Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Floating Dry Dock Project at Naval Base San Diego in San Diego, California, 21179-21198 [2020-08006]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 85, Number 74 (Thursday, April 16, 2020)]
[Notices]
[Pages 21179-21198]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-08006]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XR106]


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to the Floating Dry Dock Project at 
Naval Base San Diego in San Diego, California

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

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

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SUMMARY: NMFS has received a request from the U.S. Navy (Navy) for 
authorization to take marine mammals incidental to the Floating Dry 
Dock Project at Naval Base San Diego in San Diego, California. Pursuant 
to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments 
on its proposal to issue an incidental harassment authorization (IHA) 
to incidentally take marine mammals during the specified activities. 
NMFS is also requesting comments on a possible one-year renewal that 
could be issued under certain circumstances and if all requirements are 
met, as described in Request for Public Comments at the end of this 
notice. NMFS will consider public comments prior to making any final 
decision on the issuance of the requested MMPA authorizations and 
agency responses will be summarized in the final notice of our 
decision.

DATES: Comments and information must be received no later than May 18, 
2020.

ADDRESSES: Comments should be addressed to Jolie Harrison, Chief, 
Permits and Conservation Division, Office of Protected Resources, 
National Marine Fisheries Service. Physical comments should be sent to 
1315 East-West Highway, Silver Spring, MD 20910 and electronic comments 
should be sent to [email protected].
    Instructions: NMFS is not responsible for comments sent by any 
other method, to any other address or individual, or received after the 
end of the comment period. Comments received electronically, including 
all attachments, must not exceed a 25-megabyte file size. Attachments 
to electronic comments will be accepted in Microsoft Word or Excel or 
Adobe PDF file formats only. 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: Wendy Piniak, Office of Protected 
Resources, NMFS, (301) 427-8401. Electronic copies of the application 
and supporting documents, as well as a list of the references cited in 
this document, may be obtained online at: https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act. In case of problems accessing these 
documents, please call the contact listed above.

SUPPLEMENTARY INFORMATION: 

Background

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

National Environmental Policy Act

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

[[Page 21180]]

Summary of Request

    On November 26, 2019, NMFS received a request from the Navy for an 
IHA to take marine mammals incidental to the Floating Dry Dock Project 
at Naval Base San Diego in San Diego, California. We received a revised 
application on February 10, 2020. The application was deemed adequate 
and complete on March 17, 2020. The Navy's request is for take of a 
small number of California sea lions by Level B harassment only. 
Neither the Navy nor NMFS expects serious injury or mortality to result 
from this activity and, therefore, an IHA is appropriate.

Description of Proposed Activity

Overview

    Navy has requested authorization for take of marine mammals 
incidental to in-water activities associated with the Floating Dry Dock 
Project at Naval Base San Diego in San Diego, California. The Navy 
proposes to construct a floating dry dock and associated pier-side 
access in the south-central portion of San Diego Bay. The floating dry 
dock is needed to ensure the Base's capability to conduct berth-side 
repair and maintenance of vessels. Implementation of the proposed 
project requires installation of two mooring dolphins, including 
vertical and angled structural piles, as well as fender piles, 
installation of a concrete ramp wharf and vehicle bridge, and dredging 
at the proposed floating dry dock location. In-water construction will 
include installation of a maximum of 56 24-inch concrete piles using 
impact pile driving and high-pressure water jetting and a maximum of 10 
24-inch steel pipe piles using impact and vibratory pile driving. 
Sounds produced by these activities may result in take, by Level B 
harassment, of marine mammals located in San Diego Bay, California. In-
water pile-driving activities are anticipated to occur for 50 days 
during the period from September 15, 2020 to September 14, 2021.

Dates and Duration

    In-water activities (pile installation) associated with the project 
are anticipated to begin September 15, 2020, and be completed by 
September 14, 2021. Pile driving activities would occur for 50 days 
during the proposed project dates. In-water activities will occur 
during daylight hours only.

Specific Geographic Region

    The activities would occur in the south-central portion of San 
Diego Bay (Figure 1). San Diego Bay is a narrow, crescent-shaped 
natural embayment oriented northwest-southeast with an approximate 
length of 24 kilometers (km) (15 miles (mi)) and a total area of 
roughly 4 km\2\ (11,000 acres; Port of San Diego, 2007). The width of 
the Bay ranges from 0.3 to 5.8 km (0.2 to 3.6 mi), and depths range 
from 23 m (74 ft) Mean Lower Low Water (MLLW) near the tip of Ballast 
Point to less than 1.2 m (4 ft) at the southern end (Merkel and 
Associates, Inc., 2009). Approximately half of the Bay is less than 4.5 
meters (m) (15 feet (ft)) deep and much of it is less than 15 m (50 ft) 
deep (Merkel and Associates, Inc., 2009). The northern and central 
portions of the Bay have been shaped by historical dredging and filling 
to support large ship navigation and shoreline development. The United 
States Army Corps of Engineers dredges the main navigation channel in 
the Bay to maintain a depth of 14 m (47 ft) MLLW and is responsible for 
providing safe transit for private, commercial, and military vessels 
within the bay (NOAA 2012). Outside of the navigation channel, the bay 
floor consists of platforms at depths that vary slightly (Merkel and 
Associates, Inc., 2009). Within the Central Bay, typical depths range 
from 10.7-11.6 m (35-38 ft) MLLW to support large ship turning and 
anchorage, and small vessel marinas are typically dredged to depths of 
4.6 m (15 ft) MLLW (Merkel and Associates, Inc., 2009). The area around 
the proposed project site is approximately 0.01 km\2\ (2.72 acres) with 
bathymetry ranging from 2.5-4 m (8-13 ft) MLLW (Triton Engineers 2019). 
Proposed dredging in the project area in preparation for the floating 
dry dock would increase this depth at the project site to 12 m (39 ft).

[[Page 21181]]

[GRAPHIC] [TIFF OMITTED] TN16AP20.000

    Benthic substrate in San Diego Bay is largely sand (Naval 
Facilities Engineering Command, Southwest and Port of San Diego Bay, 
2013) as tidal currents tend to keep the finer silt and clay fractions 
in suspension, except in harbors and elsewhere in the lee of structures 
where water movement is diminished. Much of the shoreline consists of 
riprap and manmade structures. The project site is a shallow subtidal 
area and contains an eelgrass bed less 1-acre in size (Triton 
Engineers, 2019; Merkel and Associates, Inc., 2018). Over-water 
structures such as the existing MGBW piles and dock structures provide 
substrates for the growth of algae and invertebrates off the bottom and 
support abundant fish populations. Eelgrass present within the project 
site is important habitat for invertebrates, fish, and birds (Naval 
Facilities Engineering Command, Southwest and Port of San Diego Bay, 
2013).
    San Diego Bay is heavily used by commercial, recreational, and 
military vessels, with an average of 82,413 vessel movements (in or out 
of the Bay) per year (approximately 225 vessel transits per day), a 
majority of which are presumed to occur during daylight hours. This 
number of transits does not include recreational boaters that use San 
Diego Bay, estimated to number 200,000 annually (San Diego Harbor 
Safety Committee 2009). Background (ambient) noise in the south-central 
San Diego Bay was an average of 126 decibels (dB) (L50) in 2019 (Dahl 
and Dall'Osto 2019). This is similar to ambient noise levels measured 
in the northern San Diego Bay which ranged from 126 to 137 dB (L50) in 
2014, 2015, and 2016 (Naval Facilities Engineering Command, Southwest, 
2018). Sound levels in the south-central San Diego Bay are likely lower 
due to the reduced ship traffic relative to the north San Diego Bay. 
Noise from non-impulsive sources associated with the proposed 
activities is, therefore assumed to become indistinguishable from 
background noise as it diminishes to 126 dB re: 1 micropascal 
([micro]Pa) with distance from the source (Dahl and Dall'Osto, 2019).

Detailed Description of Specific Activity

    The Navy proposes to construct a floating dry dock and associated 
pier-side access in the south-central portion of San Diego Bay. The 
floating dry dock is needed in order to address current and projected 
shortfall of dry dock space required for maintenance of the Pacific 
Fleet, and ensure the Naval Base San Diego's capability to conduct 
berth-side repair and maintenance of vessels. The proposed activities 
will allow for the emplacement and operation of a floating dry dock and 
associated pier-side access at MGBW Commercial Out Lease (COL) in the 
southern edge of Naval Base San Diego. The proposed project site is 
located immediately adjacent to the MGBW National City Boatyard, a 
full-service facility that specializes in refits, repairs, and new 
construction.
    Implementation of the proposed project requires in-water activities 
that will produce sounds that may result in take of marine mammals 
located in the San Diego Bay including dredging, installation of two 
mooring dolphins,

[[Page 21182]]

including vertical and angled structural piles, as well as fender 
piles, and installation of a concrete ramp wharf and vehicle bridge. 
Two mooring dolphins would be located forward and aft of the proposed 
dry dock. The mooring dolphins would each be supported by up to 16 
vertical 24-inch octagonal concrete piles (32 total) installed using 
impact pile driving and high-pressure water jetting. The aft mooring 
dolphin would also require approximately 2 24-inch angled steel pipe 
piles. Up to 8 additional 24-inch steel pipe piles are anticipated to 
be required for the forward and aft mooring dolphins. Cast-in-place 
reinforced concrete caps, 9.1 by 9.1 m (30 by 30 ft), would be 
installed at each mooring dolphin location. Grippers would be secured 
to the dolphins' concrete pile caps and used to hold the floating dry 
dock in position. Construction materials would be delivered by truck 
and the piles would be installed using a floating crane and an impact 
or vibratory pile driver aided by jetting methods. Fender piles 
associated with the aft mooring dolphin would consist of 2 steel pipe 
piles, 24-inches in diameter or less. All steel pipe piles would 
initially be installed using vibratory pile driving, followed by the 
use of an impact pile driver.
    Two pedestrian bridges and a vehicle bridge would be constructed to 
provide landside access and servicing to the proposed floating dry 
dock. The port-side pedestrian bridge, which would provide access to 
the port wing deck, would be 35 m (115 ft) long and supported by a 
landside concrete abutment. The proposed ramp wharf would be 
approximately 17 by 24 m (80 by 55 ft) long and would support an 18-m 
(60-ft) long vehicle bridge that would provide vehicle access to the 
MGBW COL floating dry dock. The ramp wharf would also support the 
starboard pedestrian bridge, which would provide access to the 
starboard wing deck. The concrete ramp wharf and vehicle bridge would 
cover approximately 0.12 acres (5,360 ft\2\) and would be supported by 
24 24-inch octagonal concrete piles installed using vibratory pile 
driving and high-pressure water jetting. These access structures, which 
would be similar to those currently provided at the south berth of the 
Mole Pier and other Navy piers in the vicinity, would allow for 
construction vehicles and heavy equipment to be used during maintenance 
of Navy vessels.
    Proposed pile driving activities are planned to occur from 
September 15, 2020 through September 14, 2021. The total number of pile 
driving days would not exceed 50 days during this time period.
    Proposed mitigation, monitoring, and reporting measures are 
described in detail later in this document (please see Proposed 
Mitigation and Proposed Monitoring and Reporting).

Description of Marine Mammals in the Area of Specified Activities

    Sections 3 and 4 of the application summarize available information 
regarding status and trends, distribution and habitat preferences, and 
behavior and life history, of the potentially affected species. 
Additional information regarding population trends and threats may be 
found in NMFS's Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments) and more general information about these species 
(e.g., physical and behavioral descriptions) may be found on NMFS's 
website (https://www.fisheries.noaa.gov/find-species).
    Table 1 lists all species or stocks for which take is expected and 
proposed to be authorized for this action, and summarizes information 
related to the population or stock, including regulatory status under 
the MMPA and ESA and potential biological removal (PBR), where known. 
For taxonomy, we follow Committee on Taxonomy (2019). PBR is defined by 
the MMPA as the maximum number of animals, not including natural 
mortalities, that may be removed from a marine mammal stock while 
allowing that stock to reach or maintain its optimum sustainable 
population (as described in NMFS's SARs). While no mortality is 
anticipated or authorized here, PBR and annual serious injury and 
mortality from anthropogenic sources are included here as gross 
indicators of the status of the species and other threats.
    Marine mammal abundance estimates presented in this document 
represent the total number of individuals that make up a given stock or 
the total number estimated within a particular study or survey area. 
NMFS' stock abundance estimates for most species represent the total 
estimate of individuals within the geographic area, if known, that 
comprises that stock. For some species, this geographic area may extend 
beyond U.S. waters. All managed stocks in this region are assessed in 
NMFS' U.S. Pacific Stock Assessment Reports (e.g., Carretta et al., 
2019). All values presented in Table 1 are the most recent available at 
the time of publication and are available in the 2018 Final SARs 
(Carretta et al., 2019) (available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments).

