[Federal Register Volume 76, Number 16 (Tuesday, January 25, 2011)]
[Notices]
[Pages 4300-4322]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-1528]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XA075
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to a Test Pile Program
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Notice; proposed incidental harassment authorization; request
for comments.
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SUMMARY: NMFS has received an application from the U.S. Navy (Navy) for
an Incidental Harassment Authorization (IHA) to take marine mammals, by
harassment, incidental to pile driving activities as part of a test
pile program. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS
is requesting comments on its proposal to issue an IHA to the Navy to
take, by Level B Harassment only, five species of marine mammals during
the specified activity.
DATES: Comments and information must be received no later than February
24, 2011.
ADDRESSES: Comments on the application should be addressed to Michael
Payne, Chief, Permits, Conservation and Education Division, Office of
Protected Resources, National Marine Fisheries Service, 1315 East-West
Highway, Silver Spring, MD 20910-3225. The mailbox address for
providing e-mail comments is [email protected]. NMFS is not responsible
for e-mail comments sent to addresses other than the one provided here.
Comments sent via e-mail, including all attachments, must not exceed a
10-megabyte file size.
Instructions: All comments received are a part of the public record
and will generally be posted to http://www.nmfs.noaa.gov/pr/permits/incidental.htm 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.
A copy of the application containing a list of the references used
in this document may be obtained by writing to the address specified
above, telephoning the contact listed below (see FOR FURTHER
INFORMATION CONTACT), or visiting the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm. The Navy has prepared a
draft Environmental Assessment (EA) titled ``Test Pile Program NBK
Bangor Waterfront, Naval Base Kitsap Bangor, Silverdale, WA'', and has
prepared a draft Essential Fish Habitat Assessment titled ``Test Pile
Program NBK Bangor Waterfront Draft Essential Fish Habitat
Assessment''. These associated documents, prepared in compliance with
the National Environmental Policy Act (NEPA) and Magnuson-Stevens
Fishery Conservation and Management Act, respectively, are also
available at the same internet address. Documents cited in this notice
may also be viewed, by appointment, during regular business hours, at
the aforementioned address.
FOR FURTHER INFORMATION CONTACT: Ben Laws, Office of Protected
Resources, NMFS, (301) 713-2289.
SUPPLEMENTARY INFORMATION:
Background
Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.)
direct the Secretary of Commerce 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 authorization is
provided to the public for review.
Authorization for incidental takings shall be granted if NMFS finds
that the taking will have a negligible impact on the species or
stock(s), will not have an unmitigable adverse impact on the
availability of the species or stock(s) for subsistence uses (where
relevant), and if the permissible methods of taking and requirements
pertaining to the mitigation, monitoring and reporting of such takings
are set forth. NMFS has defined ``negligible impact'' in 50 CFR 216.103
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.''
Section 101(a)(5)(D) of the MMPA established an expedited process
by
[[Page 4301]]
which citizens of the U.S. can apply for an authorization to
incidentally take small numbers of marine mammals by harassment.
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS review of
an application followed by a 30-day public notice and comment period on
any proposed authorizations for the incidental harassment of marine
mammals. Within 45 days of the close of the comment period, NMFS must
either issue or deny the authorization.
Except with respect to certain activities not pertinent here, the
MMPA defines ``harassment'' as:
Any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
Summary of Request
NMFS received an application on November 2, 2010 from the Navy for
the taking of marine mammals incidental to pile driving in association
with a test pile program in the Hood Canal at Naval Base Kitsap in
Bangor, WA (NBKB). This test pile program is proposed to occur between
July 16, 2011 and October 31, 2011. Six species of marine mammals may
be present within the waters surrounding NBKB: Steller sea lions
(Eumetopias jubatus), California sea lions (Zalophus californianus),
harbor seals (Phoca vitulina), killer whales (Orcinus orca), Dall's
porpoises (Phocoenoides dalli), and harbor porpoises (Phocoena
phocoena). These species may occur year-round in the Hood Canal, with
the exception of the Steller sea lion. Steller sea lions are present
only from fall to late spring (November-June), outside of the project's
timeline (July 16-October 31). Additionally, while the Southern
Resident killer whale (listed as endangered under the Endangered
Species Act [ESA]) is resident to the inland waters of Washington and
British Columbia, it has not been observed in the Hood Canal in decades
and was therefore excluded from further analysis. Only the five species
which may be present during the project's timeline may be exposed to
sound pressure levels associated with vibratory and impulsive pile
driving, and will be analyzed in detail in this document.
The Navy proposes to install up to 29 test and reaction piles at
NBKB to gather geotechnical and noise data to validate the design
concept for the building of a new Explosive Handling Wharf (EHW-2), as
well as for future projects at the NBKB waterfront. The test pile
program will require a maximum of forty work days for completion. The
forty work day duration of the program includes the time for the
initial pile installations, time for performing loading tests, and time
to remove all of the test piles. The pile lengths will range from 100-
197 ft (30-60 m), and range in diameter from 30-60 in (0.8-1.5 m). The
test pile program will involve driving eighteen steel pipe piles, at
pre-determined locations within the proposed footprint of EHW-2. Some
of the initial eighteen piles will be removed and re-driven as part of
lateral load and tension tests. A total of eleven piles will be
installed to perform lateral load and tension load tests. All piles
will be driven with a vibratory hammer for their initial embedment
depths, and select piles will be impact driven for their final 10-15 ft
(3-4.6 m) for proofing. ``Proofing'' involves driving a pile the last
few feet into the substrate to determine the capacity of the pile. The
capacity during proofing is established by measuring the resistance of
the pile to a hammer that has a piston with a known weight and stroke
(distance the hammer rises and falls) so that the energy on top of the
pile can be calculated. The blow count in ``blows per inch'' is
measured to verify resistance, and pile compression capacities are
calculated using a known formula. Noise attenuation measures (i.e.,
bubble curtain) will be used during all impact hammer operations and on
two of the vibratory-driven piles. Hydroacoustic monitoring will be
performed to assess effectiveness of noise attenuation measures.
For pile driving activities, the Navy used NMFS-promulgated
thresholds for assessing pile driving impacts (NMFS 2005b, 2009),
outlined later in this document. The Navy used recommended spreading
loss formulas (the practical spreading loss equation for underwater
sounds and the spherical spreading loss equation for airborne sounds)
and empirically-measured source levels from other 30-72 in (0.8-1.8 m)
diameter steel pile driving events to estimate potential marine mammal
exposures. Predicted exposures are outlined later in this document. The
calculations predict that no Level A harassments would occur associated
with pile driving activities, and that 1,180 Level B harassments may
occur during the test pile program from underwater sound. No incidents
of harassment were predicted from airborne sounds associated with pile
driving. Some assumptions (including marine mammal densities and other
assumptions) used to estimate the exposures are conservative, and may
overestimate the potential number of exposures and their severity.
Description of the Specified Activity
NBKB is located on the Hood Canal approximately twenty miles (32
km) west of Seattle, WA (see Figures 1-1 and 1-2 in the Navy's
application). NBKB provides berthing and support services to Navy
submarines and other fleet assets. The entirety of NBKB, including the
land areas and adjacent water areas in the Hood Canal are restricted
from general public access. The Navy proposes a test pile program to
support the design of the future construction of EHW-2. The proposed
actions with the potential to affect marine mammals within the
waterways adjacent to NBKB that could result in harassment under the
MMPA are vibratory and impulsive pile driving operations associated
with the test pile program. The proposed pile driving activities will
occur between July 16, 2011 and October 31, 2011. All in-water
construction activities within the Hood Canal are only permitted during
July 16-February 15 in order to protect spawning fish populations. The
further restriction of in-water work window proposed by the Navy avoids
the possibility of incidental harassment of Steller sea lions. The
Eastern Distinct Population Segment (DPS) of Steller sea lions, present
in the Hood Canal outside of the proposed project time period, is
listed as threatened under the ESA.
As part of the Navy's sea-based strategic deterrence mission, the
Navy Strategic Systems Programs directs research, development,
manufacturing, test, evaluation, and operational support of the TRIDENT
Fleet Ballistic Missile program. Maintenance and development of
necessary facilities for handling of explosive materials is part of
these duties. The proposed action for this IHA request is to install
and remove up to 29 test and reaction piles, conduct loading tests on
select piles, and measure in-water sound propagation parameters (e.g.,
transmission loss) during pile installation and removal. Geotechnical
and sound propagation data collected during pile installation and
removal will be integrated into the design, construction, and
environmental planning for the Navy's proposed EHW-2. Future
construction projects at the NBKB waterfront may also benefit from the
geotechnical data gathered for use in their environmental planning
documentation. The Navy proposes to install the test piles in the
location planned for the future EHW-2, which will be adjacent to the
existing
[[Page 4302]]
Explosive Handling Wharf (EHW-1) at NBKB. The test pile program will
require a maximum of forty work days for completion. Hydroacoustic
monitoring will be undertaken to assess the effectiveness of noise
attenuation measures. The presence of marine mammals will also be
monitored during pile installation and removal.
The test pile program has been designed to collect adequate
geotechnical and sound propagation data. Under the proposed action, the
Navy will install 29 test and reaction piles in the Hood Canal. The
pile lengths will range from 100-197 ft (30-60 m), and range in
diameter from 30-60 in (0.8-1.5 m). All piles will subsequently be
removed at the completion of the test pile program. These test piles
will be situated throughout the footprint of the future EHW-2,
currently in the preliminary planning process. Figure 1-3 of the Navy's
application shows in detail the locations of each of the test piles.
The installation of the test piles will involve driving eighteen
steel pipe piles into the substrate. Additionally, three lateral load
and two tension load tests will be performed. The lateral load test
involves measurements of lateral displacement versus load for the
piles. The lateral load tests will require re-installing two 60-in (1.5
m) diameter piles and one 48-in (1.2 m) diameter pile. The tension load
test measures the vertical capacity of a pile. The tension load tests
will require driving four reaction piles for each of the two tension
load tests. The lateral load test in combination with the tension load
test will result in the installation of an additional eleven piles. The
Navy expects that some of the initial eighteen test piles will be
removed and re-driven as part of lateral load and tension tests. Please
see the Navy's application for a diagram of the lateral load and
tension load tests, and for more specific information regarding each
test pile (Figure 1-4 and Table 1-1 of the Navy's application,
respectively).
According to the Navy, previous soil boring studies, as well as
experience at EHW-1, confirms that the substrate appears to be
relatively consistent in nature across the site. Therefore, all of the
piles will be driven by a vibratory hammer to their initial embedment
depths. The eighteen test piles would likely require the use of an
impact hammer to drive the piles the remaining 10-15 ft (3-4.6 m) into
the substrate and for proofing. The impact driver will perform a few
blows to warm up the hammer and a number of blows to verify capacity. A
Pile Dynamic Analyzer will be utilized to confirm capacity. As a
contingency, any piles that cannot be driven to their desired depth
using the vibratory hammer may require the use of the impact hammer to
finish installation. This contingency has been accounted for in the
modeling analysis.
The contractor is expected to mobilize two floating barges, one
large barge up to 80 ft wide x 300 ft (24 x 91 m) long and one medium
sized barge approximately 60 ft wide x 150 ft (18 x 46 m) long, for the
test pile program. These barges will be moved into location with a 44
ft (13 m) tug boat. The two barges will share the work load, with the
smaller barge working the inboard test piles and the larger barge
working the outboard test piles. The smaller barge will likely be on
site for approximately two weeks of pile driving while the larger barge
will be on site for the full duration of the program which is expected
to be no longer than forty days. Only one pile driving rig will be
operated at a time.
Sound attenuation measures (e.g., bubble curtain) will be used
during all impact hammer operations, and on two of the vibratory-driven
piles, to test the practicability of using bubble curtains with a
vibratory hammer. The Navy will monitor hydroacoustic levels, as well
as the presence and behavior of marine mammals during pile installation
and removal. All piles will be removed at or before the completion of
the test pile program because they could pose a potential navigation
risk if left in place. Removal is also necessary because the test piles
will not be incorporated into the proposed EHW-2, as exact pile
locations for the future structure have not yet been finalized.
The test pile program will require a maximum of forty work days for
completion. A work day is limited to the hours from two hours post-
sunrise to two hours prior to sunset. The forty work day duration of
the program includes the time for the initial pile installations, time
for performing the loading tests, and time to remove all of the test
piles. A 108-day authorization window (16 July-31 October) was
requested to take into account delays that could occur due to the
permitting process, materials availability, and inclement weather that
may preclude construction.
The Navy's contractor estimates that pile installation could occur
at a maximum rate of four piles per day. However, the Navy anticipates
that an average of two piles will be installed and removed per day. For
each pile installed, the driving time is expected to include no more
than one hour for vibratory driving and fifteen minutes for the impact
driving portion of the project, with a maximum 100 blows executed per
day. The U.S. Fish and Wildlife Service (USFWS) requested that a
maximum of 100 blows be executed per day in order to minimize potential
injurious impacts to fish species which the marbled murrelet, listed as
threatened under the ESA, prey upon. All piles will be extracted using
a vibratory hammer. Extraction is anticipated to take approximately
thirty minutes per pile. Overall, this results in an estimated maximum
of two hours for driving and removal per pile, or approximately four
hours per day. Therefore, while forty days of total in-water work time
is proposed, only a fraction of the total work time will actually be
spent on pile driving and removal.
An average work day (two hours post-sunrise to two hours prior to
sunset) ranges from six to twelve hours (for an average of
approximately eight to nine hours), depending on the month. Although it
is anticipated that only four hours would need to be spent on pile
driving and removal per day, the Navy modeled potential impacts as if
the entire day (i.e., eight to nine hours) could be spent pile driving
to take into account deviations from the estimated times for pile
installation and removal and to account for the additional use of the
impact pile driver in case of failure of the vibratory hammer to reach
the desired embedment depth. Based on the proposed action, the total
pile driving time from vibratory or impact pile driving would be less
than fifteen days (29 piles at an average of two per day, assuming an
average of eight to nine hours of pile driving per day).
Description of Noise Sources
Underwater sound levels are comprised of multiple sources,
including physical noise, biological noise, and anthropogenic noise.
Physical noise includes waves at the surface, earthquakes, ice, and
atmospheric noise. Biological noise includes sounds produced by marine
mammals, fish, and invertebrates. Anthropogenic noise consists of
vessels (small and large), dredging, aircraft overflights, and
construction noise. Known noise levels and frequency ranges associated
with anthropogenic sources similar to those that would be used for this
project are summarized in Table 1. Details of each of the sources are
described in the following text.
[[Page 4303]]
Table 1--Representative Noise Levels of Anthropogenic Sources
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Frequency Underwater noise level (dB
Noise source range (Hz) re 1 [micro]Pa) Reference
----------------------------------------------------------------------------------------------------------------
Small vessels............................ 250-1,000 151 dB root mean square Richardson et al. 1995.
(rms) at 1 m.
Tug docking gravel barge................. 200-1,000 149 dB rms at 100 m (328 ft) Blackwell and Greene 2002.
Vibratory driving of 72-in (1.8 m) steel 10-1,500 180 dB rms at 10 m (33 ft).. CALTRANS 2007.
pipe pile.
Impact driving of 36-in (0.9 m) steel 10-1,500 195 dB rms at 10 m.......... WSDOT 2007.
Pipe pile.
Impact driving of 66-in (1.7 m) CISS\1\ 100-1,500 195 dB rms at 10 m.......... Reviewed in Hastings and
piles. Popper 2005.
----------------------------------------------------------------------------------------------------------------
\1\ CISS = cast-in-steel-shell.
In-water construction activities associated with the project would
include impact pile driving and vibratory pile driving. The sounds
produced by these activities fall into one of two sound types: pulsed
and non-pulsed (defined in next paragraph). Impact pile driving
produces pulsed sounds, while vibratory pile driving produces non-
pulsed (or continuous) sounds. The distinction between these two
general 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). Please see Southall et al. (2007)
for an in-depth discussion of these concepts.
Pulsed sounds (e.g., explosions, gunshots, sonic booms, seismic
pile driving pulses, and impact pile driving) are brief, broadband,
atonal transients (ANSI 1986; Harris 1998) and occur either as isolated
events or repeated in some succession. Pulsed sounds are all
characterized by a relatively rapid rise from ambient pressure to a
maximal pressure value followed by a decay period that may include a
period of diminishing, oscillating maximal and minimal pressures.
