project sites, if any, are expected to be mild, short-term, and
temporary. Given that the removal of 192 piles would occur over 86 days
and the installation of 192 piles would occur over 85 days for the NBPL
Project, and the removal of 544 piles would occur over 69 days and the
installation of 936 piles would occur over 121 days for the NBSD
Project, respectively (all of which may not necessarily be
consecutive), any harassment is expected be to temporary and
intermittent. Marine mammals within the Level B harassment zones may
not show any visual cues that they are disturbed by activities, or they
may 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 the region would
be present only 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.
However, this reaction has been observed primarily associated with
impact pile driving. While vibratory pile driving associated with the
proposed projects may produce sound at distances of many kilometers
from the project sites, thus overlapping with some likely less-
disturbed habitat, the project sites are located in a busy bay, and the
majority of sound fields produced by the specified activities are close
to the bay. Animals disturbed by project sounds would be expected to
avoid the area and use nearby higher-quality habitats. Pinnipeds in the
area would be able to haul out on nearby man-made structures to avoid
the activities, and no in-air harassment is anticipated from the
construction.
The potential for harassment is minimized by implementing the
proposed mitigation measures. During all impact driving, the
implementation of soft-start procedures and the monitoring of
established shutdown zones by trained and qualified PSOs shall be
required, significantly reducing the risk 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 impact on marine mammal prey that would occur during the Navy's
proposed activities would have, at most, short-term effects on the
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 construction are expected to be minor, and these
effects are unlikely to cause substantial individual-level impacts on
marine mammals, with no expected impact on annual recruitment or
survival rates.
In addition, 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 individual, much less the stocks' annual rates of
recruitment or survival. Taken together, we believe that these factors,
along with the available body of evidence from similar activities,
demonstrate that the potential effects of the specified activities
would be only minor and short-term for individuals. Overall, the
specified activities for the NBPL and NBSD are not expected to impact
rates of recruitment or survival; therefore, these effects would not be
expected to result in population-level impacts.
In summary and as described above, the following factors primarily
support our preliminary determinations that the impacts resulting from
the two separate specified activities are not expected to adversely
affect any of the species or stocks through effects on annual rates of
recruitment or survival:
No mortality or serious injury is anticipated or proposed
for authorization, and no Level A harassment (AUD INJ) is anticipated
or proposed for authorization incidental to the NBSD Chollas Creek Quay
Wall Repair Project;
Any Level A harassment (AUD INJ) is anticipated to be
slight AUD INJ (i.e., of a few decibels) within the lower frequencies
associated with pile driving and not encompassing a species' full
hearing range;
The anticipated incidents of Level B harassment would
consist of, at worst, temporary modifications in behavior that would
not result in fitness impacts on individuals;
The area affected by the specified activity is very small
relative to the overall habitat ranges of all species, does not include
any rookeries, does not include ESA-designated critical habitat, and
does include any BIAs;
Effects on species that serve as prey for marine mammals
from the activities 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
adverse impacts on their populations;
[[Page 4903]]
The project area is located in a highly industrialized and
commercial bay; therefore, species are likely acclimated to
anthropogenic activities and behavioral reactions are expected to be
minor (if at all); and
The proposed mitigation measures, such as soft-starts, 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 activities on marine mammals and their habitat, and taking
into consideration the implementation of the proposed monitoring and
mitigation measures, NMFS preliminarily finds for both of the two
separate proposed IHAs that the total marine mammal take from the
proposed activities would 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, so, in practice, when estimated numbers
are available, NMFS compares the number of individuals taken to the
most appropriate abundance estimate for the relevant species or stock
in determining whether an authorization is limited to small numbers of
marine mammals. When the predicted number of individuals to be taken is
fewer than one-third of the species or stock abundance, the take is
considered to be of small numbers (see 86 FR 5322, January 19, 2021).
Additionally, other qualitative factors may be considered in the
analysis, such as the temporal or spatial scale of the activities.
For the NBPL Project, with the exception of the California coastal
stock of bottlenose dolphin (see below), the maximum proposed number of
instances of takes by Level A harassment and Level B harassment,
relative to the best available population abundance, is less than one-
third for five of the species impacted. For the NBSD Project, the
maximum proposed number of instances of takes by Level B harassment is
less than one-third for the three species impacted (see table 9).
