[Federal Register Volume 78, Number 99 (Wednesday, May 22, 2013)]
[Notices]
[Pages 30273-30294]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-12151]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
RIN 0648-XC647
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to a Barge Mooring Project
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 construction activities as part of a barge
mooring project. 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, four species of marine mammals
during the specified activity.
DATES: Comments and information must be received no later than June 21,
2013.
ADDRESSES: Comments on the application should be addressed to Michael
Payne, Chief, Permits and Conservation Division, Office of Protected
Resources, National Marine Fisheries Service, 1315 East-West Highway,
Silver Spring, MD 20910. The mailbox address for providing email
comments is [email protected]. NMFS is not responsible for email
comments sent to addresses other than the one provided here. Comments
sent via email, including all attachments, must not exceed a 10-
megabyte file size.
Instructions: All comments received are a part of the public
record. 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 as well as a list of the references used
in this document may be obtained by writing to the address specified
above, telephoning
[[Page 30274]]
the contact listed below (see FOR FURTHER INFORMATION CONTACT), or
visiting the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm. Supplemental documents provided by the U.S. Navy may be
found at the same web address. Documents cited in this notice may also
be viewed, by appointment only, at the aforementioned physical address.
FOR FURTHER INFORMATION CONTACT: Ben Laws, Office of Protected
Resources, NMFS, (301) 427-8401.
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 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
We received an application on February 6, 2013, from the Navy for
the taking of marine mammals incidental to pile driving and removal in
association with a barge mooring project in the Hood Canal at Naval
Base Kitsap in Bangor, WA (NBKB). The Navy submitted a revised version
of the application on April 8, 2013, which we deemed adequate and
complete. The barge mooring project is expected to require
approximately eight weeks and would occur between July 16 and September
30, 2013. Four species of marine mammals are expected to be affected by
the specified activities: California sea lion (Zalophus californianus
californianus), harbor seal (Phoca vitulina richardii), harbor porpoise
(Phocoena phocoena vomerina), and killer whale (transient only; Orcinus
orca). These species may occur year-round in the Hood Canal, with the
exception of the California sea lion, which is only present from late
summer to late spring (August to early June).
NBKB provides berthing and support services to Navy submarines and
other fleet assets. Commander Submarine Development Squadron Five
(CSDS-5) is a tenant command on NBKB and is the working repository for
deep ocean technology and operational, at-sea application of that
technology. CSDS-5 currently moors and operates a research barge at the
Service Pier on NBKB and is proposing to install mooring for a new
larger research barge equipped with upgraded technology necessary for
continuing the Navy mission. CSDS-5 currently conducts research
equipment operations from an existing 115-ft by 35-ft barge with a 4-ft
draft that was constructed in 1940 and cannot accommodate the new
research equipment. A new larger barge measuring 260 ft by 85 ft with a
10-ft draft would replace the existing barge. Activities associated
with the project include the removal of an existing mooring dolphin,
the relocation and addition of floating pier sections, and the
installation of up to twenty steel piles to support the barge,
electrical transformer platform, and relocated pier sections (see
Figures 1-2 and 1-3 in the Navy's application). All steel piles would
be driven with a vibratory hammer for their initial embedment depths
and may be finished with an impact hammer for proofing, as necessary.
Proofing involves striking a driven pile with an impact hammer to
verify that it provides the required load-bearing capacity, as
indicated by the number of hammer blows per foot of pile advancement.
Sound attenuation measures (i.e., bubble curtain) would be used during
all impact hammer operations.
For pile driving activities, the Navy used thresholds recommended
by NMFS for assessing project impacts, outlined later in this document.
The Navy assumed practical spreading loss and used empirically-measured
source levels from a similar project conducted at NBKB to estimate
potential marine mammal exposures. Predicted exposures are outlined
later in this document. The calculations predict that only Level B
harassments would occur associated with pile driving or construction
activities.
Description of the Specified Activity
NBKB is located on the Hood Canal approximately twenty miles (32
km) west of Seattle, Washington (see Figures 1-1 and 2-1 in the Navy's
application). The proposed actions with the potential to cause
harassment of marine mammals within the waterways adjacent to NBKB,
under the MMPA, are vibratory and impact pile driving and removal of
piles via vibratory driver associated with the barge mooring project.
All in-water construction activities within the Hood Canal are only
permitted during July 16-February 15 in order to protect spawning fish
populations; however, the entire barge mooring project is scheduled to
be completed by September 30, 2013.
Specific Geographic Region
The Hood Canal is a long, narrow fjord-like basin of the western
Puget Sound. Throughout its 67-mile length, the width of the canal
varies from one to two miles and exhibits strong depth/elevation
gradients and irregular seafloor topography in many areas. Although no
official boundaries exist along the waterway, the northeastern section
of the canal extending from the mouth of the canal at Admiralty Inlet
to the southern tip of Toandos Peninsula is referred to as the northern
Hood Canal. NBKB is located within this region (see Figures 2-1 and 2-2
of the Navy's application). Please see Section 2 of the Navy's
application for more information about the specific geographic region,
including physical and oceanographic characteristics.
[[Page 30275]]
Project Description
The project consists of three components: The relocation and
addition to the Port Operations pier, the removal of existing
infrastructure, and the installation of the CSDS-5 research barge
mooring piles. Each element is described below. The barge mooring
project is expected to require approximately forty work days and would
occur between July 16 and September 30, 2013. Please see Figures 2-2
and 2-3 for details of the proposed project area and site plan.
Relocation of Port Operations
In order to accommodate the new, larger CSDS-5 research barge, some
portions of the Port Operations floating pier would be relocated to the
south side of the Service Pier trestle. Several floating pier sections/
modules would be relocated and seven new modules would be installed to
complete the Port Operations infrastructure. Anchoring of the relocated
and new floating pier modules would require the installation of three
24-in diameter hollow steel pipe piles. Additionally, four 20-in
diameter piles would be installed to support a 12-ft by 16-ft
electrical transformer platform.
Removal of Existing Infrastructure
Existing infrastructure must be removed in order to accommodate the
new barge, including the existing mooring dolphin and concrete pile cap
located north of the proposed relocated floating pier modules. Multiple
steel piles would be removed, including six 24-in diameter steel batter
piles and two 30-in diameter steel vertical piles. However, only one
24-inch steel pile would be removed with the use of vibratory pile
driving equipment. The remaining piles would be removed by cutting them
down at the mudline with hydraulic shears or by a diver utilizing a
thermal lance, and lifting them out of the water for proper disposal.
Installation of the Barge Mooring Piles
The new research barge will be located at the east side of the
Service Pier, and will be moored by five 36-in diameter and up to eight
48-in diameter hollow steel pipe piles. It is more likely that only
four 48-in diameter piles would be needed, but this is a conservative
estimate in order to ensure some flexibility is maintained for the
final design.
In summary, the following is the maximum scenario for project pile
driving/removal:
Four 20-in diameter steel pipe piles approximately 100 ft
long will be driven to depth of 55 ft,
Three 24-in diameter steel pipe piles approximately 60 ft
long will be driven to depth of 34 ft,
Five 36-in diameter steel pipe piles approximately 100 ft
long will be driven to depth of 55 ft,
As many as eight 48-in diameter steel pipe piles
approximately 115 ft long may be driven to depth of 70 ft, and
One 24-in diameter steel pipe will be removed using
vibratory pile driving equipment.
Methods
It is anticipated that a maximum of four piles can be driven per
day, although this total is unlikely to be reached due to various
delays that may be expected during construction work. The total number
of days for both extraction and installation are not likely to exceed
twenty workdays. Piles will be installed using mainly vibratory pile
driving, which involves use of hydraulic-powered weights to vibrate a
pile until the surrounding sediment liquefies, enabling the weight of
the pile plus the pile driver to push the pile into the ground. For
some piles, impact driving may be required to ensure load bearing
capacity (proofing) or if substrate conditions do not allow the pile to
reach the specified tip elevation with a vibratory driver. An impact
hammer uses a rising and falling piston to repeatedly strike a pile and
drive it into the ground. When the impact driver is required, it is
expected that 500 strikes will be necessary per pile, resulting in
approximately 2,000 strikes per day under the maximum scenario. All
piles driven with an impact hammer will be surrounded by a bubble
curtain or other sound attenuation device over the full water column to
minimize in-water noise.
Description of Sound Sources
Sound travels in waves, the basic components of which are
frequency, wavelength, velocity, and amplitude. Frequency is the number
of pressure waves that pass by a reference point per unit of time and
is measured in Hz or cycles per second. Wavelength is the distance
between two peaks of a sound wave; lower frequency sounds have longer
wavelengths than higher frequency sounds and attenuate more rapidly in
shallower water. Amplitude is the height of the sound pressure wave or
the `loudness' of a sound and is typically measured using the decibel
(dB) scale. A dB is the ratio between a measured pressure (with sound)
and a reference pressure (sound at a constant pressure, established by
scientific standards). It is a logarithmic unit that accounts for large
variations in amplitude; therefore, relatively small changes in dB
ratings correspond to large changes in sound pressure. When referring
to SPLs (SPLs; the sound force per unit area), sound is referenced in
the context of underwater sound pressure to 1 microPascal ([mu]Pa). One
pascal is the pressure resulting from a force of one newton exerted
over an area of one square meter. The source level represents the sound
level at a distance of 1 m from the source (referenced to 1 [mu]Pa).
The received level is the sound level at the listener's position.
Root mean square (rms) is the quadratic mean sound pressure over
the duration of an impulse. Rms is calculated by squaring all of the
sound amplitudes, averaging the squares, and then taking the square
root of the average (Urick, 1983). Rms accounts for both positive and
negative values; squaring the pressures makes all values positive so
that they may be accounted for in the summation of pressure levels
(Hastings and Popper, 2005). This measurement is often used in the
context of discussing behavioral effects, in part because behavioral
effects, which often result from auditory cues, may be better expressed
through averaged units than by peak pressures.
When underwater objects vibrate or activity occurs, sound-pressure
waves are created. These waves alternately compress and decompress the
water as the sound wave travels. Underwater sound waves radiate in all
directions away from the source (similar to ripples on the surface of a
pond), except in cases where the source is directional. The
compressions and decompressions associated with sound waves are
detected as changes in pressure by aquatic life and man-made sound
receptors such as hydrophones. Underwater sound levels (`ambient
sound') are comprised of multiple sources, including physical (e.g.,
waves, earthquakes, ice, atmospheric sound), biological (e.g., sounds
produced by marine mammals, fish, and invertebrates), and anthropogenic
sound (e.g., vessels, dredging, aircraft, construction). Even in the
absence of anthropogenic sound, the sea is typically a loud
environment. A number of sources of sound are likely to occur within
Hood Canal, including the following (Richardson et al., 1995):
Wind and waves: The complex interactions between wind and
water surface, including processes such as breaking waves and wave-
induced bubble oscillations and cavitation, are a main source of
naturally occurring ambient noise for frequencies between 200 Hz and 50
kHz (Mitson, 1995). In
[[Page 30276]]
general, ambient noise levels tend to increase with increasing wind
speed and wave height. Surf noise becomes important near shore, with
measurements collected at a distance of 8.5 km (5.3 mi) from shore
showing an increase of 10 dB in the 100 to 700 Hz band during heavy
surf conditions.
Precipitation noise: Noise from rain and hail impacting
the water surface can become an important component of total noise at
frequencies above 500 Hz, and possibly down to 100 Hz during quiet
times.
Biological noise: Marine mammals can contribute
significantly to ambient noise levels, as can some fish and shrimp. The
frequency band for biological contributions is from approximately 12 Hz
to over 100 kHz.