Pulsed sounds generally have an increased capacity to induce physical
injury as compared with sounds that lack these features.
Non-pulse (intermittent or continuous sounds) can be tonal,
broadband, or both. Some of these non-pulse sounds can be transient
signals of short duration but without the essential properties of
pulses (e.g., rapid rise time). Examples of non-pulse sounds include
vessels, aircraft, machinery operations such as drilling or dredging,
vibratory pile driving, and active sonar systems. The duration of such
sounds, as received at a distance, can be greatly extended in a highly
reverberant environment.
Ambient Noise
By definition, ambient noise is background noise, without a single
source or point (Richardson et al. 1995). Ambient noise varies with
location, season, time of day, and frequency. Ambient noise is
continuous, but with much variability on time scales ranging from less
than one second to one year (Richardson et al. 1995). Ambient
underwater noise at the project area is widely variable over time due
to a number of natural and anthropogenic sources. Sources of naturally
occurring underwater noise include wind, waves, precipitation, and
biological noise (e.g., shrimp, fish, cetaceans). There is also human-
generated noise from ship or boat traffic and other mechanical means
(Urick 1983). Other sources of underwater noise at industrial
waterfronts could come from cranes, generators, and other types of
mechanized equipment on wharves or the adjacent shoreline.
In the vicinity of the project area, the average broadband ambient
underwater noise levels were measured at 114 dB re 1[micro]Pa between
100 Hz and 20 kHz (Slater 2009). Peak spectral noise from industrial
activity was noted below the 300 Hz frequency, with maximum levels of
110 dB re 1[micro]Pa noted in the 125 Hz band. In the 300 Hz to 5 kHz
range, average levels ranged between 83-99 dB re 1[micro]Pa. Wind-
driven wave noise dominated the background noise environment at
approximately 5 kHz and above, and ambient noise levels flattened above
10 kHz.
Airborne noise levels at NBKB vary based on location but are
estimated to average around 65 dBA (A-weighted decibels) in the
residential and office park areas, with traffic noise ranging from 60-
80 dBA during daytime hours (Cavanaugh and Tocci 1998). The highest
levels of airborne noise are produced along the waterfront and at the
ordnance handling areas, where estimated noise levels range from 70-90
dBA and may peak at 99 dBA for short durations. These higher noise
levels are produced by a combination of sound sources including heavy
trucks, forklifts, cranes, marine vessels, mechanized tools and
equipment, and other sound-generating industrial or military
activities.
Sound Thresholds
Since 1997, NMFS has used generic sound exposure thresholds to
determine when an activity in the ocean that produces sound might
result in impacts to a marine mammal such that a take by harassment
might occur (NMFS 2005b). To date, no studies have been conducted that
examine impacts to marine mammals from pile driving sounds from which
empirical noise thresholds have been established. Current NMFS practice
regarding exposure of marine mammals to high level sounds is that
cetaceans and pinnipeds exposed to impulsive sounds of 180 and 190 dB
rms or above, respectively, are considered to have been taken by Level
A (i.e., injurious) harassment. Behavioral harassment (Level B) is
considered to have occurred when marine mammals are exposed to sounds
at or above 160 dB rms for impulse sounds (e.g., impact pile driving)
and 120 dB rms for continuous noise (e.g., vibratory pile driving), but
below injurious thresholds. For airborne noise, pinniped disturbance
from haul-outs has been documented at 100 dB (unweighted) for pinnipeds
in general, and at 90 dB (unweighted) for harbor seals. NMFS uses these
levels as guidelines to estimate when harassment may occur.
Distance to Sound Thresholds
Underwater Sound Propagation Formula--Pile driving would generate
underwater noise that potentially could result in disturbance to marine
mammals transiting the project area. Transmission loss (TL) underwater
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
formula for transmission loss is:
TL = B * log10(R) + C * R, where
B = logarithmic (predominantly spreading) loss
C = linear (scattering and absorption) loss
R = range from source in meters
[[Page 4304]]
For all underwater calculations in this assessment, linear loss (C) was
not used (i.e., C = 0) and transmission loss was calculated using only
logarithmic spreading. Therefore, using practical spreading (B = 15),
the revised formula for transmission loss is TL = 15 log10
(R).
Underwater Noise from Pile Driving--The intensity of pile driving
sounds is greatly influenced by factors such as the type of piles,
hammers, and the physical environment in which the activity takes
place. A large quantity of literature regarding sound pressure levels
recorded from pile driving projects is available for consideration. In
order to determine reasonable sound pressure levels and their
associated affects on marine mammals that are likely to result from
pile driving at NBKB, studies with similar properties to the proposed
action were evaluated. Studies which met the following parameters were
considered: (1) Pile materials--steel pipe piles (30-72 in [0.8-1.8 m]
diameter); (2) Hammer machinery--vibratory and impact; and (3) Physical
environment--shallow depth (less than 100 ft [30 m]). Table 2 details
representative pile driving activities that have occurred in recent
years. Due to the similarity of these actions and the Navy's proposed
action, they represent reasonable sound pressure levels which could be
anticipated.
Table 2--Underwater Sound Pressure Levels From Similar In-Situ Monitored Construction Activities
----------------------------------------------------------------------------------------------------------------
Installation Measured sound
Project & location Pile size & type method Water depth pressure levels
----------------------------------------------------------------------------------------------------------------
Mukilteo Test Piles, WA\1\...... 36-in (0.9 m) Impact............ 7.3 m (24 ft)..... 195 dB re 1
steel pipe. [micro]Pa (rms)
at 10 m (33 ft).
Richmond-San Rafael Bridge, CA 66-in (1.7 m) Impact............ 4 m (13.1 ft)..... 195 dB re 1
\2\. steel CISS pile. [micro]Pa (rms)
at 10 m.
Unknown Location, CA \2\........ 72-in (1.8 m) Vibratory......... Approximately 5 m 180 dB re 1
steel pipe pile. (16.4 ft). [micro]Pa (rms)
at 10 m.
----------------------------------------------------------------------------------------------------------------
\1\ WSDOT 2007.
\2\ CALTRANS 2007.
Several noise reduction measures can be employed during pile
driving to reduce the high source pressures associated with impact pile
driving. Among these is the use of bubble curtains, cofferdams, pile
caps, or the use of vibratory installation. The efficacy of bubble
curtains is dependent upon a variety of site-specific factors,
including environmental conditions such as water current, sediment
type, and bathymetry; the type and size of the pile; and the type and
energy of the hammer. For the test pile program, the Navy intends to
employ noise reduction techniques during impact pile driving, including
the use of the Gunderboom Sound Attenuation System (SAS) or traditional
bubble curtain sound attenuation system. Additionally, vibratory pile
driving will be the primary installation method, which has lower source
levels than impact pile driving. The calculations of the distances to
the marine mammal noise thresholds described previously were calculated
for impact installation with and without consideration for mitigation
measures. Thorson and Reyff (2004) determined that a properly designed
bubble curtain could provide a reduction of 5 to 20 dB. Based on
information contained therein, distances calculated with consideration
for mitigation assumed a 10 dB reduction in source levels from the use
of sound attenuation devices, and the Navy used the mitigated distances
for impact pile driving for all analysis in their application.
Calculations for the marine mammal noise thresholds for vibratory
installation were done based on in-situ recordings of vibratory
installation and extraction data from CALTRANS (2007) which indicated a
sound pressure level (SPL) of 180 db re 1[micro]Pa at 10 m (33 ft).
This concurred with published literature from other studies which have
in the past used a 15 dB reduction factor from source levels from
impact driving recordings to calculate source levels for vibratory pile
driving. Sound levels associated with vibratory pile removal are the
same as those during vibratory installation (CALTRANS 2007) and have
been taken into consideration in the modeling analysis. All calculated
distances to and the total area encompassed by the marine mammal noise
thresholds are provided in Tables 3 and 4, respectively. Calculated
distance to thresholds using unmitigated impact driving is provided as
reference; no unmitigated impact driving will occur. The USFWS has
requested this as a measure to protect prey of the ESA-endangered
marbled murrelet.
Table 3--Calculated Distance(s) to Underwater Marine Mammal Noise Thresholds From Pile Driving
----------------------------------------------------------------------------------------------------------------
Distance in meters (ft) to threshold
---------------------------------------------------------------
Description Vibratory
Impact Level A Impact Level A Impact Level B Level B (120
(190 dB \1\) (180 dB \1\) (160 dB \1\) dB \1\)
----------------------------------------------------------------------------------------------------------------
Impact Driving, no mitigation................... 22 (72) 100 (328) 2,154 (7,067) N/A
Impact Driving with bubble curtain (Mitigation = 5 (16) 22 (72) 464 (1,522) N/A
10 dB reduction in SPLs).......................
Vibratory pile driver........................... 2 (7) 10 (33) N/A \2\ 100,000
(328,084)
----------------------------------------------------------------------------------------------------------------
All sound levels expressed in dB re 1 [micro]Pa rms.
Practical spreading loss (15 log, or 4.5 dB per doubling of distance) used for water depths 10-50 ft (3-15 m).
\1\ Sound pressure levels used for calculations were: 195 dB re 1 [micro]Pa @ 10 m (33 ft) for impact and 180 dB
re 1 [micro]Pa @ 10 m for vibratory.
\2\ Range calculated is greater than what would be realistic. Hood Canal average width at site is 2.4 km (1.5
mi), and is fetch limited from N to S at 20.3 km (12.6 mi).
[[Page 4305]]
Calculated distances to thresholds, and calculated areas
encompassed by thresholds, assume a field free of obstruction. This is
unrealistic, however, because the Hood Canal does not represent open
water conditions (free field) and therefore, sounds would attenuate as
they encountered land masses or bends in the canal. As a result, some
of the distances and areas of impact calculated cannot actually be
attained within the project area. The actual distances to the
behavioral disturbance thresholds for both impact and vibratory pile
driving (464 m and 100,000 m [1,522 and 328,084 ft], respectively) may
be shorter than those calculated due to the irregular contour of the
waterfront, the narrowness of the canal, and the maximum fetch
(furthest distance sound waves travel without obstruction [i.e., line
of sight]) at the project area. Table 4 presents the calculated area
encompassed for each threshold, as well as the actual area that is
predicted to be encompassed due to obstructions as described above.
Please see figures 6-1 and 6-2 in the Navy's application for graphical
depictions of these areas for cetaceans and pinnipeds.
Table 4--Area Encompassed (Per Pile) by the Underwater Marine Mammal Noise Thresholds From Pile Driving,
Calculated and Actual
----------------------------------------------------------------------------------------------------------------
Area in square kilometers (mi\2\) encompassed by the threshold
---------------------------------------------------------------
Description Vibratory
Impact Level A Impact Level A Impact Level B Level B (120
(190 dB \1\) (180 dB \1\) (160 dB \1\) dB \1\)
----------------------------------------------------------------------------------------------------------------
Impact Driving with bubble curtain, calculated 0.000 0.002 (0.001) 0.676 (0.261) N/A
(Mitigation = 10 dB reduction in SPLs).........
Impact Driving with bubble curtain, actual 0.000 0.002 (0.001) 0.509 (0.197) N/A
(Mitigation = 10 dB reduction in SPLs).........
Vibratory pile driver, calculated............... 0.000 0.000 N/A 31,416
(12,130)
Vibratory pile driver, actual................... 0.000 0.000 N/A 41.5 (16)
----------------------------------------------------------------------------------------------------------------
\1\ Sound pressure levels used for calculations were: 195 dB re 1 [micro]Pa @ 10 m (33 ft) for impact and 180 dB
re 1 [micro]Pa @ 10 m for vibratory.
Airborne Sound Propagation Formula--Pile driving can generate
airborne noise that could potentially result in disturbance to marine
mammals (specifically, pinnipeds) which are hauled out or at the
water's surface. As a result, the Navy analyzed the potential for
pinnipeds hauled out or swimming at the surface near NBKB to be exposed
to airborne sound pressure levels that could result in Level B
behavioral harassment. The appropriate airborne noise threshold for
behavioral disturbance for all pinnipeds, except harbor seals, is 100
dB re 20 [micro]Pa rms (unweighted). For harbor seals the threshold is
90 dB re 20 [micro]Pa rms (unweighted). A spherical spreading loss
model, assuming average atmospheric conditions, was used to estimate
the distance to the 100 dB and 90 dB re 20 [micro]Pa rms (unweighted)
airborne thresholds. The formula for calculating spherical spreading
loss is:
TL = 20log r
TL = Transmission loss
r = Distance from source to receiver
*Spherical spreading results in a 6 dB decrease in sound pressure
level per doubling of distance.
Airborne Sound from Pile Driving--As was discussed for underwater
noise from pile driving, the intensity of pile driving sounds is
greatly influenced by factors such as the type of piles, hammers, and
the physical environment in which the activity takes place. In order to
determine reasonable airborne sound pressure levels and their
associated effects on marine mammals that are likely to result from
pile driving at NBKB, studies with similar properties to the proposed
action, as described previously, were evaluated. Table 5 details
representative pile driving activities that have occurred in recent
years. Due to the similarity of these actions and the Navy's proposed
action, they represent reasonable sound pressure levels which could be
anticipated.
Table 5--Airborne Sound Pressure Levels From Similar In-situ Monitored Construction Activities
----------------------------------------------------------------------------------------------------------------
Installation Measured sound
Project & location Pile size & type method Water depth pressure levels
----------------------------------------------------------------------------------------------------------------
Northstar Island, AK \1\........ 42-in (1.1 m) Impact............ Approximately 12 m 97 dB re 20
steel pipe pile.. (40 ft). [micro]Pa (rms)
at 525 ft (160
m).
Keystone Ferry Terminal, WA \2\. 30-in (0.8 m) Vibratory......... Approximately 9 m 98 dB re 20
steel pipe pile. (30 ft). [micro]Pa (rms)
at 36 ft (11 m).
----------------------------------------------------------------------------------------------------------------
\1\ Blackwell et al. 2004.
\2\ WSDOT 2010.
Based on in-situ recordings from similar construction activities,
the maximum airborne noise levels that would result from impact and
vibratory pile driving are estimated to be 97 dB re 20 [micro]Pa (rms)
at 525 ft (160 m) and 98 dB re 20 [micro]Pa (rms) at 36 ft (11 m),
respectively (Blackwell et al. 2004; WSDOT 2010). The distances to the
airborne thresholds were calculated with the airborne transmission loss
formula presented previously. All calculated distances to and the total
area encompassed by the airborne marine mammal noise thresholds are
provided in Tables 6 and 7, respectively.
[[Page 4306]]
Table 6--Calculated Distances to the Marine Mammal Noise Thresholds In-Air From Pile Driving
----------------------------------------------------------------------------------------------------------------
Airborne behavioral disturbance
-------------------------------------------------
Species Threshold Distance to threshold Distance to threshold
impact pile driving vibratory pile driving
----------------------------------------------------------------------------------------------------------------
Pinnipeds (except harbor seal)....... 100 dB re 20 [micro]Pa 113 m (371 ft)......... 9 m (30 ft).
rms (unweighted).
Harbor seal.......................... 90 dB re 20 [micro]Pa 358 m (1,175 ft)....... 28 m (92 ft).
rms (unweighted).
----------------------------------------------------------------------------------------------------------------
Table 7--Calculated Area Encompassed (Per Pile) by the Marine Mammal Noise Thresholds In-Air From Pile Driving
----------------------------------------------------------------------------------------------------------------
Airborne behavioral disturbance
-------------------------------------------------
Species Threshold Area encompassed by the Area encompassed by the
threshold for impact threshold for vibratory
pile driving pile driving
----------------------------------------------------------------------------------------------------------------
Pinnipeds (except harbor seal)....... 100 dB re 20 [micro]Pa 0.040 km\2\ (.015 0.000 km\2\.
rms (unweighted). mi\2\).
Harbor seal.......................... 90 dB re 20 [micro]Pa 0.403 km\2\ (0.156 0.002 km\2\ (.001
rms (unweighted). mi\2\). mi\2\).