                     Table 1--Marine Mammals Potentially Present Within Central San Diego, California, During the Specified Activity
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                                                                                                        Stock abundance
                                                                                                        (CV, Nmin, most
            Common name                Scientific name             Stock          ESA/ MMPA  status;    recent abundance        PBR        Annual  M/SI
                                                                                 strategic  (Y/N) \1\     survey) \2\                           \3\
 
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                                                         Order Carnivora--Superfamily Pinnipedia
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Family Otariidae (eared seals and sea lions):
    California sea lion...........  Zalophus               U.S.................  -, -, N.............      257,606 (N/A,          14,011            >321
                                     californianus.                                                       233,515, 2014)
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\1\ Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed
  under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality
  exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
  under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\2\ NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments assessments. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable. California sea lion
  population size was estimated from a 1975-2014 time series of pup counts (Lowry et al. 2017), combined with mark-recapture estimates of survival rates
  (DeLong et al. 2017, Laake et al. 2018).

[[Page 21183]]

 
\3\ These values, found in NMFS' SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial
  fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated
  with estimated mortality due to commercial fisheries is presented in some cases.
NOTE--Italicized species are not expected to be taken or proposed for authorization.

    As indicated above, one species (with one managed stock) in Table 1 
temporally and spatially co-occurs with the activity to the degree that 
take is reasonably likely to occur, and we have proposed authorizing 
it. The most frequently observed marine mammal species in San Diego Bay 
are the California sea lion (Zalophus californianus), which often rests 
on buoys and other structures and occurs throughout the North to North-
Central Bay; coastal bottlenose dolphin (Tursiops truncatus), which is 
regularly seen in the North Bay; Pacific harbor seal (Phoca vitulina), 
which frequently enters the North Bay; and common dolphins (Delphinus 
spp.), which are rare visitors in the North Bay. Gray whales 
(Eschrichtius robustus) are occasionally sighted near the mouth of San 
Diego Bay during their winter migration (Naval Facilities Engineering 
Command, Southwest and Port of San Diego Bay, 2013). Based on many 
years of observations and numerous Navy-funded surveys in San Diego Bay 
(Merkel and Associates, Inc., 2008; Sorensen and Swope, 2010; Graham 
and Saunders, 2014; Tierra Data Inc., 2016), marine mammals rarely 
occur south of the Coronado Bay Bridge, are not known to occur near 
Naval Base San Diego with any regularity, and any occurrence in the 
project area would be very rare. Therefore, while coastal bottlenose 
dolphins, Pacific harbor seals, common dolphins, and gray whales have 
been reported in San Diego Bay, they are not anticipated to occur in 
the project area and no take of these species is anticipated. The only 
species that is anticipated to occur south of the Coronado Bridge with 
any regularity is the California sea lion, based on the sighting of two 
individuals during 2010 surveys (Sorensen and Swope, 2010). Therefore, 
only impacts to the California sea lion are evaluated in this IHA.

Pinnipeds

California Sea Lion
    California sea lions inhabit the eastern North Pacific Ocean from 
Islas Marias north of Puerto Vallarta, Mexico, north throughout the 
Gulf of California, and along the Baja California Peninsula north to 
the Gulf of Alaska. The U.S. stock ranges from the U.S./Mexico border 
to Canada. They occupy shallow ocean waters and prefer sandy beaches or 
rocky coves for breeding and haul-out sites, however they also commonly 
haul out on marina docks, jetties, and buoys. Pupping and breeding 
occur from May through July outside of the proposed project timeframe. 
Rookery sites in Southern California include San Miguel Island and to 
the more southerly Channel Islands of San Nicolas, Santa Barbara, and 
San Clemente (Lowry et al. 2017). California sea lions commonly forage 
on a variety of prey including fish and squid, and exhibit annual 
migratory movements between breeding and foraging habitats. From August 
to December, adult and sub-adult males migrate north along the U.S. 
west coast to foraging areas along the coasts of California, Oregon, 
Washington, British Columbia, Canada, and southeast Alaska. In the 
spring, males migrate southward to breeding rookeries in the Channel 
Islands and Mexico. Females and pups/juveniles commonly stay near 
breeding areas (Lowry et al. 2017), but some females may migrate as far 
north as San Francisco Bay in winter, and during El Ni[ntilde]o events, 
have been observed as far north as central Oregon. The California sea 
lion molts gradually over several months during late summer and fall.
    As with most sea lions, a complete population count of all harbor 
seals in California is not possible as all members of the population 
are not ashore simultaneously. Population estimates for the U.S. stock 
have increased since the 1970s and are derived from 3 primary data 
sources: 1) annual pup counts (Lowry et al. 2017); 2) annual 
survivorship estimates from mark-recapture data (DeLong et al. 2017); 
and 3) estimates of human-caused serious injuries, mortalities, and 
bycatch (Carretta and Enriquez 2012a, 2012b, Carretta et al. 2016, 
Carretta et al. 2018a, 2018b). Using a logistic growth model and 
reconstructed population size estimates from 1975-2014, Laake et al. 
(2018) estimated a net productivity rate of 7 percent per year. The 
population is considered within the range of its optimum sustainable 
population (OSP) size (Laake et al. 2018).
    From January 2013 through September 2016, a greater than expected 
number of young malnourished California sea lions stranded along the 
coast of California and NMFS declared this an Unusual Mortality Event. 
Sea lions stranding from an early age (6-8 months old) through two 
years of age (hereafter referred to as juveniles) were consistently 
underweight without other disease processes detected. The primary cause 
of the UME was malnutrition of sea lion pups and yearlings due to 
ecological factors. These factors included shifts in distribution, 
abundance and/or quality of sea lion prey items around the Channel 
Island rookeries during critical sea lion life history events (nursing 
by adult females, and transitioning from milk to prey by young sea 
lions). Threats to the U.S. stock include interactions with fisheries, 
entanglement in marine debris, entrainment in power plant intakes, oil 
exposure, vessel strikes, dog attacks, and human interactions/
harassment (shootings, direct removals) (Carretta et al., 2019).
    In San Diego Bay, in general, California sea lions regularly occur 
on rocks, buoys and other structures, and especially on bait barges, 
although numbers vary greatly. California sea lion occurrence in the 
project area is expected to be rare based on sighting of only two 
individuals in the water off of Navy Base San Diego during one 2010 
survey (Sorensen and Swope, 2010). The Sorenson and Swope (2010) survey 
is the only known survey to provide marine mammal observation data 
below the San Diego Coronado Bridge (in mid San Diego Bay). The single 
survey was on February 16, 2010. During this survey one single sea lion 
was observed off Pier 3 and one single sea lion was observed ~600m from 
the proposed project site.

Habitat

    No ESA-designated critical habitat or Biologically Important Areas 
overlap with the project area.

Marine Mammal Hearing

    Hearing is the most important sensory modality for marine mammals 
underwater, and exposure to anthropogenic sound can have deleterious 
effects. To appropriately assess the potential effects of exposure to 
sound, it is necessary to understand the frequency ranges marine 
mammals are able to hear. Current data indicate that not all marine 
mammal species have equal hearing capabilities (e.g., Richardson et 
al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect 
this, Southall et al. (2007) recommended that marine mammals be divided 
into functional hearing groups based on directly measured or estimated 
hearing ranges on the basis of available behavioral response data, 
audiograms

[[Page 21184]]

derived using auditory evoked potential techniques, anatomical 
modeling, and other data. Note that no direct measurements of hearing 
ability have been successfully completed for mysticetes (i.e., low-
frequency cetaceans). Subsequently, NMFS (2018) described generalized 
hearing ranges for these marine mammal hearing groups. Generalized 
hearing ranges were chosen based on the approximately 65 dB threshold 
from the normalized composite audiograms, with the exception for lower 
limits for low-frequency cetaceans where the lower bound was deemed to 
be biologically implausible and the lower bound from Southall et al. 
(2007) retained. Marine mammal hearing groups and their associated 
hearing ranges are provided in Table 2.

                  Table 2--Marine Mammal Hearing Groups
                              [NMFS, 2018]
------------------------------------------------------------------------
            Hearing group                 Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen  7 Hz to 35 kHz.
 whales).
Mid-frequency (MF) cetaceans          150 Hz to 160 kHz.
 (dolphins, toothed whales, beaked
 whales, bottlenose whales).
High-frequency (HF) cetaceans (true   275 Hz to 160 kHz.
 porpoises, Kogia, river dolphins,
 cephalorhynchid, Lagenorhynchus
 cruciger & L. australis).
Phocid pinnipeds (PW) (underwater)    50 Hz to 86 kHz.
 (true seals).
Otariid pinnipeds (OW) (underwater)   60 Hz to 39 kHz.
 (sea lions and fur seals).
------------------------------------------------------------------------
* Represents the generalized hearing range for the entire group as a
  composite (i.e., all species within the group), where individual
  species' hearing ranges are typically not as broad. Generalized
  hearing range chosen based on ~65 dB threshold from normalized
  composite audiogram, with the exception for lower limits for LF
  cetaceans (Southall et al. 2007) and PW pinniped (approximation).

    The pinniped functional hearing group was modified from Southall et 
al. (2007) on the basis of data indicating that phocid species have 
consistently demonstrated an extended frequency range of hearing 
compared to otariids, especially in the higher frequency range 
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth and Holt, 
2013).
    For more detail concerning these groups and associated frequency 
ranges, please see NMFS (2018) for a review of available information. 
One marine mammal species (otariid pinniped species) has the reasonable 
potential to co-occur with the proposed activities. Please refer to 
Table 1.

Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat

    This section includes a summary and discussion of the ways that 
components of the specified activity may impact marine mammals and 
their habitat. The Estimated Take by Incidental Harassment section 
later in this document includes a quantitative analysis of the number 
of individuals that are expected to be taken by this activity. The 
Negligible Impact Analysis and Determination section considers the 
content of this section, the Estimated Take by Incidental Harassment 
section, and the Proposed Mitigation section, to draw conclusions 
regarding the likely impacts of these activities on the reproductive 
success or survivorship of individuals and how those impacts on 
individuals are likely to impact marine mammal species or stocks.

Description of Sound Sources

    The marine soundscape is comprised of both ambient and 
anthropogenic sounds. Ambient sound is defined as the all-encompassing 
sound in a given place and is usually a composite of sound from many 
sources both near and far (ANSI, 1995). The sound level of an area is 
defined by the total acoustical energy being generated by known and 
unknown sources. These sources may include physical (e.g., waves, wind, 
precipitation, earthquakes, ice, atmospheric sound), biological (e.g., 
sounds produced by marine mammals, fish, and invertebrates), and 
anthropogenic sound (e.g., vessels, dredging, aircraft, construction).
    The sum of the various natural and anthropogenic sound sources at 
any given location and time--which comprise ``ambient'' or 
``background'' sound--depends not only on the source levels (as 
determined by current weather conditions and levels of biological and 
shipping activity) but also on the ability of sound to propagate 
through the environment. In turn, sound propagation is dependent on the 
spatially and temporally varying properties of the water column and sea 
floor, and is frequency-dependent. As a result of the dependence on a 
large number of varying factors, ambient sound levels can be expected 
to vary widely over both coarse and fine spatial and temporal scales. 
Sound levels at a given frequency and location can vary by 10-20 dB 
from day to day (Richardson et al., 1995). The result is that, 
depending on the source type and its intensity, sound from the 
specified activity may be a negligible addition to the local 
environment or could form a distinctive signal that may affect marine 
mammals.
    In-water construction activities associated with the project would 
include impact pile driving, vibratory pile driving, and high pressure 
water jetting. The sounds produced by these activities fall into one of 
two general sound types: Impulsive and non-impulsive. Impulsive sounds 
(e.g., explosions, gunshots, sonic booms, impact pile driving) are 
typically transient, brief (less than 1 second), broadband, and consist 
of high peak sound pressure with rapid rise time and rapid decay (ANSI, 
1986; NIOSH, 1998; ANSI, 2005; NMFS, 2018). Non-impulsive sounds (e.g. 
aircraft, vessels, machinery operations such as drilling or dredging, 
vibratory pile driving, and active sonar systems) can be broadband, 
narrowband or tonal, brief or prolonged (continuous or intermittent), 
and typically do not have the high peak sound pressure with raid rise/
decay time that impulsive sounds do (ANSI, 1995; NIOSH, 1998; NMFS, 
2018). The distinction between these two sound types is important 
because they have differing potential to cause physical effects, 
particularly with regard to hearing (e.g., Ward, 1997 in Southall et 
al., 2007).
    Two types of pile hammers would be used on this project: Impact and 
vibratory. Impact hammers operate by repeatedly dropping a heavy piston 
onto a pile to drive the pile into the substrate. Sound generated by 
impact hammers is characterized by rapid rise times and high peak 
levels, a potentially injurious combination (Hastings and Popper 2005). 
Vibratory hammers install piles by vibrating them and allowing the 
weight of the hammer to push the pile into the sediment. Vibratory 
hammers produce significantly less sound than impact hammers. Peak 
sound pressure level (SPL) may be 180 dB or greater,

[[Page 21185]]

but are generally 10 to 20 dB lower than SPLs generated during impact 
pile driving of the same-sized pile (Oestman et al., 2009). Rise time 
is slower, reducing the probability and severity of injury, and sound 
energy is distributed over a greater amount of time (Nedwell and 
Edwards, 2002; Carlson et al., 2005).
    The likely or possible impacts of Navy's proposed activity on 
marine mammals could involve both non-acoustic and acoustic stressors. 
Potential non-acoustic stressors could result from the physical 
presence of the equipment and personnel; however, any impacts to marine 
mammals are expected to primarily be acoustic in nature. Acoustic 
stressors include effects of heavy equipment operation during pile 
installation.

