[Federal Register Volume 85, Number 239 (Friday, December 11, 2020)]
[Notices]
[Pages 80027-80044]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-27225]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XA687]


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to Naval Base San Diego Pier 6 
Replacement Project, 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 Naval Base San 
Diego Pier 6 Replacement Project 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 January 
11, 2021.

ADDRESSES: Comments should be addressed to Jolie Harrison, Chief, 
Permits and Conservation Division, Office of Protected Resources, 
National Marine Fisheries Service and 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-

[[Page 80028]]

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: Dwayne Meadows, Ph.D., 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 IHA) 
with respect to potential impacts on the human environment.
    This action is consistent with categories of activities identified 
in Categorical Exclusion B4 (IHAs with no anticipated serious injury or 
mortality) of the Companion Manual for 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.

Summary of Request

    On July 14, 2020, NMFS received an application from the Navy 
requesting an IHA to take small numbers of California sea lions 
incidental to pile driving and removal associated with the Naval Base 
San Diego Pier 6 Replacement Project. The application was deemed 
adequate and complete on November 25, 2020. The Navy's request is for 
take of a small number of California sea lions by Level B harassment. 
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

    The purpose of the project is to remove and replace a decaying and 
inadequate pier for Navy ships. Specifically, in-water construction 
work includes removing the existing pier (by vibratory pile extraction, 
water jetting, hydraulic underwater chainsaw, direct pulling, and/or 
pile clippers) consisting of a total of 1,998 12 to 24-inch piles, 
after removing above water structures and utilities. Once demolition 
has opened up space, construction will begin in the same location on a 
new pier measuring 37 m (120 ft) wide by 457 m (1,500 ft) long. New 
construction work involves impact driving of 966 piles. This includes 
528 24-inch structural concrete piles, 208 24-inch concrete fender 
piles, 4 20-inch piles for a load-out ramp, and 226 16-inch fiberglass 
secondary and corner fender piles. Pile driving/removal is expected to 
take no more than 250 days. Pile driving would be by vibratory pile 
driving until resistance is too great and driving would switch to an 
impact hammer.
    The pile driving/removal can result in take of marine mammals from 
sound in the water which results in behavioral harassment or auditory 
injury.

Dates and Duration

    The work described here is scheduled for October 1, 2021 through 
September 30, 2022. In-water activities are planned for 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).

[[Page 80029]]

[GRAPHIC] [TIFF OMITTED] TN11DE20.009

    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 averaged 126 decibels (dB) in 2019 (Dahl and 
Dall'Osto 2019). 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).
    Section 2.2 of the application provides extensive additional 
details about the project area.

Detailed Description of Specific Activity

    The purpose of the project is to remove and replace a decaying and 
inadequate pier built in 1945 that is now too narrow, structurally 
weakened and decaying. A new, wider pier is needed to provide adequate 
ship berthing infrastructure to support modern Navy ships and fleet 
readiness. The Navy will abate any hazardous materials, and then 
disconnect and remove all utilities and mechanical equipment from the 
old pier. After the old pier deck and associated structures are 
removed, the exiting 1,998 in-water piles will be removed. Existing 
piles include 1,833 20 or 24-inch concrete piles, 149 12-inch timber-
plastic composite piles, and 16 16-inch steel I piles (Table 1). 
Workers would initially attempt to remove the piles by dead-pull with 
or without water jetting the pile (where an external high-pressure 
water jet is used to loosen the sediment around the pile). A vibratory 
hammer may also be used to loosen the piles prior to removal. If a pile 
cannot be removed by these methods, workers would use a hydraulic 
cutter or underwater hydraulic chainsaw to cut the piles at the 
mudline. Once the piles are cut, a crane would remove the pile and set 
it onto a barge for transport to a concrete processing yard. The Navy 
expects to be able to remove up to 8 piles per day, meaning 250 days of 
work will be required to remove all old piles.
    Once demolition has opened up space, construction will begin in the 
same location on the new pier. New construction work involves vibratory 
and impact driving of 966 piles (Table

[[Page 80030]]

1). This includes 528 24-inch structural concrete piles, 208 24-inch 
concrete fender piles, 4 20-inch piles for a load-out ramp, and 226 16-
inch fiberglass secondary and corner fender piles. Pile driving/removal 
is expected to take no more than 250 days. Pile driving would be by 
impact hammer only. The total length of the piles would range from 
approximately 26 m (85 ft) (fender piles) to 34 m (110 ft) (structural 
piles); the length of the portion of the piles in the water column 
would range from approximately 3 to 9 m (10 to 30 ft), depending on 
pile type, location, and tide. The Navy estimates they will install 7 
piles per day, meaning in-water construction will take 138 days.
    It is anticipated that overlap between demolition and installation 
activities would occur over the 250-day project period. Pile removal 
would begin on day 1 while pile installation is anticipated to begin 
after removal of one third of the piles (after approximately 83 days of 
pile removal). Pile installation is expected to periodically occur 
alongside ongoing pile removal activities over 138 days of the 
remaining 167 project days of pile removal. Because pile installation 
cannot continue where demolition activities are incomplete, there would 
be 29 days (167 days--138 days of pile installation) where only pile 
removal would occur after pile installation has started. In summary, 
the 250-day project period would include 112 days of pile removal-only 
activities and 138 days of concurrent pile removal and installation 
activities. There may be simultaneous use of no more than two of the 
various pile extraction methods (pile clippers, water jetting, 
underwater chainsaws or vibratory pile removal) during pile removal.
    The pile driving equipment will be deployed and operated from 
barges, on water. Materials will be delivered on barges.

                                   Table 1--Summary of Pile Driving Activities
----------------------------------------------------------------------------------------------------------------
                                                                     Number of                         Total
                Method                          Pile type              piles         Piles/day    estimated days
----------------------------------------------------------------------------------------------------------------
                                           Demolition of Existing Pier
----------------------------------------------------------------------------------------------------------------
Vibratory Extraction High-pressure      24-inch square pre-cast            1,833               8             250
 Water Jetting Hydraulic Pile Clipper    concrete, 20-inch
 Hydraulic Chainsaw.                     square pre-stressed/pre-
                                         cast concrete piles.
rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr
                                        12-inch composite                    149
                                         (timber-plastic) piles.
                                       ------------------------------------------
Vibratory Extraction..................  16-inch I-shaped steel                16
                                         piles.
                                       ------------------------------------------
    Total.......................................................           1,998
----------------------------------------------------------------------------------------------------------------
                                            Construction of New Pier
----------------------------------------------------------------------------------------------------------------
Impact Pile Driving...................  24-inch octagonal                     15               7             138
                                         concrete structural
                                         test piles.
rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr
                                        24-inch octagonal                    513
                                         concrete structural
                                         piles.
                                       ------------------------------------------
                                        24-inch square concrete                4
                                         fender system test
                                         piles.
                                       ------------------------------------------
                                        24-inch square concrete              204
                                         primary fender piles.
                                       ------------------------------------------
                                        20-inch square concrete                4
                                         pile for load-out ramp
                                         cradle.
                                       ------------------------------------------
                                        16-inch fiberglass                   226
                                         secondary and corner
                                         fender piles.
----------------------------------------------------------------------------------------------------------------
High-pressure Water Jetting...........  20- and 24-inch concrete                Within Above Counts
                                         piles.
----------------------------------------------------------------------------------------------------------------
    Total..................................................966..
----------------------------------------------------------------------------------------------------------------

    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 2 lists all species with expected potential for occurrence in 
the project area in San Diego Bay and summarizes information related to 
the population or stock, including regulatory status under the MMPA and 
Endangered Species Act (ESA) and potential biological removal (PBR), 
where known. For taxonomy, we follow Committee on Taxonomy (2020). 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

[[Page 80031]]

as gross indicators of the status of the species and other threats.
    Marine mammal abundance estimates presented in this document 
represent the total number of individuals that make up a given stock or 
the total number estimated within a particular study or survey area. 
NMFS's stock abundance estimates for most species represent the total 
estimate of individuals within the geographic area, if known, that 
comprises that stock. For some species, this geographic area may extend 
beyond U.S. waters. All managed stocks in this region are assessed in 
NMFS's U.S. Pacific SARs (e.g., Caretta et al., 2020).