----------------------------------------------------------------------------------------------------------------
The distance to the sea lion airborne threshold would be 113 m (371
ft) for impact pile driving, and 9 m (30 ft) for vibratory pile
driving. The distance to the harbor seal airborne threshold would be
358 m (1,175 ft) for impact pile driving, and 28 m (92 ft) for
vibratory pile driving. These distances are all less than the distances
calculated for underwater sound thresholds. Since protective measures
are in place out to the distances calculated for the underwater
thresholds, the distances for the airborne thresholds will be covered
fully by mitigation and monitoring measures in place for underwater
sound thresholds. All construction noise associated with the project
would not extend beyond the buffer zone for underwater sound that would
be established to protect seals and sea lions. No haul-outs or
rookeries are located within these radii. Please see figures 6-3 and 6-
4 of the Navy's application for graphical depictions of the distances
and total area encompassed by each airborne sound threshold for
pinnipeds that are predicted to occur at the project area due to pile
driving.
Description of Marine Mammals in the Area of the Specified Activity
There are six marine mammal species, three cetaceans and three
pinnipeds, which may inhabit or transit through the waters nearby NBKB
in the Hood Canal. These include the transient killer whale, harbor
porpoise, Dall's porpoise, Steller sea lion, California sea lion, and
the harbor seal. While the Southern Resident killer whale is resident
to the inland waters of Washington and British Columbia, it has not
been observed in the Hood Canal in decades, and therefore was excluded
from further analysis. The Steller sea lion is the only marine mammal
that occurs within the Hood Canal which is listed under the ESA; the
Eastern DPS is listed as threatened. As noted previously, and in Table
8, Steller sea lions are not present in the project area during the
proposed project timeframe (July 16-October 31). Steller sea lions will
not be discussed in detail. All marine mammal species are protected
under the MMPA. This section summarizes the population status and
abundance of these species, followed by detailed life history
information. Table 8 lists the marine mammal species that occur in the
vicinity of NBKB and their estimated densities within the project area
during the proposed timeframe.
Table 8--Marine Mammals Present in the Hood Canal in the Vicinity of NBKB
----------------------------------------------------------------------------------------------------------------
Density in
Relative warm season
Species Stock abundance \1\ occurrence in Hood Season of \3\
Canal occurrence (individuals/
km\2\)
----------------------------------------------------------------------------------------------------------------
Steller sea lion; Eastern U.S. \2\ 50,464 Rare to occasional Fall to late N/A
DPS. use. spring (Nov-mid
April).
California sea lion; U.S. Stock. 238,000 Common............ Fall to late \4\ 0.410
spring (Aug-May).
Harbor seal; WA inland waters 14,612 (CV = 0.15) Common............ Year-round; \5\ 1.31
stock. resident species
in Hood Canal.
Killer whale; West Coast 314 Rare to occasional Year-round........ \6\ 0.038
transient stock. use.
Dall's porpoise; CA/OR/WA stock. 48,376 (CV = 0.24) Rare to occasional Year-round........ \7\ 0.043
use.
Harbor porpoise; WA inland 10,682 (CV = 0.38) Rare to occasional Year-round........ \7\ 0.011
waters stock. use.
----------------------------------------------------------------------------------------------------------------
\1\ NMFS marine mammal stock assessment reports at: http://www.nmfs.noaa.gov/pr/sars/species.htm.
\2\ Average of a given range.
\3\ Warm season refers to the period from May-Oct.
\4\ DoN 2010a.
\5\ Jeffries et al. 2003; Huber et al. 2001.
\6\ London 2006.
\7\ Agness and Tannenbaum 2009a.
[[Page 4307]]
California Sea Lion
Species Description--California sea lions are members of the
Otariid family (eared seals). The species, Zalophus californianus,
includes three subspecies: Z. c. wollebaeki (in the Galapagos Islands),
Z. c. japonicus (in Japan, but now thought to be extinct), and Z. c.
californianus (found from southern Mexico to southwestern Canada;
referred to here as the California sea lion) (Carretta et al. 2007).
The California sea lion is sexually dimorphic. Males may reach 1,000 lb
(454 kg) and 8 ft (2.4 m) in length; females grow to 300 lb (136 kg)
and 6 ft (1.8 m) in length. Their color ranges from chocolate brown in
males to a lighter, golden brown in females. At around five years of
age, males develop a bony bump on top of the skull called a sagittal
crest. The crest is visible in the dog-like profile of male sea lion
heads, and hair around the crest gets lighter with age.
Population Abundance--The U.S. stock of California sea lions may
occur in the marine waters nearby NBKB. The stock is estimated at
238,000 and the minimum population size of this stock is 141,842
individuals (Carretta et al. 2007). These numbers are from counts
during the 2001 breeding season of animals that were ashore at the four
major rookeries in southern California and at haul-out sites north to
the Oregon/California border. Sea lions that were at-sea or hauled-out
at other locations were not counted (Carretta et al. 2007). An
estimated 3,000 to 5,000 California sea lions migrate to waters of
Washington and British Columbia during the non-breeding season from
September to May (Jeffries et al. 2000). Peak numbers of up to 1,000
California sea lions occur in Puget Sound (including Hood Canal) during
this time period (Jeffries et al. 2000).
Distribution--The geographic distribution of California sea lions
includes a breeding range from Baja California, Mexico to southern
California. During the summer, California sea lions breed on islands
from the Gulf of California to the Channel Islands and seldom travel
more than about 31 mi (50 km) from the islands (Bonnell et al. 1983).
The primary rookeries are located on the California Channel Islands of
San Miguel, San Nicolas, Santa Barbara, and San Clemente (Le Boeuf and
Bonnell 1980; Bonnell and Dailey 1993). Their distribution shifts to
the northwest in fall and to the southeast during winter and spring,
probably in response to changes in prey availability (Bonnell and Ford
1987).
The non-breeding distribution extends from Baja California north to
Alaska for males, and encompasses the waters of California and Baja
California for females (Reeves et al. 2008; Maniscalco et al. 2004). In
the non-breeding season, an estimated 3,000-5,000 adult and sub-adult
males migrate northward along the coast to central and northern
California, Oregon, Washington, and Vancouver Island from September to
May (Jeffries et al. 2000) and return south the following spring (Mate
1975; Bonnell et al. 1983). Along their migration, they are
occasionally sighted hundreds of miles offshore (Jefferson et al.
1993). Females and juveniles tend to stay closer to the rookeries
(Bonnell et al 1983).
Peak abundance in the Puget Sound is September to May. Although
there are no regular California sea lion haul-outs within the Hood
Canal (Jeffries et al. 2000), they often haul out at several opportune
areas. They are known to utilize man-made structures such as piers,
jetties, offshore buoys, and oil platforms (Riedman 1990). California
sea lions in the Puget Sound sometimes haul out on log booms and Navy
submarines, and are often seen rafted off river mouths (Jeffries et al.
2000; DoN 2001). As many as forty California sea lions have been
observed hauled out at NBKB on manmade structures (e.g., submarines,
floating security fence, barges) (Agness and Tannenbaum 2009a;
Tannenbaum et al. 2009a; Walters 2009). California sea lions have also
been observed swimming in the Hood Canal in the vicinity of the project
area on several occasions and likely forage in both nearshore marine
and inland marine deeper waters (DoN 2001a).
Behavior and Ecology--California sea lions feed on a wide variety
of prey, including many species of fish and squid (Everitt et al. 1981;
Roffe and Mate 1984; Antonelis et al. 1990; Lowry et al. 1991). In the
Puget Sound region, they feed primarily on fish such as Pacific hake
(Merluccius productus), walleye pollock (Theragra chalcogramma),
Pacific herring (Clupea pallasii), and spiny dogfish (Squalus
acanthias) (Calambokidis and Baird 1994). In some locations where
salmon runs exist, California sea lions also feed on returning adult
and out-migrating juvenile salmonids (London 2006). Sexual maturity
occurs at around four to five years of age for California sea lions
(Heath 2002). California sea lions are gregarious during the breeding
season and social on land during other times.
Acoustics--On land, California sea lions make incessant, raucous
barking sounds; these have most of their energy at less than 2 kHz
(Schusterman et al. 1967). Males vary both the number and rhythm of
their barks depending on the social context; the barks appear to
control the movements and other behavior patterns of nearby
conspecifics (Schusterman 1977). Females produce barks, squeals,
belches, and growls in the frequency range of 0.25-5 kHz, while pups
make bleating sounds at 0.25-6 kHz. California sea lions produce two
types of underwater sounds: clicks (or short-duration sound pulses) and
barks (Schusterman et al. 1966, 1967; Schusterman and Baillet 1969).
All underwater sounds have most of their energy below 4 kHz
(Schusterman et al. 1967).
The range of maximal hearing sensitivity underwater is between 1-28
kHz (Schusterman et al. 1972). Functional underwater high frequency
hearing limits are between 35-40 kHz, with peak sensitivities from 15-
30 kHz (Schusterman et al. 1972). The California sea lion shows
relatively poor hearing at frequencies below 1 kHz (Kastak and
Schusterman 1998). Peak hearing sensitivities in air are shifted to
lower frequencies; the effective upper hearing limit is approximately
36 kHz (Schusterman 1974). The best range of sound detection is from 2-
16 kHz (Schusterman 1974). Kastak and Schusterman (2002) determined
that hearing sensitivity generally worsens with depth--hearing
thresholds were lower in shallow water, except at the highest frequency
tested (35 kHz), where this trend was reversed. Octave band noise
levels of 65-70 dB above the animal's threshold produced an average
temporary threshold shift (TTS; discussed later in ``Potential Effects
of the Specified Activity on Marine Mammals'') of 4.9 dB in the
California sea lion (Kastak et al. 1999).
Harbor Seal
Species Description--Harbor seals, which are members of the Phocid
family (true seals), inhabit coastal and estuarine waters and shoreline
areas from Baja California, Mexico to western Alaska. For management
purposes, differences in mean pupping date (i.e., birthing) (Temte
1986), movement patterns (Jeffries 1985; Brown 1988), pollutant loads
(Calambokidis et al. 1985) and fishery interactions have led to the
recognition of three separate harbor seal stocks along the west coast
of the continental U.S. (Boveng 1988). The three distinct stocks are:
(1) inland waters of Washington (including Hood Canal, Puget Sound, and
the Strait of Juan de Fuca out to Cape Flattery), (2) outer coast of
Oregon and Washington, and (3) California (Carretta et al. 2007).
[[Page 4308]]
The inland waters of Washington stock is the only stock that is
expected to occur within the project area.
The average weight for adult seals is about 180 lb (82 kg) and
males are slightly larger than females. Male harbor seals weigh up to
245 lb (111 kg) and measure approximately 5 ft (1.5 m) in length. The
basic color of harbor seals' coat is gray and mottled but highly
variable, from dark with light color rings or spots to light with dark
markings (NMFS 2008c).
Population Abundance--Estimated population numbers for the inland
waters of Washington, including the Hood Canal, Puget Sound, and the
Strait of Juan de Fuca out to Cape Flattery, are 14,612 individuals
(Carretta et al. 2007). The minimum population is 12,844 individuals.
The harbor seal is the only species of marine mammal that is
consistently abundant and considered resident in the Hood Canal
(Jeffries et al. 2003). The population of harbor seals in Hood Canal is
a closed population, meaning that they do not have much movement
outside of Hood Canal (London 2006). The abundance of harbor seals in
Hood canal has stabilized, and the population may have reached its
carrying capacity in the mid-1990s with an approximate abundance of
1,000 harbor seals (Jeffries et al. 2003).
Distribution--Harbor seals are coastal species, rarely found more
than 12 mi (20 km) from shore, and frequently occupy bays, estuaries,
and inlets (Baird 2001). Individual seals have been observed several
miles upstream in coastal rivers. Ideal harbor seal habitat includes
haul-out sites, shelter during the breeding periods, and sufficient
food (Bjorge 2002). Haul-out areas can include intertidal and subtidal
rock outcrops, sandbars, sandy beaches, peat banks in salt marshes, and
man-made structures such as log booms, docks, and recreational floats
(Wilson 1978; Prescott 1982; Schneider and Payne 1983; Gilber and
Guldager 1998; Jeffries et al. 2000). Human disturbance can affect
haul-out choice (Harris et al. 2003).
Harbor seals occur throughout Hood Canal and are seen relatively
commonly in the area. They are year-round, non-migratory residents, and
pup (i.e., give birth) in Hood Canal. Surveys in the Hood Canal from
the mid-1970s to 2000 show a fairly stable population between 600-1,200
seals (Jeffries et al. 2003). Harbor seals have been observed swimming
in the waters along NBKB in every month of surveys conducted from 2007-
2010 (Agness and Tannenbaum 2009b; Tannenbaum et al. 2009b). On the
NBKB waterfront, harbor seals have not been observed hauling out in the
intertidal zone, but have been observed hauled-out on man-made
structures such as the floating security fence, buoys, barges, marine
vessels, and logs (Agness and Tannenbaum 2009a; Tannenbaum et al.
2009a). The main haul-out locations for harbor seals in Hood Canal are
located on river delta and tidal exposed areas at Quilcene,
Dosewallips, Duckabush, Hamma Hamma, and Skokomish River mouths (see
Figure 4-1 of the Navy's application), with the closest haul-out area
to the project area being ten miles (16 km) southwest of NBKB at
Dosewallips River mouth (London 2006).
Behavior and Ecology--Harbor seals are typically seen in small
groups resting on tidal reefs, boulders, mudflats, man-made structures,
and sandbars. Harbor seals are opportunistic feeders that adjust their
patterns to take advantage of locally and seasonally abundant prey
(Payne and Selzer 1989; Baird 2001; Bj[oslash]rge 2002). The harbor
seal diet consists of fish and invertebrates (Bigg 1981; Roffe and Mate
1984; Orr et al. 2004). Although harbor seals in the Pacific Northwest
are common in inshore and estuarine waters, they primarily feed at sea
(Orr et al. 2004) during high tide. Researchers have found that they
complete both shallow and deep dives during hunting depending on the
availability of prey (Tollit et al. 1997). Their diet in Puget Sound
consists of many of the prey resources that are present in the
nearshore and deeper waters of NBKB, including hake, herring and adult
and out-migrating juvenile salmonids. Harbor seals in Hood Canal are
known to feed on returning adult salmon, including ESA-threatened
summer-run chum (Oncorhynchus keta). Over a five-year study of harbor
seal predation in the Hood Canal, the average percent escapement of
summer-run chum consumed was eight percent (London 2006).
Harbor seals mate at sea and females give birth during the spring
and summer, although the pupping season varies by latitude. In coastal
and inland regions of Washington, pups are born from April through
January. Pups are generally born earlier in the coastal areas and later
in the Puget Sound/Hood Canal region (Calambokidis and Jeffries 1991;
Jeffries et al. 2000). Suckling harbor seal pups spend as much as forty
percent of their time in the water (Bowen et al. 1999).
Acoustics--In air, harbor seal males produce a variety of low-
frequency (less than 4 kHz) vocalizations, including snorts, grunts,
and growls. Male harbor seals produce communication sounds in the
frequency range of 100-1,000 Hz (Richardson et al. 1995). Pups make
individually unique calls for mother recognition that contain multiple
harmonics with main energy below 0.35 kHz (Bigg 1981; Thomson and
Richardson 1995). Harbor seals hear nearly as well in air as underwater
and had lower thresholds than California sea lions (Kastak and
Schusterman 1998). Kastak and Schusterman (1998) reported airborne low
frequency (100 Hz) sound detection thresholds at 65.4 dB re 20 [mu]Pa
for harbor seals. In air, they hear frequencies from 0.25-30 kHz and
are most sensitive from 6-16 kHz (Richardson 1995; Terhune and Turnbull
1995; Wolski et al. 2003).
Adult males also produce underwater sounds during the breeding
season that typically range from 0.25-4 kHz (duration range: 0.1 s to
multiple seconds; Hanggi and Schusterman 1994). Hanggi and Schusteman
(1994) found that there is individual variation in the dominant
frequency range of sounds between different males, and Van Parijs et
al. (2003) reported oceanic, regional, population, and site-specific
variation that could be vocal dialects. In water, they hear frequencies
from 1-75 kHz (Southall et al. 2007) and can detect sound levels as
weak as 60-85 dB re 1 [mu]Pa within that band. They are most sensitive
at frequencies below 50 kHz; above 60 kHz sensitivity rapidly
decreases.