Acoustic Impacts

    The introduction of anthropogenic noise into the aquatic 
environment from pile driving is the primary means by which marine 
mammals may be harassed from Navy's specified activity. In general, 
animals exposed to natural or anthropogenic sound may experience 
physical and psychological effects, ranging in magnitude from none to 
severe (Southall et al., 2007). Exposure to in-water construction noise 
has the potential to result in auditory threshold shifts and behavioral 
reactions (e.g., avoidance, temporary cessation of foraging and 
vocalizing, changes in dive behavior) and/or lead to non-observable 
physiological responses such an increase in stress hormones (Richardson 
et al., 1995; Gordon et al., 2004; Nowacek et al., 2007; Southall et 
al., 2007; Gotz et al., 2009). Additional noise in a marine mammal's 
habitat can mask acoustic cues used by marine mammals to carry out 
daily functions such as communication and predator and prey detection. 
The effects of pile driving on marine mammals are dependent on several 
factors, including, but not limited to, sound type (e.g., impulsive vs. 
non-impulsive), the species, age and sex class (e.g., adult male vs. 
mom with calf), duration of exposure, the distance between the pile and 
the animal, received levels, behavior at time of exposure, and previous 
history with exposure (Wartzok et al., 2004; Southall et al., 2007). 
Here we discuss physical auditory effects (threshold shifts), followed 
by behavioral effects and potential impacts on habitat.
    Richardson et al. (1995) described zones of increasing intensity of 
effect that might be expected to occur, in relation to distance from a 
source and assuming that the signal is within an animal's hearing 
range. First is the area within which the acoustic signal would be 
audible (potentially perceived) to the animal, but not strong enough to 
elicit any overt behavioral or physiological response. The next zone 
corresponds with the area where the signal is audible to the animal and 
of sufficient intensity to elicit behavioral or physiological 
responsiveness. Third is a zone within which, for signals of high 
intensity, the received level is sufficient to potentially cause 
discomfort or tissue damage to auditory or other systems. Overlaying 
these zones to a certain extent is the area within which masking (i.e., 
when a sound interferes with or masks the ability of an animal to 
detect a signal of interest that is above the absolute hearing 
threshold) may occur; the masking zone may be highly variable in size.
    We describe the more severe effects (i.e., permanent hearing 
impairment, certain non-auditory physical or physiological effects) 
only briefly as we do not expect that there is a reasonable likelihood 
that Navy's activities would result in such effects (see below for 
further discussion). NMFS defines a noise-induced threshold shift (TS) 
as a change, usually an increase, in the threshold of audibility at a 
specified frequency or portion of an individual's hearing range above a 
previously established reference level (NMFS, 2018). The amount of 
threshold shift is customarily expressed in dB. A TS can be permanent 
or temporary. As described in NMFS (2018), there are numerous factors 
to consider when examining the consequence of TS, including, but not 
limited to, the signal temporal pattern (e.g., impulsive or non-
impulsive), likelihood an individual would be exposed for a long enough 
duration or to a high enough level to induce a TS, the magnitude of the 
TS, time to recovery (seconds to minutes or hours to days), the 
frequency range of the exposure (i.e., spectral content), the hearing 
and vocalization frequency range of the exposed species relative to the 
signal's frequency spectrum (i.e., how animal uses sound within the 
frequency band of the signal; e.g., Kastelein et al., 2014b), and the 
overlap between the animal and the source (e.g., spatial, temporal, and 
spectral).
    Permanent Threshold Shift (PTS)--NMFS defines PTS as a permanent, 
irreversible increase in the threshold of audibility at a specified 
frequency or portion of an individual's hearing range above a 
previously established reference level (NMFS 2018). Available data from 
humans and other terrestrial mammals indicate that a 40 dB threshold 
shift approximates PTS onset (see Ward et al., 1958, 1959; Ward, 1960; 
Kryter et al., 1966; Miller, 1974; Ahroon et al., 1996; Henderson et 
al., 2008). PTS levels for marine mammals are estimates, as with the 
exception of a single study unintentionally inducing PTS in a harbor 
seal (Kastak et al. 2008), there are no empirical data measuring PTS in 
marine mammals largely due to the fact that, for various ethical 
reasons, experiments involving anthropogenic noise exposure at levels 
inducing PTS are not typically pursued or authorized (NMFS 2018).
    Temporary Threshold Shift (TTS)--A temporary, reversible increase 
in the threshold of audibility at a specified frequency or portion of 
an individual's hearing range above a previously established reference 
level (NMFS, 2018). Based on data from cetacean TTS measurements (see 
Southall et al., 2007), a TTS of 6 dB is considered the minimum 
threshold shift clearly larger than any day-to-day or session-to-
session variation in a subject's normal hearing ability (Schlundt et 
al. 2000; Finneran et al. 2000, 2002). As described in Finneran (2016), 
marine mammal studies have shown the amount of TTS increases with 
cumulative sound exposure level (SELcum) in an accelerating fashion: At 
low exposures with lower SELcum, the amount of TTS is typically small 
and the growth curves have shallow slopes. At exposures with higher 
higher SELcum, the growth curves become steeper and approach linear 
relationships with the noise SEL.
    Depending on the degree (elevation of threshold in dB), duration 
(i.e., recovery time), and frequency range of TTS, and the context in 
which it is experienced, TTS can have effects on marine mammals ranging 
from discountable to serious (similar to those discussed in auditory 
masking, below). For example, a marine mammal may be able to readily 
compensate for a brief, relatively small amount of TTS in a non-
critical frequency range that takes place during a time when the animal 
is traveling through the open ocean, where ambient noise is lower and 
there are not as many competing sounds present. Alternatively, a larger 
amount and longer duration of TTS sustained during time when 
communication is critical for successful mother/calf interactions could 
have more serious impacts. We note that reduced hearing sensitivity as 
a simple function of aging has been observed in marine mammals, as well 
as humans and other taxa (Southall et al., 2007), so we can infer that 
strategies exist for coping with this condition to some degree, though 
likely not without cost.

[[Page 21186]]

    Currently, TTS data only exist for four species of cetaceans 
(bottlenose dolphin, beluga whale (Delphinapterus leucas), harbor 
porpoise (Phocoena phocoena), and Yangtze finless porpoise (Neophocoena 
asiaeorientalis)) and five species of pinnipeds exposed to a limited 
number of sound sources (i.e., mostly tones and octave-band noise) in 
laboratory settings (Finneran, 2015). TTS was not observed in trained 
spotted (Phoca largha) and ringed (Pusa hispida) seals exposed to 
impulsive noise at levels matching previous predictions of TTS onset 
(Reichmuth et al. 2016). In general, harbor seals and harbor porpoises 
have a lower TTS onset than other measured pinniped or cetacean species 
(Finneran, 2015). Additionally, the existing marine mammal TTS data 
come from a limited number of individuals within these species. No data 
are available on noise-induced hearing loss for mysticetes. For 
summaries of data on TTS in marine mammals or for further discussion of 
TTS onset thresholds, please see Southall et al. (2007), Finneran and 
Jenkins (2012), Finneran (2015), and Table 5 in NMFS (2018). Installing 
piles requires a combination of impact pile driving and vibratory pile 
driving. For the project, these activities would not occur at the same 
time and there would likely be pauses in activities producing the sound 
during each day. Given these pauses and that many marine mammals are 
likely moving through the action area and not remaining for extended 
periods of time, the potential for TS declines.
    Behavioral Harassment--Behavioral disturbance may include a variety 
of effects, including subtle changes in behavior (e.g., minor or brief 
avoidance of an area or changes in vocalizations), more conspicuous 
changes in similar behavioral activities, and more sustained and/or 
potentially severe reactions, such as displacement from or abandonment 
of high-quality habitat. Disturbance may result in changing durations 
of surfacing and dives, number of blows per surfacing, or moving 
direction and/or speed; reduced/increased vocal activities; changing/
cessation of certain behavioral activities (such as socializing or 
feeding); visible startle response or aggressive behavior (such as 
tail/fluke slapping or jaw clapping); avoidance of areas where sound 
sources are located. Pinnipeds may increase their haul out time, 
possibly to avoid in-water disturbance (Thorson and Reyff 2006). 
Behavioral responses to sound are highly variable and context-specific 
and any reactions depend on numerous intrinsic and extrinsic factors 
(e.g., species, state of maturity, experience, current activity, 
reproductive state, auditory sensitivity, time of day), as well as the 
interplay between factors (e.g., Richardson et al., 1995; Wartzok et 
al., 2003; Southall et al., 2007; Weilgart, 2007; Archer et al., 2010). 
Behavioral reactions can vary not only among individuals but also 
within an individual, depending on previous experience with a sound 
source, context, and numerous other factors (Ellison et al., 2012), and 
can vary depending on characteristics associated with the sound source 
(e.g., whether it is moving or stationary, number of sources, distance 
from the source). In general, pinnipeds seem more tolerant of, or at 
least habituate more quickly to, potentially disturbing underwater 
sound than do cetaceans, and generally seem to be less responsive to 
exposure to industrial sound than most cetaceans. Please see Appendices 
B-C of Southall et al. (2007) for a review of studies involving marine 
mammal behavioral responses to sound.
    Habituation can occur when an animal's response to a stimulus wanes 
with repeated exposure, usually in the absence of unpleasant associated 
events (Wartzok et al., 2003). Animals are most likely to habituate to 
sounds that are predictable and unvarying. It is important to note that 
habituation is appropriately considered as a ``progressive reduction in 
response to stimuli that are perceived as neither aversive nor 
beneficial,'' rather than as, more generally, moderation in response to 
human disturbance (Bejder et al., 2009). The opposite process is 
sensitization, when an unpleasant experience leads to subsequent 
responses, often in the form of avoidance, at a lower level of 
exposure.
    As noted above, behavioral state may affect the type of response. 
For example, animals that are resting may show greater behavioral 
change in response to disturbing sound levels than animals that are 
highly motivated to remain in an area for feeding (Richardson et al., 
1995; NRC, 2003; Wartzok et al., 2003). Controlled experiments with 
captive marine mammals have showed pronounced behavioral reactions, 
including avoidance of loud sound sources (Ridgway et al., 1997; 
Finneran et al., 2003). Observed responses of wild marine mammals to 
loud pulsed sound sources (typically seismic airguns or acoustic 
harassment devices) have been varied but often consist of avoidance 
behavior or other behavioral changes suggesting discomfort (Morton and 
Symonds 2002; see also Richardson et al., 1995; Nowacek et al., 2007).
    Available studies show wide variation in response to underwater 
sound; therefore, it is difficult to predict specifically how any given 
sound in a particular instance might affect marine mammals perceiving 
the signal. If a marine mammal does react briefly to an underwater 
sound by changing its behavior or moving a small distance, the impacts 
of the change are unlikely to be significant to the individual, let 
alone the stock or population. However, if a sound source displaces 
marine mammals from an important feeding or breeding area for a 
prolonged period, impacts on individuals and populations could be 
significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007; NRC, 
2005). However, there are broad categories of potential response, which 
we describe in greater detail here, that include alteration of dive 
behavior, alteration of foraging behavior, effects to breathing, 
interference with or alteration of vocalization, avoidance, and flight.
    Changes in dive behavior can vary widely, and may consist of 
increased or decreased dive times and surface intervals as well as 
changes in the rates of ascent and descent during a dive (e.g., Frankel 
and Clark 2000; Costa et al., 2003; Ng and Leung 2003; Nowacek et al., 
2004; Goldbogen et al., 2013a,b). Variations in dive behavior may 
reflect interruptions in biologically significant activities (e.g., 
foraging) or they may be of little biological significance. The impact 
of an alteration to dive behavior resulting from an acoustic exposure 
depends on what the animal is doing at the time of the exposure and the 
type and magnitude of the response.
    Disruption of feeding behavior can be difficult to correlate with 
anthropogenic sound exposure, so it is usually inferred by observed 
displacement from known foraging areas, the appearance of secondary 
indicators (e.g., bubble nets or sediment plumes), or changes in dive 
behavior. As for other types of behavioral response, the frequency, 
duration, and temporal pattern of signal presentation, as well as 
differences in species sensitivity, are likely contributing factors to 
differences in response in any given circumstance (e.g., Croll et al., 
2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko et al., 
2007). A determination of whether foraging disruptions incur fitness 
consequences would require information on or estimates of the energetic 
requirements of the affected individuals and the relationship between 
prey availability, foraging effort and success, and the life history 
stage of the animal.
    Variations in respiration naturally vary with different behaviors 
and