                    Table 2--Species That Spatially Co-Occur With the Activity to the Degree That Take Is Reasonably Likely to Occur
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                        ESA/ MMPA  status;   Stock abundance  (CV,
             Common name                  Scientific name               Stock             Strategic  (Y/N)     Nmin, most recent       PBR     Annual M/
                                                                                                \1\          abundance survey) \2\               SI\3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Carnivora--Superfamily Pinnipedia.................................................................................................................
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otariidae (eared seals and
 sea lions):
    California Sea Lion.............  Zalophus californianus.  United States..........  -, -, N             257,606 (N/A, 233,515,     14,011       >321
                                                                                                             2014).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\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.
\3\--These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g.,
  commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV
  associated with estimated mortality due to commercial fisheries is presented in some cases.

    California sea lions (Zalophus californianus) spatially co-occur 
with the activity to the degree that take is reasonably likely to 
occur, and we have proposed authorizing take of this species. Other 
marine mammal species observed in San Diego Bay are the 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), these other marine mammals rarely occur south of the 
Coronado Bay Bridge, are not known to occur near Naval Base San Diego, 
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 or proposed to be authorized.

California Sea Lion

    California sea lions occur from Vancouver Island, British Columbia, 
to the southern tip of Baja California. Sea lions breed on the offshore 
islands of southern and central California from May through July (Heath 
and Perrin, 2008). During the non-breeding season, adult and subadult 
males and juveniles migrate northward along the coast to central and 
northern California, Oregon, Washington, and Vancouver Island 
(Jefferson et al., 1993). They return south the following spring (Heath 
and Perrin 2008, Lowry and Forney 2005). Females and some juveniles 
tend to remain closer to rookeries (Antonelis et al., 1990; Melin et 
al., 2008).
    Pupping occurs primarily on the California Channel Islands from 
late May until the end of June (Peterson and Bartholomew 1967). Weaning 
and mating occur in late spring and summer during the peak upwelling 
period (Bograd et al., 2009). After the mating season, adult males 
migrate northward to feeding areas as far away as the Gulf of Alaska 
(Lowry et al., 1992), and they remain away until spring (March-May), 
when they migrate back to the breeding colonies. Adult females 
generally remain south of Monterey Bay, California throughout the year, 
feeding in coastal waters in the summer and offshore waters in the 
winter, alternating between foraging and nursing their pups on shore 
until the next pupping/breeding season (Melin and DeLong, 2000; Melin 
et al., 2008).
    In San Diego Bay, California sea lions regularly occur on rocks, 
buoys and other structures, and especially on bait barges. 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). Different age 
classes of California sea lions are found in the San Diego region 
throughout the year (Lowry et al., 1991). Although adult male 
California sea lions feed in areas north of San Diego, animals of all 
other ages and sexes spend most, but not all, of their time feeding at 
sea during winter. During warm-water months, a high proportion of the 
adult males and females are hauled-out at terrestrial sites.

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

[[Page 80032]]

Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al. 
(2007) recommended that marine mammals be divided into functional 
hearing groups based on directly measured or estimated hearing ranges 
on the basis of available behavioral response data, audiograms derived 
using auditory evoked potential techniques, anatomical modeling, and 
other data. Note that no direct measurements of hearing ability have 
been successfully completed for mysticetes (i.e., low-frequency 
cetaceans). Subsequently, NMFS (2018) described generalized hearing 
ranges for these marine mammal hearing groups. Generalized hearing 
ranges were chosen based on the approximately 65 decibel (dB) threshold 
from the normalized composite audiograms, with the exception for lower 
limits for low-frequency cetaceans where the lower bound was deemed to 
be biologically implausible and the lower bound from Southall et al. 
(2007) retained. Marine mammal hearing groups and their associated 
hearing ranges are provided in Table 3.

                  Table 3--Marine Mammal Hearing Groups
                              [NMFS, 2018]
------------------------------------------------------------------------
            Hearing group                 Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen  7 Hz to 35 kHz.
 whales).
Mid-frequency (MF) cetaceans          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)                 50 Hz to 86 kHz.
 (underwater)(true seals).
Otariid pinnipeds (OW)                60 Hz to 39 kHz.
 (underwater)(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. 
California sea lions are in the otariid family group.

Potential Effects of Specified Activities on Marine Mammals and their 
Habitat

    This section includes a summary and discussion of the ways that 
components of the specified activity may impact marine mammals and 
their habitat. The Estimated Take section later in this document 
includes a quantitative analysis of the number of individuals that are 
expected to be taken by this activity. The Negligible Impact Analysis 
and Determination section considers the content of this section, the 
Estimated Take section, and the Proposed Mitigation section, to draw 
conclusions regarding the likely impacts of these activities on the 
reproductive success or survivorship of individuals and how those 
impacts on individuals are likely to impact marine mammal species or 
stocks.
    Acoustic effects on marine mammals during the specified activity 
can occur from vibratory and impact pile driving/removal and underwater 
chainsaws, pile clippers and water jetting. The effects of underwater 
noise from the Navy's proposed activities have the potential to result 
in Level A or Level B harassment of marine mammals in the action area.

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 1994, 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 and vibratory pile removal as well as water 
jetting, underwater chainsaws, and pile clippers. 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., machinery operations such as 
drilling or dredging, vibratory pile driving, water jetting, chainsaws, 
pile clippers, 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).

[[Page 80033]]

    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 them into the sediment. Vibratory 
hammers produce significantly less sound than impact hammers. Peak 
Sound pressure Levels (SPLs) may be 180 dB or greater, but are 
generally 10 to 20 dB lower than SPLs generated during impact pile 
driving of the same-sized pile (Oestman et al., 2009). 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).
    Pile clippers and underwater chainsaws are hydraulically operated 
equipment. A pile clipper is a large, heavy elongated horizontal 
guillotine-like structure that is mechanically lowered over a pile down 
to the mudline or substrate where hydraulic force is used to push a 
sharp blade to cut a pile. The underwater chainsaws are operated by 
SCUBA divers. Water jet systems use very high pressure jets of water to 
move and even cut materials. Sounds generated by this demolition 
equipment are non-impulsive and continuous (NAVAC Southwest, 2020)
    The likely or possible impacts of the 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 and removal.