Killer Whale
Species Description--Killer whales are members of the Delphinid
family and are the most widely distributed cetacean species in the
world. Killer whales have a distinctive color pattern, with black
dorsal and white ventral portions. They also have a conspicuous white
patch above and behind the eye and a highly variable gray or white
saddle area behind the dorsal fin. The species shows considerable
sexual dimorphism. Adult males develop larger pectoral flippers, dorsal
fins, tail flukes, and girths than females. Male adult killer whales
can reach up to 32 ft (9.8 m) in length and weigh nearly 22,000 lb
(10,000 kg); females reach 28 ft (8.5 m) in length and weigh up to
16,500 lb (7,500 kg).
Based on appearance, feeding habits, vocalizations, social
structure, and distribution and movement patterns there are three types
of populations of killer whales (Wiles 2004; NMFS 2005). The three
distinct forms or types of killer whales recognized in the North
Pacific Ocean are: (1) Resident, (2) Transient, and (3) Offshore. The
resident and transient populations have
[[Page 4309]]
been divided further into different subpopulations based mainly on
genetic analyses and distribution; not enough is known about the
offshore whales to divide them into subpopulations (Wiles 2004). Only
transient killer whales are known from the project area.
Transient killer whales occur throughout the eastern North Pacific,
and have primarily been studied in coastal waters. Their geographical
range overlaps that of the resident and offshore killer whales. The
dorsal fin of transient whales tends to be more erect (straighter at
the tip) than those of resident and offshore whales (Ford and Ellis
1999; Ford et al. 2000). Saddle patch pigmentation of transient killer
whales is restricted to two patterns, and never has the large areas of
black pigmentation intruding into the white of the saddle patch that is
seen in resident and offshore types. Transient type whales are often
found in long-term stable social units that tend to be smaller than
resident social groups (e.g., fewer than ten whales); these social
units do not seem as permanent as matrilines are in resident type
whales. Transient killer whales feed nearly exclusively on marine
mammals (Ford and Ellis 1999), whereas resident whales primarily eat
fish. Offshore whales are presumed to feed primarily on fish, and have
been documented feeding on sharks.
Within the transient type, association data (Ford et al. 1994; Ford
and Ellis 1999; Matkin et al. 1999), acoustic data (Saulitis 1993; Ford
and Ellis 1999) and genetic data (Hoelzel et al. 1998, 2002; Barrett-
Lennard 2000) confirms that three communities of transient whales exist
and represent three discrete populations: (1) Gulf of Alaska, Aleutian
Islands, and Bering Sea transients, (2) AT1 transients (Prince William
Sound, AK; listed as depleted under the MMPA), and (3) West Coast
transients. Among the genetically distinct assemblages of transient
killer whales in the northeastern Pacific, only the West Coast
transient stock, which occurs from southern California to southeastern
Alaska, may occur in the project area.
Population Abundance--The West Coast transient stock is a trans-
boundary stock, with minimum counts for the population of transient
killer whales coming from various photographic datasets. Combining
these counts of cataloged transient whales gives a minimum number of
314 individuals for the West Coast transient stock (Allen and Angliss
2010). However, the number in Washington waters at any one time is
probably fewer than twenty individuals (Wiles 2004).
Distribution--The geographical range of transient killer whales
includes the northeast Pacific, with preference for coastal waters of
southern Alaska and British Columbia (Krahn et al. 2002). Transient
killer whales in the eastern North Pacific spend most of their time
along the outer coast, but visit Hood Canal and the Puget Sound in
search of harbor seals, sea lions, and other prey. Transient occurrence
in inland waters appears to peak during August and September (Morton
1990; Baird and Dill 1995; Ford and Ellis 1999) which is the peak time
for harbor seal pupping, weaning, and post-weaning (Baird and Dill
1995). In 2003 and 2005, small groups of transient killer whales
(eleven and six individuals, respectively) visited Hood Canal to feed
on harbor seals and remained in the area for significant periods of
time (59 and 172 days, respectively) between the months of January and
July.
Behavior and Ecology--Transient killer whales show greater
variability in habitat use, with some groups spending most of their
time foraging in shallow waters close to shore while others hunt almost
entirely in open water (Felleman et al. 1991; Baird and Dill 1995;
Matkin and Saulitis 1997). Transient killer whales feed on marine
mammals and some seabirds, but apparently no fish (Morton 1990; Baird
and Dill 1996; Ford et al. 1998; Ford and Ellis 1999; Ford et al.
2005). While present in Hood Canal in 2003 and 2005, transient killer
whales preyed on harbor seals in the subtidal zone of the nearshore
marine and inland marine deeper water habitats (London 2006). Other
observations of foraging transient killer whales indicate they prefer
to forage on pinnipeds in shallow, protected waters (Heimlich-Boran
1988; Saulitis et al. 2000). Transient killer whales travel in small,
matrilineal groups, but they typically contain fewer than ten animals
and their social organization generally is more flexible than that of
resident killer whales (Morton 1990, Ford and Ellis 1999). These
differences in social organization probably relate to differences in
foraging (Baird and Whitehead 2000). There is no information on the
reproductive behavior of killer whales in this area.
Acoustics--Killer whales produces a wide variety of clicks and
whistles, but most of their sounds are pulsed, with frequencies ranging
from 0.5-25 kHz (dominant frequency range: 1-6 kHz) (Thomson and
Richardson 1995; Richardson et al. 1995). Source levels of echolocation
signals range between 195-224 dB re 1 [mu]Pa-m peak-to-peak (p-p),
dominant frequencies range from 20-60 kHz, with durations of about 0.1
s (Au et al. 2004). Source levels associated with social sounds have
been calculated to range between 131-168 dB re 1 [mu]Pa-m and vary with
vocalization type (Veirs 2004).
Both behavioral and auditory brainstem response technique indicate
killer whales can hear in a frequency range of 1-100 kHz and are most
sensitive at 20 kHz. This is one of the lowest maximum-sensitivity
frequencies known among toothed whales (Szymanski et al. 1999).
Dall's Porpoise
Species Description--Dall's porpoises are members of the Phocoenid
(porpoise) family and are common in the North Pacific Ocean. They can
reach a maximum length of just under 8 ft (2.4 m) and weigh up to 480
lb (218 kg). Males are slightly larger and thicker than females, which
reach lengths of just under 7 ft (2.1 m) long. The body of Dall's
porpoises is a very dark gray or black in coloration with variable
contrasting white thoracic panels and white `frosting' on the dorsal
fin and tail that distinguish them from other cetacean species. These
markings and colorations vary with geographic region and life stage,
with adults having more distinct patterns.
Based on NMFS stock assessment reports, Dall's porpoises within the
Pacific U.S. Exclusive Economic Zone are divided into two discrete,
noncontiguous areas: (1) waters off California, Oregon, and Washington,
and (2) Alaskan waters (Carretta et al. 2008). Only individuals from
the CA/OR/WA stock may occur within the project area.
Population Abundance--The NMFS population estimate, recently
updated in 2008 for the CA/OR/WA stock, is 48,376 (CV = 0.24) which is
based on vessel line transect surveys by Barlow and Forney (2007) and
Forney (2007) (Carretta et al. 2008). The minimum population is
considered to be 39,709. Additional numbers of Dall's porpoises occur
in the inland waters of Washington, but the most recent estimate was
obtained in 1996 (900 animals; CV = 0.40; Calambokidis et al. 1997) and
is not included in the overall estimate of abundance for this stock due
to the need for more up-to-date information.
Distribution--The Dall's porpoise is found from northern Baja
California, Mexico, north to the northern Bering Sea and south to
southern Japan (Jefferson et al. 1993). The species is only common
between 32-62[deg]N in the eastern North Pacific (Morejohn 1979; Houck
and Jefferson 1999). North-south movements in California, Oregon, and
[[Page 4310]]
Washington have been suggested. Dall's porpoises shift their
distribution southward during cooler-water periods (Forney and Barlow
1998). Norris and Prescott (1961) reported finding Dall's porpoises in
southern California waters only in the winter, generally when the water
temperature was less than 15[deg]C (59[deg]F). Seasonal movements have
also been noted off Oregon and Washington, where higher densities of
Dall's porpoises were sighted offshore in winter and spring and inshore
in summer and fall (Green et al. 1992).
In Washington, they are most abundant in offshore waters. They are
year-round residents in Washington (Green et al. 1992), but their
distribution is highly variable between years, likely due to changes in
oceanographic conditions (Forney and Barlow 1998). Dall's porpoises are
observed throughout the year in the Puget Sound north of Seattle
(Osborne et al. 1998) and are seen occasionally in southern Puget
Sound. Dall's porpoises may also occasionally occur in Hood Canal
(Jeffries 2006, personal communication). Nearshore habitats used by
Dall's porpoises could include the marine habitats found in the inland
marine waters of the Hood Canal. A Dall's porpoise was observed in the
deeper water at NBKB in summer 2008 (Tannenbaum et al. 2009a).
Behavior and Ecology--Dall's porpoises can be opportunistic feeders
but primarily consume schooling forage fish. They are known to eat
squid, crustaceans, and fishes such as blackbelly eelpout (Lycodopsis
pacifica), herring, pollock, hake, and Pacific sandlance (Ammodytes
hexapterus) (Walker et al. 1998). Groups of Dall's porpoises generally
include fewer than ten individuals and are fluid, probably aggregating
for feeding (Jefferson 1990, 1991; Houck and Jefferson 1999). Dall's
porpoises become sexually mature at three and a half to eight years of
age (Houck and Jefferson 1999) and give birth to a single calf after
ten to twelve months. Breeding and calving typically occurs in the
spring and summer (Angell and Balcomb 1982). In the North Pacific,
there is a strong summer calving peak from early June through August
(Ferrero and Walker 1999), and a smaller peak in March (Jefferson
1989). Resident Dall's porpoises breed in Puget Sound from August to
September.
Acoustics--Only short duration pulsed sounds have been recorded for
Dall's porpoises (Houck and Jefferson 1999); this species apparently
does not whistle often (Richardson et al. 1995). Dall's porpoises
produce short duration (50-1,500 [mu]s), high-frequency, narrow band
clicks, with peak energies between 120-160 kHz (Jefferson 1988). There
is no published data on the hearing abilities of this species.
Harbor Porpoise
Species Description--Harbor porpoises belong to the Phocoenid
(porpoise) family and are found extensively along the Pacific U.S.
coast. Harbor porpoises are small, with males reaching average lengths
of approximately 5 ft (1.5 m); Females are slightly larger with an
average length of 5.5 ft (1.7 m). The average adult harbor porpoise
weighs between 135-170 lb (61-77 kg). Harbor porpoises have a dark grey
coloration on their backs, with their belly and throats white. They
have a dark grey chin patch and intermediate shades of grey along their
sides.
Recent preliminary genetic analyses of samples ranging from
Monterey, CA to Vancouver Island, BC indicate that there is small-scale
subdivision within the U.S. portion of this range (Chivers et al.
2002). Although geographic structure exists along an almost continuous
distribution of harbor porpoises from California to Alaska, stock
boundaries are difficult to draw because any rigid line is generally
arbitrary from a biological perspective. Nevertheless, based on genetic
data and density discontinuities identified from aerial surveys, NMFS
identifies eight stocks in the Northeast Pacific Ocean. Pacific coast
harbor porpoise stocks include: (1) Monterey Bay, (2) San Francisco-
Russian River, (3) northern California/southern Oregon, (4) Oregon/
Washington coastal, (5) inland Washington, (6) Southeast Alaska, (7)
Gulf of Alaska, and (8) Bering Sea. Only individuals from the
Washington Inland Waters stock may occur in the project area.
Population Abundance--Aerial surveys of the inland waters of
Washington and southern British Columbia were conducted during August
of 2002 and 2003 (J. Laake, unpubl. data). These aerial surveys
included the Strait of Juan de Fuca, San Juan Islands, Gulf Islands,
and Strait of Georgia, which includes waters inhabited by the
Washington Inland Waters stock of harbor porpoises as well as harbor
porpoises from British Columbia. An average of the 2002 and 2003
estimates of abundance in U.S. waters resulted in an uncorrected
abundance of 3,123 (CV= 0.10) harbor porpoises in Washington inland
waters (J. Laake, unpubl. data). When corrected for availability and
perception bias, the estimated abundance for the Washington Inland
Waters stock of harbor porpoise is 10,682 (CV = 0.38) animals (Carretta
et al. 2008). The minimum population estimate is 7,841.
Distribution--Harbor porpoises are generally found in cool
temperate to subarctic waters over the continental shelf in both the
North Atlantic and North Pacific (Read 1999). This species is seldom
found in waters warmer than 17[deg]C (63[deg]F; Read 1999) or south of
Point Conception (Hubbs 1960; Barlow and Hanan 1995). Harbor porpoises
can be found year-round primarily in the shallow coastal waters of
harbors, bays, and river mouths (Green et al. 1992). Along the Pacific
coast, harbor porpoises occur from Monterey Bay, California to the
Aleutian Islands and west to Japan (Reeves et al. 2002). Harbor
porpoises are known to occur in Puget Sound year round (Osmek et al.
1996, 1998; Carretta et al. 2007), and may occasionally occur in Hood
Canal (Jeffries 2006, pers. comm.). Harbor porpoise observations in
northern Hood Canal have increased in recent years (Calambokidis 2010,
pers. comm.). A harbor porpoise was seen in deeper water at NBKB during
2010 field observations (SAIC 2010, staff obs.).
Behavior and Ecology--Harbor porpoises are non-social animals
usually seen in small groups of two to five animals. Little is known
about their social behavior. Harbor porpoises can be opportunistic
foragers but primarily consume schooling forage fish (Osmek et al.
1996; Bowen and Siniff 1999; Reeves et al. 2002). Along the coast of
Washington, harbor porpoises primarily feed on herring, market squid
(Loligo opalescens) and eulachon (Thaleichthys pacificus) (Gearin et
al. 1994). Females reach sexual maturity at three to four years of age
and may give birth every year for several years in a row. Calves are
born in late spring (Read 1990; Read and Hohn 1995). Dall's and harbor
porpoises appear to hybridize relatively frequently in the Puget Sound
area (Willis et al. 2004).
Acoustics--Harbor porpoise vocalizations include clicks and pulses
(Ketten 1998), as well as whistle-like signals (Verboom and Kastelein
1995). The dominant frequency range is 110-150 kHz, with source levels
of 135-177 dB re 1 [mu]Pa-m (Ketten 1998). Echolocation signals include
one or two low-frequency components in the 1.4-2.5 kHz range (Verboom
and Kastelein 1995).
A behavioral audiogram of a harbor porpoise indicated the range of
best sensitivity is 8-32 kHz at levels between 45-50 dB re 1 [mu]Pa-m
(Andersen 1970); however, auditory-evoked potential studies showed a
much higher frequency of approximately 125-130 kHz (Bibikov 1992). The
auditory-
[[Page 4311]]
evoked potential method suggests that the harbor porpoise actually has
two frequency ranges of best sensitivity. More recent psycho-acoustic
studies found the range of best hearing to be 16-140 kHz, with a
reduced sensitivity around 64 kHz (Kastelein et al. 2002). Maximum
sensitivity occurs between 100-140 kHz (Kastelein et al. 2002).
Potential Effects of the Specified Activity on Marine Mammals
NMFS has determined that pile driving, as outlined in the project
description, has the potential to result in behavioral harassment of
California sea lions, harbor seals, harbor porpoises, Dall's porpoises,
and killer whales that may be swimming, foraging, or resting in the
project vicinity while pile driving is being conducted. Pile driving
could potentially harass those pinnipeds that are in the water close to
the project site, whether their heads are above or below the surface.
Marine Mammal Hearing
The primary effect on marine mammals anticipated from the specified
activities will result from exposure of animals to underwater sound.