[[Page 21187]]

alterations to breathing rate as a function of acoustic exposure can be 
expected to co-occur with other behavioral reactions, such as a flight 
response or an alteration in diving. However, respiration rates in and 
of themselves may be representative of annoyance or an acute stress 
response. Various studies have shown that respiration rates may either 
be unaffected or could increase, depending on the species and signal 
characteristics, again highlighting the importance in understanding 
species differences in the tolerance of underwater noise when 
determining the potential for impacts resulting from anthropogenic 
sound exposure (e.g., Kastelein et al., 2001, 2005b, 2006; Gailey et 
al., 2007).
    Marine mammals vocalize for different purposes and across multiple 
modes, such as whistling, echolocation click production, calling, and 
singing. Changes in vocalization behavior in response to anthropogenic 
noise can occur for any of these modes and may result from a need to 
compete with an increase in background noise or may reflect increased 
vigilance or a startle response. For example, in the presence of 
potentially masking signals, humpback whales and killer whales have 
been observed to increase the length of their songs (Miller et al., 
2000; Fristrup et al., 2003; Foote et al., 2004), while right whales 
(Eubalaena glacialis) have been observed to shift the frequency content 
of their calls upward while reducing the rate of calling in areas of 
increased anthropogenic noise (Parks et al., 2007b). In some cases, 
animals may cease sound production during production of aversive 
signals (Bowles et al., 1994).
    Avoidance is the displacement of an individual from an area or 
migration path as a result of the presence of a sound or other 
stressors, and is one of the most obvious manifestations of disturbance 
in marine mammals (Richardson et al., 1995). For example, gray whales 
(Eschrictius robustus) are known to change direction--deflecting from 
customary migratory paths--in order to avoid noise from seismic surveys 
(Malme et al., 1984). Avoidance may be short-term, with animals 
returning to the area once the noise has ceased (e.g., Bowles et al., 
1994; Goold 1996; Stone et al., 2000; Morton and Symonds, 2002; Gailey 
et al., 2007). Longer-term displacement is possible, however, which may 
lead to changes in abundance or distribution patterns of the affected 
species in the affected region if habituation to the presence of the 
sound does not occur (e.g., Blackwell et al., 2004; Bejder et al., 
2006; Teilmann et al., 2006).
    A flight response is a dramatic change in normal movement to a 
directed and rapid movement away from the perceived location of a sound 
source. The flight response differs from other avoidance responses in 
the intensity of the response (e.g., directed movement, rate of 
travel). Relatively little information on flight responses of marine 
mammals to anthropogenic signals exist, although observations of flight 
responses to the presence of predators have occurred (Connor and 
Heithaus, 1996). The result of a flight response could range from 
brief, temporary exertion and displacement from the area where the 
signal provokes flight to, in extreme cases, marine mammal strandings 
(Evans and England, 2001). However, it should be noted that response to 
a perceived predator does not necessarily invoke flight (Ford and 
Reeves 2008), and whether individuals are solitary or in groups may 
influence the response.
    Behavioral disturbance can also impact marine mammals in more 
subtle ways. Increased vigilance may result in costs related to 
diversion of focus and attention (i.e., when a response consists of 
increased vigilance, it may come at the cost of decreased attention to 
other critical behaviors such as foraging or resting). These effects 
have generally not been demonstrated for marine mammals, but studies 
involving fish and terrestrial animals have shown that increased 
vigilance may substantially reduce feeding rates (e.g., Beauchamp and 
Livoreil 1997; Fritz et al,, 2002; Purser and Radford 2011). In 
addition, chronic disturbance can cause population declines through 
reduction of fitness (e.g., decline in body condition) and subsequent 
reduction in reproductive success, survival, or both (e.g., Harrington 
and Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). However, 
Ridgway et al. (2006) reported that increased vigilance in bottlenose 
dolphins exposed to sound over a five-day period did not cause any 
sleep deprivation or stress effects.
    Many animals perform vital functions, such as feeding, resting, 
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption 
of such functions resulting from reactions to stressors such as sound 
exposure are more likely to be significant if they last more than one 
diel cycle or recur on subsequent days (Southall et al., 2007). 
Consequently, a behavioral response lasting less than one day and not 
recurring on subsequent days is not considered particularly severe 
unless it could directly affect reproduction or survival (Southall et 
al., 2007). Note that there is a difference between multi-day 
substantive behavioral reactions and multi-day anthropogenic 
activities. For example, just because an activity lasts for multiple 
days does not necessarily mean that individual animals are either 
exposed to activity-related stressors for multiple days or, further, 
exposed in a manner resulting in sustained multi-day substantive 
behavioral responses.
    Stress responses--An animal's perception of a threat may be 
sufficient to trigger stress responses consisting of some combination 
of behavioral responses, autonomic nervous system responses, 
neuroendocrine responses, or immune responses (e.g., Seyle, 1950; 
Moberg, 2000). In many cases, an animal's first and sometimes most 
economical (in terms of energetic costs) response is behavioral 
avoidance of the potential stressor. Autonomic nervous system responses 
to stress typically involve changes in heart rate, blood pressure, and 
gastrointestinal activity. These responses have a relatively short 
duration and may or may not have a significant long-term effect on an 
animal's fitness.
    Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that 
are affected by stress--including immune competence, reproduction, 
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been 
implicated in failed reproduction, altered metabolism, reduced immune 
competence, and behavioral disturbance (e.g., Moberg, 1987; Blecha, 
2000). Increases in the circulation of glucocorticoids are also equated 
with stress (Romano et al., 2004).
    The primary distinction between stress (which is adaptive and does 
not normally place an animal at risk) and ``distress'' is the cost of 
the response. During a stress response, an animal uses glycogen stores 
that can be quickly replenished once the stress is alleviated. In such 
circumstances, the cost of the stress response would not pose serious 
fitness consequences. However, when an animal does not have sufficient 
energy reserves to satisfy the energetic costs of a stress response, 
energy resources must be diverted from other functions. This state of 
distress will last until the animal replenishes its energetic reserves 
sufficient to restore normal function.
    Relationships between these physiological mechanisms, animal 
behavior, and the costs of stress responses are well-studied through 
controlled experiments and for both laboratory and free-ranging animals 
(e.g., Holberton et al., 1996; Hood et al.,

[[Page 21188]]

1998; Jessop et al., 2003; Krausman et al., 2004; Lankford et al., 
2005). Stress responses due to exposure to anthropogenic sounds or 
other stressors and their effects on marine mammals have also been 
reviewed (Fair and Becker 2000; Romano et al., 2002b) and, more rarely, 
studied in wild populations (e.g., Romano et al., 2002a). For example, 
Rolland et al. (2012) found that noise reduction from reduced ship 
traffic in the Bay of Fundy was associated with decreased stress in 
North Atlantic right whales. These and other studies lead to a 
reasonable expectation that some marine mammals will experience 
physiological stress responses upon exposure to acoustic stressors and 
that it is possible that some of these would be classified as 
``distress.'' In addition, any animal experiencing TTS would likely 
also experience stress responses (NRC, 2003).
    Masking--Sound can disrupt behavior through masking, or interfering 
with, an animal's ability to detect, recognize, or discriminate between 
acoustic signals of interest (e.g., those used for intraspecific 
communication and social interactions, prey detection, predator 
avoidance, navigation) (Richardson et al., 1995). Masking occurs when 
the receipt of a sound is interfered with by another coincident sound 
at similar frequencies and at similar or higher intensity, and may 
occur whether the sound is natural (e.g., snapping shrimp, wind, waves, 
precipitation) or anthropogenic (e.g., pile driving, shipping, sonar, 
seismic exploration) in origin. The ability of a noise source to mask 
biologically important sounds depends on the characteristics of both 
the noise source and the signal of interest (e.g., signal-to-noise 
ratio, temporal variability, direction), in relation to each other and 
to an animal's hearing abilities (e.g., sensitivity, frequency range, 
critical ratios, frequency discrimination, directional discrimination, 
age or TTS hearing loss), and existing ambient noise and propagation 
conditions.
    Masking of natural sounds can result when human activities produce 
high levels of background sound at frequencies important to marine 
mammals. Conversely, if the background level of underwater sound is 
high (e.g. on a day with strong wind and high waves), an anthropogenic 
sound source would not be detectable as far away as would be possible 
under quieter conditions and would itself be masked. San Diego Bay is 
an active, industrialized harbor and hosts numerous recreational and 
commercial vessels; therefore, background sound levels in the San Diego 
Bay are already elevated by these activities.
    The frequency range of the potentially masking sound is important 
in determining any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation 
sounds produced by odontocetes but are more likely to affect detection 
of mysticete communication calls and other potentially important 
natural sounds such as those produced by surf and some prey species. 
The masking of communication signals by anthropogenic noise may be 
considered as a reduction in the communication space of animals (e.g., 
Clark et al., 2009) and may result in energetic or other costs as 
animals change their vocalization behavior (e.g., Miller et al., 2000; 
Foote et al., 2004; Parks et al., 2007b; Di Iorio and Clark, 2009; Holt 
et al., 2009). Masking can be reduced in situations where the signal 
and noise come from different directions (Richardson et al., 1995), 
through amplitude modulation of the signal, or through other 
compensatory behaviors (Houser and Moore, 2014). Masking can be tested 
directly in captive species (e.g., Erbe 2008), but in wild populations 
it must be either modeled or inferred from evidence of masking 
compensation. There are few studies addressing real-world masking 
sounds likely to be experienced by marine mammals in the wild (e.g., 
Branstetter et al., 2013).
    Masking affects both senders and receivers of acoustic signals and 
can potentially have long-term chronic effects on marine mammals at the 
population level as well as at the individual level. Low-frequency 
ambient sound levels have increased by as much as 20 dB (more than 
three times in terms of SPL) in the world's ocean from pre-industrial 
periods, with most of the increase from distant commercial shipping 
(Hildebrand, 2009). All anthropogenic sound sources, but especially 
chronic and lower-frequency signals (e.g., from vessel traffic), 
contribute to elevated ambient sound levels, thus intensifying masking.