Acoustic Impacts

    The introduction of anthropogenic noise into the aquatic 
environment from pile driving and removal and the various demolition 
equipment is the primary means by which marine mammals may be harassed 
from the Navy's specified activity. In general, animals exposed to 
natural or anthropogenic sound may experience physical and 
psychological effects, ranging in magnitude from none to severe 
(Southall et al., 2007). Generally, exposure to pile driving and 
removal and other 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). Exposure to anthropogenic noise can also lead to non-
observable physiological responses such an increase in stress hormones. 
Additional noise in a marine mammal's habitat can mask acoustic cues 
used by marine mammals to carry out daily functions such as 
communication and predator and prey detection. The effects of pile 
driving and demolition noise on marine mammals are dependent on several 
factors, including, but not limited to, sound type (e.g., impulsive vs. 
non-impulsive), the species, age and sex class (e.g., adult male vs. 
mom with calf), duration of exposure, the distance between the pile and 
the animal, received levels, behavior at time of exposure, and previous 
history with exposure (Wartzok et al., 2004; Southall et al., 2007). 
Here we discuss physical auditory effects (threshold shifts) followed 
by behavioral effects and potential impacts on habitat.
    NMFS defines a noise-induced threshold shift (TS) as a change, 
usually an increase, in the threshold of audibility at a specified 
frequency or portion of an individual's hearing range above a 
previously established reference level (NMFS, 2018). The amount of 
threshold shift is customarily expressed in 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., 2014), and the 
overlap between the animal and the source (e.g., spatial, temporal, and 
spectral).
    Permanent Threshold Shift (PTS)--NMFS defines PTS as a permanent, 
irreversible increase in the threshold of audibility at a specified 
frequency or portion of an individual's hearing range above a 
previously established reference level (NMFS 2018). Available data from 
humans and other terrestrial mammals indicate that a 40 dB threshold 
shift approximates PTS onset (see Ward et al., 1958, 1959; Ward, 1960; 
Kryter et al., 1966; Miller, 1974; Ahroon et al., 1996; Henderson and 
Hu, 2008). PTS levels for marine mammals are estimates, 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 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.
    Currently, TTS data only exist for four species of cetaceans 
(bottlenose

[[Page 80034]]

dolphin, beluga whale (Delphinapterus leucas), harbor porpoise, and 
Yangtze finless porpoise (Neophocoena asiaeorientalis)) and five 
species of pinnipeds exposed to a limited number of sound sources 
(i.e., mostly tones and octave-band noise) in laboratory settings 
(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). The potential for TTS from impact pile driving exists. After 
exposure to playbacks of impact pile driving sounds (rate 2760 strikes/
hour) in captivity, mean TTS increased from 0 dB after 15 minute 
exposure to 5 dB after 360 minute exposure; recovery occurred within 60 
minutes (Kastelein et al., 2016). 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 impact pile driving. 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 - Exposure to noise from pile driving and 
removal also has the potential to behaviorally disturb marine mammals. 
Available studies show wide variation in response to underwater sound; 
therefore, it is difficult to predict specifically how any given sound 
in a particular instance might affect marine mammals perceiving the 
signal. If a marine mammal does react briefly to an underwater sound by 
changing its behavior or moving a small distance, the impacts of the 
change are unlikely to be significant to the individual, let alone the 
stock or population. However, if a sound source displaces marine 
mammals from an important feeding or breeding area for a prolonged 
period, impacts on individuals and populations could be significant 
(e.g., Lusseau and Bejder, 2007; Weilgart, 2007; NRC, 2005).
    Disturbance may result in changing durations of surfacing and 
dives, number of blows per surfacing, or moving direction and/or speed; 
reduced/increased vocal activities; changing/cessation of certain 
behavioral activities (such as socializing or feeding); visible startle 
response or aggressive behavior (such as tail/fluke slapping or jaw 
clapping); avoidance of areas where sound sources are located. 
Pinnipeds may increase their haul out time, possibly to avoid in-water 
disturbance (Thorson and Reyff, 2006). Behavioral responses to sound 
are highly variable and context-specific and any reactions depend on 
numerous intrinsic and extrinsic factors (e.g., species, state of 
maturity, experience, current activity, reproductive state, auditory 
sensitivity, time of day), as well as the interplay between factors 
(e.g., Richardson et al., 1995; Wartzok et al., 2004; 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 and C of Southall et 
al. (2007) for a review of studies involving marine mammal behavioral 
responses to sound.
    Disruption of feeding behavior can be difficult to correlate with 
anthropogenic sound exposure, so it is usually inferred by observed 
displacement from known foraging areas, the appearance of secondary 
indicators (e.g., bubble nets or sediment plumes), or changes in dive 
behavior. As for other types of behavioral response, the frequency, 
duration, and temporal pattern of signal presentation, as well as 
differences in species sensitivity, are likely contributing factors to 
differences in response in any given circumstance (e.g., Croll et al., 
2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko et al., 
2007). A determination of whether foraging disruptions incur fitness 
consequences would require information on or estimates of the energetic 
requirements of the affected individuals and the relationship between 
prey availability, foraging effort and success, and the life history 
stage of the animal.
    In 2016, the Alaska Department of Transportation and Public 
Facilities (ADOT&PF) documented observations of marine mammals during 
construction activities (i.e., pile driving) at the Kodiak Ferry Dock 
(see 80 FR 60636, October 7, 2015). In the marine mammal monitoring 
report for that project (ABR 2016), 1,281 Steller sea lions were 
observed within the Level B disturbance zone during pile driving or 
drilling (i.e., documented as Level B harassment take). Of these, 19 
individuals demonstrated an alert behavior, 7 were fleeing, and 19 swam 
away from the project site. All other animals (98 percent) were engaged 
in activities such as milling, foraging, or fighting and did not change 
their behavior. In addition, two sea lions approached within 20 meters 
of active vibratory pile driving activities. Three harbor seals were 
observed within the disturbance zone during pile driving activities; 
none of them displayed disturbance behaviors. Fifteen killer whales and 
three harbor porpoise were also observed within the Level B harassment 
zone during pile driving. The killer whales were travelling or milling 
while all harbor porpoises were travelling. No signs of disturbance 
were noted for either of these species. Given the similarities in 
activities and habitat, we expect similar behavioral responses of 
marine mammals to the Navy's specified activity. That is, disturbance, 
if any, is likely to be temporary and localized (e.g., small area 
movements).
    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).

[[Page 80035]]