Anthropogenic noise: Sources of ambient noise related to
human activity include transportation (surface vessels and aircraft),
dredging and construction, oil and gas drilling and production, seismic
surveys, sonar, explosions, and ocean acoustic studies (Richardson et
al., 1995). Shipping noise typically dominates the total ambient noise
for frequencies between 20 and 300 Hz. In general, the frequencies of
anthropogenic sounds are below 1 kHz and, if higher frequency sound
levels are created, they will attenuate (decrease) rapidly (Richardson
et al., 1995). Known sound 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.
Table 1--Representative Sound Levels of Anthropogenic Sources
----------------------------------------------------------------------------------------------------------------
Frequency Underwater sound level (dB
Sound source range (Hz) re 1 [mu]Pa) Reference
----------------------------------------------------------------------------------------------------------------
Small vessels........................... 250-1,000 151 dB rms at 1 m (3.3 ft) Richardson et al., 1995.
Tug docking gravel barge................ 200-1,000 149 dB rms at 100 m (328 Blackwell and Greene,
ft). 2002.
Vibratory driving of 72-in (1.8 m) steel 10-1,500 180 dB rms at 10 m (33 ft) Reyff, 2007.
pipe pile.
Impact driving of 36-in steel pipe pile. 10-1,500 195 dB rms at 10 m........ Laughlin, 2007.
Impact driving of 66-in cast-in-steel- 10-1,500 195 dB rms at 10 m........ Reviewed in Hastings and
shell pile. Popper, 2005.
----------------------------------------------------------------------------------------------------------------
In-water construction activities associated with the project would
include impact pile driving, vibratory pile driving and removal, and
possibly pneumatic chipping. The sounds produced by these activities
fall into one of two sound types: pulsed and non-pulsed (defined in
next paragraph). 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, 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
those produced by 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.
Impact hammers operate by repeatedly dropping a heavy piston onto a
pile to drive the pile into the substrate. Sound generated by impact
hammers is characterized by rapid rise times and high peak levels, a
potentially injurious combination (Hastings and Popper, 2005).
Vibratory hammers install piles by vibrating them and allowing the
weight of the hammer to push them into the sediment. Vibratory hammers
produce significantly less sound than impact hammers. Peak SPLs may be
180 dB or greater, but are generally 10 to 20 dB lower than SPLs
generated during impact pile driving of the same-sized pile (Oestman et
al., 2009). Rise time is slower, reducing the probability and severity
of injury, and sound energy is distributed over a greater amount of
time (Nedwell and Edwards, 2002; Carlson et al., 2005).
Ambient Sound
The underwater acoustic environment consists of ambient sound,
defined as environmental background sound levels lacking a single
source or point (Richardson et al., 1995). The ambient underwater sound
level of a region is defined by the total acoustical energy being
generated by known and unknown sources, including sounds from both
natural and anthropogenic sources. The sum of the various natural and
anthropogenic sound sources at any given location and time depends not
only on the source levels (as determined by current weather conditions
and levels of biological and shipping activity) but also on the ability
of sound to propagate through the environment. In turn, sound
propagation is dependent on the spatially and temporally varying
properties of the water column and sea floor, and is frequency-
dependent. As a result of the dependence on a large number of varying
factors, the ambient sound levels at a given frequency and location can
vary by 10-20 dB from day to day (Richardson et al., 1995).
Underwater ambient noise was measured at approximately 113 dB re
1[mu]Pa rms between 50 Hz and 20 kHz during the recent Test Pile
Program (TPP) project, approximately 1.85 mi from the project area
(Illingworth & Rodkin, Inc., 2012). In 2009, the average broadband
ambient underwater noise levels were measured at 114 dB re 1[mu]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[mu]Pa noted in the 125 Hz band. In the 300 Hz to
5 kHz range, average levels ranged between 83 and 99 dB re 1[mu]Pa.
Wind-driven wave noise dominated the background noise environment at
approximately 5 kHz and above, and ambient noise levels flattened above
10 kHz.
Sound Attenuation Devices
Sound levels can be greatly reduced during impact pile driving
using sound attenuation devices. There are several
[[Page 30277]]
types of sound attenuation devices including bubble curtains,
cofferdams, and isolation casings (also called temporary noise
attenuation piles [TNAP]), and cushion blocks. The Navy proposes to use
bubble curtains, which create a column of air bubbles rising around a
pile from the substrate to the water surface. The air bubbles absorb
and scatter sound waves emanating from the pile, thereby reducing the
sound energy. Bubble curtains may be confined or unconfined. An
unconfined bubble curtain may consist of a ring seated on the substrate
and emitting air bubbles from the bottom. An unconfined bubble curtain
may also consist of a stacked system, that is, a series of multiple
rings placed at the bottom and at various elevations around the pile.
Stacked systems may be more effective than non-stacked systems in areas
with high current and deep water (Oestman et al., 2009).
A confined bubble curtain contains the air bubbles within a
flexible or rigid sleeve made from plastic, cloth, or pipe. Confined
bubble curtains generally offer higher attenuation levels than
unconfined curtains because they may physically block sound waves and
they prevent air bubbles from migrating away from the pile. For this
reason, the confined bubble curtain is commonly used in areas with high
current velocity (Oestman et al., 2009).
Both environmental conditions and the characteristics of the sound
attenuation device may influence the effectiveness of the device.
According to Oestman et al. (2009):
In general, confined bubble curtains attain better sound
attenuation levels in areas of high current than unconfined bubble
curtains. If an unconfined device is used, high current velocity may
sweep bubbles away from the pile, resulting in reduced levels of sound
attenuation.
Softer substrates may allow for a better seal for the
device, preventing leakage of air bubbles and escape of sound waves.
This increases the effectiveness of the device. Softer substrates also
provide additional attenuation of sound traveling through the
substrate.
Flat bottom topography provides a better seal, enhancing
effectiveness of the sound attenuation device, whereas sloped or
undulating terrain reduces or eliminates its effectiveness.
Air bubbles must be close to the pile; otherwise, sound
may propagate into the water, reducing the effectiveness of the device.
Harder substrates may transmit ground-borne sound and
propagate it into the water column.
The literature presents a wide array of observed attenuation
results for bubble curtains (e.g., Oestman et al., 2009, Coleman, 2011,
California Department of Transportation, 2012). The variability in
attenuation levels is due to variation in design, as well as
differences in site conditions and difficulty in properly installing
and operating in-water attenuation devices. As a general rule,
reductions of greater than 10 dB cannot be reliably predicted. The TPP
reported a range of measured values for realized attenuation mostly
within 6 to 12 dB (Illingworth & Rodkin, Inc., 2012). For 36-inch piles
the average peak and rms reduction with use of the bubble curtain was 8
dB, where the averages of all bubble-on and bubble-off data were
compared. For 48-inch piles, the average SPL reduction with use of a
bubble curtain was 6 dB for average peak values and 5 dB for rms values
(see Table 3). To avoid loss of attenuation from design and
implementation errors, the Navy has required specific bubble curtain
design specifications, including testing requirements for air pressure
and flow prior to initial impact hammer use, and a requirement for
placement on the substrate. We considered previous assumptions
regarding effectiveness of the bubble curtain (approximately 10 dB
realized attenuation, TPP measurements (approximately 7 dB overall),
and other monitored projects (typically at least 8 dB realized
attenuation), and determined that 8 dB is a realistic and achievable
estimate of average SPL (rms) reduction.
Sound Thresholds
NMFS uses generic sound exposure thresholds to determine when an
activity that produces sound might result in impacts to a marine mammal
such that a take by harassment might occur. To date, no studies have
been conducted that examine impacts to marine mammals from pile driving
sounds from which empirical sound thresholds have been established.
Current NMFS practice (in relation to the MMPA) regarding exposure of
marine mammals to sound 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 sound
(e.g., vibratory pile driving), but below injurious thresholds. For
airborne sound, 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 in the project area. Transmission loss (TL) is the decrease in
acoustic intensity as an acoustic pressure wave propagates out from a
source. TL parameters vary with frequency, temperature, sea conditions,
current, source and receiver depth, water depth, water chemistry, and
bottom composition and topography. The general formula for underwater
TL is:
TL = B * log10(R1/R2)
where:
R1 = the distance of the modeled SPL from the driven
pile, and
R2 = the distance from the driven pile of the initial
measurement.
This formula neglects loss due to scattering and absorption, which is
assumed to be zero here. The degree to which underwater sound
propagates away from a sound source is dependent on a variety of
factors, most notably by the water bathymetry and presence or absence
of reflective or absorptive conditions including in-water structures
and sediments. Spherical spreading occurs in a perfectly unobstructed
(free-field) environment not limited by depth or water surface,
resulting in a 6 dB reduction in sound level for each doubling of
distance from the source (20*log[range]). Cylindrical spreading occurs
in an environment in which sound propagation is bounded by the water
surface and sea bottom, resulting in a reduction of 3 dB in sound level
for each doubling of distance from the source (10*log[range]). A
practical spreading value of 15 is often used under conditions, such as
Hood Canal, where water increases with depth as the receiver moves away
from the shoreline, resulting in an expected propagation environment
that would lie between spherical and cylindrical spreading loss
conditions. Practical spreading loss (4.5 dB reduction in sound level
for each doubling of distance) is assumed here.
Underwater Sound--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. The Navy
previously conducted measurements for driving of steel piles
[[Page 30278]]
at NBKB as part of the TPP (Illingworth & Rodkin, Inc., 2012), and we
have determined that use of those values is appropriate to determine
reasonable SPLs and their associated affects on marine mammals that are
likely to result from pile driving at NBKB. During the TPP, SPLs from
driving of 24-, 36-, and 48-in piles by impact and vibratory hammers
were measured. Because 20-in piles were not measured during the TPP, we
use sound pressure levels from the 24-in piles as a conservative
estimate. Sound levels associated with vibratory pile removal are
assumed to be the same as those during vibratory installation (Reyff,
2007)--which is likely a conservative assumption--and have been taken
into consideration in the modeling analysis. Results of the TPP are
shown in Table 2.
Table 2--Summary of Measured Underwater SPLs From TPP
------------------------------------------------------------------------
Method Pile size Measured SPLs
------------------------------------------------------------------------
Impact................. 24-in................. 180 dB re 1 [mu]Pa
(rms) at 10 m.
Impact................. 36-in................. 196 dB re 1 [mu]Pa
(rms) at 10 m.
Impact................. 48-in................. 194 dB re 1 [mu]Pa
(rms) at 10 m.
Vibratory.............. 24-in................. 160 dB re 1 [mu]Pa
(rms) at 10 m.
Vibratory.............. 36-in................. 169 dB re 1 [mu]Pa
(rms) at 10 m.
Vibratory.............. 48-in................. 172 dB re 1 [mu]Pa
(rms) at 10 m.
------------------------------------------------------------------------
Because it is unknown what size pile may be driven on any given
day, the Navy uses the most conservative values (i.e., 196 dB for
impact driving and 172 dB for vibratory driving), and practical
spreading loss, to estimate distances to relevant thresholds and
associated areas of ensonification (presented in Table 3). Predicted
distances to thresholds for different sources are shown in Figures 6-1
and 6-2 of the Navy's application. The predicted area exceeding the
threshold assumes a field free of obstruction, which is unrealistic due
to land masses or bends in the canal. The actual distance to the
behavioral disturbance thresholds for pile driving may be shorter than
the calculated distance 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 site]) at the
project area.
Table 3--Distances to Relevant Sound Thresholds and Areas of Ensonification
--------------------------------------------------------------------------------------------------------------------------------------------------------
Effective Distance to threshold (m) and associated area of ensonification (km \2\)
source level -----------------------------------------------------------------------------------------------
Description (dB at 10 m)
\1\ 190 dB 180 dB 160 dB 120 dB
--------------------------------------------------------------------------------------------------------------------------------------------------------
Steel piles, impact..................... 188 7, 0.0002 34, 0.0036 736, 1.702 n/a
Steel piles, vibratory.................. 164 1, <0.0001 3, <0.0001 n/a 29,286 \2\, 16.1
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ 8 dB attenuation was assumed from use of bubble curtain.