Underwater Acoustic Effects

Potential Effects of High-Pressure Water Jetting Sound
    High-pressure water jetting may be used to assist with installation 
of concrete piles. Based on existing reference values, high-pressure 
water jetting noise was estimated to be 158 dB re: 1 [mu]Pa (rms) at 10 
m based on Naval Facilities Engineering Command, Southwest (2018) 
measures of high pressure jetting used on 16-inch round and 24x30-inch 
concrete piles. As previously described, San Diego Bay is an 
industrialized harbor and hosts numerous recreational and commercial 
vessels; therefore, background sound levels in the San Diego Bay are 
elevated by sounds produced by these vessels. The sounds produced by 
this activity are of similar frequencies to the sounds produced by 
vessels, and are anticipated to diminish to background noise levels (or 
be masked by background noise levels) in the Bay relatively close to 
the project site. Further, these activities are anticipated to occur on 
the same day as other installation methods. These animals would 
previously have been `taken' because of exposure to underwater sounds 
produced by pile driving. Thus, in these cases, behavioral harassment 
of these animals would already accounted for in these estimates of 
potential take. Therefore, for the reasons described above, we do not 
believe that authorization of incidental take resulting from high-
pressure water jetting is warranted, and impacts of water jetting are 
not discussed further.
Potential Effects of Pile Driving Sound
    The effects of sounds from pile driving might include one or more 
of the following: Temporary or permanent hearing impairment, non-
auditory physical or physiological effects, behavioral disturbance, and 
masking (Richardson et al., 1995; Gordon et al., 2003; Nowacek et al., 
2007; Southall et al., 2007). The effects of pile driving on marine 
mammals are dependent on several factors, including the type and depth 
of the animal; the pile size and type, and the intensity and duration 
of the pile driving sound; the substrate; the standoff distance between 
the pile and the animal; and the sound propagation properties of the 
environment. Impacts to marine mammals from pile driving activities are 
expected to result primarily from acoustic pathways. As such, the 
degree of effect is intrinsically related to the frequency, received 
level, and duration of the sound exposure, which are in turn influenced 
by the distance between the animal and the source. The further away 
from the source, the less intense the exposure should be. The substrate 
and depth of the habitat affect the sound propagation properties of the 
environment. In addition, substrates that are soft (e.g., sand) would 
absorb or attenuate the sound more readily than hard substrates (e.g., 
rock), which may reflect the acoustic wave. Soft porous substrates 
would also likely require less time to drive the pile, and possibly 
less forceful equipment, which would ultimately

[[Page 21189]]

decrease the intensity of the acoustic source.
    In the absence of mitigation, impacts to marine species could be 
expected to include physiological and behavioral responses to the 
acoustic signature (Viada et al., 2008). Potential effects from 
impulsive sound sources like pile driving can range in severity from 
effects such as behavioral disturbance to temporary or permanent 
hearing impairment (Yelverton et al., 1973). Due to the nature of the 
pile driving sounds in the project, behavioral disturbance is the most 
likely effect from the proposed activity. Marine mammals exposed to 
high intensity sound repeatedly or for prolonged periods can experience 
hearing threshold shifts. PTS constitutes injury, but TTS does not 
(Southall et al., 2007).
Non-Auditory Physiological Effects
    Non-auditory physiological effects or injuries that theoretically 
might occur in marine mammals exposed to strong underwater sound 
include stress, neurological effects, bubble formation, resonance 
effects, and other types of organ or tissue damage (Cox et al., 2006; 
Southall et al., 2007). Studies examining such effects are limited. In 
general, little is known about the potential for pile driving to cause 
non-auditory physical effects in marine mammals. Available data suggest 
that such effects, if they occur at all, would presumably be limited to 
short distances from the sound source and to activities that extend 
over a prolonged period. The available data do not allow identification 
of a specific exposure level above which non-auditory effects can be 
expected (Southall et al., 2007) or any meaningful quantitative 
predictions of the numbers (if any) of marine mammals that might be 
affected in those ways. We do not expect any non-auditory physiological 
effects because of mitigation that prevents animals from approach the 
source too closely, as well as source levels with very small Level A 
harassment isopleths. Marine mammals that show behavioral avoidance of 
pile driving, including some odontocetes and some pinnipeds, are 
especially unlikely to incur on-auditory physical effects.
Disturbance Reactions
    Responses to continuous sound, such as vibratory pile installation, 
have not been documented as well as responses to pulsed sounds. With 
both types of pile driving, it is likely that the onset of pile driving 
could result in temporary, short term changes in an animal's typical 
behavior and/or avoidance of the affected area. These behavioral 
changes may include (Richardson et al., 1995): Changing durations of 
surfacing and dives, number of blows per surfacing, or moving direction 
and/or speed; reduced/increased vocal activities; changing/cessation of 
certain behavioral activities (such as socializing or feeding); visible 
startle response or aggressive behavior (such as tail/fluke slapping or 
jaw clapping); avoidance of areas where sound sources are located; and/
or flight responses (e.g., pinnipeds flushing into water from haul-outs 
or rookeries). Pinnipeds may increase their haul out time, possibly to 
avoid in-water disturbance (Thorson and Reyff, 2006). If a marine 
mammal responds to a stimulus by changing its behavior (e.g., through 
relatively minor changes in locomotion direction/speed or vocalization 
behavior), the response may or may not constitute taking at the 
individual level, and is unlikely to affect the stock or the species as 
a whole. However, if a sound source displaces marine mammals from an 
important feeding or breeding area for a prolonged period, impacts on 
animals, and if so potentially on the stock or species, could 
potentially be significant (e.g., Lusseau and Bejder, 2007; Weilgart, 
2007).
    The biological significance of many of these behavioral 
disturbances is difficult to predict, especially if the detected 
disturbances appear minor. However, the consequences of behavioral 
modification could be expected to be biologically significant if the 
change affects growth, survival, or reproduction. Significant 
behavioral modifications that could potentially lead to effects on 
growth, survival, or reproduction include:
     Drastic changes in diving/surfacing patterns (such as 
those thought to cause beaked whale stranding due to exposure to 
military mid-frequency tactical sonar);
     Longer-term habitat abandonment due to loss of desirable 
acoustic environment; and
     Longer-term cessation of feeding or social interaction.
    The onset of behavioral disturbance from anthropogenic sound 
depends on both external factors (characteristics of sound sources and 
their paths) and the specific characteristics of the receiving animals 
(hearing, motivation, experience, demography) and is difficult to 
predict (Southall et al., 2007).
Auditory Masking
    Natural and artificial sounds can disrupt behavior by masking. The 
frequency range of the potentially masking sound is important in 
determining any potential behavioral impacts. The most intense 
underwater sounds in the proposed action are those produced by impact 
pile driving. Given that the energy distribution of pile driving covers 
a broad frequency spectrum, sound from these sources would likely be 
within the audible range of marine mammals present in the project area. 
Impact pile driving activity is relatively short-term, with rapid 
pulses occurring for less than fifteen minutes per pile. The 
probability for impact pile driving resulting from this proposed action 
masking acoustic signals important to the behavior and survival of 
marine mammal species is low. Vibratory pile driving is also relatively 
short-term, with rapid oscillations occurring for approximately 10 
minutes per pile. It is possible that vibratory pile driving resulting 
from this proposed action may mask acoustic signals important to the 
behavior and survival of marine mammal species, but the short-term 
duration and limited affected area would result in insignificant 
impacts from masking. Any masking event that could possibly rise to 
Level B harassment under the MMPA would occur concurrently within the 
zones of behavioral harassment already estimated for vibratory and 
impact pile driving, and which have already been taken into account in 
the exposure analysis. Active pile driving is anticipated to occur for 
less than two hours per day and for 50 days between September 15, 2020 
and September 14, 2021, so we do not anticipate masking to 
significantly affect marine mammals.
Airborne Acoustic Effects
    Pinnipeds that occur near the project site could be exposed to 
airborne sounds associated with pile driving that have the potential to 
cause behavioral harassment, depending on their distance from pile 
driving activities.
    Airborne noise would primarily be an issue for pinnipeds that are 
swimming or hauled out near the project site within the range of noise 
levels elevated above the acoustic criteria. Based on the lack of any 
pinniped haul-outs in the immediate vicinity of the project site, 
airborne noise associated with construction are not expected to have 
any impact on pinnipeds. We recognize that pinnipeds in the water could 
be exposed to airborne sound that may result in behavioral harassment 
when looking with their heads above water. Most likely, airborne sound 
would cause behavioral responses similar to those discussed above in 
relation to underwater sound. For instance, anthropogenic sound could 
cause hauled out pinnipeds to exhibit changes

[[Page 21190]]

in their normal behavior, such as reduction in vocalizations, or cause 
them to temporarily abandon the area and move further from the source. 
However, these animals would previously have been `taken' because of 
exposure to underwater sound above the behavioral harassment 
thresholds, which are in all cases larger than those associated with 
airborne sound. Thus, the behavioral harassment of these animals would 
already accounted for in these estimates of potential take. Therefore, 
we do not believe that authorization of incidental take resulting from 
airborne sound for pinnipeds is warranted, and airborne sound is not 
discussed further here.

Marine Mammal Habitat Effects

    The area likely impacted by the project is relatively small 
compared to the available habitat for California sea lions, and does 
not include any known areas of important habitat. Navy's proposed 
construction activities in San Diego Bay are of short duration and 
would not result in permanent negative impacts to habitats used 
directly by marine mammals, but could have localized, temporary impacts 
on marine mammal habitat and their prey by increasing underwater and 
airborne SPLs and slightly decreasing water quality. Increased noise 
levels may affect acoustic habitat (see masking discussion above) and 
adversely affect marine mammal prey in the vicinity of the project area 
(see discussion below). During pile driving, elevated levels of 
underwater noise would ensonify the San Diego Bay where both fish and 
mammals occur and could affect foraging success.
    There are no known foraging hotspots or other ocean bottom 
structure of significant biological importance to marine mammals 
present in the marine waters of the project area. Therefore, the main 
impact issue associated with the proposed activity would be temporarily 
elevated sound levels and the associated direct effects on marine 
mammals, as discussed previously in this document. The primary 
potential acoustic impacts to marine mammal habitat are associated with 
elevated sound levels produced by vibratory and impact pile driving in 
the area. Physical impacts to the environment such as construction 
debris are unlikely.
    In-water pile driving activities would also cause short-term 
effects on water quality due to increased turbidity. Silt curtains were 
considered but not included as a mitigation measure for turbidity 
because: (1) The sediments of the project site are sandy and will 
settle out rapidly when disturbed; (2) fine sediment that remains 
suspended would be rapidly dispersed by tidal currents; and (3) tidal 
currents would tend to collapse the silt curtains and make them 
ineffective. The waters of San Diego Bay are degraded and turbidity 
levels vary greatly depending on location, season, and tidal state. 
Navy would employ standard construction best management practices 
(BMPs; see Section 11 of the application), thereby reducing any 
potential impacts. Therefore, the impact from increased turbidity 
levels is expected to be discountable.
In-water Construction Effects on Potential Foraging Habitat
    Pile installation may temporarily increase turbidity resulting from 
suspended sediments. Any increases would be temporary, localized, and 
minimal. In general, turbidity associated with pile installation is 
localized to about a 25-foot (7.6 m) radius around the pile (Everitt et 
al. 1980). Pinnipeds could avoid these localized areas of turbidity. 
Therefore, the impact from increased turbidity levels is expected to be 
discountable to marine mammals.
    Essential Fish Habitat (EFH) for several species or groups of 
species overlaps with the project area including: Groundfish, coastal 
pelagic species, krill, finfish, dorado, and common thresher shark. 
NMFS (West Coast Region) is currently reviewing the proposed action for 
potential effects to EFH pursuant to the Magnuson-Stevens Fishery 
Conservation and Management Act.
    Avoidance by potential prey (i.e., fish) of the immediate area due 
to the temporary loss of this foraging habitat is also possible. The 
duration of fish avoidance of this area after pile driving stops is 
unknown, but a rapid return to normal recruitment, distribution and 
behavior is anticipated. Any behavioral avoidance by fish of the 
disturbed area would still leave significantly large areas of fish and 
marine mammal foraging habitat in the nearby vicinity.
    The duration of the construction activities is relatively short. 
Pile driving activities would occur for 50 days during the proposed 
project dates. Impacts to habitat and prey are expected to be minimal 
based on the short duration of activities.
    In-water Construction Effects on Potential Prey (Fish)--
Construction activities would produce continuous (i.e., vibratory pile 
driving) and pulsed (i.e. impact driving) sounds. Fish react to sounds 
that are especially strong and/or intermittent low-frequency sounds. 
Short duration, sharp sounds can cause overt or subtle changes in fish 
behavior and local distribution (summarized in Popper and Hastings, 
2009). Hastings and Popper (2005) reviewed several studies that suggest 
fish may relocate to avoid certain areas of sound energy. Additional 
studies have documented physical and behavioral effects of pile driving 
on fish, although several are based on studies in support of large, 
multiyear bridge construction projects (e.g., Scholik and Yan, 2001, 
2002; Popper and Hastings, 2009). Sound pulses at received levels of 
160 dB may cause subtle changes in fish behavior. SPLs of 180 dB may 
cause noticeable changes in behavior (Pearson et al., 1992; Skalski et 
al., 1992). SPLs of sufficient strength have been known to cause injury 
to fish and fish mortality (summarized in Popper et al., 2014).
    The most likely impact to fish from pile driving activities at the 
project area would be temporary behavioral avoidance of the area. The 
duration of fish avoidance of this area after pile driving stops is 
unknown, but a rapid return to normal recruitment, distribution and 
behavior is anticipated. In general, impacts to marine mammal prey 
species are expected to be minor and temporary due to the short 
timeframe for the project.
    In summary, given the short daily duration of sound associated with 
individual pile driving events and the relatively small and currently 
industrialized areas being affected, pile driving activities associated 
with the proposed action are not likely to have a permanent, adverse 
effect on any fish habitat, or populations of fish species. Thus, we 
conclude that impacts of the specified activity are not likely to have 
more than short-term adverse effects on any prey habitat or populations 
of prey species. Further, any impacts to marine mammal habitat are not 
expected to result in significant or long-term consequences for 
individual marine mammals, or to contribute to adverse impacts on their 
populations.