Exposure to sound can affect marine mammal hearing. When considering
the influence of various kinds of sound on the marine environment, it
is necessary to understand that different kinds of marine life are
sensitive to different frequencies of sound. Based on available
behavioral data, audiograms derived using auditory evoked potential
techniques, anatomical modeling, and other data, Southall et al. (2007)
designate functional hearing groups for marine mammals and estimate the
lower and upper frequencies of functional hearing of the groups. The
functional groups and the associated frequencies are indicated below
(though animals are less sensitive to sounds at the outer edge of their
functional range and most sensitive to sounds of frequencies within a
smaller range somewhere in the middle of their functional hearing
range):
Low frequency cetaceans (thirteen species of mysticetes):
functional hearing is estimated to occur between approximately 7 Hz and
22 kHz;
Mid-frequency cetaceans (32 species of dolphins, six
species of larger toothed whales, and nineteen species of beaked and
bottlenose whales): functional hearing is estimated to occur between
approximately 150 Hz and 160 kHz;
High frequency cetaceans (six species of true porpoises,
four species of river dolphins, two members of the genus Kogia, and
four dolphin species of the genus Cephalorhynchus): functional hearing
is estimated to occur between approximately 200 Hz and 180 kHz; and
Pinnipeds in water: functional hearing is estimated to
occur between approximately 75 Hz and 75 kHz, with the greatest
sensitivity between approximately 700 Hz and 20 kHz.
As mentioned previously in this document, two pinnipeds and three
cetacean species are likely to occur in the proposed project area. Of
the three cetacean species likely to occur in the project area, two are
classified as high frequency cetaceans (Dall's and harbor porpoises)
and one is classified as a mid-frequency cetacean (killer whales)
(Southall et al. 2007).
Underwater Noise Effects
Potential Effects of Pile Driving Noise--The effects of sounds from
pile driving might result in one or more of the following: temporary or
permanent hearing impairment, non-auditory physical or physiological
effects, behavioral disturbance, and masking (Richardson et al. 1995;
Gordon et al. 2004; Nowacek et al. 2007; Southall et al. 2007). The
effects of pile driving on marine mammals are dependent on several
factors, including the size, type, and depth of the animal; the depth,
intensity, and duration of the pile driving sound; the depth of the
water column; the substrate of the habitat; the standoff distance
between the pile and the animal; and the sound propagation properties
of the environment. Impacts to marine mammals from pile driving
activities are expected to result primarily from acoustic pathways. As
such, the degree of effect is intrinsically related to the received
level and duration of the sound exposure, which are in turn influenced
by the distance between the animal and the source. The further away
from the source, the less intense the exposure should be. The substrate
and depth of the habitat affect the sound propagation properties of the
environment. Shallow environments are typically more structurally
complex, which leads to rapid sound attenuation. In addition,
substrates that are soft (e.g., sand) will absorb or attenuate the
sound more readily than hard substrates (e.g., rock) which may reflect
the acoustic wave. Soft porous substrates would also likely require
less time to drive the pile, and possibly less forceful equipment,
which would ultimately decrease the intensity of the acoustic source.
In the absence of mitigation, impacts to marine species would be
expected to result from physiological and behavioral responses to both
the type and strength of the acoustic signature (Viada et al. 2008).
The type and severity of behavioral impacts are more difficult to
define due to limited studies addressing the behavioral effects of
impulsive sounds on marine mammals. Potential effects from impulsive
sound sources can range in severity, ranging from effects such as
behavioral disturbance, tactile perception, physical discomfort, slight
injury of the internal organs and the auditory system, to mortality
(Yelverton et al. 1973; O'Keefe and Young 1984; DoN 2001b).
Hearing Impairment and Other Physical Effects
Marine mammals exposed to high intensity sound repeatedly or for
prolonged periods can experience hearing threshold shift (TS), which is
the loss of hearing sensitivity at certain frequency ranges (Kastak et
al. 1999; Schlundt et al. 2000; Finneran et al. 2002, 2005). TS can be
permanent (PTS), in which case the loss of hearing sensitivity is not
recoverable, or temporary (TTS), in which case the animal's hearing
threshold will recover over time (Southall et al. 2007). Marine mammals
depend on acoustic cues for vital biological functions, (e.g.,
orientation, communication, finding prey, avoiding predators); thus,
TTS may result in reduced fitness in survival and reproduction, either
permanently or temporarily. However, this depends on both the frequency
and duration of TTS, as well as the biological context in which it
occurs. TTS of limited duration, occurring in a frequency range that
does not coincide with that used for recognition of important acoustic
cues, would have little to no effect on an animal's fitness. Repeated
noise exposure that leads to TTS could cause PTS. PTS, in the unlikely
event that it occurred, would constitute injury, but TTS is not
considered injury (Southall et al. 2007). It is unlikely that the
project would result in any cases of temporary or especially permanent
hearing impairment or any significant non-auditory physical or
physiological effects for reasons discussed later in this document.
Some behavioral disturbance is expected, but it is likely that this
would be localized and short-term because of the short project
duration.
Several aspects of the planned monitoring and mitigation measures
for this project (see the ``Proposed Mitigation'' and ``Proposed
Monitoring and Reporting'' sections later in this document) are
designed to detect marine mammals occurring near the pile driving to
avoid exposing them to sound pulses that might, in theory, cause
hearing impairment. In addition, many cetaceans are likely to show some
[[Page 4312]]
avoidance of the area where received levels of pile driving sound are
high enough that hearing impairment could potentially occur. In those
cases, the avoidance responses of the animals themselves will reduce or
(most likely) avoid any possibility of hearing impairment. Non-auditory
physical effects may also occur in marine mammals exposed to strong
underwater pulsed sound. It is especially unlikely that any effects of
these types would occur during the present project given the brief
duration of exposure for any given individual and the planned
monitoring and mitigation measures. The following subsections discuss
in somewhat more detail the possibilities of TTS, PTS, and non-auditory
physical effects.
Temporary Threshold Shift--TTS is the mildest form of hearing
impairment that can occur during exposure to a strong sound (Kryter
1985). While experiencing TTS, the hearing threshold rises, and a sound
must be stronger in order to be heard. In terrestrial mammals, TTS can
last from minutes or hours to days (in cases of strong TTS). For sound
exposures at or somewhat above the TTS threshold, hearing sensitivity
in both terrestrial and marine mammals recovers rapidly after exposure
to the sound ends. Few data on sound levels and durations necessary to
elicit mild TTS have been obtained for marine mammals, and none of the
published data concern TTS elicited by exposure to multiple pulses of
sound. Available data on TTS in marine mammals are summarized in
Southall et al. (2007).
Given the available data, the received level of a single pulse
(with no frequency weighting) might need to be approximately 186 dB re
1 [mu]Pa\2\-s (i.e., 186 dB sound exposure level [SEL] or approximately
221-226 dB pk-pk) in order to produce brief, mild TTS. Exposure to
several strong pulses that each have received levels near 190 dB re 1
[mu]Pa rms (175-180 dB SEL) might result in cumulative exposure of
approximately 186 dB SEL and thus slight TTS in a small odontocete,
assuming the TTS threshold is (to a first approximation) a function of
the total received pulse energy. Levels greater than or equal to 190 dB
re 1 [mu]Pa rms are expected to be restricted to radii no more than 5 m
(16 ft) from the pile driving. For an odontocete closer to the surface,
the maximum radius with greater than or equal to 190 dB re 1 [mu]Pa rms
would be smaller.
The above TTS information for odontocetes is derived from studies
on the bottlenose dolphin (Tursiops truncatus) and beluga whale
(Delphinapterus leucas). There is no published TTS information for
other species of cetaceans. However, preliminary evidence from a harbor
porpoise exposed to pulsed sound suggests that its TTS threshold may
have been lower (Lucke et al. 2009). To avoid the potential for injury,
NMFS has determined that cetaceans should not be exposed to pulsed
underwater noise at received levels exceeding 180 dB re 1 [mu]Pa rms.
As summarized above, data that are now available imply that TTS is
unlikely to occur unless odontocetes are exposed to pile driving pulses
stronger than 180 dB re 1 [mu]Pa rms.
Permanent Threshold Shift--When PTS occurs, there is physical
damage to the sound receptors in the ear. In severe cases, there can be
total or partial deafness, while in other cases the animal has an
impaired ability to hear sounds in specific frequency ranges (Kryter
1985). There is no specific evidence that exposure to pulses of sound
can cause PTS in any marine mammal. However, given the possibility that
mammals close to pile driving activity might incur TTS, there has been
further speculation about the possibility that some individuals
occurring very close to pile driving might incur PTS. Single or
occasional occurrences of mild TTS are not indicative of permanent
auditory damage, but repeated or (in some cases) single exposures to a
level well above that causing TTS onset might elicit PTS.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals but are assumed to be similar to those in humans and
other terrestrial mammals. PTS might occur at a received sound level at
least several decibels above that inducing mild TTS if the animal were
exposed to strong sound pulses with rapid rise time. Based on data from
terrestrial mammals, a precautionary assumption is that the PTS
threshold for impulse sounds (such as pile driving pulses as received
close to the source) is at least 6 dB higher than the TTS threshold on
a peak-pressure basis and probably greater than 6 dB (Southall et al.
2007). On an SEL basis, Southall et al. (2007) estimated that received
levels would need to exceed the TTS threshold by at least 15 dB for
there to be risk of PTS. Thus, for cetaceans, Southall et al. (2007)
estimate that the PTS threshold might be an M-weighted SEL (for the
sequence of received pulses) of approximately 198 dB re 1 [mu]Pa\2\-s
(15 dB higher than the TTS threshold for an impulse). Given the higher
level of sound necessary to cause PTS as compared with TTS, it is
considerably less likely that PTS could occur.
Non-auditory Physiological Effects--Non-auditory physiological
effects or injuries that theoretically might occur in marine mammals
exposed to strong underwater sound include stress, neurological
effects, bubble formation, resonance effects, and other types of organ
or tissue damage (Cox et al. 2006; Southall et al. 2007). Studies
examining such effects are limited. In general, little is known about
the potential for pile driving to cause auditory impairment or other
physical effects in marine mammals. Available data suggest that such
effects, if they occur at all, would presumably be limited to short
distances from the sound source and to activities that extend over a
prolonged period. The available data do not allow identification of a
specific exposure level above which non-auditory effects can be
expected (Southall et al. 2007) or any meaningful quantitative
predictions of the numbers (if any) of marine mammals that might be
affected in those ways. Marine mammals that show behavioral avoidance
of pile driving, including some odontocetes and some pinnipeds, are
especially unlikely to incur auditory impairment or non-auditory
physical effects.
Measured source levels from impact pile driving can be as high as
214 dB re 1 [mu]Pa at 1 m (3.3 ft). Although no marine mammals have
been shown to experience TTS or PTS as a result of being exposed to
pile driving activities, captive bottlenose dolphins and beluga whales
exhibited changes in behavior when exposed to strong pulsed sounds
(Finneran et al. 2000, 2002, 2005). The animals tolerated high received
levels of sound before exhibiting aversive behaviors. Experiments on a
beluga whale showed that exposure to a single watergun impulse at a
received level of 207 kPa (30 psi) p-p, which is equivalent to 228 dB
p-p re 1 [mu]Pa, resulted in a 7 and 6 dB TTS in the beluga whale at
0.4 and 30 kHz, respectively. Thresholds returned to within 2 dB of the
pre-exposure level within four minutes of the exposure (Finneran et al.
2002). Although the source level of pile driving from one hammer strike
is expected to be much lower than the single watergun impulse cited
here, animals being exposed for a prolonged period to repeated hammer
strikes could receive more noise exposure in terms of SEL than from the
single watergun impulse (estimated at 188 dB re 1 [mu]Pa\2\-s) in the
aforementioned experiment (Finneran et al. 2002). However, in order for
marine mammals to experience TTS or PTS, the animals have to be close
enough to be exposed to high intensity noise levels
[[Page 4313]]
for a prolonged period of time. Based on the best scientific
information available, these SPLs are far below the thresholds that
could cause TTS or the onset of PTS.
Disturbance Reactions
Disturbance includes a variety of effects, including subtle changes
in behavior, more conspicuous changes in activities, and displacement.
Reactions to sound, if any, depend on species, state of maturity,
experience, current activity, reproductive state, time of day, and many
other factors (Richardson et al. 1995; Wartzok et al. 2004; Southall et
al. 2007; Weilgart 2007). Behavioral responses to sound are highly
variable and context specific. For each potential behavioral change,
the magnitude of the change ultimately determines the severity of the
response. A number of factors may influence an animal's response to
noise, including its previous experience, its auditory sensitivity, its
biological and social status (including age and sex), and its
behavioral state and activity at the time of exposure.
Habituation can occur when an animal's response to a stimulus wanes
with repeated exposure, usually in the absence of unpleasant associated
events (Wartzok et al. 2003/04). Animals are most likely to habituate
to sounds that are predictable and unvarying. The opposite process is
sensitization, when an unpleasant experience leads to subsequent
responses, often in the form of avoidance, at a lower level of
exposure. Behavioral state may affect the type of response as well. For
example, animals that are resting may show greater behavioral change in
response to disturbing noise levels than animals that are highly
motivated to remain in an area for feeding (Richardson et al. 1995; NRC
2003; Wartzok et al. 2003/04).
Controlled experiments with captive marine mammals showed
pronounced behavioral reactions, including avoidance of loud sound
sources (Ridgway et al. 1997; Finneran et al. 2003). Observed responses
of wild marine mammals to loud pulsed sound sources (typically seismic
guns or acoustic harassment devices, but also including pile driving)
have been varied but often consist of avoidance behavior or other
behavioral changes suggesting discomfort (Morton and Symonds 2002;
CALTRANS 2001, 2006; see also Gordon et al. 2004; Wartzok et al. 2003/
04; Nowacek et al. 2007). Responses to continuous noise, such as
vibratory pile installation, have not been documented as well as
responses to pulsed sounds.
With both types of pile driving, it is likely that the onset of
pile driving could result in temporary, short term changes in an
animal's typical behavior and/or avoidance of the affected area. These
behavioral changes may include (Richardson et al. 1995): Changing
durations of surfacing and dives, number of blows per surfacing, or
moving direction and/or speed; reduced/increased vocal activities;
changing/cessation of certain behavioral activities (such as
socializing or feeding); visible startle response or aggressive
behavior (such as tail/fluke slapping or jaw clapping); avoidance of
areas where noise sources are located; and/or flight responses (e.g.,
pinnipeds flushing into water from haul-outs or rookeries). Pinnipeds
may increase their haul-out time, possibly to avoid in-water
disturbance (CALTRANS 2001, 2006). Since pile driving will likely only
occur for a few hours a day, over a short period of time, it is
unlikely to result in permanent displacement. Any potential impacts
from pile driving activities could be experienced by individual marine
mammals, but would not be likely to cause population level impacts, or
affect the long-term fitness of the species.
The biological significance of many of these behavioral
disturbances is difficult to predict, especially if the detected
disturbances appear minor. However, the consequences of behavioral
modification could be expected to be biologically significant if the
change affects growth, survival, or reproduction. Significant
behavioral modifications that could potentially lead to effects on
growth, survival, or reproduction include:
Drastic changes in diving/surfacing patterns (such as
those thought to be causing beaked whale stranding due to exposure to
military mid-frequency tactical sonar);
Habitat abandonment due to loss of desirable acoustic
environment; and
Cessation of feeding or social interaction.
The onset of behavioral disturbance from anthropogenic noise
depends on both external factors (characteristics of noise sources and
their paths) and the specific characteristics of the receiving animals
(hearing, motivation, experience, demography) and is difficult to
predict (Southall et al. 2007).
Auditory Masking
Natural and artificial sounds can disrupt behavior by masking, or
interfering with, a marine mammal's ability to hear other sounds.
Masking occurs when the receipt of a sound is interfered with by
another coincident sound at similar frequencies and at similar or
higher levels. Chronic exposure to excessive, though not high-
intensity, noise could cause masking at particular frequencies for
marine mammals that utilize sound for vital biological functions.
Masking can interfere with detection of acoustic signals such as
communication calls, echolocation sounds, and environmental sounds
important to marine mammals. Therefore, under certain circumstances,
marine mammals whose acoustical sensors or environment are being
severely masked could also be impaired from maximizing their
performance fitness in survival and reproduction. If the coincident
(masking) sound were man-made, it could be potentially harassing if it
disrupted hearing-related behavior. It is important to distinguish TTS
and PTS, which persist after the sound exposure, from masking, which
occurs during the sound exposure. Because masking (without resulting in
TS) is not associated with abnormal physiological function, it is not
considered a physiological effect, but rather a potential behavioral
effect.