\2\ This distance cannot actually be attained at the project location. The area presented is actual.
Airborne Sound--Pile driving can generate airborne sound 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 SPLs that could result
in Level B behavioral harassment. Although there is no official
airborne sound threshold, NMFS assumes for purposes of the MMPA that
behavioral disturbance can occur upon exposure to sounds above 100 dB
re 20 [mu]Pa rms (unweighted) for all pinnipeds, except harbor seals.
For harbor seals, the threshold is 90 dB re 20 [mu]Pa rms (unweighted).
As was discussed for underwater sound 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. As before, measured values from the TPP were
used to determine reasonable airborne SPLs and their associated effects
on marine mammals that are likely to result from pile driving at NBKB.
During the TPP, vibratory driving was measured at 102 dB re 20 [mu]Pa
rms at 15 m and impact driving at 109 dB re 20 [mu]Pa rms at 15 m.
Based on these values and the assumption of spherical spreading
loss, distances to relevant thresholds and associated areas of
ensonification are presented in Table 4; these areas are depicted in
Tables 6-3 and 6-4 of the Navy's application. There are no haul-out
locations within these zones, which are encompassed by the zones
estimated for underwater sound. Protective measures would be in place
out to the distances calculated for the underwater thresholds, and the
distances for the airborne thresholds would be covered fully by
mitigation and monitoring measures in place for underwater sound
thresholds. We recognize that pinnipeds in water that are within the
area of ensonification for airborne sound could be incidentally taken
by either underwater or airborne sound or both. We consider these
incidences of harassment to be accounted for in the take estimates for
underwater sound.
Table 4--Distances to Relevant Sound Thresholds and Areas of Ensonification, Airborne Sound
----------------------------------------------------------------------------------------------------------------
Distance to threshold (m) and associated area of
Threshold, re 20 [mu]Pa ensonification (km\2\)
Group rms (unweighted) -------------------------------------------------
Impact driving Vibratory driving
----------------------------------------------------------------------------------------------------------------
Harbor seals........................ 90 dB................... 134, 0.0564 60, 0.0113
California sea lions................ 100 dB.................. 42, 0.0055 19, 0.0011
----------------------------------------------------------------------------------------------------------------
[[Page 30279]]
Description of Marine Mammals in the Area of the Specified Activity
There are seven marine mammal species, four 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 (Phocoenoides dalli dalli), Steller sea lion
(eastern stock only; Eumetopias jubatus monteriensis), California sea
lion, harbor seal, and humpback whale (Megaptera novaeangliae). The
Steller sea lion and humpback whale are the only marine mammals that
may occur within the Hood Canal that are listed under the Endangered
Species Act (ESA); the humpback whale is listed as endangered and the
eastern distinct population segment (DPS) of Steller sea lion is listed
as threatened. The Steller sea lion is typically present in low numbers
in the Hood Canal only from approximately October through mid-April.
The humpback whale is not typically present in Hood Canal, with no
confirmed sightings found in the literature or the Orca Network
database prior to January and February 2012, when one individual was
observed repeatedly over a period of several weeks. No sightings have
been recorded since that time and we consider the humpback whale to be
a rare visitor to Hood Canal at most. 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 over 15 years.
Therefore, these three stocks were excluded from further analysis.
This section summarizes the population status and abundance of
these species. We have reviewed the Navy's detailed species
descriptions, including life history information, for accuracy and
completeness and refer the reader to Sections 3 and 4 of the Navy's
application instead of reprinting the information here. Table 5 lists
the marine mammal species with expected potential for occurrence in the
vicinity of NBKB during the project timeframe. The following
information is summarized largely from NMFS Stock Assessment Reports.
Table 5--Marine Mammals Present in the Hood Canal in the Vicinity of NBKB
----------------------------------------------------------------------------------------------------------------
Stock abundance \1\ (CV, Relative occurrence in
Species Nmin) Hood Canal Season of occurrence
----------------------------------------------------------------------------------------------------------------
California sea lion U.S. Stock...... 296,750 (n/a, 153,337) Common................. Fall to late spring
(Aug to early June).
Harbor seal WA inland waters stock.. 14,612 \2\ (0.15, Common................. Year-round; resident
12,844) species in Hood Canal.
Killer whale West Coast transient 354 (n/a) Rare to occasional Year-round.
stock. presence.
Dall's porpoise CA/OR/WA stock...... 42,000 (0.33, 32,106) Rare to occasional Year-round.
presence.
Harbor porpoise WA inland waters 10,682 (0.38, 7,841) Possible regular to Year-round.
stock. occasional presence.
----------------------------------------------------------------------------------------------------------------
\1\ NMFS marine mammal stock assessment reports at: http://www.nmfs.noaa.gov/pr/sars/species.htm. CV is
coefficient of variation; Nmin is the minimum estimate of stock abundance.
\2\ This abundance estimate is greater than eight years old and is therefore not considered current.
Harbor Seal
Harbor seals inhabit coastal and estuarine waters and shoreline
areas of the northern hemisphere from temperate to polar regions. The
eastern North Pacific subspecies is found from Baja California north to
the Aleutian Islands and into the Bering Sea. Multiple lines of
evidence support the existence of geographic structure among harbor
seal populations from California to Alaska (Carretta et al., 2011).
However, because stock boundaries are difficult to meaningfully draw
from a biological perspective, three separate harbor seal stocks are
recognized for management purposes along the west coast of the
continental U.S.: (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., 2011). Multiple stocks are recognized in Alaska.
Samples from Washington, Oregon, and California demonstrate a high
level of genetic diversity and indicate that the harbor seals of
Washington inland waters possess unique haplotypes not found in seals
from the coasts of Washington, Oregon, and California (Lamont et al.,
1996). Only the Washington inland waters stock may be found in the
project area.
Washington inland waters harbor seals are not protected under the
ESA or listed as depleted under the MMPA. Because there is no current
abundance estimate for this stock, there is no current estimate of
potential biological removal (PBR). However, because annual human-
caused mortality (13) is significantly less than the previously
calculated PBR (771) the stock is not considered strategic under the
MMPA. The stock is considered to be within its optimum sustainable
population (OSP) level.
The best abundance estimate of the Washington inland waters stock
of harbor seals is 14,612 (CV = 0.15) and the minimum population size
of this stock is 12,884 individuals (Carretta et al., 2011). Aerial
surveys of harbor seals in Washington were conducted during the pupping
season in 1999, during which time the total numbers of hauled-out seals
(including pups) were counted (Jeffries et al., 2003). Radio-tagging
studies conducted at six locations collected information on harbor seal
haul-out patterns in 1991-92, resulting in a correction factor of 1.53
(CV = 0.065) to account for animals in the water which are missed
during the aerial surveys (Huber et al., 2001), which, coupled with the
aerial survey counts, provides the abundance estimate. Because the
estimate is greater than eight years old, NMFS does not consider it
current. However, it does represent the best available information
regarding stock abundance. Harbor seal counts in Washington State
increased at an annual rate of ten percent from 1991-96 (Jeffries et
al., 1997). However, a logistic model fit to abundance data from 1978-
99 resulted in an estimated maximum net productivity rate of 12.6
percent (95% CI = 9.4-18.7%) and the population is thought to be stable
(Jeffries et al., 2003).
Historical levels of harbor seal abundance in Washington are
unknown. The population was apparently greatly reduced during the 1940s
and 1950s due to a state-financed bounty program and
[[Page 30280]]
remained low during the 1970s before rebounding to current levels
(Carretta et al., 2011). Data from 2004-08 indicate that a minimum of
3.8 harbor seals are killed annually in Washington inland waters
commercial fisheries (Carretta et al., 2011). Animals captured east of
Cape Flattery are assumed to belong to this stock. The estimate is
considered a minimum because there are likely additional animals killed
in unobserved fisheries and because not all animals stranding as a
result of fisheries interactions are likely to be recorded. Another 9.2
harbor seals per year are estimated to be killed as a result of various
non-fisheries human interactions (Carretta et al., 2011). Tribal
subsistence takes of this stock may occur, but no data on recent takes
are available.
Harbor seals are the most abundant marine mammal in Hood Canal,
where they can occur anywhere year-round, and are the only pinniped
that breeds in inland Washington waters and the only species of marine
mammal that is considered resident in the Hood Canal (Jeffries et al.,
2003). They are year-round, non-migratory residents, pup (i.e., give
birth) in Hood Canal, and the population is considered closed, meaning
that they do not have much movement outside of Hood Canal (London,
2006). Surveys in the Hood Canal from the mid-1970s to 2000 show a
fairly stable population between 600-1,200 seals, and the abundance of
harbor seals in Hood Canal has likely stabilized at its carrying
capacity of approximately 1,000 seals (Jeffries et al., 2003).
Harbor seals were consistently sighted during Navy surveys and were
found in all marine habitats including nearshore waters and deeper
water, and have been observed hauled out on manmade objects such as
buoys. Harbor seals were commonly observed in the water during
monitoring conducted for other projects at NBKB in 2011. 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. Since
there are no known pupping sites in the vicinity of the project area,
harbor seal neonates would not generally be expected to be present
during pile driving. Otherwise, during most of the year, all age and
sex classes could occur in the project area throughout the period of
construction activity. 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. From April through mid-July, female harbor seals haul
out on the outer coast of Washington at pupping sites to give birth.
The main haul-out locations for harbor seals in Hood Canal are located
on river delta and tidal exposed areas, with the closest haul-out to
the project area being approximately ten miles (16 km) southwest of
NBKB at Dosewallips River mouth, outside the potential area of effect
for this project (London, 2006; see Figure 4-1 of the Navy's
application).
California Sea Lion
California sea lions range from the Gulf of California north to the
Gulf of Alaska, with breeding areas located in the Gulf of California,
western Baja California, and southern California. Five genetically
distinct geographic populations have been identified: (1) Pacific
Temperate, (2) Pacific Subtropical, (3) Southern Gulf of California,
(4) Central Gulf of California and (5) Northern Gulf of California
(Schramm et al., 2009). Rookeries for the Pacific Temperate population
are found within U.S. waters and just south of the U.S.-Mexico border,
and animals belonging to this population may be found from the Gulf of
Alaska to Mexican waters off Baja California. For management purposes,
a stock of California sea lions comprising those animals at rookeries
within the U.S. is defined (i.e., the U.S. stock of California sea
lions) (Carretta et al., 2011). Pup production at the Coronado Islands
rookery in Mexican waters is considered an insignificant contribution
to the overall size of the Pacific Temperate population (Lowry and
Maravilla-Chavez, 2005).
California sea lions are not protected under the ESA or listed as
depleted under the MMPA. Total annual human-caused mortality (at least
431) is substantially less than the potential biological removal (PBR,
estimated at 9,200 per year); therefore, California sea lions are not
considered a strategic stock under the MMPA. There are indications that
the California sea lion may have reached or is approaching carrying
capacity, although more data are needed to confirm that leveling in
growth persists (Carretta et al., 2011).
The best abundance estimate of the U.S. stock of California sea
lions is 296,750 and the minimum population size of this stock is
153,337 individuals (Carretta et al., 2011). The entire population
cannot be counted because all age and sex classes are never ashore at
the same time; therefore, the best abundance estimate is determined
from the number of births and the proportion of pups in the population,
with censuses conducted in July after all pups have been born.