Estimated Take

    This section provides an estimate of the number of incidental takes 
proposed for authorization through this IHA, which will inform both 
NMFS' consideration of ``small numbers'' and the negligible impact 
determination.
    Harassment is the only type of take expected to result from these 
activities. Except with respect to certain activities not pertinent 
here, section 3(18) of the MMPA defines ``harassment'' as any act of 
pursuit, torment, or annoyance, which (i) has the potential to injure a 
marine mammal or marine mammal stock in the wild (Level A harassment); 
or (ii) has the potential to disturb a marine mammal or marine mammal

[[Page 21191]]

stock in the wild by causing disruption of behavioral patterns, 
including, but not limited to, migration, breathing, nursing, breeding, 
feeding, or sheltering (Level B harassment).
    Authorized takes would be by Level B harassment only, in the form 
of disruption of behavioral patterns for individual California sea 
lions resulting from exposure to pile driving activities. Based on the 
nature of the activity and the anticipated effectiveness of the 
mitigation measures (i.e., shutdown)--discussed in detail below in 
Proposed Mitigation section, Level A harassment is neither anticipated 
nor proposed to be authorized.
    As described previously, no mortality is anticipated or proposed to 
be authorized for this activity. Below we describe how the take is 
estimated.
    Generally speaking, we estimate take by considering: (1) Acoustic 
thresholds above which NMFS believes the best available science 
indicates marine mammals will be behaviorally harassed or incur some 
degree of permanent hearing impairment; (2) the area or volume of water 
that will be ensonified above these levels in a day; (3) the density or 
occurrence of marine mammals within these ensonified areas; and, (4) 
and the number of days of activities. We note that while these basic 
factors can contribute to a basic calculation to provide an initial 
prediction of takes, additional information that can qualitatively 
inform take estimates is also sometimes available (e.g., previous 
monitoring results or average group size). Below, we describe the 
factors considered here in more detail and present the proposed take 
estimate.

Acoustic Thresholds

    Using the best available science, NMFS has developed acoustic 
thresholds that identify the received level of underwater sound above 
which exposed marine mammals would be reasonably expected to be 
behaviorally harassed (equated to Level B harassment) or to incur PTS 
of some degree (equated to Level A harassment).
    Level B Harassment for non-explosive sources--Though significantly 
driven by received level, the onset of behavioral disturbance from 
anthropogenic noise exposure is also informed to varying degrees by 
other factors related to the source (e.g., frequency, predictability, 
duty cycle), the environment (e.g., bathymetry), and the receiving 
animals (hearing, motivation, experience, demography, behavioral 
context) and can be difficult to predict (Southall et al., 2007, 
Ellison et al., 2012). Based on what the available science indicates 
and the practical need to use a threshold based on a factor that is 
both predictable and measurable for most activities, NMFS uses a 
generalized acoustic threshold based on received level to estimate the 
onset of behavioral harassment. NMFS predicts that marine mammals are 
likely to be behaviorally harassed in a manner we consider Level B 
harassment when exposed to underwater anthropogenic noise above 
received levels of 120 dB re: 1 [mu]Pa root mean square (rms) for 
continuous (e.g., vibratory pile-driving, drilling) and above 160 dB 
re: 1 [mu]Pa (rms) for non-explosive impulsive (e.g., seismic airguns) 
or intermittent (e.g., scientific sonar) sources.
    Navy's proposed activity includes the use of continuous (vibratory 
pile driving) and impulsive (impact pile driving) sources, and 
therefore the 120 and 160 dB re: 1 [mu]Pa (rms) thresholds are 
applicable. As previously discussed, background (ambient) noise in the 
south-central San Diego Bay was measured at 126 dB re: 1 [mu]Pa (L50) 
in 2019 (Dahl and Dall'Osto 2019), therefore, 126 dB re: 1 [mu]Pa was 
used to calculate the Level B harassment isopleth.
    Level A harassment for non-explosive sources--NMFS' Technical 
Guidance for Assessing the Effects of Anthropogenic Sound on Marine 
Mammal Hearing (Version 2.0) (Technical Guidance, 2018) identifies dual 
criteria to assess auditory injury (Level A harassment) to five 
different marine mammal groups (based on hearing sensitivity) as a 
result of exposure to noise from two different types of sources 
(impulsive or non-impulsive). Navy's proposed activity includes the use 
includes the use of continuous (vibratory pile driving) and impulsive 
(impact pile driving) sources.
    These thresholds are provided in the table below. The references, 
analysis, and methodology used in the development of the thresholds are 
described in NMFS 2018 Technical Guidance, which may be accessed at 
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.

                     Table 3--Thresholds Identifying the Onset of Permanent Threshold Shift
----------------------------------------------------------------------------------------------------------------
                                                         PTS onset thresholds\*\ (received level)
             Hearing group              ------------------------------------------------------------------------
                                                  Impulsive                         Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans...........  Lp,0-pk,flat: 219 dB;       LE,p,LF,24h: 199 dB.
                                          LE,p,LF,24h: 183 dB.
Mid-Frequency (MF) Cetaceans...........  Lp,0-pk,flat: 230 dB;       LE,p,MF,24h: 198 dB.
                                          LE,pMF,24h: 185 dB.
High-Frequency (HF) Cetaceans..........  Lp,0-pk,flat: 202 dB;       LE,p,HF,24h: 173 dB.
                                          LE,p,HF,24h: 155 dB.
Phocid Pinnipeds (PW) (Underwater).....  Lp,0-pk.flat: 218 dB;       LE,p,PW,24h: 201 dB.
                                          LE,p,PW,24h: 185 dB.
Otariid Pinnipeds (OW) (Underwater)....  Lp,0-pk,flat: 232 dB;       LE,p,OW,24h: 219 dB.
                                          LE,p,OW,24h: 203 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS
  onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds
  associated with impulsive sounds, these thresholds are recommended for consideration.
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, thresholds are abbreviated to be
  more reflective of International Organization for Standardization standards (ISO 2017). The subscript ``flat''
  is being included to indicate peak sound pressure are flat weighted or unweighted within the generalized
  hearing range of marine mammals (i.e., 7 Hz to 160 kHz). The subscript associated with cumulative sound
  exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF
  cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The weighted
  cumulative sound exposure level thresholds could be exceeded in a multitude of ways (i.e., varying exposure
  levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the
  conditions under which these thresholds will be exceeded.


[[Page 21192]]

Ensonified Area

    Here, we describe operational and environmental parameters of the 
activity that will feed into identifying the area ensonified above the 
acoustic thresholds, which include source levels and transmission loss 
coefficient.
    The sound field in the project area is the existing background 
noise plus additional construction noise from the proposed project. 
Pile driving generates underwater noise that can potentially result in 
disturbance to marine mammals in the project area. The maximum 
(underwater) area ensonified is determined by the topography of the San 
Diego Bay including hard structures directly to the south of the 
project site. Additionally, vessel traffic and other commercial and 
industrial activities in the project area may contribute to elevated 
background noise levels which may mask sounds produced by the project.
    Transmission loss (TL) is the decrease in acoustic intensity as an 
acoustic pressure wave propagates out from a source. TL parameters vary 
with frequency, temperature, sea conditions, current, source and 
receiver depth, water depth, water chemistry, and bottom composition 
and topography. The general formula for underwater TL is:

TL = B * Log10 (R 1/R 2),

Where

TL = transmission loss in dB
B = transmission loss coefficient; for practical spreading equals 15
R 1= the distance of the modeled SPL from the driven 
pile, and
R 2= the distance from the driven pile of the initial 
measurement

    This formula neglects loss due to scattering and absorption, which 
is assumed to be zero here. The degree to which underwater sound 
propagates away from a sound source is dependent on a variety of 
factors, most notably the water bathymetry and presence or absence of 
reflective or absorptive conditions including in-water structures and 
sediments. Spherical spreading occurs in a perfectly unobstructed 
(free-field) environment not limited by depth or water surface, 
resulting in a 6 dB reduction in sound level for each doubling of 
distance from the source (20*log[range]). Cylindrical spreading occurs 
in an environment in which sound propagation is bounded by the water 
surface and sea bottom, resulting in a reduction of 3 dB in sound level 
for each doubling of distance from the source (10*log[range]). A 
practical spreading value of fifteen is often used under conditions, 
such as the project site where water increases with depth as the 
receiver moves away from the shoreline, resulting in an expected 
propagation environment that would lie between spherical and 
cylindrical spreading loss conditions. Practical spreading loss is 
assumed here.
    The intensity of pile driving sounds is greatly influenced by 
factors such as the type of piles, hammers, and the physical 
environment in which the activity takes place. In order to calculate 
distances to the Level A harassment and Level B harassment thresholds 
for the 24-inch octagonal concrete piles and the 24-inch steel pipe 
piles proposed in this project, acoustic monitoring data from other 
locations were used. Empirical data from recent sound source 
verification (SSV) studies reported in CALTRANS (2015) were used to 
estimate sound source levels (SSLs) for impact pile driving. For impact 
pile driving of 24-inch octagonal concrete piles measurements from San 
Francisco Bay, California were used (SELs-s: 166 dB re: 1 [mu]Pa\2\s; 
SPLrms: 176 dB re: 1 [mu]Pa; SPLpeak: 188 dB re: 1 [mu]Pa) (CALTRANS, 
2015). For impact pile driving of 24-inch steel pipe piles measurements 
from Carquinez Bay, California were used (SELs-s: 178 dB re: 1 
[mu]Pa\2\s; SPLrms: 194 dB re: 1 [mu]Pa; SPLpeak: 207 dB re: 1 [mu]Pa) 
(CALTRANS, 2015). For vibratory pile driving of 24-inch steel pipe 
piles measurements, average data collected from four projects (3 in 
Washington and 1 in California) reported by United States Navy (2015) 
were used. The highest project average SPLrms of 162 dB re: 1 [mu]Pa 
was selected as the most reasonable proxy for 24-inch steel pipe piles.
    For piles requiring use of vibratory pile driving, it is 
anticipated that 10 minutes (min) per pile will be required. The number 
of final strikes via impact pile driving for each pile installed would 
be dependent on the underlying geology and the exact placement of the 
pile. For example, pile-driving activities associated with the Pier 12 
replacement required between 500 and 600 blows per pile (Alberto 
Sanchez 2019, personal communication). To be conservative, 600 strikes 
per pile is estimated for impact pile driving.
    Navy used NMFS' Optional User Spreadsheet, available at https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance, to input project-specific parameters and 
calculate the isopleths for the Level A harassment zones for impact and 
vibratory pile driving. When the NMFS Technical Guidance (2018) was 
published, in recognition of the fact that ensonified area/volume could 
be more technically challenging to predict because of the duration 
component in the new thresholds, we developed a User Spreadsheet that 
includes tools to help predict a simple isopleth that can be used in 
conjunction with marine mammal density or occurrence to help predict 
takes. We note that because of some of the assumptions included in the 
methods used for these tools, we anticipate that isopleths produced are 
typically going to be overestimates of some degree, which may result in 
some degree of overestimate of Level A harassment take. However, these 
tools offer the best way to predict appropriate isopleths when more 
sophisticated 3D modeling methods are not available, and NMFS continues 
to develop ways to quantitatively refine these tools, and will 
qualitatively address the output where appropriate. For stationary 
sources pile driving, the NMFS User Spreadsheet predicts the distance 
at which, if a marine mammal remained at that distance the whole 
duration of the activity, it would incur PTS.
    Table 4 provides the sound source values and input used in the User 
Spreadsheet to calculate harassment isopleths for each source type. For 
impact pile driving, isopleths calculated using the cumulative SEL 
metric (SELs-s) will be used as it produces larger isopleths than 
SPLpeak. Isopleths for Level B harassment associated with impact pile 
driving (160 dB) and vibratory pile driving (126 dB) were also 
calculated and are can be found in Table 5.