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., 1998; Jessop et al., 2003; 
Krausman et al., 2004; Lankford et al., 2005). Stress responses due to 
exposure to anthropogenic sounds or other stressors and their effects 
on marine mammals have also been reviewed (Fair and Becker 2000; Romano 
et al., 2002b) and, more rarely, studied in wild populations (e.g., 
Romano et al., 2002a). For example, Rolland et al. (2012) found that 
noise reduction from reduced ship traffic in the Bay of Fundy was 
associated with decreased stress in North Atlantic right whales. These 
and other studies lead to a reasonable expectation that some marine 
mammals will experience physiological stress responses upon exposure to 
acoustic stressors and that it is possible that some of these would be 
classified as ``distress.'' In addition, any animal experiencing TTS 
would likely also experience stress responses (NRC, 2003), however 
distress is an unlikely result of this project based on observations of 
marine mammals during previous, similar projects in the area.
    Masking--Sound can disrupt behavior through masking, or interfering 
with, an animal's ability to detect, recognize, or discriminate between 
acoustic signals of interest (e.g., those used for intraspecific 
communication and social interactions, prey detection, predator 
avoidance, navigation) (Richardson et al., 1995). Masking occurs when 
the receipt of a sound is interfered with by another coincident sound 
at similar frequencies and at similar or higher intensity, and may 
occur whether the sound is natural (e.g., snapping shrimp, wind, waves, 
precipitation) or anthropogenic (e.g., pile driving, shipping, sonar, 
seismic exploration) in origin. The ability of a noise source to mask 
biologically important sounds depends on the characteristics of both 
the noise source and the signal of interest (e.g., signal-to-noise 
ratio, temporal variability, direction), in relation to each other and 
to an animal's hearing abilities (e.g., sensitivity, frequency range, 
critical ratios, frequency discrimination, directional discrimination, 
age or TTS hearing loss), and existing ambient noise and propagation 
conditions. Masking of natural sounds can result when human activities 
produce high levels of background sound at frequencies important to 
marine mammals. Conversely, if the background level of underwater sound 
is high (e.g., on a day with strong wind and high waves), an 
anthropogenic sound source would not be detectable as far away as would 
be possible under quieter conditions and would itself be masked. The 
San Diego area contains active military and commercial shipping, cruise 
ship and ferry operations, as well as numerous recreational and other 
commercial vessel and background sound levels in the area are already 
elevated as described in Dahl and Dall'Osta (2019).
    Potential Effects of High-Pressure Water Jetting, Underwater 
Chainsaw, and Pile Clipper Sounds--High-pressure water jetting, 
underwater chainsaws, and pile clippers may be used to assist with 
removal of piles (and water jetting may be used to aid installation). 
The sounds produced by these activities are of similar frequencies to 
the sounds produced by vessels (NAVFAC Southwest, 2020), 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. Therefore, the effects of this equipment are likely to be similar 
to those discussed above in the Behavioral Harassment section.
    Airborne Acoustic Effects--Pinnipeds that occur near the project 
site could be exposed to airborne sounds associated with pile driving 
and removal that have the potential to cause behavioral harassment, 
depending on their distance from pile driving activities. Cetaceans are 
not expected to be exposed to airborne sounds that would result in 
harassment as defined under the MMPA.
    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. We recognize that 
pinnipeds in the water could be exposed to airborne sound that may 
result in behavioral harassment when looking with their heads above 
water. Most likely, airborne sound would cause behavioral responses 
similar to those discussed above in relation to underwater sound. For 
instance, anthropogenic sound could cause hauled-out pinnipeds to 
exhibit changes in their normal behavior, such as reduction in 
vocalizations, or cause them to 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 is already accounted for in these estimates of 
potential take. Therefore, we do not believe that authorization of 
incidental take resulting from airborne sound for pinnipeds is 
warranted, and airborne sound is not discussed further here.

Marine Mammal Habitat Effects

    The Navy's construction activities could have localized, temporary 
impacts on marine mammal habitat and their prey by increasing in-water 
sound pressure levels 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 impact and vibratory pile driving 
or removal, elevated levels of underwater noise would ensonify San 
Diego Bay where both fishes and mammals occur and could affect foraging 
success. Additionally, marine mammals may avoid the area during 
construction, however, displacement due to noise is expected to be 
temporary and is not expected to result in long-term effects to the 
individuals or populations. Construction activities are of short 
duration and would likely have temporary impacts on marine mammal 
habitat through increases in underwater and airborne sound.
    A temporary and localized increase in turbidity near the seafloor 
would occur in the immediate area surrounding the area where piles are 
installed or removed. In general, turbidity associated with pile 
installation is localized to about a 25-foot (7.6-meter) radius around 
the pile (Everitt et al. 1980). The sediments of the project site are 
sandy and will settle out rapidly when disturbed. Cetaceans are not 
expected to be close enough to the pile driving areas to experience 
effects of turbidity, and any pinnipeds could

[[Page 80036]]

avoid localized areas of turbidity. Local strong currents are 
anticipated to disburse any additional suspended sediments produced by 
project activities at moderate to rapid rates depending on tidal stage. 
Therefore, we expect the impact from increased turbidity levels to be 
discountable to marine mammals and do not discuss it further.

In-Water Construction Effects on Potential Foraging Habitat

    The area likely impacted by the project is relatively small 
compared to the available habitat (e.g., the impacted area is in the 
south central bay only) of San Diego Bay and does not include any 
Biologically Important Areas or other habitat of known importance. The 
area is highly influenced by anthropogenic activities. The total 
seafloor area affected by pile installation and removal is a very small 
area compared to the vast foraging area available to marine mammals in 
the San Diego Bay. At best, the impact area provides marginal foraging 
habitat for marine mammals and fish. Furthermore, pile driving and 
removal at the project site would not obstruct movements or migration 
of marine mammals.
    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.
    In-water Construction Effects on Potential Prey--Sound may affect 
marine mammals through impacts on the abundance, behavior, or 
distribution of prey species (e.g., crustaceans, cephalopods, fish, 
zooplankton). Marine mammal prey varies by species, season, and 
location. Here, we describe studies regarding the effects of noise on 
known marine mammal prey.
    Fish utilize the soundscape and components of sound in their 
environment to perform important functions such as foraging, predator 
avoidance, mating, and spawning (e.g., Zelick and Mann, 1999; Fay, 
2009). Depending on their hearing anatomy and peripheral sensory 
structures, which vary among species, fishes hear sounds using pressure 
and particle motion sensitivity capabilities and detect the motion of 
surrounding water (Fay et al., 2008). The potential effects of noise on 
fishes depends on the overlapping frequency range, distance from the 
sound source, water depth of exposure, and species-specific hearing 
sensitivity, anatomy, and physiology. Key impacts to fishes may include 
behavioral responses, hearing damage, barotrauma (pressure-related 
injuries), and mortality.
    Fish react to sounds which are especially strong and/or 
intermittent low-frequency sounds, and behavioral responses such as 
flight or avoidance are the most likely effects. Short duration, sharp 
sounds can cause overt or subtle changes in fish behavior and local 
distribution. The reaction of fish to noise depends on the 
physiological state of the fish, past exposures, motivation (e.g., 
feeding, spawning, migration), and other environmental factors. 
Hastings and Popper (2005) identified several studies that suggest fish 
may relocate to avoid certain areas of sound energy. Additional studies 
have documented effects of pile driving on fish, although several are 
based on studies in support of large, multiyear bridge construction 
projects (e.g., Scholik and Yan, 2001, 2002; Popper and Hastings, 
2009). Several studies have demonstrated that impulse sounds might 
affect the distribution and behavior of some fishes, potentially 
impacting foraging opportunities or increasing energetic costs (e.g., 
Fewtrell and McCauley, 2012; Pearson et al., 1992; Skalski et al., 
1992; Santulli et al., 1999; Paxton et al., 2017). However, some 
studies have shown no or slight reaction to impulse sounds (e.g., Pena 
et al., 2013; Wardle et al., 2001; Jorgenson and Gyselman, 2009; Cott 
et al., 2012).
    SPLs of sufficient strength have been known to cause injury to fish 
and fish mortality. However, in most fish species, hair cells in the 
ear continuously regenerate and loss of auditory function likely is 
restored when damaged cells are replaced with new cells. Halvorsen et 
al. (2012a) showed that a TTS of 4-6 dB was recoverable within 24 hours 
for one species. Impacts would be most severe when the individual fish 
is close to the source and when the duration of exposure is long. 
Injury caused by barotrauma can range from slight to severe and can 
cause death, and is most likely for fish with swim bladders. Barotrauma 
injuries have been documented during controlled exposure to impact pile 
driving (Halvorsen et al., 2012b; Casper et al., 2013).
    Because of the rarity of use and research, the effects of pile 
clippers, underwater chainsaws, and water jetting are not fully known; 
but given their similarity to ship noises we do not expect unique 
effects from these activities.
    The most likely impact to fish from pile driving and removal and 
demolition 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.
    Construction activities, in the form of increased turbidity, have 
the potential to adversely affect forage fish in the project area. 
Forage fish form a significant prey base for many marine mammal species 
that occur in the project area. Increased turbidity is expected to 
occur in the immediate vicinity (on the order of 10 feet (3 m) or less) 
of construction activities. However, suspended sediments and 
particulates are expected to dissipate quickly within a single tidal 
cycle. Given the limited area affected and high tidal dilution rates 
any effects on forage fish are expected to be minor or negligible. 
Finally, exposure to turbid waters from construction activities is not 
expected to be different from the current exposure; fish and marine 
mammals in San Diego Bay are routinely exposed to substantial levels of 
suspended sediment from natural and anthropogenic sources.
    In summary, given the short daily duration of sound associated with 
individual pile driving events and the relatively small 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. Any behavioral avoidance by fish of the 
disturbed area would still leave significantly large areas of fish and 
marine mammal foraging habitat in the nearby vicinity. Thus, we 
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,