Specifically, the pup count for rookeries in southern California from
2008 was adjusted for pre-census mortality and then multiplied by the
inverse of the fraction of newborn pups in the population (Carretta et
al., 2011). The minimum population size was determined from counts of
all age and sex classes that were ashore at all the major rookeries and
haul-out sites in southern and central California during the 2007
breeding season, including all California sea lions counted during the
July 2007 census at the Channel Islands in southern California and at
haul-out sites located between Point Conception and Point Reyes,
California (Carretta et al., 2011). An additional unknown number of
California sea lions are at sea or hauled out at locations that were
not censused and are not accounted for in the minimum population size.
Trends in pup counts from 1975 through 2008 have been assessed for
four rookeries in southern California and for haul-outs in central and
northern California. During this time period counts of pups increased
at an annual rate of 5.4 percent, excluding six El Ni[ntilde]o years
when pup production declined dramatically before quickly rebounding
(Carretta et al., 2011). The maximum population growth rate was 9.2
percent when pup counts from the El Ni[ntilde]o years were removed.
However, the apparent growth rate from the population trajectory
underestimates the intrinsic growth rate because it does not consider
human-caused mortality occurring during the time series; the default
maximum net productivity rate for pinnipeds (12 percent per year) is
considered appropriate for California sea lions (Carretta et al.,
2011).
Historic exploitation of California sea lions include harvest for
food by Native Americans in pre-historic times and for oil and hides in
the mid-1800s, as well as exploitation for a variety of reasons more
recently (Carretta et al., 2011). There are few historical records to
document the effects of such exploitation on sea lion abundance (Lowry
et al., 1992). Data from 2003-09 indicate that a minimum of 337 (CV =
0.56) California sea lions are killed annually in commercial fisheries.
In addition, a summary of stranding database records for 2005-09 shows
an annual average of 65 such events, which is likely a gross
underestimate because most carcasses are not recovered. California sea
lions may also be removed because of predation on endangered salmonids
(17 per year, 2008-10) or incidentally captured during scientific
research (3 per year, 2005-09) (Carretta et al., 2011). Sea lion
mortality has also been linked to the
[[Page 30281]]
algal-produced neurotoxin domoic acid (Scholin et al., 2000). There is
currently an Unusual Mortality Event (UME) declaration in effect for
California sea lions. Future mortality may be expected to occur, due to
the sporadic occurrence of such harmful algal blooms. Beginning in
January 2013, elevated strandings of California sea lion pups have been
observed in Southern California, with live sea lion strandings nearly
three times higher than the historical average. The causes of this UME
are under investigation (http://www.nmfs.noaa.gov/pr/health/mmume/californiasealions2013.htm; accessed April 10, 2013).
An estimated 3,000 to 5,000 California sea lions migrate northward
along the coast to central and northern California, Oregon, Washington,
and Vancouver Island during the non-breeding season from September to
May (Jeffries et al., 2000) and return south the following spring
(Mate, 1975; Bonnell et al., 1983). 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).
California sea lions are present in Hood Canal during much of the
year with the exception of mid-June through August, and occur regularly
at NBKB, as observed during Navy waterfront surveys conducted from
April 2008 through June 2010 (Navy, 2010). They are known to utilize a
diversity of man-made structures for hauling out (Riedman, 1990) and,
although there are no regular California sea lion haul-outs known
within the Hood Canal (Jeffries et al., 2000), they are frequently
observed hauled out at several opportune areas at NBKB (e.g.,
submarines, floating security fence, barges). As many as 81 California
sea lions have been observed hauled out on a single day at NBKB (Agness
and Tannenbaum, 2009a; Tannenbaum et al., 2009a; Navy, 2011). All
documented instances of California sea lions hauling out at NBKB have
been on submarines docked at Delta Pier, approximately 0.85 mi north of
Service Pier, and on pontoons of the security fence. California sea
lions have also been observed swimming near the Explosives Handling
Wharf on several occasions, approximately 1.85 mi north of Service Pier
(Tannenbaum et al. 2009; Navy 2010), and likely forage in both
nearshore and inland marine deeper water habitats in the vicinity.
Killer Whale
Killer whales are one of the most cosmopolitan marine mammals,
found in all oceans with no apparent restrictions on temperature or
depth, although they do occur at higher densities in colder, more
productive waters at high latitudes and are more common in nearshore
waters (Leatherwood and Dahlheim, 1978; Forney and Wade, 2006; Allen
and Angliss, 2011). Killer whales are found throughout the North
Pacific, including the entire Alaska coast, in British Columbia and
Washington inland waterways, and along the outer coasts of Washington,
Oregon, and California. On the basis of differences in morphology,
ecology, genetics, and behavior, populations of killer whales have
largely been classified as ``resident'', ``transient'', or ``offshore''
(e.g., Dahlheim et al., 2008). Several studies have also provided
evidence that these ecotypes are genetically distinct, and that further
genetic differentiation is present between subpopulations of the
resident and transient ecotypes (e.g., Barrett-Lennard, 2000). The
taxonomy of killer whales is unresolved, with expert opinion generally
following one of two lines: Killer whales are either (1) a single
highly variable species, with locally differentiated ecotypes
representing recently evolved and relatively ephemeral forms not
deserving species status, or (2) multiple species, supported by the
congruence of several lines of evidence for the distinctness of
sympatrically occurring forms (Krahn et al., 2004). Resident and
transient whales are currently considered to be unnamed subspecies
(Committee on Taxonomy, 2011).
The resident and transient populations have been divided further
into different subpopulations on the basis of genetic analyses,
distribution, and other factors. Recognized stocks in the North Pacific
include Alaska Residents, Northern Residents, Southern Residents, Gulf
of Alaska, Aleutian Islands, and Bering Sea Transients, and West Coast
Transients, along with a single offshore stock. West Coast Transient
killer whales, which occur from California through southeastern Alaska,
are the only type expected to potentially occur in the project area.
West Coast Transient killer whales are not protected under the ESA
or listed as depleted under the MMPA. The estimated annual level of
human-caused mortality (0) does not exceed the calculated PBR (3.5);
therefore, West Coast Transient killer whales are not considered a
strategic stock under the MMPA. It is thought that the stock grew
rapidly from the mid-1970s to mid-1990s as a result of a combination of
high birth rate, survival, as well as greater immigration of animals
into the nearshore study area (DFO, 2009). The rapid growth of the
population during this period coincided with a dramatic increase in the
abundance of the whales' primary prey, harbor seals, in nearshore
waters. Population growth began slowing in the mid-1990s and has
continued to slow in recent years (DFO, 2009). Population trends and
status of this stock relative to its OSP level are currently unknown,
as is the actual maximum productivity rate. Analyses in DFO (2009)
estimated a rate of increase of about six percent per year from 1975 to
2006, but this included recruitment of non-calf whales into the
population. The default maximum net growth rate for cetaceans (4
percent) is considered appropriate pending additional information
(Carretta et al., 2011).
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 an abundance estimate of 354 individuals for the
West Coast transient stock (Allen and Angliss, 2011). Although this
direct count of individually identifiable animals does not necessarily
represent the number of live animals, it is considered a conservative
minimum estimate (Allen and Angliss, 2011). However, the number in
Washington waters at any one time is probably fewer than twenty
individuals (Wiles, 2004). The West Coast transient killer whale stock
is not designated as depleted under the MMPA or listed under the ESA.
The estimated annual level of human-caused mortality and serious injury
does not exceed the PBR. Therefore, the West Coast Transient stock of
killer whales is not classified as a strategic stock.
The estimated minimum mortality rate incidental to U.S. commercial
fisheries is zero animals per year (Allen and Angliss, 2011). However,
this could represent an underestimate as regards total fisheries-
related mortality due to a lack of data concerning marine mammal
interactions in Canadian commercial fisheries known to have potential
for interaction with killer whales. Any such interactions are thought
to be few in number (Allen and Angliss, 2011). Other mortality, as a
result of shootings or ship strikes, has been of concern in the past.
However, no ship strikes have been reported for this stock, and
shooting of transients is thought to be minimal because their diet is
based on marine mammals rather than fish. There are no reports of a
subsistence harvest of killer whales in Alaska or Canada.
Transient occurrence in inland waters appears to peak during August
and September which is the peak time for harbor seal pupping, weaning,
and post-
[[Page 30282]]
weaning (Baird and Dill, 1995). In 2003 and 2005, small groups of
transient killer whales (eleven and six individuals, respectively) were
present in Hood Canal for significant periods of time (59 and 172 days,
respectively) between the months of January and July. While present,
the whales preyed on harbor seals in the subtidal zone of the nearshore
marine and inland marine deeper water habitats (London, 2006).
Dall's Porpoise
Dall's porpoises are endemic to temperate waters of the North
Pacific, typically in deeper waters between 30-62[deg]N, and are found
from northern Baja California to the northern Bering Sea. Stock
structure for Dall's porpoises is not well known; because there are no
cooperative management agreements with Mexico or Canada for fisheries
which may take this species, Dall's porpoises are divided for
management purposes into two discrete, noncontiguous areas: (1) Waters
off California, Oregon, and Washington, and (2) Alaskan waters
(Carretta et al., 2011). Only individuals from the CA/OR/WA stock may
occur within the project area.
Dall's porpoises are not protected under the ESA or listed as
depleted under the MMPA. The minimum estimate of annual human-caused
mortality (0.4) is substantially less than the calculated PBR (257);
therefore, Dall's porpoises are not considered a strategic stock under
the MMPA. The status of Dall's porpoises in California, Oregon and
Washington relative to OSP is not known (Carretta et al., 2011).
Dall's porpoise distribution on the U.S. west coast is highly
variable between years and appears to be affected by oceanographic
conditions (Forney and Barlow, 1998); animals may spend more or less
time outside of U.S. waters as oceanographic conditions change.
Therefore, a multi-year average of 2005 and 2008 summer/autumn vessel-
based line transect surveys of California, Oregon, and Washington
waters was used to estimate a best abundance of 42,000 (CV = 0.33)
animals (Forney, 2007; Barlow, 2010). The minimum population is
considered to be 32,106 animals. Dall's porpoises also 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. Because
distribution and abundance of this stock is so variable, population
trends are not available (Carretta et al., 2011). No information is
available regarding productivity rates, and the default maximum net
growth rate for cetaceans (4 percent) is considered appropriate
(Carretta et al., 2011).
Data from 2002-08, from all fisheries for which mortality data are
available, indicate that a minimum of 0.4 animals are killed per year
(Carretta et al., 2011). Species-specific information is not available
for Mexican fisheries, which could be an additional source of mortality
for animals beyond the stock boundaries delineated for management
purposes. No other sources of human-caused mortality are known.
In Washington, Dall's porpoises are most abundant in offshore
waters where they are year-round residents, although interannual
distribution is highly variable (Green et al., 1992). Dall's porpoises
are observed throughout the year in the Puget Sound north of Seattle,
are seen occasionally in southern Puget Sound, and may also
occasionally occur in Hood Canal. However, only a single Dall's
porpoise has been observed at NBKB, in deeper water during a 2008
summer survey (Tannenbaum et al., 2009a).
Harbor Porpoise
Harbor porpoises are found primarily in inshore and relatively
shallow coastal waters (< 100 m) from Point Barrow to Point Conception.
Various genetic analyses and investigation of pollutant loads indicate
a low mixing rate for harbor porpoise along the west coast of North
America and likely fine-scale geographic structure along an almost
continuous distribution from California to Alaska (e.g., Calambokidis
and Barlow, 1991; Osmek et al., 1994; Chivers et al., 2002, 2007).