The frequency range of the potentially masking sound is important
in determining any potential behavioral impacts. Because noise
generated from in-water pile driving is mostly concentrated at low
frequency ranges, it may have less effect on high frequency
echolocation sounds made by porpoises. However, lower frequency man-
made noises are more likely to affect detection of communication calls
and other potentially important natural sounds such as surf and prey
noise. It may also affect communication signals when they occur near
the noise band and thus reduce the communication space of animals
(e.g., Clark et al. 2009) and cause increased stress levels (e.g.,
Foote et al. 2004; Holt et al. 2009).
Masking has the potential to impact species at population,
community, or even ecosystem levels, as well as at individual levels.
Masking affects both senders and receivers of the signals and can
potentially have long-term chronic effects on marine mammal species and
populations. Recent research suggests that low frequency ambient sound
levels have increased by as much as 20 dB (more than three times in
terms of SPL) in the world's ocean from pre-industrial periods, and
that most of these increases are from distant shipping (Hildebrand
2009). All anthropogenic noise sources, such as those from vessel
traffic, pile driving, and dredging activities, contribute to the
elevated ambient noise levels, thus intensifying masking. However, the
sum of noise from the proposed activities is confined in an area of
inland waters (Hood Canal) that
[[Page 4314]]
is bounded by landmass; therefore, the noise generated is not expected
to contribute to increased ocean ambient noise.
The most intense underwater sounds in the proposed action are those
produced by impact pile driving. Given that the energy distribution of
pile driving covers a broad frequency spectrum, sound from these
sources would likely be within the audible range of California sea
lions, harbor seals, transient killer whales, harbor porpoises, and
Dall's porpoises. Impact pile driving activity is relatively short-
term, with rapid pulses occurring for approximately fifteen minutes per
pile. The probability for impact pile driving resulting from this
proposed action masking acoustic signals important to the behavior and
survival of marine mammal species is likely to be negligible. Vibratory
pile driving is also relatively short-term, with rapid oscillations
occurring for approximately one and a half hours per pile. It is
possible that vibratory pile driving resulting from this proposed
action may mask acoustic signals important to the behavior and survival
of marine mammal species, but the short-term duration and limited
affected area would result in a negligible impact from masking. Any
masking event that could possibly rise to Level B harassment under the
MMPA would occur concurrently within the zones of behavioral harassment
already estimated for vibratory and impact pile driving, and which have
already been taken into account in the exposure analysis.
Airborne Noise Effects
Marine mammals that occur in the project area could be exposed to
airborne sounds associated with pile driving that have the potential to
cause harassment, depending on their distance from pile driving
activities. Airborne pile driving noise would have less impact on
cetaceans than pinnipeds because noise from atmospheric sources does
not transmit well underwater (Richardson et al. 1995); thus, airborne
noise would only be an issue for hauled-out pinnipeds in the project
area. Most likely, airborne sound would cause behavioral responses
similar to those discussed above in relation to underwater noise. 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 their habitat and
move further from the source. Studies by Blackwell et al. (2004) and
Moulton et al. (2005) indicate a tolerance or lack of response to
unweighted airborne sounds as high as 112 dB peak and 96 dB rms.
Anticipated Effects on Habitat
The proposed activities at NBKB will not result in permanent
impacts to habitats used directly by marine mammals, such as haul-out
sites, but may have potential short-term impacts to food sources such
as forage fish and salmonids. There are no rookeries or major haul-out
sites within 10 km (6.2 mi), foraging hotspots, or other ocean bottom
structure of significant biological importance to marine mammals that
may be present in the marine waters in the vicinity of the project
area. Therefore, the main impact issue associated with the proposed
activity will be temporarily elevated noise levels and the associated
direct effects on marine mammals, as discussed previously in this
document. The most likely impact to marine mammal habitat occurs from
pile driving effects on likely marine mammal prey (i.e., fish) near
NBKB and minor impacts to the immediate substrate during installation
and removal of piles during the test pile program.
Pile Driving Effects on Potential Prey (Fish)
Construction activities will produce both pulsed (i.e., impact pile
driving) and continuous (i.e., vibratory pile driving) sounds. Fish
react to sounds which are especially strong and/or intermittent low-
frequency sounds. Short duration, sharp sounds can cause overt or
subtle changes in fish behavior and local distribution. Hastings and
Popper (2005, 2009) identified several studies that suggest fish may
relocate to avoid certain areas of noise energy. Additional studies
have documented effects of pile driving (or other types of continuous
sounds) on fish, although several are based on studies in support of
large, multiyear bridge construction projects (Scholik and Yan 2001,
2002; Govoni et al. 2003; Hawkins 2005; Hastings 1990, 2007; Popper et
al. 2006; Popper and Hastings 2009). Sound pulses at received levels of
160 dB re 1 [mu]Pa may cause subtle changes in fish behavior. SPLs of
180 dB may cause noticeable changes in behavior (Chapman and Hawkins
1969; Pearson et al. 1992; Skalski et al. 1992). SPLs of sufficient
strength have been known to cause injury to fish and fish mortality
(CALTRANS 2001; Longmuir and Lively 2001). The most likely impact to
fish from pile driving activities at the project area would be
temporary behavioral avoidance of the area. The duration of fish
avoidance of this area after pile driving stops is unknown, but a rapid
return to normal recruitment, distribution and behavior is anticipated.
In general, impacts to marine mammal prey species are expected to be
minor and temporary due to the short timeframe for the test pile
program. However, adverse impacts may occur to a few species of
rockfish (bocaccio (Sebastes paucispinis) and yelloweye (S. ruberrimus)
and canary (S. pinniger) rockfish) and salmon (chinook (Oncorhynchus
tshawytscha) and summer run chum) which may still be present in the
project area despite operating in a reduced work window in an attempt
to avoid important fish spawning time periods. Impacts to these species
could result from potential impacts to their eggs and larvae.
Pile Driving Effects on Potential Foraging Habitat
In addition, the area likely impacted by the test pile program is
relatively small compared to the available habitat in the Hood Canal.
Potentially a maximum of 1.82 m\2\ (19.6 ft\2\; based on a 60 in [1.5
m] diameter pile) of marine mammal foraging habitat may have decreased
foraging value as each pile is driven. 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 Hood Canal and nearby vicinity.
Given the short daily duration of noise associated with individual
pile driving and removal, the short duration of the entire test pile
program (forty work days), 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 essential
fish habitat, or populations of fish species. Therefore, pile driving
and removal is not likely to have a permanent, adverse effect on marine
mammal foraging habitat at the project area. For more information, see
the Navy's Draft Essential Fish Habitat Assessment (see ADDRESSES).
Proposed Mitigation
In order to issue an incidental take authorization (ITA) under
Section 101(a)(5)(D) of the MMPA, NMFS must, where applicable, set
forth the permissible methods of taking pursuant to such activity, and
other means of
[[Page 4315]]
effecting the least practicable impact on such species or stock and its
habitat, paying particular attention to rookeries, mating grounds, and
areas of similar significance, and on the availability of such species
or stock for taking for certain subsistence uses (where relevant).
The modeling results for zones of influence (ZOIs; see ``Estimated
Take by Incidental Harassment'') were used to develop mitigation
measures for pile driving activities at NBKB. The ZOIs effectively
represent the mitigation zone that would be established around each
pile to prevent Level A harassment to marine mammals. While the ZOIs
vary between the different diameter piles and types of installation
methods, the Navy is proposing to establish mitigation zones for the
maximum zone of influence for all pile driving conducted in support of
the test pile program. In addition to the measures described later, the
Navy will employ the following standard mitigation measures:
(a) Conduct briefings between construction supervisors and crews,
marine mammal monitoring team, acoustical monitoring team, and Navy
staff prior to the start of all pile driving activity, and when new
personnel join the work, in order to explain responsibilities,
communication procedures, marine mammal monitoring protocol, and
operational procedures.
(b) Comply with applicable equipment noise standards of the U.S.
Environmental Protection Agency and ensure that all construction
equipment has noise control devices no less effective than those
provided on the original equipment.
(c) For in-water heavy machinery work other than pile driving (if
it exists; e.g., standard barges, tug boats, barge-mounted excavators,
or clamshell equipment used to place or remove material), if a marine
mammal comes within 50 m (164 ft), operations shall cease and vessels
shall reduce speed to the minimum level required to maintain steerage
and safe working conditions.
Shutdown and Buffer Zone
The following measures will apply to the Navy's mitigation through
shutdown and buffer zones:
(a) The Navy will implement a minimum shutdown zone of 50 m (164
ft) radius around all pile driving activity. Shutdown zones typically
include all areas where the underwater SPLs are anticipated to equal or
exceed the Level A (injury) harassment criteria for marine mammals
(180-dB isopleth for cetaceans; 190-dB isopleth for pinnipeds). In this
case, piledriving sounds are expected to attenuate below 180 dB at
distances of 22 m or less (Table 3), but the 50-m shutdown is intended
to further avoid the risk of direct interaction between marine mammals
and the equipment.
(b) The buffer zone shall include all areas where the underwater
SPLs are anticipated to equal or exceed the 160-dB harassment
isopleths. The radius of this zone will be 464 m (1,522 ft) at the
start of pile driving work, but may be adjusted according to empirical,
site-specific data after the project begins. The size of the 120-dB
buffer zone for vibratory pile driving makes monitoring impracticable
(see ``Sound Thresholds''; Table 3).
(c) The shutdown and buffer zones will be monitored throughout the
time required to drive a pile. If a marine mammal is observed entering
the buffer zone, a ``take'' would be recorded and behaviors documented.
However, that pile segment would be completed without cessation, unless
the animal approaches or enters the shutdown zone, at which point all
pile driving activities would be halted.
(d) All buffer and shutdown zones will initially be based on the
distances from the source that are predicted for each threshold level.
However, in-situ acoustic monitoring will be utilized to determine the
actual distances to these threshold zones, and the size of the shutdown
and buffer zones will be adjusted accordingly based on received sound
pressure levels.
Visual Monitoring
Impact Installation--Monitoring will be conducted for a minimum 50
m (164 ft) shutdown zone and a 464 m (1,522 ft) buffer zone (Level B
harassment) surrounding each pile for the presence of marine mammals
before, during, and after pile driving activities. Monitoring will take
place from thirty minutes prior to initiation through thirty minutes
post-completion of pile driving activities.
Vibratory Installation--Monitoring will be conducted for a 50 m
(164 ft) shutdown zone. The 120-dB disturbance criterion predicts an
affected area of 41.5 km\2\ (16 mi\2\). Due to the impracticality of
effectively monitoring such a large area, the Navy intends to monitor a
buffer zone equivalent to the size of the Level B disturbance zone for
impact pile driving (464 m) surrounding each pile for the presence of
marine mammals before, during, and after pile driving activities.
Sightings occurring outside this area will still be recorded and noted
as a take, but detailed observations outside this zone will not be
possible, and it would be impossible for the Navy to account for all
individuals occurring in such a zone with any degree of certainty.
Monitoring will take place from thirty minutes prior to initiation
through thirty minutes post-completion of pile driving activities.
The following additional measures will apply to visual monitoring:
(a) Monitoring will be conducted by qualified observers. A trained
observer will be placed from the best vantage point(s) practicable
(e.g., from a small boat, the pile driving barge, on shore, or any
other suitable location) to monitor for marine mammals and implement
shut-down or delay procedures when applicable by calling for the shut-
down to the hammer operator.
(b) Prior to the start of pile driving activity, the shutdown and
safety zones will be monitored for thirty minutes to ensure that they
are clear of marine mammals. Pile driving will only commence once
observers have declared the shutdown zone clear of marine mammals;
animals will be allowed to remain in the buffer zone (i.e., must leave
of their own volition) and their behavior will be monitored and
documented.
(c) If a marine mammal approaches or enters the shutdown zone
during the course of pile driving operations, pile driving will be
halted and delayed until either the animal has voluntarily left and
been visually confirmed beyond the shutdown zone or thirty minutes have
passed without re-detection of the animal.
Sound Attenuation Devices
Sound attenuation devices will be utilized during all impact pile
driving operations. Impact pile driving is only expected to be required
to proof, or drive the last 10-15 ft (3-4.6 m) of each pile. The Navy
plans to use a Gunderboom Sound Attenuation System (SAS) as mitigation
for in-water sound during construction activities. The Gunderboom SAS
is a multipurpose enclosure that absorbs sound, attenuates pressure
waves, excludes marine life from work areas, and controls the migration
of debris, sediments and process fluids. The Gunderboom SAS is
comprised of a water-permeable double layer of polypropylene/polyester
fabric. Compressed air is released at the bottom of the fabric and
moves up to the top of the fabric, inflating the fabric and creating a
wall. A traditional bubble curtain will be used as a backup mitigation
if the Navy cannot obtain the Gunderboom SAS or if it does not achieve
the proposed noise attenuation. The Navy will also test the feasibility
and effectiveness of using sound attenuation devices with vibratory
[[Page 4316]]
hammers. The Navy will employ the Gunderboom SAS or bubble curtain on
two of the vibratory-driven piles to test the practicability of this
concept.
Acoustic Measurements
Acoustic measurements will be used to empirically verify the
proposed shutdown and buffer zones. For further detail regarding the
Navy's acoustic monitoring plan see ``Proposed Monitoring and
Reporting''.
Timing Restrictions
The Navy has set timing restrictions for pile driving activities to
avoid in-water work when ESA-listed fish populations are most likely to
be present. The in-water work window for avoiding negative impacts to
fish species is July 16-February 15. Further, the Navy has narrowed its
work window to avoid times of year when ESA-listed Steller sea lions
may be present at the project area. Therefore, all pile driving would
only occur between July 16-October 31 of the approved in-water work
window from July 16 through February 15 to minimize the number of fish
exposed to underwater noise and other disturbance, and to avoid times
when Steller sea lions are expected to be present.
Soft Start
The use of a soft-start procedure is believed to provide additional
protection to marine mammals by warning, or providing marine mammals a
chance to leave the area prior to the hammer operating at full
capacity. The test pile program will utilize soft-start techniques
(ramp-up and dry fire) recommended by NMFS for impact and vibratory
pile driving. The soft-start requires contractors to initiate noise
from vibratory hammers for fifteen seconds at reduced energy followed
by a one minute waiting period. This procedure will be repeated two
additional times. For impact driving, contractors will be required to
provide an initial set of three strikes from the impact hammer at forty
percent energy, followed by a one minute waiting period, then two
subsequent three strike sets.
Daylight Construction
Pile driving will only be conducted between two hours post-sunrise
through two hours prior to sunset (civil twilight).
Mitigation Effectiveness
It should be recognized that although marine mammals will be
protected from Level A harassment by the utilization of a bubble
curtain and protected species observers (PSOs) monitoring the near-
field injury zones, mitigation may not be 100 percent effective at all
times in locating marine mammals in the buffer zone. The efficacy of
visual detection depends on several factors including the observer's
ability to detect the animal, the environmental conditions (visibility
and sea state), and monitoring platforms.
All observers utilized for mitigation activities will be
experienced biologists with training in marine mammal detection and
behavior. Due to their specialized training the Navy expects that
visual mitigation will be highly effective. Trained observers have
specific knowledge of marine mammal physiology, behavior, and life
history, which may improve their ability to detect individuals or help
determine if observed animals are exhibiting behavioral reactions to
construction activities.
The Puget Sound region, including the Hood Canal, only infrequently
experiences winds with velocities in excess of 25 kt (Morris et al.
2008). The typically light winds afforded by the surrounding highlands
coupled with the fetch-limited environment of the Hood Canal result in
relatively calm wind and sea conditions throughout most of the year.
The test pile program project site has a maximum fetch of 8.4 mi (13.5
km) to the north, and 4.2 mi (6.8 km) to the south, resulting in
maximum wave heights of from 2.85-5.1 ft (0.9-1.6 m) (Beaufort Sea
State (BSS) between two and four), even in extreme conditions (30 kt
winds) (CERC 1984). Visual detection conditions are considered optimal
in BSS conditions of three or less, which align with the conditions
that should be expected for the test pile program at NBKB.
Observers will be positioned in locations which provide the best
vantage point(s) for monitoring. This will likely be an elevated
position, providing a better range of viewing angles. Also, the
shutdown and buffer zones have relatively small radii to monitor, which
should improve detectability.