[[Page 80037]]

which (i) has the potential to injure a marine mammal or marine mammal 
stock in the wild (Level A harassment); or (ii) has the potential to 
disturb a marine mammal or marine mammal stock in the wild by causing 
disruption of behavioral patterns, including, but not limited to, 
migration, breathing, nursing, breeding, feeding, or sheltering (Level 
B harassment).
    Authorized takes would be by Level B harassment, as use of the 
acoustic source (i.e., vibratory or impact pile driving) has the 
potential to result in disruption of behavioral patterns for individual 
marine mammals. 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 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). Due to the lack of 
marine mammal density, NMFS relied on local occurrence data and group 
size to estimate take. Below, we describe the factors considered here 
in more detail and present the proposed take estimate.

Acoustic Thresholds

    NMFS recommends the use of acoustic thresholds that identify the 
received level of underwater sound above which exposed marine mammals 
would be reasonably expected to be behaviorally harassed (equated to 
Level B harassment) or to incur PTS of some degree (equated to Level A 
harassment).
    Level B Harassment 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 microPascal ([mu]Pa) (root mean square 
(rms)) for continuous (e.g., vibratory pile-driving) and above 160 dB 
re 1 [mu]Pa (rms) for non-explosive impulsive (e.g., impact pile 
driving) or intermittent (e.g., scientific sonar) sources.
    The Navy's proposed activity includes the use of continuous 
(vibratory pile-driving, water jetting, chainsaw and pile clippers) and 
impulsive (impact pile-driving) sources, and therefore the 120 and 160 
dB re 1 [mu]Pa (rms) thresholds are applicable. However, as discussed 
above, the Navy has established that the ambient noise in the project 
area is 126 dB re 1 [mu]Pa (rms). Since this is louder than the 120 dB 
threshold for continuous sources, 126 dB becomes the effective 
threshold for Level B harassment for continuous sources.
    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). The Navy's activity includes the use of 
impulsive (impact pile-driving) and non-impulsive (vibratory pile 
driving/removal and other removal methods) sources.
    These thresholds are provided in Table 4. 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 4--Thresholds Identifying the Onset of Permanent Threshold Shift
----------------------------------------------------------------------------------------------------------------
                                                    PTS onset acoustic thresholds *  (Received level)
             Hearing group              ------------------------------------------------------------------------
                                                  Impulsive                         Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans...........  Cell 1: Lpk,flat: 219 dB;   Cell 2: LE,LF,24h: 199 dB.
                                          LE,LF,24h: 183 dB.
Mid-Frequency (MF) Cetaceans...........  Cell 3: Lpk,flat: 230 dB;   Cell 4 LE,MF,24h: 198 dB.
                                          LE,MF,24h: 185 dB.
High-Frequency (HF) Cetaceans..........  Cell 5: Lpk,flat: 202 dB    Cell 6 LE,HF,24h: 173 dB.
                                          LE,HF,24h: 155 dB.
Phocid Pinnipeds (PW) (Underwater).....  Cell 7: Lpk,flat: 218 dB    Cell 8: LE,PW,24h: 201 dB.
                                          LE,PW,24h: 185 dB.
Otariid Pinnipeds (OW) (Underwater)....  Cell 9: Lpk,flat:232 dB     Cell 10: LE,OW,24h: 219 dB.
                                          LE,OW,24h: 203 dB.
----------------------------------------------------------------------------------------------------------------
* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for
  calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level
  thresholds associated with impulsive sounds, these thresholds should also be considered.
Note: Peak sound pressure (Lpk) has a reference value of 1 [micro]Pa, and cumulative sound exposure level (LE)
  has a reference value of 1[micro]Pa\2\s. In this Table, thresholds are abbreviated to reflect American
  National Standards Institute standards (ANSI 2013). However, peak sound pressure is defined by ANSI as
  incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript
  ``flat'' is being included to indicate peak sound pressure should be flat weighted or unweighted within the
  generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates
  the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds)
  and that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could
  be exceeded in a multitude of ways (i.e., varying exposure levels and durations, duty cycle). When possible,
  it is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be
  exceeded.


[[Page 80038]]

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. 
Marine mammals are expected to be affected via sound generated by the 
primary components of the project (i.e., impact pile driving, vibratory 
pile removal, water jetting, pile clippers and underwater chainsaws).
    Vibratory hammers produce constant sound when operating, and 
produce vibrations that liquefy the sediment surrounding the pile, 
allowing it to penetrate to the required seating depth or be withdrawn 
more easily. An impact hammer is a steel device that works like a 
piston, producing a series of independent strikes to drive the pile. 
Impact hammering typically generates the loudest noise associated with 
pile installation. The actual durations of each installation method 
vary depending on the type and size of the pile.
    In order to calculate distances to the Level A harassment and Level 
B harassment sound thresholds for piles of various sizes being used in 
this project, NMFS used acoustic monitoring data from other locations 
to develop source levels for the various pile types, sizes and methods 
(see Table 5). Data for the removal methods including water jetting, 
pile clippers and underwater chainsaws come from data gathered at other 
nearby Navy projects in San Diego Bay (NAVFAC SW, 2020), the source 
levels used are from the averages of the maximum source levels 
measured, a somewhat more conservative measure than the median sound 
levels we typically use.

                                      Table 5--Project Sound Source Levels
----------------------------------------------------------------------------------------------------------------
                Pile driving activity                    Estimated sound source level at 10
------------------------------------------------------       meters without attenuation         Data source and
                                                      ---------------------------------------        proxy
             Method                    Pile Type          dB RMS       dB SEL      dB peak
----------------------------------------------------------------------------------------------------------------
Vibratory Extraction............  12-inch timber/              152  ...........  ...........  Greenbusch Group
                                   plastic.                                                    (2018).
                                  20 and 24-inch               160  ...........  ...........  Caltrans (2015),
                                   concrete.                                                   Table I.2-2, 24-
                                                                                               inch steel sheet.
                                  16-inch steel......          160  ...........  ...........  Caltrans (2015),
                                                                                               Table I.2-2, 24-
                                                                                               inch steel sheet.
Water Jetting...................  20-inch concrete...          158  ...........  ...........  NAVFAC SW (2020),
                                                                                               24 x 30-inch
                                                                                               concrete.
Underwater Chainsaw.............  12 to 24-inch                150  ...........  ...........  NAVFAC SW (2020),
                                   concrete.                                                   16-inch
                                                                                               concrete.*
Small Pile Clipper..............  12-inch timber/              154  ...........  ...........  NAVFAC SW (2020),
                                   plastic.                                                    13-inch
                                                                                               polycarbonate.
Large Pile Clipper..............  20-inch concrete...          161  ...........  ...........  NAVFAC SW (2020),
                                                                                               24-inch concrete.
Impact Hammer...................  20 and 24-inch               176          166          188  Caltrans (2015),
                                   concrete.                                                   Table I.2-1, 24-
                                                                                               inch concrete.
                                  16-inch fiberglass.          153       ** 144       ** 177  Caltrans (2015),
                                                                                               13-inch plastic.
----------------------------------------------------------------------------------------------------------------
Note: SEL = single strike sound exposure level; dB peak = peak sound level; rms = root mean square.
* Source level was 147 dB at 17m from source, back calculated to 150dB using transmission loss coefficient of
  15.
** Average of the peak values was 166 and that value was used in modelling in Dell'Osto and Dahl (2019) rather
  than the absolute peak we recommend for use in the user spreadsheet, SEL calculated from assumed strike rate
  in Dell'Osto and Dahl (2019).