However, stock boundaries are difficult to draw because any rigid line
is generally arbitrary from a biological perspective. On the basis of
genetic data and density discontinuities identified from aerial
surveys, eight stocks have been identified in the eastern North
Pacific, including northern Oregon/Washington coastal and inland
Washington stocks (Carretta et al., 2011). The Washington inland waters
stock includes individuals found east of Cape Flattery and is the only
stock that may occur in the project area.
Harbor porpoises of Washington inland waters are not protected
under the ESA or listed as depleted under the MMPA. Because there is no
current abundance estimate for this stock, there is no current estimate
of PBR. However, because annual human-caused mortality (2.6) is less
than the previously calculated PBR (63) the stock is not considered
strategic under the MMPA. The status of harbor porpoises in Washington
inland waters relative to OSP is not known (Carretta et al., 2011).
The best estimate of abundance for this stock is derived from
aerial surveys of the inland waters of Washington and southern British
Columbia conducted during August of 2002 and 2003. When corrected for
availability and perception bias, the average of the 2002-03 estimates
of abundance for U.S. waters resulted in an estimated abundance for the
Washington Inland Waters stock of harbor porpoise of 10,682 (CV = 0.38)
animals (Laake et al., 1997; Carretta et al., 2011), with a minimum
population estimate of 7,841 animals. Because the estimate is greater
than eight years old, NMFS does not consider it current. However, it
does represent the best available information regarding stock
abundance.
Although long-term harbor porpoise sightings in southern Puget
Sound declined from the 1940s through the 1990s, sightings and
strandings have increased in Puget Sound and northern Hood Canal in
recent years and harbor porpoise are now considered to regularly occur
year-round in these waters (Carretta et al., 2011). Reasons for the
apparent decline, as well as the apparent rebound, are unknown. Recent
observations may represent a return to historical conditions, when
harbor porpoises were considered one of the most common cetaceans in
Puget Sound (Scheffer and Slipp, 1948). No information regarding
productivity is available for this stock and NMFS considers the default
maximum net productivity rate for cetaceans (4 percent) to be
appropriate.
Data from 2005-09 indicate that a minimum of 2.2 Washington inland
waters harbor seals are killed annually in U.S. commercial fisheries
(Carretta et al., 2011). Animals captured in waters east of Cape
Flattery are assumed to belong to this stock. This estimate is
considered a minimum because the Washington Puget Sound Region salmon
set/drift gillnet fishery has not been observed since 1994, and because
of a lack of knowledge about the extent to which harbor porpoise from
U.S. waters frequent the waters of British Columbia and are, therefore,
subject to fishery-related mortality. However, harbor porpoise takes in
the salmon drift gillnet fishery are unlikely to have increased since
the fishery was last observed, when few interactions were recorded, due
to reductions in the number of participating vessels and available
fishing time. Fishing effort and catch have declined throughout all
salmon fisheries in the region due to management efforts to recover
ESA-listed salmonids (Carretta et al., 2011).
[[Page 30283]]
In addition, an estimated 0.4 animals per year are killed by non-
fishery human causes (e.g., ship strike, entanglement). In 2006, a UME
was declared for harbor porpoises throughout Oregon and Washington, and
a total of 114 strandings were reported in 2006-07. The cause of the
UME has not been determined and several factors, including
contaminants, genetics, and environmental conditions, are still being
investigated (Carretta et al., 2011).
Prior to recent construction projects conducted by the Navy at
NBKB, harbor porpoises were considered to have only occasional
occurrence in the project area. A single harbor porpoise had been
sighted in deeper water at NBKB during 2010 field observations
(Tannenbaum et al., 2011). However, while implementing monitoring plans
for work conducted from July-October, 2011, the Navy recorded multiple
sightings of harbor porpoise in the deeper waters of the project area
(HDR, Inc., 2012). Following these sightings, the Navy conducted
dedicated line transect surveys, recording multiple additional
sightings of harbor porpoise, and have revised local density estimates
accordingly.
Potential Effects of the Specified Activity on Marine Mammals
We have determined that pile driving and removal (depending on
technique used), as outlined in the project description, has the
potential to result in behavioral harassment of marine mammals present
in the project area. Pinnipeds spend much of their time in the water
with heads held above the surface and therefore are not subject to
underwater noise to the same degree as cetaceans (although they are
correspondingly more susceptible to exposure to airborne sound). For
purposes of this assessment, however, pinnipeds are conservatively
assumed to be available to be exposed to underwater sound 100 percent
of the time that they are in the water.
Marine Mammal Hearing
The primary effect on marine mammals anticipated from the specified
activities would 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.
Two pinniped and three cetacean species could potentially occur in
the proposed project area during the project timeframe. Of the cetacean
species that may occur in the project area, the killer whale is
classified as a mid-frequency cetacean, and the two porpoises are
classified as high-frequency cetaceans (Southall et al., 2007).
Underwater Sound Effects
Potential Effects of Pile Driving Sound--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) would absorb or attenuate the
sound more readily than hard substrates (e.g., rock) which may reflect
the acoustic wave. Soft porous substrates would also likely require
less time to drive the pile, and possibly less forceful equipment,
which would ultimately 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).
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 would
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. 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 sound exposure that leads to
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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
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 would 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 sound 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.
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 sound
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 sound levels 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.
Non-auditory Physiological Effects--Non-auditory physiological
effects or
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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.
Disturbance Reactions
Disturbance includes a variety of effects, including subtle changes
in behavior, more conspicuous changes in activities, and displacement.
Behavioral responses to sound are highly variable and context-specific
and reactions, if any, depend on species, state of maturity,
experience, current activity, reproductive state, auditory sensitivity,
time of day, and many other factors (Richardson et al., 1995; Wartzok
et al., 2003/2004; Southall et al., 2007).
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 sound levels than animals that are highly
motivated to remain in an area for feeding (Richardson et al., 1995;
NRC, 2003; Wartzok et al., 2003/04).
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; Thorson and Reyff, 2006; see also Gordon et al., 2004;
Wartzok et al., 2003/04; Nowacek et al., 2007). Responses to continuous
sound, such as vibratory pile installation, have not been documented as
well as responses to pulsed sounds.
With both types of pile driving, it is likely that the onset of
pile driving could result in temporary, short term changes in an
animal's typical behavior and/or avoidance of the affected area. These
behavioral changes may include (Richardson et al., 1995): Changing
durations of surfacing and dives, number of blows per surfacing, or
moving direction and/or speed; reduced/increased vocal activities;
changing/cessation of certain behavioral activities (such as
socializing or feeding); visible startle response or aggressive
behavior (such as tail/fluke slapping or jaw clapping); avoidance of
areas where sound sources are located; and/or flight responses (e.g.,
pinnipeds flushing into water from haul-outs or rookeries). Pinnipeds
may increase their haul-out time, possibly to avoid in-water
disturbance (Thorson and Reyff, 2006). Since pile driving would 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 sound
depends on both external factors (characteristics of sound sources and
their paths) and the specific characteristics of the receiving animals
(hearing, motivation, experience, demography) and is difficult to
predict (Southall et al., 2007).
Auditory Masking
Natural and artificial sounds can disrupt behavior by masking, 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, sound 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 sound
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 sounds are more likely to affect detection of communication calls
and other potentially important natural sounds such as surf and prey
sound. It may also affect communication signals when they occur near
the sound 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
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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 sound
sources, such as those from vessel traffic, pile driving, and dredging
activities, contribute to the elevated ambient sound levels, thus
intensifying masking. However, the sum of sound from the proposed
activities is confined in an area of inland waters (San Diego Bay) that
is bounded by landmass; therefore, the sound generated is not expected
to contribute to increased ocean ambient sound.
The most intense underwater sounds in the proposed action are those
produced by impact pile driving. Given that the energy distribution of
pile driving covers a broad frequency spectrum, sound from these
sources would likely be within the audible range of marine mammals
present in the project area. Impact pile driving activity is relatively
short-term, with rapid pulses occurring for 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 insignificant impacts from
masking. Any masking event that could possibly rise to Level B
harassment under the MMPA would occur concurrently within the zones of
behavioral harassment already estimated for vibratory and impact pile
driving, and which have already been taken into account in the exposure
analysis.
Airborne Sound 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 sound would have less impact on
cetaceans than pinnipeds because sound from atmospheric sources does
not transmit well underwater (Richardson et al., 1995); thus, airborne
sound 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 sound. For
instance, anthropogenic sound could cause hauled-out pinnipeds to
exhibit changes in their normal behavior, such as reduction in
vocalizations, or cause them to temporarily abandon 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 would 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, 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
would be temporarily elevated sound 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 wharf construction project.
Pile Driving Effects on Potential Prey (Fish)
Construction activities would 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 sound 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 (e.g., Scholik and Yan,
2001, 2002; 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 (Pearson et al.,
1992; Skalski et al., 1992). SPLs of sufficient strength have been
known to cause injury to fish and fish mortality. 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 wharf
construction project. However, adverse impacts may occur to a few
species of rockfish (bocaccio [Sebastes paucispinis], 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
The area likely impacted by the project is relatively small
compared to the available habitat in the Hood Canal. 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 sound associated with individual
pile driving events and the relatively small areas being affected, pile
driving activities associated with the proposed action are not likely
to have a permanent, adverse effect on any fish habitat, or populations
of fish species. Therefore, pile driving is not likely to have a
permanent, adverse effect on marine mammal foraging habitat at the
project area.
Proposed Mitigation
In order to issue an incidental take authorization (ITA) under
Section 101(a)(5)(D) of the MMPA, we must, where applicable, set forth
the permissible methods of taking pursuant to such activity, and other
means of
[[Page 30287]]
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).
Measurements from similar pile driving elsewhere at NBKB were
coupled with practical spreading loss to estimate zones of influence
(ZOIs; see ``Estimated Take by Incidental Harassment''); these values
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 providing estimates of the areas within which Level B
harassment might occur. In addition to the measures described later in
this section, the Navy would 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 sound standards and ensure
that all construction equipment has sound control devices no less
effective than those provided on the original equipment.
(c) For in-water heavy machinery work other than pile driving
(using, e.g., standard barges, tug boats, barge-mounted excavators, or
clamshell equipment used to place or remove material), if a marine
mammal comes within 10 m, operations shall cease and vessels shall
reduce speed to the minimum level required to maintain steerage and
safe working conditions. This type of work could include the following
activities: (1) Movement of the barge to the pile location; (2)
positioning of the pile on the substrate via a crane (i.e., stabbing
the pile); (3) removal of the pile from the water column/substrate via
a crane (i.e., deadpull); or (4) the placement of sound attenuation
devices around the piles. For these activities, monitoring would take
place from 15 minutes prior to initiation until the action is complete.
Monitoring and Shutdown for Pile Driving
The following measures would apply to the Navy's mitigation through
shutdown and disturbance zones:
Shutdown Zone--For all pile driving and removal activities, the
Navy will establish a shutdown zone intended to contain the area in
which SPLs equal or exceed the 180/190 dB rms acoustic injury criteria.
The purpose of a shutdown zone is to define an area within which
shutdown of activity would occur upon sighting of a marine mammal (or
in anticipation of an animal entering the defined area), thus
preventing injury, serious injury, or death of marine mammals. Radial
distances for shutdown zones are shown in Table 4. However, a minimum
shutdown zone of 10 m will be established during all pile driving and
removal activities, regardless of the estimated zone. These
precautionary measures are intended to prevent the already unlikely
possibility of physical interaction with construction equipment and to
further reduce any possibility of acoustic injury.