NMFS has carefully evaluated the applicant's proposed mitigation
measures and considered a range of other measures in the context of
ensuring that NMFS prescribes the means of effecting the least
practicable impact on the affected marine mammal species and stocks and
their habitat. Our evaluation of potential measures included
consideration of the following factors in relation to one another: (1)
The manner in which, and the degree to which, the successful
implementation of the measure is expected to minimize adverse impacts
to marine mammals; (2) the proven or likely efficacy of the specific
measure to minimize adverse impacts as planned; and (3) the
practicability of the measure for applicant implementation, including
consideration of personnel safety, and practicality of implementation.
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 of
effecting the least practicable impact on marine mammal 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 ITA for an activity, Section 101(a)(5)(D) of
the MMPA states that NMFS must, where applicable, 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 ITAs 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.
Acoustic Measurements
The Navy will conduct acoustic monitoring for impact driving of
steel piles in order to determine the actual distances to the 190-,
180-, and 160-dB (re 1 [mu]Pa rms) isopleths and to determine the
relative effectiveness of the bubble curtain system at attenuating
noise underwater. The Navy will also conduct acoustic monitoring for
vibratory pile driving in order to determine the actual distance to the
120-dB isopleth for behavioral harassment relative to background
levels. The monitoring plan addresses both underwater and airborne
sounds from the test pile program. At a minimum, the methodology will
include:
(1) A stationary hydrophone placed at mid-water depth and 10 m (33
ft) from the source pile to measure the effectiveness of the bubble
curtain system; a weighted tape measure will be used to determine the
depth of the water. The hydrophone will be attached to a nylon cord or
steel chain if current is swift enough, to maintain a constant distance
from the pile. The nylon cord or chain will be attached to a float or
[[Page 4317]]
tied to a static line at the surface 10 m from the piles.
(2) All hydrophones will be calibrated at the start of the action
and will be checked at the beginning of each day of monitoring
activity.
(3) For each monitored location, a two-hydrophone setup will be
used, with the first hydrophone at mid-depth and the second hydrophone
at approximately 1 m (3.3 ft) from the bottom in order to evaluate site
specific attenuation and propagation characteristics that may be
present throughout the water column.
(4) In addition to determining the area encompassed by the 190-,
180-, 160-, and 120-db rms isopleths for marine mammals, hydrophones
would also be placed at other distances as appropriate to accurately
capture spreading loss occurring at the test pile project area.
(5) Ambient conditions, both airborne and underwater, would be
measured at the project site in the absence of construction activities
to determine background sound levels. Ambient levels are intended to be
recorded over the frequency range from 10 Hz to 20 kHz. Ambient
conditions will be recorded for one minute every hour of the work day,
for one week of each month of the test pile program.
(6) Sound levels associated with soft-start techniques will also be
measured.
(7) Underwater sound pressure levels would be continuously
monitored during the entire duration of each pile being driven. Sound
pressure levels will be monitored in real time. Sound levels will be
measured in Pascals, which are easily converted to decibel units.
(8) Airborne levels would be recorded as unweighted, as well as in
dBA, and the distance to marine mammal thresholds would be measured.
(9) The effectiveness of using a bubble curtain system with a
vibratory hammer will be tested during the driving of two vibratory
piles. The on/off regime described in Table 9 will be utilized during
the pile installation:
Table 9--Schedule for Testing Effectiveness of Sound Attenuation Device
------------------------------------------------------------------------
Sound attenuation device
Pile driving timeframe condition
------------------------------------------------------------------------
Initial 30 s............................... Off
Next minute (minimum)...................... On
Middle of pile driving segment 30 s........ Off
Next minute (minimum)...................... On
Final 30 s................................. Off
------------------------------------------------------------------------
(10) Environmental data would be collected, including, but not
limited to: wind speed and direction, air temperature, humidity,
surface water temperature, water depth, wave height, weather conditions
and other factors that could contribute to influencing the airborne and
underwater sound levels (e.g., aircraft, boats).
(11) The chief inspector would supply the acoustics specialist with
the substrate composition, hammer model and size, hammer energy
settings and any changes to those settings during the piles being
monitored, depth of the pile being driven, and blows per foot for the
piles monitored.
(12) Post-analysis of the sound level signals will include
determination of absolute peak overpressure and under pressure levels
recorded for each pile, rms value for each absolute peak pile strike,
rise time, average duration of each pile strike, number of strikes per
pile, SEL of the absolute peak pile strike, mean SEL, and cumulative
SEL (accumulated SEL = single strike SEL + 10*log (number of hammer
strikes) and a frequency spectrum both with and without mitigation,
between 10-20,000 Hz for up to eight successive strikes with similar
sound levels.
Visual Marine Mammal Observations
The Navy will collect sighting data and behavioral responses to
construction for marine mammal species observed in the region of
activity during the period of activity. All observers will be trained
in marine mammal identification and behaviors. NMFS requires that the
observers have no other construction related tasks while conducting
monitoring.
Methods of Monitoring--The Navy will monitor the shutdown zone and
safety (buffer) zone before, during, and after pile driving. Based on
NMFS requirements, the Marine Mammal Monitoring Plan would include the
following procedures for impact pile driving:
(1) MMOs would be located at the best vantage point(s) in order to
properly see the entire shutdown zone and safety zone. This may require
the use of a small boat to monitor certain areas while also monitoring
from one or more land based vantage points.
(2) During all observation periods, observers would use binoculars
and the naked eye to search continuously for marine mammals.
(3) To verify the required monitoring distances, the zones would be
clearly marked with buoys or other suitable aquatic markers.
(4) If the shut down or safety zones are obscured by fog or poor
lighting conditions, pile driving would not be initiated until all
zones are visible.
(5) The shut down and safety zones around the pile will be
monitored for the presence of marine mammals before, during, and after
any pile driving activity.
Pre-Activity Monitoring--The shutdown and buffer zones will be
monitored for thirty minutes prior to initiating the soft start for
pile driving. If marine mammal(s) are present within the shut down zone
prior to pile driving or during the soft start, the start of pile
driving would be delayed until the animal(s) leave the shut down zone.
Pile driving would resume only after the PSO has determined, through
sighting or by waiting approximately thirty minutes, that the animal(s)
has moved outside the shutdown zone.
During Activity Monitoring--The shutdown and buffer zones will also
be monitored throughout the time required to drive a pile. If a marine
mammal is observed entering the buffer zone, a ``take'' would be
recorded and behaviors documented. However, that pile segment would be
completed without cessation, unless the animal enters or approaches the
shutdown zone, at which point all pile driving activities will be
halted. Pile driving can only resume once the animal has left the
shutdown zone of its own volition or has not been re-sighted for a
period of thirty minutes.
Post-Activity Monitoring--Monitoring of the shutdown and buffer
zones would continue for thirty minutes following the completion of
pile driving.
Data Collection
NMFS requires that the PSOs use NMFS-approved sighting forms. In
addition to the following requirements, the Navy will note in their
behavioral observations whether an animal remains in the project area
following a Level B taking (which would not require cessation of
activity). This information will ideally make it possible to determine
whether individuals are taken (within the same day) by one or more
types of pile driving (i.e., impact and vibratory). NMFS requires that,
at a minimum, the following information be collected on the sighting
forms:
(1) Date and time that pile driving begins or ends;
(2) Construction activities occurring during each observation
period;
(3) Weather parameters identified in the acoustic monitoring (e.g.,
wind, humidity, temperature);
(4) Tide state and water currents;
(5) Visibility;
(6) Species, numbers, and, if possible, sex and age class of marine
mammals;
[[Page 4318]]
(7) Marine mammal behavior patterns observed, including bearing and
direction of travel, and if possible, the correlation to sound pressure
levels;
(8) Distance from pile driving activities to marine mammals and
distance from the marine mammals to the observation point;
(9) Locations of all marine mammal observations; and
(10) Other human activity in the area.
Reporting
A draft report would be submitted to NMFS within 45 days of the
completion of acoustic measurements and marine mammal monitoring. The
results would be summarized in graphical form and include summary
statistics and time histories of impact sound values for each pile. A
final report would be prepared and submitted to NMFS within thirty days
following receipt of comments on the draft report from NMFS. At a
minimum, the report shall include:
(1) Size and type of piles;
(2) A detailed description of the SAS or bubble curtain, including
design specifications;
(3) The impact or vibratory hammer force used to drive and extract
the piles;
(4) A description of the monitoring equipment;
(5) The distance between hydrophone(s) and pile;
(6) The depth of the hydrophone(s);
(7) The depth of water in which the pile was driven;
(8) The depth into the substrate that the pile was driven;
(9) The physical characteristics of the bottom substrate into which
the piles were driven;
(10) The ranges and means for peak, rms, and SELs for each pile;
(11) The results of the acoustic measurements, including the
frequency spectrum, peak and rms SPLs, and single-strike and cumulative
SEL with and without the attenuation system;
(12) The results of the airborne noise measurements including dBA
and unweighted levels;
(13) A description of any observable marine mammal behavior in the
immediate area and, if possible, the correlation to underwater sound
levels occurring at that time;
(14) Results, including the detectability of marine mammals,
species and numbers observed, sighting rates and distances, behavioral
reactions within and outside of safety zones; and
(15) A refined take estimate based on the number of marine mammals
observed in the safety and buffer zones. This may be reported as one or
both of the following: a rate of take (number of marine mammals per
hour), or take based on density (number of individuals within the
area).
Estimated Take by Incidental Harassment
With respect to the activities described here, the MMPA defines
``harassment'' as:
any act of pursuit, torment, or annoyance which (i) has the
potential to injure a marine mammal or marine mammal stock in the
wild [Level A harassment]; or (ii) has the potential to disturb a
marine mammal or marine mammal stock in the wild by causing
disruption of behavioral patterns, including, but not limited to,
migration, breathing, nursing, breeding, feeding, or sheltering
[Level B harassment].
All anticipated takes would be by Level B harassment, involving
temporary changes in behavior. The proposed mitigation and monitoring
measures are expected to minimize the possibility of injurious or
lethal takes such that take by Level A harassment, serious injury or
mortality is considered remote. However, as noted earlier, there is no
specific information demonstrating that injurious or lethal ``takes''
would occur even in the absence of the planned mitigation and
monitoring measures.
If a marine mammal responds to an underwater sound by changing its
behavior or moving a small distance, the response may or may not rise
to the level of ``taking'', or affect the stock or the species as a
whole. However, if a sound source displaces marine mammals from an
important feeding or breeding area for a prolonged period, impacts on
animals or on the stock or species could potentially be significant
(Lusseau and Bejder 2007; Weilgart 2007). Given the many uncertainties
in predicting the quantity and types of impacts of noise on marine
mammals, it is common practice to estimate how many mammals are likely
to be present within a particular distance of a given activity, or
exposed to a particular level of sound. This practice potentially
overestimates the numbers of marine mammals taken. For example, during
the past ten years, killer whales have been observed within the project
area twice. While a pod of killer whales could potentially visit again
during the project timeframe, and thus be ``taken'', it is more likely
that they will not.
The proposed project area is not believed to be particularly
important habitat for marine mammals, nor is it considered an area
frequented by marine mammals, although harbor seals are year-round
residents of Hood Canal. Therefore, behavioral disturbances that could
result from anthropogenic noise associated with the proposed activities
are expected to affect only a small number of marine mammals on an
infrequent basis.
The Navy is requesting authorization for the potential taking of
small numbers of California sea lions, harbor seals, transient killer
whales, Dall's porpoises, and harbor porpoises in the Hood Canal that
may result from pile driving during construction activities associated
with the test pile program described previously in this document. The
takes requested are expected to have no more than a minor effect on
individual animals and no effect on the populations of these species.
Any effects experienced by individual marine mammals are anticipated to
be limited to short-term disturbance of normal behavior or temporary
displacement of animals near the source of the noise.
Description of Take Calculation
The take calculations presented here rely on the best data
currently available for marine mammal populations in the Hood Canal, as
discussed in preceding sections. The formula was developed for
calculating take due to impact pile driving and applied to each group-
specific noise impact threshold. The formula is founded on the
following assumptions:
(a) Each species population is at least as large as any previously
documented highest population estimate.
(b) All pilings to be installed would have a noise disturbance
distance equal to the piling that causes the greatest noise disturbance
(i.e., the piling furthest from shore).
(c) Pile driving could potentially occur every day of the forty day
in-water work window. However, it is estimated that an average of two
piles will be installed and removed per day. Therefore, a best estimate
of the number of days during which pile driving would occur is fifteen
days, and this was used in all modeling calculations.
(d) Some degree of mitigation (i.e., sound attenuation system,
etc.) will be utilized, as discussed previously.
(e) An individual can only be taken once per method of installation
during a 24 hr period.
The calculation for marine mammal takes is estimated by:
Take estimate = (n * ZOI) * 15 days of total activity
Where:
n = density estimate used for each species/season
ZOI = noise threshold zone of influence (ZOI) impact area; the area
encompassed by all locations where the sound pressure levels equal
or exceed the threshold being evaluated
[[Page 4319]]
n * ZOI produces an estimate of the abundance of animals that could
be present in the area for exposure
The ZOI impact area is the estimated range of impact to the noise
criteria. The distances (actual) specified in Table 4 were used to
calculate ZOI around each pile. All impact pile driving take
calculations were based on the estimated threshold ranges using a
bubble curtain with 10 dB attenuation as a mitigation measure. The ZOI
impact area took into consideration the possible affected area of the
Hood Canal from the pile driving site furthest from shore with
attenuation due to land shadowing from bends in the canal. Because of
the close proximity of some of the piles to the shore, the narrowness
of the canal at the project area, and the maximum fetch, the ZOIs for
each threshold are not necessarily spherical and may be truncated.
As discussed previously in this document, the project entails forty
days of total in-water work time. However, the Navy estimates that only
fifteen days of pile driving will occur, with two piles driven per day.
For each pile installed, vibratory pile driving is expected to be no
more than one hour. The impact driving portion of the project is
anticipated to take approximately fifteen minutes per pile with no more
than 100 blows executed per day. All piles will be extracted using a
vibratory hammer. Extraction is anticipated to take approximately
thirty minutes per pile. Overall, this results in a maximum of two
hours of pile driving per pile, or approximately four hours per day.
Impacts were modeled as if the action were to occur for a duration of
fifteen days, and conservatively used an average of eight to nine hours
per workday (two hours post-sunrise to two hours prior to sunset).
The exposure assessment methodology is an estimate of the numbers
of individuals exposed to the effects of pile driving activities
exceeding NMFS-established thresholds. Of significant note in these
exposure estimates, additional mitigation methods (i.e., visual
monitoring and the use of shutdown zones) were not quantified within
the assessment and successful implementation of this mitigation is not
reflected in exposure estimates. However, modeling did incorporate, for
impact driving, a 10 dB reduction in SPL resulting from the use of
sound attenuation devices. Results from acoustic impact exposure
assessments should be regarded as conservative estimates that are
strongly influenced by limited biological data. While the numbers
generated from the pile driving exposure calculations provide
conservative estimates of marine mammal exposures for consultation with
NMFS, the short duration and limited geographic extent of the test pile
project would likely further limit actual exposures.
California Sea Lion
California sea lions are present in the Hood Canal almost year-
round with the exception of mid-June through August. The Navy conducted
year round waterfront surveys for marine mammals at NBKB in 2008 and
2009 (DoN 2010a). During these surveys, the daily maximum number of
California sea lions hauled out for the months July-October (the
timeframe of the test pile program), were 0, 0, 12, and 47 in 2008 and
0, 1, 32, and 44 in 2009, respectively. The monthly average of the
maximum number of California sea lions observed per day was seventeen
individuals. Females are rarely observed north of the California-Oregon
border (NMFS 2008c); therefore only adult and sub-adult males are
expected in the Hood Canal. Breeding rookeries are in California;
therefore pups are not expected to be present in the Hood Canal.
California sea lions are not likely to be present at the project
site during the entire period of work (i.e., are infrequent visitors
during July-August). However, because the proportion of pile driving
that could occur in a given month is dependent on several factors
(e.g., availability of materials, weather) the Navy assumed that pile
driving operations could occur at any time in the construction window.