              Table 4--User Spreadsheet Input Parameters Used for Calculating Harassment Isopleths
----------------------------------------------------------------------------------------------------------------
                                       Impact pile driving  24-                           Vibratory pile driving
      User Spreadsheet parameter       inch octagonal concrete  Impact pile driving  24-    24-inch steel pipe
                                                piles            inch steel pipe piles            piles
----------------------------------------------------------------------------------------------------------------
Spreadsheet Tab Used.................  (E.1) Impact pile        (E.1) Impact pile        (A.1) Vibratory pile
                                        driving.                 driving.                 driving.
Source Level (SELs-s or SPL rms).....  166 SELs-s\a\..........  178 SELs-s\a\..........  162 dB SPL rms\b\.
Source Level (SPLpeak)...............  188....................  207....................  N/A.

[[Page 21193]]

 
Weighting Factor Adjustment (kHz)....  2......................  2......................  2.5.
Number of piles per day..............  3......................  1......................  1.
Number of strikes per pile...........  600....................  600....................  N/A.
Number of strikes per day............  1,800..................  600....................  N/A.
Estimate driving duration (min) per    N/A....................  N/A....................  10.
 pile.
Activity Duration (h) within 24-h      N/A....................  N/A....................  0.167.
 period.
Propagation (xLogR)..................  15 Log R...............  15 Log R...............  15 Log R.
Distance of source level measurement   10.....................  10.....................  10.
 (meters).
----------------------------------------------------------------------------------------------------------------
\a\ CATRANS, 2015.
\b\ United States Navy, 2015.


    Table 5--Calculated Distances to Level A Harassment and Level B Harassment Isopleths During Pile Driving
----------------------------------------------------------------------------------------------------------------
                                                              Level A            Level B            Level B
                                                          harassment zone    harassment zone    harassment zone
                                                              (meters)           (meters)       ensonified area
                         Source                         --------------------------------------      (km\2\)
                                                                                              ------------------
                                                         Otariid pinnipeds      Pinnipeds          Pinnipeds
----------------------------------------------------------------------------------------------------------------
Impact Pile Driving 24-inch octagonal concrete piles...                  4                117              0.043
----------------------------------------------------------------------------------------------------------------
Impact Pile Driving 24-inch steel pipe piles...........                 13              1,848               3.68
----------------------------------------------------------------------------------------------------------------
Vibratory Pile Driving 24-inch steel pipe piles........                 <1              2,512               6.94
----------------------------------------------------------------------------------------------------------------
                         Source                              PTS onset
                                                           Isopleth--peak
                                                              (meters)
---------------------------------------------------------------------------
Impact Pile Driving 24-inch octagonal concrete piles...                N/A
---------------------------------------------------------------------------
Impact Pile Driving 24-inch steel pipe piles...........                N/A
----------------------------------------------------------------------------------------------------------------

Marine Mammal Occurrence and Take Calculation and Estimation

    In this section we provide the information about the presence, 
density, or group dynamics of marine mammals that will inform the take 
calculations, and how this information is brought together to produce a 
quantitative take estimate.
    No California sea lion density information is available for south 
San Diego Bay. Potential exposures to impact and vibratory pile driving 
noise for each threshold for California sea lions were estimated using 
data collected during a 2010 survey as reported in Sorensen and Swope 
(2010). The Sorenson and Swope (2010) survey is the only known survey 
to provide marine mammal observation data below the San Diego Coronado 
Bridge (in mid San Diego Bay). The single survey was on February 16, 
2010. During this survey one single sea lion was observed off Pier 3 
and one single sea lion was observed ~600m from the proposed project 
site.

Level B harassment Calculations

    The estimation of takes by Level B harassment uses the following 
calculation:

Level B harassment estimate = N (number of animals in the ensonified 
area) * Number of days of noise generating activities.

    The available survey data suggests from Sorenson and Swope (2010) 
suggests 2 California sea lions could be present each day in the 
project area, however given the limited data available, to be 
conservative we have estimated 4 California sea lions could be present 
each day.

Level B harassment estimate = 4 (number of animals in the ensonified 
area) * 50 (Number of days of noise generating activities) = 200.

Level A Harassment Calculations

    Navy intends to avoid Level A harassment take by shutting down 
activities if a California sea lion approaches with 25 m of the project 
site, which encompasses all Level A harassment (PTS onset) 
ensonification zones described in Table 5. Therefore, no take by Level 
A harassment is anticipated or proposed for authorization.

Proposed Mitigation

    In order to issue an IHA under Section 101(a)(5)(D) of the MMPA, 
NMFS must set forth the permissible methods of taking pursuant to the 
activity, and other means of effecting the least practicable impact on 
the species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of the species or stock for taking for certain 
subsistence uses (latter not applicable for this action). NMFS 
regulations require applicants for incidental take authorizations to 
include information about the availability and feasibility (economic 
and technological) of equipment, methods, and manner of conducting the 
activity or other means of effecting the least practicable adverse 
impact upon the affected species or stocks and their habitat (50 CFR 
216.104(a)(11)).
    In evaluating how mitigation may or may not be appropriate to 
ensure the

[[Page 21194]]

least practicable adverse impact on species or stocks and their 
habitat, as well as subsistence uses where applicable, we carefully 
consider two primary factors:
    (1) The manner in which, and the degree to which, the successful 
implementation of the measure(s) is expected to reduce impacts to 
marine mammals, marine mammal species or stocks, and their habitat. 
This considers the nature of the potential adverse impact being 
mitigated (likelihood, scope, range). It further considers the 
likelihood that the measure will be effective if implemented 
(probability of accomplishing the mitigating result if implemented as 
planned), the likelihood of effective implementation (probability 
implemented as planned), and;
    (2) the practicability of the measures for applicant 
implementation, which may consider such things as cost, impact on 
operations, and, in the case of a military readiness activity, 
personnel safety, practicality of implementation, and impact on the 
effectiveness of the military readiness activity.
    In addition to the measures described later in this section, Navy 
will employ the following standard mitigation measures:
     Conduct briefings between construction supervisors and 
crews and the marine mammal monitoring team prior to the start of all 
pile driving activity, and when new personnel join the work, to explain 
responsibilities, communication procedures, marine mammal monitoring 
protocol, and operational procedures;
     For in-water heavy machinery work other than pile driving 
(e.g., standard barges, etc.), if a marine mammal comes within 10 m, 
operations shall cease and vessels shall reduce speed to the minimum 
level required to maintain steerage and safe working conditions. This 
type of work could include the following activities: (1) Movement of 
the barge to the pile location; or (2) positioning of the pile on the 
substrate via a crane (i.e., stabbing the pile);
     Though not required, Navy has indicated that in-water pile 
driving will only be conducted at least 30 minutes after sunrise and up 
to 30 minutes before sunset, when visual monitoring of marine mammals 
can be conducted;
     For those marine mammals for which Level B harassment take 
has not been requested, in-water pile driving will shut down 
immediately if such species are observed within or entering the 
monitoring zone (i.e., Level B harassment zone); and
     If take reaches the authorized limit for an authorized 
species, pile installation will be stopped as these species approach 
the Level B harassment zone to avoid additional take.
    The following measures would apply to Navy's mitigation 
requirements:
    Establishment of Shutdown Zone for Level A Harassment--For all pile 
driving activities, Navy would establish a shutdown zone. The purpose 
of a shutdown zone is generally to define an area within which shutdown 
of activity would occur upon sighting of a marine mammal (or in 
anticipation of an animal entering the defined area). Conservative 
shutdown zones of 25 m for impact and vibratory pile driving activities 
would be implemented for California sea lions. The placement of PSOs 
during all pile driving activities (described in detail in the 
Monitoring and Reporting Section) will ensure shutdown zones are 
visible.
    Establishment of Monitoring Zones for Level B Harassment--Navy 
would establish monitoring zones to correlate with Level B harassment 
zones which are areas where SPLs are equal to or exceed the 160 dB re: 
1 [micro]Pa (rms) threshold for impact pile driving and the 126 dB re: 
1 [micro]Pa (rms) threshold during vibratory pile driving (Table 6). 
Monitoring zones provide utility for observing by establishing 
monitoring protocols for areas adjacent to the shutdown zones. 
Monitoring zones enable observers to be aware of and communicate the 
presence of marine mammals in the project area outside the shutdown 
zone and thus prepare for a potential cease of activity should the 
animal enter the shutdown zone.

    Table 6--Monitoring and Shutdown Zones for Each Project Activity
------------------------------------------------------------------------
                                            Monitoring     Shutdown zone
                 Source                      zone  (m)          (m)
------------------------------------------------------------------------
Impact pile driving 24-inch octagonal                120              25
 concrete piles.........................
Impact Pile Driving 24-inch steel pipe             1,850              25
 piles..................................
Vibratory Pile Driving 24-inch steel               2,515              25
 pipe piles.............................
------------------------------------------------------------------------

    Soft Start--The use of soft-start procedures are believed to 
provide additional protection to marine mammals by providing warning 
and/or giving marine mammals a chance to leave the area prior to the 
hammer operating at full capacity. For impact pile driving, contractors 
would be required to provide an initial set of strikes from the hammer 
at reduced energy, with each strike followed by a 30-second waiting 
period. This procedure would be conducted a total of three times before 
impact pile driving begins. Soft start would be implemented at the 
start of each day's impact pile driving and at any time following 
cessation of impact pile driving for a period of 30 minutes or longer. 
Soft start is not required during vibratory pile driving activities.
    Pre-Activity Monitoring--Prior to the start of daily in-water 
construction activity, or whenever a break in pile driving of 30 
minutes or longer occurs, PSOs will observe the shutdown and monitoring 
zones for a period of 30 minutes. The shutdown zone will be cleared 
when a marine mammal has not been observed within the zone for that 30-
minute period. If a marine mammal is observed within the shutdown zone, 
a soft-start cannot proceed until the animal has left the zone or has 
not been observed for 15 minutes. If the Level B harassment zone has 
been observed for 30 minutes and non-permitted species are not present 
within the zone, soft start procedures can commence and work can 
continue even if visibility becomes impaired within the Level B 
harassment monitoring zone. When a marine mammal permitted for take by 
Level B harassment is present in the Level B harassment zone, 
activities may begin and Level B harassment take will be recorded. If 
work ceases for more than 30 minutes, the pre-activity monitoring of 
both the Level B harassment and shutdown zone will commence again.
    Due to strong tidal fluctuations and associated currents in San 
Diego Bay, bubble curtains would not be implemented as they would not 
be effective in this environment.
    Based on our evaluation of the applicant's proposed measures, NMFS 
has preliminarily determined that the

[[Page 21195]]

proposed mitigation measures provide the means effecting the least 
practicable impact on the affected species or stocks and their habitat, 
paying particular attention to rookeries, mating grounds, and areas of 
similar significance.