Disturbance Zone--Disturbance zones are the areas in which SPLs
equal or exceed 160 and 120 dB rms (for pulsed and non-pulsed sound,
respectively). Disturbance zones provide utility for monitoring
conducted for mitigation purposes (i.e., shutdown zone monitoring) by
establishing monitoring protocols for areas adjacent to the shutdown
zones. Monitoring of disturbance zones enables observers to be aware of
and communicate the presence of marine mammals in the project area but
outside the shutdown zone and thus prepare for potential shutdowns of
activity. However, the primary purpose of disturbance zone monitoring
is for documenting incidents of Level B harassment; disturbance zone
monitoring is discussed in greater detail later (see ``Proposed
Monitoring and Reporting''). Nominal radial distances for disturbance
zones are shown in Tables 4 and 5. Given the size of the disturbance
zone for vibratory pile driving), it is impossible to guarantee that
all animals would be observed or to make comprehensive observations of
fine-scale behavioral reactions to sound, and only a portion of the
zone (e.g., what may be reasonably observed by visual observers
stationed within the WRA) would be observed.
In order to document observed incidences of harassment, monitors
record all marine mammal observations, regardless of location. The
observer's location, as well as the location of the pile being driven,
is known from a GPS. The location of the animal is estimated as a
distance from the observer, which is then compared to the location from
the pile. If acoustic monitoring is being conducted for that pile, a
received SPL may be estimated, or the received level may be estimated
on the basis of past or subsequent acoustic monitoring. It may then be
determined whether the animal was exposed to sound levels constituting
incidental harassment in post-processing of observational and acoustic
data, and a precise accounting of observed incidences of harassment
created. Therefore, although the predicted distances to behavioral
harassment thresholds are useful for estimating incidental harassment
for purposes of authorizing levels of incidental take, actual take may
be determined in part through the use of empirical data. That
information may then be used to extrapolate observed takes to reach an
approximate understanding of actual total takes.
Monitoring Protocols--Monitoring would be conducted before, during,
and after pile driving activities. In addition, observers shall record
all incidences of marine mammal occurrence, regardless of distance from
activity, and shall document any behavioral reactions in concert with
distance from piles being driven. Observations made outside the
shutdown zone will not result in shutdown; 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. Monitoring will take place from 15 minutes prior to initiation
through 15 minutes post-completion of pile driving activities. Pile
driving activities include the time to remove a single pile or series
of piles, as long as the time elapsed between uses of the pile driving
equipment is no more than 30 minutes.
The following additional measures apply to visual monitoring:
(1) Monitoring will be conducted by qualified observers, who will
be placed at the best vantage point(s) practicable to monitor for
marine mammals and implement shutdown/delay procedures when applicable
by calling for the shutdown to the hammer operator. Qualified observers
are trained biologists, with the following minimum qualifications:
Visual acuity in both eyes (correction is permissible)
sufficient for discernment of moving targets at the water's surface
with ability to estimate target size and distance; use of binoculars
may be necessary to correctly identify the target;
Advanced education in biological science, wildlife
management,
[[Page 30288]]
mammalogy, or related fields (bachelor's degree or higher is required);
Experience and ability to conduct field observations and
collect data according to assigned protocols (this may include academic
experience);
Experience or training in the field identification of
marine mammals, including the identification of behaviors;
Sufficient training, orientation, or experience with the
construction operation to provide for personal safety during
observations;
Writing skills sufficient to prepare a report of
observations including but not limited to the number and species of
marine mammals observed; dates and times when in-water construction
activities were conducted; dates and times when in-water construction
activities were suspended to avoid potential incidental injury from
construction sound of marine mammals observed within a defined shutdown
zone; and marine mammal behavior; and
Ability to communicate orally, by radio or in person, with
project personnel to provide real-time information on marine mammals
observed in the area as necessary.
(2) Prior to the start of pile driving activity, the shutdown zone
will be monitored for 15 minutes to ensure that it is 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 shutdown zone (i.e., must leave of their own volition)
and their behavior will be monitored and documented. The shutdown zone
may only be declared clear, and pile driving started, when the entire
shutdown zone is visible (i.e., when not obscured by dark, rain, fog,
etc.). In addition, if such conditions should arise during impact pile
driving that is already underway, the activity would be halted.
(3) If a marine mammal approaches or enters the shutdown zone
during the course of pile driving operations, activity will be halted
and delayed until either the animal has voluntarily left and been
visually confirmed beyond the shutdown zone or 15 minutes have passed
without re-detection of the animal. Monitoring will be conducted
throughout the time required to drive a pile.
Sound Attenuation Devices
Bubble curtains shall be used during all impact pile driving. The
device will distribute air bubbles around 100 percent of the piling
perimeter for the full depth of the water column, and the lowest bubble
ring shall be in contact with the mudline for the full circumference of
the ring. Testing of the device by comparing attenuated and
unattenuated strikes is not possible because of requirements in place
to protect marbled murrelets (an ESA-listed bird species under the
jurisdiction of the USFWS). However, in order to avoid loss of
attenuation from design and implementation errors in the absence of
such testing, a performance test of the device shall be conducted prior
to initial use. The performance test shall confirm the calculated
pressures and flow rates at each manifold ring. In addition, the
contractor shall also train personnel in the proper balancing of air
flow to the bubblers and shall submit an inspection/performance report
to the Navy within 72 hours following the performance test.
Timing Restrictions
In Hood Canal, designated exist timing restrictions for pile
driving activities to avoid in-water work when salmonids and other
spawning forage fish are likely to be present. The in-water work window
is July 16-February 15. The barge mooring project would occur during a
portion of that period, from July 16-September 30. During the majority
of this timeframe, impact pile driving will only occur starting two
hours after sunrise and ending two hours before sunset due to marbled
murrelet nesting season. After September 23, in-water construction
activities will occur during daylight hours (sunrise to sunset).
Soft Start
The use of a soft-start procedure is believed to provide additional
protection to marine mammals by warning or providing a chance to leave
the area prior to the hammer operating at full capacity, and typically
involves a requirement to initiate sound from vibratory hammers for
fifteen seconds at reduced energy followed by a 30-second waiting
period. This procedure is repeated two additional times. However,
implementation of soft start for vibratory pile driving during previous
pile driving work at NBKB has led to equipment failure and serious
human safety concerns. Project staff have reported that, during power
down from the soft start, the energy from the hammer is transferred to
the crane boom and block via the load fall cables and rigging resulting
in unexpected damage to both the crane block and crane boom. This
differs from what occurs when the hammer is powered down after a pile
is driven to refusal in that the rigging and load fall cables are able
to be slacked prior to powering down the hammer, and the vibrations are
transferred into the substrate via the pile rather than into the
equipment via the rigging. One dangerous incident of equipment failure
has already occurred, with a portion of the equipment shearing from the
crane and falling to the deck. Subsequently, the crane manufacturer has
inspected the crane booms and discovered structural fatigue in the boom
lacing and main structural components, which will ultimately result in
a collapse of the crane boom. All cranes were new at the beginning of
the job. In addition, the vibratory hammer manufacturer has attempted
to install dampers to mitigate the problem, without success. As a
result of this dangerous situation, the measure will not be required
for this project. This information was provided to us after the Navy
submitted their request for authorization and is not reflected in that
document.
For impact driving, soft start will be required, and contractors
will provide an initial set of three strikes from the impact hammer at
40 percent energy, followed by a 30-second waiting period, then two
subsequent three strike sets.
We have carefully evaluated the applicant's proposed mitigation
measures and considered a range of other measures in the context of
ensuring that we prescribe 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, we have 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 we must, where applicable, set forth
``requirements
[[Page 30289]]
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 would 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.
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 and are required to have
no other construction-related tasks while conducting monitoring. The
Navy will monitor the shutdown zone and disturbance zone before,
during, and after pile driving, with observers located at the best
practicable vantage points. Based on our requirements, the Navy would
implement the following procedures for pile driving:
MMOs would be located at the best vantage point(s) in
order to properly see the entire shutdown zone and as much of the
disturbance zone as possible.
During all observation periods, observers will use
binoculars and the naked eye to search continuously for marine mammals.
If the shutdown zones are obscured by fog or poor lighting
conditions, pile driving at that location will not be initiated until
that zone is visible. Should such conditions arise while impact driving
is underway, the activity would be halted.
The shutdown and disturbance zones around the pile will be
monitored for the presence of marine mammals before, during, and after
any pile driving or removal activity.
Individuals implementing the monitoring protocol will assess its
effectiveness using an adaptive approach. Monitoring biologists will
use their best professional judgment throughout implementation and seek
improvements to these methods when deemed appropriate. Any
modifications to protocol will be coordinated between NMFS and the
Navy.
Data Collection
We require that observers use approved data forms. Among other
pieces of information, the Navy will record detailed information about
any implementation of shutdowns, including the distance of animals to
the pile and description of specific actions that ensued and resulting
behavior of the animal, if any. In addition, the Navy will attempt to
distinguish between the number of individual animals taken and the
number of incidences of take. We require that, at a minimum, the
following information be collected on the sighting forms:
Date and time that monitored activity begins or ends;
Construction activities occurring during each observation
period;
Weather parameters (e.g., percent cover, visibility);
Water conditions (e.g., sea state, tide state);
Species, numbers, and, if possible, sex and age class of
marine mammals;
Description of any observable marine mammal behavior
patterns, including bearing and direction of travel, and if possible,
the correlation to SPLs;
Distance from pile driving activities to marine mammals
and distance from the marine mammals to the observation point;
Locations of all marine mammal observations; and
Other human activity in the area.
Reporting
A draft report would be submitted to NMFS within 90 working days of
the completion of marine mammal monitoring. The report will include
marine mammal observations pre-activity, during-activity, and post-
activity during pile driving days, and will also provide descriptions
of any adverse responses to construction activities by marine mammals
and a complete description of all mitigation shutdowns and the results
of those actions and a refined take estimate based on the number of
marine mammals observed during the course of construction. A final
report would be prepared and submitted within 30 days following
resolution of comments on the draft report.
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 discountable. However, as noted earlier, it is
unlikely 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 (e.g., through relatively minor changes in locomotion
direction/speed or vocalization behavior), the response may or may not
constitute taking at the individual level, and is unlikely to affect
the stock or the species as a whole. However, if a sound source
displaces marine mammals from an important feeding or breeding area for
a prolonged period, impacts on animals 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 sound on marine mammals, it is common practice to estimate
how many animals 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
actually subject to disturbance that would correctly be considered a
take under the MMPA. For example, during the past ten years, transient
killer whales have been observed within the project area twice. On the
basis of that information, an estimated amount of potential takes for
killer whales is presented here. However, while a pod of killer whales
could potentially visit again during the project timeframe, and thus be
taken, it is more likely that they would not. Although incidental take
of killer whales and Dall's porpoises was authorized for 2011-12
activities at NBKB on the basis of past observations of these species,
no such takes were recorded and no individuals of these species were
observed. Similarly, estimated actual take levels (observed takes
extrapolated to the remainder of unobserved but ensonified area) were
significantly less than authorized levels of take for the remaining
species.
The 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 and sea lions are known to haul-out on submarines and other man-
made objects at the
[[Page 30290]]
NBKB waterfront (although typically at a distance of a mile or greater
from the project site). Therefore, behavioral disturbances that could
result from anthropogenic sound associated with these activities are
expected to affect relatively small numbers of individual marine
mammals, although those effects could be recurring over the life of the
project if the same individuals remain in the project vicinity.
The Navy has requested authorization for the incidental taking of
small numbers of California sea lions, harbor seals, transient killer
whales, and harbor porpoises in the Hood Canal that may result from
pile driving during construction activities associated with the barge
mooring project described previously in this document.
The humpback whale is not expected to occur in the project area,
and Steller sea lions are not expected to occur during the project
timeframe. The earliest documented occurrence of Steller sea lions at
NBKB occurred on September 30, 2010, when five individuals were
observed at Delta Pier during daily surveys. During monitoring
associated with the 2011 TPP, Steller sea lions were documented as
arriving on October 8, but had not previously been regularly observed
prior to November.