Therefore, exposures were calculated using the monthly average of the
maximum number of California sea lions observed per day (seventeen
individuals), divided by the potential acoustic impact area (41.5 km\2\
[16 mi\2\]) and the formula given previously. Table 10 depicts the
number of acoustic harassments that are estimated from vibratory and
impact pile driving both underwater and in-air for each season. The
modeling indicated that zero California sea lions were likely to be
exposed to sound in the 160-dB zone. However, the Navy feels that,
based on the abundance of this species in the waters along NBKB and
including their presence at nearby haul-outs, it is possible that an
individual could pass through this zone in transit to or from a haul-
out. Therefore, the Navy is requesting a behavioral harassment take of
California sea lion by impact pile driving each day of pile driving,
for a total of fifteen takes over the course of the proposed action.
Harbor Seal
Harbor seals are present in the Hood Canal year-round and would be
expected at the project site. Harbor seal numbers increase from January
through April and then decrease from May through August as the harbor
seals move to adjacent bays on the outer coast of Washington for the
pupping season. Harbor seals are the most abundant marine mammal in the
Hood Canal. Jeffries et al. (2003) did a stock assessment of harbor
seals in the Hood Canal in 1999 and counted 711 harbor seals hauled
out. This abundance was adjusted using a correction factor of 1.53 to
account for seals in the water and not counted to provide a population
estimate of 1,088 harbor seals in the Hood Canal. The Navy conducted
boat surveys of the waterfront area in 2008 from July to September
(Agness and Tannenbaum 2009a). Harbor seals were sighted during every
survey and were found in all marine habitats including near and hauled-
out on man-made objects such as piers and buoys. During most of the
year, all age and sex classes (except newborn pups) could occur in the
project area throughout the period of construction activity. From April
through mid-July, female harbor seals haul out on the outer coast of
Washington at pupping sites to give birth. Since there are no known
pupping sites in the vicinity of the project, harbor seal pups are not
expected to be present during pile driving. The main haul-out locations
for harbor seals in Hood Canal are located on river delta and tidal
exposed areas at Quilcene, Dosewallips, Duckabush, Hamma Hamma, and
Skokomish River mouths, with the closest haul-out area to the project
area being ten miles (16 km) southwest of NBKB at Dosewallips River
mouth (London 2006). Please see Figure 4-1 of the Navy's application
for a map of haul-out locations in relation to the project area.
Research by Huber et al. (2001) indicates that approximately 35
percent of harbor seals are in the water at any one time. Exposures
were calculated using a density derived from the number of harbor seals
that are present in the water at any one time (35 percent of 1,088, or
approximately 381 individuals), divided by the area of the Hood Canal
(291 km\2\ [112 mi\2\]) and the formula presented previously.
While Huber et al.'s (2001) data suggest that harbor seals
typically spend 65 percent of their time hauled out, the Navy's
waterfront surveys found that it is extremely rare for harbor seals to
haul out in the vicinity of the test pile project area. Therefore, the
only population of
[[Page 4320]]
harbor seals that could potentially be exposed to airborne sounds are
those that are in-water but at the surface. Based on the diving cycle
of tagged harbor seals near the San Juan Islands, the Navy estimates
that seals are on the surface approximately 16.4 percent of their total
in-water duration (Suryan and Harvey 1998). Therefore, by multiplying
the percentage of time spent at the surface (16.4 percent) by the total
in-water population of harbor seals at any one time (approximately 381
individuals), the population of harbor seals with the potential to
experience airborne impacts (approximately 63 individuals) can be
obtained. Airborne exposures were calculated using a density derived
from the maximum number of harbor seals available at the surface
(approximately 63 individuals), divided by the area of the Hood Canal
(291 km\2\) and the formula presented previously. Table 10 depicts the
number of acoustic harassments that are estimated from vibratory and
impact pile driving both underwater and in-air for each season.
Killer Whales
Transient killer whales are uncommon visitors to Hood Canal.
Transients may be present in the Hood Canal anytime during the year and
traverse as far as the project site. Resident killer whales have not
been observed in Hood Canal, but transient pods (six to eleven
individuals per event) were observed in Hood Canal for lengthy periods
of time (59-172 days) in 2003 (January-March) and 2005 (February-June),
feeding on harbor seals (London 2006).
These whales used the entire expanse of Hood Canal for feeding.
Subsequent aerial surveys suggest that there has not been a sharp
decline in the local seal population from these sustained feeding
events (London 2006). Based on this data, the density for transient
killer whales in the Hood Canal for January to June is 0.038/km\2\
(0.015/mi\2\; eleven individuals divided by the area of the Hood Canal
[291 km\2\]). Since this timeframe overlaps the period in which the
test pile program will occur (July-October), this density was used for
all exposure calculations. Exposures were calculated using the formula
presented previously. Table 10 depicts the number of acoustic
harassments that are estimated from vibratory and impact pile driving
for each season. The modeling indicated that zero killer whales were
likely to be exposed to sound in the 160-dB zone. However, while
transient killer whales are rare in the Hood Canal, when these animals
are present they occur in pods, so their density in the project area is
unlikely to be uniform, as was modeled. If they are present during
impact pile driving it is possible that one or more individuals within
a pod could travel through the behavioral harassment zone. Therefore,
the Navy is requesting nine behavioral takes of transient killer
whales--based on the average size of pods seen previously in the Hood
Canal--by impact pile driving over the course of the proposed action.
Dall's Porpoise
Dall's porpoises may be present in the Hood Canal year-round and
could occur as far as the project site. Their use of inland Washington
waters, however, is mostly limited to the Strait of Juan de Fuca. The
Navy conducted boat surveys of the waterfront area in 2008 from July to
September (Agness and Tannenbaum 2009a). During one of the surveys a
Dall's porpoise was sighted in August in the deeper waters off Carlson
Spit.
In the absence of an abundance estimate for the entire Hood Canal,
a seasonal density (warm season only [May-Oct]) was derived from the
waterfront survey by the number of individuals seen divided by total
number of kilometers of survey effort (six surveys with approximately
3.9 km\2\ [1.5 mi\2\] of effort each), assuming strip transect surveys.
In absence of any other survey data for the Hood Canal, this density is
assumed to be throughout the project area. Exposures were calculated
using the formula presented previously. Table 10 depicts the number of
acoustic harassments that are estimated from vibratory and impact pile
driving for each season. The modeling indicated that zero Dall's
porpoises were likely to be exposed to sound in the 160-dB zone. Dall's
porpoises are rare in the Hood Canal; only one animal, seen in deep
waters offshore from the base, has been seen in the project area in the
past few years. However, it is possible that additional animals exist
or that this single individual could pass through the behavioral
harassment zone for impulse sounds (160-dB) while transiting along the
waterfront. Therefore, the Navy is requesting a single behavioral
harassment take of a Dall's porpoise by impact pile driving over the
course of the proposed action.
Harbor Porpoise
Harbor porpoises may be present in the Hood Canal year-round;
however, their presence is rare. During waterfront surveys of NBKB over
the past two years (2008-present) only one harbor porpoise has been
seen in 24 surveys.
The Navy conducted boat surveys of the waterfront area from July to
September over the past few years (2008-present) (Agness and Tannenbaum
2009a). During one of the surveys a single harbor porpoise was sighted
in the deeper waters offshore from the waterfront. In the absence of an
abundance estimate for the entire Hood Canal, a seasonal density (warm
season only) was derived from the waterfront survey by the number of
individuals seen divided by total number of kilometers of survey effort
(24 surveys with approximately 3.9 km\2\ [1.5 mi\2\] of effort each),
assuming strip transect surveys. In the absence of any other survey
data for the Hood Canal, this density is assumed to be throughout the
project area. Exposures were calculated using the formula presented
previously; Table 10 depicts the number of acoustic harassments that
are estimated from vibratory and impact pile driving for each season.
The modeling indicated that zero harbor porpoises were likely to be
exposed to sound in the 120-dB zone. However, while harbor porpoises
are rare, one has been sighted in surveys over the last few years in
the deep waters offshore from the base. It is possible this offshore
region is encapsulated within the vibratory disturbance zone due to its
size (41.5 km\2\ [16 mi\2\]). Therefore, based on the possibility that
this animal could be present in the offshore waters during every day of
construction, the Navy is requesting a single behavioral take of harbor
porpoise by vibratory pile driving each day of pile driving, for a
total of fifteen takes over the course of the proposed action.
Potential takes could occur if individuals of these species move
through the area on foraging trips when pile driving is occurring.
Individuals that are taken could exhibit behavioral changes such as
increased swimming speeds, increased surfacing time, or decreased
foraging. Most likely, individuals may move away from the sound source
and be temporarily displaced from the areas of pile driving. Potential
takes by disturbance would have a negligible short-term effect on
individuals and would not result in population-level impacts.
[[Page 4321]]
Table 10--Number of Potential Warm Season (May-Oct) Exposures of Marine Mammals Within Various Acoustic Threshold Zones
--------------------------------------------------------------------------------------------------------------------------------------------------------
Underwater Airborne
---------------------------------------------------------------- Total (percent
Impact Vibratory Impact & of stock or
Species Density Impact injury disturbance disturbance vibratory population
threshold \1\ threshold (160 threshold (120 disturbance \3\)
dB) dB) threshold \2\
--------------------------------------------------------------------------------------------------------------------------------------------------------
California sea lion..................................... 0.410 0 *15 255 0 270 (0.01)
Harbor seal............................................. 1.31 0 15 810 0 \4\ 825 (5.6)
Killer whale............................................ 0.038 0 *9 30 N/A 39 (12.4)
Dall's porpoise......................................... 0.043 0 *1 30 N/A 31 (0.06)
Harbor porpoise......................................... 0.011 0 0 *15 N/A 15 (0.1)
-----------------------------------------------------------------------------------------------
Total............................................... 0 40 1140 0 1180 ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
* See species descriptions for discussion of these estimates.
\1\ Acoustic injury threshold for impact pile driving is 190 dB for pinnipeds and 180 dB for cetaceans.
\2\ Acoustic disturbance threshold is 100 dB for California sea lions; 90 dB for harbor seals. The airborne exposure calculations assume that 100% of
the in-water densities were available at the surface to be exposed to airborne sound.
\3\ See Table 8 for stock or population numbers.
\4\ Airborne densities were based on the percentage (16.4 percent) of in-water density available at the surface to be exposed (Suryan and Harvey 1998).
During the project timeframe, which occurs entirely in the May to
October warm season, there is the potential for forty Level B
disturbance takes (160-dB, impulse sound) of various species from
impact pile driving operations, and an additional 1,140 Level B
disturbance takes (120-dB, continuous sound) of various species from
vibratory pile driving due to underwater sound. The following species
and numbers of Level B disturbance takes could occur due to underwater
sound as a result of impact pile driving operations: fifteen California
sea lions, fifteen harbor seals, nine transient killer whales, and one
Dall's porpoise. The following species and numbers of Level B
disturbance takes could occur due to underwater sound as a result of
vibratory pile driving operations: 255 California sea lions, 810 harbor
seals, thirty transient killer whales, thirty Dall's porpoises, and
fifteen harbor porpoises. Due to their lack of presence within the
project area during the timeframe for the test pile program (July 16-
Oct 31), no Steller sea lions would be harassed. Lastly, no species of
pinnipeds are expected to be exposed to airborne sound pressure levels
that would cause harassment.
Negligible Impact and Small Numbers Analysis and Preliminary
Determination
NMFS has defined ``negligible impact'' in 50 CFR 216.103 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.'' In making a negligible impact determination,
NMFS considers a variety of factors, including but not limited to: (1)
The number of anticipated mortalities; (2) the number and nature of
anticipated injuries; (3) the number, nature, intensity, and duration
of Level B harassment; and (4) the context in which the take occurs.
Pile driving activities associated with the test pile program, as
outlined previously, have the potential to disturb or displace small
numbers of marine mammals. Specifically, the proposed activities may
result in take, in the form of Level B harassment (behavioral
disturbance) only, from airborne or underwater sounds generated from
pile driving. Level A harassment is not anticipated given the methods
of installation and measures designed to minimize the possibility of
injury to marine mammals. Specifically, vibratory hammers will be the
primary method of installation, which are not expected to cause injury
to marine mammals due to the relatively low source levels (less than
190 dB). Also, no impact pile driving will occur without the use of a
noise attenuation system (e.g., bubble curtain), and pile driving will
either not start or be halted if marine mammals approach the shutdown
zone (described previously in this document). Furthermore, the pile
driving activities analyzed are similar to other nearby construction
activities within the Hood Canal, such as test piles driven in 2005 for
the Hood Canal Bridge (SR-104) constructed by the Washington Department
of Transportation, which have taken place with no reported injuries or
mortality to marine mammals.
NMFS has preliminarily determined that the impact of the previously
described test pile program may result, at worst, in a temporary
modification in behavior (Level B harassment) of small numbers of
marine mammals. No mortality or injuries are anticipated as a result of
the specified activity, and none are proposed to be authorized.
Additionally, animals in the area are not expected to incur hearing
impairment (i.e., TTS or PTS) or non-auditory physiological effects.
For pinnipeds, the absence of any major rookeries and only a few
isolated haul-out areas near or adjacent to the project site means that
potential takes by disturbance will have an insignificant short-term
effect on individuals and would not result in population-level impacts.
Similarly, for cetacean species the absence of any regular occurrence
adjacent to the project site means that potential takes by disturbance
will have an insignificant short-term effect on individuals and would
not result in population-level impacts. Due to the nature, degree, and
context of behavioral harassment anticipated, the activity is not
expected to impact rates of recruitment or survival. This activity is
expected to result in a negligible impact on the affected species or
stocks. None of the species for which take authorization is requested
are either ESA-listed or considered depleted under the MMPA.
For reasons stated previously in this document, the negligible
impact determination is also supported by the likelihood that, given
sufficient ``notice'' through mitigation measures including soft start,
marine mammals are expected to move away from a noise source that is
annoying prior to its becoming potentially injurious, and the
likelihood that marine mammal detection ability by trained observers is
high under the environmental conditions described for
[[Page 4322]]
Hood Canal, enabling the implementation of shut-downs to avoid injury,
serious injury, or mortality. As a result, no take by injury or death
is anticipated, and the potential for temporary or permanent hearing
impairment is very low and will be avoided through the incorporation of
the proposed mitigation measures.
While the number of marine mammals potentially incidentally
harassed will depend on the distribution and abundance of marine
mammals in the vicinity of the survey activity, the number of potential
harassment takings is estimated to be small relative to regional stock
or population number, and has been mitigated to the lowest level
practicable through incorporation of the proposed mitigation and
monitoring measures mentioned previously in this document.
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 mitigation and monitoring
measures, NMFS preliminarily finds that the proposed test pile program
will result in the incidental take of small numbers of marine mammal,
by Level B harassment only, and that the total taking from the activity
will have a negligible impact on the affected species or stocks.
Impact on Availability of Affected Species or Stock for Taking for
Subsistence Uses
No tribal subsistence hunts are held in the vicinity of the project
area; thus, temporary behavioral impacts to individual animals would
not affect any subsistence activity. Further, no population or stock
level impacts to marine mammals are anticipated or authorized. As a
result, no impacts to the availability of the species or stock to the
Pacific Northwest treaty tribes are expected as a result of the
proposed activities. Therefore, no relevant subsistence uses of marine
mammals are implicated by this action.
Endangered Species Act (ESA)
There is one marine mammal species that is listed as endangered
under the ESA with confirmed or possible occurrence in the study area:
the Eastern DPS of the Steller sea lion. However, as described
previously, the project will occur from July 16-October 31 only, a time
at which Steller sea lions are not present in the project area. The
Navy conducted an informal consultation with the NWRO under Section 7
of the ESA; the NWRO concurred that there would be no presence of ESA-
listed marine mammals during the project and that formal consultation
was not required.
National Environmental Policy Act (NEPA)
In November 2010, the Navy prepared a draft EA, which has been
posted on the NMFS Web site (see ADDRESSES) concurrently with the
publication of this proposed IHA and public comments have been
solicited. NMFS will review the draft EA and the public comments
received and subsequently either adopt it or prepare its own NEPA
document before making a determination on the issuance of an IHA.
Proposed Authorization
As a result of these preliminary determinations, NMFS proposes to
authorize the take of marine mammals incidental to the Navy's test pile
program, provided the previously mentioned mitigation, monitoring, and
reporting requirements are incorporated.
Dated: January 18, 2011.
Helen M. Golde,
Deputy Director, Office of Protected Resources, National Marine
Fisheries Service.
[FR Doc. 2011-1528 Filed 1-24-11; 8:45 am]
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