    During pile driving installation activities, there may be times 
when two pile extraction methods (pile clippers, water jetting, 
underwater chainsaws or vibratory pile removal) are used 
simultaneously. The likelihood of such an occurrence is anticipated to 
be infrequent, will depend on the specific methods chosen by the 
contractor, and would be for short durations on that day. In-water pile 
removal occurs intermittently, and it is common for removal to start 
and stop multiple times as each pile is adjusted and its progress is 
measured. Moreover, the Navy has multiple options for pile removal 
depending on the pile type and condition, sediment, and how stuck the 
pile is, etc. When two continuous noise sources, such as pile clippers, 
have overlapping sound fields, there is potential for higher sound 
levels than for non-overlapping sources. When two or more pile removal 
methods (pile clippers, water jetting, underwater chainsaws or 
vibratory pile removal) are used simultaneously, and the sound field of 
one source encompasses the sound field of another source, the sources 
are considered additive and combined using the following rules (see 
Table 6): For addition of two simultaneous methods, the difference 
between the two sound source levels (SSLs) is calculated, and if that 
difference is between 0 and 1 dB, 3 dB are added to the higher SSL; if 
difference is between 2 or 3 dB, 2 dB are added to the highest SSL; if 
the difference is between 4 to 9 dB, 1 dB is added to the highest SSL; 
and with differences of 10 or more dB, there is no addition (NMFS 
2018b; WSDOT 2018).

 Table 6--Rules for Combining Sound Levels Generated During Pile Removal
------------------------------------------------------------------------
      Difference in SSL           Level A zones         Level B zones
------------------------------------------------------------------------
0 or 1 dB...................  Add 3 dB to the       Add 3 dB to the
                               higher source level.  higher source
                                                     level.
2 or 3 dB...................  Add 2 dB to the       Add 2 dB to the
                               higher source level.  higher source
                                                     level.
4 to 9 dB...................  Add 1 dB to the       Add 1 dB to the
                               higher source level.  higher source
                                                     level.

[[Page 80039]]

 
10 dB or more...............  Add 0 dB to the       Add 0 dB to the
                               higher source level.  higher source
                                                     level.
------------------------------------------------------------------------
Source: Modified from USDOT 1995, WSDOT 2018, and NMFS 2018b
Note: dB = decibels; SSL = sound source level.

    There is also the possibility that impact installation of piles 
could happen simultaneously with any of the non-impulsive removal 
methods over large portions of the project as described above. On days 
when this occurs the Level A harassment zones would be based on the 
zones calculated for impact pile driving while the Level B harassment 
zone would be the largest of the zones for whatever construction 
methods are being used that day.

Level B Harassment Zones

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

TL = B * Log10 (R1/R2),

where

TL = transmission loss in dB
B = transmission loss coefficient; for practical spreading equals 15
R1 = the distance of the modeled SPL from the driven pile, and
R2 = the distance from the driven pile of the initial measurement

    The recommended TL coefficient for most nearshore environments is 
the practical spreading value of 15. This value results in an expected 
propagation environment that would lie between spherical and 
cylindrical spreading loss conditions, which is the most appropriate 
assumption for the Navy's proposed activity in the absence of specific 
modelling. For this project however, the Navy did model sound 
propagation for the impact and vibratory hammering methods (Dall'Osto 
and Dahl 2019). For all other pile removal methods we used the 
practical spreading value.
    The Navy determined underwater noise would fall below the 
behavioral effects threshold of 126 dB rms for marine mammals at 
distances of less than 10 to 7,140 m depending on the pile type(s) and 
methods (Table 7). It should be noted that based on the bathymetry and 
geography of San Diego Bay, sound will not reach the full distance of 
the Level B harassment isopleths in all directions. Because the Navy's 
as yet unhired contractor has not decided which of the various pile 
removal methods it will use, we only calculate a worst-case scenario of 
simultaneous operation of two of the loudest sound producing methods 
(large pile clippers) to consider the largest possible harassment zones 
for simultaneous pile removal.

                  Table 7--Level A and Level B Isopleths for Each Pile Driving Type and Method
----------------------------------------------------------------------------------------------------------------
                     Pile Driving Activity                         Radial distance or maximum modeled length x
----------------------------------------------------------------                    width (m)
                                                                ------------------------------------------------
                Method                         Pile type              Level A                 Level B
----------------------------------------------------------------------------------------------------------------
Vibratory Extraction.................  12-inch timber/plastic..               <10  2167 x 1065.
                                       20 and 24-inch concrete.               <10  6,990 x 1,173.
                                       16-inch steel...........               <10  7,140 x 1,595.
Water Jetting........................  20-inch concrete........               <10  1359.
Underwater Chainsaw..................  12 to 24-inch concrete..               <10  398.
Small Pile Clipper...................  12-inch timber/plastic..               <10  736.
Large Pile Clipper...................  20 to 24-inch concrete..               <10  2154.
Two Large Pile Clippers..............  20 to 24-inch concrete..               <10  3415.
Impact Hammer........................  20 and 24-inch concrete.               <10  192.
                                       16-inch fiberglass......               <10  <10.
----------------------------------------------------------------------------------------------------------------

Level A Harassment Zones

    When the NMFS Technical Guidance (2016) was published, in 
recognition of the fact that ensonified area/volume could be more 
technically challenging to predict because of the duration component in 
the new thresholds, we developed a User Spreadsheet that includes tools 
to help predict a simple isopleth that can be used in conjunction with 
marine mammal density or occurrence to help predict takes. We note that 
because of some of the assumptions included in the methods used for 
these tools, we anticipate that isopleths produced are typically going 
to be overestimates of some degree, which may result in some degree of 
overestimate of take by Level A harassment. However, these tools offer 
the best way to predict appropriate isopleths when more sophisticated 
3D modeling methods are not available, and NMFS continues to develop 
ways to quantitatively refine these tools, and will qualitatively 
address the output where appropriate. For stationary sources such as 
impact/vibratory pile driving or removal using any of the methods 
discussed above, NMFS User Spreadsheet predicts the closest distance at 
which, if a marine mammal remained at that distance the whole duration 
of the activity, it would not incur PTS.
    As discussed above, the Navy modelled sound propagation for impact 
and vibratory hammering of piles (Dall'Osto and Dahl 2019) and used 
those models to calculate Level A harassment isopleths. For all other 
pile removal methods we used the User Spreadsheet to determine the 
Level A harassment isopleths. Inputs used in the User Spreadsheet or 
models are reported in Table 8 and the resulting isopleths are reported 
in Table 7 for each of construction methods.