The takes requested are expected to have no more than a minor
effect on individual animals and no effect at the population level for
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 sound.
Marine Mammal Densities
For all species, the best scientific information available was used
to derive density estimates and the maximum appropriate density value
for each species for each site was used in the marine mammal take
assessment calculation. These values were derived or confirmed by
experts convened to develop such information for use in Navy
environmental compliance efforts in the Pacific Northwest (Navy, 2013).
For harbor seals, this involved published literature describing harbor
seal research conducted in Washington and Oregon as well as more
specific counts conducted in Hood Canal (Huber et al., 2001; Jeffries
et al., 2003). The best information available for the remaining species
in Hood Canal came from surveys conducted by the Navy at the NBKB
waterfront or in the vicinity of the project area.
Beginning in April 2008, Navy personnel have recorded sightings of
marine mammals occurring at known haul-outs along the NBKB waterfront,
including docked submarines or other structures associated with NBKB
docks and piers and the nearshore pontoons of the floating security
fence. Sightings of marine mammals within the waters adjoining these
locations were also recorded. Sightings were attempted whenever
possible during a typical work week (i.e., Monday through Friday), but
inclement weather, holidays, or security constraints often precluded
surveys. These sightings took place frequently, although without a
formal survey protocol. During the surveys, staff visited each of the
above-mentioned locations and recorded observations of marine mammals.
Surveys were conducted using binoculars and the naked eye from
shoreline locations or the piers/wharves themselves. Because these
surveys consist of opportunistic sighting data from shore-based
observers, largely of hauled-out animals, there is no associated survey
area appropriate for use in calculating a density from the abundance
data. Data were compiled for the period from April 2008 through
November 2011 for analysis in this proposed IHA, and these data provide
the basis for take estimation for California sea lions. Other
information, including sightings data from other Navy survey efforts at
NBKB, is available for this species, but these data provide the most
conservative (i.e., highest) local abundance estimates (and thus the
highest estimates of potential take).
In addition, vessel-based marine wildlife surveys were conducted
according to established survey protocols during July through September
2008 and November through May 2009-10 (Tannenbaum et al., 2009, 2011).
Eighteen complete surveys of the nearshore area resulted in
observations of four marine mammal species (harbor seal, California sea
lion, harbor porpoise, and Dall's porpoise). These surveys operated
along pre-determined transects parallel to the shoreline from the
nearshore out to approximately 1,800 ft (549 m) from shoreline, at a
spacing of 100 yd, and covered the entire NBKB waterfront
(approximately 3.9 km\2\ per survey) at a speed of 5 kn or less. Two
observers recorded sightings of marine mammals both in the water and
hauled out, including date, time, species, number of individuals, age
(juvenile, adult), behavior (swimming, diving, hauled out, avoidance
dive), and haul-out location. Positions of marine mammals were obtained
by recording distance and bearing to the animal with a rangefinder and
compass, noting the concurrent location of the boat with GPS, and,
subsequently, analyzing these data to produce coordinates of the
locations of all animals detected. These surveys resulted in the only
observation of a Dall's porpoise near NBKB.
The Navy also conducted vessel-based line transect surveys in Hood
Canal on non-construction days during the 2011 TPP in order to collect
additional data for species present in Hood Canal. These surveys were
primarily detected three marine mammal species (harbor seal, California
sea lion, and harbor porpoise), and included surveys conducted in both
the main body of Hood Canal, near the project area, and baseline
surveys conducted for comparison in Dabob Bay, an area of Hood Canal
that is not affected by sound from Navy actions at the NBKB waterfront.
The surveys operated along pre-determined transects that followed a
double saw-tooth pattern to achieve uniform coverage of the entire NBKB
waterfront. The vessel traveled at a speed of approximately 5 kn when
transiting along the transect lines. Two observers recorded sightings
of marine mammals both in the water and hauled out, including the date,
time, species, number of individuals, and behavior (swimming, diving,
etc.). Positions of marine mammals were obtained by recording the
distance and bearing to the animal(s), noting the concurrent location
of the boat with GPS, and subsequently analyzing these data to produce
coordinates of the locations of all animals detected. Sighting
information for harbor porpoises was corrected for detectability (g(0)
= 0.54; Barlow, 1988; Calambokidis et al., 1993; Carretta et al.,
2001). Distance sampling methodologies were used to estimate densities
of animals for the data. This information provides the best information
for harbor porpoises.
The cetaceans, as well as the harbor seal, appear to range
throughout Hood Canal; therefore, the analysis in this proposed IHA
assumes that harbor seal, transient killer whale, harbor porpoise, and
Dall's porpoise are uniformly distributed in the project area. However,
it should be noted that there have been no observations of cetaceans
within the floating security barriers at NBKB; these barriers thus
appear to effectively prevent cetaceans from approaching the shutdown
zones. Although the Navy will implement a precautionary shutdown zone
for cetaceans, anecdotal evidence suggests that cetaceans are not at
risk of Level A harassment at NBKB
[[Page 30291]]
even from louder activities (e.g., impact pile driving). The California
sea lion does not appear to utilize most of Hood Canal. The sea lions
appear to be attracted to the man-made haul-out opportunities along the
NBKB waterfront while dispersing for foraging opportunities elsewhere
in Hood Canal. California sea lions were not reported during aerial
surveys of Hood Canal (Jeffries et al., 2000).
Description of Take Calculation
The take calculations presented here rely on the best data
currently available for marine mammal populations in the Hood Canal.
The formula was developed for calculating take due to pile driving
activity and applied to each group-specific sound impact threshold. The
formula is founded on the following assumptions:
Mitigation measures (e.g., bubble curtain) would be
utilized, as discussed previously;
All marine mammal individuals potentially available are
assumed to be present within the relevant area, and thus incidentally
taken;
An individual can only be taken once during a 24-h period;
and,
There were will be twenty total days of activity.
Exposures to sound levels above the relevant thresholds
equate to take, as defined by the MMPA.
The calculation for marine mammal takes is estimated by:
Exposure estimate = (n * ZOI) * days of total activity
Where:
n = density estimate used for each species/season
ZOI = sound threshold ZOI impact area; the area encompassed by all
locations where the SPLs equal or exceed the threshold being
evaluated
n * ZOI produces an estimate of the abundance of animals that
could be present in the area for exposure, and is rounded to the
nearest whole number before multiplying by days of total activity.
The ZOI impact area is the estimated range of impact to the sound
criteria. The distances specified in Table 3 were used to calculate
ZOIs around each pile. All impact pile driving take calculations were
based on the estimated threshold ranges assuming attenuation of 8 dB
from use of a bubble curtain. 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.
While pile driving can occur any day throughout the in-water work
window, and the analysis is conducted on a per day basis, only a
fraction of that time (typically a matter of hours on any given day) is
actually spent pile driving. Acoustic monitoring conducted as part of
the TPP demonstrated that Level B harassment zones for vibratory pile
driving are likely to be significantly smaller than the zones estimated
through modeling based on measured source levels and practical
spreading loss. Also of note is the fact that the effectiveness of
mitigation measures in reducing takes is typically not quantified in
the take estimation process. Here, we do explicitly account for an
assumed level of efficacy for use of the bubble curtain, but not for
the soft start associated with impact driving. In addition, equating
exposure with response (i.e., a behavioral response meeting the
definition of take under the MMPA) is simplistic and conservative
assumption. For these reasons, these take estimates are likely to be
conservative.
Airborne Sound--No incidents of incidental take resulting solely
from airborne sound are likely, as distances to the harassment
thresholds would not reach areas where pinnipeds may haul out. Harbor
seals can haul out at a variety of natural or manmade locations, but
the closest known harbor seal haul-out is at the Dosewallips River
mouth (London, 2006) and Navy waterfront surveys and boat surveys have
found it rare for harbor seals to haul out along the NBKB waterfront
(Agness and Tannenbaum, 2009; Tannenbaum et al., 2009, 2011; Navy,
2010). Individual seals have occasionally been observed hauled out on
pontoons of the floating security fence within the restricted areas of
NBKB, but this area is not with the airborne disturbance ZOI. The
Service Pier is elevated at least twenty feet above the surface of the
water and is inaccessible to pinnipeds, and seals have not been
observed hauled out on the floating Port Operations pier sections or on
the shoreline adjacent to the Service Pier. Sea lions typically haul
out on submarines docked at Delta Pier, approximately one mile from the
project site.
We recognize that pinnipeds in the water could be exposed to
airborne sound that may result in behavioral harassment when looking
with heads above water. However, these animals would previously have
been `taken' as a result of exposure to underwater sound above the
behavioral harassment thresholds, which are in all cases larger than
those associated with airborne sound. Thus, the behavioral harassment
of these animals is already accounted for in these estimates of
potential take. Multiple incidents of exposure to sound above NMFS'
thresholds for behavioral harassment are not believed to result in
increased behavioral disturbance, in either nature or intensity of
disturbance reaction. Therefore, we do not believe that authorization
of incidental take resulting from airborne sound for pinnipeds is
warranted.
California Sea Lion--California sea lions occur regularly in the
vicinity of the project site from August through mid-June, as
determined by Navy waterfront surveys conducted from April 2008 through
December 2011 (Table 6). With regard to the range of this species in
Hood Canal and the project area, it is assumed on the basis of
waterfront observations (Agness and Tannenbaum, 2009; Tannenbaum et
al., 2009, 2011) that the opportunity to haul out on submarines docked
at Delta Pier is a primary attractant for California sea lions in Hood
Canal, as they are not typically observed elsewhere in Hood Canal.
Their haul-out sites are not within the largest underwater ZOI, because
sound would encounter land before reaching the haul-out site (see
Figure 6-2 in the Navy's application). Abundance is calculated as the
monthly average of the maximum number observed in a given month, as
opposed to the overall average (Table 6). That is, the maximum number
of animals observed on any one day in a given month was averaged for
2008-11, providing a monthly average of the maximum daily number
observed. The largest monthly average (58 animals) was recorded in
November, as was the largest single daily count (81 in 2011). The first
California sea lion was observed at NBKB in August 2009, and their
occurrence has been increasing since that time (Navy, 2012).
California sea lion density for Hood Canal was calculated to be
0.28 animals/km\2\ for purposes of the Navy Marine Species Density
Database (Navy, 2013). However, this density was derived by averaging
data collected year-round. This project will occur during the months
when California sea lions are the least abundant in Hood Canal, so it
is more appropriate to use data collected at the NBKB waterfront during
those months (July-September). The highest number of individual
California sea lions observed hauled out at NBKB during this timeframe
during this time was 33, which occurred at the end of September 2010.
Exposures were calculated assuming 33 individuals could be present, and
therefore exposed
[[Page 30292]]
to sound exceeding the behavioral harassment threshold, on each day of
pile driving. This methodology is still conservative in that it uses
the maximum abundance without considering the much lower observed
abundances from July and August (when the majority of project activity
is likely to be completed) and assumes that all individuals potentially
would be taken on any given day of activity.
Table 6--California Sea Lion Sighting Information From NBKB, April 2008-December 2012
----------------------------------------------------------------------------------------------------------------
Number of
Number of surveys with Frequency of
Month surveys animals presence \1\ Abundance \2\
present
----------------------------------------------------------------------------------------------------------------
January......................................... 47 36 0.77 31.0
February........................................ 50 43 0.86 38.0
March........................................... 47 45 0.96 53.3
April........................................... 67 55 0.82 45.4
May............................................. 72 58 0.81 29.4
June............................................ 73 17 0.23 7.4
July............................................ 61 1 0.02 0.6
August.......................................... 65 12 0.18 2.6
September....................................... 54 31 0.57 20.4
October......................................... 65 61 0.94 51.8
November........................................ 56 56 1 60.2
December........................................ 54 44 0.81 49.6
---------------------------------------------------------------
Total or average (in-water work period only) 180 44 0.24 7.3
----------------------------------------------------------------------------------------------------------------
Totals (number of surveys) and averages (frequency and abundance) presented for work period (July-September)
only. Information from October-June presented for reference.