Proposed Monitoring and Reporting

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

Marine Mammal Visual Monitoring

    Monitoring shall be conducted by NMFS-approved observers. Trained 
observers shall be placed from the best vantage point(s) practicable to 
monitor for marine mammals and implement shutdown or delay procedures 
when applicable through communication with the equipment operator. 
Observer training must be provided prior to project start, and shall 
include instruction on species identification (sufficient to 
distinguish the species in the project area), description and 
categorization of observed behaviors and interpretation of behaviors 
that may be construed as being reactions to the specified activity, 
proper completion of data forms, and other basic components of 
biological monitoring, including tracking of observed animals or groups 
of animals such that repeat sound exposures may be attributed to 
individuals (to the extent possible).
    Monitoring would be conducted 30 minutes before, during, and 30 
minutes after pile driving activities. In addition, observers shall 
record all incidents of marine mammal occurrence, regardless of 
distance from activity, and shall document any behavioral reactions in 
concert with distance from piles being driven. Pile driving activities 
include the time to install a single pile or series of piles, as long 
as the time elapsed between uses of the pile driving equipment is no 
more than 30 minutes.
    At least 1 land-based PSO will be located at the project site, and 
for the Navy has indicated that when possible and appropriate during 
vibratory pile driving activities, 1 additional boat-based PSO would be 
located at the edge of the Level B harassment isopleth (see Figure 1-2 
of the Marine Mammal Monitoring Plan dated March, 2020).
    PSOs would scan the waters using binoculars, and/or spotting 
scopes, and would use a handheld GPS or range-finder device to verify 
the distance to each sighting from the project site. All PSOs would be 
trained in marine mammal identification and behaviors and are required 
to have no other project-related tasks while conducting monitoring. In 
addition, monitoring will be conducted by qualified observers, who will 
be placed at the best vantage point(s) practicable to monitor for 
marine mammals and implement shutdown/delay procedures when applicable 
by calling for the shutdown to the hammer operator. Navy would adhere 
to the following PSO qualifications:
    (i) Independent observers (i.e., not construction personnel) are 
required;
    (ii) At least one observer must have prior experience working as an 
observer;
    (iii) Other observers may substitute education (degree in 
biological science or related field) or training for experience;
    (iv) Where a team of three or more observers are required, one 
observer shall be designated as lead observer or monitoring 
coordinator. The lead observer must have prior experience working as an 
observer; and
    (v) Navy shall submit observer CVs for approval by NMFS.
    Additional standard observer qualifications include:
     Ability to conduct field observations and collect data 
according to assigned protocols;
     Experience or training in the field identification of 
marine mammals, including the identification of behaviors;
     Sufficient training, orientation, or experience with the 
construction operation to provide for personal safety during 
observations;
     Writing skills sufficient to prepare a report of 
observations including but not limited to the number and species of 
marine mammals observed; dates and times when in-water construction 
activities were conducted; dates and times when in-water construction 
activities were suspended to avoid potential incidental injury from 
construction sound of marine mammals observed within a defined shutdown 
zone; and marine mammal behavior; and
     Ability to communicate orally, by radio or in person, with 
project personnel to provide real-time information on marine mammals 
observed in the area as necessary.
    Observers will be required to use approved data forms (see proposed 
data collection forms in the applicant's Marine Mammal Mitigation and 
Monitoring Plan). Among other pieces of information, Navy will record 
detailed information about any implementation of shutdowns, including 
the distance of animals to the pile and description of specific actions 
that ensued and resulting behavior of the animal, if any. In addition, 
Navy will attempt to distinguish between the number of individual 
animals taken and the number of incidences of take. We require that, at 
a minimum, the following information be collected on the sighting 
forms:
     Dates and times (begin and end) of all marine mammal 
monitoring;
     Construction activities occurring during each daily 
observation period, including how many and what type of

[[Page 21196]]

piles were driven or removed and by what method (i.e., impact or 
vibratory);
     Weather parameters and water conditions during each 
monitoring period (e.g., wind speed, percent cover, visibility, sea 
state);
     The number of marine mammals observed, by species, 
relative to the pile location and if pile driving or removal was 
occurring at time of sighting;
     Age and sex class, if possible, of all marine mammals 
observed;
     PSO locations during marine mammal monitoring;
     Distances and bearings of each marine mammal observed to 
the pile being driven or removed for each sighting (if pile driving or 
removal was occurring at time of sighting);
     Description of any marine mammal behavior patterns during 
observation, including direction of travel and estimated time spent 
within the Level A and Level B harassment zones while the source was 
active;
     Number of individuals of each species (differentiated by 
month as appropriate) detected within the monitoring zone, and 
estimates of number of marine mammals taken, by species (a correction 
factor may be applied to total take numbers, as appropriate);
     Detailed information about any implementation of any 
mitigation triggered (e.g., shutdowns and delays), a description of 
specific actions that ensued, and resulting behavior of the animal, if 
any;
     Description of attempts to distinguish between the number 
of individual animals taken and the number of incidences of take, such 
as ability to track groups or individuals;
     An extrapolation of the estimated takes by Level B 
harassment based on the number of observed exposures within the Level B 
harassment zone and the percentage of the Level B harassment zone that 
was not visible; and
     Submit all PSO datasheets and/or raw sighting data (in a 
separate file from the Final Report referenced immediately above).
    A draft report would be submitted to NMFS within 90 days of the 
completion of marine mammal monitoring, or 60 days prior to the 
requested date of issuance of any future IHA for projects at the same 
location, whichever comes first. The report will include marine mammal 
observations pre-activity, during-activity, and post-activity during 
pile driving days (and associated PSO data sheets), and will also 
provide descriptions of any behavioral responses to construction 
activities by marine mammals and a complete description of all 
mitigation shutdowns and the results of those actions and an 
extrapolated total take estimate based on the number of marine mammals 
observed during the course of construction. A final report must be 
submitted within 30 days following resolution of comments on the draft 
report.
    In the event that personnel involved in the construction activities 
discover an injured or dead marine mammal, the IHA-holder shall report 
the incident to the Office of Protected Resources (OPR) (301-427-8401), 
NMFS and to the West Coast Region Stranding Coordinator (562-980-3230) 
as soon as feasible. The report must include the following information:
     Time, date, and location (latitude/longitude) of the first 
discovery (and updated location information if known and applicable);
     Species identification (if known) or description of the 
animal(s) involved;
     Condition of the animal(s) (including carcass condition if 
the animal is dead);
     Observed behaviors of the animal(s), if alive;
     If available, photographs or video footage of the 
animal(s); and
     General circumstances under which the animal was 
discovered.
    NMFS will work with Navy to determine what, if anything, is 
necessary to minimize the likelihood of further prohibited take and 
ensure MMPA compliance. Navy must not resume their activities until 
notified by NMFS.

Negligible Impact Analysis and Determination

    NMFS has defined negligible impact as an impact resulting from the 
specified activity that cannot be reasonably expected to, and is not 
reasonably likely to, adversely affect the species or stock through 
effects on annual rates of recruitment or survival (50 CFR 216.103). A 
negligible impact finding is based on the lack of likely adverse 
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough 
information on which to base an impact determination. In addition to 
considering estimates of the number of marine mammals that might be 
``taken'' through harassment, NMFS considers other factors, such as the 
likely nature of any responses (e.g., intensity, duration), the context 
of any responses (e.g., critical reproductive time or location, 
migration), as well as effects on habitat, and the likely effectiveness 
of the mitigation. We also assess the number, intensity, and context of 
estimated takes by evaluating this information relative to population 
status. Consistent with the 1989 preamble for NMFS's implementing 
regulations (54 FR 40338; September 29, 1989), the impacts from other 
past and ongoing anthropogenic activities are incorporated into this 
analysis via their impacts on the environmental baseline (e.g., as 
reflected in the regulatory status of the species, population size and 
growth rate where known, ongoing sources of human-caused mortality, or 
ambient noise levels).
    Pile driving activities associated with the Floating Dry Dock 
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 B harassment (behavioral 
disturbance) from underwater sounds generated from impact and vibratory 
pile driving. Potential takes could occur if individuals of California 
sea lions are present in the ensonified zone when these activities are 
underway.
    No mortality or Level A harassment is anticipated given the nature 
of the activity and measures designed to minimize the possibility of 
injury to marine mammals. The potential for harassment is minimized 
through the construction method and the implementation of the planned 
mitigation measures (see Proposed Mitigation section).
    Navy's proposed activities are localized and of relatively short 
duration (a maximum of 50 days of pile driving for 66 piles). The 
project area is also very limited in scope spatially, as all work is 
concentrated on a single pier. Localized and short-term noise exposures 
produced by project activities may cause short-term behavioral 
modifications in pinnipeds. Moreover, the proposed mitigation and 
monitoring measures are expected to further reduce the likelihood of 
injury, as it is unlikely an animal would remain in close proximity to 
the sound source, as well as reduce behavioral disturbances.
    Effects on individuals that are taken by Level B harassment, on the 
basis of reports in the literature as well as monitoring from other 
similar activities, will likely be limited to reactions such as 
increased swimming speeds, increased surfacing time, or decreased 
foraging (if such activity were occurring) (e.g., Thorson and Reyff, 
2006; HDR, Inc., 2012; Lerma, 2014; ABR, 2016). Most likely, 
individuals will move away from the sound source and be temporarily 
displaced from the areas of pile driving, although even this reaction 
has been observed primarily only in association with impact pile 
driving.

[[Page 21197]]

The pile driving activities analyzed here are similar to, or less 
impactful than, numerous other construction activities conducted in 
California, which have taken place with no known long-term adverse 
consequences from behavioral harassment. Level B harassment will be 
reduced to the level of least practicable adverse impact through use of 
mitigation measures described herein and, if sound produced by project 
activities is sufficiently disturbing, animals are likely to simply 
avoid the area while the activity is occurring. While vibratory pile 
driving associated with the proposed project may produce sounds above 
ambient at distances of several kilometers from the project site, thus 
intruding on some habitat, the project site itself is located in an 
industrialized bay, and sounds produced by the proposed activities are 
anticipated to quickly become indistinguishable from other background 
noise in Bay as they attenuate to near ambient SPLs moving away from 
the project site. Therefore, we expect that animals annoyed by project 
sound would simply avoid the area and use more-preferred habitats.
    The project also is not expected to have significant adverse 
effects on affected marine mammal habitat. The project activities would 
not modify existing marine mammal habitat for a significant amount of 
time. The activities may cause some fish to leave the area of 
disturbance, thus temporarily impacting marine mammal foraging 
opportunities in a limited portion of the foraging range. However, 
because of the short duration of the activities, the relatively small 
area of the habitat that may be affected, the impacts to marine mammal 
habitat are not expected to cause significant or long-term negative 
consequences.
    In summary and as described above, the following factors primarily 
support our preliminary determination that the impacts resulting from 
this activity are not expected to adversely affect the species or stock 
through effects on annual rates of recruitment or survival:
     No mortality or Level A harassment is anticipated or 
proposed for authorization;
     The anticipated incidents of Level B harassment consist 
of, at worst, temporary modifications in behavior that would not result 
in fitness impacts to individuals;
     The specified activity and ensonification area is very 
small relative to the overall habitat ranges of California sea lions 
and does not include habitat areas of special significance (BIAs); and
     The presumed efficacy of the proposed mitigation measures 
in reducing the effects of the specified activity to the level of least 
practicable adverse impact.
    Based on the analysis contained herein of the likely effects of the 
specified activity on marine mammals and their habitat, and taking into 
consideration the implementation of the proposed monitoring and 
mitigation measures, NMFS preliminarily finds that the total marine 
mammal take from the proposed activity will have a negligible impact on 
all affected marine mammal species or stocks.

Small Numbers

    As noted above, only small numbers of incidental take may be 
authorized under Sections 101(a)(5)(A) and (D) of the MMPA for 
specified activities other than military readiness activities. The MMPA 
does not define small numbers and so, in practice, where estimated 
numbers are available, NMFS compares the number of individuals taken to 
the most appropriate estimation of abundance of the relevant species or 
stock in our determination of whether an authorization is limited to 
small numbers of marine mammals. Additionally, other qualitative 
factors may be considered in the analysis, such as the temporal or 
spatial scale of the activities.
    The Marine Mammal Occurrence and Take Calculation and Estimation 
section describes the number of California sea lions that could be 
exposed to received noise levels that could cause Level B harassment 
for the Navy's proposed activities in the project area site relative to 
the total stock abundance. Based on the estimated stock abundance 
presented in the 2018 Final SARs (257,606), our analysis shows that 
less than 1 percent of the affected stock could be taken by harassment.
    Based on the analysis contained herein of the proposed activity 
(including the proposed mitigation and monitoring measures) and the 
anticipated take of marine mammals, NMFS preliminarily finds that small 
numbers of marine mammals will be taken relative to the population size 
of the affected species or stocks.

Unmitigable Adverse Impact Analysis and Determination

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

Endangered Species Act (ESA)

    Section 7(a)(2) of the Endangered Species Act of 1973 (ESA: 16 
U.S.C. 1531 et seq.) requires that each Federal agency insure that any 
action it authorizes, funds, or carries out is not likely to jeopardize 
the continued existence of any endangered or threatened species or 
result in the destruction or adverse modification of designated 
critical habitat. To ensure ESA compliance for the issuance of IHAs, 
NMFS consults internally whenever we propose to authorize take for 
endangered or threatened 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 Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to the Navy for conducting the Floating Dry Dock Project 
at Naval Base San Diego in San Diego, California from September 15, 
2020 to September 14, 2021, provided the previously mentioned 
mitigation, monitoring, and reporting requirements are incorporated. A 
draft of the proposed IHA can be found at https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act.

Request for Public Comments

    We request comment on our analyses, the proposed authorization, and 
any other aspect of this Notice of Proposed IHA for the proposed 
[action]. We also request at this time comment on the potential Renewal 
of this proposed IHA 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 this IHA or a subsequent 
Renewal IHA.
    On a case-by-case basis, NMFS may issue a one-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, or nearly identical, activities as described in the 
Specified Activities section of this notice is planned or (2) the 
activities as described in the Specified Activities 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

[[Page 21198]]

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 one 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., 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); 
and
    (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; and
     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: April 10, 2020.
Donna S. Wieting,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2020-08006 Filed 4-15-20; 8:45 am]
 BILLING CODE 3510-22-P