[[Page 80040]]



Table 8--NMFS Technical Guidance User Spreadsheet Input to Calculate Level A Isopleths for a Combination of Pile
                                                     Driving
----------------------------------------------------------------------------------------------------------------
                     Pile Driving Activity                         Radial distance or maximum modeled length x
----------------------------------------------------------------                    width (m)
                                                                ------------------------------------------------
                Method                         Pile Type                            Strikes per pile/duration to
                                                                   Piles per day        drive a single pile
----------------------------------------------------------------------------------------------------------------
Vibratory Extraction.................  12-inch timber/plastic..                 8  10 minutes.
                                       20 and 24-inch concrete.                 8  10 minutes.
                                       16-inch steel...........                 8  10 minutes.
Water Jetting........................  20-inch concrete........                 8  20 minutes.
Underwater Chainsaw..................  12 to 24-inch concrete..                 8  10 minutes.
Small Pile Clipper...................  12-inch timber/plastic..                 8  10 minutes.
Large Pile Clipper...................  20-inch concrete........                 8  10 minutes.
Impact Hammer........................  20 and 24-inch concrete.                 7  600 strikes.
                                       16-inch fiberglass......                 7  600 strikes.
----------------------------------------------------------------------------------------------------------------

    The above input scenarios lead to PTS isopleth distances (Level A 
thresholds) of less than 10 m for all methods and piles (Table 7).

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. Here we describe how the information provided above 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). During this survey two separate sea lions were observed in the 
project area.
    The available survey data from Sorenson and Swope (2010) and other 
unpublished monitoring data from recent nearby projects on Naval Base 
San Diego suggests two California sea lions could be present each day 
in the project area. However given the limited data available and the 
more northerly location of this project relative to the recent dry dock 
project (https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-navy-floating-dry-dock-project-naval-base-san-diego) 
where we estimate two California sea lions per day, to be conservative, 
we have estimated four California sea lions could be present each day. 
As noted above, there are 250 days of in-water work for this project. 
Multiplication of the above estimate of animals per day (4) times the 
days of work (250) results in a proposed Level B harassment take of 
1000 California sea lions (Table 9). The Navy intends to avoid Level A 
harassment take by shutting down activities if a California sea lion 
approaches within 20 m of the project site, which encompasses all Level 
A harassment ensonification zones. Therefore, no take by Level A 
harassment is anticipated or proposed for authorization.

   Table 9--Proposed Authorized Amount of Taking, by Level A Harassment and Level B Harassment, by Species and
                                       Stock and Percent of Take by Stock
----------------------------------------------------------------------------------------------------------------
                                                                    Authorized Take
                        Species                         --------------------------------------  Percent of Stock
                                                              Level B            Level A
----------------------------------------------------------------------------------------------------------------
California sea lion (Zalophus californianus) U.S. Stock              1000                  0                0.4
----------------------------------------------------------------------------------------------------------------

Proposed Mitigation

    In order to issue an IHA under section 101(a)(5)(D) of the MMPA, 
NMFS must set forth the permissible methods of taking pursuant to the 
activity, and other means of effecting the least practicable impact on 
the species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of the species or stock for taking for certain 
subsistence uses (latter not applicable for this action). NMFS 
regulations require applicants for incidental take authorizations to 
include information about the availability and feasibility (economic 
and technological) of equipment, methods, and manner of conducting the 
activity or other means of effecting the least practicable adverse 
impact upon the affected species or stocks and their habitat (50 CFR 
216.104(a)(11)).
    In evaluating how mitigation may or may not be appropriate to 
ensure the least practicable adverse impact on species or stocks and 
their habitat, as well as subsistence uses where applicable, 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.
    The following mitigation measures are proposed in the IHA:
     For in-water heavy machinery work other than pile driving, 
if a marine

[[Page 80041]]

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);
     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 those marine mammals for which Level B harassment take 
has not been requested, in-water pile installation/removal will shut 
down immediately if such species are observed within or entering the 
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 mitigation measures would apply to the Navy's in-
water construction activities.
     Establishment of Shutdown Zones--The Navy will establish 
shutdown zones for all pile driving and removal activities. The purpose 
of a shutdown zone is generally to define an area within which shutdown 
of the activity would occur upon sighting of a marine mammal (or in 
anticipation of an animal entering the defined area). Shutdown zones 
typically vary based on the activity type and marine mammal hearing 
group (Table 4). In this case there is only one species affected and 
all level A harassment isopleths are less than 10 m radius. To be 
conservative, the Navy will establish a 20 m shutdown zone for all pile 
driving or removal activities.
     The placement of Protected Species Observers (PSOs) during 
all pile driving and removal activities (described in detail in the 
Proposed Monitoring and Reporting section) will ensure that the entire 
shutdown zone is visible during pile installation. Should environmental 
conditions deteriorate such that marine mammals within the entire 
shutdown zone would not be visible (e.g., fog, heavy rain), pile 
driving and removal must be delayed until the PSO is confident marine 
mammals within the shutdown zone could be detected.
     Monitoring for Level B Harassment--The Navy will monitor 
the Level A and B harassment zones. 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 halt of 
activity should the animal enter the shutdown zone. Placement of PSOs 
will allow PSOs to observe marine mammals within the Level B harassment 
zones.
     Pre-activity Monitoring--Prior to the start of daily in-
water construction activity, or whenever a break in pile driving/
removal 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 considered 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. When a 
marine mammal for which Level B harassment take is authorized is 
present in the Level B harassment zone, activities may begin and Level 
B harassment take will be recorded. If the entire Level B harassment 
zone is not visible at the start of construction, pile driving 
activities can begin. If work ceases for more than 30 minutes, the pre-
activity monitoring of the shutdown zones will commence.
     Soft Start--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 impact 
hammer operating at full capacity. For impact pile driving, contractors 
will be required to provide an initial set of three strikes from the 
hammer at reduced energy, followed by a 30-second waiting period. This 
procedure will be conducted three times before impact pile driving 
begins. Soft start will be implemented at the start of each day's 
impact pile driving and at any time following cessation of impact pile 
driving for a period of 30 minutes or longer.
    Based on our evaluation of the applicant's proposed measures, as 
well as other measures considered by NMFS, NMFS has preliminarily 
determined that the proposed mitigation measures provide the means 
effecting the least practicable impact on the affected species or 
stocks and their habitat, paying particular attention to rookeries, 
mating grounds, and areas of similar significance.

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.

Visual Monitoring

    Marine mammal monitoring must be conducted in accordance with the 
Monitoring Plan and Section 5 of the IHA. Marine mammal monitoring 
during pile driving and removal must be conducted by NMFS-approved PSOs 
in a manner consistent with the following:

[[Page 80042]]