\1\ Frequency is the number of surveys with California sea lions present/number of surveys conducted.
\2\ Abundance is calculated as the monthly average of the maximum daily number observed in a given month.
Harbor Seal--Jeffries et al. (2003) conducted aerial surveys of the
harbor seal population in Hood Canal in 1999 for the Washington
Department of Fish and Wildlife and reported 711 harbor seals hauled
out. The authors adjusted this abundance with a correction factor of
1.53 to account for seals in the water, which were not counted, and
estimated that there were 1,088 harbor seals in Hood Canal. The
correction factor (1.53) was based on the proportion of time seals
spend on land versus in the water over the course of a day, and was
derived by dividing one by the percentage of time harbor seals spent on
land. These data came from tags (VHF transmitters) applied to harbor
seals at six areas (Grays Harbor, Tillamook Bay, Umpqua River, Gertrude
Island, Protection/Smith Islands, and Boundary Bay, BC) within two
different harbor seal stocks (the coastal stock and the inland waters
of WA stock) over four survey years. The Hood Canal population is part
of the inland waters stock, and while not specifically sampled,
Jeffries et al. (2003) found the VHF data to be broadly applicable to
the entire stock. The tagging research in 1991 and 1992 conducted by
Huber et al. (2001) and Jeffries et al. (2003) used the same methods
for the 1999 and 2000 survey years. These surveys indicated that
approximately 35 percent of harbor seals are in the water versus hauled
out on a daily basis (Huber et al., 2001; Jeffries et al., 2003).
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 (358.44 km\2\) and the formula presented previously. The
aforementioned area of Hood Canal represents a change from that cited
previously for authorizations associated with Navy activities in Hood
Canal, and represents a correction to our understanding of the
methodology used in Jeffries et al. (2003).
We recognize that over the course of the day, while the proportion
of animals in the water may not vary significantly, different
individuals may enter and exit the water. However, fine-scale data on
harbor seal movements within the project area on time durations of less
than a day are not available. Previous monitoring experience from Navy
actions conducted from in the same project area has indicated that this
density provides an appropriate estimate of potential exposures.
However, the density of harbor seals calculated in this manner (1.06
animals/km\2\) is corroborated by results of the Navy's vessel-based
marine mammal surveys at NBKB in 2008 and 2009-10, in which an average
of five individual harbor seals per survey was observed in the 3.9
km\2\ survey area (density = 1.3 animals/km\2\) (Tannenbaum et al.,
2009, 2011).
Killer Whales--Transient killer whales are uncommon visitors to
Hood Canal, and may be present anytime during the year. 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. West Coast transient
killer whales most often travel in small pods (Baird and Dill 1996).
Houghton reported to the Navy, from unpublished data, that the most
commonly observed group size in Puget Sound (defined as from Admiralty
Inlet south and up through Skagit Bay) from 2004-2010 data is six
whales.
The density value derived for the Navy Marine Species Density
Database is 0.0019 animals/km\2\ (Navy, 2013), which would result in a
prediction that zero animals would be harassed by the project
activities. However, while transient killer whales are rare in the Hood
Canal, it is possible that a pod of animals could be present. In the
event that this occurred, the animals would not assume a uniform
distribution as is implied by the density estimate. Therefore, we
conservatively assume that a single pod of whales (defined as six
whales) could be present in the vicinity of the project for the entire
duration.
Dall's Porpoise
Dall's porpoises may be present in the Hood Canal year-round and
could occur as far south as the project site. Their use of inland
Washington waters, however,
[[Page 30293]]
is mostly limited to the Strait of Juan de Fuca. One individual has
been observed by Navy staff in deeper waters of Hood Canal (Tannenbaum
et al., 2009, 2011). The Navy Marine Species Density Database assumes a
negligible value of 0.001 animals/1,000 km\2\ for Dall's porpoises in
the Hood Canal, which represents species that have historically been
observed in an area but have no regular presence. Use of this density
value results in a prediction that zero animals would be exposed to
sound above the behavioral harassment threshold, and the Navy is not
requesting any take authorization for Dall's porpoises.
Harbor Porpoise
During vessel-based line transect surveys on non-construction days
during the TPP, harbor porpoises were frequently sighted within several
kilometers of the base, mostly to the north or south of the project
area, but occasionally directly across from the Bangor waterfront on
the far side of Toandos Peninsula. Harbor porpoise presence in the
immediate vicinity of the base (i.e., within 1 km) remained low. These
data were used to generate a density for Hood Canal. Based on guidance
from other line transect surveys conducted for harbor porpoises using
similar monitoring parameters (e.g., boat speed, number of observers)
(Barlow, 1988; Calambokidis et al., 1993; Caretta et al., 2001), the
Navy determined the effective strip width for the surveys to be one
kilometer, or a perpendicular distance of 500 m from the transect to
the left or right of the vessel. The effective strip width was set at
the distance at which the detection probability for harbor porpoises
was equivalent to one, which assumes that all individuals on a transect
are detected. Only sightings occurring within the effective strip width
were used in the density calculation. By multiplying the trackline
length of the surveys by the effective strip width, the total area
surveyed during the surveys was 471.2 km\2\. Thirty-eight individual
harbor porpoises were sighted within this area, resulting in a density
of 0.0806 animals per km\2\. To account for availability bias, or the
animals which are unavailable to be detected because they are
submerged, the Navy utilized a g(0) value of 0.54, derived from other
similar line transect surveys (Barlow, 1988; Calambokidis et al., 1993;
Carretta et al., 2001). This resulted in a corrected density of 0.149
harbor porpoises per km\2\. For comparison, 274.27 km\2\ of trackline
survey effort in nearby Dabob Bay produced a corrected density estimate
of 0.203 harbor porpoises per km\2\.
Table 7--Number of Potential Incidental Takes of Marine Mammals Within Various Acoustic Threshold Zones
----------------------------------------------------------------------------------------------------------------
Underwater
-------------------------------
Vibratory
Species Density Impact injury disturbance
threshold \1\ threshold
(120 dB) \2\
----------------------------------------------------------------------------------------------------------------
California sea lion............................................. \4\ 0.28 0 660
Harbor seal..................................................... 1.06 0 341
Killer whale.................................................... 0.0019 0 120
Dall's porpoise................................................. 0.000001 0 0
Harbor porpoise................................................. 0.149 0 40
----------------------------------------------------------------------------------------------------------------
\1\ Acoustic injury threshold for impact pile driving is 190 dB for pinnipeds and 180 dB for cetaceans.
\2\ Impact pile driving would always occur on the same day as vibratory pile driving, and the 160-dB acoustic
harassment zone associated with impact pile driving is considered subsumed by the 120-dB harassment zone
produced by vibratory driving. Therefore, takes are not calculated separately for the two zones.
\4\ An maximum abundance estimate of 33 animals present per day during the project timeframe was used for take
estimation.
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 likely have a negligible short-term effect
on individuals and not result in population-level impacts.
Negligible Impact and Small Numbers Analyses and Preliminary
Determinations
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,
we 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 barge mooring project,
as outlined previously, have the potential to disturb or displace
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. No
mortality, serious injury, or Level A harassment is anticipated given
the methods of installation and measures designed to minimize the
possibility of injury to marine mammals and Level B harassment would be
reduced to the level of least practicable adverse impact. Specifically,
vibratory hammers, which do not have significant potential to cause
injury to marine mammals due to the relatively low source levels (less
than 190 dB), would be the primary method of installation. Also, no
impact pile driving will occur without the use of a sound attenuation
system (e.g., bubble curtain), and pile driving will either not start
or be halted if marine mammals approach the shutdown zone. The pile
driving activities analyzed here are similar to other similar
construction activities, including recent projects conducted by the
Navy in the Hood Canal as well as work conducted in 2005 for the Hood
Canal Bridge (SR-104) by the Washington Department of Transportation,
which have taken place with no reported injuries or mortality to marine
mammals.
[[Page 30294]]
The proposed numbers of animals authorized to be taken for
California sea lions, harbor seals, and harbor porpoise would be
considered small relative to the relevant stocks or populations (each
less than five percent) even if each estimated taking occurred to a new
individual--an extremely unlikely scenario. For transient killer
whales, we estimate take based on an assumption that a single pod of
whales, comprising six individuals, is present in the vicinity of the
project area for the entire duration of the project. These six
individuals represent a small number of transient killer whales. For
pinnipeds, no rookeries are present in the project area, there are no
haul-outs other than those provided opportunistically by man-made
objects, and the project area is not known to provide foraging habitat
of any special importance.
Repeated exposures of individuals to levels of sound that may cause
Level B harassment are unlikely to result in hearing impairment or to
significantly disrupt foraging behavior. Thus, even repeated Level B
harassment of some small subset of the overall stock is unlikely to
result in any significant realized decrease in viability, and thus
would not result in any adverse impact to the stock as a whole in terms
of adverse effects on rates of recruitment or survival. The potential
for multiple exposures of a small portion of the overall stock to
levels associated with Level B harassment in this area is expected to
have a negligible impact on the affected stocks.
We have preliminarily determined that the impact of the previously
described project 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 and opportunistic haul-
out areas near or adjacent to the project site means that potential
takes by disturbance would have an insignificant short-term effect on
individuals and would not result in population-level impacts.
Similarly, for cetacean species the absence of any known regular
occurrence adjacent to the project site means that potential takes by
disturbance would 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.
For reasons stated previously in this document, the negligible
impact determination is also supported by the likelihood that marine
mammals are expected to move away from a sound 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 Hood Canal, enabling the
implementation of shutdowns 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 would be avoided through the incorporation of the proposed
mitigation measures.
While the numbers of marine mammals potentially incidentally
harassed would depend on the distribution and abundance of marine
mammals in the vicinity of the survey activity, the numbers are
estimated to be small relative to the affected species or population
stock sizes, and have been mitigated to the lowest level practicable
through incorporation of the proposed mitigation and monitoring
measures mentioned previously in this document. This activity is
expected to result in a negligible impact on the affected species or
stocks. No species for which take authorization is requested are either
ESA-listed or considered depleted under the MMPA. No take would be
authorized for humpback whales, Steller sea lions, southern resident
killer whales, or Dall's porpoises, and the Navy would take appropriate
action to avoid unauthorized incidental take should one of these
species be observed in the project area.
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, we preliminarily find that the proposed barge mooring project
would result in the incidental take of small numbers of marine mammals,
by Level B harassment only, and that the total taking from the activity
would have a negligible impact on the affected species or stocks.
Impact on Availability of Affected Species 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 will 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 activities.
Therefore, no relevant subsistence uses of marine mammals are
implicated by this action.
Endangered Species Act (ESA)
There are no ESA-listed marine mammals expected to occur in the
action area during the proposed action timeframe; therefore, no
consultation under the ESA is required for such species.
National Environmental Policy Act (NEPA)
The Navy has 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. We will review
the draft EA and the public comments received and subsequently either
adopt it or prepare our own NEPA document before making a determination
on the issuance of an IHA.
Proposed Authorization
As a result of these preliminary determinations, we propose to
authorize the take of marine mammals incidental to the Navy's barge
mooring project, provided the previously mentioned mitigation,
monitoring, and reporting requirements are incorporated.
Dated: May 17, 2013.
Helen M. Golde,
Acting Director, Office of Protected Resources, National Marine
Fisheries Service.
[FR Doc. 2013-12151 Filed 5-21-13; 8:45 am]
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