For the NBPL Project, the total number of takes proposed to be
authorized for the California coastal stock of bottlenose dolphins (n =
224) is 49.39 percent of the total stock abundance estimate (453),
assuming each take is to a different individual (i.e., no repeated
takes to the same individual). However, it is likely that a relatively
small subset of California coastal bottlenose dolphins would be
incidentally harassed repeatedly by NBPL Project activities, and
therefore, the number of individuals taken is less than 49.39 percent
of the population. California coastal bottlenose dolphins range from
San Francisco Bay to San Diego (and south into Mexico), and the
specified activity would be stationary within an enclosed water body
that is not recognized as an area of any special significance for
coastal bottlenose dolphins (and is, therefore, not an area of dolphin
aggregation, as evident in Navy observational records and monitoring
reports (e.g., see NAVFAC SW, 2014; NAVFAC SW, 20015)). We, therefore,
believe that the estimated number of takes likely represents repeated
exposures of a much smaller number of bottlenose dolphins and that,
based on the limited region of exposure in comparison with the known
distribution of the coastal bottlenose dolphin, these estimated
incidents of take represent small numbers of bottlenose dolphins.
Based on the analysis contained herein of the proposed activities
(including the proposed mitigation and monitoring measures) and the
anticipated take of marine mammals, NMFS preliminarily finds for both
of the two separate proposed IHAs that small numbers of marine mammals
would be taken relative to the population size of the affected species
or stocks.
Unmitigable Adverse Impact Analysis and Determination
There are no relevant subsistence uses of the affected marine
mammal stocks or species implicated by this action. Therefore, NMFS has
determined that the total taking of affected species or stocks for both
the NBPL and NBSD Projects would not have an unmitigable adverse impact
on the availability of such species or stocks for subsistence purposes.
Endangered Species Act
Section 7(a)(2) of the ESA of 1973 (16 U.S.C. 1531 et seq.)
requires that each Federal agency ensure that any action it authorizes,
funds, or carries out is not likely to jeopardize the continued
existence of any endangered or threatened species or result in the
destruction or adverse modification of designated critical habitat. To
ensure ESA compliance in issuing an ITA, NMFS consults internally
whenever we propose to authorize take of ESA-listed species.
No incidental take of ESA-listed species is proposed for
authorization or expected to result from this activity. Therefore, NMFS
has determined that formal consultation under section 7 of the ESA is
not required for this action.
Proposed Authorizations
As a result of these preliminary determinations, NMFS proposes to
issue two IHAs to the Navy: one IHA authorizing harassment incidental
to the Deperming Pier Replacement Project at Naval Base Point Loma, and
one IHA authorizing harassment incidental to the Chollas Creek Quay
Wall Repair Project at Naval Base San Diego, provided the previously
mentioned mitigation, monitoring, and reporting requirements are
incorporated. Drafts of both proposed IHAs can be found at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities.
Request for Public Comments
We request comment on our analyses, the proposed authorizations,
and any other aspect of this notice. We also request comments on the
potential renewal of each of these proposed IHAs as described in the
paragraph below. Please include with your comments any supporting data
or literature citations to help inform decisions on the request for
these IHAs or a subsequent IHA renewal.
On a case-by-case basis, NMFS may issue a one-time, 1-year renewal
IHA following notice to the public providing an additional 15 days for
public comments when (1) up to another year of identical or nearly
identical activities as described in the Description of Proposed
Activity section of this notice is planned or (2) the activities as
described in the Description of Proposed Activity section of this
notice would not be completed by the time the IHA expires and a renewal
would allow for completion of the activities beyond that described in
the Dates and Duration section of this notice, provided all of the
following conditions are met:
A request for renewal is received no later than 60 days
prior to the needed renewal IHA effective date (recognizing that the
renewal IHA expiration date cannot extend beyond 1 year from expiration
of the initial IHA).
The request for renewal must include the following:
1. An explanation that the activities to be conducted under the
requested renewal IHA are identical to the activities analyzed under
the initial IHA, are a subset of the activities, or include changes so
minor (e.g.,
[[Page 4904]]
reduction in pile size) that the changes do not affect the previous
analyses, mitigation and monitoring requirements, or take estimates
(with the exception of reducing the type or amount of take).
2. A preliminary monitoring report showing the results of the
required monitoring to date and an explanation showing that the
monitoring results do not indicate impacts of a scale or nature not
previously analyzed or authorized.
Upon review of the request for renewal, the status of the
affected species or stocks, and any other pertinent information, NMFS
determines that there are no more than minor changes in the activities,
the mitigation and monitoring measures will remain the same and
appropriate, and the findings in the initial IHA remain valid.
Dated: January 30, 2026.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries
Service.
[FR Doc. 2026-02173 Filed 2-2-26; 8:45 am]
BILLING CODE 3510-22-P