     Independent PSOs (i.e., not construction personnel) who 
have no other assigned tasks during monitoring periods must be used;
     At least one PSO must have prior experience performing the 
duties of a PSO during construction activity pursuant to a NMFS-issued 
incidental take authorization.
     Other PSOs may substitute education (degree in biological 
science or related field) or training for experience;
     Where a team of three or more PSOs are required, a lead 
observer or monitoring coordinator must be designated. The lead 
observer must have prior experience performing the duties of a PSO 
during construction activity pursuant to a NMFS-issued incidental take 
authorization; and
     The Navy must submit PSO Curriculum Vitae for approval by 
NMFS prior to the onset of pile driving.
    PSOs must have the following additional qualifications:
     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, times, and reason for implementation 
of mitigation (or why mitigation was not implemented when required); 
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.
    Up to four PSOs will be employed. PSO locations will provide an 
unobstructed view of all water within the shutdown zone, and as much of 
the Level A and Level B harassment zones as possible. PSO locations are 
as follows:
    (1) At the pile driving/removal site or best vantage point 
practicable to monitor the shutdown zones;
    (2) For activities with Level B harassment zones larger than 400 m 
two additional PSO locations will be used. One will be across from the 
project location along Inchon Road at Naval Amphibious Base Coronado; 
and
    (3) Two additional PSOs will be located in a small boat. The boat 
will conduct a pre-activity survey of the entire monitoring area prior 
to in-water construction. The boat will start from south of the project 
area (where potential marine mammal occurrence is lowest) and proceed 
to the north. When the boat arrives near the northern boundary of the 
Level B harassment zone (e.g., just north of the western side of the 
Coronado Bridge as depicted in the Figures in the monitoring plan) it 
will set up station so the PSOs are best situated to detect any marine 
mammals that may approach from the north. The two PSOs aboard will 
split monitoring duties in order to monitor a 360 degree sweep around 
the vessel with each PSO responsible for 180 degrees of observable 
area.
    Monitoring will be conducted 30 minutes before, during, and 30 
minutes after pile driving/removal 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 or removed. Pile driving 
activities include the time to install or remove a single pile or 
series of piles, as long as the time elapsed between uses of the pile 
driving or drilling equipment is no more than 30 minutes.

Hydroacoustic Monitoring and Reporting

    The Navy has volunteered to conduct hydroacoustic monitoring of all 
pile driving and removal methods. Data will be collected for a 
representative number of piles (three to five) for each installation or 
removal method. As part of the below-mentioned report, or in a separate 
report with the same timelines as above, the Navy will provide an 
acoustic monitoring report for this work. Hydroacoustic monitoring 
results can be used to adjust the size of the Level B harassment and 
monitoring zones after a request is made and approved by NMFS. The 
acoustic monitoring report must, at minimum, include the following:
     Hydrophone equipment and methods: recording device, 
sampling rate, distance (m) from the pile where recordings were made; 
depth of recording device(s).
     Type of pile being driven or removed, substrate type, 
method of driving or removal during recordings.
     For impact pile driving: Pulse duration and mean, median, 
and maximum sound levels (dB re: 1[micro]Pa): SELcum, peak sound 
pressure level (SPLpeak), and single-strike sound exposure level (SELs-
s).
     For vibratory removal and other non-impulsive sources: 
Mean, median, and maximum sound levels (dB re: 1[micro]Pa): root mean 
square sound pressure level (SPLrms), SELcum.
     Number of strikes (impact) or duration (vibratory or other 
non-impulsive sources) per pile measured, one-third octave band 
spectrum and power spectral density plot.

Reporting

    A draft marine mammal monitoring report will be submitted to NMFS 
within 90 days after the completion of pile driving and removal 
activities, or 60 days prior to a requested date of issuance of any 
future IHAs for projects at the same location, whichever comes first. 
The report will include an overall description of work completed, a 
narrative regarding marine mammal sightings, and associated PSO data 
sheets. Specifically, the report must include:
     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 piles were 
driven or removed and by what method (i.e., impact or vibratory and if 
other removal methods were used);
     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;
     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; and

[[Page 80043]]

     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.
    If no comments are received from NMFS within 30 days, the draft 
final report will constitute the final report. If comments are 
received, a final report addressing NMFS comments must be submitted 
within 30 days after receipt of comments.

Reporting Injured or Dead Marine Mammals

    In the event that personnel involved in the construction activities 
discover an injured or dead marine mammal, the Navy shall report the 
incident to the Office of Protected Resources (OPR), NMFS and to the 
regional stranding coordinator as soon as feasible. If the death or 
injury was clearly caused by the specified activity, the Navy must 
immediately cease the specified activities until NMFS is able to review 
the circumstances of the incident and determine what, if any, 
additional measures are appropriate to ensure compliance with the terms 
of the IHA. The IHA-holder must not resume their activities until 
notified by NMFS. 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.

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 have the potential to disturb or displace 
marine mammals. Specifically, the project activities may result in 
take, in the form of Level B harassment from underwater sounds 
generated from pile driving and removal. Potential takes could occur if 
individuals are present in the ensonified zone when these activities 
are underway.
    The takes from Level B harassment would be due to potential 
behavioral disturbance, TTS, and PTS. No mortality 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).
    The nature of the pile driving project precludes the likelihood of 
serious injury or mortality. Take would occur within a limited, 
confined area (south-central San Diego Bay) of the stock's range. Level 
B harassment will be reduced to the level of least practicable adverse 
impact through use of mitigation measures described herein. Further the 
amount of take proposed to be authorized is extremely small when 
compared to stock abundance.
    Behavioral responses of marine mammals to pile driving at the 
project site, if any, are expected to be mild and temporary. Marine 
mammals within the Level B harassment zone may not show any visual cues 
they are disturbed by activities (as noted during modification to the 
Kodiak Ferry Dock) or could become alert, avoid the area, leave the 
area, or display other mild responses that are not observable such as 
changes in vocalization patterns. Given the short duration of noise-
generating activities per day and that pile driving and removal would 
occur across six months, any harassment would be temporary. There are 
no other areas or times of known biological importance for any of the 
affected species.
    In addition, it is unlikely that minor noise effects in a small, 
localized area of habitat would have any effect on the stocks' ability 
to recover. In combination, we believe that these factors, as well as 
the available body of evidence from other similar activities, 
demonstrate that the potential effects of the specified activities will 
have only minor, short-term effects on individuals. The specified 
activities are not expected to impact rates of recruitment or survival 
and will therefore not result in population-level impacts.
    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 
authorized;
     No important habitat areas have been identified within the 
project area;
     For all species, San Diego Bay is a very small and 
peripheral part of their range;
     The Navy would implement mitigation measures such as 
vibratory driving piles to the maximum extent practicable, soft-starts, 
and shut downs; and
     Monitoring reports from similar work in San Diego Bay have 
documented little to no effect on individuals of the same species 
impacted by the specified activities.
    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 section 101(a)(5)(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

[[Page 80044]]

determination of whether an authorization is limited to small numbers 
of marine mammals. When the predicted number of individuals to be taken 
is fewer than one third of the species or stock abundance, the take is 
considered to be of small numbers. Additionally, other qualitative 
factors may be considered in the analysis, such as the temporal or 
spatial scale of the activities.
    The amount of take NMFS proposes to authorize is below one third of 
the estimated stock abundance of California sea lions (in fact, take of 
individuals is less than 1% of the abundance of the affected stock). 
This is likely a conservative estimate because they assume all takes 
are of different individual animals which is likely not the case. Some 
individuals may return multiple times in a day, but PSOs would count 
them as separate takes if they cannot be individually identified.
    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

    Section 7(a)(2) of the 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, in this 
case with the West Coast Region Protected Resources Division Office, 
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 to conduct the Naval Base San Diego Pier 6 
Replacement project in San Diego, CA from October 1, 2021 through 
September 30, 2022, 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 Naval 
Base San Diego Pier 6 Replacement project. 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-time 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, activities as described in the Description of Proposed 
Activity section of this notice is planned or (2) the activities as 
described in the Description of Proposed Activity section of this 
notice would not be completed by the time the IHA expires and a Renewal 
would allow for completion of the activities beyond that described in 
the Dates and Duration section of this notice, provided all of the 
following conditions are met:
     A request for renewal is received no later than 60 days 
prior to the needed Renewal IHA effective date (recognizing that 
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: December 7, 2020.
Donna S. Wieting,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2020-27225 Filed 12-10-20; 8:45 am]
BILLING CODE 3510-22-P